Due to the broadcast nature of radio propagation, the wireless air interface is open and accessible to both authorized and illegitimate users. This completely differs from a wired network, where communicating devices are physically connected through cables and a node without direct association is unable to access the network for illicit activities. The open communications environment makes wireless transmissions more vulnerable than wired communications to malicious attacks, including both the passive eavesdropping for data interception and the active jamming for disrupting legitimate transmissions. Therefore, this paper is motivated to examine the security vulnerabilities and threats imposed by the inherent open nature of wireless communications and to devise efficient defense mechanisms for improving the wireless network security. We first summarize the security requirements of wireless networks, including their authenticity, confidentiality, integrity, and availability issues. Next, a comprehensive overview of security attacks encountered in wireless networks is presented in view of the network protocol architecture, where the potential security threats are discussed at each protocol layer. We also provide a survey of the existing security protocols and algorithms that are adopted in the existing wireless network standards, such as the Bluetooth, Wi-Fi, WiMAX, and the long-term evolution (LTE) systems. Then, we discuss the state of the art in physical-layer security, which is an emerging technique of securing the open communications environment against eavesdropping attacks at the physical layer. Several physical-layer security techniques are reviewed and compared, including information-theoretic security, artificial-noise-aided security, security-oriented beamforming, diversity-assisted security, and physical-layer key generation approaches. Since a jammer emitting radio signals can readily interfere with the legitimate wireless users, we also introduce the family of various jamming attacks and their countermeasures, including the constant jammer, intermittent jammer, reactive jammer, adaptive jammer, and intelligent jammer. Additionally, we discuss the integration of physical-layer security into existing authentication and cryptography mechanisms for further securing wireless networks. Finally, some technical challenges which remain unresolved at the time of writing are summarized and the future trends in wireless security are discussed.

/pdf/a-survey-on-wireless-security-technical-challenges-recent-3uamoalvot.pdf

A Survey on Wireless Security: Technical Challenges, Recent Advances, and Future Trends

This paper examines the security vulnerabilities and threats imposed by the inherent open nature of wireless communications and to devise efficient defense mechanisms for improving the wireless network security. We first summarize the security requirements of wireless networks, including their authenticity, confidentiality, integrity and availability issues. Next, a comprehensive overview of security attacks encountered in wireless networks is presented in view of the network protocol architecture, where the potential security threats are discussed at each protocol layer. We also provide a survey of the existing security protocols and algorithms that are adopted in the existing wireless network standards, such as the Bluetooth, Wi-Fi, WiMAX, and the long-term evolution (LTE) systems. Then, we discuss the state-of-the-art in physical-layer security, which is an emerging technique of securing the open communications environment against eavesdropping attacks at the physical layer. We also introduce the family of various jamming attacks and their counter-measures, including the constant jammer, intermittent jammer, reactive jammer, adaptive jammer and intelligent jammer. Additionally, we discuss the integration of physical-layer security into existing authentication and cryptography mechanisms for further securing wireless networks. Finally, some technical challenges which remain unresolved at the time of writing are summarized and the future trends in wireless security are discussed.

/pdf/a-survey-on-wireless-security-technical-challenges-recent-k705wofne7.pdf

A Survey on Wireless Security: Technical Challenges, Recent Advances and Future Trends

An automated irrigation system was developed to optimize water use for agricultural crops. The system has a distributed wireless network of soil-moisture and temperature sensors placed in the root zone of the plants. In addition, a gateway unit handles sensor information, triggers actuators, and transmits data to a web application. An algorithm was developed with threshold values of temperature and soil moisture that was programmed into a microcontroller-based gateway to control water quantity. The system was powered by photovoltaic panels and had a duplex communication link based on a cellular-Internet interface that allowed for data inspection and irrigation scheduling to be programmed through a web page. The automated system was tested in a sage crop field for 136 days and water savings of up to 90% compared with traditional irrigation practices of the agricultural zone were achieved. Three replicas of the automated system have been used successfully in other places for 18 months. Because of its energy autonomy and low cost, the system has the potential to be useful in water limited geographically isolated areas.

