Wireless terminal and method thereof

Abstract

This device for radio communication (1, 3) determines or detects, from an upper layer Protocol Data Unit (PDU) flow, the boundary between a plurality of upper layer PDU sets each of which is constituted by one or more upper layer PDUs. The device (1, 3) maps, on the basis of the attributes of the respective upper layer PDU sets, the plurality of upper layer PDU sets onto a plurality of different data radio bearers (DRBs). This can provide an improvement, for example, for the handling of an upper layer PDU set in a radio protocol layer.

Description

Apparatus and method for wireless communication

[0001] The present disclosure relates to wireless communication systems, and more particularly to air interface radio protocol stacks.

[0002] For the 3rd Generation Partnership Project (3GPP®) Release 18, 3GPP is discussing 5G New Radio (NR) enhancements for Extended Reality (XR) services (see, for example, Non-Patent Documents 1 and 2). Extended Reality (XR) services are also called XR and media (XRM) services or XR / media (XRM) services.

[0003] In the XR service, PDUs of the Protocol Data Unit (PDU) layer between the User Equipment (UE) and the Data Network (DN) need to be transferred through the core network and the Radio Access Network (RAN). In one example, the PDU layer is the Internet Protocol (IP) Version 4 (v4) or Version 6 (v6) layer, and the PDUs of the PDU layer are IP packets.

[0004] XR service PDUs are interdependent 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 are PDUs that carry fragments of intra-coded (I) frames, and other PDUs are PDUs that carry fragments of predicted (P) frames or bi-directional predicted (B) frames.

[0005] 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 Function (AF) or the XR application server and provided to the core network as part of the PDU set-related information.

[0006] 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, even if some PDUs are missing, the application layer can recover all or part of the information unit. 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.

[0007] 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 in this type of PDU set, all PDUs in the PDU set are said to be essential PDUs.

[0008] 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.

[0009] In 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. In this type of PDU set, no PDUs are essential, and the K parameter must be included in the PDU set related information.

[0010] Nokia, "New SID "Study on XR Enhancements for NR"", RP-213587, 3GPP TSG RAN Meeting #94e, December 6-17, 20213GPP TR 23.700-60 V1.1.0 (2022-09), "3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; Study on XR (Extended Reality) and media services (Release 18)", September 2022 SA4 (3GPP TSG SA WG4), "[DRAFT] LS Reply on QoS support with PDU Set granularity", S4-220505, 3GPP TSG-WG SA4 Meeting #118E, April 6-14, 2022

[0011] As mentioned above, a new concept called a PDU set will be introduced in relation to XR services. A PDU set is a set of PDUs in layers above the radio protocol layers (specifically, PDU layers (e.g., IPv4 layer, IPv6 layer)). Therefore, the terms "upper layer PDU set" and "upper layer PDUs" are used as appropriate in this specification to distinguish upper layer PDUs and PDU sets from PDUs in multiple radio protocol layers, such as the Service Data Adaptation Protocol (SDAP) and Packet Data Convergence Protocol (PDCP) sublayers. To avoid redundancy, the terms "PDU set" and "PDUs" are also used, but unless otherwise clear from the context, they have the same meaning as "upper layer PDU set" and "upper layer PDUs."

[0012] The new concept of PDU sets or upper layer PDU sets may affect the radio protocol between the UE and the radio access network. The inventors have studied the handling of upper layer PDU sets in the radio protocol layer and found various problems.

[0013] One of these challenges relates to the mapping of PDU sets to Data Radio Bearers (DRBs). In the current 5G NR specification, one QoS flow is mapped to only one DRB in the Service Data Adaptation Protocol (SDAP) sublayer. However, in some implementations, this restriction may increase the burden on the Packet Data Convergence Protocol (PDCP) sublayer below SDAP. If there are multiple types of PDU sets within one QoS flow and each PDU set type needs to be treated differently, such as with SDU discarding, PDCP is forced to identify which PDU set type each PDCP SDU (or SDAP Data PDU) in the DRB belongs to.

[0014] Another issue concerns how to transport multiple upper layer PDUs belonging to an upper layer PDU set at the radio protocol layer. As mentioned above, for some PDU set types, one or more specific PDUs in the PDU set are required by the application layer to use the corresponding information unit, while the remaining PDUs are not necessarily required by the application layer. In this case, it may be effective to handle the essential PDU(s) collectively at the radio protocol layer.

[0015] Another issue concerns SDU discard at the radio protocol layer, taking into account the upper layer PDU set. In the current 5G NR specification, the PDCP layer supports timer-based SDU discard. Specifically, when a PDCP SDU's discard timer (i.e., discardTimer) expires or a PDCP status report confirms the successful delivery of the PDCP SDU, the transmitting PDCP entity established for each DRB must discard the PDCP SDU along with the corresponding SDAP Data PDU. If the corresponding PDCP Data PDU has already been transmitted to the lower layer, the transmitting PDCP entity instructs the lower layer (i.e., the Radio Link Control (RLC) sublayer) to discard it. At present, it is unclear how to perform SDU discard taking into account the upper layer PDU set.

[0016] One of the objectives that the embodiments disclosed in this specification aim to achieve is to provide an apparatus, a method, and a program that contribute to solving at least one of the problems, including the problems described above. It should be noted that this objective is only one of the objectives that the embodiments disclosed in this specification aim to achieve. Other objectives or objectives and novel features will become apparent from the description of this specification or the accompanying drawings.

[0017] In a first aspect, an apparatus for wireless communication is configured to provide an intermediate layer function between an upper layer and a lower layer, the intermediate layer function including identifying boundaries of a plurality of upper layer PDU sets from a first upper layer PDU flow, each upper layer PDU set consisting of one or more upper layer PDUs, and mapping the plurality of upper layer PDU sets to a plurality of different data radio bearers based on one or more attributes of each upper layer PDU set.

[0018] In a second aspect, a method performed by an apparatus for wireless communication includes providing an intermediate layer function between an upper layer and a lower layer, the intermediate layer function including identifying boundaries of a plurality of upper layer PDU sets from a first upper layer PDU flow, each upper layer PDU set consisting of one or more upper layer PDUs, and mapping the plurality of upper layer PDU sets to a plurality of different data radio bearers based on one or more attributes of each upper layer PDU set.

[0019] In a third aspect, an apparatus for wireless communication is configured to provide an intermediate layer function between an upper layer and a lower layer, the intermediate layer function including selecting a subset of important intermediate layer SDUs from an intermediate layer SDU set corresponding to an upper layer PDU set, and further including concatenating or assembling the subset of intermediate layer SDUs into an intermediate layer PDU.

