Direction Finding System for Mobile Phones Using LTE SRS
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Solution Overview
Problem
Existing methods for localizing cellphones, such as IMSI Catchers, require cooperation from cell network service providers and can be invasive, lacking accuracy and independence from network operations.
Innovation Solution
A system that uses active and passive segments to cause target cellphones to transmit unique signals, allowing for accurate Direction Finding (DF) and geo-location measurements without network cooperation, utilizing SRS codes in LTE protocols to identify and track cellphones across GSM, UMTS, and LTE networks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If IMSI Catchers are used to track mobile users and disclose IMSI, then location tracking capability is improved, but network cooperation and interference with external networks are required which reduces independence and reliability
Solution Approach 1:
The patent extracts the localization function from the cellular network infrastructure and implements it independently using passive DF/geolocation modules that receive and analyze uplink signals directly from cellphones without requiring network cooperation. This separates the tracking capability from network operations, achieving independence while maintaining accuracy.
Solution Approach 2:
The patent introduces a catcher device as an intermediary between the cellphone and the DF/geolocation system. The catcher captures unique signals from target cellphones and relays them to the localization module, enabling accurate tracking without direct network involvement or interference with external cellular networks.
2Measurement precision
If active manipulation of target UE by changing RAT to quiet frequency is used for direction finding, then geo-location accuracy is improved, but the complexity of operation and device control increases
Solution Approach 1:
The patent utilizes periodic SRS (Sounding Reference Signal) transmissions from LTE cellphones as the basis for localization. Instead of manipulating the target device through multiple RAT changes, the system passively receives these periodic uplink signals which naturally contain the necessary information for accurate geo-location, significantly simplifying operation.
Solution Approach 2:
The patent leverages the cellphone's own transmitted signals (SRS, uplink communications) for localization purposes. The target device inadvertently provides its own localization data through normal network operations, eliminating the need for external manipulation or control changes, and making the system extremely easy to operate.
3Measurement precision
If passive fixed sensors on base stations are deployed for TOA-based localization, then localization capability is improved, but cooperation with cell network service companies is required which reduces system independence
Solution Approach 1:
The patent segments the localization function into independent DF/geolocation modules that operate separately from the cellular network infrastructure. These modules receive signals directly from cellphones and perform localization calculations independently, eliminating the need for integration with base station sensors or network service company cooperation while maintaining accurate localization capability.
Data Source
AI summary
A system for localizing cellphones served by commercial network of base-stations and operative in conjunction with at least one catcher including a catcher-controller, and at least one transmitter and at least one receiver, thereby to define an area of coverage for the catcher, the system comprising at least one DF/geolocation module including a DF/geolocation controller and at least one set of receivers operative to receive uplink signal/s transmitted by cellphone/s.