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Most Frequently Asked Questions
Top recurring IOE board exam questions for Telecommunication with verified mark schemes, formula notation, and recurrence frequency.
Showing 30 of 30 top repeated questions
Introduction
2 Questions
#1Repeated 2 Times[6 Marks]Introduction
What are the purposes and functions of the International Telecommunication Union (ITU)? Explain the regulatory and policy role of the Nepal Telecommunications Authority (NTA) in the development of the telecom sector in Nepal.
Appeared in:2082 Chaitra2080 Chaitra
#2Repeated 1 Times[5 Marks]Introduction
Explain National and International Numbering Plans according to ITU-T Recommendation E.164 (Country Code, National Destination Code, and Subscriber Number).
Appeared in:2082 Shrawan
Switching and Multiplexing
14 Questions
#1Repeated 3 Times[8 Marks]Switching and Multiplexing
Explain Space-Division Switching and Time-Division Switching. Derive the minimum number of crosspoints for a non-blocking 3-stage Clos Network $N_c = 2Nk + k(N/n)^2$, and state Clos's condition $k \ge 2n - 1$.
Appeared in:2082 Chaitra2080 Chaitra2079 Chaitra
#2Repeated 3 Times[8 Marks]Switching and Multiplexing
Explain Time Slot Interchange (TSI) and Time-Multiplexed Space (TMS) switching modules. Contrast Time-Space-Time (TST) and Space-Time-Space (STS) multi-stage digital switches with complexity analysis.
Appeared in:2082 Chaitra2081 Chaitra2078 Kartik
#3Repeated 3 Times[8 Marks]Switching and Multiplexing
Describe Common Channel Signaling System No. 7 (SS7) architecture. Explain the four levels of the SS7 protocol stack (MTP-1, MTP-2, MTP-3, and SCCP/ISUP/TCAP) and signaling network nodes (SP, STP, SCP).
Appeared in:2082 Chaitra2080 Chaitra2076 Chaitra
#4Repeated 3 Times[6 Marks]Switching and Multiplexing
Explain Channel-Associated Signaling (CAS) vs Common-Channel Signaling (CCS). Discuss why CCS replaced CAS in modern telecommunication networks with respect to trunk utilization, setup speed, and fraud prevention.
Appeared in:2082 Chaitra2081 Chaitra2077 Magh
#5Repeated 3 Times[8 Marks]Switching and Multiplexing
Describe the Plesiochronous Digital Hierarchy (PDH) and Synchronous Digital Hierarchy (SDH). Detail the E1 primary rate frame structure ($2.048\text{ Mbps}$, 32 time slots of $64\text{ kbps}$, frame alignment in TS0, signaling in TS16).
Appeared in:2082 Chaitra2080 Chaitra2078 Bhadra
#6Repeated 3 Times[8 Marks]Switching and Multiplexing
Describe Synchronous Digital Hierarchy (SDH) and SONET frame structures. Explain STM-1 frame structure ($155.52\text{ Mbps}$, 9 rows $\times$ 270 columns), Section Overhead (SOH), Path Overhead (POH), and pointer justification mechanisms.
Appeared in:2082 Chaitra2081 Chaitra2079 Chaitra
#7Repeated 3 Times[8 Marks]Switching and Multiplexing
Explain Wavelength Division Multiplexing (WDM) and Dense WDM (DWDM). Describe optical transponders, optical add-drop multiplexers (OADM/ROADM), and Erbium-Doped Fiber Amplifiers (EDFA) in long-haul optical networks.
Appeared in:2082 Chaitra2080 Chaitra2076 Chaitra
#8Repeated 3 Times[8 Marks]Switching and Multiplexing
Describe Asynchronous Transfer Mode (ATM). Explain the fixed 53-byte ATM cell structure (5-byte header, 48-byte payload), Virtual Path Identifier (VPI), Virtual Channel Identifier (VCI), and ATM Adaptation Layer (AAL) classes.
Appeared in:2082 Chaitra2080 Chaitra2078 Kartik
#9Repeated 2 Times[8 Marks]Switching and Multiplexing
Explain three different operational modes of dual-processor architecture used in Stored Program Control (SPC) electronic switching systems: (a) Standby mode, (b) Synchronous duplex mode, and (c) Load sharing mode. Discuss reliability and fault tolerance.
Appeared in:2082 Chaitra2080 Chaitra
#10Repeated 2 Times[8 Marks]Switching and Multiplexing
Explain the operation of Time-Space-Time (TST) and Space-Time-Space (STS) multi-stage digital switches with necessary block diagrams. Compare their blocking probabilities, implementation complexity, and cross-point requirements.
Appeared in:2082 Chaitra2080 Chaitra
#11Repeated 2 Times[8 Marks]Switching and Multiplexing
What is Common Channel Signaling (CCS)? Describe the SS7 protocol stack architecture (MTP Level 1-3, SCCP, TCAP, ISUP) with a neat block diagram and compare CCS with channel-associated in-band signaling.
Appeared in:2082 Chaitra2080 Chaitra
#12Repeated 2 Times[8 Marks]Switching and Multiplexing
Explain the operation of Circuit Switching, Message Switching, and Packet Switching (Virtual Circuit vs Datagram networks) with timing diagrams and compare them in terms of call setup delay, dedicated bandwidth, and latency.
Appeared in:2082 Chaitra2081 Chaitra
#13Repeated 2 Times[8 Marks]Switching and Multiplexing
Describe Stored Program Control (SPC) in digital telephone exchanges. Explain centralized vs distributed SPC architectures and detail the basic software call processing steps from off-hook to call teardown.
