Digital Switching Systems - Dec 2014

Electronics & Communication (Semester 8)

TOTAL MARKS: 100
TOTAL TIME: 3 HOURS (1) Question 1 is compulsory.
(2) Attempt any four from the remaining questions.
(3) Assume data wherever required.
(4) Figures to the right indicate full marks. 1 (a) Explain briefly the network structures used in telecommunication network.(10 marks) 1 (b) With neat diagram, explain the hierarchy used in the national Public Switched Telephone Network (PSTN).(6 marks) 1 (c) With neat diagram of elementary time-division multiplexing system, explain the principle of time-division mutiplex transmission.(4 marks) 2 (a) Briefly explain the functions of a switching system.(8 marks) 2 (b) With the neat block-diagram of subscribers line interface circuit, mention the functions implemented by it.(4 marks) 2 (c) With neat block-diagram explain the different functions performed by stored program control switching system.(8 marks) 3 (a) Define traffic intensity, holding time, congestion, grade of service and occupancy.(5 marks) 3 (b) Derive the expression for Grade of Service (GOS) of a lost-call system having N trunks, when the offered traffic is A Erlangs.(10 marks) 3 (c) 10 E of traffic is offered to switches that hunt sequentially over a group of trunks. Estimate the traffic carried by each of the first three trunks.(5 marks) 4 (a) Define grading. Explain different types of gradings.(5 marks) 4 (b) Design a grading for connecting 20 trunks to switches having 10 outlets. Find the best grading. Represent the different possible gradings using grading diagram.(10 marks) 4 (c) Design a three stage network for 100 incoming and 100 outgoing trunks.(5 marks) 5 (a) With a neat diagram, briefly explain the space switch K incoming and m-outgoing PCM highways.(6 marks) 5 (b) With neat diagram explain time-space-time switching (T-S-T) network.(6 marks) 5 (c) With neat diagram explain the frame-alignment of PCM signals entering a digital exchange.(8 marks) 6 (a) With a neat diagram, explain the classification of digital switch software.(10 marks) 6 (b) Write a short note on a basic call model.(10 marks) 7 (a) Write a short note on the interface of typical digital switching system central office.(10 marks) 7 (b) Write a short note on strategy for improving software quality.(10 marks) 8 (a) Write a short note on digital switching system hardware architecture.(10 marks) 8 (b) Write a short note on digital switching system software architecture.(10 marks)