Optimizing enforcement of uplink aggregate maximum bit rate (AMBR) in o-ran networks

Abstract

A method for splitting data traffic from a UE in an O-RAN where UL data is transmitted from the UE to a MeNB.DU and to a SgNB.DU according to an UL AMBR for the UE where if the UL data packet split between the MeNB.DU and SgNB.DU violates a UL AMBR associated with either DU, the UL data packets are buffered at the DU and a message is transmitted to the other DU to determine if it can accept the buffered data packets such that the DU will analyze its UL AMBR and will accept the data packets or a portion thereof, if its UL AMBR is not violated. Also, a method where MeNB DU and SgNB.DU negotiate with each other to decide suitable values of UL AMBR via their respective air-interfaces.

Description

Optimizing Enforcement of Uplink Aggregate Maximum Bit Rate (AMBR) in 0- RAN NetworksBACKGROUND1. Field of the Disclosure

[0001] The present disclosure relates to Open Radio Access Network (0-RAN) wireless networks and relates more particularly to optimization of UL AMBR (Uplink Aggregate Maximum Bit Rate) enforcement in 0-RAN networks.2. Description of Related Art

[0002] Presented is an overview of the Next Generation Radio Access Network (NG-RAN) architecture and Fifth Generation New Radio (5G NR) stacks. 5G NR user and control plane functions with monolithic gNode Base Station (gNB) are shown in FIGS, la, lb and 2. For the user plane (shown in FIG. la), PHY (physical), MAC (Medium Access Control), RLC (Radio Link Control), PDCP (Packet Data Convergence Protocol) and SDAP (Service Data Adaptation Protocol) sublayers originate in the User Equipment (UE) 101 and are terminated in the gNB 102 on the network side.

[0003] FIG. lb is a block diagram illustrating the user plane protocols stacks for a protocol data unit (PDU) session where PDU layer 9010 corresponds to the PDU carried between the UE 101 and the data network (DN) 9011 over the PDU session. A PDU is a single unit of information that is transmitted. As shown in FIG. lb, UE 101 is connected to the 5G access network (AN) 902, which is in turn connected via the N3 interface to Intermediate UPF (I-UPF) 903a, which is in turn connected via the N9 interface to the PDU session anchor 903b portion of the UPF 903, which in turn, is connected to DN 9011. Control Unit-User Plane (CU-UP) of AN 902 is connected to UPF 903b via a Backhaul (BH) path. The PDU session can correspond to IPv4, IPv6, or both types of IP packets, when the PDU session is of type IPv4, IPv6 or IPv4v6, respectively. General packet radio service Tunnelling Protocol - User Plane (GTP-U) shown in FIG. lb supports tunnelling user plane data over N3 and N9 interfaces and provides encapsulation of end user PDUs for N3 and N9 interfaces.

[0004] FIG. 2 illustrates the control plane including RRC (Radio Resource Control), PDCP, RLC, MAC and PHY sublayers that originate in the UE 101 and are terminated in the gNB 102 on the network side, and NAS (Non-Access Stratum) that originates in the UE 101 and is terminated in the AMF (Access Mobility Function) 103 on the network side.

[0005] NG-RAN architecture is illustrated in FIGS. 3-4. As shown in FIG. 3, the NG-RAN 301 comprises a set of gNBs 302 connected to the 5GC 303 through the NG interface. Each gNB comprises gNB-CU 304 and one or more gNB-DU 305 (see FIG. 3). As shown in FIG. 4 (which illustrates separation of CU-CP (CU-Control Plane) and CU-UP (CU-User Plane)), El is the interface between gNB-CU-CP (CU-Control Plane) 304a and gNB-CU-UP (CU-User Plane) 304b, Fl-C is the interface between gNB-CU-CP 304a and gNB-DU 305, and Fl-U is the interface between gNB-CU-UP 304b and gNB-DU 305. As shown in FIG. 4, gNB 302 can have a gNB-CU-CP 304a, multiple gNB-CU-UPs (or gNB-CU-UP instances) 304b and multiple gNB- DUs (or gNB-DU instances) 305. One gNB-DU 305 is connected to one gNB-CU-CP 304a, and gNB-CU-UP 304b is connected to one gNB-CU-CP 304a.

[0006] An overview of Layer 2 (L2) of 5G NR is discussed in connection with FIGS. 5-7. FIG. 5 is a block diagram illustrating DL L2 structure. L2 of 5G NR is split into the following sublayers.

[0007] 1) Medium Access Control (MAC) 501 in FIGS. 5-7: Logical Channels (LCs) are SAPs (Service Access Points) between the MAC and RLC layers. This layer runs a MAC scheduler to schedule radio resources across different LCs (and their associated radio bearers). For the downlink direction, the MAC layer processes and sends RLC PDUs received on LCs to the Physical layer as Transport Blocks (TBs). For the uplink direction, it receives transport blocks (TBs) from the physical layer, processes these and sends them to the RLC layer using the LCs.

[0008] 2) Radio Link Control (RLC) 502 in FIGS. 5-7: The RLC sublayer presents RLC channels to the Packet Data Convergence Protocol (PDCP) sublayer. The RLC sublayer supports three transmission modes: RLC-Transparent Mode (RLC-TM), RLC -Unacknowledged Mode (RLC -UM) and RLC-Acknowledgement Mode (RLC-AM). RLC configuration is per logical channel. It hosts ARQ (Automatic Repeat Request) protocol for RLC-AM mode.

[0009] 3) Packet Data Convergence Protocol (PDCP) 503 in FIGS. 5-7: The PDCP sublayer presents Radio Bearers (RBs) to the SDAP sublayer. There are two types of Radio Bearers: Data Radio Bearers (DRBs) for data and Signaling Radio Bearers (SRBs) for control plane.

[0010] 4) Service Data Adaptation Protocol (SDAP) 504 in FIGS. 5-7: The SDAP maps QoS flows within a PDU session to a specific Data Radio Bearer.

[0011] Open Radio Access Network (0-RAN) is based on disaggregated components, which are connected through open and standardized interfaces based on 3 GPP NG-RAN. FIG. 6 provides an overview of 0-RAN with disaggregated RAN CU (Centralized Unit), DU (Distributed Unit), and RU (Radio Unit), near-real-time Radio Intelligent Controller (RIC) and non-real-time RIC.

[0012] As shown in FIG. 6, the CU (shown split as O-CU-CP 801a and O-CU-UP 801b) and the DU (shown as O-DU 802) are connected using the Fl interface (with Fl-C for control plane and Fl-U for user plane traffic) over a mid-haul (MH) path. One DU can host multiple cells (e.g., one DU may host 24 cells) and each cell may support many users. For example, one cell may support 800 Radio Resource Control (RRC)-connected users and out of these 800, there may be 250 Active users (i.e., users that have data to send at a given point of time).

[0013] A cell site can comprise multiple sectors, and each sector can support multiple cells. For example, one site could comprise three sectors and each sector could support eight cells (with each cell being on a different frequency band in each sector). One CU-CP (CU-Control Plane) could support multiple DUs and thus multiple cells. For example, a CU-CP could support 500 cells and around 100,000 User Equipment (UE). Each UE could support multiple Data Radio Bearers (DRBs) and there could be multiple instances of CU-UP (CU-User Plane) to serve these DRBs. For example, each UE could support 4 DRBs, and 400,000 DRBs (corresponding to 100,000 UEs) can be served by five CU-UP instances (and one CU-CP instance).

[0014] The DU can be physically located in a private data center, or it could be located at a cell site. The CU could also be in a private data center or even hosted on a public cloud system. The DU and CU are typically located at different physical locations, which could be quite a distance apart. The CU communicates with a 5G core system, which could also be hosted in the same public cloud system (or could be hosted by a different cloud provider). A RU (Radio Unit)(shown as O-RU 803 in FIG. 6) is located at a cell-site and communicates with the DU via a front-haul (FH) interface.

