Abstract: Techniques are provided for a multi-user reservation sequence used when transmitting a multi-user transmission in a wireless network. At a wireless access point device configured to operate in a wireless network, a multi-user request-to-send packet is transmitted as part of a multi-user reservation sequence prior to a multi-user transmission from the wireless access point device to a plurality of wireless client devices that are the intended recipients for the multi-user transmission. The multi-user request-to-send packet comprises duration information and address information configured to address at least some of the plurality of wireless client devices. Clear-to-send packets transmitted from two or more of the plurality of wireless client devices in response to the multi-user request-to-send packet are received at the wireless access point device. Each clear-to-send packet comprises identical content.

Abstract: A method and system are provided for improving the performance of a trellis-based decoder. States with reduced uncertainty (SRUs) are defined for one or more predetermined fields in an encoded message. Metrics are set for the SRUs such that candidate paths through a trellis-based decoding process are eliminated for those states that are not SRUs.

Abstract: Retransmitting a data sequence over a wireless network according to channel conditions proceeds by transmitting a first transmitting signal representing the data using a first set of beamforming weighting vectors generated according to a first channel condition. A request for re-transmitting the data sequence is received when the first transmitting signal suffers from unrecoverable errors. A re-transmission function is computed according to a second channel condition, and a second transmitting signal is transmitted as generated by using the re-transmission function that is created according to the second channel condition. The data sequence is demodulated and decoded using the first transmitting and the second transmitting signals.

Abstract: Disclosed in an example embodiment is an apparatus comprising a transmitter and processing logic coupled with the transmitter. The processing logic is configured to send data via the transmitter. The processing logic generates a request to send frame. The processing logic encodes data representative of a bandwidth parameter set in the request to send frame. The processing logic transmits the request to send frame via the transmitter.

Abstract: Techniques are provided for crest factor reduction of a symbol to be transmitted by a communication device. The symbol may be an orthogonal frequency division multiplexed (OFDM) formatted symbol. In a communication device, samples of the symbol are clipped with a clipping level. A signal quality of the symbol is computed after it is clipped. A determination is made as to whether the signal quality satisfies a predetermined criterion. When the signal quality does not satisfy the predetermined criterion, the clipping level is adjusted. The clipping, computing, determining and adjusting operations are repeated until the signal quality satisfies the predetermined criterion. The symbol clipped by the clipping level determined to result in satisfying the predetermined criterion is output for supply to a transmitter in the communication device.

Abstract: The present invention discloses a method for selecting a transmission scheme in a multiple-input-multiple-output (MIMO) wireless communications system. The method comprises receiving a downlink request to transmit a data stream to a wireless station, checking the availability of channel state information (CSI) associated with the wireless station, determining the validity characteristic of beamforming weighting vectors associated with the wireless station, selecting a transmission scheme from a plurality of predetermined transmission schemes based on the availability of the CSI and the validity characteristic of the beamforming weighting vectors.

Abstract: An adaptive transmission selection technique is provided. A retransmission scheme is selected for a multiple-input-multiple-output wireless system. A plurality of communication techniques is provided for when a first device needs to retransmit a signal to a second device. The first device determines when the original signal, transmitted to the second device using beamforming techniques, needs to be retransmitted to the second device. If a retransmission is needed, the first device determines channel conditions with respect to the second device. The first device selects a retransmission scheme from a plurality of transmission schemes based on the channel conditions for retransmitting the signal. A first retransmission technique is selected when the channel conditions are static. A second retransmission technique is selected when the channel conditions are relatively slowly changing, and a third retransmission technique is selected when the channel conditions are relatively quickly changing.

Abstract: Techniques are provided to enable wireless communication between first and second wireless communication devices each having a plurality of antennas, where the second device sends the transmissions via less than all of its plurality of antennas. Each transmission may comprise a plurality of time-frequency instances. At the first communication device, data is derived representing parameters of a communication channel between the plurality of antennas of the first device and all of the plurality of antennas of the second device from the transmissions received at the plurality of antennas of the first device. Beamforming weights for transmitting one or more signal streams via the plurality of antennas of the first device to the plurality of antennas of the second device are computed based on the data representing parameters of the communication channel between the plurality of antennas of the first device and the plurality of antennas of the second device.

Abstract: A method for partitioning a plurality of antennas in a wireless communication system, in which the antennas are grouped into a first set of partitions and a second set of partitions. One or more signal transmission schemes are performed with the antennas grouped into the first set of partitions for a first time period, and then with the antennas grouped into the second set of partitions for a second time period.

Abstract: A method is provided for creating an artificial a fast fading channel in a MIMO communication system. The method includes encoding a series of source data to generate a first plurality of encoded output signals and multiplying the first plurality of encoded output signals by a plurality of random complex numbers to generate a second plurality of encoded output signals, and transmitting the second plurality of encoded output signals via the corresponding plurality of antennas. The transmitted signals vary in time and frequency independent of the channel conditions.

