Table of Content

20 February 2015 Volume 42 Issue 1

  

Original Articles

Spectrum compression space-time adaptive processing method for TOPS SAR-GMTI

LI Xueshi;XING Mengdao;SHAO Peng;SUN Guangcai;LIANG Yi;BAO Zheng

J4. 2015, 42(1):  1-9.  doi:10.3969/j.issn.1001-2400.2015.01.001

Abstract ( 627 )   PDF (6284KB) ( 656 )   Save

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Moving targets detection and imaging for multichannel terrain observation by progressive scans (TOPS) synthetic aperture radar ground moving targets indication (SAR-GMTI) has important application prospects. However, the azimuth bandwidth of the background clutter is much larger than the instantaneous signal bandwidth. Therefore, the background clutter will be highly aliased if the pulse repetition frequency (PRF) is limited. Direct application of space-time adaptive processing (STAP) techniques will significantly compromise the clutter suppression performance. Hence, we propose a space-time adaptive processing method based on spectrum compression. The spectrum compression process can reduce the azimuth bandwidth of the background clutter to the instantaneous signal bandwidth. Space-time adaptive processing is then performed to effectively suppress the clutter, and the clutter suppression performance is greatly improved. Furthermore, Deramp processing is used to focus the moving target in order to avoid the target ambiguities arising from the Doppler shift. Meanwhile, we can perform the moving targets tracking by utilizing the highly overlapping full-aperture images which are obtained by the TOPS SAR mode. Simulation results validate the effectiveness of the proposed algorithm.

Continuous time ΣΔADC design with 256MHz sampling and 71dB DR

YANG Yintang;YUAN Jun;ZHANG Zhaofeng

J4. 2015, 42(1):  10-15.  doi:10.3969/j.issn.1001-2400.2015.01.002

Abstract ( 725 )   PDF (1152KB) ( 786 )   Save

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A wide bandwidth continuous time ΣΔADC is widely used in the wireless communication field. A ΣΔADC with the 3 order 4bit modulator is designed with the 256MHz sampling frequency. In order to reduce the clock jitter, the nonreturn-to-zero (NRZ) DAC feedback pulse is used. And the loop asynchronous problem is improved by introducing a half of clock cycle delay. Also how to reduce the effect of the DAC mismatch is discussed. A low voltage, low power, and high speed operational amplifier is designed with feedforward compensation technology. Finally, based on the 0.13μm technology, the SNDR is 62.5dB and DR is 71dB with a 1.2V supply.

Particle swarm optimization user-priority virtual network embedding algorithm

CHANG Lei;GU Huaxi;ZHANG Zhiyi;YU Xiaoshan;ZHAO Yan

J4. 2015, 42(1):  16-22.  doi:10.3969/j.issn.1001-2400.2015.01.003

Abstract ( 821 )   PDF (657KB) ( 710 )   Save

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In the forwarding and control separation network, we model the user-priority virtual network embedding problem as an integer linear programming, which is achieved with resource grabbing and re-mapping aiming at maximizing the resource utilization of the substrate physical network. And we propose a modified discrete particle swarm optimization algorithm (M_DPSO) for short to solve the VN embedding problem. In the M_DPSO, the particle evolves more directionally, and the mutually exclusive factor of different particle positions is introduced to resolve the problem of premature and easily becoming local optimal solution. Finally, the performance parameters, including node resource utilization, link resource utilization, the VN accept rate, the average jump number and the long-term operators benefit cost ratio, are evaluated by emulation experiments. In contrast to the greedy algorithm and binary particle swarm optimization algorithm, the M_DPSO is verified to be of high performance.

Method of evaluating countermeasure effectiveness for an adaptive nulling antenna based on the analytic hierarchy process

LIU Congfeng;ZHAO Ziyue

J4. 2015, 42(1):  23-28+173.  doi:10.3969/j.issn.1001-2400.2015.01.004

Abstract ( 608 )   PDF (561KB) ( 671 )   Save

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For the problem of evaluating countermeasure effectiveness against the adaptive nulling antenna, the evaluating method using the analytic hierarchy process (AHP) is proposed. First, evaluating indexes of countermeasure effectiveness are selected and the hierarchical structure model is established. Then, the method of evaluating countermeasure effectiveness is obtained by using the AHP. Finally, the performance indexes of three classical adaptive nulling algorithms are evaluated with various space jammings. The results of simulation show that the method can evaluate different countermeasure means reasonably and effectively, and it also has a strong adaptability. The research can be not only used in optimizing countermeasure means and their effectiveness evaluation, but also helpful for improving the anti-jamming technology of the adaptive nulling antenna.

