Hello OsmoDevCon participants,
As much as I would love to join you this weekend, I am currently unable to travel outside of USA+Canada+Mexico territory - that's what happens when you lose citizenship in your birth country without acquiring new citizenship in the country of residence...
However, I hear that there will be an Ericsson BTS set up in the meeting room at ODC, and I wonder if someone among the attendees could perform a few experiments for me which I would have performed myself if I could attend.
I am seeking a full capture of the uplink output from the BTS on a TRAU sub-timeslot (or capture the whole TS to make it easier) for a call, in all 3 classic codecs: FR, HR, EFR. With all 3 codecs, I am looking for BTS UL output with 'dtx uplink' enabled in OsmoBSC config, and with these two tricks performed during the test call:
a) alternate between speaking into the mic and silence, so the MS will go into some DTXu pauses;
b) press some DTMF keys during speech (not during silence) to exercise the scenario of active speech frames being stolen for FACCH.
My main interest is to see what the BTS puts into traffic payload bits (alongside with BFI=1) when absolutely nothing was received on UL (no burst midables picked up) or when the received UL was FACCH - but of course I might spot something else that looks interesting if and when I get to look at some TRAU-UL captures with my own eyes.
I have never owned or laid my hands on any kind of T1/E1 BTS, hence I have read the specs, read Osmocom code, but have no actual experience seeing what real historical BTS implementations actually do. Hence I am looking for some real UL output captures from _some_ E1 BTS.
Note how I said "some" E1 BTS: at this point I would be happy to see a capture from any E1 BTS, no matter which vendor. I am asking about Ericsson right now simply because I keep hearing that there will be an Ericsson BTS in the ODC meeting room, but if someone has a Nokia BTS available/accessible for play, I would be just as happy with a UL capture from that one. In fact, a Nokia BTS UL capture might be even more interesting: I am in the process of acquiring a Nokia TCSM2 system (Nokia's term for the bank of TRAUs, 2nd generation), and if I had captured UL output from Nokia Abis, I could feed it directly to the Ater input of the TRAU. But back to Ericsson BTS at ODC, given how well GSM 08.60 format is standardized, if I had a UL capture from Ericsson, it would probably work just as fine as input to Nokia TRAU - and of course I can always tweak the bits in my TRAU experiments.
If someone at OsmoDevCon could do these E1 BTS experiments for me, I would be very grateful.
TIA, Mychaela
Hi Mychaela,
just a quick response here ... OsmoDevCon was quite busy with communication, the amount of time spent hacking on things low in comparison. We saw a fax over CSD, an HF link to Hannover, and a bit of 4G testing (VoLTE IIRC); otherwise, there was not a single moment left -- could say the remote message queue was blocked by local I/O.
~N
On Wed, May 01, 2024 at 10:58:18PM -0800, Mychaela Falconia wrote:
Hello OsmoDevCon participants,
As much as I would love to join you this weekend, I am currently unable to travel outside of USA+Canada+Mexico territory - that's what happens when you lose citizenship in your birth country without acquiring new citizenship in the country of residence...
However, I hear that there will be an Ericsson BTS set up in the meeting room at ODC, and I wonder if someone among the attendees could perform a few experiments for me which I would have performed myself if I could attend.
I am seeking a full capture of the uplink output from the BTS on a TRAU sub-timeslot (or capture the whole TS to make it easier) for a call, in all 3 classic codecs: FR, HR, EFR. With all 3 codecs, I am looking for BTS UL output with 'dtx uplink' enabled in OsmoBSC config, and with these two tricks performed during the test call:
a) alternate between speaking into the mic and silence, so the MS will go into some DTXu pauses;
b) press some DTMF keys during speech (not during silence) to exercise the scenario of active speech frames being stolen for FACCH.
My main interest is to see what the BTS puts into traffic payload bits (alongside with BFI=1) when absolutely nothing was received on UL (no burst midables picked up) or when the received UL was FACCH - but of course I might spot something else that looks interesting if and when I get to look at some TRAU-UL captures with my own eyes.
I have never owned or laid my hands on any kind of T1/E1 BTS, hence I have read the specs, read Osmocom code, but have no actual experience seeing what real historical BTS implementations actually do. Hence I am looking for some real UL output captures from _some_ E1 BTS.
Note how I said "some" E1 BTS: at this point I would be happy to see a capture from any E1 BTS, no matter which vendor. I am asking about Ericsson right now simply because I keep hearing that there will be an Ericsson BTS in the ODC meeting room, but if someone has a Nokia BTS available/accessible for play, I would be just as happy with a UL capture from that one. In fact, a Nokia BTS UL capture might be even more interesting: I am in the process of acquiring a Nokia TCSM2 system (Nokia's term for the bank of TRAUs, 2nd generation), and if I had captured UL output from Nokia Abis, I could feed it directly to the Ater input of the TRAU. But back to Ericsson BTS at ODC, given how well GSM 08.60 format is standardized, if I had a UL capture from Ericsson, it would probably work just as fine as input to Nokia TRAU - and of course I can always tweak the bits in my TRAU experiments.
If someone at OsmoDevCon could do these E1 BTS experiments for me, I would be very grateful.
TIA, Mychaela
-
Mychaela Falconia -
Neels Hofmeyr