Propagation Measurements and Channel Models in Indoor Environment at 24 GHz FR3 Spectrum for 6G Orbital Angular Momentum Communications

In recent years, orbital angular momentum (OAM) has garnered significant attention as a promising technology for 6G. Extensive research on OAM channel measurements and characteristic analysis has been carried out to address the needs of future OAM-based wireless communications. However, the traditional plane wave model fails to accurately capture the unique propagation loss characteristics of OAM, resulting in low accuracy when describing OAM path loss. Furthermore, existing models do not fully characterize the path loss characteristics of OAM. To address these issues, we propose a Bessel function-based OAM path loss model in this letter, which describes the relationship between power propagation loss and transmission distance for different OAM mode signals. In addition, we conduct OAM channel measurements at 24 GHz in indoor environments. Based on these measurements, we propose the floating-intercept OAM (FI-OAM) and close-in OAM models, which are compared with the measurements to validate their accuracy. The results show that the FI-OAM model not only achieves high accuracy but also effectively captures the fluctuation loss of OAM during propagation.