Proper scheduling of downlink (RSU-to-vehicle) communication reduces power consumption of Road Side Unit (RSU) in green vehicular networks. In highway scenarios, due to high deployment cost of RSUs, it is necessary to leave some areas uncovered in which vehicles cannot get direct access to the RSUs. Therefore, a vehicle with large data requirement may enter into an uncovered area without completely downloading from the RSU and such a vehicle is referred as target vehicle. In this paper, we provide an energy efficient offline downlink scheduling for store-carry-forward vehicles (relays) to satisfy the residual data requirement of the target vehicle moving in the uncovered area. An integer linear programming problem is formulated for relay scheduling and evaluated its NP-hardness by reduction from well-known Seminar Assignment Problem. A polynomial time solution is presented by modeling the problem as a Minimum Cost Flow (MCF) graph. Furthermore, we propose a cluster-based approach to identify vehicles in energy favorable locations and multi-hop distance to relay vehicles. These vehicles forward data to relay vehicles using off-channel vehicle-to-vehicle (V2V) forwarding. Combining the V2V forwarding with relay scheduling further reduces the power consumption of the RSU. Extensive simulations show that the proposed approach augmented with MCF reduces the power consumption of RSU when compared to offline schedulers Nearest Fastest Set (NFS), MCF and two more basic algorithms First Come First Serve (FCFS) and Fastest First (FF). In addition, the proposed approach improves data delivery to the target vehicle in the uncovered area.

对下行链路（RSU到车辆）通信的正确调度可以减少绿色车辆网络中路边单元（RSU）的功耗。在高速公路场景中，由于RSU的部署成本高昂，因此有必要将一些区域留在未被覆盖的区域，使车辆无法直接进入RSU。因此，具有大数据需求的车辆可能会进入未覆盖区域而没有从RSU完全下载，因此这种车辆称为目标车辆。在本文中，我们为储运车辆（中继器）提供了一种高效节能的离线下行链路调度，以满足目标车辆在未覆盖区域内行驶的剩余数据需求。制定了整数线性规划问题以用于继电器调度，并通过减少著名的研讨会分配问题来评估其NP硬度。通过将问题建模为最小成本流（MCF）图，可以提供多项式时间解决方案。此外，我们提出了一种基于聚类的方法来识别处于能量有利位置和中继车的多跳距离的车辆。这些车辆使用通道外车辆到车辆（V2V）转发将数据转发到中继车辆。V2V转发与中继调度相结合，进一步降低了RSU的功耗。大量的仿真表明，与离线调度程序“最近的最快集”（NFS），MCF以及另外两个基本算法“先到先得”（FCFS）和“最快的先来”（FF）相比，以MCF增强的拟议方法可以降低RSU的功耗。另外，所提出的方法改善了向未覆盖区域中的目标车辆的数据传递。