Self-Adjusting Congestion Avoidance Routing Protocol for Ad Hoc Networks *

In an ad hoc network, the wireless media is shared by multiple nodes. The contention among neighbors for the access to the shared media is the major cause fornelwork congestion. As wireless links usually have low capacity, congestion in ad hoc networks is a morc severe problem than in wired networks. The main thrust of our work is to avoid congestion at IP layer by minimizing conlemions for channel access. The intermediate delay, which characterizes!.he impacis of channel contention, lraffic load, and lhe length of a route, is developed as a new routing melric. Two approaches are proposed to locally estimate delay using statistic and probability methods respectively. An ad hoc routing protocollhat uses intermediate delay as melric is developed, namely self-adjusting congestion avoidance (SACA) protocol. The perfonnance of SACA is compared against that of AODV and DSR using three types of traffic. SACA is able to deliver more than 80 % data packets even under heavy uaffic load. It is 50 %- 60 % more efficient than DSR in terms of delivery ratio. It introduces 50 % less protocol overhead than DSR does. SACA delivers 40 %- 400 % more packets than AODV depending on the type of traffic.