USOO6992621B2
`
`(12) United States Patent
`Casas et al.
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 6,992,621 B2
`Jan. 31, 2006
`
`(54) WIRELESS COMMUNICATION AND BEAM
`FORMING WITH PASSIVE BEAMFORMERS
`(75) Inventors: Eduardo Casas, Vancouver (CA);
`Marcus da Silva, Spokane, WA (US)
`
`(73) Assignee: Vivato, Inc., San Francisco, CA (US)
`* ) Notice:
`Subject to any disclaimer, the term of this
`y
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`(21) Appl. No.: 10/384,380
`(22) Filed:
`Mar. 7, 2003
`(65)
`Prior Publication Data
`US 2004/0174299 A1
`Sep. 9, 2004
`(51) Int. Cl.
`(2006.01)
`HOIO 3/24
`(52) U.S. Cl. ....................................... 342/373; 342/374
`(58) Field of Classification Search ................ 342/373,
`342/374
`See application file for complete Search history.
`References Cited
`
`(56)
`
`U.S. PATENT DOCUMENTS
`
`6,470,192 B1 * 10/2002 Karlsson et al. ......... 455/562.1
`2001/OO16504 A1
`8/2001 Dam et al. .................. 455/562
`2002/O163478 A1 11/2002 Pleva et al. ................. 343/853
`
`OTHER PUBLICATIONS
`P. Lehne et al., An Overview of Smart Antenna Technology
`for Mobile Communications Systems, IEEE Communica
`tions Surveys, vol. 2(4), p. 2-13, 1999.*
`K. Uehara et al., A planar Sector antenna for indoor high
`Speed wireleSS communication terminals, IEEE Antennas
`and Propagation Society International Symposium Digest,
`vol. 2, p. 1352-1355, Jul. 1997.*
`F. Caldwell Jr. et al., Design and implementation of a
`Switched-beam Smart antenna for an 802.11b wireless access
`point, IEEE Radio and Wireless Conference, p. 55-58, Aug.
`2002.*
`
`(Continued)
`Primary Examiner Thomas H. Tarcza
`ASSistant Examiner-F H Mull
`(74) Attorney, Agent, or Firm-Lee & Hayes, PLLC
`(57)
`ABSTRACT
`
`WireleSS communication and beam forming is improved by
`depopulating one or more ports of a passive beam former
`Such as a Butler matrix and/or by increasing the order
`thereof. In an exemplary implementation, an acceSS Station
`
`3.295,134. A * 12/1966 Lowe - - - - - - - - - - - - - - - - - - - - - - - - - 342/368
`
`includes: a Butler matrix having “M” antenna ports and “N
`
`transmit and/or receive (TRX) ports; wherein at least a
`3,836,970 A : 9/1974 Reitzig ....................... 342/373
`portion of the “M” antenna ports and/or at least a portion of
`3,858,218 A 12/1974 Masak et al. ............... 342/406
`the "N' TRX ports are depopulated. In another exemplar
`4,231,040 A * 10/1980 Walker ....................... 342/373
`4,639,732 A
`1/1987 Acoraci et al. ............. E implementati p
`p E. includes: a Buil
`E. y
`5,115,248 A
`5/1992 Roederer .................... 342.373
`Implementauon, an access Slauon includes: a tsuuer matrix
`5,162,804 A * 11/1992 Uyeda ........................ 342/373
`that has multiple antenna ports and multiple TRX ports, a
`5,610,617 A
`3/1997 Gans et al. ................. 342/373
`Signal processor, and a Signal Selection device that is capable
`5,666,123 A * 9/1997 Chrystie ..................... 342/373
`of coupling the Signal processor to a Subset of the multiple
`6,104.935 A * 8/2000 Smith et al. .
`... 455/562.1
`TRX ports responsive to a signal quality determination, the
`6,167.036 A 12/2000 Beven ........................ 455/440
`Signal Selection device adapted to Switch the Signal proces
`6.252,544 B1
`6/2001 Hoffberg
`sor from a first TRX port to a second TRX port of the Subset
`6,340,948 B1
`1/2002 Munoz-Garcia et al.
`of TRX ports.
`6,353,410 B1* 3/2002 Powell ....................... 342/373
`6,397,082 B1* 5/2002 Searle ..................... 455/562.1
`6,429,812 B1
`8/2002 Hoffberg
`
`39 Claims, 10 Drawing Sheets
`
`208(1)
`
`208(6)
`208(7)
`
`208(0) hit...If.
`
`A: O 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
`
`
`
`
`
`BUTLER MATRIX
`
`302
`
`TRX: 0 1 2 3 4 5 6 7 8 9 10 11 12 1314 15
`
`304(O) B
`
`304(1)
`
`304(7)
`
`304(6)
`
`VWGoA EX1026
`U.S. Patent No. 10,965,512
`
`

