Joint Relay Selection and Flight Path Optimization for UAV-Assisted Vehicular Delay Tolerant Networks

This paper introduces the application of the unmanned aerial vehicles (UAV) into vehicular delay tolerant networks (VDTNs). In UAV-assisted VDTNs, vehicles adopt the storage-carry-forward mechanism to transmit data, and UAVs can be utilized as mobile relays. For the considered network, we investigate the data transmission problem by jointly considering the relay selection and flight path optimization. We formulate a multi-objective optimization problem, which composes of two parts: a) the transmission delay; b) the flight path cost. Due to the intractability of the formulated NP-hard problem, we design a heuristic algorithm to solve it. Specifically, according to the encounter probability, we present a relay selection scheme, which can limit the maximum number of hops and copies. Then, by considering the flight path cost, we present a flight path optimization scheme based on the improved particle swarm optimization algorithm. Finally, the numerical results show that compared with the current works, our proposed data transmission strategy significantly reduces the transmission delay and the flight path cost.