Source: https://patents.google.com/patent/WO1998018272A1/en
Timestamp: 2019-05-23 03:43:57
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WO1998018272A1 - Spectrally efficient high capacity wireless communication systems with spatio-temporal processing - Google Patents
Spectrally efficient high capacity wireless communication systems with spatio-temporal processing Download PDF
WO1998018272A1
WO1998018272A1 PCT/US1997/019172 US9719172W WO9818272A1 WO 1998018272 A1 WO1998018272 A1 WO 1998018272A1 US 9719172 W US9719172 W US 9719172W WO 9818272 A1 WO9818272 A1 WO 9818272A1
PCT/US1997/019172
1996-10-23 Priority to US08/735,520 priority
1996-10-23 Priority to US08/735,520 priority patent/US5828658A/en
1997-10-17 Application filed by Arraycomm, Inc. filed Critical Arraycomm, Inc.
1997-10-17 Priority claimed from EP97913745.2A external-priority patent/EP0932986B1/en
1998-04-30 Publication of WO1998018272A1 publication Critical patent/WO1998018272A1/en
2007-09-11 First worldwide family litigation filed litigation Critical https://patents.darts-ip.com/?family=27499764&utm_source=google_patent&utm_medium=platform_link&utm_campaign=public_patent_search&patent=WO1998018272(A1) "Global patent litigation dataset” by Darts-ip is licensed under a Creative Commons Attribution 4.0 International License.
A wireless system comprising a network of base stations (1) for receiving uplink signals transmitted from a plurality of remote terminals and for transmitting downlink signals to the remote terminals using a plurality of channels including a plurality of antenna elements (19) at each base station for receiving uplink signals, a plurality of antenna elements (18) at each base station for transmitting downlink signals, a signal processor (13) at each base station connected to the receiving antenna elements (19) and to the transmitting antenna elements (18) for determining spatio-temporal multiplexing and demultiplexing functions for each remote antenna for each channel, and a multiple base station network controller for optimizing network performance, whereby communication between the base stations and the remote terminals in each channel can occur simultaneously.
SPECTRALLY EFF I CI ENT H I GH CAPACI TY WI RELESS COMMUN I CAT I ON SYSTEMS WI TH SPAT IO-TEMPORAL PROCESS I NG Cross Reference to Related Applications
This application is a continuation-in-part of co-pending U.S. patent application Serial No. 08/375,848 filed 20 January 1995 for Spectrally Efficient High Capacity Wireless Communication Systems, which in turn is a continuation-in-part of U.S. patent applications Serial No. 07/806,695 filed 12 December 1991 for Spatial Division Multiple Access Wireless Communication Systems and Serial No. 08/234,747 filed 28 April 1994 for Method and Apparatus for Calibrating Antenna Arrays.
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 a channel. In conventional communication systems, the channels are designed to be separate or non-overlapping (in time, frequency and/or code) this will be referred to herein as conventional channels. Herein, the channels share a common resourse, they may be non-overlapping, partially overlapping or full overlapping. 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 pre-determined 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.
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 the 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.
In the co-pending parent U.S. patent application No. 08/375,848 entitled "Spectrally Efficient High Capacity Wireless Communication Systems" , filed 20 January 1995, we have previously disclosed using antenna arrays and signal processing to separate combinations of received (uplink) signals. We also disclosed using transmit spatially multiplexed downlink signals. The result is an increase in spectral efficiency, capacity, signal quality, and coverage of wireless communication systems. Capacity is increased by allowing multiple users to simultaneously share the same communication channel within a cell without interfering with one another, and further by allowing more frequent reuse of the same channel within a geographic area covering many cells. Signal quality and coverage area are improved through appropriate processing of signals received from and transmitted by multiple antenna elements. Moreover, a goal of invention described in the parent application No. 08/375,848 and herein is to provide capacity gains by dynamically allocating channels among base stations and remote terminals.
Briefly, the invention of the parent application No. 08/375,848 comprises antenna arrays and signal processing means for measuring, calculating, storing, and using spatial signatures of receivers and trans- mitters in wireless communication systems to increase system capacity, signal quality, and coverage, and to reduce overall system cost. The antenna array and signal processing means can be employed at base stations (PoPs) and remote terminals. Generally 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.
Briefly, as described in the parent application No. 08/375,848, there, are two spatial signatures associated with each remote terminal/base station pair on a particular frequency channel, where for the purpose of this discussion it is assumed that only base stations have antenna arrays. Base stations associate with each remote terminal in their cell a spatial signature related to how that remote terminal receives signals transmitted to it by the base station's antenna array, and a second spatial signature related to how the base station's receive antenna array receives signals transmitted by the remote terminal. In a system with many channels, each remote terminal/base station pair has transmit and receive spatial signatures for each channel.
The receive spatial signature characterizes how the base station antenna array receives signals from the particular remote unit in a particular channel. In one embodiment, it is a complex vector containing responses (amplitude and phase with respect to a reference) of each the antenna element receivers., i.e., for an m-element array, hr = [hi, hr, . . . , h-]T , (1) where hj. is the response of the ith receiver to a unit power transmitted signal from the remote terminal. Assuming that a narrowband signal sr(t) is transmitted from the remote terminal, the base station receiver outputs at time t are then given by xr(t) = hrsr(t - τ) + nr(t) , (2) where τ accounts for the mean propagation delay between the remote terminal and the base station antenna array, and nr(t) represents noise present in the environment and the receivers.
In the parent application No. 08/375,848, the transmit spatial signature characterizes how the remote terminal receives signals from each of the antenna array elements at the base station in a particular channel. In one embodiment, it is a complex vector containing relative amounts (amplitude and phase with respect to a reference) of each the antenna element transmitter outputs that are contained in the remote terminal receiver output, i.e., for an m-element array, ht = [ht ι, ht 2, . . . , hr]τ, (3) where h. is the amplitude and phase (with respect to some fixed reference) of the remote terminal receiver output for a unit power signal transmitted from the ith element in the base station array. Assuming that a vector of complex signals st(t) = [stι(t), . . . , stm(t)]τ were transmitted from the antenna array, the output of the remote terminal receiver would be given by zt(t) = hj t(t - τ) + nt(t), (4) where nt(t) represents noise present in the environment and the receiver. These spatial signatures are calculated (estimated) and stored at each base station for each remote terminal in its cell and for each channel. For fixed remote terminals and base stations in stationary environments, the spatial signatures can be updated infrequently. In 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 parent application No. 08/375,848, 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 channel. In a system with m receive and m transmit antenna elements, up to m remote terminals can share the same channel at the same time.
Therefore, in the parent application No. 08/375,848, the signal processing means facilitates simultaneous communication between a base station and multiple remote terminals on the same channel. The 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.
When there are wideband channels and/or when there is significant delay spread or scattering, it is well known to use time equalization, and in the parent application No. 08/375,848, it is assumed that such time equalization, if required, is carried out after spatial demultiplexing. Channelization in FDMA (or CDMA) systems is the filtering to separate out the frequency (or code) channels, and is carried out before spatial processing. So decoupling the the spatial processing from the temporal processing such as equalization and channelization is most likely not optimal, and there may be performance advantages to combining the spatial and temporal processing. Thus there is a need in the art for methods and apparatus to define spatial and temporal processing together as a single spatio-temporal processing step, and for methods and apparatus for carrying out such spatio-temporal processing.