`

`US 6,992.621 B2
`Page 2
`
`OTHER PUBLICATIONS
`W.X. Sheng et al., Super-resolution DOA estimation in
`Switch beam Smart antenna, Proceedings of the 5th Interna-
`tional Symposium on Antennas, Propagation and EM
`Theory, p. 603-606, Aug. 2000.*
`
`M.V. Clark et al., Outdoor IEEE 802.11 cellular networks:
`radio link performance, IEEE International Conference on
`Communication, vol. 1, p. 512-516, 2002.
`
`c:
`
`* cited by examiner
`
`

`

`U.S. Patent
`
`Jan. 31, 2006
`
`Sheet 1 of 10
`
`US 6,992,621 B2
`
`100 y
`
`
`
`ACCESS
`STATION
`
`102 -
`
`ul
`
`106(2)
`- ZZ
`
`-zo
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`ETHERNET
`BACKBONE
`
`WIRELESS
`INPUT)
`OUTPUT
`UNIT
`
`
`
`ACCESS STATION
`202
`
`
`
`272, 2
`
`

`

`U.S. Patent
`
`Jan. 31, 2006
`
`Sheet 2 of 10
`
`US 6,992,621 B2
`
`WRELESS INPUT/OUTPUT UNIT
`
`
`
`208(1)
`208(O)
`
`208(14)
`208(15)
`
`2 3 4 5 - 6 7 8 9 10 11 12 13 14 15
`
`BUTLER MATRIX
`
`O2
`
`2 3 4 5 6 7 8 9 10 11 12 13 14 15
`
`SSSSSSSSSSSSSSSS
`PPPPPPPPPPPPPPPP
`
`304(O)
`304(1)
`
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`304(15)
`304(14)
`
`BASEBAND PROCESSOR(S)
`
`

`

`U.S. Patent
`
`Jan. 31, 2006
`
`Sheet 3 of 10
`
`US 6,992,621 B2
`
`402(0)
`
`402(1) 2N.
`
`3-\:
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`402(15)
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`

`

`U.S. Patent
`
`Jan. 31, 2006
`
`Sheet 4 of 10
`
`US 6,992,621 B2
`
`208(1)
`208(O)
`
`208(14)
`208(15)
`
`
`
`A: O 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
`
`BUTLER MATRIX
`
`3O
`
`TRX: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
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`P.
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`304(1)
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`304(7)
`304(6)
`
`272, 6
`
`

`

`U.S. Patent
`
`Jan. 31, 2006
`
`Sheet 5 of 10
`
`US 6,992,621 B2
`
`208(1)
`208(O)
`
`208(6)
`208(7)
`
`
`
`: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
`
`BUTLER MATRIX
`
`3O2
`
`: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
`
`SSSSSSSSSSSSSSSS
`PPPPPPPPPPPPPPPP
`
`304(O)
`304(1)
`
`304(15)
`304(14)
`
`272, 7
`
`

`

`U.S. Patent
`
`Jan. 31, 2006
`
`Sheet 6 of 10
`
`US 6,992,621 B2
`
`208(1)
`208(O)
`
`208(6)
`208(7)
`
`
`
`A: O 1 2 3 4 5 6 7 8 9 10 1 1 12 13 14 15
`
`BUTLER MATRIX
`
`302
`
`TRX: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
`
`S
`P.
`
`IS
`P.
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`
`304(O)
`304(1)
`
`304(7)
`304(6)
`
`272, S
`
`

`

`U.S. Patent
`
`Jan. 31, 2006
`
`Sheet 7 of 10
`
`US 6,992,621 B2
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`208(0)
`
`208(1)
`
`208(2)
`
`208(3)
`
`
`
`A: O 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
`
`BUTLER MATRIX
`
`O2
`
`TRX: 0 1 2 3 4 5 6 7 8 9 10 1 1 12 13 14 15
`
`s
`
`S
`P
`
`S
`P
`
`S
`P
`
`304(O)
`
`304(1)
`
`(2)
`304
`
`304(3)
`
`276, 9
`
`

