Wireless Communications

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Wireless Communications

• By Kyle Heys
• Engr 302
• Prof Ribeiro

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Overview

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

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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

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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.

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Electromagnetic Spectrum

• 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

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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

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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

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High Bandwidth Applications

• Packet Switched
• Without it 9.6 Kbps
• With it 28.8 Kbps
• General Packet Radio Service packet-switching
• 115 Kbps
• Universal Mobile Telephone Service
• over 2Mbps

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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

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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

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Questions?