Time-of-Flight Localization Using Overhearing Access Points
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Solution Overview
Problem
Indoor localization techniques face challenges in accuracy, cost, and scalability due to cumbersome site-survey requirements, expensive infrastructure, and scalability issues with time-of-flight (ToF) based localization methods, which overwhelm wireless networks with excessive probe-ACK packet exchanges.
Innovation Solution
The solution reduces network traffic by computing distances using time-of-flight information from a designated access point and overhearing access points, where the overhearing access points observe and record probe-ACK packet exchanges, rather than participating in them, thereby minimizing the number of required packet exchanges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ToF based localization uses multiple access points to compute distances, then localization accuracy is improved, but network traffic increases excessively due to multiple probe-ACK packet exchanges
Solution Approach 1:
The patent introduces an intermediary mechanism where a single probe packet from the client device is overheard and recorded by multiple access points simultaneously. This intermediary approach allows multiple APs to contribute to localization without each AP initiating separate probe-ACK exchanges, thus reducing network traffic while maintaining the ability to compute distances from multiple APs for accurate localization.
Solution Approach 2:
The patent merges the probe packet transmission into a single action that serves multiple access points simultaneously. Instead of separate probe-ACK exchanges with each AP, one probe packet is combined to provide distance information to multiple APs, which then independently record the exchange. This combining reduces the total number of packet exchanges while still enabling multi-AP based localization.
2Measurement precision
If site-survey techniques are used to improve localization accuracy, then measurement precision is improved, but device complexity and cost increase due to cumbersome procedures
Solution Approach 1:
The patent enables the system to self-configure for localization without requiring manual site-survey procedures. Access points automatically record probe-ACK packet exchanges as they occur in normal operation, and the location server automatically processes this data to determine client device locations. This self-service approach eliminates the need for separate, complex site-survey procedures while still achieving accurate localization.
Solution Approach 2:
The patent performs preliminary setup by having access points pre-configured to monitor and record probe-ACK packet exchanges. Rather than requiring post-deployment site-survey calibration, the system is prepared in advance to automatically capture the necessary timing information from normal packet exchanges, simplifying the overall system complexity.
3Measurement precision
If traditional ToF localization initiates probe-ACK packet exchanges with multiple access points, then distance measurement accuracy is improved, but scalability deteriorates due to network overload
Solution Approach 1:
The patent uses the probe packet itself as an intermediary that carries timing information observable by multiple access points simultaneously. This single intermediary packet enables multiple distance measurements without requiring multiple separate exchanges, thus maintaining measurement precision while improving scalability by reducing the total number of packet exchanges that could overload the network.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly reduces network traffic and enhances the scalability of ToF-based localization, making it more attractive for widespread deployment by minimizing the overhead of probe-ACK packet exchanges.
Implementation Method 1
computing a first distance between a first node and a target node based on a first time-of-flight (ToF) of a communication sequence between the first node and the target node
Data Source
AI summary
A first distance between a first node and a target node is computed based on a first time-of-flight (ToF) of a communication sequence between the first node and the target node. A second distance between a second node and the target node is computed based on a second ToF of the communication sequence between the first node and the target node, as recorded by the second node. A location of the target node is determined based on the first distance and the second distance.