Multi-retransmission Route Discovery Schemes for Ad Hoc Wireless Networks with a Realistic Physical Layer

During the route discovery process, each node receiving the route request packet (RReq) will retransmit it exactly once. A distant neighbor may accidentally receive/loose the only RReq and use it to announce a new route, although that link is inferior/superior for route reply packet (RRep) or actual message routing. Overall, the constructed route may be far from the optimal. All existing route discovery schemes (including DSR/AODV) apply retransmission during route discovery exactly once (1R). Based on a realistic physical layer model, we propose two new route discovery schemes: n-retransmission (nR, retransmitting exactly n times) and n-retransmission c-reception (ncRR), retransmitting until either a total of n own retransmissions or c copies from neighbors are heard. We compare our two new scheme with traditional one, under otherwise same conditions (same metric, same packet reception probability on each link) and same choices about possibly retransmitting again upon discovering better route (R+) or discarding it (R1), generating route reply packet for every received RRep (B*), or for first and better discovered route (B2), and retransmit ting RRep exactly once (A1), maximum three times (A3), or optimally u times decided by link quality (Au). Experimental results also show that the proposed ncRR scheme (for n=2 and c=3 or c=4) achieves the best tradeoff between quality of route, success rate and message overhead in route discovery process, followed by nR scheme, and both of them are superior to the existing traditional based schemes.