Unit-1
What is
data communication?
Data communication is the process
of exchanging data or information between two or more devices or systems over a
communication channel or network. It involves the transmission, reception, and
processing of data using various technologies and protocols.
In data communication, data is
usually transmitted in the form of signals, which can be analog or digital.
Analog signals are continuous waves that vary in amplitude, frequency, or
phase, while digital signals are discrete, binary values (0 or 1) that represent
data.
Data communication can occur over
various types of communication channels, such as wired or wireless networks,
satellite links, or optical fibers. The communication channel can
also be classified based on its transmission medium, such as guided media (e.g.,
coaxial cable, twisted pair cable) or unguided media (e.g., radio waves,
microwaves).
Data communication also involves
the use of various protocols, such as TCP/IP, HTTP, SMTP, FTP, and others,
which provide rules and standards for formatting, transmitting, and receiving
data. These protocols ensure that data is transmitted accurately, efficiently,
and securely across the network.
In summary, data communication is
the process of exchanging data between devices or systems over a communication
channel or network using various technologies and protocols.
v Components of a data communication
system
A data communication system
consists of several components that work together to transmit and receive data
over a communication channel or network. Here are the key components of a data
communication system:
Sender: The sender or transmitter is the device that initiates the
data transmission. It converts the data into a suitable format and sends it
over the communication channel.
Receiver: The receiver is the device that receives the data
transmitted by the sender. It decodes the data and converts it into a usable
format.
Communication channel: The communication channel is the medium through which the
data is transmitted from the sender to the receiver. It can be a wired or
wireless medium, and it can use guided or unguided transmission.
Modem: A modem is a device that converts digital data into analog
signals that can be transmitted over a communication channel. It also converts
analog signals received from the communication channel into digital data that
can be processed by the receiver.
Protocols: Protocols provide a set of rules and standards for
formatting, transmitting, and receiving data over a communication channel. They
ensure that data is transmitted accurately, efficiently, and securely.
Network interface
card (NIC): A NIC is a hardware
component that connects a computer or other device to a network. It provides a
physical connection between the device and the network, and it also handles the
transmission and reception of data packets.
Repeaters, hubs, switches, and
routers: These are networking devices that
help to extend the range of a communication channel, manage network traffic,
and direct data packets to their intended destinations.
What is
duplex and its types?
The three duplex
modes used in data communication are:
Simplex: In simplex mode, data can only be transmitted in
one direction. In other words, communication can occur in only one direction,
from the sender to the receiver. Examples of simplex mode
communication include television broadcast and one-way radio
communication.
Half-duplex: In half-duplex mode, data can be transmitted in both
directions, but not simultaneously. In other words, communication can occur in
both directions, but only one direction at a time. Examples of half-duplex mode
communication include walkie-talkies and two-way radios.
Full-duplex: In full-duplex mode, data can be transmitted in both
directions simultaneously. In other words, communication can occur in both
directions at the same time. Examples of full-duplex mode communication include
telephone conversations and video conferencing.
Each of these modes has its
advantages and disadvantages, and the choice of mode depends on the specific
requirements of the communication application. For example, simplex mode is
useful for applications that require data to be transmitted in one direction
only, while full-duplex mode is useful for applications that require real-time,
two-way communication.
What is
the difference between Analog and digital signal?
Analog and digital signals are
two types of signals used in data communication, and they differ in the way
they represent data. Here are the key differences between analog and digital
signals:
Representation: Analog signals are continuous signals that
vary in amplitude, frequency, or phase, whereas digital signals are discrete
signals that represent data using binary values (0 or 1).
Transmission: Analog signals are more prone to noise and distortion
during transmission, which can affect the accuracy of the data. Digital
signals, on the other hand, are less prone to noise and distortion, and they
can be transmitted accurately over long distances.
Processing: Analog signals require continuous processing and
amplification to maintain their quality, whereas digital signals can be
processed and transmitted without the need for continuous amplification.
Digital signals can also be manipulated and processed more easily than analog
signals.
Storage: Analog signals are difficult to store and reproduce
accurately, whereas digital signals can be stored and reproduced without loss
of quality.
