+ NAS message S1AP : Initial UE Message + Service Request Security Procedures and NAS Procedures S1AP : Initial Context Setup Request PDCCH/DCI2/C - RNTI; PDSCH/DL- SCH/DCCH/SRB1 : RRC Connection Reconfiguration PUCCH: Scheduling Request PDCCH/DCI0/C-RNTI PUSCH/UL-SCH/DCCH/SRB1: RRC Reconfiguration Complete S1AP : Initial Context Setup Response Figure 12.8 Call setup signalling MSG1 - RACH: RA Preamble MSG2 - PDCCH/DCI1C/RA-RNTI ; PDSCH/DL-SCH/CCCH/SRB0 MSG3 - PUSCH/UL-SCH/CCCH/SRB0: RRC Connection Request MSG4 - PDCCH/DCI1A/T-C-RNTI ; PDSCH/DL- SCH/CCCH/SRB0: Contention Resolution + RRC Connection Setup PUCCH: Scheduling Request PDCCH/DCI0/C-RNTI MSG5 - PUSCH/UL-SCH/DCCH/SRB1 : RRC Connection Setup Complete + NAS message Figure 12.9 Radio resource control connection establishment LTE Small Cell Optimization hence the optimization of initial transmission power level, number of repetitions, timer values, initial PDCCH control channel element (CCE) aggregation level and PDSCH coding rates as well as initial modulation and coding scheme (MCS) selection both in uplink and in downlink during the call setup is very important. All these aspects are discussed in the following sections. As random access signalling is part of RRC connection setup signalling and therefore part of call setup signalling, poor random access setup success rate can cause poor overall CSSR. Also random access signalling is part of handover procedure and therefore call setup and handover procedures share large number of parameters which are used for selection of transmission power levels and capacity allocations. Hence, poor random access signalling performance causes poor call setup success performance and poor handover performance and eventually poor dropped call performance. Handover procedure is explained in Section 12.5.1. In the following the call setup procedure analysis and optimization actions are split into the random access setup, RRC setup and E-RAB setup and each of those phases is discussed in separate sections. 12.4.1 Random Access 