Distributed Space-Time Code Designs Via Cayley Transform

Distributed space-time coding achieves full diversity in wireless relay networks without channel information at the relays. This paper is on the design of specific distributed space-time codes. By Cayley transform, the design of unitary matrices is transformed to that of Hermitian matrices. Gradient-descent method is used in the optimization to find codes that are "close" to orthogonal designs, which is known to be optimal in both coding gain and diversity. The proposed code design method can be used for networks with any relays and transmission rate. The optimized codes are adaptive to the information symbol constellation. Simulation shows that the designed codes achieve full diversity, and outperform the random code and other existing distributed space-time codes.