Master node, secondary node, communication node, and method therefor

Abstract

In the present invention, a secondary node with dual connectivity sends, to a master node with dual connectivity, an information element indicating whether Protocol Data Unit (PDU) set-based handling is supported by the secondary node. The foregoing helps to provide improvements relating to support for PDU set-based handling, Explicit Congestion Notification (ECN) marking, or congestion information reporting, for example.

Description

Master node, secondary node, communication node, and methods thereof

[0001] The present disclosure relates to wireless communication networks, and more particularly to signaling between communication nodes.

[0002] The 3rd Generation Partnership Project (3GPP®) Release 18 supports enhancements for high data rate, low latency services such as eXtended Reality (XR) services and interactive media services, including PDU set-based handling, Explicit Congestion Notification (ECN) marking for Low Latency, Low Loss, and Scalable Throughput (L4S), and congestion information monitoring (see, for example, Sections 5.37.3, 5.37.4, 5.37.5, and 5.45.3 of 3GPP 2.0, RFC 2544).

[0003] A PDU set is one or more PDUs carrying the payload of one unit of information (e.g., frame(s) or video slice(s) of an XR service) generated at the application level. All PDUs in a PDU set are transmitted within the same Quality of Service (QoS) flow. For uplink transmission, PDU set-based discarding by the User Equipment (UE) is supported. The Next Generation Radio Access Network (NG-RAN) can configure PDU set-based discarding in the UE for a Data Radio Bearer (DRB) associated with a QoS flow carrying PDU sets. The NG-RAN requests the UE to perform PDU set-based discarding for a specific DRB via Radio Resource Control (RRC) signaling, specifically by setting the pdu-SetDiscard field in the Packet Data Convergence Protocol (PDCP) configuration (PDCP-Config) for that specific DRB. If PDU set-based discarding is configured for a particular DRB, the transmitting PDCP entity of the UE associated with that DRB performs PDU set-based PDCP Service Data Unit (SDU) discarding. Specifically, when a PDCP SDU belonging to a PDU set is discarded due to the expiration of its discard timer, the transmitting PDCP entity of the UE discards all PDCP SDUs belonging to the PDU set to which that PDCP SDU belongs, along with the corresponding PDCP data PDUs.

[0004] Non-Patent Document 2 specifies Xn Application Protocol (XnAP) signaling between NG-RAN nodes for supporting PDU set-based handling. Specifically, during a handover procedure, a HANDOVER REQUEST ACKNOWLEDGE message sent from a target RAN node to a source RAN node can include a PDU Set based Handling Indicator information element (IE). This IE indicates whether the target NG-RAN node supports PDU set-based handling. If the PDU Set based Handling Indicator IE set to "supported" is included in the HANDOVER REQUEST ACKNOWLEDGE message, for QoS flows established using PDU set QoS parameters, the source NG-RAN node shall include PDU set information in the transferred data if supported. Otherwise, the source NG-RAN node may not include PDU set information in the transferred data. The PDU Set information includes the PDU Set Sequence Number, Indication of End PDU of the PDU Set, PDU Sequence Number within a PDU Set, PDU Set Size in bytes, and PDU Set Importance (PSI), which indicates the relative importance of the PDU Set compared to other PDU Sets in the QoS Flow.

[0005] In the event of congestion, the NG-RAN can use the PDU Set Importance (PSI) for PDU set-based discard. The PSI specifies the relative importance of a PDU set compared to other PDU sets in the same QoS flow. In the uplink, the NG-RAN can request the UE to apply a short discard timer to less important SDUs in PDCP via a dedicated downlink signal. This dedicated downlink signal is the Activation / Deactivation of PSI-based SDU Discard Medium Access Control (MAC) Control Element (CE). In response to receiving the Activation / Deactivation of PSI-based SDU Discard MAC CE requesting activation of PSI-based SDU discard for a specific DRB, the UE initiates PSI-based SDU discard for that DRB in the PDCP entity for that DRB. When a PDCP SDU is received from upper layers, the PDCP entity operates as follows: If the short discard timer (i.e., discardTimerForLowImportance) is configured by RRC, PSI-based SDU discard is activated, and the PDCP SDU belongs to the low importance PDU Set, the PDCP entity starts the short discard timer (i.e., discardTimerForLowImportance) associated with the PDCP SDU. Otherwise, the PDCP entity starts the regular long discard timer (i.e., discardTimer) associated with the PDCP SDU (if configured).

[0006] Non-Patent Document 5 proposes improving the F1 Application Protocol (F1AP) signaling between a gNB Central Unit (CU) and a gNB Distributed Unit (DU) defined in Non-Patent Document 3 for PSI-Based SDU Discard. Specifically, Non-Patent Document 5 proposes sending a PSI-based SDU Discard UL IE from a gNB-CU to a gNB-DU via a UE CONTEXT SETUP REQUEST or UE CONTEXT MODIFICATION REQUEST message in the DRB to Be Setup Item IEs. If the PSI-based SDU Discard UL IE is included in the DRB To Be Setup List IE, the gNB-DU takes this IE into account to activate or deactivate Uplink (UL) PSI-based SDU discarding for the indicated DRB.

[0007] In addition, Non-Patent Document 1 describes in Section 5.37.5.2 that NG-RAN can use PDU set importance within a QoS flow for PDU set-level packet discard when congestion exists. Furthermore, this section also states that in addition to considering the importance of PDU sets within a QoS flow, NG-RAN can also consider the relative importance of PDU sets between QoS flows at the same priority level when determining which PDU sets need to be discarded. In other words, Non-Patent Document 1 suggests that an NG-RAN node may perform PDU set-based and PSI-based PDCP SDU discarding for the downlink (DL).

[0008] Non-Patent Document 6 proposes an improvement to the E1 Application Protocol (E1AP) signaling between the gNB-CU Control Plane (CP) and the gNB-CU User Plane (UP) required for PSI-based and PDU-set-based PDCP SDU discard in the downlink direction. Specifically, Non-Patent Document 6 points out that in the downlink direction, the DL PSI-based discard timer applicable to the less important PDU set must be configured in the gNB-CU-UP by the gNB-CU-CP. The gNB-CU-CP can send a PDCP Configuration IE per DRB to the gNB-CU-UP via a BEARER CONTEXT SETUP REQUEST message or a BEARER CONTEXT MODIFICATION REQUEST message. Non-Patent Document 6 also proposes that the gNB-CU-CP may include a PSI-Based Discard Timer IE in the PDCP Configuration IE. The PSI-Based Discard Timer IE indicates the length of the PDCP discard timer used by the PDCP entity in the gNB-CU-UP for DL ​​PSI-based discard. The length of the PDCP discard timer used for DL ​​PSI-based discard may correspond to the length of the PDCP discard timer used for UL PSI-based discard by the UE, as specified by the PDCP configuration provided to the UE by the gNB.

[0009] ECN marking for L4S exposes congestion information and triggers application layer rate adaptation by marking ECN bits in the IP header of user Internet Protocol (IP) packets between the UE and the application server. 5G systems may support ECN marking for L4S. ECN marking is enabled per QoS flow in the UL and / or DL ​​directions and can be used for Guaranteed Bit Rate (GBR) and non-GBR QoS flows. ECN marking in the IP header is supported in either the NG-RAN or PDU Session Anchor (PSA) User Plane Function (UPF).

[0010] In the case of ECN marking by PSA UPF, the NG-RAN is instructed to perform congestion information monitoring and report congestion information (i.e., a percentage of packets that UPF uses for ECN marking for L4S) of QoS flows in the UL and / or DL ​​directions to the PSA UPF via a General Packet Radio Service Tunneling Protocol User Plane (GTP-U) header extension. Specifically, the Session Management Function (SMF) of the core network (5G Packet Core (5GC)) requests the NG-RAN (e.g., gNB) to report congestion information per QoS flow level as part of the PDU session resource management procedure. If the NG-RAN supports ECN marking for L4S at UPF, it returns a status indication to the SMF. This status indication is used by the SMF as specified in 3GPP TS 36544-1010.

[0011] In the case of ECN marking by NG-RAN, the SMF provides ECN marking requests per QoS flow level to the NG-RAN (e.g., gNB) as part of the PDU session resource management procedure. If the NG-RAN supports ECN marking for L4S in NG-RAN, the NG-RAN returns a status indication to the SMF. This status indication is used by the SMF as specified in 3GPP TS 26.110.

[0012] The 5G system supports UL and / or DL ​​congestion information exposure based on an Application Function (AF) request. For congestion information exposure, the PSA UPF exposes UL and / or DL ​​congestion information via the Nupf_EventExposure service or via the SMF, Policy Control Function (PCF), or Network Exposure Function (NEF). The SMF can request the NG-RAN to report information to the PSA UPF via the GTP-U header. The UPF can be requested to monitor and expose UL and / or DL ​​QoS flow congestion information reported by the NG-RAN. This NG-RAN reported information is common to support congestion information exposure in the PSA UPF and to support ECN marking for L4S in the PSA UPF. If the NG-RAN supports congestion information reporting, the NG-RAN returns a status indication to the SMF. This status indication is used by the SMF as specified in 3GPP TS 36544-01.

[0013] When the serving NG-RAN node (e.g., gNB) changes, such as during a handover, the target NG-RAN node must continue to perform ECN marking for QoS flows, if supported. During the Xn handover preparation procedure, the source NG-RAN node provides an ECN marking request or congestion information request to the target NG-RAN node.

[0014] Non-Patent Document 2 specifies XnAP signaling between NG-RAN nodes to support ECN marking and congestion information reporting. Specifically, during a handover procedure, a HANDOVER REQUEST message sent from a source NG-RAN node to a target NG-RAN node can include an ECN Marking or Congestion Information Reporting Request IE in its PDU Session Resources To Be Setup List IE. The ECN Marking or Congestion Information Reporting Request IE instructs the target NG-RAN node to perform ECN marking, report information for ECN marking, or report congestion information for QoS flows. If supported, the target NG-RAN node uses it according to the specific QoS flow.

[0015] Similarly, in the Retrieve UE Context procedure, the RETRIEVE UE CONTEXT RESPONSE message sent from the old NG-RAN node to the new NG-RAN node can include an ECN Marking or Congestion Information Reporting Request IE in its PDU Session Resources To Be Setup List IE. This IE instructs the new NG-RAN node to perform ECN marking, report information for ECN marking, or report congestion information for QoS flows. The new NG-RAN node will use it, if supported, depending on the specific QoS flow.

[0016] Furthermore, Non-Patent Document 3 specifies F1AP signaling between the gNB-CU and gNB-DU to support ECN marking and congestion information reporting. Specifically, the UE CONTEXT SETUP REQUEST message and UE CONTEXT MODIFICATION REQUEST message sent from the gNB-CU to the gNB-DU can include an ECN Marking or Congestion Information Reporting Request IE. This IE instructs the gNB-DU to report ECN marking or congestion information for the DRB.

[0017] The UE CONTEXT SETUP RESPONSE message and the UE CONTEXT MODIFICATION RESPONSE message sent from the gNB-DU to the gNB-CU may include an ECN Marking or Congestion Information Reporting Status IE. This IE indicates the status of ECN marking information reporting or congestion information reporting for the DRB. Specifically, this IE indicates whether ECN marking information reporting or congestion information reporting is active.

[0018] 3GPP TS 23.501 V18.4.0 (2023-12)3GPP TS 38.423 V18.0.0 (2023-12)3GPP TS 38.473 V18.0.0 (2023-12)3GPP TS 38.322 V18.0.0 (2023-12)Huawei, Qualcomm, Lenovo, CATT, China Telecom, ZTE, Xiaomi, Nokia, Nokia Shanghai Bell, Ericsson, "Correction on PSI based discard", R3-241043, 3GPP TSG-RAN WG3 Meeting #123, Athens, Greece, February 26 - March 1, 2024Huawei, Qualcomm, Lenovo, CATT, Xiaomi, China Telecom, ZTE, Nokia, Nokia Shanghai Bell, Ericsson, "Correction on PSI based discard", R3-241154, 3GPP TSG-RAN WG3 Meeting #123, Athens, Greece, February 26 - March 1, 2024

[0019] The inventors have investigated signaling within NG-RAN related to PDU set-based handling, ECN marking, and congestion information reporting specified in 3GPP Release 18 and have found various issues. Some of these issues relate to signaling between NG-RAN nodes (XnAP signaling) for supporting PDU set-based handling in dual connectivity. The current 3GPP Release 18 specifications, particularly Non-Patent Document 2, do not adequately specify XnAP signaling related to Multi-Radio Dual Connectivity (MR-DC), which is necessary for supporting PDU set-based handling.

[0020] As mentioned above, Non-Patent Document 2 specifies that a HANDOVER REQUEST ACKNOWLEDGE message sent from a target RAN node to a source RAN node during a handover procedure may include a PDU Set-based Handling Indicator IE. However, Non-Patent Document 2 does not specify that MR-DC-related messages include a PDU Set-based Handling Indicator IE. For example, it may be beneficial for a dual connectivity secondary node (SN) to inform the dual connectivity master node (MN) whether the SN supports PDU set-based handling.

[0021] Furthermore, Non-Patent Document 2 does not specify that MR-DC-related messages include information elements for activating and deactivating UL PSI-based SDU discard. In MR-DC, a PDCP entity for a certain DRB may be located in the MN, and the lower layers of the DRB, including a Radio Link Control (RLC) entity, may be located in the SN. This type of DRB is a type of MN terminated bearer, and is also called an MN terminated Secondary Cell Group (SCG) bearer or an MN terminated split bearer. Similarly, in MR-DC, a PDCP entity for a certain DRB may be located in the SN, and the lower layers of the DRB, including an RLC entity, may be located in the MN. This type of DRB is a type of SN terminated bearer, and is also called an SN terminated Master Cell Group (MCG) bearer or an SN terminated split bearer. For example, when an MN terminated SCG or a split bearer is used, it would be preferable for the MN to be able to request the MAC entity located in the SN to activate or deactivate UL PSI-based SDU discard, i.e., to send an Activation / Deactivation of PSI-based SDU Discard MAC CE. Similarly, when an SN terminated MCG or a split bearer is used, it would be preferable for the SN to be able to request the MAC entity located in the MN to activate or deactivate UL PSI-based SDU discard. However, Non-Patent Document 2 does not specify XnAP signaling between NG-RAN nodes for these purposes. Note that Non-Patent Document 5 only proposes an improvement to F1AP signaling between gNB-CU and gNB-DU, and does not describe an improvement to XnAP signaling between NG-RAN nodes (or between CUs).

[0022] Some other issues relate to the discarding of RLC SDUs by the RLC sublayer. The discarding of RLC SDUs by the RLC sublayer in 3GPP Release 18 remains unchanged from that defined in 3GPP Release 17. In other words, no changes corresponding to or related to PDU set-based PDCP SDU discarding or PSI-based PDCP SDU discarding have been made to RLC SDU discarding. The discarding of RLC SDUs by the RLC sublayer is specified in Section 5.4 of 3GPP TS 36.210. According to this specification, when an upper layer (e.g., PDCP) instructs a transmitting Acknowledged Mode (AM) RLC entity or a transmitting Unacknowledged Mode (UM) RLC entity to discard a specific RLC SDU if the RLC SDU or a segment thereof has not been transmitted to the lower layer.

[0023] The inventors have considered improving the discarding of DL SDUs at the RLC sublayer. Consider the case where the PDCP entity and the RLC entity for a given DRB are located in different nodes. This can occur in both the CU-DU configuration and the MR-DC configuration. Specifically, the PDCP entity for a given DRB may be located in the gNB-CU (or gNB-CU-UP), and the RLC entity for that DRB may be located in the gNB-DU. The PDCP entity for a given MN-terminated bearer (MN-terminated DRB) may be located in the MN, and the RLC entity for that DRB may be located in the SN. Similarly, the PDCP entity for a given SN-terminated bearer (SN-terminated DRB) may be located in the SN, and the RLC entity for that DRB may be located in the MN. In these cases, the arrival of an instruction to discard an RLC SDU from the PDCP entity to the RLC entity may be delayed. During this delay, the RLC entity may transmit an RLC SDU or a segment thereof that should have been discarded to a lower layer. This may hinder efficient RLC SDU discarding at the RLC entity.

[0024] To address this issue, it is conceivable that the RLC entity could use a discard timer similar to that used by the PDCP entity for RLC SDU discard. In this case, it may be preferable for a node (e.g., CU, MN, or SN) with a PDCP entity for a certain DRB to instruct a node (e.g., DU, SN, or MN) with an RLC entity for that DRB to activate or deactivate timer-based SDU discard at the RLC entity. Additionally or alternatively, it may be preferable for a node (e.g., CU, MN, or SN) with a PDCP entity for a certain DRB to configure the length of the discard timer for timer-based SDU discard at the RLC entity for that node (e.g., DU, SN, or MN). Current 3GPP specifications do not specify XnAP or F1AP signaling for these purposes.

[0025] Still other issues relate to signaling (XnAP signaling) between NG-RAN nodes for supporting ECN marking and congestion information reporting in dual connectivity. The current 3GPP Release 18 specifications, particularly Non-Patent Document 2, do not adequately define XnAP signaling for MR-DC, which is necessary for supporting ECN marking and congestion information reporting.

[0026] As described above, Non-Patent Document 2 specifies that in a handover procedure, a HANDOVER REQUEST message sent from a source NG-RAN node to a target NG-RAN node can include an ECN Marking or Congestion Information Reporting Request IE in its PDU Session Resources To Be Setup List IE. Non-Patent Document 2 also specifies that in a Retrieve UE Context procedure, a RETRIEVE UE CONTEXT RESPONSE message sent from an old NG-RAN node to a new NG-RAN node can include an ECN Marking or Congestion Information Reporting Request IE in its PDU Session Resources To Be Setup List IE. However, Non-Patent Document 2 does not specify that MR-DC-related messages include an ECN Marking or Congestion Information Reporting Request IE. Similarly, Non-Patent Document 2 does not specify that MR-DC-related messages include an ECN Marking or Congestion Information Reporting Status IE. For example, to support ECN marking and congestion information reporting in MR-DC, it may be beneficial for the MN to be able to instruct the SN to perform ECN marking at the SN, report information from the SN to the MN for UPF or ECN marking at the MN, or report congestion information from the SN to the MN for a QoS flow. Similarly, it may be beneficial for the SN to be able to report the status of ECN marking or congestion information reporting to the MN.

[0027] One of the objectives to be achieved by the embodiments disclosed in this specification is to provide an apparatus, a method, and a program that contribute to solving at least one of multiple problems related to PDU set-based handling, ECN marking, or signaling for congestion information reporting, including the above-mentioned problems. It should be noted that this objective is only one of multiple objectives to be achieved by the multiple embodiments disclosed in this specification. Other objectives or objectives and novel features will be apparent from the description of this specification or the accompanying drawings.

