Communication method and user device

Abstract

According to the present invention, a communication method that is to be executed by a user device within a mobile communication system that supports L1 / L2-Triggered Mobility (LTM) involves generating an event-triggered L1 measurement report Medium Access Control (MAC) Control Element (CE), generating a buffer status report MAC CE, and transmitting the L1 measurement report MAC CE with priority over the buffer status report MAC CE to a network node according to a prescribed rule.

Description

Communication method and user device

[0001] This disclosure relates to a communication method and user equipment used in a mobile communication system.

[0002] The 3GPP (3rd Generation Partnership Project) (registered trademark; hereinafter the same) defines the technical specifications for NR (New Radio), a fifth-generation (5G) wireless access technology. In 3GPP mobile communication systems, the switching of serving cells (serving cell change) of a user device in a Radio Resource Control (RRC) connected state is instructed by sending an RRC layer message (a so-called handover command) corresponding to Layer 3 (L3) from the network node to the user device.

[0003] Meanwhile, in 3GPP Release 18, a technical specification for LTM (L1 / L2-Triggered Mobility), a new procedure for serving cell switching, has been established. LTM is a procedure in which a network node receives a Layer 1 (L1) measurement report from a user device, and based on that, the network node changes the serving cell of the user device in response to a cell switching command signaled to the user device by a MAC (Medium Access Control) CE (Control Element).

[0004] 3GPP Technical Specification "3GPP TS 38.300 V18.4.0"

[0005] This disclosure provides technology for improving LTM.

[0006] The first aspect of the communication method is a communication method performed by a user device in a mobile communication system that supports LTM (L1 / L2-Triggered Mobility), and includes generating an event-triggered L1 measurement report MAC (Medium Access Control) CE (Control Element), generating a buffer status report MAC CE, and transmitting the L1 measurement report MAC CE to a network node with priority over the buffer status report MAC CE according to predetermined rules.

[0007] The user device according to the second embodiment is a user device used in a mobile communication system that supports LTM (L1 / L2-Triggered Mobility), and comprises a control unit and a transmission unit. The control unit generates an event-triggered L1 measurement report MAC (Medium Access Control) CE (Control Element) and a buffer status report MAC CE. The transmission unit transmits the L1 measurement report MAC CE to the network node with priority over the buffer status report MAC CE according to predetermined rules.

[0008] This figure shows an example configuration of a mobile communication system according to an embodiment. This figure shows an example configuration of a UE (User Equipment) according to an embodiment. This figure shows an example configuration of a gNB (Network Node) according to an embodiment. This figure shows the configuration of the protocol stack of the wireless interface of the user plane that handles data. This figure shows the configuration of the protocol stack of the wireless interface of the control plane that handles signaling (control signals). This figure shows the configuration related to measurement by the UE according to an embodiment. This figure shows an example of a cell switching procedure by LTM in an intraCU (i.e., within the same gNB) according to an embodiment. This figure shows an example of an L1 measurement report for an event trigger according to an embodiment. This figure shows an example configuration of a MAC PDU according to an embodiment. This figure shows example 1 of UE operation according to an embodiment. This figure shows example 2 of UE operation according to an embodiment. This figure shows the first half of example 3 of UE operation according to an embodiment. This figure shows the second half of example 3 of UE operation according to an embodiment. This figure shows an example configuration of a BSR MAC CE according to an embodiment. This figure shows example 1 of the measurement report MAC CE according to an embodiment. This figure shows example 2 of the measurement report MAC CE according to an embodiment. This figure shows example 3 of the measurement report MAC CE according to an embodiment. This figure shows example 4 of the measurement report MAC CE according to an embodiment. This figure shows a measurement report according to an embodiment, illustrating example 5 of the MAC CE configuration.

[0009] A mobile communication system according to an embodiment will be described with reference to the drawings. In the drawings, identical or similar parts are denoted by the same or similar reference numerals.

[0010] (1) The mobile communication system configuration diagram 1 is a diagram showing an example of the configuration of the mobile communication system 1 according to this embodiment. The mobile communication system 1 conforms to the 5th generation system (5GS) of the 3GPP standard. In the following explanation, 5GS will be used as an example, but the mobile communication system may also have an LTE (Long Term Evolution) system applied to it at least partially. The mobile communication system may also have a 6th generation (6G) system applied to it at least partially.

