Cooperative diversity system achieving full-rate and full-diversity by constellation rotation

We introduce and analyze an enhanced cooperative diversity system where the source, relay, and destination are equipped with single antenna, respectively. A time-division multiple-access (TDMA) based cooperative protocol is considered. This protocol has full data rate because the source transmits two symbols during two time slots. However, the protocol does not obtain full diversity gain, because each column of effective channel matrix has a different distribution. We propose the constellation rotation scheme to solve the problem. Also, we analyze the diversity gain of the proposed system with the maximum-likelihood (ML) receiver by deriving the pairwise error probability (PEP). The analysis proves that the system applying the constellation rotation scheme achieves a full diversity. Also, we verify the superiority of the proposed scheme from the simulations.