`

`U.S. Patent
`
`Jan. 31, 2006
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`Sheet 8 of 10
`
`US 6,992,621 B2
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`208(2)
`208(O)
`
`208(12)
`208(15)
`
`
`
`A: O 2 4 6 8 10 12 14 16 1820 22 24 26 28 30 31
`
`BUTLER MATRIX
`
`02
`
`TRX: O 2 4 6 8 10 12 14 16 1820 22 24 26 28 30 31
`
`SSSSSSSSSSSSSSSS
`PPPPPPPPPPPPPPPP
`
`304(O)
`304(2)
`
`304(15)
`304(14)
`
`272, to
`
`

`

`U.S. Patent
`
`Jan. 31, 2006
`
`Sheet 9 of 10
`
`US 6,992,621 B2
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`1106(O)
`1106(1) x-A-A. 1106(N-1)
`
`t
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`A.
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`
`- "
`
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`
`208(O)
`
`208(1)
`
`208(M-1)
`
`
`
`MXN BUTLER MATRIX
`
`O2
`
`
`
`SIGNAL
`SELECTION
`
`SIGNAL
`QUALITY
`DETERMINER
`
`104
`
`304(O)
`
`272, it
`
`

`

`U.S. Patent
`
`Jan. 31, 2006
`
`Sheet 10 of 10
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`US 6,992,621 B2
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`1200 y
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`1218(A)
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`
`
`
`
`
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`
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`
`
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`
`
`
`
`
`
`SWITCH SIGNAL CRUALITY DETERMINERTO
`A FIRST TRXPORT OF A BUTLER MATRIX
`
`1202
`
`DETERMINE SIGNAL OUALITY FROMA
`A FIRST BEAM OF THE BUTLER MATRIX
`
`SWITCH SIGNAL OUALITY DETERMINERTO
`A SECONDTRXPORT OF THE BUTLER MATRIX
`
`DETERMINE SIGNAL OUALITY FROMA
`A SECOND BEAM OF THE BUTLER MATRIX
`
`COMPARESIGNAL OUALITIES FROM THE
`FIRST AND SECOND BEAMS OF THE BUTLER MATRIX
`
`1204
`
`1206
`
`1208
`
`1210
`
`
`
`SELECT FIRST
`TRXPORT FOR
`TRANSCEIVING
`
`1218(B)
`
`SIGNAL CR OF
`FIRST > SIGNALC)
`OF SECOND
`?
`
`
`
`SELECT SECOND
`TRXPORT FOR
`TRANSCEIVING
`
`1218(C)
`
`272, 12
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`
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`
`
`
`
`
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`
`
`
`
`

