ACOUSTIC ECHO ELIMINATION IN A DIGITAL MOBILE COMMUNICATIONS SYSTEM

摘要

The invention relates to a method and arrangement for eliminating acoustic echo generated in a mobile station in a mobile communications system. According to the invention, an echo suppressor is placed on the side of the mobile network for eliminating the acoustic residual echo of the echo canceller of the mobile station. The echo suppressor comprises a downlink voice activity detector (35) because it is possible that the downlink speech returns from the mobile station as an acoustic echo superimposed to the uplink signal. When the detector (35) detects the downlink speech, a selector (303) disconnects the uplink signal from the speech decoder (38) and supplies in its place noise from the generator (302). The spectral characteristics and intensity of the comfort noise are similar to those of the background noise in the operating environment of the mobile station at each moment. Generation of the noise is started after a predetermined delay from detecting the voice activity, and terminated after a predetermined delay from the end of the voice activity.