An apparatus and method for optimizing the performance of satellite communication system receivers by using the Soft-Input Soft-Output (SISO) BCJR (Bahl, Cocke, Jelinek and Raviv) algorithm to detect a transmitted information sequence is disclosed. A Sliding Window technique is used with a plurality of reduced state sequence estimation (RSSE) equalizers to execute the BCJR algorithm in parallel. A serial data stream is converted into a plurality of data blocks using a serial-to-parallel converter. After processing in parallel by the equalizers, the output blocks are converted back to a serial data stream by a parallel-to-serial converter. A path history is determined using maximum likelihood (ML) path history calculation.

A method may include at least partially initializing a trellis of an SE engine at least partially based on predetermined state information about a communication channel associated with an incoming data stream; and processing, via the MLSE engine, the incoming data stream to further initialize the trellis and decode the incoming data stream.

A method of decoding a signal that has been encoded by a tail-biting code based on at least one encoding parameter is disclosed. The at least one encoding parameter may be a trellis size or a quantity of aggregated encoding elements or a code rate. The method is suitable for use in a communication device and comprises receiving the signal, performing a first decoding attempt of the signal based on a first set of starting state metrics and a first encoding parameter hypothesis, the first decoding attempt resulting in a first set of ending state metrics. The method further comprises performing, if the first decoding attempt fails, a second decoding attempt of the signal based on a second set of starting state metrics based on the first set of ending state metrics and a second encoding parameter hypothesis different from the first encoding parameter hypothesis.

Methods and devices are disclosed for receiving and decoding sparsely encoded data sequences using a message passing algorithm (MPA) or maximum likelihood sequence estimation (MLSE). Such data sequences may be used in wireless communications systems supporting multiple access, such as sparse code multiple access (SCMA) systems. The Methods and devices reduce the number of states in a search space for each received signal and associated function node based on a search threshold based on a characteristic related to the received signal and/or to a quality of a resource element over which the received signal is transmitted.