`(12) Patent Application Publication (10) Pub. No.: US 2006/0182017 A1
`Hansen et al.
`(43) Pub. Date:
`Aug. 17, 2006
`
`US 2006O182017A1
`
`(54) METHOD AND SYSTEM FOR COMPROMISE
`GREENFELD PREAMBLES FOR 802.11N
`
`(76) Inventors: Christopher J. Hansen, Sunnyvale, CA
`(US); Rajendra T. Moorti, Mountain
`View, CA (US); Jason A. Trachewsky,
`Menlo Park, CA (US)
`
`Correspondence Address:
`MCANDREWS HELD & MALLOY, LTD
`SOO WEST MAIDSON STREET
`SUTE 34OO
`CHICAGO, IL 60661
`
`(21) Appl. No.:
`
`11/151,772
`
`(22) Filed:
`
`Jun. 9, 2005
`
`Related U.S. Application Data
`(60) Provisional application No. 60/653,429, filed on Feb.
`16, 2005.
`
`Publication Classification
`
`(51) Int. Cl.
`(2006.01)
`H04 II/00
`(2006.01)
`H04B 700
`(52) U.S. Cl. ............................................ 370/208: 370/310
`(57)
`ABSTRACT
`Aspects of the invention described herein may enable a
`greenfield access mode in IEEE 802.11n WLAN systems in
`comparison to an alternative approach that may not provide
`greenfield access. The utilization of greenfield access may
`reduce the portion of time required to transmit data due to
`overhead comprising preamble fields and header fields. This
`may enable higher data throughput rates to be achieved. This
`may further enable more robust transmission of data by
`enabling comparable data rates to be maintained while
`reducing the coding rate of encoded transmitted data. The
`reduction of the coding rate may enable comparable data
`rates to be maintained for transmission via RF channels
`characterized by lower SNR while still achieving desired
`target levels of packet error rates. In another aspect of the
`invention, mixed mode access may be achieved while reduc
`ing the portion of time required for transmitting data due to
`overhead.
`
`- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
`28a.
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`Conversion
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`Transform
`
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`Estimates
`
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`
`Demapper
`
`Demapper
`
`
`
`
`
`INTEL-1005
`10,079,707
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`US 2006/0182017 A1
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`Aug. 17, 2006
`
`METHOD AND SYSTEM FOR COMPROMISE
`GREENFELD PREAMBLES FOR 802.11N
`
`CROSS-REFERENCE TO RELATED
`APPLICATIONS/INCORPORATION BY
`REFERENCE
`0001. This application makes reference, claims priority
`to, and claims the benefit of U.S. Provisional Application
`Ser. No. 60/653,429 filed Feb. 16, 2005.
`0002 This application makes reference to:
`0003 U.S. patent application Ser. No. 10/973,595 filed
`Oct. 26, 2004;
`0004 U.S. patent application Ser. No. 11/052,353 filed
`Feb. 7, 2005; and
`0005 U.S. patent application Ser. No. 11/052,389 filed
`Feb. 7, 2005.
`0006 All of the above state applications are hereby
`incorporated herein by reference in their entirety.
`
`FIELD OF THE INVENTION
`0007 Certain embodiments of the invention relate to
`wireless communication. More specifically, certain embodi
`ments of the invention relate to a method and system for
`compromise greenfield preambles for 802.11n.
`
`BACKGROUND OF THE INVENTION
`0008. Within the IEEE organization, IEEE 802.11 task
`group N (TGn) has been chartered to develop a standard to
`enable WLAN devices to achieve throughput rates beyond
`100 Mbits/s. This standard may be documented in IEEE
`resolution 802.11n.
`0009. The Institute for Electrical and Electronics Engi
`neers (IEEE), in resolution IEEE 802.11, also referred as
`“802.11, has defined a plurality of specifications which are
`related to wireless networking. With current existing 802.11
`standards, such as 802.11(a),(b), (g), which may support up
`to 54 Mbps data rates, either in 2.4 GHz or in 5 GHz
`frequency bands. Within the IEEE organization, IEEE
`802.11 task group N (TGn) has been chartered to develop a
`standard to enable WLAN devices to achieve throughput
`rates beyond 100 Mbits/s. This standard may be documented
`in IEEE resolution 802.11n. A plurality of proposals is
`emerging as candidates for incorporation in IEEE resolution
`802.11n. Among them are proposals from TGn Sync, which
`is a multi-industry group working to define proposals for
`next generation wireless networks that are to be submitted
`for inclusion in IEEE 802.11n. The proposals may be based
`upon what may be referred as a “sounding frame'. The
`Sounding frame method may comprise the transmitting of a
`plurality of long training sequences (LTSs) that match the
`number of transmitting antenna at the receiving mobile
`terminal. The Sounding frame method may not utilize beam
`forming or cyclic delay diversity (CDD). In the sounding
`frame method, each antenna in a multiple input multiple
`output (MIMO) system may transmit independent informa
`tion.
