SC161-Lecture4-1

Chapter 4

S C 1 6 1 : P r i n c i p l e s o f I n f o r m a t i o n T e c h n o l o g y

Communication and NetworkPart 1: Data Communication

Thiti Theerathean

Center for Teaching Excellence University of the Thai Chamber of Commerce

E-mail : [email protected]

2

• Introduction to Data Communication.- Data Communication and Telecommunication- Type of Signals - The Basic Components of Communication

• Data Transmission.- Line configurations- Direction of Transmisssion- Transmission Mode

• Communication Channel.- Guided Media- Unguided Media

• Wireless Technology.- Long-distance wireless communication- Short-range wireless communication

SC161: Principles of Information Technology

3SC161: Principles of 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)


SenderCommunication 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.

http://www.resilience.com.au/images/radio_icon.jpg

http://www.resilience.com.au/images/radio_icon.jpg


Data is transmitted in two ways.

Sender Receiver

01110011 01110011

1 1 0 0 1 1 1 0

Sender Receiver

01110011 0111001101110011

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

1100111001011100

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

1100111001011100



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 bps2 - T-1 and ISBN line, 4 Mbps 3 - 16 MHz of bandwidth; 10 Mbps 4 - 20 MHz of bandwidth; 16 Mbps 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 CableA 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-index multimode

Graded-index multimode


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

Twisted pairCategory 1 - 2Category 3 - 6

Telephone systemLANs

Less than 2 Mbps100 Mbps

5 km.100 m (328 feet)

Coaxial CableThin (Single channel)Thick (Multi channel)

LANsLANs

Cable TV

10 Mbps10 Mbps

100 m.5 km.

Fiber Optic CableSingle-modeMulti-mode

LANsWANs

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

Technology

information travels

communication system

voice communication

transfer of data

lowspeed communication

wireless communication

limited data rates

twistedpair cable categories