Random access process in carrier aggregation

1. A method comprising:

receiving, by a wireless device:

at least one radio resource control (RRC) message indicating a maximum counter value; and

a control order to transmit a preamble as a part of a random access (RA) procedure on a cell;

instructing, a physical layer by a medium access control (MAC) layer, to transmit the preamble on the cell; and

when a corresponding RA response is not received:

considering the RA procedure unsuccessfully completed if a preamble transmission counter reaches the maximum counter value regardless of whether the cell is a licensed or licensed-assisted-access (LAA) cell, wherein the preamble transmission counter is configured to count a number of physical layer transmissions of the preamble,

otherwise considering the RA procedure unsuccessfully completed if a preamble transmission opportunity counter reaches the maximum counter value and the cell is a LAA cell, wherein:

the preamble transmission opportunity counter is employed only if the cell is a LAA cell,

the preamble transmission opportunity counter is configured to be increased when the physical layer performs listen-before-talk (LBT) for transmission of the preamble; and

the preamble transmission opportunity counter is configured to limit a time duration that the preamble is used for the RA procedure on the cell.

2. The method of claim 1 , further comprising setting a preamble power parameter employing the preamble transmission counter.

3. The method of claim 1 , further comprising, in response to receiving the control order:

starting the preamble transmission counter; and

starting the preamble transmission opportunity counter.

4. The method of claim 1 , further comprising, when the cell is a LAA cell:

performing, by the physical layer, LBT for transmission of the preamble at a transmission opportunity;

transmitting, by the physical layer, the preamble if the LBT succeeds, otherwise dropping transmission of the preamble; and

receiving, by the MAC layer, a power ramping suspension indication from the physical layer when the transmission of the preamble is dropped due to a failure of the LBT.

5. A method of claim 1 , further comprising considering the RA procedure successfully completed when the wireless device receives the corresponding RA response.

6. The method of claim 5 , further comprising selecting RA resources for preamble transmission if:

the corresponding RA response is not received;

the preamble transmission counter is less than the maximum counter value; and

the preamble transmission opportunity counter is less than the maximum counter value.

7. The method of claim 1 , wherein the preamble transmission opportunity counter is configured to count a number of transmission opportunities of the preamble.

8. The method of claim 1 , further comprising monitoring a downlink channel for the corresponding RA response within a RA response window, the corresponding RA response comprising a preamble identifier that matches the preamble.

9. The method of claim 1 , wherein the control order is a physical downlink control channel (PDCCH) comprising a preamble index and a RA mask index.

10. The method of claim 1 , wherein the at least one RRC message further comprises:

configuration parameters of a plurality of cells comprising the cell;

RA resource information elements of a RA channel (RACH) on the cell;

a RA response window information element; and

a maximum RA transmission counter information element.

11. A method comprising:

receiving, by a wireless device, at least one radio resource control (RRC) message indicating a maximum counter value;

instructing, a physical layer by a medium access control (MAC) layer, to transmit a preamble as a part of a random access (RA) procedure on a licensed assisted access (LAA) cell;

performing a listen-before-talk (LBT) for transmission of the preamble at a transmission opportunity of the preamble;

when a corresponding RA response is not received:

increasing a preamble transmission counter when the LBT is successful;

increasing a preamble transmission opportunity counter when the LBT is performed regardless of success or failure of the LBT; and

considering the RA procedure unsuccessfully completed if the preamble transmission counter reaches the maximum counter value,

otherwise considering the RA procedure unsuccessfully completed if the preamble transmission opportunity counter reaches the maximum counter value.

12. The method of claim 11 , further comprising transmitting, by the physical layer, the preamble if the LBT succeeds, otherwise dropping transmission of the preamble.

13. The method of claim 11 , further comprising considering the RA procedure successfully completed when the wireless device receives the corresponding RA response.

14. The method of claim 11 , further comprising:

receiving a control order configured to initiate the RA procedure on the LAA cell;

starting the preamble transmission counter in response to receiving the control order; and

starting the preamble transmission opportunity counter in response to receiving the control order.

15. The method of claim 11 , further comprising setting a preamble power parameter employing the preamble transmission counter.

16. A wireless device comprising:

one or more processors; and

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

receive at least one radio resource control (RRC) message indicating a maximum counter value;

instruct, a physical layer by a medium access control (MAC) layer, to transmit a preamble as a part of a random access (RA) procedure on a licensed assisted access (LAA) cell;

perform a listen-before-talk (LBT) for transmission of the preamble at a transmission opportunity of the preamble;

when a corresponding RA response is not received:

increase a preamble transmission counter when the LBT is successful;

increase a preamble transmission opportunity counter when the LBT is performed regardless of success or failure of the LBT; and

consider the RA procedure unsuccessfully completed if the preamble transmission counter reaches the maximum counter value,

otherwise consider the RA procedure unsuccessfully completed if the preamble transmission opportunity counter reaches the maximum counter value.

17. The wireless device of claim 16 , wherein the instructions, when executed, further cause the wireless device to transmit, by the physical layer, the preamble if the LBT succeeds, otherwise dropping transmission of the preamble.

18. The wireless device of claim 16 , wherein the instructions, when executed, further cause the wireless device to consider the RA procedure successfully completed when the wireless device receives the corresponding RA response.

19. The wireless device of claim 16 , wherein the instructions, when executed, further cause the wireless device to:

receive a control order configured to initiate the RA procedure on the LAA cell;

start the preamble transmission counter in response to receiving the control order; and

start the preamble transmission opportunity counter in response to receiving the control order.

20. The wireless device of claim 16 , wherein the instructions, when executed, further cause the wireless device to set a preamble power parameter employing the preamble transmission counter.