Support for new SDR devices

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Harald Welte laforge at gnumonks.org
Wed Sep 16 16:58:31 UTC 2020


Hi Xaver,

On Sun, Sep 13, 2020 at 10:49:56AM +0200, Xaver Zu wrote:
> > Yes.  But, as other people stated, it is likely a significant effort,
> > and there are other SDR devices that ship with fully open source
> > software, sometimes not only software but even FPGA gateware or even
> > open source hardware.
> 
> Which SDRs with PCIe do you remember?

I was indeed thinking about LimeSDR-PCIe and XTRX.

> I know about XTRX. Master osmo-trx does not support it. 

well, neither does osmo-trx have for PCIe-SDR :P  There were some patches submitted
by Fairwaves to gerrit.osmocom.org (https://gerrit.osmocom.org/c/osmo-trx/+/15685)
which received reasonable feedback, but Fairwaves did not have the time/capacity
to follow-up and re-submit.

Given that you have demonstrated you can implement an entire osmo-trx backend
and submit it to osmcoom and go through the review cycle, maybe you can convince
Fairwaves that they should support you with a free or subsidized XTRX if you 
move their patches ahead and get them merged?

> And I know about limesdr-pcie, I'm not convinced that it makes sense
> to buy in this state of development.

I'm not following the detailed status of this device.  We do have one at
sysmocom, but our focus has been on the USB-attached devices.

> I don't know about GPL compatible PCIe SDR with Analog Devices AD93XX
> family chip. 

I'm not aware of any, but I'm not the expert on available SDR hardware,
to be honest.

> Results of SDR based on the Analog Devices versus Lime chip
> are in favor of Analog Devices. 

That reflects the general impression I get from many people so far.

> Does anyone know of an SDR combining PCIe and an AD93XX chip that has the
> potential to be supported by osmo-trx?

> Does anyone know about such a CPRI for PCIe? I don't need it but libsdr.so
> supports it. I think this can be of benefit to the community.

The main problem regarding CPRI interfaces is that there are no CPRI
radio heads with publicly documented "command and control" interfaces.
While the I/Q sample formats on CPRI/eCPRI are standardized, the
command+control is not.  So unless somebody reverse engineers those
interfaces within CPRI, there will not be any radio head you can use.

And without any usable radio head, why would anyone build a CPRI PCIe
interface card.

Some people within Osmocom had started to investigate commercially
available CPRI radio heads e.g. from Ericsson, but I think it's
primarily a "lack of resources / contributions" situation.  Several
people in Osmocom do have the equipment and even purchased some R&S
CPRI test equipment.

I'm sure if a radio head was available with (published or reverse
engineered) command and control, people would be interested in building
a PCIe CPRI interface.  sysmocom might even be interested in
contributing financially to such a development at such a point in time.

Regards,
	Harald
-- 
- Harald Welte <laforge at gnumonks.org>           http://laforge.gnumonks.org/
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