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This article provides an overview of wireless media frequencies, including radio, phones, microwave, satellite communication, light, X-ray, and gamma ray radio. It discusses the spectrum of frequencies, how they are assigned by the FCC, and their uses in different technologies. The article also covers various wireless technologies such as Bluetooth, Wi-Fi, and cellular networks, and explains the factors to consider in choosing between wired and wireless connections. Additionally, it touches on the challenges of interference, security, and environmental factors in wireless communication.
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Day 6 Wireless Media
Frequencies • Spectrum of frequencies divided up • Frequencies are assigned by FCC for task • Radio • Phones • Microwave • Satellite communication • Light • XRay • Gamma Ray
Radio • AM750 • 750,000 Hz • 50,000 Watt • Clear Channel • Local, Regional, Clear Channel • Omni directional
Analogue Cell phones • Cells • 1 block (1/2 mile) – 50 miles • Adjacent blocks use different frequencies • Low power transmission ensures no crosstalk • Setup channel • Sends signal that phone is on and in this cell area • Used when dialing a number • Used to receive a call • Technologies • Advanced Mobile Phone Service (AMPS) • Frequency Division • Digital-Advanced Mobile Phone Service (DAMPS) • Frequency and Time Division
Digital Cells • PCS – 2nd generation • Code Division Multiple Access (CDMA) • Verizon, Sprint, • Global System for Mobile Communication (GSM) [also time division] • Uses TDMA (Time division multiple access) • Tmobile, Cingular (AT&T)
Bluetooth (802.15.1) • 2.45Ghz • Rotates over 79 channels ever 1/1600 second • Class 1 • 100M • Class 2 • 10M • Class 3 • 1M • Can transmit through objects • V1, 1.1, 1.2: 721,000 bits/second • Most current phones/earpieces are 1.2 • V2: 2.1mbps
802.11 • B • 11Mbps (max), 6.5Mbps (norm) • 2.4Ghz • Range 100 feet • A • 54Mbps (max), 25Mbps (norm) • 5.3Ghz • Range 100 feet • G • 54Mbps (max), 25Mbps (norm) • 2.4Ghz • Range 100 feet • N • 540Mbps (max), 200Mbps (norm) • 2.4Ghz or 5Ghz • Range 160 feet
Microwave • 100,000,000Hz – 1,000,000,000Hz (Ghz) • Used all the time in rural and urban areas • Directional and line of sight • Range 15-30 miles • Bad in snow, rain • Can be blocked by buildings, trees etc.
Satellite • Up and down to satellite • Can send signals long distances around earth • 2,500 in orbit today • http://science.nasa.gov/Realtime/jtrack/3d/JTrack3D.html
Orbit • Close (Low Earth Orbit LEO) • 100 – 1000 Miles • Less propagation delay • Constantly must orbit • Changes position • Passes over point 15-16 times/day • Middle-Earth-Orbit (MEO) • 1000 – 22,300 miles • GPS (29 satellites) • Each circles earth twice per day @ 12,600 miles • 4 satellites are in line of sight always from anywhere on earth • Each contain an atomic clock • 1575.42Mhz
Geosynchronous • Stays in same position over earth • 22,300 miles out • 0.25 seconds to reach & return from satellite • Easy to transmit to because you only have to lock on once, no tracking • If over equator they don’t move from the prospective of the earth. • If not over equator, they oscillate and require a tracking motor to keep a lock on
Infrared • Remote controls • IR ports on laptops, printers etc. • Close range only • Typically <5 feet • Line of sight only • Low bandwidth • Typically 9600baud • Can be as high as 16Mbps
Laser • Without fiber can be used to transmit • Not very popular • Can be very high speed • Line of sight
Choice Decision • Cost • Installation • Maintenance • Right of way • Speed • Max data transfer speed • Propagation speed • Distance • Choice of wire/wireless • Interference • Environment • Wind, rain, snow, sunspots • Security • Wiretapping
