Resource allocation for multiple description coding multicast in OFDM-based cognitive radio systems with non-full buffer traffic

This paper investigates the resource allocation problem for multiple description coding (MDC) multicast in OFDM-based cognitive radio (CR) systems, where secondary users (SUs) share the primary spectrum under the interference constraints of primary users (PUs). The previous multicast model is usually based on the full buffer traffic in which there are sufficient data for multicast groups (MGs) to receive. However, it does not consider the nature of limited traffic in practical systems. Taking this case into consideration, saturation rate (SR) is introduced to describe the characteristic of non-full buffer traffic. Aiming at maximizing the weighted sum rate (WSR), a modified resource allocation algorithm based on the Lagrangian dual decomposition is proposed. Simulation results show that the proposed scheme significantly outperforms the conventional multicast. Furthermore, our scheme is meaningful in non-full buffer traffic scenarios, because it can avoid the resource redundancy for users with good channel conditions and the resource starvation for users with bad channel conditions, and hence will reduce the resource wasting.