Power Line Time Synchronization via AC Zero-Crossing
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Solution Overview
Problem
The challenge lies in coordinating time-keeping and communication between numerous endpoint devices and a command center over power distribution lines, particularly in utility metering and reporting systems, where synchronization, signal interference, and time zone differences complicate data communication and billing accuracy.
Innovation Solution
A method and system that utilize a power line communication system with a command center, collector devices, and endpoint devices, where the communication protocol is synchronized using a collector network time derived from a time server, with endpoint network time adjusted to account for location-based times, utilizing AC power as a time base for maintaining metrological time and facilitating accurate data transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple time bases are used for different network times (collector network time, endpoint network time, location-based time), then time-keeping flexibility and accuracy are improved, but system complexity increases
Solution Approach 1:
The patent segments time-keeping into multiple independent time bases: collector network time using crystal oscillators, endpoint network time using AC zero-crossing events, and location-based time accounting for time zones and daylight saving time. Each segment operates independently with its own time base, allowing precise local time-keeping while maintaining overall system coordination through defined relationships between the time bases.
Solution Approach 2:
The patent introduces AC zero-crossing events as an intermediary time reference that bridges collector network time and endpoint network time. The AC signal serves as a common intermediary that both the collector and endpoint devices can reference, enabling time synchronization without requiring direct coupling between all devices in the network.
2Adaptability or versatility
If downstream data communication is implemented over power distribution lines, then communication coverage and data collection capability are improved, but signal interference and communication reliability deteriorate
Solution Approach 1:
The patent utilizes the periodic AC power signal (50Hz or 60Hz) as a time base for data communication synchronization. By aligning communication protocols with the periodic AC cycles, devices can coordinate data transmission timing, reducing signal interference and improving communication reliability over the power distribution lines.
Solution Approach 2:
The patent replaces traditional electrical signal-based communication with a time-synchronized communication approach using AC zero-crossing events as references. This substitution allows data to be transmitted over the same power lines without direct electrical signal conflicts, as the time base provides a coordination mechanism that separates data communication from power transmission.
3Manufacturing precision
If time synchronization is maintained across all devices, then billing accuracy and data coordination are improved, but communication bandwidth and processing requirements increase
Solution Approach 1:
Each device maintains its own local time base independently (collector using crystal oscillators, endpoints using AC zero-crossing events). The devices self-synchronize to their respective time bases without requiring constant communication or processing resources, reducing the bandwidth and processing requirements compared to centralized synchronization approaches.
Solution Approach 2:
The patent changes the time base parameter from a centralized reference to distributed local references. By allowing each device to use its own time base (AC zero-crossing events for endpoints, crystal oscillators for collectors), the system achieves synchronization without requiring continuous communication bandwidth for time adjustment, as each device independently tracks its local time reference.
Data Source
AI summary
Particular embodiments are directed towards a method for communicating time-based data in a power line communication system. The communication system utilized in the method includes: a command center; a collector device; and a plurality of endpoint devices. The method includes communicating, from the collector device, downstream data to the plurality of endpoint devices. This downstream communication utilizes a communication protocol that is relative to a collector network time, and is over a set of power distribution lines carrying alternating current (AC). The collector network time uses the local oscillator. The AC zero-crossing event can be used as a time base for other versions of the network time. Conceptually, the AC can be thought of as acting as a reference clock for maintaining these other network times, although the clocking function can be carried out in the digital realm, e.g., using a digital-signal processor (DSP).