Signal Processing of Multi-Mode-Multi-Spatial (MOMS) in Line-of-Sight Channels

Orbital angular momentum (OAM) is a special branch of the traditional multi-input multi-output (MIMO) system, when the antennas sensitive to the linear momentum of the electromagnetic (EM) field are used to detect radio waves carrying OAM. In essence, the special pattern of the OAM wavefront phase distribution information is a special group of orthogonal bases of the EM field in the spatial dimension. The multi-mode multi-spatial (MOMS) scheme discussed in this paper is a generalized closed-loop multi-antenna communication system solution. To adapt more mobile application scenarios, and taking the divergence characteristic of OAM transmission into consideration, we no longer maintain the orthogonality between multiple OAM modes, and use successive interference cancellation (SIC) to obtain the spatial multiplexing gain of OAM. Compared with the traditional MIMO detection schemes, the MOMS scheme is more robust in the sparse multipath channel scenarios, and can obtain most spatial degrees of freedom (DoF) in terms of antenna aperture and channel geometry. Simulation results show that the performance of OAM-MIMO system using MOMS-SIC provides about 0.5 ~ 1.5dB for the system with different supported modes.