# Fog Computing Enabling Industrial Internet of Things: State-of-the-Art and Research Challenges
## 2 Evolution and Enablers of Industrial Internet of Things
### Industry 4.0-Key Enabling Technologies  
With the use of advance technologies of wireless communication, diverse new emerging protocols and architectures are supporting automated industry 4.0 development. Resources can be efficiently used after integration of communication technology and big data processing in real time, this will result in better performance. Industry 4.0 development involves many communication technologies; however, big data, IoT, 5G, mobile computing and cloud/fog/edge computing are the key enabling technologies [2; 34; 35]. An extensive range of IIoT projects have been deployed in domains of building automation, manufacturing systems, health care systems, transportation systems, processing food and agricultural systems in the past few years. Reaching a common task in an IIoT application; sensing, integration, and communication are main steps. RFID tags are used for sensing, network topologies and protocols are used for communication. All these smart devices are associated with each other using internet. Many connectivity technologies are available for supporting IIoT applications. Critical requirements of IIoT applications have many open challenges in all domains (smart grid, smart cities, smart devices, D2D, healthcare) such as capacity, real-time connectivity, remote maintenance and topology of communication networks. Figure 6 gives a general overview of technologies to connect things to the Internet, representing short-range and long-range wireless technologies. All technologies work differently with aim of low-latency, low-power consumption, low-bandwidth requirement, and reliable communication. Figure 6: Different connectivity technologies in IIoT. For connecting IIoT devices, all technologies have to work with the objective of maximum throughput, minimum power consumption, minimum transmission delay, and maximum transmission distance range. 2G, 3G, 4G, LTE are cellular technologies that were used for long range connectivity in wireless wide area networks (WWAN). IIoT application's critical requirements and the increasing number of smart devices need additional resources for connectivity. Increase in smart devices results in more data processing for which connectivity technology is moving towards 5G. The 3_rd_ Generation Partnership Project (3 GPP) proposed Extended Coverage-Global System for Mobile Communications for the Internet of Things (EC-GSM-IoT) and Narrowband-Internet of Things (NB-IoT) for supporting M2M, enhanced MTC (eMTC), massive MTC (mMTC) and critical MTC (cMTC) communication networks for IIoT applications [5]. 5G cellular technology gives super low latency, ultra-reliable and high availability to cMTC applications (industrial application and control, remote surgery, remote training, remote manufacturing, and traffic safety and control). Low cost, low energy, and the massive number of intelligent devices in smart agriculture, smart meter, tracking, fleet management, and logistics domain are supported by 5G as well. 5G is beneficial for IIoT applications comprising from mMTC, cMTC to enhanced mobile broadband. The distributed model of IIoT applications require a massive amount of data rate with minimum latency, 5G technology gives 10 Gbps with 1 ms latency. 5G is use case driven communication technology for upcoming IIoT applications. For distributed ultra-low-latency and reliable connectivity in IIoT applications, 5G-IoT is an emerging solution. 5G-IoT scenario extends capabilities of IoT smart devices used in all domains. Recent research is focusing on low-latency, end-to-end reliability, and low energy consumption for both uplink and downlink communication. There is a lot of potential in research on IIoT with 5G communication technologies, to overcome challenges. This research will help in the industrial revolution.