Method and apparatus of configuring timing of uplink transmission

1. A method of configuring timing of an uplink (UL) transmission of a carrier aggregation (CA) system, the method comprising:

receiving, by a user equipment (UE), information related to a first time advance offset for the CA system which includes both at least one frequency division duplex (FDD) cell and at least one time division duplex (TDD) cell, wherein the first time advance offset is configured by a base station (BS) for a first secondary cell (Scell);

adjusting, by the UE, a starting timing of a UL subframe in a second Scell participating in the CA system based on a second time advance offset and the first time advance offset; and

transmitting data based on the adjusted starting timing of the UL subframe,

wherein the first Scell and the second Scell belong to a time advance group (TAG) to which a primary cell (Pcell) does not belong, and the first Scell is duplexed in a mode different from the second Scell.

2. The method of claim 1 , wherein:

adjusting, by the UE, the starting timing of the UL subframe in the second Scell comprises making the starting timing of the UL subframe of the UE in the second Scell (N TA +N TA offset )×T S seconds prior to a starting timing of a downlink (DL) subframe in the first Scell in the TAG to which the second Scell belongs, and

N TA denotes the first time advance offset configured for the first Scell and N TA offset denotes the second time advance offset for the second Scell.

3. The method of claim 1 , wherein information related to the second time advance offset is obtained from radio resource control (RRC) signaling sent by a primary cell (Pcell) participating in the CA system, from broadcast signaling from the second Scell, or from RRC signaling from the second Scell.

4. The method of claim 1 , wherein a starting timing of a UL subframe in another Scell participating in the CA system is adjusted by using the second time advance offset and the first time advance offset.

5. The method of claim 1 , wherein the second time advance offset has a value of 624.

6. The method of claim 1 , wherein the second time advance offset is pre-defined.

7. The method of claim 1 , wherein a random access preamble is transmitted at the starting timing of the UL subframe.

8. An apparatus comprising:

a transceiver configured to receive information related to a first time advance offset for a carrier aggregation (CA) system which includes both at least one frequency division duplex (FDD) cell and at least one time division duplex (TDD) cell, wherein the first time advance offset is configured by a base station (BS) for a first secondary cell (Scell); and

a controller including a processor and a memory, wherein the controller is configured to adjust a starting timing of an uplink (UL) subframe in a second Scell participating in the CA system by using a second time advance offset and the first time advance offset,

wherein the transceiver is configured to transmit data based on the adjusted starting timing of the UL subframe,

wherein the first Scell and the second Scell belong to a time advance group (TAG) to which a primary cell (Pcell) does not belong, and the first Scell is duplexed in a mode different from the second Scell.

9. The apparatus of claim 8 , wherein:

the controller is configured to make the starting timing of the UL subframe in the second Scell (N TA +N TA offset )×T S seconds prior to a starting timing of a downlink (DL) subframe in the first Scell in the TAG to which the second Scell belongs, and

N TA denotes the first time advance offset configured for the first Scell and N TA offset denotes the second time advance offset for the second Scell.

10. The apparatus of claim 8 , wherein information related to the second time advance offset is obtained from radio resource control (RRC) signaling sent by a primary cell (Pcell) participating in the CA system, from broadcast signaling from the second Scell, or from RRC signaling from the second Scell.

11. The apparatus of claim 8 , wherein a starting timing of a UL subframe in another Scell participating in the CA system is adjusted by using the second time advance offset and the first time advance offset.

12. The apparatus of claim 8 , wherein the second time advance offset has a value of 624.

13. The apparatus of claim 8 , wherein the second time advance offset is pre-defined.

14. The apparatus of claim 8 , wherein a random access preamble is transmitted at the starting timing of the UL subframe.