Review Questions
1. What is white noise and how does it affect a signal?

2. What is impulse noise and why is it the most disruptive?

5. What is jitter and why is it a digital signal problem?

10. What is the ratio of check bits to data bits for longitudinal parity?

11. What types of errors will simple parity not detect?

13. What is a generating polynomial?

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14. What types of errors will cyclic checksum not detect?

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15. Frame relay practices which form of error control?
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16. How many packets can be sent at one time using Stop-and-wait ARQ?

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19. In communication systems, what does timeout mean?

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21. What is the difference between Go-back-N ARQ and Selective-reject ARQ?

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Exercises

1. Which type of noise is the most difficult type of noise to remove from an analog signal? Why?

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2. Which type of noise is the most difficult type of noise to remove from a digital signal? Why?

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7. Generate the parity bits and longitudinal parity bits for even parity for the characters 0101010, 0011010, 0011110, 1111110, and 0000110.

8. List the types of errors that can escape a cyclic redundancy checksum system.

11. In a Stop-and-wait ARQ system, Station A sends packet 0, and it is lost. What happens next?

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14. In a sliding window system with Go-back-N ARQ, Station A sends packets 0, 1, 2, 3, 4, 5, and 6. Packet 0 arrives corrupted. What does Station B send back to Station A? What is Station A's response?

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15. In a sliding window system with Selective-reject ARQ, Station A sends packets 0, 1, 2, 3, 4, 5, and 6. Packet 0 arrives corrupted. What does Station B send back to Station A? What is Station A's response?

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16. What might be the only disadvantage of the Selective-reject ARQ method as compared to the Go-back-N ARQ method?

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17. Assume a sliding window protocol has a 3-bit field to hold the window size. A 3-bit value gives 8 combinations, from 0 to 7. Why then can a transmitter send out only a maximum of seven packets at one time and not eight? Show an example.
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18. If a 7-bit sliding window size is used, how many packets can be sent before the transmitter has to stop and wait for an acknowledgment?

19. Is Stop-and-wait ARQ a half duplex protocol or a full duplex protocol? Explain your response.