BLE Clock Synchronization Using Physical-Layer Timestamping
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Solution Overview
Problem
Existing system clock synchronization techniques, particularly over Bluetooth Low Energy (BLE) wireless links, face challenges in achieving accurate synchronization due to high variability in message propagation delays and asymmetric delays, leading to substantial synchronization errors, especially in IoT devices powered by small batteries where power consumption is a concern.
Innovation Solution
Perform timestamping at the physical layer of the BLE protocol stack using a shunt resistor to monitor supply current, enabling precise detection of BLE radio ON/OFF states and reducing message propagation delays to τPROP, thereby minimizing synchronization errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If timestamping is performed at higher layers of the BLE protocol stack, then device complexity is reduced, but message propagation delays increase due to processing overhead at application and link layers
Solution Approach 1:
The patent introduces a dedicated timestamping unit as an intermediary component that operates independently from the main BLE protocol stack processing. This unit captures timestamps at the physical layer before data packets undergo processing at the link and application layers, thereby eliminating the processing overhead delays while maintaining system architecture simplicity.
Solution Approach 2:
The patent segments the timestamping function from the main BLE protocol processing by implementing a separate timestamping unit that operates in parallel. This segmentation allows timestamp capture to occur independently at the physical layer without interfering with or being delayed by higher-layer processing operations.
2Loss of time
If timestamping is performed at the physical layer, then message propagation delays are minimized, but device complexity increases due to additional hardware components
Solution Approach 1:
The patent introduces a dedicated timestamping unit as an intermediary component that operates independently from the main BLE protocol stack processing. This unit captures timestamps at the physical layer before data packets undergo processing at the link and application layers, thereby eliminating the processing overhead delays while maintaining system architecture simplicity.
Solution Approach 2:
The timestamping unit is designed to be self-contained and autonomous, capturing timestamps directly from the physical layer signals without requiring intervention from or coordination with higher-layer processing units. This self-service approach minimizes the need for additional complex control logic and inter-component communication.
3Reliability
If conventional system clock synchronization techniques are used over BLE, then synchronization can be achieved, but synchronization errors increase due to high variability in message propagation delays
Solution Approach 1:
The patent introduces a dedicated timestamping unit as an intermediary component that operates independently from the main BLE protocol stack processing. This unit captures timestamps at the physical layer before data packets undergo processing at the link and application layers, thereby eliminating the processing overhead delays while maintaining system architecture simplicity.
Solution Approach 2:
The patent replaces the conventional software-based timestamping approach (which occurs at higher protocol layers) with a hardware-based timestamping unit that operates at the physical layer. This substitution of mechanical/hardware implementation for software processing eliminates the variability introduced by software execution and processing overhead, achieving more precise and consistent timestamp measurements.
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
Accurately synchronizes system clocks with reduced power consumption by minimizing message propagation delays, especially in IoT devices, achieving precise time synchronization with minimal error.
Implementation Method 1
using a shunt resistor to monitor supply current, enabling precise detection of BLE radio ON/OFF states
Data Source
AI summary
Mechanism and method are disclosed for the synchronization of communicating devices via Bluetooth Low Energy (BLE) wireless links. Specifically, the invention pertains to synchronizing an Internet-of-Things (IoT) peripheral device, which includes hardware additions for performing timestamping at the BLE physical layer, to a mobile device, such as a smartphone or tablet, that executes the BLE protocol in software, By equalizing the processing time of the transmitted data to the BLE connection interval, accurate synchronization can be achieved without the need for timestamping at the BLE physical layer on the mobile device, This disclosure addresses a longstanding challenge in synchronization over BE wireless links, which has persisted in the industry since the introduction of the BLE wireless communication protocol.