A Fresh Look At LowPower Mobile Computing

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A Fresh Look AtLow-Power Mobile Computing

• Michael Franz

In COLP 2001
Presented by Yonghyun Hwang
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Introduction

• Latency and Bandwidth
• high latency low bandwidth
• 3rd generation mobile networks
• cannot solve problem
• e.g., battery vs required system performance
• Traditional Solution
• downloadable applet
• mobile agent
• conduct computation locally

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Problem Proposal

• Problem in Traditional Solution
• downloading executing mobile code requires
  considerable resources
• so, it implies significant power consumption
• Proposal in This Paper
• a three level MS(Mobile Station)-XU(Execution
  Unit)-Server architecture
• off-loading the resource-intensive parts of the
  client program to the mobile base station

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Proposed System Overview
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Proposed System

• Key Characteristic
• there is direct connection btn XU and MS
• connection has sufficient bandwidth
• to server, the XU-MS pair acts as an atomic
  entity
• One Possible Scenario (JAVA)
• MS downloads class file
• XU executes most of JAVA class

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Two Issues

• Handover
• MS is physically moving
• so, transfer state from one XU to another to keep
  low-latency connection btn MS and XU
• Segmentation of Functionality
• the XU-MS pair acts as an atomic entity, to
  server
• so, functionality should be divided btn XU and MS
  on the fly

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Handover

• Four Issues of Actual Transfer
• XU must have sufficient resources
• XU must have the required libraries available
  locally
• there must be sufficient network resources to
  enable the transfer of state information btn XU
  within a useful time frame
• standardization of execution environments
  parameter

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Segmentation of Functionality

• Considerable Factor
• communication overhead
• to minimize power consumption of MS, include
  power used for communication
• special end-to-end application requirements
• some special codes (e.g., some codes for login)
  must be executed in the trusted parts resided on
  MS
• imagine a banking application

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Segmentation of Functionality

• Most Simple Case Dumb Terminal Sol.
• MS dumb terminal, XU run a virtual terminal
• imagine the X-window system

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Segmentation of Functionality

• Alternative Methods
• annotation based
• future format of mobile code include annotations
  that guide in the partitioning
• similar algorithm such as partitioning for
  parallel execution
• XU directive based
• first mobile code is transformed to intermediate
  format
• XU adjust these bindings on-the-fly in reaction
  to changing user activities on the MS
• XU send MS an updated configuration

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Research Vision

• Contribution
• We have identified several topics requiring
  further research
• Our Vision
• elevate good power management into a system-wide
  quality of mobile code systems