부산대학교 도서관

Connected-dominating-set (CDS) is a representative technique for constructing virtual backbones of wireless networks and thus facilitates implementation of many tasks including broadcasting, routing, etc. Most of existing works on CDS aim at constructing the minimum CDS (MCDS), so as to reduce the communication overhead over the CDS. However, MCDS may not work well in cognitive radio networks (CRNs) where communication links are prone to failure due to stochastic activities of primary users (PUs). A MCDS without consideration of the stochastic activities of PUs easily becomes invalid when the PUs become active. This study addresses a new CDS construction problem by considering the PUs’ activities. Our problem is to maximize the lifetime of the CDS while minimizing the size of the CDS, where the lifetime of a CDS is defined as the expected duration that the CDS is maintained valid. We show that the problem is NP-hard and propose a three-phase centralized algorithm. Given a CRN, the centralized algorithm can compute a CDS such that the lifetime of the CDS is maximized (optimal), and the size of the CDS is upper-bounded. We further present a two-phase localized algorithm which requires 2-hop information. Extensive simulations are conducted to evaluate the proposed algorithms.