ace test series 2018

Question

Comments

mi quest  is when to stuffed after 3 consecutive or take   everytime five consecutive 1..

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after every 2 consicutive 1

Answer 1

Data Frame: 1011101111011111110

Stuff bit pattern : 01110

We will insert 0 after every two consecutive 1's

So the final data that has to be transmitted is 1011010110110011011011010

Number of zero stuffed is 6.

Comments

bro why to stuffed after two  ....not three

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Stuff bit pattern or flag is used as start and end delimiter. If this pattern matches with data then receiver will think that it is end of message and will discard further data. So if data contains pattern same as delimiter/flag we change it and we change it by removing that pattern from data. We remove that pattern from by inserting 0 after every 0 followed by n-1 consecutive 1, here it is 011. Here n is number of 1 in flag.

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Would we stuff 0 after every two consecutive 1s or after every 011?

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Number of zero's Stuffed are 6.

The final bit pattern will be,

1011 0 1011 0 11 0 011 0 11 0 11 0 10.

The given Stuff bit pattern is 01110.

Hence a zero will be stuffed for every occurence of 011.