Nortel NN43001-504 Installation Manual page 197

Voice-quality issues
The transport, or IP data network, are the most likely causes of voice-quality
issues. In some circumstances, product issues (such as echo or Digital
Signal Processor (DSP) errors) can cause problems with voice quality.
The data network does not introduce echo into a conversation, but it can
enhance existing echo.
In a converged environment, voice competes with data traffic for bandwidth
and processor time. As a result, the IP data network must be optimized for
efficient processing of the real-time voice packets.
Table 25
Typical voice quality issues
Issue
Choppy voice
First or last part
of word syllables
missing
Clicks or pops
heard during
conversation
One-way speech
path
Voice delay
(users talk over
each other)
Echo
Copyright © 2004-2007, Nortel Networks
.
Type of
issue
Network
(usually)
Product
(usually)
Network
Product
Network
Network
Product
(primarily)
Nortel Communication Server 1000
WLAN IP Telephony Installation and Commissioning
NN43001-504 01.02 Standard
Release 5.0 15 June 2007
Check for
Network delay caused by:
Excessive intermittent end-to-end round-trip
delay
Congestion
Queuing
Network configuration errors
Packet loss caused by:
Physical errors in data network
Network configuration errors
Incorrect Voice Activity Detection (VAD)
configuration
OR
Incorrect AP configuration (if the issue occurs
only during roaming)
Packet loss, cause depends on the codec
IP routing issues
Congestion issues
Incorrect configuration
Excessive network delay
Data network can enhance echo
Troubleshooting 197