Reliable buffered clock tree routing algorithm with process variation tolerance

1 Introduction The clock distribution network design is a very challenging task, because the per-formance and functionality of the whole synchronous system directly depend upon the clock signals. Clock skew is manifested by a lead/lag relationship between the clock signals. Conventional clock designs always demand a zero clock skew system, since they think that clock skew may limit the maximum operation frequency. Exact zero skew was first accomplished in ref. [1], and then DME (Deferred-Mer…     

一种基于结群的零偏差时钟布线算法

介绍了一种基于结群的零偏差时钟布线算法,该算法采用新的单元匹配策略,递归地把时钟节点划分成2个负载和半径比较均衡的子集,结合缓冲器的适当插入,产生一棵零偏差的时钟布线树。实验表明,结群处理对处理规模较大的电路快速有效,时钟延迟得到了明显减少。     

给定偏差约束下的时钟布线局部拓扑构造优化算法

提出一种时钟树布线算法,在给定偏差约束下,采用新的匹配策略考虑偏差约束进行局部拓扑优化,优先匹配延迟目标大的结点,将其置于时钟树拓扑结构底层;结合缓冲器的插入,抑制了蛇行线的产生．实验结果表明,对使用过时钟偏差调度算法优化后的电路,该算法可在时钟布线阶段有效地减少时钟线网中连线与缓冲器的总电容．     

GHz零时滞时钟树物理布图的虚拟通道布线算法

随着集成电路技术的发展和GHz频率的应用需求,已有的基于线长或RC延迟模型的时钟树布图算法已不能适用．针对GHz频率宏模块中时钟树的平面布图,依据流水线技术,提出一种虚拟通道布线算法;根据时钟树的拓扑结构,分别进行粗略布线和虚拟通道内的布线调整,完成时钟树的平面布线．该算法在开发软件原型ClockStar中得以应用．     

基于Linux嵌入式系统按需路由协议架构设计与实现

针对在Linux操作系统原有的路由体系结构上实现按需路由的制约问题,分析了Linux操作系统路由体系结构特点以及实现按需路由的难点,提出了一种适合按需路由的通用路由体系结构,并基于Linux系统实现了按需路由之一的Aodv路由协议的嵌入式实现。结果表明了此路由体系结构很好地解决了Linux传统的路由体系结构瓶颈。     

A graph-to-layout correspondence in single layer routing

A new method of attacking the hierarchically decomposed single layer routing problem is proposed.A placement is used to orient the initial graph structure. Such a structure becomes an encoded picture of future interconnections. The router is capable of decoding it to produce a blocking-free wiring pattern.     

基于延迟合并嵌入的带障碍的时钟树布线算法

提出一种在带障碍情况下,基于延迟合并嵌入方法的时钟树构建算法,并在时钟树构造过程中引入了轨迹图以保证布线可以绕过障碍．该算法以已知障碍为布线约束,首先自底向上计算时钟树内部节点的可能位置,然后自顶向下确定每个节点的确切位置．实验结果表明,该算法能够正确、有效地实现有障碍存在时的时钟树布线,线长优化率超过7％．     

A degree-constrained QoS-aware routing algorithm for application layer multicast

Application layer multicast (ALM) provides a low-cost solution for multicast over the Internet. It overcomes the deployment hurdle of IP multicast by moving all multicast related functions from network routers to end-hosts. However, since packet replication is performed on end-hosts, the system performance of an ALM is limited by the bandwidth of end-hosts. Therefore, degree-constrained QoS-aware multicast routing becomes one of the key concerns for implementing realtime multicast services, such as continuous streaming applications. In this paper, we claim that the QoS gained by most users will be better evaluated using the overall latency, and we explore the optimization of Degree-Constrained Minimum Overall Latency Spanning Tree (DCMOLST). The process for optimizing the overall latency is divided into two phases, i.e., the initialization phase and the dynamic adjustment phase. In the former phase, we present a heuristic DCMOLST algorithm which negotiates both transmission delay and node bandwidth simultaneously, so as to avoid QoS degradation caused by any single metrics. In the later phase, we define a set of distributed iterative optimizing operations to swap the position between nearby end-hosts for further optimization. Experimental results show that the proposed degree-constrained QoS-aware routing algorithm could improve the overall performance of application layer multicast services.     

