Evaluation of probability mass function of flow in a communication network considering a multistate model of network links

This paper presents two efficient algorithms for exact evaluation of probability mass function (pmf) from source node to sink node of a large communication network considering a multistate capacity model of links, using composite path and composite cut methods. The capacities of various states of each link of the network are assumed to be mutually exclusive. From the pmf the performance index is obtained without difficulty. The applicability of the proposed algorithms has been tested for various networks (two-state and multistate). However, the latter method (composite cut) is found to be more efficient. An interesting finding is that when a three-state model is replaced by an analogous two-state model, system reliability is underestimated. Thus, if a system is to be represented by a multistate model, one should not use a simplified two-state model for mathematical convenience alone.     

Reliability Evaluation of Multistate Systems with Multistate Components

This paper presents two efficient algorithms for reliability evaluation of monotone multistate systems with s-independent multistate components. The algorithms are based on the Doulliez & Jamoulle decomposition method. Algorithm 1 requires the minimal paths to be known; Algorithm 2 requires the minimal cuts to be known (the state of the system need not be specified for each vector of component states). Computer programs for implementing the algorithms are given. Computational-times are presented, and compared with the ``Inclusion-Exclusion Method' and the ``State Enumeration Method'. The results demonstrate clearly the superiority of the algorithms to the two other methods.     

Reliability evaluation of multistage interconnection networks with multi-state elements

This paper presents a graph-theoretic method for the reliability evaluation of multistage interconnection networks with multistate elements. For the purpose of analysis, the generalized cube (GC), a unique-path MIN and an extra-stage cube (ESC), a fault-tolerant variation of GC, are considered. An algorithm is presented to evaluate three reliability measures, i.e. terminal reliability (TR), broadcast reliability (BR) and network reliability (NR) of MINs for different reliability values of links and switches. The proposed method is found to be simple and computationally efficient compared to the existing techniques, and therefore can be applied for reliability evaluation of other large interconnection networks used in parallel computing systems.     

Reliability evaluation of flow networks considering multistate modelling of network elements

This paper presents a simple method for evaluating the reliability of a multistate flow network. A system is considered reliable only if it successfully transmits at least the required system capacity from the transmitter to the receiver station. All successful states are obtained from the knowledge of the max-flow min-cuts of the system graph. Examples are solved to demonstrate the applicability of proposed method. It is observed that the method is simple, computationally fast and efficient.     

Incorporating common-cause failures into nonrepairable multistateseries-parallel system analysis

This paper adapts the universal generating function method of multistate system reliability analysis to incorporate common-cause failures (CCF). An implicit 2-stage approach is used. In stage #1, a polynomial representation of system-output performance distribution is obtained without considering system elements which are subject to CCF. In stage #2, the contribution of CCF is correctly included based on information stored in vector-indicators that describe states of system elements belonging to various common-cause groups. A straightforward procedure is suggested for evaluating reliability functions of nonrepairable series-parallel multistate systems with CCF. This procedure allows the reliability functions to be obtained numerically. Examples are given     

服务质量约束下的IP组播通信可靠性评估方法

In order to estimate the reliability performance of multicast communication under multiple constraint conditions, the weight of service rate and the reliability index are defined, accompanying the calculation method. Firstly, according to the Quality of Service requirements, the appropriate routings between the central node and target nodes that meet the requirements are calculated using the iterative method in the weighted internet. Then, the disjoint set of network state and the coefficients of weighted service rate are calculated by decomposition and merge methods. Lastly, the formula for calculating the service rate is obtained based on the disjoint set of network state and the calculation of the reliability index will be completed. The simulation result shows that the reliability of multicast communication can be appropriately reflected by the weight of service rate and the calculation method, which can provide the theoretical basis for the reliability evaluation of multicast communication.     

Using the Decomposition-Tree of a Network in Reliability Computation

Available algorithms for measures of network reliability require computation time f(n) where f is at least exponential in n, the number of failure-prone elements in the system. Modularization is a familiar method of decomposing a network reliability problem into a set of subproblems. This decomposition reduces required computation time from f(n) to a sum of f(ni), ni < n, usually a considerable saving. For a 2-terminal communication network, the decomposition tree of a network provides the identity of the modules and an easily read map of the relations among them. The decomposition tree is derived by finding the triconnected components of the underlying graph. Reducing computation time by finding and analyzing the triconnected components of a network has been proposed for the reliability problems of 2-terminal communication, all-terminal communication, and feasible transportation flow. This paper introduces the use of the decomposition tree for reliability computation purposes, presents a general algorithm based on the tree, and demonstrates its application to the problems named above, as well as to the problem of feasible shortest path.     

Reliability Evaluation in Computer-Communication Networks

The network reliability for a computer-communication network is defined and a method based on spanning trees is proposed for its evaluation. The network reliability expression and s-t terminal reliability expression are compared assuming an equal probability of survival for each communication link. Examples illustrate the method.     

