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Comp 222: Telecommunications And Computers Question Paper
Comp 222: Telecommunications And Computers
Course:Bachelor Of Telecommunication And Information Engineering ()
Institution: Kabarak University question papers
Exam Year:2011
KABARAK UNIVERSITY
UNIVERSITY EXAMINATIONS
2011/2012 ACADEMIC YEAR
FOR THE DEGREE OF BACHELOR OF COMPUTER SCIENCE
COMP 222: TELECOMMUNICATIONS AND COMPUTERS
DAY: TUESDAY DATE: 31/07/2012
TIME: 9.00 – 11.00 A.M. STREAM: Y2S2
INSTRUCTIONS:
1. Answer all questions in part one and any two questions in part two
2. Any extra questions answered will not be marked
PART ONE
Question One (30 marks)
a. With regard to telecommunication networks, describe noise and three methods that can be used to reduce the effects of noise. (6 marks)
b. Describe a bandpass filter. (2 marks)
c. A transmission medium has a capacity of 100Kbps and a loss of 30dB. The medium can transmit frequency components between 3200Hz and 9700Hz.
i. Calculate the signal to noise ratio at the output of the medium. (3 marks)
ii. If the noise power at the output of the medium is 6 microwatts determine the signal power at the input of the medium. (3 marks)
d. Encode the data 11100011 using
i. Non return to zero invert code. (2 marks)
ii. Alternate mark inversion code. (2 marks)
e. Give one disadvantage of return to zero code as compared to unipolar code. (2 marks)
f. Describe asynchronous serial transmission. (6 marks)
g. An analog signal with frequency components between 250Hz and 9060Hz is digitized using pulse code modulation. The analog signal is sampled at the Nyquist rate and quantized using 101 quantization levels. Determine the bit rate of the resultant digital signal. (4 marks)
PART TWO
Question Two (20 marks)
a. Describe
i. Frequency modulation. (2 marks)
ii. Phase shift keying. (2 marks)
iii. Quadrature amplitude modulation (2 marks)
b. A digital signal with a bit rate of 7.5Kbps is used to modulate a carrier with a frequency of 15 KHz using QPSK. Determine the maximum and minimum frequency components of the modulated signal. (4 marks)
c. A transmission medium has a bandwidth of 10KHz. Calculate the maximum bit rate at which data can be transmitted on the medium when the following modulation techniques are used.
i. 64QAM. (3 marks)
ii. Frequency shift keying is used to modulate the digital data. Frequencies 2550Hz and 7200Hz are used to represent binary zero and one respectively. (3 marks)
d. What is the disadvantage of
i. Frequency modulation as compared to amplitude modulation. (2 marks)
ii. Amplitude modulation as compared to phase modulation. (2 marks)
Question Three (20 marks)
a. 24 analog signals, each having frequency components between 200Hz and 2400Hz, are frequency division multiplexed (FDM) using a guard band of 600Hz. The multiplexing process uses amplitude modulation.
i. Determine the number of oscillators, modulators, demodulators and bandpass filters required to for the frequency division multiplexing and demultiplexing processes. (4 marks)
ii. What is the use of guard bands in FDM? (2 marks)
iii. Calculate the minimum bandwidth required to transmit the FDM signal. (3 marks)
b. 25 digital signals are time division multiplexed, such that duration of each time slot in the TDM signal is 0.8 milliseconds.
i. Calculate the frame rate of the TDM signal. (2 marks)
ii. If the number of bits per slot is 16, calculate the bit rate of the TDM signal. (2 marks)
c. Using a diagram explain how a TDM bus switch works. (4 marks)
d. What is the main disadvantage of a TSI switch as compared to a TDM bus switch? Explain your answer. (3 marks)
Question Four (20 marks)
a. Describe
i. Time division multiple access. (2 marks)
ii. Reservation access method. (3 marks)
b. Give one advantage of controlled access methods as compared to random access methods. (2 marks)
c. Describe the simple parity error detection method. (5 marks)
d. A checksum error detection scheme uses a checksum of 8 bits. Determine the checksum of the following data.
101011100011001100011101 (3 marks)
e. Describe the Go Back to N automatic repeat request error correction method. (5 marks)
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