2009 Vol. 18, No. 1

Display Method:
Decentralized Secure Interoperation in Multi-Domain Environments
FENG Dengguo, WANG Xingang, XU Zhen
2009, 18(1): 1-7.
Abstract(458) PDF(735)
Abstract:
The current schemes for security interoperation in multi-domain environments are in a centralizedway, which makes security interoperation hard to be scaledup. And these schemes do not deal well with policy evolution and thus cannot be applied in dynamic environments.In this paper, we present a scheme for secure interoperation in a decentralized way. First, we present a decentralized multi-domain policy model, representing the elementsand characters of the policies kept by each domain. Thenwe give distributed algorithms for creating or maintainingsuch policies, including algorithms for the initialization ofpolicy interoperation and for policy evolution respectively.Our scheme is easy to be scaled up and appropriate for thedynamic environments where policy evolution happens often.
An Improved SIR Model for Analyzing theDynamics of Worm Propagation in WirelessSensor Networks
WANG Xiaoming, LI Yingshu
2009, 18(1): 8-12.
Abstract(513) PDF(2196)
Abstract:
By introducing the new concept of deadstate of nodes in WSNs and the Susceptible-infectiousrecovered-susceptible (SIRS) mechanism of worm propagation, this paper improves the SIR (Susceptible-infectiousrecovered) model, and proposes a novel model to analyzethe dynamics of worm propagation in Wireless sensor networks (WSNs), called the iSIRS model. The iSIRS modelis based on the epidemic theory, consists of a group ofdifferential equations, and it can effectively describe theprocess of worm propagation with energy consumption ofnodes in WSNs. Simulation results demonstrate the validity of the iSIRS model.
Differential Fault Attack on Camellia
ZHOU Yongbin, WU Wenling, XU Nannan, FENG Dengguo
2009, 18(1): 13-19.
Abstract(658) PDF(6873)
Abstract:
Camellia is the final winner of 128-bit blockcipher in NESSIE project, and is also certified as the international IETF standard cipher for SSL/TLS cipher suites.In this study, we present an effcient differential fault attack on Camellia. Ideally, by using our techniques, on average, the complete key of Camellia-128 is recovered with64 faulty ciphertexts while the full keys of Camellia-192and Camellia-256 are retrieved with 96 faulty ciphertexts.Our attack is applicable to generic block ciphers with overall Fiestel structure using a SPN round function.All theseattacks have been successfully put into experimental simulations on a personal computer.
Statistical Analysis of Full-Chip Leakage Powerfor 65nm CMOS Node and Beyond
LI Tao, YU Zhiping
2009, 18(1): 20-24.
Abstract(483) PDF(703)
Abstract:
In this paper we address the growing issue of statistical full-chip leakage power analysis for 65nmCMOS node and beyond at the circuit level. Specifically, we first develop a fast approach to analyze the statedependent total leakage power of a large circuit block,considering junction tunneling leakage (Ijunc), subthresholdleakage (Isub), and gate oxide leakage (Igate). We then propose our algorithm to estimate the full-chip leakage powerwith consideration of both Gaussian and non-Gaussian parameter distributions, capturing spatial correlations using a grid-based model. The proposed approach is implemented and compared with Monte Carlo simulationson ISCAS85 benchmark circuits and shows high accuracy.Comparison with measurement results of SRAMs is alsolisted to demonstrate the significance of our method. Fora circuit with G gates, the complexity of our approach isO(G).
Web Video Duplicate Detection Basedon Video Vocabulary
LIU Lu, SUN Lifeng, YANG Shiqiang
2009, 18(1): 25-30.
Abstract(450) PDF(1275)
Abstract:
With the rapid development of Internettechnology and the prevalence of easy-use video capturing devices, the amount of videos is growing explosivelyon the web. Meanwhile digital processing tools make itquite easy to copy, reformat, modify and republish "new"video files, resulting in a large volume of duplicate content.Web video duplicate detection and measurement can facilitate effective video search and intellectual property protection. In this paper we mainly investigate this problem. Wefirst explain the concept of video vocabulary and employa heuristic searching method to build it. Based on videovocabulary, we propose two kinds of video signatures thatare robust to changing compression formats, compressionratios, frame sizes and frame rates and then develop thecorresponding signature comparison schemes. The experiments demonstrate that our approaches are both effcientand effective for web video duplicate detection, even forreal-time applications.