`

`1
`WIRELESS COMMUNICATION AND BEAM
`FORMING WITH PASSIVE BEAMFORMERS
`
`TECHNICAL FIELD
`
`This disclosure relates in general to wireleSS communi
`cation and beam forming using passive beam formers and in
`particular, by way of example but not limitation, to improv
`ing at least one aspect of wireleSS communication by
`depopulating one or more ports of a passive beam former
`and/or by increasing the order of a passive beam former Such
`as a Butler matrix.
`
`BACKGROUND
`
`15
`
`In wireleSS communication, Signals are Sent from a trans
`mitter to a receiver using electromagnetic waves that ema
`nate from an antenna. These electromagnetic waves may be
`Sent equally in all directions or focused in one or more
`desired directions. When the electromagnetic waves are
`focused in a desired direction, the pattern formed by the
`electromagnetic wave is termed a “beam' or “beam pattern.”
`Hence, the production and/or application of Such electro
`magnetic beams are typically referred to as “beam forming.”
`Beamforming may provide a number of benefits Such as
`greater range and/or coverage per unit of transmitted power,
`improved resistance to interference, increased immunity to
`the deleterious effects of multipath transmission Signals, and
`So forth. Beamforming can be achieved (i) using a finely
`tuned vector modulator to drive each antenna element to
`thereby arbitrarily form beam shapes, (ii) by implementing
`full adaptive beam forming, and (iii) by connecting a trans
`mit/receive Signal processor to each port of a Butler matrix.
`A traditional Butler matrix is a passive device that forms
`beams of a pre-determined size and shape that emanate from
`an antenna array that is connected to the Butler matrix. The
`Butler matrix includes a first set of ports that connect to the
`antenna array and a Second Set of ports that connect to
`multiple transmit/receive signal processors. The first Set of
`ports are denoted as antenna ports, and the Second set of
`ports are denoted as transmit/receive ports. The number of
`ports in each of the first and Second Sets may be considered
`to determine the order of the Butler matrix. While not
`required, Butler matrices typically have an order that is a
`power of two, Such as 4, 8, 16, 32, and So forth. In a
`conventional wireleSS communications environment, every
`port of the Set of antenna ports of a Butler matrix is
`connected to an antenna element, and every port of the Set
`of transmit/receive ports of a Butler matrix is connected to
`a signal processor.
`By way of example, a Butler matrix may have an order of
`16. In this case, there are 16 transmit/receive signal proces
`sors connected to the 16 transmit/receive ports of the Butler
`matrix, and there are 16 antenna elements connected to the
`16 antenna ports of the Butler matrix. In operation, multiple
`individual beams of a fixed size and shape emanate from the
`antenna array. Signals transmitted in and received from each
`of the respective 16 beams map to a predetermined one of
`the 16 Signal processors on the 16 transmit/receive ports of
`the Butler matrix. Thus, there is a one-to-one correspon
`dence between (i) each beam formed by the combination of
`the Butler matrix and the antenna array and (ii) each signal
`processor that is connected to the Butler matrix.
`Accordingly, there is a need for Schemes and/or tech
`niques for improving the variety and Versatility of wireleSS
`communication and beam forming options.
`
`25
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`35
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`40
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`US 6,992,621 B2
`
`2
`SUMMARY
`
`Improving at least one aspect of wireleSS communication
`and beam forming is enabled by depopulating one or more
`ports of a passive beam former Such as a Butler matrix and/or
`by increasing the order thereof. In conjunction with Such
`depopulation, one or more signal Selection Schemes may be
`employed to select a transmit/receive (TRX) port for wire
`leSS communication from among multiple TRX ports of a
`passive beam former.
`In an exemplary described acceSS Station implementation,
`an acceSS Station for wireleSS communications includes: a
`Butler matrix that has “M” antenna ports and “N” TRX
`ports; wherein at least a portion of the “M” antenna ports
`and/or at least a portion of the “N' TRX ports are depopu
`lated.
`In another exemplary described access Station implemen
`tation, an acceSS Station for wireleSS communications
`includes: a Butler matrix that has multiple antenna ports and
`multiple TRX ports, a signal processor; and a Signal Selec
`tion device that is capable of coupling the Signal processor
`to a Subset of the multiple TRX ports responsive to a signal
`quality determination, the Signal Selection device adapted to
`Switch the signal processor from a first TRX port of the
`Subset of TRX ports to a second TRX port of the Subset of
`TRX ports.
`In yet another exemplary described acceSS Station imple
`mentation, an acceSS Station for wireleSS communications
`includes: a passive beam former having multiple antenna
`ports and multiple TRX ports, and an antenna array having
`multiple antenna elements that are coupled to at least a
`portion of the multiple antenna ports of the passive beam
`former, the multiple TRX ports numbering more than the
`multiple antenna elements, wherein signals that are applied
`to the multiple TRX ports of the passive beam former are
`transceived on multiple communication beams that are
`formed jointly by the passive beam former and the antenna
`array, and wherein the acceSS Station is adapted to have an
`aiming resolution for communication beams of the multiple
`communication beams that is finer than a width of a nar
`rowest communication beam of the multiple communication
`beams.
`In an exemplary described method implementation, a
`method for an access Station includes the actions of com
`paring a first Signal quality from a first communication beam
`to a Second Signal quality from a Second communication
`beam; if the first Signal quality is greater than the Second
`Signal quality, then transceiving from a first TRX port of a
`Butler matrix; and if the Second Signal quality is greater than
`the first signal quality, then transceiving from a Second TRX
`port of the Butler matrix.
`Other method, System, apparatus, acceSS Station, Butler
`matrix, arrangement, etc. implementations are described
`herein.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The same numbers are used throughout the drawings to
`reference like and/or corresponding aspects, features, and
`components.
`FIG. 1 is an exemplary general wireleSS communications
`environment.
`FIG. 2 is an exemplary wireless LAN/WAN (Wi-Fi)-
`Specific wireleSS communications environment that includes
`a wireless input/output (I/O) unit.
`FIG. 3 is an exemplary wireless I/O unit as shown in FIG.
`2 that includes a Butler matrix and an antenna array.
`
`

