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2009 Vol. 31, No. 4

Display Method:
Study of Point Target Spectrum for Bistatic SAR Imaging
Ding Jin-shan, Otmar Loffeld, Holger Nies, Xing Meng-dao, Bao Zheng
2009, 31(4): 763-767. doi: 10.3724/SP.J.1146.2007.01955
An exact analytic solution for the 2-dimensional point target reference spectrum is difficult to find for bistatic SAR image formation due to a double hyperbola in the bistatic range migration equation. Four methods of the point target reference spectrum are analyzed, namely Loffelds Bistatic Formula (LBF), Method of Series Reversion (MSR), Geometry-based Bistatic Formula (GBF) and the Dip Move Out (DMO) approach. The link between GBF and DMO is given in detail in this paper, and also the link between MSR and LBF is validated by simulation results.
Minimizing Sum of Image Amplitudes Autofocus Algorithm
Liu Bi-dan, Han Song, Wang Yan-fei
2009, 31(4): 768-771. doi: 10.3724/SP.J.1146.2007.01964
High resolution Synthetic Aperture Radar (SAR) imaging requires that the azimuth frequency modulation rate is accurately estimated. A new autofocus algorithm is presented which minimizing sum of amplitudes in this paper. This paper analyses the relationship between the image contrast function and the sum of amplitudes, when the matched functions amplitude in azimuth direction is invariable. Based on the relationship between the image contrast function and the focus degree of the image, the minimizing sum of amplitudes autofocus algorithm is presented. The performance of this algorithm is verified by the computer simulation and RADARSAT-1 raw data imaging. Experimental results show that the algorithm has better convergence speed and estimation accuracy than traditional Map Drift (MD) auto focus algorithm. It has better convergence speed and less computation cost than the Contrast Optimization Autofocus Algorithm (COAA). It can be implemented by hardware easily and help to improve the performance of real time imaging processor.
Wide Swath Imaging with MIMO-SAR
Wu Qi-song, Jing Wei, Xing Meng-dao, Bao Zheng
2009, 31(4): 772-775. doi: 10.3724/SP.J.1146.2007.01959
This paper proposes an approach for wide swath imaging with Multiple-Input Multiple-Output Synthetic Aperture Radar (MIMO-SAR) system. In the system the Discrete Frequency Coding Waveform (DFCW) is applied to obtain high range resolution; and low PRF is adopted to achieve unambiguous wide swath, however, a reduction of the PRF raises Doppler ambiguities. The spatial filter is used to resolve the Doppler ambiguities. As the MIMO-SAR system provides more degrees of freedom than the channel number, the filter is successfully capable of resolving the Doppler ambiguities whose times are more than the channel number. Simulation result confirms the validity of the proposed method.
Imaging Study of High Squint SAR Based on FMCW
Liang Yi, Wang Hong-xian, Xing Meng-dao, Bao Zheng
2009, 31(4): 776-780. doi: 10.3724/SP.J.1146.2007.01851
Based on the differences of work mechanism between Frequency Modulated Continuous Wave (FMCW) Synthetic Aperture Radar (SAR) and Pulsed Synthetic Aperture Radar, which leads to different form of received signal, this paper establishes the model of high squint FMCW SAR echo, analyzes its characteristics, and reveals the Doppler frequency shift effect induced by the continuous motion in range direction while radar transmitting and receiving signal. Meanwhile, this paper proposes a modified RD Algorithm (RDA) for high squint FMCW SAR dechirp data, which compensates for range walk in time domain, Doppler frequency shift and range curvature in frequency domain. Point target simulation verifies the analysis and validity of the algorithm. In addition, for the Doppler frequency shift induced by the platform continuous motion, this paper also analyses its effect on imaging.
Recognition and Parameters Estimation of Polyphase-coded Radar Signals
Deng Zhen-miao, Liu Yu
2009, 31(4): 781-785. doi: 10.3724/SP.J.1146.2007.01899
Recognition and parameters estimation of the polyphase-coded radar signals are discussed in this paper. First the code period of the received signals is estimated. When the pulse width and the code period are of prior knowledge, phase modulation of the polyphase-coded signals can be determinated, therefore the local reference signals can be generated and then multiplied with the conjugated received signals. When one of the local reference signals and the received signals had the same modulation mode, the result of multiplication is a sinusoid, thus the polyphase-coded signals can be classified and the carrier frequency can be obtained by estimating frequency of the sinusoid. Finally, the spectral structure is analyzed under asynchronous circumstance. Simulation results show that this method can recognize the polyphase-coded signals at low signal-to-noise ratio and estimate the carrier frequency and code period accurately.
Cramer-Rao Bounds of DOA Estimation for MIMO Radars in Compound-Gaussian Clutter
Wang Ju-ting, Jiang Sheng-li, Liu Zhong
2009, 31(4): 786-789. doi: 10.3724/SP.J.1146.2007.01984
This paper studies the Average Cramer-Rao Bounds (ACRB) for estimating Direction Of Arrival (DOA) in compound-Gaussian clutter using Multi-Input Multi-Output (MIMO) radars. Firstly, the MIMO radar signal and compound-Gaussian clutter models are introduced. Secondly, the general ACRB expression is derived. Then, a closed-form ACRB is given for the inverse-Gamma distributed texture component. Thirdly, the Outage CRB is introduced as a supplement to the divergence of ACRB when there is only one transmit radar element. Finally, the DOA estimation performances of MIMO radars are simulated through computer simulations under different conditions. Theoretical analyses and computer simulations show that the spatial diversity of MIMO radar can improve the performance of DOA estimation effectively. The ACRB decreases as the number of the transmit radar elements increases. It is also found that the ACRB in compound-Gaussian clutter is inferior to that in Gaussian clutter. The research conducted in this paper reveals the fundamental performances of the MIMO radars.
Adaptive Pulse Compression via MSN Criteria
Zhang Jin-dong, Wang Hai-qing, Zhu Xiao-hua, Li Yu-sheng
2009, 31(4): 790-793. doi: 10.3724/SP.J.1146.2007.01892
Traditional matched filter could only suppress range sidelobes to a certain extent, so the weak target may be covered by the range sidelobes of the strong one. To solve this problem, adaptive pulse compression algorithm based on reiteration and maxim output signal-to-noise rate criteria is proposed. This algorithm uses the apriori information to adaptively suppress range sidelobes and noises. Algorithm steps are given according to the principle and convergence is also considered. Simulation results show that this algorithm could effectively suppress sidelobes and still works effectively under conditions of multiple targets and moving target.