Practical Escape Analysis in an Open World
SHI Xiaohua, JIN Maozhong, WU Gansha, LUEH Gueiyuan
2009, 18(1): 31-36.
Abstract(428) PDF(654)
Abstract:
A novel escape analysis framework thathandles the Java open-world features is proposed and evaluated. The novel approach analyzes a Java program withan optimistic view that the program is in a closed worldand applies optimizations aggressively. The framework alsoprovides a mechanism that controls the analysis complexity. The results show that the escape analysis framework,which has been implemented in Intel's Open Runtime Platform on X86, eliminated about 70% and 94% synchronization operations, and improved the runtime performance15.77% and 31.28%, for SPECjbb2000 and 209 db respectively.
An Algorithm for Role Mapping Across Multi-domains Employing RBAC
WANG Xiaoqing, GU Tianyang, GUO Yong, ZHENG Yanxing, ZONG Jianjian, GONG Bo
2009, 18(1): 37-41.
Abstract(443) PDF(784)
Abstract:
The problem of access control across multiple security domains in data sharing environment is addressed and a rule-based algorithm for role mapping acrossmulti-domains is presented. The algorithm resolves effciently the conflicts of cyclic inheritance and separation ofduties, and the problem of regression inheritance. The algorithm takes the "Least privilege theorem" into accountand prohibits accesses from illegal domains. Further more,the algorithm makes the establishment of role mappingacross multi-domains more effciently by preserving historical information of role mapping paths established successfully before, and satisfies preferably the access controlrequirement across dynamic multi-domains in data sharing environment. Evaluation by access instances shows theeffciency of our algorithm.
An Effcient Method for Calculating Qualitative Spatial Relations
WANG Shengsheng, LIU Dayou
2009, 18(1): 42-46.
Abstract(446) PDF(805)
Abstract:
Qualitative spatial relations are widelyused in geospatial ontologies, geospatial (semantic) webservices, spatial description logics etc. Methodology to obtain qualitative spatial relations (especially complex spatial relations) from Geographical information system (GIS)has not been studied in previous literatures. An effcientmethod for calculating complex qualitative spatial relations is discussed here. First, the multi-granularities approximate representation of spatial objects is proposed,it is designed for GIS object types (such as polygon),and requires less process time. Then some algorithms forcalculating complex spatial relations based on the multigranularities approximate representation are given. Finally, this method is implemented and used to obtain topology and direction relations from world map. The analysisand test results show that this method supports complexand integrated spatial relations and requires less processtime than traditional method. This method is suitablefor obtaining spatial relations for geospatial ontologies andother applications.
Workflow Model Verification Based on Matrix Transformation
DUN Haiqiang, ZHAO Wen, ZHANG Shikun, WANG Lifu
2009, 18(1): 47-53.
Abstract(458) PDF(764)
Abstract:
Synchronet is a workflow model which hasthree layers, i.e. workflow logic, case semantics and workflow management. Throughness is an important propertyin workflow logic layer. As a simple and widely used technique, graph reduction method can be employed to verifyworkflow logic via reduction rules. However, the graph reduction method is low effcient and space-consuming. Inthis paper, a workflow logic verification method based onmatrix transformation is proposed to solve above problems. Firstly, the incidence matrix of workflow logic isgenerated by its net representation. Then, matrix transformations can be conducted according to rows characteristic and columns characteristic of the incidence matrix.Related algorithms are implemented and experiments areconducted. Experiment results show that this method ismore effcient and space-saving than the graph reductionmethod. Moreover, a worked example is provided to illustrate the transformation process.
Co-optimization of Dynamic/Static Test Power inScan Test
WANG Wei, HAN Yinhe, LI Xiaowei, FANG Fang
2009, 18(1): 54-58.
Abstract(436) PDF(655)
Abstract:
Low-power design has become a challengeof test. We propose an effective low-power scan architecture named PowerSluice to minimize power consumptionduring scan test, which is based on scan chain modifications. On one hand, a kind of blocking logic is insertedinto the scan chain to reduce the dynamic power and twokinds of controlling units are also inserted to decrease theleakage power during the shift cycle. On the other hand,using genetic algorithm, the exact values of control signalsare found out to control the process. Experiments resultsindicate that this architecture can effectually reduce powerduring scan test with probably minimum area cost.
