Hi Alina,
How can I utilize the iCE40 E1 USB adapter to
transition from E1 to IP in a
GSM network, connecting a physical Siemens BSC (which has a BTS
connected) to OsmoMSC?
Only the BTS and BSC are physical.
Did you say that you have only one BTS connected to your Siemens BSC?
I am not certain whether or not OsmoMSC has any support for talking to
non-Osmocom BSCs: I know that Sysmocom support (for their commercial
customers) the arrangement where OsmoBSC talks to pre-existing
proprietary MSCs, but I don't know if there is any support for going
the other way around. I am reasonably certain that OsmoMSC plus its
associated OsmoMGW cannot talk to a BSC via TDM, be it osmo-e1d or
otherwise - OsmoMSC+OsmoMGW combo is designed to talk 3GPP AoIP to
BSCs, not the TDM version.
However, OsmoBSC plus its associated OsmoMGW instance do support the
possibility of driving E1-based legacy BTS gear. Therefore, if you
have only one E1-based (also Siemens?) BTS connected to your Siemens
BSC, you may be able to migrate that BTS to Osmocom CNI environment by
taking the legacy BSC out of the equation and making the E1-to-IP
transition at the BSC (OsmoBSC+OsmoMGW) rather than at the MSC.
What are the actual models of your BTS and BSC? The specific BTS model
will matter for OsmoBSC support, whereas the model of Siemens BSC is
more for general education.
I also have to disclose that I have an ulterior motive in helping you
with this project - I have been searching the world high and low,
looking for someone who has some kind of legacy GSM BSC (at opposed to
just BTS) in operation, and you may have what I've been looking for.
Does your Siemens BSC include a TRAU component? If you don't know
what GSM TRAU is, let me phrase the question differently: the voice
channels that come out of your BSC toward the A interface (toward the
MSC), what do they look like? Are they like Abis, carrying GSM-encoded
speech, or are they full 64 kbit/s voice channels carrying G.711 A-law?
(Either A-law or mu-law would be fine, but I am guessing A-law based
on your time zone and inferred geopolitical location.)
If your Siemens BSC puts out G.711 A-law (or mu-law), then it has to
include a TRAU component, and you are that precious unicorn I've been
looking for! Do you have access to the management interface of that
BSC, where one would presumably find an option to enable or disable
TFO? Is it enabled, or can you enable it?
If your BSC is indeed TRAU-equipped and TFO-capable, I would be very
happy to not only help you free-of-charge in whatever ways I can with
your migration project, but possibly also pay you generously if we can
work out some mechanism through which you could let me remotely play
with that BSC of yours.
Sincerely,
Mychaela Nadezhda Falconia
(aka Nadezhda Mikhailovna in Russian)
GSM/2G network operator, extreme GSM & retro-telecom enthusiast
and occasional Osmocom contributor, based in USA