[0011] The mobile communication system 1 comprises User Equipment (UE) 100, a 5G radio access network (NG-RAN) 10, and a 5G core network (5GC) 20. Hereinafter, NG-RAN 10 may be simply referred to as RAN 10, and 5GC 20 may be simply referred to as core network (CN) 20. RAN 10 and CN 20 constitute the network 5 of the mobile communication system 1.

[0012] UE100 is a mobile wireless communication device. UE100 can be any device used by a user. For example, UE100 can be a mobile phone terminal (including a smartphone) and / or a tablet terminal, a notebook PC, a communication module (including a communication card or chipset), a sensor or a device attached to a sensor, a vehicle or a device attached to a vehicle (Vehicle UE), or an aircraft or a device attached to an aircraft (Aerial UE). The link from UE100 to network 5 in the transmission direction is called the uplink (UL), and the link from network 5 to UE100 in the transmission direction is called the downlink (DL).

[0013] NG-RAN10 includes a base station (referred to as "gNB" in the 5G system) 200, which is a type of network node. The gNBs 200 are interconnected via the Xn interface, which is an inter-base station interface. The gNBs 200 manage one or more cells. The gNBs 200 perform wireless communication with UEs 100 that have established a connection with their own cell. The gNBs 200 have radio resource management (RRM) functions, user data (hereinafter simply referred to as "data") routing functions, measurement and control functions for mobility control and scheduling, etc. "Cell" is used as a term to indicate the smallest unit of a wireless communication area. "Cell" is also used as a term to indicate a function or resource that performs wireless communication with a UE 100. "Cell" is identified by a cell identifier (cell ID). One cell belongs to one carrier frequency (hereinafter simply referred to as "frequency").

[0014] Furthermore, gNBs can also connect to the Evolved Packet Core (EPC), which is the core network of LTE. LTE base stations can also connect to 5GC. LTE base stations and gNBs can also be connected via an inter-base station interface.

[0015] The 5GC20 includes an AMF (Access and Mobility Management Function) and a UPF (User Plane Function) 300. The AMF performs various mobility controls for the UE100. The AMF manages the mobility of the UE100 by communicating with it using NAS (Non-Access Stratum) signaling. The UPF controls data transfer. The AMF and UPF are connected to the gNB200 via the NG interface, which is the base station-core network interface.

[0016] Figure 2 shows an example configuration of UE100 (user device) according to this embodiment. UE100 includes a receiving unit 110, a transmitting unit 120, and a control unit 130. The receiving unit 110 and the transmitting unit 120 constitute a wireless communication unit 140 that performs wireless communication with gNB200.

[0017] 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 the radio signal received by the antenna into a baseband signal (received signal) and outputs it to the control unit 130.

[0018] The transmitting unit 120 performs various types of transmissions under the control of the control unit 130. The transmitting unit 120 includes an antenna and a transmitter. The transmitter converts the baseband signal (transmission signal) output by the control unit 130 into a wireless signal and transmits it from the antenna.

[0019] The control unit 130 performs various control and processing operations in the UE 100. Such processing includes processing in each layer described later. The operation of the UE 100 described above and later may also be controlled by the control unit 130. The control unit 130 includes at least one processor and at least one memory. The memory stores programs executed by the processor and information used for processing by the processor. The processor may include a baseband processor and a CPU (Central Processing Unit). The baseband processor performs modulation, demodulation, encoding, and decoding of baseband signals. The CPU executes programs stored in memory and performs various processing operations.

[0020] Figure 3 shows an example configuration of a gNB200 (network node) according to this embodiment. The gNB200 includes a transmitting unit 210, a receiving unit 220, a control unit 230, and a network communication unit 240. The transmitting unit 210 and the receiving unit 220 constitute a wireless communication unit 250 that performs wireless communication with the UE100. The network communication unit 240 includes a transmitting unit 241 that performs transmission and a receiving unit 242 that performs reception.

[0021] The transmitting unit 210 performs various types of transmissions under the control of the control unit 230. The transmitting unit 210 includes an antenna and a transmitter. The transmitter converts the baseband signal (transmission signal) output by the control unit 230 into a wireless signal and transmits it from the antenna.

[0022] 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 the radio signal received by the antenna into a baseband signal (received signal) and outputs it to the control unit 230.

[0023] The control unit 230 performs various control and processing operations in the gNB 200. Such processing includes processing in each layer described later. The operation of the gNB 200 described above and later may also be controlled by the control unit 230. The control unit 230 includes at least one processor and at least one memory. The memory stores programs executed by the processor and information used for processing by the processor. The processor may include a baseband processor and a CPU. The baseband processor performs modulation, demodulation, encoding, decoding, etc. of the baseband signal. The CPU executes programs stored in memory and performs various processing operations.