一种基于神经网络的通信网节点重要性评价方法

准确地评估通信网中节点的重要性,对于通信网的设计、维护管理以及提高整个通信网的可靠性都有重要作用。现有的一些评估方法通常只是考虑单一的影响因素,其评估结果不准确。提出一种基于自组织神经网络的通信网节点重要性评估模型,将通信网中节点的度、节点的网络凝聚度、节点对通信网生成树的影响程度和节点对通信网可靠性的影响程度作为节点重要性的评价指标,对通信网中的节点进行重要性等级的划分。实验结果表明该模型能够全面地评估节点的重要性。     

通信网可靠性综合评估

影响通信网的可靠性因素很多。在考虑多个测度指标的情况下,通信网可靠性评估是多指标的综合评价,提出了三种综合评估方法。其中基于神经网络的综合评判较好地解决了综合评价指标中各指标的权数确定又尽可能地排除了人为因素的影响这一难题。     

Analysis of Coherent Multistate Systems

The structure and reliability of homogeneous s-coherent multistate systems is studied. Homogeneous systems have two properties: 1) their components can be rearranged internally in any arbitrary way without affecting the mapping of the component states onto the system state; 2) all components, all subsystems composed of them, and the system have the same set of states. Because of the s-coherence and homogeneity properties, mapping of the component states onto the system state, as well as calculating probabilities of system states from those of the component states, become very simple. In homogeneous systems, states can be ranked according to their relative dominance, and the state ranking completely determines the structure of such a system. Any homogeneous s-coherent system belongs to one of four categories which differ in whether the identity property is satisfied or not, or on details of the state ranking. As an application, the high pressure injection system of a pressurized water reactor is modeled as a multistate system composed of homogeneous s-coherent multistate subsystems.     

通信网络系统可靠性评测技术研究

通过指出现有通信网络系统可靠性评测技术的不足,有针对性地提出解决的思路和方法,并介绍了改进方法的步骤,同时探讨了网络抗毁性的问题。     

Reliability Analysis of a Communication Network with Multimode Components

This paper presents a model to calculate the reliability of communication networks with multimode components. Previous research on network reliability has focused on models in which each component may be in one of two modes, namely, operative or failed. In reality, a component may undergo degradations in performance before a complete outage, and will therefore operate in more than two modes. Traditional network reliability measures, such as the probability that a pair of nodes is connected, are not meaningful in a multimode model. Therefore, the mean message delay of the network is defined as the performance measure. An exact calculation of this reliability measure is not feasible due to the large number of network states, corresponding to network components being in different modes. We have developed an approximation method to calculate this reliability measure. This method requires us to work with the states of the network in order of decreasing probability. An algorithm ORDER-Mis developed to generate these states in the proper order.     

Reliability Evaluation of a Network with Delay

In a computer or communication network, the reliability and transfer-delay of communication are important measures of performance. This paper describes a method of evaluating the reliability of a network with delay. When network elements fail, delay is defined as the length of the shortest remaining path between two specified nodes. We find the occurrence probability of events that a central node can communicate with a group of terminal nodes so that a specified delay is not exceeded. The desired events are mutually exclusive and contain a tree. Our algorithm efficiently generates all the events by noting network topology. The paper includes the case of several central nodes.     

军用通信网可靠性测试任务剖面研究

任务剖面是系统可靠性测试工程研究的重要范畴,从满足军用通信网络可靠性测试为出发点,对任务剖面的设计要求和组成要素进行了深入的研究,着重对军用通信网络的业务流量的建模进行了分析,首次提出了军用通信网络可靠性测试中任务剖面的架构和设计方法,为军用通信网络可靠性测试提供更全面可行的有效的工程化方法。     

基于多因素的Ad Hoc网络连通可靠性仿真方法

移动Ad Hoc网络的连通可靠性对于战场的指挥控制、警察与医疗部门的抢险救灾等众多领域具有重要意义。然而当前的移动Ad Hoc网络连通可靠性评估方法大多建模简单,考虑因素单一,而以OPNET为代表的网络仿真只针对网络普通性能分析而没有可靠性分析。因此,目前缺少一种能够涵盖真实场景中节点移动、无线通信特性和复杂地形环境的移动Ad Hoc网络连通可靠性评价方法。针对此问题提出了多因素模型连通可靠性仿真方法,同时结合可靠性定时标准实验方法给出了系统的移动Ad Hoc网络可靠性仿真实验设计方案。并根据具体移动Ad Hoc网络案例,在OPNET中进行二次开发建模与仿真,验证了该多因素连通可靠性仿真方法的可行性。     

微波通信应急组网仿真系统设计

针对通信保障方案生成方式及评估手段落后的问题,设计了微波通信应急组网仿真系 统。系统以模块化的形式设计了体系结构,采用层次分析法构建了通信装备建模框架,通过 流程图描述了仿真过程并提出仿真实现方法,实现了数据库管理,给出了通信效果评估依据 及评估实现方法。最后通过日常组网训练仿真验证了系统的可行性与可靠性。系统通过虚拟 评估手段为用户提供较精确的数据支撑和结果分析,可对通信保障方案生成起辅助决策作用 ,有效提高应急通信保障效率。     

Reliability analysis of a multistate one-unit repairable system operating under a changing environment

This paper studies a multistate repairable system operating under changing environment subject to a Markov process with two states. Failure rates are constant while the repair rates are general. Regenerative technique in MRP is applied to obtain several reliability characteristics of interest to system designers.     

Generalized multistate monotone coherent systems

Most available models for multistate coherent systems (MCS) assume that the state sets of the system and its components are totally ordered-an assumption that greatly limits the application of the usual MCS models. This paper presents a new MCS model-a generalized multistate coherent system (GMCS) model-which assumes, more generally, that the state sets of the system and its components are partially ordered. Since the structure of a partially ordered set is very flexible, the model applies to the reliability analysis of various multistate coherent systems. As a result, the GMCS model generalizes the coherent system theory from the binary-state case to the multistate case. The authors investigate some of the properties of this generalized model. Then, system reliability is redefined and bounds for its evaluation are derived