The Internet of Things (IoT) has attracted much attention from the Information and Communication Technology (ICT) community in recent years. One of the main reasons for this is the availability of techniques provided by this paradigm, such as environmental monitoring employing user data and everyday objects. The facilities provided by the IoT infrastructure allow the development of a wide range of new business models and applications (e.g., smart homes, smart cities, or e-health). However, there are still concerns over the security measures which need to be addressed to ensure a suitable deployment. Distributed Denial of Service (DDoS) attacks are among the most severe virtual threats at present and occur prominently in this scenario, which can be mainly owed to their ease of execution. In light of this, several research studies have been conducted to find new strategies as well as improve existing techniques and solutions. The use of emerging technologies such as those based on the Software-Defined Networking (SDN) paradigm has proved to be a promising alternative as a means of mitigating DDoS attacks. However, the high granularity that characterizes the IoT scenarios and the wide range of techniques explored during the DDoS attacks make the task of finding and implementing new solutions quite challenging. This problem is exacerbated by the lack of benchmarks that can assist developers when designing new solutions for mitigating DDoS attacks for increasingly complex IoT scenarios. To fill this knowledge gap, in this study we carry out an in-depth investigation of the state-of-the-art and create a taxonomy that describes and characterizes existing solutions and highlights their main limitations. Our taxonomy provides a comprehensive view of the reasons for the deployment of the solutions, and the scenario in which they operate. The results of this study demonstrate the main benefits and drawbacks of each solution set when applied to specific scenarios by examining current trends and future perspectives, for example, the adoption of emerging technologies based on Cloud and Edge (or Fog) Computing.

Long-Range Wide-Area Network (LoRaWAN) enables flexible long-range service communications with low power consumption which is suitable for many IoT applications. The densification of LoRaWAN, which is needed to meet a wide range of IoT networking requirements, poses further challenges. For instance, the deployment of gateways and IoT devices are widely deployed in urban areas, which leads to interference caused by concurrent transmissions on the same channel. In this context, it is crucial to understand aspects such as the coexistence of IoT devices and applications, resource allocation, Media Access Control (MAC) layer, network planning, and mobility support, that directly affect LoRaWAN's performance. We present a systematic review of state-of-the-art works for LoRaWAN optimization solutions for IoT networking operations. We focus on five aspects that directly affect the performance of LoRaWAN. These specific aspects are directly associated with the challenges of densification of LoRaWAN. Based on the literature analysis, we present a taxonomy covering five aspects related to LoRaWAN optimizations for efficient IoT networks. Finally, we identify key research challenges and open issues in LoRaWAN optimizations for IoT networking operations that must be further studied in the future.

Ultradense Networks (UDNs) seek to scale the 5th-Generation mobile network systems at unforeseen amounts of networks, users, and mobile traffic. We believe that the Wi-Fi sharing service is an asset in expanding 5G UDN capacity requirements for higher coverage and ubiquitous wireless broadband connectivity. However, the limitations of the Wi-Fi sharing pioneer deployment, along with other related works, has led our team to carry out further research. As a result, it was found that FOg CloUd Slicing for Wi-Fi sharing (FOCUS) is a suitable means of expanding 5G UDN capacities. FOCUS applies end-to-end Network-Cloud slice definitions on top of the Wi-Fi sharing technology, with the aim of offering multitenancy and multiservice support for a wide range of services, while meeting carrier-grade requirements and resource control at runtime and making full use of a “softwarized” approach. The feasibility of the FOCUS system is assessed in a real testbed deployment prototype, which allows an accurate view to be obtained of the basic functional principles and system-level proof-of-concept alongside the FON de facto Wi-Fi sharing service. The results suggest that FOCUS offers much greater benefits than FON, owing to its capacity to provide end-to-end Network-Cloud Slices while ensuring independent/isolated service delivery with resource adaptation at runtime.

The decoupling of the data plane and the control plane that became real through the advent of the Software‐Defined Networking (SDN) paradigm, has made possible the fast and flexible customized prototyping of testbed environments. One of the critical challenges that must be faced is the deployment of low‐cost high‐performance open testbeds. Our group built a low‐cost testbed that is highly flexible and customizable, and able to leverage a set of Key Performance Indicators (KPIs) for the minimal combination of components needed to achieve more efficient outcomes in specific scenarios. In light of this, we assessed the use of ONOS, Floodlight, and Ryu mainstream SDN controllers, on top of low‐cost open routers/switches platforms in which both OpenWrt and LEDE operating systems are embedded, to provide in‐depth discussions on different aspects of the subject. When measured in terms of (a) throughput and (b) network topology discovery time, the results of the assessment provided unpublished performance and scalability perspectives about the relationship between the controller and the operating system.

In the context of next-generation mobile networks, mobility control mechanisms are anticipated to provide infrastructures that can adapt to a broad range of requirements enforced by heterogeneous devices and applications. A mechanism that is central to this adaptability is the handover. During this critical phase of mobility lifecycle management, an appropriate technique for selecting the most suitable Point of Attachment (PoA) must be employed to ensure that mobile devices maintain optimal connectivity. Among the various strategies employed to tackle the handover decision problem, the Multiple Attribute Decision-Making (MADM) method is one of the most cost-effective, given the benefits provided by its decision-making approach. Despite its popularity, mobility management mechanisms often employ MADM methods without conducting a thorough performance analysis to justify the approach. One of the main reasons for such blind handover technique adoptions is the lack of studies that could inform researchers, developers, mobility managers, and operators about the primary differences among available MADM methods. To fill this knowledge gap, in this paper, we conduct a comprehensive review of the literature on MADM methods in the domain of handover decisions. In particular, our contribution includes providing a detailed summary of the step-wise mathematical implementation in addition to a broad discussion of the mainMADMmethods in the quality-oriented mobility decision domain, thoroughly classifying their characteristics and analyzing strengths and limitations. We also compare different categories of MADM methods and discuss some open issues and research challenges in this area.