[USRP-users] FDD transmission with b210?

Ernest Szczepaniak ernest.szczepaniak.en2 at gmail.com
Wed Mar 23 15:02:15 EDT 2016


Dear Marcus,

Thanks for your quick and detailed reply.

My question was asked from PHY designing perspective. When im looking at
baseband, pre IFFT frame (in frequency domain), I can assign carriers for
the whole system (these carrier indices are used for uplink, and those for
downlink for both transmission sides respectively), making it more flexible
for the future. It could be done by tunning RX and TX to different
frequencies, but now, carrier indices have to be calculated for both sides
independently (dunno if you understand this way of thinking :D ). And this,
as you said, is achievable from hardware perspective.

Im trying to make a system similar to 4G style.

And now correct me if im wrong.

Does LTE FDD mode works that way? (transmitter and receiver working on same
frequency). Or is it just impossible to be done? I read that in LTE uplink
(SC-FDMA), there is an additional DFT block after constellation mapping,
and after that, even so called "distribution mapping" could be done,
spreading uplink transmision to non adjecent carriers. I think it would be
impossible to receive this with TX and RX working on different frequencies.
Correct or not?

Im curious after this movie:

https://www.youtube.com/watch?v=9zmAH_ewkSk

Best regards,
Ernest



2016-03-23 16:07 GMT+01:00 Marcus Müller <usrp-users at lists.ettus.com>:

> Dear Ernest,
>
> On 23.03.2016 12:19, Ernest Szczepaniak via USRP-users wrote:
> > Does B210 supports full duplex transmission?
> Yes!
> > Any reference to detailed information about how it is realized onboard?
> Well, on the ettus.com product page you'll find the product brief PDF
> with a schematic. You'll notice that all parts in the signal chain are
> fully duplexed (which is true down to everything but the USB interrupt
> handling in the USB controller processor).
> So maybe you could specify that question.
> >
> > Is it possible to design system like this? (thats my mathworks topic)
> >
> >
> http://www.mathworks.com/matlabcentral/answers/274985-frequency-division-duplex-simulation-am-i-correct
> >
> Well, the idea of FDD is that, yes, signals overlay each other in time,
> but not in time domain, so you can just build a receiver that listens
> only to specific frequencies, and not the ones it's transmitting on.
>
> From a hardware perspective, when doing FDD, you're always tempted to
> tune RX so that the TX is not even in RX's analog input, which could
> otherwise lead to nonlinearity, and hence, RX distortion, due to the
> fact that sensitive receivers become non-perfect when exposed to high
> powers (like the crosstalk from the TX antenna at the same frequency).
>
> Now, I've seen FDD be done with USRPs, and I think it's easy to do, as
> long as the sender and receiver aren't too far apart even with RX and TX
> tuned to the same frequency. For more complicated situations, one would
> calculate the TX and RX as two separate passbands, and use the fact that
> you can use analog filters to limit the crosstalk.
>
> Can you give us a few corner data of your planned FDD setup?
>
> Best regards,
> Marcus
>
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