Methods, apparatus and systems relating to data radio bearer inactivity

1. A method in a distributed unit of a base station, the base station further comprising a centralized unit, the method comprising:

determining inactivity of one or more data radio bearers, established between the distributed unit and a user equipment, for carrying user data;

determining a level of activity of one or more signaling radio bearers, established between the distributed unit and the user equipment, for carrying control data; and

determining, based on the level of activity of the one or more signaling radio bearers, whether to transmit, to the centralized unit, a report message comprising an indication of the inactivity of the one or more data radio bearers.

2. The method of claim 1 , wherein determining whether to transmit a report message comprises comparing the level of activity of one or more of the one or more signaling radio bearers to one or more thresholds and determining whether to transmit the report message based on the comparison, and wherein the method further comprises refraining from transmitting the report message, responsive to the level of activity exceeding the threshold.

3. A method in a network node for a wireless communication network, the method comprising:

obtaining an indication of inactivity of a first data radio bearer of a plurality of data radio bearers established between a user equipment and one or more distributed units of a base station for carrying user data, the base station further comprising a centralized unit; and

based on the indication of inactivity:

removing the first data radio bearer from a radio bearer configuration for the user equipment; and

transferring traffic intended for the first data radio bearer to a second data radio bearer of the plurality of data radio bearers.

4. The method of claim 3 , wherein the first data radio bearer is established between the user equipment and a first distributed unit, and the second data radio bearer is established between the user equipment and a second distributed unit.

5. The method of claim 4 , wherein the steps of removing the first data radio bearer and transferring traffic to the second data radio bearer are performed responsive further to a determination that transfer of traffic intended for the first data radio bearer to the second data radio bearer will not cause an overload condition in the second distributed unit.

6. A distributed unit for a base station, the base station further comprising a centralized unit, the distributed unit comprising processing circuitry and a memory storing instructions that, when executed by the processing circuitry, cause the distributed unit to:

determine inactivity of one or more data radio bearers, established between the distributed unit and a user equipment, for carrying user data;

determine a level of activity of one or more signaling radio bearers, established between the distributed unit and the user equipment, for carrying control data; and

determine, based on the level of activity of the one or more signaling radio bearers, whether to transmit, to the centralized unit, a report message comprising an indication of the inactivity of the one or more data radio bearers.

7. The distributed unit of claim 6 , wherein the distributed unit is configured to determine whether to transmit a report message by comparing the level of activity of one or more of the one or more signaling radio bearers to one or more thresholds and determining whether to transmit the report message based on the comparison.

8. The distributed unit of claim 7 , wherein the distributed unit is configured to refrain from transmitting the report message responsive to the level of activity exceeding the threshold.

9. The distributed unit of claim 7 , wherein the distributed unit is configured to transmit the report message responsive to the level of activity being lower than the threshold.

10. A network node for a wireless communication network, the network node comprising processing circuitry and a memory storing instructions that, when executed by the processing circuitry, cause the network node to:

obtain an indication of inactivity of a first data radio bearer of a plurality of data radio bearers established between a user equipment and one or more distributed units of a base station for carrying user data, the base station further comprising a centralized unit; and

based on the indication of inactivity:

remove the first data radio bearer from a radio bearer configuration for the user equipment; and

transfer traffic intended for the first data radio bearer to a second data radio bearer of the plurality of data radio bearers.

11. The network node of claim 10 , wherein the first data radio bearer is established between the user equipment and a first distributed unit, and the second data radio bearer is established between the user equipment and a second distributed unit.

12. The network node of claim 11 , wherein the network node is configured to remove the first data radio bearer and transfer traffic to the second data radio bearer responsive to a determination that transfer of traffic intended for the first data radio bearer to the second data radio bearer will not cause an overload condition in the second distributed unit.

13. The network node of claim 12 , wherein the network node is configured to determine whether transfer of traffic intended for the first data radio bearer to the second data radio bearer will cause an overload condition in the second distributed unit by comparing a sum of the traffic intended for the first data radio bearer and traffic intended for the second data radio bearer to a threshold.

14. The network node of claim 10 , wherein the network node is the centralized unit.

15. The network node of claim 14 , wherein the network node is configured to obtain an indication of inactivity of the first data radio bearer by receiving a report message from the distributed unit comprising the indication of inactivity of the first data radio bearer.

16. The network node of claim 14 , wherein the network node is configured to obtain an indication of inactivity of the first data radio bearer by monitoring the activity of the first data radio bearer.

17. The network node of claim 16 , wherein the network node is configured to monitor the activity of the first data radio bearer in a user plane entity implemented in the centralized unit.

18. The network node of claim 17 , wherein the network node is configured to monitor the activity of the first data radio bearer in a packet data convergence protocol (PDCP) layer in the user plane entity.

19. The network node of claim 10 , wherein the centralized unit implements one or more of: a Radio Resource Control (RRC), a Service Data Adaptation Protocol (SDAP), and a Packet Data Convergence Protocol (PDCP).

20. The network node of claim 10 , wherein the distributed unit implements one or more of: a Radio Link Control (RLC), a Medium Access Control (MAC), and the physical layer of the air interface.