RAN and UE driven L4S marking and processing for congestion management in an O-RAN based network architecture

1 . A system for reducing bottleneck queues in the Open Radio Access Network (O-RAN) comprising:

a Centralized Unit-User Plane (CU-UP) server;

a Distributed Unit (DU) server coupled to said CU-UP server;

a User Equipment (UE) coupled to said DU server;

an application source coupled to said UE;

software executing on said CU-UP server comprising a CU Congestion Indicator that measures data congestion in a Packet Data Convergence Protocol (PDCP) queue of said CU-UP server, the CU Congestion Indicator analyzing and classifying a Data Radio Bearer (DRB) x in the PDCP queue;

software executing on said DU server comprising a DU Congestion Indicator that measures data congestion in a Radio Link Control (RLC) queue of the said DU server, the DU Congestion Indicator analyzing and classifying a DRB y in the RLC queue;

wherein if the CU Congestion Indicator or the DU Congestion Indicator classifies the DRB x or DRB y respectively as Congestion Experienced (CE), said DU server transmits a CE indication to said UE;

said UE uses the CE indication to communicate a congestion occurrence message to said application source using: Low Latency, Low Loss, and Scalable throughput Medium Access Control (L4S MAC) Control Element (MAC CE) or Explicit Congestion Notification (ECN) bits in a Transmission Control Protocol (TCP) header from a PDCP header; and

wherein said application source modifies a data rate for data traffic that is sent to said UE based on the CE indication.

2 . The system according to claim 1 , wherein the CU Congestion Indicator comprises an L4S module at said CU-UP server.

3 . The system according to claim 1 , wherein the ECN bits in the TCP header comprise two reserved bits from a PDCP header and are used to communicate the CE indication from said CU-UP server to said DU server for each DRB.

4 . The system according to claim 3 , wherein the first bit is used to indicate whether the DRB is carrying L4S traffic, and the second bit is used to indicate the CE indication.

5 . The system according to claim 4 , wherein the second bit is updated as a packet moves from said CU-UP server to said DU server.

6 . The system according to claim 4 , wherein the UE continues to send the CE indication to said application source until:

said DU server indicates to the UE that a select DRB is no longer experiencing congestion; or

said DU server sends a message to the UE indicating that said DU server has adapted a data transmission rate in response to information received from the UE.

7 . The system according to claim 1 , wherein

the PDCP queue for DRB x at said CU-UP server is categorized as high, medium or low, and

the RLC queue for DRB y at said DU server is categorized as high, medium or low.

8 . The system according to claim 7 , wherein once a category for the RLC or the PDCP queues has been derived at said DU server, the category is transmitted to the CU-CP server by adding objects in a F1-C interface protocol.

9 . The system according to claim 8 , wherein the CE indication is sent to said UE via a UE-specific Radio Resource Control (RRC) message.

10 . The system according to claim 9 , further comprising a field that is added in the UE-specific RRC message to indicate the occurrence of congestion.

11 . The system according to claim 1 , wherein the CU Congestion Indicator further monitors and classifies an air-interface and a Mid-haul link, which indications are transmitted to the UE.

12 . The system according to claim 1 , wherein the CE indication comprises L4S MAC Control Element (MAC CE).

13 . A method for reducing bottleneck queues in the Open Radio Access Network (O-RAN) having a Centralized Unit-User Plane (CU-UP) server, a Distributed Unit (DU) server coupled to the CU-UP server, a User Equipment (UE) coupled to the DU server and an application source coupled to the UE, the method comprising the steps of:

measuring data congestion in a Packet Data Convergence Protocol (PDCP) queue of the CU-UP server with a CU Congestion Indicator;

the CU Congestion Indicator analyzing and classifying a Data Radio Bearer (DRB) x in the PDCP queue;

measuring data congestion in a Radio Link Control (RLC) queue of the DU server with a DU Congestion Indicator;

wherein the DU Congestion Indicator analyzes and classifies a Data Radio Bearer (DRB) y in the RLC queue;

wherein when the CU Congestion Indicator or the DU Congestion Indicator classifies the DRB x or DRB y respectively as Congestion Experienced (CE), the DU server transmits the CE indication to the UE;

wherein the UE communicates a congestion occurrence message to the application source based on the received CE indication, the UE transmitting the congestion occurrence message using: L4S MAC Control Element (MAC CE) or Explicit Congestion Notification (ECN) bits in a Transmission Control Protocol (TCP) header from a PDCP header; and

wherein the application source modifies a data rate for data traffic that is sent to the UE based on the CE indication.

14 . The method according to claim 13 , wherein the CU Congestion Indicator is an L4S module.

15 . The method according to claim 13 , wherein the ECN bits in the TCP header are two reserved bits from a PDCP header and are used to communicate the CE indication from the CU-UP server to the DU server for each DRB.

16 . The method according to claim 15 , wherein the first bit is used to indicate whether the DRB is carrying L4S traffic, and the second bit is used to indicate the CE indication.

17 . The method according to claim 13 , wherein

the PDCP queue for DRB x at the CU-UP server is categorized as high, medium or low, and

the RLC queue for DRB y at the DU server is categorized as high, medium or low.