Читать книгу Industry 4.0 Vision for the Supply of Energy and Materials - Группа авторов - Страница 22

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 signaling methods are involved in 5G NX-radio, where new coding techniques along with the short and flexible radio frames structure are employed in the design of 5G-air interface [39]. 5G NX-radio encompasses two key technologies: (1) massive multiple-input, multiple-output (MIMO) and beamforming; and (2) ultra-lean design. Beamforming combats the challenging radio propagation and enables reduced interference along with very high throughput at high frequencies [40]. Low latency is achieved by ultra-lean design of 5G NX-radio and through minimizing the transmission time of the control command over the radio interface [38]. Consequently, the transmission time of a single packet over the air is short and expected to be a fraction of LTE’s [39]. In addition, the ultra-lean design in 5G NX-radio facilitates retransmission of packets within the constrained latency.

Ultimately, mobile technologies comprise various applications with different requirements and purposes. General requirements of mobile communication technologies are seamless integration, reliability, and scalability. Some requirements in industrial settings such as suitable bandwidth, and security mechanism are highly application dependent.