Systems and methods for detecting data in a received multiple-input-multiple-output signal are provided. N signals are received from N antennas, with M being greater than or equal to three. The N signals form a vector y and are associated with M sets of data values, where the M sets of data values form a vector x. A channel matrix (H) is estimated, and a QR decomposition of the channel matrix is performed, such that H=QR. The vector y is transformed into a vector z according to z=Q.sup.Hy. The R matrix and the rotated signal vector z are transformed such that one or more elements of the R matrix having complex number values are set equal to zero. Distance values are calculated using the transformed vector z and the vector x. Log likelihood ratio (LLR) values are calculated based on the distance values.

An approach is provided for increasing transmission throughput rates for a source signal transmitted over a wireless channel, applying faster-than-Nyquist (FTN) signaling rates combined with tight frequency roll-off to the a source signal. A receiver is provided that compensates for ISI effects induced by the FTN rate and tight frequency roll-off, where the complexity of the receiver grows only linearly with the interference memory. The receiver comprises an equalizer configured to compensate for the ISI effects, and a decoder configured to decode the output of the equalizer to determine and regenerate the source signal. The receiver processes the received signal via a plurality of processing iterations. For one processing iteration, the decoder generates a set of a posteriori soft information based on the output of the equalizer, and the equalizer uses the a posteriori soft information as a priori soft information for a subsequent processing iteration.

A communication device comprising at least a receiver and a demodulator. The receiver receives first receiving signals and second receiving signals, wherein the first receiving signals are allocated to a first set of subcarriers composed of two or more continuous subcarriers, the second receiving signals are allocated to a second set of subcarriers composed of two or more continuous subcarriers, and at least a portion of the second set of subcarriers overlaps a portion of the first set of subcarriers in a time frame. The demodulator configured to detect the second receiving signals transmitted using one or more subcarriers from receiving signals including the first receiving signals and the second receiving signals, wherein the one or more subcarriers are subcarriers such that the first set of subcarriers overlap the second set of subcarriers, and the demodulator being demodulates the first receiving signals.

Systems and methods for improved coherent demodulation that account for variation of an effective channel estimation error with transmitted symbols are provided. In one embodiment, a wireless node includes a receiver front-end, a channel estimator, and a soft-value processor. The receiver front-end is adapted to output samples of a received signal. The channel estimator is adapted to estimate a channel between a transmitter of the received signal and the wireless node based on the samples of the received signal. The soft-value processor is adapted to process the samples of the received signal according to a soft-value generation scheme that accounts for variation of an effective channel estimation error with transmitted symbols to thereby provide corresponding soft values. By accounting for the variation of the effective channel estimation error with transmitted symbols, the soft-value processor provides improved performance, particularly in a low Signal-to-Noise Ratio (SNR) scenario.

A communication unit for performing soft-decision demodulation includes a receiver that receives a transmitted signal conveying a first set of bits including k bits selected from a set of 2.sup.k possible signals. A demodulator includes a bank of 2.sup.k correlators that detects a transmission of each possible transmitted signal, and outputs 2.sup.k magnitudes of correlator outputs, based on the detected possible transmitted signals, as a first set of inputs. A de-mapper circuit receives the first set of inputs and determines derived from a plurality of aggregated correlator output magnitude distributions of the first set of inputs, wherein the plurality of aggregated correlator output magnitude distributions is fewer than 2.sup.2k; and calculates therefrom a first set of aposteriori soft bits including k soft bits. In this manner, high quality soft-decisions can be obtained in a robust and practical manner.

A transmitter may be operable to generate a sequence of symbols which may comprise information symbols and one or more pilot symbols. The transmitter may transmit the information symbols at a first power and transmit the one or more pilot symbols at a second power. In instances when a particular performance indicator is below a determined threshold, the first power may be set to a first value and the second power may be set to zero value. In instances when the particular performance indicator is above the determined threshold, the first power may be set to a second value and the second power may be set to a non-zero value. A value of the first power and a value of the second power may be based on an applicable average power limit determined by a communications standard with which the transmitter is to comply.

Systems (100) and methods for co-channel separation of communication signals. The methods involve: simultaneously receiving a plurality of communication signals transmitted at disparate relative Doppler frequencies from different locations within a multi-access system; performing matched filtering operations to pre-process each of the plurality of communication signals so as to generate pre-processed digitized samples using a priori information contained in pre-ambles (302, 304) of messages present within the plurality of communication signals; using estimated signal parameters to detect the plurality of communication signals from the pre-processed digitized samples; and demodulating the plurality of communication signals without using a Viterbi decoder.

A nonbinary iterative detector-decoder (IDD) system. The IDD system comprises a detector, a decoder; and a nonbinary interface electrically connected between the detector and decoder. The interface is operative to convert a soft symbol and variance that is output by the detector into a corresponding nonbinary log likelihood ratio (LLR) vector that comprises one or more nonbinary LLRs, and to provide the LLR vector to the decoder. The interface is further configured to convert a nonbinary LLR vector comprised of one or more nonbinary LLRs that is output by the decoder into a corresponding soft symbol and variance, and to provide the soft symbol and variance to the detector.

Systems and methods are disclosed that may detect data transmitted using MIMO communications. Data may be received, on a wireless channel, as a plurality of spatial streams. A channel matrix characterizing the wireless channel may also be received. The channel matrix may be decomposed into a first sub-channel matrix and a second sub-channel matrix, each having a lower dimension than the channel matrix. A first estimated data signal may be generated based at least in part on the plurality of spatial streams and the first sub-channel matrix. A second estimated data signal may be generated based at least in part on the plurality of spatial streams and the second sub-channel matrix. The first and second estimated data signals may be combined to recover the data.

In a time-reversal wireless system, a transceiver receives a combined signal that includes signals from a plurality of devices, each device sending a signal to the transceiver through multiple wireless propagation paths. Signals sent from each of the devices are estimated based on the combined signal and a signature waveform associated with the device. Interference associated with the estimated signal from each of the devices is determined based on the estimated signals from the devices. The signal sent from each of the devices is determined by subtracting the interference associated with the estimated signal associated with the device from the estimated signal associated with the device.