Factories present challenging environments for wireless systems, and the National Institute of Standards and Technology wants to help.
In its blog on Thursday, the nonregulatory federal agency said that factories and production plans could gain a lot from wireless technology like robotic controls, RFID tag monitoring, and LAN communications.
But NIST's researchers suggest that many factories have highly reflective environments that scatter radio waves. Such environments interfere with or block wireless transmissions and make it difficult for some factories, like auto production plants, to take advantage of wireless networks.
NIST said it plans to partner with the U.S. Council for Automotive Research (USCAR), to develop a statistical representation of the radio propagation environment of a production floor as a basis for developing standards to pre-qualify wireless devices for factories.
Researchers began to test wireless signals at an auto assembly plant in August 2006. They completed additional tests this month at an engine plant and a metal stamping plant.
Metal structures like fabrication and testing machinery, platforms, fences, beams, conveyors, mobile forklifts, maintenance vehicles, and automobiles in various stages of production crowded the plants. NIST monitored frequencies below 6 GHz for 24 hours at a time to understand the background ambient radio environment.
The spectrum survey showed that "machine noise," interference from heavy equipment, can impair signals for low-frequency applications such as those used to in some controllers on production floors.
A detailed analysis of wireless LAN frequency on channels from 2.4 to 2.5 GHz found dense and constant traffic by data transmitting nodes, wireless scanners and industrial equipment.
Signal-scattering tests revealed the potential for high levels of "multipath" interference, where radio signals travel in multiple complicated paths from transmitter to receiver, arriving at slightly different times.
NIST said its researchers plan to use the data in studies that will attempt to pre-qualify wireless devices for industrial plants.
In the meantime, NIST researchers have identified actions to minimize radio interference. They include the use of licensed frequency bands where possible, and restrictions on use of personal electronics in high-traffic frequency bands such as 2.4 GHz. NIST also said that absorbing material can help if it is installed in key locations. Wireless systems with high immunity to electromagnetic interference, equipment that emits little machine noise, and use of directional antennas can help mitigate multipath interference when transmitter and receiver are close together, NIST said.