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WLT620S - WIRELESS TECHNOLOGIES - 2ND OPP - JAN 2024 |
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nAmlBIA unlVERSITY
OF SCIEnCE Ano TECHnOLOGY
FACULTYOF COMPUTING AND INFORMATICS
DEPARTMENTOF COMPUTERSCIENCES
QUALIFICATION:BACHELOROF COMPUTERSCIENCE
QUALIFICATIONCODE: 07BCCS& 07BACS
COURSECODE: WLT620S
SESSION:JANUARY2024
DURATION: 3 HOURS
LEVEL: 7
COURSENAME: WIRELESSTECHNOLOGIES
PAPER: PAPER1
MARKS: 100
SECONDOPPORTUNITY/SUPPLEMENTARYEXAMINATION QUESTION PAPER
EXAMINER(S) PROF DHARM SINGH JAT
MODERATOR: MS LOINI IIYAMBO
INSTRUCTIONS
1. Answer ALL the questions in section A and any THREEquestions in section B.
2. Read all the questions carefully before answering.
3. Number the answers clearly
4. NUST's examination rules and regulations apply.
THIS QUESTION PAPERCONSISTSOF FOUR PAGES{Excluding this front page)
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SECT/ONA
{40Marks]
Thissection contains TWO questions.
Attempt ALLquestions.
Q1 Choose the correct answer for each of the following multiple-choice question
[20 marks, 2 marks for each]
(i). Garage door opener is a............
a) Transmitter
b) Receiver
c) Transceiver
d) d. None of the above.
(ii). A wireless network uses_ waves to transmit signals.
A. Mechanical
8. Sound
C. Radio
D. Water
(iii). Five channels, each with a 100kHz 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
8. 540 kHz
C. 560 kHz
D. 500 kHz
(iv). Which multiple accesstechnique is used by IEEE802.11 standard for
wireless LAN?
A. CDMA/CA
8. CSMA
C. ALOHA
D. None of the mentioned.
(v). In wireless LAN, there are many hidden stations so we cannot detect the
A. Frames
8. Collision
C. Signal
D. Data
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(vi). 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
(vii). What is handoff?
A. Forward channel
B. Switching technique
C. Roamer
D. Guard channel
(viii). Carrier frequency of a TV remote control is in the range
A. 50 MHz-100 MHz
B. 500 MHz- 1 GHz
C. of Infrared
D. lGHz- 2 GHz.
(ix). 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
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
(x). In wireless ad-hoc network
A. access point is must
B. nodes are not required
C. none of the mentioned
D. access point is not required
Q2 (i). Explain wireless communications.
[4]
(ii). Give two advantages and two disadvantages of wireless LANs.
[4]
(iii). Describe frequency division multiplexing techniques in wireless
[4]
communication.
(iv). Explain how multipath propagation affects signal quality.
[4]
(v). Explain the frequency reuse concept in GSM.
[4]
2
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SECTIONB {60Marks]
Thissection contains FOUR questions
Attempt any THREEquestions.
Q3 a)
Given a bandwidth of 15 MHz and a frequency reuse factor of one (01) and
Radio Frequency (RF)channel size of 1.25 MHz and 38 calls per RFchannel,
find
(a) The number of RFchannels for CDMA.
[SJ
(b) The number of permissible calls per cell (CDMA).
[SJ
b) Consider GSM, which is a TDMA/FDD system that uses 25MHz of
bandwidth for the uplink and 25MHz of bandwidth for the downlink. This
25MHz bandwidth is divided into 125 TOMA channels. EachTOMA channel
consists of 8 user timeslots, and if no guard band is assumed.
Find the total
(a) number of simultaneous users that can be supported in the GSM [SJ
system and
(b) the channel bandwidth of each user.
[SJ
Q4 a)
If GSM uses a frame structure where each frame consists of eight {08) time
slots, and each time slot contains 156.25 bits, and data are transmitted at
270.833 kbps in the channel, find
(a) the time duration of a bit,
(3]
(b) the time duration of a slot,
(3]
(c) the time duration of a frame,
(3]
(d) how long must a user occupying a single time slot wait between 131
two successive transmissions?
b) What is frequency Reuse? How is it used in the GSM Cellular network?
[8J
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QS a)
b)
Explain the functions of the Physical layer and Data link layer in a wireless [8J
and mobile environment.
Draw MSK signal for the data 10110 and frequencies are shown in
[8J
following figure of Minimum Shift Keying {MSK).
clata
low
frequem:s'.'·
high
frequency
c) What is the wavelength if frequency of a radio wave is {a) 15 kHz {b)
[4J
30kHz.
Q6 a) (i) Draw and explain the architecture of an infrastructure-based IEEE [SJ
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 [SJ
with two independent Basic service Sets {IBSSs).
b) What does SSIDstand for when using a WiFi network?
[SJ
c) What is the use of Tethering (Hotspot) in Wireless Networks?
[SJ
GOOD LUCK!
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