Efficient Routing Algorithms Of Vehicular Ad-hoc Networks In Highway Scenarios

Vehicular ad hoc networks, referred to as vehicular networks (VANET), is a new type of mobile self-organizing network developing rapidly in recent years. VANET can integrate a variety of sensor data on vehicles, providing an important basis support for the intelligent transportation systems (ITS) in the future. Through improving the degree of automation and intelligence of vehicles, VANET will thereby reduce traffic accidents, enhance traffic safety, efficiency, comfort, and so on. With so important significance and bright application prospects, Vehicular network is expected to support the practical application including traffic safety alarm, dynamic route planning, vehicle multimedia entertainment etc.VANET has the following characteristics such as high-speed moving nodes, topology changing frequently, lower linking reliability, large transmission delay, limited bandwidth, prone to network partitions etc. The requirement of information transmission is very high for practical application, especially in the case of road traffic safety, related information forwarded is often real-time or near real-time, so the traditional network routing protocol is not suitable for VANET. All these existing characteristics restrict the popularization and application of VANET, thus how to provide stable and reliable network connection, improve throughput rate and safety, and reduce the transmission delay is becoming a hot spot of research in VANET recently. The high effective routing algorithm and protocol in VANET is to ensure that the foundation of the network communication is smooth, VANET routing research is so becoming the most challenging research focus and hot spot in this field.This dissertation, aiming to research the problem of VANET’s link real-time packet loss rate in the highway scenario, proposes that RPLE based on gaussian mixture model method can estimate the real-time packet loss rate in VANET; And then based on the cooperative mechanism, the multi-channel environment in VANET routing problem is studied and a new distributed routing algorithm MCCR is designed; the object-oriented solutions to such problems often occurred in VANET’s network partition, being attacked easily and large transmission delay, include a trusted opportunistic unicast routing algorithm TMCOR and a multicast routing algorithm TMCOM, the former may enhance the network connectivity, robustness, and the latter will transmit the information timely in VANET.1. Real-time wireless link packet loss rate estimation in VANETVehicular ad hoc network (VANET), as a subset of the mobile ad hoc network (MANET), is an effective method for vehicle to communicate and guarantee the traffic safety. It turns out that the present packet loss estimation of VANET impacts routing protocol and transmission control algorithm, which then needs to be upgraded. In this dissertation, we propose a new estimation algorithm for packet loss on VANET, RPLE (Real time packet loss estimation), which uses few probe packets and enhances the estimation accuracy than traditional methods for packet loss on wireless networks. Based on mass on-road measurements, we have obtained the general statistical principals of packet loss rate (PLR) by distances on VANET, and we use Gaussian Mixture Model (GMM) to present PLR probability density. In that case, to get real-time PLR by sending a few probe packets, RPLE maximizes a posteriori probability method to estimate the current PLR based on the GMM of PLR probability density and the probing result. In real urban road scenario, the experiment results indicate that RPLE can get more accurate PLR estimation by few probe packets immediately.2. Research of distributed routing algorithm MCCR in VANETIn order to improve the throughput of VANET, abandon the limitation of single channel over wireless networks, this dissertation, based on the cooperation mechanism, studies a multi-channel environment in VANET. In order to make full use of channel resources, the effective channel allocation algorithm in a multi-channel environment is designed. To overcome the transmit delay and the number of links conflict, we put forward a new routing criterion MCCM (Multi-channel Contention-aware Cooperative Metric), which not only considers the criterion of path interference and path between the interference, but also reflects the influence of multi-channel environment. When MCCM routing criterion is applied to the route choice, the design of routing algorithm can better adapt to the virtual node and virtual link in VANET, and a new distributed routing protocol MCCR (Multi-channel Contention-aware Cooperative Routing)is thus designed. The simulation experiment results show that the high density of nodes, network load heavy, MCCR routing algorithm can effectively improve the throughput of wireless networks, reduce the information transfer delay, thus improve the network performance.3. Trusted opportunistic routing algorithm in the highway scenario VANETAs a new branch of wireless network with important application prospects, reliable and efficient unicast and multi-cast routing protocols are critical for VANETs. As a possible solution, opportunistic routing (OR) has received much attention recently. This dissertation focuses on the aspect of soft security by building trust opportunistic forwarding model in VANET. It incorporates the trust mechanism into OR to enhance the security of routing in resisting malicious attacks. we propose a trusted minimum cost opportunistic unicast routing protocol (TMCOR) and a multicast routing protocol (TMCOM). The simulation results show that both TMCOR and TMCOM have better throughput, average delay and security gains compared with existing protocols.