Multi-phase Device-to-Device relay algorithms for data dissemination in a cluster

In cellular networks, Device-to-Device (D2D) links can be utilized for data dissemination via unicast or/and multicast within a cluster. For traditional D2D relay schemes, D2D links with poor channel conditions may be the bottleneck and result in conservative resource utilization. Therefore, we suggest preferentially selecting the good quality D2D links with high achievable data rates, which induces multi-phase transmissions. Such selective transmissions require us to pre-define a data rate threshold. Obviously, a larger threshold leads to more phases, which is harmful to efficient resource utilization. Hence, there is a tradeoff in selecting the data rate threshold. In the paper, we gradually design three rules to set the threshold and accordingly propose three D2D relay schemes, which can adaptively select the optimal relays, routing and number of phases according to the D2D links quality and our pre-defined thresholds. Simulation results show that our proposed schemes, in turn, yield ascending gains in terms of resource utilization and the best of them achieves a significant resource efficiency compared to the existing single-phase schemes.