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190 Troubleshooting WLAN IP Telephony installations
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
Type of
issue Check for
Network delay caused by:
Excessive intermittent end-to-end round-trip
delay
Congestion
Queuing
Network configuration errors
Choppy voice Network
(usually)
Packet loss caused by:
Physical errors in data network
Network configuration errors
First or last part
of word syllables
missing
Product
(usually)
Incorrect Voice Activity Detection (VAD)
configuration
OR
Incorrect AP configuration (if the issue occurs
only during roaming)
Clicks or pops
heard during
conversation
Packet loss, cause depends on the codec
Network IP routing issues
Congestion issues
One-way speech
path
Product Incorrect configuration
Voice delay
(users talk over
each other)
Network Excessive network delay
NetworkEcho
Product
(primarily)
Data network can enhance echo
Nortel Communication Server 1000
WLAN IP Telephony Installation and Commissioning
NN43001-504 03.04 Standard
23 September 2008
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.