Nortel Networks NN43001-563 - Manual (Page 84)

84 System description
Codec profiles
Codec refers to the voice coding and compression algorithm used by the
DSPs on the IP trunk card. The G.XXX series of codecs are standards
defined by the International Telecommunications Union (ITU). Different
codecs have different QoS and compression properties. The specific
codecs and the order in which they are to be used for codec negotiation is
configured in TM 3.1.
When configuring the IP Trunk 3.01 (and later) node in TM 3.1, select the
image containing the needed codecs, and the preferred codec negotiation
order. The final codec used is determined by the codec negotiation process
with the far end during call setup. Parameters can be configured for each
codec in an image.
IP Trunk 3.01 (and later) supports the following codecs:
• G.711
• G.729AB
• G.729B
• G.723.1
G.711
The G.711 codec delivers "toll quality" audio at 64 kbit/s. This codec is
optimal for speech quality, as it has the smallest delay and is resilient
to channel errors. However, it uses the largest bandwidth. The G.711
codec is the default codec if the preferred codec of the originating node
is not available on the destination IP Trunk 3.01 (and later) node. Voice
Activity Detection/Silence Suppression is configurable through TM 3.1. An
ITG-Pentium 24-port trunk card supports 24 channels per card with G.711.
A Media Card 32-port trunk card supports 32 channels per card with G.711.
G.729AB
The G.729AB codec is the default preferred codec when adding a new IP
Trunk 3.01 (and later) node in TM 3.1. This codec provides near toll-quality
voice at a low delay. The G.729AB codec uses compression at 8 kbit/s (8:1
compression rate). Optional B Voice Activity Detection/Silence Suppression
is configurable through TM 3.1. An ITG-Pentium 24-port trunk card supports
24 channels per card with G.729AB. A Media Card 32-port trunk card
supports 32 channels per card with G.729AB.
G.729B
The G.729B codec uses compression at 8 kbit/s (8:1 compression rate).
Optional B Voice Activity Detection/Silence Suppression is configurable
through TM 3.1. An ITG-Pentium 24-port trunk card supports only 16
channels per card with G.729B due to higher DSP resources required for
this codec. The Media Card 32-port trunk card does not support G.729B.
Nortel Communication Server 1000
IP Trunk Fundamentals
NN43001-563 01.01 Standard
Release 5.0 30 May 2007
Copyright © 2007, Nortel Networks
.