Communication control method, user device, processor, and program

Abstract

To provide a communication control method in a mobile communication system in which radio communication is performed between a user device and a base station device.SOLUTION: In a mobile communication system, a user device 100 in a radio resource control (RRC) connected state transmits first preference information to a base station device 200, and the base station device receives the first preference information. The first preference information is information for desiring at least any one of the user device in a RRC inactive state transmitting data by using a message of a random access procedure and the user device transmitting data by using a preset radio resource.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a communication control method used in a mobile communication system. [Background technology]

[0002] The standards of 3GPP (Third Generation Partnership Project) (registered trademark; the same applies hereinafter), a standardization project for mobile communication systems, prescribe early data transmission (EDT) for transmitting and receiving data during a random access procedure (see, for example, Non-Patent Document 1).

[0003] EDT includes MO-EDT (Mobile Originated-EDT) and MT-EDT (Mobile Terminated-EDT).

[0004] The MO-EDT is an EDT for transmitting uplink data. The MO-EDT is initiated when a higher layer of the user equipment requests establishment or resumption of a Radio Resource Control (RRC) connection for user equipment-originated data and the size of the uplink data becomes equal to or smaller than the transport block (TB) size indicated in the system information. Note that the MO-EDT also allows downlink data transmission following uplink data transmission during the random access procedure.

[0005] On the other hand, MT-EDT is an EDT for downlink data transmission. In MT-EDT, when a user equipment receives a paging message including an MT-EDT instruction from a base station, the user equipment performs a random access procedure and receives downlink data from the base station at the timing for receiving downlink data in MO-EDT.

[0006] 3GPP also defines Preconfigured Uplink Resource (PUR), in which uplink transmission is performed from an RRC idle (RRC_IDLE) state using preconfigured uplink resources without performing a random access procedure.

[0007] A user equipment in an RRC connected (RRC_CONNECTED) state transmits a PUR Configuration Request message to a base station and receives an RRC Connection Release message including PUR resources from the base station. The RRC Connection Release message includes information necessary for PUR configuration, such as resources used for data transmission (hereinafter sometimes referred to as "PUR resources").

[0008] A user equipment in the RRC idle state can use the PUR resource to transmit data to the base station together with an RRC Connection Resume Request message, and can also optionally receive downlink data together with an RRC Connection Release message following the RRC Connection Resume message. [Prior art documents] [Non-patent literature]

[0009] [Non-Patent Document 1] 3GPP TS 38.300 V16.2.0 (2020-07) Summary of the Invention

[0010] A communication control method according to a first aspect is a communication control method in a mobile communication system in which wireless communication is performed between a user equipment (UE) and a base station. The communication control method includes the steps of: the user equipment in an RRC (Radio Resource Control) connected state transmitting first preference information to the base station; and the base station receiving the first preference information. The first preference information indicates that the user equipment in an RRC inactive state desires at least one of a first data transmission in which data is transmitted using a message of a random access procedure and a second data transmission in which data is transmitted using a preset radio resource.

[0011] A communication control method according to a second aspect is a communication control method in a mobile communication system in which wireless communication is performed between a base station device having a first plurality of cells and a user device, or between the base station device and another base station device, each of which has at least one cell, forming a second plurality of cells, and the user device, and the other base station device. The communication control method includes the base station device transmitting configuration information to the user device in an RRC (Radio Resource Control) connected state, the user device in the RRC connected state receiving the configuration information, and the user device in an RRC inactive state transmitting data using preset radio resources in the first or second plurality of cells based on the configuration information. The configuration information is information for the user device in the RRC inactive state to transmit the data using the preset radio resources in the first or second plurality of cells.

[0012] A communication control method according to a third aspect is a communication control method in a mobile communication system in which wireless communication is performed between a base station device and a user equipment. The communication control method includes the base station device transmitting configuration information to the user equipment in an RRC (Radio Resource Control) connected state, and the user equipment in the RRC connected state receiving the configuration information. The communication control method also includes the user equipment in an RRC inactive state performing, based on the configuration information, at least one of a first data transmission in which data is transmitted using a random access procedure message and a second data transmission in which data is transmitted using preset radio resources, using at least one of carrier aggregation, dual connectivity, and PDCP (Packet Data Convergence Protocol) duplication.

[0013] A communication control method according to a fourth aspect is a communication control method for a user equipment that performs wireless communication with a base station apparatus. The communication control method includes, when the user equipment in an RRC (Radio Resource Control) inactive state fails to transmit data using a message of a random access procedure or fails to transmit data using a preset radio resource, storing information about the failure in a memory of the user equipment, and the user equipment in an RRC inactive state or the user equipment in an RRC connected state transmitting the information about the failure stored in the memory to the base station apparatus. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a diagram illustrating a configuration of a mobile communication system according to an embodiment. [Figure 2] FIG. 1 is a diagram illustrating a configuration of a user device according to an embodiment. [Figure 3] FIG. 2 is a diagram illustrating a configuration of a base station according to an embodiment. [Figure 4]FIG. 2 is a diagram illustrating an example of the configuration of a user plane protocol stack. [Figure 5] FIG. 2 is a diagram illustrating an example of the configuration of a protocol stack of a control plane. [Figure 6] FIG. 2 is a diagram illustrating an example of operation of the first embodiment. [Figure 7] FIG. 10 is a diagram illustrating an example of UE assistance information. [Figure 8] FIG. 8(A) shows an example of the operation of EDT, and FIG. 8(B) shows an example of the operation of PUR. [Figure 9] 9(A) and 9(B) are diagrams showing an example of operation using a UE context acquisition message. [Figure 10] FIG. 10 is a diagram showing an example of an operation using a handover request message. [Figure 11] Figure 11(A) shows an example where two cells exist in one gNB, and Figure 11(B) shows an example where one cell exists in each gNB. [Figure 12] 12(A) and 12(B) are diagrams showing examples of PUR areas. [Figure 13] FIG. 13 is a diagram illustrating an example of the operation of the second embodiment. [Figure 14] 14(A) and 14(B) are diagrams showing examples of CA. [Figure 15] FIG. 15(A) shows an example of DC, and FIG. 15(B) shows an example of PDCP duplication. [Figure 16] FIG. 16 is a diagram illustrating an example of the operation of the third embodiment. [Figure 17] 17(A) and 17(B) are diagrams showing an example of the operation when an SD procedure fails. [Figure 18] FIG. 18 is a diagram illustrating an example of operation of the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] A mobile communication system according to an embodiment will be described with reference to the drawings. In the description of the drawings, the same or similar parts are denoted by the same or similar reference numerals.

[0016] (Configuration of a mobile communication system) First, a configuration of a mobile communication system according to an embodiment will be described. The mobile communication system according to an embodiment is a 3GPP 5G system, but LTE (Long Term Evolution) may be applied at least in part to the mobile communication system.

[0017] FIG. 1 is a diagram showing a configuration of a mobile communication system according to an embodiment.

[0018] As shown in FIG. 1, the mobile communication system includes a user equipment (UE) 100, a 5G radio access network (NG-RAN) 10, and a 5G core network (5GC) 20.

[0019] The UE 100 is a mobile device. The UE 100 may be any device that is used by a user, but for example, the UE 100 is a device capable of wireless communication, such as a mobile phone terminal (including a smartphone), a tablet terminal, a notebook PC, a communication module (including a communication card or a chipset), a sensor or a device provided in a sensor, a vehicle or a device provided in a vehicle (Vehicle UE), or an aircraft or a device provided in an aircraft (Aerial UE).

