Punjab University 2005 B.Tech Electronics and Communications Engineering COMMUNICATION SYSTEM II - Question Paper

COMMUNICATION SYSTEM II

Note: part A is compulsory. Attempt any 4 ques. from part B and any 2 ques. from part C. provide examples wherever possible. describe explicitly the notations used.

part A Marks: two every

1.
(a) Differentiate with the help of neat diagram ranging from sampling and quantization.
(b) What is a band limited signal?
(c) discuss the term ‘Nyquist interval’.
(d) If the amplitudes of a signal m(t) is confined to the range of (-mp, mp) and the range is divided into L zones, every of step size ?, obtain out the expression for quantization noise.
(e) Draw the waveforms of an unmodulated carrier, data, ASK, PSK and FSK.
(f) State the advantages of DPSK and PSK.
(g) Sketch the QPSK waveform for the sequences 1101010010 assuming the carrier frequency to be equal to the bit rate.
(h) What is a spread spectrum modulation? explain briefly.
(i) What do you understand by paging? elaborate the various components of a paging system?
(j) List the various fault control and detection techniques in a computer network. What do you understand by ARQ?

part B Marks: five every

2. discuss the receiver for the detection of DPSK signals.

3. Illustrate with the help of a neat diagram the phase relationship ranging from symbols intervals of 2 users of a CDMA system.

4. provided the signal m(t)= 10* cos 200* ?* t cos* 800* ?* t. What is the minimum sampling rate based on:

(a) The low pass uniform sampling theorem.
(b) Band pass sampling theorem.

5. In a binary PCM system, the output signal-to-quantizing-noise ratio is to be held to a minimum of 40 dB. Determine the number of needed levels and obtain the corresponding output signal-to-quantizing-noise ratio.

6. elaborate the various elements of switching? explain cellular digital switching requirement.

part C Marks: 10 every

7. discuss the subsequent kinds of computer communication networks with proper diagram wherever applicable:
I. TYMNET
II. ARPANET
III. ISDN
IV. LAN

8. (a) Consider an audio signal comprised of the sinusoidal term

s(t) = 3* cos* 500* ?* t
(i) obtain the signal to quantization noise ratio when this is quantized using 10-bit PCM.
(ii) How many bits of quantization are needed to achieve a signal to quantization noise ratio at lowest 40 dB?
(b) explain the advantages and disadvantages of the subsequent signaling formats:
(i) Unipolar NRZ
(ii) Bipolar RZ
(iii) Alternate mask inversion RZ

9 (a) obtain the bit fault probability for a BPSK system with a bit rate fo one Mbit/s. The received waveforms s1(t) = A cos wot are coherently detected with a matched filter. The value of a is 10 mV. presume that the single-sided noise power spectral density is No= 10-11 W/Hz and that signal power and energy per bit are normalized relative to a one ohm load.
(b) Derive the expression for the throughput of Carrier Sense Multiple Access (CSMA)

Earning:   Approval pending.