Test by Bikram | Computer Networks | Test 1 | Question: 8

Question

The message $11011011$ should be transmitted using CRC polynomial $x3+x+1$, to protect it from errors  that message will be transmitted as ________

Comments

plzz solve this

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11011011 is                   x⁷ +  x⁶+x⁴+  x³ + x +1 

and CRC polynomial x³+x+1

now calculate

http://www.cs.jhu.edu/~scheideler/courses/600.344_S02/CRC.html

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i am getting last 3 bit as  010

please  check again...

Answer 1

I hope this helps !

Answer 2

1011 )11011011  then we get remainder as 010

hence sequence which will be transmitted is 11011011010

Comments

We can verify the answer by dividing it again by the divisor and if the remainder is 0, means there is no error. But for the above ans, we don't ger remainder as 0.
According to me, 3 zeros should be padded to the dividend before division. The remainder would then be 110.

Therefor msg will be transmitted as 11011011110

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i'm also getting 110 as remainder

Answer 3

For the given CRC polynomial the CRC generator will be of 4 bits as 1011.

Now, we have to put (4-1)=3 bits of 0's in message. hence message will become now, 11011011000.

Then we will keep on taking EX-OR between the above message and CRC generator until we get less number of bits than in CRC generator(4) by taking leading 1. then last 3 bits will be actual CRC.

Finally we have to replace that dummy zeroes with this 3 bit CRC.

this whole thing is for sender side.