United States Patent [19J
`Ottersten et al.
`
`[54] SPECTRALLY EFFICIENT HIGH CAPACITY
`WIRELESS COMMUNICATION SYSTEMS
`WITH SPATIO-TEMPORAL PROCESSING
`
`[75]
`
`Inventors: Bjorn E. Ottersten, Lidingii , Sweden;
`Craig H. Barratt, Redwood City,
`Calif.; David M. Parish, Amherst,
`N.Y.; Richard H. Roy, III, Mountain
`View, Calif.
`
`[73] Assignee: Arraycomm, Inc., San Jose, Calif.
`
`[21] Appl. No.: 735,520
`
`[22]
`
`Filed:
`
`Oct. 23, 1996
`
`Related U.S. Application Data
`
`[63]
`
`[51]
`[52]
`[58]
`
`Continuation-in-part of Ser. No. 375,848, Jan. 20, 1995, Pat.
`No. 5,592,490, which is a continuation-in-part of Ser. No.
`806,695, Dec. 12, 1991, Pat. No. 5,515,378, and Ser. No.
`234,747, Apr. 28, 1994, Pat. No. 5,546,090.
`Int. Cl.6
`....................................................... H04Q 7/00
`U.S. Cl. ............................................. 370/310; 370/329
`Field of Search ..................................... 370/277, 310,
`370/334, 347, 328, 329, 546; 375/200;
`342/386, 417, 443, 444; 364/572, 578,
`581; 455/525, 450; 702/179
`
`[56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`I 1111111111111111 11111 111111111111111 11111 11111 1111111111111111 Ill lllll llll
`US005828658A
`[11] Patent Number:
`[45] Date of Patent:
`
`5,828,658
`Oct. 27, 1998
`
`5,255,210
`5,260,968
`5,262,789
`5,515,378
`5,546,090
`5,592,490
`
`10/1993 Gardner et al. ......................... 364/574
`11/1993 Gardner et al. ......................... 375/200
`11/1993 Silverstein .............................. 342/368
`5/1996 Roy, III et al. ......................... 370/334
`8/1996 Roy, III et al. ......................... 342/174
`1/1997 Barratt et al. ........................... 370/310
`
`Primary Examiner-Chau Nguyen
`Attorney, Agent, or Firm-Henry K. Woodward; Townsend
`and Townsend and Crew LLP
`
`[57]
`
`ABSTRACT
`
`A wireless system includes 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 chan(cid:173)
`nels. A plurality of antenna elements at each base station
`receives uplink signals, and a plurality of antenna elements
`at each base station for transmits downlink signals. A signal
`processor at each base station is connected to the receiving
`antenna elements and to the transmitting antenna elements
`for determining spatio-temporal signatures. Spatio-temporal
`multiplexing and demultiplexing functions are provided for
`each remote terminal antennae for each channel, and a
`multiple base station network controller optimizies network
`performance, whereby communication between the base
`stations and the plurality of remote terminals in each of the
`channels can occur simultaneously.
`
`5,103,459
`
`4/1992 Gilhousen et al.
`
`..................... 375/200
`
`80 Claims, 11 Drawing Sheets
`
`18a
`
`18m
`
`23
`
`24
`
`10
`
`11
`
`13
`
`6
`
`12
`
`Spatio-Temporal
`Multiplexers
`
`Spatio(cid:173)
`Temporal
`Pro(cid:173)
`cessor
`
`9
`
`7
`
`Signal
`Modulators
`
`8
`
`5
`
`Signal
`Demodulators
`
`4
`
`33
`
`25
`
`Base Station
`' - - - - - - I
`Controller
`
`- - -~
`
`3
`
`2
`
`Samsung Ex. 1018
`Page 1
`
`

