Optimal resource utilization for intra-cluster D2D retransmission and cooperative communications in VANETs

Abstract

D2D communications are treated as potential services to achieve data re-transmissions among multicast vehicle-to-vehicle communications within one cluster, which can be used to improve the performance in vehicular ad hoc networks (VANETs). In this paper, we investigate the problem of resource utilization with D2D communications based on vehicles dynamic change characteristics in one cluster to maximize the ratio of spectral efficiency to transmission power for data re-transmissions. Firstly, given the transmission resources for intra-cluster D2D communications, a continuous time Markov chain model is established to capture the dynamic change characteristics of vehicles in intra-cluster, which is related to the change in number of allocated resources. And then, based on each intra-cluster steady state of the probability model, we design an adaptive re-transmitters selection approach in the cluster to solve the maximization problem that is a combinational programming problem with fractional objective. In this approach, a sub-cluster partition algorithm is proposed to optimize resource utilization in D2D re-transmissions. Besides these, the cooperative communication scheme is combined with the proposed approach to further enhance performance by selecting relays reasonably in different sub-clusters. By simulations, we evaluate the performance of the proposed approach (with or without cooperative communication) and the D2D retransmissions approach with one fixed re-transmitter which serves as a benchmark. The results show that the proposed approach with cooperative communication achieves a significant performance enhancement about average retransmission performance.