User interface tone echo cancellation

A mobile communications device comprising:

• a processor to generate a user interface audible tone signal;
• a downlink digital signal processor to process a downlink audio signal received from a far-end user's communications device;
• an uplink digital signal processor to process an uplink audio signal to be transmitted to the far-end user's device;
• a baseband processor coupled to provide the downlink signal to the digital downlink processor, and to receive the uplink signal from the uplink processor;
• and
• an analog conversion circuit to interface between the downlink and uplink digital signal processors on one side and a microphone and a speaker on another side,
• wherein the uplink digital signal processor is to perform echo cancellation upon the uplink signal, by filtering the downlink audio signal and the user interface audible tone signal to generate an estimate of an echo signal and subtracting the echo signal from the uplink signal.

A method for performing a call between a near-end user and a far-end user, the method comprising the following digital audio operations performed during the call by the near-end user's communications device:

• processing a downlink digital audio signal from the far-end user's communications device;
• processing an uplink digital audio signal and then transmitting the uplink signal to the far-end user's device,
• generating a user interface digital audio signal;
• estimating an echo signal, by filtering the downlink digital audio signal and the user interface digital audio signal, and subtracting the estimated echo signal from the uplink signal prior to transmission to the far-end user's device.