Abstract: A system and method for detecting Spatially Multiplexed (SM), Space Time Block Coded (STBC), or Hybrid Space Time Block Coded-Spatially Multiplexed (STBC-SM) Multiple-Input Multiple-Output (MIMO) signals is disclosed. QR decomposition of the MIMO signal is performed. A constellation of symbols present in the MIMO signals is partitioned into subsets of symbols, using a set partitioning technique. A-posteriori probability (APP) of each branch is determined. Log Likelihood Ratios (LLRs) corresponding to the transmitted bits are determined using the a-posteriori probabilities. Successively, transmitted bits are determined by providing the LLRs corresponding to the transmitted bits, to a Viterbi decoder.

Abstract: A system and method for detecting Spatially Multiplexed (SM), Space Time Block Coded (STBC), or Hybrid Space Time Block Coded-Spatially Multiplexed (STBC-SM) Multiple-Input Multiple-Output (MIMO) signals is disclosed. QR decomposition of the MIMO signal is performed. A constellation of symbols present in the MIMO signals is partitioned into subsets of symbols, using a set partitioning technique. A-posteriori probability (APP) of each branch is determined. Log Likelihood Ratios (LLRs) corresponding to the transmitted bits are determined using the a-posteriori probabilities. Successively, transmitted bits are determined by providing the LLRs corresponding to the transmitted bits, to a Viterbi decoder.

Abstract: A method and a communication receiver have been described for calculating log-likelihood ratios in a communication receiver. The log-likelihood ratio is calculated for each bit of one or more subsymbols of each of the one or more spatial streams by computing effective noise on one or more spatial streams after considering noise terms resulting from MIMO detection estimates of the subsymbols on each spatial stream. Finally, signal to noise ratio is determined for one or more spatial streams from the effective noise and scaling bit log-likelihood ratios with the signal to noise ratio.

Abstract: A method and a communication receiver have been described for calculating log-likelihood ratios in a communication receiver. The log-likelihood ratio is calculated for each bit of one or more subsymbols of each of the one or more spatial streams by computing effective noise on one or more spatial streams after considering noise terms resulting from MIMO detection estimates of the subsymbols on each spatial stream. Finally, signal to noise ratio is determined for one or more spatial streams from the effective noise and scaling bit log-likelihood ratios with the signal to noise ratio.

Abstract: Methods, apparatuses and systems for identifying a channel bandwidth and channel offset of an orthogonal frequency division multiplexing (OFDM) signal. The OFDM signal is received by a receiver apparatus that may be tuned to RF bandwidth of 20 MHz, 40 MHz or 80 MHz. The method utilized by the apparatus includes identifying the location of the primary channel and subsequently determining a sequence of equalized frequency domain sub-symbols of the signal field in the lower and the upper frequency band. Further, a cross-correlation between the sequence of equalized frequency domain sub-symbols is computed along with the computing energy of the sequence of equalized frequency domain sub-symbols. Finally, the cross-correlation and the computed energy are compared for identifying the channel offset and the channel bandwidth.

Abstract: Methods, apparatuses and systems for identifying a channel bandwidth and channel offset of an orthogonal frequency division multiplexing (OFDM) signal. The OFDM signal is received by a receiver apparatus that may be tuned to RF bandwidth of 20 MHz, 40 MHz or 80 MHz. The method utilized by the apparatus includes identifying the location of the primary channel and subsequently determining a sequence of equalized frequency domain sub-symbols of the signal field in the lower and the upper frequency band. Further, a cross-correlation between the sequence of equalized frequency domain sub-symbols is computed along with the computing energy of the sequence of equalized frequency domain sub-symbols. Finally, the cross-correlation and the computed energy are compared for identifying the channel offset and the channel bandwidth.

Abstract: A low latency transmitter and receiver for an OFDM system are disclosed. The low latency transmitter includes an FFT module and a baseband modulator. The FFT module computes IDFT of PSK constellation data symbols or QAM constellation data symbols. The baseband modulator performs complex modulation of the IDFT samples by multiplying these samples with 1 and ?1 alternatively in time domain. The low latency receiver includes a baseband demodulator and another FFT module. The baseband demodulator performs complex demodulation of the received samples of OFDM symbols by multiplying the samples of OFDM symbols with 1 and ?1 alternatively in time domain thereby obtaining baseband demodulated symbols. The FFT module of the receiver computes DFT of samples of the baseband demodulated symbols to obtain samples of the OFDM demodulated symbols.

Abstract: Method and system for decomposing a complex channel matrix at MIMO receiver is disclosed. The method comprises determining a real channel matrix from the complex channel matrix, wherein the number of rows and columns of the real channel matrix depends on a number of transmitting chains and a number of receiving chains. Thereafter, the below mentioned steps repeated predetermined number of times: A pre-Householder vector is determined based on the real channel matrix. A Householder vector is determined based on the pre-Householder vector. Thereafter a Householder matrix is determined based on the Householder vector and a transpose of the Householder vector without performing division operation. Finally, an orthogonal matrix and an upper triangular matrix are determined based on the Householder matrix, wherein the upper triangular matrix comprises a predetermined number of zeros in an upper triangle.

