basic terms in information technology

Information Technology

1/42copyright © 2015 by schlager communications services GmbH

Basic Terms inInformation Technology

ronaldschlager.com © Ronald Schlager



Overview

Numbering System

Coding

Information

Transmission

Multiplexing

Modulation



Numbering System

General:

Numbering Systems are used in mathematics and digital electronics to represent numeric values using different symbols

Typical symbols are: 0, 1, 6, A, C, F

Numbering systems appeared already in ancient cultures in e.g. China, Egypt or India



Numbering System

General:

Basis: base of the numbering system, e.g. 10

Symbols: all symbols (digit, letters), e.g. 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F

Position, valence: „importance“ of a digit or letter at the specific location within a number, e.g.

Decimal number 968 = 9*102 + 6*101 + 8*100 = = 900 + 60 + 8 = 968



Numbering System

Decimal system:

Basis: 10

Symbols: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9

Representation examples:

D.968254

968254decimal

96825410

107

0

106

0

105

9

104

6

103

8

102

2

101

5

100

4



Numbering System

Binary system:

Basis: 2

Symbols: 0, 1


B.10010110

100101102

10010110B

27

1

26

0

25

0

24

1

23

0

22

1

21

1

20

0



Numbering System

Binary system:

Conversion into decimal values

20

21

22

23

24

25

26

27

1

2

4

8

16

32

64

128

28

29

210

211

256

512

1024

2048

212

213

214

215

4096

8192

16384

32768



Numbering System

Hexadecimal system:

Basis: 16

Symbols: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F


H.C13FE81A

C13FE81AH

0xC13FE81A

167

C

166

1

165

3

164

F

163

E

162

8

161

1

160

A



Numbering System

Conversion hexadecimal binary:

0 00001 00012 00103 00114 01005 01016 01107 0111

8 10009 1001A 1010B 1011C 1100D 1101E 1110F 1111



Coding – Why?

Problem:

Natural information is analog (e.g. music)

Computer: can only distinguish between „0“ and „1“ (digital)

100

11



Coding – Why?

Solution: digitalization in computer

Digital transmission through networks

10

01

1

10

01

1

10

01 network

(digital)



Coding

Why coding?

Non-time-critical (static) information:

For input, storing or presentation of information time component is not relevant

Examples: texts, graphics, images

Time-critical (dynamic) information:

Time component may be very important for recording or presentation of information

Examples: interactive audio, interactive video

Audio or video communication (dialogs) allows only very short delays (real-time)!



Coding

What is a code?

“A code is a rule to convert a piece of information into an other form or

representation”

Used for unique assignment of “symbols” from a source alphabet to

certain “symbols” of a target alphabet



Coding

Examples: general

a b c d

Symbols

Letters

House

Symbol

LettersCombination of multiple letters =

code word


15/42

Examples: digital technology

copyright © 2015 by schlager communications services GmbH

00 01 10 11

Symbols

Digital characters

Coding

0100 0001

SymbolA

Kombination mehrerer Zeichen = Codewort

Digital characters



Coding

Examples: Morse Code

Invented by Samual F.B. Morse

Binary code (electric current on/off, tone or light signal on/off), variable character length

Code word elements: 1 - 5 symbols (“.”, “-”)

Used for transmission of characters between telegraphs using electric current along wires (1836) or later for radio telegraphy

Examples:

a: “.-” e: “.” k: “-.-” s: “...” x: “-..-”



Coding

Examples:

Baudot code

Binary code (electric current on/off), fixed character length (5 bits per character)

Invented by Emile Baudot (1845 - 1903)

Initially used for exchange of characters between telegraphs using electric current along wires (1874)



Coding

Examples:

ASCII-Code

American Standard Code for Information Interchange

7-bit binary code for computers

1951 invented by Robert Bemer, IBM,standardized by ANSI in 1963, ISO standard since 1974

Example: letter “A” - B.0100 0001 - H.41



Coding

Examples: Unicode

32-bit binary code for computers

Invented in 1987 (Apple, Xerox), ISO standard since 1992

Supports multilingual text processing

Supports many commonly and rarely used scripts and characters

Supports e.g. Asian charactersets or Egyptian Hieroglyphs

มหาวิ�ทยาลัยเชี�ยงใหม�



Information

Information, message = piece of news

Between humans

Hi, how old are you?

I am 35!



