Optimizing the performance of OFDM-based cooperative networks by relay selection, power allocation and relay localization

We investigate the outage probability for amplify-and-forward (AF) and decode-and-forward (DF) relaying in OFDM-based cooperative networks. To minimize the outage probability, the relay which has the maximum received SNR is selected as the cooperative relay. Based on the relay selection, the problems of optimal power allocation and placing relays in the optimal position are discussed. And the expressions of optimal power allocation and optimal position are finally achieved. The analysis and simulation results show that through the proposed relay selection scheme, M orders of diversity is achieved, where M is the number of potential relays. It also shows that optimal power allocation and optimal position to placing relays achieve much better performance.