A Cooperative RSU Caching Policy for Vehicular Content Delivery Networks in Two-Way Road with a T-junction

In this paper, a cooperative roadside unit (RSU) caching policy is proposed for vehicular content delivery networks (VCDNs) in two-way road with a T-junction to reduce the average download delay of contents. In our system model, due to the constraint of base station (BS) transmission capacity, vehicles can achieve better download delay performance if the requested contents are stored in the cache-enabled RSUs. According to the traffic situations, vehicles are classified into four types. With this framework, the closed-from result of the average download delay is derived based on the proposed cooperative RSU caching policy, the arrival rates of vehicles belonging to different types, and the popularity distributions of contents. The problem of minimizing the average download delay with the proposed cooperative caching policy is formulated subject to the cache capacity constraint of RSUs. Since the optimization problem falls into an NP-hard problem, we adopt a fast simulated anneal (FSA) algorithm for content allocation. Simulation results show that the proposed FSA algorithm based cooperative RSU caching policy is more efficient for the average download delay reduction compared with the conventional popularity based caching policy.