New Research Tracks 700 MHz In-Building Signal Penetration
May 05, 2010
In March, the National Institute of Standards and Technology (NIST) released the sixth in a series of NIST technical notes on penetration of 700 MHz radio signals into large building structures, including apartment complexes, hotels, office buildings, sports stadiums and shopping malls. The reports are intended to give emergency responders and system designers a better understanding of what to expect from the radio propagation environment in emergency response situations.
In the most recent technical note, measurements were carried out in the 750 MHz frequency band. Because the FCC is in the process of auctioning the D block spectrum with plans for public-safety use, NIST researchers studied radio signal penetration in this frequency band into four different large building structures: a convention center, a high-rise office building, a laboratory/office building and an apartment building.
A fundamental challenge to radio communications into and out of large buildings is the strong attenuation of radio signals caused by losses and scattering in a building’s materials and structures. A second issue is the large amount of signal variability because of multipath that occurs throughout the large structures.
Following are photos of the buildings where the research was conducted and graphs with some research data.
Colorado Convention Center
The Colorado Convention Center in Denver is a massive three-level structure constructed of reinforced concrete, steel and standard interior finish materials. The exterior building is a combination of glass, metal and concrete.
Republic Plaza Building
The construction materials of the 57-story Republic Plaza building in Denver are a combination of concrete and steel. The interior building materials are a combination of metal framing, dry wall and trim with stone finishes in the lobby. The exterior is a combination of glass and metal.
The NIST building is the main building — referred to as the radio building — at the NIST laboratories in Boulder, Colo. The four-story building is constructed of reinforced concrete. However, the building is built on a hillside and consequently, some locations in the building are below ground level.
Horizon West Apartment
The 11-story Horizon West apartment building in Boulder is constructed of reinforced concrete, steel and brick with standard interior finish materials. The building was fully furnished and occupied during the experiments. Measurements were performed during the daytime hours and, as a result, people were moving throughout the building during the experiments.
NIST receive site 1 was located near the 57-story Republic Plaza in Downtown Denver. The site was at the base of the building.
RMS Delay Spread
RMS delay spread calculated over several different frequency bands for the Republic Plaza building.
For more in-depth coverage of measurement methods, examples of the measurement data collected by NIST and a brief interpretation of the results, see “In-Building Signal Tests” in the May issue
of MissionCritical Communications
Photos and graphics courtesy NIST staff.