August
1999 QUESTION 2 Total Marks: 20 Marks |
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| Channel allocation is
a procedure of dividing the communication facility (the media) in a manner that maximizes
the channel capacity. The allocation procedure is independent of the media access control
technique. Access Control deals with how to regulate the use of a shared medium.
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| (a) | Explain what is meant by multiplexing in the
context of data communications.
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[2] |
| (b) | How does the statistical time division
multiplexing (Statmux) make it possible that twelve 1200bps terminals could share a
composite line with a rate of only 4800bps? What line capacity would a synchronous TDM
multiplexer need in order to support the same terminals?
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[4] |
| (c) | Briefly explain Code Division Multiplexing
(CDM).
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[4] |
| (d) | What is the full form of the acronym CSMA/CD?
What media access technique does CSMA/CD employ? Briefly explain this technique.
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[6] |
| (e) | Explain why random backoff is important in the
media access technique described in part (d).
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[4] |