FIG. 17 is a diagram illustrating an adaptive use of transmitter antenna diversity for a HARQ-ACK signal depending on whether or not a respective detected EPDCCH was transmitted with one ECCE or with multiple ECCEs, according to an embodiment of the present invention.

Referring to FIG. 17, a UE detects a localized EPDCCH associated with a PDSCH, in step 1710. In step 1720, it is determined whether the EPDCCH transmission consists of multiple LCCEs. If the EPDCCH transmission consists of multiple LCCEs, the UE transmits a respective HARQ-ACK signal using transmitter antenna diversity, in step 1730. The PUCCH resource for the first transmitter antenna is determined from a number of the first LCCE of the EPDCCH, n_LCCE. The PUCCH resource for the second antenna is determined from n_LCCE+1. If the EPDCCH transmission consists of a single LCCE, the UE transmits the respective HARQ-ACK signal using a single transmitter antenna, in step 1740.

When the PUCCH resources for HARQ-ACK signal transmission in response to PDCCH, distributed EPDCCH, and localized EPDCCH detections are at least partially shared, resource collision when using transmitter antenna diversity may become more difficult to avoid. However, the use of a HPRO field in DCI formats conveyed by EPDCCH can significantly alleviate scheduler restrictions for avoiding PUCCH resource collisions when transmitting HARQ-ACK signals using transmitter antenna diversity. The UE then determines a PUCCH resource for HARQ-ACK signal transmission from the second antenna as n_PUCCH=n_ECCE+HPRO+N_PUCCH^E.