DECEMBER 2006

Code: A-17 / T-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. Number of links required in a fully connected network of 10 subscribers is    

(A)  45                                                (B)  50

(C)   90                                               (D) 100

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

(A) N                                                 (B) 2N

(C) (D)

             c.   BORSCHT is  

(A) list of interface requirements          (B)  a protocol

(C) an interface circuit                          (D)  a telephone company

             d.   Grade of Service (GoS) is defined as   

(A)

(B)

(C)

(D)

             e.   Cellular communication service is expensive because of the complex design of   

(A) mobile units                                  (B)  base station

(C)  master station                               (D)  all the three

             f.    CDMA channel bandwidth is

(A) 25 MHz                                       (B) 25 kHz

(C) 1.25 MHz                                     (D) 200 kHz

             g.   Bandwidth limits of fibre optic transmission systems are mostly determined by

(A) electro optic drivers                      (B)  receivers

(C)  interfaces                                      (D)  all the three

             h.   The number of overhead bytes in the ATM transmission format is

(A) 2                                                  (B)  5

(C)  48                                                (D)  53

             i.    Potential bandwidths of fibre optic cables are in the order of

(A) (B)

(C) (D)

             j.    A multimode fibre system has attenuation of 3 dB / km. The acceptable loss on the total fibre is 45 dB.  The loss limit for the system is about

(A) 11.25 km                                      (B) 15 km

(C) 31.5 km                                        (D) 135 km

Answer any FIVE Questions out of EIGHT Questions.

Each question carries 16 marks.

Q.2     a.   Explain the working of an  three stage switching network with the help of a neat diagram.                 (8)

             b.   Derive the expression for the minimum number of switching elements required for an  three stage non-blocking configuration.                         (8)

Q.3     a.   Discuss the working of an input controlled time division space switch.                  (8)

b.   Explain random input/ random output time division time switching.                       (8)

Q.4     a.   What are the different methods of providing telephone services to rural subscribers?                       (8)

b.   Discuss transmission impairments.                                                                       (8)

Q.5     a.   What are the advantages of cellular mobile systems over land line systems?  What type of topology is required for cellular mobile systems?    (8)

     b.   Explain GSM system.                                                                                        (8)

  Q.6     a. Illustrate the wavelength division multiplexing (WDM) technique used in fibre optic cable systems.                                                              (8)

             b.   Write notes on SONET system.                                                                         (8)

Q.7     a.   Differentiate between circuit switching, message  switching and packet switching.                (8)

b.   Describe how the store and forward network is configured using packet switching.             (8)

Q.8           Write short notes on:

(i) Advantages of ISDN

(ii) Various services provided by ISDN.

(iii) ISDN architecture.

(iv) Layers of OSI.                                                                       (4x4)

Q.9     a.   Consider a fibre optic token ring with a physical length of 100 km, an operating speed of 100 Mbps, and having 100 stations, each introducing     1-bit delay.  Compute the maximum ring utilisation if the free token were to be reintroduced after the first bit arrives at the source.  Assume a frame length of 1000 bits and equal spacing of the stations.                (8)

b.   Write notes on combination switching.  (8)