Multi-Objective Optimisation of Human Exposure for Various 5G Network Topologies in Switzerland

German Castellanos, Simon De Ghesellea, Luc Martens, Niels Kuster, Wout Joseph, Margot Deruycka, and Sven Kuehn, Computer Networks, 24 October 2022, Volume 216, Article No. 109255, online 8 August 2022; doi: 10.1016/j.comnet.2022.109255

The constant increase in the amount of user capacity required and the evolution of wireless network technologies impact the exposure that users experience from wireless networks. In this paper, various 5G network topologies are evaluated regarding human exposure, mobile communication quality, and sustainability. We assess human exposure, based on a novel exposure ratio (ER) metric, in 5G networks that include massive multiple-input multiple-output (MaMIMO) and compare the findings to those under conditions of exposure to existing 4G deployments in three environments in Switzerland. The quality and sustainability of mobile communication are evaluated by extrapolating data rates from mobile operators to the year 2030. A multi-objective optimization algorithm is implemented to design the 5G network topologies, maximizing the user coverage while minimizing the downlink (DL) and uplink (UL) exposure. An extensive set of simulations were investigated in three municipalities, with three operators plus one unified network, under conditions of three use cases (UL/DL data rates), in three scenarios (indoor and outdoor coverage), and with two optimization methods. The study results confirm that human exposure in a 5G network is dominated by the UL being 10× greater than the DL exposure. Furthermore, comparison of 5G deployment at 10× the traffic capacity of a real 4G network, DL exposure increases by 36% on average, while UL exposure decreases by up to 75% depending on the scenario. Regarding indoor coverage versus outdoor only, our results show that DL exposure can be reduced by a factor of 10 if only outdoor coverage is targeted. Finally, a conclusion from the study is that, from the perspective of human exposure, the ideal network will be based on 5G MaMIMO deployment and will be optimized for both UL and DL exposure.

The scientific and technical impact of the study can be summarized as:

• The personal dose attributable to the user’s handheld device in 5G mobile networks, on average, dominates the dose from the base station network by the same ratio found for 4G networks
• Full deployment of 5G networks will on average require three times as many base stations than 4G networks to meet the targeted 10× increase in capacity
• The introduction of MaMIMO base stations in 5G network will reduce the average human exposure in both DL and UL scenarios
• Separation of indoor and outdoor coverage can reduce the dose induced by the base station network however does not significantly affect the dose from the user’s handheld device
• Separation of indoor and outdoor networks may be beneficial in locations where strong path loss is expected, e.g., large buildings and underground facilities

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