A computer-implemented method of estimating transmit symbol vectors transmitted in an overloaded communication channel includes receiving a signal represented by a received signal vector, the received signal vector corresponding to a superposition of signals representing transmitted symbols selected from a constellation of symbols and transmitted from one or more transmitters. Continuous first and second functions in a search space in a convex domain are defined. The first function and the second function are combined into a third function, and a fractional programming algorithm is applied to the third function, targeted to finding an input vector that minimizes the third function. A mapping rule translates the found input vector into an estimated transmit symbol vector, and the estimated transmit symbol vector is output to a decoder for decoding into an estimated transmit symbol from the constellation.

There is provided a decoder for decoding a data signal received through a transmission channel in a communication system, the decoder (310) comprising a symbol estimation unit (311) configured to determine estimated symbols representative of the transmitted symbols carried by the received signal, the estimated symbols being determined from nodes of a decoding tree based on a weight metric associated with each of the node. The decoder further comprises a termination alarm monitoring unit (312) for monitoring a termination alarm depending on the current decoding computation complexity, the termination alarm being associated with a metric parameter, the symbol estimation unit being configured to reduce the weight metric of each node of the decoding tree by a quantity corresponding to a function of the metric parameter associated with the termination alarm, in response to the triggering of the termination alarm.

There is provided a decoder (310) for sequentially decoding a data signal received through a transmission channel in a communication system, the received data signal carrying transmitted symbols, the decoder comprising a symbol estimation unit (311) configured to determine estimated symbols representative of the transmitted symbols carried by the received signal from information stored in a stack, the stack being filled by iteratively expanding child nodes of a selected node of a decoding tree comprising a plurality of nodes, each node of the decoding tree corresponding to a candidate component of a symbol of the received data signal and each node being associated with a predetermined metric, the stack being filled at each iteration with at least some of the expanded child nodes and being ordered by increasing values of the metrics associated with the nodes, the selected node for each iteration corresponding to the node having the lowest metric in the stack. The decoder further comprises a stack reordering activation monitoring unit (313) configured to monitor at least one stack reordering activation condition and, in response to a stack reordering activation condition being verified, to cause the symbol estimation unit to: reduce the metric associated with each node stored in the stack by a quantity, reorder the stack by increasing value of the reduced metric, and remove a set of nodes from the reordered stack so as to maintain a number N of nodes in the reordered stack, the maintained nodes corresponding to the N nodes having the lowest metrics in the reordered stack.

A processing method in a wireless telecommunications receiver receiving a digitally modulated single-carrier signal includes, between a matched filter, in the time domain, operating at a frequency drxB and a frequency equalizer, operating at the frequency B, a decimation step comprising: i/extracting, from a filtered signal frame, a first sequence of samples for aiding the decimation and having the same power; and a second sequence of payload samples intended to be equalized; ii/estimating the variance in the power of each of the drx decimation phases of the first sequence and identifying the n.sup.th decimation phase associated with the minimum variance; iii/decimating the second sequence by selecting the n.sup.th decimation phase of the second sequence and supplying the decimation phase at the input of the frequency equalizer.

Systems and methods are provided for detecting bit errors and further processing bit error information. A method, according to one implementation, includes the step of receiving a binary test sequence pattern generated by a pattern generator at an input to a digital communications system under test, wherein the binary test sequence pattern includes a plurality of sub-patterns. The method also includes the step of receiving an output binary sequence from an output of the digital communications system. Also, the method includes comparing the binary test sequence pattern with the output binary sequence to detect bit errors. Based on correlation characteristics between the bit errors and each of the sub-patterns, the method also includes the step of determining whether the bit errors are caused by random factors or are caused by deterministic factors associated with the digital communications system.

Quasi-reduced state trellis equalization techniques achieve low-latency inter-symbol interference (ISI) equalization by selecting a subset of accumulated path metrics (APMs) for a leading symbol to propagate over a trellis to candidate states of a trailing symbol. This simplifies the computation of APMs for candidate states of the trailing symbol. Thereafter, APMs for candidate states of the trailing symbol are computed based on the subset of APMs for the leading symbol that were propagated over the trellis. Propagating fewer than all APMs for the leading symbol to the trailing symbol reduces the complexity of APM computation at the trailing symbol.

Systems and methods related to improved coherent demodulation and, in particular, improved channel equalization that accounts for variation in an effective channel estimation error with transmitted symbols are disclosed. In one embodiment, a wireless node includes a receiver front-end, a channel estimator, and an equalizer. 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 equalizer is adapted to process the samples of the received signal according to a modified equalization scheme that compensates for variation in an effective channel estimation error with transmitted symbols to thereby provide corresponding bit or symbol decisions. In this manner, channel equalization is improved, particularly for a wireless system that utilizes a modulation scheme with varying amplitude.

Described is a data processing method and apparatus that aims to estimate an unknown parameter required to improve interference cancellation capability of a maximum likelihood (ML) receiver. The ML receiver may perform channel estimation on a serving cell and an interference cell to obtain a channel estimation matrix. In addition, the ML receiver may calculate first and second metrics for received signals and the channel estimation matrix to determine one or more survivor paths of the serving cell and calculate an Log-Likelihood Ratio (LLR) according to the survivor paths.

A receiver estimates a vector of emitted symbols over a MIMO transmission channel which is emitted by emitting antennas. The receiver receives a vector of received symbols on receiving antennas. Estimation of the vector of emitted symbols is made by calculating a metric associated with a criterion for each vector of a subset of all possible vectors of emitted symbols and selecting an estimation for said vector of emitted symbols as the vector of emitted symbols among said subset which minimizes said metric.

In one embodiment, physical layer error signatures of a communications link are determined by ascertaining characteristics of erred and correct modulation symbols received by a physical receiver of a communications device, such as, but not limited to, by a receiver of a packet switching device in a communications network normally used to receive data traffic. In one embodiment, a physical receiver of a physical communications device receives a particular modulation symbol and determines whether the received particular modulation symbol is an expected modulation symbol in a predetermined sequence of modulation symbols. One or more storage devices are maintained with one or more error signature measurements based on determining whether the particular modulation symbol is the expected modulation symbol in the predetermined sequence of modulation symbols, with the error signature measurements including performing a comparison to a threshold value or a current maximum value.