In applications where different downlink signals are to be sent from the base station to the remote terminals, the signal processor computes spatio-temporal 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.
The invention and objects and features thereof will be more readily apparent from the following detailed description together with the figures and appended claims. Formulation and Notation
The receive spatio-temporal signature characterizes how the base station antenna array receives signals from the particular remote unit in a particular channel. In one embodiment, it is a matrix containing impulse responses of the antenna element receivers as described below.
Assume that a signal sr(t) is transmitted from the remote terminal. Let m be the number of antennas and associated receivers at the base station. Then, in one embodiment the TO base station receiver outputs, at time t can be expressed as
-(<) = hr β*'(< - r) + nr( (5)
and hr is the channel response matrix and is in this embodiment assumed to be accurately characterized by a finite impulse response filter. The mean propagation delay between the remote terminal and the base station antenna array is denoted by r, T is the sampling time and is in this embodiment assumed to satisfy Nyquist's well known sampling theorem, Mr is the length of the channel response, and nr(t) represents noise present in the environment and the receivers. The channel response at antenna element receiver i, is given by the row vector hr(i). The channel response matrix is the collection of the individual channel responses
Mi) hr = (7) hr(m)
If the impulse response of the communication channel, antenna elements, receiver and transmitter filters is of length Mr , then the impulse response is equal to the channel response matrix, hr. If the impulse response is of longer duration, the channel response matrix, hr, is an approximation of the impulse response and the resulting error is then incorporated in the noise term nr(t). In one embodiment, the time-delayed receiver outputs, here termed the spatio-temporal receive vector, zr(t), is modeled by xr(t)
Xr(* - T) zr(t) = = Hrs^+L - 1 (t - τ) + er(t) . (8) xr(t - T(Lr - l)) where Lr is the length of a sliding window
The mLr by ( r + Lτ — 1) matrix Hr is called the receive spatio-temporal signature for the remote terminal transmitting sr(t) at the base station receiving zr(t) on a particular channel.
When a plurality of remote terminals are active on the same channel, the individual receive spatio- temporal signatures are collected in the demultiplexing spatio-temporal signature matrix, 7ir. For each channel, 7ir, is formed from the individual spatio-temporal receive signatures
Hr = [Hr, Hr , • • ' i H"'], (10) where HJ. is the receive spatio-temporal signature, as shown in equation (9), for ith remote terminal currently active on the channel and nr is the total number of remote terminals on the channel.
Note that when the channel response length is one, Mr = 1, and the sliding window length is also one, Lr = 1, this spatio-temporal signature corresponds to the spatial signature as described in our co-pending U.S. patent application No 08/375,848 entitled "Spectrally Efficient High Capacity Wireless Communication Systems" , filed 20 January 1995. For this case, the channel response matrix, hr, is a column vector and the receive vector has the form zr(t) = hrSr(t - r) + nr(t) . (11)
This is an appropriate model for narrow band communication signals in a propagation environment with limited time-delay spread. For this case, spatial processing may be used in designing a high capacity wireless communication system as described in our co-pending U.S. patent application No 08/375,848 entitled "Spectrally Efficient High Capacity Wireless Communication Systems" , filed 20 January 1995. Another special case of the model above is obtain by letting the number of antennas be equal to one, TO = 1, and letting the sliding window length also be one, Lr = 1. The single receiver output is then given by
Zr(t) = r(l)s?'(t - τ) + nr(t) (12)
This model corresponds to the often used discrete time representation of a time dispersive communication channel. The channel is modeled by a finite impulse response filter of length r. For this case, temporal processing may be applied to counter act the effects of the communication channel. How to apply such temporal processing for the single antenna case is well known in the art.
Let the matrix h< be the channel response matrix from the base station transmitters to the remote terminal. The ith row of the matrix h« is the channel response from transmitter i, to the remote terminal. The maximum length of the channel responses is Mt. If the impulse response of the communication channel, antenna element, transmit and receive filters is of length t , then the impulse response of the channel is equal to the channel response. If the impulse response is of longer duration, the channel response is an approximation of the impulse response matrix. Let su t) be the complex signal transmitted from the zth base station antenna and let
The remote terminal receiver output, zt(t), is now given by zt(t) = [hftl) • • • J(Mt)} s > (t - r) + nt(t) (14) where
h( = [ht(l), h((2), . . . , h,( ()] , (15)
1)T) when the signals st(t) are transmitted from the base station antenna array. The term nt(t) represents noise and interference present in the environment and the receiver and model errors.
Consider now the case when the signal st(t) at the base station is constructed from a scalar signal. d(t), st(t) = W* txdL<(t) (16) where W^ is the Lt x m multiplexing weight matrix composed of complex scalars, (•)* is the complex conjugate transpose of a matrix, and d(t) d*' (t) = (17) d(t - (Lt - l)T) The following relation then holds
Use equation (18) above in equation (14) to express the signal received at the terminal zt(t) in terms of the signal d(t) sent from the base station
W, 0 ... o
0 W tx . . . 0 zt(t) = [hJ(l) - - - (Mt)} d «+£,-ι^ _ r) + nt(t) (1Q)
0 0 0 o w;
It is straight forward to rewrite equation (19) into the following form zt(t) = wt * tΕltdMt+L*-l(t - τ) + nt(t) , (20) where
wtc is (Lt x TO) (21)
and ht 0 • • • 0
0 ht • • • 0
Ht = (22) o ' ■ • ' • • 0
The transmit spatio-temporal signature, Ht, is an mLt χ Mt + t — 1) matrix that describes the relation between the spatio-temporal transmit vector, dMi+L,~ 1(t), and the received signal, zt(t), at the remote terminal.
When a plurality of remote terminals are active on the same channel, the individual transmit spatio-temporal signatures are collection in the multiplexing spatio-temporal signature matrix, Ti - For each channel, Ht, is formed using the transmit spatio-temporal signatures:
where H is the transmit spatio-temporal signature, as shown in equation (22), for the ith remote terminal currently active on the channel and nt is the total number of remote terminals on the channel. Note that henceforth, the sampling time T is assumed to be unity without loss of generality. Brief Description of The Drawings
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 spatio-temporal demultiplexer in the base station.
Figure 4 is a functional block diagram of a temporal filter of the spatio-temporal demultiplexer in the base station.
Figure 5 is a functional block diagram of a spatio-temporal multiplexer in the base station.
Figure 7 is a functional block diagram of a multichannel transmitter in the base station.
Figure 8 is a functional block diagram of a spatio-temporal processor in the base station.
Figure 9 is a functional block diagram of a remote terminal with a transponder switch.
Figure 10 is a functional block diagram of a remote terminal.
Figure 11 is a schematic diagram of a network system comprised of three base stations and a multiple base station controller.
