Higher order differential matrix modulation

We propose an extension of differential unitary space-time matrix modulation by an additional differential amplitude modulation for bandwidth-efficient transmission with noncoherent detection in a wireless system with multiple transmit antennas. The input bits are subdivided into two groups. The first group chooses a unitary matrix, the second group determines the amplitude of the transmit matrix. Compared to differential unitary space-time modulation, the proposed scheme has lower detection complexity and provides superior performance for bandwidth-efficient transmission, particularly in time-varying channels.