Multi-Radio Multi-Channel无线传感器网络中信道分配和路由策略

针对无线传感器网络中传输时延长、传输冲突大和吞吐量低等问题,提出了一种在Multi-Radio Multi-Channel无线传感器网络中信道分配和路由策略.该策略动态地建立k元n立方体拓扑结构,使用优化的静态信道分配算法提高节点的吞吐量,使用维序寻径的路由算法减少传输冲突.该方法适用于网络节点稠密、节点相互之间通信冲突大的情况,并且在单跳和多跳的网络环境下均适用.实验结果表明,基于k元n立方体这一拓扑结构的信道分配和路由策略与传统方法相比,有效地减少了端到端时延,降低了网络冲突,减少了节点能量消耗,延长了网络寿命,提高了网络吞吐量.     

一种支持多维资源描述的高效P2P路由算法

在分析现有P2P(peer to peer)路由算法的基础上,提出了一种基于二阶矩定位、支持多维资源数据描述的高效资源路由算法--FAN(flabellate addressable network)路由算法.FAN算法将节点映射到统一的多维笛卡尔空间,并以节点相对空间原点的二阶矩作为子空间管理和资源搜索的依据.FAN路由算法具有O(log(N/k))的高路由效率,在节点加入和退出FAN网络时,更新路由信息的代价为O(klog(N/k)).实验结果表明,FAN路由算法具有路由效率高、维护代价小的优点,是一种P2P环境中支持多维资源数据描述的高效结构化资源路由算法.而且,目前部分基于CAN(content-addressable network)网络的改进算法也可以在FAN网络中适用,并获得更好的路由效率和更低的维护代价.     

基于重路由匿名通信系统的负载分析

基于重路由匿名通信系统,如Mixes,Onion Routing,Crowds等,采用重路由机制在应用层转发数据,使实体之间的通信以间接的方式进行,从而有效地隐藏通信实体的身份信息,如主机的IP地址等.在性能方面,这种机制导致系统中产生额外的开销,如通信延时、负载等.着重从理论上分析了系统中的成员负载.通过深入考查基于重路由匿名通信系统的重路由机制,推导出了基于重路由匿名通信系统中成员负载的概率公式,证明了成员负载由系统中成员数目重路由路径数目以及重路由路径长度的概率分布所决定.应用该公式计算Crowds系统中成员的负载,得出精确的负载期望值为1/(1(P_f)+1,改进了Reiter等人的分析结果O((n+1)/((1(P_f)²n), 证明了Crowds系统的成员负载不受系统中成员数目n的影响,具有良好的可伸缩性.并通过仿真实验验证了该分析结果.其结论为设计和规划匿名网络提供了理论依据.     

Construct Control Meshes of Helicoids over Trapezium Domain

In this paper, we present a geometric construction of control meshes of helicoids over trapezium domain. We first introduce the quasi-Bézier basis in the space spanned by {1;t;cos t;sin t;t sin t;t cos t}; with t [0;α];α [0;2π). We denote the curves ex-pressed by the quasi-Bézier basis as algebraic-trigonometric Bézier curves, for short AT-Bézier curves. Then we find out the transform matrices between the quasi-Bézier basis and {1;t;cos t; sin t;t sin t; tcos t}. Finally, we present the control mesh representation of the heli-coids and the geometric construction of the control mesh. In detail, we construct the controlpolygon of the planar Archimedean solenoid, which is also expressed with the quasi-Bézier basis, and then generate the mesh vertices by translating points of the control polygon.     

不需要可信任方的门限不可否认签名方案

在1992年澳大利亚密码会议上, Harn and Yang 第一次提出了(t,n)门限不可否认签名的概念.其中,只有成员个数不少于t的子集才能代表群体产生、确认和否认签名.随后,一些研究者又提出了几个方案,但这些方案都是不安全的.因此,到目前为止,怎样设计一个安全的(t,n)门限不可否认签名方案仍然是个公开问题.提出了一个基于离散对数密码系统的(t,n)门限不可否认签名方案.该方案不仅安全、高效,而且不需要可信任方.另外,方案还具有一个很好的性质,即成员的诚实性是可以验证的.这是由于在分发密钥时,采用了Schoenmakers在1999年美洲密码会议上提出的可公开验证秘密共享方案和两个用来提供正确性证据的离散对数恒等式协议.     

