1 Transmission Media Lesson 04 NETS2150/2850

2 Lesson Outline Wired or guided Media –Electromagnetics waves are guided along a solid medium Wireless or unguided media –Transmission occurs through atmosphere, outer space or water Understand media characteristics and typical applications

3 McGraw-Hill © The McGraw-Hill Companies, Inc., 2004

4 Classes of transmission media McGraw-Hill © The McGraw-Hill Companies, Inc., 2004

5 Electromagnetic Spectrum

6 Twisted-pair cable McGraw-Hill © The McGraw-Hill Companies, Inc., 2004 Note: Single pair represents one communication link Twisting reduces crosstalk interference between pairs

7 UTP and STP McGraw-Hill © The McGraw-Hill Companies, Inc., 2004

8 Categories of unshielded twisted-pair cables CategoryBandwidthData RateDigital/AnalogUse 3 very low< 100 kbpsAnalogueTelephone 4 20 MHz 20 MbpsDigitalLANs MHz 100 MbpsDigitalLANs MHz 200 MbpsDigital High-speed LANs MHz 600 MbpsDigital High-speed LANs McGraw-Hill © The McGraw-Hill Companies, Inc., 2004

9 UTP connector McGraw-Hill © The McGraw-Hill Companies, Inc., 2004

10 Twisted Pair - Applications Most common medium Unshielded Twisted Pair (UTP) –Cheapest –Easiest to install –Voice Grade: Telephone wire (Cat 3) –Data Grade: Better quality (Cat 5) For LAN, 100 Mbps over 100 m possible Shielded Twisted Pair (STP) –Metal braid reduces interference –More expensive –Harder to handle (thick, heavy)

11 Coaxial Cable McGraw-Hill © The McGraw-Hill Companies, Inc., 2004

12 Coaxial Cable Applications Most versatile medium Television distribution –Arial to TV –Cable TV Short distance computer systems links Local area networks

13 Bending of light ray for transmission McGraw-Hill © The McGraw-Hill Companies, Inc., 2004

14 Optical Fibre

15 Figure 7.12 Propagation modes McGraw-Hill © The McGraw-Hill Companies, Inc., 2004

16 Figure 7.13 Modes McGraw-Hill © The McGraw-Hill Companies, Inc., 2004

17 Optical Fibre - Benefits Great for “ noisy ” environments! Tremendous bandwidth –Data rates of hundreds of Gbps Smaller size & weight Lower attenuation –Greater amplifier spacing –40-60 km at least before amplification required for SMF Used in backbone and high traffic inter-city or inter continent links (submarine cables - undersea)

18 Wireless transmission waves McGraw-Hill © The McGraw-Hill Companies, Inc., 2004

19 Wireless Spectrum BandRangePropagationApplication VLF3–30 KHzGroundLong-range radio navigation LF30–300 KHzGround Radio beacons and navigational locators MF300 KHz–3 MHzSkyAM radio HF3–30 MHzSky Citizens band (CB), ship/aircraft communication VHF30–300 MHz Sky and line-of-sight VHF TV, FM radio UHF300 MHz–3 GHzLine-of-sight UHF TV, cellular phones, paging, satellite SHF3–30 GHzLine-of-sightSatellite communication EHF30–300 GHzLine-of-sightLong-range radio navigation McGraw-Hill © The McGraw-Hill Companies, Inc., 2004

20 Wireless Transmission 30MHz to 1GHz –Suitable for Omnidirectional –Broadcast radio 2GHz to 40GHz –Microwave range –Highly directional –Point to point 3 x to 2 x Hz –Infrared range –Used within confined areas

21 Broadcast Radio Omnidirectional FM radio UHF and VHF television Requires line of sight

22 Omnidirectional antennas McGraw-Hill © The McGraw-Hill Companies, Inc., 2004

23 Radio waves are used for broadcast communications, such as radio and television, and paging systems. McGraw-Hill © The McGraw-Hill Companies, Inc., 2004

24 Terrestrial Microwave Uses parabolic dish as antenna Focused beam Requires line of sight Used for mobile phones, satellite networks Higher frequencies give higher data rates

25 Line of Sight Propagation

26 Satellite Microwave Satellite is a relay station It receives on one frequency (uplink), amplifies or repeats signal and transmits on another frequency (downlink) Requires geo-stationary orbit –Height of 35,863 km Applications: –Television live cast –Long distance telephone –Private business networks

27 Satellite Point to Point Link

28 Satellite Broadcast Link

29 © NASA.GOV 2004 Primary Mission: Four- year tour to study Saturn, its rings, moons and magnetosphere Launch: 15 October 1997 from Cape Canaveral Air Force Station, Florida Arrival at Saturn: 1 July 2004 Distance Travelled: 3.5 billion km

30 Infrared Line of sight (or reflection) Shirt-range communications Blocked by walls e.g. TV remote control, infrared port on printers, laptops, mobile phones, PDAs etc.

31 Summary Guide Media –Twisted pair, Coaxial cable, Optical fibre Unguided or wireless media –Uses antenna as transmitter and receiver (transceiver) –Terrestrial microwave, satellite microwave, Broadcast radio, Infrared Characteristics and quality determined by medium and signal For guided transmission, the medium is more important For unguided, the bandwidth produced by the antenna is more important