[0024] The network communication unit 240 is connected to an adjacent base station via the Xn interface, which is an inter-base station interface. The network communication unit 240 is connected to the AMF / UPF 300 via the NG interface, which is an inter-base station-core network interface. The gNB 200 may consist of a central unit (CU) and a distributed unit (DU) (i.e., functionally divided), and the two units may be connected by the F1 interface, which is a front-haul interface. In this case, each of the gNB-DU and gNB-CU may have a functional block configuration similar to the one shown in Figure 3. However, the gNB-CU is assumed not to have a wireless communication unit 250.

[0025] Figure 4 shows the configuration of the protocol stack for the user plane's wireless interface that handles data.

[0026] The user plane radio interface protocol consists of a physical (PHY) layer, a MAC (Medium Access Control) layer, an RLC (Radio Link Control) layer, a PDCP (Packet Data Convergence Protocol) layer, and an SDAP (Service Data Adaptation Protocol) layer.

[0027] 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 UE100 and the PHY layer of gNB200 via a physical channel. The PHY layer of UE100 receives downlink control information (DCI) transmitted from gNB200 on the physical downlink control channel (PDCCH). Specifically, UE100 performs blind decoding of the PDCCH using a Radio Network Temporary Identifier (RNTI) and acquires the successfully decoded DCI as the DCI addressed to its own UE. The DCI transmitted from gNB200 has a CRC (Cyclic Redundancy Check) parity bit added, which is scrambled by the RNTI.

[0028] The MAC layer performs data priority control, retransmission processing using Hybrid ARQ (HARQ: Hybrid Automatic Repeat reQuest), and random access procedures. Data and control information are transmitted between the MAC layer of UE100 and the MAC layer of gNB200 via the transport channel. The MAC layer of gNB200 includes a scheduler. The scheduler determines the transport format for the up and down links (transport block size, modulation and coding scheme (MCS)) and the resource blocks to be allocated to UE100.

[0029] The RLC layer transmits data to the receiving RLC layer using the functions of the MAC layer and PHY layer. Data and control information are transmitted between the RLC layer of UE100 and the RLC layer of gNB200 via a logical channel.

[0030] The PDCP layer performs header compression / decompression, encryption / decryption, etc.

[0031] The SDAP layer maps IP flows, which are the units under which the core network performs QoS (Quality of Service) control, to wireless bearers, which are the units under which the AS (Access Stratum) performs QoS control. Note that if the RAN is connected to the EPC, the SDAP is not required.

[0032] Figure 5 shows the configuration of the protocol stack of the wireless interface of the control plane that handles signaling (control signals).

[0033] The control plane's wireless interface protocol stack includes an RRC (Radio Resource Control) layer and a NAS (Non-Access Stratum) layer, instead of the SDAP layer shown in Figure 4.

[0034] RRC signaling for various settings is transmitted between the RRC layer of the UE100 and the RRC layer of the gNB200. The RRC layer controls the logical channel, transport channel, and physical channel in response to the establishment, re-establishment, and release of the radio bearer. If there is a connection (RRC connection) between the RRC of the UE100 and the RRC of the gNB200, the UE100 is in the RRC connected state. If there is no connection (RRC connection) between the RRC of the UE100 and the RRC of the gNB200, the UE100 is in the RRC idle state. If the connection between the RRC of the UE100 and the RRC of the gNB200 is suspended, the UE100 is in the RRC inactive state.

[0035] The NAS layer (also simply referred to as "NAS"), located above the RRC layer, handles session management and mobility management, among other things. NAS signaling is transmitted between the NAS layer of the UE100 and the NAS layer of the AMF300A. The UE100 also has an application layer in addition to the wireless interface protocol. Furthermore, the layer below the NAS layer is called the AS layer (also simply referred to as "AS").

[0036] (2) Measurement by UE The UE 100 in the RRC connected state measures at least one beam of a cell, averages the measurement results (power values), and derives the radio quality of the cell. At this time, the UE 100 is set to consider a subset of the detected beams.

[0037] Here, filtering, which is measurement averaging, is performed at two different levels. The UE 100 first derives the beam quality by L1 filtering, which is filtering at the physical layer (PHY, layer 1 (L1)), and then derives the cell quality from a plurality of beams by L3 filtering, which is filtering at the RRC layer (layer 3 (L3)) level. Note that the cell quality from beam measurements is derived in the same way for both the serving cell and non-serving cells. The UE 100 may include the measurement results of X best beams in the L3 measurement report according to the setting by the gNB 200.

