Cell of origin (COO) or Cell-ID is a purely network-based location positioning solution. The solution uses the latitude and longitude coordinates of the base station serving the mobile device as the location of the user. As such, COO has the highest response time and was the most widely deployed positioning solution in 2001. It can, however, be very inaccurate.
Accuracy is dependent on the size of the network cells. The simplest cell networks have transmitters that are omnidirectional, transmitting equally in all directions and producing a circle. Because circles don't tessellate well, mobile network architects try to approximate them to hexagons, as shown in Figure 5.3.
Cell size in a typical large urban network is from 100 to 1,000 meters, which is the approximate accuracy of COO. A typical response time is from 2 to 5 seconds, with 2.5 seconds being a normal response.
COO is often also referred to as cell global identity (CGI) and complemented with timing advance (TA) information. The TA is the time difference between the start of a radio frame and a data burst, which is used to approximate where the user is within the cell.
Commercial vendors that provide products that support COO positioning methods include Cellpoint (http://www.cellpt.com), Ericsson (http://www.ericsson.com), and Nokia (http://www.nokia.com). Products that support COO also typically support various other more accurate positioning methods that should be used when possible.