`0010 Further limitations and disadvantages of conven
`tional and traditional approaches will become apparent to
`one of skill in the art, through comparison of Such systems
`
`with some aspects of the present invention as set forth in the
`remainder of the present application with reference to the
`drawings.
`BRIEF SUMMARY OF THE INVENTION
`0011) A system and/or method for compromise greenfield
`preambles for 802.11n, substantially as shown in and/or
`described in connection with at least one of the figures, as set
`forth more completely in the claims.
`0012. These and other advantages, aspects and novel
`features of the present invention, as well as details of an
`illustrated embodiment thereof, will be more fully under
`stood from the following description and drawings.
`BRIEF DESCRIPTION OF SEVERAL VIEWS OF
`THE DRAWINGS
`0013 FIG. 1 is a block diagram of an exemplary system
`for wireless data communications, which may be utilized in
`accordance with an embodiment of the invention.
`0014 FIG. 2a is an exemplary block diagram of a
`transceiver which may be utilized in accordance with an
`embodiment of the invention.
`0015 FIG. 2b is an exemplary block diagram of a
`transceiver comprising a transmitter and a receiver in a
`MIMO system, which may be utilized in accordance with an
`embodiment of the invention.
`0016 FIG. 3a illustrates an exemplary physical layer
`protocol data unit, which may be utilized in connection with
`an embodiment of the invention.
`0017 FIG. 3b illustrates an exemplary data field in a
`PPDU, which may be utilized in connection with an embodi
`ment of the invention.
`0018 FIG. 4a shows exemplary training fields and
`header fields for mixed mode access in accordance with a
`TGn Sync proposal that may be utilized in connection with
`an embodiment of the invention.
`0.019
`FIG. 4b shows an exemplary L-SIG header field
`for mixed mode access in accordance with a TGn Sync
`proposal that may be utilized in connection with an embodi
`ment of the invention.
`0020 FIG. 4c shows an exemplary HT-SIG header field
`for mixed mode access in accordance with a TGn Sync
`proposal that may be utilized in connection with an embodi
`ment of the invention.
`0021
`FIG. 5a shows exemplary training fields and
`header fields for greenfield access in accordance with a
`WWiSE proposal for N=2, in accordance with an embodi
`ment of the invention.
`0022 FIG. 5b shows an exemplary Signal-N header field
`for greenfield access in accordance with a WWiSE proposal,
`in accordance with an embodiment of the invention.
`0023 FIG. 5c shows exemplary training fields and
`header fields for greenfield access in accordance with a
`WWiSE proposal for N=4, in accordance with an embodi
`ment of the invention.
`0024 FIG. 6a shows exemplary training fields and
`header fields with trailing signal field for greenfield access
`for N>2, in accordance with an embodiment of the inven
`tion.
`
`
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`
`FIG. 6b shows exemplary training fields and
`0.025
`header fields with early signal field for greenfield access for
`N>2, in accordance with an embodiment of the invention.
`0026 FIG. 7 shows exemplary training fields and header
`fields for mixed mode access for N>2, in accordance with
`an embodiment of the invention.
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`0027 Certain embodiments of the invention relate to a
`method and system for compromise greenfield preambles for
`802.11n, which utilizes a channel sounding mechanism to
`communicate information between a transmitter and a
`receiver. Various embodiments of the invention may enable
`a greenfield access mode in IEEE 802.11n WLAN systems
`compared to an alternative approach that may not provide
`methods for greenfield access. The utilization of greenfield
`access may reduce the portion of time required to transmit
`data due to overhead comprising preamble fields and header
`fields. This may enable higher data throughput rates to be
`achieved. This may further enable more robust transmission
`of data by enabling comparable data rates to be maintained
`while reducing the coding rate of encoded transmitted data.
