Addressing conversion cascading constraint in OBS networks through proactive routing

The negative impact of cascaded wavelength conversions has been largely ignored in optical burst switching performance evaluations. When optical bursts are transmitted all optically from source to destination, each wavelength conversion performed along the lightpath may cause some signal-to-noise deterioration. If the distortion of the signal quality becomes significant enough, the receiver would not be able to recover the original data. In this paper we examine the performance degradation when an upper bound on the number of wavelength conversions that a signal can go through is enforced. We refer to this constraint as conversion cascading constraint. We propose a novel proactive routing scheme under this constraint that considers the instantaneous link congestion at the moment when the bursts arrive. It has three major advantages: (1) utilize the same offset times for the same node pairs while providing dynamic routing without using any fiber delay lines (FDL); (2) decrease burst loss probability to a great extent; (3) mitigate unfairness among the bursts with different hop counts, which is even worse under the conversion cascading constraint if without any special treatment. We also extend the proposed mechanism to embrace a variant of regulated deflection routing which can further improve network performance.

光脉冲通过F-P滤波器后峰值功率的变化

通过推导出的啁啾光脉冲通过F-P滤波器后输出脉冲光强的解析表达式,对不同情况下输出脉冲的峰值功率进行了研究.发现对于一确定的滤波器,峰值输出功率随输入脉冲的宽度及啁啾因子的大小而变化.     

Design of minimum-phase FIR digital filter through cepstrum

A method to design an equiripple minimum-phase FIR filter using the cepstrum is described. This method avoids the complicated polynomial root-finding algorithm of Herrman and Schuessler (1970), or the phase-unwrapping algorithm associated with the complex cepstrum of Mian and Nainar (1982). The differential cepstrum method proposed by Pei and Lu (1986) has aliasing problems and requires the computation of three FFTs. The proposed method requires only two FFT computations and avoids the processing of phase.     

Addressing the coal conundrum

While utopian dreams and advancing technology humankind toward carbon-free energy, today's reality is that fossil fuels drive major economies like China's and India's. Coal, above all, is plentiful and readily available. While everyone's best interests are best served by developing hydrogen-rich and/or carbon-free forms of energy that will emit none (or at least much less) of the gases that cause climate change, those options are not yet fully realized. With this in mind, this paper re-examines the situation in China and India and examines what is being done-and what can be done-to address the current fossil fuel situation     

Speckle reduction through interactive evolution of a general order statistics filter for clinical ultrasound imaging

This communication presents an interactive tool performing adaptive speckle filtering so that the medical expert who runs the algorithm has permanent control over the output and guides the process towards obtaining enhanced images that agree to his/her subjective quality criteria. The core of the filtering tool is an Interactive Genetic Algorithm that adapts online the coefficients of a general order statistics filter. Preliminary results show the potential of the method in comparison to other powerful speckle reduction filters on a test bed comprising obstetrics and gynecology ultrasound images.     

Complex IIR filter design through balance model reduction of FIRprototypes

The author extend the use of the balance model truncation and Hankel-norm optimal approximation to permit close approximation of complex FIR prototypes by IIR filters     

Robust design and planning of a worldwide intelligent network

The authors describe the structure of the worldwide intelligent network (WIN), describe methods for its design and planning, investigate the adequacy of decentralized control for problem-free worldwide call completion, explore the feasibility of adaptive routing and control concepts, discuss network robustness/reliability objectives, and describe a strategy for achieving these objectives for all cooperating international carriers. Several decentralized adaptive routing policies that are particularly attractive in the WIN environment and network performance improvements that can be achieved with the introduction of flexible routing capabilities are characterized. It is shown by example that network integration coupled with flexible routing and bandwidth allocation for preferential treatment of new services provides an effective approach for robust and economical new service provisioning     

Reconstruction of band-limited periodic nonuniformly sampled signals through multirate filter banks

A band-limited signal can be recovered from its periodic nonuniformly spaced samples provided the average sampling rate is at least the Nyquist rate. A multirate filter bank structure is used to both model this nonuniform sampling (through the analysis bank) and reconstruct a uniformly sampled sequence (through the synthesis bank). Several techniques for modeling the nonuniform sampling are presented for various cases of sampling. Conditions on the filter bank structure are used to accurately reconstruct uniform samples of the input signal at the Nyquist rate. Several examples and simulation results are presented, with emphasis on forms of nonuniform sampling that may be useful in mixed-signal integrated circuits.     

