Title of Invention	A WIRELESS SYSTEM FOR CALCULATING UPLINK SIGNALS TRANSMITTED FROM A PLURALITY OF REMOTE TERMINALS USING A COMMON UPLINK CHANNEL
Abstract	(57) Abstract: A wireless system comprising a network of base stations for receiving uplink signals transmitted from a plurality of remote terminals and for transmitting downlink signals to said plurality of remote terminals using a plurality of conventional channels including a plurality of antenna elements at each base station for receiving uplink signals, a plurality of antenna elements at each base station for transmitting downlink 'signals, a signal processor at each base station connected to the receiving antenna elements and to the transmitting antenna elements for determining spatial signatures and multiplexing and demultiplexing functions for each remote terminal antenna for each conventional channel, and a multiple base station network controller for optimizing network performance, whereby communication between said base stations and a plurality of remote terminals in each of the conventional channels can occur simultaneously. \| PRICE: THIRTY RUPEES

Title of Invention

A WIRELESS SYSTEM FOR CALCULATING UPLINK SIGNALS TRANSMITTED FROM A PLURALITY OF REMOTE TERMINALS USING A COMMON UPLINK CHANNEL

Abstract

(57) Abstract: A wireless system comprising a network of base stations for receiving uplink signals transmitted from a plurality of remote terminals and for transmitting downlink signals to said plurality of remote terminals using a plurality of conventional channels including a plurality of antenna elements at each base station for receiving uplink signals, a plurality of antenna elements at each base station for transmitting downlink 'signals, a signal processor at each base station connected to the receiving antenna elements and to the transmitting antenna elements for determining spatial signatures and multiplexing and demultiplexing functions for each remote terminal antenna for each conventional channel, and a multiple base station network controller for optimizing network performance, whereby communication between said base stations and a plurality of remote terminals in each of the conventional channels can occur simultaneously. | PRICE: THIRTY RUPEES

