A decentralized relay strategy for asynchoronous cooperative communications

In this paper, we propose an asynchronous cooperative scheme with a decentralized relay strategy. The single carrier block transmission (SCBT) technique is used to mitigate the effect of relay synchronization error. By utilizing an orthogonal space-time code with cyclic delay transmission, cooperative diversity can be achieved. Specifically, each relay node transmits a combination of all rows of the deployed space-time code and each row is randomly cyclic-shifted and scaled. The scale factor and the cyclic shift of each row at each relay node are generated locally. The random cyclic shift operation renders a good scalability to the number of relay nodes (or the network node density) while the random scale operation improves the performance greatly. Moreover, the proposed scheme is a decentralized scheme in the sense that it is independent of the number of relay nodes and does not need any side information exchange among cooperative nodes. The proposed scheme can inherently support both the amplify-and-forward (AF) and decode-and-forward (DF) cooperative mechanisms.