Node caching enhancement of reactive ad hoc routing protocols

Enhancing route request broadcasting constitutes a substantial part of recent research in mobile ad-hoc network (MANET) routing. We suggest a novel approach to constrain route request broadcast which is based on node caching. Intuition behind node caching is that the nodes involved in recent data packet forwarding have more reliable information about its neighbors and have better locations (e.g., on the intersection of several data routs) than other nodes. We cache nodes which are recently involved in data packet forwarding, and use only them to forward route requests. Dropping route request forwarding from the other nodes considerably reduces routing overhead at the expense of possible destination missing. The suggested node caching techniques can be also viewed as a dynamic implementation of a connected dominating set (CDS). We overcome the known drawback of CDS - overuse of dominating (cached) nodes by a new load-balancing scheme. Our contributions include: (i) a new node caching enhancement of route request broadcast for reactive ad hoc routing protocols; (ii) implementation of AODV-NC, the node caching enhancement of AODV; (iii) an extensive simulation study of AODV-NC in NS-2 showing (for stressed MANET's) 10-fold reduction in overhead, significant improvement of the packet delivery ratio and the end-to-end delay; (iv) an evaluation of routing load distribution among MANET nodes; and (v) an implementation and simulation study in NS-2 of forwarding load balancing for AODV-NC sustaining considerable improvement in overhead and delivery ratio.