mprove and even the uplink data volume increases as shown in Figure 13.9. The PUSCH RSSI also decreases significantly when RRC connection setup attempts decrease. This behaviour of PUSCH SINR and RSSI compared to RRC connection setup attempts and uplink data volume means that very large portion of uplink interference is caused by signalling and can be explained by the UE transmission power control (TPC) behaviour for PUSCH for signalling messages. As explained in Chapter 12, message 1 and message 3 (i.e. preamble and RRC connection request message respectively) are following open-loop power control based on parameters given by the network plus power increase offsets for message 3 on top of message 1 power. Similarly, message 5 follows message 3 Capacity Optimization PUSCH SINR PUSCH RSSI Poly. (PUSCH SINR) Poly. (PUSCH RSSI) Uplink data volume (MB) Figure 13.9 Uplink data volume versus uplink (PUSCH) signal to interference and noise ratio (SINR) and uplink (PUSCH) received signal strength indicator (RSSI) per cell per 15-minute data samples transmission power as there are no PUSCH RSSI or SINR measurements available at the eNodeB for closed-loop power control to adjust the UE transmission power. Therefore, the UE transmission power should be minimized for message 1 and message 3 transmissions. More examples of power control impact on different performance indicators during mass event are shown in Section 13.3.3. 13.3.1 PUSCH Transmission Power Control The purpose of the uplink TPC is to maintain high enough energy per transmitted bit to fulfil certain quality of service requirement and on the other hand to minimize the inter- cell interference. The uplink TPC operation is presented in [1]. The GPP-specified [2] uplink transmitted power control scheme is based on open-loop and closed-loop power control as depicted in Figure 13.10. Note that Chapter 12 contains more details on uplink power control scheme and therefore here only the most important factors impacting on mass event performance are considered. The open-