Frequency Hopping Network Node Synchronization via Coordinator Messages
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Solution Overview
Problem
Low-cost low-duty-cycle wireless sensor networks face challenges in maintaining channel hop synchronization without frequent messaging, which often leads to significant power consumption and reduced battery life due to the need for nodes to wake up frequently or scan for active channels.
Innovation Solution
A frequency hopping network method where a coordinator node transmits hop announcements and dwell start messages on control channels to synchronize subordinate nodes, allowing them to adjust their channel frequencies and extend dwell times as needed for message transmission, reducing the frequency of channel changes and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If nodes wake up frequently to maintain clock accuracy for synchronization, then synchronization accuracy is improved, but power consumption increases and battery life decreases
Solution Approach 1:
The patent introduces an intermediary mechanism (the synchronization message exchange between coordinator and subordinate nodes) that allows synchronization to be maintained through periodic communication rather than continuous clock maintenance. The coordinator node acts as a reference, and subordinate nodes adjust their clocks based on received synchronization messages, eliminating the need for each node to independently maintain high-precision clocks through frequent wake-ups.
Solution Approach 2:
The system implements periodic synchronization actions where the coordinator node transmits synchronization messages at regular intervals during active periods. Subordinate nodes wake up periodically to receive these messages and adjust their clocks accordingly, then return to sleep mode. This periodic approach maintains synchronization accuracy while minimizing power consumption compared to continuous operation.
2Reliability
If nodes scan the network to re-find active channels when out of synchronization, then synchronization is restored, but power consumption increases due to frequent scanning
Solution Approach 1:
The patent applies preliminary action by having the coordinator node proactively transmit synchronization messages to subordinate nodes before they lose synchronization. This allows subordinate nodes to maintain accurate timing information during sleep periods without needing to perform energy-consuming scanning operations to re-find channels. The synchronization information is provided in advance during the dwelling period, enabling nodes to remain synchronized upon waking.
3Device complexity
If dwell time is kept constant for simple protocol design, then device complexity is reduced, but network adaptability decreases
Solution Approach 1:
The patent implements dynamics by allowing the dwell time to be variable rather than fixed. The coordinator node can adjust the dwell time duration based on network conditions, traffic requirements, and synchronization needs. This dynamic approach enables the system to adapt to different scenarios (e.g., longer dwell times for synchronization-critical operations, shorter dwell times for power-saving scenarios) without requiring complex protocol redesign, maintaining relative simplicity while enhancing adaptability.
Data Source
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AI summary
Method for synchronizing a node in a frequency hopping network includes monitoring a hop frequency channel to detect a hop announcement transmitted on a group of control channels in use by a network coordinator node. The hop announcement specifies a second hop frequency channel which will be utilized subsequent to a first hop frequency in a hopping sequence. Responsive to receiving the hop announcement a node monitors the second hop frequency to receive a dwell start message. The dwell start message is transmitted from the coordinator node to signal the beginning of a dwell period during which the second hop frequency will be used by the network for communicating data.