SC161-Lecture4-1

Chapter 4
SC161: Principles of Information Technology
Communication and Network
Part 1: Data Communication
Thiti Theerathean
Center for Teaching Excellence
University of the Thai Chamber of Commerce
E-mail : thiti_the@utcc.ac.th

2
• Introduction to Data Communication.
- Data Communicationand Telecommunication
- Type of Signals
- The Basic Components of Communication
• Data Transmission.
- Line configurations
- Directionof Transmisssion
- TransmissionMode
• Communication Channel.
- Guided Media
- Unguided Media
• Wireless Technology.
- Long-distance wireless communication
- Short-range wirelesscommunication
SC161: Principlesof Information Technology

3SC161: Principlesof Information Technology
Data Communications is any transfer of data within a computer, between a computer
and another device, or between two computers.
Telecommunication is communications over a distance.
Tele- distance

Data and Information travels through a communication system in the form of
eletromagnetic signals. Signals are represented in two ways
• Continuous waveform.
• Three basic components :
- Amplitude (Volt)
- Frequency (Hz)
- Phase (Radian)
• Infinite number of points between minimum and maximum amplitude.
• Use an Amplifier to increase power for transmission over long distances and
reduce noise by Filter.
• Used for Voice Communication.

Data and Information travels through a communication system in the form of
eletromagnetic signals. Signals are represented in two ways
• Discrete waveform.
• Only two different values:
- 1 is high voltage/on electrical pulses.
- 0 is low voltage/off electrical pulses.
• The number of times a signal changes value per second is called “Baud rate”
• Use Repeater to transmission the data over long distances.
• Used for Data Communication.
time
amplitude(power)

Sender
Communication Channel
Receiver
Step 1: ……
Step 2: …...
Step 3: …...
Step 1: ……
Step 2: …...
Step 3: …...
Protocol
Message
The Basic Components of Communication.

There are two principal line configurations.

When two computers are in communication, data can flow in three ways:
A B
Only transmits. Only receives.
A B
Transmits when B receives. Transmits when A receives.
A B
Transmits and receives
while B transmits and received.
Transmits and receives
while A transmits and received.

Data is transmitted in two ways.
Sender Receiver
01110011 01110011
1 1 0 0 1 1 1 0
Sender Receiver
01110011 01110011
0
1
1
1
0
0
1
1
Bits are transmitted sequentially, one after
the other.
Bits are transmitted through separate lines
simultaneously.

How does the receiving equipment know where one byte ends
and another begins ?
Sender Receiver
1 1 0 0 1 1 1 0
11001110
01011100
0 1 0 1 1 1 0 0 100 1
Start bit
0
Stop bit
1
Parity check bit
• Start bit and Stop bit are added.
• High overhead.
• low-speed communication

How does the receiving equipment know where one byte ends
and another begins ?
Sender Receiver
Parity check bit
1
• basic unit transmitted is called a “packet”
• Use sync bytes to announce the beginning
and end of an entire packet.
SyncSyncSync Sync
Sync byte
1 1 0 0 1 1 1 00 1 0 1 1 1 0 0
Packet
11001110
01011100

Communication channels are the means by which data are transmitted from one device
in a network to another. A channel can utilize different kinds of communication
transmission media :
- Twisted-Pair Cable
- Coaxial Cable
- Fiber Optics Cable
- Infrared Transmission
- Radio Frequency
- Microwave and Satellite

Twisted-Pair Cable
• Two insulated copper wires that are twisted together.
• The pairs can be shielded (STP) or unshielded (UTP).
• The standard connector for unshielded twisted pair cabling is an RJ-45 connector.