Bandwidth: Analog signals require a larger bandwidth to transmit
the same amount of data as digital signals. This is because analog signals
transmit data in a continuous stream, whereas digital signals transmit data in
discrete packets.
What is
the difference in noisy and noiseless channel?
A noisy channel is
a communication channel that introduces errors or distortions into
the transmitted signal, while a noiseless channel is a communication
channel that does not introduce any errors or distortions into the transmitted
signal.
In a noisy channel, the received
signal may differ from the transmitted signal due to various factors such
as interference, attenuation, or distortion. As a result, the receiver may need
to use error-correction techniques to detect and correct errors in the received
signal. Examples of noisy channels include wireless networks, satellite links,
and telephone lines.
In contrast, a noiseless channel
allows for perfect transmission of data without any errors or distortions.
However, in practice, it is difficult to achieve a completely noiseless
channel. Examples of nearly noiseless channels include fiber-optic cables and
some types of wired networks.
v Performance of a Network
The performance of a network can
be measured in various ways depending on the application and the specific
characteristics of the network. Here are some common metrics used to evaluate
network performance:
Bandwidth: Bandwidth is the amount of data that can be transmitted
over a network connection in a given amount of time. A network with a higher
bandwidth can transmit more data and hence has better performance.
Latency: Latency is the time it takes for a data packet to travel
from one point in the network to another. Lower latency means faster
communication and better network performance.
Packet loss: Packet loss occurs when data packets are dropped or lost
during transmission. A network with low packet loss has better performance.
Jitter: Jitter is the variation in latency between packets. A
network with low jitter has more consistent and reliable performance.
Throughput: Throughput is the amount of data that can be transmitted
over a network in a given time period. A network with higher throughput can
transmit more data and hence has better performance.
Reliability: Reliability refers to the ability of a network to
maintain stable and consistent performance over time. A reliable network has
fewer disruptions and outages, which can affect the overall performance.
What do
you mean by digital and Analog transmission?
Digital and analog
transmission are two different methods of transmitting data over
a communication channel.
Analog transmission involves
the continuous transmission of signals that vary in amplitude,
frequency, or phase. In analog transmission, the original signal is converted
into a continuous waveform that can be transmitted over the communication
channel. Examples of analog transmission include traditional telephone
lines and AM/FM radio broadcasts.
In contrast, digital transmission
involves the transmission of discrete signals that represent data
using binary values (0 or 1). In digital transmission, the original signal is
converted into a series of binary digits (bits) that can be
transmitted over the communication channel. Examples of digital transmission
include computer networks, digital television, and satellite communication.
The choice between digital and analog transmission depends on various factors, such as the type of data being transmitted, the distance of the transmission, and the available communication technologies. Digital transmission is generally preferred over analog transmission because it is more accurate, less prone to noise and distortion, and can be transmitted over longer distances without loss of quality.
What are
data encoding and modulation techniques?
·
Modulation is a modification of a frequency to
carry data. In other word, we can say modulation is a process of converting
digital signal into analog signal.
·
The process of converting analog signal back to
digital signal is known as Demodulation. Thus the term Modem is used
for modulation and demodulation.
·
Analog to digital conversion:
1.
PCM(Pulse Amplitude Modulation)
2.
DM(Delta Modulation)
What is
broadband and baseband transmission?
Broadband and baseband transmission
are two methods of transmitting data over a communication channel.
Baseband transmission uses the
entire bandwidth of the communication channel to transmit a single digital
signal. In other words, the digital signal is transmitted without any
modulation or multiplexing. Baseband transmission is typically used in
short-distance communication such as between a computer and a printer, or
between a computer and a local network.
Advantages
and Disadvantages of Baseband Transmission
There are various
advantages and disadvantages of baseband transmission. Some advantages and
disadvantages of baseband transmission are as follows:
Advantages
It has a simple
structure.
It is easy to
install.
Its maintenance is
simple and easy.
It has low-cost
installation.
Disadvantages
It may be only
utilized for voice and data.
It has a short
coverage and a limited range.
It works only on a
limited distance.