Particle Filter Based Track-before-detect Algorithm for Over-the-horizon Radar TargetDetection and Tracking
SU Hongtao, SHUI Penglang, LIU Hongwei, BAO Zheng
2009, 18(1): 60-64.
Abstract(469) PDF(1981)
Abstract:
A particle filter based Track-before-detect(TBD) algorithm for Over-the-horizon radar (OTHR) target detection and tracking is proposed in this paper. In theTBD algorithm the unthresholded measurements are integrated over time, thus it can potentially detect and tracktargets with a much lower signal-to-noise ratio than conventional methods. Such a characteristic make the TBDtechnique adequate for OTHR target detection and tracking. The performance of the proposed algorithm employsdifferent unthresholded measurements, such as complexmeasurements, amplitude measurements and power measurements, are compared and discussed. Simulation resultsshow that the proposed algorithm is capable to detect andtrack dim targets for OTHR and the amplitude measurements are preferred for the proposed algorithm.
Tracking Maneuvering Ground Target with Variable Structure IMM Estimator Based on Dynamic Characteristic
ZHAO Wei, ZHEN Xinyan, LI Yangshi
2009, 18(1): 65-68.
Abstract(485) PDF(692)
Abstract:
To track maneuverable ground target without topography information or road constraint, a Variablestructure Interacting multiple model (VS-IMM) estimator based on target Dynamic characteristic (DC VS-IMM)was proposed. This estimator considered target maneuvers and divided target motion into several different modesegments. Suitable model set was designed for each modesegment. In tracking process, model set switched depending on the estimated target state. The design and implementation of this estimator to track a tank in a battlefieldscenario without topography information was described.Simulation results show the benefits of this DC VS-IMMestimator over the standard IMM estimator.
A New Implementation of Dedicated Circuit for CORDIC Algorithm
CUI Wei, WU Siliang
2009, 18(1): 69-73.
Abstract(447) PDF(943)
Abstract:
The novel technique for effcient implementation of Field programmable gate array (FPGA)based wave-pipelined Coordinate rotation digital computer(CORDIC) algorithm is presented in this paper. A newclock adjustment scheme which permits finer tuning ofthe skew between on-chip clocks is developed. All datain FPGA-based Wave pipelined CORDIC circuit (WPCC)pass through the same number of logic gates, and all pathsare routed using identical routing resources for achievingbest path balancing. Experimental results show that a 256LUT logic depth WPCC mapped on XC2V6000-4 runs ashigh as 256 MHz, which is a little slower than the speedof 262 MHz based on the 16-stage Conventional pipelinedCORDIC circuit (CPCC) in the same chip. But the latency of the WPCC is 39.1 ns, which is 36% shorter thanthe latency of 16 clock cycles (i.e. 61.1 ns in this example)of 16-stage CPCC.
A New Method for Facial Landmarks Detection
PENG Xiaoning, ZOU Beiji, WANG Lei
2009, 18(1): 74-78.
Abstract(472) PDF(747)
Abstract:
The techniques for face detection and facial features detection have evolved separately with littleoverlap. However our brains seem to process the differentvision tasks in the interactive and cooperative ways. Sowe present a new method for facial landmarks detection.It can share the mutual features with face detection andfinds the landmarks by regression. The method is fast andslim because of the shared computing and discriminativedetection. Its accuracy is also promising. Additionally weshow the application of the method for human body features detection.
Extending Weight-Balanced Key Tree without Adjustment-Propagation
WANG Wei, ZHAO Wenhong, LI Fenghua, MA Jianfeng
2009, 18(1): 79-83.
Abstract(409) PDF(699)
Abstract:
An Extending weight-balanced tree (EWBtree) for group key managements is presented. By introducing a special path in the weight-balanced key tree, theEWB tree does not cause adjustment-propagation aftermember adding or member deleting. The bounds ratioof the EWB tree based algorithm to that of the optimaltree shows that the bounds of EWB tree is better thanthose of the height-balanced 2-3 tree and equal to those ofthe weight-balanced 2-3 tree. The analysis also shows thatthe proposed scheme has fewer rekeying cost than the onesbased on the weight-balanced 2-3 tree, height-balanced 2-3tree, LTM tree and NSBHO tree.
Input-Adaptive Models Based Multiple-Model Algorithm for Maneuvering Target Tracking
LAN Jian, MU Chundi
2009, 18(1): 84-88.
