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WLT620S - WIRELESS TECHNOLOGIES - 2ND OPP SUPL - JAN 2023 |
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nAmlBIA unlVERSITY
OF SCIEnCE Ano TECHnOLOGY
Faculty of Computing and Informatics
Department of Computer Science
QUALIFICATION : BACHELOR OF COMPUTER SCIENCE
QUALIFICATION CODE: 07BCCS & 07BACS
CO URSE: WIRELESS TECHNOLOGIES
DATE: JANUARY 2023
DURATION: 3 HOURS
LEVEL: 7
COURSE CODE: WLT620S
SESSION: 2
MARKS: 100
SECOND OPPORTUNITY/SUPPLEMENTARY EXAMINATION QUESTION PAPER
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EXAMINER(S) PROF DHARM SINGH JAT
MODERATOR: MS LOINI IIYAMBO
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THIS QUESTION PAPER CONSISTS OF FOUR PAGES
(Excluding this front page)
INSTRUCTIONS
L. Write clearly and neatly.
L Write all your answers in the answer booklet provided.
J. Number the answers clearly.
,1-. 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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SECT/ONA
{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). What device is the wireless equivalent of a wired hub?
a) bridge
b) repeater
c) antenna
d) access-point
(ii). Which multiple accesstechnique is used by IEEE802.11 standard for
wireless LAN?
a) CDMA
b) CSMA/CA
c) ALOHA
d) d) None of the mentioned.
(iii). 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.
(iv). GSM is a non-cellular network
(a) True
(b) False
(v). What is WPA?
a) wi-fi protected access
b) wired protected access
c) wired process access
d) wi-fi process access.
(vi). 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. At which of the following frequencies
are both systems operating at to cause this issue?
(a) 2.4GHz
(b) 900MHz
(c) 1.1GHz
(d) 5GHz
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(vii). Why is WPA encryption preferred over WEP?
(a) A WPA key is longer and requires more special characters than
the WEP key.
(b) The access point and the client are manually configured with
different WPA key values.
(c) WPA key values remain the same until the client configuration is
changed.
(d) The values of WPA keys can change dynamically while the system
is used.
(viii).
In which layer do Wireless LANs implement security measures?
(a) System Layer
(b) Data Link Layer
(c) Sub Layer
(d) Multi-Layer
(ix). What is the standard form of WI-Fl?
(a) Wired Fidelity
(b) Wired Function
(c) Wirelss Fidelity
(d) None of the option
(x). In a full-rate TOMA system the duration of a TOMA voice frame is 3.72
ms and the number oftime slots in a frame are six (6). The duration of a
time slot of a voice frame is:
(a) 0.57 ms
(b) 0.62 ms
(c) 0.57 s
(d) 3.72 ms
Q2 (i). Explain the hand-off mechanism in mobile communications.
[4]
(ii). What is Time multiplex? Write an advantage and a disadvantage of Time [4]
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 [60Marks]
This section contains FOUR questions
Attempt any THREEquestions.
Q3 a) (i) Draw and explain the architecture of an infrastructure-based IEEE [S]
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 [S]
with two independent Basic service Sets (IBSSs).
-one mark for each correct event in figure (i) [2}
- one mark for each correct statement in figure (i) [3}
- one mark for each correct event in figure (ii)[2]
- one mark for each correct statement in figure (ii)[3}
b) In an full-rate TOMA system used in United States Digital Cellular IS-54
standard, calculate, the duration of guard time is 246µs 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.
[S]
Q4 a)
(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)
b) What are the differences between Ad-Hoc and infrastructure mode?
[S]
Explain.
c) Why does wireless networking use CSMA/CA instead of CSMA/CD? [S]
Explain.
QS a)
b)
If the frequency of a radio wave is 30 GHz, what is the wavelength of the [4]
wave (velocity of light=3x108m/s)?
(i). From the values 1, 3, 4, 6, 12, 19 what values are possible for a
(12]
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]
(i)?
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Q6 a)
b)
If allocated frequency spectrum is 900-924 MHz for a duplex wireless
cellular system and each simplex channel has 30 kHz RF bandwidth. Find
(i). The number of duplex channels
[3]
(ii). Compute the number of channels available per cell if a system [3]
uses:
[4]
(a) four-cell reuse and
(b) seven-cell reuse
The allocated frequency spectrum is 900-924 MHz for a duplex wireless
cellular system which uses two 30 kHz simplex channel to provide full
duplex voice and control channels. If 960 KHz of the allocated spectrum is
dedicated to control channels,
(i) find the total number of control channels and voice channels [3]
available in the system
(ii) determine an equitable distribution of control channels and voice
channels in each cell for each of the following systems.
[3]
(a) four-cell reuse and
(b) seven-cell reuse
[4]
GOOD LUCK!
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