students

1. (Note on class topic )
Line code
Course Title: Data Communication
Course Code: CSE 313
Submitted To Submitted by
Pronab nath bondhu Fairuz Fatemi
Lecturer ID:1834902087
City University Batch:49(B)Day
B.S.C in CSE
D:23/09/2021
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2. Line coding :
• Data as well as signals that represents data can either be digital or
Analog. Line coding is the process of converting digital data to digital
signals. By this technique we converts a sequence of bits to a digital
signal. At the sender side digital data are encoded into a digital signal
and at the receiver side the digital data are recreated by decoding the
digital signal.
We can roughly divide line coding schemes into three categories:
• Unipolar ( NRZ scheme).
• Polar (NRZ-L, NRZ)
• Bipolar
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3. • Properties of Line Coding
• For a given bandwidth, the power is efficiently used.
• The probability of error is much reduced.
• Error detection is done and the bipolar too has a correction capability.
• Power density is much favorable.
• The timing content is adequate.
• Long strings of 1s and 0s is avoided to maintain transparency.
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4. Unipolar
• In this scheme, all the signal levels are either above or below the axis.
• Non return to zero (NRZ) – It is unipolar line coding scheme in which positive
voltage defines bit 1 and the zero voltage defines bit 0. Signal does not return to
zero at the middle of the bit thus it is called NRZ. For example: Data = 10110.
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5. Polar
In polar schemes, the voltages are on the both sides of the axis.
• NRZ-L and NRZ-I – These are somewhat similar to unipolar NRZ
scheme but here we use two levels of amplitude (voltages). For NRZ-
L(NRZ-Level), the level of the voltage determines the value of the bit,
typically binary 1 maps to logic-level high, and binary 0 maps to
logic-level low,
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6. • Bipolar
• In this scheme there are three voltage levels positive, negative, and
zero. The voltage level for one data element is at zero, while the
voltage level for the other element alternates between positive and
negative.
• Alternate Mark Inversion (AMI) – A neutral zero voltage represents
binary 0. Binary 1’s are represented by alternating positive and
negative voltages.
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7. • Advantages & Disadvantages
• Following are the advantages −
• It is simple.
• No low-frequency components are present.
• Occupies low bandwidth than unipolar and polar NRZ schemes.
• A single error detection capability is present in this.
• Following are the disadvantages −
• No clock is present.
• Long strings of data causes loss of synchronization.
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8. Encapsulation
Network models are used to standardize network communication. When
sending data from one location to the other, the data goes through a
number of layers. The TCP/IP model has four layers. They are
application layer, transport layer, internet layer and network access
layer. Each layer performs a specific role in the TCP/IP model. The
application layer has all the end user services such email facilities, web
browsing etc. The transport layer manages the host to host
communication. In network layer, the data is known as packets.
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9. Decapsulation
• If preliminary nondestructive inspection suggests that analysis at the
chip level is required, then decapsulation of the package is required.
Prior X-ray or acoustic imaging may be necessary to ascertain the
orientation and dimensions of the package contents. This will set
guidelines for how much mechanical grinding can be tolerated.
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10. • Encapsulation vs Decapsulation
• A network is a connection with a large number of devices. These
devices are different from one to another. That can create compatibility
issues. To avoid that, all devices in the network use the standard
network model for data communication. One major network model is
TCP/IP model. These models consist of a number of layers. The data
which should be transmitted to a new location should go through each
layer. When reaching each layer, the information is added to the data.
It is called encapsulation. When the data reaches the destination, in
each layer the added information is unpacked. That process is known
as decapsulation.
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11. Reference –
• Data Communications and Networking By Behrouz A.Forouzan (Book)
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https://www.geeksforgeeks.org/difference-between-unipolar-
polar-and-bipolar-line-coding-schemes/
https://www.tutorialspoint.com/digital_communication/digital_communica
tion_line_codes.htm
https://www.sumologic.com/glossary/encapsulation/