Mobile Station Database for GPS Signal Acquisition

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Solution Overview

Problem

Existing GPS systems face delays in signal acquisition due to large search spaces, especially after a cold start or when signals are lost, and assisted GPS systems rely on frequent updates and external communication, which can be inefficient and power-intensive.

Innovation Solution

A mobile station database is created to store cellular identifications and associated position information, allowing the mobile station to reduce the uncertainty region for satellite signal search based on both stored position data and platform dynamics, enabling more focused signal acquisition and reducing dependence on external updates.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If GPS receiver performs signal acquisition without prior knowledge (cold start), then complete signal search space must be searched, but signal acquisition time becomes very long (several minutes)

Engineering Contradiction:

Improvesignal acquisition completenessVSAvoidsignal acquisition time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The system performs preliminary actions by maintaining a database of previously observed satellite signal parameters (Doppler frequency, code phase, elevation) and predicted satellite positions. Before a cold start acquisition, the receiver uses this pre-collected information to narrow the search space, eliminating the need to search the entire two-dimensional search space from scratch.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system creates a copy of relevant signal acquisition information (satellite almanac, Doppler predictions, code phase estimates) and stores it in local memory. This copied information is then used to guide the acquisition process, replacing the need to perform a complete search and reducing acquisition time from several minutes to much shorter durations.

Inventive Principle:

Principle #26Copying

2Reliability

If GPS receiver uses large search space to ensure high sensitivity, then signal detection capability is improved, but signal re-acquisition delay increases to tens of seconds

Engineering Contradiction:

Improvesignal detection sensitivityVSAvoidsignal re-acquisition delay

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system applies local quality by concentrating search resources on specific regions of the search space where signals are most likely to be found, based on predicted satellite positions and previously observed parameters. Instead of uniformly searching the entire search space, the receiver focuses computational effort on localized regions with higher probability of signal presence, maintaining sensitivity while reducing overall acquisition time.

Inventive Principle:

Principle #3Local quality

3Measurement precision

If assisted GPS system frequently updates satellite orbit data and assistance information, then position determination accuracy is improved, but power consumption and communication overhead increase

Engineering Contradiction:

Improveposition determination accuracyVSAvoidpower consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The system implements periodic action by updating satellite orbit data and assistance information at predetermined intervals rather than continuously or on-demand. The receiver periodically requests and processes assistance data from the network, balancing the need for accurate position determination with the constraints of power consumption and communication overhead.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The system performs preliminary actions by maintaining a database of previously received satellite almanac and ephemeris data. Instead of frequently requesting updated assistance information, the receiver uses this pre-collected data to extend the period between updates, reducing communication overhead and power consumption while maintaining acceptable position determination accuracy.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS7706975B2Mobile cellular identification database for enhanced GPS performance

Publication Date: 2010.04.27 QUALCOMM INC

AI summary

A mobile station database of cellular identifications and associated position information is stored in mobile station memory. The mobile station uses the position information in the database to assist in determining a current position for the mobile based on an identifier, such as cell ID, base station BSIC, PSC, or carrier frequency. A satellite vehicle signal is searched in an uncertainty region that is a function of position information associated with the current identifier. The uncertainty region can be limited by assumed platform dynamics via predefined velocity and acceleration information. Time maintenance for the mobile station can also be achieved through known approximate position from the position database and measurement of a single satellite vehicle propagation delay. The mobile station can compare a position determination obtained through satellite vehicle signals with position database information to determine the validity of that position. Out-of-network position information is also stored in the position database and is optionally shared with a network.