Combined equalization and decoding techniques

摘要

Combined equalization and decoding of codewords in a coded modulation symbol sequence that has been received from a channel is accomplished in a number of ways. In an intersymbol interference (ISI) cancellation technique, channel impulse response (CIR) estimates corresponding to each received symbol of the coded modulation symbol sequence are determined. Codeword k of the received symbol sequence is then decoded using a maximum likelihood decoding trellis with a path metric that depends upon the CIR estimates and that includes at least one term representing intersymbol interference resulting from symbols of previously decoded codewords. The decoding step is repeated until all of the codewords of the received coded modulation symbol sequence have been decoded. In a maximum likelihood sequence estimation (MLSE)-based technique, an MLSE trellis is advanced from one stage to a next stage by updating a path metric having dependence on the CIR estimates and upon symbols of a codeword corresponding to a state in a previous trellis stage. The trellis-advancing step is repeated until all stages of the MLSE trellis are completed. Then, the codewords are decoded by using a traceback along the best path in the completed MLSE trellis. In another embodiment, a hybrid MLSE-ISI technique utilizes a path metric that depends upon the CIR estimates and upon symbols of a codeword corresponding to a state in a previous trellis stage. The path metric further includes at least one term that represents intersymbol interference resulting from symbols of previously decoded codewords.