Behavior trust fuzzy evaluation model

ZHANG Guanghua;ZHANG Yuqing;LIU Xuefeng;YAN Jingbo

J4. 2015, 42(1):  29-34.  doi:10.3969/j.issn.1001-2400.2015.01.005

Abstract ( 633 )   PDF (534KB) ( 618 )   Save

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To cope with malicious behavior in cognitive radio networks such as providing false spectrum information and seizing spectrum resources, this paper proposes a behavior trust fuzzy evaluation model. With spectrum sensing behavior and spectrum utilization behavior as two evaluation factors, this model implements nodes' trust evaluation using the fuzzy comprehensive evaluation and decision method based on subjectivity and uncertainty of trust. In cooperative spectrum sensing, this model identifies malicious nodes based on the result of comprehensive evaluation to eliminate false feedback. In spectrum allocation, this model uses the definition of the lattice degree of nearness between fuzzy sets to calculate the difference between the actual comprehensive evaluation set and the ideal comprehensive evaluation set, and thereby quantifies the trustworthiness of non-malicious nodes and, combining with the multi-target optimization algorithm, determines the spectrum resources to be allocated to these nodes. This mechanism inhibits malicious behavior while encouraging cooperative behavior of nodes, thus achieving a joint design for spectrum sensing at the physical layer and spectrum allocation at the MAC layer. Simulation results and analysis show that the proposed model outperforms existing models in the system's sensing performance, throughput and fairness of spectrum allocation under malicious attacks.

DOA estimation method by utilizing sparse representation of the covariance matrix

XIE Hu;FENG Dazheng;YUAN Mingdong

J4. 2015, 42(1):  35-41.  doi:10.3969/j.issn.1001-2400.2015.01.006

Abstract ( 650 )   PDF (807KB) ( 1425 )   Save

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A direction of arrival (DOA) estimation method based on a new sparse representation model of the covariance matrix is proposed. Without requiring the prior-knowledge on the noise level, the proposed method only utilizes partial information on the covariance matrix for the DOA estimation and provides robustness to noise at the cost of a tiny aperture loss. Although the proposed method is based on the statistical information on samples (i.e., covariance matrix), its principle is different from that of the traditional high-resolution DOA estimation methods (e.g., MUSIC, CAPON). The proposed method can effectively distinguish the signal sources with any coherence without decorrelation processing.

Novel full aperture imaging algorithm for highly squinted TOPS SAR

YANG Jun;LI Zhenyu;SUN Guangcai;XING Mengdao;ZHOU Feng

J4. 2015, 42(1):  42-48+55.  doi:10.3969/j.issn.1001-2400.2015.01.007

Abstract ( 797 )   PDF (1574KB) ( 699 )   Save

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Due to its special imaging geometry, the highly squinted Terrain Observation by Progressive Scans (TOPS) SAR imaging mode is confronted with two main issues: severe range-azimuth coupling caused by high squint angles and azimuth spectrum aliasing caused by the steered azimuth beam. To solve these issues, a full aperture imaging algorithm based on the modified range migration algorithm (RMA) and spectral analysis (SPECAN) is proposed in this paper. Firstly, the two-dimensional (2-D) spectrum without aliasing is obtained by azimuth preprocessing. Then the modified RMA is used to complete range cell migration correction (RCMC) and range compression. Finally, the signal is focused in the Doppler domain by SPECAN and Deramping. Simulations and real data processing results validate the effectiveness of the proposed algorithm.

