EXTREMEOPPORTUNISTICROUTING Extreme Opportunistic Routing (ExOR) [1] is a state-of-the-art OR protocol for wireless multi hop networks and has been implemented on the RoofNet testbed at Massachusetts Institute of Technology (MIT). ExOR integrates routing and MAC protocols. It improves routing perfor mance by utilizing long-range but lossy links. ExOR is designed for batch forwarding. The source node includes a forwarder list in each packet, prioritized by ETX distance to the destination: the shorter the distance, the higher the priority. Only those nodes that are closer to the
destination than the source are included in the forwarder set. Each packet has a BITMAP option, which marks those packets that have been received by the sending node or nodes with higher priorities. All packets are broadcast. A forwarder transmits a packet only if no for warder with higher priority has explicitly acknowledged receipt of it, as indicated in the BITMAP position for this packet. ExOR has good routing performance. However, it also has the following drawbacks. First, it reduces spatial reuse because it enforces global coordination among forwarders. Second, for warders connected with low-quality links or no links can make inconsistent decisions on packet forwarding because a forwarder may not hear the acknowledgment from other forwarders with higher priorities, which causes duplicate trans missions.