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10/28/2014 Data Communication and Networking Submitted to: Md. Abdus Sobur Sikdar SYLHET INTERNATIONAL UNIVERSITY Roll No.: 22065 Registration No.: 121101065 Mr. Sushanta Acharjee Assistant Professor Department of CSE Sylhet International University
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Page 1: Data Communication & Networking

10/28/2014

Data Communication

and Networking Submitted to:

Md. Abdus Sobur Sikdar SYLHET INTERNATIONAL UNIVERSITY Roll No.: 22065 Registration No.: 121101065

Mr. Sushanta Acharjee Assistant Professor

Department of CSE

Sylhet International University

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Page 2: Data Communication & Networking

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Table of Contents

Table of Contents ................................................................................................................................... 1

Data Communications and Networking .................................................................................................. 3

Types of Computer Networking .............................................................................................................. 3

Personal Area Network (PAN): _____________________________________________________ 3

Local Area Network (LAN): ________________________________________________________ 3

Metropolitan Area Network (MAN): _________________________________________________ 3

Wide Area Network (WAN): _______________________________________________________ 3

Communication Model ........................................................................................................................... 3

Source ............................................................................................................................................. 4

Transmitter ..................................................................................................................................... 4

Receiver ........................................................................................................................................... 4

Destination ...................................................................................................................................... 4

Basic Element of a Communication System ............................................................................................ 4

Tasks of communication system ............................................................................................................. 5

Basic terms in data communication ........................................................................................................ 5

Analog Signal: __________________________________________________________________ 5

Digital Signal: ___________________________________________________________________ 5

Analog Data: ___________________________________________________________________ 6

Digital Data: ____________________________________________________________________ 6

Bandwidth: ____________________________________________________________________ 6

Bitrates: _______________________________________________________________________ 6

Data Transmission Modes ....................................................................................................................... 6

Types of Data Transmission Modes ........................................................................................................ 6

Simplex Mode __________________________________________________________________ 6

Half-Duplex Mode _______________________________________________________________ 6

Full-Duplex Mode _______________________________________________________________ 7

Advantage of digital transmission___________________________________________________ 7

Protocol ................................................................................................................................................... 7

Syntax .............................................................................................................................................. 7

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Transmission Impairment ....................................................................................................................... 8

Attenuation ____________________________________________________________________ 8

Distortion _____________________________________________________________________ 8

Noise _________________________________________________________________________ 9

Data rate depends on? ............................................................................................................................ 9

Formula to Calculate data rate ............................................................................................................. 10

Transmission Impulse ........................................................................................................................... 10

Problem (1): __________________________________________________________________ 10

Problem (2): __________________________________________________________________ 11

Problem (3): __________________________________________________________________ 11

Problem (4): __________________________________________________________________ 12

Problem (5): __________________________________________________________________ 12

Questions .............................................................................................................................................. 13

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Data Communications and Networking

Data Communication is the process of transferring data (message) from one point to another.

Data communications refers to the transmission of this digital data between two or more

computers and a computer network or data network is a telecommunications network that

allows computers to exchange data. The physical connection between networked computing

devices is established using either cable media or wireless media. The best-known computer

network is the Internet.

Types of Computer Networking

Generally, networks are distinguished based on their geographical span. A network can be as

small as distance between your mobile phone and its Bluetooth headphone and as large as the

Internet itself, covering the whole geographical world, i.e. the Earth. There are four types of

computer network as given below.

a. PAN

b. LAN

c. MAN

d. WAN

Personal Area Network (PAN): A Personal Area Network or simply PAN, is smallest

network which is very personal to a user. This may include Bluetooth enabled devices or

infra-red enabled devices.

Local Area Network (LAN): A computer network spanned inside a building and operated

under single administrative system is generally termed as Local Area Network. Usually,

Local Area Network covers an organization’s offices, schools, college/universities etc.

Metropolitan Area Network (MAN): MAN, generally expands throughout a city such as

cable TV network. It can be in form of Ethernet, Token-ring, ATM or FDDI.

Wide Area Network (WAN): As name suggests, this network covers a wide area which

may span across provinces and even a whole country. Generally, telecommunication

networks are Wide Area Network. These networks provides connectivity to MANs and

LANs. Equipped with very high speed backbone, WAN uses very expensive network

equipment.

Communication Model

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The fundamental purpose of a communications system is the exchange of data between two

parties. I begin my study with a simple model of communications, illustrated by the block

diagram in Figure (1).

Figure (1): General block diagram

Source: This device generates the data to be transmitted; examples are telephones and

personal computers.