[0028] A first aspect is directed to a secondary node of a dual connectivity system, the secondary node being configured to send an information element to the master node of the dual connectivity system indicating whether PDU set-based handling is supported by the secondary node or not.

[0029] A second aspect is directed to a method performed by a dual connectivity secondary node, the method including sending an information element to the dual connectivity master node indicating whether PDU set-based handling is supported by the secondary node.

[0030] A third aspect is directed to a dual connectivity master node, configured to receive from the dual connectivity secondary node an information element indicating whether PDU set-based handling is supported by the secondary node.

[0031] A fourth aspect is directed to a method performed by a dual connectivity master node, the method including receiving, from the dual connectivity secondary node, an information element indicating whether PDU set-based handling is supported by the secondary node.

[0032] A fifth aspect is directed to a dual connectivity master node configured to send to the dual connectivity secondary node via a dual connectivity related message an information element for activation or deactivation of PSI-based uplink PDCP SDU discarding by a wireless terminal for a data radio bearer terminated at the master node.

[0033] A sixth aspect is directed to a method performed by a dual connectivity master node, the method including sending, via a dual connectivity related message to the dual connectivity secondary node, an information element for activation or deactivation of PSI-based uplink PDCP SDU discarding by a wireless terminal for a data radio bearer terminated at the master node.

[0034] A seventh aspect is directed to a dual connectivity secondary node configured to receive, from the dual connectivity master node via a dual connectivity related message, an information element for activation or deactivation of PSI-based uplink PDCP SDU discarding by a wireless terminal for a data radio bearer terminated at the master node.

[0035] An eighth aspect is directed to a method performed by a dual connectivity secondary node, the method including receiving, from the dual connectivity master node via a dual connectivity related message, an information element for activation or deactivation of PSI-based uplink PDCP SDU discarding by a wireless terminal for a data radio bearer terminated at the master node.

[0036] A ninth aspect is directed to a dual connectivity master node, configured to receive, from the dual connectivity secondary node via a dual connectivity related message, an information element for activation or deactivation of PSI-based uplink PDCP SDU discarding by a wireless terminal for a data radio bearer terminated at the secondary node.

[0037] A tenth aspect is directed to a method performed by a dual connectivity master node, the method including receiving, from the dual connectivity secondary node via a dual connectivity related message, an information element for activation or deactivation of PSI-based uplink PDCP SDU discarding by a wireless terminal for a data radio bearer terminated at the secondary node.

[0038] An eleventh aspect is directed to a dual connectivity secondary node configured to send, via a dual connectivity related message to the dual connectivity master node, an information element for activation or deactivation of PSI-based uplink PDCP SDU discarding by a wireless terminal for a data radio bearer terminated at the secondary node.

[0039] A twelfth aspect is directed to a method performed by a dual connectivity secondary node, the method including sending, to the dual connectivity master node, via a dual connectivity related message, an information element for activation or deactivation of PSI-based uplink PDCP SDU discarding by a wireless terminal for a data radio bearer terminated at the secondary node.

[0040] A thirteenth aspect is directed to a first communication node configured to, for a data radio bearer terminated at the first communication node, send to a second communication node providing an RLC entity for the data radio bearer a configuration for downlink RLC SDU discard in the RLC entity, the configuration including an indication of activation or deactivation of timer-based downlink RLC SDU discard, an indication of a length of a discard timer used for the timer-based downlink RLC SDU discard, or both.

[0041] A fourteenth aspect is directed to a method performed by a first communication node, the method comprising, for a data radio bearer terminated at the first communication node, sending a configuration for downlink RLC SDU discard in an RLC entity to a second communication node providing an RLC entity for the data radio bearer, the configuration including an indication of activation or deactivation of timer-based downlink RLC SDU discard, an indication of a length of a discard timer used for the timer-based downlink RLC SDU discard, or both.

[0042] A fifteenth aspect is directed to a second communication node configured to receive from a first communication node configuration related to downlink RLC SDU discard in an RLC entity for a data radio bearer terminated at the first communication node, and to provision the RLC entity for the data radio bearer, the configuration including an indication of activation or deactivation of timer-based downlink RLC SDU discard, an indication of a length of a discard timer used for the timer-based downlink RLC SDU discard, or both.

[0043] A sixteenth aspect is directed to a method performed by a second communication node, the method comprising: receiving from a first communication node configuration for downlink RLC SDU discard in an RLC entity for a data radio bearer terminated at the first communication node, and providing the RLC entity for the data radio bearer, the configuration including an indication of activation or deactivation of timer-based downlink RLC SDU discard, an indication of a length of a discard timer to be used for the timer-based downlink RLC SDU discard, or both.

[0044] A seventeenth aspect is directed to a dual connectivity master node, configured to send a first information element to the dual connectivity secondary node, the first information element indicating whether ECN marking is required to be performed at the secondary node for a QoS flow associated with a data radio bearer terminated at the secondary node; whether information for ECN marking at a UPF in a core network is required to be reported from the secondary node to the UPF; or whether congestion information is required to be reported from the secondary node to the UPF.

[0045] An eighteenth aspect is directed to a method performed by a dual connectivity master node, the method including sending a first information element to the dual connectivity secondary node, the first information element indicating whether ECN marking is required to be performed at the secondary node for a QoS flow associated with a data radio bearer terminated at the secondary node; whether information for ECN marking at a UPF in a core network is required to be reported from the secondary node to the UPF; or whether congestion information is required to be reported from the secondary node to the UPF.

[0046] A nineteenth aspect is directed to a secondary node of dual connectivity, configured to receive a first information element from the dual connectivity master node, the first information element indicating whether ECN marking is required to be performed at the secondary node for a QoS flow associated with a data radio bearer terminated at the secondary node; whether information for ECN marking at a UPF in a core network is required to be reported from the secondary node to the UPF; or whether congestion information is required to be reported from the secondary node to the UPF.

[0047] A twentieth aspect is directed to a method performed by a secondary node in dual connectivity, the method including receiving a first information element from the dual connectivity master node, the first information element indicating whether ECN marking is required to be performed at the secondary node for a QoS flow associated with a data radio bearer terminated at the secondary node; whether information for ECN marking at a UPF in a core network is required to be reported from the secondary node to the UPF; or whether congestion information is required to be reported from the secondary node to the UPF.

[0048] A twenty-first aspect is directed to a dual connectivity master node, configured to send a first information element to the dual connectivity secondary node, the first information element instructing the secondary node to report information about ECN marking or congestion to the master node for data radio bearers terminated at the master node.

[0049] A twenty-second aspect is directed to a method performed by a dual connectivity master node, the method including sending a first information element to the dual connectivity secondary node, the first information element indicating the secondary node to report information regarding ECN marking or congestion to the master node for data radio bearers terminated at the master node.

[0050] A 23rd aspect is directed to a dual connectivity secondary node, the secondary node being configured to receive a first information element from the dual connectivity master node, the first information element instructing the secondary node to report information regarding ECN marking or congestion to the master node for data radio bearers terminated at the master node.

[0051] A twenty-fourth aspect is directed to a method performed by a dual connectivity secondary node, the method including receiving a first information element from the dual connectivity master node, the first information element indicating the secondary node to report information regarding ECN marking or congestion to the master node for data radio bearers terminated at the master node.

[0052] A twenty-fifth aspect is directed to a dual connectivity master node, the master node being configured to receive a first information element from the dual connectivity secondary node, the first information element instructing the master node to report information regarding ECN marking or congestion to the secondary node for data radio bearers terminated at the secondary node.

[0053] A twenty-sixth aspect is directed to a method performed by a dual connectivity master node, the method including sending and receiving a first information element from the dual connectivity secondary node, the first information element indicating to the master node to report ECN marking-related or congestion-related information to the secondary node for data radio bearers terminated at the secondary node.

[0054] A 27th aspect is directed to a dual connectivity secondary node, the secondary node being configured to receive a first information element from the dual connectivity secondary node, the first information element indicating to the master node to report information regarding ECN marking or congestion to the secondary node for data radio bearers terminated at the secondary node.

[0055] A twenty-eighth aspect is directed to a method performed by a dual connectivity secondary node, the method including receiving a first information element from the dual connectivity secondary node, the first information element indicating to the master node to report information regarding ECN marking or congestion to the secondary node for data radio bearers terminated at the secondary node.

[0056] A twenty-ninth aspect is directed to a program, the program including a group of instructions (software code) that, when loaded into a computer, causes the computer to perform a method according to any one of the above aspects.

[0057] According to the above-described aspects, it is possible to provide an apparatus, a method, and a program that contribute to solving at least one of a plurality of problems related to PDU set-based handling, ECN marking, or signaling for congestion information reporting, including the problems described above.

[0058] FIG. 1 illustrates an example configuration of a wireless communication system according to one or more embodiments. FIG. 2 illustrates an example configuration of a wireless communication system according to one or more embodiments. FIG. 3 illustrates an example configuration of a wireless communication system according to one or more embodiments. FIG. 4 illustrates an example user plane protocol stack according to one or more embodiments. FIG. 5 illustrates a sequence diagram of example signaling according to one or more embodiments. FIG. 6 illustrates an example format of a PDU Session Resource Setup Response Info - SN terminated IE according to one or more embodiments. FIG. 7 illustrates an example format of a PDU Session Resource Setup Info - MN terminated IE according to one or more embodiments. FIG. 8 illustrates an example format of a PSI based SDU Discard UL IE according to one or more embodiments. FIG. 9 illustrates an example sequence diagram of example signaling according to one or more embodiments. FIG. 10 illustrates an example format of a PDU Session Resource Setup Response Info - SN terminated IE according to one or more embodiments. FIG. 11 illustrates an example format of a PSI based SDU Discard UL IE according to one or more embodiments. FIG. 1 illustrates an example format for a PDU Session Resource Setup Info - MN terminated IE, which is relevant to one or more embodiments; FIG. 2 illustrates an example format for a PSI Based RLC SDU Discard Timer DL IE, which is relevant to one or more embodiments; FIG. 3 illustrates an example sequence diagram of signaling, which is relevant to one or more embodiments; and FIG. 4 illustrates an example format for a PDU Session Resource Setup Response Info - SN terminated IE, which is relevant to one or more embodiments.

[0023] Figure 1 is a sequence diagram illustrating example signaling according to one or more embodiments.

[0024] Figure 2 is a diagram illustrating an example format of a UE CONTEXT SETUP REQUEST message according to one or more embodiments.

[0025] Figure 3 is a diagram illustrating an example format of a PDU Session Resource Setup Info - SN terminated IE according to one or more embodiments.

[0026] Figure 4 is a diagram illustrating an example format of an ECN Marking or Congestion Information Reporting Request IE according to one or more embodiments.

[0027] Figure 5 is a diagram illustrating an example format of a PDU Session Resource Setup Response Info - SN terminated IE according to one or more embodiments.

[0028] Figure 6 is a diagram illustrating an example format of an ECN Marking or Congestion Information Reporting Status IE according to one or more embodiments.

[0029] Figure 7 is a diagram illustrating example signaling according to one or more embodiments.

[0030] Figure 8 is a diagram illustrating an example format of a PDU Session Resource Setup Info - MN terminated IE according to one or more embodiments.

[0031] Figure 9 is a diagram illustrating an example format of an ECN Marking or Congestion Information Reporting Request - RLC bearer IE according to one or more embodiments. 1 illustrates an example format for a PDU Session Resource Setup Response Info - MN terminated IE, 2 illustrates an example format for an ECN Marking or Congestion Information Reporting Status - RLC bearer IE, 3 illustrates an example sequence diagram of signaling, 4 illustrates an example signaling sequence, 5 illustrates an example signaling sequence, 6 illustrates an example signaling sequence, 7 illustrates an example signaling sequence, 8 illustrates an example signaling sequence, 9 illustrates an example signaling sequence, 10 illustrates an example signaling sequence, 11 illustrates an example signaling sequence, 12 illustrates an example signaling sequence, 13 illustrates an example signaling sequence, 14 illustrates an example signaling sequence, 15 illustrates an example signaling sequence, 16 illustrates an example signaling sequence, 17 illustrates an example signaling sequence, 18 illustrates an example signaling sequence, 19 ...20 illustrates an example signaling sequence, 20 illustrates an example signaling sequence, 20 illustrates an example signaling sequence, 20 illustrates an example signaling sequence, 20 illustrates an example signaling sequence, 21 illustrates an example signaling sequence, 22 illustrates an example signaling sequence, 23 illustrates an example signaling sequence, 24 illustrates an example signaling sequence, 25 illustrates an example signaling sequence, 26 illustrates an example signaling sequence, 27 illustrates an example signaling sequence, 28 illustrates an example signaling sequence, 29 illustrates an example signaling sequence, 30 illustrates an example signaling sequence, 31 illustrates an example signaling sequence, 32 illustrates an example signaling sequence, 33 illustrates an example signaling sequence, 34 illustrates an example signaling sequence, 35 illustrates an example signaling sequence, 36 illustrates an example signaling sequence, 37 illustrates an example signaling sequence, 31 illustrates an example format of a PDU Session Resource Setup Response Info - SN terminated IE in accordance with one or more embodiments; 2 illustrates an example configuration of a UE in accordance with one or more embodiments; 3 illustrates an example configuration of a RAN node in accordance with one or more embodiments; 4 illustrates an example configuration of a core network node in accordance with one or more embodiments;

[0059] Hereinafter, specific embodiments will be described in detail with reference to the drawings. In each drawing, the same or corresponding elements are designated by the same reference numerals, and for clarity of explanation, duplicate explanations will be omitted as necessary.

[0060] The multiple embodiments described below may be used independently, or two or more embodiments may be combined as appropriate. These multiple embodiments may have different novel features. Therefore, these multiple embodiments may contribute to achieving different objectives or solving different problems, and may contribute to achieving different effects.

[0061] Each drawing is merely an example for describing one or more embodiments. Each drawing may not relate to only one particular embodiment, but may also relate to one or more other embodiments. As will be understood by those skilled in the art, various features or steps described with reference to any one drawing can be combined with features or steps shown in one or more other drawings to create, for example, an embodiment not explicitly shown or described. Not all features or steps shown in any one drawing are necessary to describe an exemplary embodiment, and some features or steps may be omitted. The order of steps described in any drawing may be changed as appropriate.

[0062] The following embodiments are described primarily for the 3GPP 5th generation mobile communication system (5G system). However, these embodiments may also be applied to other wireless communication systems employing techniques similar to PDU set-based handling, ECN marking, or congestion information reporting defined in 3GPP Release 18.

[0063] As used herein, depending on the context, "if" may be interpreted to mean "when," "while," "at or around the time," "after," "upon," "in response to determining," "in accordance with a determination," or "in response to detecting." These expressions may be interpreted to have the same meaning, depending on the context.

[0064] First, the configurations and operations of multiple network elements common to multiple embodiments will be described. Figure 1 shows an example configuration of a wireless communication system according to multiple embodiments. Each of the elements shown in Figure 1 is a network function, and provides an interface defined by, for example, 3GPP. Each element (network function) shown in Figure 1 can be implemented, for example, as a network element on dedicated hardware, as a software instance running on dedicated hardware, or as a virtualized function instantiated on an application platform.

[0065] The wireless communication system shown in Fig. 1 may be provided by a Mobile Network Operator (MNO) or a Non-Public Network (NPN) provided by a party other than an MNO. If the cellular network shown in Fig. 1 is an NPN, it may be an independent network called a Stand-alone Non-Public Network (SNPN), or an NPN that works in conjunction with an MNO network called a Public network integrated NPN (PNI-NPN).

[0066] In the example of FIG. 1, the wireless communication system includes a UE 1, an NG-RAN 2, and a 5G Core Network (5GC) 4. The UE 1 may be referred to by other terms, such as a wireless terminal, a mobile terminal, a mobile station, or a wireless transmit receive unit (WTRU). The NG-RAN 2 includes one or more RAN nodes 3. The 5GC 4 includes one or more network functions or nodes in the control plane and one or more functions or nodes in the user plane. FIG. 1 illustrates some representative network functions or nodes in the 5GC 4, including an Access and Mobility Management Function (AMF) 5, an SMF 6, and a UPF 7. The UPF 7 may include multiple interconnected UPFs. More specifically, the UPF 7 includes a PDU Session Anchor (PSA) UPF and may include one or more intermediate UPFs. The intermediate UPFs may provide an Uplink Classifier (UL CL) or Branching Point (BP) function.

[0067] UE1 uses 5G connectivity services provided by NG-RAN2 and 5GC4 to communicate with Data Network (DN) 8. More specifically, UE1 is connected to RAN node 3 in NG-RAN2 and communicates with DN8 via UPF 7 in 5GC4. UE1 establishes one or more Protocol Data Unit (PDU) sessions 100 between UE1 and UPF 7 (i.e., PSA UPF) to which UE1 and DN8 are connected. The PDU session 100 is an association, session, or connection between UE1 and DN8. The PDU session 100 is used to provide PDU connectivity services (i.e., exchange of PDUs between UE1 and DN8). From a data transfer perspective, the PDU session 100 consists of a tunnel within 5GC4 (N9 tunnel), a tunnel between 5GC4 and NG-RAN2 (N3 tunnel), and one or more radio bearers. Although not shown in FIG. 1, the UE 1 may establish multiple PDU sessions with multiple PDU session anchors (UPFs) 7, respectively, to access multiple DNs 8 concurrently.

[0068] The 5G QoS model is based on QoS flows. It supports both QoS flows that require flow bit rate guarantees (GBR QoS flows) and QoS flows that do not require flow bit rate guarantees (Non-GBR QoS flows). QoS flows are the finest granularity of QoS differentiation within a PDU session. In other words, QoS flows are the finest granularity for QoS forwarding treatment in a 5G system. All traffic mapped to the same 5G QoS flow receives the same forwarding treatment (e.g., scheduling policy, queue management policy, rate shaping, Radio Link Control (RLC) settings, etc.). To provide different QoS forwarding treatments, separate QoS flows are required.

[0069] Every QoS flow is characterized by a QoS profile; one or more QoS rules and optional QoS flow level parameters; and one or more uplink and downlink Packet Detection Rule(s) (PDR(s)). The QoS profile is provided from the SMF 6 to the NG-RAN 2 (or RAN node 3) via the AMF 5 over the N2 reference point. One or more QoS rules and QoS flow level parameters are provided from the SMF 6 to the UE 1 via the AMF 5 over the N1 reference point. One or more uplink and downlink PDR(s) are provided from the SMF 6 to the UPF 7.

[0070] As shown in FIG. 1 , multiple QoS flows 120 associated with different QoS requirements can be established for one PDU session 100. One or more applications 10 in a UE 1 transmit or receive multiple packet flows to or from one or more applications 80 in a DN 8 via the multiple QoS flows 120. For example, an application 80 or one or more application servers in a DN 8 may provide an XR service to a UE 1 via a 5GC 4 and an NG-RAN 2. The DN 8 may be an Edge Data Network (EDN) or a Local Area Data Network (LADN). One or more application servers in the DN 8 may include one or more edge computing servers located near the NG-RAN 2. In other words, the application 80 in the DN 8 may be hosted on one or more edge computing servers located near the NG-RAN 2.

