Multidimensional OAM-Based Secure High-Speed Wireless Communications

To address key challenges for beyond 5G wireless technologies in a simultaneous manner, we propose an orbital angular momentum (OAM)-based, secure, energy-efficient multidimensional coded modulation. The key idea is to employ all available degrees of freedom (DOFs) to convey the information over the wireless links, including amplitude, phase, polarization state, and spatial-domain DOFs. In particular, the OAM is associated with the azimuthal phase dependence of the wavefront, and represents an underutilized DOF. Given that OAM eigenstates are orthogonal, an arbitrary number of bits per symbol can be transmitted. Here, we propose utilizing OAM DOF not only to improve spectral and energy efficiencies, but also to significantly improve the physical-layer security of future wireless networks. To implement the OAM multiplexer and demultiplexer in the RF domain, we propose using properly designed antenna arrays. We also propose employing the Slepian sequences as either basis functions in baseband or impulse responses of antenna arrays in passband to further increase the dimensionality of the wireless system and enable beyond 1-Tb/s wireless transmission. Monte Carlo simulations demonstrate high tolerance to fading effects of LDPC-coded multidimensional signaling schemes compared with the conventional LDPC-coded QAM.