Sources of ToA estimation error in LoS scenario

Time-of-arrival (ToA) estimation technique used with ultra-wideband (UWB) transmission can be used for accurate indoor ranging. In the indoor multipath rich environment, these techniques often suffer from significant inaccuracy in ranging estimation. It is generally believed that the main cause of the ToA estimation error in the Line-of-sight (LoS) scenario is noise, usually modeled as white Gaussian noise. Through the established analytical framework for the analysis of the ToA estimation error, it is argued in this paper that the ToA estimation errors are caused by multipath interference and the fading statistics of the direct path. Therefore, variance of fading statistics of the direct path are considered on top of the noise variance for better prediction of the ToA estimation error. A comparison of predicted error with those obtained based on experimental measurements in an indoor environment confirms the validity of our analytical approach.