Estimation method of DOA for DS-UWB signal

Direction of arrival (DOA) estimation is one of the key technologies in smart antennas in the direct sequence ultra wideband (DS-UWB) system. Traditional DOA estimation methods based on narrow-band signals are not suitable for such system. Therefore, a fourth-order cumulant-based estimation method ofDOA for DS-UWB signal is proposed. This method is set on the frequency domain model of DS-UWB array signal. Simulation results show that the algorithm is effective and can guarantee adequate estimation accuracy. __________ Translated from Journal of University of Electronic Science and Technology of China, 2007, 36(2): 190–192 [译自: 电子科技大学学报]     

Highly robust ground moving target detection and relocation method for distributed satellites

The performance of ground moving target detection for distributed satellites will be affected significantly when there is an image registration error, clutter decorrelation and array error. In this paper, a new approach to moving target detection and relocation is proposed based on multi-channel and multi-pixel adaptive signal processing in an image domain. First, multichannel and multi-pixel joint data are equated to a simple array model. Given that there is an image registration error, the real steering vector of the moving target can be estimated through a space projection approach. The optimal beam forming approach is used to cancel clutter, and at the same time the cross-track velocity of the moving target can be determined by searching for the peak value of the cost function. The moving target can then be relocated on the SAR image. The simulation results indicate that this method has a good robustness to image registration error, clutter decorrelation and array error. The detection performance and the estimation accuracy are significantly improved. __________ Translated from Acta Electronica Sinica, 2007, 35(6): 1009–1014 [译自: 电子学报]     

New mutual coupling compensation method and its application in DOA estimation

A new mutual coupling compensation method based on a new mutual impedance matrix, as well as its application to dipole arrays, are proposed. This new mutual impedance matrix is deduced by electromotive force (EMF) method, based on the current distribution obtained by the characteristic basis function method. It appears in a concise and explicit formulation that facilitates the numerical calculation. The compensation performance is demonstrated and evaluated through its application in direction of arrival (DOA) estimation. Numerical results show that the proposed method exhibits excellent compensation performance compared with conventional mutual impedance matrix approaches. __________ Translated from Chinese Journal of Radio Science, 2007, 22(4): 541–545 [译自: 电波科学学报]     

Text clustering based on fusion of ant colony and genetic algorithms

Focusing on the problem that the ant colony algorithm gets into stagnation easily and cannot fully search in solution space, a text clustering approach based on the fusion of the ant colony and genetic algorithms is proposed. The four parameters that influence the performance of the ant colony algorithm are encoded as chromosomes, thereby the fitness function, selection, crossover and mutation operator are designed to find the combination of optimal parameters through a number of iteration, and then it is applied to text clustering. The simulation results show that compared with the classical k-means clustering and the basic ant colony clustering algorithm, the proposed algorithm has better performance and the value of F-Measure is enhanced by 5.69%, 48.60% and 69.60%, respectively, in 3 test datasets. Therefore, it is more suitable for processing a larger dataset. __________ Translated from Journal of Xi’an Jiaotong University, 2007, 41(10): 1146–1150 [译自: 西安交通大学学报]     

Power allocation scheme for multicell interference coordination in OFDMA systems

To coordinate inter-cell interference, a multicell adaptive power allocation scheme is proposed for downlink orthogonal frequency division multiple access (OFDMA) cellular systems. This scheme uses the difference of the signal to interference plus noise ratio (SINR) between the co-subchannels of adjacent cells to balance SINR for coordinating the transmit power in the co-subchannels. The scheme can improve edge user performance, reduce interference between the co-subchannels of adjacent cells and improve radio resource utility. Simulation results show that the scheme can balance system performance and ensure system throughput. __________ Translated from Journal of Beijing University of Posts and Telecommunications, 2008, 31(1): 71–74 [译自: 北京邮电大学学报]     

Indoor and outdoor people detection and shadow suppression by exploiting HSV color information

