Table of Content

20 April 2008 Volume 35 Issue 2

  

Original Articles

Joint parameter estimation for MIMO systems


DONG Wei;LI Jian-dong;L Zhuo;HE Peng

J4. 2008, 35(2):  189-195. 

Abstract ( 2420 )   PDF (775KB) ( 1459 )   Save

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This paper addresses the problem of frequency offsets and channel gains estimation for a multi-input multi-output (MIMO) system in flat-fading channels. The general case where frequency offsets are possibly different for each transmit antenna is considered. The maximum-likelihood(ML) estimation of the joint frequency offsets and channel gains is investigated, assuming that a training sequence is available. The exact solution to this estimation problem turns out to be too complex as it involves a search over a multi-dimensional domain. To solve this complex estimation problem, a novel joint estimation algorithm for frequency offsets and channel gains is proposed. The new algorithm involves two steps. Frequency offsets are first estimated by the particle swarm optimization(PSO) theory. Then channel gains are estimated by the ML estimator. Simulation results show that the proposed algorithm has a larger frequency offset estimation range than the correlation-based estimation algorithm and asymptotically achieves the Cramer-Rao lower bound (CRLB).


Iterative channel estimation with noise reduction for MIMO-OFDM systems


GUO Yi;LIU Gang;GE Jian-hua

J4. 2008, 35(2):  196-200. 

Abstract ( 2549 )   PDF (734KB) ( 1166 )   Save

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To eliminate the effect of inter-carrier interference(ICI) on MIMO-OFDM systems, an iterative channel estimation algorithm is proposed. Based on the frequency-domain orthogonal block pilot pattern, the new algorithm obtains a temporal channel response by the discrete Fourier transform(DFT) based channel estimation algorithm, and improves the estimation performance by the iterative channel estimation with noise reduction. With the channel pre-correcting and appropriate time-domain filtering, the new algorithm can effectively eliminate the effect of ICI and channel noises. Furthermore, owing to avoiding the inversion of a large matrix to decouple the inter-antenna interference, the new algorithm can be easily realized compared with the traditional algorithms.


SNR aided RCFO estimation method for OFDM systems


REN Guang-liang;XING Jiang-tao;CHANG Yi-lin

J4. 2008, 35(2):  201-205. 

Abstract ( 6439 )   PDF (636KB) ( 1163 )   Save

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A new residual carrier frequency offset(RCFO) estimation method is proposed for orthogonal frequency division multiplexing(OFDM) systems in wireless fading channel. In the method, the SNRs on all the sub-carriers are estimated and used to select high quality sub-channels. And then the hard decision data on the high quality sub-channels are combined with the pilot data to estimate the RCFO. The new method has the advantages of both pilot tone assisted(PTA) and decision directed(DD) methods. Simulation results show that the estimation accuracy of the proposed method has an improvement at least 4 times better than that of the PTA method, and at least 21 times better than that of the DD method when the SNR is more than 10dB.


Low-complexity Zigzag codes coded orthogonal modulation with non-coherent detection


CHE Shu-ling;WANG Xin-mei

J4. 2008, 35(2):  206-209. 

Abstract ( 2371 )   PDF (639KB) ( 1264 )   Save

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A low-complexity orthogonal modulation scheme with non-coherent detection is presented, which is suitable to the low-rate region. Information bits are first encoded by a Zigzag encoder and then the coded bits satisfying a single parity check constraint are mapped into a PPM symbol. According to the equivalence between soft-out demodulation and decoding of orthogonal Hadamard codes, demodulation and decoding can be considered as a whole at the receiver side, so not only can the iterative operations between decoding and demodulation be avoided, but also the fast Hadamard transform(FHT) and the so-called a posteriori probability fast Hadamard transform(APP-FHT) algorithm can be adopted to further decrease decoding complexity. Furthermore, linear interleavers with a joint design are used to improve the error floor problem in our scheme. Simulation results show that our scheme can lead to performance comparable to that of other non-coherent orthogonal modulation schemes.


Optimized-approximate integer-to-integer wavelet transform and its VLSI architecture of JPEG2000 codec


GUO Jie;WU Cheng-ke;WANG Ke-yan;MA Jing;ZHANG Lei

J4. 2008, 35(2):  210-215. 

