E
?
-
?
CCE
2
?
+
N
PUCCH
E
.
FIG. 18 is a diagram illustrating an adaptive functionality for a UE to determine a resource for a HARQ-ACK signal transmission in response to an EPDCCH detection, according to an embodiment of the present invention.
Referring to FIG. 18, a DCI format associated with PDSCH scheduling to a UE through a respective EPDCCH is transmitted with an aggregation level of one ECCE, in step 1810 (as determined by a UE from a number of REs available for EPDCCH transmission in a PRB in a respective subframe). A UE uses the first (lowest) ECCE index, nECCE, to determine a resource for a respective HARQ-ACK signal transmission, in step 1820. Conversely, a same DCI format is only transmitted through an EPDCCH using an aggregation level of at least two ECCEs, in step 1830. A respective resource for a HARQ-ACK signal transmission is determined as in the case of an aggregation level of one ECCE by additionally subtracting
from nECCE or, equivalently, using
