UNIT 1
General features and tasks of communication system
A communication system is a system for transmitting information from a sender to a receiver.
The main features of a communication system are:
1.A source of information: This is the sender of the message.
2.A transmitter: This is the device or system that encodes the message and converts it into a
form that can be transmitted.
3.A channel: This is the medium through which the message is transmitted, such as a wire, cable,
or wireless connection.
4.A receiver: This is the device or system that decodes the message and converts it back into a
form that can be understood by the recipient.
5.A destination: This is the intended recipient of the message.
Some common tasks of a communication system include:
1.Encoding: The process of converting the message into a form that can be transmitted.
2.Transmission: The process of sending the encoded message through the channel.
3.Decoding: The process of converting the received message back into a form that can be
understood.
4.Error detection and correction: The process of detecting and correcting errors that may have
occurred during transmission.
5.Compression: The process of reducing the size of the message to reduce the amount of data
that needs to be transmitted.
6.Multiplexing: The process of combining multiple messages into a single stream of data for
transmission.
The Need For Modulation
Modulation is the process of modifying the characteristics of a periodic waveform, called the
carrier signal, in order to transmit information.
The need for modulation arises because most communication channels are limited in the
frequency range of signals that they can transmit.
, For example, the frequency range of a telephone line is limited to a few kilohertz, while the
frequency range of a radio frequency (RF) transmission is much higher.
Modulation allows the information-bearing signal, called the message signal, to be encoded into
the carrier signal in a way that is suitable for transmission over the communication
channel.Modulation can be analog or digital. In analog modulation, the message signal is an
analog waveform, such as a sine wave or a square wave. In digital modulation, the message
signal is a digital signal, such as a stream of bits.
There are several different types of modulation, including amplitude modulation (AM),
frequency modulation (FM), and phase modulation (PM).Each type of modulation has its own
advantages and disadvantages, and is suited to different types of communication
systems.Modulation is an important part of MANy communication systems, as it allows the
message signal to be transmitted over a wide range of frequencies and distances.
Theory of Amplitude Modulation
Amplitude modulation (AM) is a type of analog modulation in which the amplitude (strength) of
the carrier signal is varied in proportion to the message signal.
In AM, the message signal is superimposed on the carrier signal by multiplying the two signals
together. This results in the carrier signal being "modulated" by the message signal, such that
the amplitude of the carrier signal varies according to the strength of the message signal.
The resulting modulated signal can be expressed mathematically as:
AM = (1 + m(t)) * c(t)
where AM is the modulated signal, m(t) is the message signal, and c(t) is the carrier signal.
The process of demodulating an AM signal involves separating the message signal from the
carrier signal. This can be done using a process called envelope detection, which involves
filtering the modulated signal to remove the carrier frequency and leaving only the envelope of
the modulated signal. The envelope of the modulated signal is a replica of the original message
signal.
AM is widely used in radio broadcasting, and is also used in some types of telephone systems.
One of the main advantages of AM is that it is relatively simple to implement and does not
require complex processing equipment. However, AM is susceptible to interference from other
signals and can suffer from poor signal-to-noise ratio, particularly in the presence of strong
interfering signals.
General features and tasks of communication system
A communication system is a system for transmitting information from a sender to a receiver.
The main features of a communication system are:
1.A source of information: This is the sender of the message.
2.A transmitter: This is the device or system that encodes the message and converts it into a
form that can be transmitted.
3.A channel: This is the medium through which the message is transmitted, such as a wire, cable,
or wireless connection.
4.A receiver: This is the device or system that decodes the message and converts it back into a
form that can be understood by the recipient.
5.A destination: This is the intended recipient of the message.
Some common tasks of a communication system include:
1.Encoding: The process of converting the message into a form that can be transmitted.
2.Transmission: The process of sending the encoded message through the channel.
3.Decoding: The process of converting the received message back into a form that can be
understood.
4.Error detection and correction: The process of detecting and correcting errors that may have
occurred during transmission.
5.Compression: The process of reducing the size of the message to reduce the amount of data
that needs to be transmitted.
6.Multiplexing: The process of combining multiple messages into a single stream of data for
transmission.
The Need For Modulation
Modulation is the process of modifying the characteristics of a periodic waveform, called the
carrier signal, in order to transmit information.
The need for modulation arises because most communication channels are limited in the
frequency range of signals that they can transmit.
, For example, the frequency range of a telephone line is limited to a few kilohertz, while the
frequency range of a radio frequency (RF) transmission is much higher.
Modulation allows the information-bearing signal, called the message signal, to be encoded into
the carrier signal in a way that is suitable for transmission over the communication
channel.Modulation can be analog or digital. In analog modulation, the message signal is an
analog waveform, such as a sine wave or a square wave. In digital modulation, the message
signal is a digital signal, such as a stream of bits.
There are several different types of modulation, including amplitude modulation (AM),
frequency modulation (FM), and phase modulation (PM).Each type of modulation has its own
advantages and disadvantages, and is suited to different types of communication
systems.Modulation is an important part of MANy communication systems, as it allows the
message signal to be transmitted over a wide range of frequencies and distances.
Theory of Amplitude Modulation
Amplitude modulation (AM) is a type of analog modulation in which the amplitude (strength) of
the carrier signal is varied in proportion to the message signal.
In AM, the message signal is superimposed on the carrier signal by multiplying the two signals
together. This results in the carrier signal being "modulated" by the message signal, such that
the amplitude of the carrier signal varies according to the strength of the message signal.
The resulting modulated signal can be expressed mathematically as:
AM = (1 + m(t)) * c(t)
where AM is the modulated signal, m(t) is the message signal, and c(t) is the carrier signal.
The process of demodulating an AM signal involves separating the message signal from the
carrier signal. This can be done using a process called envelope detection, which involves
filtering the modulated signal to remove the carrier frequency and leaving only the envelope of
the modulated signal. The envelope of the modulated signal is a replica of the original message
signal.
AM is widely used in radio broadcasting, and is also used in some types of telephone systems.
One of the main advantages of AM is that it is relatively simple to implement and does not
require complex processing equipment. However, AM is susceptible to interference from other
signals and can suffer from poor signal-to-noise ratio, particularly in the presence of strong
interfering signals.
