ExOR: Opportunistic Multi-Hop Routing for Wireless Network

The paper presents design, implementation and evaluation of a new link/network-layer routing technique. Depending on periodic measurement of delivery probability of node pairs, sub set of the useful nodes between the source and destination will agree to receive broadcasted packets from the source. Each packet contains a list of candidate and prioritized forwarders. The closest node to the destination (with the highest priority) will forward the packet by broadcasting it again to new sub set and so on till it reaches the destination. this requires time scheduling to avoid collision and agreement to choose one forwarder to avoid duplication. But the agreement overhead is propotional to the number of nodes, so the sub set must be chosen carefuly to avoid including useless nodes or that enforce transmission more than once.

ExOR header is longer than that of traditional one and depends on the forwarder list size. It is unlike traditional routing can deal with asymmetric links and also with long route with high loss rate that are avoided by tradtional routing.

ExOR was evaluated on outdoor roof-top 802.11 network. It has been found that ExOR's throughput is higher than the throughput using traditional routing over long and short links, where the highest achievement is over longest routes of five and seven hops. It ensure fewer transmission of each packet which results in less interference for network's users on the same spectrum.
But if ExOR routing achieves improvement in the throughput, why it is applied to transfer just 90% of the packets while the remaining packets are transferred with traditional routing.