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`PTO/SB/16 (12-04)
`Approved for use through 07/31/2006. 0MB 0651;()032
`U.S. Patent and Trademark Office; U.S. DEPARTMENT OF COMMERCE
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`PROVISIONAL APPLICATION FOR PATENT COVER SHEET
`This is a request for filing a PROVISIONAL APPLICATION FOR PATENT under 37 CFR 1.53 (c).
`Express Mail Label No. EV 435257643 us
`
`t::m
`. (\J
`WV
`. ('I')
`=>LO
`v(O
`C\lr
`.,.:. (1;
`,...
`
`Given Name (first and middle [if any))
`
`Family Name or Surname
`
`Christopher J
`
`Hansen
`
`Residence
`(Citv and either State or Foreign Country}
`Sunnyvale, CA
`
`INVENTOR(S)
`
`Moorti
`MusharT.
`Trachewskv
`Jason
`Additional inventors are being named on the O separately numbered sheets attached hereto
`TITLE OF THE INVENTION (500 characters max)
`METHOD AND SYSTEM FOR COMPROMISE GREENFIELD PREAMBLES FOR 802.11 N
`
`Mountain View, CA
`Menlo Park, CA
`
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`ENCLOSED APPLICATION PARTS (check all that apply)
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`The invention was made by an agency of the United States Government or under a contract with an agency of the United States Government.
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`SIGNATURE c_ ~ / " 7 /P~
`
`Date
`
`February 16, 2005
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`-
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`TELEPHONE
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`312-775-8000
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`TYPED or PRINTED NAME
`
`Christopher C. Winslade
`
`36,308
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`(if appropriate)
`16490US01
`Docket Number:
`USE ONLY FOR FILING A PROVISIONAL APPLICATION FOR PATENT
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`

`"Express Mail" Mailing Label No.: EV 435257643 US
`
`Date of Deposit: February 16, 2005
`
`ATTORNEY DOCKET NO. 16490US01
`
`METHOD AND SYSTEM FOR COMPROMISE GREENFIELD
`PREAMBLES FOR 802.11 N
`
`CROSS-REFERENCE TO RELATED APPLICATIONS/INCORPORATION BY
`REFERENCE
`
`[01) This application makes reference to:
`
`United States Patent Application Serial No. 10/973,595 filed October 26, 2004;
`
`United States Patent Application Serial No.
`
`(Attorney Docket No.
`
`16354US02) filed February 7, 2005; and
`
`United States Patent Application Serial No.
`
`(Attorney Docket No.
`
`16307US02) filed February 7, 2005.
`
`[02) All of the above state applications are hereby incorporated herein by reference in
`
`their entirety.
`
`FIELD OF THE INVENTION
`
`[03) 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 802.11 n.
`
`BACKGROUND OF THE INVENTION
`
`[04) 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. Among them are specifications for "closed loop"
`
`feedback mechanisms by which a receiving mobile terminal may feed back information
`1
`
`

`

`to a transmitting mobile terminal to assist the transmitting mobile terminal in adapting
`signals which are sent to the receiving mobile terminal.
`
`(05] Smart antenna systems combine multiple antenna elements with a signal
`processing capability to optimize the pattern of transmitted signal radiation and/or
`reception in response to the communications medium environment. The process of
`optimizing the pattern of radiation is sometimes referred to as "beamforming," which
`may utilize linear array mathematical operations to increase the average signal to noise
`ratio (SNR) by focusing energy in desired directions.
`In conventional smart antenna
`systems, only the transmitter or the receiver may be equipped with more than one
`antenna, and may typically be located in the base transceiver station (BTS) where the
`cost and space associated with smart antenna systems have been perceived as more
`easily affordable than on mobile terminals such as cellular telephones. Such systems
`are also known as multiple input single output {MISO) when a multiple antenna
`transmitter is transmitting signals to a single antenna receiver, or single input multiple
`output (SIMO) when a multiple antenna receiver is receiving signals that have been
`transmitted from a single antenna transmitter. With advances in digital signal
`processing {DSP) integrated circuits (ICs) in recent years, multiple antenna multiple
`output (MIMO) systems have emerged in which mobile terminals incorporate smart
`antenna systems comprising multiple transmit antenna and multiple receive antenna.
`One area of early adoption of MIMO systems has been in the field of wireless
`networking, particularly as applied to wireless local area networks (WLANs) where
`transmitting mobile terminals communicate. with receiving mobile terminals.
`IEEE
`resolution 802.11 comprises specifications for communications between mobile
`terminals in WLAN systems.
`
`(06] Signal fading is a significant problem in wireless communications systems, often
`leading to temporary loss of communications at mobile terminals. One of the most
`pervasive forms of fading is known as multipath fading, in which dispersion of
`transmitted signals due to incident reflections from buildings and other obstacles, results
`
`2
`
`

