System information Page 55 of 206
WLAN IP Telephony Installation and Configuration
Codecs
G.711, G.729 A, and G.729B codecs are supported. The RTP packets which
transit between the wireless handsets and the WLAN IP Telephony Manager
2245 always contain 30 msecs of voice. The WLAN IP Telephony Manager
2245 repackages the voice data to the correct packet size. The jitter buffer is
always configured to 70 msecs and any UNIStim messages which configure
the jitter buffer are ignored.
If it is necessary for the IP Phone to use a codec that is not supported on the
wireless handsets, such as G.723.1, then the wireless handsets must be
configured on their own separate node.
If a remote endpoint is configured for G.723.1 as the Best Bandwidth (BB)
Codec and G.711 as the Best Quality (BQ) Codec, (G.729 is not configured),
the media path negotiates to G.711 which may have unexpected
consequences on a narrow-band link.
Jitter buffer
The 2210 and 2211 do not support a configurable jitter buffer. If they receive
the “Jitter Buffer Configuration” UNIStim message, the command is ignored.
The jitter buffer is fixed at 70 msecs.
There are two implications of a fixed jitter buffer setting:
• If the system jitter buffer setting is less than 70 msec (default is 50 msec),
there will be a slightly longer delay in the IP Phone “receive” direction.
• If the system jitter buffer setting is longer than 70 msec to accommodate
severe network jitter, there could be slightly higher packet loss in the IP
Phone “receive” direction.
IMPORTANT!
If the wireless handset is registered to the same LTPS as the IP Phones,
then configure only the subset of codecs which is supported by both the
wireless handsets and the IP Phones.
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