NIST tests wireless systems; ISA pursues standard
Washington, DC, and Research Triangle Park, NC —According to the
National Institute of Standards and Technology (NIST)
, recent tests verify that heavy industrial plants are challenging environments for wireless systems. Partnering with the U.S. Council for Automotive Research (USCAR), NIST has addressed what it refers to as a “nebulous problem.” In other wireless news, ISA continues to pursue a multi-protocol standard.
Heavy industrial plants, such as auto production plants, can be highly reflective environments, scattering radio waves erratically and interfering with or blocking wireless transmissions. Electromagnetic interference may hinder the auto industry and other sectors in the use of wireless networking.
NIST will 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. Initial tests at an auto assembly plant were performed last month. In September, testing took place at an engine and a metal stamping plant.
These plants were crowded with stationary and mobile metal structures– fabrication and testing machinery, platforms, fences, beams, conveyors, mobile forklifts, maintenance vehicles, and automobiles in various stages of production. Frequencies below 6 GHz were monitored for 24-hour periods to understand the background ambient radio environment. The spectrum surveyshowed that interference from heavy equipment can impair signals for low-frequency applications such as those used in some controllers on the floor. A detailed analysis of a common wireless local area network (LAN) frequency band was performed. Signal-scattering tests showed potential for high levels of multipath interference.
NIST reported that its researchers have identified steps to minimize radio interference on the factory floor. These include the use of licensed frequency bands, where possible, and restrictions on the use of personal electronics in high-traffic frequency bands, as well as the installation of absorbing material in key locations, use of wireless systems with high immunity to electromagnetic interference, use of equipment that emits minimal machine noise, and use of directional antennas to help mitigate multipath interference when transmitters and receivers are close to each other.
The work is part of a larger NIST / USCAR collaboration established in 2004.
In other news, the
Instrumentation, Systems, and Automation Society (ISA)
reported its ISA-100, the “Wireless Systems for Automation,” standards committee is at work to develop a family of wireless standards. During a recent meeting in Vancouver, Canada, the ISA-100.11a Principles of Operation were affirmed by all task groups for release to the committee for review and comment; the schedule also was reaffirmed.
The brief, non-detailed overview of draft ISA-100.11a was written as a “cohesive overview and summary of the individual task group resolutions at this point.” Details of operation are not present in the document; details will be defined later in the draft standard document.
According to ISA-100 chair Wayne Manges of Oak Ridge National Labs, there was tremendous user support at the meeting. “This standard is for the end user, so the more end user input we have, the better our standard will be,” he said.
Jim Reizner, section head of corporate engineering at Procter & Gamble, added that he was extremely happy with the way the editorial team dealt with “contradictory requirements of systems that offer options, flexibility, and differentiation among vendors and the end-user desires.”
The standard is intended to provide reliable and secure operation for non-critical monitoring, alerting, supervisory control, open loop control, and soft closed loop control applications. It defines the open systems interconnection (OSI) stack, system management, gateway, and security specifications for low data rate wireless connectivity with fixed, portable, and moving devices with no battery or very limited battery consumption requirements. The standard is set for release early next year.
The committee has scheduled an interest meeting during
ISA Expo 2007
(Oct. 2-4) in Houston. A multi-vendor technology demonstration will showcase the major principles of operation of the committee’s work, and products from more than 15 vendors are expected to beicited at the meeting to form interest groups for each family of standards.
—Edited by Barb Axelson, contributing editor
Control Engineering Weekly News
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