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22IT501 ��DATA COMMUNICATION AND COMPUTER NETWORKS

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Department: IT

��Batch/Year: 2023-27 / III YEAR / V SEMESTER

�Created by:

Dr K Saravanan/Prof/IT/RMKEC

Ms D S Deepika/AP/IT/RMDEC

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�Date: 09.05.2025�

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Table of Contents

• Course Objectives
• Pre Requisites
• Syllabus
• Course outcomes
• CO- PO/PSO Mapping
• Lecture Plan
• Activity based learning
• Unit 1 :
• Lecture Notes
• Lecture Notes – Links to Videos
• Lecture Notes – e book reference
• Lecture Notes – PPTs
• Lecture Notes - Quiz
• Lecture Notes - References
• Assignments
• Part A Q & A (with K level and CO)
• Part B Qs (with K level and CO)
• Supportive online Certification courses
• Real time Applications in day to day life and to Industry
• Contents beyond the Syllabus
• Assessment Schedule
• Prescribed Text Books & Reference Books
• Gate question and answers
• Mini Project suggestions

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Course Objectives�

• Understand the fundamentals of Data communication and networks
• Analyze the Transmission Media and Switching media
• Compare Error detection and correction process
• Configure network topologies and network devices
• Create and configure small computer network

Pre Requisites

• 22CS101 – Programming in C++
• 22EC101 - Digital Principles and System Design

Syllabus

UNIT I Fundamentals of Data Communication and Computer Network

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Process of data communication and its components: Transmitter, Receiver, Medium, Message, Protocol. Protocols, Standards, Standard organizations. Bandwidth, Data Transmission Rate, Baud Rate and Bits per second. Modes of Communication (Simplex, Hall duplex, Full Duplex). Analog Signal and Digital Signal, Analog and Digital transmission: Analog To Digital ,Digital To Analog Conversion Fundamental Of Computer Network: Definition And Need Of Computer Network,App1ications,Network Benefits. Classification Of Network: LAN,WAN,MAN Network Architecture: Peer To Peer, Client Server Network

List of Exercise/Experiments

1. Configure Peer-to-Peer Network with at least three hosts

UNIT II Transmission Media and Switching

Communication Media: Guided Transmission Media Twisted-Pair Cable, Coaxial Cable- Fiber-Optic Cable Unguided Transmission Radio Waves, Microwaves, Infrared, Satellite - Line-of-Sight Transmission Point to Point, Broadcast Multiplexing: Frequency-Division Multiplexing Time –Division Multiplexing. Switching: Circuit-Switched Packet -Switched networks

List of Exercise/Experiments

Create detailed standard network cable including cross cable and test by using cable tester

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UNIT III Error Detection, Correction and Wireless Communication

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Types of Errors: Single Bit Error and Burst Error, Redundancy Error Detection: Longitudinal Redundancy Check(LRC),Vertical Redundancy Check(VRC),Cyclic Rediindancy Check(CRC)Forward 3.3

Error Correction: Forward error Correction IEEE standards: 802.1, 802.2, 802.3, 802.4, 802.5 Wireless LANs: 802.11 Architecture, MAC Sub1ayer, Addressing Mechanism Bluetooth Architecture: Pico net, Scatter net Mobile Generations: IG, 2G, 3G, 4G and 5G

List of Exercise/Experiments

1. Connect Computers using given topology with wired Media
2. Connect Computers using wireless media
3. Write a C program to CRC Error Detection
4. Create a Network Using Bluetooth-(Pico net/Scatter net)

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UNIT IV Network Topologies and Network Devices

Network Topologies : Introduction,

Definition, Selection, Criteria, Types of Topology- i) Bus ii) Ring iii) Star iv)Mesh v)Tree vi)Hybrid Network Connecting Devices: Hub, Switch, Router, Repeater, Bridge, Gateway, Modem, Wireless infrastructure Components and OSI Reference Model

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List of Exercise/Experiments

1. Share Printer and Folder in a network and transfer a file from one computer to another
2. Instal Operating System(Windows/Linux/Red hat/Ubuntu)
3. Configure File Server
4. Configure Client to File Server and use file services
5. Setting up a wireless network

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UNIT V TCP/IP Model Layered Architecture

TCP/IP Model: Layered Architecture- Data Link Layer .Nodes and Iinks ,services, two categories of links-two sub layers-Link Layer addressing-three types of address-Address Resolution Protocol-Network layer-Address: Address space-Classful and Classless addressing, Dynamic Host Configuration Protocol-Network Address Resolution-Transport Layer Protocol-Transport layer services-Connectionless and Connection Oriented Protocol-Address Mechanism in Internet IP Addressing-IP Address Classes-Classless IP Addressing-Sub netting- Super netting-Masking IPV4 and IPV6

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Course outcomes

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CO- PO/PSO Mapping

Lecture Plan

Activity based learning

• Topology
• Topology refers to the physical or logical layout of devices and connections within a network. It describes how devices such as computers, routers, switches, and other network components are interconnected to enable communication and data exchange.
• There are several types of network topologies, each with its own advantages and disadvantages:

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Lecture Notes

Unit 2: Transmission Media and Switching

Transmission Media

In data communication terminology, a transmission medium is a physical path between the transmitter and the receiver i.e. it is the channel through which data is sent from one place to another.

Types of Transmission Media

Transmission Media is broadly classified into the following types:

1. Guided Media:

It is also referred to as Wired or Bounded transmission media. Signals being transmitted are directed and confined in a narrow pathway by using physical links.

Features:

• High Speed
• Secure
• Used for comparatively shorter distances

There are 3 major types of Guided Media:

Lecture Notes

1. Twisted Pair Cable –
• It consists of 2 separately insulated conductor wires wound about each other. Generally, several such pairs are bundled together in a protective sheath.
• It is made by putting two separate insulated wires together in a twisted pattern and running them parallel to each other which helps to reduce crosstalk or
• electromagnetic induction between pairs of wires.
• When electrical current flows through a wire, it creates a small, circular magnetic field around the wire. Noise is generated within signal lines through magnetic fields. Therefore the noise in data outlines is the consequence of the magnetic field.
• Within the straight cable connection, all sound current is moving in the same direction, exactly like within a regular transformer coils. Once the cable is actually twisted, their magnetic fields are opposite to each other.

• Thus, the two magnetic fields cancel each other and any outside magnetic fields. Due to this, the noise current in a twisted cable is lower than in an ordinary cable.

They are the most widely used Transmission Media. Twisted Pair is of two types:

1. Unshielded Twisted Pair (UTP):

Lecture Notes

This type of cable has the ability to block interference and does not depend on a physical shield for this purpose. It is used for telephonic applications.

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Advantages:

• Least expensive
• Easy to install
• High speed capacity

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• Disadvantages:
• Susceptible to external interference
• Lower capacity and performance in comparison to STP
• Short distance transmission due to attenuation

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2. Shielded Twisted Pair (STP):

Shielded twisted pair (STP) cable combines the technique of shielding, cancellation and wire twisting. Each pair of wires is wrapped in a metallic foil. The four pairs of wires then are wrapped in an overall metallic braid of foil. STP cable is used to eliminate inductive and capacitive coupling.

