midterm 1

Question 1

Define duty-cycling and its benefits.

Answer 1

Duty-cycling is the process of turning sensor node components (especially radios) on and off periodically to conserve energy.

Benefits include prolonged battery life, reduced energy consumption, and extended network lifetime.

Question 2

What are mobile sensor nodes, and how are they used?

Answer 2

Mobile sensor nodes are sensors with the ability to move, either autonomously or controlled, to cover larger or dynamic areas.

Use cases include wildlife monitoring, mobile robot sensors, or smart vehicles.

Question 3

What is the role of a base station in a WSN?

Answer 3

A base station (or sink node) collects data from sensor nodes, processes or forwards it to external networks or cloud services.

Question 4

Compare static, mobile, and UAV-based base stations.

Answer 4

Static: Fixed in location; reliable but limited coverage.
Mobile: Moves (e.g., on robots); improves coverage and adaptability.
UAV-based: Uses drones; ideal for hard-to-reach or disaster zones; fast deployment, flexible.

Question 5

How do energy-harvesting base stations operate?

Answer 5

They collect energy from external sources (solar, wind, vibration) to power themselves, reducing dependency on batteries and enabling long-term deployment in remote areas.

Question 6

Explain the relationship between IoT and WSNs.

Answer 6

WSNs are a core component of IoT, providing the sensing and data collection capabilities.

Question 7

Provide two examples where WSNs are used in healthcare.

Answer 7

• Patient monitoring (heart rate, body temperature)
• Wearable sensors for elderly fall detection or chronic disease tracking

Question 8

List two applications of WSNs in agriculture.

Answer 8

• Soil moisture and temperature monitoring for irrigation
• Crop disease detection using environmental data sensors

Question 9

What are the primary uses of WSNs in disaster management?

Answer 9

• Early warning systems (earthquakes, floods)
• Real-time monitoring of disaster zones
• Search and rescue assistance via mobile/UAV sensors

Question 10

What are some challenges faced by WSNs?

Answer 10

• Limited energy supply
• Data security
• Harsh environmental conditions
• Scalability and coverage
• Network reliability and latency

Question 11

What are the four main hardware components in a sensor node?

Answer 11

• Sensing unit
• Processing unit
• Transceiver (communication unit)
• Power unit

Question 12

How does a temperature sensor work?

Answer 12

It measures temperature changes and converts them into electrical signals using thermistors, thermocouples, or semiconductor-based sensors.

Question 13

Give an example of a resistive sensing mechanism.

Answer 13

Thermistors – their resistance changes with temperature and can be measured to infer temperature.

Question 14

Describe the function of the processing unit in a WSN.

Answer 14

Processes sensor data, manages tasks like data filtering, compression, and communication.

Question 15

Compare microcontrollers and FPGAs used in sensor nodes.

Answer 15

Microcontrollers: Low power, simpler, cost-effective, good for basic tasks.
FPGAs: More powerful, reconfigurable, suitable for parallel processing and complex computations.

Question 16

What is the purpose of data filtering in processing units?

Answer 16

Reduces redundant/noisy data, saves bandwidth and power, and improves data accuracy before transmission.

Question 17

What is edge processing, and how does it differ from centralized processing?

Answer 17

Edge processing: Data is processed locally on the sensor node.
Centralized processing: Data is sent to a central server for processing.

Question 18

List three wireless communication technologies used in WSNs.

Answer 18

• Zigbee
• Bluetooth Low Energy (BLE)
• LoRaWAN

Question 19

What power sources are commonly used in WSNs?

Answer 19

• Batteries
• Energy harvesting (solar, thermal, vibration)
• Supercapacitors

Question 20

What is the role of memory units in WSNs?

Answer 20

Store sensor data, program instructions, and buffering for communication.

Question 21

Compare RAM and Flash memory in sensor nodes.

Answer 21

RAM: Volatile, fast, used for temporary data.
Flash: Non-volatile, stores firmware and sensor readings.

Question 22

Why is clock synchronization important?

Answer 22

To ensure accurate timestamping, event coordination, and data consistency across nodes.

Question 23

What are real-time clocks (RTC)?

Answer 23

Low-power clocks used to maintain time when the main processor is off.

Question 24

How do actuators enhance interaction?

Answer 24

By converting signals into physical actions (e.g., movement, light, sound) for environmental interaction.

Question 25

Name two challenges in actuator design.

Answer 25

* Limited power supply * Precision and reliability in harsh environments

Question 26

List three WSN operating systems.

Answer 26

* TinyOS * Contiki * RIOT OS

Question 27

What is middleware, and its importance?

Answer 27

Middleware bridges hardware and applications, enabling reusability, interoperability, and scalability.

Question 28

Give an example of middleware.

Answer 28

Mate or ContikiMAC for dynamic reprogramming.

Question 29

What is 6LoWPAN?

Answer 29

Enables IPv6 over low-power wireless networks (e.g., IEEE 802.15.4).

Question 30

What is the importance of encryption?

Answer 30

Protects data confidentiality, integrity, and prevents unauthorized access.

Question 31

What is TOSSIM?

Answer 31

A simulator for TinyOS-based WSNs used to test code virtually before deployment.

Question 32

What is data aggregation in software?

Answer 32

Combines data from multiple sensors to reduce redundancy and conserve energy.

Question 33

What is fault detection in WSN software?

Answer 33

Detects anomalies, node failures, or communication breakdowns through diagnostic checks.

