Early Detection and Trellis Splicing Reduced Complexity Soft Iterative Decoding
The excellent bit error rate performance of new soft iter ative decoding algorithms eg turbo codes is achieved at the expense of a computationally burdensome itera tive decoding procedure In this paper we present a new method called early detection that can be used to reduce the computational complexity of a variety of soft iterative decoding methods Using a con dence criterion some in formation symbols state variables and codeword symbols are detected early on in the iterative decoding procedure leading to a reduction in the computational complexity of further processing After presenting a general Markov ran dom eld framework eg the Tanner graph for compound codes we use this framework to show how early detection leads to computational savings We then present an easily implemented instance of this algorithm called trellis splic ing that can be used with turbo codes For a simulated turbo code system at low BERs we obtain a reduction in computational complexity of over a factor of four relative to conventional turbo decoding without any increase in BER