If your processing delay is 1 second, that has nothing to do with the daughtercard. It has to do with the way you've implemented your code.
The delay through the USRP is a few sample-times at the input sample rate, and then the latency of to-host
link buffering, which is negligible, and then the link latency to host, which is again negligible--none of that adds up
to 1 second of processing delay.
Now, on the duplex issue:
Imagine for a moment that there's someone shining a bright light in your eyes, and there's another person, several hundred meters away, trying to signal you in morse-code, using a candle and their hand. It's unlikely you'll be able to see the remote person signalling you with a candle, unless you do some clever things. Like move the candle spectrum outside the spectrum of the flashlight...
Now, there are things you can do, like subtracting-out your transmitted signal from your RX signal by phase-shifting it by 180 degrees and mixing it with the RX signal. This is essentially how circulators work. The results aren't that great, and when you have a wide-band, noise-like signal, it's rather hard to shift it by exactly 180 degrees, because it has more than one frequency component.
Which is why for same-frequency operation, many systems use half-duplex architectures like TDD.
on Jul 26, 2013, Dong Wang <kingeas...@gmail.com> wrote:
Hi Marcus,Thank you for your help.I tried to implement the TDD on my USRP with a half-duplex daughterboard XCVR2450 using same frequency.But because of the processing time delay, the receiver can not receive the packet until maybe 1 second after the transmitter send it.that means I can hardly do real-time communication between two USRPs.So I want to try some duplex daughterboard. It seems that these duplex daughterboard can only implement dul-band.
Best regards!Dong Wang
2013/7/26 Marcus Leech <mle...@ripnet.com>
You can use two widely-separated antennae, or use a single antenna and a circulator--circulators are necessarily quite frequency-specific, and only offer about 20dB isolation from one port to the next.But, if it really is same-frequency at exactly the same time (as opposed to TDD), how do you propose to keep yourvery-strong TX signal from completely swamping the incoming RX signal?on Jul 26, 2013, Dong Wang <kingeas...@gmail.com> wrote:Hi all,I plan to implement duplex with USRP n210.I have a question whether the SBX daughterboard support duplex on the same band?Like transmit at 2.4GHz and at the same time receive at 2.4GHz.Thanks a lot.
Best regards!Dong Wang
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