Polar-NRZ & Polar-RZ encoding schemes

Polar-NRZ and Polar-RZ scheme discussed with examples. The comparison with the unipolar encoding techniques are drawn here. the advantages and disadvantages to both the schemes are discussed.

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
IOverview of polar encoding
IVariants of polar encoding schemes
INRZ-L and NRZ-I scheme
IPolar-RZ scheme

3. Polar Encoding
IPolar encoding uses.
I'1' represented by +ve and '0' represented by -ve voltage levels(or
vice-versa).
IBecause 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)
IIn Polar-NRZ,0and1encoded as +ve and -ve voltage levels(or
vice-versa)
ITwo variants of NRZ we get to see
NRZ-L: NRZ Level
NRZ-I: NRZ Inverted
IIn this scheme the voltage either +ve or -ve, but never return to
zero.

6. Polar-NRZ(2)
NRZ-L (NRZ Level):
IIn NRZ-L the level of the signal is dependent upon the state of the
bit.
I+ve voltage depicts "1" and -ve voltage depicts "0" or vice-versa.
NRZ-I (NRZ Inverted):
IIn this method, the inversion of voltage level depicts "1".
IHere not exactly the data represented as any level voltage, rather a
transition between two polar voltages represented as "1".
I"0" represents
Iapplication: Used in USB, CD and fast ethernet(IEEE 802.3).

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

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

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

10. Assignments
ITry to nd the mathematical formulation for waveforms represents
NRZ-L and NRZ-I.
IRepresent the data-stream starting from 1, e.g. 1100011001 in
NRZ-L and NRZ-I scheme.
IIn 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)
IIn polar-RZ encoding the waveform not changing between bits but
during each bit.
IHere three voltage levels are used, 0, +ve and -ve.
IThe signal state decided by the voltage during the
data, e.g. 0 or 1.
IThe waveform returns to zero(RZ) in the second half of each data
bit; can be thought as a.
I1and0in the data represented by the +ve and -ve voltage levels.

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

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

14. Thank You
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