Abstract: This paper presents a new power management technique aimed at
increasing the energy efficiency of client-server multimedia applications
running on wireless portable devices. We focus on reducing the energy
consumption of the wireless network interface of the client by allowing the
remote server to control the power configuration of the network card depending
on the workload. In particular, we exploit server knowledge of the workload to
perform an energy-efficient traffic reshaping, without compromising on the
quality of service. We tested our methodology on the SmartBadge IV wearable
device running an MPEG4 streaming video application. Using our technique we
measured energy savings of more than 67% compared to no power management being
used on the WLAN interface. In addition, we save as much as 50% of energy with
respect to the standard 802.11b power management. All of the energy savings are
obtained with no performance loss on the video playback.