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.

In cognitive radio networks (CRNs), hybrid overlay and underlay sharing transmission mode is an effective technique to improve the efficiency of radio spectrum. Unlike existing works in literatures where only one secondary user (SU) uses both overlay and underlay mode, the different transmission modes should dynamically be allocated to different SUs according to their different quality of services (QoS) to achieve the maximal efficiency of radio spectrum. However, dynamic sharing mode allocation for heterogeneous services is still a great challenge in CNRs. In this paper, we propose a new resource allocation method based on dynamic allocation hybrid sharing transmission mode of overlay and underlay (DyHySOU) to obtain extra spectrum resource for SUs without interfering with the primary users. We formulate the Dy-HySOU resource allocation problem as a mixed-integer programming to optimize the total system throughput with simultaneous heterogeneous QoS guarantee. To decrease the algorithm complexity, we divide the problem into two sub-problems: subchannel allocation and power allocation. Cutset is used to achieve the optimal subchannel allocation, and the optimal power allocation is obtained by Lagrangian dual function decomposition and subgradient algorithm. Simulation results show that the proposed algorithm further improves spectrum utilization with simultaneous fairness guarantee, and the achieved Dy-HySOU diversity gain is satisfying.

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