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Parameter allocation of parallel array bistable stochastic resonance and its application in communication systems 被引量:1
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作者 刘健 王友国 +1 位作者 翟其清 刘进 《Chinese Physics B》 SCIE EI CAS CSCD 2016年第10期58-68,共11页
In this paper, we propose a parameter allocation scheme in a parallel array bistable stochastic resonance-based communication system(P-BSR-CS) to improve the performance of weak binary pulse amplitude modulated(BPAM) ... In this paper, we propose a parameter allocation scheme in a parallel array bistable stochastic resonance-based communication system(P-BSR-CS) to improve the performance of weak binary pulse amplitude modulated(BPAM) signal transmissions. The optimal parameter allocation policy of the P-BSR-CS is provided to minimize the bit error rate(BER)and maximize the channel capacity(CC) under the adiabatic approximation condition. On this basis, we further derive the best parameter selection theorem in realistic communication scenarios via variable transformation. Specifically, the P-BSR structure design not only brings the robustness of parameter selection optimization, where the optimal parameter pair is not fixed but variable in quite a wide range, but also produces outstanding system performance. Theoretical analysis and simulation results indicate that in the P-BSR-CS the proposed parameter allocation scheme yields considerable performance improvement, particularly in very low signal-to-noise ratio(SNR) environments. 展开更多
关键词 stochastic resonance parameter allocation bit error rate channel capacity
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Generative Multi-Modal Mutual Enhancement Video Semantic Communications
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作者 Yuanle Chen Haobo Wang +3 位作者 Chunyu Liu Linyi Wang Jiaxin Liu Wei Wu 《Computer Modeling in Engineering & Sciences》 SCIE EI 2024年第6期2985-3009,共25页
Recently,there have been significant advancements in the study of semantic communication in single-modal scenarios.However,the ability to process information in multi-modal environments remains limited.Inspired by the... Recently,there have been significant advancements in the study of semantic communication in single-modal scenarios.However,the ability to process information in multi-modal environments remains limited.Inspired by the research and applications of natural language processing across different modalities,our goal is to accurately extract frame-level semantic information from videos and ultimately transmit high-quality videos.Specifically,we propose a deep learning-basedMulti-ModalMutual Enhancement Video Semantic Communication system,called M3E-VSC.Built upon a VectorQuantized Generative AdversarialNetwork(VQGAN),our systemaims to leverage mutual enhancement among different modalities by using text as the main carrier of transmission.With it,the semantic information can be extracted fromkey-frame images and audio of the video and performdifferential value to ensure that the extracted text conveys accurate semantic information with fewer bits,thus improving the capacity of the system.Furthermore,a multi-frame semantic detection module is designed to facilitate semantic transitions during video generation.Simulation results demonstrate that our proposed model maintains high robustness in complex noise environments,particularly in low signal-to-noise ratio conditions,significantly improving the accuracy and speed of semantic transmission in video communication by approximately 50 percent. 展开更多
关键词 Generative adversarial networks multi-modal mutual enhancement video semantic transmission deep learning
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Design and Implementation of Initial Cell Search in 5G NR Systems 被引量:8
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作者 Fatang Chen Xiu Li +1 位作者 Yun Zhang Yanan Jiang 《China Communications》 SCIE CSCD 2020年第5期38-49,共12页
