Abstract: System performance in wireless communication is improved by increasing diversity in time, space and frequency. Information to be transmitted is processed by a convolution encoder to produce encoded bits. The encoded bits are interleaved and mapped to subcarriers. Symbols are created from the subcarriers and the symbols are transmitted so as to increase diversity in time, space and frequency. Circulation transmission in addition to interleaving is used to increase diversity. For example, circulation transmission can be symbol based or subcarrier based.

Abstract: A quadrature frequency division multiplexing (“OFDM”) wireless receiver, including methods and devices for adaptive quantization of OFDM signals according to modulation and coding schemes and sub-carrier frequency responses, is provided. Efficient quantization may be utilized to reduce the large dynamic range of signals to achieve circuit simplification and chip area reduction. In one embodiment, a quantization circuit includes a quantization selector to select quantization thresholds according to modulation and coding schemes and sub-carrier frequency responses, and a non-uniform quantizer to reduce input dynamic range so that an output is represented by fewer bits than an input.

Abstract: System performance in wireless communication is improved by increasing diversity in time, space and frequency. In OFDM-based MIMO systems in which the number of antennas M is greater then the number of simultaneously transmitted OFDM symbols N, circulation transmissions according to the present invention improve signal diversity. In symbol-based circulation transmission, N antennas are chosen from the M available antennas to transmit the N OFDM symbols. In subcarrier-based circulation transmission, M output OFDM symbols are composed from the QAM-mappled samples of the N input OFDM symbols. These M output OFDM symbols are then transmitted from the M antennas simultaneously.

Abstract: The present invention discloses a generating method for short training field in IEEE 802.11n communication systems, mainly comprising the steps of: storing only a first set of time-domain HT-STF sequences in the memory; and deriving a second set of the time-domain HT-STF sequences from the first set of the time-domain HT-STF sequences. The first set of time-domain HT-STF sequences is the time-domain HT-STF sequences either for lower 20 MHz of 40 MHz BW or upper 20 MHz of 40 MHz BW. According to the invention, it is shown that only one set of time-domain HT-STF sequence needs to be stored in the memory. The other three sets of time-domain HT-STF sequence can be generated easily from simple calculation. Therefore, the saving in buffer size to implement all four configurations is significant.

Abstract: The present invention discloses an effective apparatus and method to measure the received signal quality for digital communication systems by measuring error vector measurement (EVM) with embedded EVM measurement block in receivers. The distinction of the present invention is that the EVMSIG and the EVMDATA are measured in the receiver for the SIGNAL fields and DATA fields, respectively. EVMSIG is a good indicator for one spatial stream and EVMDATA is a good indicator for current multiple streams. The receiver determines the optimum number of spatial data streams for feedback to the transmitter based on the combinations of EVMSIG and EVMDATA with or without other algorithms such as analysis on periodically requested sounding packet. The receiver also determines the optimum modulation and coding schemes for feedback based on the EVM measurements.

Abstract: An apparatus and method for receiving layered modulation signals is disclosed. A typical method includes receiving a layered modulation signal including an upper layer signal and a lower layer signal, demodulating and decoding the upper layer signal from the received layered modulation signal, estimating an upper layer amplitude factor and an upper layer phase factor from the received layered modulation signal. A substantially ideal upper layer signal is reconstructed from the demodulated and decoded upper layer signal including matching an ideal amplitude and an ideal phase by applying the upper layer amplitude factor and the upper layer phase factor to the reconstructed ideal upper layer signal. Finally, the reconstructed ideal upper layer signal is subtracted from the received layered modulation signal to produce the lower layer signal for processing.

Abstract: A quadrature frequency division multiplexing (“OFDM”) wireless receiver, including methods and devices for adaptive quantization of OFDM signals according to modulation and coding schemes and sub-carrier frequency responses, is provided. Efficient quantization may be utilized to reduce the large dynamic range of signals to achieve circuit simplification and chip area reduction. In one embodiment, a quantization circuit includes a quantization selector to select quantization thresholds according to modulation and coding schemes and sub-carrier frequency responses, and a non-uniform quantizer to reduce input dynamic range so that an output is represented by fewer bits than an input.

Abstract: A complementary code keying (CCK) demodulator used in a RAKE receiver receiving CCK symbols in a multipath environment computes multipath interferences (MPIs) required for canceling intra-codeword chip interference (ICI). The algorithmic structure jointly computes the ICI of a plurality of possible codewords. The algorithmic structure is similar to the optimal architecture required for CCK correlation computations. The similarity between these two structures allows for the use of the same hardware at different times to compute MPIs and to compute the CCK correlation of a plurality of possible codewords.

