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…
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.
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.
antennas systems, if I take something like 2 cheap WiFi nodes both
I think that diagram shows the WiFi card transmitting to the USRP
able to avoid this
-Because WiFi and other standards that use TDD share a single antenna, they
must near-simultaneously transmit and receiver. If a USRP Transmission is
heard by the original node, it will create a feedback loop
That is why you need either 2 USRPN210’s or 1 USRP1. The USRP1 can
have 2 daughterboards which allows you to have 2 independent RX/TX
ports. The circulators handle the rest for you.
You’re correct that using a single TX on a single daughterboard isn’t
good enough.
For the fading I was thinking of just using gnuradio without any FPGA
alterations, (theres a fading model/noise sources/notch filters), my only
uncertainty is the ability to receiver and transmit to the same USRP on
different antenna ports.
I believe there are latency requirements in 802.11 that may be
difficult/impossible to achieve if you’re shipping samples back and
forth. If latency isn’t a concern, I think that the above setup
should be valid.
Do you agree?
Brian
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