WO2001086850A1

WO2001086850A1 - Method and apparatus for virtual band-splitting

Info

Publication number: WO2001086850A1
Application number: PCT/US2001/009914
Authority: WO
Inventors: Rodrigo Garces; Michael W. Ritter; Robert J. Friday
Original assignee: Ricochet Networks, Inc.
Priority date: 2000-05-10
Filing date: 2001-03-27
Publication date: 2001-11-15
Also published as: AU2001247843A1

Abstract

A wireless digital communication system (figure 4), and in particular a microcellular packet communication system, employing frequency hopping spread spectrum techniques using channels for receiving and transmitting information to different elements of the system. An exemplar embodiment of the present invention provides a method for transferring information between a network device (310 and 312) and a user system (332, 334 amd 336). The user system receives information over a downlink channel (416, 412 and BAD D) of a first plurality of frequency channels from the network device and the user system transmits information over a uplink channel (416, 414 and BAND U) of a second plurality of frequency hopping channels to the network device. This has the function of separating the communications channel into non-interfering bands between the user system and the network device. Another embodiment provides for using a channel mask at either the network device or the user system or both to perform band-splitting, as well as backward compatibility with an existing frequency hopping system that does not use this method.

Description

METHOD AND APPARATUS FOR VIRTUAL BAND-SPLITTING

CROSS-REFERENCES TO RELATED APPLICATIONS The following patent is hereby incorporated by reference in its entirety for all purposes:

U.S. Patent No. 5,479,400 in the names of Robert P. Dilworth, et. al., titled "Transceiver Sharing Between Access and Backhaul in a Wireless Digital Communication System," issued December 26, 1995.

BACKGROUND OF THE INVENTION

This invention relates to wireless digital communication systems, and in particular to microcellar packet communication systems, employing frequency hopping spread spectrum techniques using different channels for receiving and transmitting information to some systems. As personal wireless commiinication systems such as in cellular telephony proliferate, the spectrum available to the wireless user for accessing cell sites for interactive communication becomes premium. There is great pressure to shrink the cell size of cellular telephone systems, for example, in order to promote frequency reuse and ultimately increase user density and capacity, as well as to reduce the required transmitter power for battery-operated portables. This is part of the trend toward so-called microcellar systems.

A major drawback of conventional microcellular architectures and systems is self-interference (also known as co-channel interference), which arises because of the frequency reuse philosophy. Transmissions occurring throughout the network may cause self-interference. For example, there is self-interference if two different pairs of senders and receivers are nearby each other and are transmitting in the same channel. Each pair has an effect on the signal of the other pair. If the interference signal is strong enough it will corrupt the carrier signal. Since transmissions outside microcells are not likely to be coordinated, this effect which reduces successful transmission is typically a random phenomenon, with the length, power, and frequency of interference bursts varying over the short term (burst transfers from nearby stations) and the long term (time of day, growth of network subscribers). Thus there is a need for reducing the self-interference in a micro-cell network in order to increase performance.

SUMMARY OF THE INVENTION According to the invention, a microcellular digital packet communication system is provided for digital communication having a plurality of repeating packet-mode fixed-site transceivers each being at a plurality of different sites and each being capable of communicating on mutually-common frequencies, including for example by means of frequency-hopping spread spectrum, wherein the frequency band is dynamically allocated between channels for user systems and channels for network devices. The system is applicable to both data and voice communication.

