Communication terminal, communication method, and program

Abstract

To reduce the transmission delay of a PDU set that is divided and transmitted.SOLUTION: A communication terminal that operates as UE (User Equipment) includes transmission means for transmitting a PDU set, which is one or more PDUs (Protocol Data Units) containing predetermined application data, and notification means for, when the PDU set is divided and transmitted, including division transmission information regarding the division transmission of the PDU set in a BSR (Buffer Status Report) and notifying a base station.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a communication device, a control method, and a program for performing mobile wireless communication. [Background technology]

[0002] The Third Generation Partnership Project (3GPP (registered trademark)) has formulated cellular communication standards. Standardization of virtual reality (XR) eXtended Reality (TR) is underway within the 3GPP cellular communication standards (hereinafter referred to as "3GPP standards"), and various use cases are described in TR26.928 (TR: Technical Report). Patent Document 1 also proposes improving UL (Uplink) scheduling delays by having a base station calculate the average wireless transmission size and estimate the amount of data remaining in the buffer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-5254 A Summary of the Invention [Problem to be solved by the invention]

[0004] In UL scheduling using BSR (Buffer Status Report), a 5G base station (gNB) allocates resources to UEs in UL time slots in order based on the transmission buffer capacity reported by the UE via BSR. Therefore, depending on the scheduler's operation, the PDU set that makes up the XR frame may be divided into multiple parts and transmitted over the air. When a PDU set is divided into multiple parts and transmitted, the base station can receive PDUs from the beginning to the middle of the divided PDU set, but the remaining untransmitted PDUs cannot be received until the next UL transmission timing, which may result in a PDU set reception timeout.

[0005] An object of one aspect of the present invention is to provide a communication terminal, a communication method, and a program that enable a reduction in transmission delay of a PDU set that is divided and transmitted. [Means for solving the problem]

[0006] A communication terminal according to one embodiment of the present invention is a communication terminal that operates as a UE (User Equipment) and has a transmission means for transmitting a PDU set, which is one or more PDUs (Protocol Data Units) containing specified application data, and a notification means for, when the PDU set is divided and transmitted, including division transmission information regarding the division transmission of the PDU set in a BSR and notifying a base station. [Effects of the Invention]

[0007] According to one aspect of the present invention, it is possible to provide a communication terminal, a communication method, and a program that can reduce the transmission delay of a PDU set that is divided and transmitted. [Brief explanation of the drawings]

[0008] [Figure 1] An example of the configuration of a wireless communication system that supports XR [Figure 2] Diagram showing an example of UE hardware configuration [Figure 3] A diagram showing an example of the hardware configuration of a base station [Figure 4] An example showing the U-Plane protocol stack [Figure 5] Example of UL scheduling sequence using conventional BSR [Figure 6] Diagram of an example configuration when an XR frame is divided [Figure 7] Embodiment 1: Example of UL scheduling sequence using BSR [Figure 8] Example of a flowchart for BSR / SR notification in the UE [Figure 9]BSR message format example [Figure 10] Example of a flowchart for a base station assigning UEs using BSR / SR [Figure 11] Embodiment 2: Example of UL scheduling sequence using SR [Figure 12A] SR message format example (part 1) [Figure 12B] SR message format example (part 2) DETAILED DESCRIPTION OF THE INVENTION

[0009] The following describes embodiments of the present invention with reference to the drawings. Note that the following embodiments do not limit the scope of the invention as claimed, and not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention.

[0010] <Explanation of the operation of a 5G system that supports XR based on 3GPP specifications> FIG. 1 shows an example configuration of a wireless communication system that supports XR in this embodiment. In the following description, embodiments and examples of the present disclosure will be described with reference to a 5G system. However, it should be understood that the present disclosure is not intended to be limited to a 5G system and can be used in any wireless communication system that supports XR or a similar service. For example, the present disclosure can be applied to systems other than 5G (e.g., 5G Advanced, 6G, etc.). Furthermore, when this embodiment is applied to 6G, the base station may be a 6G base station, and the core network (CN) may be a 6GCN. Furthermore, the base station serving as the MN (Master Node) may be a gNB, and the base station serving as the SN (Secondary Node) may be a 6gNB. In other words, this embodiment can also be applied to DC (Dual Connectivity) of different RATs (Radio Access Technologies), such as 5G and 6G.

[0011] The system 100 includes user equipment (UE) 101, 151, base stations (gNB) 110, 111, and a 5G core network (CN) 102. The UE 101 and UE 151 can wirelessly communicate with one or more CNs via one or more radio access networks (RANs). The CN 102 includes a user plane function (UPF) 161 and a control plane function (C-plane Function) 162. The control plane function includes an access and mobility management function (AMF) and a session management function (SMF). The UE 101 and UE 151 may be wearable terminals that realize augmented reality, such as helmets or goggles. The UE 101 and UE 151 may also be wireless communication devices, apparatuses, or terminals, IoT devices, or machine type communication (MTC) devices. Furthermore, the UE 101 and the UE 151 may be any wireless device such as a device-to-device (D2D) terminal, a user device, etc. Furthermore, the user device may be, for example, a smartphone, a desktop computer, a mobile phone, a tablet, a camera, a game console, a wearable device, etc.

[0012] In the following description, when there is no particular need to distinguish between the UE 101 and the UE 151, they will be referred to as "UE." Furthermore, when there is no particular need to distinguish between the base station 110 and the base station 111, they will be referred to as "base station."

[0013] The base stations 110, 111 are network nodes that provide access points to the CN 102 for UEs and are part of the radio access network. In the following, the terms RAN node, base station, and base station are used interchangeably. The base stations 110 and 111 are interconnected by an Xn interface (specified, for example, in TS 38.423) implemented on a wired or wireless link 130. Each base station is connected to the CN 102 by an NG interface (specified in TS 38.413) implemented on wired or wireless links 140 and 141.

