Optimizing inter-du downlink radio resource management in o-ran networks

Abstract

In a system for implementing optimized coordinated multi-point transmission (CoMP) in an Open Radio Access Network (O-RAN) wireless system including at least one centralized unit (CU) of the O-RAN; a first distributed unit (DU) of the O-RAN; and a second DU of the O-RAN, optimized CoMP is implemented based on information provided by at least one of the CU, the first DU and the second DU regarding at least one of i) interference experienced by a user equipment (UE) in a first serving cell of the first DU from a neighbor cell of the first serving cell, and ii) interference experienced in a second serving cell of the second DU from a neighbor cell of the second serving cell. Coordination of the optimized CoMP is implemented by at least one of the first DU, the second DU and a near-real time radio intelligent controller (near-RT RIC).

Description

Optimizing Inter-DU Downlink Radio Resource Management in O-RAN NetworksBACKGROUND OF THE DISCLOSURE1. Field of the Disclosure

[0001] The present disclosure relates to Open Radio Access Network (O-RAN) systems, and relates more particularly to optimization of inter-DU downlink radio resource management in O-RAN systems.2. Description of Related Art

[0002] In the following sections, an overview of Next Generation Radio Access Network (NG-RAN) architecture and 5GNew Radio (NR) stacks will be presented. 5GNew Radio (NR) user and control plane functions with monolithic gNB (gNodeB) are shown in FIGS. 1a, 1b and 2. For the user plane (shown in FIG. 1a, which is in accordance with 3GPP TS 38.300), physical (PHY), Medium Access Control (MAC), Radio Link Control (RLC), Packet Data Convergence Protocol (PDCP) and Service Data Adaptation Protocol (SDAP) sublayers originate in the UE 101 and are terminated in the gNB 102 on the network side.

[0003] As shown in FIG. 1b, which is a block diagram illustrating the user plane protocols stacks for a PDU session, in accordance with 3GPP TS 23.501, PDU layer 9010 corresponds to the PDU carried between the UE 101 and the data network (DN) 9011 over the PDU session. As shown in FIG. 1b, UE 101 is connected to the 5G access network (AN) 902, which AN 902 is in turn connected via the N3 interface to the Intermediate UPF (I-UPF) 903a portion of the UPF 903, which I-UPF 903a is in turn connected via the N9 interface to the PDU session anchor 903b portion of the UPF 903, and which PDU session anchor 903b is connected to the DN 9011. 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. GTP-U shown in FIG. 1b supports tunnelling user plane data over N3 and N9 interfaces and provides encapsulation of end user PDUs for N3 and N9 interfaces.

[0004] For the control plane (shown in FIG. 2, which is in accordance with 3GPP TS 38.300), Radio Resource Control (RRC), PDCP, RLC, MAC and PHY sublayers originate in the UE 101 and are terminated in the gNB 102 on the network side, and Non- Access Stratum (NAS) originate in the UE 101 and is terminated in the Access & Mobility Function (AMF) 103 on the network side.

[0005] NG-Radio Access Network (NG-RAN) architecture from 3GPP TS 38.401 is shown in FIGS. 3-4. As shown in FIG. 3, the NG-RAN 301 consists of 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-Control Plane (CU-CP) and CU-User Plane (CU-UP)), El is the interface between gNB-CU-CP 304a and gNB-CU-UP 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 consist of 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 only one gNB-CU- CP 304a, and one gNB-CU-UP 304b is connected to only one gNB-CU-CP 304a. Note that F1-Application Protocol (F1-AP) running on F1-C is specified in 3GPP TS38.473 version 18.1.0, and NR User Plane (NR-U) running on F1-U is specified in 3GPP TS38.425 version 18.0.0.

[0006] In this section, an overview of Layer 2 (L2) of 5G NR will be provided in connection with FIG. 5. L2 of 5G NR is split into the following sublayers (in accordance with 3GPP TS 38.300):1) Medium Access Control (MAC) 501 in FIGS. 5: Logical Channels (LCs) are Service Access Points (SAPs) 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 to the RLC layer using the LCs.2) Radio Link Control (RLC) 502 in FIG. 5: The RLC sublayer presents RLC channels tothe 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 Automatic Repeat Request (ARQ) protocol for RLC-AM mode.3) Packet Data Convergence Protocol (PDCP) 503 in FIG. 5: 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.4) Service Data Adaptation Protocol (SDAP) 504 in FIG. 5: The SDAP maps QoS flows within a PDU session to a specific Data Radio Bearer.FIG. 5 is a block diagram illustrating DL L2 structure, in accordance with 3GPP TS 38.300.

[0007] Open Radio Access Network (O-RAN) is based on disaggregated components which are connected through open and standardized interfaces based on 3 GPP NG-RAN. An overview of O-RAN with disaggregated RAN CU (Centralized Unit), DU (Distributed Unit), and RU (Radio Unit), near-real-time Radio Intelligent Controller (Near-RT-RIC) and non-real-time RIC is illustrated in FIG. 6.

[0008] 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 could 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).

[0009] 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 a given sector). One CU-CP could support multiple DUs and thus multiple cells. For example, a CU-CP could support 500 cells and around 100,000 User Equipments (UEs). Each UE could support multiple DRBs and there could be multiple instances of CU-UP to serve these DRBs. Forexample, each UE could support 4 DRBs, and 400,000 DRBs (corresponding to 100,000 UEs) may be served by five CU-UP instances (and one CU-CP instance).

[0010] The DU could be located in a private data center, or it could be located at a cellsite. The CU could also be in a private data center or even hosted on a public cloud system. The DU and CU, which are typically located at different physical locations, could be tens of kilometers 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 Radio Unit (shown as 0-RU 803 in FIG. 6) is located at a cell-site and communicates with the DU via a front-haul (FH) interface.

[0011] 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 atNon-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).