`The reduction of the coding rate may enable comparable
`data rates to be maintained for transmission via RF channels
`characterized by lower SNR while still achieving desired
`target levels of packet error rates.
`0028. In another embodiment of the invention, mixed
`mode access may be achieved while reducing a portion of
`time required for transmitting data due to overhead com
`prising preamble fields and header fields. Long training
`fields among a plurality of transmitted spatial streams may
`comprise orthonormal long training sequences, which may
`obviate tone interleaving. Utilizing orthonormal long train
`ing sequences may enable the transmission of identical
`symbols via a plurality of spatial streams.
`0029 FIG. 1 is a block diagram of an exemplary system
`for wireless data communications, which may be utilized in
`accordance with an embodiment of the invention. With
`reference to FIG. 1 there is shown a distribution system
`(DS) 110, an extended service set (ESS) 120, and an IEEE
`802.x LAN 122. The ESS 120 may comprise a first basic
`service set (BSS) 102, and a second BSS 112. The first BSS
`102 may comprise a first 802.11 WLAN station 104, a
`second 802.11 WLAN station 106, and an access point (AP)
`108. The second BSS 112 may comprise a first 802.11
`WLAN station 114, a second 802.11 WLAN station 116, and
`an access point (AP) 118. The IEEE 802.x LAN 122 may
`comprise an 802.x LAN station 124, and a portal 126.
`0030) The BSS 102 or 112 may be part of an IEEE 802.11
`WLAN that comprises at least 2 IEEE 802.11 WLAN
`stations, for example, the first 802.11 WLAN station 104,
`the second 802.11 WLAN station 106, and the AP 108,
`which may be members of the BSS 102. Non-AP stations
`within BSS 102, the first 802.11 WLAN station 104, and the
`second 802.11 WLAN station 106, may individually form an
`association with the AP 108. An AP, such as AP108, may be
`implemented as an Ethernet switch, bridge, or other device
`in a WLAN, for example. Similarly, non-AP stations within
`BSS 112, the first 802.11 WLAN station 114, and the second
`802.11 WLAN station 116, may individually form an asso
`ciation with the AP 118. Once an association has been
`
`formed between a first 802.11 WLAN Station 104 and an AP
`108, the AP 108 may communicate reachability information
`about the first 802.11 WLAN Station 104 to other APS
`associated with the ESS 120, such as AP 118, and portals
`such as the portal 126. In turn, the AP118 may communicate
`reachability information about the first 802.11 WLAN sta
`tion 104 to stations in BSS 112. The portal 126, which may
`be implemented as, for example, an Ethernet switch or other
`device in a LAN, may communicate reachability informa
`tion about the first 802.11 WLAN station 104 to stations in
`LAN 122 such as the 802.x LAN station 124. The commu
`nication of reachability information about the first 802.11
`WLAN station 104 may enable WLAN stations that are not
`in BSS 102, but are associated with ESS 120, to commu
`nicate with the first 802.11 WLAN Station 104.
`0.031) The DS 110 may provide an infrastructure which
`enables a first 802.11 WLAN station 104 in one BSS 102, to
`communicate with a first 802.11 WLAN station 114 in
`another BSS 112. The DS 110 may also enable a first 802.11
`WLAN station 104 in one BSS 102 to communicate with an
`802.x LAN station 124 in an IEEE 802.x LAN 122, imple
`mented as, for example a wired LAN. The AP 108, AP 118,
`or portal 126 may provide a means by which a station in a
`BSS 102, BSS 112, or LAN 122 may communicate infor
`mation via the DS 110. The first 802.11 WLAN Station 104
`in BSS 102 may communicate information to a first 802.11
`WLAN station 114 in BSS 112 by transmitting the infor
`mation to AP 108, which may transmit the information via
`the DS 110 to AP 118, which in turn may transmit the
`information to Station 114 in BSS 112. The first 802.11
`WLAN station 104 may communicate information to the
`802.x LAN station 124 in LAN 122 by transmitting the
`information to AP108, which may transmit the information
`via the DS 110 to the portal 126, which in turn may transmit
`the information to the 802.x LAN station 124 in LAN 122.
