EUROPEAN UNIVERSITY CYPRUS | SCHOOL OF SCIENCE
DEPARTMENT OF COMPUTER SCIENCE AND ENGINEERING | FALL 2013 SEMESTER
CSC322 – DATA COMMUNICATIONS AND COMPUTER NETWORKS – ASSIGNMENT(S) 1 & 2
SET ON MONDAY 18-NOV-2013  DUE ON MONDAY 25-NOV-2013 (BY 23:59)
BY ANDREAS GRONDOUDIS
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Answer the following questions
Questions
1. What is a PDU (Protocol Data Unit)?
How are PDUs used?
2. Define the term wavelength
3. For any signal, which is greater (wider),
absolute or effective bandwidth?
4. What happens to the data rate if we
half the bandwidth?
5. Which type of signals is more
susceptible to noise, analog or digital?
6. A transmission system is using 8 signals
levels and has a bandwidth of 2GHz,
what (according to Nyquist) is the
channel capacity?
7. A signal with fundamental frequency of
200
MHz
is
(using
Fourier)
approximated using the first 7
components frequencies. What is the
absolute bandwidth of this signal?
Explain your answer
8. The same signal as above is (using
Fourier) approximated using the first 17
component frequencies. What is the
absolute bandwidth of this signal?
9. Given the signals in questions 7 and 8, if
they were used in a channel utilizing 2
signal levels; what will their respective
capacities be (according to Nyquist)?
Answers
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10. An optical fiber link is right next to a
power cable. Is it affected by
interference and why?
11. What does microwave require that
broadcast radio does not?
12. NRZI encodes a zero as what?
13. What is the common feature between
the Manchester and Differential
Manchester encoding schemes?
14. How does Manchester encode a 1 bit?
15. In multilevel encoding techniques,
which is better Bipolar AMI or
Pseudoternary?
16. What is scrambling and why is it used
for?
17. Given 2 signals one with frequency f
and another with a frequency of 3f,
which of the two attenuates more and
why?
18. The signal to noise ratio of a line is very
high. Is this bad or good and why?
19. List (just list) wireless transmission
impairments?
20. How does binary frequency shift keying
work?
21. What is quantizing noise?
22. Parity is not able to detect which type
of errors?
23. A MODEM (using asynchronous
transmission) is transmitting the 7
character word Andreas. Assuming that
each character will be encoded to 7
bits, and that parity is not used, and
that the stop element is 2 bits long,
how many bits will be needed to
transmit the word? (Please explain your
answer)
24. What is the Hamming distance between
the following streams:
a. 01000 and 01011
b. 01111 and 01000
c. 10101 and 01010
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For questions 25-28 below, the following codeword mapping has been used:
Data
000
001
010
100
Codeword
11111
10101
00000
11000
25. What is the minimum distance of the
codeword set?
26. Given the answer to above question
what is the maximum number of error
bits that this set can detect?
27. If the following stream: 10010 was
received; what can you say about it?
(explain your answer)
28. If the following stream: 10001 was
received; what can you say about it?
(explain you answer)
29. If we are encoding MFSK with 16
frequencies, then how many bits can
we encode? (explain you answer)
30. Theoretically speaking, if we combined
a shift keying scheme with 8
frequencies and 4 of those where using
two different amplitudes and the other
4 were using two different phases then
how many bits would we be able to
encode? (explain your answer)
31. Consider
the
scenario
(again
theoretically) that we now have 8
frequencies and all 8 can have 2
different amplitudes as well as 4
different phases. How many bits would
we be able to encode now? (again,
please explain your answer)
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32. If Delta Modulation was used to encode the information, what would the resulting bit stream
be?
15
10
5
0
1
2
3
4
5
6
7
8
9
10 11 12 13 14 15 16 17 18 19 20
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33. Using decimal (rather than binary)
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arithmetic, given a dividing pattern of
256; calculate a 3 digit CRC number that
must be inserted after the number
564378. (See footnote 1 on this)
1
Similar to the example seen in class and explained on the ‘additional’ slides for chapter 6