Double-Differential Decode-and-Forward Cooperative Communications over Nakagami-m Channels with Carrier Offsets

In this paper, we propose double-differential modulation for cooperative communications to overcome the problem of carrier offsets in Nakagami-m channels. The performance analysis of decode-and-forward relaying with double-differential modulation is performed. We derive an upper bound of the symbol error rate and also propose optimized and numerical power allocation to improve the performance of the system. The proposed scheme outperforms the same rate direct transmission scheme for moderate to high SNR values and the previously proposed single differential scheme based on amplify-and-forward protocol.