[0020] The NG-RAN 10 includes a base station device (called "gNB" in the 5G system) 200. The gNB 200 is sometimes called an NG-RAN node. The gNBs 200 are connected to each other via an Xn interface, which is an interface between base stations. The gNB 200 manages one or more cells. The gNB 200 performs wireless communication with a UE 100 that has established a connection with its own cell. The gNB 200 has a radio resource management (RRM) function, a routing function for user data (hereinafter simply referred to as "data"), a measurement control function for mobility control and scheduling, etc. The term "cell" is used to indicate the smallest unit of a wireless communication area. The term "cell" is also used to indicate a function or resource that performs wireless communication with a UE 100. One cell belongs to one carrier frequency.

[0021] Note that the gNB 200 may be connected to an EPC (Evolved Packet Core), which is an LTE core network, or an LTE base station may be connected to the 5GC 20. Also, an LTE base station (called an "eNB" in the LTE system) and a gNB may be connected via an inter-base station interface.

[0022] The 5GC20 includes an Access and Mobility Management Function (AMF) and a User Plane Function (UPF) 300-1, 300-2. The AMF performs various mobility controls for the UE 100. The AMF manages information about the area in which the UE 100 is located by communicating with the UE 100 using NAS (Non-Access Stratum) signaling. The UPF controls data forwarding. The AMF and UPF are connected to the gNB 200 via an NG interface, which is an interface between the base station and the core network.

[0023] FIG. 2 is a diagram showing a configuration of a UE 100 (user equipment) according to an embodiment.

[0024] As shown in FIG. 2, the UE 100 includes a receiving unit 110, a transmitting unit 120, and a control unit .

[0025] The receiving unit 110 performs various types of reception under the control of the control unit 130. The receiving unit 110 includes an antenna and a receiver. The receiver converts (down-converts) a radio signal received by the antenna into a baseband signal (received signal) and outputs the baseband signal to the control unit 130.

[0026] The transmitting unit 120 performs various transmissions under the control of the control unit 130. The transmitting unit 120 includes an antenna and a transmitter. The transmitter converts (up-converts) a baseband signal (transmission signal) output by the control unit 130 into a radio signal and transmits it from the antenna.

[0027] The control unit 130 performs various controls in the UE 100. The control unit 130 includes at least one processor and at least one memory electrically connected to the processor. The memory stores programs executed by the processor and information used in processing by the processor. The processor may include a baseband processor and a CPU (Central Processing Unit). The baseband processor performs modulation / demodulation and encoding / decoding of baseband signals. The CPU executes programs stored in the memory to perform various processes.

[0028] FIG. 3 is a diagram showing the configuration of a gNB200 (base station) according to one embodiment.

[0029] As shown in FIG. 3, the gNB 200 includes a transmitter 210, a receiver 220, a controller 230, and a backhaul communication unit 240.

[0030] The transmission unit 210 performs various transmissions under the control of the control unit 230. The transmission unit 210 includes an antenna and a transmitter. The transmitter converts (up-converts) a baseband signal (transmission signal) output by the control unit 230 into a radio signal and transmits it from the antenna.

[0031] The receiving unit 220 performs various types of reception under the control of the control unit 230. The receiving unit 220 includes an antenna and a receiver. The receiver converts (down-converts) a radio signal received by the antenna into a baseband signal (received signal) and outputs the baseband signal to the control unit 230.

[0032] The control unit 230 performs various controls in the gNB 200. The control unit 230 includes at least one processor and at least one memory electrically connected to the processor. The memory stores programs executed by the processor and information used in processing by the processor. The processor may include a baseband processor and a CPU. The baseband processor performs modulation / demodulation, encoding / decoding, etc. of baseband signals. The CPU executes programs stored in the memory to perform various processes. Instead of the CPU, a processor or controller such as a DSP (Digital Signal Processor) or FPGA (Field Programmable Gate Array) may be used.

[0033] The backhaul communication unit 240 is connected to neighboring base stations via an inter-base station interface. The backhaul communication unit 240 is connected to the AMF / UPFs 300-1 and 300-2 via a base station-core network interface. Note that the gNB 200 may be configured (i.e., functionally divided) with a CU (Central Unit) and a DU (Distributed Unit), and both units may be connected via an F1 interface.

[0034] (About protocol stack) FIG. 4 is a diagram showing the configuration of a protocol stack of a radio interface of a user plane that handles data.

[0035] As shown in Figure 4, the user plane radio interface protocol includes a physical (PHY) layer, a medium access control (MAC) layer, a radio link control (RLC) layer, a packet data convergence protocol (PDCP) layer, and a service data adaptation protocol (SDAP) layer.

[0036] The PHY layer performs encoding / decoding, modulation / demodulation, antenna mapping / demapping, and resource mapping / demapping. Data and control information are transmitted between the PHY layer of the UE 100 and the PHY layer of the gNB 200 via a physical channel.

[0037] The MAC layer performs data priority control, retransmission processing using Hybrid ARQ (HARQ), random access procedures, etc. Data and control information are transmitted between the MAC layer of UE 100 and the MAC layer of gNB 200 via a transport channel. The MAC layer of gNB 200 includes a scheduler. The scheduler determines the uplink and downlink transport format (transport block size, modulation and coding scheme (MCS)) and the resource blocks to be allocated to UE 100.

[0038] The RLC layer transmits data to the RLC layer on the receiving side using the functions of the MAC layer and PHY layer. Data and control information are transmitted between the RLC layer of the UE 100 and the RLC layer of the gNB 200 via logical channels.

[0039] The PDCP layer performs header compression / decompression and encryption / decryption.

[0040] The SDAP layer maps IP flows, which are the units for QoS control by the core network, to radio bearers, which are the units for QoS control by the AS (Access Stratum). Note that if the RAN is connected to the EPC, SDAP is not necessary.

[0041] FIG. 5 is a diagram showing the configuration of a protocol stack of a radio interface of a control plane that handles signaling (control signals).

[0042] As shown in FIG. 5, the protocol stack of the radio interface of the control plane has a Radio Resource Control (RRC) layer and a Non-Access Stratum (NAS) layer instead of the SDAP layer shown in FIG.

[0043] RRC signaling for various settings is transmitted between the RRC layer of UE100 and the RRC layer of gNB200. The RRC layer controls logical channels, transport channels, and physical channels in accordance with the establishment, re-establishment, and release of radio bearers. When there is a connection (RRC connection) between the RRC of UE100 and the RRC of gNB200, UE100 is in an RRC connected state. When there is no connection (RRC connection) between the RRC of UE100 and the RRC of gNB200, UE100 is in an RRC idle state. When the RRC connection is suspended, UE100 is in an RRC inactive state.

[0044] The NAS layer, which is positioned above the RRC layer, performs session management, mobility management, etc. NAS signaling is transmitted between the NAS layer of the UE 100 and the NAS layer of the AMFs 300-1 and 300-2.

[0045] The UE 100 has an application layer and the like in addition to the radio interface protocol.

[0046] (About EDT) Next, EDT will be described. Hereinafter, an embodiment in which EDT of LTE is introduced into a 5G system (NR) will be described.

[0047] In the EDT, the UE 100 in the RRC idle state can transmit and receive data using a message of the random access procedure. As described above, the EDT includes the MO-EDT and the MT-EDT.

[0048] In the MO-EDT, uplink data transmission is performed. In addition, in the MO-EDT, downlink data transmission following uplink data transmission is also possible during the random access procedure. When the upper layer of the UE 100 requests establishment or resumption of an RRC connection for UE-originating (MO: Mobile Originated) data and the size of the uplink data becomes equal to or smaller than the transport block (TB) size indicated in the system information, the EDT is started. In the MO-EDT, the UE 100 transmits uplink data using Msg3 in the random access procedure.