A first embodiment of the present invention provides a method for transferring information between a network device, having a processor, a memory and a transceiver, and a user system, having a processor, memory and a transceiver, using wireless communication channels. The user system receives information over a downlink channel of a first plurality of frequency hopping channels from the network device, where the first plurality of frequency hopping channels are the only channels used for receiving information by the user system. The user also transmits information over an uplink channel of a second plurality of frequency hopping channels to the network device, where the second plurality of frequency hopping channels are the only channels used for transmitting information by the user system. This has the function of splitting the communications channel between the user system and the network device into separate non-interfering bands. The first plurality of frequency hopping channels may be interleaved with the second plurality of frequency hopping channels. A second embodiment of the present invention provides a method for transferring information between a first device and a second device using spread spectrum wireless communication channels, where the first device may be, for example a network device, and the second device may be, for example, a network or user system/device. The first device receives a first information item over a first frequency channel, where the first information item includes a transmit channel for responding to the second device by the first device. Next a second information item is transmitted by the first device over a second frequency channel, for example the transmit channel, to the second device, where the second information item includes a receive channel for responding to the first device by the second device. Another embodiment provides for a method for communicating an information item between a first device and a second device, each including a processor, memory and transceiver, using a set of transmit frequencies from among a plurality of frequency hopping spread spectrum frequencies of a communications network. A first transmit frequency is selected from the set of transmit frequencies using a first channel mask, where the first channel mask allows only the set of transmit frequencies from a plurality of spread spectrum transmit frequencies to be available for transmitting the information item. An example channel mask may be 162 bits long in groups of bytes with the bit position set to "1" indicating the allowed transmit frequencies. The information item is then transmitted from the first device to the second device using one of the allowed channels. In another embodiment, the second device includes a second channel mask that allows only a set of receive frequencies from a plurality of frequency hopping spread spectrum frequencies to be available for receiving and processing the information item by the second device. The invention will be better understood by reference to the following detailed description in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a simplified block diagram of an embodiment of the present invention showing a microcellular system (half duplex, single channel, single transceiver);

Fig. 2 is a simplified block diagram of another embodiment of the present invention showing a microcellular system (full duplex, dual channel dual transceiver);

Fig. 3 illustrates a simplified block diagram of another embodiment of the wireless communication system of the present invention;

Fig. 4 discloses an expanded portion of Figure 3 of a specific embodiment of the present invention;

Fig. 5 illustrates a portion of a band plan for a band splitting frequency system; Fig. 6 is a simplified diagram illustrating the connection establishment and data transfer phases of a specific embodiment of the present invention; and

Figs. 7 A, 7B illustrate examples of when the frequency information field may be used in a data packet. DESCRIPTION OF THE SPECIFIC EMBODIMENTS Referring to Fig. 1, there is shown an example microcellular wireless communication system 10 comprising user systems 120, 121, 124, 125, which include packet terminal node controller-equipped transceivers 122 and typically a user terminal device 123, which includes a processor and a memory (not shown), for example, a Personal Computer (PC), Personal Digital Assistant (PDA), mobile telephone or laptop/notebook computer. The user systems may communicate over conventional wired telecommunication lines 162, 164 with other like devices, e.g., a PC 151 having a modem 152, connected to a central office switch 160. Trunk terminals or concentrators 170, 172 may provide the interface to the telephone lines 164, 166. In accordance with an embodiment of the invention, the microcellular wireless system 10 employs a plurality of fixed site repeaters 100, 101, 102,103 to capture the signals of the transceivers. Other embodiments of the invention have both mobile and portable user systems, as well as fixed user systems, e.g., a room containing a plurality of user PC's with transceivers. An illustrative example is useful in understanding an embodiment of the invention. A mobile transceiver node equipped vehicle 124 originates a message comprising a sequence of message segments, such as a self-contained digitized message segment A in packet format (with address header, etc.) on a frequency FI. Because it is in packet format, the message segment A is essentially self-contained and includes in its header information to address it to a local destination and an ultimate destination, namely, a number of fixed site repeaters 100, 101, 102, and ultimately another terminal, such as mobile transceiver node 125. The message A is sent to one or more fixed site repeaters 100, 101, 102 known to the mobile transceiver 124, either in a broadcast format (on the same frequency) or targeted in a sequence of directed acknowledgeable message segments via a communication link maintained between the terminal 124 and each of the various repeaters 100, 101, 102, each having a different local address. Imbedded within the fixed site repeaters are controllers 181, 182, 183 for responding to, readdressing and distributing the packets containing message segment A received from the mobile transceiver 124. The message segment A is relayed according to the embodiment under supervision of the controllers 181, 182 183 by the fixed site repeaters 100, 101,102 following receipt of the message segment originating at terminal 124 on the same frequency FI, the message segment A addressed initially for example to fixed site repeater 102 being readdressed and relayed to fixed site repeater 100, and only one message segment A from fixed site relay 100 being readdressed to a fixed site relay, such as relay 140. The message segment A is captured by relay 140 and relayed through telephone lines, if needed, to another relay 141, which transmits the readdressed message segment A on frequency F2 from its relay station to the fixed site repeater 103. The message segment A is then directed by fixed site repeater 103 on frequency F2 to the ultimate destination transceiver terminal 125.

