Wireless CommunicationsWireless CommunicationsBy Kyle Heys

Engr 302Prof Ribeiro

OverviewOverview

Wave Propagation Electromagnetic Spectrum Applications

Cellular vs. PCS GPS

High Bandwidth Applications Conclusion

Wave PropagationWave 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

Effect of Frequency on LossesEffect 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.

Electromagnetic SpectrumElectromagnetic 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

CellularCellular

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

Personal Communication ServicesPersonal 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

High Bandwidth ApplicationsHigh 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

Satellite CommunicationsSatellite 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

ConclusionConclusion

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

Questions?Questions?