Full Text	This invention relates to a wireless system tor calculating uplink signals transmitted from a plurality of remote terminals using a common uplink channel. Wireless communication systems can be used to complement and in some instances replace conventional wired communication systems in areas where conventional wire-line systems are unavailable, unreliable or excessively expensive. Examples of such areas are : rural areas with a small number of widespread users, underdeveloped areas with little or no current infrastructure, reliability sensitive applications in areas where wired infrastructure is unreliable and political environments where monopolistic wired service providers maintain artificially high prices. Even in metropolitan areas and highly developed countries, wireless communication systems may be used for low-cost ubiquitous communication, new flexible data services and emergency communication systems. In general, wireless communication systems may be used for voice communications just like conventional telephone systems, and for data communications in a radio-based wide area or local area network as well. Wireless users access wireless communication systems using remote terminals such as cellular telephones and data modems equipped with radio transceivers. Such systems (and in particular the remote terminals) have protocols for initiating calls, receiving calls and general transfer of information. The information transfer can be performed in real-time such as is the case for circuit-switched voice conversations and faxes, or in a store-and forward manner such as is often the case for electronic mail, paging and other similar message transfer systems. Wireless communication systems are generally allocated a portion of the radio frequency spectrum for their operation. The allocated portion of the spectrum is divided up into communication channels. These channels may be distinguished by frequency, by time, by code, or by some combination of the above. Each of these communication channels will be referred to herein as conventional channels. Depending on the available frequency allocations, the wireless system might have from one to several hundred communication channels. To provide full-duplex communication links, typically some of the communication channels are used for communication from base stations to users' remote terminals (the downlink) and others are used for communication from users' remote terminals to base stations (the uplink). Wireless communication systems generally have one or more radio base stations, each of which provide coverage to a geographic area known as a cell and often serve as a point-of-presence (PoP) providing connection to a wide area network such as a Public Switched Telephone Network (PSTN). Often a predetermined subset of the available communication channels is assigned to each radio base station in an attempt to minimize the amount of interference experienced by users of the system. Within its cell, a radio base station can communicate simultaneously with many remote terminals by using different conventional communication channels for each remote terminal As alorementioned. base stations can act as Pol's, providing connection to one or morn wired commu¬nication systems. Such systems include local data networks, wide area data networks, and PSTNs. Tlius. remote users are provided access to local and/or wide area data services and the local public telephone system. Base stations can also be used to provide local connectivity without direct access to a wired net¬work such as in local area emergency and mobile battlefield communication systems. Base stations can provide connectivity of various kinds as well. In the aforementioned examples, point-to-point communica¬tions where roughly equal amounts of information flow in both directions between two users were assumed. In other applications such as interactive television, information is broadcast to all users simultaneously, and responses from many of the remote units are to be processed at the base stations. However, conventional wireless communication systems are comparatively spectrally inefficient. In conventional wireless communication systems, only one remote terminal can use any one conventional channel within a cell at any one time. If more than one remote terminal in a cell attempts to use the same channel at the same time, the downlink and uplink signals associated with the remote terminals interfere with each other. Since conventional receiver technology can not eliminate the interference in these combined uplink and downlink signals, remote terminals are unable to communicate effectively with the base station when interference is present. Thus, the total capacity of the system is limited by the number of conventional channels the base station has available, and in the overall system, by to way in which these channels are re-used among multiple cells. Consequently, conventional wireless systems are unable to provide capacity anywhere near that of wired communication systems. Briefly, the invention comprises antenna arrays and signal processing means for measuring crdriilatm. storing, and using spatial signatures of receivers and transmitters in wireless communication systems to increase system capacity, signal quality, and coverage, and to reduce overall system cost. I he antenna array and signai processing means can be employed at base stations I PoPs) and remote terminals (ienerally there can be different processing requirements at base stations where many signals are being concentrated than at remote terminals where in general only a limited number of communication links are being managed. As an example, in a wireless local loop application, a particular base station might stet as a PoP for many remote terminals and employ the antenna array and signal processing described herein. Additionally, remote terminals could employ antenna arrays and signal processing to further improve their capacity and signal quality over simpler remote terminals that handle fewer communication links. Herein, the distinction between base stations and remote terminals is that base stations generally act as concentrators connecting network. While for tne sake of clarity much of the ensuing discussion is couched' in terms of .simple remote terminals that do not, employ antenna arrays, nothing herein should he interpreted as preventing such an application. Thus, while hereafter spatial signatures will he associated primarily with remote terminals, when antenna arrays are employed at remote terminals, hase stations will have associated spatial signatures as well. Briefly, there are two spatial signatures associated with each remote terminal/ hase station pair on a particular frequency channel, where for the purpose of this discussion it is assumed that only hase stations have antenna arrays. Rase stations associate with each remote terminal in their cell a spatial signature related to how that remote terminal receives signals transmitted to it hy the hase station's antenna array, and a second spatial signature related to how the hase station's receive antenna array receives signals transmitted hy the remote terminal. In a system with many conventional channels, each remote terminal/base station pair has transmit and receive spatial signatures for each conventional channel. The receive spatial signature characterizes how the hase station antenna array receives signals from the particular remote unit in a particular conventional channel. In one embodiment, it is a complex vector containing responses (amplitude and phase with respect to a reference) of each the antenna element where 7)r(t) represents noise present in the environment and the receiver. These spatial signatures are calculated (estimated) and stored at each bcise station for each remote terminal in its cell and for each conventional channel. For fixed remote terminals and base stations in stationary environments, the spatial signatures can be updated infrequently, h general, however, changes in the RF propagation environment, between the base station and the remote terminal can alter the signatures and require that they be updated. .Note that henceforth, the time argument in parentheses will be suppressed: integers inside parentheses will be used solely for indexing into vectors and matrices. In the previous discussion, temporally matched receivers and transmitters were assumed. If there are differences in the temporal responses, these can be equalized using temporal filtering techniques as is well-known. Furthermore, the channel bandwidths were assumed to be small compared to the center frequency of operation. Large bandwidth channels may require more than one complex vector to accurately describe the outputs as is well known. When more than one remote terminal wants to communicate at the same time, the signal processing means at the base station uses the spatial signatures of the remote terminals to determine if subsets of them can communicate with the base station simultaneously by sharing a conventional channel. In a system with m receive and m transmit antenna elements, up to m remote terminals can share the same conventional channel at the same time. When multiple remote terminals are sharing a single conventional uplink channel, the multiple antenna elements at the base station each measure a combination of the arriving uplink signals and noise. These combinations result from the relative locations of the antenna elements, the locations of the remote termi¬nals, and the RF propagation environment. The signal processing means calculates spatial demultiplexing weights to allow the uplink signals to be separated from the combinations of uplink signals measured by the multiple antenna elements. In applications where different downlink signals are to be sent from the base station to the remote terminals, the signal processing means computes spatial multiplexing weights that are used to produce multiplexed downlink signals, which when transmitted from the antenna elements at the base station result in the correct downlink signal being received at each remote terminal with appropriate signal quality. In applications where the same signal is to be transmitted from the base station to a large number (more than the number of antenna elements) of remote terminals, the signal processing means computes weights appropriate for broadcasting the signal, covering the area necessary to reach all the remote terminals. Therefore, the signal processing means facilitates simultaneous communication between a base station and multiple remote terminals on the same conventional channel. The conventional channel may be a frequency channel, a time slot in a time division multiplexed system, a code in a code division multiplexed system, or any combination of the above. In one embodiment, all elements of a single antenna array transmit and receive radio frequency signals. while in another embodiment the antenna array includes separate transmit antenna elements and receive antenna elements. The number of transmit and receive elements need not be the same. If they are not the same, the maximum number of point-to-point links that can simultaneously be established in one> conventional channel is given by the smaller of the two numbers. Accordingly the present invention provides a wireless system for calculating uplink signals transmitted from a plurality of remote terminals using a common uplink channel, said system including at least one base station, said system comprising : receiving means at said at least one base station including a plurality of antenna elements and receivers for producing measurements of combinations of said uplink signals from said plurality of remote terminals using said common uplink channel, receive spatial processing means for determining and storing receive spatial signatures for said plurality of remote terminals using said measurements, spatial demultiplexing means using said receive spatial signatures and said measurements to calculate said uplink signals: transmission means including a plurality of transmit antenna elements and transmitters for transmitting multiplexed downlink signals to said plurality of remote terminals using a common downlink channel; transmit spatial processing means for determining and storing transmit spatial signatures for said plurality of remote terminals: and spatial multiplexing means using said transmit spatial signatures and downlink signals to produce said multiplexed downlink signals. The invention and objects and features thereof will be more readily apparent from the following detailed description together with the accompanying drawings, in which : Figure 1 is a functional block diagram of a base station in accordance with the invention. Figure 2 is a functional block diagram of multichannel receivers in the base station. Figure 3 is a functional block diagram of a spatial demultiplexer in the base station. Figure 4 is a functional block diagram of a spatial multiplexer for one remote terminal on a particular conventional channel. Figure 5 is a functional block diagram of a multichannel transmitter in the base station. Figure 6 is a functional block diagram of a spatial processor in the base station. Figure 7 is a functional block diagram of a remote terminal with a transponder switch Figure 8 is a functional block diagram of a remote terminal. Figure 9 is a schematic diagram of a network system comprised of three base stations and a multiple base station controller. List of reference numerals 1. base station 2. base station communication link 3. base station controller 4. demodulated received signal 5. spatially separated uplink signals 6. received signal measurements 7. demultiplexing weights 8. data to be transmitted directionally 9. modulated signal to be multiplexed for transmission 10. modulated, spatially multiplexed signals to be transmitted 11. calibration signals to be transmitted 12. multiplexing weights 13. spatial processor 14. multichannel transmitters 15. multichannel receivers 16a. multichannel receiver 16m. multichannel receiver 17a multichannel transmitter 17m multichannel transmitter 18a transmit antenna 18m transmit antenna 19a receive antenna 19m receive antenna 20. spatial demultiplexer 21. adder 22a multipliers 22m multipliers 23 spatial multiplexer 24 signal modulator 25 signal demodulator 26a multipliers 26m multipliers 27. spatial control data 28. spatial parameter data 29. common receiver oscillator 30. receiver control data 31. transmitter control data 32. common transmitter oscillator 33. spatial processor controller .34. active remote tormina! list 35. channel selector 36. remote terminal database .37. spatial weight processor 38. spatial signature processor 39. remote terminal antenna 40. remote terminal dnplexer 41. remote terminal duplexer output 42. remote terminal receiver 43 remote terminal received signal 44. remote terminal received calibration signal 45. remote terminal demodulator 46. remote terminal demodulated data 47. remote terminal keyboard and keyboard controller 48. remote terminal keyboard data 49. remote terminal display data 50. remote terminal display and display controller 51. remote terminal modulator 52. remote terminal data to be transmitted 53. remote terminal modulated data to be transmuted 54. remote terminal transmitter 55. remote terminal transmitter output 56. remote terminal transmitter control data 57. remote terminal receiver control data 58. remote terminal microphone 59. remote terminal microphone signal 60. remote terminal speaker .61. remote terminal speaker signal 62. remote terminal central processing unit 63. remote terminal transponder switch 64. remote terminal transponder switch control 65. wide area network 66. multiple base station controller ' 67a cell boundary 67b. coll boundary 67c. coll boundary 68. high speed message link (69. remote terminal Description of In rent ion Figure 1 depicts the preferred embodiment, of a lia.se st.auon 1. A base station controller 3 acts as an interface between ba.se station I and any external connection via a base station communication link 2. and serves to coordinate the overall operation of ba.se station 1. In the preferred embodiment, b.ise station controller 3 is implemented with a conventional central processing unit and associated memory and programming. Incoming or uplink radio transmissions impinge on an antenna array composed of a number, in. of receive antenna elements l!j(a.. ..in) each of whose outputs is connected to one of in multichannel receivers in a bank of phase-coherent multichannel receivers l.">. Multichannel receivers I") have well-matched amplitude and phase responses across the frequency bands of interest, or. as is well known, correction filters are implemented to account for any differences. The illustrative embodiment describes a conventional frequency division multiple access system. Fach multichannel receiver is capable of handling multiple frequency channels. The symbol A',,, will be used to reference the maximum number of conventional frequency channels that can be handled by the receivers. Depending on the frequencies allocated for the operation of the wireless communication system and the bandwidths chosen for particular communication links. A',.,- could be ;is small ;LS one la single frequency channel) or as large as thousands. In alternate embodiments, multichannel receivers If) might instead .handle multiple time slots, multiple codes, or some combination of these well known multiple access techniques. In each conventional channel, receive antenna elements 19(a in) each measure a combination of the arriving uplink signals from the remote terminals sharing this conventional channel. These combinations result from the relative locations of the antenna elements, the locations ot the remote terminals, and the R.F propagation environment, and for narrowband signals are given by equation ('_'). Figure 2 depicts individual multichannel receivers lfi(a ml with antenna --lenient connections. common local receiver oscillators 2!). one for each conventional frequency channel u, be used ai that base station, and received signal measurements t>. Comnjon local receiver oscillators 2!) ensure that the smnals from receive antenna elements l'.)(a in) are coherently down-converted to baseband: its A,-, frequencies are set so that multichannel receivers lb'(a in) extract all A'.-r frequency channels of interest. The frequencies of common local receiver oscillators 21) are controlled by a spatial processor 13 (figure li via receiver control data 30. In an alternate embodiment, where multiple frequency channels are ail contained in a contiguous frequency band, a common local oscillator is used to downconvert. the entire baud which is then digitized, and digital filters and decitnators extract the desired subset of channels using well known technique:;. The illustrative embodiment describes a frequency division multiple access system. In a time division multiple access or code division multiple access system, common oscillators 2'.) would be augmented to relay common time slot or mmon code signals respectively from spatial processor l.'l. via receiver control data 111), to multichannel receivers 16(a ni). In these embodiments, multichannel receivers lb(a m) perform selection of inventional time division channels or conventional code division channels in addition to down conversion to baseband. Referring again to Figure I. multichannel receivers 15 produce received -signal measurements (i which are supplied to spatial processor 13 and to a set, of spatial demultiplexers 20. In this embodiment, received signal measurements 6 contain m complex baseband signals for each of A'PC frequency channels. Figure ti shows a more detailed, block diagram of spatial processor l.'i. Spatial processor l,'! produces and maintains spatial signatures for each remote terminal for each conventional frequency channel, and calculates spatial multiplexing and demultiplexing weights for use by spatial demultiplexers 20 and spatial multiplexers 23. In the preferred embodiment, spatial processor 115 is implemented iismt a conventional central processing unit. Received signal measurements o' go into a spatial signature processor 38 which estimates and updates spatial signatures. Spatial signatures are stored in a spatial signature list m a remote terminal database 36 and are used by channel selector 3F) and spatial weight processor 37. which also produces demultiplexing weights 7 and multiplexing weights 12. A spatial processor controller 33 connects to spatial weight processor 37 and also produces receiver control data 30 transmitter control data 31 and spatial control data 27. Referring again to Figure 1. spatial demultiplexers 20 combine received signal measurements ti accord¬ing to spatial demultiplexing weights 7. Figure 3 shows a spatial demultiplexer 20 for a simile conventional channel. In this embodiment, arithmetic operations in spatial demultiplexer 20 are carried out using gen¬eral purpose arithmetic chips. In figure 3. Zb(i) denotes the ith component of received signal measurement vector ti for a single conventional channel, and wr(i) denotes the complex conjugate of the r"' component of the spatial demultiplexing weight vector 7 for a remote terminal using this conventional hannel For each remote terminal on each conventional channel, the spatial demultiplexer 2:; ompines the inner-product of the spatial demultiplexing weights 7 for the conventional channel with the received signal channel is available. For transmission, signal modulators 24 produce modulated signals !) for each remote terminal the ba.se station is transmitting to. and a set of spatial multiplexing weights 12 for each remote, terminal are applied to the respective modulated singal in spatial multiplexers 23 to produce spatially multiplexed signals to he transmitted 10 for each of the rn transmit antennas l In the illustrative embodiment the number Nrr of downlink conventional channels is the same a.s the number A',.,, of uplink conventional channels. In other embodiments, there may be different numbers of uplink and downlink conventional channels. Furthermore, the channels may be of dilferent types and bandwidths as is the case for an interactive television application where the downlink is comprised of wideband video channels and the uplink employs narrowband audio/data channels. Additionally, the illustrative embodiment shows the same number of antenna elements, in. for transmit and receive. In other embodiments, the number of transmit antenna elements and the number of receive antenna elements may be different, up to and including the case where transmit employs only one transmit antenna element in an omnidirectional sense such as in an interactive television application. Figure 4 shows the spatial multiplexer for one remote terminal on a particular conventional channel. Arithmetic operations in spatial multiplexer 23 are carried out using general purpose arithmetic chips. The component of modulated signals 9 destined for this remote terminal on this conventional channel is denoted by »(,. and w(r(/) denotes the i'h component of spatial multiplexing weight vector 12 for this remote terminal on this conventional channel. For each remote terminal on each conventional channel, the spatial multiplexer 23 computes t he product of its spatial multiplexing weight vector (from the spatial multiplexing weights 12) with its modulated signal Modulated and spatially multiplexed signals 10 arc inputs to a bank of in phase coherent multichannel transmitters 14. Multichannel transmitters 14 either have well-matched amplitude and phase r.wponses across the frequency bands of interest, or. as is well known, correction lilters are implemented to account for any differences. .Figure •"• depicts multichannel transmitters 17(a in) with antenna connections. common local transmitter oscillators 32. and digital inputs 10. Common local transmitter oscillators 32 ensure that the relative phases of spatially multiplexed signals 10 are preserved during transmission by transmit antennas 18(a in). The frequencies of common local transmitter oscillators ;i2 are controlled by sftatial processor 13 (see figure 1) via transmitter control data 31. In an alternate embodiment, spatial multiplexer 23 uses well known baseband multiplexing techniques to multiplex all the calculated conventional channel signals to be transmitted into a single wideband signal to be upconverted and transmitted by each of the multichannel transmitters 17(a in). The multiplexing can be performed either digitally or in analog as appropriate. 