Appeared in:2080 Chaitra2079 Chaitra
#14Repeated 1 Times[6 Marks]Switching and Multiplexing
What is Time Division Multiplexing (TDM)? How does Statistical TDM (STDM) overcome the limitations and bandwidth wastage of synchronous TDM? Explain STDM frame structure with address overhead.
Appeared in:2080 Chaitra
Telephone Traffic
4 Questions
#1Repeated 3 Times[8 Marks]Telephone Traffic
Define Erlang, Grade of Service (GoS), and blocking probability in telephone traffic engineering. State Erlang-B formula: $B(c, A) = \frac{A^c / c!}{\sum_{k=0}^c A^k / k!}$. During busy hour, an average of $30\text{ Erlangs}$ is offered to a group of trunks; calculate carried traffic, lost traffic, and required number of lines for a given GoS.
Appeared in:2082 Chaitra2081 Chaitra2080 Chaitra
#2Repeated 3 Times[8 Marks]Telephone Traffic
Derive Erlang's Lost Call Formula (Erlang-B formula) $B(c, A) = \frac{A^c / c!}{\sum_{k=0}^c A^k / k!}$ for a telephone trunk group of $c$ circuits with offered traffic load $A$ in Erlangs under Blocked Calls Cleared (BCC) assumptions. Calculate blocking probability for $c=4, A=2\text{ Erlangs}$.
Appeared in:2082 Chaitra2080 Chaitra2078 Bhadra
#3Repeated 3 Times[8 Marks]Telephone Traffic
Explain Erlang's Delay Formula (Erlang-C formula) for Blocked Calls Delayed (BCD) queuing systems. Derive average queue length, average waiting time in queue ($W_q$), and probability of delay exceeding $t$ seconds in call center switching systems.
Appeared in:2082 Chaitra2081 Chaitra2077 Magh
#4Repeated 2 Times[8 Marks]Telephone Traffic
Differentiate between Infinite Source (Lost Calls Cleared - Erlang B), Lost Calls Delayed (Erlang C queuing model), and Finite Source (Engset model) traffic systems in telecommunication networks.
Appeared in:2081 Chaitra2080 Chaitra
Physical and Data Link Layer
1 Question
#1Repeated 2 Times[8 Marks]Physical and Data Link Layer
Compare guided transmission media used in telecommunication networks: Twisted Pair, Coaxial Cable, and Optical Fiber. Explain the propagation of light through optical fiber, acceptance angle, and single-mode versus multi-mode fiber characteristics.
Appeared in:2080 Chaitra2079 Chaitra
Network Layer
1 Question
#1Repeated 2 Times[8 Marks]Network Layer
Explain Routing and Congestion Control in packet switching networks: compare Distance Vector Routing (Bellman-Ford) with Link State Routing (Dijkstra), and explain Leaky Bucket and Token Bucket traffic shaping algorithms.
Appeared in:2082 Shrawan2081 Chaitra
Advanced Topics
8 Questions
#1Repeated 3 Times[8 Marks]Advanced Topics
Describe Integrated Services Digital Network (ISDN). Compare Basic Rate Interface ($2B + D = 144\text{ kbps}$) and Primary Rate Interface ($30B + D = 2.048\text{ Mbps}$) architectures, reference points ($R, S, T, U$), and terminal equipment.
Appeared in:2082 Chaitra2081 Chaitra2077 Magh
#2Repeated 3 Times[8 Marks]Advanced Topics
Explain Optical Access Networks: Fiber-to-the-Home (FTTH) and Passive Optical Networks (PON). Compare Gigabit PON (GPON) and Ethernet PON (EPON) architectures, optical splitters, Optical Line Terminal (OLT), and Optical Network Unit (ONU/ONT).
Appeared in:2082 Chaitra2081 Chaitra2079 Chaitra
#3Repeated 3 Times[8 Marks]Advanced Topics
Explain Multi-Protocol Label Switching (MPLS). Describe Label Switched Routers (LSR), Label Edge Routers (LER), Label Distribution Protocol (LDP), and how MPLS enables Traffic Engineering and Layer-3 VPNs.
Appeared in:2082 Chaitra2080 Chaitra2078 Bhadra
#4Repeated 3 Times[8 Marks]Advanced Topics
Explain Next Generation Network (NGN) and IP Multimedia Subsystem (IMS). Describe the architectural separation of transport layer, control layer (Softswitch/MGC), and application service layer with the Session Initiation Protocol (SIP).
Appeared in:2082 Chaitra2081 Chaitra2076 Chaitra
#5Repeated 2 Times[6 Marks]Advanced Topics
What is Softswitch and Next Generation Network (NGN)? Explain the functional separation of Call Control and Bearer Transport, Media Gateways (MG), and Media Gateway Controllers (MGC) using SIP and MEGACO protocols.
Appeared in:2082 Shrawan2080 Chaitra
#6Repeated 2 Times[6 Marks]Advanced Topics
Explain Voice over IP (VoIP) network operation: Describe the roles of RTP/RTCP for media transport and SIP (Session Initiation Protocol) for session setup, modification, and termination.
Appeared in:2082 Chaitra2079 Chaitra
#7Repeated 1 Times[8 Marks]Advanced Topics
What is ISDN? Explain the architectural reference model, reference points (R, S, T, U), functional devices (NT1, NT2, TE1, TE2, TA), and compare Basic Rate Interface ($2B+D$) and Primary Rate Interface ($30B+D$).
Appeared in:2079 Chaitra
#8Repeated 1 Times[6 Marks]Advanced Topics
Explain Digital Subscriber Line (xDSL) architecture: compare ADSL, VDSL, and HDSL. Explain Discrete Multi-Tone (DMT) modulation, POTS splitters, and downstream/upstream frequency division.