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Robust cooperative spectrum sensing schemes for fading channels in cognitive radio networks

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Science china(Information Sciences) 2011年第2期54卷 348-359页

作者： YUE WenJing1,2, ZHENG BaoYu1,2, MENG QingMin1, CUI JingWu1 & XIE PeiZhong1 1Institute of Signal Processing and Transmission, Nanjing university of Posts and Telecommunications, Nanjing 210003, china 2department of electronic engineering, shanghai jiaotong university, shanghai 200240, china 1. Institute of Signal Processing and Transmission Nanjing University of Posts and Telecommunications Nanjing 210003 China2. Department of Electronic Engineering Shanghai Jiaotong University Shanghai 200240 China

In cognitive radio systems, cooperative spectrum sensing can detect the presence of the primary user accurately. In practice, however, since the sensing observations are forwarded to a data collector through fading channels, the sensing performance is severely degraded. To deal with this problem, in this paper, we first propose a secondary user selection based cooperative spectrum sensing method to improve sensing performance by decreasing the reporting errors introduced by the fading channels. More specifically, only the secondary users with better signal-to-noise ratio (SNR) for reporting channels are allowed to send their local binary decisions (0 or 1) to the data collector while the others will send nothing. Additionally, we further propose a diversity based cooperative spectrum sensing method which applies existing space-time coding. By exploiting space diversity in CR network, the reporting errors introduced by the fading channel can be decreased and then the sensing performance is improved significantly. For either proposed cooperative spectrum sensing method, the sensing performance is derived and the analytical performance results are given. Our analysis and numerical results verify that proposed methods outperform the conventional cooperative spectrum sensing with OR-rule by taking into account the error effect on the reporting channels.

关键词： cognitive radio (CR) spectrum sensing energy detection diversity technique space-time coding

Optimal power allocation for cognitive relay networks: amplify-and-forward versus selection relay

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Science china(Information Sciences) 2011年第4期54卷 861-872页

作者： YUE WenJing 1,2,ZHENG BaoYu 1,2,MENG QingMin 1,YUE WenJie 3 & CUI JingWu 1 1 Institute of Signal Processing and Transmission,Nanjing university of Posts and Telecommunications,Nanjing 210003,china 2 department of electronic engineering,shanghai jiaotong university,shanghai 200240,china 3 Shanxi Institute of Educational Science,Taiyuan 030009,china 1. Institute of Signal Processing and Transmission Nanjing University of Posts and Telecommunications Nanjing 210003 China2. Department of Electronic Engineering Shanghai Jiaotong University Shanghai 200240 China3. Shanxi Institute of Educational Science Taiyuan 030009 China

We consider a cognitive relay network which is defined by a source,a destination,and cognitive relay nodes and primary user *** this network,a source is assisted by cognitive relay nodes which allow coexisting with primary user nodes by imposing severe constraints on the transmission power so that they operate below the noise floor of primary user *** this paper,we mainly study the power allocation strategies of this system to minimize the outage probability subject to total and individual power constraints for cognitive relay nodes and subject to interference constraints for primary user nodes.A relay transmission scheme,namely amplify-and-forward (AF),is *** first present an optimal power allocation (OPA) scheme to minimize the system outage probability,based on instantaneous channel state information among the source,destination and relay nodes and mean channel gains between primary user nodes and cognitive ***,we propose a selection AF scheme (S-AF) where the single best relay is chosen to assist in the transmission and study power allocation strategy for S-AF to minimize outage *** analytical power allocation strategies have been validated through numerical *** results indicate that the AF with OPA and S-AF with OPA have significantly better outage behavior and average throughput than AF and S-AF schemes *** also find that S-AF with OPA achieves a higher throughput,and hence lower outage probability than AF with OPA.

关键词： cognitive radio (CR) relay networks power allocation outage probability

Cyclostationary Property Based Spectrum Sensing Algorithms for Primary Detection in Cognitive Radio Systems

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Journal of shanghai jiaotong university(Science) 2009年第6期14卷 676-680页

作者：岳文静郑宝玉孟庆民 department of electronic engineering Shanghai Jiaotong University Institute of Signal Processing and Transmission Nanjing University of Posts and Telecommunications

To implement the primary signal without interference in cognitive radio systems, cognitive radios can detect the presence of the primary user in low SNR. Currently, energy detector is the most common way of spectrum sensing because of its low computational complexity. However, performunce of the method will be possibly degraded due to the uncertainty noise. This paper illustrates the benefits of one-order and two-order cyclostationary properties of primary user＇s signals in time domain. These feature detection techniques in time domain possess the advantages of simple structure and low computational complexity comparing with spectral feature detection methods. Furthermore, performance of the one-order and two-order feature detection is studied and the analytical results are given. Our analysis and numerical results show that the sensing performance of the one-order feature detection is improved significantly comparing with conventional energy detector since it is robust to noise. Meanwhile, numerical results show that the two-order feature detection technique is better than the one-order feature detection. However, this benefit comes at the cost of hardware burdens and power consumption due to the additional multiplying algorithm.

关键词： cognitive radio spectrum sensing cyclostationary feature detection

Some variational principles in electroelastic media under finite deformation

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Science china(Physics,Mechanics & Astronomy) 2008年第9期51卷 1390-1402页

作者： KUANG ZhenBang department of engineering Mechanics,shanghai jiaotong university,shanghai 200240,china department of engineering Mechanics Shanghai Jiaotong University Shanghai 200240 China

It is proposed that the universal thermodynamic energy variational principle is in-cluded in the first law of thermodynamics. Some variational principles in the elec-troelastic media under finite deformation are derived from this universal thermo-dynamic variational principle. It is suggested that in the general electroelastic analysis the environment should be considered together with the discussed elec-troelastic medium. For the variational principle of nonlinear electroelastic media the variation of the electric potential is coupled with the virtual displacement,and the variation of the initial volume should be considered. The Maxwell stress in the initial configuration is naturally derived from this variational principle and it is unique in the second order precision.

