The mobile Ad Hoc network architecture has several attractive features that distinguish it from the classic cellular architecture including: self-organizing, infrastructure-free, and dynamic adaptation to the fast-changing wireless and mobile environment. Handover is a key technology to implement the VANET system. However, under the WLAN environment and considering the goals of transparent universal access, ubiquitous computing, and seamless mobility, the traditional signal strength comparisons are not sufficient to make a handover decision, as they do not take into account the current context or the various attachment options for the mobile user.IEEE802.11p protocol and the features, the latest research developments and the system structure of the VANET system are surveyed in this paper firstly. Secondly we introduce the handover algorithms in wireless networks in detail, and make a comparison and discussion of their respective merits and faults. We study the mechanisms of V2I and V2V environments. We conduct a simulation experiment in the MATLAB environment and analyze the results.Finally, on the basis of verifying the performance of the handover algorithm, we come up with some practical advice about the key factors and system design for V2I handover mechanism and V2V handover mechanism. In the meantime, we point out the directions which are still worth to further research in the area. |