Geo-Location Technology for UMTS
The use of geo-located Measurement Reports (MRs) has been proven to be useful in applications like traffic map generation or accurate radio propagation modeling. A first approach is to use Received Signal Level (RSL) measurements, which are widely and easily available. However, distance-dependency is measured with very high intrinsic uncertainty leading to poor geo-location accuracy, and therefore current trends support the use of time-delay measurements [1, 2] or a combination of both . Some studies [4, 5] also claim that tracking techniques instead of geo-location of single events provide better accuracy.
Geo-location algorithms based on time-delay measurements make use of the so-called Observed Time Differences (OTDs)  reported every time an MR is triggered. OTDs are subject to a certain number of constraints that will affect the accuracy when geo-locating the User Equipment (UE), such as multipath propagation, limited number of measured Base Transceiver Stations (BTSs), nonperfect BTS synchronization recovery, measurement errors and MRs not being sent in a continuous way but in an event-driven fashion.
Although there is wide literature [1-5] on geo-location and tracking algorithms for mobile networks, those studies mostly analyze theoretical scenarios using unrealistic tracking paths and too optimistic sets of MRs. This Appendix quantifies the effect of the aforementioned limitations in real ...