V. 5G TECHNOLOGIES
In this section a brief evolution of cellular technology is provided as well as a detailed discussion on how Fifth Generation cellular technology (5G) can support the Industrial Internet of Things and Industry 4.0.
A. Evolution of Cellular technology
Currently, wireless cellular technology has reached the Fifth generation milestone. Since the conception of analogue cellular systems in the 1980’s which is termed the First Generation (1G), there has been a rapid and significant evolution of these technologies as shown in Fig. 6 below [13].
Fig. 6: Evolution of cellular technology (From [13]).
In the 1990s the Second Generation (2G) came about and made use of Code-Division Multiple Access (CDMA), Global System for Mobile communication (GSM) standard, Time division multiple access (TDMA) as well as digital transmission in place of analogue transmission techniques. Short Message Service (SMS) which is a text messaging service also came with 2G. This transition brought with it more power efficiency and therefore increased battery life in devices. The 2000s saw the advent of 3G which brought in high-speed IP (Internet Protocol) data networking. A main contributor to the success of this technology was the use of packet switching instead of circuit switching which had been used in earlier generations. Evolution-Data Optimised (EVDO) and Evolved High Speed Packet Access (HSPA) enabled faster data rates (114 kbits/s) which enabled Global Positioning Systems (GPS) and mobile web. As a result, media streaming of digital content became possible to 3G handsets. In the 2010s an extension of 3G emerged as 4G. This made use of Worldwide Interoperability for Microwave Access (WiMAX) and Long Term Evolution (LTE) technology. With 4G came a growth in mobile broadband as well as improved speed. It also offered higher bandwidth and more services. With 4G LTE, It is possible to achieve Data transfer speeds of up to 100 Mbits/s (download).
While 4G has offered significant improvements to previous generations, it still has several shortcomings which include high energy consumption, low reliability of the wireless connections, end to end delays and support of only a low density of devices. These shortcomings limit its use in IIOT applications and industry 4.0. The Industrial Internet of Things (IIOT) has several unique communication requirements. These include low latency (real-time operation), reliability, flexibility (system interoperability and integrability) and high security. 5G promises to offer superior performance compared to 4G in all aspects including much higher data rates, an expansion of Enhanced Mobile Broadband (eMBB), Ultra-Reliable and Low Latency Communication (URLLC) and Massive Machine Type Communication (MMTC) which is sometimes referred to as massive Internet of Things (mIoT). Enhancements in these three areas ( eMBB, URLLC, and MMTC/mIoT) make 5G an attractive candidate for meeting the demands of IIOT and Industry 4.0.
B. 5G Enabling Technologies
1) Dense Heterogeneous Networks (HetNets): The deployment of a large number of small networks which result in heterogeneous networks (HetNets) is a key enabling technology as it allows 5G to handle large volumes of Data. These HetNets comprise of small cells which have low transmission power and are found beside the legacy [14]. These low power nodes could be small cells, relays or remote radio heads (RRH) as well as a provision for Peer to Peer (P2P) communication which may be Device to Device (D2D) or Machine to Machine (M2M) communication [14]. These low power Base stations significantly improve the capacity of the network and help to address with coverage holes. Using HetNets also improves spectral efficiency through higher spectrum reuse. Fig. 7 below shows a comparison between a conventional singletier cellular network and a Heterogeneous Multi-Tier Network [14].
Fig. 7: Single-Tier and Heterogeneous Multi-Tier Networks (From [14])
2) Cloud Radio Access Network (C-RAN): In conventional (4G) networks, the radio and baseband processing is integrated within the Base station. When Cloud-Based radio access is used, baseband processing units (BBUs) which perform functions such as encoding, FFT, and modulation is performed in the cloud (BBU pool) [14]. In this architecture, the radio unit such as a Remote Radio Head (RRH) is located with the antennas and performs signal processing operations such filtering. amplifications, analog to digital conversion and digital to analog conversion. The digital baseband signals generated are then transmitted to the cloud based BBU pool which consists of powerful processors that can perform baseband processing. Using C-RAN allows for several inexpensive RRHs to be used and thus increasing coverage of 5G systems as shown in Fig. 8 below.
Fig. 8: A system enhanced with cloud-based radio access network (From [14])
3) Full Duplex Wireless: With previous technology, it was generally accepted that a wireless node would not be able to decode a received signal while transmitting a signal on the same frequency band because of the interference that would occur between the transmitter and receiver circuitry. This Phenomenon is known as self-interference (SI) [14], [15]. However, there have been advancements in antennas and digital baseband technologies which in combination with Radio Frequency cancellation techniques, make it possible to have full duplex communication within the same band [15]. This is a key enabler of 5G as it doubles the spectrum efficiency by removing the need for separate frequency bands and time slots for uplink and downlink transmission. This full duplex solution yields higher data rates than Half Duplex systems. Half Duplex systems also reduce Latency [14].
