1. Data Communication Network
331: STUDY DATA COMMUNICATIONS AND NETWORKS

2. 331: STUDY DATA COMMUNICATIONS AND NETWORKS
1. Discuss computer networks (5 hrs)
2. Discuss data communications (15 hrs)

3. 331.2: Discuss Data Communications
PERFORMANCE STANDARD
Given a network system, identify and illustrate the different data communications components clearly
Objectives:
Define elements of a communication system
Define data communications
Discuss various types of transmission media and their characteristics
Discuss encoding of information tor transmission
Discuss types of signal & their characteristics
Relate data capacity of a channel and bandwidth
Classify media based on bandwidth
Discuss channel organization

4. Discuss various types of transmission media and their characteristics
SKILL AREA
Discuss various types of transmission media and their characteristics

5. Types of transmission media
twisted pair – telephone cable
coaxial cable –Thick black cable used for higher bandwidth communications than twisted pair (i.e. Optus cable)
fibre optic – data transferred through pulses of light. Extremely fast.
Non cable methods such as satellite, microwave, wireless and Bluetooth

6. Types of transmission media

7. Twisted Pair Cable
Twisted pair cable

8. Twisted pair Cable Twisted pair cable application Most common medium
Telephone network
Between house and local exchange (subscriber loop)
Within buildings
To private branch exchange (PBX)
For local area networks (LAN)
10Mbps or 100Mbps

9. Twisted pair Cable Twisted pair cable pro and contra Advantages Cheap
Easy to work with
Disadvantages
Low data rate
Short range

10. Twisted pair Cable 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

11. Twisted pair Cable Twisted pair (UTP and STP)
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)

12. Twisted pair Cable
The Electronic Industries Association (EIA) has developed standards to grade UTP.
Category 1. The basic twisted-pair cabling used in telephone systems. This level of quality is fine for voice but inadequate for data transmission.
Category 2. This category is suitable for voice and data transmission of up to 2Mbps.
Category 3.This category is suitable for data transmission of up to 10 Mbps. It is now the standard cable for most telephone systems.
Category 4. This category is suitable for data transmission of up to 20 Mbps.
Category 5. This category is suitable for data transmission of up to 100 Mbps.

13. CAT cable characteristic
Category
Bandwidth
Data Rate
Digital/Analog
Use 1
very low
< 100 kbps
Analog
Telephone 2
< 2 MHz
2 Mbps
Analog/digital
T-1 lines 3
16 MHz
10 Mbps
Digital
LANs 4
20 MHz
20 Mbps 5
100 MHz
100 Mbps
6 (draft)
200 MHz
200 Mbps
7 (draft)
600 MHz
600 Mbps

14. Connector
The most common UTP connector is RJ45 (RJ stands for Registered Jack).

15. Coaxial Cable Coaxial Cable (or coax)
Coaxial cable carries signals of higher frequency ranges than twisted-pair cable.
Coaxial Cable standards:
RG-8, RG-9, RG-11 are used in thick Ethernet
RG-58 Used in thin Ethernet
RG-59 Used for TV

16. Coaxial Cable Coaxial Cable Used for cable television, LANs, telephony
Has an inner conductor surrounded by a braided mesh
Both conductors share a common center axial, hence the term “co-axial”

17. Coaxial Cable Coax Layers outer jacket (polyethylene)
copper or aluminum
conductor
insulating material
shield (braided wire)
outer jacket
(polyethylene)

18. Coaxial Cable

19. Coaxial Cable 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

20. Coaxial Cable 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

21. Fiber Optic Cable Fiber Optic Cable
Relatively new transmission medium used by telephone companies in place of long- distance trunk lines
Also used by private companies in implementing local data communications networks
Require a light source with injection laser diode (ILD) or light-emitting diodes (LED)

22. Fiber Optic Cable consists of three concentric sections plastic jacket
glass or plastic
cladding
fiber core

23. Fiber Optic Cable Fiber Optic Cable
Metal cables transmit signals in the form of electric current.
Optical fiber is made of glass or plastic and transmits signals in the form of light.
Light, a form of electromagnetic energy, travels at 300,000 Kilometers/second (186,000 miles/second), in a vacuum.
The speed of the light depends on the density of the medium through which it is traveling (the higher density, the slower the speed).

