Block coding replaces groups of m bits with groups of n bits, where n is greater than m, adding redundancy. It is applied before line coding to improve the performance of line coding. Specifically, 4B/5B block coding replaces each 4-bit block with a 5-bit block, using the extra bit for control or signaling. The process involves dividing the bit sequence into m-bit groups, substituting each m-bit group with an n-bit group, and combining the n-bit groups into an output stream.

1. Block Coding
By
Md. Fazle Rabbi
16CSE057

2. 4.2
Block Coding
• Block coding is applied before line coding
• It provides redundancy and improves the
performance of line coding.

3. 4.3
Block Coding
mB/nB
It replaces each blocks of m-bits with block of n-bits
where n>m

4. 4.4
Block Coding

5. 4.5
1. In the division step, a sequence of bits is divided
into groups of m bits.
2. In the substitution step, we substitute an m bit
group for an n bit group
3. Finally the n-bit groups are combined together to
form a stream
Block Coding

6. 4.6
Figure 1 Block coding concept

7. 4.7
Block Coding
4B/5B
It replaces each blocks of 4-bits with block of 5-bits

8. 4.8
Figure 2 Using block coding 4B/5B with NRZ-I line coding scheme

9. 4.9
Block Coding

10. 4.10
Table 1 4B/5B mapping codes

11. 4.11
Block Coding
• A 4 bit data word can have 24
=16 combinations.
• A 5 bit word can have 25=32 combinations.
• We therefore have 32 - 16 = 16 extra words.
• Some of the extra words are used for
control/signalling purposes.

12. 4.12
Example

13. 4.13
Figure 3 4B/5B block coding

14. 4.14
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