Preface

Wireless Sensor Networks (WSNs) are networks of spatially distributed autonomous sensor nodes that monitor a variety of ambient conditions, physical characteristics, or events and transmit the data they collect to a central processing hub or server. These networks have attracted a lot of attention because of the diverse variety of applications they might be used in, including surveillance, health care, agriculture, industrial automation, and environmental monitoring. Some key aspects of a typical WSN are highlighted in the paragraphs that follow.

*Sensor Nodes*: The basic components of WSNs are sensor nodes. They are made up of a variety of parts, including memory, communication interfaces, processing units, sensing units to measure physical parameters like temperature, humidity, light, and so on, and processing units to process acquired data.

*Communication*: Wireless communication techniques are often used over radio frequencies for communication between sensor nodes. Data may have to travel via several nodes in the communication process to reach the center or the sink node.

*Data Aggregation*: Due to the large number of nodes in a network, it is essential to minimize the amount of data transmitted to conserve energy and reduce network congestion. Data aggregation techniques help to combine and summarize data at intermediate nodes before transmitting it to a central node.

*Energy Constraints*: One of the significant challenges in WSNs is the limited energy resources of individual sensor nodes. Many nodes are often deployed in remote or hardto-reach areas, making battery replacement or recharging impractical. Energy-efficient protocols and algorithms are crucial to prolong the network's operational lifetime.

*Routing Protocols*: The routing protocols used in WSNs need to be power efficient so that data transmissions from source nodes to the destination nodes occur with minimal energy consumption. Based on network features and application requirements, many routing strategies, including hierarchical routing, data-centric routing, and geographic routing, are used.

*Localization*: For applications that need spatial awareness, such as target tracking or monitoring environmental changes, accurate localization of sensor nodes is crucial. For localization, usually several methods are utilized, such as global positioning systems (GPS), triangulation, and distance estimates.

*Security*: Since WSNs very often involve processing and communication of sensitive data, security of communication and privacy of data is a major challenge for these networks. These networks must deploy protocols for data encryption, authentication, and secure communication because sensor nodes can be physically attacked and eavesdropped on.

*Scalability*: Because many applications of WSNs involve a very large number of nodes, scalability must be guaranteed in the network design without compromising computing and communication efficiencies. Effective management of large-scale networks most often requires the use of hierarchical network design and clustering approaches.

*Applications*: WSNs find applications in diverse fields, including environmental monitoring (e.g., tracking pollution levels), agriculture (e.g., monitoring soil moisture), health care (e.g., patient monitoring), smart cities (e.g., traffic monitoring), and industrial automation (e.g., monitoring equipment conditions).

Overall, WSNs have the potential to revolutionize various industries by providing real-time data insights, enabling automation, and improving decision-making processes. Despite their numerous applications in various domains, WSNs face several challenges. These challenges include designing energy-efficient routing protocols, enhancing the robustness of networks, ensuring security in communication and privacy of data, and minimizing the delay in real-time communications as far as possible. These challenges require ongoing research to develop better algorithms, protocols, and hardware solutions.

The chapters of this volume deal with various research issues and applications of WSNs, including key management, routing, machine learning-based applications in WSNs, temperature sensors and their different applications, automatic fault detection in WSNs, and more.

In Chapter 1, "Introductory Chapter: Temperature Sensing and Advanced Applications", Mingqiang Yi and Fenglei Niu highlight various temperature sensors and their applications in the real world. The authors briefly point out the recent advances in smart temperature sensing including control of the pandemic, point-of-care health care, and monitoring of remote and geographically challenging environments.

In Chapter 2, "A Survey of Cryptography and Key Management Schemes for Wireless Sensor Networks", Jaydip Sen presents a comprehensive overview of various cryptographic and key management schemes for WSNs. The author first discusses symmetric key and public key cryptographic approaches and highlights their merits and demerits. The key management schemes are then further categorized into three groups: network-topology-based, deterministic key distribution-based, and probabilistic key distribution-based. The author critically analyzes several propositions in the current literature under each category and highlights some open research questions for future exploration.

In Chapter 3, "Machine Learning Algorithms from Wireless Sensor Network's Perspective", Rakesh Chandra Gangwar and Roohi Singh present an empirical study of architecture, applications, and challenges in WSNs. The authors highlight the critical importance of energy efficiency, security, delay tolerance, localization, and data aggregation in sensor networks. Further, the authors present a taxonomy of machine learning algorithms for dynamic adaptations of WSNs in response to the changes in their working environment.

In Chapter 4, "Efficient Machine Learning Classifier for Fault Detection in Wireless Sensor Networks" Poornima G. Miathali presents a study on the faults in WSNs

**V**

caused by denial of service (DoS), probe, remote-to-local (R2L), and user-to-root (U2R) attacks. The KDD Cup 99 dataset is used with 41 features in total, and for each fault type, the relevant features are identified using a recursive feature elimination method. Different classifiers are trained on the training dataset and their performances are evaluated on the test sample. The author observes that the random forest model

In Chapter 5, "Wireless Sensor Networks Challenges and Solutions", Sumana Naskar summarizes various important aspects of WSNs, including their architecture, applications, challenges, and potential solutions. The author identifies some of the research directions as well, which include sensor node deployment, relay node and cluster head node selection, energy optimization, security and privacy issues, dela minimization,