Abstract: Techniques are provided to compute the carrier to interference-plus-noise ratio (CINR) in a wireless communication system using log-likelihood ratio (LLR) data generated from a received transmission. The LLR data are collected as they are sent from a detector to a forward error correction (FEC) decoder in a wireless communications device. In one embodiment, decision-aided LLR based CINR is computed using the decoded bits output from the FEC decoder as feedback. In another embodiment, blind LLR based CINR is computed without feedback. The CINR may be used to adjust a modulation and/or coding parameters associated with wireless communication between wireless communication devices.

Abstract: A method and system are provided for achieving spatial diversity of a wireless communications network. The method comprises arranging antennas on a transmitting wireless station into a plurality of antenna subgroups, wherein each of the antenna subgroups forms a virtual antenna, creating a plurality of beamformed MIMO channels using the plurality of virtual antennas, wherein each of the beamformed MIMO channel comprises a plurality of sub-carriers and corresponds to a virtual antenna, dividing sub-carriers in each of the plurality of beamformed MIMO channels into at least a first and second cluster, distributing a first amount of transmitting power to the first cluster and a second amount of transmitting power to the second cluster, wherein the first amount of transmitting power is substantially larger than the second amount of transmitting power.

Abstract: A method and system are provided for detecting messages using enhanced distributed signaling in a wireless communication network that offers transmission diversity to improve the throughput of participating wireless stations.

Abstract: Techniques are provided for receiving uplink transmissions at a plurality of antennas at a base station from a plurality of client stations. Uplink spatial transmissions are analyzed to produce a plurality of direction of arrival (DOA) components associated with the plurality of client stations. The DOA components associated with the plurality of client stations are compared and two or more client stations are selected to participate in an uplink collaborative spatial multiplexing transmission session based on dissimilarities of their DOA components.

Abstract: Energy in a frequency band is received at a wireless communication device and data is generated representing samples of a received time domain waveform from the received energy. Data for groups of samples of the received time domain waveform is processed to transform the data for the received time domain waveform to produce data for an intermediate domain signal that is in neither the time domain nor the frequency domain. The data representing the intermediate domain signal is analyzed to determine whether a sequence having a predetermined pattern from a set of possible sequences is present in the received energy, and ultimately to determine a sequence of the predetermined pattern whose presence is detected in the received energy.

Abstract: Techniques are provided for computing downlink beamforming weights based on the received data at a base station from a mobile station in a MIMO communication system. An uplink transmission is received at a plurality of antennas at a first communication device from a second communication device, where the uplink transmission comprises a plurality of uplink subbands. The uplink spatial signature is estimated for each of the plurality of uplink subbands. The uplink spatial signature is decomposed into a plurality of direction of arrival (DOA) components for each uplink subband using a transform. Data representing multiple propagation paths between the first communication device and the second communication device is computed for each DOA component. A plurality of direction of departure (DOD) components for each of a plurality of downlink subbands is computed based on the data representing the multiple propagation paths.

Abstract: A system for detecting one or more localized burst errors in a receiving message comprised of a plurality of codewords. The system comprises a trellis code decoder for decoding a receiving message with a plurality of codewords and calculating one or more cumulative metrics of a maximum likelihood path and one or more alternative paths from the receiving message, an error detection code (EDC) decoder for detecting existence of one or more errors in the decoded receiving message received from the trellis decoder, and a localized burst error detector activated by the EDC decoder upon detecting the existence of one or more errors in the decoded receiving message to identify at least one corrupted codeword among the plurality of codewords using the one or more cumulative metrics of a maximum likelihood path and the one or more alternative paths, wherein the system requests the re-transmission of the corrupted codeword.

Abstract: Described herein is a method for obtaining a downlink beamforming weighting vector in a wireless communications system based on channel information about an uplink channel. The method comprises obtaining the channel information about the uplink channel by a means selected from the group comprising of training signals, pilot signals, and data signals, wherein the uplink channel comprises a set of uplink sub-channels, calculating a spatial signature of the uplink channel with the channel information, and computing a downlink beamforming weighting vector of a downlink channel with the spatial signature of the uplink channel, wherein the downlink channel comprises a set of downlink sub-channels that share few or no sub-carriers with the set of uplink sub-channels.

Abstract: A wireless communications system is provided with reduced sideband noise and carrier leakage. In the system, at least one transmitter modulates at least one input signal with a first carrier to generate a modulated output signal, and at least one receiver receives the modulated output signal and demodulates the same with a second carrier to generate at least one demodulated output signal. The first and second carriers are at different frequencies, such that the sideband noise and carrier leakage generated by different sources can be distinguished.

Abstract: A method for decoding tail-biting convolutional codes is disclosed. In the method, all beginning states of a trellis diagram are initialized. Forward Viterbi metrics are calculated for the trellis diagram. A trace-back process is performed from an ending state of the trellis diagram at a first time instance to a first state where all surviving paths converge at a second time instance. Backward Viterbi metrics are calculated for a predetermined period of time from the first state at the second time instance to a second state at a third time instance. A trace-back process is performed from a designated state, which is equal to the second state, at the first time instance to determine a most likely path for the convolutional codes in the trellis diagram.