Abstract(469) PDF(896)
Abstract:
The dynamic models with multilevel inputs are adopted in a kind of multiple model estimatorfor highly maneuvering target tracking. While the target maneuvers with the continuous time-varying accelerations, the estimator increases the levels to improve thepercentage of coverage, which induces two problems: theincrease of calculation burden and the decrease of the estimation precision due to the competition between the models. A multilevel Input-adaptive multiple-model (IAMM)algorithm is proposed, in which the inputs are adjustedaccording to the prior value and the on-line estimated maneuver parameters by introducing a binary distribution.The adaptabilities of the inputs can depict the actual maneuver process better compared with the static multilevelinputs. The simulation proves the effectiveness of IAMMalgorithm compared with the IMM (Interacting multiplemodel) algorithm with models containing multilevel staticinputs.
A Novel Non-Symmetry and Anti-Packing Modelfor Image Representation
CHEN Chuanbo, ZHENG Yunping, Mudar Sarem
2009, 18(1): 89-94.
Abstract(440) PDF(861)
Abstract:
Inspired by the concept of the packingproblem, we presented a novel Non-symmetry and antipacking model (NAM) for image representation. Also, weproposed an abstract algorithm of the NAM and analyzedthe complexity and the data amount of this algorithm. Bytaking color images for example, we implemented the abstract algorithm as a concrete algorithm of the NAM andmade a comparison with the algorithm of the popular linear quadtree. The theoretical and experimental resultspresented show that our implemented algorithm can reduce the data storage much more effectively than that ofthe linear quadtree and it is a better method to representcolor images. The representation method of the NAM, asenvisaged in this paper, shows a very strong promise, andit is valuable for the further theoretical research and potential business foreground, such as decreasing the storageroom, quickening the process procedure, and increasingthe transmission speed.
Effcient Certificateless Designated Verifier Signatures and Proxy Signatures
DU Hongzhen, WEN Qiaoyan
2009, 18(1): 95-100.
Abstract(522) PDF(830)
Abstract:
Certificateless public key cryptography isa recently proposed attractive paradigm which combinesthe advantages of both certificate-based and identity-basedcryptosystems as it avoids the use of certificates and doesnot suffer from key escrow. In this paper, we present anew Certificateless designated verifier signature (CLDVS)scheme and provide the security proofs and effciency analysis for our scheme. Based on the proposed CLDVS, thefirst notion and construction of the Certificateless designated verifier proxy signature (CLDVPS) scheme is proposed. It proves that our CLDVPS scheme satisfies all therequirements of the designated verifier proxy signatures inthe certificateless public key cryptography.
New Approaches for Construction of Time-Frequency Kernels
WANG Yong, JIANG Yicheng
2009, 18(1): 101-104.
Abstract(442) PDF(731)
Abstract:
The time-frequency distributions of Cohen's class produce cross-terms for mono-component nonlinear frequency modulated signal or multi-component signal, which make it diffcult to analyze and represent theauto-terms of the signal. In this paper, the new approachesfor construction of time-frequency kernels are presentedbased on the Wigner-Ville distribution (WVD) and the LWigner-Ville distribution (LWVD) in order to reduce thecross-terms. Two kinds of Phase adjust function (PAF),namely, the Exponential PAF (EPAF) and the ComplexLag PAF (CLPAF) are designed, then combining themwith WVD and LWVD, the new time-frequency kernelswith four structures-WVD-EPAF, WVD-CLPAF, LWVDEPAF and LWVD-CLPAF are constructed, and the crossterms induced by the nonlinearity of the signal can bedeleted or reduced. Simulated results demonstrate the validity of the methods proposed.
An Optimal Spectral Clustering Approach Based on Cauchy-Schwarz Divergence
XU Haixia, TIAN Zheng
2009, 18(1): 105-108.
Abstract(466) PDF(703)
Abstract:
A new global criterion, the CauchySchwarz (CS) cut, for spectral clustering is presented basedon the Cauchy-Schwarz divergence. It is proved thatwhen the sum of intra-cluster and inter-cluster similarity is fixed, optimizing the CS cut criterion can ensureintra-cluster similarity maximized and inter-cluster similarity minimized simultaneously. An effcient computational technique is developed based on eigenvalue problem.Experimental results on artificial data sets and natural images show that the proposed approach is very encouraging.
