Since you mentioned this, the code in gr-digital performs channel estimation base on known pilots. It is in the ./gr-digital/lib/digital_ofdm_frame_acquisition.cc
Channel estimation is based on preamble which contains known pilots each second carrier. Therefore the unknown carrier channel estimation is calculated by linear interpolation between the adjacent values.
But before that, the module does a coarse frequency estimation in frequency domain, by shifting the freq domain so that the correlation of the known pilots with the received signal after FFT is maximum. The result will be a number of FFT bins to shift the signal with.
I was looking at this before and one question was always unanswered in my mind: why the factor gr_expj(-M_TWOPI*freq_delta*d_cplen/d_fft_length*symbol_count) is used for frequency
correction, after finding out the frequency offset? I'm especially interested in the role of cp_len in this.
Thanks,
Bogdan
From: Yahya Ezzeldin <address@hidden>
To: discuss-gnuradio <address@hidden>
Sent: Tuesday, April 16, 2013 9:21 AM
Subject: [Discuss-gnuradio] Channel Estimation in benchmark OFDM Code
Dear All,
Does the benchmark OFDM Code perform Channel synchronization ?
I am moving through the code however I can't seem to get the part where this is done ?
Can anyone give any pointers regarding this ?
The number of pilots ? Estimation technique used ?
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