In a similar manner, a message segment B from transceiver 122 on frequency FI is relayed to and by each of repeaters 100, 101, also on frequency FI to the relay 140, by which means of the concentrator 170 and the central switch 160 it is relayed to PC 151 via modem 152. In the embodiment hereinabove, the interchange thus far described between wireless sites has been illustrated in terms of a single mutually common frequency channel or frequency hopping sequence within a geographic region. Referring to Fig. 2, there is shown an alternative embodiment to the present invention, wherein the signaling scheme is full duplex. In Fig. 2, the signal interchange is substantially simultaneous on both a first frequency FI and a second frequency F2. For example, a message C originating with a transceiver 121 may be involved in a packet interchange on frequency FI while another unrelated message D (originating typically from the destination of message C) is involved in a packet interchange on a frequency F2, both messages being relayed through fixed site repeater 100 under control of controller 181, and an inband backhaul channel pair on frequencies FI and F2 are used to communicate with relay 140 connected to concentrator 170 in turn wired to telephone lines 164, 162 through a central office switch to PC 151. To/from message routing need not be via the same paths for each packet.

FIG. 3 illustrates a simplified block diagram of another embodiment of the wireless communication system of the present invention. The network backbone includes network devices 310, 312, 314. A network device, such as 310 or 312, may include a fixed site repeater or a network device, such as 314, may include a wired access point (WAP). The WAP may include a concentrator or a multiplexer or a trunk terminal, and it is the interface to the telephone network which includes the Internet 320. There are a plurality of user systems 330, 332, 334, 336, 340, 342, 344, which communicate with the network backbone 310, 312, 314; and some user systems, 332, 334, 336, and 340, 342 communicate with each other. The user systems may include a transceiver, such as 121, 122, or 124, and the user system may further include a processor and a memory, such as, user terminal device 123. The network devices 310, 312, 314 may include, for example, one or more fixed site repeaters, such as 100, 101, 102 or a relay, such as 140 or 141

(Fig. 1).

Figure 4 illustrates an expanded portion of Figure 3 of a specific embodiment of the present invention. The network devices include network device 1, 310 and network device 2, 312. The user systems include user system 1, 332, user system 2, 334, and user system 3, 336. Each user system 332, 334, 336 may include a processor, a memory and a transceiver. Network device 310 communicates with network device 312 over a plurality of frequency hopping channels, 410. Each of these plurality of frequency hopping channels is in a Band D. For example, the Band D may include fifty frequency hopping channels of either 320 kHz or 160 kHz bandwidth in the Federal

