GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER-VII (NEW) EXAMINATION - WINTER 2018
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Subject Code: 2171004 Date: 26/11/2018Subject Name: Wireless Communication
Time: 10:30 AM TO 01:00 PM Total Marks: 70
Instructions:
1. Attempt all questions.
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2. Make suitable assumptions wherever necessary.3. Figures to the right indicate full marks.
MARKS
Q.1 (a) Why hexagonal cell shape is preferred in cellular architecture? 03
(b) Illustrating the upgrade paths 2G and 3G cellular network and describe in brief. 04
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(c) Draw and Explain GSM system architecture. 07Q.2 (a) Explain the following terms : 03
(i) Cell dragging (ii) RSSI (iii) Dwell time
(b) Explain the concept of frequency reuse in cellular system. 04
(c) For a regular hexagonal geometry show that co-channel reuse ratio is 07
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Q = v3N, where N= i2+ij+j2.OR
(c) If a signal to interference ratio of 15 dB is required for satisfactory 07
forward channel performance of a cellular system, what is the
frequency reuse factor and cluster size that should be used for
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maximum capacity if the path loss exponent is (1) n=4 (2) n=3 ?Assume that there are six co channel cells in the first tier and all of
them are at the same distance from the mobile. Use suitable
approximations.
Q.3 (a) Briefly describe Hand-off strategies in cellular system. 03
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(b) Briefly explain different channel assignment strategies. 04(c) Consider a transmitter which radiates a sinusoidal carrier frequency 07
of 1850 Mhz. For a vehicle moving 60 mph, compute the received
carrier frequency if the mobile is moving:
i. Directly toward the transmitter.
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ii. Directly away from the transmitter.iii. In a direction which is perpendicular to the direction of arrival of transmitted signal.
OR
Q.3 (a) Explain the concept of umbrella cell. 03
(b) Mention the techniques to improve the capacity in cellular system 04
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and explain any one.(c) A unit gain antenna with a maximum dimension of 1 m produces 50 07
W power at 900 MHz. Find (i) the transmit power in dBm and dB,
(ii) the received power at a free space distance of 5 m and 100 m.
Q.4 (a) What is Brewster angle? 03
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(b) Explain: 1-persistent CSMA, non-persistent CSMA, p-persistent 04CSMA.
(c) Explain free space propagation model with necessary equations. 07
OR
Q.4 (a) What is Huygen's principle? 03
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(b) Compare TDMA, FDMA and CDMA techniques. 04(c) Describe the various outdoor propagation models. 07
Q.5 (a) Explain three types of soft handoffs in IS-95 standard. 03
(b) Compare Wi-Fi and WIMAX. 04
(c) Explain the working of UWB radio. Discuss the features, advantages 07
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and disadvantages of UWB technology.OR
Q.5 (a) Give the classification of GSM channels. 03
(b) Determine frame efficiency of a TDMA frame structure used in 04
GSM system.
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(c) Write a short note on OFDM. 07--- Content provided by FirstRanker.com ---
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