State of Industrial Wireless

State of Industrial Wireless

 
February 2010
 
By Bill Lydon - Editor
 
There a number of standards and technology in existence and proposed for use in industrial wireless. The options can be confusing. The confusion will continue until there is more clarity, but this should not stop engineers from applying wireless now.
 
Radio technology is certainly not new and has been refined over a number of years. The number of industrial wireless products being introduced is growing at a high rate and engineers are finding many interesting and valuable applications. General use of unlicensed radios has dramatically increased with virtually all laptop computers, PDA and other commercial devices equipped with radios.
 
As long as I have been a control engineer, it has been a wish to eliminate wires with wireless sensors. I was an engineer on a design project over 20 years ago trying to develop an economical wireless sensor but the costs were too high and the technology was not refined enough for it to be practical. This has clearly changed. Processor and radio technology have been integrated into single chip solutions, lowering cost and increasing reliability. Many of the bands that had been considered unusable in the past employ spread spectrum modulation that has become practical and economical due to new chip solutions.
 
National governments currently allocate unlicensed bands of spectrum for use by anyone as long as they meet certain technical limits, most notably, a limit on total transmission power. These unlicensed spectrums require no license payments. Devices must meet limits imposed by government regulations including limiting power, frequency of transmission, and length of transmission to ensure that these devices operate within non-licensed limits. Devices must prove they comply with requirements for non-licensed implementations.
 
There are number of pieces to the puzzle. Technologies and standards are evolving with each standards group declaring themselves the winner. The reality is that industrial wireless applications are being implemented based on economics and only a small percentage of users are really concerned with standards, considering all industries, including discrete manufacturing and building automation. These applications are mainly for non-critical control/monitoring and particularly to avoid costly wiring. Tank farm level monitoring is a good example.
 
Technologies & Standards
 
802.11
802.11 are an evolving family of specifications for wireless local area networks (WLANs) developed by a working group of the Institute of Electrical and Electronics Engineers (IEEE).  The 802.11 specifications use the Ethernet protocol and Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) for path sharing.
 
In a sense, with 802.11, Ethernet has come “full circle” since its roots are from the ALOHA network created at the University of Hawaii in 1970 which was a shared frequency radio system. ALOHA's situation was similar to issues faced by Ethernet and Wi-Fi networks, requiring shared medium access control schemes like CSMA/CD (Carrier Sense Multiple Access With Collision Detection.) ALOHA proved that it was possible to have a shared media network and this sparked interest in others, most significantly Bob Metcalfe and other researchers working at Xerox PARC. This team went on to create the Ethernet protocol.
 
802.11 has become a workhorse for computer and VoIP (Voice over IP) phone systems. Most industrial protocols can be transported over 802.11 networks.
 
802.15.4
IEEE 802.15.4 is a standard which specifies the physical layer and media access control for low-rate wireless personal area networks (LR-WPANs). It is maintained by the IEEE 802.15 working group. It is the basis for the ZigBee, WirelessHART, proprietary solutions, and chip vendor specific solutions such as the MiWi (Microchip) specification, each offering a complete networking solution by developing the upper layers not covered by the standard. The most common configuration for sensors uses Mesh networking where each node in the network may act as an independent router, regardless of whether it is connected to another network or not. It allows for continuous connections and reconfiguration around broken or blocked paths by “hopping” from node to node until the destination is reached. Mesh networks differ from other networks in that the component parts can all connect to each other via multiple hops. As a result, the network may typically be very reliable, as there is often more than one path between a source and a destination in the network.
 
6LoWPAN
The ‘new kid on the block,’ 6LoWPAN, has the potential for every sensor and actuator to have an IP address. 6LoWPAN is IPv6 over Low power Wireless Personal Area Networks and has been created by The Internet Engineering Task Force (IETF). IETF is a large open international community that promotes Internet standards, cooperating closely with the W3C and ISO/IEC standard bodies and dealing in particular with standards of the TCP/IP and Internet protocol suite. IETF members include network designers, operators, vendors, and researchers concerned with the evolution of the Internet architecture and the smooth operation of the Internet. It is open to any interested individual.
 
The charter of the IETF 6LoWPAN working group was to define how to carry IP-based communication over IEEE 802.15.4 links while conforming to open standards and assuring interoperability with other IP devices.   IPv6 provides a 128 bit IP address, which is significantly larger than IPv4’s 32 bit, and IPv6 inherently supports multicast.
 
IPv4 address example: 015.0B4.FC0.A10
IPv6 address example: 015.0B4.FC0.A10.010.C1A.8B4.34F
 
The very large IPv6 address space supports a total of 2128 (about 3.4×1038) addresses - approximately 5x1028 addresses for each of the roughly 6.5 billion people alive in 2006.
 
The goal the of IETF 6LoWPAN is to achieve a very compact and efficient implementation of IP, removing the factors that previously gave rise to an array of ad hoc standards and proprietary protocols.
 
ZigBee
ZigBee is a low-power wireless mesh networking standard. The ZigBee Alliance is an association of companies promoting a protocol solution for monitoring and control products based on 802.15.4.  The ZigBee alliance has cooperation with the BACnet association to develop a way to communicate between ZigBee devices and BACnet devices.    www.zigbee.org
 
EnOcean
EnOcean technology is a very low power radio technology that uses energy harvesting to transmit wireless signals over a distance of up to 300 meters.   A good example is a light switch that when pushed generates power for an EnOcean radio to transmit the command to turn on the light. 
 
