Pre-scanning and dynamic caching for fast handoff at MAC layer in IEEE 802.11 wireless LANs

In recent years, wireless LANs have been widely deployed in public places because of its low cost and high-speed connectivity. To cover larger areas, many APs are required which necessitate the use of handoff between different APs. Therefore handoff latency has become essential issue in wireless LANs. The delay caused by handoff process affects the quality of real-time applications like VoIP. So, in order to resolve this problem, an improved fast handoff mechanism is required that can minimize the overall handoff latency enough to run voice and video applications seamlessly. Handoff consists of three phases including scanning, reauthentication, and reassociation. Scanning is the most time consuming phase among all three. We propose a fast handoff scheme in which channels are scanned prior to the time of handoff. This novel approach almost eliminates scanning delay by using a pre-scanning algorithm and it takes only few milli seconds by using a dynamic caching mechanism