Code: AE-17 / AT-17                                        Subject: TELECOMMUNICATION SYSTEMS

Time: 3 Hours                                                                                                     Max. Marks: 100

NOTE: There are 9 Questions in all.

· Question 1 is compulsory and carries 20 marks. Answer to Q. 1. must be written in the space provided for it in the answer book supplied and nowhere else.

· Out of the remaining EIGHT Questions answer any FIVE Questions. Each question carries 16 marks.

· Any required data not explicitly given, may be suitably assumed and stated.

Q.1       Choose the correct or best alternative in the following:                                         (2x10)

a. The number of links required for a fully connected network servicing n subscribers is  

(A) (B)

(C) (D)

b. The number of switching elements required for a three stage NN non blocking configuration is

(A) 2N (B)  2N

(C)  3N                                               (D)

             c.   The effect of impedance mismatch in hybrid will give rise to 

(A) interruption                                   (B)  echo

(C) noise                                             (D)  distortion

             d.   The most common form of modulation used in analog cellular communication is  

(A) AM                                             (B)  FM

(C) FSK                                             (D) Narrow band FM

             e.   The bandwidth of RF channels in GSM is  

(A) 25 kHz                                        (B)  30 kHz

(C)  200 kHz                                       (D)  25 MHz

             f.    CDMA uses

(A) time division multiplexing               (B) spread spectrum technique

(C) frequency division multiplexing       (D) quadrature multiplexing

             g.   A basic rate ISDN digital subscriber loop provides bidirectional data rate of 

(A) 64 kbps                                       (B)  144 kbps

(C)  200 kbps                                     (D)  256 kbps

             h.   A 3 kHz telephone channel can support 60 kbps data rate when S/N ratio is above

(A) 0 dB                                            (B)  10 dB

(C) 20 dB                                           (D)  30 dB

             i.    The size of an ATM transmission cell is

(A) 48 bytes                                       (B)  53 bytes

(C) 64 bytes                                        (D) 128 bytes

             j.    The switching capacity of a non-blocking  two stage switching network is

(A) (B)

(C) N                                                  (D) 2 N

Answer any FIVE Questions out of EIGHT Questions.

Each question carries 16 marks.

Q.2     a.   Compare single stage and multi stage switching networks.  Draw the block diagram of a two stage network and work out the number of switches required for a non-blocking  two stage network.         (8)

             b.   Write a note on pair-gain systems.                                                                      (8)

Q.3     a.   What is two dimensional switching?  Describe STS switching.                             (8)

b.   Explain the time multiplexed space switching with a block diagram.                      (8)

Q.4           Write short notes on :

(i) two wire to four wire conversion                                                (6)

(ii) transmission impairments                                                            (5)

(iii) BORSCHT                                                                               (5)

Q.5     a.   Determine the switch advantage ratio of a three-stage network with N                               

                    inlets and N outlets for the cases when

                    (i)    N = 128                                      (ii)  N = 32,768                                      (8)

     b.   Discuss CDMA cellular system and enumerate the advantages of CDMA over GSM system.                                                                    (8)

  Q.6     a. Explain the terms

(i)    Grade of service                           (ii)   blocking probability

                   (iii)  Delay probability                           (iv)  Quality of service

                   How these terms are used to qualify a network?                                                 (8)

             b.   Write a note on delay systems.                                                                           (8)

Q.7     a.   Describe the various line codes used in fibre optic transmission.                           (8)

b.   Describe SONET system.                                                                                  (8)

Q.8     a.   What are the different services supported by ATM networks? Write notes on ATM service categories.                                                                 (8)

b.   Discuss the ISO-OSI model for data networks.                                                  (8)

Q.9           Explain segregated and integrated architectures for ISDN networks. Modelling these as M/M/c and M/M/1 queueing systems, analyse their performance and draw a comparison.               (16)