CN1894914B

CN1894914B - High speed media access control with legacy system interoperability

Info

Publication number: CN1894914B
Application number: CN2004800373124A
Authority: CN
Inventors: 罗德尼·J·沃尔顿; 约翰·W·凯彻姆; 桑吉夫·南达
Original assignee: Qualcomm Inc
Current assignee: Qualcomm Inc
Priority date: 2003-10-15
Filing date: 2004-10-15
Publication date: 2010-06-16
Anticipated expiration: 2024-10-15
Also published as: TW200529619A; TW200527868A; CN101860925A; CN101860925B; TWI380633B; CN1894914A; TW200531489A; CN102612076A; CN102571801B; TWI385993B; TWI384793B; CN102612076B; TWI383302B; TWI466517B; TW200525375A; TW200527846A; TW200536306A; BRPI0415426A; CN102571801A; BRPI0415422A

Abstract

Techniques for MAC processing for efficient use of high throughput systems that is backward compatible with various types of legacy systems are disclosed. In one aspect a first signal is transmitted according to a legacy transmission format to reserve a portion of a shared medium, and communication according to a second transmission format transpires during the reserved portion. In another aspect, a communication device may contend for access on a legacy system, and then communicate according to a new class communication protocol with one or more remote communication devices during the access period. In another aspect, a device may request access to a shared medium according to a legacy protocol, and, upon grant of access, the device may communicate with or facilitate communication between one or more remote stations according to a new protocol.

Description

Has high speed media access control with the legacy system interoperability

Require priority according to 35U.S.C § 119

Present patent application requires to enjoy the priority of following U.S. Provisional Patent Application:

On October 15th, 2003 submitted to, exercise question is the provisional application No.60/511 of " Method and Apparatus forProviding Interoperability and Backward Compatibility in WirelessCommunication Systems ", 750;

On October 15th, 2003 submitted to, exercise question is the provisional application No.60/511 of " Method, Apparatus, and Systemfor Medium Access Control in a High Performance Wireless LANEnvironment ", 904;

On October 21st, 2003 submitted to, exercise question is the provisional application No.60/513 of " Peer-to-Peer Connections inMIMO WLAN System ", 239;

On December 1st, 2003 submitted to, exercise question is the provisional application No.60/526 of " Method, Apparatus, and Systemfor Sub-Network Protocol Stack for Very High Speed Wireless LAN ", 347;

On December 1st, 2003 submitted to, exercise question is the provisional application No.60/526 of " Method; Apparatus; and Systemfor Multiplexing Protocol data Units in a High Performance WirelessLAN Environment ", 356;

On December 23rd, 2003 submitted to, exercise question is the provisional application No.60/532 of " Wireless CommunicationsMedium Access Control (MAC) Enhancements ", 791;

On February 18th, 2004 submitted to, exercise question is the provisional application No.60/545 of " Adaptive CoordinationFunction (ACF) ", 963;

On June 2nd, 2004 submitted to, exercise question is the provisional application No.60/576 of " Method and Apparatus for RobustWireless Network ", 545;

On July 8th, 2004 submitted to, exercise question is the provisional application No.60/586 of " Method and Apparatus forDistribution Communication Resources Among Multiple Users ", 841; And

On August 11st, 2004 submitted to, exercise question is the provisional application No.60/600 of " Method, Apparatus, and Systemfor Wireless Communications ", 960; Above-mentioned provisional application all transfers the application's assignee, so incorporate into herein with way of reference clearly.

Technical field

The present invention relates generally to communication, relate in particular to the medium access control.

Background technology

For the various communications such as voice-and-data are provided, widespread deployment wireless communication system.Typical radio data system or network provide access to one or more shared resources for a plurality of users.A kind of system can use multiple access technology, as frequency division multiplexing (FDM), Time Division Multiplexing, code division multiplexing (CDM) etc.

The wireless network of example comprises the data system based on honeycomb.Some such examples are as follows: (1) " TIA/EIA-95-B Mobile Station-Base Station CompatibilityStandard for Dual-Mode Wideband Spread Spectrum Cellular System " (IS-95 standard); (2) standard (W-CDMA standard) that (3GPP) provides by " 3rd Generation Partnership Project " by name, it is included among one group of document 3G TS 25.211,3G TS25.212,3G TS 25.213 and 3G TS 25.214; (3) standard (IS-2000 standard) that (3GPP2) provides by " 3rd GenerationPartnership Project 2 " by name, it is included in " TR-45.5 Physical Layer Standard for cdma2000 Spread SpectrumSystems "; (4) follow high data rate (HDR) system of TIA/EIA/IS-856 standard (IS-856 standard).

Other examples of wireless system comprise wireless lan (wlan), as IEEE 802.11 standards (i.e. 802.11 (a) and (b) or (g)).Employing comprises multiple-input and multiple-output (MIMO) WLAN of OFDM (OFDM) modulation technique, can realize the improvement to these networks.In order to improve some shortcomings of standard before 802.11, introduced IEEE 802.11 (e).

Along with the development of wireless system design, can provide higher data rate.Higher data rate has been created possibility for advanced the application, as voice, video, high speed data transfer and various other application.But different application has different requirements for its transfer of data separately.Numerous types of data has time-delay and throughput requirement, perhaps needs certain service quality (QoS) to guarantee.Do not having to reduce the capacity of system under the situation of resource management, and system possibly can't work efficiently.

Medium access control (MAC) agreement is often used in distributing between a plurality of users the communication resource of sharing.The MAC agreement is joined together with the physical layer that is used for transceive data high-rise usually.For benefit from data rate increases, the MAC agreement must be designed to utilize efficiently shared resource.Usually also wish to keep interoperability with communication standard that replace or tradition (legacy).Therefore, need to utilize efficiently the MAC of high throughput systems to handle in this area.Also this need keep the MAC of backward compatibility to handle with various types of legacy systems in this area.

Summary of the invention

Embodiment disclosed herein has solved utilizing high throughput systems efficiently and can keeping the demand of the MAC processing of backward compatibility with various legacy systems.In one aspect, send the part of first signal according to the conventional transmission form, and during the part of reserving, communicate according to second kind of transformat with the reservation shared medium.

In one aspect, communication equipment can be competed access on legacy system, and subsequently during access period, communicates according to new a class communication protocol and one or more telecommunication equipment.In one aspect of the method, equipment can insert shared medium according to the legacy protocol request, and when granting access, this equipment can communicate (perhaps being convenient to communicating by letter between two or more distant stations) according to New Deal with one or more distant stations.

In another aspect, novel (new class) access point has distributed uncontended periods and competing cycle, wherein the part of uncontended periods is distributed to communication, and the second portion of uncontended periods is distributed to communication according to conventional communication protocols according to novel agreement.Competing cycle can use the combination of one of two kinds of agreements or two kinds of agreements.Give various others.

Description of drawings

Fig. 1 is a kind of exemplary embodiment of system, and it comprises high speed WLAN;

Fig. 2 has provided an exemplary embodiment of Wireless Telecom Equipment, and it can be configured to access point or user terminal;

Fig. 3 has provided 802.11 interFrameGap parameters;

Fig. 4 has provided an exemplary physical layer (PHY) span line (segment), is used for illustrating that using DIFS to add back off time (backoff) according to DCF inserts;

Fig. 5 has provided an exemplary physical layer (PHY) span line, is used for explanation and used SIFS before ACK, and it has than the higher priority of DIFS access;

Fig. 6 shows big packet fragmentation is become little burst (fragment), and the latter has the SIFS that is associated;

Fig. 7 has provided an exemplary physical layer (PHY) span line, is used to illustrate that every frame all has the TXOP of affirmation;

Fig. 8 shows has the TXOP that piece is confirmed;

Fig. 9 has provided an exemplary physical layer (PHY) span line, is used to illustrate the poll TXOP that uses HCCA;

Figure 10 is the exemplary embodiment of TXOP, and it comprises a plurality of continuous transmission without any the gap;

Figure 11 is the exemplary embodiment of TXOP, is used for explanation and reduces required preamble transmissions amount;

An exemplary embodiment of the method that Figure 12 shows various aspects integrated, it comprise merge lead code, deletion such as SIFS the gap and insert GIF as required;

Figure 13 has provided an exemplary physical layer (PHY) span line, is used to illustrate that the wheel of merging inquires about corresponding TXOP;

Figure 14 has provided an illustrative methods that is used to merge poll;

Figure 15 has provided an exemplary mac frame;

Figure 16 has provided an exemplary MAC PDU;

Figure 17 has provided an exemplary point to point link;

Figure 18 shows the physical layer bursts (burst) of a prior art;

Figure 19 has provided an exemplary physical layer bursts, and it can be used for point to point link;

Figure 20 has provided an exemplary embodiment of mac frame, and it comprises optional self-organizing (ad hoc) section;

Figure 21 has provided an exemplary physical layer bursts;

Figure 22 shows an exemplary point-to-point data transmission method;

Figure 23 has provided an exemplary point to point link method;

Figure 24 has provided and has been used for connecting the illustrative methods that Rate Feedback is provided at point-to-point;

The managed point-to-point that Figure 25 shows between two stations and the access point connects;

The point-to-point that Figure 26 shows based on competition (or self-organizing) connects;

Figure 27 has provided an exemplary mac frame, is used to illustrate the managed point to point link between the station;

Figure 28 shows and support tradition and novel station on identical Frequency Distribution;

Figure 29 shows tradition and new media access control is combined;

Figure 30 has provided a kind of illustrative methods of getting transmission opportunity;

Figure 31 has provided a kind of illustrative methods of sharing single FA with a plurality of BSS;

Figure 32 shows the overlapping BSS that uses single FA;

Figure 33 provided with traditional B SS interoperability in carry out a kind of illustrative methods of high speed point to point link;

Figure 34 shows the point to point link that uses the MIMO technology, and it competes access on traditional B SS;

Figure 35 shows one or more mac frames (or burst) is encapsulated in the aggregate frame;

Figure 36 shows a traditional mac frame;

Figure 37 shows an exemplary decompressed frame;

Figure 38 has provided an exemplary condensed frame;

Figure 39 has provided another exemplary condensed frame;

Figure 40 has provided an exemplary polymerization header;

Figure 41 has provided an exemplary embodiment of the scheduling access period frame (SCAP) that uses in ACF;

How Figure 42 shows SCAP and HCCA and EDCA is combined use;

Figure 43 shows beacon (Beacon) at interval, comprises a plurality of SCAP, has interted therebetween based on the access period of competing;

Figure 44 shows the low delay operation of adopting a large amount of MIMO STA;

Figure 45 has provided an exemplary SCHED message;

Figure 46 has provided an exemplary power management field;

Figure 47 has provided an exemplary MAP field;

Figure 48 has provided and has been used for the exemplary SCHED control frame that TXOP distributes;

Figure 49 shows a traditional 802.11PPDU;

Figure 50 has provided an exemplary MIMO PPDU who is used for transfer of data;

Figure 51 has provided an exemplary SCHED PPDU;

Figure 52 has provided an exemplary FRACH PPDU; And

Figure 53 show can with another embodiment of the method for legacy system interoperability.

Embodiment

The physical layer of the very high bit rate of combining wireless LAN (perhaps, using the similar application of emerging transmission technology) discloses the exemplary embodiment of supporting efficient operation here.This exemplary WLAN supports to surpass the bit rate of 100Mbps (MBPS) in the 20MHz bandwidth.

Various exemplary embodiments have kept the simplicity and the robustness of the distributed collaboration operation of traditional wlan system, and for example, they are 802.11 (a-e).Can realize the advantage of various embodiment, keep backward compatibility simultaneously with these legacy systems.(should be noted in the discussion above that in the following description, is exemplary legacy system with 802.11 system descriptions.Those skilled in the art will find that these improve system and operating such same and replacement.)

A kind of exemplary WLAN can comprise the Subnetwork protocol stack.The Subnetwork protocol stack can be supported the physical layer transmission mechanism of high data rate, high bandwidth usually, including, but not limited to: based on the mechanism of OFDM modulation; The single-carrier modulated technology; Use system's (multiple-input and multiple-output (MIMO) system comprises the single output of many inputs (MISO) system) of a plurality of emissions and a plurality of reception antennas, be used for the very operation of high bandwidth efficiency; With a plurality of transmit and receive antenna and space multiplexing technique combine use with in the identical time interval to a plurality of user terminal to transmit data or receive the system of data from a plurality of user terminals; And employing code division multiple access (CDMA) technology realizes a plurality of users system for transmitting simultaneously.The example of replacing comprises single many outputs of input (SIMO) and the single output of single input (SISO) system.

One or more exemplary embodiment given here is launched to introduce at the wireless data communication system environment.Though preferably in this environment, use, also different embodiments of the invention can be applied to different environment or configuration.Generally, processor, integrated circuit or the discrete logic of various systems described herein available software control are realized.The data that run through the application and quote, instruction, order, information, signal, symbol and chip preferably make up with voltage, electric current, electromagnetic wave, magnetic field or particle, light field or particle or its to be represented.In addition, the square frame shown in every width of cloth block diagram can be represented the step of hardware or method.Under the situation that does not depart from protection range of the present invention, method step can exchange." exemplary " used herein speech means " as example, example or explanation ".Here being described to any embodiment of " exemplary " or design should not be interpreted as more preferred or have an advantage than other embodiment or design.

Fig. 1 is an exemplary embodiment of system 100, and it comprises an access point (AP) 104, and this access point 104 is connected to one or more user terminals (UT) 106A-N.According to 802.11 terms, in this article, AP and UT are also referred to as station or STA.AP and UT communicate via wireless lan (wlan) 120.In this exemplary embodiment, WLAN 120 is high speed MIMO ofdm systems.But WLAN 120 also can be any WLAN.Access point 104 communicates via network 102 and any amount of external equipment or processing procedure.Network 102 can be the Internet, Intranet or any other wired, wireless or optical-fiber network.Connect 110 physical layer signal is sent to access point 104 from network.Equipment or processing procedure can be connected to network 102, perhaps, and as the UT on the WLAN 120 (or via with its be connected).The example of the equipment that can be connected with network 102 or WLAN 120 comprises: phone; PDA(Personal Digital Assistant); Various types of computers (terminal of laptop computer, personal computer, work station, any kind); Video equipment is as camera, video camera, web camera; And the data equipment of any other type in fact.Process can comprise voice, video, data communication etc.Various data flow may have different transmission requirements, and these can be met by using different service quality (QoS) technology.

System 100 can dispose with a centralized AP 104.In an exemplary embodiment, all UT 106 communicate with this AP.In an alternative embodiment can carry out direct point to point link, and need not the modification system between two UT, this is conspicuous to those skilled in the art, will describe its example below.Access can be managed by AP, or (that is, based on what compete) of self-organizing, will be elaborated to this below.

In one embodiment, AP 104 provides Ethernet self adaptation (adaptation).In this case, except that AP, can also dispose an ip router, with the connection (not showing its details here) that is provided to network 102.Ethernet frame can transmit (below will describe in detail) by the WLAN subnet between router and UT 106.Ethernet self adaptation and connectivity are the known technologies in this area.

In an alternative embodiment, AP 104 provides IP self adaptation.In this case, for the set that connects UT, AP serves as a gateway router (not showing its details).In this case, AP 104 can be routed to IP datagram UT 106, and, the IP datagram from UT 106 is carried out route.IP self adaptation and connectivity are the known technologies in this area.

Fig. 2 has provided an exemplary embodiment of Wireless Telecom Equipment, and this Wireless Telecom Equipment can be configured to access point 104 or user terminal 106.Fig. 2 shows access point 104 configurations.Transceiver 210 receives and sends in connection 110 according to the physical layer requirement of network 102.From or be sent to the equipment that is connected with network 102 or the data of application are passed to mac processor 220.These data are called as stream 260 here.Stream may have different characteristics, and the type based on the application that is associated with this stream may need different processing.For example, the feature of video or voice is low delay stream (video has higher throughput than voice usually and requires).A lot of data are used time-delay not too responsive, require (that is, some packet loss can be tolerated in voice, but file transfer can't stand packet loss usually) but may have the higher data integrality.

Mac processor 220 receives stream 260, and processor they so that on physical layer, transmit.Mac processor 220 also receives physical layer data, and handles this data, to be formed for the grouping of output stream 260.Between AP and UT, also transmit internal control and signaling.Medium Access Control (MAC) Protocol Data Unit (MAC PDU), be also referred to as physical layer (PHY) protocol Data Unit (PPDU), perhaps frame (sayings according to 802.11) is passed to WLAN transceiver 240 by connecting 270, and receives them from WLAN transceiver 240.Become MAC PDU with command conversion and convert the example technique that flows and order to and will be elaborated below from stream from MAC PDU.The embodiment that replaces can adopt any switch technology.Can turn back to mac processor 220 from physical layer (PHY) 240 with the corresponding feedback 280 of various MAC ID, be used for various purposes.Feedback 280 can comprise any physical layer information, comprise channel (comprising Multicast Channel and unicast tunnel) but supporting rate, modulation format and various other parameters.

In one exemplary embodiment, adaptation layer (ADAP) and data link control layer (DLC) are carried out in mac processor 220.Physical layer (PHY) is carried out on WLAN transceiver 240.One skilled in the art will appreciate that and under arbitrary configuration, to carry out cutting apart of various functions.Mac processor 220 can be carried out part or all of physical layer process.The WLAN transceiver can comprise a processor, is used to carry out MAC and handles or its part.Can adopt any amount of processor, specialized hardware or its combination.

Mac processor 220 can be general purpose microprocessor, digital signal processor (DSP) or application specific processor.Mac processor 220 can be connected with specialized hardware, to assist each task (not showing its details here).Various application may operate on the outer processor that connects, and as the computer that connects outward, or connect on the Attached Processor that may operate in access point 104 (not shown)s by network, perhaps, may operate on one's body 220 of the mac processors.Shown mac processor 220 is connected with memory 255, and the latter can be used to store data and instruction, so that carry out various program described herein and method.It will be appreciated by those skilled in the art that memory 255 can comprise one or more various types of memory units, can embed in the mac processor 220 in whole or in part.

Except storage is used to carry out the instruction and data of function described here, memory 255 also can be used to store the data that are associated with individual queue.

WLAN transceiver 240 can be the transceiver of any kind.In an exemplary embodiment, WLAN transceiver 240 is OFDM transceivers, and it can utilize MIMO or the work of MISO interface.To those skilled in the art, OFDM, MIMO and MISO are known.On August 27th, 2003 submitted to, title is the U.S. Patent application No.10/650 common co-pending of " FREQUENCY-INDEPENDENT SPATIAL-PROCESSING FORWIDEBAND MISO AND MIMO SYSTEMS ", in 295, described OFDM, MIMO and the MISO transceiver of various exemplary, this part application has transferred assignee of the present invention.The embodiment that replaces can comprise SIMO or SISO system.

Shown WLAN transceiver 240 is connected with antenna 250A-N.In different embodiment, can support any amount of antenna.Antenna 250 can be used to send and receive on WLAN 120.

WLAN transceiver 240 can comprise the spatial processor that is connected with one or more antennas 250.This spatial processor can be handled the data that each antenna will send independently, perhaps, the signal that receives on all antennas is carried out Combined Treatment.The example of independent process can be based on channel estimating, the feedback from UT, channel counter-rotating (channel inversion) or multiple other technologies as known in the art.This processing is to use one of any execution in the multiple spatial processing technique.A plurality of such transceivers can use wave beam formation, beam steering (beamsteering), feature guiding (eigen-steering) or other space technologies, improve the throughput that is sent to a given user terminal and from the throughput of a given user terminal.In an exemplary embodiment that wherein sends the OFDM symbol, this spatial processor can comprise a plurality of subspaces processor, is used for handling each OFDM subchannel or frequency range (bin).

In an example system, this AP can have N antenna, and an exemplary UT can have M antenna.Therefore, the MxN paths is arranged between the antenna of this AP and this UT.In the art, the various space technologies of using described mulitpath to improve throughput all are known.In a kind of space-time emission diversity (STTD) system (, being also referred to as " diversity " here), the transmission data format and encode, and then, go out by all antenna transmission as individual traffic.Use M transmitting antenna and N reception antenna, can form MIN (M, N) individual independent channel.Spatial reuse utilizes these independent pathways, and can send different data on every independent pathway, thereby improves transmission rate.

The various technology that are used to learn and adapt to the characteristic of channel between AP and the UT are known.Can send unique pilot tone from each transmitting antenna.Receive and measure these pilot tones at each reception antenna place.Then, the channel condition information feedback can be returned to transmitter, for use in transmission.Can carry out the feature decomposition of measured channel matrix, to determine the channel characteristics pattern.The technology that another kind is avoided carrying out the feature decomposition of channel matrix in receiver is to use the feature of pilot tone and data to lead, and comes the spatial manipulation in the simplified receiver.

Therefore, according to current channel status, the transmission for each user terminal in system can provide different data rates.Particularly, the particular link between AP and each UT has superior performance than multicast link or broadcasting link, and multicast link or broadcasting link can be shared from AP to above UT.Further the example of this respect is elaborated below.Use which kind of spatial manipulation based on the physical link between AP and the UT, WLAN transceiver 240 can be determined supported speed.This information can feedback by connecting 280, handles to be used for MAC.

The quantity of antenna can be disposed according to the demand data of UT and size and form factor.For example, because its higher bandwidth requirement, the high definition video display can comprise, for example, and four antennas; And PDA can have two antennas.An exemplary access point can have four antennas.

Can dispose user terminal 106 by the mode similar to access point shown in Figure 2 104.Not to allow stream 260 be connected to the LAN transceiver (although UT can comprise such transceiver, be wired or wireless), stream 260 is normally from one or more application of being attached thereto the equipment that connects or UT work or handle and receive, or is delivered to and is attached thereto the equipment or the UT that connect and goes up the one or more application or the processing of working.The high level that is connected with AP 104 or UT 106 can be an any kind.Layer described herein only is illustrative.

Traditional 802.11MAC

As mentioned above, in order to keep compatible, can adopt various embodiment described herein with legacy system.IEEE 802.11 (e) function is gathered (with 802.11 standards maintenance backward compatibility early) and is comprised the various functions that will sum up in this section, and in the function of introducing in the standard morning.For the detailed description of these functions, please refer to corresponding IEEE 802.11 standards.

Basic 802.11MAC comprises based on the Carrier Sense Multiple Access/conflict of distributed coordination function (DCF) and point coordination function (PCF) and avoids (CSMA/CA).DCF can insert medium under the situation that does not have central authorities' control.In AP, use PCF that central control is provided.For fear of conflict, DCF and PCF utilize the various gaps between the transmission continuously.Transmission is called as frame, and the gap between the frame then is called as interFrameGap (IFS).Frame can be user data frame, control frame or management frames.

The type of interFrameGap duration according to the insertion gap changes.Fig. 3 shows 802.11 interFrameGap parameters: short interFrameGap (SIFS), some interFrameGap (PIFS) and DCF interFrameGap (DIFS).Note that SIFS＜PIFS＜DIFS.Therefore, compare, be positioned at the transmission afterwards of shorter duration and will have higher priority with before attempting access channel, waiting for the transmission of long period.