[0049] On the other hand, in MT-EDT, downlink data transmission is performed. When UE 100 receives a paging message including an instruction for MT-EDT from an eNB (evolved NodeB: LTE base station), it executes a random access procedure. Then, UE 100 can receive downlink data by using Msg4 of the random access procedure.

[0050] There are two types of EDT: User Plane Optimization and Control Plane Optimization. In User Plane Optimization, user data is not included in RRC messages in EDT, but user data (DTCH) and RRC messages (CCCH) are multiplexed into one MAC PDU at the MAC layer and transmitted. On the other hand, in Control Plane Optimization, user data is included in RRC messages in EDT.

[0051] User Plane Optimization is applicable when the UE 100 is in an RRC inactive state. In the RRC inactive state, context information of the UE 100 is maintained in the gNB 200. In User Plane Optimization, the RRC message constituting Msg3 is an RRC Connection Resume Request message, and the RRC message constituting Msg4 is basically an RRC Connection Release message. When the UE 100 receives the RRC Connection Release message, it terminates the random access procedure while maintaining the RRC inactive state. In this embodiment, User Plane Optimization will be described as an example.

[0052] (About PUR) PUR is a communication method that performs uplink transmission from an RRC idle state using pre-configured uplink radio resources (hereinafter sometimes referred to as "PUR resources") without using a random access procedure. A series of processes in PUR is, for example, as follows.

[0053] That is, when the UE 100 is in the RRC connected state, it transmits a PUR configuration request message to the gNB 200. The PUR configuration request message includes the number of PUR opportunities, the period of the PUR opportunities and the offset time until the first PUR opportunity, the transport block size, whether ACK is required, and the like.

[0054] When the gNB 200 receives the PUR configuration request message, it decides to transition the UE 100 to an RRC idle state and provides PUR resources for the UE 100. Then, the gNB 200 transmits an RRC connection release message to the UE 100. The RRC connection release message includes information indicating details of the PUR configuration, such as the PUR resources.

[0055] UE100 receives the RRC connection release message and transitions to the RRC idle state. UE100 in the RRC idle state transmits data to the gNB200 using pre-configured uplink resources included in the RRC connection release message. At this time, UE100 multiplexes an RRC connection request message and uplink data, and transmits the multiplexed data to the gNB200. Note that in this embodiment, PUR transmission from the RRC inactive state is possible, as will be described later. Instead of the above-mentioned RRC idle state, UE100 that has transitioned to the RRC inactive state can multiplex an RRC connection resume request message and uplink data, and transmit the multiplexed data to the gNB200. Also, UE100 can multiplex an RRC early data request message, which is a message for CP-EDT (Control Plane-Early Data Transfer), and uplink data, instead of the RRC connection resume request message, and transmit the multiplexed data to the gNB200.

[0056] Note that the PUR can also optionally transmit downlink data. That is, after the RRC connection resumption request message, the downlink data is multiplexed into an RRC connection release message (or an RRC early data complete message) transmitted from the gNB 200, and the UE 100 in the RRC idle state receives the downlink data together with the RRC connection release message.

[0057] Furthermore, when the UE 100 in the RRC idle state transmits data that is too large to transmit using the PUR resource, it transmits an RRC connection resumption request message and a data segment to the gNB 200 using the PUR resource. Thereafter, the gNB 200 executes a connection resumption procedure with the UE 100, and the UE 100 transitions to the RRC connected state and transmits the uplink data that could not be transmitted.

[0058] The above-described process is an example in which the UE 100 is in an RRC idle state. In this embodiment, PUR transmission is possible even when the UE 100 is in an RRC inactive state. In the above-described example, the RRC idle state can be replaced with the RRC inactive state.

[0059] (About SDT) In this embodiment, EDT and PUR may be collectively referred to as SDT (Small Data Transmission). Data transmitted using SDT may be data of a predetermined size or less (or small data, or small data), and may be of a size that can be transmitted using EDT or PUR.

[0060] In the following, data transmission using EDT may be referred to as EDT transmission (first data transmission), data transmission using PUR as PUR transmission (second data transmission), and data transmission using SDT as SDT transmission.

[0061] Example 1 In the communication control method of the first embodiment, the UE 100 in the RRC connected state transmits preference information to the gNB 200. The preference information here is preference information indicating that the UE 100 in the RRC inactive state desires at least one of transmitting data using a random access procedure message and transmitting data using pre-configured uplink resources. Hereinafter, such preference information may be referred to as SDT preference information. By the UE 100 transmitting the SDT preference information to the gNB 200, the gNB 200 can grasp information necessary for PUR transmission or EDT transmission when transitioning the UE 100 to the RRC inactive state, thereby making it possible to improve the efficiency of subsequent processing.

[0062] Next, a description will be given of an example of operation in the present embodiment 1. Fig. 6 is a diagram illustrating an example of operation in the present embodiment 1.

[0063] As shown in Figure 6, in step S101, UE100 is in an RRC connected state with gNB200.

[0064] In step S102, UE100 transmits data to gNB200 and receives data transmitted from gNB200.

[0065] In step S103, if UE 100 desires to transmit data using EDT or PUR, it transmits SDT preference information to gNB 200. For example, when control unit 130 determines that there is such a desire, it generates SDT preference information and transmits it to gNB 200 via transmission unit 120.

[0066] The SDT preference information may be transmitted, for example, in a UE assistance information message. The UE assistance information message is a message that the UE 100 in the RRC connected state transmits a desire or request regarding the establishment of its own RRC connection. The UE assistance information message includes, for example, the power saving preference of the UE 100 and SPS (Semi Persistent Scheduling) assistance information.

[0067] Figure 7 is a diagram showing an example of a UE assistance information message including SDT preference information. As shown in Figure 7, the UE assistance information message includes an information element ("sdtPreference-r17", (Y) in Figure 7) indicating that SDT preference information is included. The information element includes the items "EDT", "MO-EDT-Only", "MT-EDT-Only", "PUR", and "EDT-and-PUR" ((Z) in Figure 7).

[0068] That is, if UE 100 desires EDT, "EDT" is included in the information element shown in (Y) of Fig. 7. Furthermore, if UE 100 desires MO-EDT (only), "MO-EDT-Only" is included in (Y) of Fig. 7. If UE 100 desires MT-EDT (only), "MT-EDT-Only" is included in (Y) of Fig. 7. Furthermore, if UE 100 desires EDT and PUR, "EDT-and-PUR" is included in the information element shown in (Y) of Fig. 7. If UE 100 desires EDT or PUR, this may be indicated by the information element "EDT-or-PUR", or only "SDT setting request" may be included in the information element and notified.

[0069] The SDT preference information may be linked to the information element "releasePreference-r16" of the UE assistance information message shown in Fig. 7. "releasePreference-r16" is an information element used when the UE 100 wishes to release the RRC connection, for example. "releasePreference-r16" includes the elements "Idle", "Inactive", and "Connected". For example, they may be linked as follows:

[0070] That is, UE100 may notify (or transmit) SDT preference information (only) when "releasePreference-r16" includes "Inactive". Alternatively, UE100 may not transmit SDT preference information when "releasePreference-r16" includes "Idle". Alternatively, even if UE100 transmits a UE assistance information message including SDT preference information when "releasePreference-r16" includes "Idle", gNB200 may ignore the SDT preference information included in the UE assistance information message.

[0071] The above example describes an example in which the SDT preference information is included in the UE Assistance Information message. The SDT preference information may also be included in other (RRC) messages.

