CRC

Question 1
A computer network uses polynomials over GF(2) for error checking with 8 bits as information bits and uses x3+x+1 as the generator polynomial to generate the check bits. In this network, the message 01011011 is transmitted as
A
01011011010
B
01011011011
C
01011011101
D
01011011100
       Computer Networks        CRC       Gate 2017 set-01
Question 1 Explanation: 
Given CRC generator polynomial =x3+x+1
=1∙x3+0∙x2+1∙x1+1∙x0
=1011
Message =01011011

So, the message 01011011 is transmitted as
Question 2
The message 11001001 is to be transmitted using the CRC polynomial x3+1 to protect it from errors. The message that should be transmitted is:
A
11001001000
B
11001001011
C
11001010
D
110010010011
       Computer Networks        CRC       Gate-2007
Question 2 Explanation: 
CRC polynomial = x3+1 [∵ In data 3-zero’s need to be append to data]
= 1001

∴ Data transmitted is: 11001001011
There are 2 questions to complete.