Practical One-Way Time Synchronization Schemes with Experimental Evaluation

Time synchronization (sync) is a critical part of wireless communication and sensor networks to support applications like MAC scheduling, event detection and positioning. In this paper we propose two solutions for time sync based on one-way exchange of sync packets in a master-slave configuration. First solution is a BLUE estimator based on a precise quadratic clock model that gives good sync accuracy over a long time span. This estimator involves matrix inversion, which is a computationally demanding task for resource constrained devices. For such cases we propose a recursive clock sync scheme based on simple linear clock model that does not require any matrix computation. We evaluated the proposed methods with implementation on a hardware testbed using UWB wireless access technology. The results show that, in case of the recursive solution, it is possible to restrict absolute sync error below a nanosecond for 95% of the time with sync interval of 0.1 s. With the quadratic model based BLUE solution, same performance can be achieved with interval length as big as 0.4 s.