[0014] Each of these base stations controls one or more cells. For example, base station 110 controls cell 120, and base station 111 controls cell 121. A cell is a geographical area of ​​a wireless network defined by the frequency used to transmit data and can be uniquely identified by an identifier broadcast throughout the geographical area. Each base station 110, 111 can serve several UEs 101, 151. After a UE establishes an RRC connection with a base station, the base station to which the UE is connected is called the UE's serving base station. The cell controlled by the serving base station and containing the UE is called the serving cell. Various protocols are defined in the Uu interface between the base station and the UE as protocol sublayers of the user plane (U-Plane), such as the Service Data Adaptation Protocol (SDAP) and Packet Data Convergence Protocol (PDCP), the Radio Link Control (RLC) Protocol, the Medium Access Control (MAC) Protocol, and the Physical Layer (PHY) Protocol. In addition, protocols such as Radio Resource Control (RRC), PDCP, RLC, MAC, and PHY are specified as protocol sublayers of the control plane (C-Plane).

[0015] In this embodiment, the UE 101 transmits and receives XR data of one or more multicast XR sessions established with the XR application server 103. An XR application is an example of a "predetermined application." To realize a high-quality XR service, a large amount of XR data, including image (video) data and audio data, is transmitted and received between the XR application server 103 and the UEs 101 and 151. Therefore, the system 100 is required to transmit the large amount of XR data transmitted and received between the XR application server 103 and the UEs 101 and 151 while maintaining low latency and high reliability. According to the 3GPP specifications, application data packets generated at the XR application level are transported using a series of Protocol Data Units (PDUs) or Packet Data Units (PDUs). Application data contains one or more application data packets. In the downlink (DL), the PDUs are formatted by the PDU layer in the core network (CN). Similarly, in the uplink (UL), the PDUs are formatted by the PDU layer in the UE.

[0016] A PDU set refers to one or more PDUs used to carry the payload of a unit of information (such as a frame of an XR service, a video slice, etc.) generated at the XR application level.

[0017] According to TS38.300 (TS: Technical Specification), the delimitation of PDU sets is not provided by the application but is generated by the CN's media transport protocol packet inspection.

[0018] In some implementations, all PDUs in a PDU set are required for the application layer to use the corresponding information unit. In other implementations, the application layer can recover some or all of the information unit even if some PDUs are missing. For example, one PDU set may contain the data for one image or frame from a video stream.

[0019] The XR data generated by the XR application server 103 is transmitted to a User Plane Function (UPF) 161 of the CN 102 via a data network 160. The XR data is also transmitted to the base station 111 via a transport bearer (or a GTP-U tunnel) 106. The XR data is also transmitted from the base station 111 to the UE 101 via a Data Radio Bearer (DRB) 153.

[0020] The UE 151 receives data via the DRB 154. A radio bearer is a set of PHY (Layer 1) and MAC (Layer 2) parameters that enable higher layer data connectivity between the UE and the base station. 5G defines several types of radio bearers, including signaling radio bearers (SRBs) for the control plane, data radio bearers (DRBs) that enable point-to-point communication with one UE in the user plane (e.g., unicast), and multicast radio bearers (MRBs) that enable point-to-point and point-to-multipoint communication with multiple UEs in the user plane (e.g., multicast / broadcast).

[0021] The XR data generated by the XR applications of UE 101 and UE 151 is transmitted to the XR application server 103 via the base station 111 and the core network 102. The base station is responsible for scheduling UL traffic and allocates (schedules) radio resources to each UE based on one of the following mechanisms: A: Dynamic scheduling where each UE issues requests; the UE dynamically issues requests for radio resources. B: Semi-static scheduling by the base station; configured to issue periodic resource allocations to at least one UE. C: Scheduling based on the buffer status report (BSR) from the UE; resources are allocated based on the BSR indicating the amount of UL data stored in the UE's buffer.

[0022] The BSR method in C reduces the need for periodic transmissions between the base station and the UE compared to other methods, and also reduces the computational load in the UE, thus reducing the overhead in the network.

[0023] The buffer status reporting mechanism operates based on logical channel groups (LCGs: Logical Channel Group), and the UE reports the buffer status of the logical channel group to the base station collectively. Multiple MAC logical channels (LCHs: Logical CHannel) can be mapped to an LCG. The BSR trigger conditions and the BSR format are defined in TS38.321. The base station can receive the BSR and use the BSR to perform resource scheduling. For example, the base station schedules to prioritize the LCG with the most available data while preventing resource depletion in the low-throughput LCG.

[0024] <Hardware Configuration of UE> FIG. 2 is a hardware configuration block diagram of a UE. The UE 101 and UE 151 in FIG. 1 have a hardware configuration similar to that of the UE 205 shown in FIG. 2. The UE includes components for transmitting and receiving communications. For example, the UE includes at least one of a UE communications manager 220, an I / O controller 255, a transceiver 235, a set of antenna controllers 245, a data storage unit 225, and a processor (CPU: central processing unit) 215. All of these elements can communicate with each other. The data storage unit 225 includes random access memory (RAM), read-only memory (ROM), or a combination of both. Alternatively, the data storage unit 225 can include a mass storage device such as a disk or solid-state drive (SSD). Basic input / output system (BIOS) instructions can be stored in the data storage unit 225.

[0025] The CPU 215 is configured to execute machine-readable instructions. Execution of these machine-readable instructions causes the UE to perform various functions. These functions may relate to communication or interaction with peripheral devices, such as a keyboard, screen, mouse, etc. (not shown in FIG. 2). The processor may execute an operating system, such as iOS®, Windows®, Android®, etc., and the CPU 215 may be a single processor or may include two or more processors that perform the processing necessary for the operation of the UE 205.

[0026] The I / O controller 255 enables these interactions with external peripherals by providing the necessary hardware and managing input and output signals. For example, the I / O controller 255 may interact with all or part of an image capture device, an image rendering device, an audio capture device, an audio rendering device, or a sensor device capable of determining a location of use.

