检索结果-南通市图书馆

Design and development of high linearity millimeter wave traveling-wave tube for satellite communications

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2015年第10期24卷 172-176页

作者：何俊黄明光李现霞李海强赵磊赵建东李跃赵石雷 research and Development center of Space Traveling-wave Tubes Institute of ElectronicsChinese Academy of Sciences

The linearity of the traveling-wave tube is a very important characteristic for a modern communication system. To improve the linearity of the traveling-wave tube at no expense of the saturated output power and overall efficiency, a modified pitch profile combined with a small adjustment of operating parameters is proposed. The optimal design of the helix circuit is evaluated theoretically by a large signal analysis, and the experimental test is also carried out to make a comparison of performance between the novel and original designed traveling-wave tubes. The experiments show that the saturated output powers and efficiencies of these two tubes are close to each other, while the linearity of the traveling-wave tube is obviously improved. The total phase shift and AM/PM conversion at saturation of the novel tube, averaged over the operating band, are only 30.6°/d B and 2.5°/d B, respectively, which are 20.1°/d B and 1.6°/d B lower than those of the original tube, respectively. Moreover, the third-order intermodulation of the novel tube is up to 2.2 d Bc lower than that of the original tube.

关键词： helix traveling-wave tube digital modulation nonlinear distortion pitch profile optimization

Cooperative resource allocation in cognitive wireless powered communication networks with energy accumulation and deadline requirements

在线全文

学校读者我要写书评

暂无评论

Science China(Information Sciences) 2019年第8期62卷 145-158页

作者： Ding XU Qun LI wireless Communication Key Lab of Jiangsu Province Nanjing University of Posts and Telecommunications Engineering research center of Health Service system Based on Ubiquitous wireless Networks Nanjing University of Posts and Telecommunications

This study investigates a multi-carrier cognitive wireless powered communication network(CWPCN) with a wirelessly powered primary user(PU). A two-stage cooperative protocol between the PU and the secondary user(SU) is adopted so that the PU can harvest energy from the SU while the SU gains transmission opportunities. It is assumed that the energy harvested by the PU can be accumulated for future usage, and the quality of service of the PU is guaranteed by satisfying the required minimum number of data bits for a given deadline. Herein, we maximize the SU rate by considering the time allocation,subcarrier allocation, and power allocation in both an offline setting(in which the future channel gains are known a priori) and an online setting(in which only the current channel gains are known). In the offline and online schemes, the maximization problem is solved using the block-coordinate descent method and the Lagrange duality method. The effectiveness of the proposed schemes is evaluated and verified via simulation experiments against benchmark schemes.

关键词： wireless powered communication networks energy harvesting cognitive radio deadline constraint energy accumulation

Accurate and broadband manipulations of harmonic amplitudes and phases to reach 256 QAM millimeter-wave wireless communications by time-domain digital coding metasurface

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

National Science Review 2022年第1期9卷 36-46页

作者： Ming Zheng Chen Wankai Tang Jun Yan Dai Jun Chen Ke Lei Zhang Cheng Zhang Jin Yang Lianlin Li Qiang Cheng Shi Jin Tie Jun Cui Institute of Electromagnetic Space Southeast University State Key Laboratory of terahertz and millimeter waves City University of Hong Kong State Key Laboratory of Advanced Optical Communication systems and Networks Department of Electronics Peking University National Mobile Communications research Laboratory Southeast University State Key Laboratory of millimeter waves Southeast University center of Intelligent Metamaterials Pazhou Laboratory

We propose a theoretical mechanism and new coding strategy to realize extremely accurate manipulations of nonlinear electromagnetic harmonics in ultrawide frequency band based on a time-domain digital coding metasurface(TDCM).Using the proposed mechanism and coding strategy,we design and fabricate a millimeter-wave(mmwave) TDCM,which is composed of reprogrammable meta-atoms embedded with positive-intrinsic-negative *** controlling the duty ratios and time delays of the digital coding sequences loaded on a TDCM,experimental results show that both amplitudes and phases of different harmonics can be engineered at will simultaneously and precisely in broad frequency band from 22 to33 GHz,even when the coding states are imperfect,which is in good agreement with theoretical *** on the fabricated high-performance TDCM,we further propose and experimentally realize a large-capacity mmwave wireless communication system,where 256 quadrature amplitude modulation,along with other schemes,is *** new wireless communication system has a much simpler architecture than the currently used mmwave wireless systems,and hence can significantly reduce the hardware *** believe that the proposed method and system architecture can find vast application in future mmwave and terahertz-wave wireless communication and radar systems.

