DEP3273 :
COMMUNICATION SYSTEM
FUNDAMENTALS
1
COURSE LEARNING
OUTCOME
Upon completion of this course, students should be able to:1.
apply the basic concept of communication system elements,
various types of modulation techniques, transmission system
and basic data communication in electronic communication by
using appropriate diagram. (C3, PLO1)
2.
solve a well-defined problems related to noise parameters,
modulation parameters, character encoding and information
capacity using designated method and formula. (C3, PLO2)
3.
construct and test various applications of related communication
equipments in performing the assigned practical work using
standard test equipment. (P4, PLO5)
4.
demonstrate ability to work in a team to complete assigned
tasks during practical work sessions. (A3, PLO11)
2
CHAPTER 4
DATA COMMUNICATION
(04 : 04)
LEARNING OUTCOME
4.1 Know the principle of data communication.
4.2 Know and apply the communication codes
4.3 Understand and apply bit, bit rate, baud rate
and
information capacity.
4.4 Understand the elements of Data
Communication
4.5 Understand Data Transmission.
3
4.1 Know and understand the principle of data
communication
At the end of this learning session,
student should be able to explain :
- Definition of Data Communication
- Principles of Data Communication
- Components of Data Communication
- Application of Data Communication
4
INTRODUCTION TO DATA
COMMUNICATION
5
INTRODUCTION
 Data generally are defined as information that is stored in
digital form.
 Information is defined as knowledge or intelligence or
original source information. (refer Topic 1)
 Information that has been processed, organized, and stored
by computer(or any digital system) is called data.
 Data communication is the process of transferring digital
information signal between two or more points.
 Character is a kind of information that consist alphabet,
numeric and symbol.(eg: 0, 1, 8, a, A, *,&, “ )
6
INTRODUCTION
 The fundamental purpose of data communication circuit is to
transfer digital information from one place to another.
 Data communication can be summarized as the
transmission, reception, and processing of digital information.
 The original source information can be analog form
(human voice or music), or in digital form (binary-coded
numbers or alphanumeric codes).
 If the source information is in analog form, it must be
converted to digital form (using PCM technique) at the
transmitter and then converted back to analog form at the
receiver.
7
PRINCIPLE of DATA COMMUNICATION

For data communications to occur, the communicating
devices must be part of a communication system
made up of a combination of hardware (physical
equipment) and software (programs).

The effectiveness of a data communications system
depends on four fundamental characteristics:
i. Delivery
ii. Accuracy
iii. Timeliness
iv. Jitter
8
PRINCIPLE of DATA COMMUNICATION
 Delivery: The system must deliver data to the correct destination.
Data must be received by the intended device or user and only by
the device or user.
 Accuracy: The system must deliver the data accurately. Data
that have been altered in transmission and left uncorrected are
unusable.
 Timeliness: The system must deliver data in timely manner. Data
delivered late are useless.
 Jitter: Jitter refers to the variation in the packet arrival time. It is
uneven delay in the delivery of audio or video packets. For
example, let us assume that video packets are sent every 30ms.
If some of the packets arrive with 30ms delay and others with
40ms delay, uneven quality in the video is the result.
9
Components of Data Communication
Data communications system has five
components:
1. Message: is the information (data) to be
transmitted. The information may includes
characters, text (combination of characters),
images, audio, or video (combination of text,
image and audio).
2. Transmitter/Sender: is an equipment that sends
the data message. It can be a host computer,
terminals, mainframe, workstation, telephone
handset, video camera, and so on.
10
Components of Data Communication
3. Receiver: is an equipment that receives the message. It
can be a computer, workstation, telephone handset,
television, and so on.
4. Transmission medium: is the physical path by which a
message travels from sender to receiver. For example,
twisted-pair cable, coaxial cable, and fibre optic cable.
5. Protocol: is a set of rules that govern the data
communication. It represents an agreement between
the communicating devices. Without a protocol, two
devices may be connected but not communicating, just
as a person speaking French cannot be understood by a
person who speaks only Japanese.
11
Application of Data Communication

Electronic Mail (e-mail) - replaces snail mail. E-mail is the forwarding of electronic
files to an electronic post office for the recipient to pick up.

Scheduling Programs - allow people across the network to schedule appointments
directly by calling up their fellow worker's schedule and selecting a time.

