Distorted Channel Correction for UCA Based OAM Communication

Orbital Angular Momentum(OAM) has attracted great attention for its potential to increase channel capacity. OAM has infinite modes orthogonal to each other, which provides a new degree of freedom for wireless communication. Uniform Circular Antenna Array(UCA) based OAM generation method is promising as each array element can be independently controlled, so that OAM modulation and multiplexing can be realized on digital domain. However, communication performance of OAM will deteriorate rapidly when there exists small-scale fading, which causes channel distortion. To deal with OAM channel distortion, we construct OAM baseband model using Inverse Discrete Fourier Transform(IDFT). Based on the model, we theoretically analyze the principle that small scale fading causes OAM inter-mode interference. A novel joint precoding and postprocessing method for channel correction is then proposed to cancel the inter-mode interference and restore inter-mode orthogonality. Simulation results show that in the case of single-reflection channel model, inter-mode interference is canceled and spectrum efficiency is greatly improved using our correction method.