wireless communication for the installed base and industry ... need to get access the installed base...

Whitepaper Best practices for choosing the wireless technology for your application

© HMS Industrial Networks, 1 January 2015 www.hms-networks.com

Wireless communication for the installed base and Industry 4.0 applications

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Introduction

The increasing numbers of wireless installations in various industrial applications areas proves that wireless communication is reliable and trustful. Today, when starting the implementation of Industry 4.0 /Internet of Things solutions there are a number of new use cases coming up.

Wireless Advantages

Today devices like I/O-units, PLC’s, drives, etc. are networked and exchange data with other devices and people. For many applications that include moving parts and devices that before were using flexible cables, swivels or other similar solutions, the cables are replaced by wireless solutions. The advantage of using wireless for such applications has been proven in the field for many years. In addition to these applications we also see many other applications where the installation costs are dramatically decreased by using wireless communication instead of wires. Besides the decreased installation cost many users also report less stoppage of services because there are no longer any worn out cables.

Cable replacement

Regardless of if it is a traditional serial interface (UART, RS232, RS422 or RS485) running for example, Modbus, and industrial Ethernet based communication (EtherCAT, EtherNet/IP, Modbus TCP, PROFINET) or needs to connect devices to a Wireless LAN infrastructure, there are transparent Ethernet to wireless adapters and gateways that are easy to set-up and use providing the needed performance and reliability.

Well-known fieldbuses (Profibus, CANopen, DeviceNet, InterBus-S, etc.) have a large installed base and a wide range of available products/devices. However for some fieldbuses there could be timing requirements that have to be taken into account when replacing a fieldbus with a wireless link.

Commonly Used Scenarios

Caption: A simple point-to-point Ethernet cable replacement based on two Wireless Ethernet Port Adapters. For the wireless connection, Wireless LAN would be used for applications requiring high band width and Bluetooth technology would be used when robust data transfer and/or high system density is needed.


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Caption: The configuration above is used when connecting devices such as PLC’s and HMI panels to an existing wireless infrastructure which is typically a Wireless LAN network. Whether the devices have Ethernet ports or serial port interfaces there are industrial adapters available that can act as standard Wireless LAN access point transfer transparent data over the Wireless LAN network to the wired network backbone.

Roaming is another feature that is commonly used in industrial applications where there are moving devices, such as Automatic Guided Vehicles (AGVs), or where the device’s data communication path changes from one access point to another. In these cases, the existing connection performance is affected by the roaming procedure since a scan for new wireless networks is required. The established wireless connection therefore must be terminated before a new connection is up and running. However for such applications it varies from 100 milliseconds down to few milliseconds for special solutions.

Industry 4.0 / Internet of things

With Industry 4.0 / Internet of Things there is huge potential for improvements and efficiency when it comes to usage of energy, raw material and other resources, as well as, improved up-time. In order to realize these opportunities there is a need to get access the installed base as well as new devices and complementary sensors to make it possible to analyze and use the data. This is a fundamental question for the success of Industry 4.0.

To get a cost efficient and flexible installation many of these additional sensors are predicted to be connected wirelessly either by Bluetooth Low Energy for devices with demand for lower power consumption (maybe battery driven) or Wireless based for devices with higher demand on band-with.


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In distributed IoT solutions, it is important to be able to get access to plant data remotely as well as the possibility to configure and maintain the systems remotely. A cost-efficient solution for this function is of course to use a smart phone or a tablet connected either locally via a short range wireless link (Bluetooth Low Energy, Classic Bluetooth or Wireless LAN) or the cellular network.

By creating tailor-made apps, it is possible to establish easy-to-use and secure handling that could easily be tailored for individual applications as needed. Of course, the same app can be designed to perform other tasks such as act as an HMI panel for a machine.

Gateways can also serve as the interface between the wide-area network (Internet) and the short-range network. The gateways can be fixed devices connected to a backbone network or they could also be embedded within other devices e.g. in an Internet router (ADSL or GSM/3G/4G routers or similar). Smartphones or other mobile devices can also serve as temporary gateways. For example, when the IoT device is carried together with the phone as a body-worn sensor or when a phone is used for authentication access of an IoT device using an Internet service. Gateways are also useful as they can help create a system with interconnecting multiple technologies. The gateways are then used to perform the necessary translation to a common backbone.

Making the right wireless technology choice

Not just one wireless technology offers all the features and strengths that fit the various industrial application requirements; and therefore, standardized wireless technologies Wireless LAN, Bluetooth technology and IEEE 802.15.4, as well as, a number of proprietary technologies are all used. The main requirements could be high data throughput, robustness or low power (the latter especially for battery operated devices). Wireless LAN is often used for production planning, data acquisition as well as applications where rapid roaming is required. Bluetooth technology is used for Human Machine Interfaces (HMI), programming, service/maintenance as well as real-time control tasks. During the last few years, other technologies like IEEE 802.15.4 (ZigBee, Wireless Hart etc.) and Bluetooth low energy technology became increasingly used for sensors, actuators and other small devices that needed to be interconnected.