According to carrier sense (CSMA) function of CSMA/CA, channel is when idle in the duration at least one DIFS detecting, and stand (STA) can obtain the access right of channel.(employed here term " STA " can refer to an access any station of WLAN, and can comprise access point and user terminal).For fear of conflict, except that DIFS, each STA also waits for a back off time () of selecting at random, then could access channel.STA with longer back off time will be noted that when high priority STA begins to send on channel, therefore avoided conflicting mutually with this STA.(STA of each wait can reduce its corresponding back off time it and listen to the time quantum of waiting for before other transmission on this channel, thereby keeps its relative priority).Therefore, avoid (CA) function according to the conflict of this agreement, STA keeps out of the way a random time section between [0, CW], and wherein selecting CW at first is CWmin, increases the factor 2 when conflicting, till maximum CWmax at every turn.

Fig. 4 has provided an exemplary physical layer (PHY) span line 400, is used for illustrating that how to use DIFS to add back off time according to DCF inserts.Existing transmission 410 busy channels.In this embodiment, when transmission 410 stops, the access of higher priority does not appear, so, after DIFS and the back off time section that is associated, begin new transmission 420.In the following discussion, think that transmitting 420 STA has obtained this transmission opportunity by competition in this case.

Only expecting that a specific STA makes current transmission in the frame sequence of response, using SIFS.For example, when sending an acknowledgement frame (ACK) in response to the Frame of receiving, can receive that data send this ACK after adding SIFS immediately.Other transfer sequence also can use SIFS between frame.After a request sends (RTS) frame, can follow SIFS and one and permit sending (CTS) frame, then, and transmission data during SIFS that can be CTS after, after this, the SIFS after data can follow an ACK.As mentioned above, these frame sequences all are interspersed with SIFS.The SIFS duration can be used for: (a) detect the energy on the channel, and judge whether energy exhausts (that is channel clear); (b) if having time previous message is decoded and judge whether the ACK frame shows that transmission is correctly received; (c) the STA transceiver switches to emission and switches to reception from emission from reception if having time.

Fig. 5 has provided an exemplary physical layer (PHY) span line 500, is used for illustrating how to use SIFS before ACK, and it inserts than DIFS has higher priority.An existing transmission 510 takies this channel.In this embodiment, when transmission 510 stops, when finishing a back SIFS, transmission 510 followed ACK 520.Note that ACK 520 DIFS at the expiration before beginning, so any other STA that attempts to win transmission can be not successful.In this embodiment, ACK 520 access of higher priority do not occur after finishing, so, after DIFS and the back off time that is associated (if any), begin new transmission 530.

RTS/CTS frame sequence (except flow control function is provided) can be used to improve the protection to data frame transfer.RTS and CTS comprise the duration information of subsequent data frame and ACK and any middle SIFS.Listen to the STA of RTS or CTS and on their network allocation vector (NAV), mark the shared duration, and in this duration, medium are considered as busy.Typically, utilize RTS/CTS, the frame longer than designated length can be protected, and short frame is sent out away under the unprotect situation.

PCF can be used to make AP that the centralized control of channel is provided.Detecting medium when PIFS is the free time in the duration, AP can obtain the control to these medium.PIFS is shorter than DIFS, so have higher priority than DIFS.Compare with DCF, in case AP has obtained the access right to channel, it just can provide uncompetitive access chance to other STA, thereby improves MAC efficient.PCF note that SIFS has higher priority than PIFS, so must wait for, till all SIFS EOSs before control channel.

In case AP uses the access right of PIFS acquisition to medium, it just can establish a uncontended periods (CFP), and in this cycle, AP can provide the poll formula to insert to the STA that is associated.Uncompetitive poll (CF-Poll), or be simply referred to as poll is sent and it is followed later is transmission from the STA that is subjected to poll to AP by AP.Equally, STA must wait for the SIFS duration after CF-Poll, although be subjected to the STA of poll needn't wait for DIFS or any back off time.802.11 (e) introduced various enhancings, comprise enhancing to poll, below in conjunction with Fig. 9 such example is described in further detail.

The beacon that AP sends is established the duration of CFP.This is similar to and uses RTS or CTS to prevent that competition from inserting.But some terminal can't be heard this beacon, but its transmission may cause interference to the transmission of being dispatched by AP, so hidden terminal problem still can occur.Each terminal that begins to transmit in CFP can realize further protection by using CTS-to-self.

ACK and CF-Poll can be contained in the frame, and can be included in Frame, thereby improve MAC efficient.Note that it is that the channel access provides a kind of certainty priority mechanism that SIFS＜PIFS＜DIFS closes.In DCF, it is probabilistic that the competition between the STA inserts based on avoidance mechanism.

802.11 early stage standards have also been stipulated big packet fragmentation is become less burst.An advantage of this segmentation is: the mistake in section needs less re-transmission than the mistake in the bigger grouping.Segmentation shortcoming is in these standards: for the transmission of affirmation type, need send an ACK for each section, wherein, additional SIFS is corresponding to additional ACK transmission and burst transmission.Fig. 6 shows this point.This exemplary physical layer (PHY) span line 600 has provided N section and the corresponding transmission of confirming thereof.Existing transmission 610 is sent out away.When transmission 610 finished, a STA waited for DIFS 620 and back off time 630, to obtain the access right to channel.The one STA sends N section 640A-640N to the 2nd STA, and the delay of the individual corresponding SIFS 650A-650N of N must arranged respectively thereafter.The 2nd STA sends N acknowledgement frame 660A-660N.Between each burst, a STA must wait for SIFS, so, there be N-1 SIFS 670A-670N-1.Therefore, compare with a SIFS with a grouping of transmission, an ACK, the grouping through segmentation needs the identical transmitted in packets time, but N ACK and 2N-1 SIFS are arranged.

802.11 (e) standard has been added enhancement function so that improve 802.11 (a) and (b) and (g) in former MAC.802.11 all be ofdm system (g) and (a), they are very similar, but work in different frequency bands.The various functions of the low speed MAC agreement such as 802.11 (b) pass on to forward has the more system of high bit rate, thereby has introduced poor efficiency, and the back will be elaborated to this.

In 802.11 (e), DCF has obtained enhancing, strengthens distributed channel access (EDCA) so be called as.It is to have introduced arbitration frame interbody spacer (AIFS) that the main service quality (QoS) of EDCA strengthens.AIFS[i] be associated with the type of service (TC) that identifies with numbering i.AP can use with other STA can employed AIFS[i] AIFS[i that value is different] value.Have only AP can use the AIFS[i that equates with PIFS] value.In other cases, AIFS[i] more than or equal to DIFS.Under the default situation,, select to equal the AIFS of DIFS for " voice " and " video " type of service.If AIFS is bigger, then is indicated as type of service " best effort (besteffort) " and " background " and has selected lower priority.

The size of competition window also is the function of TC.The limit priority type allows to be provided with CW=1,, does not have back off time that is.For other TC, different contention window size provides probabilistic relative priority level, postpones to guarantee but can not be used for reaching.

802.11 (e) introduced transmission opportunity (TXOP).In order to improve MAC efficient, when STA got access to medium by EDCA or by the access of the poll formula among the HCCA, STA can send more than one frame.These one or more frames are called as TXOP.In the media, the maximum length of TXOP depends on type of service and is determined by AP.In addition, for the TXOP that is subjected to poll, AP indicates the allowance duration of TXOP.During TXOP, STA can send a series of frame, is interspersed with SIFS therebetween and from the ACK of purpose side.Except waiting for that DIFS adds the back off time to each frame, the STA that has won a TXOP can know that it can keep this channel to be used for subsequent transmission.

During TXOP, can be (just as in the 802.11MAC early) of every frame from the ACK of purpose side, perhaps, can use piece ACK at once or delay, as described below.In addition, for specific Business Stream,, allow the strategy of no ACK as broadcast or multicast.

Fig. 7 has provided an exemplary physical layer (PHY) span line 700, is used to illustrate have the TXOP that confirms frame by frame.An existing transmission 710 is sent out away.After transmission 710 and after wait DIFS 720 and the back off time 730 (if any), STA wins TXOP 790.TXOP 790 comprises N frame 740A-740N, and N corresponding SIFS 750A-750N followed in each frame back.The STA that receives makes response with N corresponding ACK760A-760N.ACK follows 760 back N-1 SIFS 770A-770N-1.Should be noted in the discussion above that each frame 740 comprises lead code 770, and header and grouping 780.The exemplary embodiment that describes in detail below can be reduced to the transmission time amount that lead code is reserved greatly.

Fig. 8 shows has the TXOP 810 that piece is confirmed.TXOP 810 can win by competition or poll.TXOP 810 comprises N frame 820A-820N, and N corresponding SIFS 830A-830N followed in each frame back.After the transmission of frame 820 and SIFS 830, send a piece ACK request 840.The STA that receives will ask to make response in a certain moment in future to this piece ACK.This piece ACK can perhaps can postpone immediately following after the piece end of transmission of frame, to allow the software processes of receiver.

The exemplary embodiment that describes in detail below can significantly reduce the transmission time amount (being SIFS in this embodiment) between the frame.In some embodiments, there is no need delay continuously between the transmission (being frame).

Should be noted in the discussion above that in 802.11 (a) and other standards for specific transformat, defined a kind of signal extension (Signal Extension), its end at every frame increases additional delay.Although be not included in technically in the definition of SIFS, each embodiment that describes in detail below also can remove signal extension.

Piece ACK function can be raised the efficiency.In an example, STA can send and 1024 corresponding maximum 64 MAC service data units of frame (SDU) (each can also be divided into 16 bursts), and purpose side STA can provide single response in the end of the piece of frame, to show each the ACK state in this 1024 frame.Typically, when speed was high, MAC SDU can not be carried out burst, and for low delay, before need the piece ACK from purpose side, can send and was less than 64 MAC SDU.In this case, in order to send M frame, total time reduces to M frame+M SIFS+ piece ACK from M frame+M SIFS+M ACK+M-1 SIFS.The embodiment that describes in detail below further improves the efficient of piece ACK.

802.11 (e) the direct link agreement (DLP) of Yin Ruing can directly be transmitted to frame STA to be in another the purpose side STA (by identical AP control) in the set of basic (BSS).AP can provide the TXOP of poll for this direct frame transmission between the STA.Before introducing this function, in poll formula access procedure, from the purpose side of the frame that is subjected to poll STA AP always, and AP is transmitted to purpose side STA with these frames.Transmit by the frame of eliminating double bounce, medium efficient is improved.The embodiment that further describes below increases tangible efficient for the DLP transmission.

802.11 (e) also introduced in-dash computer F, be called as Hybrid Coordination Function (HCF).Channel in HCF control inserts in (HCCA), and AP is access channel at any time, thereby sets up controlled access phase (CAP), and this is similar to CFP, and any time that is used in the competitive stage provides transmission opportunity, rather than only immediately following behind beacon.AP inserts medium then not having to wait for PIFS under the situation of back off time.

Fig. 9 has provided an exemplary physical layer (PHY) span line 900, is used to illustrate the TXOP that is subjected to poll that uses HCCA.In this embodiment, AP competes this poll.An existing transmission 910 is sent out away.After transmission 910, AP waits for PIFS, and sending the recipient then is the poll 920 of a STA.Other STA that should be noted in the discussion above that this channel of competition must wait for DIFS at least, because the poll 920 that sends causes this can not occur, as shown in the figure.Be subjected to the STA of poll after poll 920 and SIFS 930, to send the TXOP 940 that is subjected to poll.AP can continue poll, waits for PIFS between TXOP 940 that respectively is subjected to poll and poll 920.In another kind of situation, AP can wait for PIFS from transmitting 910, thereby establishes CAP.AP can send one or more polls during CAP.

MAC improves

As mentioned above, the various poor efficiency functions of former MAC also pass in later on the version.For example, the very long lead code that designs for the 11Mbps relative with 64Mbps can cause poor efficiency.Along with the increase of speed, Medium Access Control (MAC) Protocol Data Unit (MPDU) constantly dwindles, so, make various interFrameGaps and/or lead code keep the constant corresponding reduction that just means channel utilization.For example, high data rate MIMO MPDU is transmitted on the length may have only several microseconds, and by contrast, 802.11 (g) have the lead code of 72 μ s.Eliminate or the reduction delay,, will improve the throughput and the utilance of channel as SIFS, signal extension and/or lead code.

Figure 10 is the exemplary embodiment of TXOP 1010, and it comprises a plurality of continuous transmission frames, and without any the gap.TXOP 1010 comprises N frame 1020A-1020N, and they are (SIFS required among this and the TXOP 810 shown in Figure 8 are compared) of transmission in an orderly manner under without any the situation in gap.The quantity of the frame among this TXOP only is subject to the buffer and the decoding capability of receiver.When STA sends successive frame together with piece ACK in TXOP 1010, needn't intert (intersperse) SIFS duration, this is because there are not other STA need obtain access right to medium between successive frame.Behind N frame, add an optional piece ACK request 1030.The business of some type may not need to confirm.Be right after after TXOP, can make response, perhaps can send after a while a piece ACK request.The expansion of frame 1020 undesired signals.Any embodiment that TXOP 1010 can be used for describing in detail here is as long as wherein need TXOP.

As shown in figure 10, when sending all frames, between the successive frame of TXOP, needn't send SIFS by same STA.In 802.11 (e), these gaps have been reserved, so that the complexity requirement at restriction receiver place.In 802.11 (e) standard, the SIFS period of 10 μ s and the ofdm signal of 6 μ s expand to receiver 16 μ s altogether are provided, and are used to handle the frame of receiving (comprising the demodulation sign indicating number).But if PHY speed is very big, this 16 μ s can lower efficiency significantly.In some embodiments, handle by introducing MIMO, even if 16 μ s also are not enough to finish processing.And in this exemplary embodiment,, do not need SIFS and ofdm signal expansion (using the direct link agreement) from a STA to AP or to the continuous transmission of another STA.Therefore, if a receiver needs the additional period section to be used for processing of MIMO receiver and channel-decoding (for example, turbo/ convolution/LDPC decoding) after the end of transmission, then this receiver can be carried out these functions, simultaneously medium is used to additional transmitted.After a while, can send an affirmation, (for example, use piece ACK) as mentioned above.

Because the different propagation delays between the STA; different STA between transmission can with the protection period separately; the receiver place that is transmitted in continuously from different STA bumps (Figure 10 does not show, but will make further detailed description in the back) on these medium to avoid.In one exemplary embodiment, (4 μ s) all working environment for 802.11 all is enough the protection period of an OFDM symbol.Transmission from same STA to various objectives side STA does not need to separate (as shown in figure 10) with the protection period.Also will further describe below, these protection periods can be called as protection frequency band interFrameGap (GIFS).

Do not use SIFS and/or signal extension, by using ARQ scheme (rollback N or repetition selectively) based on window, the required receiver processing time (for example, being used for MIMO processing and decoding) can be provided, and these technology are known for those skilled in the art.Stop-and-wait (stop-and-wait) the MAC layer ACK of tradition 802.11 has been enhanced to the mechanism of window type in 802.11 (e), reach 1024 frames and piece ACK in this embodiment at most.The ARQ scheme based on window of preferred introducing standard, but not the self-organizing piece ACK scheme of design among 802.11 (e).

The maximized window that is allowed depends on receiver processing complexity and buffering.Transmitter can according to transmitter-receiver between accessible peak value PHY speed, send enough data and fill up receiver window.For example,, receiver possibly can't get caught up in PHY speed, so receiver may need to store the output of soft (soft) decoder, till they can be decoded because handling.Therefore, the buffer requirement of physical layer process can be used to determine the maximum window that allows during peak value PHY speed.

In one exemplary embodiment, receiver can be announced it and can the maximum with a specific PHY rate processing allow PHY piece size under the situation that its physical layer buffer is overflowed.Perhaps, receiver also can be announced it and can the maximum with maximum PHY rate processing allow PHY piece size under the situation that its physical layer buffer is overflowed.When PHY speed is low, can under the situation that does not have buffer to overflow, handle long piece size.The maximum of announcing during according to maximum PHY speed allows PHY piece size, and the maximum that transmitter can use known formula to calculate for specific PHY speed allows PHY piece size.

If the maximum PHY piece size of announcement is a static parameter, then in that can to handle physical layer buffer and the receiver time quantum before being ready to receive next PHY burst be known at the transmitter place for another and also be known receiver parameters at the scheduler place.Perhaps, according to the situation that takies of physical layer buffer, the maximum PHY piece size of being announced can dynamically change.

The receiver processing delay can be used to determine that ARQ come and go (round-trip) postpones, and the latter can be used to determine the observed delay of application program.Therefore, in order to support the low delay service, can limit the PHY piece size of permission.

Figure 11 has provided the exemplary embodiment of TXOP 1110, is used to the preamble transmissions amount that illustrates that reduction is required.TXOP 1110 comprises lead code 1120, and that follow later is N transmission 1130A-1130N continuously.Can add an optional piece ACK request 1140.In this embodiment, transmission 1130 comprises a header and a grouping.TXOP 1110 is compared with the TXOP 790 of Fig. 7, and each frame 740 also comprises a lead code among the latter except that header and grouping.For the transmission data of same amount, by sending single lead code, required preamble transmissions only is a lead code, rather than N lead code.

Therefore, lead code 1120 can be excluded from continuous transmission.Receiver can use initial preamble 1120 to obtain signal and obtain with the fine frequency that is used for OFDM.For the MIMO transmission, to compare with current OFDM lead code, initial preamble 1120 can be expanded, so that receiver can the estimation space channel.But the subsequent frame in the same TXOP can not need the lead code of adding.Pilot tone in the OFDM symbol is enough to carry out signal trace usually.In an alternative embodiment, additional (being similar to lead code) symbol can interlock on TXOP 1110 intercycle ground.But, can obviously reduce total lead code expense.Can only just send lead code where necessary, and can differently send lead code based on the time quantum of since the last lead code that sends, having passed.

Should be noted in the discussion above that TXOP 1110 also can combine with the function of legacy system.For example, piece ACK is optional.Also can support more frequent ACK.Even so, less clearance as GIFS, can be replaced long SIFS and (add signal extension, if you are using).Continuous transmission 1130 can also comprise a plurality of sections of bigger grouping, as mentioned above.The header that should also be noted that the continuous transmission 1130 of mailing to same recipient STA can be carried out compression.Also will describe an example of header compression below in detail.

Figure 12 has provided an exemplary embodiment of method 1200, and it is combined with above-mentioned each side, comprises merging lead code, remove the gap such as SIFS and inserting GIFS as required.This flow process starts from frame 1210, wherein, uses any technology of describing in detail here, and a STA has won a TXOP.In frame 1220, as required, send a lead code.Equally, traditional lead code can is longer than or be shorter than to this lead code, and can change according to various parameters (for example, the time that has passed since last transmission lead code), so that recipient STA can estimate the MIMO space channel.In frame 1230, STA sends one or more groupings (perhaps, more generally, the continuous transmission of any kind) to purpose side.Should be noted in the discussion above that does not need to send additional lead code.In an alternative embodiment also can send one or more additional lead codes alternatively, perhaps, as required, can intert the symbol of similar lead code.In frame 1240, STA can send signal to an additional recipient STA alternatively.In this case, insert GIFS as required, and, one or more continuous transmission can be sent to additional recipient STA.Then, this flow process can finish.In various embodiments, STA can continue to send signal to plural STA, inserts required GIFS and/or the lead code of estimated performance grade.

Therefore, as mentioned above,, can further improve MAC efficient, much or all protect the period and reduce the lead code expense thereby save by the transmission from a STA to a plurality of purpose side STA is merged into continuous transmission.For a plurality of continuous transmission, can use single lead code (perhaps, pilot transmission) from same STA to various objectives side STA.

Merge by poll, can obtain extra efficient.In one exemplary embodiment, several polls can be merged in the control channel, will describe its example in detail below.In an example, AP can send signal to a plurality of purpose side STA, comprising the polling message that is used for distribution T XOP.By contrast, in 802.11 (e), have before each TXOP from the CF-Poll of AP and the SIFS that follows.When several such CF-Poll message being merged into single control channel message (in the exemplary embodiment that is discussed in more detail below, being referred to as SCHED message) when being used for distributing several TXOP, can raise the efficiency.In a common embodiment, any time section can be distributed to poll and the corresponding TXOP thereof after the merging.Describe an exemplary embodiment below in conjunction with Figure 15, and this paper also comprises other examples.

In order further to raise the efficiency, can encode to control channel (being SCHED) message with the speed structure of layering.Correspondingly, the polling message that mails to any STA can be encoded according to the channel quality between AP and the STA.The order of transmission of polling message needs not to be the order of the distribution T XOP of institute, but can be ranked according to the coding robustness.

Figure 13 has provided an exemplary physical layer (PHY) span line 1300, is used to illustrate the poll and the corresponding TXOP thereof of merging.The poll 1310 that merges is sent out away.Can use the control channel structure of describing its example here in detail, perhaps can use to it will be apparent to those skilled in the art that various other technologies, send these polls.In this embodiment, in order need between poll and any forward link TXOP, not use interFrameGap, directly send forward link TXOP 1320 in poll 1310 backs that merge.After forward link TXOP1320, send various reverse link TXOP 1330A-1330N, wherein can insert GIFS 1340 as required.Should be noted in the discussion above that when when a STA transmits in order, needn't comprise GIFS (be similar to for the forward link transmissions that sends to different STA from AP, do not need GIFS).In this embodiment, reverse link TXOP comprises the TXOP (for example, use DLP) of STA to STA (that is point-to-point).Order of transmission shown in should be noted in the discussion above that is illustrative.Forward direction and reverse link TXOP (comprising the point-to-point transmission) can exchange, and perhaps, intert mutually.The number of gaps that some configuration is eliminated may be different from the number of gaps that other configurations are eliminated.By the enlightenment here, those skilled in the art can revise out multiple interchangeable embodiment at an easy rate.

Figure 14 shows an exemplary embodiment of the method 1400 that is used to merge poll.Flow process starts from frame 1410, wherein, with channel resource allocation in one or more TXOP.Can use any scheduling feature, make this TXOP and distribute definite.In frame 1420, coming the poll of distribution T XOP to merge according to this assignment information.In frame 1430,, the poll of this merging is sent to one or more STA (that is, in the exemplary embodiment that is discussed in more detail below, the CTRLJ section of SCHED message) by one or more control channels.In an alternative embodiment can use any message delivery techniques to send the poll of merging.In frame 1440, STA distributes according to the poll in the poll of this merging and sends TXOP.Then, this flow process can finish.This method can be used in conjunction with the polling interval of the merging of any length, and the poll of the merging of described any length can comprise all or part of of system's beacon interval.As mentioned above, the poll of merging can be used for off and on based on the access of competition or traditional poll.In one exemplary embodiment, can periodically or according to other parameters repeat method 1400, described other parameters such as system load or transfer of data requirement.

Below in conjunction with Figure 15 and 16, describe an exemplary embodiment of MAC agreement in detail, with the explanation various aspects.In the U.S. Patent Application Publication No. of submitting to simultaneously with the application common co-pending 20050135416 " Wireless Lan Protocol Stack " (file number is 030428), publication number is 20050135403 " Method; Apparatus; and system for MediumAccess Control " (file number is 030433), publication number is this MAC agreement to be described in further detail, these three pieces of assignees that application has transferred the application in 20050135291 " Method; Apparatus; and system for Multiplexing Protocol Data Units " (file number is 030436).

