Researches On VANET Middleware For Service Discovery Based On QoS

VANET(Vehicular Ad-hoc Network)is composed of vehicles and Roadside Unit.Through Wireless Local Area Networks VANET realizes the communication of vehicle-to-vehicle and vehicle-to-road,which provide an implementation platform for traffic system management,data communication and vehicle safety guarantee.Due to different vehicle equipments and application systems have heterogeneity,middleware is designed between application software and embedded devices to make vehicles in VANET can exchange information more smoothly,providing unified and common interfaces to manage and invoke automotive basic services.With the increase of vehicles in urban VANET,the type and number of services is sharply increasing,therefore,how to provide services with hige quality while decoupling applications from devices has become the main problems need to be solved in the VANET middleware.This paper proposes a QoS(Quality of Service)based middleware for VANET service discovery based on OSGi(Open Services Gateway initiative),called VsdOSGi.This middleware platform has the advantage of OSGi service orented architecture at the same time,various kinds of basic functions provided by equipped devices in vehicles are virtually abstracted as services in network,which provides a unified platform for data exchange among vehicles and decouples software applications from underlying devices.In this middleware,we design two service selection mechanisms according to different requirement of vehicls to improve the QoS.There are several types of services in VANET,and vehicles have different requirments of services in different type,so this paper proposes a QoS based service discovery algorithm.Fistly,we and design different quality standards for intelligent tranffic services and comfort application services,and then calculate all registed services in the same type,as a result,the request vehicle can select the best service which has the highest quality.Through demand analysis for VANET applications,there exist large services that occupy a large network space,and this kind of service will lead to concentration of resource consumption and low service discovery success rate.This paper introduces the concept of service provide capacity and proposes a cooperative service discovery algorithm to solve this problem.When a vehicle requests a large service and there are not only one vehicle has registered this service,this algorithm will used to calculate the service provide capacity of each providers and distribute this large service to these prociders,then multi vehicles will provide this large service at the same time instand of one vehicle as the only service provider.Simulation results show that this algorithm can effectively improve the service discovery success rate and reduce service binding time.