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Lecture Notes

This type of cable consists of a special jacket to block external interference. It is used in fast-data-rate Ethernet and in voice and data channels of telephone lines.

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Advantages:

• Better performance at a higher data rate in comparison to UTP
• Eliminates crosstalk
• Comparitively faster

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Disadvantages:

• Comparitively difficult to install and manufacture
• More expensive
• Bulky

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3. Coaxial Cable –
• Sometimes It is known as coax cable, is an electrical cable which transmits radio frequency (RF) signals from one point to another.
• Coaxial cables are a popular choice because their shielded design allows the centre conductor to transmit data quickly while being protected from damage and interference.
• Coaxial cables are mainly built up of these four different layers:
1. A centre conductor which is usually a copper wire, which data and video travels through
2. Surrounding the copper wire is a dielectric plastic insulator
3. A braided mesh made from copper then helps to shield the cable from electromagnetic interference (EMI)
4. The external layer is a plastic coating which protects the internal layers from damage

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• Coaxial cable works by carrying data in the centre conductor, while the surrounding layers of shielding stop any signal loss (also called attenuation loss) and help reduce EMI.
• The first layer, called the dielectric, provides distance between the core conductor and the outer layers, as well as some insulation.
• The next layers, collectively referred to as the shield, keep electrical impulses and radio transmissions out. The different layers of a coaxial cable are shown in the image below:

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It has an outer plastic covering containing 2 parallel conductors each having a separate insulated protection cover. Coaxial cable transmits information in two modes: Baseband mode(dedicated cable bandwidth) and Broadband mode(cable bandwidth is split into separate ranges). Cable TVs and analog television networks widely use Coaxial cables.

Advantages:

• High Bandwidth
• Better noise Immunity
• Easy to install and expand
• Inexpensive

Disadvantages:

• Single cable failure can disrupt the entire network

2. Optical Fibre Cable –
• It sends information coded in a beam of light down a glass or plastic pipe.
• A fiber-optic cable is made up of incredibly thin strands of glass or plastic known as optical fibers; one cable can have as few as two strands or as many as several hundred. Each strand is less than a tenth as thick as a human hair and can carry something like 25,000 telephone calls, so an entire fiber-optic cable can easily carry several million calls.
• Light travels down a fiber-optic cable by bouncing repeatedly off the walls. Each tiny photon (particle of light) bounces

down the pipe like a bobsleigh going down an ice run. Now you might expect a beam of light, traveling in a clear glass pipe, simply to leak out of the edges. But if light hits glass at a really shallow angle (less than 42 degrees), it reflects back in again—as though the glass were really a mirror. This phenomenon is called total internal reflection. It's one of the things that keep light inside the pipe.

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Types of fiber-optic cables

1. Single Mode:

The simplest type of optical fiber is called single-mode. It has a very thin core about 5-10 microns (millionths of a meter) in diameter. In a single-mode fiber, all signals travel straight down the middle without bouncing off the edges. Cable TV, Internet,

and telephone signals are generally carried by single-mode fibers, wrapped together into a huge bundle. Cables like this can send information over 100 km (60 miles).

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2. multi-mode:

Another type of fiber-optic cable is called multi-mode. Each

optical fiber in a multi- mode cable is about 10 times bigger than one in a single-mode cable. This means light beams can travel through the core by following a variety of different paths —in other words, in multiple different modes. Multi-mode cables can send information only over relatively short distances and are used (among other things) to link computer networks together.

It uses the concept of reflection of light through a core made up of glass or plastic. The core is surrounded by a less dense glass or plastic covering called the cladding. It is used for transmission of large volumes of data.

Advantages:

• Increased capacity and bandwidth
• Light weight
• Less signal attenuation
• Immunity to electromagnetic interference
• Resistance to corrosive materials Disadvantages:
• Difficult to install and maintain
• High cost
• Fragile
• unidirectional, i.e., will need another fibre, if we need bidirectional communication

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2. Unguided Media:

It is also referred to as Wireless or Unbounded transmission media. No physical medium is required for the transmission of electromagnetic signals.

Features:

• Signal is broadcasted through air
• Less Secure

Used for larger distances

There are 3 major types of Unguided Media:

1. Radiowaves –

These are easy to generate and can penetrate through buildings. The sending and receiving antennas need not be aligned. Frequency Range:3KHz – 1GHz. AM and FM radios and cordless phones use Radiowaves for transmission.

• Radio waves are the electromagnetic waves that are transmitted in all the directions of free space.
• Radio waves are omnidirectional, i.e., the signals are propagated in all the directions.
• The range in frequencies of radio waves is from 3Khz to 1 khz.

• In the case of radio waves, the sending and receiving antenna are not aligned, i.e., the wave sent by the sending antenna can be received by any receiving antenna.
• An example of the radio wave is FM radio.

Applications Of Radio waves:

• A Radio wave is useful for multicasting when there is one sender and many receivers.
• An FM radio, television, cordless phones are examples of a radio wave.

Advantages Of Radio transmission:

• Radio transmission is mainly used for wide area networks and mobile cellular phones.
• Radio waves cover a large area, and they can penetrate the walls.

Radio transmission provides a higher transmission rate.

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)ii) Microwaves –

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Microwaves are of two types

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• Terrestrial microwave
• Satellite microwave communication

It is a line of sight transmission i.e. the sending and receiving antennas need to be properly aligned with each other. The distance covered by the signal is directly proportional to the height of the antenna. Frequency Range:1GHz – 300GHz. These are majorly used for mobile phone communication and television distribution.

Terrestrial Microwave Transmission

• Terrestrial Microwave transmission is a technology that transmits the focused beam of a radio signal from one ground-based microwave transmission antenna to another.
• Microwaves are the electromagnetic waves having the frequency in the range from 1GHz to 1000 GHz.
• Microwaves are unidirectional as the sending and receiving antenna is to be aligned, i.e., the waves sent by the sending antenna are narrowly focused
• In this case, antennas are mounted on the towers to send a beam to another antenna which is km away.
• It works on the line of sight transmission, i.e., the antennas mounted on the towers are the direct sight of each other.

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Characteristics of Microwave:

• Frequency range: The frequency range of terrestrial microwave is from 4-6 GHz to 21-23 GHz.
• Bandwidth: It supports the bandwidth from 1 to 10 Mbps.
• Short distance: It is inexpensive for short distance.
• Long distance: It is expensive as it requires a higher tower for a longer distance.

Attenuation: Attenuation means loss of signal. It is affected by environmental conditions and antenna size.

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Advantages Of Microwave:

• Microwave transmission is cheaper than using cables.
• It is free from land acquisition as it does not require any land for the installation of cables.
• Microwave transmission provides an easy communication in terrains as the installation of cable in terrain is quite a difficult task.

Communication over oceans can be achieved by using microwave transmission

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Disadvantages of Microwave transmission:

• Eavesdropping: An eavesdropping creates insecure communication. Any malicious user can catch the signal in the air by using its own antenna.
• Out of phase signal: A signal can be moved out of phase by using microwave transmission.
• Susceptible to weather condition: A microwave transmission is susceptible to weather condition. This means that any environmental change such as rain, wind can distort the signal.
• Bandwidth limited: Allocation of bandwidth is limited in the case of microwave transmission.

