Hi Dan,
Firstly I don't know if the list is still active or not.
I likewise don't know if openbsc ML is still functioning or not - but I am able to converse with you since you listed me as a direct email recipient. :)
We are trying again to connect the Siemens BTS to OsmoBSC.
Sounds like a fun project - but I'm sure you are aware that an extra 2 y have passed since the last time you brought it up on openbsc ML.
I suppose that the protocol that our BTS is speaking is very similar to the BS-11 one
Please correct me if I misunderstood you, but based on what you and Alina wrote so far, you are currently _hoping_ that the Abis dialect spoken by your Siemens BTS will be similar to the already supported BS-11 - but it is only a hope currently, not a confirmed fact yet.
so it will be easy to take the code from there and modify it.
*If* the Abis dialect proves to be similar enough - but that part needs to be confirmed first.
What we are trying to do now is to trace the initialization of BTS when is connected the Siemens BSC that we have and try to add the message sequence to the code of OsmoBSC.
You do have the advantage of having a real Siemens BSC - certainly use this advantage!
The next question is exactly how to sniff the communication between your Siemens BSC and BTS. I saw your woes regarding K1297-G20 test instruments that no longer boot; I wish I could help, but I never worked with such instruments (never even saw one with my own eyes) and I don't have any help to offer there.
There is, however, this alternative:
https://osmocom.org/projects/e1-t1-adapter/wiki/E1_tracer
The linked wiki page says "Fully assembled products based on this hardware are going to be made available by sysmocom" - but I don't see this product in the webshop. You can try asking Harald, or bite the bullet and build it yourself based on the published design files.
I remember that you are interested in the configuration that we have.
Please keep in mind that our last exchange was in 2024 - a lot of new developments happened over the past 2 y. :-) Back in the early summer of 2024 I was indeed interested in your BSC setup for its TRAU component, specifically hoping that you might have a TFO-capable TRAU that might be amenable to remote play. However, my quest for a TFO-capable TRAU has been satisfied since then: I now have a Nokia TCSM2 setup in my lab, which includes TFO support for FR, HR and EFR codecs.
What do you think about this approach?
If by "this approach" you mean sniffing communication between your Siemens BSC and BTS, and then getting OsmoBSC to talk to the same BTS instead, I say yes, it is a good approach.
I also remember that you previously considered another approach where you would connect your Siemens BSC to OsmoMSC, which would require significant work on OsmoMSC to talk to E1-based BSCs. Comparing the two approaches, the approach of OsmoBSC driving your Siemens BTS has the advantage of sharing/reusing the work of American 2G Cooperative.
In the 2 y period that elapsed since our last exchange, I co-founded a cooperative that seeks to operate a new GSM/2G network in some rural locations in USA, and we are moving ahead with Nokia Flexi Multiradio (sourced from the surplus market) as our choice of BTS hardware. Our architecture includes having OsmoBSC drive this E1-based BTS, with an osmo-bsc instance at each cell site, connecting to an MSC via a WireGuard tunnel running over public Internet. Each of our MSCs will consist of an osmo-msc process plus a bunch of our own add-ons described in our Hera MSC architecture spec.
If you manage to connect your Siemens BTS to OsmoBSC, you will be able to benefit from all of the improvements I've made to the subsystem of OsmoBSC driving E1-based BTS, including the new tw-e1abis-mgw that partially replaces osmo-mgw in E1 role. And when Hera MSC (suite of add-ons to OsmoMSC) becomes a reality (hoping to get to it this year), you will likewise be able to run this very powerful MSC together with OsmoBSC, tw-e1abis-mgw and your E1-based Siemens BTS.
OTOH, if you pursue the alternative approach of extending OsmoMSC to talk to an existing E1-based BSC (Siemens or any other), while such project would be very interesting and exciting from philosophical PoV, there won't be any real opportunity to share work in common with American 2G Cooperative. While I love the idea of using real historical BSCs as a philosophical (or lab!) exercise, it is impractical for the needs of A2GC. Surplus telecom hardware is inherently scarce and hard to obtain, plus it has the requirement of physical space and TDM transport to cell sites. When the BSC is reduced to a piece of software, as OsmoBSC is, it becomes trivial to outfit each individual cell site with its own BSC, with the physical hw of this per-site BSC being a Raspberry Pi or some other SBC of negligible physical size and power requirements, compared to the macrocell BTS it will sit next to. OTOH, a traditional BSC from any of the legacy vendors requires a physical building somewhere to house it, plus physical leased lines to haul Abis from each of many cell sites to this BSC hut - completely unaffordable to our tiny co-op. Contrast with our chosen approach where each cell site needs only a regular consumer-grade Internet connection, whatever happens to be available at the site, which can even be Starlink if nothing else is available on a barren mountaintop or wherever.
Hopefully I have given you some food for thought.
M~