关键词： metasurface time-domain digital coding accurate and broadband harmonic control 256 QAM millimeter-wave wireless communications

Physical layer security in multi-antenna cognitive heterogeneous cellular networks: a unified secrecy performance analysis

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Science China(Information Sciences) 2018年第2期61卷 149-163页

作者： Xiaohui QI Kaizhi HUANG Bin LI Liang JIN Xinsheng JI National Digital Switching system Engineering & Technological research center School of Information and electronics Beijing Institute of Technology

Cognitive heterogeneous cellular networks(CHCNs) are emerging as a promising approach to next-generation wireless communications owing to their seamless coverage and high network *** this paper, we describe our reliance on multi-antenna technology and a secrecy transmission protocol to ensure the reliability and security of downlink underlay CHCNs. First, we introduce a two-tier CHCN model using a stochastic geometry framework, and derive the probability distribution of the indicator function for a secrecy transmission scheme. We then investigate the connection outage probability, secrecy outage probability(SOP), and transmission SOP of both primary and cognitive users under a secrecy guard scheme and a threshold-based scheme. Furthermore, we reveal some insights into the secrecy performance by properly setting the predetermined access threshold and the radius of detection region for the secrecy transmission scheme. Finally, simulation results are provided to show the influence of the antenna system, eavesdropper density, predetermined access threshold, and radius of the detection region on the reliability and security performance of a CHCN.

关键词： cognitive heterogeneous cellular network physical layer security secrecy guard scheme threshold-based scheme multi-antenna technique

Transceiver designs with matrix-version water-filling architecture under mixed power constraints

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Science China(Information Sciences) 2016年第10期59卷 169-180页

作者： Chengwen XING Zesong FEI Yiqing ZHOU Zhengang PAN Hualei WANG School of Information and electronics Beijing Institute of Technology wireless Communication research center Institute of Computing TechnologyChinese Academy of Sciences China Mobile research Institute

In this paper, we investigate the multiple-input multiple-output(MIMO) transceiver design under an interesting power model named mixed power constraints. In the considered power model, several antenna subsets are constrained by sum power constraints while the other antennas are subject to per-antenna power constraints. This kind of transceiver designs includes both the transceiver designs under sum power constraint and per-antenna power constraint as its special cases. This kind of designs is of critical importance for distributed antenna systems(DASs) with heterogeneous remote radio heads(RRHs) such as cloud radio access networks(C-RANs). In our work, we try to solve the optimization problem in an analytical way instead of using some famous software packages e.g., CVX or Se Du Mi. In our work, to strike tradeoffs between performance and complexity, both iterative and non-iterative solutions are proposed. Interestingly the non-iterative solution can be interpreted as a matrix-version water-filling solution extended from the well-known and extensively studied vector version. Finally, simulation results demonstrate the accuracy of our theoretical results.

关键词： convex optimization MIMO matrix-version water-filling transceiver designs mix power constraints

State estimation with quantized innovations in wireless sensor networks: Gaussian mixture estimator and posterior Cramér–Rao lower bound

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2015年第6期28卷 1735-1746页

作者： Zhang Zhi Li Jianxun Liu Liu Liu Zhaolei Han Shan Department of Automation Shanghai Jiao Tong University Key Laboratory of System Control and Information Processing Ministry of Education of China Nanjing research Institute of electronics Technology Engineering research center of Wideband wireless Communication Technology Ministry of EducationNanjing University of Posts and Telecommunications

Since the features of low energy consumption and limited power supply are very impor- tant for wireless sensor networks （WSNs）, the problems of distributed state estimation with quan- tized innovations are investigated in this paper. In the first place, the assumptions of prior and posterior probability density function （PDF） with quantized innovations in the previous papers are analyzed. After that, an innovative Gaussian mixture estimator is proposed. On this basis, this paper presents a Gaussian mixture state estimation algorithm based on quantized innovations for WSNs. In order to evaluate and compare the performance of this kind of state estimation algo- rithms for WSNs, the posterior Cram6r-Rao lower bound （CRLB） with quantized innovations is put forward. Performance analysis and simulations show that the proposed Gaussian mixture state estimation algorithm is efficient than the others under the same number of quantization levels and the performance of these algorithms can be benchmarked by the theoretical lower bound.

