Performance of Turbo Decoder with Iterative DFE in Shallow Water Acoustic Channels

A shallow water acoustic channel model including time-varying fading, multipath and additive noise is introduced in this paper. Based on the model a new structure of turbo decoder with iterative decision feedback equalizer (DFE) is built. In the structure, the conventional turbo decoder is modified to generate all coded bits (information and parity bits), and a DFE is implemented in the turbo decoding iteration loop, so that the turbo decoder and the DFE operate in a mutual support fashion. Compared with turbo equalizer which adopts soft-in-soft-out channel equalizer, the structure is much simpler but efficient because hard decisions are passed from turbo decoder to DFE and trellis search corresponding to turbo equalization is needless. Simulations are carried out for a rate 1/3 turbo code with g=(15,13) in a three-path shallow water acoustic channel. Compared with the conventional DFE with iterative turbo decoder, the structure improves 2 dB in the performance.