A simple relay selection algorithm in multi user OFDM based cooperative CR networks

This paper presents a simple relay selection algorithm in multiuser orthogonal frequency-division multiplexing (MU-OFDM) cooperative Cognitive Radio (CR) networks to enhance normalized sum capacity of secondary users (SUs). After simplifying three node relay network to its equivalent two node network with equivalent gain on each subcarrier, a simple method for relay selection is used which considers interference on primary users. In addition simple relay selection algorithm proposed. This simple algorithm selects the relay-node for each source-node by a fixed power allocation on all subcarriers (SCs) in independent phase before joint subcarrier and power allocation algorithm are performed. Simulation results demonstrate that this relay selection algorithm can significantly enhance normalized sum capacity of SUs compared to random relay selection algorithm.