Mobile Subscriber Position Estimation Using Terrestrial Base Station Signals
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Solution Overview
Problem
GPS receivers face challenges in accurately determining position due to satellite clock errors, attenuated signal reception, and large frequency uncertainty, which can lead to prolonged time-to-first-fix (TTFF) and difficulties in receiving signals from the required number of satellites, especially in indoor locations.
Innovation Solution
A method that combines GPS signals with terrestrial base station signals to estimate position, using two-way communication with serving base stations to provide timing and frequency information, reducing search space complexity and improving signal acquisition by correlating satellite and terrestrial signal times of arrival.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If GPS receiver uses standalone satellite signals for position estimation, then the system structure remains simple, but positioning accuracy deteriorates due to satellite clock errors and signal attenuation
Solution Approach 1:
The patent combines GPS satellite signals with terrestrial base station signals (such as WiMAX) to estimate position. The mobile station receives both satellite transmitted signals and terrestrial base station signals, then uses a combined positioning algorithm to calculate position based on both signal sources. This merging of signal sources compensates for the weaknesses of standalone GPS in indoor or urban canyons where satellite signals are attenuated or blocked.
2Device complexity
If GPS receiver operates without terrestrial signal assistance, then the device complexity is low, but time-to-first-fix increases due to large frequency uncertainty
Solution Approach 1:
The patent uses terrestrial base station signals to provide preliminary timing and frequency synchronization before GPS signal acquisition. The mobile station first acquires timing information from terrestrial base stations (which have more stable and predictable signal characteristics), then uses this preliminary synchronization to reduce the search space and accelerate GPS satellite signal acquisition. This preliminary action significantly reduces the time-to-first-fix by avoiding a complete blind search of the GPS signal space.
3Reliability
If GPS receiver attempts to acquire signals from multiple satellites for accurate positioning, then positioning reliability improves, but difficulty of detecting and measuring increases due to signal attenuation in indoor locations
Solution Approach 1:
The patent introduces terrestrial base station signals as an intermediary to assist GPS signal detection and measurement. The mobile station uses terrestrial signals (which are stronger and more reliably received indoors) to establish initial position estimates and timing references, then uses these to aid in detecting and measuring the weaker GPS satellite signals. The terrestrial signals act as a mediator that bridges the gap when direct GPS signal reception is difficult.
Data Source
AI summary
A method and apparatus of a mobile subscriber (MS) estimating position are disclosed. One method includes the MS receiving at least one satellite transmitted signal with a first receiver, and estimating a time of arrival of the at least one satellite transmitted signal. The MS additionally receives at least one terrestrial base station signal with a second receiver, and estimates a time of arrival of the at least one terrestrial base station signal. The MS estimates its position based on the estimated time of arrival of the at least one satellite transmitted signal and the estimated time of arrival of the at least one terrestrial base station signal.