The initial cell search plays an important role during the process of downlink synchronization establishment between the User Equipment(UE) and the base station. In particular, the uncertainty of the synchronization s... The initial cell search plays an important role during the process of downlink synchronization establishment between the User Equipment(UE) and the base station. In particular, the uncertainty of the synchronization signals on the frequency domain and the flexibility of frame structure configuration have brought great challenges to the initial cell search for the fifth-generation(5G) new radio(NR). To solve this problem, firstly, we analyze the physical layer frame structure of 5G NR systems. Then, by focusing on the knowledge of synchronization signals, the 5G NR cell search process is designed, and the primary synchronization signal(PSS) timing synchronization algorithm is proposed, including a 5G-based coarse synchronization algorithm and conjugate symmetry-based fine synchronization algorithm. Finally, the performance of the proposed cell search algorithm in 5G NR systems is verified through the combination of Digital Signal Processing(DSP) and personal computer(PC). And the MATLAB simulation proves that the proposed algorithm has better performance than the conventional cross-correlation algorithm when a certain frequency offset exists. 展开更多
关键词 5G NR systems physical layer cell search PSS timing synchronization algorithm Conjugate symmetry
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Circuitry implementation of a novel four-dimensional nonautonomous hyperchaotic Liu system and its experimental studies on synchronization control 被引量:2
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作者 罗小华 周围 +2 位作者 李锐 梁亦龙 罗明伟 《Chinese Physics B》 SCIE EI CAS CSCD 2009年第6期2168-2175,共8页
Based on the three-dimensional Liu chaotic system, this paper appends a feedback variable to construct a novel hyperchaotic Liu system. Then, a control signal is further added to construct a novel nonautonomous hyperc... Based on the three-dimensional Liu chaotic system, this paper appends a feedback variable to construct a novel hyperchaotic Liu system. Then, a control signal is further added to construct a novel nonautonomous hyperchaotic Liu system. Through adjusting the frequency of the control signal, the chaotic property of the system can be controlled to show some different dynamic behaviors such as periodic, quasi-periodic, chaotic and hyperchaotic dynamic behaviours. By numerical simulations, the Lyapunov exponent spectrums, bifurcation diagrams and phase diagrams of the two new systems are studied, respectively. Furthermore, the synchronizing circuits of the nonautonomous hyperchaotic Liu system are designed via the synchronization control method of single variable coupling feedback. Finally, the hardware circuits are implemented, and the corresponding waves of chaos are observed by an oscillograph. 展开更多
关键词 Liu chaotic system Liu hyperchaotic system nonautonomous system synchronization control
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Design of two-dimensional spatially coupled LDPC codes for combating burst erasures
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作者 刘洋 HE Jinglin +1 位作者 WANG Bin ZHANG Yuzhi 《High Technology Letters》 EI CAS 2023年第3期288-294,共7页
Spatially-coupled low-density parity-check(SC-LDPC)codes are prominent candidates for fu-ture communication standards due to their‘threshold saturation’properties.However,when facing burst erasures,the decoding proc... Spatially-coupled low-density parity-check(SC-LDPC)codes are prominent candidates for fu-ture communication standards due to their‘threshold saturation’properties.However,when facing burst erasures,the decoding process will stop and the decoding performances will dramatically de-grade.To improve the ability of burst erasure corrections,this paper proposes a two-dimensional SC-LDPC(2D-SC-LDPC)codes constructed by parallelly connecting two asymmetric SC-LDPC coupled chains for resistance to burst erasures.Density evolution algorithm is presented to evaluate the as-ymptotic performances against burst erasures,by which the maximum correctable burst erasure length can be computed.The analysis results show that the maximum correctable burst erasure lengths of the proposed 2D-SC-LDPC codes are much larger than the SC-LDPC codes and the asym-metric SC-LDPC codes.Finite-length performance simulation results of the 2D-SC-LDPC codes over the burst erasure channel confirm the excellent asymptotic performances. 展开更多
关键词 burst erasure channel SC-LDPC code density evolution decoding performance
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Attention-relation network for mobile phone screen defect classification via a few samples 被引量:1
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作者 Jiao Mao Guoliang Xu +1 位作者 Lijun He Jiangtao Luo 《Digital Communications and Networks》 SCIE CSCD 2024年第4期1113-1120,共8页
