Unsynchronized Terminal Ranging with Physical-Layer Timestamping
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Solution Overview
Problem
Existing systems struggle to accurately determine the distance between unsynchronized communication terminals over a line-of-sight channel without requiring additional equipment or synchronization, and they are limited in range and accuracy.
Innovation Solution
A method using timestamping at the physical layer to calculate the distance by measuring the residence time of a range response message and adjusting communication parameters based on these measurements, which includes incorporating a range request flag and optimizing buffer management to minimize residence time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If timestamping is performed at the physical layer with residence time measurement, then measurement precision is improved, but device complexity increases
Solution Approach 1:
Each terminal uses its own local timestamp counter to record transmission and reception times independently. The ranging calculation is performed autonomously by the receiving terminal using the stored timestamps and the residence time from the response message, without requiring external synchronization equipment or complex coordinated timing systems.
Solution Approach 2:
The patent replaces complex mechanical synchronization systems and additional ranging equipment with an electronic/software-based timestamping mechanism at the physical layer. This substitution uses standard digital timing components already present in communication terminals, eliminating the need for specialized synchronization hardware while achieving accurate ranging measurements.
2Measurement precision
If additional equipment is added to improve ranging accuracy, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The existing communication terminals perform ranging measurements using their own built-in timestamping capabilities and processing units. No external ranging equipment, synchronization devices, or additional hardware are required - the terminals serve their own ranging needs using resources already present in the communication system.
Solution Approach 2:
The communication terminals perform multiple functions: data communication and ranging measurement. The same physical layer infrastructure, timestamp counters, and processing units used for normal communication operations are also utilized for ranging measurements, eliminating the need for dedicated ranging equipment and achieving multi-functionality from existing components.
3Measurement precision
If synchronization is implemented between terminals, then measurement precision is improved, but device complexity increases
Solution Approach 1:
Each terminal independently records timestamps using its own local clock without requiring synchronization with the other terminal. The ranging calculation compensates for the lack of synchronization by using the residence time information provided in the response message, allowing each terminal to autonomously perform accurate measurements despite unsynchronized clocks.
Solution Approach 2:
The residence time parameter acts as an intermediary that bridges the gap between unsynchronized terminals. By measuring and communicating the time the responding terminal takes to process and reply to the ranging request, the system enables accurate ranging calculations without requiring the terminals' clocks to be synchronized, effectively mediating the time reference issue.
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
Enables accurate ranging measurements over longer distances and improved communication quality by calculating distance without synchronization, reducing the need for extra equipment and enhancing bit error rate and quality of service.
Implementation Method 1
The first terminal transmits a range request to a second terminal... The first terminal communicates with the second terminal over a line of sight communication channel... a roundtrip time for the range request is calculated. This roundtrip time can be used to calculate a distance between the first terminal and the second terminal based on the roundtrip time. The distance can be calculated by multiplying half of the calculated roundtrip time by the speed of light.
Data Source
AI summary
A range is determined between two unsynchronized communications terminals in which a first terminal transmits a range request to a second terminal. The first terminal stores a first timestamp in memory corresponding to a time at which the range request message was transmitted. A range response is later received by the first terminal from the second terminal. The range response includes a residence time that characterizes an amount of time the second terminal required to send the range response after receiving the range request. The first terminal later stores a second timestamp in memory corresponding to a time at which the range response was received. Based on the second timestamp minus the first timestamp and the residence time, a roundtrip time for the range request is calculated. This roundtrip time can be used to calculate a distance between the first terminal and the second terminal based on the roundtrip time.