Question 34

What is the role in remote monitoring?

Answer 34

Enables users to track data and network status without being physically present.

Question 35

Define throughput.

Answer 35

Amount of data successfully transmitted over time, measured in bits/sec.

Question 36

What are the components of end-to-end delay?

Answer 36

* Transmission delay * Propagation delay * Processing delay * Queuing delay

Question 37

What is the PDR formula?

Answer 37

PDR = (Packets received / Packets sent) × 100%

Question 38

What is routing overhead?

Answer 38

Extra communication and computation required to maintain routing paths.

Question 39

What is the importance of scalability?

Answer 39

Allows the network to grow without performance loss.

Question 40

How is energy consumption calculated?

Answer 40

Based on energy used in sensing, processing, and communication over time.

Question 41

What are the functions of the Application Layer?

Answer 41

Data formatting, service access, and application-specific processing.

Question 42

What is the purpose of MAC protocols?

Answer 42

Control how nodes access the channel to avoid collisions and save energy.

Question 43

What does TDMA protocol assign?

Answer 43

Time slots to each node to avoid interference.

Question 44

What is a disadvantage of S-MAC?

Answer 44

High latency and low throughput in high-traffic scenarios due to sleep schedules.

Question 45

What is the best deployment for disaster recovery?

Answer 45

Mobile or UAV-based nodes—quick deployment, coverage flexibility.

Question 46

What topology has high fault tolerance?

Answer 46

Mesh topology—multiple paths ensure data reaches destination.

Question 47

Calculate coverage probability.

Answer 47

Coverage probability = (18 × 50) / 1000 = 900 / 1000 = 0.9 or 90%

Question 48

What is a common energy harvesting method in wearables?

Answer 48

Kinetic energy (e.g., from movement) via piezoelectric or thermoelectric generators.

Question 49

How does blockchain improve energy efficiency?

Answer 49

Secures data without centralized servers, reduces data redundancy, and improves trust with fewer transmissions.

Question 50

What is the Pump-Slow mechanism?

Answer 50

Regulates traffic by increasing data flow slowly and decreasing it rapidly upon congestion detection.

Question 51

1. What is a Wireless Sensor Network (WSN)?

Answer 51

A WSN is a network of spatially distributed sensor nodes that wirelessly collect and transmit environmental data (like temperature, humidity, motion) to a central system for monitoring or analysis.

Question 52

2. What component is typically included in a basic Wireless Sensor Network (WSN) architecture?

Answer 52

A sensor node, which includes a sensing unit, processing unit, communication (transceiver), and power source.

Question 53

3. Which data transmission technique in WSNs helps reduce redundant data and conserve energy?

Answer 53

Data aggregation – it combines data from multiple nodes before transmission to reduce redundancy.

Question 54

4. Which sensor mechanism detects stimuli through changes in electrical resistance?

Answer 54

Resistive sensors, like thermistors and strain gauges.

Question 55

5. What is the primary role of a microcontroller in a sensor node?

Answer 55

To process data, manage sensor operations, and control communication tasks.

Question 56

6. Name an operating system that is optimized for low-power wireless devices commonly used in WSNs.

Answer 56

TinyOS or Contiki OS

Question 57

7. What does the Packet Delivery Ratio (PDR) represent in a Wireless Sensor Network?

Answer 57

The ratio of successfully delivered packets to the total packets sent – it measures network reliability.

Question 58

8. Which type of base station is typically used for battlefield surveillance in Wsn Mobile or UAV-based base stations

Answer 58

they offer flexibility and dynamic coverage.

Question 59

9. What is the main advantage of using edge processing instead of centralized processing in sensor networks?

Answer 59

It reduces data transmission, saving energy and bandwidth, and provides faster local decision-making.

Question 60

10. Which middleware used in WSNs allows for dynamic reprogramming and adaptation?

Answer 60

TinyDB, Mate, or Deluge are commonly used for dynamic WSN middleware.

Question 61

11. What performance metric measures the total time taken by a data packet to travel from the source node to the destination node?

Answer 61

Latency (or End-to-End Delay)

Question 62

12. List three key features of WSNs.

Answer 62

Self-organization Energy efficiency Wireless multi-hop communication

Question 63

13. Why is energy efficiency important in WSNs?

Answer 63

Sensor nodes often run on limited battery power, and replacing batteries is costly or impossible in remote or hazardous locations.

Question 64

14. How have WSNs evolved since the 1980s?

Answer 64

From large, wired military systems to miniaturized, wireless, low-power, and versatile devices used in healthcare, agriculture, smart cities, and more.

Question 65

15. What are the three main components of WSN architecture?

Answer 65

Sensor nodes Base stations Communication infrastructure

Question 66

16. What is the difference between flat and cluster-based WSN topologies?

Answer 66

Flat topology: All nodes are equal and communicate directly or via multi-hop. Cluster-based: Nodes are grouped into clusters, each led by a cluster head to manage communication and reduce load.

Question 67

17. Explain direct transmission in WSNs.

Answer 67

Sensor nodes send data directly to the base station without intermediaries; simple but energy-intensive for distant nodes.

Question 68

18. What are the advantages of multi-hop transmission?

Answer 68

Saves energy Reduces long-distance transmission load Extends network lifespan

Question 69

19. What is data aggregation in WSNs?

Answer 69

Combining data from multiple nodes (e.g., averaging) to reduce redundancy and minimize transmission.

Question 70

20. How does event-driven transmission help in saving energy?