Robust adaptive beamforming algorithm based on Bayesian approach

The performance of adaptive array beamforming algorithms substantially degrades in practice because of a slight mismatch between actual and presumed array responses to the desired signal. A novel robust adaptive beamforming algorithm based on Bayesian approach is therefore proposed. The algorithm responds to the current environment by estimating the direction of arrival (DOA) of the actual signal from observations. Computational complexity of the proposed algorithm can thus be reduced compared with other algorithms since the recursive method is used to obtain inverse matrix. In addition, it has strong robustness to the uncertainty of actual signal DOA and makes the mean output array signal-to-interference-plus-noise ratio (SINR) consistently approach the optimum. Simulation results show that the proposed algorithm is better in performance than conventional adaptive beamforming algorithms. __________ Translated from Journal of Northeastern University (Natural Science), 2007, 28(6): 793–796 [译自: 东北大学学报 (自然科学版)]     

Research on food-chain algorithm and its parameters

Based on the characteristics of colony emergence of artificial organisms, their dynamic interaction with the environment, and the food-chain crucial to the life system, the rules of local activities of artificial organisms at different levels are defined. The article proposes an artificial life-based algorithm, which is referred to as the food-chain algorithm. This algorithm optimizes computation by simulating the evolution of natural ecosystems and the information processing mechanism of natural organisms. The definition, idea and flow of the algorithm are introduced, and relevant rules on metabolic energy and change in the surroundings where artificial-life individuals live are depicted. Furthermore, key parameters of the algorithm are systematically analyzed. Test results show that the algorithm has quasi-life traits that include being autonomous, evolutionary, and self-adaptive. These traits are highly fit for optimization problems of life-like systems such as the location-allocation problem of a distribution network system. __________ Translated from Journal of Northeastern University (Natural Science), 2007, 28(7): 993–997 [译自: 东北大学学报(自然科学版)]     

Multi-image gradient-based algorithms for motion measurement using wavelet transform

A multi-image wavelet transform motion estimation algorithm based on gradient methods is presented by using the characteristic of wavelet transform. In this algorithm, the accuracy can be improved greatly using data in many images to measure motions between two images. In combination with the reliability measure for constraints function, the reliable data constraints of the images were decomposed with multi-level simultaneous wavelet transform rather than the traditional coarse-to-fine approach. Compared with conventional methods, this motion measurement algorithm based on multi-level simultaneous wavelet transform avoids propagating errors between the decomposed levels. Experimental simulations show that the implementation of this algorithm is simple, and the measurement accuracy is improved. __________ Translated from Journal of South China University of Technology (Natural Science Edition), 2007, 35(1): 39–43 [译自: 华南理工大学学报(自然科学版)]     

Blind source separation algorithm for communication complex signals in communication reconnaissance

Most blind source separation algorithms are only applicable to real signals, while in communication reconnaissance processed signals are complex. To solve this problem, a blind source separation algorithm for communication complex signals is deduced, which is obtained by adopting the Kullback-Leibler divergence to measure the signals’ independence. On the other hand, the performance of natural gradient is better than that of stochastic gradient, thus the natural gradient of the cost function is used to optimize the algorithm. According to the conclusion that the signal’s mixing matrix after whitening is orthogonal, we deduce the iterative algorithm by constraining the separating matrix to an orthogonal matrix. Simulation results show that this algorithm can efficiently separate the source signals even in noise circumstances. __________ Translated from Journal of Huazhong University of Science and Technology (Natural Science Edition), 2007, 35(4): 33–36 [译自: 华中科技大学学报(自然科学版)]     

Using Petri nets to verify acyclic rule-based system

A series of Petri net-based definitions were formulated for describing four types of structural errors in a rule-based system (RBS), including inconsistency, incompleteness, redundancy and circularity. A marked ω-Petri net model of acyclic RBS was constructed. Then, its reachability tree was generated to record all reachable relations between propositions in RBS. Moreover, a backward reasoning forest of a reachable marking was generated for explicitly representing reachable paths in RBS. Finally, a set of theorems and algorithms were provided to analyze and check structural errors. The usability of the research results presented in this paper was illustrated by an example. __________ Translated from Journal of Tongji University (Natural Science), 2007, 35(2): 232–238 [译自: 同济大学学报(自然科学版)]     