关键词： first law of thermodynamics variational principle the electroelastic media the governing equation

A NONLINEAR THERMOCAPILLARY MIGRATION OF DROPLETS DUE TO DEPENDENCE OF PHYSICAL PROPERTIES ON TEMPERATURE

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Journal of Hydrodynamics 2006年第4期18卷 469-474页

作者： SUN Ren department of engineering Mechanics Shanghai Jiaotong University Shanghai 200240 China

A slow thermocapillary migration of a droplet at vanishingly small Reynolds and Marangoni numbers was theoretically investigated. A force on the droplet released in another liquid subjected to arbitrary configuration of the gravitational field and an imposed thermal gradient for the case of constant liquid properties was derived using the general solutions given by Lamb. A solution to the migration was thereby obtained, which corresponds to the well-known YGB result as t →∞. In the case of variable physical properties with temperature, a nonlinear migration of the droplet was described by the dynamical equation of motion, and the numerical results were compared with available experimental data. The comparison exhibits a reasonable agreement between the theoretical prediction and the experimental results, which shows the dependence of physical properties on temperature is a primary cause of the continuous velocity variation in the thermocapillary droplet migration.

关键词： thermocapillary migration droplet/bubble dynamics interfacial tension thermal gradient

An analytical model for SMAC protocol in multi-hop wireless sensor networks

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Science china(Information Sciences) 2010年第11期53卷 2323-2331页

作者： LUO Jun, JIANG LingGe& HE Chen department of electronic engineering, shanghai jiaotong university, shanghai 200240, china 1. department of electronic engineering Shanghai Jiaotong University Shanghai 200240 China

Considering the active/sleep dynamics and the contention backoscheme of SMAC protocol in multi-hop wireless sensor networks (WSNs), we model each node as a finite single server queue with server shutdown, and model each node’s states as a two-dimensional continuous-time Markov chain. Based on the model, we derive the network performance in terms of average packet loss ratio, network throughput, average packet delay and average power consumption. Experiment comparisons show that the analytical results match well with the simulation results, which validates the accuracy of the analytical model. Furthermore, using the analytical model can enable us to investigate the performance tradeobetween energy efficiency and QoS requirement, and give us theoretical insight into the optimal parameters such as duty cycle, mean active period and buffer size in multi-hop wireless sensor networks.

关键词： multi-hop wireless sensor networks Markov chain energy efficiency QoS

NUMERICAL SIMULATION OF MORPHOLOGY OF POLYMER CHAIN COILS IN COMPLEX FLOWS

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Chinese Journal of Polymer Science 2005年第5期23卷 453-462页

作者： Hong Zheng Wei Yu Chi-xing Zhou department of Polymer Materials Science & engineering,shanghai jiaotong university,shanghai 200240,china shanghai Jiao Tong Univ Dept Polymer Mat Sci & Engn Shanghai 200240 Peoples R China

A new coupled finite element formulation is proposed to calculate a conformation tensor model in two complex flows： a planar contraction flow and a planar flow around a symmetrically placed cylinder. The components of conformation tensor are first computed together with the velocity and pressure to describe the change of morphology of polymer chain coils in flow fields. Macroscopic quantities of viscoelastic flow are then calculated based on the conformation tensor. Comparisons between the numerical simulations and experiments for stress patterns and velocity profiles are carried out to prove the validity of the method.

关键词： Viscoelastic flow Morphology Complex flows Conformation tensor model Finite element method (FEM).

Delayed feedback control experiments on some flexible structures

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Acta Mechanica Sinica 2010年第6期26卷 951-965页

作者： Guo-Ping Cai·Long-Xiang Chen department of engineering Mechanics, State Key Laboratory of Ocean engineering, shanghai jiaotong university,200240 shanghai,china department of engineering Mechanics State Key Laboratory of Ocean Engineering Shanghai Jiaotong University Shanghai China

In recent decades,studies on delayed system dynamics have attracted increasing attention and advances have been achieved in stability,nonlinearity,delay identification, delay elimination and ***,most of the existing work is on the theoretical basis and little is on the *** paper presents our experimental studies on delayed feedback control conducted in recent years with the focus on the discussion of a DSP-based delayed experiment *** phenomena in our delay experiments are discussed and a few topics of interest for further research are brought forward.

关键词： Flexible beam Flexible plate Flexible manipulator Delayed feedback control Experiment

A Probability Approach to Anomaly Detection with Twin Support Vector Machines

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Journal of shanghai jiaotong university(Science) 2010年第4期15卷 385-391页

作者：聂巍何迪 department of electronic engineering Shanghai Jiaotong University

Classification of intrusion attacks and normal network flow is a critical and challenging issue in network security study. Many intelligent intrusion detection models are proposed, but their performances and efficiencies are not satisfied to real computer networks. This paper presents a novel effective intrusion detection system based on statistic reference model and twin support vector machines （TWSVMs）. Moreover, a network flow feature selection procedure has been studied and implemented with TWSVMs. The performances of proposed system are evaluated through using the fifth international conference on knowledge discovery and data mining in 1999 （KDD＇99） data set collected at MIT＇s Lincoln Labs and the results indicate that the proposed system is more efficient and effective than conventional support vector machines （SVMs） and TWSVMs.

关键词： intrusion detection system (IDS) twin support vector machines (TWSVMs) probability