I 1111111111111111 11111 1111111111 11111 1111111111 11111 11111 111111111111111111
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`US00873 7189B2
`
`(IO) Patent No.: US 8,737,189 B2
`
`
`c12) United States Patent
`(45)Date of Patent:
`
`May 27, 2014
`Hansen et al.
`
`2005/0170831 Al* 8/2005 Magee et al. ................. 455/434
`
`
`(54)METHOD AND SYSTEM FOR COMPROMISE
`
`
`
`
`2005/0276347 Al* 12/2005 Mujtaba et al. ............... 375/299
`
`GREENFIELD PREAMBLES FOR 802.llN
`
`
`
`2006/0251193 Al* 11/2006 Kopmeiners et al. ......... 375/345
`
`
`2007 /0060073 Al* 3/2007 Boer et al. .................... 455/101
`(75) Inventors: Christopher J. Hansen, Sunnyvale, CA
`
`
`
`
`
`
`2007/0147336 Al* 6/2007 Lee et al. ...................... 370/350
`
`
`(US); Rajendra T. Moorti, Mountain
`
`
`2007 /0217 546 Al* 9/2007 Sandell et al. ................ 375/299
`
`View, CA (US); Jason A. Trachewsky,
`Menlo Park, CA (US)
`
`(Continued)
`
`
`
`(73)Assignee: Broadcom Corporation, Irvine, CA
`
`
`
`(US)
`
`FOREIGN PATENT DOCUMENTS
`
`
`
`1594275 A 11/2005
`
`W02005006699 1/2005
`
`OTHER PUBLICATIONS
`
`EP
`WO
`
`
`( *) Notice: Subject to any disclaimer, the term ofthis
`
`
`
`patent is extended or adjusted under 35
`
`
`U.S.C. 154(b) by 1105 days.
`Christopher J. Hansen, IEEE 802.11 Wireless LANs WWiSE Pro­
`
`
`
`
`
`
`
`
`
`
`posal: High Throughput Extension to the 802.11 Standard, Dec. 20,
`2004.
`
`(21)Appl. No.: 11/151,772
`
`
`
`(22)Filed:Jun.9,2005
`
`(Continued)
`
`(65)
`
`
`
`Prior Publication Data
`
`
`
`(7 4) Attorney, Agent, or Firm - Garlick & Markison; Bruce
`
`
`
`Related U.S. Application Data
`
`
`
`(60)
`
`
`16, 2005.
`
`ABSTRACT
`
`(2006.01)
`
`Primary Examiner - Mark Rinehart
`
`
`
`
`Assistant Examiner - Peter Cheng
`US 2006/0182017 Al Aug. 17, 2006
`
`
`
`
`E.Stuckman
`
`(57)
`Provisional application No. 60/653,429, filed on Feb.
`Aspects of the invention described herein may enable a green­
`
`
`
`
`
`
`
`
`
`field access mode in IEEE 802.1 ln WLAN systems in com­
`
`
`
`parison to an alternative approach that may not provide green­
`(51)
`Int. Cl.
`
`
`
`
`field access. The utilization of greenfield access may reduce
`H04J 11100
`
`
`
`the portion of time required to transmit data due to overhead
`(52)
`U.S. Cl.
`
`
`
`
`comprising preamble fields and header fields. This may
`
`USPC .......................................................... 370/203
`
`
`
`
`enable higher data throughput rates to be achieved. This may
`(58)
`
`Field of Classification Search
`
`
`
`
`further enable more robust transmission of data by enabling
`
`USPC .......................................................... 370/203
`
`
`
`comparable data rates to be maintained while reducing the
`
`
`
`
`See application file for complete search history.
`
`
`
`
`coding rate of encoded transmitted data. The reduction of the
`
`
`coding rate may enable comparable data rates to be main­
`
`
`
`
`tained 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
`
`
`7,340,000 Bl* 3/2008 Hart et al. ..................... 375/260
`
`
`
`access may be achieved while reducing the portion of time
`
`
`
`7,366,250 B2 * 4/2008 Mujtaba et al. ............... 375/267
`
`
`
`required for transmitting data due to overhead .
`
`
`7,382,832 B2 * 6/2008 Magee et al. ................. 375/267
`
`
`2003/0072452 Al 4/2003 Mody et al.
`
`2004/0192216 Al* 9/2004 Marzetta et al. ........... 455/67.14
`
`
`13 Claims, 11 Drawing Sheets
`
`(56)
`
`
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`604a
`
`606a
`
`612a
`
`602a
`
`HT-STF,
`8 µs
`
`HT-LTF1.
`1
`8 µs
`
`Signal*-N
`8 µs
`
`1
`
`•••
`
`624a
`
`626a
`
`632a
`
`628a
`
`630a
`
`622a
`
`HT-STF2
`8 µs
`
`HT-LTF2,1
`8 µs
`
`Signa1·-N
`2
`8 µs
`
`HT-LTF2.2
`4 µs
`
`HT-LTF2,N
`4 µs
`
`...
`
`644a
`
`646a
`
`652a
`
`648a
`
`650a
`
`.
`•
`
`.
`
`642a
`
`HT-STFNss
`8 µs
`
`HT-LTFNSS,1
`8 µs
`
`Signal*-N
`Nss
`8 µs
`
`HT-LTFNss,2
`4 µs
`
`•••
`
`INTEL-1010
`10,079,707
`
`

