Field Enhancement and Size of Radio-Frequency Hotspots Induced by Maximum Ratio Field Combining in Fifth Generation Network

Abstract

The goal of this paper is to experimentally assess the field enhancement and hotspot size of radio frequency electromagnetic fields created by the Maximum Ratio Combining (MRC) precoding scheme using lab measurements at 3.5, 5.5 and 11 GHz. MRC is an adaptive precoding scheme used by Massive Multiple Input Multiple Output systems, one of the enabling techniques of the fifth generation of telecommunications (5G). A virtual antenna array was used to compare MRC with two passive precoding schemes: the Random Phase Model (RPM) and the Centerline Beam Model (CBM). The field enhancement going from CBM to MRC was largest in obstructed line of sight (OLOS), ranging from 1.9 to 7.4 dB. The field enhancement going from RPM to MRC was about 9.5 dB across frequency bands in both line of sight (LOS) and OLOS. The hotspot size, quantified by the full width at half maximum (FWHM), ranged from 0.5 wavelengths to one wavelength.

Measurement and Simulation-Based Exposure Assessment at a Far-Field for a Multitechnology Cellular Site up to 5G NR

“…Both methods have focused on single technology assessment (2G, 3G, 4G, IoT, or 5G), and recently there is some focus given on accumulated exposure from multi-technology coexisting at a single site, and few studies investigated this subject [37] which we believe is important to address. More factors need to be considered and require further investigation, such as the co-location of the multi-operator situation at the same site, accumulated radiation from neighboring and surrounding sites, actual radiation considering the number of users, traffic load (system utilization), and especially for 5G NR, the time-averaged power and spectral efficiency [38,39].…”

Multi-Technology Multi-Operator Site Sharing: Compliance Distance Analysis for EMF Exposure

“…For N3500, which has a high grade of mMIMO (64T/64R), we used 0.22 as a realistic power factor. This was taken from the interesting results and findings of the studies [ 28 , 29 , 30 ]; it indicates that the realistic transmitted power of mMIMO reaches 16–22% of the maximum equipment power when it operates at a full system load.…”

“…With the introduction of 5G NR, which uses a high grade of massive Multi-Input Multi-Output (mMIMO), some recent studies have investigated EMF exposure by considering more factors [ 28 , 29 , 30 , 31 , 32 ], such as the actual radiated power, system utilization load, and spatial/time duty cycle [ 32 , 33 ]. Furthermore, according to IEC 62232 [ 22 ], EMF assessments for human exposure can be performed on the basis of actual situations.…”