Device-to-device (D2D) communication is an excellent technology for improving the system capacity through sharing the spectrum resources of cellular networks. Multicast service is considered an effective transmission mode for the future mobile social contact services. Therefore, multicast with D2D technology can improve the resource efficiency. In this paper, a resource allocation scheme based on cognitive radio (CR) for D2D underlay multicast communication (CR-DUM) is proposed to improve system performance. In each D2D multicast group of the cognitive cellular system, the secondary users reuse the different orthogonal cellular resources to accomplish a multicast transmission. To maximise the total system capacity under the condition of interference and noise impairment, the authors formulate an optimal transmitting power allocation for the cellular and D2D multicast communications jointly. The proposed scheme includes two steps. First, two channel allocation rules are proposed to reduce the interference from cellular networks to receivers in D2D multicast group. Second, the optimal power allocation is formulated as a non-linear programming problem and the optimal solution is achieved by searching from a finite set for the allocated channel. The simulation results show that the proposed method can ensure the quality of service (QoS) and improve the system capacity.

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