[0027] The transceiver 235 is configured to provide bidirectional wireless communication with other wireless devices. For example, the transceiver 235 may provide a modem (e.g., a router) and a frequency shifter necessary to connect to one or more wireless networks such as Wi-Fi, Bluetooth, LTE, 5G NR, etc. The transceiver 235 may include a PDCP transmitter and receiver. The PDCP transmitter and the PDCP receiver may be implemented by the CPU 215. The PDCP transmitter and the PDCP receiver may be software-only functions implemented by the CPU 215.

[0028] The wireless communication uses an antenna 246 that is matched to the spectrum of the frequency transposed signal issued by the baseband modem. The antenna 246 may be limited to a single antenna, but preferably includes multiple antennas (antenna sets) to provide beamforming capabilities.

[0029] The UE communication management unit 220 controls the establishment of communication between the UE and the radio access network. The UE communication management unit 220 may also be configured to control communication between the UE and the base station based on instructions from the base station. The UE receives information from the base station indicating the allocation of radio resources available for communication between the UE and the base station. Thus, the UE knows when and how often to receive data. Furthermore, the UE knows when and how often data can be transmitted. The UE communication management unit 220 implements a Uu interface.

[0030] <Base station hardware configuration> FIG. 3 illustrates the hardware blocks of a base station. The base station 110 and the base station 111 in FIG. 1 have a similar hardware configuration to the base station device 305 shown in FIG. 3. The base station device 305 includes components for transmitting and receiving communications. For example, the base station device 305 includes a base station communication manager 320, a core network communication manager 355, a transceiver 335, and a set of antenna controllers 345 and antennas 346. The base station device 305 also includes a data storage unit 325, a processor (e.g., a CPU) 315, and an inter-station communication manager 365. All of these elements can communicate with each other. The base station communication manager 320 is configured to control communications with multiple UEs. The base station communication manager 320 is responsible for establishing, controlling, and releasing communications with multiple UEs. For example, the base station communication manager 320 implements a Uu interface. The base station communication manager 320 includes a scheduler that allocates time-frequency slots to different UE communications. Information regarding the schedules of these slots is periodically transmitted to the relevant UEs.

[0031] The CN communication manager 355 manages communications between the base station and the core network. The CN communication manager 355 may provide a standardized NG interface defined in 3GPP standards to support these communications. The transceiver 335 is configured to provide bidirectional wireless communications with other wireless devices. These other wireless devices may be UEs or other base stations. The transceiver 335 provides the modem and frequency shifter necessary to simultaneously connect multiple UEs using different frequency carriers in time division duplex (TDD) or frequency division duplex (FDD). The transceiver 335 may include a PDCP transmitter and a PDCP receiver. The PDCP transmitter / receiver may be implemented by the CPU 315. The PDCP transmitter / receiver may be a software-only function implemented by the CPU 315. The transceiver 335 is connected to the antenna controller 345. The antenna 346 may be limited to one antenna, but preferably includes multiple antennas (antenna sets) to provide beamforming capabilities. The data storage unit 325 includes RAM, ROM, or a combination thereof. Alternatively, or in addition, data storage 325 may include a mass storage device such as a disk or SSD. BIOS instructions may be stored in data storage 325 to support the operating system. Inter-station communication manager 365 manages communications with other base stations and may provide a standardized Xn interface to support these communications.

[0032] <Explanation of the U-Plane protocol stack for data transmission> Figure 4 is a block schematic diagram 400 of a U-Plane protocol stack representing data transmission in the 5G NR system shown in Figure 1. The DN (Data Network) in Figure 5 corresponds to the XR application server 103 in Figure 1.

[0033] Details of the U-Plane protocol stack are described in TS23.501 and TS38.300. In the downlink direction (DL), the XR application server 103 connects to the U-Plane Function (UPF) 161 via the data network 160 at the level of the PDU layer 402. The PDU layer corresponds to the PDUs transmitted between the UE and the DN via a PDU session. Depending on the PDU session type, the PDU corresponds to an IPv4 packet, an IPv6 packet, or an Ethernet frame. At the start of a PDU session, the CN provides the UPF, the base station, and the UE with PDU session QoS parameters. The PDU session QoS parameters include PDU set QoS parameters. The PDU set QoS parameters include the following information:

[0034] PDU Set Delay Budget (PSDB): indicates the time from when the UE or UPF (UE in DL, UPF in UL) receives the first PDU in a PDU set until all PDUs are successfully received.

[0035] PDU Set Error Rate (PSER): Upper limit of the loss rate of a PDU set between a UE and a base station.

[0036] PDU Set Integrated Handling Information (PSIHI): indicates whether the application needs to use all PDUs in the PDU set.

[0037] 4, unless otherwise specified, PDUs refer to packets processed by PDU layer 402. PDUs belonging to one of the other layers are referred to with a prefix corresponding to the respective layer name, e.g., PDCP PDU or MAC PDU. When a PDU arrives at the UPF PDU layer 402, the UPF performs application packet inspection to determine the PDU set boundary. The PDU set information described in TS38.300 is determined by the UPF and sent to the NG-RAN via the GTP-U header. The PDU set information includes the following information:

[0038] PDU set sequence number; Display of the end PDU of a PDU set; PDU sequence number within the PDU set; PDU set size; Importance of a PDU set: Information identifying the relative importance of a PDU set compared to other PDU sets within the same QoS flow.

[0039] The application in the UL is located on the UE. The UE obtains the PDU session QoS parameters from the CN when the PDU session is established (the PDU session establishment procedure is defined in TS23.502, chapter 4.3.2). When the PDU generated by the application 403 arrives at the UE PDU layer 402, the UE performs application packet inspection to determine the PDU set boundary.

[0040] In both DL and UL, the application 103 sends and receives data to and from the NG-RAN via a GTP (GPRS Tunneling Protocol) tunnel (defined in TS 29.281), where GPRS stands for General Packet Radio Service.

