CN1156528A - Method and apparatus for coordinating multi-point-to-point communications in multi-tone data transmission system - Google Patents

Method and apparatus for coordinating multi-point-to-point communications in multi-tone data transmission system Download PDF

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CN1156528A
CN1156528A CN 95194297 CN95194297A CN1156528A CN 1156528 A CN1156528 A CN 1156528A CN 95194297 CN95194297 CN 95194297 CN 95194297 A CN95194297 A CN 95194297A CN 1156528 A CN1156528 A CN 1156528A
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far
end unit
center cell
signal
transmission
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J·M·西奥菲
J·宾汉姆
K·S·雅各森
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Texas Instruments Inc
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Amati Communications Corp
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Abstract

A variety of bi-directional data transmission systems that facilitate communications between a plurality of remote units (15) and a central unit (10) using a frame based discrete multi-carrier transmission scheme are disclosed. In each of the systems, frames transmitted from the plurality of remote units (15) are synchronized at the central unit (10). A variety of novel modem arrangements and methods for coordinating communications between a plurality of remote units and a central unit to facilitate multi-point-to-point transmission are disclosed. The invention has application in a wide variety of data transmission schemes including Asymmetric Digital Subscriber Line systems that includes the transmission of signals over twisted pair, fiber and/or hybrid telephone lines, cable systems that includes the transmission of signals over a coaxial cable, and digital cellular television systems that include the transmission of radio signals.

Description

Coordinate the method and apparatus of multiple spot in the multitone data transmission system to some communication
Background of the present invention
The present invention relates generally to that center cell serves the Discrete Multitone communication system of a plurality of remote units.Particularly, it relates to the method for coordination from the uplink communication of remote unit.
Discrete Multitone (DMT) data transmission scheme has been used to promote the high-performance data transmission.The advantage of DMT structure is that they have high spectrum efficiency and can avoid various signal skew and noise problem adaptively.Because they have very high data transmission capacity, in majority is used, select the DMT data transmission scheme to require to provide enough spaces of activating business for the data transmission system that increases.Therefore, the Discrete Multitone technology all has application in the several data transmission environment.For example, organizing Alliance ForTelecommunications information Solutions (ATIS) to finalize a text one for one of ANSI (AmericanNational Standard institute) Standard Group mandate is used in ADSL (Asymmetric Digital Subscriber Line) (Asymmetric Digital Subscriber Lines, ADSL) standard based on Discrete Multitone of last transmission of digital data.This standard plan is transmitting video data on ordinary telephone line at first, though it also can be used for other different application.This North American Standard (North America standard) is also referred to as ANSI T1.413 ADSL standard.
The plan of ADSL standard transmission speed promotes that speed is at least 6 MBPSs (that is message transmission 6+Mbit/s), on the twisted pair telephone line.Standardized Discrete Multitone (DMT) system goes up " subchannel " that uses 256 " sounds " or each wide 4.3125kHz at forward direction (descending).In the environment of telephone system, down direction is commonly considered as (typically being had by telephone operator) to remote location (may be an end user, i.e. resident or business user) from the central office and is transmitted.In other systems, the number of employed sound may be very different.Yet after the IFFT modulation was finished, the representative value of possible subchannel (sound) number was 2 integer power, for example, and 128,256,512,1024 or 2048 subchannels.
The ADSL (Asymmetric Digital Subscriber Line) standard also plans to use data transfer rate at 16 reverse signals that arrive in the 800Kbit/s scope.Reverse signal is equivalent to the up direction transmission, for example, and from the remote location to the central office.Therefore, the term ADSL (Asymmetric Digital Subscriber Line) is higher than oppositely this fact from the forward data transmission rate.This is planning particularly useful in the system of programming of remote location transmission of video or video conference information on the telephone wire.As an example, a possible application is that system allows the dwelling house client to obtain the video information resemble the film rather than remove to rent videotape on telephone wire or cable.Another possible application is video conference.
Discrete Multitone (DMT) transmission plan also has very big potentiality in the application except that the phone line transmission of data.In fact, DMT also can be used for other multiple access system of digital subscriber.For example, it can be used for custom system and the such wireless subscriber system of digital cellular TV based on cable (typical case is a coaxial cable).In cable system, typically, single center cell (center modulator-demodulator) is distributed to digital signal a plurality of users of a plurality of far-end units of representative (far-end modulator-demodulator).Although all far-end modulator-demodulators can receive same digital signal reliably, uplink must be coordinated at center modulator-demodulator place the upward signal source to be obscured avoiding.In some existing cable systems (they do not use the Discrete Multitone transmission plan), each far-end unit is assigned with the frequency range of a special use, communicates by letter with central station thereon.Yet such means itself are exactly to use and typically require to use analog filter to separate the transmission from different far-end units to the transmission bandwidth poor efficiency.Other existing cable system is used for all far-end units with a single broadband, and it uses time division multiple access (TDMA) to insert up channel.These means are poor efficiencys, because the lower total capacity of single channel is also handled required time because insert.The stationary digital cellular transmission system also will be faced similar obstacle.The ability of access channel will more effectively be utilized transmission channel on time-division and frequency division basis.Yet the intrinsic multiplexing person's character of DMT has limited its application in point-to-point transmission previously, because from the transmission of homology must be digital not multiplexing correctly to carry out synchronously.
ADSL uses also has similar problem, though in fact it typically has more restrictions.Especially, a plurality of line of fall points that single line can be served special record keeping address (family or an office typically).That is to say that the there has a plurality of users and wishes to be used for the telephone socket of received signal.In order to promote on single line, to serve, planned to use a primary modem to promote synchronously for a plurality of positions (socket).Yet this is considered to a relatively costly and unwelcome solution.Therefore, need in the Discrete Multitone data transmission system, provide the synchronous of the signal of a kind of mechanism promotion from a plurality of far-ends, make center cell can coordinate and explain reliably the signal that far-end sends.
Current another characteristic that is used for the transmission system from far-end unit to center cell communication is that or they are at maximum rate (frequency division multiplexing) transmitting data that designs, or become bag (time-based multiplexing) transmission data by specific size.They do not allow the two together.This has just limited the service efficiency of transmission channel.Therefore, be desirable to provide a kind of mechanism, by it, when needed, far-end unit can specify requirement to transmit on specific data transfer rate, and when not considering data transfer rate, far-end unit can indicate it to wish the information of transmission specified quantity.
The present invention's general introduction
In order to realize aforementioned and other purpose and, disclose several uses and promoted the bidirectional data transmission system of communicating by letter between a plurality of far-end units and the center cell based on the Discrete Multitone transmission plan of frame according to purpose of the present invention.In each system, synchronous at center cell from the frame of a plurality of far-end unit transmission.Disclosed the communication of coordinating between a plurality of far-end units and the center cell, to promote multiple new modem apparatus and the method for multiple spot to some transmission.The present invention can be applied to be included in the ADSL (Asymmetric Digital Subscriber Line) system of transmission signals on twisted-pair feeder, optical fiber and/or the hybrid phone line, in the digital cellular television system of the cable system of transmission over coaxial cable signal and transmitting wireless signals in interior very many data transmission schemes.
In one embodiment, the Discrete Multitone data transmission system has a plurality of discrete subchannels, comprises an overhead bus.Aspect method, when a far-end of choosing is wanted to start communication, it is its clock time and the clock loop of center cell, then the synchronizing signal that starts to far-end of center cell transmission on the overhead subchannel of special use or the group system overhead subchannel in the overhead bus.Center cell starts with a center, comprises better first far-end unit of being chosen is replied with the synchronizing signal of the synchronous desired indication frame boundaries phase shift information of other current far-end unit of communicating by letter with center cell.Far-end responds by the indicated phase in-migration of synchronizing signal that the center starts by the frame with its output.Can carry out repeatedly synchronously or one the step finish.This frame boundaries with the far-end unit output frame chosen is synchronous with the frame boundaries of current far-end unit output frame of communicating by letter with center cell.To when being received by center cell, they become consistent substantially from the frame boundaries of different far-ends synchronously.
In one embodiment of the invention, the overhead bus comprises that the synchronizing signal that the overhead subchannel of two special uses and far-end start transmits on two different overhead subchannels with the synchronizing signal that the center starts.In other embodiments, may use one or more overhead subchannels.In certain embodiments, the far-end unit of choosing can with the number of subchannels to center cell transmission data be dynamic assignment.Realize that to being suitable for the concrete center of such system and the design of far-end modulator-demodulator also disclose.
In another aspect of the present invention, the synchronous silence period periodically provides in uplink communication stream.This synchronous silence period is used to handle the function of multiple overhead type as new far-end unit startup, transmission channel quality inspection and deal with data transmission request.
In one embodiment, described a kind of with one from the far-end unit of firm startup to the frame of center cell transmission with from the method for other far-end unit to the frame synchronization of center cell transmission.In this embodiment, the synchronous silence period periodically appears at a plurality of discrete subchannel that is used for uplink communication.When a far-end unit was activated, it transmitted a broadband enabling signal to center cell in synchronize quiet in the time.This broadband enabling signal comprises a plurality of enabling signals of transmitting on different subchannels.In a preferred embodiment, far-end unit when wanting to start, monitor downlink communication and downstream signal that the frame boundaries of broadband enabling signal and far-end unit are received in the frame timing index that carries synchronous substantially.Center cell receives the broadband enabling signal and to synchronizing signal of the first far-end unit loopback.This synchronizing signal comprises the frame boundaries of the signal that better this far-end unit is sent and the information of the synchronous desired indication frame boundaries of the frame boundaries phase shift of the signal of other far-end unit of communicating by letter with center cell transmission.This far-end unit is synchronous to promote with the frame phase shift of its output then.
The synchronize quiet time of Shi Yonging has the sufficiently long cycle in this embodiment, so that be transferred to the silence period sign of distance center unit far-end unit farthest and turn back to the enabling signal of center cell all during synchronous silence period from farthest far-end unit from center cell.
The method of the subcarrier transmission quality of a kind of dynamic chek from the far-end unit to the center cell has been described in another embodiment.This has promoted the allocated bandwidth of center cell to far-end unit.In this embodiment, at the synchronize quiet time durations of choosing, transmit on a plurality of subchannels of uplink communication being used to promote from the training signal of a far-end unit.This training signal is monitored that by center cell it determines that one group is represented that different subchannels transport the characteristic of channel from the bit capacity of the signal of choosing far-end.Then, center cell can use this group characteristic of channel when determining which subchannel distributed to the far-end unit of choosing and be used for uplink communication.
In a preferred embodiment, transmission can repeat a plurality of different far-end units with monitoring step, to be identified for the characteristic of channel of each different far-end unit.Different far-end units preferably are arranged to their training signals separately of transmission in the different silence periods.The characteristic of channel group that is used for each far-end can be stored in a characteristic of channel matrix that comprises the channel capacity information of indication from each far-end unit to center cell.Channel characteristic information can be used to promote the Dynamic Bandwidth Allocation to different far-end units subsequently.In a further advantageous embodiment, far-end unit is only according to their training signals separately of retraining signal transmission from center cell that receive.This has promoted system-wide control.
Remain in another embodiment of the present invention, described a kind of method of notifying the transmission request of center cell far-end unit.In this embodiment, wish to start or change the time of far-end unit beyond the silence period interval of communication to data request signal of center cell transmission.Center cell sends an authorization signal to far-end unit subsequently and distributes a specific silence period.Far-end unit then in the silence period of distributing in a plurality of discrete subchannel transmitting data solicited messages.Learn the request of far-end unit, center cell is that far-end unit distributes one or more subchannels according to request of data information.
In a preferred embodiment, data request signal can be indicated the information of wanting to transmit or want to transmit specific quantity on specific data transfer rate.In the previous case, center cell is that far-end unit distributes enough subchannels to transmit on the data transfer rate that promotes to ask in request of data information.At latter event, center cell distributes one or more subchannel time enough amounts to be transmitted in the amount of information of appointment in the request of data information.
In a further advantageous embodiment, far-end unit can send the packet request signal of a qualification after request of data information has limited and sent.When this happens, center cell is the directly packet request of response qualification immediately, is that first far-end unit of choosing distributes at least one subchannel.
In a further advantageous embodiment, far-end unit monitored the information that appears in the downlink communication stream and only transmit request of data thereon when the report subchannel is unoccupied before sending data request signal.Remain in a further advantageous embodiment first value designation data rate request of data request signal, second value designation data bag request of data request signal, and the 3rd the packet request that the value indication limits of data request signal.In such scheme, data request signal can be little as the dibit signal.
Remain in a further advantageous embodiment, each frame of Discrete Multitone signal comprises that a plurality of symbols and each far-end unit have been endowed a relevant symbol, and it can transmit its request of data symbol betwixt.In this embodiment, center cell at least a portion is determined the sign of the particular remote unit of transmission data request signal based on this symbol (data request signal receives betwixt).
Should be appreciated that different embodiment not only can use separately but also can use together in conjunction with one or more other embodiment.The different silence periods of describing needn't have same length and typically, in conjunction with the silence period that the 3rd embodiment describes will be more frequent than other two.
