Statistical Characterization and Modeling of Indoor RF-EMF Down-Link Exposure

Abstract

Statistical Characterization and Modeling of Indoor RF-EMF Down-Link Exposure Mulugeta BA, Wang S, Ben Chikha W, Liu J, Roblin C, Wiart J. Statistical Characterization and Modeling of Indoor RF-EMF Down-Link Exposure. Sensors (Basel). 2023 Mar 29;23(7):3583. doi: 10.3390/s23073583. Abstract With the increasing use of wireless communication systems, assessment of exposure to radio-frequency electromagnetic field (RF-EMF) has now become very important due to the rise of public risk perception. Since people spend more than 70% of their daily time in indoor environments, including home, office, and car, the efforts devoted to indoor RF-EMF exposure assessment has also increased. However, assessment of indoor exposure to RF-EMF using a deterministic approach is challenging and time consuming task as it is affected by uncertainties due to the complexity of the indoor environment and furniture structure, existence of multiple reflection, refraction, diffraction and scattering, temporal variability of exposure, and existence of many obstructions with unknown dielectric properties. Moreover, it is also affected by the existence of uncontrolled factors that can influence the indoor RF-EMF exposure such as the constant movement of people and random movement of furniture and doors as people are working in the building. In this study, a statistical approach is utilized to characterize and model the total indoor RF-EMF down-link (DL) exposure from all cellular bands on each floor over the length of a wing since the significance of distance is very low between any two points on each floor in a wing and the variation of RF-EMF DL exposure is mainly influenced by the local indoor environment. Measurements were conducted in three buildings that are located within a few hundred meters vicinity of two base station sites supporting several cellular technologies (2G, 3G, 4G, and 5G). We apply the one-sample Kolmogorov-Smirnov test on the measurement data, and we prove that the indoor RF-EMF DL exposure on each floor over the length of a wing is a random process governed by a Gaussian distribution. We validate this proposition using leave-one-out cross validation technique. Consequently, we conclude that the indoor RF-EMF DL exposure on each floor over the length of a wing can be modeled by a Gaussian distribution and, therefore, can be characterized by the mean and the standard deviation parameters. Conclusions This paper analyzes the indoor RF-EMF DL exposure with outdoor cellular antennas located more than 200 m from the buildings. In the three buildings, 1176 measurements have been performed with a broadband probe at both corridors and offices on different floors. With the base station antenna far away, the exposure is well below 1% of the ICNIRP reference levels as expected. A statistical approach has been implemented to characterize and model the indoor RF-EMF DL exposure. The measurement data were analyzed and the p-values of the one-sample K-S test are above 0.05. Therefore, it has been statistically proved that the indoor RF-EMF DL exposure on each floor over the length of a wing can be modeled by a Gaussian distribution when the size of the building is small compared to the distance to the base station antennas. In such case, the mean and the standard deviation characterize the RF-EMF DL exposure distribution in the indoor environment. Finally, the result of this work can be used as a step-stone to install a global indoor RF-EMF DL exposure monitoring system in ATOS via the implementation of measurements carried out by RF sensors distributed in the buildings. Open access paper: ncbi.nlm.nih.gov

AI evidence extraction

Main findings

In three buildings near two base station sites, 1176 indoor measurements (corridors and offices across floors) indicated that down-link RF-EMF exposure on each floor over the length of a wing can be modeled as a Gaussian random process (one-sample KolmogorovSmirnov p-values > 0.05; validated with leave-one-out cross validation). With outdoor base station antennas located >200 m away, measured exposure was well below 1% of ICNIRP reference levels.

Outcomes measured

• Indoor RF-EMF down-link exposure levels (all cellular bands; 2G/3G/4G/5G)
• Statistical distribution/model fit of indoor RF-EMF DL exposure (Gaussian; mean and standard deviation)
• Comparison to ICNIRP reference levels (% of reference levels)

Limitations

• Frequency-specific exposure values not reported in the abstract (all cellular bands combined)
• Study context limited to three buildings within a few hundred meters of two base station sites; generalizability to other building types/distances not stated
• Modeling claim specified for cases where building size is small compared to distance to base station antennas

Suggested hubs

• who-icnirp (0.72)
  Exposure levels are explicitly compared to ICNIRP reference levels.
• 5g-policy (0.45)
  Includes 5G among assessed cellular technologies, though focus is exposure characterization rather than policy.

{
    "study_type": "exposure_assessment",
    "exposure": {
        "band": "RF",
        "source": "base station",
        "frequency_mhz": null,
        "sar_wkg": null,
        "duration": null
    },
    "population": null,
    "sample_size": 1176,
    "outcomes": [
        "Indoor RF-EMF down-link exposure levels (all cellular bands; 2G/3G/4G/5G)",
        "Statistical distribution/model fit of indoor RF-EMF DL exposure (Gaussian; mean and standard deviation)",
        "Comparison to ICNIRP reference levels (% of reference levels)"
    ],
    "main_findings": "In three buildings near two base station sites, 1176 indoor measurements (corridors and offices across floors) indicated that down-link RF-EMF exposure on each floor over the length of a wing can be modeled as a Gaussian random process (one-sample KolmogorovSmirnov p-values > 0.05; validated with leave-one-out cross validation). With outdoor base station antennas located >200 m away, measured exposure was well below 1% of ICNIRP reference levels.",
    "effect_direction": "no_effect",
    "limitations": [
        "Frequency-specific exposure values not reported in the abstract (all cellular bands combined)",
        "Study context limited to three buildings within a few hundred meters of two base station sites; generalizability to other building types/distances not stated",
        "Modeling claim specified for cases where building size is small compared to distance to base station antennas"
    ],
    "evidence_strength": "moderate",
    "confidence": 0.7800000000000000266453525910037569701671600341796875,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "RF-EMF",
        "indoor exposure",
        "downlink",
        "base station",
        "2G",
        "3G",
        "4G",
        "5G",
        "Gaussian distribution",
        "Kolmogorov-Smirnov test",
        "leave-one-out cross validation",
        "ICNIRP reference levels",
        "measurement campaign"
    ],
    "suggested_hubs": [
        {
            "slug": "who-icnirp",
            "weight": 0.7199999999999999733546474089962430298328399658203125,
            "reason": "Exposure levels are explicitly compared to ICNIRP reference levels."
        },
        {
            "slug": "5g-policy",
            "weight": 0.450000000000000011102230246251565404236316680908203125,
            "reason": "Includes 5G among assessed cellular technologies, though focus is exposure characterization rather than policy."
        }
    ]
}

Comments

Log in to comment.

No comments yet.