Rajasthan Technical University 2009 B.Tech Computer Science and Engineering Telecommunication Fundamentals - Question Paper

UNIT I

a) In a telecom network, the length of the cable is 5000 kms and speed of signal through the cable is 2.3*100000000 m/sec.
i) obtain the round trip propagation delay for the system.
ii) If a system is transmitting data at i Mbps, how many bits will be in transit?
iii) Compare the total time to be taken in receiving a 1- byte acknowledgment for a 48000 byte file on the above system. [Marks 2+2+4]

b) Determine the height of antenna for a TV station that must be able to reach customers up to 80 kms away. [Marks 4]

c) Compare suitability of subsequent media for a 100 mtr, 10 mbps communication system.
i) Cat - three WTP [marks 4]
ii) Cat - five WTP
iii) Thin Ethernet


OR


a) Show that doubling the transmission frequency or doubling the distance ranging from transmitting antenna and receiving antenna attenuates the received signal by equal amount. Compare the attenuation in dB. [marks 8]

b)A microwave transmitter has an output of 0.1 W at two GHz. assuming this to be used in a microwave communication system where the transmitting and receiving antenna are parabolas, every of 1.2 m diameter.
i)Calculate the antenna gain in decibels.
ii)Considering antenna gain. What is the effective radiated power of the transmitted signal?
iii)If the receiving antenna is located 24 kms from the transmitting antenna over a free space path, obtain the loss in dB. [marks 8]



UNIT II


2 a) A telephone line is known to have a loss of 20 dB. The input signal power Is measured as 0.5W, and the output noise level is measured as 4.5micro W.
compute (SNR)dB. [Marks 4]

b) A high quality speech signal has a bandwidth of eight kHz.

i) If the speech signal is to transmitted at 28.8 kbps digital channel, what SNR (Signal – to – Noise Ratio) shall be maintained?

ii) What will be the SNR for a 64 kbps channel?

iii) For a 40 dB SNR, calculate the channel capacity

Also comment upon the effect of SNR over achievable data rates. [Marks 2*3+2=8]


c) A 10 kHz baseband channel is used by a digital transmission system. Ideal pulses are sent at Nyquist rate and the pulses can take 16 levels. What is the bit rate of the system? [Marks 4]



OR



a) Suppose a radio transmission system has a large band of bandwidth that is to be used by a central office to transmit and receive from a large number of users. Compare the subsequent 2 approaches to organizing the system.

i) A single TDM system.

ii) A hybrid TDM/FDM system in which frequency band is divided into multiple channels and TDM is
used within every channel.
Draw block diagram of every scheme. [marks 6+2=8]

b) define the frame format of STS-1. Also discuss the add-drop capability of the SONET system. [marks 4+4=8]


UNIT III


3 a) Suppose tat ALOHA protocol is used to share a 56 kbps satellite channel. Suppose frames are1000 bits long. obtain the maximum throughput of the system in frames/second. [marks 3]

b) What will be the throughput if slotted ALOHA is used in place of ALOHA?
Justify the variation in the throughput of ALOHA and slotted ALOHA through mathematical derivations. [marks 2+5=7]

c) explain the effect of length of channel on the performance of ALOHA and CSMA protocols. How CSMA- CD protocols improve the performance of such systems. [Marks 6]


OR


a) discuss working of CDMA system. Clearly define the system will work only when the chip sequences are orthogonal vectors. [Marks 8]

b) discuss with the help of phase diagram. Working of PPP. List all the activities carried out during every phase. [Marks 8]


UNIT IV


a) define working of ADSL. Also explain the 2 systems used in ADSL. [Marks 8]

b) With the help of a schematic, define working of
i) Time Division Switch
ii) Space Division Switch [marks 8]

OR


a) N input lines are to be connected to N output lines using space division switches the designer has a option of connecting them using a single stage switching scheme or a 3-stage switching scheme. Comment on relative merits and demerits of the 2 approaches in terms of
i) Ease of operation
ii) No. of Cross points
iii) Growth of cross points as a function of N.
iv) No. of simultaneous connections possible. [Marks 8]

b) Classify and discuss the signaling schemes used in telephone networks. [Marks 8]


UNIT V


5 a) Write short note on the subsequent
i) Functions of Gateway, Router, switch
ii) Difference in proxy server and web server
iii) Remote Access server [marks 6+5+5]


OR

a) discuss the call set up and hands off procedure in GSM under the subsequent conditions
I) Caller is a mobile user on the move and the called is a fixed line subscriber
ii) Caller is a fixed line subscriber and called is a mobile subscriber currently standing at a particular point in a car.
iii) Caller and called both are mobile subscriber riding cars which are moving.
[Marks 3+3+3=9]

b) discuss working of Bluetooth. [Marks 7]

Earning:   Approval pending.