CO3 Introduction Communication Systems videolecture

Summary

This script offers an introductory overview of communication systems, explaining their purpose to transmit messages from source to destination. It outlines the necessity of a transmission medium, known as a channel, which can be either wired or wireless. The script details the system's components, including the information source, transmitter, receiver, and destination. It further explains the process of modulation, which involves converting low-frequency signals to high-frequency signals for efficient transmission over long distances, and its benefits such as reduced antenna height, noise reduction, and enabling multiplexing. The concept of baseband communication, which does not use modulation, is also briefly discussed.

Takeaways

• 📡 **Communication Systems Purpose**: To transmit messages from a source to a destination.
• 🔌 **Types of Channels**: There are wired channels like twisted copper pair and fiber optic, and wireless channels like air and free space.
• 🏗️ **Building Blocks of a Communication System**: Includes an information source, transmitter, channel, receiver, and destination.
• 🔄 **Modulation Process**: Involves multiplying the message signal with a high-frequency carrier to create a modulated wave for transmission.
• 🌐 **Channel Function**: Acts as a medium to connect the source and destination, can be wired or wireless.
• 📈 **Receiver's Role**: Performs demodulation to recover the original message signal from the received modulated signal.
• 🗣️ **Information Source**: Generates the message signal, which can be from a human or a machine, and is converted to an electrical signal.
• 📶 **Transmitter's Role**: Converts the low-frequency message signal into a high-frequency signal for transmission over long distances.
• 📊 **Antenna Height Reduction**: Modulation allows for reducing the height of the antenna by increasing the frequency of the signal.
• 🔒 **Noise Reduction**: Modulation helps to separate the message signal from noise, reducing its effect on the transmission.
• 🌐 **Baseband Communication**: Refers to communication without modulation, where the original message signal is transmitted directly at baseband frequencies.

Q & A

What is the primary function of a communication system?

The primary function of a communication system is to transmit messages, also known as information signals or modulating signals, from a source to a destination.

What are the two types of channels used for transmitting messages?

There are two types of channels: wired channels, such as twisted copper pair used in landline telephones and fiber optic used in fiber optic networks, and wireless channels, which use air and free space.

What is the role of the transmitter in a communication system?

The transmitter performs modulation, converting the low-frequency message signal into a high-frequency signal with more energy, which can be transmitted over a larger distance.

How does the process of modulation help in long-distance transmission?

Modulation allows for long-distance transmission by converting low-frequency signals into higher frequency signals, which have more energy and can travel further.

What is the significance of the receiver in a communication system?

The receiver performs demodulation, which is the inverse operation of modulation, to recover the original message signal from the modulated signal received through the channel.

Why is modulation necessary to reduce the antenna height?

Modulation reduces the antenna height because the height of the antenna is inversely proportional to the frequency of the signal. By modulating to a higher frequency, the wavelength shortens, thus reducing the required antenna height.

How does modulation facilitate multiplexing?

Modulation allows for multiplexing by using different carrier frequencies for different messages, enabling the simultaneous transmission of multiple messages over a single communication channel.

What is the purpose of reducing the effect of noise through modulation?

By modulating the message signal to a higher frequency range, the signal and noise are separated in frequency, which reduces the impact of noise on the message.

What is baseband communication and how does it differ from modulated communication?

Baseband communication involves transmitting the original message signal without using a high-frequency carrier for modulation. It uses encoding and filtering techniques to transmit signals at the original low frequency.

What is the role of the information source in a communication system?

The information source generates the message signal, which can be a human voice or a machine. It often includes a transducer, like a microphone, to convert the signal into an electrical form suitable for transmission.

Can you provide an example of a wired channel and its application?

An example of a wired channel is the twisted copper pair, which is used in landline telephones for transmitting voice signals.

What is the role of the destination in a communication system?

The destination is where the message is received, which can be a human listener in the case of a telephone conversation or a machine that processes the reconstructed message.

Outlines

00:00

📡 Introduction to Communication Systems

The paragraph introduces the concept of communication systems, emphasizing their purpose to transmit messages from a source to a destination. It explains that messages are often referred to as information signals or modulating signals and are denoted as M(t). The necessity of a transmission medium, or channel, is highlighted, with two types being discussed: wired (like twisted copper pair and fiber optic) and wireless (air and free space). The building blocks of a communication system are outlined: the information source, transmitter, channel, receiver, and destination. The process of modulation is introduced, where a low-frequency message signal is converted into a high-frequency signal using a high-frequency carrier. The resulting modulated wave is represented as s(t). The paragraph also discusses the impact of noise, n(t), during transmission and the role of the receiver in demodulating the signal to recover the original message.

