Signals, Systems, and 5G Network Fundamentals

Posted on Dec 23, 2025 in Computer Engineering

Signal Transformation for Continuous-Time Signals

Q1 (a) — Explain the signal transformation needed for transforming the independent variable for continuous-time signals.

Signal transformation changes the independent variable (usually time) to modify or analyze signals. Common transformations include:

  • Time shifting: Shifts the signal by a time constant t₀.
  • Time scaling: Compresses the signal (if a > 1) or expands it (if a < 1).
  • Time reversal: Flips the signal around the vertical axis.

These transformations help in synchronization, modulation, and system analysis in telecommunications.

Properties of Discrete-Time Sequences

Q1 (b) — State and explain the properties of sequences for discrete-time signals.

Properties of discrete-time sequences include:

  • Linearity: The system’s output equals the sum of individual responses.
  • Time shifting: Shifts the sequence by an integer n₀.
  • Time reversal: Mirrors the sequence across the origin.
  • Periodic/Aperiodic: Repeats after N samples (periodic) or does not repeat (aperiodic).
  • Energy and Power: Useful metrics for analyzing finite and infinite sequences.

System Definition and Classification

Q1 (c) — Define a system and give its classification.

A system is a device or process that transforms an input signal into an output signal.

Classification of Systems:

  1. Linear / Non-linear: Whether the system follows the superposition principle.
  2. Time-invariant / Time-variant: Whether system behavior is constant or changes with time.
  3. Causal / Non-causal: Depends only on present and past inputs or also on future inputs.
  4. Stable / Unstable: Whether a bounded input results in a bounded output (BIBO).
  5. Static / Dynamic: Depends only on the present input (memoryless) or also on past inputs (has memory).

Functions and Sequences in Detail

Q1 (d) — Explain the concept of functions and sequences in detail.

A function represents a continuous-time signal x(t), where t can take any real value. A sequence represents a discrete-time signal x[n], where n takes integer values.

Functions are primarily used in analog systems, while sequences are used in digital systems. Both describe how a signal changes with respect to time. Conversion between them is achieved through sampling (continuous to discrete) and interpolation (discrete to continuous).

The Seven Pillars of 5G Technology

Q2 (a) — Describe any 7 pillars of 5G.

  1. Enhanced Mobile Broadband (eMBB): High data rates for HD video and VR.
  2. Ultra-Reliable Low Latency Communication (URLLC): Real-time control for IoT and autonomous vehicles.
  3. Massive Machine Type Communication (mMTC): Connects billions of IoT devices.
  4. Network Slicing: Divides a physical network into multiple virtual networks for different applications.
  5. Edge Computing: Processing data closer to users to reduce latency.
  6. Massive MIMO: Uses multiple antennas to increase spectral efficiency.
  7. Energy Efficiency: Focuses on reduced power consumption and better resource management.

Challenges Faced by Small Cells

Q2 (b) — What are the challenges faced by small cells?

  • Interference management: Overlapping cells can cause signal issues.
  • Backhaul connectivity: Requires strong network links to connect to main servers.
  • Deployment cost: High expenses related to installation and maintenance.
  • Security concerns: More points of entry for potential hackers.
  • Power and location constraints: Requires reliable power and suitable physical placement.

The Internet of Things (IoT)

Q2 (c) — Write a short note on IoT.

The Internet of Things (IoT) connects everyday devices to the internet for data sharing and automation. Examples include smart homes, wearables, and industrial monitoring.

  • Key features: Sensors, connectivity, cloud storage, data analysis, and automation.
  • Benefits: Efficiency, remote control, and smart decision-making.
  • Challenges: Privacy, data security, and power consumption.

Software Defined Networking (SDN)

Q2 (d i) — Explain SDN.

Software Defined Networking (SDN) separates the control plane (decision making) from the data plane (traffic forwarding).

  • Centralized control through an SDN controller.
  • Programmable and flexible network management.
  • Enables automation and faster configuration.
  • Improves network performance and reduces operational costs.
  • Used in modern telecom networks and data centers.

Wi-Fi and Femtocells as Small Cell Technologies

Q2 (d ii) — Wi-Fi and femtocells as small cell technologies.

Wi-Fi: A Wireless Local Area Network (WLAN) technology that uses unlicensed spectrum to provide high-speed internet in small areas.

Femtocells: Small cellular base stations used in homes or offices to improve indoor mobile coverage.

Benefits:

  1. Extends coverage and increases network capacity.
  2. Offloads traffic from macro cells.
  3. Low power consumption.
  4. Improves call quality and data rates.

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