A Survey on Industrial Internet of Things: A Cyber-Physical Systems Perspective <s> b: RESOURCE SCHEDULING <s> Wireless sensor-actuator networks (WSANs) are being adopted in process industries because of their advantages in lowering deployment and maintenance costs. While there has been significant theoretical advancement in networked control design, only limited empirical results that combine control design with realistic WSAN standards exist. This paper presents a cyber-physical case study on a wireless process control system that integrates state-of-the-art network control design and a WSAN based on the WirelessHART standard. The case study systematically explores the interactions between wireless routing and control design in the process control plant. The network supports alternative routing strategies, including single-path source routing and multi-path graph routing. To mitigate the effect of data loss in the WSAN, the control design integrates an observer based on an Extended Kalman Filter with a model predictive controller and an actuator buffer of recent control inputs. We observe that sensing and actuation can have different levels of resilience to packet loss under this network control design. We then propose a flexible routing approach where the routing strategy for sensing and actuation can be configured separately. Finally, we show that an asymmetric routing configuration with different routing strategies for sensing and actuation can effectively improve control performance under significant packet loss. Our results highlight the importance of co- joining the design of wireless network protocols and control in wireless control systems. <s> BIB001 </s> A Survey on Industrial Internet of Things: A Cyber-Physical Systems Perspective <s> b: RESOURCE SCHEDULING <s> Internet of Things (IoT) in a real world scenario involves collecting data by sensor devices and communicating the sensed data, through gateway devices, to the IoT Cloud (or the Internet) using direct or multi-hop communication. A gateway typically supports multiple wireless sensor networks (WSNs) and each WSN might use a different technology for communication. Hence gateways are designed to be heterogeneous, having necessary hardware support only for those technologies corresponding to their associated WSNs. Due to their heterogeneity, the technology specific channel access mechanisms need not provide fairness in data communication at each gateway. In this paper, we propose two centralized techniques that involve an efficient link selection per technology and time based scheduling among gateways. This improves fairness in data transmission for every gateway, resulting in an increased data transmission. The first technique uses a multinomial probability based link selection thereby reducing contention within each technology link for a given network topology. The second technique incorporates adaptation to the changing traffic patterns in the network. Our extensive simulation results show that the proposed techniques outperform default technology specific channel access mechanism in IoT networks in terms of total data transmitted, packet delivery ratio, and fairness. <s> BIB002 </s> A Survey on Industrial Internet of Things: A Cyber-Physical Systems Perspective <s> b: RESOURCE SCHEDULING <s> Wireless sensor networks (WSNs) have been widely used in industrial systems that demand a high degree of reliability and real-time performance in communications. However, because of limited network resources and delays caused by transmission conflicts and channel contention, many industrial applications cannot meet these demands. To resolve these issues, we introduce Narrow Band Internet of Things (NB-IoT) technology into industrial networks to reduce transmission delays. Two challenges are addressed in this work: (1) the primary goal is to guarantee the schedulability of the system, so the controller must determine when NB-IoT nodes transmit to base stations; and (2) because communication through the base station is a paid service, the controller must minimize the use of NB-IoT slots. We resolve these issues via a scheduling analysis and transmission mode selection. In addition, we propose a Path Selection Algorithm (PSA) to improve the schedulability of the industrial system. Experiments indicate the effectiveness and efficacy of our approach. <s> BIB003 </s> A Survey on Industrial Internet of Things: A Cyber-Physical Systems Perspective <s> b: RESOURCE SCHEDULING <s> With the emergence of the Industrial Internet of Things (IIoT), process industries have started to adopt wireless sensor-actuator networks (WSANs) for control applications. It is crucial to achieve real-time communication in this emerging class of networks, and routing has significant impacts on end-to-end communication delays in WSANs. However, despite considerable research on real-time transmission scheduling and delay analysis for such networks, real-time routing remains an open question for WSANs. This paper presents a conflict-aware real-time routing approach for WSANs, leveraging a key observation that conflicts among transmissions involving a common field device can contribute significantly to communication delays in industrial WSANs, such as WirelessHART networks. By incorporating conflict delays into the routing decisions, conflict-aware real-time routing algorithms allow a WSAN to accommodate more real- time flows while meeting their deadlines. Both evaluations based on simulations and experiments on a physical WSAN testbed show that conflict-aware real-time routing can lead to as much as a three-fold improvement in the real-time capacity of WSANs. <s> BIB004
The problem of resource scheduling plays a critical role in network performance and information delivery. Traffic scheduling schemes can manage a large amount of traffic with the consideration of system performance metrics and requirements, including latency, utilization of network resources, etc. In I-IoT, latency is a critical requirement, as most data and control information are time-sensitive. As a result, delayed delivery or lost communication may lead to reduced productivity, low efficiency, system failure and safety issues. Real-time information delivery requires that each traffic flow shall be delivered with latency guarantee requirements. Designing appropriate scheduling schemes to meet these performance requirements is challenging as I-IoT involves a massive number of devices (sensors, actuators, etc.) and those devices have diverse performance requirements. Commonly, resource scheduling algorithms are devoted to solving channel contention or transmission conflicts. Channel contention causes transmission delay, because all channels are assigned to other transmissions, while transmission conflict indicates that multiple transmissions contend over a shared resource. There existing some research efforts toward conducted resource optimization via scheduling in I-IoT BIB004 , BIB001 , BIB002 . For instance, to solve the channel contention problem, Narayanan et al. BIB002 proposed a link selection mechanism to reduce the channel contention caused by unfair opportunities for channel access. Each gateway performs the link selection mechanism based on the multinomial probability to select a fixed link schedule. With the link selection mechanism, the data transmission in the network is maximized and channel contention is minimized. To address the transmission conflict delay, Wu et al. BIB004 proposed a conflict aware routing (CAR) algorithm for industrial networks. Likewise, Xia et al. BIB003 proposed the path selection algorithm (PSA) to improve the scheduling in industrial networks with enabled narrow band Internet of Things (NB-IoT) modules on sensor nodes.