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Chapter 7 Transmission Media
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Figure 7.1 Transmission medium and physical layer
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Figure 7.17 Electromagnetic spectrum for wireless communication
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Figure 7.2 Classes of transmission media
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7.1 Guided Media Twisted-Pair Cable Coaxial Cable Fiber-Optic Cable
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Twisted Pair Cable
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Figure 7.3 Twisted-pair cable
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Figure UTP and STP
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Effect of Noise on Parallel Lines
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Noise on Twisted-Pair Lines
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Table 7.1 Categories of unshielded twisted-pair cables (EIA)
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Figure UTP connector
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UTP Pin Assignment (Normal UTP cable)
Hub or Switch Both sides of Cable
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UTP Pin Assignment (Cross UTP cable)
One side of Cable The other side of Cable
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Figure 7.6 UTP performance
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Shielded Twisted-Pair Cable
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Coaxial Cable
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Figure Coaxial cable
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Figure Coaxial cable
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Figure Coaxial cable
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Figure Coaxial cable
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Figure Coaxial cable
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Figure Coaxial cable
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Table 7.2 Categories of coaxial cables Category Impedance Use RG-59
75 W Cable TV RG-58 50 W Thin Ethernet RG-11 Thick Ethernet Radio Government (RG) rating
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Figure 7.9 Coaxial cable performance
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Coaxial Connectors
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Figure BNC connectors
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Figure Coaxial cable
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Figure Coaxial cable
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Fiber Optic Cable
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Fiber Optic Glass or Plastic 125 um
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Total Internal Reflection
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Figure Optical fiber
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Figure 7.12 Propagation modes
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Figure Modes
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Multimode, graded-index
Table 7.3 Fiber types Type Core Cladding Mode 50/125 50 125 Multimode, graded-index 62.5/125 62.5 100/125 100 7/125 7 Single-mode
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Figure 7.14 Fiber construction
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Figure 7.15 Fiber-optic cable connectors
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Fiber Optic Connector FC connector SC connector ST connector
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Figure 7.16 Optical fiber performance
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7.2 Unguided Media: Wireless
Radio Waves Microwaves Infrared
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Figure 7.17 Electromagnetic spectrum for wireless communication
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Figure 7.18 Propagation methods
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Table 7.4 Bands
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Figure 7.19 Wireless transmission waves
Bluetooth
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Figure 7.20 Omnidirectional antennas
Radio waves are used for multicast communications, such as radio and television, and paging systems.
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Figure 7.21 Unidirectional antennas
Microwaves are used for unicast communication such as cellular telephones, satellite networks, and wireless LANs.
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Microwave Terrestrial Microwave Satellite Microwave
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Terrestrial Microwave
Land-based, line-of-sight transmission Approximately miles maximum between towers Transmits data at hundreds of millions of bits per second Popular with telephone companies and business to business transmissions
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Often the microwave antennas are on towers and buildings
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Satellite Communication
Similar to terrestrial microwave except the signal travels from a ground station on earth to a satellite and back to another ground station. Satellites can be classified by how far out into orbit each one is (LEO, MEO, GEO, and HEO).
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Satellite Microwave LEO - Low Earth Orbit – 100 miles Used for pagers, wireless , special mobile telephones, spying, videoconferencing. GEO - Geosynchronous Orbit - 22,300 miles. Used for weather, television, and government operations. MEO - Middle Earth Orbit miles. Used for GPS and government.
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Geosynchronous Orbit
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HEO Orbit A fourth type of orbit used by the military for spying and by scientific organizations for photographing celestial bodies. When satellite is far out into space, it takes photos. When satellite is close to earth, it transmits data.
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Cellular System
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Infared Transmission Infrared signals can be used for short-range communication in a closed area using line-of-sight propagation.
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Infared Transmission Short-range communication Frequency
100 GHz – 1000 THz Use a focused ray of light Point-to-point Line-of-sight 100 Kbps – 16 Mbps Broadcast Reflective 1 Mbps Device-to-device transfers remote control PDA Notebook Cellular phone IrDA standard: Infrared Data Association
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Bluetooth
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Bluetooth Operate in noisy radio frequency environments
2.402 GHz GHz omni-directional Point-to-multipoint frequency-hopping scheme 79 hops (RF channels) 1 MHz apart. bandwidth is reduced in Japan, France and Spain The maximum frequency hopping rate is 1600 hops/s link range Usually 10 centimeters to 10 meters Can be extended to more than 100 meters by increasing the transmit power Small amounts of data 1Mbps over short distances (up to 10 meters).
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Bluetooth Very Low power device Based on the IEEE 802.11 standard
Not designed to carry heavy traffic loads Fast acknowledgement
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Media Selection Criteria
Cost Speed Distance Delay Expandability Environment Security
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