15. multichannel receivers 16a. multichannel receiver 6m. multichannel receiver
17a. multichannel transmitter 7m. multichannel transmitter
18a. transmit antenna 8m. transmit antenna
19a. receive antenna 9m. receive antenna
22i. temporal filter 2m. temporal filter 23. spatio-temporal multiplexer
25. signal demodulator 6a. multipliers 6b. multipliers 6L. multipliers 7a. sample delay 7b. sample delay 7L. sample delay
28. adder 9a. temporal filters
29i. temporal filters m. temporal filters 0a. multipliers 0b. multipliers 0L. multipliers 1a. sample delay 1b. sample delay 1L. sample delay
58. remote terminal data to be transmitted 59. remote terminal modulated data to be transmitted
72. multiple base station controller 73a. cell boundary
73b. cell boundary 73c. cell boundary
Incoming or uplink radio transmissions impinge on an antenna array composed of a number, m, of receive antenna elements 19(a,. . . ,m) each of whose outputs is connected to one of TO multichannel receivers in a bank of phase-coherent multichannel receivers 15.
In each channel, receive antenna elements 19(a,. . . ,m) each measure a combination of the arriving uplink signals from the remote terminals sharing this channel. These combinations result from the relative locations of the antenna elements, the locations of the remote terminals, the frequency characteristics of the receiver and transmitter, the spectral content of the signals, and the RF propagation environment, and are given by equation (5).
Figure 2 depicts individual multichannel receivers 16(a, . . . ,m) with antenna element connections, common local receiver oscillators 35, one for each frequency channel to be used at that base station, and received signal measurements 6. Common local receiver oscillators 35 ensure that the signals from receive antenna elements 19(a, . . . ,m) are coherently down-converted to baseband; its Nc frequencies are set so that multichannel receivers 16(a, . . . ,m) extract all Ncc frequency channels of interest. The frequencies of common local receiver oscillators 35 are controlled by a spatio-temporal processor 13 (figure 1) via receiver control data 36. In an alternate embodiment, where multiple frequency channels are all contained in a contiguous frequency band, a common local oscillator is used to down-convert the entire band which is then digitized, and digital filters and decimators extract the desired subset of channels using well known techniques.
Referring again to Figure 1, multichannel receivers 15 produce received signal measurements 6 which are supplied to spatio-temporal processor 13 and to a set of spatio-temporal demultiplexers 20. In this embodiment, received signal measurements 6 contain m complex baseband signals for each of Nc frequency channels.
Figure 8 shows a more detailed block diagram of spatio-temporal processor 13. Spatio-temporal processor 13 produces and maintains spatio-temporal signatures for each remote terminal for each frequency channel, and calculates spatio-temporal multiplexing and demultiplexing weights for use by spatio-temporal demultiplexers 20 and spatio-temporal multiplexers 23. In the preferred embodiment, spatio-temporal processor 13 is implemented using a digital signal processor (DSP) device which includes a conventional central processing unit. Received signal measurements 6 go into a spatio-temporal signature processor 44 which estimates and updates spatio-temporal signatures. Spatio-temporal signatures are stored in a spatio-temporal signature list in a remote terminal database 42 and are used by channel selector 41 and spatio-temporal weight processor 43, which also produces demultiplexing weights 7 and multiplexing weights 12. A spatio-temporal processor controller 39 connects to spatio-temporal weight processor 43 and also produces receiver control data 36 transmitter control data 37 and spatio-temporal control data 33.
Referring again to Figure 8, the spatio-temporal demultiplexers 20 combine received signal measurements 6 according to the spatio-temporal demultiplexing weights 7. Figure 3 shows a spatio-temporal demultiplexer 20 for a single channel. In figure 3, xri denotes the ith component of the receive measure- ment vector 6 for a single channel, and wr'x denotes the complex conjugate transpose of the ith column of the demultiplexing weight matrix.
W-s = [wr l x, w;x, - (24)
for a remote terminal using this channel.
Figure 4 illustrates the processing of the fth received signal xrι- for a single channel. In this embodiment, arithmetic operations in temporal filters 22(a, . . . ,m) are carried out using general purpose arithmetic chips. In figure 4, xri denotes the i h component of the receive measurement vector 6 for a single channel, and wr'*x (j) denotes the complex conjugate of the jth component of the jth vector component of the spatio-temporal demultiplexing weight vector 7
«&(1)
Wf*rr — ^rx(j) = [wr 1 χ(j), - - - , Wr (j)} (25) w: :(Lr) for a remote terminal using this channel.
For each remote terminal on each channel, the ith temporal filter 22i computes wi'χ(l)xri(t) + x(2)xτi(t - T) + . . . + Wrχ(Lr)Xri(t - T(Lr - 1)) . (26)
Referring again to Figure 1, the outputs of spatio-temporal demultiplexers 20 are the separated uplink signals 5 for each remote terminal communicating with the base station. The separated uplink signals 5 are demodulated by signal demodulators 25, producing demodulated received signals 4 for each remote terminal communicating with the base station. Demodulated received signals 4 and corresponding spatio-temporal control data 33 are available to base station controller 3.
In embodiments where channel coding of the signals sent by remote terminals is performed, base station controller 3 sends the demodulated received signals 4 to spatio-temporal processor 13 which, using well known decoding techniques, estimates Bit-Error-Rates (BERs) and compares them against acceptable thresholds stored in the remote terminal database 42. If the BERs are unacceptable, spatio- temporal processor 13 reallocates resources so as to alleviate the problem. In one embodiment, links with unacceptable BERs are assigned to new channels 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 receive signature for that remote terminal/base station pair is performed when that channel is available.
For transmission, signal modulators 24 produce modulated signals 9 for each remote terminal the base station is transmitting to, and a set of spatio-temporal multiplexing weights 12 for each remote terminal are applied to the respective time-delayed versions of the modulated signals in spatio-temporal multiplexers 23 to produce multiplexed signals to be transmitted 10 for each of the m transmit antennas 18(a,. . . ,m) and each of the Nec channels.
In the illustrative embodiment the number Ncc of downlink channels is the same as the number Nec of uplink channels. In other embodiments, there may be different numbers of uplink and downlink channels. Furthermore, the channels may be of different 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, TO, 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 5 shows the spatio-temporal multiplexer for one remote terminal on a particular channel. Arithmetic operations in spatio-temporal multiplexer 23 are carried out using general purpose arithmetic chips. The component of modulated signals 9 destined for this remote terminal on this channel is denoted by d(t) and the multiplexing weight vector is denoted by vrtx . The multiplexing weight vector, wtI, is related to the multiplexing weight matrix, Wtx, through
tx = is (Lt x m) (28)
For each remote terminal on each channel, the spatio-temporal multiplexer 23 computes the product of its multiplexing weight matrix 12 with delayed versions of the modulated signal d(t) 9: ι>t*(l) d(t)
St(t) = WtxdL'(t) = (29)
Wtx Lt) d(t - (Lt - 1)T)
The temporal filters 29(a,. . . ,m) compute the products of the rows of the multiplexing weight matrix with delayed versions of the modulated signal d(t) 9. For each remote terminal on each channel, the ith temporal filter 29i computes
- T(Lt - 1)) (30)
The multiplication is performed by multipliers 30(a,b,. . . ,L), and the addition is performed by adder 32. For each channel, equation (29) is evaluated by the spatio-temporal multiplexer 23 for each remote terminal that is being transmitted to on this channel. Corresponding to each remote terminal is a different multiplexing weight vector, multiplexing weight matrix, and modulated signal. For each channel, spatio-temporal multiplexer 23 adds the multiplexed signals for each remote terminal being transmitted to on this channel, producing modulated and multiplexed signals 10, st(i), that are the signals to be transmitted for each downlink channel from each antenna.