Residual Distributed Video Coding Based on LQR-Hash
WANG Anhong, ZHAO Yao, PAN Jeng-Shyang
2009, 18(1): 109-112.
Abstract(473) PDF(687)
Abstract:
Distributed source coding (DSC) and Distributed video coding (DVC) have aroused high researchinterest due to their property of low-complexity encoding. This paper presents a residual DVC based on Lowquality reference (LQR) hash compressed by 0-motionH.264/AVC. SW-SPIHT is applied to the residual betweenWyner-Ziv frame and the decoded LQR hash, which exploits the temporal and spatial correlations so improvesthe coding effciency. At the decoder, the decoded LQR isused for more accurate motion estimation and better sideinformation. And a refinement reconstruction with sideinformation is proposed for better SPIHT decoding. Theexperimental results indicate the proposed scheme achievesbetter rate-distortion performance than current literaturesunder the constraint of similar encoding complexity.
EAQR: An Energy-effcient ACO Based QoS Routing Algorithm in Wireless Sensor Networks
WANG Jietai, XU Jiadong, XIANG Mantian
2009, 18(1): 113-116.
Abstract(560) PDF(1345)
Abstract:
Considering the features of non-uniformlydistributed traffc load and possibly existing of the traffics requiring different performance in wireless sensor networks, this paper proposes EAQR, a novel routing protocol based on an improved Ant colony optimization (ACO)algorithm. The algorithm concentrates on the provisionof QoS and balanced energy-consumption over the wholenetwork. With the introduction of some metrics like theminimum path energy and path hop count and by means ofadvancing pheromone trail model of the ant colony system,the algorithm innovatively provides two heuristic ways respectively based on the length and the comfort of path tomeet the different performance requirements of real timeand common traffcs. Simulation experiments show thatEAQR has the following advantages comparing with existing algorithm: (1) differentiates dissemination service forReal time (RT) and Best effort (BE) traffc; (2) achieveslower delay for RT traffc; (3) exhibits substantially longernetwork lifetime; (4) behaves more scalable and robust.
Application of Trigonometric Spline Wavelets in ECG Detection
GUO Qi, WANG Kuanquan, YUAN Yongfeng, YANG Yongtian
2009, 18(1): 117-119.
Abstract(467) PDF(1086)
Abstract:
This paper presents a new kind of trigonometric spline wavelet on the interval on the basis of trigonometric spline function. The proposed method has moreadvantages than any other traditional methods, such assymmetry and anti-symmetry-linear phases or generalizedlinear phases, good time-frequency locality, short support, semi-orthogonal. In the numerical experiment, thetrigonometric spline wavelet is applied to Electrocardiogram (ECG) detection. It shows stronger capability ofgetting more concentrated information in singular positionthan other wavelets. Therefore, the accuracy of detectionis improved greatly.
Study on Complexity-Reduced Iterative Equalization Algorithm for Mobile OFDM
XI Xiaoping, ZHANG Can
2009, 18(1): 120-124.
Abstract(447) PDF(598)
Abstract:
In high mobility Orthogonal-frequency division multiplexing (OFDM) systems, time-varying channels destroy the orthogonality among subcarriers and theresultant Intercarrier interference (ICI) degrades the receiver performance. To obtain an effective balance of performance and complexity at the receiver, we proposed tosplit the Channel frequency response (CFR) matrix into asequence of submatrices rather than using the whole CFRmatrix. Then, we derived a soft information based sequentially iterative Minimum mean square error (MMSE)equalizer, which fully exploits the ICI distribution property. Analysis and simulations demonstrate that thisscheme provides a flexible and controllable approach totrade off performance for complexity, since it can be simplydone by choosing different size of the parameter Q. Meanwhile, superior ability of the ICI suppression is maintainedwhen compared with previous equalization schemes. Thisfeature indicates its potential application for future wireless communications.
SMART: A Strengthened Model of Access RouterTree for Multihoming in Nested Mobile Network
HUANG Songhua, WU Xiaobing, LU Yin, HUANG Hao, CHEN Guihai
2009, 18(1): 125-131.
