On Crossbar Switching Networks

For networks that exhibit neither concentration nor expansion, the well-known probabilistic model of C. Y. Lee is refined so as to take account of the dependence of events in different stages. For series-parallel networks, the refined model yields exact expressions for the point-to-point blocking probability. These expressions bear the same relationship to the refined model as the KittredgeMolina expressions do to Lee's model. Comparison between the two sets of expressions shows that Lee's model tends to overestimate the blocking probability. Asymptotic analysis of the new expressions leads to improved upper bounds on the cost: it is shown that a network that carriesNerlangs with a blocking probability at mostepsilon > 0can be built with6N log_{2} N + O(N log log 1/epsilon)contacts.     

光学榕树网络与全混洗网络之间的转换及实现

光学榕树网络的快速控制需要在全混洗网络和光学植树网络间进行快速的相互转换．分别给出了光学榕树网络转换成全混洗网络及全混洗网络转换成光学植树网络时结点、链路、输入端口、输出端口的映射规则，并用电子学进行快速实现．     

光学全交叉网络与榕树网络拓扑等价的多样性

本文对有关互连网络拓扑等价的分析方法作了简单评述并采用互连网络拓扑等价的图分析法分析了自由空间光学互连全交叉网与榕树网的拓扑等价及其多样性，拓展了全交叉网络在数字光计算、光子交换及多处理机系统的潜在应用。     

Ternary Schedules for Energy-Limited Sensor Networks

Medium access control for multihop wireless sensor networks (WSNs) must be energy efficient because the battery-operated nodes are not practical to recharge. We give constructions for ternary schedules in which each node is in one of three states: transmitting, receiving, or asleep. For each hop (v_i, v_j), communication is effective only when v_i is transmitting, v_j is receiving, and no other node in proximity of v_j is also transmitting. Since sensor nodes are prone to failure, the schedules should be independent of the detailed topology while supporting spatial reuse. We use arc-decompositions of the complete lambda-fold directed graph Koarr_n into directed complete bipartite subgraphs Koarr_a,b as a model for ternary scheduling in WSNs. We associate the vertices of Koarr_n with the nodes of the WSN, and occurrences of Koarr_a,bs (blocks) in the decomposition with time slots in the schedule. A block with out-vertices A and in-vertices B corresponds to a slot in which the a nodes in A are transmitting, the b in B are receiving, and all others are asleep. Such a decomposition of lambdaKoarr_nguarantees that every ordered pair of nodes in the WSN can communicate in lambda time slots.     

一类Banyan网在ATM环境中的性能分析

本文对于一类Ｂａｎｙａｎ网作成的ＡＴＭ交换节点，提出了一种新的性能分析方法，并与计算机模拟结果进行了比较。该方法计算比较简单，计算结果具有很高准确性     

基于Banyan网的快速分组交换网络的硬件复杂度分析

为提高交换网络的性能，人们已提出了许多不同的网络结构技术，如并联Ｂａｎｙａｎ、串联Ｂａｎｙａｎ、扩张Ｂａｎｙａｎ，并对这些结构的性能进行了分析。但关于这些结构的硬件复杂性的研究却很少。本文通过建立几种结构技术的性能与网络设计参数的直接表达式，研究了给定性能下它们的硬件复杂度随网络规模的变化关系，并给出了它们复杂度的量级。研究表明，扩张Ｂａｎｙａｎ是一种更好的网络结构技术。     

光学全交叉网络与SW榕树（F＝S＝2）网络拓扑等价的多样性

本文对有关互连网络拓扑等价的分析方法作了简单评述。并采用互连网络拓扑等价的图分析法分析了自由空间光学互连全交叉网络与ＳＷ榕树网络的拓扑等价及其多样性，拓展了全交叉网络在数字光计算、光子交换及多处理机系统的潜在应用。     

Performance Analysis of ATM Replicated Banyan Networks with External Input–Output Queueing

This paper develops an improved analysis of ATM switching architectures adopting a replicated banyan interconnection network provided with dedicated input and output queues, one per switch inlet and outlet. Two different plane selection policies are studied, random choice and alternate sharing, and two different operation modes are considered for the interaction between input and output queues, backpressure and output queue loss. These different internal operations are ranked in terms of traffic performance and the problem of optimal allocation of a given buffer budget between input and output queues is addressed. The analysis, which assumes that the network is loaded by uniform traffic, always provides conservative results whereas known models are less accurate and give optimistic traffic results. Packet delay and loss probability performance is evaluated for the ATM switch and its accuracy is assessed using computer simulation also in comparison with results given by previous models.     

Optimal Block Design for Asynchronous Wake-Up Schedules and Its Applications in Multihop Wireless Networks

In this paper, we consider the problem of designing optimal asynchronous wake-up schedules to facilitate distributed power management and neighbor discovery in multihop wireless networks. We first formulate it as a block design problem and derive the fundamental trade-offs between wake-up latency and the average duty cycle of a node. After the theoretical foundation is laid, we then devise a neighbor discovery and schedule bookkeeping protocol that can operate on the optimal wake-up schedule derived. To demonstrate the usefulness of asynchronous wake-up, we investigate the efficiency of neighbor discovery and the application of on-demand power management, which overlays a desirable communication schedule over the wake-up schedule mandated by the asynchronous wake-up mechanism. Simulation studies demonstrate that the proposed asynchronous wake-up protocol has short discovery time which scales with the density of the network; it can accommodate various traffic characteristics and loads to achieve an energy savings that can be as high as 70 percent, while the packet delivery ratio is comparable to that without power management.     

