Cramér-Rao Bounds of Near-Field Positioning Based on Electromagnetic Propagation Model

The adoption of large-scale antenna arrays at high-frequency bands is widely envisioned in the beyond 5G wireless networks. This leads to near-field regime where wavefront no longer planar but spherical, bringing new opportunities and challenges for communications positioning. In this paper, we improve positioning technology from classical spherical model (SWM) more accurate true electromagnetic propagation (EPM). A generic with different observation capabilities three electric field types (vector, scalar, overall scalar field) developed based on complete EPM. For these observed types, Cram\'er-Rao bound (CRB) adopted evaluate achievable estimation accuracy. expressions CRBs observations are derived by combining concepts theory. Closed-form can be further obtained as terminal assumed central perpendicular line (CPL) receiving surface. Moreover, above discussions extended system multiple antennas. case, using various derived, effect numbers antennas deeply investigated. Numerical results provided quantify validate analytical results. Also, impact parameters, including type, wavelength, size antenna, number antennas, evaluated.