[0071] As can be understood from the above description, a QoS flow can be considered as a packet flow between UE1 and 5GC4 consisting of one or more packet flows transferred between UE1 and DN8. Alternatively, a QoS flow can be considered as a transmission path or connection set up or established between UE1 and 5GC4 for forwarding one or more packet flows transferred between UE1 and DN8.

[0072] The RAN node 3 provides one or more cells. The UE 1 may be simultaneously connected to multiple cells provided by the RAN node 3. In other words, the UE 1 may perform carrier aggregation (CA) between multiple cells provided by the RAN node 3. In addition, the UE 1 may be simultaneously connected to the RAN node 3 and another RAN node (e.g., an NG-RAN node or an Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (E-UTRAN) node) for dual connectivity (DC). This dual connectivity may be Multi-Radio Dual Connectivity (MR-DC).

[0073] The RAN node 3 may be a gNB or an ng-eNB, which provides Evolved UMTS Terrestrial Radio Access (E-UTRA) user plane and control plane protocol termination to the UE and is connected to the 5GC via an NG interface.

[0074] The RAN node 3 may be a Central Unit (e.g., gNB-CU) in a cloud RAN (C-RAN) deployment, or a combination of a CU and one or more Distributed Units (e.g., gNB-DUs). C-RAN is also referred to as a CU / DU split. Furthermore, a CU may include a Control Plane (CP) Unit (e.g., gNB-CU-CP) and one or more User Plane (UP) Units (e.g., gNB-CU-UP). Thus, the RAN node 3 may be a CU-CP or a combination of a CU-CP and a CU-UP. The CU may be a logical node that hosts the Radio Resource Control (RRC), Service Data Adaptation Protocol (SDAP), and Packet Data Convergence Protocol (PDCP) protocols of the gNB (or the RRC and PDCP protocols of the gNB). The DU may be a logical node that hosts the Radio Link Control (RLC), Medium Access Control (MAC), and Physical (PHY) layers of the gNB. The DU may host the high PHY layer, and the low PHY layer may be located in one or more Transmission-Reception Points (TRPs) connected to the gNB-DU. A TRP may also be called a Radio Unit (RU) or Remote Radio Head (RRH).

[0075] The CU-CP may be a logical node that hosts the control plane functions of the CU, e.g., the control plane parts of the RRC and PDCP protocols of the gNB-CU. The CU-UP may be a logical node that hosts the user plane functions of the CU, e.g., the user plane parts of the PDCP protocol and the SDAP protocol of the gNB-CU.

[0076] FIG. 2 shows a configuration example in which the RAN node 3 is a gNB. In the example of FIG. 2, the gNB-CU 30 includes a gNB-CU-CP 31 and one or more gNB-CU UPs 32. The gNB-CU-CP 31 is a logical node that hosts the control plane portion of the gNB-CU 30's RRC and PDCP protocols. The gNB-CU-CP 31 terminates an E1 interface connected to each gNB-CU-UP 32 and an F1-C interface connected to each of one or more gNB-DUs 35. The E1 interface uses the E1 Application Protocol (E1AP). The F1-C interface also uses the F1 Application Protocol (F1AP). In addition, the gNB-CU-CP 11 terminates an NG-C interface connected to a control plane node (i.e., AMF 5) in the core network. The NG-C interface may also be referred to as an N2 interface. The NG-C interface uses the NG Application Protocol (NGAP).

[0077] The gNB-CU-UP 32 is a logical node that hosts the user plane portion of the PDCP protocol of the gNB-CU 30 for the en-gNB, or the user plane portion of the PDCP protocol and the SDAP protocol of the gNB-CU 30 for the gNB. The gNB-CU-UP 32 terminates the E1 interface connected to the gNB-CU-CP 31 and the F1-U interface connected to each of one or more gNB-DUs 35. The F1-U interface uses the General Packet Radio Service Tunneling Protocol User Plane (GTP-U) protocol. The GTP-U protocol uses GTP-U tunnels to carry encapsulated user data packets (i.e., T-PDUs) and signaling messages. In addition, the gNB-CU-UP 32 terminates the NG-U interface connected to a user plane node (i.e., UPF7) in the core network. The NG-U interface may also be referred to as the N3 interface. The NG-U interface uses the GTP-U protocol.

[0078] Figure 3 shows an example of a dual connectivity configuration. In the example of Figure 3, a RAN node 33A and a RAN node 33B operate as a master node (MN) and a secondary node (SN) of dual connectivity, respectively. Hereinafter, the RAN node 3A may be referred to as an MN 3A, and the RAN node 3B may be referred to as an SN 3B. A UE 1 communicates with the MN 3A and the SN 3B via air interfaces 301 and 302, and performs dual connectivity for a Master Cell Group (MCG) and a Secondary Cell Group (SCG). The MCG is a group of serving cells associated with (or provided by) the MN 3A, and includes a Special Cell (SpCell) (i.e., a Primary Cell (PCell)) and, optionally, one or more Secondary Cells (SCells). On the other hand, the SCG is a group of serving cells associated with (or provided by) the SN 3B, and includes a Primary SCG Cell (PSCell) and, optionally, one or more SCells. A PSCell is an SpCell of the SCG, and supports Physical Uplink Control Channel (PUCCH) transmission and contention-based Random Access.

[0079] DRBs used in dual connectivity include MN-terminated bearers and SN-terminated bearers. MN-terminated bearers and SN-terminated bearers may be referred to as MN-terminated DRBs and SN-terminated DRBs, respectively. An MN-terminated bearer is a DRB for which the PDCP entity is located in the MN 3A. An SN-terminated bearer is a DRB for which the PDCP entity is located in the SN 3B.

[0080] An MN terminated bearer can be an MN terminated MCG bearer, an MN terminated SCG bearer, or an MN terminated split bearer. Similarly, an SN terminated bearer can be an SN terminated SCG bearer, an SN terminated MCG bearer, or an SN terminated split bearer. An MCG bearer is a radio bearer that has an RLC bearer only in the MCG. An SCG bearer is a radio bearer that has an RLC bearer only in the SCG. A split bearer is a radio bearer that has RLC bearers in both the MCG and the SCG. An RLC bearer refers to the RLC and MAC logical channel configuration of a radio bearer in one cell group.

[0081] Therefore, in the case of an MN terminated SCG bearer or an MN terminated split bearer, the PDCP entity for the DRB is located in the MN 3A, and the lower layers of the DRB, including the RLC entity for the DRB, are located in the SN 3B. In the case of an SN terminated MCG bearer or an SN terminated split bearer, the PDCP entity for the DRB is located in the SN 3B, and the lower layers of the DRB, including the RLC entity, are located in the MN 3A.

[0082] Returning to FIG. 1 , the description continues. The AMF 5 is one of the network functions in the 5G control plane. The AMF 5 provides the termination of the RAN Control Plane (CP) interface (i.e., the N2 interface). The AMF 5 terminates a single signaling connection (i.e., a Non-Access Stratum (NAS) signaling connection) with the UE 1 and provides registration management, connection management, and mobility management. Registration management is used to register or deregister the UE 1 with the network (5G system). Connection management is used to establish and release the NAS signaling connection between the UE 1 and the AMF 5. Mobility management is used to keep track of the location of the UE 1. Mobility management uses a periodic registration update procedure and a mobility registration update procedure. Therefore, in a 5G system, mobility management can also be said to be included in registration management.

[0083] The AMF 5 provides NF services to Network Function (NF) consumers (e.g., other AMFs and the SMF 6) over a service-based interface (i.e., the Namf interface). The NF services provided by the AMF 5 include a communication service (Namf_Communication). The communication service enables the NF consumers (e.g., the SMF 6) to communicate with the UE 1 or the NG-RAN 2 via the AMF 5.

[0084] The SMF 6 is one of the network functions in the 5GC control plane. The SMF 6 provides session management. The session management is used to establish, modify, and release a PDU session to provide a PDU connectivity service to the UE 1. The session management includes signaling between the UE 1, the NG-RAN 2, the AMF 5, and the UPF 7 for establishing, modifying, and releasing a PDU session.

[0085] The SMF 6 transmits and receives SM signaling messages (NAS-SM messages, N1 SM messages) to and from the NAS Session Management (SM) layer of the UE 1 via the communication service provided by the AMF 5. In addition, the SMF 6 transmits and receives N2 SM information to and from the NG-RAN 2 (or RAN node 3) via the communication service provided by the AMF 5. The N2 SM information sent from the SMF 6 to the NG-RAN 2 via the AMF 5 can include, among other information, a PDU session ID, QoS flow identifiers (QFIs) of one or more QoS flows, and QoS profiles.

[0086] The SMF 6 provides NF services to NF consumers (e.g., AMF 5 and other SMFs) over a service-based interface (i.e., the Nsmf interface). The NF services provided by the SMF 6 include a session management service (Nsmf_PDUSession), which allows NF consumers (e.g., AMF 5) to handle PDU sessions.

[0087] Figure 4 shows an example of a user plane protocol stack provided by the wireless communication system of Figure 1. UE1 and DN8 (e.g., application server) can exchange PDUs (e.g., Internet Protocol (IP) packets) at the PDU layer. The application layer refers to a layer above the PDU layer. Therefore, if the PDU layer is the IP layer, the application layer may include transport layer protocols of the Open Systems Interconnection (OSI) model (e.g., Transmission Control Protocol (TCP) and User Datagram Protocol (UDP)). For example, in the case of an XR service, the PDU layer protocol may be IP, while the application layer protocol may include H.264, H265, or H.266 codec, Real-time Transport Protocol (RTP), and UDP.

[0088] If the upper layer PDUs are XR service PDUs, they may be dependent on each other and have different levels of importance. For example, PDUs that depend on other PDUs are expected to be more important. For example, PDUs that depend on other PDUs may be PDUs carrying fragments of intra-coded (I) frames, or other PDUs may be PDUs carrying fragments of predicted (P) frames or bi-directional predicted (B) frames.

[0089] For example, consecutive PDUs with the same importance level (e.g., PDUs carrying fragments of an I-frame) can be treated as one PDU set. Alternatively, PDUs carrying a payload of one unit of information generated at the application level can be treated as one PDU set. Therefore, an XR service flow can be considered as a flow of consecutive PDU sets. In other words, XR service data can be categorized as a list of consecutive PDU sets. For example, one PDU set may correspond to PDUs carrying the data of one video frame. Except for the importance level, the Quality of Service (QoS) requirements of an XR service flow are consistent. Therefore, an XR service flow can be mapped to a QoS flow. In this case, one QoS flow contains multiple PDU sets with different importance levels. The importance level for each PDU set is defined or determined by the application 80 (e.g., an XR application, an Application Function (AF), or an application server) and provided to the 5GC 4 as part of the PDU set-related information.

[0090] A PDU set consists of one or more PDUs carrying a payload of one unit of information (e.g., a frame or video slice of an XR service) generated at the application level. In some implementations, all PDUs in a PDU set are required by the application layer to use the corresponding information unit. In other implementations, the application layer can recover all or part of the information unit even if some PDUs are missing. That is, multiple PDU sets can be classified into different types based not only on importance or dependency, but also on differences in encoding methods, for example.

[0091] For example, in a certain type of PDU set, all PDUs in the PDU set are required by the application layer to use the corresponding information unit, and for this type of PDU set, all PDUs in the PDU set are said to be essential PDUs.

[0092] In another type of PDU set, one or more specific PDUs in the PDU set are required by the application layer to use the corresponding information unit, but the remaining PDUs are not necessarily required by the application layer. In this type of PDU set, some PDUs, or a subset of PDUs, in the PDU set can be said to be essential PDUs.

[0093] For yet another type of PDU set, the application layer must receive at least K of the N PDUs in the entire PDU set in order to use the corresponding information unit. For this type of PDU set, no PDUs are essential, and the K parameter must be included in the PDU set related information.

[0094] As can be seen from the above explanation, a PDU set is based on the dependency of PDUs belonging to one QoS flow. A PDU set is one or more PDUs that carry the payload of one unit of information (e.g., frame(s) or video slice(s) of an XR service) generated at the application level. All PDUs in one PDU set are transmitted within the same Quality of Service (QoS) flow.

[0095] In UL transmission, PDU set-based discarding by UE1 is supported. NG-RAN2 (e.g., RAN node 3) can configure PDU set-based discarding for UE1 for DRBs associated with QoS flows carrying PDU sets. NG-RAN2 requests UE1 to perform PDU set-based discarding for a specific DRB via RRC signaling, specifically by setting the pdu-SetDiscard field in the PDCP configuration (PDCP-Config) for that specific DRB. If PDU set-based discarding is configured for a specific DRB, the transmitting PDCP entity of UE1 associated with that DRB performs PDU set-based PDCP SDU discarding. Specifically, when a PDCP SDU belonging to a PDU set is discarded due to the expiration of its discard timer, the transmitting PDCP entity of UE1 discards all PDCP SDUs belonging to the PDU set to which that PDCP SDU belongs, along with the corresponding PDCP data PDUs.

[0096] Furthermore, in the event of congestion, the NG-RAN 2 can use the PSI for PDU set-based discard. The PSI specifies the relative importance of a PDU set compared to other PDU sets in the same QoS flow. In the uplink, the NG-RAN 2 (e.g., RAN node 3) can request the UE to apply a short discard timer to less important SDUs in PDCP via a dedicated downlink signal. This dedicated downlink signal is the Activation / Deactivation of PSI-based SDU Discard MAC CE. In response to receiving the Activation / Deactivation of PSI-based SDU Discard MAC CE requesting activation of PSI-based SDU discard for a specific DRB, the UE 1 initiates PSI-based SDU discard for that DRB in the PDCP entity for that DRB. When receiving a PDCP SDU from upper layers, the PDCP entity operates as follows: If the short discard timer (i.e., discardTimerForLowImportance) is configured by RRC, PSI-based SDU discard is activated, and the PDCP SDU belongs to the low importance PDU Set, the PDCP entity starts the short discard timer (i.e., discardTimerForLowImportance) associated with the PDCP SDU. Otherwise, the PDCP entity starts the regular long discard timer (i.e., discardTimer) associated with the PDCP SDU (if configured).

[0097] In DL transmissions, NG-RAN 2 (e.g., RAN node 3) may perform PDU set-based PDCP SDU discarding similar to that in UL transmissions by UE 1. Additionally, in DL transmissions, NG-RAN 2 may perform PSI-based PDCP SDU discarding similar to that in UL transmissions by UE 1.

[0098] NG-RAN2 and 5GC4 may support one or both of ECN marking (i.e., ECN marking for L4S) and congestion information reporting.

[0099] ECN marking exposes congestion information and triggers application layer rate adaptation by marking ECN bits in the IP header of user IP packets between UE 1 and an application server (i.e., one or more applications 80 in DN 8). ECN marking is enabled per QoS flow in the UL and / or DL ​​directions and can be used for GBR and non-GBR QoS flows. ECN marking in the IP header is supported in either NG-RAN2 or PSA UPF.

[0100] In the case of ECN marking by PSA UPF (i.e., UPF7), the NG-RAN2 is instructed to perform congestion information monitoring and report congestion information (i.e., a percentage of packets that UPF uses for ECN marking for L4S) of QoS flows in the UL and / or DL ​​directions to the PSA UPF via a GTP-U header extension. Specifically, the SMF6 of the 5GC4 requests the NG-RAN2 (e.g., RAN node 3) via the AMF5 to report congestion information per QoS flow level as part of the PDU session resource management procedure. If the NG-RAN2 supports ECN marking for L4S at UPF, the NG-RAN2 (e.g., RAN node 3) returns a status indication to the SMF6. This status indication is used by the SMF6 as specified in 3GPP TS 36.110.

[0101] In case of ECN marking by NG-RAN2, SMF6 provides ECN marking request per QoS flow level to NG-RAN2 (e.g., RAN node 3) as part of PDU session resource management procedure. If NG-RAN2 supports ECN marking for L4S in NG-RAN, NG-RAN2 returns a status indication to SMF6. This status indication is used by SMF as specified in 3GPP TS 36.110.

[0102] In the case of congestion information disclosure, the PSA UPF (i.e., UPF7) exposes UL and / or DL ​​congestion information via the Nupf_EventExposure service or via SMF6, PCF, or NEF. SMF6 can request NG-RAN2 (e.g., RAN node 3) to report congestion information to PSA UPF via the GTP-U header. This NG-RAN reported information is common to support congestion information disclosure in PSA UPF and ECN marking for L4S in PSA UPF. If NG-RAN2 supports congestion information reporting, NG-RAN2 (e.g., RAN node 3) returns a status indication to SMF6. This status indication is used in the SMF as specified in 3GPP TS 36.110. How NG-RAN2 (e.g., RAN node 3) measures and reports congestion information is up to the NG-RAN implementation.

[0103] When the serving RAN node changes, such as during a handover, the target RAN node must continue to perform ECN marking for QoS flows if supported. During the Xn handover preparation procedure, the source RAN node provides an ECN marking request or congestion information request to the target RAN node.

[0104] Some or all of the embodiments described below provide improvements to signaling within NG-RAN2 regarding PDU set-based handling, ECN marking, or congestion information reporting.

[0105] <First Embodiment> This embodiment provides an improvement of dual connectivity related signaling within the NG-RAN 2 for PDU set-based handling. Figure 5 shows an example of signaling between the MN 3A and the SN 3B. In step 501, the SN 3B sends a dual connectivity related message including a PDU Set based Handling Indicator IE to the MN 3A. The PDU Set based Handling Indicator IE indicates whether the PDU set-based handling is supported by the SN 3B.

[0106] The dual connectivity-related message in step 501 may be sent in an SN addition procedure or an SN modification preparation procedure initiated by MN 3A. The dual connectivity-related message may be an SN addition request acknowledgement (i.e., S-NODE ADDITION REQUEST ACKNOWLEDGE) message. Alternatively, the dual connectivity-related message may be an SN modification request acknowledgement (i.e., S-NODE MODIFICATION REQUEST ACKNOWLEDGE) message.

[0107] As mentioned above, Non-Patent Document 2 specifies that in a handover procedure, a HANDOVER REQUEST ACKNOWLEDGE message sent from a target RAN node to a source RAN node can include a PDU Set-based Handling Indicator IE. However, Non-Patent Document 2 does not specify that MR-DC-related messages include a PDU Set-based Handling Indicator IE. The signaling described with reference to Figure 5 can address this issue. The signaling described with reference to Figure 5 enables SN 3B to inform MN 3A whether SN 3B supports PDU set-based handling. This can be beneficial to MN 3A.

[0108] For example, if SN 3B supports PDU set-based handling, MN 3A may include PDU set information in data to be transferred to SN 3B. Otherwise, MN 3A may not include PDU set information in data to be transferred. The PDU set information includes one or any combination of a PDU set sequence number, an indication of end PDU of the PDU set, a PDU sequence number within a PDU set, a PDU set size in bytes, and a PDU set importance (PSI).