Modulated and multiplexed signals 10 are inputs to a bank of TO phase coherent multichannel transmitters 14. Figure 7 depicts multichannel transmitters 17(a, . . . ,m) with antenna connections, common local transmitter oscillators 38, and digital inputs 10. Common local transmitter oscillators 38 ensure that the relative phases of multiplexed signals 10 are preserved during transmission by transmit antennas 18(a, . . . ,m). The frequencies of common local transmitter oscillators 38 are controlled by spatio-temporal processor 13 (see figure 1) via transmitter control data 37.
Referring again to figure 1, in applications where transmit spatio-temporal signatures are required, spatio-temporal processor 13 is also able to transmit predetermined calibration signals 11 for each antenna on a particular downlink channel. Spatio-temporal processor 13 instructs multichannel transmitters 17(a, . . . ,m), via transmitter control data 37, to transmit predetermined calibration signals 11 in place of the multiplexed signals 10 for a particular downlink channel. This is one mechanism used for determining the transmit spatio-temporal signatures of the remote terminals on this downlink channel.
Figure 9 depicts the component arrangement in a remote terminal that provides voice communication. The remote terminal's antenna 45 is connected to a duplexer 46 to permit antenna 45 to be used for both transmission and reception. In an alternate embodiment, separate receive and transmit antennas are used eliminating the need for duplexer 46. In another alternate embodiment where reception and transmission occur on the same frequency channel but at different times, a transmit/receive (TR) switch is used instead of a duplexer as is well known. Duplexer output 47 serves as input to a receiver 48. Receiver 48 produces a down-converted signal 49 which is the input to a demodulator 51. A demodulated received voice signal 67 is input to a speaker 66.
Demodulated received control data 52 is supplied to a remote terminal central processing unit 68 (CPU). Demodulated received control data 52 is used for receiving data from base station 1 during call setup and termination, and in an alternate embodiment, for determining the quality (BER) of the signals being received by the remote terminal for transmission back to the base station as described above.
Remote terminal CPU 68 is implemented with a standard DSP device. Remote terminal CPU 68 also produces receiver control data 63 for selecting the remote terminal's reception channel, transmitter control data 62 for setting the remote terminal's transmission channel and power level, control data to be transmitted 58, and display data 55 for remote terminal display 56. Remote terminal CPU 68 also receives keyboard data 54 from remote terminal keyboard 53.
Referring again to figure 9, the remote terminal allows received data 49 to be transmitted back to base station 1 via switch 69 controlled by remote terminal CPU 68 through switch control signal 70. In normal operation, switch 69 drives transmitter 60 with modulated signal 59 of modulator 57. When the remote terminal is instructed by base station 1 to enter calibration mode, the remote terminal CPU 68 send a predetermined calibration signal 58 to the modulator 57 in place of the remote terminal microphone signal 65. This is one mechanism used for determining the receive spatio-temporal signatures of the remote terminals on this uplink channel. In transponder mode, remote terminal CPU 68 toggles switch control signal 70, which instructs switch 69 to drive transmitter 60 with received data 49.
Figure 10 shows an alternate embodiment of the remote terminal transponder function. Switch 69 of figure 9 is no longer used. Instead, the output of receiver 48 is supplied to remote terminal CPU 68 by data connection 50. In normal operation remote terminal CPU 68 ignores data connection 50. In calibration mode, remote terminal CPU 68 uses data connection 50 to compute the remote terminal's transmit spatio-temporal signature, which is transmitted back to base station 1 through modulator 57 and transmitter 60 as control data to be transmitted 58.
In many respects, the spectrally efficient base station shown in figure 1 behaves much like a standard wireless communication system base station. The primary distinction is that the spectrally efficient base station supports more simultaneous conversations than a conventional base station using the same time/frequency resources. The communication channels may be frequency channels, time channels, code channels, or any combination of these. The spatio-temporal multiplexer/demultiplexer increases the system capacity by allowing multiple simultaneous communication links on each of these channels. Moreover, by combining signals from multiple receive antennas, the spatio-temporal demultiplexer 20 produces separated uplink signals 5 that are equalized in simultaneously spatially and temporally. The separate uplink signals 5 will as a consequence have substantially improved signal-to-noise, reduced interference, and improved quality in multipath environments compared to a standard base station.
In the illustrative embodiment, a wireless communication system comprised of multiple remote terminals and base stations incorporating antenna arrays and spatio-temporal signal processing is described. Such systems have application, for example, in providing wireless access to the local PSTN. Information transfers (or calls) are initiated by either a remote terminal or by communication link 2 through base station controller 3. Call 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 18(a,. . . ,m). In an alternate embodiment, the downlink control channel is broadcast from a single, omnidirectional antenna. Base station controller 3 passes the identification of the remote terminal to be involved in the call to spatio-temporal processor 13 which uses the stored spatio-temporal signatures of that remote terminal to determine which communication channel the remote terminal should use. The selected channel may already be occupied by several remote terminals, however spatio-temporal processor 13 uses the spatio-temporal signatures of all of the remote terminals on that channel to determine that they can share the channel without interference.
Spatio-temporal processor 13 uses calculated spatio-temporal multiplexing and demultiplexing weights for the selected channel and the remote terminal in question to configure spatio-temporal multiplexer 23 and spatio-temporal demultiplexer 20. Spatio-temporal 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 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 it monitors the downlink control channel awaiting its next call. Temporal and Spatial Processing — Base Station
Figure 8 shows a block diagram of spatio-temporal processor 13. It is controlled by spatio-temporal processor controller 39, which interfaces to base station controller 3 via link 33. Spatio-temporal processor controller 39 controls the gain and frequency settings of multichannel transmitters 14 and multichannel receivers 15 by control lines 37 and 36.
The spatio-temporal signature list in the remote terminal database 42 contains a transmit spatio- temporal signature, Ht, and a receive spatio-temporal signature, Hr, for every channel of operation for each remote terminal. In another embodiment, a set of basis vectors that span the same column space as the transmit and receive spatio-temporal signatures are stored, for example by storing the largest singular values and the corresponding singular vectors of the signatures. In another embodiment, parameters from which the signature can be formed are stored, for example by storing the transmit and receive channel response matrices. In another embodiment, estimates of the quality (e.g., estimate error covariances) of the spatio-temporal signatures are stored as well. In yet another embodiment, parameters describing the uncertainty due to time variations of the spatio-temporal signatures are stored as well. The transmit spatio-temporal signature includes the effects of the propagation environment between the base station and the remote terminal, as well as any differences in frequency characteristics of the transmitters 14, antenna cables, and transmission antennas 18(a, . . . ,m).
