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MNA810S - MOBILE NETWORKS AND ARCHITECTURES - 2ND OPP - JULY 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 HONOURS
QUALIFICATION CODE: 08BCHC
LEVEL: 8
COURSE: MOBILE NETWORKS AND
ARCHITECTURES
DATE: JULY 2023
COURSE CODE: MNA810S
. •.
SESSION: ' 1
DURATION: 3 HOURS
MARKS: 100
SECOND OPPORTUNITY/ SUPPLEMENTARY EXAMINATION QUESTION PAPER
EXAMINER(S) PROF DHARM SINGH JAT
MODERATOR: DR LINCH MAGAGULA
THIS QUESTION PAPER CONSISTS OF 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.
{40Marks]
SECT/ONA
{40Marks]
This section contains TWO questions.
Attempt All questions.
This section contains TWO questions.
Attempt All questions.
Ql Choose the correct answer for each of the following multiple-choice questions.
[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). What is the Normalised repeat distance when a cluster size in a cellular
topology is 13:
A. 6.5
B. 13.0
C. 3.6
D. 2.0
(iii). The shape of the cellular region for maximum radio coverage is
A. circular
B. square
C. oval
D. hexagon.
(iv). Which of the following is a component of a 3G network architecture?
A. User Equipment (UE)
B. Radio Access Network (RAN)
C. Core Network
D. All of the options
(v). 3G W-CDMA is also known as
A. UMTS
B. DECT
C. DCS-1800
D. ETACS
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(vi). IMSI stands for?
A. Internet Mobile Subscriber Identity
B. International Mobile Subscriber Identity
C. International Mobile Subscriber Identification
D. International Mobility Subscriber Identity
(vii). A wireless network uses _ waves to transmit signals.
A. Mechanical
B. Radio
C. Sound
D. Water
(viii). Which multiple accesstechnique is used by IEEE802.11 standard for
wireless LAN?
A. CDMA
B. CSMA/CA
C. ALOHA
D. None of the mentioned.
(ix). What causes 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
(x). Which of the following is part of a BSS(Base Station Subsystem) in a GSM
network?
A. BTS- BaseTransceiver Station
B. BSC- Base Station Controller
C. BTSand BSC
D. None
Q2 (i). Write two functions of the Mobility Management (MM) protocol in UMTS. [4]
(ii). Write two functions of the eNB in E-UTRANsystems.
[4]
(iii). What is the difference between LTEFDDand LTETDD?
[4]
(iv). Why is Temporary Mobile Subscriber Identity (TMSI) required when we [4]
have an international mobile subscriber identity (IMSI)?
(v). Explain how CSMA/CA solves the Hidden and exposed terminals problems. [4]
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SECTION B {60Marks]
This section contains FOUR questions
Attempt any THREE questions.
Q3 a)
A TDMA/FDD-based GSM cellular system has a band of 25 MHz for the
forward link, divided into radio channels of 200 kHz each. Suppose eight [8]
speech channels (time slots) are supported on a single radio channel.
Calculate the maximum number of simultaneous subscribers that can be
accommodated in the GSM system.
b) The GSM System uses a frame structure where each frame consists of
eight-time slots and each time slot contains 156.25 bits, and data is
transmitted at 270.833 kbps in the channel, find:
a. Time duration of a bit
[3]
b. Time duration of a slot
[3]
C. Time duration of a frame
[3]
d. How long must a user occupy a single slot and wait between two
[3]
simultaneous transmissions?
Q4 a)
b)
Consider a cellular system in which the total available voice channels to
handle the traffic are 960. The area of each cell is 6 km2• and the total
coverage area of the system is 2000 km2. Calculate:
(a) The system capacity in terms of total number of channels if the
cluster size N is 4
[4]
(b) The system capacity in terms of total number of channels if the
[4]
cluster size is 7.
(c) How many times would a cluster of size 4 have to be replicated to [4]
cover the entire cellular area? Does decreasing N increase the
system capacity? Explain.
Consider two scenarios: 1. A simple high-power transmitter that can [8]
support 100 voice channels covering a given service area. 2. Let the service
area be divided into seven smaller area cells, as shown in figure below,
each supported by a lower power transmitter. The available spectrum of
100 voice channels is divided into four groups of 25 channels each. The
cells (1,7), (2,4), (3,5) and 6 are assigned distinct four channel groups.
Show that the total number of channels that can be supported by the
second scenario is enhanced to 175 to cover the same service area as the
first scenario.
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Q5 a) If a total of 33 MHz of bandwidth is allocated to a particular FDD cellular
~ystem
which uses two 25 kHz simplex channels to provide full
dtrp·l-exvoice and control channels, compute the number of duplex
channels available per cell if the system us.es:
(i). four-cell reuse
[3]
(ii). seven-cell reuse, and
[3]
(iii). 12-cell reuse.
[4)
b) A total of 33 MHz of bandwidth is allocated to a particular FDD cellular [3]
telephone system which uses two 25 kHz simplex channels to provide full [3]
duplex voice and control channels. If 1 MHz of the allocated spectrum is [4]
dedicated to control channels, determine an equitable distribution of
control channels and voice channels in each cell for each of the three
systems.
(i). four-cell reuse
(ii). seven-cell reuse, and
(iii). 12-cell reuse.
Q6 a) With the help of an appropriate diagram, explain the basic steps of
[8]
Mobile originated call (MOC).
b) With the help of an appropriate diagram discuss how Encryption is [6]
achieved in a GSM network.
c) What is the difference between LTEFDDand LTETDD?
[6]
GOOD LUCK!
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