A fast MAC layer handoff protocol for WiFi-based wireless networks

In next generation mobile heterogeneous networks, WiFi-based wireless networks are becoming important components, because WiFi devices are widely used in laptops, PDAs and other mobile computing machines. In a WiFi-based wireless network, handoff management is a key service, as the radio range of the WiFi device is limited. Moreover, providing seamless roaming in wireless networks is mandatory for supporting realtime applications in a mobile environment, such as VoIP, online games, and eConference. Recently, many solutions have been introduced to reduce MAC layer handoff latency; however, these solutions consider every mobile node separately, which would not be suitable for a large-scale environment. This paper proposes a novel MAC layer handoff protocol for large-scale WiFi-based wireless networks to support seamless real-time applications. In our scheme, before the mobile node starts initiating the MAC layer handoff process, it selects several neighboring nodes to help it scan available channels. All channels are divided into groups and scanned by these neighbors separately. Therefore, the number of scanning channels in each node is reduced, and scanning latency is minimized. According to simulation results in ns2, we conclude that our scheme can shorten MAC layer handoff latency greatly, and also achieve seamless handoff in terms of loss ratio of data packets.