Optimal time-frequency deconvolution filter design fornonstationary signal transmission through a fading channel: AF filterbank approach

The purpose of this paper is to develop a new approach-time-frequency deconvolution filter-to optimally reconstruct the nonstationary (or time-varying) signals that are transmitted through a multipath fading and noisy channel. A deconvolution filter based on an ambiguity function (AF) filter bank is proposed to solve this problem via a three-stage filter bank. First, the signal is transformed via an AF analysis filter bank so that the nonstationary (or time-varying) component is removed from each subband of the signal. Then, a Wiener filter bank is developed to remove the effect of channel fading and noise to obtain the optimal estimation of the ambiguity function of the transmitted signal in the time-frequency domain. Finally, the estimated ambiguity function of the transmitted signal in each subband is sent through an AF synthesis filter bank to reconstruct the transmitted signal. In this study, the channel noise may be time-varying or nonstationary. Therefore, the optimal separation problem of multicomponent nonstationary signals is also solved by neglecting the transmission channel     

Addressing Scalability in a Laboratory-Based Multihop Wireless Testbed

The MeshTest wireless testbed allows users to conduct repeatable mobile experiments with real radio hardware under controlled conditions. The testbed uses shielded enclosures and a matrix switch of programmable attenuators to produce multi-hop scenarios and simulate the effects of mobility and fading. Previous work focused on the theory and performance of a single-switch testbed. Connecting more than 16 nodes requires multiple matrix switches and introduces theoretical and practical challenges. In this paper we examine, in theoretical and practical terms, two potential designs for a scalable version of the MeshTest testbed, and identify one design that seems to provide the most promising test environment. For this type of multi-switch system, performance improves a great deal if nodes that are close together in the physical scenario are also connected to the same RF switch. Rather than restrict the mobility of the nodes, we show how software virtualization can be used to migrate running node images from one switch to another to maintain the proximity of the nodes attached to each RF switch and improve testbed performance. We also describe our new testbed control architecture, that is an important part of making MeshTest scalable.     

Reducing the computational load of a Kalman filter

The Kalman filter is a powerful tool in linear-systems analysis. The authors present a particular application in which there are more measurements than states. In such an application, the state-space system can be replaced by an equivalent one that has the same number of measurements as states. The Kalman filter will produce the same state estimates for both systems. Using the equivalent system leads to a substantial saving in computer operations     

全球2018年DRAM产业预估预测

本文介绍了2017年DRAM市场状况,并对2018年的DRAM市场进行了分析预测.2018年预计仅增长19.6%,无大规模增产计划下,供给将延续吃紧走势.     

世界半导体市场展望

正半导体市场美国Microchip Technology曾于10月曾预测今年3季度公司营收下降的消息,并指出该公司以及Intel和TI的股票都下降了,意味着今年世界半导体业或将下行,"一石掀起千层浪","True or False?"引起了debate!未几日Intel宣布说3季度营收,达到147亿美元,创历史新高。同时,TI也发表了同期的业绩超过预期,涤荡了Microchip Technology几天前所散布的半導体業容或低迷的阴霾。事实上,据10月     

中外石墨烯产业化发展管窥

石墨烯因其优异的热学、电学、力学等性能,在各领域备受青睐。本文对石墨烯在新能源电池、复合材料、功能涂料等领域呈现的良好商业化前景进行概述。同时,还分析对比了各国石墨烯产业的发展现状和政策支持。     

DSP处理器循环寻址和位翻转寻址的设计

文章介绍了DSP（digital signal processing)处理器中面向滤波，FFT，卷积、相关等算法的循环寻址和位翻转寻址方式的设计，先讨论了循环寻址和位翻转寻址的设计思想和硬件实现算法，再根据算法设计了相应的电路，并且用Cadence工具Verilog-XL进行了逻辑仿真。