Positioning models and systems based on digital television broadcasting signals

The requirement and feasibility of the positioning system using digital television (DTV) broadcasting signals are analyzed. The principle of DTV positioning on the basis of frame synchronization is brought forward and the ranging characteristic is studied that the observables are asynchronously measured during the same epoch interval. The models of the pseudo-range observation and Doppler carrier phase integral are researched. The system observation and state equations are presented on the basis of the above models. The simulation results showed that DTV positioning technology could remarkably improve the precision of system state estimates using smoothing methods for positioning systems or integrated navigation systems. The DTV positioning that has a sub-meter level ranging error and meter level positioning accuracy can parallel with and even taken as a beneficial substitute for the tradition positioning technology. __________ Translated from Journal of Southeast University (Natural Science Edition), 2006, 36(5): 690–694 [译 自: 东南大学学报(自然科学版)]     

Study and simulation of video communications under wireless environment based on blind source separation

A new scheme is proposed to separate several compressed video signals transferred in multiple wireless channels using the blind source separation method. The scheme selects IEEE 802.11b and XVID compression as the wireless communications channel and MPEG-4 video compression, respectively. A simulation model is then made for the video communications under a wireless environment. The model can separate several video signals using blind source separation. Simulations show that the normalized whiten plus cyclic whiten based on cyclostationary (NWCW-CS) algorithm based upon the cyclostationary characteristics of signals has the best separation performance and fast convergence. Besides, the algorithm can solve the mixing of video signals. The image of the transferred video signals decompressed by XVID is nearly consistent with the source ones. The new method meets the requirement of real-time video communications. __________ Translated from Journal of Southeast University (Natural Science Edition), 2007, 37(1): 13–17 [译自: 东南大学学报(自然科学版)]     

PRF-ambiguity resolution for SAR by contrast minimization in range-Doppler domain

An algorithm was developed to accurately estimate the Doppler centroid, which is needed for high-quality synthetic aperture radar (SAR) image formation by resolving the SAR pulse repetition frequency (PRF) ambiguity. The algorithm uses the SAR range migration to resolve the PRF-ambiguity by searching for a PRF-ambiguity number that minimizes the intensity contrast in the range-Doppler domain. Experimental results show that the approach, compared with traditional methods for resolving the SAR PRF ambiguity, is more suitable for both high contrast scenes such as urban areas and low contrast scenes such as mountains. Moreover, the approach is more computationally efficient for there are no time-consuming correlations or fast Fourier transform (FFT) operations needed in the range-Doppler domain and only part of the range cells are used in the calculation. Translated from Journal of Tsinghua University (Science and Technology), 2006, 46(7): 1 259–1 261 [译自: 清华大学学报(自然科学版)]     

Document image retrieval based on multi-density features

The development of document image databases is becoming a challenge for document image retrieval techniques. Traditional layout-reconstructed-based methods rely on high quality document images as well as an optical character recognition (OCR) precision, and can only deal with several widely used languages. The complexity of document layouts greatly hinders layout analysis-based approaches. This paper describes a multi-density feature based algorithm for binary document images, which is independent of OCR or layout analyses. The text area was extracted after preprocessing such as skew correction and marginal noise removal. Then the aspect ratio and multi-density features were extracted from the text area to select the best candidates from the document image database. Experimental results show that this approach is simple with loss rates less than 3% and can efficiently analyze images with different resolutions and different input systems. The system is also robust to noise due to its notes and complex layouts, etc. Translated from Journal of Tsinghua University (Science and Technology), 2006, 46(7): 1 231–1 234 [译自: 清华大学学报 (自然科学版)]     

Medical image lossless compression based on combining an integer wavelet transform with DPCM

