Downlink data of small data transmission procedure

1. A method comprising:

sending, by a second base station to a wireless device, an indication of a data radio bearer (DRB) configured for a small data transmission (SDT) procedure of the wireless device;

receiving, by the second base station from a first base station, a request for a context of the wireless device;

sending, by the second base station to the first base station, in response to the request, a response message indicating:

not to relocate the context of the wireless device; and

the DRB configured for the SDT procedure;

receiving, by the second base station from the first base station, downlink data forwarding information associated with the DRB configured for the SDT procedure; and

based on the downlink data forwarding information, sending, by the second base station to the first base station, downlink data of the SDT procedure received from a core network node.

2. The method of claim 1 , wherein the downlink data is subsequent to uplink data of the SDT procedure.

3. The method of claim 2 , further comprising receiving, by the second base station from the first base station, the uplink data.

4. The method of claim 1 , further comprising sending, to the first base station, the downlink data.

5. The method of claim 1 , further comprising receiving, from the first base station, assistance parameters of the SDT procedure.

6. The method of claim 2 , wherein the downlink data forwarding information indicates a tunnel address for the subsequent downlink data.

7. The method of claim 1 , further comprising receiving, from the core network node, the downlink data of the SDT procedure.

8. The method of claim 1 , further comprising transmitting, to the wireless device, a radio resource control release message indicating transition of the wireless device to a radio resource control inactive state or a radio resource control idle state.

9. The method of claim 8 , wherein the radio resource control release message comprises the indication of the DRB configured for the SDT procedure of the wireless device.

10. The method of claim 8 , further comprising transitioning, by the second base station based on the transmitting the radio resource control release message, a radio resource control state of the wireless device to the radio resource control inactive state or the radio resource control idle state.

11. A second base station comprising:

one or more processors; and

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

send, to a wireless device, an indication of a data radio bearer (DRB) configured for a small data transmission (SDT) procedure of the wireless device;

receive, from a first base station, a request for a context of the wireless device;

send, to the first base station, in response to the request, a response message indicating:

not to relocate the context of the wireless device; and

the DRB configured for the SDT procedure;

receive, from the first base station, downlink data forwarding information associated with the DRB configured for the SDT procedure; and

based on the downlink data forwarding information, send, to the first base station, downlink data of the SDT procedure received from a core network node.

12. The second base station of claim 11 , wherein the downlink data is subsequent to uplink data of the SDT procedure.

13. The second base station of claim 12 , further comprising receiving, by the second base station from the first base station, the uplink data.

14. The second base station of claim 11 , further comprising sending, to the first base station, the downlink data.

15. The second base station of claim 11 , further comprising receiving, from the first base station, assistance parameters of the SDT procedure.

16. The second base station of claim 12 , wherein the downlink data forwarding information indicates a tunnel address for the subsequent downlink data.

17. The second base station of claim 11 , further comprising receiving, from the core network node, the downlink data of the SDT procedure.

18. The second base station of claim 11 , further comprising transmitting, to the wireless device, a radio resource control release message indicating transition of the wireless device to a radio resource control inactive state or a radio resource control idle state.

19. The second base station of claim 18 , wherein the radio resource control release message comprises the indication of the DRB configured for the SDT procedure of the wireless device.

20. A system comprising:

a second base station comprising: one or more processors; and memory storing instructions that, when executed by the one or more processors, cause the second base station to:

send, to a wireless device, an indication of a data radio bearer (DRB) configured for a small data transmission (SDT) procedure of the wireless device;

receive, from a first base station, a request for a context of the wireless device;

send, to the first base station, in response to the request, a response message indicating:

not to relocate the context of the wireless device; and

the DRB configured for the SDT procedure; and

receive, from the first base station, downlink data forwarding information associated with the DRB configured for the SDT procedure;

based on the downlink data forwarding information, send, to the first base station, downlink data of the SDT procedure received from a core network node; and

the first base station, wherein the first base station comprises: one or more processors; and memory storing instructions that, when executed by the one or more processors, cause the first base station to:

receive, from the wireless device, a radio resource control request message;

send, to the second base station, based on the RRC request message, the request for the context of the wireless device;

receive, from the second base station, the response message;

send, to the second base station, the downlink data forwarding information; and

receive, from the second base station, the downlink data.