WO1996039749A1 - Commande de reglage de synchronisation servant a realiser des telecommunications en duplex a repartition dans le temps - Google Patents

Commande de reglage de synchronisation servant a realiser des telecommunications en duplex a repartition dans le temps Download PDF

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Publication number
WO1996039749A1
WO1996039749A1 PCT/US1996/007905 US9607905W WO9639749A1 WO 1996039749 A1 WO1996039749 A1 WO 1996039749A1 US 9607905 W US9607905 W US 9607905W WO 9639749 A1 WO9639749 A1 WO 9639749A1
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WIPO (PCT)
Prior art keywords
user
base
base station
station
message
Prior art date
Application number
PCT/US1996/007905
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English (en)
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WO1996039749A9 (fr
Inventor
Logan Scott
Original Assignee
Omnipoint Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US08/463,220 external-priority patent/US5689502A/en
Priority claimed from US08/464,285 external-priority patent/US5959980A/en
Priority claimed from US08/465,555 external-priority patent/US5802046A/en
Priority claimed from US08/465,137 external-priority patent/US5745484A/en
Application filed by Omnipoint Corporation filed Critical Omnipoint Corporation
Priority to AU60257/96A priority Critical patent/AU6025796A/en
Priority to BR9608548A priority patent/BR9608548A/pt
Priority to EP96917850A priority patent/EP0873593A4/fr
Priority to JP50080997A priority patent/JP3455227B2/ja
Publication of WO1996039749A1 publication Critical patent/WO1996039749A1/fr
Publication of WO1996039749A9 publication Critical patent/WO1996039749A9/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W56/00—Synchronisation arrangements
    • H04W56/0055—Synchronisation arrangements determining timing error of reception due to propagation delay
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/69—Spread spectrum techniques
    • H04B1/707—Spread spectrum techniques using direct sequence modulation
    • H04B1/709—Correlator structure
    • H04B1/7093—Matched filter type
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/24—Radio transmission systems, i.e. using radiation field for communication between two or more posts
    • H04B7/26—Radio transmission systems, i.e. using radiation field for communication between two or more posts at least one of which is mobile
    • H04B7/2662—Arrangements for Wireless System Synchronisation
    • H04B7/2671—Arrangements for Wireless Time-Division Multiple Access [TDMA] System Synchronisation
    • H04B7/2678—Time synchronisation
    • H04B7/2681—Synchronisation of a mobile station with one base station
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J3/00—Time-division multiplex systems
    • H04J3/02—Details
    • H04J3/06—Synchronising arrangements
    • H04J3/0635—Clock or time synchronisation in a network
    • H04J3/0682—Clock or time synchronisation in a network by delay compensation, e.g. by compensation of propagation delay or variations thereof, by ranging
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W56/00—Synchronisation arrangements
    • H04W56/004—Synchronisation arrangements compensating for timing error of reception due to propagation delay
    • H04W56/0045—Synchronisation arrangements compensating for timing error of reception due to propagation delay compensating for timing error by altering transmission time
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J13/00—Code division multiplex systems
    • H04J13/0007—Code type
    • H04J2013/0037—Multilevel codes

