Wireless Signal Characteristic Difference Estimation for Positioning
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Solution Overview
Problem
Global Navigation Satellite Systems (GNSS) face challenges in accuracy and availability, particularly in dense urban environments and indoors, where traditional positioning methods fail due to limited satellite signal reception, and there is a need to exploit 'signals of opportunity' for improved positioning and timing determinations.
Innovation Solution
A method is developed to estimate characteristic differences between wireless signals transmitted from the same location, including relative offset in time of transmission, carrier phase relationship, and amplitude relationship, which are processed to support timing and positioning measurements, even when signals are not coherently transmitted and have unknown properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional GNSS trilateration is used for positioning, then positioning can be achieved in open environments, but positioning accuracy deteriorates and availability is lost in dense urban environments and indoors
Solution Approach 1:
The patent changes the fundamental parameter of signal source from satellite-based GNSS to terrestrial wireless signals (cellular, Wi-Fi, broadcast). By estimating characteristic differences (time offset, phase relationship, amplitude relationship) between multiple terrestrial signals transmitted from known locations, the system achieves positioning in environments where satellite signals are unavailable, thereby improving positioning availability without sacrificing accuracy through the use of multiple signal characteristics
Solution Approach 2:
The patent makes the positioning system universal by enabling it to function with multiple types of wireless signals (cellular communications signals, terrestrial broadcast signals, Wi-Fi signals) rather than being limited to GNSS satellite signals. The method estimates characteristic differences between signals from the same location across different frequency ranges, allowing the system to adapt to various signal types and environments, thus improving both availability and accuracy
2Measurement precision
If multiple wireless signals are combined for positioning, then positioning accuracy is improved, but the complexity of signal processing increases
Solution Approach 1:
The patent segments the complex task of combining multiple wireless signals into distinct processing stages: first estimating the time offset between signals, then estimating the phase relationship, and finally estimating the amplitude relationship. This segmentation of the signal processing task reduces overall complexity by breaking down the multi-signal combination problem into manageable sequential steps, while still achieving improved positioning accuracy through the use of all three characteristic differences
Data Source
AI summary
A method and apparatus are provided for estimating characteristic differences between wireless signals transmitted from the same location in spaced apart frequency ranges. Also provided are a method and apparatus for estimating a combined time of arrival of the wireless signals, using the characteristic differences. A further method is provided, for identifying that two signals have been transmitted from the same location. Also disclosed is a method of maintaining a database of characteristic difference information.