`

`US 6,992,621 B2
`
`3
`FIG. 4 illustrates an exemplary Set of communication
`beams that emanate from an antenna array as shown in FIG.
`3.
`FIG. 5 illustrates exemplary beam widths of the set of
`communication beams as shown in FIG. 4.
`FIG. 6 illustrates an exemplary Butler matrix with mul
`tiple transmit/receive (TRX) ports in a depopulated State.
`FIG. 7 illustrates an exemplary Butler matrix with mul
`tiple antenna ports in a depopulated State.
`FIG. 8 illustrates an exemplary Butler matrix with both
`multiple TRX ports in a depopulated State and multiple
`antenna ports in a depopulated State.
`FIG. 9 illustrates another exemplary Butler matrix with
`both multiple TRX ports in a depopulated State and multiple
`antenna ports in a depopulated State.
`FIG. 10 illustrates yet another exemplary Butler matrix
`with both multiple TRX ports in a depopulated state and
`multiple antenna ports in a depopulated State.
`FIG. 11 illustrates a Butler matrix having at least one TRX
`port in a depopulated State that is coupled to an exemplary
`Signal Selection device.
`FIG. 12 is a flow diagram that illustrates an exemplary
`method for using a Butler matrix having a TRX port that is
`in a depopulated State in conjunction with a signal Selection
`device for transceiving communication signals.
`
`15
`
`25
`
`4
`output (I/O) unit 206. Exemplary access station 202 is an
`example of an access station 102 (of FIG. 1) that operates in
`accordance with a Wi-Fi-compatible or similar standard.
`Access station 202 is coupled to an Ethernet backbone 204.
`Access Station 202, especially because it is illustrated as
`being directly coupled to Ethernet backbone 204 without an
`intervening Ethernet router or Switch, may itself be consid
`ered a Wi-Fi Switch.
`Access station 202 includes wireless I/O unit 206. Wire
`less I/O unit 206 includes an antenna array 208 that is
`implemented as two or more antennas, and optionally as a
`phased array of antennas. Wireless I/O unit 206 is capable of
`transmitting and/or receiving (i.e., transceiving) wireless
`communication(s) 106 via antenna array 208. These wireless
`communication(s) 106 are transmitted to and received from
`(i.e., transceived with respect to) remote client 104.
`FIG. 3 is an exemplary wireless I/O unit 206 as shown in
`FIG. 2 that includes a Butler matrix 302 and an antenna array
`208. Wireless I/O unit 206 also includes multiple signal
`processors (SPs) 304 and one or more baseband processors
`306. Baseband processors 306 accept communication sig
`nals from and provide communication Signals to the multiple
`transmit and receive signal processors 304. A Separate
`baseband processor 306 may be assigned to each Signal
`processor 304, or a single baseband processor 306 may be
`assigned to more than one, and up to all, of the multiple
`signal processors 304.
`Exemplary Butler matrix 302 is a passive device that
`forms, in conjunction with antenna array 208, communica
`tion beams using Signal combiners, Signal Splitters, and
`signal phase shifters. Butler matrix 302 includes a first side
`with multiple antenna ports (designated by “A”) and a
`Second Side with multiple transmit and/or receive signal
`processor ports (designated by “TRX”). The number of
`antenna ports and TRX ports indicate the order of the Butler
`matrix. Butler matrix 302 includes 16 antenna ports and 16
`TRX ports. Thus, Butler matrix 302 has an order of 16.
`Although Butler matrix 302 is so illustrated, antenna ports
`and TRX ports need not be distributed on separate, much
`less opposite, Sides of a Butler matrix. Also, although not
`necessary, Butler matrices usually have an equal number of
`antenna ports and transmit and/or receive signal processor
`ports (or TRX ports). Furthermore, although Butler matrices
`are typically of an order that is a power of two (e.g., 2, 4, 8,
`16, 32, 64. . . 2"), they may alternatively be implemented
`with any number of ports.
`The sixteen antenna ports of Butler matrix 302 are num
`bered from 0 to 15. Likewise, the sixteen TRX ports are
`numbered from 0 to 15. Antenna ports 0, 1 . . . 14, and 15
`are coupled to and populated with sixteen antennas 208(0),
`208(1). 208(14), and 208(15), respectively. Likewise, TRX
`ports 0, 1... 14, and 15 are coupled to and populated with
`sixteen signal processors 304(0), 304(1) . . .304(14), and
`304(15), respectively. These signal processors are also
`directly or indirectly coupled to baseband processors 306 as
`indicated by the dashed lines. It should be noted that one or
