Automatic and Cooperative Sleep Control Strategies for Power-Saving in Radio-on-Demand WLANs

This paper focuses on Radio-On-Demand (ROD) wireless LANs (WLANs) in which the operating mode of Access Points (APs) changes from an `active´ communication state to `sleep´ state in case where there is no data traffic transferred from/to the AP in order to avoid unnecessary power consumption. We propose an automatic sleep control strategy, which frequently monitors APs data traffic conditions and executes the change of APs communication state if traffic conditions changes. Frequent mode transitions, which are likely to increase the waiting time and transmission delay perceived by the user, are critical when ROD APs are deployed. In this paper, we discuss the tradeoff between power-saving effects and delay-reduction of an automatic sleep control scheme and investigate the performance of our proposed sleep control strategy by using real-world WLAN data. In addition, we propose a cooperative sleep control method for large-scale WLANs, where the mode of APs is affected by the network deployment topology of WLAN APs and WLAN stations (STAs). We conducted a thorough numerical analysis in which we show that, in large-scale WLANs, a significant amount of AP power consumption can be reduced when our proposed automatic and cooperative sleep control method is applied in WLANs.