`

`in multiple versions of the transmitted signals arriving at a receiving mobile terminal.
`
`The multiple versions of the transmitted signal may interfere with each other and may
`
`result in a reduced signal level detected at the receiving mobile terminal. When
`versions of the transmitted signal are 180° out of phase they may cancel each other
`such that a signal level of O is detected. Locations where this occurs may correspond to
`"dead zones" in which communication to the wireless terminal is temporarily lost. This
`type of fading is also known as "Rayleigh" or "flat" fading.
`
`[07] A transmitting mobile terminal may transmit data signals in which data is
`
`transmission of symbols may be constrained such that
`arranged as "symbols". The
`after a symbol is transmitted, a minimum period of time, Ts, must transpire before
`another symbol may be transmitted. After transmission of a symbol from a transmitting
`
`mobile terminal, some period of dispersion time, Td, may transpire which may be the
`
`time over which the receiving mobile terminal is able to receive the symbol, including
`multipath reflections. The time Td may not need to account for the arrival of all multipath
`reflections because interference from later arriving reflected signals may be negligible.
`If the period Ts is less than Td there is a possibility that the receiving mobile terminal will
`start receiving a second symbol from the transmitting mobile terminal while it is still
`receiving the first symbol. This may result in inter-symbol interference (ISi), producing
`
`distortion in received signals, and possibility resulting in a loss of information. The
`quantity 1/Td is also referred to as the "coherence bandwidth" which may indicate the
`maximum rate at which symbols, and correspondingly information, may be transmitted
`via a given communications medium. One method to compensate for ISi in signals may
`
`entail utilizing DSP algorithms which perform adaptive equalization.
`
`(08] Another important type of fading is related to motion. When a transmitting mobile
`
`terminal, or a receiving mobile terminal is in motion, the Doppler phenomenon may
`affect the frequency of the received signal. The frequency of the received signal may
`be changed by an amount which is a function of the velocity at which a mobile terminal
`is moving. Because of the Doppler effect, ISi may result when a mobile terminal is in
`
`3
`
`

`

`motion, particularly when the mobile terminal is moving at a high velocity. Intuitively, if a
`
`receiving mobile terminal is in motion and nearing a transmitting mobile terminal, the
`
`distance between the two mobile terminals will change as a function of time. As the
`
`distance is reduced, the propagation delay time, Tp, which is the time between when a
`
`transmitter first transmits a signal and when it first arrives at a receiver, is also reduced.
`
`As the mobile terminals become closer it is also possible that T d may be increased if, for
`
`example, the transmitting mobile terminal does not reduce the radiated power of
`
`transmitted signals.
`
`If Tp becomes less than Td, there may be ISi due to the Doppler
`
`effect. This case, which illustrates why data rates may be reduced for mobile terminals
`
`that are in motion, is referred to as "fast fading". Because fast fading may distort signals
`
`at some frequencies while not distorting signals at other frequencies, fast fading may
`
`also be referred to as "frequency selective" fading.
`
`[09] Smart antenna systems may transmit multiple versions of a signal in what is
`
`known as "spatial diversity". A key concept in spatial diversity is that the propagation of
`
`multiple versions of a signal, or "spatial stream", from different antenna may significantly
`
`reduce the probability of flat fading at the receiving mobile terminal since not all of the
`
`transmitted signals would have the same dead zone.
`
`[1 O] Current transmission schemes in MIMO systems typically fall into two categories:
`
`data rate maximization, and diversity maximization. Data rate maximization focuses on
`
`increasing the aggregate data transfer rate between a transmitting mobile terminal and
`
`a receiving mobile terminal by transmitting different spatial streams from different
`
`antenna. One method for increasing the data rate from a transmitting mobile terminal
`
`would be to decompose a high bit rate data stream into a plurality of lower bit rate data
`
`streams such that the aggregate bit rates among the plurality of lower bit rate data
`
`streams is equal to that of the high bit rate data stream. Next, each of the lower bit rate
`
`data streams may be mapped to at least one of the transmitting antenna for
`
`transmission. In addition, each signal comprising one of the lower bit rate data streams
`
`is multiplicatively scaled by a weighting factor prior to transmission. The plurality of
`
`4
`
`

