两线阵立体测绘CCD相机光学系统设计

为使嫦娥二号卫星CCD立体相机在100km高度的圆轨上能够获取地元分辨率力为7m的图像,设计了一种两线阵立体测绘CCD相机光学系统。介绍了两线阵立体测绘相机的工作原理。根据卫星总体的指标要求,对光学系统的主要参数进行了详细计算,确定系统的焦距为144.4mm,视场角为42°,相对孔径为F/9,光谱范围为450～520nm。光学系统采用6组7片型消畸变复杂化的双高斯结构形式,在50lp/mm奈奎斯特空间频率下平均调制传递函数为0.67。给出了嫦娥二号卫星CCD立体相机在100km高度的首轨图像和极区图像,图像清晰、层次丰富,表明该光学系统能满足任务要求。     

泛在共享移动宽带网络体系结构与设计

目前,专用移动通信网(简称专网)大多采用集群通信系统,主要功能局限在语音和低速数据,网络覆盖范围有限,各专网之间也难以实现漫游和互通。如何利用一个共用的技术平台实现不同专网之间、专网与公网之间的融合,并且支持宽带互联网应用例如高分辨率图像、视频和大数据量传输,是目前各国政府和相关行业、产业面临的重要课题。LTE是公认的未来移动宽带发展的主流技术,具有高吞吐量、低延时、无线频谱适应性强等优势。本文提出泛在共享移动宽带网(ubiquitous shared mobile broadband network)的概念,介绍了其设计的基本思想、全新的网络架构、严格的安全管理机制、提供的业务和优势,最后提出了泛在共享移动宽带网的发展策略。     

Performance Evaluation of Packet Mobile Communications through Level Crossing Analysis

In this paper the performance of a packet mobile radio network is studied inthe presence of shadow fading outage intervals.Under quite general assumptions for the medium access protocol,the probability mass function of the sequence of packets that may be lostdue to an outage interval is derived. It is seen that long sequences of lostpackets are likely to occur for typical values of the mobile speed andshadowing correlation parameters.For delay constrained sources, e.g., voice, the analysis is mainly focused atderiving the probability function of the sequence of dropped packetsand the probability of dropping. For data sources, the delay statistic isalso derived. In the latter case, the effect of finite buffer length isaddressed. Simulation is used to verify the accuracy of approximations introduced in the analysis.     

承载移动互联网的传输网络组网模式分析

为更好满足移动互联网业务传输承载和网络架构变化,通过分析移动互联网业务特点和发展趋势,比较承载移动通信系统的典型传输技术,提出了承载移动互联网的3种传输组网模式：SDH/MSTP/OTN＋PTN混合组网模式、SDH/MSTP/OTN：PTN独立组网模式和DWDM/OTN/ASON＋PTN联合组网模式,并对其系统组成和网络结构分析与讨论,得出在不同条件下应选择最适合承载移动互联网的传输组网。     

具有变时滞的Hopfield型神经网络的全局指数稳定性

 本文利用推广的Halanay时滞微分不等式和Lyapunov函数来研究具有可变时滞的Hopfield型神经网络的平衡状态的全局指数稳定性,得到了不依赖含任何未知函数存在性的简便代数判据,为实际应用提供方便.     

Low‐jitter slot assignment algorithm for deadline‐aware packet transmission in wireless video surveillance sensor networks

This work presents a distributed time‐slot assignment algorithm which adopts TDMA as Medium Access Control, specially suited to support applications with strict delay, jitter, and throughput requirements characterized by convergecast traffic pattern in sensor networks. (e.g. wireless video surveillance sensor networks). The proposed algorithm has three characteristics: (1) every node is guaranteed a path to the base station for its data delivery. In the path, sufficient resource is reserved and weighted fairness can be achieved. (2) It uses cascading time‐slot assignment and jitter minimization algorithm in each node to minimize jitter and end‐to‐end delay. (3) Nodes are only active during their scheduled slots and sleep otherwise. This offers energy saving by reducing idle listening and avoiding overhearing. The performance of the proposed algorithm is evaluated over simulations and analyzed theoretically in comparison with existing slot assignment algorithm. The results show that our algorithm provides lower end‐to‐end delay, jitter, and higher throughput. Copyright © 2010 John Wiley & Sons, Ltd.     

0.18μm CMOS工艺条件下的信号完整性分析

通过模拟分析了0 18μmCMOS工艺条件下的信号完整性问题.在进行串扰延迟和噪声分析中发现了一些规律,这些规律对以后的设计有一定的指导意义.     

PTN芯片中IP组播查找电路的设计与实现

网络数据量的急剧增加,带来了带宽的急剧消耗和网络拥挤问题,这些问题对分组传输网络芯片的转发容量、速率、拥塞避免和流量管理等方面提出了更高的要求。为了提高分组传输网络芯片中 IP组播查找电路的工作速率和降低电路设计复杂度,采用流水线结构,并利用 RAM(随机访问存储器)记录查找中间状态信息等技术完成了对 IP 组播查找电路的设计。在Altera系列FPGA(现场可编程门阵列)开发板EP4SGX230KF40C2ES上进行了硬件验证,结果表明,该电路能够完成IP组播查找功能,并稳定工作在200 MHz频率下。     

基于FDL和TWC的光突发竞争解决方案及性能分析

在光突发交换(OBS)网络中,突发竞争是影响网络性能的一个重要因素,因此如何有效地解决它,成了OBS网络非常重要的问题.在分析当前文献中的解决方案的优缺点后,提出了一种突发竞争解决方案的系统实现.该实现将光纤延迟线(FDL)时城缓存与波长转换器(TWC)波长变换、空城技术结合在一起,构造了一个基于前向转发缓存和反馈循环缓存的两级交换结构.最后从多方面对该系统实现的竞争解决有效性进行了性能分析和计算机仿真,结果表明:它在适当的业务强度(小于0.6)下,能有效改善突发丢失率和突发延迟;同时能降低系统所需的光器件数目.     

An Adaptive Time Delay Estimator Based on ETDE Algorithm with Noisy Measurements

We address the problem of adaptive time delay estimation with noisy measurements. We develop a computationally efficient adaptive time delay estimator based on Explicit time delay estimation (ETDE) algorithm, by applying the unbiased impulse response estimation ap-proach. In this algorithm, a weighted error function is de-rived, and the time delay is explicitly parameterized in the filter coefficients and iteratively updated directly by uti-lizing the modified error function. Simulations validate the performance of the proposed algorithm for colored input and low signal-to-noise ratio scenarios.