Transmitter: Usually, the data generated by a source system are not transmitted directly in

the form in which they were generated. Rather, a transmitter transforms and encodes the

information in such a way as to produce electromagnetic signals that can be transmitted

across some sort of transmission system. For example, a modem takes a digital bit stream

from an attached device such as a personal computer and transforms that bit stream into an

analog signal that can be handled by the telephone network. Transmission system. This can

be a single transmission line or a complex network connecting source and destination.

Receiver: The receiver accepts the signal from the transmission system and converts it into

a form that can be handled by the destination device. For example, a modem will accept an

analog signal coming from a network or transmission line and convert it into a digital bit

stream.

Destination: Takes the incoming data from the receiver. This simple narrative conceals a

wealth of technical complexity.

Basic Element of a Communication System

The Basic Element of a Communication System are

The following are the basic requirements for working of a communication system.

Sender: A sender (source), which creates the message to be transmitted.

Source Transmitter Transmission

System Receiver Destination

Medium Sender Receiver

Figure (2): Communication System

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Medium: A medium that carries the message.

Receiver: A receiver (sink), which receives the message.

Example: A modem.

Tasks of communication system

Tasks of Communication System list are given below:

Transmission System Utilization (Multiplexing)

Interfacing

Signal Generation (Codding)

Synchronization between transmitter and receiver

Exchange Management (Connection Management)

Error Detection and Correction

Flow control

Addressing

Routing

Recovery

Message formatting

Security

Network Management

Basic terms in data communication

In data communication four basic terms are frequently used. They are

Data: A collection of facts in raw form that become information after processing.

Signals: Electric or electromagnetic encoding of data.

Signaling: Propagation of signals across a communication medium.

Transmission: Communication of data achieved by the processing of signals.

Analog Signal: A continues waveform that charge smoothly over time.

Digital Signal: A discrete signal with limited number of values.

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Analog Data: That is continuous and smooth and not limited to specific number of values.

Example: Audio, Video, Human voice.

Digital Data: That is representing by discrete values. Example: Text, String

Bandwidth: The range of frequencies that a medium can pass is called bandwidth. It is the

different between the highest and lowest frequency.

Bitrates: The number of bit transmitted per second is called bitrate.

Data Transmission Modes

The way in which data is transmitted from one place to another is called data transmission mode. It is

also called the data communication mode. It is indicates the direction of flow of information.

Sometimes, data transmission modes are also called directional modes.

Types of Data Transmission Modes

The types of data transmission modes are as follows:

a. Simplex Mode

b. Half-duplex Mode

c. Full-duplex Mode

Simplex Mode

In simplex mode, data can flow in only one direction. In this mode, a sender can only send

data and cannot receive it. Similarly, a receiver can only receive data but cannot send it. Data

sent from computer to printer is an example of simplex mode.

Half-Duplex Mode

In half-duplex mode, data can flow in both directions but only in one direction at a time. In

this mode, data is sent and received alternatively. It is like a one-lane bridge where two-way

traffic must give way in order to cross the other.

Sender Receiver

Figure (3): Simplex

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Full-Duplex Mode

In full duplex-mode, data can flow in both directions at the same time. It is the fastest

directional mode of data communication. The telephone communication system is an

example of full-duplex communication mode. Two persons can talk at the same time.

Another example of fully-duplex mode in daily life is automobile traffic on a two-lane road.

The traffic can move in both directions at the same time.

Advantage of digital transmission a. Digital technology

b. Data integrity

c. Capacities utilization

d. Security and privacy

e. Integration

Protocol

A protocol is a set of rules that permit/govern data communication. Or a protocol define what

is communication how it is communicated & when it is communicated the key elements of a

protocol are.

The key elements of protocol are syntax, semantics and timing.

Syntax: Syntax relates to the structure or format of the data, meaning the order in which they are

presented. For example; a simple protocol may expect the first 8 bits of data to be the address of the

sender, the second 8 bits to be the address of receiver, and the rest of the stream to be the message

itself.

Semantics: Semantics relates to the meaning of each section of bits. How is a specified pattern to be

interpreted; and what action is to be taken based on that interpretation? For instance does an

address identify the route to be taken or the final destination of the message?

Sender/Receiver Receiver/Sender

Figure (4): Half-duplex

Sender/Receiver Receiver/Sender

Figure (5): Full-duplex

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Timing: Timing refers to two vital characteristics: when data should be sent and how fast they can

be sent. For example if a sender produces data at 100 Mbps but the receiver can process data at

only 1 Mbps, the transmission will overload the receiver and data will be largely lost.

Transmission Impairment

Signals travel through transmission media, which are not perfect. The imperfection causes

signal impairment. This means that the signal at the beginning of the medium is not the same

as the signal at the end of the medium. What is sent is not what is received. Three causes of

impairment are attenuation, distortion, and noise.