To improve the classical lossless compression of low efficiency, a method of image lossless compression with high efficiency is presented. Its theory and the algorithm implementation are introduced. The basic approach of medical image lossless compression is then briefly described. After analyzing and implementing differential plus code modulation (DPCM) in lossless compression, a new method of combining an integer wavelet transform with DPCM to compress medical images is discussed. The analysis and simulation results show that this new method is simpler and useful. Moreover, it has high compression ratio in medical image lossless compression. __________ Translated from Journal of Northeastern University (Natural Science), 2007, 28(10): 1454–1457 [译自 : 东北大学学报 (自然科学版)]     

Multi-scale Kalman filters algorithm for GPS common-view observation data based on correlation structure of discrete wavelet coefficients

Global positioning system (GPS) common-view observation data were processed by using the multi-scale Kalman algorithm based on a correlative structure of the discrete wavelet coefficients. Suppose that the GPS commonview observation data has the 1/f fractal characteristic, the algorithm of wavelet transform was used to estimate the Hurst parameter H of GPS clock difference data. When 0<H<1, the 1/f fractal characteristic of the GPS clock difference data is a Gaussian zero-mean and non-stationary stochastic process. Thus, the discrete wavelet coefficients can be discussed in the process of estimating multi-scale Kalman coefficients. Furthermore, the discrete clock difference can be estimated. The single-channel and multi-channel common-view observation data were processed respectively. Comparisons were made between the results obtained and the Circular T data. Simulation results show that the algorithm discussed in this paper is both feasible and effective. Translated from Journal of Jilin University (Engineering and Technology), 2006, 36(4): 599–603 [译自: 吉林大学学报 (工学版)]     

A novel distributed algorithm for media access control address assignment in wireless sensor networks

This paper presents a novel distributed media access control (MAC) address assignment algorithm, namely virtual grid spatial reusing (VGSR), for wireless sensor networks, which reduces the size of the MAC address efficiently on the basis of both the spatial reuse of MAC address and the mapping of geographical position. By adjusting the communication range of sensor nodes, VGSR algorithm can minimize the size of MAC address and meanwhile guarantee the connectivity of the sensor network. Theoretical analysis and experimental results show that VGSR algorithm is not only of low energy cost, but also scales well with the network size, with its performance superior to that of other existing algorithms. __________ Translated from Journal of Xidian University, 2006, 33(5): 716–720 [译自: 西安电子科技大学学报 (自然科学版)]     

Image content authentication technique based on Laplacian Pyramid

This paper proposes a technique of image content authentication based on the Laplacian Pyramid to verify the authenticity of image content. First, the image is decomposed into Laplacian Pyramid before the transformation. Next, the smooth and detail properties of the original image are analyzed according to the Laplacian Pyramid, and the properties are classified and encoded to get the corresponding characteristic values. Then, the signature derived from the encrypted characteristic values is embedded in the original image as a watermark. After the reception, the characteristic values of the received image are compared with the watermark drawn out from the image. The algorithm automatically identifies whether the content is tampered by means of morphologic filtration. The information of tampered location is p resented at the same time. Experimental results show that the proposed authentication algorithm can effectively detect the event and location when the original image content is tampered. Moreover, it can tolerate some distortions produced by compression, filtration and noise degradation. __________ Translated from Journal of South China University of Technology (Natural Science Edition), 2007, 35(1): 34–38 [译自: 华南理工大学学报(自然科学版)]     

Power allocation in opportunistic cooperative relaying systems

To enhance the performance of opportunistic cooperative relaying systems, this paper proposes power allocation algorithms aimed at minimizing the outage probability. The optimization model of the system is constructed and proved to be a convex optimization problem. Then the optimal power allocation algorithm and its operation steps are presented. Furthermore, a simple and effective near-optimal power allocation strategy is developed, which only depends on the average channel gains of the relays and thus incurs little overhead. Simulation and numerical results show that significant performance gains can be achieved by the two proposed power allocation algorithms. __________ Translated from Acta Electronica Sinica, 2008, 36(10): 1944–1948 [译自: 电子学报]     

