Can anyone explain the function of coarse_freq_comp in OFDM channel estimation process?

Hi guys,

The gnuradio calculate the channel estimated value* d_hestimate* using
the
received symbol and known symbol. However, I dont know the exact meaning
of
coarse_freq_comp(d_coarse_freq,1) when performing the calculation. Can
anyone explain this function?

Please refer to the following formula,

d_hestimate[i] = d_known_symbol[i] /
(coarse_freq_comp(d_coarse_freq,1)*(symbol[i+zeros_on_left+d_coarse_freq]));

Thanks in advance.

Best,
Kay