16-05-2012, 11:08 AM
Challenges of Mobile Computing
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Research Issues in Mobile Computing
• Wireless Communications
– Quality of connectivity
– Bandwidth limitations
• Mobility
– Location transparency
– Location dependency
• Portability
– Power limitations
– Display, processing, storage limitations
Classes of Mobile Devices
• Display Only
– InfoPad model: limited portable processing
– Constrained to operation within prepared infrastructure,
like a cordless phone
– Advantages with respect to power consumption, upgrade
path, lightweight, impact of lost/broken/stolen device
• Laptop Computer
– Thinkpad model: significant portable processing,
operates independently of wireless infrastructure
– Disadvantages: power consumption, expensive,
significant loss exposure, typically greater than 5 pounds
• Personal Digital Assistant
– Somewhere between these extremes
Wireless Communications
• Harsh communications environment:
– Lower bandwidth/higher latency:
good enough for videoconferencing?
– Higher error rates
– More frequent disconnection
– Performance depends on density of nearby users but inherent
scalability of cellular/frequency reuse architecture helps
• Connection/Disconnection
– Network failure is common
– Autonomous operation is highly desirable
» Caching is a good idea, e.g., web cache
– Asynchronous/spool-oriented applications, like mail or printing
» Trickle back data when bandwidth is available
– Disconnected file systems: CODA (CMU), Ficus (UCLA)