Sparsity Adaptive Expectation Maximization Algorithm for Estimating Channels in MIMO Cooperation systems

( Aihua Zhang ),( Shouyi Yang ),( Jianjun Li ),( Chunlei Li ),( Zhoufeng Liu ) 한국인터넷정보학회 2016 KSII Transactions on Internet and Information Syst Vol.10 No.8

We investigate the channel state information (CSI) in multi-input multi-output (MIMO) cooperative networks that employ the amplify-and-forward transmission scheme. Least squares and expectation conditional maximization have been proposed in the system. However, neither of these two approaches takes advantage of channel sparsity, and they cause estimation performance loss. Unlike linear channel estimation methods, several compressed channel estimation methods are proposed in this study to exploit the sparsity of the MIMO cooperative channels based on the theory of compressed sensing. First, the channel estimation problem is formulated as a compressed sensing problem by using sparse decomposition theory. Second, the lower bound is derived for the estimation, and the MIMO relay channel is reconstructed via compressive sampling matching pursuit algorithms. Finally, based on this model, we propose a novel algorithm so called sparsity adaptive expectation maximization (SAEM) by using Kalman filter and expectation maximization algorithm so that it can exploit channel sparsity alternatively and also track the true support set of time-varying channel. Kalman filter is used to provide soft information of transmitted signals to the EM-based algorithm. Various numerical simulation results indicate that the proposed sparse channel estimation technique outperforms the previous estimation schemes.

Adaptive Sampling for Low Power Mobile Sign Language Video Communication

Xiaolei Chen,Aihua Zhang,Xinzhu Yang 보안공학연구지원센터 2016 International Journal of Signal Processing, Image Vol.9 No.12

In this paper, we propose an adaptive sampling technique that achieves considerable energy savings while maintaining the required intelligibility level for mobile sign language video communication. The adaptive sampling scheme adjusts the sampling rate of the camera sensors dynamically according to the properties of sign language video communication and available battery power of mobile devices. Experimental results show that this adaptive scheme performs better than continuous sensing scheme in balancing the energy- intelligibility tradeoffs.

Power-aware Regions-of-Interest Computational Resource Allocation for Mobile Sign Language Video Encoding

Xiaolei Chen,Aihua Zhang,Xinzhu Yang 보안공학연구지원센터(IJSIP) 2013 International Journal of Signal Processing, Image Vol.6 No.6

Suppression and stability analysis of frequency coupling effect in grid‑connected inverters

Xiaohuan Wang,Aihua Yang,Yang Liu,Xiaojun Zhao 전력전자학회 2023 JOURNAL OF POWER ELECTRONICS Vol.23 No.6

With the proposal of the “dual carbon target” in China, the rapid development of renewable energy, mainly photovoltaic and wind power, has been promoted. However, a large amount of renewable energy connected to a grid results in its proportion in the power system going from a low state to a high state. Under a high proportion, the asymmetry of the control structure or parameters in the three-phase grid-connected inverter controller lead to a strong coupling relationship between the sub/super synchronous frequency components, or frequency coupling effect (FCE). This phenomenon can deteriorate the power quality of the inverter system, amplify the harm of frequency oscillation, and even cause system disassembly. To solve the above problems, a unified impedance model considering the FCE induced by the phase-locked loop (PLL), the current loop (CL), and the power outer loop (POL) is established. Based on the established output impedance model, a parameter optimization theoretical analysis method is designed considering the critical stability of the PLL bandwidth and the CL asymmetry degree. Meanwhile, an improved control strategy for the PLL and the POL is proposed. Experimental results show that the proposed parameter optimization and structure improvement strategies can effectively suppress the infl uence of frequency coupling and enhance system stability. Finally, simulation and experimental results verify the correctness of the theoretical analysis and the eff ectiveness of the proposed strategy.

