Energy Efficient Scheduler Design in Wireless Networks

Minimizing energy consumption is crucial for portable wireless communication systems because they operate on a limited battery supply. For example, the IEEE 802.11 standard includes a mechanism called power-saving mode (PSM), which allows a network interface on a mobile station to enter a sleep state whenever possible to reduce its energy consumption. However, the scheme needs to be complemented by an efficient scheduling mechanism to maximize the energy savings. The purpose of this paper is to show how well-designed scheduling disciplines along with a power-saving mode can achieve significant improvement in saving energy consumption. We propose a generic wireless system composed of an access point and several portable stations that offer a PSM to its users. Our PSM is different from that of the IEEE 802.11 in the sense that to save more energy our PSM is driven and controlled by the access point, while the process is much more under the control of the stations in IEEE 802.11. We study how to design the downlink scheduler in the access point so as to minimize the total energy consumption of all the portable stations that are in PSM. We formulate two scheduling problems (in a static context and in a dynamic one) and propose several heuristic scheduling policies to solve them. Extensive simulations show the significant improvement on energy saving of our policies over more traditional scheduling schemes.