Journal of Information Security Research Quangang Zhao 6 4 2015 http://www.dline.info/jisr/fulltext/v6n4/v6n4_2.pdf In wireless sensor networks, which can be configured to put some sensor nodes in sleep mode to save energy. This approach is a special case of a randomized scheduling algorithm, in which k subsets of sensors work alternatively. In this paper, we first study the performance of the randomized scheduling algorithm via both analysis and simulation in terms of intrusion coverage intensity, and detection probability, then, we also study the asymptotic coverage and other properties. Finally, we analyze a problem of maximizing network lifetime under Quality of Service constraints such as bounded detection delay, detection probability, and network coverage intensity. We prove that the optimal solution exists, and provide conditions of the existence of the optimal solutions.