Form-finding method of equal tension cable networks for space mesh antennas

FAN Yesen;LI Tuanjie;MA Xiaofei;LI Zhengjun

J4. 2015, 42(1):  49-55.  doi:10.3969/j.issn.1001-2400.2015.01.008

Abstract ( 655 )   PDF (1593KB) ( 763 )   Save

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To design large space deployable antennas with lightweight and stable cable-net structures, a form-finding method is presented to design equal tension cable networks. The nodes of the networks are regarded as the points that move on the ideal reflective surface. The nodes move on the ideal surfaces of the mesh antennas under the action of the resultant forces acting on the nodes, and the tensions in the cables remain equivalent. After a period of movement, the resultant forces acting on the nodes decrease to zero gradually, and the whole system is considered to be in equilibrium. The unstrained length of each cable can be determined according to the deformed length of the cable and the tension force in the cable. A numerical example of a hoop truss cable-net antenna was calculated, and the equal tension cable structure of the mesh antenna was obtained, whose equilibrium state was validated by the finite element method. The calculated results show that the method presented is accurate, valid and feasible. The calculated results are compared with the calculated results based on the minimum norm method and the equal force density method, which shows that the mechanical performance of the network that was obtained using the equal tension method is better than that by using the other two methods. The method can be used to design the cable-net structures of space mesh antennas.

3×V_DD-tolerant ESD detection circuit in a 90nm CMOS process

YANG Zhaonian;LIU Hongxia;ZHU Jia

J4. 2015, 42(1):  56-61+206.  doi:10.3969/j.issn.1001-2400.2015.01.009

Abstract ( 657 )   PDF (1120KB) ( 697 )   Save

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A new low leakage 3×V_DD-tolerant electrostatic discharge (ESD) detection circuit only using the low-voltage device is proposed in a 90nm 1.2V CMOS process. Gate leaky characteristics of the nanoscale MOSFET and the feedback technique are used to control the trigger MOSFET and turn on the clamp device silicon-controlled rectifier (SCR). The multi-stage stacked-transistors structure is used to sustain a high voltage stress. The proposed detection circuit can generate 38mA current to turn on the clamp device SCR under the ESD stress. Under normal 3×V_DD operating conditions, all the devices are free from over-stress voltage threat. The leakage current is 52nA under the 3×V_DD bias at 25℃. Simulation result shows that the circuit can be successfully used for the 3×V_DD-tolerant I/O buffer.

Analysis of the two-dimensional spatial resolution for the curved trajectory of GEO SAR

CHEN Jianlai;LI Zhenyu;YANG Jun;SUN Guangcai;XING Mengdao

J4. 2015, 42(1):  62-68.  doi:10.3969/j.issn.1001-2400.2015.01.010

Abstract ( 1000 )   PDF (888KB) ( 5516 )   Save

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In geosynchronous earth orbit synthetic aperture radar(GEO SAR), because of such factors as the curve track of the satellite, the influence of earth rotation and so on, there is no explicit expression for the moving track of the satellite with respect to the target, and the track velocity varies greatly on different obit positions of the satellite, so the method of calculating resolution for uniform line motion in airborne and LEO SAR is not suitable for GEO SAR. Aiming at the mentioned problems, this paper proposes a method of calculating the two-dimensional spatial resolution based on phase gradient analysis in GEO SAR. In this paper, a conjecture is presented and proved by introducing the intermediate value theorem. There exists an equal track velocity, which can ensure the theoretical azimuth resolution within a range, and that azimuth resolution range is calculated. Finally, the Back projection (BP) algorithm simulation experiments validate the proposed method.

Optimized design method on elliptic curve cryptography

CUI Xining;YANG Jingwei;YE Hong;DAI Xiaodi

J4. 2015, 42(1):  69-74.  doi:10.3969/j.issn.1001-2400.2015.01.011

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Elliptic Curve Cryptography algorithm, which depends on the difficulty of the discrete logarithm problem, has some characteristics of low computational overhead and high security. The main operation of Elliptic Curve Cryptography is point multiplication which is the most time-consuming part in the encryption and decryption process. This paper optimizes the point multiplication, proposes a hardware architecture to implement Elliptic Curve Cryptography algorithm and designs encryption and decryption system basing on FGPA. The proposed method improves the encryption and decryption efficiency by the multiplication, squaring and division optimization in the finite binary field. Analysis and testing show that the proposed architecture has some advantages with low hard resource consumption, low complexity of module interface and scalability, the designed encryption and decryption system supports key length of 113bit, 163bit, 193bit and so on, and relative to the software Elliptic Curve Cryptography system running on embedded processor, this encryption and decryption processor can achieve thousands of times faster.

