Re: [Discuss-gnuradio] Real-time fading simulation?

[Brian Padalino]

On Tue, May 29, 2012 at 9:47 PM, J Mc <address@hidden> wrote:
> I have been considering using GnuRadio with the USRPN210 as a realtime
> fading simulator for radio hardware testing, however any approaches I've
> considered in doing this seem to fall down fundamentally if I limit to using
> a single USRP. I'm still relatively sure it could be done, was wondering if
> anyone had any advice/input.
>
> The main issue I've had is trying to understand how to do this with single
> antennas systems, if I take something like 2 cheap WiFi nodes both attached
> to a common Tx and Rx port is there any way to prevent the transmitting
> node's signal feedback when it hits the receiving node's antenna. If anyone
> has looked at this question, opinions would be appreciated...

I think you can do it with an one USRP1, or two USRPN210s using some
circulators and a special FPGA load.

Circulators move in a clockwise motion:

[WiFi] <-> [ Circulator ] <-> [USRP Rx/Tx]
                 ^
                 |
                 v
           [ Circulator ] <-> [WiFi]
                 ^
                 |
                 v
            [USRP Rx/Tx]

I think that diagram shows the WiFi card transmitting to the USRP
Rx/Tx port, the Tx from the USRP goes to the other circulator, and
into WiFi card.

The second WiFi card transmits into the circulator then into the USRP
Rx/Tx port, and the Tx from the USRP goes to the original circulator,
and into the original WiFi card.

FPGA load would essentially be programmable with your noise/fading
profile, and with little host intervention create noise on the
baseband then retransmit.

Does that work?

Brian