Opportunistic Any-Path Forwarding in Multi-Hop Wireless Mesh Networks

Routing protocols for multi-hop wireless networks have traditionally focused on finding the best path for forwarding packets between a pair of nodes. While such single-path forwarding is suitable for wired networks with relatively stable point-topoint links, it is not an ideal approach for wireless networks with broadcast links of time varying qualities. Opportunistic routing schemes, which exploit the broadcast nature of wireless transmissions, have been proposed to make packet forwarding insensitive to link quality variations. However, previously proposed opportunistic schemes select candidates and prioritize them based on single-path metrics such as ETX, which do not capture the real closeness between a node pair under opportunistic forwarding. In this paper, we propose a new metric expected any-path transmissions (EAX) for a pair of nodes with a given set of candidates that captures the expected number of transmissions between them under opportunistic forwarding. Based on EAX, we develop a candidate selection and prioritization method which guarantees that each candidate contributes to packet delivery. We then design a hop-by-hop routing scheme, opportunistic any-path forwarding (OAPF), which can handle multiple interactive traffic flows. We evaluate the performance of OAPF using NS2 and show that OAPF provides significant throughput improvement over traditional best-path routing.