How to use a few defect samples to complete the defect classification is a key challenge in the production of mobile phone screens.An attention-relation network for the mobile phone screen defect classification is pro... How to use a few defect samples to complete the defect classification is a key challenge in the production of mobile phone screens.An attention-relation network for the mobile phone screen defect classification is proposed in this paper.The architecture of the attention-relation network contains two modules:a feature extract module and a feature metric module.Different from other few-shot models,an attention mechanism is applied to metric learning in our model to measure the distance between features,so as to pay attention to the correlation between features and suppress unwanted information.Besides,we combine dilated convolution and skip connection to extract more feature information for follow-up processing.We validate attention-relation network on the mobile phone screen defect dataset.The experimental results show that the classification accuracy of the attentionrelation network is 0.9486 under the 5-way 1-shot training strategy and 0.9039 under the 5-way 5-shot setting.It achieves the excellent effect of classification for mobile phone screen defects and outperforms with dominant advantages. 展开更多
关键词 Mobile phone screen defects A few samples Relation network Attention mechanism Dilated convolution
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Implementation of a novel two-attractor grid multi-scroll chaotic system 被引量:2
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作者 罗小华 涂正伟 +3 位作者 刘希瑞 蔡昌 梁亦龙 龚璞 《Chinese Physics B》 SCIE EI CAS CSCD 2010年第7期123-128,共6页
This paper proposed a method of generating two attractors in a novel grid multi-scroll chaotic system. Based on a newly generated three-dimensional system, a two-attractor grid multi-scroll attractor system can be gen... This paper proposed a method of generating two attractors in a novel grid multi-scroll chaotic system. Based on a newly generated three-dimensional system, a two-attractor grid multi-scroll attractor system can be generated by adding two triangular waves and a sign function. Some basic dynamical properties, such as equilibrium points, bifurcations, and phase diagrams, were studied. Furthermore, the system was experimentally confirmed by an electronic circuit. The circuit simulation results and numerical simulation results verified the feasibility of this method. 展开更多
关键词 CHAOS grid multi-scroll attractor two-attractor grid multi-scroll chaotic system circuit simulation
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A Self-Adaptive Back-off Optimization Scheme Based on Beacons Probability Prediction for Vehicle Ad-Hoc Networks 被引量:1
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作者 Haitao Zhao Aiqian Du +2 位作者 Hongbo Zhu Dapeng Li Nanjie Liu 《China Communications》 SCIE CSCD 2016年第12期132-138,共7页
In order to improve the broadcast reception rates of beacon messages in vehicle ad-hoc networks,a conclusion that the relationship between collision probability and minimum contention window size and the relationship ... In order to improve the broadcast reception rates of beacon messages in vehicle ad-hoc networks,a conclusion that the relationship between collision probability and minimum contention window size and the relationship between expiration probability and minimum window size was reached by building a Markov model. According to this conclusion, a back-off algorithm based on adjusting the size of minimum contention window called CEB is proposed, and this algorithm is on the basis of the differential size between the number of expiration beacons and preset threshold. Simulations were done to compare the performance of CEB with that of RBEB and BEB, and the results show that the performance of the new proposed algorithm is better than that of RBEB and BEB. 展开更多
关键词 vehicle ad-hoc networks back off BEACON expiration probability collision probability
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Deep learning-based time-varying channel estimation with basis expansion model for MIMO-OFDM system 被引量:1
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作者 HU Bo YANG Lihua +1 位作者 REN Lulu NIE Qian 《High Technology Letters》 EI CAS 2022年第3期288-294,共7页
For high-speed mobile MIMO-OFDM system,a low-complexity deep learning(DL) based timevarying channel estimation scheme is proposed.To reduce the number of estimated parameters,the basis expansion model(BEM) is employed... For high-speed mobile MIMO-OFDM system,a low-complexity deep learning(DL) based timevarying channel estimation scheme is proposed.To reduce the number of estimated parameters,the basis expansion model(BEM) is employed to model the time-varying channel,which converts the channel estimation into the estimation of the basis coefficient.Specifically,the initial basis coefficients are firstly used to train the neural network in an offline manner,and then the high-precision channel estimation can be obtained by small number of inputs.Moreover,the linear minimum mean square error(LMMSE) estimated channel is considered for the loss function in training phase,which makes the proposed method more practical.Simulation results show that the proposed method has a better performance and lower computational complexity compared with the available schemes,and it is robust to the fast time-varying channel in the high-speed mobile scenarios. 展开更多
