A received signal delivered through a transmission line can be compensated for carrier frequency offset and direct-current offset to improve the signal-to-noise ratio of the received signal, eventually resulting in an effective improvement in the error rate. The received signal has convoluted influences through the transmission line, so that observation of continual symbols of periodic pilot signals on the frequency axis shows just a phase shift by the carrier frequency offset. Therefore, the carrier frequency offset can be analytically found from the continual symbols of periodic pilot signals, thereby allowing the direct-current offset to be estimated and both the carrier frequency offset and the direct-current offset to be compensated for.