Differential space-time block codes with iterative detection

Various differential space-time coding schemes were proposed, where neither the transmitter nor the receiver has the channel state information (CSI). In [1], a differential space-time block code (DSTBC) based on orthogonal designs was constructed by Tarokh and Jafarkhani (TJ). The performance of TJ'DSTBC is 3 dB worse than the corresponding coherent space-time block code (STBC). In this paper, we propose a new DSTBC scheme, which provides a coding gain due to the redundancy introduced by the differential encoder. The new code can be represented by a trellis. If the Viterbi algorithm is used in decoding, the code performs 1 dB better than TJ's scheme and is only 2 dB away from the coherent STBC [2]. Furthermore, the new scheme has a recursive structure. If concatenated with an outer code, the new scheme with iterative decoding and no CSI can outperform the corresponding concatenated STBC with ideal CSI.