Wireless Ad Hoc and Sensor Networks

360 Wireless Ad Hoc and Sensor NetworksTo accommodate quality of service (QoS) issues in routing, a new routingscheme using the OLSR algorithm is presented in Ying et al. (2003),which routes packets based on the path with maximum bandwidth bottleneck.However, in an attempt to find the maximum bandwidth path,the protocol can result in longer paths with an increase in the E2E delayfrom the source to the destination, especially in large dense networks. Bycontrast, energy efficiency is more important than minimizing the numberof hops in wireless ad hoc networks because minimal transmission energyconsumption implies a good wireless channel, and further minimizingE2E delay renders the best possible throughput. It is important to noticethat two nodes close to each other may still require significant transmissionenergy if the wireless channel between them is highly undesirable.The first few sections of this chapter present an OEDR proactive protocol(Regatte and Jagannathan 2005) for ad hoc wireless networks. The proposedalgorithm is fully distributed in nature. The control packets (HELLO andTC) are generated similar to the OLSR protocol (Jacquet et al. 2001, Clausenand Jacquet 2003). However, the HELLO packets in OEDR are used tocalculate the energy consumed and delay experienced during transmissionfrom the neighbors and the energy levels of the neighbors, along with theneighbor sensing. Using this information, the multipoint relay nodes(MPRs) (Qayyum et al. 2002) are selected among the one-hop neighbors toreach all the two-hop neighbors with the minimum energy-delay metric asthe link cost. MPR nodes, in turn, transmit the TC messages with link costinformation from their respective MPR selectors to all the nodes in thenetwork. Once available, the link cost information in the network is usedby the minimum-cost spanning tree algorithm, to compute optimal routesbetween a source and the destination pair.Analytical results are included to prove that the MPR selection algorithmof the proposed OEDR protocol will result in an optimal route both betweentwo-hop neighbors and source–destination pairs. The NS-2 simulation resultsindicate that the proposed scheme renders minimum delay, a better throughput/delayratio, and a smaller energy-delay product over the OLSR andAODV protocols. Section 8.2 provides the description of the OLSR protocol.Section 8.3 describes the novel OEDR protocol. In Section 8.4 the optimalityof the OEDR is demonstrated analytically. Section 8.5 presents the NS simulatorresults to evaluate the performance of the OEDR algorithm.8.2 Optimized Link State Routing (OLSR) ProtocolBefore presenting the OEDR protocol, it is important to understand theOLSR protocol. The OLSR protocol (Jacquet et al. 2001, Clausen andJacquet 2003) inherits the stability of a link state algorithm and has the