LimeSDR (was Re: Alternatives to CalypsoBTS?)

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Mychaela Falconia mychaela.falconia at gmail.com
Sat Sep 12 02:39:19 UTC 2020


Hi Harald,

Thanks for the explanation regarding different LimeSDR devices.  Just
in case I wasn't clear, the present inquiry was *not* for me - instead
I was trying to make a pre-emptive move, trying to prepare a canned
answer for that inevitable case when some very green newbie asks about
getting the anticipated cheaper-than-FCDEV3B Calypso board for the
purpose of misusing it as CalypsoBTS.  I was (and still am to some
extent) looking for a canned answer along the lines of "no, please
don't misuse Calypso devices as a poor man's BTS, they are meant to be
MS rather than BTS, if you need absolute lowest cost BTS, please use
$This_lowend_SDR instead" - and I was looking to see what that
$This_lowend_SDR metavariable should be set to.

Unfortunately the very existence of that CalypsoBTS hack has seriously
muddied the waters we all have to swim in - the world would have been
a cleaner place had that hack never been invented.  I don't know if
you have noticed it or not, but over the last few years there has been
a very significant influx of very green noobs coming to OsmocomBB not
for the purpose of doing research or tinkering from GSM MS side, but
who seek old Motorola phones for the *sole* purpose of turning them
into a poor's man BTS via that CalypsoBTS hack, and who seem to have
no interest whatsoever in GSM MS side.

Remember that guy a few years ago who was adamantly asking for a port
of OsmocomBB to Qualcomm phones and who thought it would be a slam
dunk because there apparently exist some leaked QC sources?  A careful
reading of his posts, parsing to see exactly what he sought out of OBB
and out of that hypothetical Qualcomm port, reveals that he was *not*
seeking a FOSS or research-oriented implementation of GSM MS (or of
3G/4G UE) on a newer platform, instead he was seeking to turn his
QC-based phone into a BTS in the spirit of CalypsoBTS!  I was truly
disgusted and sickened to my stomach when I saw what we was really
after - but he was not alone by any means, there are a great plenty of
them.

I assume that this attitude that leads people to seeking Motorola
phones for the sole purpose of turning them into CalypsoBTS stems out
of ignorance, rather than intentional hostility toward those who work
on the MS side of the air interface - but ignorance needs to be
treated with education, we need to educate those green newbies that
GSM MS devices make a *very* poor BTS and that they should get
something more appropriate for the BTS role - and my question was
exactly what should be recommended to those greenest of newbies.

> Please note that - as far as I know - the CPU power of the RPi compute
> module is insufficient for operating multiple software
> transceivers/carriers within one wideband channel ('multi-arfcn mode').
> So you are constrained to 1TRX operation.  If you don't need that, the
> LimeNET-Micro might be a good choice.

But this 1TRX operation is still better than CalypsoBTS, or is it not?
Remember that the goal is to convince the super-newbie to follow some
path other than CalypsoBTS...

You may not be able to relate because you are not in my shoes, but as
a maker of Calypso GSM MS devices and as the world's most active
supporter of that chipset in the present time, I stand as the front-
line target for those people seeking a Calypso device for the purpose
of misusing it as a BTS - I am typically the first person they reach
out to, usually in extremely terse inquiries in half-broken English,
typically asking for subsidized hardware, and only revealing their
true intentions several emails later, after I have already wasted a
ton of emotional energy on them.  So yeah, I seriously resent the very
existence of CalypsoBTS.

M~



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