Vertical Assessment of RF-EMF Exposure in a Building Adjacent to a Multi-Operator Shared Base Station

I. INTRODUCTION

• Prior work on building exposure included scenario modeling, and in-situ measurement campaigns –.The studies used different approaches to characterize or predict exposure in buildings.Source: §I · p. 1
• Earlier multi-building studies used antenna data to identify exposed buildings, but did not estimate which floors might face worst-case exposure.Other studies were limited to single buildings with exact antenna and installation information,.Source: §I · p. 1
• The proposed approach uses publicly available BS configuration and location data to select exposed buildings and estimate floors likely to have worst-case exposure.In 2024, measurements in four of Natal’s 22 target buildings reached average electric field strengths of 13.14 V/m and peaks of 22.79 V/m.Source: §I · p. 1
• This study reapplies the approach in 2025 and adds continuous vertical measurements across all floors of a directly exposed building.The campaign provides additional empirical validation and characterizes exposure in a high-exposure scenario.Source: §I · p. 1

II. EVALUATED SCENARIO

• The target building was selected as the most critical of 34 buildings because of its proximity and nearby telecommunications installations.It is directly across the street from a shared site with two BSs.Source: §II · p. 2
• The assessment used geodesic distance, horizontal zone-of-interest diagrams, and ANATEL Mosaico data to identify directed emissions and potential transmitter power.Table I provides information about the target BSs.Source: §II · p. 2, Table I · p. 2
• The -2° and 0° emissions from the 120°-azimuth antennas centered on the 11th floor, which also lay at the center of the horizontal zone of interest.Figure 1 depicts the horizontal and vertical zones and the 11th floor relative to the antennas.Source: §II · p. 2

III. MEASUREMENT PROCEDURE

• One-minute time-averaged measurements covered all levels from an accessible façade; 30-minute measurements followed on the three floors with the highest field levels.The building’s technical area allowed measurements without entering apartments.Source: §III · p. 2
• A broadband NBM-520 meter and EF 0691 probe measured RMS electric-field intensity from 100 kHz to 6 GHz.The probe was set 1.7 m high and at least 2 m from people and reflective or absorptive surfaces; phones remained in airplane mode.Source: §III · p. 2
• The study used a 27.70 V/m limit for broadband assessment and compared results with the 38.35 V/m most restrictive limit for target-BS bands.The 27.70 V/m limit corresponds to Natal broadcast services at 88–108 MHz; the 38.35 V/m limit corresponds to the 778 MHz LTE band.Source: §III · p. 3
• Post-processing evaluated the Exposure Ratio using measured electric field and the public-exposure reference limit.Equation 1 defines Erms as measured RMS electric field in V/m and Elim as the regulatory public-exposure limit.Source: §III · p. 3

• In the one-minute campaign, the 10th floor had the highest average electric-field intensity at 17.16 V/m and the highest peak at 28.47 V/m.Source: Table V · p. 3, §IV · p. 4
• The 30-minute campaign produced higher average and peak electric-field values than the first campaign on floors 9–11; the 10th floor averaged 17.34 V/m and peaked at 31.86 V/m.Source: §IV · p. 4, Table VI · p. 4
• The reported electric-field strength was 31.86 V/m, 23.95 times higher than the peak value recorded at street level.Source: §IV · p. 4
• Some floors showed unexpected value patterns, possibly because short one-minute measurements were more sensitive to changes from nearby services such as Wi-Fi.Source: §IV · p. 4
• Despite a discrepancy between the estimated zone-of-interest center floor and the measured floor, the analysis anticipated the floors with the highest values, which exceeded ground-level exposure.Source: §IV · p. 4
• The discrepancy may reflect uncertain antenna tilt information, while broadband measurements cannot isolate contributions by operator or radio access technology.Source: §IV · p. 4

V. CONCLUSIONS

• The study assessed RF-EMF exposure on every floor of a building in a critical scenario near telecommunications infrastructure operated by multiple operators.Source: §V · p. 4
• Average and peak electric field intensity rose significantly as the measurement floor approached the antenna HPBW center.The study calls for methods that consider BS antenna configuration when assessing RF-EMF exposure.Source: §V · p. 5
• A discrepancy between the target floor and the floor with the highest exposure underscores the importance of reliable, continuously updated BS parameter databases for accurate and efficient measurements.Source: §V · p. 5
• Future work will use narrowband equipment to examine each technology’s contribution and extend vertical measurements, including apartment interiors when access is needed.Source: §V · p. 5
• The authors plan to obtain exact antenna models and configurations from operators to improve estimates and develop a predictive model incorporating frequency, antenna configuration, and distance.Source: §V · p. 5
• Future measurements will relate field intensity to channel conditions, network configuration, and traffic load, including dense co-channel deployments with simultaneous transmissions.Source: §V · p. 5