Radio Distance Estimation via Channel Sounding Inversion
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Solution Overview
Problem
Existing methods for estimating the distance between two radio equipment items in environments with multiple propagation paths, such as buildings, suffer from significant errors due to the assumption of direct line signal paths, leading to high energy consumption and costly measurements in ad hoc networks.
Innovation Solution
The method involves a first device estimating a first flight time and then sending a channel sounding frame, where the second device detects the difference in flight time between the strongest and first propagation paths, allowing it to calculate a corrected flight time and distance, with the first device initiating the channel sounding frame transmission to distribute the load and reduce energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the device sends multiple channel sounding frames to estimate distance in environments with multiple propagation paths, then the distance estimation accuracy is improved, but the energy consumption increases
Solution Approach 1:
Instead of having the first device send multiple channel sounding frames, the patent inverts the approach by having the second device send a single channel sounding frame back to the first device. The first device then uses the received signal to estimate both the strongest path and first path, thereby reducing energy consumption while maintaining distance estimation accuracy in environments with multiple propagation paths.
Solution Approach 2:
The channel sounding frame sent by the second device serves multiple functions: it allows the first device to estimate the strongest propagation path, estimate the first propagation path, calculate the time of flight difference, and ultimately determine the straight-line distance. This multi-functionality reduces the need for multiple separate measurements and lowers energy consumption.
2Measurement precision
If the first device sends channel sounding frames to all neighboring devices for distance estimation, then the positioning accuracy is improved, but the energy consumption of the first device increases significantly
Solution Approach 1:
The patent inverts the traditional approach where the first device actively sends sounding frames to all neighbors. Instead, each neighboring device (second device) sends a single channel sounding frame back to the first device when it receives a positioning request. This inversion dramatically reduces the energy consumption of the first device while still enabling it to estimate distances to multiple neighbors and calculate accurate positions.
3Device complexity
If the measurement process is simplified by assuming direct line signal paths, then the calculation complexity is reduced, but the distance estimation accuracy deteriorates in environments with multiple propagation paths
Solution Approach 1:
The patent extracts and separately analyzes the different propagation paths (strongest path and first path) from the complex multi-path environment. By identifying and measuring the time of flight difference between these specific paths using channel sounding, the system accurately determines the straight-line distance without being misled by other reflection paths, thus maintaining simplicity while improving accuracy.
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 reduces the energy consumption of new nodes in ad hoc networks by distributing the load of channel sounding frames and improves distance estimation accuracy by accounting for multiple propagation paths, while maintaining control over sensitive information.
Implementation Method 1
an estimation phase, implemented by the first device, of a first flight time between the two devices corresponding to the duration of signal transmission to go from one to the other device following a path of propagation, called 'strongest path'
Implementation Method 2
from the received radio signals corresponding to said channel sounding frame, estimating a difference in flight time between the strongest propagation path and a first propagation path
Data Source
Figure 1~2
Figure 3
Figure 4A~4B
AI summary
The process includes an estimation phase, implemented by the first piece of equipment (A), of a first time-of-flight between the two pieces of equipment (A, Z) corresponding to the signal transmission time to go from one to the other piece of equipment along a propagation path, called the "strongest path", taken by a main part of the signal energy, an estimation phase of a time-of-flight difference comprising the sending of a channel sounding frame by the first piece of equipment to the second and, from the received radio signals corresponding to said channel sounding frame, the estimation of a time-of-flight difference between the strongest propagation path and a first propagation path, carried out by the second piece of equipment, and a calculation phase of the distance between the two pieces of equipment (A,Z) comprising the determination of a second flight time by subtracting the difference in estimated flight time from the first estimated flight time (E30) and the calculation of the distance between the two devices from the second flight time thus determined.