Mobile Device Positioning Using Cell-to-Cell Distance References
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Solution Overview
Problem
Existing cellular positioning systems face challenges in accurately estimating the position of mobile devices due to errors caused by multipath propagation in time-based systems and uncertainty in received signal strength measurements, particularly in asynchronous systems like GSM and UMTS, which require additional hardware and are susceptible to environmental factors.
Innovation Solution
A method and system that estimate the position of a mobile device by designating a serving cell and neighboring cells, determining distances between them, and applying weighting factors based on signal strength and cell-to-cell distances to calculate a weighted average position, which does not require additional hardware or site-specific measurements, and is resistant to modeling errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If time-based systems (TOA/TDOA) are used for position estimation, then position estimation capability is achieved, but synchronization complexity and cost increase significantly in asynchronous systems
Solution Approach 1:
The patent introduces cell-to-cell distance information as an intermediary parameter that mediates between the mobile device and the positioning system. Instead of directly measuring time-based distances requiring synchronization, the system uses known distances between cellular installations as reference data to estimate mobile position through signal strength comparisons, thereby avoiding synchronization complexity while maintaining positioning capability
Solution Approach 2:
The patent replaces the mechanical/time-based synchronization system with a signal-strength-based measurement system. Instead of relying on precise time synchronization between cellular installations (mechanical timing system), the system uses received signal strength measurements combined with cell-to-cell distance data to estimate position, substituting the complex synchronization mechanism with a simpler signal strength comparison approach
2Measurement precision
If additional hardware is installed at each cell for time-based range estimation, then position estimation accuracy improves, but system cost increases significantly
Solution Approach 1:
The patent enables the existing cellular infrastructure to serve the positioning function using its own existing resources. The system uses already-deployed cellular installations and their existing signal transmission capabilities, combined with publicly available cell-to-cell distance information, to perform positioning without requiring additional specialized hardware at each cell site
Solution Approach 2:
The patent makes the existing cellular network infrastructure multi-functional by enabling it to perform both communication and positioning functions simultaneously. The same cellular installations that provide voice and data services also provide positioning capabilities through signal strength measurements, eliminating the need for separate dedicated positioning hardware
3Device complexity
If received signal strength measurements are used for position estimation, then system simplicity is maintained, but measurement accuracy deteriorates due to environmental factors
Solution Approach 1:
The patent incorporates feedback by using cell-to-cell distance information as a reference to validate and refine position estimates. The system compares measured signal strengths against expected signal strengths based on known cell-to-cell distances, and uses this feedback to correct for environmental variations and improve overall measurement accuracy
Solution Approach 2:
The patent changes the measurement parameters from raw signal strength alone to a combination of signal strength ratios and cell-to-cell distance information. By transforming the measurement approach to use ratios and incorporating spatial relationship data, the system compensates for environmental factors that affect absolute signal strength measurements
4Measurement precision
If time-based range estimation is used in multipath environments, then position estimation is achieved, but error rates increase due to multipath propagation
Solution Approach 1:
The patent uses cell-to-cell distance information as an intermediary reference that is immune to multipath effects. Since these distances are determined by geometric relationships between fixed cellular installations rather than wireless signal propagation, they provide a stable reference that does not suffer from multipath propagation errors affecting direct signal-based measurements
Data Source
AI summary
A method of and system for estimating the range of a mobile device to a wireless installation is disclosed. A method of estimating the position of a mobile device includes receiving signals transmitted by fixed-position wireless communication stations in range of a mobile device. One of the wireless communication stations from which signals are received by the mobile device is designated as a serving station and location information is retrieved for said serving station and at least one other neighboring station from which signals are received. For each of the at least one other neighboring stations, a corresponding distance between the serving station and said neighboring station is determined based on the location information. A position of the mobile device is estimated based on the location information for the serving station and said neighboring stations and further based on the distances between the serving station and said neighboring stations.