Acceleration and Velocity Estimation of Targets in Bistatic Multi-Frequency FMCW Radar
Qin Guo-dong, Chen Bai-xiao, Yang Ming-lei, Zhang Shou-hong
2009, 31(4): 794-797. doi: 10.3724/SP.J.1146.2008.00106
The bistatic multi-frequency FMCW radar uses sparse-array to transmit the FMCW signals of multiple carrier frequencies, and an array to receive the echoes. The Doppler spectrum is widened because the Doppler signals are modulated by acceleration and velocity of maneuvering target, which leads to the degeneration of radars detection performance. The signal model of bistatic multi-frequency FMCW radar is analyzed in this paper. A method using Discrete Polynomial-phase Transform(DPT) and phase difference is presented to obtain the high-accuracy acceleration and velocity estimation of target. The performance of the proposed method is analyzed when the data is divided into different segments. The simulation indicates that the method can obtain a high-accuracy estimation of both acceleration and velocity with a small computational complexity.
The Application of Thinned Array Time Division Multiple Phase Center Synthesis
Hou Ying-ni, Li Dao-jing, Hong Wen
2009, 31(4): 798-802. doi: 10.3724/SP.J.1146.2008.00024
The three-dimensional imaging radar system based on thinned array is investigated to reduce the system complexity. The multiple phase center aperture synthesis method in time division mode is proposed to eliminate the high side lobes of thinned array. Combine with motion compensation, the synthesized phase center both in quantity and distribution are same as the full array. Using simulated annealing algorithm to optimize the location of antennas, so as to minimize the number of antennas used. For the array length of cross-track is far small than the scene width, the sub-aperture three-dimension imaging method is adopted. The simulation results denote the validity of the method proposed in the paper.
A New Image Registration Method for Repeat-Pass InSAR Based on Fourier-Mellin Transformation and Correlation-Coefficient Algorithm
Shi Xiao-jin, Zhang Yun-hua
2009, 31(4): 803-807. doi: 10.3724/SP.J.1146.2008.00088
Compared with one pass InSAR system with two antennae, the registration of image pair of repeat-pass InSAR system is much more difficult due to parallel tracks are usually not guaranteed. In this paper, a new image co-registration algorithm for repeat-pass InSAR, which combines the Fourier-Mellin transform and correlation-coefficient algorithm, is proposed to perform accurate co-registration for complex image pair having rotation angle due to unparallel tracks. When the method is used as coarse co-registration step, a nonlinear amplitude transformation is introduced as pre-processing to overcome the failure of Fourier-Mellin transformation method in case of image pair with large dynamic amplitude range and non-uniform amplitude distribution, and when used as fine co-registration step, correlation-coefficient algorithm is incorporated to accurately estimate the small rotation angle between image pair. SIR-C/X X-band experimental data are used to test the proposed algorithm through comparing with traditional correlation-coefficient algorithm in both accuracy and run time. The experimental results prove the effectiveness of the proposed algorithm.
Formation Optimization for Distributed Satellites SAR Based on Height Error
Li Fang, Wang Yan-fei, Yan Hong-hui
2009, 31(4): 808-812. doi: 10.3724/SP.J.1146.2007.01940
The key point of guaranteeing the distributed satellites system performance is to design the formation of the satellites appropriately. This paper studies the satellite formation optimization of distributed satellites system which moves on flying around orbit, and presents a new optimization method based on height-measure error. A composite pixel height error model after combining the multiple baseline measurements is presented, and the height error of the given scene is presented. Finally, the height error model of given scene is used to optimize the satellite formation of distributed satellites system by using genetic algorithm. The simulation results show that this method can decrease the height error of the given scene.
The Lossless Compression Method for Hyperspectral Images Based on Optimized Prediction Tree
Xia Hao, Zhang Rong
2009, 31(4): 813-817. doi: 10.3724/SP.J.1146.2007.01933
Prediction tree is a traditional and efficient method for lossless compression of hyperspectral image. In this paper an optimized method based on prediction tree is presented. To express the variation of local context of two neighboring bands, a partial extending factor is introduced to compensate the predicted value of current pixel so as to reduce the prediction error. Furthermore, a synthetical prediction based lossless compression scheme for AVIRIS hyperspectral images is proposed. Experimental results demonstrate that the proposed method works efficiently on AVIRIS images with low complexity and limited memory.
A Method of Intercalibration for GPS and High Precision Baro-Altimeter on Line
Gong Xiao-lin, Fang Jian-cheng, Sheng Wei
2009, 31(4): 818-821. doi: 10.3724/SP.J.1146.2008.00161
According to the different characteristic of the height errors measurement between Global Positioning System(GPS) and baro-altimeter, an error model of baro-altimeter based on third differential is established, and a method of intercalibration for GPS and high precision baro-altimeter on line is proposed. The adaptive Kalman filter based on the current statistical model is used in this method, which combined GPS and baro-altimeter efficaciously. This method can track the acceleration mean and covariance adaptively, and adjust the process noise covariance matrix and state parameters adaptively. At the same time, fading factor is used to make the best of current measurement data, and then improve the dynamics of filter. Based on the trajectory of real fairway, the semi-physical simulation results illustrate the validity of this method.
A Heterogeneous Dual-Core High-Speed Processing System for High Resolution Catadioptric Panorama
Chen Li-dong, Zhang Mao-jun, Wang Wei, Bao Wei-dong, Jin Han-jing
2009, 31(4): 822-826. doi: 10.3724/SP.J.1146.2008.00133
To realize the high-speed processing of high resolution catadioptric panorama, a heterogeneous dual-core embedded system based on DSP+FPGA is presented, which can do rapid capturing, unrolling and displaying of 20481536 resolution catadioptric panorama at 12fps, by using multi-level ping-pong caches, a panorama unrolling algorithm based on lookup-table method and block prefetch strategy. The system was characterized by dynamic reconfiguration and high efficiency of computation. It can be applied in panoramic surveillance and robot vision.
