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.
