11 Sep
2020
11 Sep
'20
10:33 p.m.
Hi Mychaela,
On Fri, Sep 11, 2020 at 09:54:37AM -0800, Mychaela Falconia wrote:
LimeSDR-USB is the oldest and best supported device. LimeSDR mini does not
have a clock input for an external reference clock. Yes, with some board
rework it can be added, but even then it has much stricter requirements on
the clock (IIRC phase noise), as it doesn't have any onboard PLL but directly
feeds that input to the Transceiver chip which is very sensitive to phase noise.
Throwing a
quick glimps at the OsmoTRX wiki page I think the cheapest
hardware that should work well is the LimeSDR - coming in at around 300 USD.
Looking around myself, I came to the same general conclusion - but
there are several different members of the Lime family. It looks like
LimeSDR-Mini is the cheapest of all of them, but does it have some
problem compared to the original LimeSDR-USB? Does it have a worse clock that isn't good enough
to run a GSM BTS?
Any SDR without a a built-in or external OCXO, Rubidium or GPS-DO has a clock
that is insufficient for operating a GSM BTS.
And what about LimeNET-Micro? It appears to be priced
the same as the original
LimeSDR-USB, but has a built-in RPi microcomputer that the software
would run on, and its GPSDO seems like a better clock option than all
of the predecessors - but I could be missing something...
OsmoTRX + OsmoBTS will run on it (and we actually even provide Raspbian
binar packages in our nightly and latest feeds, for people who don't
want to build everything from source).
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. If you do, go for a LimeSDR-USB
within the Lime device portfolio, but add a GPS-DO like a BG7TBL if you
don't already have a 10MHz reference around in your lab.
--
- Harald Welte <laforge(a)osmocom.org> http://laforge.gnumonks.org/
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