CFOSynt: Carrier frequency offset assisted clock syntonization for wireless sensor networks

System-level timing inconsistency and wireless communication delays are the main uncertainties of existing synchronization mechanisms for wireless sensor networks. Existing solutions mainly rely on timestamp exchanges to estimate clock offset and skew, which results in frequent synchronization, high overhead, and high energy consumption to maintain a well-synchronized network. This paper introduces a novel clock syntonization approach to estimate the differences between clock frequencies of network nodes without the need for timestamp exchanges. The carrier frequency offset (CFO) assisted syntonization (CFOSynt) utilizes the carrier information obtained from wireless packet transmission for clock skew compensation. The key idea of CFOSynt is that, in any wireless communication system, where carrier modulation is employed, carrier frequency delivers information about the transmitter RF clock. Consequently, clock frequency offset between a pair of sensor nodes will result in a carrier frequency offset detected by the receiver node. By leveraging the CFO information, CFOSynt can estimate the system clock skew based on digital counter theory. Extensive experiments and numerical analysis have been demonstrated to evaluate clock skew estimation.