Abstract ( 2521 )   PDF (726KB) ( 1044 )   Save

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A new optimized-approximate integer-to-integer wavelet transform of the JEPG2000 scheme is proposed. And from the hardware perspective, the corresponding line-based VLSI based on the lifting scheme is put forward. Considering that the dynamic range of the wavelet coefficients is limited, this scheme ensures higher precision of the wavelet transform and accordingly improves the quality of image compression by preserving efficiently fractions of wavelet coefficients in lifting steps. Thanks to the line-based architecture in hardware implementation, the horizontal transform and vertical transform can be executed in a parallel way. Experiments show that on a Xilinx FPGA marked XC2V3000, the architecture requires only 27％ resources and achieves a higher clock frequency up to 66MHz. Compared with other existing wavelet transform architectures, the proposed architecture not only advances performance of the integer-to-integer wavelet transform, with advantages of high parallelism and reduction in storage, but also guarantees total levels of the wavelet transform during the time T that an image is scanned line by line.


Space-time two-dimensional pre-filtering for clutter suppression in the phased array airborne radar


LI Xiao-ming;FENG Da-zheng;LIU Hong-wei;LUO Ding

J4. 2008, 35(2):  216-222. 

Abstract ( 2121 )   PDF (729KB) ( 1155 )   Save

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The location of the ground clutter in angle-Doppler space is mainly dependent on the platform movement and phased array airborne radar parameters. In this paper, we propose a pre-filtering approach by using a two-dimensional (2-D) pulse-to-pulse non-adaptive canceller which makes full use of such a-priori information. The 2-D pulse-to-pulse non-adaptive canceller is more easily designed and does not require significant additional processing. Therefore, it can be used as an efficient pre-filtering tool before the conventional MTI processing and the adaptive processing. Theoretical analysis and computer simulation results illustrate that the proposed pre-filtering approach can effectively suppress the clutter not only for the sidelooking airborne radar but also for the non-sidelooking airborne radar, and can further improve the moving target detection performance. Experimental results by using the measured data show the validity of the proposed pre-filtering approach.


Covariance matrix estimation for the STAP based on the Bayes criterion


LIU Cong-feng;LIAO Gui-sheng

J4. 2008, 35(2):  223-227. 

Abstract ( 2061 )   PDF (806KB) ( 1047 )   Save

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For the environment in which the clutter power changes slowly with distance, a novel weighting maximum likelihood estimation (WMLE) algorithm is proposed that uses the Bayes criterion to improve the approximative covariance matrix estimation for Space-Time Adaptive Processing (STAP). By the event definition and the Bayes criterion, the precise computing method for the weight coefficient is given, this method also gives the efficient solution to finding the weight coefficient for WMLE. Simulation attests its correctness and effectiveness.


New method for signal sparse decomposition over a redundant dictionary


LIU Dan-hua;SHI Guang-ming;ZHOU Jia-she

J4. 2008, 35(2):  228-232. 

Abstract ( 2491 )   PDF (625KB) ( 3361 )   Save

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For the extremely high complexity of usual algorithms for sparse decomposition, a new group matching pursuit algorithm is presented based on a redundant dictionary with several orthonormal bases. The algorithm adopts the the idea of iterative group matching pursuit and selects the optimal basis from the dictionary by comparing the matching degree between the signal or the residua and every basis. Each operation of decomposing results in a few important coefficients by using the fast calculating algorithm of orthogonal decomposition. After several such iterations, the original signal is approximated with a few coefficients eventually. Simulation results show that the calculating speed of the algorithm in this paper increases by about thirty times compared with MP’s. Moreover, this algorithm can avoid over-matching.


Block recursive blind source separation method


LIU Jian-qiang;FENG Da-zheng

J4. 2008, 35(2):  233-236. 

