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Information Technology
1/42copyright © 2015 by schlager communications services GmbH
Basic Terms inInformation Technology
ronaldschlager.com © Ronald Schlager
Information Technology
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Overview
Numbering System
Coding
Information
Transmission
Multiplexing
Modulation
Information Technology
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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
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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
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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
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Numbering System
Binary system:
Basis: 2
Symbols: 0, 1
Representation examples:
B.10010110
100101102
10010110B
27
1
26
0
25
0
24
1
23
0
22
1
21
1
20
0
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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
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Numbering System
Hexadecimal system:
Basis: 16
Symbols: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F
Representation examples:
H.C13FE81A
C13FE81AH
0xC13FE81A
167
C
166
1
165
3
164
F
163
E
162
8
161
1
160
A
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Numbering System
Conversion hexadecimal binary:
0 00001 00012 00103 00114 01005 01016 01107 0111
8 10009 1001A 1010B 1011C 1100D 1101E 1110F 1111
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Coding – Why?
Problem:
Natural information is analog (e.g. music)
Computer: can only distinguish between „0“ and „1“ (digital)
100
11
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Coding – Why?
Solution: digitalization in computer
Digital transmission through networks
10
01
1
10
01
1
10
01 network
(digital)
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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)!
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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
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Coding
Examples: general
a b c d
Symbols
Letters
House
Symbol
LettersCombination of multiple letters =
code word
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Examples: digital technology
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00 01 10 11
Symbols
Digital characters
Coding
0100 0001
SymbolA
Kombination mehrerer Zeichen = Codewort
Digital characters
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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: “-..-”
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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)
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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
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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�
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Information
Information, message = piece of news
Between humans
Hi, how old are you?
I am 35!
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Information
Information, message = piece of news
Between humans and machines
LDA,STA,CMP
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Information
Information, message = piece of news
Between machines
1000101010000
011000111101
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Information
Information, message = piece of news
Goal: complex processing of information
Network
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Transmission
Infosource
Sender,Coder
Transmission system,channel
Receiver,Decoder
Infosink
Disturbances
Infosource Info
sink
Disturbances
Infoloss
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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
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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
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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):
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Multiplexing
Problem: bottleneck des Transmissionskanals
Infosource
Sender,Coder
Transmissionsystem,channel
Receiver,Decoder
Infosink
Disturbances
Goal: better utilisationof transmission systems
(time, frequency, code)
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Multiplexing
Solution: multiplexer
Information of different low speed lines will be multiplexed and transferred over highspeed links
Multiplexer Multiplexer
analog, digital
digital
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Multiplexing
Example: time division multiplexing technology (schematic illustration):
Multiplexer Multiplexer
„Synchronized“ symbolic switchesA
B
C
D
E
F
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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
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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
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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
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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
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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
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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
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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
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Modulation
Carriers and modifiable signal parameters:
Current
Current
t
Parameters: AmplitudeFrequencyPhase
Parameters: AmplitudeFrequencyLengthPhaseCode
t
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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
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Modulation
Digital carrier signals – Pulse Modulation
Amplitude, length, frequency, phase, code:
Used in digital transmission systems (efficiency!)
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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
+
-
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Resources
Visit Ronald Schlager´s resources for more information:
Courseware: „Basics in Data Communications - Part 1/3“
Courseware: „Basics in Data Communications - Part 2/3“
Courseware: „Basics in Data Communications - Part 3/3“
Courseware: „OSI Model - Tutorial“
Book: „Abbreviations in Communications Technologies“
Book: „The OSI Model – simply explained“
Web:
Ronald Schlager´s Blog
www.ronaldschlager.com