Channel selector 41 calculates functions of these signature matrices to assess whether or not communication between the base station and the new remote terminal can be successfully carried out on the selected channel. In the preferred embodiment, channel selector 41 first calculates spatio-temporal multiplexing and demultiplexing weights for that remote terminal and then uses these weights to estimate link performance. In the illustrative embodiment, spatio-temporal multiplexing weight vector are the columns of the matrix Wtx . The kth column of W(I is given in equation (31):
{Wt,}* = {W«(WΪW*)" 1}roL((*_1)+1 k = l, . . . , nt , (31) where (-)- 1 is the inverse of a matrix, {-}k is the kth column of a matrix, Ht is the multiplexing spatio- temporal signature matrix associated with the relevant channel, and s is the the amplitude of the kth signal to be transmitted. If the resulting multiplexing matrix is not stable, a stable approximation of the multiplexing matrix is formed as is well known in the art. The amplitudes to be transmitted, sjj. , are calculated in the preferred embodiment using the remote terminal receiver mean-square noise voltages Nk) and the minimum desired signal qualities (SNR es) as given in equation (32):
Now channel selector 41 calculates the average mean-square voltage (power) Pt to be transmitted from each element as the sum of squares of the appropriate elements of the weights
where WtJ. is the weight matrix for the k h user as defined in equation (21) and diag(-) is a vector obtained by stacking the diagonal elements of a matrix. The peak square voltage (power) Pfea to be transmitted from each element is computed as the square of sum of the magnitude of the appropriate weights
Pt peak (34)
where abs(-) is element- wise absolute value. Channel selector 41 compares these values against the limits for each of the transmitters for each of the elements. 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 alternative embodiment employing time division duplexing (TDD), the multiplexing weights are chosen to be scaled versions of the demultiplexing weights since the channels and interference are assumed to be reciprocal. The scale parameter is chosen to provide sufficient SINR at the remote terminal.
To test the uplink, channel selector 41 calculates spatio-temporal demultiplexing weights WrJ7 using the demultiplexing spatio-temporal signature matrix Hr, associated with the relevant channel. In the illustrative embodiment, spatio-temporal demultiplexing weight vectors are the columns of the matrix Wrx given in equation (35): rr = (HrPrK + flnn)_1Wr r , (35) where the k h column of Pr is given by equation (36)
{Pr = {Pr}Lrlh-l)+l k = l, . . . , nr , (36) where Pr is a (diagonal) matrix of mean-square amplitudes (powers) of the signals s*,ir, transmitted by the remote terminals
Pr = E{ (37)
and Rnn — E{er(t)e*(t)} is the base station noise covariance. Then, the expected value of the normalized mean-squared error covariance is calculated in one embodiment as follows:
MSE = Pr~1/2((I - W;xHr)Pr(I - W;xHr)* + Wr*xRnnWrχ)Pr~*/2 (38) where the notation (•)~*/2 indicates complex conjugate transpose of the square root of the matrix. The inverse of MSE is an estimate of the expected Signal-to-Interference-plus-Noise Ratio (SINR) at the output of the spatio-temporal demultiplexer:
SINR = MSE . (39)
Spatio-temporal weight processor 43 then sends the new spatio-temporal demultiplexing weights to spatio-temporal demultiplexers 20 and the new spatio-temporal multiplexing weights to the spatio- temporal multiplexers 23 for this channel, updates the active remote terminal list 40, and informs spatio-temporal processor controller 39 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 that instructs the remote terminal to switch to the desired channel.
W xHt = diag(si 1 , - - - , st nt) , (40) where diag(-) is a diagonal matrix with diagonal elements formed from a vector. This means that at the kth remote terminal, the signal intended to be sent to that terminal is received with a sufficient (positive real) amplitude s*/.. The fact that W*xHt has zero off-diagonal elements means that at the kth remote terminal, none of the other signals being transmitted are received by that remote terminal. In this manner, each remote terminal receives only the signals intended for it at the necessary power levels to ensure proper communications. In alternate embodiments, uncertainties in the estimates of Ht are incorporated in setting base station transmit power levels and calculating weights so as to minimize the effect of errors and/or changes in Ht ■
Equations (31) and (35) represent only one way to calculate spatio-temporal multiplexing and demultiplexing weights. There are other similar strategies that demonstrate properties similar to those shown in equation (40) and described in the previous paragraph. Other well known techniques for calculating weights Wtx and Wrr account for uncertainty in multiplexing and demultiplexing spatio- temporal signature matrices H and Hr , and can incorporate more complex power and dynamic range constraints.
Determining the Spatio- Temporal Signatures
As shown in figure 8, spatio-temporal processor 13 also contains a spatio-temporal signature processor 44 for finding the spatio-temporal signatures of the remote terminals. In the illustrative embodiment, spatio-temporal signature processor 44 uses the calibration techniques similar to the ones described in our U.S. patent 5,546,090 (issued 13 August 1996) entitled "Method and Apparatus for Calibrating Antenna Arrays" .
In the illustrative embodiment, each remote terminal is capable of entering a calibration mode. In the calibration mode, the remote terminal can transmit predetermined signals and also enter transponder mode where the received signal 49 is transmitted back to base station 1. The calibration mode is controlled by remote terminal CPU 68. Referring to figure 9, the transponsder mode is provided by switch 69 controlled by remote terminal CPU 68 through switch control signal 70.
To determine the transmit and receive spatio-temporal signatures of a remote terminal, spatio- temporal signature processor 44 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 spatio-temporal processor controller 39, and modulated by signal modulators 24. In an alternative embodiment, calibration mode is entered regularly at predetermined instances.
The remote terminal then transmits predetermined terminal calibration signal on the channel. In the present embodiment, the terminal calibration signal is a known pseudo random noise sequence confined to the frequency band of of the current channel. In another embodiment, the predetermined terminal calibration signal is any known signal. Time samples of the received data are stored in an TO by Nr data matrix X which according to equation (5) and in the absence of noise and parameter offsets is given by
X = hrSr (42) where Sr is the Mr by Nr matrix of predetermined terminal calibration signals. The receive channel response matrix is then given by
where Sj is the well known Moore-Penrose pseudo-inverse of the matrix Sr satisfying SrsJ = I (the identity matrix) for full-rank matrices Sr having more columns than rows, SjSr = I for full-rank matrices Sr having more rows than columns. The receive spatio-temporal signature Hr can now be constructed from the channel matrix hr .
Z = HrSr (44) where in this case Sr is the Mr + Lr — 1 by JV- matrix of predetermined terminal calibration signals. The receive spatio-temporal signature is then given by
Hr = ZS} . (45)
Receive spatio-temporal signatures may be determined while other terminals are using the same channel. In alternate embodiments the spatio-temporal demultiplexing weight vector is determined directly from equation (46): ^Z = Sr . (46) where in this case Sr is the 1 by Nr vector containing the predetermined terminal calibration signal. The spatio-temporal demultiplexing weight vector is then given by
W; rx = Z*ts; . (47)
In alternate embodiments related to those described in U.S. patent 5,546,090 (issued 13 August 1996) entitled "Method and Apparatus for Calibrating Antenna Arrays" , well known techniques are used to account for noise present in the system and parameter variations such as oscillator frequency offsets.
Once Hr is known, demultiplexing weights are computed and the remote terminal enters transponder mode. Spatio-temporal signature processor 44 then transmits predetermined base station calibration signals 11, on the channel occupied by the remote terminal, by instructing multichannel transmitters 17(a, . . . ,m) via transmitter control data 37 and spatio-temporal processor controller 39. In the present embodiment, the TO signals (for each antenna) among the predetermined base station calibration signals 11 are different known pseudo random noise sequences confined to the frequency band of the current channel. In another embodiment, the predetermined base station calibration signals 11 are any known, distinct, signals.
