A Novel Efficient Acquisition Scheme for a High Sensitivity Assisted GPS Receiver

Automatic location identifications are required for emergency calls in Japan and many other countries. However, giving a reliable position promptly is a problem in places where the global positioning system (GPS) signal is extremely weak. We propose an acquisition scheme for assisted GPS (AGPS) architecture based on a timingsynchronized mobile network. System errors as well as code uncertainty range are discussed. With this method, the C/A code search range is significantly reduced, and long-time coherent correlation is possible. Simulations prove that the method is fast, efficient and power-saving for the user handset. Furthermore, the AGPS receiver can perform a short TTFF (Time To First Fix) start even with no ephemeris kept in the handset.