Multi-mode frequency compensation in mobile terminals

A mobile terminal, comprising:

• an oscillator;
• a receiver circuit configured to downconvert signals received from a communication system using a frequency signal from the oscillator;
• a transmit circuit configured to upconvert a baseband signal to a transmission frequency using the frequency signal from the oscillator;
• a memory;
• a processor coupled to the receive circuit, the transmit circuit and the memory;
• and
• instructions stored in the memory and executable by the processor to:
• receive from the receiver circuit a downconverted first receive signal received from the communication system;
• operate in an acquisition mode comprising:
• processing the first receive signal to determine a first receive frequency error;
• determining a first frequency correction by applying a first correction procedure to the first receive frequency error, wherein the first correction procedure compensates for a first oscillator error within the first receive frequency error due to the oscillator;
• transmitting to the communication system via the transmit circuit a first transmit signal that is frequency-corrected by the first frequency correction;
• receiving a first message from the communication system, the first message indicating a first Doppler shift of the first receive frequency error as determined by the communication system using the first transmit signal;
• determining the first oscillator error based on the first receive frequency error and the first Doppler shift;
• and
• storing the determined first oscillator error as a preceding oscillator error;
• and
• switching operation from the acquisition mode to a tracking mode, the tracking mode comprising iteratively performing operations comprising:
• processing a second receive signal received from the communication system after downconversion by the receiver circuit to determine a second receive frequency error, the second receive frequency error including a second oscillator error due to the oscillator and a second Doppler shift;
• determining a second frequency correction by applying a second correction procedure to the second receive frequency error, wherein the second correction procedure compensates for the preceding oscillator error and the second Doppler shift;
• transmitting via the transmit circuit a second transmit signal to the communication system that is frequency-corrected by the second frequency correction;
• and
• updating the stored preceding oscillator error based on a subsequent message received from the communication system, the subsequent message indicating a difference between the second oscillator error and the preceding oscillator error that was determined by the communication system using the second transmit signal.