05:00

🔌 Components of a Communication System

This section delves deeper into the components of a communication system. The transmitter, also known as a modulator, is described as the component that multiplies the message signal M(t) with a high-frequency carrier to create a modulated wave s(t). The channel's role as a transmission medium is further elaborated, distinguishing between wired channels like fiber optic cable and twisted copper pair, and wireless channels that use air or free space. The receiver's function is explained as the inverse operation of modulation, demodulation, which reconstructs the message signal M(t). The destination, which can be a human or a machine, is also discussed. The paragraph concludes by discussing the need for modulation, including long-distance transmission, reduced antenna height due to higher frequencies, ease of multiplexing, and noise reduction.

10:03

🌐 Baseband Communication

The final paragraph contrasts baseband communication with modulated communication. In baseband communication, the original message M(t) is not modulated but is encoded and passed through a transmit filter to create a transmitted signal s(t). This signal is then directly transmitted over the channel. At the receiver, the noise-corrupted signal s(t) + n(t) is processed through a receive filter and a decoder to reconstruct the message. The benefits of using modulation, such as reduced antenna height and noise reduction, are reiterated. The paragraph concludes with a brief mention of the block diagram of baseband communication, highlighting the absence of high-frequency carrier modulation in this process.

Keywords

💡Communication System

A communication system is a network that allows the transmission of messages between a source and a destination. In the script, it is described as the central focus, with the purpose of transmitting messages, which could be voice, data, or any form of information. The video discusses both wired and wireless channels, emphasizing the system's role in facilitating long-distance communication.

💡Message Signal

The message signal, also known as the information signal or modulating signal and denoted as M(t), is the original form of data that needs to be transmitted in a communication system. The script explains that this signal can be generated by a human, like a voice in a telephone conversation, and is then converted into an electrical form using a transducer such as a microphone.

💡Channel

A channel in communication systems refers to the medium that carries the message signal from the source to the destination. The script differentiates between wired channels, such as twisted copper pair and fiber optic, and wireless channels, which use air or free space. Channels are crucial for the transmission of the modulated signal over distances.

💡Transmitter

The transmitter is a component of the communication system that performs modulation, converting the low-frequency message signal into a high-frequency signal suitable for transmission over a channel. As described in the script, it uses a high-frequency carrier to modulate the message signal, creating a modulated wave that can travel longer distances.

💡Modulation

Modulation is the process of varying one or more properties of a high-frequency carrier signal in proportion to the message signal. The script explains that modulation is necessary for long-distance transmission, reducing antenna height, allowing multiplexing, and reducing the effect of noise. It's a key operation that prepares the message signal for efficient transmission.

💡Demodulation

Demodulation is the inverse process of modulation and is performed by the receiver. It involves extracting the original message signal from the modulated signal that has been received, which may include noise picked up during transmission. The script mentions that demodulation allows the receiver to recover the message signal, which is then passed on to the destination.

💡Noise

Noise in the context of the script refers to unwanted signals or interference that can affect the quality of the transmitted message. It is introduced during the transmission through the channel and is represented as n(t). The script discusses how modulation helps in reducing the effect of noise by separating the message signal and noise in frequency.

💡Antenna Height

The height of an antenna is related to the wavelength of the signal it transmits or receives. The script explains that modulation allows for the reduction of antenna height by increasing the frequency of the transmitted signal, which is beneficial for practical communication systems that require compact and efficient antenna designs.

💡Multiplexing

Multiplexing is the process of transmitting multiple messages simultaneously over a single communication channel. The script mentions that modulation facilitates multiplexing by using different carrier frequencies for each message, allowing for the efficient use of the communication channel.

💡Baseband Communication

Baseband communication refers to the transmission of the original message signal without the use of a high-frequency carrier, as opposed to modulated communication. The script describes baseband communication as involving encoding, filtering, and direct transmission of the low-frequency message signal over the channel, which is then received and decoded to reconstruct the original message.

💡Transducer

A transducer is a device that converts one form of energy to another, which in the context of the script, is used to convert the human voice into an electrical signal. This electrical signal, M(t), is then suitable for processing and transmission by the communication system, highlighting the transducer's role in the initial stages of signal generation.

