Maximum-SNR-based adaptive protocol with subcarrier selection for OFDM cooperative communications

In this paper, we propose a maximum signal-to-noise-ratio (SNR)-based adaptive protocol for two-user OFDM cooperative communications with fairness. Specifically, two users in this system mutually act as a source or relay in each time, where the transmission rate and the total transmit power remain constant. The proposed protocol operates by adaptively selecting a half of maximum-SNR subcarriers in each OFDM frame to help transmitting the partner information, and the remaining subcarriers are used by the source node. In addition, the proposed protocol yields a maximum average total SNR to a selected channel. Simulation results show that the proposed adaptive protocol provides a lower symbol error rate (SER) compared with existing fixed-subcarrier-selection protocols.