dth available the more downlink data volume can be delivered with certain CQI value and therefore the slope is much improved for high band 20 MHz bandwidth compared to 10 MHz bandwidth cells (also note that the transmission power per sub-carrier is the same regardless of the carrier bandwidth). 13.4.2 Physical Downlink Control Channel PDCCH is used to deliver all the resource allocation grants (number of allocated PRBs, MCS, used transmission mode, etc.) for PDSCH and PUSCH; therefore, the capacity of PDCCH defines the amount of UEs that can be scheduled in single TTI. The PDCCH contains CCEs and each CCE is formed from nine resource-element groups and the total size is 36 quadrature phase shift keying (QPSK) symbols, that is, 72 bits. The resource allocation grants, called DCI messages, are then mapped onto one or several CCEs depending on the coding rate required for successful reception by the UE. In case low coding rate is needed then several CCEs might be needed and hence aggregation of CCEs is needed. The DCIs are fixed in terms of size and purpose according to [2] (uplink resource allocation grant, downlink resource allocation grant Capacity Optimization for dual stream and SO on) and the level of aggregation is fixed to steps of 1, 2, 4 or 8 CCEs per DCI. This is done in order to reduce the UE complexity to decode the DCIs without any prior knowledge of what to expect, that is, UE is required to perform blind decoding of several different DCIs with different aggregation level per each TTI. PDCCH CCEs are split into two groups of CCEs: UE-specific search space CCEs are used for DCIs that are UE specific and therefore meant for only single and known UE. The aggregation level can be 1, 2, 4 or 8 depending on the requirement per UE. Common search space CCEs are used for common DCIs that are targeted to be received by all the UEs under the cell, for example, for paging message, for system information or for message 2 resource allocation grant delivery. The aggregation level can be either 4 or 8. According to [