The remote terminal shown in figure 9 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 spatio-temporal signature processor 44 shown in figure 8. Time samples of the received data are processed by the demultiplexing weights and the resulting signal is stored in a 1 by Nt data matrix Zt which according to equation (14) and in the absence of noise and parameter offsets is given by
Zf = t [h?'(l) . . . h?'(Lt)] St (48) where St is the mLt by Nt matrix of predetermined base station calibration signals and k is a known amount by which the signal is amplified in the remote terminal before transmission back to the base station.
[l$(l) . - . }$(Lt)]
In alternate embodiments also described in U.S. patent 5,546,090 (issued 13 August 1996) entitled "Method and Apparatus for Calibrating Antenna Arrays" , well known techniques are used to account for noise present in the system and parameter variations such as oscillator frequency offsets.
In an alternative embodiment, the calibration mode only consists of the transponder model described above. The receive channel matrix is then determined through one of several techniques described in the literature, see for example E. Moulines, P. Duhamel, J.-F. Cardoso, and S. Mayrargue, "Subspace methods for the blind identification of multichannel FIR filters," IEEE Transactions on Signal Processing, 43(2):516-525, February 1995.
In one alternate embodiment, computation of remote terminal transmit spatio-temporal signatures can be performed directly by the remote terminals. This embodiment of the remote terminal is shown in figure 10. In calibration mode, spatio-temporal signature processor 44 transmits predetermined calibration signals 11, on the channel to be calibrated by the remote terminals, as before. Remote terminal CPU 68 uses received calibration signals 50 and the known transmitted waveforms to compute the remote terminal's transmit spatio-temporal signature using the same techniques used by spatio-temporal signature processor 44 in the previous embodiment. The computed transmit spatio-temporal signature is transmitted back to base station 1 through modulator 57 and transmitter 60 as control data to be transmitted 58. When received by base station 1, spatio-temporal signature processor 44 stores the new transmit spatio-temporal signature in remote terminal database 42. Since each remote terminal performs the transmit spatio-temporal signature calculation independently, this arrangement allows multiple remote terminals to compute their own transmit spatio-temporal signature simultaneously on the same channel. In this embodiment, remote terminal receive spatio-temporal signatures are computed by spatio-temporal signature processor 44 in the same manner as in the previous embodiment.
Using these techniques, spatio-temporal signature processor 44 can measure remote terminal transmit and receive spatio-temporal signatures for a particular channel any time that channel is idle. The efficiency of these calibration techniques allow spatio-temporal signature processor 44 to update the spatio-temporal signatures of numerous remote terminals for a particular channel while occupying that channel for only a short time. In an alternative embodiment, the receive spatio-temporal signatures are obtained in a decision- directed feedback mode. The receive data is demodulated and then remodulated to produce an estimate of the original modulated signal. These techniques allow receive spatio-temporal signatures to be estimated even when multiple remote terminals are occupying a single channel.
Network Level Spatio- Temporal Processing
In the embodiment illustrated herein, the spatio-temporal processor for 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 spatio-temporal processor from each base station communicates with and coordinates its efforts with the spatio-temporal processors from other nearby cells. A specific embodiment is shown in figure 11.
Each spatio-temporal processor contained in base stations 1 (a,b,c) measures and stores the spatio- temporal signatures of the remote terminals in its cell and also of the remote terminals in adjacent cells. The determination of spatio-temporal signatures of the remote terminals in adjacent cells is coordinated by multiple base station controller 72 through base station communication links 2 (a,b,c). Through base station communication links 2 (a,b,c) and multiple base station controller 72, spatio-temporal processors in base stations 1 (a,b,c) from adjacent cells inform each other of which remote terminals they are communicating with on which channels. Each spatio-temporal processor includes the spatio- temporal signatures of remote terminals that are currently active in adjacent cells to form extended multiplexing and demultiplexing spatio-temporal signature matrices Ht and Hr which are sent to all the adjacent base stations. The channel selectors in each base station, using these extended spatio-temporal signature matrices, jointly assign remote terminals to each channel in each of base stations 1 (a,b,c).
The resulting multiplexing and demultiplexing weights Wtx and Wrx for each base station are then calculated using extended multiplexing and demultiplexing signature matrices Ht and Hr ■ 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 72 assigns remote terminals requesting access to base stations dynamically using a list of active remote terminal/base station/ channel links, the associated remote terminal databases, and the particular requirements for 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 72 to further increase system capacity.
The apparatus and method in accordance with the invention provides a significant advantage over the prior art in that it allows many more remote terminals to simultaneously share the same communication channel by simultaneous spatio-temporal multiplexing/ demultiplexing. Moreover, signals received from and transmitted to the remote terminals have substantially improved signal-to-noise, reduced interference, and improved quality in multipath environments compared to a standard base station.
In one alternate embodiment, transmission antennas 18(a,. . . ,m) and reception antennas 19(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 be processed in real time using the spatio-temporal processing described in co-pending patent application 07/806,695. This would allow multiple remote terminals to request a communication channel at the same time.
1. 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 spatio-temporal processing means for determining and storing receive spatio- temporal signatures for said plurality of remote terminals using said measurements; and spatio-temporal demultiplexing means using said receive spatio-temporal signatures and said measurements to produce separated uplink signals.
2. In a wireless system a method 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 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, said method comprising the steps of: receiving at the receivers of said at least one base station measurements of combinations of said uplink signals from said plurality of remote terminals using said common uplink channel; receive spatio-temporal processing for determining and storing receive spatio- temporal signatures for said plurality of remote terminals using said measurements; and spatio-temporal demultiplexing using said receive spatio-temporal signatures and said measurements to produce separated uplink signals.
7. The wireless system as defined by claim 5 wherein said receive spatio-temporal processor determines said spatio-temporal demultiplexing weights as the columns of matrix Wr as follows:
Wrc = (HrPrH* + Rnn)~ HrPr ,
where (•)* denotes the complex conjugate transpose of a matrix, (-)-1 denotes the inverse of a matrix, Rn is the noise covariance matrix of said receiver means, Pr is a matrix of transmit powers of the remote terminals in said plurality of remote terminals, and Hr is a demultiplexing spatio- temporal signature matrix composed of said receive spatio-temporal signatures for said plurality of remote terminals and said common uplink channel.
8. The method as defined by claim 6 wherein said receive spatio-temporal processing step determines said spatio-temporal demultiplexing weights as the columns of matrix Wr5r as follows:
Wr, = (HrPr +
, where (•)* denotes the complex conjugate transpose of a matrix, (-)-1 denotes the inverse of a matrix, Rnn is the noise covariance matrix of said receivers, Pr is a matrix of transmit powers of the remote terminals in said plurality of remote terminals, and Hr is a demultiplexing spatio- temporal signature matrix composed of said receive spatio-temporal signatures for said plurality of remote terminals and said common uplink channel.
15. The wireless system as defined by claim 1 wherein said spatio-temporal demultiplexing means calculates spatio-temporal demultiplexing weights for said common uplink channel as the columns of a matrix Wrs as follows:
Wrr = HrPrHr + Rnn)~ HrPr, where (•)* denotes the complex conjugate transpose of a matrix, (-)-1 denotes the inverse of a matrix, Rnn is the noise covariance matrix of said receiver means, Pr is a matrix of transmit powers of the remote terminals in said plurality of remote terminals, and Hτ is a demultiplexing spatio- temporal signature matrix composed of said receive spatio-temporal signatures for said plurality of remote terminals and said common uplink channel, said spatio-temporal demultiplexing means using said spatio-temporal demultiplexing weights to calculate said uplink signals.
