Bandwidth-Efficient Differential Space–Time Modulation

We propose an extension of differential unitary space–time 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, whereas the second group determines the amplitude of the transmit matrix. We derive a noncoherent soft-output detector that does not require knowledge of channel state or statistical channel properties. The modulation parameters are optimized based on an analytical bit error rate (BER) analysis and mutual information. Furthermore, we propose a pragmatic scheme for outer forward error control coding and interleaving. 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.