Hybrid Massive MIMO for Urban V2I: Sub-6 GHz vs mmWave Performance Assessment

The relevance of vehicle communications in next-generation networks entails the necessity of studying their performance in the framework of upcoming massive architectures. In this regard, a study of the wireless channel between a hybrid massive MIMO BS and a vehicular platform is proposed. Adequate metrics and methodology are provided for the assessment of such scenarios. The impact of different multi-antenna geometries and MIMO architectures in both vehicle and BS is modeled based on a numerical simulation of a realistic urban area. We compare several massive hybrid BS configurations with distinct multi-antenna vehicular rooftop solutions. This paper studies the channel eigenvalues and capacities for sub-6 GHz (3.6 GHz) and millimeter-wave (mmWave) (26 GHz) bands under different propagation conditions. The results suggest that the use of hybrid massive configurations increase the channel capacity by subdividing the massive BS into two or four logical radio channels. It is also shown that the greater available bandwidth at mmWave band can compensate the larger attenuation of radio channels in small size cells. The use of adequate metrics to measure the temporal coherence of the channel is also discussed for the beam switching update.