Highlights

Introduction to communication systems

Purpose of communication systems is to transmit messages

Messages are also called information signals or modulating signals

Transmission medium is required for message transmission, called a channel

Two types of channels: wired and wireless

Examples of wired channels are twisted copper pair and fiber optic

Wireless channels use air and free space

Building blocks of a communication system include Source, Transmitter, Channel, Receiver, and Destination

Transmitter performs modulation using a high-frequency carrier

Modulation is the multiplication of the message signal with the carrier

Noise is added to the signal during transmission

Receiver performs demodulation to recover the message signal

Information Source generates the message signal

Transmitter converts low-frequency voice signal into high-frequency signal

Channel connects source and destination as a transmission medium

Receiver converts modulated signal plus noise back into a reconstructed message

Destination can be a human or a machine

Modulation allows long-distance transmission by increasing signal energy

Modulation reduces antenna height by increasing frequency

Modulation allows ease of multiplexing by using different carrier frequencies

Modulation reduces the effect of noise by separating message signal and noise in frequency

Baseband communication does not use high-frequency carriers

Baseband communication uses encoding and filtering instead of modulation

Thank you for the audience's patient hearing

Transcripts

we are going to discuss about the

introduction to the communication

systems

now we are going to have a brief

introduction to communication systems

now the purpose of any communication

system is to transmit some messages

between the source and the

destination the message is also called

information signal or modulating signal

and usually denoted as M

oft now between the source and the

destination for the message to be

transmitted there should be some kind of

transmission medium that is called a

channel there are two types of channels

channel one is the wired channel the

other is a wireless Channel now a common

wired channels are uh twisted uh copper

pair which is used in the landline

telephones and uh also fiber optic which

is used in fiber optic networks now the

wireless channels are simply air and

free

space now we are going to discuss what

are the various uh building blocks of a

communication system information Source

followed by the transmitter then the

channel and the receiver and finally the

destination next we are going to see the

block diagram of a communication system

the information Source it generates the

message signal M oft which is given to

the transmitter this transmitter it

performs the operation called modulation

and this transmitter Is Us using a high

frequency carrier C of T and the

transmitter simply performs the

modulation operation which is a simple

multiplication of the message M of t

with the high frequency carrier C oft

and it will generate a high frequency

version called modulated wave this is

represented as s of T now this modulated

wave is given to the channel passed

through a huge amount of distance Maybe

100 km or maybe up to, kilm and during

this process the noise n oft gets added

so on the receiver side after the

modulated signal has traveled a very

large distance of let us say 500 km or

in some cases even 10,000 km this signal

at the receiver side is s of t plus n

oft this n oft is the noise that is

added during the trans Mission through

the channel so this receiver then it

performs a operation called demodulation

and it recovers the message signal or

reconstructed message Mr of which is

given to the test

mission now we are going to discuss uh

about each of these blocks the

information Source it simply generates

the information or the message signal M

oft The Source can be a human being or a

machine now in most of the telephone

conversations the message signal is

usually the voice signal that is spoken

by the human being

speakers now this message signal M oft

it is actually converted into the

electrical form using a transducer such

as a

microphone so when we are representing

the information Source we are actually

assuming that the information source

which is the speaker is also fitted with

along with that there is a small block

that is a transducer so it is generating

that electrical signal M

oft now the next block is the

transmitter this transmitter it performs

the operation called modulation this

modulation it converts the message

signal M oft which is usually a low

frequency voice signal and that is

converted into a high frequency signal

which will have higher energy and this

is called

modulated wave that can be transmitted

over a large distance now the

transmitter is sometimes even called a

modulator the modulator will simply

multiply the message signal M oft with

the high frequency carrier and it

generates a high frequency version of

the message signal called modulated wave

s

of now a very simple blog diagram of a

modulator the modulator takes the low

frequency message M of t as one input

and high frequency carrier C of t as

another input then it multiplies both M

of T into C of T and it will generate

the modulated wave s oft which is simply

a high frequency version of the message

signal M

oft now next we are going to discuss uh

the channel the channel is simply a

transmission medium which is connecting

the source and the destination and uh

there are two types of communication

channels as we already discussed the

wired Channel such as a fiber optic

cable or a twisted copper pair and the

other type of channel is the wireless

Channel air air is the transmission

medium for the wireless channel for all