[0015] The E2 nodes (CU and DU) are connected to the near-real-time RIC 132 using the E2 interface. The E2 interface is used to send data (e.g., user and / or cell KPMs) from the RAN and deploy control actions and policies to the RAN at near-real-time RIC 132. The applications or services at the near-real-time RIC 132 that deploys the control actions and policies to the RAN are called xApps. During the E2 setup procedures, the E2 node advertises the metrics it can expose, and an xApp in the near-RT RIC can send a subscription message specifying key performance metrics which are of interest. The near-real-time RIC 132 is connected to the non- real-time RIC 133 (which is shown as part of Service Management and Orchestration (SMO) Framework 805 in FIG. 6) using the Al interface. The applications that are hosted at non-RT- RIC are called rApps. Also shown in FIG. 6 are O-eNB 806 (which is shown as being connected to the near-real-time RIC 132 and the SMO Framework 805) and O-Cloud 804 (which is shown as being connected to the SMO Framework 805).

[0016] In 5G networks, PDU connectivity service is a service that provides exchange of PDUs between a UE and a Data Network (DN) identified by a Data Network Name (DNN). The PDU Connectivity service is supported via PDU sessions that are established upon request from the UE. The DNN defines the interface to a specific external data network. One or more QoS flows can be supported in a PDU session. All the packets belonging to a specific QoS flow have the same 5QI (5G QoS Identifier). A PDU session has the following: Data Radio Bearers which are between UE and CU in RAN; and an NG-U GTP tunnel which is between CU and UPF (User Plane Function) in the core network. FIG. 7 illustrates an example PDU session comprising multiple DRBs, where each DRB can comprise multiple QoS flows. In FIG. 7, three components are shown for the PDU session 901 : UE 101; access network (AN) 902; and UPF 903, which includes Packet Detection Rules (PDRs) 9031.

[0017] Referring to FIGS. 8 and 9, it should be noted for 3GPP 5G network architecture in FIG. 8 (in the context of multiple PDU sessions involving multiple DRBs and QoS Flow Identifiers (QFIs), which PDU sessions are implemented involving UE 101, gNB 102, UPF 903, and DNNs 9011a and 901 lb) and FIG. 9 (in the context of Radio Resource Management (RRM) forconnecting UE 101 to the network via RU 306 with a MAC Scheduler 1001).

[0018] 1) The transport connection between the base station (i.e., CU-UP 304b of FIG. 9) and the UPF 903 uses a single GTP-U tunnel per PDU session, as shown in FIGS. 8 and 9. The PDU session is identified using GTP-U TEID (Tunnel Endpoint Identifier).

[0019] 2) The transport connection between the DU 305 and the CU-UP 304b of FIG. 9 uses a single GTP-U tunnel per DRB (see also FIG. 8 and FIG. 9). The DU is provided with an UL GTP-U TEID and the CU is provided with the corresponding DL GTP-U TEID to allow for data communication for that DRB between DU and CU-UP.

[0020] 3) SDAP: a) The SDAP (Service Adaptation Protocol) 504 Layer receives downlink data from the UPF 903 across the NG-U interface (see FIG. 9); b) The SDAP 504 maps one or more QoS Flow(s) onto a specific DRB; and c) The SDAP header is present between the UE 101 and the CU (when reflective QoS is enabled), and includes a field to identify the QoS flow within a specific PDU session.

[0021] 4) GTP-U protocol includes a field to identify the QoS flow and is present between CU and UPF 903 (in the core network).

[0022] 5) One (logical) DU (or RLC) queue exists per DRB (or per logical channel) for RLC PDUs that are to be transmitted for the first time, as shown in FIG. 9. Separate logical queues may exist in DU for packets that are to be retransmitted to UE.

[0023] One-to-one mapping of standardized 5QI values to 5G QoS characteristics is specified in Table 1. The first column lists the 5QI value. The second column lists different resource types, i.e., as one of Non-GBR (non-Guaranteed Bit Rate), GBR, Delay-critical GBR. The third column (“Default Priority Level”) lists a priority level Priority5QI (e.g., the lower the value, the higher the priority of the corresponding QoS flow). The fourth column lists the Packet Delay Budget (PDB), defining an upper time bound a packet may be delayed between the UE and the N6 termination point at the UPF. The fifth column lists the Packet Error Rate (PER). The sixth column lists the maximum data burst volume for delay-critical GBR types. The seventh column lists an averaging window for GBR, delay critical GBR types.Table 1 - Note that only a subset of 5QI values defined in 3GPP TS 23.501 are shown in Table 1 .

[0024] As can be seen in Table 1, 5QI value 1 is of resource type GBR with the default priority value of 20, PDB of 100ms, PER of 0.01, and an averaging window of 2000ms. Conversational voice falls under this category. Similarly, as shown in Table 1, 5QI value 7 is of resource type non-GBR with the default priority value of 70, PDB of 100ms and PER of 0.001. Voice, video (live streaming), and interactive gaming fall under this category.

[0025] Radio Resource Management (RRM) is illustrated in FIG. 9 including a block diagram, for example, RRM with a MAC Scheduler. L2 methods (such as MAC scheduler) play a criticalrole in allocating radio resources to different UEs in a cellular network.

[0026] Referring now to FIGS. 10 - 12, FIG. 10 shows CU-UP sending DL User Data (DUD) to DU. FIG. 11 shows flow control feedback from CU-UP to DU. This is indicated as DL Data Delivery Status (DDDS) in FIG. 11. DU can send Assistance Information Data (AID) to CU-UP as shown in FIG. 12 and this provides radio information to CU-UP over the Fl-U interface.

[0027] UE-Aggregate Maximum Bit Rate (AMBR) limits the aggregate bit rate that can be expected to be provided across all non-GBR QoS flows for a UE. Uplink and downlink UE- AMBR are specified separately for each UE. A UE could be a 5G NR Standalone UE, a 4G LTE Standalone UE, a Non-Standalone (NS A) UE or a UE supporting Multiple Radio Access Technologies (Multi-RAT) or some other cellular technology. UE-AMBR is applicable to each such UE, and it is defined separately for uplink and downlink direction. For uplink traffic for a UE, AMBR is denoted as UL UE-AMBR and for downlink traffic for that UE, it is denoted as DL UE-AMBR.

[0028] For 5G Standalone (5G SA) networks, Session Management Function (SMF) in the 5GC (i.e., 5G Core) retrieves DL and UL UE-AMBR from the Unified Data Management (UDM) and provides this to Access and Mobility Management (AMF) in 5GC. As shown in FIG. 13, the AMF communicates the DL and UL UE-AMBR to CU-CP of gNB using NGAP (Next Generation Application Protocol) via N2 interface.

[0029] For 5G NR base station (i.e., for gNB), gNB CU-CP communicates DL UE-AMBR to CU-UP using the E1AP protocol (as shown in FIG. 13). The Information Element to communicate DL UE-AMBR from CU-CP to CU-UP is denoted as id-UEDL AggregateMaxi mumB itRate.

[0030] For 5G NR base station (i.e. for gNB), gNB CU-CP communicates UL UL-AMBR to DU using the F1AP protocol (as shown in FIG. 13). The Information Element to communicate UL UE-AMBR from CU-CP to DU is denoted as id-GNB-DU-UE-AMBR-UL.

[0031] Similarly, for 4G Standalone networks, MME (Mobility Management Entity) from the 4G EPC communicates DL UE-AMBR and UL UE-AMBR to the 4G base station (i.e., eNB)across Sl-C interface. eNB CU-CP communicates DL UE-AMBR to CU-UP, and UL UE- AMBR to DU across the VI -C interface as shown in FIG. 14.

[0032] For 5G NR network, Session-AMBR limits the aggregate bit rate that can be expected to be provided across all non-GBR QoS flows for a specific PDU session. It can be defined separately for UL and DL direction. For UL traffic for a session, it is denoted as UL Session- AMBR and for DL traffic for that session, it is denoted as DL Session-AMBR. UL Session- AMBR is enforced by the UE and the UPF for UL traffic while DL session AMBR is enforced by the UPF for DL traffic. Session AMBR is signaled to the UPF, to the UE and to the base station (i.e., 5G gNB). UE is provided with the UL Session-AMBR from the 5GC (specifically by AMF from the 5G Core Network).

