Abstract
Accurate path loss modeling is essential to capture the unique characteristics of outdoor millimeter-wave (mmWave) propagation. This study analyzes the outdoor propagation path loss of mmWave signals at 28, 38, 66, 71, and 90 GHz in three urban locations in Istanbul, Turkey, using Ray Tracing (RT) simulations for both Line of Sight (LOS) and Non-Line of Sight (NLOS) conditions. Four large-scale empirical path loss models were examined: the Close In (CI) free-space reference distance model, the Floating Intercept (FI) model, the CI model with frequency dependence (CIF), and the Alpha–Beta–Gamma (ABG) model. Results show that the path loss exponent fluctuated between 2.35 and 2.86 in LOS and 2.54–3.3 in NLOS scenarios, with standard deviation of 3–11.79 dB. The FI model achieved the lowest errors values in LOS conditions, while ABG and CIF delivered comparable accuracy under NLOS and multi-frequency conditions. Also, angular and temporal analysis showed that angles of arrival (AoA) and delay metrics are very important for how mmWave channels behavior. In urban streets, the maximum AoA ranged from − 0.99 rad to + 3.14 rad, and in open squares, it ranged from − 2.58 rad to + 1.66 rad. This shows that multipath dispersion is stronger at lower frequencies and in open spaces.