Definitions

  • FDD frequency division duplex
  • TDD time division duplex
  • FDD refers to a technique for
  • TDD refers to a technique for establishing full duplex communications having both forward and reverse links separated in frequency
  • TDD refers to a technique for establishing full duplex communications having both forward and reverse links occurring on the same frequency but separated in time to avoid collisions.
  • Other techniques for communication are time division multiple access (TDMA), wherein transmissions by a plurality of users are separated in time to avoid conflicts, frequency division multiple access (FDMA), wherein transmissions by a plurality of users are separated in frequency to avoid conflicts, and time division multiplex (TDM), wherein multiple data streams are time multiplexed together over a single carrier.
  • TDMA time division multiple access
  • FDMA frequency division multiple access
  • TDM time division multiplex
  • FDD Frequency Division Duplex
  • TDD Time Division Duplex
  • FDMA Frequency Division Multiple Access
  • TDMA Time Division Multiple Access
  • a base station is
  • each user station is allocated a different frequency over which it may transmit to the base station.
  • a new pair of frequencies is required to support the communication link between the base station and the new user station. The number of users that can be supported by a single base station is therefore limited by the number of available frequency slots.
  • the same frequency is used for all user stations in communication with a particular base station. Interference between user stations is avoided by requiring that user stations transmit at different times from one another and from the base station. This is accomplished by dividing a time period into a plurality of time frames, and each time frame into a plurality of time slots. Typically, the base station communicates with only one user station during a time slot, and communicates with all the user
  • the base station communicates with a particular user station once during each time frame.
  • the base station is allocated a first portion of each time slot during which the base station transmits to a particular user station, and the user station is allocated a second portion of the time slot during which the user station responds to the base station.
  • the base station may transmit to a first user station, await a response, and, after receiving a response from the first user station, transmit to a second user
  • Time division duplex has an advantage over FDD and FDMA of requiring use of only a single frequency bandwidth.
  • the base station generally does not know in advance how long the propagation delay will be for communicating with a particular user station.
  • conventional TDD systems typically provide a round-trip guard time to ensure that communication will be completed with the first user station before
  • the required round-trip guard time can add substantial overhead
  • FIG. 1 is an illustration of the basic round trip timing for a TDD system from a base station perspective.
  • a polling loop 101, or time frame, for a base station is divided into a plurality of time slots 103.
  • Each time slot 103 is used for communication from the base station to a particular user station.
  • each time slot comprises a base
  • the user station processes and generates a responsive user transmission 107, and the user transmission 107 propagates to the base station.
  • the base station can expect to hear from the user station immediately after finishing its transmission and switching to a receive mode. As the distance between the user station and the base station grows, the time spent by the base station waiting for a response grows as well. The base station will not hear from the user station immediately but will have to wait for signals to propagate to the user station and back.
  • a first time slot 110 the user transmission 107 arrives at the base station at a time approximately equidistant between the end of the base transmission 105 and the start of the user transmission 107, indicating that the user station is about half a cell radius from the base station.
  • the user transmission 107 appears very close to the end of the base transmission 105, indicating that the user station is very close to the base station.
  • the user transmission 107 appears at the very end of the time slot 112, indicating that the user station is near or at the cell boundary. Because the third time slot 112 corresponds to a user station at the maximum communication distance for a particular base station, the delay 106 shown in the third time slot 112 represents the maximum round-trip propagation time and, hence, the maximum round-trip guard time.
  • Typical transmit/receive switching times are about two microseconds, but additional allocations may be made to account for channel ringing effects associated with multipath.
  • TDD guard time must increase to account for longer propagation times. In such a case, guard time consumes an increasingly large portion of the available time slot, particularly for shorter round trip frame dura- tions.
  • the percentage increase in time spent for overhead is due to the fact that TDD guard time is a fixed length
  • DECT Cordless Telecommunications
  • ETSI European Telecommunications Standards Institute
  • a base station transmits a long burst of data segmented into time slots, with each time slot having data associated with a particular user station. After a guard time, user stations respond in a designated group of
  • GSM Global System for Mobile communications
  • communication between a base station and user stations is divided into eight burst periods 402. Up to eight different user stations can communicate with a base station, one in each burst period 402.
  • GSM standards require two separate frequency bands.
  • the base station transmits over a first frequency F A
  • the user stations transmit over a second frequency F B .
  • the user station shifts in frequency by 45 MHz to the second frequency F B and transmits a user transmission 406 in response to the base transmission 405 approximately three burst periods 402 later.
  • the three burst period delay is assumed to be large enough to account for propagation time between the base station and the user station.
  • each burst period 402 is surrounded by a guard times 407 to account for uncertain signal propagation delays between the base station and the user station.
  • the base station may command the user station to advance or retard its transmission timing in order to fall within the proper burst period 402, a feature known as adaptive frame alignment.
  • WACS Wide Area Coverage System
  • GSM Global System for Mobile communications
  • Standard WACS does not support spread spectrum communication (a known type of communication wherein the bandwidth of the transmitted signal exceeds the bandwidth of the data to be transmitted), and has an overall structure that may be characterized as relatively rigid.
  • the channel structure is such that a user station may have to transmit a response to a base station while receiving information on another channel.
  • TDMA/FDMA system wherein user stations are not required to be fitted with a diplexer. It would further be advantageous to provide a time frame structure readily adaptable to single or multiple frequency bands, and for use in either a variety of communication environments.
  • the present invention in one aspect provides an efficient means for carrying out time division multiplexed
  • a base station in a first portion of a time frame, issues consecutive base transmissions directed to each of the communicating user stations.
  • a single collective guard time is allocated while the base station awaits a response from the first user station.
  • the user stations then respond, one by one, in allocated time slots on the same frequency as the base station, with only minimal guard times between each reception.
  • the base station commands the user stations to advance or retard their transmission timing.
  • each base transmission may have a header
  • the user station responds with a brief message in its designated portion of the slot pair.
  • the user portion of the slot pair includes a full round-trip guard time allowance to account for the uncertain distance between the base station and the user station upon initial communication.
  • the base station compares the actual time of receiving the user transmission with the expected time of reception, and determines how far away the user station is. In subsequent time frames, the base station may command the user station to advance or retard its timing as necessary so that full
  • base transmissions are alternated with user transmissions over the same frequency band.
  • the base station and user stations may precede their main data transmissions with a preamble, such as, for example, where desired for synchronization of spread spectrum communication signals or for conducting power control.
  • the preamble may be transmitted at a designated time interval between two data transmissions.
  • the base station may command the user station to advance or retard its timing based on a calculated round-trip propagation time.
  • multiple frequency bands are utilized.
  • one frequency band may be used for base station transmissions, and another frequency band may be used for user station transmissions.
  • Reverse-link user station transmissions are offset from the base station transmissions by a predetermined amount.
  • a base station and user stations may transmit a preamble prior to a time slot designated for a main data transmission, and may interleave the preamble in a designated time interval between two time other time slots.
  • the preamble may consist of multiple bursts, one burst from each a different antenna, to allow channel sounding at the target.
  • the base station may command the user station to advance or retard its timing based on a calculation of round-trip propagation delay time.
  • a universal frame structure for use in a TDMA or TDMA/FDMA system.
  • a suitable frame structure employing ranging employing ranging
  • timing elements which may include provision for data transmissions, preambles, guard times, and the like.
  • a frame structure may be constructed suitable for operation in various embodiments in either a high tier or a low tier environment, by selecting an appropriate combination of the generic timing elements.
  • a dual-mode base station structure is also provided capable of multiple frequency band operation.
  • the base station takes advantage of a low IF digital correlator design.
  • Figure 1 is an illustration of the basic round trip timing for a prior art TDD system, from a base station
  • Figure 2 is a graph of round-trip guard time as a
  • Figures 3A and 3B are diagrams of cellular environments for communication.
  • Figure 4 is an illustration of a timing pattern according to existing GSM standards.
  • Figure 5A is an illustration of the basic round trip timing of a TDD/TDM/TDMA system, from a base station
  • Figure 5B is a timing diagram showing an initial
  • Figure 5C is a timing diagram showing a variation of the TDD/TDM/TDMA system of Fig. 5A using an interleaved symbol transmission format.
  • Figure 5D is a chart comparing performance of the system of Fig. 5A, without forward error correction, and the system of Fig. 5C, with forward error correction.
  • Figure 6 is a graph of round-trip guard time as a
  • Figure 7 is an illustration of an alternative timing protocol for reducing total round trip guard time.
  • FIG. 8A is a hardware block diagram of a base station in accordance with an embodiment of the invention.
  • Figure 8B is a hardware block diagram of an alternative embodiment of a base station.
  • Figure 9 is a hardware block diagram of a user station in accordance with an embodiment of the present invention.
  • Figure 10A is a diagram of timing sub-elements in
  • Figures 10B through 10E are diagrams of time frame
  • Figure 11A is a diagram of timing sub-elements in
  • Figures 11B through 11D are diagrams of time frame
  • Figures 12A-C are tables of a preferred message formats for base station and user station transmissions.
  • Figures 13A-B are diagrams showing the construction of concatenated preambles
  • Figure 13C is a chart comparing preamble performance
  • Figures 13D-E are graphs comparing preamble performance using matched and mismatched filters.
  • Figures 14-17 are charts comparing various performance aspects of high tier and low tier air interfaces incorporating selected features of the embodiments described herein.
  • Figure 18 is a block diagram of a low IF digital
  • Figure 19A is a block diagram of a dual-mode base station capable of operating over multiple frequencies and having both spread spectrum and narrowband communication capabilities
  • Fig. 19B is a chart showing selected frequencies and other parameters for use in the dual-mode base station of Fig. 19A.
  • the present invention provides in one aspect an efficient means for carrying out time division duplex communication, and is well suited for a large cell environment.
  • Embodiments of the invention may take advantage of spread spectrum
  • CDMA code division multiple access
  • FDMA frequency division multiple access
  • Figure 3A is a diagram of a cellular environment for a communication system having base stations and user stations.
  • a communication system 301 for communication among a plurality of user stations 302 includes a plurality of cells 303, each with a base station 304, typically located at the center of the cell 303.
  • Each station (both the base stations 304 and the user stations 302) generally comprises a receiver and a transmitter.
  • the user stations 302 and base stations 304 may communicate using time division duplex or any of the other communication techniques disclosed herein.
  • Figure 3B is a diagram of a cellular environment in which the invention may operate. As shown in Fig. 3B, a
  • geographical region 309 is divided into a plurality of cells 303.
  • Associated with each cell 303 is an assigned frequency F1, F2 or F3 and an assigned spread spectrum code or code set C1 through C7.
  • F1, F2 and F3 are assigned in such a manner that no two adjacent cells 303 have the same assigned frequency F1, F2 or F3.
  • the same frequency F1, F2 or F3 is used for all user stations 302 in communication with a particular base station 304. Interference between user stations 302 is avoided by requiring that different user stations 302 do not transmit at the same time, or at the same time as the base station 304.
  • the base station 304 is allocated a first portion of a time slot during which the base station 304 transmits to a particular user station, and each user station 302 is allocated a second portion of the time slot during which it responds.
  • the base station 304 may transmit to a first user station 302, await a response, and, after
  • the base station 304 generally does not know in advance how long the propagation delay will be for
  • Typical round trip guard times are 6.7 microseconds per kilometer of cell radius; thus, for a cell 303 of 3 kilometer radius, a round trip guard time of 20 microseconds is needed.
  • the round-trip guard time is applied in each time slot 103 regardless of how near or far a user station 302 is from the base station 304.
  • the required round- trip guard time therefore increases timing overhead and inherently limits the number of users in such conventional TDD systems .
  • TDD guard time must increase to account for longer propagation times.
  • the relationship between cell radius and guard time can be established as follows :
  • TDD Guard Time 2 x (Cell Radius) / (Speed of Light)
  • Figure 2 is a graph of round-trip guard time as a
  • Fig. 2 illustrates that, because TDD guard time is a fixed length, determined by the cell radius, while actual round trip transmission time varies according to the distance of the user station 302, an
  • Figure 5A is an illustration of the basic round trip timing of a TDD/TDM/TDMA system, from a base station
  • a time frame 501 is divided into a transmission portion 502, a collective guard time portion 503, and a receiving portion 504.
  • the transmission portion 502 comprises a plurality of transmit time slots 510.
  • the receiving portion 504 comprises a plurality of receive time slots 504.
  • the base station 304 transmits to a plurality of user stations 302, one in each of the transmit time slots 510 of the transmission portion 502 of the time frame 501. During the collective guard time portion 503, the base station 304 waits for the last base transmission from the last transmit time slot 510 to be received by the appropriate user station 302, and for the first user
  • the base station 304 receives user transmissions, one in each receive time slot 511 of the receiving portion 504 of the time frame 501.
  • a particular transmit time slot 510 and its corresponding receive time slot 511 may be thought of as collectively comprising a duplex time slot analogous to time slots 110, 111 and 112 shown in Fig. 1. Although there are eight time slots 510, 511 shown in Fig. 5A, more than eight or fewer than eight time slots 510, 511 can be used as needed for a particular application.
  • the base station 304 preferably transmits messages to and receives messages from each of the user stations 302 in a duplex fashion once during each time frame 501.
  • the user station 302 receiving a base transmission from the first transmit time slot 510 is the first to send a responsive user transmission in the first receive time slot 511
  • the user station 302 receiving the base transmission from the second transmit time slot 510 is the second to send a responsive user transmission in the second receive time slot 511, and so on.
  • the base station 304 sends a series of consecutive base transmissions, each directed to a separate user station 302, and receives a series of consecutive user transmissions in matching return order .
  • the base station may include a command, in a header or otherwise, instructing a particular user station 302 to respond in a different position.
  • the collective guard time portion 503 of the time frame 501 is essentially a single collective idle time during which the base station 304 awaits a response from the first user station 302.
  • the collective guard time portion 503 is
  • the collective guard time portion 503 therefore needs to be roughly the same length as the delay 106 shown in the third time slot 112 of Fig. 1, which, as noted, represents the maximum round-trip guard time of the Fig. 1 system. However, unlike the Fig. 1 system, only one maximum round-trip guard time (i.e., the collective guard time portion 503) is needed in the Fig. 5A embodiment.
  • the base station 304 in the Fig. 5A embodiment may need to only switch once from transmit to receive mode and back again in a given time frame 501. Also unlike the Fig. 1 system, in which the base station must wait in each time slot 103 for the user station to switch from receive to transmit mode, only the first user station 302 responding in the time frame 501 of the Fig. 5A embodiment potentially adds a receive/transmit
  • the timing structure is preferably organized such that user-to-base messages from the user stations 302 arriving at the base station 304 during the receiving portion 504 do not overlap. If each user station 302 were to begin reverse link transmissions at a fixed offset from the time of forward link data reception according to its time slot number, overlapping messages and resulting
  • each user station 302 biases its transmission start timing as a function its own two-way propagation time to the base station 304, as further explained below.
  • Reverse link messages thus arrive in the receiving portion 504 of the time frame 501 at the base station 304 in sequence and without overlap.
  • abbreviated guard bands 512 are provided between each pair of receive time slots 511. These abbreviated guard bands 512 are significantly shorter than the maximum round trip guard time 106 as described with respect to Fig. 1.
  • the base station 304 is provided with means for determining round trip propagation delay to each user station 302.
  • a round trip timing (RTT) measurement is preferably accomplished as a cooperative effort between the base station 304 and the user station 302 and therefore comprises a
  • An RTT transaction may be done upon initial establishment of communication between a base station 304 and a user station 302, and periodically thereafter as necessary.
  • the measured round-trip time from the RTT transaction may also be averaged over time.
  • the base station 304 sends an RTT command message instructing the user station 302 to return a short RTT reply message a predetermined delay period ⁇ T after reception.
  • the predetermined delay period ⁇ T may be sent as part of the RTT command message, or may be pre-programmed as a system parameter.
  • the base station 304 measures the time at which it receives the RTT reply message.
  • the base station 304 then computes the propagation delay to the user station 302 based on the time of sending the RTT command message, the predetermined delay period ⁇ T, and the time of receiving the short RTT reply message.
  • the base station 304 Once the base station 304 has computed the propagation delay to the user station 302, the base station 304 then sends a bias time message to the user station 302 either informing the user station 302 of the propagation delay measured in the RTT transaction, or providing a specific timing adjustment command. The user station 302 thereafter times its
  • Timing adjustment command control may be carried out, for example, according to the techniques described in GSM specification TS GSM 05.10, which is incorporated by reference as if set forth fully herein.
  • the base station 304 may maintain closed loop control over the timing of the user station 302 by adjusting timing of the user station transmission as often as each time frame 501 if necessary.
  • communication between the user station 302 and the base station 304 is preferably carried out using a direct sequence spread spectrum modulation format .
  • Other formats can be used but may result in less accurate RTT measurements, leading to larger allowances needed in the abbreviated guard bands 512 for timing errors in the user station 302 transmissions.
  • FIG. 5B is a timing diagram showing an example of initial communication link-up between a base station 304 and a user station 302 in accordance with the system of Fig. 5A.
  • each base transmission during a transmit time slot 510 may have a brief header 550 preceding a data link message 551 indicating whether or not the particular slot pair 510, 511 is available. If a slot pair 510, 511 is available, a user station 302 desiring to establish
  • the receive time slot 511 should have a duration of at least a full round-trip guard time, plus the length of a reply message 562, to account for the initial maximum distance uncertainty between the base station 304 and the user station 302 upon initial communication.
  • the base station 304 compares the actual time of
  • the base station 304 may command the user station 302 to advance or retard its timing as necessary so that full length information messages may thereafter be sent without interference among user stations 302.
  • a user station 302 desiring to establish communication with a base station 304 listens to the headers 550 transmitted from a base station 304 at the start of each transmit time slot 510.
  • the user station 302 detects a header 550 containing a status message indicating that the corresponding time slot pair 510, 511 is available or unoccupied, the user station 302 attempts to respond with a reply message.
  • the header 550 may contain bits which define a delay time ⁇ T and indicate to the responding user station 302 a predetermined delay time before it should transmit in reply.
  • the delay time ⁇ T may by measured with respect to a variety of references, but is preferably measured relative to the start of the corresponding receive time slot 511.
  • the user station 302 preferably comprises means (such as timers and/or
  • the delay time ⁇ T represents a relative delay time measured from the start of the appropriate receive time slot 511.
  • An exploded view of the receive time slot 511 is shown in Fig. 5B.
  • the user station 302 delays for a delay time ⁇ T before sending a reply message 562.
  • the delay time ⁇ T may be used by the user station 302 for error processing or other internal housekeeping tasks.
  • Fig. 5B is illustrated from the perspective of the base station 304 awaiting receipt of the reply message 562, the base station 304 will perceive a propagation delay 561 from the time the user station 302 transmits the reply message 362 until the time of actual receipt of the reply message 362.
  • the base station 304 may ascertain the propagation delay 561.
  • the reply message 562 may therefore serve the function of the RTT reply message described earlier, in that the base station 304 ascertains the proper timing for the user station 302 by measuring the propagation delay 561 in receiving the reply message 562.
  • the base station 304 can command the user station 302 to advance or retard its timing by a desired amount.
  • the base station 304 in the exemplary Fig. 5B system may command the user station 302 to advance its timing by an amount of time equal to the propagation delay time 561, so that the user station 302 transmits essentially at the very end of the abbreviated guard band 512.
  • the timing advance command will be set to zero (not including the delay ⁇ T, which is implicit in the user station transmissions).
  • the timing advance command will be set close to the full guard time provided (i.e., the maximum propagation delay time).
  • the timing advance command may be expressed as a number of bits or chips, so that the user station 302 will respond by advancing or retarding its timing by the number of bits or chips
  • timing advance command may be expressed as a fractional amount of seconds (e.g., 2
