How good is Assisted GPS?

Assisted GPS (A-GPS) is being increasingly recognised by the public, users expecting to have a better performance of the A-GPS enabled devices than the conventional GPS receivers. This paper reported the evaluation of several A-GPS enabled receivers using a GPS signal generator and a specifically developed software. Under ideal conditions, several different scenarios were created to test the devices. Time To First Fix (TTFF) and positioning accuracy were the two aspects of most interest. The results show that these A-GPS enabled receivers can obtain reasonable position solutions in well under 30 seconds, especially the newer receivers which have TTFF typically less than 10 seconds, can be as low as 3 seconds. Better performance of the new receivers in the market is expected.