Early detection and trellis splicing: Reduced-complexity iterative decoding

The excellent bit-error rate (BER) performance of new iterative decoding algorithms (e.g., turbodecoding) is achieved at the expense of a computationally burdensome decoding procedure, In this paper, we present a method called early defection that can be used to reduce the computational complexity of a variety of iterative decoders, Using a confidence criterion, some information symbols, state variables, and codeword symbols are detected early on during decoding, In this way, the computational complexity of further processing is reduced with a controllable increase in BER. We present an easily implemented instance of this algorithm, called trellis splicing, that can be used with turbodecoding, For a simulated system of this type, we obtain a reduction in computational complexity of up to a factor of four, relative to a turbodecoder that obtains the same increase in BER by performing fewer iterations.