[0109] Additionally or alternatively, the MN 3A may inform the 5GC 4 (specifically, the SMF 6) whether the SN 3B supports PDU set-based handling. More specifically, the MN 3A may inform the 5GC 4 (specifically, the SMF 6) whether PDU set-based handling is supported in the NG-RAN 2 for a QoS flow transferred via the SN 3B.

[0110] Figure 6 shows an example of the format of the PDU Session Resource Setup Response Info - SN terminated IE extended to include the PDU Set based Handling Indicator IE. In 3GPP Release 18, the format of the PDU Session Resource Setup Response Info - SN terminated IE is specified in Section 9.2.1.6 of 3GPP TS 36544-1. The PDU Session Resource Setup Response Info - SN terminated IE can be included in the S-NODE ADDITION REQUEST ACKNOWLEDGE message sent from SN 3B to MN 3A. In the example of Figure 6, the PDU Session Resource Setup Response Info - SN terminated IE is extended to include a PDU Set based Handling Indicator IE 601. The format of the PDU Set based Handling Indicator IE 601 may be similar to that specified in Section 9.2.3.206 of 3GPP TS 36544-1 in connection with the HANDOVER REQUEST ACKNOWLEDGE message.

[0111] As in the example of Fig. 6, the PDU Session Resource Modification Response Info - SN terminated IE may be extended to include the PDU Set based Handling Indicator IE. In 3GPP Release 18, the format of the PDU Session Resource Modification Response Info - SN terminated IE is specified in Section 9.2.1.12 of Non-Patent Document 2. The PDU Session Resource Modification Response Info - SN terminated IE can be included in the S-NODE MODIFICATION REQUEST ACKNOWLEDGE message sent from the SN 3B to the MN 3A.

[0112] Second Embodiment This embodiment provides an improvement to dual connectivity-related signaling within the NG-RAN 2 for PDU set-based handling. FIG. 7 relates to an improvement that enables the MN 3A to activate or deactivate UL PSI-based SDU discarding for an MN-terminated bearer via the SN 3B. FIG. 7 shows an example of signaling between the MN 3A and the SN 3B. In step 701, the MN 3A sends an information element (IE) for activation or deactivation of PSI-based UUL PDCP SDU discarding by the UE 1 for an MN-terminated bearer to the SN 3B via a dual connectivity-related message. The MN-terminated bearer is an MN-terminated SCG bearer or an MN-terminated split bearer. In other words, the MN-terminated bearer is a DRB in which a PDCP entity for the DRB is located in the MN 3A and the lower layers of the DRB, including an RLC entity for the DRB, are located in the SN 3B.

[0113] In response to receiving the IE, the SN 3B sends a PSI-Based SDU Discard Activation / Deactivation MAC CE to the UE 1. In other words, the IE causes or requests the SN 3B to send a PSI-Based SDU Discard Activation / Deactivation MAC CE to the UE 1 according to the IE. The name of the IE may be, for example, but not limited to, a PSI based SDU Discard UL IE. If the IE indicates activation of UL PSI-based SDU discard, the SN 3B sends a PSI-Based SDU Discard Activation / Deactivation MAC CE indicating activation to the UE 1. If the IE indicates deactivation of UL PSI-based SDU discard, the SN 3B sends a PSI-Based SDU Discard Activation / Deactivation MAC CE indicating deactivation to the UE 1.

[0114] The dual connectivity related message in step 701 may be transmitted in an SN addition procedure or an SN modification preparation procedure initiated by MN 3A. The dual connectivity related message may be an SN addition request message (i.e., S-NODE ADDITION REQUEST) message. Alternatively, the dual connectivity related message may be an SN modification request message (i.e., S-NODE MODIFICATION REQUEST) message.

[0115] Non-Patent Document 2 does not specify that MR-DC related messages include information elements for activating and deactivating UL PSI-based SDU discard. The signaling described with reference to Figure 7 can address this issue. The signaling described with reference to Figure 7 enables MN 3A to instruct or request SN 3B to send a PSI-Based SDU Discard Activation / Deactivation MAC CE for MN terminated SCG or split bearer.

[0116] Figure 8 shows an example of the format of the PDU Session Resource Setup Info - MN terminated IE extended to include the PSI based SDU Discard UL IE. In 3GPP Release 18, the format of the PDU Session Resource Setup Info - MN terminated IE is specified in Section 9.2.1.7 of 3GPP TS 36544-1. The PDU Session Resource Setup Info - MN terminated IE can be included in an S-NODE ADDITION REQUEST message sent from the MN 3A to the SN 3B. In the example of Figure 8, the PDU Session Resource Setup Info - MN terminated IE is extended to include a PSI based SDU Discard UL IE 801. Specifically, the PDU Session Resource Setup Info - MN terminated IE includes a list of DRBs to be set up. The PSI based SDU Discard UL IE 801 indicates the activation or deactivation of UL PSI-based SDU discard on a DRB-by-DRB basis within the DRB list.

[0117] Figure 9 shows an example of the format of the PSI based SDU Discard UL IE 801. In the example of Figure 9, the PSI based SDU Discard UL IE 801 is enumerated and indicates "start" or "stop". The PSI based SDU Discard UL IE 801 indicates whether UL PSI-based SDU discard is (re)configured or released for the associated DRB. The codepoint "start" means that UL PSI-based discard is (re)configured. The codepoint "stop" means that UL PSI-based discard is released.

[0118] Similar to the example shown in Fig. 8, the PDU Session Resource Modification Info - MN terminated IE may be extended to include the PSI based SDU Discard UL IE. In 3GPP Release 18, the format of the PDU Session Resource Modification Info - MN terminated IE is specified in Section 9.2.1.11 of Non-Patent Document 2. The PDU Session Resource Modification Info - MN terminated IE can be included in an S-NODE MODIFICATION REQUEST message sent from MN 3A to SN 3B.

[0119] FIG. 10 relates to an improvement that enables the SN 3B to activate or deactivate UL PSI-based SDU discarding for an SN-terminated bearer via the MN 3A. FIG. 10 shows an example of signaling between the MN 3A and the SN 3B. In step 1001, the SN 3B sends to the MN 3A via a dual connectivity-related message an information element (IE) for activating or deactivating PSI-based UUL PDCP SDU discarding by the UE 1 for an SN-terminated bearer. The SN-terminated bearer is an SN-terminated MCG bearer or an SN-terminated split bearer. In other words, the SN-terminated bearer is a DRB in which a PDCP entity for the DRB is located in the SN 3B and the lower layers of the DRB, including an RLC entity for the DRB, are located in the MN 3A.

[0120] In response to receiving the IE, the MN 3A transmits a PSI-Based SDU Discard Activation / Deactivation MAC CE to the UE 1. In other words, the IE causes or requests the MN 3A to transmit a PSI-Based SDU Discard Activation / Deactivation MAC CE to the UE 1 according to the IE. The name of the IE may be, but is not limited to, a PSI based SDU Discard UL IE. If the IE indicates activation of the UL PSI-based SDU discard, the MN 3A transmits a PSI-Based SDU Discard Activation / Deactivation MAC CE indicating the activation to the UE 1. If the IE indicates deactivation of the UL PSI-based SDU discard, the MN 3A transmits a PSI-Based SDU Discard Activation / Deactivation MAC CE indicating the deactivation to the UE 1.

[0121] The dual connectivity related message of step 1001 may be sent in an SN addition procedure, an SN modification preparation procedure initiated by MN 3A, or an SN modification procedure initiated by SN 3B. The dual connectivity related message of step 1001 may be an SN addition request acknowledgement (i.e., S-NODE ADDITION REQUEST ACKNOWLEDGE) message. Alternatively, the dual connectivity related message may be an SN modification request acknowledgement (i.e., S-NODE MODIFICATION REQUEST ACKNOWLEDGE) message. Alternatively, the dual connectivity related message may be an SN modification required (i.e., S-NODE MODIFICATION REQUIRED) message.

[0122] Non-Patent Document 2 does not specify that MR-DC related messages include information elements for activating and deactivating UL PSI-based SDU discard. The signaling described with reference to Figure 10 can address this issue. The signaling described with reference to Figure 10 enables the SN 3B to instruct or request the MN 3A to send a PSI-Based SDU Discard Activation / Deactivation MAC CE for an SN-terminated MCG or split bearer.

[0123] Figure 11 shows an example of the format of the PDU Session Resource Setup Response Info - SN terminated IE extended to include the PSI based SDU Discard UL IE. In 3GPP Release 18, the format of the PDU Session Resource Setup Response Info - SN terminated IE is specified in Section 9.2.1.6 of 3GPP TS 36544-1. The PDU Session Resource Setup Response Info - SN terminated IE can be included in an S-NODE ADDITION REQUEST ACKNOWLEDGE message sent from SN 3B to MN 3A. In the example of Figure 11, the PDU Session Resource Setup Response Info - SN terminated IE is extended to include a PSI based SDU Discard UL IE 1101. Specifically, the PDU Session Resource Setup Response Info - SN terminated IE includes a list of DRBs to be set up. The PSI based SDU Discard UL IE 1101 indicates activation or deactivation of UL PSI-based SDU discard on a DRB-by-DRB basis within the DRB list. The format of the PSI based SDU Discard UL IE 1101 may be the same as the example shown in FIG. 9.

[0124] Similar to the example shown in Figure 11, the PDU Session Resource Modification Response Info - SN terminated IE may be extended to include the PSI based SDU Discard UL IE. In 3GPP Release 18, the format of the PDU Session Resource Modification Response Info - SN terminated IE is specified in Section 9.2.1.10 of 3GPP TS 36544-1 (2013) RFC 2548 Session Resource Modification Response Info - SN terminated IE can be included in the S-NODE MODIFICATION REQUEST ACKNOWLEDGE message.

[0125] Similar to the example shown in Figure 11, the PDU Session Resource Modification Required Info - SN terminated IE may be extended to include the PSI based SDU Discard UL IE. In 3GPP Release 18, the format of the PDU Session Resource Modification Required Info - SN terminated IE is specified in Section 9.2.1.20 of 3GPP TS 36544-1 (2013) 3GPP RFC 2544-1 (2013) ...

[0126] Third Embodiment This embodiment provides an improvement to signaling within NG-RAN 2 for PDU set-based handling. Figure 12 relates to an improvement that enables a node hosting PDCP for a certain DRB (i.e., PDCP hosting node) to configure timer-based RLC SDU discarding in a node hosting RLC for the same DRB (i.e., RLC hosting node). Figure 12 shows an example of signaling between a PDCP hosting node 1201 and an RLC hosting node 1202. In step 1220, the PDCP hosting node 1201 sends a control message to the RLC hosting node 1202.

[0127] The control message includes, for a DRB terminated by the PDCP hosting node 1201, configuration for timer-based DL RLC SDU discard at the RLC entity in the RLC hosting node 1202 for the DRB. Specifically, the configuration includes an indication of activation or deactivation of timer-based downlink RLC SDU discard, an indication of the length of the discard timer used for timer-based downlink RLC SDU discard, or both. The name of the IE including the configuration may be, for example, but not limited to, a PSI Based RLC SDU Discard Timer DL IE.

[0128] The configuration causes or requests the RLC entity to start a discard timer for the DL RLC SDU received from the upper layer (i.e., the PDCP entity in the PDCP hosting node 1201) and discard the DL RLC SDU upon expiration of the discard timer. The RLC hosting node 1202 operates the RLC entity for the DRB in accordance with the received configuration. The RLC entity starts a discard timer for the DL RLC SDU received from the upper layer based on the configuration and discards the DL RLC SDU upon expiration of the discard timer.

[0129] In some implementations, an RLC entity may apply timer-based downlink RLC SDU discard to an RLC SDU if PSI-based SDU discard is activated and the RLC SDU belongs to a predetermined set of low-importance PDUs. Conversely, an RLC entity may not apply timer-based downlink RLC SDU discard to an RLC SDU if PSI-based SDU discard is deactivated or if the RLC SDU does not belong to a predetermined set of low-importance PDUs. If timer-based downlink RLC SDU discard is not applied to an RLC SDU, the RLC entity may discard the RLC SDU as specified in Section 5.4 of 3GPP TS 38.322. Specifically, when an RLC entity receives an instruction from a higher layer (e.g., PDCP) to discard a specific DL RLC SDU, the RLC entity may discard the instructed DL RLC SDU if the DL RLC SDU or a segment thereof has not been transmitted to a lower layer.

[0130] In another implementation, the configuration sent in step 1220 includes at least an indication of the lengths of the discard timers, which may specify the length of a first timer and the length of a second timer that is shorter than the first timer. The RLC entity may start the second timer for an RLC SDU if PSI-based SDU discarding is activated and the RLC SDU belongs to a predetermined set of low-importance PDUs. Conversely, the RLC entity may start the first timer for an RLC SDU if PSI-based SDU discarding is deactivated or if the RLC SDU does not belong to a predetermined set of low-importance PDUs.

[0131] The operations described with reference to Figure 12 can provide inter-node signaling that contributes to realizing a configuration in which an RLC entity uses a discard timer similar to that used by a PDCP entity for RLC SDU discard. Specifically, this operation enables the PDCP hosting node 1201 to instruct the RLC hosting node 1202 to activate or deactivate timer-based SDU discard in the RLC entity. Alternatively, this operation enables the PDCP hosting node 1201 to configure in the RLC hosting node 1202 the length of the discard timer for timer-based SDU discard in the RLC entity.

[0132] If dual connectivity is used and the DRB is an MN terminated SCG or split bearer, the PDCP hosting node 1201 may be the MN 3A and the RLC hosting node 1202 may be the SN 3B. Additionally or alternatively, if dual connectivity is used and the DRB is an SN terminated MCG or split bearer, the PDCP hosting node 1201 may be the SN 3B and the RLC hosting node 1202 may be the MN 3A. Additionally or alternatively, if a CU-DU split architecture (FIG. 2) is adopted, the PDCP hosting node 1201 may be the CU 30 and the RLC hosting node 1202 may be the DU 35. The following describes the signaling details for these three cases.

[0133] 13 shows an example of signaling between MN 3A and SN 3B. In step 1301, MN 3A sends to SN 3B via a dual connectivity related message a configuration for timer-based DL RLC SDU discard in the RLC entity in SN 3B for an MN terminated SCG or split bearer. The operation of SN 3B upon receiving the configuration is similar to the operation of RLC hosting node 1202 described with reference to FIG. 12.

[0134] The dual connectivity related message in step 1301 may be an SN addition request message (i.e., S-NODE ADDITION REQUEST) message, or may be an SN modification request message (i.e., S-NODE MODIFICATION REQUEST).

[0135] Figure 14 shows an example of the format of the PDU Session Resource Setup Info - MN terminated IE extended to include the PSI Based RLC SDU Discard Timer DL IE. In 3GPP Release 18, the format of the PDU Session Resource Setup Info - MN terminated IE is specified in Section 9.2.1.7 of 3GPP Non-Patent Document 2. The PDU Session Resource Setup Info - MN terminated IE can be included in an S-NODE ADDITION REQUEST message sent from MN 3A to SN 3B. In the example of Figure 14, the PDU Session Resource Setup Info - MN terminated IE is extended to include a PSI Based RLC SDU Discard Timer DL IE 1401. Specifically, the PDU Session Resource Setup Info - MN terminated IE includes a list of DRBs to be set up. The PSI Based RLC SDU Discard Timer DL IE 1401 indicates the timer-based DL RLC SDU discard setting for each DRB in the DRB list.

[0136] Figure 15 shows an example of the format of the PSI Based RLC SDU Discard Timer DL IE 1401. In the example of Figure 15, the PSI Based RLC SDU Discard Timer DL IE 1401 is an enumerated type and indicates an integer value that indicates the length of the discard timer in milliseconds.

[0137] Similar to the example shown in Figure 14, the PDU Session Resource Modification Info - MN terminated IE may be extended to include the PSI Based RLC SDU Discard Timer DL IE. In 3GPP Release 18, the format of the PDU Session Resource Modification Info - MN terminated IE is specified in Section 9.2.1.11 of 3GPP TS 36544-01 (2016) ...

[0138] 16 shows an example of signaling between MN 3A and SN 3B. In step 1601, SN 3B sends to MN 3A, via a dual connectivity related message, a setting for timer-based DL RLC SDU discard in the RLC entity in MN 3A for an SN-terminated MCG or split bearer. The operation of MN 3A that receives the setting is similar to the operation of RLC hosting node 1202 described with reference to FIG. 12.

[0139] The dual connectivity-related message of step 1601 may be sent in an SN addition procedure, an SN modification preparation procedure initiated by MN 3A, or an SN modification procedure initiated by SN 3B. The dual connectivity-related message of step 1601 may be an SN addition request acknowledgement (i.e., S-NODE ADDITION REQUEST ACKNOWLEDGE) message. Alternatively, the dual connectivity-related message may be an SN modification request acknowledgement (i.e., S-NODE MODIFICATION REQUEST ACKNOWLEDGE) message. Alternatively, the dual connectivity-related message may be an SN modification required (i.e., S-NODE MODIFICATION REQUIRED) message.

[0140] Figure 17 shows an example of the format of the PDU Session Resource Setup Response Info - SN terminated IE extended to include the PSI Based RLC SDU Discard Timer DL IE. In 3GPP Release 18, the format of the PDU Session Resource Setup Response Info - SN terminated IE is specified in Section 9.2.1.6 of 3GPP TS 36.2(1)(v) ... The PSI Based RLC SDU Discard Timer DL IE 1701 indicates the timer-based DL RLC SDU discard setting for each DRB in the DRB list. The format of the PSI Based RLC SDU Discard Timer DL IE 1701 may be the same as the example shown in FIG. 15 .

[0141] Similar to the example shown in Figure 17, the PDU Session Resource Modification Response Info - SN terminated IE may be extended to include the PSI Based RLC SDU Discard Timer DL IE. In 3GPP Release 18, the format of the PDU Session Resource Modification Response Info - SN terminated IE is specified in Section 9.2.1.10 of 3GPP TS 36544-1 (2013) RFC 2548 S-Node Modification Request Acknowledgement (S-Node Modification Request Acknowledgement) can be included in the S-Node Modification Request Acknowledgement (S-Node Modification Request Acknowledgement) message.

[0142] Similar to the example shown in Figure 17, the PDU Session Resource Modification Required Info - SN terminated IE may be extended to include the PSI Based RLC SDU Discard Timer DL IE. In 3GPP Release 18, the format of the PDU Session Resource Modification Required Info - SN terminated IE is specified in Section 9.2.1.20 of 3GPP TS 36544-1 (2013) ...

[0143] 18 shows an example of signaling between the CU 30 (or CU-CP 31) and the DU 35. In step 1801, the CU 30 sends, via a control message (e.g., an F1AP message), configuration regarding timer-based DL RLC SDU discard in the RLC entity in the DU 35 for DRBs terminated in the PDCP entity of the CU 30 (or CU-UP 32). The operation of the DU 35 that receives the configuration is similar to the operation of the RLC hosting node 1202 described with reference to FIG. 12.

