Abstract: A mobile device transmits data over a shared spectrum in an uplink channel to a base station in a contention-based access scheme. The mobile device obtains data to be wirelessly transmitted over the shared spectrum in the uplink channel to the base station. The uplink channel is formatted with a frame/subframe structure with a predetermined timing. The mobile device determines whether the shared spectrum is free for transmission according to a listen before transmit procedure. When the shared spectrum is free for transmission, the mobile device contends with other mobile device to gain access to the uplink channel. After gaining access to the uplink channel, the mobile device transmits the data over the shared spectrum in the uplink channel to the base station.

Abstract: A mobile device transmits data over a shared spectrum in an uplink channel to a base station in a contention-based access scheme. The mobile device obtains data to be wirelessly transmitted over the shared spectrum in the uplink channel to the base station. The uplink channel is formatted with a frame/subframe structure with a predetermined timing. The mobile device determines whether the shared spectrum is free for transmission according to a listen before transmit procedure. When the shared spectrum is free for transmission, the mobile device contends with other mobile device to gain access to the uplink channel. After gaining access to the uplink channel, the mobile device transmits the data over the shared spectrum in the uplink channel to the base station.

Abstract: A mobile device obtains data to be wirelessly transmitted over a shared spectrum in an uplink channel to a base station. The uplink channel is formatted with a frame/subframe structure with a predetermined timing. The mobile device determines whether the shared spectrum is free for transmission according to a Listen Before Transmit procedure. When the shared spectrum is free for transmission, the mobile device selects a start time in the uplink channel that mitigates interference from other mobile devices in proximity to the mobile device. Beginning at the start time, the mobile device transmits the data over the shared spectrum in the uplink channel to the base station.

Abstract: A mobile device obtains data to be wirelessly transmitted over a shared spectrum in an uplink channel to a base station. The uplink channel is formatted with a frame/subframe structure with a predetermined timing. The mobile device determines whether the shared spectrum is free for transmission according to a Listen Before Transmit procedure. When the shared spectrum is free for transmission, the mobile device selects a start time in the uplink channel that mitigates interference from other mobile devices in proximity to the mobile device. Beginning at the start time, the mobile device transmits the data over the shared spectrum in the uplink channel to the base station.

Abstract: Systems and techniques relating to wireless signal processing.

Abstract: A beamforming technique used in a MIMO wireless transmission system determines a transmitter beamforming steering matrix using a matrix equalizer of a transmitter or a receiver within the MIMO communication system, to thereby increase the speed and/or to decrease the processing needed to implement effective beamforming within the transmitter of the communication system. This beamforming technique can be used when a transmitter, with multiple transmitter antennas, is used to communicate with one or with multiple receivers within the communication system.

Abstract: An estimate of a multiple input, multiple output (MIMO) channel is computed, and an equalizer to be applied to signals received via the MIMO channel is computed. The equalizer is initialized based on the estimate of the MIMO channel. The equalizer is applied to a received signal, and the received signal is demodulated to generate a demodulated signal. The demodulated signal is decoded according to an error correction code to generate decoded data, and the decoded data is re-encoded according to the error correction code to generate re-encoded data. The re-encoded data is re-modulated to generate a re-modulated signal. The received signal is compared to the re-modulated signal, and the equalizer is updated based on the comparison. After updating the equalizer, the equalizer is applied to the received signal.

Abstract: A transceiver utilizes a spatial spreading matrix to distribute two or more encoded spatial data streams to multiple antennas. The spatial spreading matrix satisfies one or more of the following two constraints: (a) the ratio of squared norms of the sum of the components of a row, for different rows of the spatial spreading matrix, is equal to a first constant sequence, and (b) the ratio of squared norms of the sum of a symbol S1 to be transmitted, when the symbol S1 is equal to 1 or ?1, multiplied by each of the components of a row, for different rows of the spatial spreading matrix, is equal to a second constant sequence.

Abstract: Systems and methods are provided for whitening noise of a received signal vector in a multiple-input multiple-output (MIMO) transmission or storage system. The whitening filter may be designed to whiten an interference component of the received signal vector, where the interference component is derived from modeling transmitter and receiver imperfections as a first coupling between MIMO transmitter outputs and a second coupling between MIMO receiver. The whitening filter may be computed based on the covariance matrix of the interference component.

Abstract: A system including a physical layer module and a control module. The physical layer module is configured to generate a first clear channel assessment for a first sub-channel of a communication channel and generate a second clear channel assessment for a second sub-channel of the communication channel. The first clear channel assessment indicates whether the first sub-channel is free or busy. The second clear channel assessment indicates whether the second sub-channel is free or busy. The control module is configured to, in response to the second sub-channel being busy, extend a duration of the second clear channel assessment by a predetermined period of time, and transmit data via (i) only the first sub-channel or (ii) both the first sub-channel and the second sub-channel based on (a) the first clear channel assessment, (b) the second clear channel assessment, and (c) the extended duration of the first clear channel assessment.

