Differential Transceiver Design for Quasi-Orthogonal Space-Time Block Codes

In this paper, we report a general and simple differential modulation scheme that can be applied to both partial-diversity quasi-orthogonal space-time block codes and full-diversity quasi-orthogonal space-time block codes for four transmit antennas. The differential encoding and decoding can be simplified to differential Alamouti codes by grouping the signals in the transmitted matrix and decoupling the detection of data symbols, respectively. For the codes with partial transmit diversity, the new scheme can achieve constant amplitude of transmitted signals, and avoid signal constellation expansion, and it has a linear signal detector with very low complexity. Simulation results show that these partial-diversity codes can provide very useful results at low SNR for current communication systems. For the codes with full transmit diversity achieved by constellation rotation, our scheme has performance equal to the best full-rate quasi-orthogonal schemes previously described in the literature with a simpler detector.