Hierarchical Time Synchronization in Wireless Sensor Networks
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Solution Overview
Problem
In wireless sensor networks, existing time synchronization methods are inefficient due to high power consumption and unnecessary precision, as upper nodes broadcast synchronization data to all lower nodes, leading to increased overhead and power loss, without mechanisms for managing synchronization levels according to application requirements.
Innovation Solution
A time synchronization method where an upper node provides back-off scheduling to lower nodes in a hierarchical structure, using local clocks to calculate back-off times based on received synchronization packet data, allowing lower nodes to synchronize and broadcast response packets, which are then used to adjust synchronization levels and reduce collision risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an upper node broadcasts synchronization data to all lower nodes, then time synchronization is achieved, but power consumption and packet overhead increase
Solution Approach 1:
The patent segments the synchronization process into two phases: a broadcast phase where the upper node sends synchronization data to all lower nodes, and a unicast response phase where only selected lower nodes send response packets back. This segmentation allows the system to achieve reliable time synchronization while reducing overall power consumption by avoiding continuous full-duplex communication.
Solution Approach 2:
The patent applies partial action by having lower nodes selectively respond to synchronization broadcasts based on their synchronization needs. Not all lower nodes need to participate in every synchronization cycle, so the system uses response limit seeds and back-off scheduling to let only necessary nodes send response packets, reducing unnecessary power consumption while maintaining adequate synchronization reliability.
2Reliability
If an upper node broadcasts synchronization data to all lower nodes, then time synchronization is achieved, but packet overhead increases
Solution Approach 1:
The synchronization protocol is segmented into directed unicast responses rather than requiring all lower nodes to send full synchronization responses. The upper node sends a broadcast synchronization packet, and only selected lower nodes send back unicast response packets, significantly reducing the total packet overhead while maintaining synchronization reliability.
Solution Approach 2:
The patent extracts only the necessary synchronization information from full synchronization packets. The upper node includes minimal essential data (time stamp, response duration, response limit seed) in the broadcast packet, and lower nodes send back only their specific response information, removing unnecessary data overhead while preserving synchronization functionality.
3Device complexity
If synchronization is performed without managing synchronization levels, then synchronization technology is simple, but unnecessary precise synchronization causes overhead and power loss
Solution Approach 1:
The patent introduces dynamic synchronization level management where the upper node adjusts the response limit seed based on the current synchronization state and network conditions. This dynamic adaptation allows the system to automatically tune the synchronization precision to match actual needs, preventing unnecessary energy consumption from overly aggressive synchronization while maintaining adequate precision when required.
Solution Approach 2:
The system changes the parameter of response limit seed dynamically during operation. The upper node modifies this parameter based on synchronization progress and network conditions, allowing the synchronization mechanism to adapt its precision requirements. This parameter adjustment prevents fixed high-precision synchronization from causing unnecessary overhead and power loss when lower precision is sufficient.
4Reliability
If lower nodes continuously synchronize, then time synchronization is maintained, but repeated synchronization causes overhead
Solution Approach 1:
The patent implements periodic synchronization with intelligent scheduling. The upper node broadcasts synchronization data at regular intervals, but lower nodes use back-off scheduling to determine when to send response packets. This periodic action with built-in pauses prevents continuous collision and redundant transmission, improving overall synchronization efficiency while maintaining reliability.
Solution Approach 2:
The system uses feedback mechanisms where lower nodes send response packets containing their synchronization status and timing information back to the upper node. The upper node uses this feedback to adjust future synchronization schedules and response limit seeds, creating a closed-loop system that optimizes synchronization frequency and efficiency based on actual network conditions.
Data Source
AI summary
A time synchronization method in a wireless sensor network, has an upper node that provides back-off scheduling to lower nodes in the wireless sensor network of a hierarchical structure. Each of the lower nodes synchronizes time according to the back-off scheduling based on its local clock. The time synchronous method also allows the number of packets required for synchronization in the wireless sensor network to sharply decrease, and the life time of the network to increase. Additionally, the time synchronous method provides a response packet from a lower node in response to a synchronization packet from an upper node, which is used as a synchronization start packet for secondary lower nodes, so that synchronization in the entire network is rapidly processed.