[0033] Session-AMBR and UE-AMBR are not applicable for GBR QoS flows. EN-DC (E- UTRA-NR Dual Connectivity) architecture is shown in FIG. 15 and FIG. 16. In this architecture, the UE has a single RRC (Radio Resource Control) state, based on MN (Master Node) RRC and a single C-plane (Control plane) connection towards the MME (Mobility Management Entity) of 4G EPC (Evolved Packet Core) as shown in FIG. 15. LTE eNB is the MN (denoted as Master eNB or MeNB) and 5G gNB is the SN (Secondary Node), denoted as SgNB (or Secondary gNB), in this EN-DC architecture. NR RRC messages can be routed from SgNB to MeNB via the X2-C interface and to the UE via the LTE-U air-interface.

[0034] FIG. 16 shows the data (user) plane for this EN-DC architecture. MeNB is connected to S-GW (Serving Gateway) of 4G EPC via the Sl-U interface. Similarly, the SgNB is connected to the S-GW via the Sl-U interface. For SN terminated split bearer, 4G EPC communicates data with SgNB via the Sl-U interface and for MN terminated split bearer, 4G EPC communicates data with MeNB via the Sl-U interface. X2-U is used for user plane traffic between MeNB and SgNB.

[0035] FIG. 17 shows MCG (Master Cell Group), SCG (Secondary Cell Group) and split bearers from a UE perspective. In the EN-DC architecture, MCG comprises a group of 4G LTE cells and SCG comprises a group of 5G NR cells. As in FIG. 17, NR-PDCP is used at higher layers, and LTE (E-UTRA) RLC / MAC / PHY and NR RLC / MAC / PHY are used at lower layers for split bearers.

[0036] FIG. 18 shows MCG, SCG and split bearers from base station perspective. For SN terminated split bearer, NR-PDCP is used at higher layers, and LTE (E-UTRA) RLC / MAC / PHY and NR RLC / MAC / PHY are used at lower layers for split bearer.

[0037] As shown in FIG. 19, for EN-DC (or other dual connectivity) architecture, UE-AMBR is split into MeNB UE-AMBR and SgNB UE-AMBR, which are enforced by MeNB and SgNB respectively.

[0038] As in FIG. 20, MME communicates DL UE-AMBR and UL UE-AMBR to MeNB. UUCP across the Sl-C interface. The MeNB splits this into DL MeNB UE-AMBR, UL MeNB UE- AMBR, DL SgNB UE-AMBR and UL SgNB UE-AMBR. Next, the MeNB.CU-CP communicates DL MeNB UE-AMBR to MeNB.CU-UP and UL MeNB UE-AMBR to MeNB. DU. Also, MeNB.CU-CP communicates DL SgNB UE-AMBR and UL SgNB UE- AMBR to SgNB.CU-CP across the X2-C interface. Next, the SgNB.CU-CP communicates DL SgNB UE-AMBR to SgNB.CU-UP across the El interface and UL SgNB UE-AMBR to SgNB. DU across the Fl-C interface.

[0039] EN-DC (E-UTRA-NR Dual Connectivity) architecture with downlink split bearer operation is described in FIG. 21. In FIG. 21, DL data (i.e. IP packets or NR PDCP SDUs) is communicated from 4G EPC to SgNB-CU-UP across the Sl-U interface and the DL traffic splitting operation for split bearer is carried out at the SgNB-CU-UP after doing NR PDCP processing at the SgNB-CU-UP. Note that incoming downlink NR PDCP SDUs (or IP packets) at the SgNB-CU-UP are transformed to NR PDCP PDUs after NR PDCP processing at the SgNB-CU-UP.

[0040] In FIG. 21, VI is the interface between MeNB-DU and MeNB-CU. Sl-C (Sl-Control plane) interface exists between MeNB-CU and 4G EPC for SN terminated split bearers. DDDS and AID messages are sent from SgNB-DU to SgNB-CU-UP across the Fl-U interface. Also, DDDS and AID messages are sent from MeNB-DU to SgNB-CU-UP via the X2-U interface. Note that UE can start with an MCG bearer (i.e., along the UE - MeNB - 4G EPC) path and MeNB can decide to switch this bearer to an SN terminated split bearer. Alternatively, MeNB can directly decide to establish a SN terminated split bearer for a UE. As part of DL traffic splitting operation at the SgNB-CU-UP, some of these NR PDCP PDUs are communicated fromSgNB-CU-UP to SgNB-DU (across the Fl-U interface as in FIG. 21) and eventually to the UE via the 5G NR-U air-interface. These also get processed via NR RLC and NR MAC at SN (i.e., at SgNB-DU) as was shown in FIG. 18. Additionally, some other NR PDCP PDUs are communicated from SgNB-CU-UP to MeNB-DU (across the X2-U interface as in FIG. 21) and eventually to the UE via the 4G LTE-U air-interface. Note that these NR PDCP PDUs are also processed via E-UTRA RLC and E-UTRA MAC at MN (i.e. at MeNB-DU) as shown in FIG. 18 for split bearers.

[0041] A problem may arise when for UL split bearer scenarios, UE takes the UL splitting decision and decides how to split UL traffic across 4G and 5G legs. In this situation, the splitting decision taken by UE for splitting UL traffic along the 4G and 5G leg may not align with the UL UE-AMBR that the network wants to enforce on the MeNB and the SgNB for this UE. For example, base station (MeNB or SgNB) will typically need to support GBR, GBR-delay critical as well as non-GBR applications. For GBR-delay critical applications, base station also needs to consider requirements related to maximum burst data volume. A base station may estimate requirements of uplink traffic at a time for a UE (including the GBR, GBR-delay critical and non-GBR bearers of that UE) and give an uplink grant to that UE. In general, the UE decides how it wants to utilize uplink grant that it has received from the base station. For example, it can decide to send more non-GBR traffic across a specific air-interface (i.e. 4G or 5G) than what the network is expecting it to do and it may result in violation of UL AMBR at that interface (i.e. at MeNB. DU or at SgNB. DU. Note that For UE-AMBR enforcement, the base station accounts for data sent as part of non-GBR DRBs only though it gives uplink grants which are meant for all types of DRBs of that UE (including GBR, GBR-delay critical and non-GBR)

[0042] The MeNB. DU enforces UL MeNB UE-AMBR and can drop UL packets for the UE at the MeNB if this UL MeNB UE-AMBR constraint is violated for that UE. This is true even if the overall UL UE-AMBR constraint (across MeNB and SgNB) is not violated.

[0043] Additionally, the SgNB. DU enforces UL SgNB UE-AMBR for a given UE and can drop UL packets for a UE at the SgNB. DU if the corresponding UL SgNB UE-AMBR constraint is violated for that UE. Again, this is true even if the overall UL UE-AMBR constraint is not violated.SUMMARY

[0044] Accordingly, what is needed is a system and a method that facilitates UL split bearer scenarios where UE takes an UL splitting decision for splitting UL traffic across 4G and 5G legs.

[0045] It is further desired to provide a system and a method where UL splitting decisions taken by the UE for splitting UL traffic across 4G and 5G legs addresses a splitting decision that does not align with the UL UE-AMBR the network wants to enforce on the MeNB and the SgNB for the UE.

[0046] It is also desired to provide a system and a method that addresses the problem where an MeNB. DU enforcing UL MeNB UE-AMBR drops UL packets for the UE at the MeNB when the UL MeNB UE-AMBR constraint is violated for that UE but the overall UL UE-AMBR constraint (across MeNB and SgNB) is not violated.

[0047] It is still further desired to provide a system and a method that addresses the problem where an SgNB .DU enforcing UL SgNB UE-AMBR drops UL packets for the UE at the SgNB. DU when the UL SgNB UE-AMBR constraint is violated for that UE, but the overall UL UE-AMBR constraint is not violated.

[0048] The methods presented here reduce packet drop due to UL UE AMBR enforcement in the EN-DC architecture. These are also applicable for other dual connectivity architectures, such as Multi-RAT Dual Connectivity (MR-DC), including NR-NR DC.

[0049] In the first method, the MeNB .DU and the SgNB DU coordinate with each other to enforce UL UE-AMBR more effectively. The MeNB. DU enforces UL MeNB UE-AMBR and it can drop UL packets for the UE at the MeNB if this UL MeNB UE-AMBR constraint is violated for the UE. The same applies to the SgNB. DU that enforces UL SgNB UE-AMBR for the UE and can drop UL packets if the corresponding UL SgNB UE-AMBR constraint is violated.

