An Analysis of Topology Information Gathering in Mobile Ad Hoc Networks
|關鍵字:||拓樸;機率分析;單一跳躍鄰居列表;廣播;行動隨意網路;topology;probability analysis;1-hop neighbor list;broadcast;mobile ad hoc networks (MANETs)|
Topology information is frequently used in many network functions such as broadcast, route discovery, etc. One-hop neighbor lists are the basic of topology information and used for complicated topology information. The lists can be obtained by all nodes of the network exchanging hello packets exactly once. However, the mobility feature of the wireless Mobile Ad Hoc Networks (MANETs) causes the list different frequently. It also causes the error of the 1-hop neighbor lists. In this paper, we analyze the relationship between the degree of mobility and neighbor information error rate by deriving the probability that a node leaves its original transmission range. We also verify the influence of neighbor information error rate on network performance so as to determine the transmission period of hello packets. According to the probability model, we can deduce the link change rate. The proper hello period can also be obtained by the value of link change rate. In order to obtain accurate 1-hop neighbor information, the hello packets must be sent periodically. However, the accuracy is highly related with the hello transmission period. It means that a large number of hello packets are needed to maintain high accuracy, and consequently a considerable overhead follows. Many researches make an assumption that 1-hop neighbor lists are already known, thereby neglecting the overheads stem from hello messages. It is not reasonable when it comes to real world implementation. We demonstrate the problem through a series of simulations. Hello packet period is also in connection with mobility model. The mobility model dominates the variation speed of topology information. Therefore, the accuracy of topology information is also affected. In this paper, we analyze the relationship between hello packet period, mobility model and the accuracy of topology information. We also derive the probability that a node leaves its original transmission in certain time. The probability can be used to determine proper hello packet period. Last, the ns2 simulator was adopted to compare the results of the analysis and simulation.
|Appears in Collections:||Thesis|
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