Proactive context transfer in WLAN-based access networks

In recent years, many protocols have been developed to support mobility of wireless network nodes, e.g. Mobile IP suite of protocols designed to support IP routing to mobile nodes. However, support for truly seamless mobility requires more than just routing; every service associated with the mobile user needs to be transferred smoothly to the new access network. In this paper, we consider the problem of transferring service state (context) at both the link and IP layers. Based on the rate of SNR change in the wireless access channel, we propose a scheme that proactively transfers context information associated with the mobile user. The proposed scheme estimates the best moment in time for transferring context information, to assure the shortest waiting time of the transferred context at the new access network. We also propose and describe a new concept, forced handover, helpful in proactive transfer of context information when the mobile node moves from one access sub network to another. We present preliminary simulation results and a discussion on the performance of the proposed scheme. The scheme is shown to be helpful in ensuring seamless mobility, while the number of unnecessary handovers resulting from the proactive nature of the scheme can be kept at a controllable level.