A Signalling Technique for Disseminating Neighbouring AP Channel Information to Mobile Stations

摘要

Fast handoff is a major problem in the wireless networks and this problem is further aggravated due to limited range of 802.11 Access points. Scanning phase is the major contributor to 802.11 handoff delays; it can be decreased by reducing the number of channels that are scanned at the handoff time. Prior knowledge of the neighbouring Access points (AP) can help in reducing the number of channels to be scanned and thus can assist a mobile station (STA) in making a fast and accurate handoff decision. Dissemination of the neighbouring AP information to all the STA attached to a given AP is a challenging task and it needs to be accomplished without making major changes to the 802.11 standard or significant client/AP modifications. Low computational complexity and backward compatibility are the other issues which have to be taken into account while designing such handoff schemes. We have proposed a new method of providing neighbouring AP channel information to the STA. This method provides the neighboring channel information to the mobile nodes with the help of specially crafted Null CTS frames sent by the access points. We have shown that the overheads due to this scheme are well within the permissible limits.