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MDLCE04U

M S RAMAIAH INSTITUTE OF TECHNOLOGYAUTONOMOUS INSTITUTE, AFFILIATED TO VTU)

B NG LORE 560 054SEMESTER END EXAMINATIONS JUNE 2010

Course Branch M.Tech (Digital Electronics andCommunication Se mester Subec :Wireless and Mobile Communications Ma x. M a rks 0Subject Code : MDLCE04 Du ration 3 Hrs

Instructions to the Candidates:1. Answer any Five Full questions.2. Assume the missing data suitably.

1. a) Discuss the evolution of mobile communication systems in terms of (07)generations

b) Explain the principle of frequency reuse for cellular communication. (07)c) A cellular system has 1001 radio channels available for handling (06)

traffic. Area of the entire system is 2100 km2 and each cell has anarea equal to 6 km2.

i) Find the system capacity if the cluster size is 7.ii) Calculate the system capacity if the cluster size is 4.iii) Explain the effect of decreasing cluster size on the system

capacity.2 . a Explain the handoff strategies employed with the associated practical

problems with handoff.06

b How is the linked spectrum available for cellular systems shared?Discuss in brief.

(08)c A receiver is located 10km from a 50 W transmitter. The carrier

frequency is 900MHz with free space propagation assumed, find(06)

i) The power at the receiverii) The rms voltage applied to the receiver input when thereceiver antenna has pure real impedance of 500 and ismatched to the receiver. Take Gt=1, Gr=2.

3. a) Discuss the free space propagation model and its practical 08).limitations.

b) What are the factors considered for Okumara and Hata outdoor (08)models? Explain in brief.

c) If the received power at a reference distance do=lkm is equal to 1 (04)microwatt, find the received power at distances of 2km, 10km fromthe same transmitter for free space path loss model.

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MDLCE044. a) Explain flat fading and frequency selective fading with the help of (08)

channel characteristics.b) Differentiate between co-channel interference and adjacent channel (08)

interference in a cellular radio system.c) What is meant by the term diversity reception? Discuss the various (06)

categories of diversity.5. a) Explain maximal ratio combining method. How is it useful in (06)

combating fading effect?b) Discuss carrier-to- interference ratio performance improvement with (06)

diversity techniques applied.c) With block schematics, discuss the performance of a Rake receiver in (08)

CDMA systems.6. a) Integration between terrestrial and mobile networks is progressing in (08)

a number of phases. Discuss the concept to justify the statement.b) In a cellular system the system bandwidth is 12.5 MHz, the channel (06)

spacing is 30KHz and the guard spacing is 10KHz. The number ofchannels allocated for control signaling is 21. Obtain

i) The number of channels available for message transmissionusing FDMA

ii) Spectral efficiency.c) Wteexpanatory noteon SDMA 06)7. a) Discuss the salient features of IS-95 CDMA channe forward link 10)

structure.b) Explain the reverse link closed loop power control in IS-95 CDMA (10)

system.8. a) A CDMA system operates at 9600 bps. It spreads this signal to 04)

1.25MHz. What is the processing gain in dBs?b) Explain CDMA- 2000 layering structure with suitable illustrations. (08)c) Explain how set up and end off soft handoff takes place in CDMA (08)

system.

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