Near-Optimal Low-Complexity Hybrid Precoding for THz Massive MIMO Systems

Yuke Sun,Aihua Zhang,Hao Yang,Di Tian,Haowen Xia 한국인터넷정보학회 2024 KSII Transactions on Internet and Information Syst Vol.18 No.4

Terahertz (THz) communication is becoming a key technology for future 6G wireless networks because of its ultra-wide band. However, the implementation of THz communication systems confronts formidable challenges, notably beam splitting effects and high computational complexity associated with them. Our primary objective is to design a hybrid precoder that minimizes the Euclidean distance from the fully digital precoder. The analog precoding part adopts the delay-phase alternating minimization (DP-AltMin) algorithm, which divides the analog precoder into phase shifters and time delayers. This effectively addresses the beam splitting effects within THz communication by incorporating time delays. The traditional digital precoding solution, however, needs matrix inversion in THz massive multiple-input multiple-output (MIMO) communication systems, resulting in significant computational complexity and complicating the design of the analog precoder. To address this issue, we exploit the characteristics of THz massive MIMO communication systems and construct the digital precoder as a product of scale factors and semi-unitary matrices. We utilize Schatten norm and Hölder's inequality to create semi-unitary matrices after initializing the scale factors depending on the power allocation. Finally, the analog precoder and digital precoder are alternately optimized to obtain the ultimate hybrid precoding scheme. Extensive numerical simulations have demonstrated that our proposed algorithm outperforms existing methods in mitigating the beam splitting issue, improving system performance, and exhibiting lower complexity. Furthermore, our approach exhibits a more favorable alignment with practical application requirements, underlying its practicality and efficiency.

Energy Efficiency Optimization for multiuser OFDM-based Cognitive Heterogeneous networks

( Bing Ning ),( Aihua Zhang ),( Wanming Hao ),( Jianjun Li ),( Shouyi Yang ) 한국인터넷정보학회 2019 KSII Transactions on Internet and Information Syst Vol.13 No.6

Reducing the interference to the licensed mobile users and obtaining the energy efficiency are key issues in cognitive heterogeneous networks. A corresponding rate loss constraint is proposed to be used for the sensing-based spectrum sharing (SBSS) model in cognitive heterogeneous networks in this paper. Resource allocation optimization strategy is designed for the maximum energy efficiency under the proposed interference constraint together with average transmission power constraint. An efficiency algorithm is studied to maximize energy efficiency due to the nonconvex optimal problem. Furthermore, the relationship between the proposed protection criterion and the conventional interference constraint strategy under imperfect sensing condition for the SBSS model is also investigated, and we found that the conventional interference threshold can be regarded as the upper bound of the maximum rate loss that the primary user could tolerate. Simulation results have shown the effectiveness of the proposed protection criterion overcome the conventional interference power constraint.

The Attenuation Mechanism and Live Vaccine Potential of a Low-Virulence Edwardsiella ictaluri Strain Obtained by Rifampicin Passaging Culture

Wang Shuyi,Hao Jingwen,Yang Jicheng,Zhang Qianqian,Li Aihua 한국미생물·생명공학회 2023 Journal of microbiology and biotechnology Vol.33 No.2

The rifampicin-resistant strain E9-302 of Edwardsiella ictaluri strain 669 (WT) was generated by continuous passage on BHI agar plates containing increasing concentrations of rifampicin. E9-302 was attenuated significantly by 119 times to zebrafish Danio rerio compared to WT in terms of the 50% lethal dose (LD50). Zebrafish vaccinated with E9-302 via intraperitoneal (IP) injection at a dose of 1 × 103 CFU/fish had relative percentage survival (RPS) rates of 85.7% when challenged with wild-type E. ictaluri via IP 14 days post-vaccination (dpv). After 14 days of primary vaccination with E9-302 via immersion (IM) at a dose of 4 × 107 CFU/ml, a booster IM vaccination with E9-302 at a dose of 2 × 107 CFU/ml exhibited 65.2% RPS against challenge with wild-type E. ictaluri via IP 7 days later. These results indicated that the rifampicin-resistant attenuated strain E9-302 had potential as a live vaccine against E. ictaluri infection. A previously unreported amino acid site change at position 142 of the RNA polymerase (RNAP) β subunit encoded by the gene rpoB associated with rifampicin resistance was identified. Analysis of the whole-genome sequencing results revealed multiple missense mutations in the virulence-related genes esrB and sspH2 in E9-302 compared with WT, and a 189 bp mismatch in one gene, whose coding product was highly homologous to glycosyltransferase family 39 protein. This study preliminarily explored the molecular mechanism underlying the virulence attenuation of rifampicin-resistant strain E9-302 and provided a new target for the subsequent study of the pathogenic mechanism of E. ictaluri.