将SYBASE的数据转换成WATCOM SQL的数据

本文绘出了一种将SYBASE的数据转换为WATCOM SQL中的数据的实现途径，并给出了用Powerscipt语言实现的程序。对本程序略加修改就可以实现任何两个支持SQL语句的数据库门的数据转换     

光RP(k)网络上Hypercube通信模式的波长指派算法

波长指派是光网络设计的基本问题,设计波长指派算法是洞察光网络通信能力的基本方法.基于光RP(k)网络,讨论了其波长指派问题. 含有N=2ⁿ个节点的Hypercube通信模式,构造了节点间的一种排列次序Xn,并设计了RP(k)网络上的波长指派算法.在构造该算法的过程中,得到了在环网络上实现n维Hypercube通信模式的波长指派算法.这两个算法具有较高的嵌入效率.在RP(k)网络上,实现Hypercube通信模式需要max{2,「5(2^n-5/3」}个波长.而在环网络上,实现该通信模式需要复用(N/3+N/12(个波长,比已有算法需要复用「N/3+N/4」个波长有较大的改进.这两个算法对于光网络的设计具有较大的指导价值.     

一类实际网络中的最小截算法

讨论了节点和边都有容量限制的无向平面网络中的两点间的最小截问题.传统方法是把节点和边都有容量的网络中的最小截问题转化为只有边有容量的问题,但该方法用在平面网络时不能保持网络的平面性,因此网络的平面性不能得到利用.使用传统方法的计算时间为O(n²logn)(其中n为网络的节点数).给出了可以充分利用网络平面性的方法.对源和汇共面的s-t平面网络,把最小截问题转化为平面图上两点间的最短路径问题,从而可以得到O(n)时间的算法;对一般的平面网络,给出了新的将节点和边都有容量的问题转化为仅边有容量问题的方法,这种转化方法不破坏网络的平面性,从而可以利用平面网络中仅边有容量问题的计算方法,使原问题在O(nlogn)时间内获得解决.     

结合信源特性与网络拥塞控制的可靠性视频传输算法

提出了一种用于在无线网络中传输视频的结合信源特性及网络拥塞控制的鲁棒性算法.通过场景建模以及特性分析,将分级编码产生的所有码流层划分成不同的类型,并根据它们对网络拥塞控制的贡献以及对重建图像质量的贡献不同,将其分成两个不同的队列.系统根据不同的网络丢包状态(即丢包是由网络拥塞引起还是由无线信道的不可靠传输引起)动态地调整信源速率、不等错误保护强度以及拥塞控制策略.仿真结果表明,该方法与MPEG-4信源编码加固定速率Turbo码方法以及动态调整信源、信道编码速率加选择性丢I,B,P包的网络拥塞控制方法相比,能够提供更好的性能.     

在消息传递并行机上的高效的最小生成树算法

基于传统的Borǔ vka串行最小生成树算法,提出了一个在消息传递并行机上的高效的最小生成树算法.并且采用3种方法来提高该算法的效率,即通过两趟合并及打包收缩的方法来减少通信开销,通过平衡数据分布的办法使各个处理器的计算量平衡.该算法的计算和通信复杂度分别为O(n²/p)和O((t_sp+t_wn)n/p).在曙光-1000并行机上运行的实际效果是,对于有10 000个顶点的稀疏图,通过16个节点的运行加速比是12.     

Fast algorithms for generalized predictive control

Fast algorithms for generalized predictive control (GPC) are derived by adopting an approach whereby dynamic programming and a polynomial formulation are jointly exploited. They consist of a set of coupled linear polynomial recursions by which the dynamic output feedback GPC law is recursively computed wwith only O(Nn) computations for an n-th order plant and N-steps prediction horizon.     

A high performance optimal dynamic routing algorithm with unicast multichannel QoS guarantee in communication systems

