A method for a FDR scheme-using communication device transmitting reference signals for estimating a channel of a non-linear self-interference signal comprises the step of transmitting, on a specific symbol of a corresponding subframe, reference signals for estimating the channel of the non-linear self-interference signal, wherein a sequence mapped to the reference signals is a sequence generated in a frequency domain by being discrete Fourier transform (DFT)-converted, and the generated sequence may be mapped, on the frequency domain, to a RE for the reference signals.