Quasi-orthogonal Space Time Block Code for Decode-and-Forward Relay Networks

A kind of quasi-orthogonal space time block code for decode-and-forward relay networks is analyzed in this paper. At the source, 4 single-antenna users transmit the quasi-orthogonal space time block code matrix. At the relay node, maximum-likelihood decoding algorithm is adopted and the decoded symbols are then encoded into quasi-orthogonal code which is transmitted through transmit antenna. At the destination, pair-wise decoding algorithm is utilized. Finally we compare the performance of the quasi-orthogonal space time block code in relay networks with that of the quasi-orthogonal space time block code in traditional communication system. Simulation results show that at the given BER of 10-3, the new code can provide a gain of 4 dB and 1.8 dB comparing with that for the traditional quasi-orthogonal code. And at the given BER of 10-5, the new code can provide a gain of 4.5 dB and 3.5 dB comparing with that for the old quasi-orthogonal code.