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Cross layer optimization of downlink power allocation in multi-user wireless communication systems
CHEN Wei, CAO Zhigang, FAN Pingyi, Khaled B. Letaief
Front. Electr. Electron. Eng.. 2007, 2 (4): 381-387.
https://doi.org/10.1007/s11460-007-0071-2
In multi-user wireless communication systems, dynamic power allocation is an important means to deal with the time-varying nature of the physical and network layers. However, the current layer optimization approach to power allocation cannot achieve the global optimum of the overall system performance. To solve this problem, a cross-layer optimization framework is presented for downlink power allocation, which takes both the channel and buffer states into account. A cross-layer optimization problem is formulated to optimize the total throughput with queue length and power constraints. An analytical solution and a low complexity dynamic programming algorithm, which are referred as water-filling in cellar (WFIC) policy, are presented to optimize the downlink power allocation. Finally, simulation results are presented to demonstrate the potential of the proposed method.
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A non-linear spatial hearing model based on bases pursuit algorithm
ZHANG Jie
Front. Electr. Electron. Eng.. 2007, 2 (4): 388-394.
https://doi.org/10.1007/s11460-007-0072-1
In the research on spatial hearing and realization of virtual auditory space, it is important to effectively model the head-related transfer functions (HRTFs) or head-related impulse responses (HRIRs). In our study, we managed to carry out adaptive non-linear approximation in the field of wavelet transformation. The results show that the HRIRs adaptive non-linear approximation model is a more effective data reduction model, is faster, and is 5 dB on average better than the traditional principal component analysis (PCA) (Karhunen-Lo?ve transform) model based on relative mean square error (MSE) criterion. Furthermore, we also discussed the best bases choice for the time-frequency representation of HRIRs, and the results show that local cosine bases are more propitious to HRIRs adaptive approximation than wavelet and wavelet packet base. However, the improved effect of local cosine bases is not distinct. Here, for the sake of modeling the HRIRs more truthfully, we consider choosing optimal time-frequency atoms from redundant dictionary to decompose this kind of signals of HRIRs and achieve better results than all the previous models.
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Study on the ionospheric effects with different heat-conditions
HE Fang, ZHAO Zhengyu, NI Binbin, ZHANG Yuannong
Front. Electr. Electron. Eng.. 2007, 2 (4): 420-424.
https://doi.org/10.1007/s11460-007-0078-8
A numerical model has been developed. Based on the numerical simulation results, the spatial effects of the ionosphere, mainly consisting of the change on electron density (ED) and electron temperature (ET), heated by the high frequency (HF) pump wave have been analyzed quantitatively. Results are presented as the space-time evolution regulation on the main parameters of the ionosphere resulted by the HF heating waves under the different heat-conditions, just as different regions, such as high latitude and mid-low latitude; different heating power or frequency, such as under-dense heating and over-dense heating and regions at different altitudes. The heating effects in different regions with different heating conditions have been presented in figures. Finally, some primary conclusions are given by comparing the simulation results with experimental observation.
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One airport detection method based on support vector machine
QU Yanyun, ZHENG Nanning, LI Cuihua
Front. Electr. Electron. Eng.. 2007, 2 (4): 444-448.
https://doi.org/10.1007/s11460-007-0083-y
This paper proposes a novel airport detection method, which integrates the texture features and shape features of the airport. Eight texture features, such as the mean of the region, the deviation of the region, the smoothness of the region, the skewness of a histogram, the uniformity of the region, the randomness of the region, the mean of the gradient image and the deviation of the gradient image, are used to represent the features of the region. In this method, first the long lines are detected and the regions where the lines locate are segmented. Second, support vector machine (SVM) based on Gaussian kernel is used as a classifier which discriminates the runway from other candidate regions. Experimental results show that the error rate of the proposed method is lower than those of conventional methods which detect airport only by the shape feature of runway. The detection accuracy of the proposed method is nearly ten times higher than that of Liu s methods, and the method has favorable speed for a real-time system.
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Pattern synthesis of antennas based on a modified particle swarm optimization algorithm
JIN Ronghong, YUAN Zhihao, GENG Junping, FAN Yu, LI Jiajing
Front. Electr. Electron. Eng.. 2007, 2 (4): 454-458.
https://doi.org/10.1007/s11460-007-0085-9
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.
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19 articles
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