`The DS 110 may utilize wireless communications via an RF
`channel, wired communications, such as IEEE 802.x Eth
`ernet, or a combination thereof.
`0032) The IEEE resolution 802.11n may enable WLAN
`devices compatible with IEEE 802.11 in to also interoperate
`with IEEE 802.11 devices that are not compatible with IEEE
`802.11n. WLAN devices that are compatible with IEEE
`802.11 but are not compatible with IEEE 802.11 in may be
`referred to as legacy IEEE 802.11 WLAN devices. WLAN
`devices that are compatible with IEEE 802.11n and com
`municate with other IEEE 802.11n compatible WLAN
`devices in an IEEE basic service set (BSS) of which no
`legacy IEEE 802.11 WLAN devices are currently members
`may be capable of communicating in a greenfield access
`mode. When utilizing greenfield access, communications
`between the WLAN devices may utilize capabilities speci
`fied in IEEE 802.11n that may not be accessible to legacy
`WLAN devices. WLAN devices that are compatible with
`IEEE 802.11n, and that communicate with IEEE 802.11n
`compatible WLAN devices in an IEEE BSS, of which
`legacy IEEE 802.11 WLAN devices are currently members,
`may utilize mixed mode access. When utilizing mixed mode
`access, IEEE 802.11n compatible WLAN devices may uti
`lize spoofing to avoid interference from legacy IEEE 802.11
`WLAN devices during communications between IEEE
`802.11n compatible devices in a BSS.
`0033 Among proposals received by TGn are proposals
`from, the worldwide spectrum efficiency (WWiSE) group,
`
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`
`and TGn Sync. Current proposals from TGn Sync may not
`provide a mechanism to support greenfield access. As such,
`mixed mode access communications based on current TGn
`Sync may be required to comprise information that may not
`be required in greenfield access communications.
`0034. The WWiSE proposals may comprise a plurality of
`enhancements to legacy IEEE 802.11 WLAN devices for
`incorporation in IEEE 802.11n WLAN devices. Legacy
`IEEE 802.11 WLAN devices may utilize 20 RF MHz
`channels. IEEE 802.11n may utilize 20 MHZ channels, with
`an optional utilization of 40 RF MHZ channels. Legacy
`IEEE 802.11 WLAN devices may utilize 52 sub-band fre
`quencies, or Subcarriers, in a 20 MHZ channel, comprising
`pilot tones at 4 sub-band frequencies, and 48 data-bearing
`Subcarriers. IEEE 802.11n WLAN devices based on WWiSE
`proposals may utilize a total of 56 subcarriers in a 20 MHz
`channel, comprising 2 pilot tones, and 54 data-bearing
`subcarriers. The subcarriers may be distributed symmetri
`cally around a frequency that comprises the center frequency
`of a 20 MHZ channel. The frequency spacing between
`subcarriers in an IEEE 802.11n WLAN device may be
`approximately equal to 312.5 KHZ. Therefore, an IEEE
`802.11n 20 MHZ channel may comprise a plurality of
`Subcarriers for which the frequency of a Subcarrier, f(i),
`may be represented as:
`equation1
`f(i)=fenter-hiAr where,
`the frequency, f, may represent the center frequency in
`a 20 MHZ channel, the frequency increment, Ar may rep
`resent the frequency spacing between Subcarriers, and the
`value of the Subcarrier index, i, may comprise a plurality of
`integer values represented as:
`equation2a
`0<isN/2, or
`equation2b
`-N/2si <0, where
`N may represent the number of subcarriers present in a 20
`MHZ channel.
`0035) An IEEE 802.11n 40 MHZ channel may comprise
`a plurality of subcarriers for which the frequency of a
`subcarrier f'(i) may be represented as:
`equation3a
`fe"(i)=fimary+iAp, or
`equation3b
`f(i)=feconday+iAf, where
`final may represent the center frequency of a primary 20
`MHZ channel, feesday may represent the center frequency
`of a secondary 20 MHZ channel, and the index, i, may be as
`defined in equations 3a and 3b). The primary and second
`ary 20 MHZ channels may be adjacent channels such that:
`?econdary ?primary t20 MHz, where
`equation4
`the secondary 20 MHZ channel may be located at an adjacent
`channel for which the center frequency fenda is either 20
`MHz higher or 20 MHz lower than the center frequency of
`the primary 20 MHz channel final. A 40 MHz channel
`may comprise a plurality of N Subcarriers located at the
`primary 20 MHz channel, and subsequent plurality of N.
