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Wireless mesh networks (WMNs) are a promising networking concept to extend the range of wireless gateways by leveraging fixed relays as packet forwarders for nodes further away. WMNs use ad-hoc routing protocols such as AODV or OLSR to route packets between wireless gateways, fixed relays, and mobile nodes (MNs). This paper focuses on handoff-related delays specific to WMNs: delays due to re-discovery and setup of multihop routes after handoffs. Since in case of OLSR routing information is only sent periodically to reduce routing overhead, route discovery can take up to a few seconds, which is far too long for delay-sensitive applications like Voice over IP. Therefore, we propose the FastSync extension for OLSR, which enables MNs to obtain all topology and gateway information immediately after handoff from a fixed relay of the handoff-target WMN. As a result, the long waiting phase for the first regular routing update after handoff is avoided. We implemented our concept and performed extensive simulations. The results show that OLSR-FastSync reduces handoff-related route setup delays significantly.
Date of Conference: 25-28 Sept. 2006