[0020] In a fourth aspect, a method performed by an apparatus for wireless communication includes providing an intermediate layer function between an upper layer and a lower layer, the intermediate layer function including selecting a subset of important intermediate layer SDUs from a set of intermediate layer SDUs corresponding to a set of upper layer PDUs, and combining or assembling the subset of intermediate layer SDUs into a single intermediate layer PDU.

[0021] In a fifth aspect, an apparatus for wireless communication is configured to provide an intermediate layer function between an upper layer and a lower layer, the intermediate layer function including, when a discard timer for an intermediate layer SDU set corresponding to an upper layer PDU set expires, discarding all intermediate layer SDUs belonging to the intermediate layer SDU set.

[0022] In a sixth aspect, a method performed by an apparatus for wireless communication includes providing an intermediate layer function between an upper layer and a lower layer, the intermediate layer function including, when a discard timer for an intermediate layer SDU set corresponding to an upper layer PDU set expires, discarding all intermediate layer SDUs belonging to the intermediate layer SDU set.

[0023] In a seventh aspect, an apparatus for wireless communication is configured to provide an intermediate layer function between an upper layer and a lower layer, the intermediate layer function including, when a delivery failure of one or more intermediate layer SDUs belonging to an intermediate layer SDU set corresponding to an upper layer PDU set is determined, discarding all intermediate layer SDUs belonging to the intermediate layer SDU set.

[0024] In an eighth aspect, a method performed by an apparatus for wireless communication includes providing an intermediate layer function between an upper layer and a lower layer, the intermediate layer function including, when a delivery failure of one or more intermediate layer SDUs belonging to an intermediate layer SDU set corresponding to an upper layer PDU set is determined, discarding all intermediate layer SDUs belonging to the intermediate layer SDU set.

[0025] A ninth aspect is directed to a program, which includes a set of instructions (software code) that, when loaded into a computer, causes the computer to perform the method according to the second, fourth, sixth, or eighth aspect.

[0026] According to the above-mentioned aspects, it is possible to provide an apparatus, a method, and a program that contribute to solving at least one of a number of problems related to handling of upper layer PDU sets at radio protocol layers, including the problems described above.

[0027] 1 is a diagram illustrating an example of the configuration of a wireless communication system according to an embodiment. FIG. 2 is a diagram illustrating an example of a user plane protocol stack according to an embodiment. FIG. 3 is a flowchart illustrating an example of the operation of an apparatus (e.g., UE, RAN node) according to an embodiment. FIG. 4 is a diagram illustrating an example of the operation of an apparatus (e.g., UE, RAN node) according to an embodiment. FIG. 5 is a flowchart illustrating an example of the operation of an apparatus (e.g., UE, RAN node) according to an embodiment. FIG. 6 is a diagram illustrating an example of the operation of an apparatus (e.g., UE, RAN node) according to an embodiment. FIG. 7 is a flowchart illustrating an example of the operation of an apparatus (e.g., UE, RAN node) according to an embodiment. FIG. 8 is a flowchart illustrating an example of the operation of an apparatus (e.g., UE, RAN node) according to an embodiment. FIG. 9 is a flowchart illustrating an example of the operation of an apparatus (e.g., UE, RAN node) according to an embodiment.

[0028] 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.

[0029] The following embodiments are described with respect to the 3GPP fifth generation mobile communication system (5G system) and its evolution, but may also be applied to other wireless communication systems.

[0030] As used herein, depending on the context, "if" may be interpreted to mean "when," "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.

[0031] 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.

[0032] The network system shown in Figure 1 includes a UE 1, a RAN 2, a core network 4, and a data network (DN) 6. The RAN 2 may be a Next Generation Radio Access Network (NG-RAN). The RAN 2 includes one or more RAN nodes 3. The one or more RAN nodes 3 may be gNBs.

[0033] 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).

[0034] The core network 4 may be a 5G Core (5GC). The core network 4 includes one or more core network nodes. These core network nodes include one or more control plane nodes and one or more user plane (or data plane) nodes. In a 5G system, the control plane nodes include an Access and Mobility Management Function (AMF), a Session Management Function (SMF), a Unified Data Management (UDM), a Policy Control Function (PCF), and a Network Exposure Function (NEF). The user plane nodes include a PDU Session Anchor (PSA) User Plane Function (UPF) 5 and may include one or more intermediate UPFs. The intermediate UPF may provide an Uplink Classifier (UL CL) or Branching Point (BP) function.

[0035] The UE 1 communicates with an application server 7 in the DN 6 via a connectivity service provided by the core network 4 and the RAN 2, specifically, a PDU Connectivity service in a 5G system. The PDU Connectivity service provides a PDU Session and enables the exchange of PDUs on the PDU layer between the UE 1 and the DN 6. For example, the application server 7 may provide an XR service to the UE 1 via the core network 4 and the RAN 2.

[0036] The DN 6 may be an Edge Data Network (EDN) or a Local Area Data Network (LADN). The application server 7 may include one or more edge computing servers located near the RAN 2.

[0037] Figure 2 shows an example of a user plane protocol stack provided by the wireless communication system of Figure 1. The UE 1 and the application server 7 can exchange PDUs (e.g., 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 (e.g., Transmission Control Protocol (TCP) and User Datagram Protocol (UDP)) of the Open Systems Interconnection (OSI) model. For example, in the case of an XR service, the PDU layer protocol may be IP, while the application layer protocol may include an H.264, H265, or H.266 codec, Real-time Transport Protocol (RTP), and UDP.

[0038] 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 are dependent on other PDUs are expected to be more important. For example, PDUs that are dependent on other PDUs may be PDUs carrying fragments of an I-frame, and other PDUs may be PDUs carrying fragments of a P-frame or B-frame.

[0039] 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 Function (AF) or the XR application server and provided to the core network as part of the PDU set-related information.

[0040] 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, even if some PDUs are missing, the application layer can recover all or part of the information unit. 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.

[0041] 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 in this type of PDU set, all PDUs in the PDU set are said to be essential PDUs.

[0042] 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.

[0043] In 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. In this type of PDU set, no PDUs are essential, and the K parameter must be included in the PDU set related information.

[0044] The UE 1 and the RAN 2 (or RAN node 3) provide handling of the upper layer PDU set at the radio protocol layer, which will be described in detail in the following embodiments.

[0045] First Embodiment This embodiment provides an improvement for handling of upper layer PDU sets in radio protocol layers. Fig. 3 shows an example of operations performed by an apparatus for wireless communication. The apparatus for wireless communication may be a UE 1 or a RAN node 3. The apparatus for wireless communication provides an intermediate layer function or service between the upper layer and the lower layer. The operations shown in Fig. 3 relate to mapping of PDU sets to DRBs. Therefore, the intermediate layer may be an SDAP sublayer. More specifically, the operations in Fig. 3 may be performed by a transmitting SDAP entity.

