A Novel Method for Enhanced Quasi-orthogonal Space Time Block Codes in Wireless Communication

A complex orthogonal design that provides full diversity and full transmission rate for a space–time block code is not possible for more than two antennas. We design rate one codes which are quasi-orthogonal and provide partial diversity. The decoder of the proposed codes works with pairs of transmitted symbols instead of single symbols. A number of QuasiOrthogonal Space-Time Block Codes (QOSTBC) have been proposed for using in multiple transmit antennas systems. In this paper, based on circulant matrix, we propose a novel method of extending any QOSTBC constructed for 4 transmit antennas to a closed-loop scheme. We show that with the aid of multiplying the entries of QOSTBC code words by the appropriate phase factors which depend on the channel information, the proposed scheme can improve its transmit diversity with one bit feedback. The performances of the proposed scenario extended from Jafarkhani’s QOSTBC as well as its optimal constellation rotated scheme are analyzed. The simulation results suggest that there is a significant Eb/No advantage in the proposed scheme which is able to be designed easily.