Configuring Hardware Echo Cancellation on T1 E1 Multiflex Voice WAN Interface Cards
The multiflex trunk (MFT) dedicated echo cancellation modules (dedicated ECAN modules) are daughter cards that attach to the second generation multiflex voice/WAN interface cards (MFT VWIC2 family). The dedicated ECAN modules are available in 32-channel and 64-channel configurations (EC-MFT-32 and EC-MFT-64), which match the requirements of the 1- and 2-port T1/E1 MFT VWIC2s, respectively. This chapter describes the configuration to enable additional echo cancellation effectiveness:
Control of the echo canceller provided through the size of the echo cancellation buffer, ranging from 24 milliseconds (ms) to 128 ms
Processing and memory resources to ensure robust echo canceller coverage independent from the configuration of the echo canceller or the demand placed on the general voice DSP resources
Your software release may not support all the features documented in this module. For the latest caveats and feature information, see
Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table at the end of this module.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to
www.cisco.com/go/cfn. An account on Cisco.com is not required.
To run hardware echo cancellation on T1/E1 interfaces, you must install an IP Plus or IP Voice image (minimum) of Cisco IOS Release 12.3(14)T or a later release.
Baseboard and Daughter Card Configuration
Hardware echo cancellation is restricted to the same baseboard voice/WAN interface card (VWIC) on which the daughter card (EC-MFT-32 and EC-MFT-64) is installed and cannot be shared by other T1/E1 controllers.
If you are using hardware echo cancellation, the value for tail length is set to 128 ms. This is not configurable and cannot be changed.
Accurate TDM ERL Readings for Echo Cancellation
To ensure accurate statistics for network monitoring and troubleshooting, an estimate of the quality of the TDM connection and the ECAN's ability to discern and cancel out echo might be necessary. To ensure accurate readings, you must configure software-based echo cancellation by entering the
echo-cancelenabletypesoftware command (Step 6 in the procedure in
How to Configure Hardware Echo Cancellation). If you accept the default (hardware echo cancellation) or enter the
echo-cancelenabletypehardware command, the output for the
showvoicecall command always displays "TDM ERL Level(dBm0): +6.0."
If you enter the
echo-cancelenabletypesoftware command to enable software-based echo cancellation, the
showvoicecall command output displays accurate real-time TDM ERL measurements. The sample output examples provided in the following sections demonstrate the difference:
slot--Specifies the slot number. Range can be 0 to 6, depending on the platform.
subslot--Specifies the VWIC slot number. Range can be 0 to 3, depending on the host module or platform.
When the command is used for the first time, the configuration takes effect immediately.
A subsequent change in the card type will not take effect unless you enter the reloadcommand or reboot the router.
When you are using the cardtype command to change the configuration of an installed card, you must enter the nocardtypee1|t1}
slotsubslot command first. Then enter the cardtype
slotsubslot command for the new configuration information.
Router(config)# voice card 1
Enters voice card configuration mode.
Specify the slot location using a value from 0 to 5.
Enters voice port configuration mode and specifies the voice port.
The slot-numberargument identifies the slot where the voice interface card (VIC) is installed. Valid entries are from 0 to 3, depending on the slot in which it has been installed.
The subunit-number identifies the subunit on the VIC where the voice port is located. Valid entries are 0 or 1.
The port argument identifies the voice port number. Valid entries are 0 and 1.
The slot argument is the slot in which the voice port adapter is installed. Valid entries are from 0 to 3.
The port argument is the voice interface card location. Valid entries are 0 to 3.
The ds0-group-numberargument indicates the defined DS0 group number. Each defined DS0 group number is represented on a separate voice port. This allows you to define individual DS0s on the digital T1/E1 card.
The commands, keywords, and arguments that you are able to use may differ slightly from those presented here, based on your platform, Cisco IOS release, and configuration. When in doubt, use Cisco IOS command help to determine the syntax choices that are available.
router(config-voiceport)# echo-cancel enable type hardware
Enables hardware echo cancellation.
Thehardwarekeywordis the default. Echo cancel coverage is hardcoded for 128 ms.
This command is needed only to configure the softwarekeywordto effect software-based (DSP) echo cancellation or to restore the hardware default.
The hardware and software keywords are available only when the optional hardware echo cancellation module (EC-MFT-32 or EC-MFT-64) is installed on the multiflex VWIC.
If you need to obtain accurate, real-time readings for the quality of the TDM connection and the echo canceller's ability to discern and cancel out echo, you should enter the echo-cancelenabletypesoftware command. See theRestrictions for Hardware Echo Cancellation for more information.
The output in this section shows that hardware echo cancellation is enabled on slot 1.
Router_3725# show echo-cancel hardware status 1
VWIC HWECAN 1/0 is UP.
Software version:4.4.803 , Date:Feb 6 16:58:57 2004
Tail length:128 Tone disabler type:G.165 Fax notify: Off
Device:VWIC_8MBPS_1TIEC_TL128_MS_1P Max Channels:32
Only Port0 have Local HWECAN Connectivity.