Wireless Sensor Network (WSN)

Wireless Sensor Network (WSN) is an infrastructure-less wireless network that is deployed in

a large number of wireless sensors in an ad-hoc manner that is used to monitor the system,
physical or environmental conditions.

Sensor nodes are used in WSN with the onboard processor that manages and monitors the
environment in a particular area. They are connected to the Base Station which acts as a
processing unit in the WSN System.
Base Station in a WSN System is connected through the Internet to share data.

WSN can be used for processing, analysis, storage, and mining of the data.

Applications of WSN:

1. Internet of Things (IoT)

2. Surveillance and Monitoring for security, threat detection
3. Environmental temperature, humidity, and air pressure
4. Noise Level of the surrounding
5. Medical applications like patient monitoring
6. Agriculture
7. Landslide Detection
Challenges of WSN:

1. Quality of Service
2. Security Issue
3. Energy Efficiency
4. Network Throughput
5. Performance
6. Ability to cope with node failure
7. Cross layer optimisation
8. Scalability to large scale of deployment
A modern Wireless Sensor Network (WSN) faces several challenges, including:
• Limited power and energy: WSNs are typically composed of battery-powered sensors
that have limited energy resources. This makes it challenging to ensure that the network
can function for
long periods of time without the need for frequent battery replacements.
• Limited processing and storage capabilities: Sensor nodes in a WSN are typically small
and have limited processing and storage capabilities. This makes it difficult to perform
complex tasks or store large amounts of data.
• Heterogeneity: WSNs often consist of a variety of different sensor types and nodes with
different capabilities. This makes it challenging to ensure that the network can function
effectively and
efficiently.
• Security: WSNs are vulnerable to various types of attacks, such as eavesdropping,
jamming, and spoofing. Ensuring the security of the network and the data it collects is a
major challenge.
• Scalability: WSNs often need to be able to support a large number of sensor nodes and
handle large amounts of data. Ensuring that the network can scale to meet these demands is
a significant
challenge.
• Interference: WSNs are often deployed in environments where there is a lot of
interference from other wireless devices. This can make it difficult to ensure reliable
communication between sensor nodes.
• Reliability: WSNs are often used in critical applications, such as monitoring the
environment or controlling industrial processes. Ensuring that the network is reliable and
able to function correctly
in all conditions is a major challenge.
Components of WSN:
1. Sensors:
Sensors in WSN are used to capture the environmental variables and which is used for data
acquisition. Sensor signals are converted into electrical signals.
2. Radio Nodes:
It is used to receive the data produced by the Sensors and sends it to the WLAN access
point. It consists of a microcontroller, transceiver, external memory, and power source.
3. WLAN Access Point:
It receives the data which is sent by the Radio nodes wirelessly, generally through the
internet.
4. Evaluation Software:
The data received by the WLAN Access Point is processed by a software called as
Evaluation Software for presenting the report to the users for further processing of the data
which can be used for processing, analysis, storage, and mining of the data.
Advantages of Wireless Sensor Networks (WSN):
Low cost: WSNs consist of small, low-cost sensors that are easy to deploy, making them a
cost-effective solution for many applications.
Wireless communication: WSNs eliminate the need for wired connections, which can be
costly and difficult to install. Wireless communication also enables flexible deployment and
reconfiguration of the network.
Energy efficiency: WSNs use low-power devices and protocols to conserve energy, enabling
long-term operation without the need for frequent battery replacements.
Scalability: WSNs can be scaled up or down easily by adding or removing sensors, making
them suitable for a range of applications and environments.
Real-time monitoring: WSNs enable real-time monitoring of physical phenomena in the
environment, providing timely information for decision making and control.
Disadvantages of Wireless Sensor Networks (WSN):
Limited range: The range of wireless communication in WSNs is limited, which can be a
challenge for large-scale deployments or in environments with obstacles that obstruct radio
signals.
Limited processing power: WSNs use low-power devices, which may have limited
processing power and memory, making it difficult to perform complex computations or
support advanced applications.
Data security: WSNs are vulnerable to security threats, such as eavesdropping, tampering, and
denial of service attacks, which can compromise the confidentiality, integrity, and availability
of data.
Interference: Wireless communication in WSNs can be susceptible to interference from other
wireless devices or radio signals, which can degrade the quality of data transmission.
Deployment challenges: Deploying WSNs can be challenging due to the need for proper
sensor placement, power management, and network configuration, which can require
significant time and resources.
Types of Wireless Sensor Networks

There are five types of Wireless Sensor Networks depending on the environment. Different
Types of WSNs are:

1. Terrestrial Wireless Sensor Networks: Terrestrial WSNs are used for communicating base
stations efficiently, and comprise thousands of wireless sensor nodes deployed either in an
unstructured (ad hoc) or structured (Pre-planned) manner.

In an unstructured mode (ad hoc), the sensor nodes are randomly distributed within the target
area that’s dropped from a set plane.

In WSNs, the battery power is limited, however, the battery is provided with solar cells as a
secondary power source. The conservation of energy of the WSNs gets by using low duty cycle
operations, optimal routing, minimizing delays, and so on.
2. Underground Wireless Sensor Networks: In terms of deployment, maintenance, equipment
cost considerations, and careful planning, underground wireless sensor networks are more
expensive than terrestrial WSNs.

The Underground Wireless sensor networks UWSNs comprises several sensory nodes that are
hidden in the ground to observe underground conditions.