`

`US 8,737,189 B2
`Page 2
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`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`2009/0238299 A1*
`2011/O255488 A1*
`2012/O195391 A1*
`2012,0327.915 A1*
`
`9, 2009
`10, 2011
`8, 2012
`12, 2012
`
`Van Zelstet al. .............. 375,267
`Lee et al. .....
`370,329
`Zhang et al. .
`375,295
`Kang et al. .................... 370,336
`
`
`
`OTHER PUBLICATIONS
`
`Syed Aon Mujtaba, IEEE 802.11 Wireless LANs TGn Sync Proposal
`Technical Specification, Jan. 18, 2005.
`
`* cited by examiner
`
`

`

`U.S. Patent
`U.S. Patent
`
`May 27, 2014
`May 27, 2014
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`U.S. Patent
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`US 8,737,189 B2
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`

`1.
`METHOD AND SYSTEM FOR COMPROMISE
`GREENFELD PREAMBLES FOR 802.11N
`
`US 8,737,189 B2
`
`CROSS-REFERENCE TO RELATED
`APPLICATIONS/INCORPORATION BY
`REFERENCE
`
`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.
`This application makes reference to:
`U.S. patent application Ser. No. 10/973,595 filed Oct. 26,
`2004;
`U.S. patent application Ser. No. 11/052,353 filed Feb. 7,
`2005; and
`U.S. patent application Ser. No. 11/052,389 filed Feb. 7,
`2005.
`All of the above state applications are hereby incorporated
`herein by reference in their entirety.
`
`10
`
`15
`
`FIELD OF THE INVENTION
`
`Certain embodiments of the invention relate to wireless
`communication. More specifically, certain embodiments of
`the invention relate to a method and system for compromise
`greenfield preambles for 802.11n.
`
`25
`
`BACKGROUND OF THE INVENTION
`
`Within the IEEE organization, IEEE 802.11 task group N
`(TGn) has been chartered to develop a standard to enable
`30
`WLAN devices to achieve throughput rates beyond 100
`Mbits/s. This standard may be documented in IEEE resolu
`tion 802.11n.
`The Institute for Electrical and Electronics Engineers
`(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
`40
`(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 resolu
`tion 802.11n. A plurality of proposals is emerging as candi
`dates for incorporation in IEEE resolution 802.11n. Among
`45
`them are proposals from TGn Sync, which is a multi-industry
`group working to define proposals for next generation wire
`less 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 orcyclic delay diversity
`(CDD). In the sounding frame method, each antenna in a
`multiple input multiple output (MIMO) system may transmit
`independent information.
`Further limitations and disadvantages of conventional 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.
`
`35
`
`50
`
`55
`
`60
`
`BRIEF SUMMARY OF THE INVENTION
`
`A system and/or method for compromise greenfield pre
`ambles for 802.11n, substantially as shown in and/or
`
`65
`
`2
`described in connection with at least one of the figures, as set
`forth more completely in the claims.
`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 understood from the
`following description and drawings.
`
`BRIEF DESCRIPTION OF SEVERAL VIEWS OF
`THE DRAWINGS
`
`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.
`FIG. 2a is an exemplary block diagram of a transceiver
`which may be utilized in accordance with an embodiment of
`the invention.
`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.
`FIG. 3a illustrates an exemplary physical layer protocol
`data unit, which may be utilized in connection with an
`embodiment of the invention.
`FIG. 3b illustrates an exemplary data field in a PPDU,
`which may be utilized in connection with an embodiment of
`the invention.
`FIG. 4a shows exemplary training fields and header fields
`for mixed mode access in accordance with a TGn Sync pro
`posal that may be utilized in connection with an embodiment
`of the invention.
`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 embodiment of the
`invention.
`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 embodiment of the
`invention.
`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 embodiment of the inven
`tion.
`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.
`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 embodiment of the inven
`tion.
`FIG. 6a shows exemplary training fields and header fields
`with trailing signal field for greenfield access for NP2, in
`accordance with an embodiment of the invention.
`FIG. 6b shows exemplary training fields and header fields
`with early signal field for greenfield access for N>2, in
`accordance with an embodiment of the invention.
`FIG. 7 shows exemplary training fields and header fields
`for mixed mode access for NC2, in accordance with an
`embodiment of the invention.
`
`DETAILED DESCRIPTION OF THE INVENTION
`
`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
`
`