关键词 MIMO-OFDM high-speed mobile time-varying channel deep learning(DL) basis expansion model(BEM)
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Adaptive Optimal Capacity Perception and Control for Wireless Multi-Hop Networks 被引量:1
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作者 Zhao Haitao Dong Yuning +2 位作者 Liu Nanjie Zhang Hui Tian Feng 《China Communications》 SCIE CSCD 2012年第11期23-30,共8页
In wireless multimedia communications, it is extremely difficult to derive general end-to-end capacity results because of decentralized packet scheduling and the interference between communicating nodes. In this paper... In wireless multimedia communications, it is extremely difficult to derive general end-to-end capacity results because of decentralized packet scheduling and the interference between communicating nodes. In this paper, we present a state-based channel capacity perception scheme to provide statistical Quality-of-Service (QoS) guarantees under a medium or high traffic load for IEEE 802.11 wireless multi-hop networks. The proposed scheme first perceives the state of the wireless link from the MAC retransmission information and extends this information to calculate the wireless channel capacity, particularly under a saturated traffic load, on the basis of the interference among flows and the link state in the wireless multi-hop networks. Finally, the adaptive optimal control algorithm allocates a network resource and forwards the data packet by taking into consideration the channel capacity deployments in multi-terminal or multi-hop mesh networks. Extensive computer simulations demonstrate that the proposed scheme can achieve better performance in terms of packet delivery ratio and network throughput compared to the existing capacity prediction schemes. 展开更多
关键词 wireless multi-hop networks capacity perception: statistical Quality of Service (QoS) CROSS-LAYER
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Efficient Virtual Network Embedding Algorithm Based on Restrictive Selection and Optimization Theory Approach 被引量:2
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作者 Haotong Cao Zhicheng Qu +1 位作者 Yishi Xue Longxiang Yang 《China Communications》 SCIE CSCD 2017年第10期39-60,共22页
Network virtualization(NV) is widely considered as a key component of the future network and promises to allow multiple virtual networks(VNs) with different protocols to coexist on a shared substrate network(SN). One ... Network virtualization(NV) is widely considered as a key component of the future network and promises to allow multiple virtual networks(VNs) with different protocols to coexist on a shared substrate network(SN). One main challenge in NV is virtual network embedding(VNE). VNE is a NPhard problem. Previous VNE algorithms in the literature are mostly heuristic, while the remaining algorithms are exact. Heuristic algorithms aim to find a feasible embedding of each VN, not optimal or sub-optimal, in polynomial time. Though presenting the optimal or sub-optimal embedding per VN, exact algorithms are too time-consuming in smallscaled networks, not to mention moderately sized networks. To make a trade-off between the heuristic and the exact, this paper presents an effective algorithm, labeled as VNE-RSOT(Restrictive Selection and Optimization Theory), to solve the VNE problem. The VNERSOT can embed virtual nodes and links per VN simultaneously. The restrictive selection contributes to selecting candidate substrate nodes and paths and largely cuts down on the number of integer variables, used in the following optimization theory approach. The VNE-RSOT fights to minimize substrate resource consumption and accommodates more VNs. To highlight the efficiency of VNERSOT, a simulation against typical and stateof-art heuristic algorithms and a pure exact algorithm is made. Numerical results reveal that virtual network request(VNR) acceptance ratio of VNE-RSOT is, at least, 10% higher than the best-behaved heuristic. Other metrics, such as the execution time, are also plotted to emphasize and highlight the efficiency of VNE-RSOT. 展开更多
关键词 network virtualization virtual network embedding NP-hard heuristic exact restrictive selection optimization theory
