Mobile Device Clock Calibration for Indoor SPS Signal Acquisition

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Solution Overview

Problem

Current mobile devices face challenges in accurately determining their position in indoor environments due to uncertainties in satellite positioning system (SPS) time, which increases the search window for acquiring SPS signals, leading to higher power consumption and longer time-to-fix.

Innovation Solution

A method is implemented where a mobile device calibrates its local carrier network time to SPS time by time-tagging multiple SPS position fixes, reducing uncertainty in SPS time and using a calibrated base station clock drift rate to minimize the search window for acquiring SPS signals, and crowdsourcing measurements from multiple devices to refine clock accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the mobile device uses a larger search window to account for SPS time uncertainty, then the device can acquire SPS signals more reliably, but power consumption increases and time-to-fix increases

Engineering Contradiction:

ImproveSPS signal acquisition reliabilityVSAvoidpower consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent applies preliminary action by calibrating the SPS time offset before the actual positioning operation. The mobile device performs time offset calibration using time-tagged SPS position fixes and base station timing information in advance, storing the calibrated offset value. When acquiring SPS signals later, the device uses this pre-calibrated offset to define a much smaller search window, thereby reducing power consumption and time-to-fix while maintaining reliable signal acquisition.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If the mobile device uses a larger search window to account for SPS time uncertainty, then the device can acquire SPS signals more reliably, but the time-to-fix increases

Engineering Contradiction:

ImproveSPS signal acquisition reliabilityVSAvoidtime-to-fix

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

Inventive Principle:

Principle #10Preliminary action

3Measurement precision

If the mobile device calibrates its local network time to SPS time using time-tagged position fixes, then SPS time uncertainty is reduced, but the device complexity increases

Engineering Contradiction:

ImproveSPS time accuracyVSAvoidclock management complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent applies self-service by enabling the mobile device to autonomously calibrate its own SPS time offset using readily available information from the network and SPS signals. The device independently performs time-tagging of position fixes, calculates the offset between local network time and SPS time, and stores the calibrated value for future use, without requiring external calibration services or additional hardware components.

Inventive Principle:

Principle #25Self-service

4Use of energy by moving object

If the mobile device operates in lower power state with sleep counter, then power consumption is reduced, but clock accuracy deteriorates due to sleep counter increment cycle uncertainty

Engineering Contradiction:

Improvepower consumptionVSAvoidclock accuracy

Core Design Contradiction:

Use of energy by moving objectVSMeasurement precision

Solution Approach 1:

The patent applies feedback by using the calibrated SPS time offset to correct and verify the sleep counter-based time tracking. The mobile device monitors the accuracy of its sleep counter increments by comparing against the known SPS time reference and adjusts its timekeeping accordingly, ensuring that even during low-power sleep periods, the clock remains synchronized with SPS time when positioning operations are performed.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS10149261B2Methods and systems for mobile device clock management

Publication Date: 2018.12.04 QUALCOMM INC

AI summary

Disclosed are methods, systems and/or devices to calibrate a network time by acquisition of satellite positioning system (SPS) signals and different instances of time, and time-tagging SPS times according to the network time. In particular, the network time may be calibrated based, at least in part, on a first difference between first and second SPS times obtained at two SPS position fixes and a second difference between corresponding first and second time stamps.