[0038] FIG. 6 is a diagram showing a configuration related to measurement by the UE 100.

[0039] The control unit 130 of the UE 100 includes an L1 filter 11, a beam integration / selection unit 12, an L3 filter 13, an evaluation unit 14, an L3 beam filter 15, and a beam selection unit 16.

[0040] The L1 filter 11 includes K L1 filters 11 corresponding to K beams. The L1 filter 11 receives K beam measurement values A obtained by the UE 100 (reception unit 110) measuring the radio quality for each of the K beams. The K beam measurement values A of the K beams are measurement values inside the physical layer (beam-specific samples), and are measurement values of SSB (SS / PBCH block) or CSI (Channel State Information) reference signal resources detected by the UE 100 (reception unit 110) at L1. The L1 filter 11 performs L1 filtering on the K measurement values A of the K beams at L1, and outputs the beam-specific measurement value A after L1 filtering １ to the beam integration / selection unit 12 and the L3 beam filter 15.

[0041] The beam integration / selection unit 12 integrates the measurement value A specific to the beam １ to derive the radio quality (Cell quality) B of the cell, and outputs the cell quality B to the L3 filter 13. The operation of the beam integration / selection unit 12 is set by RRC signaling from the gNB 200.

[0042] The L3 filter 13 performs filtering at L3 on the measurement value (cell quality B) output by the beam integration / selection unit 12, and outputs the measured value C after L3 filtering to the evaluation unit 14. The operation of the L3 filter 13 is set by RRC signaling from the gNB 200. The measured value C after L3 filtering is used as an input for one or more evaluations of the L3 measurement report from the UE 100 to the gNB 200.

[0043] The L3 filter 13 filters the measurement results for each cell measurement quantity and each beam measurement quantity according to the following formula (1) before evaluating the reporting criteria or using them in the L3 measurement report: F ｎ = (1 - a) × F ｎ－１ + a × M ｎ ...(1) Here, M ｎ is the latest measurement result from the physical layer (L1). F ｎ is the updated filtered measurement result, which is used for evaluating the reporting criteria or the L3 measurement report. F ｎ－１ is the old filtered measurement result, and when receiving the first measurement result from the physical layer (L1), F ０ is set to M １ .

[0044] When MeasObjectNR is set in RRC, a = 1 / 2 （ｋｉ／４） is used. Here, k ｉ is the filter coefficient (filterCoefficient) of the corresponding measurement quantity of the i-th QuantityConfigNR in the quantityConfigNR-List, and i is indicated by the quantityConfigIndex in MeasObjectNR. For other measurement values, a = 1 / 2 （ｋ／４）Here, k is the filter coefficient of the corresponding measured quantity received by quantityConfig.

[0045] The L3 filter 13 adapts the filter so that the filter's time characteristics are preserved at different input rates, assuming a sample rate where the filter coefficient k is equal to X milliseconds. The value of X corresponds to the L1 measurement period within one frequency assuming non-DRX operation and is frequency range dependent.

[0046] Note that if the filter coefficient k is set to 0 (zero), L3 filtering will not be applied.

[0047] The evaluation unit 14 evaluates whether an L3 measurement report D to the gNB200 is necessary. This evaluation can be performed based on multiple measurement flows at a reference point C, for example, a comparison of different measurement values. This is done by comparing input C and input C １ This is shown. The evaluation unit 14 determines that at least the new measurement results are at points C, C １ Each time a report is made, an event evaluation corresponding to the reporting criteria is performed. The setting of the reporting criteria is provided by RRC signaling from gNB200. L3 Measurement Report D represents the measurement report information (RRC message) sent from UE100 to gNB200. L3 Measurement Report D includes the measurement ID of the associated measurement setting that triggered the report.

[0048] The L3 beam filter 15 measures k values ​​A １ (That is, beam-specific measurements) are filtered on a beam-by-beam basis, and k measurement values ​​E (that is, beam-specific measurements) are output to the beam selection unit 16. The measurement values ​​E are used as input for selecting X measurement values ​​to be reported.

[0049] The beam selection unit 16 selects X measurement values ​​F from k measurement values ​​E and outputs the X measurement values ​​F. The X measurement values ​​F are beam measurement information included in the measurement report information (RRC message) transmitted from UE100 to gNB200.

[0050] (3) Overview of LTM The mobile communication system 1 according to this embodiment supports LTM (L1 / L2-Triggered Mobility).