`

`US 8,737,189 B2
`
`10
`
`15
`
`25
`
`30
`
`40
`
`50
`
`55
`
`60
`
`3
`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 char
`acterized by lower SNR while still achieving desired target
`levels of packet error rates.
`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 comprising
`preamble fields and header fields. Long trainingfields among
`a plurality of transmitted spatial streams may comprise
`orthonormal long training sequences, which may obviate tone
`interleaving. Utilizing orthonormal long training sequences
`may enable the transmission of identical symbols via a plu
`rality of spatial streams.
`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 ref
`erence 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.
`The BSS 102 or 112 may be part of an IEEE 802.11 WLAN
`35
`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
`45
`station 116, may individually forman association 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 AP118, and portals such as the portal 126. In turn, the
`AP118 may communicate reachability information about the
`first 802.11 WLAN Station 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 information about the first 802.11 WLAN station
`104 to stations in LAN 122 such as the 802.x LAN station
`124. The communication of reachability information about
`the first 802.11 WLAN station 104 may enable WLAN sta
`tions that are not in BSS 102, but areassociated with ESS 120,
`to communicate with the first 802.11 WLAN station 104.
`The DS 110 may provide an infrastructure which enables a
`first 802.11 WLAN station 104 in one BSS 102, to commu
`nicate with a first 802.11 WLAN Station 114 in another BSS
`112. The DS 110 may also enable a first 802.11 WLAN
`65
`station 104 in one BSS 102 to communicate with an 802.X
`LAN station 124 in an IEEE 802.x LAN 122, implemented as,
`
`4
`for example a wired LAN. The AP108, AP 118, orportal 126
`may provide a means by which a station in a BSS 102, BSS
`112, or LAN 122 may communicate information 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 information to AP108, 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 commu
`nicate information to the 802.x LAN station 124 in LAN 122
`by transmitting the information to AP108, which may trans
`mit 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 commu
`nications via an RF channel, wired communications, such as
`IEEE 802. X Ethernet, or a combination thereof.
`The IEEE resolution 802.11n may enable WLAN devices
`compatible with IEEE 802.11nto 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 802.11n may be referred to as
`legacy IEEE 802.11 WLAN devices. WLAN devices that are
`compatible with IEEE 802.11n and communicate 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 commu
`nicating in a greenfield access mode. When utilizing green
`field access, communications between the WLAN devices
`may utilize capabilities specified in IEEE 802.11n that may
`not be accessible to legacy WLAN devices. WLAN devices
`that are compatible with IEEE 802.11n, and that communi
`cate 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 utilize spoofing to avoid interference
`from legacy IEEE 802.11 WLAN devices during communi
`cations between IEEE 802.11n compatible devices in a BSS.
`Among proposals received by TGn are proposals from the
`worldwide spectrum efficiency (WWiSE) group 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.
`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 frequencies, or sub
`carriers, 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, com
`prising 2 pilot tones, and 54 data-bearing Subcarriers. The
`subcarriers may be distributed symmetrically around a fre
`quency 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 fre
`quency of a Subcarrier, f(i), may be represented as:
`
`f(i) feel+iA where,
`
`equation1
`
`

