Distributed Cooperative Framework and Algorithms for wireless Network Performance Optimization

In Wireless Local Access Networks (WLANs), the Medium Access Control (MAC) protocol is the primary element that determines the efficiency of sharing the limited communication bandwidth of the wireless channel. IEEE 802.11 MAC uses the contention-based Distributed Coordination Function (DCF) as a fundamental medium access mechanism. However, the dynamic nature of the wireless environment creates mobility challenges of maintaining maximum channel capacity, of obtaining optimal throughput and latency, and of retaining good security in a distributed wireless network. This dissertation first introduces a set of parameters to characterize the medium status and radio environment, and a mechanism for mobile devices to exchange measurements in order to obtain broad and comprehensive knowledge of the wireless environment. Then the dissertation proposes a distributed cooperative wireless architecture and framework, and three cooperative algorithms to optimize wireless network performance. The cooperative algorithms allow wireless devices to cooperatively adjust configurations and optimize operations based on the characteristics of the environment. The first algorithm adaptively adjusts the contention window size to reduce the number of collisions as the number of mobile devices increases, in order to reach maximum channel utilization. However, if a channel reaches the saturated state, the throughput per user decreases significantly. Therefore, the second algorithm discussed in this dissertation is to select the best Access Point (AP) in overlapped AP coverage areas to balance network loads and maximally utilize the network capacity. When the mobile device transitions from one AP to another AP, it may take milliseconds to seconds due to required re-association and re-authentication with the new AP. Thus, the third cooperative algorithm optimizes the device transition to provide an acceptable balance of latency and security. The corresponding simulation or experiment results that demonstrate a significant improvement of wireless network performance are explained for each algorithm. Forgery and confidentiality are major concerns for distributed radio resource measurement and cooperation. Thus, this dissertation concludes with an analysis of security threats to radio resource measurement and cooperation, and proposes an action frame protection scheme to ensure secure distributed cooperative wireless networks

Real-Time Sensor Networks and Systems for the Industrial IoT

The Industrial Internet of Things (Industrial IoT—IIoT) has emerged as the core construct behind the various cyber-physical systems constituting a principal dimension of the fourth Industrial Revolution. While initially born as the concept behind specific industrial applications of generic IoT technologies, for the optimization of operational efficiency in automation and control, it quickly enabled the achievement of the total convergence of Operational (OT) and Information Technologies (IT). The IIoT has now surpassed the traditional borders of automation and control functions in the process and manufacturing industry, shifting towards a wider domain of functions and industries, embraced under the dominant global initiatives and architectural frameworks of Industry 4.0 (or Industrie 4.0) in Germany, Industrial Internet in the US, Society 5.0 in Japan, and Made-in-China 2025 in China. As real-time embedded systems are quickly achieving ubiquity in everyday life and in industrial environments, and many processes already depend on real-time cyber-physical systems and embedded sensors, the integration of IoT with cognitive computing and real-time data exchange is essential for real-time analytics and realization of digital twins in smart environments and services under the various frameworks’ provisions. In this context, real-time sensor networks and systems for the Industrial IoT encompass multiple technologies and raise significant design, optimization, integration and exploitation challenges. The ten articles in this Special Issue describe advances in real-time sensor networks and systems that are significant enablers of the Industrial IoT paradigm. In the relevant landscape, the domain of wireless networking technologies is centrally positioned, as expected