Assisted GPS Positioning Reducing Time-to-First-Fix
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Solution Overview
Problem
Standard satellite positioning systems, such as GPS, face challenges in quickly determining user position, especially in emergency situations, due to signal obstruction and weak signal reception, leading to prolonged time-to-first-fix and inaccurate location data.
Innovation Solution
The system employs assisted positioning by using additional satellites to derive unambiguous time, eliminating the need for direct timing data from GPS signals, and incorporates pseudorange difference measurements to solve for position and time, allowing for faster and more accurate location determination without requiring precise timing information from the server.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If standard satellite positioning systems are used, then positioning function is provided, but time-to-first-fix is prolonged and positioning accuracy deteriorates in obstructed environments
Solution Approach 1:
The server performs preliminary actions by collecting and processing satellite signal data, ephemeris information, and timing data in advance. This pre-processed information is then transmitted to the portable device, enabling faster acquisition and reducing the time-to-first-fix without compromising positioning accuracy in obstructed environments.
Solution Approach 2:
A server acts as an intermediary between satellites and the portable device. The server receives satellite signals, processes the data including timing and ephemeris information, and transmits processed results to the portable device. This intermediary approach enables the device to obtain pre-processed data, significantly reducing acquisition time while maintaining positioning accuracy.
2Measurement precision
If additional satellites are used to derive unambiguous time, then positioning accuracy is improved, but device complexity increases
Solution Approach 1:
The server serves as an intermediary that handles the complex task of processing signals from multiple satellites to derive unambiguous time information. The portable device simply receives the processed timing data from the server, avoiding the need to implement complex multi-satellite signal processing algorithms locally, thus reducing device complexity while improving time determination accuracy.
Solution Approach 2:
The patent replaces the mechanical approach of directly processing multiple satellite signals with the portable device with a network-based approach. The server performs the complex signal processing and time derivation using computational methods, then transmits the results to the device. This substitution reduces the processing burden on the portable device while achieving accurate time determination.
3Loss of time
If assisted positioning is implemented, then time-to-first-fix is reduced, but communication infrastructure requirements increase
Solution Approach 1:
The server implements a multi-functional system that handles satellite signal reception, data processing, timing information generation, and communication with portable devices. This universal approach consolidates multiple functions into a single infrastructure, reducing the need for separate specialized systems while achieving rapid positioning through assisted positioning.
Solution Approach 2:
The communication infrastructure centered around the server acts as an intermediary that bridges satellite signals and portable devices. The server receives complex satellite data, processes it, and transmits simplified results to devices, reducing the communication burden on individual devices while enabling fast assisted positioning through centralized processing.
Data Source
AI summary
A base station (server) transmits assisting information to the user's receiver (rover). Signals from at least 5 satellites are used for 3-dimensional positioning. Pseudorange measurements are made in a system of equations having a minimum set of unknowns X,Y,Z, and T. (X,Y,Z) is the 3D rover position in a predefined coordinate system, and T is the time at which simultaneous measurements are made to determine pseudoranges to all satellites. The position of each satellite is a vector-valued function ƒk (T) of said time T, where fk is determined from satellite ephemeris data or its equivalent, sent to the rover over a communication link, as well as from knowledge of the approximate position of the rover.