1 he illustrative embodiment shows a system with multiple frequency multiple access or code division multiple access system, common oscillators 32 would he augmented to relay common time slot or common code signals respectively from spatial processor I.'!, via transmitter control data 31. to multichannel transmitters 17(a in). Referring again to figure I. in applications where transmit spatial signatures are required, spatial processor 13 is also able to transmit predetermined calibration signals 11 for each antenna on a particular conventional downlink channel. Spatial processor l.'i instructs multichannel transmitters I7(a m), via transmitter control data 31. to transmit predetermined calibration signals 11 in place of spatially multiplexed signals 10 for a particular conventional downlink channel. This is one mechanism used for determining the transmit spatial signatures of the remote terminals on this conventional downlink channel. In alternate embodiments where well known channel coding techniques are used to encode t he signals to be transmitted to remote terminals, remote terminals employ well known decoding techniques to estimate BERs which are then reported back to the base station on their uplink channel. If these BERs exceed acceptable limits, corrective action is taken. In one embodiment, the corrective active involves reallocating resources by using the same strategy as adding a new user with the exception that the current channel is not acceptable unless the current set of users of that particular channel changes. Additionally, recalibration of the transmit signature for that remote terminal/base station pair is performed when thai conventional channel is available. Figure 7 depicts the component arrangement in a remote terminal that provides voice communication. The remote terminal's antenna 3!) is connected to a dupiexer 40 to permit antenna 30 to be used for both transmission and reception. In an alternate embodiment, separate receive and transmit antennas are used eliminating the need for dupiexer ■10. In another alternate embodiment where reception and transmission occur on the same frequency channel but at different times, a transmit /'receive i TR) switch is used instead of a dupiexer as is well known. Dupiexer output. II serves as input to a receiver 42. Receiver VI produces a down-converted signal 13 which is the input to a demodulator 45. A demodulated received voice signal til is input to a speaker 00. Demodulated received control data -4ti is supplied to a remote terminal central processing unit, (12 (CPl). Demodulated received control data -16 is useii for receiving data from base station 1 during call setup and termination, and in an alternate embodiment, for determining the quality (HER) of the signals being received by the remote terminal for transmission back to the base station a-s described above. Remote terminal ('IT 02 is implemented with a. standard microprocessor. Remote terminal CPU 02 also produces receiver control data. 57 for selecting the- icmuic terminals reception channel, transmitter control data 50 for setting the remote terminal's transmission channel and power ievei. control data to be transmitted 52. and display data -10 for remote terminal display 50. Remote terminal The remote terminal's voice signal to be transmitted 59 from microphone 5IS is input to a modulator%51. Control data to be transmitted 52 is supplied by remote terminal CPU 1)2. Control data to be transmit¬ted 52 is used for transmitting data to base station 1 during call setup and termination as well as for transmitting information during the call such as measures of call quality (e.g.. bit error rates I RER.s)). The modulated signal to be transmitted 53. output by modulator 51. is up-converted and amplified by a trans¬mitter 54. producing a transmitter output signal 55. Transmitter output 55 is then input to dupiexer 40 for transmission by antenna 39. In an alternate embodiment, the remote terminal provides digital data communication. Demodulated received voice signal til. speaker li(). microphone 5S. and voice signal to be transmitted a!) are replaced by digital interfaces well-known in the art that allow data lo be transmitted to and From an external data processing device (for example, a computer). Referring again to ligure 7. the remote terminal allows received data i'.\ to be transmitted back to base station 1 via switch t53 controlled by remote terminal CPU 62 through switch control signal 64. In normal operation, switch (iii drives transmitter 54 with modulated signal 53 of modulator 51. When the remote terminal is instructed by base station 1 to enter calibration mode, remote terminal ('IT 62 toggles switch control signal 64. which instructs switch 63 to drive transmitter 54 with received data 43. Figure 8 shows an alternate embodiment of the remote terminal calibration function. Switch til! of figure 7 is no longer used. Instead, the output of receiver 42 is supplied to remote terminal In an alternate embodiment, special calibration procedures in the remote terminal are not required. In many conventional wireless protocol standards, remote terminals regularly report received signal strength or receive signal quality back the base station. In this embodiment, the received signal strength reports are sufficient to compute the remote terminal's transmit spatial signature, as described below. Operation of Invention General Principles Dase Station In many respects, the spectrally efficient base station shown in ligure 1 behaves much like a standard wireless communication system base station. The primary distinction is that the spectrally efficient base station supports many more simultaneous conversations than it has conventional communication chan¬nels. The conventional communication channels may be frequency channels, time channels, code channels, or any combination of these. The spatial multiplexer/demultiplexer increases the system capacity by al¬lowing muitipie spatial channels on each of these conventional channels. Moreover, by combining signals from multiple receive antennas, the spatial demultiplexer 20 produces spatially separated uplink signals 5 that have substantially improved signal-to-noise, reduced interference, and improved qualify in multinatli invironments compared to a standard base station. nals and base stations incorporating antenna arrays and spatial signal processing is described. Such systems have application, for example, in providing wireless access to the local PSTN. Information transfers (ur calls) are initiated by either i remote terminal or by communication link 2 through base station controller II. i 'all initialization takes place on a downlink and uplink control channel as is well known in the art. In the present embodiment the downlink control channel is transmitted using transmission antennas I8(a in). In an alternate embodiment, the downlink control channel is broadcast from a single, omnidirectional an¬tenna. Base station controller 3 passes the identification of the remote terminal to be involved in the call to spatial processor 115 which uses the stored spatial signatures of that remote terminal to determine, which conventional communication channel the remote terminal should use. The selected channel may already be occupied by several remote terminals, however spatial processor 13 uses the spatial signatures of all of the remote terminals on that channel to determine that they can share the channel without interference. in a system with m receive and in transmit antenna elements, up to w remote terminals can share the same conventional channel. More generally, the number of point-to-point full-duplex communication links that can occupy the same conventional channel at the same time is given by the smaller of the number of receive and transmit elements. Spatial processor 13 uses calculated spatial multiplexing and demultiplexing weights fur the selected channel and the remote terminal in question to configure spatial multiplexer 211 and spatial demultiplexer '20. Spatial processor 13 then informs controller 3 of the selected channel. As in a conventional base station, controller 3 then commands the remote terminal (via the downlink control channel) to switch to the selected channel for continued communications. In the event that the remote terminal has power control capabilities, as is well known in the art. controller 3 also commands the remote terminal to adjust its power to an appropriate level based on parameters such as the power levels of the other remote terminals sharing the same conventional channel and the required signal quality for each link as discussed below. At the termination of communications, the remote terminal returns to its idle state where n monitors the downlink control channel awaiting its next call. This frees up that "spatial channel" for another remote terminal. multichannel receiver 16 given a single unit power narrow hand .signal being transmitted by that particular remote terminal, at that particular frequency. When the base station controller 1 forwards a call initialization request for a particular remote terminal via link '27. a channel selector 35 searches active remote terminal list 'M to find a conventional communication channel that can accommodate the remote terminal. In the [(referred embodiment, there is a receive active remote terminal list and a transmit active remote terminal list which are used by channel.selector :!5 in forming both a multiplexing and a demultiplexing spatial signature matrix for each conventional channel. For each conventional channel, the columns of the demultiplexing and rows of the multiplexing spatial signature matrices are the stored receive and transmit spatial signatures of each of the remote terminals currently active on (using) that channel plus one more column containing the appropriate spatial signature where I is a matrix of all ones of the appropriate size and abs{) is elementwise absolute value. Channel selector 35 compares these values against the limits for each of the transmitters for each of the demerits. If any of the average or peak values exceed the acceptable limits, the remote terminal in question is not assigned to the candidate channel. Otherwise, the ability to successfully receive from the remote terminal is checked. In an alternate embodiment, the transmitter limits are used as inequality constraints in an optimization algorithm for calculating transmit weights that meet the specifications given and that also result in the minimum amount of transmitted power possible. If transmit weights satisfying the constraints can not be found, the remote terminal in question is not assigned to the candidate channel. Such optimization algorithms are well known. To test the uplink, channel selector 35 calculates spatial demultiplexing weights U'rj. using Ai,r. 'lie demultiplexing spatial signature matrix /Ur.P associated with the relevant conventional channel, as given If all of the diagonal elements of SIXR are above the'desired thresholds based on the signal quality required to be received from each remote terminal, the remote terminal is allowed access to the channel. If the candidate, remote terminal is below its threshold and has thee ability to increase its outout power, the. same computations are again performed for increasing remote terminal power output until either the maximum output power for that remote terminal is reached and the SINR is still insufficient, another remote terminal SINR falls below its threshold in which case its power is increased if possible, or ail thresholds are exceeded. If acceptable remote terminal transmit powers can be found, the remote terminal is granted access to this particular conventional channel, otherwise it is denied access and another conventional channel is checked. In an alternate embodiment, the calculation of demultiplexing weights is performed using well known optimization procedures with the objective of miniming remote terminal transmit powers subject to estimated signals at the base station meeting or exceeding their minimum desired SIXR's. Also, in an alternate embodiment, in the case that no conventional channel can be found to accom¬modate the remote terminal, channel selector 35 calculates whether some rearrange.nent of the existing remote terminals among the conventional channels would allow the remote terminal to be some conventional channel. In this ca.se, the remote terminal wi.ll only he denied •communication at this time if no rearrangement of existing users allows the remote terminal to lie accommodated. In an alternate embodiment employing frequency division duplexing (FDD), remote terminals are not restricted to being assigned' a lixed conventional channel pair for transmit and receive A sufficiently flexible system architecture is employed where channel selector 35 may choose to assign a particular remote to transmit and receive conventional channels separated by different frequency duplex offsets in order to minimize overall system interference levels. Spatial multiplexing and demultiplexing weights for remote terminals already using a conventional channel must be recalculated because adding a new remote terminal to that conventional channel may change them significantly. In the preferred embodiment, channel selector 35. having already done the nec¬essary calculations, sends the new spatial multiplexing and demultiplexing weights to the spatial weight processor 37 for use in setting up the spatial multiplexer 23 and demultiplexer 20. In an alternate embod¬iment, spatial weight processor 37 uses the spatial signature matrices sent to it by channel selector 35 to calculate different sets of spatial multiplexing and demultiplexing weights for all of the f-mote terminals on that conventional channel. Spatial weight processor 37 then sends the new spatial demultiplexing weights to spatial demultiplex¬ers 20 and the new spatial multiplexing weights lo the spatial multiplexers 23 for this conventional channel, updates the active remote terminal list 34, and informs spatial processor controller 33 which in turn informs base station controller 3 of the selected channel. Base station controller 3 then transmits a message to the remote terminal using the downlink, control channel tiiat instructs the remote terminal to switch to the desired conventional channel. It can be shown from equation (!)) that the multiplexing weight matrices \Vtr have T h.• property: are the most accurate in the sense of least mean-squared error. It: particular, they most closely match the signals transmitted by the remote terminals given the measurements made at tin; base station by the multiple antenna elements. Equations (9) and (13) represent only one way to calculate spatial multiplexing and demultiplexing weights. There are other similar strategies that demonstrate properties similar to those shown in equation (16) and described in the previous paragraph. Other well known techniques for calculating weight matrices Determining Spatial Signatures As shown in figure ti. spatial processor 13 also contains a spatial signature processor 38 Tor finding the spatial signatures of the remote terminals. Fn the illustrative embodiment, spatial signature processor 38 uses the calibration techniques described in copending U.S. patent application 08/234.747. In the illustrative embodiment, each remote terminal is capable of entering a.calibration mode in which the signal received by the remote terminal 43 is transmitted back to base station 1 Referring to figure 7. this function is provided by switch 63 controlled by remote terminal (TV (>2 through switch control signal 64. To determine the transmit and receive spatial signatures of a remote terminal, spatial signature pro¬cessor 38 commands the remote terminal to enter calibration mode by transmitting a command to it on the downlink channel. This command is generated by base station controller 3. based on a request from spatial processor controller 33. and modulated by signal modulators 24. Spatial signature processor 3S then transmits predetermined calibration signals 11. on the conventional channel occupied by the remote terminal, by instructing multichannel transmitters 17(a in) via transmitter control data 31 and spatial processor controller 33. In the present embodiment, the ?n signals (for each antenna) among the prede¬termined calibration signals 11 are different frequency complex sinusoids. In another embodiment, the predetermined calibration signals 11 are any known, distinct, signals. The remote terminal shown'm figure 7 transmits back the signal received at the remote terminal. This transponded signal is received by multichannel receivers 15) in base station 1 shown in figure 1 and supplied to spatial signature processor 38 shown in figure 6. In one embodiment described in patent application 08/234.747. spatial signature processor 38 computes the receive and transmit spatial signatures of the remote terminal from the received signal measurements b and predetermined calibration signals II as follows. Time samples of the received data are stored in an tn by n data matrix Z which IN the absence of noise and parameter offsets is given by well known techniques are used to account, for noise present in the system and parameter variations such as oscillator frequency offsets. Spatial signature processor 38 stores the new spatial signatures in remote terminal database 36. Upon completion, spatial signature processor 38 commands the remote terminal to exit calibration mode by transmitting a command to it on the downlink channel. In one alternate embodiment, computation of remote terminal transmit spatial signatures can be per¬formed directly by the remote terminals. This embodiment of the remote terminal is shown in figure H. In calibration mode, spatial signature processor .'58 transmits predetermined calibration signals 11. on the conventional channel to be calibrated by the remote terminals, as before. Remote terminal CPU 62 uses received calibration signals 11 and the known transmitted waveforms to compute ihe remote terminal's transmit spatial signature using the same techniques used by spatial signature processor 3S in the previous embodiment. The computed transmit spatial signature is transmitted back to base station 1 through mod¬ulator 51 and transmitter 51 as control data to be transmitted 52. When received by base station 1. spatial signature processor 38 stores the new transmit spatial signature in remote terminal database 3(5. Since each remote terminal performs the transmit spatial signature calculation independently, this arrangement allows multiple remote terminals to compute their own transmit spatial signature simultaneously on the same conventional channel. In this embodiment, remote terminal receive spatial signatures are computed by spatial signature processor 38 in the same manner as in the previous embodiment. Using these techniques, spatial signature processor 38 can measure a remote terminal transmit and receive spatial signatures for a particular channel any time that channel is idle. I lie Hficiency ot these calibration techniques allow spatial signature processor 38 to update the spatial signatures of numerous remote terminals for a particuiar channel while occupying that channel for only a short time. receive spatial signatures for remote terminals. A further example is decision-directed feedback techniques, also well known in the art. where receive data is demodulated and then remodulated to produce an estimate of the original modulated signal. These techniques allow receive spatial signatures to lie estimated even when multiple remote terminals are occupying a single conventional channel. In some RF environments, transmit spatial signatures for remote terminals can be calculated explicitly, as is well known, using knowledge of the remote terminal locations and the locations and directivity patterns of the base station transmit antennas. This requires no special capability on the part of the remote terminal. If the remote terminal has the ability to measure and report the strength of the signal it is receiving, ihe system can use this information to derive transmit spatial signatures! albeit in a less efficient manner than the embodiment shown in figure 7 when the has full transponder capabilities, or the ' embodiment shown in figure S where the remote terminal directly computes its transmit spatial signature The transmit spatial signature is determined based solely on received- signal power reports Irom the remote terminal as follows. First, spatial signature processor 38 transmits identical unit power signals from two of the rn antenna elements at a time. Spatial signature processor 38 then changes the amplitude and phase of one of the two signals until the remote terminal reports that it is receiving no signal. The set of complex weights for antenna elements 2 through m required to null a unit power signal from element I are changed in sign and inverted to produce the transmit spatial signature for the remote terminal. In yet another embodiment, the system can be designed to continuously update the spatial signatures of the remote terminals in a "closed loop" manner. This is done to account for the time variation of spatial signatures due to. for example, motion of the remote terminal or changes in the RF propagation conditions. To do this, both the base station and the remote terminal periodically transmit predetermined training sequences. Each remote terminal currently active on a particular channel is assigned a different predetermined training sequence and is given the training sequences for all