Time delay estimation in the presence of clock frequency error

The time difference localization suffers from the performance deterioration of time delay estimation (TDE) due to the presence of clock frequency error in incoherent systems. Based on the modified signal model of TDE, the joint maximum-likelihood (ML) estimation of time delay and system clock frequency error is proposed. Then, the Cramér-Rao lower bounds (CRLBs) of time delay and clock frequency error estimations are given. The performance of time delay estimation may be significantly improved to approach CRLB by proposed method. Further, the accuracy of proposed time delay estimator is unaffected by performance of system clock in moderate condition, that is verified by simulation results.