Mobile Switching Center Location Determination Using GPS Timing
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Solution Overview
Problem
The high cost and complexity of implementing Wireless Location Sensors (WLS) at each Base Transceiver Station (BTS) in mobile communications networks for precise caller location determination in emergency services, particularly in areas with lower population density, where the density of BTS is optimized for communications rather than location services.
Innovation Solution
The solution involves leveraging synchronization features of GSM networks to remove WLS equipment from selected cell sites, utilizing Time Difference of Arrival (TDOA) and other location technologies, and employing an offset table at the Mobile Switching Center (MSC) for automated location determination, allowing for sparse network deployment while maintaining accurate location services.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Wireless Location Sensors (WLS) are installed at each Base Transceiver Station (BTS) for precise location determination, then location accuracy is improved, but system cost and complexity increase significantly
Solution Approach 1:
The patent extracts the location determination function from individual BTS units and consolidates it at the MSC level. Instead of each BTS having WLS capability, the system uses existing BTS timing information combined with GPS synchronization at the MSC to perform centralized location calculation, thereby reducing device complexity while maintaining location accuracy
Solution Approach 2:
The patent makes the MSC a universal location determination point that serves all BTS in its coverage area. The MSC uses its GPS receiver to obtain absolute timing information and processes location requests from multiple BTS, eliminating the need for each BTS to have independent WLS functionality
2Measurement precision
If Wireless Location Sensors (WLS) are installed at each Base Transceiver Station (BTS) for precise location determination, then location accuracy is improved, but equipment and maintenance costs increase
Solution Approach 1:
The patent merges the location determination function with the existing MSC infrastructure. By combining GPS synchronization capability at the MSC with centralized processing of BTS timing information, the system eliminates the need for separate WLS equipment at each BTS, significantly reducing deployment and maintenance costs
Solution Approach 2:
The system uses the existing BTS timing information and GPS synchronization capabilities that are already part of the cellular network infrastructure. Rather than adding new specialized equipment, the patent makes the existing network elements serve the location determination function
3Productivity
If BTS are added based on population density for communications optimization, then communication service quality is improved, but location service coverage in low-density areas deteriorates
Solution Approach 1:
The patent changes the dimension of location determination from spatial distribution of WLS equipment to temporal measurement of signal arrival times. By using TDOA (Time Difference of Arrival) calculations based on signal timing at the MSC, the system can determine locations in areas with fewer BTS, as location accuracy depends on timing precision rather than BTS density
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 approach reduces costs significantly by eliminating the need for WLS at all BTS, achieving precise location determination using existing BTS timing information and GPS synchronization, thereby meeting FCC E911 requirements with improved network efficiency.
Implementation Method 1
The MSC includes a GPS receiver for obtaining absolute time information from GPS satellites
Implementation Method 2
One method of determining the location of a wireless caller via a terrestrial-based system is by Time Difference of Arrival (TDOA) technology. The TDOA technique works based on trilateration by measuring the time of arrival of a mobile station radio signal at three or more separate cell sites.
Data Source
AI summary
Emergency Services architecture for determining the location of a wireless caller. The architecture leverages a synchronization feature of GSM networks of the Base Station Subsystem (BSS) to enable employment of sparse networks by removing WLS (Wireless Location Sensor) equipment from selected cell sites. Thus, the location of a wireless caller within a sparse site can be determined. Sparse network location services can be provided further utilizing Time Difference of Arrival (TDOA) technology, and other network-based location technologies such as Enhanced Observed Time Difference (EOTD) and Angle of Arrival (AOA). Hybrid network-based/handset-based location technologies may also be used with the disclosed invention.