[0046] In step 301, the device identifies or detects boundaries of multiple upper layer PDU sets, each consisting of one or more upper layer PDUs, from an upper layer PDU flow. In other words, the device identifies or detects each PDU set included in the upper layer PDU flow. The upper layer PDU flow may be a QoS flow (i.e., 5G QoS Flow). A QoS flow is the finest granularity for QoS forwarding treatment in a 5G system. All traffic mapped to the same 5G QoS flow is subject to the same forwarding treatment (e.g., scheduling policy, queue management policy, rate shaping, RLC configuration, etc.). To provide different QoS forwarding treatments, separate 5G QoS flows are required.

[0047] If the device is a RAN node 3 performing downlink transmission, the device may identify boundaries of multiple upper layer PDU sets based on header information (e.g., General Packet Radio Service Tunneling Protocol User (GTP-U) header) of upper layer PDUs or header information and payload information of upper layer PDUs. The header information, payload information, or a combination thereof of each upper layer PDU may indicate the sequence number of the PDU set, the PDU set boundary, or both. More specifically, to indicate the PDU set boundary, a start mark (e.g., a one-bit flag) may be included in the PDU header information. The start mark is enabled only for the first PDU of the PDU set. Additionally or alternatively, an end mark (e.g., a one-bit flag) may be included in the PDU header information. The end mark is enabled only for the last PDU of the PDU set. Alternatively, the device may detect the PDU set boundary based on a change in the PDU set sequence number.

[0048] The header information or payload information, or a combination thereof, of each upper layer PDU may indicate attributes of the PDU set. The attributes of the PDU set may include the type of PDU set, an importance level, a dependency, or any combination thereof. The header information or payload information, or a combination thereof, of each upper layer PDU may indicate the sequence number of the PDU within the PDU set.

[0049] If the device is a UE 1 performing uplink transmission, the device may receive a QoS profile including PDU set handling parameters from the core network 4. The PDU set handling parameters include information about internal headers (e.g., RTP header, RTP payload header) necessary to identify the boundaries (and attributes) of PDU sets. The information carried by the RTP header and the information carried by the RTP payload header can be used to identify PDUs belonging to a PDU set or to distinguish the importance of PDU sets. For example, the Marker (M) bit in the RTP header is intended to mark important events, such as frame boundaries, in a packet stream and can therefore be used to detect PDU set boundaries.

[0050] In step 302, the device maps the multiple upper layer PDU sets to multiple different DRBs based on the attributes of each upper layer PDU set. In other words, the device maps multiple PDU sets with different attributes within one QoS flow to different DRBs. The attributes of each upper layer PDU set may be one or any combination of the type, importance, and dependency of the PDU set.

[0051] After step 302, the device adds intermediate layer (e.g., SDAP sublayer) headers to each upper layer PDU (i.e., intermediate layer SDU) as needed, and generates intermediate layer PDUs (e.g., SDAP Data PDUs) and sends them to the lower layer (e.g., PDCP sublayer).

[0052] According to the operation described with reference to Fig. 3, PDU sets with different attributes are mapped to different DRBs. Therefore, an entity in a lower layer (e.g., PDCP) established for each DRB only needs to operate on a PDU set with a specific attribute and does not need to specify the attribute of the PDU set. This can contribute to reducing the load on the entity in the lower layer (e.g., PDCP).

[0053] The device may perform the operations of Fig. 2 only for a specific type of upper layer PDU flow or QoS flow that includes an upper layer PDU set. The specific type of upper layer PDU flow or QoS flow may be referred to as, for example, an XR QoS flow, an XR service QoS flow, or an XR-specific QoS flow. For a non-specific type or normal upper layer PDU flow or QoS flow, the device may operate in the same manner as radio bearer mapping in current 5G NR. Specifically, the device may map all upper layer PDUs belonging to a non-specific type of upper layer PDU flow to one DRB.

[0054] 4 shows an example of the operation of a transmitting SDAP entity. In step 401, the transmitting SDAP entity determines whether the QoS flow from the upper layer is of a specific type. If the QoS flow is not of a specific type, the transmitting SDAP entity maps the QoS flow to one DRB based on the configured mapping rules from QoS flows to DRBs (step 402).

[0055] In contrast, if the QoS flow is of a specific type (e.g., XR type), the transmitting SDAP entity performs steps 403 and 404. Steps 403 and 404 are similar to steps 301 and 302 in Fig. 3. Specifically, in step 403, the transmitting SDAP entity identifies or detects upper layer PDU set boundaries based on configured PDU set handling parameters. In step 404, the transmitting SDAP entity maps multiple PDU sets with different attributes to different DRBs based on configured mapping rules from PDU sets to DRBs.

[0056] In step 405, the transmitting SDAP entity adds an SDAP header to each upper layer PDU (i.e., SDAP SDU) if necessary, and then generates SDAP Data PDUs and sends them to the lower layer (i.e., PDCP sublayer).

[0057] Second Embodiment This embodiment provides concatenation or assembly of PDUs belonging to one upper layer PDU set into one radio protocol layer PDU. Figure 5 shows an example of operations performed by wireless communication. The device for wireless communication may be a UE 1 or a RAN node 3. The device for wireless communication provides functions or services of an intermediate layer between the upper layer and the lower layer. The intermediate layer may be an SDAP sublayer or a PDCP sublayer.

[0058] In step 501, an intermediate layer entity of a device selects a subset of important intermediate layer SDUs from an intermediate layer SDU set corresponding to an upper layer PDU set. In some implementations, the important intermediate layer SDUs (i.e., upper layer PDUs) may be PDUs that must be received in order for the upper layer PDU set to be available to a peer device (receiving side).

[0059] If the intermediate layer entity is an SDAP entity, the upper layer PDU set is a PDU set of the PDU layer. Furthermore, the upper layer PDUs are PDUs (or GTP-U packets) of the PDU layer. In this case, the header information (e.g., GTP-U header) of each upper layer PDU may indicate the importance level of each upper layer PDU, i.e., each intermediate layer SDU. The intermediate layer entity (i.e., the transmitting SDAP entity) may recognize the importance level of each upper layer PDU, i.e., each intermediate layer SDU, based on the header information (e.g., GTP-U header) of the upper layer PDUs.

[0060] On the other hand, if the intermediate layer entity is a PDCP entity, the upper layer PDU set is a set of SDAP Data PDUs corresponding to the PDU layer PDU set. The upper layer PDUs are also SDAP Data PDUs. In this case, the header information (e.g., SDAP header) of each upper layer PDU (i.e., SDAP Data PDU) may indicate the importance level of each SDAP Data PDU, i.e., each PDCP SDU. The intermediate layer entity (i.e., transmitting PDCP entity) may recognize the importance level of each upper layer PDU, i.e., intermediate layer SDU, based on the header information (i.e., SDAP header) of the upper layer PDU. Alternatively, the intermediate layer entity (i.e., transmitting PDCP entity) may recognize the importance level of each upper layer PDU, i.e., intermediate layer SDU, by inspecting the PDU layer PDU (e.g., IP packet) included in the payload of the upper layer PDU (i.e., SDAP Data PDU).