[0050] The MeNB has access to a threshold for each split bearer associated with UE. If the UL data buffered (or pending) at EN-DC UE for a split bearer exceeds the threshold, the UE can split data across 5G leg and 4G leg as opposed to just sending it on the primary path when the UL data pending at UE is below the threshold. However, a decision to split the UL traffic taken bythe UE may not align with UL UE-AMBR that the network is using for MeNB and SgNB because once UL grant is given to the UE, the UE largely determines how to split the traffic on the legs on its own. UL data packets may be dropped at MeNB. DU (due to violation of UL MeNB UE-AMBR) or dropped at SgNB. DU (due to violation of UL SgNB UE-AMBR) but the overall UL UE-AMBR constraint may not violated. In this case, if MeNB. DU is required to drop UL packets for a UE (due to violation of UL MeNB UE-AMBR constraint), the system will buffer such packets for a short interval at MeNB. DU and MeNB. DU will transmit a message to SgNB. DU to determine if it can admit these packets (or a fraction of total length of these packets in bytes) without violating the overall UL UE-AMBR constraint.

[0051] It could occur that UL MeNB UE-AMBR may be violated but UL SgNB UE-AMBR is not violated if the set of packets which are in buffered at MeNB .DU are counted towards the computation of UL SgNB UE-AMBR and this results in UL UE-AMBR not being violated. Thus, SgNB. DU can instruct MeNB. DU whether to admit this group of (non-GBR) packets or a subset of packets. If SgNB. DU instructs MeNB. DU to admit this set of packets, the MeNB. DU transmits these packets to SgNB.CU-UP for SN terminated split bearer. Other packets from this group of packets are dropped at the MeNB .DU. As an example, SgNB. DU could instruct MeNB. DU to accept 60% of total bytes for this set of (non-GBR) packets buffered at MeNB. DU and drop the remaining 40% to enforce overall UL UE-AMBR across MeNB and SgNB for the UE.

[0052] Similarly, if SgNB. DU needs to drop UL non-GBR packets for a UE due to violation of UL SgNB UE-AMBR constraint, it buffers these packets (instead of dropping right away) and sends a message to MeNB.DU to determine if it can transmit these packets without violating the UL UE-AMBR constraint. If MeNB.DU instructs SgNB. DU to transmit this set of packets (or a subset of these packets), the SgNB. DU transmits these to the SgNB.CU-UP for SN terminated split bearer. If not, the corresponding packets are dropped.

[0053] In a second method, if MeNB.DU receives UL packets from a UE it cannot accept due to UL MeNB UE-AMBR restrictions, it buffers these over a short time interval and transmits a message to SgNB. DU to check if some or all of these can be counted towards UL SgNB UE- AMBR (i.e., without violating the overall UL UE-AMBR constraint for that UE). If SgNB. DUcan accept some of these packets and specifies the total length of the packets that it can accept, MeNB.DU transmits these to SgNB.DU, which forwards these to SgNB CU-UP.

[0054] In this configuration, transmission of UL packets that SgNB.DU receives but cannot accept, are first buffered at SgNB.DU and a message is sent to MeNB.DU to see if the data can be counted toward UL MeNB UE-AMBR. If so, SgNB.DU forwards these packets to MeNB.DU which forwards these to SgNB.CU-UP.

[0055] In a third method, if MeNB.DU determines that it can reduce packet drop for a UE after coordinating with SgNB.DU as previously discussed in the first and second methods but the number of packets (or bytes) to drop exceeds a pre-specified (or dynamically computed) threshold, the MeNB.DU proposes to SgNB.DU to increase UL MeNB UE-AMBR. This request is then evaluated by SgNB.DU to see if it can decrease UL SgNB UE-AMBR to accommodate the request to ensure the overall UL UE-AMBR constraint is satisfied. If so, SgNB.DU sends the new value of UL MeNB UE-AMBR to MeNB.DU and starts using the new value of UL SgNB UE-AMBR. The new UL MeNB UE-AMBR and UL SgNB UE-AMBR values are then transmitted to SgNB.CU-CP, which in turn, transmits these new values to MeNB.CU-CP. The reverse is also true, namely SgNB.DU can propose to MeNB.DU to increase UL SgNB UE- AMBR and the process above if followed in reverse order.

[0056] Reference is made to Third Generation Partnership Project (3GPP), 0-RAN Alliance and the Internet Engineering Task Force (IETF) and related standards bodies in accordance with embodiments of the present disclosure. The abbreviations, terms and technology used herein are defined in accord with Third Generation Partnership Project (3GPP), 0-RAN Alliance and / or Internet Engineering Task Force (IETF) technology standards and papers.

[0057] Additionally, for this application the following terms and definitions shall apply:

[0058] The term “data” as used herein means any indicia, signals, marks, symbols, domains, symbol sets, representations, and any other physical form or forms representing information, whether permanent or temporary, whether visible, audible, acoustic, electric, magnetic, electromagnetic or otherwise manifested. The term “data” as used to represent predetermined information in one physical form shall be deemed to encompass any and all representations ofthe same predetermined information in a different physical form or forms.

[0059] The term “network” as used herein includes both networks and internetworks of all kinds, including the Internet, and is not limited to any particular type of network or inter-network.

[0060] The terms “first” and “second” are used to distinguish one element, set, data, object or thing from another, and are not used to designate relative position or arrangement in time.

[0061] The terms “coupled”, “coupled to”, “coupled with”, “connected”, “connected to”, and “connected with” as used herein each mean a relationship between or among two or more devices, apparatus, files, programs, applications, media, components, networks, systems, subsystems, and / or means, constituting any one or more of (a) a connection, whether direct or through one or more other devices, apparatus, files, programs, applications, media, components, networks, systems, subsystems, or means, (b) a communications relationship, whether direct or through one or more other devices, apparatus, files, programs, applications, media, components, networks, systems, subsystems, or means, and / or (c) a functional relationship in which the operation of any one or more devices, apparatus, files, programs, applications, media, components, networks, systems, subsystems, or means depends, in whole or in part, on the operation of any one or more others thereof.

[0062] As used herein, the phrases "at least one" ,"one or more" ,"or" and "and / or" are open- ended expressions that are both conjunctive and disjunctive in operation. For example, each of the expressions "at least one of A, B and C", "at least one of A, B, or C", "one or more of A, B, and C", "one or more of A, B, or C" ,"A, B, and / or C" and "A, B, or C" means A alone, B alone, C alone, A and B together, A and C together, B and C together, or A, B and C together.

[0063] In one configuration, a method for splitting data traffic from a User Equipment (UE) in an Open Radio Access Network (O-RAN) where uplink (UL) data is transmitted from the UE to a Master evolved Node B Distributed Unit (MeNB.DU) and to a Secondary evolved Node B Distributed Unit (SgNB.DU) according to an Uplink Aggregate Maximum Bit Rate (UL AMBR) for the UE is provided, the method comprising the steps of: setting a UL MeNB UE-AMBR governing a maximum bit rate that can be transmitted from the UE to the MeNB.DU for a time period (Ti), and setting a UL SgNB UE-AMBR governing a maximum bit rate that can betransmitted from the UE to the SgNB.DU for Ti. The method is provided such that UL MeNB UE-AMBR and UL SgNB UE-AMBR collectively equal UL UE-AMBR. The method further comprises the step of splitting UL data packets from the UE between the MeNB.DU and the SgNB.DU such that: 1) if the UL data packet splitting violates UL MeNB UE-AMBR, the data packets that violate UL MeNB UE-AMBR are buffered for a time period (T2) and MeNB.DU will transmit a message to SgNB.DU to determine if SgNB.DU can admit the buffered data packets without violating UL SgNB UE-AMBR, and if SgNB.DU can admit the buffered data packets without violating UL SgNB UE-AMBR, MeNB.DU allows the buffered data packets to be transmitted directly to the SgNB Control Unit (SgNB.CU) for Secondary Node (SN) terminated split bearer; 2) if the UL data packet splitting violates UL SgNB UE-AMBR, the data packets that violate UL SgNB UE-AMBR are buffered for a time period (T3) and SgNB.DU will transmit a message to MeNB.DU to determine if MeNB.DU can admit the buffered data packets without violating UL MeNB UE-AMBR, and if MeNB.DU can admit the buffered data packets without violating UL MeNB UE-AMBR, SgNB.DU allows the buffered data packets to be transmitted directly to the SgNB.CU for SN terminated split bearer; and 3) any buffered data packets that violate UL MeNB UE-AMBR or UL SgNB UE-AMBR are dropped.

