How Time-of-Departure knowledge relates to Time-of-Arrival localization accuracy?

Many localization systems have been developed and tested. However, most works only analyze the performance of the concrete systems in question. Few examine the effects of the underlying system assumptions. In this paper, we analyze the accuracy of source localization methods based on time-of-arrival (ToA) measurements from a set of cooperating receivers (anchors). We examine three different system models, one with and two without the knowledge of the time-of-departure (ToD) of the signal. Our analysis is based on Cramér–Rao Bound (CRB) ellipsoids for each model. We use these to provide insight into the geometric properties of the models. The analysis reveals that the impact of ToD knowledge on the achievable accuracy is very large outside the convex hull of the anchors, but only modest inside. The presented results show that certain system design choices can be reliably traded for batter accuracy, while others cannot.