Wireless Sensor and Actuator Networks: Algorithms and Protocols for Scalable Coordination and Data Communication

2.6 PHYSICAL LAYER-BASED FLOODING, NEIGHBOR DETECTION AND ROUTE DISCOVERY

2.6.1 Route Discovery with Realistic Physical Layer

In reactive routing protocols, such as dynamic source routing (DSR) (Johnson et al., 1996) and ad hoc on-demand distance vector (AODV) (Perkins et al., 1999), each node receiving a route discovery message will retransmit the message if a better route, for example. in terms of hop count and power consumption, is found. However, each node retransmits the route discovery message at most once. An important neighbor may miss the message under the given realistic physical layer, and thus either the route cannot be found or the constructed route may be far from the optimal one. Therefore, a single transmission cannot guarantee to reach each potential neighbor which may provide the best or the only route. Stojmenovic et al. (2005a,b) proposed design guidelines for routing protocols with a realistic physical layer. They suggested that each node could retransmit the given route discovery message several times rather than once as in the UDG model. Such multiple retransmissions may also serve to measure or reevaluate the packet reception probability. The basic idea is as follows. Upon receiving a route discovery message, a node checks if the received message contains information about a better route. If so, the node stops retransmission of the previously known best route, if it is still ongoing, and retransmits the new route discovery with a fresh counter. The optimal ...