Abstract(408) PDF(857)
Abstract:
Load balance and failure tolerance are thecrucial issues for multihomed mobile network. However,existing solutions are still far away from our expectation.In this paper, we first analyze the problems of multihoming in a nested mobile network and review their existingschemes in the eye of load balance and failure tolerance.Then we give a strengthened model of access router tree,where a novel and comprehensive metric for best pathrecognition is proposed to realize the load balance. In order to enhance the failure tolerance of the system, we further propose fast handover algorithms which can be usedwhen burst access failure appears. We perform extensivesimulations to evaluate the proposed scheme. Results indicate that comprehensive load balance and failure tolerance can be achieved. Moreover, our proposed handoveralgorithm achieves least latency of package transmissioncompared with its existing counterparts.
An Orthogonal Code-Division Multiplexing and Time-hopping Multiple Access Transmission Scheme for UWB Communications
LV Tiejun
2009, 18(1): 132-136.
Abstract(432) PDF(1113)
Abstract:
We propose an Orthogonal code-divisionmultiplexing and Time-hopping multiple access (OCDMTHMA) transmission scheme for Ultra-wide bandwidth(UWB) communications in a multi-user and multipath environment. The design achieves high data throughput dueto the use of the orthogonal code division multiplexingtransmission technology for individual users. The databits from each user are mapped by using the serial-paralleltransform, and then are summed and transmitted simultaneously after being modulated by their correspondingorthogonal code sequences. At the receiving side, we employ a Rake-receiver to combat multipath fading. The Biterror-rate (BER) performance in the presence of Multipleaccess interference (MAI) is analyzed for multipath channels.
A Trade off Power Allocation Algorithm over Multibeam Satellite Downlinks
SHANG Yong, QIAO Dan
2009, 18(1): 137-140.
Abstract(443) PDF(834)
Abstract:
Multibeam satellite systems have the potential to substantially increase the capacity of the wholesystem. In this paper, we study the criteria in multibeamsatellite downlinks weighting vector design and propose anew tradeoff power allocation algorithm. Traditional algorithms, such as maximum capacity and proportional fairness, can not make a compromise between total capacitymaximization and uses' fairness. The new algorithm, whichwe call `tradeoff allocation', is based on maximum capacityalgorithm, and simply changes its cost function to provide asensible compromise between total capacity maximizationand fairness. Compared with other compromise algorithm,tradeoff allocation algorithm is simpler and more flexible,because the different choose of parameter can provide different allocation. In addition, we also propose priority allocation strategy and it can optimize traditional allocationalgorithm and make the power allocation more reasonablein special practical application.
Construction of Low-Density Parity-Check Codes Based on Frequency-Hopping Sequences
ZHANG Guohua, WANG Xinmei
2009, 18(1): 141-144.
Abstract(474) PDF(804)
Abstract:
Three classes of structured regular Lowdensity parity-check (LDPC) codes with girth at least 6are constructed from frequency-hopping sequences. Theparity-check matrices of these codes have uniform row andcolumn weights, simple and explicit structure, as well asa large variety of candidate parameters. Simulation results show that the new codes perform very similar to therandomly constructed LDPC codes over Additive whiteGaussian noise (AWGN) channels.
A Secure and Effcient Certificateless Signature Scheme Using Bilinear Pairing
ZHANG Lei, ZHANG Futai, HUANG Xinyi
2009, 18(1): 145-148.
Abstract(474) PDF(755)
Abstract:
Recent years, certificateless signatureshave got fruitful achievements. However, some of the mosteffcient schemes are vulnerable to the key replacementattack. We present an effcient certificateless signaturescheme from bilinear parings, which is up to now the mosteffcient provably-secure scheme compared with other existing schemes in the literature. The security of our schemeis proved based on the intractability of the computationalDiffe-Hellman problem in the random oracle model.
An Optimal Time Spread Multiple Access Scheduling Policy for Ad Hoc Networks
LI Wei, WANG Shan, WEI Jibo
2009, 18(1): 149-154.
Abstract(436) PDF(822)
Abstract:
The performance of Medium access control (MAC) protocol has an immediate and fundamental impact on the overall effciency of the ad hoc network. Thus, the transmission scheduling policy employedby schedule-based MAC protocol is a key design problem in ad hoc networks. However, many of the existingtopology-transparent schedule-based MAC protocols employ transmission scheduling policies are not well-suited tocope with the dynamically changing network conditions.Following the TSMA (Time spread multiple access) protocol, we propose an Optimal time spread multiple access(OTSMA) scheduling policy that is based on an optimalparameter setting mechanism and a hybrid channel access strategy. According to the current network topologyand traffc load, our proposed OTSMA scheduling policycan control each node to utilize its assigned slots and itsnon-assigned slots effectively. Simulation results show thatour proposed OTSMA scheduling policy gives better performance than the existing topology-transparent schedulebased policies.