  • the user station 302 may advance or retard its timing using techniques already developed and conventionally used for the GSM system described earlier, or by any other suitable means.
  • the delay time ⁇ T is preferably set equal to the receive/transmit switching time of the user station 302.
  • the delay time ⁇ T should also be selected short enough so that there will be no overlap between the reply message 562 of a particular user station 302 and the user-to-base transmissions in other receive time slots 511.
  • the reply messages 562 may or may not overlap depending on how far each user station 302 is positioned from the base station 304. In some situations the simultaneous reply messages 562 will cause jamming. Should the base station 304 receive two reply messages 562 in the same receive time slot 511, the base station 304 may select the user station 302 with the stronger signal for communication .
  • the base station 304 may initiate a backoff procedure or otherwise resolve the conflict as
  • the base station 304 may issue a backoff command which causes each user station 302 to back off for a variable period based on an internal programming parameter unique to each user station 302 (e.g., such as a unique user identification number).
  • an internal programming parameter unique to each user station 302 e.g., such as a unique user identification number.
  • the base station 304 may instruct one or both user stations 302 to relocate to a different slot pair 510, 511.
  • Figs. 5A-5B thus depicts in one aspect a combined TDD/TDM/TDMA message structure that adjusts reverse link transmission timing so that user-to-base messages
  • the base station 304 uses a TDM technique, transmits during the transmission portion 502 of a time frame 501 a single, long burst of data comprising a plurality of base-to-user messages, one base-to- user message per transmit time slot 510.
  • the base station 304 switches to a receive mode.
  • Each user station 302 extracts from the long base station burst the particular data that is intended for it. Reverse link transmissions are not allowed to commence until all user stations 302 have had a chance to receive their forward link data.
  • the user stations 302 then respond, one by one, in allocated receive time slots 511 on the same frequency as used by the base station 304, with only minimal guard times 512 between each reception.
  • the base station 304 commands the user stations 302 to advance or retard their transmission timing as necessary.
  • Figure 6 is a graph of total round trip guard time (i.e., the collective guard portion 503 plus abbreviated guard bands 512 and transmit/receive switching delays) as a percentage of frame time for the system of Figs. 5A-5B.
  • Four microseconds has been added to account for transmit/receive switching delays, and it is assumed that reverse link TDMA time slots are separated by 2 microseconds to allow for timing errors.
  • a time frame 501 having a duration of 4 milliseconds is selected for the example of Fig. 6.
  • the graph of Fig. 6 illustrates that relatively modest overhead requirements are possible even with cell diameters approaching 25 miles.
  • the graph of Fig. 6 also shows that, as the number of time slots increases, more total time per time frame 501 is allocated for user station timing errors, but that total overhead is nevertheless held to less than 10% for a 25 mile radius cell.
  • FIG. 7 is an illustration of a TDD/TDM/TDMA timing structure having an alternative initial timing protocol for reducing total round trip guard time. Like Figs. 5A-5B, the TDM aspect of Fig. 7 relates to the base transmissions, while the TDMA aspect relates to the user transmissions.
  • the Fig. 7 embodiment uses the collective guard portion 503 (as previously shown in Fig. 5A) for initial establishment of communication and RTT measurement.
  • the approach of Fig. 7 contrasts with the approach described with respect to Fig. 5B, wherein each of the receive time slots 511, as noted, are preferably of a duration no less than the maximum round-trip guard time (plus reply message length) due to the initial round trip timing uncertainty.
  • the time frame 501 comprises many receive time slots 511 of relatively short duration
  • the initial round trip timing uncertainty may cover several receive time slots 511. In such a case, attempts to send a reply message 562 during initial link-up by one user station 302 could interfere with the data link transmissions from other user stations 302, leading to interference or
  • each of the receive time slots in the Fig. 5B system should, as noted, be of a duration no less than the sum of the maximum round-trip guard time plus the duration of a reply message 562.
  • the maximum round trip propagation time therefore places a maximum limit on the number of time slots (and hence users) in the Fig. 5B system.
  • the Fig. 7 system resolves this same problem by using a designated portion of the time frame 501 for initial
  • the collective guard portion 503 is thereby utilized in the Fig. 7 system for conducting RTT measurements and to assist in establishing an initial communication link between the base station 304 and a new user station 302.
  • a transmission time slot 510 may comprise a header, similar to the header 550 shown in Fig. 5B.
  • the header may indicate whether a particular time slot pair 510, 511 is free. If a time slot pair 510 is free, a user station 302 desiring to establish communication responds with a message indicating the desired time slot of communication. If no header is used, the user station 302 responds with a general request for access, and the base station 304 may in the following time frame 501 instruct the user station 302 to use a particular time slot pair 510, 511 for communication.
  • the general request for access by the user station 302 may comprise a user station identifier, to allow the base station 304 to specifically address the user station 302 requesting access.
  • the header 550 in the Fig. 7 system may include a command indicating a delay time ⁇ T after which a user station 302 desiring to establish communication may respond.
  • such a delay time ⁇ T may be pre-programmed as a system parameter, such that the user station 302 delays its response until the delay time ⁇ T elapses. After detecting the end of the base transmission 502 and waiting for the delay time ⁇ T to elapse, the user station 302 transmits an RTT reply message 701 or 702.
  • the RTT reply message 701 will appear to the base station 304 immediately after the end of the base transmission 502, and presumably within the collective guard portion 503.
  • the RTT reply message 702 will appear to the base station 304 either towards the end of the collective guard portion 503 or within the first receive time slot 511 of the receiving portion 504 of the time frame 501, depending on the particular system definition and timing.
  • the first receive time slot 511 available for established data link communication is the first receive time slot 511 designated after the maximum round-trip propagation delay (including message length) of a reply message from a user station 302 at the maximum cell periphery. Some guard time allowance may also be added to ensure that reply messages from more distant user stations 302 will not interfere with the reverse data link transmissions from user stations 302 in established communication.
  • headers 550 contain
  • the RTT reply message 701 or 702 may contain a time slot identifier indicating which available time slot the user station 302 desires to use for communication.
  • the user station 302 may also determine time slot availability by monitoring the base transmission 502 and/or user transmissions 504 for a period of time, and thus transmit a RTT reply message 701 or 702 containing a time slot identifier
  • the base station 304 may issue a command
  • the user station 302 may still transmit an RTT reply message 701 or 702 as a general request for access.
  • the base station 304 may issue a command instructing the user station 302 to use a specific time slot pair 510, 511 for communication, or
  • the general request for access by the user station 302 may comprise a user station identifier, to allow the base station 304 to specifically address the user station 302 requesting access.
  • the first receive time slot 511 of the receiving portion 504 is used solely for receiving RTT reply messages 701 or 702 to establish
  • the first receive time slot 511 could be used for data link communication.
  • the user station 302 occupying the first receive time slot 511 may be transferred to the available receive time slot 511, thus opening up the first receive time slot 511 for access by a new user station 302 seeking to establish
  • the combined length of the collective guard time 503 and the first receive time slot 511 should be no less than the sum of the maximum round trip propagation time plus the duration of an RTT reply message 701 or 702.
  • the combined length of the collective guard time 503 and the first receive time slot 511 should be no less than the sum of the maximum round trip propagation time plus the duration of an RTT reply message 701 or 702.
  • the collective guard portion 503 is used for initial communication link-up, and for receiving RTT reply messages 701.
  • the first receive time slot 511 in this embodiment is not used for such a purpose.
  • the length of the collective guard portion 503 should be no less than the sum of the maximum round trip propagation time plus the duration of an RTT reply message 701.
  • the manner of response of the base station 304 depends on the particular system protocol. As noted, the base station 304 may transmit using headers 550, but need not; the user station 302 may respond with an RTT reply message 701 or 702, with or without a specific time slot request; and the first receive time slot 511 may or may not be used to receive RTT reply messages 701 or 702.
  • the manner of response of the base station 304 therefore depends on the particular structure of the system, and the particular embodiments described herein are not meant to limit the possible base/user station initial communication processes falling within the scope of the invention.
  • the base station 304 may respond to an RTT reply message 701 or 702 with an initial communication response message in the first transmit time slot 510 of the transmit portion 502 of the immediately following time frame 501.
  • the base station 304 may utilize a particular transmit time slot 510 (e.g., the first transmit time slot 510) for assisting in the initiation.
  • an RTT reply message 701 or 702 identifies a specific time slot pair 510, 511 which the user station 302 desires to use for communication, then the base station 304 may respond to the user station 302 in either the header 550, the data message portion 551, or both, of the designated transmit time slot 510 in the next immediate time frame 510.
  • the base station 304 may send a response in the header 550 of the designated transmit time slot 510 selecting one of the two user stations 302 and instructing the other user station 302 to use a different time slot pair 510, 511 or instruct it to backoff for a period of time, and may in the same time frame 501 transmit a data message in the data message portion 551 of the designated transmit time slot 510 intended for the selected user station 302.
  • the base station 304 may select the user station 302 with the stronger signal.
  • the base station 304 may initiate a backoff procedure or otherwise resolve the conflict as
  • the base station 304 may issue a backoff command which causes each user station 302 to back off for a variable period based on an internal programming parameter unique to each user station 302 (e.g., such as a unique user identification number).
  • an internal programming parameter unique to each user station 302 e.g., such as a unique user identification number
  • the base station 304 may instruct one or both user stations 302 to relocate to a different slot pair 510, 511. If the reply messages 701, 702 each contain a different time slot identifier (assuming that the user
  • the base station 304 could initiate communication simultaneously with both user stations 302 provided the reply messages 701, 702 were not corrupted by mutual interference (which may occur, for example, when the different user stations 302 are the same distance away from the base station 504).
  • the RTT reply message 701 or 702 may be used by the base station 304 to ascertain the proper timing for the user station 302 by measuring the propagation delay in receiving the reply message 701 or 702.
  • a user station 302 seeking to establish communication delays for a delay time ⁇ T before sending a reply message 701 or 702 after receiving the base transmission 502.
  • the base station 304 determines the
  • propagation delay from the user station 302 to the base station 304 by measuring the round trip propagation delay from the end of the base transmission 502 to the time of actual receipt of the reply message 701 or 702, taking into account the delay time ⁇ T.
  • the base station 304 can command the user station 302 to advance or retard its timing by a desired amount, relative to the appropriate time slot pair 510, 511 to be used for
  • the base station 304 may command the user station 302 to advance its timing by an amount of time equal to the round trip propagation time, so that the user station 302 transmits essentially at the very end of the abbreviated guard band 512.
  • the user station 302 may, for example, advance or retard its timing using techniques
  • the time delay ⁇ T in Fig. 7 is preferably set equal to the larger of the transmit/receive switching time of the base station 304 and the receive/transmit switching time of the user station 302. This is to ensure that if the responding user station 302 is located extremely close to the base station 304, the delay of the user station 302 in switching from a receive mode to a transmit mode will not be included in the RTT measurement, and to allow the user station 302
  • the user station 302 may commence its reply message 562 immediately after the delay time ⁇ T without fear of interference, as it is not physically possible for the reply message 562 to overtake the outward-radiating forward link message so as to cause interference with the forward link reception by other user stations 302.
  • FIG. 8A is an hardware block diagram of a base station 304 in accordance with an embodiment of the invention.
  • the base station 304 of Fig. 8A comprises a data interface 805, a timing command unit 806, a transmitter 807, an antenna 808, a receiver 809, a mode control 810, a TDD state control 811, and a propagation delay calculator 812.
  • Timing control for the system of Fig. 8A is carried out by the TDD state control 811.
  • the TDD state control 811 comprises appropriate means, such as counters and clock circuits, for maintaining synchronous operation of the TDD system.
  • the TDD state control 811 thereby precisely times the duration of the time frame 501 and its constituent parts, including each of the transmit time slots 510, the receive time slots 511, the abbreviated guard bands 512, and the collective guard portion 503.
  • the TDD state control 811 may be synchronized from time to time with a system clock such as may be located in a base station controller, a cluster controller, or an associated network, so as to permit global synchronization among base stations in a zone or cluster.
  • a system clock such as may be located in a base station controller, a cluster controller, or an associated network, so as to permit global synchronization among base stations in a zone or cluster.
  • the mode control 810 selects between a transmit mode and a receive mode of operation.
  • the mode control 810 reads information from the TDD state control 811 to determine the appropriate mode. For example, at the end of the transmission portion 502, as indicated by status bits in the TDD state control 811, the mode control 810 may switch modes from transmit mode to receive mode. At the end of the receiving portion 504, as indicated by status bits in the TDD state control 811, the mode control 810 may switch modes from receive mode to transmit mode.
  • data to be transmitted is provided to the data interface 805 from a data bus 813.
  • the data interface 805 provides the data to be transmitted to a timing command unit 806.
  • the timing command unit 806 formats the data to be transmitted to include, if desired, a timing adjustment command 815.
  • the data output by the timing command unit 806 may be in a format such as the transmission portion 502 shown in Fig. 5A, whereby data targeted for each user station 302 is properly
  • the output of the timing command unit 806 is provided to the transmitter 807, which modulates the data for
  • transmitter 807 obtains necessary timing information from either the mode control 810, or directly from the TDD state control 811.
  • the transmitter 807 may comprise a spread spectrum modulator such as is known in the art.
  • the data is transmitted by transmitter 807 from antenna 808.
  • the user stations 302 receive the transmitted data, formulate responsive user-to-base messages, and send the user- to-base messages in return order.
  • the messages from the user stations 302 appear at the base station 304 in the receive time slots 511.
  • the antenna 808 After switching from transmit mode to receive mode, the antenna 808 is used to receive data from the user stations 302. Although a single antenna 808 is shown in the Fig. 8A embodiment, different antennas may be used for transmit and receive functions, and multiple antennas may be used for purposes of achieving the benefits of antenna diversity.
  • the antenna 808 is coupled to a receiver 809.
  • the receiver 809 may comprise a demodulator or a spread spectrum correlator, or both.
  • Demodulated data is provided to the data interface 805 and thereupon to the data bus 813. Demodulated data is also provided to the propagation delay calculator 812, which calculates the propagation delay time for the RTT transaction.
  • the timing command unit 806 inserts a timing adjustment command, such as a time period T (which may or may not include the delay period ⁇ T used in the initial round trip timing transaction), into the transmit time slot 510 instructing the user station 302 to delay sending its response by an amount of time equal to the time period T.
  • the timing adjustment command may be placed at a designated position in a base-to-user message sent during the appropriate transmit time slot 510.
  • the timing adjustment command may be placed in a header 550 or a data message portion 551 of the transmit time slot 510.
  • the timing adjustment command is preferably set to the receive/transmit switching delay time of a user station 302, and is thereafter adjusted based on a calculated propagation delay time.
  • the user station 302 receiving the timing adjustment command delays sending its response by an amount of time designated thereby.
  • the responsive message sent by the user station 302 is received by the receiver 809 and provided to the propagation delay calculator 812.
  • the propagation delay calculator 812 obtains precise timing information from the TDD state control 811, so that the propagation delay calculator 812 may accurately determine the over-air propagation delay of the responsive message sent from the user station 302.
  • the propagation delay may be calculated as the difference in time between the time of actual receipt of the responsive message from the user station 302, and the amount of time equal to the time T past the beginning of the
  • the calculator 812 then calculates a new timing adjustment command 815 for the particular user station 302.
  • the new timing adjustment command 815 is preferably selected so that the responsive message from the user station 302 in the following time frame 501 begins at the end of the abbreviated guard band 512 and does not overlap with the responsive message from any other user station 302. For example, the new timing
  • adjustment command 815 may be equal to the calculated round- trip propagation time for the particular user station 302.
  • the timing adjustment command 815 may be updated as often as necessary to maintain a sufficient quality of communication between the base station 304 and all of the user stations 302.
  • the propagation delay calculator 812 therefore preferably stores the calculated timing adjustment command 815 for each independent user station 302. As the user station 302 moves closer to the base station 304, the timing adjustment command 815 is increased, while as the user station 302 moves farther away from the base station 304, the timing adjustment command 815 is decreased.
  • the timing of the user stations 302 is advanced or retarded, and the ongoing communications between the base station 304 and the user stations 302 will not be interrupted by overlapping responsive user-to-base messages received from the user stations 302.
  • FIG. 8B is a hardware block diagram of an alternative embodiment of a base station 304.
  • the Fig. 8B base station is similar to that of Fig. 8A, except that a start counter command and a stop counter command are employed as follows.
  • a start counter command 830 is sent from the transmitter 807 to the TDD state control 811 for the target user station 302.
  • the receiver 809 receives a response from the target user station 302
  • the user station sends a stop counter command 831 to the TDD state control 811 for the target user station 302.
  • the value stored in the counter for the particular user station 302 represents the round trip propagation delay time.
  • a separate counter may be employed for each user station 302 with which the base station 304 is in contact.
  • FIG. 9 is a hardware block diagram of a user station 302 in accordance with an embodiment of the present invention.
  • the user station 302 of Fig. 9 comprises a data interface 905, a timing command interpreter 906, a transmitter 907, an antenna 908, a receiver 909, a mode control 910, and a TDD state control 911.
  • Timing control for the system of Fig. 9 is carried out by the TDD state control 911.
  • the TDD state control 911 controls the TDD state control 911.
  • the TDD state control 911 thereby precisely times the duration of the time frame 501 and its constituent parts, including each of the transmit time slots 510, the receive time slots 511, the abbreviated guard bands 512, and the collective guard portion 503.
  • the mode control 910 selects between a transmit mode and a receive mode of operation.
  • the mode control 910 reads information from the TDD state control 911 to determine the appropriate mode.
  • the mode control 910 in response to status bits in the TDD state control 911, may switch modes to a receive mode during the appropriate transmit time slot 510 of the time frame 501.
  • the mode control 910 may- switch modes, in response to status bits in the TDD state control 911, to transmit mode during the appropriate receive time slot 511.
  • the mode control 910 may- maintain a dormant mode, or may be kept in a receive mode in order to monitor transmissions from the base station 304, to monitor the activity of other nearby base stations 304, or for other purposes .
  • data to be transmitted is provided to the data interface 905 from a data bus 913.
  • the data interface 905 provides the data to be transmitted to the transmitter 907, which modulates the data for communication and transmits the data in the appropriate receive time slot 511.
  • the transmitter 907 obtains necessary timing information from either the mode control 910, or directly from the TDD state control 911.
  • the transmitter 907 may (but need not) comprise a spread spectrum modulator such as is known in the art.
  • the data is transmitted by transmitter 907 from antenna 908.
  • the base station 304 receives the transmitted data, formulates responsive base-to-user messages as desired, and sends the base-to-user messages in the appropriate transmit time slot 510.
  • the antenna 908 is used to receive data from the base station 304. Although a single antenna 908 is shown in the Fig. 9 embodiment, different antennas may be used for transmit and receive functions, or multiple antennas may be used to obtain antenna diversity.
  • the antenna 908 is coupled to a receiver 909.
  • the receiver 909 may comprise a demodulator or a spread spectrum correlator, or both.
  • Demodulated data is provided to the data interface 905 and thereupon to the data bus 913. Demodulated data is also provided to the timing command interpreter 906, which applies the timing adjustment command received from the base station 304.
  • the timing command interpreter 906 parses the data received from the base station 304 to determine the timing adjustment command. Assuming the timing adjustment command comprises a time T equal to the calculated round-trip propagation (RTT) time, the timing command interpreter 906 may reset the clocks and/or timers in the TDD state control 911 at the appropriate instant (such as around the start of the next time frame 501) so as to achieve global re-alignment of its timing. If the timing adjustment command is an instruction to advance timing by an amount of time T, then the timing command interpreter 906 may reset the TDD state control 911 at a period of time T just prior to the elapsing of the current time frame 501. If the timing adjustment command is an instruction to retard timing by an amount of time T, then the timing command interpreter 906 may reset the TDD state control 911 at a period of time T just after the elapsing of the current time frame 501.
  • RTT round-trip propagation
  • the timing adjustment command may, as noted, be expressed in terms of a number of bits or chips by which the user station 302 should advance or retard its timing.
  • the timing adjustment command may also be expressed in terms of a
  • fractional timing unit e.g., milliseconds
  • the timing command interpreter 906 may maintain an internal timing adjustment variable, thereby utilizing a delta modulation technique.
