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The message $11001001$ is to be transmitted using the CRC polynomial $x^3 +1$ to protect it from errors. The message that should be transmitted is:

  1. $11001001000$

  2. $11001001011$

  3. $11001010$

  4. $110010010011$

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4 Comments

CRC Calculation

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How come 1100-1001 is 101? Should it not be 11?
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We are not doing division of binary numbers, we are doing XOR operation.

XOR of 1100 and 1001 is 101
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4 Answers

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52 votes
Best answer

Answer - B.

Degree of generator polynomial is $3$ hence $3\text{-bits}$ are appended before performing division

After performing division using $2's$ complement arithmetic remainder is $011$

The remainder is appended to original data bits and we get  $M' = 11001001\bf{011}$ from $M = 11001001.$

Courtesy, Anurag Pandey

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4 Comments

Polynomial function is $x^{3}$ +1 

It can be interpreted as 1$x^{3}$ + 0$x^{2}$ + 0$x^{1} + 1$$x^{0}$

Considering all the coefficients: 1001 is the required divisor.

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@Sumaiya23 Since the degree of CRC polynomial is 3 that's why 3 bits are appended.

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In polynmial method , We continue to divide until degree of rmainder is less than degree of divisor => x3 degree 3 so remainder of the form x2 + x + 1 , hence 3 bits.
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–3 votes
–3 votes
110011 011 where 011 is crc
–4 votes
–4 votes
Answer is d the no. Of bits u add for n degree poly is n+ 1
by
–8 votes
–8 votes
ans a)

3 Comments

Can you please give detailed explanation?
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seriously she does nt explain anything....
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how are you xoring 1011 with 1001 such that you are taking in the next step 1001?
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Answer:

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