Improvement on Tzeng-Tzeng's Robust Forward-Secure Signature Schemes with Proactive Security
QIU Gang, WANG Hong, XIAO Hong, XIAO Guozhen
2009, 18(1): 155-158.
Abstract(425) PDF(652)
Abstract:
The main effcient scheme but needinga manager, proposed by W.G.Tzeng and Z.J.Tzeng inPKC'01, was investigated. We present an improved fullydistributed forward-secure signature scheme without amanager based on Tzeng-Tzeng Scheme. The improvement is achieved through a secure distributed key generation protocol and a modified key-evolving procedure. Thesecurity proof of our scheme is also given.
A New QoS-oriented Hybrid Admission Controlin IEEE 802.11 WLAN
ZHU Changhua, PEI Changxing, LI Jiong, CHEN Nan, YI Yunhui
2009, 18(1): 159-163.
Abstract(414) PDF(632)
Abstract:
A number of Notebook PCs, mobilephones, and PDAs are currently integrated with IEEE802.11 Wireless local area network (WLAN) modules orcards for mobile Internet access or other data service. Anew QoS (Quality of services)-oriented hybrid admissioncontrol (QHAC) scheme in IEEE 802.11 WLAN is proposed, with which the performance degradation of WLANincurred by the mobile station at slow transmission rateis overcome by limiting its packet size. In addition, endto-end performance metrics are measured and applied tomake a decision to admission control of new request. Performance analysis and simulation results show that QHACalgorithm can effciently improve the total throughput andfairness index.
Investigation of the Focus Characteristics of aTriode Structure in FED
ZHANG Zichen, LEI Wei, ZHANG Xiaobing, WANG Baoping, YIN Hanchun, TU Yan
2009, 18(1): 164-165.
Abstract(426) PDF(618)
Abstract:
In a field emission display panel, the triode structure[1] has been used to decrease the driving voltage. Because a very strong electric field has been appliedin front of the field emitters, the electron beam usuallydivergences in a normal triode structure[2;3]. A new triode structure with an additional focus electrode has beenproposed[4]. A numerical program has been used to calculate the focus characteristic of this triode structure. Wealso analyze the variation of the current density distribution on the screen with different focus voltages.
Minimax Design of Time-domain Constrained FIR Filters by a Sequential Constrained Least-Square Method
LAI Xiaoping, ZHAO Ruijie
2009, 18(1): 166-170.
Abstract(441) PDF(820)
Abstract:
Since minimax FIR filters with timedomain constraints may not satisfy the alternating theorem, the Remez-type exchange algorithms are not guaranteed to converge or may not converge to optimal filters.A Sequential constrained least-square (SCLS) method converts a constrained minimax problem into a series of Constrained least-square (CLS) problems with unique solutionswhich positively converge to one of the minimax solutions.This paper presents an SCLS method for the minimax design of FIR filters with time-domain constraints. The effectiveness and effciency of the SCLS method are demonstrated by design examples of Nyquist, and step-responseconstrained FIR filters in comparison with several existingmethods.
Small-signal Modeling and Analysis of the Weinberg Converter for High-Power Satellites Bus Application
LEI Weijun, LI Yanjun
2009, 18(1): 171-176.
Abstract(482) PDF(2407)
Abstract:
Power condition unit (PCU) regulates thewhole power of man-made satellites, spacecrafts and etc.The greater the total power of spacecrafts becomes, thegreater that of the PCU becomes. This paper is to analyzethe basic operation principle of the non-isolated WeinbergConverter, which is also called the Battery discharge regulator (BDR) used in the PCU for High-Power Bus Satellites. According to the ac small-signal modeling and analysis based on this operation principle, we get the voltagecontrol mode and current control mode transfer functionsrespectively. Moreover, a regulator system has been designed to meet the requirements of the transient response,and stability, which is to be used in a 9kW communicationsatellite, adopting six modules with the power of 1.5kW foreach. Work of this kind has been studied from the open andclose loop control curves under the voltage control modeand current control mode respectively, and the practicalwaves of a high-effciency non-isolated 1.5kW Weinbergconverter with the current control mode are also givenpartly. Simulation using Saber and experimental resultswill be employed to verify our theoretical work.
