Cisco Cisco 2600 3600 Series 1-Port 30-Channel J1 Voice Fax Network Module Data Sheet
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BENEFITS
Benefits of the Cisco enhanced ITU-T G.168 ECAN feature using either Cisco dedicated ECAN modules or general voice resources include:
•
Investment protection through a state-of-the-art echo cancellation feature
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Enhanced ITU-T G.168 ECAN feature complies with and exceeds the performance requirements specified in the ITU-T Recommendation
G.168 Digital Network Echo Cancellers (2000) standard
G.168 Digital Network Echo Cancellers (2000) standard
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Provides future echo cancellation enhancement capability through Cisco IOS
®
Software upgrades
•
Increased echo cancellation effectiveness by providing capabilities and controls
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Provides control of the echo canceller coverage through the size of the echo cancellation buffer, ranging from 8 to 64 ms (128 ms of echo
cancellation coverage requires dedicated ECAN module)
cancellation coverage requires dedicated ECAN module)
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Configures the worst-case echo return loss (ERL), ranging from 0 to 6 dB
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Provides control over echo cancellation convergence, enabling faster convergence for multiple echo reflectors and improved double-talk
detection
detection
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Provides control for enabling and disabling the nonlinear processor (NLP), which replaces the residual echo at the output of the echo
canceller with comfort noise based on the actual background noise of the voice path
canceller with comfort noise based on the actual background noise of the voice path
•
Improved network manageability by providing various echo cancellation performance metrics and testing capabilities
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Reports various metrics, including combined echo return loss (ACOM), ERL, and worst-case echo return loss
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Reports statistics for location of the largest reflector (tail) and the internal state of the G.168 ECAN feature
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Provides test-mode support for manually freezing, thawing, and clearing the echo canceller registers
Additional benefits of the Cisco enhanced ITU-T G.168 ECAN feature when used with the Cisco dedicated ECAN modules include:
•
Additional echo cancellation effectiveness through extended capabilities and features
–
Control of the echo canceller is provided through the size of the echo cancellation buffer, ranging from 8 to 128 ms
–
Additional processing and memory resources help ensure robust echo canceller coverage independent from the echo canceller configuration
or the demand placed on the general voice DSP resources
or the demand placed on the general voice DSP resources
APPLICATIONS
Packet Voice Solutions: Echo Cancellation for Demanding Network Conditions
In a voice telephone call, an echo is the audible leak-through of your own voice from the transmit path into your own receive (return) path. Leak-
through happens only in analog circuits; digital voice traffic does not leak. Analog signals can leak either electrically from one wire to another (call
cross-talk), or acoustically through the air from a loudspeaker to a microphone. Analog signals are often leaked from the send path to the receive
path through a hybrid transformer, which converts 4-wire analog to or from 2-wire analog.
Two characteristics of echo are loudness and delay. The louder the echo or the longer the round-trip delay, the more annoying it is for the users.
Cisco MFT dedicated ECAN modules are designed to help reduce echo in networks where long delays are present in the sections of the networks
that create the echo problems.
An echo canceller is a component of a voice gateway that faces the public-switched-telephone network (PSTN) side of the gateway and reduces the
level of echoes that have leaked from the transmit (Tx) path into the receive (Rx) path. The portion of the network connected to the PSTN side of the
gateway, including all switches, multiplexers, private branch exchanges (PBXs), other IP networks, and analog or IP phones, is called the tail circuit.
The analog component of the tail circuit, known as the analog tail circuit, is the source of all potential echoes on this side of the network. An echo
canceller removes the echo portion of the signal coming out of the tail circuit and heading back into the WAN. Many voice-over-IP (VoIP) networks
have two PSTN or basic-telephone-service (POTS) components. In these cases, another gateway facing the tail circuit on the other end of the
network will be responsible for canceling the echo coming from that direction.