Spatial Correlation in Indoor Massive MIMO: Measurements and Ray Tracing

Abstract

This paper investigates spatial correlation properties of radio-frequency Massive MIMO channels. The correlation between channel vectors at the receive side is studied for the interreceiver distances up to several wavelengths. This is an important property of 5G wireless networks and its accurate prediction is desirable in many applications. Measured and simulated channels are compared using an alternative formulation of the channel correlation function, the argument of which is the distance between any two receivers in proximity of a selected region. The measurements were conducted using a Massive MIMO basestation (BS) test-bed and virtual arrays of receivers, positioned with a robotic system. The simulations were performed using the Ray-Tracing (RT) technique in a simplified model of an indoor environment, augmented with stochastic geometry elements. In addition, a Line-of-Sight channel model was derived from the RT results, and the role of the scattered power on the correlation was evaluated. The results show that the RT model predicts the correlation with an error not exceeding 10%. The variation of the correlation function profile with increasing receiver to BS separation distance is also captured by the RT model. The simulated Line-of-Sight model predictions, which account solely for direct propagation paths, were found to significantly underestimate the correlation at the sub-wavelength distance, and overestimate it at larger distances.

Numerical Assessment of Human EMF Exposure to Collocated and Distributed Massive MIMO Deployments in an Industrial Indoor Environment

“…The wireless propagation modeling was performed using a ray-launching [17] variant of the general RT method [18] using REMCOM Wireless InSite 3.3 [19]. The RT method was shown to accurately reproduce the correlation properties of massive MIMO channels in indoor environments [20], [21]. with smaller cuboid scatterers distributed within it, similar to [22].…”

IN-SITU 5G NR BASE STATION EXPOSURE OF THE GENERAL PUBLIC: COMPARISON OF ASSESSMENT METHODS

“…Research about measurement methodologies for 5G NR signals is ongoing, including simulations (4) and measurements (5)(6)(7)(8) . In general, two different exposure metrics can be considered, (i) actual momentary or instantaneous time-averaged field levels on the one hand and (ii) extrapolated maximal field levels on the other hand.…”