Soft concatenation of space-time block codes and multilevel coding

Space-time block codes (STBC) are designed to achieve the maximum possible diversity benefit. However STBC are not designed to achieve an additional coding gain. Multilevel coding (MLC) has been paid more attention to for its rate change ability and the ease of the use of the capacity rule. It is shown that MLC are optimal outer codes to be concatenated with STBC in a Rayleigh fading environment. Based on the capacity rule and MLC/MSD (multi-stage decoding) system, this paper presents three concatenation themes of STBC and MLC/MSD. Punctured convolutional codes are selected as component codes according to the capacity rule. If the symbols input in the MSD decoder are soft output symbols of STBC decoder the concatenation is soft; if hard symbols, then hard. The performance of different soft and hard concatenation schemes in Rayleigh fading channels are analyzed at the same time. Then we present the best concatenation scheme for a mobile environment.