Research On Multi-channel Scheduling For Vehicular Ad Hoc Networks

Vehicle transportation is, and will remain, an inseparable part of people’s life in spite of increasing oil prices, environmental concerns and huge property losses attribute to traffic accidents. One of the solutions to ease these problems is the research and deployment of Intelligent Transportation System(ITS) and Vehicular Ad-hoc Network(VANET). ITS provides ways to manage the vehicle traffic efficiently, which can effectively reduce the traffic and low-speed moving time, thereby reducing unnecessary fuel consumption. What’s more, information related security provided by ITS can help the drivers avoid life and property losses in time. VANET, as the most important part of ITS, has several new features compared with the traditional networks. Driver behavior, constraints on mobility, and high speeds create unique characteristics in VANET. WAVE standard protocol is featured by multi-channel in split phase form, which is able to meet the low latency and some other performance requirements in vehicle environment, and it already become one of the mainstream protocols of VANET.Through analyzing WAVE, we found the standard has no certain mechanisms of the Channel Assignment(CA) and Channel Access Assignment(CAA) because of compatibility between multi-radio and single-radio. The procedure of specifying a channel for the service request in case that the requesting entity didn’t preset one is refered as CA. CAA is triggered when there is a need to assigning local radio channel resources in support of service requests. This includes assigning radio resources to particular service channel to provide data communication opportunities for the requesting entities. In consideration of hardware cost, single-radio form was chosen. The research on the related literature of multi-channel mechanism concluded that the single-radio protocols rely on channel selection mechanisms to find the best channel for the next data transmission by considering only local conditions. With the constraints of single-radio and the WAVE standard, a concept named balancing channel resources was put forward which is measured by the supply and demand factor of channel and channel fairness index. Then the concept was applied to CA and CAA mechanism. Channel Assignment mechanism takes supply and demand factor as the leading role of selection, while the latter takes service priority.In order to verify the correctness of proposed mechanisms, the Veins simulation model was improved using OMNe T++. Goal of this improvement was the devolepement of general models which were sepcified in WAVE standard: design of Application’s basic unit and application management model, the IEEE 1609.3 part; IEEE 1609.4 part. Finally, CA and CAA were implemented with the improved model. Experimental results show the proposed mechanisms can balance channel resources well, while transmission delay and valid data traffic both are improved effectively.