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Satellite Microwave Communication

• A satellite is a physical object that revolves around the earth at a known height.
• Satellite communication is more reliable nowadays as it offers more flexibility than cable and fibre optic systems.
• We can communicate with any point on the globe by using satellite communication.

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How Does Satellite work?

The satellite accepts the signal that is transmitted from the earth station, and it amplifies the signal. The amplified signal is retransmitted to another earth station.

Advantages Of Satellite Microwave Communication:

• The coverage area of a satellite microwave is more than the terrestrial microwave.
• The transmission cost of the satellite is independent of the distance from the centre of the coverage area.
• Satellite communication is used in mobile and wireless communication applications.
• It is easy to install.
• It is used in a wide variety of applications such as weather forecasting, radio/TV signal broadcasting, mobile communication, etc.

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Disadvantages Of Satellite Microwave Communication:

• Satellite designing and development requires more time and higher cost.

• The Satellite needs to be monitored and controlled on regular periods so that it remains in orbit.
• The life of the satellite is about 12-15 years. Due to this reason, another launch of the satellite has to be planned before it becomes non-functional.

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2. Infrared –

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Infrared waves are used for very short distance communication. They cannot penetrate through obstacles. This prevents interference between systems.

Frequency Range:300GHz – 400THz. It is used in TV remotes, wireless mouse, keyboard, printer, etc.

• An infrared transmission is a wireless technology used for communication over short ranges.
• The frequency of the infrared in the range from 300 GHz to 400 THz.

It is used for short-range communication such as data transfer between two cell phones, TV remote operation, data transfer between a computer and cell phone resides in the same closed area.

What Is Satellite Communication?

Satellite communication is transporting information from one place to another using a communication satellite in orbit around the Earth. Watching the English Premier League every weekend with your friends would have been impossible without this. A communication satellite is an artificial satellite that transmits the signal via a transponder by creating a channel between the transmitter and the receiver at different Earth locations.

Telephone, radio, television, internet, and military applications use satellite communications. Believe it or not, more than 2000 artificial satellites are hurtling around in space above your heads.

Satellite Communication Block Diagram

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Need for Satellite Communication

We know that there are different ways to communicate, and the propagation of these waves can occur in different ways. Ground wave propagation and skywave propagation are the two ways communication takes place for a certain distance.

The maximum distance covered by them is 1500 km, which was overcome by the introduction of satellite communication.

How Satellite Communications Work?

The communication satellites are similar to the space mirrors that help us bounce signals such as radio, internet data, and television from one side of the earth to another. Three stages are involved, which explain the working of satellite communications. These are:

• Uplink
• Transponders
• Downlink

Let’s consider an example of signals from a television. In the first stage, the signal from the television broadcast on the other side of the earth is first beamed up to the satellite from the ground station on the earth. This process is known as uplink.

The second stage involves transponders such as radio receivers, amplifiers, and transmitters. These transponders boost the incoming signal and change its frequency so that the outgoing signals are not altered. Depending on the incoming signal sources, the transponders vary.

The final stage involves a downlink in which the data is sent to the other end of the receiver on the earth. It is important to understand that usually, there is one uplink and multiple downlinks.

Types of Satellite Systems

Satellites have been put in space for various purposes and their placement in space and orbiting shapes have been determined as per their specific requirements.

Four different types of satellites orbits have been identified. These are:

• GEO (Geostationary Earth Orbit) at about 36,000km above the earth's surface.
• LEO (Low Earth Orbit) at about 500-1500km above the earth's surface.
• MEO (Medium Earth Orbit) or ICO (Intermediate Circular Orbit) at about 6000-20,000 km above the earth's surface.
• HEO (Highly Elliptical Orbit

GEO (Geostationary Earth Orbit)

• If a satellite should appear in fixed in the sky, it requires a period of 24 hours. Using the equation of distance earth and satellite, r = (g.r² /2.r.f)²)^1/3 and the period of 24 hours f = 1/24 h. the resulting distance is 35,786 km. the orbit must have an inclination of 0 degree.
• Geostationary satellites have a distance of almost 36,000 km to the earth. Examples are almost all TV and radio broadcast satellites, any weather satellites and satellites operating as backbones for the telephone network.
• Objects in GEO moves around the earth at the same speed as the earth rotates. This means geostationary satellites remain in the same position relative to the surface of earth.

Advantages of GEO satellite

• Three Geostationary satellites are enough for a complete coverage of almost any spot on earth.
• Receivers and senders can use fixed antenna positions, no adjusting is needed.
• GEOs are ideal for TV and radio broadcasting.
• Lifetime expectations for GEOs are rather high, at about 15 years.
• Geostationary satellites have a 24 hour view of a particular area.
• GEOs typically do not need handover due to the large footprints.
• GEOs don't exhibit any Doppler shift because the relative movement is zero.

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Disadvantages of GEO satellite

• Northern or southern regions of the earth have more problems receiving these satellites due to the low elevation above latitude of 60 degree, i.e. larger antennas are needed in this case.
• Shading of the signals in cities due to high buildings and the low elevation further away from the equator limits transmission quality.
• The transmit power needed is relatively high (about 10 W) which causes problems for battery powered devices.
• These satellites can't be used for small mobile phones.
• The biggest problem for voice and also data communication is high latency of over 0.25s one way-retransmission schemes which are known from fixed networks fail.
• Transferring a GEO into orbit is very expensive.

LEO (Low Earth Orbit)

• As LEOs circulate on a lower orbit, it is obvious that they exhibit a much shorter period (the typical duration of LEO periods are 95 to 120 minutes). Additionally, LEO systems try to ensure a high elevation for every spot on earth to provide a high quality communication link.
• Each LEO satellite will only be visible from the earth for about ten minutes.
• A further classification of LEOs into little LEOs with low bandwidth services (some 100 bit/s), big LEOs (some 1,000 bit/s) and broadband LEOs with plans reaching into the Mbits/s range can be found in Comparetto (1997).
• LEO satellites are much closer to earth than GEO satellites, ranging from 500 to 1,500 km above the surface. LEO satellites do not stay in fixed position relative to the surface, and are only visible for 15 to 20 minutes each pass.

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Advantages of LEO satellite

• Using advanced compression schemes, transmission rates of about 2,400 bit/s can be enough for voice communication.
• LEOs even provide this bandwidth for mobile terminals with omni-directional antennas using low transmit power in the range of 1 W.
• A LEO satellite smaller area of coverage is less of a waste of bandwidth.
• Using advanced compression schemes, transmission rates of about 2,400 bit/s can be enough for voice communication.
• A LEO satellite's proximity to earth compared to a Geostationary satellite gives it a better signal strength and less of a time delay, which makes it better for point to point communication.
• Smaller footprints of LEOs allow for better frequency reuse, similar to the concepts used for cellular networks.

