Base stations for data bearer handling associated with small data transmission

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 first request for a context of the wireless device, wherein the first request includes SDT assistance information;

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

that the context of the wireless device is not being relocated, wherein the decision to not relocate the context of the wireless device is based, at least in part, on the SDT assistance information; and

the DRB configured for the SDT procedure;

receiving, by the second base station from the first base station, after sending the first response message, downlink data forwarding information associated with the DRB configured for the SDT procedure for establishing a tunnel for subsequent downlink data transmission, wherein said downlink data forwarding information is provided by the first base station in response to the first response message sent by the second base station; and

consistent with 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, the first base station identifying the downlink data based on the assistance information.

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 first request for a context of the wireless device, wherein the first request includes SDT assistance information;

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

that the context of the wireless device is not being relocated, wherein the decision to not relocate the context of the wireless device is based, at least in part, on the SDT assistance information; and

the DRB configured for the SDT procedure;

receive, after sending the first response message, from the first base station, downlink data forwarding information associated with the DRB configured for the SDT procedure for establishing a tunnel for subsequent downlink data transmission, wherein said downlink data forwarding information is provided by the first base station in response to the first response message sent by the second base station; and

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

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 first base station comprising:

one or more processors; and

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

send, to a second base station, a first request for a context of a wireless device, wherein the wireless device is associated with a data radio bearer (DRB) configured for a small data transmission (SDT) procedure of the wireless device;

receive, from the second base station, in response to the first request, a first response message, wherein the first request includes SDT assistance information and indicates:

that the context of the wireless device is not being relocated, said decision to not relocate the context of the wireless device being based, at least in part, on the SDT assistance information; and

the DRB configured for the SDT procedure;

after receiving the first response message, send, to the second base station, downlink data forwarding information associated with the DRB configured for the SDT procedure for establishing a tunnel for subsequent downlink data transmission, wherein said downlink data forwarding information is provided in response to receipt of the first response message sent by the second base station; and

consistent with the downlink data forwarding information, receive, from the second base station, downlink data of the SDT procedure obtained from a core network node and identify the downlink data based on the assistance information.