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SUMMARY:Algorithmic Market Design: Spectrum Sales and BitTorrent Communiti
 es - Ian Kash\, Harvard University
DTSTART:20110426T124500Z
DTEND:20110426T134500Z
UID:TALK30982@talks.cam.ac.uk
CONTACT:Microsoft Research Cambridge Talks Admins
DESCRIPTION:Markets are a powerful tool for producing desirable outcomes i
 n an engineered system.  As computers allow us to build new and more compl
 ex markets\, we need new algorithmic tools to understand and improve them.
   In this talk I'll discuss two examples of such markets.\n\nUntil recentl
 y\, if you wanted to start a business that requires using wireless spectru
 m\, you would either have to pay tens of millions of dollars for an exclus
 ive license or use one of the few congested frequencies that are available
  without a license (such as the one used by WiFi).  Recently\, people have
  begun investigating how auctions can be used to sell smaller amounts of s
 pectrum.  I'll present a new auction algorithm that takes advantage of the
  ability of devices to share spectrum to significantly improve both spectr
 um utilization and social welfare.\n\nOver the years\, private file-sharin
 g communities built on the BitTorrent protocol have developed their own po
 licies and mechanisms for motivating members to share content and contribu
 te resources.\nOne popular mechanism is to require members to maintain a m
 inimum ratio between uploads and downloads.  By doing so\, private communi
 ties effectively establish an economy. I'll present a year-long measuremen
 t study of DIME—a community for sharing live concert recordings—throug
 h which we find that users rationally react to cost differentials when mak
 ing decisions on what files to consume. We observe significant disparities
  in the cost of new and old files\, where by consuming newer files frequen
 t visitors can quickly earn credit. We find that users compensate for the 
 high cost of older files by downloading more copies of newer files\, and b
 y preferentially consuming older files during a ‘free leech’ period.
LOCATION:Small lecture theatre\, Microsoft Research Ltd\, 7 J J Thomson Av
 enue (Off Madingley Road)\, Cambridge
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