Disadvantages of LEO satellite

• The biggest problem of the LEO concept is the need for many satellites if global coverage is to be reached.
• The high number of satellites combined with the fast movement's results in a high complexity of the whole satellite system.
• The short time of visibility with a high elevation requires additional mechanism for connection handover between different satellites.
• One general problem of LEO is the short lifetime of about five to eight years due to atmospheric drag and radiation from the inner Van Allen belt.
• The low latency via a single LEO is only half of the story.
• Other factors are the need for routing of data packets from satellite to satellite (or several times from base stations to satellites and back) if a user wants to communicate around the world.
• A GEO typically does not need this type of routing, as senders and receivers are most likely in the same footprints.

MEO (Medium Earth Orbit)

• A MEO satellite situates in orbit somewhere between 6,000 km to 20,000 km above the earth's surface.
• MEO satellites are similar to LEO satellites in the context of functionality.
• MEO satellites are similar to LEO satellite in functionality.
• Medium earth orbit satellites are visible for much longer periods of time than LEO satellites usually between 2 to 8 hours.
• MEO satellites have a larger coverage area than Low Earth Orbit satellites.
• MEOs can be positioned somewhere between LEOs and GEOs, both in terms of their orbit and due to their advantages and disadvantages.

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Advantages of MEO

• Using orbits around 10,000km, the system only requires a dozen satellites which is more than a GEO system, but much less than a LEO system.
• These satellites move more slowly relative to the earth's rotation allowing a simpler system design (satellite periods are about six hours).
• Depending on the inclination, a MEO can cover larger populations, so requiring fewer handovers.
• A MEO satellite's longer duration of visibility and wider footprint means fewer satellites are needed in a MEO network than a LEO network.

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Disadvantages of MEO

• Again due to the larger distance to the earth, delay increases to about 70-80 ms.
• The satellites need higher transmit power and special antennas for smaller footprints.
• A MEO satellite's distance gives it a longer time delay and weaker signal than LEO satellite.

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4. HEO (High Earth Orbit)

• The High Earth orbit satellite is the only non-circular orbit of the four types.
• HEO satellite operates with an elliptical orbit, with a maximum altitude (apogee) similar to GEO, and a minimum altitude (perigee) similar to the LEO.
• The HEO satellites used for the special applications where coverage of high latitude locations is required.

line of sight (LOS)

What is line of sight?

Line of sight (LOS) is the imaginary line between an observer and the target. In communication, line of sight is the direct path from a transmitter to the receiver and the obstructions that may fall in that path. A clear line of sight is important to high-speed communication.

Line of sight is the direct path between two points. It's called the "line of sight" because if a person was standing at one point, the LOS would be the path they look along. If an object were blocking the view, it would be considered out of sight or an obstructed line of sight.

The concept of lines of sight have been important for much of history. Imagine a guard atop a watchtower. His high-up position would give him an unobstructed view, or clear lines of sight across a large area. If he lit a signal fire, everyone in the area would have a clear line of sight to see the fire and raise the alarm.

The curvature of the earth has been the limiting factor of lines of sight. As two objects get further apart, the earth will obstruct the LOS between them. Eventually it will disappear over the horizon and break the LOS.

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Line of sight in wireless communication

Line of sight is a vital factor in wireless  communication. Some forms of wireless transmission are completely blocked if anything comes between the transmitter and receiver. Other forms of transmission can penetrate less dense objects, like walls and building, but are blocked by large objects, like mountains.

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Most wireless transmission uses radio waves, which travel in straight lines from the transmitter. Putting the transmitter up high will give it a clearer line of sight. Just like in visual lines of sight, the curvature of the earth will eventually block a radio wave. This sets the limit on how far any radio tower can transmit on its own.

Signal reflection or refraction can be used to extend the useable range of a radio signal farther than the line of sight. Reflecting radio waves off the earth's ionosphere at night was an early method to extend radio transmission beyond LOS.

Communication satellites revolutionized wireless transmission. Their position high above the earth gives them a clear line of sight to terrestrial communication towers. A tower transmits to a satellite, and the satellite retransmits the signal to another tower beyond the first tower's LOS. The higher a satellite's orbit, the more of the earth it can cover. A single satellite in geostationary orbit has LOS over half the earth's surface. Low earth orbit (LEO) satellites may only cover a relatively small area.

Satellites often work together in constellations to cover the needed area. Satellites have tradeoffs between the greater cost of higher orbits, the greater latency to higher orbits, and the number of satellites needed to cover an area. For example, Starlink his high speed and low latency but requires thousands of satellites, while HughsNet only uses one satellite but with greater latency.

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The ability of a radio signal to tolerate an obstructed line of sight is determined by the signal wavelength. The longer the wavelength, the greater its ability to penetrate through obstructions. Conversely, the shorter the wavelength, the less it can go through an obstruction, but the greater the data it can transmit.

The line of sight should be considered when placing Wi-Fi access points. Putting them up high will limit the obstructions from furniture. The thickness and composition of walls play a major factor. The slower 2.4 Ghz bands will go through walls better than the faster 5 GHz band of Wi-Fi AC and Wi-Fi 6.

The lines of sight for cellular base stations are also very important. They are often put in the highest points in a town, such as on water towers. 5G-NR data will have different abilities based on the wavelength used. Wideband signals cover greater distances and penetrate buildings well but won't offer the fastest speeds. Narrowband offers greater speed but doesn't work as well inside buildings. The fastest forms of 5G are heavily dependent on clear lines of sight. Millimeter waves can even be blocked by the hand holding the phone.

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Most point-to-point wireless backhauls require a clear line of sight. Microwave data transmissions can be blocked or degraded by obstructing objects. Fog or rain can even degrade performance.

Types of Transmission Technology

Transmission is actually the process of sending and propagating analog or signals of digital information. Transmission technology generally refers to physical layer protocol duties like modulation, demodulation, line coding, and many more. It might also include higher-level protocol duties such as digitizing analog signals, data compression, etc. 

Types of Transmission Technology : �Transmission media is basically divided into two categories:  Broadcast Networks, Point-to-Point Networks. These are explained as following below. 

1. Broadcast Networks : �Broadcast networks are also known as terrestrial networks. It is basically a group of radio stations, television stations, or any other electronic media outlets that simply generate agreement to air, or broadcast, content generally from a centralized source. Broadcasting is simply a method of transferring messages to all the recipients simultaneously. 

In this network, a message that is sent by a node is received by all the other nodes connected to the network and share a common medium of communication. Broadcast networks also avoid procedures of complex routing of switched network by simply confirming and ensuring that each transmission of nodes is basically received by all the other nodes in the network. This is the reason why the broadcast network has single communications channel.

In this network, each receiving station just receives all signals that are sent by transmitters. Even routing of signals is highly affected passively. These networks generally have single communication that is shared by all machines present on the network. Short messages also are known as packets that are sent by any of the machines present are received by all of the others present over there. Some of the systems of broadcast also support transmission to subset of machines also known as multicasting. It just links, in contrast, communication channel that is basically shared by all of machines in network.

