Fundamentals of Telecommunication ICT – TE - BVF- 4.1 Hassan Mesfer ICT-TE-7 27/04/2017 TTC Riyadh, ICT–BVF–4.1 1 1

Lecture 3 Transmission Media 27/04/2017 TTC Riyadh, ICT–BVF–4.1 2

Overview Physical path between transmitter and receiver Guided - wire Unguided - wireless Characteristics and quality of a data transmission determined by medium and signal For guided, the medium is more important For unguided, the bandwidth produced by the antenna is more important (directionality) In designing of data transmission systems Key concerns are data rate and distance (greater better) 27/04/2017 TTC Riyadh, ICT–BVF–4.1 3

Design Factors Bandwidth Transmission impairments Interference Higher bandwidth gives higher data rate Transmission impairments Attenuation, limits the distance Interference From competing signals in overlapping frequency bands Number of receivers In guided media More receivers (multi-point) introduce more attenuation 27/04/2017 TTC Riyadh, ICT–BVF–4.1 4

Electromagnetic Spectrum

Guided Transmission Media Twisted Pair Coaxial cable Optical fiber The transmission capacity depends on: Distance Point-to-point or multipoint 27/04/2017 TTC Riyadh, ICT–BVF–4.1 6

Transmission Characteristics of Guided Media   Point-to-point applications   Frequency Range Typical Attenuation Typical Delay Repeater Spacing Twisted pair (with loading) 0 to 3.5 kHz 0.2 dB/km @ 1 kHz 50 µs/km 2 km Twisted pairs (multi-pair cables) 0 to 1 MHz 0.7 dB/km @ 1 kHz 5 µs/km Coaxial cable 0 to 500 MHz 7 dB/km @ 10 MHz 4 µs/km 1 to 9 km Optical fiber 186 to 370 THz 0.2 to 0.5 dB/km 40 km W. Stalling, 7th Edition 27/04/2017 TTC Riyadh, ICT–BVF–4.1 7

Unshielded Twisted-Pair Cable Unshielded twisted-pair cable (UTP) is a four-pair wire medium Each of the 8 individual copper wires in the UTP cable is covered by insulating material. In addition, each pair of wires is twisted around each other. This type of cable relies solely on the cancellation effect produced by the twisted wire pairs, to limit signal degradation caused by EMI and RFI. CAT 5e is the one most frequently recommended and implemented in installations today. 27/04/2017 TTC Riyadh, ICT–BVF–4.1 8

Twisted Pair 27/04/2017 TTC Riyadh, ICT–BVF–4.1 9

UTP Pros and Cons Unshielded twisted-pair cable has many advantages. It is easy to install Less expensive than other types of networking media. However, the real advantage is the size. Small external diameter, UTP does not fill up wiring ducts as rapidly as other types of cable. Disandvantages: Low data rate Short range 4/27/2017 TTC Riyadh, ICT - BVF – 4.1

Unshielded Twisted Pair 27/04/2017 TTC Riyadh, ICT–BVF–4.1 11

Twisted Pair - Applications Most common Telephone network Between house and local exchange (subscriber loop) Within buildings To private branch exchange (PBX) For local area networks (LAN) 10Mbps or 100Mbps 27/04/2017 TTC Riyadh, ICT–BVF–4.1 12

Twisted Pair - Transmission Characteristics Analog Amplifiers every 5km to 6km Digital Use either analog or digital signals Repeater every 2km or 3km Limited distance Limited bandwidth (1MHz) Limited data rate (100MHz) Susceptible to interference and noise 27/04/2017 TTC Riyadh, ICT–BVF–4.1 13

Near End Crosstalk Coupling of signal from one pair to another Coupling takes place when transmit signal entering the link couples back to receiving pair i.e. near transmitted signal is picked up by near receiving pair 27/04/2017 TTC Riyadh, ICT–BVF–4.1 14

UTP Categories Cat 3 Cat 4 Cat 5 Cat 5E (Enhanced) Up to 16MHz Voice grade found in most offices Twist length of 7.5 cm to 10 cm Cat 4 Up to 20 MHz Cat 5 Up to 100MHz Commonly pre-installed in new office buildings Twist length 0.6 cm to 0.85 cm Cat 5E (Enhanced) Cat 6 - up to 200MHz Cat 7 - up to 600MHz 27/04/2017 TTC Riyadh, ICT–BVF–4.1 15

Shielded Twisted-Pair Cable Shielded twisted-pair cable (STP) combines the techniques of shielding, cancellation, and twisting of wires. Each pair of wires is wrapped in metallic foil. The four pairs of wires are wrapped in an overall metallic braid or foil. STP affords greater protection from all types of external interference, but is more expensive and difficult to install than UTP. The metallic shielding materials in STP need to be grounded at both ends. 4/27/2017 TTC Riyadh, ICT - BVF - 4.1

Shielded Twisted-Pair Cable 4/27/2017 TTC Riyadh, ICT - BVF – 4.1

Unshielded and Shielded TP Unshielded Twisted Pair (UTP) Ordinary telephone wire Cheapest Easiest to install Suffers from external EM interference Shielded Twisted Pair (STP) Metal braid or sheathing that reduces interference More expensive Harder to handle (thick, heavy) 27/04/2017 TTC Riyadh, ICT–BVF–4.1 18