[0144] Figure 19 shows an example of the format of a UE CONTEXT SETUP REQUEST message extended to include a PSI Based RLC SDU Discard Timer DL IE. The UE CONTEXT SETUP REQUEST message is used by the CU 30 to request the DU 35 to set up a UE context. In 3GPP Release 18, the format of the F1AP: UE CONTEXT SETUP REQUEST message is specified in Section 9.2.2.1 of 3GPP TS 36544-1 (3GPP TS 36544-1) ... The format of the PSI Based RLC SDU Discard Timer DL IE 1901 may be the same as the example shown in FIG.

[0145] <Fourth Embodiment> This embodiment provides an improvement to dual connectivity-related signaling within the NG-RAN 2 regarding ECN marking and congestion information reporting. Fig. 20 shows an example of signaling between the MN 3A and the SN 3B. In step 2001, the MN 3A sends a dual connectivity-related message including an ECN Marking or Congestion Information Reporting Request IE to the SN 3B. The ECN Marking or Congestion Information Reporting Request IE instructs the SN 3B to perform ECN marking, report information for ECN marking, or report congestion information for a QoS flow associated with an SN-terminated bearer.

[0146] The dual connectivity related message in step 2001 may be sent in an SN addition procedure or an SN modification preparation procedure initiated by MN 3A. The dual connectivity related message may be an SN addition request (i.e., S-NODE ADDITION REQUEST) message. Alternatively, the dual connectivity related message may be an SN modification request (i.e., S-NODE MODIFICATION REQUEST) message.

[0147] Based on a request for a QoS flow received from a control node of the 5GC4, specifically the SMF 6, the MN 3A may send an ECN Marking or Congestion Information Reporting Request IE for the QoS flow to the SN 3B. As already explained, in the case of ECN marking by the PSA UPF (i.e., UPF 7), the SMF 6 can request the NG-RAN 2 (e.g., RAN node 3) via the AMF 5 to report congestion information per QoS flow level as part of the PDU session resource management procedure. Alternatively, in the case of ECN marking by the NG-RAN 2, the SMF 6 can provide the NG-RAN 2 (e.g., RAN node 3) with an ECN marking request per QoS flow level as part of the PDU session resource management procedure. Alternatively, in the case of congestion information disclosure, the SMF 6 can request the NG-RAN 2 (e.g., RAN node 3) to report congestion information to the PSA UPF via the GTP-U header. MN3A may receive any of these requests from SMF6 via AMF5 and may send the ECN Marking or Congestion Information Reporting Request IE of step 2001 to SN3B when requesting SN3B to set up an SN terminated bearer associated with the QoS flow related to the SMF6 request.

[0148] In response to receiving the ECN Marking or Congestion Information Reporting Request IE, the SN 3B activates the performance of ECN marking at the SN 3B or the reporting of congestion information via GTP-U headers to the UPF 7 for the QoS flows associated with the SN terminated bearer, if supported.

[0149] In step 2002, the SN 3B may send a dual connectivity related message including an ECN Marking or Congestion Information Reporting Status IE to the MN 3A. The ECN Marking or Congestion Information Reporting Status IE indicates whether ECN marking at the SN 3B, (congestion) information reporting for ECN marking at the UPF 7, or congestion information reporting is active for the requested QoS flow.

[0150] The dual connectivity related message of step 2002 may be transmitted in an SN addition procedure or an SN modification preparation procedure initiated by MN 3A. The dual connectivity related message may be an SN addition request acknowledgement (i.e., S-NODE ADDITION REQUEST ACKNOWLEDGE) message. Alternatively, the dual connectivity related message may be an SN modification request acknowledgement (i.e., S-NODE MODIFICATION REQUEST ACKNOWLEDGE) message.

[0151] In response to receiving the ECN Marking or Congestion Information Reporting Status IE in step 2002, the MN 3A may inform the SMF 6 whether ECN marking at the SN 3B, (congestion) information reporting for ECN marking at the UPF 7, or congestion information reporting is active for the requested QoS flow.

[0152] Non-Patent Document 2 specifies that in a handover procedure, a HANDOVER REQUEST message sent from a source NG-RAN node to a target NG-RAN node can include an ECN Marking or Congestion Information Reporting Request IE in its PDU Session Resources To Be Setup List IE. Non-Patent Document 2 also specifies that in a Retrieve UE Context procedure, a RETRIEVE UE CONTEXT RESPONSE message sent from an old NG-RAN node to a new NG-RAN node can include an ECN Marking or Congestion Information Reporting Request IE in its PDU Session Resources To Be Setup List IE. However, Non-Patent Document 2 does not specify that MR-DC-related messages include an ECN Marking or Congestion Information Reporting Request IE. Similarly, Non-Patent Document 2 does not specify that MR-DC-related messages include an ECN Marking or Congestion Information Reporting Status IE.

[0153] The signaling described with reference to Figure 20 can address these issues. The signaling described with reference to Figure 20 enables MN 3A to instruct or request SN 3B to perform ECN marking at SN 3B, to report information for ECN marking at UPF 7, or to report congestion information for QoS flows associated with SN-terminated bearers. Additionally or alternatively, the signaling described with reference to Figure 20 enables SN 3B to indicate to MN 3A whether ECN marking at SN 3B, to report (congestion) information for ECN marking at UPF 7, or to report congestion information is active for QoS flows associated with SN-terminated bearers.

[0154] 21 shows an example of the format of the PDU Session Resource Setup Info - SN terminated IE extended to include an ECN Marking or Congestion Information Reporting Request IE. In 3GPP Release 18, the format of the PDU Session Resource Setup Info - SN terminated IE is specified in Section 9.2.1.5 of Non-Patent Document 2. The PDU Session Resource Setup Info - SN terminated IE can be included in an S-NODE ADDITION REQUEST message sent from MN 3A to SN 3B. In the example of FIG. 21, the PDU Session Resource Setup Info - SN terminated IE is extended to include an ECN Marking or Congestion Information Reporting Request IE 2101. Specifically, the PDU Session Resource Setup Info - SN terminated IE includes a list of QoS flows to be set up. The ECN Marking or Congestion Information Reporting Request IE 2101 indicates, on a QoS flow basis within the QoS flow list, an instruction to perform ECN marking at the SN 3B, to report information for ECN marking at the UPF 7, or to report congestion information.

[0155] The format of the ECN Marking or Congestion Information Reporting Request IE 2101 may be similar to that specified in Section 9.2.3.205 of Non-Patent Document 2 in connection with the HANDOVER REQUEST message and the RETRIEVE UE CONTEXT RESPONSE message. Figure 22 shows the format of the ECN Marking or Congestion Information Reporting Request IE specified in Section 9.2.3.205 of Non-Patent Document 2.

[0156] Similar to the example shown in Figure 20, the PDU Session Resource Modification Info - SN terminated IE may be extended to include an ECN Marking or Congestion Information Reporting Request IE. In 3GPP Release 18, the format of the PDU Session Resource Modification Info - SN terminated IE is specified in Section 9.2.1.9 of 3GPP TS 36544-1 (2013) ...

[0157] Figure 23 shows an example of the format of the PDU Session Resource Setup Response Info - SN terminated IE extended to include an ECN Marking or Congestion Information Reporting Status IE. In 3GPP Release 18, the format of the PDU Session Resource Setup Response Info - SN terminated IE is specified in Section 9.2.1.6 of Non-Patent Document 2. The PDU Session Resource Setup Response Info - SN terminated IE can be included in an S-NODE ADDITION REQUEST ACKNOWLEDGE message sent from SN 3B to MN 3A. In the example of Figure 23, the PDU Session Resource Setup Response Info - SN terminated IE is extended to include an ECN Marking or Congestion Information Reporting Status IE 2301.

[0158] Fig. 24 shows an example of the format of the ECN Marking or Congestion Information Reporting Status IE 2301. In the example of Fig. 24, the ECN Marking or Congestion Information Reporting Status IE 2301 indicates a list 2401 of one or more QoS flows, and indicates the activation status (2403) for each QoS flow (2402). The activation status IE 2403 is an enumerated type and indicates "active" or "not active".

[0159] Similar to the example shown in Figure 23, the PDU Session Resource Modification Response Info - SN terminated IE may be extended to include an ECN Marking or Congestion Information Reporting Status IE. In 3GPP Release 18, the format of the PDU Session Resource Modification Response Info - SN terminated IE is specified in Section 9.2.1.10 of 3GPP TS 36544-1 (2013) ...

[0160] Fifth Embodiment This embodiment provides an improvement to dual connectivity-related signaling within the NG-RAN 2 regarding ECN marking and congestion information reporting. Figure 25 shows an example of signaling between the MN 3A and the SN 3B. In step 2501, the MN 3A sends a dual connectivity-related message including an ECN Marking or Congestion Information Reporting Request - RLC bearer IE to the SN 3B. The ECN Marking or Congestion Information Reporting Request - RLC bearer IE indicates to the SN 3B to report ECN marking-related or congestion-related information to the MN 3A regarding the MN terminated SCG or split bearer. The ECN marking-related or congestion-related information may include congestion information measured by the SN 3B regarding the SCG RLC bearer part of the MN terminated SCG or split bearer. How the SN 3B measures and reports the congestion information is up to the implementation of the SN 3B.

[0161] The dual connectivity related message of step 2501 may be transmitted in an SN addition procedure or an SN modification preparation procedure initiated by MN 3A. The dual connectivity related message may be an SN addition request message (i.e., S-NODE ADDITION REQUEST) message. Alternatively, the dual connectivity related message may be an SN modification request message (i.e., S-NODE MODIFICATION REQUEST) message.

[0162] Based on a request for a QoS flow received from a control node of the 5GC4, specifically the SMF 6, the MN 3A may send an ECN Marking or Congestion Information Reporting Request - RLC bearer IE for the QoS flow to the SN 3B. As already explained, in the case of ECN marking by the PSA UPF (i.e., UPF 7), the SMF 6 can request the NG-RAN 2 (e.g., RAN node 3) via the AMF 5 to report congestion information per QoS flow level as part of the PDU session resource management procedure. Alternatively, in the case of ECN marking by the NG-RAN 2, the SMF 6 can provide the NG-RAN 2 (e.g., RAN node 3) with an ECN marking request per QoS flow level as part of the PDU session resource management procedure. Alternatively, in the case of congestion information disclosure, the SMF 6 can request the NG-RAN 2 (e.g., RAN node 3) to report congestion information to the PSA UPF via the GTP-U header. MN3A may receive any of these requests from SMF6 via AMF5 and, when requesting SN3B to set up an MN terminated SCG or split bearer associated with the QoS flow related to the SMF6 request, send an ECN Marking or Congestion Information Reporting Request - RLC bearer IE in step 2501 to SN3B.

[0163] The IE name "ECN Marking or Congestion Information Reporting Request - RLC bearer" is an example, and other names may be adopted. For example, the name of the IE may be "ECN Marking or Congestion Information Reporting Request - MN terminated."

[0164] In response to receiving the ECN Marking or Congestion Information Reporting Request - RLC bearer IE, the SN 3B activates the reporting of congestion information to the MN 3A using the GTP-U header for the MN terminated SCG or split bearer, if supported.

[0165] In step 2502, the SN 3B may send a dual connectivity related message including an ECN Marking or Congestion Information Reporting Status - RLC bearer IE to the MN 3A. The CN Marking or Congestion Information Reporting Status - RLC bearer IE indicates the status of ECN marking information reporting or congestion information reporting (at the UPF 7 or MN 3A) for the MN terminated bearer. That is, the CN Marking or Congestion Information Reporting Status - RLC bearer IE indicates whether ECN marking information reporting or congestion information reporting (at the UPF 7 or MN 3A) is active for the requested MN terminated SCG or split bearer.

[0166] The dual connectivity-related message of step 2502 may be transmitted in an SN addition procedure or an SN modification preparation procedure initiated by MN 3A. The dual connectivity-related message may be an SN addition request acknowledgement (i.e., S-NODE ADDITION REQUEST ACKNOWLEDGE) message. Alternatively, the dual connectivity-related message may be an SN modification request acknowledgement (i.e., S-NODE MODIFICATION REQUEST ACKNOWLEDGE) message.

[0167] In response to receiving the ECN Marking or Congestion Information Reporting Status - RLC bearer IE in step 2502, the MN 3A may inform the SMF 6 whether ECN marking at the NG-RAN 2 or SN 3B, (congestion) information reporting for ECN marking at the UPF 7, or congestion information reporting is active for the requested QoS flow.

[0168] The name of the IE "ECN Marking or Congestion Information Reporting Status - RLC bearer" is an example, and other names may be adopted. For example, the name of the IE may be "ECN Marking or Congestion Information Reporting Status - MN terminated."

[0169] Non-Patent Document 2 does not specify signaling for an MN to request an SN to report congestion information to the MN with respect to an MN-terminated SCG or the SCG RLC bearer portion of a split bearer. The signaling described with reference to FIG. 25 can address this issue. The signaling described with reference to FIG. 25 enables an MN 3A to request an SN 3B to report congestion information to the MN 3A with respect to an MN-terminated SCG or a split bearer. This allows the MN 3A to receive congestion information reports from the SN 3B. This is useful for the MN 3A to perform ECN marking at the MN 3A with respect to an MN-terminated SCG or a split bearer. Additionally or alternatively, this is useful for the MN 3A to report congestion information to the UPF 7 via a GTP-U header for ECN marking or congestion information exposure at the UPF 7.

[0170] Figure 26 shows an example of the format of the PDU Session Resource Setup Info - MN terminated IE extended to include the ECN Marking or Congestion Information Reporting Request - RLC bearer IE. In 3GPP Release 18, the format of the PDU Session Resource Setup Info - MN terminated IE is specified in Section 9.2.1.7 of Non-Patent Document 2. The PDU Session Resource Setup Info - MN terminated IE can be included in an S-NODE ADDITION REQUEST message sent from MN 3A to SN 3B. In the example of Figure 26, the PDU Session Resource Setup Info - MN terminated IE is extended to include ECN Marking or Congestion Information Reporting Request - RLC bearer IE 2601. Specifically, the PDU Session Resource Setup Info - MN terminated IE includes a list of DRBs to be set up. The ECN Marking or Congestion Information Reporting Request - RLC bearer IE 2601 indicates, for each DRB in the DRB list, whether or not a report of congestion information from the SN 3B to the MN 3A is required.

[0171] Figure 27 shows an example of the format of the ECN Marking or Congestion Information Reporting Request - RLC bearer IE 2601. In the example of Figure 27, the ECN Marking or Congestion Information Reporting Request - RLC bearer IE 2601 is of choice type, and includes an ECN Marking Request IE 2702 in the case of ECN marking in the RAN, and a Congestion Information Request IE 2703 in the case of congestion information reporting.

[0172] The ECN Marking Request IE 2702 indicates whether the SN 3B is requested to report information (e.g., congestion information) for ECN marking at the MN 3A for a QoS flow associated with an MN-terminated bearer. Furthermore, if information reporting for ECN marking at the MN 3A is requested, the ECN Marking Request IE 2702 indicates whether information is requested for the UL direction, the DL direction, or both directions. In the example of FIG. 27 , the ECN Marking Request IE 2702 is enumerated and indicates "ul", "dl", "both", or "stop". The code points "ul", "dl", and "both" mean that information reporting for ECN marking at the MN 3A is (re)configured for the UL direction, the DL direction, and both directions, respectively. The code point "stop" means that information reporting for ECN marking at the MN 3A is canceled.

[0173] The Congestion Information Request IE 2703 indicates whether a congestion information report is requested from the SN 3B for reporting congestion information to the UPF 7. Furthermore, if a congestion information report is requested, the Congestion Information Request IE 2703 indicates whether congestion information is requested for the UL direction, the DL direction, or both directions. In the example of Figure 27, the Congestion Information Request IE 2703 is enumerated and indicates "ul", "dl", "both", or "stop".

[0174] Similar to the example shown in Figure 27, the PDU Session Resource Modification Info - MN terminated IE may be extended to include an ECN Marking or Congestion Information Reporting Request - RLC bearer IE. In 3GPP Release 18, the format of the PDU Session Resource Modification Info - MN terminated IE is specified in Section 9.2.1.11 of Non-Patent Document 2. The PDU Session Resource Modification Info - MN terminated IE can be included in an S-NODE MODIFICATION REQUEST message sent from MN 3A to SN 3B.

[0175] Figure 28 shows an example of the format of the PDU Session Resource Setup Response Info - MN terminated IE extended to include the ECN Marking or Congestion Information Reporting Status - RLC bearer IE. In 3GPP Release 18, the format of the PDU Session Resource Setup Response Info - MN terminated IE is specified in Section 9.2.1.8 of 3GPP TS 36.2(1)(v) ... The ECN Marking or Congestion Information Reporting Status - RLC bearer IE 2801 indicates the status of information reporting to the MN 3A on a DRB-by-DRB basis within the DRB list.

[0176] Figure 29 shows an example of the format of ECN Marking or Congestion Information Reporting Status - RLC bearer IE 2801. In the example of Figure 29, ECN Marking or Congestion Information Reporting Status - RLC bearer IE 2801 indicates whether information reporting for ECN marking or congestion information reporting is active or not. ECN Marking or Congestion Information Reporting Status - RLC bearer IE 2801 is an enumerated type and indicates "active" or "not active".

[0177] Figure 30 shows an example of signaling between MN 3A and SN 3B. The operations shown in Figure 30 are similar to those described with reference to Figure 25, except that they are performed for an SN terminated MCG or split bearer rather than an MN terminated SCG or split bearer.

[0178] In step 3001, the SN 3B sends a dual connectivity related message including an ECN Marking or Congestion Information Reporting Request - RLC bearer IE to the MN 3A. The ECN Marking or Congestion Information Reporting Request - RLC bearer IE indicates to the MN 3A to report ECN marking or congestion information to the SN 3B for the SN terminated MCG or split bearer. The ECN marking or congestion information may include congestion information measured by the MN 3A for the MCG RLC bearer part of the SN terminated MCG or split bearer. How the MN 3A measures and reports the congestion information is up to the implementation of the MN 3A.

[0179] The dual connectivity related message of step 3001 may be sent in an SN addition procedure, an SN modification preparation procedure initiated by MN 3A, or an SN modification procedure initiated by SN 3B. The dual connectivity related message of step 3001 may be an SN addition request acknowledgement (i.e., S-NODE ADDITION REQUEST ACKNOWLEDGE) message. Alternatively, the dual connectivity related message may be an SN modification request acknowledgement (i.e., S-NODE MODIFICATION REQUEST ACKNOWLEDGE) message. Alternatively, the dual connectivity related message may be an SN modification required (i.e., S-NODE MODIFICATION REQUIRED) message.