Attenuation: attenuation means a loss of energy. When a signal, simple or composite, travels

through a medium, it loses some of its energy in overcoming the resistance of the medium.

That is why a wire carrying electric signals gets warm, if not hot, after a while. Some of the

electrical energy in the signal is converted to heat. To compensate for this loss, amplifiers are

used to amplify the signal.

Distortion: Distortion means that the signal changes its form or shape. Distortion can occur

in a composite signal made of different frequencies. Each signal component has its own

propagation speed through a medium and, therefore, its own delay in arriving at the final

destination. Differences in delay may create a difference in phase if the delay is not exactly

the same as the period duration. In other words, signal components at the receiver have

phases different from what they had at the sender. The shape of the composite signal is

therefore not the same.

Figure (6)

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Noise: Noise is another cause of impairment. Several types of noise, such as thermal noise,

induced noise, crosstalk, and impulse noise, may corrupt the signal. Thermal noise is the

random motion of electrons in a wire which creates an extra signal not originally sent by the

transmitter. Induced noise comes from sources such as motors and appliances. These devices

act as a sending antenna, and the transmission medium acts as the receiving antenna.

Crosstalk is the effect of one wire on the other. One wire acts as a sending antenna and the

other as the receiving antenna. Impulse noise is a spike (a signal with high energy in a very

short time) that comes from power lines, lightning, and so on.

Data rate depends on?

A very important consideration in data communications is how fast we can send data, in bits

per second, over a channel.Data depends on three factors

i. The bandwidth available

Figure (7)

Figure (8)

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ii. The level of the signals we use

iii. The quality of the channel (the level of noise)

Formula to Calculate data rate

Formula to calculate data rate are

1. Nyquist bitrates for noiseless channel

Bitrate =2 × Bandwidth × log2 𝐿

2. Shannon capacity for noisy channel

Capacity = Bandwidth × log2(1 + 𝑆𝑁𝑅)

Transmission Impulse

The rules of transmission impulse

SNR (Signal to Noise Ratio)

SNR = 𝑆𝑖𝑔𝑛𝑎𝑙 𝑃𝑜𝑤𝑒𝑟

𝑁𝑜𝑖𝑠𝑒 𝑃𝑜𝑤𝑒𝑟

SNRdB= 10 log10 𝑆𝑁𝑅

Problem (1): We need to download text document at the rate of 100 pages per minute. What is

the required bitrates of the channel? (A page is an average of 24 lines with 80 characters in each

line?

Solution:

Character per page is 80×24=1920

Character 100 pages are 1920×100=192000

We know 1bit equal minimum 8byte

So 192000×8=1536000 bps

1536000÷1024=1500 kbps

1500÷1024=1.465 mbps

1.465 mbps bitrates is required.

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Problem (2): Consider a noiseless channel with a bandwidth of 3000Hz transmitting signal with

two signal levels. Find out the maximum bitrate?

Solution:

Here, Bandwidth B = 3000Hz

Signal Level L =2

Bitrate =?

By Nyquis bitrates formula we know,

Bitrate =2 × Bandwidth × log2 𝐿

Bitrate =2 ×3000 ×log2 2

Bitrate =2×3000×1

Bitrate =6000 bps

Problem (3): Consider a noiseless channel with a bandwidth of 30MHz transmitting signal with four

signal levels. Find out the maximum bitrate?

Solution:

Here, Bandwidth B = 30MHz

=30×1000×1000

=30×106Hz

Signal Level L =4

Bitrate =?

By Nyquis bitrate formula we know,

Bitrate =2 × Bandwidth × log2 𝐿

Bitrate =2 ×30×106 ×log2 4

Bitrate =120 ×106bps

Bitrate =120 mbps

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Problem (4): We need to send 265 kbps over a noiseless channel with a bandwidth of 20 KHz. How

many signal level do we need?

Solution:

Here,

Bitrate = 265 kbps

= 265×103bps

Bandwidth = 20 KHz

= 20 × 103Hz

Level L =?

By Nyquis bitrates formula we know,

Bitrate =2 × Bandwidth × log2 𝐿

265×103 = 2×20 × 103× log2 𝐿

log2 𝐿 = 265×103

20×103

log2 𝐿 = 6.625

L = 26.625

L = 98.7 Levels.

Since the result is not power of 2 we need to either increase the number of level or reduce the

bitrate. We have 128 levels the bitrate is 280 kbps. If we have 64 levels the bit rate is 240

kbps.

So level will be 64 or 128.