[0041] The DL UPF detects the PDU set information and obtains a set of mapping rules from the CN. The mapping rules define how to map each PDU set to a QoS flow. The QoS flow is identified by an identifier, and the GTP-U PDUs are marked according to the determined QoS flow identifier. The relay layer 406 maps the PDU set information and QoS flow identifier to the GTP-U PDUs to the SDAP QoS flow in the base station. During an XR session, multiple PDU sets can be mapped to the same QoS flow. Also, one or more PDU sets can be mapped to different QoS flows. Next, according to TR38.835, in a first alternative arrangement, each SDAP QoS flow can be mapped to a different PDCP Data Radio Bearer (DRB). In a second alternative arrangement, all SDAP QoS flows from the same XR session can be mapped to a PDCP DRB.

[0042] The UL UE detects PDU set information in the PDU layer 402 and obtains a set of mapping rules from the CN. The mapping rules define how each PDU set is mapped to a QoS flow. The UE maps XR PDUs to the associated SDAP QoS flow according to the filtering rules. Similar to DL, multiple PDU sets can be mapped to the same or different QoS flows in an XR session during UL.

[0043] The UL application layer 403 generates at least one application flow (e.g., one or more video flows, one or more audio flows, etc.) destined for the XR application server 103. Next, the PDU layer 402 arranges the application flow into PDU sets. At least one or each application flow is divided into multiple PDU sets of the same or different types, and each PDU set type is mapped to a QoS flow. Thus, multiple application flows can be multiplexed into one QoS flow, or each application flow can be mapped to a different QoS flow. Alternatively, an application flow can be split into multiple QoS flows. Next, the SDAP layer 407 maps the QoS flows to DRBs, and at least one or each radio bearer is handled by a dedicated PDCP entity. For QoS flows, multiple application flows can be multiplexed into one DRB, or each application flow can be mapped to a separate DRB. Alternatively, an application flow can be split into multiple DRBs. Then, at least one DRB is mapped to at least one RLC channel, which is then mapped to at least one MAC logical channel (LCH).

[0044] According to known network configurations, to schedule UL traffic, the base station MAC layer 410 allocates radio resources to the UE based on at least one of the mechanisms A to C described above.

[0045] In certain situations, a PDU Set Delay Budget (PSDB) may be included as part of the XR data (as defined in TS38.321). The application and advantages of the delay status reporting mechanism will be explained with reference to Figures 1 and 4. During DL, the UPF 161 calculates the XR data from the XR application server 102 and inserts the calculated information into the GTP-U header 404 (as described in TS29.281). GTP-U is a protocol used by the UPF to forward data from the CN 102 to the base station 110, 111 (transmitted from the CN via a GTP-U tunnel). When the PDU arrives at the base station 110, 111, the GTP-U header 404 is removed. This means that the PDU set information is not transmitted to the UE 101, 151 via the SDAP layer 407 (as described in TS37.324). Thus, during DL from the base station to the UE, the PDU set information is not provided "in-band." Therefore, the UE 101, 151 cannot access the PDU set information.

[0046] During the UL, the PDU set information (e.g., calculated by the UE PDU layer 402) is not inserted into the header as shown in Figure 4. Therefore, the PDU set information is not provided "in-band" during the uplink from the UE 101, 151. Therefore, the base station 110, 111 does not have access to the PDU set information.

[0047] In summary, at all protocol layers (including the RLC layer 402 and the PDCP layer 401), the receiving entity, whether in DL or UL, does not know the PDU set information. On the transmitting side, all layers below the SDAP layer 407 do not have access to the "in-band" PDU set information. However, internal mechanisms can be used to associate "out-of-band" PDU set delimitation information with each transmitted PDU. An example of such an internal mechanism could use PDU context information to determine the PDU set delimitation information.

[0048] According to an exemplary method during DL, the GTP-U receiving entity 404 at the base station can associate "out-of-band" PDU set delimitation information with each PDU and pass the delimitation information to the transmitting entity of the PDCP layer 401. This passes the PDU set delimitation information from the base station to the UE via the PDCP layer 401. Then, for the UL, the UE PDU layer 402 associates "out-of-band" PDU set delimitation information with each PDU and passes the information to the transmitting entity of the UE PDCP layer. <Issues with conventional UL scheduling based on 3GPP specifications> Figure 5 shows an example of a UL scheduling sequence using a conventional BSR. When uplink (UL) data to be transmitted to the base station 111 occurs, the UE 101 requests scheduling by transmitting a BSR indicating the amount of uplink data remaining in the base station 111's buffer (TS38.321 V18.0.0).

[0049] When the UE 101 is assigned a dedicated UL resource, it transmits a scheduling request (SR) to the base station 111 (S501).

[0050] In response to the scheduling request transmitted by UE 101 in S501, base station 111 transmits a UL Grant including UL allocation resource information (S502). UE 101 transmits UL data on a PUSCH (Physical Uplink Shared CHannel) at the timing of the UL slot specified by the base station based on the UL allocation resource information received in S502 (S503). If untransmitted data remains in the buffer after transmitting the UL data in S503, UE 101 transmits the remaining buffer amount in a BSR (S505). The BSR transmitted by UE 101 to base station 111 calculates and reports the buffer retention amount for each logical channel group (LCG) in which data exists. In other words, UE 101 reports the buffer retention amount for each LCG consisting of one or more logical channels (LCHs). Here, it is assumed that the UE uses only one LCG.