`

`multiplicative scale factors applied to the plurality of signals comprising the lower bit rate
`
`data streams may be utilized to form the transmitted "beam" in the beamforming
`
`technique. An example of a data rate maximization scheme is orthogonal frequency
`division multiplexing (OFDM), in which each of the plurality of signals is modulated by a
`
`different frequency carrier signal prior to mapping and multiplicative scaling. OFDM
`transmission may be resistant to multipath fading in that a portion, but most likely not all,
`
`of the data transmitted may be lost at any instant in time due to multipath fading.
`
`[11] Diversity maximization focuses on
`
`increasing the probability that a signal
`
`transmitted by a transmitting mobile terminal will be received at a receiving mobile
`terminal, and on increasing the SNR of received signals.
`In diversity maximization,
`multiple versions of the same signal may be transmitted by a plurality of antenna. The
`case in which a transmitting mobile terminal is transmitting the same signal via all of its
`
`transmitting antenna may be the pure spatial diversity case in which the aggregate data
`transfer rate may be equal to that of a single antenna mobile terminal. There is a
`
`plurality of hybrid adaptations of the data rate and spatial diversity maximization
`schemes which achieve varying data rates and spatial diversities.
`
`the simultaneous
`[12] MIMO systems employing beamforming may enable
`transmission of multiple signals occupying a shared frequency band, similar to what
`
`may be achieved in code division multiple access (CDMA) systems. For example, the
`multiplicative scaling of signals prior to transmission, and a similar multiplicative scaling
`
`of signals after reception, may enable a specific antenna at a receiving mobile terminal
`
`to receive a signal which had been transmitted by a specific antenna at the transmitting
`mobile terminal to the exclusion of signals which had been transmitted from other
`antenna. However, MIMO systems may not require the frequency spreading techniques
`used in CDMA transmission systems. Thus, MIMO systems may make more efficient
`utilization of frequency spectrum.
`
`[13] One of the challenges in beamforming is that the multiplicative scale factors
`which are applied to transmitted and received signals may be dependent upon the
`
`5
`
`

`

`characteristics of the communications medium between the transmitting mobile terminal
`
`and the receiving mobile terminal. A communications medium, such as a radio
`
`frequency (RF) channel between a transmitting mobile terminal and a receiving mobile
`
`terminal, may be represented by a transfer system function, H. The relationship
`
`between a time varying transmitted signal, x(t), a time varying received signal, y(t), and
`
`the systems function may be represented as shown in equation [1 ]:
`
`y(t) = H x x(t) + n(t) , where
`
`equation[1]
`
`n(t) represents noise which may be introduced as the signal travels through the
`
`communications medium and the receiver itself.
`
`In MIMO systems, the elements in
`
`equation[1] may be represented as vectors and matrices.
`
`If a transmitting mobile
`
`terminal comprises M transmitting antenna, and a receiving mobile terminal comprises
`
`N receiving antenna, then y(t) may be represented by a vector of dimensions Nx1, x(t)
`
`may be represented by a vector of dimensions Mx1, n(t) by a vector of dimensions Nx1,
`
`and H may be represented by a matrix of dimensions NxM.
`
`In the case of fast fading,
`
`the transfer function, H, may itself become time varying and may thus also become a
`
`function of time, H(t). Therefore, individual coefficients, hij(t), in the transfer function H(t)
`
`may become time varying in nature.
`
`[14]
`
`In MIMO systems which communicate according to specifications in
`
`IEEE
`
`resolution 802.11, the receiving mobile terminal may compute H(t) each time a frame of
`
`information is received from a transmitting mobile terminal based upon the contents of a
`
`preamble field in each frame. The computations which are performed at the receiving
`
`mobile terminal may constitute an estimate of the "true" values of H(t) and may be
`
`known as "channel estimates". For a frequency selective channel there may be a set of
`
`H(t) coefficients for each tone that is transmitted via the RF channel. To the extent that
`
`H(t), which may be referred to as the "channel estimate matrix", changes with time and
`
`to the extent that the transmitting mobile terminal fails to adapt to those changes,
`
`information loss between the transmitting mobile terminal and the receiving mobile
`
`terminal may result.
`
`6
`
`

