UNIVERSITYexampapers.nust.na/greenstone3/sites/localsite/collect...SECTION A [40Marks] This section...
Transcript of UNIVERSITYexampapers.nust.na/greenstone3/sites/localsite/collect...SECTION A [40Marks] This section...
I‘IFIITI’IBIH UNIVERSITY
OF scuznce nnD TECHI‘IOLOGY
Faculty of Computing and Informatics
Department of Computer Science
QUALIFICATION: BACHELOR OF COMPUTER SCIENCE HONOURS
QUALIFICATION CODE: OSBCHCLEVEL: 8
COURSE: MOBILE NETWORKS AND
ARCHITECTURESCOURSE CODE: MNA81OS
DATE: JULY 2017 SESSION: 2
DURATION: ZHOURS MARKS: 100
SUPPLEMENTARY/SECOND OPPORTUNITY EXAMINATION QUESTION PAPER
EXAMINER(S): PROF DHARM SINGH JAT
MODERATOR:DR LINOH MAGAGULA
sopofipwsnesvrve
THIS QUESTION PAPER CONSISTS OF THREE PAGES
(Excluding this front page)
INSTRUCTIONS
Write clearly and neatly.Write all your answers in the answer booklet provided.Number the answers clearly.
This paper consists of two sections; Section A and B.
Answer ALL questions in section A.
Answer any 3 questions in section B.
Begin each section on a new page.
Marks/scores per question are given in H.
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.
SECTION A
[40Marks]
This section contains two questions.
Attempt all questions.
Q1
Q2
8)
b)
b)
Explain functions of the Physical layer and Data link layer in a wireless and
mobile environment.
- 2 marks for each correct statement for each layer
(i). Give 4 advantages of wireless LANs.
(ii). Give 4 disadvantages of wireless LANs.
- one mark for each advantage- one markfor each disadvantage
What are the differences between Ad-Hoc and infrastructure mode?
Explain.- two marks for each correct statement.
Describe 4 multiplexing techniques in wireless communication.
Give an example for each technique.- three marks for each multiplexing technique.
Describe how CSMA/CA solves the Hidden and exposed terminals
problems.- two marks for each correct statement.
[8]
[4]
[4]
[4]
[12]
[8]
SECTION B
[60Marks]This section contains four questions
Attempt any three questions.
QB a)
bl
Q4 a)
b)
C)
Q5 a)
bl
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). One-cell reuse
(ii). four-cell reuse
(iii). seven-cell reuse
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. If 1 MHz of the allocated spectrum is
dedicated to control channels, determine an equitable distribution of
control channels and voice channels in each cell for each of the three
systems.
(i). One cell reuse
(ii). four-cell reuse
(iii). Seven-cell reuse
What is a good code for CDMA?
Explain how multipath propagation affects signal quality.
Consider a sender A wants to send the data bit 1 with key = 100101 and a
sender B wants to send the data bit 0 with key = 010110. Assume we code
a binary 0 as -1, a binary 1 as +1. Both signals are transmitted at the same
time. The noise to the transmitted signal is (0, +1, -1, 0, 0, ~1).
(i.) What signal is received by a receiver?
(ii.) What can the receiver detect for sender A and B respectively?
Why is hexagonal cell shape preferred over square or triangular cell shapes
to represent the cellular architecture?
What would be the minimum distance between the centers of two cells
with the same band of frequencies if cell radius is 1 km and the reuse factor
is 12?
[3]
[3]
[3]
[3]
[4]
[4]
[4]
[4]
l6]
[6]
[4]
[4]
06
C)
d)
a)
Generate orthogonal variable spreading factor (OVSF) code from a set of
orthogonal codes for UMTS communication systems which are primarilyused to preserve orthogonality between different channels in a
communication system.
Assume the root has depth 0 and depth of the tree is 4.
[Each correct depth = 1 Mark]
Illustrate how fixed TDM patterns are used to implement multiple access
and a duplex channel between a base station and mobile station in DECT
cordless phone system.
Discuss the two spread spectrum techniques with the help of a diagram.
Network and signaling are crucial aspects of any cellular mobile
communication network.
i) Describe the roles of the VLR and HLR.
ii) Give two roles of the MSC in a GSM network.
GOOD LUCK
[8]
[4]
[12]
A