## December 17, 2011

### CELLULAR AND MOBILE COMMUNICATIONS ECE JNTU previous years question papers

Time: 3 hours Max Marks: 80

Answer any FIVE Questions

All Questions carry equal marks

1. (a) Explain the terms GSM & GPRS.
(b) Write notes on Digital cellular systems. [8+8]

2. (a) For a cellular system, If blocking probability is 40% and assuming each subscriber generates 0.1 Erlangs traffic load, find the no. of. subscribers if no. of channels are
i. 1
ii. 5
iii. 10
iv. 20
v. 100. Use Erlang B model charts.
(b) In a total 33MHz of BW allocated to a particular FDD system which uses two 25kHZ simplex channels to provide full duplex voice & control channels. Compute the no. of channels available per cell if a system uses:
i. four cell reuse
ii. seven cell reuse
iii. 12 cell reuse.
1 MHz of allocated spectrum is dedicated to control channels. Determine a equitable distribution of control & Voice channels in each cell for each of three systems. [8+8]

3. Explain the designing of the directional antenna, for k=4, k=12 and k=7 with all suitable values explaining each of them, consider a noise margin of 6dB. [16]

4. (a) From the free space propagation model derive the equation for received power.
(b) Discuss Lee model of point to point propagation. [6+10]

5. (a) What are the different synthesis of sum pattern? Explain them briefly.
(b) What are the antennas used at cellsite? Explain them. [8+8]

6. (a) What type of messages are received to the set up channels when the mobile unit monitors strongest signal strength?
(b) What are the advantages of Reuse-partition scheme?
(c) What is channel sharing and channel borrowing?7. (a) What are the different types of handoffs? Explain how to implement them?
(b) Define a dropped call rate and explain how it differ from blocked call? [10+6]

8. (a) Explain the significance of SIM in Mobile station.
(b) What is the function of transcoder rate adoption unit in BSS?
(c) What are the different kinds of downlink common channels?

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