Wireless LAN (IEEE 802.11) is well suited for monitoring, configuring and acquiring data, but can also be used for time critical control. Further, the built-in roaming functionality is useful in factory automation applications with moving devices. Implementing Wireless LAN in these types of applications often requires customized solutions such as tailored or proprietary roaming software as well as specific installation means (for example, the use of expensive leakage-cables). With the tailoring of the wireless solution, one achieves stable latency and low roaming hand-over delays.

The classic Bluetooth technology (IEEE 802.15.1) is well suited for wireless integration of automation devices in serial, fieldbus and industrial Ethernet networks. Bluetooth technology is specified for small devices with high demands on small footprint, low power consumption and cost-efficiency.

Bluetooth Low Energy Technology

During 2011, Bluetooth v4.0 low energy technology entered the market. Bluetooth low energy technology is well suited for sensors, actuators and other small devices that require extremely low power consumption. Bluetooth Low Energy offers in addition high numbers of communication nodes with limited latency requirements, robustness equal to Classic Bluetooth technology, and good real-time features (if a small number of nodes are connected).


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ZigBee, WirelessHART, ISA SP-100

IEEE 802.15.4 is available in a number of standards as well as part of proprietary wireless protocols. ZigBee, WirelessHART and ISA SP-100 are all used in Industrial applications and all are based on IEEE 802.15.4. The 802.15.4 technologies are mostly used for process and building automation application and the low power features makes it well suited for battery operated devices. The technology also offers mesh network functionality that makes it capable to cover wide areas when there are now requirements on low latency.

WLAN Bluetooth 802.15.4 Bluetooth LEData throughput ++ O - -Robustness +/- ++ +/- ++Range 50-300 m 50-1000 m 75 m + mesh 10-300 mLocal system security - ++ +/- ++Roaming ++ + - -Large scale network +/- - ++ ++Low latency +/- ++ - ++Pairing speed +/- - + ++Power consumption - + ++ +++Cost - + + ++

Caption: The table offers a quick overview of the differences between the wireless technologies offered in industrial applications. Note: The Bluetooth SIG has recently announced that the implementation of mesh functionality is ongoing.

Disturbance free communication

As most of wireless technologies operate in the 2.4 GHz band there could be potential disturbances which is prohibited in an industrial application. Therefore, it is important to optimize co-existence of various wireless technologies in order to get a disturbance free operation.

Caption: Wireless LAN, Bluetooth technology and IEEE 802.15.4 work in the same 2.4 GHz frequency band.

The 2.4 GHz frequency band is very crowded, especially for Wireless LAN which is well-established throughout offices on to the production planning. In order to get disturbance free communication, first ensure that Wireless LAN is not disturbed.

Bluetooth Wireless LAN 802.15.4

ISM Band 2.4 - 2.4835 GHz


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In order to secure that, less suitable technologies are used which applies complicated and cost-intensive installation alternatives and/or carry out extensive frequency planning.

Another solution is to use the 5 GHz band (IEEE 802.11 a) instead of the 2.4 GHz band for the Wireless LAN communication links. However, even though the 5 GHz band is increasing in popularity in industrial applications, there is a large installed base of IEEE 802.11 b/g networks that requires a good co-existence solution.

In cases where Wireless LAN and IEEE 802.15.4 are used in parallel, co-existence can be implemented by making room for some IEEE 802.15.4 channels in-between the three Wireless LAN channels. By doing so, it is possible for Wireless LAN and IEEE 802.15.4 to work reliably in parallel.

Thanks to the AFH (Adaptive Frequency Hopping) Bluetooth solves most of the co-existence problems in an automatic way.

Caption : HMS offers different Wireless LAN Rugged Ethernet Port Adapters – one for the 2.4 GHz band, one for the 5GHz band as well as one dual band version besides the Bluetooth version. These ready-to-use wireless devices are especially well-suited for mobile, rotating and temporary installations where there is a need for replacing the Ethernet cable with a robust and maintenance-free wireless connection, or to connect to a Wireless LAN infrastructure.

Summary

One wireless technology does not offer all the features and strengths that fit every application requirement. A simple rule of thumb is:

• Choose Classic Bluetooth for wireless connectivity in tough environments. Robust features include Adaptive Frequency Hopping (AFV), Forward Error Correction (FEC), automatic power control, high system density (many independent Wireless links in one radio environment) which offers trouble-free communication without complicated, time consuming frequency planning and complex, expensive installations.

• Choose Bluetooth low energy for periodic connectivity with small battery-operated devices, smartphones, tablets, gateways, etc.

• Choose WLAN 802.11 a, b, g, n (commonly referred to as WiFi) for wireless connectivity with the existing LAN / WLAN infrastructure or to create high throughput ad-hoc networks.


wireless communication for the installed base and industry ... need to get access the installed base...

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