Zero Scanning Time for 802.11 Networks by Using Media Independent Information Server (MIIS)

Abstract

Handover efficiency in wireless and mobile communication networks is an important factor in providing QoS guarantees for real time applications. The 802.11 standard requires a Mobile Node (MN) to scan all the possible channels (11 in the US) to discover available Access Points (AP's) during a handover. In a given 802.11 cell several channels are expected to be empty. Due to a full scan the MN ends up wasting precious time scanning empty channels. This results in a high handover delay. This handover delay can be simply reduced by making the MN aware of the channel configuration of its future Point of Attachment (PoA). In this paper we propose that when an MN concludes that a handover is imminent, it should inquire the Media Independent Information Server (MIIS) of the Media Independent Information Handover (MIH), for channel configuration information of the future access point rather than scan for this information by itself. The query for this information should contain the current GPS coordinates of the MN. The MIIS first locates the MN on a virtual map with the help of the GPS coordinates and then returns the precise channel configuration information of the future AP to the MN. The MN stores this information locally and uses it to scan just one channel or to skip the scanning completely and associate directly with an access point during a handover. We define a new parameter NET_CHANNEL_CONFIG which is passed in the query by the MN to the MIIS, so that the MIIS knows which information is being requested by the MN. We also define an MIH Information Element Container IE_CONTAINER_802.11_CHINFO which is used by the MIIS to return the requested channel configuration information of the PoA to the MN. The communication overhead for our scheme is just one message exchange with the MIIS as part of the handover preparation phase. Simulation results shows that our scheme Intelligent-Scan One, that scans just one channel, results in a 93% improvement over standard 802.11 scanning. Our second scheme Intelligent-Scan None avoids channel scanning completely and results in a 99% improvement over standard 802.11 scanning delays.