A Novel Beam Domain Channel Model for Orbital Angular Momentum Communication Systems with Massive Uniform Circular Array.

Spatial domain is explored to improve system performance in the sixth generation (6G) wireless communication system. Massive multiple-input multiple-output (MIMO) and orbital angular momentum (OAM) are key technologies to achieve this purpose. In this paper, a novel beam domain channel model (BDCM) for OAM communication systems with massive uniform circular array (UCA) is proposed. The generation of OAM waves proves feasible for UCA. Frequency invariant beamforming (FIBF) is applied to transform OAM basis to plane-wave or spherical-wave basis to make full use of the spatial domain in the multipath scenario. Furthermore, near-field characteristic and mutual coupling (MC) are considered in this model. Statistical properties like temporal autocorrelation function (TACF) and beam spread are analyzed and simulated. Complexity of the proposed BDCM is evaluated. Non-negligible impacts caused by the antenna like configuration and MC on TACF are revealed.