ISF Parameters Concealment Algorithm Based on the HMM Clustering Means for Wideband Speech
Wang Shi-kui, Zhou Lin, Wu Zhen-yang, You Hong-yan
2009, 31(4): 827-831. doi: 10.3724/SP.J.1146.2008.00014
There exist inevitably frame losses in the transmission of wideband speech. Due to the influence of error propagation, the quality of the received speech decays rapidly. In this paper, large hidden Markov model is adopted to model the ISF parameter in wideband speech, and the best state sequences of ISF parameters of the several speech frames before the lost frame are determined using Viterbi Algorithm. Because of the large redundancy of the HMM states, the lost ISF parameters are substituted by the weighted values between the clustering means and the real values of the ISF parameters of the nearest received frame. The speech compensated by this algorithm is compared to which by Annex I of G.722.2 specification. Simulation shows that the algorithm in this paper can result in best speech, and smaller waveform and spectrum distortion.
A Multichannel Loudness Compensation Method for Digital Hearing Aids
Wang Qing-yun, Zhao Li, Zhao Li-ye, Zou Cai-rong
2009, 31(4): 832-835. doi: 10.3724/SP.J.1146.2007.01449
A new multichannel loudness compensation method is proposed in this paper. According to the method, analysis and reconstruction sub-band filters for near perfect reconstruction oversampled filter bank are designed, then nonuniform multichannel loudness compensation based on human auditory, the sensitive feature of frequency and sound pressure level is implemented. Simulations and experiments for the typical senile patient demonstrate that the loss energy of the high frequency sound is well compensated, the intelligibility of patient is improved, and the speech detection threshold is decreased notably.
A New Method for Estimating the Primary Quantization Step of JPEG Double-Compression
Wang Jun-wen, Liu Guang-jie, Dai Yue-wei, Zhou Lin-na, Guo Yun-biao
2009, 31(4): 836-839. doi: 10.3724/SP.J.1146.2007.01968
This paper presents a method for estimating the primary quantization step of double compressed JPEG image. The method in accordance with the relationship between the two quantization steps contains three situations. When the primary quantization step is larger than the second quantization step, the histogram can be used to calculate directly. To resolve the issue of multi-value caused by Fourier spectrum analysis and the problem that the primary quantization step is the factor of the second quantization step, the uncompressed image can be approximated by narrowing the image by 98%. This method can resolve the problem that the primary quantization step is the factor of the second quantization step, and uses spectrum analysis to reduce the complexity. The experimental results show that this method has higher accuracy of the estimation.
Fast Global Motion Estimation Based on Symmetry Elimination and Difference of Motion Vectors
Zheng Ya-yu, Tian Xiang, Chen Yao-wu
2009, 31(4): 840-843. doi: 10.3724/SP.J.1146.2008.00176
To reduce the computational complexity of Global Motion Estimation (GME), a fast GME method based on the principle of the symmetry elimination and difference of motion vectors is proposed. First, the translational parameters are estimated by using the technique of the symmetry elimination of motion vectors. And then the transform parameters are estimated by utilizing the principle of the difference of motion vectors and the strategy of the belief judgment. Experimental results on five geometric global motion models and the real video sequence show that the proposed method, compared with the estimation methods based on the Iterative Least Square (ILS) and the Partial Derivative (PD), only need approximately 50% of their computational time while achieving the comparable estimation accuracy.
Target Tracking Based on Particle Filtering in Passive Sensor Array
Li Liang-qun, Huang Jing-xiong, Xie Wei-xin
2009, 31(4): 844-847. doi: 10.3724/SP.J.1146.2008.00201
In this paper, a new Multiple Model Rao-Blackwellized Particle Filter (MMRBPF) based algorithm is proposed for maneuvering target tracking in passive sensor array. The advantage of the proposed approach is that the Rao-Blackwellization allows the algorithm to be partitioned into target tracking and model selection sub-problems, where the target tracking can be solved by the extend Kalman filter, and the model selection by multiple model Rao-Blackwellized particle filter. The analytical relationship between target state and model is exploited to improve the efficiency and accuracy of the proposed algorithm. Finally, a nonlinear measurement model of multiple passive sensors is founded. The simulation results show that the proposed algorithm results in more accurate tracking than the IMM (Interacting Multiple Model) method.
A Data Association Method for Maneuvering Target Tracking in Three-Dimensional Space under the Circumstance of Clutter
Liu Zong-xiang, Xie Wei-xin, Huang Jing-xiong
2009, 31(4): 848-852. doi: 10.3724/SP.J.1146.2007.01880
In maneuvering track tracking, the inaccurateness of the moving model leads to that of the forecasting center, which causes error data association. To solve the problem of data association for maneuvering target tracking in three-dimensional space under the circumstance of clutter, an assume that the current turn rate of a maneuvering target changes within a limited range and its turn may be in arbitrary direction is proposed for data association, thus the forecasting center of a target is a curved surface in 3-D space. The distance between a measurement and the curved surface is used to compute the degree of association between the measurement and the target. In order to reduce the computational complexity, the computing formula of the maneuvering direction and turn rate corresponding to a special measurement is presented. Simulation results show the proposed method improves the correctness of data association, reduces the percentage of lost tracks and improves the state estimating accuracy in tracking a maneuvering target under the circumstance of clutter.
A New Security and Privacy on RFID Mutual Authentication Protocol Based on Partial ID
Zhang Hui, Hou Chao-huan, Wang Dong-hui
2009, 31(4): 853-856. doi: 10.3724/SP.J.1146.2007.01901
The method of implementation of security and privacy in low cost tags is a key technique which needs to be solved in research field. Based on the use of partial ID, CRC checksum and dynamic update ID, this paper proposes a new RFID mutual authentication protocol which possesses forward security ability and can defeat location privacy attack, relay attack, eavesdropping attack and denial-of-service attack. The new scheme conforms to EPC Class1 Gen2 standards and effectively solves problems of RFID security and privacy with lower complexity of hardware, so it is useful for low cost RFID tags.
Hermite Interpolation-Based Wavelet Transform Modulus Maxima Reconstruction Algorithms Application to EMG De-noising
Luo Zhi-zeng, Shen Han-xiao
2009, 31(4): 857-860. doi: 10.3724/SP.J.1146.2007.01954
In order to eliminate the noise mixed in EMG signal, a Hermite interpolation- based wavelet transform modulus maxima reconstruction algorithm is proposed. The obtained EMG signal is decomposed using the wavelet transform; the singularity and different properties of the signal and noise of the wavelet coefficient modulus under the different scales of wavelet transformation are used to separate the signal and noise; then the wavelet coefficients are reconstructed using Hermite interpolation; Finally, the de-noised signal is got by the wavelet reconstructed algorithm. Experiments show that, the method has good performance in removing noise, improving the signal-to-noise ratio and reserving the detailed information, which brings in favorable conditions to feature extraction and pattern recognition of EMG.
