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Wireless Communications

Wireless Communications. By Kyle Heys Engr 302 Prof Ribeiro. Overview. Wave Propagation Electromagnetic Spectrum Applications Cellular vs. PCS GPS High Bandwidth Applications Conclusion. Wave Propagation. Waves in three space travel 3 dimensionally

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Wireless Communications

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  1. Wireless Communications By Kyle Heys Engr 302 Prof Ribeiro

  2. Overview • Wave Propagation • Electromagnetic Spectrum • Applications • Cellular vs. PCS • GPS • High Bandwidth Applications • Conclusion

  3. Wave Propagation • Waves in three space travel 3 dimensionally • Energy per unit surface area decreases as the square of the distance • Wireless requires much more energy than wired systems • Waves in free space are subject to other losses: Diffraction, Reflection, Refraction, and Scattering

  4. Effect of Frequency on Losses • Low Frequencies (up to 50 MHz) • Reflected by Ionosphere • Can go around obstacles • Very and Ultra High Frequencies • No longer reflected by Ionosphere • Can be blocked by obstacles causing “shaddows” • Microwave Frequencies • Completely blocked by obstacles • Line of sight transmissions.

  5. Finding an appropriate frequency is difficult Often companies or organizations will fight over who will get to use which frequency. FCC regulates what applications can use which range Electromagnetic Spectrum

  6. Cellular • Cellular communications breaks the coverage area into cells • Calls are passed between cells as the caller moves • Allows the reuse of frequencies • Requires a base station in each cell. • Allotted the 800 MHz range

  7. Personal Communication Services • Almost the same as cellular • Higher frequency: 1.9 GHz • Higher emphasis on Digital • Uses several Methods to optimize the spectrum: • Time Division Multiple Access • Code Division Multiple Access • Has the advantages of Digital Technology: • Error checking • Lower power requirements

  8. High Bandwidth Applications • Packet Switched • Without it: 9.6 Kbps • With it: 28.8 Kbps • General Packet Radio Servicepacket-switching • 115 Kbps • Universal Mobile Telephone Service • over 2Mbps

  9. Satellite Communications • Communications Satellites are classified by Height • Low Earth orbit • Medium Earth orbit • Geosynchronous Earth orbit • Requires high power and high frequency • Long Delays: 250 ms

  10. Conclusion • Wave propagation causes problems for wireless communications • New Technology can expand the current range allowing broadband and clear communication • Look for big developments to come

  11. Questions?

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