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Com 430E: Ata Communication, Antennas And Propagation Question Paper
Com 430E: Ata Communication, Antennas And Propagation
Course:Data Communication
Institution: University Of Eldoret question papers
Exam Year:2016
UNIVERSITY OF ELDORET
SCHOOL OF SCIENCE
DEPARTMENT OF MATHEMATICS AND COMPUTER SCIENCE
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UNIVERSITY EXAMINATIONS
2015/2016 ACADEMIC YEAR.
FOURTH YEAR, SECOND SEMESTER: EXAMINATION FOR THE DEGREE OF BACHELOR OF SCIENCE IN COMPUTER SCIENCE
REGULAR EXAMINATIONS
COURSE CODE: COM 427E
COURSE TITLE: DATA COMMUNICATION, ANTENNAS AND PROPAGATION
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INSTRUCTIONS TO CANDIDATES ANSWER QUESTION ONE (COMPUSARY) AND ANY OTHER TWO QUESTIONS - DURATION OF THE EXAMINATION: 3 HOURS
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QUESTION ONE (30 Marks)
a). Differentiate between the following terminologies as used in data communication.
i. analog data and digital data. (2 marks)
ii. Analog signal and digital signal (2 marks)
iii. Period and frequency (2 marks)
iv. Data rate and baud rate (2 marks)
b). One of the major functions of the physical layer is to move data in the form of electromagnetic signals across a transmission medium. Explain why? (3 marks)
c). What is a composite signal according to Fourier analysis? (4 marks)
d). Discuss the following line encoding schemes.
i. Unipolar scheme (2 marks)
ii. Non-Return-Zero (NRZ- I) (2 marks)
iii. Polar Schemes (2 marks)
iv. Non-Return-Zero (NRZ- L) (2 marks)
e). An analog signal carries 4 bits per signal element. If 1000 signal elements are sent per second, find the bit rate. (2 marks)
f). Discuss the principle and applications of an omnidirectional antenna.(2 marks)
QUESTION TWO (20 Marks)
a). A very important consideration in data communications is how fast we can send data, in bits per second over a channel. Identify three (3) factors that data rate depends on.(3 marks)
b). Discus the listed theoretical formulas:
i. Noiseless channel: Nyquist Bit Rate (4 marks)
ii. Noisy channel: Shannon capacity (4 marks)
c). We need to send 265 kbps over a noiseless channel with a bandwidth of 20 kHz. How many signal levels do we need? 3 marks)
d). We can calculate the theoretical highest bit rate of a regular telephone line. A telephone line normally has a bandwidth of 3000 Hz (300 to 3300 Hz) assigned for data communications. The signal-to-noise ratio is usually 3162. Calculate the capacity of the channel. (3 marks)
e). Identify any three characteristics of microwave propagation. (3 marks)
QUESTION THREE (20 Marks)
a). Explain the following network performance characteristics. (4 marks)
i. bandwidth
ii. throughput
iii. Latency
iv. jitters
b). One important issue in networking is the performance of the network and how good is. Calculate the following with regard to network performance:
i. A network with bandwidth of 10 Mbps can pass only an average of 12,000 frames per minute with each frame carrying an average of 10,000 bits. What is the throughput of this network? (2 marks)
ii. What is the propagation time if the distance between the two points is 12,000 km? Assume the propagation speed to be 2.4 × 108 m/s in cable. (2 marks)
iii. What are the propagation time and the transmission time for a 2.5-kbyte message (an e-mail) if the bandwidth of the network is 1 Gbps? Assume that the distance between the sender and the receiver is 12,000 km and that light travels at 2.4 × 108 m/s. (2 marks)
iv. What are the propagation time and the transmission time for a 5-Mbyte message (an image) if the bandwidth of the network is 1 Mbps? Assume that the distance between the sender and the receiver is 12,000 km and that light travels at 2.4 × 108 m/s. (2 marks)
c). Distinguish between amplitude shift keying (ASK), frequency shift keying (FSK), and phase shift keying (PSK).
QUESTION FOUR (20 Marks)
a). Discus the following serial transmission modes:
i. Asynchronous transmission (3 marks)
ii. Synchronous transmission (3 marks)
iii. Isochronous transmission (3 marks)
b). Why Quadrature PSK (QPSK) is considered a better mechanism. (5 marks)
c). Find the bandwidth for a signal transmitting at 12 Mbps for QPSK. The value of d=0.
(2 marks)
d). Discus the concept of a constellation diagram. (4 marks)
QUESTION FIVE (20 Marks)
a). Distinguish between the following:
i. Bit rate and frequency (2 marks)
ii. Bit length and wavelength (2 marks)
b). A digital signal is a composite and analog signal with an infinite bandwidth. Why?
(6 marks)
c). Identify and explain four types of noise in a transmission media. (8 marks)
d). State the importance of ionospheric. (2 marks)
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