Videotext - is the capability of having a two-way transmission of picture and sound.
For example, games like Red Alert, distance education lectures, etc.
12
Application of Data Communication

Groupware - is the latest network application. It allows user
groups to share documents, schedules, data bases, etc. (ex.
Lotus Notes)

Teleconferencing - allows people in different regions to
"attend" meetings using telephone lines.

Telecommuting - allows employees to perform office work
at home by "Remote Access" to the network.

Automated Banking Machines - allow banking
transactions to be performed everywhere: at grocery stores,
drive-in machines etc.
13
4.2 Know and apply the communication codes
At the end of this learning session,
student should be able to know:
- Communication Codes
- Character Encoding
14
COMMUNICATION CODES
15
Communication Codes

In Data Communication, the communication occurs in digital
form which is in binary number (0 and 1).

Therefore, any information such as character, text, image,
audio and video must be converted into digital signal.

Communication Code is a combination of bit 0 and bit 1 to
represent a character.

A character can be represented in 8 bits, or 16 bits or maybe
32bits.

We need the communication codes to encode the characters
into digital signal.
16
Communication Codes


There are a few standard codes that have been
designed for character encoding which are;

Morse Code

Baudot Code

ASCII Code

EBCDIC Code

Unicode
However, there two most popular codes in character
encoding which are ASCII code and EBCDIC code.
17
i. Morse Code

Morse Code is the first communication code which have been
invented by Samuel Morse (1791-1872) in the 1830s and 1840s
for Telegraph technology.

This code contains the combination of dot and dash ( • and - )

A dot represents a unit of time. While one single dash represents
three units of time.

Samuel Morse developed a code that assigned a set of dots and
dashes to each letter of the English alphabet and allowed for the
simple transmission of complex messages across telegraph
lines.

Below Table 3.1 shows the Morse Code.
18
Table 3.1: International Morse Code
1. A dash is equal to 3
dots.
2. The space between
parts of the same letter
is equal to one dot.
3. The space between two
letters is equal to 3
dots.
4. The space between two
words is equal to 7
dots.
19
ii. Baudot Code

First code was invented for Computer technology.

It uses binary number, bit 0 and bit 1 to represent
the character where each character represent in 5
bits.

Also known as Murray, CCITT Alphabet No 2,
International Alphabet No 2 or Telex Code.

Below Table 3.2 shows the Baudot Code.
20
CHARACTER
LOWER CASE
UPPER CASE
A
B
?
C
:
D
$
E
3
F
!
G
&
H
#
I
8
J
‘
K
(
L
)
M
.
N
,
O
9
P
0
Q
1
R
4
S
BELL
T
5
U
7
V
;
W
2
X
/
Y
6
Z
“
Shift to lowercase
Shift to Uppercase
Space
Carrige Return
Line Feed
Blank
5
0
1
0
0
0
0
1
1
0
0
0
1
1
0
1
1
1
0
0
1
0
1
1
1
1
1
1
1
0
0
0
0
4
0
1
1
1
0
1
1
0
0
1
1
0
1
1
1
0
0
1
0
0
0
1
0
1
0
0
1
1
0
1
0
0
BINARY
3
0
0
1
0
0
1
0
1
1
0
1
0
1
1
0
1
1
0
1
0
1
1
0
1
1
0
1
0
1
0
0
0
2
1
0
1
0
0
0
1
0
1
1
1
1
0
0
0
1
1
1
0
0
1
1
1
0
0
0
1
1
0
0
1
0
1
1
1
0
1
1
1
0
0
0
1
1
0
0
0
0
0
1
0
1
0
1
0
1
1
1
1
1
1
0
0
0
0
Table 3.2:
Baudot Code
21
iii. ASCII Code

ASCII is stand for American Standard Code for Information Interchange.

This code was developed by American National Standard Institution (ANSI) and had
become an international standard for character encoding.

This code has 7 bits data and 1 parity bit of binary code (bit 0 and 1) to represents a
character. A parity bit is used for error checking.

That means ASCII code has 27= 128 characters to be encoded. Extended ASCII code
use 8 bits to represent a character, where parity bit is turned to data bit.

Besides Binary code, ASCII code also has Decimal, Octal and Hexa-decimal code.

