Improved Differential Unitary Space-Time Signal Design for Two to Six Transmit Antennas

This paper addresses optimization of differential unitary space-time modulation (DUSTM) for more than two transmit antennas. We demonstrate that the union bound on the block error probability of DUSTM codes can be considerably simplified for various cases of non-group DUSTM constellations. We also demonstrate that rotation matrices applied to diagonal DUSTM codes can be considered as special cases of Alamouti style block codes. Utilizing these two results, and some simplified design criteria, various DUSTM codes are derived for more than two transmit antennas which give superior performance to previously proposed codes over a wide range of SNR.