Re-transmission of PDCP PDUS by centralized nodes of a RAN architecture
A centralized RAN architecture that includes lower layer transmission nodes (referred to as distributed units (DUs) herein) that connect to an upper layer RAN node (referred to as a centralized unit (CU) herein). A centralized RAN architecture may include a functional split, between the CU and DU, corresponding to the Packet Data Convergence Protocol (PDCP) and Radio Link Control (RLC) layers. In one embodiment, a CU may store copies of downlink PDCP PDUs that are transmitted to a first DU. The CU may retransmit, to a second DU, those of the PDCP PDUs which were previously transmitted to the source DU but have not been acknowledged as successfully delivered by the source DU.
1. A Centralized Unit of a Next Generation NodeB (gNB-CU) comprising:
circuitry to provide an interface to a plurality of Distributed Units of the Next Generation NodeB (gNB-DUs); and
one or more processors to:
buffer packet data convergence protocol (PDCP) Protocol Data Units (PDUs) already transmitted to a first gNB-DU of the plurality of gNB-DUs until the PDCP PDUs have been acknowledged to be successfully delivered to a user equipment (UE);
receive an indication, from the first gNB-DU of the plurality of gNB-DUs, of a radio link outage between the first gNB-DU and the UE;
detect that particular PDCP Protocol Data Units (PDUs) transmitted, via the circuitry to provide the interface, to the first gNB-DU from which the indication is received, were undelivered by the first gNB-DU to the UE; and
retransmit, via the circuitry to provide the interface and in response to the detection that the particular PDCP PDUs were undelivered, the particular PDCP PDUs to a second gNB-DU, of the plurality of gNB-DUs, to which the UE is attached.
2. The gNB-CU of claim 1 , wherein the detection that the particular PDCP PDUs were undelivered to the first gNB-DU is based on an indication, from the first gNB-DU, that the particular PDCP PDUs were not successfully delivered to the UE.
3. The gNB-CU of claim 1 , wherein the one or more processors are further to:
trigger, before retransmission of the particular PDCP PDUs, a PDCP status report from the UE, the PDCP status report indicating PDCP PDUs that have been received by the UE.
4. The gNB-CU of claim 1 , wherein the gNB-CU implements Radio Resource Control (RRC) layer and Packet Data Convergence Protocol (PDCP) layer functionality of the gNB and the gNB-DUs implement Radio Link Control (RLC) layer, Media Access Control (MAC) layer, Physical (PHY) layer, and Radio Frequency (RF) layer functionality of the gNB.
5. An apparatus including a Centralized Unit of a Next Generation NodeB (gNB-CU) comprising:
one or more processors to:
communicate with a plurality of Distributed Units of the Next Generation NodeB (gNB-DUs);
buffer packet data convergence protocol (PDCP) Protocol Data Units (PDUs) already transmitted to a first gNB-DU of the plurality of gNB-DUs until the PDCP PDUs have been acknowledged to be successfully delivered to a user equipment (UE);
detect mobility of the UE receiving the PDCP PDUs from the first gNB-DU of the plurality of gNB-DUs to a second gNB-DU of the plurality of gNB-DUs;
detect that particular PDCP PDUs transmitted to the first gNB-DU from which the mobility of the UE is detected, were undelivered by the first gNB-DU, to the UE; and
retransmit, in response to the detection that the particular PDCP PDUs were undelivered, the particular PDCP PDUs to the second gNB-DU to which the mobility of the UE is detected.
6. The apparatus of claim 5 , wherein the detection that the particular PDCP PDUs were undelivered to the first gNB-DU is based on an indication, from the first gNB-DU, that the particular PDCP PDUs were not successfully delivered to the UE.
7. The apparatus of claim 5 , wherein the one or more processors are further to:
trigger, before retransmission of the particular PDCP PDUs, a PDCP status report from the UE, the PDCP status report indicating PDCP PDUs that have been received by the UE.
8. A system to implement a portion of a Radio Access Network (RAN), comprising:
a plurality of Distributed Units of a Next Generation NodeB (gNB-DU); and
a Centralized Unit of the Next Generation NodeB (gNB-CU), the gNB-CU being connected to the plurality of gNB-DUs, the gNB-CU operating to:
buffer packet data convergence protocol (PDCP) Protocol Data Units (PDUs) already transmitted to a first gNB-DU of the plurality of gNB-DUs until the PDCP PDUs have been acknowledged to be successfully delivered to a user equipment (UE);
receive an indication, from the first gNB-DU of the plurality of gNB-DUs, of a radio link outage between the first gNB-DU and the UE;
detect that particular PDCP PDUs transmitted to the first gNB-DU from which the indication is received, were undelivered by the first gNB-DU to the UE; and
retransmit, in response to the detection that the particular PDCP PDUs were undelivered, the particular PDCP PDUs to a second gNB-DU, of the plurality of gNB-DUs, to which the UE is attached.
9. The system of claim 8 , wherein the detection that the particular PDCP PDUs were undelivered to the first gNB-DU is based on an indication, from the first gNB-DU, that the particular PDCP PDUs were not successfully delivered to the UE.
10. The system of claim 8 , wherein the gNB-CU is further to:
trigger, before retransmission of the particular PDCP PDUs, a PDCP status report from the UE, the PDCP status report indicating PDCP PDUs that have been received by the UE.
11. The system of claim 8 , wherein each of the plurality of gNB-DUs implements Radio Link Control (RLC) layer, Media Access Control (MAC) layer, Physical (PHY) layer, and Radio Frequency (RF) layer functionality of the gNB, and wherein the gNB-CU implements Radio Resource Control (RRC) and Packet Data Convergence Protocol (PDCP) layer functionality of the gNB.