No abstract

Access to information services while on the move is becoming increasingly prevalent within transport systems. Whereas Internet access is now common place in trains, it still remains a challenge for vehicles, particularly when travelling through high speed motorways. Motorway vehicles equipped with wireless communication nodes form an ad hoc network have been examined by which data can be exchanged among them without the need for a pre-installed infrastructure. The main challenge with such an infrastructure-less network is developing communications and protocols that can deliver robust and reliable ad hoc communications between vehicles, when the relative speed between vehicles that can be extremely high under opposite traffic conditions. To address this opposite direction effect, a solution has been presened by minimising the effect of opposite traffic on routing packets. Firstly, a router direction index is introduced to enhance the performance of ad hoc on demand distance vector protocol in updating its routing table and secondly, a new queue priority mechanism is proposed which is based on crosslayer collaboration. Simulations were performed for an ad hoc network consisting of 200 vehicles driving with speeds between 90 and 120 km/h on a two-way motorway for different traffic loads sent through a Gateway adjacent to the motorway. The results obtained demonstrate a performance increase in the average data goodput and less routing overhead for the proposed solution.

Mobile Ad Hoc Networks in road transport applications exhibit special characteristics, mainly due to their dynamic chain behaviour. In this paper, we introduce a node decision algorithm in both the routing and packet priority mechanism, based on the node's driving direction with respect to the next hope towards packet destination. In the routing algorithm, a Router Direction Index (RDI) parameter is introduced to enhance the performance of AODV in updating its routing table, as well as to assist the destination nodes to choose route requests from different paths in inter-vehicular ad hoc network scenarios. A packet transmission priority is set according to the driving direction of both transmitter and receiver of the packet. Simulation results of the proposed algorithm for 200 vehicles travelling at speeds between 60 ~ 120 km/h on a 2-directional highway demonstrate a performance increase in the packet delivery ratio, and decrease in the packet end to end delay and routing overhead for the proposed algorithm.

No abstract