`subcarriers located at the secondary 20 MHZ channel, where
`N may represent the number of subcarriers in a 20 MHz
`channel. In this regard, a 40 MHZ channel may comprise a
`total of 2N subcarriers. The state of the secondary 20 MHz
`channel may not be evaluated during communications
`between IEEE 802.11n WLAN devices.
`
`40.
`
`40.
`
`0036) The WWiSE proposals may incorporate a plurality
`of MIMO antenna configurations represented as NXN,
`where NT may represent the number of transmitting
`antenna at a station. Transmitting antennas may be utilized
`to transmit signals via an RF channel. Nix may represent the
`number of receiving antenna at a station that receives the
`signals transmitted by the NT transmitting antenna. The
`MIMO antenna configuration may enable IEEE 802.11n
`WLAN devices to achieve higher data rates than legacy
`IEEE 802.11 WLAN devices. A legacy 802.11 WLAN
`device may achieve data rates of 54 Mbits/s based on IEEE
`802.11a specifications. By comparison, an IEEE 802.11n
`WLAN device may achieve data rates of 540 Mbits/s in a
`4x4 MIMO configuration.
`0037 FIG. 2a is an exemplary block diagram of a
`transceiver which may be utilized in accordance with an
`embodiment of the invention. With reference to FIG. 2a is
`shown a baseband processor 272, a transceiver 274, an RF
`front end 280, a plurality of receive antennas 276a, . . .
`.
`276n, and a plurality of transmitting antennas 278a. . .
`. .
`278n. The transceiver 274 may comprise a processor 282, a
`receiver 284, and a transmitter 286.
`0038. The processor 282 may be adapted to perform
`digital receiver and/or transmitter functions in accordance
`with applicable communications standards. These functions
`may comprise, but are not limited to, tasks performed at
`lower layers in a relevant protocol reference model. These
`tasks may further comprise the physical layer convergence
`procedure (PLCP), physical medium dependent (PMD)
`functions, and associated layer management functions. The
`baseband processor 272 may be adapted to perform func
`tions in accordance with applicable communications stan
`dards. These functions may comprise, but are not limited to,
`tasks related to analysis of data received via the receiver
`284, and tasks related to generating data to be transmitted
`via the transmitter 286. These tasks may further comprise
`medium access control (MAC) layer functions as specified
`by pertinent standards.
`0039 The receiver 284 may be adapted to perform digital
`receiver functions that may comprise, but are not limited to,
`fast Fourier transform processing, beam forming processing,
`equalization, demapping, demodulation control. deinterleav
`ing, depuncture, and decoding. The transmitter 286 may
`perform digital transmitter functions that comprise, but are
`not limited to, coding, puncture, interleaving, mapping,
`modulation control, inverse fast Fourier transform process
`ing, beam forming processing. The RF front end 280 may
`receive analog RF signals via antennas 276a, .
`. . , 276n,
`converting the RF signal to baseband and generating a
`digital equivalent of the received analog baseband signal.
`The digital representation may be a complex quantity com
`prising I and Q components. The RF front end 280 may also
`transmit analog RF signals via an antenna 278a. . . . , 278n,
`converting a digital baseband signal to an analog RF signal.
`0040. In operation, the processor 282 may receive data
`from the receiver 284. The processor 282 may communicate
`received data to the baseband processor 272 for analysis and
`further processing. The baseband processor 272 may gen
`erate data to be transmitted via an RF channel by the
`transmitter 286. The baseband processor 272 may commu
`nicate the data to the processor 282. The processor 282 may
`generate a plurality of bits that are communicated to the
`receiver 284.
`
`
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`FIG. 2b is an exemplary block diagram of a
`0041
`transmitter and a receiver in a MIMO system, which may be
`utilized in accordance with an embodiment of the invention.
`With reference to FIG. 2b is shown a transmitter 200 a
`receiver 201, a processor 240, a baseband processor 242, a
`plurality of transmitter antennas 215a, . . . , 215m, and a
`plurality of receiver antennas 217a. . . . . 217n. The trans
`mitter 200 may comprise a coding block 202, a puncture
`block 204, an interleaver block 206, a plurality of mapper
`blocks 208a, . . . . 208m, a plurality of inverse fast Fourier
`transform (IFFT) blocks 210a, ..., 210n, a beam forming V
`matrix block 212, and a plurality of digital to analog (D/A)
`conversion and antenna front end blocks 214a. . . . , 214n.
