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A.1.2 Bandwidth Requirements
When using the SIP-GW4 card, you must ensure that the WAN has enough bandwidth to support VoIP
communications. Refer to the table below and ensure that the sum of the required bandwidth for each channel
is smaller than the amount the WAN (e.g., ADSL network) can provide.
Note that the amount in the table is only a guide. Subscribe to a network that has enough bandwidth. If the
amount of bandwidth required for VoIP communications is larger than what the network can accommodate,
speech quality will be compromised.
Note
If you use an ADSL network, note that it has a narrow bandwidth for outgoing IP packets. Specify the
bandwidth of the ADSL network for outgoing IP packets in "3.5.5 Bandwidth".
Required Bandwidth for Each Channel
The required bandwidth depends on what combination of CODECs and packet sending interval is used. Keep
in mind the following points about the type of CODEC and packet sending interval, in terms of the speech
quality:
•
The speech quality of the CODECs varies as follows: G.711 (High), G.729 (Low)
•
The shorter the packet sending interval, the higher the speech quality.
•
The higher the speech quality the SIP-GW4 card provides, the more bandwidth the WAN requires.
CODEC
20 ms
G.711
90.4 kbps
G.729
34.4 kbps
Document Version 2008-10
Packet Sending Interval
30 ms
40 ms
81.6 kbps
77.2 kbps
25.6 kbps
21.2 kbps
A.1.2 Bandwidth Requirements
50 ms
60 ms
74.6 kbps
72.8 kbps
18.6 kbps
16.8 kbps
Installation Manual
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