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USN 06EC81

Eighth Semester B.E. Degree Examination, December 2010Wireless Communication

Time: 3 hrs. Max. Marks: 100Note: Answer any FIVEfull questions, selecting at least TWO questions from each part.

PART-A1 a. With a neat block diagram, explain different components of SS7 system and their functions.

(10 Marks)b. Explain AMPS handoff operation using various control messages, with the help of message

sequence chart. (10 Marks)

2 a. Explain the following terms: (10 Marks)i) MSISDN ii) IMST iii) COI iv) RBSIC v) OTT

b. Explain mobile originated call operations in a cellular network, with a neat diagram showingthe components and steps. (10 Marks)

3 a. Explain the following capacity expansion techniques : cell splitting, cell sectoring andoverlaid cells. (10 Marks)

b. A service provider wants to provide cellular communication to a particular geographic area.The total bandwidth the service provider licensed is 5 MHz and system subscriber requires10KHz of bandwidth. Determine the system capacity, if the service provider implements acellular system with 35 transmitter sites and cluster size of 7. (06 Marks)

c. Determine frequency reuse distance for a cell radius of 2 kilometers and cluster size of 8.(04 Marks)

4 a. Discuss the frame format of OSM hyper frame, super frame, multi frame and TDMA frame.(10 Marks)

b. Draw a neat diagram for OSM signaling model. Explain the different protocols used in thediagram. (10 Marks)

PART-B5 a. Explain the steps needed for setting up a call in GSM using MSRN, with a neat diagram.

(10 Marks)b. Explain GAM intra BSC handover, with a neat diagram. (10 Marks)

6 a. Describe generation of CDMA reverse traffic channel, with a neat diagram. (10 Marks)b. How does the use of spreading codes increase the bandwidth? What is the length of CDMA

burst PN spreading code? (10 Marks)

7 a. Describe operation of RAKE receiver, with a neat diagram. (06 Marks)b. If transmitted power is 600 mw at a frequency of 850 MHz, determine the path loss at a

distance of 5000 meters and received signal power in dBm. Use free space path loss model.(10 Marks)

c. If an OFDM system transmits 32 Kbps over each carrier and uses 16 carriers, what is theoverall data rate? (04 Marks)

8 a. Discuss the design issues of IEEE 802.11 and also provide the working of BSS, DS and ESSnetworks. (10 Marks)

b. List three fundamental ways in which wireless LANs and wireless PANs differ from eachother and explain them. (05 Marks)

c. What kind of wireless network can be used to connect buildings in a city to exchangeinformation? Name the IEEE standard and explain a typical network based on the standard.

(05 Marks)

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Eighth Semester B.E. Degree Examination, May/June 2010Wireless Communication

Time: 3 hrs. Max. Marks: 100======---===================----============~()lte:~7i~ll~~~=;rfidl=~~~s,~electilf~======-===========--==========

at least TWO questions from each part.

a. Briefly explain the different generations of cellular systems.b. Explain the AMPS (advanced mobile phone system) network

originated call.

(10 Marks)operations, for a mobile

(10 Marks)

a. What is the function of the visitor location register? (04 Marks)b. Explain the purpose of global title and global title translation for a cellular system.(06 Marks)c. What are the functions of the mobile switching centre (MSC)? With a neat block diagram,

explain the components of the MSC. (10 Marks)

a. Explain the differences between cell splitting and cell sectoring.b. Explain the concept of mobility management. With a figure,

functions performed by the location management.c. Write a note on network security.

(06 Marks)explain the three basic

(10 Marks)(04 Marks)

a. Explain with a neat schematic, the GSM network interfaces and protocols.b. Briefly explain the GSM channel concept.

(10 Marks)(10 Marks)

a. Define MSRN. What is the purpose of mobile station roaming number? Also explain theGSM call setup using the MSRN. (10 Marks)

b. Explain the TDMA concept. How it is implemented in GSM? (10 Marks)

a. Explain with a neat diagram, the network nodes found in a CDMA 2000 wireless system.(10 Marks)

b. Explain with a neat block diagram, the generation of the CDMA paging channel signal.(10 Marks)

a. Define OFDM. Briefly explain,this OFDM technique. (06 Marks)b. Explain the basic operation and characteristics of spread spectrum modulation systems.

