(ii) Explain Cyclic Redundancy Check (CRC). Given a data message D(x)= 1100001 a Generator polynomial G(x) = x³ +1. Calculate the codeword at the sender side. Als do the calculations on the receiver side.

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### Cyclic Redundancy Check (CRC)

**Problem Statement:**
Given a data message \( D(x) = 1100001 \) and Generator polynomial \( G(x) = x^3 + 1 \). Calculate the codeword at the sender side. Also do the calculations on the receiver side.

**Solution:**

#### 1. Introduction to CRC
Cyclic Redundancy Check (CRC) is a method used in digital networks and storage devices to detect accidental changes to raw data. The CRC employs a generator polynomial to perform binary division of the input data and appends the remainder of this operation to the input data to form the codeword.

#### 2. Given:
- Data message \( D(x) \): 1100001
- Generator polynomial \( G(x) \): \( x^3 + 1 \)

#### 3. Steps at the Sender Side:
1. **Append Zeros:**
   - Append \( n \) zeros to the end of \( D(x) \), where \( n \) is the degree of \( G(x) \). 
   - Degree of \( G(x) = 3 \)
   - Modified data message: \( 1100001000 \)
   
2. **Binary Division:**
   - Perform binary division of the modified data message by the generator polynomial.
   - The generator polynomial \( G(x) = x^3 + 1 \) corresponds to 1001 in binary.
   - Use XOR division (each division step will be modulo 2).

3. **Calculate Remainder:**
   - The remainder after the binary division will be the CRC.

4. **Form Codeword:**
   - Append the CRC remainder to the original data message to form the codeword.

#### 4. Example Calculation:
Let's break down the binary division:

1. **Initial Data Message**: \( 1100001000 \)
2. **Generator Polynomial**: \( 1001 \)

#### Binary Division Steps (simplified overview):

- Perform XOR starting from the leftmost bit where we encounter a '1':

\[
\begin{aligned}
1100 001000 \quad \text{(Initial Step)} \\
1001 & \quad \text{XOR} \\
\hline
0101000 \\
\end{aligned}
\]

- The process continues, repeatedly applying the XOR and bringing down the next bit until all
Transcribed Image Text:### Cyclic Redundancy Check (CRC) **Problem Statement:** Given a data message \( D(x) = 1100001 \) and Generator polynomial \( G(x) = x^3 + 1 \). Calculate the codeword at the sender side. Also do the calculations on the receiver side. **Solution:** #### 1. Introduction to CRC Cyclic Redundancy Check (CRC) is a method used in digital networks and storage devices to detect accidental changes to raw data. The CRC employs a generator polynomial to perform binary division of the input data and appends the remainder of this operation to the input data to form the codeword. #### 2. Given: - Data message \( D(x) \): 1100001 - Generator polynomial \( G(x) \): \( x^3 + 1 \) #### 3. Steps at the Sender Side: 1. **Append Zeros:** - Append \( n \) zeros to the end of \( D(x) \), where \( n \) is the degree of \( G(x) \). - Degree of \( G(x) = 3 \) - Modified data message: \( 1100001000 \) 2. **Binary Division:** - Perform binary division of the modified data message by the generator polynomial. - The generator polynomial \( G(x) = x^3 + 1 \) corresponds to 1001 in binary. - Use XOR division (each division step will be modulo 2). 3. **Calculate Remainder:** - The remainder after the binary division will be the CRC. 4. **Form Codeword:** - Append the CRC remainder to the original data message to form the codeword. #### 4. Example Calculation: Let's break down the binary division: 1. **Initial Data Message**: \( 1100001000 \) 2. **Generator Polynomial**: \( 1001 \) #### Binary Division Steps (simplified overview): - Perform XOR starting from the leftmost bit where we encounter a '1': \[ \begin{aligned} 1100 001000 \quad \text{(Initial Step)} \\ 1001 & \quad \text{XOR} \\ \hline 0101000 \\ \end{aligned} \] - The process continues, repeatedly applying the XOR and bringing down the next bit until all
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