`

`[15] Higher layer communications protocols, such as the transmission control protocol
`(TCP) may attempt to adapt to detected information losses, but such adaptations may
`
`be less than optimal and may result in slower information transfer rates. In the case of
`fast fading, the problem may actually reside at lower protocol layers, such as the
`
`physical (PHY) layer, and the media access control (MAC) layer. These protocol layers
`may be specified under IEEE 802.11 for WLAN systems. The method by which
`
`adaptations may be made at the PHY and MAC layers, however, may comprise a
`mechanism by which a receiving mobile terminal may provide feedback information to a
`
`transmitting mobile terminal based upon channel estimates which are computed at the
`receiving mobile terminal.
`
`[16] Existing closed loop receiver to transmitter mechanisms, also referred as "RX to
`TX feedback mechanisms", that exist under IEEE 802.11 include acknowledgement
`(ACK) frames, and transmit power co.ntrol (TPC) requests and reports. The TPC
`mechanisms may allow a receiving mobile terminal to communicate information to a
`transmitting mobile terminal about the transmit power level that should be used, and the
`link margin at the receiving mobile terminal. The link margin may represent the amount
`
`of signal power that is being received, which is in excess of a minimum power required
`by the receiving mobile terminal to decode message information, or frames, that it
`receives.
`
`[17] A plurality of proposals is emerging for new feedback mechanisms as candidates
`
`for incorporation in IEEE resolution 802.11. Among the proposals for new feedback
`
`mechanisms are proposals from TGn (task group N) sync, which is a multi-industry
`
`group that is working to define proposals for next generation wireless networks which
`are to be submitted for inclusion in IEEE 802.11, and Qualcomm. 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
`
`7
`
`

`

`sounding frame method may not utilize beamforming or cyclic delay diversity (CDD). In
`
`the sounding frame method, each antenna may transmit independent information.
`
`[18] The receiving mobile terminal may estimate a complete reverse channel estimate
`
`matrix, Hup, for the channel defined in an uplink direction from the receiving mobile
`
`terminal to the transmitting mobile terminal. This may require calibration with the
`
`transmitting mobile terminal where the transmitting mobile terminal determines the
`
`forward channel estimate matrix, Hdown, for the channel defined in a downlink direction
`
`from the transmitting mobile terminal to the receiving mobile terminal. To compensate
`
`for possible differences between Hup and Hdown the receiving mobile terminal may be
`
`required to receive Hdown from the transmitting mobile terminal, and to report Hup - Hdown
`as feedback information. The TGn sync proposal may not currently define a calibration
`
`response. A channel estimate matrix may utilize 24 or more bits for each channel and
`
`for each tone, comprising 12 or more bits in an in-phase (I) component and 12 or more
`
`bits in a quadrature (Q) component.
`
`[19] According to the principle of channel reciprocity, the characteristics of the RF
`channel in the direction from the transmitting mobile terminal to the receiving mobile
`
`terminal may be the same as the characteristics of the RF channel in the direction from
`
`the receiving mobile terminal to the transmitting mobile terminal Hup = Hdown•
`
`In actual
`
`practice, however, there may be differences in the electronic circuitry between the
`
`respective transmitting mobile terminal and receiving mobile terminal such that, in some
`
`cases, there may not be channel reciprocity. This may require that a calibration process
`
`be performed in which Hup and Hdown are compared to reconcile differences between the
`channel estimate matrices. However, there may be limitations inherent in some
`calibration processes. For example, some proposals for new IEEE 802.11 feedback
`
`mechanisms may be limited to performing "diagonal calibrations". These methods may
`
`not be able to account for conditions in which there are differences in non-diagonal
`
`coefficients between Hup and Hdown• These non-diagonal coefficient differences may be
`the result of complicated antenna couplings at the respective transmitting mobile
`
`8
`
`

`

`terminal and/or receiving mobile terminal. Accordingly, it may be very difficult for a
`calibration process to correct for these couplings. The ability of a calibration technique
`to accurately characterize the RF channel at any instant in time may be dependent upon
`a plurality of dynamic factors such as, for example, temperature variations. Another
`limitation of calibration procedures is that it is not known for how long a calibration
`renders an accurate characterization of the RF channel. Thus, the required frequency
`at which the calibration technique must be performed may not be known.
`
`[20] 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.
`
`9
`
`

`

`BRIEF SUMMARY OF THE INVENTION
`
`[21] A system and/or method for compromise greenfield preambles for 802.11 n.
`
`[22] 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.
`
`10
`
`

