LINE CODING
Hiten Galiya (20BEC036)
Dept. of Electronics And Communication Engineering
Institute of Technology, Nirma University
Ahmedabad, India
20bec036@nirmauni.ac.in
Abstract— The ways of sending data in form of
1’s and 0’s. In this advantage and disadvantage of
such method is going to shown. This paper propose
the way of transmission of data in the form of
binary signal 0’s and 1’. There are different types
of with their power spectral density diagram and
efficiency of each line code.
INTRODUCTION
There are different types of line coding. Signal
generated from the information source can be in
2 forms.
A) Analog
B) digital
When we are talking about analog the
transmission of information takes place only
when analog signal is converted to digital
signal.we can termed them as baseband signals.
When theses signals are transmitted without
modulation i.e. not super imposing the carrier
signal on message signal is known as baseband
communication system.We can use different
method to convert analog signal into digital
signal but there is an efficient method for
conversion of analog signal to digital signal in
communication system i.e. the pcm. The various
steps in pulse code modulation are sampling,
quantizing and coding due to ISI the pulse code
modulation signal cannot be directly transmitted
there is less synchronization between transmitter
and receiver and undesired dc level occur if a
long string of 1 and 0 is present in the data. A
another problem associated with pulse code
modulation is large channel bandwidth and high
signaling rate which can be overcome delta
modulation.
I.
Maurya Shah(20BEC065)
Dept. Of Electronics And Communication Engineering
Institute Of Technology, Nirma University
Ahmedabad, India
20bec065@nirmauni.ac.in
The most basic line coding techniques are often
employed for very low-speed asynchronous
transmission, in which data is provided in tiny
independent blocks and the receiver can resynchronize with the transmitter at the start of each
incoming block. Timing becomes significantly more
crucial in high-speed synchronous applications,
where much bigger blocks of information are
conveyed, as do variables like as noise and the
probable presence of a net DC component in a signal.
All line coding systems have one thing in common:
they adjust signal levels in some way in order to
represent digital data. The line code manipulates
voltage or current levels in wired channels made up
of twisted-pair or coaxial cables in order to create
electrical pulses that represent data values. It
displays data values in optical fiber channels by
varying the intensity of light pulses.
LINE CODING
Line coding is a term used to describe digital
baseband transmission. Digital signals on a cable
do not often average to zero DC volts. The DC
offset creates issues with the receiver as well as
DC power loss in the lines. One way is to utilize
a code that averages to zero DC volts while still
transmitting data to the receiver. In the early days
of data transfer, the old Bell phone system
established such codes. These digital baseband
systems are described using words like as RZ,
NRZ, Manchester, bipolar, and so on.
II.
As SPC (Stored Program Control) switching
transitioned from analogue to digital, the usage of
Line Codes became increasingly prevalent.
Simultaneously, the Transmission Network has to
be upgraded for Digital (e.g. PDH, SDH).The Line
Code aids in error recovery and allows clock data to
be recovered and processed. Line Code also aids in
the reduction of a "DC component," which can
cause
problems
with
telecommunications
equipment.
III.
TYPES OF LINE CODING
Line coding methods are classified into five primary
types:
•
Unipolar
▪ Advantages:
The following are the benefits of Unipolar NRZ:
•
Polar
i.
Simple to put into action.
•
Bipolar
ii.
Requires a little amount of bandwidth.
•
Differential (multi-transition)
•
Multi-level
1.
UNIPOLAR NRZ
All non-zero signalling elements in a
Unipolar signalling system have the same
polarity - they are either all positive or all
negative. It is similar to a basic on-off keying
method in which the presence of a voltage
pulse represents a binary one and the
absence of a pulse represents a binary zero.
It is also the most basic type of line-code we
shall see. Non-return-to-zero (NRZ) systems,
in which the signal does not return to zero in
the midst of the bit time, are the earliest
unipolar line coding techniques. A positive
voltage denotes a binary one, whereas a
zero value denotes a binary zero.
▪
Dis-advantages:
i.
There is a substantial DC component, which
implies that power is lost owing to the
heating of the transmission line's
conductors.
ii.
There is no way to integrate a clock signal in
the line code.
2.
UNIPOLAR RZ
A return-to-zero (RZ) variation of Unipolar line
coding exists as well, in which the logic high
(binary one) signal voltage returns to zero half
way through the bit time.
▪
i.
ii.
Advantages:
Simple to put into action.
The additional transitions can aid in
iii.
▪
i.
ii.
iii.
3.
synchronization.
The DC component of bipolar NRZ is half
that of Unipolar NRZ.
Dis-advantages:
It necessitates double the bandwidth of
Unipolar NRZ.
Long zero sequences can still cause
synchronization problems at the receiver.
Because there is still a considerable DC
component, some power is wasted, and AC
coupling is still an issue.
ones and zeros is about equal.
4.Polar RZ:
The logic used to represent data in RZ is that half
of the signal for bit 1 is represented by +V and half
by zero voltage, and half of the signal for bit 0 is
represented by -V and half by zero voltage.[6] To
understand the same, an example can be seen in Fig
-2 having the input data as 01001.
