INTEROPERABILITY NOW
6-1
6
ARA-1 FAQ (Frequently Asked Questions)
6.1
General
This section provides answers to some frequently asked questions about the installation and
operation of the ARA-1.
How much network bandwidth does the ARA-1 consume?
The ARA-1 bandwidth usage varies depending on the application. When COR is inactive and
silence suppression is enabled (or VOX is enabled and no audio is being transmitted across the
link), the bandwidth usage is essentially zero. During an active call when COR is activated and
the GSM voice compression method is used, audio will be sent across the link in each direction
at approximately 35 Kbps. The G.711u vocoder will require approximately 86 Kbps. The unit
uses the same bandwidth as a SIP Phone using the same vocoders.
Can I use the ARA-1 on a dialup connection?
No. The ARA-1’s network connection is via Ethernet. Most dialup (telephone line) modems only
provide RS-232 connections, but even if an Ethernet connection to a dialup is available, the ARA-
1 may not operate properly since the connection speed is not guaranteed on a dialup connection.
Poor telephone lines or varying line conditions may cause a dialup modem to reduce its
connection speed without the user being aware of this condition. For this and other reasons,
dialup connections are not supported by the ARA-1.
My application does not provide a COR line. What should I do?
COR is usually obtained from a radio and indicates that a signal is being received. If you do not
have a COR line, you can use
VOX
mode.
VOX
mode essentially derives a COR signal from the
presence of incoming audio from the radio.
I have a 100 Mbps Ethernet. Can I connect the 10 Mbps port on the ARA-1 to my network?
Most 100 Mbps equipment (hubs, switches, routers) will work with either a 10 Mbps or
100 Mbps connection, so it should work without any problems. Check with your network
administrator if you are unsure about your network equipment capabilities.
Where can I find a description of the VoIP protocols used by the ARA-1?
The ARA-1 uses the following open protocols: SIP, SDP, RTP, and STUN. These protocols are
available from
http://www.ietf.org
.