24. Fiber Optic Cable
Optical Fiber

25. Fiber Optic Types multimode step-index fiber
the reflective walls of the fiber move the light pulses to the receiver
multimode graded-index fiber
acts to refract the light toward the center of the fiber by variations in the density
single mode fiber
the light is guided down the center of an extremely narrow core

26. Fiber Optic Signals fiber optic multimode step-index
graded-index
fiber optic single mode

27. Fiber Optic Advantages
greater capacity (bandwidth of up to 2 Gbps)
smaller size and lighter weight
lower attenuation
immunity to environmental interference
highly secure due to tap difficulty and lack of signal radiation

28. Fiber Optic Disadvantages
expensive over short distance
requires highly skilled installers
adding additional nodes is difficult

29. Unguided media
Unguided media, or wireless communication, transport electromagnetic waves without using a physical conductor.
Instead the signals are broadcast though air or water, and thus are available to anyone who has a device capable of receiving them.
The section of the electromagnetic spectrum defined as radio communication is divided into eight ranges, called bands.

30. Antennas
Electrical conductor (or system of..) used to radiate electromagnetic energy or collect electromagnetic energy
Transmission
Radio frequency energy from transmitter
Converted to electromagnetic energy
By antenna
Radiated into surrounding environment
Reception
Electromagnetic energy impinging on antenna
Converted to radio frequency electrical energy
Fed to receiver
Same antenna often used for both

31. Wireless (Unguided Media) Transmission
transmission and reception are achieved by means of an antenna
directional
transmitting antenna puts out focused beam
transmitter and receiver must be aligned
omnidirectional
signal spreads out in all directions
can be received by many antennas

32. Directional Antenna
Directional Antennas provide great efficiency of power transmission because the power can be focused into a narrow beam directed toward the station of interest.

33. Omnidirectional Antenna
Omnidirectional Antenna is widely used for radio broadcasting antennas, in mobile devices that use radio such as cell phones, FM radios, walkie-talkies, wireless computer networks, cordless phones, GPS

34. Propagation of Radio Waves
Radio technology considers the earth as surrounded by two layers of atmosphere: the troposphere and the ionosphere.
The troposphere is the portion of the atmosphere extending outward approximately 30 miles from the earth's surface.
The troposphere contains what we generally think of as air. Clouds, wind, temperature variations, and weather in general occur in the troposphere.
The ionosphere is the layer of the atmosphere above the troposphere but below space.

35. Propagation of Radio Waves

36. Propagation of Radio Waves
Ground propagation: radio waves travel through the lowest portion of the atmosphere, hugging the earth. These low-frequency signals emanate in all directions from the transmitting antenna and follow the curvature of the planet. The distance depends on the power in the signal.
In Sky propagation, higher-frequency radio waves radiate upward into the ionosphere where they are reflected back to earth. This type of transmission allows for greater distances with lower power output.
In Line-of-Sight Propagation, very high frequency signals are transmitted in straight lines directly from antenna to antenna.

37. Bands Band Range Propagation Application VLF 3–30 KHz Ground
Long-range radio navigation LF
30–300 KHz
Radio beacons and navigational locators MF
300 KHz–3 MHz
Sky
AM radio HF
3–30 MHz
Citizens band (CB), ship/aircraft communication
VHF
30–300 MHz
Sky and line-of-sight
VHF TV, FM radio
UHF
300 MHz–3 GHz
Line-of-sight
UHF TV, cellular phones, paging, satellite
SHF
3–30 GHz
Satellite communication
EHF
30–300 GHz

39. Satellite Microwave Satellite is relay station
Satellite receives on one frequency, amplifies or repeats signal and transmits on another frequency
Requires geo-stationary orbit
Height of 35,784km
Television
Long distance telephone
Private business networks

40. Satellite Point to Point Link

41. Satellite Broadcast Link

42. QUESTION?