The Research On Routing Protocols In Vehicluar Ad Hoc Networks

Vehicular Ad Hoc Networks (VANETs) can be viewed as a special form of Mobile Ad Hoc Networks (MANETs). The main goal is to build a network platform for communications between vehicles, thus helps to improve the transport efficiency, provide reliability, safety and multiple facilities to the drivers and comfort to the travelers. Compared with traditional MANETs, there are some important differences between them as follows:highly dynamic topology, frequently disconnected network, sufficient energy and storage, various communications environments, hard delay constraints, and so on. These characteristics, however, brings some great challenges in the routes designing in VANETs.In this paper, through in-depth studing and analysing of the routing protocols in Vehicular Ad Hoc Networks, we sum up its strenths and weaknesses. According to characteristics of Vehicular Ad Hoc Networks, we present a unicast routing protocol based on mobility prediction and a geocast routing protocol based on grid.The contributions are as follows:This paper presents a unicast routing protocol based on mobility prediction (MPR). Some routing ptotocols have recently been proposed,but they only take the node mobility into account to reduce the routing overhead, without taking into account the network communication delay and load balancing, which could cause various congestion and serious delay. According to this situation, we present an improved routing protocol based on mobility prediction. The main principle behind the algorithm is that the local routing decision is made according to the selection probability which results in swarm intelligence. The selection probabilities are calculated considering each participating vehicle's parameters such as speed, direction, position, and transmission delay in addition. The simulation results indicate that the proposed routing algorithm is suitable for rapid topology changes in VANETs.Based on the grid,this paper presents a geocast routing protocol.The main concern of the current geocast routing protocols is how to improve the efficient that the data packets are transmitted from the source node to the geocast region, but a simple flooding is taken when the multicast data packets are passed to the geocast region, which leads to great data transmitting redundancy. In view of this situation,we present a new routing mechanism to reduce the data transmitting redundancy. The geocast region is divided into grid.When one car node in the geocast receive a data packet, it broadcast the packet only if its communication coverage area can cover a new grid. Compared with the simple flooding, the proposed solution can effectively reduce the data transmitting redundancy in the geocast region.