# Six-Gear Roadmap towards the Smart Factory
## 5 The Six-Gear Roadmap
### Gear 2: Connectivity
#### 5.2.2 Industrial Internet of Things (IIoT) Connectivity  
The currency of the online world today is data as it drives business and services [53]. Data is in abundance in the manufacturing sector. To access this data, physical assets and operations in the factory floor needs to be connected. Connectivity technologies have become more accessible and affordable due to the considerable drop in the cost of sensors and computing in the last few decades, further enabled by the advancement of the internet [28]. An IIoT system is a collection of an ecosystem of combined technology elements that collect, store and harness data [54] in order to provide information, trigger events and recommended actions to be taken. There has been several initiatives and close collaboration between research and industry to standardize the reference architectures for IIoT connectivity in industrial applications. Figure 6: Gear 2—connectivity stage and Industry 4.0 technology jigsaw. These reference architectures all serve as a general guide and aim to facilitate interoperability, simplicity and ease of development [55]. Reference architectures like the Industrial Internet Reference Architecture (IIRA) and the Industrial Internet Connectivity Framework (IICF) by the Industrial Internet Consortium (IIC) facilitate broader industry applications to help evaluate connectivity of IIoT solution [56]. The Internet of Things-Architecture (IoT-A) provides detailed overview of the IoT information technology aspects [57]. RAMI 4.0 provides a three-dimensional map for smart factories covering manufacturing and logistics applications [58]. The International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC) provides six domain model frameworks for the (IoT) Reference Architecture focusing on resilience, safety and security [59]. An illustration on an IIoT stacks system is shown on Figure 7. IIoT systems contains different layers that communicate and integrate in coherence with one another without interfering with existing automation logic of the physically connected entities. There are multiple options to consider when building the IIoT stack, this can depend upon existing capability and the application needs. The 'Thing' layer represents the core hardware of the physical entity where the raw data normally exists. The 'Sensor' layer is where the embedded sensors are used to detect and measure the parameter(s) of interest. The 'Edge' layer normally consists of embedded computing hardware and/or software that operates and controls the functionality of the sensors and performs onboard processing of the data. For example, CNC machines/robots used in manufacturing normally consists of the first three layers. They have embedded sensors wired to the PLC unit, interfaced and controlled via a supervisory control and data acquisition (SCADA) system built within for management and control acting as the edge layer. However, that's not the case with legacy machines as further additional sensors and edge devices are needed to access and communicate data to upper layers of the stack. The 'Communication' layer consists of multiple communication standards and protocols that enable communication and data transportation. Key networking technologies for transporting the data can be wired or wireless (e.g., Ethernet, Wi-Fi, Bluetooth, Cellular 4G/5G, LoRa, Sigfox, NB-IoT, etc.). The amount of information generated may increase exponentially and there is a need for fast communication network for acquiring such  
Figure 7: IIoT connectivity stack. (Author’s creation). information in real-time [60]. Although Industrial Ethernet has been the de-facto backbone of many plant floor connectivity, it is worth to mention that the emergence of 5G technologies are a key enabler of the next generation communication technologies operating at much higher frequencies and larger bandwidth [61].