An exemplary TDD mac frame interval 1500 has been shown among Figure 15.Term " the TDD mac frame at interval " used in this occasion refers to a period of time, wherein, has defined the various span lines of describing in detail below.The TDD mac frame 1500 is different from the term " frame " of general use at interval, so that describe the transmission in 802.11 systems.In 802.11 terms, TDD mac frame interval 1500 is similar to the sub-fraction of beacon interval or beacon interval.In conjunction with Figure 15 and 16 parameters of describing in detail only is illustrative.Some or all of the use parts of describing and various parameter value, those of ordinary skills can make this example be adapted to multiple other embodiment at an easy rate.MAC function 1500 is distributed between following transmission channel section: broadcasting, control, forward direction and reverse traffic (being called as downlink phase and uplink phase respectively) and access at random.

In this exemplary embodiment, TDD mac frame interval 1500 is time division duplex (TDD) in 2 milliseconds the time interval, is divided into five transmission channel section 1510-1550, as shown in the figure.In the embodiment that replaces, can use other order and different frame sizes.Duration distribution on the TDDMAC frame period 1500 can be quantized into a certain mini-bus time interval.

TDD mac frame 1500 these interior five exemplary transmission channels at interval comprises: (a) broadcast channel (BCH) 1510, and it transmits Broadcast Control Channel (BCCH); (b) control channel (CCH) 1520, it transmits frame control channel (FCCH) on the forward link and inserts feedback channel (RFCH) at random; (c) Traffic Channel (TCH), it transmits user data and control information, and further is subdivided into forward traffic channel (F-TCH) 1530 and the (ii) reverse traffic channel (R-TCH) 1540 on the reverse link on (i) forward link; (d) Random Access Channel (RCH) 1550, it transmits and inserts request channel (ARCH) (be used for UT and insert request).Pilot beacon also is to send in section 1510.

The downlink phase section of the comprising 1510-1530 of frame 1500.The uplink phase section of comprising 1540-1550.Section 1560 next TDD mac frame of expression beginnings at interval.Further describe the embodiment of a replacement that comprises the point-to-point transmission below.

Broadcast channel (BCH) and beacon 1510 are sent by AP.The first of BCH 1510 comprises the common physical layer expense, as pilot signal, comprises that sequential and frequency obtain pilot tone.In an exemplary embodiment, beacon comprises by UT and is used for 2 short OFDM symbols that frequency and sequential are obtained, and the back is 8 short OFDM symbols that are used to estimate the public MIMO pilot tone of channel by UT.

The second portion of BCH 1510 is a data division.The BCH data division has defined the distribution condition with respect to transmission channel section CCH 1520, F-TCH 1530, R-TCH 1540 and RCH 1550, TDDMAC frame period, also defines the combination with respect to subchannel, CCH.In this embodiment, BCH 1510 has defined the coverage of WLAN 120, so sent under the most healthy and the strongest available data-transmission mode.The length of whole BCH is fixed.In an exemplary embodiment, BCH has defined the coverage of MIMO-WLAN, and uses the binary phase shift keying (BPSK) of 1/4 rate coding to send under space-time emission diversity (STTD) pattern.In this embodiment, the length of BCH is fixed as 10 short OFDM symbols.In the embodiment that replaces, can use various other signaling technologys.

The control channel (CCH) 1520 that is sent by AP has defined the combination of TDD mac frame remainder at interval, and shows the poll that how to use merging.CCH 1520 usefulness very robust transmission pattern send in a plurality of subchannels, and each subchannel has different data rates.First subchannel is the most healthy and the strongest, and expection can be decoded by all UT.In an exemplary embodiment, the BPSK of 1/4 rate coding is used for a CCH subchannel.Also provide other robustnesss to reduce the subchannel of (efficient rising).In one exemplary embodiment, use maximum three additional subchannels.Each UT attempts all subchannels are decoded in order, till the decoding failure.CCH transmission channel section in each frame has length variable, and this length depends on the quantity of CCH message in each subchannel.For reverse link at random the affirmation information of access burst be on the most healthy and the strongest (first) subchannel of CCH, to transmit.

CCH is included in physical layer bursts assignment information on forward direction and the reverse link (being similar to the poll for the merging of TXOP).Distribute and be used in forward direction or reverse link transmitting data.Usually, the physical layer bursts distribution comprises: (a) MAC ID; (b) value of an interior time started (in F-TCH or R-TCH) of distributing of this frame of expression; (c) length of Fen Peiing; (d) length of special-purpose physical layer overhead; (e) transmission mode; (f) be used for the coding and the modulation scheme of physical layer bursts.

The assignment information of last other exemplary types of CCH comprises: the assignment information on the reverse link is used to transmit the dedicated pilot from UT; Assignment information on the reverse link is used to transmit buffer and link-state information from UT.CCH can also define the reservation unused portion of frame.These unused portions of this frame can be used for carrying out noise floor (and interference) by UT to be estimated, and measures the adjacent system beacon.

Random Access Channel (RCH) the 1550th, reverse chain channel, UT can send access burst at random by it.For each frame, in BCH, specify the variable-length of RCH.

Forward traffic channel (F-TCH) 1530 comprises one or more physical layer bursts that send from AP 104.A specific MAC ID who indicates is all pointed in each burst in the CCH assignment information.Each burst comprises special-purpose physical layer overhead, for example, and the pilot signal (if any) and the MAC PDU that send according to the transmission mode of indicating in the CCH assignment information and coding and modulation scheme.F-TCH has length variable.In an exemplary embodiment, special-purpose physical layer overhead can comprise the MIMO pilot tone of a special use.Figure 16 has provided an exemplary MAC PDU in detail.

Reverse traffic channel (R-TCH) 1540 comprises the physical layer bursts transmission from one or more UT 106.Each burst is to be sent by one that indicates in the CCH assignment information specific UT.Each burst can comprise a dedicated pilot lead code (if any) and MAC PDU who sends according to the transmission mode of indicating in the CCH assignment information and coding and modulation scheme.R-TCH has length variable.

In this exemplary embodiment, F-TCH 1530, R-TCH 1540 or the two, can usage space transmit multiplexing or CDMA (Code Division Multiple Access) realizes with different UT are associated MAC PDU the time, comprise the MAC ID that is associated with MAC PDU (promptly, transmit leg on the up link, or the expection recipient on the down link) a field can be included in the MACPDU header.All addressing uncertain problems that this can may occur when solving the multiplexing or CDMA of usage space.In the embodiment that replaces, when multiplexing during strictly based on time division technique, do not need MAC ID in the MAC PDU header, because addressing information is included in the CCH message, CCH message has been given a concrete MAC ID with the special time period allocated in the TDD mac frame interval.Can adopt the combination of spatial reuse, code division multiplexing, time division multiplexing and any other technology known in the art.

Figure 16 shows the exemplary MAC PDU 1660 from a grouping 1610, and in this embodiment, grouping 1610 can be IP datagram or ethernet segment.Exemplary field type and size have been described in diagram.One skilled in the art will recognize that in protection scope of the present invention various other sizes, type and configuration also can be imagined and obtain.

As shown in the figure, segmentation is carried out in packet 1610 in adaptation layer.One of in each these section 1620 of self adaptation sublayer PDU 1630 carryings.In this embodiment, packet 1610 is divided into N section 1620A-N.Self adaptation sublayer PDU 1630 comprises payload 1634, and payload 1634 comprises corresponding section 1620.Type field 1632 (being a byte in this embodiment) is affixed among the self adaptation sublayer PDU 1630.

Logical links (LL) header 1642 (being 4 bytes in this embodiment) is added in the payload 1644, and payload 1644 comprises adaptation layer PDU 1630.The exemplary information of LL header 1642 comprises flow identifier, control information and sequence number.Calculate CRC 1646 at header 1642 and payload 1644, and this CRC1646 of affix is to form logical links sublayer PDU (LL PDU) 1640.Logic link control (LLC) and Radio Link control (RLC) PDU can form by similar fashion.LL PDU 1640 and LLC PDU and RLC PDU are placed on (for example, high QoS formation, best effort formation or control messages formation) in the formation, with the service that is used for being provided by the MUX function.

MUX header 1652 is affixed on each LL PDU 1640.An exemplary MUX header 1652 can comprise length and type (in this embodiment, header 1652 is two bytes).For each control PDU (that is, LLC and RLC PDU), can form similar header.LL PDU 1640 (or LLC or RLC PDU) constitutes payload 1654.Header 1652 and payload 1654 constitute MUX sublayer PDU (MPDU) 1650 (MUX sublayer PDU is also referred to as MUX PDU here).

In this embodiment, the communication resource on the shared medium is distributed in a series of TDDMAC frame periods by the MAC agreement.To describe in detail below in the alternative embodiment of its example, the TDD mac frame of these types at interval can be by interspersed various other MAC functions, comprise based on compete or poll, and comprise that the access protocol and the legacy system that use other types carry out alternately.As mentioned above, scheduler can determine to distribute to the size (being similar to the TXOP of the poll of merging) of the physical layer bursts of one or more MAC ID in each TDD mac frame interval.Should be noted in the discussion above that not to be that each MAC ID that has data to send can both be assigned to the interior at interval space of any specific T DD mac frame.In protection scope of the present invention, can use any access control or scheduling scheme.When carrying out the branch timing at MAC ID, the corresponding MUX function of this MAC ID will constitute MAC PDU 1660, and it comprises one or more MUX PDU 1650, so that be included in this TDD mac frame interval.One or more MUX PDU 1660 at one or more MAC ID that distributed will be included in a TDD mac frame interior at interval (that is, TDD mac frame interval 1500 is described in detail in conjunction with Figure 15 above).

In one exemplary embodiment, an aspect makes it possible to send a part MPDU1650, thereby realizes efficient packing in MAC PDU 1660.In this embodiment, all part MPDU 1650 remaining byte that do not send in preceding once transmission can be included, and by part MPDU 1664 signs.In present frame, these bytes 1664 will send before at all new PDU 1666 (that is, LL PDU or control PDU).Header 1662 (being 2 bytes in this embodiment) comprises the MUX pointer, and it points to the beginning of first new MPDU (being MPDU 1666A in this embodiment) that will send in the present frame.Header 1662 also comprises MAC Address.

MAC PDU 1660 comprises MUX pointer 1662, begins to locate possible part MUXPDU 1664 (remaining after preceding primary distribution), the back is zero or an a plurality of complete MUX PDU 1666A-N and a possible part MUX PDU 1668 (from current primary distribution), or other filling informations, be used to fill up the distribution portion of physical layer bursts.MAC PDU 1660 is carried in the physical layer bursts of distributing to this MAC ID.

Therefore, this exemplary MAC PDU 1660 shows a transmission (perhaps, being frame by 802.11 terms), and it can send to another STA from a STA, comprises the data division from the one or more streams that point to this purpose side STA.By using part MUX PDU alternatively, can realize efficient packing.The time of indicating in the poll of the merging that comprises in CCH, each MAC PDU can send in a TXOP (using 802.11 terms).

The exemplary embodiment of describing in detail among Figure 15 and 16 has been listed various aspects, comprise by from each STA (comprising AP) thus sending physical layer bursts in an orderly manner merges poll, reduces preamble transmissions and eliminates the gap.These aspects also are applicable to any MAC agreement, comprise 802.11 systems.Further provide the embodiment of replacement below, other various technology are described, these technology can realize the high efficiency of MAC, and support the point-to-point transmission, and can existing legacy protocol or system combine and/or cooperate.

As mentioned above, the various embodiment that describe in detail here can adopt channel estimating and strict rate controlled.By the unnecessary transmission on the medium is minimized, the MAC efficient that can obtain to improve, still, in some cases, inadequate rate controlled feedback will reduce overall throughput.Therefore, for channel estimating and feedback, can provide enough chances, so that the maximization of the transmission rate under all MIMO patterns, thereby prevent that inadequate channel estimating can be offset any MAC efficient to be increased because the throughput that insufficient channel estimating caused reduces.Therefore, MAC embodiment that can design example so that enough preamble transmissions chances to be provided, and allows receiver have an opportunity to provide the rate controlled feedback to transmitter, above this is introduced, and also will further describe below.

In an example, AP is periodically interspersed MIMO pilot tone (every at least TP millisecond, wherein, TP can be fixing or variable parameter) in its transmission.Each STA can begin the TXOP that it is subjected to poll with a MIMO pilot tone, and this MIMO pilot tone can be used for estimating channel by other STA and AP.For the transmission of using direct link agreement (below will further describe) to AP or another STA, the MIMO pilot tone can be a guiding reference signal (steeredreference), so that the receiver that helps to simplify among the purpose side STA is handled.

AP also can offer an opportunity to purpose side STA, so that allow it that ACK is provided feedback.Purpose side STA also can use these feedback chances, and the rate controlled feedback of available MIMO pattern is provided to transmit leg STA.Such rate controlled feedback is not defined in tradition 802.11 systems that comprise 802.11 (e).Introduce the total amount (at every kind of MIMO pattern) that MIMO can improve rate control information.In some cases, for will be at improved maximum effect aspect the MAC efficient, these can replenish by the rate controlled feedback of strictness.

Here by the agency of and what below will further describe is deposit (backlog) information and the scheduling of STA on the other hand.Each STA can begin its TXOP with a lead code, and the request duration of next TXOP is followed in this lead code back.This information purpose guiding AP.AP collects next request TXOP for information about from a plurality of different STA, and determines for next TDD mac frame at interval TXOP duration distribution condition in the media.AP can use different priority or QoS rule, determines how to share these medium, and perhaps it can use very simple rule to come according to share these medium from the request of STA proportionally.Can also adopt any other dispatching technique.TXOP distribution at interval is what to be assigned in the back control channel message from AP for next TDD mac frame.

The access point of appointment

Here among the embodiment of Xiang Shuing, network can be supported real access point or not have operation under the situation of real access point.When having real AP, for example, it can be connected to wired extra heavy pipe road and connect (that is, cable, optical fiber, DSL or T1/T3, Ethernet) or home entertainment server.In this case, this real AP can be the information source and the stay of two nights of most of data that equipment room flows in the network.

When not having real AP, a plurality of stations still can be used as enhanced distributed channel access of aforesaid distributed coordination function (DCF) or 802.11b/g/a or 802.11e etc. and be communicated mutually.What also will further describe below is, when the needs additional resource, adopts centralized scheduling scheme, can use medium more efficiently.For example, this network architecture may occur in the family, and wherein a lot of distinct devices (that is, DVD-TV, CD-Amp-Speaker etc.) need communicate mutually.In this case, these network stations specify a station to serve as AP automatically.Should be noted in the discussion above that as described belowly, self adaptation coordination function (ACF) can be used by the access point by appointment, and can be at centralized scheduling, insert at random, adopt under the situation of self-organizing communication or its combination in any.

Some non-AP equipment but not every non-AP equipment has the MAC ability of enhancing is so be suitable for as the AP of appointment and work.Should be noted in the discussion above that not all equipment all needs to be designed to have the AP MAC ability of appointment.When QoS (for example, secure time-delay), high-throughput and/when efficient was very important, an equipment in the network must be able to be supported the operation of the AP of appointment.

This means that the ability of the AP of appointment is associated with the equipment that possesses high ability usually, for example, has one or more attributes, as line power (line power), a large amount of antenna and/or transmit or high-throughput requirement.(additive factor of the AP that is used to select appointment below will be described in further detail).Therefore, low side devices as low side camera or phone, do not need to possess the ability of the AP of appointment, and high-end equipment as high-end video source or high definition video display, can possess the ability of the AP of appointment.

In not having the network of AP, the AP of appointment is bringing into play the effect of real AP, and can or can not have still less functional.In various embodiments, the AP of appointment can carry out following function: (a) establish network set of basic (BSS) ID; (b) by sending beacon and broadcast channel (BCH) network configuration information (BCH can define the media combination before next BCH), the network sequential is set; (c) use forward control channel (FCCH),, connect thereby manage by the transmission at the station in the network is dispatched; (d) management related (association); (e) for providing, QoS stream admits control; And/or (f) various other functions.The AP of appointment can realize complicated scheduler, the perhaps dispatching algorithm of any kind.Can adopt simple scheduler, its example is described in further detail below.

Below in conjunction with point to point link, describe improved physical layer convergence protocol (plcp) header in detail, this also is applicable to the AP of appointment.In one embodiment, the PLCP header of all transmission sends with the master data speed that can be stood by all (AP that comprises appointment) decodes.The data reserve that comprises the place, station that is associated with certain priority or stream from the PLCP header of the transmission at a plurality of stations.Perhaps, it comprises a duration request for a back transmission opportunity of certain priority or stream.

By " spying upon (snooping) " in the PLCP header of all station transmission, the AP of appointment can determine by the deposit of these station requests or transmission opportunity duration.Based on load, conflict or other congested indexs, the AP of appointment can determine portion of time is distributed to (distributed access) based on EDCA, portion of time is distributed to uncompetitive poll (centralized) insert.The AP of appointment can move a basic scheduler, and it distributes and the proportional bandwidth of request, and in uncontended periods it is dispatched.The scheduler that strengthens also is fine, but is not necessary.The transmission of process scheduling is by specifying AP at the enterprising announcement that works of CCH (control channel).

The AP of appointment does not need another station (that is, serving as springboard) is arrived in the transmission loopback (echo) at a station, but this function is also permitted.Real AP can possess loop-back capabilities.

When selecting the access point of appointment, can create a kind of hierarchical system, determine which equipment should serve as access point.Admissible example factors comprises following when selecting the access point of appointment: (a) user's configuration (over-ride); (b) higher preference grade; (c) safe class; (d) ability: line power; (e) ability: antenna amount; (f) ability: maximum transmission power; (g) based on the additional consideration (break a tie) of other factors: medium access control (MAC) address; (h) equipment of first start; (i) any other factor.

In fact, the AP of appointment preferably is positioned at the center, and has best total Rx signal to noise ratio cumulative distribution function (SNR CDF) (that is, can receive all stations under the situation of good SNR).Usually, the antenna that station has is many more, and receiving sensitivity is just good more.In addition, the AP of appointment can have higher transmitting power, thereby makes the AP of this appointment to be listened to by a large amount of stations.When adding the station and/or stand when mobile, can assess these attributes, and utilize them, so that network can dynamically reconfigure.

If network configuration has the AP of a real AP or an appointment, then can support point-to-point to connect.Next joint will be described point-to-point in detail and connect.In one embodiment, can support two types point-to-point to connect: (a) managed point-to-point connects, and wherein, AP dispatches the transmission that each station participated in; (b) connection of self-organizing, wherein, AP do not participate in the standing management or the scheduling of transmission.

The AP of appointment can set mac frame at interval, and sends a beacon when frame begins.Broadcasting and control channel can be specified the duration of having distributed in the frame that allows the station send.Asked the station (for AP, these requests are known) that transmission distributes concerning point-to-point for those, AP can provide the dispensing section that has passed through scheduling.AP can announce these dispensing sections in control channel, for example, and in each mac frame.

Alternatively, AP can also be included in A-TCH (self-organizing) section in this mac frame (below will be elaborated to this).Whether exist A-TCH to indicate in the mac frame at BCH and FCCH kind.In A-TCH, stand and to use the CSMA/CA process to carry out point to point link.Can revise the CSMA/CA process of IEEE WLAN standard 802.11, to get rid of the requirement of ACK at once.Rob when accounting for channel when a station, this station can send a MAC-PDU (protocol Data Unit), and it comprises a plurality of LLC-PDU.One stands in the maximum duration that can take among the A-TCH and provides in BCH.For LLC, can window size and maximum affirmation be postponed to hold consultation according to required application delay through confirming.Describe improved mac frame in detail below in conjunction with Figure 20, it has the A-TCH section, can be used for the real AP and the AP of appointment.

In one embodiment, non-guiding (unsteered) MIMO pilot tone can make all stations understand they self and dispatching station between channel.In some cases, this is useful.In addition, the AP of appointment can use non-guiding MIMO pilot tone, to carry out channel estimating and to be convenient to carry out the demodulation of PCCH, can therefrom derive distribution then.In case the AP of appointment receives all requested distribution in the frame of a special MAC, then it can be dispatched them at follow-up mac frame.Should be noted in the discussion above that rate control information needn't be included among the FCCH.

In one embodiment, scheduler can be carried out following operation: at first, for next mac frame, scheduler is collected all requested dispensing sections, and calculates total dispensing section (Total Requested) that is requested.The second, scheduler calculates the total available resources (Total Available) that can distribute to F-TCH and R-TCH.The 3rd, if Total Requested, then uses the ratio of being determined by Total Available/Total Requested greater than TotalAvailable, all requested dispensing sections are carried out convergent-divergent.The 4th, for less than dispensing section behind any convergent-divergent of 12 OFDM symbols, these dispensing sections are increased to 12 OFDM symbols (like this in this exemplary embodiment, but the embodiment that replaces can use different parameters).The 5th, in order to hold the dispensing section of gained in F-TCH+R-TCH, by reducing all dispensing sections greater than 12 OFDM symbols in a looping fashion, from maximum, next symbol can hold any extra OFDM symbol and/or guard time.

An example can illustrate the foregoing description.Consider following request for allocation: 20,40,12,48.So, Total Requested=120.Suppose Total Available=90.Suppose that more required guard time is 0.2 OFDM symbol.Therefore, as described in the 3rd top operation, the dispensing section behind the convergent-divergent is: 15,30,9,36.As described in the 4th top operation, dispensing section 9 is increased to 12.According to the 5th operation, with amended dispensing section and guard time addition, the total allocation section is 93.8.This means that dispensing section will reduce by 4 symbols.From maximum, once remove a symbol, thereby determine that final dispensing section is 14,29,12,34.(that is, 89 symbols and be used for 0.8 symbol of guard time) altogether

In one exemplary embodiment, when having appointment AP, it can be set up the beacon of BSS and the network sequential is set.A plurality of equipment are associated with the AP of this appointment.When needing a QoS to be connected with two equipment of specifying AP to be associated, for example, have the HDTV link of low delay and high-throughput requirement, so, they provide operational indicator to this appointment AP, so that admit control.This appointment AP can admit or refuse this connection request.

If the medium utilance is enough low, then can use CSMA/CA, reserve the whole duration of medium between beacon, be used for the EDCA operation.If EDCA operation operation is smooth and easy, for example, do not have excessive conflict, keep out of the way and postpone, then this appointment AP needn't provide coordination function.

The AP of appointment can continue to monitor the medium utilance by the PLCP header of monitoring station transmission.According to observation to medium, and storage level or the request of transmission opportunity duration, specify AP can determine when the satisfied required QoS that permits stream of EDCA operation.For example, it can observation station the storage level of report and the trend of duration of being asked, and, itself and desired value are compared based on the stream of permitting.

When the AP of appointment determined not satisfy required QoS under distributed access situation, it can convert the operation on the medium to the operation with poll and scheduling.The latter provides and has more deterministic time-delay and higher throughput efficiency.To describe the example of this operation below in detail.

Therefore, from the transmission opportunity request of dispatching station with will ask to carry out comparison, can convert scheduling (centralized) operation adaptively to by observation medium utilance, conflict, congested and observation from EDCA (distributed access mechanism) with allowance QoS stream.

As previously mentioned, described therein among any embodiment that the application of access point describes in detail, it will be appreciated by those skilled in the art that this embodiment can adapt to and real access point arranged or specifying under the situation of access point and work.Just as what describe in detail, can adopt and/or select one to specify access point here, this appointment access point can be according to any agreement work, comprises the agreement do not mentioned among the application or any combination of various protocols.