other remotes currently active on that particular channel. In one embodiment, the different training sequences are orthogonal in the sense that the inner product of any two of the training sequence waveforms is zero. Fach time the training sequences are transmitted, each remote terminal calculates how mucti of each training sequence it has received using well known techniques, and transmits this information to the ba.se station. In the illustrative embodiment, the base station uses the receiver outputs and knowledge of the trans¬mitted waveforms to calculate the remote terminal receive spatial signatures. In another embodiment, the base station calculates how much of each remotely transmitted training sequence has come through on each output of the spatial demultiplexer, expressed as a complex vector of coupling coefficients. Knowledge of these coupling coefficients allows the currently active receive and transmit spatial signatures to be corrected so as to reduce mutual interference using well know techniques. Finally, in systems that use time division duplexing (TOD) for lull-duplex communications, as is well known in the art. the transmit and receive frequencies are the same. In this case using the well known principle of reciprocity, the transmit and receive spatial signatures are directly related. Thus, this embodiment determines only one of the signatures.: for example the receive spatial signature, and the her in this case the transion spanai signature, is calculated trom the tirst (receive) spatial signature and knowledge of the relative phase and amplitude characteristics of multichannel receivers 15 and multichannel transmitters 14. Network Luvel Spatial Processing In the embodiment illustrated herein, the spatial processor tor each base station in the cellular-like wireless communication system operates independently to maximize the number of communication channels in the immediate cell. However, significant system capacity improvements can be realized if the spatial processor from each base .station communicates with and coordinates its elforts with the spatial processors from other nearby cells. A specific embodiment is shown in figure 9.. A multiple base station controller 66 acts as the interface between the wide area network 65 through link 68 and base stations i (a.b.c) via base station communication links 'I (a.b.c). Fach base station is responsible for providing coverage to a number of remote terminals. In one embodiment, each remote terminal is assigned to only one base station thus defining cell boundaries ti7 (a.b.c) within which all remotes attached to a particular base station are located. [sers equipped with remote terminals 69. are' ' identified by a boxed "R" in the figure. Each spatial processor contained in base stations 1 (a.b.c) measures and stores the spatial signatures of the remote terminals in its cell and also of the remote terminals in adjacent cells. The determination of spatial signatures of the remote terminals in adjacent cells is coordinated by multiple base station con¬troller 66 through base station communication links 2 (a.b.c). Through base station communication links 2 (a.b.c) and multiple base station controller 66. spatial processors in base stations 1 a.b.c, from adjacent cells inform each other of which remote terminals they are communicating with on which conventional channels. Each spatial processor includes the spatial signatures of remote terminals that are currently active in adjacent cells to form extended transmit and receive spatial signature matrices A and A which are sent to all the adjacent base stations. The channel selectors in each ba.se station, using these extended spatial signature matrices, jointly assign remote terminals to each conventional channel in each of base stations 1 (a,b,c). The resultant weight matrices Wtx and \Vrr for each base station are then calculated using extended spatial signature matrices Arh and .-Ur. In calculating the weights, the objective is to minimize the signal transmitted to and received from the adjacent cell's active remote terminals, thereby allowing many more remote terminals to simultaneously communicate. In an alternate embodiment, multiple base station controller 66 assigns remote terminals requesting access to base stations dynamically using a list of active remote terminal/ base station/conventional channel links, the associated remote terminal databases, and the particular requirements tor the link to be assigned. Additionally, remote terminals can employ multiple (directional! transmit and receive antennas, to facilitate directive links to multiple nearby base stations as instructed by multiple base station controller 6(5 to further increase system capacity. Alternate Embodiments In one alternate embodiment, transmission antennas 18(a m I and reception antennas l!)(a m ) at base station 1 are replaced by a single array of m antennas. Each element in this array is attached to both its respective component of multichannel transmitters 14 and its respective component of multichannel receivers 15 by means of a duplexer. In another alternate embodiment, signals on the uplink control channel may he processed in rea time using the spatial processing described in copending patent application 07/806.605). This would allow multiple remote terminals to request a communication channel at the same time. In yet another embodiment for applications involving data transfer of short bursts or packets of data, no separate uplink control channel is required and the system may service requests for communication and other control functions during control time intervals that are interspersed with communications intervals. As stated above, many techniques are known for measuring the spatial signatures of the remote terminal radios and using these spatial signatures to calculate multiplexing and demultiplexing weights that will allow multiple simultaneous conversations and/or data transfers on the same conventional communication channel. While the above description contains many specificities, these should not be construed as limitations on the scope of the invention, but rather as an exemplification of one preferred embodiment thereof. Many other variations are possible. .Accordingly, the scope of the invention should be determined not by the illustrated embodiments, but by the appended claims and their legal equivalents. WE CLAIM : A wireless system for calculating uplink signals transmitted from a plurality of remote terminals using a common uplink channel, said system including at least one base station (1). said svstem comprising : receiving means at said at least one base station (1) including a plurality of antenna elements (19a-m) and receivers (15) for producing measurements of combinations of said uplink signals from said plurality of remote terminals using said common uplink channel, receive spatial processing means (13) for determining and storing receive spatial signatures for said plurality of remote terminals using said measurements, spatial demultiplexing means (20) using said receive spatial signatures and said measurements to calculate said uplink signals; transmission means including a plurality of transmit antenna elements (18a-m) and transmitters (14) for transmitting miiftinlfived downlink signals to said plurality of remote terminals using a common downlink channel; transmit spatial processing means (13) for determining and storing transmit spatial signatures for said plurality of remote terminals; and spatial multiplexing means (23) using said transmit spatial signatures and downlink signals to produce said multiplexed downlink signals. The wireless system as claimed in claim 1, wherein said receive spatial processing means (13) comprises: a spatial signature list (36) comprising a receive spatial signature for each remote terminal in said plurality of remote terminals and said common uplink channel, receive spatial signature determining means (38) for determinine said receive spatial signatures, and a receive channel selector (35) utilizing said receive spatial signatures to determine whether said common uplink channel can be further shared by an additional remote terminal. The wireless system as claimed in claim 2, wherein said receive spatial processing means (13) comprises: a receive spatial weight processor (37) for calculating spatial demultiplexing weights for said plurality of remote terminals, said spatial demultiplexing weights heing utilized by said spatial demultiplexing means to calculate said uplink signals. The wireless system as claimed in claim 3, wherein said receive spatial weight processor determines said spatial dermiltinl»Ying weights as the columns of matrix Wn as follows: where ()* denotes the complex conjugate transpose of a matrix, R„n is the noise covariance matrix of said receiving means, Pr is the diagonal matrix of transmit powers of the remote terminals in said plurality of remote terminals, and Ab is a demultiplexing spatial signature matrix whose columns are said receive spatial signatures for said plurality of remote terminals and said common uplink channel. The wireless system as claimed in claim 1, wherein said common uplink channel is one of a plurality of unlink- channel and wherein said receive spatial processing means (13) comprises: an active remote terminal list (34) comprising a list of remote terminals assigned to at least one channel of said plurality of uplink channels, a spatial signature list (36) comprising a receive spatial signature for each remote terminal of said plurality of remote terminals and each channel of said plurality of uplink channels, receive spatial signature determining means (38) for determining said receive spatial signatures in said spatial signature list a receive channel selector (35) using said active remote terminal list (34) and said spatial signature list (36) to determine assignments of each remote terminal in said active remote terminal list (34) to at least one of the channels of said plurality of unlink channels, and a receive spatial weight processor (37) for calculating spatial demultiplexing weights for each of the terminals in said active, remote, terminal list and each channel of said plurality of uplink channels assigned to at least one of the terminals in said active remote terminal list, said spatial demultiplexing weights being utilized by said spatial demultiplexing means (20) to calculate said uplink signals. The wireless system as claimed in claim I, wherein said common uplink channel is one of a plurality of uplink channels, said at least one base station (1) is one of a plurality of base stations, said receive spatial processing means (13) is one of a plurality of receive spatial processing means, each base station in said plurality of base stations having a corresponding receive spatial processing means in said plurality of receive spatial processing means, each receive spatial processing means in said plurality of receive spatial processing means comprising: an active remote terminal list (34) comprising a list of remote terminals assigned to at least one channel of said plurality of uplink channels, a spatial signature list (36) comprising a receive spatial signature for each remote terminal of said plurality of remote terminals and each channel of said plurality of uplink channels, receive spatial signature determining means (38) for determining said receive spatial signatures in said spatial signature list (36), and a receive spatial weight processor (37) for calculating spatial demultiplexing weights for each of the terminals in said active remote terminal list (34) and each channel of said plurality of uplink channels assigned to at least one of the terminals in said active remote terminal list (34). said spatial demultiplexing weights being utilized by said spatial demultiplexing means (20) to calculate said uplink signals, said system further comprising: joint channel selector means (35) for jointly determining assignments of each remote terminal in each said active remote terminal list (34) to at least one of the channels of said plurality of uplink channels and to at least one of base stations of said plurality of base stations, and communication means (66) for communicating the status of said assignments between each base-station in said plurality of base stations and said joint channel selector means. The wireless system as claimed in claim 1, wherein said spatial demultiplexing means calculates spatial demultiplexing weights for said common uplink channel as the columns of a matrix Wn as follows: where ()* denotes the complex conjugate transpose of a matrix, Rnn is the noise covariance matrix of said receiver means, Pr is the diagonal matrix of transmit powers of the remote terminals in said plurality of remote terminals. and Abr is a demultiplexing spatial signature matrix whose columns are said receive spatial signatures for said plurality of remote terminals and said common uplink channel, said spatial demultiplexing means using said spatial demultiplexing weights to calculate said uplink signals. The wireless system as claimed in claim 1, wherein said system comprises a transponder co-located with each remote terminal of said plurality of remote terminals and wherein receive spatial processing means (13) determines said receive spatial signatures using signals transponded from at least one of the transponders. The wireless system as claimed in claim 1, wherein each remote terminal of said plurality of remote terminals has a transponder and said receive spatial processing means (13) determines said receive spatial signatures using signals transponded from at least one of the transponders. The wireless system as claimed in claim 1, wherein said receive spatial processing means (13) determines said receive spatial signatures using the known location and directivity of said antenna elements (19a-m). and estimates of the directions of arrival of said uplink signals from said plurality of remote terminals. The wireless system as claimed in claim 1, wherein said receive spatial processing means (13) determines said receive spatial signatures using the known location and directivity of said antenna elements and the known location of said plurality of remote terminals. The wireless system as claimed in claim 1, wherein said uplink signals have predetermined modulation format parameters, and said receive spatial processing means (13) determines said receive spatial signatures using said predetermined modulation format parameters of said uplink signals from said plurality of remote terminals. The wireless system as claimed in claim 1, wherein said receiving means and said transmission means share common antenna elements using duplexers. The wireless system as claimed in claim 1, wherein said receiving means and said transmission means share common antenna elements using transmit/receive switches. The wireless system as claimed in claim 1, wherein said common uplink channel is one of a plurality of uplink channels, said common downlink channel is one of a plurality of downlink channels, and wherein said receive spatial processing means (13) and said transmit spatial processing means (13) comprise: an active remote terminal list (34) comprising a list of remote terminals assigned to at least one of the channels of said plurality of uplink channels and remote terminals assigned to at least one of the channels of said plurality of downlink channels, a spatial signature list (36) comprising a receive spatial signature for each remote terminal of said plurality of remote terminals and each channel of said plurality of uplink channels, and a transmit spatial signature for each remote terminal of said plurality of remote terminals and each channel of said plurality of downlink channels, receive spatial signature determining means (38) for determining said receive spatial signatures, transmit spatial signature determining means (38) for determining said transmit spatial signatures, and a channel selector (35) using said active remote terminal list (34) and said spatial signature list to determine assignments of each remote terminal in said active remote terminal list (34) to at least one of the channels of said plurality of uplink channels and at least one of the channels of said plurality of downlink channels. 16. The wireless system as claimed in claim 15. wherein said receive spatial processing means (13) and said transmit spatial processing means (13) further comprise: a receive spatial weight processor (37) for calculating spatial demultiplexing weights for each of the terminals in said active remote terminals list to which a uplink channel is assigned and for each channel of said plurality of uplink channels assigned to at least one of the terminals in said active remote terminal list, said spatial demultiplexing weights being utilized by said spatial demultiplexing means to calculate said uplink signals, and a transmit spatial weight processor (37) for calculating spatial multiplexing weights for each of the terminals in said active remote terminal list to which a downlink channel is assigned and each channel of said plurality of downlink channels assigned to at least one of the terminals in said active remote terminal list, said spatial multiplexing weights being utilized by said spatial multiplexing means to produce said multiplexed downlink signals. 17. The wireless system as claimed in claim 1, wherein said at least one base station (1) is one of a plurality of base stations, said common uplink channel is one of a plurality of uplink channels, said common downlink channel is one of a plurality of downlink channels, said receive spatial processing means (13) is one of a plurality of receive spatial processing means, said transmit spatial processing means (13) is one of a plurality of transmit spatial processing means, each base station in said plurality of base stations having a corresponding receive spatial processing means in said plurality of receive spatial processing means and a corresponding transmit spatial processing means in said plurality of transmit spatial processing means, each receive spatial processing means in said plurality of receive spatial processing means and each transmit spatial processing means in said plurality of transmit spatial processing means comprising: an active remote terminal list (34) comprising a list of remote terminals assigned to at least one of the channels of said plurality of uplink channels and remote terminals assigned to at least one of the channels of said plurality of downlink channels, a spatial signature list (36) comprising a receive spatial signature for each remote terminal of said plurality of remote terminals and each channel of said plurality of uplink channels, and a transmit spatial signature for each remote terminal of said plurality of remote terminals and each channel of said plurality of downlink channels, receive spatial signature determining means (38) for determining said receive spatial signatures, transmit spatial signature determining means (38) for determining said transmit spatial signatures, a receive spatial weight processor (37) for calculating spatial demultiplexing weights for each of the terminals in said active remote terminal list to which a uplink channel is assigned and each channel of said plurality of uplink channels assigned Lo at least one of the terminals in said active remote terminal list, said spatial demultiplexing weights being utilized by said spatial demultiplexing means to calculate said uplink signals, and a transmit spatial weight processor (37) for calculating spatial multiplexing weights for each of the terminals in said active remote terminal list to which a downlink channel is assigned and each channel of said plurality of downlink channels assigned to at least one of the terminals in said active remote terminal list, said spatial multiplexing weights being utilized by said spatial multiplexing means to produce said multiplexed downlink signals, said system further comprising: joint channel selector means (35) for jointly determining assignments of each remote terminal in each said active remote terminal list to at least one of the channels of said plurality of uplink channels, to at least one of the channels of said plurality of downlink channels and to at least one of the base stations of said plurality of base stations, and communication means (66) for communicating said assignments between each base station in said plurality of base stations and said joint channel selector means. The wireless system as claimed in claim 1, wherein said spatial multiplexing means determines spatial multiplexing weights for said common downlink channel as the rows of a matrix W x as follows: where () denotes the complex conjugate transpose of a matrix, Sv, is the diagonal matrix of amplitudes of said downlink signals, and Ab is a signatures for said plurality of remote terminals and said common downlink channel, and wherein said spatial multiplexing means utilizes said spatial multiplexing weights to produce said multiplexed downlink, signals. The wireless system as claimed in claim 1, wherein said system comprises a transponder co-located with each remote terminal of said plurality of remote terminals and wherein transmit spatial processing means (13) determines said transmit spatial signatures using signals transponded from at least one of the transponders. The wireless system as claimed in claim 1, wherein each remote terminal in said plurality of remote terminals has a transponder, and wherein said transmit spatial processing means (13) determines said transmit spatial signatures using signals transponded from at least one of the transponders. The wireless system as claimed in claim 1, wherein said downlink signals have predetermined modulation format parameters, and said transmit spatial signatures are determined by the corresponding terminals in said plurality of remote terminals using the predetermined modulation format parameters of said downlink signals. The wireless system as claimed in claim 1, wherein said transmit spatial processing means (13) determines said transmit spatial signatures using the known location and directivity of said transmit antenna elements and estimates of directions of arrival of said uplink signals from said plurality of remote tenninals. 23. The wireless system as claimed in claim I. wherein said downlink signals and said uplink signals are transmitted on the same radio frequency and said transmit spatial processing means (13) determines said transmit spatial signatures by calculating them directly from said receive spatial signatures. 24. The wireless system as claimed in claim I, wherein said transmit spatial processing means (13) determines said transmit spatial signatures using the known location and directivity of said antenna elements (18a-m) and the known location of said plurality of remote terminals. 25. A wireless system for calculating uplink signals transmitted from a plurality of remote terminals using a common uplink channel substantially as herein described with reference to the accompanying drawings.

