5 Echo Cancellation

Echo cancelers have become essential components in many applications, especially in communications. Echo cancelers can be divided into two main categories, namely Network Echo Cancelers (NEC) and Acoustic Echo Cancelers (AEC). Both types of echo cancelers rely on an adaptive filter to estimate the echo and subsequently use this estimate to reduce the echo in transmitted signals. The requirements, performance, underlying structure, and adaptive algorithms used to implement a NIC are usually different from those used to implement an AEC. The NEC and AEC are discussed separately in more details in Section 2.4.5.1 and 2.4.5.2, respectively.