What is Wireless Sensor Network?

By Techie Teacher On Sep 1, 2024

Currently, designing efficient Wireless Sensor Networks (WSNs) is a leading research focus. WSNs are technologies that detect and respond to inputs from physical or environmental conditions like heat, pressure, and light.

The sensors generate electrical signals that are transmitted to a controller for further processing. This article will cover the overview, types, and applications of Wireless Sensor Networks.

What Is Wireless Sensor Network?

Wireless Sensor Networks (WSNs) are self-configuring, infrastructure-free networks designed to monitor physical or environmental conditions such as temperature, pressure, motion, sound, vibration, or pollutants. They transmit data through the network to a central location, known as the sink, where the information is analyzed.

The base station or sink acts as an interface between users and the network. It can retrieve necessary information by sending queries and collecting results from the sink. Typically, a WSN comprises thousands of sensor nodes.

These sensor nodes communicate using radio signals and are equipped with sensors, radio transceivers, computing devices, and power components. Sensor nodes are resource-constrained, with limited processing speed, storage capacity, and communication bandwidth. Once installed, they self-organize into a network, often using multi-hop communication.

The onboard sensors collect data of interest, and specialized devices in the WSN respond to queries from a control site, either by performing specific tasks or providing sensing samples.

Sensor nodes can operate in either continuous or event-driven modes. GPS (Global Positioning System) and local positioning algorithms (LPA) can be used for location and positioning information.

Wireless sensor devices may also include actuators to respond to certain conditions, leading to the term Wireless Sensor and Actuator Network.

Types of Wireless Sensor Networks

Wireless Sensor Networks (WSNs) can be categorized into five types based on their environment:

Terrestrial Wireless Sensor Networks: These networks use thousands of sensor nodes to efficiently communicate with base stations and can be deployed either ad hoc (randomly) or in a structured manner. In ad hoc deployment, nodes are scattered randomly within the target area. Due to limited battery power, WSNs use solar cells as a secondary power source and conserve energy through low duty cycles, optimal routing, and minimizing delays.
Underground Wireless Sensor Networks: These are more costly to deploy, maintain, and plan compared to terrestrial WSNs. Underground WSNs consist of sensor nodes embedded in the ground to monitor subterranean conditions. Additional sink nodes located above ground relay information from the underground sensors to the base station. Challenges include the difficulty of recharging batteries and the high attenuation and signal loss in underground environments.
Underwater Wireless Sensor Networks: Covering more than 70% of Earth’s surface, these networks deploy sensor nodes and autonomous vehicles underwater to collect data. Challenges include long propagation delays, bandwidth limitations, sensor failures, and energy conservation, as the batteries used are often non-rechargeable.
Multimedia Wireless Sensor Networks: Designed to track and monitor events through multimedia formats such as video, images, and audio, these networks use low-cost sensor nodes with cameras and microphones. These nodes are interconnected wirelessly for data retrieval, compression, and correlation. Challenges include high bandwidth requirements, energy consumption, and processing needs for multimedia content.
Mobile Wireless Sensor Networks (MWSNs): These networks consist of mobile sensor nodes that can move and interact with their environment. MWSNs offer greater versatility compared to static networks, with benefits including enhanced coverage, improved channel capacity, and better energy efficiency.

Classification of Wireless Sensor Networks

Wireless Sensor Networks (WSNs) can be classified as follows:

Static and Mobile WSNs: Static WSNs consist of sensor nodes that do not move and are used in many applications. In contrast, mobile WSNs feature sensor nodes that can move, which is essential for certain applications such as animal monitoring.
Deterministic and Nondeterministic WSNs: In deterministic WSNs, the positions of sensor nodes are predetermined and fixed. This approach is suitable for applications where node positioning can be controlled. Nondeterministic WSNs, on the other hand, operate in environments where sensor node positioning is influenced by factors such as harsh conditions, requiring more complex systems to manage node placement.
Single Base Station and Multi Base Station WSNs: Single base station WSNs use only one base station located near the sensor nodes, while multi base station WSNs employ multiple base stations, allowing sensor nodes to transmit data to the nearest base station.
Static Base Station and Mobile Base Station WSNs: Similar to sensor nodes, base stations can also be static or mobile. A static base station remains fixed, usually close to the sensing area, whereas a mobile base station moves within the sensing region to balance the load among sensor nodes.
Single-hop and Multi-hop WSNs: In single-hop WSNs, sensor nodes are directly connected to the base station. Multi-hop WSNs use intermediate peer nodes and cluster heads to relay information, which helps in reducing energy consumption.
Self-Reconfigurable and Non-Self Configurable WSNs: Non-self-configurable WSNs require a control unit to organize and gather data as the sensor nodes cannot autonomously form a network. In contrast, self-reconfigurable WSNs can organize themselves, maintain connections, and work together to achieve their tasks.
Homogeneous and Heterogeneous WSNs: Homogeneous WSNs consist of sensor nodes with the same energy consumption, storage, and computational capabilities. Heterogeneous WSNs include sensor nodes with varying levels of computational power and energy requirements, with tasks distributed according to the capabilities of each node.