[0072] Furthermore, the UE 100 may transmit packet information to the gNB 200 together with the SDT preference information. The packet information may include, for example, the size of a packet including data transmitted by the UE 100 via SDT, the period and / or generation timing of the packet, etc. The packet information may also include a service type. Examples of the service type include "delay tolerant," "mission critical," "normal data," and "signaling." Such a service type may be represented by QoS (Quality of Service), 5QI (5G QoS Indicator), or NSSAI (Network Slice Selection Assistance Information). In addition, in the UE 100, information related to such a service type may be notified from a NAS (Non Access Stratum) layer or an application layer. Alternatively, the service type may be estimated in an AS (Access Stratum) layer based on a transmission history or the like in the UE 100.

[0073] Furthermore, UE 100 may add frequency preference information (hereinafter referred to as "frequency preference information") to the SDT preference information and transmit the information. The frequency preference information is, for example, preference information regarding a frequency that UE 100 desires to use when transmitting data (or SDT transmission). The frequency preference information may be, for example, a carrier number, a BWP (Bandwidth Part), or a bandwidth desired by UE 100.

[0074] Furthermore, UE 100 may add information on whether multi-cell PUR is desired to gNB 200 to the SDT preference information and transmit the information to gNB 200. Multi-cell PUR will be described in (Example 2). Furthermore, UE 100 may transmit the SDT preference information including information on the movement state of UE 100 itself. Such information on the movement state may include information on the current movement state (geographically fixed, slow movement, fast movement, etc.) and may also include a predicted value of future movement of UE 100. Furthermore, UE 100 may transmit the SDT preference information including information on whether it will stay in the current serving cell (or serving gNB 200) in the future.

[0075] The SDT preference information, additional information, UE assistance information message, etc. described above may be generated in the control unit 130 and transmitted to the gNB 200 via the transmission unit 120.

[0076] Returning to Fig. 6, upon receiving the SDT preference information, the gNB 200 makes a configuration decision in step S104. That is, the gNB 200 makes configuration for the UE 100 based on the SDT preference information. For example, the gNB 200 makes the following configuration.

[0077] That is, the gNB200 may set ON / OFF of ROHC (Robust Header Compression), which is a header compression technique in the PDCP layer, or may set an NCC (Next Hop Changing Counter) value used for data encryption, etc. for SDT (i.e., EDT or PUR transmission). The gNB200 may also set uplink radio resources of an appropriate size. Such radio resources are particularly used as PUR resources. In addition to PUR resources, the gNB200 may also set information required when the UE100 performs transmission using SDT. The above setting determination may be performed by the control unit 230.

[0078] In step S105, the gNB 200 transmits an RRC connection release message to the UE 100. In this case, the gNB 200 transmits the RRC connection release message by including the information configured in step S104 in the RRC connection release message. The RRC connection release message may also include Suspend Config. That is, the RRC connection release message may include configuration information for SDT transmission, which is used when the UE 100 in the RRC inactive state performs SDT transmission. In this case, for example, the configuration information may include both configuration information for when the UE 100 performs EDT and when it performs PUR. Then, the UE 100 that has received both pieces of configuration information may perform, for example, the following processing.

[0079] That is, UE 100 may determine to perform either EDT or PUR according to a predetermined condition, and may perform EDT or PUR using configuration information for the determined EDT or PUR. The predetermined condition may be, for example, A) UE 100 performs SDT notified by SDT preference information, B) UE 100 performs PUR when UE 100 is present in the same cell, and performs EDT when UE 100 moves to another cell, C) UE 100 performs PUR when TA (Timing Advance) is enabled, and performs EDT when TA is disabled, D) determination is made based on a radio state (a threshold may be set by gNB 200), or E) depending on the implementation of UE 100.

[0080] The "radio condition" in D) above refers to the quality of the received signal, such as RSRP (Reference Signal Received Power), RSRQ (Reference Signal Received Quality), and SINR (Signal to Interference plus Noise Ratio).

[0081] Furthermore, when UE 100 has received setting information for both EDT and PUR, UE 100 may preferentially execute PUR transmission. For example, UE 100 executes PUR transmission when PUR transmission is executable (determination may be made according to B), C), or D) above). When PUR transmission is not executable, UE 100 executes EDT.

[0082] Alternatively, when the UE 100 receives the setting information of both EDT and PUR and executes PUR transmission, if the PUR transmission fails, the UE 100 may execute EDT. For example, when the UE 100 attempts packet transmission using PUR but does not receive a response from the gNB 200, the UE 100 falls back to executing EDT and transmits the packet using Msg3 or MsgA.

[0083] Alternatively, UE 100 may receive setting information for both EDT and PUR, and if either EDT or PUR transmission is successful, UE 100 may discard the EDT and / or PUR setting.

[0084] In the following description, it is assumed that the UE 100 executes EDT or PUR in consideration of a predetermined condition.

[0085] For example, the control unit 230 may generate an RRC connection release message and transmit it via the transmission unit 210. Furthermore, the above-described determination, execution, etc. may be performed by the control unit 230 in the gNB 200 and the control unit 130 in the UE 100, respectively.

[0086] In step S106, the UE 100 transitions to the RRC inactive state. For example, when the control unit 130 receives the RRC connection release message via the receiving unit 110, the control unit 130 transitions the UE 100 to the RRC inactive state in accordance with the information included in the message.

[0087] The RRC inactive state is, for example, a state in which the connection between the RRC of the UE 100 and the RRC of the gNB 200 is interrupted (suspended). In the RRC inactive state, the UE context is maintained in the UE 100, the gNB 200, and the network. This allows the UE 100 to reduce the number of signals required for the procedure to return from the RRC inactive state to the RRC connected state. Furthermore, since the UE 100 in the RRC inactive state is similar to the RRC idle state, it is also possible to save power in the UE 100. The RRC inactive state allows, for example, IoT (Internet of Things) scenarios to be taken into consideration, and makes it possible to set an RRC connection state suitable for SDT communication.

[0088] In step S107, UE100 transmits data using SDT in accordance with the setting by gNB200 (step S105).

[0089] FIG. 8A is a diagram showing an example of data transmission operation using EDT.

[0090] In step S1070, when data is generated (S1070), the UE 100 transmits and receives a series of messages according to a random access procedure (steps S1071 to S1074).

[0091] That is, in step S1071, the UE 100 transmits Msg1 (random access preamble) to the gNB 200. Note that "Msg" is an abbreviation for message.

[0092] In step S1072, gNB200 transmits Msg2 (random access response) to UE100, which includes scheduling information indicating the uplink resources allocated to UE100.

[0093] In step S1073, UE 100 transmits Msg3 to gNB 200 in accordance with the scheduling information. Msg3 is, for example, an RRC Connection Resume Request message. UE 100 multiplexes the RRC Connection Resume Request message and data (DTCH) into one MAC PDU and transmits the multiplexed message in the MAC layer. This performs uplink EDT. Alternatively, UE 100 may encapsulate data in the RRC Connection Resume Request message in the RRC layer.

[0094] In step S1074, the gNB 200 transmits Msg4 to the UE 100. Msg4 is, for example, an RRC connection release message. The gNB 200 may multiplex or encapsulate downlink data into Msg4 and transmit the data. This performs downlink EDT. Upon receiving the RRC connection release message, the UE 100 terminates the random access procedure while maintaining the RRC inactive state.

[0095] For example, the generation of Msg1 and Msg3 and the multiplexing of data may be performed by the control unit 130, and the generation of Msg2 and Msg4 and the multiplexing of data may be performed by the control unit 230. In the case of a 2-step RACH, for example, the generation of MsgA may be performed by the control unit 130, and the generation of MsgB may be performed by the control unit 230.