Still in another embodiment, provide quick access transmission mode.In this embodiment, a communication access request that comprises unique distal marker symbol is transferred to center cell from the far-end of asking.This request is used and is not required in the center cell equilibrium with the modulation scheme of decoding at least one unappropriated subchannel transmission.Center cell distributes suitable subchannel for the far-end unit of request subsequently.
In another aspect of this invention, the discrete multiple spot transmitter and receiver that can realize distinct methods has been described.Be to be appreciated that different embodiment not only can use separately but also can use together in conjunction with one or more other embodiment.The system that is described can be no matter whether downstream signal also be to use under the situation of discrete multitone, DMT.In several preferred embodiments, though also considered other system, bidirectional data transmission system is the cable system that is included in the transmission over coaxial cable data.
Brief description of the drawings
With reference to following description, will get the best understanding in conjunction with the accompanying drawings the present invention and its other purpose and advantage, wherein:
Fig. 1 is the block diagram of a communication system, and this system comprises the center cell of the front end of a plurality of far-end units of service.
Fig. 2 is the spectrogram of use of the subchannel of a plurality of demarcation of using in the DMT system of an explanation, and this system comprises the overhead subchannel of a pair of special use.
Fig. 3 is one and is applicable to the block diagram of realizing synchronous central office modem structure of the present invention.
Fig. 4 is one and is applicable to the block diagram of realizing synchronous far-end unit modem structure of the present invention.
Fig. 5 is the block diagram that an explanation is applicable to the far-end unit synchronization scenario of realizing synchronous and up symbol location.
Fig. 6 is a figure that differs for frequency.Slope and timing error is proportional and differing of y intercept and carrier wave is proportional.
Fig. 7 is the timing diagram of a DMT data transmission system according to an embodiment of the invention.
Fig. 8 is the flow chart that an explanation starts the method for far-end unit according to an aspect of the present invention.
Fig. 9 is one the flow chart of the method for retraining far-end unit according to another aspect of the present invention is described.
Figure 10 is the flow chart that the far-end unit of an explanation request and center cell are set up the step that signal post carries out.
Figure 11 (a) is a flow chart that is illustrated as the method for the far-end unit distribution bandwidth of carrying out the packet request.
Figure 11 (b) is that a far-end unit that is illustrated as the packet request that limits distributes the flow chart of the method for bandwidth.
Figure 11 (c) is a flow chart that is illustrated as the method for the far-end unit distribution bandwidth of carrying out data rate request.
Figure 12 is the figure of an explanation based on the frame transfer sequence in the data transmission scheme of time division multiple access.
Detailed description of the present invention
Discrete Multitone (DMT) data transmission scheme has shown and has promoted high performance transfer of data.The advantage of DMT structure is that they have spectral efficient and can avoid various signal skew and noise problem adaptively.Because they have very high data transmission capacity, in majority is used, select the DMT data transmission scheme to require to provide enough spaces of activating business for the data transmission system that increases.The Discrete Multitone technology all has application in the several data transmission environment.For example, plan to use ATIS ADSL (Asymmetric Digital Subscriber Line) (ASDL) the North America standard of Discrete Multitone data transmission scheme.
Being described in detail in the ATIS works above-mentioned of the agreement of ATIS ADSL North America normal scatter multitone (DMT) transmission plan.Standardized system uses 256 " sounds ", and each accounts for 4.3125kHz in forward direction (descending).The frequency range of sound from 0 to 1.104MHz.32 lower sounds also can be used for the duplex data transfer on the up direction.The plan of the present invention in this system has been intended for use in other application with the improvement that transmission bandwidth is increased to the requested number level.In other systems, the number of employed subchannel and/or subchannel bandwidth can be very different.But when carrying out the IFET modulation, the typical amounts of available subchannels is 2 integral number power, for example 128,256,1024,2048 subchannels.
As described in the background of this application, a restriction of Discrete Multitone transmission system is in order to support a plurality of drawing (drop) point on uniline, and upward signal must be synchronous when they arrive center cell.This stationary problem has limited the glamour of Discrete Multitone (DMT) data transmission scheme in resembling the such application-specific of cable system and radio honeycomb transmission of television, because these systems use a large amount of relatively independent far-end unit of uniline (medium) service, these far-end units are typically by different user's operations.
With reference to figure 1, will the principle transmission plan that typically is used for multi-user's user network be described earlier.Center cell 10 (comprising a center modulator-demodulator) is communicated by letter with a plurality of far-end units by the common transmission line that is divided into many feeder lines 18.Relevant far-end unit of every feeder line 18 services, typically, this far-end unit comprises far-end modulator-demodulator 15 and far end device 22 that uses data of a received signal.Typically, service supplier 19 data that provide the data that are transferred to far-end unit 15 and processing center modulator-demodulator to receive to the center modulator-demodulator from the far-end unit modulator-demodulator.Service supplier 19 can adopt any suitable form.For example, service supplier can be a webserver in form.The webserver can be a special-purpose computer or a distributed system.Transmission line can use different transmission mediums.For example, twisted pair telephone, coaxial cable, optical fiber and the mixing in conjunction with two or more different medium can.This approach also can be used for wireless system.
Those skilled in the art will recognize, a demand of all those Discrete Multitone data transmission systems as discussed here is, if two and more multiple unit (typical case is two unit) want information is transferred to one the 3rd unit (promptly independently, center cell 10), must be synchronously from the signal of far-end unit or at least some signals can not be understood by center cell 10.Using the problem of Discrete Multitone transfer of data in such system is that the length of feeder line 18 is very different for different far-ends.Therefore, even the clock synchronization of far-end and center cell 10, the communication that they get back to center cell 10 will have a phase-shift phase, and this amount depends on the length of relevant feeder line at least in part.In fact, the phase shift of this class will make the communication of far-end startup can't understand the center modulator-demodulator.
A representational DMT transmission band has been described among Fig. 2.As shown in the figure, transmission band comprises a plurality of subchannels 23, can transmit independently carrier signal (being called subcarrier 27) thereon.The DMT transmission is divided into a plurality of subchannels 23 inherently with transmission medium, and each subchannel carries data independently.Data on each subchannel 23 can be equivalent to different signals or can be combined into the more High Data Rate that expression is single or the transmission bandwidth width is less.These subchannels 23 all are to realize by the Digital Signal Processing among the DMT, and it does not need to simulate separation filter and has maximum spectrum efficiency.The number of used subchannel can be very inequality according to the needs of concrete system.Yet when using contrary fast Flourier (IFFT) when modulating, the representative value of the number of available subchannels 23 is integer powers of 2, for example, and 128,256,512,1024 or 2048 subchannels.For example, in an embodiment who is applicable to based on the custom system of cable, can use 1024 subcarriers 27, each carrier wave is limited in the subchannel 23 of 32kHz.This provides the frequency bandwidth of about 32MHz to be used for far-end unit and has communicated by letter with center cell.
The number of the far-end unit that can use in any concrete system can be very huge according to the needs of concrete system.For example, in the embodiment based on the custom system of cable of a description, may wish to allow 500 far-end units of as many as to communicate by letter with a center cell.Have in the system of many like this far-end units in plan, may wish far-end unit by set of dispense.Certainly, each group does not need to comprise same number of unit.For example, one allows the system of as many as 500 far-end units far-end unit can be divided into 8 groups, and each group allows 90 far-end units of as many as, and each far-end unit group is assigned with the frequency band of an appointment.For example, frequency spectrum can be divided into the frequency band of big or small appointment such as a plurality of grade.In the specific embodiment of describing, will be 1/8th of each set of dispense 32MHz, or about 4MHz.Therefore, each group will have about 4MHz, and correspondingly, 128 subchannels 23 are used for to center cell 10 transmission.A kind of method that is easy to manage of grouping permission center cell 10 usefulness keeps the tracking to them when far-end unit is reached the standard grade and go offline.
Grouping can be used the method for any kind.For example, can be made up of continuous subchannel 0-127 for first group, second group by subchannel 128-255 or the like.In addition, the distribution to the subchannel 23 of each group can interlock in entire spectrum.For example, can be the first set of dispense subchannel 0,8,16,24,32 It is the second set of dispense subchannel 1,9,17,25,33 The 3rd group 2,10,18,26,32 Or the like.With staggered each group of distributing to of subchannel, the noise that helps to reduce in the special area of frequency spectrum worsens the most possibility of transmitting in single group.On the contrary, pseudo noise will only influence the part of every group frequency band.Those of skill in the art recognize that the size of frequency bandwidth, subchannel 23 of up channel and grouping are not subjected to the restriction of the embodiment that describes among the embodiment but can select to be suitable for the concrete application need of transmission system.
A kind of method of the stationary problem that solution is pointed out above can consider to use dedicated system overhead subchannel 28 and 29 (Fig. 2) to promote synchronously.In this embodiment, upstream overhead subchannel 28 is carried to the center modulator-demodulator with the synchronizing signal of different far-ends.Downstream overhead subchannel 29 synchronizing signals with the center modulator-demodulator are carried to different far-ends.Overhead subchannel 28 and 29 can be arranged in any suitable frequency location of transmission band.In many examples, the upper frequency edge or the lower frequency edge of downstream signal may be expected the overhead subchannel is placed by ADSL (Asymmetric Digital Subscriber Line) as discussed above system, so that make the interference minimum between they and the contiguous subchannel.When system constraint allows, wish that also the subchannel that overhead subchannel and other are used for transfer of data separates at least one or two subchannels, so that minimize the potential interference that synchronizing signal produces.Expectation is because synchronizing signal will be always asynchronous with other transmission like this.Therefore, they will produce more distortion than other signal owing to step-out.In view of the above, a minibuffer device is helpful.Along the same line road, may wish also that the overhead subcarrier uses lower powered relatively signal so that further in some cases minimise interference problem.
As following will more careful description, in another aspect of this invention, periodically provide the synchronize quiet time in the ascending communication system stream.The synchronize quiet time can be used to handle dissimilar overhead functions, as initialization, transmission channel quality inspection and the deal with data transmission request of new far-end unit.Referring again to Fig. 7, the transmit timing sequence that a representational frame is delimited has been described, it provides a plurality of synchronize quiet periods that are applicable to the treatment system overhead functions.As shown in this embodiment, transmission is broken down into transmission frame 32 strings.Each transmission frame comprises a transmission intercal 33 and one first quiet interval S1.A plurality of signal periods 35 shown in each transmission intercal 33 is divided into again.Then, a plurality of transmission frames 32 are formed a superframe 36.Except that transmission frame 32, each superframe 36 also comprises one second silence period interval 38.In the embodiment that describes, second silence period interval 38 can be used for initialization interval (S2) or retraining interval (S3).
The actual cycle that offers transmission intercal 33, silence period at interval S1, initialization interval S2 and retraining S3 can be according to the needs of particular system and far from it at interval.Similarly, the number of the transmission frame 32 in the superframe 36 also can differ widely.For example, one is suitable for the embodiment that uses in described custom system based on cable, considers that transmission intercal 33 is made as the cycle of 63 symbols of enough transmission and is made as the time span of a symbol S1 time interval 34.Initialization interval S2 can be used for synchronous far-end unit as another kind of scheme.Therefore, the length at second silence period interval 38 is determined by the physics aspect of communication system that typically this will describe below more meticulously.In general, require far-end unit broadcasting in S1 or S3 silence period interval, unless center cell allows.In certain embodiments, far-end unit also be required the S2 silence period at interval in broadcasting, unless their following will descriptions are being sought initial installation.
Following main reference Fig. 2-4 will describe using the auxiliary system overhead subchannel to promote the far-end that increases newly to do synchronously in more detail.At first, far-end modulator-demodulator 50 comprises a far-end isochronous controller 80 of cooperating with the master controller 60 in the modulator-demod of center.As top simple discussion, in described embodiment, provide two communications between the auxiliary system overhead subchannel promotion controller.When far-end modulator-demodulator 50 was initialised and asks to begin to flow, its remote controller 80 was observed the downstream signal transmission that comprises center modulator-demodulator clock information inherently.This some the time marquis be to use steering signal to finish, though also can use other scheme.Then, far-end unit " loop timing ".That is to say that its is with phase-locked its clock of the clock of center modulator-demodulator.Then, far-end unit sends synchronizing signal by overhead subchannel 28 to center cell 30.This synchronizing signal enters the receiving unit of center modulator-demod 30 by transmission medium.When center modulator-demodulator 30 receives (up) synchronizing signal that far-end starts, and it is being when communicating by letter with other far-end unit, and the frame boundaries of the synchronizing signal that it starts far-end and the frame boundaries of the signal that receives from other far-end unit are relatively.Typically, controller 60 can be monitored the phase shift that exists between the frame boundaries.Then, controller 60 produces a downlink synchronous signal and passes far-end unit back by overhead subchannel 29.
