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

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 propose a sub optimal but more feasible approach to solve the power allocation problem with relay selection and sub-carrier pairing. The proposed method is based on selective sub-carrier relaying concept where the relays forward only a selected set of sub-carriers of the received OFDM symbol. Transmit power allocation is performed such that the end-to-end system capacity is maximized under individual power constraints at each node. The proposed technique outperforms the all sub-carrier relaying scheme when the relays are distributed between the source and the destination.