`US008416862B2
`
`c12) United States Patent
`Aldana et al.
`
`(IO) Patent No.:
`(45) Date of Patent:
`
`US 8,416,862 B2
`Apr. 9, 2013
`
`(54) EFFICIENT FEEDBACK OF CHANNEL
`INFORMATION IN A CLOSED LOOP
`BEAMFORMING WIRELESS
`COMMUNICATION SYSTEM
`
`7/2003 Medvedev et al ............. 455/522
`2003/0139196 Al*
`2004/0042558 Al*
`3/2004 Hwang et al. ................. 375/267
`2005/0286663 Al* 12/2005 Poon ............................. 375/347
`
`OTHER PUBLICATIONS
`
`(75)
`
`Inventors: Carlos Aldana, San Francisco, CA (US);
`Joonsuk Kim, San Jose, CA (US)
`
`(73) Assignee: Broadcom Corporation, Irvine, CA
`(US)
`
`A unified algebraic transformation approach for parallel recursive
`and adaptive filtering and SYD algorithms Jun Ma; Parhi, K.K.;
`Deprettere, E.F.; Signal Processing, IEEE Transactions on [see also
`Acoustics, Speech, and Signal Processing, IEEE Transactions on]
`vol. 49, Issue 2, Feb. 2001 pp. 424-437.*
`
`( *) Notice:
`
`Subject to any disclaimer, the term ofthis
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 2247 days.
`
`(21) Appl. No.: 11/237,341
`
`(22) Filed:
`
`Sep.28,2005
`
`(65)
`
`Prior Publication Data
`
`US 2006/0239374 Al
`
`Oct. 26, 2006
`
`Related U.S. Application Data
`
`Continuation-in-part of application No. 11/168, 793,
`filed on Jun. 28, 2005.
`
`Provisional application No. 60/673,451, filed on Apr.
`21, 2005, provisional application No. 60/698,686,
`filed on Jul. 13, 2005.
`
`Int. Cl.
`(2006.01)
`H04K 1110
`U.S. Cl. ......................... 375/260; 375/267; 375/350
`Field of Classification Search ................... 375/267
`See application file for complete search history.
`
`References Cited
`
`(63)
`
`(60)
`
`(51)
`
`(52)
`(58)
`
`(56)
`
`U.S. PATENT DOCUMENTS
`5,541,607 A *
`7/1996 Reinhardt ..................... 342/372
`2002/0187753 Al* 12/2002 Kim et al. ....................... 455/69
`
`* cited by examiner
`
`Primary Examiner - Shuwang Liu
`Assistant Examiner - Michael Neff
`(74) Attorney, Agent, or Firm - Garlick & Markison; Holly
`L. Rudnick
`
`(57)
`
`ABSTRACT
`
`A method for feeding back transmitter beamforming infor(cid:173)
`mation from a receiving wireless communication device to a
`transmitting wireless communication device includes a
`receiving wireless communication device receiving a pre(cid:173)
`amble sequence from the transmitting wireless device. The
`receiving wireless device estimates a channel response based
`upon the preamble sequence and then determines an esti(cid:173)
`mated transmitter beamforming unitary matrix based upon
`the channel response and a receiver beamforming unitary
`matrix. The receiving wireless device then decomposes the
`estimated transmitter beamforming unitary matrix to produce
`the transmitter beamforming information and then wirelessly
`sends the transmitter beamforming information to the trans(cid:173)
`mitting wireless device. The receiving wireless device may
`transform the estimated transmitter beamforming unitary
`matrix using a QR decomposition operation such as a Givens
`Rotation operation to produce the transformer beamforming
`information.