[0012] Near-RT -Architecture is specified in the O-RAN Alliance specification O-RAN Near-RT -Architecture 6.0, O-RAN E2 Service Model (E2SM) KPM 5.0, O-RAN E2 Application Protocol (E2AP) 5.0 and O-RAN Al Interface: Application Protocol 4.02.

[0013] The following should be noted for 3GPP 5G network architecture, which is illustrated in FIG. 7 in the context of Radio Resource Management (RRM) for connecting UE 101 to the network via RU 306 with a MAC Scheduler 1001:1) The transport connection between the base station (i.e., CU-UP 304b of FIG. 7) and the UPF (in 5G core network) uses a single GTP-U tunnel per PDU session, as shown in FIG. 7. The PDU session is identified using GTP-U TEID (Tunnel Endpoint Identifier).2) The transport connection between the DU 305 and the CU-UP 304b of FIG. 7 uses a single GTP-U tunnel per DRB. 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.3) SDAP:a) The Service Adaptation Protocol (SDAP) 504 Layer receives downlink data from the UPF 903 across the NG-U interface (see FIG. 7).b) The SDAP 504 maps one or more QoS Flow(s) onto a specific DRB.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.4) GTP-U protocol includes a field to identify the QoS flow and is present between CU and UPF 903 (in the core network).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. 7. Separate logical queues may exist in DU for packets that are to be retransmitted to UE.

[0014] In this section, standardized 5QI to QoS characteristics mapping will be discussed. As per 3GPP TS 23.501, the one-to-one mapping of standardized 5QI values to 5G QoS characteristics is specified in Table 1 shown below. The first column represents the 5QI value. The second column lists the different resource types, i.e., as one of Non-GBR, GBR, Delay-critical GBR. The third column (“Default Priority Level”) represents the priority level Priority5QI, for which lower the value the higher the priority of the corresponding QoS flow. The fourth column represents the Packet Delay Budget(PDB), which defines an upper bound for the time that a packet may be delayed between the UE and the N6 termination point at the UPF. The fifth column represents the Packet Error Rate (PER). The sixth column represents the maximimum data burst volume for delay-critical GBR types. The seventh column represents averaging window for GBR, delay critical GBR types. Note that only a subset of 5QI values defined in 3GPP TS 23.501 are shown in Table 1 below.

[0015] For example, as shown 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 averaging widnow of 2000 ms. Conversational voice falls under this catogery. 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 catogery.Table 1

[0016] In this section, Radio Resource Management (RRM) will be discussed (a block diagram for an example RRM with a MAC Scheduler is shown in FIG. 7). L2 methods (such as MAC scheduler) play a critical role in allocating radio resources to different UEs in a cellular network. For example, the scheduling priority of a logical channel (PLC) could be determined as part of MAC scheduler using one of the following (or some other variant) for a LC sending data in the downlink direction:PLC= W5QI*P5QI+ WGBR*PGBR+WPDB* PPDB +WBO*PBO + WPF*PPF, orPLC= (W5QI*P5QI) *(WPF*PPF) * (WGBR*PGBR)*(WPDB* PPDB), orPLC= (W5QI*P5QI+ WPF*PPF) * maximum (WGBR*PGBR, WPDB* PPDB) + WBO*PBO, orPLC= (W5QI*P5QI+ WPF*PPF) + maximum (WGBR*PGBR, WPDB* PPDB) + WBO*PBOOnce one of the above methods is used to compute scheduling priority of a logical channel corresponding to a UE in a cell, the same method is used for all other UEs and these scheduling priorities are used to determine the resources to be allocated to each LC in each cell.

[0017] In the above expressions, the parameters are defined as follows:

[0018] a) P5QI is the priority metric corresponding to the QoS class (5QI) of the logical channel. Incoming traffic from a DRB is mapped to Logical Channel (LC) at RLC level. P5QI is a function of the default 5QI priority value, Priority5QI, of a QoS flow that is mapped to the current LC. The lower the value of Priority5QI the higher the priority of the corresponding QoS flow. For example, Voice over New Radio (VoNR) (with 5QI of 1) will have a higher P5QI compared to web browsing (with 5 QI of 9).

[0019] b) PGBR is the priority metric corresponding to the target bit rate of the corresponding logical channel. The GBR metric PGBR represents the fraction of data thatmust be delivered to the UE within the time left in the current averaging window Tavgwin (as per 5QI table, default is 2000 msec.) to meet the UE’s GBR requirement. PGBR is calculated as follows:PGBR = remData / targetDatawheretargetData is the total data bits to be served in each averaging window TaVg win in order to meet the GFBR (Guaranteed Flow Bit Rate) of the given QoS flow;remData is the amount of data bits remaining to be served within the time left in the current averaging window;PGBR is reset to 1 (or some other suitable value) at the start of each averaging window TaVg win, and should go down to 0 towards the end of this window if the GBR criterion is met; andPGBR = 0 for non-GBR flows.For GBR DRB m corresponding to UE h, remData at time t is denoted as remData(h, m; t) and targetData at time t is denoted as targetData(h, m; t).

[0020] c) PPDB is the priority metric corresponding to the packet delay budget at DU for the corresponding logical channel. PPDB = 1 if PDBDU<=QDelayRLc and PPDB = 1 / (PDBDU- QDelayRLc) if PDBDU> QDelayRLc where both PDBDU(Packet Delay Budget at DU) and RLC Queuing delay, QDelayRLc, are measured in terms of (time) slots. For example, each (time) slot could be equal to 1 ms or 0.5 ms.

[0021] ‘Slot’ and ‘time slot’ are used interchangeably in this document.

[0022] d) QDelayRLc = (t -TRLC) is the delay of the oldest RLC packet in the QoS flow that has not been scheduled yet, and it is calculated as the difference in time between the SDU insertion in RLC queue to current time where t:= current time instant, TRLC:= time instant when oldest SDU was inserted in RLC.

[0023] e) Packet delay budget at DU is denoted as PDBDU. Waiting time for HoL RLC packet for DRB m corresponding to UE h at time t (i.e., in slot t) is denoted as QDelayRLc(h, m; t).

