[Discuss-gnuradio] Measure the Distance to another 802.11 device

[Florian Adamsky]

Hi all,

in one of our projects we need to measure the distance between two
802.11 devices as accurately as possible. Our idea is to use the
round-trip time (RTT). To avoid any delay from the operation system and
from the network stack, our idea is to measure the arrival time of the
acknowledgment control frame. Means, we take a timestamp when device A
sent a small data frame to device B; when B has received the frame, it
replies with an acknowledgment control frame and when A has received it
we will take another timestamp. Of course we would repeat that n-times
to avoid outliers.

We bought a HackRF and tried to get the examples from gr-ieee802-11
running. After some minor problems (dc offset) we were able to receive
802.11 frames. However, we are not able to send any 802.11 packets,
because the hackrf driver does not support burst transmission with
tagged streams. One reader of this mailing list suggested to give
soapysdr a try. We did that as well, but again without success. Here we
didn't see any "UUUUU" in the debug console but we were still not able
to see any packets with another wireless card in monitor mode.

Now we begin to think if the HackRF is the right device to get the job
done. Is the HackRF maybe the wrong device and we need to get a better
one? If yes, which one would you suggest? Or do you think there is
better approach to solve our problem like modifying one of the open
firmware for wireless cards?

Thanks in advance.

Cheers!
--
Dr. Florian Adamsky
http://florian.adamsky.it/