Novel full-rate noncoherent alamouti encoding that allows polynomial-complexity optimal decoding

We consider Alamouti encoding that draws symbols from M-ary phase-shift keying (M-PSK) and develop a new differential modulation scheme that attains full rate for any constellation order. In contrast to past work, the proposed scheme guarantees that the encoded matrix maintains the characteristics of the initial codebook and, at the same time, attains full rate so that all possible sequences of space-time matrices become valid. The latter property is exploited to develop a polynomial-complexity maximum-likelihood noncoherent sequence decoder whose order is solely determined by the number of receive antennas. We show that the proposed scheme is superior to contemporary alternatives in terms of encoding rate, decoding complexity, and performance.