  • the internal timing adjustment variable is updated each time a timing adjustment command is received from the base station 304. If the timing adjustment command is an instruction to advance timing, then the timing adjustment variable is decreased by an amount T. If the timing adjustment command is an instruction to retard timing, then the timing adjustment variable is increased by an amount T.
  • the timing adjustment variable may be added to the output of the TDD state control 511 in order to synchronize to the base station timing. Alternatively, the timing adjustment variable may be provided directly to the transmitter 907 and the receiver 909, which alter the timing of their operations accordingly.
  • the timing command interpreter 906 may comprise a first order tracking circuit which integrates the requested change in transmission timing from time period to time period, and adjusts the timing of the user station 302 transmission on such a basis.
  • Figure 5C is a timing diagram, illustrated from a base station perspective, showing a variation of the TDD/TDM/TDMA system of Fig. 5A using an interleaved symbol transmission format.
  • a time frame 570 is divided into a transmission portion 571, a collective guard time portion 576, and a receiving portion 572, similar to Fig. 5A or Fig. 7.
  • the base station 304 transmits to a plurality of user stations 302 during a
  • each transmit time slot 574 rather than sending a message directed to a single user station 302, the base station 304 sends an interleaved message 578 containing a sub-message 589 for each of the user stations 302 (or a sub-message 589 for general polling or other functions if the receive time slot is unoccupied) .
  • the user stations 302 therefore receive a portion of their total incoming message from each of the transmit time slots 574, and must listen over the entire transmission portion 571 to obtain their entire message for the time frame 570.
  • each transmit time slot 574 comprises a plurality of sub-messages 589, preferably one sub-message 589 for each receive time slot 575 (and therefore one sub-message 589 for each potential user station 302) .
  • each transmit time slot 574 would comprises 16 sub-messages 589, denoted in order 589-1, 589-2,... 589-16.
  • Each sub-message 589 preferably comprises the same number of symbols, e.g. 40 symbols.
  • the first sub- message 589-1 is intended for the first user station 302
  • the second sub-message 589-2 is intended for the second user station 302, and so on, up to the last sub-message 589-16.
  • a user station 302 reads part of its incoming message from the appropriate sub-message 589 in the first transmit time slot 574, the next part of its incoming message from the
  • each transmit time slot 574 preceding the interleaved message 578 is a preamble 577.
  • the preamble 577 assists the user station 302 in synchronization, and may comprise a spread spectrum code.
  • Preambles 577 appear in each transmit time slot 574 and are dispersed throughout the transmission portion 574, therefore allowing the user station 302 to support channel sounding operations useful for setting up a rake receiver (e.g., synchronization) and/or selection diversity. Because the user station 302 obtains its information over the entire transmission portion 571, the communication path is less sensitive to sudden fading or interference affecting only a relatively brief period of the transmission portion 571. Thus, if interference or fading corrupt information in a particular transmit time slot 574 (e.g., the second transmit time slot 574), the user station 302 would still have 15 sub- messages 589 received without being subject to such
  • the user station 302 can correct for one or more sub-messages 589 received in error.
  • a preferred forward error correction technique utilizes Reed-Solomon codes, which can be generated by algorithms generally known in the art.
  • INT represents the function of rounding down to the nearest integer.
  • Fig. 5C Although a particular symbol interleaving scheme is shown in Fig. 5C, other symbol interleaving techniques, such as diagonal interleaving, may also be used.
  • the user stations 302 respond over the reverse link in generally the same manner as described with respect to Figs. 5A or 7. Thus, the user stations 302 respond with a user transmission in a designated receive time slot 575 of the receive portion 572.
  • the receive time slot 575 comprises a preamble 579 and a user message 580.
  • the receive time slots 575 are separated by abbreviated guard times 573, and ranging may be used to instruct the user stations 302 to advance or retard their timing as previously mentioned.
  • Figure 5D is a chart comparing performance of a
  • Figure 5D plots frame error probability against signal-to- noise ratio (Eb/No), in dB.
  • Eb/No signal-to- noise ratio
  • Fig. 5D are shown separate plots for different rake diversity channels L (i.e.,
  • FIG. 5D thus illustrates a substantial reduction in frame error probability over the Fig. 5A system by use of interleaved symbol transmission and forward error correction.
  • FIG. 10A is a diagram of timing sub-elements having predefined formats for use in a time division duplex system.
  • the three timing sub-elements shown in Fig. 10A may be used to construct a time division duplex frame structure, such as the frame structures shown in Figs. 10B-E.
  • Figs. 10A-E preferably use spread spectrum for communication, spread spectrum is not required. However, the following description assumes the use of spread spectrum techniques. For the present example, a chipping rate of 5 MHz is preferred.
  • Fig. 10A a base timing sub-element 1001, a user datalink timing sub-element 1011, and a range timing sub- element 1021. For each of these sub-elements 1001, 1011, and 1021, as explained more fully below, timing is shown from the perspective of the base station 304 with the initial range of the user station 302 at zero for range timing sub-element 1021.
  • the base timing sub-element 1001 comprises a base
  • the base preamble interval 1002 may be 56 chips in length.
  • the base message interval 1003 may be 205 bits in length (or, equivalently, 1312 chips if using 32-ary encoding). In a preferred 32-ary encoding technique, each sequence of five data bits is
  • the base message interval 1003 comprises a total of up to 41 5-bit data sequences, for a total of 205 bits; thus, a transmission in the base message interval 1003 may comprise a series of up to 41 spread
  • spectrum codes each selected from the set of 32 spread spectrum codes, for a total of 1312 chips.
  • Figs 10A-E is described using a 32-ary spread spectrum coding technique
  • other spread spectrum techniques including other M-ary encoding schemes (such as 4-ary, 16-ary, etc.) may also be used, depending on the particular system needs.
  • the transmit/receive switch interval 1004 is preferably selected as a length of time sufficient to enable the
  • switching of the base station 304 from a transmit mode to a receive mode or, in some embodiments, to enable the switching of a user station 302 from a receive mode to a transmit mode and may be, for example, two microseconds in length.
  • the user datalink timing sub-element 1011 and the range timing sub-element 1021 each generally provide for
  • each of these timing sub-elements 1011, 1021 provides for transmission by a first user station 302 of a data message or a ranging message in the first part of the timing sub-element 1011 or 1021, and transmission by a second user station 302 of a control pulse preamble in the latter part of the timing sub-element 1011 or 1021.
  • the control pulse preamble generally allows the base station 304 to carry out certain functions (e.g., power control) with respect to the second user station 302.
  • the user datalink timing sub-element 1011 comprises a datalink preamble interval 1012, a user message interval 1013, a guard band 1014, a transmit/receive switch interval 1015, a second preamble interval 1016, an antenna adjustment interval 1017, a second guard band 1018, and a second transmit/receive switch interval 1019.
  • the preamble intervals 1012, 1016 may each be 56 chips in length.
  • the user message interval 1013 may be 205 bits in length, or 1312 chips, using the 32-ary spread spectrum coding technique described above with respect to the base timing sub-element 1001.
  • the transmit/receive switch intervals 1015, 1019 may each be of a duration
  • the antenna adjustment interval 1017 may be of sufficient duration to allow transmission of a data symbol indicating selection of a particular antenna beam or permitting minor adjustments to the angle of a directional antenna at the base station 302, or permitting selection of one or more antennas if the base station 302 is so equipped.
  • the range timing sub-element 1021 comprises a ranging preamble interval 1022, a user ranging message interval 1023, a ranging guard band 1024, a transmit/receive switch interval 1025, a second preamble interval 1026, an antenna adjustment interval 1027, a second guard band 1028, and a second
  • the transmit/receive switch interval 1029 may each be 56 chips in length.
  • the user ranging message interval 1023 may be 150 bits in length, or 960 chips, using the 32-ary spread spectrum coding technique described above with respect to the base timing sub-element 1001.
  • the ranging guard band 1024 may be 454.5 chips in length.
  • the other guard band 1028 may be 102.5 chips in length.
  • the transmit/receive switch intervals 1025, 1029 may each be of a duration sufficient to allow proper switching between transmit and receive modes, or between receive and transmit modes, as the case may be.
  • the antenna adjustment interval 1027 may be of sufficient duration to allow transmission of a data symbol for selecting a particular antenna beam or permitting minor adjustments to the angle of a directional antenna at the base station 302, or permitting selection of one or more antennas if the base station 302 is so equipped.
  • the total length of the base timing sub-element 1001 may be 1400 chips.
  • the total length of each of the user datalink timing sub-element 1011 and the range timing sub-element 1021 may be 1725 chips. For these particular exemplary values, a chipping rate of 5 MHz is assumed.
  • Figure 10B is a timing diagram for a fixed time division duplex frame structure (or alternatively, a zero offset TDD frame structure) using the timing sub-elements depicted in Fig. 10A.
  • the frame structure of Fig. 10B, as well as of Figs. 10C-E described below, is shown from the perspective of the base station 304.
  • a time frame 1040 comprises a plurality of time slots 1041.
  • time slots are also designated in sequential order as TS1, TS2, TS3, etc.
  • Each time slot 1041 comprises a base timing sub-element 1001 and either a user datalink timing sub-element 1011 or a range timing sub-element 1021. While the frame structure of Fig. 10B supports range timing sub-elements 1021, it is
  • Fig. 10B which may be denoted a fixed framing structure, will ordinarily occur using user datalink timing sub-elements 1011.
  • the designated starting point of the time slots TS1, TS2, TS3, etc. is to some degree arbitrary in the Fig. 10B frame structure and various of the other
  • the frame structure may be defined such that time slots each start at the beginning of the user timing sub-elements 1011 or 1021, or at the start of the preamble interval 1016, or at the start or end of any particular timing interval, without changing the operation of the system in a material way.
  • the base station 304 transmits, as part of the base timing sub-element 1001 of each time slot 1041, to user stations 302 in sequence with which it has established communication.
  • the base station 304 transmits a
  • preamble during the preamble interval 1002 and a base-to-user message during the base message interval 1003.
  • the base station 304 switches from a transmit mode to a receive mode.
  • the user station 302 during the transmit/receive switch interval 1004 switches from a receive mode to a transmit mode.
  • the base-to-user message transmitted in the base message interval 1003 is directed to a first user station M1, which may be mobile.
  • the first user station M1 responds with a preamble during the datalink preamble interval 1012 and with a user-to-base message during the user message interval 1013.
  • Proper timing is preferably set upon initial establishment of communication, and the transmissions from the user stations, such as the first user station M1, may be maintained in time alignment as seen at the base station 304 by timing adjustment commands from the base station 304, such as the timing adjustment commands described with respect to Figs. 8-9 and elsewhere herein.
  • a round-trip guard time must be included in each time slot 1041 so as to allow the base-to-user message to propagate to the user station 302 and the user-to-base message to propagate to the base station 304.
  • the depiction of the exploded time slot TS1 in Fig. 10B is generally shown with the assumption that the user station M1 is at zero distance from the base station 304; hence, the user-to-base messages appear in Fig. 10B directly after the transmit/receive switch interval 1004 of the base timing sub-element 1001.
  • the user station M1 is not immediately adjacent to the base station 304, then part of guard time 1014 will be consumed in the propagation of the user-to-base message to the base station 304.
  • the user-to- base message will appear at the base station 304 after the elapsing of a time period equal at most to the duration of guard time 1014. Timing adjustment commands from the base station 304 may allow a shorter maximum necessary guard time 1014 than would otherwise be possible.
  • a control pulse preamble is received from a second user station M2 during the preamble interval 1016.
  • the function of the control pulse preamble is explained in more detail below.
  • an antenna adjustment interval 1017 is an antenna adjustment interval 1017, during which the base station 304 adjusts its transmission antenna, if necessary, so as to direct it towards the second user station M2.
  • guard band 1018 which accounts for the propagation time of the control pulse preamble to the base station 304.
  • the preamble interval is another transmit/receive switching interval 1019 to allow the base station 304 opportunity to switch from a receive mode to a transmit mode, and to allow the second user station M2 opportunity to switch from a transmit mode to a receive mode .
  • the control pulse preamble received during the preamble interval 1016 preferably serves a number of functions.
  • the control pulse preamble may be used by the base station 304 to determine information about the communication link with the user station 302. Thus, the control pulse preamble may provide the base station 304 with a power measurement
  • the base station 304 may determine the quality of the received signal, including the received power and the signal-to-noise ratio. The base station 304 may also determine, in response to the power, envelope, or phase of the control pulse preamble, the direction or distance of the user station 302, and the degree of noise or multipath error to which the communication link with the user station 302 may be prone .
  • the base station 304 may if necessary send a message commanding the user station 302 to adjust its power. Based on the quality of the received signal, the base station 304 may command the user station 302 to change (i.e., increase or decrease) its
  • the base station 304 may adjust its own power as well.
  • the base station 304 may adjust its power separately for each time slot 1041.
  • a preferred power control command from the base station 304 to the user station 302 may be encoded according to the Table 10-1 below:
  • control pulse preamble i.e., control pulse
  • the base station 304 transmits a preamble during the base preamble interval 1002 and transmits a base- to-user message during the base message interval 1003, both directed to the second user station M2.
  • the base station 304 thereby rapidly responds to the control pulse preamble sent by the user station M2.
  • following the base message interval 1003 is a transmit/receive switch interval 1004 during which the base station 304 switches to a receive mode and the user station M2 switches to a transmit mode.
  • the user station M2 responds with a preamble in the datalink preamble interval 1012 and a user-to- base message in the user message interval 1013.
  • the remaining steps in time slot TS2 are similar to those of the first time slot TSl, except with respect to the preamble interval 1016 as noted below.
  • the base station 304 may indicate that a particular time slot 1041, such as time slot TS3 , is available for communication by, for example,
  • the third user station M3 desires to establish communication with the base station 304, then, in response to the base station 304 transmitting a general polling message during the base message interval 1003 of the third time slot TS3 , the third user station M3 sends a general polling
  • the base station 304 may determine the range of the user station M3 and thereby
  • the guard times 1014 and 1018 are preferably kept to a minimum.
  • the guard times 1014, 1018 will not be of sufficient duration to allow a full ranging transaction to occur.
  • a ranging transaction (such as may be carried out using timing sub- element 1021 instead of timing sub-element 1011) may result in interference between the transmission of a user station 302 seeking to establish communication and the control pulse preamble of the user station 302 already in communication in the immediately following time slot 1041 with the base station 304. If the guard times are lengthened to permit ranging transactions, then fewer user stations 302 can be supported, particularly in a large cell environment.
  • the latter portion of the time slot TS3 may comprise a range timing sub-element 1021, as described
  • a ranging transaction is carried out between the base station 304 and user station M3 , instead of timing sub-element 1011.
  • the user station M3 transmits a preamble during a ranging preamble interval 1022 of time slot TS3, and transmits a ranging message during the user ranging message interval 1023 of time slot TS3.
  • the user station M3 delays
  • the delay time ⁇ T may be communicated by the base station 304 as part of the general polling message, or may be a pre-programmed system parameter.
  • the base station 304 determines the propagation delay from the user station M3 to the base station 304 by measuring the round trip propagation delay from the end of the base message interval 1003 (i.e., the earliest possible receipt of the preamble and ranging message) to the time of actual receipt of the responsive preamble and ranging message from the user station M3 , taking into account the delay time ⁇ T.
  • the ranging guard band 1024 in time slot TS3 is
  • the length of the ranging guard band 1024 is determined in part by the radius of the cell 303 in which the base station 304 is located, or may be determined in part by the maximum cell radius of the cellular system.
  • the base station 304 may issue a timing adjustment command to the user station M3 in the next time frame 1040 instructing the user station M3 to advance or retard its timing by a
  • the timing adjustment command may be set equal to the round-trip propagation time as determined by the base station 304 during the ranging transaction.
  • the timing adjustment command is selected so as to cause the user transmission from the user station M3 to the base station 304 in the subsequent time frame 1040 to be received by the base station 304 immediately after the end of the transmit/receive switch interval 1004, as described with respect to Fig. 1OA.
  • the ranging message may also contain other information to assist the base station 304 in handshaking with the user station M3.
  • the ranging message may contain as data a user identifier for the user station M3 seeking to establish communication.
  • the ranging message may also indicate a preferred spread spectrum code to be used by the base station 304 and the particular user station M3 in subsequent
  • the base station 304 may determine the range of the user station 302 by using the reception time of the control pulse preamble (or, alternatively, the user-to-base message) and periodically issue a timing adjustment command during the base-to-user message interval directed to the user station 302.
  • Figure 1OC shows a subsequent time frame 1040 after communication has been established between the base station 304 and the third user station M3 , with or without the use of a ranging transaction.
  • the transactions
  • the transactions occurring in the first time slot TSl between the user station Ml and the base station 304 are the same as those for Fig. 1OB.
  • the transactions occurring in the second time slot TS2 between the user station M2 and the base station 304 are the same as those for Fig. 1OB.
  • the third user station M3 instead of there being no transmitted control pulse preamble in the preamble interval 1016, the third user station M3 transmits a control pulse preamble during the preamble interval 1016 of the second time slot TS2.
  • the user station M3 may wait until the base station 304 acknowledges its ranging message, sent in the prior time frame 1040, before transmitting a control pulse preamble in each time slot TS2 preceding its designated time slot TS3 for communication.
  • the base station 304 may use the control pulse preamble for a variety of purposes, including power control and other purposes, as previously described.
  • the base station 304 may send an acknowledgment signal to the user station M3 during the base message interval 1003.
  • the acknowledgment signal may be sent using a spread spectrum code determined by a user identifier sent by the user station M3 as part of the ranging message.
  • the base station 304 sends a timing adjustment command instructing the user station M3 to advance or retard its timing by a
  • time frames 1040 after establishing communication with the third user station M3 in the manner described above, communication may be carried out between the base station 304 and the third user station M3 in time slot TS3.
  • the user station M3 transmits a control pulse preamble allowing the base station 304 to exercise power control, synchronize to the user station M3 , or determine the distance of the user station M3.
  • the base station 304 then sends a transmission directed to the user station M3 in the first portion of the third time slot TS3 , and the user station M3 responds with a transmission directed to the base station 304 in the latter portion of the third time slot TS3.
  • the base station 304 may update the timing adjustment command to the user station M3.
  • the base station 304 may begin to transmit a general polling message during the newly opened time slot 1041, indicating that the time slot 1041 is free for communication. New user stations 302 may thereby establish communication with the same base station 304.
  • Figure 1OD is a timing diagram for another embodiment of a frame structure in accordance with certain aspects of the present invention.
  • Figure 1OD shows an interleaved time division duplex frame structure using the timing sub-elements depicted in Fig. 1OA.
  • a time frame 1050 comprises a plurality of time slots 1051.
  • time slots 1051 are designated in sequential order as TSl', TS2', TS3 ' , etc.
  • Each time slot 1051 comprises a base timing sub-element 1001 and either a user datalink timing sub-element 1011 or a user ranging sub-element 1021, as described in more detail below.
  • the primary difference between the frame structure of Figs. lOB-C and the frame structure of Fig. 1OD is that the frame structure of Fig. 1OD may be considered interleaved in the sense that each user station 302 does not respond
  • the interleaved frame structure of Fig. 1OD is that guard times can be shorter, allowing more time slots 1051 per time frame 1050, and therefore more user stations 302 per base station 304.
  • the interleaved frame structure of Fig. 10D also allows efficient use of ranging transactions between the base station and the user stations, particularly upon initial link-up of communication. Because the frame structure of Fig. 10D is interleaved, the first time slot TS1' comprises a transmission from the base station 304 to the first user station M1 and a responsive transmission, not from the first user station M1, but from the last user station MN.
  • the base station 304 transmits, as part of the base timing sub-element 1001 of each time slot 1051, to user stations 302 with which it has
  • the base station 304 thus provides a wireless local area network (WLAN) to the base station 304 .
  • the base station 304 switches from a transmit mode to a receive mode.
  • the base-to-user message transmitted in the base message interval 1003 is directed to a first user station M1, which may be mobile.
  • the last user station MN to have been sent a message from the base station in the last time slot TSN' of the prior time frame 1050 transmits a preamble during the datalink preamble interval 1012 and a user-to-base message during the user message interval 1013.
  • the frame structure of Fig. 10D, as noted previously, is shown from a perspective of the base station 304, and the
  • transmissions from the user stations are maintained in time alignment as seen by the base station 304 by timing adjustment commands from the base station 304, similar to the timing adjustment commands described elsewhere herein.
  • Proper timing is preferably set upon initial
  • a control pulse preamble is received from a second user station M2 during the preamble interval 1016.
  • the control pulse preamble sent during the preamble interval 1016 may serve functions such as those described with respect to the Fig. lOB-C
  • the base station 304 may determine, in response to the power, envelope, or phase of the control pulse preamble, the direction or distance of the user station M2, and/or the degree of noise or multipath error to which the communication link with the user station M2 may be prone.
