Wireless Infrastructure: Overview and Issues

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Wireless Infrastructure Overview and Issues

• H. Scott Matthews
• February 24, 2004

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Homework 2

• Average 24/30
• Midterm due March 4

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Source Lawrence Berkeley Labs http//www.lbl.go
v/MicroWorlds/ALSTool/EMSpec/EMSpec2.html
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Early Radio/Wireless Events

• More detail on other telephone/wireless
• http//www.privateline.com/PCS/history2.htm
• Wireless by induction/conduction/radiation
• Marconi First radio system created (1901)
• Application ships - intended wireless telegraph
• 1906 Radio band-wave comm. - speech
• 1910 Ericsson - first car telephone
• 1924 First mobile car radio telephone
• 1927 US Federal Radio Commission started
• 1934 Federal Communications Commission
• Telephone radio under jurisdiction - licenses
  for spectrum
• Early history - very/too close to industry to
  manage

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More Wireless Events

• 1958 Invention of integrated circuit (IC)
• In this era, FCC lazy in giving spectrum
• 1973 First handheld cell phone in US
• Originally analog (handout) now digital
• Analog in 800 MHz range, Dig 800/1900
• Cellular networks - freq reuse and handoff
• Freq reuse allows more use of spectrum, manages
  potential interference
• Handoff trades ownership of signal to other cells
• Antennas associated with cells
• Cell size can be 1-50km radius - digital 10km
• Some cells have hierarchy of smaller cells
• Base station manages freq and power of handsets

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ATT Breakup Effects

• Originally ATT monopoly on telephone service in
  US, broken up in 1980s
• Created baby bells - RBOCs
• Intended to compete w/ each other
• 1990s - started merging
• Now provide wireless service in competition (e.g.
  Cingular Bell South, Verizon Bell Atlantic
  NE bells, etc)

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Antenna/Cell Locations

• Generally want to have 90 of an area covered
  and usable 90 of time
• Includes base station/equip and antenna
• Siting depends on demographics, population,
  growth, road usage, future trends
• Dont want too abandon cells, so choose now and
  add capacity/split cells later
• Height of antenna effects range of cell
• Consider absorption of natural environment (I.e.
  leaves on trees absorb some of signal!)
• Need more power in summer than winter
• Unlike rest of world, US was worried about
  backward compatibility when going A-gtD

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System Statistics (mid 2002)

• From CTIA Industry Surveys (US only)
• http//www.wow-com.com/industry/stats/surveys/
• 135 million subscribers (all sectors)
• Still rapid growth, but slowing (50
  penetration!)
• Almost 90 digital
• 131,000 cell sites (each using 3-5kW power)
• About 500 billion wireless minutes used/yr
• Avg call length 3 minutes
• Number of wired subscribers - about same
• And decreasing as DSL, mobile phones happen
• What are infrastructure management issues?

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Wired and Wireless Users
Source ITU World Telecom Development Report,
March 2002
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Sample Wireless Telephone Coverage Map - What
Is/Is Not Covered by this Manufacturer - and is
this total US coverage?
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Other Issues

• Wireless not really wireless
• High dependence on wired (PSTN) network
• FCC - defined above - communications
• Regulates activities, mergers of telecoms
• State PUCs - also involved
• Industry Groups
• Big difference is less oversight of these
  companies now that monopoly effects lower

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Miscellaneous

• Wireless generally a radio technology
• Dependent on antennas (cell sites)
• Cell sizes getting generally smaller
• Spectrum allocation has become an increasingly
  complex problem as there have been more demands
  for it (FCC)
• Number wired/wireless users equal

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FCCs involvement

• In telecom, the government tends to regulate the
  devices not the network
• E.g. licenses spectrum for use
• Certifies devices (e.g. phones) compliant
• Industry/professional groups (e.g. IEEE)
  generally set equipment/network standards

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Management Metrics

• Different type of problem since networks are
  generally private
• Subscribers
• Number, growth, net additions
• Voice quality
• Time to login to system, call access time
• Percent completed calls or call failure rate
• Coverage area
• Percent of US, Percent of population, ..
• Financial
• Margin (profit) per minute, subscriber
• Others?

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Wireless Data Networks

• IEEE 802.11b (used on campus)
• 11 Mbps, using 2.4 GHz spectrum (unlicensed!)
• 14 channels, 2.4 to 2.4835 GHz (80 MHz)
• Different channels legal around world, only chan.
  1, 6, and 11 have no overlap
• Designing a big network means reusing channels
  and considering overlaps
• Usually uses PC cards, access points wired
• Industry group (WiFi alliance) certifies products
• 802.11a 54Mbps _at_ 5 Ghz, 12 channels no overlap -
  500 MHz of frequency
• 802.11g backwards compatible with 802.11b, but
  boosts speed to 54 Mbps

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CMU Campus Wi-Fi Network

• CMU campus ubiquitous wired, wireless networks
• Every room on campus wired, every space
  wireless
• 10,000 users 350 wireless antennas (about 30
  users each)
• How much electricity used?
• Functional, but not equivalent, comparison
• Show energy to network 10,000 users
  wired/wireless
• Only network - not attached devices - in
  boundary

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Campus Network Model
Office/room equipment
Main computer center
350 Wireless Antennas
120 Wiring Closets
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Two Data Sources

• Campus has building-level electricity meters
  installed
• Several buildings have more than one meter when
  areas have higher than average use
• Used for Main computer center electricity
• Not so useful for electricity of room/equipment
• Portable power meters to measure electricity use
  of pieces of equipment
• Measure one of each, scale up via inventory

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Summary of Estimates

• Network electricity 6 of total campus - 1.7
  kWh/ft2
• Wireless endpoints use 10x less electricity than
  wired
• Caveats speeds, installation and maintenance
  requirements different
• Wireless speed bump coming (10x) but electricity
  use expected go up only 50
• Relevance more voice wireless than wired in the
  world

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Overall Voice Network Elec

• Do similar analysis, estimate PSTN and wireless
  voice network electricity use
• PSTN Public Switched Telephone Net
• Consider number and kW of cell sites
• Total energy use of sector, etc.
• Get estimate of 30 TWh/yr
• lt 1 of US electricity consumption

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Other Issues

• Ad hoc latin for for this (time)
• Ad hoc networks are temporary, maybe one use
  systems
• Difference in use and design of networks
• Dont have to be operating all the time
• Beaming with palm pilots is an example
• New Bluetooth devices will be too
• Useful for sensor networks (coming soon!)
• Issues with designing/managing ad hoc?

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See publicinternetproject.org For details, more
research
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Open/Public Wireless Nets

• Example of more formalized/larger ad hoc networks
  (not fully ad hoc)
• Campus wireless is not an example because you
  need to be registered to use
• Communities building small-medium wireless
  networks with their own broadband connection and
  wireless points (hotspots)
• Could have network name commonality but no
  password/authentication/registration
• There are people who drive around looking for
  open wireless networks just for fun
• Note these guys need more work / less free time

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Implications of Open Nets

• Coordination (e.g. same network name)
• Security!
• Preventing questionable traffic
• Hacking/cracking/spamming
• Leeching (free rider problem)