Table of Content

20 April 2011 Volume 38 Issue 2

  

Original Articles

Power allocation algorithm based on outage probability for DF cooperative systems

SONG Jing;GE Jianhua;LI Jing

J4. 2011, 38(2):  1-7.  doi:10.3969/j.issn.1001-2400.2011.02.001

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Since the equal power allocation (EPA) between the source node and the relay node in the decode-forward (DF) cooperative communication system results in resource inefficiency, a power allocation algorithm based on outage probability analysis is proposed. This algorithm aims to reduce the average outage probability of the system, in which the upper and lower bound expressions for the system average outage probability of the model are derived according to the average signal to noise ratios of the upper link channels of and the channels between users. The power allocation factor that leads to a lower system average outage probability is obtained by the golden section method. Simulation results show that, all conditions being the same, this power allocation scheme can achieve a better performance than the equal power allocation (EPA) scheme.

Simplified decoding algorithm for LDPC over GF(q)

HU Shukai;WANG Xinmei

J4. 2011, 38(2):  8-12+196.  doi:10.3969/j.issn.1001-2400.2011.02.002

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A simple, yet effective decoding algorithm for LDPC (low-density parity-check) codes over GF(q) is presented. By taking advantages of the first-term Taylor's series expansion to approximate the correction term of the Jacobian logarithm used in LLR-SPA(log-likelihood ratio sum-product algorithm), we propose an algorithm which significantly simplifies the check node update computation of the optimal LLR-SPA. Compared to the offset min-sum algorithm, the proposed algorithm achieves a gain of about 0.2dB at the BER of 10^-4. Moreover, unlike the offset min-sum algorithm, parameters of this algorithm are independent of the order of the Galois Filed.

Novel low complexity sphere detection algorithm for MIMO spatial multiplex systems

REN Guangliang;DUAN Xinli;YU Guanghui;YANG Lihua

J4. 2011, 38(2):  13-17.  doi:10.3969/j.issn.1001-2400.2011.02.003

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A new hierarchical modulation based sphere detection algorithm (HBSD) is presented for the MIMO (multi-input multi-output) spatial multiplex system with high order modulation. In the algorithm, the constellations of MQAM (M-Quadrature Amplitude Modulation) are divided into many regions by the hierarchical data in MQAM modulation. The candidate regions of the constellations are determined by the hard decision data of the layers with great weight factors in hierarchical modulation. The constellations are selected as the reserved constellations in the candidate regions using the minmum distance rule. SD (Sphere detection) is used to find the optimum transmitted vectors by searching for the reserved constellations in the candidate regions of all detection layers. Simulation results show that the performance of the proposed HBSD algorithm is better than that of the MSD (Multi-SD) algorithm, with its complexity being about one fifth that of the MSD algorithm.

Study of the DTN routing algorithm based on the Markov decision

ZHANG Wenzhu;SUN Fayong;WANG Xuan

J4. 2011, 38(2):  18-22+81.  doi:10.3969/j.issn.1001-2400.2011.02.004

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Since the major application scenarios of the DTN (delay/disruption tolerant network) are extremely particular, routing protocols designed for the traditional networks are not suitable for it. In order to raise the transfer efficiency while reducing the network delay and network cost in the DTN, a routing algorithm based on the Markov Decision, named MRDDTN (Markov Route Decision in the DTN), is proposed. The MRDDTN is self-learning and can solve problems in the complex network environment characterized by very long delay paths and frequent network partitions. Through simulative analysis, the MRDDTN is found to be able to achieve a better performance than Epidemic and PROPHET routing algorithms under the same network conditions.

No-reference quality assessment model for networked speech based on the content feature of packets

LI Wei;YANG Fuzheng

J4. 2011, 38(2):  23-28+98.  doi:10.3969/j.issn.1001-2400.2011.02.005

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Packet loss is a primary element to impair the quality of network speech, and the impairment extent is related not only to the number of lost packets, but also to their content feature. This paper proposes a no-reference quality assessment model for networked speech based on analysis of the content feature of packets. This model first estimates the content feature of lost packets by resorting to the voice active detection technology and the level of non-lost frame. Based on the content feature analysis, the proposed model calculates the speech packet loss rate and then predicts the quality of networked speech. Experimental results show that high prediction accuracy can be obtained by the proposed model. Compared with the speech quality evaluation model in G.1070, the average performance gain of the proposed model is raised 8.4% in terms of relativity to subjective results.