BACnet International and the EnOcean Alliance are cooperating with BACnet’s Wireless Networking-Working Group (WN-WG) to develop a vendor independent gateway specification for integrating EnOcean-based wireless energy-harvesting nodes.
 
 
WirelessHART
WirelessHART is a wireless mesh network communications protocol that adds wireless capabilities to the HART Protocol while maintaining compatibility with existing HART devices, commands, and tools that have been used for a number of years. HART is viewed by most companies in the industry as the smart 4-20 ma replacement and WirelessHART extends that capability. www.hartcomm.org
 
ISA 100
The ISA organization (International Society of Automation) is developing the ISA 100 standards for wireless standard to encompass security, wireless field devices, interoperability, latency, plant information, power, interference requirements, and specifications designed to accommodate all plant needs. They plan to support tunneling to transfer other protocols.  www.isa.org
 
Wireless Cooperation Team (WCT)
The WCT is a collaborative effort sponsored by the Fieldbus Foundation (www.fieldbus.org), HART Communication Foundation (www.hartcomm.org), and Profibus Nutzerorganisation (www.profibus.com) to develop a Common Wireless Interface for HART, Foundation fieldbus, PROFIBUS and PROFINET Communications. The wireless project is an extension of the organization’s collaboration on Electronic Device Description Language (EDDL - www.eddl.org). As was done with their EDDL cooperation, the three organizations have also agreed to develop a common set of compliance guidelines for incorporation into their respective product registration processes.
 
Wireless Control System
Standards will be important if wireless is proven reliable for general control and if it becomes the network backbone of systems. It is likely this will be like hardwired industrial network standards with users selecting a particular network for their system. (Example: choosing Profibus or DeviceNet for a plant system.)
 
IP
IP(Internet Protocol)-based communications is intriguing since it is the backbone for the vast majority of information in the world. It might be ideal if all devices used secure IP-based networks with prioritized messaging from business systems to sensors.   It was not that long ago when VoIP phones systems were considered novel. 6LoWPAN is relatively new and could be the enabler to make IP sensors practical.   Using an IP from sensor to boardroom to create a complete enterprise systems that knits together all information could simplify deployment and lower lifecycle cost.
 
Cyber Security
Having secure industrial control networks is an important consideration for both wired and wireless networks. The Department of Homeland Security has the Control System Security Program (CSSP) that provides information resource to help industry understand and prepare for ongoing and emerging control systems cyber security issues, vulnerabilities and mitigation strategies.   They have recommended practices to help users reduce their exposure and susceptibility to cyber attacks. http://csrp.inl.gov/Introduction.html
 
Different View
Is it possible that sometime in the future, enterprise computing will encompass all communications? To achieve greater production efficiencies, enterprise computing is communicating down to sensors through information and control system networks. The trend is collaboration between the IT department and controls people to make this happen.   Most plants have hardwired and wireless 802.11 IP based networks in place for information, VoIP, and in some cases video. There is a case to be made to use this communications investment as much as possible.   The requirements for industrial network communications can be demanding and must be reliable. It is interesting that VoIP requirements also have stringent requirements with 125 microsecond audio samples transmitted in every packet and high Quality of Service (QoS) requirements. Couple this with 6LoWPAN and it could be interesting…
 
Where are we?
There is value in wireless but it is unlikely that there will be one dominant industrial wireless standard, just like industrial networks.
 
One way to look at this is the classical five stages in technology life cycles. Consider wireless for industrial monitoring and control relative to the five stages.
 
Stage 1 – Bleeding edge – When a technology shows high potential but hasn't demonstrated its value or settled down into any kind of consensus. Early adopters may win big, or may be stuck with a white elephant.
Stage 2 - Leading edge – When a technology that has proven itself in the marketplace but is still new enough that it may be difficult to find knowledgeable personnel to implement or support it.
Stage 3 - State of the art - When everyone agrees that a particular technology is the right solution.
Stage 4 - Dated but still useful – When technology is still sometimes implemented, but a replacement leading edge technology is readily available.
Stage 5 - Obsolete – When a technology has been superseded by state-of-the-art technology, maintained but no longer implemented.
 
We are not at Stage 3 where everyone agrees but there are emerging standards that are becoming solid. The majority of stage 3 standards for industrial sensor networks are Modbus, DeviceNet, Profibus, and ASi.  I would expect wireless to have more stage 3 standards because running multiple wireless networks in a plant does not require the installation of separate cables.
 
My thought is to use wireless today in applications that have less than a one year payback or net savings over wired installations and are low risk if there is an interruption in communications. My major selection criteria would be finding the right sensor/actuator with a wireless interface that has a track record of reliably and performance.
 
What do you think?
Industrial wireless is still at an early stage of evolution and adoption so I am interested any thoughts on the topic. Please share your thoughts.
 
Hannover Messe Focus on Wireless Automation
 
For those readers who will be attending Hannover Messe, please be sure to stop by the Automation.com-sponsored Wireless Pavilion in Hall 7.
 
As mobile automation solutions play an increasingly important role, the demand for wireless communication continues to grow. Reflecting this trend, HANNOVER MESSE is once again staging its highly successful special display Wireless Automation.
 
Hall 7 will present a display of components and complete solutions for communications technologies such as ZigBee, Bluetooth and WLAN.  WirelessHART is of special interest to visitors from the process industry as it enables them to combine components from different manufacturers with existing systems.
 
A new focus topic in 2010 will be M2M applications, telemetry and telecontrol. The exchange of data between devices via private and public wireless networks streamlines business processes and resource management. This means increased potential for manufacturing industry. Market research organizations therefore expect strong growth in this market.