Millimeter-wave (mmWave) frequencies are considered as candidate bands for 5G/6G mobile networks. Diffraction models are significant for predicting non-line-of-sight (NLOS) wireless channels while it is shown that the line of sight (LOS) path is usually blocked by buildings in urban area environments. A lot of investigations on the diffraction loss have been performed, and most of them just considered a one obscuring object and a short propagation distance. In this paper, we conduct a statistical analysis of the diffraction loss in the outdoor NLOS in Urban Micro Cell, considering a transmitter (TX) and a receiver (RX) which are located at an aggregation point on the roof of a building. We have focused on analyzing the diffraction loss suffered by mmWave signals when they hit one or two obscuring points located over rooftop of the buildings. The objects have different heights located at various distances between TX and RX. We have considered the bands: 28 GHz, 38 GHz, 60 GHz, 73 GHz and 100 GHz. The analysis is based on the diffraction model named the Knife Edge Diffraction (KED). We have strictly followed the ITU Recommendations ITU-R P.526-15 (10/2019). In this work, we use two schemes that characterize the KED model, namely Single KED (SKED) and Double Isolated KED (DIKED). Different scenarios are performed by varying different parameters of the channel between TX and RX. The results show that the diffraction loss is inversely proportional to the distance between the obscuring object and the transmitter, the wavelength, and the distance between the TX and RX.
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