Advantages of Broadcast Networks – 

• In this network, packets are generally transmitted and received by all of computers. 
• It allows multicasting in the network. 
• It has no limit. Even events can also run as long as required. 
• It ensures better utilization of all resources available. �

Disadvantages of Broadcast Networks – 

• It cannot accommodate huge number of devices. 
• It doesn’t allow personalization of message. 

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2. Point-to-Point Networks : �Point-to-Point Networks or Point-to-Point Connection is type of private data connection that is connecting securely two or more locations for private data services. It might also be configured to usually carry voice, internet, and data services together all over same point-to-point network. It simply refers to type of communication connection among two endpoints or nodes of communication. It is connection among pairs of machines. Transmission from point-to-point with one sender and receiver is commonly known as unicasting. 

This network is generally used for two locations that are required to securely send data that is very sensitive and confidential among each of locations. A point-to-point or P2P (Data Link) also gives or provides path from one point that is fixed to other point being fixed. It is very closed network data transport service that does not travel through public Internet. This network includes various connections among individual pairs of machine. A packet present on these types of networks might be needed to go through intermediate computers before they reach desired or destination computer. The packets also need to follow multiple routes of different length sizes. 

Therefore, routing algorithms are very essential and important in point-to-point connection. This network is generally available in range of bandwidth speeds along with point-to-point T1, point-to-point Ethernet, or many more.

Advantages of Point-to-Point Networks – 

• It increases productivity. 
• It generally uses leased lines so that speeds are guaranteed. 
• It provides better security so that data can be transferred securely with confidence. 

Disadvantages of Point-to-Point Networks – 

• With this network, we can only connect two sites.
• It is very expensive for distant locations. 

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What is Multiplexing?

Multiplexing is a technique used to combine and send the multiple data streams over a single medium. The process of combining the data streams is known as multiplexing and hardware used for multiplexing is known as a multiplexer.

Multiplexing is achieved by using a device called Multiplexer (MUX) that combines n input lines to generate a single output line. Multiplexing follows many-to-one, i.e., n input lines and one output line.

Demultiplexing is achieved by using a device called Demultiplexer (DEMUX) available at the receiving end. DEMUX separates a signal into its component signals (one input and n outputs). Therefore, we can say that demultiplexing follows the one-to-many approach.

Why Multiplexing?

The transmission medium is used to send the signal from sender to receiver. The medium can only have one signal at a time.

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• If there are multiple signals to share one medium, then the medium must be divided in such a way that each signal is given some portion of the available bandwidth. For example: If there are 10 signals and bandwidth of medium is100 units, then the 10 unit is shared by each signal.
• When multiple signals share the common medium, there is a possibility of collision. Multiplexing concept is used to avoid such collision.
• Transmission services are very expensive.

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Concept of Multiplexing

• The 'n' input lines are transmitted through a multiplexer and multiplexer combines the signals to form a composite signal.
• The composite signal is passed through a Demultiplexer and demultiplexer separates a signal to component signals and transfers them to their respective destinations.

Advantages of Multiplexing:

• More than one signal can be sent over a single medium.
• The bandwidth of a medium can be utilized effectively.

Multiplexing Techniques

Frequency-division Multiplexing (FDM)

• It is an analog technique.
• Frequency Division Multiplexing is a technique in which the available bandwidth of a single transmission medium is subdivided into several channels.

• In the above diagram, a single transmission medium is subdivided into several frequency channels, and each frequency channel is given to different devices. Device 1 has a frequency channel of range from 1 to 5.
• The input signals are translated into frequency bands by using modulation techniques, and they are combined by a multiplexer to form a composite signal.

• The main aim of the FDM is to subdivide the available bandwidth into different frequency channels and allocate them to different devices.
• Using the modulation technique, the input signals are transmitted into frequency bands and then combined to form a composite signal.
• The carriers which are used for modulating the signals are known as sub-carriers. They are represented as f1,f2..fn.
• FDM is mainly used in radio broadcasts and TV networks.

Advantages Of FDM:

• FDM is used for analog signals.
• FDM process is very simple and easy modulation.
• A Large number of signals can be sent through an FDM simultaneously.
• It does not require any synchronization between sender and receiver.

Disadvantages Of FDM:

• FDM technique is used only when low-speed channels are required.
• It suffers the problem of crosstalk.
• A Large number of modulators are required.
• It requires a high bandwidth channel.

Applications Of FDM:

• FDM is commonly used in TV networks.
• It is used in FM and AM broadcasting. Each FM radio station has different frequencies, and they are multiplexed to form a composite signal. The multiplexed signal is transmitted in the air.

Time Division Multiplexing

• It is a digital technique.
• In Frequency Division Multiplexing Technique, all signals operate at the same time with different frequency, but in case of Time Division Multiplexing technique, all signals operate at the same frequency with different time.
• In Time Division Multiplexing technique, the total time available in the channel is distributed among different users. Therefore, each user is allocated with different time interval known as a Time slot at which data is to be transmitted by the sender.
• A user takes control of the channel for a fixed amount of time.

• In Time Division Multiplexing technique, data is not transmitted simultaneously rather the data is transmitted one-by-one.
• In TDM, the signal is transmitted in the form of frames. Frames contain a cycle of time slots in which each frame contains one or more slots dedicated to each user.
• It can be used to multiplex both digital and analog signals but mainly used to multiplex digital signals.

There are two types of TDM:

• Synchronous TDM
• Asynchronous TDM

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Synchronous TDM

• A Synchronous TDM is a technique in which time slot is preassigned to every device.
• In Synchronous TDM, each device is given some time slot irrespective of the fact that the device contains the data or not.
• If the device does not have any data, then the slot will remain empty.
• In Synchronous TDM, signals are sent in the form of frames. Time slots are organized in the form of frames. If a device does not have data for a particular time slot, then the empty slot will be transmitted.
• The most popular Synchronous TDM are T-1 multiplexing, ISDN multiplexing, and SONET multiplexing.
• If there are n devices, then there are n slots.

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Concept Of Synchronous TDM

In the above figure, the Synchronous TDM technique is implemented. Each device is allocated with some time slot. The time slots are transmitted irrespective of whether the sender has data to send or not.

Disadvantages Of Synchronous TDM:

• The capacity of the channel is not fully utilized as the empty slots are also transmitted which is having no data. In the above figure, the first frame is completely filled, but in the last two frames, some slots are empty. Therefore, we can say that the capacity of the channel is not utilized efficiently.
• The speed of the transmission medium should be greater than the total speed of the input lines. An alternative approach to the Synchronous TDM is Asynchronous Time Division Multiplexing.

Asynchronous TDM

• An asynchronous TDM is also known as Statistical TDM.
• An asynchronous TDM is a technique in which time slots are not fixed as in the case of Synchronous TDM. Time slots are allocated to only those devices which have the data to send. Therefore, we can say that Asynchronous Time Division multiplexor transmits only the data from active workstations.
• An asynchronous TDM technique dynamically allocates the time slots to the devices.
• In Asynchronous TDM, total speed of the input lines can be greater than the capacity of the channel.
• Asynchronous Time Division multiplexor accepts the incoming data streams and creates a frame that contains only data with no empty slots.
• In Asynchronous TDM, each slot contains an address part that identifies the source of the data.

