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?