Problem (5): The spectrum of a channel is between 3MHz and 4MHz and SNRdB =24dB. How many

signaling levels are required?

Solution:

Here,

Bandwidth B = 4-3=1MHz

= 106Hz

SNRdB = 24 dB

Signal level L =?

We Know that,

SNRdB= 10 log10 SNR

log10 SNR= SNR𝑑𝐵

10

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log10 SNR= 24

10

log10 SNR= 2.4

SNR = 102.4

SNR = 251

Again, Bitrate = Bandwidth × log2(1 + 𝑆𝑁𝑅)

Bitrate = 106× log2(1 + 251)

Bitrate = 106× log2 252

Bitrate = 106× log2 28

Bitrate = 106× 8 log2 2

Bitrate = 106× 8 bps

From Nyquist bitrate we know,

Bitrate =2 × Bandwidth × log2 𝐿

log2 𝐿 = Bitrate

2×Bandwidth

log2 𝐿 = 8×106

2×106

log2 𝐿 = 4

L = 24

L = 16 levels.

Questions

1. What is Protocol and Bandwidth? We need to download text document at the rate of 100

pages per minute. What is the required bitrates of the channel? (A page is an average of 24

lines with 80 characters in each line?

2. Write down the Basic Element of a Communication System. Describe the types of

data transmission modes.

3. Write down the formulas to calculate data rate. The spectrum of a channel is between

5MHz and 6MHz and SNRdB =24dB. How many signaling levels are required?

Answer to the Q no. 1:

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Protocol: A protocol is a set of rules that permit/govern data communication. Or a protocol

define what is communication how it is communicated & when it is communicated the key

elements of a protocol are.

Bandwidth: The range of frequencies that a medium can pass is called bandwidth. It is the

different between the highest and lowest frequency.

Solution:

Character per page is 80×24=1920

Character 100 pages are 1920×100=192000

We know 1bit equal minimum 8byte

So 192000×8=1536000 bps

1536000÷1024=1500 kbps

1500÷1024=1.465 mbps

1.465 mbps bitrates is required.

Answer to the Q no. 2:

The Basic Element of a Communication System are

The following are the basic requirements for working of a communication system.

Sender: A sender (source), which creates the message to be transmitted.

Medium: A medium that carries the message.

Receiver: A receiver (sink), which receives the message.

Example: A modem.

Types of Data Transmission Modes

The types of data transmission modes are as follows:

a. Simplex Mode

b. Half-duplex Mode

c. Full-duplex Mode

Simplex Mode In simplex mode, data can flow in only one direction. In this mode, a sender can only send

Medium Sender Receiver

Figure (2): Communication System

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data and cannot receive it. Similarly, a receiver can only receive data but cannot send it. Data

sent from computer to printer is an example of simplex mode.

Half-Duplex Mode

In half-duplex mode, data can flow in both directions but only in one direction at a time. In

this mode, data is sent and received alternatively. It is like a one-lane bridge where two-way

traffic must give way in order to cross the other.

Full-Duplex Mode

In full duplex-mode, data can flow in both directions at the same time. It is the fastest

directional mode of data communication. The telephone communication system is an

example of full-duplex communication mode. Two persons can talk at the same time.

Another example of fully-duplex mode in daily life is automobile traffic on a two-lane road.

The traffic can move in both directions at the same time.

Answer to the Q no. 3:

Formula to calculate data rate are

1. Nyquist bitrates for noiseless channel

Bitrate =2 × Bandwidth × log2 𝐿

2. Shannon capacity for noisy channel

Capacity = Bandwidth × log2(1 + 𝑆𝑁𝑅)

Solution:

Here,

Bandwidth B = 6-5=1MHz

Sender/Receiver Receiver/Sender

Figure (4): Half-duplex

Sender Receiver

Figure (3): Simplex

Sender/Receiver Receiver/Sender

Figure (5): Full-duplex

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= 106Hz

SNRdB = 24 dB

Signal level L =?

We Know that,

SNRdB= 10 log10 SNR

log10 SNR= SNR𝑑𝐵

10

log10 SNR= 24

10

log10 SNR= 2.4

SNR = 102.4

SNR = 251

Again, Bitrate = Bandwidth × log2(1 + 𝑆𝑁𝑅)

Bitrate = 106× log2(1 + 251)

Bitrate = 106× log2 252

Bitrate = 106× log2 28

Bitrate = 106× 8 log2 2

Bitrate = 106× 8 bps

From Nyquist bitrate we know,

Bitrate =2 × Bandwidth × log2 𝐿

log2 𝐿 = Bitrate

2×Bandwidth

log2 𝐿 = 8×106

2×106

log2 𝐿 = 4

L = 24

L = 16 levels.