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Ccs 208:Data Communications Question Paper
Ccs 208:Data Communications
Course:Bachelor Of Science In Computer Science
Institution: Maseno University question papers
Exam Year:2016
INSTRUCTIONS:
Answer ALL questions in SECTION A and any other TWO from SECTION B
SECTION A:30 MARKS
Question 1:
a)(i)What is data communication?(1mk)
ii)State the five components that make up data communication system?(5mks)
b)(i)Differentiate between networks and topologies and give two examples in each .(3mks)
ii)State the three criteria necessary for an effective and efficient network and explain the essence of each.(3mks)
c)(i)State the difference between communication standards and protocols. (1mk)
ii)State the two categories of data communications standards. (1mk)
iii)Why are standards necessary in communication?(1mk)
d)Outline the advantages and disadvantages of the following network topologies: (8mks)
i)Mesh
ii)Star
e)(i)An analog signal carries 4 bits in each signal unit.If 500 signal units are transmitted per second ,find the bandwidth and bit rate. (2mks)
ii)Data signal occupying a frequency band of 2.4kHz is used to modulate a carrier of frequency of 100kHz.If amplitude modulation is used,determine the bandwidth of the modulated signal.(2mks)
f)(i)Define Baud rate and bit rate. (2mks)
ii)If the interval between two samples in a digitized signal is 125us,what is the sampling rate?(1mk)
SECTION B:EACH 20 MARKS
Question 2:
a)State the Nyquist sampling theorem in signal transmission.(2mks)
b)Determine the maximum bit rate for noiseless channel having a bandwidth of 3kHz,transmitting a signal with 4 signal levels.(5mks)
c)A channel has a signal to noise ratio (SNR) of 63 and a bandwidth of 1mHz,determine its bit rate.(4mks)
d)A signal travels from point A to point B .At point A,the signal power is 100watts and at point B,the signal is 80watts.Determine the attenuation (loss) in dB.(3mks)
e)State the three transmissions impairment and briefly explain the effect of each.(6mks)
Question 3:
a)(i)Explain the difference between guided and unguided transmission media.(4mks)
ii)State the three modes of wireless communications. (3mks)
b)State the areas of application for which the following media are suited. (3mks)
i)Coaxial cable
ii)Optical fibre
iii)Twisted pair
c)For each of the following networks,explain the consequences if a connection fails.(8mks)
i)Five devices connected in a star topology.
ii)Five devices connected in a ring topology
d)i)Differentiate between periodic and aperiodic signal(1mk)
ii)A periodic signal completes one cycle in 0.1 milliseconds, determine its frequency (1mk)
Question 4:
a)(i)State one advantage and one disadvantage of Amplitude Shift Keying(ASK).(2mks)
ii)Draw the constellation diagram for 8-QAM,assuming two amplitude and four phases .(4mks)
b)(i)Explain the essence of multiplexing in signal transmission and state three multiplexing techniques that may be used.(5mks)
ii)In u-law ,the T-2 lines offer a 6.312 Mbps service. Explain why this number is not 4 X 1.544 Mbps.(2mks)
c)(i)State four advantages of using an optical fibre as a transmission mmedium (2mks)
ii)Sketch a typical loss characteristic for optical fibres and indicate the transmission windows.(3mks)
iii)State the source(at least four) of fibre losses.(2mks)
Question 5:
a)Differentiate between half and full duplex data transmission. (4mks)
b)Explain the following terms as used in data communications: (6mks)
i)Circuit switching
ii)Message switching
iii)Packet switching
c)(i)Explain how parity bits can be used in error detection in data communication system. (4mks)
ii)What are the limitations of parity bit method as a means of detecting and correcting errors?(2mks)
d)Sketch the output wave form for the following modulation techniques if the input is 1101001.(4mks)
i)PSK
ii)FSK
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