erference levels. LTE Small Cell Optimization Peak to average ratio (eNB level) E-RAB Incoming Outgoing Paging attempts releases setups handovers handovers Figure 13.41 Peak to average ratios for signalling actions per eNodeB, average is given based on 15-minute samples per eNodeB 13.5.1 Signalling Load The eNodeB limits for signalling load values are given as call setups per second or transactions per second and therefore the peak signaling load value per second during the event should be evaluated. Typically the statistics from eNodeBs are collected in 15-minute intervals containing sums of counters over the period. Then calculating any average per second values based on those 15-minute sums does not reflect the real peak value. Therefore, peak to average values are needed to multiply the average values calculated from 15-minute average to get the peak per second value. Figure 13.41 shows one example of the peak to average values for some signalling messaging averaged over the highest loaded eNodeBs. Peak value is the highest value per second during the measurement period and average per second is calculated based on 15-minute measurement period eNodeB level counters. For mass events the signalling load can be estimated per cell-based average number of RRC-connected users as shown in Figure 13.42. The signalling attempts per RRC-connected user decreases while the number of RRC-connected users increases. At low (~100-200) RRC- connected users per cell the average RRC attempts per RRC-connected user is between 42 and 48 but at high RRC-connected users (~300) the average RRC attempts per RRC-connected user is around 42. By combining the graphs in Figures 13.41 and 13.42 it is then possible to calculate the amount of signalling messages per second per eNodeB limit. The number of RRC-connected users can also be translated into number of subscribers as explained in Section 13.5.2. 13.5.2 RRC-Connected Users The peak number of RRC-connected users per cell needs to be properly set for mass event to avoid unnecessary RR