and personnel management provides real-time visibility of fleet, processes, and value networks. This reduces labor, transportation, and installation costs while highly improving operation in remote sites. Currently, there are various services and techniques for asset management, personnel tracking, and identification of materials, inventory, and tools. GPS3 and public navigation services cannot meet the requirements applicable to most industrial applications and are not viable solutions for asset management in industrial applications. Some applications use wireless technologies such as Bluetooth, Wi-Fi, and ultra-wideband (UWB) for positioning and should be chosen according to the specific usage scenario [41, 42, 43]. In such techniques, precision, infrastructure demands, maintenance, and real-time requirements with respect to position update should be optimized. Since asset management is performed in smart environments where devices are often connected, four main features should be considered: ubiquitous connectivity, power efficiency, security, and reliability [44]. In this context, the usage of wireless communications is highly beneficial, especially in remote areas.
1.2.4 Safety Management and Systems
Safety-related applications are always of critical nature. Such systems are of two main types: safety monitoring and safety integration systems [45]. The former relates to quick safety reaction times to prevent physical damages to humans or materials, and the latter requires real-time communication and immediate reaction. Safety monitoring applications (e.g., gas leakage monitoring) may tolerate certain levels of delay and loss; however, safety integration systems (e.g., steam pressure control) require a communication network with very low latency, ultra-high reliability, and resiliency. Due to the impact of interference on wireless communication, safety integration systems rarely use wireless networks as their primary communication channel.
In addition, the transmission channel for safety systems must use a so-called safety protocol as the supervision mechanism [46, 47]. The protocol constantly verifies performance metrics of the transmission channel (e.g., latency, synchronicity, reliability). If the safety protocol detects any violation in its key metrics, the safety application is switched into an unsafe or fail-safe state. Considering that functional safety is a part of safety system that acts in response to risky circumstances, it exploits industrial automation and smart techniques to actively minimize system risk and failure.
1.2.5 Security and Surveillance
This class of applications often relies on commercial communication technologies such as Wi-Fi when wired solutions are cost prohibited to transmit voice, video, and identification information related to the security of industry space. In wireless video surveillance systems, cameras are mounted on drones, land vehicles, and remote fixed locations. The transmitted video delivers footages to enhance critical awareness and to assist in decision-making in a wide range of applications such as seismic changes and natural disasters, harbor inspection, object detection on assembly lines, and rescue operations. Naturally, wireless video surveillance systems require high bandwidth, scalable and robust networks, and video analysis algorithms to properly address security requirements.
1.3 Design Criteria and Communication Requirements in the Industry 4.0 Era
Wireless technologies are an essential aspect of Industry 4.0 implementation, where all instances involved in value creation are properly interconnected. To provide better communication between service users, marketplace, and service providers, cellular networks supplement communication systems to promote potential transformation to Industry 4.0. Obviously, provisioning of wireless communication throughout a large industrial site with wide range of heterogeneous applications creates trade-offs between performance parameters and complicates the design of the overall wireless solution. Therefore, communication technologies should take into account certain design criteria specifically adapted for the industrial space. In this section, we present the main selection criteria and requirements for industrial wireless technologies.
1.3.1 Reliability
In the context of wireless communication, reliability could be identified as the capability of a wireless technology to seamlessly communicate in the presence of wide range of obstructions in space. The reliability of a wireless system is quantified by a number of key performance indexes such as its radio frequency (RF) spectrum usage, RF agility, and link budget [48]. Because of the physical nature of RF waves, the utilization of RF spectrum is fully regulated by government bodies to minimize interference. RF agility improves reliability through interference reduction or avoidance techniques in the RF spectrum. The link budget metric estimates the power of the received signal, accounting for the transmit power and gain wireless medium gain and loss. A higher link budget value corresponds to reduced interference and offers increased level of reliability.
Reliability of a wireless network also depends on network topology, media access control (MAC) design, and the adopted modulation, and coding scheme [49]. Other factors may also affect the reliability of a given wireless system. For instance, if reliability is characterized in terms of power consumption, the longevity of wireless network should be adjusted above a certain threshold level to ensure no significant degradation in system performance and reliability.
1.3.2 Latency
Industry 4.0 applications often require low latency networks to collect, store, or analyze data and to make decisions based on updated information. In the wireless medium, the variation of link quality deteriorates uplink/downlink transmissions over time, leading to higher latency and subsequent system failure [50]. In time-critical applications, if the communication does not meet the low latency requirement, data may lose its original value [51]. MAC design has a significant impact on latency of the network [49].
1.3.3 Coverage
Transmission range is defined as the maximum distance a signal is sent by a transceiver and can be reached and interpreted at the receiver. Given that industrial environment is RF hostile and constantly changing, the coverage range is affected by transmission power, complexity, and propagation properties [49]. Generally, higher data rates degrade penetration capabilities in an industrial site full of obstacles but at the cost of reduced coverage for network. Coverage of wireless solutions can be extended by deployment of routing, peer-to-peer (P2P) communication, and increasing transmission power using repeaters and power amplifiers. Nevertheless, these techniques increase system complexity and result in less reliability. To summarize, it is necessary to identify the requirements of an individual application and identify the proper trade-off between key performance metrics correspondingly.
1.3.4 Power Efficiency
Power efficiency is a qualitative metric that represents energy consumption of system components. In wireless networks, energy consumption depends on data rate, network topology, MAC protocol, and hardware design [49]. One possible solution to optimize system power consumption is using dynamic power management to boost system efficiency. Power efficiency and reliability are also closely interconnected. In fact, while better power efficiency will lead to higher reliability, system demands on ultra-reliable low latency communication may cause significant energy consumption [52]. It is thus necessary to consider well-thought trade-offs under the acceptable level of system complexity.
1.3.5 Simplicity
Although adopting Industry 4.0 unveils great potentials in industrial landscape, interconnected supply chain will be highly affected by additional complexity in mobility, sensory systems, machines, and information [53]. Recently, a number of technologies have been standardized, and many proprietary alternatives are constantly being offered for wireless communication [54]. Wireless solutions and their heterogeneous connectivity foreseen in the context of Industry 4.0 result in increased amount of generated data, parameters, and variables in networks. Integrating novel automation systems and advanced monitoring techniques increases the overall degree of complexity in products, enterprises, and the underlying network