Echo Canceler Initialization Without Test Sequence
Original Publication Date: 1988-May-01
Included in the Prior Art Database: 2005-Feb-15
In a voice transmission network wherein two-to-four wire conversions are operated using hybrid transformers, echoes normally spoil the signal. For instance, some of the signal xout sent by locutor T1 to T2 would return through xin . Conventionnaly, these echoes are neutralized using either echo suppress or echo cancel means. Echo suppress is achieved by simply opening the echo path, thus disabling one locutor path (e.g., xin path) in a conversation. Echo canceling avoids such a drastic solution by using an adaptive filter (EC filter) synthesizing the echo path impulse response and generating an echo replica (ER) to be subtracted from xin, thus cleaning the signal flowing back to T1. The EC filter is dynamically adapted by computing and setting its tap coefficients h(k) using a gradient method leading to a convergence algorithm.