Improved Handoff Efficiency with the help of Neighbour Graph using Carrier to Interference Ratio

Abstract

Presently, IEEE 802.11 based wireless local area networks (WLAN) have been widely deployed for business and personal applications. The main issue regarding wireless network technology is handoff or hand over management. When a mobile station (MS) moves outside the range of its current access point (AP) it needs to perform a link layer handover. This causes data loss and interruption in communication. According to IEEE 802.11, link layer2 (L2) handoff is performed in three phases – scanning, authentication and re-association. Scanning process causes 90% of the total handoff delay. Throughout the last few years, plenty of researches had been done to reduce the hand off delay by reducing the scanning delay. In this paper, we propose to reduce handoff latency for IEEE 802.11 wireless networks with Neighbor Graphs (NG) pre-scanning mechanisms. IEEE 802.11 uses 11 channels of which the channels 1, 6 and 11 do not mutually overlap. So these channels are expected to have a lower carrier-to-interference ratio (CI) compared to other channels under the same base station, which increases the channel‟s availability during handoff. Based on the NG prescanning mechanism, when handoff criterions have been met, we design an algorithm to first scan the channels 1, 6 and 11, if present under the next Access Point (AP), to reduce the scanning delay. We also introduce pre-authentication mechanism, which will effectively reduce the message processing delay.