C. Potential of 5G Use in Industrial Automation
As already mentioned, 5G is a key enabler of IIOT and Industry 4.0 and therefore finds several applications in Industrial Automation. For instance in time critical applications such as communicating sensor data and controlling actuators, 5G can provide low latency communication at high reliability. Another sector that is time sensitive is in vision systems and vision controlled robots in an assembly line. These would need low latency as well as high bandwidth to communicate [16].
5G can also be used for non critical communication within the industrial automation domain and factories. Examples of such applications include the acquisition of data that will be used at a later stage, logistics processes, packaging and shipping of goods as well as communication amongst factory personnel. Whilst these examples are not time critical, there is a need for high availability and reliability in these scenarios [16].
Another use case of 5G is with regard to outside factory communication between remote workers and the factory (remote control of factory). Because 5G can handle high data rates, augmented reality can be supported which allows for precise remote factory control. Another important application is with regard to connected factories which are in different geographical locations. Seamless real-time operations of these factories can be achieved though 5G.
Another application of 5G is industrial automation is brought about through Machine to machine/man (M2M) and device to device (D2D) technology. M2M provides seamless interaction among man machine and system and not just data exchange. The data transmission required for this sort of experience can be facilitated by 5G [16].
Another key application of 5G in Automation is in Big Data Technology. The large volume of data that can be communicated though 5G will allow for smart decision making and manufacturing intellectualization.
VI. OPC (OLE FOR PROCESS CONTROL)
An important aspect of the IIOT is a high level of connectivity between different industrial entities. This connectivity together with intelligent software enables the development of complex technical systems which allow remote monitoring and control of these industrial entities through the use of software applications. As a result, software has increasingly become an essential components in automation and control systems. However, the automation and control softwares that are used in industrial processes are usually developed by different vendors [17]. Because of this, a key challenge that arises from having different vendors is the wide heterogeneity of devices, operating systems, platforms and services. In order to facilitate interoperability of vendor solutions, there is a need to replace proprietary approaches with standardised solutions[17]. Therefore, it is important to have a way for different software components which are developed by different vendors to be able to communicate with each other seamlessly and effectively. This
section discusses OPC (OLE for Process Control) which has been established as a worldwide defacto industrial interface standard for automation software providers [17].
A. OPC motivation
Before the advent of OPC, industrial software applications used to access the data from control devices by making use of device specific drivers that were independently developed . While this facilitated communication between applications, it became evident that this was not a sustainable solution as each application needed to have a driver for every hardware device as shown in Fig.9 below.
Fig. 9: Challenges Experienced without OPC (From [18]).
Another challenge that was observed was the conflict that occurred between drivers as some hardware features were not supported by all drivers developers. This method also proved to be limiting as changes in hardware capabilities would result in failure of existing drivers therefore an update of the drivers would be needed for each upgrade in hardware capability [17].
B. The OPC Solution
In order to address these issues, a taskforce which included Rockwell Automation, FisherRosemount, Opto 22, Siemens, Intellution and Microsoft worked together to provide standardised access to automation data on Windows-based systems [19]. This resulted in the formation of the OPC Foundation and the development of OPC technology. This first version of OPC is today known as OPC-Classic. It defines an interface over which PC-based software components can exchange data as shown in Fig. 10 below [19].
There are three major specifications that were developed for OPC-Classic these were Data Access (DA) which specifies access to current data, Alarm and Events (A&E) which specifies
Fig. 10: OPC clients and servers (From [19]).
the interface which handles even based information which includes the acknowledgement of processes alarms and Historical Data Access (HDA) which specifies accessing archived data [19]. OPC makes use of a client-server model in order to facilitate the flow of information. The OPC server can be thought of as containing the source of process information and makes this information available through its interface whilst the client connects to the server and can access the data [19]. OPC-Classic is based on the Microsoft COM (Component Object Model) and DCOM (Distributed COM) technologies as shown in Fig. 10 above [19].
Making use of COM and DCOM by Microsoft was advantageous as it available on all PC based Windows operating systems and therefore reduced the developmental time of the technology. However, after some time the dependency of OPC on the Windows platform provided some limitations. For instance, DCOM proved to be difficult to configure for internet communication. This led to the development of OPC UA (Unified Architecture) which does not rely on OLE and DCOM and is not dependant on Windows but can operate with many other operating systems such as Linux, Unix and other RTOS (Real Time Operating Systems) [19].
C. OPC UA (Unified Architecture)
Improvements found in OPC UA make it a key enabler of the industrial internet of things and Industry 4.0 [19]. OPC-UA specifically aims to address the requirements of IIOT. For instance, IIOT requires that there should be independence of communication technology form a particular manufacturer, operating system or programming language. The OPC foundation addresses this requirement by being vendor independant and by being technology sector neutral. OPC-UA can also be implemented in all programming languages such as Jave, .NET and C/C++ [19]. It is platform independent which means it can facilitate communication from a low level such as a micro-controller all the way to cloud based infrastructure. OPC UA also provides security by making use of encryption, authentication and auditing. IIOT also requires a vertical and horizontal intergration of the Automation hierarchy. OPC-UA facilitates this by scaling from 15kB footprint (Fraunhofer Lemgo) to CPU architectures such as interl and ARM. It is also used in virtually all controllers and SCADA, HMI products as well as MES/ERP systems as shown in Fig. 11 below.