`

`U.S. Patent
`
`Oct. 27, 1998
`
`Sheet 1 of 11
`
`5,828,658
`
`18a
`
`18m
`
`■ ■ ■
`
`Multichannel
`Transmitters
`
`14
`37
`
`--------~
`
`19m
`
`15
`
`...-L----''-l
`
`36 Multichannel
`Receivers
`
`13
`
`6
`
`10
`
`11
`
`12
`
`Spatio-Temporal
`Multiplexers
`
`23
`
`9
`
`Signal
`Modulators
`.._ _
`____,
`
`24
`
`/
`
`Spatio(cid:173)
`Temporal
`Pro(cid:173)
`cessor
`
`Spatio-Temporal
`Demultiplexers
`
`7
`
`20
`
`5
`
`Signal
`Demodulators
`
`25
`
`33
`
`8
`
`._____
`
`Base Station
`Controller
`
`4
`
`~--~
`
`1
`
`3
`
`2
`
`FIG. 1
`
`Samsung Ex. 1018
`Page 2
`
`

`

`U.S. Patent
`
`Oct. 27, 1998
`
`Sheet 2 of 11
`
`5,828,658
`
`19a
`
`19m
`
`35
`
`Common
`Oscillators
`
`Multichannel
`Receiver
`
`16a
`
`Multichannel
`Receiver
`
`16m
`
`15
`
`36
`
`6
`
`FIG. 2
`
`Samsung Ex. 1018
`Page 3
`
`

`

`U.S. Patent
`
`Oct. 27, 1998
`
`Sheet 3 of 11
`
`5,828,658
`
`Spatio-Temporal
`
`Multichannel
`
`Processor
`
`Receivers
`
`13
`
`15
`
`6
`
`xr1(t)
`
`22a
`
`Xrm(t)
`
`22m
`
`w1* rx
`
`Temporal
`Filter
`I
`
`■ ■ ■
`
`wm* rx
`
`Temporal
`Filter
`
`20
`
`21
`
`5
`
`Signal
`Demodulator
`
`25
`
`FIG. 3
`
`Samsung Ex. 1018
`Page 4
`
`

`

`U.S. Patent
`
`Oct. 27, 1998
`
`Sheet 4 of 11
`
`5,828,658
`
`wi* rx
`
`;;.
`
`D
`
`26a
`
`wt:(2)
`
`27ag27b
`D
`-;;► D
`
`26b
`
`■ ■ ■
`
`w~:(Lr)
`
`27L
`
`26L
`
`22i
`
`28
`
`FIG. 4
`
`Samsung Ex. 1018
`Page 5
`
`

`

`U.S. Patent
`
`Oct. 27, 1998
`
`Sheet 5 of 11
`
`5,828,658
`
`Spatio-Temporal
`
`'Processor
`
`Multichannel
`
`Transmitters
`
`13
`
`14
`
`10
`
`29a
`
`29m
`
`Temporal
`Filter
`
`■ ■ ■
`
`Temporal
`Filter
`
`d(t)
`
`23
`
`9
`
`Signal
`Modulator
`
`24
`
`FIG. 5
`
`Samsung Ex. 1018
`Page 6
`
`

`

`U.S. Patent
`
`Oct. 27, 1998
`
`Sheet 6 of 11
`
`5,828,658
`
`d(t)
`
`wi* tx
`
`>
`
`D
`
`30a
`
`wf;(I)
`
`w;;(2)
`
`31
`
`31b
`
`D
`
`~ D
`
`• • •
`
`wf;(Lt)
`
`31L
`
`30L
`
`29i
`
`32
`
`FIG. 6
`
`Samsung Ex. 1018
`Page 7
`
`

`

`U.S. Patent
`
`Oct. 27, 1998
`
`Sheet 7 of 11
`
`5,828,658
`
`18a
`
`17a
`
`18m
`
`17m
`
`38
`
`Multichannel
`Transmitter
`
`Multichannel
`Transmitter
`
`Common
`Oscillators
`
`14
`
`10
`
`37
`
`FIG. 7
`
`Samsung Ex. 1018
`Page 8
`
`

