Iterative decoding of a differential space-time block code with low complexity

Like differential phase shift keying (DPSK), a differential space-time block code has recursive encoding structure and then, when it is concatenated serially with a channel code, additional coding gain from the concatenation is obtained. To obtain the additional gain, recent research has introduced serial concatenation of the differential space-time block code and channel code, and its sub-optimal iterative receiver. The receiver consists of two APP decoders, which not only has considerable computational complexity, but also is not suitable, especially for the differential space-time block code. This paper proposes a simpler, more suitable decoder for the differential space-time block code in the serial concatenation than the APP decoder. The core idea of the proposed decoder is to employ a maximum likelihood decoding method. With low complexity, a receiver with the proposed decoder shows performance almost identical to the conventional one in a time-correlated fading channel.