10 William Webb E Comm Europe2009

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10 William Webb E Comm Europe2009

  1. 1.
  2. 2. Turning junk into gold and then back againHow unlicensed usage has become a core part of modern communications<br />Professor William Webb<br />October 2009<br />
  3. 3. WiFi is becoming ever more prevalent<br />2<br />Source: Perspective<br />
  4. 4. WiFi plays an increasing role in keeping the cellular networks from congestion<br />3<br />
  5. 5. But the WiFi band is showing signs of congestion<br />Height of bars indicates number of base stations<br />Colour indicates quality of link<br />4<br />Source: Work conducted by MASS for Ofcom<br />
  6. 6. Solutions exist<br />Prevent interference in 2.4GHz (for example by banning video senders or encouraging “WiFi friendly” systems<br />May be too late<br />Somewhat contrary to the whole idea of unlicensed bands<br />Move to 5GHz (around 400MHz of spectrum available compared with 80MHz at 2.4GHz)<br />Limited take-up – perhaps to do with the reduced range<br />Make use of femtocells to avoid unlicensed spectrum<br />See later<br />Move to “cognitive” or “white space” systems<br />See later<br />5<br />
  7. 7. Femtocells can make a difference<br />Strong industry support<br />But key issues remain around “openness”<br />In the home can only off-load traffic from home owner and perhaps not even all family members<br />In urban areas need one per operator, not desirable for owners of malls or buildings<br />Closed femtocells can create small coverage holes<br />And the commercial model still not certain<br />Will the operators need to subsidise?<br />Will they be prepared to do this?<br />6<br />
  8. 8. Considerable evidence of little-used spectrum<br />7<br />Source: Measurements by CRFS for Ofcom<br />
  9. 9. Cognitive devices have evolved from sensing to databases<br />Original idea was to sense whether the spectrum was used<br />Considerable work has shown that the “hidden terminal problem” requires devices to be extremely sensitive<br />Focus has now shifted to a “geo-location database”<br />Device locates itself<br />Asks a master database for local channel availability<br />8<br />
  10. 10. Is regulatory change needed to prevent a meltdown in unlicensed bands?<br />A low-value “best effort” service has become a key part of our communications infrastructure<br />But the openness of the spectrum that helped make it successful is now contributing to the problem<br />Is it time to change the rules?<br />Dedicate some spectrum to WiFi?<br />Open up enough spectrum to all to avoid congestion?<br />Move WiFi ?<br />Clear out the 2.4GHz band of other uses?<br />Is “TV white space” the key hope for the future?<br />9<br />

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