Threshold-based opportunistic routing protocol in multi-hop wireless networks

Unlike traditional unicast routing where a transmitting node needs to specify its single next-hop forwarder in a multi-hop wireless networks in an a priori manner, Opportunistic Routing allows multiple potential next-hop forwarders to be selected. Any selected node may forwards the packet towards the destination if it can decode the packet correctly. Existing opportunistic routing protocols tend to limit the size of the forwarding set for each transmitting node due to the communication overheads required to suppress unnecessary packet duplicates generated by multiple eligible next-hop forwarders. As such, they fail to capitalize on the key advantage of opportunistic routing, namely, the ability to utilize a large number of long but unreliable wireless links in progressing towards the destination. In this paper, we propose TORP, the Threshold-based Opportunistic Routing Protocol, which applies a novel threshold-based forwarding technique to reduce the coordination requirements between multiple potential next-hop nodes. This in turn, enables TORP to exploit the advantage of using numerous distant downstream nodes as next-hop forwarders. Simulation results show significant improvements in the end-to-end delay and total traffic load generated by TORP over unicast routing. Compared with the state-of-the-art ExOR protocol, TORP reduces the average end-to-end delays by 25-40% under typical network configurations and has the advantage of being more amenable to a fully-distributed implementation.