[0051] Here, a mechanism for the case where data remains in the buffer even after UE 101 transmits data at S503 will be described with reference to FIG. 6. In the description of FIG. 6, a combination of an SDU and a header (H) is referred to as a PDU. In FIG. 6, there is a PDU set 601 consisting of three PDUs (IP packets 602 to 604) in the PDU layer. Here, PDU set 601 is considered to be equivalent to the PDU set that is the transmission / reception unit of an XR frame. In the RLC layer, RLC PDU 605 and RLC PDU 606 are integrated into one RLC PDU (LCH1) and stored in the same transport block (TB) via MAC. Note that an RLC PDU refers to an RLC SDU with a header (H) added. PDCP PDU 607 (corresponding to the higher-level PDCP PDU) is divided into two RLC PDUs 608 and 609 (LCH2), one segment is stored in the transport block, and the other segment remains. This is called a remaining segment. The size of the UL transport block varies depending on the amount of resources allocated by the base station based on factors such as radio quality. Therefore, as described above, there are cases where the two divided RLC SDUs 608 and 609 (the upper PDCP PDU 607) cannot be transmitted in the transport block 610 of a single TTI (Time To Interval). That is, under the current BSR control, depending on the size of the transport block, it may not be possible to transmit all PDUs included in one PDU set in one transport block. If it is not possible to transmit all PDUs in one transport block, the UE 101 has no choice but to store the remaining PDUs in a transport block 611 transmitted at a different time. In this way, if multiple PDUs included in a PDU set are divided and stored in multiple transport blocks transmitted at different times, a delay may occur in the transmission of all PDUs included in the PDU set.

[0052] Assume that the PDU segmentation described above occurs in FIG. 5. In the example of FIG. 5, UE 101, UE 151, and base station 111 transmit and receive radio signals using TDD (Time Division Duplex) with a frame configuration that takes into account synchronization with LTE. Also, assume that the data volume of a PDU set is 2,500 bytes. The size of one UL transport block varies depending on the radio quality, but for convenience of explanation, it is assumed to be 1,000 bytes. Assume that the transmission buffer of UE 101 in FIG. 5 contains 2,500 bytes of transmission data as the PDU set data, and that the TB size of one TTI is 1,000 bytes in S503. In this case, UE 101 transmits 1,000 bytes of data to base station 111 in S503, and notifies base station 111 by BSR in S505 that there is 1,500 bytes of untransmitted data in the transmission buffer. In addition, the UE 151 transmits a scheduling request (SR) to the base station 111 in the same slot (TTI) (S504).

[0053] If the UEs have the same priority, base station 111 allocates UL slots to the UEs in the order of reception timing, so it transmits a UL Grant (S506) to UE 151 and then transmits a UL Grant (S507) to UE 101.

[0054] Here, because base station 111 is communicating using synchronous TDD, the timing at which base station 111 is assigned UL resources is the next UL slot (eight slots later). As described above, base station 111 transmitted a UL Grant to UE 151 first, and therefore UE 151 transmits UL data on the PUSCH earlier than UE 101 (S508). Therefore, UE 101 transmits 1000 bytes of data from the 1500 bytes of data remaining in the buffer in the slot with the next UL transmission timing (one slot later) after the slot in which UE 151 transmitted the UL data (S509). However, because 500 bytes remain in the buffer, UE 101 notifies base station 111 of a BSR for 500 bytes in the same slot (S510). After this, the base station 111 transmits an UL Grant (S511) to the UE 101 in response to the BSR (S510), but the UE 101 waits until the next UL transmission timing (eight slots later) before transmitting the remaining 500 bytes of UL data (S512). Thus, when the UL data transmission of the UE 101 is considered as an XR frame (PDU set), a delay of 9.5 ms (19 slots, assuming a subcarrier spacing of 30 kHz) occurs from S503, when the transmission of UL data including the PDUs of the PDU set begins, to S512, when the transmission of the final UL data of the PDU set is completed. This delay is assumed for two UEs, but if there are multiple UEs with the same priority, there is a high possibility that a delay will occur for each of the existing UEs.

[0055] <First embodiment: UL scheduling based on notification of divided transmission information using BSR> In response to the problem with the conventional UL scheduling described using Fig. 5, an example of a method for solving the waiting time for receiving a PDU set by notifying the UE of segmented transmission information for a PDU set including an XR frame using a BSR will be described using the sequence in Fig. 7. In the example of Fig. 7, as in Fig. 5, it is assumed that the UE 101, UE 151, and base station 111 transmit and receive radio signals using TDD with a frame configuration that takes into account synchronization with LTE. It is also assumed that the data size of the PDU set is 2500 bytes. For convenience of explanation, it is also assumed that the size of one UL transport block is 1000 bytes.

[0056] When UE 101 is assigned individual UL resources, it transmits a scheduling request to base station 111 (S701). In response to the scheduling request transmitted in S701, UE 101 receives from base station 111 a UL Grant including information on UL resources to be assigned to UE 101 (S702). UE 101 transmits UL data (PDU set) on PUSCH in accordance with the assigned UL resources (S703). At this time, UE 101 transmits 1000 Bytes of UL data to base station 111 in accordance with the UL Grant (S703). Furthermore, triggered by the presence of 1500 Bytes of untransmitted data remaining in the transmission buffer, which is an untransmitted PDU in the PDU set, UE 101 notifies base station 111 of the BSR containing information indicating the segmented transmission of the PDU set (S705). The information indicating the segmented transmission of the PDU set will be described later.

[0057] In addition, the UE 151 transmits a scheduling request (SR) to the base station 111 in the same slot (S704).

[0058] Here, the process in which the UE 101 notifies the BSR that an XR frame (PDU set) will be segmented and transmitted over the radio section will be described with reference to the flowchart in Fig. 8. First, a PDU set is transferred from an upper layer such as the RLC layer of the UE 101 to the MAC layer (S801). Next, the UE 101 determines whether the PDU set will be segmented and transmitted using multiple transport blocks with different transmission timings (S802). For example, the UE 101 may detect that the PDU set will be segmented and transmitted using multiple transport blocks by comparing the data size of the PDU set with the transport block size.

[0059] When UE 101 detects that a PDU set is to be segmented and transmitted using multiple transport blocks with different transmission timings, it operates as follows: In other words, it creates a BSR that adds information indicating the segmented transmission of the PDU set to the buffer retention amount information specified in the 3GPP specifications (S803). In the following description, the information indicating the segmented transmission of the PDU set is referred to as "segmented transmission information." If there is no PDU set to be segmented and transmitted in S802 (i.e., if it is determined that all data in the PDU set can be transmitted in a single transport block), UE 101 creates a BSR that includes only buffer retention amount information and does not include segmented transmission information (S804).

