A Simple Statistical Signal Loss Model for Deep Underground Garage

Abstract

In this paper we address the channel modeling aspects for a deep-indoor scenario with extreme coverage conditions in terms of signal losses, namely underground garage areas. We provide an in- depth analysis with regard to the path loss (gain) and large-scale signal shadow fading, and propose a simple propagation model which can be used to predict cellular signal levels in similar deep- indoor scenarios. The measurement results indicate that the signal at 800 MHz band penetrates external concrete walls to reach the lower levels, while for 2000 MHz wall openings are required for the signal to propagate. It is also evident from the study that the shadow fading at different levels of an underground garage are highly correlated. The proposed frequency-independent floor attenuation factor (FAF) is shown to be in range of 5.2 dB per meter deep. Therefore, the attenuation rate in the z dimension is much higher than the in-building attenuation in x and y dimension, which is often assumed at 0.6 dB/m.