May05 Cellular Mobile Communications

Set No.1

Code No: NR420401

IV B.Tech. II Semester Regular Examinations, April/May -2005 CELLULAR & MOBILE COMMUNICATIONS ( Common to Electronics & Communication Engineering, Information Technology and Electronics & Computer Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ????? 1. (a) What are the differences between the first and second generation systems? (b) Explain the terms GSM and GPRS? 2. (a) Differentiate the analytical situation and simulation? (b) During a busy hour the number of calls per hour Qi for each of 10 cells is 2000,1500,3000,500,1000,1200,1800,2500,2800 and 900 Assume that 60% of the car phones will be used during the busy period and that one call is made per phone Find out the total number of customers in the system? 3. What are the different types of Non-co channel interference? Explain. 4. (a) Determine the equation for received power between two fixed stations? (b) Let a distance between two fixed stations be 30Km the effective antenna height at one end is h1 is 150m above sea level. Find the h2 at the other end so that the received power is always meets the condition pr < po at 850 MHz transmission. For the above find the range of h2 which would keep pr > po and find the maximum received power.6 5. (a) Classify the mobile unit antennas? (b) Explain about the sectorised cells? 6. The U.S AMPS system is allocated 50MHz of spectrum in the 800 Mhz range and provides 832 channels. 42 of those channels are control channels. The forward channel frequency is exactly 45MHz greater then the reverse channel frequency. (a) If the AMPS system is simplex, half duplex or full duplex? What is the band width for each channel and how is it distributed between the base station and subscriber? (b) Assume a base station transmits control information on channel 352, operating at 880.560MHz What is the transmission frequency of the subscriber unit on transmitting on channel 352? (c) The A- side and B - Side cellular carriers evenly split the AMPS channels. Find the number of voice channels and the number of control channels for each carrier?

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Set No.1

Code No: NR420401

(d) let suppose you are chief engineer of a cellular system using seven cell reuse purpose a channel assignment strategy for a uniform distribution of user through out your cellular system specifically , assume that each cell has three control channels (1200 sector is employed)and specify the number of voice channels you would assign to each control in your system? (e) For an ideal hexagonal cellular layout which has an identical cell coverage, what is the distance between the centers of two nearest co channel cells for seven cell reuse? For four cell reuse? 7. Explain the following types of Handoffs (a) Forced Handoff (b) Mobile associated Handoff (c) Inter system handoff (d) Intra system handoff. 8. (a) Discuss the various vehicle locating methods at the cell site. (b) Discuss how antenna mountings used on the mobile units affect system performance. ?????

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Set No.2

Code No: NR420401

IV B.Tech. II Semester Regular Examinations, April/May -2005 CELLULAR & MOBILE COMMUNICATIONS ( Common to Electronics & Communication Engineering, Information Technology and Electronics & Computer Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ????? 1. (a) What are the differences between the first and second generation systems? (b) Explain the terms GSM and GPRS? 2. (a) Differentiate the analytical situation and simulation? (b) During a busy hour the number of calls per hour Qi for each of 10 cells is 2000,1500,3000,500,1000,1200,1800,2500,2800 and 900 Assume that 60% of the car phones will be used during the busy period and that one call is made per phone Find out the total number of customers in the system? 3. (a) What is the importance of the demultiplexer at the receiver to reduce the non co channel interference? (b) Explain about a typical cell site receiver? 4. (a) Discuss about the multi path propagation present the associated losses and place the problem? (b) Discuss about the point to point and area to area prediction model for cell coverage? 5. (a) Explain the fundamentals of antenna gain? (b) Explain the concept of horizontally space diversity antennas 6. (a) What do you understood by non fixed channel assignment ? Describe the corresponding algorithms? (b) Explain in detail access channels and operational techniques? 7. (a) Discuss the relationship among capacity, voice quality and dropped call rate. (b) Calculate the dropped call rate using general formula. 8. Present the concept of the narrow beam sector. How does it increase the traffic capacity? Consider K = 7. ?????

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Set No.3

Code No: NR420401

IV B.Tech. II Semester Regular Examinations, April/May -2005 CELLULAR & MOBILE COMMUNICATIONS ( Common to Electronics & Communication Engineering, Information Technology and Electronics & Computer Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ????? 1. (a) Discuss analog cellular system (AMPS) in detail? (b) Discuss the mobile radio transmission medium? 2. (a) Explain about the time division multiple accessing technique(TDMA). (b) What is the general formula to find the value of K and find out the frequency reuse distance with available K value? 3. Briefly explain the test methods used for the measurement of co-channel interference. 4. Discuss in detail the various factors affecting the mobile radio communication medium with appropriate figures and graphs. 5. (a) Concern to the cell site antennas explain start up configuration and abnormal antenna configuration of start up system? (b) How interference can be reduced by using the directional antennas at cell site? 6. (a) Discuss the concept of frequency management concern to the numbering the channels and grouping into the subsets? (b) Give the structure of the channels in 800MHz system with frequency ranges? 7. Explain how δ and µ. are improved due to the natural two-site diversity in the hand off region. 8. (a) Prove that sectoring decreases trunking efficiency with an example. (b) Explain how lowering the threshold level of a received signal increases the coverage area. ?????

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Set No.4

Code No: NR420401

IV B.Tech. II Semester Regular Examinations, April/May -2005 CELLULAR & MOBILE COMMUNICATIONS ( Common to Electronics & Communication Engineering, Information Technology and Electronics & Computer Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ????? 1. (a) Explain the direct wave path, line of sight path, out of sight path, and obstructive path? (b) What are the different types of noises in cellular frequency ranges Explain in detail? (c) Explain about the marketing of hexagonal cells? 2. (a) Differentiate the analytical situation and simulation? (b) During a busy hour the number of calls per hour Qi for each of 10 cells is 2000,1500,3000,500,1000,1200,1800,2500,2800 and 900 Assume that 60% of the car phones will be used during the busy period and that one call is made per phone Find out the total number of customers in the system? 3. (a) Explain briefly about reduction of co-channel interference in mobile radio system. (b) Write detailed notes on the different diversity schemes and combining techniques used in mobile communication. 4. Why statistical analysis of mobile signal gains importance? How do you measure local mean from observed mobile data? 5. (a) Discuss the characteristics of cell site antennas? (b) If the antenna heights are varying what are the effects you are getting at the time of operation of mobile system? 6. (a) Explain the concept the dynamic channel assignment in detail? (b) Describe the non fixed channel assignment algorithms? 7. (a) Explain clearly how to calculate δ and µ for single cell? (b) Why hand off is necessary for cellular systems Determine the two types of handoffs based on signal strength and C/I ratio? 8. Explain how cell splitting improves capacity in cellular system. Discuss the two techniques. ?????

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