The Research On Unicast Routing Protocols For Urban Vehicular Ad Hoc Networks

Vehicular ad hoc network plays a very important role in improving traffic efficiency and enhancing traffic safety, which greatly supports the intelligent traffic system, so it has important academic value and broad application fields. Efficient routing is the basis of network interconnect, and it is the key element of realizing traffic safety and sharing resource for vehicular ad hoc network. In urban vehicular ad hoc networks, unicast routing provides the most widely and most basic needs, so it has become our research emphasis. The achievement of each protocol must be based on a specific scenario and model, but the scene and model of many current protocols considered is too idealistic. It is not applicable when in some special scenarios (such as a 3D scenario) or the analysis of specific models (such as the street model with traffic light consideration). Therefore, the author analyzes the street model with traffic light consideration and explores the research on special three-dimensional (3D) scenario.According to different urban scenario and street properties, the author proposes two vehicular ad hoc unicast routing protocols for urban scenarios:(1) The author stud-ies the street model with traffic light consideration and analyzes the effects of traffic light on routing performance, and describes the reason of vehicle clustered phenomenon happened first. When to select a next street of the route, the author considers both the global static properties and the local dynamic properties, divides a street into three ar-eas based on the vehicle movement and street properties, and analyzes the connectivity of each region respectively, the author notes that the street connectivity is determined by the connectivity of L2 (the middle part of the street). When to choose a next hop relay node in the street, we balance the geographic forward and link quality. Finally, the author proposes a traffic-light-aware routing protocol based on street connectivity for urban vehicular ad hoc networks (TLRC). (2) Due to the ramp, viaduct and other 3D constructions have a great interference on wireless signal transmission, which acceler-ates the degree of the wireless signal attenuation, traditional wireless signal attenuation model for plane protocol cannot be applicable. When in the 3D street scenario, the vehi-cle coordinate tends into 3D, the relative movement direction between vehicles becomes diversification, and the analysis of vehicle movement model becomes more complex. Therefore, it requires to take a new wireless signal attenuation model and analysis ap-proach for vehicle movement. The author uses the inter-vehicle relative direction and street construction as a global guideline for data transmission. When to choose a next hop relay node, the author takes opportunistic strategy that the routing metric consid-ers the link quality and geographic forward. Through the global guidelines and local optimization to improve routing performance. Finally, we propose a vehicular ad hoc network opportunistic routing protocol for 3D scenario (VOTD).Simulation results show that, routing performance of TLRC and VOTD meet our expectations, having good performance in packet delivery ratio and end-to-end delay. Compared with other unicast routing protocols, TLRC and VOTD can better adapt to the complex urban environment. Moreover, TLRC and VOTD will have effects on further studies of urban vehicular ad hoc network routing protocols.