Iterative design for the joint analog network and channel coding

ZHANG Bing;WANG Feng

J4. 2011, 38(2):  29-35.  doi:10.3969/j.issn.1001-2400.2011.02.006

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A new relay scheme based on analog network coding and joint iterative detection & decoding method is proposed for the multiple-access full-duplex relay system to further improve the bit error rate and frame error rate. The information packets from different users are superimposed after interleaving and modulation at the relay node, and then transmitted to the destination node. At the destination, the joint iterative detection and decoding approach is utilized to obtain source information. A higher coding gain can be obtained by fully exploiting information redundancy from analog network coding. Simulation results show that the proposed scheme can achieve about 5dB improvement on the SNR compared with iterative decoding scheme based on code superposition in the case of the ideal channel condition between source and relay node.

Multi-user cooperative communications scheme design based on opportunistic network coding

SHI Yuchen;BAI Baoming;WANG Jing

J4. 2011, 38(2):  36-41+53.  doi:10.3969/j.issn.1001-2400.2011.02.007

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In order to select the relay node and improve the system throughput, a new multi-user cooperative communication protocol is proposed based on the opportunistic communication and network coding. On the basis of outage probability, each user decides whether to help forward its partner's information as a relay or not. The relay node processes its own information and the partner's information by the use of network coding, and transmits it to the receiver. The receiver can obtain several transmitters' information using coherent detection. Compared with traditional cooperative protocols, the proposed protocol can improve the average per user throughput and the network throughput in the quasi-static Rayleigh fading channel. The probability of system outage is reduced with fewer time resources.

Low complexity iterative demapping algorithm in BICM systems

MA Zhuo;DU Shuanyi;WANG Xinmei

J4. 2011, 38(2):  42-46.  doi:10.3969/j.issn.1001-2400.2011.02.008

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The complexity of the iterative Demapping algorithm in Bit-Interleaved Coded Modulation systems is related to the product of the order of modulation and the constellation points number, so that it is not suitable for real-time applications. To reduce its complexity, we give a shortcut calculation based on the Hard Decision Feedback for the BICM system using LDPC codes. A soft information calculation algorithm based on the decision boundary is used in the first iteration, where no feedback information is available to be used. Simulation result shows that the BWE performance of the algorithm proposed in the AWGN channel has only a distance of 0.04~0.06dB from the soft information iteration algorithm. On the other hand, the calculation complexity of this algorithm is only related to the order of the modulation, which is more suitable for application.

Image retrieval by using local distribution features of interest points and multiple-instance learning

MENG Fanjie;GUO Baolong

J4. 2011, 38(2):  47-53.  doi:10.3969/j.issn.1001-2400.2011.02.009

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A novel method for image retrieval based on interest points is presented. The interest points are detected in the scale space. Then the image is divided into fan-shaped sub-regions of equal area according to the distribution of the interest points. Local features representing the spatial distribution information on the interest points are extracted to describe the image, and they are also robust to the image's rotation, scale and translation. In the relevant feedback, images are regarded as multiple-instance bags consisting of the local domain of the interest points in every fan-shaped sub-region. Labeled images chosen by the user are generated corresponding positive and negative bags, and the multiple-instance learning algorithm is employed to obtain the target concept reflecting the query image semantics. The method can reduce the ambiguity of the user query. Experimental results based on the Core image database show that our method improves the average retrieval precision by 7 percent or more, compared with other interest points based retrieval methods.

Study and improvement of bluetooth-based WPAN throughput

ZHANG Chao;ZHUANG Yiqi;LI Zhenrong;JIN Zhao;LIU Weifeng

J4. 2011, 38(2):  54-60.  doi:10.3969/j.issn.1001-2400.2011.02.010

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To improve the Bluetooth-based WPAN (Wireless Personal Area Network) throughput, the system models were built, and the chaotic algorithm was designed to improve the WPAN throughput. The system models includes the WPAN network model and the data collision model. The data collision crushes the data packet and makes the data resending, and then the function of WPAN data throughput is deduced with the aforementioned conclusion. It can be proved that the number of piconets and the hamming correlation ability of the FH (Frequency Hopping) algorithm decide the WPAN throughput. The new chaotic FH algorithm based on the Chebyshev map was built. It has a better hamming correlation ability than the Bluetooth FH algorithm and can improve the WPAN throughput. The computational simulation and actual test were done. The test used the ARM1510 SoC (System on Chip)+nRF2401 radio chip to build the WPAN. Simulation and test results prove that the new chaotic FH algorithm can increase the WPAN maximum throughput about twice, in other words it can improve the number of piconets in the WPAN about twice with the same throughput.

