CalypsoBTS + GPRS and SDR suggestion

Vadim Yanitskiy axilirator at
Mon May 8 21:52:39 UTC 2017


> I setup CalypsoBTS to work with 2 old motorola c123, I know that isn't the
> best way to do that, but I would like to have a cheap solution. I got the
> setup working with a normal phone and the BTS seems to work correctly
> (using jolly/testing), but from my understanding it support only GSM calls
> and SMS and GPRS is not implemented into the transceiver. I'm wrong or
> part has not been implemented yet?

Right, isn't implemented. When you run OsmoBTS, it first does some basic
configuration of transceiver, including timeslot type setting. PDCH has
its own dedicated type, which is being indicated by the SETSLOT command.
So you can look at OsmocomBB sources, and check whether the transceiver
handles this type or not.

> Also, given that CalypsoBTS can only provide single (or two?) timeslot,
> there are a long list of reasons why it would not work straight-forward.
> But technically also possible to make work.

With two Calypso phones it becomes possible to serve two timeslots.
Basically, second phone serves one TCH timeslot, but (if I am correct)
PDCH has no fundamental differences from TCH, so its support could be
implemented too.

After a quick look at OsmoTRX source code, I can assume, that the only
difference between TCH channel combinations (I, II and III) and PDCH
channel combination (XIII) is a fillerModulus value. Correct me if I am

With best regards,
Vadim Yanitskiy.
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