| 摘要 |
To provide accurate and quick position measurements in a practical mobile position location system, the GPS receiver is calibrated, a frequency error in the next time period is predicted using a first frequency locked to an externally transmitted signal, and a second frequency is generated by a GPS oscillator. To predict the error in the next time period, several measurements are made over time, error estimations are made, an error function is approximated responsive to the set of error estimations. This predicted error is then used to correct the GPS receiver in the next time period. In one implementation, a multiple function portable device is disclosed for providing cellular communication using a network of cellular stations that operate at predefined ideal cellular frequencies, and also for providing position location using GPS satellites that transmit GPS signals at a predefined GPS frequency. |
