Feedback Cancellation for IP-based Teleconferencing Systems

In IP-based teleconferences disturbing howling artifacts might occur whenever multiple participants are in the same room using different communication devices. In this paper it is described how the feedback problem can be reformulated as a system identification task and what are the specifics compared to the classical field of feedback cancellation. The deployment of a Kalman filter based adaptation in the frequency domain is proposed due to its robustness against long phases of double talk and near-end single talk. In order to account for sudden changes in the network delay or in the feedback path a shadow filter system is additionally introduced. Simulation results confirm that the proposed system performs an effective feedback cancellation improving the communication quality significantly.