Structure of Wireless Sensor Network

The structure of Wireless Sensor Networks (WSNs) includes various topologies for radio communication:

Star Network: Also known as a single point-to-multipoint topology, a star network features one base station that can send and receive messages from multiple remote nodes. The remote nodes cannot send messages themselves. This topology offers simplicity and low power consumption for remote nodes, as communication is directly between the base station and the nodes. However, it requires the base station to be within the radio range of all nodes and is less robust due to its reliance on a single base station to manage the network.
Mesh Network: In a mesh network, data can be transmitted from one node to another within its radio range, enabling multi-hop communications. If a node needs to send a message to another node outside its direct range, it can use intermediate nodes to relay the message. This topology provides redundancy and scalability; if one node fails, communication can still occur via other nodes within range. The network’s range can be extended by adding more nodes.
Hybrid Star Network: A hybrid star network combines elements of both star and mesh topologies, creating a robust and versatile network while minimizing power consumption for wireless sensor nodes. In this topology, low-power nodes do not forward messages, which helps conserve their energy. Nodes with higher power and multi-hop capability handle message forwarding and are often connected to a power source. This setup balances energy efficiency with network reliability.

Applications of wireless sensor network

Wireless Sensor Networks (WSNs) are widely used across various fields. Their applications include:

Military Applications: WSNs are not only a key area of research but also have practical applications in the military. They are used for tracking, environment monitoring, and surveillance. Sensor nodes are deployed in targeted areas and controlled remotely by users. These networks are also utilized for security detection and enemy tracking.
Health Applications: In healthcare, WSNs are employed by doctors to track and monitor patients, providing valuable data for medical management.
Transport Systems: WSNs are commonly used in transportation for dynamic routing management, traffic monitoring, and parking lot surveillance.
Environmental Tracking: WSNs are extensively used to monitor environmental changes. They assist in forest detection, animal tracking, weather prediction, flood detection, and forecasting. Additionally, they support commercial applications such as seismic activity prediction and monitoring air and water quality.
Threat Detection: WSNs, including the Wide Area Tracking System (WATS), are employed for detecting ground-based nuclear devices and other threats. They are also used in industrial process monitoring, rapid emergency response, automated building climate control, area monitoring, civil structural health monitoring, and ecosystem and habitat monitoring.

Characteristics of Wireless Sensor Network

Key characteristics of Wireless Sensor Networks (WSNs) include:

Power Consumption Constraints: Nodes typically rely on energy harvesting or batteries. Examples of suppliers in this area include ReVibe Energy and Perpetuum.
Resilience: The network is designed to handle node failures effectively.
Mobility: Nodes can exhibit some degree of mobility; for highly mobile nodes, refer to Mobile Wireless Sensor Networks.
Scalability: The network can be deployed on a large scale.
Environmental Robustness: The network is capable of withstanding harsh environmental conditions.
Node Heterogeneity: The network can accommodate nodes with varying capabilities.
Node Homogeneity: The network may consist of nodes with similar capabilities.
User-Friendliness: The network is designed to be easy to use.
Cross-Layer Optimization: The network supports optimization across different layers.

Issues in Wireless Sensor Networks

Wireless Sensor Networks (WSNs) face various challenges, including design, topology, and other issues:

Design Complications:

Low latency
Transmission media
Fault tolerance
Coverage problems
Scalability

Topology Complications:

Sensor holes
Coverage topology
Geographic routing

Major Issues Affecting Design and Performance:

Operating systems and hardware for WSNs
Medium access schemes
Deployment strategies
Middleware
Wireless radio communication characteristics
Network architecture
Calibration
Database-centric and querying processes
Network layer concerns
Localization
Sensor network programming models
Synchronization
Transport layer issues
Data dissemination and aggregation

The Advantages and Disadvantages of wireless sensor networks

Advantages of Wireless Sensor Networks (WSNs):

Suitable for inaccessible areas such as over the sea, in mountains, rural regions, or deep forests.
Reduces the need for extensive wiring.
Allows for the addition of new devices at any time.
Can be monitored centrally.
Offers flexibility for unexpected situations requiring additional workstations.
Cost-effective implementation.
Adaptable to physical partitions.

Disadvantages of Wireless Sensor Networks:

Less secure, as hackers can potentially access data through the network’s access points.
Slower speeds compared to wired networks.
Vulnerable to hacking due to uncontrolled wave propagation.
More complex than wired networks.
Susceptible to interference from environmental factors such as walls, microwaves, and large distances, leading to signal attenuation.
Lower communication speed.
Prone to disruptions from elements like Bluetooth.
Still relatively costly.

FAQ’s

What is a Wireless Sensor Network (WSN)?

Answer: WSNs are self-configuring networks that monitor physical or environmental conditions. They consist of sensor nodes that wirelessly transmit data to a central sink for analysis.

What are common issues in Wireless Sensor Networks?

Design: Low latency, fault tolerance, and scalability.
Topology: Sensor holes and coverage.
Performance: Operating systems, medium access, and data aggregation.

Conclusion

Wireless Sensor Networks (WSNs) are essential for monitoring various conditions and have wide applications in fields like military, healthcare, and environmental tracking. Despite their advantages, such as flexibility and suitability for difficult environments, they face challenges like security risks and slower speeds. Future advancements will likely enhance their efficiency and broaden their applications.