Abstract: A low latency transmitter and receiver for an OFDM system are disclosed. The low latency transmitter includes an FFT module and a baseband modulator. The FFT module computes IDFT of PSK constellation data symbols or QAM constellation data symbols. The baseband modulator performs complex modulation of the IDFT samples by multiplying these samples with 1 and ?1 alternatively in time domain. The low latency receiver includes a baseband demodulator and another FFT module. The baseband demodulator performs complex demodulation of the received samples of OFDM symbols by multiplying the samples of OFDM symbols with 1 and ?1 alternatively in time domain thereby obtaining baseband demodulated symbols. The FFT module of the receiver computes DFT of samples of the baseband demodulated symbols to obtain samples of the OFDM demodulated symbols.

Abstract: Method and system for decomposing a complex channel matrix at MIMO receiver is disclosed. The method comprises determining a real channel matrix from the complex channel matrix, wherein the number of rows and columns of the real channel matrix depends on a number of transmitting chains and a number of receiving chains. Thereafter, the below mentioned steps repeated predetermined number of times: A pre-Householder vector is determined based on the real channel matrix. A Householder vector is determined based on the pre-Householder vector. Thereafter a Householder matrix is determined based on the Householder vector and a transpose of the Householder vector without performing division operation. Finally, an orthogonal matrix and an upper triangular matrix are determined based on the Householder matrix, wherein the upper triangular matrix comprises a predetermined number of zeros in an upper triangle.

Abstract: A method for detecting a format of a frame in a communication system is presented. An embodiment of the method includes receiving the frame comprising a plurality of orthogonal frequency division multiplexing (OFDM) symbols. The plurality of OFDM symbols may include at least one signal field symbol. The method further includes determining a modulation associated with the at least one signal field symbol. The modulation may be a first modulation or a second modulation. Also, the method includes estimating a position of the at least one signal field symbol among the plurality of symbols, and extracting a coding rate of the received frame. The method then includes detecting the format of the received frame based on the determined modulation and the estimated position of the at least one signal field symbol, and the extracted coding rate of the received frame.

Abstract: A method of estimating a symbol boundary for adaptive time synchronization in a communication system is presented. An embodiment of the method includes receiving a signal comprising a plurality of OFDM symbols from receiver chains. The OFDM symbols include at least a long training field (LTF) symbol. The method further includes determining a normalized correlation signal based on correlation between the received LTF symbol and a reference symbol for each of the receiver chains for different lags. Also, the method includes estimating an energy window length for the normalized correlation signal. The energy window length includes at least one of channel delay spread and a maximum cyclic shift applied to the signal. The method then includes estimating the symbol boundary associated with the received LTF symbol based on a position of peak energy of the normalized correlation signal using the estimated energy window length.

Abstract: A method of estimating a symbol boundary for adaptive time synchronization in a communication system is presented. An embodiment of the method includes receiving a signal comprising a plurality of OFDM symbols from receiver chains. The OFDM symbols include at least a long training field (LTF) symbol. The method further includes determining a normalized correlation signal based on correlation between the received LTF symbol and a reference symbol for each of the receiver chains for different lags. Also, the method includes estimating an energy window length for the normalized correlation signal. The energy window length includes at least one of channel delay spread and a maximum cyclic shift applied to the signal. The method then includes estimating the symbol boundary associated with the received LTF symbol based on a position of peak energy of the normalized correlation signal using the estimated energy window length.

Abstract: A method for detecting a format of a frame in a communication system is presented. An embodiment of the method includes receiving the frame comprising a plurality of orthogonal frequency division multiplexing (OFDM) symbols. The plurality of OFDM symbols may include at least one signal field symbol. The method further includes determining a modulation associated with the at least one signal field symbol. The modulation may be a first modulation or a second modulation. Also, the method includes estimating a position of the at least one signal field symbol among the plurality of symbols, and extracting a coding rate of the received frame. The method then includes detecting the format of the received frame based on the determined modulation and the estimated position of the at least one signal field symbol, and the extracted coding rate of the received frame.

Abstract: A computationally efficient method and system for decoding shortened cyclic codes is presented. The increase in computational efficiency is achieved by improvement of the syndrome calculation step. Two embodiments of the present invention are described; the first embodiment is optimized for a hardware implementation and the second embodiment is optimized for a Digital Signal Processor (DSP) implementation. The present invention is applicable to decoding of all the binary shortened cyclic codes, including Fire codes used for Coding Scheme-1 (CS-1) for GSM.