`

`BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS
`
`[23] FIG. 1 is an exemplary block diagram of a transmitter and a receiver in a MIMO
`
`system, in accordance with an embodiment of the invention.
`
`[24] FIG. 2a illustrates an exemplary physical layer protocol data unit, in accordance
`with an embodiment of the invention.
`
`[25] FIG. 2b illustrates an exemplary data field in a PPDU, in accordance with an
`embodiment of the invention.
`
`[26] FIG. 3a shows exemplary training sequences and headers for mixed mode
`access in accordance with a Tgnsync proposal, in accordance with an embodiment of
`
`the invention.
`
`[27] FIG. 3b shows an exemplary L-SIG header field for mixed mode access in
`
`accordance with a Tgnsync proposal, in accordance with an embodiment of the
`
`invention.
`
`[28] FIG. 3c shows an exemplary HT-SIG header field for mixed mode access in
`accordance with a Tgnsync proposal, in accordance with an embodiment of the
`
`invention.
`
`[29] FIG. 4a shows exemplary training sequences and headers for greenfield access
`in accordance with a WWiSE proposal for N55=2, in accordance with an embodiment of
`the invention.
`
`[30] FIG. 4b shows an exemplary Signal-N header field for greenfield access in
`accordance with a WWiSE proposal, in accordance with an embodiment of the
`
`invention.
`
`[31] FIG. 4c shows exemplary training sequences and headers for greenfield access
`in accordance with a WWiSE proposal for N55=4, in accordance with an embodiment of
`the invention.
`
`11
`
`

`

`[32] FIG. 5 shows exemplary training sequences and headers for greenfield access
`for N55>2, in accordance with an embodiment of the invention.
`
`[33] FIG. 6 shows exemplary training sequences and headers for mixed mode access
`
`for Nss>2, in accordance with an embodiment of the invention.
`
`12
`
`

`

`DETAILED DESCRIPTION OF THE INVENTION
`
`[34] Certain embodiments of the invention relate to a method and system for
`
`compromise greenfield preambles for 802.11 n, which utilizes a channel sounding
`
`mechanism to communicate information between a transmitter and a receiver.
`
`[35] Aspects of the method are provided, substantially as shown and described with
`
`respect to at least one of FIGs. 1-6, for a sounding mechanism to communicate
`
`information between a transmitter and a receiver in a closed loop MIMO WLAN system.
`
`[36] Another embodiment of the invention may provide a machine-readable storage,
`
`having stored thereon, a computer program having at least one code section executable
`
`by a machine, thereby causing the machine to perform the steps as described above for
`
`compromise greenfield preambles for 802.11 n, which utilizes a channel sounding
`
`mechanism to communicate information between a transmitter and a receiver.
`
`[37] Aspects of the system are provided, substantially as shown and described with
`
`respect to at least one of FIGs. 1-6, for compromise greenfield preambles for 802.11 n.
`
`[38] 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 802.11 n.
`
`An objective of TGn, which may represent a group that is separate from Tgnsync, is to
`
`develop a standard that will enable WLAN devices compatible with IEEE 802.11 n to
`
`also interoperate with IEEE 802.11 devices that are not compatible with IEEE 802.11 n.
`
`WLAN devices that are compatible with IEEE 802.11 but are not compatible with IEEE
`
`802.11 n may be referred to as legacy IEEE 802.11 WLAN devices. WLAN devices
`
`which are compatible with IEEE 802.11 n that communicate with other IEEE 802.11 n
`
`compatible WLAN devices in an IEEE basic service set (BSS) to which no legacy IEEE
`
`802.11 WLAN devices are currently associated may be capable of operating in a
`
`greenfield access mode.
`
`In greenfield access, communications between the WLAN
`
`devices may utilize capabilities specified in IEEE 802.11 n which may not be accessible
`
`13
`
`