Shown in and among the embodiment that describes, when the far-end modulator-demodulator was wanted to start with the communicating by letter of center modulator-demodulator, controller 80 was responsible for producing uplink synchronizing signals.Uplink synchronizing signals slave controller 80 is fed to multiplexer/encoder 143 and points to specific up-link overhead subchannel 28.Should be appreciated that because the characteristic of synchronizing signal is known, so it also can be guided to the transmitter of other position or directly offer analog interface 148.Typically, until finish synchronously, synchronizing signal and/or sequence should be unique signals that far-end is launched.Then, uplink synchronizing signals is transferred to the center modulator-demodulator by overhead subchannel 28, is received machine 70 and receives.Subsequently, the demodulator 76 of receiver is fed to the synchronizing signal of demodulation the controller 60 of center modulator-demodulator.Master controller 60 detects synchronizing signal that far-ends start and with the frame boundaries of its frame boundaries and all signals that receive from other far-end simultaneously relatively.When center modulator-demodulator 30 is communicated by letter with other far-end, because the difference of feeder line length, the frame boundaries that the far-end request inserts may have a phase shift with the frame boundaries of center modem communication with those.In this case, master controller 60 starts a loopback (descending) synchronizing signal, indicates the required phase shift of this adjustment frame boundaries (by the form of time-delay).Subsequently, loopback synchronizing signal is transferred to far-end by the second overhead subchannel 29.The same with uplink synchronizing signals, downlink synchronous signal will be introduced to the downstream data flow at encoder place.
The characteristics of downlink synchronous signal can be different, yet for example, only indicating remote is in advance or postpone 1 sampling of frame boundaries for synchronizing signal.In some more complicated systems, controller can attempt calculating the sampling number that frame boundaries must shift to an earlier date or postpone, and sends the signal that the indication frame boundaries should the several sampling of phase shift.Also can use other signal interpretation.As what will go through below, in many examples, the sampling rate of uplink communication will be the integer factor of the sampling rate of downlink communication.Described time-delay is based on the sampling rate rather than the far-end of center modulator-demodulator.
Because a plurality of far-ends all are connected on the identical transmission line 17, the far-end modulator-demodulator of all working all will receive synchronizing signal.Subsequently, this signal from the decoder of each far-end modulator-demodulator to they relevant controllers 80.Yet remote controller 80 is designed to ignore the synchronizing signal on the overhead subchannel, unless they are attempting starting and the communicating by letter of center modulator-demodulator.This can finish by diverse ways.For example, downlink synchronous signal can comprise an address of pointing to particular remote.Perhaps, far-end can suppose simply that if they are attempting starting communication, the center modem signal points to them so.Attempt starting the synchronizing signal that remote controller 80 receives and send at the explanation center and the guidance frame synchronizer 147 of the far-end unit of communication and realizing required phase-shift time delay (or in advance).Subsequently, the synchronizing signal that second far-end starts will be sent.If new synchronizing signal step-out will repeat same process.In one embodiment, synchronizing signal with a guidance frame synchronizer in advance or postpone a sampling.Be desirably in the majority application of DMT, such incremental system will be carried out the synchronous fast of far-end unit well.For example, symbol (frame) speed that is equivalent to 64Kbps is in the system of 8kHz (so symbol period is 125 μ s), each frame has 128 sampling and adds a prefix, in distributed network, nearly 2 miles of feeder line length variations are used simple single sampling shift to an earlier date/to postpone to approach still can make synchronously less than about 10 milliseconds.
When determining that signal that far-end sends is synchronous, master controller will send a loopback synchronizing signal by the second overhead subchannel 29, and indication no longer needs phase shift and the far-end unit can be in conjunction with the required phase shift startup and the full communication of center modulator-demodulator.When far-end by before the center modulator-demodulator identification just synchronously the time, the data tones that sends after initialization is used to identify the far-end modulator-demodulator.The relative phase shift of expectation frame boundaries is main according to fixing constraint, as the transmission length by different feeder lines.Therefore, in case far-end is by synchronously, unless binding stops or disconnection does not need synchronous again.
Should be appreciated that if center cell is not communicated by letter with any other far-end unit when the request of receiving starts communication, synchronizing signal of 60 needs loopbacks of center cell controller, indication does not need phase shift and whole communication to begin.Certainly, similarly signal can be attempted starting communication for the first time at the far-end of request and just by chance with under the situation of other far-end modem synchronization produces.When the far-end modulator-demodulator receives such signal, only need carry out same processing as the phase shift that requires with 0.
Typically, master controller 60 also provides the information of transmission which subchannel the indicating remote unit should be used for it or the like.As mentioned above, subchannel distributes and can in use dynamically change.Though this characteristic is important for Discrete Multitone transmission system scheme, not very relevant for the present invention, and therefore only do concise and to the point description, though it has detailed description in the list of references of quoting.
The synchronous requirement of far-end modulator-demodulator and center modulator-demodulator obtains the sampling clock and the carrier wave of center modulator-demodulator.In a preferred embodiment, these clocks are by monitoring the recovery that differs of at least two sounds.The phase error of these sounds can be calculated by fixing known transmission phase place (that is " guiding " sound) on the sound.In addition, their judgements that can explain in words defeated phase place by vacation be correct and calculate before and the back judge that the skew between the phase place determines (that is, judging the auxiliary calculating that differs).As shown in Figure 6, slope and the timing phase error of phase error figure are proportional, and the constant part of phase error figure (y intercept) is that carrier wave differs.Regularly (sampling) differ with carrier wave differ be determine by phase discriminator 181 and be input to phase-locked loop 182,184, synthetic sampling clock and carrier frequency on the center modem frequencies of recovering are as Fig. 5 explanation.Carrier wave is used for downstream signal separated is transferred to base band and sampling clock (behind frequency divider 189 frequency divisions) is used as the clock pulse of A-D converter (ADC).If data tones and signal tone occupy sound separately, just may use the ADC clock that replaces a single higher rate more than the A-D converter of low sampling clock.Comprising the embodiment clock of notch filter 185, voltage-controlled oscillator (VCO) 183,186 is used to control the position of trap.
Same sampling clock (behind frequency divider 189 frequency divisions) also is used for up digital-to-analog converter.Up-link carrier can synchronously can be not with descending carrier yet.When it is asynchronous, the uplink receiver of center modulator-demodulator will need to recover the uplink carrier phase, recover otherwise the receiver of center modulator-demodulator can be used for the reasonable phase-locked multiple of descending carrier data.The broadband remote modulator-demodulator will preferably use and the same sampling clock of center modulator-demodulator sampling clock.These far-end modulator-demodulators are the sampling clock of frequency division extraction not.The arrowband far-end modulator-demodulator that receives only several sounds is the sampling clock of the integer approximate number of the sampling clock that recovers with use.In view of the above, far-end modulator-demodulator in arrowband is relatively more cheap in realization.
The same time that must discuss in the above from the DMT symbol of far-end modulator-demodulator uplink arrives the center modulator-demodulator, produces even they are different modulator-demodulators.Therefore, postpone synchronizer 147 and in the signal of uplink, insert an integer sampling clock delay.This postpones as discussed earlier, programmes under the control of downlink synchronous signal.In addition, should be appreciated that sampling rate rather than the far-end that postpones to be based on the center modulator-demodulator.Specifically, as Fig. 5 explanation, the far-end sampling rate can be the integer factor of center sampling speed.Yet signal must be at center modulator-demodulator place by synchronously, so synchronous modulation must be carried out on the basis of the sampling rate of center modulator-demodulator.
Under two far-ends attempt starting the situation of communicating by letter with the center modulator-demodulator simultaneously, will produce conflict and master controller 60 and may be mixed up unrest by uplink synchronizing signals.In this case, its downlink synchronous signal will be indicated an incorrect phase shift and be confirmed that synchronizing signal will not be an accurate synchronization.In one embodiment, master controller 60 will identify that this problem and order far-end unit stop and setting up communication reattempting after a while.In another embodiment, master controller will send the downlink synchronous signal of the required additional phase shift of another indication simply.In either case, far-end unit will identify existing problems apace and suppose to have taken place conflict.In this case, can use suitable conflict solution.A simple conflict solution is, make each far-end postpone one at random time and this time at random after trial restart communication.As long as time delay is always not follow the method for identical time delay pattern with a kind of far-end, the separation that their request is enough at last makes each to reach the standard grade independently.Can use the different stand-by period to distribute.For example, Poisson distributes and just works finely.
The IFFT modulation scheme that should be appreciated that description to the transmission relatively large number according to piece and therefore require very good more than the system works of a sound.Yet under many circumstances, far-end does not need to transmit regularly big data block.In this case, use simple conventional modulated scheme more worthwhile to center cell transmission information from far-end.Under these circumstances, distant transmitter closes the center receiver and all will be replaced by appropriate parts.Yet still need by synchronous far-end as above is discussed.
In operation, the center modulator-demodulator sends a gathering dmt signal that uses all (or available) sounds in one way, and each far-end is known the bit number that distributes on its sound with the sound of reception and its reception at each like this.The far-end modulator-demodulator, each only uses a subclass of available up sound.The signal that is transferred to far-end from the center modulator-demodulator can be used for dynamically distributing the sound that can use for specific receiver.Perhaps, in static system, distribution can be carried out in downlink synchronous signal.Dynamic assignment both can be carried out in another dedicated system expense or control channel also can be multiplexing with other non-control signal.In the system of describing, upward signal is regularly, so they arrive the center modulator-demodulator in the substantially same time.Do not need accurately to adjust; Yet, on the border according to the accurate Adjustment System work of the sampling rate of center modulator-demodulator the best.
With reference to figure 8, will describe according to a further aspect in the invention again, between the installation period that uses the second silence period S2 that describes, start the another kind of method of first far-end unit.As discussed above, must initialization when far-end unit is reached the standard grade for the first time, when arriving the center modulator-demodulator from the transmission of first far-end unit like this and current any other far-end unit of having installed synchronous.Just, the frame boundaries of the up DMT communication from different far-end units to center cell must be substantially synchronously so that center cell be understood this transmission at center cell.The method of describing with reference to figure 8 is to use the silence period of description to realize so synchronous a kind of method.
At first, the far-end unit that install must be set up one with transmission network and is connected in step 302.This connection can be monitored from the transmission of center cell 10 and not sending on the subchannel of usefulness arbitrarily at up channel far-end unit.In some systems, has the obsolete particular frequency range of some systems.For example, in many cable systems, has the network of the foundation of using specific frequency band.For fear of disturbing and safeguard downward compatibility, it is very important that far-end never transmits in the forbidden frequencies scope.Certainly, specific frequency band also can be because other reason be under an embargo between the starting period.In view of the above, in step 303, center cell will be broadcasted the frequency sign of not using periodically.As discussed above, use in the system of far-end unit group notion, center cell also can be broadcasted the group number that the next far-end unit that will install should use periodically.In addition, the distribution of group can be carried out after a while the time.
The new far-end unit that connects is intercepted the information whether downstream signal has certain subchannel of indication not to be used.Downstream signal also comprises far-end unit and synchronously required frame timing and the silence period identifier of center cell.When far-end unit with it own and downstream signal synchronously after, in step 304, begin to locate it in the S2 silence period and send an enabling signal.In a kind of system, this finishes by send an enabling signal immediately when receiving S2 silence period identifier signal, and enabling signal indication center cell has a far-end unit request to be installed in the system.Far-end unit can determine S2 to start the beginning of silence period in any suitable manner.For instance, in downlink communication, indicate and to provide by center cell 10.Far-end unit can the concrete system of root a tree name demand, on whole subchannels 23, sending its enabling signal on one group of subchannel 23 or on single subchannel 23.In a preferred embodiment, the group that the downstream signal indication will be used by the unit that the next one will be installed, and send on whole subchannels of enabling signal in this group.
10 up startup transmission can realize with the modulation scheme that is fit to transmitting digital information arbitrarily from the far-end unit to the center cell.For example, amplitude, frequency and Quadrature Phase Shift Keying (QPSK) modulation scheme can be used.For synchronizing signal, what expect in a preferred embodiment is that differential QPSK (DQPSK) modulation is to reduce the possibility that noise causes interference.In addition, can use a large amount of error correction and redundancy encoding to guarantee coherent communication synchronously.
Enabling signal preferably includes the information of relevant far-end unit.In a preferred embodiment, enabling signal is carried the global address of far-end unit and the maximum transmission data rate request of first far-end unit.Global address is similar to the address of using with Taihe county cellular device.Such address is built among the communication equipment and is different with the address of all other communication equipments.The maximum data rate of far-end unit request depends on the device type of far-end unit.For example, if far-end unit is a television set, it will may only use upward signal to send the information of relevant film selection or audience feedback to the minimum message capacity of center cell 10 requests.On the other hand, if far-end unit is a video conference transceiver, will ask a large amount of bandwidth to be used for from far-end unit so to center cell 10 transmission of video and audio-frequency information.In other embodiments, the information about first other relevant portion of far-end unit also can send with enabling signal.
After the enabling signal that receives from first far-end unit, center cell 10 in step 306, determine from the enabling signal of first far-end unit whether with conflict from another enabling signal of another far-end unit of attempting at one time being connected.If monitor conflict, center cell 10 returns a collision message to far-end in step 308.This collision message indicating remote unit is attempted connecting again.Subsequently, the far-end unit of each conflict is waited for the S2 cycle of number at random before retransmitting enabling signal.The possibility that two far-end units attempt connecting at one time is very little.Wait for a random time independent of each other by the unit that requires to conflict, the possibility of repeated collisions is just littler.
