midterm 1 Flashcards
Define duty-cycling and its benefits.
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.
What are mobile sensor nodes, and how are they used?
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.
What is the role of a base station in a WSN?
A base station (or sink node) collects data from sensor nodes, processes or forwards it to external networks or cloud services.
Compare static, mobile, and UAV-based base stations.
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.
How do energy-harvesting base stations operate?
They collect energy from external sources (solar, wind, vibration) to power themselves, reducing dependency on batteries and enabling long-term deployment in remote areas.
Explain the relationship between IoT and WSNs.
WSNs are a core component of IoT, providing the sensing and data collection capabilities.
Provide two examples where WSNs are used in healthcare.
- Patient monitoring (heart rate, body temperature)
- Wearable sensors for elderly fall detection or chronic disease tracking
List two applications of WSNs in agriculture.
- Soil moisture and temperature monitoring for irrigation
- Crop disease detection using environmental data sensors
What are the primary uses of WSNs in disaster management?
- Early warning systems (earthquakes, floods)
- Real-time monitoring of disaster zones
- Search and rescue assistance via mobile/UAV sensors
What are some challenges faced by WSNs?
- Limited energy supply
- Data security
- Harsh environmental conditions
- Scalability and coverage
- Network reliability and latency
What are the four main hardware components in a sensor node?
- Sensing unit
- Processing unit
- Transceiver (communication unit)
- Power unit
How does a temperature sensor work?
It measures temperature changes and converts them into electrical signals using thermistors, thermocouples, or semiconductor-based sensors.
Give an example of a resistive sensing mechanism.
Thermistors – their resistance changes with temperature and can be measured to infer temperature.
Describe the function of the processing unit in a WSN.
Processes sensor data, manages tasks like data filtering, compression, and communication.
Compare microcontrollers and FPGAs used in sensor nodes.
Microcontrollers: Low power, simpler, cost-effective, good for basic tasks.
FPGAs: More powerful, reconfigurable, suitable for parallel processing and complex computations.
What is the purpose of data filtering in processing units?
Reduces redundant/noisy data, saves bandwidth and power, and improves data accuracy before transmission.
What is edge processing, and how does it differ from centralized processing?
Edge processing: Data is processed locally on the sensor node.
Centralized processing: Data is sent to a central server for processing.
List three wireless communication technologies used in WSNs.
- Zigbee
- Bluetooth Low Energy (BLE)
- LoRaWAN
What power sources are commonly used in WSNs?
- Batteries
- Energy harvesting (solar, thermal, vibration)
- Supercapacitors
What is the role of memory units in WSNs?
Store sensor data, program instructions, and buffering for communication.
Compare RAM and Flash memory in sensor nodes.
RAM: Volatile, fast, used for temporary data.
Flash: Non-volatile, stores firmware and sensor readings.
Why is clock synchronization important?
To ensure accurate timestamping, event coordination, and data consistency across nodes.
What are real-time clocks (RTC)?
Low-power clocks used to maintain time when the main processor is off.
How do actuators enhance interaction?
By converting signals into physical actions (e.g., movement, light, sound) for environmental interaction.
Name two challenges in actuator design.
- Limited power supply
- Precision and reliability in harsh environments
List three WSN operating systems.
- TinyOS
- Contiki
- RIOT OS
What is middleware, and its importance?
Middleware bridges hardware and applications, enabling reusability, interoperability, and scalability.
Give an example of middleware.
Mate or ContikiMAC for dynamic reprogramming.
What is 6LoWPAN?
Enables IPv6 over low-power wireless networks (e.g., IEEE 802.15.4).
What is the importance of encryption?
Protects data confidentiality, integrity, and prevents unauthorized access.
What is TOSSIM?
A simulator for TinyOS-based WSNs used to test code virtually before deployment.
What is data aggregation in software?
Combines data from multiple sensors to reduce redundancy and conserve energy.
What is fault detection in WSN software?
Detects anomalies, node failures, or communication breakdowns through diagnostic checks.
What is the role in remote monitoring?
Enables users to track data and network status without being physically present.