Automated Irrigation System Using a Wireless Sensor Network and GPRS Module

Blended learning has become an increasingly popular form of e-learning, and is particularly suitable to the process of transitioning towards e-learning from traditional forms of learning and teaching. This paper describes the use of the blended e-learning model, which is based on a mixture of collaborative learning, problem-based learning (PBL) and independent learning, in a course ldquoTeaching Methods in Information Science,rdquo given at the University of Rijeka, Rijeka, Croatia. This model is realized as a combination of a face-to-face environment and online learning, using a proprietary learning management system (LMS) named adaptive hypermedia courseware (AHyCo). AHyCo is based on adaptive hypermedia and in addition to supporting learning and testing, introduces completely new constructivist and cognitivist elements to education. By supporting collaborative and project-oriented activities AHyCo promotes students' motivation for learning and establishes learning as an active and interactive process. This paper describes both the technology for, and the methodological approach to, course design and development which is aimed at supporting the evolution from traditional teaching to active learning, and raising interest in the topics of e-learning and Web courseware development among IT students. A survey conducted in the end of the course showed that students were satisfied with the pedagogical approach, and their academic achievements were also better than expected. Particularly important is that the dropout rate was greatly diminished, which could be related to students' satisfaction with the support they received from the instructor and the system.

A Blended Learning Approach to Course Design and Implementation

Structural health monitoring (SHM) using wireless sensor networks (WSNs) has gained research interest due to its ability to reduce the costs associated with the installation and maintenance of SHM systems. SHM systems have been used to monitor critical infrastructure such as bridges, high-rise buildings, and stadiums and has the potential to improve structure lifespan and improve public safety. The high data collection rate of WSNs for SHM pose unique network design challenges. This paper presents a comprehensive survey of SHM using WSNs outlining the algorithms used in damage detection and localization, outlining network design challenges, and future research directions. Solutions to network design problems such as scalability, time synchronization, sensor placement, and data processing are compared and discussed. This survey also provides an overview of testbeds and real-world deployments of WSNs for SH.

Structural Health Monitoring Using Wireless Sensor Networks: A Comprehensive Survey

Recent decades have experienced a breakthrough in the study of Wireless Sensor Networks (WSNs) as a key technology for Internet of Things (IoT). Operating Systems (OSes) for resource-constraint WSN devices have been developed during the last years, facilitating application development for these networks. However, these OSes are static software modules and do not take into account environmental changes to optimize themselves. In this paper we present YetiOS, a novel OS that can change its properties dynamically through an adaptive core. This way, the OS adapts itself to the environment and can optimize the performance, power consumption, security or tasks latency on different scenarios while maintaining the same developing interface. YetiOS also includes a dynamic layered network stack architecture, allowing different sensor network protocols to be implemented. Besides, it features Linux-like device drivers, a FreeRTOS based process management module, an I/O interface module and an energy management module. Performance tests presented in this work demonstrate YetiOS suitability for low-power resource-constraint WSN nodes. In addition, a use case of the adaptive core is presented, and its performance test demonstrates the dynamic optimization achieved.

YetiOS: an Adaptive Operating System for Wireless Sensor Networks

Security of sensor networks is a complicated task, mostly due to the limited resources of sensor units Encryption and authentication are useless if an attacker has entered the system Thus, a second line of defense known as Intrusion Detection must be added in order to detect and eliminate attacks In the recent past, various solutions for detecting intrusions have been proposed Most of them are able to detect only a limited number of attacks The solutions that deploy machine learning techniques exhibit higher level of flexibility and adaptability Yet, these techniques consume significant power and computational resources In this work we propose to implement unsupervised algorithms (genetic algorithm and self-organized maps) for detecting intrusions using the energy-efficient SORU architecture Separate detectors are further organized in a distributed system using the idea of immune system organization Our solution offers many benefits: ability to detect unknown attacks, high adaptability and energy efficiency First testing results obtained in real environment demonstrate its high potential