[0064] In another configuration, a system for splitting data traffic from a User Equipment (UE) in an Open Radio Access Network (0-RAN) where uplink (UL) data is transmitted from the UE to multiple Distributed Units (DUs) according to an Uplink Aggregate Maximum Bit Rate (UL AMBR) for the UE is provided, the system comprising: a Master evolved Node B Distributed Unit (MeNB.DU) receiving split data traffic from the UE, the MeNB.DU having UL MeNB UE- AMBR governing a maximum bit rate that can be transmitted from the UE to the MeNB.DU for a time period (Ti) and a Secondary evolved Node B Distributed Unit (SgNB.DU) receiving split data traffic from the UE, the SgNB.DU having UL SgNB UE-AMBR governing a maximum bit rate that can be transmitted from the UE to the SgNB.DU for Ti. The system is provided such that UL MeNB UE-AMBR and UL SgNB UE-AMBR collectively equal to UL UE-AMBR and the UL data packets from the UE is split and routed between the MeNB.DU and the SgNB.DU such that: 1) if the UL data packet splitting violates UL MeNB UE-AMBR, the data packets that violate UL MeNB UE-AMBR are buffered for a time period (T2) and MeNB.DU will transmit a message to SgNB.DU to determine if SgNB.DU can admit the buffered data packets (fromMeNB.DU) without violating UL SgNB UE-AMBR, and if SgNB.DU can admit the buffered data packets without violating UL SgNB UE-AMBR, MeNB.DU sends these (buffered) packets to SgNB.DU which allows these data packets to be transmitted to a SgNB Control Unit (SgNB.CU) for Secondary Node (SN) terminated split bearer; 2) if the UL data packet splitting violates UL SgNB UE-AMBR, the data packets that violate UL SgNB UE-AMBR are buffered for a time period (T3) and SgNB.DU will transmit a message to MeNB.DU to determine if MeNB.DU can admit the buffered data packets without violating UL MeNB UE-AMBR, and if MeNB.DU can admit the buffered data packets without violating UL MeNB UE-AMBR, SgNB.DU sends the buffered data packets to MeNB.DU which allows the buffered data packets to be transmitted to the SgNB.CU for SN terminated split bearer; and 3) any buffered data packets that violate UL MeNB UE-AMBR or UL SgNB UE-AMBR are dropped.

[0065] The above-described and other features and advantages of the present disclosure will be appreciated and understood by those skilled in the art from the following detailed description, drawings, and appended claims.BRIEF DESCRIPTION OF THE DRAWINGS

[0066] FIG. la is a block diagram illustrating an overview of Next Generation Radio Access Network (NG-RAN) architecture and Fifth Generation New Radio (5G NR) stacks according to the prior art;

[0067] FIG. lb is a block diagram showing user plane protocols stacks for a protocol data unit (PDU) session according to FIG. la;

[0068] FIG. 2 is a block diagram of a control plane according to FIG. la;

[0069] FIGS. 3 & 4 are block diagrams depicting NG-RAN architecture according to FIG. la;

[0070] FIG. 5 is a block diagram illustrating DL L2 structure for 5G NR according to FIG. la;

[0071] FIG. 6 is a block diagram illustrating an overview of 0-RAN with disaggregated RAN CU, DU, and RU, near-real-time RIC and non-real-time RIC according to FIG. la;

[0072] FIG. 7 illustrates one example of a PDU session comprising multiple DRBs, where each DRB may comprise multiple QoS flows according to FIG. 1 a;

[0073] FIG. 8 is data flow diagram showing multiple PDU sessions involving multiple DRBs and QoS Flow Identifiers according to FIG. la;

[0074] FIG. 9 is a block diagram illustrating the context of RRM for connecting UE to the network via an RU with a MAC Scheduler according to FIG. la;

[0075] FIG. 10 is a block diagram showing CU-UP sending DL User Data to DU according to FIG. la;

[0076] FIG. 11 is a block diagram showing DL Data Delivery Status according to FIG. la;

[0077] FIG. 12 is a block diagram showing the DU can send Assistance Information Data to CU- UP according to FIG. la;

[0078] FIG. 13 is a block diagram illustrating a 5G Standalone network, where SMF in the 5GC retrieves DL and UL UE-AMBR from the Unified Data Management and provides this to Access and Mobility Management in 5GC according to FIG. la;

[0079] FIG. 14 is a block diagram illustrating a 4G Standalone network, where MME from the 4G EPC communicates DL UE-AMBR and UL UE-AMBR to the 4G base station according to FIG. la;

[0080] FIG. 15 is a block diagram illustrating EN-DC (E-UTRA-NR Dual Connectivity) architecture where UE has a single RRC state, based on Master Node RRC and a single Control plane connection towards the Mobility Management Entity of 4G Evolved Packet Core according to FIG. 14;

[0081] FIG. 16 is a block diagram illustrating the data (user) plane for the EN-DC architecture according to FIG. 15;

[0082] FIG. 17 is a block diagram illustrating Master Cell Group, Secondary Cell Group and split bearers from a UE perspective according to FIGS. 13 & 14;

[0083] FIG. 18 is a block diagram illustrating shows Master Cell Group, Secondary Cell Group and split bearers from base station perspective according to FIGS. 13 & 14;

[0084] FIG. 19 is a block diagram illustrating EN-DC (or other dual connectivity) architecture, where UE-AMBR is split into MeNB UE-AMBR and SgNB UE-AMBR, which are enforced by MeNB and SgNB respectively according to FIGS. 13 & 14;

[0085] FIG. 20 is a block diagram showing the MME communicates DL UE-AMBR and UL UE-AMBR to MeNB.CU-CP and the MeNB splits this into DL MeNB UE-AMBR, UL MeNB UE-AMBR, DL SgNB UE-AMBR and UL SgNB UE-AMBR according to FIG. 19;

[0086] FIG. 21 is a block diagram illustrating EN-DC (E-UTRA-NR Dual Connectivity) architecture with downlink split bearer operation according to FIG. 20;

[0087] FIGS. 22 - 23 depict a functional flow diagram illustrating secondary node (SgNB in the EN-DC architecture) addition and DL traffic splitting procedures according to FIG. 21;

[0088] FIG. 24 is a block diagram illustrating EN-DC architecture with UL split bearer operation according to one configuration of the present disclosure; and

[0089] FIG. 25 is a block diagram illustrating MeNB. DU and SgNB. DU coordinating with each other to enforce UL UE-AMBR more effectively according to FIG. 24.DETAILED DESCRIPTION

[0090] Referring to the drawings and in particular to FIGS. 22 and 23, some of the steps for secondary node (i.e., SgNB in the EN-DC architecture) addition and DL traffic splitting procedures are illustrated.

