Hello everyone,
I've been playing around with GR and specifically gr-ieee802-11 lately, as I intend to use it soon for a university lab. This tinkering might even result in some code contributions later on (not promising anything though...). At the moment I'm mainly interested in running simulations using the module. I've read the relevant papers linked on
wime-project.net and went through the code, but some questions still remain open:
1. In the Sync Long block, the input is put through a matched filter defined by the long training sequence in time domain. I'm probably overseeing something here, but I would expect this sequence to be the same as the sequence given in table I-6 of the standard (well, a part of it at least, since it repeats 2.5 times). Now, I understand the LONG vector is generated using the create_long.R script and not knowing any R I tried to reproduce this in MATLAB. However, after some experiments I figured that in order to reproduce the same sequence I have to run in MATLAB (a is the freq. domain sequence):
fliplr(fft(ifftshift(a)/sqrt(52)))
where from the R script I would actually expect (as we're transforming the sequence from frequency to time domain and also conjugating it to create a matched filter):
fliplr(conj(ifft(fftshift(a)/sqrt(52))))
I think I might be missing something here and would be glad if someone could shed some light on this.
2. As seen in the provided examples, the (Random) Periodic Message Source from gr-foo is useful for simulations. However, due to a bug in GR 3.7, flowgraphs using it won't stop automatically. I'm aware that this has already been fixed by this PR:
https://github.com/gnuradio/gnuradio/pull/797 . However, I would like to be able to use a vanilla GR 3.7 and the fix was applied to the next branch due to API change. Are there any known workarounds not requiring patching?
That's it for now, more questions probably coming soon.
Cheers,
Tal