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Industry 4.0 Vision for the Supply of Energy and Materials


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coordinator. Since it offers various features for protocols of all the layers above MAC and PHY, it can be properly adapted to large deployments.

      ISA100.11a. The International Society of Automation (ISA) developed industry standards that offer reliable and secure systems for automation and control applications. ISA100.11a is an industrial wireless communication standard ratified in 2009 and operates in a 2.4 GHz band (ISM band) [64]. A PHY layer of ISA100.11a is based on the IEEE 802.15.4 standard; however, its MAC layer is built on a modified, noncompliant MAC protocol of IEEE 802.15.4 and utilizes a combination of contention- and scheduled-based MAC scheme. To achieve real-time networking, a MAC protocol of ISA100.11.a exploits TDMA and carrier-sense multiple access (CSMA) along with additional spatial, frequency, and temporal diversity. Channel blacklisting and frequency hopping are also leveraged to address mutual interference from coexisting wireless systems and enhance network robustness [70].

      Wireless networks for industrial automation-process automation (WIA-PA). The Chinese Industrial Wireless Alliance introduced WIA-PA in 2008 as the national standard that proposes architecture and communication specifications for industrial automation and process use cases. Later, this standard was approved by the IEC (International Electrotechnical Commission) [58]. The WIA-PA PHY layer complies with the IEEE 802.15.4 standard, though its MAC layer applies a hybrid scheme (a combination of scheduled- and contention- based mechanisms) on IEEE 802.15.4 MAC protocol. It also exploits TDMA, CSMA, and frequency-division multiple access (FDMA) approaches for channel access. Given that WIA-PA MAC layer leverages adaptive frequency hopping, time slot hopping, and adaptive frequency switching, it can cope with varying network conditions and is considered a self-healing network [78]. Similar to WirelessHART and ISA100.11a, this standard employs a reactive approach that exploits redundant routing and gateway devices to prevent failures in networks, further enhancing its reliability and self-organizing characteristics [78].

      1.4.1.2 IEEE 802.15.1 Standard