`more active components (e.g., a power amplifier (PA), a
`low-noise amplifier (LNA), etc.) may also be coupled on the
`antenna port side of Butler matrix 302.
`In an exemplary transmission operation, communication
`signals are provided from baseband processors 306 to the
`multiple transmit and/or receive signal processors (SP) 304.
`The multiple signal processors 304 forward the communi
`cation signals to the TRX ports 0, 1... 14, and 15 of Butler
`matrix 302. After Signal combination, Signal Splitting, and
`Signal phase shifting, Butler matrix 302 outputs communi
`cation signals on the antenna ports 0, 1 . . . 14, and 15.
`
`DETAILED DESCRIPTION
`
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`FIG. 1 is an exemplary general wireleSS communications
`environment 100. Wireless communications environment
`100 is representative generally of many different types of
`wireless communications environments, including but not
`limited to those pertaining to wireleSS local area networks
`(LANs) or wide area networks (WANs) (e.g., Wi-Fi) tech
`nology, cellular technology, trunking technology, and So
`forth. In wireless communications environment 100, an
`access Station 102 is in WireleSS communication with remote
`clients 104(1), 104(2). . . 104(N) via communication links
`106(1), 106(2). .
`. 106(N), respectively. Although not
`required, access Station 102 is typically fixed, and remote
`clients 104 are typically mobile. Also, although only three
`remote clients 104 are shown, access station 102 may be in
`wireless communication with many such remote clients 104.
`With respect to a Wi-Fi wireless communications system,
`access station 102 and/or remote clients 104 may operate in
`accordance with any IEEE 802.11 or similar standard. With
`respect to a cellular System, access Station 102 and/or 11
`remote clients 104 may operate in accordance with any
`analog or digital Standard, including but not limited to those
`using time division/demand multiple access (TDMA), code
`division multiple access (CDMA), spread spectrum, Some
`combination thereof, or any other Such technology.
`AcceSS Station 102 may be, for example, a nexus point, a
`trunking radio, a base Station, a Wi-Fi Switch, an acceSS
`point, Some combination and/or derivative thereof, and So
`forth. Remote clients 104 may be, for example, a hand-held
`device, a desktop or laptop computer, an expansion card or
`Similar that is coupled to a desktop or laptop computer, a
`personal digital assistant (PDA), a car having a wireless
`communication device, a tablet or hand/palm-sized com
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`puter, a portable inventory-related Scanning device, Some
`combination thereof, and so forth. Remote clients 104 may
`operate in accordance with any Standardized and/or Special
`ized technology that is compatible with the operation of
`access station 102.
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`FIG. 2 is an exemplary Wi-Fi-specific wireless commu
`nications environment 200 that includes a wireless input/
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`6
`central beam 0. Thus, beams 2 and 14 are both 7 wide, and
`beams 6 and 10 are both 8 wide. Table 1 also indicates the
`beam widths in degrees for the sixteen beams 0 . . . 15.
`
`S
`Individual antennas 208 wirelessly transmit the communi
`cation signals, as altered by Butler matrix 302, from the
`antenna ports in predetermined beam patterns. The beam
`patterns are predetermined by the shape, orientation, con
`stituency, etc. of antenna array 208 and by the alteration of
`the communication signals as “performed by Butler matrix
`302. In addition to transmissions, wireleSS Signals. Such as
`wireless communications 106 (of FIGS. 1 and 2) are
`received responsive to the communication beams formed by
`antenna array 208 in conjunction with Butler matrix 302 in
`an inverse proceSS.
`FIG. 4 illustrates an exemplary Set of communication
`beams 402 that emanate from the antenna array 208 as
`shown in FIG. 3. In a described implementation, antenna
`array 208 includes sixteen antennas 208(0), 208(1). .
`.
`208(14), and 208(15) (as shown in FIG. 3). Also, a Butler
`matrix 302 (not explicitly shown in FIG. 4) that is coupled
`to antenna array 208 is of a 16" order.
`From the sixteen antennas 208(0) . . . 208(15), sixteen
`different communication beams 402(0) .
`. . 402(15) are
`formed as the wireleSS Signals emanating from antennas 208
