sion bandwidth, the UE transmit power at this point is almost 20 dBm which is near the maximum possible with 16QAM modulation. 13 As the path loss increases further (RSRP decreases) the link adaptation in the measured network starts reducing PRBs to maintain the received power target per PRB in the uplink. Hence in the measured network the link adaptation sacrifices bandwidth to maintain received power target per PRB. At this point the uplink SINR is about 19 dB which is the difference between target received power per PRB (P = -100 dBm) and the uplink thermal noise power per PRB, which is about - -119 dBm assuming eNodeB noise figure of 2.5 dB. Comparing Figure 15.9 at RSRP = -85 dBm to Figure 15.7 at SNR = 19 dB, it can be seen that the throughput is about 40 Mbps in both cases and hence at this operating point the uplink performance curves still coincide. Increasing path loss by 20 dB brings the RSRP down to about-105 dBm and SNR in Figure 15.7 to -1 dB. Now, comparing the performance in the two figures shows a 100% difference of about 4 Mbps in Figure 15.9 versus 8 Mbps in Figure 15.7. This difference is due to the different link adaptation configurations in the two cases. This illustrates that, for the uplink in particular, it can be dangerously misleading to blindly compare performance curves of different networks. Another point worth noting is the severe throughput limitation caused by the limited uplink transmission power. In the example of Figure 15.9 the maximum uplink transmit power is reached at RSRP = -85 dBm, below which the system peak throughput cannot be maintained anymore. Therefore, at RSRP of -115 dBm the uplink is 30 dB below the peak performance operation point. Uplink link adaptation attempts to compensate the missing power headroom of 30 dB either by reducing transmission bandwidth or by reducing MCS, or both. Regardless, the compensation works only up to a point and in many networks RSRP levels below -115 to -120 dBm start causing connectivity and throughput problems in the uplink. If dow