基于贪婪算法的WDM网络组播路由算法的研究

文章首先用贪婪算法找出在现有网络结构中完成任务所需的波长数较少的波长集,然后依据其上每条链路的权值,用最短路径算法生成一棵组播树,使其跳数和阻塞率较低,以保证网络能够在使用较少波长资源的情况下,快速、有效地传送数据.     

Mixing greedy and predictive approaches to improve geographic routing for VANET

In recent years, thanks to the development and popularization of wireless network technologies, the issue of vehicular ad hoc network (VANET) has received great attention, and more and more VANET‐related researches have been brought up. Generally speaking, the biggest difference between VANET and traditional ad hoc network is the velocity of carriers because in VANET, the velocity of vehicles, the carriers, is much higher than those in traditional ad hoc. Therefore, it would be a great challenge to forward data efficiently in VANETs and many researches proposed have focused on the development of routing protocols. The current proposed routing protocols are all assumed to simulate in a distributed and ideal environment. As for the complex geographic environments, such as urban scenarios, extra amendments must be needed to improve the efficiency of the routing protocols. Thus, the main purpose of this paper is to design a suitable routing protocol for urban scenarios with better performance and adaptability. For this reason, greedy on straight roads and predictive at the intersections (GSPI) routing protocol is proposed to use greedy mode on straight roads and to use predictive mode at the intersections. In greedy mode, we choose the next hop according to the weight value that combines the distances and multi‐rate. In predictive mode, we predict the directions of the vehicles to determine the next hop. The simulation results reveal that our proposed algorithm indeed proves its feasibility. Copyright © 2010 John Wiley & Sons, Ltd.     

面向多网络体制并存的开放式可重构路由器体系结构设计与实践

针对现有网络设备在支持可重构和多网络体制并存方面存在的不足,提出了一种面向多网络体制并存的开放式可重构路由器体系结构。通过在控制、转发和交换体系结构设计上,采用虚拟化和硬件分区配置技术,能够对控制、转发和交换进行资源划分与隔离,将路由器中同一个硬件资源虚拟化为多个功能上独立、资源上隔绝的逻辑路由器实例,提高了核心路由器设备的开放性和安全性。     

Hierarchical channel router

The channel routing problem is a special case of the wire routing problem when interconnections have to be performed within a rectangular strip having no obstructions, between terminals located on opposite sides of the rectangle.We present here a new channel routing algorithm, based on reduction of the problem to the case of a (2 × n) grid and on consistent utilization of a ‘divide-and-conquer’ approach. For the current implementation of the algorithm, the running time is proportional to N 1 n log(m) where N is the number of nets, n the length of the channel (number of columns) and m the width of the channel (number of tracks).Traditional technological restrictions are assumed, i.e., net terminals are located on vertical grid lines, two wiring layers are available for interconnections — one layer is used exclusively for vertical segments, another for horizontal and vias are introduced for each layer change.This algorithm consistently outperforms several known routers in quality of wiring. We tested the algorithm on several benchmark problems. One of them — Deutsch's ‘difficult example’ — was routed with only 19 horizontal wiring tracks (the absolute minimum for this case), whereas all other known routers required 20 or more tracks.     

SR软件路由器的设计与实现

分段路由(segment routing,SR)是近几年IETF提出的一种路由机制,其目的是使IP/MPLS网络面向服务并且更高效.SR减少现有MPLS网络控制平面复杂的协议(LDP/RSVP-TE),并实现流量工程等机制.与基于RSVP的显式路径中隧道中间节点维护报文流的状态不同,基于SR的显式路径只在入口边界路由器中维护报文流的状态,从而提高了网络的可扩展性,因此SR对于下一代互联网具有重要的研究意义.对SR的实现机制进行了研究,利用软件路由平台Click,对基于PCE架构的SR控制平面子系统和基于MPLS的SR数据平面子系统的各个模块进行实现,并在实际中进行部署,以验证SR软件路由器的可行性.     

A stochastic evolution algorithm based 2D VLSI global router

In this work we present a global router that uses the features of the Stochastic Evolution (StocE) algorithm to perform the rip-up and re-route (R&R) process. The unique features of the proposed global router are its simple design and ability to produce good results. It has two main components: (i) maze routing with framing (MRF) that act as a means of routing the nets; and (ii) a StocE algorithm that controls the R&R process and adjusts the parameters of the MRF method. This work shows that the StocE algorithm can perform the net selection in the R&R process and also adjust the parameter values of the MRF method in order to successfully solve 2D global routing problems. The performance of the proposed global router on the ISPD98 and ISPD2008 benchmarks was found to be better than some of the existing global routers.     