Abstract ( 1808 )   PDF (671KB) ( 1014 )   Save

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The natural gradient algorithm works more efficiently than the ordinary gradient algorithm, and the block recursive method is feasible to real-time processing. To benefit from the above advantages, a block recursive blind source separation (BSS) approach is presented. Firstly, based on natural gradient and nonlinear principle component analysis, a matrix equation is obtained by block recursive updating, and then the matrix equation is solved by using QR factorization and back substitution to obtain the optimal separating matrix. Compared with other existing recursive-type BSS methods, the proposed algorithm leads to 10dB improvement in orthogonality performance index, and the average running time reduces by 65％, which is verified by extensive numerical simulation experiments.


Improved particle filters for MIMO demodulation


ZHENG Jian-ping;BAI Bao-ming;WANG Xin-mei

J4. 2008, 35(2):  237-241. 

Abstract ( 3619 )   PDF (584KB) ( 1166 )   Save

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In particle filters (PF), sequential importance sampling will result in sample impoverishment and further the loss of diversity after resampling. Note that the signal points of modulation constellation are discrete and finite. The loss of diversity will result in performance degradation when PF is utilized to demodulate the multi-input multi-output (MIMO) systems. Therefore, an artificially noise enhancement (ANE) method is first introduced in importance sampling to increase the number of different particles, which will alleviate the sample impoverishment. Second, the partially deterministic reallocation (PDR) scheme is introduced to replace the resampling. The PDR scheme can increase the surviving probability of particles with small importance weights, thereby decreasing the loss of diversity. Analyses and simulation results show that the proposed method can significantly improve the bit error performance of MIMO systems.


Least squares interacting multiple model algorithm for passive multi-sensor maneuvering target tracking


SONG Li-ping;JI Hong-bing

J4. 2008, 35(2):  242-247. 

Abstract ( 1880 )   PDF (662KB) ( 1095 )   Save

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In multi-sensor bearings-only passive target tracking, the state of the target has a nonlinear relation with the bearings measurements. Existing methods focus mainly on the process of linearization. However, in this process, a precision decrease is obviously unavoidable and even filter divergence will occur so as to lose the target. Therefore a new algorithm is proposed. The state of the target is approximately estimated by least squares first which is taken as pseudo measurements for the Kalman filter, and then the IMM algorithm is employed for maneuvering target tracking. Simulation results demonstrate that the algorithm for multi-sensor maneuvering target tracking is realizable and that the tracking error is far lower than that by the existing methods.


Multiple objects detecting and tracking with the pseudo particle filter


SUN Wei;GUO Bao-long

J4. 2008, 35(2):  248-253. 

Abstract ( 2293 )   PDF (1232KB) ( 1636 )   Save

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For the problem of divergence of the classical particle filter method for multiple object tracking in image sequences, a new particle filter, the so-called Pseudo Particle Filter (PPF), is proposed. The PPF invokes subset particles of generic particle filters to form a continuous estimate of the posterior density function of the objects. After importance-sampling resampling(ISR), the subset particles converge to the observations. It is proved that, using the appropriate kernel function of the mean-shift algorithm, we can get the subset particles of the observations and the fixed points of clustering results as the state of the objects. A multi-object data association and state estimation technique is proposed to resolve the subset particles correspondence ambiguities that arise when multiple objects are present. Experimental results demonstrate the efficiency and effectiveness of the algorithm for single and multiple object tracking.


Composite right／left-handed transmission line based on split-ring resonator DGS


WU Bian;LIANG Chang-hong;CHEN Liang;LI Gang

J4. 2008, 35(2):  254-257. 

Abstract ( 1921 )   PDF (933KB) ( 1183 )   Save

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This paper presents a novel CRLH transmission line using the split-ring resonator defected ground structure (SRR DGS). The equivalent-circuit values of the cell model are extracted by the curve-fitting technology, and then the transmission zero location, dispersive relation, refraction index and transmission characteristic of the cascaded structures are derived. Both theoretical and experimental results indicate that this structure possesses a composite right／left-handed property. The novel CRLH transmission line has an out-of-band transmission zero and compact structure with no grounded via, which can be widely applied in microwave integrated circuits.


Design of the compact 5-bit time delay line


WANG Ting-lei1;WEI Wen-bo1;LIU Qi-zhong1;GONG Lan2

J4. 2008, 35(2):  258-261. 