An adaptive background model based on maximum statistical probability and a shadow suppression scheme for indoor and outdoor people detection by exploiting hue saturation value (HSV) color information is proposed. To obtain the initial background scene, the frequency of R, G, and B component values for each pixel at the same position in the learning sequence are respectively calculated; the R, G, and B component values with the biggest ratios are incorporated to model the initial background. The background maintenance, or the socalled background re-initiation, is also proposed to adapt to scene changes such as illumination changes and scene geometry changes. Moving cast shadows generally exhibit a challenge for accurate moving target detection. Based on the observation that a shadow cast on a background region lowers its brightness but does not change its chromaticity significantly, we address this problem in the article by exploiting HSV color information. In addition, quantitative metrics is introduced to evaluate the algorithm on a benchmark suite of indoor and outdoor video sequences. The experimental results are given to show the performance of the algorithm. __________ Translated from Journal of Huaqiao University (Natural Science), 2007, 28(1): 30–33 [译自: 华侨大学学报 (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)]     

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)]     

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]     

Robust adaptive output feedback control of nonlinearly parameterized systems

The ideas of adaptive nonlinear damping and changing supply functions were used to counteract the effects of parameter and nonlinear uncertainties, unmodeled dynamics and unknown bounded disturbances. The high-gain observer was used to estimate the state of the system. A robust adaptive output feedback control scheme was proposed for nonlinearly parameterized systems represented by input-output models. The scheme does not need to estimate the unknown parameters nor add a dynamical signal to dominate the effects of unmodeled dynamics. It is proven that the proposed control scheme guarantees that all the variables in the closed-loop system are bounded and the mean-square tracking error can be made arbitrarily small by choosing some design parameters appropriately. Simulation results have illustrated the effectiveness of the proposed robust adaptive control scheme. Translated from Journal of Sichuan University (Engineering Science Edition), 2006, 38(4): 136–140 [译自: 四川大学学报 (工程科学版)]     

Analytical delay models for RLC interconnects under ramp input

Analytical delay models for Resistance Inductance Capacitance (RLC) interconnects with ramp input are presented for different situations, which include overdamped, underdamped and critical response cases. The errors of delay estimation using the analytical models proposed in this paper are less by 3% in comparison to the SPICE-computed delay. These models are meaningful for the delay analysis of actual circuits in which the input signal is ramp but not ideal step input. Translated from Journal of Shanghai Jiaotong University, 2006, 40(3): 373–376 [译自: 上海交通大学学报]     

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]     

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)]     

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]     

Adaptive fuzzy sliding mode control of Lorenz chaotic system

By using the exponential reaching law technology, a sliding mode controller was designed for Lorenz chaotic system subject to an unknown external disturbance. On this basis, considering the unknown disturbance, an adaptive law was introduced to adaptively estimate the parameters of the disturbance bounds. Furthermore, to eliminate the chattering resulting from the discontinuous switch controller and to guarantee system transient performance, a new adaptive fuzzy sliding mode controller was designed. The results of the simulation show the effectiveness of the proposed control scheme. Translated from Journal of Harbin Institute of Technology, 2006, 38(4): 499–502 [译自: 哈尔滨工业大学学报]     

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)]     

A cross-layer adaptive transmission scheme over correlated fading channels

Conventional adaptive transmission schemes perform poorly in wireless correlated slow-fading channels. A cross-layer adaptive transmission scheme combined with selective repeat automatic repeat request (SR-ARQ) is proposed. We apply a multi-state Markov system model for analyzing the performance of systems and optimizing the selection of modulation levels and packet sizes in correlated fading channels, which is also described by a finite-state Markov chain. A general closed-form expression of the average throughput for our suggested scheme is presented. Numerical results show that our adaptive scheme combined with SR-ARQ can obtain good performance in correlated fading channels. Translated from Journal on Communications, 2006, 45(1): 35–41 [译自: 通信学报]     

A new method for improving efficiency of protocol testing

Traditional solutions have encountered some bottleneck in improving the efficiency of protocol testing. A novel method that records the test sequence dynamically is proposed. Three dynamically reordering algorithms are brought forward in line with different fault conditions. The impact of the new method of testing efficiency is also presented. Simulation results demonstrate that the proposed solution is better than the traditional ones in terms of testing efficiency. Translated from Journal of University of Science and Technology of China, 2006, 36(8): 882–886 [译自: 中国科学技术大学学报]     

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)]     

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]