Center cell 10 is after first far-end unit receives an effective enabling signal, and synchronizing signal of center cell 10 loopbacks 310 is to far-end unit.In one embodiment, synchronizing signal comprises the global address of first far-end unit, distributes to the node address of first far-end address, the information of the delay correction information and the distribution of relevant up channel sub-channels 23.No matter global address still is a node address can be regarded unique far-end unit identifier, though the degree difference of efficiency of transmission.Global address allows first far-end unit identification synchronizing signal to be used for it.It is in order to promote the efficient of future communications that node address is distributed to first far-end unit.Global address can grow very much (for example 48 bits) so that all communication equipments that have the global address of sufficient amount to be used for making.Node address is a short address, because have only the far-end unit of limited quantity to communicate by letter with single center cell 10 arbitrarily.When using group system more than, node address also comprises set of identifier information, and for example, relevant first far-end unit is distributed in the information of which group.Among the embodiment of Miao Shuing, comprise 8 groups altogether in the above, the part of address will be 3 bits to identify first far-end unit which in 8 groups.Remaining bit can identify this node uniquely, for example, and the appointment far-end unit in its group.
Those those skilled in the art should be appreciated that when far-end unit needs unique identification to be connected to the itself of center cell, that part of designated groups in the node address, and promptly set of identifier information can be omitted fully.This is because center cell can determine the message of far-end unit sends by checking the frequency band of unique identifier message from which group.In this way, far-end unit only need be sent in the group bit combination in the node address of sign itself, that is, identifier information in unique group is to identify it oneself uniquely to center cell.Identifier bit combination in the group of this reception in conjunction with the set of identifier information of determining, just provides the complete node address of the far-end unit of request for center cell.In the preferred embodiment of every group of 128 subchannels, the unique far-end unit identifier information on up direction may be as little to 7 bits.
Delay correction information tells how many frames first far-end unit must postpone from the broadcasting of first far-end unit, with the signal Synchronization of the far-end unit that is connected from other.Delay correction is to determine by the retardation between the enabling signal of silence period (S2) sign of its transmission of center cell monitoring and its reception.For example, if the maximum delay in the channel is TRT (MAX), maximum round trip delay for example, and the delay relevant with given far-end unit is TRT (i), the delay correction of far-end unit is exactly that TRT (the MAX)-round-trip delay of TRT (i) far-end unit is defined as signal and is transferred to far-end unit from center cell, and response turns back to the required time of center cell at once, comprises all small postponing owing to handling cause accidental.Use this information, first far-end unit can adjust its transmission and the far-end unit that is connected with other synchronous, the frame of far-end unit just arrives center cell 10 at one time like this.First far-end unit can remember that also just connected other far-end unit of which subchannel 23 uses.In another embodiment, the information of relevant subchannel 23 characteristics is transferred to all far-end units regularly by down channel.In such system, do not require that channel uses information to send with synchronizing signal.
An advantage at the wide portion transmission start signal of usable spectrum is, postpones to change greatly according to the frequency of signal transmission.Therefore, when enabling signal was transmitted on different subchannel 23, desired phase shift can on average calculating based on indivedual delays.
The length in the S2 time interval as described previously, depends on the physical characteristic of communication network.In a preferred embodiment, the S2 time interval only need add the poor of the minimum and maximum round-trip delay of network greater than the enabling signal cycle.For example, using fiber optic backbone as transmission line 17 and coaxial cable in the canonical system as feeder line 18, fiber optic backbone all is public to all paths between center and the far-end unit, and the difference of the minimum and maximum round-trip delay of network only depends on the cable section of network.Using coaxial line and given its propagation time of 2 miles of length approximately is 7.5 milliseconds every mile, and minimum and maximum round-trip delay is approximately 32 and 2 milliseconds.In a preferred embodiment, a symbol is approximately 30 milliseconds long, and an enabling signal will comprise two symbols, so for example, the S2 time interval of 4 symbols is appropriate.
In certain embodiments, may need repeating step 304-310, with the information that confirm to receive also/or guarantee that far-end is correctly synchronous.
After finishing synchronously, in step 312, first far-end unit is at the available S2 of the next one or S3 in the time interval, responds by send one group of synchronous broadband training signal on whole subchannels 23.Specific training step will be described with reference to figure 9 below in more detail.In certain embodiments, center cell 10 will specify first far-end unit to use the specific S3 time interval (for example, waiting for the 3rd S3).Receive after the training signal, center cell 10 determines that the capacity of different subchannels 23 is to handle the transmission (step 314) between first far-end unit and the center cell 10.Center cell 10 preferably has the priori of the content of training signal.This makes center cell 10 can access the best equilibrium of subchannel 23 and the Maximum Bit Rate that the subcarrier 27 on the subchannel 23 between first far-end unit and the center cell 10 can carry.Center cell 10 is preserved subchannels 23 characteristic of channel relevant with first far-end unit 316.In a preferred embodiment, there is information in the bit/carrier wave matrix in center cell 10, and this matrix comprises the indication of the bit number that each subchannel 23 can carry from each far-end unit.Such matrix makes center cell 10 can follow the tracks of the capacity of each different subchannel 23 and can use when distributing bandwidth for far-end unit.This has also promoted the subchannel dynamic assignment based on the current characteristic of transmission environment.
Below with reference to Fig. 9, the method for a kind of periodic test from the far-end unit chosen to the different subchannel capacities of center cell will be described.Can recognize that as those those skilled in the art the capacity of transmission line on different frequency is more or less different in time.Therefore, need be updated periodically the information of relevant subchannel 23 characteristics of each far-end unit of serving with it in the center cell.In the embodiment that describes, such being updated in the S3 silence period finished.In an illustrated embodiment, the S3 silence period is the same with the S2 silence period long.Should be appreciated that single transmission line inspection handle can be used for initial training and periodic test these two.
In the embodiment that describes, center cell 10 starts a retraining incident by sending a retraining order to current first far-end unit of just communicating by letter with center cell 10 (far-end unit x) in step 330.First far-end unit waits for that the next available S3 retraining silence period is at interval with one group of training signal of transmission on available subchannel 23.(step 23).In another embodiment, center cell 10 can distribute a specific S3 quiet interval to replace the next available S3 time interval to be used to transmit the retraining signal.The training signal group typically will be limited to the subchannel that is assigned to this group, and for cost-effective design is provided, further will be limited to certain subclass in the whole available subchannels group.Therefore, the demand of the concrete system of number root a tree name of the actual training signal that uses differs widely.As in start-up course, center cell 10 is analyzed the signal that its receives and is upgraded corresponding to the bit/carriers rate in the characteristic of channel matrix of associated remote ends unit (step 334).Center cell 10 determines whether and need distribute for far-end unit changes subchannel subsequently.That is to say determine whether to be that first far-end unit allocation subchannel 23 outer and still less is with the throughput of satisfied first far-end unit and the requirement of error rate.Change if desired, in step 338, center cell is the heavy allocated sub-channels 23 of first far-end unit so.
If determine needn't proofread and correct or make in step 338 after the necessary change in step 336, whether center cell 10 is checked in step 340 has other far-end unit to make retraining request immediately.If determine not retraining request immediately in step 340, whether center cell 10 exists effective old address (oldx) to check that the retraining of first far-end unit is the result of retraining request immediately by checking in step 347.If there is not effective old address, center cell 10 increases counter (x) and turns back to step 330 in step 349, to retraining signal of next far-end unit broadcasting.On the other hand, if define effective old address in step 340, center cell 10 will be adjusted counter, and it reads more than an old address, the address of the next far-end unit when it is equivalent to receive retraining request immediately like this.(step 350).Just, X=Oldx+1.
If detect the retraining request in step 340, center cell 10 saves as an old address (oldx) with the address of first far-end unit in step 342.Central location 10 is provided with the address of counter for unit, request station far away subsequently, and it is used as current just in the address of the next far-end unit of retraining 344.Logic turns back to step 330 then.The retraining process can repeat in current and all far-end units that center cell 10 is communicated by letter constantly.Certainly, the algorithm of selection retraining unit can be very inequality to satisfy the needs of particular system.
In one embodiment, started but the far-end unit of not communicating by letter as yet with center cell 10 also by retraining.Under the sort of situation, center cell 10 does not need to determine whether will be for changed the distribution of subchannel 23 by the far-end unit of retraining, because in fact it does not communicate by letter with center cell 10.When the far-end unit request was communicated by letter with center cell 10, center cell 10 can only be preserved the renewal characteristic of channel.
Center cell 10 preferably is suitable for receiving the retraining request during the Transmission Time Interval 32 on untapped subchannel 23.In a preferred embodiment, Transmission Time Interval 32 is that 64 symbols are long, the maximum possible far-end unit number in being equivalent to organize.Ask to send a sign in the symbol time of the far-end unit of the request of distributing to of far-end unit in Transmission Time Interval 32 of retraining immediately.In this way, center cell 10 can determine that immediately which far-end unit sends request by the position of sign.For example, the far-end unit 0-63 in the 8th group can distribute symbol 0-63 respectively in Transmission Time Interval.If a sign arrives not the using on the subchannel 23 of frequency band at the 8th group during the 9th character position, center cell 10 just knows that the 9th far-end unit in the 8th group sent a retraining request so.Can understand as those those skilled in the art, can finish with a lot of methods for far-end unit distributes symbol.
As discussed above, in order to promote the dynamic assignment of Discrete Multitone transmission plan, some mechanism must be arranged, can be by their far-end units with a data transfer request notice center cell.In one embodiment, S1 silence period binding data transmission request is used, to promote the startup of transmission.In the embodiment that describes, far-end unit sends three class request of data to center cell.They comprise packet request (DPR), limited packet request (DDPR) and data rate request (DRR).As using the hope of the transmission specified quantitative information of packet request indicating remote unit (typically representing to be exactly the data word joint number) among this embodiment with term.The transmission of limited packet request indicating remote unit has the hope of the bag and the package of center cell known features.For example, the center cell far-end unit that may store relevant request in its memory will send the information of packet to that far-end unit.The out of Memory that center cell is known may comprise, for example, and the required number of subchannels of far-end unit of the desired transmission rate of packet, request, or the like.Data rate request indicating remote unit is in the hope of particular rate transmitting data.
In one embodiment, the data transfer request of description can be combined into 2 bit signals that simply comprise 4 states with the request of above-described retraining immediately.For example, a state (1,1) can be corresponding to data rate request; Second state (1,0) can be corresponding to the packet request, and the third state (0,1) can correspondence retraining request immediately, and the corresponding limited packet request of four condition (0,0).Certainly, same information can be included in wherein and/or the meaning of various states can be different as the part than large-signal.As described above, 2 Bit data transfer request signals can be transmitted on the subchannel of usefulness not by far-end unit.By being that each far-end unit specifies a specific symbol period, center cell does not require that the independent identification information in the data transmission request signal just can promptly discern request unit.This is specified the transmission mode of a specific symbol period for each far-end unit and is called the polled transmission pattern.
Those skilled in the art will recognize as those, removing the identification far-end unit wishes beyond the type of the information that sends, under the situation of data rate request and packet request, general far-end need provide in fact more information so that center cell can correctly be handled request to center cell.For be provided quick turn-on time, extra information is relayed to center cell in the available S1 of next one interim silence period.More specifically, when unit, center 10 received an effective data packets request and an effective data rate request, the far-end unit of center cell 10 directed requests transmitted other the relevant additional information of request with the far-end unit of asking in the available S1 silence period 34 of the next one.In the S1 silence period, the far-end unit of request is linked in its required majority subchannel with the transmission header.Because the distribution of S1 silence period is in fact only asked in data rate request and packet request, so they can share an a single state in the 2 Bit data transfer request signals easily.Therefore, in another embodiment, can provide an a single state indication to distribute the hope of S1 silence period and the characteristic of request to transmit with out of Memory in the cycle at S1.
When system was not used by severe, for far-end unit, having relatively large number purpose subchannel was available when it sends its data transfer request.In the meantime, may be able in identical symbol period, transmit the header of whole requests with the transmission of request of data.Therefore, in another embodiment, the idle condition in the data transfer request can be used to signal the center cell far-end unit is just transmitting request simultaneously with data transfer request on untapped subchannel header.In the polled transmission pattern, the timing of data transfer request will identify the far-end unit of the request of transmission.Therefore, the advantage of this realization is that in the light relatively time of using, will further reduce the turn-on time of data transfer rate and packet request.Because each far-end unit only transmits in the symbol period that distributes for it, so can not clash between two far-end units.When accepting the header of all requests in the symbol period that far-end unit is determined not have enough bandwidth distributing, it will be as above-described, and request distributes the S1 silence period simply.
In another embodiment, center cell 10 can distribute a special S1 interval 34 for the far-end unit of request.This is very useful when two or more far-end units carry out packet or data rate request between two S1 intervals.
