Hello again everyone,
I have done a little more investigation into the problem of why voice
calls aren't working in my OsmoCNI+nanoBTS setup. Here are my configs
and a syslog excerpt showing the problem:
https://www.freecalypso.org/members/falcon/osmo-cni/t200-fail-config+log.ta…
The behaviour I'm seeing seems to point toward a bug in nanoBTS fw,
probably tickled by the officially-unsupported combo of running it
with OsmoCNI instead of whatever proprietary sw ip.access requires
officially.
Looking at the OsmoBSC log (captured with maximum verbosity in the
posted syslog excerpt), the behaviour I'm seeing is that the BTS
appears to stop successfully receiving transmissions from the MS when
the lchan moves from SDCCH to TCH. For as long as the conversation
with the MS stays on SDCCH, everything is happy: measurement reports
from the BTS in the OsmoBSC log look good (including DL measurements
received from the MS), and successful LU/SMS/USSD prove that all LAPDm
control traffic passes as it should. But the moment the lchan moves
from SDCCH to TCH, all subsequent measurement reports in the OsmoBSC
log show "NOT VALID" for the part that comes from MS, and the UL RXQ
numbers reported by the BTS are also highly suspect - usually 7. And
then the BTS signals an error to the BSC, saying that T200 expired
N200+1 times - whatever LAPDm exchange it is trying to do with the MS
times out when the BTS is failing to receive anything sent by the MS.
And then a little further down the road, the BTS declares Radio Link
Failure, probably on the basis of not receiving any SACCH from the MS.
All of this misbehaviour is visible in the syslog excerpt contained in
the tarball linked above.
If the problem is indeed a bug in nanoBTS fw that can't be troubleshot
because it's a black box, then I may be SOL until I can shell out big
bucks for a sysmoBTS unit to replace this nanoBTS. However, I am
doing my due diligence first by demonstrating to the community the
nanoBTS misbehaviour I'm seeing, and asking in the hope that someone
might know of a solution. These nanoBTS units are extremely attractive
for economic reasons: it's a box that is purpose-made to be a GSM BTS,
rather than just an SDR from which you have to build a BTS yourself
with major extra effort, yet they are often available for dirt-cheap
prices - hence it would be really awesome to have these units actually
work with OsmoCNI, including voice calls.
The part that I find difficult to reconcile is that these nanoBTS
units did once work with OpenBSC/OsmoNITB/OsmoCNI, and presumably
voice calls worked too, otherwise there would have been warnings all
over the docs that only SDCCH-based services work. So what has
changed between the setups of other people in the past who had working
Osmocom+nanoBTS combos and my present setup in which the BTS goes
bonkers when the lchan moves from SDCCH to TCH? Could it be that my
nanoBTS fw version is newer or older or otherwise different from what
Osmocom people got to work in the past through reverse eng? Or is it
perhaps the case that today's OsmoCNI sw is not tested as much with
nanoBTS any more because the community moved on to OsmoBTS-based
solutions, meaning either sysmoBTS or SDR platforms?
Here are the versions of all Osmocom CNI components and supporting
libraries I am currently running:
libasn1c-0.9.33
libdbi-0.9.0
libdbi-drivers-0.9.0
libosmo-abis-1.2.0
libosmo-netif-1.1.0
libosmo-sccp-1.5.0
libosmocore-1.6.0
libsmpp34-1.14.1
lksctp-tools-1.0.17
osmo-bsc-1.8.1
osmo-hlr-1.4.0
osmo-mgw-1.9.0
osmo-msc-1.8.0
(Any non-Osmocom components in the list above are external libraries
which were required for getting OsmoCNI to compile and run, but which
were not already present in Slackware 14.2 and which I thus count as
being strictly OsmoCNI dependencies.)
My nanoBTS (PCS1900) hw and fw versions are:
Equipment_Version='165b029_49'
Software_Version='168d462_v200b207d0'
Is there anyone in this community who still runs with nanoBTS hw
(hasn't moved on to OsmoBTS-based sysmoBTS or SDR) and who has working
voice calls? If any such successful Osmocom+nanoBTS users exist, may
you perhaps be able and willing to share the following:
* Your Osmocom sw version - the closer it is to latest OsmoCNI
releases, the better;
* Your nanoBTS hw and fw versions;
* Your working configs for OsmoBSC and other Osmocom sw components,
with any private stuff redacted out, obviously.
TIA,
Mychaela