WLAN Access Point Calibration via Reverse-Trilateration

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Solution Overview

Problem

Calibrating WLAN access points in GPS-unavailable locations, such as indoor environments, is complex, tedious, and error-prone, making it difficult to achieve accurate location services due to the lack of satellite line-of-sight and the rigidity of existing calibration methods.

Innovation Solution

A system and method using user equipment (UE) to transmit time-stamped packets from known locations, allowing access points to determine their positions through reverse-trilateration algorithms, with a calibration algorithm that calculates optimal transmission locations to minimize the number of required transmissions and account for access point ranges, and a server to process calibration data for accurate location calculations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional calibration methods are used in GPS-unavailable locations, then location services can be provided, but the calibration process becomes complex, tedious, and error-prone

Engineering Contradiction:

Improvelocation service accuracyVSAvoidcalibration process complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The calibration system performs self-calibration by automatically determining access point locations using reverse-trilateration algorithms. The system uses time-stamped packet transmissions from user equipment to automatically calculate positions without requiring manual surveyor intervention, thereby reducing complexity while maintaining accuracy through automated data collection and processing

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent replaces manual mechanical calibration processes with electronic and algorithmic systems. Instead of physical surveying equipment and manual measurements, the system uses electronic packet transmissions, timestamped data collection, and reverse-trilateration algorithms to automatically determine access point locations, eliminating the need for complex manual calibration procedures

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If manual calibration methods are used, then access point locations can be determined, but the process is time-consuming and expensive

Engineering Contradiction:

Improveaccess point location accuracyVSAvoidcalibration time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The system performs preliminary calibration actions by having user equipment transmit time-stamped packets from multiple known locations before location calculation begins. This preliminary data collection enables the reverse-trilateration algorithm to compute access point positions automatically, significantly reducing the time required compared to manual calibration while maintaining precision through pre-collected transmission data

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent uses copying by having user equipment transmit identical time-stamped calibration packets from multiple predetermined locations. These replicated transmissions create a dataset that can be processed through the reverse-trilateration algorithm to accurately determine access point positions, reducing calibration time while preserving measurement precision through consistent data replication

Inventive Principle:

Principle #26Copying

3Adaptability or versatility

If access points are relocated to improve coverage, then service area expands, but recalibration is required which increases complexity and cost

Engineering Contradiction:

Improvenetwork reconfiguration flexibilityVSAvoidrecalibration complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The calibration system is designed to be dynamic and adaptive, automatically recalibrating when access points are relocated. The system continuously collects transmission data from user equipment and uses the reverse-trilateration algorithm to update access point positions in real-time, enabling flexible network reconfiguration without requiring complex manual recalibration procedures

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system implements feedback by continuously monitoring transmission data from user equipment and using this information to automatically adjust and update access point location calculations. When access points are relocated, the system receives feedback from ongoing packet transmissions and automatically recalculates positions through the reverse-trilateration algorithm, maintaining accuracy while simplifying the reconfiguration process

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS9781564B2Calibration of WLAN access points for location services

Publication Date: 2017.10.03 AVAGO TECHNOLOGIES INTERNATIONAL SALES PTE LTD

AI summary

Wireless access points within a GPS-Unavailable environment can provide location services to user equipment devices within the environment provided that the access points are aware of their precise locations. In order to calibrate the locations of the wireless access points, a user equipment is moved to specific locations within the environment. At each of those locations, the user equipment transmits calibration signals that include the transmission location as well as a timestamp of the transmission time. Upon receipt by the access points, these signals are timestamped with a reception timestamp by a clock that is synchronized with the clock of the user equipment. After accumulating sufficient calibration information from a sufficient number of calibration locations, the access points can accurately determine their locations using trigonometric and other functions.