This is merely a historical archive of years 2008-2021, before the migration to mailman3.
A maintained and still updated list archive can be found at https://lists.osmocom.org/hyperkitty/list/OpenBSC@lists.osmocom.org/.
Dieter Spaar spaar at mirider.augusta.deHello Philipp,
On Sun, 26 Jul 2009 21:43:22 +0200, "dexter" <zero-kelvin at gmx.de> wrote:
>
> I have no experience in those things, i never connected a sender and a
> receiver directly for measurement proposes. I am afraid to damage BTS
> and/or MS by trying the first solution.
If you want to connect the BTS and an MS directly, you have to use
an attenuator to reduce the signal to some "reasonable" level. To
give you some numbers about "reasonable": The maximum RF output level
of two different GSM tester which are intended for direct connection
to an MS are -14 dBm for one of them and -40 dBm for the other. To be
on the safe side I would make sure that the level is below -40 dBm,
this is more than enough for good receiption (poor receiption is around
-100 dBm). If the signal is too strong, you can damage the MS and/or BTS.
Please note that I have not tried to connect a BTS and an MS yet, my
experience comes from the GSM testers only.
One problem I see with this approach is how to handle the separate
RX and TX connectors of the BS-11.
> What do you think, what would you do? How do you ensure that you do not
> interfere with the with the official GSM networks? I think sometimes it
> would be very nice to make 100% sure that no HF signals leave the desktop.
I you can't make sure that no RF signal is emitted, you can at least try
to cause as little trouble as possible:
- use a GSM channel which is not used by an official network, make sure
that there is at least one free guard channel in between the channel
you use and the official channels.
- set the power level of the BTS to its minimum (0.03 Watt for the BS-11)
and set the NM_ATT_RF_MAXPOWR_R attribute to its maximum (6 for the
BS-11). For the BS-11 the RF output level should then be around 1 dBm.
- If you want to further reduce the BTS power, you can put an attenuator
between antenna and TX output.
- for the MS make sure that the power class is as low as possible when
activatig a channel.
- set the power for RACH access to a low level (in SYSTEM INFORMATION
TYPE 3 and 4).
- use an MCC and MNC which is not an official one.
- only allow a know MS to register on your network.
- To make sure that normal MSs won't be able to see your network,
you can set the cell to "barred". However you then need a special
MS to test, for example the Nokia Network Monitor allows to
set the MS in a mode which allows to access barred cells. And
with a special Test SIM it should be possible to access such
a cell with other phones too (the "cell test" operation mode
has to be enabled on the SIM).
Best regards,
Dieter
--
Dieter Spaar, Germany spaar at mirider.augusta.de