28,784 views

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. $110010010011$

CRC Calculation

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

XOR of 1100 and 1001 is 101

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

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.

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

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.
110011 011 where 011 is crc
Answer is d the no. Of bits u add for n degree poly is n+ 1
by
ans a)

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