rong wang cgs3285 january 2004
Download
Skip this Video
Download Presentation
Rong Wang CGS3285 January 2004

Loading in 2 Seconds...

play fullscreen
1 / 27

Rong Wang CGS3285 January 2004 - PowerPoint PPT Presentation


  • 163 Views
  • Uploaded on

Wireless Transmission. Rong Wang CGS3285 January 2004. Recommended Reading. From textbooks: Chapter 7 of Data Communications and Networking, 3rd Edition, by Behrouz A. Forouzan (ISBN: 0-07-251584-8)

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Rong Wang CGS3285 January 2004' - freira


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
rong wang cgs3285 january 2004
Wireless Transmission

Rong Wang

CGS3285

January 2004

recommended reading
Recommended Reading
  • From textbooks:
    • Chapter 7 of Data Communications and Networking, 3rd Edition, by Behrouz A. Forouzan (ISBN: 0-07-251584-8)
    • Page 78~81 of Data Communications: From Basics to Broadband, 3rd Edition, by William J. Beyda (ISBN: 0-13-096139-6)
  • From references:
    • Chapter 4 of Data and Computer Communications, 7th Edition,

by William Stallings (ISBN:0-13-100681-9)

Unguided Transmission Media

slide3
Unguided Media: Wireless

Antennas

Satellite

Terrestrial

Broadcast Radio

Infrared

Unguided Transmission Media

wireless transmission frequencies
Wireless Transmission Frequencies

Unguided Transmission Media

antenna
Antenna
  • Electrical conductor (or system of..) used to radiate electromagnetic energy or collect electromagnetic energy
  • Transmission
    • Electrical energy is converted into electromagnetic energy by antenna
    • Radiated into surrounding environment
  • Reception
    • Electromagnetic energy impinging on antenna
    • Converted to electrical energy
    • Fed to receiver
  • Same antenna often used for both

Unguided Transmission Media

radiation pattern
Radiation Pattern
  • Power radiated in all directions
  • Not same performance in all directions
  • Isotropic antenna is (theoretical) point in space
    • Radiates in all directions equally
    • Gives spherical radiation pattern

Unguided Transmission Media

omnidirectional antennas
Omnidirectional antennas

Unguided Transmission Media

slide8
Figure 7.21Unidirectional antennas

Unguided Transmission Media

wireless propagation methods
Wireless Propagation Methods
  • Signal travels along three routes
    • Ground wave
    • Sky wave
    • Line of sight

Unguided Transmission Media

ground wave propagation
Ground Wave Propagation
  • Follows contour of earth
  • Up to 2MHz
  • AM radio

Unguided Transmission Media

sky wave propagation
Sky Wave Propagation
  • Signal reflected from ionosphere layer of upper atmosphere
  • Amateur radio, BBC world service, Voice of America
  • (Actually refracted)

Unguided Transmission Media

line of sight
Line-of-Sight
  • Above 30Mhz
  • May be further than optical line of sight due to refraction

Unguided Transmission Media

satellite
Satellite
  • Satellite is a relay station
  • Satellite receives on one frequency, amplifies or repeats signal and transmits on another frequency
  • GEO (geosynchronous-earth orbit) satellites
    • Height of 22,230 miles
    • Requires 3 GEO satellites
  • LEO (low – earth orbit) satellites
    • A few hundred miles above the earth
    • Require more 66 LEO satellites
  • MEO (medium-earth orbit) satellites
    • 6434 miles above the earth
    • Require 12 MEO satellites
  • Advantage: cheaper over long distances than fiber optics or twisted pair
  • Problem:
    • susceptible to noise and interference caused by a variety of sources
    • Security risk

Unguided Transmission Media

satellite communication configurations
Satellite Communication Configurations
  • Point-to-Point
  • Multipoint

Unguided Transmission Media

point to point transmission
Point-to-Point Transmission

Unguided Transmission Media

satellite broadcast link
Satellite Broadcast Link

Unguided Transmission Media

satellite transmission characteristics
Satellite – Transmission Characteristics
  • Optimum frequency range
    • 1~10 GHz
  • Point-to-point service 4/6-GHz band
    • 5.925 ~ 6.425GHz (uplink)
    • 3.7 ~ 4.2GHz (downlink)
  • Point-to-point service 12/14-GHz band
    • 14 ~ 14.5GHz (uplink)
    • 11.7~12.2GHz(downlink)
  • Point-to-point service 23/30-GHz band
    • 27.5 ~ 30GHz (uplink)
    • 17.7 ~ 20.2GHz(downlink)
  • Subject to noise and delays

Unguided Transmission Media

satellite applications
Satellite Applications
  • Television
    • Satellites are well suited to television distribution because its broadcast nature
    • TV programs are transmitted to the satellite and then broadcast down to a number of stations
    • Stations then distribute the programs to individual viewers
    • PBS (Public Broadcasting Service)
    • Commercial networks
    • Cable television
    • DBS (direct broadcast satellite)
  • Long distance telephone: point-to-point trunks

Unguided Transmission Media

terrestrial microwave
Terrestrial Microwave
  • Parabolic dish
  • Fixed rigidly
  • Focused beam
  • Line of sight
  • Antennas are located above ground level to
    • Extend the range between antennas
    • Be able to transmit over intervening obstacles
  • Microwave relay towers are used

Unguided Transmission Media

terrestrial microwave20
Terrestrial Microwave

Unguided Transmission Media

terrestrial microwave applications
Terrestrial Microwave - Applications
  • Long haul telecommunications
    • Less amplifiers or repeaters than coaxial cable
  • Short point-to-point links between buildings
    • Closed-circuit TV
    • LAN data link
    • Bypass application
    • Cellular systems
  • Higher frequencies give higher data rates

Unguided Transmission Media

terrestrial microwave transmission characteristics
Terrestrial Microwave – Transmission Characteristics
  • Long-haul telecommunication
    • 4 ~ 6 GHz bands
  • Cable TV system
    • 12-GHz band
  • Short point-to-point buildings
    • 22-GHz band

Unguided Transmission Media

broadcast radio
Broadcast Radio
  • Physical description
    • Omnidirectional
    • Does not require dish-shaped antennas and antennas need not to be rigidly mounted to a precise alignment
  • Transmission characteristics
    • 3kHz ~ 1GHz
    • Line of sight
    • Less sensitive to attenuation from rainfall
    • Suffers from multipath interference
      • Reflections
  • Applications
    • FM radio
    • UHF and VHF television

Unguided Transmission Media

infrared
Infrared
  • Frequencies from 300Ghz to 400ThZ
  • Used only for short ranged communications
  • Can not penetrate walls and require line of sight (or reflection
  • Can not used outside a building
  • e.g. TV remote control, wireless keyboard

Unguided Transmission Media

slide25
Note:

Radio waves are used for multicast communications, such as radio and television, and paging systems.

slide26
Note:

Microwaves are used for unicast communication such as cellular telephones, satellite networks, and wireless LANs.

slide27
Note:

Infrared signals can be used for short-range communication in a closed area using line-of-sight propagation.

ad