[0061] In step 502, an intermediate layer entity of the device combines or assembles a subset of intermediate layer SDUs of high importance into one intermediate layer PDU.

[0062] The device may generate multiple intermediate layer PDUs, each including a respective one of the remaining intermediate layer SDUs (i.e., upper layer PDUs) belonging to the intermediate layer SDU set (i.e., upper layer PDU set). In other words, the device may generate multiple intermediate layer PDUs, each including a respective one of the intermediate layer SDUs (i.e., upper layer PDUs) of less importance included in one intermediate layer SDU set. The intermediate layer SDUs (i.e., upper layer PDUs) of less importance may be upper layer PDUs that are not necessarily required for the application layer to use the corresponding information unit.

[0063] According to the operation described with reference to FIG. 5, the radio protocol layer can collectively handle the most important PDU(s) among all upper layer PDUs belonging to one upper layer PDU set.

[0064] Figure 6 shows an example of generation of an SDAP Data PDU by a transmitting SDAP entity. The transmitting SDAP entity selects the most important upper layer PDUs (e.g., essential upper layer PDUs) in a set of upper layer PDUs and combines or assembles them into a single SDAP Data PDU.

[0065] Figure 7 shows an example of PDCP Data PDU generation by a transmitting PDCP entity. First, the transmitting SDAP entity generates SDAP Data PDUs, each containing one upper layer PDU, and provides them to the PDCP entity. The header of each SDAP Data PDU may indicate the importance level of each SDAP Data PDU, i.e., each PDCP SDU. The importance level indicated by the header of each SDAP Data PDU may be the same as the importance level of the contained upper layer PDU (PDU layer PDU). Next, the transmitting PDCP entity selects highly important SDAP PDUs (e.g., essential SDAP PDUs) included in one SDAP Data PDU set and combines or assembles them into one PDCP Data PDU.

[0066] Third Embodiment This embodiment provides SDU (and PDU) discarding at the radio protocol layer taking into account the upper layer PDU set. Figure 8 shows an example of operations performed by a wireless communication. The device for wireless communication may be a UE 1 or a RAN node 3. The device for wireless communication provides functions or services of an intermediate layer between the upper layer and the lower layer. The intermediate layer may be an SDAP sublayer, a PDCP sublayer, or an RLC sublayer.

[0067] In step 801, the intermediate layer entity of the device detects the expiration of a discard timer for an intermediate layer SDU set corresponding to an upper layer PDU set. In step 802, the intermediate layer entity of the device discards all intermediate layer SDUs belonging to the intermediate layer SDU set. In addition, the intermediate layer entity of the device discards intermediate layer PDUs corresponding to the discarded intermediate layer SDUs.

[0068] The length of the discard timer may be based on the corresponding upper layer PDU-Set Delay Budget (PSDB). The PSDB defines the upper limit of the time a PDU set may be delayed between the UE 1 and the N6 termination point of the PSA UPF 5 (the termination point of the N6 interface with the DN 6). Note that the upper layer PDU set delay budget may also be based on the Access Network (AN) PSDB, which is determined by subtracting a fixed value of the Core Network (CN) PSDB from the PSDB. The CN PSDB represents the delay between any N6 termination point in the UPF (any UPF that may be selected for the PDU Session) and the 5G-AN.

[0069] More specifically, the length of the discard timer may be determined based on the sum of a first value configured by the Radio Resource Control (RRC) layer and a second value corresponding to the PSDB, where the first value, i.e., the RRC configured value, may be based on the importance (or importance level) of the corresponding higher layer PDU set.

[0070] In one example, the mapping of multiple upper layer PDU sets belonging to one QoS flow to different DRBs described in the first embodiment may be utilized, in which case the first value for determining the length of the discard timer, i.e., the RRC configuration value, may be configured for each DRB.

[0071] In another example, the mapping described in the first embodiment may not be used, and all upper layer PDUs belonging to one QoS flow may be mapped to one DRB. In this case, the first value for determining the length of the discard timer, i.e., the RRC configuration value, may be set for each PDU set attribute (e.g., for each type or importance level).

[0072] The operations described with reference to FIG. 8 provide for SDU discarding taking into account upper layer PDU sets.

[0073] Fourth Embodiment This embodiment provides SDU discarding at the radio protocol layer taking into account the upper layer PDU set. Figure 9 shows an example of operations performed by a wireless communication. The device for wireless communication may be a UE 1 or a RAN node 3. The device for wireless communication provides functions or services of an intermediate layer between the upper layer and the lower layer. The intermediate layer may be an SDAP sublayer, a PDCP sublayer, or an RLC sublayer.

[0074] In step 901, the intermediate layer entity of the device determines delivery failure of one or more intermediate layer SDUs belonging to an intermediate layer SDU set corresponding to an upper layer PDU set. In step 902, the intermediate layer entity of the device discards all intermediate layer SDUs belonging to the intermediate layer SDU set. In addition, the intermediate layer entity of the device discards intermediate layer PDUs corresponding to the discarded intermediate layer SDUs.

[0075] The operation of Fig. 9 can contribute to suppressing the delivery of unnecessary SDUs and PDUs. Figs. 10 and 11 show more specific cases of the operation of Fig. 9.

[0076] In step 1001 of Fig. 10, the intermediate layer entity of the device determines delivery failure of one or more specific intermediate layer SDUs of high importance belonging to an intermediate layer SDU set corresponding to an upper layer PDU set. In step 1002, the intermediate layer entity of the device discards all intermediate layer SDUs belonging to the intermediate layer SDU set. In addition, the intermediate layer entity of the device discards intermediate layer PDUs corresponding to the discarded intermediate layer SDUs.

[0077] The operations of Fig. 10 may be selectively performed only for a particular type of PDU set. As already explained, in a certain 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, while the remaining PDUs are not necessarily required by the application layer. In this type of PDU set, some PDUs, or a PDU subset, in the PDU set can be said to be essential PDUs. The operations of Fig. 10 may be selectively performed only for such a PDU set.

[0078] The operation of FIG. 10 can enable SDU discarding taking into account the characteristics of a particular type of PDU set, and can help prevent delivery of unnecessary SDUs and PDUs.