Adaptive bacterial foraging optimization algorithm

JIANG Jianguo;ZHOU Jiawei;ZHENG Yingchun;WANG Tao

J4. 2015, 42(1):  75-81.  doi:10.3969/j.issn.1001-2400.2015.01.012

Abstract ( 768 )   PDF (552KB) ( 727 )   Save

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An adaptive bacterial foraging optimization algorithm is presented due to the classic optimization algorithm's poor performance when optimizing high-dimensional complex functions. The fixed chemotactic step is improved as the adaptive sliding step which decreases nonlinearly with the result of strengthening the ability of local search. The adaptive dimension learning method for the optimal bacterium in the current cycle of chemotaxis is proposed so as to increase the accuracy of the solution and enhance the search efficiency. The elite bacterium is used as the initial point for Tent chaotic mapping to initialize the position of bacteria which meet the conditions of migration, and therefore the convergence speed of the algorithm is accelerated. Experimental result indicates that the algorithm outperforms the classic algorithm both in terms of  solution accuracy and convergence speed. And, the algorithm has a higher efficiency.

Fluorescence molecular tomography method using simplified spherical harmonics approximation and Laplace regularization

LI Wei;YI Huangjian;ZHANG Qitan;LIANG Jimin

J4. 2015, 42(1):  82-85.  doi:10.3969/j.issn.1001-2400.2015.01.013

Abstract ( 520 )   PDF (968KB) ( 632 )   Save

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As an emerging optical molecular imaging technology, fluorescence molecular tomography can efficiently reconstruct concentrations and three dimensional distributions of the buried fluorophore in small animals and diagnose the early cancer. For the purpose of improving the performance of the reconstructed image, simplified spherical harmonics approximation (SP_N) based on the radiative transport equation (RTE)is proposed to perform the forward simulation. To overcome the influence of ill-posedness and receive a more accurate reconstructed image, the Laplace regularization method is introduced to reconstruct the inverse problem. Numerical experiments reveal that the proposed method can acquire high-quality reconstructed images, especially of the small object and multi-objects.

Improvement of a two-party quantum key agreement protocol

SHEN Dongsu;MA Wenping;YIN Xunru;WANG Lili

J4. 2015, 42(1):  86-90+186.  doi:10.3969/j.issn.1001-2400.2015.01.014

Abstract ( 593 )   PDF (438KB) ( 600 )   Save

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To avoid the weakness that the sender can fully control the shared key alone in the Hsueh and Chen's two-party quantum key agreement (QKA) protocol with maximally entangled states, a possible solution is presented by adding the receiver's unitary operation. The unitary operation instead of the security checking is utilized, which makes this protocol fundamentally meet the basic requirement that in a quantum key agreement each participant equally contribute to the generation and distribution of the shared key. Therefore the security against the participant attack is based on basic physical principles rather than on the checking photons technique. Security analysis shows that this protocol is secure against the outside attack and participant attack. Compared with the previous improved protocol, the weakness is avoided with less qubits and the efficiency of the protocol is improved.

Cyclostationary signal DOA estimation under complex environment

ZHANG Gege;WANG Jun;WU Riheng

J4. 2015, 42(1):  91-97.  doi:10.3969/j.issn.1001-2400.2015.01.015

Abstract ( 636 )   PDF (994KB) ( 654 )   Save

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Because in the unknown complex battlefield environment, there may be multiple illuminators around the receiver, the basic information on the illuminator is unknown, and it is impossible to distinguish between interested and interfering signals, so that it is impossible to obtain accurate direction information on the interested station, we propose a cyclostianarity-based direction of arrival estimation method. First, for unknown cyclostiaonarity in the passive bistatic radar, we propose to use the cyclic autocorrelation function of the received signal to obtain cycle-frequency information on each base station signals. Then the cyclostianarity of the signal of interest is applied to enhance the signal of interest, while suppressing other clutters. Finally, the simulation method verifies that the proposed method can obtain more accurate direction estimation than the conventional method, and that it is also applicable to the underdetermined case where the number of antennas is less than the number of sources.

