Vortex Beam Selection for A2G-RV Wireless Communications

Orbit angular momentum (OAM) based radio vortex wireless communication with the characteristic of orthogonal mode division multiplexing (MDM) enables higher spectrum efficiency (SE) than conventional multiple-input-multiple-output (MIMO) communications. However, MDM techniques are only suitable for line-of-sight (LOS) environments and suffer from a strict limitation in applications due to the physical property of divergence of the vortex beams. The flexibility of unmanned aerial vehicle (UAV) can rapidly establish LOS communication links, and the corresponding air-to-ground (A2G) channels furthest utilize the spatial distributing characteristics of the energy of vortex beams. For the A2G channel, we proposed the joint beam selection and water-filling power allocation (JBS-WPA) schemes to improve the SE of the A2G wireless communication system. Numerical results indicate that the proposed system with JBS-WPA algorithm can obtain a higher SE than conventional MDM-MIMO systems. Therefore, OAM techniques can offer a brand new solution for future air-to-ground (A2G) networks.