Abstract: A ZF joint detection apparatus for a downlink receiver, the apparatus comprising: a channel estimator for estimating a channel impulse response of a multipath fading channel of a received signal; a channel equalizer for estimating a transmission signal by performing channel compensation and removing multipath interference by a deconvolution technique based on the estimated channel impulse response; and a user detector for detecting a symbol-level data sequence transmitted by a specific user by despreading the transmission signal estimated by the channel equalizer with a spreading code for the specific user and a scrambling code.

Abstract: A method is provided for mitigating the multipath interference experienced by a present CCK symbol. This method first obtains a set of initial candidates for the present CCK symbol and a set of initial candidates for the next CCK symbol based on the ICI-corrected correlation outputs for the present and next CCK symbols, respectively. The method then obtains, for each of the candidates for the present CCK symbol, first ISI-mitigated correlation outputs where both the ICI due to the present CCK symbol and the ISI due to the next CCK symbol have been corrected. Thereafter, for each of the candidates for the present CCK symbol, and based on the first ISI-mitigated correlation outputs, the method obtains second ISI-mitigated correlation outputs where the ISI due to the previous CCK symbol has also been corrected. The present CCK symbol is then decoded based on the second ISI-mitigated correlation outputs.

Abstract: System performance in wireless communication is improved by increasing diversity in time, space and frequency. In OFDM-based MIMO systems in which the number of antennas M is greater then the number of simultaneously transmitted OFDM symbols N, circulation transmissions according to the present invention improve signal diversity. In symbol-based circulation transmission, N antennas are chosen from the M available antennas to transmit the N OFDM symbols. In subcarrier-based circulation transmission, M output OFDM symbols are composed from the QAM-mappled samples of the N input OFDM symbols. These M output OFDM symbols are then transmitted from the M antennas simultaneously.

Abstract: System performance in wireless communication is improved by increasing diversity in time, space and frequency. Information to be transmitted is processed by a convolution encoder to produce encoded bits. The encoded bits are interleaved and mapped to subcarriers. Symbols are created from the subcarriers and the symbols are transmitted so as to increase diversity in time, space and frequency. Circulation transmission in addition to interleaving is used to increase diversity. For example, circulation transmission can be symbol based or subcarrier based.

Abstract: An apparatus and method for receiving layered modulation signals is disclosed. A typical method includes receiving a layered modulation signal including an upper layer signal and a lower layer signal, demodulating and decoding the upper layer signal from the received layered modulation signal, estimating an upper layer amplitude factor and an upper layer phase factor from the received layered modulation signal. A substantially ideal upper layer signal is reconstructed from the demodulated and decoded upper layer signal including matching an ideal amplitude and an ideal phase by applying the upper layer amplitude factor and the upper layer phase factor to the reconstructed ideal upper layer signal. Finally, the reconstructed ideal upper layer signal is subtracted from the received layered modulation signal to produce the lower layer signal for processing.

Abstract: A method is provided for mitigating the multipath interference experienced by a present CCK symbol. This method first obtains a set of initial candidates for the present CCK symbol and a set of initial candidates for the next CCK symbol based on the ICI-corrected correlation outputs for the present and next CCK symbols, respectively. The method then obtains, for each of the candidates for the present CCK symbol, first ISI-mitigated correlation outputs where both the ICI due to the present CCK symbol and the ISI due to the next CCK symbol have been corrected. Thereafter, for each of the candidates for the present CCK symbol, and based on the first ISI-mitigated correlation outputs, the method obtains second ISI-mitigated correlation outputs where the ISI due to the previous CCK symbol has also been corrected. The present CCK symbol is then decoded based on the second ISI-mitigated correlation outputs.

Abstract: An optimal algorithmic structure is provided for use in a RAKE receiver to compute multipath interferences (MPIs) required for canceling intra-codeword chip interference (ICI). The algorithmic structure jointly computes the ICI of a plurality of possible codewords. This algorithmic structure is similar to the optimal architecture required for CCK correlation computations. The similarity between these two structures allows for the use of the same hardware at different times to compute MPIs and to compute the CCK correlation of a plurality of possible codewords.

Abstract: A ZF joint detection apparatus for a downlink receiver, the apparatus comprising: a channel estimator for estimating a channel impulse response of a multipath fading channel of a received signal; a channel equalizer for estimating a transmission signal by performing channel compensation and removing multipath interference by a deconvolution technique based on the estimated channel impulse response; and a user detector for detecting a symbol-level data sequence transmitted by a specific user by despreading the transmission signal estimated by the channel equalizer with a spreading code for the specific user and a scrambling code.