Uplink Time Difference of Arrival
U-TDOA is a position-location technology for mobile phone networks. It uses advanced triangulation techniques to determine the precise location of a mobile phone.
Unlike competing E-OTD technology, U-TDOA works with any mobile phone; it does not require special hardware or software in the phone.
U-TDOA has been widely embraced by major U.S. GSM carriers to meet the government's E-911 requirements.