[0091] As shown in FIG. 22, MCG bearer is already established for this UE and MeNB decides to convert this to SgNB terminated split bearer. As part of Step 1) in FIG. 22, MeNB, specifically MeNB.CU-CP of MeNB, sends ‘SgNB Addition Request’ to SgNB.CU-CP. It contains information about the bearer for which SN (i.e., SgNB) split bearer needs to be established. It also informs DL SgNB UE-AMBR and UL SgNB UE-AMBR to SgNB.CU-CP.In step 2), SgNB.CU-CP sends ‘Bearer Context Setup Request’ message to SgNB.CU-UP using the El AP protocol. As part of step 3), SgNB.CU-UP sends ‘Bearer Context Setup Response’ message to SgNB.CU-CP. Along with other parameters, QoS information about bearer is shared with SgNB.CU-UP as part of step 2) and 3). In step 4), ‘UE Context Setup Request’ message is sent from SgNB.CU-CP to SgNB.DU across the Fl-C interface using the F1AP protocol. In Step 5), SgNB.DU responds with ‘UE Context Setup Response’ message to SgNB.CU-CP. Along with other parameters, QoS information about the bearer is shared with SgNB.DU as part of step 5) and 6). In step 6), ‘Bearer Context Setup Request’ is sent from SgNB.CU-CP to SgNB.CU-UP, and in step 7), ‘Bearer Context Setup Response’ message is sent from SgNB.CU- UP to SgNB.CU-CP. In step 8), SgNB.CU-CP sends ‘SgNB Addition Request Acknowledge’ message to MeNB (and specifically to MeNB.CU-CP of MeNB). GTP-U tunnel to carry traffic between SgNB.CU-UP and SgNB.DU for 5G leg of SgNB terminated split bearer is also established as part of the steps shown in FIG. 22.

[0092] FIG. 23 shows some additional steps with which GTP-U tunnel to carry traffic on 4G leg is completely established between SgNB.CU-UP and MeNB (or specifically between SgNB.CU- UP and MeNB. DU for disaggregated base station architecture). It also shows the part where UE carries out random access procedure with SgNB to directly start getting data via SgNB (for the 5G leg). In step 9) of FIG. 23, MeNB, specifically MeNB.CU-CP of MeNB, sends RRC Connection Reconfiguration to (EN-DC) UE and in step 10), this UE responds with ‘RRC Reconfiguration Complete’ message. In step 11), MeNB, specifically MeNB.CU-CP of MeNB, sends ‘SgNB Reconfiguration Complete’ to SgNB.CU-CP. As part of step 12), UE carries out random access procedure with SgNB. In step 13), MeNB, specifically MeNB.CU-CP of MeNB, sends ‘SN Status Transfer’ to SgNB-CU-CP’ (if bearer is using RLC AM). Data forwarding from MeNB (specifically from MeNB.CU-UP of MeNB) to SgNB.CU-UP happens as part of steps 14) and 15). Next, SgNB.CU-UP also starts splitting traffic across 5G and 4G legs of the network. DL Data towards 4G leg is sent as part of steps 16) and 17). DL data towards 5G leg is sent as part of steps 18) and 19). As part of step 20), MeNB interacts with 4G EPC to carry out path switch to make it SN terminated split bearer. 4G EPC starts sending DL data towards SgNB.CU-UP as part of step 21) after the path switch operation. SgNB.CU-UP continues to split traffic across 4G and 5G legs of the network.

[0093] Referring now to FIG. 24, EN-DC architecture with UL split bearer operation is illustrated. For the UL split bearer in the EN-DC (NSA) architecture, uplink data from the EN- DC UE 105 towards the SgNB-DU 152 and MeNB.DU 142 is split at the (EN-DC) UE 105. After splitting, some packets are sent on the 5G leg 154 (towards SgNB.CU-UP 151) and others on the 4G leg 144 of the network (towards SgNB.CU-UP 151). SgNB.CU-UP eventually sends these towards 4G EPC 140.

[0094] The MeNB.CU 141 provides a threshold value, indicated as ul-DataSplitThreshold, to each (EN-DC) UE 105 for each split DRB. ul-DataSplitThreshold ::= ENUMERATED { bO, blOO, b200, b400, b800, bl600, b3200, b6400, bl2800, b25600, b51200, bl02400, b204800, b409600, b819200, bl228800, bl638400, b2457600, b3276800, b4096000, b4915200, b5734400, b6553600, infinity, spare8, spare7, spare6, spare5, spared, spare3, spare2, sparel }

[0095] Here bl 00 means 100 bytes, b400 means 400 bytes and so on. If UL data accumulated at the EN-DC UE for a split DRB is above this threshold, the EN-DC UE can split data across 5G leg 154 and 4G leg 144 of the network using its own internal logic. If UL data accumulated at (EN-DC) UE 105 is below this threshold, the (EN-DC) UE 105 sends data for that DRB along the primary path. For example, the primary path could be 5G leg 154 and secondary path could be 4G leg 144 for a split bear (for a given deployment scenario).

[0096] In FIG. 24, VI 234 is the interface between MeNB.DU 142 and MeNB.CU 141. Sl-C (Sl-Control plane) interface exists between MeNB.CU 141 and 4G EPC 140. EN-DC UE 105 uses RRC signaling between itself and MeNB.CU 141. MeNB.DU enforces UL MeNB UE- AMBR and SgNB.DU enforces UL SgNB UE-AMBR. Inter-DU interface can be used for DU- to-DU communication. The protocol used for inter-DU communication is called D2-AP (D2- Application Layer) over D2-C (D2-Control plane interface). This is used for the control plane information exchange between MeNB.DU and SgNB.DU in the EN-DC architecture. Protocol used for user plane communication over D2 is denoted by D2-U (D2 - User plane).

[0097] Method 1 Referring now to FIG. 25, one configuration is depicted. In this case, MeNB.DU and SgNB.DU coordinate with each other over the D2 interface to enforce UL UE-AMBR more effectively.

[0098] MeNB.DU enforces UL MeNB UE-AMBR and it can drop UL packets for this UE at MeNB if this UL MeNB UE-AMBR constraint is violated for that UE. Similarly, SgNB.DU enforces UL SgNB UE-AMBR for a given UE, and it can drop UL packets for a UE if the corresponding UL SgNB UE-AMBR constraint is violated for that UE.

[0099] As described earlier, MeNB informs a threshold value, ul-DataSplitThreshold, for each split bearer to the corresponding UE. If UL data accumulated at EN-DC UE for a split bearer is above this threshold, UE can split data across 5G leg 154 and 4G leg 144 of the network using its own internal logic (as in FIG. 24). If UL data accumulated at (EN-DC) UE 105 is below this threshold, the (EN-DC) UE 105 sends data for that DRB along the primary path.

[0100] In this architecture, it can easily happen that the decision taken by the UE for splitting UL traffic along the 4G and 5G legs does not align with UL UE-AMBR that network wants to enforce on MeNB and SgNB for this UE. For example, base station (MeNB or SgNB) will typically need to support GBR, GBR-delay critical as well as non-GBR applications. For GBR-delay critical applications, base station also needs to consider requirements related to maximum burst data volume. A base station may estimate requirements of uplink traffic at a time for a UE (including the GBR, GBR-delay critical and non-GBR bearers of that UE) and give an uplink grant to that UE. In general, the UE decides how it wants to utilize uplink grant that it has received from the base station. For example, it can decide to send more non-GBR traffic across a specific air-interface (i.e. 4G or 5G) than what the network is expecting it to do and it may result in violation of UL AMBR at that interface (i.e. at MeNB.DU or at SgNB.DU. Note that For UE-AMBR enforcement, the base station accounts for data sent as part of non- GBR DRBs only though it gives uplink grants which are meant for all types of DRBs of that UE (including GBR, GBR-delay critical and non-GBR).

[0101] With above, UE may send more UL non-GBR traffic on 4G leg (compared to 5G leg) during a specific time interval, but the network may not want to allow this during this specific time interval (and this is enforced by MeNB.DU using the UL MeNB UE-AMBR for that UE). In this scenario, it could also happen that the UL SgNB UE-AMBR constraint is not violated (for 5G leg of the network) but UE is more interested in sending higher amount of ULnon-GBR data via 4G leg during this time.

[0102] As another example of the above scenario, UE may send more UL non-GBR traffic on the 5G leg (compared to the 4G leg) during a specific time interval but the network may not want to allow this in that specific time interval (and this is enforced by SgNB.DU as indicated by UL SgNB UE-AMBR). In this scenario, it could also happen that the UL MeNB UE-AMBR constraint is not violated (for 4G leg of the network) but this UE is more interested in sending higher amount of UL non-GBR data via 5G leg during this time.

