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Pondicherry University 2009 M.Tech Wireless Communication / systems - Question Paper

Sunday, 27 January 2013 11:10Web

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Unit-Ill

10. (a) Consider a (7, 4) cyclic code with the generator polynomial g(X) = 1 + X² + X³.

Determine if the codeword given by the polynomial c(X) = 1 + X² + X³+X⁵ + X⁶ is a valid
codeword for this generator polynomial.	(5)
(b) Explain the coding techniques suitable for bursty errors	(5)
(OR)
(a) Explain the concept of Trellis coded modulation '	(5)
(b) Obtain the output sequence for the rate (1/2) encoder shown below when
the input sequence is (110). Draw the state diagram for this encoder	(5)

Unit-IV

12. (a) Draw and explain the transmission and reception of coherent QPSK (5) (b) Compare the performance of different digital modulation techniques in a flat fading environment with neat diagram and expressions (5) ^(0R)

13.<fDerive aml-explain the performance of DSSS (5) (Explain the geometric representation of modulatierrrsignals with two examples

' T5J

Unit-V

14.(a)Explain the LMS algorithm used in adaptive equalizers (5) (b) Explain the different types of space diversity (5)

. (OR)

15.JTCompare the TDMA and FDMA techniques - (5) JkfDiscuss the packet radio techniques of multiple access' (5)

PONDICHERRY ENGINEERING COLLEGE, PONDICHERRY M.TECH(WC) EXAMINATION (CBCS) JAN. 2010

FIRST SEMESTER EC911 WIRELESS COMMUNICATION SYSTEMS

Time :3 Hours Max. Marks:60

PART - A Answer all Questions (5X2 = 10)

1. If a total bandwidth of 33 MHz is allocated to a FDD system which uses two 25 KHz simplex channels for providing full duplex voice and control channels, find the number of channels available per cell if the system uses 12 cell reuse

2. Consider a transmitter which radiates a sinusoidal carrier frequency of 1800 MHz. For a vehicle moving at 60mph, find the received carrier frequency if the mobile is moving in a ' direction which is directly away from the transmitter

3. A (5,2) code is defined by the set of code words C = (00000, 10100,01111,11011). Check whether this code is linear

4. What is the theoretical maximum data rate that can be supported in a 200 KHz channel for SNR of lOdB?

5. Give the principle of RAKE receivers

PART-B

Answer five questions choosing one full question from each unit. (5X10= 50)

Unit-I

(a) A cellular service provider decides to use a digital cellular scheme which can tolerate an S/I of 15 dB in the worst case. Find the optimal value of cluster size for maximum capacity if the path loss exponent is n =3. Assume that there are six co-channel cells in the first tier and all are at equal distance from the mobile (4)

Explain the different approaches of improving the capacity and coverage of a mobile 'cellular system (6)

(OR)

(a) Compare Okumura and Hata outdoor propagation models. How are these models different from Durkins model? (5)

(b) If 50 W power is applied to a unity gain antenna, find the received power in dBm at a free space distance of 100 m from the antenna. The carrier frequency is 900 MHz. Assume unity gain for the receiver antenna (5).

Unit-II

Explain the different types of small sale fading in detail " (5)

(b) Defme level crossing rate and average fading duration. Compute the positive going level crossing rate and the average fade duration for a threshold level of 1. Assume the maximum Doppler frequency as 20 Hz (5)

(Or)

9. Explain the impulse response model for multipath channel. Describe the relationship between bandwidth and received power (10)