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Voice over IP (VoIP)
9.3
Media Gateway (MGW)
The Media Gateway transforms VoIP voice data into PCM audio data. This function
converts voice data between VoIP telephones and all other terminal types.
Without the Media Gateway, VoIP telephones can only exchange call data directly
with other VoIP telephones. Media Gateway functionality is also required for pro-
ducing dial tones and making external phone calls with a VoIP telephone. A Media
gateway card makes 8 channels available. One Media gateway channel should be
available for a maximum of 3 VoIP terminals.
The Media Gateway also takes over the routing function for external SIP connec-
tions, making 8 external SIP connections possible.
9.3.1 Software MGW
The system software of the OpenCom 100 provides one limited Media Gateway
function. Depending on system process utilisation and available system memory,
up to four MGW channels are available. The software MGW function will be auto-
matically activated when no Media Gateway card is present.
Using the OpenCom 131 no Media Gateway cards can be used. Here only the
software MGW function can be used for VoIP.
The Media Gateway function implemented in system software has the following
limitations:
■
Up to four channels can be used simultaneously.
■
The MGW channels are not compressed, so only the G.711 codec is available.
■
There is no echo suppression.
■
Voice quality may be reduced during high system utilisation.
For optimal call quality and high availability, you should consider using a MGW
interface card (see also MGW Interface Card starting on page 114).
Media Gateway (MGW)
113
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