Propagation Models in Vehicular Communications

In the advent of becoming reality, era autonomous vehicles is closer than ever, and with it, need for faster reliable wireless connections. The propagation channel determines performance limits communications, aid empirical measurements, modeling best approach to predict recreate how signal conditions may perform. To this end, many different approaches techniques have been implemented, from specific applications general models, considering characteristics environment (geometry-based or non-geometry-based) as well seeking high algorithms in order achieve good balance between accuracy computational cost. This paper provides an updated overview models vehicular beginning some these complex heterogeneous environments terms diverse communication scenarios, combinations link types, antenna placement/diversity, potentially Doppler shifts, non-stationarity, among others. presented are classified four categories: empirical, non-geometry-based stochastic, geometry-based deterministic following classical approach. features key concepts communications presented, sub 6 GHz millimeter wave (mmWave) frequency bands. advantages disadvantages main works area discussed compared a comprehensive way, outlining their contributions. Finally, future critical challenges research directions introduced, such effects vegetation, pedestrians, common scatterers, micro-mobility spherical wavefront, which context near opportunities.