The Deviation in the Phase of SAR Echoes Dueto INS Error
SHENG Wei, LV Tianhui, CAO Juanjuan
2009, 18(1): 177-182.
Abstract(481) PDF(810)
Abstract:
Quadratic phase error (QPE) of SAR (Synthetic aperture radar) echo accumulated during SAR integration interval, determines SAR image resolution. QPEdepends on quadratic position error of SAR antenna.Though INS (Inertial navigation system)/GPS (Globe position system) integrated navigation system is widely usedin SAR motion compensation, in each coherent time, however only INS data is used for the measurement of SARantenna position and GPS data is avoided due to its highfrequency errors. So INS errors play main role in the SARimage resolution. There are many sources of INS errors,such as gyro drift, accelerometer bias etc. In order tofind the analytical relation between INS errors and QPEof SAR we have written their transfer functions in Laplacedomain. These transfer functions depict the different effects of different INS errors on QPE of SAR. Time domainsimulations and SAR imaging simulations prove the analytical conclusions. In this paper the analytical relations havebeen verified by computer simulations. The results in thispaper are useful for developing SAR motion compensationsystem with high performance and cost ratio.
Design and Fabrication of a NMR-Spectroscopy Microcoil for Nano-Liter Sample
LI Xiaonan, ZHAO Wuyi, WANG Ming, SONG Tao, YANG Wenhui
2009, 18(1): 183-186.
Abstract(475) PDF(1221)
Abstract:
A new kind of NMR receiving microcoilwith planar shape is presented. It is used in detecting1V-level signal referred as the Free Induction Decay radiated from nano-liter biochemical samples having spin nuclear. It was fabricated by the photolithography and homedeveloped copper electroplating technology. SU-8 photoresist was used for construction of electroplating mask withhigh aspect ratio. Several geometries of planar microcoilfabricated are with ri 200 to 10001m, wire width/separate20 to 801m and optimal number of turns 3 to 7. The Characterization of planar microcoils fabricated were performedwith Agilent Impedance Analyzer 4294A and in agree withprediction by theory. The results for Microcoil 1000 1 under 85MHz is the resistance under AC of 7.25-, inductanceof 285nH and quality value of 21.
Modified Frequency Scaling Algorithm for Synthetic Aperture Imaging Ladar Imaging Through the Turbulence
GUO Liang, XING Mengdao, LIANG Yi, TANG Yu
2009, 18(1): 187-191.
Abstract(428) PDF(676)
Abstract:
In strip-mode synthetic aperture imaging radar, the spatial resolution in range is given by afrequency-swept waveform, whereas the resolution in theorthogonal direction is derived from the record of phaseas the beam footprint executes linear motion over the object. The combination of the laser and SAR processingtechniques should pave the way for a higher resolution airborne or space borne remote sensor. Regarding the ladartransmitting FMCW signal, the motion during the transmission of a sweep and the reception of the correspondingecho were expected to be one of the major problems. Thegiven modified frequency scaling algorithm is taking thecontinuous motion into account, which can compensate forthe Doppler shift induced by the continuous motion effciently. And then, simulation of Phase screen (PS) distorted by atmospheric turbulence following the von Karman spectrum by using Fourier Transform is implementedin order to simulate turbulence. Finally, the computer simulation shows the validity of the modified algorithm and ifin the turbulence the synthetic aperture length does notexceed the similar coherence length of the atmosphere forSAIL, we can ignore the effect of the turbulence.
Flight Path Detection of Bird Targets in RadarImages
CHEN Weishi, NING Huansheng, LI Jing, MAO Xia, WANG Baofa
2009, 18(1): 192-194.
Abstract(486) PDF(865)
Abstract:
A sequence of radar images containing birdflock targets was obtained by using a self-development BirdDetection radar system (BDRS) for predicting Bird strikehazard (BSH) applications. We modified standard marineradar to establish the system. Bird flock targets were separated from complicated radar images mainly based on Principal component analysis (PCA) and mathematical morphology. PCA was used to reject the background from theimage sequence, and morphology was applied for marginalde-noising. After mass center of bird flock target in everyimage was calculated, a flight path was detected approximately by data regression algorithm.