Below Table 3.3 shows the Binary ASCII Code.
22
Table 3.3: ASCII Code
Bit
7
Bit
6
Bit
5
Bit
4
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
Bit
3
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
Bit
2
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
Bit
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
0
0
0
0
1
0
1
0
0
1
1
1
0
0
1
0
1
1
1
0
1
1
1
NUL
SOH
STX
ETX
EOT
ENQ
ACK
BEL
BS
HT
LF
VT
FF
CR
SO
SI
DLE
DC1
DC2
DC3
DC4
NAK
SYN
ETB
CAN
EM
SUB
ESC
FS
GS
RS
US
SP
!
“
#
$
%
&
‘
(
)
*
+
,
.
/
0
1
2
3
4
5
6
7
8
9
:
;
<
=
>
?
@
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
V
W
X
Y
Z
[
\
]
^
-
\
a
b
c
d
e
f
g
h
i
j
k
l
m
n
o
p
q
r
s
t
u
v
w
x
y
z
l
:
;
~
DEL
23
iii. ASCII Code

From above table, there are 7 data bits start from bit 1 until bit 7
for each character.

Bit 1 is LSB (less significant bit), while Bit 7 is MSB (most
significant bit).

How to encode the character using this ASCII code is by reading
the code from bit 1 until bit 7 and then Bit 8 which is parity bit.
Parity bit is either bit 0 or 1.

For example, letter Z is encoded as 1011010. Assume parity bit is
0, then;
Z= 0
1
0
1
1
0
1
0
b8 b7 b6 b5 b4 b3 b2 b1
Parity Bit MSB
LSB
Data flow
24
iv. EBCDIC Code

EBCDIC is stand for Extended Binary Coded Decimal Interchanged Code.

This code was developed by International Business Machines Corporation
(IBM).

Another famous code besides ASCII code. Most of the IBM computers and
devices use this code.

This code uses 8 data bits. Therefore, there are 28 = 256 characters can be
encoded using EBCDIC code.

This code is extended from BCD code (Binary Coded Decimal).

Below Table 3.4 shows the EBCDIC Code.
25
Kedudukan bit 8 7 6 5
Kedudukan
bit 4 3 2 1
0000
0001
0010
0000
NULL
DLE
DS
0001
SOH
DC1
SOS
0010
STX
DC2
FS
0011
ETX
TN
0100
PF
RES
BYP
0101
HT
NL
0110
LC
0111
DEL
0011
0100
0101
0110
SP
&
_
0111
/
1000
1001
a
j
b
k
c
PN
LF
BS
IL
Table 3.4: EBCDIC Code
1010
1011
1100
1101
1110
1111
\
0
A
J
s
B
K
S
2
l
t
C
L
T
3
d
m
u
D
M
U
4
RS
e
n
v
E
N
V
5
EOP
UC
f
o
w
F
O
W
6
PRE
EOT
g
p
x
G
P
X
7
SYN
1
1000
CAN
h
q
y
H
Q
Y
8
1001
EM
i
r
z
I
R
Z
9
1010
SMM
CC
SM
1011
VT
CU1
CU2
1100
FF
IFS
1101
CR
IGS
ENQ
1110
SO
IRS
ACK

!
CU3
.
$
,
#
DC4
<
*
%
@
NAK
(
)
-
‘
+
;
>
=
:
26
iv. EBCDIC Code

The space in the EBCDIC table can be used for others character
such as graphic and so on.

From above table, there are 8 data bits start from bit 1 until bit 8
for each character.

How to encode the character using this code is by reading the
code from bit 1 until bit 8.

For example, letter Z is encoded as 11101001.
A= 1
MSB
b8
1
1
0
1
0
0
1
b7 b6Data
b5 flow
b4 b3 b2LSB
b1
27
Communication Codes
EXAMPLE 4.1
Encode the following text dEp_3 by using
i.
ASCII code
ii.
EBCDIC code
SOLUTION:
i. ASCII code
d = 01100100
E = 01000101
p = 01110000
_ = 01011111
3 = 00110011
ii EBCDIC code
d = 10000100
E = 11000101
p = 10010111
_ = 01100000
3 = 11110011
28
4.3
Understand and apply bit, bit rate, baud rate and
information capacity.
At the end of this learning session,
student should be able to explain :
- Bit
- Bit rate
- Baud rate
- Information capacity
29