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Wireless Ad Hoc Podcasting

Wireless Ad Hoc Podcasting. Ad hoc . ad hoc network typically refers to a system of network requiring little or no planning a decentralized type of wireless network The network is ad hoc because it does not rely on a preexisting infrastructure. Wireless Ad Hoc Podcasting.

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Wireless Ad Hoc Podcasting

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  1. Wireless Ad Hoc Podcasting

  2. Ad hoc • ad hoc network typically refers to a system of network requiring little or no planning • a decentralized type of wireless network • The network is ad hoc because it does not rely on a preexisting infrastructure

  3. Wireless Ad Hoc Podcasting • Podcasting used for media content • But inflexible • Based on Delay-Tolerant Network

  4. outline • Podcasting in the Internet • Delay-tolerant network • Wireless Ad Hoc Podcasting • Solicitation Strategies • Evaluation and simulation • Conclusion and comment

  5. Podcasting • Podcasting: dissemination of streaming contents over the Internet. • Playback off line.

  6. Podcasting in the Internet • Fairly simple • Channel to define a feed and make it accessible on a web server • Feed is an XML file, which contains a list of entries. • Subscribe to podcast channel by entering feed URI into Podcatcher

  7. Podcasting in the Internet • Retrieves and processes data from the feed URI • Automatically downloads new entries

  8. Podcasting in the Internet • Atom Syndication Protocol • Based on XML

  9. outline • Podcasting in the Internet • Delay-Tolerant Network • Wireless Ad Hoc Podcasting • Solicitation Strategies • Evaluation and simulation • Conclusion and comment

  10. Delay-Tolerant Network • Loosely connected network for asynchronous communication • Intermittent connectivity

  11. Delay-Tolerant Network • Every node scans periodically the network neighborhood • Nodes associate pair wise • IEEE 802.11, Bluetooth • Receiver-driven, No flooding

  12. outline • Podcasting in the Internet • Delay-Tolerant Network • Wireless Ad Hoc Podcasting • Solicitation Strategies • Evaluation and simulation • Conclusion and comment

  13. Wireless Ad Hoc Podcasting • Enhancement of podcasting

  14. Wireless Ad Hoc Podcasting • No means to search for podcast channels • Feed channel should be known priori • Enhancement: discovery channel • List of the feed channel, which may be empty

  15. Wireless Ad Hoc Podcasting • Entries must update constantly to reflect the latest status • Entries will reach a node in arbitrary order • Atomic unit • Feed channel is composed of a mixture of entries of music, news items, weather updates ,etc

  16. Wireless Ad Hoc Podcasting • Subscribed channel • Public channel

  17. Wireless Ad Hoc Podcasting • Request for contents: • Any content • Feed channel • Entry • Feed channel + entry • Time • Uniqueness : matches any entry not in a provided list of entry ID’s.

  18. Wireless Ad Hoc Podcasting • False positive • Possible • False negative • Impossible!

  19. Wireless Ad Hoc Podcasting • Data Structure • Distinct identifiers • Meta data • Internal structure • Public cache or subscribed channel • Request list for solicitation decision • Download status

  20. Wireless Ad Hoc Podcasting • Protocol design • Receiver-driven • State machine • First state • Second state • Unbeknownst to its user (public cache)

  21. outline • Podcasting in the Internet • Delay-Tolerant Network • Wireless Ad Hoc Podcasting • Solicitation Strategies • Evaluation and simulation • Conclusion and comment

  22. Solicitation Strategies • An open question : how to solicit to satisfy the future request.

  23. Solicitation Strategies • Most solicited • Least solicited • Uniform • Inverse proportional • No caching

  24. Most solicited • Increase the probability in a popular feed • history-based ranking • Request list of locality

  25. Least solicited • Opposite goal against most solicted • May waste resources

  26. Inverse proportional • Mitigate the waste of unpopular cache • Inverse proportional to its popularity

  27. Uniform and no caching • Feed channel are treated equally and requested randomly • No caching is used for benchmark

  28. outline • Podcasting in the Internet • Delay-Tolerant Network • Wireless Ad Hoc Podcasting • Solicitation Strategies • Evaluation and simulation • Conclusion and comment

  29. Network and simulation model • Two nodes can communicate with if distance is smaller than a threshold value • No collision and interference • Random waypoint mobility model

  30. Scenario Setting • Scenario • Radio range 10 m • Moving speed 1 m/s • Rate of radio devices 1 Mb/s • Entry size 250 KB • Square 300 m X 300 m • Popularity

  31. Performance metrics • Freshness • Overall and per channel average freshness • Max-min fairness

  32. Result • 50 nodes and 7 different channels. • varying

  33. Result • Uneven popularity for ,a larger value increases the probability that unpopular channels are solicited

  34. Result

  35. Result • Varying Publishing rate

  36. Result • Varying Publishing rate

  37. Result

  38. outline • Podcasting in the Internet • Delay-tolerant network • Wireless Ad Hoc Podcasting • Solicitation Strategies • Evaluation and simulation • Conclusion and comment

  39. Conclusion and comments • The best overall performance is uniform strategy. • Security problem • Based on Bluetooth? • Useful in sparse district?

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