Cellular-Assisted GPS Timekeeping Circuit for Power Saving
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Solution Overview
Problem
Satellite positioning receivers, such as GPS, face challenges in maintaining accurate time estimates when powered down or without satellite signal coverage, and when connected to cellular networks with less accurate time bases, especially during handovers between base stations.
Innovation Solution
A wireless circuit and method that utilize a processor to generate pulse edges representing network-based receiver synchronization instances, combined with timekeeping circuitry including oscillators and counters, to maintain and adjust time components during network coverage, loss, and handovers, ensuring gapless time accounting and accurate time generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the satellite positioning receiver is powered down to save power, then energy consumption is reduced, but time accuracy deteriorates
Solution Approach 1:
The system performs preliminary time synchronization with the cellular network before powering down the satellite receiver. The timekeeping circuitry maintains continuous time tracking using network-based receiver synchronization instances, so when the satellite receiver is powered down, it can quickly reacquire accurate time without requiring full satellite signal reacquisition, thus saving power while maintaining time accuracy
Solution Approach 2:
The patent introduces an intermediary timekeeping circuitry that acts as a bridge between the cellular network and the satellite positioning receiver. This intermediary maintains continuous time tracking using network signals and transfers time information to the satellite receiver when needed, allowing the receiver to be powered down while time accuracy is preserved through the intermediary's continuous timekeeping
2Ease of operation
If the satellite positioning receiver connects to asynchronous cellular networks for time information, then convenience and accessibility are improved, but time accuracy deteriorates due to network delay
Solution Approach 1:
The system implements feedback mechanisms where the timekeeping circuitry continuously monitors network-based receiver synchronization instances and adjusts its time tracking accordingly. By measuring the actual time delays in network transmissions and incorporating this feedback into time calculations, the system compensates for network delay effects while maintaining the convenience of using asynchronous cellular networks
Solution Approach 2:
The patent employs dynamic time adjustment mechanisms that adapt to changing network conditions. The timekeeping circuitry dynamically adjusts for variable network delays by continuously tracking synchronization instances and adjusting time estimates in real-time, allowing the system to maintain accuracy despite the dynamic and variable nature of asynchronous cellular networks
3Use of energy by moving object
If the satellite positioning receiver is powered down during intervals, then power savings are achieved, but time-to-first-fix increases when powered back up
Solution Approach 1:
Before powering down the satellite receiver, the system performs preliminary time synchronization with the cellular network and stores time reference information. When the receiver is powered back up, it can quickly reacquire satellite signals and compute position using the pre-synchronized time information, dramatically reducing time-to-first-fix compared to starting from scratch
Solution Approach 2:
The timekeeping circuitry creates and maintains a copy of accurate time information from the cellular network that can be used by the satellite receiver when it is powered down. This time information copy allows the receiver to quickly resume operations without requiring full time resynchronization, reducing time-to-first-fix upon power-up
4Measurement precision
If the system maintains continuous satellite signal reception for accurate time, then time accuracy is improved, but energy consumption increases
Solution Approach 1:
Instead of continuous operation, the satellite positioning receiver is powered down periodically and only activated when needed for position fixes or time updates. The system uses periodic satellite signal acquisition combined with continuous but low-power cellular network time tracking, achieving acceptable time accuracy while dramatically reducing energy consumption compared to continuous satellite reception
Solution Approach 2:
The timekeeping circuitry is designed to serve multiple functions: it maintains time tracking using cellular network signals during periods when the satellite receiver is powered down, and it provides time information to both the satellite positioning system and other system functions. This multi-functionality allows the system to maintain time accuracy without requiring continuous satellite signal reception
Data Source
AI summary
An electronic circuit for use with time of arrival signals from a network, including a position determination unit, a first clock, a second clock, and processing circuitry coupled to said first clock, said second clock, and said position determination unit. The processing circuitry is operable to project a relatively-accurate subsequent global time based on said first and second clocks and to then return said relatively-accurate subsequent global time to said position determination unit to facilitate a subsequent position determination by said position determination unit.