Energy Efficient and Subcarrier Allocation for OFDMA based Cooperative Relay Networks

Energy efficient wireless communication is important for battery constrained mobile devices. For mobile devices in a cellular system, uplink power consumption dominates the wireless power budget because of RF power requirements for reliable transmission over long distances. In this work we developed a low-complexity subcarrier-power allocation and relay selection scheme has been developed for maximizing energy efficiency per user in an Orthogonal Frequency Division Multiple Access (OFDMA) cooperative relay network, using full channel state information (CSI), which is available at both relay and BS nodes. The previous works in this area focused on optimizing energy efficiency by maximizing the instantaneous bits-per-Joule metric through Equal-Power Allocation (EPA) schemes resulted in significant energy savings for uplink cellular OFDMA transmissions. It also shows that the proposed scheme has significant improvement on the energy efficiency performance as compared with EPA schemes which allocate equal transmit power to the assigned subcarriers. The simulation results show that the proposed scheme can achieve better performance with less computational complexity as compared to the exhaustive search scheme.