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WLT620S - WIRELESS TECHNOLOGIES - 2ND OPP - JAN 2025 |
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nAm I BIA un IVERSITY
OF SCIEnCE Ano TECHnOLOGY
Faculty of Computing and Informatics
Department of Computer Science
QUALIFICATION: BACHELOROF COMPUTERSCIENCE
QUALIFICATIONCODE: 07BCCS& 07BACS
COURSE: WIRELESSTECHNOLOGIES
DATE:JANUARY2025
DURATION: 3 HOURS
LEVEL: 7
COURSECODE: WLT620S
SESSION: 2
MARKS: 100
SECONDOPPORTUNITY/SUPPLEMENTARYEXAMINATION QUESTION PAPER
EXAMINER(S) PROFDHARM SINGH JAT
MODERATOR: MS LOINI IIYAMBO
THIS QUESTIONPAPERCONSISTSOF FOUR PAGES
(Excluding this front page)
1. Write clearly and neatly.
INSTRUCTIONS
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). What is an access point (AP) in a wireless LAN?
A. device that allows wireless devices to connect to a wired network
B. wireless devices itself
C. both (A) and (B)
D. none of the mentioned.
(ii). Which multiple accesstechnique is used by IEEE802.11 standard for
wireless LAN?
A. CDMA
B. CSMA/CA
C. ALOHA
D. None of the mentioned.
(iii). What causes the fading of the received radio signals in a mobile
communication environment?
A. Direct propagation
B. Multipath Propagation
C. Bi-path Propagation
D. None of the above
(iv). What is Wired Equivalent Privacy (WEP)?
A. security algorithm for ethernet
B. security algorithm for wireless networks
C. security algorithm for USBcommunication
D. none of the mentioned.
(v). The shape of the cellular region for maximum radio coverage is
A. circular
B. square
C. oval
D. hexagon.
(vi). What is the primary goal of a Man-in-the-Middle (MITM) attack?
A. Unauthorized access to sensitive information
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B. Encryption of files for ransom
C. Intercepting and manipulating communication between two
parties
D. Disrupting network services
(vii). Which of the following is a type of wireless communication?
A. LAN
B. WAN
C. PAN
D. All of the above
(viii).
Which of the following specifies a set of rnedia access control (MAC) and
physical layer specifications for implementing WLANs?
A. IEEE802.11
B. IEEE802.16
C. IEEE802.15
D. IEEE802.3
(ix). An administrator receives reports from users in an office that their
802.llg wireless connectivity has been problematic since the installation
of the new wireless phone system. Which of the following frequencies are
both systems operating at to cause this issue?
A. 2.4GHz
B. 900MHz
C. 1.1GHz
D. 5GHz
(x). In which layer do Wireless LANs implement security measures?
A. System Layer
B. Data Link Layer
C. Sub Layer
D. Multi-Layer
Q2 (i). Explain the hand-off mechanism in mobile communications.
[4]
(ii). What is Time multiplex? State one advantage and one disadvantage of. [4]
Time multiplexing system in wireless communication.
(iii). Explain two functions of the Physical layer in a wireless and mobile [4]
environment.
(iv). What is Wi-Fi Protected Access 2 (WPA2)?
[4]
(v). Give two features of ZigBee technology.
[4]
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SECTIONB {60 Marks]
This section contains FOUR questions
Attempt any THREEquestions.
Q3 a) (i) Draw and explain the architecture of an infrastructure-based IEEE [5)
802.11 WLAN with two access points or Basic service Sets (BSSs).
(ii) Draw and explain the architecture of IEEE802.11 ad-hoc wireless LANs [5)
with two independent Basic service Sets (IBSSs).
b) In a full-rate TOMA system used in United States Digital Cellular IS-54
standard, calculate, the duration of guard time is 123µs, and the speed of
light is 300000km/sec).
Calculate the
(a) The maximum total round-trip distance
[5)
(b) Maximum distance between cell site and mobile.
[5)
Q4 a)
b)
c)
(i). Given an 802.11 WLAN, draw a medium access and inter-frame [4)
spacing that shows the three different parameters that define the
priorities of medium access.
(ii). Explain the following inter-frame spacing:
[2)
(a) Short inter-frame spacing (SIFS)
[2)
(b) PCFinter-frame spacing (PIFS)
[2)
(c) DCFinter-frame spacing (DIFS)
Describes the Exposed node problem in wireless network using diagram? [5)
Why does wireless networking use CSMA/CA instead of CSMA/CD? [5)
Explain.
Q5 a) What is the wavelength if the frequency of a radio wave is (a) 301<Hz(b) [4)
300MHz, and (c) 3THz?The velocity of light is 3x108m/s.
b)
(i). From the values 2, 3, 5, 6, 7, 13, 17,18, 21 what values are
[12)
possible for a cluster size in a cellular topology if we use a
hexagonal cell geometry. Explain your answer.
(ii). What is the Normalised repeat distance for the possible values in [4)
part (i)?
Q6 a)
If the allocated frequency spectrum is 900-949MHz for a duplex wireless
cellular system which uses two 35 kHz simplex channels to provide full
duplex voice and control channels. If 1050 l<Hzof the allocated spectrum
is dedicated to control channels
(i). The total number of duplex channels
[4)
(ii). Compute the number of channels available per cell if a system
uses:
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(a) four-cell reuse and
[4]
(b) nine cell reuses
[4]
b) If the allocated frequency spectrum is 900-949MHz for a duplex wireless
cellular system which uses two 35 kHz simplex channels to provide full
duplex voice and control channels. If 1050 l<Hzof the allocated spectrum
is dedicated to control channels. Find the total number of
(i). control channels and
[4]
(ii). voice channels available in the system
[4]
GOOD LUCI<!
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