`
`20 Claims, 8 Drawing Sheets
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`U.S. Patent
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`Apr. 9, 2013
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`Sheet 1 of 8
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`U.S. Patent
`
`Apr. 9, 2013
`
`Sheet 4 of 8
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`US 8,416,862 B2
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`U.S. Patent
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`Apr. 9, 2013
`
`Sheet 5 of 8
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`US 8,416,862 B2
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`Apr.9, 2013
`Apr. 9, 2013
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`Sheet 6 of 8
`Sheet 6 of 8
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`US8,416,862 B2
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`i
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`Transmitter uses feedback components to alter its transmitter
`
`Transmit feedback components from receiver to transmitter
`
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`
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`
`
`
`US 8,416,862 B2
`
`1
`EFFICIENT FEEDBACK OF CHANNEL
`INFORMATION IN A CLOSED LOOP
`BEAMFORMING WIRELESS
`COMMUNICATION SYSTEM
`
`CROSS REFERENCES TO RELATED
`APPLICATIONS
`
`This application is a continuation-in-part of U.S. Utility
`application Ser. No. 11/168,793, filed Jun. 28, 2005 which
`claims priority to U.S. Provisional Patent Application Ser.
`No. 60/673,451, filed Apr. 21, 2005, and this application also
`claims priority to U.S. Provisional Patent Application Ser.
`No. 60/698,686, filed Jul. 13, 2005, all of which are incorpo(cid:173)
`rated herein by reference for all purposes.
`
`BACKGROUND OF THE INVENTION
`
`1. Technical Field of the Invention
`This invention relates generally to wireless communica(cid:173)
`tion systems and more particularly to wireless communica(cid:173)
`tions using beamforming.
`2. Description of Related Art
`Communication systems are known to support wireless
`and wire lined communications between wireless and/or wire
`lined communication devices. Such communication systems
`range from national and/or international cellular telephone
`systems to the Internet to point-to-point in-home wireless
`networks. Each type of communication system is con(cid:173)
`structed, and hence operates, in accordance with one or more
`communication standards. For instance, wireless communi(cid:173)
`cation systems may operate in accordance with one or more
`standards including, but not limited to, IEEE 802.11, Blue(cid:173)
`tooth, advanced mobile phone services (AMPS), digital
`AMPS, global system for mobile communications (GSM),
`code division multiple access (CDMA), local multi-point
`distribution systems (LMDS), multi-channel-multi-point dis(cid:173)
`tribution systems (MMDS), and/or variations thereof.
`Depending on the type of wireless communication system,
`a wireless communication device, such as a cellular tele- 40
`phone, two-way radio, personal digital assistant (PDA), per(cid:173)
`sonal computer (PC), laptop computer, home entertainment
`equipment, et cetera communicates directly or indirectly with
`other wireless communication devices. For direct communi(cid:173)
`cations (also known as point-to-point communications), the 45
`participating wireless communication devices tune their
`receivers and transmitters to the same channel or channels
`( e.g., one of the plurality of radio frequency (RF) carriers of
`the wireless communication system) and communicate over
`that channel(s). For indirect wireless communications, each 50
`wireless communication device communicates directly with
`an associated base station ( e.g., for cellular services) and/or
`an associated access point ( e.g., for an in-home or in-building
`wireless network) via an assigned channel. To complete a
`communication connection between the wireless communi- 55
`cation devices, the associated base stations and/or associated
`access points communicate with each other directly, via a
`system controller, via the public switch telephone network,
`via the Internet, and/or via some other wide area network.
`For each wireless communication device to participate in
`wireless communications, it includes a built-in radio trans(cid:173)
`ceiver (i.e., receiver and transmitter) or is coupled to an asso(cid:173)
`ciated radio transceiver (e.g., a station for in-home and/or
`in-building wireless communication networks, RF modem,
`etc.). As is known, the receiver is coupled to the antenna and
`includes a low noise amplifier, one or more intermediate
`frequency stages, a filtering stage, and a data recovery stage.
`
`2
`The low noise amplifier receives inbound RF signals via the
`antenna and amplifies then. The one or more intermediate
`frequency stages mix the amplified RF signals with one or
`more local oscillations to convert the amplified RF signal into
`baseband signals or intermediate frequency (IF) signals. The
`filtering stage filters the baseband signals or the IF signals to
`attenuate unwanted out of band signals to produce filtered
`signals. The data recovery stage recovers raw data from the
`filtered signals in accordance with the particular wireless
`10 communication standard.
