Method and apparatus for supporting a control plane and a user plane in a wireless communication system

1. A method for supporting a control plane (C-plane) and a user plane (U-plane) in a wireless communication system supporting multiple carriers, performed by a wireless device, the method comprising:

receiving a signal to initiate inter-frequency measurement from a macro cell;

performing the inter-frequency measurement;

determining to configure a small cell for data transmission based on the inter-frequency measurement,

wherein the macro cell for the C-plane is aggregated as a primary serving cell (PCell), and the small cell for the U-plane is aggregated as a secondary serving cell (SCell),

wherein the PCell and the SCell are connected via X2 or Xa interface;

receiving system information of the small cell for the U-plane via the macro cell for the C-plane,

wherein the system information of the small cell for the U-plane is assigned by the C-plane with one of a Cell Radio Network Temporary Identifier (C-RNTI) and a new Identifier (ID) for the U-Plane selection; and

determining whether the system information between a primary serving cell (PCell) and a secondary serving cell (SCell) are same or different.

2. The method of claim 1 , further comprising:

configuring a measurement object for the inter-frequency measurement from the signal, and

triggering the inter-frequency measurement by receiving a downlink control information (DCI) through a physical downlink control channel (PDCCH) or optionally an Enhanced PDCCH (EPDDCH).

3. The method of claim 2 , further comprising:

performing the inter-frequency measurement for a duration C after triggering the inter-frequency measurement at n+4th subframe, and herein the C is greater than 5 msec.

4. The method of claim 2 , the receiving the signal comprising:

the signal includes at least one of a center frequency, a measurement period, a Signal to Interference plus Noise Ratio(SINR) threshold, a number of reports, a desired load, a desired QoS level.

5. The method of claim 2 , the configuring step further comprising:

setting a threshold or a selection criteria for a radio resource management (RRM) report from the signal.

6. The method of claim 1 , further comprising:

determining information including a load information or an quality related information to be used a cell selection for the U-Plane, and

wherein the information is transmitted by a discovery channel via the macro cell or the small cell selectively by confirming load of the small cell.

7. The method of claim 6 , further comprising:

determining to use the information to prune a choice of the small cell for the U-plane before reporting the cell selection result to the macro cell for the C-plane.

8. The method of claim 1 , further comprising:

determining to reuse uplink frequency of the macro cell for downlink and/or uplink transmission of the small cell.

9. The method of claim 8 , further comprising:

the small cell is applied to Time Division Duplex(TDD) scheme.

10. The method of claim 8 , further comprising:

determining to not transmit data transmission on a subset of subframes configured by the macro cell.

11. The method of claim 10 , the determining further comprising:

determining whether at least one subframe in a radio frame is reserved for the macro cell, and

determining to not use for the downlink or uplink transmission of the small cell,

wherein the at least one subframe is reserved for the macro cell to transmit uplink transmission, the uplink transmission includes an Hybrid Automatic Repeat Request (HARQ) acknowledgement (ACK)/not-acknowledgement (NACK) or Channel State Information (CSI).

12. The method of claim 10 , the determining further comprising:

determining whether at least one subframe in a radio frame is reserved for the macro cell,

determining whether the at least one subframe is configured for a restricted radio resource management (RRM) measurement for the SCell, and

determining to perform radio resource monitoring on the PCell not by using the at least one subframe for the downlink or uplink transmission of the small cell,

wherein the restricted RRM measurement for the SCell is configured from the measurement object for the inter-frequency measurement.

13. A wireless device for supporting a control plane (C-plane) and a user plane (U-plane) in a wireless communication system supporting multiple carriers, comprising:

a radio frequency unit for receiving a radio signal; and

a processor, operatively coupled with the radio frequency unit, configured to:

receive a signal to initiate inter-frequency measurement from a macro cell,

perform the inter-frequency measurement, and

determine to configure a small cell for data transmission based on the inter-frequency measurement,

wherein the macro cell for the C-plane is aggregated as a primary serving cell (PCell), and the small cell for the U-plane is aggregated as a secondary serving cell (SCell),

wherein the PCell and the SCell are connected via X2 or Xa interface,

receive system information of the small cell for the U-plane via the macro cell for the C-plane,

wherein the system information of the small cell for the U-plane is assigned by the C-plane with one of a Cell Radio Network Temporary Identifier (C-RNTI) and a new Identifier (ID) for the U-Plane selection, and

determine whether the system information between a primary serving cell (PCell) and a secondary serving cell (SCell) are same or different.