In Chapter 6, "Novel PTC Composites for Temperature Sensors (and Related Applications)", Radu Setnescu and Eduard-Marius Lungulescu present an overview of conductive polymer composites, focusing on those that exhibit abrupt changes in resistivity with variations in temperature, known as the positive temperature coefficient (PTC) and negative temperature coefficient (NTC) effects. The authors further analyze the factors that affect the quality of polymer composites such as polymeric matrix, conductive filters, and treatments. Temperature sensors based

In Chapter 7, "Current Status and State-of-Art Developments in Temperature Sensor Technology" Deqi Chen et al. argue that while the traditional temperature sensors currently in use are simple and reliable, their performance in challenging and harsh environments is questionable. Accordingly, the authors discuss various types of advanced temperature sensors that offer unique benefits and applications compared to their traditional counterparts. Some specific examples are discussed in the chapter, including acoustic temperature sensors for monitoring high-temperature boilers, fiber-optic temperature sensors for long-distance cables, and micro- and nano-scale

In Chapter 8, "Types of Temperature Sensors", Reuben S. Diarah et al. discuss various types of temperature sensors and their applications. In particular, the authors present three types of temperature sensors: thermometers, resistance temperature detectors, and thermocouples. Further, the authors delve into the working principles, sizes, and ranges of temperature, and applications for each category of sensors.

I am hopeful that this volume will prove to be a valuable resource for researchers, engineers, doctoral students, and faculty members from graduate schools and universities who are engaged in the design, implementation, and deployment of WSNs. The content presented in the chapters addresses advanced topics within the realm of WSNs, making it essential for readers to possess a foundational understanding of the covered subjects. This book is tailored to individuals with the necessary background

I extend my heartfelt gratitude to all the esteemed authors for their invaluable contributions. Their collaborative efforts and scholarly input have paved the way for the successful publication of this book. I would like to express my sincere appreciation to

on PTC composites are also discussed as illustrative examples.

performed the best among all classifiers.

sensors for monitoring microstructures.

knowledge to fully grasp and benefit from its contents.

and fault tolerance.

caused by denial of service (DoS), probe, remote-to-local (R2L), and user-to-root (U2R) attacks. The KDD Cup 99 dataset is used with 41 features in total, and for each fault type, the relevant features are identified using a recursive feature elimination method. Different classifiers are trained on the training dataset and their performances are evaluated on the test sample. The author observes that the random forest model performed the best among all classifiers.

In Chapter 5, "Wireless Sensor Networks Challenges and Solutions", Sumana Naskar summarizes various important aspects of WSNs, including their architecture, applications, challenges, and potential solutions. The author identifies some of the research directions as well, which include sensor node deployment, relay node and cluster head node selection, energy optimization, security and privacy issues, dela minimization, and fault tolerance.

In Chapter 6, "Novel PTC Composites for Temperature Sensors (and Related Applications)", Radu Setnescu and Eduard-Marius Lungulescu present an overview of conductive polymer composites, focusing on those that exhibit abrupt changes in resistivity with variations in temperature, known as the positive temperature coefficient (PTC) and negative temperature coefficient (NTC) effects. The authors further analyze the factors that affect the quality of polymer composites such as polymeric matrix, conductive filters, and treatments. Temperature sensors based on PTC composites are also discussed as illustrative examples.

In Chapter 7, "Current Status and State-of-Art Developments in Temperature Sensor Technology" Deqi Chen et al. argue that while the traditional temperature sensors currently in use are simple and reliable, their performance in challenging and harsh environments is questionable. Accordingly, the authors discuss various types of advanced temperature sensors that offer unique benefits and applications compared to their traditional counterparts. Some specific examples are discussed in the chapter, including acoustic temperature sensors for monitoring high-temperature boilers, fiber-optic temperature sensors for long-distance cables, and micro- and nano-scale sensors for monitoring microstructures.

In Chapter 8, "Types of Temperature Sensors", Reuben S. Diarah et al. discuss various types of temperature sensors and their applications. In particular, the authors present three types of temperature sensors: thermometers, resistance temperature detectors, and thermocouples. Further, the authors delve into the working principles, sizes, and ranges of temperature, and applications for each category of sensors.

I am hopeful that this volume will prove to be a valuable resource for researchers, engineers, doctoral students, and faculty members from graduate schools and universities who are engaged in the design, implementation, and deployment of WSNs. The content presented in the chapters addresses advanced topics within the realm of WSNs, making it essential for readers to possess a foundational understanding of the covered subjects. This book is tailored to individuals with the necessary background knowledge to fully grasp and benefit from its contents.

I extend my heartfelt gratitude to all the esteemed authors for their invaluable contributions. Their collaborative efforts and scholarly input have paved the way for the successful publication of this book. I would like to express my sincere appreciation to Author Service Manager Ms. Paula Gavran at IntechOpen for her unwavering support, patience, and cooperation throughout the publication process. My thanks also go to Commissioning Editor Ms. Danijela Vladika at IntechOpen for entrusting me with the significant responsibility of editing this academic volume.

I am indebted to my colleagues and graduate students at the Praxis Business School, Kolkata, India, for their constant support and cooperation. My family members have been a constant source of inspiration and motivation, and I dedicate this volume to the memory of my beloved sister, Ms. Nabanita Sen, who sadly succumbed to cancer on September 27, 2021. She was my steadfast pillar of strength. Lastly, I am profoundly grateful for the unwavering encouragement and motivation from my wife, Ms. Nalanda Sen, my daughter, Ms. Ritabrata Sen, and my mother, Ms. Krishna Sen. Their support and inspiration have been the driving force behind the publication of this book.