`As is also known, the transmitter includes a data modula(cid:173)
`tion stage, one or more intermediate frequency stages, and a
`power amplifier. The data modulation stage converts raw data
`into baseband signals in accordance with a particular wireless
`15 communication standard. The one or more intermediate fre(cid:173)
`quency stages mix the baseband signals with one or more
`local oscillations to produce RF signals. The power amplifier
`amplifies the RF signals prior to transmission via an antenna.
`In many systems, the transmitter will include one antenna
`20 for transmitting the RF signals, which are received by a single
`antenna, or multiple antennas, of a receiver. When the
`receiver includes two or more antennas, the receiver will
`select one of them to receive the incoming RF signals. In this
`instance, the wireless communication between the transmit-
`25 ter and receiver is a single-output-single-input (SISO) com(cid:173)
`munication, even if the receiver includes multiple antennas
`that are used as diversity antennas (i.e., selecting one of them
`to receive the incoming RF signals). For SISO wireless com(cid:173)
`munications, a transceiver includes one transmitter and one
`30 receiver. Currently, most wireless local area networks
`(WLAN) that are IEEE 802.11, 802.1 la, 802,11 b, or 802.1 lg
`employ SISO wireless communications.
`Other types of wireless communications include single(cid:173)
`input-multiple-output (SIMO), multiple-input-single-output
`35 (MISO), and multiple-input-multiple-output (MIMO). In a
`SIMO wireless communication, a single transmitter pro(cid:173)
`cesses data into radio frequency signals that are transmitted to
`a receiver. The receiver includes two or more antennas and
`two or more receiver paths. Each of the antennas receives the
`RF signals and provides them to a corresponding receiver
`path ( e.g., LNA, down conversion module, filters, andADCs ).
`Each of the receiver paths processes the received RF signals
`to produce digital signals, which are combined and then pro(cid:173)
`cessed to recapture the transmitted data.
`For a multiple-input-single-output (MISO) wireless com(cid:173)
`munication, the transmitter includes two or more transmis(cid:173)
`sion paths ( e.g., digital to analog converter, filters, up-conver(cid:173)
`sion module, and a power amplifier) that each converts a
`corresponding portion of baseband signals into RF signals,
`which are transmitted via corresponding antennas to a
`receiver. The receiver includes a single receiver path that
`receives the multiple RF signals from the transmitter. In this
`instance, the receiver uses beam forming to combine the
`multiple RF signals into one signal for processing.
`For a multiple-input-multiple-output (MIMO) wireless
`communication, the transmitter and receiver each include
`multiple paths. In such a communication, the transmitter par(cid:173)
`allel processes data using a spatial and time encoding func(cid:173)
`tion to produce two or more streams of data. The transmitter
`60 includes multiple transmission paths to convert each stream
`of data into multiple RF signals. The receiver receives the
`multiple RF signals via multiple receiver paths that recapture
`the streams of data utilizing a spatial and time decoding
`function. The recaptured streams of data are combined and
`65 subsequently processed to recover the original data.
`To further improve wireless communications, transceivers
`may incorporate beamforming. In general, beamforming is a
`
`
`
`3
`processing technique to create a focused antenna beam by
`shifting a signal in time or in phase to provide gain of the
`signal in a desired direction and to attenuate the signal in other
`directions. Prior art papers (1) Digital beamforming basics
`(antennas) by Steyskal, Hans, Journal of Electronic Defense,
`Jul. 1, 1996; (2) Utilizing Digital Down converters for Effi(cid:173)
`cient Digital Beamforming, by Clint Schreiner, Red River
`Engineering, no publication date; and (3) Interpolation Based
`Transmit Beamforming for MIMO-OFMD with Partial Feed(cid:173)
`back, by Jihoon Choi and Robert W. Heath, University of 10
`Texas, Department of Electrical and Computer Engineering,
`Wireless Networking and Communications Group, Sep. 13,
`2003 discuss beamforming concepts.
