The use of larger antenna arrays at higher frequency bands is envisioned in the beyond 5G wireless networks. This takes advantage of the near-field propagation regime where the wavefront is no longer plane but spherical, bringing both new opportunities and challenges for the high-precision positioning. In this paper, a generic near-field positioning model with different observation capabilities for three electric fields (vector, scalar, and overall scalar electric field) is proposed. For these three electric field types, the Cram\'er-Rao bound (CRB) is adopted to evaluate the achievable estimation accuracy. The expressions of the CRBs using different electric field observations are derived by combining electromagnetic theory with estimation theory. Closed-form expressions can be further obtained if the terminal is located on the central perpendicular line (CPL) of the receiving antenna surface. In addition, the above discussions are extended to the system with multiple distributed receiving antennas under the CPL assumption. The CRBs using various electric fields in this case are derived and the effect of different numbers of receiving antennas on estimation accuracy is investigated. Numerical results are provided to quantify the CRBs and validate the analytical results. Also, the impact of various system parameters, including different electric fields and multiple antennas, on the near-field positioning performance is evaluated.
翻译:高频波段的大型天线阵列设想在5G无线网络中使用,这利用了近地传播系统,即波头不再是平面,而是球形的,为高精度定位带来了新的机会和挑战;在本文中,提议为三个电场(矢量、scalar和总体弧电场)建立一个通用近地定位模型,具有不同的观测能力;对于这三种电场类型,将采用Cram\'er-Rao绑定(CRB)来评估可实现的估计准确性;利用电磁理论与估计理论相结合,得出了电磁场观测的表达方式;如果终端位于接收天线表面的中央直径直径线(CPL)上,则可以进一步获得封闭式表达方式;此外,上述讨论还扩展到了在CPL假设下多个分布式接收天线的系统;对本案中使用各种电场的Cram\'er-rao(CRB)进行了计算,对接收天线的不同数目对估计准确性的影响进行了调查。Numerical-结果将在接近CARB和不同天线上对不同位置进行定量评估,还评估。