[0096] FIG. 8B is a diagram showing an example of data transmission using PUR.

[0097] When data is generated in step S1070, in step S1075, UE 100 uses the configured PUR resource to transmit, for example, an RRC connection resume request message to gNB 200. As in the case of EDT, UE 100 multiplexes the RRC connection resume request message and data into one MAC PDU at the MAC layer and transmits the multiplexed message. This performs uplink PUR. Alternatively, UE 100 may encapsulate data in the RRC connection resume request message at the RRC layer.

[0098] In addition, in the UE 100, if the data is too large to be transmitted using the PUR resource, the UE 100 transmits an RRC connection release request message and a segment of user data to the gNB 200 using the PUR resource. After that, the legacy RRC connection resumption procedure is started, and data transmission is performed after the RRC connection is established.

[0099] In step S1076, the gNB 200 transmits an RRC connection release message to the UE 100. As in the case of EDT, the gNB 200 may multiplex or encapsulate downlink data into the RRC connection release message and transmit the message, thereby performing downlink PUR.

[0100] In the first embodiment, it is also possible to perform both EDT and PUR. For example, after performing the procedure shown in Fig. 8(A), it is also possible to perform the procedure shown in Fig. 8(B), or vice versa. For example, when the information element "sdtPreference-r17" in the UE assistance information message shown in Fig. 7 includes "EDT-and-PUR", such a procedure may be performed.

[0101] (Example 1-1) Next, Example 1-1 will be described. Example 1-1 is an example in which the gNB 200 that has received preference information associates the SDT preference information with the UE context and transmits the SDT preference information to another gNB.

[0102] The UE 100 in the RRC inactive state can perform cell selection and cell reselection in the same way as in the RRC idle state. For example, the UE 100 can select a cell of another gNB other than the gNB 200 that transmitted the SDT preference information and transmit data to that gNB. In this case, if the other gNB does not have the SDT preference information of the UE 100, the UE 100 will transmit the SDT preference information to the other gNB again. This does not allow for power saving of the UE 100, nor does it allow for processing efficiency to be improved.

[0103] Therefore, in this embodiment 1-1, the gNB 200 that receives the preference information transmits the received SDT preference information to another gNB, thereby achieving power saving and processing efficiency of the UE 100.

[0104] Specifically, there are two cases: one in which a UE Context Retrieval message of the Xn interface is used, and one in which a Handover Request message is used.

[0105] 9(A) and 9(B) show examples of operations when a UE context acquisition message is used. Of these, Fig. 9(A) is an example of a procedure for UE 100 triggering transition from an RRC_INACTIVE to an RRC CONNECTED state. On the other hand, Fig. 9(B) is an example of an RRC reestablishment procedure.

[0106] In the example of Figure 9(A), the gNB that received SDT preference information from UE100 is represented as last serving gNB200-2.

[0107] In step S201, UE100, which is in an RRC inactive state, transmits an RRC connection resumption request message to gNB200-1, which is different from gNB200-2 that transmitted the SDT preference information in step S202. The message includes an I-RNTI (Inactive-Radio Network Temporary Identifier) ​​provided to UE100 by the last serving gNB200-2. In step S203, when gNB200-1 is able to resolve the gNB identification information included in the I-RNTI, it transmits a UE context acquisition request message to that gNB, i.e., the last serving gNB200-2. In step S204, the last serving gNB200-2 transmits a UE context acquisition response message to gNB200-1. The UE context acquisition response message includes the SDT preference information received from UE100 along with the UE context data. As a result, the gNB 200-1, which has received the RRC connection request from the UE 100, can acquire SDT preference information from the last serving gNB 200-2. After that, a series of transition procedures are performed in steps S205 and S206. Note that in the example of Figure 9(A), an RRC connection release message may be transmitted in addition to the RRC connection resumption message in step S205.

[0108] In the example of Figure 9(B), similar to Figure 9(A), the last serving gNB200-2 is a gNB that receives SDT preference information from UE100.

[0109] In step S210, the UE 100 in the RRC connected state transmits an RRC reestablishment request message to the gNB 200-1 in step S211. The RRC reestablishment request message includes UE identification information (PCI (Physical Cell Identifier) ​​and C-RNTI (Cell-RNTI)). In step S212, if the UE context is not available locally, the gNB 200-1 transmits a UE context acquisition request message to the last serving gNB 200-2. In step S213, the last serving gNB 200-2 transmits a UE context acquisition response message to the gNB 200-1. The UE context acquisition response message includes the UE context of the UE 100 as well as the SDT preference information acquired from the UE 100. Thereafter, in step S214, a series of reestablishment procedures are performed.

[0110] 10 is a diagram showing an example of an operation in which SDT preference information is transmitted using a handover request message. In the example of FIG. 10, source gNB 200-1 is the gNB that received the SDT preference information from UE 100.

[0111] In step S220, UE100 and source gNB200-1 perform measurement control and measurement reporting. In step S221, source gNB200-1 decides to perform handover. In step S222, source gNB200-1 sends a handover request (HO Request) message to target gNB200-2 (S222). At this time, source gNB200-1 includes the SDT preference information received from UE100 in the handover request message along with the UE context of UE100 and sends the message to target gNB200-2. Thereafter, a series of handover processes are performed in steps S223 and S224.

[0112] The series of processes shown in Figures 9(A) to 10 may be performed, for example, by the control unit 230 and transmitted to other gNBs via the backhaul communication unit 240.

[0113] Example 2 In the second embodiment, PUR is supported in multiple cells. Such PUR is sometimes called "multi-cell PUR."

[0114] In the current 3GPP, when UE100 receives a PUR configuration from a base station in a certain cell and accesses a cell other than the cell, the PUR configuration is released in UE100 and the (ng-)eNB (3GPP TS 36.300 V16.2.0(2020-07)).

[0115] 11(A) and 11(B) are diagrams for explaining examples of such situations. Of these, FIG. 11(A) is an example where one gNB 200 has two cells, and FIG. 11(B) is an example where each of gNBs 200-1 and 200-2 has one cell. In either case, UE 100 transmits a PUR Configuration Request message to gNB 200 or gNB 200-1 in cell #1 and receives a PUR Configuration message from gNB 200 or gNB 200-1. Then, as shown in FIG. 11(A) and FIG. 11(B), when UE 100 moves to cell #2 and accesses gNB 200 or gNB 200-2 in cell #2, the PUR configuration included in the PUR configuration message is released.

[0116] In the second embodiment, the PUR setting is supported in a plurality of cells (or multiple cells, hereinafter sometimes referred to as "multiple cells"). That is, in the multi-cell PUR, setting information used when transmitting data using pre-configured uplink radio resources can be used in a plurality of cells. As a result, even if the UE 100 moves to a cell other than the cell from which the PUR setting message was received, the UE 100 can transmit data by PUR in the other cell by using the PUR setting included in the PUR setting message as it is. Therefore, the UE 100 can reduce power consumption and improve processing efficiency on the network side compared to a case where a series of procedures related to the PUR setting are performed every time the UE 100 moves to a cell.

[0117] In the second embodiment, in order to realize multi-cell PUR, an area where the PUR setting is valid (hereinafter, sometimes referred to as a "PUR area") is set.

[0118] 12(A) and 12(B) are diagrams showing examples of PUR areas. The example of Fig. 12(A) is an example in which two cells #1 and #2 exist in one gNB 200, and a PUR area is set for the two cells #1 and #2.

[0119] In addition, the example of Figure 12(B) is an example in which two gNBs 200-1 and 200-2 each have one cell #1 and one cell #2.

