stem information RNTI (SI-RNTI) for common search space. Based on hashing function there are six candidate positions defined for aggregation level 1 and aggregation level 2 and two candidate positions are defined for aggregation level 4 and aggregation level 8. This means that, for example, there can be maximum two UEs scheduled per TTI in case both of those UEs require aggregation level 8 for their resource allocation grants. Also due to the hashing algorithm the candidate positions of several UEs can be overlapping and therefore blocking of CCE allocations (using the required aggregation level) can occur even if all the CCEs are not used. The CCE allocation blocking increases rapidly during mass events due to the increased traffic and especially due to the CQI decrease and thus more aggregation level 8 is required as shown in Figure 13.39 below. The high aggregation level can be decreased by increasing the power of those CCEs used for UE requiring high aggregation level (doubling the aggregation level can be replaced by using the same aggregation level but 3 dB higher power) and therefore the CCE blocking, especially due to hashing algorithm, can be reduced. This type of mechanism requires advanced algorithms in the eNodeB SO that the power of CCEs used for the UEs requiring lower aggregation level than the allocated one can be re-allocated to UEs requiring higher aggregation level than the one available. If the downlink inter-cell interference can be improved the spectral efficiency will be improved as well as the PDCCH capacity in terms of number of UEs that can be scheduled per TTI. Figure 13.40 shows the average aggregation level as a function of CQI for the highest Control channel element allocation blocking Figure 13.39 Average channel quality indicator per cell per 15 minutes as a function of control channel element allocation blocking Capacity Optimization Low band (10 MHz) High band (10 MHz) High band (20 MHz) Linear (low band (10 MHz)) Linear (high band (10 MHz)) Linear (high band (20 MHz)) y = -0.545