As previously mentioned, when system is not used by severe, just may exist big figure not with subchannel and can be used for the far-end unit request and insert.When the unit, center determines that system is slightly used, promptly use to be lower than a predetermined usage threshold, center cell can send an order to all far-end units and allow far-end unit to use the quick transmission mode that inserts to insert request to their communication of center cell transmission.Inserting fast transmission mode is different from above-described each far-end unit of giving and distributes a symbol period to be used to transmit the polled transmission pattern of its data transfer request.Represented as name, insert fast transmission mode in fact the far-end unit by allowing request no matter whether distribute in its any symbol period, one not usefulness with unappropriated subchannel on transport communication insert the access speed that request improves the far-end unit of request.Far-end unit knows which subchannel is a usefulness not, because for example, center cell monitors the use of subchannel and the information of using to the broadcast related subchannel of all far-end units every now and then.
Because far-end unit needn't be distributed to its symbol period by the time and send communication access request again, it can be once there being the communication that need send it to insert request.The information of the sign of relevant far-end unit of asking is not provided in the timing that inserts the request in the transmission mode fast on the other hand.Sent received communication access request signal in order to discern which far-end unit, inserted transmission mode fast so require the far-end unit of each request and then to ask to insert unique far-end unit identifier of transmission.As previously mentioned, unique far-end unit identifier can have only 7 bits in every group of system with 128 subchannels.
In one embodiment, communication access request signal comprises a data transfer request.As previously mentioned, data transfer request indicates the request of data type that far-end unit needs, for example DPR, DDPR or DRR.If use dibit identification data transmission request, then last a kind of state can be used for the indicating head data be identical symbol period send simultaneously or followed by the S1 cycle send.Obviously,, just there is not header if request of data is DDPR, because center cell has been known the transmission request relevant with specific far-end unit, for example target of packet, bag size, priority or the like.If request of data is DPR or DRR, the final state of two bits of data transmission request definition is checked to determine when header is sent out by center cell.
In another embodiment, communication inserts and asks also to comprise the header that is used for DDR and DPR request of data.Included header has increased at the quick bit number that sends in the transmission mode that inserts.When bit number increased, the chance of conflict had also increased.Conflict occurs in two far-end units and produces when identical communication of sending them on not with subchannel simultaneously inserts request.As a result, it is the least possible that the preferred embodiment preferably keeps inserting the bit number that sends in the transmission mode fast, so that conflict minimizes.Obviously, insert transmission mode fast and be suitable for most the DDPR request of data, because it does not need from far-end unit to center cell delivery header information.
Therefore, communication inserts unique far-end unit identifier and the two bits of data transmission request that request preferably includes only far-end unit.Yet, in a preferred embodiment, do not comprise two bits of data transmission request if communication inserts request, center cell can suppose that desired is DDPR request of data and based on the far-end unit allocated sub-channels of packet definitions information for asking of relevant that far-end unit of being stored.
Preferably, insert the transmission mode requirement fast and insert the modulator approach that does not require equilibrium during the request use is decoded from the communication that far-end unit is transferred to center cell.Equilibrium requires center cell to know the characteristic of subchannel and far-end unit at those, and for example the absolute amplitude of the signal of Jie Shouing and phase place are necessary in the specific debugging scheme with the data of decoding.Obviously, during fast inserting transmission mode, when communication inserted request and arrives center cell, center cell was not known the sign of the far-end unit of asking before decoding.This is because inserting fast in the transmission mode, and far-end unit can send it in any symbol period communication inserts request, and the timing of request does not provide the information of relevant far-end unit sign of asking.
Since do not know the sign of the far-end unit of asking before the decoding, communication inserts adjustment method (for example QAM) decoding that request can not be required to know in advance subchannel and far-end unit sign.In one embodiment, the present invention uses the communication of Differential Quadriphase Shift Keying (DQPSK) coding far-end unit to insert request easily.When using DQPSK, insert the relevant information stores of request in the difference of phase place rather than in the absolute phase with communication.In addition, also can select appropriate constellation, amplitude is exactly what have nothing to do like this.In this way, communication inserts request and can be received by center cell and decode and the sign that do not require the far-end unit of knowing request in advance.
As previously mentioned, insert far-end unit that transmission mode do not require request fast and wait until that the symbol period of distribution asks to insert again.As a result, may diminish to turn-on time and equal its and send the time that subchannel information that time that communication inserts request adds that center cell uses the far-end unit of request for allocation sends to the far-end unit of request.
In one embodiment, when system is slightly used, for example be lower than a predetermined usage threshold, center cell allows to insert fast transmission mode.Owing to exist more one or more far-end unit can send the subchannel of not using that communication inserts request, in these times, allow to insert fast transmission mode, reduced the chance of conflict.If conflict takes place, center cell will receive the data of obscuring, and for example, data can not be decoded.Do not know which far-end unit request inserts, therefore center cell can not distribute to subchannel suitable far-end unit.In this case, the far-end unit of request can insert the request back in the communication of sending it and wait for a preset time cycle, if and distributed generation, it would just be retransmitted to communicate by letter with inserting and asks, preferably will be to reduce the possibility of another time conflict after a time cycle at random.In one embodiment, if center cell receives the transfer of data of obscuring on subchannel any not usefulness or unappropriated, it is just supposed to have taken place conflict and asks with its communication access of strong request far-end unit repeating transmission to institute's far-end unit broadcasting " detecting conflict " message between two or more communications accesses are asked, preferably after waiting for a time cycle at random.
Obviously, when a large amount of conflict because the repeating transmission behavior of far-end unit and in one embodiment the broadcasting behavior of center cell may increase the use of subchannel.If too many conflict takes place, system uses and may surpass predetermined usage threshold, causes center cell to send control command to all far-end units in one embodiment and stops inserting the transfer of data in the transmission mode fast and recover each far-end unit and only distributing to transfer of data in the poll pattern of its request of data of transmission in its symbol period.
Figure 10 is the flow chart of the far-end unit of the explanation request step of communicating by letter with center cell foundation.With reference now to Figure 10,, after step 360 beginning, method proceeds to step 362, and the far-end unit of request determines that transmission mode is to insert fast or poll.If the far-end unit of request is determined work at present in the polled transmission pattern, for example, center cell is replied a control signal when system's severe is used, and method proceeds to step 366, in poll pattern transmission data.In the polled transmission pattern, the far-end unit of request only transmits its request of data on the subchannel of one or more not usefulness in the symbol period that distributes.
On the other hand, if the far-end unit of request is determined work at present and is being inserted transmission mode fast, for example, center cell is replied a control signal when system slightly uses, method proceeds to step 364 from step 362, and its communication of transmission inserts request on the subchannel of one or more not usefulness in symbol period arbitrarily.As previously explained, the far-end unit of request needn't be distributed to the communication that its symbol period transmits it more by the time and inserts request inserting fast transmission mode.
From step 364 or 366, whether method proceeds to the request of step 368 specified data is a packet request (DPR).If method proceeds to step 370, carry out the step of Figure 11 (a).On the other hand, if request of data is not a DPR (determining in step 368), method proceeds to step 372, and whether the specified data request is a limited packet request (DDPR).If request of data is a DPRR, method proceeds to the step that step 374 is carried out Figure 11 (b).On the other hand, if request of data is not a DDPR (determining in step 273), whether method proceeds to the request of step 376 specified data is a data rate request (DRR).If request of data is a DRR, method proceeds to step 378, carries out the step of Figure 11 (c).If request of data is not top any, method proceeds to step 380, finishes the step of Figure 10.Be appreciated that certain embodiments may comprise that extra request of data type and this method may be suitable for suitably handling those extra request of data.Transforming disclosed method is within those skilled in the art's limit of power to handle specific excessive data request type.
With reference to Figure 11 (a), will the method for handle packet request be described in more detail.Originally, center cell 10 distributes the next available S1 time for the far-end unit of request, and transmits the message (step 204) that a verification distributes in downstream signal.Then, in step 206, the far-end unit of request is transmitting additional information in the S1 time interval 34 of distributing.For example, the extraneous information request may comprise address, bag size and the priority that data send to.As discussed earlier, far-end unit can also resemble in identical symbol period and transmit extra transmission request the transmission request.
Center cell 10 is stored the excessive data package informatin that it receives in step 208.Then, center cell 10 determine to distribute to the far-end unit request subchannel number and send instruction to as the subchannel that uses with admissible every channel bit rate of returning the far-end unit of request.Should be appreciated that center cell 10 will be based on the characteristic of channel collection allocated sub-channels 23 corresponding to the far-end unit 210 of asking of being stored.In this way, center cell 10 can dynamically distribute the subchannel 23 of the most effective number to handle the request of far-end unit.Should be appreciated that center cell receiver (in the information that receives) knows data quantity transmitted from the S1 silence period, also know data transmission rate (this is that far-end unit indicates).Therefore, center cell is known and is finished required time of transmission.Therefore, 10 subchannels 23 that specify number for its distribution in its required time of bag of far-end unit transmission of request of center cell.After specific time quantum (buffering that comprises all necessity), the subchannel 23 that first far-end unit distributed in center cell 10 record now not with and be ready to distribute to any other far-end unit (step 212).
With reference to Figure 11 (b), the method for handling limited packet request (DDPR) will be described again.In a limited packet request, center cell must rely on the excessive data package definition information of storage in the step 208.In addition, this may comprise and resembles the address that is sent to of bag and the big or small such thing of bag.Therefore, in the embodiment that describes, limited packet request is that sent in the past by one could be processed under the situation that the far-end unit of DPR sends at it only.In another embodiment, provide suitable default value, even make that not sending the packet request also can use limited packet request.
As explanation among Figure 11 (b), in step 223, center cell is sought the limited packet transmission requests of storage and is used this information guiding and/or handle the packet that receives.Should be appreciated that center cell 10 needn't receive any extraneous information in the prosign cycle or the S1 time interval 34, and can in step 225, distribute one and a plurality of subchannels 23 immediately for the far-end unit of asking.In addition, because information transmitted amount and data transmission rate all are known, center cell is allocated sub-channels in the required time of this bag of transmission only.After the suitable past in transmission time, center cell 10 writes down the 23 present free time of subchannels and will heavily distribute in 227.
When many communication equipments are communicated by letter effectively by the communication of packing, the transmission rate that other device request is constant, this is to be difficult to realize in the transmission system of using packing sometimes.Such far-end unit can be regulated by distribute a plurality of subchannels 23 of enough handling the data transmission rate of request in the uncertain time.That is to say, till the far-end unit indication no longer needs this bandwidth or detects a mistake.For example, video conference resembles such request that has.In the embodiment that describes, such data transfer request is handled by using data rate request.
With reference to Figure 11 (c), the method that is applicable to the request of deal with data rate will be described again.Typically, center cell 10 will ask to resemble the such additional transmissions information of data transfer rate of address and request after receiving the DRR request.In view of the above, in step 252, center cell distributes next available S1 silence period to send information requested for the far-end unit of request.Then, in step 254, the far-end unit of request sends additional transmissions information at the S1 that distributes in the time interval.As discussed earlier, far-end unit also can resemble and transmit extra indication request in the cycle at prosign the transmission request.
Know the bit rate that data rate request and each subcarrier allow, center cell 10 distributes the subchannel 23 of proper number to handle the throughput of request in step 256.When the far-end unit of request no longer needed to send, it sent new data rate request indication request 0 capacity in step 258.Center cell 10 is understood this and is one and stops request and in step 260 suitable subchannel is designated as not using.
The desirable specified period that does not have repetition S1 silence period.On the one hand, the S1 silence period is frequent more, and the turn-on time that polled transmission pattern or DPR and DRR request can obtain is just short more.Therefore, system responsiveness is good more.On the other hand, frequent more S1 silence period requires many more overheads, has reduced the capacity of whole system.Therefore the suitable frequency in S1 cycle will be according to the needs of particular system and some difference.In an illustrated embodiment, the S1 silence period is used for frame delimits, and is not necessary condition though be to be appreciated that this.Generally speaking, the use of S1 silence period will reduce and start the desired turn-on time of communicating by letter.Under suitable situation, the use meeting of DDPR reduces the turn-on time of the far-end unit of request more.
As described above, start-up time at interval, the S2 and the retraining time interval, S3, do not resemble the S1 silence period many because start and retraining needn't resemble usually immediately and promptly to reply the communication request.In one embodiment, S2 ' s's and S3 ' s's in a superframe 36 alternately.In another embodiment, S2 ' s's and S3 ' s can be by center cell 10 dynamic assignment with at the environment adjustment that changes.For example, can in the time that far-end unit is more likely installed and asked to start, for example daytime, distribute more retention time interval 38 as interval start-up time.At night,, can 38 be assigned as the retraining time interval with more keeping at interval when possibility being installed hour.