`

`U.S. Patent
`
`Oct. 27, 1998
`
`Sheet 8 of 11
`
`5,828,658
`
`/40
`
`Active Remote
`
`Terminal List
`
`JI\
`
`-
`
`/41
`
`Channel
`
`Selector
`
`J
`
`I/
`
`' - - -
`
`Spatio-Temporal
`
`Weight Processor
`
`/ 13
`/42
`
`~
`Remote
`
`Terminal
`
`Database
`
`I
`
`12
`
`-"" -
`-/
`7
`
`37
`
`-""
`36 -/
`
`I
`
`/39,1,
`
`Spatio-Temporal
`
`Processor Controller
`
`I~
`
`.~33
`
`Basestation
`Controller
`
`""43
`
`-
`
`Spatio-Temporal
`
`Signature Processor
`
`----
`
`~
`
`~44
`
`11 /
`
`To
`Multichannel
`Transmitters
`
`6
`
`From
`Multichannel
`Receivers
`
`FIG. 8
`
`Samsung Ex. 1018
`Page 9
`
`

`

`U.S. Patent
`
`Oct. 27, 1998
`
`Sheet 9 of 11
`
`5,828,658
`
`45
`
`46
`
`47
`
`61
`
`Duplexer
`
`60
`
`62
`
`63
`
`48
`
`Transmitter 1,E-----L..---.
`
`Receiver
`
`69
`
`Switch
`
`59
`
`70 _____. _ ___.__
`
`CPU
`
`68
`
`49
`
`57
`
`64
`
`56
`
`Modulator
`
`58
`
`65
`
`Microphone
`
`Speaker
`
`54
`
`Display
`
`Keypad
`
`51
`
`66
`
`53
`
`55
`
`FIG. 9
`
`Samsung Ex. 1018
`Page 10
`
`

`

`U.S. Patent
`
`Oct. 27, 1998
`
`Sheet 10 of 11
`
`5,828,658
`
`45
`
`61
`
`Duplexer
`
`62
`
`CPU
`
`59
`
`68
`
`Modulator
`
`46
`
`47
`
`63
`
`Receiver
`
`50
`
`49
`
`58
`
`65
`
`52
`
`67
`
`Microphone
`
`Speaker
`
`54
`
`Display
`
`Keypad
`
`48
`
`51
`
`66
`
`53
`
`57
`
`64
`
`56
`
`55
`
`FIG. 10
`
`Samsung Ex. 1018
`Page 11
`
`

`

`U.S. Patent
`
`Oct. 27, 1998
`
`Sheet 11 of 11
`
`5,828,658
`
`73c
`
`~
`
`Base
`Station
`
`~
`/ 1c
`
`75
`~
`
`/73a
`
`1a
`~
`
`~
`
`~
`
`Base
`Station
`
`~
`
`~
`
`~
`
`~
`
`~
`
`1b ~
`
`Base
`Station
`
`~
`
`73b
`
`2c
`
`Multiple Base
`Station Controller
`
`/
`
`-74
`
`Wide Area Network
`
`72
`
`71
`
`FIG. 11
`
`Samsung Ex. 1018
`Page 12
`
`