Additional sink nodes are located above the bottom to transfer information from the sensor
nodes to the base station, These underground WSNs deployed into the ground are difficult to
recharge.

The sensor battery nodes equipped with limited battery power are also difficult to recharge.
Additionally, the underground environment makes wireless communication a challenge because
of the high attenuation and signal loss level.

3. Underwater Wireless Sensor Networks: About more than 70% of the earth’s planet is occupied
with water. These networks contain several sensor nodes and vehicles deployed underwater.
Autonomous underwater devices and vehicles are used to collect data from these sensor nodes.

A challenge of underwater communication may be a long propagation delay, and bandwidth and
sensor failures. Underwater, WSNs are equipped with a limited battery that can’t be recharged or
replaced.

The difficulty of energy conservation for underwater WSNs involves the development of
underwater communication and networking techniques.

4. Multimedia Wireless Sensor Networks: Multimedia wireless sensor networks are proposed to
enable tracking and monitoring of events in the sort of multimedia, like video, imaging, and
audio.

These networks contain low-cost sensor nodes equipped with cameras and microphones. These
sensory nodes of Multimedia WSNs are interconnected together over a wireless connection for
data retrieval, data compression, and correlation.

The challenges with the Multimedia WSNs include high bandwidth requirements, high energy
consumption, processing, and compressing techniques. Additionally, multimedia contents need
high bandwidth for the content to be delivered properly and easily.
5. Mobile Wireless Sensor Networks MWSNs: Mobile WSNs networks comprise a group of
sensor nodes that can be moved on their own and can be interacted with the physical
environment. The mobile nodes can also compute sense and communicate respectively.

Mobile wireless sensor networks are way more versatile than static sensor networks. The benefits
of Mobile WSNs over Static WSNs include better and improved coverage, superior channel
capacity, better energy efficiency, and so on.

Classification of Wireless Sensor Networks

Classification of Wireless Sensor Networks are as follows:

1. Static and Mobile WSN: All the sensor nodes are connected without movement and these are
static networks in many applications. Some applications especially in biological systems- mobile
sensor nodes are needed. These are called mobile networks. An example of a mobile network is
animal monitoring.

2. Deterministic and Nondeterministic WSN: In deterministic wireless sensor networks, the

sensor node position is calculated and fixed.

The deployment of sensor nodes is possible in a limited number of applications. The position of
sensor nodes determination isn’t possible because of several factors like harsh environments or
hostile operating conditions. Such kinds of networks are non-deterministic and need a complex
system.

3. Single Base Station and Multi Base Station WSN: In single base station WSNs, only one base
station is used that is found close to the sensor node region.

All the nodes communicate with this base station, in the case of a multi-base station WSNs, more
than one base station is used and a sensor node can transfer data to the closest base station.

4. Static Base Station and Mobile Base Station WSN: It is similar to sensor nodes, even base
stations of the WSN are often either static or mobile. A static base station contains a fixed
position usually close to the sensing region.

A mobile base station WSN moves around the sensing region because a load of sensor nodes is
balanced.
5. Single-hop and Multi-hop WSN: In single-hop WSNs, the sensor nodes are directly connected
to the base station. And in the case of multi-hop WSNs, peer nodes and cluster heads are used to
relay the information to reduce energy consumption.

6. Self Reconfigurable and Non- Self Configurable WSN: In non-Self Configurable WSNs, the
sensor networks cannot organize themselves in a network and consider a control unit to gather
data.

In many WSNs, the sensor nodes can be able to organize and maintain the connection and work
collaboratively with other sensor nodes to accomplish the task.

7.Homogeneous and Heterogeneous WSN: In the case of homogeneous WSNs, all the sensor
nodes have the same energy consumption, storage capabilities, and computational power.

And in the case of heterogeneous WSNs, some sensor nodes have higher computational power
and energy requirements than others and also the processing and communication tasks are
divided accordingly.

Structure of Wireless Sensor Network

The structure of WSNs includes different types of topologies for radio communications
networks.

1. Star Network: A star network is also called a single point-to-multipoint is a communications

topology where one base station can send and receive a message to a variety of remote nodes.
The remote nodes aren’t permitted to send messages.

The benefit of these kinds of networks for wireless sensor networks includes simplicity, ability to
keep the remote node’s power consumption to a minimum. It allows low-power communications
between the remote node and the base station.

The disadvantage of such a network is that the base station must be within the radio transmission
range of all the individual nodes and isn’t as robust as other networks because of its dependency
on a single node to manage the whole network.

2. Mesh Network: A mesh network allows transmitting data from one node to another in the
network that’s within its radio transmission range.
This enables what is called multi-hop communications, i.e. if a node wants to send a message to
a different node that’s out of radio communications range, it can use an intermediate node to
forward the message to the particular node.

This topology has the power of redundancy and scalability. When an individual node fails to
work, a remote node still can communicate to the other node in its range, which successively,
can forward the message to the specified location.

Additionally, the range of the network isn’t necessarily limited by the range in between single
nodes, it can simply be extended by adding more nodes to the system.

3. Hybrid Star: A hybrid Star is a combination between the star network and a mesh network that
provides a strong and versatile communications network while maintaining the ability to keep
the wireless sensor node’s power consumption to a minimum.

In network topology, the sensor nodes with the lowest power aren’t enabled with the ability to
forward messages. This permits for minimal power consumption to be maintained.

Similarly, the various other nodes on the network are having multi-hop capability, allowing them
to forward messages from the low power nodes to another on the network.