16. The method as defined by claim 2 wherein said spatio-temporal demultiplexing calculates spatio- temporal demultiplexing weights for said common uplink channel as the columns of a matrix Wrx as follows:
Wrr = HrPr + Rnn)-lHrPr, where (•)* denotes the complex conjugate transpose of a matrix, (-)- 1 denotes the inverse of a matrix, Rnn is the noise covariance matrix of said receivers, Pr is a matrix of transmit powers of the remote terminals in said plurality of remote terminals, and Hr is a demultiplexing spatio- temporal signature matrix composed of said receive spatio-temporal signatures for said plurality of remote terminals and said common uplink channel, said spatio-temporal demultiplexing method using said spatio-temporal demultiplexing weights to calculate said uplink signals.
18. The method as defined by claim 2 wherein said uplink signals have predetermined modulation format parameters, and wherein said receive spatio-temporal processing step determines said spatio- temporal demultiplexing weights using said predetermined modulation format parameters of said uplink signals from said plurality of remote terminals.
21. The wireless system as defined by claim 1 wherein said system includes a transponder co-located with each remote terminal of said plurality of remote terminals and wherein said receive spatio- temporal processing means determines said receive spatio-temporal signatures using signals trans- ponded from at least one of the transponders.
24. The method as defined by claim 2 wherein each remote terminal of said plurality of remote terminals includes a transponder, said method includes transponding signals received at least one of said remote terminals, and said receive spatio-temporal processing step determines said receive spatio- temporal signatures using said transponded signals.
26. The method as defined by claim 2 wherein the location and directivity of said antenna elements are known, and wherein said receive spatio-temporal processing step determines said receive spatio- temporal signatures using the known location and directivity of said antenna elements, and wherein said receive spatio-temporal processing step estimates the directions of arrival of said uplink signals from said plurality of remote terminals.
28. The method as defined by claim 2 wherein the location and directivity of said antenna elements, and the location of said plurality of remote terminals are known, and wherein said receive spatio- temporal processing step determines said receive spatio-temporal signatures using the known location and directivity of said antenna elements and the known location of said plurality of remote terminals.
34. The method as defined by claim 2, wherein said system further comprises a plurality of transmit antenna elements and transmitters for transmitting multiplexed downlink signals to said plurality of remote terminals using a common downlink channel, the method further comprising: transmitting the multiplexed downlink signals to said plurality of remote terminals using a common downlink channel, transmit spatio-temporal processing for determining and storing transmit spatio- temporal signatures for said plurality of remote terminals, and spatio-temporal multiplexing using said transmit spatio-temporal signatures and downlink signals to produce said multiplexed downlink signals.
39. The wireless system as defined by claim 33 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 spatio-temporal processing means and said transmit spatio- temporal processing means comprises: an active remote terminal list 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 spatio-temporal signature list comprising a receive spatio-temporal signature for each remote terminal of said plurality of remote terminals and each channel of said plurality of uplink channels, and a transmit spatio-temporal signature for each remote terminal of said plurality remote terminals and each of channel of said plurality downlink channels, receive spatio-temporal signature determining means for determining said receive spatio-temporal signatures, transmit spatio-temporal signature determining means for determining said transmit spatio-temporal signatures, and a channel selector using said active remote terminal list and said spatio-temporal signature list to determine assignments of each remote terminal of said active remote terminal list 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.
forming an active remote terminal list 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; determining as part of said receive spatio-temporal processing step a receive spatio- temporal signature for each remote terminal of said plurality of remote terminals and each channel of said plurality of uplink channels; determining as part of said transmit spatio-temporal processing step a transmit spatio-temporal signature for each remote terminal of said plurality remote terminals and each of channel of said plurality downlink channels; forming a spatio-temporal signature list comprising the determined receive spatio- temporal signatures and the determined transmit spatio-temporal signatures; and channel selecting using said active remote terminal list and said spatio-temporal signature list to determine assignments of each remote terminal of said active remote terminal list 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.
41. The wireless system as defined by claim 39 wherein said receive spatio-temporal processing means and said transmit spatio-temporal processing means further comprise: a receive spatio-temporal weight processor for calculating spatio-temporal demultiplexing weights for each of the terminals in said active remote terminal list to which an 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 spatio-temporal demultiplexing weights being utilized by said spatio-temporal demultiplexing means to calculate said uplink signals, and a transmit spatio-temporal weight processor for calculating spatio-temporal 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 spatio-temporal multiplexing weights being utilized by said spatio-temporal multiplexing means to produce said multiplexed downlink signals.
44. The method as defined by claim 34 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, each base station in said plurality of base stations carrying out said receive spatio-temporal processing step and said transmit spatio-temporal processing step, wherein said receive spatio-temporal processing step and said transmit spatio-temporal processing step further comprise: forming an active remote terminal list 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; determining as part of said receive spatio-temporal processing step a receive spatio- temporal signature for each remote terminal of said plurality of remote terminals and each channel of said plurality of uplink channels; determining as part of said transmit spatio-temporal processing step a transmit spatio-temporal signature for each remote terminal of said plurality remote terminals and each of channel of said plurality downlink channels; forming a spatio-temporal signature list comprising the determined receive spatio- temporal signatures and the determined transmit spatio-temporal signatures; and receive spatio-temporal weight processing for determining spatio-temporal demultiplexing weights for each of the terminals in said active remote terminal list to which an uplink channel is assigned and each channel of said plurality of uplink channels assigned to at least one of the terminals in said active remote terminal list, said spatio-temporal demultiplexing weights being utilized by said spatio-temporal demultiplexing step to calculate said uplink signals; transmit spatio-temporal weight processing for determining spatio-temporal 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 spatio-temporal multiplexing weights being utilized by said spatio-temporal multiplexing step to produce said multiplexed downlink signals; joint channel selecting channel 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 communicating said determined assignments between each base station in said plurality of base stations.
where (•)* denotes the complex conjugate transpose of a matrix, (-)- 1 denotes the inverse of a matrix, {-}jt denotes the fcth column of a matrix, Sj. is the amplitude of the kth said downlink signal, and Ht is a multiplexing spatio-temporal signature matrix composed of said transmit spatio- temporal signatures for said plurality of remote terminals and said common downlink channel and wherein said spatio-temporal multiplexing means utilizes said spatio-temporal multiplexing weights to produce said multiplexed downlink signals.
{Wtx}* =
l, . . . , nt,
where (•)* denotes the complex conjugate transpose of a matrix, (■)~1 denotes the inverse of a matrix, {•}& denotes the kth column of a matrix,
is the amplitude of the kth said downlink signal, and Ht is a multiplexing spatio-temporal signature matrix composed of said transmit spatio- temporal signatures for said plurality of remote terminals and said common downlink channel and wherein said spatio-temporal multiplexing method utilizes said spatio-temporal multiplexing weights to produce said multiplexed downlink signals.
