Osmocom + USRP

Harald Welte laforge at gnumonks.org
Thu Sep 8 06:56:56 UTC 2011

Hi Alexander,

On Mon, Sep 05, 2011 at 11:32:53PM +0400, Alexander Chemeris wrote:

> I have a client who is interested in an USRP-based MS side implementation. I
> think that that OsmocomBB is a natural choice for the higher-level stack,
> but I have only vague idea about its current state. 

It's fairly complete, you can do FR/EFR/HR voice calls (AMR still
missing), it does cell (re)selection, encryption, hand-over, etc.

What's mostly missing is SMS support.

> As I understand, burst coding/modulation, reference clock management
> and GSM clock management should be implemented to get a working MS. Is
> there anything else to implement? How well is API to Calypso DSP is
> abstracted in OsmocomBB?

The actual layer1 firmware (on the calypso ARM side) is probably very
calyps specific, as it uses its various hardware components.
Nonetheless, there may be things like the TDMA scheduler and multiframe
scheduler which may make sense in different environments, too.

The entire L1 is abstracted from L2 using an interface called L1CTL.

This interface is specified as a protocol, and we normally speak it over
RS232 to the calypso phone.  It is defined in l1ctl_proto.h

As the calypso is the only hardware we support so far, there may be some
leakage into L1CTL, i.e. some things might not be perfect for other L1
implementations.  But we're happy to make changes to it.

Please note: there are two alternative solutions
 * kestrel/range have a proprietary product calledo OpenMS based on
   OpenBTS.  It's not Open Source, though.
 * The L1 of the upcoming sysmoBTS already has limited support for
   behaving like a MS.  It's not a primary feature, as we think it's
   just too expensive compared to a cheap calypso phone.  However, the
   L1 interface is definitely better defined as L1CTL.

I think Andreas Eversberg, Dieter Spaar or Sylvain Munaut would be good
candidates to take care of the implementation, in case you're looking
for somebody to take on that project.

- Harald Welte <laforge at gnumonks.org>           http://laforge.gnumonks.org/
"Privacy in residential applications is a desirable marketing option."
                                                  (ETSI EN 300 175-7 Ch. A6)

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