[0024] f) PPF is the priority metric corresponding to proportional fair metric of the UE.raiPPF is the PF Metric, calculated on a per-UE basis as PPF=avgwhere:“r” represents the UE’s achievable data rate. DU considers CSI (Channel Status Information) which also includes CQI (Channel Quality Indicator), reported by UE to compute this; andRavg(t) = a*Ravg(t-l) + (l-a)*b(t), where Ravg(t) is UE’s exponentially weighted moving average throughput at time t, RaVg(t-l) is UE’s exponentially weighted moving average throughput at time t-1, b(t) >= 0 is the number of bits scheduled in the current slot at time t, and parameter ‘a’ is selected such that 0 < a <= 1.

[0025] al and pi are configurable parameters. For example, if one sets al=l and pi — 0, the priority metric, PPF, works in greedy way and favors UEs in good channel conditions. This helps to improve cell throughput, but need not be fair to individual logical channels, and some of these LCs may not meet their QoS requirements.

[0026] For some existing systems, al and pi are in the range of 0 to 1. We allow a to be upper bounded by aljnax (and lower bounded by zero). As a LC is eventually selected by the overall scheduling priority of a logical channel (PLC) which has multiple other factors (and not only the PPF metric), we allow aljnax to be even higher than one (for example, aljnax = 1.2) to help design and enforce various type of policies (and associated service level agreements at per-cell, per-DU and per-logical channel level). Similarly, pl, is upper bounded by pljnax, and lower bounded by zero.

[0027] g) For UE h, achievable data rate in slot t is denoted as r(h; t) and this is influenced by CSI reported by UE h for slot t which is denoted as CSI(h; t). Also, UE’sweighted average throughput for UE h at the beginning of slot t or at the end of the slot (t-1) is denoted as Ravg(h; t-1).

[0028] h) BO is the (normalized) buffer occupancy in the RLC queue (e.g., in the RLC queue at DU for traffic in downlink direction for a DRB). PBO is the normalized value of buffer occupancy across all DRBs which could be proportional to the value of BO.

[0029] i) (Normalized) BO of RLC queue for DRB m corresponding to UE at time t is denoted as RLCBO(A, m; / ).

[0030] In addition, the following weights are defined: W? QI is the weight of PSQI; WGBR is the weight of PGBR; WPDB is the weight of PPDB; WBOIS the weight of PBO and WPF is the weight of PPF. For example, each of the above weights could be set to a value between 0 and 1 though other suitable set of values can be chosen too.

[0031] An RRC CONNECTED UE shall derive cell measurement results by measuring one or multiple beams associated per cell as configured by the network. Network will configure UE to report, e.g., Reference Signal Received Power (RSRP), Reference Signal Received Quality (RSRQ), Signal to Interference Noise Ratio (SINR), etc., based on certain reporting criteria. The UE measures many different signals, including the main ones which are based on the SSB and CSLRS. NR measurement reporting events are summarized in Table 2 below.Table 2

[0032] Inter-DU interface can be used for DU to DU communication. In an example embodiment, one such interface, denoted as D2 interface, is provided.

[0033] Protocol used for inter-DU communication is called D2-AP (D2-Application Protocol) Layer in the present disclosure. This is used for control plane information exchange between different DUs (e.g., from same or different vendors).

[0034] The Channel State Information (CSI) Reference Signal is a multi-purpose downlink transmission. The Base Station can configure the UE to use the CSI Reference Signal for procedures such as CSI Reporting, Beam Management and Connected Mode Mobility.

[0035] UE provides CSI reports based upon measurements from the CSI Reference Signal. CSI report consists of Channel Quality Indicators (Wide-band CQI and Subband CQI), Rank Indicators (RI) and Precoding Matrix Indicators (PMI).

[0036] For CSI reporting, a UE can be configured via higher layer signaling with one out of two possible sub-band sizes, where a sub-band is defined as NPRBSBcontiguous PRBs and depends on the total number of PRBs in the bandwidth part according to Table 3 shown below.Table 3

[0037] The reportFreqConfiguration contained in a CSI-ReportConfig indicates the frequency granularity of the CSI Report. A CSI Reporting Setting configurationdefines a CSI reporting band as a subset of sub-bands of the bandwidth part, where the reportFreqConfiguration indicates the following:- The csi-ReportingBand as a contiguous or non-contiguous subset of sub-bands in the bandwidth part for which CSI shall be reported.- Wideband CQI or sub-band CQI reporting, as configured by the higher layer parameter cqi-FormatIndicator. When wideband CQI reporting is configured, a wideband CQI is reported for each codeword for the entire CSI reporting band. When sub-band CQI reporting is configured, one CQI for each codeword is reported for each sub-band in the CSI reporting band.- Wideband PMI or sub-band PMI reporting as configured by the higher layer parameter pmi-FormatIndicator. When wideband PMI reporting is configured, a wideband PMI is reported for the entire CSI reporting band. When sub-band PMI reporting is configured, except with 2 antenna ports, a single wideband indication is reported for the entire CSI reporting band and one sub-band indication is reported for each sub-band in the CSI reporting band. When sub-band PMIs are configured with 2 antenna ports, a PMI is reported for each sub-band in the CSI reporting band.

[0038] Inter-cell interference, generally caused by using the same resources in neighboring cells, is a major problem for wireless cellular networks, and the intercell interference limits the overall network performance and impacts the signal quality of cell-edge users. Coordinated Multi-Point Transmission (CoMP) techniques are used to improve cell-edge performance and cell capacity, either by minimizing the negative impact of the interfering signal or by coordinating transmission and reception.

[0039] Downlink coordinated multi-point transmission (CoMP) is a relatively general term referring to different types of coordination in the downlink transmission from multiple geographically separated transmission points (TPs). This includes coordination in the scheduling, including any beam-forming functionality, between geographically separated transmission points and jointtransmission from geographically separated transmissions points. In the following description, CoMP, Coordinated Radio Resource Management and Coordinated Scheduling (CS) are used interchangeably.

