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Voice over IP (VoIP)
The following table provides an overview of the required bandwidth for a tele-
phone connection with various parameter settings. The values apply to half-
duplex ethernet; for full-duplex the values can be halved.
Required bandwidth (kbit/s) with respect to Packet Length and Codec
Packet
G.711 (not
Length (ms)
compressed)
20
180.8
30
40
50
60
70
80
You will require a licence with which you can activate the G.729 codec for oper-
ation (in the System: Licences menu).
9.2.3 Voice Quality
The achievable voice quality depends on various factors. It is possible to optimise
voice-data transmission on an existing network using the available configuration
settings. Measuring the network quality may also help. The following comparison
provides a guide to voice quality with specific quality levels:
Quality Levels for Voice Transmission with VoIP
Level
Voice Comprehensibility
1
Very Good
2
Good
G.729A
approx. 8 kbit
/s
68.8
51.2
42.4
37.12
33.6
31.09
29.2
Note: To ensure SIP compatibility, the older system tele-
phones OpenPhone 63 IP and OpenPhone 65 IP do not sup-
port the G.723 codec any more.
G.723.1
6.3 kbit/s
48.0
30.4
Comparable to
ISDN
DECT
Fundamentals
G.723.1
5.3 kbit/s
45.9
28.3
109
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