[0079] 11, in step 1101, the intermediate layer entity of the device determines delivery failure of a predetermined number of intermediate layer SDUs belonging to an intermediate layer SDU set corresponding to an upper layer PDU set. In step 1102, the intermediate layer entity of the device discards all intermediate layer SDUs belonging to the intermediate layer SDU set. In addition, the intermediate layer entity of the device discards intermediate layer PDUs corresponding to the discarded intermediate layer SDUs.

[0080] The operations of Fig. 11 may be selectively performed only for a specific type of PDU set. As already explained, for a certain type of PDU set, the application layer needs to 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. The operations of Fig. 11 may be selectively performed only for such PDU sets.

[0081] The operation of FIG. 11 can enable SDU discarding taking into account the characteristics of a particular type of PDU set, and can help prevent delivery of unnecessary SDUs and PDUs.

[0082] In the operations described with reference to Figures 9-11, an intermediate layer entity of a device may determine delivery failure of one or more intermediate layer SDUs based on a delivery status report received from a peer device (e.g., a receiving intermediate layer entity). If the operations described with reference to Figures 9-11 are performed by a transmitting SDAP entity, the delivery status report may be defined as an SDAP layer Control PDU sent from the receiving SDAP entity to the transmitting SDAP entity. On the other hand, if the operations described with reference to Figures 9-11 are performed by a transmitting PDCP entity, the delivery status report may be defined as an extension of the existing PDCP status report.

[0083] The delivery status report may indicate the PDCP Count value of the last PDCP PDU or PDCP SDU that was successfully received, or the delivery status report may indicate the PDCP Count value of the first PDCP PDU or PDCP SDU that has not yet been received.

[0084] The delivery status report may be sent from the peer device (e.g., a receiving intermediate layer entity) in response to the expiration of a timer in the peer device. For example, the peer device may start a timer in response to receiving the first PDU of a PDU set and send the delivery status report in response to the expiration of the timer. The length of the timer may be configured by the transmitting intermediate layer entity using the header of the intermediate layer Control PDU or Data PDU. Alternatively, the length of the timer may be configured by the RRC layer as one of the PDU set attributes.

[0085] Alternatively, the peer device (e.g., a receiving intermediate layer entity) may transmit a delivery status report based on the number of intermediate layer SDUs or PDUs received by the peer device. Specifically, the peer device may transmit a delivery status report each time a predetermined number of PDCP PDUs or SDUs are successfully received. The predetermined number may be configured by the transmitting intermediate layer entity using the header of the intermediate layer Control PDU or Data PDU. Alternatively, the predetermined number may be configured by the RRC layer as one of the PDU set attributes.

[0086] Alternatively, the peer device (e.g., a receiving intermediate layer entity) may periodically transmit the delivery status report at a predetermined time interval or period, which may be configured by the RRC layer as one of the PDU set attributes.

[0087] Next, exemplary configurations of the UE 1 and the RAN node 3 according to the above-described embodiments will be described. FIG. 12 is a block diagram illustrating an exemplary configuration of the UE 1. A radio frequency (RF) transceiver 1201 performs analog RF signal processing for communication with the RAN 2. The RF transceiver 1201 may include multiple transceivers. The analog RF signal processing performed by the RF transceiver 1201 includes frequency up-conversion, frequency down-conversion, and amplification. The RF transceiver 1201 is coupled to an antenna array 1202 and a baseband processor 1203. The RF transceiver 1201 receives modulation symbol data (or Orthogonal Frequency-Division Multiplexing (OFDM) symbol data) from the baseband processor 1203, generates a transmit RF signal, and provides the transmit RF signal to the antenna array 1202. The RF transceiver 1201 also generates a baseband receive signal based on the receive RF signal received by the antenna array 1202 and provides the baseband receive signal to the baseband processor 1203. The RF transceiver 1201 may include an analog beamformer circuit for beamforming, which may include, for example, multiple phase shifters and multiple power amplifiers.

[0088] The baseband processor 1203 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).

[0089] For example, the digital baseband signal processing by the baseband processor 1203 may include signal processing of an SDAP layer, a PDCP layer, an RLC layer, a Medium Access Control (MAC) layer, and a Physical (PHY) layer. Also, the control plane processing by the baseband processor 1203 may include processing of a Non-Access Stratum (NAS) protocol, an RRC protocol, MAC Control Elements (CEs), and Downlink Control Information (DCI).

[0090] The baseband processor 1203 may perform Multiple Input Multiple Output (MIMO) encoding and precoding for beamforming.

[0091] The baseband processor 1203 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 an 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 1204, which will be described later.

[0092] The application processor 1204 is also referred to as a central processing unit (CPU), a micro processing unit (MPU), a microprocessor, or a processor core. The application processor 1204 may include multiple processors (multiple processor cores). The application processor 1204 executes a system software program (operating system (OS)) and various application programs (e.g., a call application, a web browser, a mailer, a camera operation application, and a music playback application) read from the memory 1206 or a memory not shown, thereby realizing various functions of the UE 1.

[0093] In some implementations, the baseband processor 1203 and the application processor 1204 may be integrated on a single chip, as indicated by the dashed line (1205) in Figure 12. In other words, the baseband processor 1203 and the application processor 1204 may be implemented as a single System on Chip (SoC) device 1205. An SoC device is sometimes called a system Large Scale Integration (LSI) or chipset.

[0094] The memory 1206 is volatile memory, nonvolatile memory, or a combination thereof. The memory 1206 may include multiple physically independent memory devices. The volatile memory may be, for example, static random access memory (SRAM), dynamic RAM (DRAM), or a combination thereof. The nonvolatile memory may be mask read only memory (MROM), electrically erasable programmable ROM (EEPROM), flash memory, a hard disk drive, or any combination thereof. For example, the memory 1206 may include an external memory device accessible from the baseband processor 1203, the application processor 1204, and the SoC 1205. The memory 1206 may also include an internal memory device integrated within the baseband processor 1203, the application processor 1204, or the SoC 1205. Furthermore, the memory 1206 may include memory within a Universal Integrated Circuit Card (UICC).

[0095] The memory 1206 may store one or more software modules (computer programs) 1207 including instructions and data for performing the processes described in the above embodiments by the UE 1. In some implementations, the baseband processor 1203 or the application processor 1204 may be configured to read and execute the software modules 1207 from the memory 1206 to perform the processes of the UE 1 described in the above embodiments using the drawings.

[0096] 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 1201 and the antenna array 1202, namely, at least one of the baseband processor 1203 and the application processor 1204, and the memory 1206 storing the software module 1207.

