Sheet 7 (Chapter 10)

Transcription

1 King Saud University College of Computer and Information Sciences Department of Information Technology CAP240 First semester 1430/1431 Multiple-choice Questions Sheet 7 (Chapter 10) 1. Which error detection method consists of a parity bit for each data unit as well as an entire data unit of parity bits? 2. Which error detection method uses ones complement arithmetic? 3. Which error detection method consists of just one redundant bit per data unit? 4. Which error detection method involves polynomials? 5. If the ASCII character G is sent and the character D is received, what type of error is this? a. Single-bit b. Multiple-bit c. Burst error d. Recoverable 6. If the ASCII character H is sent and the character I is received, what type of error is this? a. Single-bit b. Multiple-bit c. Burst d. Recoverable Dr. Gihan NAGUIB 1

2 7. In cyclic redundancy checking, what is the CRC? a. The divisor b. The quotient c. The dividend d. The remainder 8. In cyclic redundancy checking, the divisor is the CRC a. The same size as b. 1 bit less than c. 1 bit more than d. 2 bits more than 9. If the data unit is , the divisor 1010, and the remainder 110, what is the dividend at the receiver? a b c d If the data unit is and the divisor 1010, what is the dividend at the transmitter? a b c d If odd parity is used for ASCII error detection, the number of 0s per 8-bit symbol is a. Even 8. Odd c. Indeterminate d The sum of the checksum and data at the receiver is if there are no errors. a. -0 b. +0 c. The complement of the checksum d. The complement of the data 13. The Hamming code is a method of a. Error detection b. Error correction c. Error encapsulation d. (a)and(b) Dr. Gihan NAGUIB 2

3 14. In CRC there is no error if the remainder at the receiver is a. Equal to the remainder at the sender b. Zero c. Nonzero d. The quotient at the sender 15. In CRC quotient at the sender. a. Becomes the dividend at the receiver b. Becomes the divisor at the receiver c. Is discarded d. Is the remainder 16. Which error detection method involves the use of parity bits? c.crc d. (a) and (b) 17. Which error detection method can detect a single-bit error? h. Two-dimensional parity check d. All the above 18. At the CRC generator, added to the data unit before the division process. a. 0s are b. 1s are c. A polynomial is d. A CRC remainder is 19. At the CRC generator, added to the data unit after the division process. a. 0s are b. ls are c. The polynomial is d. The CRC remainder is 20. At the CRC checker, means that the data unit is damaged. a. A string of Os b. A string of ls c. A string of alternating Is and Os d. A nonzero remainde Dr. Gihan NAGUIB 3

4 Exercises 21. What is the maximum effect of a2-ms burst of noise on data transmitted at: a bps? b. 12,000 bps? c. 96,000 bps? 22. Assuming even parity, find the parity bit for each of the following data units. a b c d A receiver receives the bit pattern If the system is using even parity, is the pattern in error? 24. A sender sends l; the receiver receives If simple parity is used, can the receiver detect the error? Explain your answer. 25. A system uses two-dimensional parity. Find the parity unit for the following two data units. Assume even parity Find the parity bits for the following bit pattern, using simple parity. Do the same for two-dimensional parity. Assume even parity The following block is received by a system using two-dimensional even parity. Which bits are in error? A system using two-dimensional even parity sends a block of 8 bytes. How many redundant bits are sent per block? What is the ratio of useful bits to total bits? 29. If a divisor is , how many bits long is the CRC? 30. Given a 10-bit sequence and a divisor of 1011, find the CRC. Check your answer. 31. Given a remainder of 111, a data unit of , and a divisor of 1001, is there an error in the data unit? 32. Find the checksum for the following bit sequence. Assume a 16-bit segment size Dr. Gihan NAGUIB 4

5 33. Add and in ones complement. Interpret the result. 34. For each data unit of the following sizes, find the minimum number of redundancy bits needed to correct one single-bit error a. 12 b 16 c. 24 d Construct the Hamming code for the bit sequence Find the binary equivalent of x 8 +x 3 + x Find the polynomial equivalent of A receiver receives the code When it uses the Hamming encoding algorithm, the result is Which bit is in error? What is the correct code? 39. Find out how many redundant bits should be in a 10-bit codeword to detect an error.? 40. The code word was received. Using the Hamming encoding algorithm, what is the original data sent? Dr. Gihan NAGUIB 5