Research On Handoff Of Infrastructure-based Vehicular Network

Vehicular Network is an important application of Ad-hoc network, and a branch of Network of things. When vehicles move along the road, they need to connect with the internet to get network service through an Access Point (AP). Since the range of an AP is limited, vehicles have to transform its network connectivity from one AP to another to keep always-on-line, which is called handoff. Handoff will cause packet loss and degrade network performance. If handoff time is too long, vehicles will lose network connectivity, which is unacceptable to many real-time applications. So it’s a hot topic to reduce handoff delay, further to reduce packet loss rate and improve throughput.Based on the characteristics of Vehicular Network, we propose a Cross-layer and neighbor Vehicle-aided Fast Handoff (CVFH) protocol. In our proposed protocol, when the Received Signal Strength Indicator (RSSI) continually decreases and the packet loss rate is higher than the predefined threshold, the vehicle thinks that it’s moving away from the service AP (SAP) and should execute handoff in advance. Then the vehicle node checks its neighbor list of network layer routing to acquire its neighbors. If it does have neighbors, the vehicle will send neighbor request to them and continue to communicate with its SAP. Neighbors that received the request will check whether they meet the neighbor-aided selection criteria. After selection, the most qualified neighbor will be selected as the neighbor aided vehicle (NAV) and its SAP will be the vehicle’s target AP. The NAV will send request for authentication, IP address and part of transmission parameters instead of the vehicle. After the whole help process is completed, the NAV will send the related information to the vehicle to help the mobile node to complete handoff.The simulation results show that our proposed handoff protocol CVFH can effectively reduce handoff delay, decrease packet loss rate, extend the communication time and improve the whole throughput compared to the 802.11 handoff protocol.