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Investigation of Upstream near-far Problem in VDSL Systems via Complete Adaptive Iterative Water Filling Algorithm

Communications and Network 2011年第4期3卷 210-219页

作者： Mohammad Sadeghi Vahid T. Vakili Mansour J. Nejati 不详

Crosstalk is the main degrading factor in Digital Subscriber Line (DSL) systems which are the result of electromagnetic coupling between two adjacent twisted pairs in a cable. Very-high bit-rate Digital Subscriber Line (VDSL) systems which use higher frequencies for data transmission than the other DSL systems, this effect is more considerable in Bit Error Rate (BER) degradation. This paper considers a complete adaptive iterative water-filling (IWF) algorithm for Resolving Upstream near-far Problem in VDSL Systems. The new distributed dynamic spectrum management algorithm is proposed, which improve achievable bit rate of iterative water-filling algorithm. The paper proffers a new power back-off strategy of the spectral mask at the near-end users, in order to protect the far-end users. Simulation of the proposed algorithm indicates that the bit rate is increased considerably rather the IWF and adaptive water-filling (AIWF) algorithms by keeping their low complexity. Furthermore, by adding the number of users in network, the new algorithm achieves performance gains over the AIWF, completely adaptive.

关键词： Dynamic Spectrum Management Very-High Bit-Rate Digital Subscriber Line (VDSL) near-far Problem Iterative Water-Filling

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Generation and Propagation of Tsunami by a Moving Realistic Curvilinear Slide Shape with Variable Velocities in Linearized Shallow-Water Wave Theory

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Engineering（科研） 2010年第7期2卷 529-549页

作者： Hossam Shawky Hassan Khaled Tawfik Ramadan Sarwat Nageeb Hanna 不详

The process of tsunami evolution during its generation under the effect of the variable velocities of realistic submarine landslides based on a two-dimensional curvilinear slide model is investigated. Tsunami generation from submarine gravity mass flows is described in three stages. The first stage represented by a rapid curvilinear down and uplift faulting with rise time. The second stage represented by a unilaterally propagation in the positive x direction to a significant length to produce curvilinear two-dimensional models represented by a depression slump, and a displaced accumulation slide model. The last stage represented by the time variation in the velocity of the accumulation slide (block slide). By using transforms method, Laplace in time and Fourier in space, tsunami waveforms within the frame of the linearized shallow water theory for constant water depth are analyzed analytically for the movable source model. Effect of the water depths on the amplification factor of the tsunami generation by the submarine slump and slide for different propagation lengths and widths has been studied and the results are plotted. Comparison of tsunami peak amplitudes is discussed for different propagation lengths, widths and water depths. In addition, we demonstrated the tsunami propagation waveforms after the slide stops moving at different propagation times.

关键词： near-far Field Tsunami Amplitudes Shallow Water Theory Water Wave Submarine Slumps and Slides Laplace and Fourier Transforms

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Effects of Antenna Tilting on Transmitting Power in Mobile Cellular Communication Systems

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International Journal of Communications, Network and System Sciences 2011年第7期4卷 464-467页

作者： Gbenga E. Aderibigbe Michael O. Kolawole Victor S. A. Adeloye 不详

Radio resources must be wisely managed, in wireless communication systems, when implementing different multiple access techniques. This perspective is pivotal since the variations in propagation channel are very fast and the system is highly complex due to random and unpredictable movement of mobile users continuously. The complexity in the cellular system periodically contributes to different interference levels, high or low, resulting in the degradation of the system capacity. Transmitter power control is an efficient technique to mitigate the effect of interference under fading conditions, combat the near-far problem and conserve the battery life. Several remedial measures—like space diversity, frequency diversity, route diversity, increase in antenna height, antenna tilting, etc.—have been tried by many operators to overcome the debilitating effect of multipath fading in fixed line-of-sight microwave and mobile communication links. Among these remedial measures, diversity techniques have been extensively studied in terms of improvement factor, whereas the concept of antenna tilting is relatively less explored compared with other remedial measures. In this study, the effect of antenna tilting on fixed and mobile communication links is investigated to find out the optimum tilting angles in terms of design parameters, as well as on quality of service (QoS). The paper established that a deviation of more than 1.5o in antenna elevation angle would impact on QoS requirements and seriously affect the quality of signal to be received by the mobile systems.

关键词： Optimum Tilting Angle QoS near-far Effect Mobile Station Carrier-to-Interference Ratio

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接力通信抗干扰技术研究

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电子科技大学学报 1996年第S3期25卷 318-318页

作者：廖仕珍

接力通信抗干扰技术研究主研人员：李仲令龚耀寰吕明葛造坤张洋王晓蕾陆斌王自力赵红霞该成果包括码分多路调制／解调和自适应干扰抑制二部分。码分多路调制技术利用码分复用将高速数字信号分解成多个低速信号，完成扩频、调制和多路复... 详细信息

接力通信抗干扰技术研究主研人员：李仲令龚耀寰吕明葛造坤张洋王晓蕾陆斌王自力赵红霞该成果包括码分多路调制／解调和自适应干扰抑制二部分。码分多路调制技术利用码分复用将高速数字信号分解成多个低速信号，完成扩频、调制和多路复用，收端用多路解扩、解调完成信号的...

关键词： mobile communicaions mobile cellular communictions spread spectrum codedivision multiple access near-far effect adaptive powet control

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