 overlooking a bay of water, the number of interfering cells seen by the receiver is SO large that this fluctuation is averaged out and a stable interference power floor is effectively created. RSRQ could be an effective trigger in such cases, albeit there is a danger that the whole cell under interference could be emptied of UEs if the RSRQ trigger is set too high. The only solution to the root cause problem is physical RF optimization of the existing network or building local RF dominance by, for example, indoor solution or well-placed small cells. To proceed with the example, the uplink layer change trigger will be based on RSRP and noise rise, while for the downlink RSRQ could also be used. To add the impact of uplink noise rise to the uplink path loss calculations is readily done, since the noise rise is simply subtracted from the path loss target. The uplink noise rise in LTE can be much higher than in Rel99 WCDMA since there is no fast power control. Figure 15.13 shows an example simulation of uplink noise for full buffer data model where 20% of TTIs are fully utilized as a network average, corresponding to the boundary con- dition of 20% PRB utilization. In urban areas with small ISD the noise rise on 800 MHz can be quite high, since due to lower path loss UEs from several tiers away are still con- tributing to the uplink noise. Furthermore, in the example the non-optimal downtilt of 4 degrees is used in all cases; optimizing downtilts and uplink power control parameters would result in drastically reduced noise rise especially for the ISD of 500 metres scenario. Inter- ference rejection receivers and intelligent interference-aware power control at eNodeB could also help. For the purposes of this example uplink noise rise of 3 dB is assumed which is a compromise between different environments and also in line with the field experience from pre-launch optimized networks with similar parameters and low load. For urban area LTE800 with small ISD, the noise rise could be higher (if downtilts and power control