Mobile Device Tracking via IMSI-TMSI Segmentation
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Solution Overview
Problem
The 3GPP specification for GSM protocols has implementation deficiencies that allow for surface-level identification and passive tracking of intruders using GSM signals emitted by cellular devices, but existing methods struggle with unique identification and location accuracy due to random generation of temporary identities.
Innovation Solution
A system utilizing a software-defined radio (SDR) coupled with hardware components to receive GSM frequencies, implement stateful inspection of GSM/LTE packets, and employ algorithms for identifying mobile devices through IMSI and TMSI analysis, along with Bluetooth Low Energy packet detection, to determine device presence and location within a premises.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If temporary identities (TMSI) are randomly generated for mobile devices, then device privacy is protected and identification complexity is reduced, but unique identification and location accuracy deteriorate due to identity collisions and inability to distinguish authorized from unauthorized individuals
Solution Approach 1:
The system segments the identification process into multiple stages: first capturing TMSI for initial device detection, then obtaining IMSI for unique identification, and finally using location area code triangulation for precise positioning. This multi-stage segmentation resolves the contradiction by using simple random TMSI for initial filtering while employing more precise IMSI and triangulation methods for final identification and location accuracy.
Solution Approach 2:
The system introduces an intermediary authentication server that mediates between the mobile device and the tracking system. The server facilitates the transition from TMSI to IMSI by receiving attach requests, validating subscriber identities, and returning unique IMSI identifiers. This intermediary resolves the identification problem by providing a controlled channel to obtain unique device identifiers without requiring direct access to device hardware.
2Use of energy by moving object
If GSM signals are passively monitored for intruder detection, then system energy consumption is reduced and operational simplicity is improved, but identification reliability deteriorates due to inability to uniquely identify devices among multiple users
Solution Approach 1:
The system implements feedback by continuously monitoring GSM signals and using captured TMSI identifiers to query the authentication server for IMSI information. When a device is detected, the system receives feedback from the server confirming the subscriber identity, which then triggers location triangulation. This feedback loop ensures that only verified devices are tracked, maintaining high identification reliability while keeping the system in passive monitoring mode most of the time to conserve energy.
3Area of stationary object
If multiple mobile devices are tracked simultaneously using random TMSI, then tracking coverage area is expanded, but measurement precision deteriorates due to identity collisions and loss of individual device identification
Solution Approach 1:
The system dynamically transitions device identification from static TMSI (random temporary identifier) to dynamic IMSI (unique permanent identifier) when needed. During normal operation, devices are tracked using TMSI for broad coverage. When identification precision is required (such as for authorization verification or collision detection), the system dynamically requests IMSI from the authentication server, ensuring unique identification while maintaining expanded tracking coverage.
Data Source
AI summary
Systems and methods for tracking mobile devices are provided. One system comprises at least one processor and memory storing code which when executed by the at least one processor configure the at least one processor to perform a method of tracking a mobile device. The method comprises receiving broadcasting an IMSI message, receiving an IMSI attach request message from a mobile device, and identifying the mobile device within a location area.