# Overview of Computer Networks - College of Engineering

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```					                      CPET 355
2. The Physical Layer -
Wireless Transmission

Paul I-Hai Lin, Professor
Electrical and Computer Engineering Technology
Purdue University, Fort Wayne Campus

Feb. 2, 2004                Prof. Paul Lin               1
The Electromagnetic Spectrum
    NASA
• http://imagine.gsfc.nasa.gov/docs/science/kno
w_l1/emspectrum.htm
• http://imagers.gsfc.nasa.gov/ems/waves3.htm
l
    Berkeley Lab: Electromagnetic
Spectrumhttp://www.lbl.gov/MicroWorlds/
ALSTool/EMSpec/EMSpec2.html
    Naval Spectrum Management Support-
http://www.navemscen.navy.mil/index.ht
m
Feb. 2, 2004             Prof. Paul Lin             2
Frequency Allocation
• Radio wave- < 3 x109 Hz
• Microwave – 3.0x109 – 3x1012 Hz
• Infrared    - 3.0x1012 – 4.3x1014 Hz
• Visible     - 4.3x1014 – 7.5x1014 Hz
• Ultraviolet - 7.5x1014 – 3.0x1017 Hz
• X-Rays      - 3.0x1017 – 3.0x1019 Hz
• Gamma Rays - > 3.0x1019 Hz
f = c
Wavelength*Frequency = speed of light
Feb. 2, 2004           Prof. Paul Lin          3
Wavelength
    f = c
Wavelength*Frequency = speed of light
    Electromagnetic Wave
• http://www.geo.mtu.edu/rs/back/spectr
um/
    An Applet Example -
http://lectureonline.cl.msu.edu/~mm
p/applist/Spectrum/s.htm
Feb. 2, 2004          Prof. Paul Lin          4
Spectrum for Wireless
Transmission
Microwave, Infrared, and Visible light
f = c            f = c/ 
df/d = c/ 2    f = c  / 2
    Narrow frequency band
f/f << 1, best reception (watts/Hz)
• Military application, 802.11, Bluetooth,
Feb. 2, 2004            Prof. Paul Lin             5
Wireless Transmission
    Federal Regulations
• Wireless Telecommunication Bureau,
http://wireless.fcc.gov/
    Emerging Wireless Technologies,
http://www.fcc.gov/initiatives.html
   3G Wireless
   Digital TV
   Lower Power FM
   Rural Wireless ISP
   Voice Over IP
Feb. 2, 2004                            Prof. Paul Lin   6
Wireless Transmission
    Microwave Transmission
    Lightwave Transmission
    Satellite Communications

Feb. 2, 2004            Prof. Paul Lin   7
   Omnidirectional systems
•   For indoor and outdoor
•   No need for physical alignment
•   Can penetrate buildings easily
•   Low bandwidth
   Examples
• Paging – short message, 10s of k meters
• Cordless telephone – analog/digital, 10s of
meters
• Cellular phone – analog/digital/data, k meters
• Personal communication services – digital
of
voice and data, 100sPaul Lin meters
Feb. 2, 2004                 Prof.                        8
Microwave Transmission
    Wave > 100 MHz can penetrate haze, light
rain and snow, clouds, and smoke
    Do not passing through building well, and
has multipath fading effect (some delay
waves that may cancel the signals)
    Wave can travel in nearly straight line and
can be narrowly focused for transmitting
information (data & voice)
    100 meter tower, repeaters can be spaced
by 80 km apart

Feb. 2, 2004           Prof. Paul Lin          9
Microwave Transmission
    Microwave Spectrum
• http://imagers.gsfc.nasa.gov/ems/micro.html
    ISM bands – Industrial, Scientific and
• International Telecommunication Union
http://en.wikipedia.org/wiki/ITU-T
• 900 MHz – crowded, not available world wide
• 2.4 GHz – available worldwide; 802.11
wireless LAN
• 5.7 GHz – new; 802.11a use it
Feb. 2, 2004             Prof. Paul Lin               10
Microwave Transmission
    Applications
wavelength)
• Transmitting information: data and
phone (can penetrate haze, light rain
and snow, clouds, and smoke)
• Remote sensing – weather forecasting
• Wireless LAN

Feb. 2, 2004           Prof. Paul Lin           11
Lightwave Transmission
    IrDA Association -
http://www.irda.org/
    Wavelength range – 850 nm to 900
nm
    IrDA-C
• 75 kbps, up to 8 meters
    IrDA-D
• 115 kbps to 4Mbps, up to 1 meter
Feb. 2, 2004           Prof. Paul Lin      12
Satellite Communications
    GOES (Geostationary Satellite)
Systems
• 36,000 km above the equator
• Transponder data rate – 50 Mbps, at
4/6. 11/14, and 20/30 GHz bands
    LEOS (Low-Earth Orbit Satellite)
Systems
    MEOS (Multiple-mission Earth
Observatory Satellite) Systems
Feb. 2, 2004          Prof. Paul Lin          13
GOES Satellite
Communications
 Significant satellite operators & Industries
http://www.3g-generation.com/satellite.htm
 GOES Satellites
http://ww2010.atmos.uiuc.edu/(Gh)/guide
s/rs/sat/goes/home.rxml
 GOES Science Projects
http://rsd.gsfc.nasa.gov/goes/
 GOES Servers
• http://www.goes.noaa.gov/
• http://www.goes.noaa.gov/g8hu.html

Feb. 2, 2004            Prof. Paul Lin       14
Satellite Communications
    Overview of LEO Satellite Systems
• http://www.its.bldrdoc.gov/meetings/art/art99
/slides99/red/red_s.pdf
    LEOS (Low-Earth Orbit Satellite)
• Technologies and Trends -
http://www.mindbranch.com/listing/product/R
201-084.html
    Routing and Multicasting in LEO Satellite
IP Networks
• http://users.ece.gatech.edu/~cchen/routing/dr
p.html
Feb. 2, 2004             Prof. Paul Lin             15
MEOS Satellite
    Multiple-mission Earth Observatory
Satellite
• http://www.eumetsat.de/en/area2/proc
eedings/eump33/pdf/session_5/softwar
e/oynes.pdf

Feb. 2, 2004          Prof. Paul Lin       16
Web References
    Hughes Network Systems, www.hns.com
• http://research.mwjournal.com/data/detail?id
=988922143_314&type=ORG
    NEC Optical Network Division
http://www.necpng.com/press/
    Panduit Network Connectivity Solutions
http://www.panduit.com/
    www.commscope.com
    Errcsson Microwave Systems AB
http://www.ericsson.com/microwave/
    Northrop Grumman – California Microwave
Systemshttp://sensor1.northgrum.com/calmw/
Feb. 2, 2004             Prof. Paul Lin                17

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