Enhanced Power Saving Mechanism for Large-Scale 802.11ah Wireless Sensor Networks
Taewoon Kim, J. Morris Chang · IEEE Transactions on Green Communications and Networking · 2017
We consider the power saving mechanism for 802.11ah on large-scale sensor networks. Power saving mode allows sensor nodes to switch to low-power state while APs buffer incoming frames for them. Also, 802.11ah introduced the TIM and page segmentation scheme to cope with a large number of nodes. Although it is a powerful tool for reducing contention and increasing sleep intervals, the advantage comes at the expense of additional energy waste, which becomes exacerbated as the number of nodes increases. This paper aims at minimizing such energy waste and enhancing energy efficiency which is critical to large-scale 802.11ah networks. We propose a method that selectively and dynamically changes the membership of nodes and rearranges their traffic to maximize overall sleeping intervals without causing delay to data delivery. To this end, we propose a temporary membership change scheme and a traffic scheduling algorithm which reduce overall power consumption. Also, to make the problem tractable and scalable, we apply a relaxation technique and devise a low-complex scheduling algorithm, respectively, of which performance is comparable to optimum. Evaluation results show that the proposed scheme can enhance energy efficiency by decreasing the number of active nodes by up to 37.8% compared to 802.11ah.