Configuring echo cancellation
An echo is the sound of your own voice going back to the phone receiver when you are speaking. The echo cancellation feature can alleviate the echo problem.
The time when an echo occurs and the size of the echo are relatively fixed. As shown in Figure 8, there is a voice signal at time 0, and an echo occurs after about 40 milliseconds (ms). To cancel this echo, perform the following tasks:
Set the echo cancellation delay (the time between when an interface sends out a signal and when the interface receives an echo) to 33 ms.
Set the echo cancellation coverage to 16 ms.
Figure 8: Echo
Configuring the echo cancellation feature
Step | Command | Remarks |
|---|---|---|
1. Enter system view. | system-view | N/A |
2. Enter analog voice interface view. | subscriber-line line-number | N/A |
3. Enable the echo cancellation feature. | echo-canceler enable | By default, this feature is enabled. |
4. Set the echo cancellation delay. | echo-canceler delay milliseconds | The default is 0 milliseconds. |
5. Set the echo cancellation coverage. | echo-canceler tail-length milliseconds | The default is 128 milliseconds. |
Adjusting echo cancellation parameters
Table 1 describes how to adjust echo cancellation parameters for different symptoms.
Table 1: Adjusting echo cancellation parameters
Symptom | Parameters adjusted |
|---|---|
A user hears echoes or loud background noises from the peer when speaking. | Speed up the convergence of comfortable noise amplitudes. |
There are loud environment noises. | Increase the maximum amplitude of comfortable noises. |
A user hears echoes when speaking. | Enlarge the mixture proportion control factor of comfortable noises. |
There are echoes when both parties speak at the same time. | Enlarge the two-way judgment threshold. |
To adjust echo cancellation parameters:
Step | Command | Remarks |
|---|---|---|
1. Enter system view. | system-view | N/A |
2. Enter voice view. | voice-setup | N/A |
3. Adjust echo cancellation parameters. | echo-canceler { convergence-rate value | max-amplitude value | mix-proportion-ratio value | talk-threshold value } | By default:
These parameters take effect only when the echo-canceler enable command is configured. |
Enabling the nonlinear feature of echo cancellation
After echo cancellation is enabled, nonlinear parts in the line can cause residual echo. The nonlinear feature (also called residual echo suppression) can remove the residual echo.
To enable the nonlinear feature of echo cancellation:
Step | Command | Remarks |
|---|---|---|
1. Enter system view. | system-view | N/A |
2. Enter analog voice interface view. | subscriber-line line-number | N/A |
3. Enable the nonlinear feature of echo cancellation. | nlp-on | By default, this feature is enabled. This command takes effect only when the echo-canceler enable command is configured. This command is not supported on the following interface modules:
|