Point-to-point transmission and direct link agreement (DLP)

As mentioned above, point-to-point (or abbreviate as " point-point ") transmission makes a STA directly send data to another STA, and needn't send the data to AP earlier.Here the various aspects of Xiang Ximiaoshuing can be used to the point-to-point transmission.In one embodiment, can revise direct link agreement (DLP), as described below.Figure 17 shows an exemplary point to point link in the system 100.System 100 in this example is similar to system shown in Figure 1 100, and it is through revising, and can realize the direct transmission (in this embodiment, show between UT 106A and the UT 106B transmission 1710) from a UT to another UT.UT 106 can pass through WLAN 120, directly communicates with AP 104, will be described in greater detail here.

In various exemplary embodiments, can support a point-connection of two types: (a) managed point-connection, wherein, AP dispatches the transmission that each STA participates in; (b) point of a self-organizing-connection, wherein, AP does not participate in the management or the scheduling of STA transmission.Embodiment can comprise a kind of of these two kinds of connections or the two.In one exemplary embodiment, the signal that sends can comprise: a part, and it comprises the public information that can be received by one or more stations (also may comprise access point); And, carried out format specially so that by information that point-receiving station receives.Public information can be used for scheduling and (for example, as shown in figure 25), perhaps is used for competition by various neighbours station and keeps out of the way (for example, as shown in figure 26).

The various exemplary embodiments of describing in detail below introduce a little-the closed loop rate control of a connection.Can adopt this rate controlled, make full use of available high data rate.

For ease of explanation, do not describe various functions (that is, confirming) in the exemplary embodiment in detail.It will be recognized by those skilled in the art that function disclosed herein can combine, thereby in different embodiment, form the set or the subclass of any amount.

Figure 18 shows the physical layer bursts 1800 of prior art.Can send lead code 1810 earlier, the back is a physical layer convergence protocol (plcp) header 1820 and then.802.11 traditional system definitions a kind of PLCP header, comprise speed type and modulation format, be used for as data symbol 1830 and the data of transmission.

Figure 19 has provided an exemplary physical layer bursts 1900, and it can be used for a little-transmission.As Figure 18, lead code 1810 and PLCP header 1820 are includable, and what follow later is a point-transmission that is marked as P2P 1940.P2P 1940 can comprise the MIMO pilot tone of being used by recipient UT 1910.MIMO Rate Feedback 1920 is also includable, so that used in the transmission in future that sends back to transmit leg UT by recipient UT.Rate Feedback can generate in response to last transmission from the receiving station to the dispatching station.Then, data symbol 1930 can send according to the selected rates and the modulation format of a point-connection.Should be noted in the discussion above that physical layer bursts,, can be used for a point-connection of AP management as PHY burst 1900, and the point of a self-organizing-transmission.The Rate Feedback embodiment of following detailed description exemplary.The embodiment that also comprises the replacement of the physical layer transmission burst that comprises these aspects below.

In an exemplary embodiment, AP sets the TDD mac frame at interval.Can use broadcasting and control channel to indicate the duration of having distributed in the TDD mac frame interval.For having asked a point-STA (is known for AP) that transmission distributes, AP can provide the distribution through scheduling, and announces them in each TDD mac frame interval in control channel.Top Figure 15 has provided an exemplary system.

Figure 20 shows a TDD mac frame exemplary embodiment of 2000 at interval, and it comprises an optional self-organizing section, is identified as A-TCH 2010.Can comprise and the identical part of top numbering described in conjunction with Figure 15 in the TDD mac frame interval 2000.Can indicate among BCH1510 and/or the CCH 1520 in the TDD mac frame interval 2000 and whether have A-TCH 2010.During A-TCH 2010, STA can use any competition process to carry out point to point link.For example, can use 802.11 technology, as the SIFS, the DIFS that describe in detail above, back off time etc.Also can use the QoS technology, as those (that is AIFS) technology, of introducing among 802.11 (e).Can also use various other schemes based on competition.

In one exemplary embodiment, the CSMA/CA process that is used to compete for example, has been carried out the process of definition in 802.11, can carry out following modification.Do not need ACK at once.When robbing when accounting for channel, a STA can send and comprise that a plurality of PDU are (that is, LLC-PDU) at interior Medium Access Control (MAC) Protocol Data Unit (MAC-PDU).Can indicate STA shared maximum duration in A-TCH among the BCH.When hope during through the transmission confirmed, can be according to required application delay, consult window size and maximumly confirm to postpone.

In this embodiment, F-TCH 1530 is TDD mac frame parts at interval, is used for the transmission from AP to STA.In A-TCH 2010, can carry out the point to point link of the use competition technology between the STA.In R-TCH 1540, can carry out the point to point link of the scheduling between the STA.In these three sections any one can be made as sky.

Figure 21 has provided an exemplary physical layer bursts 2100, is also referred to as " PHY burst ".PHY 2100 point that the can be used for dispatching-connection that happen suddenly for example during R-TCH 1540, or during the self-organizing such as A-TCH 2010 connects, are described in detail this in conjunction with Figure 20 above.PHY burst 2100 comprises non-guiding MIMO pilot tone 2110, reciprocity Common Control Channel (PCCH) 2120 and one or more data symbol 2130.Non-guiding MIMO pilot tone 2110 can receive at place, one or more stations, and, can be by receiving station with the respective channel of estimating between dispatching station and the receiving station for referencial use.This exemplary PCCH comprises following field: (a) purpose side MAC-ID; (b) for next TDD mac frame request for allocation of transmitting continuous time of expection at interval; (c) transmission rate designator is used to indicate current data transmission packets form; (d) (that is, CCH) subchannel is used to receive any distribution from AP to control channel; And (e) CRC.PCCH 2120 and non-guiding MIMO pilot tone 2110 are common segment, so can be received by various monitoring stations (comprising access point).Can in PCCH, insert request for allocation, so that in the TDD in future mac frame interval, realize a managed point-connection.Such PHY burst can be included in the self-organizing connection, and, still can ask the point-to-point of the scheduling in following TDD mac frame interval to connect.In this exemplary embodiment, non-guiding MIMO pilot tone is 8 OFDM symbols (among the embodiment of Ti Huaning, less symbol just is enough to realize channel estimating in the following detailed description of), and PCCH is two OFDM symbols.In common segment (comprising non-guiding MIMO pilot tone 2110 and PCCH2120) afterwards, use spatial reuse and/or the higher modulation form determined by each STA in the point-connection, send one or more data symbols 2130.The rate control information that embeds in the data division of this part of transmission according to transmission is encoded.Therefore, the part of PHY burst 2100 can be received by a plurality of peripheries station, and actual data have been passed through special finishing, so that high efficiency of transmission is to the station or the AP of one or more specific point-connection.Data 2130 can as access point distributed send or, connect according to self-organizing and to send (that is, based on the CSMA/CA process of competition).

An exemplary embodiment of PHY burst comprises a lead code, and this lead code is made of 8 OFDM symbols of non-guiding MIMO reference.Equity Common Control Channel (PCCH) MAC-PDU header is included in 2 follow-up OFDM symbols, has used the STTD pattern, encodes with R=1/2BPSK.MAC-ID is 12 bits.The request for allocation that also comprises one 8 bit is so that by receiving (therefore, largest request is 256 short OFDM symbols) in the expected duration of AP in next TDD mac frame interval.TX speed is 16 bits, is used for the speed of indicating current group to use.FCCH subchannel preference is two bits, and corresponding to the preference of maximum four sub-interchannels, based on this, AP makes any suitable distribution.CRC is 10 bits.Any amount of other fields and/or field size can be included among the PHY burst embodiment of replacement.

In this embodiment, the spatial reuse determined by each STA in the point-connection and the modulation of Geng Gao are used in remaining MAC-PDU transmission.This part of this transmission is to encode according to the rate control information that embeds in the data division that transmits.

Figure 22 has provided the illustrative methods 2200 of point-point data transmission.In frame 2210, flow process begins, and wherein, a station sends non-guiding MIMO pilot tone.In frame 2220, but this station sends the information of together decode.For example, non-guiding MIMO pilot tone 2110 and the example of PCCH2120 as the mechanism of request distribution in managed the connection, AP or other control stations need and can decode to the signal section that comprises this request.Those skilled in the art can recognize to also have the request mechanism of countless replacements, be used on shared channel a point-connection being dispatched.In frame 2230, according to the transformat that consults, data are sent to another station from a station.In this embodiment, the guiding data are to use determined speed of measurement result and parameter according to non-guiding MIMO pilot tone 2110 to send.Those skilled in the art can recognize to also have the means of multiple replacement to can be used to be sent as a concrete point-channel and the data of special finishing.

Figure 23 shows a kind of illustrative methods 2300 of point to point link.This illustrative methods 2300 has provided many aspects, and the part of these aspects can be used in any specific embodiment.In decision box 2310, flow process begins.In decision box 2310,, then enter decision box 2320 if there are data will carry out the STA-STA transmission.If no, then enter frame 2370, carry out the communication of any other type, comprise other access styles (if any).Enter frame 2360, flow process can be returned decision box 2310 and carry out repetition, and perhaps, flow process can finish.

In decision box 2320, if there are the STA-STA data to transmit, then judge this a point-connection be scheduling or self-organizing.If this transmission is dispatched, then enter frame 2330, and ask to divide to be equipped with to win a TXOP.Should be noted in the discussion above that and can send request for allocation as mentioned above in the part of access at random of TDDMAC frame period, perhaps, it can be included in the self-organizing transmission.In case make distribution, just can in frame 2350, send a STA-STA physical burst.In one exemplary embodiment, method 2200 can be used for class STA-STA PHY burst.

In decision box 2320, if do not wish the point-connection of dispatching, then enter in the frame 2340, so that the competition access right.For example, can use at interval 2010 sections of 2000 A-TCH of TDD mac frame.When by compete successfully win access right after, enter frame 2350, and send STA-STA PHY burst, as mentioned above.

Enter decision box 2360 from frame 2350, wherein, flow process can repeat, and as mentioned above, perhaps, can stop.

Figure 24 shows a kind of illustrative methods 2400 that Rate Feedback is provided, and is used for a little-connection.Other steps that the figure shows various transmission and can carry out by two stations STA1 and STA2.STA1 sends a non-guiding pilot tone 2410 to STA2.STA2 when receiving non-guiding pilot tone 2410, measured channel 2420.In one exemplary embodiment, but STA2 determines the supporting rate of the transmission on the measured channel.This speed is determined that the result sends to STA1 as Rate Feedback 2430.In the embodiment of various replacements, can transmit other parameters, judge so that in STA1, make Rate Feedback.In 2440, STA1 receives the distribution through scheduling, and perhaps contention transmission opportunities is for example in A-TCH.In case won transmission opportunity, in 2450, STA1 just with according to Rate Feedback 2430 determined speed and modulation formats, sends data to STA2.

Method shown in Figure 24 can be promoted the use of among the various embodiment, this is conspicuous to those skilled in the art.A bit integrated-point velocity feedback and more otherwise examples will be described in further detail below.

Method 2500 among Figure 25 shows the managed point-connection between two station STA1 and STA2 and access point (AP).In 2505, STA1 sends non-guiding pilot tone, and request for allocation.Also can will be explained below according to sending data than distribution early and previous Rate Feedback.In addition, the Rate Feedback according to communicating by letter from the self-organizing of a previous managed point-connection or next free STA1 or STA2 initiation can send any such data.STA2 and access point all can be received non-guiding pilot tone and transmission request (can be received by various other stations in this zone).

Access point is received transmission request, and a kind of according in the multiple dispatching algorithm, determines when and whether make the distribution that is used for point to point link.The STA2 measured channel, simultaneously in 2505, non-guiding pilot tone is sent out away, but and STA2 can determine to carry out the supporting rate of point to point link with STA1.Alternatively, STA2 also can receive feedback and/or data from STA1 according to preceding once transmission.

In this embodiment, access point has been determined and will have been distributed at the transmission of being asked.In 2515, a distribution is transferred to STA1 from access point.In this embodiment, the distribution to R-TCH 1540 is to transmit in control channel (as above-mentioned CCH 520).Equally, in 2520,, make the distribution on the R-TCH at STA2.In 2525, STA1 receives the distribution from access point.In 2530, STA2 receives the distribution from access point.

In 2535, according to distributing 2520, STA2 transmission rate feedback.Alternatively, can comprise the request of the aforesaid transmission that is used to dispatch, and any data that will send according to last request.As mentioned above, the Rate Feedback of transmission is selected according to channel measurement 2510.2535 PHY burst also can comprise non-guiding pilot tone.In 2540, STA1 measures the channel from STA2, receives feedback, and can receive optional data.

In 2545, according to distributing 2515, STA1 sends data according to the Rate Feedback information of receiving.In addition,, can make request, and, provide Rate Feedback according to the channel measurement result in 2540 for the distribution in future.Data are that the concrete channel measurement result according to point to point communication sends.In 2550, STA2 receives data, and, any rate controlled that sends alternatively.STA2 also can measured channel, so that provide Rate Feedback for the transmission in future.

Should be noted in the discussion above that transmission 2535 and 2545 all can be access in a little and receives, is that non-targeting part can be received, as mentioned above at least.Therefore, for any request that comprises, access point can provide the additional allocation that is used for following transmission, respectively by distribution 2555 of mailing to STA1 and STA2 and 2560 expressions.In 2565 and 2570, STA1 and STA2 receive distribution separately.Then, this flow process ad infinitum repeats, wherein, the access on the access point management shared medium, STA1 and STA2 directly send point to point communication mutually according to supported selected speed and modulation format on the point-channel.Note that in the embodiment that replaces, also can carry out the self-organizing point to point communication, also carry out managed point to point communication as shown in figure 25 simultaneously.

Figure 26 shows (or, the self-organizing) point-connection based on competition.STA1 and STA2 communicate mutually.Other STA also can be in the range of receiving, and can insert shared channel.In 2610, the STA1 that has data will send to STA2 monitors shared channel, and the competition access right.In case won transmission opportunity, just a point-PHY burst 2615 is sent to STA2, PHY burst 2615 also may be received by other STA.In 2620, other STA of supervision shared channel may receive the transmission from STA1, and the old friend avoids in the road inserting this channel.For example, above-described PCCH can be included in the transmission 2615.In 2630, STA2 comes measured channel according to PHY 2615 pilot tones that happen suddenly, and the return on the competition shared channel inserts.STA2 also can send data as required.Notice that the competition time can change.For example, in traditional 802.11 systems, after SIFS, can return an ACK.Because SIFS priority is the highest, so STA2 can make response under the situation of not losing channel.Different embodiment can allow lower delay, and can provide high priority for return data.

In 2635, STA2 is to STA1 transmission rate feedback and optional data.In 2640, STA1 receiving velocity feedback is competed the access right to shared channel again, and in 2645, according to the Rate Feedback of receiving, sends signal to STA2.In 2640, all right measured channel of STA1, so that be provided for the Rate Feedback of following transmission to STA2, and can receive any optional data that sends out by STA2.In 2650, speed and modulation format that STA2 determines according to measured channel conditions receive transfer of data 2645.STA2 also can feed back by receiving velocity, to be used for returning a transmission to STA1.STA2 also can measured channel, so that following Rate Feedback to be provided.Therefore, get back in 2635, allow STA2 return Rate Feedback and data, this flow process can repeat.

Therefore, self-organizing communication can be carried out by the competition access right in two stations two-wayly.Transmission by using Rate Feedback and special finishing to mail to receiving station, make a little-connection itself is very efficient.But when using the public receiving unit (as PCCH) of PHY burst, so, shown in 2620, other STA can visit this information, and cause interference in the known holding time of avoiding showing in PCCH on channel.As shown in figure 25, before step shown in Figure 26, point to point communication managed or self-organizing can be initiated transfer of data, and, can be used for proceeding subsequently point to point communication.Therefore, can use any combination scheduling and point to point communication self-organizing.

Figure 27 has provided an exemplary TDD mac frame interval 2700, is used to illustrate the managed point to point communication between the station.In this embodiment, F-TCH and A-TCH duration all are set as 0.Beacon/BCH 1510 and CCH 1520 transmissions the same as before.Beacon/BCH1560 represents the beginning of next frame.CCH 1520 indicates the distribution that is used for point to point communication.Distribute according to these, during the burst 2710 that has distributed, STA1 sends signal to STA2.Note that STA2 distributes the section of obtaining 2730, is used for STA1 is made response in identical TDD mac frame interval.Can comprise above-mentioned various compositions in the arbitrary specific point-PHY layer burst, as Rate Feedback, request, guiding and/or non-guiding pilot tone, guiding and/or non-guiding data.Distributing in 2720, STA3 sends signal to STA4.Distributing in 2740, STA4 sends signal to STA3 in a similar manner.Can comprise various other rl transmission among the R-TCH, comprise a non-point-connection.Further provide the additional exemplary embodiment of these and other aspects of explanation below in detail.

Note that in Figure 27, as required, can dispatch at interval the protection between the section.A major issue about point to point communication is, generally, be unknown path delay between two STA.To this, a kind of processing method is, allows each STA keep its transmitting time to fix, thereby makes the clock synchronised ground of they and AP arrive AP.In this case, AP can provide guard time at the two ends that each point-to-point distributes, to compensate the unknown path delay between two STA in the communication.Under many circumstances, Cyclic Prefix will be enough, and needn't adjust at STA receiver place.Then, STA must determine their time migrations separately, so that know the transmission that when receives other STA.The STA receiver may need to keep two receive clocks: one is used for AP frame sequential, and another is used for a little-connection.

As top various embodiment were described, receiver can obtain confirming and channel feedback in it distributes, and feed back to transmitter.Even if total Business Stream is unidirectional, receiver also can send reference and request distributes with acquisition.The AP scheduler is guaranteed to provide enough resources for feedback.

With the traditional station and the interoperability of access point

Just as what describe in detail here, described various embodiment provide the improvement with respect to legacy system.But because legacy system extensively existed already, a system preferably can keep backward compatibility with existing legacy system and/or legacy user terminals.Term used herein " novel " is used for distinguishing mutually with traditional system.The system of newtype can be integrated with one or more aspects or the feature of describing in detail here.An exemplary novel system is to describe the MIMO ofdm system below in conjunction with Figure 35-52.In addition, being used to of describing in detail below makes the aspect of novel system and legacy system interoperability also be applicable to the system that other wait to develop, and no matter whether comprise any particular refinement of describing in detail in this system here.

In an exemplary embodiment, by using different Frequency Distribution (FA), can keep backward compatibility, thereby a novel system is worked on the FA different with the legacy user with other system.Therefore, novel system can be searched for the available FA that works thereon.Dynamic frequency selects (DFS) algorithm can be implemented in this New WLAN to realize this function.Preferably adopt the AP of multicarrier.

The traditional STA that attempts to insert WLAN can adopt two kinds of scan methods: active scan and drive sweep.Under the situation of drive sweep, by the scanning work frequency band, STA obtains near the tabulation of the feasible set of basic (BSS) it.Under the situation of active scan, STA sends an inquiry, with the response of request from other STA among the BSS.

Traditional standard does not relate to STA and how to determine to add which BSS, still, in case make a decision, just can attempt carrying out association.If unsuccessful, STA will move by its BSS tabulation, till success.When a traditional STA can't understand the beacon message that is sent, this STA can not attempt to be associated with a New WLAN.But as a kind of method of keeping single WLAN type on single FA, a novel AP (and UT) can ignore the request from traditional STA.

A kind of technology of replacement is, allows new A P or New type of S TA use effectively tradition (that is, 802.11) message delivery techniques, refuses the request of any traditional STA.If a legacy system is supported this message delivery techniques, then can provide redirect message for this tradition STA.

Be to support the frequency spectrum that two types STA need add with the obvious drawback that is associated of on different FA, working.A benefit is, is convenient to manage different WLAN, kept as functions such as QoS.But, just as describing in detail among the application, for as the high data rate supported of the novel system of the mimo system embodiment that describes in detail here, traditional CSMA MAC agreement (as, those agreements of describing in detail in traditional 802.11 standards) is efficient inadequately usually.Therefore, preferably adopt the mode of operation of backward compatibility, so that novel MAC coexists on identical FA with traditional MAC.Several exemplary embodiments are described below, and wherein, tradition can be shared identical FA with novel system.

Figure 28 shows method 2800, be used on identical Frequency Distribution supporting tradition and novel station the two.In this embodiment, for ease of explanation, suppose BSS work (that is, between a plurality of overlapping BSS less than coordination) isolatedly.Flow process starts from the frame 2810, uses traditional signaling to establish a uncontended periods.

Be the several illustrated examples that are used for traditional 802.11 systems below, wherein, New WLAN AP can use built-in hook in traditional 802.11 standards to reserve time by the special use of novel station.In addition, for various types of legacy systems, can use any amount of other signaling technologys to establish a uncontended periods.

A kind of technology is to establish uncontended periods (CFP) under the PCF/HCF pattern.AP can establish a beacon interval, and announces a uncontended periods in this beacon interval, and wherein, it can provide service for novel and traditional STA under poll pattern.This makes all traditional STA its network allocation vector (NAV) is arranged to the duration of the CFP that announced, and network allocation vector is the counter that is used for following the tracks of CFP.So, in CFP, receive that traditional STA of this beacon must not use channel, unless by the AP poll.

Another kind of technology is by RTS/CTS and duration/id field, establishes CFP and NAV is set.In this case, this new A P can send a specific RTS with reservation address (RA), and this RTS shows that to all New type of S TA this AP is reserving this channel.Traditional STA resolves to this RA field and points to a specific STA, and does not make response.Novel STA makes response with a specific CTS, thereby, remove BSS in the time period that in the duration/id field of CTS/RTS message pair, provides.At this point, channel can freely be used in novel station in the reservation duration, and not conflict.

In frame 2820, the STA that has received the traditional type of the signal that is used to establish uncontended periods waits for, till polled or uncontended periods finish.Like this, access point has become distribution of work shared medium uses for novel MAC agreement.In frame 2830, new STA can insert according to this agreement.Here any set of the aspect of Xiang Xishuominging or subclass may be used in a kind of so novel MAC agreement.For example, can adopt the forward direction and the rl transmission of scheduling, and, managed point-some the transmission, self-organizing or based on the competition communication (comprising a little-point), perhaps, the combination in any of above-mentioned transmission.In frame 2840, use any in the multiple signal type, finish novel access period, signal type can change according to the legacy system that is adopted.In this exemplary embodiment, send a uncontended periods end signal.In an alternative embodiment, in uncontended periods, also can poll tradition STA.Such access can perhaps, can intert therein after novel access.

In frame 2850, if stipulated a competing cycle for legacy system, then all STA can compete access right.Like this, the legacy system that in uncontended periods, can not the communicate request of just can sending and/or attempt to send signal.In decision box 2860, this flow process can be continued by turning back to frame 2810, perhaps, also can stop.

Figure 29 shows the combination of tradition and new media access control.On novel agreement 2930, provided traditional MAC agreement 2910, when these two combines, just formed a MAC agreement, as the MAC agreement 2950 after the combination.In this embodiment, for purpose of explanation, 802.11 traditional signaling message have been used.It will be recognized by those skilled in the art that technology disclosed herein also is applicable to any and any novel MAC agreement in the multiple legacy system, comprises the combination of function disclosed herein.

