UNIVERSITY EXAMINATIONS: 2017/2018
EXAMINATION FOR THE DEGREE OF MASTER OF SCIENCE IN DATA
COMMUNICATIONS/MASTER OF SCIENCE IN INFORMATION SYSTEMS
MDCN5306 MISM5202 WIRELESS NETWORK TECHNOLOGIES
DATE: AUGUST, 2018 TIME: 2 HOURS
INSTRUCTIONS: Answer Question One & ANY OTHER TWO questions.
Question One Total Mark – 20 Compulsory
(a) One of the techniques used in detection and possibly correction of errors in wireless
communications is coding. Cyclic Redundancy Check (CRC) is an example of these
techniques. Assuming that the transmitted data is 1 0 0 1 0 0 and the generator polynomial is
X3 + X + 1 and the received data is 1 0 0 0 0 0 0 0 1, show that the received data is erroneous.
(a) Define the following terms, by use of relevant examples, as they relate to wireless network
i. Fundamental frequency [1 Mark]
ii. Absolute bandwidth [1 Mark]
(c) Explain, in principle, the main difference between Frequency Hoping Spread Spectrum (FHSS)
and Direct Sequence Spread Spectrum (DSSS). [4 Marks]
(d) Briefly explain how WAP enables a mobile device to communicate over the internet.
(e) Discuss the functions of Medium Access Control (MAC) Layer within the Data Link Layer
with particular focus to Wireless communications. [6 Marks]
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Question Two Total Mark – 15
(a) Identify and briefly explain any three (3) differences between 3G and 4G cellular network
generations. [6 Marks]
(b) Briefly discuss the factors that affect the satellite link performance. [6 Marks]
(c) Explain the reasons behind the increase in use of TDM techniques in satellite communications.
Question Three Total Mark – 15
(a) Mobile phone networks use the concept of “frequency re-use” in deployment of their services.
(i) Define frequency re-use and give one fundamental requirement that should govern
frequency re-use. [2 Marks]
(ii) Determine the portion of the frequency band that can be used in one cell in a 4-cell
reuse pattern and 7-cell reuse pattern, assuming a 25 MHz band allocated to the
operator. [2 Marks]
(b) A signal can be looked from two perspectives: as a function of time and a function of
frequency. Differentiate the tow perspectives. [4 Marks]
(c) (i) Explain the difference between Dipole antenna and parabolic reflective antennas. [2 Marks]
(ii) How do the two types of antennas in (c(i)) differ from isotropic antennas? [2 Marks]
(d) Multipath is one of the impairments that wireless transmissions suffer. Multipath is manifested
in three ways. List and briefly explain them. [3 Marks]
Question Four Total Mark – 15
(a) (i) What factors does the receiver need to consider if it is to interpret a received signal correctly?
(ii) Why are these factors important [3 Marks]
(b) With the aid of relevant diagrams using the bit stream provided, describe the following:
0 1 1 0 1 1 1 0 0 1 1
(i) Amplitude Shift Keying (ASK) [2 Marks]
(ii) Frequency Shift Keying (FSK) [2 Marks]
(iii) Phase Shift Keying [2 Marks]
(c) One of the issues of concern in Mobile Ad-hoc Networks (MANETs) is routing. Explain why.