实时时钟芯片在实时监控系统中的应用

结合实时监控系统的应用特点,本文对实时时钟芯片MSM62X42B在实时故障处理中的应用设计加以阐述。试验结果充分验证了该方案的可行性和有效性。     

A routing algorithm for a single transfer crane to load export containers onto a containership

It is discussed how to route transfer crane during loading operation of export containers in port container terminal. We determine the number of containers which transfer crane picks up at each yard-bay as well as the sequence of yard-bays which transfer crane visits during the tour. The objective is to minimize the total container handling time of the transfer crane including the set-up time at each yard-bay and the travel time between consecutive yard-bays. This routing problem is formulated as an integer programming. An efficient optimizing algorithm is also developed for the crane routing problem.     

一种基于温补时钟芯片的授时系统

针对传统天文测量授时系统结构复杂、操作繁琐、便携性差等缺点,研究开发了一种基于DS12C887温补时钟芯片的功耗低、体积小且携带方便的天文授时系统。简要介绍了系统的基本构成和主要部件的功能特性及各种参数。介绍了授时系统的计时原理和工作流程,介绍了授时系统比时平台的构成以及比时的基本原理。做了大量的实验测试,分析了授时系统的稳定性和精度,收集了22d的时间比对实验数据。经实验验证,授时系统计时精度高,运行稳定,自动化程度高,可方便运用于野外天文测量与其他时间服务。     

一种应用于机场廊桥监控网络的路由算法

针对民航机场廊桥监控网络在机场停机坪现场测试中暴露的网络节点过早死亡、网络生命周期短的问题,对该系统无线网络架构中路由层算法进行优化,采用基于剩余能量和位置的改进LEACH算法,根据网络环境的因素综合考虑节点剩余能量、网络平均剩余能量以及节点位置,分步选出最优簇头,同时,采用能量估算方法确定网络平均剩余能量,达到均衡网络能耗且延长网络生命周期的目的.最终利用Matlab软件对民航机场廊桥监控管理系统建模仿真,仿真结果表明：提出的算法比网络原有路由层LEACH算法在均衡网络能耗和提高网络生命周期上均具有优越性.     

无线Mesh网络中一种分布式路由方案

在多射频多信道无线Mesh网络中,链路负载和节点位置的变化将导致网络性能的下降。针对此问题,在混合无线网状路由协议反应式路由基础上,设计了一种新的混合信道分配的分布式路由算法。该算法在路由建立的同时可实现以数据流为单位的最优信道分配,且能避免因单节点失效导致整个网络崩溃的危险。仿真结果表明,提出的RHCA算法较传统算法在网络吞吐量和端到端平均时延方面均有显著优势。另外,在节点移动场景下,所提出的分布式路由算法较其他方法能获得更高的吞吐量和更好的稳健性。     

电路原理图中两边网格通道布线的类贪婪算法

贪婪算法是VLSI设计中通道布线的常用算法,在电路原理图的自动布图中,也会遇到通道布线的问题。但传统的贪婪算法着重于使通道面积最小化,不能满足原理图中对布线结果有序化的要求。提出类贪婪算法,在原贪婪算法的基础上,通过修改处理规则,使得布线结果更加整齐有序,便于阅读,同时也保留了原算法简洁的优点。     

物联网安全架构与关键技术

从信息安全的机密性、完整性和可用性等三个基本属性出发,分析了物联网安全需求和面临的安全问题,提出了物联网安全的系统架构,并对一些安全关键技术进行了深入研究,希望为建立物联网可靠的信息安全体系提供参考依据。     

