Secondary base station change

1. A method comprising:

receiving, by a first base station from a second base station, at least one first message indicating a first secondary base station addition request for a wireless device, wherein the at least one first message comprising a base station identifier of a third base station that the second base station has a backhaul interface with;

transmitting, by the first base station to the second base station, a second message indicating an acceptance of the first secondary base station addition request;

receiving, by the first base station from the wireless device, a measurement report for one or more cells of the third base station;

determining, by the first base station, a secondary base station change for the wireless device to the third base station based on the measurement report and the at least one first message; and

transmitting, by the first base station to the second base station, a third message indicating a request of the secondary base station change, wherein the third message comprises the base station identifier of the third base station.

2. The method of claim 1 , wherein the measurement report comprises at least one of:

a reference signal received power; or

a reference signal received quality.

3. The method of claim 1 , wherein the at least one first message comprises at least one of:

an X2 interface setup request message;

an X2 interface setup response message;

a base station configuration update message;

a secondary base station addition request message; or

a secondary base station modification request message.

4. The method of claim 1 , wherein the backhaul interface comprises an X2 interface between the second base station and the third base station.

5. The method of claim 1 , wherein the at least one first message comprises at least one of:

a wireless device identifier of the wireless device;

one or more bearer identifiers of one or more bearers associated with the wireless device;

a measurement result of at least one first cell of the first base station; or

at least one second cell identifier of at least one second cell of the second base station.

6. The method of claim 1 , wherein the third message further comprises a wireless device identifier of the wireless device.

7. The method of claim 1 , wherein the second base station:

transmits, to the third base station and in response to receiving the third message, a fourth message indicating a second secondary base station addition request for the wireless device;

receives, from the third base station, a fifth message indicating an acceptance of the second secondary base station addition request; and

transmits, to the first base station and in response to receiving the fifth message, a sixth message indicating a response for the third message, wherein the first base station releases a wireless device context of the wireless device based on the sixth message.

8. A base station comprising:

one or more processors; and

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

receive, from a second base station, at least one first message indicating a first secondary base station addition request for a wireless device, wherein the at least one first message comprising a base station identifier of a third base station that the second base station has a backhaul interface with;

transmit, to the second base station, a second message indicating an acceptance of the first secondary base station addition request;

receive, from the wireless device, a measurement report for one or more cells of the third base station;

determine a secondary base station change for the wireless device to the third base station based on the measurement report and the at least one first message; and

transmit, to the second base station, a third message indicating a request of the secondary base station change, wherein the third message comprises the base station identifier of the third base station.

9. The base station of claim 8 , wherein the measurement report comprises at least one of:

a reference signal received power; or

a reference signal received quality.

10. The base station of claim 8 , wherein the at least one first message comprises at least one of:

an X2 interface setup request message;

an X2 interface setup response message;

a base station configuration update message;

a secondary base station addition request message; or

a secondary base station modification request message.

11. The base station of claim 8 , wherein the backhaul interface comprises an X2 interface between the second base station and the third base station.

12. The base station of claim 8 , wherein the at least one first message comprises at least one of:

a wireless device identifier of the wireless device;

one or more bearer identifiers of one or more bearers associated with the wireless device;

a measurement result of at least one first cell of the base station; or

at least one second cell identifier of at least one second cell of the second base station.

13. The base station of claim 8 , wherein the third message further comprises a wireless device identifier of the wireless device.

14. The base station of claim 8 , wherein the second base station:

transmits, to the third base station and in response to receiving the third message, a fourth message indicating a second secondary base station addition request for the wireless device;

receives, from the third base station, a fifth message indicating an acceptance of the second secondary base station addition request; and

transmits, to the base station and in response to receiving the fifth message, a sixth message indicating a response for the third message, wherein the base station releases a wireless device context of the wireless device based on the sixth message.

15. A method comprising:

transmitting, by a second base station to a first base station, at least one first message indicating a first secondary base station addition request for a wireless device, wherein the at least one first message comprising a base station identifier of a third base station that the second base station has a backhaul interface with;

receiving, by the second base station from the first base station, a second message indicating an acceptance of the first secondary base station addition request; and

receiving, by the second base station from the first base station, a third message indicating a request of a secondary base station change for the wireless device to the third base station, wherein:

the third message comprises the base station identifier of the third base station; and

the request of the secondary base station change is based on the at least one first message and a measurement report of the wireless device for one or more cells of the third base station.

16. The method of claim 15 , wherein the measurement report comprises at least one of:

a reference signal received power; or

a reference signal received quality.

17. The method of claim 15 , wherein the at least one first message comprises at least one of:

an X2 interface setup request message;

an X2 interface setup response message;

a base station configuration update message;

a secondary base station addition request message; or

a secondary base station modification request message.

18. The method of claim 15 , wherein the backhaul interface comprises an X2 interface between the second base station and the third base station.

19. The method of claim 15 , wherein the at least one first message comprises at least one of:

a wireless device identifier of the wireless device;

one or more bearer identifiers of one or more bearers associated with the wireless device;

a measurement result of at least one first cell of the first base station; or

at least one second cell identifier of at least one second cell of the second base station.

20. The method of claim 15 , further comprising:

transmitting, by the second base station to the third base station and in response to receiving the third message, a fourth message indicating a second secondary base station addition request for the wireless device;

receiving, by the second base station from the third base station, a fifth message indicating an acceptance of the second secondary base station addition request; and

transmitting, by the second base station to the first base station and in response to receiving the fifth message, a sixth message indicating a response for the third message, wherein the first base station releases a wireless device context of the wireless device based on the sixth message.