Dynamic routing protocols play an important role in today??s networks. In communication networks, in a current data transmission session, failing nodes and links is a destructor event which loses packets immediately and it can also waste network resources and services seriously. Sometimes failing nodes can disconnect data transmission and, therefore, lost packets must be retransmitted by new session. In this situation, the routing algorithm must discard failed nodes and must repair paths of session by rerouting them. In this case, static routing algorithms and some existing dynamic routing algorithms cannot manage faulty paths fairly and network efficiency is seriously declined. The capability to compensate for topology changes is the most important advantage dynamic routing offers over static routing. An efficient dynamic routing algorithm tries to reroute and change faulty paths without disconnecting sessions and keeps packet transmission in a desirable rate. It is important to tell that a dynamic routing algorithm should provide multi essential parameters, such as acceptable delay, jitter, bandwidth, multichannel paths, virtual channel connections, label switching technology, optimal resource allocation, optimal efficiency in the case of multimedia, and real time applications. This paper proposes a new dynamic framework which transforms static routing algorithms to dynamic routing algorithms. Using the new dynamic framework, this paper constructs an Optimal Dynamic Unicast Multichannel QoS Routing (ODUMR) algorithm based on the Constrained Based Routing (CBR) and Label Switching Technology which is called as ODUMR Algorithm. The performance of ODUMR is analyzed by network simulator tools such as OpNet, MATLAB, and WinQSB. ODUMR produces results better than the existing static and dynamic routing algorithms in terms of necessary parameters.     

基于单向函数的动态密钥分存方案

给出了一个基于单向函数的动态(t,n)-门限方案,它具有下述特点:(1) 系统在更新系统密钥时,无须更改每个成员的子密钥;(2) 当某个成员的子密钥泄密时,系统只需为该成员重新分配子密钥而不必更改其他成员的子密钥;(3) 当有新成员加入时,系统只需为新成员分配一个子密钥,而其他成员不受任何影响;(4) 子密钥可无限制地多次使用;(5) 只需公开n+1个信息(在需要确认欺骗者时需公开2n+1个);(6) 恢复系统密钥时,采用并行过程.     

Maximum <Emphasis Type="Italic">k</Emphasis>-Splittable <Emphasis Type="Italic">s</Emphasis>,<Emphasis Type="Italic">t</Emphasis>-Flows

Given a graph with a source and a sink node, the NP-hard maximum k-splittable s,t-flow (M k SF) problem is to find a flow of maximum value from s to t with a flow decomposition using at most k paths. The multicommodity variant of this problem is a natural generalization of disjoint paths and unsplittable flow problems. Constructing a k-splittable flow requires two interdepending decisions. One has to decide on k paths (routing) and on the flow values for the paths (packing). We give efficient algorithms for computing exact and approximate solutions by decoupling the two decisions into a first packing step and a second routing step. Usually the routing is considered before the packing. Our main contributions are as follows: (i) We show that for constant k a polynomial number of packing alternatives containing at least one packing used by an optimal M k SF solution can be constructed in polynomial time. If k is part of the input, we obtain a slightly weaker result. In this case we can guarantee that, for any fixed ε>0, the computed set of alternatives contains a packing used by a (1−ε)-approximate solution. The latter result is based on the observation that (1−ε)-approximate flows only require constantly many different flow values. We believe that this observation is of interest in its own right. (ii) Based on (i), we prove that, for constant k, the M k SF problem can be solved in polynomial time on graphs of bounded treewidth. If k is part of the input, this problem is still NP-hard and we present a polynomial time approximation scheme for it.     

主被动结合的网络测量技术研究

网络测量技术可以有效地帮助网络研究者和管理者更好地理解网络性能和结构。鉴于单一的主动测量或被动测量技术难以实现对网络信息进行精准而有效的测量,提出一种主被动结合的网络测量技术。针对被动测量方式获得的数据采用基于正则表达式的匹配和信息筛选机制提炼有效数据信息;基于这些信息,提出一种周期动态调整的主动发包方式测量目标网络的丢包率,并采用泊松分布的采样方式采集丢包率的测量数据;同时提出一种多路径动态路由测量算法,测量目标网络的路由路径信息。实验结果显示,周期动态调整的主动发包方式与固定周期发包的测量方式相比,可以将链路丢包率降低60%以上;多路径动态路由测量方法与Traceroute和Dijkstra路由寻路探测方式相比,路由探测准确率虽然相差很小,但是平均路由跟踪时间分别减少了大约10%和42%。表明周期动态调整的主动发包方式在网络突发时段可以适当调整发包周期;多路径动态路由测量方法可以有效地减少探测过程中的平均路由跟踪时间。     