[0103] If UL data packets from UE are dropped at MeNB.DU (due to violation of UL MeNB UE-AMBR) or dropped at SgNB.DU (due to violation of UL SgNB UE-AMBR) but the overall UL UE-AMBR constraint is not violated, this method reduces packet drop for such scenarios and improves performance of applications running at the UE. For example, if MeNB.DU needs to drop UL packets for a UE (due to violation of UL MeNB UE-AMBR constraint), it buffers such packets for a short interval at MeNB.DU and sends a message to SgNB.DU across the D2 interface to check if it can admit these packets (or a fraction of total length of these packets in bytes) without violating the overall UL UE-AMBR constraint.

[0104] For example, it can happen that UL MeNB UE-AMBR is violated but UL SgNB UE-AMBR is not violated if this set of packets, which is buffered at MeNB.DU (for a specified time interval) is counted towards the computation of UL SgNB UE-AMBR (and thus overall, UL UE-AMBR is also not violated). Depending on the policies implemented in the system, SgNB.DU informs MeNB.DU across the D2 interface whether to admit this group of packets (or a subset of packets).

[0105] If SgNB.DU instructs MeNB.DU to admit this set of packets (or a fraction of total length of this set of packets), the MeNB.DU processes the corresponding packets further and communicates this group of packets to SgNB.CU-UP for SN terminated split bearer. Other packets from this group of packets are dropped at the MeNB.DU.

[0106] For example, SgNB.DU could communicate to MeNB.DU to accept 60% of total bytes for this set of packets buffered at MeNB.DU and drop the remaining 40% at MeNB.DU to enforce overall UL UE-AMBR across MeNB and SgNB for the UE supporting split bearers inthe EN-DC architecture.

[0107] Similarly, if SgNB.DU needs to drop UL packets for a UE (due to violation of UL SgNB UE-AMBR constraint), it buffers such packets for a short interval and sends a message to MeNB.DU across the D2 interface to check if it can admit these packets without violating the overall UL UE-AMBR constraint.

[0108] If MeNB.DU informs SgNB.DU to admit this set of packets (or a fraction of the total number of bytes for this set of packets), the SgNB.DU processes these packets and communicates this set of packets (or a fraction of these packets) to the SgNB.CU-UP for SN terminated split bearer. On the other hand, if MeNB.DU informs SgNB.DU not to accept these packets (or a fraction of the total number of bytes), the corresponding packets are dropped by the SgNB.DU.

[0109] Method 2. As in Method 1, if MeNB.DU receives UL packets from a UE that it cannot accept due to UL MeNB UE-AMBR restrictions for that UE, it buffers these over a short time interval and sends a message to SgNB.DU across the D2-C (D2-Control) interface using D2AP (D2 Application Protocol) to check if some or all of these can be counted towards UL SgNB UE-AMBR (without violating the overall UL UE-AMBR constraint for that UE). If SgNB.DU informs MeNB.DU that it can accept some of these packets from this set of packets and specifies total length of the packets that it can accept from this set of packets, MeNB.DU forwards these to SgNB.DU using a GTP-U tunnel across the D2-U (i.e. D2-User plane) interface and SgNB.DU forwards these to SgNB.CU-UP across Fl-U for SN terminated split bearer.

[0110] Similarly, if SgNB.DU receives UL packets from a UE that it cannot accept due to UL SgNB UE-AMBR restrictions for that UE, it buffers these over a short time interval and sends a message to MeNB.DU across the D2-C interface (using D2AP) to check if some or all of these can be counted towards UL MeNB UE-AMBR (without violating the overall UL UE- AMBR constraint for that UE). If MeNB.DU informs SgNB.DU that it can accept some of the packets from this set of packets and specifies total length of the packets that it can accept from this set of packets, SgNB.DU forwards these to MeNB.DU using a GTP-U tunnel across the D2- U (i.e., D2-User plane) interface and MeNB.DU forwards these to SgNB.CU-UP across X2-Ufor SN terminated split bearer.

[0111] Method 3. If MeNB.DU determines it can reduce packet drop for this UE after coordinating with SgNB.DU (as in Method 1 or 2) and if this occurs over a time interval exceeding a threshold, MeNB.DU proposes to increase its value of UL MeNB UE-AMBR (to a value denoted as proposed.UL. MeNB .UE-AMBR) and sends a message to SgNB.DU across the D2-C interface (using D2AP) for the same. SgNB.DU evaluates this request and analyzes various performance parameters available for UL traffic for that UE. If it determines it can allow MeNB.DU to increase UL MeNB.DU UE-AMBR and can decrease its own UL SgNB UE- AMBR, it determines new values for UL SgNB UE-AMBR and UL MeNB UE-AMBR so that the overall UL UE-AMBR constraint is still satisfied for that UE. SgNB.DU sends the new value of UL MeNB UE-AMBR to MeNB.DU across the D2-C interface and starts using the new value of UL SgNB UE-AMBR (at SgNB.DU for this UE).

[0112] SgNB.DU also transmits the new values of UL MeNB UE-AMBR and UL SgNB UE-AMBR to SgNB.CU-CP using the Fl-C interface. Fl AP running over Fl -C is enhanced for this purpose. The SgNB.CU-CP transmits these updated UL MeNB UE-AMBR and UL SgNB UE-AMBR values to MeNB.CU-CP using the X2-C interface. X2AP running over X2-C is enhanced for this purpose.

[0113] On the other hand, if SgNB.DU observes it can reduce packet drop for this UE after coordinating with MeNB.DU (as in Methods 1 and 2), and if this happens over a time interval exceeding a threshold, SgNB.DU proposes to increase its value of UL SgNB UE-AMBR (to a value denoted as proposed. UL. SgNB. UE-AMBR) and sends a message to MeNB.DU across the D2-C interface (using D2AP) for the same. MeNB.DU evaluates this request and analyzes various performance parameters available for UL traffic for that UE. If it determines that it can allow SgNB.DU to increase UL SgNB.DU UE-AMBR and it can decrease its own UL MeNB UE-AMBR, it selects new values for UL MeNB UE-AMBR and UL SgNB UE-AMBR so that the overall UL UE-AMBR constraint is still satisfied for that UE. MeNB.DU sends the new value of UL SgNB UE-AMBR to SgNB.DU across the D2-C interface and starts using the new value of UL MeNB UE-AMBR (at MeNB.DU for this UE).

[0114] SgNB.DU transmits the new values of UL MeNB UE-AMBR and UL SgNB UE-AMER to SgNB.CU-CP using the Fl-C interface. SgNB.CP transmits these updated UL MeNB UE-AMBR and UL SgNB UE-AMBR values to MeNB.CU-CP using the X2-C interface. X2AP running over X2-C is enhanced for this purpose.

[0115] Alternatively, SgNB. DU transmits the new values of UL MeNB UE-AMBR andUL SgNB UE-AMBR to SgNB.CU-UP using the AID field across the X2-U interface. The AID field is enhanced for this purpose. Next, SgNB.CU-UP communicates the updated UL MeNB UE-AMBR and UL SgNB UE-AMBR values to SgNB.CU-CP using the El interface. El AP running over El interface is enhanced for this purpose. After this, the SgNB.CP transmits these updated UL MeNB UE-AMBR and UL SgNB UE-AMBR values to MeNB.CU-CP using the X2-C interface. X2AP running over X2-C is enhanced for this purpose.

[0116] The methods presented here reduce packet drop due to UL UE AMBR enforcement in the EN-DC architecture. These are also applicable for other dual connectivity architectures such as Multi-RAT Dual Connectivity (MR-DC), including NR-NR DC.

[0117] While the present disclosure has been described with reference to one or more exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents can be substituted for elements thereof without departing from the scope of the present disclosure. In addition, many modifications can be made to adapt a particular situation or material to the teachings of the disclosure without departing from the scope thereof. Therefore, it is intended that the present disclosure not be limited to the particular embodiment(s) disclosed as the best mode contemplated, but that the disclosure will include all embodiments falling within the scope of the appended claims.

