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.