Cell of Origin (COO) is a mobile positioning technique for finding a caller's cell (the basic geographical coverage unit of a cellular telephone system) location. It may be used by emergency services or commercial use. COO is the only positioning technique that is widely used in wireless networks and is used for Phase 1 of 911 service in the United States.
For COO positioning, the location of the base station is ascertained and considered to be the location of the caller. COO is a variable and not a very precise locator; depending on the number of base stations in the search area, accuracy may be as close as within one hundred meters of the target (in an urban area) or as far off as thirty kilometers away from the target where base stations are less densely concentrated. For this reason, when precision is important COO is often used in conjunction with some other technology, such as the Global Positioning System (GPS) or Time of Arrival (TOA).
Although COO positioning is not as precise as other methods, it offers unique advantages: it can very quickly identify the location (generally in about three seconds) and does not require equipment or network upgrades, which makes it easily deployed to existing customer bases. The American National Standards Institute (ANSI), and the European Telecommunications Standards Institute (ETSI) recently formed the T1P1 subcommittee dedicated to creating standardization for positioning systems using TOA, Assisted GPS, and Enhanced Observed Time Difference in addition to COO.