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Channel Capacity Optimization Based on Riemannian Trust Region Algorithm in IRS-Aided Communication System
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作者 Jinzhi Liu Dan Wang +1 位作者 Jiamin Liang Zhiqiang Mei 《China Communications》 SCIE CSCD 2022年第10期21-37,共17页
Intelligent Reflecting Surface (IRS) can offer unprecedented channel capacity gains since it can reconfigure the signal propagation environment. We decide to maximize the channel capacity by jointly optimizing the tra... Intelligent Reflecting Surface (IRS) can offer unprecedented channel capacity gains since it can reconfigure the signal propagation environment. We decide to maximize the channel capacity by jointly optimizing the transmit-power-constrained precoding matrix at the base station and the unit-modulus-constrained phase shift vector at the IRS in IRS-assisted multi-user downlink communication. We first convert the resulting non-convex problem into an equivalent problem, then use the alternate optimization algorithm. While fixing the phase shift vector, we can obtain the optimal precoding matrix directly by adopting standard optimization packages. While fixing the precoding matrix, we propose the Riemannian Trust-Region (RTR) algorithm to solve this optimization problem. And the key of the RTR algorithm is the solution of the trust-region sub-problem. We first adopt the accurate solution based on Newton's (ASNT) method to solve this sub-problem, which can obtain the global solution but cannot guarantee that the solution is optimal since the initial iteration point is difficult to choose. Then, we propose the Improved-Polyline (IPL) method, which can avoid the difficulty of the ASNT method and improve convergence speed and calculation efficiency. The numerical results show that the RTR algorithm has more significant performance gains and faster convergence speed compared with the existing approaches. 展开更多
关键词 intelligent reflecting surface(IRS) MULTI-USER MIMO channel capacity unit modulus constraint Riemannian manifold optimization
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Circuitry implementation of a novel nonautonomous hyperchaotic Liu system based on sine input
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作者 罗小华 《Chinese Physics B》 SCIE EI CAS CSCD 2009年第8期3304-3308,共5页
Based on the three-dimensional Liu system with a nonlinear term of square, this paper appends a state variable to the system, and further adds a driving signal of the sine signal to construct a novel 4-demensional non... Based on the three-dimensional Liu system with a nonlinear term of square, this paper appends a state variable to the system, and further adds a driving signal of the sine signal to construct a novel 4-demensional nonautonomous hyperchaotic Liu system. The appended variable is formed by the product of the nonlinear quadratic term of the original state variables and the driving signal. Through adjusting the frequency of the driving signal, the system can be controlled to show some different dynamic behaviors. By numerical simulations, the Lyapunov exponent spectrums, bifurcation diagrams and phase diagrams of the novel systems are analyzed. Furthermore, the corresponding hardware circuits are implemented. Both the experimental results and the simulation results confirm that the method is feasible. The method, which adjusts the frequency of the input sine signal to control the system to show different dynamic behaviors, can make the dynamic property of the system become more complex, but easier to be controlled accurately as well. 展开更多
关键词 CHAOS HYPERCHAOS Liu system frequency control
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Deep learning based Doppler frequency offset estimation for 5G-NR downlink in HSR scenario
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作者 YANG Lihua WANG Zenghao +1 位作者 ZHANG Jie JIANG Ting 《High Technology Letters》 EI CAS 2022年第2期115-121,共7页
In the fifth-generation new radio(5G-NR) high-speed railway(HSR) downlink,a deep learning(DL) based Doppler frequency offset(DFO) estimation scheme is proposed by using the back propagation neural network(BPNN).The pr... In the fifth-generation new radio(5G-NR) high-speed railway(HSR) downlink,a deep learning(DL) based Doppler frequency offset(DFO) estimation scheme is proposed by using the back propagation neural network(BPNN).The proposed method mainly includes pre-training,training,and estimation phases,where the pre-training and training belong to the off-line stage,and the estimation is the online stage.To reduce the performance loss caused by the random initialization,the pre-training method is employed to acquire a desirable initialization,which is used as the initial parameters of the training phase.Moreover,the initial DFO estimation is used as input along with the received pilots to further improve the estimation accuracy.Different from the training phase,the initial DFO estimation in pre-training phase is obtained by the data and pilot symbols.Simulation results show that the mean squared error(MSE) performance of the proposed method is better than those of the available algorithms,and it has acceptable computational complexity. 展开更多
