Set No. 1

Code No: R05420401

1. (a) Discuss analog cellular system (AMPS) in detail.

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IV B.Tech II Semester Regular Examinations, Apr/May 2009 CELLULAR AND MOBILE COMMUNICATIONS ( Common to Electronics & Communication Engineering and Electronics & Telematics) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆

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(b) Discuss the special features in AMPS and compare them with 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 1 5 10 20 100. Use Erlang B model charts.

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i. ii. iii. iv. v.

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(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.

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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. (a) Write notes on power control and diversity receiver. (b) Explain the different types of Noncochannel interference.

[10+6]

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4. (a) Determine the phase difference between direct path and reflected path. (b) Explain mobile propagation through obstructive path.

[8+8]

5. (a) Write the equation of general pattern for a 2N elements array equi-spaced by a separation ‘d’. (b) Differentiate between Roof-mounted and glass-mounted antennas. (c) What are the advantage of using umbrella pattern antennas at cell site? [4+6+6]

6. (a) Explain the following operational functions of access channels: 1 of 2

Set No. 1

Code No: R05420401 i. FOCC ii. RECC. (b) Write the channel sharing algorithm.

[8+8]

7. (a) Explain how to calculate the number of handoffs per call? (b) What are the circumstances where handoffs are necessary but cannot be made? [6+6+4]

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(c) Explain how a handoff is initiated? 8. (a) Explain the various logical GSM channels.

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(b) Explain the SSD update message flow from Base Station to Mobile Station and vice versa. [8+8]

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Set No. 2

Code No: R05420401

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IV B.Tech II Semester Regular Examinations, Apr/May 2009 CELLULAR AND MOBILE COMMUNICATIONS ( Common to Electronics & Communication Engineering and Electronics & Telematics) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆

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1. (a) What is the difference between frequency selective fading & flat fadings. (b) What are the major problems in AMPS system & how these are overcome in GSM system? [8+8]

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2. (a) Explain about the co-channel interference reduction factor and derive the general formula for C/I. (b) If the maximum no of calls per hour Qi in one cell be 5000 and an average calling time T be 1.76 min. The blocking probability is 2%. Find the offered load. If Qi is 30000. Find the offered load compare this with no. of channels by using Erlang B model charts. [10+6]

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3. (a) Explain how co-channel interference is measured in real time mobile radio transceivers. (b) Explain different methods to reduce the cochannel interferences. [8+8] 4. (a) Discuss in detail about small scale multipath propagation. (b) Write the general formula of Lee Model and Explain the remarks.

[10+6]

5. (a) Explain the synthesis of difference patterns. (b) Draw the setup for space diversity antennas used at cell site and explain how to design it. [8+8]

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6. (a) What is the function of frequency management? (b) Explain how the 666 channels are divided into groups? (c) Write notes on setup channels.

[4+6+6]

7. Explain the following terms: Mobile Assisted Handoff Soft Handoff Delaying Handoff Cellsite Handoff

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(a) (b) (c) (d)

[4×4=16]

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? ⋆⋆⋆⋆⋆ 1 of 1

[6+4+6]

Set No. 3

Code No: R05420401

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IV B.Tech II Semester Regular Examinations, Apr/May 2009 CELLULAR AND MOBILE COMMUNICATIONS ( Common to Electronics & Communication Engineering and Electronics & Telematics) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆

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1. (a) Differentiate the analog & digital cellular systems with their operating capacities.

(b) Explain the relation between the received power & the range of subsystem in detail. [8+8] 2. (a) Mention the two frequency reuse schemes and explain N-Cell reuse pattern in detail for four & seven cell reuse with illustrative diagrams.

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(b) During a busy hour the no. of calls per hour Qi for each 10 cells is 2000, 1500, 3000, 500, 1000, 1200, 1800, 3200, 2600, 800. Assume that 60% of the car phones will be used during this period and that one call is made per car phone. Find the no. of customers in the system. [10+6]

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3. (a) What is Near-end-far-end interference ratio and explain its effect. (b) Write notes on channel combiners.

[8+8]

4. (a) Explain ground incident angle, elevation angle, ground reflection and reflection point with respect to signal coverage. (b) Briefly explain about multiple knife edge diffraction.

[8+8]

5. (a) Draw the symmetrical difference pattern and compare it with symmetrical sum pattern.

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(b) Draw the cell site antenna for omni cells for 45 and 90 channels and explain them. [8+8]

6. (a) What are the different techniques for increasing frequency spectrum?

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(b) Compare the average blocking in spatially uniform and nonuniform traffic distribution for FCA, BCA and FBCA. [8+8]

7. (a) Explain how the handoffs implemented based on signal strength? (b) How the dropped call rate is related to the capacity and voice quality. (c) What are the different factors that limit the size of splitting cells?

8. Explain the following terms of CDMA Digital Cellular Systems: (a) Active set (b) Long code 1 of 2

[6+4+6]

Set No. 3

Code No: R05420401 (c) Multiple sub-layer (d) Paging channel.

[4×4=16]

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Set No. 4

Code No: R05420401

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IV B.Tech II Semester Regular Examinations, Apr/May 2009 CELLULAR AND MOBILE COMMUNICATIONS ( Common to Electronics & Communication Engineering and Electronics & Telematics) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆

(b) Write notes on Digital cellular systems.

[8+8]

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1. (a) Explain the terms GSM & GPRS.

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 1 5 10 20 100. Use Erlang B model charts.

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i. ii. iii. iv. v.

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(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.

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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.

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(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? [6+4+6] 1 of 2

Set No. 4

Code No: R05420401

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? [6+4+6]

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(c) What are the different kinds of downlink common channels?

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