DOA Estimation of Rectilinear Signals Using Defective Electromagnetic Vector Arrays
Xu You-gen, Liu Zhi-wen
2009, 31(4): 861-864. doi: 10.3724/SP.J.1146.2007.01471
Noncircular polarimetric-MUSIC (Multiple Signal Classification) is herein proposed for Direction Of Arrival (DOA) estimation of rectilinear signals (such as AM, BPSK communications signals) by using one or a number of possibly defective (incomplete) electromagnetic vector-sensors. As an extension of the existing noncircular MUSIC, this new MUSIC variant can incorporate the redundancy in the nonvanishing conjugate moments and polarization diversity present in a polarization-sensitive array. It can also be directly extended to a defective acoustic vector array. Simulation results are given to validate the proposed method.
A Research of Fast and Accurate Recursive Algorithm for Frequency Estimation of Sinusoid Signal
Xu Jia-jia, Liu Yu, Deng Zhen-miao, Chen Yi-tao
2009, 31(4): 865-869. doi: 10.3724/SP.J.1146.2008.00075
A frequency offset correcting algorithm is presented for frequency estimation of sinusoid signal, and a fast and accurate recursive algorithm for frequency estimation of sinusoid signal is investigated by associating the advantage of high accuracy of the M-Rife algorithm and the advantage of small computational load of the frequency offset correcting algorithm. Firstly, an initial estimation is obtained by the M-Rife algorithm for a truncated signal series which has a few points. Next, with the initial estimation result, a more accurate estimation is obtained by the frequency offset correcting algorithm for a longer truncated signal series. And then, deduce the rest by analogy. Finally, the ultimate estimation is obtained by the M-Rife algorithm for the entire signal series. The computational complexity of the recursive algorithm is lower than that of an FFT operation when the signal series is long. Simulation results show that the performance of this algorithm is stable, and the estimation variance is nearly the same as the M-Rife algorithm, approaching to CRLB(Cramer-Rao Lower Bound). The algorithm is convenient for realizing real-time frequency estimation accurately.
An Improved Approach of Pilot Design for MIMO OFDM Systems
Hu Die, He Liang-hua
2009, 31(4): 870-873. doi: 10.3724/SP.J.1146.2007.01995
For Multi-Input Multi-Output (MIMO) Orthogonal Frequency Division Multiplexing (OFDM) systems with virtual subcarriers, conventional equispaced pilot tones are no longer applicable in some situations. To obtain the optimal pilot sequence in such cases, this paper proposes an improved pilot-design approach based on the criterion of minimum Mean-Square-Error (MSE) of the Least Squares (LS) channel estimate. The proposed approach can quickly and efficiently find the optimal pilot sequence, or suboptimal pilot sequences when the optimal ones do not exist. The simulation results demonstrate the effectiveness of the proposed approach.
Performance Analysis on Reduced-Complexity UWB SRAKE Receiver under NLOS Environment
Xiao Zhu, Xiang Xin, Yu Quan, Yi Ke-chu
2009, 31(4): 874-877. doi: 10.3724/SP.J.1146.2008.00394
In this paper, a Reduced-Complexity Selective RAKE (RC-SRAKE) receiver scheme is proposed, which can be adopted in ultra-wideband multipath channel under NLOS environment. It employs a convolution based finger selection algorithm, which has low complexity because it does not require precise channel information or channel estimation. A closed-form expression for symbol error probability of the proposed RC-SRAKE is derived in term of the combined fingers and impulse noise. The derived expressions are evaluated numerically with IEEE 802.15.4a NLOS channel models. It is demonstrated that RC-SRAKE can achieve the approximate performance as to ideal SRAKE with a fewer fingers.
Coded-modulation Scheme for Interferences Mitigation from MB-OFDM Cognitive Radio and Its Performance Analysis
Yang Cheng, Weng Wei-wen, Zhou Zheng
2009, 31(4): 878-881. doi: 10.3724/SP.J.1146.2007.01897
In order to satisfy the requirement of mitigating interferences caused by MB-OFDM cognitive radio systems, a type of coded-modulation scheme among two, four or several sub-carriers, is proposed, which is derived from side-lobe interference expressions. Based on this method, the side-lobe signal of MB-OFDM decreases quickly, and then the frequency notch, overlapping with other radio services, is deep enough. Consequently, interferences from cognitive radio systems is decreased, and the coexistence with other narrow band radio services is realized. In addition, theoretic analysis and simulation results show that the coded-modulation scheme has an additional merit: when SNR arrives at a certain value, compared with traditional modulation, much better Bit Error Rate (BER) performance can be achieved over Rayleigh fading channels.
Design of Decomposable-Rate-Compatible LDPC Codes and HARQ Scheme
Shen Jin-qi, Xu You-yun, Yu Hui, Gan Xiao-ying
2009, 31(4): 882-884. doi: 10.3724/SP.J.1146.2008.00047
A novel method is proposed to construct Decomposable-Rate-Compatible LDPC (D-RC-LDPC) codes. The H matrix of a high rate LDPC codes constructed by this method contains a series of LDPC codes with low rate. The low rate codes can be encoded and decoded respectively which make the system more flexible. A new HARQ scheme based on D-RC-LDPC is also proposed, which is called DB-HARQ (D-RC-LDPC Based HARQ). It can transmit more information through re-transmit scheme and improve the performance of Error Correction Code (ECC) by lowering rate of the ECC. The scheme can improve the FER and throughput performance with 1.5 dB compared with normal ARQ scheme when the code length of is about 2000 and the code rate is 1/2 to 2/3.
Unfolding Graphs for Constructing of Short and Moderate-Length LT Codes
Gong Mao-kang
2009, 31(4): 885-888. doi: 10.3724/SP.J.1146.2008.00218
This paper proposes one construction method for short and moderate-length Luby Transform (LT) codes by unfolding Tanner graphs from every output node as root. For each output node, when the stopping criterion is satisfied, one uncovered input node or one input node on the deepest layer is randomly selected and connected to the root. Two parameters, the unfolding depth threshold and the maximal unfolding depth, are adjusted to control the girth of short cycles and make the range of random selection as large as possible. Simulation shows the performance improvements of the proposed algorithms are obvious compared with the random graph method for short and moderate length LT code.