Again with reference to figure 3, will describe be suitable for realizing describing synchronously and the central office structure of coordinating.Center cell among the embodiment that illustrates comprises a center modulator-demodulator 30, the webserver 19 and a network interface 41.The center modulator-demodulator comprises a transmitter 40, a receiver 70 and a controller 60.Controller 60 is used for clock and the clock of center modulator-demodulator and the frame of far-end unit transmission synchronously of synchronous far-end modulator-demodulator.The webserver 19 provides numerical data by an asynchronous transmission modulator-demodulator switch 41 (being designated as network interface in the drawings) to transmitter 40.Consider ability, the transmission range of transmitter, the type of the order wire of quality transmission lines and use, the webserver 19 can provide data at height to any data transfer rate of the maximum data rate that allows.Transmitter 40 has comprised several parts, comprises an encoder 43, a Discrete Multitone modulation device 45 and a window filter 46.That encoder 43 is used as is multiplexing, synchronously and the coding signal (as video data) that will transmit.More specifically, it in a plurality of subchannels each go into the component that bit stream is transformed to homophase and quadrature.This coding can be finished by forward error correction and/or trellis code.Encoder typically is designed to export a plurality of sub-symbol that equal the number of subchannels that system can use.For example, in a system with 256 subchannels, encoder will be exported 256 sub-symbol.In the ATIS standard of reference in the above, each sub-symbol is represented 4Kbps.These inputs are multiple inputs of delivering to Discrete Multitone modulation device 45.For example, in the ATIS of reference standard, described a suitable encoder in detail.
Modulator 45 is IFFT modulators that an any appropriate algorithm of usefulness is calculated inverse Fourier transform.Suitable IFFT encoder is at be entitled as " the Multicarrier Modulation:An Idea WhoseTime Has Come " of J.Bingham, IEEE Communication Magazine, May nineteen ninety, article in describe.Because the output of encoder is plural number, so the IFFT modulator receives the twice input of available subchannel.Bit Allocation in Discrete adapts to discrete multisound system and determines.In order to promote it, transmitter 40 also comprises the line monitor of a monitor communication circuit with the line quality of definite each available subchannels.In one embodiment, this line monitor (it can be the part of controller 60) is determined noise level, single gain and the phase shift of each subchannel.This line monitor will typically be used to discern the S3 retraining quality of signals of description.Purpose is to estimate the signal to noise ratio of each subchannel.Therefore, other parameter parameter that also can monitor or replace describing.Determine on which subchannel the transmission coded data with the same in how many data of transmission on each subchannel be dynamically to determine on the basis in Several Factors.These factors comprise line quality parameter, subchannel gains parameter, the power coverage (mask) that is allowed and the maximum subcarrier bit error rate of needs of monitoring.Should be noted that various factors needn't be identical and in use also different really at different subchannels.It should be noted that most that the line quality parameter may need to check repeatedly and in real time modulation scheme is adjusted, adjust modulation with change dynamics ground according to circuit on the different subchannels between the operating period.For example, a suitable Discrete Multitone modulation device has been described prevailingly in identical ATIS standard literary composition retaining.
After encoded signals had been modulated and formed the Discrete Multitone signal, the Discrete Multitone code signal was added the cocycle prefix.This Cyclic Prefix is mainly used in the demodulation of simplifying the Discrete Multitone signal and is not strict the needs.In the ATIS standard, use the Cyclic Prefix of 32 bits.Yet, in the system that uses bigger bandwidth, preferably increase the length of Cyclic Prefix.For example, in signal, find that the work of 40 sampling Cyclic Prefix gets fine with 512 sampling.
Then, the signal of modulation is with outer energy by window filter 46 and/or other filter to minimize.This analog interface that helps avoid remote receiver is saturated.Windowing can realize by a variety of traditional windowing agreements.Transmitter also comprises an analog interface 48 that the Discrete Multitone signal is provided to transmission medium.Twisted pair telephone line to the such hard-wired system of coaxial cable in, analog interface can be the form of line driver.
Center modulator-demodulator 30 also comprises a receiver 70 that receives multi-tone signal from far-end unit.Receiver 70 comprises an analog interface 72, window filter 74, demodulator 76 and decoder 78.Originally the signal that center modulator-demodulator 30 receives receives by analog filter 72.Window filter 74 is designed to effectively to carry out signal windowing and/or the filter function to receiving.A kind of suitable filters device is a time-domain equalizer 74.In addition, windowing can realize by a variety of traditional windowing agreements.The Discrete Multitone signal of demodulator 76 demodulation equilibriums and remove Cyclic Prefix.The signal of decoder 78 decoding demodulation.Demodulator 76 and decoder 78 are finished the reverse function of modulator 45 and encoder 43 respectively effectively.Then, the signal of decoding is delivered to other appropriate users of the webserver 19 or information by interface 41 from decoder 78.The function of time-domain equalizer 74, demodulator 76 and decoder 78 and realize that these function suitable algorithm that need all have in more detail and describe in No. the 5th, 285,474, the United States Patent (USP) of Chow et al..
Again with reference to figure 4, description is suitable for the far-end unit structure that realizes that the present invention is synchronous.In many aspects, the far-end modulator-demodulator is similar to the center modulator-demodulator, though its uplink and downlink message capacity may be different.The signal of center modulator-demodulator 30 transmission is received by analog filter 172 by far-end unit 50.Far-end unit 50 comprises the Discrete Multitone signal of analog interface 172, time-domain equalizer (TEQ) 174, demodulation equilibrium and peels off the demodulator 176 of Cyclic Prefix and the decoder 178 of the signal of the demodulation of decoding.Time-domain equalizer 174 carries out the filter function to the signal that receives effectively.May also to use one to add window filter.Demodulator 176 and decoder 178 carry out the reverse function of modulator 45 and encoder 43 respectively.Xie Ma signal is delivered to remote equipment 22 from decoder 178 then, as TV, computer or other suitable receiving system.The function class of time-domain equalizer 174, demodulator 176 and decoder 178 is similar to the function of corresponding component in the modulator-demodulator of center.Energy outside the upward position of the analog filter 172 of receiver provides the frequency band of notch filter 185 relates to far-end unit with obstruction subchannel alternatively.Can help like this to avoid analog filter saturated.By the filtering mechanism of the outer energy of notch filter and other suitable filtering band is provided, can use the low-cost receiver element, because do not need receiver self to handle so multipotency.
Up coding and modulation can be by finishing with the identical method of the top downlink data transmission of describing in the modulator-demod of center.Therefore, far-end modulator-demodulator 50 will also comprise an encoder 143, multitone modulator 145, window or a filter 146 and an analog interface 148.It requires a frame synchronizer 147 equally, so as aforesaid with suitable amount of multi-tone signal delay, synchronous to be suitable for the far-end of center modem communication with far-end modulator-demodulator 50 and other.In the application of user class, typically make the subchannel of peanut can be used for promoting uplink communication.Yet, should be appreciated that the subchannel that can make any number can be used for such uplink communication.
If the polled transmission pattern is effective, encoder 143 can be represented, for example, and a QAM encoder.For example, one 16 constellation QAM encoders are working properly in many systems.If by inserting the transmission mode transmission fast, encoder 143 can be represented, for example, one 4 constellation difference quadrature phase shift keyings (DQPSK) encoder.For example, at J.Wiley ﹠amp; In the article that is entitled as " Theory and Practice of Modem Design " of the J.Bingham work that Sons (1988) publishes a kind of suitable DQPSK encoder has been described.In the mode switch example of describing, cause in polled transmission and insert the control signal of switching between the transmission mode fast also being input to encoder, though be to be appreciated that also and can be added on another position.Similarly, when poll pattern was effective, the decoder 78 of center cell can be represented, for example, and a QAM decoder.If by inserting the transmission mode transmission fast, center cell decoder 78 can be represented, for example, a difference quadrature phase shift keying (DQPSK) decoder.
Above-described most embodiment is primarily aimed at from the far-end unit to the center cell processing of 10 uplink communication.Therefore the downlink communication class also can be used for such system without limits.Down channel can use the Discrete Multitone modulation of the modulation that is similar to the uplink communication use, and perhaps it can use other suitable technique, as residual sideband (VSB) or QAM.In addition, down channel can also be made up of the dedicated system overhead channel that is used to transmit related pattern signal, synchronizing signal and the assignment information of relevant subchannel 23, the related pattern signal as but be not limited to: S1, S2 and S3 sign.Skilled person understands that as those and can propose various methods that relate to the transmission plan of down channel of the present invention.
Compare when higher when Discrete Multitone transmission is used for uplink and downlink data direction and required data transmission rate, may need in conjunction with transmission plan (that is, " table tennis ") based on the data time division multiple access.That is to say that downlink communication transmits by given frame or superframe number in full bandwidth.Thereafter, uplink communication transmits by given frame or superframe number in full bandwidth.In of the application of many high data rate applications as 25.6 and 51.2 MBPSs, use will be saved cost based on the transmission plan of table tennis in the transmitter and receiver design, because the filter that it does not need to provide expensive is in order to isolate the uplink and downlink communication of carrying out simultaneously, when data transfer rate was higher than 10 MBPSs, the table tennis scheme was especially useful.
With reference to Figure 12, use description to the transmission plan based on table tennis of asymmetric application again.In this embodiment, 8 continuous downlink data superframes (DSF) 885 of transmission on down direction are then at the defeated up superframe (USF) 886 of uplink direction.In other embodiments, being used for the actual frame number that transmits on each direction can change according to the needs of particular system.For example, can be very inequality in order to help the asymmetric speed of downlink communication, transmission cycle can be symmetry or uplink communication obtain more the access.In the system that allows the dynamic bandwidth allocation between uplink and downlink communication, can also provide a controller dynamically to distribute frame between the uplink and downlink communication.Signal at center cell and far-end unit experiences in the system of relative longer distance, may wish to provide behind the DTD of a direction stabilization time 887 to allow transition stable.In an illustrated embodiment, provide a stable period after the uplink, but after downlink transfer not.In fact, be suitable for stable period 887 after both direction one or both of transmission.
Should be appreciated that far-end unit starts and/or synchronous, up subchannel inserts request and/or training can use any technology discussed above to realize at interval.The major advantage of the time division multiple access method of describing is, do not need expensive filter isolation bandwidth may the system of heavy load in simultaneous uplink and downlink communication.Another advantage is, can improve asymmetric transmission in first frequency scope and downlink transfer at the standard frequency division multiplexing of the second frequency scope transmission plan of relatively rattling with uplink, and transmission rate can be brought up to the rank of the system that adopts Echo Cancellation really.But the table tennis transmission plan is compared with the system that requires to use frequency division systems or echo cancelltion and (is used the technology of today) just obtain these transmission rates on low analog element cost.
Though only describe several embodiments of the present invention in detail, should be appreciated that do not break away from spirit and scope of the invention, the present invention can be embodied as other specific forms of many kinds.For example, the present invention mainly describes on Discrete Multitone transmission system background.Yet, should be appreciated that same technology also can be used for other discrete multitone, DMT system, as discrete wavelet multitone, vector coding and other multi carrier modulation scheme.Should also be appreciated that in the embodiment of combination system overhead subchannel, such subchannel on each direction can be share also can be different.Using two subchannels to do very in the overhead bus describes in detail.Yet, should be appreciated that and in uplink and downlink communication, also can use list channel (if particularly using echo cancelltion).In addition, if specific system force to specify and to provide more than two subchannels, so just the communication that is used for some directions (or the two) more than one subchannel is arranged.For example, in the system of the far-end that has the relatively small number mould, each far-end (or child group of far-end) can distribute the subchannel of a special use.In addition, provide redundancy can reduce the danger of noise jamming.Same method can be used for the downlink system overhead communication.Certainly, each far-end uses the shortcoming of private subchannel to be the waste of bandwidth.In addition, the dedicated system overhead subchannel has been described.Yet, in some environment, can multiplexing other overhead information (as control information) on identical subchannel.According to aforementioned, should be appreciated that the example that provides is the consideration for explanation rather than restriction, and the invention is not restricted to details given here, but can in the scope of appended claim, revise.

Claims (55)

1. in the bidirectional data transmission system that has a plurality of discrete subchannels that comprise the overhead bus in use, promotes based on the discrete multitone, DMT transmission plan of frame to communicate by letter between center cell and a plurality of far-end units, be transferred to the method for the frame of center cell synchronously from selected far-end unit, this method may further comprise the steps:
A) wish to set up when communicate by letter when the first selected far-end unit, receive first signal and use the clock of first far-end unit that the clock signal loop timing that carries first signal selectes from center cell with center cell;
B) wish to set up when communicate by letter when the first selected far-end unit, send the synchronizing signal of a far-end startup on the overhead subchannel in the overhead bus from the first selected far-end unit of loop timing to center cell with center cell;
C) when the unit, center receives the synchronizing signal of far-end startup, send the synchronizing signal that a center starts from center cell to the first selected far-end unit, wherein, the synchronizing signal that starts of center comprises the information of first far-end unit that an indication will select better and the synchronous desired frame boundaries phase shift of other far-end unit of communicating by letter with center cell; With
D) frame of the synchronizing signal phase shift output of selected first far-end unit responsing center startup, synchronous better with the frame boundaries that first far-end unit that will select is exported with the frame boundaries of other far-end unit of just communicating by letter output with center cell;
Being to arrange so synchronously, when complete synchronously the time, is consistent from the frame boundaries of different far-ends when arriving center cell substantially.