[0040] Coordinated Schedulingis used to semi-statically or dynamically prevent transmission at certain time frequency resource to reduce the interference to be experienced by a user in its serving cell from a neighboring transmission point (interfering cell). The interfering cell may be in the same gNB-DU as the serving cell (intra-DU) or a different gNB-DU, but under the same gNB-CU (inter-DU) or a different gNB-CU (inter-CU). For the CoMP scenario shown in FIG. 8a, serving cell (cell 1) and neighboring intra-frequency cell (cell 2) can be in same gNB-DU (DU 801), and this is referred to as intra-DU CoMP (or intra-DU CS). In this case, an interference management entity or a master (or coordinator) cell in the gNB-DU (DU 801) will co-ordinate scheduling between the cells.

[0041] For the CoMP scenario shown in FIG. 8b, serving cell (cell 1 in DU 801) and neighboring intra-frequency cell (cell 5 in DU 802) are in different DUs, and this is referred to as inter-DU CoMP (or inter-DU CS). In the case of inter-DU CS, there is no direct provision for exchanging radio resource information at short timescale (e.g., every 1 ms) to perform coordinated scheduling. Other interfaces between different base stations (such as Xn for 5G, or X2 for 4G) can be enhanced to exchange relevant information between different base stations, but exchanging information using these other interfaces usually incurs high delays and reduced efficiency of inter-DU CoMP operation.

[0042] Accordingly, there is a need for a system and a method for improving the efficiency of inter-DU CoMP operation.SUMMARY

[0043] According to an example embodiment, the inter-DU D2 interface is optimized over SCTP to exchange information between different DUs at a short time scale (e.g., every 1 ms) to improve efficiency of inter-DU CoMP operation.

[0044] According to an example embodiment, gNB-DUs communicate over the D2- User Plane (D2-U) interface which runs over GPRS Tunneling Protocol - User Plane (GTP-U), User Datagram Protocol (UDP) and Internet Protocol [IP] layers.

[0045] In another example embodiment, the E2AP (E2 Application Protocol) running over the E2 interface is enhanced to improve the efficiency of inter-DU and inter-CU CoMP operation, e.g., when D2 interface doesn't exist between the serving DU and the neighboring DU.

[0046] According to an example embodiment, the synchronization (CoMP) operation involves the first gNB-DU sending a message to a second gNB-DU requesting to blank some of the PRBs in its cells by providing various per-cell information of the cells served by second gNB-DU.

[0047] According to an example embodiment, a master gNB-DU is provided, which master gNB-DU processes the information received from the affected gNB-DUs and decides a scheduling strategy for each cell, e.g., the scheduling strategy can consist of the PRBs that can be used by each cell for downlink (DL) transmission for the nextT ms.

[0048] According to an example embodiment, the CoMP module is hosted as part of a near-RT-RIC, and the E2 interface (and associated protocol) is enhanced to communicate various performance measures and counters from gNB-DUs and gNB- CUs to the Near-RT RIC.BRIEF DESCRIPTION OF THE DRAWINGS

[0049] FIG. la is a block diagram illustrating the user plane stack of 5G NR.

[0050] FIG. lb is a block diagram illustrating the user plane protocol stacks for a PDU session of 5G NR.

[0051] FIG.2 is a block diagram illustrating the control plane stack of 5G NR.

[0052] FIG. 3 is a block diagram illustrating NG-RAN architecture.

[0053] FIG.4 is a block diagram illustrating separation of CU-CP and CU-UP in NG- RAN architecture.

[0054] FIG. 5 is a block diagram illustrating DL L2 structure.

[0055] FIG.6 illustrates an overview of 0-RAN architecture.

[0056] FIG.7 is a block diagram illustrating an example radio resource management (RRM) with a MAC Scheduler.

[0057] FIG.8a is a block diagram illustrating an example case of intra-DU CoMP.

[0058] FIG.8b is a block diagram illustrating an example case of inter-DU CoMP.

[0059] FIG.9 is a block diagram illustrating a first example variant of network architecture for a first example embodiment according to the present disclosure.

[0060] FIG. 10 is a block diagram illustrating a second example variant of network architecture for the first example embodiment according to the present disclosure.

[0061] FIG. 11 is a block diagram illustrating an example network architecture for a second example embodiment according to the present disclosure.

[0062] FIG. 12 illustrates a third example embodiment according to the present disclosure.

[0063] FIG. 13 is a signal flow diagram illustrating a fourth example embodiment according to the present disclosure.DETAILED DESCRIPTION

[0064] According to a first example embodiment of a system and a method according to the present disclosure, two DUs coordinate with each other over the D2 interface (e.g., as shown in FIG.9 and FIG. 10, which illustrate two example variantsof network architecture for the first example embodiment) to improve the efficiency of the coordinated scheduling operation for the corresponding cells (and UEs). In the first example network architecture variant shown in FIG. 9, the 5G core 303 is communicatively connected to a gNB-CU-CP 304a via Next Generation Application Protocol (NGAP) 901a. In turn, gNB-CU-CP 304a is communicatively connected to gNB-DU 305a and gNB-DU 305b via Fl Application Protocol (F1AP) 902a and 902b, respectively. gNB-DU 305a and gNB-DU 305b are communicatively connected via D2 Application Protocol (D2-AP) 903, which is implemented over a D2-C interface, for example. gNB-DU 305a is communicatively connected to UE 101a via over-the- air interface NR-Uu 904a, and gNB-DU 305b is communicatively connected to UE 101b via over-the-air interface NR-Uu 904b. Although not explicitly shown in FIG. 9, 5G Core 303 is also communicatively connected to a gNB-CU-UP via Next Generation User Plane (NG-U) Protocol and gNB-CU-UP is communicatively connected to gNB- DU via Fl User (Fl-U) plane.

