# cs601 assignment 3 solution fall 2019 2020

**Question No. 1 **

Suppose a message consisting of following four-bit numbers is being sent to a destination. By writing all necessary calculation steps, you are required to calculate four-bit Checksum number, the sender will append with the original message:

9, 8,11, 15, 14

**Solution:**** **

Sum of the numbers= 9+8+11+15+14=57

(9, 8, 11, 15, 14) is the message appended with the checksum where 57 is the sum of original numbers.

Here the = 9+8+11+15+14 are 4-bits because each number is less than 15

The number57 cannot be written in 4-bits

The number 57 is equal to (111001)2 which is also greater than 4-bits

To change it to 4-bits number we add extra left most bit to the right four bits as shown below

Left bits=(11)2 , right four bits=(1001)2

(1110)2=14 which is 4-bits

**Question No. 2 **

Considering the Generator Polynomial (Divisor): X3+1, by writing all necessary calculations steps involved in Cyclic Redundancy Check, you are required to determine the codeword of the following data word:

10110

**Solution:**** **

Polynomial=X3+1, the degree of polynomial is three

The divisor will be X3+1=1001

**Question No. 3**

Find the Polynomials equivalent of bits given in the following table:

Bits |
Polynomial |

1010000 |
X7+X5+0 |

10001001 |
X8+X4+1 |

1010000 |
X7+X5+0 |

10001001 |
X8+X4+1 |