Run-Time Support for Adaptive Communication Services

By: SeyedMasoud Sadjadi

Advisor: Dr. Philip K. McKinley

Computer Science and Engineering

Michigan State University

This work was supported in part by the U.S. Office of Naval Research under Grant No. N00014-01-1-0744, and in part by National Science Foundation grants CDA-9617310, NCR-9706285, CCR-9912407, EIA-0000433, and EIA-0130724.

• Motivation: – Wireless networks are improving rapidly.– Mobile computers are gaining more popularity.– Lots of Software is being developed for this new

infrastructure.

• Problem?– Dynamic changes in wireless networks.– Heterogeneity of mobile devices.

• Standard solution:– Developing adaptive application.

• Problems with adaptive software?– Adaptive code is scattered all over the application.– Development, deployment, and maintenance are

difficult.

• Our solution:– Using Adaptive Java (developed by E. Kasten) to

develop adaptive applications.

• Case Study:• Audio Multicasting Application (AMA)

• A traditional real-time distributed application that multicasts a live audio stream over a wired network.

• Motivation:• Using AMA over a wireless network.

• Problem?• Wireless network dynamically changes.

• Standard solution:• Writing an adaptive AMA that uses FEC.

• Problem with adaptive AMA?• Adaptive code is scattered all over the application.• Development, deployment, and maintenance are

difficult.• Our solution:

• Using Adaptive Java to develop a “metamorphic” socket (or metasocket) that makes AMA adaptive.

• Adaptive code is not tangled to the application code.

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Wireless Network

Error Control in Wireless Networks

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Java Virtual Machine

Java MulticastSocket

Java Virtual Machine

MetaSocket

Adaptive Code is factorized in one component to

better support the development of evolutionary software

Adaptive Code (the cross-cutting concern)

is scattered all over the application

code

Java Virtual Machine

Java MulticastSocket

We decided to factorize all of the adaptive code needed to adapt AMA to the dynamic changes of wireless networks and put them in a “metamorphic” component named MetaMulticastSocket (MetaSocket in brief). MetaSocket “absorb”s and “metafy”s the original Java MulticastSocket.You can follow the steps for building this component in Adaptive Java in the next slides.

First we extended the original Java MulticastSocket to support a filter pipeline. This way we could add, remove,or modify different filters. In this study we just used FECFilters, but it can work with other filters.

Then we “absorb”ed MulticastSocketSender using “absorb”construct in Adaptive Java to create a component from thisJava class. We defined all the invocations that this component support to provide service to other components.

In this step we “metafy”ed this new component, MulticastSocket-SenderComponent using “metafy” construct in Adaptive Java and defined “refraction”s and “transmutation”s. Refraction methods can only read the status of a component. Transmutation methods, in contrast, can only write to the component.

Java Virtual Machine

Now that MetaSocket is developed, we need a component that knows about our specific application (AMA) and customizes MetaSockets dynamically. We call this component a “Decision Maker”. A decision maker gets the state of other components using their refraction methods and adapt them using their transmutation methods.

This is how the whole Microphone application works.

Data loss in 35% Signal Strength

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801 5 9 13 17 21 25 29 33 37 41 45 49 53 57

packets grouped in 200 packets

Pac

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loss

in g

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pac

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k=4 n=8

k=4 n=10

k=4 n=12

k=4 n=20

k=4 n=40

FECinserted

FECremoved

• Conclusion:– Developing MetaSocket in Adaptive Java

demonstrated that we can write adaptive application so that the adaptive code is separated from the application code.

– Developing, deploying, and maintaining such applications is much easier.

• Future Work:– MetaSocket is just one application written in

Adaptive Java. Further investigation on other adaptive applications showed that Adaptive Java should be extended.

– Some of the design decision made while developing Adaptive Java makes its use limited.