Sec.0a--Intro to pervasive computing 3.ppt

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© 2007 by Leszek T. Lilien
Based on: M. Satyanarayanan, “Pervasive Computing: Vision and Challenges,” IEEE Personal Communications, 2001
Pervasive Computing vs. Distributed Systems & Mobile Computing (13)
Pervasive Computing (7)
2.3.3) Localized Scalability
 Basic model of pervasive computing interactions:
 User’s personal computing space (UPCS)
 User’s surroundings (US)
 Interactions between UPCS & US
 Scalability problems in pervasive computing
 The smarter is the space, the larger is interaction intensity
 This has severe bandwidth, energy and distraction implications for
a wireless mobile user.
 The more users in the smart space the more interactions

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3) Localized Scalability – cont.
 Scalability research
 Previous work typically ignored physical distance
 A web server or file server should ignore distance
 Handle as many clients as possible, regardless of whether they
are located next door or overseas
 Scalability in PERV must consider physical distance
 Interaction density has to fall off with distance
 Otherwise both the user and his computing system will be
overwhelmed by distant interactions that are of little relevance
 A mobile user far from home will still generate some distant
interactions with sites relevant to him
 But the preponderance of his interactions will be local

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3) Localized Scalability – cont.
 Good PERV design: scalability achieved by
severely reducing distant interactions
 Like the inverse square laws of nature
 .g., the inverse square law for gravitation)
 This directly contradicts the current ‘‘death of
distance’’ ethos of the Internet

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2.3.4) Masking Uneven Conditioning
 ‘‘Smartness’’ of different spaces varies significantly
(“The rate of penetration of pervasive computing technology into the infrastructure will vary
considerably […]”)
 Well-equipped conference room, office, or classroom smarter
than other locations
 Space smartness depends on:
 Technical factors
 How well the space is saturated with smart devices
 Non-technical factors
 Organizational structure, economics and business models, …
 Uniform ‘‘smartness’’ of spaces is years or decades away
(if ever achieved)

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4) Masking Uneven Conditioning – cont.
 Differences in ‘‘smartness’’ can be distracting
 Can detract from the goal of invisible pervasive computing
 One idea: Reduce the amount of variation in smartness
seen by a user
 Example implementation of the idea:
User’s personal computing space (UPCS) compensates
for ‘‘dumbness’’ of its environments
 E.g., a laptop masks the absence of wireless coverage
 The laptop notices me leaving the CEAS building and downloads
my mail as I leave the area covered by CEAS hot spots
 I can read my new mail at a restaurant without a hot spot
 Complete compensation (achieving complete invisibility) may be
impossible
 But reduced variability of space smartness within reach

Sec.0a--Intro to pervasive computing 3.ppt

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3. Example Scenarios
 What would it be like to live in a world with
pervasive computing?
 Two hypothetical ‘‘look and feel’’ scenarios follow
 Deliberately chosen simple scenarios that appear
feasible soon (in just a few years)
 Examples use [CMU’s] Aura (http://www.cs.cmu.edu/~aura/)
as the pervasive computing system
 But the illustrated concepts are of broad relevance

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Example Scenarios (2)
3.1) Scenario 1
 Jane is at Gate 23 in the Pittsburgh airport, waiting for her flight.
 She has edited many large documents, and would like to use her
wireless connection to e-mail them. Unfortunately, bandwidth is
miserable since many passengers at Gate 23 and nearby gates are
surfing the web.
 Aura observes that at the current bandwidth Jane won’t be able to
finish sending her documents before her flight departs.
 Consulting the airport network’s flight schedule service, Aura
discovers that wireless bandwidth is excellent at Gate 15, and that
there are no departing or arriving flights at nearby gates for 30 min.
 Aura displays a dialog box on Jane’s screen suggesting that she
goes to Gate 15, which is only three minutes away. It also asks her
to prioritize her e-mail, so that the most critical messages are
transmitted first.
 Jane accepts Aura’s advice and walks to Gate 15. She watches CNN
on the TV there until Aura informs her that it is close to being done
with her messages, and that she can start walking back.
 Jane starts walking back to Gate 23.
 The last message is transmitted during her walk, and she is back at
Gate 23 in time for her boarding call.

Sec.0a--Intro to pervasive computing 3.ppt

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