Method on weights decision of green-assessment-indexes for electromechanical products

GUO Jinwei;ZHANG Yongan;GAO Xiang;PU Xuqiang

J4. 2015, 42(1):  98-103.  doi:10.3969/j.issn.1001-2400.2015.01.016

Abstract ( 512 )   PDF (542KB) ( 624 )   Save

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Aiming at the problem of weights decision of green-assessment-indexes, a new method based on the analytic network process (ANP) and theory of life cycle assessment (LCA) is proposed to compute the assessment indexes' weights. Firstly, the assessment indexes in life cycles of a product are presented. Secondly, according to the correlations among different indexes in the same hierarchy, the weights of green-assessment-indexes in different life cycles of a product are decided by the ANP. The results indicate that the analysis by the proposed method is more comprehensive and objective than that by the AHP alone.

Parallel clutter suppression algorithm for passive radar in CUDA

WU Yong;WANG Jun;ZHANG Peichuan;CAO Yunhe

J4. 2015, 42(1):  104-111.  doi:10.3969/j.issn.1001-2400.2015.01.017

Abstract ( 757 )   PDF (962KB) ( 643 )   Save

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In order to solve the problem that the direct matrix inverse(DMI) algorithm for clutter suppression can not be real-time processing in the passive radar engineering application, a segmented parallel DMI algorithm(called P-DMI) is proposed. By considering the feature of the DMI algorithm, the entire operation block is broken up into several identical sub-blocks, and in the Compute Unified Device Architecture, these sub-blocks are processed in parallel to achieve the purpose of improving the processing efficiency. Experimental results indicate that this algorithm's computation efficiency is raised more than 25 times compared with the traditional serial algorithm when the sampling rate is 200kHz and the clutter cancelation order is equal to 128. Also, the method has been used in real-time signal processing for passive radar successfully.

Principle research on the frequency chain of the rubidium atomic clock based on group phase processing

MIAO Miao;ZHOU Wei;LI Zhiqi;ZHANG Xueping;LU Weihao

J4. 2015, 42(1):  112-117.  doi:10.3969/j.issn.1001-2400.2015.01.018

Abstract ( 607 )   PDF (579KB) ( 664 )   Save

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The rubidium atomic clock is most commonly used. The traditional circuit scheme usually adopts the comparison of the same frequency signals as a closing loop. Due to the existence of many frequency multipliers, the short stability of the rubidium clock is changing. Based on the principle of phase group synchronization and phase group continuation, the construction of the clock is improved by the frequency link in the generalized phase processing. The frequency link method in the generalized phase processing is spreading into the phase measurement between different frequency signals. Compared with the traditional method, the scheme simplifies the frequency transforming circuit and decreases the phase noise from them. With the simple construction the phase group synchronization improves the stability and reduces the phase noise.

Improved shuffled frog-leaping algorithm for low-power network-on-chip mapping

ZANG Mingxiang;WANG Meng;ZHOU Wenhong;CHEN Huicang

J4. 2015, 42(1):  118-123.  doi:10.3969/j.issn.1001-2400.2015.01.019

Abstract ( 686 )   PDF (524KB) ( 630 )   Save

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With the density of network-on-chip(NoC) integration getting higher, the low-power mapping has become a hotspot research. A novel shuffled frog-leaping algorithm(SFLA) is used for solving the NoC mapping problem based on the concept of adjustment sequence. To further enhance searching capability, the proposed SFLA is improved with the adaptive chaos tactic and strategy of multi-neighborhood annealing. Experimental results shows that the improved SFLA has the advantage over the SFLA and annealing SFLA of better optimizing performance, thus reducing the communication power further.

Low-power and low-delay sheep scheduling algorithm based on the data aggregation tree

QI Xiaogang;LU Zanzan;ZHENG Gengzhong;SUN Erkun;HU Mingming;XIE Mande

J4. 2015, 42(1):  124-129.  doi:10.3969/j.issn.1001-2400.2015.01.020

Abstract ( 769 )   PDF (704KB) ( 2562 )   Save

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Based on the maximum independent set and first-fit algorithm, we design a data aggregation algorithm, Peony-tree-based Data Aggregation (PDA). On the basis of the PDA, using the time-division multiplexing method, we introduce the concept of low-power sleep schedule in the cyclical time slot of data aggregation. It is largely possible to reduce the amount of data transmission,network time delay and achieve low-power data aggregation. Simulation results show that the proposed algorithm can reduce network energy consumption, prolong the network lifetime and reduce the network delay cost.

