The impact of antenna beamwidth on the correlation distance of 60 GHz indoor and outdoor channels

Due to narrow antenna beamwidth and channel sparseness, millimetre-wave receivers will detect far fewer multipath components than their microwave counterparts, fundamentally changing the small-scale fading properties. By corollary, the de facto Rayleigh-Rice model, which assumes a rich multipath environment interpreted by the Clarke-Jakes omnidirectional ring of scatterers, does not provide an accurate description of this fading nor of the correlation distance that it predicts. Rather, a model interpreted by a directional ring of scatterers, recently proposed in seminal work by Va et al., theoretically demonstrated a strong dependence of correlation distance on beamwidth. To support Va’s model through actual measurement, we conducted an exhaustive measurement campaign in five different environments – three indoor and two outdoor – with our 60 GHz 3D double-directional channel sounder, compiling over 36,000 channel captures. By exploiting the super-resolution capabilities of the channel sounder, we were the first, to our knowledge, to measure correlation distance as a function of continuous beamwidth. We showed that for narrow beamwidth, correlation was maintained for much longer distances than predicted by the Rayleigh-Rice model, validating Va’s model. As the beamwidth approached omnidirectionality, with increasing number of multipath detected, the behavior indeed approached the Rayleigh-Rice model. We also demonstrated how virtual arrays implemented using a robotic arm can realize variable beamwidth antenna apertures at a fraction of the cost of the multi-element array used in this study, albeit with some restrictions on the types of the channels that can be characterized, and revealed that the relationship between estimated and actual rms delay spread is simply related to the dynamic range of the measurement.Applied Science, Faculty ofElectrical and Computer Engineering, Department ofGraduat