The increased likelihood of a localized first EPDCCH transmission being over a single LCCE places strong restrictions in a use of transmitter antenna diversity for a respective HARQ-ACK signal when the conventional method is used to derive a PUCCH resource for the second antenna. This is because this second resource corresponds to the next LCCE, after the first LCCE of the first EPDCCH transmission, which is likely to be the first LCCE of a second EPDCCH transmission. PUCCH resource collision will then occur unless the second EPDCCH is not associated with a PDSCH. However, this is often not possible as DL traffic is typically larger than UL traffic and channel state information required by a NodeB to transmit localized EPDCCHs is associated with PDSCH transmissions and not with PUSCH transmissions.

In a first approach, transmitter antenna diversity for a HARQ-ACK signal from a UE configured to use it is adaptively applied depending on whether the detected EPDCCH is a distributed or a localized one. In the former case, a UE transmits a HARQ-ACK signal using transmitter antenna diversity. In the latter case, a UE transmits a HARQ-ACK signal using a single transmitter antenna (predetermined or UE selected).

FIG. 16 is a diagram illustrating an adaptive use of antenna diversity for transmitting an HARQ-ACK signal in response to an EPDCCH detection depending on whether the EPDCCH transmission is localized or distributed, according to an embodiment of the present invention.