Chain effect of route recoveries and MAC layer collisions in wireless multi-hop networks

Routing protocols for mesh and ad-hoc networks are designed under the assumption that the underlying channel is unreliable and nodes may be mobile. Therefore, route failure detection and recovery are important components of the design. However, under high traffic scenarios, an aggressive route failure detection technique may create a chain of routing messages which interfere with the data communication triggering another route failure detection. This paper investigates the chain effect in two popular routing protocols, OLSR and AODV, with emphasis on cross layer feedback based route error detection mechanism. NS2 based simulations are performed in static and mobile scenarios. Random as well as group mobility scenarios were evaluated. Simulation results reveal that under high traffic load, a chain of route recoveries and MAC collisions are triggered due to localized MAC layer contention rather than mobility in AODV due to direct MAC feedback.