The document discusses polar encoding techniques, specifically polar-nrz and polar-rz schemes, which utilize two voltage levels to represent binary data. It outlines the pros and cons of each encoding variant, detailing applications, implementation issues, and technical characteristics. Additionally, it includes assignments related to the mathematical representation of the waveforms in these encoding methods.

1. Polar-NRZ & Polar-RZ
Line Coding: Polar encoding Techniques
CMS-A-CC-4-8
Lockdown Talk Series: DCNIT-LDTalks-5
Arunabha Saha
Department of Computer Science, Vidyasagar College
University of Calcutta
May 2020

2. Outline
Overview of polar encoding
Variants of polar encoding schemes
NRZ-L and NRZ-I scheme
Polar-RZ scheme

3. Polar Encoding
Polar encoding uses two voltage levels.
’1’ represented by +ve and ’0’ represented by -ve voltage levels(or
vice-versa).
Because of using both levels, the average voltage level on the line is
reduced & so the DC component problem in unipolar encoding.

4. Polar Encoding Variants

5. Polar-NRZ(1)
In Polar-NRZ, 0 and 1 encoded as +ve and -ve voltage levels(or
vice-versa)
Two variants of NRZ we get to see
– NRZ-L: NRZ Level
– NRZ-I: NRZ Inverted
In this scheme the voltage either +ve or -ve, but never return to
zero.

6. Polar-NRZ(2)
NRZ-L (NRZ Level):
In NRZ-L the level of the signal is dependent upon the state of the
bit.
+ve voltage depicts "1" and -ve voltage depicts "0" or vice-versa.
NRZ-I (NRZ Inverted):
In this method, the inversion of voltage level depicts "1".
Here not exactly the data represented as any level voltage, rather a
transition between two polar voltages represented as "1".
"0" represents no change in the data.
application: Used in USB, CD and fast ethernet(IEEE 802.3).

7. NRZ-L & NRZ-I encoding(1)
when "0" is taken as low voltage.

8. NRZ-L & NRZ-I encoding(2)
when "0" is taken as high voltage.

9. Pros & Cons of Polar-NRZ
Pros:
Its easy to implement
By using level voltages, DC component problem reduced.
NRZ-I provides better synchronization due to transition at the
occurrence of "1"; this allows receiver to resynchronize.
Cons:
Baseline wandering issue persists.
Synchronization problem for long sequence of consecutive 0s or 1s.

10. Assignments
Try to find the mathematical formulation for waveforms represents
NRZ-L and NRZ-I.
Represent the data-stream starting from 1, e.g. 1100011001 in
NRZ-L and NRZ-I scheme.
In NRZ-I, what will happen, if transition occurs if the next bit is 0
instead of 1. Describe for the previous mentioned data-stream.

11. Polar-RZ(1)
In polar-RZ encoding the waveform not changing between bits but
during each bit.
Here three voltage levels are used, 0, +ve and -ve.
The signal state decided by the voltage during the first half of each
data, e.g. 0 or 1.
The waveform returns to zero(RZ) in the second half of each data
bit; can be thought as a resting state.
1 and 0 in the data represented by the +ve and -ve voltage levels.

12. Polar-RZ(2)
[assignment: find the mathematical expression for the waveform]

13. Pros & Cons of Polar-RZ
Pros:
It solves the problem of synchronization in NRZ; when receiver don’t
know when one bit is ended and the next bit is starting1
Reduce the problem with DC component.
Cons:
It requires two signal changes to encode a bit and so it occupies
greater bandwidth.
Sudden change in polarity resulting all as interpreted as 1s and all 1s
interpreted as as.
It requires greater bandwidth.
1 Data Communication and Networking, 4e, B. A. Forouzan

14. Thank You
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