question about channel.py

[WenBingo]

I would like to consult the 'channel.py -> Channel.forward ', where code of "
output_real = batch_conv1d(signal_real, cof_real) - batch_conv1d(signal_imag, cof_imag) # (NxP)x(L+SMK-1)
output_imag = batch_conv1d(signal_real, cof_imag) + batch_conv1d(signal_imag, cof_real) # (NxP)x(L+SMK-1) "
Why is the code written here？

[aprilbian]

it is the time domain convolution between the ofdm signal and the channel response