A Time Synchronization Method for Hierarchical Wireless Sensor Networks

Abstract

The invention relates to a hierarchical wireless sensor network time synchronization method and belongs to a wireless sensor network time synchronization method. The method respectively adopts different synchronization mechanisms aiming at response nodes and ordinary non-response sub nodes and adopts different estimation methods to calculate the clock offset and the clock frequency offset relative to reference nodes; the hierarchical time synchronization method is divided into two stages, namely a hierarchical discovery and sub node collection stage and a time synchronization stage, wherein during the hierarchical discovery and sub node collection stage, a hierarchical structure of a wireless sensor network is established, and the response nodes on each layer are determined through collecting sub node information; during the time synchronization stage, a maximum likelihood estimation method and a least square method are utilized for calculating the clock offset and the frequency offset between the sub nodes and the reference nodes, a clock is further compensated, and by parity of reasoning, the synchronization within a whole network range is finally achieved. The hierarchical wireless sensor network time synchronization method has the advantages that the synchronous message overhead is reduced, and the energy consumption is reduced; the time synchronization accuracy is improved; the expandability is enlarged on aspect of new node addition.

Description

technical field [0001] The invention relates to a wireless sensor network time synchronization method, in particular to a layered wireless sensor network time synchronization method. Background technique [0002] Wireless sensor networks (WSNs) are networks composed of a large number of micro-sensor nodes in a wireless self-organizing manner. They are widely used in military and civilian fields. WSNs have gradually become a hot topic in modern research, and time synchronization is a key aspect of wireless sensor networks. It is an important supporting technology that affects the operation and application of the sensor network's own protocol. The hardware clock inside the WSNs node has a certain error, which leads to deviations in the local time of different nodes. Many applications of WSNs need to maintain the accuracy of the entire network or some nodes. Time synchronization, such as multi-sensor data compression and fusion, low-power MAC protocol and routing protocol, tran...

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Problems solved by technology

Existing time synchronization mechanisms suitable for wireless sensor networks can be divided into traditional centralized synchronization mechanisms, such as TPSN, Tiny-sync and Mini-sync, which are based on the interaction between the sender and receiver. bandwidth and storage space, as well as receiver-receiver-based time synchronization algorithms RBS and Adaptive RBS, as well as receiver-only synchronization algorithms, in which other groups of nodes monitor the information exchange of a pair of nodes to achieve synchronization; and Hu A et al. proposed an algorithm based on a cooperative synchronization mechanism for a network with a high node density. This algorithm eliminates the result of single-hop accumulation of synchronization errors, and the higher the node density, the smaller the synchronization error; Synchronization mechanism, such as the firefly synchronization algorithm, some scholars have obtained a synchronization accuracy of about 100us through 24 node networking experiments; two authors, RuiFan and Nancy Lynch of the Massachusetts Institute of Technology, first proposed the GCS (Gradient Synchronization System) based on the gradient synchronization mechanism. ClockSynchronization) synchronization algorithm, and simulate the protocol on the Mica2 node, through 20 node experiments, and add timestamp technology in the MAC layer, it is obtained that the average synchronization accuracy between adjacent nodes reaches 4.0us, and the average synchronization accuracy of the entire network The synchronization accuracy reaches 14.0us, but the energy consumption is relatively high

[0005] Synchronization accuracy and synchronization energy consumption are contradictory but important performance indicators in time synchronization. Classical time synchronization algorithms do not achieve a good balance between the two

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