Sensor Time Synchronization via Identification Signal
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Solution Overview
Problem
Existing methods for time synchronization in distributed systems, such as smart grids and IoT-based systems, are costly and inaccurate, especially in wireless communication networks where GPS signals are unreliable and radio time synchronization sources have limited availability, leading to temporal deviations in sensor data acquisition.
Innovation Solution
A method where a regular identification signal is sent in a radio network, allowing sensor units to store their internal time values with the transmitter identification, enabling central evaluation to determine a common reference time base and synchronize sensor data with high accuracy by assigning time values and transmitter identifications to sensor data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If GPS clocks or radio clocks are used for time synchronization in wireless networks, then time synchronization accuracy is improved, but device cost and complexity increase
Solution Approach 1:
The patent replaces expensive GPS clocks and radio clocks with inexpensive internal time units (crystal oscillators) that have limited accuracy but sufficient for the application. The system accepts that these simple time units drift over time but compensates through synchronization protocols, effectively using cheap, short-lived time references instead of expensive, stable ones.
Solution Approach 2:
The patent introduces a central unit as an intermediary that collects time data from multiple sensor units and performs centralized time synchronization. This mediator coordinates the timing across the network without requiring each sensor unit to have expensive GPS or radio clocks, distributing the synchronization function centrally rather than requiring expensive hardware at each node.
2Measurement precision
If GPS signals or radio time synchronization sources are used, then time synchronization is achieved, but reliability decreases in environments with limited signal availability
Solution Approach 1:
The patent makes the time synchronization system self-sufficient by having sensor units synchronize with each other through the central unit using their internal time units, eliminating dependence on external GPS or radio time signals. The system serves its own timing needs internally rather than relying on external sources that may be unavailable in factory or tunnel environments.
Solution Approach 2:
Instead of having sensor units independently receive time signals from external sources (GPS/radio), the patent inverts the approach by having the central unit collect time data from sensor units and distribute synchronized time references back to them. This reversal makes the system resilient to external signal availability issues.
3Device complexity
If internal time units without absolute time reference are used in sensor units, then device cost is reduced, but the ability to establish temporal relationships between sensor data from different units deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where sensor units transmit their internal time unit values to the central unit, which then calculates time offsets and sends correction information back to the sensor units. This feedback loop enables sensor units with simple internal time units to maintain accurate temporal relationships by continuously adjusting their time references based on centralized coordination.
Data Source
AI summary
The invention relates to a method for time synchronization of sensor units in a distributed system. Each sensor unit contains an internal time unit without an absolute time reference. Sensor data is acquired by the sensor units and transmitted via a radio network to a central unit for evaluation. A characteristic signal (101) is transmitted at regular intervals over the radio network, and its reception is monitored in the respective sensor units (102). Upon reception of a characteristic time feature of the respective signal, a current value of the internal time unit of the respective sensor unit is stored, along with a sender identification contained in the signal (103). When sensor data is acquired, another current value of the internal time unit of the respective sensor unit is stored (104).The sensor data acquired by the sensor unit are then assigned the value of the internal time unit stored upon reception of the characteristic time feature of the identification signal, the associated transmitter identification of the identification signal, the further value of the internal time unit stored upon acquisition of the sensor data, and a sensor identification of the respective sensor unit, and are transmitted together with the sensor data to the central unit (105). During central evaluation, a reference time base can then be derived from the transmitter identification, and a temporal relationship between the transmitted sensor data of the respective sensor unit and the reference time base can be derived from the value of the internal time unit of the respective sensor unit stored upon reception of the characteristic time feature of the identification signal and the further value of the internal time unit of the respective sensor unit stored upon acquisition of the sensor data (106).