I want to have a clear understanding on how the channel state information is being estimated in GnuRadio.
I have tried out the OFDM example of tx & rx which works fine and I am also able to extract the CSI. Now I want to understand how it is being actually measured.
From what I see & understand, OFDM carrier allocator has pilot carriers & Sync words defined. On the Rx end the same Sync words are present. The received symbols are then compared with these pre-defined sync word & CSI is calculated.
- Why there are 2 sync words?
- Are these sync word used to measure CSI ? Or is it the pilot symbols ?
- How these sync words are being derived as shown in the example ? i.e what format has been followed for this?
- What might happen if I change these values. (As it should work the same unless they are different at tx/rx)?