Assignment5

CHAROTAR INSTITUTE OF TECHNOLOGY, CHANGA

Sub: DCN-I

Assignment5: Error Detection and Correction

Class: 4CE2

Last Date: 21/3/07

Que: 1 Short Question:

1. What are the difference between packet errors and bit errors?
2. What are even and odd parity?
3. What is the difference in between a single bit error and a burst error?
4. What are the different types of redundancy checks used in data communication?
5.  What kind of error VRC can detect?
6.  What is LRC?
7. Is CRC superior to LRC? Why?
8. What is an error syndrome?
9. Which error detection method uses one’s complement arithmetic?
10. Which error detection method consists of just one redundant bit per data?
11. Which error detection method involves polynomials?
12. Let a protection switch on a D53 (45 Mbps) takes 10ms to complete. What is the worst case error burst length?
13. In cyclic redundancy checking, the CRC is ______. [the divisor, the quotient, the dividend, the remainder]
14. Hamming code is a method of _____. [error detection, error correction, both]
15. CRC can detect all burst of up to m errors, if generator polynomial G(x) is of ___ degree. [m, m-1, m+1, one]
16. Find the binary equivalent of

x8 + x3 + x +1

1. If a divisor is 101101, how many bits long is the CRC.
2. Find the polynomial equivalent of 100001110001.
3. Find the complement of 1110010001110011
4. Error detection is usually done in the ____ layer of the OSI model. [Physical, Data link, Network].

Que: 2 Give answer:

1. Calculate the VRC and LRC for the following bit pattern using even parity.

0011101 1100111 1111111 0000000 [May 2004]

1. Given a 10-bit sequence 1010011110 and a divisor of 1011, find the CRC. Check your answer.
2. Discuss VRC and LRC mechanism for error detection. [May 2005]
3. Generate CRC code for the data 11001 with divisor 1001. Also perform CRC checking procedure. [ May 2005]
4. Construct the Hamming Code for the bit sequence 10011101
5. The code 11110101101 was received. Using the Hamming encoding algorithm, what is the original code sent?
6. A receiver receives the code 11001100111. When it uses the Hamming encoding algorithm, the result is 0101. Which bit is in error? What is the correct code?
7. What kind of error is undetected by checksum?
8. What is the formula to calculate the number of redundancy bits required to correct a bit error in a given number of data bits?
9. What are the conditions for the polynomial used by CRC generator?