Research On Distributed Fast Handover Scheme Based On QoS Guaranteed In VANETs

With the proposed of the new concept of intelligent transportaion and smart city, Vehiclar Ad Hoc Networks(VANETs) have become a research hotspot of current research. As a kind of special mobile ad hoc networks(MANETs), VANETs have many characteristics such as high speed of mobile node, short communication link duration and fast topology change. All of these features put forward new challenges to the mobile handover technology. The traditional switching technology directly used in MANETs is not suitable for VANETs environment and can not achieve very good handover effect. This also brings a bad network experience for the occupants and hamper the market penetration of VANETs. This paper makes a comparative analysis of the existing handover technology of VANETs and summarize the shortcomings of the existing switching technology. On the basis of this, the handover management protocols were designed to improve the handover efficiency and Qo S level. The main works of this paper are as follows:1. After in-depth study, it is found that the existing handover technology can not meet the requirements of VANETs fast handover, thereby affection traffic safety on the basis of summarizing and analyzing the existing VANETs related handover management protocols. There is a space for further reducing the handoff delay. In VANETs, vehicles need to switch from one infrastructure to another one frequently in the case of urban traffic congestion, resulting in handoff delay of handover management protocols too long. The NEMO enhanced fast handover scheme based on mobile gateway mechanism was proposed as a solution to the problem. The method that proxy mobile router in 3G/WiMAX communication domain switching trigger other vehicles in 802.11 p communication domain handover occurs was proposed to achieve a purpose that macro switch combined with micro switch. And then, this method can achieve the goal of mass quickly switch.2. Given the vast majority of the handover management protocols using the pre-registration method, exsisting VANETs handover management protocols have the problem of repeated data interference because the effect of hyteresis on the specific scenario which leads to the decrease of QoS level. This paper proposed a kind of anti interference handover technology based on delayed activation mechanism through the analysis of the causes of the problem. The basic idea of the scheme is that by using the IPv6 bidirectional reachability detection mechanism, the base station can obtain the accurate time of channel switching and activate the new binding update message at the right time to ensure that the next base station will not carry out the data cache too early.3. The network simulation experiment using NS-2 simulation tool for the scheme 1 and 2 is to verify the correctness and feasibility of the proposed method. The experimental results were comapred with the existing handover schemes in handoff delay and Qo S evaluation index to prove the effectiveness of the proposed scheme.