Towards an Energy-Star WLAN Infrastructure

Mobile users' demand for omnipresent, reliable, and high throughput services from a wireless LAN infrastructure has led a significant number of enterprises and public bodies to deploy large-scale high-density IEEE 802.11-based WLANs. These WLANs feature several hundreds to thousands of APs that are managed centrally and are typically dimensioned for peak user demands. Unfortunately, peak demands are occasional and WLANs often under-utilized. Using measurements from two different WLANs we show that the under-utilization of WLANs leads to a significant energy wastage, primarily due to their always-on nature. We discuss designs that can render such WLANs energy efficient and describe energy star infrastructures that can maximize energy savings in different scenarios. We also propose a simple algorithm, Green-clustering for energy star WLAN infrastructures that can lead to up to 90% energy savings. We argue that current and future large-scale WLANs must integrate energy efficiency as a design constraint. We also discuss avenues of further research on energy-star WLAN infrastructures.