Decoding of high-rate turbo codes using a syndrome trellis

In this paper we present a new iterative decoding algorithm of the high-rate turbo codes which employ high-rate convolutional codes as component codes. This algorithm constructs a syndrome trellis using the parity check matrix of the code, and produces soft-output of each bit of a codeword. The algorithm is named “turbo syndrome decoding” (TSD). In the trellis diagram, only two paths merge into a node. It therefore leads to the significant reduction in both computational complexity of add-compare-select (ACS) operations and storage requirement for the soft-output to the subsequent decoder as compared with the classical decoding of the high-rate turbo codes. Nevertheless, the TSD algorithm has the same capability as the classical one in a sense that the most probable path is selected