New algorithm for normalization of the face image

JIN Wei;ZHANG Jianqi;LIANG Jianxia;WANG Jiaqiang

J4. 2011, 38(2):  61-65+111.  doi:10.3969/j.issn.1001-2400.2011.02.011

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This paper presents a novel face normalization method by integrating the location of eyes and the corner of the mouth for the normalization in the vertical direction. In the first step, the regions of eyes and the mouth are roughly detected by making use of Adaboost all through the whole face image. The Grey Integral Projection and the improved Local Gradient Operator algorithms are then applied to find the accurate positions of the eyes and the corner of the mouth in the face image, respectively. Finally, the face image is rotated and zoomed according to the relative position of eyes and the mouth in vertical and horizontal directions. Experimental results demonstrate that the proposed method can locate the feature points accurately and present better normalization performance by introducing the zoom criterion in the vertical direction.

Non-homogenous image segmentation with global optimization

LIU Jianlei;FENG Dazheng

J4. 2011, 38(2):  66-71.  doi:10.3969/j.issn.1001-2400.2011.02.012

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In order to solve the problem that the traditional geometric active contour model can not adaptively segment a non-homogenous image, a global optimization non-homogenous image segmentation algorithm is proposed. Firstly, a new energy function is defined by importing gradient information on the inhomogeneous image which is filtered by the Gaussian filter. Then, the domain of the energy function is extended by the level set method. Thus, the energy function has the solution of global optimization. We introduce a level set function control term for avoiding the re-initialization procedure of the level set function. Finally, a partial difference equation of the level set function evolvement is derived by minimizing the energy function. The non-homogenous image segmentation is implemented by the numerical solution of the partial difference equation. Experimental results show that the proposed algorithm not only can automatically determine the evolvement orientation of the active contour cure, but also can effectively segment non-homogenous images.

Novel algorithm for high maneuvering target tracking based on fuzzy reasoning MIE

YANG Jinlong;JI Hongbing;FAN Zhenhua

J4. 2011, 38(2):  72-76+128.  doi:10.3969/j.issn.1001-2400.2011.02.013

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When tracking high maneuvering targets, the sudden changes of target states may cause serious decline and even divergence in the performance of conventional modified input estimation(MIE) algorithms. Taking this into account, this paper presents a novel adaptive tracking algorithm for high maneuvering targets. Fuzzy multiple modified factors are introduced on the basis of the MIE algorithm. Using the statistics residuals distance and the 2-norm of the acceleration vector as the input of the fuzzy controller, multiple modified factors are self-adapatively worked out to adjust predicted covariance, and the tracking capacity of this algorithm towards high maneuvering targets is improved. This algorithm also keeps a good performance for general uniform or low maneuvering targets. Simulation results obtained show the effectiveness of this algorithm. Compared with the constant factor MIE algorithm, this algorithm can lead to a higher estimation accuracy and a faster convergence speed.

Research on novel low cost phase shifting technology

ZHANG Hou;YIN Xiong;GONG Shuxi;WANG Jian

J4. 2011, 38(2):  77-81.  doi:10.3969/j.issn.1001-2400.2011.02.014

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The basic phase shifting unit for the Radant lens is modeled and simulated by use of the commercial simulating software HFSS which is based upon FEM and the main structural parameters that influence the inserting phase shifting are obtained. Based on the above work, two novel basic phase shifting units that meet the requirements in the engineering are devised, and simulated results demonstrat that these two novel units achieve phase imbalance of less than 60 and good transmission characteristics in the 8% operating frequency band with 10GHz as the center frequency. Finally, a new Radant lens phase shifter with a 5-bit digital phase setting is designed by a combination of these new units, which shows a more precise 2D scanning capability in comparison with the traditional 4-bit digital Radant lens phase shifter.