(10 Marks)c. Define ultra - wide band radio technology. (04 Marks)

8 a. Explain the details of Bluetooth protocol stack, with a figure.b. Describe the basic wireless MAN.c. Describe the basic difference between a wireless LAN and a wireless PAN.

(10 Marks)(04 Marks)(06 Marks)

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Seventh Semester B.E. Degree Examination, May/June 2010Wireless Communication

1 a. Which interference is more problematic, adjacent channel interference or co-channelinterference?Explain your answer. (06 Marks)

b. Why are cells designed as hexagon despite the fact that antenna coverage is generallyuniformin all directions? (06 Marks)

c. A city has an area of 4550 square miles. Find the total number of hexagonal cells that can beaccommodated, if the diameter of the circle perfectly encompassing the hexagon is 10m?

(08 Marks)

2 a. Explain power control in cellular communication. How does this help in reducinginterference? (06 Marks)

b. Name some techniques used to improve coverage and capacity in cellular systems. Explainanyone of them. (08 Marks)

c. A city has 180 cells with each cell having 19 channels each. It has been found that users inthis city average three calls per hour at an average call duration of two minutes. For a GOSof 0.02, it is found that the total carried traffic A is 12 Erlangs. Calculate the total number ofsubscribersthat can be supported by the cellular system. (06 Marks)

3 a. What are the different types of handoff strategies? Explain their differences. (06 Marks)b. Calculate the worst case signal-to-interference ratio where the radius of the cell is R and the

distance between centers of the nearest co-channel cells is D. Assume a path loss exponentn = 4 and a seven cell reuse pattern. For calculation purpose, omni directional antennas andonly the first tier of interfering cell can be considered. (08 Marks)

c. Calculate the worst case signal-to-interference ratio under the same conditions in 2(b),except instead of omni-directional antennas, consider 1200 directional antennas. What is thechange in S/1? (06 Marks)

4 a. What are the basic propagation mechanisms which impact propagation in a mobilecommunication system? Explain any two of them. (10 Marks)

b. Calculate the received signal in dB in a free space propagation model if the transmittedsignal is 40 dB at 900 MHz and the distance between the transmitter and receiver is 10m.Assumethe gain of the transmitting antenna to be 5 and the gain of the receiving antenna tobe 10. (10 Marks)

5 a. Write short notes on the following:i) Nonuniform quantizationii) Adaptive differential pulse code modulation (ADPCM)iii) Vocodersiv) USDC codec.

For a 3 bit uniform quantizer that spans the range (OV, 3.5V), determine the step size of theb. quantizer. Assuming no error in transmission, plot the output voltage magnitude as a

function of time if the output received is 001100101010. (08 Marks)

6 a. Explain some of the factors influencing small scale fading. (06 Marks)b. A vehicle is moving at a speed of 60 meters/see towards a base station transmitting at a

frequency of 3000 MHz. Calculate the received frequency and the Doppler shift. What is thereceived frequency ifthe vehicle was moving away from the base station? (08 Mar~)

c. Explain the types of small scale fading based on Doppler spread. (06 Marks)

7 a. What are the various types of pulse shaping techniques? Explain anyone of them. (08 Marks)b. With a neat illustration, explain how the differential encoding process takes place in DPSK.

(06 Marks)c. Assume the code 111001 needs to be sent by n/4 QPSK. Determine the values of h and Qk

during transmission if eO = 0°. (06 Marks)

8 a. Explain the salient features of FDMA, TDMA, CDMA. (08 Marks)b. Explain the differences between slotted and unslotted (Pure) ALOHA packet transmission.

(06 Marks)c. A total of 28.525 MHz is allocated to a particular FDD cellular telephone system. 25 kHz is

the bandwidth given to each channel (simplex band). If the numbers of control channels are21, find the total number of users that can be simultaneously supported in this network.What is the number of users that can be simultaneously supported in each cell if a seven-cellreuse pattern is used? (06 Marks)