Interference Mitigation Based on Optimal Modes Selection Strategy and CMA-MIMO Equalization for OAM-MIMO Communications

Transmitting multiple independent data streams through the same medium can increase the capacity of line-of-sight-based wireless communication systems. One of the promising approaches is to utilize spatial multiplexing with multiple spatially separated transmission/reception pairs, for which inter-channel interference can be declined by employing multiple-input multiple-output (MIMO) signal processing at the receiving ends. The other approach is to use orbital angular momentum (OAM) multiplexing transmitting multiple data streams, which makes use of the orthogonality among OAM beams to reduce inter-channel interference and enable efficient demultiplexing. However, due to the practical limitations, the two methods are hard to maximize their advantages independently. In order to utilize the two merits, this paper proposes an OAM-MIMO communication scheme to employ the potential of both multiplexing methods. Based on the system, we implement the measurement of inter-channel interference and then utilize the optimal modes selection strategy and constant modulus algorithm MIMO equalization to further improve the system performance. Our work indicates that the combination of these two interference mitigation methods can guarantee the communication quality when pursuing high-speed communications. Simulation results are given to corroborate the proposed scheme.