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In wireless sensor networks (WSNs), connecting disjoint segments is significant for network restoration, especially in some mission critical applications. However, the variability of distances between disjoint segments has tremendous influence on relay nodes deployment. In fact, finding the optimal solution for connecting disjoint segments in terms of the number and positions of relay nodes is NP-hard. To address this issue, plenty of heuristics, such as STP-MSP (Cheng et al., 2008), MST-1tRN (Lloyd et al., 2007), and CORP (Lee and Younis, 2010) are deeply pursued. In this paper, we propose a distributed restoration algorithm based on optimal relay node placement (simply, ORNP). It aims at federating separated segments by populating the minimum number of relay nodes in a WSN that has suffered a significant damage. In addition, both of complexity and upper bound of the relay count for ORNP are explored. The simulation results show that ORNP performs better than STP-MSP, MST-1tRN, and CORP in terms of relay count and the connectivity of resulting topology. [ABSTRACT FROM AUTHOR]

In this article, an improved malicious code intrusion detection method is presented based on the target tree for space information network, so as to adapt to the characteristics of space information network and the security requirements. The satellite system could realize the quick determination of the malicious code attacks formed by joint cooperation behaviors step by step, with the help of attack roadmap analysis at ground and malicious code behavior analyzing process at satellite. The simulation results show that the proposed method has the advantages of high detection rate, low satellite resource consumption, low latency, and in-depth analysis to those malicious code behaviors. It is demonstrated that the proposed detection method of malicious code is suitable for the space information network. [ABSTRACT FROM AUTHOR]