Low complexity compressed sensing based Doppler high resolution algorithm

LIU Yin;WU Shunjun;ZHANG Huaigen;WU Mingyu;LI Chunmao

J4. 2011, 38(2):  82-87.  doi:10.3969/j.issn.1001-2400.2011.02.015

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Exploiting the sparsity of radar targets in the Doppler frequency domain, compressed sensing based Doppler estimation methods can lead to high resolution estimates of targets' Doppler frequencies in the very limited coherent integration time. However, this involves a large amount of computation even via an efficient algorithm—Orthogonal Matching Pursuit (OMP). For further reduction of computational complexity, the 1D Doppler estimation is translated into a 2D sparse signal recovery problem through a pulse grouping method. Then a low complexity OMP algorithm optimized for 2D sparse signals is utilized. Simulation results indicate that high resolution Doppler estimates approximating those of the OMP can be obtained with an improved efficiency.

Localized reduced-dimension clutter suppression method for the airborne MIMO radar

Lü Hui;FENG Dazheng;HE Jie;XIANG Cong

J4. 2011, 38(2):  88-92.  doi:10.3969/j.issn.1001-2400.2011.02.016

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This paper presents a new reduced-dimension space-time adaptive processing (STAP) method for clutter suppression in the airborne MIMO radar. The received data in the element-pulse domain is firstly transformed to the angle-Doppler domain using the two-dimensional spatial beamforming and temporal Doppler filtering. Then, the partially adaptive processing is performed in a group of three-dimensional beams around the angle-Doppler bin of interest based on the linearly constrained minimum variance (LCMV) criteria. Simulation results demonstrate that the proposed method can significantly reduce the computational load and training requirements, and provide a better performance than the existing classic reduced-dimension STAP methods.

Array location error calibrating algorithm based on toeplitz pre-processing

YANG Jie;LIU Congfeng

J4. 2011, 38(2):  93-98.  doi:10.3969/j.issn.1001-2400.2011.02.017

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High resolution array direction finding techniques (such as the MUSIC algorithm) are usually used under the assumption that the array sensor locations are known precisely. However, the sensor location uncertainties always exist in practical circumstances. When the array sensor locations are randomly perturbed,the performance of the class algorithm then tends to deteriorate greatly and even becomes invalid. In this paper, a method based on the Toeplitz pre-processing of the covariance matrix is proposed. In order to enhance the capabilities further, an iterative algorithm is proposed to iteratively reconstruct both the Toeplitz and eigenstructure from the covariance matrix. Theoretical analysis and simulation indicate that the proposed algorithm improves the robustness of the MUSIC algorithm efficiently, as well as the multi-signal direction resolution.

Extended radar target tracking before detection using the modified particle filter

WU Zhaoping;ZHU Kairan;SU Tao;LU Jin

J4. 2011, 38(2):  99-104.  doi:10.3969/j.issn.1001-2400.2011.02.018

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The system dynamic model and measurement model in the particle filter(PF) are established in a sequence of radar range-Doppler measurements and a linear extended target model is proposed, which is more suitable for describing a maneuvering target than the conventional point target model. Furthermore, the likelihood ratio function of the new model is also derived. In addition, the conventional PF is improved here to reduce the number of particles. Due to the macthing between the proposed target model and the integration function of TBD algorithm over time, an improved probability of detection for the dim target is obtained. Simulation results demonstrate that the proposed method is capable of detecting and tracking a target with the SNR of 1dB stably.

Micro-motion characteristic analysis and recognition of cone-shaped targets

GUANG Yongsheng;ZUO Qunsheng;LIU Hongwei;DU Lan;LI Yanbing

J4. 2011, 38(2):  105-111.  doi:10.3969/j.issn.1001-2400.2011.02.019

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When the cone-shaped target is flying in exo-atmosphere, the micro-motion of the target belongs to a precession and that of the decoy belongs to a spin or a wobble. Because they are different in micro-motion, the characteristic spectrum is extracted as a recognition feature. The paper models multi-section radar signals and analyzes the micro-Doppler signature of the warhead and the decoy. Although the micro-Doppler Spectrum of precession targets,wobble targets and spin targets is approximated as a line-Spectrum, but there is a significant difference. Based on the harmonic model, eigenvalue decomposition is applied to compute the eigenvalue as the recognition feature. Simulation proves that the method is effective.

