Passive Uplink TDOA Tracking System for Covert Mobile Transmitter Positioning
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Solution Overview
Problem
Current mobile terminal location systems rely on GPS and cellular network cooperation, which can be unreliable indoors, require active participation from mobile terminals, and increase network complexity and cost, especially in surveillance settings where clandestine tracking is desired.
Innovation Solution
A tracking system that uses dynamically assigned communication slots and uplink probes to determine the position of a mobile transmitter without requiring active participation from the cellular provider or mobile terminal, utilizing a cell monitor and correlator to analyze downlink scheduling transmissions and measured uplink probes for time difference analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If GPS is used for location determination, then location accuracy is improved, but system reliability deteriorates indoors or in areas with large buildings
Solution Approach 1:
The patent introduces uplink probes as intermediary devices deployed at known locations to receive and measure uplink transmissions from the mobile terminal. These probes act as mediators between the terminal and the positioning system, enabling location determination through time difference of arrival measurements without requiring GPS signals. The probes are synchronized with the network timing, allowing accurate position calculation even when GPS is unavailable.
2Measurement precision
If GPS tracking is activated, then location measurement capability is improved, but device complexity increases
Solution Approach 1:
The patent extracts the positioning function from the mobile terminal itself and relocates it to the network side. Instead of requiring the terminal to perform complex GPS measurements and calculations, the system uses simple uplink transmission timing measurements at distributed probes. The heavy computational burden of position calculation is performed by the network using the measured time differences and known probe locations, thereby simplifying the terminal device while maintaining positioning capability.
3Measurement precision
If cellular network cooperation is required for positioning, then location tracking is improved, but ease of operation deteriorates in surveillance settings
Solution Approach 1:
The patent implements self-service positioning where the mobile terminal autonomously performs positioning measurements without requiring active cooperation or triggering from the cellular network. The terminal naturally transmits uplink signals during its normal communication cycles, and the network passively measures the time difference of arrival at distributed probes. This eliminates the need for network-initiated positioning commands, handovers, or special signaling sequences, enabling covert surveillance operations.
4Measurement precision
If traditional uplink positioning systems are used, then location determination is improved, but device complexity increases due to multiple components
Solution Approach 1:
The patent makes the uplink probes multi-functional by having them serve both as communication receivers for normal cellular operations and as positioning measurement devices. The same probes that receive standard uplink transmissions for network communication also simultaneously perform time difference of arrival measurements for positioning. This eliminates the need for separate dedicated positioning infrastructure, reducing overall system complexity while maintaining positioning precision.
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
Enables accurate and covert tracking of mobile transmitters without relying on GPS or active cellular network assistance, reducing complexity and cost by using synchronized uplink probes and correlating scheduling and observation records to determine transmitter location.
Implementation Method 1
measuring the time difference in the arrival of uplink transmissions from the mobile terminal
Data Source
AI summary
A system that tracks a mobile transmitter within a communication system is disclosed. The mobile transmitter transmits in one or more predetermined communication slots, the communication slots being dynamically assigned by a system node in the communication system. The tracking system includes at least three uplink probes spatially separated from one another, each uplink probe measuring transmissions in each of the communication slots as a function of time. A cell monitor monitors downlink scheduling transmissions from the system node directed to the mobile transmitter, the scheduling transmissions specifying a time and communication slot to be utilized by the mobile transmitter in a subsequent transmission. A correlator receives the measured transmissions and the monitored downlink scheduling transmissions. The correlator uses the monitored downlink scheduling transmissions and the measured transmissions to determine a time at which a transmission from the mobile transmitter was detected at each of the uplink probes.