By Doug Page
The vulnerabilities of wireless industrial sensors to radio frequency interference have inhibited wider acceptance and spawned worries that saboteurs could exploit these weaknesses. Now, recent work by a government engineer may remedy this reliability problem.
Wireless sensor technology is becoming a key component in contemporary industry. Wireless sensor devices can now be found in nuclear power plants, dams and reservoirs, municipal water and sewer facilities, natural gas storage, and major manufacturing facilities.
Radio interference comes from many directions, including from nearby sensors, other IT applications or industrial equipment used in the factory next to the sensors.
“The radio frequency environment is getting more congested so that will cause disruptions and cause problems with the control systems,” said John Buttles, a senior engineer at Idaho National Laboratory. “So you need to recognize the problem and put policies and equipment in place to identify and prevent network problems.”
Industry finds wireless sensors attractive because they’re less expensive than legacy wired connections. The process of running miles of wires and cables throughout a plant is becoming impractical. Wireless sensors are also easier and cheaper to move when processes or operations change.
However, there is a serious risk. Wireless sensors might be less expensive than cable connections, but the flow of information from wireless devices is not as reliable.
Wireless devices are subject to radio interference from industrial equipment or even other sensors that can slow down, corrupt or even stop sensor data from reaching its destination. The result is that control systems are placed in jeopardy.
This may not be a homeland security concern if you’re baking potato chips, but data disruption at a nuclear power plant would be a different matter.
“Even a five-second disruption at some sites could have serious consequences,” Buttles said. It’s also feared that these frequency vulnerabilities could be exploited by terrorists.
Wireless sensors are designed to help measure and manage the operation of industrial control systems. They’re composed of a number of nodes that monitor environmental conditions such as temperature, pressure and volume.
The nodes relay readings to a central control system, which then makes decisions based on current information. Transmitting and receiving sensor data in a timely and consistent manner is therefore necessary to keeping a control system running smoothly.
Each node has a built-in radio transmitter and receiver that communicates with the central gateway and other nodes using unlicensed frequencies, usually 2.4 GHz.
Buttles has designed several full-scale wireless networks in his lab so he can evaluate the precise causes of radio interference. The test bed contains various sensor models from different manufacturers. Once the sources of interference are identified, the devices can be hardened and industry standards developed.
“More reliable and resilient wireless networks will help ensure that power plants, factories and other critical infrastructure assets are more secure,” he said.