Random access preambles using transmit beams of a base station

1. A method comprising:

receiving, by a wireless device from a first base station, configuration parameters indicating:

a cell radio identifier of the wireless device; and

random access preambles of a cell of a second base station;

transmitting, to the second base station via the cell, one or more random access preambles of the random access preambles using transmit beams;

receiving at least one random access response identified by the cell radio identifier of the wireless device, wherein:

the at least one random access response comprises a first preamble identifier corresponding to a first random access preamble of the one or more random access preambles; and

the first random access preamble is transmitted by a first transmit beam of the transmit beams; and

transmitting, by the wireless device to the second base station, data using the first transmit beam.

2. The method of claim 1 , further comprising starting a timer in response to the transmitting the one or more random access preambles.

3. The method of claim 2 , further comprising monitoring a downlink control channel of the second base station for the at least one random access response.

4. The method of claim 1 , further comprising monitoring a downlink control channel of the second base station for the at least one random access response.

5. The method of claim 1 , wherein the at least one random access response comprises:

a medium access control subheader comprising the first preamble identifier; and

a medium access control random access response corresponding to the medium access control subheader.

6. The method of claim 5 , wherein the medium access control random access response comprises a timing advance command and an uplink grant.

7. The method of claim 1 , wherein the configuration parameters indicate a number of allowed transmissions of the one or more random access preambles.

8. The method of claim 7 , wherein a number of the one or more random access preambles is equal to or less than the number of allowed transmissions of the one or more random access preambles.

9. The method of claim 1 , wherein the cell radio identifier is a cell radio network temporary identifier.

10. The method of claim 1 , wherein the configuration parameters further indicate a handover to the second base station.

11. 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, from a first base station, configuration parameters indicating:

a cell radio identifier of the wireless device; and

random access preambles of a cell of a second base station;

transmit, to the second base station via the cell, one or more random access preambles of the random access preambles using transmit beams;

receive at least one random access response identified by the cell radio identifier of the wireless device, wherein:

the at least one random access response comprises a first preamble identifier corresponding to a first random access preamble of the one or more random access preambles; and

the first random access preamble is transmitted by a first transmit beam of the transmit beams; and

transmit, to the second base station, data using the first transmit beam.

12. The wireless device of claim 11 , wherein the instructions, when executed by the one or more processors, further cause the wireless device to start a timer in response to the one or more random access preambles being transmitted.

13. The wireless device of claim 12 , wherein the instructions, when executed by the one or more processors, further cause the wireless device to monitor a downlink control channel of the second base station for the at least one random access response.

14. The wireless device of claim 11 , wherein the instructions, when executed by the one or more processors, further cause the wireless device to monitor a downlink control channel of the second base station for the at least one random access response.

15. The wireless device of claim 11 , wherein the at least one random access response comprises:

a medium access control subheader comprising the first preamble identifier; and

a medium access control random access response corresponding to the medium access control subheader.

16. The wireless device of claim 15 , wherein the medium access control random access response comprises a timing advance command and an uplink grant.

17. The wireless device of claim 11 , wherein the configuration parameters indicate a number of allowed transmissions of the one or more random access preambles.

18. The wireless device of claim 17 , wherein a number of the one or more random access preambles is equal to or less than the number of allowed transmissions of the one or more random access preambles.

19. The wireless device of claim 11 , wherein the cell radio identifier is a cell radio network temporary identifier.

20. A system comprising:

a first base station; and

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, from the first base station, configuration parameters configuration parameters indicating:

a cell radio identifier of the wireless device; and

random access preambles of a cell of a second base station;

transmit, to the second base station via the cell, one or more random access preambles of the random access preambles using transmit beams;

receive at least one random access response identified by the cell radio identifier of the wireless device, wherein:

the at least one random access response comprises a first preamble identifier corresponding to a first random access preamble of the one or more random access preambles; and

the first random access preamble is transmitted by a first transmit beam of the transmit beams; and

transmit, to the second base station, data using the first transmit beam.