[0065] In the second example network architecture variant shown in FIG. 10, the 5G core 303 is communicatively connected to i) a gNB-CU-CP 304al via Next Generation Application Protocol (NGAP) 901a, and ii) a gNB-CU-CP 304a2 via NGAP 901b. gNB-CU-CP 304al is communicatively connected to gNB-CU-CP 304a2 via Xn Control Plane (Xn-C) interface 905. gNB-CU-CP 304al is communicatively connected to gNB-DU 305a via Fl Application Protocol (F1AP) 1002a (e.g., implemented over Fl-C interface), and gNB-CU-CP 304a2 is communicatively connected to gNB-DU 305a via Fl Application Protocol (F1AP) 1002b (e.g., implemented over Fl-C interface). gNB-DU 305a and gNB-DU 305b are communicatively connected via D2 Application Protocol (D2-AP) 903, which is implemented over a D2-C interface, for example. gNB-DU 305a is communicatively connected to UE 101a via over-the-air interface NR-Uu 904a, and gNB-DU 305b is communicatively connected to UE 101b via over-the-air interface NR-Uu 904b.

[0066] In the example variants of network architecture shown in FIGS. 9 and 10, UE 101a (in the corresponding cell of gNB-DU 305a) and UE 101b (in the correspondingcell of gNB-DU 305b) are configured with sub-band CQI reporting. Next, gNB-CU-CP (e.g., 304a, 304al and / or 304a2) sends A2 measurements received from UEs (e.g., 101a and / or 10 lb ) to gNB-DU (e.g., 305a and / or 305b) over F1AP (e.g., 902a and / or 902b in FIG.9, 1002a and / or 1002b in FIG. 10, implemented over Fl-C interface), and gNB-DU (e.g., 305a and / or 305b) uses this information to find celledge UEs.

[0067] For the identified cell-edge UEs (e.g., 101a and 101b), gNB-DU (e.g., 305a and / or 305b) asks gNB-CU-CP (e.g., 304a, 304al and / or 304a2) to trigger A3 / A4 measurements to find the intra-frequency neighbors (cells), and gNB-CU-CP (e.g., 304a, 304al and / or 304a2) configures A3 / A4 measurements with thresholds specifically applicable to CoMP for the UEs (e.g., 101a and 101b) identified by the gNB-DU (e.g., 305a and / or 305b). gNB-CU-CP (e.g., 304a, 304al and / or 304a2) forwards the received A3 / A4 measurement report from UEs (e.g., 101a and 101b) to the gNB-DU (e.g., 305a and / or 305b). The gNB-DU (e.g., 305a and / or 305b) finds the interfering neighbor (cell) for each UE based on the RSRPs measurements reported for the neighbor cells by the UE. The interfering neighbor cell can belong to the same gNB-DU (as the gNB-DU for the respective cell-edge UE) or to a different gNB-DU.

[0068] According to an example embodiment of the present disclosure, F1AP (e.g., 902a and / or 902b in FIG. 9, 1002a and / or 1002b in FIG. 10) implemented over the Fl-C interface (e.g., between gNB-DU and CU-CP of the gNB-CU) is enhanced for measurement report triggering and reporting purposes.

[0069] For a given cell-edge UE, if the interfering neighbor is not in the same gNB- DU as the gNB-DU for the serving cell of the give cell-edge UE, then the serving cell gNB-DU communicates with the gNB-DU of the interfering neighbor cell using the D2AP (e.g., implemented over the D2-C interface between these gNB-DUs). As part of the initial D2AP connection establishment, gNB-DUs (e.g., 305a and 305b) exchange information regarding the cells served by them. This information is laterused by each gNB-DU to i) identify which gNB-DU the interfering neighbor cell belongs to, and ii) for communication of messages for coordinated scheduling.

[0070] According to an example embodiment of the present disclosure, the gNB-DUs are synchronized using a common source. For example, gNB-DU 305a sends a message to gNB-DU 305b requesting to blank some of the PRBs in its cells by providing the following per-cell information of the cells served by gNB-DU 305b over D2AP 903:- Message identifier- Cell Id (identification of the cell)- Absolute Radio-Frequency Channel Number (ARFCN)- List of Interfering Neighborso Interfering Neighbor Cell Ido PRBs required to be blankedD2AP 903 (e.g., implemented over the D2-C interface) is enhanced to communicate the above parameters.

[0071] gNB-DU 305b evaluates the information received from gNB-DU 305a and checks the load conditions (e.g. PRB load or UE load) of the cells reported as interfering neighbors. If the load is less than a pre-specified threshold, gNB-DU 305b tries to blank the PRBs as requested by gNB-DU 305a for these cells and sends the result to gNB-DU 305a over D2AP 903.

[0072] For example, gNB-DU 305b can accept the request and agree to blank PRBs as asked by gNB-DU 305a. In this case, gNB-DU 305b acknowledges the request sent by gNB-DU 305a by sending the following per-cell information:- Message identifier- Cell Id (identification of the cell)ARFCN- List of PRBs blanked or an acknowledgement that gNB-DU2 has completely accepted the request of gNB-DU1 for this particular cell id

[0073] Alternatively, gNB-DU 305b can reject the PRB blanking request and inform gNB-DU 305a about this by sending a message using the D2AP 903 (over the D2-C interface). On receiving the rejection of the PRB blanking request, gNB-DU 305a can send another proposal of PRBs to blank (along with the corresponding cell id and ARFCN).

[0074] According to an alternate example embodiment, gNB-DU 305b can send an alternate proposal to gNB-DU 305a (e.g., with an alternate set of PRBs to blank, where a subset of these PRBs may overlap with the PRBs initially proposed by gNB- DU 305a, or a set of PRBs to blank for another cell). gNB-DU 305a evaluates this alternate proposal and responds by either accepting or rejecting it.

