Distributed Antenna System for Centimeter-Level Wireless Positioning
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Solution Overview
Problem
Current wireless network technologies face challenges in achieving centimeter-level accuracy for positioning end terminals, particularly in environments like production floors and warehouses, due to limitations in measuring Differential Time of Arrival (DToA) effectively.
Innovation Solution
A Distributed Antenna System (DAS) with multiple antenna elements connected to a common Radio Unit (RU) processes replicas of radio signals using Fast Fourier Transform (FFT) to calculate phase differences, enabling accurate DToA measurements without complex calibration, and supports 3D positioning by triangulation, reducing the need for synchronization and canceling random time shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional DToA measurement methods are used in wireless networks, then the system can perform basic positioning, but the positioning accuracy is insufficient to achieve centimeter-level precision
Solution Approach 1:
The system divides the antenna array into multiple independent antenna elements, each equipped with its own frontend receiver. This segmentation allows parallel processing of signals at multiple locations, enabling high-precision DToA measurement through distributed observation points without requiring a single complex centralized system.
Solution Approach 2:
The patent replaces traditional mechanical synchronization methods with a common reference clock distributed to all antenna elements. This eliminates the need for complex mechanical synchronization hardware while achieving precise time alignment across all antenna elements for accurate DToA measurement.
2Measurement precision
If multiple antenna elements with separate frontend receivers are deployed, then DToA measurement accuracy is enhanced, but the system complexity and calibration requirements increase
Solution Approach 1:
The patent merges all antenna element signals into a common processing framework at the Radio Unit, which receives signals from all antenna elements and performs unified FFT processing. This combining approach simplifies the system architecture by centralizing signal processing while maintaining the benefits of distributed antenna elements for accurate DToA measurement.
Solution Approach 2:
The system performs preliminary signal processing at each antenna element's frontend receiver, including FFT transformation and phase difference calculation, before signals are combined at the Radio Unit. This preliminary action distributes computational tasks and reduces the complexity of centralized processing while maintaining measurement accuracy.
3Measurement precision
If synchronization between multiple antenna elements is implemented, then measurement accuracy improves, but random time shifts and synchronization complexity increase
Solution Approach 1:
Each antenna element's frontend receiver uses its own local clock synchronized to a common reference, allowing independent time measurement. The system self-corrects for time shifts through the common reference mechanism, eliminating the need for complex active synchronization protocols while maintaining precise time measurement across all elements.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enhances positioning accuracy up to 2-3 magnitudes compared to regular DToA measurements, reduces the need for synchronization, and minimizes random time shifts, achieving centimeter-level accuracy and improving measurement resolution.
Implementation Method 1
The RU converts s the radio signal to frequency domain by Fast Fourier Transform (FFT)
Implementation Method 2
receiving, by a distributed antenna system (DAS) with at least three antenna elements, replicas of a radio signal transmitted by a target end terminal
Data Source
AI summary
The subject matter discloses at a single site (a site with a single base station), connecting a distributed antenna to a Radio Unit (RU) of a 4G/5G base station such that the antenna elements are deployed at the target area apart from each other. According to some embodiments the RU receives from each antenna element a replica of the radio signal that is transmitted by the end terminal. The RU processes the phase differences between the subcarriers of each pair of signal replicas which are received by the antenna elements. The RU calculates the DToA (Difference in Time of Arrival) per each pair of replicas of the received signal according to the phase difference. The location measurements of the end terminal are carried out by performing triangulation using the DToA measurements.