Control Message Reduction Techniques in Backward Learning Ad Hoc Routing Protocols

Most existing wireless ad hoc routing protocols rely upon the use of backward learning technique with explicit control messages to route packets. In this paper we propose a set of techniques that can be applied in a backward learning routing algorithm in order to minimize or even eliminate explicit control messages for route discovery, setup, and maintenance, while minimally using implicit data-like control messages that need no special processing. We also show that such an algorithm does not need to prevent routing loops at all costs, such as by means of extensive network-wide spanning trees in traditional LAN bridges, or destination sequence numbers in AODV, or source- routing in DSR. In fact, we prove that transient loops can be safely allowed to occur when a simple route refresh mechanism is coupled with the use of packet identification field to effectively bound the lifetime of such transient loops without negatively impacting the network performance. Results demonstrate that even a routing algorithm without explicit control messages can perform competitively in comparison to AODV and DSR protocols while significantly reducing the protocol complexity.