AMIETE – ET (NEW SCHEME)   –   Code: AE64

 

Subject: TELECOMMUNICATION SWITCHING SYSTEMS

Flowchart: Alternate Process: JUNE 2010Time: 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 the best alternative in the following:                                     (210)

                           

         a.       A switching system allows:

              

                  (A)  Direct connectivity always.            

                  (B)  Random access connectivity depending on availability.

                  (C)  Sequential connectivity for all subscribers.

                  (D)  Frequency dependent connectivity.

       

         b.      Crossbar switching provides:

 

                                                                              (A) Step by step switching.                                    

                                                                              (B) Coordinating matrix switching

                                                                              (C) Stored program switching.

                                                                              (D) Differential switching.

 

         c.      The blocking probability is:

 

                  (A) Probability that a subscriber may get blocked.

                  (B)  Probability that a call may not get through an exchange. 

                  (C) An exchange is not accessible.

                  (D) A subscriber cannot forward the calls.

 

         d.      Queuing signifies:

 

                                                                              (A) Non availability of a subscriber.                       

                                                                              (B) Transfer of call from on exchange to another.

                                                                              (C) Non availability of a server in the exchange.      

                                                                              (D)  Loss during switching.

 

        e.        In a telephone network call waiting feature requires two switching paths to be set up simultaneously and the both paths must use __________.

            

                                                                              (A)  different signalling scheme.

                                                                              (B)  same signalling scheme

                  (C)  two orthogonal signalling scheme   

                                                                              (D)  two signalling scheme with appropriate phase delay.

 

            f.                                                               Three stage non-blocking is achieved ____________.

 

                                                                              (A)  by increasing the inlets in fist stages                 

                                                                              (B)  by reducing the number of subscribers

                      (C)  by using more number of switches                                                                           

                                                                              (D)  by introducing adequate number of blocks in second stages

       

             g.                                                              In an 8 bit PCM using 12 voice channels TDM the transmission rate is ________.

 

                                                                              (A) 64 kbps                                     (B) 1544 kbps

                                                                              (C) 776 kbps                                    (D) 512 kbps

 

             h.                                                             In  FDM system _________________.

 

                     (A) a base band is built with multiple sources                                                                   

                           (B) a number of channels can access a server

                  (C) a number of sources are transmitted at different times sequentially.                                

                                                                              (D) the same source can be transmitted on different carriers.

       

i.      SS7 uses layered architecture like _________.

 

                                                                              (A) Ethernet                                       (B) ISO-OSI

                                                                              (C) SPC                     (D) ATM                            

 

             j.                                                               A distributed network configuration in which all data / information pass through a central computer is:

 

                                                                              (A) Bus network.                         (B) Star network.

                                                                              (C) Ring network.         (D) Point to point network.

 

 

Answer any FIVE Questions out of EIGHT Questions.

Each question carries 16 marks.

 

 

  Q.2     a.                                                              Draw a 100 line exchange using uni-selectors and two-motion selectors, explain how it works to set up a call.                                                                                (8)

 

             b.                                                              Bring out the major differences between electromechanical and electronic switching systems.                                                                                          (8)

 

 Q.3    a.                                                             Define the following and explain its usefulness in traffic calculation:

                                                                              (i)  Busy Hour  (ii) Grade of service (iii) Offered traffic                                            (6)

 

             b. In a particular exchange during busy hour 1200 calls were offered to a group of trunks, during this time 6 calls were lost. The average call duration being 3 minutes. Calculate:

    

                  (i)    Traffic offered in erlangs.

                  (ii)   Traffic lost.                                                                                                 

                  (iii)  Grade of service and                                                                                               (4)

                  (iv)   Period of congestion.

                                                                                                              

            c.                                                                Explain why queuing is used in taking care of traffic.            (6)

 

    Q4     a.  What are the advantages and disadvantages of a multiple stage system over single

                                                                                                                                       stage system?                 (8)  

             b. Explain how Lee’s graph helps in determining blocking probability. A three stage network is designed with the following parameters:

                  M=N=512, p=g=16 and =0.7. Calculate the blocking of the network if (a) s=16   

                  and (b) s=24.                                                                                                                 (8)

            

  Q.5     a.   Draw an input controlled time division space switching and explain how the bus is being time shared by N connections.                                                                                                                   (8)

 

             b. Explain the principle of Time slot interchange switch in time multiplexed time switching. Calculate the maximum access time that can be permitted for data and control in TSI with single input and single output trunk multiplexing of 4096 channels. The cycle time is 125 microseconds.                                                                                                                         (8)

 

  Q.6     a.  Show how finite stage machine model helps in designing a switching system and give example.                                                                                                                                                                                                                                       (8)

 

             b.  Explain the process of load sharing in a centralized SPC.                                                 (8)

 

  Q.7     a.  What is the need to have trunk circuits? Explain how a CCITT super group is transmitted in FDM.                                                                                                                                               (8)

 

             b.  Where is a high level data link control protocol used?  Give example.                              (8)

 

  Q.8     a.  Distinguish between circuit switching and packet switching.                                             (4)

 

             b.  Draw the X.25 frame format and show how virtual calls are setup.                                  (6)

 

             c. What was the need to introduce ATM, explain principal of ATM networks.                     (6)                                    

            

  Q.9     a.  Describe briefly the various types of ISDN services. What are the various international numbering plans used?                                                                                                                                                                         (8)

 

             b.  How a cellular radio network is implemented, explain its important entities.                      (8)