• The difference between Asynchronous TDM and Synchronous TDM is that many slots in Synchronous TDM are unutilized, but in Asynchronous TDM, slots are fully utilized. This leads to the smaller transmission time and efficient utilization of the capacity of the channel.
• In Synchronous TDM, if there are n sending devices, then there are n time slots. In Asynchronous TDM, if there are n sending devices, then there are m time slots where m is less than n (m<n).
• The number of slots in a frame depends on the statistical analysis of the number of input lines.

Concept Of Asynchronous TDM

In the above diagram, there are 4 devices, but only two devices are sending the data, i.e., A and C. Therefore, the data of A and C are only transmitted through the transmission line.

Frame of above diagram can be represented as:

The above figure shows that the data part contains the address to determine the source of the data.

Switching

• When a user accesses the internet or another computer network outside their immediate location, messages are sent through the network of transmission media. This technique of transferring the information from one computer network to another network is known as switching.
• Switching in a computer network is achieved by using switches. A switch is a small hardware device which is used to join multiple computers together with one local area network (LAN).
• Network switches operate at layer 2 (Data link layer) in the OSI model.
• Switching is transparent to the user and does not require any configuration in the home network.
• Switches are used to forward the packets based on MAC addresses.
• A Switch is used to transfer the data only to the device that has been addressed. It verifies the destination address to route the packet appropriately.
• It is operated in full duplex mode.

• Packet collision is minimum as it directly communicates between source and destination.
• It does not broadcast the message as it works with limited bandwidth.

Rise of Switching: From Hubs to Switches

As computer networks evolved and the need for high-quality communication expanded, the restrictions of hub-based networks have grown to be obvious. This is about the evolution of network switching, with switches replacing hubs because they are the principal connecting devices. Network switches perform on Layer 2 of the OSI version, facilitating more efficient and selective data transmission. Unlike hubs, switches use MAC addresses to provide information only to the particular device they are meant for, decreasing needless community congestion and enhancing average overall performance.

Types of Network Switching

A multifaceted approach to network switching has developed into numerous types, each catering to specific requirements and conditions.

The primary kinds are discussed below:

Circuit Switching: In traditional smartphone networks, circuit switching establishes a dedicated communication route amongst devices during their verbal exchange. While effective, it has boundaries in terms of scalability and overall performance.

Packet Switching: Packet switching, in contrast to circuit switching, breaks down records into packets, which might be transmitted independently across the network. This method, employed via the internet, allows for greater, inexperienced use of bandwidth and superior scalability.

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Message Switching: Message switching includes the whole message being sent from delivery to destination. In current computer networks, it changed into an early form of data transmission.

Virtual Circuit Switching: Combining factors of both circuit and packet switching, digital circuit switching establishes a dedicated path in the path of a conversation consultation, just like circuit switching; however, it makes use of packet-like transmission to maintain overall performance.

Ethernet Switching: Ethernet switching has come to be the fundamental form of community switching in local location networks (LANs). It operates at Layer 2 of the OSI version. The usage of MAC addresses beforehand the facts simplest to the supposed recipient.

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Why is Switching Concept required?

Switching concept is developed because of the following reasons:

• Bandwidth: It is defined as the maximum transfer rate of a cable. It is a very critical and expensive resource. Therefore, switching techniques are used for the effective utilization of the bandwidth of a network.
• Collision: Collision is the effect that occurs when more than one device transmits the message over the same physical media, and they collide with each other. To overcome this problem, switching technology is implemented so that packets do not collide with each other.

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Advantages of Switching:

• Switch increases the bandwidth of the network.
• It reduces the workload on individual PCs as it sends the information to only that device which has been addressed.
• It increases the overall performance of the network by reducing the traffic on the network.
• There will be less frame collision as switch creates the collision domain for each connection.

Disadvantages of Switching:

• A Switch is more expensive than network bridges.
• A Switch cannot determine the network connectivity issues easily.
• Proper designing and configuration of the switch are required to handle multicast packets

LECTURE SLIDES AND LECTURE VIDEOS

Lecture Notes - e-book reference

Assignment-I (Toppers)

Assignment-I (Above Average)

Assignment-I (Average)

Assignment-I (Below Average)

Assignment-I (Slow Learner)

Part A Q & A

1. What is the position of the transmission media in the OSI or the Internet model?

Ans: The transmission media is located beneath the physical layer and controlled by the physical layer.

2. Name the two major categories of transmission media.

Ans: The two major categories of transmission media are guided media and unguided media.

3. How do guided media differ from unguided media?

Ans:

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4. What are the three major classes of guided media?.

Ans: The three major classes of guided media are twisted-pair cables, coaxial cables, and fiber optic cables.

5. What is the significance of the twisting in twisted-pair cable?

Ans: The main reason for twisting in a twisted pair cable is cancelling out any electromagnetic interference (EMI) that may be given out by external sources. These external sources could include crosstalk from other nearby pairs of cables or electromagnetic radiation given out by pairs of twisted cables that are not shielded (UTP - unshielded twisted pair). This method was created by Alexander Graham Bell.  

Part A Q & A

6. What is refraction? What is reflection?

Ans:

Reflection: This occurs when a wave travelling in one medium strikes the surface of a different medium and changes direction so that it returns back into the medium in which it was originally travelling in. Simply put the waves bounce back. Examples of reflection are light waves striking a mirror or echoes in which sound waves are reflected of a solid surface.

Refraction: The speed at which a wave travels is dependent upon the medium in which it travels along or through. The speed of a wave changes when a wave moves from one medium to another. This change in wave speed is accompanied by a change in wavelength and change in direction. It is this change of direction or bending of the wave as it passes from one medium to another that is called refraction. Example, light travelling from air into water.

7. What is the purpose of cladding in an optical fiber?

Ans: Optical fiber transmits optical signals using refraction of that signal. For refraction to happen the densities at the refracting media should be different. For this purpose a cladding is used. Cladding is of higher density so that optical signal can undergo refraction and transmit the signal to long distances.

Part A Q & A

8. Name the advantages of optical fiber over twisted-pair and coaxial cable.

Ans: Advantages of optical fiber over twisted-pair and co -axial cable are:

1. Higher Bandwidth
2. Less signal attenuation and other losses
3. Electromagnetic isolation
4. Less weight
5. Smaller in the size but Great capacity.

9. How does sky propagation differ from line-of-sight propagation?

Ans: Sky propagation is not limited to send signals to receivers, line-of-sight is dependent on direction, range and objects which may occur between sender and receiver.

Sky propagation is not limited in sense of distance of source and destination and not restricted by being in range or in direction with antennas. In this case, signals are sent towards space and then signals have vast range to reach receivers back to the earth. We should consider this thing, Sky is the beyond the troposphere and ionosphere. When signals gone beyond these spheres so when satellite will reflect those signals back, they will have much vast access to receivers.

On other hand line-of-sight propagation is limited because of earth curvature. If antennas (source and target) are not directional, not facing each other or something preventing to establish the connection so communication won’t be made.