Abstract ( 1815 )   PDF (877KB) ( 1422 )   Save

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A new compact 5-bit digital delay line is designed and fabricated. In this design, small time delay units are realized with right-handed transmission lines, and large delay units are designed with left-handed transmission lines. This method can avoid the disadvantages of big dimensions and losses which appear in large time delay units realized with right-handed transmission lines. This delay line operates at 9GHz~10GHz, provides 100ps up to 3100ps time delay with an interval of 100ps. The dimension of whole delay line is 10mm×20mm×0.5mm, and the insert losses are less than 6.2dB.


Novel FDTD method for modeling arbitrary linear lumped networks


CHEN Zhi-hui1;CHU Qing-xin2

J4. 2008, 35(2):  262-266. 

Abstract ( 1799 )   PDF (609KB) ( 896 )   Save

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A novel finite-difference time-domain(FDTD) modeling method for arbitrary linear lumped networks is presented. First, the admittance parameters in the frequency domain of the lumped networks are expressed as a summation of several rational fractions, which are converted into those in the time-domain by means of the inverse Fourier transform(IFT) technique. Then, the piecewise linear recursive convolution(PLRC) method is proposed, the admittance parameters in the time domain are incorporated into the FDTD updated equation directly with the aid of the method. Compared with the modeling methods based on Z-transformation, the proposed algorithm needs fewer variables, preserves the explicit nature, and keeps the same computation accuracy as well. Finally, the method is applied to model some one-, and two-port micro-strip transmission line networks, and simulation results agree well with those obtained by the modeling method available based on Z-transformation.


Novel short time interval measurement method


WANG Hai;ZHOU Wei;LIU Chang-sheng;WANG Shui-sheng

J4. 2008, 35(2):  267-271. 

Abstract ( 2554 )   PDF (663KB) ( 2572 )   Save

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A new method for short time interval measurement based on the delay line principle is presented. By utilizing a group of delay lines to generate multi-path reference frequency signals delayed uniformly in a reference frequency period, then counting them under the same gate generated by the short time interval, with the average as the count of the reference frequency, the measurement error can be reduced by 1~2 orders of magnitude. Error analysis shows that its accuracy is determined by the delay time of the delay unit. Actual measurement data show that when the reference frequency is 200MHz, the delay time of the delay unit is 500ps, its accuracy is better than 500ps and improved by 10 times compared with the pulse-filling measurement method under the same condition. Compared with the analog interpolating, time-to-voltage conversion and time vernier method, the proposed new method has the characteristic of easy implementation, low cost and high feasibility.


The design and realization of wide input and fast start up high precision voltage reference


WANG Hui1;WANG Song-lin1;LAI Xin-quan2;DAI Guo-ding2;GUO Bao-long1

J4. 2008, 35(2):  272-276. 

Abstract ( 1765 )   PDF (972KB) ( 1553 )   Save

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By adopting the BCD technology, a high precise voltage reference circuit starting-up quickly and without trimming is designed. The TTL_BUFFER using the voltage stabilizing characteristic of the Zener diode causes the variation of input voltage with voltage reference to be about 1V and improves the precision of the voltage reference. Using the self off-set characteristic, the MOS biases the voltage reference quickly, and then the fast starting-up of the whole circuit is completed. Combining the voltage reference, the circuit has its reference voltage swing of less than 2mV and a start-up time of about 20μs when the input voltage lies between 6.3V and 14V. Compared with the circuits of the same type, the output swing of the voltage reference decreases by 60％ and the start up time shortens by 40％.


A class of quantum stabilizer codes based on classical convolutional codes


XING Li-juan;LI Zhuo;WANG Xin-mei

J4. 2008, 35(2):  277-281. 

Abstract ( 1857 )   PDF (478KB) ( 957 )   Save

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A new class of quantum stabilizer codes is presented. The problem of finding stabilizer quantum-error-correcting codes can be transformed into the problem of finding self-orthogonal codes over the Galois field GF(4) under a trace inner product. Based on this connection, the necessary and sufficient condition is proved under which classical convolutional codes over GF(4) are self-orthogonal with respect to the trace inner product, and then corresponding codes satisfying the condition are found. Tail-biting codes with a simple block structure are obtained by “tail-biting” transformation, which are self-orthogonal with respect to the trace inner product. Finally, relative quantum stabilizer codes are constructed. The code construction is simple, and the minimum distance of the code approaches the upper bound.


