Wireless Distance Measurement Using Time of Flight
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Solution Overview
Problem
Current wireless data exchange protocols, such as Bluetooth Low Energy (BLE), lack effective security measures to prevent attacks like replay, relay, and man-in-the-middle attacks, especially for non-connected devices, and existing indoor positioning systems using BLE are inaccurate and power-intensive.
Innovation Solution
A method and system for authenticating broadcaster devices in a wireless data exchange protocol using nonces and encryption, where a broadcaster device sends an advertising channel PDU with a first nonce, and an observer device responds with a scan request PDU containing a second nonce, both devices perform encryption functions, and authentication is confirmed if the results match, also incorporating time of flight calculations to determine distance between devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If RSSI-based proximity measurement is used to determine distance between devices, then the system can provide indoor positioning capability, but the measurement accuracy is poor and power consumption is high
Solution Approach 1:
The patent replaces the RSSI-based distance estimation method with a Time of Flight (TOF) measurement system. Instead of inferring distance from signal strength (which is inaccurate and power-intensive), the system uses precise timing measurements of signal propagation time multiplied by the speed of light to calculate distance, achieving both high accuracy and low power consumption
Solution Approach 2:
The patent changes the measurement parameter from signal strength (RSSI) to time of flight (TOF). By measuring the time it takes for a signal to travel between devices and multiplying by the speed of light, the system achieves accurate distance measurement without the high power consumption associated with traditional RSSI methods
2Reliability
If traditional BLE security protocols are used for connected devices, then authentication is provided, but non-connected devices remain vulnerable to replay, relay, and man-in-the-middle attacks
Solution Approach 1:
The patent implements preliminary authentication actions during the advertising and scanning phases, before actual data exchange begins. Devices exchange nonces and perform encryption verification in advance, establishing security credentials that protect subsequent communications even for devices that remain in non-connected mode
Solution Approach 2:
The patent introduces nonce-based encryption verification as an intermediary security mechanism. Instead of relying on connection-oriented security protocols, the system uses ephemeral random values (nonces) that are exchanged and verified during the advertising scan process, providing a security layer that works independently of connection state
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 solution enhances security by preventing replay and man-in-the-middle attacks and provides accurate, low-power distance determination between devices, improving the reliability and efficiency of indoor positioning systems.
Implementation Method 1
calculating a time of flight (TOF) for at least one of the sent PDUs; and determining the distance between the first and second devices using the calculated TOF
Data Source
AI summary
A method of determining a distance between a first and a second device in a wireless data exchange protocol is presented. The method includes sending an advertising channel Protocol Data Unit (PDU) from the first device; receiving the advertising channel PDU at the second device and responsively sending a scan request scanning PDU from the second device to the first device; receiving the scan request scanning PDU at the first device and responsively sending a scan response scanning PDU from the first device to the second device; calculating a time of flight (TOF) for at least one of the sent PDUs; and determining the distance between the first and second devices using the calculated TOF.