An Efficient Pre-scanning Scheme for Handoff in Cooperative Vehicular Networks

In Wireless Access in Vehicular Environments (WAVE), the terminal devices are usually highly mobile vehicles or transportation tools, which handoff much more frequently than those in wireless networks. However, the quality of network services, like VoIP and multimedia streaming, will be seriously influenced by too frequent handoff or too long handoff latency. As a result, traditional handoff mechanisms no longer satisfy the need of vehicular communications. At present, most existing fast handoff mechanisms are based on the signal strength of the APs, which does not suit vehicular communications fully. Generally speaking, the regional traffic in Vehicular Ad-hoc Networks (VANETs) keep changing and varying. For example, on busy roads or in rush hours, the increase of number of vehicles may lead to the network congestion and degrade the performance of vehicular communications substantially. Therefore, this paper presents the QualityScan scheme, an efficient pre-scanning method to improve the handoff performance in VANETs. With the attempt to reduce the handoff latency and maintain the load balance among the APs, our proposed scheme regularly collects the loading states of the nodes by the pre-established AP controller (APC), and predicts the network traffic of the next moment. Consequently, Mobile Nodes (MNs) can select the most suitable AP for the best QoS according to the parameters received by passive scanning, while more QoS parameters should participate in cooperation. The simulation result proves that our proposed scheme not only maintains the QoS and the load balance among the nodes, but also further enhances the handoff performance in VANETs.