4. block coding

block coding

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 In the division step, a sequence of bits is divided into groups of m bits. In the substitution step, we substitute an m bit group for an n bit group 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 =16 combinations. A 5 bit word can have =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 Thank you