关键词 fifth-generation new radio(5G-NR) high-speed railway(HSR) deep learning(DL) back propagation neural network(BPNN) Doppler frequency offset(DFO)estimation
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TRACKING DEFORMABLE AND OCCLUDED OBJECTS USING PARTICLE FILTERING AND GVF-SNAKE
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作者 Dong Chunli Dong Yuning +2 位作者 Wang Li Zhang Hui Liu Jie 《Journal of Electronics(China)》 2009年第6期819-824,共6页
An adaptive object tracking algorithm based on particle filtering and a modified Gradient Vector Flow (GVF) Snake is proposed for tracking moving and deforming objects. The original contours of objects are obtained by... An adaptive object tracking algorithm based on particle filtering and a modified Gradient Vector Flow (GVF) Snake is proposed for tracking moving and deforming objects. The original contours of objects are obtained by using the background differencing method,and the true contours of objects can be converged by means of the powerful searching ability of a modified GVF-Snake. Finally,an Energetic Particle Filtering (EPF) algorithm is obtained by combining particle filtering and a modified GVF-Snake,and by using K-means and the EPF algorithm,multiple objects can be tracked. The proposed tracking tactic for partially occluded objects can effectively improve its anti-occlusion ability. Experiments show that this algorithm can obtain better tracking effect even though the tracked object is occluded. 展开更多
关键词 TRACKING Energetic Particle Filtering (EPF) Gradient Vector Flow (GVF) Snake model Deformable objects
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AN EFFICIENT SIMULATION OF MULTIPLE CORRELATED RAYLEIGH FADING ENVELOPES
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作者 Zhou Ke Cao Shike Song Rongfang 《Journal of Electronics(China)》 2008年第5期697-701,共5页
In order to better assess the performance of wireless communication systems,it is desirable to produce multiple Rayleigh fading envelopes with specified correlations.In this paper,we analyze theoretically a procedure ... In order to better assess the performance of wireless communication systems,it is desirable to produce multiple Rayleigh fading envelopes with specified correlations.In this paper,we analyze theoretically a procedure which generates correlated Gaussian random variables from independent Gaussian random variables and give a physical explanation for the limitation of this procedure.Then,based on some uncorrelated Rayleigh fading envelopes,a simple but efficient procedure for generating an arbitrary number of cross-correlated Rayleigh fading envelopes is proposed.Simulation results and computational complexity analysis are presented,which show that the proposed method has some advantages,such as high accuracy,low computational complexity and easy implementation,over the conventional simulation method. 展开更多
关键词 Rayleigh fading envelopes Correlated Gaussian random variables Linear transformation
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Design on the Coal Management System for Small and Medium Enterprises
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作者 Wenfeng LI Haipeng LEI Youfei XU 《International Journal of Technology Management》 2015年第5期99-101,共3页
According to the analysis of the problem of contract management, financial settlement and placement of coal trucks in coal business, a study is made on the coal management system. This system combines B/S and C/S toge... According to the analysis of the problem of contract management, financial settlement and placement of coal trucks in coal business, a study is made on the coal management system. This system combines B/S and C/S together, and it also uses three-tire application of ASP.NET which sets up a business subsystem based on functional module management in vehicle. Additionally, MFC solves the problems in weighing management systems. This system goes with unit testing, integration testing, and system testing, and the whole process realizes an effective monitoring from coal trucks applying for delivery, checking in, and weighing to checking out. Besides, it also secures precise and accurate weighing data, and deals with the new coming coal contract in a faster way. The real project indicates this system wins a very good reputation and it is worthy of spreading in a broader context. 展开更多
