Embodiments of the invention provide a decoder for decoding a signal received through a transmission channel in a communication system, said signal comprising a vector of information symbols, said transmission channel being represented by an upper triangular matrix, wherein the decoder comprises: a processing unit (309) configured to determine a set of division parameters depending on at least one division metric derived from components of said upper triangular matrix; a decoding unit (311) configured to divide said upper triangular matrix into two or more sub-matrices using said set of division parameters in accordance with a division of said vector of information symbols into two or more sub-vectors, and to determine at least one estimate of each sub-vector of information symbols by applying a symbol estimation algorithm,
wherein the decoder is configured to determine at least one estimate of said vector of information symbols from the estimates of said sub-vectors of information symbols.

A method, system, and apparatus are provided for computing soft bits in a non-linear MIMO detector which decodes a signal received at a plurality of receive antennas using channel estimate information and a decoding tree to produce output data for a bit estimation value which includes a maximum likelihood solution along with a naturally ordered vector identifying all explored node metrics and node indices, where soft bits are computed for each bit estimation value by determining a set of bit-masks through repetition and indexing operations applied on the explored node indices, masking the naturally ordered vector with the set of bit-masks to generate masked node metrics, determining candidate soft bit values by subtracting metrics of all nodes that form the maximum likelihood solution from the masked node metrics, and determining a final soft bit value by identifying which of the candidate soft bit values has a lowest value.

Communication device adapted for receiving a MIMO signal is provided. The device comprises a first detector adapted to perform a first symbol detection on the MIMO signal using a first detection method, a detection error determination unit adapted to determine a first detection error of the first symbol detection, a detection error judging unit adapted to determine if the first detection error is above or below a detection threshold, and a second detector, adapted to perform a second symbol detection on the MIMO signal using a second detection method, if the detection error judging unit has determined that the first detection error is above the detection threshold. The communication device is adapted to use results of the symbol detection as final symbol detection results, if the detection error judging unit has determined that the first detection error is below the detection threshold.

Embodiments of the invention provide a decoder for decoding a signal received through a transmission channel in a communication system, said signal comprising a vector of information symbols, wherein the decoder comprises: a processing unit (307) configured to determine at least one candidate set of division parameters and to perform a division of said vector of information symbols into a set of sub-vectors in association with each candidate set of division parameters, each pair of sub-vectors being associated with a division metric; a selection unit (309) configured to select one of said candidate sets of division parameters according to a selection criterion depending on said division metric; and a decoding unit (311) configured to determine at least one estimate of each sub-vector associated with said selected set of division parameters by applying a symbol estimation algorithm,
wherein the decoder is configured to determine at least one estimate of the vector of information symbols from said at least one estimate of each sub-vector of information symbols.

A method, system, and apparatus are provided for computing soft bits in a non-linear MIMO detector which decodes a signal received at a plurality of receive antennas using channel estimate information and a decoding tree to produce output data for a bit estimation value which includes a maximum likelihood solution along with a naturally ordered vector identifying all explored node metrics and node indices, where soft bits are computed for each bit estimation value by determining a set of bit-masks through repetition and indexing operations applied on the explored node indices, masking the naturally ordered vector with the set of bit-masks to generate masked node metrics, determining candidate soft bit values by subtracting metrics of all nodes that form the maximum likelihood solution from the masked node metrics, and determining a final soft bit value by identifying which of the candidate soft bit values has a lowest value.

There is provided a decoder for sequentially decoding a data signal received through a transmission channel in a communication system, said data signal carrying transmitted symbols, said decoder comprising a symbol estimation unit (301) configured to determine estimated symbols representative of the transmitted symbols carried by the received signal from information stored in a stack, said symbol estimation unit (301) being configured to iteratively fill the stack by 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 said data signal and each node being assigned a metric, the stack being filled at each iteration with a set of expanded child nodes and being ordered by increasing values of the metrics assigned to the nodes, the selected node for each iteration corresponding to the node being assigned the lowest metric in the stack, the decoder comprising a metric determination unit (302) configured to determine an initial metric for each child node of said set of expanded child nodes, wherein the decoder further comprises a modified metric calculation unit (303) configured to calculate a modified metric for at least one of the expanded child nodes from the metric associated with said expanded child node and a weighting coefficient, said weighting coefficient being a function of the level of said node in the decoding tree, the decoder assigning said modified metric to said at least one of the expanded child nodes.

Communication device adapted for receiving a MIMO signal is provided. The device comprises a first detector adapted to perform a first symbol detection on the MIMO signal using a first detection method, a detection error determination unit adapted to determine a first detection error of the first symbol detection, a detection error judging unit adapted to determine if the first detection error is above or below a detection threshold, and a second detector, adapted to perform a second symbol detection on the MIMO signal using a second detection method, if the detection error judging unit has determined that the first detection error is above the detection threshold. The communication device is adapted to use results of the symbol detection as final symbol detection results, if the detection error judging unit has determined that the first detection error is below the detection threshold.

Embodiments of the invention provide a decoder for decoding a signal received through a transmission channel in a communication system, said signal comprising a vector of information symbols, wherein the decoder comprises: a processing unit (307) configured to determine at least one candidate set of division parameters and to perform a division of said vector of information symbols into a set of sub-vectors in association with each candidate set of division parameters, each pair of sub-vectors being associated with a division metric; a selection unit (309) configured to select one of said candidate sets of division parameters according to a selection criterion depending on said division metric; and a decoding unit (311) configured to determine at least one estimate of each sub-vector associated with said selected set of division parameters by applying a symbol estimation algorithm,
wherein the decoder is configured to determine at least one estimate of the vector of information symbols from said at least one estimate of each sub-vector of information symbols.

Embodiments of the invention provide a decoder for decoding a signal received through a transmission channel in a communication system, said signal comprising a vector of information symbols, said transmission channel being represented by an upper triangular matrix, wherein the decoder comprises: a processing unit (309) configured to determine a set of division parameters depending on at least one division metric derived from components of said upper triangular matrix; a decoding unit (311) configured to divide said upper triangular matrix into two or more sub-matrices using said set of division parameters in accordance with a division of said vector of information symbols into two or more sub-vectors, and to determine at least one estimate of each sub-vector of information symbols by applying a symbol estimation algorithm,
wherein the decoder is configured to determine at least one estimate of said vector of information symbols from the estimates of said sub-vectors of information symbols.

A method (10) of non-linear propagation impairment equalization, the method comprising the steps of: a. receiving (12) communications traffic carried by an optical communications signal transmitted over an optical communications link; b. generating (14) a time dependent filter representation of a nonlinear time-variant impulse response of the inverse of the optical communications link; and c. applying (16) the time dependent filter representation to the received communications traffic to form non-linear propagation impairment equalized communications traffic. An optical communications link nonlinear propagation impairment equalizer and optical communications signal receiver apparatus are also provided.