Anna University Chennai 2011-8th Sem B.E Electronics & Communication Engineering /B.Tech il/ , ester, Electronics and Communication Engineering, EC1451-MOBILE COMMUNICATION. - Question Paper

Part-A
(10*2=20)

1. What is the consequence of increased link performance in CDMA systems?
2. Define signal to interface ratio in terms of distance ranging from cell centers and radius of cell in a cellular scenario.
3. How does micro zone concept decrease hand off?
4. Differentiate fast fading and slow fading with respect to coherence time and Doppler speed.
5. Specify the kind of model that can be used to predict path loss for GSM frequency range.
6. What is the probability of fault (BER) in QPSK modulation systems? Comment on the performance.
7. Write the DPSK sequence for the data stream 110110.
8. Differentiate ranging from PCM and DPCM with respect to fault performance. Which source coding is suitable for speech signals?
9. What kind of channel coding is used for GSM network?
10. Give the specification of ideal uplink and down link characteristics of W-CDMA.

Part-B
(5*16=80)

11.(a) discuss the various techniques to decrease CCI and ACI in a 7 cell reuse cellular system. Derive the signal to interference for the worst conditions. Also discuss the effect of path loss on interference.(16)
Or
(b)(i) Derive the probability of blocking in a trunked Lost Call Cleared (LCC) and Lost Call Delayed (LCD) systems.(6)
(ii) In a cellular system there are 12 clusters available with 120 cells with 10,000 subscribers. every subscriber uses the cell phone for 1 hour every day. On an avg. 30 minutes of time is used during peak hours. obtain the avg. and peak traffic for the entire cellular system and also for 1 cell considering all callers are distributed evenly over the system.(10)

12.(a)(i) elaborate the various indoor propagation models available for path loss calculation? discuss the long distance path loss model.(8)
(ii) compute the propagation loss for a radio signal at 850 MHz. The transmitter antenna height is 30m over a distance of 11km. Use mobile propagation model and free space model and compare them.(8)
Or
(b)(i) discuss the various statistical models available for multipath fading channels. (8)
(ii) discuss the fading effects due to Doppler spread. (8)

13.(a) How does Maximal ratio combining techniques combat deep fades in wireless environment? Derive the expression for the maximum gain of the transmitting antennas. (16)
Or
(b) Derive the BER for MSK with respect to symbol energy and symbol time period. Why MSK is preferred in mobile environment. Draw the spectral characteristics of the MSK modulation scheme. (16)

14. (a)(i) Derive the general expression that relates SNR due to quantization as a function of number of bits. (8)
(ii) discuss the various kinds of vocoders. (8)
Or
(b) Derive the radio capacity for FDMA in terms of path loss, total allocated spectrum, channel bandwidth and carrier to interface (C/I) ratio. Compare with capacity of cellular CDMA. (16)

15.(a) discuss the functions of DECT. elaborate the different entities? List the specifications for DECT Radio. (16)
Or
(b) elaborate the different GSM control channels? discuss the different control channels by original a cellular call through the GSM Network. Draw the timing diagrams.(16)

Earning:   Approval pending.