Implications of EMF Exposure Limits on Output Power Levels for 5G Devices Above 6 GHz

Spectrum is a scarce resource, and the interest for utilizing frequency bands above 6 GHz for future radio communication systems is increasing. The possible use of higher frequency bands implies new challenges in terms of electromagnetic field (EMF) exposure assessments since the fundamental exposure metric (basic restriction) is changing from specific absorption rate (SAR) to power density. In this study, the implication of this change is investigated in terms of the maximum possible radiated power (P_max) from a device used in close proximity to the human body. The results show that the existing exposure limits will lead to a non-physical discontinuity of several dB in P_max as the transition is made from SAR to power density based basic restrictions. As a consequence, to be compliant with applicable exposure limits at frequencies above 6 GHz, P_max might have to be several dB below the power levels used for current cellular technologies. Since the available power in uplink has a direct impact on the system capacity and coverage, such an inconsistency, if not resolved, might have a large effect on the development of the next generation cellular networks (5G).