`

`5,828,658
`
`1
`SPECTRALLY EFFICIENT HIGH CAPACITY
`WIRELESS COMMUNICATION SYSTEMS
`WITH SPATIO-TEMPORAL PROCESSING
`
`CROSS REFERENCE TO RELATED
`APPLICATIONS
`
`This application is a continuation-in-part of U.S. patent
`application Ser. No. 08/375,848 filed 20 Jan., 1995 now U.S.
`Pat. No 5,592,490 issued Jan. 7, 1997 for Spectrally Efficient
`High Capacity Wireless Communication Systems, which in
`turn is a continuation-in-part of U.S. patent application Ser.
`No. 07/806,695 filed 12 Dec., 1991 now U.S. Pat. No.
`5,515,378 issued May 7, 1996 for Spatial Division Multiple
`Access Wireless Communication Systems and Ser. No.
`08/234,747 filed 28 Apr., 1994 now U.S. Pat. No. 5,546,090
`issued Aug. 13, 1996 for Method and Apparatus for Cali(cid:173)
`brating Antenna Arrays.
`
`BACKGROUND OF THE INVENTION
`
`This invention relates to wireless communication systems
`and, more particularly, to using antenna arrays and signal
`processing to dramatically increase the capacity and perfor(cid:173)
`mance of wireless communication systems.
`Wireless communication systems can be used to comple(cid:173)
`ment and in some instances replace conventional wired
`communication systems in areas where conventional wire(cid:173)
`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, 35
`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 communi(cid:173)
`cations just like conventional telephone systems, and for 40
`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 infor(cid:173)
`mation. The information transfer can be performed in real(cid:173)
`time such as is the case for circuit-switched voice conver(cid:173)
`sations 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 distin(cid:173)
`guished by frequency, by time, by code, or by some com(cid:173)
`bination of the above. Each of these communication chan(cid:173)
`nels 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 chan(cid:173)
`nels. Herein, the channels share a common recourse, they
`may be non-overlapping, partially overlapping or full over(cid:173)
`lapping. Depending on the available frequency allocations,
`the wireless system might have from one to several hundred
`communication channels. To provide full-duplex communi-
`
`5
`
`2
`cation 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 sta-
`tions (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
`10 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
`15 base station can communicate simultaneously with many
`remote terminals by using different conventional communi(cid:173)
`cation channels for each remote terminal.
`As aforementioned, base stations can act as PoPs, pro(cid:173)
`viding connection to one or more wired communication
`20 systems. Such systems include local data networks, wide
`area data networks, and PSTNs. Thus, 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
`25 wired network such as in local area emergency and mobile
`battlefield communication systems. Base stations can pro(cid:173)
`vide connectivity of various kinds as well. In the aforemen(cid:173)
`tioned examples, point-to-point communications where
`roughly equal amounts of information flow in both direc-
`30 tions 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 communications 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 commu(cid:173)
`nicate effectively with the base station when interference is
`45 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
`50 provide capacity anywhere near that of wired communica(cid:173)
`tion systems.
`In the co-pending parent U.S. patent application Ser. No.
`08/375,848 entitled "Spectrally Efficient High Capacity
`Wireless Communication Systems", filed 20 Jan., 1995, we
`55 have previously disclosed using antenna arrays and signal
`processing to separate combinations of received (uplink)
`signals. We also disclosed using transmit spatially multi(cid:173)
`plexed downlink signals. The result is an increase in spectral
`efficiency, capacity, signal quality, and coverage of wireless
`60 communication systems. Capacity is increased by allowing
`multiple users to simultaneously share the same communi(cid:173)
`cation 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.
`65 Signal quality and coverage area are improved through
`appropriate processing of signals received from and trans(cid:173)
`mitted by multiple antenna elements. Moreover, a goal of
`
`Samsung Ex. 1018
`Page 13
`
`

