Passive Clock Synchronization for TDOA-based UWB Indoor Positioning Systems
Han Zhang, Le Yang · 2018
This paper considers the problem of estimating the parameters of the quadratic clock model to achieve clock synchronization for time difference of arrival (TDOA)-based ultra wideband (UWB) indoor positioning systems. It is assumed that a reference node with a master clock is available and as a result, we are able to synchronize an arbitrary number of receiving nodes in a passive manner using wireless connections. A practical algorithm for identifying the quadratic clock model parameters is proposed by tailoring and enhancing an existing solution. In particular, the clock synchronization is accomplished in two steps, where in the first step, the clock drift is estimated while the clock offset and skew are found in the second step. Both processing steps utilize the closed-form weighted least squares (WLS) optimization only. Method for simplifying the evaluation of the weighting matrices is introduced and is shown to be capable of reducing the computational time greatly. Simulation results show that the newly developed clock parameters estimation technique is approximately efficient in the sense that it can attain the Cramér-Rao lower bound (CRLB) performance. Experiments using data from a real TDOA-based UWB indoor localization system further confirm the advantage of using the quadratic clock model over the simplified linear clock model in maintaining long-term synchronization.