This document summarizes line coding, which is the process of converting digital data to digital signals for transmission. It discusses how digital data in the form of text, numbers, images, audio or video are stored as bit sequences in computer memory. Line coding converts these bit sequences into digital signals for transmission, and decoding reconstructs the digital data at the receiver. Some key properties and characteristics of line coding that help efficient transmission are reduced bandwidth usage, efficient power use, error detection and correction capabilities, and avoidance of long strings of 1s and 0s. Specific line coding techniques like NRZ-L, NRZ-I and Differential Manchester are also outlined.

1. Line coding
Unit – 2
Presented By
Mrs. M.P.Sasirekha

2. Line coding
• Line coding is the process of converting digital data to digital
signals.
• The data may be in the form of text, numbers, graphical images,
audio, or video, are stored in computer memory as sequences of
bits.
• Line coding converts a sequence of bits to a digital signal. At the
sender, digital data are encoded into a digital signal; at the
receiver, the digital data are recreated by decoding the digital
signal.

3. Data Encoding

5. Properties of Line Coding
• Following are the properties of line coding −
• As the coding is done to make more bits transmit on a single signal,
the bandwidth used is much reduced.
• 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.

6. Characteristics of Line coding
• Data Rate
• Signal level versus data level
• Pulse rate versus bit rate
• DC components
• Self synchronization
• Baseline wandering

7. Characteristics of Line coding
• Data Rate: It represents the number of data bits transmitted per
second. The unit is bits per second. The data rate should be increased
to increase the data transmission speed.
• Baseline wandering: A receiver will evaluate the average power of the
received signal (called the baseline) and use that to determine the
value of the incoming data elements.
• If the incoming signal does not vary over a long period of time, the
baseline will drift and thus cause errors in detection of incoming data
elements. A good line encoding scheme will prevent long runs of fixed
amplitude.

17. NRZ-L(NRZ-Level)
NRZ-I(NRZ-Invert)

29. Differential Manchester
• Inversion at the middle of the bit interval is used for synchronization,
but the presence or absence of an additional transition at the
beginning of the interval is used to identify the bit.
• A transition means binary 0 and no transition means binary 1 .
• 1 - Absence of transition at the beginning of the bit interval
• 0 - Presence of transition at the beginning of the bit interval

34. Thank you