rate Handover decision success rate 100.0 enabled Figure 12.36 Handover decision success rate and handover execution success rate before and after enabling ANR feature. Network-level daily statistics same time handover execution success rate improved further close to 99.6%. Therefore, ANR feature is excellent but the operation must be carefully controlled SO that it does not add all neighbours measured by the UEs. The addition of neighbours by ANR feature can be seen as increased handover attempts (comparing after ANR activation to before ANR activation) as shown in Figure 12.37. Figure 12.37 Number of handover attempts increase due to the activation of ANR LTE Small Cell Optimization Average number of late HO attempts to total number of HO attempts ratio Average number of successful RRC re-establishments to total number of HO attempts ratio Number of E-RAB drops to HO attempt ratio (%) Figure 12.38 Late handover to total number of handover attempts ratio and successful RRC re- establishment to total number of handover attempts as a function of the number of E-RAB drops to total number of handover attempts The handover attempts increased due to the ANR around four times during the highest traffic times (6-9 AM and 5-8 PM). This increase in signalling activity needs to be taken into account for the highest traffic cells and during the special events, that is, neighbour lists need to be further optimized for those cells. The MRO algorithms can be used to further improve the UE mobility performance and therefore the E-RAB performance. As shown in Figure 12.38 the bigger the share of late handovers the higher the amount of drops per handover attempt and the higher the amount of successful re-establishments. Therefore, by enabling the MRO algorithms the too late handover share could be reduced and the end-user-experienced quality improved. The end- user experienced quality here refers to dropped calls as well as the RRC re-establishments. The RRC re-establishments cause short break in connection which is experienced a