Joint estimation of polarization and direction of arrival based on the wideband L-shaped sparse array

CHANG Hong;ZHAO Guoqing;SHI Haijie

J4. 2011, 38(2):  112-115+146.  doi:10.3969/j.issn.1001-2400.2011.02.020

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A high accuracy algorithm for direction of arrival (DOA) and polarization estimation for the wideband signal is proposed. The L-shaped sparse array is exploited in this method, which consists of multi baseline phase-polarization interferometers. Joint estimation is realized by utilizing direction and polarization information involved in the cross-correlation spectrum phase from the outputs of sensors with different polarizations in two linear arrays. It has the advantage of simple configuration which is suitable for realization. Parameter estimations are given by weighting and averaging the results from different baseline interferometers. The optimum weighting coefficients are given by the square of baseline lengths. Simulation results show the correctness of the algorithm.

Wide baseline image matching based on a new local descriptor

CHEN Bing;ZHAO Yigong;LI Xin

J4. 2011, 38(2):  116-123.  doi:10.3969/j.issn.1001-2400.2011.02.021

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In order to overcome the differences in 3D viewpoint, scale, rotation and grayscale, and achieve stable wide baseline image matching, a new feature descriptor based on Local Binary Pattern Histogram Fourier features is constructed and a new wide baseline image matching approach is proposed according to comparison and analysis. First, Maximally Stable Extremal Regions (MSER) of the reference image and real-time image which are scale and affine invariant are extracted, respectively. Second, rotation and grayscale invariant descriptors are constructed. Then the matching MSER features of the two images are extracted based on the nearest neighbor Euclid distance ratio strategy. The epipolar geometry of the two images is estimated according to the Progressive Sample Consensus (PROSAC) algorithm. Simulation results show that the proposed method is robust to changes in 3D viewpoints, scale, rotation and grayscale, and can achieve stable wide baseline image matching.

Antenna-mode RCS reduction optimization for array antennas with additional delay lines

WANG Wentao;ZHANG Pengfei;GONG Shuxi;WANG Xing;HONG Tao;LU Bao

J4. 2011, 38(2):  124-128.  doi:10.3969/j.issn.1001-2400.2011.02.022

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The radiation performance of an antenna must be ensured when reducing the antenna radar cross section (RCS), which makes the in-band RCS difficult to control. For this reason, this paper presents the method of loading delay lines with a varying length to achieve the antenna-mode RCS reduction of an array antenna. Antenna-mode scattering is essentially the reradiation of reflected energy, which comes from the electromagnetic wave received by the antenna and reflects at the mismatched point of the feed network. When a group of delay lines is loaded between the array elements and the feed network, the radiation energy passes through these delay lines once, while the scattering energy passes them twice. Therefore, by optimizing the length of each delay line and adjusting the phase difference between radiation and scattering, the antenna RCS can be reduced with a little degradation in radiation performance. The proposed examples of monostatic and bistatic RCS reduction show that the antenna-mode RCS can be reduced more than 14dB by this method.

Improved modular exponentiation and VLSI implementation for RSA cryptosystem

XIE Yuanbin;SHI Jiangyi;HAO Yue

J4. 2011, 38(2):  129-134+179.  doi:10.3969/j.issn.1001-2400.2011.02.023

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Modular multiplication and exponentiation severely restrict the RSA performance. The paper displays a modified Montgomery modular multiplication algorithm based on the two-level carry-save addition (CSA) tree. By inserted registers, the algorithm shortens the critical path and guarantees operands arriving at the CSA input ports simultaneously, which significantly improves the speed of modular multiplication. The modular-multiplication sequence is adjusted in modular exponentiation, which avoids most format conversion and reduces the conversion time. The proposed modular exponentiation circuit improves the throughput rate by 36% and saves hardware cost by 18% compared with the most representative design based on FPGA. For ASIC implementation, the throughput rate is improved by 75%, and area is decreased by 33%.

Design of a high output power step down DC/DC converter with the peak current control mode

LIU Lianxi;YANG Yintang;ZHU Zhangming

J4. 2011, 38(2):  135-140.  doi:10.3969/j.issn.1001-2400.2011.02.024

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This paper presents a high output-power step-down DC/DC converter based on the CSMC 0.5μm BCD (Bipolar-CMOS-DMOS) process. This chip provides a fast transient response and eases loop stabilization by using the current mode operation with the peak-current-control and slope compensation scheme. A power MOSFET with the conduct-resistor less than 0.18Ω is integrated in the chip, and it can provide an over 3.0A continuous output current. Simulation results and measurement show that the oscillating frequency is 400kHz, that the output power is more than 10W, and that the average efficiency is up to 85% over a wide supply range from 4.7V to 24V. The die area is less than 1.6mm×1.3mm, and the chip can be widely used in various distributed power systems.

