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Electronics and Communication Engineering
EC 1451 – MOBILE COMMUNICATION
(Common to B.E. (Part – Time) Seventh Semester Regulation 2005)
Time : Three hours Maximum : 100 marks
Answer ALL questions.
PART A – (10 X 2 = 20 marks)
1. Define coherence bandwith.
2. Define grade of service?
3. What is meant by soft handoff? What are the advantages does it have?
4. What are piconets?
5. What is air interference.
6. Draw the frame structure of GSM.
7. What are the advantages of the 2 ray ground reflection model in the analysis of path loss?
8. What is Doppler shift?
9. Explain adjkacent channel interface.
10. In an FDMA system the total spectrum bandwidth is 12.5 mHZ. Each channel is of 30 kHZ and the guard band is 10 k?HZ. Find the total number of channels available in the system.
PART B – (5 X 16 = 80 marks)]
11. (a) (i) Explain the various methods of increasing the capacity of users in cellular system.
(ii) Show that the frequency reuse factor for a celluar system is given by k/S, where k is the average number of channels per call and S is the total no of channels available.
(b) (i) Explain the procedure for making a call from a mobile to another mobile.
(ii) Explain how the interference between the base and the mobile transmission is reduced in PCS.
12. (a) (i) Explain how the diffraction affects the signal propagation using knife edge diffraction model.
(ii) Explain the propagation of signal in outdoor using Durkin’s Model.
(b) What are the types of small scale fading. Explain each fading effects in detail.
13. (a) (i) Explain the generation and detection of GMSK signal.
(ii) Discuss the nonlinear equalization methods using Maximum likelihood sequence estimation (MLSE).
(b) (i) What are the benefits of RAKE receiver?
(ii) Draw the constellation points of 16-QAM signal and derive the average probability error.
14. (a) (i) Explain the LPC vocoder and determine the predictive coefficients.
(ii) Explain the working of GSM codec with block diagram.
(b) (i) Draw the frame structure of TDMA and derive its efficiency.
(ii) Derive the equation to calculate the number of users in a CDMA cellular system.
15. (a) (i) What are the advantages and disadvantages of WLL.
(ii) Draw the functional block of DECT systems and explain its working principle.
(b) (i) Explain the forward and reverse channel parameters in IS-95 CDMA.
(ii) Explain the GSM system architecture and give its protocol specifications.