一种基于能量感知的无线传感器网络混合路由协议

针对无线传感器网络的资源局限性、自组织性和网络拓扑结构的不确定性,提出了一种基于能量感知的平面路由和层次路由的混合路由协议。该协议可根据节点剩余能量的表现来判断节点的当前状态和路由选择,网络中各节点以"尽力而为"传输数据和"不得已"动态建立自适应簇头的方式进行网络通信。仿真结果比较表明:该协议具有较高簇头生成率和可靠的数据交付率,能更有效降低网络能量消耗。     

On random routing in wireless sensor grids: A mathematical model for rendezvous probability and performance optimization

Random routing protocols in Wireless Sensor Networks (WSNs) forward packets to randomly selected neighbors. These packets are ‘agents’ carrying information about events or ‘queries’ seeking such information. A novel mathematical framework is proposed for analyzing random routing protocols. Exact probability of a packet visiting a given node within a given hop count as well as the rendezvous probability of agents and queries meeting at a given node in a 2-D grid-based WSN are derived. The basic relationship needed for extending the models to a 3-D grid topology is provided. Exact probabilities of agents meeting queries are derived while ignoring physical boundary effects and packet losses, under two different strategies for forwarding the packet to a neighbor: (a) with equal probability, and (b) self-avoiding forwarding. We then extend the model to account for packet losses by considering the case where a packet is forwarded to a neighbor with equal probability. Also provided is the extension of the analysis for a network with rectangular boundaries. The exact solutions presented, unlike existing models relying on asymptotic behavior, are also applicable to small and medium scale networks. They can be used to set parameters and optimize performance of several classes of random routing protocols. All the models are validated using Monte Carlo simulations. Simulation results indicate that the model is also a good approximation for sparse arrays with 75% or higher node density. Finally, the utility of the model is demonstrated by determining the protocol parameters to optimize the performance of rumor routing protocol under a fixed energy budget.     

A distributed multicast routing algorithm for real-time applications in wide area networks

The problem of constructing a minimal cost multicast routing tree (MRT) with delay constraints in wide area networks (WAN) is considered. A new distributed token-passing based algorithm that constructs a sub-optimal MRT satisfying given delay constraints for all members in the multicast group is presented. In contrast with the previous works by Jia [A distributed algorithm of delay-bounded multicast routing for multimedia applications in wide area networks, IEEE/ACM Trans. Network. 6 (1998) 828–837] and several others [Y. Im, Y. Lee, S. Wi, Y. Choi, Delay constrained distributed multicast routing algorithm, Comput. Comm. 20 (1997) 60–66; X. Jia, Y. Zhang, N. Pissinou, K. Makki, A distributed multicast routing protocol for real-time multicast applications, Comput. Networks 31 (1999) 101–110; Q. Sun, H. Langendorfer, A distributed delay-constrained dynamic multicast routing algorithm, Telecommun. Systems 11 (1999) 47–58], in which cycles may occur, we show that the multicast routing network produced by our algorithm is indeed a tree, namely, cycle free. Also the success rate of our algorithm to find a feasible solution, if one exists, is guaranteed to be 100%, while Jia's algorithm is not. Furthermore, our algorithm is fault tolerant and can also adapt to cases where the multicast group members are allowed to join or leave the multicast session dynamically. Simulations have been conducted and the results show that the MRT generated by our algorithm has better performance compared to previous methods.     

一种基于入侵检测的空间网络安全路由技术

随着空间信息网络在各领域尤其是军方的广泛应用,空间网络安全技术成为研究人员越来越关注和重视的研究方向,其中空间网络的路由安全是重要的研究热点之一.针对基于入侵检测的空间网络安全路由技术进行了研究,以无线Mesh网络开发的OLSR路由协议为例,对空间信息网络中基于入侵检测的安全路由技术进行仿真分析,证明了此安全机制的可行性.