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.tar...
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