Broadband transmission, on the other
hand, uses multiple channels to transmit multiple signals simultaneously. In
broadband transmission, the available bandwidth is divided into multiple
channels, each of which can be used to transmit a different signal. Broadband
transmission is typically used in long-distance communication such as cable
television, broadband internet, and satellite communication.
Advantages
and Disadvantages of Broadband Transmission
There are various
advantages and disadvantages of broadband transmission. Some advantages and
disadvantages of broadband transmission are as follows:
Advantages
The main advantage of
broadband transmission is its speed. It offers a fast speed for data
transmission.
It has a large
bandwidth provision for data transmission.
The data transmission
may take place for a large distance.
Disadvantages
It needs some extra
hardware for data transmissions like Multiplexers and De-multiplexers.
The broadband
transmission maintenance and cost are high.
The main difference between baseband
and broadband transmission is that baseband transmission uses the entire
bandwidth of the communication channel to transmit a single digital signal,
while broadband transmission uses multiple channels to transmit multiple
signals simultaneously.
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.
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.
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.
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
Multiplexing techniques can be classified as:
What is
Transmission media?
Transmission media is a
communication channel that carries the information from the sender to the
receiver. Data is transmitted through the electromagnetic signals.
The main functionality of the
transmission media is to carry the information in the form of bits
through LAN(Local Area Network).
It is a physical path between
transmitter and receiver in data communication.
The characteristics and quality of
data transmission are determined by the characteristics of medium and signal.
Transmission media is of two types
are wired media and wireless media. In wired media, medium characteristics are
more important whereas, in wireless media, signal characteristics are more
important.
Different transmission media have
different properties such as bandwidth, delay, cost and ease of installation
and maintenance.
Causes Of
Transmission Impairment:
Classification
Of Transmission Media:
What are Transmission Errors?
Transmission errors are errors
that occur during the transmission of data over a communication channel. These
errors can be caused by various factors such as noise, interference,
attenuation, and distortion in the communication channel.
There are two main types of transmission
errors: bit errors and burst errors.
Bit errors: Bit errors occur when a single bit in the
transmitted data is corrupted or lost during transmission. Bit errors can occur
due to noise, interference, or other factors that affect the accuracy of the
signal.
Burst errors: Burst errors occur when multiple bits in the transmitted
data are corrupted or lost during transmission. Burst errors can occur due to
factors such as interference, attenuation, or distortion in the communication
channel. Burst errors can be more difficult to correct than bit errors, as they
can affect multiple bits in the transmitted data.
To detect and correct transmission errors, error detection and correction techniques are used. These techniques involve adding redundant information to the transmitted data, which can be used to detect and correct errors in the received data. Examples of error detection and correction techniques include checksums, cyclic redundancy checks (CRC), and forward error correction (FEC).
What are
the error Handling mechanism?
Error handling mechanisms are
used in data communication to detect and correct errors that occur during the
transmission of data over a communication channel. Here are some commonly used error
handling mechanisms:
Automatic Repeat
Request (ARQ): ARQ is a protocol
that is used to detect and correct errors in transmitted data. In ARQ, the
receiver sends an acknowledgement (ACK) signal to the sender to confirm the
successful receipt of the data. If the receiver detects an error in the
received data, it sends a negative acknowledgement (NAK) signal to the sender,
requesting the sender to retransmit the data.
Forward Error
Correction (FEC): FEC is a
technique that is used to detect and correct errors in transmitted data without
the need for retransmission. FEC involves adding redundant
information to the transmitted data that can be used to correct errors in
the received data.
Checksums: Checksums are used to detect errors in transmitted data.
A checksum is a value that is calculated from the transmitted data and is sent
along with the data. The receiver calculates a checksum from the received data
and compares it to the checksum received with the data. If the two checksums do
not match, an error is detected.
Cyclic Redundancy Check (CRC): CRC is a technique that is used to detect errors in
transmitted data. CRC involves calculating a checksum from the transmitted data
using a polynomial function. The receiver calculates a checksum from the
received data using the same polynomial function and compares it to
the checksum received with the data. If the two checksums do not match, an
error is detected.