Question

.a) Obtain the CRC code word for the data bit sequence (10011101) using the generator 1001 .b) For the resulted codeword show the steps performed by the receiver to check message correctness

Answer 1

solution @ Given bit sequence = 10011101 generator code = 1001. number of bits in generator = 4 so we add 4-1 bit to the given sequence. : bit sequence = 10011101000 1000l100 1001100111oooo 1001111 00001 0000 OoU OOOO 0110 00001 1101 1001 O1000 1001 000100€ Reminder we add Reminderin bit sequence ;: 10011101000 Too 10011101100 CRC for it sequence =10011101100

- 6 At Receiver side, It Receives message as 1001 101100 then receiver again calculate modulo division of received bit sequence by using generator lool if reminder is o then it deceived a correct message: 10ool 10011101100 1001 00001 000011 00011 Ooooh oollo ooooh 11011 TODI 01001 100 l wa 000000 K Reminder is o Hence receiver receives correct message.

Summary: To obtain CRC code we do modulo division between bit sequence and generator then we concat reminder to the original bit sequence and transmit it. At receving side we again do modulo division between received bit sequence and generator if we get reminder zero(0) then we receive correct message otherwise error in received bit sequence.