Forwarding Group Maintenance of ODMRP in MANETs

Abstract

ODMRP builds and refreshes routes by flooding Join Queries periodically. However, excessive flooding wastes the limited bandwidth of ad-hoc networks and causes high control overhead. In addition, flooding often causes congestion and collisions. Finding the optimal flooding interval is critical in ODMRP performance. Moreover, there is no such value for flooding interval that is appropriate for all various types of ad-hoc network applications. The present paper aims to reduce the high control overhead that ODMRP suffers from. We propose two schemes to improve this protocol. Both schemes use the link state prediction method that depends on the received signal power strength for predicting the exact link breakage time of an active link before the breakage actually occurs. By using link state prediction, routes are reconstructed only when they will be soon broken, and thus we utilize the bandwidth efficiently and reduce the power consumption when the mobility of nodes is low. The proposed two schemes are ODMRP-GM and ODMRP-LM. In ODMRP-GM, source nodes flood Join Queries only when the topology is changed. In ODMRP-LM, routes are updated locally by the nodes that predict future breakage time of an active route between refresh intervals. The impact of our improvements is evaluated via simulation.