Ray-Based Modeling of Directional Millimeter-Wave V2V Transmissions in Highway Scenarios

Due to the need for larger bandwidth, future mobile networks may primarily operate over millimeter-wave (mmWave) bands. In this regard, one of the central research topics today is mmWave channel modeling. However, highly mobile vehicle-to-vehicle (V2V) mmWave channels pose an open question because conducting measurements may be challenging in this environment. The existing publications on mmWave V2V channel modeling consider line-of-sight (LoS) or single-blocker scenarios. Accordingly, the impact of interference from adjacent vehicles is not taken into account. Conventional analytical models suggest that path loss (PL) strikes equally in all directions whereas measurements are inherently directional, especially in the case of mmWave propagation. Recently, it was proposed to synthesize the omnidirectional PL from directional measurements. However, with this method, the resulting PL is underestimated. Moreover, theoretical models assume that vehicular transceivers follow a certain predetermined distribution, which may not be accurate in real-world scenarios. Several works take into account the directionality of an antenna pattern when the antenna orientation is known. However, the effects of reflection, diffraction, and transmission through obstacles are not considered. One way to avoid these limitations is to use ray-based simulations. However, the ray-launching (RL) approach does not specify any criteria for the directionality of the antenna patterns. Assuming omnidirectional PL appears impractical for mmWave transmission where directional communication is crucial to combat high PL. In this paper, we propose an approach for synthesizing directional PL based on extensive RL modeling. For the obtained directional and omnidirectional PL, we parametrize the close-in (CI) and float-intercept (FI) channel models. As a result of our modeling, from 0.1 to 2.7 for the LoS and from 0.1 to 2.6 for the non-LoS (NLoS) higher PL exponent is observed as compared to the omnidirectional case.