The ECCE aggregation levels that may be used for an EPDCCH transmission may vary per subframe in order to adjust to a respective varying number of REs available for EPDCCH transmission in respective PRBs assigned to a UE in a subframe. For example, in FIG. 4, REs available for localized EPDCCH transmissions in a PRB exclude REs used by a conventional DL control region in the first 3 OFDM symbols, and REs used for transmitting various RS types (DMRS, CRS, etc.). Therefore, in FIG. 4, a total number of REs available for localized EPDCCH transmissions in a PRB is equal to 96, and an LCCE size is equal to 24 REs for 4 LCCEs in a PRB. Assuming QPSK modulation conveying 2 bits per RE and typical payloads of DCI formats exceeding 40 bits, a resulting code rate for a DCI format transmission with an aggregation level of 1 LCCE is at least about 0.83 (40/(2*24)), which is typically too high to reliably convey a DCI format. Conversely, if only 1 OFDM symbol is used by a conventional DL control region, a total number of REs available for localized EPDCCH transmissions in a PRB is equal to 120, and an LCCE size is 30 REs for 4 LCCEs per PRB. In such case, a resulting code rate for transmitting a DCI format consisting of at least 40 bits with an aggregation level of 1 LCCE is at least about 0.67 (40/(2*30)), and the DCI format transmission can be reliably conveyed to UEs experiencing at least moderate DL SINRs. Therefore, depending on whether a number of REs per PRB is larger than or smaller than a threshold, ECCE aggregation levels used for a respective EPDCCH transmission can vary. This approach for varying the supported ECCE aggregation levels per subframe in order to account for a variable number of REs per PRB, when transmitting an EPDCCH from a NodeB and detecting an EPDCCH at a UE, is described in U.S. Patent Application No. 61/552,846, titled “Search Process for Physical Downlink Control Channels in a Communication System”.