[0180] In step 3002, the MN 3A may send a dual connectivity related message including an ECN Marking or Congestion Information Reporting Status - RLC bearer IE to the SN 3B. The CN Marking or Congestion Information Reporting Status - RLC bearer IE indicates the status of information reporting for ECN marking or congestion information reporting (at the UPF 7 or SN 3B) for the SN terminated bearer. That is, the CN Marking or Congestion Information Reporting Status - RLC bearer IE indicates whether information reporting for ECN marking or congestion information reporting (at the UPF 7 or SN 3B) is active for the requested SN terminated MCG or split bearer.

[0181] The details and advantages of the procedure of Figure 30 are similar to those described with reference to Figure 25, except that it is for an SN terminated MCG or split bearer rather than an MN terminated SCG or split bearer, and therefore a duplicate description thereof will be omitted.

[0182] The procedure of Figure 30 can be used in combination with the procedure shown in Figure 20. Specifically, in step 2001 of Figure 20, the SN 3B can receive from the MN 3A an SN Add Request or SN Modify Request message instructing the SN 3B to perform ECN marking at the SN 3B, report information for ECN marking from the SN 3B to the UPF 7, or report congestion information from the SN 3B to the UPF 7 for a QoS flow associated with an SN terminated bearer. The SN 3B can then decide to set up the SN terminated bearer for the requested QoS flow as an SN terminated MCG bearer or an SN terminated split bearer. In this case, in step 3001 of Figure 30, the SN 3B can indicate to the MN 3A via an SN Add Acknowledge or SN Modify Acknowledge message to report information about ECN marking or congestion to the SN 3B for the SN terminated MCG or split bearer. The message in step 3001 of Figure 30 may be common to the message in step 2002 of Figure 20. This combination of procedures facilitates the configuration within NG-RAN2 required for ECN marking and congestion status disclosure for QoS flows associated with SN terminated bearers.

[0183] Figure 31 shows an example of the format of the PDU Session Resource Setup Response Info - SN terminated IE extended to include the ECN Marking or Congestion Information Reporting Request - RLC bearer IE. In 3GPP Release 18, the format of the PDU Session Resource Setup Response Info - SN terminated IE is specified in Section 9.2.1.6 of 3GPP TS 36544-1 (2013) ... The ECN Marking or Congestion Information Reporting Request - RLC bearer IE 3101 indicates whether or not a congestion information report from the MN 3A to the SN 3B is required for each DRB in the DRB list. The format of the ECN Marking or Congestion Information Reporting Request - RLC bearer IE 3101 may be the same as that shown in FIG.

[0184] Similar to the example shown in Figure 31, the PDU Session Resource Modification Response Info - SN terminated IE may be extended to include an ECN Marking or Congestion Information Reporting Request - RLC bearer IE. In 3GPP Release 18, the format of the PDU Session Resource Modification Response Info - SN terminated IE is specified in Section 9.2.1.10 of 3GPP TS 36544-1 (2013) RFC 2544 Routing Information Reporting Request for RLC bearer IEs. The PDU Session Resource Modification Response Info - SN terminated IE can be included in an S-NODE MODIFICATION REQUEST ACKNOWLEDGE message.

[0185] Similar to the example shown in Figure 31, the PDU Session Resource Modification Required Info - SN terminated IE may be extended to include an ECN Marking or Congestion Information Reporting Request - RLC bearer IE. In 3GPP Release 18, the format of the PDU Session Resource Modification Required Info - SN terminated IE is specified in Section 9.2.1.20 of 3GPP TS 36544-1 (2013) 3GPP RFC 2544-1 (2013) ...

[0186] Next, exemplary configurations of the UE 1, RAN node 3, AMF 5, SMF 6, and UPF 7 related to the above-described embodiments will be described below. FIG. 32 is a block diagram showing an exemplary configuration of the UE 1. The RF transceiver 3201 performs analog RF signal processing for communication with the RAN node 3. The RF transceiver 3201 may include multiple transceivers. The analog RF signal processing performed by the RF transceiver 3201 includes frequency up-conversion, frequency down-conversion, and amplification. The RF transceiver 3201 is coupled to the antenna array 3202 and the baseband processor 3203. The RF transceiver 3201 receives modulation symbol data (or OFDM symbol data) from the baseband processor 3203, generates a transmit RF signal, and provides the transmit RF signal to the antenna array 3202. The RF transceiver 3201 also generates a baseband receive signal based on the receive RF signal received by the antenna array 3202 and provides the baseband receive signal to the baseband processor 3203. The RF transceiver 3201 may include an analog beamformer circuit for beamforming, which may include, for example, multiple phase shifters and multiple power amplifiers.

[0187] The baseband processor 3203 performs digital baseband signal processing (data plane processing) and control plane processing for wireless communications. Digital baseband signal processing includes (a) data compression / decompression, (b) data segmentation / concatenation, (c) transmission format (transmission frame) generation / decomposition, (d) transmission path coding / decoding, (e) modulation (symbol mapping) / demodulation, and (f) generation of OFDM symbol data (baseband OFDM signal) using Inverse Fast Fourier Transform (IFFT). Meanwhile, control plane processing includes communication management for Layer 1 (e.g., transmit power control), Layer 2 (e.g., radio resource management and hybrid automatic repeat request (HARQ) processing), and Layer 3 (e.g., signaling related to attachment, mobility, and call management).

[0188] For example, the digital baseband signal processing by the baseband processor 3203 may include signal processing of a PDCP layer, an RLC layer, a MAC layer, and a PH layer. Also, the control plane processing by the baseband processor 3203 may include processing of a Non-Access Stratum (NAS) protocol, an RRC protocol, MAC CEs, and Downlink Control Information (DCIs).

[0189] The baseband processor 3203 may perform MIMO encoding and precoding for beamforming.

[0190] The baseband processor 3203 may include a modem processor (e.g., a Digital Signal Processor (DSP)) that performs digital baseband signal processing and a protocol stack processor (e.g., a Central Processing Unit (CPU) or a Micro Processing Unit (MPU)) that performs control plane processing. In this case, the protocol stack processor that performs control plane processing may be shared with the application processor 3204, which will be described later.

[0191] The application processor 3204 is also referred to as a CPU, MPU, microprocessor, or processor core. The application processor 3204 may include multiple processors (multiple processor cores). The application processor 3204 executes a system software program (operating system (OS)) and various application programs (e.g., a calling application, a web browser, a mailer, a camera operation application, and a music playback application) read from the memory 3206 or other memories, thereby realizing various functions of the UE 1.

[0192] In some implementations, the baseband processor 3203 and the application processor 3204 may be integrated on a single chip, as indicated by the dashed line (3205) in Figure 32. In other words, the baseband processor 3203 and the application processor 3204 may be implemented as a single System on Chip (SoC) device 3205. An SoC device is sometimes called a system Large Scale Integration (LSI) or chipset.

[0193] The memory 3206 is volatile memory, nonvolatile memory, or a combination thereof. The memory 3206 may include multiple physically independent memory devices. Volatile memory is, for example, static random access memory (SRAM), dynamic RAM (DRAM), or a combination thereof. Nonvolatile memory is mask read only memory (MROM), electrically erasable programmable ROM (EEPROM), flash memory, a hard disk drive, or any combination thereof. For example, the memory 3206 may include an external memory device accessible from the baseband processor 3203, the application processor 3204, and the SoC 3205. The memory 3206 may also include an internal memory device integrated within the baseband processor 3203, the application processor 3204, or the SoC 3205. Furthermore, the memory 3206 may include memory within a universal integrated circuit card (UICC).

[0194] The memory 3206 may store one or more software modules (computer programs) 3207 containing instructions and data for processing by the UE 1. In some implementations, the baseband processor 3203 or the application processor 3204 may be configured to read and execute the software modules 3207 from the memory 3206 to perform the processing of the UE 1 described in one or more of the embodiments.

[0195] It should be noted that the control plane processing and operations performed by UE 1 described in the above embodiment can be realized by elements other than the RF transceiver 3201 and the antenna array 3202, namely, at least one of the baseband processor 3203 and the application processor 3204, and the memory 3206 storing the software module 3207.

[0196] FIG. 33 is a block diagram showing an example configuration of a RAN node 3. Referring to FIG. 33, the RAN node 3 includes an RF transceiver 3301, a network interface 3303, a processor 3304, and a memory 3305. The RF transceiver 3301 performs analog RF signal processing to communicate with multiple UEs including UE 1. The RF transceiver 3301 may include multiple transceivers. The RF transceiver 3301 is coupled to an antenna array 3302 and a processor 3304. The RF transceiver 3301 receives modulation symbol data from the processor 3304, generates a transmit RF signal, and provides the transmit RF signal to the antenna array 3302. The RF transceiver 3301 also generates a baseband receive signal based on the receive RF signal received by the antenna array 3302 and provides the baseband receive signal to the processor 3304. The RF transceiver 3301 may include an analog beamformer circuit for beamforming. The analog beamformer circuit includes, for example, multiple phase shifters and multiple power amplifiers.

[0197] The network interface 3303 is used to communicate with network nodes (e.g., other RAN nodes, and control and forwarding nodes of the core network), and may include, for example, a network interface card (NIC) compliant with the IEEE 802.3 series.

[0198] The processor 3304 performs digital baseband signal processing (data plane processing) and control plane processing for wireless communication. The processor 3304 may include multiple processors. For example, the processor 3304 may include a modem processor (e.g., a Digital Signal Processor (DSP)) that performs digital baseband signal processing and a protocol stack processor (e.g., a CPU or MPU) that performs control plane processing. The processor 3304 may include a digital beamformer module for beamforming. The digital beamformer module may include a MIMO encoder and a precoder.

[0199] The memory 3305 is configured by a combination of volatile memory and non-volatile memory. The volatile memory is, for example, SRAM or DRAM, or a combination thereof. The non-volatile memory is, for example, MROM, EEPROM, flash memory, or a hard disk drive, or any combination thereof. The memory 3305 may include storage located remotely from the processor 3304. In this case, the processor 3304 may access the memory 3305 via the network interface 3303 or another I / O interface.

[0200] The memory 3305 may store one or more software modules (computer programs) 3306 containing instructions and data for processing by the RAN node 3. In some implementations, the processor 3304 may be configured to read and execute the software modules 3306 from the memory 3305 to perform the processing of the RAN node 3 described in one or more of the embodiments.

[0201] The control plane processing and operations performed by the RAN node 3 described in the above embodiments can be realized by elements other than the RF transceiver 3301 and the antenna array 3302, namely the processor 3304 and the memory 3305 storing the software modules 3306.

[0202] If the RAN node 3 includes a CU 30 and one or more DUs 35, the CU 30, CU-CP 31, CU-UP 32, and DU 35 may not include an RF transceiver 3301 (and antenna array 3302).

[0203] Figure 34 shows an example configuration of the AMF 5. The configurations of other core network nodes such as the SMF 6 and the UPF 7 may also be similar to the configuration shown in Figure 34. Referring to Figure 34, the AMF 5 includes a network interface 3401, a processor 3402, and a memory 3403.

[0204] The network interface 3401 is used, for example, to communicate with other network functions (NFs) or nodes. The network interface 3401 may include, for example, a network interface card (NIC) compliant with the IEEE 802.3 series.

[0205] The processor 3402 may be, for example, a microprocessor, an MPU, or a CPU. The processor 3402 may include multiple processors.

[0206] The memory 3403 is composed of volatile memory and nonvolatile memory. The memory 3403 may include multiple physically independent memory devices. The volatile memory is, for example, SRAM or DRAM, or a combination thereof. The nonvolatile memory is, for example, MROM, EEPROM, flash memory, or a hard disk drive, or any combination thereof. The memory 3403 may include storage located remotely from the processor 3402. In this case, the processor 3402 may access the memory 3403 via the network interface 3401 or the I / O interface.

[0207] The memory 3403 may store one or more software modules (computer programs) 3404 including instructions and data for performing processing by the AMF 5 described in the above-described embodiments. In some implementations, the processor 3402 may be configured to read and execute the software modules 3404 from the memory 3403, thereby performing the processing of the AMF 5 described in the above-described embodiments.

[0208] As described with reference to Figures 32, 33, and 34, each of the processors included in the UE 1, RAN node 3, AMF 5, SMF 6, and UPF 7 according to the above-described embodiments can execute one or more programs including instructions for causing a computer to perform the algorithms described with reference to the drawings. The programs include instructions (or software code) that, when loaded into a computer, cause the computer to perform one or more functions described in the embodiments. The programs may be stored on a non-transitory computer-readable medium or a tangible storage medium. By way of example and not limitation, computer-readable media or tangible storage media include random-access memory (RAM), read-only memory (ROM), flash memory, solid-state drive (SSD) or other memory technology, CD-ROM, digital versatile disk (DVD), Blu-ray (registered trademark) disc or other optical disk storage, magnetic cassette, magnetic tape, magnetic disk storage, or other magnetic storage device. The programs may also be transmitted on a transitory computer-readable medium or a communication medium. By way of example, and not limitation, transitory computer-readable or communication media include electrical, optical, acoustic, or other forms of propagated signals.

[0209] The above-described embodiments are merely examples of application of the technical ideas obtained by the inventors of the present invention. In other words, the technical ideas are not limited to the above-described embodiments, and various modifications are possible.

[0210] For example, some or all of the above embodiments may also be described as, but are not limited to, the following appendices. Some or all of the elements (e.g., configurations and functions) described in appendices directed to devices (e.g., master node, secondary node, communication node) may naturally also be described as appendices directed to methods and programs. For example, some or all of the elements described in appendices 2-3, which are dependent on appendices 1, may also be described as appendices dependent on appendices 4 and 5, due to the same dependency relationship as appendices 2-3. Similarly, some or all of the elements described in appendices 7-8, which are dependent on appendices 6, may also be described as appendices dependent on appendices 9 and 10, due to the same dependency relationship as appendices 7-8. Some or all of the elements described in any appendice may be applicable to various hardware, software, recording means for recording software, systems, and methods.

[0211] The above-described embodiments are merely examples of application of the technical ideas obtained by the inventors of the present invention. In other words, the technical ideas are not limited to the above-described embodiments, and various modifications are possible.

[0212] For example, some or all of the above embodiments can be described as, but are not limited to, the following supplementary notes.

