Network Echo Cancellers: Requirements, Applications and Solutions

Echo in the telephone network is a well-known phenomenon -long delays and noticeable echo may create significant or even unbearable disturbance in a telephone conversation. Echo cancellation is a technique to reduce the echo to an acceptable level. In fact, network echo canceller is considered as the single most critical element impacting overall voice quality in typical communication networks. The challenge is to maintain the Quality of Service (QoS) at low computational cost. In order to meet the challenge echo canceller vendors have made great efforts to develop carrier-grade echo cancellers aiming at offering high voice quality and high channel density solutions. Key elements in the competitive marketplace include advanced and better tuned echo cancellation algorithms, better processor architectures with more processing capabilities, and better implementation techniques. This article covers the following aspects of the echo cancellation: (1) General market requirements; (2) Typical echo cancellation architectures and applications; (3) Basic echo cancellation algorithms; (4) Echo cancellation implementations; (5) Echo canceller testing and deployment related issues.