Analysis of thermal axial symmetry in the LD side-pumped laser

LIN Lin;GUO Zhen;WANG Shiyu;LI Haiqiang;CAI Defang;LI Bingbin

J4. 2011, 38(2):  141-145+186.  doi:10.3969/j.issn.1001-2400.2011.02.025

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Based on the analysis of phase delay distribution between two ends of the laser crystal, thermal axial symmetry in an LD side-pumped laser is investigated. A new parameter for describing the thermal axial symmetry is proposed. The influence of pumping power, quantity, angular deviation and pumping distance deviation of LDs is analyzed by the finite element method. The result obtained indicates that the lower the pumping power is, or the more symmetrically the LDs are distributed, the more symmetrical the thermal effect appears; during the assembling process, the LD angular deviation and pumping distance deviation prevent the thermal lens effect from symmetrical axial distribution, which needs to be paid attention to and avoided.

Multi-clock router designed for the network-on-chip

LIU Yi;YANG Yintang;ZHOU Donghong

J4. 2011, 38(2):  146-150.  doi:10.3969/j.issn.1001-2400.2011.02.026

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The router is a core element of the NoCs(Network-on-Chips). Aiming at NoC communication issues among different clock domains, the paper proposes a multi-clock router microarchitecture, which applies to 2D mesh topology NoC and uses dual-clock asynchronous FIFOs(First In First Out) instead of cross-clock domain interface circuits in usual routers. Designed by the Verilog HDL, the router's integrated results on FPGA show that it uses fewer resources and operates at a high frequency of up to 475.29MHz, effectively increasing the data transmission rate. Based on SMIC 0.13μm CMOS technology, by comparing the integrated results of routers with different FIFO depth values, impacts of the buffer size on the router's performance and cost are analyzed further.

Stutter-invariant propositional interval temporal logic

YANG Chen;DUAN Zhenhua

J4. 2011, 38(2):  151-156.  doi:10.3969/j.issn.1001-2400.2011.02.027

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To apply the propositional interval temporal logic (PITL) in compositional verification with minor risk of state-exlopsion, a stutter-invariant PITL (PITLst) is proposed, which is structure-related since it inherits the structural relativity of PITL operators much like constructs of imperative programming, such as chop operator for sequential composition and projection opertor for iteration, thus when used as a specification language PITLst can specify the structure of concurrent systems. Moreover, it is shown that PITLst can express all stutter-invariant properties expressible in PITL, so it surpports modular abstraction for compositional verification. In this way, the overall system is of small size, so the risk of state-explosion is accordingly reduced. In addition, an automatic gas station system, as an example, is compositionally verified against PITLst properties, which illustrates that PITLst well supports compositional verfication.

Generalized Cauchy-Riemann equations and the n-variate harmonic function

LIANG Changhong;CHEN Xi;HUANG Kai;HE Zhili

J4. 2011, 38(2):  157-161.  doi:10.3969/j.issn.1001-2400.2011.02.028

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Analytic functions are the important research area in complex variable functions. It is not extensive because the real and imaginary parts of the analytic functions are harmonic functions with only two variables. Therefore, this paper proposes the Generalized Cauchy-Riemann equations with n variables by the Jacobian determinant. The Generalized Cauchy-Riemann equations with two variables are extended to n variables as well as the harmonic function. This kind of function has the superiority of conformal orthogonality in three dimensional geometric space.

RLS blind multiuser detection based on a novel subspace tracking strategy

HUANG Ruhao;HE Peiyu;YU Wenjun;GAO Yong

J4. 2011, 38(2):  162-166.  doi:10.3969/j.issn.1001-2400.2011.02.029

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To overcome the issue that the performance of the subspace-based blind multiuser detector degrades due to underestimation of the sources' number in direct sequence/code division multiple access (DS/CDMA) systems, a novel subspace tracking strategy is presented and the recursive least square (RLS) blind multiuser detection algorithm is modified. As for the novel subspace tracking strategy, the desired user's signature waveform constitutes one part of the signal subspace and its orthogonal complement is tracked as the other parts of that signal. This brings the benefits of a small signal subspace estimation error and lower computational complexity. Even in the underestimation of the sources' number, the performance of the detector does not degrade significantly because the signal subspace always maintains the information on the desired user. The RLS blind multiuser detection algorithm is combined with the subspace approach. As a result of forward error feedback, this algorithm can reduce sensitivity to signal subspace estimation. Simulations are provided to demonstrate the effectiveness of the proposed detector.

