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Adapting to Varying Demands in Resource Constrained Real-Time Devices
Publication Type:
Doctoral Thesis
Publisher:
Mälardalen University
Abstract
In-home entertainment systems are becoming popular because they allow
a variety of consumer electronic (CE) devices to be connected, using
a wireless network, to form a system capable of handling multimedia
content. Using such a system provide the end-users the possibility of
transparently streaming multimedia content between devices of varying
capabilities. This is possible because the system adapts the multimedia
content to match the capabilities of the receiving device.
What looks simple to the end-user, is actually a very complex system
that manages all existing multimedia streams and resources. It must
manage all the varying resource demands, on all the constrained devices,
in such a way that the resulting quality (video or audio playback) is
acceptable to all the end-users of the system.
In this thesis we investigate two different, but still related, issues
within the in-home entertainment network. First, we look at how we
can adapt to the the capabilities of the nodes, which contains processors
of varying capabilities and also operating systems which also provide
different capabilities. Secondly, we have to adapt to the varying capabilities
of the wireless network when it is used for video streaming in
the presence of other network traffic.
For nodes, we present two scheduling methods that are extensions
to the off-line scheduling paradigm.
The first method aims at improving the handling of soft aperiodic
tasks in an off-line scheduled system, which are normally handled in
the background resulting in long response times. The method creates space within an off-line schedule in order to allow a Total Bandwidth
Server to use it during run-time in order to improve the response times.
The second method deals with overload caused by firm aperiodic
tasks in an off-line scheduled system. The method deals with the overload
by selecting which aperiodic tasks to execute, and which tasks
to drop, without disturbing the execution of the more critical off-line
scheduled tasks.
We also present a third scheduling related method that presents an
plug-in based scheduling architecture with the purpose of allowing easy
change of scheduling algorithm within operating systems.
In order to deal with the wireless network issues we present an architecture
that decrease the network congestion in order to improve packet
delivery reliability and decrease packet delays. In order to accomplish
this, the architecture continuously predicts the available bandwidth, then
uses this information to adapt the transmission rate of the node in order
not to exceed what is available.
Bibtex
@phdthesis{Lennvall871,
author = {Tomas Lennvall},
title = {Adapting to Varying Demands in Resource Constrained Real-Time Devices},
number = {17},
month = {September},
year = {2005},
school = {M{\"a}lardalen University},
url = {http://www.es.mdu.se/publications/871-}
}