on fixed parameter value. The actual resource allocation for message 5, that is, MCS and number of PRBs should be optimized together with the transmission power control in order to maximize the RRC connection setup success rate while minimizing the transmission power from the UE. The link adaptation can adjust the MCS (and number of PRBs) during retransmissions as message 5 is the very first message sent on dedicated control channel (DCCH) using acknowledged mode (AM) radio link control (RLC) protocol on signalling radio bearer one (SRB1). In addition to HARQ retransmissions, there are also RLC retransmissions and in between RLC transmissions the link adaptation can change the MCS and number of PRBs (in case of HARQ transmissions, the MCS and number of PRBs cannot change from the initial transmission). Therefore, the link adaptation operation must also be considered when optimizing message 5 decoding performance. Message 5 typically contains piggybacked NAS message; for example, in case of RRC connection setup initiated for the attach request, the attach request message is combined together with the RRC connection setup complete, hence the resource allocation for message 5 should be large enough for both RRC connection setup complete and possible NAS message. Figure 12.16 shows one example of RRC connection setup success rate improvement by parameter optimization to improve message 4 decoding at the UE and message 5 decoding at the eNodeB in coverage-limited cluster. The random access setup success rate and RRC connection setup success rate are highly correlated as shown in Figure 12.17. In high loaded cells (PRB utilization > -50%) the RRC connection setup success rate quickly degrades when random access setup success rate drops below 80%. Therefore, in order to maintain high RRC connection setup success rate during high load the random access setup success rate should be maintained above 80%. Both random access setup success rate and RRC connection setup success rate are impacted by the increase of inter-cell i