Orthogonal Mode Division Multiplexing for Radio Vortex Wireless Communication

Orthogonal frequency division multiplexing (OFDM), which has attracted much attention during the past few decades, can be used for not only anti-multipath but also high spectrum efficiency in wireless communications. However, as the spectrum becoming more and more crowded and the amount of traffic eventually increasing, it is very difficult to increase the spectrum efficiency in wireless communications. Recently, orbital angular momentum (OAM), which provides a novel mode dimension, offers the potential to achieve high spectrum efficiency for wireless communications. In this paper, we propose the orthogonal mode division multiplexing (OMDM) scheme for high capacity in wireless communications. In particular, we propose to transmit half-integer and integer OAM-modes signals within two narrowbands to avoid the inter-mode interference. Second, we propose the mode inverse fast Fourier transform (M-IFFT) algorithm at the transmitter to modulate signals and mode fast Fourier transform (M-FFT) algorithm at the receiver to demodulate signals, respectively. Finally, we develop the dynamic power allocation scheme to solve the problem of how to maximize the capacity of OMDM. Numerical results show that our developed OMDM scheme can achieve high capacity. Furthermore, we can jointly use our developed OMDM scheme with the conventional OFDM scheme to increase the capacity of wireless communications.