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WLT620S - WIRELESS TECHNOLOGIES - 1ST OPP - NOV 2024 |
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n Am I BIA u n IVER s ITY
OF SCIEnCE Ano TECHnOLOGY
Faculty of Computing and Informatics
Department of Computer Science
QUALIFICATION: BACHELOROF COMPUTERSCIENCE
QUALIFICATIONCODE: 07BCCS& 07BACS
COURSE: WIRELESSTECHNOLOGIES
DATE: NOVEMBER 2024
DURATION: 3 HOURS
LEVEL: 7
COURSECODE: WLT620S
SESSION: 2
MARKS: 100
FIRSTOPPORTUNITYEXAMINATION QUESTION PAPER
EXAMINER(S) PROFDHARM SINGH JAT
MODERATOR: MS LOINI IIVAMBO
THIS QUESTIONPAPERCONSISTSOF FOUR PAGES
(Excluding this front page)
INSTRUCTIONS
1. Write clearly and neatly.
2. Write all your answers in the answer booklet provided.
3. Number the answers clearly.
4. This paper consists of two sections; Section A and B.
5. Answer ALL questions in section A.
6. Answer any 3 questions in section B.
7. Begin each section on a new page.
8. Marks/scores per question are given in [ ].
9. Do not use or bring into the examination venue books, programmable calculators,
mobile devices and other material that may provide you with unfair advantage. Should
you be in possession of one right now, draw the attention of the examination officer
or invigilator.
10. NUST's examination rules and regulations apply.
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SECT/ONA
{40 Marks]
This section contains TWO questions.
Attempt ALLquestions.
Ql Choose the correct answer for each of the following multiple-choice question
[20 marks, 2 marks for each]
(i). In which layer do Wireless LANs implement security measures?
A. System Layer
B. Data Link Layer
C. Sub Layer
D. Multi-Layer
(ii). Which of the following multiple accesstechniques allocates different
time slots for the different users?
A. TOMA
B. CDMA
C. FDMA
D. FGMA
(iii). Five channels, each with a 100-kHz bandwidth, are to be multiplexed
together. What is the minimum bandwidth of the link if there is a need for
a guard band of 10 kHz between the channels to prevent interference?
A. 550 kHz
B. 540 kHz
C. 560 kHz
D. 500 kHz
(iv). What is a cluster in a cellular system?
A. Group of frequencies
B. Group of cells
C. Group of subscribers
D. Group of mobile systems
(v). An administrator receives reports from users in an office that their
802.11 wireless connectivity has been problematic since the installation
of the new wireless phone system. At which of the following frequencies
are both systems operating at to cause this issue?
A. 2.4GHz
B. 900MHz
C. 1.1GHz
D. 6.0GHz
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(vi). A wireless network uses_ waves to transmit signals.
A. Mechanical
B. Sound
C. Radio
D. Water
(vii). Which multiple access technique is used by IEEE802.11 standard for
wireless LAN?
A. CDMA/CA
B. CSMA
C. ALOHA
D. None of the mentioned
(viii). In wireless LAN, there are many hidden stations so we cannot detect the
A. Frames
B. Collision
C. Signal
D. Data
(ix). Which of the following wireless standards has the highest maximum data
rate?
A. 802.lln
B. 802.llb
C. 802.lla
D. 802.11g
(x). In Bluetooth technology, radio waves can communicate with other
Bluetooth devices up to the range of:
A. 60-100 feet
B. 15-50 feet
C. 100-120 feet
D. None of the above
Q2 (i). What is wireless communications? Explain.
[4]
(ii). Give two advantages and two disadvantages of wireless LANs.
[4]
- one mark for each advantage
- one mark for each disadvantage
(iii). Describe frequency division multiplexing in wireless communication.
[4]
(iv). What is the. use of Tethering (Hotspot) in Wireless Networks?
[4]
(v). What is Wi-Fi Protected Access 2 (WPA2)?
[4]
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SECTIONB [60 Marks]
This section contains FOUR questions
Attempt any THREEquestions.
Q3 a)
b)
c)
Assume a spectrum of 960 KHz is allocated over a base frequency for
communication between station A and B.
(i) Divide the entire bandwidth into 4 sub bands.
[4]
(ii) Why do we divide the entire bandwidth into sub-bands?
[2]
(iii) Should we allocate a guard band? Why?
[2]
What is the wavelength if frequency of a radio wave is (a) 151<Hz(b)
[6]
1.5MHz, and (c) 6GHz?
Describe the hidden node problem in wireless network using a diagram? [6]
Q4 a)
b)
What is Multi-path propagation? Explain.
[4]
(i) Of the following, what values are possible for a cluster size in a
cellular topology? Assume a hexagonal geometry: 2, 4, 5, 6, 8, 9, 12, [4]
19, 20
(ii) Explain your answer in (i).
[6]
(iii) What is the Normalised repeat distance for the possible values in (i)? [6]
QS a)
b)
If a total of 36 MHz of bandwidth is allocated to a particular FDD cellular
telephone system which uses two 25 kHz simplex channels to provide full
duplex voice and control channels, compute the number of channels
available per cell if a system uses:
(i). four-cell reuse
[3]
(ii). nine-cell reuse, and
[3]
(iii). 12-cell reuse
[4]
In a full-rate TOMA system used in United States Digital Cellular (USDC) IS-
54 standard the
• duration of a TOMA voice frame= 40ms
• number of time slots in a frame = 6
• number of bits in a voice frame = 1944
• Number of bits in guard band= 6
Calculate
a) the duration of a time slot of a voice frame
[3]
b) the number of bits in a time slot of a voice frame
[3]
[2]
c) the duration of a bit
[2]
d) the duration of guard time
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Q6 a) Draw and explain the Infrastructure wireless local area network (LAN)
[10]
architecture.
b)
i. Explain a Man-In-The-Middle (MITM) attack; use diagrams to aid [7]
your explanation.
ii. Explain also why an attacker may perform the MITH attack.
[3]
GOOD LUCK!
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