15 Jan
2018
15 Jan
'18
3:14 p.m.
Thanks Alex.
Do you know if this GPSDO would work:
https://www.ebay.com/itm/GPS-Receiver-GPSDO-10MHz-1PPS-GPS-Disciplined-Cloc…
Feature:
POWER:DC12V 1.5A
GPS ANT POWER:DC3.3V
1PPS OUTPUT:Square WAVE,3.3Vpp
10M OUTPUT :SINE WAVE,1Vrms (13dBm+-2dB)
RS232 OUTPUT:GPS NMEA SIGNAL
SIZE:W*H*D=107*55*120mm
ACCESSORY:AC110-220-DC12V ADAPTER,GPS ANT.
Thanks!
Rafael Diniz
On 01/15/2018 11:46 AM, Alexander Huemer wrote:
Hi!
On Mon, Jan 15, 2018 at 10:07:50AM -0200, Rafael Diniz wrote:
I'm doing some tests with an old USRP2 +
RF900 daughterboard, and I get
a very unstable system (with osmo-trx, osmo-bts-trx and osmo-nitb) -
some phones can connect, some dont. I'd like to identify the problem -
is it a bad GBit ethernet or the lack of a GPSDO connected to the 10MHz
port?
According to [1] the clock accuracy of the USRP2 is 20ppm.
GSM 05.10[2] states that accuracy has to be 0.05ppm or better.
That's quite a bit off, so I don't think it's surprising that you don't
see much stability.
I believe it makes a difference whether the MSs see other BTSs or not.
If the MSs see only the unstable BTS it is more likely to work out.
Not sure what is the case here.
And after some time, osmo-trx stops reading
samples from UHD and
osmo-bts-trx shuts down.
Not sure if that is a possible effect of an unstable clock. I could
imagine so, but again, I am not sure.
I guess the obvious advice is to attach a more stable clock and try
again.
Kind regards,
-Alex
[1] http://openbts.org/w/index.php?title=Ettus_Research_USRP
[2] http://www.etsi.org/deliver/etsi_gts/05/0510/05.00.00_60/gsmts_0510v050000p…