Grey wolf optimizer (GWO) is an efficient swarm intelligence algorithm for kinds of optimization problems. However, GWO tends to be trapped in local optimum when solving large-scale problems. Social hierarchy is one of the main characteristics of GWO which affect the searching efficiency. Thus, an improved algorithm called hierarchy strengthened GWO (HSGWO) is proposed in this paper. Firstly, the pack of wolves is roughly divided into two categories: dominant wolves and omega wolves. Secondly, the enhanced elite learning strategy is performed for dominant wolves to prevent the misguidance of low-ranking wolves and improve the collective efficiency. Then, the hybrid GWO and differential evolution (DE) strategy is executed for omega wolves to avoid falling into local optimum. In addition, a new hybrid one-dimensional and total-dimensional selection strategy is designed for omega wolves to balance the exploration and the exploitation during optimization. Finally, a perturbed operator is used to maintain the diversity of the population and further improve the exploration. To make a complete evaluation, the proposed HSGWO is first compared with six representative GWO variants for 50-dimensional problems based on CEC2014 benchmarks. The scalability of HSGWO is further tested by comparing it with eight state-of-the-art non-GWO algorithms for large-scale optimization problems with 100 decision variables. In addition, feature selection problem is used for testing the effectiveness of HSGWO on real-world applications. Experimental results demonstrated that the proposed algorithm outperforms other algorithms in terms of solution quality and convergence rate in most of the experiments.

The accurate localization of nodes in wireless sensor networks (WSNs) can be jeopardized in certain applications of fields, such as those in security and military. In order to detect the nodes that are captured as malicious anchors, a malicious node detection algorithm named MNDC and its improved version named EMDC are proposed in this paper. The algorithms utilize the density-based spatial clustering to acquire the abnormal clusters, which are further examined via a sequential probability ratio test. The malicious nodes that jeopardize networks are then determined. The conducted simulation results and corresponding analysis demonstrate that the proposed algorithms outperform other state-of-art schemes in terms of detection accuracy and effectiveness.

The simultaneous flooding scheduling is popular for Low-Density Parity-Check (LDPC) Belief Propagation (BP) decoding. Non-simultaneous sequential scheduling is superior to the flooding scheduling, and asynchronous dynamic scheduling has better FER performance than the sequential scheduling. However, all strategies encounter the trouble of locating the error variable node. This paper proposes an informed dynamic scheduling strategy, which utilizes the instability of the variable node and the residual of the variable-to-check message to locate the message to be updated first. The informed dynamic scheduling overcomes the trapping sets effectively. This paper also designs an informed dynamic scheduling strategy with adaptivity to pass more messages in parallel, which effectively postpones the influence of cycles in the Tanner graph. In some sense, the strategy lengthens cycles. Simulation results show that the two informed dynamic scheduling strategies outperform other algorithms.

It is essential to acquire the location of sensor nodes in the wireless sensor networks (WSNs), since the data collected with nodes would become meaningless without their location. In the existing studies, rangefree localization schemes have been proved suitable to large-scaled WSNs due to the low cost in hardware implementation. However, the defect of those schemes is their poor accuracy in anisotropic networks with coverage holes. To tackle this problem, we propose a range-free localization scheme that combines the advantages of geometric constraint and hop progress-based methods. The geometric information provided by the combination of anchor pairs and unknown nodes is used to design the discrimination conditions, and each node divides the anchor pairs into one of three proposed categories. For different categories of anchor pairs, corresponding methods are proposed to estimate the distancse between sensor nodes. In this way, the tradeoff between distance estimation accuracy and anchor utilization can be achieved. Simulation results indicate that the proposed scheme outperforms other schemes in terms of localization accuracy and proportion of outliers with acceptable computational and time complexity, where the localization accuracy and proportion of outliers in the proposed scheme are improved by up to 47% and 61% compared to DV-maxHop.

Among the belief-propagation (BP) decoding algorithms of low-density parity-check (LDPC) codes, the algorithms based on dynamic scheduling strategy show excellent performance. In this letter, we propose a variable-node-based dynamic scheduling decoding algorithm. For the proposed algorithm, the reliability of variable nodes is evaluated based on the log-likelihood ratio (LLR) values and the parity-check equations; then, a more accurate dynamic selection strategy is presented. Simultaneously, the oscillating variable nodes are processed so that the influence of the spread of error messages caused by oscillation are suppressed. In addition, the proposed algorithm updates the same number of messages in one iteration as the original BP decoding algorithm does, which is different from some other dynamic decoding algorithms. Simulation results demonstrate that the proposed algorithm outperforms other algorithms.