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Unformatted text preview: IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS, VOL. 22, NO. 7, SEPTEMBER 2004 1357 Modeling Path Duration Distributions in MANETs and Their Impact on Reactive Routing Protocols Fan Bai , Student Member, IEEE , Narayanan Sadagopan , Student Member, IEEE , Bhaskar Krishnamachari , Member, IEEE , and Ahmed Helmy , Member, IEEE Abstract— We develop a detailed approach to study how mobility impacts the performance of reactive mobile ad hoc network routing protocols. In particular, we examine how the statistics of path dura- tions including probability density functions vary with the parame- ters such as the mobility model, relative speed, number of hops, and radio range. We find that at low speeds, certain mobility models may induce multimodal distributions that reflect the characteris- tics of the spatial map, mobility constraints and the communicating traffic pattern. However, this paper suggests that at moderate and high velocities the exponential distribution with appropriate pa- rameterizations is a good approximation of the path duration dis- tribution for a range of mobility models. Analytically, we show that the reciprocal of the average path du- ration has a strong linear relationship with the throughput and overhead of dynamic source routing (DSR), which is also confirmed by simulation results. In addition, we show how the mathematical expression obtained for the path duration distribution can also be used to prove that the nonpropagating cache hit ratio in DSR is independent of velocity for the freeway mobility model. These two case studies illustrate how various aspects of protocol performance can be analyzed with respect to a number of significant parameters including the statistics of link and path durations. Index Terms— Communication system, modeling, simulation. I. INTRODUCTION A VAILABILITY of small, inexpensive wireless communi- cating devices has played an important role in moving ad hoc networks closer to reality. Consequently, mobile ad hoc net- works (MANETs) are attracting a lot of attention from the re- search community. MANETs are advantageous because of their readily deployable nature as they do not need any centralized infrastructure. Various MANET routing protocols are proposed in the recent years. Some of them are categorized as proactive routing protocol, because the routing table of node is periodi- cally exchanged and updated. Some others are classified as re- active routing protocol, since, for each node, the route to desti- nation is on demand discovered only when it is needed. Manuscript received October 1, 2003; revised March 15, 2004. This work was supported in part by a Grant from the National Science Foundation (NSF) Career Award 0134650. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation. This paper was presented at ACM MobiHoc, June 2003, Annapolis, MD....
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This note was uploaded on 05/27/2011 for the course CIS 4930 taught by Professor Staff during the Spring '08 term at University of Florida.
- Spring '08