关键词 Coal Sales System Management DATABASE RFID
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Intelligent reflecting surfaces-assisted millimeter wave communication:Channel estimation based on deep learning
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作者 Kang Xiaofei Wang Tian Liang Xian 《The Journal of China Universities of Posts and Telecommunications》 EI CSCD 2024年第1期49-56,共8页
In response to the challenge posed by the complexity of the system and the difficulty in obtaining accurate channel state information(CSI)for millimeter wave communication assisted by intelligent reflecting surfaces(I... In response to the challenge posed by the complexity of the system and the difficulty in obtaining accurate channel state information(CSI)for millimeter wave communication assisted by intelligent reflecting surfaces(IRS),we propose a deep learning-based channel estimation scheme.The proposed scheme employs a hybrid active/passive IRS architecture,wherein the least square(LS)algorithm is initially utilized to acquire the channel estimate from the active elements.Subsequently,this estimation is interpolated to obtain a preliminary channel estimation and ultimately refined into an accurate estimate of the channel using the channel super-resolution convolutional neural network(Chan-SRCNN)deep learning network.The simulation results demonstrate that the proposed scheme surpasses LS,orthogonal matching pursuit(OMP),synchronous OMP(SOMP),and deep neural network(DNN)channel estimation algorithms in terms of normalized mean squared error(NMSE)performance,thereby validating the feasibility of the proposed approach. 展开更多
关键词 intelligent reflecting surface millimeter wave channel estimation deep learning
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Analysis of M-LWDF fairness and an enhanced M-LWDF packet scheduling mechanism 被引量:8
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作者 XIAN Yong-ju TIAN Feng-chun +1 位作者 XU Chang-biao YANG Yue 《The Journal of China Universities of Posts and Telecommunications》 EI CSCD 2011年第4期82-88,共7页
Modified largest weighted delay first (M-LWDF) is a typical packet scheduling algorithm for supporting hybrid real-time services over wireless networks. However, so far, there is little literature available regardin... Modified largest weighted delay first (M-LWDF) is a typical packet scheduling algorithm for supporting hybrid real-time services over wireless networks. However, so far, there is little literature available regarding the theoretic analysis of M-LWDF fairness. This paper gives a theoretic analysis of M-LWDF fairness, which shows that M-LWDF fairness is related to channel condition, packet's arrival process and the ratio of quality of service (QoS) requirements of different service queues. Given service QoS requirements and other parameters related to channel model and packet's arrival process, the fairness is merely related to the ratio of the number of users in the service queues. Based on the analysis, an enhanced M-LWDF algorithm (EM-LWDF) is proposed and demonstrated in this paper. EM-LWDF is strictly designed in light of the fairness criteria of QoS requirements, so its fairness is almost not related to the ratio of the number of users in the service queues, and the theoretical value of fairness index is equal to 1. Simulation results validate the theoretic analysis and show the effectiveness of EM-LWDF in improving fairness. 展开更多
关键词 wireless resource management packet scheduling QOS M-LWDF EM-LWDF
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基于改进大津法和模糊聚类的CT图像肺实质分割方法的比较研究(英文) 被引量:6
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作者 陈晶晶 赵德春 +1 位作者 彭承琳 吴向旭 《航天医学与医学工程》 CAS CSCD 北大核心 2014年第6期448-452,共5页
目的比较改进后的大津阈值法和模糊C均值聚类(FCM)两种分割算法在CT图像肺实质分割中的应用。方法选取40例肺部图像,分别采用改进的大津阈值法和模糊C均值聚类法,分割出肺实质区域,同时剔除肺部纵膈、气管。最后,采用主观评价和客观分析... 目的比较改进后的大津阈值法和模糊C均值聚类(FCM)两种分割算法在CT图像肺实质分割中的应用。方法选取40例肺部图像,分别采用改进的大津阈值法和模糊C均值聚类法,分割出肺实质区域,同时剔除肺部纵膈、气管。最后,采用主观评价和客观分析(图象一致性和信息熵指标)评价分割效果。结果主观分析显示,改进的大津法得到的图像中虽仍存在肺实质内部间隙,但图中孤立像素点明显减少,且颗粒的边缘也更加光滑。FCM算法分割出的肺实质空洞较少,获得的图像较完整。但有些许粘连,且提取中主气管容易错误地分割到肺实质区域,造成肺实质分割不彻底。客观分析表明,在一致性准则上,两种方法分割结果相差不大,分割出的区域都具有较高的内部区域一致性;从信息熵的角度,FCM法分割效果较好。结论肺部CT图像肺实质的分割中,对于目标与背景灰度有强对比的图像,Otsu法优于FCM法,但在阈值自适应和运算时间方面需要进一步提升;而对于存在不确定性和模糊性的图像,FCM法优于Otsu法,但在抗噪性和分割精度方面需要进一步改进。 展开更多
关键词 肺实质 模糊C均值聚类 大津法 阈值分割
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