On optimal routing and power allocation for D2D communications

In this paper, we propose algorithms for finding the optimum multi-hop routes and corresponding transmit powers that maximize the throughput between a pair of device-to-device (D2D) nodes, under a constraint on the maximum interference caused to the cellular network. Our solution involves two steps. In the first step, we determine the set of feasible D2D links, based on the interference constraint. In the second step, we use the celebrated Dijkstra´s algorithm to find throughput-optimal routes between a given pair of D2D nodes under two scenarios: a) The Fixed Rate Scheme and b) The Fixed Power Scheme. The dependency of the net D2D throughput on the system parameters such as target SINR is analyzed for both the schemes, and a procedure to find the optimum parameter setting is proposed. The performance of the algorithms is illustrated using computer simulations. The results show that, depending on the network topology, a significantly higher throughput can be achieved by using multi-hop paths compared to using single-hop, direct D2D communication.