where N
DMRS=0,1,2,3 is the DMRS port number and N
PUCCHL is an offset signaled to the UEs by higher layer signaling (if it is different than N
PUCCH) It is noted that N
DMRS may also be limited to 0 or 1 and can have different sets of possible values for EPDCCH transmissions to a UE than for PDSCH transmissions to the same UE. For example, for EPDCCH transmissions to a UE, N
DMRS=0,1,2,3, while for PDSCH transmissions to the same UE, N
DMRS=0,1.
FIG. 13 is a diagram illustrating a PUCCH resource determination for HARQ-ACK signal transmission in response to an EPDCCH detection, according to an embodiment of the present invention.
Referring to FIG. 13, a first LCCE and DMRS port for transmission of a first EPDCCH to a first UE are, respectively, nLCCE and NDMRS1 1310, while a first LCCE and DMRS port for transmission of a second EPDCCH to a second UE are, respectively, nLCCE and NDMRS2 1320. The first UE determines a first PUCCH resource for a HARQ-ACK signal transmission in response to the detection of the first EPDCCH as nPUCCH(1)=nLCCE+NDMRS1+NPUCCHE 1330. The second UE determines a second PUCCH resource for a HARQ-ACK signal transmission in response to the detection of the second EPDCCH as nPUCCH(2)=nLCCE+NDMRS2+NPUCCHE 1340. Therefore, even through multiple EPDCCHs may have the same LCCE as the first one for their transmissions, a one-to-one mapping exists among the EPDCCHs 1350 and respective PUCCH resources 1360, and collisions can be avoided.