Research on a New Spread Spectrum Sequence Pairs
Li Zhao-bin, Jiang Ting, Zou Wei-xia, Zhou Zheng
2009, 31(4): 889-892. doi: 10.3724/SP.J.1146.2007.01944
A new perfect correlation signal is proposed, which can be called as Pseudorandom Punctured Sequence Pairs (PPSP). The properties and combinatorial admissibility conditions of PPSP are studied. By making use of these properties and conditions, the efficiency of searching the PPSP can be improved significantly. As a computational illustration, a set of pseudorandom punctured sequence pairs are given. The performances of PPSP are analyzed and compared with m sequence in spread spectrum communication. The simulation results show that the performances of PPSP are better than m sequence in some conditions.
A Joint Load Control Algorithm with Terminal Selection for the Reconfigurable Systems
Feng Zhi-yong, Zhang Ping, Zhang Yong-jing, Cai Hu-ying
2009, 31(4): 893-896. doi: 10.3724/SP.J.1146.2007.01895
Based on the current end-to-end reconfigurable system architecture, an enhanced dynamic threshold joint load control algorithm is proposed to adapt to the load balancing requirements under different load conditions in order to achieve efficient resource utilization. Considering the terminal reconfigurability and the service variety, an AHP-based terminal selection algorithm is adopted for the network-initiated vertical handover process to balance the load of heterogeneous networks while reducing the system overhead as well as the impact on end-user. Simulation results show that the proposed algorithms are effective in relieving congestion and improving the system performance across the overlapped networks while guaranteeing the users satisfaction.
A Microeconomics Based Dynamic Spectrum Management Algorithm for Cognitive Wireless Networks
Le Van-bien, Lin Yue-wei, Wang Xiao-meng, Feng Zhi-yong, Zhang-Ping
2009, 31(4): 897-902. doi: 10.3724/SP.J.1146.2007.01890
This paper investigates a Microeconomics Based Dynamic Spectrum Management (MB-DSM) scheme to enhance the spectrum utilization and maximize the profit of operators for cognitive heterogeneous networks. The economic factor of the spectrum is considered in order to guarantee the rationality for the spectrum trading. Especially, a space division model is proposed based on Geographical Information System (GIS) to handle the interference issue among wireless systems. As a potential tool for promoting distributed autonomous radio resource optimization algorithms, game theory is applied to investigate a win-win solution for spectrum trading. The simulation results reveal that MB-DSM scheme not only improves the spectrum utilization and the operators profit, but also mitigates effectively the interference between wireless networks.
A Frequency Reuse Scheme for OFDMA Systems
Xu Fang-min, Tao Xiao-feng, Zhang Ping
2009, 31(4): 903-906. doi: 10.3724/SP.J.1146.2007.01663
Frequency reuse, as an efficient strategy to improve Cell-Edge User (CEU) performance, has already been well studied. However, improving spectral efficiency, as well as enhancing performance for CEU, is still left for an open research issue, especially for Orthogonal Frequency Division Multiple Access (OFDMA)-based 4th generation (4G) systems. Hence, a frequency reuse scheme which improves CEU performance by inter-cell interference mitigation is proposed for OFDMA systems here. In the meantime, to achieve a frequency reuse factor near 1, different frequency reuse strategies are assigned to cell-edge and cell-center due to the discrepancy between them. Simulation results demonstrate that, compared with full frequency reuse without frequency planning, the proposed frequency reuse scheme improves system throughput and CEU throughput significantly.
Adaptive Bandwidth and Sub-carrier Allocation for OFDMA Downlinks
Liu Min, Xu Da-zhuan
2009, 31(4): 907-910. doi: 10.3724/SP.J.1146.2007.01786
This paper addresses adaptive resource allocation for OFDMA downlinks. A sub-optimal two-step sub-carrier allocation scheme is proposed to minimize the outage probability for a total transmit power budget. A characteristic of bandwidth and sub-carrier allocation is analyzed, and a two-step sub-carrier allocation scheme is proposed, which distributes bandwidth and sub-carriers among users based on available resource, QoS requirements and channel state information. Simulation results demonstrate that the proposed algorithms can achieve low outage probability while meet the total power budget.
Decision Feedback Blind Equalization Algorithm Based on RENYI Entropy for Underwater Acoustic Channels
Zhang Yin-bing, Zhao Jun-wei, Li Jin-ming, Sun Yong
2009, 31(4): 911-915. doi: 10.3724/SP.J.1146.2008.00056
In order to depress the severe Inter-Symbol Interference (ISI) caused by multi-path fading, channels must be equalized in underwater communication systems. To enhance the convergence ability of the traditional Constant Modulus Algorithm with Decision Feedback Equalization (CMA-DFE), a decision feedback blind equalization algorithm based on RENYI entropy is proposed in this paper. The proposed algorithm adjusts the forward equalizer coefficients with RENYI entropy algorithm and the backward equalizer coefficients with CMA algorithm. Compared with CMA-DFE, RENYI-DFE algorithm has accelerated the convergence speed of the blind equalizer with only little computational cost. The performance of the algorithm is validated by computer simulations.
Indirect Adaptive Equalization Algorithm for Shallow Water Acoustic Communication
Wei Xin, Zhao Li, Zou Cai-rong
2009, 31(4): 916-919. doi: 10.3724/SP.J.1146.2007.01979
To eliminate inter-symbol interference brought from the shallow water acoustic channel which has property of time varying and multi path, an indirect adaptive equalization algorithm is proposed in this paper. A frame structure is designed, adapted to shallow water acoustic communication system in the transmitter. At receiver, frame header is used to perform fast channel estimation and initialization of equalization tap coefficients, the thresholds are set to activate taps of special position, and a variable step LMS adaptive algorithm is chosen to reduce further error when receiving frame body symbols. Theoretical analysis and simulation results show that the algorithm has fast convergence and low hardware complexity. Besides, it has good effect on the high-order modulated signal. Therefore, it will be suitable for shallow water high speed digital communication system.
