Path loss in high frequency bands above 6GHz is the most fundamental and significant propagation characteristic of IMT-2020. To develop and evaluate such high frequency bands, ITU-R SG5 WP5D recently released channel models applicable up to 100GHz. The channel models include path loss models applicable to 0.5-100GHz. A path loss model is used for cell design and the evaluation of the radio technologies, which is the main purpose of WP5D. Prediction accuracy in various locations, Tx positions, frequency bands, and other parameters are significant in cell design. This article presents the prediction accuracy of UMa path loss models which are detailed in Report ITU-R M.2412 for IMT-2020. We also propose UMa_A' as an extension model of UMa_A. While UMa_A applies different equations to the bands below and above 6GHz to predict path loss, UMa_A' covers all bands by using the equations of UMa_A below 6GHz. By using the UMa_A' model, we can predict path loss by taking various parameters (such as BS antenna height) into account over a wide frequency range (0.5-100GHz). This is useful for considering the deployment of BS antennas at various positions with a wide frequency band. We verify model accuracy by extensive measurements in the frequency bands from 2 to 66GHz, distances up to 1600 m, and an UMa environment with three Tx antenna heights. The UMa_A' extension model can predict path loss with the low RMSE of about 7dB at 2-26.4GHz, which is more accurate than the UMa_A and UMa_B models. Although the applicability of the UMa_A' model at 66GHz is unclear and needs further verification, the evaluation results for 66GHz demonstrate that the antenna height may affect the prediction accuracy at 66GHz.

This paper proposes a path loss model for crowded outdoor environments that can consider the density of people. Measurement results in an anechoic chamber with three blocking persons showed that multiple human body shadowing can be calculated by using finite width screens. As a result, path loss in crowded environments can be calculated by using the path losses of the multipath and the multiple human body shadowing on those paths. The path losses of the multipath are derived from a ray tracing simulation, and the simulation results are then used to predict the path loss in crowded environments. The predicted path loss of the proposed model was examined through measurements in the crowded outdoor station square in front of Shibuya Station in Tokyo, and results showed that it can accurately predict the path loss in crowded environments at the frequencies of 4.7GHz and 26.4GHz under two different conditions of antenna height and density of people. The RMS error of the proposed model was less than 4dB.