Chapter 4. Transmission Media Guided Transmission Media Unshielded and Shielded Twisted pair Coaxial cable Optical Fiber Wireless Media Terrestrial Microwave Satellite Microwave Broadcast Radio Infrared

Data Transmission System Key concerns Data rate and Distance Design Factors Bandwidth Transmission impairments Interference Number of receivers

Electromagnetic Spectrum

Characteristics of Guided Media Frequency Range Typical Attenuation Typical Delay Repeater Spacing Twisted pair (w/ loading) 0 to 3.5 kHz 0.2 dB/km @ 1kHz 50 ms/km 2km (multi-pair cables) 0 to 1 MHz 3 dB/km @ 1kHz 5 ms/km Coaxial cable 0 to 500 MHz 7 dB/km @ 10MHz 4 ms/km 1 ~ 9 km Optical fiber 180 to 370 THz 0.2 ~ 0.5 dB/km 40km

Twisted Pair Twisting Reduces low-frequency interference Use of different twist length in adjacent pairs reduces crosstalk

Twisted Pair (cont) STP: Shielded Twisted Pair reduce interference EIA-568A: by Electronic Industries Association, 1991, 1995 Category 3: up to 16 MHz 3 ~ 4 twists per foot (7.5 ~ 10cm) Category 4: up to 20 MHz Category 5: up to 100 MHz 3 ~ 4 twists per inch (0.6 ~ 0.85cm)

Coaxial Cable Up to 400 MHz Outer conductor

Optical Fiber

Comparison Table 3.1 Point-to-Point Transmission Characteristics of Guided Media Transmission Medium Total Data Rate Bandwidth Repeater Spacing Twisted Pair 4 Mbps 3 MHz 2 to 10 km Coaxial Cable 500 Mbps 350 MHz 1 to 10 km Optical Fiber 2 Gbps 2 GHz 10 to 100 km

Unguided Media via antenna Terrestrial Microwave Satellite Microwave 2 GHz ~ 40 GHz Satellite Microwave Optimal frequency range: 1 GHz ~ 10 GHz Broadcast Radio 30 MHz ~ 1 GHz Infrared 3x1011 ~ 2x1014 Hz