`

`5,828,658
`
`(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 i'h element in the base
`station array. Assuming that a vector of complex signals
`s,(t)=[s,i(t), ... , s,,u(t)Y were transmitted from the antenna
`array, the output of the remote terminal receiver would be
`given by
`
`4
`In the parent application Ser. 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,
`
`3
`invention described in the parent application Ser. 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 Ser. No. 5
`08/375,848 comprises antenna arrays and signal processing
`means for measuring, calculating, storing, and using spatial
`signatures of receivers and transmitters in wireless commu(cid:173)
`nication systems to increase system capacity, signal quality,
`and coverage, and to reduce overall system cost. The 10
`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 com- 15
`munication links are being managed.
`As an example, in a wireless local loop application, a
`particular base station might serve as a PoP for many remote
`terminals and employ the antenna array and signal process(cid:173)
`where n,(t) represents noise present in the environment and
`ing described herein. Additionally, remote terminals could 20
`the receiver. These spatial signatures are calculated
`employ antenna arrays and signal processing to further
`( estimated) and stored at each base station for each remote
`improve their capacity and signal quality over simpler
`terminal in its cell and for each channel. For fixed remote
`remote terminals that handle fewer communication links.
`terminals and base stations in stationary environments, the
`Herein, the distinction between base stations and remote
`spatial signatures can be updated infrequently. In general,
`terminals is that base stations generally act as concentrators 25
`however, changes in the RF propagation environment
`connecting to multiple remote units simultaneously, possibly
`between the base station and the remote terminal can alter
`providing a high capacity connection to a wide area network.
`the signatures and require that they be updated. Note that
`While for the sake of clarity much of the ensuing discussion
`henceforth, the time argument in parentheses will be sup(cid:173)
`is couched in terms of simple remote terminals that do not
`pressed; integers inside parentheses will be used solely for
`employ antenna arrays, nothing herein should be interpreted 30
`indexing into vectors and matrices.
`as preventing such an application. Thus, while hereafter
`In the previous discussion, temporally matched receivers
`spatial signatures will be associated primarily with remote
`and transmitters were assumed. If there are differences in the
`terminals, when antenna arrays are employed at remote
`temporal responses, these can be equalized using temporal
`terminals, base stations will have associated spatial signa(cid:173)
`35 filtering techniques as is well-known. Furthermore, the
`tures as well.
`channel bandwidths were assumed to be small compared to
`Briefly, as described in the parent application Ser. No.
`the center frequency of operation. Large bandwidth channels
`08/375,848, there are two spatial signatures associated with
`may require more than one complex vector to accurately
`each remote terminal/base station pair on a particular fre(cid:173)
`describe the outputs as is well known.
`quency channel, where for the purpose of this discussion it
`In the parent application Ser. No. 08/375,848, when more
`is assumed that only base stations have antenna arrays. Base 40
`than one remote terminal wants to communicate at the same
`stations associate with each remote terminal in their cell a
`time, the signal processing means at the base station uses the
`spatial signature related to how that remote terminal receives
`spatial signatures of the remote terminals to determine if
`signals transmitted to it by the base station's antenna array,
`subsets of them can communicate with the base station
`and a second spatial signature related to how the base
`station's receive antenna array receives signals transmitted 45 simultaneously by sharing a channel. In a system with m
`receive and in transmit antenna elements, up to m remote
`by the remote terminal. In a system with many channels,
`terminals can share the same channel at the same time.
`each remote terminal/base station pair has transmit and
`When multiple remote terminals are sharing a single
`receive spatial signatures for each channel.
`uplink channel, the multiple antenna elements at the base
`The receive spatial signature characterizes how the base
`50 station each measure a combination of the arriving uplink
`station antenna array receives signals from the particular
`signals and noise. These combinations result from the rela(cid:173)
`remote unit in a particular channel. In one embodiment, it is
`tive locations of the antenna elements, the locations of the
`a complex vector containing responses ( amplitude and phase
`remote terminals, and the RF propagation environment. The
`with respect to a reference) of each the antenna element
`signal processing means calculates spatial demultiplexing
`receivers., i.e., for an m-element array,
`55 weights to allow the uplink signals to be separated from the
`h,-[h,',h/, ... ,h, my,
`combinations of uplink signals measured by the multiple
`(1)
`antenna elements.
`where h/ is the response of the ith receiver to a unit power
`In applications where different downlink signals are to be
`transmitted signal from the remote terminal. Assuming that
`sent from the base station to the remote terminals, the signal
`a narrowband signal sr{t) is transmitted from the remote
`60 processing means computes spatial multiplexing weights
`terminal, the base station receiver outputs at time t are then
`that are used to produce multiplexed downlink signals,
`given by
`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
`65 quality.
`In applications where the same signal is to he transmitted
`from the base station to a large number (more than the
`
`z,(t)-h,Ts,(t-,;)+n,(t),
`
`(4)
`
`(2)
`x,(t)-h,s,(t-,;)+n,(t),
`where -i: 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.
`
`Samsung Ex. 1018
`Page 14
`
`

