I. Introduction
In recent years, graph spectral measures (e.g., the effective graph resistance, the algebraic connectivity and the spectral radius) have attracted attention as means for analyzing the characteristics of a communication network as well as estimating its internal properties. Among several spectral measures, it has been known that the effective graph resistance is effective for estimating the robustness of a communication network against random failures [1]. In addition to the effective graph resistance, the algebraic connectivity has been proposed as a measure for estimating network robustness [2], [3]. The algebraic connectivity is related to classical geometric graph metrics such as the node/link connectivity, and it can be regarded as an index quantifying the difficulty of the network partitioning [2].