Blind recognition method for the Turbo coding parameter

ZHANG Yongguang

J4. 2011, 38(2):  167-172.  doi:10.3969/j.issn.1001-2400.2011.02.030

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In order to solve the problem of the blind recognition of Turbo codes,some methods for blind recognition of the Turbo coding parameter with trellis termination are proposed for the first time. Based on the analysis of the sub-encoder structure of Turbo codes,some analytical models of convolutional codes at a rate of 1/2 are proposed, and by recoverying the interleaver sequence of Turbo codes,interleaver mapping is decided by exhaust comparison, and blind recognition of Turbo codes with trellis termination is realized.Simulation results illustrate that given the unknown Turbo encoded data sequence, the recognized coding parameters are correct by comparing prior conditions which validates the accuracy of the proposed methods.

Surface surveillance system of main station off-center and performance analysis

GONG Fengxun;LEI Yanping;MA Yanqiu

J4. 2011, 38(2):  173-179.  doi:10.3969/j.issn.1001-2400.2011.02.031

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Since location accuracy for low-altitude targets is not good in the Short-Baseline system, a program of the main station off-center of eight-station arrangement is proposed. Firstly factors are analyzed which influence the location accuracy for line-of-sight environments. Then the relationship between main station position and location performance is researched, and a location method for the main station off-center of eight-stations is put forward by increasing the base-station number and layout of the main station off-center, which realizes multiple coverage of the monitoring area using the redundant measurement information by the main station off-center and more base stations provided. Finally the number of base stations and optimal disposition way for low-altitude targets are obtained in the airport by simulating the geometric dilution of precision (GDOP) distribution. Simulation figures and data show that the main station off-center of eight-station arrangement can be achieved over 95% coverage of the airport for low-altitude targets location.

Effectively modified topology sequence track correlation algorithm

WU Zemin;JIANG Yejin;REN Shujie

J4. 2011, 38(2):  180-186.  doi:10.3969/j.issn.1001-2400.2011.02.032

Abstract ( 1389 )   PDF (833KB) ( 1106 )   Save

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To release the huge calculation load for the track correlation algorithm based on the topology sequence facing large sensor system errors, the approximate linear transformation relationship between topology sequences from different sensors is firstly discussed, where sensor system errors are considered. The SVD method for space points set matching problem is directly used to estimate the linear transformation. A decision for topology sequences matching is made after validating the linear parameters. The SVD based track correlation algorithm is efficient, especially for far-away targets. The efficiency of the SVD based algorithm is validated by simulation. Because of removing the dilemma of choosing the angle and range search step sizes for the basic topology sequence algorithm, not only is the computational time reduced about 90%, but also the successful rate of correlation is improved.

Research on the approximation algorithm of the evidential thoeory

MIAO Zhuang;CHENG Yongmei;PAN Quan;HOU Jun

J4. 2011, 38(2):  187-193.  doi:10.3969/j.issn.1001-2400.2011.02.033

Abstract ( 1612 )   PDF (492KB) ( 1172 )   Save

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In the Dempster-Shafer theory, the computational complexity is one of the main points of criticism this theory has to face. To solve this problem, many approximation algorithms, which always reduce the focal elements, are proposed. In this paper, a simple optimal approximation is proposed by analyzing its reasonability in quality and quantity. The genetic algorithm is applied for approximation for the first time. Then two fast algorithms, one step approximation and multi-step approximation, are proposed. As a conclusion of simulation these algorithms are better than other algorithms in accuracy and computation burden.

Research on printed Vivaldi antennas

LI Ping;YU Jiaao

J4. 2011, 38(2):  194-196.  doi:10.3969/j.issn.1001-2400.2011.02.034

Abstract ( 1532 )   PDF (1750KB) ( 1491 )   Save

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Based on the vivaldi antenna, we analyze the impendance bandwidth of the antenna affected by the tapered slot-line structure, and propose the method for improving and optimizing the antenna's structure by the way of adding slots on the metal patch. The results of the simulated data and measured data show that the VSWR is less than 2, with the bandwidth ranging from 320MHz to 1GHz, and between 1.16GHz and 1.3GHz. At the same time, the VSWR of the application bandwidth is 1.2. So the Vivaldi antenna has the excellent properties of high gain, miniaturization and wide-band.