Dual-band ultra-thin metamaterial absorber and its application in reducing RCS of the microstrip antenna

GAO Jun;ZHANG Hao;CAO Xiangyu;YANG Huanhuan;YANG Qun;LI Wenqiang

J4. 2015, 42(1):  130-135.  doi:10.3969/j.issn.1001-2400.2015.01.021

Abstract ( 709 )   PDF (3591KB) ( 574 )   Save

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A novel ultra-thin dual-band metamaterial absorber is designed. Its absorbing mechanism is illuminated by calculating the effective impedance and analyzing the electric fields as well as currents distributions. Then the absorber is applied to the dual-band microstrip antenna to reduce its in-band RCS (Radar Cross Section). The results show that this absorber achieves high absorption in two frequency bands. Moreover, its absorbing properties are incident angle insensitivity and polarization independence, and when it is loaded to the dual-band microstrip antenna, it can reduce the antenna's RCS by 8.59dB and 9.9dB at 4.29GHz and 6.49GHz, respectively, which are the working frequencies of the dual-band antenna. There is a good agreement between simulated and measured results, showing that this absorber can be used for the improvement of the dual-band antenna's in-band invisibility of the antenna.

GPS receiver autonomous integrity monitoring algorithm using the genetic particle filter

WANG Ershen;ZHANG Shufang;CAI Ming;PANG Tao

J4. 2015, 42(1):  136-141.  doi:10.3969/j.issn.1001-2400.2015.01.022

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According to the measurement noise feature of the GPS receiver and the degeneracy phenomenon and for alleviating the sample impoverishment problem in the particle filter (PF), the GPS receiver autonomous integrity monitoring (RAIM) method based on an algorithm combining the genetic resampling particle filter with the likelihood ratio is presented. By setting up the test statistic of satellite fault detection, satellite fault detection is undertaken by checking the cumulative log-likelihood ratio (LLR) of system states. The selection, crossover and mutation of the genetic algorithm are melted into the particle filter, the accuracy of the particle filter is improved, and the genetic of particles is manipulated in the real domain. However, the coding of genetic manipulation is avoided. Simulation results demonstrate that the proposed algorithm can effectively detect and isolate fault satellite and improve the detection performance under conditions of non-Gaussian measurement noise. Therefore, the feasibility and validity of the proposed algorithm for RAIM are verified.

Research on the distributed cooperative wideband spectrum sensing

WU Di;GE Lindong;PENG Hua

J4. 2015, 42(1):  142-148.  doi:10.3969/j.issn.1001-2400.2015.01.023

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In order to solve the problems of high communication overhead and computational complexity for reconstructing the sparse frequency spectrum in conventional cooperative wideband spectrum sensing, a novel decentralized algorithm based on distributed subspace estimation is proposed. In the proposed method, the subspace is estimated directly from the sub-Nyquist samples and then the orthogonality property of the signal subspace and noise subspace can be exploited to complete spectrum sensing. To obtain the spatial diversity gain, the global signal subspace is estimated by using the distributed algorithm based on the diffusion adaptation cooperation scheme. Theoretical analysis and simulation results show that the method does not reconstruct the original signal spectrum, with lower computational complexity. The fully distributed cooperative scheme improves the performance of spectrum sensing and has a lower communication amount.

Image enhancement based on estimating the upper and lower boundary

ZHANG Ming;BAI Songhao

J4. 2015, 42(1):  149-154.  doi:10.3969/j.issn.1001-2400.2015.01.024

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A novel image enhancement algorithm based on estimating the upper and lower boundary is presented. The method employs the upper and lower boundary to adjust the image details adaptively and dehaze the image, respectively and control the extent of image enhancement flexibly by adjusting the distance between the upper and lower boundary. The weighted median filter is adopted to calculate the upper and lower boundary for preserving image edges. Simulation results show that the proposed algorithm can improve the visual quality of the image efficiently, preserve the details, compress the high dynamic range, reduce halo artifacts and make the image more realistic and natural.