`In order for a transmitter to properly implement beamform(cid:173)
`ing (i.e., determine the beamforming matrix [VJ), it needs to 15
`know properties of the channel over which the wireless com(cid:173)
`munication is conveyed. Accordingly, the receiver must pro(cid:173)
`vide feedback information for the transmitter to determine the
`properties of the channel. One approach for sending feedback
`from the receiver to the transmitter is for the receiver to 20
`determine the channel response (H) and to provide it as the
`feedback information. An issue with this approach is the size
`of the feedback packet, which may be so large that, during the
`time it takes to send it to the transmitter, the response of the
`channel has changed.
`To reduce the size of the feedback, the receiver may
`decompose the channel using singular value decomposition
`(SYD) and send information relating only to a calculated
`value of the transmitter's beamforming matrix (V) as the
`feedback information. In this approach, the receiver calcu- 30
`!ates (V) based on H=UDV*, where H is the channel
`response, D is a diagonal matrix, and U is a receiver unitary
`matrix. While this approach reduces the size of the feedback
`information, its size is still an issue for a MIMO wireless
`communication. For instance, in a 2x2 MIMO wireless com- 35
`munication, the feedback needs four elements that are all
`complex Cartesian coordinate values [Vl 1 Vl 2; V21 V22]. In
`general, Vik=aik + j *bik, where aik and bik are values between
`[ -1, 1]. Thus, with 1 bit express per each element for each of
`the real and imaginary components, aik and bik can be either 40
`-½ or ½, which requires 4x2xl =8 bits per tone. With 4 bit
`expressions per each element ofV(f) in an orthogonal fre(cid:173)
`quency division multiplexing (OFDM) 2x2 MIMO wireless
`communication, the number of bits required is 1728 per tone
`( e.g., 4*2*54*4=1728, 4 elements per tone, 2 bits for real and 45
`imaginary components per tone, 54 data tones per frame, and
`4 bits per element), which requires overhead for a packet
`exchange that is too large for practical applications.
`Therefore, a need exists for a method and apparatus for
`reducing beamforming feedback information for wireless 50
`communications.
`
`BRIEF SUMMARY OF THE INVENTION
`
`BRIEF DESCRIPTION OF THE SEVERAL
`VIEWS OF THE DRAWINGS
`
`US 8,416,862 B2
`
`4
`FIG. 2 is a schematic block diagram illustrating an embodi(cid:173)
`ment of a wireless communication device in accordance with
`the present invention;
`FIG. 3 is a schematic block diagram illustrating another
`embodiment of another wireless communication device in
`accordance with the present invention;
`FIG. 4 is a schematic block diagram of baseband transmit
`processing in accordance with the present invention;
`FIG. 5 is a schematic block diagram of baseband receive
`processing in accordance with the present invention;
`FIG. 6 is a schematic block diagram of a beamforming
`wireless communication in accordance with the present
`invention;
`FIG. 7 is a flow chart illustrating another embodiment of
`the present invention for providing beamforming feedback
`information from a receiver to a transmitter; and
`FIG. 8 is a flow chart illustrating another embodiment of
`the present invention for providing beamforming feedback
`information from a receiver to a transmitter
`
`DETAILED DESCRIPTION OF THE INVENTION
`
`FIG. 1 is a schematic block diagram illustrating a commu-
`25 nication system 10 that includes a plurality of base stations
`and/or access points 12, 16, a plurality of wireless communi(cid:173)
`cation devices 18-32 and a network hardware component 34.
`Note that the network hardware 34, which may be a router,
`switch, bridge, modem, system controller, et cetera provides
`a wide area network connection 42 for the communication
`system 10. Further note that the wireless communication
`devices 18-32 may be laptop host computers 18 and 26,
`personal digital assistant hosts 20 and 30, personal computer
`hosts 24 and 32 and/or cellular telephone hosts 22 and 28. The
`details of the wireless communication devices will be
`described in greater detail with reference to FIG. 2.
`Wireless communication devices 22, 23, and 24 are located
`within an independent basic service set (IBSS) area and com(cid:173)
`municate directly (i.e., point to point). In this configuration,
`these devices 22, 23, and 24 may only communicate with each
`other. To communicate with other wireless communication
`devices within the system 10 orto communicate outside of the
`system 10, the devices 22, 23, and/or 24 need to affiliate with
`one of the base stations or access points 12 or 16.