Abstract: A network station includes a sampling device configured to generate samples of radio frequency activity on a medium. A first correlator is configured to autocorrelate the samples based on a first delay to generate a first autocorrelation value. The first delay matches periodicity of a jam signal. The jam signal indicates a second station is to transmit data. The second station is separate from the network station. A second correlator is configured to autocorrelate the samples to generate a second autocorrelation value. The second autocorrelation value indicates whether the radio frequency activity includes periodic noise. A controller is configured to prevent the network station from transmitting a radio frequency signal on the medium based each of the first autocorrelation value and the second autocorrelation value.

Abstract: A transmitter beamforming technique for use in a MIMO wireless communication system determines a partial description of a reverse channel without determining a full dimensional description of the reverse channel. A correction matrix is developed from the partial description of the reverse channel and a description of the forward channel. The correction matrix is used to process signals to be transmitted via the forward channel, and a steering matrix is used to perform beamforming in the forward channel.

Abstract: A system including a plurality of filter modules to respectively communicate with a plurality of antennas, filter signals from channels other than a communication channel of a first wireless network, where the communication channel includes a first channel and a second channel, and generate a plurality of signals. A sensing module senses, based on the plurality of signals, whether radio frequency signals from a second network are present in at least one of the first channel and the second channel, and generates a plurality of control signals indicating presence or absence of the radio frequency signals in at least one of the first channel and the second channel. A channel identification module determines, based on the plurality of control signals, availability of the first channel and the second channel in response to whether the radio frequency signals are present in the first channel and the second channel.

Abstract: A method for performing a clear channel assessment to determine whether a wireless channel is clear for transmission of a transmit signal. The method includes receiving, through the wireless channel, a plurality of signals, wherein the plurality of signals are respectively received via a plurality of antennas of the receiver determining a signal strength of each of the plurality of signals, autocorrelating the plurality of signals to respectively generate a plurality of autocorrelated signals, weighting each autocorrelated signal of the plurality of autocorrelated signals based on one or more of the signal strengths determined for each of the plurality of signals, combining each autocorrelated signal, as weighted, to generate a combined signal, demodulating the combined signal, and determining, based at least in part on the demodulation of the combined signal, whether the wireless channel is clear for the transmission of the transmit signal onto the wireless channel.

Abstract: Methods and apparatus are provided for performing log-likelihood ratio (LLR) computations in a pipeline. Portions of a metric used to compute LLR values are computed in one pipeline part. The portions correspond to all permutations of some received signal streams. The portions are combined with one permutation x2 of the received signal stream that was not included in the previous pipeline computation in a subsequent pipeline part to produce M values associated with a particular bit position. At each subsequent clock cycle, a different permutation of x2 is combined with the previously computed portions producing different M values. State values corresponding to different values of bit positions of the received stream are computed by finding the minimum among the M values, in each clock cycle, that affect a particular bit position. The state values are combined to compute the LLR values for the bit position in a final pipeline part.

Abstract: A low-density parity check (LDPC) encoder that calculate parity check values for a message using an LDPC parity check matrix is provided. A matrix-vector multiplication unit is operative to multiply a portion of the LDPC parity check matrix and the message to obtain an intermediate vector. A parallel recursion unit is operative to recursively calculate a first plurality of parity check values for the message based on the intermediate vector and to recursively calculate a second plurality of parity check values for the message based on the intermediate vector. The first plurality of parity check values are calculated in parallel with the second plurality of parity check values.

Abstract: A transceiver utilizes a spatial spreading matrix to distribute two or more encoded spatial data streams to multiple antennas. The spatial spreading matrix satisfies one or more of the following two constraints: (a) the ratio of squared norms of the sum of the components of a row, for different rows of the spatial spreading matrix, is equal to a first constant sequence, and (b) the ratio of squared norms of the sum of a symbol Sl to be transmitted, when the symbol Sl is equal to 1 or ?1, multiplied by each of the components of a row, for different rows of the spatial spreading matrix, is equal to a second constant sequence.

Abstract: Systems and methods are provided for whitening noise of a received signal vector in a multiple-input multiple-output (MIMO) transmission or storage system. The whitening filter may be designed to whiten an interference component of the received signal vector, where the interference component is derived from modeling transmitter and receiver imperfections as a first coupling between MIMO transmitter outputs and a second coupling between MIMO receiver. The whitening filter may be computed based on the covariance matrix of the interference component.

Abstract: An estimate of a multiple input, multiple output (MIMO) channel is computed, and an equalizer to be applied to signals received via the MIMO channel is computed. The equalizer is initialized based on the estimate of the MIMO channel. The equalizer is applied to a received signal, and the received signal is demodulated to generate a demodulated signal. The demodulated signal is decoded according to an error correction code to generate decoded data, and the decoded data is re-encoded according to the error correction code to generate re-encoded data. The re-encoded data is re-modulated to generate a re-modulated signal. The received signal is compared to the re-modulated signal, and the equalizer is updated based on the comparison. After updating the equalizer, the equalizer is applied to the received signal.

Abstract: One or more communications parameters associated with a multiple input, multiple output (MIMO) signal transmitted by a transmitter are identified. The one or more communications parameters include one or more of (i) a number of receive antennas via which the MIMO signal is received, (ii) a number of spatial streams in the MIMO signal, and (iii) a signal to noise ratio (SNR) corresponding to the MIMO signal. A particular data detection technique of a plurality of data detection techniques employed by a receiver is selected in accordance with at least one of the one or more communications parameters.