An ad hoc network is a collection of computing nodes communicating over wireless channels without relying on any fi xed infrastructure such as servers and towers. Such networks are useful in rescue operations, and in rural and military settings. Clock synchronization is an essential building block for many ad hoc wireless network applications. It provides the participatingcomputing nodes with logical clocks whose di erences can be bounded.Several traditional distributed clock synchronization algorithms use strict communication structures such as spanning trees. In such protocols, a node corrects its logical clock when it receives a new time-stamped message fromits parent. In this thesis, we present a new clock synchronization protocol that exploits the broadcast medium in wireless networks, allowing nodes toopportunistically correct their logical clocks in order to converge to a reference time provided by a designated root node. Our protocol does not rely on a communication structure and is lightweight due to its low overhead. We also propose a variation of our opportunistic protocol, which further reducesoverhead through randomized broadcast techniques. Our simulation-based experimental evaluation of the protocols illustrates that our opportunisticalgorithms improve the accuracy of the nodes' logical clocks, when compared to a tree-based protocol. However, we show that the level of improvement is a function of the density of the wireless network. Additionally, the resultsshow that our algorithms can produce around half the overhead, compared to an existing protocol that achieves higher levels of precision.
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Opportunistic clock synchronization for ad hoc networks
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