A BCJR-DFE Based Receiver for Achieving Near Capacity Performance on Inter Symbol Interference Channels

A non-iterative receiver is proposed to achieve near capacity performance on inter-symbol interference channels. There are two main ingredients in the proposed design i) the use of a BCJR-DFE equalizer which produces optimal soft estimates of the inputs to the ISI channel given all the observations from the channel and L past symbols exactly, where L is the memory in the ISI channel. ii) The use of an encoder structure that ensures that L past symbols can be used in the DFE in an error free manner through the use of a capacity achieving code for a memoryless channel. This DFE based receiver has several advantages over an iterative (turbo) receiver such as low complexity, codes that are optimized for memoryless channels can be used with channels with memory and finally the channel does not need to be known at the transmitter, making this a better choice than turbo equalizers when long latencies can be tolerated. This general principle also applies to other signal processing functions such as non-coherent detection, synchronization, timing recovery etc making the proposed encoder and receiver structure a viable alternative to iterative signal processing.