2. as the method for claim 1 narration, wherein the overhead bus comprises the overhead subchannel of two special uses, and the synchronizing signal that far-end starts is transmitted on different overhead subchannels with the synchronizing signal that the center starts.
3. as the method for claim 1 narration, wherein provide the synchronizing signal of a single dedicated system overhead subchannel and far-end startup and the synchronizing signal of center startup all on this single dedicated system overhead subchannel, to transmit.
4. as the method for claim 1 narration, wherein when two far-end units send the synchronizing signal that their relevant far-end starts substantially simultaneously, identify the synchronizing signal that a conflict and each far-end unit are retransmitted relevant far-end startup.
5. as the method for claim 1 narration, wherein step b, c and d are repeated until that selected far-end unit is synchronous fully, and comprise the proper communication of startup from selected far-end unit to center cell.
6. be used to promote the discrete multitone, DMT center modulator-demod of the bidirectional data transmission system of communicating by letter between center modulator-demod and a plurality of far-end modulator-demod, this center modulator-demod comprises:
The encoder of an encoded digital information;
Monitor communication circuit in a plurality of subchannels each, to determine the monitor of expression noise level line quality parameter, each subchannel is corresponding to a relevant sub-carrier frequencies;
Digital information with coding is modulated to based on the modulator on a plurality of subcarriers in the Discrete Multitone signal of frame, each subcarrier is corresponding to a relevant sound and a relevant subchannel, modulation is to cover the parameter arrangement according to line quality parameter that detects and admissible power at least, and wherein modulation has the ability of data quantity transmitted on the subchannel of the use of dynamically updating and each subchannel during the transmission, with the change of real-time adaptation special parameter;
One before the Discrete Multitone signal is delivered on the transmission line, on it, add the device of Cyclic Prefix; With
A synchronizer, the signal that supervision receives on the dedicated system overhead subchannel, be identified in the synchronizing signal of the far-end startup that receives on the overhead subchannel, determine the phase shift between the frame boundaries of the frame boundaries of the synchronizing signal that far-end starts and above-mentioned Discrete Multitone signal, and produce a synchronizing signal that is transferred to the center startup of far-end modulator-demod, indication starts the selected far-end modulator-demodulator and the synchronous required frame boundaries phase shift of other far-end unit of communicating by letter with the center modulator-demod of the synchronizing signal of far-end startup.
7. be used to promote the discrete multitone, DMT far-end modulator-demod of the bidirectional data transmission system of communicating by letter between center modulator-demod and a plurality of said distal ends modulator-demod, this far-end modulator-demod comprises:
The demodulator of the first Discrete Multitone signal of first group digital information is indicated in a demodulation, this demodulator is used to receive the modulation intelligence as the part of Discrete Multitone signal, wherein demodulator can upgrade dynamically at the modulation intelligence of reception period response change, to adapt to the real-time change of modulation scheme, demodulator is used for peelling off Cyclic Prefix from the Discrete Multitone signal;
The decoder of the digital information of a real-time decoding demodulation;
The encoder of coding second group digital information;
Second group digital information that to encode is modulated to the modulator on a plurality of subcarriers in the second Discrete Multitone signal, and each subcarrier in the second Discrete Multitone signal is corresponding to a relevant sound and a relevant subchannel; With
A synchronizer, when Discrete Multitone far-end modulator-demodulator is wished to start with the communicating by letter of center modulator-demodulator, produce first synchronizing signal of delivering on the overhead subcarrier, reception is from second synchronizing signal of center modulator-demodulator, its indicating remote modulator-demodulator and the required frame boundaries phase shift synchronously of other far-end unit of just communicating by letter with the center modulator-demod, the phase shift second Discrete Multitone signal makes at the multi-tone signal of center modulator-demodulator place and above-mentioned other far-end unit transmission synchronous.
8. as the far-end modulator-demodulator of claim 7 narration, wherein demodulator also comprises a time-domain equalizer.
9. as the far-end modulator-demodulator of claim 7 narration, wherein demodulator and decoder are the parts of receiver, and far-end unit also comprises an analogue notch, is used for before the first Discrete Multitone signal is delivered to receiver the energy level of its filtering with the signal of minimizing receiver processing.
10. have a plurality of discrete subchannels that comprise the overhead bus in use, promote based on the discrete multitone, DMT transmission plan of frame in center cell and the bidirectional data transmission system that a plurality of far-end units are communicated by letter, be transferred to the method for the frame of center cell synchronously from selected far-end unit, this method may further comprise the steps:
When the first selected far-end unit wishes to set up when communicate by letter with center cell, receive first signal and use the clock of first far-end unit that the clock signal loop timing that carries first signal selectes from center cell;
When the clock signal loop timing in the clock and first signal, the synchronizing signal that starts to far-end of center cell transmission from the first selected far-end unit on the dedicated system overhead subchannel in the overhead bus;
The synchronizing signal that the response far-end starts receives the synchronizing signal that starts from the center that far-end unit sends, wherein, the synchronizing signal that starts of center comprises the information of first far-end unit that an indication will select and the synchronous desired frame boundaries phase shift of other far-end unit of communicating by letter with center cell; With
The frame of first far-end unit output that the synchronizing signal phase shift that responsing center starts is selected, synchronous better with the frame boundaries that the frame boundaries of the frame of first far-end unit that will select output and other far-end unit of just communicating by letter with center cell are exported, arrange synchronously to produce such effect, when their frame boundaries from different far-ends when center cell is received are consistent substantially.
11. have the discrete subchannel of uplink communication between a plurality of far-end units of a plurality of promotions and the center cell in use, promote center cell to communicate by letter with a plurality of far-end units in the bidirectional data transmission system based on the discrete multitone, DMT transmission plan of frame, to send to the frame of center cell and the frame synchronization that sends to center cell from other far-end unit from the first selected far-end unit, make the frame boundaries of the frame that sends from first far-end unit when arriving center cell substantially with the synchronous method of frame boundaries of the frame that sends from other far-end unit, this method may further comprise the steps:
On a plurality of discrete subchannels that are used to promote uplink communication, periodically provide the synchronous silence period; With
In the first synchronous silence period of selecting, send a broadband enabling signal from first far-end unit to center cell, this broadband enabling signal comprises a plurality of enabling signals of transmitting on different subchannels, this broadband enabling signal has frame boundaries.
12. as the method for claim 11 narration, wherein:
When first far-end unit wishes to set up when communicate by letter with center cell, the downlink communication broadcasting of the described first far-end unit central monitoring position unit and with the frame boundaries of broadband enabling signal substantially with the downstream signal of far-end unit reception in the frame timing index that carries synchronous;
Center cell receives the broadband enabling signal and sends a synchronizing signal to first far-end unit, and this synchronizing signal has the frame boundaries of the signal that indication sends first far-end unit better and the information of the synchronous desired frame boundaries phase shift of frame boundaries of the signal of other far-end unit of communicating by letter with center cell transmission; And
The response synchronizing signal, the frame frame boundaries of phase shift first far-end unit output is with synchronous better with the frame boundaries of other far-end unit of just communicating by letter with center cell output with the frame boundaries of first far-end unit output; And
Being to arrange so synchronously, when complete synchronously the time, is consistent from the frame boundaries of different far-ends when arriving center cell substantially.
13. the method for narration also is included in the step of the training time that periodically provides synchronous on a plurality of discrete subchannels that are used to promote uplink communication in claim 11 or 12, does not wherein need to train the far-end unit with retraining to mourn in silence in that specific training time in the specific training time.
14. also comprise the step that makes first far-end unit on a plurality of subchannels that are used to promote uplink communication, send a plurality of training signals at selected time durations as the method for narration in the claim 13.
15. also comprise as the method for narration in the claim 14 and to determine that indication is used to promote the step of first group of characteristic of channel of channel capacity of a plurality of subchannels of uplink communication.
16. the method as narration in the claim 15 also is included in the step of preserving first group of characteristic of channel in the characteristic of channel matrix, wherein above-mentioned matrix comprises the information of the channel capacity of a plurality of discrete subchannels between all far-end units of indication and the center cell.
17. the method as any one narration among the claim 11-16 is further comprising the steps of:
Conflict of qualification when in first selected lock in time, sending a relevant broadband enabling signal more than a described far-end unit;
When conflict was identified, response broadband enabling signal sent collision signal to a plurality of far-end units; And
Wherein the far-end unit of each conflict is retransmitted its broadband enabling signal after a while one in described synchronous silence period, and the far-end unit of each conflict was arranged to wait for an independently random interval before the broadband enabling signal of retransmitting it.
18. method as any one narration among the claim 11-17, wherein the synchronize quiet time has a sufficiently long cycle, the silence period sign that sends from center cell can be transferred to decentre unit far-end unit farthest like this, and response silence period sign turn back to the enabling signal of center cell can be among the time in synchronize quiet.
19. as the method for claim 18 narration, wherein the synchronize quiet time has a cycle in about 50 to 500 milliseconds of scopes.
20. as the method for claim 11-19 narration, comprise also from center cell and periodically transmit an indication of forbidding the subchannel that far-end unit uses that wherein far-end unit determines that the broadband enabling signal does not comprise any transmission on the subchannel that bans use of.
21. as the method for claim 12 narration, wherein downlink communication is that the frame timing index that carries in the downstream signal of Discrete Multitone signal and far-end unit reception is the frame boundaries of descending Discrete Multitone signal.
22. as the method for claim 12 narration, wherein downlink communication is to select from the group that comprises quadrature amplitude modulation signal and vestigial sideband signal.
23. have the discrete subchannel of uplink communication between a plurality of far-end units of a plurality of promotions and the center cell in use, promote center cell to communicate by letter with a plurality of far-end units in the bidirectional data transmission system based on the discrete multitone, DMT transmission plan of frame, the subcarrier transmission quality of dynamic chek from the far-end unit to the center cell, to promote the method for center cell to the allocated bandwidth of far-end unit, this method may further comprise the steps:
A) on the discrete subchannel of a plurality of promotion uplink communications, periodically provide the synchronize quiet time, wherein during that specific training time, mourn in silence at the far-end unit that does not require training or retraining during the specific training time;
B), be used to promote to send training signal from first far-end unit on a plurality of subchannels of uplink communication in selected synchronize quiet in the time; And
C) during the selected training time, at the training signal of center cell monitor transmissions and determine that indication is used to promote first group of characteristic of channel of capacity of a plurality of subchannels of uplink communication.
When which subchannel first far-end unit that is defined as selecting distributed be used for uplink communication, center cell can use first group of characteristic of channel.
24. as the method for claim 23 narration, also be included in the step of preserving first group of characteristic of channel in the characteristic of channel matrix, wherein said matrix comprises the information of the channel capacity of a plurality of discrete subchannels between all far-end units of indication and the center cell.
25. the method as claim 24 narration comprises that also according to the one group of information that obtains, the step of the groups of subchannels of the first selected far-end unit is distributed in adjustment from a plurality of training signals that are transferred to center cell.
26. also comprise as the method for any narration among the claim 23-25 and to repeat the step transmitting and monitor a plurality of different far-end units, to determine each the characteristic of channel in a plurality of different far-end units, promote the Dynamic Bandwidth Allocation to different far-end units, wherein different far-end units send their training signals separately during the different silence periods.
27. the method as claim 23-26 narration also comprises the step that sends the retraining signal to the first selected far-end unit, wherein Xuan Ding first far-end unit only responds its training signal of retraining signal transmission of reception.
28. have the discrete subchannel of uplink communication between a plurality of far-end units of a plurality of promotions and the center cell in use, promote center cell to communicate by letter with a plurality of far-end units in the bidirectional data transmission system based on the discrete multitone, DMT transmission plan of frame, the subcarrier transmission quality of dynamic chek from the far-end unit to the center cell is to promote the method for center cell to the allocated bandwidth of far-end unit, and this method may further comprise the steps:
A) on the discrete subchannel of a plurality of promotion uplink communications, periodically provide the synchronize quiet time, wherein during that specific training time, mourn in silence at the far-end unit that does not require training or retraining during the specific training time;
B) send a retraining signal to first selected far-end unit;
C), be used to promote to send training signal from first selected far-end unit to center cell on a plurality of subchannels of uplink communication in selected synchronize quiet in the time; And
D) during the selected training time, at the training signal of center cell monitor transmissions and determine that indication is used to promote the characteristic of channel of capacity of a plurality of subchannels of uplink communication.
E) in characteristic of channel matrix, preserve first group of characteristic of channel, wherein said matrix comprises the information of the channel capacity of a plurality of discrete subchannels between indication different far-end units and the center cell, and center cell can use this matrix when being defined as the first different far-end units and distributing which subchannel to be used for uplink communication; And
F) repeat transmission, transmission, supervision and preservation step to additional far-end unit, wherein different far-end units transmits their training signals separately in the different silence periods.
If 29. as the method for claim 28 narration also comprise determine whether the far-end unit request upgrade immediately and have far-end unit, send the step of next retraining signal to the far-end unit of this request.