[0060] Regarding S803, an example of the message format of a BSR in which segment transmission information has been added is shown in Figure 9. LCG-ID (901) and Buffer Size (902) are existing BSR parameters specified in 3GPP (defined in TS38.321). Segment transmission information (PDU set segment information) 903 is a parameter added to the BSR in this embodiment. The segment transmission information includes the following multiple parameters.

[0061] (1) PDU set division flag

[0062] (2) Sequence Number (SN) of the PDU set, SN of the last PDU sent in the PDU set, SN of the last PDU in the PDU set

[0063] (3) XR frame type (priority: I frame, P frame, B frame)

[0064] (4) PDU set importance (information identifying the relative importance of a PDU set compared to other PDU sets within the same QoS flow)

[0065] (5) Number of PDU sets divided (number of PDU sets when multiple PDUs are divided into one or more PDU sets)

[0066] (*If there are multiple UEs that meet the same conditions (1) and (2), the priority of the UEs is determined based on (3), (4), and (5).) An example of the setting parameters for (2) above is shown below.

[0067] [PDUset_SN=PDUset#1, PDU_segment_SN=PDU#8, PDUset_endPDU_SN=PDU#10] The scheduling operation performed by a base station that receives a BSR of the proposed method from a UE is shown in the flowchart of Figure 10. After receiving the BSR of the proposed method in S1001, the base station checks whether the BSR contains segmentation transmission information (S1002). If segmentation transmission information is present, the base station determines whether it has received BSRs containing segmentation transmission information from multiple UEs (S1003). If it has received BSRs containing segmentation transmission information from multiple UEs, it prioritizes UEs with a smaller proportion of remaining data in the PDU set (untransmitted PDUs remaining in the buffer) and allocates consecutive UL slots equal to the number of times the PDU set is divided (S1004). If the base station 111 receives a single UE with a BSR containing segmentation transmission information, it allocates UL resources preferentially over other UEs that have received an existing BSR (which can transmit all PDUs in the PDU set) (S1005). If there is no UE that has received "segmentation transmission information," the base station 111 allocates resources to the UEs that have received the BSR in order (S1006).

[0068] 7, when the base station 111 is notified in S705 by the UE 101 that the PDU set will be divided and transmitted, the base station 111 transmits to the UE 101 an UL Grant equal to the number of times the PDU set is divided (here, two times) in accordance with the base station flowchart in Fig. 10 (S706).Then, the base station 111 transmits an UL Grant to the UE 151 (S707).

[0069] For the two UL slots eight slots after this timing, base station 111 preferentially allocates the remaining two PDU sets (1000 Bytes, 500 Bytes) for UE 101. Therefore, after UE 101 transmits the remaining 1000 Bytes of UL data on the PUSCH (S708), it transmits the remaining 500 Bytes of UL data on the PUSCH in the next slot (S709). UE 151 is then permitted to transmit UL data (S710). The proposed UL scheduling makes it possible to transmit UE 101's divided PDU sets in 12 slots, improving the delay by 7 slots compared to the 19 slots of the conventional method.

[0070] <Second embodiment: UL scheduling based on notification of divided transmission information using SR> In response to the problem with the conventional UL scheduling described with reference to FIG. 5, an example of a method for solving the waiting time for receiving a PDU set by using an SR to notify segmentation and transmission of a PDU set including an XR frame will be described with reference to the sequence in FIG. 11. The difference from the first embodiment is that the message notifying segmentation information of a PDU set is changed from a BSR to an SR. The flowchart (FIG. 8) in which a UE determines segmentation and transmission, and the flowchart (FIG. 10) in which a base station performs UL scheduling based on receiving segmentation information from the UE, are the same as those in the first embodiment. In the example of FIG. 11, similar to FIG. 5, it is assumed that the UE 101, UE 151, and base station 111 transmit and receive radio signals using TDD with a frame configuration that takes synchronization with LTE into consideration. It is also assumed that the data size of a PDU set is 1800 bytes. For ease of explanation, it is also assumed that the size of one UL transport block is 1000 bytes.

[0071] In FIG. 11 , it is assumed that UE 101 is assigned individual UL resources capable of transmitting an SR. For example, it is assumed that the data size of a PDU set is 1800 bytes, and the TB size that can be transmitted in one TTI in a radio section is 1000 bytes. In this case, before transmitting the SR, UE 101 determines that there is a possibility that the PDU set will be segmented and transmitted using multiple transport blocks with different transmission timings. Note that, because UE 101 has not yet received UL resources assigned by a UL grant, strictly speaking, it is not possible for UE 101 to determine whether the PDU set will be transmitted using a single transport block without segmentation, or whether the PDU set will be segmented and transmitted using multiple transport blocks. Therefore, in the second embodiment, UE 101 may store an average transport block size used when transmitting UL data. Furthermore, UE 101 may determine, based on the average transport block size, whether the PDU set will be segmented and transmitted using multiple transport blocks with different transmission timings. Alternatively, when transmitting a PDU set including an XR frame, the UE 101 may always determine that the PDU set is to be segmented and transmitted, or may determine that the PDU set is to be segmented and transmitted if the data size of the PDU set is equal to or greater than a predetermined threshold. The predetermined threshold may be set in advance in the UE 101 by RRC signaling.

[0072] When it is determined that the PDU set is to be segmented and transmitted, the UE 101 transmits the segmented transmission information by including it in the SR parameters according to the flowchart of Fig. 8. Fig. 12A and Fig. 12B show examples of the format of the segmented transmission information to be added to the SR parameters. Upon receiving a scheduling request (S1101) including segmentation transmission information from UE 101, base station 111 operates as follows. That is, according to FIG. 10, base station 111 transmits to UE 101 an UL grant allocating consecutive slots (two consecutive slots in this case) equal to the number of segments of the PDU set (S1102). UE 101 transmits two consecutive slots of UL data on the PUSCH in accordance with the UL grant (S1103, S1104). As a result, the UL data of the PDU set segmented and transmitted from UE 101 can be transmitted using control (eight slots) that minimizes the delay due to segmentation. At this time, UE 151 transmits a scheduling request to base station 111 in the same slot (S1105), receives an UL grant (S1106) from base station 111, and transmits the UL data on the PUSCH (S1107). In this case, since UE 101 has already completed UL data transmission of the PDU set, it is not affected by UL scheduling by UE 151, and the delay time does not increase.

