Regardless of whether spatial multiplexing is used for EPDCCH transmissions or transmitter antenna diversity is used for HARQ-ACK signal transmissions in response to an EPDCCH detection associated with a PDSCH, the channelization of respective PUCCH resources needs to be defined. These PUCCH resources in response to detections of EPDCCHs and in response to detections of PDCCHs can be shared or separate. Moreover, these PUCCH resources in response to detections of distributed EPDCCHs and in response to detections of localized EPDCCHs can be also shared or separate. In general, separate PUCCH resources increase UL overhead since the number of PDSCHs per subframe does not significantly vary regardless of whether the scheduling is only by PDCCHs, only by EPDCCHs, or by both.

In case a PUCCH resource n_PUCCH, in response to an EPDCCH detection associated with a PDSCH, is implicitly derived as a function of the first ECCE n_ECCE and a N_PUCCH^E parameter configured by higher layer signaling, n_PUCCH^E=f(n_ECCE)=n_ECCE+N_PUCCH^E, collisions among PUCCH resources used in response to PDCCH and EPDCCH detections by different UEs can be avoided by either one of the following approaches:

• a) The values of N_PUCCH and N_PUCCH^E are such that different PUCCH resources are always used for HARQ-ACK signal transmissions corresponding to PDCCH and EPDCCH detections, respectively.