[0120] In either case, the example shows that UE 100 receives PUR setting in cell #1 and moves to cell #2. In either case, UE 100 is capable of PUR transmission in cell #2 using the PUR setting configured in cell #1. That is, UE 100 is capable of PUR transmission with the same PUR setting from any cell within the PUR area. In this way, the information on the PUR area may include area information indicating an area in which PUR setting information is valid in multiple cells, for example, even when multiple cells exist in one gNB 200 or when multiple gNBs 200-1 and 200-2 each have at least one cell, thereby configuring multiple cells.

[0121] Fig. 13 is a diagram illustrating an example of operation of this embodiment 2. The example of Fig. 13 is an example in which two gNBs 200-1 and 200-2 each have one cell #1 and one cell #2.

[0122] As shown in Figure 13, in step S300, UE100 is in an RRC connected state with gNB200-1.

[0123] In step S301, UE100 sends a PUR Configuration Request message to gNB200-1.

[0124] In step S302, the gNB 200-1 transmits an RRC Connection Release message including information about the PUR configuration to the UE 100. At this time, the gNB 200-1 includes information about the PUR area in the information about the PUR configuration and transmits the information about the PUR area to the UE 100. Specific examples of the information about the PUR area include the following:

[0125] That is, the PUR area information may be a list of cells for which the PUR setting is valid. For example, in the example of Fig. 12(A), the PUR area information is a list of "Cell #1" and "Cell #2."

[0126] Alternatively, the PUR area information may be an ID (Identification) that identifies the PUR area. It is assumed that such an ID is defined in advance as to which PUR area corresponds to which ID, and that the information is shared between the UE 100 and the gNBs 200-1 and 200-2. For example, if the PUR area shown in FIG. 12(A) has an ID of "PUR area #1," this "PUR area #1" becomes the PUR area information.

[0127] Alternatively, the PUR area may be identical to the RNA (RAN-based Notification Area). In this case, for example, such a definition may be made and shared between UE 100 and gNBs 200-1 and 200-2. In this case, gNB 200-1 may not explicitly configure the PUR area, and information about the PUR area may not be included in the PUR configuration. Alternatively, gNB 200-1 may notify UE 100 that the PUR area is identical to RNA.

[0128] Note that, with regard to the PUR configuration, settings other than the information on the PUR area may be different for each cell. For example, in the example of FIG. 12(A), cell #1 and cell #2 may have different configuration information for each cell. In such a case, the gNB 200-1 transmits to the UE 100 an RRC connection release message including information on the PUR configuration that differs for each cell.

[0129] Returning to FIG. 13, in step S303, gNB 200-1 may transmit a PUR setting notification message including a PUR setting to gNB 200-2. For example, gNB 200-1 may transmit the PUR setting notification message using the Xn interface, or may transmit the message to gNB 200-2 using the NG interface via AMF 300-1, 300-2. gNB 200-2 may return a response message to gNB 200-1 in response to the PUR setting notification message. The response message may include information indicating whether the PUR setting notification message of step S303 is acceptable. That is, gNB 200-2 returns an acknowledgement (ACK) message if acceptable, or a negative acknowledgement (NACK) message if unacceptable.

[0130] In the example of Figure 13, gNB200-1 sends a PUR setting notification message after sending an RRC connection release message, but it may also send a PUR setting notification message to gNB200-2 before sending the RRC connection release message (or before performing PUR setting).

[0131] In step S304, UE 100 transitions to an RRC inactive state, and in step S305, moves from cell #1 to cell #2. Then, in step S306, UE 100 performs PUR transmission to gNB 200-2 having cell #2 in accordance with the PUR setting. Specifically, for example, the following operation is performed.

[0132] That is, UE 100 determines whether the serving cell is a cell included in the PUR area based on the PUR area information included in the PUR setting. If UE 100 determines that the serving cell is within a valid area included in the PUR area information, UE 100 performs PUR transmission in step S306. On the other hand, if UE 100 determines that the serving area is not a cell included in the PUR area, UE 100 does not perform PUR transmission. At this time, UE 100 may discard the information related to the PUR setting received in step S302.

[0133] In the above example, it has been described that information related to the PUR area is included in information related to the PUR configuration and is transmitted to the UE 100 using an RRC connection release message. For example, the gNB 200-1, 200-2 may broadcast information related to the PUR area, such as a PUR area ID, using a System Information Block (SIB). Alternatively, the gNB 200-1, 200-2 may broadcast information indicating that it supports multi-cell PUR using an SIB.

[0134] Furthermore, in the above example, when cell #1 and cell #2 are adjacent, gNB200-1 may broadcast a TA (Timing Advance) value applied in adjacent cell #2. For example, when UE100 accesses gNB200-2 (or gNB200-1) in cell #2, UE100 may correct timing using such a TA value and perform PUR transmission in step S306. Alternatively, gNB200-1 may broadcast information indicating that UE100 will apply the TA value applied in cell #1 as is in cell #2, or that TA=0 (or an acceptable TA value) will be applied.

[0135] The above example is an operation example using Figure 12(B) as an example, but it can also be applied to a case where two cells exist in one gNB 200, as shown in Figure 12(A), for example. The above example can also be applied to a case where three or more cells exist in one gNB 200. Furthermore, the above example can also be applied to a case where each of gNBs 200-1 and 200-2 has multiple cells.

[0136] Example 3 Next, a description will be given of Example 3. Example 3 is an example in which SDT transmission is performed using at least one of carrier aggregation (hereinafter sometimes referred to as "CA"), dual connectivity (hereinafter sometimes referred to as "DC"), and PDCP duplication.

[0137] 5G is expected to support a variety of use cases, including ultra-high speeds (Enhanced Mobile Broadband (EeMBB)), multiple simultaneous connections (Massive Machine Type Communication (mMTC)), and low latency and high reliability (Ultra-Reliable and Low Latency Communications (URLLC)). On the other hand, SDT is expected to be used in IoT applications, such as transmitting data of a non-prescribed size, using various sensors. However, even SDT can be adapted to meet the requirements of various use cases expected for 5G, such as low latency and high reliability, by using CA, DC, or PDCP duplication.

[0138] 14(A) and 14(B) are diagrams showing examples of CA. CA is, for example, wireless communication using multiple frequency bands.

[0139] The example of Figure 14 (A) shows an example in which UE 100 transmits data to one gNB 200 using CC (Component Carrier) #1 and CC #2. A cell may be configured for each CC. In this case, UE 100 performs radio communication with gNB 200 using CC #1 in cell #1 and CC #2 in cell #2.

[0140] 14(B) shows an example in which the gNB 200-1 has a PCell (Primary Cell) and the gNB 200-2 has an SCell (Secondary Cell). In this example, the UE 100 performs radio communication with the gNB 200-1 using CC#1 in the PCell and with the gNB 200-2 using CC#2 in the SCell.

[0141] 14(A) and 14(B), the UE 100 can transmit data using the SDT in this embodiment 3. Details will be described later.

[0142] FIG. 15(A) is a diagram showing an example of DC. For example, DC occurs when UE100 simultaneously performs wireless communication with two gNBs 200-1 and 200-2. gNB200-1 may be a Master Node (MN) that maintains communication connection between UE100 and the network, and gNB200-2 may be a Secondary Node (SN) that further provides wireless resources to UE100. In this case, a group including a serving cell (cell #1) of MeNB (gNB200-1) is a Master Cell Group (MCG), and a group including a serving cell (cell #2) of SeNB (gNB200-2) is a Secondary Cell Group (SCG). Note that although there are two gNBs in the example of FIG. 15(A), there may be three or more gNBs.

