NIST is developing a hybrid test chamber for over-the-air characterization of the next generation of wireless devices in spatial channel environments. By combining features of both reverberation and anechoic chambers, the hybrid chamber will produce anisotropic, multipath environments intended to test spatial diversity and beamforming capabilities of multiple-element antenna. Here, we present results that investigate our ability to control spatial channels. Syntheticaperture measurements are used to determine the channel's power-angle profile and power-delay-angle profile, which characterize the angle-of-arrival and time-of-arrival of received power. Comparisons are made between an unloaded and loaded chamber. For the loaded configuration, strategically placed RF absorber is shown to create an anisotropic, spatial channel. The hybrid chamber is expected to provide a cost-effective solution for over-the-air measurements of next-generation wireless devices.
Certain commercial entities, equipment, or materials may be identified in this document in order to describe an experimental procedure or concept adequately. Such identification is not intended to imply recommendation or endorsement by the National Institute of Standards and Technology, nor is it intended to imply that the entities, materials, or equipment are necessarily the best available for the purpose.
The National Institute of Standards and Technology (NIST) has participated in a multi-year project to support the development of performance metrics and test methods for radio-frequency (RF)-based electronic safety equipment used by the public-safety community. The work reported here focuses on side-by-side measurements of radiopropagation environment characteristics and actual wireless device performance in two key representative emergency responder environments, a subway station and a highrise building. Identifying the impacts of path loss on wireless device performance in various environments enables the development of standardized laboratory-based test methods that simulate the conditions under which electronic safety equipment will be used in the field. The test methods can then be incorporated into consensus standards for this equipment. The analysis presented here has been funded by the U.S. Department of Homeland Security Standards Branch. The work reported here focuses on RF-based personal alert safety systems (PASS), used by firefighters to indicate when a firefighter is motionless or in distress. However, the methodology, analysis, and RF propagation results presented here could easily be extended to other types of wireless devices that operate in similar environments. In previous propagation-channel studies, NIST engineers measured path loss ("attenuation") and the level of reflectivity (or "multipath," quantified by the root-meansquare delay spread) in large public structures and environments where radio communications could be challenging. (See NIST Technical Notes 1545, 1456, 1550, 1552, 1557, and 1559.) These environments included multi-story buildings; buildings with subterranean floors and tunnels; buildings with deep interior spaces; those with few windows; and outdoor "urban canyons," consisting of city streets surrounded by tall buildings. The NIST Public-Safety Communications Research Lab funded those measurements of the propagation channel. Current work focuses on the subterranean environment presented by subways, and a 100-story high-rise, the Empire State Building. The tests were completed in New York City with the help of the Fire Department of New York and several firefighters from the Research and Development Division. Access to the subway station was provided by the New York City Transit Authority. The building owners, management, and maintenance personnel provided access and support for testing the Empire State Building. To support standards development in public-safety applications, the NIST studies focus on the penetration of radio signals from outside to inside a given structure (and vice versa), as opposed to outdoor-to-outdoor or within-building tests. To simulate an incident command post in the propagation-channel studies, a receive antenna was positioned outside of each structure at a location representative of a fireground configuration. Portable RF PASS units were carried through the environment and success or failure in receipt of various alarms was noted. A continuous-wave...
Certain commercial entities, equipment, or materials may be identified in this document in order to describe an experimental procedure or concept adequately. Such identification is not intended to imply recommendation or endorsement by the National Institute of Standards and Technology, nor is it intended to imply that the entities, materials, or equipment are necessarily the best available for the purpose.
Certain commercial entities, equipment, or materials may be identified in this document in order to describe an experimental procedure or concept adequately. Such identification does not imply recommendation or endorsement by the National Institute of Standards and Technology, nor does it imply that the entities, materials, or equipment are necessarily the best available for the purpose.
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