Carrier frequency synchronization is a difficult problem in distributed wireless sensor networks (WSNs) due to its high-precision requirement. In this paper, we propose simple and easily implementable carrier frequency synchronization for distributed WSNs with a master-slave structure. The slave sensors receive the calibration signal broadcasted from the master sensor (base station) and modulate them in a novel manner such that the retransmitted signal can be easily extracted by the master sensor to compensate the carrier frequency synchronization errors.
The advantage of this method is that it does not require a priori establishment of the time synchronization between the master sensor and slave sensors and that no additional resource would be required to transmit as synchronization signal. Moreover, the impact of Doppler frequency shift is canceled to some degree in this approach. We present the carrier synchronization compensation algorithm and discuss several practical implementation issues. We also derive the stochastic Cramér-Rao lower bound performance analysis of the method and provide numerical results that validate the analysis.