A novel overlay token ring protocol for inter-vehicle communication

Reliable and fast message dissemination for safety application and quality-of-service (QoS) guarantee for data service are considered to be the most demanding requirements in vehicle ad-hoc networks. Current medium access control (MAC) protocols are insufficient to meet both requirements, while the standardization process is still ongoing. In this paper, an overlay token ring protocol (OTRP) is proposed for inter-vehicle communication (IVC). In the OTRP, the vehicular network is considered as overlapped virtual rings, each of which has a token passed in the ring as the right for transmission. The ring structure is dynamically adjusted according to the movements of vehicles. A salient feature of the OTRP is that two operation modes, namely the normal and emergency modes, are devised, whereby timely emergency message dissemination is guaranteed and desired quality-of-service (QoS) for data service can be provided. Theoretical analysis and simulations under saturated traffic condition are conducted. The results show that the OTRP can meet the stringent requirements of vehicle communications with fast and reliable emergency message broadcasting.