Sleepy Node Wake-Up Sync in Asynchronous Channel Hopping
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Solution Overview
Problem
IEEE 802.15.4e does not provide a solution for sleepy node device operation in asynchronous channel hopping networks, requiring sleepy nodes to remain awake to maintain hopping sequences, which contradicts the need for low power consumption.
Innovation Solution
Sleepy nodes utilize a real-time clock to track the coordinator's hopping sequence during sleep, changing their receive channel upon waking and advertising this change in a data request command frame, allowing them to synchronize with the coordinator's hopping schedule without maintaining their own sequence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sleepy nodes remain awake to maintain hopping sequences in asynchronous channel hopping networks, then network compatibility and synchronization are improved, but power consumption increases
Solution Approach 1:
The coordinator node pre-calculates and stores the hopping sequence information in a lookup table during network initialization. When a sleepy node needs to synchronize, it simply queries the coordinator with its wake-up time and receives the pre-computed channel information, eliminating the need for the node to maintain its own hopping sequence during sleep.
Solution Approach 2:
The coordinator node acts as an intermediary that maintains the hopping sequence information and provides it to sleepy nodes upon request. Instead of each node maintaining its own sequence, the coordinator serves as a centralized repository that nodes can query, reducing the computational burden on individual sleepy nodes.
2Productivity
If sleepy nodes always stay awake to enable channel hopping, then network throughput and reliability are improved, but power efficiency deteriorates
Solution Approach 1:
The system pre-computes the hopping sequence and stores it in the coordinator's lookup table before nodes go to sleep. This allows sleepy nodes to quickly synchronize upon waking without needing to continuously track the sequence, enabling them to sleep efficiently while maintaining network productivity when active.
Solution Approach 2:
Sleepy nodes wake up periodically to query the coordinator for their current channel information and then return to sleep mode. This periodic wake-up pattern allows the network to maintain throughput during active periods while achieving significant power savings during sleep periods, balancing productivity and energy efficiency.
Data Source
AI summary
A radio communications device includes a RTC configured to run even during sleep for receiving from a coordinator node (CN) in an asynchronous channel hopping WPAN an asynchronous hopping sequence (AHS) frame that includes the CN's hopping sequence. A processor implements a stored sleepy device operation in asynchronous channel hopping networks algorithm. The algorithm is for determining a time stamp for the AHS frame and the CN's initial timing position within the hopping sequence, storing the time stamp, going to sleep and upon waking up changing a frequency band of its receive (Rx) channel to an updated fixed channel. A data request command frame is transmitted by the device on the CN's listening channel that is calculated from the CN's hopping sequence, time stamp, CN's initial timing position and current time, and the device receives an ACK frame transmitted by the CN at the updated fixed channel of Rx operation.