[0073] <Other embodiments> The UE 101 may transmit a PDU set including XR data when transmitting UL data for the first time after establishing a connection with the base station. This enables the XR data to be quickly transmitted to the application server.

[0074] When the UE 101 transmits a BSR for the first time after establishing a connection with the base station, the UE 101 may transmit a BSR including segmented transmission information to the base station. At this time, the segmented transmission information may include information indicating at least the data length of the PDU set. This allows the base station to quickly recognize that the UE is attempting to transmit XR data, and allows the base station to allocate a large number of UL resources to the UE in a short period of time.

[0075] The present invention can also be realized by supplying a program that realizes one or more functions of each of the above-described embodiments to a system or device via a network or a storage medium, and having one or more processors in the computer of the system or device read and execute the program. It can also be realized by a circuit (e.g., ASIC or FPGA) that realizes one or more functions. ASIC is an abbreviation for Application Specific Integrated Circuit. FPGA is an abbreviation for Field Programmable Gate Array.

[0076] The following additional notes are provided regarding the above-described embodiments.

[0077] [Appendix 1] A communication terminal that operates as UE (User Equipment), a transmitting means for transmitting a PDU set, which is one or more PDUs (Protocol Data Units) including predetermined application data; a notification means for notifying a base station of segmented transmission information regarding the segmented transmission of the PDU set in a BSR (Buffer Status Report) when the PDU set is segmented and transmitted; A communication terminal comprising:

[0078] [Appendix 2] the transmitting means divides the PDU set into a plurality of transport blocks having different transmission timings and transmits the transport blocks; The communication terminal described in Supplementary Note 1, characterized in that when the PDU set is divided into multiple transport blocks with different transmission timings and transmitted, the notification means includes the division transmission information in the BSR and notifies the base station.

[0079] [Appendix 3] The communication terminal described in Appendix 1 or 2, characterized in that the notification means includes the fragmented transmission information in the BSR when triggered by the fact that an untransmitted PDU in a PDU set remains in a transmission buffer.

[0080] [Appendix 4] The notifying means adds a parameter of the divided transmission information to the BSR and notifies the base station. 4. The communication terminal according to claim 1.

[0081] [Appendix 5] The fragment transmission information includes a fragment transmission flag for the PDU set, a sequence number of the PDU set, a sequence number of the final PDU in the PDU set that has been fragmented and transmitted, a sequence number of the final PDU in the PDU set, an XR frame type, an importance of the PDU set, or a number of fragments of the PDU set. 5. A communication terminal according to any one of appendices 1 to 4.

[0082] [Appendix 6] The notification means is characterized in that, when the PDU set is not divided and transmitted, it notifies a BSR that does not include the division transmission information. 6. A communication terminal according to any one of claims 1 to 5.

[0083] [Appendix 7] A communication terminal that operates as UE (User Equipment), a transmitting means for transmitting a PDU set, which is one or more PDUs including predetermined application data; a notification means for notifying a base station of division transmission information regarding the division transmission of the PDU set in an SR (Scheduling Request) when the PDU set is divided and transmitted; A communication terminal comprising:

[0084] [Appendix 8] the transmitting means divides the PDU set into a plurality of transport blocks having different transmission timings and transmits the transport blocks; When the PDU set is divided into a plurality of transport blocks having different transmission timings and transmitted, the notification means includes the division transmission information in the SR and notifies the base station. 9. The communication terminal according to claim 7 or 8,

[0085] [Appendix 9] The communication terminal described in Supplementary Note 8, characterized in that the transmitting means detects that the PDU set is to be divided into multiple transport blocks and transmitted by comparing the data size of the PDU set with the transport block size.

[0086] [Appendix 10] The communication terminal described in Appendix 7, characterized in that the notification means includes the fragmentation transmission information in the SR when triggered by the transmission means that an untransmitted PDU in the PDU set remains in the transmission buffer.

[0087] [Appendix 11] The communication terminal according to Supplementary Note 7, wherein the notification means adds a parameter of the divided transmission information to the SR and notifies the base station.

[0088] [Appendix 12] The communication terminal described in Appendix 7, characterized in that the fragment transmission information includes a flag indicating whether the PDU set is fragmented or not, a sequence number of the PDU set, a sequence number of the final PDU in the PDU set that has been fragmented and transmitted, a sequence number of the final PDU in the PDU set, an XR frame type, an importance of the PDU set, the number of fragments of the PDU set, or a buffer capacity.

[0089] [Appendix 13] The communication terminal according to claim 7, wherein the transmitting means transmits the PDU set when transmitting the first UL data after establishing a connection with the base station.

[0090] [Appendix 14] A communication device operating as a base station, a receiving means for receiving, from a communication terminal, segmentation transmission information regarding segmentation transmission of a PDU set, which is one or more PDUs (Protocol Data Units) including predetermined application data; a control means for performing UL scheduling by giving priority to a communication terminal that receives the division transmission information over a communication terminal that does not receive the division transmission information; A communication device comprising:

[0091] [Appendix 15] 15. The communication device according to claim 14, wherein the receiving means receives a BSR or an SR transmitted from the communication terminal.

[0092] [Appendix 16] The communication device according to claim 14, wherein the control means, after receiving the divided transmission information from the communication terminal by the receiving means, schedules UL resources to the communication terminal with priority.

[0093] [Appendix 17] The communication device described in Supplementary Note 14, characterized in that when the receiving means receives divided transmission information from multiple communication terminals at the same time, the control means schedules UL resources preferentially to communication terminals with a smaller proportion of untransmitted PDUs.