`add and Subtract from each other during electromagnetic
`propagation. Communication beams 402(1) . . . 402(15)
`Spread out Symmetrically from the central communication
`beam 402(0). The narrowest beam is the central beam
`402(0), and the beams become wider as they spread outward
`from the center. For example, beam 402(15) is slightly wider
`than beam 402(0), and beam 402(5) is wider than beam
`402(15). Also, beam 402(10) is wider still than beam 402(5).
`The indices 0 . . . 15 for the sixteen different communi
`cation beams 402(0) . .
`. 402(15) may correspond to the
`indices 0 . . . 15 of the antenna ports of Butler matrix 302
`as well as the indices 0 . . . 15 of the TRX ports thereof.
`However, no single communication beam 402(x) necessarily
`corresponds to a single antenna port X of Butler matrix 302
`because each communication beam 402 is formed from the
`interplay of electromagnetic radiation with respect to mul
`tiple, including all, of the antennas of antenna array 208.
`Due to real-world effects of the interactions between and
`among the wireleSS Signals as they emanate from antenna
`array 208 (e.g., assuming a linear antenna array in a
`described implementation), communication beam 402(8) is
`degenerate Such that its beam pattern is formed on both sides
`of antenna array 208. These real-world effects also account
`for the increasing widths of the other beams 402(1... 7) and
`402(15 .
`. . 9) as they spread outward from central beam
`402(0).
`FIG. 5 illustrates exemplary beam widths of the set of
`sixteen communication beams 402(0. .
`. 15) as shown in
`FIG. 4. The different beams are indicated by the same
`indices in FIG. 5 as they are in FIG. 4 above. As also noted
`above, the beam widths of the sixteen different beams 0 . . .
`15 increase as the beams diverge from central beam 0. It
`should be noted that the overall beam pattern may be
`considered to have seventeen different beams (instead of
`Sixteen different beams) if degenerate beam 8 is counted as
`two different beams, even though transceived communica
`tion signals associated there with map to a single signal
`processor (SP) via a single TRX port of a corresponding
`Butler matrix (not shown in FIG. 5).
`The beam widths of the sixteen beams 0 . . . 15 are
`indicated in degrees within the ovals of FIG. 5. Each of the
`indicated beam widths are approximate and may be appli
`cable only to this described implementation. By way of
`example, beam 0 is 6 wide, beam 4 is 7 wide, and beam
`9 is 10 wide. The beam widths of the different beams
`increase in width with a left/right symmetry about the
`
`TABLE 1.
`
`Exemplary set of sixteen beam widths in degrees.
`
`Beam Index
`
`Approximate Beam Width
`
`O
`1 and 15
`2 and 14
`3 and 13
`4 and 12
`5 and 11
`6 and 10
`7 and 9
`8
`
`6
`6
`70
`70
`70
`8°
`8°
`10°
`16
`(x2 for both sides)
`
`In a described implementation, all sixteen beams 0 . . . 15
`are not utilized for wireleSS communications. Specifically,
`beams 7 and 9 are not used because they 8 are too wide
`and/or indiscriminate to be sufficiently beneficial. Further
`more, beam 8 is also ignored because its degenerate nature
`makes it even more difficult for it to be effectively utilized.
`These unused beams 7, 8, and 9 are indicated by dashed lines
`in FIG. 5. The effective coverage Zone is therefore less than
`180. In this described implementation, the angle measure
`ment of the covered area corresponds to approximately 96.
`This 96, which is indicated in FIG. 5 within a rectangle,
`reflects an arc between beam 6 and beam 10, as numbered.
`An access station 202 (of FIG. 2) that omits/ignores
`beams 7, 8, and 9 may therefore be placed in a corner of a
`building or other environment because of the 96° angle of
`coverage from an antenna array 208. Also, TRX ports 7, 8,
`and 9 of a Butler matrix (e.g., of FIG.3) may be depopulated
`because wireless communications on beams 7, 8, and 9 are
`not effectuated.
`It should be noted that beams 7, 8, and 9 need not be
`ignored and that the TRX ports 7, 8, and 9 of a Butler matrix
`302 may be populated with signal processors (SP) 304 even
`if the beams 7, 8, and 9 are ignored. Also, if a Butler matrix
`302 is of an order other than 16, then different communi
`cation beams and possibly a different total number of Such
`communication beams may be ignored for efficiency and/or
`Simplicity reasons when Such different communication
`beams are too indiscriminate and/or too degenerate.
`FIG. 6 illustrates an exemplary Butler matrix 302 with