[0075] As an example, in FIG. 8b, cell 1 (e.g., with channel bandwidth of 20 MHz) of gNB-DU 801 and cell 5 (e.g., with channel bandwidth of 20 MHz) of gNB-DU 802 are interfering neighbors. If the cell-load of cell 5 is below a specified threshold, gNB-DU 802 controlling cell 5 decides to blank some of the PRBs for next T ms as per the request from gNB-DU 801, and gNB-DU 802 indicates the same to gNB-DU 801. The cell-edge UEs in cell 1 which are experiencing interference from cell 5 can be scheduled during this interval of T ms using PRBs which are blanked in cell 5 to achieve higher spectral efficiency. In the same scenario, UEs in cell 4 (of gNB-DU 802) may also be experiencing interference from cell 5, and cell 4 can also use the blanked PRBs to schedule its cell-edge UEs in this time interval of T ms. Accord

[0076] According to a second example embodiment of a system and a method according to the present disclosure, the network architecture for which is shown in FIG. 11, a master gNB-DU (e.g., gNB-DU 305c) communicates with the other gNB- DUs (e.g., gNB-DU 305a and gNB-DU 305b) via D2 interfaces (e.g., D2-AP 1103a andD2-AP 1103b) to perform the coordinated scheduling. The network architecture shown in FIG. 11 is substantially similar to the network architecture shown in FIG.10, with the exception of adding gNB-DU 305c, UE 101c, and interfaces from gNB- DU 305c to gNB-CU-CP 304al (i.e., F1AP 1102c), gNB-DU 305a (i.e., D2-AP 1103a), gNB-DU 305b (i.e., D2-AP 1103b), and UE 101c (i.e., NR-Uu 904c).

[0077] In the second example embodiment illustrated in FIG. 11, each gNB-DU (e.g., 305a - 305c) searches for cell-edge UEs (e.g., 101a - 101c) which are impacted by interfering neighbor cells. If some such UEs are found in any of the cells of an affected gNB-DU, that affected gNB-DU (e.g., 305a and / or 305b) sends a message (via D2-AP, e.g., 1103a and / or 1103b, implemented over D2-C interface; the message can be sent periodically) to the master gNB-DU (e.g., 305c) providing the following per-cell information of the cells served by the affected gNB-DU:- Message id (identifier of the message)- Cell Id- Absolute Radio-Frequency Channel Number (ARFCN)- Cell PRB Load- List of Interfering Neighborso Interfering Neighbor Cell Id

[0078] The master gNB-DU (e.g., 305c) processes the information received from the affected gNB-DUs and decides a scheduling strategy for each cell for the next T ms. For example, this scheduling strategy can consist of specifying the PRBs that can be used by each cell for downlink (DL) transmission for the next T ms. The master gNB-DU (e.g., 305c) sends a message to each affected gNB-DU (e.g., 305a and / or 305b) with the following per-cell information for the cells served by the respective affected gNB-DU:Message idCell Id- Absolute Radio-Frequency Channel Number (ARFCN)- List of PRBs allowed to use- List of Interfering Neighborso Interfering Neighbor Cell Ido Li st of PRB s bl anked

[0079] In the second example embodiment explained in connection with FIG. 11, the example master gNB-DU (e.g., gNB-DU 305c) is one hop away from the other gNB- DUs (e.g., 305a and / or 305b) for which the gNB-DU 305c is acting as the master. However, a variant of the second example embodiment can be implemented such that master gNB-DU is more than one hop away from the other gNB-DUs for which it is acting as the master. For example, gNB-DU 305a can serve as the master gNB-DU for gNB-DU 305b (two hops away) and gNB-DU 305c (one hop away).

[0080] In a third example embodiment of a system and a method according to the present disclosure, the above-proposed information exchange between the gNB-DUs (e.g., as illustrated in the network architectures of FIGS.9-11) can be carried out by using an enhanced version of NR-U Protocol implemented over GTP-U, UDP, and IP protocol layers, which third example embodiment is illustrated in FIG. 12. In the third example embodiment, respective gNB-DUs (e.g., 305a and 305b) send information using Assistance Information Data (AID) PDU of the NR user plane protocol specified in 3GPP TS 38.425. This NR-U protocol is enhanced to run over D2 user plane (D2-U) interface 1201 between the two gNB-DUs (e.g., 305a and 305b), and the enhanced NR-U protocol is used to communicate information at the UE level or at the cell level. For the AID PDU to help send this information, one spare bit of the AID PDU will be utilized, which spare bit is named "CoMP Assistance Information”, and represents a new field which will be a user-defined data type that carries all information that gNB-DUs exchange for this use case. AID PDU will be enhanced accordingly for this purpose. Alternatively, a new protocol can be used to exchange this information between different gNB-DUs.

[0081] In a fourth example embodiment of a system and a method according to the present disclosure, the CoMP module is hosted as part of a near-RT-RIC. FIG. 13 is a signal flow diagram illustrating the fourth example embodiment. As shown in FIG.13, the Near-RT-RIC 132 (which hosts the CoMP module) subscribes for various performance measures and counters for CoMP xApp from gNB-DU 305 (using RIC subscription procedure 1301) and gNB-CU 304 (using RIC subscription procedure 1302). Although a single gNB-DU 305 and a single gNB-CU 304 are shown in FIG. 13 for the sake of simplicity, it should be understood that the system can contain multiple gNB-DUs and multiple gNB-CUs. The E2 interface (and associated protocol) is enhanced to communicate various performance measures and counters from gNB-DU 305 (e.g., as shown by the process arrow 1303 for transmitting DU-related performance measures and counters), gNB-CU 304 (e.g., as shown by the process arrow 1304 for transmitting CU-related UE measurement reports, performance measures and counters) to the Near-RT RIC 132. The measurements sent from gNB- DU 305 to the CoMP module at the Near-RT RIC 132 can include, e.g., the following:- UE sub-band CQI reports- Cell Load- Cell Throughput KPIsThe measurements from gNB-CU 304 to the CoMP module at the Near-RT RIC 132 can include, e.g., the following:- UE A2 / A3 / A4 Measurement reports