Traditional MAC agreement 2910 comprises beacon 2902, and it identifies beacon interval.Traditional beacon interval comprises uncontended periods 2904, and what follow later is competing cycle 2906.Various contention free-poll frame 2908A-N can produce in uncontended periods 2904.Uncontended periods 2904 stops by means of uncontended periods end 2910.In 802.11 exemplary embodiments, each beacon 2902 was sent out away in target beacon transmitting time (TBTT) time.Novel MAC agreement 2930 comprises mac frame 2932A-N.

Beacon interval 2950 after the merging has illustrated tradition and the interoperability of novel MAC agreement in uncontended periods 2904.Comprising novel TDD mac frame interval 2932, that follow later is traditional poll CF poll 2908A-N.Uncontended periods ends at CFP and finishes 2910, and what follow later is competing cycle 2906.Novel TDD mac frame interval 2932 can be an any kind, comprises the various aspects of describing in detail alternatively here.In one exemplary embodiment, novel TDD mac frame interval 2932 comprises various sections, as top those sections described in conjunction with Figure 20.Therefore, in this embodiment, novel TDD mac frame comprises pilot tone 1510, control channel 1520, fl transmission channel 1530, a self-organizing point-part (A-TCH) 2010, rl transmission channel 1540 and Random Access Channel 1550 at interval.

Note that in CFP 2904 traditional STA should not disturb any New WLAN transmission.AP can be in CFP any traditional STA of poll, thereby in this section, allow to carry out mixed mode operations.In addition, AP can reserve entire CF P 2904 for novel use, and all traditional businesses is pushed to competing cycle (CP) 2906 when beacon interval finishes.

These exemplary 802.11 traditional standards need CP 2906 to look is enough to support two exchanges between the conventional terminal.So, can adopt beacon, but this can cause the time jitter (time jitter) in the system.If necessary,, can shorten CFP at interval in order to reduce shake, thus the beacon interval that is maintained fixed.Can be provided for establishing the timer of CFP and CP, so that CFP (that is, about 1.024 seconds) is longer than CP (that is, less than 10 milliseconds).But if AP poll conventional terminal during CFP, then the duration of their transmission may be unknown, and may cause extra time jitter.Therefore, in the time of on traditional STA being contained in identical FA, must be noted that the QoS that keeps New type of S TA.802.11 traditional standards are synchronized to 1.024 milliseconds time quantum (TU).In this embodiment, adopt the mac frame duration of 2TU or 2.048 milliseconds, novel MAC can be designed to legacy system synchronous.

In some embodiments, preferably guarantee to make novel mac frame synchronous.That is to say that the mac frame clock of system can be continuous, and when sending, this mac frame border starts from the integral multiple of 2.048 milliseconds of frame periods.Like this, be easy to keep the sleep pattern of STA.

Novel transmission does not need and the conventional transmission compatibility.Header, lead code etc. can be distinctive for novel system, and their example runs through among the application to be described in detail.Tradition STA can attempt its demodulation, but can't correctly decode.Traditional STA under the sleep pattern can not be affected usually.

Figure 30 shows the method 3000 that obtains transmission opportunity.Method 3000 can be as the frame 2830 in the exemplary embodiment of aforesaid method 2800.This flow process starts from decision box 3010, wherein, access can be dispatched, and perhaps is non-scheduling type.It will be recognized by those skilled in the art,, in any specific embodiment, can support in these two kinds of access styles one or both of though this example shows two types access.In decision box 3010, if expect the access of non-scheduling type, then enter frame 3040, thus the competition access right.Can use any amount of access technology based on competition.In case obtained transmission opportunity (TXOP), then in frame 3050, sent according to this transmission opportunity.Then, flow process can finish.

In frame 3010,, insert with request if the access of expectation scheduling then enters frame 3020.This access request can be made on Random Access Channel during the self-organizing competition, perhaps, uses any other technology disclosed herein.In frame 3030, after granting this access request, will receive a distribution.Enter in the frame 3050,, send TXOP according to the distribution of receiving.

In some cases, preferably use overlapping traditional B SS, in identical Frequency Distribution, between new A P and the BSS that is associated thereof, realize interoperability.Traditional B SS can be operated under DCF or the PCF/HCF pattern, so between novel B SS and the traditional B SS may not be to reach synchronously.

If traditional B SS is operated under PCF or the HCF pattern, then new A P can attempt to be synchronized to TBTT.If this is possible, then new A P can use various mechanism to occupy channel in competing cycle, so that be operated in the overlapping BSS zone, the example of described mechanism has been made description above.If traditional B SS is operated under the DCF, then new A P also can attempt to occupy channel, and announces a CFP, to remove channel.

Under some occasion, some or all STA among the traditional B SS may can not receive new A P transmission.In this case, these traditional STA may disturb the operation of New WLAN.For fear of this interference, novel station can be given tacit consent to based on CSMA operation, and relies on a point-transmission (following also will describe in further detail it in conjunction with Figure 33-34).

Figure 31 shows a kind of exemplary method 3100, so that a plurality of BSS shares single FA.In frame 3110, traditional access point sends a beacon.The novel access point of sharing identical frequency assignments can be synchronized to the TBTT (optionally) that is associated with this beacon.In frame 3120, if traditional uncontended periods stipulate according to this beacon, then carry out it.In case uncontended periods (if any) finishes, then all STA just can compete access right in the competing cycle of regulation.In frame 3130, novel access point is competed access right in competing cycle.In frame 3140, New type of S TA can insert shared medium in novel access point has been competed time of access right.Access style between this novel access periods can comprise to be described in detail aspect any one here.Can use multiple technologies, indicate the time quantum of this access point channel reservation to traditional STA as describing in detail above.In frame 3150, in case this end cycle, then traditional STA just can compete.In decision box 3160, this flow process can continue by turning back in the frame 3110, perhaps, can finish.

Figure 32 shows the overlapping BSS that uses single FA.Legacy system 3210 sends beacon 3205 (there is shown 3205A and 3205B, be used to illustrate TBTT and total beacon interval of legacy system).Beacon 3205A identifies uncontended periods 3210 and competing cycle 3215.In uncontended periods 3210, can carry out traditional contention free-poll 3220A-N, what follow later is the end indicator 3225 of uncontended periods.

Station monitoring channel in the New WLAN 3240 receives beacon 3205, and gains control of oneself and do not insert medium, till the chance of competition access right is arrived.In this embodiment, chance the earliest is in uncontended periods.After PIFS 3230, novel access point sends a classical signal 3245, to indicate the time quantum with busy channel to the tradition station.Multiple symbol can be used to carry out this function, and their example is described in detail in the above.Can adopt various other signals, this depends on expectation and which legacy system realization interoperability.Traditional STA in the range of receiving of classical signal 3245 can avoid access channel, till novel access period 3250 finishes.Cycle 3250 comprises one or more TDD mac frames 3260 (in this embodiment, being 3260A-N) at interval.TDD mac frame interval 3260 can be an any kind, and its example comprises one or more aspects of describing in detail here.

In an exemplary embodiment, new A P occupies channel (that is, in per 40 milliseconds, 20 milliseconds of new A P busy channels) in the interval of fixed length.New A P can keep a timer, guaranteeing its only busy channel in expected duration, thereby guarantees the fairness of Channel Sharing.In seizing the process of channel, new A P can use any signaling technology.For example, can send CTS/RTS or conventional beacon, announce new CFP.

In novel interval 3250, exemplary TDD mac frame at interval can be as giving a definition: at first, send a beacon and add F-CCH, this F-CCH indicate will be in current mac frame UT in the tabulation of poll.Behind F-CCH, broadcast one section MIMO pilot tone, so that STA obtains the accurate tolerance result of mimo channel and formation mimo channel.In one exemplary embodiment, each antenna can be realized fabulous performance with 2 short OFDM symbols.This means that the F-TCH in the initial mac frame comprises 8 MIMO frequency pilot signs substantially.The R-TCH part of first mac frame can be constructed such that the STA on the polling list sends non-guiding MIMO pilot tone and rate indicator (being used for down link) to AP, and confirms.In this embodiment, at this point, all terminals on the polling list are prepared to be operated under the normal consistency type mode in next TDD mac frame interval.After this, under the coordination of AP, use any technology disclosed herein, the TDD mac frame after the TDD mac frame interval can be used for swap data at interval.

As mentioned above, (for example, when some or all STA among the traditional B SS can not receive new A P transmission) under specific circumstances, novel station acquiescence is based on the operation of CSMA, and a dependence point-transmission.At this moment, the circulation of above-described ON/OFF may not have advantage, perhaps or even impossible.In these cases, novel station can be given tacit consent to a little-point operation.

Figure 33 has provided a kind of illustrative methods 3300, and it uses various technology disclosed herein, carries out the high speed point to point communication, simultaneously with traditional B SS interoperability.Flow process starts from frame 3310, wherein, has data will issue the STA competition access right of the 2nd STA.In frame 3320, successfully compete access right after, classical signal is used at this station, those signals as described above are cleared up medium.In frame 3330, a STA sends a request (with pilot tone) to the 2nd STA.The 2nd STA can be according to the pilot tone that is sent, measured channel.The 2nd STA sends to a STA with channel feedback.Therefore, in frame 3340, first stop is received the have channel feedback response of (for example, Rate Feedback).In frame 3350, according to this feedback, a STA sends pilot tone and guiding data to second station.In frame 3360, the 2nd STA can send to a STA and confirm, and can send follow-up Rate Feedback, to be used for other transmission.The classical signal that is used for clearing up medium makes: use any high speed technology and with respect to the improvement of legacy system, those technology are carried out frame 3330 to 3360 as disclosed herein.In protection scope of the present invention,, just can use an any point-MAC agreement in case STA has cleared up medium.Shown in decision box 3370, by returning frame 3310, flow process can be continued, and perhaps flow process can finish.

In one exemplary embodiment, adopt point-dot pattern, seize channel and work according to the traditional rule of CSMA.In this embodiment, do not adopt PCF and HCF, and a centralized network architecture needn't be arranged.When a New type of S TA wishes and another New type of S TA (or AP) when communicating that this STA seizes channel.First transmission comprises enough MIMO pilot tones, adds the message that a certain request connects.Can adopt CTS and RTS to come cut-back region and set aside some time.Requesting party STA message must comprise STA BSS ID, STA MAC ID and target STA MAC ID (if knowing).Response should comprise the BSSID of response side STA.Like this, these STA just can judge whether they need to carry out the receiver correction (if having used guiding) of emission guiding vector.Note that in this embodiment and to use emission guiding and nonessential,, do like this and have superiority although if STA has used the appointment AP that coordinates BSS and calibrated.

As shown in figure 33, response can comprise MIMO pilot tone (if adopt, lead) and adds speed and indicate.In case should exchange take place, just can on each link, lead ().But if these STA belong to different BSS, the first guiding transmission of then initiating between the STA of this connection can comprise guiding MIMO pilot signal, so that the receiver of the side of response STA can be proofreaied and correct the phase difference value between the different B SS.

In this exemplary embodiment, in case initial exchange has taken place, just can lead.These exchanges should be followed the SIFS interval between down link and the ul transmissions.Owing to calculate the potential processing delay of the characteristic vector that is used for leading, this may need STA to use least mean-square error (MMSE) to handle, rather than characteristic vector is handled.In case calculate guiding vector, STA just can begin the use characteristic vector in emission side, and the recipient can continue to adopt MMSE to handle, and separates and changes towards the optimal spatial matched filter.Periodic feedback between two STA helps to follow the tracks of and rate controlled.Can follow SIFS at interval, so that allow STA keep control to channel.

Figure 34 shows point to point communication, and it uses the MIMO technology, and competition inserts (that is, managed) on traditional B SS.In this embodiment, initiator 106A competes access right on channel.Successfully rob when accounting for channel when it, send MIMO pilot tone 3405, the back and then asks 3410 again.This message can comprise the MAC ID of BSS ID, initiator STA and the MAC ID (if known) of target STA.Other signalings as CTS and RTS, can be used to further clear up channel.The side of response STA 106B sends guiding pilot tone 3420, and the back is and then confirmed and Rate Feedback 3425.Guiding pilot tone 3420 sends when the SIFS 3415 that asks after 3410.In this exemplary embodiment, traditional access point is 802.11 access points, and SIFS has limit priority, and therefore, response station 106B keeps the control to channel.The various transmission that Figure 34 describes in detail can phase mutual edge distance SIFS and send, thereby keeps the control to channel, till point to point communication finishes.

In one exemplary embodiment, can determine the maximum duration of channel occupancy.Guiding pilot tone 3430 after Rate Feedback 3425 and data 3435 are sent to response station STA 106B according to this Rate Feedback from initiator STA 106A.After data 3435, the side of response STA 106B sends guiding pilot tone 3440 and affirmation and rate controlled 3445.In response, initiator 106A sends guiding pilot tone 3450, and data 3455 are followed in the back.

This flow process can ad infinitum continue, and perhaps reaches channel at most and inserts the maximum time that is allowed, and this depends on deployment cycle.Though do not show that in Figure 34 the side of response STA also can send data, and initiator also can transmission rate control.These data segments can combine with those sections shown in Figure 34, so that maximizing efficiency (that is, SIFS needn't be inserted between these transmission).

When two or more BSS were overlapping, preferably adopting can be with the mechanism of coordination mode shared channel.Provide several exemplary mechanism and the exemplary operational process that is associated with it below.These mechanism can combine use.

First kind of exemplary mechanism is that dynamic frequency is selected (DFS).Before establishing a BSS, WLAN need search for this wireless medium and determine best Frequency Distribution (FA), so that establish the operation of BSS.In the process of search candidate FA, AP also can create neighbor list so that be redirected and AP between switch.In addition, WLAN can carry out mac frame sequential and neighbours BSS (below will further specify) synchronously.Can use DFS to distribute BSS, synchronisation requirement minimizes between BSS thereby make.

Second kind of exemplary mechanism is synchronous between BSS.In the DFS process, AP can obtain the sequential of neighbours BSS.Usually, preferably make all BSS (in one embodiment, on single FA, perhaps, in another embodiment, striding across a plurality of FA) synchronous, so that carry out switching between BSS.But, adopt this mechanism, on identical FA, work at least and synchronous its mac frame of approximating those BSS.In addition, if be total to channel BSS overlapping (that is, AP can listen to the other side each other), can there be it in then newly arrived AP situation to inform original AP, and following formulation Resource Sharing Protocol.

The third exemplary mechanism is Resource Sharing Protocol.Overlapping BSS shared channel coequally on same FA.Mac frame is replaced between BSS according to certain predetermined way, thereby realize this point.Like this, the business among each BSS just can be used channel, and can not emit the risk of being disturbed by other BSS.Shared can be implemented between two overlapping BSS like this.For example, under the overlapping situation of 2 BSS, an AP uses the mac frame of even-numbered, and another AP uses the mac frame of odd-numbered.Under the overlapping situation of 3 BSS, share and to realize for mould with 3.The embodiment that replaces can adopt the shared mechanism of any kind.Control field in the BCH Overhead Message can indicate whether to carry out the type in resource-sharing and shared cycle.In this embodiment, the sequential of all STA is adjusted to the suitable shared cycle among the BSS.In this embodiment, under the overlapping situation of BSS, time-delay will increase.

The 4th kind of exemplary mechanism is auxiliary synchronous again of STA.This situation may occur: two BSS can't hear the other side each other, but a new STA in the overlapping region can hear they two.This STA can determine the sequential of these two BSS, and this is reported to them.In addition, this STA can determine time migration, and indicates which AP should change its frame sequential and what change.This information must be transmitted to all BSS that are connected with this AP, and they all must rebulid the frame sequential to realize synchronously.Can in BCH, announcing synchronously again of frame.This algorithm can be applied to handle how unconscious overlapping BSS.

Describe in detail below and can be used for above-mentioned one or more machine-processed example process.

AP can realize synchronously when powering up or in other fixed times.By near the system search in all FA, can determine system sequence.For ease of synchronously, one group of orthogonal code can be used for assisting to distinguish different AP.For example, AP has the known beacon of repetition in each mac frame.These beacons can use Walsh sequence (for example, length is 16) to cover.Therefore, the equipment such as AP or STA can be carried out the pilot frequency intensity measuring (PSM) of local AP, to determine overlapping BSS.To further describe below, the movable STA that is associated with an AP can send echo, to assist synchronously.These echoes can use and corresponding sequential of AP overlay code (cover) and soverlay technique (covering).Therefore, when overlapping but these BSS AP separately of BSS can't detect signal from the other side, the STA echo can be received by neighbor AP, thus provide its AP for information about and neighbor AP can be synchronous signal.Note that the overlay code that on different FA, can reuse quadrature.

Can finish to certainty the selection (that is, selecting a not detected Walsh overlay code on neighbor AP) of Walsh overlay code based on the set of undetected Walsh overlay code.If all overlay codes all exist, then can reuse by new AP with the corresponding sign indicating number of the most weak received signal level (RSL).Otherwise, in one embodiment, can select to make the maximized sign indicating number in working point (see also structuring power back-off (powerbackoff) mechanism that self adaptation is reused, also will be elaborated below) of AP to this.

In this embodiment, interlaced with each other the coming of frame counter that sends by each AP.The interlace mode that is adopted is corresponding to Walsh overlay code label.Therefore, AP0 uses Walsh sign indicating number 0.When AP0 frame counter=j, APj uses Walsh overlay code j, and its frame counter equals 0.

When powering up or will carry out the synchronous any time, AP monitors neighbor AP beacon and/or STA echo.If do not detect the neighbours system, then AP establishes its time reference.This can be arbitrarily, and is perhaps relevant with GPS, or any other local time reference.If detect individual system, then correspondingly establish local sequential.If AP detects two or more systems that do with the different time lineman, then AP can carry out with the system with peak signal synchronously.If these system works are on identical Frequency Distribution (FA), then AP can attempt to be associated with more weak AP, thereby informs that it is operated near AP on the independent clock other.This new AP attempts more weak AP is informed in synchronous two required time migrations in AP district.More weak district AP can adjust its sequential.For a plurality of neighbor AP, this can repeat.With the synchronous sequence of two or more systems, new AP can establish its sequential.If all neighbor AP all can not be synchronized to single sequential (no matter being what reason), then this new AP can be synchronized to any one neighbor AP.

AP can carry out dynamic frequency and select when powering up.As mentioned above, generally, preferably can select to make the overlapping minimum of BSS by DFS, thereby the quantity of BSS that need be synchronous and any delay or the throughput reduction related with this locking phase are minimized (promptly, compare the BSS that must share these medium with one or more neighbours BSS, the BSS that can insert whole medium on a FA is more efficient).Synchronously, new AP can select to have the FA (that is, when measuring neighbor AP, or during echo) of minimum RSL.AP can periodically inquire STA, so that carry out the AP pilot measurement.Equally, AP can dispatch silence period, to assess the AP place by the level of interference that STA was caused from other districts (being neighbor bss S).If this RSL grade is excessive, then AP can attempt seeking another FA in non-dispatching cycle, and/or formulates the power back-off strategy, and is as described below.

As mentioned above, can organize AP according to the pilot tone overlay code.In this embodiment, can to use length be 16 Walsh sequence overlay code to each AP.Can use the sign indicating number of a different length arbitrarily.The pilot tone overlay code is used for the signal at a super frame period internal modulation beacon.In this embodiment, super frame period equals 32 milliseconds (that is 16 continuous N AC frame beacons).Then, STA can be in superframe interval integration coherently, with the pilot power of determining to be associated with a specific AP.As mentioned above, AP can select its Walsh sign indicating number from undetected a plurality of available Walsh sign indicating numbers.If detect all sign indicating numbers (on identical FA), then AP can be according to they be ranked to the most weak inferior ordered pair from the strongest.AP can reuse and the corresponding Walsh sign indicating number of the most weak detected Walsh sign indicating number.

For ease of the identification neighbor AP, STA can be used for sending echo, to identify their corresponding AP.Therefore, as mentioned above, an AP who does not detect neighbor AP may detect corresponding STA echo, thereby identifies this AP and sequential thereof.Each AP can send configuration information in its beacon, and each STA can serve as repeater, so that retransmit AP configuration information and sequential to the neighbor AP of any reception.

When the order of receiving from AP, movable STA need send a predetermined pattern, so that be operated in the existence that near AP on the identical FA detects this neighbours system.A kind of simple method is, a definition observation interval (for example, between FCH and RCH section) in mac frame, and it is not used for any business by AP.The duration of observation interval can be defined as long enough, with handle the STA that is associated with this AP and with STA that neighbor AP is associated between maximum different propagation delays (for example, 160 chips, perhaps, 2 OFDM symbols).For example, the STA that is associated with the AP that uses Walsh overlay code j can be in its mac frame counter=0 o'clock sends echo.Be encoded on this echo make neighbor AP detect existence and with adjacent AP district in the STA information necessary that coexists efficiently.

The structuring power back-off that can adopt self adaptation to reuse.Must quilt be reused near another AP the time, preferably can apply a kind of structurized power back-off mechanism to each FA when system is crowded, so that the terminal in two districts is all with maximal efficiency work.When detecting when congested, can use power to control the efficient that improves system.That is to say, be not whenever all to send with total power, and AP can use a kind of structurized power back-off mechanism of mac frame counter synchronisation with them.

For example, suppose that two AP are operated on the identical FA.In case these AP detect this situation, they will formulate known power back-off strategy.For example, two AP use a kind of compensation scheme, and it makes: being total power Ptot on mac frame 0, is Ptot (15/16) on mac frame 1 ..., be Ptot/16 on mac frame 15.Because AP is synchronous and their frame counter interlocks, so, there is not the AP district to use total power simultaneously.This target is the compensation model that selection makes the STAs in each AP district work with highest-possible throughput.

The used compensation model of specific AP can be the function of detected degree of disturbance.In this embodiment, a specific AP can use maximum 16 known compensation models.AP can transmit used compensation model in BCH and in the echo that the STA that is associated by AP sends.

Walton etc. make, exercise question is the United States Patent (USP) 6 of " Method and apparatus for controllingtransmissions of a communications systems ", 493, describe a kind of exemplary compensation scheme in 331 in detail, this patent has transferred assignee of the present invention.

Figure 53 shows another exemplary embodiment that can carry out the technology of interoperability with legacy system.There is shown an exemplary mac frame 1500, it is described in detail above in conjunction with Figure 15.Also introduce a kind of time slot pattern, wherein defined slot time 5310.Slot time 5310 comprises MIMO pilot interval 5315 and time slot gap 5320.As shown in the figure, inserted pilot tone 5315,, made it avoid the influence at other stations (comprising AP) of the rule work of basis such as EDCA to reserve this channel.Improved mac frame 5330 consists essentially of mac frame 1500, has wherein inserted pilot tone 5315, so that keep the control to medium.Figure 53 is illustrative, and this is conspicuous to those skilled in the art.The time slot pattern can combine with the mac frame of any kind, describes its various examples here in detail.

