Height gain modeling of outdoor-to-indoor path loss in metropolitan small cell based on measurements at 3.5 GHz

In the last few years, the growing demand of wireless data services has brought great pressure on wireless network in dense urban environment Small cells are widely deployed to increase data capacity. But when the outdoor base station and indoor users in high-rising buildings get close, indoor users begin to suffer dramatic change in path loss due to height difference between the transmitter (TX) and receiver (RX). In this paper, a measurement campaign to research the Outdoor-to-Indoor (O2I) path loss in metropolitan small cell scenario was carried out. The analysis of the measurement data shows that in typical small cell scenario, the O2I path loss has a tendency of increasing with the height difference, which is defined as height gain. Height gain is observed in both the outdoor part and the wall penetration part of the O2I path loss, and it value is also found to relate to the distance between TX and RX. By taking the height difference into consideration when calculating the distance, the path loss of the outdoor part is modified. And by introducing a height gain factor, the height gain of the wall penetration part is modeled based on measurement data. The path loss prediction with height gain model fits in well with the measurement data.