`The receiver 201 may comprise a plurality of antenna front
`end and analog to digital (A/D) conversion blocks 216a, . .
`. . 216n, a beam forming U matrix block 218, a plurality of
`fast Fourier transform (FFT) blocks 220a, . . . , 220m, a
`channel estimates block 222, an equalizer block 224, a
`plurality of demapper blocks 226a. . . . , 226n, a deinter
`leaver block 228, a depuncture block 230, and a Viterbi
`decoder block 232.
`0042. The variables V and U in beam forming blocks 212
`and 218 respectively refer to matrices utilized in the beam
`forming technique. U.S. application Ser. No. 11/052,389
`filed Feb. 7, 2005, provides a detailed description of Eigen
`beam forming and is hereby incorporated herein by reference
`in its entirety.
`0043. The processor 240 may perform digital receiver
`and/or transmitter functions in accordance with applicable
`communications standards. These functions may comprise,
`but are not limited to; tasks performed at lower layers in a
`relevant protocol reference model. These tasks may further
`comprise the physical layer convergence procedure (PLCP),
`physical medium dependent (PMD) functions, and associ
`ated layer management functions. The baseband processor
`242 may similarly perform functions in accordance with
`applicable communications standards. These functions may
`comprise, but are not limited to, tasks related to analysis of
`data received via the receiver 201, and tasks related to
`generating data to be transmitted via the transmitter 200.
`These tasks may further comprise medium access control
`(MAC) layer functions as specified by pertinent standards.
`0044) In the transmitter 200, the coding block 202 may
`transform received binary input data blocks by applying a
`forward error correction (FEC) technique such as, for
`example, binary convolutional coding (BCC). The applica
`tion of FEC techniques, also known as “channel coding.
`may improve the ability to successfully recover transmitted
`data at a receiver by appending redundant information to the
`input data prior to transmission via an RF channel. The ratio
`of the number of bits in the binary input data block to the
`number of bits in the transformed data block may be known
`as the “coding rate'. The coding rate may be specified using
`the notation i?t, where t represents the total number of bits
`that comprise a coding group of bits, while is represents the
`number of information bits that are contained in the group of
`bits t. Any number of bits t-i may represent redundant bits
`that may enable the receiver 201 to detect and correct errors
`introduced during transmission. Increasing the number of
`redundant bits may enable greater capabilities at the receiver
`to detect and correct errors in information bits. The penalty
`for this additional error detection and correction capability
`may result in a reduction in the information transfer rates
`
`between the transmitter 200 and the receiver 201. The
`invention is not limited to BCC and a plurality of coding
`techniques such as, for example, Turbo coding, or low
`density parity check (LDPC) coding may also be utilized.
`0045. The puncture block 204 may receive transformed
`binary input data blocks from the coding block 202 and alter
`the coding rate by removing redundant bits from the
`received transformed binary input data blocks. For example,
`if the coding block 202 implemented a % coding rate, 4 bits
`of data received from the coding block 202 may comprise 2
`information bits, and 2 redundant bits. By eliminating 1 of
`the redundant bits in the group of 4 bits, the puncture block
`204 may adapt the coding rate from /3 to 2/3. The interleaver
`block 206 may rearrange bits received in a coding rate
`adapted data block from the puncture block 204 prior to
`transmission via an RF channel to reduce the probability of
`uncorrectable corruption of data due to burst of errors,
`impacting contiguous bits, during transmission via an RF
`channel. The output from the interleaver block 206, may also
`be divided into a plurality of streams where each stream may
`comprise a non-overlapping portion of the bits from the
`received coding rate-adapted data block. Therefore, for a
`given number of bits in the coding rate-adapted data block,
`ba, a given number of streams from the interleaver block
`206, n, and a given number of bits assigned to an individual
`stream i by the interleaver block 206, b(i):
`
`st
`bah - Xb(i)
`
`i=1
`
`equation 5
`
`0046) The plurality of mapper blocks 208a, . . . . 208m
`may comprise a number of individual mapper blocks that is
`equal to the number of individual streams generated by the
`interleaver block 206. Each individual mapper block 208a,
`.
