Mobile station location with heterogeneous data

The hyperbolic locationing technique standardized for GSM (Global System for Mobile communications) as enhanced observed time difference (E-OTD) estimates the mobile station (MS) location in two dimensions by processing at least two relative distance measurements between the MS and pairs of base transceiver stations (BTSs). The E-OTD method cannot be applied if only two BTSs are available; nevertheless there is the need to estimate the MS location also in such circumstances. This paper presents an algorithm that extends the E-OTD concept by integrating in the location calculation additional location information available in GSM networks. The key feature of the algorithms is its capability to provide a location estimate even when only two BTSs can be used for E-OTD measurements