Resource allocation for the cluster-based cooperative multicast in OFDM-based cognitive radio systems

This paper investigates the resource allocation problem for the cluster-based cooperative multicast in orthogonal frequency division multiplexing (OFDM)-based cognitive radio (CR) systems. Aiming at maximizing the system sum rate, an efficient clustering scheme is proposed. It begins with the clustering phase where secondary users (SUs) with good channel conditions are selected as cluster heads, while others decide to which cluster they belong. When the clusters are organized, it turns to a two-stage data transmission phase: in stage 1, the secondary base station (BS) transmits data to the cluster heads; in stage 2, the cluster heads forward the received data to their cluster members. Based on this scheme, a joint subcarrier and power allocation algorithm is proposed. Simulation results show that the proposed scheme significantly outperforms the conventional multicast (CM) as well as the multiple description coding multicast (MDCM) in terms of the system sum rate.