A Simple Construction of Full-Rate Quasi-Orthogonal Space-Time Block Codes for 4 and 6 Transmit Antennas

In this paper, we present new constructions of quasi-orthogonal space-time block codes for 4 and 6 transmit antennas. The proposed codes possess the following properties: full-rate, full transmit diversity, even power distribution and low decoding complexity, which make these two codes very practical spacetime coding schemes. For the case of 4 transmit antennas, the code can be decoded pair-by-pair, with each pair containing only two real symbols. It can be proved that for QAM signals, our proposed code has the same coding gain as the existing optimal quasi-orthogonal space-time block codes with minimum decoding complexity. For the case of 6 transmit antennas, the code can be decoded triplet-by-triplet, with each triplet containing three real symbols. We also present simple concatenation schemes of our proposed space-time block (STB) codes and multi-dimensional trellis coded modulation (MTCM) codes. Simulation results show that the performance of our concatenation scheme is comparable to the previously proposed STB-MTCM concatenation scheme while having a much lower decoding complexity.