GPS Micro-Power Mode Selective Subsystem Control
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Solution Overview
Problem
Embedded GPS receivers in wireless devices face challenges in maintaining continuous operation without draining the power source, as they require significant power for near-instant position fixes and refinement, and existing power cycling modes do not effectively manage time, frequency, and position uncertainties, especially in weak signal or indoor environments.
Innovation Solution
A wireless device with a GPS section and a power controller that selectively powers GPS subsystems, implementing a Micro-Power Mode (MPM) to minimize power consumption by managing time and frequency uncertainties, reducing the need for bit and frame synchronization, and allowing continuous positioning with high probability at low power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If GPS receiver operates continuously to provide near instant position fixes, then positioning speed is improved, but power consumption increases
Solution Approach 1:
The GPS receiver implements periodic operation by alternating between active measurement periods and sleep periods. The system performs position fixes at scheduled intervals rather than continuously, allowing the receiver to enter low-power states between measurements. This periodic action maintains positioning capability while significantly reducing average power consumption compared to continuous operation.
Solution Approach 2:
The system performs preliminary actions by pre-calculating position estimates using available data (such as TCXO frequency estimates and RTC time) before actual GPS measurements are taken. This allows the receiver to prepare measurement parameters and reduce the duration of high-power active operation, thereby reducing overall power consumption while maintaining positioning speed.
2Use of energy by moving object
If power cycling modes are used to reduce power consumption, then energy expenditure is reduced, but time and frequency uncertainty management deteriorates
Solution Approach 1:
The system implements feedback mechanisms by continuously monitoring and updating TCXO frequency estimates based on GPS measurements when available. These frequency estimates are fed back into the timing system to correct RTC time calculations, thereby maintaining time and frequency accuracy even during power cycling. The feedback loop ensures that uncertainty is managed and reduced over time despite periodic power savings modes.
Solution Approach 2:
The system changes operating parameters by adjusting the duty cycle of GPS receiver activation based on operational conditions. When time and frequency accuracy requirements are high, the receiver remains active longer or more frequently. When conditions permit, the system reduces activation frequency to save power. This dynamic parameter adjustment balances energy expenditure with measurement precision requirements.
3Use of energy by moving object
If GPS receiver is turned off to save power, then power consumption decreases, but Time-To-First-Fix increases
Solution Approach 1:
The system performs preliminary actions by maintaining and updating almanac and ephemeris data in memory even when the GPS receiver is in low-power mode. It also pre-calculates expected satellite positions and maintains TCXO frequency estimates. When the receiver needs to wake for a position fix, this preliminary preparation significantly reduces the time required to acquire signals and compute position, thereby reducing Time-To-First-Fix while still allowing power savings during inactive periods.
Data Source
AI summary
A wireless device including a transceiver that utilizes a power supply is described. The wireless device includes a Global Positioning System (“GPS”) section having a plurality of GPS subsystems and a power controller in signal communication with the power supply and GPS section, wherein the power controller is configured to selectively power each GPS subsystem from the plurality of GPS subsystems.