Motorola Corporation

Brendan Ludden

Luis Lopes

Eric Villier

The invention relates to a method for estimating time of arrival of radio signals in particular as used for location determination. A known method of determining the location of a subscriber unit ( ) calculates a number of ranges based on the distance from base stations ( ) with known location. The ranges are calculated from time of arrival estimates of the signals from the different base stations but a significant source of error is the multipath signal components typical in for example cellular mobile communication systems. According to the invention, the effect of multipath is mitigated by selecting a subset of signals based on a time of arrival estimate of each of the signals. An averaged time of arrival estimate with improved accuracy is then determined from the selected subset. A typical use of the invention is for location determination in a cellular mobile communication system.

Method of and system for estimating a time of arrival of a radio signal

Apparatus for determining the location of a subscriber unit ( ) in a mobile telecommunications network, and particularly in a GSM cellular network, includes the provision of several receiver stations ( ) positioned at separate known locations within each cell. Each of the receiver stations ( ), which are synchronised by means of an on-board GPS receiver ( ), measures the time of arrival of a message transmitted from the subscriber unit ( ). The time of arrival measurements recorded by each receiver station ( ) are then transmitted to a base transceiver station ( ) for computation of the subscriber unit's location relative to the receiver stations. The apparatus can provide a reasonably accurate means for location with a low susceptibility to interference.

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Swindon, United Kingdom

Brendan Ludden