Coaxial Cable Coaxial Cable consists of a hollow outer cylindrical conductor that surrounds a single inner wire made of two conducting elements. One of these elements, located in the center of the cable, is a copper conductor. Surrounding the copper conductor is a layer of flexible insulation. Over this insulating material is a copper braid or metallic foil that acts as the second wire in the circuit and as a shield for the inner conductor. 4/27/2017 TTC Riyadh, ICT - BVF – 4.1

Coaxial Cable 27/04/2017 TTC Riyadh, ICT–BVF–4.1 20

Coaxial Cable Speed and Throughput : 10-100 Mbps Average cost per node : inexpensive Media and connector type : Medium Maximum cable length : 500m 4/27/2017 TTC Riyadh, ICT - BVF – 4.1

Coaxial Cable Applications Most versatile medium Television distribution Ariel to TV Cable TV Long distance telephone transmission Can carry 10,000 voice calls simultaneously Being replaced by fiber optic Short distance computer systems links Local area networks 27/04/2017 TTC Riyadh, ICT–BVF–4.1 22

Coaxial Cable Applications For LANs, Coaxial Cable offers several advantages. It can be run longer distances than shielded twisted pair, STP, and unshielded twisted pair, UTP, cable without the need for repeaters. Coaxial Cable is less expensive than fiber-optic cable, and the technology is well known. 4/27/2017 TTC Riyadh, ICT - BVF – 4.1

Coaxial Cable - Transmission Characteristics Analog Amplifiers every few km Closer if higher frequency Up to 500MHz Digital Repeater every 1km Closer for higher data rates 27/04/2017 TTC Riyadh, ICT–BVF–4.1 24

Optical Fiber Fiber Optics are cables that are made of optical fibers that can transmit large amounts of information at the speed of light. 4/27/2017 TTC Riyadh, ICT - BVF - 4.1

Optical Fiber 4/27/2017 TTC Riyadh, ICT - BVF – 4.1

Optical Fiber 27/04/2017 TTC Riyadh, ICT–BVF–4.1 27

Optical Fiber 4/27/2017 TTC Riyadh, ICT - BVF – 4.1

Optical Fiber - Benefits Greater capacity Data rates of hundreds of Gbps Smaller size and weight Lower attenuation Electromagnetic isolation Greater repeater spacing 10s of km at least 27/04/2017 TTC Riyadh, ICT–BVF–4.2 29

Optical Fiber - Applications Telephones Internet LANs - local area networks CATV - for video, voice and Internet connections Long-haul trunks Metropolitan trunks Rural exchange trunks Subscriber loops Security - closed-circuit TV Military - everywhere! 27/04/2017 TTC Riyadh, ICT–BVF–4.1 30

Optical Fiber - Transmission Characteristics Act as wave guide for 1014 to 1015 Hz Portions of infrared and visible spectrum Light Emitting Diode (LED) Cheaper Wider operating temp range Last longer Injection Laser Diode (ILD) More efficient Greater data rate Wavelength Division Multiplexing 27/04/2017 TTC Riyadh, ICT–BVF–4.1 31

Wireless Transmission Frequencies 2G Hz to 40 GHz Microwave Highly directional Point to point Satellite 30M Hz to 1 GHz Omnidirectional Broadcast radio 3 x 1011 to 2 x 1014 Infrared Local 27/04/2017 TTC Riyadh, ICT–BVF–4.1 32

Broadcast Radio Omnidirectional FM radio UHF and VHF television Line of sight Suffers from multipath interference Reflections 27/04/2017 TTC Riyadh, ICT–BVF–4.1 33

Infrared Modulate noncoherent infrared light Line of sight (or reflection) Blocked by walls e.g. TV remote control, IRD port 27/04/2017 TTC Riyadh, ICT–BVF–4.1 34

Wireless Propagation Signal travels along three routes Ground wave Follows contour of earth Up to 2MHz AM radio Sky wave Amateur radio, BBC world service, Voice of America Signal reflected from ionosphere layer of upper atmosphere (Actually refracted) Line of sight Above 30Mhz May be further than optical line of sight due to refraction More later… 27/04/2017 TTC Riyadh, ICT–BVF–4.1 35

Ground Wave Propagation 27/04/2017 TTC Riyadh, ICT–BVF–4.1 36

Sky Wave Propagation b) Sky-wave propagation 2 -30 MHz 27/04/2017 TTC Riyadh, ICT–BVF–4.1 37

Line of Sight Propagation 27/04/2017 TTC Riyadh, ICT–BVF–4.1 38

Line of Sight Transmission Free space loss Signal disperses with distance Greater for lower frequencies (longer wavelengths) Atmospheric Absorption Water vapour and oxygen absorb radio signals Water greatest at 22GHz, less below 15GHz Oxygen greater at 60GHz, less below 30GHz Rain and fog scatter radio waves Multipath Better to get line of sight if possible Signal can be reflected causing multiple copies to be received May be no direct signal at all May reinforce or cancel direct signal Refraction May result in partial or total loss of signal at receiver

Free Space Loss

Multipath Interference Microwave line of sight Mobile radio 27/04/2017 TTC Riyadh, ICT–BVF–4.1 41