Abstract
WiFi (IEEE 802.11 standard) networks are widely used to support real-time (RT) applications, from home environment systems to complex networked control systems (NCS). Nevertheless, the Quality of Service (QoS) extensions incorporated into the standard are still unable to guarantee some relevant RT communications requirements. This paper presents an experimental validation of the RT-WiFi architecture that was recently proposed to deal with RT communication requirements and analysed through simulation. The experimental results demonstrate the feasibility of implementing the RT-WiFi architecture and improving the QoS level of communications through a comparative analysis with the EDCA (Enhanced Distributed Channel Access) mechanism, which is a mechanism incorporated in the IEEE 802.11 standard to provide different levels of transmission priority of different types of traffic.

Abstract
This paper addresses the use of network coding algorithms combined with adequate retransmission techniques to improve the communication reliability of Wireless Sensor Networks (WSN). Basically, we assess the recently proposed Optimized Relay Selection Technique (ORST) operating together with four different retransmission techniques, three of them applying network coding algorithms. The target of this assessment is to analyze the impact upon the communication reliability from each of the proposed retransmission techniques for WSN applications. In addition, this paper presents an extensive state-of-the-art study in what concerns the use of network coding techniques in the WSN context. The initial assumption of this research work was that the ORST operating together network coding would improve the communication reliability of WNS. However, the simulation assessment highlighted that, when using the ORST technique, retransmission without network coding is the better solution.

Abstract
Emergency vehicles have been employed in rescue operations and supportive services, attending victims and managing critical situations in smart cities. Such vehicles, notably ambulances, fire trucks, police cars and transit agents vehicles, may be tracked and monitored in some applications for different functions. When such emergency vehicles are not equipped with GPS receivers, cameras can be used to view emergency signs printed on them, allowing indirect identification of emergency vehicles, although many complexities have to be considered when performing visual sensors-based tracking and monitoring. In this context, this paper proposes a mathematical model focused on the evaluation of the coverage efficiency of a group of visual sensors over moving vehicles, aimed at visual coverage of emergency signs. For that, vehicles, emergency signs and visual sensors are mathematically modelled in this paper, with coverage interactions among these elements being computed based on proposed geometry equations and algorithms. Doing so, the effectiveness of the positioning and configurations of visual sensors can be evaluated without requiring actual deployment, potentially reducing costs when assessing visual monitoring systems in this scenario.

Abstract
The rapid urbanization process in the last century has deeply changed the way we live and interact with each other. As most people now live in urban areas, cities are experiencing growing demands for more efficient and sustainable public services that may improve the perceived quality of life, specially with the anticipated impacts of climatic changes. In this already complex scenario with increasingly overcrowded urban areas, different types of emergency situations may happen anywhere and anytime, with unpredictable costs in human lives and economic losses. In order to cope with unexpected and potentially dangerous emergencies, smart cities initiatives have been developed in different cities, addressing multiple aspects of emergencies detection, alerting, and mitigation. In this context, this article surveys recent smart city solutions for crisis management, proposing definitions for emergencies-oriented systems and classifying them according to the employed technologies and provided services. Additionally, recent developments in the domains of Internet of Things, Artificial Intelligence and Big Data are also highlighted when associated to the management of urban emergencies, potentially paving the way for new developments while classifying and organizing them according to different criteria. Finally, open research challenges will be identified, indicating promising trends and research directions for the coming years.

Abstract
Wireless visual sensor networks have been adopted in different contexts to provide visual information in a more flexible and distributed way, supporting the development of different innovative applications. Although visual data may be central for a considerable set of applications in areas such as Smart Cities, Industry 4.0, and Vehicular Networks, the actual visual data quality may be not easily determined since it may be associated with many factors that depend on the characteristics of the considered application scenario. This entails several aspects from the quality of captured images (sharpness, definition, resolution) to the characteristics of the networks such as employed hardware, power consumption, and networking efficiency. In order to better support quality analysis and performance comparisons among different wireless visual sensor networks, which could be valuable in many monitoring scenarios, this article surveys this area with special concern on assessment mechanisms and quality metrics. In this context, a novel classification approach is proposed to better categorize the diverse applicable metrics for quality assessment of visual monitoring procedures. Hence, this article yields a practical guide for analyzing different visual sensor network implementations, allowing fairer evaluations and comparisons among a variety of research works. Critical analysis are also performed regarding the relevance and usage of the proposed categories and identified quality metrics. Finally, promising open issues and research directions are discussed in order to guide new developments in this research field.

Abstract
The development of factory communication system has addressed the interconnection and decentralized requirements of complex automated production plants. Fieldbus networks have provided automation solutions in real-time and provided an adequate mechanism to cope with the communication requirements of control systems at the shop-floor. High-speed LANs are found to be suitable to support traffic with tight timing requirements in the factory automation environment. The automation industrial applications rely on standard TCP/UDP/IP communication for parameterization and process data exchange. Scheduling policies for CAN networks, performance measurements in real-time Ethernet networks, and the theoretical evaluation of CSMA-based networks also address the requirements of a factory communication system.