Construction of quantitative indicator system of invulnerability for bionic spider-web farmland wireless sensor network

Combining the unique advantages of spider web with communication technology of wireless sensor network, presents high research value and broad development prospects. Nevertheless, the traditional quantitative index of invulnerability can not accurately describe the coupling relationship and overall function of failed network components, which leads to the difficulty in effectively inheriting the invulnerability mechanism of the artificial spider web model. In this paper, a sort of quantitative index system of invulnerability was proposed based on average number of node paths and average usage number of nodes and links, as the indicators for evaluating the impact degree and weight assignment of failed network components. In order to investigate effectiveness and availability of the index system, 3 independent artificial spider web models were involved in simulation analysis. The simulation experiment showed that the average number of node paths, the average usage number of nodes, chord chains and spoke chains were in consistent with the approximate regulations for different scale artificial spider-web models. Among them, in the case of the failure of nodes, chord chains and spoke chains, the attenuation of average number of node paths had unidirectional diffusion, namely the failure only affected the outer layers of failure location. Meanwhile, the attenuation of average usage number of nodes, chord chains and spoke chains had bidirectional diffusivity, and the failure affected both inside and outside of the layer where it was located. It showed that there were obvious cross-coupling relations and inter-layer coupling correlation between nodes and links. At the same time, the failure of local components would affect the whole network, and the effect of the same layer and the adjacent layer was more significant, indicating that the failure process of artificial spider-web model had obvious cascade diffusion characteristics. Moreover, the number of node paths of any node was exponentially positively correlated with the scale of the model and the number of layers in which it was located. As the layer number increasing, the average usage times of nodes, chord chains and spoke chains gradually decreased, the inner layers decreased slightly, and the outer layers had significant downward trend. In conclusion, the index system could effectively quantify the invulnerability of artificial spider web model, and evaluate the weight proportion of each network component, and the nodes, chord and spoke chains account for 50%, 39.44% and 10.56% respectively. The weight ratio of the first layer node, chord chain and spoke chain reached 33.28%, and the outermost layer only accounted for 6.72%. It manifested that the importance of nodes and chord chains was much higher than that of spoke chains, and the components closer to the network center had had higher value. Compared with the traditional index, the index system proposed in this paper had unique advantages. Field experiment adopted 3 network deployment schemes consisting of one sink node and 12 common nodes respectively. Node energy consumption, packet loss rate, delay and hops were applied as the indicators. The results showed that spider web deployment had better invulnerability than non-overlapping clustering deployment and grid deployment. In addition, the failure of nodes would cause the increase of packet loss rate, delay time and hops of adjacent outer nodes, which was similar to the theoretical simulation results. Quantitative analysis of the invulnerability of artificial spider web model can provide useful guidance for optimizing the deployment of farmland wireless sensor network and achieving reliable applications. © 2019, Editorial Department of the Transactions of the Chinese Society of Agricultural Engineering. All right reserved.