rleaving of the REGs is performed using a sub-block interleaver that is configured on a cell-specific basis. Note that the number of control channel elements or the number of control channel symbols in the subframe is transmitted by the eNB in every subframe. Since multiple control channel elements can be combined in order to reduce the effective coding rate, a UE control channel assignment would then be based on channel quality information reported. The UE monitors a set of candidate control channels in the common and/or UE-specific search spaces, as shown in Table 9-23, which may be configured by higher layer signaling. The size of the control channel elements varies with different bandwidth allocation and is a multiple of 6. It may be noted that 1, 2, 4, and 8 control channel elements can be aggregated to obtain approximate code rates of 2/3, 1/3, 1/6, and 1/12 (i.e., code repetition). The control region consists of a set of CCEs numbered from 0 to NCCE - 1, where NCCE is the total number of CCEs in the control region of subframe k. The UE monitors a set of PDCCH candidates for control information in every non-DRX subframe, where monitoring implies attempting to decode each of the PDCCHs in the set according to all the monitored DCI formats. The set of PDCCH candidates to monitor are defined in terms of search spaces, where a search space at an aggregation level L = 1, 2, 4, 8 is defined by a set of PDCCH candidates [109]. The UE is required to monitor one common search space at each of the aggregation levels 4 and 8, and one UE-specific search space at each of the aggregation levels 1, 2, 4, 8. The common and UE- specific search spaces may overlap. The aggregation levels defining the search spaces are listed in Table 9-23. The DCI formats that the UE monitors depend on the configured transmission mode. mentioned earlier, a physical control channel is transmitted on an aggregation of one or several consecutive CCEs, where a control channel element corresponds to nine resource element groups. The number of reso