User equipment and methods of bearer operation for carrier aggregation

1. A user equipment (UE) comprising:

a radio; and

a processor operably coupled to the radio and configured to cause the UE, while configured for dual connectivity with a master node and a secondary node, to:

receive downlink traffic packets from at least one of the master node and the secondary node as part of a split data radio bearer (DRB), the downlink traffic packets including downlink traffic packets received out of sequence as part of the split DRB, wherein the split DRB includes corresponding radio link control (RLC) functionalities at the master node and the secondary node;

start a Packet Data Convergence Protocol (PDCP) timer for reordering the downlink traffic packets received out of sequence as part of the split DRB, wherein when the PDCP timer is set to zero, the downlink traffic packets may be delivered to at least one upper layer without additional reordering delay at a PDCP layer due to the PDCP timer; and

deliver the downlink traffic packets to the at least one upper layer.

2. The UE of claim 1 , wherein the split DRB operates as part of a Secondary Cell (SCell) supported by the secondary node and a Primary Cell (PCell), supported by the master node.

3. The UE of claim 1 , wherein the processor is further configured to cause the UE to:

transmit uplink traffic packets for transmission to the master node when a first indicator indicates packet data units may not be communicated via the secondary node.

4. The UE of claim 3 , wherein the processor is further configured to cause the UE to:

transmit uplink traffic packets for transmission to the secondary node when the first indicator indicates packet data units may be communicated via the secondary node.

5. The UE of claim 1 , wherein the processor is further configured to cause the UE to:

bypass reordering of the downlink traffic packets received out of sequence based on an indicator.

6. The UE of claim 5 , wherein the indicator is set to a value of zero as part of the bypass.

7. The UE of claim 1 , wherein the downlink traffic packets include one or more PDCP Service Data Units (SDUs).

8. The UE of claim 1 , wherein the processor is further configured to cause the UE to:

exchange traffic packets with the master node on a primary cell (PCell) as part of a second, different DRB.

9. The UE of claim 1 , wherein the processor is further configured to cause the UE to:

receive first signaling from the master node, the first signaling including a first indicator specifying whether the UE is to transmit uplink traffic packets to the secondary node, and

based at least partly on the first indicator, transmit the uplink traffic packets for transmission to the master node or the secondary node as part of the split DRB.

10. The UE of claim 1 , wherein the processor is further configured to cause the UE to:

exchange control messages with the master node on a primary cell (PCell) supported by the master node.

11. The UE of claim 1 , wherein the processor is further configured to cause the UE to:

transmit, for reception by at least one of the master node and the secondary node a RLC status Protocol Data Unit (PDU) that includes status information for the split DRB.

12. A method, comprising:

at a master node, while in communication with a user equipment device (UE) configured for dual connectivity with the master node and a secondary node:

transmit, to the UE, a configuration for a split data radio bearer (DRB), wherein the split DRB is to be served by the master node and the secondary node; and

transmit, to the UE, downlink traffic packets as part of the split DRB, wherein the split DRB includes corresponding radio link control (RLC) functionalities at the master node and the secondary node, wherein the split DRB is associated with a Packet Data Convergence Protocol (PDCP) timer for reordering downlink traffic packets received out of sequence as part of the split DRB, wherein when the PDCP timer is set to zero, the downlink traffic packets may be delivered to at least one upper layer of the UE without additional reordering delay at a PDCP layer due to the PDCP timer.

13. The method of claim 12 , wherein the split DRB operates as part of a Secondary Cell (SCell) supported by the secondary node and a Primary Cell (PCell), supported by the master node.

14. The method of claim 12 , further comprising:

receiving uplink traffic packets at the master node when a further indicator indicates packet data units may not be communicated via the secondary node.

15. The method of claim 14 , further comprising:

receiving uplink traffic packets at the secondary node when the further indicator indicates packet data units may be communicated via the secondary node.

16. The method of claim 12 , further comprising:

setting a further indicator to zero to bypass reordering of the downlink traffic packets received out of sequence.

17. The method of claim 12 , wherein the downlink traffic packets include one or more PDCP Service Data Units (SDUs).

18. The method of claim 12 , further comprising:

exchanging traffic packets with the UE via the master node on a primary cell (PCell) as part of a second, different DRB.

19. The method of claim 12 , further comprising:

transmitting, first signaling from the master node to the UE, the first signaling including a first indicator specifying whether the UE is to transmit uplink traffic packets to the secondary node, and

receiving the uplink traffic packets via the master node or the secondary node as part of the split DRB.

20. An apparatus, comprising:

a processor configured to cause a user equipment (UE) configured for dual connectivity with a master node and a secondary node to:

receive downlink traffic packets from at least one of the master node and the secondary node as part of a split data radio bearer (DRB), the downlink traffic packets including downlink traffic packets received out of sequence as part of the split DRB, wherein the split DRB includes corresponding radio link control (RLC) functionalities at the master node and the secondary node;

start a Packet Data Convergence Protocol (PDCP) timer for reordering the downlink traffic packets received out of sequence as part of the split DRB, wherein when the PDCP timer is set to zero, the downlink traffic packets may be delivered to at least one upper layer without additional reordering delay at a PDCP layer due to the PDCP timer; and

deliver the downlink traffic packets to the at least one upper layer.

21. A method, comprising:

at a network, while in communication with a user equipment device (UE) configured for dual connectivity with a master node and a secondary node of the network:

transmit, to the UE, a configuration for a split data radio bearer (DRB), wherein the split DRB is to be served by the master node and the secondary node; and

transmit, to the UE, downlink traffic packets as part of the split DRB, wherein the split DRB includes corresponding radio link control (RLC) functionalities at the master node and the secondary node, wherein the split DRB is associated with a Packet Data Convergence Protocol (PDCP) timer for reordering downlink traffic packets received out of sequence as part of the split DRB, wherein when the PDCP timer is set to zero, the downlink traffic packets may be delivered to at least one upper layer of the UE without additional reordering delay at a PDCP layer due to the PDCP timer.

22. The method of claim 21 , wherein the split DRB operates as part of a Secondary Cell (SCell) supported by the secondary node and a Primary Cell (PCell), supported by the master node.