`

`US 8,737,189 B2
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`5
`the frequency, f, may represent the center frequency in a
`20 MHz channel, the frequency increment. A may represent
`the frequency spacing between Subcarriers, and the value of
`the Subcarrier index, i, may comprise a plurality of integer
`values represented as:
`O<isN/2, or
`
`equation2a
`
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`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 (ND) conversion blocks 216a,..., 216n, a beam form
`ing U* matrix block 218, a plurality of fast Fourier transform
`(FFT) blocks 220a, ..., 220n, a channel estimates block 222,
`an equalizer block 224, a plurality of demapper blocks
`226a. . . . , 226n, a deinterleaver block 228, a depuncture
`block 230, and a Viterbi decoder block 232.
`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 proce
`dure (PLCP), physical medium dependent (PMD) functions,
`and associated layer management functions. The baseband
`processor 272 may be adapted to perform functions in accor
`dance with applicable communications standards. 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 con
`trol (MAC) layer functions as specified by pertinent stan
`dards.
`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 per
`form digital transmitter functions that comprise, but are not
`limited to, coding, puncture, interleaving, mapping, modula
`tion control, inverse fast Fourier transform processing, beam
`forming processing. The RF frontend 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 comprising I and Q components.
`The RF frontend 280 may also transmit analog RF signals via
`an antenna 278a, . . . , 278m, converting a digital baseband
`signal to an analog RF signal.
`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 generate data to
`be transmitted via an RF channel by the transmitter 286. The
`baseband processor 272 may communicate the data to the
`processor 282. The processor 282 may generate a plurality of
`bits that are communicated to the receiver 284.
`The variables V and U* in beam forming blocks 212 and
`218, respectively, refer to matrices utilized in the beam form
`ing technique. U.S. application Ser. No. 11/052,389 filed Feb.
`7, 2005, provides a detailed description of Eigen beam form
`ing and is hereby incorporated herein by reference in its
`entirety.
`The processor 240 may perform digital receiver and/or
`transmitter functions in accordance with applicable commu
`nications 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 242 may
`similarly perform functions in accordance with applicable
`communications standards. These functions may comprise,
`
`equation2b
`-N/2si <0, where
`N may represent the number of subcarriers present in a 20
`MHZ channel.
`An IEEE 802.11n 40 MHZ channel may comprise a plu
`rality of subcarriers for which the frequency of a subcarrier
`f".(i) may be represented as:
`equation3a
`f."(i) frnatiA? or
`equation3b
`f..."(i) featiA, where
`may represent the center frequency of a primary 20
`fi
`MHz channel, f
`may represent the center frequency of
`a secondary 20 MHZ channel, and the index, i, may be as
`defined inequations 3aland 3b). The primary and secondary
`20 MHZ channels may be adjacent channels such that:
`?econday, finay-t20 MHz, where
`equation4
`the secondary 20 MHZ channel may be located at an adjacent
`channel for which the center frequency f. is either 20
`MHz higher or 20 MHz lower than the center frequency of the
`primary 20 MHz channel f. 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.
`The WWiSE proposals may incorporate a plurality of
`MIMO antenna configurations represented as NTXX NRX,
`where NTX may represent the number of transmitting anten
`nas at a station. Transmitting antennas may be utilized to
`transmit signals via an RF channel. NRX may represent the
`number of receiving antennas at a station that receives the
`signals transmitted by the NTX transmitting antennas. 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 802.11 a
`specifications. By comparison, an IEEE 802.11n WLAN
`device may achieve data rates of 540 Mbits/s in a 4+4MIMO
`configuration.
`50
`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, there 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.
`FIG.2b is an exemplary block diagram of a transmitter and
`a receiver in a MIMO system, which may be utilized in
`accordance with an embodiment of the invention. With ref
`erence to FIG.2b, there 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 transmitter 200 may
`comprise a coding block 202, a puncture block 204, an inter
`leaver block 206, a plurality of mapper blocks 208a, . . . .
`
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`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.
`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 con
`volutional coding (BCC). The application of FEC techniques,
`also known as “channel coding, may improve the ability to
`Successfully recover transmitted data at a receiver by append
`ing redundant information to the input data prior to transmis
`sion via an RF channel. The ratio of the number of bits in the
`binary input data block to the number of bits in the trans
`formed data block may be known as the “coding rate'. The
`coding rate may be specified using the notationi?t, wheret,
`represents the total number of bits that comprise a coding
`group of bits, while it, represents the number of information
`bits that are contained in the group of bits t. Any number of
`bits t-it, 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.
`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 /2 coding rate, 4 bits of data
`received from the coding block 202 may comprise 2 informa
`tion bits, and 2 redundant bits. By eliminating 1 of the redun
`dant bits in the group of 4 bits, the puncture block 204 may
`adapt the coding rate from /2 to 2/3. The interleaver block 206
`40
`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 contigu
`ous 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, b, a given number of
`50
`streams from the interleaver block 206, n, and a given num
`ber of bits assigned to an individual streami by the interleaver
`block 206, b(i):
`
`sts
`
`st
`
`bai – Xb, (i)
`
`i=1
`
`55
`
`equation 5
`
`. . . 208m may
`The plurality of mapper blocks 208a, .
`comprise a number of individual mapper blocks that is equal
`to the number of individual streams generated by the inter
`leaver block 206. Each individual mapper block 208a, . . . .
`208m may receive a plurality of bits from a corresponding
`individual stream, mapping those bits into a “symbol' by
`applying a modulation technique based on a "constellation”
`utilized to transform the plurality of bits into a signal level
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`representing the symbol. The representation of the symbol
`may be a complex quantity comprising in-phase (I) and