term “service” is an ambiguous notion that may have very different meanings depending on the context. In business and economics, a service is an intangible activity offered by a provider to its consumers and creates value for them [29]. A service may just be a software with a defined interface available over the Internet.
Typically, enterprise systems utilize computing technologies and intelligence of smart objects over the Internet to propagate information and services [26]. Similar to IoT, the concept of Internet of Service is applied to services rather than physical (virtual) elements and creates information networks among users and service providers. IoS considers all basic business components (e.g., business objectives, processes, services) and technical basics such as capabilities of smart items in processing, sensing, and communication to support a service-oriented ecosystem and business applications modeling. Given that changes in the industrial environment such as connectivity disruption and reconfiguration of processes need reorganization of employed entities, new and optimized business processes in IoS help to flexibly model a self-organized service environment that adopts the model during deployment and according to specified policies. IoS is the innovative service model of information and is considered an important pillar of Industry 4.0. For instance, in the context of smart factories and future manufacturing, IoS uses the Internet and its software to produce services as customized products for individual users and based on the system’s ability.
1.2 Drivers, Motivations, and Applications for Communication
Generally, the major driver in introducing any new technology is the potential increased revenue and its benefit to the principal sectors such as health, safety, and industry. Communication is a key technology that integrates the digital and physical world and has redefined many consumer-oriented businesses in health care, finance, and industry. The new wave in communication technology provides real-time and seamless connections between industrial assets (the things, machines, sites, and environments) and enables intelligent industrial operations for extensive and heterogeneous production line, instrumentation, and process monitoring. Thus, different industrial sectors are motivated to deploy suitable communication technologies and infrastructure with flexible installation and high availability. Typically, wired communication in industrial systems is built on an IEEE 802.3 standard (Ethernet) that offers sophisticated solutions within strict requirements. Furthermore, nonhierarchical networks, increases in number of sensors, and extended connection of operating equipment change the network topology of wired systems and increase data traffic. This highlights the needs of future systems for broadband and deterministic communication that assist functions and provides synchronicity between the production processes. Hence, the communication systems used today will either broaden or be replaced by new developments.
With the growing demand and advance in communication technologies, wireless network becomes a concise, optimized, and widely popular solution for connectivity. Another promising candidate technology for communication is cellular networks (e.g., 4G/LTE and 5G) that enable ubiquitous access to information in disparate vertical applications. Wireless technology reinforces Industry 4.0 movement, and its successful deployment enables the possibility for fully autonomous systems and platforms. Notable advantages of wireless communication are system simplicity, reduced system size, and mass as well as improved system resilience to hazards through communication diversity. The principal benefits of wireless technologies in industrial applications could be associated to the following distinct areas.
1.2.1 Wireless Instrumentation
Contrary to wired communication, wireless technologies for instrumentation are often at lower expenses, with reduced installation time, and minimum disruption. They also contribute to extend coverage into remote or hostile areas. Therefore, wireless technologies offer better insight to prospective safety issues and operational requirements in industrial plants and facilities. Some technical requirements such as long battery life and optimized data rates should be adopted to specific applications for these networks. Since wireless apparatus are integrated with available operational systems via standard industrial interfaces, they should preserve the security of system for various cyberattacks. Ultimately, major beneficial factors of wireless instrumentation are their reliability, flexibility, and cost efficiency in resources and time management.
1.2.2 Mobile Technologies
Wireless access in buildings or public spaces mainly utilizes wireless local area network (WLAN) that enables Internet access for mobile devices in the vicinity, through access points deployed within the limited area. For instance, in some industrial applications, the control room is brought to the field and local onsite WLAN provides real-time line access, fault diagnostics, and maintenance for remote centers.
Despite the proliferation of systems and standards adhering to WLANs, it might not be efficient for all industrial mobile applications. In some industries, implementing local instruments and infrastructure for expansion of wireless coverage in the processing zones is substantial. This is strongly applicable to oil, gas, and mining industries, which enact strict regulations to all electrical apparatus. For instance, there are governing rules on classification of areas and workplaces safety for hazardous environments [30, 31]. Given that network equipment and their installation in these environments must be certified to comply with standard rules, the equipment costs will drastically increase in such industries. This motivates industrial applications to embrace mobile technologies such as cellular communication, public networks, and private and dedicated mobile networks as alternative communication solutions.
The oil and gas industries have employed GPRS1 and UMTS2 as public networks for wireless connectivity. To deliver an acceptable level of service experience in IIoT, a number of performance requirements such as latency, bitrate, density, mobility, availability, and permitted level of packet loss should be set. Besides, the high diversity of devices in oil and gas enterprises generates various requirements for communication solutions. For instance, underground/open-cast mining, and offshore oil rigs require unmanned platforms; the communication networks in these complex Industry 4.0 use cases should offer denser connectivity and handle huge data transfer with low latency. Real-time data streaming also underpins effective monitoring and is a critical success factor for these use cases. In its support, modern long-term evolution (LTE)-based cellular systems could deploy optimizations and reduce latency according to the service requirements. Private LTE network is another solution that exploits dedicated radio equipment and serves the premises of enterprises’ exclusive network with customized configurations to meet their exact performance requirements. For instance, licensed-assisted access (LAA) is a standard variant of LTE-unlicensed (LTE-U) [32], which leverages the combination of free 5 GHz unlicensed spectrum and licensed spectrum in new radio (NR) operations to deliver a performance boost for mobile users [33]. However, some stringent requirements fall under the category of ultra-reliable and low latency communication (URLLC) that are not achievable with 4G/LTE networks, at least not with high speed and scale. Thereby, 5G technologies and its proclaimed benefits can meet these critical requirements through 5G, its NR access technology and its expansion to the unlicensed spectrum [34].
5G new radio unlicensed (NR-U) is a potential candidate for next generation communication for Industry 4.0 scenarios, whereas an enterprise could install NR-U access points in place of Wi-Fi gateways and provide LTE coverage for the smart industry [35, 36]. 5G NR-U is a transformation in LTE-U/LAA from 4G/LTE to 5G NR; it opens up the 6 GHz bands for unlicensed access to alleviate the spectrum scarcity [37]. The 6 GHz bands in 5G NR-U offer the additional spectrum of 1.2 GHz and are deemed critical in supporting emerging bandwidth-intensive and latency-sensitive applications such as wireless augmented/virtual reality (AR/VR).
NR access technology in 5G includes the development of a new flexible air interface, denoted as 5G NX-radio, to attain the extreme communication requirements in terms of latency and reliability. 5G NX-radio is not compatible with previous 5G air interfaces and because of the availability of larger bandwidth, it will be initially implemented at new spectrum (primarily above 6 GHz) [38]. Sophisticated
