Labeling optimization of differential unitary space-time modulation

For differential unitary space-time modulation (DUSTM), the bit-error performance is affected by the type of labeling. In this paper, we used the Binary Switching Algorithm (BSA) to optimize the labeling of cyclic constructed DUSTM constellation. Instead of time-consuming simulation, we constructed an easily-calculated cost function to estimate the impact of different types of labeling on the bit-error performance for DUSTM. And we proposed a simple and effective rule to construct the initial labeling for the application of BSA to DUSTM. Simulation results show that for DUSTM, the optimized labeling outperforms the regular labeling significantly for low SNR, and the proposed method of optimizing the initial labeling improves the performance of the traditional BSA.