Performance Limits of Direct Wideband Coherent 3D Localization in Distributed Massive MIMO Systems

Area of Science:

• Electrical Engineering
• Wireless Communications
• Signal Processing

Background:

• Accurate positioning is crucial for 5G cellular systems, especially in dense urban environments.
• Distributed antenna arrays offer potential for enhanced localization capabilities.
• Line-of-sight (LoS) propagation is common in small cells and millimeter-wave (mmWave) frequencies.

Purpose of the Study:

• To derive and analyze the accuracy limits for wideband direct position estimation (DPE) of radio transmitters.
• To investigate the impact of system parameters on localization accuracy in 5G environments.
• To evaluate the benefits of distributed antenna arrays for transmitter localization.

Main Methods:

• Derivation of Cramér-Rao bounds (CRBs) for DPE under spatially coherent LoS conditions.
• Modeling of a system with collocated, synchronized front-ends and 3D distributed antennas.
• Analysis of CRBs considering spherical wavefronts, carrier frequency, sample size, and signal-to-noise ratio (SNR).

Main Results:

• CRBs were derived for both known and random Gaussian signal models.
• Localization accuracy is shown to depend on carrier frequency, number of samples, and SNR.
• Increasing antenna count, particularly in massive MIMO configurations, substantially boosts accuracy and lowers the SNR threshold.

Conclusions:

• Distributed antenna arrays significantly enhance the accuracy of wideband direct position estimation in 5G systems.
• The proposed system achieves high localization accuracy, with bound square roots orders of magnitude below the carrier wavelength.
• The findings are particularly relevant for small cells and mmWave frequencies where LoS is prevalent.