Timing advance group configurations and uplink transmission timings in a wireless device

1. A method comprising:

receiving, by a wireless device, configuration parameters of cells grouped into timing advance groups (TAGs), wherein the cells comprise:

downlink-uplink cells, each of the downlink-uplink cells having a configured uplink and a configured downlink; and

at least one downlink-only cell, each of the at least one downlink-only cell having a configured downlink with no configured uplink; and

wherein a TAG is configurable to consist of one or more downlink-only cells in response to the wireless device having a first capability, otherwise each TAG comprises one or more downlink-uplink cells in the downlink-uplink cells;

receiving at least one timing advance command (TAC) for a first TAG; and

applying the TAC to uplink transmission timing of at least one downlink-uplink cell in the first TAG.

2. The method of claim 1 , further comprising transmitting, to a base station, one or more parameters indicating the first capability.

3. The method of claim 1 , wherein the first TAG comprises a first subset of the cells, uplink transmission timing in the first TAG being derived employing a first cell in the first TAG.

4. The method of claim 1 , wherein time alignment timer of a second TAG is disabled when the second TAG consists of one or more downlink-only cells.

5. The method of claim 1 , wherein time alignment timer is not configured for a second TAG when the second TAG consists of one or more downlink-only cells.

6. The method of claim 1 , further comprising receiving a TAG index for a TAG.

7. The method of claim 1 , wherein the TAC comprises a TAG index and a timing advance value.

8. A method comprising:

receiving, by a wireless device, at least one message comprising configuration parameters of a plurality of cells grouped into a plurality of timing advance groups (TAGs),

wherein the plurality of cells consisting of:

a plurality of downlink-uplink cells, each of the plurality of downlink-uplink cells having a configured uplink and a configured downlink; and

at least one downlink-only cell, each of the at least one downlink-only cell having a configured downlink with no configured uplink; and

wherein a TAG is configurable to consist of one or more downlink-only cells in response to the one or more downlink-only cells being unlicensed cells, otherwise the TAG comprises one or more downlink-uplink cells in the plurality of downlink-uplink cells;

receiving at least one timing advance command (TAC) for a first TAG; and

applying the TAC to uplink transmission timing of at least one downlink-uplink cell in the first TAG.

9. The method of claim 8 , wherein the first TAG comprises a first subset of the plurality of cells, uplink transmission timing in the first TAG being derived employing a first cell in the first TAG.

10. The method of claim 8 , wherein time alignment timer of a second TAG is disabled when the second TAG consists of one or more downlink-only cells.

11. The method of claim 8 , wherein time alignment timer is not configured for a second TAG when the second TAG consists of one or more downlink-only cells.

12. The method of claim 8 , wherein the at least one message comprises a TAG index for a TAG.

13. The method of claim 8 , wherein the TAC comprises a TAG index and a timing advance value.

14. A system comprising:

a base station comprising:

one or more first processors; and

first memory storing first instructions that, when executed by the one or more first processors of the base station, cause the base station to:

transmit configuration parameters of cells grouped into timing advance groups (TAGs), wherein the cells comprise:

downlink-uplink cells, each of the downlink-uplink cells having a configured uplink and a configured downlink; and

at least one downlink-only cell, each of the at least one downlink-only cell having a configured downlink with no configured uplink; and

transmit at least one timing advance command (TAC) for a first TAG; and

a wireless device comprising:

one or more second processors; and

second memory storing second instructions that, when executed by the one or more second processors of the wireless device, cause the wireless device to:

receive the configuration parameters of the cells grouped into the TAGs, wherein a TAG is configurable to consist of one or more downlink-only cells in response to the wireless device having a first capability, otherwise each TAG comprises one or more downlink-uplink cells in the downlink-uplink cells; and

receive the at least one TAC; and

apply the TAC to uplink transmission timing of at least one downlink-uplink cell in the first TAG.

15. The system of claim 14 , wherein the second instructions, when executed by the one or more second processors, further cause the wireless device to transmit, to the base station, one or more parameters indicating the first capability.

16. The system of claim 14 , wherein the first TAG comprises a first subset of the cells, uplink transmission timing in the first TAG being derived employing a first cell in the first TAG.

17. The system of claim 14 , wherein time alignment timer of a second TAG is disabled when the second TAG consists of one or more downlink-only cells.

18. The system of claim 14 , wherein time alignment timer is not configured for a second TAG when the second TAG consists of one or more downlink-only cells.

19. The system of claim 14 , wherein the second instructions, when executed by the one or more second processors, further cause the wireless device to receive a TAG index for a TAG.

20. The system of claim 14 , wherein the TAC comprises a TAG index and a timing advance value.