UNIVERSITY EXAMINATIONS: 2013/2014
ORDINARY EXAMINATION FOR THE BACHELOR OF SCIENCE
IN INFORMATION TECHNOLOGY
BIT 4302 TELECOMMUNICATIONS
DATE: APRIL, 2014 TIME: 2 HOURS
INSTRUCTIONS: Answer Question ONE and any other TWO
QUESTION ONE
(a) Explain why error-correction rarely used in data communication networks
(4 Marks)
(b) Consider a real-time network such as a one that is a part of a manufacturing
process or a chemical process. Assume that the network must carry regularly
scheduled time-sensitive commands and measurements between physical devices
and the computerized control system. Would a networking technology based on
TDM be more or less desirable than one based on CSMA/CD? Why? (5 Marks)
(c) There are three major categories of threat that lead to unauthorized access: War
drivers, Hackers (Crackers) and Employees. Describe how each of these lead to
unauthorized access. (6 Marks)
(d) Describe briefly the following telecommunications standards as they apply to
WANs:
i. EIA/TIA-232 (2 Marks)
ii. V.35 (2 Marks)
(e) State four benefits of the GSM technology. (4 Marks)
(f) Describe delay distortion as a transmission impairment and explain how it can be
dealt with in a communication system. (4 Marks)
(g) i. State the Nyquist Sampling Theorem. (1 Mark)
ii. State two ways in which the similarity of the reconstructed signal (at the
receiver) to the original analog signal can be improved. (2 Marks)
QUESTION TWO
(a) The table below highlights wireless technologies that exist on the PAN, LAN and
WAN. Please fill in the blank spaces in the table. (6 Marks)
PAN LAN WAN
Standards
Speed
Range
Applications
(b) Differentiate between connection-oriented and connectionless systems in relation
to packet-switched networks. (4 Marks)
(c) Packet-switched networks may establish routes through the switches for particular
end-to-end connections. These routes are called virtual circuits. A VC is a logical
circuit created within a shared network between two network devices. In this
regard, describe the following:
i. Permanent Virtual Circuit (PVC) (3 Marks)
ii. Switched Virtual Circuit (SVC) (3 Marks)
(d) One of the factors to consider in choosing a WAN connection option is the traffic
requirements. What does this entail? (4 Marks)
QUESTION THREE
(a) Discuss any three network quality issues that affect converged networks.
(6 Marks)
(b) Briefly describe the following types of noise in data communications:
i. Thermal noise (2 Marks)
ii. Inter-modulation Noise (2 Marks)
iii. Crosstalk (2 Marks)
(c) Discuss briefly the importance of error detection and correction, flow control and
recovery in data communications. (5 Marks)
(d) Describe briefly the three standard methods used to connect your computer to
GPRS mobile phone. (3 Marks)
QUESTION FOUR
(a) Describe the sequence of events that occur between computer and modem during
communication. (7 Marks)
(b) Telecommunications and computer networks enable voice, video and data
transfer; in doing so, they enable organizations to optimize their resources by
grouping employees. In relation to this, describe the following:
i. Main office (2 Marks)
ii. Telecommuters (2 Marks)
iii. Mobile users (2 Marks)
(c) There are three key factors that influence network uptime/availability. State these
three factors and illustrate how they affect availability. (5 Marks)
(d) Explain briefly the unlicenced frequency bands. (2 Marks)
QUESTION FIVE
(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. (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
iii. Define probability of call blocking (2 Marks)
(b) In the 2G mobile phone network, a user engaged in a conversation has an
outgoing message on one channel and an incoming message on another channel.
i. State the UPLINK frequency band and DOWNLINK frequency band as
used in the GSM900 system in Kenya. (2 Marks)
ii. A user is communicating on channel 893.6 MHz uplink channel. Determine
the downlink channel. (2 Marks)
(c) Sketch a diagram showing the basic architecture of a 2G mobile phone network,
giving the function of at least four components of the network. (8 Marks)
