Wireless Infrastructure:
Overview and Issues
H. Scott Matthews
February 24, 2004
Homework #2
 Average:
24/30
 Midterm due March 4
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
Source: Lawrence Berkeley Labs;
http://www.lbl.gov/MicroWorlds/ALSTool/EMSpec/EMSpec2.htm
Early Radio/Wireless Events
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More detail on other telephone/wireless:
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Marconi: First ‘radio’ system created (1901)
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http://www.privateline.com/PCS/history2.htm
Wireless by induction/conduction/radiation
Application: ships - intended wireless telegraph
1906:
1910:
1924:
1927:
1934:
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Radio band-wave comm. - speech
Ericsson - first car ‘telephone’
First mobile car ‘radio’ telephone
US Federal Radio Commission started
Federal Communications Commission
Telephone & radio under jurisdiction - licenses for spectrum
Early history - very/too close to industry to manage
More Wireless Events
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1958: Invention of integrated circuit (IC)
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In this era, FCC ‘lazy’ in giving spectrum
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1973: First handheld cell phone in US
 Originally analog (handout) now digital
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Analog in 800 MHz range, Dig 800/1900
‘Cellular’ networks - freq reuse and handoff
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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
AT&T Breakup Effects
 Originally AT&T
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)
Antenna/Cell Locations
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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
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Don’t 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->D
System Statistics (mid 2002)
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From CTIA Industry Surveys (US only)
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135 million “subscribers” (all sectors)
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Avg call length 3 minutes
Number of wired ‘subscribers’ - about same
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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
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http://www.wow-com.com/industry/stats/surveys/
And decreasing as DSL, mobile phones happen
What are infrastructure management issues?
Wired and Wireless Users
Sample Wireless Telephone Coverage Map - What Is/Is Not
Covered by this Manufacturer - and is this total US coverage?
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
Other Issues
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Wireless not really wireless
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FCC - defined above - communications
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High dependence on wired (PSTN) network
Regulates activities, mergers of telecoms
State PUCs - also involved
 Industry Groups
 Big difference is less oversight of these
companies now that monopoly effects lower
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
FCC’s 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
Management Metrics
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Different type of problem since networks are
generally private
Subscribers
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Coverage area
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Percent of US, Percent of population, ..
Financial
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Number, growth, net additions
Voice quality
Time to login to system, call access time
Percent completed calls or call failure rate
Margin (profit) per minute, subscriber
Others?
Wireless ‘Data’ Networks
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IEEE 802.11b (used on campus)
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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 @ 5 Ghz, 12 channels no
overlap - 500 MHz of frequency
802.11g backwards compatible with 802.11b,
but boosts speed to 54 Mbps
CMU Campus Wi-Fi Network
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CMU campus: ubiquitous wired, wireless
networks
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Every room on campus ‘wired’, every space
‘wireless’
10,000 users; 350 wireless antennas (about 30
users each)
How much electricity used?
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Functional, but not equivalent, comparison
Show energy “to network 10,000 users
wired/wireless”
Only ‘network’ - not ‘attached devices’ - in boundary
Campus Network Model
Main computer center
Office/room
equipment
350 Wireless
Antennas
120 Wiring Closets
Two Data Sources
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Campus has building-level electricity meters
installed
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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
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Measure one of each, scale up via inventory
Summary of Estimates
Main Computing Center
Office Network Equipment
Wiring Closets Π Wired Switches
Wireless Transceivers & Switches
Total
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Annual
Electricity
(MkWh)
4.2
0.01-0.11
0.2
0.03
4.4 Π4.6
Power (kW)
480
15
30
3
520
Network electricity 6% of total campus - 1.7 kWh/ft2
Wireless endpoints use 10x less electricity than wired
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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
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
<
1% of US electricity consumption
Other Issues
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Ad hoc = latin for ‘for this (time)’
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Ad hoc networks are temporary, maybe one use systems
Difference in use and design of networks
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Don’t 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?
QuickTime™ and a TIFF (Uncomp resse d) de com press or are nee ded to s ee this picture.
See
publicinternetproject.org
For details, more research
Open/Public Wireless Nets
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Example of more formalized/larger ad hoc networks
(not fully “ad hoc”)
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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
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Note: these guys need more work / less free time
Implications of Open Nets
 Coordination
(e.g. same network name)
 Security!
 Preventing
questionable traffic
 Hacking/cracking/spamming
 Leeching
(free rider problem)