[0097] FIG. 13 is a block diagram showing an example configuration of a RAN node 3 according to the above embodiment. Referring to FIG. 13, the RAN node 3 includes an RF transceiver 1301, a network interface 1303, a processor 1304, and a memory 1305. The RF transceiver 1301 performs analog RF signal processing for communication with UEs. The RF transceiver 1301 may include multiple transceivers. The RF transceiver 1301 is coupled to an antenna array 1302 and the processor 1304. The RF transceiver 1301 receives modulation symbol data from the processor 1304, generates a transmit RF signal, and provides the transmit RF signal to the antenna array 1302. The RF transceiver 1301 also generates a baseband receive signal based on the receive RF signal received by the antenna array 1302 and provides the baseband receive signal to the processor 1304. The RF transceiver 1301 may include an analog beamformer circuit for beamforming. The analog beamformer circuit may include, for example, multiple phase shifters and multiple power amplifiers.

[0098] The network interface 1303 is used to communicate with network nodes (e.g., other RAN nodes, and control plane nodes and user plane nodes of the core network), and may include, for example, a network interface card (NIC) compliant with the IEEE 802.3 series.

[0099] The processor 1304 performs digital baseband signal processing (data plane processing) and control plane processing for wireless communication. The processor 1304 may include multiple processors. For example, the processor 1304 may include a modem processor (e.g., DSP) that performs digital baseband signal processing and a protocol stack processor (e.g., CPU or MPU) that performs control plane processing.

[0100] For example, digital baseband signal processing by the processor 1304 may include signal processing of the SDAP layer, PDCP layer, RLC layer, MAC layer, and PHY layer. Control plane processing by the processor 1304 may also include processing of NAS messages, RRC messages, MAC CEs, and DCI. Control plane processing by the processor 1304 may also include processing of application layer signaling protocols such as XnAP, F1AP, and NGAP.

[0101] The processor 1304 may include a digital beamformer module for beamforming, which may include a MIMO encoder and precoder.

[0102] The memory 1305 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 1305 may include storage located remotely from the processor 1304. In this case, the processor 1304 may access the memory 1305 via the network interface 1303 or the I / O interface.

[0103] The memory 1305 may store one or more software modules (computer programs) 1306 including instructions and data for performing the processes of the RAN node 3 described in the above embodiments. In some implementations, the processor 1304 may be configured to read and execute the software modules 1306 from the memory 1305 to perform the processes of the RAN node 3 described in the above embodiments.

[0104] Note that if the RAN node 3 is a Central Unit (CU) (e.g., gNB-CU) or a CU-CP, the RAN node 3 may not include the RF transceiver 1301 (and the antenna array 1302).

[0105] As described with reference to Figures 12 and 13, each of the processors included in the UE 1 and the RAN node 3 according to the above-described embodiments may 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 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 communication medium. By way of example and not limitation, transitory computer-readable media or communication media include electrical, optical, acoustic, or other forms of propagated signals.

[0106] 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.

[0107] For example, some or all of the above embodiments can be described as, but are not limited to, the following supplementary notes.