[0143] FIG. 15(B) is a diagram illustrating an example of PDCP duplication. When a radio bearer for PDCP duplication is configured by RRC, at least one secondary RLC entity is added to the radio bearer to handle duplicated PDCP PDUs. The logical channel corresponding to the primary RLC entity is the primary logical channel (Primary LCH), and the logical channel corresponding to the secondary RLC entity is the secondary logical channel (Secondary LCH). PDCP duplication allows the same PDCP PDU to be transmitted multiple times, improving its reliability. The secondary logical channel can be activated or deactivated by the MAC Control Element (MAC CE), which allows PDCP duplication to be performed or not. In the example of FIG. 15(B), the UE 100 transmits the same PDCP PDU #1 to two gNBs 200-1 and 200-2.

[0144] Fig. 16 is a diagram illustrating an example of operation of the present embodiment 3. The example illustrated in Fig. 16 is an example in which gNB200-1 has cell #1 and gNB200-2 has cell #2. Also, this is an example in which UE100 performs SDT transmission using at least one of CA, DC, and PDCP duplication.

[0145] As shown in FIG. 16, in step S400, UE100 is in an RRC connected state with gNB200-1. In step S401, gNB200-1 transmits an RRC Connection Release message to UE100. At this time, gNB200-1 transmits the RRC Connection Release message including configuration information required for SDT transmission (hereinafter sometimes referred to as "SDT configuration information"). However, gNB200-1 may transmit the SDT configuration information by including it in another message. Examples of SDT configuration information include the following information:

[0146] That is, the SDT configuration information may include PUR configuration information for each cell. Specifically, for each cell, the information may include radio resources used for PUR transmission, a cycle and / or time of PUR transmission, a PUR-RNTI which is identification information for each PUR, an RSRP threshold used to determine whether to perform PUR transmission, and the like. In this case, the PUR configuration information may be in the form of a list for each cell. For example, radio resources etc. for cell #1 and radio resources etc. for cell #2 are in the form of a list.

[0147] The SDT configuration information may also include EDT configuration information for each cell. Specifically, the SDT configuration information may include ROHC configuration or NCC values ​​for each cell. In this case, the SDT configuration information may also be in the form of a list for each cell.

[0148] Furthermore, the SDT configuration information may include configuration information associated with a cell. Specifically, when CA is performed in the UE 100, which cell is used to perform the CA, or when DC is performed, which cell is used to perform the DC, etc. In the case of Fig. 14(B) or Fig. 15(A), two cells are used, but three or more cells may be used.

[0149] Furthermore, the SDT configuration information may include the corresponding bearer ID (or logical channel ID (LCID)). For example, in PDCP duplication, two channels (or two bearers), a primary logical channel and a secondary logical channel, are configured, and the ID of each configured logical channel (or each bearer ID) may be included in the SDT configuration information.

[0150] Furthermore, the SDT configuration information may include configuration information on whether PDCP duplication is performed. In this case, if a bearer (logical channel) used for PDCP duplication configuration already exists, this configuration may be referenced. In other words, the bearer ID or logical channel ID used for PDCP duplication may be referenced, and this information may be included in the SDT configuration information.

[0151] Furthermore, the SDT configuration information may include information on the PUR area described in Example 2. For example, when a PUR area includes a plurality of cells (a plurality of cells in FIGS. 14(A) to 15(B)), the UE 100 can use the same PUR configuration in the plurality of cells and perform PUR transmission by using at least one of CA, DC, and PDCP duplication.

[0152] Furthermore, gNB200-1 may generate SDT configuration information based on the preference information described in Example 1 and transmit it to UE100.

[0153] The generation of the SDT setting information as described above may be performed by the control unit 230 and transmitted from the transmission unit 210.

[0154] In step S402, the UE 100 transitions to the RRC inactive state.

[0155] In steps S403 and S404, UE 100 executes SDT using multiple cells. Note that in FIG. 16, steps S403 and S404 may be performed at the same timing. Furthermore, in steps S403 and S404, the same data may be transmitted, or different data may be transmitted. When the same data is transmitted, PDCP duplication is used, but PDCP duplication may be combined with CA or DC. When different data is transmitted, CA or DC may be used, or CA and DC may be combined.

[0156] In step S403, in addition to data, UE100 may also transmit, for example, the following information to gNB200-1:

[0157] That is, the UE 100 may transmit information indicating that multiple cells are used in the cell #1 (MCG or PCell). As a result, for example, in the gNB 200 that has received different data in CA or DC, such information can be used to combine the data.

[0158] The information indicating that multiple cells are used may be, for example, the ID of the cell being used, a bearer ID, a logical channel ID (LCID), an entry number of the SDT configuration information, etc. In this case, UE 100 may transmit the information indicating that multiple cells are being used by including it in data #1, or may transmit the information by including it in a separate signaling (control signal). Alternatively, UE 100 may transmit the information by using RRC or MAC CE.

[0159] Furthermore, the UE 100 may transmit information indicating whether or not PDCP duplication is being performed.

[0160] 16 shows an example in which UE 100 performs SDT transmission in steps S403 and S404 without making any particular decision after transitioning to the RRC inactive state. For example, UE 100 may make a particular decision to determine whether to perform SDT transmission.

[0161] For example, UE100 may determine whether to perform SDT using multiple cells (cells #1 and #2 in the example of FIG. 15(A)) or SDT using a single cell among the multiple cells (cell #1 in the example of FIG. 15(A)) based on the amount of transmission data, the service type (delay sensitive, etc.), the radio conditions between UE100 and gNB200-1 (or gNB200-2), etc. For such a determination, UE100 may use a threshold transmitted from gNB200-1.

[0162] The execution control of such SDT transmission in UE100 and the generation of information to be transmitted to gNB200-1 may be performed, for example, by control unit 130, and data, various information, etc. may be transmitted from transmission unit 120 in accordance with such control.

[0163] In step S405, if gNB200-1 has successfully received the data (or signaling) transmitted from UE100, it transmits a response (ACK) signal (or message) to UE100. Also, in step S406, if gNB200-2 has successfully received the data (or signaling), it transmits a response (ACK) signal. In either case, gNB200-1, 200-2 may transmit a response (NACK) signal (or message) if reception is not successful.

[0164] In addition, when UE100 performs PDCP duplication, if it receives a response (ACK) signal from at least one cell (gNB200-1 (or 200-2) that has it) among multiple cells (cells #1, #2), it determines that the transmission of the corresponding data (or signaling) has been successful. On the other hand, if UE100 does not receive a response (ACK) from any cell (or gNB200-1, 200-2), it determines that the data transmission has failed. If UE100 determines this way, it will either perform SDT again, or send an RRC connection resumption request message to transition to the RRC connected state and attempt to retransmit the data.

[0165] Example 4 Next, a description will be given of Example 4. Example 4 is an example in which the UE 100 that has failed in transmission by SDT reports an SDT Failure indicating the failure to the network.

[0166] For example, consider a case where the UE 100 transitions to the RRC connected state by transmitting an RRC connection resumption message regardless of whether it is EDT or PUR. In this case, the network side may not know whether the UE 100 has transmitted the RRC connection resumption message after failing the SDT transmission procedure, or whether the UE 100 has transmitted the RRC connection resumption message without performing the SDT transmission procedure.

[0167] In this way, when the situation is unknown from the network side, it may be difficult to realize SON (Self Organizing Networks), which collects and analyzes information and autonomously optimizes the network.