An Asynchronous Spectrum Sensing Period Optimization Model and Adaptive Fuzzy Adjustment Algorithm
Guo Cai-li, Zeng Zhi-min, Feng Chun-yan, Liu Zi-qi
2009, 31(4): 920-924. doi: 10.3724/SP.J.1146.2008.00141
Based on the analysis of primary users spectrum-usage characteristics, an asynchronous sensing period optimal model on minimal costs of channels is presented, and an Adaptive Fuzzy Adjustment Algorithm (AFAA) of spectrum sensing period is proposed for time-varying spectrum-usage characteristics. The AFAA can adjust sensing period adaptively in real time using fuzzy logic with parameters optimization. Experimental results show that the AFAA is effective under many kinds of situations where spectrum-usage probability distributives as well as the change rates of these distributive parameters are different, and has better stability when the variation of distributive parameters is high.
Wireless Ad hoc Network Flow Control Model Based on Non-Cooperative Game Theory
Feng Hui-bin, Zhang Shun-yi, Liu Chao, Wang Pan, Yan Jun-rong
2009, 31(4): 925-928. doi: 10.3724/SP.J.1146.2007.01925
According to wireless Ad hoc network flow control and wireless channel characteristic, the flow utility function based on network flow rate and delay is constructed by using non-cooperative game theory, then the no-cooperative wireless ad hoc network flow control model is proposed, finally the existence of models Nash equilibrium is proved and the Nash equilibrium idiographic form is presented. Numeric simulation results show the existence of models Nash equilibrium, it can control the network flow effectively and satisfies the QoS demand of various user flows in the network.
An ID-based Key Pre-distribution Scheme for Wireless Sensor Networks
Zhang Rui, Liu Ji-qiang, Zhao Jia
2009, 31(4): 929-932. doi: 10.3724/SP.J.1146.2007.02010
Pairwise key establishment is a fundamental security service in sensor networks. It enables sensor nodes to communicate securely with each other using cryptographic techniques. However, due to the resource constraints on sensors, it is infeasible to use traditional key management techniques. To facilitate the study of novel pairwise key predistribution techniques, this paper presents a new framework for establishing pairwise keys between sensors on the basis of an ID-based key predistribution protocol. In this paper key agreement uses hash calculation and comparison instead of broadcasting; it reduces communication consumption on sensors. This paper then analyses the security and overhead and compares with previous schemes. The results show our scheme is superior to the existing approaches, and it can save communication resources.
Research on Energy Efficiency of Clustered Communication Schemes in One-Dimensional Wireless Sensor Networks
Xie Pei-zhong, Zheng Bao-yu
2009, 31(4): 933-936. doi: 10.3724/SP.J.1146.2007.01914
On the base of analysis about energy efficient schemes for data transmissions including cluster-based traditional scheme and cooperative diversity, a communication scheme--cluster-based multiuser diversity data transmission scheme is proposed to improve energy efficiency of the wireless sensor networks. The theory analysis shows that energy consumption depends on data aggregation ratio, transmission power of intracluster communication, reception power of intercluster communication, the cost energy of circuit and number of sensors within a cluster. The simulation result verifies that the proposed communication scheme provides the best energy efficiency.
A New Hierarchical Identity-Based Encryption in the Standard Model
Zhang Le-you, Hu Yu-pu, Wu Qing
2009, 31(4): 937-941. doi: 10.3724/SP.J.1146.2007.01868
In this paper, a new Hierarchical Identity-Based Encryption(HIBE) scheme is proposed and is provable security in the generalized selective-ID model in the standard model. Under the decision Bilinear Diffie-Hellman Inversion (BDHI) assumption, this new scheme is provable security against Chosen Plaintext Attacks(CPA). Additionally, a Hierarchical Identity-Based Signature (HIBS) scheme is proposed based on the Waterss scheme and our technique in the standard model. And under Diffie-Hellman Inversion(DHI) assumption, it is provable security against existentially unforgeable under an adaptive chosen message attack.
Trace Representation of Primitive -LFSR Sequences and Its Application
Zhang Meng, Zeng Guang, Han Wen-bao, He Kai-cheng
2009, 31(4): 942-945. doi: 10.3724/SP.J.1146.2008.00028
-LFSR is a kind of word-oriented LFSR with high efficiency and good cryptographic properties, especially suitable for modern processors. It can be used in stream cipher for fast software implementation. But in practicality, primitive -LFSR sequences are of the most importance. Firstly, by the iterative relationship of the primitive -LFSR sequences and the trace function in finite fields, the explicit expression of primitive -LFSR sequences is presented. Therefore the trace representation is gotten; then a sufficient and necessary condition is obtained due to the trace representation. It can be used to check whether a -LFSR sequence is primitive or not. They provide the new tool for further research of primitive -LFSR sequences.
Analysis and Correction of Courtois Attack to KeeLoq Cipher
Zhang Bin, Wang Qiu-yan, Jin Chen-hui
2009, 31(4): 946-949. doi: 10.3724/SP.J.1146.2007.01962
KeeLoq is a block cipher designed by Willem Smit which is used in wireless devices that unlock doors in cars. Four slide-algebraic attacks that can break KeeLoq in practice are presented by Courtois et al. in 2007. The computing complexity of the fourth slide-algebraic attack is the smallest. However, the principle of Courtois fourth slide-algebraic attack is proved to be wrong in this thesis, so it can not break KeeLoq. The correction is made on Courtois fourth slide-algebraic attack and the improving attack is proposed. With 232 known plaintexts, the computing complexity of the improving attack is about O(248) KeeLoq encryptions for obtaining key and the success rate is 1. For 26% of keys in KeeLoq, the first 64 rounds of KeeLoq have 2 or more fixed points, then the computing complexity of the improving attack which uses algebraic attack could decrease to O(248) KeeLoq encryptions.
A Cheater Detectable VCS Based on Cumulative Array
Yu Bin, Xu Xiao-hui, Fang Li-guo
2009, 31(4): 950-953. doi: 10.3724/SP.J.1146.2007.01990
A cheater detectable Visual Cryptography Scheme(VCS) based on cumulative array which can find the cheater without extra information and does not show any information of the secret image is introduced in this paper. Compared to previous schemes, it is more convenient and can find more cheaters.