Communications Commission (FCC) ISM 900 MHz band (see 47 CFR, part 15, section 15.247, which is herein incorporated by reference). In another embodiment, the Band D may include two hundred frequency hopping channels of 320 kHz bandwidth in the FCC 2.4 GHz band. For a specific embodiment network device 310 and network device 312 are half duplex. In another embodiment, network device 310 and network device 312 are full duplex devices. In a specific embodiment of the present invention the frequency hopping channels in the 900 MHz band on which network device 310 communicates with user system 334 are split into a set of downlink channels 412, i.e. Band D, and a set of uplink channels 414, i.e. Band U. The downlink channels 412 include 50 frequency hopping channels in the 900 MHz band, each with a bandwidth of either 160 kHz or 320 kHz. The downlink channels 412 (Band D) are only for one-way communication from the network device 310 to the user system 334. The uplink channels 414 (Band U) are used for the one-way communication from the user system 334 to the network device 310. The uplink channels 414 include 50 frequency hopping channels at 160 kHz bandwidth in the 900 MHz band. In one embodiment the channels in Band D are interleaved with the channels in Band U. User system 334 may also communicate with user system 336 over Band D 420. Thus side to side communications between network devices, for example, 310 and 312, and side to side communications between user systems, for example 334 and 336 are via Band D, for example 410 and 420. Communications between a network device and a user system, e.g., network device 310 and user system 334 are split into Band D, e.g. 412, for downloading information from the network device to the user system and Band U, e.g. 414, for uploading information from the user system to the network device. The band-splitting of the network-user device channel into Band D and U mitigates the unbalanced behavior in the probability of packet success on the uplink, e.g., 414, compared to the downlink, e.g., 412. A possible cause for this unbalance is that in environments where network devices are located high above the surrounding clutter, network devices may see many other network devices, and packets going from the user system to the network device may have a much higher probability of interfering with other packets. The cause for many of the failures is probably due to self-interference. Thus the band-splitting mostly improves the probability of success of packets on the uplink, although it may also improve the downlink. An illustrative example is useful in explaining self-interference from neighboring transceivers, as well as why band-splitting improves performance. Figure 5 illustrates a portion of a simplified band plan for a band-splitting system, including a amplitude 452 versus frequency 454 graph for two Band D channels 460, 480 and one Band U channel 470. The first Band D channel, Dl 460 is centered at 902.88 MHz 462 with a bandwidth of 320 kHz 464 to 466. The second Band D channel, D2 480 is centered at 903.36 MHz 482 with a bandwidth of 320 kHz 474 to 475. The Band U channel, U2 470 is centered at 903.12 MHz 472 with a bandwidth of 160 kHz 466 to 474. The adjacent channel interference between Dl 460 and U2 470 is shown by the overlap area 468. The adjacent channel interference between U2 470 and D2 480 is shown by the overlap area 476. Note that these overlap areas are not to scale, but are for illustration purposes only. Thus, if network device 310 receives uplink data 414 over U2 470 from user system 334 and transmits downlink data 412 over D2 480 then there may be adjacent channel interference represented by overlap area 476.

However, while band-splitting may have some adjacent interference, e.g. 476, the splitting greatly reduces the much larger problem of self-interference. This may be seen by looking at Figure 3 and Figure 5 and assuming no band-splitting. Let network device 310 transmit data to user system 330 over channel D2480 and concurrently, let network device 312 receive data from user system 340 over the same channel D2480. Thus the network device 312 will receive interference from network device 310 over the entire region covered by D2 480 in Figure 5. With band-splitting the transmission of data from network device 310 to user system 330 would be on channel D2 480 and concurrently the receipt of data from user system 340 by network device 312 would be on channel U2 470. Thus the interference would be reduced from the self-interference region of D2 to the adjacent channel interference of overlap region 476. Therefore a major advantage of band-splitting is the significant mitigation of self-interference.

Figure 4 also shows an alternative embodiment of the user system. User system 332 may only receive and transmit information on Band D. User system 332 communicates with user system 334 over Band D 422 and user system 332 communicates with network device 310 over Band D 416. Both Band D 422 Band D 416 have channels with bandwidth of 160 kHz only in the FCC 900 MHz band. Thus, network device 310 communicates with a band-splitting device such as user system 334 which uses Band D 412 and Band U 414 and a non-band-splitting device 332 which uses a Band D 416 for both uplink and downlink. Network device 312 communicates with other band-splitting devices (e.g., system 310).

