网络全终端可靠度的近似计算

　　用可靠性多项式计算网络全终端可靠度是评估网络拓扑结构稳定程度的重要依据，精确计算可靠性多项式是一个NP-hard问题。本文通过对基于产生孤立点的概率随机事件的定义，运用概率不等式变换，给出了点可靠、边以不同的概率相互独立失效时，网络全终端可靠度的上界表达式，在可靠度近似计算过程中避免了对网络边割集和路集的搜索。最后，在网络链路寿命服从指数分布时分析了某SDH传输网络的全终端可靠性及其近似计算，以说明本文的方法。

　　Abstract:

　　Computing the all-terminal reliability of communication networks by using reliability polynomial is the important basis to evaluate the stability degree of network topology structure，and computing some coefficients exactly is NP-hard.In this paper，we give the upper bound expression on all-terminal reliability in precondition that probability of edges failure in network are all unequal by the definition of probability Random Events that can bring independent vertices and conversion of probability inequality，and sequentially avoid the searching of cut sets and path sets of network in approximate calculation.Finally， when the edge life is exponentially distributed，the paper analyses and computes the bounds of all-terminal reliability of a SDH network to demonstrate the method.