Question

ENCODE THE FOLLOWING STREAM OF BITS USING 4B/5B encoding :-

1101011011101111

what is the ratio of redundant bits in 4B/5B?

Answer 1

4B/5B encoding means it takes 4B as input and produce 5B as output

the following table is the standard of 4B5B encoding as follows

hex binary 4B5B code

0 0000 11110

1 0001 01001

2 0010 10100

3 0011 10101

4 0100 01010

5 0101 01011

6 0110 01110

7 0111 01111

8 1000 10010

9 1001 10011

A 1010 10110

B 1011 10111

C 1100 11010

D 1101 11011

E 1110 11100

F 1111 11101

NOW in 4B5B code in every digit of binary there is atmost 3 zeros this reduces the time when we decode the message

now the given code is 1101 0110 1110 1111

step 1 we have to divide it at every 4 bits as

1101 0110 1110 1111

step 2 now we have to search for the above 4 bits binary in the above table

1101--- 11011

0110-- 01110

1110-- 11100

1111--- 11101

step 3 place them according to the coding

4B5B CODING = 11011 01110 11100 11101

the above one is the encoding of the given input code

Ans: 11011 01110 11100 11101

Rout = (5/4) * Rin

= 1.25 Rin (Rout= rate of output , Rin= rate of input)

= 1.25(16)

= 20

Ratio of 4b5b redundents bits :

Rout/Rin = 5/4