1

Transmission Media

รศ.ดร. อนันต์ ผลเพิ-มAsso. Prof. Anan Phonphoem, Ph.D.

anan.p@ku.ac.thhttp://www.cpe.ku.ac.th/~anan

Computer Engineering DepartmentKasetsart University, Bangkok, Thailand

2

Outlinen Electromagnetic Energyn Cable (Wire)n Wirelessn Measuring Transmission Media

3

Electromagnetic Energyn Signals are transmitted in form of

electromagnetic energyn Electromagnetic Energy:

n a combination of electrical and magnetic fields vibration

n Travel through a vacuum, air, or other transmission media

n Some are used for communications

4

Electromagnetic Spectrum

Power,Voice

Radio communicationRadio, microwave, satellite

InfraredLight

Ultra-VioletLight

X, gamma,Cosmic rays

0 3000 Hz 300 GHz

Visible light430-750 THz

5

TransmissionMedia

Unguided MediaGuided Media

Twisted-PairCable

CoaxialCable

Fiber-OpticCable Radio Microwave Satellite

Noisen Undesirable signals added between the

transmitter and the receivern Noise sources:

n ApplianceàHeat in cablesàElectromagnetic radiation

7

Interference from nearby cable

8

Interference from noiseNoise Source

Noise Effect = 10 units

Noise Effect = 7 units

Sender Receiver

10

7

9

Twisted Pair Cable

100 Hz 5 MHz

Outer Insulator(PVC)

Solid Copper Conductors

10

Unshielded Twisted Pair Cable

UTP-Cable

Plastic Cover

Twisted pairs(4 pairs

http://www.sattvengg.com/2013/09/an-easy-explanation-of-straighr-and.html

11

Shielded Twisted-Pair Cable

STP-Cable

Plastic Cover

Metal ShieldInsulation

Copper

https://avprosupply.com/Kramer-BC-DGKat524-305M-24-AWG-STP-Cable-Optimized-for-Kramer-DVI--HDMI-Twisted-Pair-Products-BC-DGKat524-305M.html

12

UTP cable standardn EIA set the cable standardsn Categorized by the cable quality

CAT 8

n For Data Centern 2 GHz Bandwidthn 25 – 40 Gbps @30 metersn Cheaper and more energy

efiicient than Fiber

13https://www.สายแลน.com/สายแลน-CAT8-มาตรฐานใหม่ที0กาํลงัจะมา

14

Coaxial cable

100 KHz 500 MHzInsulator

Plastic Cover Outer Conductor(Shield) Inner Conductor

COAX-Cable

15

Coaxial cable

https://www.perfect-vision.com/PerfectVision/CoaxialCableGuide.aspx

16

Coaxial cable standardn Categorized by radio government (RG)n Physical specification (wire gauge,

conductor,…)n RG-8, RG-9, RG-11 : Thick Ethernetn RG-58 : Thin Ethernetn RG-59 : (older)TV à RG-6(triple/Quad shield)

17

Optical Fibern Nature of light

n In vacuum, 3x108 m/sn Higher density, slower speedn Refractionn Reflection

18

Refraction

From less dense to more dense medium

From more dense to less dense medium

19

Critical Angle

20

Reflection

21

Multimode Step-Index

22

Single Mode

Optical Fiber Types

23https://en.wikipedia.org/wiki/Optical_fiber#/media/File:Optical_fiber_types.svg

Optical Fiber Cable

24

http://www.indiamart.com/solusys/optical-fiber.html

25

Electromagnetic Spectrum

Power,Voice

Radio communicationRadio, microwave, satellite

InfraredLight

Ultra-VioletLight

X, gamma,Cosmic rays

VLF LF MF HF VHF UHF SHF EHF

TroposhpericIonosperic

Space &Line-of-sight

SpaceSurface

3KHz 300GHzRadio Frequency Allocation: 8 bands

26

Earth atmospheren Troposphere

n 30 miles from earthn Airn Clouds, wind, weathern Jet plane travel

n Ionospheren Between Troposphere and spacen Free electrically charged particles

Ionosphere

Space

27

Type of propagation

28

Satellite Communicationn Like microwaven Supertall antenna & repeater

29

Geosynchronous Satellitesn Stationary antennan Satellite moves same speed as earthn Only one orbit (22,000 miles)

Periodic table

30

Iridiumn built by Motorola, November 1998n network of 66 satellites in polar, low-Earth orbitsn communicate anywhere in the world--a first in the history

of telephony n The original concept was to have 77 satellites

named as the element with the atomic number 77

31https://en.wikipedia.org/wiki/Iridium_satellite_constellation#/media/File:Iridium_Satellite.jpg

Iridium

32

Jurassic Park 3 (July 2001)

33

34

Other Wireless n Satellite

n Low Earth Orbit (LEO)n Low Earth Orbit Satellite Arrays

n Microwaven Infrared

Measuring Transmission Median Two most important characteristics of a

transmission medium are:n Propagation delay

Time required for a signal to traverse the mediumn Channel capacity (bandwidth)

Maximum data rate that medium can support

Data Rate: Noiseless Channelsn Nyquist Theorem

n D – Data rate in bpsn B – Bandwidth in Hzn K – number of signal levels

D = 2Blog2K

265,000 = 2 ´ 20,000 ´ log2Klog2K = 6.625 K = 26.625 = 98.7 levels

We need to send 265 kbps over a noiseless channel with abandwidth of 20 kHz. How many signal levels do we need?SolutionWe can use the Nyquist formula as shown:

Since this result is not a power of 2, we need to eitherincrease the number of levels or reduce the bit rate. If wehave 128 levels, the bit rate is 280 kbps. If we have 64levels, the bit rate is 240 kbps.

Example

Data Rate: Noisy Channelsn Shannon Capacity

n C – Capacity (maximum bit rate) in bpsn B – Bandwidth of the channel in Hzn SNR – Signal-to-Noise Ratio

C = Blog2(1+SNR)

A telephone line normally has a bandwidth of 3000. The signal-to-noise ratio is usually 3162. Calculate the theoretical highest bit rate of a regular telephone line.

This means that the highest bit rate for a telephone lineis 34.860 kbps. If we want to send data faster than this,we can either increase the bandwidth of the line orimprove the signal-to-noise ratio.

Example

Measuring Power Levels

n Difference often measured in decibel (dB)

n Negative dB ® Signal power gets attenuated (reduced)n Positive dB ® Signal power gets amplified

41

Example

http://www.phys.unsw.edu.au/jw/dB.html

• 2 Loudspeakers• Speaker 1: plays sound with Power P1• Speaker 2: plays sound with Power P2•Same environment (frequency, distance)

dB = 10 log10( )P2P1

P1 P2

Condition Calculation DecibleP2 = P1 10 log10(1) 0 dBP2 = 2 P1 10 log10(2) +3 dBP2 = 0.5 P1 10 log10(0.5) – 3 dBP2 = 10 P1 10 log10(10) +10 dB

42

Summaryn Electromagnetic Energyn Wire

n Twisted Pair Cablen Coax Cablen Fiber Opticn Power cable (Powerline Networking)

n Wirelessn Radio waven Satellite

n Measuring Transmission Media