Fig. 11: OPC UA in Industrial Internet of Things (From [18])
VII. SECURITY
Security is an important aspect when discussing industrial networks and industrial automation as a whole. Industrial Automation uses Operational Technology (OT) which can be considered as the technology that monitors devices and processes within industrial workflows. Systems and devices found in OT include Industrial Control Systems (ICS), Distributed Control Sytems (DSC), Supervisory Control and Data Acquisition (SCADA), networking equipment, embedded control devices, HMI’s and I/O devices. OT is often compared to Information Technology (IT) which mainly involves the resources, storage and network that handles the generation, management and storage of information within and between organisations. These differences are shown in Fig. 12 below [20].
Fig. 12: Information Technology vs Operational Technology (From [20]).
While these two areas are different, they both have security needs. However, OT security needs are different from IT security needs in terms of Availability, Authenticity, Integrity and Confidentiality. In IT, confidentiality is the highest priority since IT may involve dealing with sensitive information. This is followed by integrity then authenticity and finally availability [20]. However, in OT the highest priority is availability of the network as unavailability can result in financial loss as well as unsafe conditions. This is then followed by authenticity, integrity and confidentiality. Authenticity, integrity and confidentiality are addressed by making use of authentication and encryption. Cryptography is a technique than can be used to achieve this [20]. The vertical integration that is observed in the Industrial Internet of things brings about an IT/OT convergence which results in unique security needs. Therefore, there is a need for collaboration between IT and OT teams. Cybersecurity is a major theme when discussing the internet of things and industry 4.0. IT solutions are usually designed with cybersecurity in mind however, this is not always the case with OT. This is particularly true for legacy OT systems which were deployed before cyber security was even a threat. Fortunately, many of these legacy systems are being replaced by more current systems that consider cybersecurity. Industry standards such as ISO/IEC 27001 — Information security management and IEC 62443 help to address these issues [20].
VIII. OPPORTUNITIES AND CHALLENGES
Advancements in industrial networks provide an opportunity for horizontal and vertical integration in industry. This is essential in facilitating Industrial Internet of Things. Horizontal Integration facilitates the seamless working together of machinery, IoT devices and engineering processes [21]. This means that there is a reliable network between individual machines or production units. Vertical integration ensures that factory data is available at higher organisational levels and can therefore be used to make informative decision. Therefore information must be able to move up and down the hierarchy from sensor level to business level of the company. When these two forms of integration occur, opportunities for smart factories and intelligent production arise [21]. There can be flexible production models with real time interactions between people, products and devices during the production process. This provides opportunities to develop Cyber physical systems (CPS) which connect all physical devices to the internet. This allows integration of the virtual and the physical worlds. CPS is at the core of Industrial internet of things and makes smart production a possibility [21].
While there are several opportunities that are brought about by Advanced industrial networks and the internet of things, there are still several challenges that will need to be addressed as this development continues.
Cost: While 5G promises to be a game changer, the network infrastructure cost is still very high. This is still a huge barrier to entry for most industries. According to [22], it costs about $200 000 to set up a macrocell while small cells cost about $10 000 each.
5G backhaul issues: A dense network of 5G small cells will need to support hundreds of GBs of traffic. The infrastructure and technology that supported 4G and solved its backhaul issues cannot handle the 5G requirements. Fortunately, there have been some fibre-optic updates to 4G installations which can support 5G however, more fibre optics will need to be installed in order to support a transition to 5G [22].
Cyber-security: One challenge that has been detailed in VII above is cybersecurity particularly when wireless technologies and the internet are used [22].
Another challenge is the cost involved in upgrading Legacy Industrial networks and equipment to protocols and equipment that support IIOT. Therefore there is a high investment cost [21].
5G Wave Spectrum: One of the main challenge in 5G technology is the use of frequencies above 6Hz because its range is short (high attenuation). While massive MIMO aims to address these issues, line of site is still a 5G problem.
IX. CONCLUSION
There have been several advances in industrial networking that have been facilitated by advancements in technologies over the years. Fieldbus systems which were originally seen as just a replacement for analog systems such as 4-20mA have expanded and can now be used on many different control layers. Ethernet Based Industrial networks have also emerged and are gaining popularity in industry. The use of Ethernet Based systems results in a flattening of the automation hierarchy resulting in easier configuration as well as horizontal and vertical integration. 5G technology has great potential in the realisation of Industrial internet of things and IIOT as it promises low latency and much higher data rates. OPC is a key enabler of Industry 4.0 as it facilitates interoperability. While there are several opportunities presented by these technologies, there are still some challenges that need to be addressed.
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