Hi,
First, what Pau said.
I would add that I think it's unlikely you're actually seeing a direct
correlation between your ignored RACH and the notification that the PCU
is not connected. Ah, If only I had a satoshi or go on, even a penny,
for everytime I've seen an assumption that a "normal" log message is
related to a problem being observed.
Normally I would expect to see that log due to a RACH for packet access,
(more logging at level debug would tell you) and I was going to ask if
you have GPRS configured in your osmo-bsc config to something other than
none, but then thinking about it, IIRC, we modify the System Info when
the PCU is disconnected and don't advertise GPRS on the cell anyway, so
you shouldn't be getting packet access requests. Doesn't matter anyway,
It's not the cause of your lack of success with USSD
Ah!!.. second thing just jumped into my memory from osmo-trx days, if
you turn up rx-gain enough or have some RF noise generation around, you
might be getting a whole lot of fake "RACH" in the logs.
I don't have and have never used a B205-mini, and I haven't even read
the specs, but the B200 was just mentioned on IRC and so I thought it
might be worth telling you that years ago, I used the USRP N210 with
osmo-trx-uhd/osmo-bts-trx and my observation was:
GPS Locked clock = reliable operations.
No GPS locked clock = all kind of problems, not least of which being,
precisely what you describe, BTS not "seeing" the RACH. (or maybe no UE
response to the assign)
I wonder, come to think of it now, maybe you have set osmotrx maxdly?
I'm not sure what the default is, but maybe, you might have more luck
increasing it. but that's just something that occurs to me right now.
Probably not going to help if you're that far off.
In the end, you need to do what Pau said. In fact, if you log the
relevant levels at debug and capture and inspect some traffic, you'll
probably have a much more clear idea of what is happening.
Also, then you can inspect your SI, either with gsmtap or off-the air
with osmocom-bb or an rtl-sdr/grgsm_livemon, you will confirm if you are
advertising PS or not.
k/