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In this correspondence, we first classify confined spaces, and then present some experimental data on the natural propagation radio signals. The effects of traffic in confined spaces on natural propagation are studied in terms of the additional loss. It is shown that the propagation losses due to confined spaces themselves are within several decibels per hundred meters, while the additional losses due to traffic could be very large. For instance, the additional loss at 900 MHz in two-lane road tunnels reaches 50 dB at 95% probability margin for the traffic density of 150 heavy trucks per hour. The measured additional loss is added to the existing model for more accurate path loss prediction. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 23: 38–42, 1999. [ABSTRACT FROM AUTHOR]

Normal incidence broadband transmission measurements across different building materials have been made in the 5.8 GHz frequency band, and transmission coefficients have been computed. Several samples of each material have been measured, showing that a single sample is not enough to obtain a good characterization, and confidence bands are needed. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 23: 7–12, 1999. [ABSTRACT FROM AUTHOR]