Wireless CommunicationsWireless Communications

By Kyle Heys

Engr 302

Prof 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?