Figure 6 is a simplified diagram illustrating the connection establishment and data transfer phases of a specific embodiment of the present invention. The leftmost column 610 shows the received channels of a network device, e.g., 310. The right hand column 612 shows the receives channel of a user system device, e.g. 334. The middle column 611 shows the packets transferred between the network device in column 610 and the user system in column 612. The process starts at 614 where the network device transmits a Poll A3 packet 616 to user system receive channel A3 618. A network device knows the sequence of frequency hopping channels the user system is hopping through and the user system knows the hopping sequence of the network device. Thus the network device at 614 knows that the user system can receive on channel A3 and the network device sends the Poll A3 packet 616 to confirm this. The Poll A3 packet 616 includes a field which contains the channel that the network device is expecting to receive a response on, in this case, "B8". The user system at 618 then sends a Poll acknowledge (ACK) packet 620 back to the network device on channel B8 622. The Poll ACK packet 620 includes a field "A3," which indicates the next channel that the user system is expecting a response on. Next the network device at 622 sends a data packet 624, including a field "B8," to the user system on channel A3 626. The user system then sends a data acknowledgment (ACK) packet 628, including a field "A3," to the network device on channel B8 630. The network device then sends another data packet 632 to the user system on channel A3 634 and receives an acknowledgment packet 636 sent on channel B8 638. As shown by 638, 640 and 642 the process of a data packet being sent from the network device on channel A3 to the user system and a data acknowledgment sent back to the network device on channel B8 is repeated until either a pre-determined time out occurs or all the data is transferred from the network device to the user system. In a specific embodiment the time from start 614 of the data establishment phase through the data transfer stage ending at 638, is normally no longer than 400 milliseconds. At the end of the 400 milliseconds the network device jumps to the next channel in the frequency hopping sequence. A further constraint may be that the connection establishment phase, for example 614 and 622, be less than 25 milliseconds. In another embodiment the communication may originate at the user system, e.g., 334, which would start the connection establishment phase and then transfer data from the user system, e.g., 334 to the network device, e.g., 310. An information item, communicated between network devices , between network devices and user systems and between user systems in a specific embodiment, may include a LI packet having, a LI header field, an optional TTLV field, a LI payload information field, and a cyclic redundancy code (CRC) field for error detection. Table 1 shows an example of a LI packet format: Table 1

In a specific embodiment a TTLV bit is set to zero if there is no optional TTLV field in Table 1. If the TTLV bit is set to one, then there are one or more bytes in the optional TTLV field having TTLV information, where the last byte in the TTLV field is a null TTLV.

For example, the TTLV field may include the next channel the first band- splitting device is to receive on, i.e., the second band-splitting device's response should be sent on this channel. Other embodiments may include TTLV fields that include modulation, forward error correction codes, and/or packet data fragmentation information.

Fig. 7 A, 7B illustrate examples of when the frequency information field may be used in a data packet. Figure 7A shows network device 1, 10, that can receive on channels 1, 3, 4 and 5 and network device 2, 712, which can receive on channels 2, 6, 7 and 8. Network device 1 starts at 714 and sends a packet 716 on channel A2 718. The packet 716 includes the frequency information field A3, which is the next channel network device 1 expects to receive information on. Network device 2 then transmits data packet 720 on the channel supplied by data packet 716, i.e., channel A3. At 722 network device 1 then reads packet 720 and then sends a data packet 724 to network device 2 on channel A2 726. Thus, Fig. 7A shows the case where neither network device has any receive channels in common and the next channel to transmit on is sent via a data packet between the two network devices. Figure 7B illustrates the case where the is one frequency channel in common. Network device 1 740 can receive on channels 1, 3, 4 and 5 and network device 2 742 can receive on channels 2, 3, 7 and 8. Network device 1 starts at 744 and transmits a data packet 746 on channel A2 748. From hereon, for example, for the remainder of the 400 milliseconds, the packet will be transferred between network device 1 and network device 2 on channel A3.

In an embodiment of the present invention the data transfer rate is typically 128 Kbps (Kilobits per second). The downlink bandwidth and bandwidth between network devices is normally 320 kHz with a Differential Quadrature Phase Shift Keying (DQPSK) Modulation, h an alternative embodiment channels of 160 kHz in 16 QAM (Quadrature Amplitude Modulation) mode may be used. The uplink is at a bandwidth of 160 kHz at Four Frequency Shift Keying (4FSK) modulation. In the exemplar embodiment the band-splitting protocol follows the

Federal Communication Commission (FCC) requirements, which include that:

(1) Frequency hopping systems have hopping channel carrier frequencies separated by a minimum of 25 kHz or the 20 dB bandwidth of the hopping channel, whichever is greater. The system hops to channel frequencies that are selected at the system-hoppmg rate from a pseudorandomly ordered list of hopping frequencies. Each transmitter uses each frequency equally on the average. The system receivers have input bandwidths that match the hopping channel bandwidths of their corresponding transmitters and shift frequencies in synchronization with the transmitted signals.

