RF Fingerprint Calibration Using Reference Terminals
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Solution Overview
Problem
Location tracking techniques based on RF fingerprints are sensitive to changes in the signal environment, such as addition or reconfiguration of base stations or obstacles, leading to degradation in location accuracy unless regularly updated.
Innovation Solution
A method and system that calibrate the mapping of signal strengths to geographical locations using a subset of subscriber terminals, employing alternative location techniques like U-TDOA or A-GPS, which are not dependent on downlink signals, to maintain accurate RF fingerprint measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If RF fingerprint-based location tracking is used, then location measurement can be performed without dedicated location hardware at the terminal, but location accuracy degrades when signal environment changes
Solution Approach 1:
The system continuously monitors location accuracy using reference terminals and feeds back calibration information to update the RF fingerprint database. When signal environment changes are detected, the system automatically triggers recalibration using alternative measurement methods (U-TDOA, A-GPS) to maintain accuracy without requiring complex dedicated hardware at each terminal.
Solution Approach 2:
The network performs self-calibration by selecting reference terminals that can provide accurate location measurements through alternative methods. The system uses these reference terminals to automatically update and maintain the RF fingerprint database, eliminating the need for manual intervention or complex calibration hardware at user terminals.
2Measurement precision
If the RF fingerprint mapping is updated frequently to account for environmental changes, then location accuracy is maintained, but system complexity and calibration resource requirements increase
Solution Approach 1:
Instead of requiring comprehensive calibration of all terminals, the system selects a partial subset of reference terminals that are strategically distributed to represent different signal environments. This partial calibration approach maintains location accuracy while significantly reducing the complexity and resource requirements compared to full network calibration.
Solution Approach 2:
The system introduces intermediary reference terminals that serve as mediators between the network and user terminals. These reference terminals perform the complex calibration measurements using alternative methods, while the network simply uses their reported locations to update the RF fingerprint database, simplifying the overall system architecture.
3Measurement precision
If alternative location techniques (U-TDOA, A-GPS) are used for calibration, then location accuracy is maintained during signal changes, but additional measurement and processing requirements are imposed
Solution Approach 1:
The system pre-configures reference terminals with alternative location measurement capabilities (U-TDOA, A-GPS) before signal environment changes occur. When calibration is needed, these pre-prepared reference terminals can immediately provide accurate location measurements without requiring real-time complex processing, improving calibration efficiency.
Solution Approach 2:
The system creates a simplified copy of the calibration process by using reference terminals that replicate the calibration function. Instead of requiring every terminal to perform complex alternative measurements, the reference terminals perform these measurements once, and their results are copied and applied to update the RF fingerprint database for all terminals.
Data Source
AI summary
Systems and methods for location tracking in a communication network. Base stations transmit downlink signals to a plurality of subscriber terminals to define a mapping between geographical locations and respective sets of signal strengths of the downlink signals received from the base stations at the geographical locations. A subset of the subscriber terminals may be selected, and for each subscriber terminal in the subset, first measurements of a geographical location of the subscriber terminal irrespective of the downlink signals is made. Second measurements of the downlink signals received at the subscriber terminal at the geographical location is made and the mapping of the subscribers terminals is updated responsively to the first and second measurements. The geographical locations of the subscriber terminals is updated using the updated mapping.