A Novel Quantum Key Distribution Protocol Based on Quantum Error Correction Code
Zhao Sheng-mei, Li Miao-miao, Zheng Bao-yu
2009, 31(4): 954-957. doi: 10.3724/SP.J.1146.2007.01866
Quantum cryptograph ensures the absolute security of key distribution on physics. However, not too high key transmission efficiency will be further reduced because of the noise in the quantum channel of key distribution. Having great flexibility with respect to block-length and rate, quantum Low Density Parity Check (LDPC) code based on sparse-graph becomes a hot topic in quantum error correction. Borrowing from the idea that the transmission reliability can be improved with error correction code in classical communications, a novel BB84 key distribution protocol is designed based on quantum LDPC in this paper. By numerical simulation, the effect of quantum error correction code on BB84 protocol is analyzed in the case of the transmission efficiency. The results show that quantum LDPC codes have good ability to overcome the noise, raise the transmission efficiency, and verify the availability of the proposed model.
2D Scattering Centers Extraction of Objects Based on GTD Model
Wang Jing, Zhou Jian-jiang, Wang Fei
2009, 31(4): 958-962. doi: 10.3724/SP.J.1146.2007.01819
To describe accurately high frequency electromagnetic scattering of the stealthy object, the GTD model is introduced in this paper, instead of the DE model which is described the normal object mainly by studying their specular scattering. Traditional matrix pencil method needs large computational load and additional step of pairing. Therefore modified matrix pencil method and two dimensional (2D) ESPRIT method are proposed in this paper to extract the scattering centers based on GTD model to avoid these drawbacks. Simulations show that these two methods can be applied to the scatterers extraction from the stealthy objects whose main scattering centers are formed by the edge diffraction.
Research on SPMs Energy Model for Low Power Compilation
Jiang Xiang-tao, Hu Zhi-gang, He Jian-biao
2009, 31(4): 963-967. doi: 10.3724/SP.J.1146.2008.00070
In order to achieve a better application effect of Scratch-Pad Memory(SPM), it,s appropriate to construct a proper SPMs performance and power-consumption model to guide the compiling optimization process. The existing power-consumption modeling can only provide SPM,s average access power-consumption which didnt reflect the characteristic that the actual circuits power-consumption varied as the input varied. It restricts further optimization. This thesis proposes to construct SPMs basic power-consumption modeling according to the circuit structure and generate modeling,s parameters based on program,s runtime information. These can reflect the circuits actual active degree when different programs executed. Shown in the experiment, the power-consumption measured is basically as accurate as the one that based on the existing statistical method on average. Furthermore, the new modeling can reflect the difference of power-consumption when different programs access SPM. This technique has an important guiding significance to the access mode as the compliers optimize SPM.
Compression of Complex Networks Based on Multiscale Geometric Analysis
Wang Xiao-hua, Yang Xin-yan, Jiao Li-cheng
2009, 31(4): 968-972. doi: 10.3724/SP.J.1146.2007.01860
Many systems are characterized by multiscale features in nature, and the systems are frequently observed and measured in different scales. Complex networks can be regarded as the refined model for describing complex systems. The multiscale geometric analysis provides a powerful microscopy to observe the structures of complex systems. Consequently, complex networks can be analyses via multiscale geometric analysis. Keeping in mind this ides, a compression strategy based on multiscale geometric analysis is proposed for depicting the structure of complex networks with the small amount of information. The analysis and the experiments indicate that the proposed method is feasible, and performs as a sparsely representing for successfully understanding and compressing networks, which can be useful for analyzing networks with the small amount of information.
Study on Clutter Suppression Algorithm for Airborne Radar with Non-sidelooking Arrays
Gong Qing-yong, Zhu Zhao-da
2009, 31(4): 977-980. doi: 10.3724/SP.J.1146.2007.01826
Since the airborne radar clutter spectrum varies with the range for non-sidelooking arrays, the clutter covariance matrix can not be estimated by the neighboring range cells due to the non-homogenous in range. To resolve the range-dependent clutter non-homogenous problem, especially for the short range cell, an improved Doppler warping algorithm is proposed in this paper, which implemented the space frequency compensation in element-Doppler domain for the Doppler warping compensated data, and results in an improved mainlobe clutter suppression performance. Compared with the original algorithm, the proposed algorithm is also simple and easy to be realized. In addition, it overcomes the performance degradation under big crab angle. Simulation results verify the validity of this method.
Effects of the Electromagnetic-Field-Combined Profile of Radar and Decoy on Direction-Finding System of Anti-Radiation Missile
Zhou Wei-guang, Luo Ji-run, Wang Hua-bin
2009, 31(4): 981-984. doi: 10.3724/SP.J.1146.2007.02003
Under the consideration of field pattern and polarization, a mathematic model related to the filed radiated from the antenna of radar and decoy is presented. Based on the mechanism of two-channel direction-finding systems with four-arm spiral antenna, the simulation algorithms and formulae are introduced and the tracking characteristic of Anti-Radiation Missile (ARM) is analyzed when the system is exposed in the electromagnetic-field-combined profile of radar and decoy. Numerical results show that ARM may be decoyed to a trapped area if the power and initial phase of the radiation filed of the decoy relative to the radar are set to some appropriate values.
Bit Confidence-Based Soft Decision Metric Generation for QAM
Zhao Jin, Zhang Jian-qiu
2009, 31(4): 985-988. doi: 10.3724/SP.J.1146.2007.01907
In modern communication systems, a channel decoder usually employs the soft input to guarantee a high channel decoding gain. A new soft decision metric for QAM is presented in this paper. Unlike traditional soft decision metric based on minimum Euclidean distance, the proposed metric is based on the bit confidences. Compared to traditional soft decision metric, the one presented in this paper can guarantee the channel decoder performance with less computation complexity. The numerical results applying the proposed method to the DTMB system indicate that the proposed soft decision metric reduces the computation complexity without any performance degradation. These results also show that the proposed metric is a good alternative for soft decision generations.
Performance Research on DDB-HARQ for Irregular LDPC Codes
Xu Cheng-xin, Chang Yong-yu, Yang Da-cheng
2009, 31(4): 989-992. doi: 10.3724/SP.J.1146.2007.01841
In this paper, a progressive HARQ scheme based on degree distribution for irregular LDPC codes is proposed. The proposed scheme considers Unequal Error Protection (UEP) of irregular LDPC codes as well as degree distribution while choosing some bits for retransmission. Compared with initial Degree Distribution Based HARQ (DDB-HARQ) scheme, this scheme improves system performance such as bit error rate and throughput.