Claims

CLAIMS1. A method for splitting data traffic from a User Equipment (UE) in an Open Radio AccessNetwork (O-RAN) where uplink (UL) data is transmitted from the UE to a Master evolved Node B Distributed Unit (MeNB.DU) and to a Secondary evolved Node B Distributed Unit (SgNB.DU) according to an Uplink Aggregate Maximum Bit Rate (UL AMBR) for the UE, the method comprising the steps of: setting a UL MeNB UE-AMBR governing a maximum bit rate that can be transmitted from the UE to the MeNB.DU for a time period (Ti); setting a UL SgNB UE-AMBR governing a maximum bit rate that can be transmitted from the UE to the SgNB.DU for Ti; wherein UL MeNB UE-AMBR and UL SgNB UE-AMBR collectively equal UL UE- AMBR; splitting UL data packets with the UE between the MeNB.DU and the SgNB.DU so that:1) if the UL data packet splitting violates UL MeNB UE-AMBR, the data packets that violate UL MeNB UE-AMBR are buffered for a time period (T2) and MeNB.DU will transmit a message to SgNB.DU to determine if SgNB.DU can admit the buffered data packets without violating UL SgNB UE-AMBR, and if SgNB.DU can admit the buffered data packets without violating UL SgNB UE-AMBR, SgNB.DU allows the buffered data packets from MeNB.DU to be transmitted, which are then transmitted to a SgNB Control Unit (SgNB.CU) for Secondary Node (SN) terminated split bearer;2) if the UL data packet splitting violates UL SgNB UE-AMBR, the data packets that violate UL SgNB UE-AMBR are buffered for a time period (T3) and SgNB.DUwill transmit a message to MeNB.DU to determine if MeNB.DU can admit the buffered data packets without violating UL MeNB UE-AMBR, and if MeNB.DU can admit the buffered data packets without violating UL MeNB UE-AMBR, MeNB.DU allows the buffered data packets from SgNB.DU to be transmitted, which are then transmitted to the SgNB.CU for SN terminated split bearer;3) wherein any buffered data packets that violate UL MeNB UE-AMBR or UL SgNB UE-AMBR are dropped.

2. The method according to claim 1, wherein only a fraction of the total length of the buffered data packets in bytes is transmitted when transmitting a total length of the buffered data packets would violate UL MeNB UE-AMBR, SgNB UE-AMBR, or UE-AMBR.

3. The method according to claim 2, wherein the step of, if the other can admit the buffered data packets without violating its own UE-AMBR, the other allows the buffered data packets to be transmitted further comprises: when the other is SgNB.DU, the SgNB.DU checks if some or all of the buffered data packets with MeNB.DU can be counted toward UL SgNB UE-AMBR without violating UL UE- AMBR; if SgNB.DU can accept some or all the buffered data packets, SgNB.DU specifies a total length of the packets that it can accept and transmits this to MeNB.DU; wherein SgNB.DU then forwards the received data to SgNB.CU-UP.

4. The method according to claim 3,wherein MeNB.DU requests SgNB.DU to increase UL MeNB UE-AMBR and SgNB.DU determines if it can reduce UL SgNB UE-AMBR to accommodate the request to ensure UL UE- AMBR is satisfied; wherein if SgNB.DU determines it can accommodate the request, SgNB.DU transmits a new larger value of UL MeNB UE-AMBR to MeNB.DU and starts using a new smaller value of UL SgNB UE-AMBR; wherein the new larger value of UL MeNB UE-AMBR and the new smaller value of UL SgNB UE-AMBR are transmitted to SgNB.CU-CP, which in turn, transmits these new values to MeNB Control Unit-Control Plane (MeNB.CU-CP).

5. The method according to claim 4, wherein the new larger value for UL MeNB UE- AMBR corresponds inversely to the new smaller value for UL SgNB UE-AMBR.

6. The method according to claim 2, wherein the step of if the other can admit the buffered data packets without violating its own UE-AMBR, the other allows the buffered data packets to be transmitted further comprises: when the other is MeNB.DU, the MeNB.DU checks if some or all of the buffered data packets with SgNB.DU can be counted toward UL MeNB UE-AMBR without violating UL UE- AMBR; if MeNB.DU can accept some or all the buffered data packets, MeNB.DU specifies a total length of the packets that it can accept and transmits this to SgNB.DU; wherein MeNB.DU then forwards the received data to SgNB.CU-UP.

7. The method according to claim 6, wherein SgNB.DU requests MeNB.DU to increase UL SgNB UE-AMBR and MeNB.DU determines if it can reduce UL MeNB UE-AMBR to accommodate the request to ensure UL UE- AMBR is satisfied; wherein if MeNB.DU determines it can accommodate the request, MeNB.DU transmits a new larger value of UL SgNB UE-AMBR to SgNB.DU and starts using a new smaller value of UL MeNB UE-AMBR; wherein the new larger value of UL SgNB UE-AMBR and the new smaller value of UL MeNB UE-AMBR are transmitted to SgNB.CU-CP, which in turn, transmits these new values to MeNB Control Unit-Control Plane (MeNB CU-CP).

8. The method according to claim 7, wherein the new larger value for UL SgNB UE-AMBR corresponds inversely to the new smaller value for UL MeNB UE-AMBR.

9. The method according to claim 1, wherein MeNB is Long Term Evolution (LTE) eNB, and wherein SgNB is 5G next generation Node B (gNB) as the SN.

10. The method according to claim 9, wherein the MeNB.DU includes a 4G Medium Access Control (MAC) Scheduler, and wherein the SgNB.DU includes a 5G MAC Scheduler.

11. The method according to claim 1, wherein MeNB informs a threshold value for each split bearer to a corresponding UE.

12. The method according to claim 1, wherein the MeNB.DU is coupled with an MeNB Control Unit (MeNB.CU), wherein the MeNB.CU includes an MeNB.CU-Control Plane (MeNB.CU-CP) and an MeNB.CU-User Plane (MeNB.CU-UP), and wherein the SgNB.CU includes an SgNB.CU-Control Plane (SgNB.CU-CP) and an SgNB.CU-User Plane (SgNB.CU- UP).

13. The method according to claim 12, wherein the MeNB.CU and the SgNB.CU are coupled to each other, and both the MeNB.CU and the SgNB.CU are coupled to a 4G Evolved Packet Core (EPC).

14. A system for splitting data traffic from a User Equipment (UE) in an Open Radio Access Network (O-RAN) where uplink (UL) data is transmitted from the UE to multiple Distributed Units (DUs) according to an Uplink Aggregate Maximum Bit Rate (UL AMBR) for the UE, the system comprising: a Master evolved Node B Distributed Unit (MeNB.DU) receiving split data traffic from the UE, the MeNB.DU having UL MeNB UE-AMBR governing a maximum bit rate that can be transmitted from the UE to the MeNB.DU for a time period (Ti); a Secondary evolved Node B Distributed Unit (SgNB.DU) receiving split data traffic from the UE, the SgNB.DU having UL SgNB UE-AMBR governing a maximum bit rate that can be transmitted from the UE to the SgNB.DU for Ti; wherein UL MeNB UE-AMBR and UL SgNB UE-AMBR collectively equal UL UE- AMBR; wherein the UE splits UL data packets between the MeNB.DU and the SgNB.DU so that: 1) if the UL data packet splitting violates UL MeNB UE-AMBR, the data packetsthat violate UL MeNB UE-AMBR are buffered for a time period (T2) and MeNB.DU will transmit a message to SgNB.DU to determine if SgNB.DU can admit, for the purpose of computation of total UL AMBR, the buffered data packets without violating UL SgNB UE-AMBR, and if SgNB.DU can admit the buffered data packets without violating UL SgNB UE-AMBR, SgNB.DU allows the buffered data packets to be transmitted by MeNB.DU, which are then transmitted to a SgNB Control Unit (SgNB.CU) for Secondary Node (SN) terminated split bearer;2) if the UL data packet splitting violates UL SgNB UE-AMBR, the data packets that violate UL SgNB UE-AMBR are buffered for a time period (T3) and SgNB.DU will transmit a message to MeNB.DU to determine if MeNB.DU can admit the buffered data packets without violating UL MeNB UE-AMBR, and if MeNB.DU can admit the buffered data packets without violating UL MeNB UE- AMBR, MeNB.DU allows the buffered data packets to be transmitted by SgNB.DU, which are then transmitted to the SgNB.CU for SN terminated split bearer;3) wherein any buffered data packets that violate UL MeNB UE-AMBR or UL SgNB UE-AMBR are dropped.

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