`multiple transmit and/or receive signal processor (TRX)
`ports in a depopulated state. Butler matrix 302 is a 16" order
`(e.g., a 16x16) Butler matrix. It has sixteen antenna (A) ports
`0... 15 and sixteen TRX ports 0 . . . 15. Each antenna port
`0 . . . 15 is coupled to an antenna 208. Thus, every antenna
`port is coupled to one of the sixteen antennas 208(0... 15).
`However, each TRX port 0 .
`. . 15 is not simultaneously
`coupled to a signal processor (SP) 304. Instead, every two
`TRX ports are coupled to one of eight signal processors
`304(0), 304(1). 304(6), and 304(7).
`Specifically, signal processor 304(0) is coupled to TRX
`port 0 or 1, and signal processor 304(1) is coupled to TRX
`port 2 or 3. Similarly, signal processor 304(6) is coupled to
`TRX port 12 or 13, and signal processor 304(7) is coupled
`to TRX port 14 or 15. Each signal processor 304 is able to
`Switch between being coupled to one of two TRX ports as
`Specifically indicated by the dashed arrows at Signal pro
`cessor 304(0). This switching may be based, for example, on
`Some quality measure. Exemplary approaches and methods
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`US 6,992,621 B2
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`for Switching between TRX ports based on one or more
`quality measures are described further below with reference
`to FIGS. 11 and 12.
`By way of example, signal processor 304(0) may trans
`ceive communication signals via TRX port 0 or TRX port 1
`of Butler matrix 302. When coupled to TRX port 0, signal
`processor 304(0) “sees” (e.g., is able to transceive wireless
`communications via) a communication beam 0 that is
`formed by the combined action/configuration of Butler
`matrix 302 and antenna array 208. On the other hand, when
`coupled to TRX port 1, transceiver 304(0) sees a commu
`nication beam 1 that is formed by the combined action/
`configuration of Butler matrix 302 and antenna array 208.
`Other signal processors 304 may similarly see two different
`communication beams one beam at a time.
`More Specifically, for an implementation that is described
`also with reference to FIG. 5, each signal processor 304 sees
`approximately twice as many total degrees of coverage as it
`would if Butler matrix 302 were in a fully populated State,
`but each Signal processor 304 Sees the Same number of
`degrees of angular coverage as it would in a fully populated
`State at any Single moment. For example, Signal processor
`304(0) is switching between TRX ports 0 and 1 and thus
`between communication beams 0 and 1. Communication
`beams 0 and 1 are both 6. Consequently, signal processor
`304(0) sees (6+6) or 12 of the total coverage area in angular
`units of 6 at any Single moment.
`A Single signal processor 304 Such as Signal processor
`304(0) is thus able to see two different antenna beam
`patterns, such as beams 402(0) and 402(1) (as shown in FIG.
`4). Signal processor 304(0) can therefore handle remote
`clients 104 that are located in either (or both) of beams
`402(0) and 402(1). Also, eight signal processors 304(0. . .
`7) can handle remote clients 104 that are located in up to
`sixteen different beams 402(0. . . 15).
`In this described implementation, financial resources can
`thus be conserved by depopulating half of the TRX ports of
`a Butler matrix 302. This depopulation precipitates several
`effects. For example, in addition to Switching overhead
`and/or delays, there is a concomitant reduction in Simulta
`neous signal handling capability at access Station 202 (of
`FIG. 2). However, when wireless communication is effec
`tuated using a packet-based approach, the same total number
`of remote clients 104 can likely be serviced, even though the
`total number of remote clients 104 that can be serviced
`Simultaneously decreases by approximately one-half.
`FIG. 7 illustrates an exemplary Butler matrix 302 with
`multiple antenna ports in a depopulated State. Butler matrix
`302 is a 16" order Butler matrix, and it also has sixteen
`antenna ports 0 . . . 15 and sixteen TRX ports 0 . . . 15. Each
`TRX port 0... 15 is coupled to a signal processor (SP) 304.
`Thus, every TRX port is coupled to one of the sixteen signal
`processors 304(0. . . 15). However, each antenna port 0...
`15 is not coupled to an antenna 208. Instead, every other
`antenna port of the Sixteen antenna ports 0 . . . 15 is coupled
`to one of eight antennas 208(0), 208(1). 208(6), and 208(7).
`Half of the sixteen antenna ports 0 . . . 15 of