Single-Message Ranging with Clock Ratio Compensation
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Solution Overview
Problem
Existing ranging technologies require multiple frames for each cycle, leading to increased power consumption, channel occupancy, and system cost, particularly in applications like automotive and IoT, due to clock offset inaccuracy and complexity.
Innovation Solution
A method involving an initial two-way ranging operation to calculate a clock ratio and multi-frame-cycle time of flight, followed by single-message ranging cycles using the calculated clock ratio to determine distance, reducing frames to one per cycle and incorporating recalibration for accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple frames are used for each ranging cycle, then measurement precision is improved, but power consumption increases
Solution Approach 1:
The patent performs an initial two-way ranging operation before single-message ranging cycles to pre-calculate the clock ratio. This preliminary action compensates for clock offset between devices, enabling accurate ranging with subsequent single-message cycles without requiring multiple frames per cycle.
Solution Approach 2:
The patent changes the ranging protocol from multiple frames per cycle to single-message cycles by introducing clock ratio compensation. This parameter change allows the system to maintain measurement precision while reducing the number of frames transmitted, thereby lowering power consumption.
2Measurement precision
If multiple frames are used for each ranging cycle, then measurement precision is improved, but channel occupancy increases
Solution Approach 1:
The initial two-way ranging operation performs clock synchronization and ratio calculation before single-message ranging cycles. This preliminary action enables subsequent ranging operations to use fewer frames, reducing channel occupancy while maintaining precision through clock ratio compensation.
Solution Approach 2:
The patent modifies the ranging protocol parameters from multiple frames per cycle to single-message cycles by implementing clock ratio-based time of flight calculation. This parameter change reduces the number of frames occupying the channel while preserving measurement accuracy.
3Measurement precision
If multiple frames are used for each ranging cycle, then clock offset compensation is improved, but device complexity increases
Solution Approach 1:
The patent performs clock ratio calculation during an initial two-way ranging operation before single-message ranging cycles. This preliminary clock synchronization establishes a reference for compensating clock offset throughout subsequent ranging operations, simplifying the overall system architecture.
Solution Approach 2:
The patent changes from complex multi-frame protocols with continuous clock synchronization to simpler single-message cycles using pre-calculated clock ratio compensation. This parameter change reduces device complexity while maintaining clock offset compensation capability.
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
Reduces power consumption and system cost while maintaining accuracy by minimizing frames and compensating for clock offset, suitable for automotive and IoT applications.
Implementation Method 1
a multi-frame-cycle-ToF as the time difference between a message being sent by the first device and being received by the second device as part of the initial-ranging-operation
Data Source
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Figure 2a~2b
Figure 3a~3b
AI summary
A method of determining a distance between a first device and a second device. The method comprises: performing an initial-ranging-operation, by exchanging two multi-frame ranging cycles between the first device and the second device, to calculate a clock ratio and a multi-frame-cycle-ToF. The method further comprises performing a plurality of single-message ranging cycles, wherein each single-message ranging cycle comprises: at a predetermined first-device-cycle-time after an earlier message is sent from the first device to the second device, the first device sending a single-ranging-message to the second device; determining a second-device-cycle-time as the time between the second device receiving the single-ranging-message and the earlier message being received by the second device; determining a current-message-ToF based on: the previous-message-ToF, the first-device-cycle-time, the clock ratio, and the second-device-cycle-time. The current-message-ToF represents the time of flight of the single-ranging-message travelling from the first device to the second device.