Mobile IP registration protocol with user anonymity


DANG Lan-jun1;KOU Wei-dong1; 2;CAO Xue-fei1;FAN Kai1

J4. 2008, 35(2):  282-287. 

Abstract ( 2035 )   PDF (563KB) ( 1039 )   Save

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In order to address the anonymous authentication problem in mobile IP registration, a mobile IP registration protocol with user anonymity is proposed. To construct its temporary identity (TID) in the registration request message, the mobile node (MN) hashes the home agent (HA)s identity together with a newly established Diffie-Hellman key and performs a bitwise XOR over the MNs real identity and the hashed value. Then HA recalculates the hash value and XORs it with the received TID to derive the MNs true identity. The user anonymity and untractability are achieved in the proposed protocol by the TID, which varies with each registration. Theoretical analysis demonstrates that the proposed protocol accomplishes both strong anonymity and mutual authentication among three mobile IP entities. Compared to the anonymous wireless authentication protocol proposed by Peng et al., the proposed protocol reduces the computation load at the MN.


Shot boundary detection algorithm based on co-histogram


TIAN Yu-min;ZHAO Jin;WU Zi-li

J4. 2008, 35(2):  288-292. 

Abstract ( 1651 )   PDF (770KB) ( 1229 )   Save

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A new algorithm based on the co-histogram between two consecutive frames is presented. In the algorithm, the similarity is defined based on the co-histogram symmetry which is high in the same shot, but low in a shot transition. The similarity effectively reveals the transition characteristics. The difference of similarities is used to enhance the abrupt transition features, and a Finite-State Automata is used to improve the robustness in detecting gradual transition. Experiments testing various videos show that the algorithm achieves a performance with 95.6％ recall and 95.8％ precision.


MAZ segmentation approach to the table-form image


WANG Quan1;WANG Lai-jing2;WANG Bo1

J4. 2008, 35(2):  293-296. 

Abstract ( 2002 )   PDF (669KB) ( 999 )   Save

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According to the features of line intersection and the dependent relations between the name fields and data fields, the layout structure is classified into six classes, and then a definition of the Maximum Attributive Zone(MAZ) is presented. Based on the MAZ, an algorithm for the table-form image segmentation is presented. Not only can this method analyse the filled-in table-form images logical layout, but also it may divide the interdependent units into the same sub-tables according to the basic layout fragments. The experimental results show that this algorithm is effective.


Hided information transmission protocol using quantum teleportation


LI Hui1;OU Hai-wen2

J4. 2008, 35(2):  297-299. 

Abstract ( 1965 )   PDF (488KB) ( 1073 )   Save

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An hided information transmission protocol using quantum teleportation is proposed. It can transmit 1 bit classic hiding information by using 2 bit of public classic information and a pair of entangled photons. An implementation frame is also presented. Finally, the performance of the transmission scheme is analyzed.


Research on the multi-hierachy and multi-domain security policy system in IPv6 networks


LI Xiao-ping1;WU Qiong1;DONG Qing-kuan2;LIU Yan-ming2

J4. 2008, 35(2):  300-304. 

Abstract ( 1880 )   PDF (1114KB) ( 1121 )   Save

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In order to solve security problems based on the policy and construct a security-policy-based network security architecture in IPv6 networks, a multi-hierarchy and multi-domain security policy system in which the central policies are uniformly stored, distributed domain by domain and local policies are obtained by negotiation is presented. The frame of the system and its realization scheme are designed in detail and the feasibility of the system is theoretically verified. The system which is flexible and expansible fits the requirements of policy management based on the security domain.


NN predistorter for the non-linear HPA in the OFDM system


CUI Hua1;SONG Guo-xiang1;YU Shao-bo2

J4. 2008, 35(2):  305-308. 

