On the Space/Time Correlation of mmWave AoAs: Concept and Experimental Validation

The Sub-6GHz multi-path channel model suggests that the angle of arrivals (AoAs) and angle of departures (AoDs) of dominant rays follow a uniform distribution. Moreover, AoA/AoD varies interdependently from one coherence time/space to another. Several of the recent works on millimeter wave (mmWave) transmissions suggest otherwise, where some presume that it is possible to predict the AoAs/AoDs from nearby users (correlation over space) while others presume that beamforming coherence distance/time is higher than the channel coherence distance/time. The results in existing works, however, are often based on abstract models (two rays model), simulation results (typically rays tracing simulator), and, in many cases, the presence of a Line-of-Sight (LoS) link. In an effort to support or refute such a conjecture, we have carried out a real-world experiment in indoor office environments with high Non-LoS (NLoS) probability. We use statistical Bayesian learning to infer a statistical model on AoAs and extract insightful information.