`The base stations or access points 12, 16 are located within
`basic service set (BSS) areas 11 and 13, respectively, and are
`operably coupled to the network hardware 34 via local area
`network connections 36, 38. Such a connection provides the
`base station or access point 12, 16 with connectivity to other
`devices within the system 10 and provides connectivity to
`other networks via the WAN connection 42. To communicate
`with the wireless communication devices within its BSS 11 or
`13, each of the base stations or access points 12-16 has an
`The present invention is directed to apparatus and methods 55 associated antenna or antenna array. For instance, base station
`or access point 12 wirelessly communicates with wireless
`of operation that are further described in the following Brief
`communication devices 18 and 20 while base station or
`Description of the Drawings, the Detailed Description of the
`access point 16 wirelessly communicates with wireless com-
`Invention, and the claims. Other features and advantages of
`munication devices 26-32. Typically, the wireless communi(cid:173)
`the present invention will become apparent from the follow(cid:173)
`cation devices register with a particular base station or access
`ing detailed description of the invention made with reference 60
`point 12, 16 to receive services from the communication
`to the accompanying drawings.
`system 10.
`Typically, base stations are used for cellular telephone
`systems and like-type systems, while access points are used
`65 for in-home or in-building wireless networks (e.g., IEEE
`802.11 and versions thereof, Bluetooth, and/or any other type
`ofradio frequency based network protocol). Regardless of the
`
`FIG. 1 is a schematic block diagram of a wireless commu(cid:173)
`nication system in accordance with the present invention;
`
`
`
`US 8,416,862 B2
`
`5
`particular type of communication system, each wireless com(cid:173)
`munication device includes a built-in radio and/or is coupled
`to a radio.
`FIG. 2 is a schematic block diagram illustrating an embodi(cid:173)
`ment of a wireless communication device that includes the
`host device 18-32 and an associated radio 60. For cellular
`telephone hosts, the radio 60 is a built-in component. For
`personal digital assistants hosts, laptop hosts, and/or personal
`computer hosts, the radio 60 may be built-in or an externally
`coupled component.
`As illustrated, the host device 18-32 includes a processing
`module 50, memory 52, a radio interface 54, an input inter(cid:173)
`face 58, and an output interface 56. The processing module 50
`and memory 52 execute the corresponding instructions that
`are typically done by the host device. For example, for a 15
`cellular telephone host device, the processing module 50
`performs the corresponding communication functions in
`accordance with a particular cellular telephone standard.
`The radio interface 54 allows data to be received from and
`sent to the radio 60. For data received from the radio 60 ( e.g.,
`inbound data), the radio interface 54 provides the data to the
`processing module 50 for further processing and/or routing to
`the output interface 56. The output interface 56 provides
`connectivity to an output display device such as a display,
`monitor, speakers, et cetera such that the received data may be
`displayed. The radio interface 54 also provides data from the
`processing module 50 to the radio 60. The processing module
`50 may receive the outbound data from an input device such
`as a keyboard, keypad, microphone, et cetera via the input
`interface 58 or generate the data itself. For data received via
`the input interface 58, the processing module 50 may perform
`a corresponding host function on the data and/or route it to the
`radio 60 via the radio interface 54.
`Radio 60 includes a host interface 62, digital receiver pro(cid:173)
`cessing module 64, an analog-to-digital converter 66, a high
`pass and low pass filter module 68, an IF mixing down con(cid:173)
`version stage 70, a receiver filter 71, a low noise amplifier 72,
`a transmitter/receiver switch 73, a local oscillation module
`74, memory 75, a digital transmitter processing module 76, a
`digital-to-analog converter 78, a filtering/gain module 80, an
`IF mixing up conversion stage 82, a power amplifier 84, a
`transmitter filter module 85, a channel bandwidth adjust mod(cid:173)
`ule 87, and an antenna 86. The antenna 86 may be a single
`antenna that is shared by transmit and receive paths as regu(cid:173)
`lated by the TxRx switch 73, or may include separate anten(cid:173)
`nas for the transmit path and receive path. The antenna imple(cid:173)
`mentation will depend on the particular standard to which the
`wireless communication device is compliant.