[0082] As shown in the box 1305 of FIG. 13, the CoMP xApp at the Near-RT RIC 132 analyzes these parameters from all the gNB-DUs (e.g., 305) and gNB-CUs (e.g., 304). Based on the analysis, the CoMP xApp at the Near-RT-RIC 132 finds the interfering neighbors for each cell based on the UE measurement reports and finds the celledge UEs for which performance is degraded. The CoMP xApp at the Near-RT RIC 132 then decides on an optimal, coordinated scheduling policies to optimize end-to- end performance. The coordinated scheduling policies can be transmitted (as shownby the process arrow 1306) to each gNB-DU (although a single representative gNB- DU 305 is shown, the system can contain multiple gNB-DUs), e.g., by communicating the PRBs which need to be blanked in each cell for every time period T, and the CoMP xApp at the Near-RT RIC 132 also indicates each cell to schedule the cell-edge UEs in specific PRBs. For communicating these information parameters to the gNB- DUs (e.g., 305), the E2 interface (and the associated protocol) is enhanced.

[0083] 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 may be substituted for elements thereof without departing from the scope of the present disclosure. In addition, many modifications may 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.

[0084] The present disclosure employs abbreviations, terms and technology defined in accordance with Third Generation Partnership Project (3GPP), 0-RAN Alliance and / or Internet Engineering Task Force (IETF) technology standards and papers. For the sake of completeness, a list of abbreviations is provided below.5GC: 5G Core Network5G NR: 5G New Radio5QI: 5G QoS IdentifierACK: AcknowledgementAl: Artificial IntelligenceAI / ML (or AIML): Artificial Intelligence and Machine LearningAM: Acknowledged ModeAPN: Access Point NameARFCN: Absolute Radio-Frequency Channel Number ARP: Allocation and Retention PriorityBO: Buffer OccupancyBS: Base StationBSR: Buffer Status ReportCNN: Convolution Neural NetworkCMS: Centralized Management SystemCN: Core NetworksCoMP: Coordinated Multi-point TransmissionCP: Control PlaneCSI: Channel State InformationCU: Centralized UnitCU-CP: Centralized Unit - Control PlaneCU-UP: Centralized Unit - User PlaneDC: Dual ConnectivityDL: DownlinkDDDS: DL Data Delivery StatusDNN: Data Network NameDNN: Deep Neural NetworkDQN: Deep Q NetworkDRB: Data Radio BearerDSS: Dynamic Spectrum SharingDU: Distributed UniteNB: evolved NodeB (4G LTE Base Station)EPC: Evolved Packet CoreEN-DC: E-UTRA-NR Dual ConnectivityE-UTRA: Evolved UMTS Terrestrial Radio Access EWMA: Exponentially Weighted Moving Average GBR: Guaranteed Bit RategNB: gNodeB (5G NR Base Station)GPRS: General Packet Radio ServiceGTP-U: GPRS Tunnelling Protocol - User PlaneIP: Internet ProtocolL1: Layer 1L2: Layer 2L3: Layer 3L4S: Low Latency, Low Loss and Scalable Throughput LG: Logical ChannelLESS: Low Energy Scheduler SolutionLTE: Long Term EvolutionMAC: Medium Access ControlMDP: Markov Decision ProcessMeNB: Master eNodeBMIB: Master Information BlockML: Machine LearningMN: Master NodeMR: Multi-RATMR-DC: Multi-RAT Dual ConnectivityMR-SS: Multi-RAT Spectrum SharingNACK: Negative AcknowledgementNAS: Non-Access StratumNG-RAN: Next Generation Radio Access Network NR: New RadioNR-U: New Radio - User PlaneNSA: Non-StandaloneNSI: Network Slice InstanceNSSI: Network Slice Subnet Instance NWDAF: Network Data Analytics FunctionO-RAN: Open Radio Access NetworkOAM: Operations, Administration Maintenance PCI: Physical Cell IdentityPDB: Packet Delay BudgetPDCP: Packet Data Convergence Protocol PDU: Protocol Data UnitPER: Packet Error RatePF: Proportional FairPHY: Physical LayerPRB: Physical Resource BlockQCI: QoS Class IdentifierQFI: QoS Flow IdentifierQoS: Quality of ServiceRAN: Radio Access NetworkRAT: Radio Access TechnologyRB: Resource BlockRDI: Reflective QoS Flow to DRB Indication RL: Reinforcement LearningRLC: Radio Link ControlRLC-AM: RLC Acknowledged ModeRLC-UM: RLC Unacknowledged Mode RNN: Recurrent Neural NetworksRQI: Reflective QoS IndicationRRC: Radio Resource ControlRRM: Radio Resource ManagementRSRP: Reference Signal Received Power RSRQ: Reference Signal Received Quality RTP: Real-Time Transport Protocol RTCP: Real-Time Transport Control Protocol RU: Radio UnitSl-U: Sl User PlaneSl-C: SI Control PlaneSA: StandaloneSCTP: Stream Control Transmission Protocol SD: Slice DifferentiatorSDAP: Service Data Adaptation Protocol SIB: System Information BlockSINR: Signal to Interference Noise RatioSLA: Service Level AgreementSN: Secondary NodeS-NSSAI: Single Network Slice Selection Assistance SpCell: Special CellSSB: Synchronization Signal BlockSST: Slice / Service TypeTB: Transport BlockTCP: Transmission Control ProtocolTEID: Tunnel Endpoint IdentifierUDP: User Datagram ProtocolUE: User EquipmentUP: User PlaneUL: UplinkUM: Unacknowledged ModeUPF: User Plane FunctionvDU: Virtual DUX2-C: X2 Control planeX2-U: X2-User plane

Claims

CLAIMS:

1. A method for implementing optimized coordinated multi-point transmission (CoMP) in an Open Radio Access Network (O-RAN) wireless system, comprising:providing at least one centralized unit (CU) of the O-RAN;providing a first distributed unit (DU) of the O-RAN;providing a second DU of the O-RAN; andimplementing the optimized CoMP based on information provided by at least one of the CU, the first DU and the second DU regarding at least one of i) interference experienced by a user equipment (UE) in a first serving cell of the first DU from a neighbor cell of the first serving cell, and ii) interference experienced in a second serving cell of the second DU from a neighbor cell of the second serving cell, wherein coordination of the optimized CoMP is implemented by at least one of the first DU, the second DU and a near-real time radio intelligent controller (near-RT RIC).