`

`5,828,658
`
`5
`number of antenna elements) of remote terminals, the signal
`processing means computes weights appropriate for broad(cid:173)
`casting the signal, covering the area necessary to reach all
`the remote terminals.
`Therefore, in the parent application Ser. No. 08/375,848, 5
`the signal processing means facilitates simultaneous com(cid:173)
`munication 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 10
`combination of the above. In one embodiment, all elements
`of a single antenna array transmit and receive radio fre(cid:173)
`quency signals, while in another embodiment the antenna
`array includes separate transmit antenna elements and
`receive antenna elements. The number of transmit and 15
`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 Ser. No.
`08/375,848, it is assumed that such time equalization, if 20
`required, is carried out after spatial demultiplexing. Chan(cid:173)
`nelization 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 equaliza- 25
`tion 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 pro(cid:173)
`cessing together as a single spatio-temporal processing step, 30
`and for methods and apparatus for carrying out such spatio(cid:173)
`temporal processing.
`
`SUMMARY OF THE INVENTION
`Accordingly, an object of the present invention is to use 35
`antenna arrays and signal processing to separate combina(cid:173)
`tions of received (uplink) signals using spatio-temporal
`signal processing. Another object of the present invention is
`to transmit spatially multiplexed downlink signals, the spa(cid:173)
`tially multiplexed downlink signals determined by spatio- 40
`temporal processing.
`Briefly, the invention comprises antenna arrays and signal
`processor for measuring, calculating, storing, and using
`spatio-temporal signatures of receivers and transmitters in
`wireless communication systems to increase system 45
`capacity, signal quality, and coverage, and to reduce overall
`system cost. The antenna array and signal processor can be
`used at base stations (Pops) and remote terminals. Generally
`there can be different processing requirements at base sta(cid:173)
`tions where many signals are being concentrated than at 50
`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 serve as a PoP for many remote
`terminals and use the antenna array and signal processing 55
`described herein. Additionally, remote terminals could use
`antenna arrays and signal processing to further improve their
`capacity and signal quality over simpler remote terminals
`that handle fewer communication links. As the terms are
`used herein, the distinction between base stations and
`remote terminals is that base stations generally act as
`concentrators connecting to multiple remote units
`simultaneously, possibly providing a high capacity connec(cid:173)
`tion to a wide area network. For simplicity, much of the
`description herein is for a system with simple remote 65
`terminals that do not use antenna arrays. However nothing
`herein should be interpreted as preventing such an applica-
`
`60
`
`6
`tion. Thus, while hereafter spatio-temporal signatures will
`be associated primarily with remote terminals, when antenna
`arrays are used at remote terminals, base stations will have
`associated spatio-temporal signatures as well.
`The spatio-temporal 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 spatio-temporal
`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.
`When more than one remote terminal wants to commu(cid:173)
`nicate at the same time, the signal processor at the base
`station uses the spatio-temporal signatures of the remote
`terminals to determine if subsets of them can communicate
`with the base station simultaneously by sharing channels.
`When multiple remote terminals are using overlapping
`uplink channels, the multiple antenna elements at the base
`station each measure a combination of the arriving uplink
`signals and noise. These combinations result from the rela(cid:173)
`tive 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. The signal processor
`calculates spatio-temporal 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 arc 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.
`In applications where the same signal is to be transmitted
`from the base station to a large number of remote terminals,
`the signal processor computes spatio-temporal transmit
`weights appropriate for broadcasting the signal, covering the
`area necessary to reach all the remote terminals.
`Therefore, the signal processor facilitates simultaneous
`communication between a base station and multiple remote
`terminals on overlapping channels. The channel may be a
`frequency channel (frequency division multiple access,
`FDMA), a time slot in a time division multiplexed system
`(time division multiple access, TDMA), a code in a code
`division multiplexed system ( code division multiple access,
`CDMA), or any combination of the above. The channel may
`also be composed of multiple conventional channels.
`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.
`The invention and objects and features thereof will be
`more readily apparent from the following detailed descrip(cid:173)
`tion together with the figures and appended claims.
`
`Formulation and Notation
`
`There are two spatio-temporal signatures associated with
`each remote terminal/base station pair on a particular fre(cid:173)
`quency channel, where for the purpose of this discussion it
`is assumed that only base stations have antenna arrays. Base
`
`Samsung Ex. 1018
`Page 15
`
`

