An Adaptive MP3 Player:
Reducing Power Consumption and
Increasing Application Performance

Thomas Kunz

Systems and Computer Engineering

Carleton University

http://kunz-pc.sce.carleton.ca/

tkunz@sce.carleton.ca

Related Work

Typically, related work focuses on bandwidth variation

Other resources are also constrained (memory, power, CPU capabilities) and may vary over time

Majority of solutions: introduce proxy between client (application executing on mobile device) and server, proxy compresses and filters data stream

sometimes, degree of compression depends on available bandwidth

user mobility often not addressed/supported

Other solutions:

view mobile purely as User Interface (WWW browsers, Teleporting, ....)

partition client application between mobile and proxy

partition directed by application (Rover, MaROS, ....)

partition transparent to application (our own focus)

Adaptive Mobile Applications:
System Overview

Proposed Architecture

Mobile Code Toolkit: Proxy Objects

Mobile Code Toolkit: Components

Extend JVM on client and proxy server

Monitor

Code Storage

Object References and Profiling

Object Server

Remote Method Invocation Protocol

Dynamic Decision

Communication Control Layer

Extend garbage collection to deal with remote references

Provide abstractions to notify runtime system about environment and changes in environment (bandwidth, power, …), based on events and event notification

Required Info: Application Object Graph

Objects

Inter-Object Communication

Experimental Results

Implemented MP3 player, decoder (set of heavily communicating objects) can execute locally or remotely

Various performance experiments, study impact of

Available Bandwidth (19.2 kbps – 2 Mbps)

Relative CPU speed (Mobile CPU: Proxy CPU)

1:4 for laptop as client device

1:116 for Windows CE palmtop as client device

Results (more details in paper):

for high bandwidth and slow client, offloading decoder to proxy can speed up application performance by a factor of 20 and reduce power consumption by 95%

For faster client devices, independent of bandwidth, no benefit (actually worse performance) when decoding sound samples in access network

Conclusions and Current Status

Implemented Mobile Code Toolkit with small footprint for Windows CE devices

Collected experimental evidence to verify validity of our approach

Built framework to study scalability

Started to improve RMI performance (reduced time by up to factor of 4, so far)

Port to Palm OS (KVM problems):

No reflection

No serialization

No JNI

Future Work

Improve toolkit: better RMI performance, automatic generation of proxy objects, port to Palm OS, build object graph “on-the-fly”, dynamic partitioning decisions

Study additional applications and more dynamic scenarios, including proxy-to-proxy handoffs

Conflicting objectives (power saving vs. application performance)

Interaction between application-aware (MP3 player reduces sound quality, sampling rate, …. ) and application-transparent (runtime system migrates decode objects from handset to proxy) adaptation


	Thomas Kunz
	Systems and Computer Engineering
	Carleton University
	http://kunz-pc.sce.carleton.ca/
	tkunz@sce.carleton.ca


Typically, related work focuses on bandwidth variation
Other resources are also constrained (memory, power, CPU capabilities) and may vary over time
Majority of solutions: introduce proxy between client (application executing on mobile device) and server, proxy compresses and filters data stream
	sometimes, degree of compression depends on available bandwidth
	user mobility often not addressed/supported
Other solutions:
	view mobile purely as User Interface (WWW browsers, Teleporting, ....)
	partition client application between mobile and proxy
		partition directed by application (Rover, MaROS, ....)
		partition transparent to application (our own focus)


	Extend JVM on client and proxy server
		Monitor
		Code Storage
		Object References and Profiling
		Object Server
		Remote Method Invocation Protocol
		Dynamic Decision
		Communication Control Layer
	Extend garbage collection to deal with remote references
	Provide abstractions to notify runtime system about environment and changes in environment (bandwidth, power, …), based on events and event notification


Implemented MP3 player, decoder (set of heavily communicating objects) can execute locally or remotely
Various performance experiments, study impact of
	Available Bandwidth (19.2 kbps – 2 Mbps)
	Relative CPU speed (Mobile CPU: Proxy CPU)
		1:4 for laptop as client device
		1:116 for Windows CE palmtop as client device
Results (more details in paper):
	for high bandwidth and slow client, offloading decoder to proxy can speed up application performance by a factor of 20 and reduce power consumption by 95%
	For faster client devices, independent of bandwidth, no benefit (actually worse performance) when decoding sound samples in access network


	Implemented Mobile Code Toolkit with small footprint for Windows CE devices
	Collected experimental evidence to verify validity of our approach
	Built framework to study scalability
	Started to improve RMI performance (reduced time by up to factor of 4, so far)
	Port to Palm OS (KVM problems):
		No reflection
		No serialization
		No JNI


	Improve toolkit: better RMI performance, automatic generation of proxy objects, port to Palm OS, build object graph “on-the-fly”, dynamic partitioning decisions
	Study additional applications and more dynamic scenarios, including proxy-to-proxy handoffs
	Conflicting objectives (power saving vs. application performance)
	Interaction between application-aware (MP3 player reduces sound quality, sampling rate, …. ) and application-transparent (runtime system migrates decode objects from handset to proxy) adaptation