Full Text

This invention relates to a wireless system tor calculating uplink signals transmitted from a plurality of remote terminals using a common uplink channel.
Wireless communication systems can be used to complement and in some instances replace conventional wired communication systems in areas where conventional wire-line systems are unavailable, unreliable or excessively expensive. Examples of such areas are : rural areas with a small number of widespread users, underdeveloped areas with little or no current infrastructure, reliability sensitive applications in areas where wired infrastructure is unreliable and political environments where monopolistic wired service providers maintain artificially high prices. Even in metropolitan areas and highly developed countries, wireless communication systems may be used for low-cost ubiquitous communication, new flexible data services and emergency communication systems. In general, wireless communication systems may be used for voice communications just like conventional telephone systems, and for data communications in a radio-based wide area or local area network as well.
Wireless users access wireless communication systems using remote terminals such as cellular telephones and data modems equipped with radio transceivers. Such systems (and in particular the remote terminals) have protocols for initiating calls, receiving calls and general transfer of information. The information transfer can be performed in real-time such as is the case for circuit-switched voice conversations and faxes, or in a store-and forward manner such as is often the case for electronic mail, paging and other similar message transfer systems.

Wireless communication systems are generally allocated a portion of the radio frequency spectrum for their operation. The allocated portion of the spectrum is divided up into communication channels. These channels may be distinguished by frequency, by time, by code, or by some combination of the above. Each of these communication channels will be referred to herein as conventional channels. Depending on the available frequency allocations, the wireless system might have from one to several hundred communication channels. To provide full-duplex communication links, typically some of the communication channels are used for communication from base stations to users' remote terminals (the downlink) and others are used for communication from users' remote terminals to base stations (the uplink).
Wireless communication systems generally have one or more radio base stations, each of which provide coverage to a geographic area known as a cell and often serve as a point-of-presence (PoP) providing connection to a wide area network such as a Public Switched Telephone Network (PSTN). Often a predetermined subset of the available communication channels is assigned to each radio base station in an attempt to minimize the amount of interference experienced by users of the system. Within its cell, a radio base station can communicate simultaneously with many remote terminals by using different conventional communication channels for each remote terminal

As alorementioned. base stations can act as Pol's, providing connection to one or morn wired commu¬nication systems. Such systems include local data networks, wide area data networks, and PSTNs. Tlius. remote users are provided access to local and/or wide area data services and the local public telephone system. Base stations can also be used to provide local connectivity without direct access to a wired net¬work such as in local area emergency and mobile battlefield communication systems. Base stations can provide connectivity of various kinds as well. In the aforementioned examples, point-to-point communica¬tions where roughly equal amounts of information flow in both directions between two users were assumed. In other applications such as interactive television, information is broadcast to all users simultaneously, and responses from many of the remote units are to be processed at the base stations.
However, conventional wireless communication systems are comparatively spectrally inefficient. In conventional wireless communication systems, only one remote terminal can use any one conventional channel within a cell at any one time. If more than one remote terminal in a cell attempts to use the same channel at the same time, the downlink and uplink signals associated with the remote terminals interfere with each other. Since conventional receiver technology can not eliminate the interference in these combined uplink and downlink signals, remote terminals are unable to communicate effectively with the base station when interference is present. Thus, the total capacity of the system is limited by the number of conventional channels the base station has available, and in the overall system, by to way in which these channels are re-used among multiple cells. Consequently, conventional wireless systems are unable to provide capacity anywhere near that of wired communication systems.

Briefly, the invention comprises antenna arrays and signal processing means for measuring crdriilatm. storing, and using spatial signatures of receivers and transmitters in wireless communication systems to increase system capacity, signal quality, and coverage, and to reduce overall system cost. I he antenna array and signai processing means can be employed at base stations I PoPs) and remote terminals (ienerally there can be different processing requirements at base stations where many signals are being concentrated than at remote terminals where in general only a limited number of communication links are being managed.
As an example, in a wireless local loop application, a particular base station might stet as a PoP for many remote terminals and employ the antenna array and signal processing described herein. Additionally, remote terminals could employ antenna arrays and signal processing to further improve their capacity and signal quality over simpler remote terminals that handle fewer communication links. Herein, the distinction between base stations and remote terminals is that base stations generally act as concentrators connecting

network. While for tne sake of clarity much of the ensuing discussion is couched' in terms of .simple remote terminals that do not, employ antenna arrays, nothing herein should he interpreted as preventing such an application. Thus, while hereafter spatial signatures will he associated primarily with remote terminals, when antenna arrays are employed at remote terminals, hase stations will have associated spatial signatures as well.
Briefly, there are two spatial signatures associated with each remote terminal/ hase station pair on a particular frequency channel, where for the purpose of this discussion it is assumed that only hase stations have antenna arrays. Rase stations associate with each remote terminal in their cell a spatial signature related to how that remote terminal receives signals transmitted to it hy the hase station's antenna array, and a second spatial signature related to how the hase station's receive antenna array receives signals transmitted hy the remote terminal. In a system with many conventional channels, each remote terminal/base station pair has transmit and receive spatial signatures for each conventional channel.
The receive spatial signature characterizes how the hase station antenna array receives signals from the particular remote unit in a particular conventional channel. In one embodiment, it is a complex vector containing responses (amplitude and phase with respect to a reference) of each the antenna element

where 7)r(t) represents noise present in the environment and the receiver. These spatial signatures are calculated (estimated) and stored at each bcise station for each remote terminal in its cell and for each conventional channel. For fixed remote terminals and base stations in stationary environments, the spatial

signatures can be updated infrequently, h general, however, changes in the RF propagation environment, between the base station and the remote terminal can alter the signatures and require that they be updated. .Note that henceforth, the time argument in parentheses will be suppressed: integers inside parentheses will be used solely for indexing into vectors and matrices.
In the previous discussion, temporally matched receivers and transmitters were assumed. If there are differences in the temporal responses, these can be equalized using temporal filtering techniques as is well-known. Furthermore, the channel bandwidths were assumed to be small compared to the center frequency of operation. Large bandwidth channels may require more than one complex vector to accurately describe the outputs as is well known.
When more than one remote terminal wants to communicate at the same time, the signal processing means at the base station uses the spatial signatures of the remote terminals to determine if subsets of them can communicate with the base station simultaneously by sharing a conventional channel. In a system with m receive and m transmit antenna elements, up to m remote terminals can share the same conventional channel at the same time.
When multiple remote terminals are sharing a single conventional uplink channel, the multiple antenna elements at the base station each measure a combination of the arriving uplink signals and noise. These combinations result from the relative locations of the antenna elements, the locations of the remote termi¬nals, and the RF propagation environment. The signal processing means calculates spatial demultiplexing weights to allow the uplink signals to be separated from the combinations of uplink signals measured by the multiple antenna elements.
In applications where different downlink signals are to be sent from the base station to the remote terminals, the signal processing means computes spatial multiplexing weights that are used to produce multiplexed downlink signals, which when transmitted from the antenna elements at the base station result in the correct downlink signal being received at each remote terminal with appropriate signal quality.
In applications where the same signal is to be transmitted from the base station to a large number (more than the number of antenna elements) of remote terminals, the signal processing means computes weights appropriate for broadcasting the signal, covering the area necessary to reach all the remote terminals.
Therefore, the signal processing means facilitates simultaneous communication between a base station and multiple remote terminals on the same conventional channel. The conventional channel may be a frequency channel, a time slot in a time division multiplexed system, a code in a code division multiplexed system, or any combination of the above.
In one embodiment, all elements of a single antenna array transmit and receive radio frequency signals. while in another embodiment the antenna array includes separate transmit antenna elements and receive antenna elements. The number of transmit and receive elements need not be the same. If they are not the same, the maximum number of point-to-point links that can simultaneously be established in one> conventional channel is given by the smaller of the two numbers.

Accordingly the present invention provides a wireless system for calculating uplink signals transmitted from a plurality of remote terminals using a common uplink channel, said system including at least one base station, said system comprising : receiving means at said at least one base station including a plurality of antenna elements and receivers for producing measurements of combinations of said uplink signals from said plurality of remote terminals using said common uplink channel, receive spatial processing means for determining and storing receive spatial signatures for said plurality of remote terminals using said measurements, spatial demultiplexing means using said receive spatial signatures and said measurements to calculate said uplink signals: transmission means including a plurality of transmit antenna elements and transmitters for transmitting multiplexed downlink signals to said plurality of remote terminals using a common downlink channel; transmit spatial processing means for determining and storing transmit spatial signatures for said plurality of remote terminals: and spatial multiplexing means using said transmit spatial signatures and downlink signals to produce said multiplexed downlink signals.
The invention and objects and features thereof will be more readily apparent from the following detailed description together with the accompanying drawings, in which :
Figure 1 is a functional block diagram of a base station in accordance with the invention.
Figure 2 is a functional block diagram of multichannel receivers in the base station.

Figure 3 is a functional block diagram of a spatial demultiplexer in the base station.
Figure 4 is a functional block diagram of a spatial multiplexer for one remote terminal on a particular conventional channel.
Figure 5 is a functional block diagram of a multichannel transmitter in the base station.
Figure 6 is a functional block diagram of a spatial processor in the base station.
Figure 7 is a functional block diagram of a remote terminal with a transponder switch
Figure 8 is a functional block diagram of a remote terminal.
Figure 9 is a schematic diagram of a network system comprised of three base stations and a multiple base station controller.
List of reference numerals
1. base station
2. base station communication link
3. base station controller
4. demodulated received signal
5. spatially separated uplink signals
6. received signal measurements
7. demultiplexing weights
8. data to be transmitted directionally
9. modulated signal to be multiplexed for transmission
10. modulated, spatially multiplexed signals to be transmitted
11. calibration signals to be transmitted
12. multiplexing weights
13. spatial processor
14. multichannel transmitters
15. multichannel receivers
16a. multichannel receiver
16m. multichannel receiver
17a multichannel transmitter
17m multichannel transmitter
18a transmit antenna
18m transmit antenna
19a receive antenna
19m receive antenna
20. spatial demultiplexer
21. adder
22a multipliers
22m multipliers
23 spatial multiplexer
24 signal modulator
25 signal demodulator
26a multipliers
26m multipliers
27. spatial control data
28. spatial parameter data
29. common receiver oscillator
30. receiver control data
31. transmitter control data
32. common transmitter oscillator

33. spatial processor controller .34. active remote tormina! list
35. channel selector
36. remote terminal database .37. spatial weight processor

38. spatial signature processor
39. remote terminal antenna 40. remote terminal dnplexer
41. remote terminal duplexer output
42. remote terminal receiver
43 remote terminal received signal
44. remote terminal received calibration signal
45. remote terminal demodulator
46. remote terminal demodulated data
47. remote terminal keyboard and keyboard controller 48. remote terminal keyboard data
49. remote terminal display data
50. remote terminal display and display controller
51. remote terminal modulator
52. remote terminal data to be transmitted
53. remote terminal modulated data to be transmuted
54. remote terminal transmitter
55. remote terminal transmitter output
56. remote terminal transmitter control data
57. remote terminal receiver control data
58. remote terminal microphone
59. remote terminal microphone signal 60. remote terminal speaker
.61. remote terminal speaker signal 62. remote terminal central processing unit
63. remote terminal transponder switch
64. remote terminal transponder switch control
65. wide area network
66. multiple base station controller ' 67a cell boundary
67b. coll boundary 67c. coll boundary
68. high speed message link
(69. remote terminal

Description of In rent ion
Figure 1 depicts the preferred embodiment, of a lia.se st.auon 1. A base station controller 3 acts as an interface between ba.se station I and any external connection via a base station communication link 2. and serves to coordinate the overall operation of ba.se station 1. In the preferred embodiment, b.ise station controller 3 is implemented with a conventional central processing unit and associated memory and programming.
Incoming or uplink radio transmissions impinge on an antenna array composed of a number, in. of receive antenna elements l!j(a.. ..in) each of whose outputs is connected to one of in multichannel receivers in a bank of phase-coherent multichannel receivers l.">. Multichannel receivers I") have well-matched amplitude and phase responses across the frequency bands of interest, or. as is well known, correction filters are implemented to account for any differences.
The illustrative embodiment describes a conventional frequency division multiple access system. Fach multichannel receiver is capable of handling multiple frequency channels. The symbol A',,, will be used to reference the maximum number of conventional frequency channels that can be handled by the receivers. Depending on the frequencies allocated for the operation of the wireless communication system and the bandwidths chosen for particular communication links. A',.,- could be ;is small ;LS one la single frequency channel) or as large as thousands. In alternate embodiments, multichannel receivers If) might instead .handle multiple time slots, multiple codes, or some combination of these well known multiple access techniques.
In each conventional channel, receive antenna elements 19(a in) each measure a combination of the
arriving uplink signals from the remote terminals sharing this conventional channel. These combinations result from the relative locations of the antenna elements, the locations ot the remote terminals, and the R.F propagation environment, and for narrowband signals are given by equation ('_').
Figure 2 depicts individual multichannel receivers lfi(a ml with antenna --lenient connections.
common local receiver oscillators 2!). one for each conventional frequency channel u, be used ai that base station, and received signal measurements t>. Comnjon local receiver oscillators 2!) ensure that the smnals
from receive antenna elements l'.)(a in) are coherently down-converted to baseband: its A,-, frequencies
are set so that multichannel receivers lb'(a in) extract all A'.-r frequency channels of interest. The
frequencies of common local receiver oscillators 21) are controlled by a spatial processor 13 (figure li via receiver control data 30. In an alternate embodiment, where multiple frequency channels are ail contained in a contiguous frequency band, a common local oscillator is used to downconvert. the entire baud which is then digitized, and digital filters and decitnators extract the desired subset of channels using well known technique:;.
The illustrative embodiment describes a frequency division multiple access system. In a time division multiple access or code division multiple access system, common oscillators 2'.) would be augmented to relay common time slot or mmon code signals respectively from spatial processor l.'l. via receiver control
data 111), to multichannel receivers 16(a ni). In these embodiments, multichannel receivers lb(a m)
perform selection of inventional time division channels or conventional code division channels in addition to down conversion to baseband.
Referring again to Figure I. multichannel receivers 15 produce received -signal measurements (i which are supplied to spatial processor 13 and to a set, of spatial demultiplexers 20. In this embodiment, received signal measurements 6 contain m complex baseband signals for each of A'PC frequency channels.