In this embodiment, for ease of explanation, the mac frame of supposing traditional 802.11 systems use is 1.204 milliseconds a integral multiple.Mac frame can be set as 2.048 milliseconds, so that synchronously.At target beacon transmitting time (TBTT), the announcement CFP duration is so that STA is provided with its NAV.During CFP, the STA among the BSS should not send signal, unless polled.Alternatively, as previously mentioned, AP also can send RTS, and allows identical CTS of STA loopback, with further cleaning BSS.This CTS can be the synchronous transmission from all STA.In this embodiment, always start from 2.048 milliseconds of borders, can eliminate shake by guaranteeing mac frame.Like this, even if under the situation that TBTT shortens, also between adjacent/overlapping BSS, hold time synchronously.Above-described various other technologies can combine with the technology that describes below.In case reserved medium for amended mac frame 5330, just can use any available techniques, employing time slot pattern keeps the right of possession corporeal right to medium, to prevent that traditional STA from disturbing the transmission of scheduling, thereby the throughput that has reduced novel system potentially increases (promptly, use scheme shown in Figure 15 or Figure 53, perhaps other schemes of describing in detail here).

In this embodiment, new A P follows the CSMA rule and seizes channel.But before this, it should or listen to beacon or other STA, attempts to determine whether to exist another BSS.But,, do not need synchronously in order to realize fair resource-sharing.

In case detect neighbours BSS, this new A P just can seize channel by sending its beacon.In order to stop (lock out) other users, this new A P sends has the pilot tone of a certain frequency, thereby prevents that other STA from using this channel (that is, not having idling cycle to be longer than the PIFS=25 microsecond).

This new A P can be provided with one can make it at the timer of determining to take in the fair fixedly duration this channel.Like this can be roughly synchronous with the beacon period of traditional AP, perhaps asynchronous (that is, per 200 milliseconds in 100 milliseconds).

This new A P can seize channel by any point in the interval that it allowed, and this can be postponed by the traditional B session service user.If there is not business to serve, this new A P can abandon channel before its time expires.When this new A P occupied channel, it was restricted to a just time period with its use.In addition, the sequential of this new A P establishment can be consistent with traditional mac frame sequential.That is to say that novel beacon appears on 2.048 milliseconds of borders of new A P clock.Like this, New type of S TA can judge whether HTAP has occupied channel by observing these specific intervals, thereby keeps synchronously.

This new A P can announce its frame parameter in beacon.The part of frame parameter can comprise the pilot interval spacing, is used to represent the frequency of pilot transmission in this mac frame.Note that this new A P can dispatch STA, so that its transmission is overlapping with periodic burst pilot.In this case, the overlapping STA of dispensing section knows this point, and ignores pilot tone in this cycle.Other STA do not know this point, therefore use a threshold supervision device, confirm what whether pilot tone sent in predetermined distance.

This situation: STA may occur and originally will send pilot signal by the moment that AP sends, perhaps, AP sends the guiding pilot tone to STA in this interval.Worsen its channel estimating in order to prevent other STA from using this pilot tone, the AP pilot tone can be used and the public guide frequency Walsh overlay code Walsh overlay code of quadrature mutually.Can adopt the structure that is used to distribute the Walsh overlay code.For example, when STA uses different Walsh overlay codes with AP, the Walsh space can comprise 2N overlay code, the overlay code of N is wherein reserved for AP, and other overlay code is to reserve for the STA that is associated with a specific AP, and the overlay code that these STA use is related with the Walsh overlay code of corresponding AP in a known way.

When this new A P when STA sends assignment information, it expects that this STA sends to it in predetermined distance.This STA may not receive this assignment information, and in this case, PIFS is longer than at the interval that channel may not be used.In order to prevent this situation, AP can detect channel in t＜SIFS, and judges whether it is occupied.If unoccupied, then AP can seize channel immediately by sending the pilot tone of corresponding phasing.

Novel channel allocation section time slot can be changed into the interval (16 microsecond) of SIFS.Like this, channel occupancy just can be protected, thereby refuses the legacy user in new exclusive in the cycle.

Must be designed to support interoperability to RCH, this is because the duration of RCH may surpass 16 microseconds.If can not provide this RCH at an easy rate In a particular embodiment, so, when novel MAC does not have the channel control (, under traditional mode, coexist), this RCH can be distributed into and be operated under the traditional mode.By allowing any time (that is, wait for 4 microseconds, and send 8 microseconds) of STA after pilot transmission to send the request of access, can hold F-RCH, shown in Figure 53.

Exemplary embodiment: enhancing property 802.11MIMO WLAN

The exemplary embodiment of describing in detail below illustrates above-mentioned various aspects and other aspects.In this embodiment, show the enhancing 802.11WLAN that uses MIMO.To describe various MAC in detail and strengthen, and, be used in corresponding data and message transferring structure on MAC layer and the physical layer.It will be recognized by those skilled in the art, only disclose an illustrative subclass of WLAN function, and they can make the enlightenment here be applicable to the interoperability of 802.11 legacy systems, and with the interoperability of various other systems.

The function of the exemplary embodiment of describing in detail below is the interoperability with traditional 802.11a, 802.11g STA, and with the interoperability of the ultimate criterion of 802.11e draft and expection.This exemplary embodiment comprises MIMO OFDM AP, and so name is in order to distinguish mutually with traditional AP.Also will describe in detail below, because backwards compatibility, traditional STA can be associated with MIMO OFDM AP.But if necessary, MIMO OFDMAP can refuse the association request from traditional STA clearly.The DFS process can be directed to the AP (can be traditional AP or another MIMO OFDM AP) that another supports traditional operation to unaccepted STA.

MIMO OFDM STA can or wherein not have the Independent B SS (IBSS) of AP to be associated with 802.11a or 802.11g BSS.Therefore, for this operation, a such STA will realize all indispensable functions of 802.11a, 802.11g and 802.11e expection final draft.

In BSS or IBSS, when sharing identical RF channel, support various functions with MIMO OFDM STA when traditional.MIMO OFDM PHY spectrum mask (spectral mask) of being advised and the spectrum mask compatibility of existing 802.11a, 802.11g, thereby, can not introduce additional adjacent-channel interference to traditional STA.The signal field backward compatibility of the signal field of the expansion in the PLCP header (following detailed description) and tradition 802.11.In traditional signal field not the rate value of usefulness be configured to define new PPDU type (below will describe in detail).Self adaptation coordination function (ACF) (below will describe in detail) can realize sharing arbitrarily of medium between traditional and MIMOOFDM STA.802.11e the cycle of EDCA, 802.11e CAP and SCAP can be punctured into arbitrarily in any beacon interval, this is determined by the AP scheduler.

As mentioned above, need to use the high-performance MAC high data rate of balance MIMO WLAN physical layer support effectively.Describe the various attributes of this exemplary MAC embodiment below in detail.Be some exemplary attributes below:

Utilized the capacity of mimo channel the self-adapted high-efficient of PHY speed and transmission mode.

The low delay service of PHY provides low end-to-end delay, to solve high-throughput (for example, multimedia) demands of applications.When hanging down load, adopt MAC technology, perhaps when the heavy duty system, use centralized or distributed scheduling, can realize the low delay operation based on competition.Low delay has a lot of benefits.For example, low delay can be realized quick self-adapted, thereby makes the physical layer data rate maximization.Low delay can be realized cheap MAC by enough minibuffer devices, and needn't delay ARQ.Use for multimedia and high-throughput, low delay also makes end-to-end delay minimize.

Another attribute is high MAC efficient and low competition expense.In the MAC based on competition, when data rate was high, time that useful transmission takies shortened, and incremental portion that should the time is wasted in expense, conflict and the idling cycle.By scheduling, and, can reduce the time of waste in the media by a plurality of high layer packets (for example, IP datagram) are aggregated in the single mac frame.Also can form aggregate frame, thereby lead code and training expense are minimized.

The high data rate that PHY supports can realize that the QoS that simplifies handles.

The exemplary MAC that describes in detail below strengthens and can solve above-mentioned performance issue to keep the mode of backward compatibility with 802.11g and 802.11a.In addition, the support and the improvement of the function that comprises among the aforesaid draft standard 802.11e comprised following function, as TXOP and direct link agreement (DLP), and, optional piece affirmation mechanism.

In description,, use new term for some notions of introducing above to following illustrative embodiment.The mapping of new terminology is as shown in table 1:

Table 1. term mapping table

Early stage term	Be mapped to new term
		The term that uses in the earlier paragraphs	The term that uses in the subsequent paragraphs
MUX PDU or MPDU	Mac frame
		Part MPDU	The mac frame burst
MAC PDU	PPDU
		Broadcast channel message (BCH) and control channel message (CCH)	SCHED message
Control channel message subchannel	The CTRLJ section of SCHED message
		The TDD mac frame at interval	Scheduling access period (SCAP)

F-TCH (forward traffic channel)	The AP-STA transmission of scheduling
		R-TCH (reverse traffic channel)	The STA-AP of scheduling or STA-STA transmission
A-TCH (the point to point service, PTP channel of self-organizing)	Shielded EDCA or MIMO OFDM EDCA
		PCCH (point-to-point control channel)	PLCP header signal field
RCH	FRACH

Frame aggregation flexibly

In this embodiment, frame aggregation flexibly is easy to realize.Figure 35 shows encapsulation one or more mac frames (or burst) in an aggregate frame.Frame aggregation can be encapsulated in one or more mac frames (or burst) 3510 in the aggregate frame 3520, wherein can add header-compressed, will be elaborated to this below.Polymerization mac frame 3520 formation PSDU (that is, and PLCPSDU) 3530, can be used as a PPDU and send.Aggregate frame 3520 can containing type be the frame (or burst) 3510 after the encapsulation of data, management or control.When the needs privacy, can encrypt frame payload.The mac frame header of encrypted frame is " being under the plaintext state (in the clear) " transmission.

Aforesaid this mac layer frame polymerization can be transferred to identical recipient STA with frame under the situation that does not have IFS or BIFS (the burst frame interbody spacer will further describe below).In some applications, expectation makes AP not have under the situation of IFS a plurality of frames or aggregate frame to be sent to a plurality of recipient STA.Can realize this point by the SCHED frame that use describes below.The time started of a plurality of TXOP of SCHED frame definition.When AP carries out back-to-back (back-to-back) when transmission to a plurality of recipient STA, can be without lead code and IFS.This is called as the PPDU polymerization, to be different from the frame aggregation of MAC layer.

It is lead code that an exemplary polymerization mac frame transmission (being PPDU) begins the place, be that MIMO OFDM PLCP header (comprises signal field then, this signal field can comprise two fields: signal 1 and signal 2), the back is a MIMO OFDM training symbol (if any) again.Further describe exemplary PPDU form below in conjunction with Figure 49-52.The polymerization mac frame neatly polymerization to send to one or more frames or the burst of identical recipient STA.(the SCHED message that describes in detail below allow will TXOP carry out polymerization) from AP to a plurality of recipient STA.For the quantity of polymerisable frame and burst, without limits.Full-size for the aggregate frame of establishing through consultation can be restricted.Typically, first frame in the aggregate frame and last frame may be the bursts of creating for efficient package.When the Frame after several encapsulation was included in the aggregate frame, the mac header of data and QoS Frame can compress, and was as described below.

By using frame aggregation flexibly, transmit leg MAC can reduce PHY and PLCP expense and idling cycle as possible.Can be by frame being carried out polymerization eliminating interFrameGap and PLCP header, and frame burst flexibly, to take the free space among the TXOP fully, realize this point.In a kind of example technique, based on current data rate and distributed or based on duration of TXOP of competition, the calculating of MAC elder generation will offer the byte number of PHY.Then, can be with the packing of the mac frame behind the complete sum burst, to take whole TXOP.

If complete frame can not be contained in the remaining space among the TXOP, then MAC can carry out burst with next frame, to take remainder bytes as much as possible among this TXOP.For package efficiently, can at random carry out burst to frame.In one exemplary embodiment, this any burst will be subjected to the restriction of maximum 16 bursts of every frame.In the embodiment that replaces, can not need this restriction.The residue of mac frame (a plurality of) burst can send in next TXOP.In TXOP subsequently, if desired, MAC can give the not burst of the frame of complete transmission higher priority.

The polymerization header that describes in detail below (being 2 bytes in this embodiment) is inserted into the mac header of each encapsulated frame (or burst), and encapsulated frame (or burst) is inserted in the aggregate frame.Length field in the polymerization header represents to encapsulate the length (unit is a byte) of back mac frame, and is used for extracting frame (and burst) by receiver from aggregate frame.The size (quantity of OFDM symbol) of the PPDU size field regulation MIMO OFDM PPDU transmission in the signal field of being advised, and the length of the mac frame after each encapsulation is indicated by the polymerization header.

The header-compressed of encapsulated frame

Figure 36 shows a traditional mac frame 3600, and it comprises mac header 3660, and what follow later is frame 3650 (can comprise a variable number N byte) and frame check symbol (FCS) 3655 (in this embodiment, being 4 bytes).The prior art mac frame form is described in detail in 802.11e.Mac header 3660 comprises: frame control field 3610 (2 bytes), duration/id field 3615 (2 bytes), sequential control field 3635 (2 bytes) and QoS control field 3645 (2 bytes).In addition, also comprise four address fields: address 1 3620, address 2 3625, address 3 3630 and address 43640 (each all is 6 bytes).Also these addresses can be called TA, RA, SA and DA.TA is a transmitter station address, and RA is the destination address, and SA is a source station address, and DA is the address, point of destination.

When comprising several encapsulation of data frame in the aggregate frame, the mac header of data and QoS Frame can be compressed.For example, Figure 37-39 shows the mac header after the compression of QoS Frame.Note that FCS calculates according to the mac header after the compression and (encryption or unencrypted) payload.

Shown in Figure 37-39, when with MIMO data PPDU (type 0000) transmit frame, in the mac header 3660 of mac frame 3600, introduce a polymerization header fields, thereby create the mac frame after the encapsulation, promptly 3705,3805 or 3905.Mac header comprises the polymerization header fields, is called as the mac header (promptly 3700,3800 or 3900) of expansion.Can be aggregated to the management after one or more encapsulation, control and/or Frame (comprising the QoS data) in the mac frame after the polymerization.When using data-privacy, can encrypt the payload of data or QoS Frame.

For each frame (or burst) that is inserted in the aggregate frame (being respectively 3705,3805 or 3905), insert polymerization header 3710.Header-compressed is indicated by the polymerization header type field of describing in detail below.The frame header of data and QoS Frame can compress, to eliminate redundant field.The aggregate frame 3705 that provides among Figure 37 shows a kind of unpressed frame, and it comprises all four addresses and duration/id fields.

After sending a unpressed aggregate frame, other aggregate frame just needn't identify dispatching station and destination address, because they are identical.Therefore, can omit address 1 3620 and address 2 3625.For the subsequent frame in the aggregate frame, needn't comprise duration/id field 3615.Duration can be used to set NAV.Duration/id field as the case may be and by the heavy duty.In polling message, it comprises inserts ID (AID).In other message, identical field indicates the duration that is used to set NAV.Corresponding frame 3805 has been shown among Figure 38.

When source address and address, point of destination comprise identical information, can provide further compression.In this case, address 3 3630 and address 4 3640 also can be omitted, thereby obtain frame shown in Figure 39 3905.

When field was removed, in order to decompress, receiver can will insert in this aggregate frame from the respective field of last header (after decompression).In this embodiment, first frame in the aggregate frame always is to use unpressed header.The deciphering of payload may be from some fields of mac header, and these fields may be removed for ease of header-compressed.After the decompression of frame header, can offer decryption engine to these fields.Length field is used for extracting frame (and burst) from aggregate frame by receiver.Length field indicates the length (unit is a byte) of the frame with header compression.

After extracting, remove the polymerization header fields.Then, the frame after decompressing is delivered to decryption engine.In decrypting process, the field in (after the decompression) mac header need be carried out the message integrity checking.

Figure 40 has provided an exemplary polymerization header 3710.For the one or more frames that in MIMO data PPDU, send (encryption, or unencrypted), be that each frame (or burst) header adds the polymerization header.This polymerization header comprises the polymerization header type field 4010 (be used for expression and whether adopted header-compressed and which kind of type) of one 2 bit and the length field 4030 of one 12 bit.Type 00 frame does not adopt header-compressed.Type 01 frame has been removed duration/ID, address 1 and address 2 fields.Class1 0 frame has the removal field identical with type 01 frame, has removed address 3 and address 4 fields in addition.Length field 4030 in the polymerization header indicates the length of the frame with header compression, and unit is a byte.2 bits 4020 are reserved.Summed up the polymerization header type in the table 2.

Table 2. polymerization header type

Bit 0	Bit 1	The meaning
			0	0	Not compression
0	1	Duration/ID, address 1 and address 2 fields have been removed
			1	0	Duration/ID, address 1, address 2, address 3 and address 4 fields have been removed
1	1	Reserve

In this exemplary embodiment, all management frames that encapsulate in the aggregate frame and control frame adopt unpressed frame header, and its polymerization header type is 00.Following management frames can be encapsulated in the aggregate frame with Frame together: related request, associated response, related request again, associated response, probe requests thereby, probe response, disassociation, authentication and releasing authentication again.Following control frame can be encapsulated in the aggregate frame with Frame: BlockAck (piece affirmation) and BlockAckRequest (piece is confirmed request).In other embodiments, can encapsulate the frame of any kind.

The self adaptation coordination function

Self adaptation coordination function (ACF) is the extended version of HCCA and EDCA, and it can realize flexibly, the operation of efficient, low delay scheduling, is suitable for the operation of the high data rate supported by MIMO PHY.Figure 41 has provided an exemplary embodiment of the scheduling access period frame (SCAP) that uses in ACF.Use SCHED message 4120, AP can dispatch one or more AP-STA, STA-AP or STA-STA TXOP simultaneously in the cycle of scheduling access period 4130 by name.These transmission through scheduling are identified as the transmission 4140 of having dispatched.SCHED message 4120 has replaced traditional HCCA poll of describing in detail above.In this exemplary embodiment, the maximum permissible value of SCAP is 4 milliseconds.

For ease of explanation, Figure 41 has provided exemplary scheduled transmissions 4140, and it comprises that AP transmits 4146 to AP transmission 4144 and STA to STA to STA transmission 4142, STA.In this embodiment, AP sends 4142A to STA B, then, sends 4142B to STA D, sends 4142C to STA G again.Note that between these TXOP and needn't introduce the gap that because for each frame, information source (AP) is identical.When information source changes, show gap between the TXOP (below exemplary clearance gap is described in further detail).In this embodiment, transmit after 4142 to STA at AP, STA C sends 4144A to AP, and then, behind a gap, STA G sends 4144B to AP, and through a gap, STA E sends 4144C to AP again.Then, a point-to-point TXOP 4146 is dispatched.In this case, STAE is information source (sending to STAF), so, if the STAE transmitting power is constant, then do not need to introduce the gap, otherwise, the BIFS gap can be used.Can other STA be dispatched to the STA transmission, but do not show these in this embodiment.According to any order, can dispatch any combination of TXOP.The order of shown TXOP type is exemplary convention.In order to reduce required gap number, expectation can be dispatched TXOP, and still, this not necessarily.

Scheduling access period 4130 also can comprise: in the FRACH cycle 4150, be exclusively used in quick Random Access Channel (FRACH) transmission (wherein, STA can send request for allocation); And/or in 4160 cycles of MIMO OFDM EDCA, wherein MIMO STA can use the EDCA process.These access periods based on competition are subjected to the protection of the NAV that sets for SCAP.In 4160 cycles of MIMO OFDM EDCA, MIMO STA uses the EDCA process to insert medium, and needn't be at war with traditional STA.MIMO PLCP header (below further describe) is used in transmission in each shielded competing cycle.In this embodiment, AP does not provide TXOP scheduling in shielded competing cycle.

When only having MIMO STA, the NAV of SCAP can set (following also the SCHED frame can be described in further detail) by the duration field in the SCHED frame.Alternatively, if wish protected traditional STA influence of avoiding, AP also can be provided with CTS-to-Self 4110 before SCHED frame 4120, thereby was the SCAP establishment NAV at all STA places among the BSS.

In this embodiment, MIMO STA observes the SCAP border.Last STA that in SCAP, sends must be before SCAP finishes its TXOP of termination PIFS duration at least.MIMO STA also observes the TXOP border of scheduling, and finishes its transmission before the TXOP that is distributed finishes.The STA of like this, follow-up scheduling just can begin its TXOP under for idle situation needn't detecting channel.

SCHED message 4120 definition dispatch lists.The assignment information of TXOP (AP-STA, STA-AP and/or STA-STA) is included in the CTRLJ item interior (following detailed description is 4515-4530) in the SCHED frame in Figure 45.SCHED message also can define: the part of SCAP 4100 is exclusively used in FRACH 4150, if any; And, the protected part of EDCA operation 4160, if any.If do not comprise the TXOP assignment information through scheduling in the SCHED frame, then the NAV that sets for SCAP reserves whole SCAP and is used for EDCA transmission (comprising any FRACH), avoids the influence of traditional STA to protect it.

Can indicate in the ACF ability item scheduling that allowed in the SCAP or based on the maximum length of the TXOP of competition.In this embodiment, the length of SCAP does not change in a beacon interval.This length can be indicated in ACF ability item.An exemplary ACF item comprises: SCAP length (10 bit), maximum SCAPTXOP length (10 bit), GIFS duration (4 bit) and FRACH response (4 bit).SCAP length is represented the length of SCAP in the current beacon interval.This field is that unit encodes with 4 μ s.Maximum SCAPTXOP length represents that the maximum in the SCAP allows TXOP length.This field is that unit encodes with 4 μ s.The GIFS duration be continuous through the protection between the STA TXOP of scheduling at interval.This field is that unit encodes with 800ns.The FRACH response is that unit represents with SCAP.AP must use FRACH PPDU, by the TXOP of process scheduling is provided to STA in FRACH response SCAP, response is made in the request of receiving.

Figure 42 has provided an example that SCAP and HCCA and EDCA is combined use.In any beacon interval (4210A-C represents with beacon), AP fully can be flexibly, will intert with 802.11e CAP, MIMO OFDM SCAP based on the duration of the access of EDCA competition adaptively and be in the same place.

Therefore, use ACF, AP can be as working in HCCA, and still, it can also be the SCAP assignment period.For example, AP can as being the operated allocated CAP of poll, perhaps, can be the operated allocated SCAP of scheduling as use CFP and CP in PCF in HCCA.As shown in figure 42, in a beacon interval, AP can use any combination based on the cycle of access (EDCA) 4220A-F, the CAP 4230A-F of competition and SCAP 4100A-I.(for the sake of simplicity, the example among Figure 42 does not show any CFP.) AP is based on its dispatching algorithm and observed result that medium are taken thereof, adjusts the ratio of the medium that taken by dissimilar access mechanisms.Can adopt any dispatching technique.AP determines whether the QoS stream of being admitted is satisfied with, and can use other observed results, comprises that the medium of measuring take situation, adjust.

HCCA and related CAP thereof have been described above.Provided an illustrative CAP 4230 among Figure 42.That AP TXOP 4232 follows later is poll 4234A.HCCA TXOP4236A follows in poll frame 4234A back.Send another poll 4234B, that it is followed later is another corresponding HCCA TXOP 4236B.

EDCA has been described above.Provided an illustrative EDCA 4220 among Figure 42.Show various EDCA TXOP 4222A-C.Omitted CFP in this example.

The form that SCAP 4100 as shown in figure 42 can adopt Figure 41 to describe in detail comprises optional CTS-to-Self4110, SCHED 4120 and scheduling access period 4130.

