UNIVERSITY EXAMINATIONS: 2013/2014
ORDINARY EXAMINATION FOR THE BACHELOR OF SCIENCE
IN INFORMATION TECHNOLOGY
BIT 3107 WIRELESS NETWORKS TECHNOLOGIES
DATE: APRIL, 2014 TIME: 2 HOURS
INSTRUCTIONS: Answer Question ONE and any other TWO
QUESTION ONE
(a) Discuss why wireless LANs (WLANs) have become so popular. (6 Marks)
(b) Portable communications have become an expectation in many countries around
the world. You can see portability and mobility in everything from cordless
keyboards and headsets, to satellite phones and global positioning systems (GPS).
The mix of wireless technologies in different types of networks allows workers to
be mobile. In this regard, state the standards, speed and applications for LAN
and WAN wireless technologies. (6 Marks)
LAN WAN
Standards
Speed
Applications
(c) The transmission of radio waves is influenced by three major factors. Describe
these factors. (6 Marks)
(d) With the aid of a diagram illustrate the three non-overlapping channels that are
available within 802.11b and 802.11g standards and explain why this is necessary
(5 Marks)
(e) Define the following terminologies in relation to satellite communications:
i. Earth Stations (1 Mark)
ii. Uplink (1 Mark)
iii. Downlink (1 Mark)
iv. Transponder (1 Mark)
v. Elevation angle (1 Mark)
(f) Differentiate between synchronous transmission and asynchronous transmission.
(2 Marks)
QUESTION TWO
(a) Sketch a diagram showing the basic architecture of a 2G mobile phone network,
giving the function of at least four components of the network. (9 Marks)
(b) 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. (4 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) 2 Marks
(c) State five benefits of the GSM technology. (5 Marks)
QUESTION THREE
(a) With the aid of diagrams, explain how satellites operate. (6 Marks)
(b) State two advantages and two disadvantages of the GEO satellite orbit. (4 Marks)
(c) State three satellite link performance factors. (3 Marks)
(d) What are the factors affecting the minimum elevation angle of a satellite earth
stations antenna (>0o
)? (3 Marks)
(e) i. Differentiate between Fixed-assignment multiple access(FAMA) and Demand-
assignment multiple access (DAMA) (2 Marks)
ii. Describe a typical GEO satellite frequency allocation (2 Marks)
QUESTION FOUR
(a) State any four features of Bluetooth network. (4 Marks)
(b) Much like a traditional wired LAN, a WLAN is a grouping of computers and
peripheral devices that share a common communications backbone. As is implied
by the name, a WLAN allows users to connect to the LAN wirelessly via radio
transmission. Describe any three most common components of a WLAN.
(6 Marks)
(c) Those unfamiliar with wireless technology commonly confuse 802.11b and
Bluetooth technologies. Both technologies use the 2.4 GHz radio frequency for
wireless communications; however, the goal, focus, and concept of Bluetooth is
different from 802.11b wireless networking. Discuss. (6 Marks)
(d) Explain briefly four major criteria that a data communication network must meet.
(4 Marks)
QUESTION FIVE
(a) PCM (Pulse Code Modulation) is the process in which a signal is sampled, and
the magnitude of the each sample with respect to a fixed reference is quantized
and converted by coding to a digital signal.
i. Define sampling, quantization and encoding. (3 Marks)
ii. State Nyquist Sampling Theorem (2 Marks)
iii. Voice has frequency ranging from (approximately) 0 to 4000 Hz. To
reconstruct the signal when digitized, at what rate should samples be taken?
(2 Marks)
(b) Two enterprise-level encryption mechanisms specified by 802.11i are certified as
WPA and WPA2 by the Wi-Fi Alliance: Temporal Key Integrity Protocol (TKIP)
and Advanced Encryption Standard (AES). Discuss how these enhance security.
(7 Marks)
(c) Explain briefly three features of
i. Circuit switching. (3 Marks)
ii. Packet switching (3 Marks)