[0094] [Appendix 18] The communication device described in Appendix 14, characterized in that after receiving divided transmission information from the communication terminal via the receiving means, the control means prioritizes the communication terminal and schedules UL resources equal to the number of times the PDU set is divided.

[0095] [Appendix 19] A communication method performed by a communication terminal operating as UE (User Equipment), transmitting a PDU set, which is one or more Protocol Data Units (PDUs) containing predetermined application data; When the PDU set is divided and transmitted, notifying a base station of division transmission information regarding the division and transmission of the PDU set in a BSR (Buffer Status Report); A communication method comprising:

[0096] [Appendix 20] A communication terminal operating as UE (User Equipment) transmitting a PDU set, which is one or more Protocol Data Units (PDUs) containing predetermined application data; When the PDU set is divided and transmitted, notifying a base station of division transmission information regarding the division and transmission of the PDU set in a BSR (Buffer Status Report); A program to execute. [Explanation of symbols]

[0097] 100 systems 101 User terminal 102 Core Network (CN) 110 Base station (gNB)

Claims

1. A communication terminal that operates as a UE (User Equipment), a transmitting means for transmitting a PDU set, which is one or more PDUs (Protocol Data Units) including predetermined application data; a notification means for notifying a base station of segmented transmission information regarding segmented transmission of the PDU set in a BSR (Buffer Status Report) when the PDU set is segmented and transmitted; A communication terminal comprising:

2. the transmitting means divides the PDU set into a plurality of transport blocks having different transmission timings and transmits the transport blocks; 2. The communication terminal according to claim 1, wherein, when the PDU set is divided into a plurality of transport blocks with different transmission timings and transmitted, the notification means includes the division transmission information in the BSR and notifies the base station.

3. 2. The communication terminal according to claim 1, wherein the notification means includes the segment transmission information in the BSR when triggered by an untransmitted PDU in a PDU set remaining in a transmission buffer.

4. 2. The communication terminal according to claim 1, wherein said notifying means adds a parameter of said divided transmission information to said BSR and notifies said base station of said BSR.

5. The communication terminal according to claim 1, characterized in that the fragmentation transmission information includes a flag indicating whether the PDU set is fragmented or not, a sequence number of the PDU set, a sequence number of the last PDU in the PDU set that has been fragmented and transmitted, a sequence number of the last PDU in the PDU set, an XR frame type, an importance of the PDU set, or a number of fragments of the PDU set.

6. 2. The communication terminal according to claim 1, wherein said notification means notifies a BSR that does not include said fragmented transmission information when a PDU set is not fragmented for transmission.

7. A communication terminal that operates as a UE (User Equipment), a transmitting means for transmitting a PDU set, which is one or more PDUs each including predetermined application data; a notification means for including segmentation transmission information regarding segmentation and transmission of the PDU set in an SR (Scheduling Request) and notifying the base station when the PDU set is segmented and transmitted; A communication terminal comprising:

8. the transmitting means divides the PDU set into a plurality of transport blocks having different transmission timings and transmits the transport blocks; When the PDU set is divided into a plurality of transport blocks having different transmission timings and transmitted, the notification means includes the division transmission information in the SR and notifies the base station.

8. The communication terminal according to claim 7, wherein:

9. The communication terminal according to claim 8, wherein the transmitting means detects that the PDU set is to be divided into a plurality of transport blocks and transmitted by comparing the data size of the PDU set with the transport block size.

10. The communication terminal according to claim 7, characterized in that the notification means includes the division transmission information in the SR when triggered by the transmission means that an untransmitted PDU in the PDU set remains in a transmission buffer.

11. 8. The communication terminal according to claim 7, wherein said notification means adds a parameter of said divided transmission information to said SR and notifies said base station of the SR.

12. The communication terminal according to claim 7, characterized in that the fragmentation transmission information includes a flag indicating whether the PDU set is fragmented or not, a sequence number of the PDU set, a sequence number of the last PDU in the PDU set that has been fragmented and transmitted, a sequence number of the last PDU in the PDU set, an XR frame type, an importance of the PDU set, the number of fragments of the PDU set, or a buffer capacity.

13. 8. The communication terminal according to claim 7, wherein the transmitting means transmits the PDU set when transmitting the first UL data after establishing a connection with the base station.

14. A communication device operating as a base station, a receiving means for receiving, from a communication terminal, segmentation transmission information regarding segmentation transmission of a PDU set, which is one or more PDUs (Protocol Data Units) including predetermined application data; a control means for performing UL scheduling by giving priority to a communication terminal that receives the division transmission information over a communication terminal that does not receive the division transmission information; A communication device comprising:

15. 15. The communication device according to claim 14, wherein the receiving means receives a BSR or an SR transmitted from the communication terminal.

16. 15. The communication device according to claim 14, wherein the control means, after receiving the division transmission information from the communication terminal by the receiving means, schedules UL resources to the communication terminal with priority.

17. The communication device according to claim 14, characterized in that, when the control means receives divided transmission information from multiple communication terminals at the same timing by the receiving means, the control means schedules UL resources by giving priority to a communication terminal having a smaller proportion of untransmitted PDUs.

18. The communication device according to claim 14, characterized in that the control means, after receiving division transmission information from the communication terminal by the receiving means, schedules UL resources for the number of divisions of the PDU set, giving priority to the communication terminal.

19. A communication method performed by a communication terminal operating as a UE (User Equipment), transmitting a PDU set (PDU set) which is one or more Protocol Data Units (PDUs) including predetermined application data; When the PDU set is segmented and transmitted, segmentation transmission information regarding segmentation and transmission of the PDU set is included in a BSR (Buffer Status Report) and notified to a base station; A communication method comprising:

20. A communication terminal operating as a UE (User Equipment) transmitting a PDU set (PDU set) which is one or more Protocol Data Units (PDUs) including predetermined application data; When the PDU set is segmented and transmitted, segmentation transmission information regarding segmentation and transmission of the PDU set is included in a BSR (Buffer Status Report) and notified to a base station; A program to execute.

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