Virtual Positioning Reference for Radio Signal Self-Localization
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Solution Overview
Problem
Existing navigation systems that rely on unsynchronized terrestrial radio signals for positioning face computational burdens and instability due to the need to calculate and compensate for transmitter clock offsets and local clock errors, especially in portable devices where processing power and battery life are limited.
Innovation Solution
The method establishes a virtual positioning reference that leverages the stability of transmitter clocks, eliminating the need to calculate transmitter clock offsets by using differential positioning and predicting the arrival times of code words based on known repeat rates, allowing for self-localization without the computational expense of clock error modeling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If transmitter clock offsets and local clock errors are calculated and compensated for using Equation 1, then positioning accuracy is improved, but computational complexity and processing time increase significantly
Solution Approach 1:
The patent extracts and eliminates the clock offset parameter from the positioning calculation by using differential measurement between two receivers. Instead of calculating absolute positions requiring clock offset compensation, the system calculates the difference in arrival times at two receivers, which removes the need to know or compensate for transmitter clock offsets, significantly simplifying the computational burden
Solution Approach 2:
The patent introduces a second receiver as an intermediary reference point. By comparing the arrival times at the mobile receiver and a second receiver with known position, the system creates a differential measurement that serves as an intermediary step, eliminating the need to directly calculate transmitter clock offsets while maintaining positioning accuracy
2Reliability
If multiple transmitters are used for effective self-localisation with clock offset calculations, then positioning reliability is improved, but energy consumption increases due to continuous calculation of offset values
Solution Approach 1:
The patent removes the energy-intensive clock offset calculation step by using differential timing measurements. The system only needs to measure arrival time differences between receivers, which can be done with simpler, lower-power processing while maintaining reliability through the use of multiple transmitters for triangulation
Solution Approach 2:
The system uses the second receiver's known position and measured arrival times to self-correct the timing measurements. The differential measurement approach allows the system to automatically compensate for timing errors without requiring external clock synchronization or continuous offset calculations, reducing energy consumption
3Ease of manufacture
If unstable local onboard clocks are used in portable navigation devices, then device portability and cost are improved, but positioning accuracy deteriorates due to clock error variations over time
Solution Approach 1:
The patent extracts the local clock error from the measurement equation by using differential timing. Instead of relying on the absolute accuracy of the local clock, the system measures the difference in arrival times at two receivers, which eliminates the need for a stable local clock and allows the use of inexpensive, portable timing devices
Solution Approach 2:
The system uses the known position of the second receiver as feedback to correct timing measurements. By comparing the expected arrival time (based on geometric relationship) with the actual measured arrival time difference, the system can compensate for local clock errors without requiring a stable onboard clock
Data Source
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AI summary
Methods and systems for radio positioning of a mobile receiver are described. When the mobile receiver (2) is at a first known position (M1), a virtual positioning reference is established by logging the known position (M1) of the mobile receiver (2) together with a local time at which a first instance of a predictably repeated code word is received by the mobile receiver (2) from a terrestrial radio signal transmitter (7). The terrestrial transmitter (7) is assumed to have a known position and the local time is measured relative to a clock local to the mobile device (2). During movement of the mobile receiver (2) from the first known position (M1) to a second unknown position (M2), the local clock is run. When the mobile receiver (2) is at the second unknown position (M2), the local clock is used to determine the time difference between when the virtual positioning reference is predicted to receive a second instance of the code word and when the mobile receiver (2) actually receives the second instance of the code word. From the time difference and the position information of the virtual positioning reference, the position of the mobile receiver (2) at the second position can thus be determined.