A New Approach to Improve the Spectrum Sensing in Cognitive Radio in Low SNR Environment
Liu Hang, Yu Dan, Kong Xiang-wei
2009, 31(4): 993-996. doi: 10.3724/SP.J.1146.2007.01999
A spectrum sensing approach is proposed to improve the spectrum sensing of Cognitive Radio (CR) in the strong noise environment. The proposed method can increase the accuracy of signals classification in the low SNR environment using spectral correlation function and two-stage classification. The results show that above 99.9% received signals that are composed of five kinds of modulation signals are correctly classified in AWGN channel at SNR=-10dB and above. The performance can satisfy the requirement of spectrum sensing in Cognitive Radio.
A Feasibility Strategy of Truncation Points for Rate Distortion Optimality
Zhou Ying-hong, Ma Zheng-ming
2009, 31(4): 997-1000. doi: 10.3724/SP.J.1146.2007.01599
A feasibility strategy of truncation points for rate distortion optimality is presented. The new algorithm reorders the positions of truncation points associated with refinement passes according to the steepest rate-distortion slope. The proposed scheme reduces the unfeasible truncation points to 50% compared with JPEG2000; gives a finely embedded bitstream, achieves an improvement of PSNR over JPEG2000 0.1dB~0.2dB, and attains a speed-up of the bit-plane encode time compared with JPEG2000.
Self-healing Strategy of Mesh Network Based on Loop Free Alternative Rerouting
Wu Jing, Guo Cheng-cheng, Yang Jian-feng
2009, 31(4): 1001-1003. doi: 10.3724/SP.J.1146.2007.02018
The low reliability of links in wireless mesh network always leads to instability and discontinuity, and proactive rerouting can relax that pressure. The self-healing strategy of wireless mesh network based on loop free alternative rerouting is researched. AODV routing is extended to support loop free alternative and AODV-LFA routing is presented. The simulation shows that AODV-LFA is more effective than AODV for self-healing of wireless mesh network.
A Novel UWB Magnetic Antenna
Zhao Bo, Zhang Xiao-juan, Fang Guang-you
2009, 31(4): 1004-1006. doi: 10.3724/SP.J.1146.2007.01952
A novel compact UWB magnetic antenna is designed and manufactured. This antenna has a balanced feed , moreover, numeric simulations and experiments are carried out to investigate its return loss, radiation behavior, and time-domain response. The antenna offers 107% impedance bandwidth under VSWR2 and 100% radiation bandwidth, which covers ultra wideband frequency spectrum applications. The achieved performance in the band has fairly constant5dB gain, and suitability for pulse transmission with minimized distortions. Further more, it have relatively large magnetic near-fields that are difficult to undesired coupling with near-by objects, so it is very suitable for application to some environment cluttered up with objects such as home. It makes some sense to the application.
A Novel Compact Wideband Planar Electromagnetic Band-Gap Structure
Liu Tao, Cao Xiang-yu, Ma Jia-jun
2009, 31(4): 1007-1009. doi: 10.3724/SP.J.1146.2007.01945
Aiming at the characteristic of relative narrower bandwidth of present Electromagnetic Band-Gap (EBG) structure, according to the physical mechanism of EBG structures and equivalent circuit model, a novel compact wideband planar EBG structure is proposed constructed on low permittivity low-cost substrate in this paper. The measured results show that relative bandwidth of the novel structure reaches 54.1% and obtain more than 100% bandwidth improvement, and simultaneously the center frequency is reduced by 25.2%. The objective of realizing compact wideband UC-EBG structure is attained.
Study of the Influence of Booms on Spaceborne Electric Field Sensors
Yang Ji, Chen Xian-xiang, Zhou Jie, Ren Ren, Xia Shan-hong
2009, 31(4): 1010-1012. doi: 10.3724/SP.J.1146.2007.01967
The electromagnetic interferences generated by the spacecraft or other payloads to the spaceborne electric field sensor can be significantly reduced by introduction of booms. However, the boom potential may differ from the sensor; so the boom sheath may extend over the sheath of the sensor probe and affect the electric field measurement. In order to evaluate the amount of disturbance, SPIS (Spacecraft Plasma Interaction System) and Particle in Cell method are used to compute the collected current of the sensor probe under the condition of different potential between the sensor probe and the boom. The plasma parameters, boom and electric field sensor models are got from the DEMETER satellite. The results indicate that when the boom potential is lower than the sensor probe, it introduces small disturbances on the sensor operation, when boom potential is higher than the sensor probe, there is a noticeable change in the sensor current collected. And the higher potential difference between the boom and sensor, the more disturbances will be introduced. With the enlarging of the plasma density, the disturbance is reduced because of the small Debye length.
Research on the Thermal Analysis of PCB Circuit
Sun Jian, Ding Yao-gen, Chen Zhong-lin
2009, 31(4): 1013-1016. doi: 10.3724/SP.J.1146.2007.01904
In this article, the ANSYS modeling problem of PCB thermal reliability analysis is studied. By ANSYS analysis, two conclusions can be drawn: (1) Copper lead on PCB has significant thermal transmission effect, so it should not be omitted in modeling. (2) Component with little inner to exterior thermal resistance can be modeling as a simple block. Based on these conclusions, the ANSYS modeling of a satelliteborne PCB equipment is largely simplified. Compared the ANSYS calculation results with experiment datas, it is proved that the simplified modeling method achieves adequate precision and is very convenience to use. This technique can be adopted in the thermal reliability analysis of PCB equipments , especially for satelliteborne or vacuum environments.
The Approach Suppressing Sidelobe of Sum Beam and Different Beam only Adopting One Kind of Analog Weighting
Hu Hang, Liu Wei-hui
2009, 31(4): 973-976. doi: 10.3724/SP.J.1146.2007.01856
For the phased array radar system at subarray level employing monopulse technique, it requires to suppress sidelobe of sum beam and different beam simultaneously. This paper investigates the approach which only applies one kind of analog weighting at element level combined with the digital weighting at subarray level to suppress sidelobe of sum and different beam. At first constructing sum channel and difference channel, then making optimum adaptive filtering for the supposed jammer within the whole sidelobe area of sum and difference beam, the desired analog weight is determined. In order to further improve sidelobe suppression effect, the digital weighting at subarray level is then adopted, which approximates to the conventional Taylor and Bayliss weight respectively. This approach reduces the hardware cost and complexity effectively, and makes full use of the flexibility of digital processing. Simulation results demonstrate the validity of the introduced approach.