Online traffic anomaly detection method for SDN

ZUO Qingyun;CHEN Ming;WANG Xiulei;LIU Bo

J4. 2015, 42(1):  155-160.  doi:10.3969/j.issn.1001-2400.2015.01.025

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Based on the centralized control plane in SDN, an online traffic anomaly detection method (OpenTAD) is proposed. Firstly the flow table statistic is collected from the controller online, and the traffic matrix and sample entropy matrix are constructed and assembled. Then the PCA method is used to detect the abnormal traffic. The result of experiments show that, compared with the traditional PCA method which disposes the traffic matrix or the entropy matrix respectively offline, the OpenTAD is simple and effective, and traffic anomaly could be isolated rapidly. This method is a lightweight online traffic anomaly detection method for SDN.

State modeling of the narrowband LMS channel suitable for dual-satellite systems

LIAO Xi;XUE Rui;ZHAO Danfeng

J4. 2015, 42(1):  161-167.  doi:10.3969/j.issn.1001-2400.2015.01.026

Abstract ( 548 )   PDF (726KB) ( 642 )   Save

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Considering the low service availability and limited usage scenarios of state modeling for the single-satellite system, the state modeling of the Land Mobile Satellite (LMS) channel, based on the model parameters extracted from the Global Navigation Satellite Systems(GNSS) measurement data, is analyzed for much more scenarios. A joint generation of the states sequence for the dual-satellite is presented by the first-order Markov chain and semi-Markov chain. Various elevation combinations and azimuth separations in terms of correlation coefficients, state probabilities, and state duration statistics are analyzed. Simulation results show that the semi-Markov model with lognormal-fit can describe the state modeling of the dual-satellite propagation channel more accurately and effectively compared with the measurements. It has better applicability for various constellations in different channel environments, and can be used in modeling of the multi-satellite channel and system performance analysis.

Real-time acoustic source localization algorithm based on the average of multiple cross correlation values

ZHANG Yiwen;LIU Jianping;ZHANG Shiquan

J4. 2015, 42(1):  168-173.  doi:10.3969/j.issn.1001-2400.2015.01.027

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The Steered Response Power(SRP)-based acoustic source localization algorithm with microphone arrays has been shown to be robust in noisy and reverberant environments. However, grid-search methods used to find a global maximum of the SRP image are computationally-intensive. In this paper, we propose a different strategy where, instead of the SRP at discrete spatial positions, the average of multiple Cross-Correlation(CC) values is evaluated as a cost function. The multi-stage region contraction is then used to find the maximum of the cost function to reduce the computational burden. The determination of CC accumulation limits does not increase the amount of calculation significantly. For incorporating additional spatial knowledge at each search grid, the proposed algorithm allows for a coarser spatial grid and reduces the computational cost with almost no loss of accuracy. Experiments carried out under different acoustic conditions confirm the validity of the proposed approach.

Detection and parameter estimation of the polyphase code signal in a low SNR

WANG Xiaofeng;ZHANG Guoyi;RUI Guosheng

J4. 2015, 42(1):  174-179.  doi:10.3969/j.issn.1001-2400.2015.01.028

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A detection and parameter estimation method based on expanded Wigner-Hough transform(WHT) is proposed to solve the detection and parameter estimation problem of the polyphase code signal in a low SNR. The polyphase code signal exhibits the characteristics of parallel multi-ridges in Wigner-Ville distribution(WVD). According to the characteristics, the expanded WHT uses the improved kernel function to cumulate the energy of polyphase code signal parallel multi-ridges in WVD. It can complete the signal detection and estimate the signal's modulation parameter. Theoretical analysis and simulation both indicate that the expanded WHT can accomplish the detection and parameter estimation of the polyphase coded signal in a low SNR, and is not affected by the coding type.

Proximate time-optimal control scheme for speed-constrained servo systems

CHENG Guoqing;HU Jingao

J4. 2015, 42(1):  180-186.  doi:10.3969/j.issn.1001-2400.2015.01.029

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A proximate time-optimal control (PTOC) scheme with mode switching is proposed for typical servo systems characterized by the double-integrator model, aiming to achieve fast and accurate position regulation under speed constraint. The PTOC law exerts the maximum control authority for acceleration and deceleration when the initial position error is large, and ensures a smooth transition to linear control when the error goes down to some specified value. To satisfy the speed constraint, a stage for speed regulation is inserted between the acceleration stage and the deceleration stage of the servo system, and a mode-switching logic is designed. A linear extended state observer is adopted to estimate the un-measured speed and the unknown disturbance, to be used for feedback and compensation, so as to remove the steady-state error. The control scheme is then applied to a permanent magnet synchronous motor (PMSM) position servo system. Experimental tests have been carried out using the TMS320F2812DSP and the results verify that the controlled system is capable of tracking a wide range of target positions with desirable performance in the presence of load disturbance and speed constraint.

Change detection for SAR images based on the particle swarm clustering algorithm using neighborhood information

LIU Yi;MU Caihong;LIU Jing

J4. 2015, 42(1):  187-193.  doi:10.3969/j.issn.1001-2400.2015.01.030

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Change detection for SAR images can be transformed into the clustering for the difference image of SAR images. Since SAR images have speckle noise, a new adaptive particle swarm clustering algorithm using neighborhood information is proposed for improving the clustering results. The degrees of membership of the neighbors around each central pixel are introduced into the new objective function based on the fuzzy c-means (FCM) clustering algorithm, and the centers of clusters are optimized by the global searching of adaptive particle swarm. By the self-study operator of the proposed method, the degree of membership of each pixel can be revised based on the degrees of membership of all the neighboring pixels. Experimental results show that the proposed method is less sensitive to noise than the FCM and quantum-inspired immune clonal clustering algorithm by reason of using neighborhood information, and is better than the fuzzy local information c-means clustering algorithm on image detail preservation and run time.

High performance CPML acceleration scheme with GPU for FDTD

BAI Bing;NIU Zhongqi

J4. 2015, 42(1):  194-199+212.  doi:10.3969/j.issn.1001-2400.2015.01.031

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To overcome computational redundancy and memory-access redundancy of the traditional GPU-accelerated CPML technique, a novel division-free and minimum-access CPML scheme is proposed. In the proposed scheme, the division operators in the CPML method are merged into a series of fixed coefficients by optimally rearranging the iteration process of CPML and then, the reduplicate memory accesses are eliminated by updating the FDTD and CPML operation in the PML region jointly. Experimental results show that the proposed structure can save up to 70% operation time compared with the traditional GPU-CPML technique and 44% of field updating in the PML region, without any loss of accuracy.

Compressive sensing of linear frequency modulated echo signals in fractional Fourier domains

FANG Biao;HUANG Gaoming;GAO Jun;ZUO Wei

J4. 2015, 42(1):  200-206.  doi:10.3969/j.issn.1001-2400.2015.01.032

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For the large bandwidth, high sampling rate, high storage capacity in linear frequency modulated(LFM) signals applied in wideband radar, this paper designs an overall solution for undersampling the radar echo of LFM signals based on compressive sensing(CS). First, by use of the good energy characteristics of LFM signals in the fractional Fourier transform(FRFT) domain, a novel orthogonal base dictionary based on the DFRFT nuclear matrix is proposed. Combining this dictionary with random demodulation and matching pursuit algorithms, an LFM radar echo signal sampling and reconstruction system model is built. Simulation results verify the feasibility and effectiveness of this scheme, and sparse representation of the LFM radar echo in the orthogonal basis dictionary is superior to the existing waveform matching dictionary, and has better anti-noise and adaptive performance.

Post nonlinear interference cancelation algorithm in satellite communication

TANG Chengkai;LIAN Baowang;ZHANG Lingling

J4. 2015, 42(1):  207-212.  doi:10.3969/j.issn.1001-2400.2015.01.033

Abstract ( 618 )   PDF (718KB) ( 637 )   Save

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Aimed at the fact that predistortion can not cancel the nonlinear interference and memory interference which are caused by the power amplifier in the satellite and the high order modulation of the signal, a post nonlinear interference cancellation algorithm is proposed. Based on the fact that the high order signal under the DVB-S2 has the multiple amplitude, and combined with the memory of the amplifier, the algorithm builds an adaptive nonlinear interference cancellation module to realize the linearization of the satellite's output signal. The algorithm can be used by high order modulation and it can remove the nonlinear effect of the satellite's power amplifier perfectly. Simulation results about the bit error radio, power spectrum power and constellation show that our proposed algorithm can eliminate the nonlinear and memory interference.