(2) For frequency hopping systems operating in the 902-928 MHz band: if the 20 dB bandwidth of the hopping channel is less than 250 kHz, the system uses at least

50 hopping frequencies and the average time of occupancy on any frequency not be greater than 0.4 seconds within a 20 second period; if the 20 dB bandwidth of the hopping channel is 250 kHz or greater, the system use at least 25 hopping frequencies and the average time of occupancy on any frequency not be greater than 0.4 seconds within a 10 second period. The maximum allowed 20-dB bandwidth of the hopping channel is 500 kHz.

(3) For frequency hopping systems operating in the 902-928 MHz band: 1 watt for systems employing at least 50 hopping channels; and, 0.25 watts for systems employing less than 50 hopping channels, but at least 25 hopping channels. (4) Frequency hopping spread spectrum systems are not required to employ all available hopping channels during each transmission. However, the system, consisting of both the transmitter and the receiver, must be designed to comply with all of the regulations in this section should the transmitter be presented with a continuous data (or information) stream.

(5) The incorporation of intelligence within a frequency hopping spread spectrum system that permits the system to recognize other users within the spectrum band so that it individually and independently chooses and adapts its hop sets to avoid hopping on occupied channels is permitted. The coordination of frequency hopping systems in any other manner for the express purpose of avoiding the simultaneous occupancy of individual hopping frequencies by multiple transmitters is not permitted.

The exemplary embodiment has a total of 100 channels, 50 channels with 160 kHz bandwidth for the uplink traffic (U channels) and 50 channels with 320 kHz bandwidth for the down and side to side link traffic (D channels). In addition the D channels can also be used as 160 kHz channels.

Channels D and U are interleaved with each other. An example is that the right and left neighbors of D channels are U channels (see Table 2). Other examples of interleaving from Table 2 are at least one D channel followed by at least one U channel. Thus there may be, for example, one D channel followed by two U channels or two D channels followed by a U channel. The channels are determined by use of a channel mask with the frequency corresponding to the bit's position in the mask. There is a channel mask of 162 bits with the bits 151-161 being reserved. Table 2 gives an example of some of the 150 channels that may be used. When we receive a channel mask from a new transceiver Table may be used to convert the set bit to a frequency corresponding to the set bit in the mask. For example in Table 2, the channel corresponding to bit number 5 in the channel mask is channel Dl which corresponds to frequency 902.88 MHz.

In a first embodiment the channel mask in the 900 band uses 21x8-bit registers to hold the 162 bits. The mask mostly consists of sets of two bytes: for example byte 1 has channel 0 at MSB bit 7 and channel 7 at LSB 0; byte 2 has channel 8 at MSB bit 7 and channel 15 at LSB 0. A user system, e.g., 332 (old), may have a channel mask

hexadecimal (old user devices). Each set bit represents a channel in its hopping sequence, i.e., the channels in which the device is capable of transmitting and receiving. The channel mask for an old network device may be " ffi ffiffiffifflffiffiSB&COOOO" (not shown in Fig. 4). The frequencies for each channel are 160 kHz apart from each other.

In the second embodiment the channel mask for a band-splitting user system, e.g., 334 or 336, is "249249249249249249249249 249249111115540000" (new user devices), which are the D channels (see Table 2). The channel mask (D mask) is equivalent to the channels in which the device has been assigned to receive. User device 334 (new) communicates with user device 336 (new) using Band D 420. The channel mask of a band-splitting network device, e.g., 310, 312, is "6DB6DB6DB6DB6DB6DB6DB6DB6DB6DB777775540000" (new network devices). The network devices receive on D and U channels (see Table 2). Thus each network device or user system may have a receiving mask (equivalent to its hopping sequence) and a transmission mask that is determined based on who is its intended receiver. For example the transmitting mask for network device 310 of Fig. 3 can differ for transmission to user system 332 and transmission to user system 334. In the above first embodiment of a user system, e.g., 332 (old), normally hops on 162 channels, 160 kHz apart from each other, starting with frequency 902.08 MHz, and with channel mask "fffifffi m ffiffimfffifP' (old user devices). The above second embodiment of network devices, e.g., 310, 312, hop on D and U channels and have the channel mask "6DB6DB6DB6DB6DB6DB6DB6DB6DB6DB777775540000" (see Table 2, UD mask, new network devices).