Cooperative Behaviors of Thermodynamic Kuramoto Model Under External Fields

Yipeng Shao,Yinghua Jin,Aihua Hu,Shuobing Yang 제어·로봇·시스템학회 2022 International Journal of Control, Automation, and Vol.20 No.12

Each oscillator, subject to external fields, interacts with all the other oscillators. Therefore, the original thermodynamic Kuramoto model (TK model) is used to study the influence of some external fields upon its cooperative behavior. Three kinds of external fields are applied to the system: (a) random noises, (b) periodic force, (c) random noises and periodic force, so as to discuss TK model’s cooperative behavior under external fields. In some adequate frameworks formulated with initial data and system parameters, the model exhibits cooperative dynamics.

New Therapeutic Concept of NAD Redox Balance for Cisplatin Nephrotoxicity

Oh, Gi-Su,Kim, Hyung-Jin,Shen, AiHua,Lee, Su-Bin,Yang, Sei-Hoon,Shim, Hyeok,Cho, Eun-Young,Kwon, Kang-Beom,Kwak, Tae Hwan,So, Hong-Seob Hindawi Publishing Corporation 2016 BioMed research international Vol.2016 No.-

<P>Cisplatin is a widely used chemotherapeutic agent for the treatment of various tumors. In addition to its antitumor activity, cisplatin affects normal cells and may induce adverse effects such as ototoxicity, nephrotoxicity, and peripheral neuropathy. Various mechanisms such as DNA adduct formation, mitochondrial dysfunction, oxidative stress, and inflammatory responses are closely associated with cisplatin-induced nephrotoxicity; however, the precise mechanism remains unclear. The cofactor nicotinamide adenine dinucleotide (NAD<SUP>+</SUP>) has emerged as a key regulator of cellular energy metabolism and homeostasis. Recent studies have demonstrated associations between disturbance in intracellular NAD<SUP>+</SUP> levels and clinical progression of various diseases through the production of reactive oxygen species and inflammation. Furthermore, we demonstrated that reduction of the intracellular NAD<SUP>+</SUP>/NADH ratio is critically involved in cisplatin-induced kidney damage through inflammation and oxidative stress and that increase of the cellular NAD<SUP>+</SUP>/NADH ratio suppresses cisplatin-induced kidney damage by modulation of potential damage mediators such as oxidative stress and inflammatory responses. In this review, we describe the role of NAD<SUP>+</SUP> metabolism in cisplatin-induced nephrotoxicity and discuss a potential strategy for the prevention or treatment of cisplatin-induced adverse effects with a particular focus on NAD<SUP>+</SUP>-dependent cellular pathways.</P>

Pharmacological activation of NQO1 increases NAD⁺ levels and attenuates cisplatin-mediated acute kidney injury in mice

Oh, Gi-Su,Kim, Hyung-Jin,Choi, Jae-Hyuck,Shen, AiHua,Choe, Seong-Kyu,Karna, Anzani,Lee, Seung Hoon,Jo, Hyang-Jeong,Yang, Sei-Hoon,Kwak, Tae Hwan,Lee, Chul-Ho,Park, Raekil,So, Hong-Seob Springer-Verlag 2014 Kidney international Vol.85 No.3

Cisplatin is a widely used chemotherapeutic agent for the treatment of various tumors. In addition to its antitumor activity, cisplatin affects normal cells and may induce adverse effects, such as ototoxicity, nephrotoxicity, and neuropathy. Various mechanisms, such as DNA adduct formation, mitochondrial dysfunction, oxidative stress, and inflammatory responses, are critically involved in cisplatin-induced adverse effects. As NAD<SUP>+</SUP> is a cofactor for various enzymes associated with cellular homeostasis, we studied the effects of increased NAD<SUP>+</SUP> levels by means of NAD(P)H:quinone oxidoreductase 1 (NQO1) activation using a known pharmacological activator (β-lapachone) in wild-type and NQO1<SUP>−/−</SUP> mice on cisplatin-induced renal dysfunction in vivo. The intracellular NAD<SUP>+</SUP>/NADH ratio in renal tissues was significantly increased in wild-type mice co-treated with cisplatin and β-lapachone compared with the ratio in mice treated with cisplatin alone. Inflammatory cytokines and biochemical markers for renal damage were significantly attenuated by β-lapachone co-treatment compared with those in the cisplatin alone group. Notably, the protective effects of β-lapachone in wild-type mice were completely abrogated in NQO1<SUP>−/−</SUP> mice. Moreover, β-lapachone enhanced the tumoricidal action of cisplatin in a xenograft tumor model. Thus, intracellular regulation of NAD<SUP>+</SUP> levels through NQO1 activation might be a promising therapeutic target for the protection of cisplatin-induced acute kidney injury.