This technical report describes evaluation methods of electromagnetic field (EMF) strengths from base station installed underground (underground base station), which is one of base stations considering the landscape, for compliance assessment regarding radio frequency (RF) exposure.

Conventional base stations emit radio waves from the antennas installed overhead toward ground surface. On the other hand, the underground base station emits radio waves from antennas installed underground toward above ground. The purpose of this report is to respond to the demands from mobile operators regarding evaluation methods of EMF strengths to determine the need for safety facilities for the underground base station of which situation of radio wave emission is different from that of conventional base stations.

Since there are many parts where the TR-T21 of the other technical report regarding evaluation methods of EMF strength from conventional base stations can be applied, this report applies the TR-T21 as much as possible and describes the part mainly specialized for the underground base station.