Figure ti shows a more detailed, block diagram of spatial processor l.'i. Spatial processor l,'! produces
and maintains spatial signatures for each remote terminal for each conventional frequency channel, and
calculates spatial multiplexing and demultiplexing weights for use by spatial demultiplexers 20 and spatial
multiplexers 23. In the preferred embodiment, spatial processor 115 is implemented iismt a conventional central processing unit. Received signal measurements o' go into a spatial signature processor 38 which estimates and updates spatial signatures. Spatial signatures are stored in a spatial signature list m a remote terminal database 36 and are used by channel selector 3F) and spatial weight processor 37. which also produces demultiplexing weights 7 and multiplexing weights 12. A spatial processor controller 33 connects to spatial weight processor 37 and also produces receiver control data 30 transmitter control data 31 and spatial control data 27.
Referring again to Figure 1. spatial demultiplexers 20 combine received signal measurements ti accord¬ing to spatial demultiplexing weights 7. Figure 3 shows a spatial demultiplexer 20 for a simile conventional channel. In this embodiment, arithmetic operations in spatial demultiplexer 20 are carried out using gen¬eral purpose arithmetic chips. In figure 3. Zb(i) denotes the ith component of received signal measurement vector ti for a single conventional channel, and w*r(i) denotes the complex conjugate of the r"' component of the spatial demultiplexing weight vector 7 for a remote terminal using this conventional hannel
For each remote terminal on each conventional channel, the spatial demultiplexer 2:; ompines the inner-product of the spatial demultiplexing weights 7 for the conventional channel with the received signal

channel is available.
For transmission, signal modulators 24 produce modulated signals !) for each remote terminal the ba.se station is transmitting to. and a set of spatial multiplexing weights 12 for each remote, terminal are applied

to the respective modulated singal in spatial multiplexers 23 to produce spatially multiplexed signals to he
transmitted 10 for each of the rn transmit antennas l In the illustrative embodiment the number Nrr of downlink conventional channels is the same a.s the number A',.,, of uplink conventional channels. In other embodiments, there may be different numbers of uplink and downlink conventional channels. Furthermore, the channels may be of dilferent types and bandwidths as is the case for an interactive television application where the downlink is comprised of wideband video channels and the uplink employs narrowband audio/data channels.
Additionally, the illustrative embodiment shows the same number of antenna elements, in. for transmit and receive. In other embodiments, the number of transmit antenna elements and the number of receive antenna elements may be different, up to and including the case where transmit employs only one transmit antenna element in an omnidirectional sense such as in an interactive television application.
Figure 4 shows the spatial multiplexer for one remote terminal on a particular conventional channel. Arithmetic operations in spatial multiplexer 23 are carried out using general purpose arithmetic chips. The component of modulated signals 9 destined for this remote terminal on this conventional channel is denoted by »(,. and w(r(/) denotes the i'h component of spatial multiplexing weight vector 12 for this remote terminal on this conventional channel.
For each remote terminal on each conventional channel, the spatial multiplexer 23 computes t he product of its spatial multiplexing weight vector (from the spatial multiplexing weights 12) with its modulated signal

Modulated and spatially multiplexed signals 10 arc inputs to a bank of in phase coherent multichannel transmitters 14. Multichannel transmitters 14 either have well-matched amplitude and phase r.wponses across the frequency bands of interest, or. as is well known, correction lilters are implemented to account
for any differences. .Figure •"• depicts multichannel transmitters 17(a in) with antenna connections.
common local transmitter oscillators 32. and digital inputs 10. Common local transmitter oscillators 32 ensure that the relative phases of spatially multiplexed signals 10 are preserved during transmission by
transmit antennas 18(a in). The frequencies of common local transmitter oscillators ;i2 are controlled
by sftatial processor 13 (see figure 1) via transmitter control data 31.
In an alternate embodiment, spatial multiplexer 23 uses well known baseband multiplexing techniques to multiplex all the calculated conventional channel signals to be transmitted into a single wideband signal
to be upconverted and transmitted by each of the multichannel transmitters 17(a in). The multiplexing
can be performed either digitally or in analog as appropriate.

1 he illustrative embodiment shows a system with multiple frequency
multiple access or code division multiple access system, common oscillators 32 would he augmented to
relay common time slot or common code signals respectively from spatial processor I.'!, via transmitter
control data 31. to multichannel transmitters 17(a in).
Referring again to figure I. in applications where transmit spatial signatures are required, spatial processor 13 is also able to transmit predetermined calibration signals 11 for each antenna on a particular
conventional downlink channel. Spatial processor l.'i instructs multichannel transmitters I7(a m),
via transmitter control data 31. to transmit predetermined calibration signals 11 in place of spatially multiplexed signals 10 for a particular conventional downlink channel. This is one mechanism used for determining the transmit spatial signatures of the remote terminals on this conventional downlink channel.
In alternate embodiments where well known channel coding techniques are used to encode t he signals to be transmitted to remote terminals, remote terminals employ well known decoding techniques to estimate BERs which are then reported back to the base station on their uplink channel. If these BERs exceed acceptable limits, corrective action is taken. In one embodiment, the corrective active involves reallocating resources by using the same strategy as adding a new user with the exception that the current channel is not acceptable unless the current set of users of that particular channel changes. Additionally, recalibration of the transmit signature for that remote terminal/base station pair is performed when thai conventional channel is available.
Figure 7 depicts the component arrangement in a remote terminal that provides voice communication. The remote terminal's antenna 3!) is connected to a dupiexer 40 to permit antenna 30 to be used for both transmission and reception. In an alternate embodiment, separate receive and transmit antennas are used eliminating the need for dupiexer ■10. In another alternate embodiment where reception and transmission occur on the same frequency channel but at different times, a transmit /'receive i TR) switch is used instead of a dupiexer as is well known. Dupiexer output. II serves as input to a receiver 42. Receiver VI produces a down-converted signal 13 which is the input to a demodulator 45. A demodulated received voice signal til is input to a speaker 00.
Demodulated received control data -4ti is supplied to a remote terminal central processing unit, (12 (CPl). Demodulated received control data -16 is useii for receiving data from base station 1 during call setup and termination, and in an alternate embodiment, for determining the quality (HER) of the signals being received by the remote terminal for transmission back to the base station a-s described above.
Remote terminal ('IT 02 is implemented with a. standard microprocessor. Remote terminal CPU 02 also produces receiver control data. 57 for selecting the- icmuic terminals reception channel, transmitter control data 50 for setting the remote terminal's transmission channel and power ievei. control data to be transmitted 52. and display data -10 for remote terminal display 50. Remote terminal The remote terminal's voice signal to be transmitted 59 from microphone 5IS is input to a modulator%51. Control data to be transmitted 52 is supplied by remote terminal CPU 1)2. Control data to be transmit¬ted 52 is used for transmitting data to base station 1 during call setup and termination as well as for transmitting information during the call such as measures of call quality (e.g.. bit error rates I RER.s)). The modulated signal to be transmitted 53. output by modulator 51. is up-converted and amplified by a trans¬mitter 54. producing a transmitter output signal 55. Transmitter output 55 is then input to dupiexer 40 for transmission by antenna 39.

In an alternate embodiment, the remote terminal provides digital data communication. Demodulated received voice signal til. speaker li(). microphone 5S. and voice signal to be transmitted a!) are replaced by digital interfaces well-known in the art that allow data lo be transmitted to and From an external data processing device (for example, a computer).
Referring again to ligure 7. the remote terminal allows received data i'.\ to be transmitted back to base station 1 via switch t53 controlled by remote terminal CPU 62 through switch control signal 64. In normal operation, switch (iii drives transmitter 54 with modulated signal 53 of modulator 51. When the remote terminal is instructed by base station 1 to enter calibration mode, remote terminal ('IT 62 toggles switch control signal 64. which instructs switch 63 to drive transmitter 54 with received data 43.
Figure 8 shows an alternate embodiment of the remote terminal calibration function. Switch til! of figure 7 is no longer used. Instead, the output of receiver 42 is supplied to remote terminal In an alternate embodiment, special calibration procedures in the remote terminal are not required. In many conventional wireless protocol standards, remote terminals regularly report received signal strength or receive signal quality back the base station. In this embodiment, the received signal strength reports are sufficient to compute the remote terminal's transmit spatial signature, as described below.
Operation of Invention
General Principles Dase Station
In many respects, the spectrally efficient base station shown in ligure 1 behaves much like a standard wireless communication system base station. The primary distinction is that the spectrally efficient base station supports many more simultaneous conversations than it has conventional communication chan¬nels. The conventional communication channels may be frequency channels, time channels, code channels, or any combination of these. The spatial multiplexer/demultiplexer increases the system capacity by al¬lowing muitipie spatial channels on each of these conventional channels. Moreover, by combining signals from multiple receive antennas, the spatial demultiplexer 20 produces spatially separated uplink signals 5 that have substantially improved signal-to-noise, reduced interference, and improved qualify in multinatli invironments compared to a standard base station.

nals and base stations incorporating antenna arrays and spatial signal processing is described. Such systems have application, for example, in providing wireless access to the local PSTN. Information transfers (ur calls) are initiated by either i remote terminal or by communication link 2 through base station controller II. i 'all initialization takes place on a downlink and uplink control channel as is well known in the art. In the
present embodiment the downlink control channel is transmitted using transmission antennas I8(a in).
In an alternate embodiment, the downlink control channel is broadcast from a single, omnidirectional an¬tenna. Base station controller 3 passes the identification of the remote terminal to be involved in the call to spatial processor 115 which uses the stored spatial signatures of that remote terminal to determine, which conventional communication channel the remote terminal should use. The selected channel may already be occupied by several remote terminals, however spatial processor 13 uses the spatial signatures of all of

the remote terminals on that channel to determine that they can share the channel without interference. in a system with m receive and in transmit antenna elements, up to w remote terminals can share the same conventional channel. More generally, the number of point-to-point full-duplex communication links that can occupy the same conventional channel at the same time is given by the smaller of the number of receive and transmit elements.
Spatial processor 13 uses calculated spatial multiplexing and demultiplexing weights fur the selected channel and the remote terminal in question to configure spatial multiplexer 211 and spatial demultiplexer '20. Spatial processor 13 then informs controller 3 of the selected channel. As in a conventional base station, controller 3 then commands the remote terminal (via the downlink control channel) to switch to the selected channel for continued communications. In the event that the remote terminal has power control capabilities, as is well known in the art. controller 3 also commands the remote terminal to adjust its power to an appropriate level based on parameters such as the power levels of the other remote terminals sharing the same conventional channel and the required signal quality for each link as discussed below. At the termination of communications, the remote terminal returns to its idle state where n monitors the downlink control channel awaiting its next call. This frees up that "spatial channel" for another remote terminal.

multichannel receiver 16 given a single unit power narrow hand .signal being transmitted by that particular remote terminal, at that particular frequency.
When the base station controller 1 forwards a call initialization request for a particular remote terminal via link '27. a channel selector 35 searches active remote terminal list 'M to find a conventional communication channel that can accommodate the remote terminal. In the [(referred embodiment, there is a receive active remote terminal list and a transmit active remote terminal list which are used by channel.selector :!5 in forming both a multiplexing and a demultiplexing spatial signature matrix for each conventional channel. For each conventional channel, the columns of the demultiplexing and rows of the multiplexing spatial signature matrices are the stored receive and transmit spatial signatures of each of the remote terminals currently active on (using) that channel plus one more column containing the appropriate spatial signature

where I is a matrix of all ones of the appropriate size and abs{) is elementwise absolute value. Channel selector 35 compares these values against the limits for each of the transmitters for each of the demerits. If any of the average or peak values exceed the acceptable limits, the remote terminal in question is not assigned to the candidate channel. Otherwise, the ability to successfully receive from the remote terminal is checked. In an alternate embodiment, the transmitter limits are used as inequality constraints in an optimization algorithm for calculating transmit weights that meet the specifications given and that also result in the minimum amount of transmitted power possible. If transmit weights satisfying the constraints can not be found, the remote terminal in question is not assigned to the candidate channel. Such optimization algorithms are well known.
To test the uplink, channel selector 35 calculates spatial demultiplexing weights U'rj. using Ai,r. 'lie demultiplexing spatial signature matrix /Ur.P associated with the relevant conventional channel, as given