30. have the discrete subchannel of uplink communication between a plurality of far-end units of a plurality of promotions and the center cell in use, promote center cell to communicate by letter with a plurality of far-end units in the bidirectional data transmission system based on the discrete multitone, DMT transmission plan of frame, the method of the transmission request of notice center cell far-end unit, this method may further comprise the steps:
Periodically provide the synchronize quiet time on a plurality of discrete subchannels that are used to promote uplink communication, wherein the unauthorized far-end unit that transmits request of data information in the specific silence period was mourned in silence in the specific silence period;
Transmit data transmission request signal from first a selected far-end unit to center cell being different from the silence period interlude;
Authorization signal of first far-end transmission to selected is selected one first silence period of first remote allocation;
During first silence period, on a plurality of discrete subchannels, transmit request of data information to center cell from the first selected far-end unit; And
The response data solicited message is for the first selected far-end unit distributes at least one subchannel to promote the uplink communication between first far-end unit and the center cell.
31. method as claim 30 narration, wherein data transmission request signal is a data transfer rate request signal, and wherein center cell distributes enough subchannels for the first selected far-end unit, makes the first selected far-end unit to transmit on the required data transfer rate of appointment in request of data information.
32. as the method for claim 31 narration, wherein center cell distributes enough subchannels for the first selected far-end unit, it wishes to change up to selected first far-end unit indication.
33. method as any one narration of claim 30-32, wherein data transmission request signal is a packet request signal, and wherein in the time enough of center cell amount of information of appointment in being transmitted in request of data information, for the first selected far-end unit distributes at least one subchannel.
34. method as any one narration of claim 30-32, wherein limited packet information is included among the request of data information, this method also comprises after the request of data message transmission of definition, transmit the step of limited packet request signal from the first selected far-end unit to center cell, wherein center cell directly respond limited packet request at least one subchannel of first far-end unit distribution for selecting.
35. as the method for any one narration of claim 30-34, first far-end unit monitor communication and only at least one subchannel transmitting data request signal of usefulness not before the transmission data request signal wherein.
36. as the method for claim 30 narration, the wherein second value designation data bag request of the first numerical value designation data rate request of data transmission request signal, data transmission request signal and the third value of data transmission request signal is indicated limited packet request.
37. as the method for claim 36 narration, data transfer request wherein is a dibit signal.
38. as the method for claim 30 narration, wherein the indication of first numerical value of data transmission request signal is one, is used to ask to distribute the second value of a silence period and data transmission request signal to indicate limited packet request.
39. method as any one narration among the claim 30-28, wherein the discrete multitone, DMT transmission is the branch frame, each frame comprise a plurality of symbols and wherein each far-end unit be assigned with a relevant symbol, it can transmit its request of data symbol betwixt, and wherein center cell is determined the sign of the specific far-end unit of transmission data transmission request signal at least according to the part of the symbol that receives data transmission request signal betwixt.
40. have the discrete subchannel of uplink communication between a plurality of far-end units of a plurality of promotions and the center cell in use, promote based on the discrete multitone, DMT transmission plan of frame in center cell and the bidirectional data transmission system that a plurality of far-end units are communicated by letter, the method of the transmission request of notice center cell far-end unit, this method may further comprise the steps:
On at least one subchannel that is not used by any far-end unit, with the special symbol of the selected first far-end unit related data frame during, transmit data transmission request signal from the first selected far-end to center cell;
On the discrete subchannel of a plurality of not usefulness,, transmit request of data information to center cell from the first selected far-end with the data transmission request signal while; With
Response promotes the request of data information of uplink communication between first far-end unit and the center cell, for the first selected far-end unit distributes at least one subchannel.
41. have the discrete subchannel of uplink communication between a plurality of far-end units of a plurality of promotions and the center cell in use, promote based on the discrete multitone, DMT transmission plan of frame in center cell and the bidirectional data transmission system that a plurality of far-end units are communicated by letter, the method of the transmission request of notice center cell far-end unit, this method may further comprise the steps:
To data transfer request of center cell transmission, wherein this data transfer request indicates whether to ask a specific data transfer rate or does not specify the information transmitted amount of wishing from the first selected far-end;
Response promotes the data transfer request of uplink communication between first far-end unit and the center cell, for the first selected far-end unit distributes at least one subchannel, wherein when asking specific data transfer rate, center cell distributes enough subchannels for the first selected far-end unit, make the first selected far-end unit on the data transfer rate of request, to transmit, and when wherein wishing transmission specified message amount, center cell distributes at least one subchannel for the first selected far-end unit in the required time enough of transmission specified message amount.
42. use discrete subchannel, promote in center cell and the bidirectional data transmission system that a plurality of far-end units are communicated by letter based on the discrete multitone, DMT transmission plan of symbol with uplink communication between a plurality of far-end units of a plurality of promotions and the center cell, the method of the transmission request of notice center cell far-end unit, this method may further comprise the steps:
Use and insert transmission mode fast, insert request from the first selected far-end unit to the center cell transport communication, this communication inserts unique far-end unit identifier that request comprises this first selected far-end unit of sign, and at least one not the subchannel of usefulness use and do not require that when center cell decode balanced modulation scheme transmits from the first selected far-end unit; And
Response promotes the communication of uplink communication between first selected far-end unit and the center cell to insert request, for the first selected far-end unit distributes at least one subchannel.
43. the method for claim 42, wherein:
Described communication inserts request and also comprises a data transmission request signal; And
This data transfer request is limited packet request signal, and wherein center cell distributes enough subchannels for the first selected far-end unit, makes that the first selected far-end unit can be according to storage and the selected relevant limited packet transmission requests transmits data packets of first far-end unit; The limited packet transmission requests of this storage is known to center cell before receiving limited packet request signal.
44. the method for claim 42 or 43 is further comprising the steps of:
Response is from the order of center cell, forbids that far-end unit uses to insert the transmission mode transmission fast, and be that use in system produces when surpassing a predetermined thresholding wherein from the order of center cell; And
Response allows far-end unit to use the poll pattern transmission from the order of center cell.
45. use discrete subchannel, promote in center cell and the bidirectional data transmission system that a plurality of far-end units are communicated by letter based on the discrete multitone, DMT transmission plan of symbol with uplink communication between a plurality of far-end units of a plurality of promotions and the center cell,, comprising to the center cell apparatus for transmitting data from selected far-end unit:
Be used to receive above-mentioned data and be the serial-parallel converter of parallel data above-mentioned data conversion;
The encoder that links to each other with above-mentioned serial-parallel converter, be used for an above-mentioned parallel data of coding according to first and second modulation schemes of responsive control signal, above-mentioned first modulation scheme is used in the polled transmission pattern, and the receiver of the above-mentioned center cell of decoding request has the priori of the sign of above-mentioned selected far-end unit, and above-mentioned second modulation scheme is used in the transmission mode and decoding does not require that the receiver of above-mentioned center cell has the priori of the sign of above-mentioned selected far-end unit inserting fast.
The IFFT modulator that links to each other with above-mentioned encoder is used to modulate the encoded data from above-mentioned encoder; With
With the parallel to serial converter that above-mentioned IFFT modulator links to each other, being used for the modulated data conversion from above-mentioned IFFT modulator is that serial form is to be transferred to above-mentioned center cell.
46. the device of claim 45, wherein said first modulation scheme are QAM and described second modulation scheme is DQPSK.
Described quick access transmission mode is operated in system and uses when being lower than above-mentioned predetermined usage threshold 47. the device of claim 45 or 46, wherein said polled transmission pattern are operated in system when use surpassing a predetermined usage threshold.
48. the device of claim 47 is wherein:
When being operated in described poll pattern, described selected far-end unit is only sending data during the specific symbol period on unappropriated subchannel, and the described special symbol cycle is specifically distributed to described selected far-end unit and is used for inserting request; And
When being operated in described quick access module, described selected far-end unit sends data and is used for inserting request no matter whether described specific symbol period has distributed to described selected far-end unit on unappropriated subchannel in any symbol period.
49. use discrete subchannel, promote in center cell and the bidirectional data transmission system that a plurality of far-end units are communicated by letter based on the discrete multitone, DMT transmission plan of symbol with uplink communication between a plurality of far-end units of a plurality of promotions and the center cell, reception comprises from the device of selected far-end unit to the data of center cell transmission:
The serial-parallel converter that is used to receive above-mentioned data and above-mentioned forward error correction data is transformed to parallel data;
The FFT demodulator that links to each other with above-mentioned serial-parallel converter is used for the parallel data of demodulation from above-mentioned serial-parallel converter;
The decoder that links to each other with above-mentioned FFT demodulator, be used for according to a decoding of first and second demodulation schemes of responsive control signal from above-mentioned FFT demodulator through demodulated data, above-mentioned first demodulation scheme in poll pattern, work and decoding request to the priori of the identifier of above-mentioned selected far-end unit, above-mentioned second demodulation scheme does not require priori to the identifier of above-mentioned selected far-end unit inserting fast to work and decode in the transmission mode; With
With the parallel to serial converter that above-mentioned decoder links to each other, being used for the data conversion through decoding from above-mentioned decoder is serial form.
50. any one described method among claim 1-5 and the 11-44, wherein bidirectional data transmission system be included in twisted pair telephone line to the ADSL (Asymmetric Digital Subscriber Line) system of transmitting data and wherein modulator encoded digital information be modulated to be equivalent on the subcarrier of subchannel that each bandwidth is approximately 4.3125kHz.
51. any one described method among claim 1-5 and the 11-44, wherein bidirectional data transmission system is a cable system that is included in the transmission over coaxial cable data.
52. any one described method among claim 1-5 and the 11-44, wherein bidirectional data transmission system is a digital cellular television system that comprises transmitting wireless signals.
53. use in the bidirectional data transmission system have between a plurality of far-end units of a plurality of promotions and the center cell the discrete subchannel of downlink communication between the uplink communication and center cell and a plurality of far-end, to promote to communicate by letter between center cell and a plurality of far-end units based on the discrete multitone, DMT transmission plan of frame, the method for transmission data may further comprise the steps:
A) use Discrete Multitone modulation scheme to transmit at least one frame downlink data at least one far-end unit, wherein during downlink data transmission, forbid transmitting uplink data from center cell;
B) use Discrete Multitone modulation scheme to transmit at least one frame upstream data to center cell, wherein during transmitting uplink data, forbid downlink data transmission from least one far-end unit; And
C) continue repeating step a) and b).
54. also be included in the step that be provided after at least one downlink frame of transmission and the uplink frame stable period as the method for claim 53 narration, wherein between stable period, all do not have transmission in any direction.
55. as the method for claim 53 or 54 narrations, wherein admissible data transmission rate is per second 10 megabits at least.
CN 95194297 1994-06-02 1995-06-02 Method and apparatus for coordinating multi-point-to-point communications in multi-tone data transmission system Pending CN1156528A (en)

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US08/377,023 1995-01-20
US08/396,132 1995-02-28
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US7089005B2 (en) 2002-07-31 2006-08-08 Interdigital Technology Corporation Handover between a cellular system and a wireless local area network
CN102014478A (en) * 2009-11-05 2011-04-13 大唐移动通信设备有限公司 Point-to-point remote clock transmission method and equipment
CN101390429B (en) * 2006-01-11 2013-05-15 汤姆森许可贸易公司 Apparatus and method for controlling channel switching in wireless networks
CN101888695B (en) * 2009-05-12 2013-10-30 大唐移动通信设备有限公司 Time service method, system and device of base station
CN105482233A (en) * 2016-01-27 2016-04-13 广东省南粤交通揭惠高速公路管理中心 Ultrahigh molecular weight polyethylene composition for extrusion molding escape pipeline
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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7089005B2 (en) 2002-07-31 2006-08-08 Interdigital Technology Corporation Handover between a cellular system and a wireless local area network
CN101390429B (en) * 2006-01-11 2013-05-15 汤姆森许可贸易公司 Apparatus and method for controlling channel switching in wireless networks
US8588115B2 (en) 2006-01-11 2013-11-19 Thomson Licensing Apparatus for controlling channel switching in wireless networks
CN101888695B (en) * 2009-05-12 2013-10-30 大唐移动通信设备有限公司 Time service method, system and device of base station
CN102014478A (en) * 2009-11-05 2011-04-13 大唐移动通信设备有限公司 Point-to-point remote clock transmission method and equipment
WO2011054287A1 (en) * 2009-11-05 2011-05-12 电信科学技术研究院 Method and system for remote point-to-point clock transmission
CN105482233A (en) * 2016-01-27 2016-04-13 广东省南粤交通揭惠高速公路管理中心 Ultrahigh molecular weight polyethylene composition for extrusion molding escape pipeline
CN108414808A (en) * 2017-02-10 2018-08-17 罗德施瓦兹两合股份有限公司 Dynamic measurement system for detecting dynamic data signal and method
CN108414808B (en) * 2017-02-10 2022-05-13 罗德施瓦兹两合股份有限公司 Dynamic measurement system and method for detecting dynamic data signals

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