47. The wireless system as defined by claim 33 wherein said downlink signals and said uplink signals are transmitted on the same radio frequency and said transmit spatio-temporal processing means determines said transmit spatio-temporal multiplexing weights directly from the receive spatio- temporal demultiplexing weights.
49. The wireless system as defined by claim 33 wherein said system includes a transponder co-located with each remote terminal of said plurality of remote terminals and wherein said transmit spatio- temporal processing means determines said transmit spatio-temporal signatures using signals transponded from at least one of the transponders.
63. In a wireless system including at least one base station, said at least one base station including a plurality of transmit antenna elements and transmitters, the method for transmitting to a plurality of remote terminals using a common downlink channel, said method comprising: transmitting multiplexed downlink signals to said plurality of remote terminals using said transmitters at said at least one base station; transmit spatio-temporal processing for determining and storing transmit spatio- temporal signatures for said plurality of remote terminals; and spatio-temporal multiplexing using said transmit spatio-temporal signatures and downlink signals to produce said multiplexed downlink signals.
64. The wireless system as defined by claim 62 wherein said common downlink channel is one of a plurality of downlink channels and wherein said transmit spatio-temporal processing means comprises: a active remote terminal list comprising a list of remote terminals assigned to at least one of the channels of said plurality of downlink channels; a spatio-temporal signature list comprising a transmit spatio-temporal signature for each remote terminal of said plurality of remote terminals and each channel of said plurality of downlink channels; transmit spatio-temporal signature determining means for determining said transmit spatio-temporal signatures; and a transmit channel selector using said active remote terminal list and said spatio- temporal signature list to determine assignments of each remote terminal in said active remote terminal list to at least one of the channels of said plurality of downlink channels.
65. The method as defined by claim 63 wherein said common downlink channel is one of a plurality of downlink channels and wherein said transmit spatio-temporal processing step comprises: forming a active remote terminal list comprising a list of remote terminals assigned to at least one of the channels of said plurality of downlink channels; determining a transmit spatio-temporal signature for each remote terminal of said plurality of remote terminals and each channel of said plurality of downlink channels; forming a spatio-temporal signature list comprising the transmit spatio-temporal signatures; and transmit channel selecting using said active remote terminal list and said spatio- temporal signature list to determine assignments of each remote terminal in said active remote terminal list to at least one of the channels of said plurality of downlink channels.
67. The method as defined by claim 65 wherein said transmit spatio-temporal processing step further comprises: transmit spatio-temporal weight processing for determining spatio-temporal multiplexing weights for each of the terminals in said active remote terminal list to which a downlink channel is assigned to at least one of the terminals in said active remote terminal list, said spatio-temporal multiplexing weights being utilized be said spatio-temporal multiplexing step to produce said multiplexed downlink signals.
{Wtr}t = 4{Wt(Wt*Wtr1 ,(*-i)+i k = l, . . . , rit,
where (•)* denotes the complex conjugate transpose of a matrix, (•)~1 denotes the inverse of a matrix, {.}fc denotes the k il column of a matrix, is the amplitude of the kth said downlink signal, and Ht is a multiplexing spatio-temporal signature matrix composed of said transmit spatio- temporal signatures for said plurality of remote terminals and said common downlink channel and said spatio-temporal multiplexing means utilizes said spatio-temporal multiplexing weights to produce said multiplexed downlink signals.
71. The method as defined by claim 63 wherein said spatio-temporal multiplexing step determines spatio-temporal multiplexing weight vectors for said common downlink channel as the columns of a matrix "Wtx as follows:
[Wtx = sl{ t H; trl}mLt(k-1)+1 k = l, ..., nt, where (•)* denotes the complex conjugate transpose of a matrix, (-)- 1 denotes the inverse of a matrix, {•}* denotes the kth column of a matrix, is the amplitude of the kth said downlink signal, and Ht is a multiplexing spatio-temporal signature matrix composed of said transmit spatio- temporal signatures for said plurality of remote terminals and said common downlink channel and said spatio-temporal multiplexing method utilizes said spatio-temporal multiplexing weights to produce said multiplexed downlink signals.
72. The wireless system as defined by claim 62 wherein said system includes a transponder co-located with each remote terminal of said plurality of remote terminals and wherein said transmit spatio- temporal processing means determines said transmit spatio-temporal signatures using signals transponded from at least one of the transponders.
77. The method as defined by claim 63 wherein said downlink signals have predetermined modulation format parameters, and said transmit spatio-temporal processing step determines said transmit spatio-temporal signatures using the transponded signals.
80. The method as defined by claim 63 wherein the location and directivity of said antenna elements and the location of said plurality of remote terminals are known, and wherein said transmit spatio- temporal processing step determines said transmit spatio-temporal signatures using the known location and directivity of said antenna elements and the known location of said plurality of remote terminals.
PCT/US1997/019172 1991-12-12 1997-10-17 Spectrally efficient high capacity wireless communication systems with spatio-temporal processing WO1998018272A1 (en)
US08/735,520 1996-10-23
EP97913745.2A EP0932986B1 (en) 1996-10-23 1997-10-17 Spectrally efficient high capacity wireless communication systems with spatio-temporal processing
AU50864/98A AU5086498A (en) 1996-10-23 1997-10-17 Spectrally efficient high capacity wireless communication systems with spatio-temporal processing
CA002266391A CA2266391A1 (en) 1996-10-23 1997-10-17 Spectrally efficient high capacity wireless communication systems with spatio-temporal processing
ES97913745.2T ES2525037T3 (en) 1996-10-23 1997-10-17 Wireless communication systems highly spectrally efficient processing capacity spatiotemporal
JP51962998A JP4173916B2 (en) 1996-10-23 1997-10-17 Spectrally efficient high capacity wireless communication system having a space-time processing
BR9712643-8A BR9712643A (en) 1996-10-23 1997-10-17 Wireless System and method for calculating interconnection sending signals transmitted from a plurality of remote terminals
WO1998018272A1 true WO1998018272A1 (en) 1998-04-30
ID=27499764
US (1) US5828658A (en)
WO (1) WO1998018272A1 (en)
WO2002045276A2 (en) * 2000-11-30 2002-06-06 Arraycomm, Inc. Training sequence for a radio communications system
CN104038332A (en) * 2008-09-12 2014-09-10 高通股份有限公司 A method and apparatus for signaling to a mobile device which set of training sequence codes to use for a communication link
IT1295392B1 (en) * 1997-09-19 1999-05-12 Francesco Vatalaro equalization and precompensation system for communications with access TDMA
1996-10-23 US US08/735,520 patent/US5828658A/en not_active Expired - Lifetime
1997-10-17 WO PCT/US1997/019172 patent/WO1998018272A1/en active Application Filing
See also references of EP0932986A4 *
KR100811577B1 (en) * 2000-08-18 2008-03-10 루센트 테크놀러지스 인크 A method and apparatus for transmitting a data signal, a transmitter and a receiver
WO2002045276A3 (en) * 2000-11-30 2002-08-01 Arraycomm Inc Training sequence for a radio communications system
CN102904707A (en) * 2000-11-30 2013-01-30 英特尔公司 Training sequence for a radio communications system
CN102904707B (en) * 2000-11-30 2015-04-01 英特尔公司 Training sequence for a radio communications system
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