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Communication technology for Industry 4.0

09 April 2014

Industry 4.0, the fourth Industrial Revolution, is a hotly-discussed initiative for industrial and manufacturing technology of the future. The factory of the future will need to be smarter, enable greater flexibility in production, and deal with far higher demands on dynamism. 

Manufacturing processes will be organized differently, and the entire production chain – along the complete value chain from suppliers to logistics and extending it to the complete product life cycle.. The smart factory will be a highly complex entity that requires holistic control and closely interlocking production steps. Every process will feel the impact – from factory planning, production planning and logistics, ERP and MES systems, right through to control systems and individual field-level sensors and actuators.

Instead of running rigidly defined programs, plant and machinery will have to be able to optimize their own processes and make autonomous decisions. The smart factory will have a different structure from what we are accustomed to today. The conventional automation pyramid model with field, control and supervisory levels will no longer apply. Field-level devices will become more intelligent and more numerous, able to acquire more information and process it locally. Many other functions will be "virtualised," running in server pools, or be transferred to some form of "cloud" where they will be processed using the best currently available resources. 

Control functions need to work closely with sensors and actuators in the field, and receive regular instructions from the supervisory level. Today, control functions are executed by software running on a PLC located close to the process itself, and therefore able to communicate with field devices in real time. A dedicated autonomous PLC device is used so that time-critical functions are able to run without being impacted by other tasks, and communication with field devices is undisturbed by other data traffic. If, however, there is a guarantee of sufficient computing power on the server, plus reliable and timely communication, then there is nothing to prevent control functions from running at any other suitable location.

If we take a look at developments in large modern data centers – with virtualisation, cloud computing and high-performance communication infrastructures – it becomes clear that such a concept will also play a fundamental role in the factory of the future. Today's virtual servers provide an enormous level of performance, and those in the future will deliver even more. Combined with state-of-the-art data center networks based on Ethernet and IP technologies, this  already guarantees data throughputs of hundreds of Gigabits per second, and delay times in the microsecond range. The advantages of concentrating processing power in the cloud are central administration and a better utilization of existing resources, leading to more cost-effective operation. It's only a matter of time before there is a move toward carrying out automation tasks in this way too.

There will be demands to not only exchange data within the factory in real time, but also to communicate continuously across company boundaries and along the entire value chain.

All production levels will be networked with each other, using fast LANs within the factory and M2M communication externally, relying on the Internet or wired/wireless provider networks. The LANs or WANs will need to comply with Service Level Agreements for communication.

Due to the demands and the size and number of devices, the network will become so complex that manual administration will scarcely be possible. This means that networks will also need to become more intelligent so that they can monitor and optimize themselves without needing constant operator intervention. 

At field level, there will be an increase in the number of communicating devices.  The data volumes produced by these devices will also grow, accompanied by heightened demands for minimum runtimes, real-time processing and reliability. Ethernet will be almost exclusively the medium used at network level, with Gigabit Ethernet becoming the standard for wired communication. Cost-effectiveness and low power consumption, the advantages currently enjoyed by Fast Ethernet with a data rate of 100 MBit/s, will as well be given by Gigabit Ethernet in the future due to the advances in semiconductor technology. As far as wireless technology is concerned, IEEE 802.11 WLAN will play the dominating role. The new 802.11ac and 802.11ad standards will permit future data rates of a Gigabit per second and higher, and Low-Power WLAN will permit extremely energy-efficient wireless solutions. WLAN's advantage over other wireless systems stems from its transparent, end-to-end communication, requiring no conversions. Extremely efficient networks can be set up by creating small radio cells linked to each other via fast Ethernet connections. 

The ongoing work on the "Time Sensitive Networks" (TSN) standard (within the IEEE 802.1 working group) is creating the basis for future field networks and will guarantee that wired networks possess the necessary real-time capabilities. TSN will be the first standardized IEEE method to enable real-time communication that challenges the boundaries of technical feasibility. The combination of Time Aware Scheduling, interruption of non-time-critical frames in favor of real-time traffic (Frame Preemption) and Cut-Through Switching permits the shortest possible runtimes with precisely calculable upper limits. 

Field devices will be equipped with efficient low-power multi-core processors, with data processing, communication protocols and LAN and WLAN interfaces running on a system-on-chip. This high level of integration onto single modules will also slash costs for efficient communication connections. 

Back-end systems, including control functions, will be distributed over computers in a server pool. As is already the case in large data centers today, the servers will be connected together via high-speed networks made up of so-called Ethernet Fabrics, ensuring the shortest runtimes, best-possible performance and loss-free transmission. Some of the technologies necessary for this are being defined by IEEE 802.1 in the Data Center Bridging working groups. These server pools will have fast data connections of 10, 40 or even 100 Gigabit/s to field-level devices, so eliminating any possible bottlenecks. On top of this, intelligent traffic control systems will ensure that priority data always arrives at its destination in good time. 

All communication systems will be automatically monitored on a continuous basis. This observation of the actual application will allow rules to be derived defining who is permitted to communicate with whom, and with what parameters. These rules will then be automatically implemented on switches and routers to ensure that the necessary service level is provided. The same mechanisms will be employed to guarantee data security and access control, permitting communication only between authorized participants.

On top of all this, there will be a Wide Area Network connecting together the geographically separate locations and the entire supply chain. As well as making Service Level Agreements possible, future extensions to the Internet will secure the required real-time capabilities on a worldwide scale and guarantee the availability of all critical data. 

This will all be based on open standards as the only strategy for ensuring interoperable, affordable and end-to-end components for Industry 4.0. What this also means, however, is that systems, plants and components will be more vulnerable and open to attack. The best possible data security is therefore an absolute prerequisite. If we are not successful in ensuring access protection and implementing robustness against incorrect handling and malicious attacks, then Industry 4.0 is destined to fail. We will need better methods of ensuring the confidentiality, availability and integrity of data. Authentication, encryption, access control and detection of unauthorized actions must all be improved to ensure reliable operations.

The communication infrastructure forms the backbone of all smart factory concepts. Ensuring its secure and reliable operation is therefore the prerequisite for successful realization of the Industry 4.0 vision. Considerable effort will still be needed before some of the required systems are defined and developed. Many of these activities are already ongoing, and in some parts existing solutions from other areas can be adopted and applied to industry applications.

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