动态层次小组多播路由的研究

在分析现有多播路由协议的基础上,本文提出了动态层次小组多播路由。多播数据源可以根据自治系统（AS）中接收者的多少而动态决定发送多播数据的方式。在一个AS中,对于一个特定的多播源,当多播数据接收者的数量较少时,用单播的方式;当自治系统中接收者较多时,用组地址的方式转发多播数据。同样,AS中的分枝节点亦可以根据该策略构造以分枝节点为根的动态管理方式,从而动态地构造层次多播路由体系结构。本文还定义了动态层次多播路由算法的数据结构以及功能模块,并从网络带宽与路由器计算两方面面分析了动态层次小组多播路由协议分发多播数据时的代价。     

Multi-period traffic on elastic optical networks planning: alleviating the capacity crunch

Advances in optical data transmission technology have allowed the current expansion of bandwidth-demanding services over the Internet. Also, the emergence of orthogonal frequency-division multiplexing (OFDM) has opened the possibility of increasing the network spectral efficiency by solving the routing, modulation and spectrum assignment (RMSA) problem. Recently, investigators have examined the effects of multiple demands or multiple virtual topologies when they are requested at different time periods over a single physical substrate. That makes the RMSA harder and with many more instances. Such analysis is required because network traffic does not remain static along time, and the demand can increase considerably as new user services arise. Therefore, planning the network considering a multi-period study becomes essential, since it can prevent a case where demands may exceed the bandwidth capacity and cause request blocking in future periods. In this work, we provide a novel mixed integer linear programming (MILP) formulation to solve the RMSA problem for several t periods of demands. This model can be used not only to find the solutions to minimize the used capacity, but also as an efficient method of network planning, since it can estimate with a single formulation and a single iteration the point of resource exhaustion in each period t. The results are found for a small network, and they show the efficiency of the proposed MILP formulation. We also propose an alternative version of this formulation with predefined paths, which is less computationally demanding. The results of this study are compared to a step-by-step planning, where the strategy is a decomposition method that breaks the previous formulation into t steps. Comparing the results of the two strategies, it can be seen that the single multi-period formulation is a good strategy to solve the problem. By contrast, the step-by-step strategy may require reconfigurations and eventual interruptions in the network, from a step to another one.

     

A method to evaluate routing policy through p minimal paths for stochastic case

In this paper, a stochastic-flow network is presented to model a computer network in which each arc has various possible capacities and may fail. In order to shorten the transmission time, the transmission protocol allowing the data to be sent through multiple minimal paths simultaneously is utilized for the computer network. However, the minimum transmission time to send a given amount of data is not fixed due to the property of stochastic capacity. Accordingly, the first addressed issue is to evaluate the probability that the network is able to send the data within a time constraint by adopting the transmission protocol. Such a probability is named as transmission reliability that is regarded as a performance indicator to measure the QoS for a computer network. Without knowing all minimal paths in advance, an efficient solution procedure is proposed to calculate transmission reliability. The experimental results of 35 random networks show that the proposed algorithm can be executed efficiently. Moreover, in order to increase transmission reliability, the network administrator decides the routing policy to designate the first and the second priority p minimal paths. The second addressed issue is to evaluate transmission reliability associated with the routing policy. A sort criterion is subsequently presented to find an ideal routing policy.     

New Results on Noncommutative and Commutative Polynomial Identity Testing

Using ideas from automata theory, we design the first polynomial deterministic identity testing algorithm for the sparse noncommutative polynomial identity testing problem. Given a noncommuting black-box polynomial f ? \mathbb F{x₁,?,x_n}f \in {\mathbb F}\{x_{1},\ldots,x_n\} of degree d with at most t monomials, where the variables x_i are noncommuting, we give a deterministic polynomial identity test that checks if C o 0C \equiv 0 and runs in time polynomial in d, n, |C|, and t. Our algorithm evaluates the black-box polynomial for x_i assigned to matrices over \mathbbF{\mathbb{F}} and, in fact, reconstructs the entire polynomial f in time polynomial in n, d and t.     

Uniform trigonometric polynomial B-spline curves

This paper presents a new kind of uniform spline curve, named trigonometric polynomial B-splines, over space Ω = span{sini,cost, tk-3,tk-4, …,t, 1} of which k is an arbitrary integer larger than or equal to 3. We show that trigonometric polynomial B-spline curves have many similar properties to traditional B-splines. Based on the explicit representation of the curve we have also presented the subdivision formulae for this new kind of curve. Since the new spline can include both polynomial curves and trigonometric curves as special cases without rational form, it can be used as an efficient new model for geometric design in the fields of CAD/CAM.