Vukmirović Nenad, Erić Miljko, Djurić Petar M
School of Electrical Engineering, University of Belgrade, 11120 Belgrade, Serbia.
Innovation Center of the School of Electrical Engineering, University of Belgrade, 11120 Belgrade, Serbia.
Sensors (Basel). 2021 May 13;21(10):3401. doi: 10.3390/s21103401.
We address the accuracy of wideband direct position estimation of a radio transmitter via a distributed antenna array in 5G cellular systems. Our derivations are based only on the presence of spatially coherent line-of-sight (LoS) signal components, which is a realistic assumption in small cells, especially in the mmWave range. The system model considers collocated time and phase synchronized receiving front-ends with antennas distributed in 3D space at known locations and connected to the front-ends via calibrated coaxial cables or analog radio-frequency-over-fiber links. Furthermore, the signal model assumes spherical wavefronts. We derive the Cramér-Rao bounds (CRBs) for two implementations of the system: with (a) known signals and (b) random Gaussian signals. The results show how the bounds depend on the carrier frequency, number of samples used for estimation, and signal-to-noise ratios. They also show that increasing the number of antennas (such as in massive MIMO systems) considerably improves the accuracy and lowers the signal-to-noise threshold for localization even for non-cooperative transmitters. Finally, our derivations show that the square roots of the bounds are two to three orders of magnitude below the carrier wavelength for realistic system parameters.
我们研究了5G蜂窝系统中通过分布式天线阵列对无线电发射机进行宽带直接位置估计的准确性。我们的推导仅基于空间相干视距（LoS）信号分量的存在，这在小小区中是一个现实的假设，尤其是在毫米波范围内。系统模型考虑了并置的时间和相位同步接收前端，天线分布在三维空间中的已知位置，并通过校准的同轴电缆或模拟光纤射频链路连接到前端。此外，信号模型假设为球面波前。我们推导了系统两种实现方式的克拉美罗界（CRB）：（a）已知信号和（b）随机高斯信号。结果表明了这些界如何依赖于载波频率、用于估计的样本数量和信噪比。它们还表明，增加天线数量（如在大规模MIMO系统中）即使对于非合作发射机也能显著提高定位精度并降低定位的信噪比阈值。最后，我们的推导表明，对于实际系统参数，这些界的平方根比载波波长低两到三个数量级。
