Line coding schemes are used to convert digital data into electrical signals for transmission over channels. This document outlines various line coding techniques such as NRZ, Manchester, and Differential Manchester coding. It discusses properties of good line coding schemes, including low transmission bandwidth, power efficiency, transparency, clock synchronization, error handling, and prevention of baseline wandering. Line coding is important for digital transmission in applications such as local and wide area networks, pulse shaping, and telephonic transmission.

1. Line Coding Schemes
Digital Transmission: D/D Conversion
CMS-A-CC-4-8
Lockdown Talk Series: DCNIT-LDTalks-2
Arunabha Saha
Department of Computer Science, Vidyasagar College
University of Calcutta
April 2020

2. Outline
Introduction to Line Coding
Classification of line coding schemes
Properties of line coding
Applications

3. Line coding(1)
What is Line coding..??
The process of converting binary(digital) data into digital signals

4. Line coding(2)
Also known as Baseband transmission
Baseband signals(or lowpass) , which includes the frequencies close
to 0 in comparison with the highest frequency
It uses baseband channel(or lowpass) to transfer the low frequencies;
e.g. serial cable, LAN.
The output of a multiplexer is coded into electrical pulses or waveforms
for the purpose of transmission ovr the channel. This process is called line
coding1
.
1 Modern Digital and Analog Communication Systems, 3e, B.P. Lathi, OUP, 1998

5. Types of line coding
NRZ, NRZ-L, NRZ-I, RZ, Manchester, Differential Manchester

6. Properties of line coding(1)
Transmission bandwidth: as small as possible
Power efficiency: for any given bandwidth B and detection error
probability e, transmitted power need to be as small as possible
Transparency: the digital signal should be transmitted correctly,
irrespective of the pattern of 0’s and 1’s in input stream.
Clock synchronization: both sender and receiver need to be
synchronized to avoid any kind of misinterpretation

7. Properties....(2)
Error handling: error should be detected and corrected properly
Baseline wandering: In decoding a digital signal, the receiver
calculates a running average of the received signal power. This
average is called the baseline. The incoming signal power is
evaluated against this baseline to determine the value of the data
element. A long string of 0s or 1s can result a drift in the baseline
(baseline wandering) and introduce errors in decoded output. A
good line coding scheme needs to prevent baseline wandering.

8. Properties....(3)
Signal element vs data element:
define r = # of data elements
# of signal elements ; r need to be well defined.
Data element = blue line, signal element = magenta line

9. Applications
Data transmission over LAN and WAN.
Pulse shaping and relocation without modulation or filtering.
e.g. in telephonic transmission, the transfer characteristics highly
attenuated bellow 300 Hz.
References
Modern Digital and Analog Communication Systems, 3e, Lathi,B.P.
(1998), OUP.
Computer Networks, 5e, Tanenbaum, A. S.; Wetherall, D.J. (2011),
Prentice Hall.

10. Thank You
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