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. 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

7. 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

8. 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

9. 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

10. 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

11. 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

12. Questions?