If all of the diagonal elements of SIXR are above the'desired thresholds based on the signal quality required to be received from each remote terminal, the remote terminal is allowed access to the channel. If the candidate, remote terminal is below its threshold and has thee ability to increase its outout power, the. same computations are again performed for increasing remote terminal power output until either the maximum output power for that remote terminal is reached and the SINR is still insufficient, another remote terminal SINR falls below its threshold in which case its power is increased if possible, or ail thresholds are exceeded. If acceptable remote terminal transmit powers can be found, the remote terminal is granted access to this particular conventional channel, otherwise it is denied access and another conventional channel is checked.
In an alternate embodiment, the calculation of demultiplexing weights is performed using well known optimization procedures with the objective of miniming remote terminal transmit powers subject to estimated signals at the base station meeting or exceeding their minimum desired SIXR's.
Also, in an alternate embodiment, in the case that no conventional channel can be found to accom¬modate the remote terminal, channel selector 35 calculates whether some rearrange.nent of the existing remote terminals among the conventional channels would allow the remote terminal to be

some conventional channel. In this ca.se, the remote terminal wi.ll only he denied •communication at this time if no rearrangement of existing users allows the remote terminal to lie accommodated.
In an alternate embodiment employing frequency division duplexing (FDD), remote terminals are not restricted to being assigned' a lixed conventional channel pair for transmit and receive A sufficiently flexible system architecture is employed where channel selector 35 may choose to assign a particular remote to transmit and receive conventional channels separated by different frequency duplex offsets in order to minimize overall system interference levels.
Spatial multiplexing and demultiplexing weights for remote terminals already using a conventional channel must be recalculated because adding a new remote terminal to that conventional channel may change them significantly. In the preferred embodiment, channel selector 35. having already done the nec¬essary calculations, sends the new spatial multiplexing and demultiplexing weights to the spatial weight processor 37 for use in setting up the spatial multiplexer 23 and demultiplexer 20. In an alternate embod¬iment, spatial weight processor 37 uses the spatial signature matrices sent to it by channel selector 35 to calculate different sets of spatial multiplexing and demultiplexing weights for all of the f-mote terminals on that conventional channel.
Spatial weight processor 37 then sends the new spatial demultiplexing weights to spatial demultiplex¬ers 20 and the new spatial multiplexing weights lo the spatial multiplexers 23 for this conventional channel, updates the active remote terminal list 34, and informs spatial processor controller 33 which in turn informs base station controller 3 of the selected channel. Base station controller 3 then transmits a message to the remote terminal using the downlink, control channel tiiat instructs the remote terminal to switch to the desired conventional channel.
It can be shown from equation (!)) that the multiplexing weight matrices \Vtr have T h.• property:

are the most accurate in the sense of least mean-squared error. It: particular, they most closely match the signals transmitted by the remote terminals given the measurements made at tin; base station by the multiple antenna elements.
Equations (9) and (13) represent only one way to calculate spatial multiplexing and demultiplexing weights. There are other similar strategies that demonstrate properties similar to those shown in equation (16) and described in the previous paragraph. Other well known techniques for calculating weight matrices

Determining Spatial Signatures
As shown in figure ti. spatial processor 13 also contains a spatial signature processor 38 Tor finding the spatial signatures of the remote terminals. Fn the illustrative embodiment, spatial signature processor 38 uses the calibration techniques described in copending U.S. patent application 08/234.747.
In the illustrative embodiment, each remote terminal is capable of entering a.calibration mode in which the signal received by the remote terminal 43 is transmitted back to base station 1 Referring to figure 7. this function is provided by switch 63 controlled by remote terminal (TV (>2 through switch control signal 64.
To determine the transmit and receive spatial signatures of a remote terminal, spatial signature pro¬cessor 38 commands the remote terminal to enter calibration mode by transmitting a command to it on the downlink channel. This command is generated by base station controller 3. based on a request from spatial processor controller 33. and modulated by signal modulators 24. Spatial signature processor 3S then transmits predetermined calibration signals 11. on the conventional channel occupied by the remote
terminal, by instructing multichannel transmitters 17(a in) via transmitter control data 31 and spatial
processor controller 33. In the present embodiment, the ?n signals (for each antenna) among the prede¬termined calibration signals 11 are different frequency complex sinusoids. In another embodiment, the predetermined calibration signals 11 are any known, distinct, signals.
The remote terminal shown'm figure 7 transmits back the signal received at the remote terminal. This transponded signal is received by multichannel receivers 15) in base station 1 shown in figure 1 and supplied to spatial signature processor 38 shown in figure 6. In one embodiment described in patent application 08/234.747. spatial signature processor 38 computes the receive and transmit spatial signatures of the remote terminal from the received signal measurements b and predetermined calibration signals II as follows. Time samples of the received data are stored in an tn by n data matrix Z which IN the absence of noise and parameter offsets is given by

well known techniques are used to account, for noise present in the system and parameter variations such as oscillator frequency offsets.
Spatial signature processor 38 stores the new spatial signatures in remote terminal database 36. Upon completion, spatial signature processor 38 commands the remote terminal to exit calibration mode by transmitting a command to it on the downlink channel.
In one alternate embodiment, computation of remote terminal transmit spatial signatures can be per¬formed directly by the remote terminals. This embodiment of the remote terminal is shown in figure H. In calibration mode, spatial signature processor .'58 transmits predetermined calibration signals 11. on the conventional channel to be calibrated by the remote terminals, as before. Remote terminal CPU 62 uses received calibration signals 11 and the known transmitted waveforms to compute ihe remote terminal's transmit spatial signature using the same techniques used by spatial signature processor 3S in the previous embodiment. The computed transmit spatial signature is transmitted back to base station 1 through mod¬ulator 51 and transmitter 51 as control data to be transmitted 52. When received by base station 1. spatial signature processor 38 stores the new transmit spatial signature in remote terminal database 3(5. Since each remote terminal performs the transmit spatial signature calculation independently, this arrangement allows multiple remote terminals to compute their own transmit spatial signature simultaneously on the same conventional channel. In this embodiment, remote terminal receive spatial signatures are computed by spatial signature processor 38 in the same manner as in the previous embodiment.
Using these techniques, spatial signature processor 38 can measure a remote terminal transmit and receive spatial signatures for a particular channel any time that channel is idle. I lie Hficiency ot these calibration techniques allow spatial signature processor 38 to update the spatial signatures of numerous remote terminals for a particuiar channel while occupying that channel for only a short time.

receive spatial signatures for remote terminals. A further example is decision-directed feedback techniques, also well known in the art. where receive data is demodulated and then remodulated to produce an estimate of the original modulated signal. These techniques allow receive spatial signatures to lie estimated even when multiple remote terminals are occupying a single conventional channel.
In some RF environments, transmit spatial signatures for remote terminals can be calculated explicitly, as is well known, using knowledge of the remote terminal locations and the locations and directivity patterns of the base station transmit antennas. This requires no special capability on the part of the remote terminal.
If the remote terminal has the ability to measure and report the strength of the signal it is receiving, ihe system can use this information to derive transmit spatial signatures! albeit in a less efficient manner than the embodiment shown in figure 7 when the has full transponder capabilities, or the

' embodiment shown in figure S where the remote terminal directly computes its transmit spatial signature The transmit spatial signature is determined based solely on received- signal power reports Irom the remote terminal as follows. First, spatial signature processor 38 transmits identical unit power signals from two of the rn antenna elements at a time. Spatial signature processor 38 then changes the amplitude and phase of one of the two signals until the remote terminal reports that it is receiving no signal. The set of complex weights for antenna elements 2 through m required to null a unit power signal from element I are changed in sign and inverted to produce the transmit spatial signature for the remote terminal.
In yet another embodiment, the system can be designed to continuously update the spatial signatures of the remote terminals in a "closed loop" manner. This is done to account for the time variation of spatial signatures due to. for example, motion of the remote terminal or changes in the RF propagation conditions. To do this, both the base station and the remote terminal periodically transmit predetermined training sequences. Each remote terminal currently active on a particular channel is assigned a different predetermined training sequence and is given the training sequences for all other remotes currently active on that particular channel. In one embodiment, the different training sequences are orthogonal in the sense that the inner product of any two of the training sequence waveforms is zero. Fach time the training sequences are transmitted, each remote terminal calculates how mucti of each training sequence it has received using well known techniques, and transmits this information to the ba.se station.
In the illustrative embodiment, the base station uses the receiver outputs and knowledge of the trans¬mitted waveforms to calculate the remote terminal receive spatial signatures. In another embodiment, the base station calculates how much of each remotely transmitted training sequence has come through on each output of the spatial demultiplexer, expressed as a complex vector of coupling coefficients. Knowledge of these coupling coefficients allows the currently active receive and transmit spatial signatures to be corrected so as to reduce mutual interference using well know techniques.
Finally, in systems that use time division duplexing (TOD) for lull-duplex communications, as is well known in the art. the transmit and receive frequencies are the same. In this case using the well known principle of reciprocity, the transmit and receive spatial signatures are directly related. Thus, this embodiment determines only one of the signatures.: for example the receive spatial signature, and the her in this case the transion spanai signature, is calculated trom the tirst (receive) spatial signature and knowledge of the relative phase and amplitude characteristics of multichannel receivers 15 and multichannel transmitters 14.
Network Luvel Spatial Processing
In the embodiment illustrated herein, the spatial processor tor each base station in the cellular-like wireless communication system operates independently to maximize the number of communication channels in the immediate cell. However, significant system capacity improvements can be realized if the spatial processor from each base .station communicates with and coordinates its elforts with the spatial processors from other nearby cells. A specific embodiment is shown in figure 9..
A multiple base station controller 66 acts as the interface between the wide area network 65 through link 68 and base stations i (a.b.c) via base station communication links 'I (a.b.c). Fach base station is responsible for providing coverage to a number of remote terminals. In one embodiment, each remote terminal is assigned to only one base station thus defining cell boundaries ti7 (a.b.c) within which all

remotes attached to a particular base station are located. [sers equipped with remote terminals 69. are' ' identified by a boxed "R" in the figure.
Each spatial processor contained in base stations 1 (a.b.c) measures and stores the spatial signatures of the remote terminals in its cell and also of the remote terminals in adjacent cells. The determination of spatial signatures of the remote terminals in adjacent cells is coordinated by multiple base station con¬troller 66 through base station communication links 2 (a.b.c). Through base station communication links 2 (a.b.c) and multiple base station controller 66. spatial processors in base stations 1 a.b.c, from adjacent cells inform each other of which remote terminals they are communicating with on which conventional channels. Each spatial processor includes the spatial signatures of remote terminals that are currently active in adjacent cells to form extended transmit and receive spatial signature matrices A and A which are sent to all the adjacent base stations. The channel selectors in each ba.se station, using these extended spatial signature matrices, jointly assign remote terminals to each conventional channel in each of base stations 1 (a,b,c).
The resultant weight matrices Wtx and \Vrr for each base station are then calculated using extended spatial signature matrices Arh and .-Ur. In calculating the weights, the objective is to minimize the signal transmitted to and received from the adjacent cell's active remote terminals, thereby allowing many more remote terminals to simultaneously communicate.
In an alternate embodiment, multiple base station controller 66 assigns remote terminals requesting access to base stations dynamically using a list of active remote terminal/ base station/conventional channel links, the associated remote terminal databases, and the particular requirements tor the link to be assigned. Additionally, remote terminals can employ multiple (directional! transmit and receive antennas, to facilitate directive links to multiple nearby base stations as instructed by multiple base station controller 6(5 to further increase system capacity.

Alternate Embodiments
In one alternate embodiment, transmission antennas 18(a m I and reception antennas l!)(a m )
at base station 1 are replaced by a single array of m antennas. Each element in this array is attached to both its respective component of multichannel transmitters 14 and its respective component of multichannel receivers 15 by means of a duplexer.

In another alternate embodiment, signals on the uplink control channel may he processed in rea time using the spatial processing described in copending patent application 07/806.605). This would allow multiple remote terminals to request a communication channel at the same time.
In yet another embodiment for applications involving data transfer of short bursts or packets of data, no separate uplink control channel is required and the system may service requests for communication and other control functions during control time intervals that are interspersed with communications intervals.
As stated above, many techniques are known for measuring the spatial signatures of the remote terminal radios and using these spatial signatures to calculate multiplexing and demultiplexing weights that will allow multiple simultaneous conversations and/or data transfers on the same conventional communication channel.
While the above description contains many specificities, these should not be construed as limitations on the scope of the invention, but rather as an exemplification of one preferred embodiment thereof. Many other variations are possible. .Accordingly, the scope of the invention should be determined not by the illustrated embodiments, but by the appended claims and their legal equivalents.