AP uses 802.11 business transferring Indication message (DTIM) message as described below to indicate scheduling operation.DTIM comprises the bitmap that inserts ID (AID), and another STA among this AP or the BSS has laid in data for it.Use DTIM, notify all STA that possess the MIMO ability after beacon, to keep wake-up states.In the BSS that traditional and MIMO STA exist, immediately following after beacon, the traditional STA of scheduling earlier.After conventional transmission, send SCHED message immediately, it shows the composition of dispatching access period.The STA that possesses the MIMO ability that does not dispatch in the particular schedule access period can sleep in remaining SCAP, wakes up then and monitors follow-up SCHED message.

Adopt ACF, can realize various other operator schemes.Figure 43 shows an exemplary operation, and wherein, each beacon interval comprises a plurality of SCAP 4100, wherein is interspersed with the access period 4220 based on competition.Under this pattern, shared medium wherein, is dispatched MIMO QoS stream during SCAP liberally, and the non-QoS stream of MIMO uses competing cycle with traditional STA (if present) simultaneously.The cycle of interting is realized the low delay service to MIMO and traditional STA.

As mentioned above, in SCAP, before the SCHED message CTS-to-Self can be arranged, be used to be protected from the influence of traditional STA.If there is no traditional STA does not then need CTS-to-Self (or other traditional cleaning signals).Beacon 4210 can be set a long CFP, avoids the influence of traditional STA of any arrival to protect all SCAP.CP when beacon interval finishes makes newly arrived traditional STA can insert medium.

Use exemplary operation shown in Figure 44, under the situation that a large amount of MIMO STA are arranged, can realize the low delay operation of optimizing.In this embodiment, suppose that traditional STA (if any) only needs Limited resources.AP sends a beacon, thereby sets up long CFP 4410 and short CP 4420.What beacon 4210 was followed later is any broadcast/multi broadcast message that is used for traditional STA.Then, lean against privately SCAP 4100 is dispatched.This operator scheme also provides the power management of optimizing, because STA need periodically be waken up in order to listen to SCHED message, and, if in current SCAP, be not scheduled, then can sleep in the SCAP interval.

FRACH that comprises in the scheduling access period 4130 by SCAP 4100 or MIMO EDCA cycle, provide the access that is used for MIMO STA based on protected competition.In CP 4420, traditional STA can carry out based on the access of competing medium.

After the transmission of SCHED frame, can dispatch transmission from the continuous scheduling of AP.The SCHED frame can send with lead code.Follow-up scheduling AP transmission can send under the situation of lead code not having.(can send the designator that is used to represent whether to comprise lead code).An exemplary PLCP lead code is described in further detail below.In this exemplary embodiment, the STA of scheduling is transmitted under the situation of lead code and begins.

Mistake is recovered

Recover in order to receive the mistake from SCHED, AP can use various processes.For example, if a STA can't decode to a SCHED message, then it can not utilize its TXOP.If the TXOP of a scheduling did not begin in the time started of being distributed, send during PIFS after then beginning by TXOP in the not scheduling of usefulness, AP can start recovery.AP can use the TXOP cycle of the not scheduling of usefulness as a CAP.In this CAP, AP can send signal, perhaps STA of poll to one or more STA.Poll can be at STA or another STA of the TXOP that has missed scheduling.Before next scheduling TXOP, this CAP finishes.

When the TXOP of a scheduling finishes too early, also can use identical process.Send during by the PIFS after last end of transmission in the TXOP of scheduling, AP can begin to recover.As mentioned above, AP can use scheduling TXOP do not use the cycle as CAP.

Shielded competition

As mentioned above, SCAP also can comprise: be exclusively used in the part of FRACH transmission and/or the part that MIMO STA can use the EDCA process therein.These access periods based on competition can be protected by the NAV that sets for SCAP.

Shielded competition is asked so that assistance AP dispatches by allowing STA indication TXOP, thereby replenishes the low delay scheduling operation.In cycle, MIMOOFDM STA can use the access (avoiding and traditional STA competition) based on EDCA to come transmit frame at shielded EDCA.Use conventional art, STA can indicate the TXOP duration to ask or buffer state in the 802.11e QoS control field in mac header.But FRACH provides a kind of more efficient means of identical function.In cycle, STA can use the competition of the Aloha formula of gapization at FRACH, access channel in the FRACH of fixed dimension time slot.FRACH PPDU can comprise that the TXOP duration asks.

In this exemplary embodiment, MIMO PLCP header is used in the transmission of MIMO frame, will be elaborated to this below.Under the situation that has non-MIMO STA; because traditional 802.11b, 802.11a and 802.11g STA can only decode to signal 1 field (being described in detail below in conjunction with Figure 50) of MIMO PLCP header; so the MIMO frame must send having under the situation of protection.When traditional and MIMO STA exist, use the STA of EDCA access procedure can use traditional RTS/CTS sequence to protect.Tradition RTS/CTS refers to and uses traditional lead code, PLCP header and mac frame form to transmit RTS/CTS.

The protection mechanism that the MIMO transmission also can use 802.11e HCCA to provide.Therefore, use control access period (CAP), the transmission from AP to STA, the polled transmission of (using the direct link agreement) from STA to AP or from STA to STA can be protected.

AP also can use traditional CTS-to-Self, and protection MIMO scheduling access period (SCAP) is avoided the influence of traditional STA.

When an AP determines that all STA that exist among the BSS can both decode to MIMO PLCP header, indicate this point in its MIMO ability item in beacon.Such BSS is called as MIMO BSS.

In MIMO BSS, under EDCA and HCCA, according to the aging rule of MIMO OFDM training symbol, MIMO PLCP header and MIMO OFDM training symbol are used in the frame transmission.MIMO PLCP is used in transmission among the MIMO BSS.

The interFrameGap that reduces

Describe the various technology that are generally used for reducing interFrameGap above in detail.Here provide the example of the interFrameGap in this exemplary embodiment of several reductions.For scheduled transmission, the time started of TXOP indicates in SCHED message.The accurate time started that transmit leg STA can indicate in SCHED message, begin its scheduling TXOP, and needn't determine that medium are idle.As mentioned above, the AP of the continuous scheduling in SCAP transmission is not have to send under the situation of minimum IFS.

In this exemplary embodiment, the STA of continuous scheduling transmission (from different STA) is to send under the situation of at least one GIFS at IFS.The default value of GIFS is 800ns.Can select bigger value, reach the value of the burst IFS (BIFS) that defines below at most.The value of GIFS can indicate in ACF ability item, as mentioned above.Other embodiment can adopt any value of GIFS and BIFS.

Continuous N IMO OFDM PPDU transmission (TXOP burst) from identical STA is separated with BIFS.In the time of in being operated in the 2.4GHz frequency band, BIFS equals 10 μ s, and MIMO OFDM PPDU does not comprise the ofdm signal expansion of 6 μ s.In the time of in being operated in the 5GHz frequency band, BIFS is 10 μ s.In an alternative embodiment, BIFS can be set as big or smaller value, comprise 0.For recipient STA automatic gain control (AGC) can be changed, when the transmitting power of transmit leg STA changes, can use gap greater than 0 between transmission.

Need not be to use MIMO OFDMPPDU to send from the frame of response at once of recipient STA.On the contrary, they are to use conventional P PDU to send, that is, and and clause 19 in the 2.4GHz frequency band or the clause 17 in the 5GHz frequency band.Provide several examples below, illustrate how tradition and MIMO OFDM PPDU are multiplexed on the medium.

At first, consider a traditional RTS/CTS, MIMO OFDM PPDU burst is followed in its back.This transfer sequence is as follows: traditional RTS-SIFS-traditional CT S-SIFS-MIMOOFDM PPDU-BIFS-MIMO OFDM PPDU.In 2.4GHz, traditional RTS or CTS PPDU use the ofdm signal expansion, and SIFS is 10 μ s.In 5GHz, do not have the OFDM expansion, but SIFS is 16 μ s.

Secondly, consider an EDCA TXOP who uses MIMO OFDM PPDU.This transfer sequence is as follows: MIMO OFDM PPDU-BIFS-traditional B lockAckRequest-SIFS-ACK.For suitable access style (AC), use the EDCA process to obtain EDCATXOP.As mentioned above, the access style of EDCA definition can use different parameters to each AC, as AIFS[AC], CWmin[AC] and CWmax[AC].Traditional BlockAckRequest sends under the situation that signal extension or 16 μ s SIFS are arranged.If send in the aggregate frame of BlockAckRequest in MIMO OFDM PPDU, then do not have ACK.

The 3rd, consider the TXOP of continuous scheduling.Transfer sequence is as follows: STA AMIMOOFDM PPDU-GIFS-STA B MIMO OFDM PPDU.If the maximum that the PPDU transfer ratio is distributed allows the TXOP time short, so, after STA A MIMO OFDMPPDU transmission, may have one period free time.

As mentioned above, encoded the decoding and the demodulation of OFDM transmission forced extra processing demands at recipient STA place.In order to solve this point, 802.11a and 802.11g allow recipient STA before must sending ACK to be arranged the additional time.In 802.11a, the SIFS time is set as 16 μ s.In 802.11g, the SIFS time is set as 10 μ s, but has introduced additional 6 μ s ofdm signals expansion.

According to identical logic, because the decoding of MIMO OFDM transmission and demodulation meeting cause more processing burden, so, can design an embodiment who improves SIFS or ofdm signal expansion, this can further lower efficiency.In this exemplary embodiment, by piece ACK and the delay block affirmation mechanism of expansion 802.11e,, needn't need ACK at once for all MIMO OFDM transmission.What replace increase SIFS or signal extension is eliminated signal extension, and for a lot of situations, the required frame interbody spacer between the transmission to have obtained reducing or eliminating continuously, thereby raises the efficiency.

SCHED message

Figure 45 shows SCHED message, it is introduced in conjunction with Figure 41 above, also will be described in further detail it below.SCHED message 4120 is polling messages more than, and it distributes one or more AP-STA, STA-AP and STA-STA TXOP in the duration of scheduling access period (SCAP).Use SCHED message, can reduce poll and competition expense, and, unnecessary IFS eliminated.

SCHED message 4120 has defined the dispatch list of SCAP.SCHED message 4120 comprises mac header 4510 (in this exemplary embodiment, being 15 bytes).In this exemplary embodiment, CTRL0, CTRL1, CTRL2 and CTRL3 section (are typically expressed as CTRLJ here, J can be 0 to 3, respectively an expression section 4515-4530) in each all be elongated, can be respectively with 6,12,18 and 24Mbps send their (when existing).

This exemplary mac header 4510 comprises: frame control 4535 (2 bytes), duration 4540 (2 bytes), BSSID 4545 (6 bytes), power management 4550 (2 bytes) and MAP 4555 (3 bytes).The bit 13-0 of duration field 4540 indicates the length of SCAP, and unit is a microsecond.Duration field 4540 is used for setting NAV for the duration of SCAP by the STA that can carry out MIMO OFDM transmission.When having traditional STA among the BSS, AP can use other means to protect SCAP, for example, and traditional CTS-to-Self.In this exemplary embodiment, the maximum of SCAP is 4 milliseconds.BSSID field 4545 sign AP.

Power management field 4550 has been shown among Figure 46.Power management 4550 comprises: SCHED counting 4610, reserved field 4620 (2 bits), transmitting power 4630 and received power 4640.AP transmitting power and AP received power show that in power management field the STA received power level is measured in STA.

The SCHED counting is a field (being 6 bits in this embodiment) that all increases progressively when each SCHED transmits.SCHED counting resets when each beacon transmissions.The SCHED counting can be used for various purposes.For example, the electricity-saving function that uses the SCHED counting is described below.

The used transmitted power level of transmitting power field 4630 expression AP.In this exemplary embodiment, the following coding of this 4 bit field: on behalf of transmitted power level, the channel that indicates in the item of information for beacon, this value be lower than the quantity of the 4dB stride of maximum transmit power level (unit is dBm).

The received power level of received power field 4640 expression AP place's expectations.In this exemplary embodiment, the following coding of this 4 bit field: on behalf of received power level, this value be higher than the minimum receiver sensitivity level (quantity of 4dB stride 82dBm).Based on the received power level at STA place, STA can followingly calculate its transmitted power level: STA transmitting power (dBm)=AP transmitting power (dBm)+AP received power (dBm)-STA received power (dBm).

In this exemplary embodiment, in the STA-STA transmission course of scheduling, control section sends with the launching electrical level that can decode at AP and recipient STA place.From the power control report of AP or the power management field 4550 in the SCHED frame, make STA can determine can be at the AP place to the control section required transmitted power level of decoding.In conjunction with Figure 22 this general aspect has been described above.STA-STA transmission for scheduling when the required power of decoding at the AP place is different from the power of decoding required at recipient STA place, sends PPDU with the higher person in these two power levels.

MAP field 4555 shown in Figure 47 is illustrated in access period and the duration thereof that whether exists during the SCAP based on protected competition.MAP field 4555 comprises: FRACH counting 4710, FRACH skew 4720 and EDCA skew 4730.This exemplary FRACH counting 4710 (4 bits) are the quantity (10 bits) that is offset the FRACH time slot that 4720 places begin to dispatch at FRACH.Each FRACH time slot is 28 μ s.If the FRACH count value is 0, then representing does not have the FRACH cycle in the current scheduling access period.EDCA skew 4730 is the beginnings in protected EDCA cycle.This exemplary EDCA skew 4730 is 10 bits.FRACH skew 4720 and EDCA skew 4730 all are that the beginning of transmitting from the SCHED frame is a unit with 4 μ s.

SCHED message 4120 is to be sent out away as a special SCHED PPDU 5100 (type 0010), below in conjunction with Figure 51 it is elaborated.Whether having CTRL0 4515, CTRL1 4520, CTRL2 4525 and CTRL34530 section and length thereof in the SCHED message 4120, is to indicate in the signal field (5120 and 5140) at the PLCP of SCHED PPDU 5100 header.

Figure 48 shows and is used for the SCHED control frame that TXOP distributes.Among 4530 sections of CTRL0 4515, CTRL1 4520, CTRL2 4525 and the CTRL3 each all has length variable, and each comprises 0 or a plurality of assignment item (being respectively 4820,4840,4860 and 4880).Each CTRLJ section is added with FCS (being respectively 4830,4850,4870 and 4890) and 6 tail bits (not shown)s of one 16 bit.For CTRL0 section 4515, FCS is at mac header 4510 and CTRL0 assignment item 4820 and calculate (so, show, before mac header is added on CTRL04515) in Figure 48 arbitrarily.In this exemplary embodiment, even do not comprise assignment item in the CTRL0 section, also comprise the FCS 4830 of CTRL0 4515.

Just describe in detail as this paper, AP sends the assignment information that AP-STA, STA-AP and STA-STA transmit in the SCHED frame.Assignment item to different STA sends in the CTRLJ section, is represented by the STA in the SCHED speed field of the PLCP header of its transmission.Note that CTRL0 to CTRL3 corresponding to the robustness of successively decreasing.Each STA begins the PLCP header of SCHED PPDU is decoded.Signal field indicates the existence and the length thereof of CTRL0, CTRL1 among the SCHED PPDU, CTRL2 and CTRL3 section.When the STA receiver begins mac header and CTRL0 section are decoded, each assignment item is decoded up to FCS, it continues decode CTRL1, CTRL2 and CTRL3 subsequently, can't the CTRLJ section place that its FCS verifies stopped.

As shown in table 3, defined five kinds of assignment item.Several assignment item can be bundled in each CTRLJ section.Each assignment item indicates the maximum that transmit leg STA inserts the TXOP of the time started of TXOP of ID (AID), recipient STAAID, scheduling and scheduling and allows length.

Table 3. assignment item type

Type (3 bit)	The assignment item type	Field (bit length)	Total bit length
Type (3 bit)	The assignment item type	Field (bit length)	Total bit length	000	Single worker AP-STA	Lead code existence (1) AID (16) start offset (10) TXOP duration (10)	40
001	Single worker STA-AP	AID (16) start offset (10) TXOP duration (10)	39	000	Single worker AP-STA		40
001	Single worker STA-AP	AID (16) start offset (10) TXOP duration (10)	39	010	Duplex AP-STA	Lead code existence (1) AID (16) start offset (10) AP TXOP duration (10) STA start offsets (10) STA TXOP duration (10)	60

Type (3 bit)	The assignment item type	Field (bit length)	Total bit length
Type (3 bit)	The assignment item type	Field (bit length)	Total bit length	011	Single worker STA-AP	Send AID (16) and receive AID (16) start offset (10) maximum PPDU sizes (10)	55
100	Duplex STA-STA	The maximum PPDU size (10) of maximum PPDU size (10) STA2 start offset (10) STA2 of AID1 (16) AID2 (16) STA1 start offset (10) STA1	75	011	Single worker STA-AP		55

In continuous transmission, can eliminate lead code from AP.If AP does not send lead code for the AP transmission of scheduling, then lead code existence bit is made as 0.For example, the benefit of eliminating lead code is, when AP has low bandwidth to several STA, low delay stream, for example, in BSS with a plurality of ip voices (VoIP) stream.Therefore, the SCHED frame can be realized the polymerization (that is, above-mentioned PPDU polymerization) of the transmission from AP to several recipient STA.The frame that above-mentioned frame aggregation allows to mail to a recipient STA carries out polymerization.

The start offset field is the integral multiple of 4 μ s, is the time started of quoting from SCHED message lead code.AID is the access ID of (a plurality of) STA of being distributed.

For all the assignment item types except that the STA-STA transmission of scheduling, TXOP duration field is that the maximum of the TXOP of scheduling allows length, is the integral multiple of 4 μ s.The actual PPDU size of the PPDU that is sent is pointed out (below will further describe) in signal 1 field of PPDU.

For the STA-STA transmission (assignment item type 011 and 100) of scheduling, maximum PPDU size field also is that the maximum of the TXOP of scheduling allows length, is the integral multiple of 4 μ s, still, also can use other rules.In this exemplary embodiment, for the STA-STA transmission of scheduling, TXOP only comprises a PPDU.Recipient STA uses the maximum PPDU size of indicating in the assignment item, determines the quantity (because the PPDU size field is replaced by the request field in the signal 1, describing in detail below in conjunction with Figure 51) of OFDM symbol among the PPDU.If the use of STA-STA stream has the standard protection OFDM symbol of (GI) at interval, then recipient STA sets the PPDU size of the TXOP of scheduling for the maximum PPDU size of distributing indication in the item.Have the OFDM symbol that shortens GI if STA-STA stream uses, then recipient STA is by amplifying maximum PPDU size field and rounding up to determine the PPDU size with the factor 10/9.Transmit leg STA can send and compare the short PPDU of maximum PPDU size that is distributed.The PPDU size is the length of mac frame after receiver provides polymerization not.The length of encapsulated frame is included in the polymerization header of each mac frame.

The side of emission is included in the assignment item with recipient STA, can makes the STA power saving that in SCAP, is not scheduled and sends or receive.The SCHED count area of introducing above recalling.The maximum that each assignment information of being dispatched by SCHED message indicates the TXOP of the time started of TXOP of transmit leg STAAID, recipient STAAID, scheduling and scheduling allows length.SCHED counting increases progressively when each SCHED transmission, and resets when each beacon transmissions.STA can indicate power-save operation to AP, and therefore is provided concrete SCHED count value, and during this period, they can be distributed transmission with being scheduled or be received TXOP by AP.Then, STA can periodically wake up, and just monitors the SCHED message with suitable SCHED counting.

The PPDU form

Figure 49 shows traditional 802.11PPDU 4970, and it comprises the afterbody 4950 and the elongated filling information 4955 of PLCP lead code 4975 (12 OFSM symbols), PLCP header 4910, elongated

PSDU

4945,6 bits.The part 4960 of PPDU 4970 comprises: signal field (1 OFDM symbol) sends with speed=1/2 with BPSK; And elongated data field 4985, send with modulation format that indicates in the signal 4980 and speed.PLCP header 4910 comprises the service field 4940 (be included in the data 4985, send according to this form) of

signal

4980 and 16 bits.Signal field 4980 comprises: speed 4915 (4 bit), reserved field 4920 (1 bit), length 4925 (12 bit), parity bit 4930 and afterbody 4935 (6 bit).

The signal field (below will describe in detail) of the expansion in this exemplary PLCP header (below will describe in detail) keeps backward compatibility with the signal field 4980 of tradition 802.11.The not usefulness value of the speed field 4915 in traditional signal field 4980 is set, to define new PPDU type (following detailed description).

Several new PPDU types have been introduced.In order to keep backward compatibility with traditional STA, the speed field in the signal field of PLCP header is modified to speed/type field.Speed be not designated as the PPDU type with value.The PPDU type is the existence and the length thereof of index signal field extension specification signal 2 also.The new value of speed/type field defines in table 4.These values of speed/type field define for traditional STA.Therefore, traditional STA can abandon the decoding to PPDU after signal 1 field successfully being decoded and find undefined value in the speed field.

Perhaps, the reserved place in the legacy signal field can be made as " 1 ", mail to the MIMO OFDM transmission of a New type of S TA with indication.Recipient STA can ignore this reserved place, and continues to attempt signal field and remaining transmission are decoded.

Receiver can be determined the length of signal 2 fields based on the PPDU type.FRACHPPDU has only occurred once in the specified portions of SCAP, and needs only to be decoded by AP.

Table 4.MIMO PPDU type

Speed/type (4 bit)	MIMO PPDU	Signal	2 field lengths (OFDM symbol)
Speed/type (4 bit)	MIMO PPDU	Signal	2 field lengths (OFDM symbol)	0000	MIMO BSS IBSS or MIMOAP transmission (except the SCHED PPDU)	1
0010	MIMO BSS SCHED PPDU	1		0000		1
0010	MIMO BSS SCHED PPDU	1	0100	MIMO BSS FRACH PPDU	2

Figure 50 shows the MIMO PPDU form 5000 that is used for transfer of data.PPDU 5000 is called as PPDU type 0000.PPDU 5000 comprises: PLCP lead code 5010, signal 1 5020 (1 OFDM symbol), signal 2 5040 (1 OFDM symbol), training symbol 5060 (0,2,3 or 4 symbol) and elongated data field 5080.In this exemplary embodiment, PLCP lead code 5010 (if present) is 16 μ s.Send signal 1 5020 and signal 2 5040 with PPDU control section speed and modulation format.Data 5080 comprise: service 5082 (16 bits); Feedback 5084 (16 bits); Elongated PSDU 5086; Afterbody 5088 (each stream has 6 bits) wherein, is used different convolution chnnel codings to each stream; Elongated filling information 5090.Send data 5080 with PPDU control section speed and modulation format.

The MIMO PLCP header of PPDU type 0000 comprises: signal (comprising signal 1 5020 and signal 2 5040), service 5082 and feed back 5084 fields.Compare with traditional 802.11, service field is constant, and is to send with this data segment speed and form.

Feedback fields 5084 is to send with this data segment speed and form.This feedback fields comprises: ES field (1 bit), data rate vector feedback (DRVF) field (13 bit) and power control field (2 bit).

The ES field is indicated preferred guidance method.In this exemplary embodiment, when the ES bit is set up, select characteristic vector guiding (ES), otherwise, the selection spatial spread (SpatialSpreading, SS).

Data rate vector feedback (DRVF) field provides feedback to station, equity side, but this feedback is about the supporting rate on each of maximum four spatial models.