Define throughput.
Amount of data successfully transmitted over time, measured in bits/sec.
What are the components of end-to-end delay?
- Transmission delay
- Propagation delay
- Processing delay
- Queuing delay
What is the PDR formula?
PDR = (Packets received / Packets sent) × 100%
What is routing overhead?
Extra communication and computation required to maintain routing paths.
What is the importance of scalability?
Allows the network to grow without performance loss.
How is energy consumption calculated?
Based on energy used in sensing, processing, and communication over time.
What are the functions of the Application Layer?
Data formatting, service access, and application-specific processing.
What is the purpose of MAC protocols?
Control how nodes access the channel to avoid collisions and save energy.
What does TDMA protocol assign?
Time slots to each node to avoid interference.
What is a disadvantage of S-MAC?
High latency and low throughput in high-traffic scenarios due to sleep schedules.
What is the best deployment for disaster recovery?
Mobile or UAV-based nodes—quick deployment, coverage flexibility.
What topology has high fault tolerance?
Mesh topology—multiple paths ensure data reaches destination.
Calculate coverage probability.
Coverage probability = (18 × 50) / 1000 = 900 / 1000 = 0.9 or 90%
What is a common energy harvesting method in wearables?
Kinetic energy (e.g., from movement) via piezoelectric or thermoelectric generators.
How does blockchain improve energy efficiency?
Secures data without centralized servers, reduces data redundancy, and improves trust with fewer transmissions.
What is the Pump-Slow mechanism?
Regulates traffic by increasing data flow slowly and decreasing it rapidly upon congestion detection.
- What is a Wireless Sensor Network (WSN)?
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.
- What component is typically included in a basic Wireless Sensor Network (WSN) architecture?
A sensor node, which includes a sensing unit, processing unit, communication (transceiver), and power source.
- Which data transmission technique in WSNs helps reduce redundant data and conserve energy?
Data aggregation – it combines data from multiple nodes before transmission to reduce redundancy.
- Which sensor mechanism detects stimuli through changes in electrical resistance?
Resistive sensors, like thermistors and strain gauges.
- What is the primary role of a microcontroller in a sensor node?
To process data, manage sensor operations, and control communication tasks.
- Name an operating system that is optimized for low-power wireless devices commonly used in WSNs.
TinyOS or Contiki OS
- What does the Packet Delivery Ratio (PDR) represent in a Wireless Sensor Network?
The ratio of successfully delivered packets to the total packets sent – it measures network reliability.
- Which type of base station is typically used for battlefield surveillance in Wsn Mobile or UAV-based base stations
they offer flexibility and dynamic coverage.
- What is the main advantage of using edge processing instead of centralized processing in sensor networks?
It reduces data transmission, saving energy and bandwidth, and provides faster local decision-making.
- Which middleware used in WSNs allows for dynamic reprogramming and adaptation?
TinyDB, Mate, or Deluge are commonly used for dynamic WSN middleware.
- What performance metric measures the total time taken by a data packet to travel from the source node to the destination node?
Latency (or End-to-End Delay)
- List three key features of WSNs.
Self-organization
Energy efficiency
Wireless multi-hop communication
- Why is energy efficiency important in WSNs?
Sensor nodes often run on limited battery power, and replacing batteries is costly or impossible in remote or hazardous locations.
- How have WSNs evolved since the 1980s?
From large, wired military systems to miniaturized, wireless, low-power, and versatile devices used in healthcare, agriculture, smart cities, and more.
- What are the three main components of WSN architecture?
Sensor nodes
Base stations
Communication infrastructure
- What is the difference between flat and cluster-based WSN topologies?
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.
- Explain direct transmission in WSNs.
Sensor nodes send data directly to the base station without intermediaries; simple but energy-intensive for distant nodes.
- What are the advantages of multi-hop transmission?
Saves energy
Reduces long-distance transmission load
Extends network lifespan
- What is data aggregation in WSNs?
Combining data from multiple nodes (e.g., averaging) to reduce redundancy and minimize transmission.
- How does event-driven transmission help in saving energy?