`

`5,828,658
`
`8
`
`x,(t)
`
`x,(t-T)
`
`5
`
`z,(t)-
`
`- H,s;:'r+L,-l(t - ,;) + e,(t).
`
`x,(t-T(L,-1))
`
`where Lr i the length of
`
`sliding window
`
`h, 0
`
`0 h,
`
`Hr=
`
`0
`
`0
`
`n,(t)
`
`n,(t-T)
`
`0
`
`0
`
`0
`
`e,(t)-
`
`0
`
`h,
`
`n,(t-T(L, -1))
`
`(8)
`
`(9)
`
`r is called t e receive
`atrix
`The mLr y (Mr+Lr-1)
`spatio-temporal signature for the remote terminal transmit(cid:173)
`ting s/t) at the base station receiving z/t) on a particular
`channel.
`When a plurality of remote terminals are active on the
`same channel, the individual receive spatio-temporal signa(cid:173)
`tures arc collected in the demultiplexing spatio-temporal
`
`signature matrix, J{ r· For each channel, J{ r' is formed
`from the individual spatio-temporal receive signatures
`
`(10)
`
`10
`
`15
`
`20
`
`25
`
`30 where H/ 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=l,
`35 and the sliding window length is also one, Lr=l, this
`spatio-temporal signature corresponds to the spatial signa(cid:173)
`ture as described in our co-pending U.S. patent application
`Ser. No. 08/375,848 entitled "Spectrally Efficient High
`Capacity Wireless Communication Systems", filed 20 Jan.,
`40 1995. For this case, the channel response matrix, hr, is a
`column vector and the receive vector has the form
`
`7
`stations associate with each remote terminal in their cell a
`transmit spatio-temporal signature related to how that
`remote terminal receives signals transmitted to it by the base
`station's antenna array, and a receive spatio-temporal sig(cid:173)
`nature 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 spatio-temporal signa(cid:173)
`tures for each channel.
`
`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 s/t) is transmitted from the remote terminal. Let
`in be the number of antennas and associated receivers at the
`base station. Then, in one embodiment the m base station
`receiver outputs, at time t can be expressed as
`
`x,(t)-
`
`xc1(t)
`
`x,z(t)
`
`Xrm(t)
`
`where
`
`s,(t-,;)
`
`s,(t-T-i:)
`
`s,(t - (M, - 1)T- i:)
`
`(5)
`
`(6)
`
`and hr is the channel response matrix and is in this embodi(cid:173)
`ment 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 -i:, T is the sampling time and is in this
`embodiment assumed to satisfy Nyquist's well known sam- 45
`pling theorem, Mr is the length of the channel response, and
`n/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
`
`50
`
`h,(1)
`
`h,(m)
`
`(7)
`
`55
`
`z,(t)-h,s,(t-i:)+n,(t).
`
`(11)
`
`This is an appropriate model for narrow band communica(cid:173)
`tion 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 applica(cid:173)
`tion Ser. No. 08/375,848 entitled "Spectrally Efficient High
`Capacity Wireless Communication Systems", filed 20 Jan.,
`1995.
`Another special case of the model above i