  • the base station 304 may command the user station M2 to adjust its power based on the quality and strength of the received control pulse preamble.
  • the preamble interval 1016 is an antenna adjustment interval 1017 during which the base station 304 has
  • an antenna adjustment interval 1017 Following the preamble interval 1016 is an antenna adjustment interval 1017, during which the base station 304 adjusts its
  • guard band 1018 which accounts for the propagation time of the control pulse preamble to the base station 304.
  • transmit/receive switching interval 1019 to allow the base station 304 " opportunity to switch from a receive mode to a transmit mode, and to allow the second user station M2
  • the base station 304 transmits a preamble during the base preamble interval 1002 and transmits a base-to-user message during the base message interval 1003, both directed to the second user station M2.
  • the base station 304 thereby rapidly responds to the control pulse sent by the user station M2.
  • a transmit/receive switch interval 1004 during which the base station 304 switches to a receive mode.
  • the latter portion of the time slot TS2' is used for receiving a transmission from the first user station M1. While the first user station M1 is in the process of transmitting, the second user station M2 thus has the opportunity to process the data received from the base station 304 during the same time slot TS2', and to transmit a responsive transmission timed to arrive at the base station 304 in the following time slot TS3' without
  • the base station receives from the first user station M1 a preamble during the datalink preamble interval 1012 and a user-to-base message in the user message interval 1013.
  • the new user station M3 waits until an open user portion of a time slot 1051, such as the fourth time slot TS4 ' in the present
  • the base station 304 receives a control pulse preamble during the preamble interval 1016 of the third time slot TS3 ' from the next user station M4.
  • the base station 304 sends a base-to-user message during the base message interval 1003 to the user station M4.
  • the user station M4 responds with a user-to-base message in the following time slot TS5' .
  • the new user station M3 attempts to establish communication with the base station 304.
  • the new user station M3 in response to the base station 304 transmitting a general polling message during the base message interval 1003 of the third time slot TS3', the new user station M3 sends a general polling response message in a user message interval 1013 of the following time slot TS4' .
  • the base station 304 may determine the range of the user station M3 and thereby determine a required timing adjustment for subsequent transmissions by the user station M3.
  • the latter portion of the time slot TS4' preferably comprises a range timing sub-element 1021 as previously described with respect to Fig. 1OA.
  • the new user station M3 in response to the base station 304 transmitting a general polling message in the base message interval 1003 of the third time slot TS3 ' , the new user station M3 sends a ranging message in a user ranging message interval 1023 of the following time slot TS4' .
  • the depiction of the exploded time slot TS4' in frame structure in Fig. 1OD assumes that the user station M3 is at zero distance from the base station 304; hence, the user-to-base messages appear in Fig. 1OD directly after the transmit/receive switch interval 1004 of the base timing sub-element 1001.
  • guard time 1014 will be consumed in the propagation of the user-to-base message to the base station 304.
  • the user station M3 is at the cell periphery, then the user-to-base message will appear at the base station 304 after the elapsing of a time period equal at most to the duration of guard time 1014. Timing adjustment commands from the base station 304 may allow a shorter maximum necessary guard time 1014 than would otherwise be possible.
  • the base station 304 may determine the range of the user station M3 and thereby determine a required timing advance for subsequent transmissions by the user station M3.
  • a ranging transaction is carried out between the base station 304 and the user station M3 , whereby the user station M3 transmits a preamble during a ranging preamble interval 1022 of time slot TS4 ' and a ranging message during the user ranging message interval 1023 of time slot TS4' .
  • the user station M3 delays transmitting the preamble and ranging message for an amount of time ⁇ T.
  • the delay time ⁇ T may be communicated by the base station 304 as part of the general polling message, or may be a pre-programmed system parameter.
  • the base station 304 determines the propagation delay from the user station M3 to the base station 304 by measuring the round trip propagation delay from the end of the base message interval 1003 in the fourth time slot TS4' (i.e., the earliest possible receipt of the preamble and ranging message) to the time of actual receipt of the responsive preamble and ranging message from the user station M3, taking into account the delay time ⁇ T.
  • the ranging guard band 1024 in time slot TS4' is
  • the length of the ranging guard band 1024 is determined in part by the radius of the cell 303 in which the base station 304 is located, or may be determined in part by the maximum cell radius of the cellular system.
  • the base station 304 may issue a timing adjustment command to the user station M3 in the next time frame 1050 instructing the user station M3 to advance or retard its timing by a
  • the timing adjustment command may be set equal to the round-trip propagation time as determined by the base station 304 during the ranging transaction.
  • the timing adjustment command is selected so as to cause the user transmission from the user station M3 to the base station 304 in the subsequent time frame 1050 to be received by the base station 304
  • the base station 304 may periodically instruct a user station 302 to adjust its timing by issuing subsequent timing adjustment commands, e.g., as often as each time frame.
  • the base station 304 may monitor the distance of the user station 302 by measuring the time of receipt of the user-to-base message.
  • the base station 304 monitors the range of the user station 302 by using the reception time of the control pulse preamble, because of the preamble's known timing and message structure, and responds during the base-to- user message interval with a timing adjustment command.
  • the ranging message may also contain other information to assist the base station 304 in handshaking with the user station M3.
  • the ranging message may contain as data a user identifier for the user station M3 seeking to establish communication.
  • the ranging message may also indicate a preferred spread spectrum code to be used by the base station 304 and the particular user station M3 in subsequent
  • Figure 10E shows a subsequent time frame 1050 after a ranging transaction has been completed with the third user station M3.
  • the transactions between the user stations M1, MN and the base station 304 occurring in the first time slot TS1' are the same as for Fig. 10D.
  • the transactions between the user stations M1, M2 and the base station 304 occurring in the second time slot TS2 are the same as for Fig. 10D.
  • the third user station M3 may transmit a control pulse preamble during the preamble interval 1016 of the second time slot TS2' .
  • the user station M3 may wait until the base station 304 acknowledges its ranging message sent in the prior time frame 1050 before transmitting a control pulse preamble during the preamble interval 1016 of each preceding time slot TS2'.
  • the base station 304 may use the control pulse preamble for a variety of purposes, including power control and other purposes, as previously described.
  • the base station 304 may respond by sending an acknowledgment signal to the user station M3 during the base message interval 1003.
  • the acknowledgment signal may be sent using a spread spectrum code determined by a user
  • the base station 304 preferably sends a timing adjustment command instructing the user station M3 to advance or retard its timing by a designated amount.
  • communication may be carried out between the base station 304 and the user station M3 in an interleaved fashion in time slots TS3' and TS4' (in addition to the receipt of the control pulse preamble in the second time slot TS2' each time frame 1050).
  • the user station M3 transmits a control pulse preamble allowing the base station 304 to take certain actions -- for example, to
  • the base station 304 then sends a communication directed to the user station M3 in the first portion of the third time slot TS3 ' , and the user station M3 responds with a communication directed to the base station 304 in the latter portion of the following time slot TS4' .
  • the base station 304 may update the timing adjustment command to the user station M3.
  • the base station 304 may begin to transmit a general polling message during the newly opened time slot 1051, indicating that the time slot 1051 is free for communication. New user stations 302 may thereby establish communication with the same base station 304.
  • two frequency bands are used for communication instead of a single frequency band.
  • Figure HA is a diagram of timing sub-elements having predefined formats for use in an FDD/TDMA system.
  • the three timing sub-elements shown in Fig. HA may be used to construct an FDD/TDMA frame structure, such as the frame structures shown in Figs. HB-D.
  • Figs. HA-D preferably use spread spectrum for communication, spread spectrum is not required.
  • the following description assumes the use of spread spectrum techniques. For the present example, unless otherwise
  • a chipping rate of 2.8 MHz is preferred, although the chipping rate selected depends upon the application.
  • Fig. HA are shown a base timing sub-element 1101, a user datalink timing sub-element HlO, and a range timing sub- element 1121.
  • HOl user datalink timing sub-element
  • HlO user datalink timing sub-element
  • range timing sub- element 1121 For each of these sub-elements HOl, HlO, and 1121, as explained more fully below, timing is shown from the perspective of the base station 304 with the range of the user station 302 at zero.
  • the base timing sub-element 1101 comprises a base
  • preamble interval 1102 a base message interval 1103, three more preamble burst intervals 1104, 1105, and 1106
  • the base preamble interval 1102 may be 56 chips in length.
  • the base message interval 1103 may be 205 bits in length, or 1312 chips using 32-ary coding, as
  • the base message interval 1103 comprises a total of up to 41 5-bit data sequences, for a total of 205 bits,- thus, a transmission in the base message interval 1103 may comprise a series of up to 41 spread spectrum codes, each selected from the set of 32 spread spectrum codes, for a total of 1312 chips.
  • Figs 11A-E is described using 32-ary spread spectrum coding techniques, other spread spectrum techniques, including other M-ary coding schemes (such as 4-ary, 16-ary, etc.) may also be used, depending on the particular system requirements.
  • M-ary coding schemes such as 4-ary, 16-ary, etc.
  • the three preamble burst intervals 1104, 1105, and 1106 are each preferably 56 chips in length; thus, the 123-preamble burst interval 1109 is preferably 168 chips in length.
  • the transmit/receive switch interval 1108 is preferably selected as a length of time sufficient to enable the switching of the base station 304 from a transmit mode to a receive mode and may be, for example, 32 chips or 11.43 microseconds in length.
  • the transmit/receive switch interval 1108 and the base fill code interval 1107 collectively comprise, in a preferred embodiment, a length of 189 chips.
  • the total length of the base timing sub-element 1101 is preferably 1750 chips (for the assumed 2.8 MHz
  • the base timing sub-element 1101 equal in length to the user timing sub-elements 1110, 1121 to maintain synchronicity in the dual-frequency band system described in Figs. 11A-D, wherein the base station 304 communicates over one frequency band and the user stations 302 over another frequency band.
  • the user datalink timing sub-element 1110 and the range timing sub-element 1121 each generally provide for
  • timing sub-elements 1110, 1121 provide for transmission by a first user station 302 of a data message or a ranging message in the first part of the timing sub- element 1110 or 1121, and transmission by a second user station 302 of a control pulse preamble in the latter part of the timing sub-element 1110 or 1121.
  • the control pulse preamble as further described below, generally allows the base station 304 to carry out certain functions (e.g., power control) with respect to the second user station 302.
  • the user datalink timing sub-element 1110 comprises a datalink preamble interval 1112, a user message interval 1113, a guard band 1114, a transmit/receive switch interval 1115, a second preamble interval 1116, an antenna adjustment interval 1117, a second guard band 1118, and a second transmit/receive switch interval 1119.
  • the preamble intervals 1112, 1116 may each be 56 chips in length.
  • the user message interval 1113 may be 205 bits in length, or 1312 chips, using the 32-ary spread spectrum coding technique described previously herein.
  • the length of the guard bands 1114, 1118 may vary, but should be sufficient to allow receipt of the pertinent message transmissions without interference.
  • the transmit/receive switch intervals 1115, 1119 may each be of a duration
  • the antenna adjustment interval 1117 may be of sufficient duration to allow transmission of a data symbol for selecting a particular antenna beam or permitting minor adjustments to the angle of a directional antenna at the base ' station 302, or permitting selection of one or more antennas if the base station 302 is so equipped.
  • the range timing sub-element 1121 comprises a ranging preamble interval 1122, a user ranging message interval 1123, a ranging guard band 1124, a transmit/receive switch interval 1125, a second preamble interval 1126, an antenna adjustment interval 1127, a second guard band 1128, and a second
  • the preamble intervals 1122, 1126 may each be 56 chips in length.
  • the user ranging message interval 1123 may be 150 bits in length, or 960 chips, using the 32-ary spread spectrum coding technique described previously herein.
  • the length of the ranging guard band 1124 may vary depending, for example, on cell radius, but should be sufficient to allow receipt of a ranging message without interference.
  • the other guard band 1128 should likewise be of sufficient length to allow receipt of the pertinent
  • the transmit/receive switch intervals 1125, 1129 may each be of a duration sufficient to allow proper switching between transmit and receive modes, or between receive and transmit modes, as the case may be.
  • the antenna adjustment interval 1127 may be of sufficient duration to allow transmission of a data symbol for selecting a
  • the total length of each of the user datalink timing sub- element 1110 and the range timing sub-element 1121 may be 1750 chips, or the same length as the base timing sub-element 1101. These particular exemplary values assume a chipping rate of 2.8 MHz.
  • Figure HB is a timing diagram for a fixed or zero offset FDD/TDMA frame structure using the timing sub-elements
  • FIG. HA The frame structures of Figs. HB-E are shown from the perspective of the base station 304.
  • Figure HB is a frame structure for a system using two frequency bands for communication in addition to certain aspects of time division multiple access.
  • a first frequency band 1170 also referred to as a base station frequency band, is used primarily for communication from a base station 304 to user stations 302.
  • a second frequency band 1171 also referred to as a base station frequency band
  • a user station frequency band referred to as a user station frequency band
  • the two frequency bands 1170, 1171 are preferably located 80 MHz apart.
  • a time frame 1140 comprises a plurality of time slots 1141.
  • time slots are designated in sequential order as TS1", TS2", TS3", and so on.
  • Each time slot 1141 comprises a base timing sub-element 1101 on the base station frequency band 1170, and either a user datalink timing sub-element 1110 or a range timing sub-element 1121 on the user station frequency band 1171.
  • the time slots 1141 are shown from the perspective of the base station 304, so that the base timing sub-elements
  • the base station 304 transmits, as part of the base timing sub-element 1101 of each time slot 1141, in sequence to user stations 302 with which the base station 304 has established communication. More specifically, the base station 304 transmits a preamble during the preamble interval
  • the base station 304 transmits three short preamble bursts in the 123- preamble burst interval 1109 directed to a different user station 302.
  • the three preamble bursts in the 123 -preamble burst interval 1109 are directed to the user station 302 to which the base station 304 will be sending a main data message two time slots 1141 later.
  • the three short preamble bursts sent in the 123-preamble burst interval 1109 may be used for forward link diversity sensing and forward link power control purposes. Each of these three preamble bursts may be transmitted on a different antenna to allow receiving user stations 302 an opportunity to make a diversity selection for an upcoming forward link data message in a subsequent time slot 1141.
  • the base fill code interval 1107 Following the 123-preamble burst interval 1109 is the base fill code interval 1107, during which the base station 304 transmits a fill code. Following the base code fill interval 1107 is the transmit/receive switch interval 1104, during which the base station 304 may switch from a transmit mode to a receive mode. If the base station 304 has separate transmit and receive hardware, however, then the base station need not switch modes, and may instead continue to transmit a fill code during the transmit/receive switch interval 1104.
  • the base station transmits a base-to-user message in the base message interval 1103 directed to a first user station M1.
  • the base station 304 transmits a 123-preamble burst during the 123-preamble burst interval 1109, directed to another user station M3. Simultaneous with the base station transmissions, the base station 304 receives, on the user station frequency band 1171, a preamble during the datalink preamble interval 1112 and a user-to-base message during the user message interval 1113 from the last user station MN with which the base station 304 is in communication. During the control pulse preamble interval 1116 of the first time slot TS1" on the user station frequency band 1171, the base station 304 receives a control pulse preamble from the user station M2 to which the base station 304 is to transmit in the following time slot TS2".
  • control pulse preamble sent during the control pulse preamble interval 1116 are similar to those described earlier with respect to the control pulse preamble of Figs. 10A-E (e.g., power control, antenna adjustment, etc.).
  • an antenna adjustment interval 1117 Following the preamble interval 1116 is an antenna adjustment interval 1117, during which the base station 304 has an opportunity to adjust its transmission antenna, if necessary, so as to direct it towards the second user station M2 based upon information acquired from receipt of the control pulse preamble.
  • another guard band 1118 is another guard band 1118, which accounts for the propagation time of the control pulse preamble to the base station 304.
  • transmit/receive switching interval 1119 to allow the base station 304 opportunity to switch from a receive mode to a transmit mode (if necessary), and to allow the second user station M2 opportunity to switch from a transmit mode to a receive mode.
  • the base station 304 transmits, using the base station frequency band 1170, a preamble during the base preamble interval 1102 and a base-to-user message during the base message interval 1103, both directed to the second user station M2.
  • the base station 304 thereby rapidly responds to the control pulse preamble sent by the user station M2. It is assumed, however, in the exemplary time frame 1140 of Fig. 11B that the base station 304 is not in established communication with any user station 302 during the fourth time slot TS4" over the base station frequency band 1170.
  • the base station 304 does not transmit a 123- preamble burst directed to a user station 302.
  • the base station 304 Simultaneous with the base station transmissions in the second time slot TS2", the base station 304 receives, on the user station frequency band 1171, a preamble during the datalink preamble interval 1112 and a user-to-base message during the user message interval 1113 from the user station M1 with which the base station 304 communicated in the first time slot TS1". Similar to the first time slot TS1", during the control pulse preamble interval 1116 of the second time slot TS2" on the user station frequency band 1171, the base station 304 receives a control pulse preamble from the user station M3 to which the base station 304 is to transmit in the following time slot TS3".
  • the base station 304 In the third time slot TS3", the base station 304
  • a base message interval 1103 Following the base message interval 1103 is a 123 -preamble burst interval 1109 during which the base station 304 transmits three short preamble bursts (i.e., the 123-preamble burst) directed to a different user station M5, with which the base station 304 intends to communicate two time slots 1141 later.
  • the base station 304 receives, on the user station frequency band 1171, a preamble during the datalink preamble interval 1112 and a user-to-base message during the user message interval 1113 from the user station M2 with which the base station 304 communicated in the previous time slot TS2". Because the base station 304 is not in established communication with any user station 302 during the fourth time slot TS4" over the base station frequency band 1170, the base station 304 does not receive a control pulse preamble during the control pulse preamble interval 1116 of the third time slot TS3" on the user station frequency band 1171.
  • a similar exchange is carried out in the fourth time slot TS4", and in subsequent time slots 1141 as well. Whether or not particular user-to-base message, base-to-user messages, and preambles or control pulse preambles are transmitted depends on whether or not the base station 304 is in communication with a user station 302 requiring such exchanges at the particular time.
  • each time frame 1140 between the particular user station 302 and the base station 304.
  • the base station 304 first sends a 123-preamble in a 123-preamble interval 1109 of the time slot 1141 two slots 1141 prior to which the base station 304 intends to transmit to the user station 302.
  • the user station 302 responds by sending a control pulse preamble, which is
  • the base station 304 transmits to the user station 304 a base-to-user message during the base message interval 1103 on the base station frequency band 1170.
  • the user station 304 responds with a user-to-base message, which is received at the base station 304 during the user message interval 1113.
  • the base station 304 is not in established communication with any user station 302 during the fourth time slot TS4" over the base station frequency band 1170.
  • the base station 304 may indicate that a particular time slot 1141, such as time slot TS4", is available for communication by, for example, transmitting a general polling message during the base message interval 1103 of the time slot TS4".
  • the new user station 302 may send a general polling response message during a user message interval 1113 of the following time slot TS5" (not shown).
  • the base station 304 may determine the range of the user station 302 and thereby determine a required timing adjustment for subsequent
  • the base station 304 may thereafter issue periodic timing adjustment commands to maintain receipt of user-to-base transmissions at the start of each user timing interval.
  • the base station 304 may monitor the distance of the user station 302 by looking to the time of receiving either the control pulse preamble or the user-to- base message from a user station 302.
  • the guard times 1114 and 1118 are preferably kept to a minimum.
  • the guard times 1114, 1118 will not be of sufficient duration to allow a full ranging transaction to occur.
  • a ranging transaction may result in interference between the
  • Proper timing is preferably set upon initial
  • a full round-trip guard time need not be included in each time slot 1141 because the user stations 302 and base station 304 transmit on different frequency bands, preventing interference between base-to-user messages and user-to-base messages.
  • Figs. 11A-B assumes that the user stations 302 are at zero distance from the base station 304, and therefore the user-to-base message appears immediately after the preamble interval 1112 or 1122. However, if the user station 302 is not immediately adjacent to the base station 304, then part of guard time 1114 shown in Fig. IIA will be consumed in the propagation of the preamble and user-to-base message to the base station 304. Thus, if the user station 302 is at the cell periphery, then the user- to-base message will appear at the base station 304 after the elapsing of a time period equal at most to the duration of guard time 1114.
  • timing adjustment commands are preferably transmitted from the base station 304 periodically so as to keep the user preambles and user-to-base messages arriving at the base station 304 as close to the start of the user timing sub-element 1110 as possible, without interfering with the transmissions of the previous use station 302.
  • the portion of a time slot 1141 on the user station frequency band 1171 may comprise a range timing sub- element 1121, as described previously with respect to Fig. 11A, during which a ranging transaction is carried out between the base station 304 and a new user station 302.