[0108] 1. An apparatus for wireless communication providing an intermediate layer function between a higher layer and a lower layer, the intermediate layer function comprising: means for identifying, from a first upper layer Protocol Data Unit (PDU) flow, boundaries of a plurality of upper layer PDU sets, each consisting of one or more upper layer PDUs; and means for mapping the plurality of upper layer PDU sets to a plurality of different data radio bearers based on one or more attributes of each upper layer PDU set. 2. The apparatus according to claim 1, wherein the mapping means is configured to, for a particular type of upper layer PDU flow, identify the boundaries and map the plurality of upper layer PDU sets to the different data radio bearers; and, for a non-specific type of upper layer PDU flow, the intermediate layer function comprises means for mapping all upper layer PDUs belonging to the non-specific type of upper layer PDU flow to one data radio bearer. (Supplementary Note 3) The apparatus according to Supplementary Note 1 or 2, wherein the one or more attributes include one or any combination of a type, importance, and dependency of each upper layer PDU set. (Supplementary Note 4) The apparatus according to any one of Supplements 1 to 3, wherein the intermediate layer functions comprise: means for selecting a plurality of upper layer PDUs with high importance from a plurality of upper layer PDUs belonging to an upper layer PDU set mapped to a first data radio bearer; and means for concatenating or assembling the selected plurality of upper layer PDUs into one intermediate layer PDU.(Supplementary Note 5) The apparatus according to any one of Supplements 1 to 3, wherein the intermediate layer functionality comprises: means for generating a plurality of intermediate layer PDUs, each including a respective one of the upper layer PDUs of the plurality of upper layer PDU sets; and means for sending the generated intermediate layer PDUs to the lower layer, wherein the apparatus is configured to provide the lower layer functionality, and the lower layer functionality comprises: means for selecting a plurality of intermediate layer PDUs including a plurality of upper layer PDUs with higher importance from the plurality of upper layer PDUs belonging to the upper layer PDU set mapped to a first data radio bearer, and means for concatenating or assembling the selected plurality of intermediate layer PDUs into one lower layer PDU. (Supplementary Note 6) The apparatus according to any one of Supplements 1 to 5, wherein the intermediate layer functionality comprises: means for discarding all upper layer PDUs belonging to an upper layer PDU set when a discard timer for that upper layer PDU set expires. (Supplementary Note 7) The apparatus of Supplementary Note 6, wherein the length of the discard timer is based on a delay budget of the associated upper layer PDU set. (Supplementary Note 8) The apparatus of Supplementary Note 6 or 7, wherein the length of the discard timer is based on the importance of the associated upper layer PDU set. (Supplementary Note 9) The apparatus of any one of Supplements 1 to 8, wherein the intermediate layer function comprises means for discarding all upper layer PDUs belonging to an upper layer PDU set when delivery failure of one or more specific upper layer PDUs belonging to the upper layer PDU set is confirmed. (Supplementary Note 10) The apparatus of any one of Supplements 1 to 8, wherein the intermediate layer function comprises means for discarding all upper layer PDUs belonging to an upper layer PDU set when delivery failure of a predetermined number of upper layer PDUs belonging to the upper layer PDU set is confirmed. (Supplementary Note 11) The apparatus of Supplementary Note 9 or 10, wherein the apparatus comprises means for determining delivery failure of one or more upper layer PDUs based on delivery status reports received from a peer apparatus.(Supplementary Note 12) The apparatus of Supplementary Note 11, wherein the delivery status report is transmitted from the peer device in response to expiration of a timer in the peer device or based on the number of PDUs received by the peer device. (Supplementary Note 13) The apparatus of Supplementary Note 11, wherein the delivery status report is transmitted from the peer device at predetermined time intervals or PDU intervals. (Supplementary Note 14) The apparatus of any one of Supplements 1 to 5, comprising means for providing a function of the lower layer or a second lower layer below the lower layer, the lower layer or the second lower layer function comprising means for discarding all lower layer or second lower layer Service Data Units (SDUs) corresponding to a set of upper layer PDUs when a discard timer for the SDUs corresponding to the set of upper layer PDUs expires. (Supplementary Note 15) The apparatus according to any one of Supplements 1 to 5, comprising: means for providing a function of the lower layer or a second lower layer lower than the lower layer, the function of the lower layer or the second lower layer comprising: means for discarding all lower-layer or second-lower-layer Service Data Units (SDUs) corresponding to a set of upper layer PDUs when it is confirmed that delivery has failed for one or more specific SDUs among a plurality of lower-layer or second-lower-layer SDUs corresponding to the set of upper layer PDUs. (Supplementary Note 16) The apparatus according to any one of Supplements 1 to 5, comprising: means for providing a function of the lower layer or a second lower layer lower than the lower layer, the function of the lower layer or the second lower layer comprising: means for discarding all lower-layer or second-lower-layer SDUs corresponding to a set of upper layer PDUs when it is confirmed that delivery has failed for a predetermined number of lower-layer or second-lower-layer Service Data Units (SDUs) corresponding to the set of upper layer PDUs. (Supplementary Note 17) The apparatus according to Supplementary Note 15 or 16, comprising means for determining delivery failure of one or more lower layer or second lower layer SDUs based on delivery status reports received from peer devices.(Supplementary Note 18) The apparatus according to any one of Supplements 1 to 17, wherein the intermediate layer is a Service Data Adaptation Protocol (SDAP) layer, and the lower layer is a Packet Data Convergence Protocol (PDCP) layer. (Supplementary Note 19) The apparatus according to any one of Supplements 1 to 18, wherein the upper layer is a PDU layer corresponding to PDUs carried on a PDU Session between a User Equipment (UE) and a Data Network (DN). (Supplementary Note 20) The apparatus according to any one of Supplements 1 to 19, wherein the apparatus is located in one radio access network node or distributed across multiple radio access network nodes. (Supplementary Note 21) The apparatus according to any one of Supplements 1 to 19, wherein the apparatus is located in User Equipment (UE). (Supplementary Note 22) A method performed by an apparatus for wireless communication, comprising: providing an intermediate layer function between an upper layer and a lower layer, the intermediate layer function comprising: identifying, from a first upper layer Protocol Data Unit (PDU) flow, boundaries of a plurality of upper layer PDU sets, each consisting of one or more upper layer PDUs, and mapping the plurality of upper layer PDU sets to a plurality of different data radio bearers based on one or more attributes of each upper layer PDU set. (Supplementary Note 23) A program for causing a computer to perform a method for wireless communication, the method comprising: providing an intermediate layer function between an upper layer and a lower layer, the intermediate layer function comprising: identifying, from a first upper layer Protocol Data Unit (PDU) flow, boundaries of a plurality of upper layer PDU sets, each consisting of one or more upper layer PDUs, and mapping the plurality of upper layer PDU sets to a plurality of different data radio bearers based on one or more attributes of each upper layer PDU set.(Supplementary Note 24) An apparatus for wireless communication providing an intermediate layer function between an upper layer and a lower layer, wherein the intermediate layer function comprises: means for selecting a subset of intermediate layer SDUs of high importance from an intermediate layer Service Data Unit (SDU) set corresponding to an upper layer Protocol Data Unit (PDU) set; and means for concatenating or assembling the subset of intermediate layer SDUs into an intermediate layer PDU. (Supplementary Note 25) The apparatus of Supplementary Note 24, wherein the intermediate layer is a Service Data Adaptation Protocol (SDAP) layer. (Supplementary Note 26) The apparatus of Supplementary Note 24, wherein the intermediate layer is a Packet Data Convergence Protocol (PDCP) layer. (Supplementary Note 27) The apparatus of any one of Supplements 24 to 26, wherein the intermediate layer function comprises means for generating a plurality of intermediate layer PDUs, each PDU containing a respective one of the remaining intermediate layer SDUs belonging to the intermediate layer SDU set. (Supplementary Note 28) The apparatus according to any one of Supplements 24 to 27, wherein the subset of intermediate layer SDUs corresponds to PDUs that must be received in order for the set of upper layer PDUs to be used in a peer device. (Supplementary Note 29) The apparatus according to any one of Supplements 24 to 28, wherein the intermediate layer is a Service Data Adaptation Protocol (SDAP) layer, and the lower layer is a Packet Data Convergence Protocol (PDCP) layer. (Supplementary Note 30) The apparatus according to any one of Supplements 24 to 29, wherein the upper layer is a PDU layer corresponding to PDUs carried on a PDU Session between a User Equipment (UE) and a Data Network (DN). (Supplementary Note 31) The apparatus according to any one of Supplements 24 to 30, wherein the apparatus is located in one radio access network node or distributed across multiple radio access network nodes.(Supplementary Note 32) The apparatus according to any one of Supplements 24 to 30, wherein the apparatus is located in User Equipment (UE). (Supplementary Note 33) A method performed by an apparatus for wireless communication, comprising providing an intermediate layer function between an upper layer and a lower layer, the intermediate layer function comprising: selecting a subset of important intermediate layer SDUs from an intermediate layer Service Data Unit (SDU) set corresponding to an upper layer Protocol Data Unit (PDU) set; and concatenating or assembling the subset of intermediate layer SDUs into an intermediate layer PDU. (Supplementary Note 34) A program causing a computer to perform a method for wireless communication, the method comprising: providing an intermediate layer function between an upper layer and a lower layer, the intermediate layer function comprising: selecting a subset of intermediate layer SDUs with high importance from an intermediate layer Service Data Unit (SDU) set corresponding to an upper layer Protocol Data Unit (PDU) set; and concatenating or assembling the subset of intermediate layer SDUs into an intermediate layer PDU. (Supplementary Note 35) An apparatus for wireless communication providing an intermediate layer function between an upper layer and a lower layer, the intermediate layer function comprising: means for discarding all intermediate layer SDUs belonging to an intermediate layer Service Data Unit (SDU) set corresponding to an upper layer Protocol Data Unit (PDU) set when a discard timer for the intermediate layer SDU set corresponding to the upper layer Protocol Data Unit (PDU) set expires. (Supplementary Note 36) The apparatus according to Supplementary Note 35, wherein a length of the discard timer is based on a delay budget for the corresponding upper layer PDU set.(Supplementary Note 37) The apparatus according to Supplementary Note 36, wherein the length of the discard timer is determined based on the sum of a first value set by a Radio Resource Control (RRC) layer and a second value corresponding to the delay budget. (Supplementary Note 38) The apparatus according to Supplementary Note 36 or 37, wherein the first value is based on the importance of the corresponding upper layer PDU set. (Supplementary Note 39) The apparatus according to any one of Supplements 35 to 38, wherein the intermediate layer is a Service Data Adaptation Protocol (SDAP) layer. (Supplementary Note 40) The apparatus according to any one of Supplements 35 to 38, wherein the intermediate layer is a Packet Data Convergence Protocol (PDCP) layer or a Radio Link Control (RLC) layer. (Supplementary Note 41) The apparatus according to any one of Supplements 35 to 40, wherein the apparatus is located in one radio access network node or distributed across multiple radio access network nodes. (Supplementary Note 42) The apparatus according to any one of Supplements 35 to 40, wherein the apparatus is located in User Equipment (UE). (Supplementary Note 43) A method performed by an apparatus for wireless communication, comprising providing an intermediate layer function between an upper layer and a lower layer, the intermediate layer function comprising, when a discard timer for an intermediate layer Service Data Unit (SDU) set corresponding to an upper layer Protocol Data Unit (PDU) set expires, discarding all intermediate layer SDUs belonging to the intermediate layer SDU set. (Supplementary Note 44) A program for causing a computer to perform the method for wireless communication, the method comprising providing an intermediate layer function between an upper layer and a lower layer, the intermediate layer function comprising, when a discard timer for an intermediate layer Service Data Unit (SDU) set corresponding to an upper layer Protocol Data Unit (PDU) set expires, discarding all intermediate layer SDUs belonging to the intermediate layer SDU set.(Supplementary Note 45) An apparatus for wireless communication providing an intermediate layer function between an upper layer and a lower layer, wherein the intermediate layer function comprises means for discarding all intermediate layer SDUs belonging to an intermediate layer Service Data Unit (SDU) set corresponding to an upper layer Protocol Data Unit (PDU) set when delivery failure of one or more intermediate layer SDUs belonging to the intermediate layer SDU set is confirmed. (Supplementary Note 46) The discarding means is configured to discard all intermediate layer SDUs belonging to the intermediate layer SDU set when delivery failure of one or more specific intermediate layer SDUs of high importance belonging to the intermediate layer SDU set is confirmed. (Supplementary Note 47) The apparatus of Supplementary Note 46, wherein the one or more specific intermediate layer SDUs of high importance carry a subset of upper layer PDUs belonging to the upper layer PDU set that must be received in order for the upper layer PDU set to be used in a peer device. (Supplementary Note 48) The device of Supplementary Note 45, wherein the discarding means is configured to discard all intermediate layer SDUs belonging to the intermediate layer SDU set when delivery failure of a predetermined number of intermediate layer SDUs belonging to the intermediate layer SDU set is confirmed. (Supplementary Note 49) The device of any one of Supplements 45 to 48, wherein the intermediate layer function comprises means for determining delivery failure of one or more intermediate layer SDUs based on a delivery status report received from a peer device. (Supplementary Note 50) The device of Supplementary Note 49, wherein the delivery status report is transmitted from the peer device in response to expiration of a timer in the peer device. (Supplementary Note 51) The device of Supplementary Note 49, wherein the delivery status report is transmitted from the peer device each time a predetermined number of intermediate layer SDUs or PDUs are successfully received. (Supplementary Note 52) The device of any one of Supplements 45 to 51, wherein the intermediate layer is a Service Data Adaptation Protocol (SDAP) layer.(Supplementary Note 53) The apparatus according to any one of Supplements 45 to 51, wherein the intermediate layer is a Packet Data Convergence Protocol (PDCP) layer or a Radio Link Control (RLC) layer. (Supplementary Note 54) The apparatus according to any one of Supplements 45 to 53, wherein the apparatus is located in one radio access network node or distributed across multiple radio access network nodes. (Supplementary Note 55) The apparatus according to any one of Supplements 45 to 53, wherein the apparatus is located in User Equipment (UE). (Supplementary Note 56) A method performed by an apparatus for wireless communication, comprising providing an intermediate layer function between an upper layer and a lower layer, the intermediate layer function comprising: discarding all intermediate layer SDUs belonging to an intermediate layer Service Data Unit (SDU) set corresponding to an upper layer Protocol Data Unit (PDU) set when delivery failure of one or more intermediate layer SDUs belonging to the intermediate layer SDU set is confirmed. (Supplementary Note 57) A program for causing a computer to perform a method for wireless communication, the method comprising providing an intermediate layer function between an upper layer and a lower layer, the intermediate layer function comprising, when a delivery failure of one or more intermediate layer SDUs belonging to an intermediate layer Service Data Unit (SDU) set corresponding to an upper layer Protocol Data Unit (PDU) set is confirmed, discarding all intermediate layer SDUs belonging to the intermediate layer SDU set.

