Cooperative multicast with short-range data sharing in OFDM-based CRNs

In this paper, cooperative multicast with the help of short-range data sharing is studied in the cognitive radio networks (CRNs). The original multicast data is split into many segments, and the transmission of each segment is divided into two stages. In the first stage, cognitive base station transmits each segment to the corresponding cooperative user, and in the second stage, the cooperative user decodes the received data and broadcasts it to other multicast users. Based on this transmission model, cooperative multicast is formulated as an optimization problem with the aim of maximizing the total transmission rate. Afterwards, we first propose a cooperative user selection strategy, which is meaningful when the multicast size is large, and then implement the resource allocation with dual translation and subgradient updating. The simulation results show that the proposed cooperative multicast scheme can achieve much higher spectrum efficiency than both conventional multicast scheme and multiple description coding multicast scheme.