Wireless Network Interface Energy Consumption Implications of Popular Streaming Formats

The proliferation of multimedia-capable mobile devices and ubiquitous high-speed network technologies to deliver multimedia objects is fueling the demand for mobile streaming multimedia. However, the end-user experience is severely constrained by the available battery capacity on the mobile clients. Wireless network interface cards (WNIC) consume significant amounts of power. Since streaming applications tend to be long running, WNIC energy consumption is particularly an acute problem. In this work, we explore the WNIC energy consumption implications of popular multimedia streaming formats from Microsoft (Windows media), Real (Real media) and Apple (Quick Time). We investigate the energy consumption under varying stream bandwidth and network loss rates. We also explore history-based client-side strategies to reduce the energy consumed by transitioning the WNICs to a lower power consuming sleep state. We show that Microsoft media tends to transmit packets at regular intervals. For high bandwidth streams, Microsoft media exploits network-level packet fragmentation, which can lead to excessive packet loss (and wasted energy) in a lossy network. However, the regularity of packet arrival rates facilitates history-based client-side policies to transition to lower power states. We show that a Microsoft media stream optimized for 28.8 Kbps can save over 80% in energy consumption with 2% data loss. A high bandwidth stream (768 Kbps) can still save 57% in energy consumption with less than 0.3% data loss. Real stream packets tend to be sent closer to each other, especially at higher bandwidths. Quicktime packets sometimes arrive in quick succession; most likely an application level fragmentation mechanism. Such packets are harder to predict at the network level without understanding the packet semantics. Our work enables multimedia proxy and server developers to suitably customize the stream to lower client energy consumption.