1. Efficient and Transparent Dynamic Content Updates for Mobile Clients
Trevor Armstrong, Olivier Trescases, Cristiana Amza, Eyal de Lara
University of Toronto,
Canada

2. Typical Mobile Browsing Scenario
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3. Mobile Browsing Problems
Current web browsing is poll based
Inconvenient, requires user’s attention
Browser caches ineffective for rapidly changing dynamic content
Wastes battery and money
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4. Key Observation Two main types of content changes:
Irrelevant
Pertinent
More irrelevant than pertinent changes
Pertinent vs irrelevant content depends on user
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6. Same color, bring out one by one
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7. Our Approach Allow user to distinguish pertinent from irrelevant
Download page only when pertinent information changes
Reduce wireless communication
Reduce battery consumption
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8. How It Works Animate screen cap to show process 11/13/2018
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9. Edge Proxy Monitors state of all web sites in profile
Batches cache updates in a single transfer
Prefetches all items in a new request
Animate screen cap to show process
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10. Client Wrapper around Pocket Internet Explorer Client profile
Select areas of interest within a web page
Select thresholds of change for numerical values
Client profile
Used by the edge proxy when updating cache
Stored as tree structure
Animate screen cap to show process
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11. Client Profile Example
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12. Cache Updates Polling Push Based Hybrid SMS
Mobile proxy explicitly requests cache updates
Push Based
Mobile proxy listens on a specific port for incoming updates
Hybrid SMS
Edge proxy sends a SMS message to client when updates are available
Includes update batch size
Try to fit the example into this slide, highlighting
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13. Poll Based Updates
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14. Push Based Updates
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15. Hybrid SMS Updates WiFi or GPRS Message Structure 11/13/2018
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16. Experiment Keep track of four dynamic content web sites
Weather (weather.cnn.com)
Currency (
Stock Values (finance.yahoo.com)
Online Auction (
Evaluation Criteria
Data transfers to and from mobile device
Energy consumption
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17. Real World Traces Three hour traces, played back for experiments
eBay auction
732 visits to page
377 page changes: 52%
6 bid changes: 0.8%
Currency value (XE.com)
733 visits to page
732 page changes: 100%
365 Euro changes: 50%
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18. Experimental Setup Mobile Device Edge Server
Desktop PC running Redhat 9
Dual Athlon processors
2 GB Ram
100 MBit Ethernet connection
Mobile Device
HP iPAQ 6325 running Windows Mobile 2003
168 MHz processor
64 MB Ram, 64 MB Rom
Built in WiFi and GSM/GPRS
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19. Wireless Communication Tradeoffs
WiFi (802.11)
High bandwidth and low latency
Power hungry
Cellular data communication (GPRS)
Lower power consumption
Reduced bandwidth and high latency
Move this to experimental section
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20. Proxy Configurations Without proxy Simple proxy Intelligent proxy
Updates whenever there is a change to the page
Intelligent proxy
Updates when pertinent information changes
Threshold proxy
Updates when pertinent information changes by a user specified amount
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21. Data Received by Mobile Device
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22. Data Sent by Mobile Device
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23. Average Energy Consumption
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24. Hybrid SMS
Experimentally determined the data size where downloading over WiFi is cheaper than GPRS
Mobile proxy uses this threshold to make an informed choice about downloading updates
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25. Hybrid SMS – Transition Point
Mention that the wifi graph will eventually start to increase, albeit slowly
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26. Hybrid SMS Energy Consumption
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27. Cold Visit Loaded a site the device hadn’t seen before
Proxy cache and browser cache totally empty
Web site details:
51 total objects
185 KB all together
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28. Cold Visit Energy Consumption
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29. Cold Visit - GPRS Current
State how and why we save energy for WiFi
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30. Related Work Proxy based systems (PAWP, WebExpress)
Not user-centric
SMS based services (Google SMS)
Monetary cost
Restricted to the data that vendor provides
Proprietary push technologies (Blackberry)
Restricted to the hardware of that manufacturer
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31. Conclusions Most changes are irrelevant to the user
Allow user to specify their areas of interest
Proxy system updates client based on profile
Our system shows data and battery savings over both GPRS and WiFi
Seamless notifications even when disconnected
Current methods of web browsing were designed for the desktop, it’s time to update those for the mobile environment
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32. Thank You Questions?
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33. System Architecture Mobile Device Edge Server
Take out and move the solution diagram to here and animate a change of the pages
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34. Cold Visit - WiFi Current
Take out
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