wireless communications by kyle heys engr 302 prof ribeiro
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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?
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