Abstract ( 2233 )   PDF (867KB) ( 1147 )   Save

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To circumvent the transmission performance degradation of the orthogonal frequency division multiplexing(OFDM) systems due to the nonlinear high power amplifiers(HPA), a new predistorter is presented which consists of two similar single-input and single-output BP neural networks(NN) in series. The former NN is the amplitude predistorter obtained by the improved indirect learning method which overcomes the shortcoming of the indirect method, and its phase predistortion based on the latter NN is implemented by the phase characteristic model rather than its inverse model. Simulation results show that the proposed predistorter can make about 15dB reduction of out-of-band spectral regrowth with fewer neurons even at 2.93dB IBO(input back-off) where another available can not work any longer, indicating this adaptive predistorter with a simpler structure outperforms other predistorters for the HPA employed in the OFDM systems.


Novel genetic algorithm for the graph coloring problem


HAN Li-xia1;WANG Yu-ping2

J4. 2008, 35(2):  309-313. 

Abstract ( 2680 )   PDF (546KB) ( 1691 )   Save

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Generic genetic algorithms need generate initial population iteratively for solving the coloring problem. Based on this problem, an improved algorithm is presented. The novel algorithm adopts a comparative mechanism to eliminate the unfeasible genes, and gives the valid individual a greater probability to survive to the next generation by using the dynamic fitness function. Thus, the proposed algorithm avoids the repetitious production of the initial population. Compared with the algorithms under the traditional architecture, the proposed algorithm can shorten the time of finding the optimal solution at least by up to 51 percent. Moreover, the novel algorithm has the advantages of jumping from a local optimal solution to next one quickly and converging to the global optimal solution in the end.


Research on multi-path channel parameters in the marine atmospheric duct


ZHAO Xiao-long1;2;HUANG Ji-ying1

J4. 2008, 35(2):  314-318. 

Abstract ( 1977 )   PDF (739KB) ( 1098 )   Save

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Based on the characteristics of EM multi-path propagation in the marine atmospheric duct and the Markov birth-and-death process in finite space, the path number in the marine atmospheric duct is presented. The excess delay three-parameter model is proposed according to the experimental data with approximate Rayleigh distribution, and the model parameters are determined by the minimum variance criteria. The angles of arrival (AOA) is estimated by the MUSIC algorithm and simulation results show that the MUSIC algorithm can significantly increase the SNR at the AOA. Finally, the multi-eigenpath channel model is proposed for contributing to the system design and performance optimization of the marine microwave communication system.


Optimal design of cable pre-tensions of the tension truss antenna


YANG Dong-wu;QIU Yuan-ying;DUAN Bao-yan

J4. 2008, 35(2):  319-323. 

Abstract ( 1874 )   PDF (1053KB) ( 1086 )   Save

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With the help of a mathematical model of some tension truss antenna, an approach to the design of a prestressed tension truss antenna, not in consideration of the elasticity of the ring truss, is presented. The approach combines two steps in getting a set of optimum pre-tensions. Based on force equations of the front net projected in a plane perpendicular to the axis of the parabolic reflector, and the characteristic of the cable net structure, an optimization model, having only two design variables and with the maximum pre-tension ratio (MTR) of cables internal in the front cable net as its objective function, is deduced. And then, based on the optimization result, a set of pre-tensions of the cable net structure is calculated. Finally, a finite element model of the cable net structure, with the designed pre-tensions as initial conditions, is analyzed. The result shows that the designed model is nearly the same as the ideal model expected and that the MTR of cables internal in the front cable net is considerably small. This approach has proved to be correct and effective.


Eigenvalues analysis of the vibration control system with stochastic parameters


CHEN Long;CHEN Jian-jun;MA Juan;ZAHNG Xue-feng

J4. 2008, 35(2):  324-329. 

Abstract ( 2020 )   PDF (541KB) ( 1062 )   Save

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Considering the randomness of structural physical parameters, after the random factor abstracted from the stiffness matrix and the mass matrix, the random factor is introduced into the vibration control equation and the randomness of parameters in the vibration control equation is represented by the random factors. By using the algebra synthesis method, the mean value and the standard variance of the eigenvalues of the vibration control equation are developed. The closed-loop stability of the vibration control equation of random structures is discussed and the stability criterion is obtained with the 3σ criterion. Finally, an example of the cantilever beam is used to illustrate the feasibility of the method given, which shows that the effect of the elastic Young’s modulus on the eigenvalues is greater than that of the mass density.


