Page 2 Lecture Notes in Computer Science 2865 Edited by G. Goos ...

22 J. Doshi and P. Kilambiquery itself thus reducing the need for an expensive Type-2 query mechanismand hence decreasing route acquisition latency.Packet Delivery RatioThis is defined as the ratio of thenumber of data packets deliveredsuccessfully to the total data packetssent. We have considered thebusy transmission channel condition,which might affect this ratio. The ratiothus, gives us a measure of the reliabilityof a route and is measuredagainst a varying transmission radius.The percentage of data packetsrouted successfully shows that SA-FAR finds routes quickly and accurately.The percentage of packetsrouted successfully increases withtransmission range. This is becauseFig. 6. Packet Delivery Ratio vs TransmissionRadiusthere is more probability of loss in a route with many hops, as the movementinformation might not have been registered.Fig. 7. Route Acquisition Latency vs. BandwidthRoute Acquisition LatencyIt is defined as the delay between generatinga route query and receivingthe corresponding reply. During oursimulation, we assume that the processingdelay of messages is negligiblebut take into consideration the delaydue to queuing of messages in thetransmission buffer.The route latency graph (Fig. 7)shows, how the latency of discoveringroutes decreases with increasingbandwidth. This substantiatesthe advantages of SAFAR. By beinghighly adaptive, it allows a highbandwidth node to use its capacityeffectively. It knows more destinationsand hence can route faster and more effectively. Even if it does not have aroute in the routing table, it can query using a Type-1 packet, which is sent tomore nodes. Thus, a high bandwidth node need not resort to Type-2 queryingwhich slows the protocol down and increases latency. Hence, the average routeacquisition latency drops with increasing bandwidth.