Clock Synchronization in Mobile Ad Hoc Networks based on an Iterative Approximate Byzantine Consensus Protocol

We consider the clock synchronization problem in wireless mobile ad hoc networks in the presence of Byzantine nodes. The communication topology is dynamic: nodes move randomly within a geographical area. We propose a clock synchronization protocol which is based on the linear approximate consensus method. Periodically each correct node broadcasts its current timestamp and gathers the timestamps provided by its current neighbors. To cope with the malicious nodes (and to improve the performance when the node density is low), each node keeps the collected timestamps in a local log. As a log may contain values received more or less recently, a transformation technique is introduced to refresh the outdated values. The accuracy of the synchronisation depends on the connectivity among the moving nodes. We use a matrix and vector based representation to model the behavior of the synchronization process and to analyze its accuracy. We show that the deviation between the different clock values can converge towards zero when a particular condition is satisfied infinitely often. The frequency at which the condition is satisfied also impacts the synchronization accuracy. Based on a particular mobility scenario, performance simulations are conducted.