The networking of two
Wireless technologies show promise, but safety and security issues persist
By Scott Bury, contributing editor -- Manufacturing Business Technology, 8/1/2005 12:00:00 AM
Manufacturers have been slow to install wireless local area networks (WLAN), primarily due to concerns about their suitability in industrial environments. However, many companies have seen ROI for wireless spending for shipping & receiving, and are bringing the technology to the production floor.
Last October, market researchers at IDC, Framingham, Mass., found 53 percent of process manufacturers and 39 percent of discrete manufacturers have implemented some wireless and mobile technologies. However, as new standards—such as Wi-Fi (IEEE 802.11); and WiMAX (IEEE 802.16)—become more widespread, and security issues are resolved, wireless data networks may surge in the manufacturing sector.
Wireless networks can be cheaper to install, configure, change, and extend than hardwired networks. They allow mobile access to the network, and they can make employees more efficient and accurate. Some manufacturers think these pluses outweigh the perceived minuses—i.e., that wireless is slower and somewhat less stable than wired networks.
A wireless network is lower in cost than a hardwired one, particularly in a large facility, because with wireless there's no need to run copper or optical cables across the factory, or through walls and floors. Wireless access points (WAP) run as little as $40, says Glen Schulz, director of the security and maintenance business at Rockwell Automation. On the other hand, more durable, efficient, and powerful devices suited to industrial use can run well over $100.
"You have to look at the total cost of ownership," says Cathy Small, manager for wireless products at Cisco Systems. Wireless networks are easier to extend than wired networks, she says. Moving a device connected to a hardwired network "takes time and money. Wireless networks can accommodate changes easily."
Extending the network and connecting devices to it are accomplished easier with WLANs, and the devices can go places cable can't. "Putting a human-machine interface [HMI] in an inaccessible place, such as alongside a machine in a hostile environment—or where a wire would require drilling through the floor, the ground, and then back up again—would be prohibitively expensive," says Cisco's Scott Westlake, a manufacturing industry specialist.
Ken Parkhill, infrastructure architect, Technical Services, CAT Logistics, a Morton, Ill.-based supply chain services and consulting firm, points to the inherent safety aspect of wireless equipment in the shipping department. "There's no cable to trip over," he says. Cables also are a point of failure in a manufacturing environment.
Wireless networks and devices tend to be more reliable because WAPs are usually suspended from the ceiling, out of harm's way. "A forklift accident could knock out a wired network, but that couldn't happen with a wireless LAN," says Rockwell's Schulz.
Cons amidst the pros
Flexibility is the main selling point of wireless networks, say vendors. "Workers and supervisors aren't just sitting at their desks anymore," says Small. "HMI devices are mobile terminals that provide flexibility and mobility, giving technicians access to data wherever and whenever they need it."
Network users can receive data on production equipment—or alerts about problems wherever they are in the plant—and access technical data, production records, or schematics.
Still, for all its potential, wireless technology hasn't made deep inroads at the automation layer. Several plant-floor automation systems use wireless networks at the fieldbus level, but so far, most manufacturers are staying with hardwired solutions unless they find a specific need for a wireless network.
"There may be an application for a wireless LAN where no network exists, and pulling cables or fiber through conduits would be expensive, but so far, there's not much application in real-time control environments," says Schultz. Wireless data communication also is not as inherently predictable as wired, he says.
Even wireless proponents admit WLANs are slower than wired networks. "Wired networks can have faster throughput. The 'gig to the desktop' race is a wired application, whereas the Wi-Fi standard is 54 kilobits per second," says Cisco's Small.
When high-speed, continuous real-time communication is essential—such as in monitoring constant-flow processes or safety conditions—a wired connection that won't be subject to radio-frequency (RF) interference may be the only solution.
Some manufacturing environments also can be "challenging" for RF-based communications, Small admits. RF signals could cause dangerous sparks in chemical processing plants, where explosive gases may be present. Metal racks or high-power equipment also can interfere with RF signals, although Cisco's Westlake points out that a site survey often shows interference isn't a major constraint.
A word about security
A WAP is a vulnerable point on the network—it's a node that can allow an unauthorized user to get to valuable data. On the other hand, a wired network is no guarantee of security either. Any connection or port is a potential weak spot, and even allowing vendors or customers to connect to a system to order or deliver products can potentially open the door to unauthorized access. However, says Small, "You can make a wireless LAN as secure as a wired network."
Says Rockwell's Schulz, "We recommend a multilayered approach to security." The latest version of the Wi-Fi standard, IEEE 802.11i, is optimized for strong security protocols and supports the latest version of the Advanced Encryption Standard. Schulz recommends companies using WLANs put WAPs on their own separate network loop or section, segregated from the rest of the network traffic in case of a security breach or other suspected problem.
Wired and wireless networks can coexist in a manufacturing plant; in fact, most systems today support integration of the two. As better security applications and standards such as Wi-Fi and WiMAX spread through the industry, expect to see wider implementations of wireless automation and control applications. The freedom and flexibility they offer are too attractive to ignore.
