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Figure 68 – Location process with U‐TDOA

The location technology uses the difference in times of arrival or U‐ TDOA to determine the location
of a mobile phone by comparing the times at which the signal of a mobile device up to special
receivers installed in multiple cellular base stations.

Receptors are highly sensitive instruments; called Location Measurement Units (Location
Measurement Units, LMU). They contain accurate and synchronized clocks that record the time a
Radiofrequency signal arrives up to location. The results of different LMU are compared to
determine the most likely location of the phone.

Under optimal conditions, where there is more density of base stations, U‐TDOA technology locates
mobile phones within a radius of 50 meters. The accuracy decreases in areas where there are less
radio bases and therefore less LMU.

The U‐TDOA method has several advantages among which include: accuracy, consistency and
reliability. It is also the method of locating cell phones that has focused on security more precisely.
Also the U‐TDOA location technology is typically able to locate a mobile phone in less than 5 seconds.

310 ITU‐T's Technical Reports and Specifications