[Hackrf-dev] Project on the decoding of WiFi-Networks

[Andreas Diehm]

Hello fellow HackRF-Devs,

I'm a german student working on a project in which we try to read the Data
of a WiFi-Network using the HackRF and Gnu Radio Companion.
I have some questions about some peculiar things that have happend to me
while exercising the lessons on SDR by Michael Ossmann.
I did the Radio in GRC and it worked only once, all the other times it
gives me "UaUaUa" as an Error-Message, is this related to my Hardware or
related to some bugs on the HackRF and what is the meaning of "U" and "a"?

Another question is about the filters in GRC. While trying to set up a
filter for my (very basic and unfinished) flowgraph (
Loading Image... ) I was unable to figure out, what value
the "transition width" needs. Is there a way of calculating it, trial and
error unfortunatly turned out to be unsuccsessful.

My last question is, if there is already a flowgraph that decodes
Wifi-Data, and is it even possible with the HackRF, Gnu Radio Companion and
a consumer-class PC to do such a complicated action?

Best regards,

Andreas Diehm

[West, Nathan]

Post by Andreas Diehm
Hello fellow HackRF-Devs,
I'm a german student working on a project in which we try to read the Data
of a WiFi-Network using the HackRF and Gnu Radio Companion.
I have some questions about some peculiar things that have happend to me
while exercising the lessons on SDR by Michael Ossmann.
I did the Radio in GRC and it worked only once, all the other times it
gives me "UaUaUa" as an Error-Message, is this related to my Hardware or
related to some bugs on the HackRF and what is the meaning of "U" and "a"?

Ua in GNU radio language is basically "audio underrun". See
http://gnuradio.org/redmine/projects/gnuradio/wiki/FAQ#I-have-a-receiver-with-acoustic-output-and-keep-getting-aUaUaU-errors
for more info.

Post by Andreas Diehm
Another question is about the filters in GRC. While trying to set up a
filter for my (very basic and unfinished) flowgraph (
http://abload.de/img/bsbphudi.png ) I was unable to figure out, what
value the "transition width" needs. Is there a way of calculating it, trial
and error unfortunatly turned out to be unsuccsessful.

Transition width is the frequency gap between your pass band edge and your
stop band edge. If you look at any textbook on DSP you should see a good
picture. Your favorite search engine might also turn up good results; it's
a fairly widespread concept.

Post by Andreas Diehm
My last question is, if there is already a flowgraph that decodes
Wifi-Data, and is it even possible with the HackRF, Gnu Radio Companion and
a consumer-class PC to do such a complicated action?

For a list of nice GNU Radio applications see http://cgran.org (disclaimer:
I'm a co-author of that page). gr-ieee802-11 is there:
http://cgran.org/pages/gr-ieee802-11.html

Post by Andreas Diehm
Best regards,
Andreas Diehm

Cheers,
-Nathan