Deadlock prevention policy for a class of petri nets S³PR


YAN Ming-ming;LI Zhi-wu;ZHONG Chun-fu

J4. 2008, 35(2):  330-333. 

Abstract ( 1972 )   PDF (546KB) ( 984 )   Save

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To solve the problem of deadlock prevention for a class of Petri nets, S³PR, an effective deadlock prevention policy is proposed. The deadlock avoidance policy of Conjunctive／Disjunctive Resources Upstream Neighborhood (C／D-RUN) is applied to the siphon-based deadlock prevention policy, and the resources of the control places are allocated reasonably to guarantee the absence of deadlock states and processes. First, strict minimal siphons of an S³PR are divided into elementary and dependent ones. From the set of elementary siphons, a set of linear inequality constraints expressed by the state vector can be formalized, and after being modified by the C／D-RUN policy, a set of generalized mutual exclusion constraints(GMEC) expressed by the marking vector can be found. Then monitors based on the marking constraints are added to the plant model to ensure that all elementary siphons in the S³PR net are invariant-controlled, thus leading to a deadlock freedom liveness-enforcing supervisor with a simple structure and much permissive behavior can be realized.


Point data reduction technique in reverse engineering


LIU De-ping1;2;CHEN Jian-jun1

J4. 2008, 35(2):  334-339. 

Abstract ( 1677 )   PDF (975KB) ( 1175 )   Save

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Advances in laser scanning technologies have facilitated sampling part surface data with speed and accuracy. It is necessary to manipulate these large amounts of point data. The adaptive minimum distance (AMD) method is proposed in this paper which is a kind of data reduction algorithm that balances efficiency and precision. Firstly the noise data is eliminated by median filtering and wavelet packet filtering, and then the curvature of the point data are analyzed and different zones are separated where a suitable minimum distance is selected. The points where the distance is larger than the given distance are neglected. This novel algorithm has merits of both precision and efficiency with the ratio of reduction being 36％.The method is applied to two sample models, and experimental results illustrate the feasibility of the new algorithm.


Study of distributed resource allocation in multi-cell OFDMA systems


QIU Jing1;2;FENG Wen-jiang2;ZOU Wei-xia1

J4. 2008, 35(2):  340-344. 

Abstract ( 2178 )   PDF (716KB) ( 1175 )   Save

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A potential game theoretic solution for distributed uplink dynamic subcarrier and power allocation in multi-cell OFDMA systems is presented, with each mobile station updating its own power level based on local information according to the best response dynamic. Theoretical analysis and simulation results show that there exists a unique steady state and that the proposed distributed power control algorithm can converge to the steady state quickly. The algorithm can achieve a much higher energy efficiency compared with the pure iterative water-filling algorithm.


Study of the intrusion detection method based on AdaBoost with a hierarchical structure


WANG Yong1;2;TAO Xiao-ling1

J4. 2008, 35(2):  345-350. 

Abstract ( 2476 )   PDF (797KB) ( 1081 )   Save

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An intelligent hierarchical intrusion detection method is proposed for getting both high precision and high speed. With this method, an improved AdaBoost algorithm is used in selecting intrusion features and constructing an Ada threshold-classifier at every level, and several hierarchical classifiers are combined for detection. A Linux IDS experimental platform is designed and implemented to train and test the intelligent intrusion detector. Experimental results show that the method reduces the complexity of computation, and that the false negative rate is reduced greatly while maintaining the high detection rate. Moreover, the method improves the processing speed and is especially appealing for the real-time processing of the intrusion detection system.


New digital signature scheme based on the discrete logarithm


JIA Xiao-yun1;3;LUO Shou-shan2;3;YUAN Chao-wei1

J4. 2008, 35(2):  351-355. 

Abstract ( 2081 )   PDF (511KB) ( 1106 )   Save

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A new chain verification digital signature scheme based on the discrete logarithm is proposed, which can avoid the equal verifying right of the verifiers which normally accompany the conventional schemes. In this scheme, by means of the sequence secret sharing scheme, the verification participators can divide the signature verifier from the chain grantors, the signature verifier cannot verify the validity of the signature until he is authorized by all chain grantors in turn, and any chain grantor(even all chain grantors are collusive)cannot verify the validity of the signature. What’s more, the signature scheme can conveniently add or delete the chain grantor and defend the secret key of the chain grantors and signature verifier.