terrestrial

transmission within the surface of the

Earth whereas if you talk about free

space when you are sending a satellite

from the Earth to the Moon then the free

space becomes the transmission medium

for the wireless Channel between the uh

Earth and also the outside Planet like

the moon or Mars okay so the air usually

refers to whatever is the virus

transmission which we are doing within

within the Earth

surface now free space means when we are

transmitting the signal from the Earth

to another planet such as uh like a

mission to the Mars then it's the free

space for the virus ch

now uh this receiver is usually the

opposite to the transmitter so it

performs the operation called D

modulation it is a inverse operation of

modulation so this receiver it will take

the modulated signal plus noise s of t

plus n of T and it will convert it into

a reconstructed message called Mr ofp

now of course this this Mr of which is a

reconstructed message it's only the

approximation to the message M of it

cannot be exactly as

M now finally the destination is usually

a human being or a machine in a simple

example of a telephone conversation or a

mobile

communication uh the destination is a

human listener who is listening to the

uh human voice on the other side of the

mobile phone call or telephone call now

in some other cases the destination can

even be a computer that is performing

some operations on the Reconstruction

message now we are going to discuss what

are the various needs for the

modulation so as we discussed

modulation converts the low frequency

message M of T into the high frequency

uh signal which is having higher energy

which is called the modulated signal and

uh uh here uh mod ation is the process

of varing one or more parameters of a

high frequency carrier such as amplitude

or Carrier frequency or Carrier phase

proportional to the message now we are

going to discuss what are the various

needs for doing this

modulation the first need is modulation

allows long distance transmission now if

we take any signal the energy of the

signal is proportional to the frequency

so if we take this low frequency signal

M of T and we convert it into a higher

frequency signal s of T by mixing it

with this high frequency carrier now

since the higher frequency modulated

wave s oft that will have higher energy

it can travel over a longer

distance now next second need is

modulation reduces the antenna height

the height of the antenna uh is

proportional to half of the wavelength

so we can write the height of the

antenna H an as K into Lambda by 2 now

we know the wave length Lambda is

inversely proportional to frequency so

Lambda is C by F where C is the speed of

light and F is the frequency so

substituting this we are going to get

the antenna height as K by 2 into C by F

or k into C by 2f now if we increase the

frequency F by using this modulation

process as F increases since f is in the

denominator the height of the antenna

decreases this is very useful for the

Practical communication systems we want

antenna with smaller

height now the third need is modulation

allows ease of multi multiplexing now

the process of transmitting multiple

messages simultaneously over a

Communication channel is called

Multiplex ing Now by using modulation

with different carrier frequencies for

different messages we can perform

multiplexing hence this modulation it

allows multiplexing which is very

useful now finally modulation reduces

the effect of noise the noise in the

communication system n oft is usually a

low frequency in nature by doing the

modulation the message signal is shifted

to the high frequency range therefore by

the modulation process the message

signal and the noise they get separated

in frequency and therefore the effect of

noise or message will be

reduced now we are going to briefly

discuss about Bas band communication

base band refers to the band of

frequencies of the original message M

oft and in baseband communication

modulation is not performed

so this baseband communication the

modulation using the high frequency

carrier is not done so this message M

oft will be encoded using a encoder and

the encoded signal is simply given to a

transmit filter G of f which is like a

raised cosine pulse shape filter and we

are going to obtain the encoded signal

without any modulation

which is processed through this transmit

filter which is called the transmitted

signal

sof and at the receiver whatever is the

noise corrupted transmitted signal s of

t plus n oft is passed through a receive

filter qf which is usually the inverse

of G of F and a decoder is also used

which performs the inverse operation of

the end coder and finally we obtain the

constructed message Mr

of now here we are showing the block

diagram of a baseband communication

again in baseband communication the

modulation using high frequency carrier

is not done so we take the source then

we perform some encoding then we use it

uh to

filter by using a transmit filter G of f

which is like a raised cosine pulse

shaping filter then we are going to get

this transmitted signal this this

transmitted signal is still at the same

low frequency range that is the baseband

frequency range of the original message

this s of T which is at the base band

frequency range of M of T is directly

transmitted over the channel and at the

receiver side the noise corrupted

transmitted signal s of t plus n of T is

passed through the receive filter which

is qf this qf is usually inverse of for

the transmit filter GF and then we apply

the decoder which will perform the

opposite operation of the encoder and

finally we obtain the reconstructed

message I want to thank all the audience

for your patient hearing thank you very

much