Third-order trajectory planning for high accuracy point-to-point motion

This article studies a third-order trajectory planning method for point-to-point motion. All available instances for third-order trajectory planning are first analyzed. To distinguish those, three criteria are presented relying on trajectory characteristics. Following that, a fast preprocessing approach considering the trajectory as a whole is given based on the criteria constructed and system constraints. Also, the time-optimality of the trajectory is obtained. The relevant formulas are derived with the combination of geometrical symmetry of trajectory and area method. As a result, an accurate algorithm and its implementation procedure are proposed. The experimental results show the effectiveness and precision of the proposed method. The presented algorithm has been applied in semiconductor manufacturing equipment successfully. __________ Translated from Journal of Huazhong University of Science and Technology (Natural Science Edition), 2007, 35(12): 58–61 [译自: 华中科技大学学报 (自然科学版)]     

A topology control algorithm for preserving minimum-energy paths in wireless ad hoc networks

In this paper, a distributed topology control algorithm is proposed. By adjusting the transmission power of each node, this algorithm constructs a wireless network topology with minimum-energy property, i.e., it preserves a minimum-energy path between every pair of nodes. Moreover, the proposed algorithm can be used in both homogenous and heterogeneous wireless networks, and it can also work without an explicit propagation channel model or the position information of nodes. Simulation results show that the proposed algorithm has advantages over the topology control algorithm based on direct-transmission region in terms of average node degree and power efficiency. Translated from Journal of Xidian University, 2006, 33(3): 341–346 [译自: 西安电子科技大学学报]     

Pattern synthesis of antennas based on a modified particle swarm optimization algorithm

In order to overcome the drawbacks of standard particle swarm optimization (PSO) algorithm, such as prematurity and easily trapping in local optimum, a modified PSO algorithm is proposed, in which special techniques, as global best perturbation and inertia weight jump threshold are adopted. The convergence speed and accuracy of the algorithm are improved. The test by some benchmark problems shows that the proposed algorithm achieves relatively higher performance. Thereafter, the applications of the modified PSO in the radiation pattern synthesis of antenna arrays are presented. __________ Translated from Chinese Journal of Radio Science, 2006, 21(6): 873–878 [译自: 电波科学学报]     

Decentralized adaptive robust controller design for complex system based on partition of unity

A new method for designing decentralized adaptive robust controllers was proposed which focuses on a class of more general uncertain complex systems, using the concept of the partition of unity in differential geometry to deal with system uncertainties. In this method the uncertainty of the system to be controlled was normalized firstly, and then the partition of unity that was subordinated to an open covering of state variables compact set was constructed. Subsequently the approximation was realized by using its property that can approximate nonlinear continuous function with arbitrary precision, and then the decentralized adaptive robust controller of complex systems and adaptive laws of approximate parameter estimation were designed. Compared to existing methods, the proposed algorithm requires simpler assumed conditions and no complicated computations. Simulation result shows that the method is valid. Translated from Journal of Xi’an Jiaotong University, 2006, 40(6): 621–625 [译自: 西安交通大学学报]     

Research on network failure handling technology based on deflection routing

A new deflection routing scheme is proposed to overcome the drawback of existing deflection routing scheme that cannot handle node failure and suffer from routing loops. A new algorithm for computing the backup shortest path tree (SPT) is proposed and a set of procedures are defined for utilizing the backup SPT in case of node or link failure. The failure can be handled swiftly and the backup routes are guaranteed to be loop-free. Experimental results show that the backup routes calculated by proposed scheme are close to the optimal routes by totally re-computing. __________ Translated from Journal of Beijing University of Posts and Telecommunications, 2007, 30(6): 1–4 [译自: 北京邮电大学学报]     

Novel P-Cycle protection strategy for asymmetric traffic in mesh optical networks

A novel prefigured-cycle (P-Cycle) algorithm was proposed to improve the protection success ratio for asymmetric traffic in mesh optical networks. The proposed algorithm was simulated in a Pan-European COST239 network environment under an asymmetric dynamic traffic model. The experimental results show that the proposed algorithm has lower capacity redundancy and higher utilization rate of configured resources than traditional P-Cycle methods. Network performance can be improved when implementing this algorithm under single-link failure circumstances. The system behavior is analyzed under different traffic volumes and the configuration strategy is also investigated for the heavyload and light-load networks respectively. __________ Translated from Journal of Beijing University of Posts and Telecommunications, 2008, 31(1): (1–4) [译自: 北京邮电大学学报]