Channel Modeling of the OMA-based Communication System in the Presence of the Reflection

Orbit Angular Momentum is a novel technology which has been used recently for increasing the channel capacity of communication systems.  In the OAM system, the Uniform Circular Array (UCA) has been widely used due to its capability in easy implement of the OAM modes orthogonality.In most of the researches, it is assumed that the transmitter and receiver antenna arrays are aligned with each other in the channel without any reflection. The effect of channel reflection is investigated only on single antenna and Uniform Linear Array (ULA) cases, which according to many difference between the UCA  and  ULA based OAM systems, the obtained results cannot been used for UCA based OAM system. In this paper, the channel modeling of the UCA based OAM system in presence of the reflection in done. For this purpose, the reflection effect is modeled by a virtual transmitter UCA. Also, the channel matrix in extreme cases is approximated, and the channel capacity using the obtained model is computed. We show that, in the presence of channel reflection, the orthogonality of OAM modes are corrupted, which leads to decreasing the channel capacity. Consequently, a proper pre-coding is needed to prevent capacity loss. We evaluated the obtained results by the simulations.