Researches On Cooperative Downloading Technologies In VANETs

In recent years,Vehicular Ad Hoc Networks(VANETs),which apply wireless communication technologies to transportation systems,have attracted extensive attention in global academic and industry.In VANETs,vehicular users are edge nodes which are far away from backbones.Content accessing and downloading for vehicular users is expected to heavily rely on the deployment of roadside units(RSUs)in VANETs.Although vehicular users can obtain a good content downloading service in the coverage of RSUs,user experience will get worse in highway scenarios,where RSUs are sparsely deployed at service areas or gas stations.In other words,the download process has a property of intermittent connectivity because many no-signal areas(dark areas)exist on the road.After a long-term research by scholars,proposed cooperative downloading schemes can significantly improve the efficiency and reduce costs.However,existing cooperative downloading schemes are still not perfect.In order to further develop the tremendous potential of cooperative downloading in VANETS,two main questions should be taken into consideration:(1)How to select optimal vehicles for cooperative downloading and maximize the downloading throughput in dark areas?(2)How to motivate vehicles to participate in cooperative downloading?Considering two problems above,this paper makes a deep research on the problem of vehicle selection and cooperation intention in cooperative downloading.The main contents and innovations are as follows:In order to solve the problem of vehicle selection in cooperative downloading,this paper first proposes an optimal multiple stopping rule-based cooperative downloading scheme.This scheme formulates the cooperative vehicle selection problem as an optimal multiple stopping problem and address the challenge via the derived optimal multiple stopping rule.Besides,to keep the system fairness and encourage more vehicles to participate in cooperative downloading,this paper also proposes a cooperative downloading incentive mechanism based on trading strategies.At the same time,in order to further investigate the cooperative intention problem in cooperative downloading,this paper proposes an infinitely repeated game-based incentive system for cooperative downloading.The clearing and lottery component of the system can ensure the high efficiency and fairness.In addition,an infinitely repeated game is presented to deduce the utility of all vehicles and analyze the threat from selfish behaviors.Experiments demonstrate the influence of different parameters on system requirements and verify the effectiveness of the proposed system in stimulating cooperative downloading.