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WLT620S - WIRELESS TECHNOLOGIES - 1ST OPP - NOV 2022 |
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nAmlBIA UnlVERSITY
OF SCIEn CE Ano TECHn OLOGY
Faculty of Computing and Informatics
Department of Computer Science
QUALIFICATION : BACHELOR OF COMPUTER SCIENCE
-QUALIFICATION CODE: 07BCCS & 07BACS
LEVEL: 7
COURSE: WIRELESS TECHNOLOGIES
COURSE CODE: WLT620S
DA fE: NOVEMBER 2022
SESSION: 2
DURATION: 3 HOURS
MARKS: 100
EX,l\\MINER(S)
FIRST OPPORTUNITY EXAMINATION QUESTION PAPER
PROF DHARM SINGH JAT
MODERATOR: MS LOINI IIYAMBO
THIS QUESTION PAPER CONSISTS OF FOUR PAGES
(Excluding this front page)
l. Write clearly and neatly.
INSTRUCTIONS
:~. Write all your answers in the answer booklet provided.
3. Number the answers clearly.
•l. This paper consists of two sections; Section A and B.
!;. Answer ALL questions in section A.
1:i. Answer any 3 questions in section B.
'7. Begin each section on a new page.
:3. 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.
LO.NUST's examination rules and regulations apply.
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SECrtONA
[40Marks]
This section contains TWO questions.
Attempt ALL questions.
Ql Choose the correct answer for each of the following multiple-choice question
[20 marks, 2 marks for each]
(i). A wireless network uses_ waves to transmit signals.
(a) Mechanical
(b) Sound
(c) Radio
(d) Water
(ii). 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 l0kHz between the channels to prevent
interference?
(a) 550 kHz
(b) 540 kHz
(c) 560 kHz
(d) 500 kHz
(iii). Which multiple accesstechnique is used by IEEE802.11 standard for
wireless LAN?
(a) CDMA/CA
(b) CSMA
(c) ALOHA
(d) None of the option
(iv). In wireless LAN, there are many hidden stations so we cannot detect the
(a) Frames
(b) Collision
(c) Signal
(d) Data
(v). Why is the size of the cell kept small in a cellular network?
(a) Increase capacity
(b) Decrease capacity
(c) Increased size of base station electronics
(d) Slow process of handoffs
(vi). Assume a spectrum of 90 kHz is allocated over a base frequency for
communication between station A and B. A whole spectrum is divided in
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(vii).
(viii).
to six (6) equal channels.
The allocated frequency spectrum for each user and number of
simultaneous users are:
(a) Spectrum of 15 kHz and six users
(b) Spectrum of 60 kHz and three users
(c) Spectrum of 20 kHz and three users
(d) Spectrum of 30 Hz and two users
Wireless LANs implement security measures in the
(a) System Layers.
(b) Data Link Layers.
(c) Sub Layers.
(d) Multi Layers
Which of the following wireless standards has the highest maximum data
rate?
(a) 802.lln
(b) 802.llb
(c) 802.lla
(d) 802.llg
(ix). In Bluetooth technology radio waves can communicate with other
Bluetooth devices upto the range of:
(a) 60-100 feet
(b) 15-50 feet
(c) 100-120 feet
(d) None of the option
(x). In wireless distribution system
(a) multiple access point are inter-connected with each other
(b) there is no access point
(c) only one access point exists
(d) none of the option
Q2 (i). Explain wireless communications?
[4]
(ii). Give two advantages and two disadvantages of wireless LANs.
[4]
- one mark for each advantage
- one mark for each disadvantage
(iii). Explain how is the separation of the different channels for wireless
[4]
communication achieved in Time division multiplexing.
(iv). Give the name of any two devices operating in the 2.4 GHz range.
[4]
(v). Explain two functions of the Data Layer in a wireless and mobile [4]
environment.
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SECTIONB [60Marks]
This section contains FOUR questions
Attempt any THREEquestions.
Q3 a)
b)
Assume a spectrum of 480 KHz is allocated over a base frequency for
communication between station A and B.
(i) Divide the entire bandwidth into 4 sub bands.
[4]
[2]
(ii) Why do we divide the entire bandwidth into sub-bands?
[2]
(iii) Should we allocate a guard band or not? Motivate your answer
What is the wavelength if the frequency of a radio wave is (a) 15KHz (b) [6]
1.5MHz, and (c) 6GHz?
c) Describe how CSMA/CA solves the Hidden and Exposed terminals [6]
problems.
Q4 a) Explain Multi-path propagation?
[4]
b) (i) Which of the following values are possible for a cluster size in a
cellular topology?
[4]
Assume a hexagonal geometry: Assume a hexagonal geometry: 5, 8,
11, 13, 20, 21.
(ii) Explain your answer in (i).
[6]
(iii) What is the Normalised repeat distance for the possible values in (i)? [6]
Q5 a)
If a total of 33 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) Find the total number of channels available in the system
[3]
(ii) Compute the number of channels available per cell if a system uses:
(a) four-cell reuse and
[3]
(b) seven-cell reuse
[4]
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b) In an 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
[3]
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
[2]
c) the duration of a bit
[2]
d) the duration of guard time
Q6 a) Draw and explain the following Mode in Wireless Networking:
[6]
(i) Infrastructure Mode and
(ii) Ad-Hoc mode
[6]
b) Describe how a man-in-the-middle attack may be performed on a Wi-Fi [4]
network and the consequences of such an attack.
c) What is the use of Tethering (Hotspot) in Wireless Networks?
[4]
GOOD LUCK!
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