Wireless Ad Hoc and Sensor Networks

358 Wireless Ad Hoc and Sensor Networksenergy, E2E delay, and distance from a node to the base station (BS), alongwith clustering, to effectively route information to the BS. Initially, thenodes are either in idle or sleep mode, but once an event is detected, thenodes near the event become active and start forming subnetworks. Formationof the inactive network into a subnetwork saves energy becauseonly a portion of the network is active in response to an event. Later, thesubnetworks organize themselves into clusters and elect cluster heads(CHs) in the subnetwork portion whereas relay nodes (RNs) are selectedoutside the subnetworks.The data from the CHs are sent to the BS via RNs that are located outsidethe subnetworks in a multihop manner. This routing protocol improvesthe lifetime of the network and the scalability. This routing protocol isimplemented in the medium access control (MAC) layer using UMRnodes. Simulation and experimental results indicate that the OEDSR protocolresults in lower average E2E delay, fewer collisions, and less energyconsumed when compared with the DSR, AODV, and Bellman Ford routingprotocols.8.1 Routing in Ad hoc Wireless NetworksWireless Ad hoc and sensor networks have gained great importance in recentyears due to an unprecedented growth in wireless communication technologiesand with the advent of the IEEE 802.11 standards. An ad hoc networkis a group of wireless mobile nodes dynamically forming a temporary networkwithout any fixed infrastructure or centralized administration.A routing protocol is used to determine an appropriate path over whichdata is transmitted in a network. It also specifies how the network nodesshare information with each other and report changes in the topology.Moreover, the decisions of the routing protocol have to be dynamic, inresponse to changes in network topology. Thus, the route selection processgreatly affects the overall network performance, defined using E2E delay,throughput, and network energy efficiency. Therefore, routing is a criticalissue in wireless ad hoc and sensor networks, where data is transmittedgenerally over multihop paths.The challenges involved in developing a routing protocol for mobile adhoc and sensor networks are very different and more complex than thoseof static wired networks. The routing protocol should be capable of rapidlyadapting to link failures and topology changes caused by node movements.Therefore, the routing protocol should work in a distributedmanner with self-organizing capability. The goal of the routing protocolis to compute the optimal path between any source–destination pair withminimal control traffic overhead. This should be achieved within the