View
216
Download
0
Embed Size (px)
Citation preview
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 cablesCategories of unshielded twisted-pair cables
Category Bandwidth Data Rate Digital/Analog Use
3 very low < 100 kbps Analogue Telephone
4 20 MHz 20 Mbps Digital LANs
5 100 MHz 100 Mbps Digital LANs
6 200 MHz 200 Mbps DigitalHigh-speed
LANs
7 600 MHz 600 Mbps DigitalHigh-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)
U T P S TP
T w is te d P a ir
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 SpectrumWireless Spectrum
BandBand RangeRange PropagationPropagation ApplicationApplication
VLFVLF 3–30 KHz Ground Long-range radio navigation
LFLF 30–300 KHz GroundRadio beacons and
navigational locators
MFMF 300 KHz–3 MHz Sky AM radio
HF HF 3–30 MHz SkyCitizens band (CB),
ship/aircraft communication
VHF VHF 30–300 MHzSky and
line-of-sightVHF TV, FM radio
UHF UHF 300 MHz–3 GHz Line-of-sightUHF TV, cellular phones,
paging, satellite
SHF SHF 3–30 GHz Line-of-sight Satellite communication
EHFEHF 30–300 GHz Line-of-sight Long-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 1011 to 2 x 1014 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