On a class of Banyan networks and tandem Banyan switching fabrics

This paper examines the operating characteristics of a class of tandem Banyan switching fabrics (TBSF's) built using bi-delta networks. We use the functional equivalence between bi-delta networks to induce an equivalence between TBSF's. A weaker form of equivalence guaranteeing identical performance under conditions of symmetric traffic is studied, and a sufficient condition for weak equivalence between functionally distinct TBSF's is established. These results hold for a variety of conflict resolution policies (CRP's) in addition to the one studied by Tobagi et al. (see IEEE J. Select. Areas Commun., vol.9, p.1173, 1991). Simulations indicate that a TBSF constructed by cascading omega networks, (or in fact any other TBSF in its weak equivalence class), performs better than the two TBSF's studied by Tobagi et al., and converges rapidly to a theoretical lower bound on the loss rate, in the region of interest. It is also shown that this loss rate is almost independent of the size of such a TBSF in the region of interest     

Approximating the Minimum Number of Maximum Power Users in Ad hoc Networks

Topology control is the problem of assigning transmission power values to the nodes of an ad hoc network so that the induced graph satisfies some specified property. The most fundamental such property is that the network/graph be connected. For connectivity, prior work on topology control gave a polynomial time algorithm for minimizing the maximum power assigned to any node (such that the induced graph is connected). In this paper we study the problem of minimizing the number of maximum power nodes. After establishing that this minimization problem is NP-complete, we focus on approximation algorithms for graphs with symmetric power thresholds. We first show that the problem is reducible in an approximation preserving manner to the problem of assigning power values so that the sum of the powers is minimized. Using known results for that problem, this provides a family of approximation algorithms for the problem of minimizing the number of maximum power nodes with approximation ratios of 5/3 + ε for every ε > 0. Unfortunately, these algorithms, based on solving large linear programming problems, are not practical. The main results of this paper are practical algorithms with approximation ratios of 7/4 and 5/3 (exactly). In addition, we present experimental results, both on randomly generated networks, and on two networks derived from proximity data associated with the TRANSIMS project of Los Alamos National Labs. Finally, based on the reduction to the problem of minimizing the total power, we describe some additional results for minimizing the number of maximum power users, both for graph properties other than connectivity and for graphs with asymmetric power thresholds. A preliminary version of this paper was presented at the ADHOC-NOW’04 conference in Vancouver, Canada, July 2004. Prepared through collaborative participation in the Communications and Networks Consortium sponsored by the U.S. Army Research Laboratory under the Collaborative Technology Alliance Program, Cooperative Agreement DAAD19-01-2-0011. The U.S. Government is authorized to reproduce and distribute reprints for Government purposes not withstanding any copyright notation thereon. Errol L. Lloyd is a Professor of Computer and Information Sciences at the University of Delaware. Previously he served as a faculty member at the University of Pittsburgh and as Program Director for Computer and Computation Theory at the National Science Foundation. From 1994 to 1999 he was Chair of the Department of Computer and Information Sciences at the University of Delaware. Concurrently, from 1997 to 1999 he was Interim Director of the University of Delaware Center for Applied Science and Engineering in Rehabilitation. Professor Lloyd received undergraduate degrees in both Computer Science and Mathematics from Penn State University, and a Ph.D. in Computer Science from the Massachusetts Institute of Technology. His research expertise is in the design and analysis of algorithms, with a particular concentration on approximation algorithms. In 1989 Professor Lloyd received an NSF Outstanding Performance Award, and in 1994 he received the University of Delaware Faculty Excellence in Teaching Award. Rui Liu received the B.S. degree in mathematics from Peking University, Beijing, China, in 1998, and the Ph.D. degree in Computer and Information Sciences from the University of Delaware in 2004. Since that time, he has been a Senior Associate Staff Scientist with Oracle|Retek. His research interests include design and analysis of algorithms for combinatorial optimization problems, and mobile computing. S.S. Ravi received his Ph.D. in Computer Science from the University of Pittsburgh in 1984. Since that time, he has been on the computer science faculty at the University at Albany – State University of New York, where he is currently a Professor. His areas of interest include design and analysis of algorithms, mobile computing, data mining and fault-tolerant computing.     

