Wireless Systems Metrology

Summary

Imagine how much safer a fire fighter's job would be if it were possible for a robot to navigate in a burning building and locate those in need of assistance. The Wireless Systems Metrology Program develops ways to measure complex telecommunication signals used by industry, public safety (rescue workers), and government. The project develops methods to measure communication and data signals, and to imitate complex environments where reliable reception may be a problem. Applications include developing tests to evaluate the effects of interference on wireless communications used in factories for the control of robots, methods to measure cellular telephone fields, test facilities for evaluating search and rescue communications, and robot communications.

Description

NIST staff measure the wireless communication link environment in an automotive factory.

The Wireless Systems Metrology Program supports the growing wireless industry by developing methods to test the operation and functionality of wireless devices in the presence of various types of distortion. This includes multipath distortion, ranging from a line-of-sight environment (low-multipath) to a pure Rayleigh environment (high-multipath).

The Wireless Systems Metrology Program is also concerned with the impact of nonlinear distortion on the transmission of wireless signals, which can be especially severe for new wideband modulated signal transmissions. Accurately measuring distortion behavior of nonlinear radio-frequency devices is a key element in understanding how the device will perform once it is incorporated into a system. Even under weakly nonlinear conditions, low-noise devices such as those used in receiver front ends will exhibit nonlinear behavior that includes harmonic generation and intermodulation distortion. The program has studied problems that commonly arise in performing and interpreting nonlinear measurements, such as power and wave-based representations and the effects of terminating impedance on intermodulation distortion. Researchers are also working to develop traceability to fundamental parameters such as power and electric field.

Major Accomplishments

• Demonstrated that a reverberation chamber can be used to generate a variable multipath environment, which allows wireless devices to be tested in the laboratory rather than in field tests.
• Developed standards to ensure reliable wireless communications for emergency responders in difficult radio environments.
• Assisted the National Institute of Environmental Health Sciences, which is conducting a long-term animal study to evaluate health risks associated with cellular telephone fields, by testing the performance of 21 reverberation chambers that will be utilized in the study.

Associated Publications/Reports:

• E. Genender, C. Holloway, K. Remley, J. Ladbury, G. Koepke, H. Garbe, "Using a Reverberation Chamber to Simulate the Power Delay Profile of a Wireless Environment," in Proc. 2008 EMC Europe Symposium (Hamburg, Germany), pp. 219-224, September 2008.
• K. Remley, G. Koepke, C. Grosvenor, R. Johnk, J. Ladbury, D. Camell, J. Coder, "NIST Tests of the Wireless Environment in Automobile Manufacturing Facilities," NIST Technical Note 1550, October 2008.
• K. Remley, G. Hough, G. Koepke, R. Johnk, D. Camell, C. Grosvenor, "Wireless Communications in Tunnels for Urban Search and Rescue Robots," in Proc. 2008 Performance Metrics for Intelligent Systems (Gaithersburg, MD), August 2008.