Low-Power ToF Measurement via Multi-Node Segmentation
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Solution Overview
Problem
Low-power wireless devices (LPWD) used in secured systems are vulnerable to relay attacks, and existing time-of-flight (ToF) systems require high power levels that exceed the capabilities of LPWD systems.
Innovation Solution
A multi-node low-power ToF measurement system that includes two or more measuring stations, each equipped with a memory, a radio, and processors. The system configures one station as the main measuring station to transmit and receive ToF packets, while other stations receive and measure time intervals, with a compute node determining the ToF measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high frequency RF signals (UWB, millimeter wave) are used for ToF measurement, then measurement precision is improved, but power consumption increases beyond LPWD capabilities
Solution Approach 1:
The system divides the ToF measurement function into two segments: a low-power LPWD that transmits RF signals and a separate ToF device that performs high-precision time interval measurement. This segmentation allows the LPWD to operate at low power while the ToF measurement precision is achieved by the dedicated ToF device with higher capability hardware.
Solution Approach 2:
The patent introduces an intermediary ToF device that acts as a mediator between the LPWD and the secured system. The ToF device receives RF signals from the LPWD, measures the time interval with high precision, and relays information back to the secured system, thereby enabling accurate ToF measurement without requiring the LPWD to have high-power transmission capabilities.
2Reliability
If multiple transmissions at high frequency are used to address multipath propagation, then measurement reliability is improved, but power consumption increases
Solution Approach 1:
The system separates the function of multiple transmissions from the LPWD. The ToF device performs multiple time interval measurements on received RF signals to address multipath propagation, while the LPWD only needs to transmit the RF signals at low power. This segmentation allows reliability improvement through multiple measurements without increasing LPWD power consumption.
Solution Approach 2:
The ToF device serves as an intermediary that performs multiple measurements and signal processing to mitigate multipath effects. By placing this functionality in the ToF device rather than the LPWD, the system achieves improved measurement reliability through multiple transmissions and processing while the LPWD maintains low power operation.
3Measurement precision
If high time resolution is implemented for ToF measurement, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The system segments the functionality between the LPWD and the ToF device. The LPWD handles simple RF signal transmission with minimal complexity, while the ToF device concentrates the high time resolution measurement capability and associated complexity. This segmentation allows high measurement precision to be achieved without requiring the LPWD to be complex.
Data Source
AI summary
Techniques related to measuring a time-of-flight (ToF), comprising switching a first measuring station to a main operating mode, transmitting, by the first measuring station, a first ToF packet to a remote device, switching the first measuring station to a receive mode to receive a first ToF response packet from the remote device, receiving, by the first measuring station, the first ToF response packet, determining, a time interval between transmitting of the first ToF packet and receiving the first ToF response packet, receiving a plurality of time intervals from one or more other measuring stations, determining a ToF measurement based on the first time interval and the plurality of time intervals, switching the first measuring station to a secondary operating mode, and transmitting to a second measuring station, an indication to switch to the main operating mode.