Nanowire Crossbar Logic and Standard Cell-Based Integration

Nanowire crossbar is one of the most promising circuit solutions for nanoelectronics. However, it is still unclear whether or how they can be competitive in implementing logic circuits, as compared to their MOSFET counterparts. We analyze nanowire crossbars in area, speed, and power, in comparison with their MOSFET counterparts. We show nanowire crossbars do not scale well in terms of logic density and speed. To achieve performance close to their MOSFET counterparts, crossbar circuits need faster field-effect transistors (FETs) to compensate the high resistance of nanowires. Motivated by the analysis and comparative study, we propose a crossbar cells design based on judicious use of silicon nanowires. The crossbar cell is compatible with the conventional MOSFET fabrication and design methodologies, in particular, standard cell-based integrated circuit design. We evaluate logic circuits synthesized with crossbar cells and MOSFET cells based on the MCNC91 benchmark. The results show that crossbar cells can provide a density advantage of more than four times over the traditional MOSFET circuits with the same process technology, while achieving close performance and consuming less than one third power.      

APON系统中交叉连接的研究与实现

介绍了一种用于通信网络的APON无源光网络系统,该系统通过ATM交换模块实现信号的转换与传输,主要讨论了ATM交换的原理、交换单元的结构以及APON系统中交叉连接的实现。     

Design Trade-offs in Customized On-chip Crossbar Schedulers

In this paper, we present a design and an analysis of customized crossbar schedulers for reconfigurable on-chip crossbar networks. In order to alleviate the scalability problem in a conventional crossbar network, we propose adaptive schedulers on customized crossbar ports. Specifically, we present a scheduler with a weighted round robin arbitration scheme that takes into account the bandwidth requirements of specific applications. In addition, we propose the sharing of schedulers among multiple ports in order to reduce the implementation cost. The proposed schedulers arbitrate on-demand (at design time) interconnects and adhere to the link bandwidth requirements, where physical topologies are identical to logical topologies for given applications. Considering conventional crossbar schedulers as reference designs, a comparative performance analysis is conducted. The hardware scheduler modules are parameterized. Experiments with practical applications show that our custom schedulers occupy up to 83% less area, and maintain better performance compared to the reference schedulers.     

APON系统中交叉连接的研究与实现

介绍了一种用于通信网络的APON无源光网络系统，该系统通过ATM交换模块实现信号的转换与传输，主要讨论了ATM交换的原理、交换单元的结构以及APON系统中交叉连接的实现。     

高速crossbar控制算法iDRR及其性能分析

DRR(Dual Round-Robin)算法^[6]是一种公平、高效、可扩展性强、硬件实现简单的crossbar控制算法.为了进一步改善算法的时延性能和公平性,文中提出了多重迭代DRR算法,即iDRR算法,它继承了DRR算法所有优点.仿真结果表明iDRR算法可达到100%吞吐量,在时延性能和公平性方面都优于DRR 算法.使用可编程逻辑器件实现了基于iDRR算法的仲裁器,工作频率达80MHz,可支持10Gbps速率的输入端口,可用于超高速、大容量的路由器中.     

多核CPU中交叉开关总线的设计

在多核CPU中,当多个处理器核心需要和存储器及输入输出口进行数据存取时就会导致竞争问题,此时传统的总线将会降低系统的性能。而采用CPU-Cache交叉开关无阻塞网络实现点对点的传输则在很大程度上解决了这一问题。本文对交叉开关与传统的共享总线做出比较,并对交叉开关进行全定制电路设计。     

Approximate analysis of a multi-plane and multi-phase Banyan ATMswitch

An approximate analysis of a multi-plane and multi-phase Banyan ATM switch with both input and output buffering is presented. The approach gives a reasonable estimate of throughput and input queueing delay, and can be refined to give more accurate results     

Analysis of Defect Tolerance in Molecular Crossbar Electronics

Molecular electronics such as silicon nanowires (NW) and carbon nanotubes (CNT) demonstrate great potential for continuing the technology advances toward future nanocomputing paradigm. However, excessive defects from bottom-up stochastic assembly have emerged as a fundamental obstacle for achieving reliable computation using molecular electronics. In this paper, we present an information-theoretic approach to investigate the intrinsic relationship between defect tolerance and inherence redundancy in molecular crossbar systems. By modeling defect-prone molecular crossbars as a non-ideal information processing medium, we determine the information transfer capacity, which can be interpreted as the bound on reliability that a molecular crossbar system can achieve. The proposed method allows us to evaluate the effectiveness of redundancy-based defect tolerance in a quantitative manner. Employing this method, we derive the gap of reliability between redundancy-based defect tolerance and ideal defect-free molecular systems. We also show the implications to the related design optimization problem.      

自由空间二维榕树网实现方法

鉴于榕树网在自由空间光子交换网络中具有重要的应用价值,分析了榕树网的特点和4×4二维榕树网的空间拓扑结构,通过偏振光分光棱镜、微闪耀光栅阵列、平面反射镜、半反半透镜和液晶空间光调制器的集成,构建二维的榕树交换网实验模块,利用微闪耀光栅的衍射特性,控制每块微闪耀光栅的周期,以实现入射光信号不同方向的闪耀输出,最终完成二维榕树网自由空间水平和竖直方向上的交叉互连,直通则由平面镜反射实现。对二维榕树网实验模块的功能分析表明,该实验模块理论上可以完成4×4二维面阵内光信号(或数据)的排序、交换、组播、广播、矩阵变换等操作,具有交换透明、速度快、空间带宽高等特点,在全光交换和光通信中具有一定的应用。