A-GPS Accuracy with Location Measurement Units
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional A-GPS systems face challenges in accurately determining the location of mobile devices in environments with low satellite visibility, such as urban canyons and indoor locations, due to the need for multiple satellite measurements and limited GPS receiver sensitivity.
Innovation Solution
The use of Location Measurement Units (LMUs) to determine the GPS-System time relationship and provide fine-time assistance information, allowing for location determination with fewer satellite measurements and enhancing GPS receiver sensitivity by providing accurate initial location estimates through uplink and downlink measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional A-GPS systems require measurements from a minimum of five satellites for location determination, then location accuracy can be maintained, but the system fails to provide location services in environments with low satellite visibility such as urban canyons and indoor locations
Solution Approach 1:
The patent introduces network timing measurements from base stations as an intermediary measurement source. Instead of relying solely on satellite measurements, the system uses base station timing signals to provide additional constraints for location determination. This mediator enables location calculation with fewer satellite measurements by supplementing the measurement set with terrestrial network timing data.
Solution Approach 2:
The patent changes the measurement parameters by incorporating network timing measurements (such as time of arrival from base stations) into the location determination process. This parameter expansion allows the system to solve for location with fewer satellite pseudo-ranges by adding different types of measurement data that provide additional geometric constraints.
2Adaptability or versatility
If the number of satellite measurements is reduced to three for location determination, then location services become available in low satellite visibility environments, but the system lacks sufficient measurements to solve for all five unknowns (three-dimensional location, user equipment clock bias, and GPS time bias)
Solution Approach 1:
Network timing measurements from synchronized base stations serve as intermediary measurements that provide additional independent equations. These measurements from multiple base stations create hyperboloid constraints that, when combined with three satellite pseudo-ranges, provide sufficient constraints to solve for all five unknowns including location, clock bias, and GPS time bias.
Solution Approach 2:
The patent adds another dimension of measurement by incorporating terrestrial network timing data into the traditionally satellite-only positioning problem. This dimensionality expansion from purely space-based measurements to combined space-terrestrial measurements provides the additional mathematical constraints needed to solve the system with fewer satellites.
3Measurement precision
If GPS receiver sensitivity is increased to detect weaker satellite signals, then location determination becomes possible in challenging environments, but the Time-to-First-Fix increases and battery consumption increases
Solution Approach 1:
The system performs preliminary location estimation using network timing measurements from base stations before attempting GPS signal acquisition. This preliminary action provides an initial location estimate that constrains the GPS search space, allowing the receiver to focus on detecting weaker satellite signals more efficiently without requiring extended integration times that would increase TTFF.
Solution Approach 2:
The patent uses network timing measurements to provide feedback constraints on the GPS solution. By continuously monitoring base station timing signals and using them to validate and refine GPS position estimates, the system can achieve reliable location determination with improved sensitivity while maintaining acceptable TTFF through iterative refinement rather than prolonged signal integration.
Data Source
AI summary
A system and method for determining the location of a mobile device. One or more location measurement units (LMUs) or components may be requested to provide timing relationship information from a respective cell site. These LMUs may then be tasked to measure uplink times of arrival of signals received by the LMUs from a target mobile device. A response message from the target mobile device may be received, the response message having reference epoch frame information whereby a Global Positioning System (GPS) time estimate at the reference epoch that the target mobile device used to make GPS satellite measurements is determined as a function of the requested timing relationship information. Satellite information may then be determined using the determined GPS time estimate, and a location of the mobile device performed using this satellite information.