System

B.E. (Electronics and Telecommunication) TELECOMMUNICATION AND SWITCHING SYSTEM

(2008 Pattern) (Sem. – II)

Time :3 Hours]                                                                           [Max. Marks :100

Instructions to the candidates:

1)            Answer 3 questions from Section -1 and 3 questions from Section – II.

2)            Answers to the two sections should be written in separate books.

3)            Neat diagrams must be drawn wherever necessary.

4)            Pigures to the right indicate full marks.

5)            Use of electronic pocket calculator is allowed.

6)            Assume suitable data, if necessary.

SECTION – I

QI) a) State and explain switching functions of switching system.                              [8]

b) Draw typical centralised SPC organisation. State the processor configuration used. Explain the various modes of this configuration in brief.                                 [8]

OR

Q2) a) Explain the operation of sequential Read/Random write time division time switching with a neat block diagram.                                                                                            [8]

b) Derive and calculate the unavailability for dual processor system with MTBF = 1500 HRS. and MTTR = 8 HRS. in 30 years.                                                           [8]

Q3) a) Define and explain                                                                               [10]

i)             Grade of service.

ii)          Average Holding time.

iii)        Call completion rate.

iv)         Erlang and CCS.

b) A group of 20 trunks provides a grade of service of 0.015 when offered 12 E of traffic.                                                                                                                               [8]

i)             How much is the grade of service improved if one extra trunk is added to the group?

ii)           How much does the grade of service deteriorates if one trunk is out of service?

Q4) a) Explain the term ‘Offered Traffic’ and ‘Carried Traffic’. How are these traffics related in loss systems and delay systems.                                                                      [8]

b) During the busy hour 1350 calls were offered to a group of trunks and 10  calls were lost. The average call duration was 210 seconds. Find[10]

i)              The Traffic Offered.

ii)           The Traffic Carried.

iii)         The Traffic Lost.

iv)         The grade of service.

v)            The total duration of period of congestion.

Q5) a) What is limited availability and full availability in switching network? Explain the principal of Grading.                                                                    [8]

b) Derive the equation for total no. of cross points required for two stage network with ‘N’ incoming and ‘N’ out going trunks.                                               [8]

OR

Q6) a) Design grading for connecting 20 trunks to switches having 10 outlets.[8] b) Draw and explain PCM signalling.                                                                                    [8]

SECTION – II

Q7) a) What is clock instability? Explain main sources of clock instability. [8] b) What is timing jitter? Draw and explain block schematic diagram for measuring timing jitter.        [8]

OR

Q8) a) Explain synchronization of a clock in a transmitter 8 receiver system using PLL.  [8]

b) What is pulse stuffing approach for network synchronization? Explain in brief.    [8]

Q9) a) Explain the circuit switched and packet switched network with the help of diagram.        [8]

b) Explain the terms with reference to ISDN.                                                         [8]

i)             Functional Groups.

ii)           Reference Points.

Q10)a) Explain the ISO-OSI reference model for communication architecture with the help of a neat diagram.                                                                                                     [10]

b) What is ISDN? Explain in brief what is the motivation for ISDN. [6]

Q11)a) Explain the following terms in brief:                                                                  [10]

i)             Frequency Reuse.

ii)           Cell Splitting.

iii)        Hand Off.

iv)         Roaming.

v)            Sectoring.

b) Explain logical and physical channels of IS – 95.                                              [8]

OR

Q12)a) State and explain cellular telephone Network Components.       [10]

Explain wireline to cellular telephone call procedure. [8]

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