The application of wavelet transform to the study of time prediction errors in clocks for use in CDMA digital communication systems

In the CDMA digital mobile communication network the system timing of the base stations are generated by referring the clock signals to CPS satellites. To keep precise system timing, the GPS receivers must constantly receive the radio waves from the satellites constantly. It is, however, impossible to receive the radio wave in a long term by the receiver location or the failure of the RF circuits. In those cases, the reliability of the communication system will be degraded because of the drift, such as aging, of the system clock in the receiver. This paper describes a technique, based on the wavelet transform, which reduces the frequency drift of the master oscillators in the GPS receivers when the carrier signals could not receive. By simulations and experiments, we have achieved that the phase error is less than 10 /spl mu/s within 48 hour period without GPS signals, demonstrating the efficiency of the proposed technique.