Multiple D2D Multicasts in Underlay Cellular Networks
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Multicasting for disseminating popular data in cellular networks is a natural solution for improving the energy and spectral efficiencies. However, the achievable throughput in a multicast enabled network may be dictated by the user with the worst channel conditions. To improve the achievable throughput of such networks, underlay device-to-device (D2D) multicast communication offers a practical solution. However, despite having significant potential for providing higher throughput and lower delay, implementing underlay D2D multicast communication poses several challenges. For example, mutual interference among cellular users (CUs) and D2D multicast groups (MGs), and overhead signaling to provide channel state information may limit potential gains. In this work, we study a scenario where multiple D2D multicast groups may share a CU's uplink channel. We formulate an optimization problem to maximize the achievable system throughput while fulfilling quality of service (QoS) requirements of every CU and D2D MGs, subject to the corresponding maximum transmit power constraints. The formulated optimization problem is an instance of mixed integer non-linear programming (MINLP) problem, which is computationally intractable, in general. Therefore, to find a feasible solution, we propose a pragmatic two-step process of channel allocation and power allocation. In the first-step, we propose a channel allocation algorithm, which determines the subset of MGs that may share a channel subject to criteria based on two different parameters: interference and outage probabilities. Then, we propose an algorithm to allocate power to these MGs subsets that maximizes the system throughput, while satisfying transmit power constraint. Numerical results show the efficacy of proposed model in terms of higher achievable sum throughput and better spectrum efficiency with respect to various existing schemes.
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