nnot be done. This due to the fact that such simple scaling assumes that the uplink interference conditions do not change at all when the PRB utilization increases and such assumption is not correct. Therefore, in case the cell throughput performance indicator calculated using the simple formula described above the results should be analysed carefully taking into account the PRB utilization. Figure 13.15 shows the example of average throughput per user (calculated as described above) as a function of the number of RRC-connected users. The cells included into the analysis are high traffic cells for which PRB utilization is above 20% per 15-minute sample. It should be noted that all the carriers are not deployed on the same sites and the optimization is performed on carrier basis trying to achieve highest possible performance per carrier. As can be seen from Figure 13.15 the low band (700, 800 or 900 MHz) 10 MHz cells provide slightly worse average user throughput compared to the high band (1800, 2100 or 2600 MHz) LTE Small Cell Optimization Low band (10 MHz) High band (10 MHz) High band (20 MHz) Expon. (low band (10 MHz)) Expon. (high band (10 MHz)) Expon. (high band (20 MHz)) 10,000 = 18095.23e-0.02 7589.70e y = 2872.92e Average number of RRC connected users Figure 13.15 Average uplink throughput per user (kbps) as a function of the number of RRC-connected users per FD LTE cell, based on 15-minute statistics 10 MHz cells. The highest average user throughput can be achieved by the high band (1800, 2100 or 2600 MHz) 20 MHz cells. If uplink throughput limit is set to, for example, 500 kbps per user then that means that on average the analysed cells can support the following amount of RRC-connected users: 20 MHz high band FD LTE can support 180 RRC-connected users 10 MHz high band FD LTE can support 90 RRC-connected users 10 MHz low band FD LTE can support 58 RRC-connected users The throughput difference between 10 MHz low band and high band allocations comes from radio quality difference between the bands, that is, 