In order to have backward compatibility between a new network device, e.g., 310, with the channel mask in the above second embodiment and an old user device, e.g., 332, first note that these two embodiments have in common 100 channels (Table 2, column 2, "Chan") out of which 50 of the channels, i.e., the U channels disagree in the frequency assigned to them. They are 80 kHz to the right or to the left of each other. Therefore, if first user system, e.g., 332 (old), targets the first network device, e.g., 310 (new), on a U channel, the transmit frequency of the first user system, e.g., 332, is 80 kHz away from the receiving frequency of the first network device, e.g., 310. However, the 50 D channels are the same, e.g., channels 2, 5, and 8 in Table 2. If the first user system, e.g., 332, targets the first network device, e.g., 310, on a D channel, the transmit frequency of the first user system, e.g., 332, is the receiving frequency of the first network device, e.g., 310. On average every other channel going up is a usable channel so that there is a delay on the up link. Coming down, the first network device, e.g., 310, is aware that the subscriber is a first user system, e.g. 332, and waits until the first user system, e.g. 332, is in an D channel so that there is a delay on the down link. Thus, backward compatibility is achieved between an old user device, e.g., 332, and a new network device, e.g., 310, by use of the D channel.

In a third embodiment the channel mask in the first user system, e.g. 332, is modified from ^uffi£EffiSffiEfflffififfiHBLWfflffiP' (old user devices with old user device masks) to "249249249249249249249249249249111115540000" (old user devices with new user device masks), i.e., the channel mask includes only the D channels. Now both devices, e.g., 332 (old user) and 310 (new network), agree on all the 50 D channels (see Table 2). There is no delay on the downlink since the network device may normally target the user system in a D channel. For the uplink the user system still waits until it can target the network device in a D channel. Thus old user devices with new user device masks at least allow for reduced delay time for the downlink over the old user devices with old user device masks. Table 2

In the foregoing specification, the invention has been described with reference to specific exemplary embodiments thereof. Other embodiments will be apparent to those of ordinary skill in the art. For example, the frequency hopping band may be in the 2.3 or 2.4 GHz range, the uplink may be on the 900 MHz band and the downlink simultaneously on the 2.4 GHz band, or the data may be encrypted. Thus, it is evident that various modifications and changes may be made thereunto without departing from the broader spirit and scope of the invention as set forth in the appended claims and their full scope of equivalents.

Claims

WHAT IS CLAIMED IS:

1. A method for transferring information between a network device and a user system using wireless communication channels, comprising: receiving information by the user system over a downlink channel of a first plurality of frequency hopping channels, wherein the first plurality of frequency hopping channels are the only channels at the user system used for receiving information; transmitting information by the user system over a uplink channel of a second plurality of frequency hopping channels, wherein the second plurality of frequency hopping channels are the only channels at the user system used for transmitting information; and wherein the first plurality of frequency hopping channels is interleaved with the second plurality of frequency hopping channels.

2. The method of claim 1 wherein the interleaving of the first plurality of frequency hopping channels with the second plurality of frequency hopping channels, comprises at least one frequency hopping channel of the first plurality of frequency hopping channels followed by at least one frequency hopping channel of the second plurality of frequency hopping channels.

3. The method of claim 1 wherein the downlink channel has a DQPSK modulation.

4. The method of claim 1 wherein the uplink channel has a 4FSK modulation.

5. The method of claim 1 wherein the uplink channel has a 160 kHz bandwidth.

6. A method for communication over a wireless network, wherein said wireless network includes a plurality of user systems and a plurality of network devices, said method comprising: transmitting or receiving information between a first network device of the plurality of network devices and a second network device of the plurality of network devices over a first channel of a first plurality of frequency hopping channels; transmitting information by the first network device to a user system of the plurality of user systems over a second channel of the first plurality of frequency hopping channels, wherein the first plurality of frequency hopping channels are the only channels at the user system used for receiving information; and receiving information by the first network device from the user system over a channel of a second plurality of frequency hopping channels, wherein the second plurality of frequency hopping channels are the only channels at the user system used for transmitting information; wherein the first plurality of frequency hopping channels is interleaved with the second plurality of frequency hopping channels.

