Method and apparatus for aggregating carriers in wireless communication systems

1. A method for transmitting an ACK/NACK (acknowledgement/not-acknowledgement) in a carrier aggregation system in which a primary cell and a secondary cell are aggregated, the method performed by a user equipment and comprising:

receiving data in a subframe n-k of the secondary cell; and

transmitting an ACK/NACK signal for the data in a subframe n of the primary cell,

wherein the primary cell uses a time division duplex (TDD) frame in which uplink subframes and downlink subframes are located at different times in the TDD frame,

wherein the secondary cell uses a frequency division duplex(FDD) frame in which uplink subframes and downlink subframes are located on two different frequencies, respectively, and

wherein when a UL-DL configuration for the primary cell is one of UL-DL configurations included in the table below, wherein D denotes a downlink subframe, S denotes a special subframe and U denotes an uplink subframe:

UL-DL

Subframe number

configuration

0

1

2

3

4

5

6

7

8

9

0

D

S

U

U

U

D

S

U

U

U

2

D

S

U

D

D

D

S

U

D

D

5

D

S

U

D

D

D

D

D

D

D

the subframe n and the subframe k are configured according to the table below:

UL-DL

Subframe n

Configuration

0

1

2

3

4

5

6

7

8

9

0

—

—

6, 5

5, 4

4

—

—

6, 5

5, 4

4

2

—

—

8, 7, 6,

—

—

—

—

8, 7, 6,

—

—

5, 4

5, 4

5

—

—

13, 12, 11,

—

—

—

—

—

—

—

10, 9, 8,

7, 6, 5, 4.

2. The method of claim 1 , further comprising:

receiving an uplink-downlink (UL-DL) configuration for the primary cell,

wherein the UL-DL configuration indicates for each subframe included in the TDD frame whether it is a downlink subframe, a special subframe or an uplink subframe, and

wherein a UL-DL configuration for the secondary cell is determined based on the UL-DL configuration for the primary cell.

3. The method of claim 1 , wherein the primary cell is a cell that performs an initial connection establishment process or a connection reestablishment process with a base station.

4. An apparatus for transmitting an ACK/NACK (acknowledgement/not-acknowledgement) in a carrier aggregation system in which a primary cell and a secondary cell are aggregated, the apparatus comprising:

a radio frequency (RF) unit that transmits and receives a radio signal; and

a processor operationally connected with the RF unit,

wherein the processor receives data in a subframe n-k of the secondary cell, and transmits an ACK/NACK signal for the data in a subframe n of the primary cell,

wherein the primary cell uses a time division duplex (TDD) frame in which uplink subframes and downlink subframes are located at different times in the TDD frame,

wherein the secondary cell uses a frequency division duplex(FDD) frame in which uplink subframes and downlink subframes are loacted on two different frequencies, respectively, and

wherein when a UL-DL configuration for the primary cell is one of UL-DL configurations included in the table below, wherein D denotes a downlink subframe, S denotes a special subframe and U denotes an uplink subframe:

UL-DL

Subframe number

configuration

0

1

2

3

4

5

6

7

8

9

0

D

S

U

U

U

D

S

U

U

U

2

D

S

U

D

D

D

S

U

D

D

5

D

S

U

D

D

D

D

D

D

D

the subframe n and the subframe k are configured according to the table below:

UL-DL

Config-

Subframe n

uration

0

1

2

3

4

5

6

7

8

9

0

—

—

6, 5

5, 4

4

—

—

6, 5

5, 4

4

2

—

—

8, 7, 6, 5, 4

—

—

—

—

8, 7, 6, 5, 4

—

—

5

—

—

13, 12, 11, 10,

—

—

—

—

—

—

 —.

9, 8, 7, 6, 5, 4

5. The apparatus of claim 4 , wherein the processor is further receives uplink-downlink (UL-DL) configuration for the primary cell,

wherein the UL-DL configuration indicates for each subframe included in the TDD frame whether it is a downlink subframe, a special subframe or an uplink subframe and

wherein an UL-DL configuration for the secondary cell is determined based on the UL-DL configuration for the primary cell.

6. The apparatus of claim 4 , wherein a UL-DL configuration for the primary cell is one of the UL-DL configurations included in the table below:

UL-DL

Subframe number

configuration

0

1

2

3

4

5

6

7

8

9

0

D

S

U

U

U

D

S

U

U

U

1

D

S

U

U

D

D

S

U

U

D

2

D

S

U

D

D

D

S

U

D

D

3

D

S

U

U

U

D

D

D

D

D

4

D

S

U

U

D

D

D

D

D

D

5

D

S

U

D

D

D

D

D

D

D

6

D

S

U

U

U

D

S

U

U

D.

7. The apparatus of claim 4 , wherein the primary cell is a cell that performs initial connection establishment process or connection reestablishment process with a base station.

8. The method of claim 1 , wherein a UL-DL configuration for the primary cell is one of the UL-DL configurations included in the table below:

UL-DL

Subframe number

configuration

0

1

2

3

4

5

6

7

8

9

0

D

S

U

U

U

D

S

U

U

U

1

D

S

U

U

D

D

S

U

U

D

2

D

S

U

D

D

D

S

U

D

D

3

D

S

U

U

U

D

D

D

D

D

4

D

S

U

U

D

D

D

D

D

D

5

D

S

U

D

D

D

D

D

D

D

6

D

S

U

U

U

D

S

U

U

D.