s' UL PRB utilization are hardly ever at 100% at the same time in real live networks as shown in Figure 13.18. Figure 13.18 shows that when the own cell UL PRB utilization increases the share of its neighbours which are having the same or higher UL PRB utilization also increases. For example, when own cell UL PRB utilization reaches 90-95% then 8% of its neighbours are having UL PRB utilization less or equal than 15%. And at the same 90-95% UL PRB utilization for own cell, 55% of its neighbours have higher than 80% DL PRB utilization at the same time. This means that in real networks the spectral efficiency can exceed the 3GPP limits due to the unbalanced load between the cells i.e. all cells (own cell and it's neighbors) are not having very high load at the same time. However, it should be noted that the UL PRB utilization imbalance seems to be much less compared to the DL as seen when comparing Figures 13.18 and 13.35. LTE Small Cell Optimization Low band (10 MHz) High band (10 MHz) A High band (20 MHz) Spectral efficiency per cell per hour (bit/s/Hz) Figure 13.17 Uplink spectral efficiency as a function of average PUSCH SINR (dB) for cells having 30% and above uplink PRB utilization over the measurement period UL PRB utilization <15% UL PRB utilization <30% UL PRB utilization <50% UL PRB utilization <80% Own cell UL PRB utilization Figure 13.18 Own cell UL PRB utilization as a function of neighbouring cell UL PRB utilization Capacity Optimization Closed-loop PC part updated P0_NOMINAL_PUSCH+PO_UE_PUCCH by eNodeB per UE basis Figure 13.19 3GPP Release 8-defined uplink transmission power control algorithm for PUCCH 13.3.2 PUCCH As explained in Chapter 12, the PUCCH power control should follow the strategy of PUSCH power control. The PUCCH power control formula is discussed more in detail in Chapter 12 and only the most important aspects in terms of mass event performance are discussed here. This means that PO_NOMINAL_PUCCH and P _UE_PUCCH in Figure 13.19 should be set following the similar strategy as used for P