Chapter9_wirelessnetwork

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Wireless Network Chapter 9 Wireless Network Korea-Vietnam Friendship IT College Wireless Network Overview • Introduction • Wireless network technologies and Standards • Wireless network protocols • Wireless network security 2 Korea-Vietnam Friendship IT College Wireless Network Introduction • Provide links to Web resources and narrowband and broadband network applications via RF (Radio Frequency) waves in free space, thus eliminating requirements for fixed wireline connections. – e-mail, E-banking transactions, distance education, and telehealthcare treatment • Operate at various rates and levels of complexity; feature a multiplicity of architectures, protocols, and topologies; and vary in size and capacity. – WPANs, WLANs, WMANs, and WWANs 3 Korea-Vietnam Friendship IT College Wireless Network Introduction Personal Area Network 1-20 Mbps Local Area Network Wide Area Network 11-54 Mbps 9-144 Kbps Three wireless Internet 4 Korea-Vietnam Friendship IT College Wireless Network Wireless Network Technology • • • • • Infrared technology Laser technology Spread spectrum technology Microwave technology Satellite technology 5 Korea-Vietnam Friendship IT College Wireless Network 6 Korea-Vietnam Friendship IT College Wireless Network Infrared Technology • Based on the use of light emissions from a Light Emitting Diode (LED). – half-duplex or one-way – full-duplex or bi-directional – data exchange at distances ranging from zero meters to one meter and higher. • Integrated into wireless terminals and devices – PDAs (Personal Digital Assistants), laptops, printers, digital cameras, overhead, projectors, cellular telephones, portable scanners, credit card readers, headsets, game controls, fax (facsimile) equipment, and bank automated teller machines. 7 Korea-Vietnam Friendship IT College Wireless Network Infrared types • Serial Infrared (SIR) – 115KBps • Fast Infrared (FIR) – 4 Mbps, supporting WLAN • Advanced Infrared (AIR) – collaborative workgroup applications via infrared LAN configurations. 8 Korea-Vietnam Friendship IT College Wireless Network Direct Infrared point-to-point links 9 Korea-Vietnam Friendship IT College Wireless Network Diffuse Infrared multipoint-to-multipoint connections 10 Korea-Vietnam Friendship IT College Wireless Network Omnidirectional IR • Single base station in LOS of all stations • The base station acts as a repeater 11 Korea-Vietnam Friendship IT College Wireless Network Standards • IrDA (Infrared Data Association) – 1993 – standards for infrared networking solutions that facilitate point-to-point, point-to-multipoint, and multipoint-to-multipoint connections. 12 Korea-Vietnam Friendship IT College Wireless Network Laser Technology • Laser (Light Amplification by Stimulated Emission of Radiation) – Lasers emit narrow light beams at precise wavelengths for enabling point-to-point connections to enable voice, video, and data transport. – A laser network requires the use of laser transceivers (laser transmitters and laser receivers) for enabling direct line-of-sight, point-to-point transmissions and a tower to which this equipment is affixed. • Supports fast implementation of high-performance communications systems that operate in diverse environments. 13 Korea-Vietnam Friendship IT College Wireless Network FSO • FSO (Free Space Optics) • Using laser light sources it is possible to achieve very high speeds (typically OC-3 (155Mbps), OC-12 (622Mbps), or 1.25Gbps; but some systems operate at 2Gbps and 10GBps) for point-to-point links • Uses Terahertz (THz) spectrum range • Short ranges - typically below 2km 14 Korea-Vietnam Friendship IT College Wireless Network Spread Spectrum Technology • Spread spectrum modulation spreads out the modulated signal bandwidth so it is much greater than the message bandwidth • Independent code spreads signal at transmitter and despreads signal at receiver interference power spread signal power detection at receiver f 15 signal spread interference f Korea-Vietnam Friendship IT College Wireless Network Spread Spectrum Technology • DS/SS (Direct Sequence Spread Spectrum): – XOR the signal with pseudonoise (PN) sequence (chipping sequence) • FH/SS (Frequency Hopping Spread Spectrum): – Discrete changes of carrier frequency 16 Korea-Vietnam Friendship IT College Wireless Network Spread Spectrum Allocation • FCC (U.S. Federal Communications Commission) – Monitors spread spectrum licensing and allocates spectrum: 902 - 928 MHz, 2.400 - 2.483 GHz for spread spectrum operations. • UK Radio Communications Agency – manages nonmilitary spread spectrum allocations and monitors spread spectrum use to prevent signal interference 17 Korea-Vietnam Friendship IT College Wireless Network Microwave Technology 18 Korea-Vietnam Friendship IT College Wireless Network Microwave Technology • A microwave communication tower acts as a signal repeater. It receives signals from one “dish” and repeats them onto another. • It requires Line-Of-Sight (LOS). 19 Korea-Vietnam Friendship IT College Wireless Network Microwave Technology • Parabolic dish antenna (typical size of 3 m in diameter). • Focused beam to achieve line of sight transmission. • Located at substantial heights above ground level. • Microwave relay towers used to achieve long distance. • Applications: – Long haul telecommunications service. – Short point-to-point links between buildings. • Higher frequencies give higher data rates and require smaller antennas. • Attenuation and interference. – Attenuation is increased with rainfall (especially above 10 GHz). – With growing applications, transmission areas overlap and resulting in interference. 20 Korea-Vietnam Friendship IT College
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