`

`to legacy WLAN devices. By contrast, WLAN devices which are compatible with IEEE
`
`802.11 n that communicate with IEEE 802.11 compatible legacy WLAN devices in an
`
`IEEE BSS to which legacy IEEE 802.11 WLAN devices are currently associated may
`
`utilize mixed mode access.
`
`In mixed mode access, communications between IEEE
`
`802.11 compatible WLAN devices may comprise information that advises legacy IEEE
`
`802.11 WLAN devices that WLAN devices in the BSS are engaged in communications
`
`based on IEEE 802.11 n.
`
`[39] Among proposals received by TGn are proposals from, the worldwide spectrum
`
`efficiency <yvVViSE) group, and TGnsync. Current proposals from TGnsync may not
`
`provide a mechanism to support greenfield access. As such, mixed mode access
`
`communications based on current TGnsync may be required to comprise information
`
`that may not be required in greenfield access communications. Embodiments of this
`
`invention may comprise a plurality of proposals that seek to define a compromise
`
`proposal to TGn which is based on aspects of current proposals from WWiSE and
`
`TGnsync.
`
`[40] FIG. 1 is an exemplary block diagram of a transmitter and a receiver in a MIMO
`system, in accordance with an embodiment of the invention. With reference to FIG. 1 is
`
`shown a transmitter 100 and a receiver 101. The transmitter 100 may comprise a
`
`coding block 102, a puncture block 104, an interleaver block 106, a plurality of mapper
`
`blocks 108a ... 108n, a plurality of inverse fast Fourier transform (IFFT) blocks
`
`110a ... 110n, a beamforming V matrix block 112, and a plurality of digital to analog (O/A)
`
`conversion and antenna front end blocks 114a ... 114n. The receiver 101 may comprise
`
`a plurality of antenna front end and analog to digital (AID) conversion blocks
`116a ... 116n, a beamforming u· matrix block 118, a plurality of fast Fourier transform
`(FFT) blocks 120a ... 120n, a channel estimates block 122, a plurality of equalizer blocks
`
`124a ... 124n, a plurality of demapper blocks 126a ... 126n, a deinterleaver block 128, a
`depuncture block 130, and a Viterbi decoder block 132.
`
`14
`
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`(41] The variables V and u· in beamforming blocks 112 and 118 respectively refer to
`matrices utilized in the beamforming technique. United States Application Serial No.
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`___ (Attorney Docket No. 16307US02) filed February 7, 2005, provides a detailed
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`description of Eigen beamforming and is hereby incorporated herein by reference in its
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`entirety.
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`In the transmitter 100, the coding block 102 may transform received binary input
`[42]
`data blocks by applying a forward error correction (FEC) technique such as, for
`example, binary convolutional coding (BCC). The application of FEC techniques, also
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`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
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`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 notion itltb, where tb represents the
`total number of bits which comprise a coding group of bits, while ib represents the
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`number of information bits that are contained in the group of bits tb. Any number of bits
`tb - ib may represent redundant bits which may enable the receiver 101 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 100
`and the receiver 101. The invention is not limited to BCC and a plurality of coding
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`techniques such as, for example, Turbo coding, or low density parity check (LDPC)
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`coding may also be utilized.
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`(43] The puncture block 104 may receive transformed binary input data blocks from
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`the coding block 102 and alter the coding rate by removing redundant bits from the
`received transformed binary input data blocks. For example, if the coding block 102
`implemented a ½ coding rate, 4 bits of data received from the coding block 102 may
`comprise 2 information bits, and 2 redundant bits. By eliminating 1 of the redundant bits
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`15
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`in the group of 4 bits, the puncture block 104 may adapt the coding rate from ½ to 2/3.
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`The interleaver block 106 may rearrange bits received in a coding rate-adapted data
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`block from the puncture block 104 prior to transmission via an RF channel to reduce the
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`probability of uncorrectable corruption of data due to burst of errors, impacting
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`contiguous bits, during transmission via an RF channel. The output from the interleaver
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`block 106 may also be divided into a plurality of streams where each stream may
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`comprise a non-overlapping portion of the bits from the received coding rate-adapted
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`data block. Therefore, for a given number of bits in the coding rate-adapted data block,
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`bdb, a given number of streams from the interleaver block 106, nst, and a given number
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`of bits assigned to an individual stream i by the interleaver block 106, bst(i):
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`equation[2]
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`[44] The plurality of mapper blocks 108a ... 108n may comprise a number of individual
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`mapper blocks which is equal to the number of individual streams generated by the
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`interleaver block 106. Each individual mapper block 108a ... 108n may receive a
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`plurality of bits from a corresponding individual stream, mapping those bits into a
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`"symbol" by applying a modulation technique based on a "constellation" utilized to
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`transform the plurality of bits into a signal level representing the symbol. The
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`representation of the symbol may be a complex quantity comprising in-phase (I) and
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`quadrature (Q) components. The mapper block 108a ... 108n for stream i may utilize a
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`modulation technique to map a plurality of bits, bst(i), into a symbol.
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`[45] The plurality of IFFT blocks 110a ..