This adds 4 pilot symbols each after 128 and 256 data symbols. These are
used for precision frequency estimation and feed-forward correction,
resulting in less decoder errors at the end of the packet.
Due to this change, this system can no longer transmit packets shorter
than 64 bytes!
This block is used to mark the start of the actual data, as needed by
the Header/Payload Demultiplexer, instead of the beginning of the
preamble, as needed by the frequency estimator.
- correct_frequency: Correct frequency by averaging the phase drift on
the preamble
- freq_est_lr: Luise & Reggiannini frequency estimator
- pid_controller: a PID controller that takes error values at the input
and generates steering values at the output
The combination of freq_est_lr and PID controller can be used together
with an NCO (signal source) to create a closed control loop for
frequency offset compensation.
This module will contain custom blocks written for GNU Radio.
Up to now, it contains one block for rotating the phase for the amount
given in a specific tag on the stream.
Thomas Kolb