A Survey of Resource Constrained Issues for Handheld Devices

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A Survey of Resource Constrained Issues for
Handheld Devices

• Arranged by
• Jason Bumgarner

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Handheld Devices vs. PCs
Why is it necessary?

• PCs
• Memory 128-1024 MB
• Hard Drive 5-100 GB
• Screen Size 1024 X 768

• Handheld Device
• Memory 2-64 MB
• Hard Drive 2 MB - 2 GB
• Screen Size 240 X 480

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Whats the impact?

• Many PC applications arent portable to handheld
  devices due to the memory constraints.
• Scaled applications lose much of their power and
  appeal
• These constraints affect usability and therefore
  market value

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Memory Constraint

• Amount of memory is significantly less
• Traditional fat client model will not be
  sufficient due to these constraints

Fat Client
Responsibilities Application Logic Presentation
Logic Data Access Logic Data Storage
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What can we do?

• We can share the workload with a server
• Two Paradigms currently in use
• The Thin Client Model
• The Client-Server Architechture

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Thin Client

• Relies on a server for all of the computation and
  storage needed by the application
• Its only responsibility is to display the
  interface and communicate with the server

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Thin Client Model
Thin Client
Server
Application Logic Presentation Logic Data Access
Logic Data Storage
User Response
UI Update
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Example X Terminal

• The X Terminal is a thin client
• Application on the PC only serves the graphics
• All computations are done by the server

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Thin Client - Advantages

• Increases application availability
• Cost
• Security

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Thin Client - Disadvantages

• Increased Server Requirements
• Dependency on Network Connection
• Increased Bandwidth
• Poorer Multimedia Performance

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Client Server Model

• Very Similar to the thin client model
• Difference Not All logic is computed by the
  server
• Client performs some tasks and calls upon the
  server for others

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Client Server Model
Client
Server
Data Access Logic Data Storage
User Response
Application Logic Presentation Logic
UI Update
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Client-Server Advantages

• Same advantages as thin client
• Reduced work load when compared to thin client
  model

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Client-Server Disadvantages

• Same as the thin client model

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Client-Server Applications

• Popular Client-Server applications include
• File Servers
• Print Servers
• Network Servers

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Additional Considerations

• Screen Size Limitations
• User Input
• Quick Response Time
• PC Connectivity
• File System

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Screen Size Limitations

• Many UIs wont even fit on the smaller screen
  size
• Some that do fit are barely useable
• Also limits the type of graphics that may be used

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User Input

• No mouse or keyboard available
• Since data entry is done easily it should be
  limited
• Should be done as widget selection as much as
  possible
• Example Rather than have the user enter the
  state theyre from, have a drop down box

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Quick Response Time

• Hand held devices are used on the go
• Usually used for quick tasks
• Check Email
• Add/Access contact information, appointment
  information, etc.
• Long load time would greatly reduce the
  effectiveness of the device

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PC Connectivity

• Most devices come with a cradle for linkage to a
  PC
• Very important that all actions between the
  device and PC be easily done, i.e. point, click,
  done.

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File System

• Due to the memory constraints and requirement for
  PC Connectivity, traditional File Systems wont
  be sufficient.
• Generally, a database approach is taken
• This reduces the amount of RAM needed because the
  data is looked up rather than being available in
  memory

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Conclusion

• Many issues that typically are not a concern of a
  PC application are concerns for handheld devices.
  Current research and practices suggest that many
  of these concerns are being addressed but are far
  from being resolved.

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References

• http//www.whyhowproveit.co.uk
• http//www.netmeister.org/palm/PalmMisc/PalmMisc.h
  tml
• http//www.mobilecoders.com/Articles/mc-01.asp
• http//fragments.turtlemeat.com/handheld-mobile-pr
  ogramming/effective-use-limited-resources.php
• http//en.wikipedia.org/wiki/Thin_client

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Any Questions?
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Thank You!