7. The method of claim 6 further comprising: transmitting or receiving information between a user system of the plurality of user systems and another user system of the plurality of user systems over a third channel of a first plurality of frequency hopping channels.

8. A method for transferring information between a network device and a user system using wireless communication channels, comprising: receiving a first information item, comprising a transmit channel of a first plurality of frequency hopping channels, by the user system over a downlink channel of a second plurality of frequency hopping channels, wherein the transmit channel is for responding to the network device; and transmitting a second information item, comprising a receive channel of a second plurality of frequency hopping channels, by the user system over a uplink channel of the first plurality of frequency hopping channels, wherein the receive channel is for responding to the user system.

9. The method of claim 8 wherein the first plurality of frequency hopping channels are the only channels at the user system used for receiving information.

10. The method of claim 8 wherein the second plurality of frequency hopping channels are the only channels at the user system used for transmitting information.

11. A method for transferring information between a first device and a second device using spread spectrum wireless communication channels, comprising: receiving a first information item by the first device over a first frequency channel, wherein the first information item comprises a transmit channel for responding to the second device by the first device; and transmitting a second information item by the first device over a second frequency channel, wherein the second information item comprises a receive channel for responding to the first device by the second device.

12. The method of claim 8 wherein the second frequency channel comprises the transmit channel.

13. The method of claim 8 further comprising receiving the second information item by the second device over the second frequency channel, and transmitting to the first device a third information item over the receive channel.

14. The method of claim 8 wherein the first device is a network device.

15. The method of claim 8 wherein the first device is a user system.

16. A method for communicating an information item between a first device and a second device, each device comprising a processor, memory and transceiver, using a transmit set of frequencies from among a plurality of frequency hopping spread spectrum frequencies over a communications network, said method comprising: selecting a first transmit frequency from said set of transmit frequencies using a first channel mask, wherein said first channel mask allows only said set of transmit frequencies from a plurality of said frequency hopping spread spectrum transmit frequencies to be available for transmitting said information item; transmitting said information item from said first device to said second device; and receiving said information item at said second device.

17. The method of claim 16 wherein said second device includes a second channel mask that allows only a set of common frequencies from said plurality of frequency hopping spread spectrum frequencies between said first and second devices to be available for receiving and processing said information item by said second device.

18. The method of claim 16 wherein said first channel mask comprises a plurality of binary bits for indicating which frequencies of said set of transmit frequencies are used to transmit information items.

19. A system for communicating an information item using a plurality of frequency hopping spread spectrum transmit frequencies comprising: a first device comprising a transceiver, wherein said transceiver sends said information item over a frequency of said plurality of spread spectrum transmit frequencies; a second device comprising a transceiver and a first channel mask, which receives said information item, wherein said information item is processed at the receiver only if said transmit frequency is specified in said first channel mask; and a communications network connecting said first device to said second device.

20. The system of claim 19 wherein said first device includes a second channel mask that allows only a set of common frequencies from a plurality of spread spectrum frequencies to be available for transmitting said information item by the first device.

21. The method of claim 19 wherein said communications network is a wireless microcellular system.

22-. A system for transferring information packets between a network device and a user system using wireless microcellar communication channels, comprising: a packet comprising a plurality of bits; a user system, comprising a processor, memory and transceiver for receiving information over a downlink channel of a first plurality of frequency hopping channels, wherein the first plurality of frequency hopping channels are the only channels at the user system used for receiving packets and for transmitting information over a uplink channel of a second plurality of frequency hopping channels, wherein the second plurality of frequency hopping channels are the only channels at the user system used for transmitting packets, wherein the first plurality of frequency hopping channels is interleaved with the second plurality of frequency hopping channels; and a network device comprising a transceiver for transmitting the packet to the user device over the downlink channel.

23. The system of claim 19 wherein said packet comprises a TTLV field.

24. The system of claim 19 wherein the TTLV field comprises a next receive channel of the network device.

25. The system of claim 19 wherein said packet comprises a header, an information field, optional TTLV field, and a cyclic redundancy code (CRC) field for error detection.