Clear and definite Rate Feedback makes the station can be fast and make the maximization of its transmission rate exactly, thereby improves system effectiveness greatly.The feedback of low delay is desirable.But the feedback chance needs not to be synchronous.Can obtain transmission opportunity by any way, for example, based on (being EDCA) of competition, (being HCF) or (being ACF) mode of scheduling of poll.Therefore, can between transmission opportunity and Rate Feedback, transmit the variable time amount.Based on the life-span of Rate Feedback, transmitter can be used avoidance mechanism, to determine transmission rate.

For the transport stream from STA A to STA B, the feedback that provided to STA A by STA B (front is described, for example, referring to Figure 24) is provided PPDU data segment rate adaptation.For ES or SS operator scheme, whenever STA B when STA A receives the MIMOOFDM training symbol, it all will estimate attainable data rate on each spatial flow.Any subsequent transmission stream from STA B to STA A, STA B is included in this estimated value in the DRVF field of feedback 5084.The DRVF field sends with data segment 5080 speed.

When STAB sends signal, which kind of transmission rate the DRVF that STA A receives from STA B based on it determines to use, and required avoidance mechanism when optionally considering to postpone.Signal field (following detailed description) comprises the DRV field 5046 of 13 bits, and this DRV field 5046 can be decoded recipient STA B to the frame that sends from STAA.DRV 5046 sends with control section speed.

The DRVF field is encoded, and it comprises: STR field (4 bit), R2 field (3 bit), R3 field (3 bit) and R4 field (3 bit).The STR field represents to flow 1 speed.With this code field is the STR value shown in the table 5.R2 represents to flow 1 STR value and flows difference between 2 the STR value.R2 value " 111 " expression stream 2 turn-offs.R3 represents to flow 2 STR value and flows difference between 3 the STR value.R3 value " 111 " expression stream 3 turn-offs.If R2=" 111 " then is made as R3 " 111 ".R4 represents to flow 3 STR value and flows difference between 4 the STR value.R4 value " 111 " expression stream 4 turn-offs.If R3=" 111 " then is made as R4 " 111 ".

When ES=0, promptly during spatial spread, the another kind of DRVF coding is as follows: the speed (4 bit) of fluxion amount (2 bit), each stream.The speed field of each stream is encoded as above-mentioned STR value.Remaining 7 bits are reserved.

Table 5.STR coding

The STR value	Encoding rate	Modulation format	The symbol of bit/each stream
The STR value	Encoding rate	Modulation format	The symbol of bit/each stream	0000	1/2	BPSK	0.5

The STR value	Encoding rate	Modulation format	The symbol of bit/each stream
The STR value	Encoding rate	Modulation format	The symbol of bit/each stream	0001	3/4	BPSK	0.75
0010	1/2	QPSK	1.0	0001	3/4	BPSK	0.75
0010	1/2	QPSK	1.0	0011	3/4	QPSK	1.5
0100	1/2	16QAM	2.0	0011	3/4	QPSK	1.5
0100	1/2	16QAM	2.0	0101	5/8	16QAM	2.5
0110	3/4	16QAM	3.0	0101	5/8	16QAM	2.5
0110	3/4	16QAM	3.0	0111	7/12	64QAM	3.5
1000	2/3	64QAM	4.0	0111	7/12	64QAM	3.5
1000	2/3	64QAM	4.0	1001	3/4	64QAM	4.5
1010	5/6	64QAM	5.0	1001	3/4	64QAM	4.5
1010	5/6	64QAM	5.0	1011	5/8	256QAM	5.0
1100	3/4	256QAM	6.0	1011	5/8	256QAM	5.0
1100	3/4	256QAM	6.0	1101	7/8	256QAM	7.0

Except DRVF, STA B also provides the power Control and Feedback to transmit leg STA A.This feedback is included in the power control field, and also sends with data segment speed.This field is 2 bits, and expression increases power or reduction power or keep power constant.Resulting transmitted power level is designated as the data segment transmitted power level.

Table 6 shows exemplary power control word segment value.The embodiment that replaces can adopt the power control field of different sizes, and the power adjustment of replacing.

Table 6. power control word segment value

The power control field	Implication
The power control field	Implication	00	No change
01	Power is increased 1dB	00	No change
01	Power is increased 1dB	10	Power is reduced 1dB

The power control field	Implication
The power control field	Implication	11	Reserve

For entire PP DU, transmitted power level remains unchanged.When data segment transmitted power level and open loop STA transmitting power (that is, AP is to the above-mentioned transport stream required power level of decoding) not simultaneously, send PPDU with the maximum in these two power levels.That is to say that the PPDU transmitted power level is the maximum in open loop STA transmitting power (dBm) and the data segment transmitting power (dBm).

In this exemplary embodiment, in first frame of any frame turnaround sequence, the power control field is made as " 00 ".In follow-up frame, its expression increases or reduces power according to the step-length of 1dB.Recipient STA will use this feedback information in all subsequent frame transmission of mailing to this STA.

Signal 1 5020 comprises: the afterbody 5030 of speed/type field 5022 (4 bit), reserved place 5024, PPDU size/request 5026 (12 bit),

parity bit

5028 and 6 bits.Signal 1 field 5020 is (in this exemplary embodiment, being 6Mbps) that send with control section speed and form.Speed/type field 5022 is set as 0000.Reserved place 5024 can be set as 0.

PPDU size/request 5026 has two effects, and this depends on transmission mode.In STA transmission and all AP transmission based on competition, this field is represented the PPDU size.Under this first kind of pattern, bit 1 expression PPDU has used the OFDM symbol of expansion, and bit 2 expression PPDU use has the OFDM symbol that shortens GI, and bit 3-12 represents the quantity of OFDM symbol.

In the non-AP STA transmission of scheduling, PPDU size/request 5026 expression requests.Under this second kind of pattern, bit 1-2 represents SCHED speed.The SCHED rate representation can be used to send to STA the SCHED field of the numbering the highest (0,1,2 or 3) of an assignment information.Between the training symbol transmission period from AP, each non-AP STA estimates that it can receive the speed of SCHED frame transmission from AP healthy and strongly.In the follow-up scheduled transmission from STA, this maximum allows speed to be included in the SCHED speed field.This field is decoded by AP.AP uses this information to come the follow-up TXOP of STA is dispatched, and definite CTRLJ (0,1,2 or 3), to be used for issuing these distribution to STA.

Under second kind of pattern, bit 3-4 represents qos field, the part of its sign TC 0 or 1 request (be 1/3rd multiple) (that is, 0%, 33%, 67%, 100%).Bit 5-12 represents the request length (in this exemplary embodiment, being the integral multiple of 16 μ s) of TXOP.

Signal 1 field 5020 is carried out verification by parity bits 5028, and finishes with 6 bit tail 5030 that are used for convolution coder.

The existence and the length thereof of signal 2 fields 5040 are indicated by the speed/type field in the signal 1 5,020 5022.Signal 2 fields 5040 are to send with control section speed and form.Signal 25040 comprises: reserved place 5042, training type 5044 (3 bit), data rate vector (DRV) 5046 (13 bit), parity bit 5048 and afterbody 5050 (6 bit).The training type field of 3 bits indicates the length and the form of MIMO OFDM training symbol.Bit 1-2 represents the quantity (0,2,3 or 4 OFDM symbol) of MIMO OFDM training symbol 5060.Bit 3 is training type fields: 0 expression SS, 1 expression ES.DRV 5046 is provided for each the speed in maximum four spatial models.DRV 5046 is identical with the coded system that DRVF adopts (to be included in the feedback 5084, as mentioned above).Signal 2 fields 5040 are carried out verification by 1 parity bit 5048, and finish with 6 bit tail 5050 that are used for convolution coder.

Figure 51 shows SCHED PPDU 5100 (speed/type=0010).SCHEDPPDU 5100 comprises: PLCP lead code 5110, signal 1 5120 (1 OFDM symbol), signal 2 5140 (1 OFDM symbol), training symbol 5160 (0,2,3 or 4 symbol) and elongated SCHED frame 5180.In this embodiment, when PLCP lead code 5110 exists, be 16 μ s.Signal 1 5020 and signal 2 5040 are to send with PPDU control section speed and modulation format.SCHED frame 5180 can comprise the above-mentioned various speed of describing in conjunction with ACF.

Signal 1 5120 comprises: speed/type 5122 (4 bit), reserved place 5124, CTRL0 size 5126 (6 bit), CTRL1 size 5128 (6 bit), parity bit 5130 and afterbody 5132 (6 bit).Speed/type 5122 is set as 0010.Reserved place 5124 can be set as 0.CTRL0 size 5126 indicates the segment length of the SCHEDPPDU that sends with minimum speed limit (being 6Mbps in this embodiment).This section comprises: the service field of PLCP header, mac header and CTRL0 section 5126.In this embodiment, this value is to encode with the integral multiple of 4 μ s.5128 expressions of CTRL1 size are with the segment length of the SCHEDPPDU of next higher rate (being 12Mbps in this embodiment) transmission.In this embodiment, this value is to encode with the integral multiple of 4 μ s.The CTRL1 size is " 0 " expression: do not have corresponding CTRL1 section among the SCHED PPDU.Signal 1 field 5120 is carried out verification by parity bit 5130, and finishes with 6 bit tail 5132 that are used for convolution coder.

Signal 2 5140 comprises reserved place 5142, training type 5144 (3 bit), CTRL2 size 5146 (5 bit), CTRL3 size 5148 (5 bit), FCS 5150 (4 bit) and afterbody 5152 (6 bit).Reserved place 5142 can be set as 0.Training type 5144 and the same (the training type 5044) that be 0000 appointment of PPDU type.

The segment length of the SCHED PPDU that CTRL2 size 5146 the following flank speeds of expression (being 18Mbps in this embodiment) send.In this embodiment, this value is to encode with the integral multiple of 4 μ s.The CTRL2 size is " 0 " expression: do not have corresponding CTRL2 section among the SCHED PPDU.5148 expressions of CTRL3 size are with the segment length of the SCHED PPDU of flank speed (being 24Mbps in this embodiment) transmission.In this embodiment, this value is to encode with the integral multiple of 4 μ s.The CTRL2 size is " 0 " expression: do not have corresponding CTRL3 section among the SCHED PPDU.

FCS 5150 calculates according to whole signal 1 and signal 2 fields.Signal 2 fields 5152 think that 6 bit tail 5152 that are used for convolution coder finish.

Figure 52 shows FRACH PPDU 5200 (speed/type=0100).FRACHPPDU 5200 comprises: PLCP lead code 5210, signal 15220 (1 OFDM symbol) and signal 25240 (2 OFDM symbols).In this exemplary embodiment, PLCP lead code 5210 (when existing) is 16 μ s.Signal 1 5220 and signal 2 5240 are to send with PPDU control section speed and modulation format.During the FRACH cycle in MIMO scheduling access period, STA sends FRACH PPDU 5200.The FRACH cycle is established by AP, so be known (as above describing in detail) for it.

Signal 1 5220 comprises: speed/type 5222 (4 bit), reserved place 5224, request 5226 (12 bits), parity bit 5228 and afterbody 5230 (6 bit).Speed/type 5222 is set as 0100.Reserved place 5224 can be set as 0.Request field 5226 and the same (5000) that are 0000 appointment of PPDU type are as above described in detail.Signal 1 field 5220 is tested by parity bit 5228, and finishes with 6 bit tail 5230 that are used for convolution coder.

Signal 2 5240 comprises reserved place 5242, source AID 5244 (16 bit), purpose AID5246 (16 bit), FCS 5248 (4 bit) and afterbody 5250 (6 bit).Reserved place 5242 can be set as 0.AID 5244 sign FRACH in source go up the STA that sends.The purpose AID 5246 sign purpose STA that TXOP asked.In this exemplary embodiment, if purpose side is AP, then the value of purpose AID field 5246 is set as 2048.The FCS 5248 of 4 bits calculates according to whole signal 1 and signal 2 fields.Before convolutional encoding, add the afterbody 5250 of one 6 bit.

In this exemplary embodiment, STA can use the Aloha of time slotization to come access channel, and sends a request message in FRACH.If successfully received by AP, then AP provides a TXOP through scheduling to requesting party STA in the one scheduling access period of back.The FRACH timeslot number of current scheduling access period indicates N_FRACH in SCHED message.

STA can also keep a variable B_FRACH.After the transmission on the FRACH, if STA receives the TXOP assignment information from AP, its B_FRACH that resets then.If STA does not receive the TXOP assignment information from AP in the SCHED of predetermined quantity (FRACH_RESPONSE) transmission, then B_FRACH is increased by 1, reach maximum 7 at most.Parameter F RACH_RESPONSE is included in the ACF item of beacon.In any FRACH, STA is with probability (N_FRACH) ^-1* 2 ^-B_FRACHChoose a FRACH time slot.

If AP does not dispatch any FRACH cycle, then MIMO STA can use the EDCA rule, is at war with in the protected competing cycle in SCAP.

It will be appreciated by those skilled in the art that and to use multiple different technologies and method representation information and signal.For example, data, instruction, order, information, signal, bit, symbol and the chip of mentioning in the description on run through can be represented with voltage, electric current, electromagnetic wave, magnetic field or particle, light field or particle or above-mentioned combination in any.

Those skilled in the art also can understand, various exemplary box, module, circuit and the algorithm steps of describing in conjunction with the disclosed embodiments all can electronic hardware here, computer software or the combination of the two realize.In order to be clearly shown that the interchangeability between the hardware and software, more than various exemplary assembly, frame, module, circuit and steps are all carried out generally description with its functional form.This functional be to realize or realize depending on the design constraint that specific application and whole system are applied with software with hardware.Those skilled in the art can realize described functional at each specific application in many ways, and still the result of this realization should not be construed as and causes deviating from scope of the present invention.

Utilize general processor, digital signal processor (DSP), application-specific integrated circuit (ASIC) (ASIC), field programmable gate array (FPGA) or other programmable logical devices, discrete gate or transistor logic, discrete hardware components or the combination in any among them, can realize or carry out various exemplary logic diagram, module and the circuit described in conjunction with embodiment disclosed herein.General processor may be a microprocessor, but in another kind of situation, this processor may be processor, controller, microcontroller or the state machine of any routine.Processor also may be implemented as the combination of computing equipment, for example, and the combination of DSP and microprocessor, a plurality of microprocessor, one or more microprocessor or any other this kind structure in conjunction with the DSP core.

In conjunction with the step of described method of embodiment disclosed herein or algorithm can directly be presented as hardware, the software module carried out by processor or the combination of these two.Software module may be present in the medium of RAM memory, flash memory, ROM memory, eprom memory, eeprom memory, register, hard disk, mobile disk, CD-ROM or any other form well known in the art.A kind of typical storage medium and processor coupling, thus make processor from this medium, to read information, and can be to this medium writing information.In the example of replacing, medium can be the part of processor.Processor and medium may be present among the ASIC.This ASIC may be present in the user terminal.In the example of replacing, the discrete assembly that processor and medium can be used as in the user terminal exists.

The title that comprises herein is used for reference and helps each joint of location.These titles are not to want to be limited in the protection range of described notion thereafter.These notions go in full.

Provide the foregoing description of described disclosed embodiment can make those skilled in the art can realize or use the present invention.To those skilled in the art, the various modifications of these embodiment are conspicuous, and the general principles of definition here also can be applied to other embodiment on the basis that does not depart from the scope of the present invention with purport.Therefore, the embodiment that the present invention is not limited to illustrate here, but consistent with the widest scope that meets principle disclosed herein and novel feature.

Claims

1. device comprises:

Transmitter, be used for sending signal according to first kind of transformat, so that shared medium is reserved one period duration, and be used for sending according to second kind of transformat at the duration of described reservation, wherein the signal according to described second kind of transformat sends in the interval that is used for according to described first kind of transformat transmission signal; And

Receiver is used for receiving according to described second kind of transformat at the duration of described reservation.

2. device comprises:

Transmitter is used for sending according at least a portion of first kind of communication format, and is used for sending according to second kind of communication format;

Receiver is used for receiving according to described second kind of communication format; And

Reserve module, be used for shared medium is reserved one period duration, so that communicate according to described second kind of transformat at the duration of described reservation,

Wherein the signal according to described second kind of communication format sends in the interval that is used for according to described first kind of communication format transmission signal.

3. wireless communication system comprises:

Sending module is used for sending signal according to first kind of transformat, so that shared medium is reserved one period duration; And

Communication module is used for communicating according to described second kind of transformat at the duration of described reservation,

Wherein the signal according to described second kind of transformat sends in the interval that is used for according to described first kind of transformat transmission signal.

4. a method is used for carrying out interoperability by shared medium between one or more equipment that communicate according to first kind of transformat and one or more equipment that communicates according to second kind of transformat, and described method comprises:

Send signal according to first kind of transformat, so that described shared medium is reserved one period duration; And

At the duration of described reservation, communicate according to described second kind of transformat,

5. method as claimed in claim 4 also comprises: before the described signal that transmission is used to reserve, insert according to described first kind of transformat competition.

6. method as claimed in claim 4 also comprises:

Request inserts described shared medium; And

Reception is in response to the distribution of described request.

7. method as claimed in claim 4, wherein, described signal is according to the transmission opportunity of IEEE 802.11 agreements (TXOP).

8. method as claimed in claim 4, wherein, described signal has been established uncontended periods.

9. method as claimed in claim 4 wherein, sends signal so that one period duration of described shared medium reservation is comprised that also sending a request sends (RTS) message, and described RTS message has been indicated the transmitting continuous time.

10. method as claimed in claim 4 wherein, sends signal so that one period duration of described shared medium reservation is comprised that also sending one permits sending (CTS) message, and described CTS message has been indicated the transmitting continuous time.

11. method as claimed in claim 4, wherein, described first kind of transformat is the IEEE802.11 form.

12. method as claimed in claim 4, wherein, described second kind of transformat comprises time division multiplexing (TDD) frame period, and this time division multiplexing frame period comprises:

Pilot tone;

The poll that merges;

According to the zero of the poll of described merging or a plurality of access point frame to distant station;

According to the zero of the poll of described merging or a plurality of distant station frame to access point;

According to the zero of the poll of described merging or a plurality of distant station frame to distant station; And

Zero or a plurality of section that inserts at random according to the poll of described merging.

13. a device comprises:

First distribution module is used for distributing for first duration for communicating on shared medium according to first kind of communication format of multiple communication format; And

Second distribution module is used for distributing for second duration for communicating on described shared medium according to second kind of communication format of multiple communication format,

14. device as claimed in claim 13 also comprises the module that is used for spatial manipulation.

15. a method that is used for communicating on shared medium comprises:

Distributed for first duration on described shared medium, communicating according to first kind of communication format in the multiple communication format; And

Distributed for second duration on described shared medium, communicating according to second kind of communication format in the multiple communication format,

16. method as claimed in claim 15, wherein, at least a communication format in the described multiple communication format comprises spatial manipulation.

17. method as claimed in claim 16, wherein, the described communication format that comprises spatial manipulation in the described multiple communication format is multiple-input and multiple-output (MIMO) communication format.

18. method as claimed in claim 17, wherein, described MIMO communication format is the single output of many inputs (MISO) communication format.

19. method as claimed in claim 15, wherein, a kind of communication format in the described multiple communication format comprises time division multiplexing (TDD) frame period, and this time division multiplexing frame period comprises:

Pilot tone;

The poll that merges; And

One or more frames according to the poll of described merging.

20. method as claimed in claim 19, wherein, one or more frames comprise the communication of access point to distant station.

21. method as claimed in claim 19, wherein, one or more frames comprise the communication of distant station to access point.

22. method as claimed in claim 19, wherein, one or more frames comprise the communication of distant station to distant station.

23. method as claimed in claim 19, wherein, one or more frames comprise the access at random to described shared medium.

24. method as claimed in claim 15, wherein, a kind of communication format and 802.11EDCA form in the multiple communication format are basic identical.

25. method as claimed in claim 15, wherein, a kind of communication format and 802.11CAP form in the multiple communication format are basic identical.

26. method as claimed in claim 15, wherein, a kind of communication format in the multiple communication format is basic identical with SCAP in fact.

27. method as claimed in claim 15, also comprise: distribute a series of one or more the 3rd duration on described shared medium, communicating according to first kind of communication format in the described multiple communication format, and distribute a series of one or more the 4th duration on described shared medium, communicating according to second kind of communication format in the described multiple communication format, described a series of the 3rd duration and a series of the 4th duration intert mutually.

28. method as claimed in claim 27, wherein, select described intert with provide between described a series of the 3rd duration maximum time at interval.

29. method as claimed in claim 15, wherein, described first duration comprises that one or more SCAP at interval.

30. method as claimed in claim 29, wherein, described second duration comprises that one or more 802.11EDCA at interval.

31. method as claimed in claim 15 also is included as described first duration establishment uncontended periods.

32. method as claimed in claim 15 also is included as described second duration establishment competing cycle.

33. a device comprises:

The competition access module is used for inserting shared medium according to first kind of communication protocol competition; And

Communication module is used for communicating on described shared medium according to second kind of communication protocol between the described access periods of competing,

Wherein the signal according to described second kind of communication protocol sends in the interval that is used for according to described first kind of communication protocol transmission signal.

34. a method that is used for communicating on shared medium comprises:

Send beacon;

Insert described shared medium according to first kind of communication protocol competition; And

Between the described access periods of competing, communicate on described shared medium according to second kind of communication protocol,

35. method as claimed in claim 34 also comprises:

Establish uncontended periods; And

During described uncontended periods, distribute poll according to described first kind of communication protocol.

36. method as claimed in claim 34 also comprises:

Insert for the second time described shared medium according to described first kind of communication protocol competition; And

Between the access periods of competing the described second time, on described shared medium, communicate according to described first kind of communication protocol.

37. method as claimed in claim 35, wherein:

First access point is established described uncontended periods; And

Second access point inserts according to described first kind of communication protocol competition, and between the described access periods of competing, communicates according to described second kind of communication protocol and one or more distant station.

38. an equipment, itself and access point interoperability, described access point is established uncontended periods and competing cycle according to first kind of communication protocol, and described equipment comprises:

The competition access module is used for inserting according to described first kind of communication protocol competition during described competing cycle;

Transmitter is used for sending according to second kind of communication protocol between the described access periods of competing; And

Receiver is used for sending according to described second kind of communication protocol between the described access periods of competing,

39. a wireless communication system comprises:

A kind of equipment is used for:

Insert shared medium according to first kind of communication protocol competition; And

Send signal so that described shared medium is reserved one period duration according to described first kind of communication protocol;

First distant station is used for sending pilot tone according to second kind of communication protocol; And

Second distant station is used for:

Measure described pilot tone and determine feedback in view of the above; And

Described feedback is sent to described first distant station,

40. wireless communication system as claimed in claim 39, wherein, according to described feedback, described first distant station also sends to described second distant station according to described second kind of communication protocol with data.

41. a method that is used for communicating on shared medium comprises:

Insert described shared medium according to first kind of communication protocol competition;

According to second kind of communication protocol pilot tone is sent to second distant station from first distant station;

Measure described pilot tone at the described second distant station place and determine feedback in view of the above;

Described feedback is sent to described first distant station from described second distant station; And

According to described feedback, according to described second kind of communication protocol data are sent to described second distant station from described first distant station,

42. a wireless communication system, it uses shared medium to receive and send, and this wireless communication system comprises:

First access point is used for communicating according to first kind of communication format; And

Second access point, be used for communicating according to second kind of communication format, described second access point is used for sending signal according to described first kind of communication format, so that described shared medium is reserved one period duration for use in communicating according to described second kind of communication format