## 4 Discussion  
Measurement data of the directional time-averaged transmit power in a commercial 5G network show that the actual values are well below the (theoretical) maximum obtained assuming peak power transmission for each beam. Telstra was among the first operators worldwide launching 5G, and the amount of traffic, which is carried, is therefore expected to be representative of the state-of-the-art 5G networks. Nevertheless, 5G NR is comparably new with respect to other existing mobile technologies, such as LTE and WCDMA, and the number of devices supporting 5G is expected to grow in the future. Since \(P_{\text{avg}}\) is directly related to the amount of downlink traffic, the total (cell-wide) six-minute time-averaged transmit power is expected to increase. At the same time, more users will result in an even larger spread of the energy over the antenna scan range, which will contribute to a reduction of \(G_{\text{avg}}\) with respect to the peak envelope gain. Therefore, \(EIRP_{\text{act}}\) is likely not to increase substantially when increasing the number of users. This is shown in Figure 6, in which \(EIRP_{\text{act}}\) for the investigated BSs is given as a function of the scheduled users in a six-minute interval. The blue solid line shows the mean value among all \(EIRP_{\text{act}}\) samples corresponding to the same number of served UEs. The red dotted line shows the maximum \(EIRP_{\text{act}}\) among these samples. The value of \(EIRP_{\text{act}}\) is normalized with respect to the EIRP envelope of the theoretical maximum, and for each time \(t\), it is determined in the angular direction \((\varphi,\theta)\), for which the ratio of \(EIRP_{\text{act}}(\varphi,\theta,t)\) to the maximum EIRP envelope is the largest. In order to correctly interpret Figure 6, it should be observed that \(P_{\text{avg}}\) (for each BS) in every fifteen-minute interval was conservatively approximated with the maximum value from the distribution of the reported six-minute time-averaged transmit power. Therefore, every six-minute averaging-period within fifteen minutes was assumed to be characterized by the same \(P_{\text{avg}}\) (disregarding of the number of users). This likely leads to a relatively large overestimate of \(P_{\text{avg}}\) and therefore \(EIRP_{\text{act}}\) when the number of users is low, and it shows that the values reported in Table 1 might therefore be overestimated. In addition, as 99% of the collected \(P_{\text{avg}}\) samples belonged to the bin corresponding to the lowest transmit power utilization (0-2.5% of the maximum), variations within this range of utilizations were  
Figure 6: \(EIRP_{\text{act}}\) as a function of the number of served users within the six-minute intervals. The red dashed line shows the maximum value among the \(EIRP_{\text{act}}\) samples, while the blue solid line corresponds to the mean. \(EIRP_{\text{act}}\) is normalized to the envelope of the theoretical maximum EIRP. not detected. As a result, while \(P_{\text{avg}}\) as used in Equation (1) is substantially constant, the spatial spread of energy (represented by \(G_{\text{avg}}\)) will increase with increasing the number of users leading to a reduction of \(E\!IRP_{\text{act}}\). 5G NR massive MIMO BSs can also support a larger number of beams compared with the 8 CSI-RS ports codebook-based beamforming software, which was running on the investigated sites (e.g., based on 16 CSI-RS or 32 CSI-RS [14]). In addition to narrower beams, such configurations might also support steering of energy in elevation and not just within the azimuth plane. Moreover, if reciprocity-based beamforming (i.e., non-codebook) is supported, sounding reference signals transmitted by the UEs will be used by the BS to estimate the radio channel, allowing energy to be transmitted in several different paths rather than in specific directions. By means of reciprocity-based beamforming, BSs might also simultaneously send different layers in separate beams to different users using the same time and frequency resource (multi-user MIMO).