DIURNAL VARIATION OF CELLULAR RADIOFREQUENCY POWER DENSITY FROM SHORT-RANGE FIELD MEASUREMENTS IN TROPICAL PROPAGATION ENVIRONMENTS

Abstract

Reliable cellular network performance depends on stable radio frequency (RF) signal propagation under varying environmental and temporal conditions. Although distance and meteorological influences on signal behaviour are well documented, few field-based studies have quantified short-range diurnal variation in broadband aggregate RF power density around base transceiver station (BTS) infrastructure, particularly in tropical urban environments. This study investigates diurnal variation in broadband RF power density around three operational BTS sites within a 2.5-3 km radius. Field measurements were obtained using a calibrated Trifield TF2 RF meter, which records broadband aggregate RF exposure, while meteorological data were sourced from the Nigeria Meteorological Agency (NiMet). Measurements were collected across morning, afternoon, and evening time blocks over twenty-eight consecutive days. Results show a clear diurnal pattern, with mean power density highest in the evening (6.00 W/m²), followed by afternoon (5.37 W/m²), and lowest in the morning (4.08 W/m²). One-way ANOVA indicated statistically significant differences (p < 0.001), with a moderate effect size (η² ≈ 0.06), and Tukey HSD testing confirmed differences between time blocks. Correlation analysis showed weak associations between power density and distance (r = -0.121), temperature (r = 0.14), and relative humidity (r = -0.142), indicating small practical effect, despite statistical significance. Regression analysis identified distance as the dominant predictor (R² = 0.015), with only marginal improvement when meteorological variables were included (R² = 0.038). These results provide short-range tropical field evidence of diurnal variability in broadband RF power density, where atmospheric effects remain secondary to distance-dependent attenuation.