The present TPC serial iterative decoding algorithm has the problems of relatively high complexity and large decoding delay. The decoding delay of Argon parallel iterative decoder is lower, but it has some performance losses. In order to solve these problems, an improved parallel iterative decoding structure of TPC was designed. The TPC decoder using the new parallel structure had the same performance with the serial structure and the latency reduces to half of the serial structure. The optimization method of the search of least reliable bit positions was proposed. The calculation of candidate codes Euclidean distances and the search of ML codeword and competing code word showed low computation and decoding latency. The 4 iterations TPC decoder had the decoding speed of 28 Mbps.