Whole-band ANC system with the FX structure based on wavelet packet decomposition


XUAN Wei;XU Xin-sheng;WU Ying-zi

J4. 2008, 35(2):  356-361. 

Abstract ( 2226 )   PDF (1218KB) ( 1104 )   Save

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The traditional Active Noise (ANC) system does not work effectively in the environment where the noise is mixed with the useful signal. An active noise cancellation system applied on the passive sonar platform of warships is designed to solve the problem said above, which can enhance the role range of the passive sonar. This ANC system uses an FX structure based on wavelet packet decomposition. Because of the orthogonal characteristics of wavelet packet decomposition, the correlation between every two weights is reduced, and the distribution of reference-input matrix’s eigenvalues is also improved. The working method of the system’s filter-group ensures that the noise in different frequency bands can be distinguished and cancelled respectively. So the system has the effect that is the same as that of the multi-frequency-band system. Combined with the LMS algorithm, this system has the flexible whole-band distinguish ability in both the time-domain and the frequency domain and a faster convergence rate. Simulations are done based on practical sea-trial data. In the condition of smaller distortion of signals, a 12.2dB noise reduction is achieved over the whole-band. It is indicated that the system designed in this paper has advantages in the complex underwater noise field. This system enhances the noise controlling capability. So it has a high practical value.


UWB call-response location system employing energy detection


QIU Hong-bing;WANG Mei;MAO Jie

J4. 2008, 35(2):  362-366. 

Abstract ( 2485 )   PDF (607KB) ( 1183 )   Save

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This paper proposes a Call-Response Location System，where the UWB pulse train is utilized as the substitute for a single impulse. The energy detection can be exploited to reduce the complexity of the system. The call-response location algorithm and minimum mean-square error estimation are applied in the calculation of the time of arrival (TOA). And the mean delay spread is introduced to correct TOA for improved location accuracy in the multi-path and non-line-of-sight (NLOS) propagation environment. Results from the simulations conducted shows that in UWB channel proposed IEEE 802.15.4a the system succeeds in achieving a position location accuracy of ＜60cm when the SNR is set at the range of -20dB to 30dB.


Novel location-aided routing in Ad Hoc networks


WANG Kun;WU Meng

J4. 2008, 35(2):  367-372. 

Abstract ( 1739 )   PDF (688KB) ( 976 )   Save

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The movement of nodes in mobile ad hoc networks results in a change in routes, requiring some mechanism for determining new routes. In this paper, a novel distance-based location-aided routing for MANET is proposed. By tracing the location information of destination nodes and the change of distance between nodes to adjust route discovery dynamically, the proposed routing algorithm can avoid flooding in the whole networks. Besides, the distance update threshold is set up to reach the balance between real-time ability and accuracy of location information of nodes. Performance results by simulation reveal that the new algorithm performs better than LAR1 in terms of the packet successful delivery ratio, average end-to-end delay and routing-load.


Faster compress coding arithmetic based on fractal


QI Li-Min;LIU Wen-Yao;L Da-Wei

J4. 2008, 35(2):  373-376. 

Abstract ( 1944 )   PDF (542KB) ( 1058 )   Save

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Fractal image compression is an efficient technique for encoding images. It can lead to a high compress ratio and decoding quality in theory. But, the speed of basic automatic fractal encoding is slow and the decoding quality is also unsatisfactory when the compress ratio is higher.This paper gives a way to get a fast speed of encoding. We reduce the original image to the 1／4 resolution, encode the 1／4 resolution image by the basic fractal algorithm, get the fractal code of the 1／4 resolution image, and decode the code to the original resolution. Then we calculate the difference between the decode image and the original image, and encode the difference image in a simple way. The code of the 1／4 resolution and the code of the difference image constitute the code of the original image.This method can speed up about 3-4 times with the same PSNR as for the basic automatic fractal algorithm.