Patent ID: 6081732
Filing Date: 2000-06-27
Classification: H04M

Abstract:
A method for eliminating acoustic echo in a digital mobile communications system, which system includes a mobile station and a fixed mobile network in which speech signal transmission occurs on a radio path in an uplink direction from the mobile station to the fixed mobile network and in a downlink direction from the fixed mobile network to the mobile station, and in which a speech coding method is employed on the radio path, the method comprising a step ofeliminating acoustic echo, in signals transmitted in the uplink direction, of signals transmitted in the downlink direction, by means of an echo canceller in the mobile station, andin the fixed mobile network, eliminating acoustic residual echo, in signals transmitted in the uplink direction, of signals transmitted in the downlink direction as follows:monitoring voice activity in signals transmitted in the downlink direction;monitoring whether a double-talk situation is present or not;replacing signals transmitted in the uplink direction with noise after a predetermined delay when detecting voice activity in signals transmitted in the downlink direction;terminating the replacing of signals transmitted in the uplink direction with noise after a predetermined delay when detecting the end of voice activity in signals transmitted in the downlink direction; andpreventing signals transmitted in the uplink direction from being replaced with noise when a double-talk situation is detected.