`.
`.
`. 208m may receive a plurality of bits from a corre
`sponding individual stream, mapping those bits into a “sym
`bol' by applying a modulation technique based on a "con
`stellation' utilized to transform the plurality of bits into a
`signal level representing the symbol. The representation of
`the symbol may be a complex quantity comprising in-phase
`(I) and quadrature (Q) components. The mapper block 208a.
`... 208m for stream i may utilize a modulation technique to
`map a plurality of bits, b(i), into a symbol.
`0047 The beam forming V matrix block 212 may apply
`the beam forming technique to the plurality of symbols, or
`“spatial modes', generated from the plurality of mapper
`blocks 208a, . . . . 208m. The beam forming V matrix block
`212 may generate a plurality of signals where the number of
`signals generated may be equal to the number of transmit
`ting antenna at the transmitter 200. Each signal in the
`plurality of signals generated by the beam forming V block
`212 may comprise a weighted Sum of at least one of the
`received symbols from the mapper blocks 208a, . . . . 208m.
`0.048. The plurality of IFFT blocks 210a, ..., 210n may
`receive a plurality of signals from the beam forming block
`212. Each IFFT block 210a, . . . , 210n may subdivide the
`bandwidth of the RF channel into a plurality of n sub-band
`frequencies to implement orthogonal frequency division
`multiplexing (OFDM), buffering a plurality of received
`signals. Each buffered signal may be modulated by a carrier
`
`
`
`US 2006/0182017 A1
`
`Aug. 17, 2006
`
`signal whose frequency is based on of one of the Sub-bands.
`Each of the IFFT blocks 210a, .
`.
`. , 210n may then
`independently sum their respective buffered and modulated
`signals across the frequency Sub-bands to performan n-point
`IFFT, thereby generating a composite OFDM signal.
`0049. The plurality of digital (D) to analog (A) conver
`sion and antenna front end blocks 214a. . . . , 214 in may
`receive the plurality of signals generated by the plurality of
`IFFT blocks 210a, . . . , 210n. The digital signal represen
`tation received from each of the plurality of IFFT blocks
`210a, . . . , 210n may be converted to an analog RF signal
`that may be amplified and transmitted via an antenna. The
`plurality of D to A conversion and antenna front end blocks
`214a. . . . , 214n may be equal to the number of transmitting
`antenna 115a, . . . , 115n at the transmitter 200. Each D to
`A conversion and antenna front end block 214a. . . . , 214n
`may receive one of the plurality of signals from the beam
`forming V matrix block 212 and may utilize an antenna
`115a, ..., 115m to transmit one RF signal via an RF channel.
`0050. In the receiver 201, the plurality antenna front end
`and A to D conversion blocks 216a, . . . . 216in may receive
`analog RF signals via an antenna, converting the RF signal
`to baseband and generating a digital equivalent of the
`received analog baseband signal. The digital representation
`may be a complex quantity comprising I and Q components.
`The number of antenna front end and A to D conversion
`blocks 216a, .
`.
`. . 216n may be equal to the number of
`receiving antenna 117a. . . . , 117n at the receiver 201.
`0051) The plurality of FFT blocks 220a, . . . , 220m may
`receive a plurality of signals from the plurality of antenna
`front end and Ato D conversion blocks 216a,..., 216 n. The
`plurality of FFT blocks 220a, . . . , 220m may be equal to the
`number of antenna front end and A to D conversion blocks
`216a, .
`. . . 216 n. Each FFT block 220a, . . . , 220m may
`receive a signal from an antenna front end and A to D
`conversion block 216a, . . . , 21.6m, independently applying
`an n-point FFT technique, demodulating the signal by a
`plurality of carrier signals based on the n Sub-band frequen
`cies utilized in the transmitter 200. The demodulated signals
`may be mathematically integrated over one Sub band fre
`quency period by each of the plurality of FFT blocks 220a,
`. . . , 220m to extract n symbols contained in each of the
`plurality of OFDM signals received by the receiver 201.
`0.052 The beam forming U* block 218 may apply the
`beam forming technique to the plurality of signals received
`from the plurality of FFT blocks 220a, . . . , 220m. The
`beam forming U* block 218 may generate a plurality of
`signals where the number of signals generated may be equal
`to the