Extended Differential Unitary Space-Time Modulation: A Non-Coherent Scheme with Error Penalty Less Than 3DB

In this paper we propose an extended differential unitary space-time modulation (xDUSTM) scheme that can offer improved error performance over the differential unitary space-time modulation (DUSTM) scheme. DUSTM is well suited to rapidly time-varying unknown channels. It has a simple structure, but incurs an error performance penalty of about 3 dB compared to its coherent counterpart. The xDUSTM scheme considers moderately fast time-varying channels, and is designated to exploit such a characteristic for performance improvement. In xDUSTM, a problem that needs to be addressed is the complexity of its non-coherent maximum-likelihood (ML) receiver. We show that by choosing the orthogonal space-time block code (OSTBC) designs, the ML problem can be reduced to a Boolean quadratic program for which highly effective algorithms are available. Simulation results illustrate that the error performance penalty in xDUSTM can be reduced to 1 dB