[0168] Therefore, in the fourth embodiment, the UE 100 is configured to report the SDT Failure to the network side. This allows the network side to know that the SDT transmission has failed in the UE 100, and by collecting such information, it becomes possible to realize SON.

[0169] Figures 17(A) and 17(B) show examples of patterns in which the procedure fails in the case of EDT. In both Figures 17(A) and 17(B), the UE 100 is in the RRC inactive state. Also, the cases in which the random access procedure is 4-step and 2-step are included. Note that a series of procedures performed in SDT transmission (e.g., Figure 8(A) or Figure 8(B)) may be referred to as the "SDT procedure" below.

[0170] As shown in FIG. 17(A), in the case of 4-step, in step S500, UE100 transmits Msg1 to gNB200, and in step S501, gNB200 transmits Msg2 including fall back information. The fall back information is, for example, information instructing that the random access procedure be restarted from the beginning. When UE100 receives the fall back information, in step S502, UE100 confirms that the SDT procedure has failed. Also, in step S501, even if UE100 is unable to receive Msg2, UE100 can confirm that the SDT procedure has failed in step S502.

[0171] 17(A), in the case of 2-step, UE100 transmits MsgA in step S500, and gNB200 transmits MsgB including fall back information in step S501. In this case, UE100 also confirms failure of the SDT procedure in step S502. Also, if UE100 cannot receive MsgB in step S501, it also confirms failure of the SDT procedure in step S502.

[0172] 17(B) shows an example in which transmission and reception of Msg1 and Msg2 (steps S510 and S511) are successful, but transmission or reception of Msg3 fails. That is, in the case of 4-step, UE100 transmits Msg3 and data in step S512, but if it fails to receive Msg4 from gNB200, it checks in step S513 whether the SDT procedure has failed. In the case of 2-step, UE100 also transmits MsgA and data in step S512, but if it fails to receive MsgB, it checks in step S513 whether the SDT procedure has failed.

[0173] On the other hand, a failure of the SDT procedure in PUR occurs, for example, when UE100 in an RRC inactive state transmits data to gNB200 using PUR resources but does not receive a response (e.g., an RRC connection release message).

[0174] In this manner, in the fourth embodiment, when the SDT procedure fails, the UE 100 records (or saves) information about the failure.

[0175] Fig. 18 is a diagram illustrating an example of operation in the fourth embodiment. When the UE 100 confirms that the SDT procedure has failed in step S502 (Fig. 17(A)) or step S513 (Fig. 17(B)), the UE 100 records information about the failure in step S520. For example, the control unit 130 generates information about the failure and records the information in the memory in the control unit 130. Examples of information about the failure include the following:

[0176] That is, the information about the failure may be information contained in a normal MDT (Minimization of Drive Tests). Information contained in the MDT header includes a timestamp, latitude, longitude, altitude, and radio measurement results.

[0177] Furthermore, the information about the failure may be the type of the executed procedure. The type of the executed procedure may be, for example, whether EDT or PUR was performed, or whether 4-step RACH or 2-step RACH was performed. Note that when 4-step RACH or 2-step RACH is indicated as the type of procedure, it is applicable not only to whether EDT was performed or not, but also to a normal RACH that is not EDT. In this case, it is possible to distinguish whether or not the RACH is 2-step from the existing RACH Failure report.

[0178] Furthermore, the information about the failure may be information about the selected resource, such as a time resource, a frequency resource, a PRB (Physical Resource Block), or a BWP.

[0179] Furthermore, the information regarding the failure may be failure distinction information. The failure distinction information is, for example, information indicating which response was not returned. In the example of FIG. 17(A), Msg2 or MsgB was not returned, so in this case, examples of the information would be "Msg2" or "MsgB". The failure distinction information may also include a specific reason for the failure (or a special reason for the failure). For example, cell reselection was performed in EDT or PUR.

[0180] Furthermore, the information about the failure may be the SFN (System Frame Number) and / or subframe information in which the data transmission was performed. That is, when a data transmission fails, this information indicates in which SFN or subframe the failure occurred, or the SFN or subframe information used in the failed data transmission.

[0181] Furthermore, the information about the failure may be the number of times of failure or a retry count identifier. For example, the number of times of failure may include the number of retries for transmitting the same data.

[0182] Furthermore, the information regarding the failure may be information regarding the data size of the failed data, or information regarding the delay time from when the data was generated until the data transmission was completed.

[0183] Returning to FIG. 18, in step S521, UE 100 transmits information related to the failure to gNB 200. As shown in FIG. 18, UE 100 may transmit the information related to the failure by including it in Msg5 (an RRC Connection Setup Complete message or an RRC Connection Resume Complete message). Alternatively, UE 100 may transmit Msg5 including information indicating that a log exists to gNB 200, and then transmit the information related to the failure to gNB 200 in response to a log acquisition request from gNB 200. Such messages and information are generated, for example, by control unit 130 and transmitted via transmission unit 120.

[0184] (Other embodiments) A program may be provided that causes a computer to execute each process performed by the UE 100 or the gNB 200. The program may be recorded on a computer-readable medium. Using the computer-readable medium, the program can be installed on a computer. Here, the computer-readable medium on which the program is recorded may be a non-transitory recording medium. The non-transitory recording medium is not particularly limited, and may be, for example, a recording medium such as a CD-ROM or a DVD-ROM.

[0185] In addition, circuits that execute each process performed by UE100 or gNB200 may be integrated, and at least a part of UE100 or gNB200 may be configured as a semiconductor integrated circuit (chipset, SoC).

[0186] Although one embodiment has been described in detail above with reference to the drawings, the specific configuration is not limited to the above, and various design changes can be made without departing from the scope of the invention. Furthermore, it is also possible to combine all or part of each embodiment within a consistent range.

[0187] This application claims priority from Japanese Patent Application No. 2020-133859 (filed August 6, 2020), the entire contents of which are incorporated herein by reference.

Claims

1. A communication control method executed by a user equipment, comprising: performing either a first data transmission in which the user equipment in an RRC inactive state transmits data to a base station using a message of a random access procedure, or a second data transmission in which the user equipment in the RRC inactive state transmits data to the base station using a preset radio resource; The performing When both first setting information for the first data transmission and second setting information for the second data transmission are configured in the user equipment from the base station, discarding the second setting information in response to performing the first data transmission. Communication control method.

2. A user device, a control unit that executes either a first data transmission in which the user equipment in an RRC inactive state transmits data to a base station using a message of a random access procedure, or a second data transmission in which the user equipment in the RRC inactive state transmits data to the base station using a preset radio resource; When both first setting information for the first data transmission and second setting information for the second data transmission are set in the user equipment from the base station, the control unit discards the second setting information in response to executing the first data transmission. User equipment.

3. a processor for controlling a user device, performing a process of performing either a first data transmission in which the user equipment in an RRC inactive state transmits data to a base station using a message of a random access procedure, or a second data transmission in which the user equipment in the RRC inactive state transmits data to the base station using a preset radio resource; The processing to be performed includes, when both first setting information for the first data transmission and second setting information for the second data transmission are configured in the user equipment from the base station, discarding the second setting information in response to performing the first data transmission. Processor.

4. A program for controlling a user device, causing the user equipment to perform a process of performing one of a first data transmission in which the user equipment in an RRC inactive state transmits data to a base station using a message of a random access procedure, and a second data transmission in which the user equipment in the RRC inactive state transmits data to the base station using a preset radio resource; The processing to be performed includes, when both first setting information for the first data transmission and second setting information for the second data transmission are configured in the user equipment from the base station, discarding the second setting information in response to performing the first data transmission. program.

5. A mobile communication system including a user equipment according to claim 3.

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