基于贪婪算法的高分辨信号源DOA估计

确定辐射源的来波方向(DOA)是阵列信号处理的重要研究内容,已经广泛应用于雷达、声纳和无线通信等领域。本文研究了远场窄带信号源的DOA高分辨估计问题。利用信号来波方向在空域具有稀疏性的特点,建立了远场窄带信号源的稀疏表示模型。根据协方差矩阵的特征值分解和贪婪匹配追踪算法原理提出了一种基于特征值分解的多重正交匹配追踪算法（EIG MOMP）。首先,利用特征值分解对阵列接收数据进行降维处理。这一降维操作使得问题转化为了一个具有多重观测向量（MMV）的欠定方程求解问题。接着利用MOMP算法对降维后的数据进行处理,最终得到信号的DOA估计值。该算法实现了在低信噪比下远场窄带信号源的高分辨DOA估计,并具有较低的运算复杂度。将本文提出的算法与传统的Capon算法、多重信号分类算法（MUSIC）以及正交匹配追踪算法（OMP）进行了对比。结果证明,该算法在低信噪比下能取得较好的DOA估计效果,可以针对任意的相干信号源,并且具有高分辨率的优点。      

贪心算法在机房排课中的应用

通过分析机房排课的概况,提出机房排课中存在机房利用率不高的问题,分析机房排课中采用贪心算法的优势,建立了机房排课问题的数学模型,研究了贪心算法对机房排课问题的具体解法,有效提高了机房利用率.     

一种贪婪的异构多信道并行合作频谱感知方法

为了同时对多个异构信道进行有效地合作频谱感知,并克服现有方法中只考虑检测准确性而忽略感知开销和系统效益,忽略不同认知用户对不同异构信道感知性能的差异以及参与合作感知的认知用户较多等问题,提出了一种贪婪的异构多信道并行合作频谱感知方法。根据对感知开销和传输收益的定义,充分考虑不同认知用户对不同异构信道感知性能的差异,利用贪婪算法在多个认知用户和多个异构信道间最优地进行感知任务分配,使总系统效益最大。仿真结果表明,所提方法与基于迭代匈牙利的并行合作频谱感知方法、改进的基于迭代匈牙利的并行合作频谱感知方法和随机的合作频谱感知方法相比,能够获得较高的总系统效益,且所需的参加合作感知的认知用户数较少。     

基于贪婪算法的多媒体教室排课算法设计

课程安排是高校教务管理工作中的点和难点,尤其是多媒体教室因为设备类型不统一、操作方式有差异等原因,为课程合理化安排增加了极大的困难.为了使课表编排的结果更加人性化,文中对多媒体教室排课约束条件进行详细分析,设计了基于贪婪算法的多媒体教室排课算法,使用该算法设计的多媒体教室排课系统安排出的课程表更加科学化、合理化和人性化.     

A load balancing bufferless deflection router for network-on-chip

The bufferless router emerges as an interesting option for cost-efficient in network-on-chip (NoC) design. However, the bufferless router only works well under low network load because deflection more easily occurs as the injection rate increases. In this paper, we propose a load balancing bufferless deflection router (LBBDR) for NoC that relieves the effect of deflection in bufferless NoC. The proposed LBBDR employs a balance toggle identifier in the source router to control the initial routing direction of X or Y for a flit in the network. Based on this mechanism, the flit is routed according to XY or YX routing in the network afterward. When two or more flits contend the same one desired output port a priority policy called nearer-first is used to address output ports allocation contention. Simulation results show that the proposed LBBDR yields an improvement of routing performance over the reported bufferless routing in the flit deflection rate, average packet latency and throughput by up to 13%, 10% and 6% respectively. The layout area and power consumption compared with the reported schemes are 12% and 7% less respectively.     

