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Lecture Wireless and mobile computing – Chapter 5: Wireless transmission media

Lecture Wireless and mobile computing – Chapter 5: Wireless transmission media. The following will be discussed in this chapter: Wireless transmission, wireless transmission examples, terrestrial microwave, satellite microwave, broadcast radio, infrared, wireless transmission systems comparison, wireless propagation modes. | Wireless Transmission Media Lecture 5 Overview Wireless Transmission Wireless Transmission Examples terrestrial microwave satellite microwave broadcast radio Infrared Wireless Transmission Systems Comparison Wireless Propagation Modes Multiplexing TDM, FDM WDM 2 Wireless (Unguided Media) Transmission transmission and reception are achieved by means of an antenna directional transmitting antenna puts out focused beam transmitter and receiver must be aligned omnidirectional signal spreads out in all directions can be received by many antennas 3 Wireless Examples terrestrial microwave satellite microwave broadcast radio infrared 4 Terrestrial Microwave used for long-distance telephone service uses radio frequency spectrum, from 2 to 40 Ghz parabolic dish transmitter, mounted high used by common carriers as well as private networks requires unobstructed line of sight between source and receiver curvature of the earth requires stations (repeaters) ~30 miles apart 5 5 Satellite Microwave Applications Television distribution Long-distance telephone transmission Private business networks 6 6 Microwave Transmission Disadvantages line of sight requirement expensive towers and repeaters subject to interference such as passing airplanes and rain 7 Satellite Microwave Transmission a microwave relay station in space can relay signals over long distances geostationary satellites remain above the equator at a height of 22,300 miles (geosynchronous orbit) travel around the earth in exactly the time the earth takes to rotate 8 8 Satellite Transmission Links earth stations communicate by sending signals to the satellite on an uplink the satellite then repeats those signals on a downlink the broadcast nature of the downlink makes it attractive for services such as the distribution of television programming 9 9 dish dish uplink station downlink station satellite transponder 22,300 miles Satellite Transmission Process 10 10 Satellite Transmission Applications television distribution a . | Wireless Transmission Media Lecture 5 Overview Wireless Transmission Wireless Transmission Examples terrestrial microwave satellite microwave broadcast radio Infrared Wireless Transmission Systems Comparison Wireless Propagation Modes Multiplexing TDM, FDM WDM 2 Wireless (Unguided Media) Transmission transmission and reception are achieved by means of an antenna directional transmitting antenna puts out focused beam transmitter and receiver must be aligned omnidirectional signal spreads out in all directions can be received by many antennas 3 Wireless Examples terrestrial microwave satellite microwave broadcast radio infrared 4 Terrestrial Microwave used for long-distance telephone service uses radio frequency spectrum, from 2 to 40 Ghz parabolic dish transmitter, mounted high used by common carriers as well as private networks requires unobstructed line of sight between source and receiver curvature of the earth requires stations (repeaters) ~30 miles apart 5 5 Satellite .