Wireless Communication - May 2015

Electronics and Comm. Engg. (Semester 7)

TOTAL MARKS: 100
TOTAL TIME: 3 HOURS (1) Question 1 is compulsory.
(2) Attempt any four from the remaining questions.
(3) Assume data wherever required.
(4) Figures to the right indicate full marks. 1 (a) How co-channel interference and system capacity are related?(7 marks) 1 (b) If 20 MHz of total spectrum is allocated for a duplex wireless cellular system and each simplex channel has 25 kHz RF bandwidth, find:
(i) The number of duplex channels
(ii) The total number of channels per cell site ,if N=4 cell reuse is used(7 marks) 2 (a) If a transmitter produces 50 W of power, express the transmit power in units of (i) dBm and (ii) dBW. If 50 W is applied to a unity gain antenna with a 900 MHz carrier frequency, find the received power in dBm at a free space distance of 100 m from the antenna. What is Pr(10 km)? Assume unity gain for the receiver Antenna.(7 marks) 2 (b) Define and explain mean excess delay, rms delay spread and excess delay spread.(7 marks) 2 (c) Explain coherence time and coherence bandwidth.(7 marks) 3 (a) Which are various multiple access schemes used in wireless communications?(7 marks) 3 (b) Explain any one technique of small-scale multipath measurements.(7 marks) 3 (c) Briefly explain GSM logical channels.(7 marks) 3 (d) With the help of timing parameters, explain frame structure for GSM.(7 marks) 4 (a) How does GSM radio subsystem work?(7 marks) 4 (b) Give differences between HLR and VLR functions.(7 marks) 4 (c) Which are commonly used wireless propagation models? How do they differ?(7 marks) 4 (d) How do diversity techniques help in improving SNR?(7 marks) 5 (a) Discuss the concept of spread spectrum.(7 marks) 5 (b) Explain how power control is achieved in CDMA.(7 marks) 5 (c) With the help of a neat sketch, describe GPRS architecture.(7 marks) 5 (d) Compare Wi-Fi and Wi-MAX system parameters .(7 marks)