Advantages:
• High availability.
• Low installation cost.
Disadvantages:
• Limited data rates.
• Limited range.
• High susceptibility to electromagnetic and
radio frequency interference.
Twisted-Pair Cable Categories:
1 - primarily for voice, less than 9600 bps
2 - T-1 and ISBN line, 4 Mbps
3 - 16 MHz of bandwidth; 10Mbps
4 - 20 MHz of bandwidth; 16Mbps
5/5e - 100 MHz of bandwidth; 100 Mbps (4 pairs/cable)
6 - 400 MHz of bandwidth; 1Gbps (4 pairs/cable)

Twisted-Pair Cable

Coaxial Cable
• A single copper wire, surrounded by an insulator and an outer conductor.
• Two primary types : Thick coaxial (10mm) and Thin coaxial (4mm).
• Speed : 56 kbps to 200 Mbps.

Coaxial Cable
Advantages:
• High capacity (370-1000 times more than twisted pair)
• Low susceptibility to noise and crosstalk (because of shielding)
Disadvantages:
• Requites Amplifier or Repeater every few km.
• High installation cost.
Common Uses:
• Cable TV (Old: RG-59; New: RG-6)
• Ethernet (RG-58:10Base2 ; RG-8:10Base5)
• Amateur radio.

Fiber Optic Cable
A thin glass core surrounded by cladding that reflects light into the core, surrounded
by a protective plastic buffer/jacket.
• Light source is called a photo diode.
• Light travels through the core and bounces off of the cladding to "make turns"
• The signal degrades because of impurities in the glass
cladding
core

Fiber Optic Cable The two basic types of optical fiber.
Multi-mode optical fiber
Single-mode optical fiber
Step-indexmultimode
Graded-indexmultimode

Advantages:
• High capacity.
• Reduce size and weight cable.
• no crosstalk and lower bit error rates.
• Signal security and difficult to tap.
Disadvantages:
• Can be bent.
• Each fiber is one-way transmission of data.
• High cost of interfaces.
• Lack of standardization.

Guided Media Typical use Data Rate Range
Twistedpair
Category 1 - 2
Category 3 - 6
Telephone system
LANs
Less than 2 Mbps
100 Mbps
5 km.
100 m (328 feet)
Coaxial Cable
Thin (Single channel)
Thick (Multi channel)
LANs
LANs
Cable TV
10 Mbps
10 Mbps
100 m.
5 km.
Fiber Optic Cable
Single-mode
Multi-mode
LANs
WANs
HD interconnection
10 Gbps 160 km.

Electromagnetic Spectrum.

Infrared Transmission • Using infrared-light waves at a frequency too low.
• Short-range communication (no more than 5 meters)
in IrDA standard.
• Cannot penetrate walls and work only in the direct
"line of sight"
• Speed less than 4 Mbps.
Radio Frequencies
• Distributes radio signals through the air.
• Speed more than 2 Mbps.
• Long distances: cellular phone, broadcast radio and TV.
• Short distances: Bluetooth and Wi-Fi

Microwave • Transmits data more than 45 Mbps as High frequency radio wave.
• Sending signals from one microwave station to another.
• Line-of-sight transmission.

Satellite • Microwave relay station in orbit around the earth.
• Transmitting a signal from a ground station is called “uplink”,
the reverse is called “downlink”

Long-distance wireless communication
The global Positioning System (GPS) consists of 24 earth-orbiting satellites
continuously transmitting timed radio signals that can be used to identify earth locations.

Long-distance wireless communication
Evolution of Mobile wireless Technology
1st Generation
2nd Generation
3rd Generation
4th Generation
• Analog cellphones
• Only voice communication.
• Digital cellphones
• launched on the GSM standard.
• Voice and data service.
• Standards defined by the ITU.
• Voice data and multimedia communication.
• High speed data rate.
• Support VoIP and interactive TV.

Short-range wireless communication
The Bluetooth is a short-range wireless digital standard aimed at linking devices via
a piconet. The piconet typically has a range of about 10 m and a transfer rate between
about 400 and 700 kbps.

Short-range wireless communication
The WiFi is a short-range wireless digital standard aimed at helping devices to
communicate with hi-speed at distances up to 10 m from access points. It is known
formally as an 802.11 Network.

SC161-Lecture4-1

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