[0213] (Supplementary Note 1) A dual connectivity secondary node comprising: means for sending an information element indicating whether Protocol Data Unit (PDU) set-based handling is supported by the secondary node to the dual connectivity master node. (Supplementary Note 2) The secondary node according to Supplementary Note 1, wherein the sending means is configured to send the information element to the master node via a Secondary Node Addition Request Acknowledgement message or a Secondary Node Modification Request Acknowledgement message. (Supplementary Note 3) The secondary node according to Supplementary Note 1 or 2, wherein the information element is a PDU Set based Handling Indicator information element. (Supplementary Note 4) A method performed by a dual connectivity secondary node, comprising sending an information element indicating whether Protocol Data Unit (PDU) set-based handling is supported by the secondary node to the dual connectivity master node. (Supplementary Note 5) A program causing a computer to perform a method for a dual connectivity secondary node, the method comprising sending to the dual connectivity master node an information element indicating whether Protocol Data Unit (PDU) set-based handling is supported by the secondary node. (Supplementary Note 6) A dual connectivity master node, the master node comprising: means for receiving, from the dual connectivity secondary node, an information element indicating whether Protocol Data Unit (PDU) set-based handling is supported by the secondary node. (Supplementary Note 7) The master node according to Supplementary Note 6, wherein the receiving means is configured to receive the information element via a Secondary Node Addition Request Acknowledgement message or a Secondary Node Modification Request Acknowledgement message. (Supplementary Note 8) The master node according to Supplementary Note 6 or 7, wherein the information element is a PDU Set based Handling Indicator information element.(Supplementary Note 9) A method performed by a dual connectivity master node, comprising receiving, from the dual connectivity secondary node, an information element indicating whether Protocol Data Unit (PDU) set-based handling is supported by the secondary node. (Supplementary Note 10) A program for causing a computer to perform a method for a dual connectivity master node, the method comprising receiving, from the dual connectivity secondary node, an information element indicating whether Protocol Data Unit (PDU) set-based handling is supported by the secondary node. (Supplementary Note 11) A dual connectivity master node comprising: means for sending, to the dual connectivity secondary node, via a dual connectivity related message, an information element for activation or deactivation of Protocol Data Unit (PDU) Set Importance (PSI)-based uplink Packet Data Convergence Protocol (PDCP) Service Data Unit (SDU) discard by a radio terminal for a data radio bearer terminated at the master node. (Supplementary Note 12) The master node according to Supplementary Note 11, wherein the information element causes the secondary node to transmit a PSI-Based SDU Discard Activation / Deactivation Medium Access Control (MAC) Control Element (CE) to the radio terminal according to the information element. (Supplementary Note 13) The master node according to Supplementary Note 11 or 12, wherein the dual connectivity related message is a Secondary Node Addition Request message or a Secondary Node Modification Request message. (Supplementary Note 14) The master node according to any one of Supplementary Notes 11 to 13, wherein the information element is a PSI based SDU Discard UL information element.(Supplementary Note 15) A method performed by a dual connectivity master node, comprising sending to the dual connectivity secondary node via a dual connectivity related message an information element for activating or deactivating Protocol Data Unit (PDU) Set Importance (PSI) based uplink Packet Data Convergence Protocol (PDCP) Service Data Unit (SDU) discarding by a wireless terminal for a data radio bearer terminated at the master node. (Supplementary Note 16) A program for causing a computer to perform a method for a dual connectivity master node, the method comprising sending, to the dual connectivity secondary node, via a dual connectivity related message, an information element for activation or deactivation of Protocol Data Unit (PDU) Set Importance (PSI)-based uplink Packet Data Convergence Protocol (PDCP) Service Data Unit (SDU) discarding by a radio terminal for a data radio bearer terminated at the master node. (Supplementary Note 17) A dual connectivity secondary node, comprising: means for receiving, from the dual connectivity master node, via a dual connectivity related message, an information element for activation or deactivation of Protocol Data Unit (PDU) Set Importance (PSI)-based uplink Packet Data Convergence Protocol (PDCP) Service Data Unit (SDU) discarding by a radio terminal for a data radio bearer terminated at the master node.(Supplementary Note 18) The secondary node according to Supplementary Note 17, further comprising means for transmitting a PSI-Based SDU Discard Activation / Deactivation Medium Access Control (MAC) Control Element (CE) to the radio terminal in accordance with the information element. (Supplementary Note 19) A method performed by a dual connectivity secondary node, comprising receiving, from the dual connectivity master node via a dual connectivity related message, an information element for activation or deactivation of Protocol Data Unit (PDU) Set Importance (PSI)-based uplink Packet Data Convergence Protocol (PDCP) Service Data Unit (SDU) discard by a radio terminal for a data radio bearer terminated at the master node. (Supplementary Note 20) A program for causing a computer to perform a method for a dual connectivity secondary node, the method comprising receiving, from the dual connectivity master node via a dual connectivity related message, an information element for activation or deactivation of Protocol Data Unit (PDU) Set Importance (PSI) based uplink Packet Data Convergence Protocol (PDCP) Service Data Unit (SDU) discarding by a wireless terminal for a data radio bearer terminated at the master node.(Supplementary Note 21) A dual connectivity master node, comprising: means for receiving, from the dual connectivity secondary node via a dual connectivity related message, an information element for activating or deactivating Protocol Data Unit (PDU) Set Importance (PSI)-based uplink Packet Data Convergence Protocol (PDCP) Service Data Unit (SDU) discard by a radio terminal for a data radio bearer terminated at the secondary node. (Supplementary Note 22) The master node according to Supplementary Note 21, further comprising means for transmitting a PSI-Based SDU Discard Activation / Deactivation Medium Access Control (MAC) Control Element (CE) to the radio terminal according to the information element. (Supplementary Note 23) A method performed by a dual connectivity master node, comprising receiving, from a dual connectivity secondary node via a dual connectivity related message, an information element for activation or deactivation of Protocol Data Unit (PDU) Set Importance (PSI) based uplink Packet Data Convergence Protocol (PDCP) Service Data Unit (SDU) discarding by a wireless terminal for a data radio bearer terminated at the secondary node.(Supplementary Note 24) A program for causing a computer to perform a method for a dual connectivity master node, the method comprising receiving, from the dual connectivity secondary node, via a dual connectivity related message, an information element for activation or deactivation of Protocol Data Unit (PDU) Set Importance (PSI)-based uplink Packet Data Convergence Protocol (PDCP) Service Data Unit (SDU) discarding by a radio terminal for a data radio bearer terminated at the secondary node. (Supplementary Note 25) A dual connectivity secondary node, comprising means for sending, to the dual connectivity master node, via a dual connectivity related message, an information element for activation or deactivation of Protocol Data Unit (PDU) Set Importance (PSI)-based uplink Packet Data Convergence Protocol (PDCP) Service Data Unit (SDU) discarding by a radio terminal for a data radio bearer terminated at the secondary node. (Supplementary Note 26) The secondary node according to Supplementary Note 25, further comprising means for transmitting a PSI-Based SDU Discard Activation / Deactivation Medium Access Control (MAC) Control Element (CE) to the wireless terminal according to the information element.(Supplementary Note 27) A method performed by a dual connectivity secondary node, comprising sending to the dual connectivity master node via a dual connectivity related message an information element for activation or deactivation of Protocol Data Unit (PDU) Set Importance (PSI) based uplink Packet Data Convergence Protocol (PDCP) Service Data Unit (SDU) discarding by a wireless terminal for a data radio bearer terminated at the secondary node. (Supplementary Note 28) A program for causing a computer to perform a method for a dual connectivity secondary node, the method comprising sending, to the dual connectivity master node, via a dual connectivity related message, an information element for activating or deactivating Protocol Data Unit (PDU) Set Importance (PSI)-based uplink Packet Data Convergence Protocol (PDCP) Service Data Unit (SDU) discarding by a wireless terminal for a data radio bearer terminated at the secondary node. (Supplementary Note 29) A first communications node, comprising: means for sending, for a data radio bearer terminated at the first communications node, configuration related to downlink RLC Service Data Unit (SDU) discard in a Radio Link Control (RLC) entity to a second communications node providing an RLC entity for the data radio bearer, wherein the configuration includes an indication of activation or deactivation of timer-based downlink RLC SDU discard, an indication of a length of a discard timer used for the timer-based downlink RLC SDU discard, or both.30. The first communication node according to Supplementary Note 29, wherein the configuration causes the RLC entity to start a discard timer for an RLC SDU received from a higher layer and to discard the RLC SDU upon expiration of the discard timer. 31. The first communication node according to Supplementary Note 30, wherein the configuration causes the RLC entity to: apply the timer-based downlink RLC SDU discard to the RLC SDU if Protocol Data Unit (PDU) Set Importance (PSI)-based SDU discarding is activated and the RLC SDU belongs to a predetermined set of low-importance PDUs; and not apply the timer-based downlink RLC SDU discard to the RLC SDU if the PSI-based SDU discarding is deactivated or the RLC SDU does not belong to the predetermined set of low-importance PDUs. (Supplementary Note 32) The first communications node according to Supplementary Note 30, wherein the configuration includes at least the indication of discard timer lengths, the indication of discard timer lengths specifying a first timer length and a second timer length shorter than the first timer, and the configuration causes the RLC entity to: start a second timer for the RLC SDU if Protocol Data Unit (PDU) Set Importance (PSI) based SDU discarding is activated and the RLC SDU belongs to a predetermined set of low-importance PDUs, and start a first timer for the RLC SDU if PSI based SDU discarding is deactivated or the RLC SDU does not belong to the predetermined set of low-importance PDUs. (Supplementary Note 33) The first communications node according to any one of Supplements 29 to 32, wherein the first communications node is a Central Unit (CU) of a base station, and the second communications node is a Distributed Unit (DU) of the base station.(Supplementary note 34) The first communication node according to any one of Supplementary notes 29 to 32, wherein the first communication node is a master node of dual connectivity, the second communication node is a secondary node of the dual connectivity, and the data radio bearer is a master node terminated bearer. (Supplementary note 35) The first communication node according to any one of Supplementary notes 29 to 32, wherein the first communication node is a secondary node of dual connectivity, the second communication node is a master node of the dual connectivity, and the data radio bearer is a secondary node terminated bearer. (Supplementary Note 36) A method performed by a first communications node, comprising sending, for a data radio bearer terminated at the first communications node, a configuration related to downlink RLC Service Data Unit (SDU) discard in a Radio Link Control (RLC) entity to a second communications node providing an RLC entity for the data radio bearer, wherein the configuration includes an indication of activation or deactivation of timer-based downlink RLC SDU discard, an indication of a length of a discard timer used for the timer-based downlink RLC SDU discard, or both. (Supplementary Note 37) A program for causing a computer to perform a method for a first communications node, the method comprising, for a data radio bearer terminated at the first communications node, sending a configuration related to downlink RLC Service Data Unit (SDU) discard in a Radio Link Control (RLC) entity to a second communications node providing an RLC entity for the data radio bearer, the configuration including an indication of activation or deactivation of timer-based downlink RLC SDU discard, an indication of a length of a discard timer used for the timer-based downlink RLC SDU discard, or both.38. A second communications node comprising: means for receiving, from a first communications node, a configuration for downlink RLC Service Data Unit (SDU) discard in a Radio Link Control (RLC) entity for a data radio bearer terminated at the first communications node; and means for providing the RLC entity for the data radio bearer, wherein the configuration includes an indication of activation or deactivation of timer-based downlink RLC SDU discard, an indication of a discard timer length used for the timer-based downlink RLC SDU discard, or both. 39. The second communications node of claim 38, wherein the RLC entity is configured to start a discard timer for RLC SDUs received from a higher layer based on the configuration, and to discard the RLC SDU upon expiry of the discard timer. (Supplementary Note 40) The second communication node according to Supplementary Note 39, wherein the RLC entity is configured to: apply the timer-based downlink RLC SDU discard to the RLC SDU if Protocol Data Unit (PDU) Set Importance (PSI)-based SDU discarding is activated and the RLC SDU belongs to a predetermined set of low-importance PDUs; and not apply the timer-based downlink RLC SDU discard to the RLC SDU if the PSI-based SDU discarding is deactivated or the RLC SDU does not belong to the predetermined set of low-importance PDUs.(Supplementary Note 41) The second communications node according to Supplementary Note 39, wherein the configuration includes at least the indication of discard timer lengths, the indication of discard timer lengths specifying a first timer length and a second timer length shorter than the first timer, and the RLC entity is configured to: start a second timer for the RLC SDU if Protocol Data Unit (PDU) Set Importance (PSI) based SDU discarding is activated and the RLC SDU belongs to a predetermined set of low-importance PDUs, and start a first timer for the RLC SDU if PSI-based SDU discarding is deactivated or the RLC SDU does not belong to the predetermined set of low-importance PDUs. (Supplementary Note 42) The second communications node according to any one of Supplements 38 to 41, wherein the first communications node is a Central Unit (CU) of a base station, and the second communications node is a Distributed Unit (DU) of the base station. (Supplementary note 43) The second communication node according to any one of Supplementary notes 38 to 41, wherein the first communication node is a master node of dual connectivity, the second communication node is a secondary node of the dual connectivity, and the data radio bearer is a master node terminated bearer. (Supplementary note 44) The second communication node according to any one of Supplementary notes 38 to 41, wherein the first communication node is a secondary node of dual connectivity, the second communication node is a master node of the dual connectivity, and the data radio bearer is a secondary node terminated bearer.(Supplementary Note 45) A method performed by a second communications node, comprising: receiving from a first communications node a configuration for downlink RLC Service Data Unit (SDU) discard in a Radio Link Control (RLC) entity for a data radio bearer terminated at the first communications node; and providing the RLC entity for the data radio bearer, wherein the configuration includes an indication of activation or deactivation of timer-based downlink RLC SDU discard, an indication of a discard timer length used for the timer-based downlink RLC SDU discard, or both. (Supplementary Note 46) A program for causing a computer to perform a method for a second communications node, the method comprising: receiving from a first communications node configuration for downlink RLC Service Data Unit (SDU) discard in a Radio Link Control (RLC) entity for a data radio bearer terminated at the first communications node; and providing the RLC entity for the data radio bearer, the configuration including an indication of activation or deactivation of timer-based downlink RLC SDU discard, an indication of a discard timer length used for the timer-based downlink RLC SDU discard, or both.(Supplementary Note 47) A dual connectivity master node comprising: means for sending a first information element to the dual connectivity secondary node, the first information element indicating, with respect to a Quality of Service (QoS) flow associated with a data radio bearer terminated at the secondary node, whether Explicit Congestion Notification (ECN) marking is required to be performed at the secondary node; whether information for ECN marking at a User Plane Function (UPF) in a core network is required to be reported from the secondary node to the UPF; or whether congestion information is required to be reported from the secondary node to the UPF. (Supplementary Note 48) The master node according to Supplementary Note 47, wherein the sending means is configured to send the first information element via a Secondary Node Addition Request message or a Secondary Node Modification Request message. (Supplementary Note 49) The master node according to Supplementary Note 47 or 48, wherein the sending means is configured to send the first information element to the secondary node based on a request for the QoS flow received from a control node of the core network. (Supplementary note 50) The master node according to any one of Supplements 47 to 49, wherein the first information element is an ECN Marking or Congestion Information Reporting Request information element. (Supplementary note 51) The master node according to any one of Supplements 47 to 50, further comprising means for receiving a second information element from the secondary node, the second information element indicating whether ECN marking at the secondary node, reporting information for ECN marking at the UPF, or reporting of congestion information is active for the QoS flow. (Supplementary note 52) The master node according to Supplementary note 51, wherein the receiving means is configured to receive the second information element via a Secondary Node Addition Request Acknowledgement message or a Secondary Node Modification Request Acknowledgement message.(Supplementary Note 53) The master node according to Supplementary Note 51 or 52, further comprising means for informing a control node of the core network whether ECN marking at the secondary node, reporting of information for ECN marking at the UPF, or reporting of congestion information is active for the QoS flow in response to receiving the second information element. (Supplementary Note 54) The master node according to any one of Supplements 51 to 53, wherein the second information element is an ECN Marking or Congestion Information Reporting Status information element. (Supplementary Note 55) The master node according to any one of Supplements 47 to 54, comprising means for receiving a third information element from the secondary node after sending the first information element, the third information element indicating the master node to report information on Explicit Congestion Notification (ECN) marking or on congestion for the data radio bearer to the secondary node. (Supplementary Note 56) The master node according to Supplementary Note 55, further comprising means for activating or deactivating reporting of information on ECN marking or on congestion to the secondary node for the data radio bearer in response to receiving the third information element. (Supplementary Note 57) The master node according to Supplementary Note 55 or 56, further comprising means for sending a fourth information element to the secondary node after receiving the third information element, the fourth information element indicating whether the reporting of information on ECN marking or on congestion is active for the data radio bearer.(Supplementary Note 58) A method performed by a dual connectivity master node, comprising sending a first information element to a dual connectivity secondary node, wherein the first information element indicates, for a Quality of Service (QoS) flow associated with a data radio bearer terminated at the secondary node, whether Explicit Congestion Notification (ECN) marking is required to be performed at the secondary node; whether information for ECN marking at a User Plane Function (UPF) in a core network is required to be reported from the secondary node to the UPF; or whether congestion information is required to be reported from the secondary node to the UPF. (Supplementary Note 59) A program for causing a computer to perform a method for a dual connectivity master node, the method comprising sending a first information element to the dual connectivity secondary node, the first information element indicating, with respect to a Quality of Service (QoS) flow associated with a data radio bearer terminated at the secondary node, whether Explicit Congestion Notification (ECN) marking is required to be performed at the secondary node; whether information for ECN marking at a User Plane Function (UPF) in a core network is required to be reported from the secondary node to the UPF; or whether congestion information is required to be reported from the secondary node to the UPF.(Supplementary Note 60) A dual connectivity secondary node, comprising: means for receiving a first information element from the dual connectivity master node, the first information element indicating, with respect to a Quality of Service (QoS) flow associated with a data radio bearer terminated at the secondary node: whether Explicit Congestion Notification (ECN) marking is required to be performed at the secondary node; whether information for ECN marking at a User Plane Function (UPF) in a core network is required to be reported from the secondary node to the UPF; or whether congestion information is required to be reported from the secondary node to the UPF. (Supplementary Note 61) The secondary node according to Supplementary Note 60, wherein the receiving means is configured to receive the first information element via a Secondary Node Addition Request message or a Secondary Node Modification Request message. (Supplementary Note 62) The secondary node according to Supplementary Note 60 or 61, further comprising means for activating or deactivating ECN marking at the secondary node, reporting of information for ECN marking in the UPF, or reporting of the congestion information for the QoS flow in response to receiving the first information element. (Supplementary Note 63) The secondary node according to any one of Supplements 60 to 62, wherein the first information element is an ECN Marking or Congestion Information Reporting Request information element. (Supplementary Note 64) The secondary node according to any one of Supplements 60 to 63, further comprising means for sending a second information element to the master node, wherein the second information element indicates whether ECN marking at the secondary node, reporting of information for ECN marking in the UPF, or reporting of the congestion information is active for the QoS flow. (Supplementary Note 65) The secondary node according to Supplementary Note 64, wherein the sending means is configured to send the second information element via a Secondary Node Addition Request Acknowledgement message or a Secondary Node Modification Request Acknowledgement message.(Supplementary Note 66) The secondary node according to Supplementary Note 64 or 65, wherein the second information element causes the master node to inform a control node of the core network whether ECN marking at the secondary node, reporting information for ECN marking in the UPF, or the congestion information reporting is active for the QoS flow. (Supplementary Note 67) The secondary node according to any one of Supplements 64 to 66, wherein the second information element is an ECN Marking or Congestion Information Reporting Status information element. (Supplementary Note 68) The secondary node according to any one of Supplements 60 to 67, comprising means for sending a third information element to the master node after receiving the first information element, the third information element indicating to the master node to report information on Explicit Congestion Notification (ECN) marking or on congestion for the data radio bearer to the secondary node. (Supplementary Note 69) The secondary node according to Supplementary Note 68, further comprising means for receiving a fourth information element from the master node after transmitting the third information element, the fourth information element indicating whether the reporting of information regarding ECN marking or congestion is active for the data radio bearer. (Supplementary Note 70) A method performed by a secondary node of dual connectivity, comprising receiving a first information element from the dual connectivity master node, the first information element indicating: whether performance of Explicit Congestion Notification (ECN) marking at the secondary node is required; whether reporting of information for ECN marking at a User Plane Function (UPF) in a core network is required from the secondary node to the UPF; or whether reporting of congestion information from the secondary node to the UPF is required.(Supplementary Note 71) A program for causing a computer to perform a method for a secondary node of dual connectivity, the method comprising receiving a first information element from the master node of dual connectivity, the first information element indicating, with respect to a Quality of Service (QoS) flow associated with a data radio bearer terminated at the secondary node, whether Explicit Congestion Notification (ECN) marking is required to be performed at the secondary node; whether information for ECN marking at a User Plane Function (UPF) in a core network is required to be reported from the secondary node to the UPF; or whether congestion information is required to be reported from the secondary node to the UPF. (Supplementary Note 72) A dual connectivity master node comprising: means for sending a first information element to the dual connectivity secondary node, the first information element instructing the secondary node to report information regarding Explicit Congestion Notification (ECN) marking or congestion for a data radio bearer terminated at the master node to the master node. (Supplementary Note 73) The master node according to Supplementary Note 72, wherein the sending means is configured to send the first information element via a Secondary Node Addition Request message or a Secondary Node Modification Request message. (Supplementary Note 74) The master node according to Supplementary Note 72 or 73, wherein the sending means is configured to send the first information element to the secondary node based on a request for a QoS flow associated with the data radio bearer received from a control node of a core network. (Supplementary Note 75) The master node according to any one of Supplements 72 to 74, wherein the first information element is an ECN Marking or Congestion Information Reporting Request information element.(Supplementary Note 76) The master node according to any one of Supplements 72 to 75, further comprising means for receiving a second information element from the secondary node, the second information element indicating whether the reporting of information on ECN marking or on congestion is active for the data radio bearer. (Supplementary Note 77) The master node according to Supplementary Note 76, wherein the receiving means is configured to receive the second information element via a Secondary Node Addition Request Acknowledgement message or a Secondary Node Modification Request Acknowledgement message. (Supplementary Note 78) The master node according to Supplementary Note 76 or 77, wherein the second information element is an ECN Marking or Congestion Information Reporting Status information element. (Supplementary Note 79) A method performed by a dual connectivity master node, comprising sending a first information element to the dual connectivity secondary node, the first information element instructing the secondary node to report to the master node information regarding Explicit Congestion Notification (ECN) marking or congestion for a data radio bearer terminated at the master node. (Supplementary Note 80) A program for causing a computer to perform a method for a dual connectivity master node, the method comprising sending a first information element to the dual connectivity secondary node, the first information element instructing the secondary node to report to the master node information regarding Explicit Congestion Notification (ECN) marking or congestion for a data radio bearer terminated at the master node.(Supplementary Note 81) A dual connectivity secondary node comprising: means for receiving a first information element from the dual connectivity master node, the first information element instructing the secondary node to report information related to Explicit Congestion Notification (ECN) marking or congestion to the master node for a data radio bearer terminated at the master node. (Supplementary Note 82) The secondary node according to Supplementary Note 81, wherein the receiving means is configured to receive the first information element via a Secondary Node Addition Request message or a Secondary Node Modification Request message. (Supplementary Note 83) The secondary node according to Supplementary Note 81 or 82, further comprising means for activating or deactivating reporting of information related to ECN marking or congestion to the master node for the data radio bearer in response to receiving the first information element. (Supplementary Note 84) The secondary node according to any one of Supplements 81 to 83, wherein the first information element is an ECN Marking or Congestion Information Reporting Request information element. (Supplementary note 85) The secondary node according to any one of Supplements 81 to 84, further comprising means for sending a second information element to the master node, the second information element indicating whether the reporting of information on ECN marking or on congestion is active for the data radio bearer. (Supplementary note 86) The secondary node according to Supplementary note 85, wherein the sending means is configured to send the second information element via a Secondary Node Addition Request Acknowledgement message or a Secondary Node Modification Request Acknowledgement message. (Supplementary note 87) The secondary node according to Supplementary note 85 or 86, wherein the second information element is an ECN Marking or Congestion Information Reporting Status information element.(Supplementary Note 88) A method performed by a dual connectivity secondary node, comprising receiving a first information element from the dual connectivity master node, the first information element instructing the secondary node to report to the master node information regarding Explicit Congestion Notification (ECN) marking or congestion for a data radio bearer terminated at the master node. (Supplementary Note 89) A program for causing a computer to perform a method for a dual connectivity secondary node, the method comprising receiving a first information element from the dual connectivity master node, the first information element instructing the secondary node to report to the master node information regarding Explicit Congestion Notification (ECN) marking or congestion for a data radio bearer terminated at the master node. (Supplementary Note 90) A dual connectivity master node comprising: means for receiving a first information element from a dual connectivity secondary node, the first information element instructing the master node to report information related to Explicit Congestion Notification (ECN) marking or congestion to the secondary node for a data radio bearer terminated at the secondary node. (Supplementary Note 91) The master node according to Supplementary Note 90, wherein the receiving means is configured to receive the first information element via a secondary node addition procedure, a secondary node modification preparation procedure initiated by the master node, or a secondary node modification procedure initiated by the secondary node. (Supplementary Note 92) The master node according to Supplementary Note 90 or 91, further comprising means for activating or deactivating reporting of information related to ECN marking or congestion to the secondary node for the data radio bearer in response to receiving the first information element.(Supplementary Note 93) The master node according to any one of Supplements 90 to 92, wherein the first information element is an "ECN Marking or Congestion Information Reporting Request" information element. (Supplementary Note 94) The master node according to any one of Supplements 90 to 93, further comprising means for sending a second information element to the secondary node, the second information element indicating whether the reporting of information on ECN marking or on congestion is active for the data radio bearer. (Supplementary Note 95) The master node according to Supplementary Note 94, wherein the second information element is an "ECN Marking or Congestion Information Reporting Status" information element. (Supplementary Note 96) A method performed by a dual connectivity master node, comprising receiving a first information element from the dual connectivity secondary node, the first information element instructing the master node to report information regarding Explicit Congestion Notification (ECN) marking or congestion for a data radio bearer terminated at the secondary node to the secondary node. (Supplementary Note 97) A program for causing a computer to perform a method for a dual connectivity master node, the method comprising receiving a first information element from the dual connectivity secondary node, the first information element instructing the master node to report information regarding Explicit Congestion Notification (ECN) marking or congestion for a data radio bearer terminated at the secondary node to the secondary node.(Supplementary Note 98) A dual connectivity secondary node comprising: means for sending a first information element to the dual connectivity master node, the first information element indicating to the master node to report information regarding Explicit Congestion Notification (ECN) marking or congestion for a data radio bearer terminated at the secondary node to the secondary node. (Supplementary Note 99) The secondary node according to Supplementary Note 98, wherein the sending means is configured to send the first information element via a Secondary Node Addition procedure, a Secondary Node Modification Preparation procedure initiated by the master node, or a Secondary Node Modification procedure initiated by the secondary node. (Supplementary Note 100) The secondary node according to Supplementary Note 98 or 99, further comprising means for sending a second information element from the master node, the second information element indicating whether the reporting of information regarding ECN marking or congestion is active for the data radio bearer. (Supplementary Note 101) The secondary node of Supplementary Note 100, wherein the second information element is an ECN Marking or Congestion Information Reporting Status information element. (Supplementary Note 102) A method performed by a dual connectivity secondary node, comprising sending a first information element to the dual connectivity master node, the first information element indicating to the master node to report information regarding Explicit Congestion Notification (ECN) marking or congestion to the secondary node for data radio bearers terminated at the secondary node.(Supplementary Note 103) A program for causing a computer to perform a method for a dual connectivity secondary node, the method comprising sending a first information element to the dual connectivity master node, the first information element instructing the master node to report information regarding Explicit Congestion Notification (ECN) marking or congestion to the secondary node for data radio bearers terminated at the secondary node.

