Method for enhancing small cell

1. An inter-site carrier aggregation (CA) method performed in a terminal interworking with a first base station and a second base station, the method comprising:

receiving physical downlink control channels (PDCCHs) or enhanced physical downlink control channels (EPDCCHs) for scheduling physical downlink shared channels (PDSCHs) of cells constituting a primary cell group (PCG) from the first base station, the PCG comprising a first primary cell and one or more secondary cells;

receiving PDCCHs or EPDCCHs for scheduling PDSCHs of cells constituting a secondary cell group (SCG) from the second base station, the SCG comprising a second primary cell and one or more secondary cells;

receiving the PDSCHs by using the cells constituting the PCG;

receiving the PDSCHs by using the cells constituting the SCG;

transmitting physical uplink control channels (PUCCHs) including acknowledgment information for the PDSCHs received by using the cells constituting the PCG through the first primary cell; and

transmitting PUCCHs including acknowledgement information for the PDSCHs received by using the cells constituting the SCG through the second primary cell.

2. The inter-site CA method according to claim 1 , further comprising:

receiving PDCCHs or EPDCCHs for scheduling physical uplink shared channels (PUSCHs) of the cells constituting the PCG from the first base station;

receiving PDCCHs or EPDCCHs for scheduling PUSCHs of the cells constituting the SCG from the second base station;

transmitting the PUSCHs of the cells constituting the PCG through the cells constituting the PCG; and

transmitting the PUSCHs of the cells constituting the SCG through the cells constituting the SCG.

3. The inter-site CA method according to claim 1 , wherein the terminal receives configuration information for the PCG, the SCG, and the second primary cell from the first base station via Radio Resource Control (RRC) signaling.

4. The inter-site CA method according to claim 1 , wherein the cells constituting the primary cell group are cells managed by the first base station, and the cells constituting the secondary cell group are cells managed by the second base station.

5. The inter-site CA method according to claim 1 , wherein the cells constituting the primary cell group are macro cells, and the cells constituting the secondary cell group are small cells.

6. The inter-site CA method according to claim 1 , wherein the terminal monitors PDCCHs or EPDCCHs set with a System Information-Radio Network Temporary Identity (SI-RNTI) on the first primary cell, and the terminal does not monitor PDCCHs or EPDCCHs set with the SI-RNTI on the second primary cell.

7. An inter-site carrier aggregation (CA) method performed in a second base station interworking with a terminal and a first base station, the first base station managing a primary cell group (PCG) comprising a first primary cell and one or more secondary cells, the method comprising:

transmitting, to the terminal, physical downlink control channels (PDCCHs) or enhanced physical downlink control channels (EPDCCHs) for scheduling physical downlink shared channels (PDSCHs) of cells constituting a secondary cell group (SCG), the SCG comprising a second primary cell and one or more secondary cells;

transmitting, to the terminal, the PDSCHs by using the SCG;

receiving, from the terminal, physical uplink control channels (PUCCHs) including acknowledgment information for the PDSCHs transmitted by using the SCG through the second primary cell

wherein configuration information for the PCG, the SCG and the second primary cell is transmitted to the terminal from the first base station via Radio Resource Control (RRC) signaling.

8. The inter-site CA method according to claim 1 , further comprising:

receiving a PDCCH including downlink control information (DCI) of format 3/3A for transferring a power control command for the PUCCHs of the PCG through the first primary cell; and

receiving a PDCCH including DCI of format 3/3A for transferring a power control command for the PUCCHs of the SCG through the second primary cell.

9. The inter-site CA method according to claim 1 , further comprising:

receiving a PDCCH including downlink control information (DCI) of format 3/3A for transferring a power control command for the PUCCHs of the PCG through the first primary cell; and

receiving a PDCCH including DCI of format 3/3A for transferring a power control command for the PUCCHs of the SCG through the second primary cell.

10. The inter-site CA method according to claim 7 , wherein the terminal monitors PDCCHs or EPDCCHs set with a Paging-Radio Network Temporary Identity (P-RNTI) on the first primary cell, and the terminal does not monitor PDCCHs or EPDCCHs set with the P-RNTI on the second primary cell.

11. The inter-site CA method according to claim 7 , wherein the cells constituting the PCG are macro cells, and the cells constituting the SCG are small cells.

12. The inter-site CA method according to claim 7 , further comprising:

transmitting a PDCCH including downlink control information (DCI) of format 3/3A for transferring a power control command for the PUCCHs of the SCG through the second primary cell.

13. The inter-site CA method according to claim 7 , further comprising:

transmitting a PDCCH including downlink control information (DCI) of format 3/3A for transferring a power control command for the PUSCHs of the SCG through the second primary cell.

14. The inter-site CA method according to claim 7 , wherein PDCCHs or EPDCCHs set with a System Information-Radio Network Temporary Identity (SI-RNTI) are not monitored by the terminal on the second primary cell.

15. The inter-site CA method according to claim 7 , wherein PDCCHs or EPDCCHs set with a Paging-Radio Network Temporary Identity (P-RNTI) are not monitored by the terminal on the second primary cell.