Hi Vinicius, you can directly feed the output of the OFDM channel estimation block into a simple general block that you write yourself[1] – even in Python – and make that block
* either save the contents of the relevant tags to a file or * output a vector of (inverse) channel coefficients taken from the `ofdm_sync_eq_taps` tag. Generally, however, never forget that OFDM channel estimations are *not* a property of the _channel_, but of the _receiver_: If you recall the effects of having a cyclic prefix in OFDM, you'll remember that it's not critical that your receiver is in perfect time synchronity with the beginning of the actual payload part of the symbol (after the CP). Instead, as long as your FFT starts *somewhere* in the cyclic prefix, you're fine synchronization-wise, since a (simulatedly) circular time shift (due to starting the FFT in the CP instead of exactly at the start of symbol after the CP) is just a point-wise multiplication with a complex sinusoid after the FFT – and that means your timing offset will just manifest as rotation of the channel coefficients. And you're correcting these, anyway. So, as long as a CP-OFDM receiver is consistent in the amount of time it starts doing the FFT before the end of CP, the rotation each subcarrier coefficient experiences is always the same and will thus be corrected (e.g. through pilot estimation). But: That means that your channel estimate is not the same you'd get when you're even a fraction of a sample off in timing compared to someone else. It's still the same, ignoring complex rotation, so the power delay profile will be right, and when you agree on e.g. an average phase of symbols, you can compare different channel estimates, but don't directly compare the channel estimates from different receivers, or the same receiver over more than a frame, or after tuning. Best regards, Marcus [1] https://tutorials.gnuradio.org PS: long-term observers will know that I fought very hard to not embed loads of LaTeX in this reply. On Tue, 2020-03-03 at 16:39 +0100, Vinicius Mesquita wrote: > Hello. > Thank you in advance for the help... > > I already searched the mailing list and could not find it how to properly > see/save the channel taps from the OFDM Channel Estimation block. I saw that > is in a tag, but how can I save it? > > What I'd love to find is a way to see the channel estimation with the 52 taps > in a QT GUI plot. Is that possible? If it's not, saving it it's already > awesome. > > Thank you!!
smime.p7s
Description: S/MIME cryptographic signature