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Tlcm 211: Telecommunications Fundamentals Question Paper
Tlcm 211: Telecommunications Fundamentals
Course:Bachelor Of Telecommunication And Information Engineering ()
Institution: Kabarak University question papers
Exam Year:2011
KABARAK UNIVERSITY
UNIVERSITY EXAMINATIONS
2011 ACADEMIC YEAR
FOR THE DEGREE OF BACHELOR OF TELECOMMUNICATIONS
TLCM 211: TELECOMMUNICATIONS FUNDAMENTALS
DAY: FRIDAY DATE: 16/12/2011
TIME: 9.00 – 12 .00 P.M. STREAM: Y2S1
INSTRUCTIONS:
• Answer ALL questions in PART ONE and any THREE questions in PART TWO
PART ONE
Question One (40 marks)
a. Name the three main components of a public switched telephone network (PSTN)
exchange. Describe their functions. (6 marks)
b. Describe the three different types of signaling used in the public switched telephone
network (PSTN). (6 marks)
c. Describe multi-frequency dialing and give two advantages in has over pulse dialing.
(6 marks)
d. Describe, using an example, why a time-space-time (TST) switch has a lower time delay
as compared to a time slot interchanger (TSI) switch. (4 marks)
e. Describe three different situations when the exchange in the public switched telephone
network (PSTN) sends a busy tone to a subscriber attempting to make a telephone call.
(6 marks)
f. A multistage crossbar switch is designed using the following information
• Number of inlets = number of outlets = 1000
• Number of stages = 3
• Number of single stage crossbar switches in first stage = 10
• Number of single stage crossbar switches in second stage = 6
• Number of single stage crossbar switches in third stage = 20
Calculate the number of crosspoints in the multistage crossbar switch. (6 marks)
f. What is a softswitch? (2 marks)
g. Describe two advantages that a telephone operator gains by incorporating intelligent
networks in their telephone networks. (4 marks)
PART TWO
Question Two (20 marks)
a. Using a well labeled diagram explain in detail the frequency division multiplexing and
demultiplexing processes. (6 marks)
b. How many analog signals, each having frequency components between 2200Hz and
4900Hz, can be frequency division multiplexed onto a transmission medium with a
bandwidth of 20 KHz using a guard band of 500Hz. The multiplexer uses amplitude
modulation as the modulation scheme. (4 marks)
c. Explain why synchronization is required in time division multiplexing. (1 mark)
d. Ten analog signals, each with a bandwidth of 3600Hz, are first digitized using pulse code
modulation (PCM) and then time division multiplexed (TDM). The PCM process uses
67 quantization levels. The number of bits per time slot is 20 and 5 framing bits are used
for synchronization purposes. The frame rate of the TDM signal is 200 frames per
second.
i. Calculate the bit rate of the TDM signal. (2 marks)
ii. Calculate the bit rate of each digitized signal. (2 marks)
iii. Calculate the sampling rate used in the digitization process of each analog signal.
(3 marks)
iv. Comment on the accuracy of the digitization process. (2 marks)
Question Three (20marks)
a. Explain why unshielded twisted pair requires more amplifiers than coaxial cable to
transmit a similar signal over the same distance. (3 marks)
b. Give two purposes of cladding used in the construction of fiber optic cables. (3 marks)
c. Describe two reasons why light emitting diodes and laser diodes are suitable for use with
fiber optic cables. (4 marks)
d. Describe how a laser diode operates. (6 marks)
e. Explain why noise is still present in optical communication systems, even though fiber
optic cables are immune to electromagnetic interference. (4 marks)
Question Four (20 marks)
a. Describe
i. Frequency division multiple access (FDMA) (2 marks)
ii. Time division multiple access (TDMA) (2 marks)
b. Describe how the Global Positioning System (GPS) works. (6 marks)
c. Describe two disadvantages of using satellite networks for data transmission as compared
to using optical networks. (4 marks)
d. What is the main advantage of using geosynchronous earth orbit (GEO) satellites as
compared to low earth orbit (LEO) satellites in satellite networks? Describe one method
which can be used to overcome this shortcoming in LEO satellite networks. (4 marks)
e. Describe forward error correction. (2 marks)
Question Five (20 marks)
a. Describe the three ways that a voice over IP (VOIP) call can be made. (6 marks)
b. Describe two advantages that an organization can gain from using VOIP as compared to
using the public switched telephone network (PSTN). (4 marks)
c. What is the advantage of using uni-directional antennas in GSM networks as opposed to
using omni-directional antennas? (3 marks)
d. Describe the handoff process in relation to cellular networks (e.g. GSM networks).
(3 marks)
e. Describe the process of setting up a telephone call on the GSM network. (4 marks)
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