`The digital receiver processing module 64 and the digital
`transmitter processing module 76, in combination with
`operational instructions stored in memory 75, execute digital
`receiver functions and digital transmitter functions, respec(cid:173)
`tively. The digital receiver functions include, but are not lim(cid:173)
`ited to, digital intermediate frequency to baseband conver(cid:173)
`sion, demodulation, constellation demapping, descrambling,
`and/or decoding. The digital transmitter functions include,
`but are not limited to, encoding, scrambling, constellation
`mapping, modulation, and/or digital baseband to IF conver(cid:173)
`sion. The digital receiver and transmitter processing modules
`64 and 76 may be implemented using a shared processing
`device, individual processing devices, or a plurality of pro(cid:173)
`cessing devices. Such a processing device may be a micro(cid:173)
`processor, micro-controller, digital signal processor, micro(cid:173)
`computer, central processing unit, field programmable gate
`array, programmable logic device, state machine, logic cir(cid:173)
`cuitry, analog circuitry, digital circuitry, and/or any device
`that manipulates signals (analog and/or digital) based on
`
`6
`operational instructions. The memory 75 may be a single
`memory device or a plurality of memory devices. Such a
`memory device may be a read-only memory, random access
`memory, volatile memory, non-volatile memory, static
`memory, dynamic memory, flash memory, and/or any device
`that stores digital information. Note that when the processing
`module 64 and/or 76 implements one or more of its functions
`via a state machine, analog circuitry, digital circuitry, and/or
`logic circuitry, the memory storing the corresponding opera-
`10 tional instructions is embedded with the circuitry comprising
`the state machine, analog circuitry, digital circuitry, and/or
`logic circuitry.
`In operation, the radio 60 receives outbound data 94 from
`the host device via the host interface 62. The host interface 62
`routes the outbound data 94 to the digital transmitter process(cid:173)
`ing module 76, which processes the outbound data 94 in
`accordance with a particular wireless communication stan(cid:173)
`dard (e.g., IEEE 802.11, Bluetooth, et cetera) to produce
`digital transmission formatted data 96. The digital transmis-
`20 sion formatted data 96 will be digital base-band signals ( e.g.,
`have a zero IF) or a digital low IF signals, where the low IF
`typically will be in the frequency range of one hundred kilo(cid:173)
`hertz to a few megahertz.
`The digital-to-analog converter 78 converts the digital
`25 transmission formatted data 96 from the digital domain to the
`analog domain. The filtering/gain module 80 filters and/or
`adjusts the gain of the analog signals prior to providing it to
`the IF mixing stage 82. The IF mixing stage 82 converts the
`analog baseband or low IF signals into RF signals based on a
`30 transmitter local oscillation 83 provided by local oscillation
`module 74. The power amplifier 84 amplifies the RF signals
`to produce outbound RF signals 98, which are filtered by the
`transmitter filter module 85. The antenna 86 transmits the
`outbound RF signals 98 to a targeted device such as a base
`35 station, an access point and/or another wireless communica(cid:173)
`tion device.
`The radio 60 also receives inbound RF signals 88 via the
`antenna 86, which were transmitted by a base station, an
`access point, or another wireless communication device. The
`40 antenna 86 provides the inbound RF signals 88 to the receiver
`filter module 71 via the TxRx switch 73, where the Rx filter 71
`bandpass filters the inbound RF signals 88. The Rx filter 71
`provides the filtered RF signals to low noise amplifier 72,
`which amplifies the signals 88 to produce an amplified
`45 inbound RF signals. The low noise amplifier 72 provides the
`amplified inbound RF signals to the IF mixing module 70,
`which directly converts the amplified inbound RF signals into
`an inbound low IF signals or baseband signals based on a
`receiver local oscillation 81 provided by local oscillation
`50 module 74. The down conversion module 70 provides the
`inbound low IF signals or baseband signals to the filtering/
`gain module 68. The high pass and low pass filter module 68
`filters, based on settings provided by the channel bandwidth
`adjust module 87, the inbound low IF signals or the