Set Ranking-Based Precaching Protocol in Vehicular Ad hoc Networks

Intermittently connected vehicular networks (ICVNs) consist of stationary roadside units (RSUs) deployed along roads and vehicles moved on them. In ICVNs, long inter-RSU distances and large-size vehicular contents lead to long downloading delays to vehicles and high traffic overheads on backhaul links. By using the mobility information of vehicles, many studies have been proposed to solve this issue by precaching contents to multiple relaying vehicles in the outage zone between neighbor RSUs. We proposes a Set Ranking-based Precaching protocol called SRP that efficiently selects multiple precaching vehicles for content precaching in outage zones. SRP chooses sets of vehicles for achieving successful precaching by a mathematical model. Then, SRP determines rankings of sets based on the number of vehicles and their available precaching amounts in each set and selects vehicles in the set with the top ranking as the optimal precaching vehicle group. Simulation results verify that SRP achieves better performances than a representative precaching protocol.