[0109] This application claims priority based on Japanese Patent Application No. 2022-155413, filed on September 28, 2022, the disclosure of which is incorporated herein by reference in its entirety.

[0110] 1 UE 2 RAN 3 RAN node 4 Core network 5 PSA UPF 6 Data network 7 Application server

Claims

1. A wireless terminal providing a Packet Data Convergence Protocol (PDCP) layer function, comprising: The PDCP layer functions include discarding all SDUs belonging to a Service Data Unit (SDU) set when a discard timer associated with the SDU set of the PDCP layer expires; The length of the discard timer is set based on the importance of the set of SDUs.

2. A wireless terminal as described in claim 1, wherein the length of the discard timer is set based on the delay budget of the corresponding SDU set.

3. A wireless terminal as described in claim 2, wherein the length of the discard timer is determined based on the sum of a first value set by a Radio Resource Control (RRC) layer and a second value corresponding to the delay budget.

4. A method performed by a wireless terminal, comprising: Provides the Packet Data Convergence Protocol (PDCP) layer functionality, The PDCP layer functionality includes discarding all SDUs belonging to a Service Data Unit (SDU) set when a discard timer associated with the SDU set of the PDCP layer expires; A method according to claim 1, wherein the length of the discard timer is set based on the importance of the set of SDUs.

5. The method of claim 4, wherein the length of the discard timer is set based on a delay budget for the corresponding SDU set.

6. The method of claim 5, wherein the length of the discard timer is determined based on the sum of a first value set by a Radio Resource Control (RRC) layer and a second value corresponding to the delay budget.

7. A program for causing a computer to perform a method for a wireless terminal, comprising: The method provides Packet Data Convergence Protocol (PDCP) layer functionality; The PDCP layer functionality includes discarding all SDUs belonging to a Service Data Unit (SDU) set when a discard timer associated with the SDU set of the PDCP layer expires; The length of the discard timer is set based on the importance of the set of SDUs.

8. The program of claim 7, wherein the length of the discard timer is set based on a delay budget for the corresponding SDU set.

9. The program of claim 8, wherein the length of the discard timer is determined based on the sum of a first value set by a Radio Resource Control (RRC) layer and a second value corresponding to the delay budget.