Statistical Path Loss Modeling of LoS–NLoS Transitions for mmWave Communications in Urban Environments

Abstract

The rapid evolution towards Sixth Generation (6G) wireless systems demands seamless connectivity, ultra-high data rates, and stringent quality-of-service requirements, particularly in dense urban environments. To meet these stringent requirements, Millimeter-Wave (mmWave) communications have emerged as a key enabler, leveraging newly allocated wide bandwidths to deliver multi-gigabit data rates in mobile networks. However, dense Urban Micro (UMi) street environments, characterized by high-rise buildings and complex geometries, introduce frequent Line-of-Sight (LoS) and Non-Line-of-Sight (NLoS) transitions that significantly impact mmWave propagation between the transmitter and receiver. This paper evaluates the conventional statistical path loss models recommended by the International Telecommunication Union - Radiocommunication (ITU-R) under UMi NLoS propagation conditions in a Manhattan-like scenario, initially developed for sub-6 GHz, and proposes an extension of this model that reduces modeling error and improves accuracy for the mmWave frequency band, particularly at 28 GHz. The proposed model extension is validated using detailed Ray Tracing (RT) simulations at 28 GHz under distinct and complex network deployment regimes. Simulation results demonstrate that the proposed model effectively captures the LoS-NLoS transition characteristics of mmWave propagation in a Manhattan grid layout, while preserving the analytical simplicity of the standardized conventional statistical model. The proposed model extension for mmWave bands achieves high spatial accuracy, enabling characterization of radio signal propagation with significantly reduced computational complexity compared to RT for dense urban communication scenarios.