Information


Between humans and machines

LDA,STA,CMP



Information


Between machines

1000101010000

011000111101



Information


Goal: complex processing of information

Network



Transmission

Infosource

Sender,Coder

Transmission system,channel

Receiver,Decoder

Infosink

Disturbances

Infosource Info

sink

Disturbances

Infoloss



Transmission - Voice

Bandwidth of a human voice signal

f20 Hz 20 kHz

Total voice bandwidth

Example of signal bandwidth transmitted

300 Hz 3400 Hz

Economic goal:sufficient audibility



Transmission - Data

Example: signal has 2 states (levels), digital signal:

Current

t

Current

t

1 symbol change = Change of the digital signal

Here:Change from one signal state

to the next: 1 bit / step

Number of distinct symbol changes per second = Baud rate



Transmission - Data

Examples:

Current

t

Current

t

Change of state contains information

Advantage: signal requires lower bandwidth

Signal has 3 states (levels): Signal has 5 states (levels):



Multiplexing

Problem: bottleneck des Transmissionskanals

Infosource

Sender,Coder

Transmissionsystem,channel

Receiver,Decoder

Infosink

Disturbances

Goal: better utilisationof transmission systems

(time, frequency, code)



Multiplexing

Solution: multiplexer

Information of different low speed lines will be multiplexed and transferred over highspeed links

Multiplexer Multiplexer

analog, digital

digital



Multiplexing

Example: time division multiplexing technology (schematic illustration):

Multiplexer Multiplexer

„Synchronized“ symbolic switchesA

B

C

D

E

F



Multiplexing

Example: time division multiplexing technology (schematic illustration):

Chronology of data transmission:

A

B

C

Link

t

t

t

t1 time slot per station Total capacity: 3 time slots



Multiplexing

Time Division Multiplexing, TDM

Time domain is divided into „time slots“ periodically used by different stations

Frequency Division Multiplexing, FDM

Frequency domain is divided into „frequency channels“ simultaneously used by different stations

t

Transmission capacity

t

Station A

Station B

Station C

Frequency

A B C A B C A B C A



Multiplexing - TDM

Plesiochronous Digital Hierarchy (PDH)

European multiplexing technology acc. ITU-T G.7xx

64.000 bpsE0

2,048 MbpsE1

8,448 MbpsE2

34,368 MbpsE3

30+2 channels4 channels

4 channels

139,264 MbpsE4

4 channels

Problems:

Technical effort for multiplexing and Demultiplexing

Synchronisation of transmission paths

Problems:

Technical effort for multiplexing and Demultiplexing

Synchronisation of transmission paths

564,992 MbpsE5

4 channels

Digital signal multiplexer

Synchronouslink

CC

CC

C

C ... Local clock generator



Multiplexing - TDM

Synchronous Digital Hierarchy (SDH)

Concept:

Advantage:

Insertion and Drop of bitstreams may occur everywhere (no pass-through of multiple multiplexing hierarchies

required!)

Advantage:

Insertion and Drop of bitstreams may occur everywhere (no pass-through of multiple multiplexing hierarchies

required!)

155 Mbps

2,048 Mbps155 Mbps622 Mbps2,5 Gbps10 Gbps

2,048 Mbps

155 Mbps



Multiplexing - CDM

Code Division Multiplexing, CDM

Systems use certain codes (= numbers, bit combinations) to distinguish between signals of different devices within the same time-slot and the same frequency channel

Application example: mobile radio technologies like „Universal Mobile Telecommunication System (UMTS)“ or „Long Term Evolution (LTE)“

Each device gets assigned a specific code(= bit combination of certain number of bit), used for unique identification

t

Station A

Station B

Station C

Code

Station A

Station B Station C

Station D

Station A



Multiplexing - WDM

Wavelength Division Multiplexing, WDM)

Used for simultaneous transmission of optical signals using optical links

The differentiation of light pulses is based on the „color“or „wavelength“ of the optical signal

Application example:

Transfer of data over great distances (e.g. between continents)

t

Station A

Station B

Station C

Wavelenght



Modulation

Infosource

Modu-lator

Transmissionsystem,channel

Demodu-lator

Infosink

Carrier Carrier

Modulation: “Modification of signal parameters of the

carrier depending on a modulating signal”

Goal:Efficient transmission

of information through the transmission system



Modulation

Carriers and modifiable signal parameters:

Current

Current

t

Parameters: AmplitudeFrequencyPhase

Parameters: AmplitudeFrequencyLengthPhaseCode

t



Analog carrier signals – Amplitude Modulation (AM)

Signal shape:

Analog carrier signals – Frequency Modulation (FM)

Signal shape :

Analog carrier signals - Phase Modulation, „Phase Shift Keying (PSK)“

Signal shape :

Modulation

" "" "1 0



Modulation

Digital carrier signals – Pulse Modulation

Amplitude, length, frequency, phase, code:

Used in digital transmission systems (efficiency!)



Modulation

Digitale carrier signals – Pulse Code Modulation: (schematic illustration)

Sig

nal

str

eng

th

t3

2

1

0

4

5

6

7

0

0

0

0

1

1

1

1

0

0

1

1

0

0

1

1

0

1

0

1

0

1

0

1

3 bit code words(= “sampling depth”)

are transported through a

transmission link

Sign of signal directionUser signal

+

-



Resources

Visit Ronald Schlager´s resources for more information:

Courseware: „Basics in Data Communications - Part 1/3“



Courseware: „OSI Model - Tutorial“

Book: „Abbreviations in Communications Technologies“

Book: „The OSI Model – simply explained“

Web:

Ronald Schlager´s Blog

www.ronaldschlager.com

http://www.ronaldschlager.com/eBooks17.htm





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basic terms in information technology

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