Part A Q & A

10. What is the difference between Omnidirectional waves and unidirectional waves?

Ans:

Distinguish between data and signal.

Ans: Data is an entity, which conveys some meaning. On the other hand, the signal is a representation of data in some electric, electromagnetic or optical form. So, whenever data needs to be sent, it has to be converted into signal of some form for transmission over a suitable medium.

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What do you mean by a “Periodic Signal”? And what are the three parameters that characterize it?

Ans: A signal is periodic signal if it completes a pattern within a measurable timeframe. A periodic signal is characterized by the following three parameters. Amplitude: It is the value of the signal at different instants of time. It is measured in volts. Frequency: It is inverse of the time period, i.e. f=1/T. The unit of frequency is Hertz (Hz) or cycles per second. Phase: It gives a measure of the relative position in time of two signals within a single period

Part A Q & A

Distinguish between time domain and frequency domain representation of a signal.

Ans: Time Domain Representation: Whenever a signal is represented as a function of time, it is called time domain representation. An electromagnetic signal can be either continuous or discrete. It is represented as s (t). Frequency Domain Representation: Whenever a signal is represented as a function of frequency, it is called frequency domain representation. It is expressed in terms of different frequency components and represented as s (f).

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What equipments are used to visualize electrical signals in time domain and frequency domain?

Ans: Cathode Ray Oscilloscope is used to visualize electrical signals in time domain and Spectrum Analyzer used to visualize electrical signals in frequency domain.

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What do you mean by the Bit Interval and Bit rate in a digital signal?

Ans: The bit interval is the time required to send one single bit. The bit rate is the number of bit intervals per second. This mean that the bit rate is the number of bits send in one second, usually expressed in bits per second (bps).

Part A Q & A

On what parameters the quality of transmission depends in case of guided transmission media?

Ans: It is mainly decided by the frequency of transmission and the characteristics of the transmission media.

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Why wires are twisted in case of twisted pair of transmission medium?

Ans: It minimizes electromagnetic interferences between the pairs of wires, which are bundled together, so that the cross talk is minimum.

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Give a popular example where co-axial cables are used for broadband signaling.

Ans: Use of co-axial cable for broadband signaling is cable TV (CATV) application.

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What devices are used as source and detector in case of single mode of fiber?

Ans: LASER is used as source and photodiode is used as detector in case of single mode of fiber.

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In what way multi-mode and single-mode fibers differ?

Ans: The core diameter of single-mode fiber is much smaller than that of multi-mode fiber. For example, For multi-mode fiber:  Core diameter lies in the range of 50-200μm  Cladding diameter lies in the range of 125-400μm  Repeater spacing is 2Km. For single-mode fiber:  Core diameter lies in the range of 8-12μm  Cladding diameter 125μm  Repeater spacing is 20Km.

Part A Q & A

Why does single-mode fibres are used for large distance communications rather than multimode fibres?

Ans: In a multi-mode fiber, the quality of signal-encoded light deteriorates more rapidly than singlemode fiber, because of interference of many light rays. As a consequence, single-mode fiber allows longer distances without repeater. For multi-mode fiber, the typical maximum length of the cable without a repeater is 2km, whereas for single-mode fiber it is 20km.

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What is crosstalk? How is it minimized in case of twisted-pair of wire?

Ans: (a) Crosstalk refers to the picking up of electromagnetic signals from other adjacent wires by electromagnetic induction. (b) When a pair of wires is twisted together, the electromagnetic signals generated by the two wires cancel each other as these are of opposite polarity. This helps to reduce the susceptibility of interference to the adjacent wires.

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What are the factors responsible for attenuation in case of terrestrial microwave communication?

Ans: Attenuation due to distance is 10 log (4πd/λ)2. Factors responsible for attenuation are given below:  Distance – Attenuation is more if distance increases.  Wavelength – Attenuation is less if wavelength is longer. (i.e. high frequency components are attenuated more than the low frequency component)  Rainfall – Attenuation is less if there is no rain.

Part A Q & A

What parameters decide the spacing of repeaters in case of terrestrial microwave communication?

Ans: Parameters are the height of the antenna ‘h’ and adjustment factor ‘k’ based on the relation d=7.14√kh, where d is the distance in Km between two the two antennas.

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Why two separate frequencies are used for uplink and downlink transmission in case of satellite communication?

Ans: Two separate frequencies are used so that one cannot interfere with the other and full duplex communication is possible. And other reason is that the Power required to transmit a signal is proportional to the frequency of the signal. And more power requirement more would be the weight of the system. As there are constraints on the load that can be carried with the satellite, mainly down linking frequency is lower than the up linking one.

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Why uplink frequencies are higher than downlink frequencies in case of satellite communication?

Ans: The satellite gets power from solar cell. So, the transmitter is not being of higher power. On the other hand the ground station can have much higher power. As we want less attenuation and better signalto-noise ratio, lower frequency is more suitable for downlink and higher frequency is commonly used for uplink.

Part B Qs

Briefly explain about Attenuation ?

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Explain AM , FM and PM

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Explain the concept of MODEM

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Explain ASK, FSK , and PSK with neat diagram

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Explain the various types of multiplexing

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Explain the concept of SONET multiplexing

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Explain the Shielded twisted pair (STP) and Unshielded twisted pair(UTP)

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Explain the coaxial cable in detail

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Explain fiber optic in detail

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Write short notes on unguided media

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Write short notes on circuit switching , packet

switching and message switching

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Supportive online Certification courses

CONTENT BEYOND THE SYLLABUS

Introduction to network security

https://www.youtube.com/watch?v=6Jubl1UnJTE

REAL TIME APPLICATIONS IN DAY TO DAY LIFE

AND TO INDUSTRY

1. Communication protocols for Vehicular Ad hoc NET works

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https://www.youtube.com/watch?v=14fOqMBn9aw

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2. 5G and the Future of Connected Cars

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https://www.youtube.com/watch?v=x6DfzkeQpQ0

Prescribed Text Books & Reference Books

• TEXT BOOKS:

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1. Forouzan Behrouz A, Data communications and networking with TCP/IP Protocol Suit, 6^th Edition, Tata McGraw Hill, New Delhi, 2022
2. Tanenbam Andrew S, Computer Networks, PHI Learning Pvt ltd, NewDelhi, 5^th Edition, 2011.
3. Forouzan Behrouz A, Data communications and networking with TCP/IP Protocol Suit, 5^th Edition, Tata McGraw Hill, New Delhi, 2010
4. Godbole Achyut, Data Communication and Networks, Tata McGraw Hill, New Delhi, 2006, ISBN : 0070472971
5. Comer Douglas. E ,Internetworking with TCP/IP Principles, Protocols and Architechtures, PHI Learning Pvt Ltd, Delhi ISBN: 81-203-2065-4
1. REFERENCE BOOKS:
1. www.nptelvideos.in/2012/11/data-communication.html
2. http://www.myrendingroom.eo.in/notes-and-studyinaterial/6S-dcii/750-dfldlOg-tO- analog-conversion-techniques.html
3. http://www.tutorial-reports.com/wireless/wlanwifi/wifi architecture.php
4. http://standards.ieee.org/about/get/802/802.11.html
5. www.tutorialspoint.com/data communication computer network/
6. http://www.studytoniglit.cont/computer-networks/overview-of-computer-networks

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Assessment Schedule

• Tentative schedule for the Assessment During 2024-2025 odd semester

114

Gate question and answers

1. GATE ECE 2014 – Guided Transmission Media

Question:�Which of the following is the primary advantage of using fiber-optic cables over twisted-pair cables in high-speed data communication?

