TE paging and RRC connection setup time, that is, several seconds. MSS needs to support the capability. The drawback is that after the paging response in LTE the call setup might fail at a later stage and the calling party may perceive this as a rejected call. 14.3.3 CSFB Call Setup Success Rate Average CSFB call setup success rate in case of redirect cannot be better than the average call setup rate in the target radio access. Therefore, increasing the CSFB call setup success rate boils down to improving the connection setup success rate in LTE and the target RAT; this can typically be improved only with basic physical RF and parameter optimization and possibly load balancing in the target RAT. In the case of CSFB PS handover it is the handover success rate that typically dominates the CSFB call setup success rate. Cell-level optimization of neighbour lists and target carrier (e.g. non-interfered target carrier) plays a significant role. It should be noted, however, that even if the PS HO fails, the call setup will be resumed by the UE at the expense of increased call setup delay and hence handover success rate is not equal to the call setup success rate. A specific use case is where the target layer has bad radio conditions, due to lack of coverage or interference. A typical example is a high-rise building without indoor cell where a blind redirect to a polluted 3G layer can result in call drop, degraded voice quality and possibly a follow-up handover to a cleaner 3G layer or 2G. For 3G target, utilizing Ec/NO measurement quantity and fine-tuned neighbour list with two or more target layers may help in this case. Besides cumbersome neighbour optimization, the obvious drawback is the increased call setup time due to UE measurements in LTE before handover can be triggered. 14.3.4 Return to LTE after CSFB Call After the CS call finishes, it is beneficial for the LTE-capable UE to return back to LTE, provided that sufficient coverage and quality are available. This can be accomplished via idle mode inter-RAT cell r