Wireless Networks: World Without Wires

May 4, 2010
Wireless networks are rapidly moving into the industrial mainstream.
Paper-making factories are huge operations, often larger than a football field. The machines that turn wood pulp into paper have thousands of sensors and actuators that can be tough to control, even when equipment runs nearly nonstop. Mohawk Fine Papers Inc. adds to that complexity by constantly stopping and starting its huge processing machines. The family-run company in Cohoes, N.Y., makes high quality papers used for prestige products such as annual reports and restaurant menus. Volumes are low and production runs may change eight or nine times per day. “Our factory is very wired, with thousands of sensors that provide an incredible breadth of data,” says Paul Stamas, vice president of information technology for Mohawk. The majority of those sensors are accessed over wires. But for more than five years, a growing number have transmitted data over wireless links. “We use Wi-Fi for sensors in areas where it’s difficult to run wires or where the environment’s too harsh, with too much heat or steam. In the warehouse, wireless is predominant. All the forklift drivers are guided to shipping packages with a wireless gun,” Stamas says. Mohawk is part of a huge trend in industrial applications. Wireless communications are now considered reliable enough for use on factory floors, so they’re being deployed to provide inexpensive communications for sensors and other components that sit in places that are hard to reach with wires. Many equipment suppliers feel this trend will dramatically alter the way that industrial networks are architected. “Wireless is a fundamental game changer in the industrial sector,” says Steven Toteda, general manager for supplier Cooper Wireless, a Cooper Bussman company in Dublin, Calif. At Mohawk, the ability to add more sensors and other components is having a direct impact on bottom-line profits. “Paper manufacturing is very energy consumptive. We always want to see when there are alarms for excessive energy usages; that’s money going out the window,” Stamas says.Wi-Fi steps up As wireless technologies gain marketing momentum, industrial customers may follow the path that led many to Ethernet in wired networking. The rapid technical advances and price declines that come from high volume mainstream markets are making Wi-Fi (for Wireless Fidelity) more viable in all but the nastiest environments. In just a few years, Wi-Fi has progressed from its initial implementation through the “n” version ratified last fall. Many technologists say that the revision will make Wi-Fi, officially known as IEEE 802.11 (a standard of the Institute of Electrical and Electronics Engineers), a much more viable alternative to proprietary frequency-hopping schemes. “802.11n is absolutely a milestone,” says Paul Brooks, business development manager for networks at supplier Rockwell Automation Inc., in Mayfield Heights, Ohio. “It’s got features that make a huge difference, like retry mechanisms that mean you won’t lose packets in the air.” Others agree that the upgrade brings a number of benefits, such as multiple in, multiple out (MIMO), that will simplify integration in complex industrial settings. “There are a lot of benefits with n, like MIMO, and if you have an n access point and have a couple older 802.11g devices, the entire network won’t drop down to the slowest speed like previous versions did,” says Tim Cutler, director of product marketing for Modules and Integrated Solutions Hardware at RF Monolithics Inc., a Dallas-based wireless products vendor. Another change is that while earlier versions were limited to 2.4 gigahertz (GHz), the new standard works on 2.4, 3.6 and 5 GHz. That’s important in large applications in which a number of wireless networks may be needed. The 2.4 GHz level is limited to three channels, so only three networks can be configured. “With 5 GHz, you can have up to 22 networks,” Brooks says.Not so fast Though there are many benefits, companies that have already set up wireless networks may not race to make the transition from alternative technologies or earlier versions of Wi-Fi. Access points are typically installed in ceiling rafters, so replacing them requires a fair amount of effort. At Mohawk, the change probably won’t come until there’s a major remodeling. “The communication that goes over wireless is different; we don’t need 100 megabits/second to say that we’ve just moved three cartons of this product from point A to point B,” Stamas says. “To change everything out, we’d have to bring cherry pickers into the plant, which is pretty costly.” Alternative technologies may fit well for sensors and other nodes that only transmit small amounts of data. Wi-Fi packets are larger than those of some alternatives, which sometimes makes alternative approaches more viable in remote nodes that run on batteries. “One tough thing for Wi-Fi is that it requires a lot of overhead,” says Gregory Heilman, principal consultant for automation supplier Invensys Operations Management (IOM), in Lake Forest, Calif. “A lot of instruments need long battery life, and today, Wi-FI can’t compete with WirelessHart and ISA100. They can provide battery life of up to eight years because they send so little data in short bursts.” (WirelessHart and ISA100 are industrial wireless standards promulgated by the Hart Communication Foundation and the International Society of Automation, respectively.)Many alternatives Though Wi-Fi is gaining momentum, it’s still a relative newcomer in a field that’s already using a range of technologies. Several companies offer proprietary schemes designed for harsh industrial applications, and a few standards are also vying for market share. For years, many proprietary products have used frequency hopping to ensure that packets arrive. Providing a number of frequencies ensures that one of them will always be available to carry signals. Many providers pair frequency hopping with Ethernet’s TCP/IP (transmission control protocol/Internet protocol) protocols to make it simple to add wireless to existing wired networks. This approach lets users integrate into existing industrial networks and boasts higher reliability than Wi-Fi.  “Our Trusted Wireless Ethernet is quite different from Wi-Fi,” says Toteda, of Cooper Wireless. “We extend Ethernet with frequency hopping.” Though various frequency-hopping networks have gained a solid foothold over the past decade or so, these networks have an Achilles Heel that may limit continuing expansion. “Frequency hopping offers a lot, but it is all proprietary. There are no standards,” Cutler says. Those who want standards that provide traits not provided by Wi-Fi have a few alternatives. Standards such as ZigBee, Bluetooth and ISA100 will play a role in at least some facilities. WirelessHart has been recently approved by the International Electrotechnical Commission (IEC) as a standard. ISA100 has been adopted by the ISA, but is still awaiting approval by the American National Standards Institute (ANSI). ZigBee was once touted as a strong option for the factory floor, but usage hasn’t materialized. The IEEE standard has seen more acceptance in energy metering and similar applications. It may leverage that in some plants. “ZigBee Smart Energy provides a structure to collect information, so it’s being used in factories to help control energy costs, running HVAC (heating, ventilation and air conditioning), lighting and other functions,” says Bob Heile, chairman of the ZigBee Alliance. Bluetooth isn’t expected to play a major role in factories, but some vendors say it’s viable in a supporting role. “If simple data access is needed in a point-to-point relationship over a distance of less than 300 feet, Bluetooth offers great connectivity,” says Ira Sharp, product marketing lead specialist for wireless at Phoenix Contact Inc., a Middletown, Pa., automation components supplier. “If you have a high number of nodes in a small area, a mesh network may service the application well, and Wireless Hart or ISA100 would be the right technology.” The broad range of options means that no vendor has much more than 10 percent of a market in which many of the providers are specialized companies that are mainly involved in wireless networking. “Wireless is a highly fragmented market. There aren’t any big winners or losers,” says Rockwell’s Brooks. Though there are a number of options, most suppliers agree that they generally address different aspects of industrial automation, so determining which fits where is not among the most complex issues surrounding network development. “Usually, it’s a very straightforward decision for the technology that should be used,” Toteda says.Resolving security concerns In the past, a perceived lack of security was among the questions that wireless providers had to overcome. That’s been largely eliminated by advances in encryption and identification. Most wireless standards now use Advanced Encryption Standard (AES) encryption, which is ideal for security data that flows through the air.  This level of encryption will make it difficult or impossible for anyone to interject bad data, or to try and receive other data being presented over the air. All new standards documents now include several security features. Safeguarding data and limiting access are as much a part of the standards as packet size and frequency selections. “Security was built into the ISA100 protocol stack from day one,” says Soroush Amidi, senior product marketing manager of OneWireless for automation vendor Honeywell Process Solutions, of Phoenix. “It’s got AES 128 bit encryption, authentication of devices and there are signatures unique to every packet that ensure no one has altered message content.” Authenticating the devices to make sure they are authorized to send and receive data makes it very difficult for outsiders to tap into the wireless data stream. “Using a strong pre-shared key (PSK) or leveraging some type of certificate-based authentication will ensure the network’s security,” Sharp says. Together, these techniques provide protection levels that some say are higher than those offered by wired networks. “There’s a perception that there’s a lack of security, but if it’s done correctly, it’s harder to break into,” says Heilman, of Invensys Operations Management. “Current encryption techniques and the ability to protect access by looking at IP addresses can make wireless more secure.” That said, most engineers feel that it’s wise to continuously monitor any network to ensure that security hasn’t been breached. One negative of the shift to Ethernet and TCP/IP is the openness that makes industrial systems more attractive to hackers. “Ongoing Wireless LAN (local area network) monitoring will insure that the wireless network continues to work as expected and will help point out malfunctions, rogue access points, and other interference sources,” says Daryl Miller, vice president of engineering at Lantronix Inc., an Irvine, Calif.-based automation products supplier.Related Sidebar - Cellular Augments Industrial NetworkingTo read the article accompanying this story, go towww.automationworld.com/feature-7028.

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