Options:�(A) Higher attenuation�(B) Higher bandwidth�(C) Lower cost�(D) Easier installation

Answer:� (B) Higher bandwidth

Explanation:�Fiber-optic cables offer significantly higher bandwidth compared to twisted-pair cables, making them suitable for high-speed data transmission over long distances. They also have lower attenuation and are immune to electromagnetic interference, but the primary advantage in high-speed communication is their higher bandwidth

2. GATE ECE 2015 – Unguided Transmission Media

Question:�Which of the following is a characteristic of microwave communication systems?

Options:�(A) They require line-of-sight propagation.�(B) They can penetrate through buildings.�(C) They operate at frequencies below 1 GHz.�(D) They are immune to atmospheric conditions.

Answer:�(A) They require line-of-sight propagation.

• Explanation:�Microwave communication systems operate at high frequencies and require line-of-sight propagation. This means that the transmitting and receiving antennas must be in direct visual contact, as microwaves do not diffract around obstacles. Atmospheric conditions, such as rain, can affect microwave transmission.

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3. GATE ECE 2016 – Satellite Communication

Question:�Which of the following is an advantage of using satellites for communication?

Options:�(A) Limited coverage area�(B) High installation cost�(C) High propagation delay�(D) Wide coverage area

Answer: (D) Wide coverage area

Explanation:�Satellites provide a wide coverage area, allowing communication over large distances, including remote and rural areas. While they have high installation costs and propagation delays, their ability to cover vast areas is a significant advantage

4. GATE ECE 2017 – Coaxial Cable

Question:�In a coaxial cable, the primary function of the outer conductor is to:

Options:�(A) Carry the signal�(B) Provide shielding from external interference�(C) Serve as a ground reference�(D) Increase the bandwidth

Answer: (B) Provide shielding from external interference

Explanation:�The outer conductor of a coaxial cable serves as a shield to protect the signal from external electromagnetic interference and to prevent the signal from radiating out of the cable. This shielding ensures the integrity of the transmitted data

5. GATE ECE 2018 – Infrared Communication

Question:�Which of the following is a limitation of infrared communication systems?

Options:�(A) Short transmission range�(B) High susceptibility to interference�(C) High power consumption�(D) Ability to penetrate walls

Answer: (A) Short transmission range

Explanation:�Infrared communication systems have a short transmission range and require line-of-sight between the transmitter and receiver. They are commonly used for short-range communication, such as remote controls and wireless peripherals.

6. GATE CSE 2015 – Frequency-Division Multiplexing (FDM)

Question:�Which of the following is a characteristic of Frequency-Division Multiplexing (FDM)?

Options:�(A) Multiple signals are transmitted over a single channel by dividing the total bandwidth into smaller frequency bands.�(B) Each signal is assigned a unique time slot for transmission.�(C) Signals are transmitted sequentially in a time-division manner.�(D) It requires a high-speed clock to synchronize the signals.

Answer:� (A) Multiple signals are transmitted over a single channel by dividing the total bandwidth into smaller frequency bands.

Explanation:�In Frequency-Division Multiplexing (FDM), the available bandwidth of the communication medium is divided into non-overlapping frequency bands, each carrying a separate signal. This allows multiple signals to be transmitted simultaneously over a single channel

7. GATE CSE 2016 – Time-Division Multiplexing (TDM)

Question:�In Time-Division Multiplexing (TDM), if the time slot duration is 1 ms and the number of time slots per frame is 100, what is the frame duration?

Options:�(A) 1 ms�(B) 10 ms�(C) 100 ms�(D) 1000 ms

Answer:� (B) 10 ms

Explanation:�In TDM, the frame duration is the product of the number of time slots and the duration of each time slot. Therefore, the frame duration is:

• Frame Duration=Number of Time Slots×Time Slot Duration=100×1 ms=10 ms\text{Frame Duration} = \text{Number of Time Slots} \times \text{Time Slot Duration} = 100 \times 1 \, \text{ms} = 10 \, \text{ms}Frame Duration=Number of Time Slots×Time Slot Duration=100×1ms=10ms

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8. GATE CSE 2015 – Circuit Switching

Question:�Which of the following is a characteristic of circuit-switched networks?

Options:�(A) Data is transmitted in discrete packets.�(B) A dedicated communication path is established between the sender and receiver.�(C) Each message is routed independently.�(D) Resources are dynamically allocated based on demand.

Answer:�(B) A dedicated communication path is established between the sender and receiver.

• Explanation:�In circuit-switched networks, a dedicated communication path is established between the sender and receiver for the duration of the communication session. This ensures a constant and predictable transmission rate.

Mini Project suggestions

TOPPERS

Multiplexing STS-1 multiple data streams, called tributaries, plays an important role in SONET. A 3:1 multiplexer multiplexes three input STS-1 tributaries onto one out put STS-3 stream. This multiplexing is done byte for byte. That is, the first three out put bytes are the first bytes of tributaries 1, 2, and 3, respectively. the next three out put bytes are the second bytes of tributaries 1, 2, and 3, respectively, and so on. Write a program that simulates this 3:1 multiplexer. Your program should consist of five processes. The main process creates four processes, one each for the three STS-1 tributaries and one for the multiplexer. Each tributary process reads in an STS-1 frame from an input file as a sequence of 810 bytes. They send their frames (byte by byte) to the multiplexer process. The multiplexer process receives these bytes and outputs an STS-3 frame (byte by byte) by writing it to standard output. Use pipes for communication among processes.

Mini Project suggestions

ABOVE AVERAGE

Write a program to implement CDMA. Assume that the length of a chip sequence is eight and the number of stations transmitting is four. Your program consists of three sets of processes: four transmitter processes (t0, t1, t2, and t3), one joiner process, and four receiver processes (r0, r1, r2, and r3). The main program, which also acts as the joiner process first reads four chip sequences (bipolar notation) from the standard input and a sequence of 4 bits (1 bit per transmitter process to be transmitted), and forks off four pairs of transmitter and receiver processes. Each pair of transmitter/receiver processes (t0,r0; t1,r1; t2,r2; t3,r3) is assigned one chip sequence and each transmitter process is assigned 1 bit (first bit to t0, second bit to t1, and so on). Next, each transmitter process computes the signal to be transmitted (a sequence of 8 bits) and sends it to the joiner process. After receiving signals from all four transmitter processes, the joiner process combines the signals and sends the combined signal to

Mini Project suggestions

AVERAGE

Configure Peer-to-Peer Network with at least three hosts

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BELOW AVERAGE

Configure Client-Server Network with at least three hosts

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SLOW LEARNERS

Investigate OSI layer model using CISCO Packet Tracer

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