| Abstract: |
In this report, we investigate radio communication problems faced by emergency responders (firefighters, police, and emergency medical personnel) in disaster situations. 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 the building materials and structure, as well as the large amount of additional signal variability due to multipath that occurs throughout these large structures. We conducted measurements in four large building structures in an effort to quantify radio-signal attenuation and variability in scenarios encountered by emergency response organizations. We performed three different types of measurements. For the first two types of measurements, we carried RF transmitters throughout the structures and placed two different types of receiving systems outside the structures. One receiver type was based on a commercial, off-the-shelf spectrum analyzer and the other on a NIST-developed narrowband communications receiver system having a high dynamic range. The transmitters were tuned to approximately 750 MHz. The third type of measurement tested the time-domain response of the channel at particular locations within the buildings using a synthetic-pulse measurement system. These measurements utilized the vector network analyzer with its output port was tethered to the receive antenna by a fiber-optic cable to enable reconstruction of the time-domain response of the propagation channel. This report summarizes the experiments performed in four large building structures. We describe the experiments, detail the measurement systems, show results from the data we collected, and discuss some of the propagation effects we observed. |
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