[0214] This application claims priority based on Japanese Patent Application No. 2024-056369, filed March 29, 2024, the disclosure of which is incorporated herein in its entirety by reference.

[0215] 1 UE 2 NG-RAN 3 RAN node 3A MN 3B MN 4 5GC 5 AMF 6 SMF 7 UPF 8 DN 1201 PDCP hosting node 1202 RLC hosting node 3203 Baseband processor 3204 Application processor 3206 Memory 3207 Modules 3304 Processor 3305 Memory 3306 Modules 3402 Processor 3403 Memory 3404 Modules

Claims

1. A dual connectivity secondary node, comprising: means for sending an information element to the dual connectivity master node indicating whether Protocol Data Unit (PDU) set-based handling is supported by the secondary node.

2. The secondary node of claim 1, wherein the sending means is configured to send the information element to the master node via a Secondary Node Addition Request Acknowledgement message or a Secondary Node Modification Request Acknowledgement message.

3. The secondary node according to claim 1 or 2, wherein the information element is a PDU Set based Handling Indicator information element.

4. A method performed by a dual connectivity secondary node, comprising sending an information element to the dual connectivity master node indicating whether Protocol Data Unit (PDU) set-based handling is supported by the secondary node.

5. A dual connectivity master node, comprising: means for receiving, from said dual connectivity secondary node, an information element indicating whether Protocol Data Unit (PDU) set-based handling is supported by said secondary node.

6. A method performed by a dual connectivity master node, comprising receiving, from the dual connectivity secondary node, an information element indicating whether Protocol Data Unit (PDU) set-based handling is supported by the secondary node.

7. A dual connectivity master node, comprising: means for sending to the dual connectivity secondary node via a dual connectivity related message an information element for activation or deactivation of Protocol Data Unit (PDU) Set Importance (PSI) based uplink Packet Data Convergence Protocol (PDCP) Service Data Unit (SDU) discarding by a radio terminal for a data radio bearer terminated at the master node.

8. The master node of claim 7, wherein the information element causes the secondary node to transmit a PSI-Based SDU Discard Activation / Deactivation Medium Access Control (MAC) Control Element (CE) to the wireless terminal in accordance with the information element.

9. The master node according to claim 7 or 8, wherein the dual connectivity related message is a secondary node addition request message or a secondary node modification request message.

10. A master node according to any one of claims 7 to 9, wherein the information element is a PSI based SDU Discard UL information element.

11. A method performed by a dual connectivity master node, comprising sending to the dual connectivity secondary node via a dual connectivity related message an information element for activation or deactivation of Protocol Data Unit (PDU) Set Importance (PSI) based uplink Packet Data Convergence Protocol (PDCP) Service Data Unit (SDU) discarding by a wireless terminal for a data radio bearer terminated at the master node.

12. A dual connectivity secondary node, comprising: means for receiving, from the dual connectivity master node via a dual connectivity related message, an information element for activation or deactivation of Protocol Data Unit (PDU) Set Importance (PSI) based uplink Packet Data Convergence Protocol (PDCP) Service Data Unit (SDU) discarding by a radio terminal for a data radio bearer terminated at the master node.

13. A method performed by a dual connectivity secondary node, comprising receiving, from the dual connectivity master node via a dual connectivity related message, an information element for activation or deactivation of Protocol Data Unit (PDU) Set Importance (PSI) based uplink Packet Data Convergence Protocol (PDCP) Service Data Unit (SDU) discarding by a wireless terminal for a data radio bearer terminated at the master node.

14. A dual connectivity master node, comprising: means for receiving, from the dual connectivity secondary node via a dual connectivity related message, an information element for activation or deactivation of Protocol Data Unit (PDU) Set Importance (PSI) based uplink Packet Data Convergence Protocol (PDCP) Service Data Unit (SDU) discarding by a radio terminal for a data radio bearer terminated at the secondary node.

15. The master node of claim 14, further comprising: means for transmitting a PSI-Based SDU Discard Activation / Deactivation Medium Access Control (MAC) Control Element (CE) to the wireless terminal in accordance with the information element.

16. A method performed by a dual connectivity master node, comprising receiving, from the dual connectivity secondary node via a dual connectivity related message, an information element for activation or deactivation of Protocol Data Unit (PDU) Set Importance (PSI) based uplink Packet Data Convergence Protocol (PDCP) Service Data Unit (SDU) discarding by a wireless terminal for a data radio bearer terminated at the secondary node.

17. A dual connectivity secondary node, comprising: means for sending to the dual connectivity master node via a dual connectivity related message an information element for activation or deactivation of Protocol Data Unit (PDU) Set Importance (PSI) based uplink Packet Data Convergence Protocol (PDCP) Service Data Unit (SDU) discarding by a radio terminal for a data radio bearer terminated at the secondary node.

18. A method performed by a dual connectivity secondary node, comprising sending to the dual connectivity master node via a dual connectivity related message an information element for activation or deactivation of Protocol Data Unit (PDU) Set Importance (PSI) based uplink Packet Data Convergence Protocol (PDCP) Service Data Unit (SDU) discarding by a wireless terminal for a data radio bearer terminated at the secondary node.

19. A first communications node, comprising: means for sending, for a data radio bearer terminated at the first communications node, configuration for downlink RLC Service Data Unit (SDU) discard in a Radio Link Control (RLC) entity to a second communications node providing an RLC entity for the data radio bearer, wherein the configuration includes an indication of activation or deactivation of timer-based downlink RLC SDU discard, an indication of a discard timer length used for the timer-based downlink RLC SDU discard, or both.

20. The first communication node according to claim 19, wherein the configuration causes the RLC entity to start a discard timer for an RLC SDU received from a higher layer and to discard the RLC SDU upon expiration of the discard timer.

21. The first communication node according to claim 19 or 20, wherein the first communication node is a Central Unit (CU) of a base station, and the second communication node is a Distributed Unit (DU) of the base station.

22. The first communication node according to claim 19 or 20, wherein the first communication node is a master node of dual connectivity, the second communication node is a secondary node of the dual connectivity, and the data radio bearer is a master node terminated bearer.

23. The first communication node according to claim 19 or 20, wherein the first communication node is a secondary node of dual connectivity, the second communication node is a master node of the dual connectivity, and the data radio bearer is a secondary node terminated bearer.

24. A method performed by a first communications node, comprising sending, for a data radio bearer terminated at the first communications node, a configuration for downlink RLC Service Data Unit (SDU) discard in a Radio Link Control (RLC) entity to a second communications node providing an RLC entity for the data radio bearer, wherein the configuration includes an indication of activation or deactivation of timer-based downlink RLC SDU discard, an indication of a discard timer length used for the timer-based downlink RLC SDU discard, or both.

25. A second communications node, comprising: means for receiving from a first communications node a configuration for downlink RLC Service Data Unit (SDU) discard in a Radio Link Control (RLC) entity for a data radio bearer terminated at the first communications node; and means for providing the RLC entity for the data radio bearer, wherein the configuration includes an indication of activation or deactivation of timer-based downlink RLC SDU discard, an indication of a discard timer length used for the timer-based downlink RLC SDU discard, or both.

26. The second communication node according to claim 25, wherein the RLC entity is configured to start a discard timer for an RLC SDU received from a higher layer based on the configuration, and to discard the RLC SDU upon expiration of the discard timer.

27. The second communication node according to claim 25 or 26, wherein the first communication node is a Central Unit (CU) of a base station, and the second communication node is a Distributed Unit (DU) of the base station.

28. The second communication node according to claim 25 or 26, wherein the first communication node is a master node of dual connectivity, the second communication node is a secondary node of the dual connectivity, and the data radio bearer is a master node terminated bearer.

29. The second communication node according to claim 25 or 26, wherein the first communication node is a secondary node of dual connectivity, the second communication node is a master node of the dual connectivity, and the data radio bearer is a secondary node terminated bearer.

30. A method performed by a second communications node, comprising: receiving from a first communications node a configuration for downlink RLC Service Data Unit (SDU) discard in a Radio Link Control (RLC) entity for a data radio bearer terminated at the first communications node; and providing the RLC entity for the data radio bearer, wherein the configuration includes an indication of activation or deactivation of timer-based downlink RLC SDU discard, an indication of a discard timer length used for the timer-based downlink RLC SDU discard, or both.

31. A dual connectivity master node, comprising: means for sending a first information element to the dual connectivity secondary node, the first information element indicating, for a Quality of Service (QoS) flow associated with a data radio bearer terminated at the secondary node, whether Explicit Congestion Notification (ECN) marking is required to be performed at the secondary node; whether information for ECN marking at a User Plane Function (UPF) in a core network is required to be reported from the secondary node to the UPF; or whether congestion information is required to be reported from the secondary node to the UPF.

32. The master node according to claim 31, wherein the sending means is configured to send the first information element via a secondary node addition request message or a secondary node modification request message.

33. A master node according to claim 31 or 32, wherein the sending means is configured to send the first information element to the secondary node based on a request for the QoS flow received from a control node of the core network.

34. A master node according to any one of claims 31 to 33, wherein the first information element is an ECN Marking or Congestion Information Reporting Request information element.

35. A master node according to any one of claims 31 to 34, further comprising means for receiving a second information element from the secondary node, the second information element indicating whether ECN marking at the secondary node, reporting of information for ECN marking at the UPF, or reporting of congestion information is active for the QoS flow.

36. The master node of claim 35, wherein the receiving means is configured to receive the second information element via a Secondary Node Addition Request Acknowledgement message or a Secondary Node Modification Request Acknowledgement message.

37. A master node according to any one of claims 31 to 36, comprising means for receiving a third information element from the secondary node after sending the first information element, the third information element instructing the master node to report information regarding Explicit Congestion Notification (ECN) marking or congestion for the data radio bearer to the secondary node.

38. A method performed by a dual connectivity master node, comprising sending a first information element to the dual connectivity secondary node, the first information element indicating, for a Quality of Service (QoS) flow associated with a data radio bearer terminated at the secondary node, whether Explicit Congestion Notification (ECN) marking is required to be performed at the secondary node; whether information for ECN marking at a User Plane Function (UPF) in a core network is required to be reported from the secondary node to the UPF; or whether congestion information is required to be reported from the secondary node to the UPF.

39. A dual connectivity secondary node, comprising means for receiving a first information element from the dual connectivity master node, the first information element indicating, for a Quality of Service (QoS) flow associated with a data radio bearer terminated at the secondary node, whether Explicit Congestion Notification (ECN) marking is required to be performed at the secondary node; whether information for ECN marking at a User Plane Function (UPF) in a core network is required to be reported from the secondary node to the UPF; or whether congestion information is required to be reported from the secondary node to the UPF.

40. A method performed by a secondary node of dual connectivity, comprising receiving a first information element from the master node of the dual connectivity, the first information element indicating, for a Quality of Service (QoS) flow associated with a data radio bearer terminated at the secondary node, whether Explicit Congestion Notification (ECN) marking is required to be performed at the secondary node; whether information for ECN marking at a User Plane Function (UPF) in a core network is required to be reported from the secondary node to the UPF; or whether congestion information is required to be reported from the secondary node to the UPF.

41. A dual connectivity master node, comprising: means for sending a first information element to the dual connectivity secondary node, the first information element indicating the secondary node to report information regarding Explicit Congestion Notification (ECN) marking or congestion to the master node for data radio bearers terminated at the master node.

42. The master node according to claim 41, wherein the sending means is configured to send the first information element via a secondary node addition request message or a secondary node modification request message.

43. A master node according to claim 41 or 42, wherein the sending means is configured to send the first information element to the secondary node based on a request for a QoS flow associated with the data radio bearer received from a control node of a core network.

44. A master node according to any one of claims 41 to 43, wherein the first information element is an ECN Marking or Congestion Information Reporting Request information element.

45. A master node according to any one of claims 41 to 44, further comprising means for receiving a second information element from said secondary node, said second information element indicating whether said reporting of information on ECN marking or on congestion is active for said data radio bearer.

46. ​​A method performed by a dual connectivity master node, comprising sending a first information element to the dual connectivity secondary node, the first information element indicating to the secondary node to report information regarding Explicit Congestion Notification (ECN) marking or congestion to the master node for data radio bearers terminated at the master node.

47. A dual connectivity secondary node, comprising: means for receiving a first information element from the dual connectivity master node, the first information element indicating the secondary node to report information regarding Explicit Congestion Notification (ECN) marking or congestion to the master node for data radio bearers terminated at the master node.

48. A method performed by a dual connectivity secondary node, comprising receiving a first information element from the dual connectivity master node, the first information element indicating to the secondary node to report information regarding Explicit Congestion Notification (ECN) marking or congestion to the master node for data radio bearers terminated at the master node.

49. A dual connectivity master node, comprising: means for receiving a first information element from the dual connectivity secondary node, the first information element indicating to the master node to report information regarding Explicit Congestion Notification (ECN) marking or congestion to the secondary node for a data radio bearer terminated at the secondary node.

50. The master node of claim 49, wherein the receiving means is configured to receive the first information element via a secondary node addition procedure, a secondary node modification preparation procedure initiated by the master node, or a secondary node modification procedure initiated by the secondary node.

51. A master node according to claim 49 or 50, further comprising means for activating or deactivating reporting of information relating to ECN marking or congestion to said secondary node for said data radio bearer in response to receiving said first information element.

52. A master node according to any one of claims 49 to 51, wherein the first information element is an ECN Marking or Congestion Information Reporting Request information element.

53. A master node according to any one of claims 49 to 52, further comprising means for sending a second information element to said secondary node, said second information element indicating whether said reporting of information on ECN marking or on congestion is active for said data radio bearer.

54. The master node of claim 53, wherein the second information element is an ECN Marking or Congestion Information Reporting Status information element.

55. A method performed by a dual connectivity master node, comprising receiving a first information element from the dual connectivity secondary node, the first information element indicating to the master node to report information regarding Explicit Congestion Notification (ECN) marking or congestion to the secondary node for a data radio bearer terminated at the secondary node.

56. A dual connectivity secondary node, comprising: means for sending a first information element to the dual connectivity master node, the first information element indicating to the master node to report information regarding Explicit Congestion Notification (ECN) marking or congestion to the secondary node for data radio bearers terminated at the secondary node.

57. A method performed by a dual connectivity secondary node, comprising sending a first information element to the dual connectivity master node, the first information element indicating to the master node to report information regarding Explicit Congestion Notification (ECN) marking or congestion to the secondary node for data radio bearers terminated at the secondary node.

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