CO3 Introduction Communication Systems videolecture
Summary
TLDRThis 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
📡 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.
🔌 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.
🌐 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.
Mindmap
Keywords
💡Communication System
💡Message Signal
💡Channel
💡Transmitter
💡Modulation
💡Demodulation
💡Noise
💡Antenna Height
💡Multiplexing
💡Baseband Communication
💡Transducer
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
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