中文摘要：

基于有序二叉判定图（OBDD），提出用结点扩张（NE）算法来评估无线传感网的可靠度和结点重要性。NE算法执行结点扩张操作来处理不可靠结点，从两方面增强了计算效率：利用OBDD结构表示网络状态，减少了大量冗余的等价状态；利用Hash表存储同构子网的OBDD，减少了同构子网的重复计算。另外，该算法对结点重要性进行了评估，为脆弱结点的保护提供参考。实验结果表明NE算法的计算开销比传统的factoring算法低，能有效评估无线传感网的可靠度。

英文摘要：

The paper proposes an ordered binary decision diagram （OBDD） algorithm, named the node expansion （NE） algo- rithm to evaluate the reliability and node importance of wireless sensor networks. This algorithm executes node expansion to deal with unreliable nodes and enhances the reliability computations from two points： firstly, the OBDD representation of network states avoids large numbers of redundant equivalent states; secondly, the Hash table of isomorphic sub-net- works decreases the repeated computations of same structure networks. Furthermore, the NE algorithm evaluates the node importance and guides the protection of weak nodes. The experiment shows that the NE algorithm＇ s computation costs are lower than the factoring algorithm＇ s and it can efficiently evaluate the reliability of wireless sensor networks.