Gsm Based Water Pump Controller
CHAPTER
4
TRANSMISSION MEDIA
4.1 Guided Transmission Media Twisted Pair Coaxial Cable Optical Fiber 4.2 Wireless Transmission Antennas Terrestrial Microwave Satellite Microwave Broadcast Radio Infrared 4.3 Wireless Propagation Ground Wave Propagation Sky Wave Propagation Line-of-Sight Propagation 4.4 Line-of-Sight Transmission Free Space Loss Atmospheric Absorption Multipath Refraction 4.5 4.6 Recommended Reading and Web Sites Key Terms, Review Questions, and Problems Key Terms Review Questions Problems
94
CHAPTER 4 / TRANSMISSION MEDIA
KEY POINTS • The transmission media that are used to convey information can be classified as guided or unguided. Guided media provide a physical path along which the signals are propagated; these include twisted pair, coaxial cable, and optical fiber. Unguided media employ an antenna for transmitting through air, vacuum, or water. • Traditionally, twisted pair has been the workhorse for communications of all sorts. Higher data rates over longer distances can be achieved with coaxial cable, and so coaxial cable has often been used for high-speed local area network and for high-capacity long-distance trunk applications. However, the tremendous capacity of optical fiber has made that medium more attractive than coaxial cable, and thus optical fiber has taken over much of the market for high-speed LANs and for long-distance applications. • Unguided transmission techniques commonly used for information communications include broadcast radio, terrestrial microwave, and satellite. Infrared transmission is used in some LAN applications. In a data transmission system, the transmission medium is the physical path between transmitter and receiver. Recall from Chapter 3 that for guided media, electromagnetic waves are guided along a solid medium, such as copper twisted pair, copper coaxial cable, and optical fiber. For unguided media, wireless transmission occurs through the atmosphere, outer space, or water. The
4
TRANSMISSION MEDIA
4.1 Guided Transmission Media Twisted Pair Coaxial Cable Optical Fiber 4.2 Wireless Transmission Antennas Terrestrial Microwave Satellite Microwave Broadcast Radio Infrared 4.3 Wireless Propagation Ground Wave Propagation Sky Wave Propagation Line-of-Sight Propagation 4.4 Line-of-Sight Transmission Free Space Loss Atmospheric Absorption Multipath Refraction 4.5 4.6 Recommended Reading and Web Sites Key Terms, Review Questions, and Problems Key Terms Review Questions Problems
94
CHAPTER 4 / TRANSMISSION MEDIA
KEY POINTS • The transmission media that are used to convey information can be classified as guided or unguided. Guided media provide a physical path along which the signals are propagated; these include twisted pair, coaxial cable, and optical fiber. Unguided media employ an antenna for transmitting through air, vacuum, or water. • Traditionally, twisted pair has been the workhorse for communications of all sorts. Higher data rates over longer distances can be achieved with coaxial cable, and so coaxial cable has often been used for high-speed local area network and for high-capacity long-distance trunk applications. However, the tremendous capacity of optical fiber has made that medium more attractive than coaxial cable, and thus optical fiber has taken over much of the market for high-speed LANs and for long-distance applications. • Unguided transmission techniques commonly used for information communications include broadcast radio, terrestrial microwave, and satellite. Infrared transmission is used in some LAN applications. In a data transmission system, the transmission medium is the physical path between transmitter and receiver. Recall from Chapter 3 that for guided media, electromagnetic waves are guided along a solid medium, such as copper twisted pair, copper coaxial cable, and optical fiber. For unguided media, wireless transmission occurs through the atmosphere, outer space, or water. The