  • the user station 302 transmits a preamble during a ranging
  • the preamble interval 1122 of time slot 1141 transmits a ranging message during the user ranging message interval 1123 of time slot 1141.
  • the user station 302 delays transmitting the preamble and ranging message for an amount of time ⁇ T.
  • the delay time ⁇ T may be communicated by the base station 304 as part of the general polling message, or may be a preprogrammed system parameter.
  • the base station 304 determines the propagation delay from the user station 302 to the base station 304 by measuring the round trip propagation delay from the end of the previous time slot 1141 to the time of actual receipt of the responsive preamble and ranging message from the user station 302, taking into account the delay time ⁇ T.
  • the ranging guard band 1124 is preferably of sufficient length to allow the ranging transaction between the base station 304 and the user station 302 to occur.
  • the length of the ranging guard band 1124 is determined in part by the radius of the cell 303 in which the base station 304 is located, or may be determined in part by the maximum cell radius of the cellular system.
  • the base station 304 may issue a timing adjustment command to the user station 302 in the next time frame 1140 instructing the user station 302 to advance or retard its timing by a
  • the timing adjustment command may be set equal to the round-trip propagation time as determined by the base station 304 during the ranging transaction.
  • the timing adjustment command is selected so as to cause the user transmission from the user station 302 to the base station 304 in the subsequent time frame 1140 to be received by the base station 304
  • the ranging message may also contain other information to assist the base station 304 in handshaking with the user station 302.
  • the ranging message may contain as data a user identifier for the user station 302 seeking to establish communication.
  • the ranging message may also indicate a preferred spread spectrum code to be used by the base station 304 and the particular user station 302 in subsequent
  • time frames 1140 after establishing communication with user station M3 in the manner described above, communication may be carried out between the base station 304 and the user station M3 in an interleaved fashion over several time slots 1140. As part of each transmission from the base station 304, the base station 304 may update the timing adjustment command to the user station M3.
  • the base station 304 may begin to transmit a general polling message during the newly opened time slot 1141, indicating that the time slot 1141 is free for communication. New user stations 302 may thereby establish communication with the same base station 304.
  • a simple means to adapt an FDD/TDMA system such as shown in Fig. 11B to emulate a TDD system is to alternately black out time slots on each of the two frequency bands 1170 and 1171.
  • the base station 304 transmits to a user station M 1 over frequency band 1170, while no transmission is conducted over frequency band 1171.
  • the user station M1 responds over frequency band 1171, while no transmission is conducted over frequency band 1170.
  • the next two time slots TS3" and TS4" are used for duplex communication between the base station 304 and the next user station M 2 , with the user slot in TS3" and the base slot in TS4" being dormant.
  • the described frame structure generally supports fewer user stations 302 than the frame structure shown in Fig. 11B due to the dormancy of alternating time slots on each frequency band 1170 and 1171, but allows a TDD interface such as shown in Fig. 10B to be emulated with minimal modification to the base and user stations (e.g., by transmitting and receiving on different frequency bands). If both frequency bands 1170 and 1171 are selected to be the same, then the system will be true TDD, thus allowing the same hardware to be capable of either
  • FDD/TDMA or TDD operation simply by appropriate selection of the frequency bands and appropriate selection of the time slots (i.e., by selecting in an alternating manner) on the forward and reverse links during which to transmit.
  • Figure 11C is a timing diagram for an offset interleaved FDD/TDMA frame structure using the timing sub-elements
  • Fig. 11A depicted in Fig. 11A, as shown from the perspective of the base station 304.
  • the offset interleaved FDD/TDMA frame structure of Fig. 11C permits larger cells by allowing time for user stations 302 to receive base station transmissions intended for them before having to reply, and may prevent the need for a costly diplexer in the user station 302.
  • Figure 11C is a frame structure for a system using two frequency bands for communication in addition to certain aspects of time division multiple access.
  • a first frequency band 1172 also referred to as a base station frequency band, is used primarily for communication from a base station 304 to user stations 302.
  • a second frequency band 1173 also referred to as a base station frequency band
  • a user station frequency band referred to as a user station frequency band
  • the two frequency bands 1172, 1173 are preferably located 80 MHz apart.
  • a time frame 1150 comprises a plurality of time slots 1151.
  • time slots are designated in sequential order as OTS1, OTS2, OTS3, and so on.
  • Each time slot 1151 comprises a base timing sub-element 1101 on the base station frequency band 1170, and either a user datalink timing sub-element 1110 or a range timing sub-element 1121 on the user station frequency band 1171.
  • the time slots 1151 are shown from the perspective of the base station 304, so that the base timing sub-elements 1101 and the user timing sub-elements 1110, 1121 appear staggered in Fig. 11C by a predetermined offset time 1160.
  • the frame structure of Fig. 11C supports both range timing sub-elements 1121 and user datalink timing sub-elements 1110 on the user station frequency band 1171.
  • the base station 304 transmits, as part of the base timing sub-element 1101 of each time slot 1151, in sequence to user stations 302 with which the base station 304 has established communication.
  • the base station 304 transmits a preamble during the preamble interval 1102 and a base-to-user message during the base message interval 1103.
  • the base station 304 transmits three short preamble bursts in the 123 -preamble burst interval 1109 directed to a different user station 302.
  • the three preamble bursts in the 123 -preamble burst interval 1109 are directed to the user station 302 to which the base station 304 will be sending a main data message two time slots 1151 later.
  • the three short preamble bursts sent in the 123-preamble burst interval 1109 may be used for forward link diversity sensing and forward link power control purposes.
  • Each of these three preamble bursts may be transmitted on a different antenna to allow receiving user stations 302 an opportunity to make a diversity selection for an upcoming forward link data message in a subsequent time slot 1151.
  • the base fill code interval 1107 Following the 123-preamble burst interval 1109 is the base fill code interval 1107, during which the base station 304 transmits a fill code. Following the base code fill interval 1107 is the transmit/receive switch interval 1104, during which the base station 304 may switch from a transmit mode to a receive mode. Preferably, however, the base station 304 has separate transmit and receive hardware, and therefore does not need to switch modes. Instead, the base station 304 may continue to transmit a fill code during the
  • the base station transmits a base-to-user message in the base message interval 1103 directed to a first user station M1.
  • the base station 304 then transmits a 123 -preamble burst during the 123 -preamble burst interval 1109, directed to another user station M3.
  • the base station 304 Simultaneous with the base station transmissions, but offset therefrom by an offset time 1160, the base station 304 receives, on the user station frequency band 1173, a preamble during the datalink preamble interval 1112 and a user-to-base message during the user message interval 1113 from the last user station MN with which the base station 304 is in communication.
  • the base station 304 receives a control pulse preamble from the user station M2 to which the base station 304 is to transmit in the following time slot OTS2.
  • control pulse preamble sent during the control pulse preamble interval 1116 are similar to those described earlier with respect to the control pulse preamble of Figs. 10A-E and 11B (e.g., power control, antenna
  • an antenna adjustment interval 1117 Following the preamble interval 1116 is an antenna adjustment interval 1117, during which the base station 304 has an opportunity to adjust its transmission antenna, if necessary, so as to direct it towards the second user station M2 based upon information acquired from receipt of the control pulse preamble. Following the antenna
  • adjustment interval 1117 is another guard band 1118, to allow for propagation of the control pulse preamble to the base station 304. After the preamble interval is another
  • the base station 304 transmits, using the base station frequency band 1172, a preamble during the base preamble interval 1102 and a base-to-user message during the base message interval 1103, both directed to the second user station M2.
  • the base station 304 thereby rapidly responds to the control pulse preamble sent by the user station M2. It is assumed, however, in the exemplary time frame 1150 of Fig.
  • the base station 304 does not transmit a 123-preamble burst directed to a user station 302.
  • the base station 304 Simultaneous with the base station transmissions in the second time slot OTS2 but offset therefrom by an offset time 1160, the base station 304 receives, on the user station frequency band 1173, a preamble during the datalink preamble interval 1112 and a user-to-base message during the user message interval 1113 from the user station Ml with which the base station 304 communicated in the first time slot OTSl.
  • the base station 304 receives, on the user station frequency band 1173, a preamble during the datalink preamble interval 1112 and a user-to-base message during the user message interval 1113 from the user station Ml with which the base station 304 communicated in the first time slot OTSl.
  • the base station 304 receives, on the user station frequency band 1173, a preamble during the datalink preamble interval 1112 and a user-to-base message during the user message interval 1113 from the user station Ml with which the base station 304 communicated in the first time slot OTS
  • the base station 304 In the third time slot OTS3 , the base station 304
  • a base message interval 1103 Following the base message interval 1103 is a 123-preamble burst interval 1109 during which the base station 304 transmits three short preamble bursts (i.e., the 123-preamble burst) directed to a different user station M5, with which the base station 304 will communicate two slots 1151 later.
  • the base station 304 Simultaneous with the base station transmissions but offset therefrom by an offset time 1160, the base station 304 receives, on the user station frequency band 1173, a preamble during the datalink preamble interval 1112 and a user-to-base message during the user message interval 1113 from the user station M2 with which the base station 304 communicated in the previous time slot 0TS2. Because the base station 304 is not in established communication with any user station 302 during the fourth time slot 0TS4 over the base station frequency band 1172, the base station 304 does not receive a control pulse preamble during the control pulse preamble interval 1116 of the third time slot 0TS3 on the user station frequency band 1173.
  • a similar exchange is carried out in the fourth time slot OTS4, and in subsequent time slots 1151 as well. Whether or not particular user-to-base message, base-to-user messages, and preambles or control pulse preambles are transmitted depends on whether or not the base station 304 is in
  • each time frame 1150 between the particular user station 302 and the base station 304 communicating during a single time slot 1151.
  • the base station 304 first sends a 123-preamble in a 123-preamble interval 1109 of the time slot 1151 two slots 1151 prior to which the base station 304 intends to transmit to the user station 302.
  • the user station 302 responds by sending a control pulse preamble, which is received at the base station 304 during the control pulse preamble interval 1116.
  • the base station 304 transmits to the user station 304 a base-to-user message during the base message interval 1103 on the base station frequency band 1172
  • the user station 304 responds with a user-to-base message, which is received at the base station 304 during the user message interval 1113.
  • the base station 304 may indicate that a particular time slot 1151, such as time slot OTS4 , is available for communication by, for example, transmitting a general polling message during the base message interval 1103 of the time slot OTS4.
  • the new user station 302 may send a general polling response message during a user message interval 1113 of the following time slot OTS5.
  • the base station 304 may determine the range of the user station 302 and thereby determine a required timing adjustment for subsequent transmissions by the user station 302.
  • guard times 1114 and 1118 are preferably kept to a minimum.
  • Proper timing is preferably set upon initial
  • a full round-trip guard time need not be included in each time slot 1151 because the user stations 302 and base station 304 transmit on different frequency bands, preventing interference between base-to-user messages and user-to-base messages.
  • Fig. 11C The depiction of the frame structure in Fig. 11C (i.e., the exploded time slots 1151) assumes that the user stations 302 are at zero distance from the base station 304. However, if the user station 302 is not immediately adjacent to the base station 304, then part of guard time 1114 (as shown in Fig. 11A) will be consumed in the propagation of the preamble and user-to-base message to the base station 304. Thus, if the user station 302 is at the cell periphery, then the user- to-base message will appear at the base station 304 after the elapsing of a time period equal at most to the duration of guard time 1114.
  • timing adjustment commands are preferably transmitted from the base station 304 periodically so as to keep the user preambles and user-to-base messages arriving at the base station 304 as close to the start of the user timing sub-element 1110 as possible, without interfering with the transmissions of the previous use station 302.
  • the time slot 1151 on the user station frequency band 1173 during which the ranging transaction is initiated preferably comprises a range timing sub-element 1121, as described previously with respect to Fig. 11A.
  • the user station 302 transmits a preamble during a ranging preamble interval 1122 of time slot 1151, and
  • the user station 302 delays transmitting the preamble and ranging message for an amount of time ⁇ T.
  • the delay time ⁇ T may be communicated by the base station 304 as part of the general polling message, or may be a pre-programmed system parameter.
  • the base station 304 determines the propagation delay from the user station 302 to the base station 304 by measuring the round trip propagation delay from the end of the previous time slot 1151 to the time of actual receipt of the responsive preamble and ranging message from the user station 302, taking into account the delay time ⁇ T.
  • the ranging guard band 1124 should be of sufficient length to allow the ranging transaction between the base station 304 and the user station 302 to occur.
  • the length of the ranging guard band 1124 is determined in part by the radius of the cell 303 in which the base station 304 is located, or may be determined in part by the maximum cell radius of the cellular system.
  • the base station 304 may issue a timing adjustment command to the user station 302 in the next time frame 1150 instructing the user station 302 to advance or retard its timing by a
  • the timing adjustment command may be set equal to the round-trip propagation time as determined by the base station 304 during the ranging transaction.
  • the timing adjustment command is selected so as to cause the user transmission from the user station 302 to the base station 304 in the subsequent time frame 1150 to be received by the base station 304
  • the ranging message may also contain other information to assist the base station 304 in handshaking with the user station 302.
  • the ranging message may contain as data a user identifier for the user station 302 seeking to establish communication.
  • the ranging message may also indicate a preferred spread spectrum code to be used by the base station 304 and the particular user station 302 in subsequent
  • a diplexer a device which allows simultaneous transmission and reception of signals, is generally not necessary in the user station 302.
  • a diplexer may be necessary to support a high density of users, particularly in a large cell environment, because a user station 302 may need to transmit in a time slot 1141 prior to receiving the entire base-to-user message intended for it sent in the previous time slot 1141.
  • Fig. HB is constructed from a perspective of the base station 304, the time slots 1141 appear lined up to the base station 304, but the user station 302 is required to send its
  • Fig. HB information in advance of the user portion of the time slot 1141 in order for the information to arrive at the base station 304 lined up as shown in Fig. HB.
  • the user station 302 may be required to send its information prior to receiving the entire base-to-user message. In order to do so, the user station 302 may require the capability to transmit and receive information simultaneously, and may thus require a diplexer. In a protocol requiring that the user station 302 receive the base message before responding, the Fig. HB system may thus not be suitable in a very large cell
  • time slots 1151 on the user frequency band 1173 are offset from those on the base
  • the offset time 1160 allows the base-to-user message to propagate to the user station 302 prior to transmission of the user-to-base message by the user station 302.
  • the user station 302 therefore does not need a diplexer, which can be a relatively expensive component. Operation without a diplexer is particularly beneficial where the user station 302 is embodied as a mobile handset, because it is often important to keep manufacturing costs of the handset as low as possible. Other hardware efficiency may also be achieved by not requiring simultaneous transmission and reception; for example, the user station 302 could use the same frequency synthesizer for both transmitting and receiving functions.
  • Figure 11D shows a subsequent time frame 1150 after a ranging transaction has been completed with the third user station M3.
  • the transactions between the user stations M1, MN and the base station 304 occurring in the first time slot OTS1 are the same as for Fig. 11C.
  • the transactions between the user stations M1, M2 and the base station 304 occurring in the second time slot OTS2 are the same as for Fig. 11C.
  • the third user station M3 may transmit a control pulse preamble during the preamble interval 1116 of the second time slot 0TS2.
  • the user station M3 may wait until the base station 304 acknowledges its ranging message sent in the prior time frame 1150 before transmitting a control pulse preamble during the preamble interval 1116 of each preceding time slot 0TS2.
  • time frames 1150 after establishing communication with the third user station M3 in the manner described above, communication may be carried out between the base station 304 and the user station M3 as shown in Fig. 11D. As part of each transmission from the base station 304, the base station 304 may update the timing adjustment command to the user station M3.
  • the base station 304 may begin to transmit a general polling message during the newly opened time slot 1151, indicating that the time slot 1151 is free for communication. New user stations 302 may thereby establish communication with the same base station 304.
  • Figures 12A-C are tables showing preferred message formats for base station and user station transmissions.
  • Tables 12B-1 through 12B-3 show message formats for
  • Tables 12C-1 through 12C-4 show message formats (both
  • Table 12A-1 shows a header format for a base polling transmission (general or specific) as described earlier.
  • the header format of Table 12A-1 comprises 21 bits.
  • the particular header format comprises 10 fields totalling 19 bits, leaving two spare bits.
  • the fields include a B/H field of 1 bit identifying whether the transmission source is a base station or a user station; an E field of 1 bit which may be used as an extension of the B/H field; a G/S field of 1 bit indicating whether the polling message is general or specific; a P/N field of 1 bit indicating whether the transmission is in a polling or traffic message; an SA field of 1 bit used for identification checking and verification; a PWR field of 3 bits used for power control; a CU field of 2 bits indicating slot utilization; an opposite link quality field of 2 bits indicating how well the sending unit is receiving the opposite sense link; a timing adjustment command of 3 bits providing a command to the user station to adjust its timing if necessary; and a header FCW (frame check word) field of 4 bits
  • a header format for a base traffic transmission is shown in Table 12A-2.
  • the header format is the same as that of Table 12A-1, except that an additional B/W grant field of 2 bits for the allocation of addition bandwidth to the user station 302 through time slot aggregation or asymmetric time slot use.
  • the header format of Table 12A-2 utilizes 21 bits.
  • a header format for a mobile or user polling transmission is shown in Table 12A-3.
  • the header format is similar to that of Table 12A-1, except that it does not include a CU field or a timing command field.
  • the header format of Table 12A- 3 includes a B/W request field of 1 bit for a request of additional bandwidth or time slots.
  • the Table 12A-3 header format includes 6 spare bits.
  • Table 12A-4 A header format for a mobile or user traffic transmission is shown in Table 12A-4.
  • the header format of Table 12A-4 is the same as that of Table 12A-3, except that the B/W request field is designated in place of a B/W grant field.
  • the header formats for user stations 302 and base stations 304 are selected to be the same length in the
  • Tables 12B-1 through 12B-3 show message formats for transmissions used in handshaking or an acquisition mode.
  • Table 12B-1 shows a message format of 205 bits for a base general polling transmission.
  • the message format of Table 12B-1 includes a header field of 21 bits, which comprises fields shown in Table 12A-1; a base ID field of 32 bits for identifying the base station 304 transmitting the general polling message; various network and system identification fields, such as a service provider field of 16 bits which may be used to indicate, e.g., a telephone network or other communication source, a zone field of 16 bits which may be used to identify, e.g., a paging cluster, and a facility field of 32 bits; a slot number field of 6 bits indicating the slot number of the associated general polling transmission so as to assist the user station 302 in synchronization; and a frame FCW field of 16 bits for error correction and transmission integrity verification.
  • a message format of 150 bits for a mobile or user station response transmission is shown in Table 12B-3.
  • the message format of Table 12B-3 includes a header field of 21 bits, which comprises fields shown in Table 12A-3; a PID field of 40 bits for identifying the user station 302 responding to the general polling message; a service provider field of 16 bits; a service request field of 16 bits indicating which of a variety of available services from the base station 304 is being sought; a mobile capability field of 8 bits; and a frame FCW field of 16 bits.
  • the mobile capability field comprises two sub-fields, a type or capability sub-field of 2 bits indicating the user station's capability (e.g., diplexer, interleaving of traffic slots) , and a home base slot number field of 6 bits for echoing the slot number received from the slot number field of the base general polling transmission.
  • the user station polling response transmission, at 150 bits, is substantially shorter than a base station polling
  • a message format of 205 bits for a base station specific polling transmission is shown in Table 12B-2.
  • the message format of Table 12B-2 includes a header field of 21 bits, which comprises fields shown in Table 12A-1; a correlative ID field of 8 bits indicating the relative slot location; a result field of 8 bits; a PID field of 40 bits for echoing the identification number received from the user station 302; a map type field of 8 bits for indicating, e.g., the number of time slots for the particular base station 304; a map field of 32 bits, indicating which slots are in use (which the user station 302 may evaluate in gauging potential slot
  • Tables 12C-1 through 12C-4 show message formats (both symmetric and asymmetric) after acquisition when in traffic mode.
  • Tables 12A-1 and 12A-2 are base station traffic mode message formats; the message format of Table 12A-1 is used for a symmetric frame structure, and the format of Table 12A-2 is used for an asymmetric frame structure.
  • Tables 12A-3 and 12A-4 are mobile or user station traffic mode message formats; the message format of Table 12A-3 is used for a symmetric frame structure, and the format of Table 12A-4 is used for an asymmetric frame structure.
  • each of the traffic mode messages is 205 bits in length.
