Mobile phone location in dedicated and idle modes

The possibility to determine the geographical position of a cellular mobile phone has become more and more important. One main reason for this, is that location of mobile phones in the case of emergency calls becomes mandatory in the US. Also commercial markers of mobile phone location are expected to grow fast in the near future. Emergency call location and some commercial applications require location, when a mobile phone is in the dedicated mode, whereas other applications do not require call to be on. This article describes a GSM 900 trial location system, that is based on the observed time difference (OTD) location method. The first location results are presented with a test mobile phone both in the idle and dedicated modes.