Optimized Differential Space Time Block Code without Constellation Expansion

Using differential transmission method, the space-time block codes (STBC) can be applied in a complicated communication environment without channel state information (CSI). However, since the differential calculation includes multiplications, additions and conjugations, differential space-time block codes (DSTBC) also cause constellation expansion and result in nonlinearity problems in a wireless transmitter. In this paper, we proposed a new double mapping method for the DSTBC. In our proposed scheme, the attribute of pre-transmitted data bits is analyzed, and one of two mappings is chosen to generate current transmitted signal block. The proposed scheme also takes the advantage of differential encoding, and then CSI is not needed at the transmit antennas or at the receive antennas. Furthermore, the proposed DSTBC scheme can achieve full code rate without constellation expansion. Simulation results show that the performance of our proposed DSTBC scheme is close to that of traditional DSTBC scheme at a high SNR environment. Among all of the exited codes without constellation expansion, our proposed DSTBC has the minimum mapping table size and the best performance.