2. The method of claim 1, wherein:the first DU and the second DU are communicatively connected via D2 application protocol (D2-AP) connection; andthe optimized CoMP comprises the first DU sending a message to the second DU requesting to blank at least one physical resource block (PRB) in at least one cell served by the second DU, and said message to the second DU comprises per-cell information of cells served by second DU.

3. The method of claim 2, wherein:the at least one CU is communicatively connected to the first DU via a first Fl application protocol (Fl-AP) connection;the at least one CU is communicatively connected to the second DU via a second Fl-AP connection; andthe first Fl-AP connection and the second Fl-AP connection are enhanced for measurement report triggering and reporting.

4. The method of claim 2, further comprising:providing a second CU;wherein the first CU is communicatively connected to the first DU via a first Fl application protocol (Fl-AP) connection;wherein the second CU is communicatively connected to the second DU via a second Fl-AP connection; andwherein the first Fl-AP connection and the second Fl-AP connection are enhanced for measurement report triggering and reporting.

5. The method of claim 4, wherein:the first CU and the second CU are communicatively connected to each other via Xn control plane (Xn-C) interface.

6. The method of claim 1, further comprising:providing a second CU, wherein the first CU and the second CU are communicatively connected to each other via Xn control plane (Xn-C) interface; andproviding a third DU communicatively connected i) to the first DU via a first D2 application protocol (D2-AP) connection, ii) to the second DU via a second D2-AP connection, and iii) to the second CU via a Fl application protocol (Fl-AP) connection.

7. The method of claim 6, wherein one of:i) the third DU is configured to serve as a master DU implementing the coordination of the optimized CoMP; orii) one of the first DU or the second DU is configured to serve as the master DU implementing the coordination of the optimized CoMP.

8. The method of claim 7, wherein:the master DU:i) receives information from at least one other DU regarding interference affecting at least one cell of the at least one other DU; andii) generates a per-cell scheduling strategy for each cell of the at least one other DU for a specified time period, wherein the scheduling strategy comprises specifying physical resource blocks (PRBs) allowed for use by each cell of the at least one other DU for downlink (DL) transmission for the specified time period.

9. The method of claim 1, wherein:the near-RT RIC implements the coordination of the optimized CoMP based on the information provided by at least one of the CU, the first DU and the second DU.

10. The method of claim 9, wherein:the near-RT RIC implements the coordination of the optimized CoMP by sending coordinated scheduling policies to the first DU and the second DU.

11. A system for implementing optimized coordinated multi-point transmission (CoMP) in an Open Radio Access Network (0-RAN) wireless system, comprising:at least one centralized unitof the 0-RAN;a first distributed unit (DU) of the 0-RAN; anda second DU of the 0-RAN;wherein the optimized CoMP is implemented based on information provided by at least one of the CU, the first DU and the second DU regarding at least one of i) interferenceexperienced by a user equipment (UE) in a first serving cell of the first DU from a neighbor cell of the first serving cell, and ii) interference experienced in a second serving cell of the second DU from a neighbor cell of the second serving cell; andwherein coordination of the optimized CoMP is implemented by at least one of the first DU, the second DU and a near-real time radio intelligent controller (near-RT RIC).

12. The system of claim 11, wherein:the first DU and the second DU are communicatively connected via D2 application protocol (D2-AP) connection; andthe first DU is configured to implement the optimized CoMP by sending a message to the second DU requesting to blank at least one physical resource block (PRB) in at least one cell served by the second DU, and said message to the second DU comprises per-cell information of cells served by second DU.

13. The system of claim 12, wherein:the at least one CU is communicatively connected to the first DU via a first Fl application protocol (Fl-AP) connection;the at least one CU is communicatively connected to the second DU via a second Fl-AP connection; andthe first Fl-AP connection and the second Fl-AP connection are enhanced for measurement report triggering and reporting.

14. The system of claim 12, further comprising:a second CU;wherein the first CU is communicatively connected to the first DU via a first Fl application protocol (Fl-AP) connection;wherein the second CU is communicatively connected to the second DU via a second Fl-AP connection; andthe first Fl-AP connection and the second Fl-AP connection are enhanced for measurement report triggering and reporting.

15. The system of claim 14, wherein:the first CU and the second CU are communicatively connected to each other via Xn control plane (Xn-C) interface.

16. The system of claim 11, further comprising:a second CU, wherein the first CU and the second CU are communicatively connected to each other via Xn control plane (Xn-C) interface; anda third DU communicatively connected i) to the first DU via a first D2 application protocol (D2-AP) connection, ii) to the second DU via a second D2-AP connection, and iii) to the second CU via a Fl application protocol (Fl-AP) connection.

17. The system of claim 16, wherein one of:i) the third DU is configured to serve as a master DU implementing the coordination of the optimized CoMP; orii) one of the first DU or the second DU is configured to serve as the master DU implementing the coordination of the optimized CoMP.

18. The system of claim 17, wherein:the master DU is configured to:i) receive information from at least one other DU regarding interference affecting at least one cell of the at least one other DU; andii) generate a per-cell scheduling strategy for each cell of the at least one other DU for a specified time period, wherein the scheduling strategy comprises specifying physical resource blocks (PRBs) allowed for use by each cell of the at least one other DU for downlink (DL) transmission for the specified time period.

19. The system of claim 11, wherein:the near-RT RIC implements the coordination of the optimized CoMP based on the information provided by at least one of the CU, the first DU and the second DU.

20. The system of claim 19, wherein:the near-RT RIC implements the coordination of the optimized CoMP by sending coordinated scheduling policies to the first DU and the second DU.

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