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A Novel and Efficient Wireless Communication System
Wei Zhao,Yuehong Shen,Zhigang Yuan,Yimin Wei,Wei Jian 보안공학연구지원센터 2015 International Journal of Future Generation Communi Vol.8 No.5
This paper aims to construct a novel wireless communication system, in which source signals are transmitted simultaneously in the same frequency band. The transmitted signals are only required to be statistically independent or statistically distinguished. Therefore, the source signals can be recovered at the receiver by utilizing the classical algorithms of blind source separation (BSS) and independent component analysis (ICA) such as the fast fixed-point algorithm (FastICA). On the one hand, because the source signals are transmitted simultaneously in the same frequency band, the spectrum efficiency of this novel system is much higher than those of time division multiplexing (TDM), frequency division multiplexing (FDM), and code division multiplexing (CDM) systems, in which TDM, FDM and CDM signals are limited in time interval, frequency band and code. On the other hand, inspired by recently proposed reference-based schemes, the reference signals are introduced to the classical separation algorithms of BSS and ICA, which makes this novel system much more efficient than classical ones in terms of computational speed. The performance of this new system is validated through realistic experiments. Additionally, it is theoretically shown that the information content of all the source signal inputs can be recovered by this novel wireless communication system.
Wei Zhao,Zhi-Gang Yuan,Yue-hong Shen,Yufan Cao,Yimin Wei,Pengcheng Xu,Wei Jian 한국전자통신연구원 2015 ETRI Journal Vol.37 No.4
This paper deals with the problem of blind source separation (BSS), where observed signals are a mixture of delayed sources. In reference to a previous work, when the delay time is small such that the first-order Taylor approximation holds, delayed observations are transformed into an instantaneous mixture of original sources and their derivatives, for which an extended second-order blind identification (SOBI) approach is used to recover sources. Inspired by the results of this previous work, we propose to generalize its first-order Taylor approximation to suit higher-order approximations in the case of a large delay time based on a similar version of its extended SOBI. Compared to SOBI and its extended version for a first-order Taylor approximation, our method is more efficient in terms of separation quality when the delay time is large. Simulation results verify the performance of our approach under different time delays and signal-to-noise ratio conditions, respectively.
Using Adaptive Bandwidth Allocation Approach to Defend DDoS Attacks
Wei-Shen Lai,Chu-Hsing Lin,Jung-Chun Liu,Hsun-Chi Huang,Tsung-Che Yang 보안공학연구지원센터 2008 International Journal of Software Engineering and Vol.2 No.4
Denial of service attacks occur when the attacks are from a single host, whereas distributed denial of service attacks occur when multiple affected systems flood the bandwidth or resources of a targeted system. Although it is not possible to exempt entirely from denial of service or distributed denial of service attacks, we can limit the malicious user by controlling the traffic flow. In the paper, we propose to monitor the traffic pattern in order to alleviate distributed denial of service attacks. A bandwidth allocation policy will be adopted to assign normal users to a high priority queue and suspected attackers to a low priority queue. Simulations conducted in network simulator of our proposed priority queue-based scheme shows its effectiveness in blocking attacking traffic while maintaining constant flows for legitimate traffic.
I-SEAD: A Secure Routing Protocol for Mobile Ad Hoc Networks
Wei-Shen Lai,Chu-Hsing Lin,Jung-Chun Liu,Yen-Lin Huang,Mei-Chun Chou 보안공학연구지원센터 2008 International Journal of Multimedia and Ubiquitous Vol.3 No.4
Ad hoc networks are highly dynamic routing networks cooperated by a collection of wireless mobile hosts without any assistance of a centralized access point. Secure Efficient Ad hoc Distance Vector (SEAD) is a proactive routing protocol, based on the design of Destination Sequenced Distance Vector routing protocol (DSDV). SEAD provides a robust protocol against attackers trying to create incorrect routing state in the other node. However, it does not provide a way to prevent an attacker from tampering the next hop or the destination field in route update. In this paper, we propose an I-SEAD protocol to solve the problem. A series of simulation experiments are conducted to evaluate the performance.
Wei Shen,Xinyu Liu,Xiaoyu Su 제어·로봇·시스템학회 2021 International Journal of Control, Automation, and Vol.19 No.11
How to improve the position tracking accuracy of electro-hydraulic servo system is a hot issue today. Full state feedback control has received widespread attention for its ability to significantly improve control performance,however, its practical application range is limited in view of the large influence of measurement noise. In terms of this issue, we propose an adaptive robust controller based on improved structure and desired compensation. Firstly,to reduce the impact of measurement noise, the actual state value is substituted by the corresponding desired value in the controller design based on model compensation and the adaptive model compensator. Then, we introducea new auxiliary variable into the controller to optimize its structure. In addition, nonlinear robust control laws are integrated in the controller to balance unstructured uncertainties. Simulation analysis shows that the proposedcontrol strategy not only achieves the asymptotic tracking when parameter perturbation exists, but also ensures a specified transient response and final tracing precision under the combined influence of structured and unstructureduncertainties. The results indicate that the control strategy has good control accuracy as well as strong robustness
Wei Shen,Jiehao Wang 제어·로봇·시스템학회 2019 International Journal of Control, Automation, and Vol.17 No.7
Control issue is the key for applying hydraulic hybrid system, especially for common pressure rail (CPR)system which has the huge potential to enhance efficiency. In the paper, the mathematical model of hydrauliccylinder speed control system using new hydraulic transformer is established. Then an adaptive fuzzy sliding modecontroller based on Pi-sigma fuzzy neutral network is designed to solve the problem of parameter uncertainty andnonlinearity without establishing the precise model. Furthermore, compared to PID and conventional adaptivefuzzy system, the controller proposed can achieve good control performance and strong robustness in the presenceof time-varying uncertainty.
Working Memory and Second Language Learning: A Review of the Past Twenty Years’ Research in China
Wei Shen,박혜숙 범태평양 응용언어학회 2020 범태평양응용언어학회지 Vol.24 No.1
This paper systematically reviews the studies of working memory in second language learning in China over the past 20 years. A total of 140 studies that were published in 13 major foreign language journals during the past 20 years (2000-2019) were categorized and analyzed according to research method, educational level, and research content. For research method, two phases could be identified: from 2000 to 2006, more attention focused on introducing theory and reviewing literature regarding the association between working memory and second language learning; and from 2007 to 2019, there is a growing body of quantitative and qualitative research. For educational level of the 75 empirical studies, the majority were targeted at adult learners, whose L2 proficiency was assumed to be at or beyond intermediate level. For the research content, they were classified into three dimensions: L2 understanding, L2 output, and the integration of L2 understanding and output. These three dimensions were sub-divided into a total of seven aspects: vocabulary, grammar, listening, reading, speaking, writing, and interpretation. Considerable advances have been made in the knowledge of working memory and second language learning. Nevertheless, more research is needed to develop a deeper understanding of the interrelationships between working memory and different domains of second language learning.