Hybrid Time Synchronization for ZigBee Networks: An Empirical Approach

Time-based wireless indoor localization recently stands as the state-of-the-art situation for the up-to-date real time application areas. Synchronizing time among the wireless nodes may still be the major challenging problem for time- based indoor localization on wireless networks. The main reason of this problem is the difficulty and complexity of using standard time synchronization protocols such as Network Time Protocol (NTP), and Coordinated Universal Time (UTC) on wireless networks. Besides, the limitations of the wireless networks restrict the consideration of which time synchronization protocols should be applied on which wireless communication technologies such as WiFi, LiFi, Bluetooth, UWB, Ultrasonic, ZigBee, etc, for wireless time synchronization. Generally, time synchronization schemes support better accuracy if and only if precise random delay model can be implemented for the estimation of random delay caused by the real environmental impacts. In this paper, a ZigBee-based hybrid wireless time synchronization approach, which is required as the first and vital step for time-based wireless indoor localization, is proposed. In order to provide precise synchronization accuracy of the proposed hybrid approach to be more precise, appropriate random delay model is implemented by applying the empirical approach on ZigBee- based test-bed. By using the empirical data obtained from anchor-to-anchor packet communications, random delay is estimated using Gaussian random delay model and then least square regression model is applied to improve synchronization accuracy. In accordance with the experimental evaluation results, it highlights that synchronization performance of the proposed approach is significantly improved.