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Efficient and Transparent Dynamic Content Updates for Mobile Clients

Efficient and Transparent Dynamic Content Updates for Mobile Clients. Trevor Armstrong, Olivier Trescases, Cristiana Amza, Eyal de Lara University of Toronto, Canada. Typical Mobile Browsing Scenario. Mobile Browsing Problems. Current web browsing is poll based

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Efficient and Transparent Dynamic Content Updates for Mobile Clients

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  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 MobiSys 2006

  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 MobiSys 2006

  4. Key Observation • Two main types of content changes: • Irrelevant • Pertinent • More irrelevant than pertinent changes • Pertinent vs irrelevant content depends on user MobiSys 2006

  5. MobiSys 2006

  6. MobiSys 2006

  7. Our Approach • Allow user to distinguish pertinent from irrelevant • Download page only when pertinent information changes • Reduce wireless communication • Reduce battery consumption MobiSys 2006

  8. How It Works MobiSys 2006

  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 MobiSys 2006

  10. Client • Wrapper around Pocket Internet Explorer • 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 MobiSys 2006

  11. Client Profile Example MobiSys 2006

  12. Cache Updates • Polling • 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 MobiSys 2006

  13. Poll Based Updates MobiSys 2006

  14. Push Based Updates MobiSys 2006

  15. Hybrid SMS Updates WiFi or GPRS Message Structure MobiSys 2006

  16. Experiment • Keep track of four dynamic content web sites • Weather (weather.cnn.com) • Currency (www.xe.com) • Stock Values (finance.yahoo.com) • Online Auction (www.ebay.ca) • Evaluation Criteria • Data transfers to and from mobile device • Energy consumption MobiSys 2006

  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% MobiSys 2006

  18. Experimental Setup • Edge Server • Desktop PC running Redhat 9 • Dual Athlon 2600+ 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 MobiSys 2006

  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 MobiSys 2006

  20. Proxy Configurations • Without proxy • Simple 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 MobiSys 2006

  21. Data Received by Mobile Device MobiSys 2006

  22. Data Sent by Mobile Device MobiSys 2006

  23. Average Energy Consumption MobiSys 2006

  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 MobiSys 2006

  25. Hybrid SMS – Transition Point MobiSys 2006

  26. Hybrid SMS Energy Consumption MobiSys 2006

  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 MobiSys 2006

  28. Cold Visit Energy Consumption MobiSys 2006

  29. Cold Visit - GPRS Current MobiSys 2006

  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 • Restricted to the data that vendor provides MobiSys 2006

  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 MobiSys 2006

  32. Thank YouQuestions? MobiSys 2006

  33. System Architecture Mobile Device Edge Server MobiSys 2006

  34. Cold Visit - WiFi Current MobiSys 2006

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