[USRP-users] B210 over Network?

Marcus Müller marcus.mueller at ettus.com
Thu Apr 16 05:06:52 EDT 2015


Hi Jason,

UHD doesn't have built-in capabilities for that -- the USB and the
Network transports are just too different.
There's a lot of things you can do to work around that limitation.

For example, if you can live with "just" getting samples streamed
anywhere after setting everything up (ie. no changing frequency, gain,
sampling rate etc later on), try the rx_samples_to_udp example that
comes with UHD [1]. If you have UHD installed, it's probably already
somewhere like /usr[/local/]/lib/uhd/examples.
Of course, that will just give you raw samples, but no control backchannel.

If you need that, you could try building your own gr-uhd-based GNU Radio
flow graph, with XML-RPC, and implement as much as you need in RPC
calls. That's still no direct UHD interface.

No matter how you solve this:
Gigabit Ethernet limits your sampling rate, effectively by enforcing
that the samples need to fit through the network cable.
Assuming you'd typically stuff 16bit-sampled values into your packets,
that upper limit would be
1e9 bit/s / (16bit I + 16 bit Q) = (1e9/32) Hz , assuming there was
absolutely zero overhead. This further illustrates why we can't simply
take the USB packets and transport them over ethernet -- managing the
overhead of the much smaller USB packets, together with the much higher
roundtrip time, would make UHD impractical.

I think the key to finding the right solution for your lab here is
knowing what you want a little better; if you, for example, just want to
plot spectrum from across the room, having a sufficiently powerful PC
with GNU Radio, doing all the calculation and just sending as little
data as necessary across the network might be the key. If you need full
interactivity, things are going to get a lot more application-specific.
You'll want to split your application into something like a
low-latency/hardware-related part, running on the computer connected
directly to the B210, and a higher-level logical/signal processing part,
running anywhere. An example of that architecture is OpenBTS, with its
transceiver modules actually being more or less separate from the whole
"how to run a GSM base station" logic.

Greetings,
Marcus

[1]https://github.com/EttusResearch/uhd/tree/master/host/examples

On 04/16/2015 10:37 AM, Jason A. Donenfeld via USRP-users wrote:
> Hi folks,
>
> I've got a B210. I'm interested in putting it on a network, making it
> accessible over TCP or UDP. The RTL project has rtl_tcp, which seems
> to work well for those tiny adapters. UHD supports network connections
> for other series of products that have integrated Ethernet
> controllers. But I haven't been able to find anything that would
> suffice for the B210. The end goal is to plug the B210 into a
> sufficiently powerful USB3/GbE box (perhaps a NUC or some shiny 64bit
> ARM hardware), and then be able to access it from anywhere in the lab,
> using UHD.
>
> Perhaps I missed a "usrp_network --start-listening" command somewhere?
>
> Any pointers would be greatly appreciated.
>
> Thanks,
> Jason
>
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> USRP-users at lists.ettus.com
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