Hybrid Device-to-Device and Device-to-Vehicle Networks for Energy-Efficient Emergency Communications

Recovering postdisaster communications has been a challenging task for search and rescue. Recently, device-to-device (D2D) and device-to-vehicle (D2V) networks have drawn attention. Nonetheless, the limited D2D coverage and onboard energy pose a new need for establishing a hybrid D2D and D2V network. In this article, we jointly establish, optimize, and integrate D2D and D2V networks to support energy-efficient emergency communications. First, we establish a D2D network by optimally dividing ground devices (GDs) into separated clusters and identifying temporary data caching centers (TDCCs) from GDs in clusters. Accordingly, emergency data returned from GDs are cached in TDCCs. Second, given the distribution of TDCCs, unmanned aerial vehicles (UAVs) are dispatched to fetch data from TDCCs. Therefore, we establish a UAV-assisted D2V network through path planning and network configuration optimization. Specifically, optimal path planning is implemented using cascaded waypoint and motion planning, and optimal network configurations are determined by multiobjective optimization. Consequently, the best tradeoff between emergency response time and energy consumption is achieved, subject to a given set of constraints on signal-to-interference-plus-noise ratios, the number of UAVs, transmit power, and energy. Simulation results show that our proposed approach outperforms benchmark schemes in terms of energy efficiency, contributing to large-scale postdisaster emergency response.