Adaptive Keep Alive Period for Wireless Node Synchronization
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Solution Overview
Problem
In multi-hop wireless networks using time-synchronized medium access control protocols, nodes experience clock drift due to manufacturing differences, temperature, and supply voltage variations, leading to desynchronization issues, especially in the absence of data traffic, where the periodicity of keep alive frames is not adequately defined to maintain synchronicity across multiple hops.
Innovation Solution
A method to compute an estimated time drift between nodes and determine a keep alive period based on this drift and the number of hops from the root node, using beacon-based time drift estimates and a keep alive time compensation factor to maintain clock synchronicity, even in the presence of network interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If nodes use fixed periodicity for keep alive frames, then implementation is simple, but clock drift causes desynchronization in multi-hop networks
Solution Approach 1:
The patent makes the keep alive period dynamic by adjusting it based on the number of hops from the root node and estimated clock drift. Nodes farther from the root or with higher drift estimates use shorter intervals, transforming the fixed periodicity system into an adaptive one that maintains synchronicity reliability without requiring complex real-time negotiation.
Solution Approach 2:
The patent performs preliminary estimation of clock drift between parent and child nodes during the network setup phase. This advance knowledge is stored and used to pre-determine appropriate keep alive intervals before actual data transmission begins, allowing nodes to proactively configure their synchronization behavior rather than reacting to drift issues as they occur.
2Reliability
If nodes resynchronize frequently to maintain clock synchronicity, then synchronicity is maintained, but power consumption increases
Solution Approach 1:
The patent changes the time interval parameter of keep alive frames based on the number of hops and estimated drift. By adjusting this temporal parameter dynamically, the system achieves optimal balance between synchronization reliability and energy efficiency - nodes use longer intervals when drift is low and hop count is small, reducing unnecessary wake-ups and power consumption.
Solution Approach 2:
The patent applies different keep alive intervals to different nodes based on their specific characteristics (hop count from root, local drift estimate). Rather than using a uniform interval for all nodes, each node receives a customized interval appropriate to its position and clock characteristics in the network, optimizing the trade-off between synchronicity and power usage locally at each node.
3Use of energy by moving object
If nodes use longer keep alive periods to reduce power consumption, then energy efficiency improves, but clock drift accumulates causing desynchronization
Solution Approach 1:
The patent modifies the keep alive period parameter based on two key factors: the number of hops from the root node and the estimated clock drift between parent and child nodes. This parameter adaptation allows the system to extend intervals when conditions permit (reducing power consumption) while automatically shortening them when drift risk increases (maintaining synchronicity).
Solution Approach 2:
The system uses feedback from drift estimation mechanisms to adjust keep alive intervals. By continuously monitoring or estimating clock drift and using this information to configure synchronization intervals, the system creates a closed-loop control that adapts to actual clock behavior, preventing both excessive power consumption and synchronization loss.
4Device complexity
If nodes in multi-hop networks use standard keep alive intervals, then implementation is straightforward, but desynchronization occurs due to cumulative drift across multiple hops
Solution Approach 1:
The patent segments the synchronization problem by treating each hop in the multi-hop network independently. Instead of attempting to synchronize all nodes to the root simultaneously with a single interval, the system configures each node based on its specific distance from the root and local drift characteristics, breaking down the complex multi-hop synchronization into manageable per-node decisions.
Solution Approach 2:
The patent implements local quality by assigning different keep alive intervals to different nodes based on their position in the network hierarchy. Nodes closer to the root use different intervals than nodes farther away, and each interval is optimized for that specific node's drift characteristics, rather than applying a uniform standard interval throughout the entire multi-hop network.
Data Source
AI summary
A method for operating a node in a wireless network is provided that includes computing an estimated time drift between the node and a parent node of the node, and using the estimated time drift and a number of hops between the node and a root node of the wireless network to determine a keep alive period for the node.