Selective sub-carrier relaying and power allocation for multi-relay-assisted cooperative OFDM systems with outdated CSI

In this paper, we investigate the relay selection, sub-carrier pairing, and power allocation problems in a two-hop, multi-relay-assisted cooperative OFDM system with amplify-and-forward (AF) relays. We study the application of selective sub-carrier relaying, where the relays collectively forward only a subset of the available sub-carriers, in a multi-relay-assisted environment. Transmit power allocation is performed such that the end-to-end system capacity is maximized under individual power constraints at each node. We evaluate the system performance when the available channel state information (CSI) is outdated and compare the performance with the all sub-carrier relaying method.