Electromagnetic Effective-Degree-of-Freedom Prediction With Parabolic Equation Method

The performance of a multiple-input-multiple-output (MIMO) wireless communication system can usually be indicated by its effective degree of freedom (EDOF). The parabolic equation (PE) method is widely used to predict electromagnetic (EM) propagation loss for its simplicity and efficiency. A novel PE-based EM channel model is first established for acquiring the EDOF in an electrically large and complex environment. At first, the accuracy of the proposed PE Model is verified by comparing it with the dyadic Green's function. It is shown that the PE Model produces the same results as the analytical one. Then, the connection between the limit of the EM EDOF and the optimal source/receiver numbers is analyzed in the inhomogeneous environment with obstacles. Finally, a complex urban environment is analyzed and the sensitivity analysis is made for the EM EDOF. Numerical results show that the EM EDOF will be stable when the number of transmitting/receiving array sources reaches a certain point. The proposed PE model can be used as an efficient tool for evaluating communication channels in complex environments.