关键词： Posterior Cramer-Rao lower bounds Quantiation State estimation Target tracking wireless sensor network

Retention Benefit Based Intelligent Cache Replacement

在线全文

学校读者我要写书评

暂无评论

Journal of Computer Science & Technology 2014年第6期29卷 947-961页

作者：李凌达陆俊林程旭 CCF ACM Microprocessor research and Development center Peking University Engineering research center of Microprocessor and system Ministry of Education School of electronics Engineering and Computer Science Peking University

The performance loss resulting from different cache misses is variable in modern systems for two reasons： 1） memory access latency is not uniform, and 2） the latency toleration ability of processor cores varies across different misses. Compared with parallel misses and store misses, isolated fetch and load misses are more costly. The variation of cache miss penalty suggests that the cache replacement policy should take it into account. To that end, first, we propose the notion of retention benefit. Retention benefits can evaluate not only the increment of processor stall cycles on cache misses, but also the reduction of processor stall cycles due to cache hits. Then, we propose Retention Benefit Based Replacement （RBR） which aims to maximize the aggregate retention benefits of blocks reserved in the cache. RBR keeps track of the total retention benefit for each block in the cache, and it preferentially evicts the block with the minimum total retention benefit on replacement. The evaluation shows that RBR can improve cache performance significantly in both single-core and multi-core environment while requiring a low storage overhead. It also outperforms other state-of-the-art techniques.

关键词： retention benefit replacement last-level cache

Design and Tool Flow of a Reconfigurable Asynchronous Neural Network Accelerator

在线全文

学校读者我要写书评

暂无评论

Tsinghua Science and Technology 2021年第5期26卷 565-573页

作者： Jilin Zhang Hui Wu Weijia Chen Shaojun Wei Hong Chen the Institute of Microelectronics Tsinghua National Laboratory for Information Science and Technologyand Beijing Engineering Center of Technology and research on Wireless Medical and Health SystemTsinghua UniversityBeijing 100084China

Convolutional Neural Networks(CNNs)are widely used in computer vision,natural language processing,and so on,which generally require low power and high efficiency in real ***,energy efficiency has become a critical indicator of CNN *** that asynchronous circuits have the advantages of low power consumption,high speed,and no clock distribution problems,we design and implement an energy-efficient asynchronous CNN accelerator with a 65 nm Complementary Metal Oxide Semiconductor(CMOS)*** the absence of a commercial design tool flow for asynchronous circuits,we develop a novel design flow to implement Click-based asynchronous bundled data circuits efficiently to mask layout with conventional Electronic Design Automation(EDA)*** also introduce an adaptive delay matching method and perform accurate static timing analysis for the circuits to ensure correct *** accelerator for handwriting recognition network(LeNet-5 model)is *** test results show that the asynchronous accelerator has 30%less power in computing array than the synchronous one and that the energy efficiency of the asynchronous accelerator achieves 1.538 TOPS/W,which is 12%higher than that of the synchronous chip.

关键词： Convolutional Neural Network(CNN)accelerator asynchronous circuit energy efficiency adaptive delay matching asynchronous design flow

Differential Fault Attack on the Stream Cipher LIZARD

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of electronics 2021年第3期30卷 534-541页

作者： MA Zhen TIAN Tian QI Wenfeng National Digital Switching system Engineering Technological research center

In this paper, we try to give a security evaluation of LIZARD stream cipher in regard to fault attacks, which, to the best of our knowledge, is the first fault analysis on LIZARD. We design a differential engine of LIZARD to track the differential trail of the keystreams. It is shown that the distributions of the keystream differences are heavily biased. Utilizing this characteristic, we propose an improved method to identify the fault location for LIZARD whose success probability approaches 1. Then we use the fault-free keystream and faulty keystreams to generate system of equations in internal state variables and solve it by SAT solver. The result shows that with 100 keystream bits, only 6 different faults are needed to recover the internal state. Finally,the comparison between LIZARD and Grain v1 shows that LIZARD is more resistable than Grain v1 in regard to fault attacks.

关键词： cryptography fault tolerant computing probability keystream differences faulty keystreams differential fault attack LIZARD stream cipher fault attacks fault analysis differential trail fault-free keystream fault location differential engine stream cipher LIZARD