无线传感器网络中基于网络嵌入的弱贪婪路由协议

贪婪路由可以划分为强贪婪和弱贪婪2种路由方式。为了解决目前研究工作中弱贪婪路由协议需要地理位置信息,而强贪婪路由协议需要设计满足贪婪属性的网络嵌入图的问题;同时为了降低操作复杂性,减少能量消耗,提出了一种轻量级的基于树的网络嵌入图(TNEG)构建方法。在基于树的网络嵌入图上,设计了具有局部单调性的贪婪函数,并提出了2个路由规则,然后设计了弱贪婪路由协议TGR和基于双树嵌入的路由协议biTGR。模拟实验表明所提路由协议在路径长度和网络负载等性能上具有明显的优势。     

分级调度算法在路由交换机上的应用

本文提出了一种两级的分级调度模型,着重研究其算法的具体实现,并分析算法在路由交换机中的应用。分级调度算法的引入,保证在现有Internet体系结构下、best-effort服务能很好地与有QoS要求的实时服务相结合,仿真实验证明该发级调度算法可行有效。     

A low overhead load balancing router for network-on-chip

The design of a router in a network-on-chip (NoC) system has an important impact on some performance criteria. In this paper, we propose a low overhead load balancing router (LOLBR) for 2D mesh NoC to enhance routing performance criteria with low hardware overhead. The proposed LOLBR employs a balance toggle identifier to control the initial routing direction of X or Y for flit injection. The simplified demultiplexers and multiplexers are used to handle output ports allocation and contention, which provide a guarantee of deadlock avoidance. Simulation results show that the proposed LOLBR yields an improvement of routing performance over the reported routing schemes in average packet latency by 26.5%. The layout area and power consumption of the network compared with the reported routing schemes are 15.3% and 11.6% less respectively.     

一种基于贪婪算法的CORDIC改进算法

针对传统串行坐标旋转数字计算方法(CORDIC)耗时且占用较多资源的缺点,提出了一种旋转模式下CORDIC算法的新型改进算法,该改进算法可用来代替直接数字频率合成器(DDS)查找表进行正余弦的计算。通过采用贪婪算法实现对CORDIC旋转方向与旋转角度的优化,从而可以达到串行转并行和减少迭代次数、节约资源的目的。该算法可以应用于三角函数的复杂函数的硬件实现中。仿真结果表明,在迭代次数相同的情况下,改进算法较传统算法可以获得更高的精度。最后,在Xilinx FPGA的Spartan-3E芯片上实现了改进的CORDIC结构。与传统CORDIC算法相比,在运算精度为10-5时,可以节省Slices、LUTs(Look Up Tables)资源分别为28%和25%。     

一种基于贪婪搜索的码率兼容LDPC码打孔算法

为了提高有限长LDPC码的打孔性能,提出一种码率兼容LDPC码的打孔算法.结合打孔变量点恢复树结构的特点,采用贪婪搜索算法逐级最大化k步可恢复节点的数量,以获得尽可能多的k值较小的k步可恢复节点,从而改善码率兼容系列子码的误码性能.针对随机构造和PEG构造下的LDPC码,验证了本文打孔算法的性能.仿真结果表明,本文方法生成的系列码率兼容子码的误码性能均优于随机打孔方法,特别是当子码的码率较高时,误码性能改善越明显.     

未来光网络中的交换路由器

IP业务的爆炸式增长与DWDM技术的突飞猛进为新的WDM网络直接承载IP业务创造了条件。光交换和交换路由器的发展提供一种集成了智能IP路由技术和大容量光交换网络的交换路由器模型。这种交换路由器支持高QoS保证 ,简化了光核心网络结构 ,是近期光联网的理想解决方案     

太比特路由器交换网络中路由算法的研究

太比特路由器在未来宽带网络建设中将发挥越来越重要的作用.作为其核心部件,大容量高性能交换网络是实现太比特路由器的关键技术之一,而交换网络中路由算法设计的优劣将直接影响交换网络的性能.本文从状态信息、路由策略、死锁活锁避免、服务质量路由和容错路由等五方面对交换网络路由算法设计进行了分析总结,最后展望了未来发展趋势.     

浅析计算机网络中的路由器

通过路由器的结构，分析了路由器的基本原理及功能，进而阐述了现有路由器的分类，路由选择协议，路由算法等，最后介绍了路由器的发展规模及前景。     

基于路由器的ARP欺骗探测

首先分析了ARP协议和ARP欺骗的原理,然后介绍ARP防火墙软件。针对ARP防火墙的功能局限,提出了基于Cisc0路由器探测ARP攻击的体系结构,由MAC—IP捕获程序、数据库服务器、攻击分析程序所组成,接下来对各个部分进行深入研究。