This paper presents a new concept of simultaneous data transfers with existence of multiple harmonic frequency channels. Contradictory to conventional approaches of multiband communication systems, which generate the desired operating frequencies with multiple local oscillators and communicate in time division basis, this proposed harmonic communication system reuse the intermodulation products generated by the intrinsic property of nonlinear devices, primarily the up-/down-converting mixers in the transceiver. In this case, duplicated data can be transferred through multiple frequency channels. Moreover, compact multiband components can be used to replace those single-band circuits in conventional multiband systems and therefore limiting the cost of such transceiver. In theoretical analysis, the optimal signal-to-noise ratio (SNR) performance can be enhanced by 3-dB whenever the number of frequency channels is doubled. As the consequence, the bit-error-rate (BER) performance can be improved, or in another point of view, the minimum required SNR for the receiver can be relaxed. The simulation results show good agreements with the theoretical ones and therefore demonstrate the usefulness of proposed harmonic frequency channels concept.