Chapter 7: Transmission Media

Transmission Media

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Chapter 7: Transmission Media by Mind Map: Chapter 7: Transmission Media

1. Definition

1.1. A medium that carry information from a source to a destination

2. Classes of transmission media

2.1. Guided (Wire)

2.1.1. Twisted Pair Cable Made from copper material Wire-twisting reduces noise and crosstalk interference Number of twists per unit length determines the quality Unshielded Twisted Pair (UTP) and Shielded Twisted Pair (STP) STP is better in terms of immunity to noise interference, but it’s bulkier and more expensive UTP performance

2.1.2. Coaxial Cable Carries signals of higher frequency ranges than twisted-pair cable but attenuation is much higher Coax has a central core conductor of solid or stranded wire The outer metallic wrapping serves both as shield against noise and as the second conductor which completes the circuit Coaxial cable performance Coaxial cable supports much higher bandwidth than twisted-pair cable Attenuation is much higher in coaxial cable than in twisted-pair cable

2.1.3. Fiber-optic Cable Fiber-optic cable is made of glass or plastic and transmits signals in the form of light Light travels in a straight line through a single uniform substance Light ray changes direction when going through from a more dense to a less Dense substance or vice versa Optical fiber (core and cladding ) Optical fibers use reflection to guide light through a channel A glass or plastic core is surrounded by a cladding of less dense glass or plastic A beam of light from the sender moving through the core is reflected off the cladding Propagation modes Current technology supports two modes for propagating light along optical channels Different mode requires different cable physical characteristics Mode Optical fiber performance Less attenuation than in the case of twisted-pair and coaxial cable Support longer distance connection, suitable for backbone networks Advantages and disadvantages of using optical fiber Advantages Disadvantages

2.2. Unguided (Wireless)

2.2.1. Unguided media transport electromagnetic waves without using a physical conductor

2.2.2. Signals are normally broadcast through air and thus are available to anyone who has a device capable of receiving them

2.2.3. Propagation method Ground Sky Line-of-sight

2.2.4. Wireless Transmission Waves Radio wave Radio waves are omnidirectional (propagate in all directions) Sky propagation Useful for multicasting (one sender many receivers) Microwave Microwaves are unidirectional, line-of-sight propagation Microwaves cannot penetrate walls Used for unicast communication such as cellular telephones, satellite networks, and wireless LANs. Infrared Used for short-range communication in a closed area using line-of-sight propagation.