POLAR NRZ
Polar line coding systems provide binary
values by using both positive and negative
voltage levels. Polar signaling, like the
unipolar line coding systems discussed above,
has both NRZ and RZ forms. However, there
are two types of NRZ schemes for polar line
coding. The first one we'll look at is known as
NRZ-level (NRZ-L). The voltage level
determines the value of a bit in this case. Logic
low (binary zero) is often represented by a
positive voltage, and logic high (binary one) is
typically represented by a negative voltage.
Figure-5: Polar RZ
A limitation of RZ encoding is that it needs
highbandwidth. Another concern is the consistency,
since three voltage ranges are used. This scheme is
not seen today, as a result of all these shortcomings.
Instead, the better-performing Manchester and
differential Manchester systems have been replaced.
▪ Advantages:
i.
ii.
iii.
▪
i.
▪
i.
ii.
▪
i.
Figure-4: Polar NRZ
Advantages:
Implementation is rather straightforward.
Requires a little amount of bandwidth.
Dis-advantages:
Neither polar-NRZ-L nor polar NRZ-I are
DC balanced, albeit the DC component of
polar NRZ-L is minimal if the number of
ii.
iii.
Implementation is rather straightforward.
It consumes less electricity than the polar
NRZ-L or polar NRZ-I.
The receiver may re-synchronize itself
thanks to transitions in the midst of each bit
time.
Dis-advantages:
More complicated than polar NRZ-L or
polar NRZ-I.
Not DC balanced, however the DC
component is minimal if the number of ones
and zeros is almost equal.
It necessitates double the bandwidth of polar
NRZ-L or polar NRZ-I.
5.Manchester Coding:
In Manchester encoding (also known as Phase
encoding, or PE), the length of the bit is broken into
two parts. During the first half, the voltage stays at
one level and transfers in the second half to the other
level. Synchronization is given by the transition at
the centre of the bit. The logic that is used to describe
data using Manchester is that there is a transition
from V to +V volts in the centre of the bit for bit 1
and a in the centre of the bit, there is a transition from
+ V to -V volts for bit 0. For instance, if the input
data provided is 010011, the signal would be in the
form given in Fig-6
Figure-6: Manchester Coding
It is a signal with no DC component that is
selfclocking. Consequently, it is simple to
galvanically separate electrical contacts using a
Manchester code. The name of the Manchester code
comes from its creation at the University of
Manchester, where the code was used to store data
on the Manchester Mark 1 computer's magnetic
drums. Before the introduction of 6250 bpi tapes, the
Manchester code was commonly used for magnetic
storage on 1600 bpi electronic tapes. In early
Ethernet physical layer standards, the Manchester.
code was used and is still used in consumer IR
protocols, RFID and near-field communication.
Differential Manchester:
There is often a change at the centre of the bit in
Differential Manchester, but the bit values are
calculated at the beginning of the bit. In the case
where the next bit is 0, the transformation occurs; if
the next bit is 1, the transition does not occur. An
example to illustrate the same can be given by having
the input data as 010011, signal would be as shown
in Fig-7
Similar to Manchester, as each bit has a positive
and negative voltage contribution, there is no
baseline wandering and no DC part in Differential
Manchester. [7] The drawback is that Manchester’s
and Differential Manchester’s minimum bandwidth
are double than that of the NRZ
Table -1: Comparison of the Line Codes
Sr. Code Name Timing
Band DC Value
width
No
.
1
NRZ
Poor
Low
High DC
clock
component
recovery
2
RZ
Good
High
High
DC
clock
component
recovery
3
Manchester Good
High
No
DC
clock
component
recovery
4
Differential Good
Mode No
Manchester clock
rate
component
recovery
Applications of Line Codes in various
Domains
Line Codes are extensively used in various fields,
so as to utilize its usage. A few of the many have
been listed
5G: Polar codes are promising techniques that will
be used in 5G systems because they have advantages
which outperform turbo codes that were used in
previous generations of cellular communications
systems. These advantages include higher gain than
other codes and there are no error floors like turbo
and LDPC codes. Polar codes are proven to be the
codes that have the lowest complexity. These codes
are considered a breakthrough in coding systems
because they are the first provably codes that attain
Shannon limit. Moreover, polar codes have the
ability to work better in control channels, hence it is
dedicated to control channels in 5G-NR systems. [8]
The drawbacks of polar codes include the code
length must be a power of two which causes coding
rate problems. The complicated design of polar
decoders make them expensive; therefore many
IV.
studies are still searching how to use these codes
efficiently.
ACKNOWLEDGMENT
This Project was performed under the guidance of
Prof. Twinkle Bhavsar and Dr. Mehul Naik of
Electronics
and
Communication
Department,Institute
of
Technology
Nirma
University. The authors of the paper are thankful to
the university and the professors for the guidance in
completion of the Project as a part of the teaching
and learning process.
REFERENCES
1. Herbert Taub Donald L. Schilling, GoutamSaha,
Principles Of Communication Systems, Tata
McGraw Hill Publishing Company private
Limited, (Third Edition)
2. Dae Kim and Jae-Kyoon Kim, "A Condition for
Stable Minimum-Bandwidth Line Codes," in IEEE
Transactions on Communications, vol. 33, no. 2,
pp. 152-157, February 1985, doi:
10.1109/TCOM.1985.1096260
3. Modern Analog and digital communication
system by B.P lathi