WE CLAIM :
A wireless system for calculating uplink signals transmitted from a plurality of remote terminals using a common uplink channel, said system including at least one base station (1). said svstem comprising : receiving means at said at least one base station (1) including a plurality of antenna elements (19a-m) and receivers (15) for producing measurements of combinations of said uplink signals from said plurality of remote terminals using said common uplink channel, receive spatial processing means (13) for determining and storing receive spatial signatures for said plurality of remote terminals using said measurements, spatial demultiplexing means (20) using said receive spatial signatures and said measurements to calculate said uplink signals; transmission means including a plurality of transmit antenna elements (18a-m) and transmitters (14) for transmitting miiftinlfived downlink signals to said plurality of remote terminals using a common downlink channel; transmit spatial processing means (13) for determining and storing transmit spatial signatures for said plurality of remote terminals; and spatial multiplexing means (23) using said transmit spatial signatures and downlink signals to produce said multiplexed downlink signals.
The wireless system as claimed in claim 1, wherein said receive spatial processing means (13) comprises: a spatial signature list (36) comprising a receive spatial signature for each remote terminal in said plurality of remote terminals and said common uplink channel, receive spatial signature determining means (38) for determinine said receive

spatial signatures, and a receive channel selector (35) utilizing said receive spatial signatures to determine whether said common uplink channel can be further shared by an additional remote terminal.
The wireless system as claimed in claim 2, wherein said receive spatial processing means (13) comprises: a receive spatial weight processor (37) for calculating spatial demultiplexing weights for said plurality of remote terminals, said spatial demultiplexing weights heing utilized by said spatial demultiplexing means to calculate said uplink signals.
The wireless system as claimed in claim 3, wherein said receive spatial weight processor determines said spatial dermiltinl*»Ying weights as the columns of matrix Wn as follows:

where ()* denotes the complex conjugate transpose of a matrix, R„n is the
noise covariance matrix of said receiving means, Pr is the diagonal matrix
of transmit powers of the remote terminals in said plurality of remote
terminals, and Ab is a demultiplexing spatial signature matrix whose
columns are said receive spatial signatures for said plurality of remote
terminals and said common uplink channel.
The wireless system as claimed in claim 1, wherein said common uplink channel is one of a plurality of unlink- channel and wherein said receive spatial processing means (13) comprises: an active remote terminal list (34) comprising a list of remote terminals assigned to at least one channel of said plurality of uplink channels, a spatial signature list (36)

comprising a receive spatial signature for each remote terminal of said plurality of remote terminals and each channel of said plurality of uplink channels, receive spatial signature determining means (38) for determining said receive spatial signatures in said spatial signature list a receive channel selector (35) using said active remote terminal list (34) and said spatial signature list (36) to determine assignments of each remote terminal in said active remote terminal list (34) to at least one of the channels of said plurality of unlink channels, and a receive spatial weight processor (37) for calculating spatial demultiplexing weights for each of the terminals in said active, remote, terminal list and each channel of said plurality of uplink channels assigned to at least one of the terminals in said active remote terminal list, said spatial demultiplexing weights being utilized by said spatial demultiplexing means (20) to calculate said uplink signals.
The wireless system as claimed in claim I, wherein said common uplink channel is one of a plurality of uplink channels, said at least one base station (1) is one of a plurality of base stations, said receive spatial processing means (13) is one of a plurality of receive spatial processing means, each base station in said plurality of base stations having a corresponding receive spatial processing means in said plurality of receive spatial processing means, each receive spatial processing means in said plurality of receive spatial processing means comprising: an active remote terminal list (34) comprising a list of remote terminals assigned to at least one channel of said plurality of uplink channels, a spatial signature list (36) comprising a receive spatial signature for each remote

terminal of said plurality of remote terminals and each channel of said plurality of uplink channels, receive spatial signature determining means (38) for determining said receive spatial signatures in said spatial signature list (36), and a receive spatial weight processor (37) for calculating spatial demultiplexing weights for each of the terminals in said active remote terminal list (34) and each channel of said plurality of uplink channels assigned to at least one of the terminals in said active remote terminal list (34). said spatial demultiplexing weights being utilized by said spatial demultiplexing means (20) to calculate said uplink signals, said system further comprising: joint channel selector means (35) for jointly determining assignments of each remote terminal in each said active remote terminal list (34) to at least one of the channels of said plurality of uplink channels and to at least one of base stations of said plurality of base stations, and communication means (66) for communicating the status of said assignments between each base-station in said plurality of base stations and said joint channel selector means.
The wireless system as claimed in claim 1, wherein said spatial demultiplexing means calculates spatial demultiplexing weights for said common uplink channel as the columns of a matrix Wn as follows:
where ()* denotes the complex conjugate transpose of a matrix, Rnn is the noise covariance matrix of said receiver means, Pr is the diagonal matrix of transmit powers of the remote terminals in said plurality of remote terminals. and Abr is a demultiplexing spatial signature matrix whose

columns are said receive spatial signatures for said plurality of remote terminals and said common uplink channel, said spatial demultiplexing means using said spatial demultiplexing weights to calculate said uplink signals.
The wireless system as claimed in claim 1, wherein said system comprises a transponder co-located with each remote terminal of said plurality of remote terminals and wherein receive spatial processing means (13) determines said receive spatial signatures using signals transponded from at least one of the transponders.
The wireless system as claimed in claim 1, wherein each remote terminal of said plurality of remote terminals has a transponder and said receive spatial processing means (13) determines said receive spatial signatures using signals transponded from at least one of the transponders.
The wireless system as claimed in claim 1, wherein said receive spatial processing means (13) determines said receive spatial signatures using the known location and directivity of said antenna elements (19a-m). and estimates of the directions of arrival of said uplink signals from said plurality of remote terminals.
The wireless system as claimed in claim 1, wherein said receive spatial processing means (13) determines said receive spatial signatures using the known location and directivity of said antenna elements and the known location of said plurality of remote terminals.

The wireless system as claimed in claim 1, wherein said uplink signals have predetermined modulation format parameters, and said receive spatial processing means (13) determines said receive spatial signatures using said predetermined modulation format parameters of said uplink signals from said plurality of remote terminals.
The wireless system as claimed in claim 1, wherein said receiving means and said transmission means share common antenna elements using duplexers.
The wireless system as claimed in claim 1, wherein said receiving means and said transmission means share common antenna elements using transmit/receive switches.
The wireless system as claimed in claim 1, wherein said common uplink channel is one of a plurality of uplink channels, said common downlink channel is one of a plurality of downlink channels, and wherein said receive spatial processing means (13) and said transmit spatial processing means (13) comprise: an active remote terminal list (34) comprising a list of remote terminals assigned to at least one of the channels of said plurality of uplink channels and remote terminals assigned to at least one of the channels of said plurality of downlink channels, a spatial signature list (36) comprising a receive spatial signature for each remote terminal of said plurality of remote terminals and each channel of said plurality of uplink channels, and a transmit spatial signature for each remote terminal of said plurality of remote terminals and each channel of said

plurality of downlink channels, receive spatial signature determining means (38) for determining said receive spatial signatures, transmit spatial signature determining means (38) for determining said transmit spatial signatures, and a channel selector (35) using said active remote terminal list (34) and said spatial signature list to determine assignments of each remote terminal in said active remote terminal list (34) to at least one of the channels of said plurality of uplink channels and at least one of the channels of said plurality of downlink channels.
16. The wireless system as claimed in claim 15. wherein said receive spatial processing means (13) and said transmit spatial processing means (13) further comprise: a receive spatial weight processor (37) for calculating spatial demultiplexing weights for each of the terminals in said active remote terminals list to which a uplink channel is assigned and for each channel of said plurality of uplink channels assigned to at least one of the terminals in said active remote terminal list, said spatial demultiplexing weights being utilized by said spatial demultiplexing means to calculate said uplink signals, and a transmit spatial weight processor (37) for calculating spatial multiplexing weights for each of the terminals in said active remote terminal list to which a downlink channel is assigned and each channel of said plurality of downlink channels assigned to at least one of the terminals in said active remote terminal list, said spatial multiplexing weights being utilized by said spatial multiplexing means to produce said multiplexed downlink signals.

17. The wireless system as claimed in claim 1, wherein said at least one base station (1) is one of a plurality of base stations, said common uplink channel is one of a plurality of uplink channels, said common downlink channel is one of a plurality of downlink channels, said receive spatial processing means (13) is one of a plurality of receive spatial processing means, said transmit spatial processing means (13) is one of a plurality of transmit spatial processing means, each base station in said plurality of base stations having a corresponding receive spatial processing means in said plurality of receive spatial processing means and a corresponding transmit spatial processing means in said plurality of transmit spatial processing means, each receive spatial processing means in said plurality of receive spatial processing means and each transmit spatial processing means in said plurality of transmit spatial processing means comprising: an active remote terminal list (34) comprising a list of remote terminals assigned to at least one of the channels of said plurality of uplink channels and remote terminals assigned to at least one of the channels of said plurality of downlink channels, a spatial signature list (36) comprising a receive spatial signature for each remote terminal of said plurality of remote terminals and each channel of said plurality of uplink channels, and a transmit spatial signature for each remote terminal of said plurality of remote terminals and each channel of said plurality of downlink channels, receive spatial signature determining means (38) for determining said receive spatial signatures, transmit spatial signature determining means (38) for determining said transmit spatial signatures, a receive spatial weight processor (37) for calculating spatial demultiplexing weights for each of the terminals in said active remote

terminal list to which a uplink channel is assigned and each channel of said plurality of uplink channels assigned Lo at least one of the terminals in said active remote terminal list, said spatial demultiplexing weights being utilized by said spatial demultiplexing means to calculate said uplink signals, and a transmit spatial weight processor (37) for calculating spatial multiplexing weights for each of the terminals in said active remote terminal list to which a downlink channel is assigned and each channel of said plurality of downlink channels assigned to at least one of the terminals in said active remote terminal list, said spatial multiplexing weights being utilized by said spatial multiplexing means to produce said multiplexed downlink signals, said system further comprising: joint channel selector means (35) for jointly determining assignments of each remote terminal in each said active remote terminal list to at least one of the channels of said plurality of uplink channels, to at least one of the channels of said plurality of downlink channels and to at least one of the base stations of said plurality of base stations, and communication means (66) for communicating said assignments between each base station in said plurality of base stations and said joint channel selector means.
The wireless system as claimed in claim 1, wherein said spatial multiplexing means determines spatial multiplexing weights for said common downlink channel as the rows of a matrix W x as follows:

where () denotes the complex conjugate transpose of a matrix, Sv, is the diagonal matrix of amplitudes of said downlink signals, and Ab is a

signatures for said plurality of remote terminals and said common downlink channel, and wherein said spatial multiplexing means utilizes said spatial multiplexing weights to produce said multiplexed downlink, signals.
The wireless system as claimed in claim 1, wherein said system comprises a transponder co-located with each remote terminal of said plurality of remote terminals and wherein transmit spatial processing means (13) determines said transmit spatial signatures using signals transponded from at least one of the transponders.
The wireless system as claimed in claim 1, wherein each remote terminal in said plurality of remote terminals has a transponder, and wherein said transmit spatial processing means (13) determines said transmit spatial signatures using signals transponded from at least one of the transponders.
The wireless system as claimed in claim 1, wherein said downlink signals have predetermined modulation format parameters, and said transmit spatial signatures are determined by the corresponding terminals in said plurality of remote terminals using the predetermined modulation format parameters of said downlink signals.
The wireless system as claimed in claim 1, wherein said transmit spatial processing means (13) determines said transmit spatial signatures using the known location and directivity of said transmit antenna elements and estimates of directions of arrival of said uplink signals from said plurality of remote tenninals.

23. The wireless system as claimed in claim I. wherein said downlink signals
and said uplink signals are transmitted on the same radio frequency and
said transmit spatial processing means (13) determines said transmit
spatial signatures by calculating them directly from said receive spatial
signatures.
24. The wireless system as claimed in claim I, wherein said transmit spatial
processing means (13) determines said transmit spatial signatures using
the known location and directivity of said antenna elements (18a-m) and
the known location of said plurality of remote terminals.
25. A wireless system for calculating uplink signals transmitted from a
plurality of remote terminals using a common uplink channel
substantially as herein described with reference to the accompanying
drawings.

Documents:

1593-mas-1995 abstract.jpg

1593-mas-1995 abstract.pdf

1593-mas-1995 claims.pdf

1593-mas-1995 correspondence-others.pdf

1593-mas-1995 correspondence-po.pdf

1593-mas-1995 description(complete).pdf

1593-mas-1995 drawings.pdf

1593-mas-1995 form-1.pdf

1593-mas-1995 form-26.pdf

1593-mas-1995 form-4.pdf

1593-mas-1995 petition.pdf

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Patent Number

193616

Indian Patent Application Number

1593/MAS/1995

PG Journal Number

08/2007

Publication Date

23-Feb-2007

Grant Date

07-Dec-2005

Date of Filing

05-Dec-1995

Name of Patentee

ARRAYCOMM, INC.,

Applicant Address

125 NICHOLSON LANE, SAN JOSE, CALIFORNIA 95134

Inventors:

#	Inventor's Name	Inventor's Address
1	CRAIG H. BARRATT	NE1060 LAKEVIEW WAY, REDWOOD CITY, CALIFORNIA 94062
2	DAVID M. PARISH	122 HIGH PARK BOULEVARD, AMHERST, NEW YORK 14226
3	RICHARD H. ROY III	3351 SHADY SPRING LANE, MOUNTAIN VIEW, CALIFORNIA 94040

PCT International Classification Number

H04Q7/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA