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A new family of windows——convolution windows and their applications

Science china(Technological Sciences) 2005年第4期48卷 468-480页

作者： ZHANG Jieqiu1,2. LIANG Changhong1 & CHEN Yanpu3.1. Department of Applied Math. & Phys., College of Science, Airforce Engineering University, xi’an 710051, china 2. national key laboratory of antennas and microwave technology, {2. University, xi’an 710071, china 3. Computer Center, xi’an Communication College, xi’an 710106, china Department of Applied Math. & Phys. College of Science Airforce Engineering University Xi’an China national key {2. of {3. and microwave technology Xidian University Xi’an China Computer Center Xi’an Communication College Xi’an China

A new family of windows is constructed by convolutions via a few rectangular windows with same time width and is thus referred to as convolution windows. The expressions of the second-order up to the eighth-order convolution windows in both the time and frequency domains are derived. Their applications in high accuracy harmonic analysis of periodic signals are investigated. Comparisons between the proposed windows and some known windows with the same width shows that, when the synchronous deviation of data sampling is slight, the proposed ones have the least effect of spectral leakage. Therefore, the new windows are well suited for high accuracy harmonic analysis and parameter estimation for periodic signals. The error analysis and computer simulations show that the estimation errors, corresponding to frequency, amplitude and phase of every harmonic component of a signal, are proportional to the pth power of the relative frequency deviation in case of the pth-order convolution window is applied to windowing signal of approximately p cycles. By introducing real time adjustment in sampling interval, the proposed algorithm can adaptively trace signal frequency and lead to less sampling synchronous deviation. The proposed approach has the advantages of easy implementation and high measure precision and can be used in harmonic analysis of quasi-periodic signals whose fundamental frequency drifts slowly with time.

关键词： signal processing harmonic analysis window function convolution window synchronous error spoctral leakage

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Fast algorithm based on triplet Markov fields for unsupervised multi-class segmentation of SAR images

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Science china(Information Sciences) 2011年第7期54卷 1524-1533页

作者： WU Yan 1,WANG xin 1,xiAO Ping 2.GAN Lu 1,LIU ChunYan 1 & LI Ming 3.1 School of Electronics Engineering,xidian University,xi’an 710071,{2. 2.Shaanxi Bureau of Surveying & Mapping,xi’an 710054,{2. 3.national key laboratory of Radar Signal Processing,xidian University,xi’an 710071,{2. School of Electronics Engineering Xidian University Xi’an China Shaanxi Bureau of Surveying & Mapping Xi’an China national key {2. of Radar Signal Processing Xidian University Xi’an China

Non-Gaussian triplet Markov fields (TMF) model is suitable for dealing with multi-class segmentation of non-stationary and non-Gaussian synthetic aperture radar (SAR) *** the complexity of the model and algorithm,as well as the requirement of real-time,and robust and efficient processing of SAR images,a fast algorithm based on TMF for unsupervised multi-class segmentation of SAR images is proposed in this *** the speckle noise in SAR images,numerical characteristic,threshold selection and QuadTree decomposition criterion are researched *** the new method,a SAR image can quickly be mapped into an edge-based pixon-representation,which results in a coarse decomposition in smooth regions,and a fine decomposition in *** by combining TMF model with the pixon-representation of SAR image,a new potential energy function of TMF based on pixon-representation is ***,the segmentation is finished by Bayesian maximum posterior mode (MPM).The effectiveness of the fast TMF algorithm is demonstrated by applying it to simulated data and real SAR images.

关键词： pixon-representation of SAR image QuadTree decomposition new potential energy function triplet Markov fields multi-class segmentation

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SAR image despeckling based on edge detection and nonsubsampled second generation bandelets

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Journal of Systems Engineering and Electronics 2009年第3期20卷 519-526页

作者： Zhang Wenge~(1,2.,Liu Fang~(1,2.,Jiao Licheng~(2.3.& Gao xinbo~(2.3. 1.School of Computer Science and technology,xidian Univ.,xi’an {2.,P.R.china 2.key Lab.of Intelligent Perception and Image Understanding of Ministry of Education of china,xi’an {2.,P.R.china 3.Inst,of Intelligent Information Processing,xidian Univ.,xi’an {2.,P.R.china School of Computer Science and technology Xidian Univ. Xi'an 710071 P. R. China key Lab. of Intelligent Perception and Image Understanding of Ministry of Education of china Xi'an 710071 P. R. China key Lab. of Intelligent Perception and Image Understanding of Ministry of Education of china Xi'an 710071 P. R. China Inst. of Intelligent Information Processing Xidian Univ. Xi'an 710071 P. R. China

To preserve the sharp features and details of the synthetic aperture radar （SAR） image effectively when despeckling, a despeckling algorithm with edge detection in nonsubsampled second generation bandelet transform （NSBT） domain is proposed. First, the Canny operator is utilized to detect and remove edges from the SAR image. Then the NSBT which has an optimal approximation to the edges of images and a hard thresholding rule are used to approximate the details while despeckling the edge-removed image. Finally, the removed edges are added to the reconstructed image. As the edges axe detected and protected, and the NSBT is used, the proposed algorithm reaches the state-of-the-art effect which realizes both despeckling and preserving edges and details simultaneously. Experimental results show that both the subjective visual effect and the mainly objective performance indexes of the proposed algorithm outperform that of both Bayesian wavelet shrinkage with edge detection and Bayesian least square-Gaussian scale mixture （BLS-GSM）.

关键词： computer image processing synthetic aperture radar speckle edge detection nonsubsampled second generation bandelet transform Canny operator threshold shrinkage.

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Quantum threshold group signature

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Science china(Physics,Mechanics & Astronomy) 2008年第10期51卷 1505-1514页

作者： YANG YuGuang1,2.3.& WEN QiaoYan4 1 College of Computer Science and technology, Beijing University of technology, Beijing 10012.,{2. 2.State key laboratory of Integrated Services Network, xidian University, xi’an 710071,{2. 3.State key laboratory of Information Security (Graduate University of Chinese Academy of Sciences), Beijing 100049,{2. 4 State key laboratory of Networking and Switching technology, Beijing University of Posts and Tele-communications, Beijing 100876,{2. College of Computer Science and technology Beijing University of Technology Beijing China State key laboratory of Integrated Services Network Xidian University Xi’an China State key laboratory of Information Security Graduate University of Chinese Academy of Sciences Beijing China State key laboratory of Networking and Switching {2. Beijing University of Posts and Telecommunications Beijing China

In most situations, the signer is generally a single person. However, when the message is written on behalf of an organization, a valid message may require the approval or consent of several persons. Threshold signature is a solution to this problem. Generally speaking, as an authority which can be trusted by all members does not exist, a threshold signature scheme without a trusted party appears more attractive. Following some ideas of the classical Shamir’s threshold signature scheme, a quantum threshold group signature one is proposed. In the proposed scheme, only t or more of n persons in the group can generate the group signature and any t-1 or fewer ones cannot do that. In the verification phase, any t or more of n signature receivers can verify the message and any t-1 or fewer receivers cannot verify the validity of the signature.

关键词： threshold quantum signature trusted party quantum cryptography

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Threshold proxy quantum signature scheme with threshold shared verification

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Science china(Physics,Mechanics & Astronomy) 2008年第8期51卷 1079-1088页

作者： YANG YuGuang1,3.4 & WEN QiaoYan2.1 College of Computer Science and technology,Beijing University of technology,Beijing 10012.,{2. 2.State key laboratory of Networking and Switching technology,Beijing University of Posts and Tele-communications,Beijing 100876,{2. 3.State key laboratory of Integrated Services Network,xidian University,xi’an {13.,{2. 4 State key laboratory of Information Security(Graduate University of Chinese Academy of Sciences) ,Beijing 100049,{2. College of Computer Science and technology Beijing University of Technology Beijing China State key laboratory of Integrated Services Network Xidian University Xi’an China State key laboratory of Information Security (Graduate University of Chinese Academy of Sciences) Beijing China State key laboratory of Networking and Switching {2. Beijing University of Posts and Telecommunications Beijing China

A threshold proxy quantum signature scheme with threshold shared verification is proposed. An original signer could authorize a group as its proxy signers. Then only t or more of n persons in the proxy group can generate the proxy signature on behalf of the original signer and any t-1 or fewer ones cannot do that. When the proxy signature needs to be verified,any t or more of n persons belonging to the verification group can verify the message and any t-1 or fewer ones cannot verify the validity of the proxy signature.

关键词： quantum signature threshold proxy quantum group signature threshold shared verification

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Threshold quantum secret sharing between multi-party and multi-party

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Science china(Physics,Mechanics & Astronomy) 2008年第9期51卷 1308-1315页

作者： YANG YuGuang1,2.3.& WEN QiaoYan4 1 College of Computer Science and technology,Beijing University of technology,Beijing 10012.,{2. 2.State key laboratory of Integrated Services Network,xidian University,xi’an 710071,{2. 3.State key laboratory of Information Security (Graduate University of Chinese Academy of Sciences),Beijing 100049,{2. 4 State key laboratory of Networking and Switching technology,Beijing University of Posts and Tele-communications,Beijing 100876,{2. College of Computer Science and technology Beijing University of Technology Beijing China State key laboratory of Integrated Services Network Xidian University Xi’an China State key laboratory of Information Security (Graduate University of Chinese Academy of Sciences) Beijing China State key laboratory of Networking and Switching {2. Beijing University of Posts and Telecommunications Beijing China

A threshold quantum secret sharing (TQSS) scheme between multi-party and multi-party was proposed using a sequence of single photons,which is useful and efficient when the parties of communication are not all present. We described the process of this TQSS scheme and discussed its security. It was shown that entan-glement is not necessary for quantum secret sharing. Moreover,the theoretic effi-ciency was improved to approach 100% as almost all the instances can be used for generating the private key,and each photon can carry one bit of information. This protocol is feasible with the present-day technique.

关键词： threshold quantum secret sharing quantum cryptography single photon multi-party and multi-party

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Super-orthogonal space-time code design based on the trellis diagram integrated operation

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Science china(Information Sciences) 2011年第7期54卷 1481-1490页

作者： AO Jun 1,2.MA ChunBo 1,AO FaLiang 1 & LIAO GuiSheng 3.1 College of Information and Communication,Guilin University of Electronic and technology,Guilin 541004,china 2.{2. key laboratory of Electromagnetic Environment,QingDao,2.6107,china 3.{2. Lab of Radar Signal Processing,xidian University,xi’an 710071,china College of Information and Communication Guilin University of Electronic and Technology Guilin China national key {2. of Electromagnetic Environment QingDao China national Lab of Radar Signal Processing Xidian University Xi’an China

By studying the super-orthogonal space-time coding designs for 2.transmit antennas and superquasi orthogonal space-time coding designs for 4 transmit antennas,a novel super-orthogonal space-time coding design for 4 transmit antennas is *** exploiting the inherent structure association between OSTBC and QOSTBC,the proposed schemes can obtain the full-rate and good performance while keeping the coding complexity as super-orthogonal space-time coding schemes for 2.transmit *** results demonstrate that the proposed schemes outperforms the existing super-quasi orthogonal space-time coding schemes by almost 2.dB.

关键词： STBC TCM SOSTTC SQOSTTC

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Exact thresholds for low-density parity-check codes over the binary erasure channel

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Progress in Natural Science:Materials International 2009年第7期19卷 897-900页

作者： Jianjun Mu a, xiaopeng Jiao a, xinmei Wangb a School of Computer Science and technology, xidian University,{2.,{3. b State key laboratory of Integrated Service Networks, xidian University,{2.,{3. School of Computer Science and technology Xidian University Xi’an 710071 China State key laboratory of Integrated Service Networks Xidian University Xi’an 710071 China

A simple method for determining the threshold of irregular LDPC codes over the binary erasure channel (BEC) under message-passing decoding is proposed. An exact formula for calculating the threshold of irregular LDPC codes over the BEC is proved. This generalizes the known result on the threshold of regular LDPC codes to irregular LDPC codes. Moreover, our new method can avoid the computation of the inverse of the degree distribution function for irregular LDPC codes. Numerical results demonstrate the correctness of our proposed method.

关键词： Binary erasure channel (BEC) LDPC codes Threshold

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Performance improvement in multi-ship imaging for ScanSAR based on sparse representation

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Science china(Information Sciences) 2012年第8期55卷 1860-1875页

作者： XU Gang1,SHENG JiaLian1,ZHANG Lei1&xiNG MengDao1,2.1N ational key laboratory of Radar Signal Processing,{2. University,xi'an 710071,china 2.5} key laboratory of microwave Imaging,Institute of Electronics,Chinese Academy of Sciences,Beijing 100080,china national key {2. of Radar Signal Processing Xidian University Xi’an China national key {2. of {3. Imaging Institute of Electronics Chinese Academy of Sciences Beijing China

There is always a compromise between unambiguous wide-swath imaging and high cross-range resolution owing to the constraint of minimum antenna area for conventional single-channel spaceborne synthetic aperture radar(SAR)*** overcome the inherent systemic limitation,multi-channel SAR imaging has been ***,this still suffers from various problems such as high system *** simplify the system structure,a novel algorithm for high resolution multi-ship ScanSAR imaging based on sparse representation is proposed in this paper,where the SAR imaging model is established via maximum a posterior estimation by utilizing the sparsity prior of multi-ship *** the scheme,a wide swath is generated in the ScanSAR mode by continuously switching the radar footprint between ***,high crossrange resolution is realized from sparse subapertures by exploiting the sparsity feature of multi-ship *** particular,the SAR observation operator is constructed approximately as the inverse of conventional SAR imaging and then high resolution SAR imaging including range cell migration compensation is achieved by solving the *** with multi-channel SAR imaging,the system complexity is effectively reduced in the ScanSAR *** addition,enhancement of the cross-range resolution is realized by incorporating the sparsity prior with sparse *** a result,the amount of data is effectively *** based on measured data have been carried out to confirm the effectiveness and validity of the proposed algorithm.

关键词： synthetic aperture radar(SAR) ScanSAR wide-swath sparse representation high resolution

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Optimal user scheduling and power control in multi-user cognitive broadcast systems

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Science china(Information Sciences) 2012年第6期55卷 1402-1414页

作者： WANG QunHuan 1,2.3.WANG HuiMing 1,2.3.& YIN QinYe 1,3.1 School of Electronic and Information Engineering,xi'an Jiaotong University,xi'an 710049,china 2.State key Lab for Integrated Services Networks,{2. University,xi'an 710071,china 3.Ministry of Education key Lab for Intelligent Networks and Network Security,xi'an Jiaotong University,xi'an 710071,china. School of Electronic and Information Engineering Xi’an Jiaotong University Xi’an China State key Lab for Integrated Services Networks Xidian University Xi’an China Ministry of Education key Lab for Intelligent Networks and Network Security Xi’an Jiaotong University Xi’an China

Cognitive radio systems should not only have the ability to sense and exploit "frequency spectrum holes",but also the ability to sense and utilize "spatial spectrum holes".In this paper,we consider the issue of maximizing the throughput of the cognitive systems by fully utilizing "spatial spectrum holes" brought in by multiple cognitive users,in the scenario where a pair of licensed users and a cognitive broadcast system share multiple spectrum *** exploiting the channel reciprocity under the premise that the licensed system adopts the time-division-duplexing (TDD) mode,we propose a more practical cognitive access scheme that can sense the interference at the licensed user caused by the cognitive transmitter,based on the existing feedback signals from the licensed user to the licensed base *** both interferences from the licensed base station to the cognitive receiver and from the cognitive transmitter to the licensed user into consideration,we investigate the optimal user scheduling and power allocation scheme that can maximize the ergodic sum rate of the cognitive *** show that scheduling the user whose channel gain to interference and noise ratio (CGINR) is the largest for each frequency band is *** also derive the dynamic power allocation scheme meeting the three practical constraints,i.e.,the transmitter's average transmission power constraint,the power amplifier's instantaneous transmission power constraint,and the interference power constraint at the licensed *** result shows that in different coherent time intervals and different frequency bands,the power allocation has a multi-level waterfilling *** analysis shows that the strategy scheduling user with the largest CGINR introduces significant performance improvement compared with the traditional strategy scheduling user with the largest channel gain to noise ratio (CGNR).We also illustrate the impact of power constraints and the number of users on system p

关键词： cognitive radio distributed spatial spectrum holes opportunistic scheduling power allocation

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