1Improving the Latency of 802.11 hand-offs using Neighbor Graphs

AbstractThe 802.11 IEEE Standard has enabled low cost and effective wireless LAN services (WLAN). With the sales and de-ployment of WLAN based networks exploding, many people be-lieve that they will become the fourth generation cellular system (4G) or a major portion of it. However, the small cell size of WLAN networks creates frequent hand-offs for mobile users. If the la-tency of these hand-offs is high, as previous studies have shown, then the users of synchronous multimedia applications such as voice over IP (VoIP) will experience excessive jitter. The domi-nating factor in WLAN hand-offs has been shown to be the dis-covery of the candidate set of next access points. In this paper, we describe the use of a novel and efcient discovery method us-ing neighbor graphs and overlap graphs. Our method reduces the total number probed channels as well as the total time spent wait-ing on each channel. Our implementation results show that this approach reduces the overall probe time signicantly when com-pared to other approaches. Furthermore, simulation results show that the effectiveness of our method improves as the number of non-overlapping channels increases, such as in the 5 GHz band used by the IEEE 802.11a standard. I