2N BRI Lite/Enterprise v1.1 - Manual (Page 15)

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Description and
Installation
This section describes the 2N ® BRI Enterprise / 2N® BRI Lite product and its
installation.
Here is what you can find in this section:
 Before You Start
 Brief Installation Guide
 Available ISDN BRI Extension Configurations
 IP Voice Transmission
 IP Voice Transmission
 Speech Encoding Methods
Voice transmission is strictly separated from signalling in VoIP networks. Modern VoIP
networks mostly use the RTP (Realtime Transport Protocol) for voice transmission. The
purpose of the RTP is only to transmit data (voice) from a source to a destination at
real time.
Codecs are used to save the channel data capacity. Codecs process the voice signal
using variable algorithms to minimise the volume of user data. The degree of
compression used by the codec affects the quality of voice transmission. Thus, the
better voice transmission is required, the wider data range (the higher transmission
rate) is needed. The MOS (Mean Opinion Score) scale is used for rating voice
transmission quality, where 1 means the worst and 5 the best quality. For a survey of
the codecs supported by 2N BRI gateway refer to the table below.
Codecs supported
Standard Algorithm Transmission rate [kbps] MOS
G.711a PCM 64 4.1
G.711u PCM 64 4.1
G.729 CS-ACELP 8 3.92