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Orthogonal Frequency and Mode Division Multiplexing for Wireless Communications

Orbital angular momentum (OAM) based radio vortex wireless communications have the potential to significantly increase the spectrum efficiency (SE) without increasing extra time and frequency resources. In this paper, we propose a hybrid orthogonal division multiplexing (HODM) scheme, which jointly uses the orthogonal mode division multiplexing and the conventional orthogonal frequency division multiplexing (OFD-M) to increase the SE of radio vortex wireless communications. In particular, we develop the mode and frequency dimensions based two-dimension inverse fast Fourier transform (2D-IFFT) algorithm at the transmitter to modulate transmit signal and two-dimension fast Fourier transform (2D-FFT) algorithm at the receiver to demodulate received signal, respectively. Then, we propose an optimal power allocation scheme to maximize the SE of our proposed HODM scheme. Numerical results show that the HODM scheme can significantly increase the SE in comparison with the conventional OFDM schemes.