Abstract
Time synchronization is an important issue in ad-hoc networks for reliable information exchange. The algorithms for time synchronization in ad-hoc networks are largely categorized into two types. One is based on a selection of a reference node, and the other is based on a consensus among neighbor nodes. These two types of methods are targeting static environments. However, synchronization errors among nodes increase sharply when nodes move or when incorrect synchronization information is exchanged due to the failure of some nodes. In this paper, we propose a synchronization technique for mobile ad-hoc networks, which considers both the mobility of nodes and the abnormal behaviors of malicious or failed nodes. Specifically, synchronization information extracted from a median of the time information of the neighbor nodes is quickly disseminated. This information effectively excludes the outliers, which adversely affect the synchronization of the networks. In addition, Kalman filtering is applied to reduce the synchronization error occurring in the transmission and reception of time information. The simulation results confirm that the proposed scheme has a fast synchronization convergence speed and low synchronization error compared to conventional algorithms.
Highlights
An ad-hoc network is adopted for various situations, such as environmental monitoring, military operation, and disaster recovery [1]
In an ad-hoc network, the nodes are equipped with computing and sensing devices operating at low power, and an accurate time synchronization is required in collecting and sharing data measured by the sensing devices [2,3]
For a high-rate time division multiple access (TDMA) system, the performance of medium access control (MAC) layer scheduling is significantly affected by time synchronization among nodes
Summary
An ad-hoc network is adopted for various situations, such as environmental monitoring, military operation, and disaster recovery [1]. As the maximum hop count among nodes is high in a widely distributed network, hop delay remains the most important issue in the reference node-based time synchronization method [14]. At the end of each round, its time information is updated by averaging the rates and offsets stored in the table The repetition of this process results in the time synchronization among all the nodes. For mobile ad-hoc networks (MANETs) [23,24], we propose a consensusbased Median Kalman-filtering Time Synchronization (MKTS) scheme, which reduces the convergence time of synchronization by rapidly spreading the time information extracted from the median values of synchronization messages to an entire network [25].
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