Several forms of wireless communication, data acquisition, monitoring, networking and control are making inroads into control and automation. Wireless, like most new technologies, is fueled by the only force stronger than corporate inertia—the constant search for cost savings, efficiency, and competitive advantage. A natural target for savings is the 50% of new control system usually spent on cabling, labor, materials, testing and verification.

Because of this driving force, wireless isn't likely to replace hardwire, but rather supplement it in hybrid applications where wireless can demonstrate efficiencies and savings—without sacrificing reliability and security.

"Wireless is possible, desirable, and can solve key problems, but this isn't going to be black and white. Wire and wireless will coexist," says Michael Evensen, NetSilicon's (Waltham, Mass.) vp for Europe. "We're seeing small islands of wireless today, but we expect it to move more into the mainstream over the next two or three years." For instance, wireless monitoring of remote water/wastewater, tanks, and mining operations could evolve into almost real-time monitoring and control of process applications.

Wireless has many cousins among traditional and emerging radio frequency (RF) communication, networking and control technologies, and can often extend them, as well as receive aid from them. These ties will no doubt hasten wireless' acceptance in the long run.

For example, Mr. Evensen says increasing use of distributed, intelligent control architectures and intelligent devices able to make decisions about input/output signals in the field are leading to more autonomous situations. This means less end-to-end network traffic, which can make wireless connections more practical and fuel their adoption. Local area networks (LANs), DeviceNet, Ethernet, and the Internet also have wireless connection strategies that can further their reach, and subsequently increase applications with wireless capabilities.

With a number of technologies able to claim some wireless capabilities, it's helpful to look at where each began, which type is most appropriate for an application, and how to implement them. Environmental factors to consider include speed, distances, compatibility and interference. (See "Types of wireless" sidebar.)

Similar to other control-related communications, different wireless protocols and methods arose from and are still associated with different RF technologies. These include traditional radio transceivers, cellular telephones and, more recently, laptop PCs, personal digital assistants or other mobile web browsers enabled by personal area networks, most notably Bluetooth.

Most wireless methods considered for control arise from decades-old spread-spectrum technology and digital packet switching. Spread-spectrum smears one transmission over many channels on one portion of bandwidth, which prevents interference, jamming, and congestion. The original signal is then reassembled, or "correlated," from identical, aligned portions of apparent noise. Packet switching also organizes signals more efficiently, allowing faster, higher-volume data transmission.

Some wireless protocols are defined and administered by the Institute of Electrical and Electronic Engineers (IEEE) as part of its 802 standards, which are multiplying as developers achieve increased speeds and add new functions.

Several wireless standards have grown out of the cellular telephone industry. These include Bluetooth, Wireless Application Protocol (WAP), and Third-Generation (3G). A few wireless efforts, such as Wireless DeviceNet, are extending traditional fieldbus standards, while others are assisting more specific industries, such as Wireless autoID enabling RF identification (RFID) and bar-code applications.

While it has close ties to many networking technologies, wireless is likely to be aided most by Ethernet. In fact, Rockwell Automation's wireless strategy is to run its control information protocol (CIP) over wireless Ethernet, IEEE's 802.11b standard. This is expected to allow Rockwell's wireless equipment to accomplish the same tasks as its wired systems, according to Kenwood Hall, architecture and systems technology vp, Rockwell Automation Advanced Technology Group (Mayfield Heights, O.).

Benson Hougland, technical marketing director, Opto 22 (Temecula, Calif.), says "Interest in 802.11b is substantial because, like Ethernet, it's prominent in the IT environment, costs are lower, it has mainstream awareness, interoperability, and infrastructure in place."

For instance, Grupo Antolin (Hopkinsville, Ky.) recently began using Opto 22's Snap Wireless LAN I/O in water jet robots from Robotic Production Technology (RPT, Auburn Hills, Mich.) that Grupo uses to trim 96 versions of its automobile headliners (interior ceilings). Snap Wireless LAN I/O communicates via RF data collection terminals, a 2.4-GHz signal, and Symbol Technologies' access point network between RPT's robot and PowerNet ControlLinc software from Control Inc. (Woodridge, Ill.). Identification, glue pattern, wiring harness and other information all flow over this wireless network, while Grupo reports increased production, improved accuracy, and reduced labor costs, specifically a move from three to two and a half shifts per day.

Though Mr. Hall maintains wireless is still more expensive than wired in many cases, he adds that wireless Ethernet allows users to work in the same way as if they were physically hooked up to their network. They can program processors; debug, monitor and maintain equipment; create multiple mobile operator interfaces for large machines; and enable wireless I/O devices or add sensors in places where traditional cabling, conduit and downtime would be too costly.

"Wireless is useful where there isn't a good wired alternative," says Mr. Hall. "This could include an application where you would otherwise be replacing festoon cable every six months."

Both wired and wireless networks are subject to signal and throughput degradation, as their communication paths become crowded with devices, higher-speed data, or new interference sources. However, wireless equipment can often overcome these and a few additional physical hurdles.

Walls, machines, moving metal and other objects common on factory floors can interrupt, reflect or even cancel original signals, and so users must install and maintain clear physical paths between transmitters' and receivers' antennas. To help with these and other unseen issues, engineers often hire wireless experts to perform site surveys, which determine access points, service arms, and other capabilities needed by an application in its particular environment.

"A network site survey will map out any issues a widespread wireless application is likely to face, such as concrete walls, attenuation, and physical and electromagnetic obstacles," says Opto 22's Mr. Hougland. "However, those considering wireless should also reexamine what they want their application to achieve, and use that perspective to help decide if wireless would be useful."

Using more secure broadcast frequency methods can also improve reliability. For example, spread-spectrum with frequency hopping is faster than traditional modulated signals because many frequencies process its packets, and these frequencies make any intercepted signal sound like noise. Also, because spread-spectrum now operates at 2.4 GHz, it no longer risks interference from microwave, variable-frequency drives, welding equipment, and ac motors that generate noise at the MHz and kHz levels, according to Bill Arnold, I/O and networks product marketing manager, Omron Electronics (Schaumburg, Ill.).

Though its unseen connections usually inspire security concerns based on fear of outside access, Mr. Hall adds that wireless Ethernet will soon accept encryption using extremely secure 128-bit keys. These will accompany existing required log-ins and other security measures.