  • Each of the traffic mode message comprises a D-channel field (or data field) of 8 bits in length for slow data rate messaging capability, and a B- channel field (or bearer field) of 160 or 176 bits in length, depending on whether or not a frame FCW field of 16 bits is used.
  • the traffic mode message from one source is a different length, usually much longer, than the traffic mode message from the other source.
  • one of the traffic mode messages is 45 bits in length, while the other traffic mode messages is 365 bits in length.
  • the total length for a forward and reverse link message still totals 410 bits, as with the symmetric frame structure.
  • Each of the traffic mode message comprises a D-channel field (or data field) of 8 bits in length for slow data rate messaging capability, and a B-channel field (or bearer field) of either 0, 16, 320 or 336 bits in length, depending on which source has the higher transmission rate, and depending on whether or not a frame FCW field of 16 bits is used.
  • Base and user messages are preferably sent using an M-ary encoding technique.
  • the base and user messages are preferably comprised of a concatenated sequence of data symbols, wherein each data symbol represents 5 bits.
  • a spread spectrum code, or symbol code is transmitted for each data symbol.
  • a transmitted symbol code may represent a whole or a portion of a data field, or multiple data fields, or portions of more than one data field, of a base or user message.
  • concatenated preamble code structures similar to those used in MPRF modes of the APG-63 radar may be used in the various communication interfaces described herein.
  • a general description of APG-63 radar may be found in Morris, Airborne Pulsed Doppler Radar (Artech House 1988) .
  • Figures 13A-B are diagrams showing the construction of concatenated preambles.
  • a length 112 preamble code is formed by taking a kronecker product between a Barker- 4 (B4) code 1302 and a Minimum Peak Sidelobe-28 (MPS28) code 1301.
  • B4 Barker- 4
  • MPS28 Minimum Peak Sidelobe-28
  • the resultant preamble can be thought of as an MPS28 code wherein each "chip" is in actuality a B4 sequence.
  • One advantage of this preamble structure is that correlation processing can be accomplished using a 4-tap B4 matched filter 1310 followed by a 28 non-zero tap MPS28 ®
  • matched filter 1311 As shown in Fig. 13B.
  • the technique of Figs. 13A-B is roughly the equivalent of a 32-tap matched filter, except with a higher memory requirement.
  • Performance can be enhanced by embodying the first stage filter 1310 as a mismatched filter instead of a matched filter, thereby reducing sidelobes in the filter response.
  • Figures 13D and 13E are graphs comparing the filter response for concatenated preambles using matched filters and mismatched filters, respectively.
  • a length 140 preamble is assumed.
  • the preamble comprises a kronecker product between a Barker-5 (B5) code and an MPS28 code.
  • Figure 13D shows a composite filter response for the MPS28 ® B5, length 140 preamble processed by a 5-tap B5 matched filter 1310 followed by a 28-tap MPS28 matched filter 1311.
  • Four sidelobe spikes 1320 of about -14 dB are apparent in the graph of Fig. 13D.
  • Figure 13E shows a
  • N detectors can be used for detection alert purposes while the full length preamble is used for detection confirmation and channel sensing/equalization purposes.
  • Code sets may be created having preambles using different MPS28 codes exhibiting low cross-correlation.
  • a potential limitation with this approach is that there are only two MPS28 codewords.
  • "near" MPS28 codewords may be included so as to enlarge the potential available preambles exhibiting favorable cross-correlation characteristics.
  • the two MPS28 codewords have peak temporal sidelobe levels of - 22.9 dB, while the near MPS28 codewords have peak temporal sidelobe levels of -19.4 dB.
  • Preamble processing may further be augmented by taking advantage of the control pulse preamble (e.g., in preamble interval 1016) and 123-preamble message transmissions
  • control pulse preamble and 123 -preamble transmissions
  • preamble transmissions e.g., in preamble intervals 1002 or 1102
  • preamble intervals 1002 or 1102 the initial preamble transmissions preceding each main user or base transmission
  • Preamble length is effectively doubled by processing both the control pulse preamble or 123-preamble, and the preambles preceding the main user or base transmission.
  • Figures 14-17 are charts comparing various performance aspects of selected high tier and low tier air interfaces incorporating designated features of the embodiments described herein.
  • high tier is generally meant system coverage over a wide area and hence low capacity.
  • low tier is generally applied to communication services for localized high capacity and/or specialized needs.
  • users are assigned to the lowest tier possible to preserve capacity in higher tiers.
  • high tier applications are characterized by relatively large cells to provide umbrella coverage and connectivity, wherein users tend to have high measured
  • High tier operations may also be characterized by high transmit power at the base station, high gain receive antennas, and high
  • phase center separation as applied to multipath and antenna diversity can be quite important.
  • increased antenna complexity and aperture size may weigh against the use of large numbers of diversity antennas in high tier applications.
  • Receiver sensitivity may also be an important limiting factor.
  • bandwidths make spread spectrum waveforms favored in high tier applications.
  • Either spread spectrum or narrowband signals may be used, and narrowband signals may be used.
  • Dynamic channel assignment algorithms are favored to provide rapid response to changing traffic requirements and to permit relatively small reuse patterns by taking advantage of physical obstructions.
  • Low tier applications may include, for example, wireless local loop, spot coverage for "holes" in high tier coverage, localized high capacity, and wireless Centrex.
  • High tier and low tier designations may be applied to operations in either the licensed or unlicensed frequency bands.
  • FCC rules essentially require a TDD or TDMA/FDD hybrid because of the narrow available frequency range, with a maximum signal bandwidth of 1.25 MHz. "Listen before talk" capability is commonly required in order to sense and avoid the
  • inventions in the isochronous band are typically of the low tier variety, and include wireless PBX, smart badges (e.g., position determining devices and passive RF radiating
  • Dynamic channel allocation and low tier structure is preferred due to the FCC requirements. Further, power limitations generally preclude large cells.
  • ISM Industrial Scientific Medical
  • applications are similar to the unlicensed isochronous band, except that the federal regulations are somewhat less restrictive.
  • Spread spectrum techniques are preferred to minimize transmission power (e.g., to 1 watt or less), with a minimum of 10 dB processing gain typically required.
  • a TDD or TDMA/FDD hybrid structure is preferred due to the small frequency range of the ISM band.
  • Figure 14 is a summary chart comparing various air interfaces, generally grouped by high tier and low tier designations.
  • the first column of Fig. 14 identifies the air interface type.
  • the air interface type is identified by the chipping rate, tier, and frame structure -- either TDD (single frequency band with time division) or FDD/TDMA (multiple frequency bands with time division), such as described earlier with respect to Figs. 10A-E and 11A-D.
  • the identifier "5.00HT" appearing in the first row of the first column of the chart of Fig. 14 identifies the air interface as having a chipping rate of 5.00 Megachips (Mcp), being high tier, and having a TDD structure.
  • the identifier "0.64LF" appearing in the sixth row of column one identifies the air interface as having a chipping rate of 0.64 Mcp, being low tier, and having an FDD/TDMA structure.
  • a total of 16 different air interfaces (10 high tier, 6 low tier) are summarized in Fig. 14.
  • the second column of the chart of Fig. 14 identifies the duplex method, which is also indicated, as described above, by the last initial of the air interface type.
  • the third column of the chart of Fig. 14 identifies the number of time slots for each particular air interface type. For the particular described embodiments, time slots range from 8 to 32.
  • the fourth column of the chart of Fig. 14 identifies the chipping rate (in MHz) for each particular air interface type.
  • the fifth column of the Fig. 14 chart indicates the number of channels in each allocation, which is an approximation of the number of supportable RF channels given a particular bandwidth allocation (e.g., 30 MHz), and may vary according to a chosen modulation technique and the chipping rate.
  • the sixth column of the Fig. 14 chart indicates the sensitivity (in dBm) measured at the antenna post.
  • the seventh and eighth columns of the Fig. 14 chart indicate the number of base stations required in different propagation environments, with 100% being a reference set with respect to the 5.00HT air
  • the propagation environments considered in the Fig. 14 chart include R 2 (open area), R 4 (urban), and R 7 (low antenna urban), as listed.
  • the air interface types in Fig. 14 are also broken into four general categories, including high tier, low tier, unlicensed isochronous, and ISM air interface types.
  • High tier operation assumes antenna diversity (L ant ) using two antennas, a number of resolvable multipaths (L rake ) of two, and a 30 MHz bandwidth allocation.
  • the number of resolvable multipaths is generally a function of receiver capability, delay spread and antenna placement.
  • Low tier operation assumes antenna diversity using three antennas, a single resolvable communication path, and a 30 MHz bandwidth
  • Unlicensed isochronous operation assumes antenna diversity using three antennas, a single resolvable
  • ISM operation assumes antenna diversity using three antennas, a single resolvable communication path, and an 83.5 MHz
  • Figure 15 compares the digital range limits (in miles) for the air interfaces described in Fig. 14.
  • Digital range depends in part upon the number of time slots employed and whether ranging (i.e., timing adjustment control) is used.
  • the multiple columns under the heading "Ranging Used” indicate whether or not timing control is implemented in the system, and correspond in the same order to the multiple columns under the "Time Slots” heading, which indicates the number of time slots used.
  • the multiple columns under the "Digital Range” heading correspond in the same order to the columns under the "Ranging Used” and the "Time Slots” headings.
  • a first embodiment uses 32 time slots and ranging (timing adjustment), leading to a digital range of 8.47 miles.
  • a second embodiment uses 32 time slots and no ranging, leading to a digital range of 1.91 miles.
  • a third embodiment uses 25 time slots and no ranging, leading to a digital range of 10.06 miles.
  • digital range may be increased either by reducing the number of time slots used, increasing the chipping rate, utilizing multiple frequency bands (i.e., using FDD and TDD techniques), or using ranging (timing adjustment).
  • Figure 16 is a chart describing the impact of various air interface structures on base-user initial handshaking
  • the ability to support ranging transactions may also impact slot aggregation potential. This impact may be
  • the user station 302 is outfitted with a diplexer, allowing the user station 302 to transmit and receive signals simultaneously.
  • specifications in more detail.
  • specifications are provided for the air interfaces designated as 5.00 HT, 2.80 HF, 1.60 HF, 1.40 HF, 0.64 LF, 0.56 LF, and 0.35 LF in various configurations.
  • Figure 13C is a chart comparing preamble detection performance in high tier and low tier environments for a number of different air interfaces previously described.
  • Shorter preambles may suffice for selected non-spread low tier and unlicensed isochronous environments, particularly where larger average N reuse patterns are employed.
  • the Fig. 13C chart tabulates preamble detection
  • preamble detection it is desirable to have at least a 99.9% detection probability to ensure reliable communications and to prevent the preamble from becoming a link performance limiting factor.
  • Antenna probe detections are not required to be as reliable because they are used only in diversity processing, so a failure to detect an antenna probe signal merely leads to a power increase command for the forward link.
  • Fig. 13C chart is an exemplary preamble codeword length in the second column thereof, and an exemplary antenna probe codeword length (for each of three antenna probe signals in three- antenna diversity) in the fourth main column thereof.
  • Codeword length is given in chips.
  • the third main column and the fifth main column of the Fig. 13C chart compare detection performance for a 99.9% detection threshold and a 90%
  • Fig. 13C chart shows that raising detection thresholds to reject cross-correlation sidelobes from other transmitters also leads to degraded preamble detection performance. A higher signal-to-noise ratio for the system may be necessary where preamble detection thresholds are raised.
  • Basic timing elements for ranging transactions and traffic mode exchanges including a provision for a control pulse preamble, are used in the definition of a suitable frame structure.
  • the basic timing elements differ slightly for TDD and FDD/TDMA frame structures, as described with respect to Figs. 10A and IIA.
  • the basic timing elements may be used in either a fixed or interleaved format, and either zero offset format or an offset format, as previously described.
  • the frame structures are suitable for use in high tier or low tier applications, and a single base station or user station may support more than one frame structure and more than one mode (e.g., spread spectrum or narrowband, or low or high tier).
  • a TDD structure more readily supports asymmetric data rates between forward and reverse links by shifting a percentage of the timeline allocated to each link.
  • a TDD structure allows for antenna diversity to be
  • a TDD structure also permits simpler phased array antenna designs in high-gain base station installations because separate forward and reverse link manifold structures are not needed. Further, TDD systems are more able to share frequencies with existing fixed microwave (OFS) users because fewer frequency bands are needed.
  • OFS fixed microwave
  • An FDD/TDMA structure may reduce adjacent channel
  • An FDD/TDMA system generally has 3 dB better sensitivity than a comparable TDD system, therefore potentially requiring fewer base stations and being less expensive to deploy.
  • An FDD/TDMA structure may lessen sensitivity to multipath induced
  • an FDD/TDMA system may use less power and be cheaper to manufacture since bandwidths are halved, D/A and A/D conversion rates are halved, and RF related signal processing elements operate at half the speed.
  • An FDD/TDMA system may require less frequency separation between adjacent high and low tier operations, and may allow base stations to operate without global
  • FIG. 18 is a block diagram of a particular low IF digital correlator for use in a receiver operating in
  • a received signal 1810 is provided to an analog-to-digital (A/D) converter 1811.
  • the A/D converter 1811 preferably performs one or two bit A/D conversion and operates at roughly four times the code rate or higher.
  • code rates of 1.023 MHz to 10.23 MHz result in sample rates for A/D converter 1811 in the range of 4 to 50 MHz.
  • the A/D converter 1811 outputs a digitized signal 1812, which is connected to two multipliers 1815 and 1816.
  • a carrier numerically controlled oscillator (NCO) block 1821 and a vector mapping block 1820 operate in conjunction to provide an appropriate frequency for demodulation and downconversion to a low IF frequency.
  • the vector mapping block 1820 outputs a sine signal 1813 and a cosine signal 1814 at the selected conversion frequency.
  • the sine signal 1813 is connected to multiplier 1815, and the cosine signal 1816 is connected to multiplier 1816, so as to generate an I IF signal 1830 and a Q IF signal 1831.
  • the I IF signal 1830 is connected to an I multiplier 1842, and the Q IF signal 1831 is connected to a Q multiplier 1843.
  • a code NCO block 1840 and a code mapping block 1841 operate in conjunction to provide a selected spread spectrum code 1846.
  • the selected spread spectrum code 1846 is coupled to both the I multiplier 1842 and the Q multiplier 1843.
  • the output of the I multiplier 1842 is connected to an I summer
  • the I summer 1844 outputs an I correlation signal 1850
  • the Q summer 1845 outputs a Q correlation signal 1851.
  • a zero IF digital correlator may be used instead of a low IF digital correlator.
  • a zero IF digital correlator performs I and Q separation prior to A/D
  • the A/D converters for the zero IF correlator may operate at the code rate, instead of at four times the code rate as is done by A/D converter 1811.
  • Figure 19A is a block diagram of an exemplary dual-mode base station capable of operating over multiple frequencies and having both spread spectrum and narrowband communication capabilities.
  • the base station block diagram of Fig. 19A includes a frequency plan architecture for use with a low IF digital transceiver ASIC 1920.
  • the base station may employ an FDD technique wherein the user stations 302 transmit at the lower duplex frequency, and the base station 304 transmits at the higher duplex frequency.
  • the base station of Fig. 19A preferably uses a direct synthesis digital CPM modulator, such as described, for example, in Kopta, "New Universal All
  • the Fig. 19A dual-mode base station comprises an antenna 1901, preferably capable of operating at a 2 GHz frequency range.
  • the antenna 1901 is connected to a diplexer 1910, which allows the base station to simultaneously transmit and receive signals through the antenna 1901.
  • the transmitted and received signals are translated to appropriate frequencies generated by multiplying or dividing a master clock frequency output from a master oscillator 1921.
  • the master oscillator 1921 generates a master frequency (e.g., 22.4 MHz) which is provided to a clock divider circuit 1922 for dividing the master frequency by a predefined factor, e.g., 28.
  • the master oscillator 1921 is also connected to another clock divider circuit 1926 which divides the master frequency by a
  • clock divider circuit 1926 may be further divided down by another clock divider 1927 which divides by a programmable parameter M2, in order to support a second mode of operation over a different physical layer, if desired.
  • Signals to be transmitted are provided by ASIC 1920 to a digital-to-analog (D/A) converter 1933, which is clocked by a signal from clock divider circuit 1926.
  • the output of the D/A converter 1933 is connected to a low pass filter 1934 to provide smoothing of the signal envelope.
  • the low pass filter 1934 is connected to a multiplier 1936.
  • An output from the clock divider circuit 1922 is connected to a frequency
  • multiplier circuit 1935 which multiplies its input by a conversion factor, such as 462.
  • the frequency multiplier circuit 1935 is connected to a multiplier 1936, which
  • the IF transmission signal 1941 is connected to a spread spectrum bandpass filter 1937 and a narrowband bandpass filter 1938.
  • the spread spectrum bandpass filter 1937 is a wideband filter, while the narrowband bandpass filter 1938 operates over a relatively narrow bandwidth.
  • the bandpass filters 1937 and 1938 filter out, among other things, CPM modulator spurs from the transmitter.
  • a multiplexer 1939 selects between an output from the spread spectrum bandpass filter 1937 and an output from the narrowband bandpass filter 1938, depending upon the mode of operation of the base
  • Multiplexer 1939 is connected to a multiplier 1931.
  • the clock divider circuit 1922 is connected to another clock divider circuit 1923, which divides its input by a factor, e.g., of 4.
  • the output of the clock divider circuit 1923 is connected to a frequency multiplier circuit 1930, which multiplies its input by a factor of (N + 400), where N defines the frequency of the receiving channel, as further described herein.
  • the frequency multiplier circuit 1930 is connected to the multiplier 1931, which multiplies its inputs to generate an output signal 1942.
  • the output signal 1942 is connected to the diplexer 1910, which allows transmission of the output signal 1942 over the antenna 1901. Signals received over the antenna 1901 pass through the diplexer 1910 and are provided to a multiplier 1951.
  • Clock divider circuit 1923 is connected to a frequency multiplier circuit 1950, which multiplies its input by a factor of, e.g., N.
  • the frequency multiplier circuit 1950 is connected to multiplier 1951, which combines its inputs and generates a first IF signal 1944.
  • the first IF signal 1944 is connected to a spread spectrum bandpass filter 1952 and a narrowband bandpass filter 1953.
  • the spread spectrum bandpass filter 1952 is a wideband filter, while the narrowband bandpass filter 1953 operates over a relatively narrow bandwidth.
  • the bandpass filters 1952 and 1953 remove image noise and act as anti-aliasing filters.
  • a multiplexer 1954 selects between an output from the spread spectrum bandpass filter 1952 and an output from the narrowband bandpass filter 1953.
  • Multiplexer 1954 is connected to a multiplier 1960.
  • An output from frequency multiplier circuit 1935 is also
  • A/D converter 1962 is clocked at a rate determined by the clock divider circuit 1926.
  • the output of the A/D converter is provided to ASIC 1920 for correlation and further processing.
  • the received signal may be processed by the low IF correlator shown in Fig. 18 and described above, in which case A/D converter 1961 may be the same as A/D converter 1811.
  • Figure 19B is a chart showing selected frequencies and other parameters for use in the dual-mode base station of Fig. 19A.
  • the Fig. 19B chart is divided according to spread spectrum and narrowband modes.
  • the first three columns relate to different transmission rates using spread spectrum
  • the frequencies in each column are given in megahertz.
  • the master oscillator frequency is designated in Fig. 19B as f0.
  • M and M2 are programmable divide ratios for clock divider circuits 1926 and 1927.
  • the sample rate in Fig. 19B applies to the A/D converter 1962 and D/A converter 1933.
  • the Fs/(IB+Fch) figure represents the sampling ratio.
  • the final IF frequency and second IF frequency are the center frequencies of the bandpass filters.
  • Towards the bottom of Fig. 19B are sample first LO and N numbers for three different input frequencies, 1850 MHz, 1850.2 MHz, and 1930 MHz.
  • the frequencies and other parameters appearing in the Fig. 19B chart may be selected by use of a microprocessor or other software controller, which may refer to the system timing information or clocks as necessary to coordinate the time of switching the selected frequencies and other
  • a user station 302 may be designed in a similar fashion to the dual-mode base station of Figs. 19A-B, except that a user station 304 may not require a diplexer 1910 in air interface structures wherein the user station 302 does not need to transmit and receive simultaneously. Also, frequency multiplier circuits 1930 and 1950 would be swapped because the user station 302 transmits and receives on the opposite frequency bands from the base station 304.
  • the invention is not limited to spread spectrum communication techniques. In some narrowband applications, no preamble would be required as code synchronization is not an issue (although synchronization within a TDD or TDMA structure would still be necessary).
  • control pulse preamble described with respect to Figs. 10A-E and 11A-D facilitates operation in some environments, these embodiments may also be implemented without the control pulse preamble.
  • the various functions carried out by the control pulse preamble e.g., power
  • control, antenna selection, and the like may be accomplished by analyzing other portions of the user transmission, or may not be necessary.
  • one or more system control channels are used so as to facilitate paging of and other transactions with user stations 302 operating within a covered region.
  • the control channel or channels provide base station or system information including traffic information at neighboring base stations to assist in handoff determinations, system identification and ownership
  • control channel or channels may also specify user station operating parameters (e.g., timer counts, or actionable thresholds for power control, handoff, and the like), provide incoming call alerting (e.g., paging), provide time frame or other
  • system resources e.g., time slots.
  • a fixed time slot may eliminate the need for periodically transmitting a general polling message from the base station in various time slots when open, and thereby eliminate possible
  • Fig. 17 A comparison of such a structure with the previous described embodiments is shown in Fig. 17. In Fig. 17,
  • the air interface type is identified in the first column as before, but with a trailing "D” indicating a user station 302 having a selection diversity antenna, and a trailing "P” indicating a user station 302 having no diversity selection antenna but employing a control pulse preamble (or "PCP").
  • digital range is improved for the alternative embodiment employing a diversity antenna, or the number of time slots may be increased.
  • user transmissions are conducted before base transmissions.
  • no control pulse preamble may be needed as the base station 304 obtains information relating to mobile power and channel quality by analyzing the user transmission.
  • transmission portion 502 of the time frame 501 may be employed.
  • systems employing error correction on the forward link i.e., the base transmission

