2N PRI Gateways - User Manual - Manual (Page 34)

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7.3. Installation Conditions
The following conditions must be met during system installation:
- appropriate location (enough free space);
- GSM signal intensity (minimum signal level: –80db). As GSM signal intensity meter you can
use NET monitor on some mobile phone (e.g. Nokia, Siemens)
- un-overloadable GSM cells into which GSM gate modules are logged (please keep in mind
that full traffic will make up to 30 calls in one time (according of configuration of the
gateway)!
- no strong electromagnetic radiation on the system installation site;
- no strong reflections in antennas installation place
- the ISDN PRI connection must be configured properly and meet ITU-T Q.931-EDSS1 and
related recommendations.
7.4. Potential GSM Network Problems
The PRIGW works reliably even under a 100% load. The following problems may be caused by
GSM networks:
1. The GSM modules cannot log in, log in slowly or log out occasionally. This problem can
have two causes:
• The GSM signal level is low – the recommended minimum signal level is
approximately
-80dB, if lower, the GSM antenna location must be changed.
• The GSM cell into which the modules try to log is overloaded – if you use directional
antennas, you can direct them to more GSM cells than one. The possibility to choose
a cell by directing your antenna is considerably limited or eliminated in municipal or
densely populated areas where multiple signal reflections occur. It is also difficult to
select a cell where the cells lie in a straight line before and behind the antenna. If no
selection can be made, you have to use another available GSM provider.
CAUTION!
You are recommended to use 32 channels at most on one installation site for one
GSM provider to avoid GSM network overload problems on the installation site.
2. One of the GSM modules is permanently logged-out or fails to receive incoming calls –
this problem indicates a GSM network overload due to heavy traffic. You can eliminate
this problem by the above mentioned solutions or extend the “relaxing time“ – i.e. the
delay between two calls via one GSM module (the recommended value is 2 seconds).
In case any of the GSM modules cannot log in the network even after reset, your GSM
provider may have located the SIM card but refused to log it in the network because
either too many calls are made using this card, or the SIM card keeps logged in the
same GSM cell and the same GSM module for too long. This problem can be solved by
occasional replacement of SIM cards between modules.