Intrusion detection in sensor networks using clustering and immune systems

The expansion of big data and the evolution of Internet of Things (IoT) technologies will play an important role in the feasibility of Smart City initiatives. In this IoT network infrastructure Cognitive Wireless Sensor Networks (WSNs), as a network of nodes that work in a cooperative way to sense the spectrum and control the environment surrounding them, are one of the main technologies. Security and privacy appear as key aspects for the development of new applications and services. In this work we propose a novel artificial noise generation strategy based on game theory in order to improve the security against privacy attacks in CWSNs. Artificial noise generation consists in introducing interferences in the spectrum in order to mask the real information. The decision whether or not to introduce artificial noise is modeled through a light non-cooperative game designed for low-resources networks that balance security enhancement and energy consumption. We show, using several simulations, that even with a cognitive attacker our strategy has reduced the information obtained by the attacker (Secrecy Outage Probability) to a value under 10%. The overhead (energy consumption and spectrum occupancy) of the strategy has also been deeply analyzed. All possible cases our approach provides better results, in the ratio energy consumption - security, than not using the strategy or using a random noise generation strategy. Also, although the saturation of the radio spectrum is strongly affected, the reliability of the network is maintained in 95% of application packages received. Therefore, we can conclude that an improvement of the privacy in the physical layer is obtained, taking into account energy consumption and maintaining levels of spectrum saturation suitable for the application proposes.

An adaptive energy aware strategy based on game theory to add privacy in the physical layer for cognitive WSNs

Wireless sensor networks (WSNs) are one of the most important users of wireless communication technologies in the coming years and some challenges in this area must be addressed for their complete development. Energy consumption and spectrum availability are two of the most severe constraints of WSNs due to their intrinsic nature. The introduction of cognitive capabilities into these networks has arisen to face the issue of spectrum scarcity but could be used to face energy challenges too due to their new range of communication possibilities. In this paper a new strategy based on game theory for cognitive WSNs is discussed. The presented strategy improves energy consumption by taking advantage of the new change-communication-channel capability. Based on game theory, the strategy decides when to change the transmission channel depending on the behavior of the rest of the network nodes. The strategy presented is lightweight but still has higher energy saving rates as compared to noncognitive networks and even to other strategies based on scheduled spectrum sensing. Simulations are presented for several scenarios that demonstrate energy saving rates of around 65% as compared to WSNs without cognitive techniques.

/pdf/a-game-theory-based-strategy-for-reducing-energy-consumption-4qh15iy2gd.pdf

A Game Theory Based Strategy for Reducing Energy Consumption in Cognitive WSN

The increase in the number of mobile and Internet of Things (IoT) devices, along with the demands of new applications and services, represents an important challenge in terms of spectral coexistence. As a result, these devices are now expected to make an efficient and dynamic use of the spectrum, and to provide processed information instead of simple raw sensor measurements. These communication and processing requirements have direct implications on the architecture of the systems. In this work, we present MIGOU, a wireless experimental platform that has been designed to address these challenges from the perspective of resource-constrained devices, such as wireless sensor nodes or IoT end-devices. At the radio level, the platform can operate both as a software-defined radio and as a traditional highly integrated radio transceiver, which demands less node resources. For the processing tasks, it relies on a system-on-a-chip that integrates an ARM Cortex-M3 processor, and a flash-based FPGA fabric, where high-speed processing tasks can be offloaded. The power consumption of the platform has been measured in the different modes of operation. In addition, these hardware features and power measurements have been compared with those of other representative platforms. The results obtained confirm that a state-of-the-art tradeoff between hardware flexibility and energy efficiency has been achieved. These characteristics will allow for the development of appropriate solutions to current end-devices’ challenges and to test them in real scenarios.

https://www.mdpi.com/1424-8220/19/22/4983/pdf

Alvaro Araujo

Papers

YetiOS: an Adaptive Operating System for Wireless Sensor Networks

Intrusion detection in sensor networks using clustering and immune systems

An adaptive energy aware strategy based on game theory to add privacy in the physical layer for cognitive WSNs

A Game Theory Based Strategy for Reducing Energy Consumption in Cognitive WSN

MIGOU: A Low-Power Experimental Platform with Programmable Logic Resources and Software-Defined Radio Capabilities.