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)
  • Time-Division Multiplex Systems (AREA)

Abstract

Système servant à réaliser des télécommunications en duplex à répartition dans le temps sur une seule bande de fréquence, ce qui permet de diminuer le dépassement du temps de protection par réglage actif de la synchronisation de la transmission à liaison inverse en fonction du temps de propagation aller-retour. En réaction à un message d'interrogation émis par la station de base, une station usager cherchant à établir une communication, émet un message de réponse. La station de base, au moyen d'un calculateur de temps de propagation (812), calcule la distance à laquelle se trouve la station usager par mesure du temps de propagation par rapport à la réception du message de réponse et en utilisant un ensemble de commande de synchronisation (806), ainsi qu'un émetteur (807), pour envoyer une instruction de réglage de synchronisation à la station usager, en lui donnant l'ordre d'avancer ou de retarder sa synchronisation. La station de base contrôle ensuite les émissions de la station usager et lui donne l'ordre périodiquement de régler sa synchronisation de façon similaire. La station usager émet un préambule de commande au départ de chaque tranche de temps, afin de permettre à la station de base d'effectuer des calculs de synchronisation aller-retour, ainsi que des réglages de la puissance ou de la sélection d'antenne de la station usager.
PCT/US1996/007905 1995-06-05 1996-05-28 Commande de reglage de synchronisation servant a realiser des telecommunications en duplex a repartition dans le temps WO1996039749A1 (fr)

Priority Applications (4)

Application Number Priority Date Filing Date Title
AU60257/96A AU6025796A (en) 1995-06-05 1996-05-28 Timing adjustment control for efficient time division duplex communication
BR9608548A BR9608548A (pt) 1995-06-05 1996-05-28 Controle de ajuste de sincronização para comunicação duplex por divisão de tempo eficiente
EP96917850A EP0873593A4 (fr) 1995-06-05 1996-05-28 Commande de reglage de synchronisation servant a realiser des telecommunications en duplex a repartition dans le temps
JP50080997A JP3455227B2 (ja) 1995-06-05 1996-05-28 無線通信の方法

Applications Claiming Priority (8)

Application Number Priority Date Filing Date Title
US08/463,220 US5689502A (en) 1995-06-05 1995-06-05 Efficient frequency division duplex communication system with interleaved format and timing adjustment control
US08/464,285 US5959980A (en) 1995-06-05 1995-06-05 Timing adjustment control for efficient time division duplex communication
US08/465,137 1995-06-05
US08/464,285 1995-06-05
US08/465,555 1995-06-05
US08/465,555 US5802046A (en) 1995-06-05 1995-06-05 Efficient time division duplex communication system with interleaved format and timing adjustment control
US08/463,220 1995-06-05
US08/465,137 US5745484A (en) 1995-06-05 1995-06-05 Efficient communication system using time division multiplexing and timing adjustment control

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Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0859495A2 (fr) * 1997-01-17 1998-08-19 Delco Electronics Corporation Réseau de données multimédia haut-débit
WO1999030523A1 (fr) * 1997-12-05 1999-06-17 Nokia Telecommunications Oy Procede d'emission dans un systeme radio reglant les moments d'emission
EP0938193A1 (fr) * 1998-02-18 1999-08-25 Sony International (Europe) GmbH Structure de l'en-tête pour des systèmes TDD
WO2000010258A1 (fr) * 1998-08-14 2000-02-24 Q-Cell Gmbh Procede et dispositif destine a un systeme de transmission radio duplex integral a acces cdma
WO2000014915A2 (fr) * 1998-09-08 2000-03-16 Siemens Aktiengesellschaft Procede de formation ou de determination d'une sequence de signaux, unite d'emission et unite de reception
WO2000067405A1 (fr) * 1999-04-29 2000-11-09 Siemens Aktiengesellschaft Procede pour former et pour determiner une sequence de synchronisation, procede de synchronisation, unite d'emission et unite de reception
WO2002049372A2 (fr) * 2000-12-13 2002-06-20 Telefonaktiebolaget Lm Ericsson (Publ) Surveillance de liaisons radio dans un reseau de telecommunications
JP2003530760A (ja) * 2000-04-06 2003-10-14 インターデイジタル テクノロジー コーポレーション タイミング前進およびタイミング偏差の同期化
EP0956654B2 (fr) † 1996-12-31 2010-08-11 Nokia Corporation Système radio et procédé de communication duplex
US7995644B2 (en) 2005-08-09 2011-08-09 Mitsubishi Electric Research Laboratories, Inc. Device, method and protocol for private UWB ranging
US8712400B2 (en) 2005-12-13 2014-04-29 Qualcomm Incorporated Range extension techniques for a wireless local area network
US9173182B2 (en) 2009-02-06 2015-10-27 Thomson Licensing Transmission method in a wireless network and corresponding reception method
US9826431B2 (en) 2012-10-18 2017-11-21 Mitsubishi Electric Corporation Weighted random selection of transmission resources based on device position
US11395296B2 (en) 2020-02-12 2022-07-19 Apple Inc. Transmission delay compensation for intra-frequency band communication

Families Citing this family (20)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
IT1313837B1 (it) * 1999-11-03 2002-09-23 Siemens Inf & Comm Networks Metodo per equalizzare i ritardi di propagazione ed ottimizzare illivello di potenza in una stazione mobile che accede ai servizi di
JP2005516469A (ja) 2002-01-22 2005-06-02 アイピーアール・ライセンシング・インコーポレーテッド 通信システムにおけるオーバーヘッドの低減
JP3644503B2 (ja) 2002-10-01 2005-04-27 日本電気株式会社 無線端末およびそのエンド間遅延制御方法とプログラム
ES2298755T3 (es) * 2003-05-16 2008-05-16 Matsushita Electric Industrial Co., Ltd. Control de acceso al medio en sistemas maestro-esclavo.
US7848754B2 (en) * 2005-01-05 2010-12-07 Sk Telecom Co., Ltd. Dual band/dual mode mobile communication terminal and control method thereof
US7769375B2 (en) * 2006-02-09 2010-08-03 Eagle River Holdings Llc System and method for communication utilizing time division duplexing
CN101039154B (zh) * 2006-03-15 2010-08-25 联芯科技有限公司 一种获取用户终端收发通道传输时间的方法
US7719994B2 (en) * 2006-04-26 2010-05-18 Honeywell International Inc. Sub-frame synchronized ranging
US20080039128A1 (en) * 2006-08-09 2008-02-14 Telefonaktiebolaget Lm Ericsson (Publ) Propagation delay based transmit power control
US8346283B2 (en) 2007-01-08 2013-01-01 Electronics And Telecommunications Research Institute Method for location determinating
WO2008103089A1 (fr) * 2007-02-22 2008-08-28 Telefonaktiebolaget Lm Ericsson (Publ) Procédé et dispositif pour réduire l'interférence dans un système d'accès cellulaire
CN101312582B (zh) * 2007-05-25 2011-09-21 中兴通讯股份有限公司 根据小区负荷动态控制业务时隙的方法
CN101335977B (zh) * 2007-06-26 2011-07-06 华为技术有限公司 正交频分复用系统中测距信号发送的方法、系统及装置
JP4386108B2 (ja) 2007-07-11 2009-12-16 日本電気株式会社 時分割多重システムおよびその送信タイミング制御方法
US9094986B2 (en) * 2008-02-07 2015-07-28 Qualcomm, Incorporated Synchronous and asynchronous interference management
US8483620B2 (en) 2008-02-07 2013-07-09 Qualcomm Incorporated Asynchronous interference management
CN103228038B (zh) * 2008-06-02 2017-02-15 富士通株式会社 定时调节方法、移动站、基站以及移动通信系统
US8385373B2 (en) * 2008-06-24 2013-02-26 Adc Telecommunications, Inc. Method and apparatus for frame detection in a communications system
US8050246B2 (en) * 2009-03-03 2011-11-01 Adc Telecommunications, Inc. Range extension for time division duplex systems
DE102017210895A1 (de) * 2017-06-28 2019-01-03 Bayerische Motoren Werke Aktiengesellschaft Verfahren, Computer-lesbares Medium, System, und Fahrzeug umfassend das System zum Validieren einer Zeitfunktion eines Masters und der Clients in einem Netzwerk eines Fahrzeugs

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4222115A (en) * 1978-03-13 1980-09-09 Purdue Research Foundation Spread spectrum apparatus for cellular mobile communication systems
US4742512A (en) * 1985-07-19 1988-05-03 Nec Corporation Multipoint communication system having polling and reservation schemes
US5109393A (en) * 1989-07-13 1992-04-28 Nec Corporation Mobile communications system insensitive to false frame sync
US5506837A (en) * 1993-02-11 1996-04-09 U.S. Philips Corporation Cellular radio communication system which is selectively convertible into a trunked radio communication system for group calls
US5528597A (en) * 1994-04-18 1996-06-18 At&T Corp. Autonomous synchronization of base stations in a digital wireless radiotelephone network

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4460992A (en) * 1982-11-04 1984-07-17 The United States Of America As Represented By The Secretary Of The Army Orthogonal CDMA system utilizing direct sequence pseudo noise codes
ATE78643T1 (de) * 1987-05-06 1992-08-15 British Telecomm Regelung von optischen systemen.
FI86236C (fi) * 1990-09-05 1992-07-27 Nokia Mobile Phones Ltd Tidsanpassningslogik foer mobiltelefon i gsm-systemet.
US5164958A (en) * 1991-05-22 1992-11-17 Cylink Corporation Spread spectrum cellular handoff method
ATE151581T1 (de) * 1992-01-31 1997-04-15 Cit Alcatel Verfahren zur bestimmung der laufzeit zwischen einer entfernten endstation und einer zentralen endstation, in einem bidirektionalen punkt-zu- mehrpunkt-übertragungssystem
US5509035A (en) * 1993-04-14 1996-04-16 Qualcomm Incorporated Mobile station operating in an analog mode and for subsequent handoff to another system
US5313489A (en) * 1993-06-25 1994-05-17 Motorola, Inc. Signal processing in communication systems

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4222115A (en) * 1978-03-13 1980-09-09 Purdue Research Foundation Spread spectrum apparatus for cellular mobile communication systems
US4742512A (en) * 1985-07-19 1988-05-03 Nec Corporation Multipoint communication system having polling and reservation schemes
US5109393A (en) * 1989-07-13 1992-04-28 Nec Corporation Mobile communications system insensitive to false frame sync
US5506837A (en) * 1993-02-11 1996-04-09 U.S. Philips Corporation Cellular radio communication system which is selectively convertible into a trunked radio communication system for group calls
US5528597A (en) * 1994-04-18 1996-06-18 At&T Corp. Autonomous synchronization of base stations in a digital wireless radiotelephone network

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See also references of EP0873593A4 *

Cited By (29)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0956654B2 (fr) † 1996-12-31 2010-08-11 Nokia Corporation Système radio et procédé de communication duplex
EP0859495A2 (fr) * 1997-01-17 1998-08-19 Delco Electronics Corporation Réseau de données multimédia haut-débit
EP0859495A3 (fr) * 1997-01-17 2004-02-04 Delphi Technologies, Inc. Réseau de données multimédia haut-débit
WO1999030523A1 (fr) * 1997-12-05 1999-06-17 Nokia Telecommunications Oy Procede d'emission dans un systeme radio reglant les moments d'emission
EP0938193A1 (fr) * 1998-02-18 1999-08-25 Sony International (Europe) GmbH Structure de l'en-tête pour des systèmes TDD
US6567383B1 (en) 1998-02-18 2003-05-20 Sony International (Europe) Gmbh Header structure for TDD systems
WO2000010258A1 (fr) * 1998-08-14 2000-02-24 Q-Cell Gmbh Procede et dispositif destine a un systeme de transmission radio duplex integral a acces cdma
AU767521B2 (en) * 1998-09-08 2003-11-13 Siemens Aktiengesellschaft Method for forming or detecting a signal sequence and transmitter unit and receiver unit
WO2000014915A2 (fr) * 1998-09-08 2000-03-16 Siemens Aktiengesellschaft Procede de formation ou de determination d'une sequence de signaux, unite d'emission et unite de reception
WO2000014915A3 (fr) * 1998-09-08 2000-06-02 Siemens Ag Procede de formation ou de determination d'une sequence de signaux, unite d'emission et unite de reception
CN100347976C (zh) * 1998-09-08 2007-11-07 西门子公司 用于将基站与移动站同步的方法
US7142584B1 (en) 1998-09-08 2006-11-28 Siemens Ag Synchronizing a bash station and a mobile station
AU777074B2 (en) * 1999-04-29 2004-09-30 Siemens Aktiengesellschaft Method for forming and determining a signal sequence, method of synchronization, transmitter unit and receiver unit
US7010071B1 (en) 1999-04-29 2006-03-07 Siemens Aktiengesellschaft Method of generating and/or detecting synchronization sequences, synchronization method, transmitter unit and receiver unit
US7062002B1 (en) 1999-04-29 2006-06-13 Siemens Aktiengesellschaft Method for synchronizing a base station with a mobile station, a base station and a mobile station
WO2000067404A1 (fr) * 1999-04-29 2000-11-09 Siemens Aktiengesellschaft Procede pour la formation et la determination d'une sequence de signaux, procede de synchronisation, unite emettrice et unite receptrice
CN100459468C (zh) * 1999-04-29 2009-02-04 西门子公司 基站与移动站同步的方法、基站和移动站
WO2000067405A1 (fr) * 1999-04-29 2000-11-09 Siemens Aktiengesellschaft Procede pour former et pour determiner une sequence de synchronisation, procede de synchronisation, unite d'emission et unite de reception
JP2003530760A (ja) * 2000-04-06 2003-10-14 インターデイジタル テクノロジー コーポレーション タイミング前進およびタイミング偏差の同期化
WO2002049372A3 (fr) * 2000-12-13 2002-11-07 Ericsson Telefon Ab L M Surveillance de liaisons radio dans un reseau de telecommunications
WO2002049372A2 (fr) * 2000-12-13 2002-06-20 Telefonaktiebolaget Lm Ericsson (Publ) Surveillance de liaisons radio dans un reseau de telecommunications
US7995644B2 (en) 2005-08-09 2011-08-09 Mitsubishi Electric Research Laboratories, Inc. Device, method and protocol for private UWB ranging
US8712400B2 (en) 2005-12-13 2014-04-29 Qualcomm Incorporated Range extension techniques for a wireless local area network
US8792877B2 (en) 2005-12-13 2014-07-29 Qualcomm Incorporated Range extension techniques for a wireless local area network
US9173182B2 (en) 2009-02-06 2015-10-27 Thomson Licensing Transmission method in a wireless network and corresponding reception method
US10117202B2 (en) 2009-02-06 2018-10-30 Thomson Licensing Method for reception in a wireless network and corresponding device for reception
US9826431B2 (en) 2012-10-18 2017-11-21 Mitsubishi Electric Corporation Weighted random selection of transmission resources based on device position
US11395296B2 (en) 2020-02-12 2022-07-19 Apple Inc. Transmission delay compensation for intra-frequency band communication
US11751182B2 (en) 2020-02-12 2023-09-05 Apple Inc. Transmission delay compensation for intra-frequency band communication

Also Published As

Publication number Publication date
IL118447A0 (en) 1996-09-12
IL118447A (en) 2000-01-31
CN1192300A (zh) 1998-09-02
EP0873593A4 (fr) 2000-03-01
BR9608548A (pt) 1999-07-06
CN1101088C (zh) 2003-02-05
EP0873593A1 (fr) 1998-10-28
CA2223321A1 (fr) 1996-12-12
AU6025796A (en) 1996-12-24
AR002311A1 (es) 1998-03-11
JP2001524268A (ja) 2001-11-27
JP3455227B2 (ja) 2003-10-14

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