RF-EMF Exposure near 5G NR Small Cells

Abstract

RF-EMF Exposure near 5G NR Small Cells Aerts S, Deprez K, Verloock L, Olsen RG, Martens L, Tran P, Joseph W. RF-EMF Exposure near 5G NR Small Cells. Sensors. 2023; 23(6):3145. doi: 10.3390/s23063145. Abstract Of particular interest within fifth generation (5G) cellular networks are the typical levels of radiofrequency (RF) electromagnetic fields (EMFs) emitted by ‘small cells’, low-power base stations, which are installed such that both workers and members of the general public can come in close proximity with them. In this study, RF-EMF measurements were performed near two 5G New Radio (NR) base stations, one with an Advanced Antenna System (AAS) capable of beamforming and the other a traditional microcell. At various positions near the base stations, with distances ranging between 0.5 m and 100 m, both the worst-case and time-averaged field levels under maximized downlink traffic load were assessed. Moreover, from these measurements, estimates were made of the typical exposures for various cases involving users and non-users. Comparison to the maximum permissible exposure limits issued by the International Commission on Non-Ionizing Radiation Protection (ICNIRP) resulted in maximum exposure ratios of 0.15 (occupational, at 0.5 m) and 0.68 (general public, at 1.3 m). The exposure of non-users was potentially much lower, depending on the activity of other users serviced by the base station and its beamforming capabilities: 5 to 30 times lower in the case of an AAS base station compared to barely lower to 30 times lower for a traditional antenna. Excerpt Scaled to small-cell powers, the measured exposure levels in this study were below the MPE limits for both occupational (at distances between 0.5 m and 1 m from the base station) and general public exposure (>1 m) issued by the International Commission on Non-Ionizing Radiation Protection (ICNIRP) [17]: the maximum exposure ratios were 0.15 (occupational) and 0.68 (general public). These theoretical worst-case exposures were higher than the actual maxima measured in situ by maximizing the downlink traffic load, and both types of worst-case exposures were much higher (3–12 times) than the exposures of a typical user, which in turn were much higher (4–9 times) than the exposures without any users. Finally, the exposure of a non-user within a mature 5G NR network depends on the distribution of users, their usage, and the AAS capabilities of the base station radio. Although adverse health effects at non-thermal exposure levels cannot be ruled out [20], the ICNIRP reference levels are still relevant to calculate exposure ratios against. The measurement values obtained in this study and reported in this paper can be directly compared to other reference or limit levels (e.g., from legislation or scientific literature), depending on the scope of the study. For a 5G NR AAS base station, the actual exposure of a given user will generally be less than the theoretical maximum exposure Emax for several reasons. First, other users (the number may vary) may be in beams other than the one the given user is using. Hence, the RF energy directed toward these users will not add (much) to the exposure of the given user. Second, the usage by the given user will generally be less than the maximum assumed for which Emax was defined. Third, there may be dynamic power control to reduce base station power to the minimum needed for communication. This was not taken into account in this study. Finally, the base station beam may be narrower or wider than that used to measure Emax. Hence, the problem of determining actual RF exposure becomes a statistical one that depends on several different variables. However, the exposure will almost always be less than Emax. Similarly, for the non-user, the difference lies in whether they are in a beam or not. Generally, the RF exposure from the base station for the non-user will be smaller than that for a user (here by at least a factor of 5 for an AAS), unless there are many users around and the MaMIMO capabilities of the base station are limited (Table 4) [19]. Open access paper: mdpi.com

AI evidence extraction

Main findings

RF-EMF measurements near two 5G NR base stations (one AAS/beamforming, one traditional microcell) under maximized downlink traffic load yielded maximum exposure ratios vs ICNIRP limits of 0.15 (occupational, at 0.5 m) and 0.68 (general public, at 1.3 m), i.e., below the limits. Typical user exposures were reported as 3–12 times lower than theoretical worst-case exposures, and exposures without any users were 4–9 times lower than typical user exposures; non-user exposure could be 5–30 times lower for an AAS base station and barely lower to 30 times lower for a traditional antenna, depending on user activity and beamforming.

Outcomes measured

• RF-EMF field levels (worst-case and time-averaged) at 0.5–100 m
• Exposure ratios relative to ICNIRP maximum permissible exposure limits (occupational and general public)
• Estimated typical exposures for users vs non-users; effect of beamforming (AAS) vs traditional microcell

Limitations

• Only two 5G NR base stations were measured (one AAS and one traditional microcell).
• Dynamic power control was not taken into account.
• Results depend on assumptions/conditions such as maximized downlink traffic load and user distribution/usage; actual exposure is described as statistical and variable.

Suggested hubs

• who-icnirp (0.86)
  Study compares measured RF-EMF levels to ICNIRP maximum permissible exposure limits and reports exposure ratios.
• occupational-exposure (0.72)
  Reports occupational exposure ratios and discusses proximity of workers to small-cell base stations.
• 5g-policy (0.64)
  Focuses on exposure near 5G NR small cells and implications for compliance with exposure limits.

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    "exposure": {
        "band": "RF",
        "source": "5G NR small cell base station",
        "frequency_mhz": null,
        "sar_wkg": null,
        "duration": null
    },
    "population": "Workers and members of the general public in proximity to 5G NR small-cell base stations (users and non-users)",
    "sample_size": null,
    "outcomes": [
        "RF-EMF field levels (worst-case and time-averaged) at 0.5–100 m",
        "Exposure ratios relative to ICNIRP maximum permissible exposure limits (occupational and general public)",
        "Estimated typical exposures for users vs non-users; effect of beamforming (AAS) vs traditional microcell"
    ],
    "main_findings": "RF-EMF measurements near two 5G NR base stations (one AAS/beamforming, one traditional microcell) under maximized downlink traffic load yielded maximum exposure ratios vs ICNIRP limits of 0.15 (occupational, at 0.5 m) and 0.68 (general public, at 1.3 m), i.e., below the limits. Typical user exposures were reported as 3–12 times lower than theoretical worst-case exposures, and exposures without any users were 4–9 times lower than typical user exposures; non-user exposure could be 5–30 times lower for an AAS base station and barely lower to 30 times lower for a traditional antenna, depending on user activity and beamforming.",
    "effect_direction": "no_effect",
    "limitations": [
        "Only two 5G NR base stations were measured (one AAS and one traditional microcell).",
        "Dynamic power control was not taken into account.",
        "Results depend on assumptions/conditions such as maximized downlink traffic load and user distribution/usage; actual exposure is described as statistical and variable."
    ],
    "evidence_strength": "low",
    "confidence": 0.7800000000000000266453525910037569701671600341796875,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "5G",
        "New Radio",
        "NR",
        "small cells",
        "base station",
        "microcell",
        "Advanced Antenna System",
        "AAS",
        "beamforming",
        "RF-EMF",
        "measurements",
        "downlink traffic load",
        "ICNIRP",
        "occupational exposure",
        "general public exposure",
        "exposure ratio"
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}

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