[0051] In a typical handover procedure, the serving cell switch is triggered by signaling at the higher layer, L3, specifically the RRC layer. This type of typical handover is also called an L3 handover. In an L3 handover, the UE100 sends an L3 Measurement Report message, which is an RRC message, to the gNB200. Based on this Measurement Report message, the gNB200 decides to hand over the UE100 and instructs the cell switch by sending a handover command (specifically, an RRC Reconfiguration message) from the gNB200 to the UE100.

[0052] On the other hand, LTM is a technique for reducing mobility delays (specifically, serving cell switching delays) compared to general handover procedures by triggering serving cell switching through signaling at the lower layers, Layer 1 (L1) and / or Layer 2 (L2). In LTM, the gNB200 receives an L1 measurement report from the UE100, and based on this, the gNB200 instructs the UE100 to switch serving cells by signaling a cell switching command via MAC CE.

[0053] Specifically, in LTM, firstly, gNB200 prepares an LTM candidate cell setting for the candidate cell to be switched to, and provides the LTM candidate cell setting to UE100 via RRC signaling.

[0054] Secondly, UE100 performs synchronization with LTM candidate cells through early sync.

[0055] Thirdly, the gNB200 receives the L1 measurement report from the UE100, decides to switch the serving cell to the target cell based on the L1 measurement report, and sends a Cell Switch Command indicating the target cell (LTM candidate cell setting) to the UE100 via the MAC control element (CE). The serving cell switching trigger is transmitted by the MAC CE, which includes at least the candidate setting index (setting ID) along with the beam indicator.

[0056] Fourthly, the UE100 switches the serving cell in response to the MAC CE cell switching command from the gNB200 (source cell).

[0057] In this way, the gNB200 triggers a serving cell switch by selecting the LTM candidate cell configuration as the target configuration. The LTM candidate cell configuration can be added, modified, and released by the gNB200 via RRC signaling.

[0058] The following principles apply to LTM:

[0059] Each LTM candidate cell setting can be provided as a differential setting (delta setting) to a baseline setting used to form the complete LTM candidate cell setting.

[0060] - When the complete LTM candidate cell configuration is applied, the current UE configuration is replaced when the serving cell switches. The reconfiguration procedure performs the replacement, but does not necessarily reset the MAC, RLC, or PDCP layers.

[0061] - The user plane will continue without resetting if configured with RRC signaling, in order to avoid additional delays in data recovery.

[0062] - Security updates are not provided in LTM versions.

[0063] - Subsequent LTMs (Last Time Machines) between subsequent LTM candidate cell settings can be performed without RRC reconfiguration. In other words, UE100 does not release other LTM candidate cell settings after an LTM has been triggered.

[0064] Figure 7 shows an example of a cell switching procedure using LTM within an intraCU (i.e., within the same gNB200). In the illustrated example, UE100 performs an LTM-based serving cell switch (i.e., LTM cell switch) from the first cell to the second cell of the gNB200.

[0065] Here, the first cell and the second cell may be formed by different TRPs (Transmission and Reception Points). In the following description of the embodiments, the second cell will also be referred to as the "LTM candidate cell (or candidate cell)" until the LTM decides to switch the serving cell, and the second cell will also be referred to as the "target cell" after the LTM decides to switch the serving cell. The first cell will also be referred to as the "source cell" or the "(current) serving cell".

[0066] In step S1, UE100 is in an RRC connected state in the cell (first cell) of gNB200.

[0067] In step S2, UE100 sends a Measurement Report message, which is an RRC message, to gNB200 (first cell). The measurement report, which includes the L3 measurement result, is also called the L3 measurement report (L3 MR).

[0068] In step S3, gNB200 decides to use LTM based on the L3 measurement report and begins preparing LTM candidate cells.

[0069] In step S4, gNB200 (first cell) sends an LTM configuration, including the LTM Candidate Configuration / LTM Candidate for one or more LTM candidate cells, to UE100 in an RRC message, specifically an RRC Reconfiguration message. The LTM candidate configuration may include a random access channel (RACH) configuration used for sending RA preambles to the corresponding LTM candidate cells, such as a conflict-free random access (CFRA) configuration. Such a RACH configuration may be referred to as an EarlyUlSyncConfig. CFRA is a random access procedure in which UE100 is allocated dedicated RACH resources (e.g., dedicated preamble sequences and / or dedicated time and frequency resources) and no RACH conflicts occur between UE100s.

[0070] In step S5, UE100 saves the LTM settings (LTM candidate cell settings) and sends an RRC Reconfiguration Complete message to gNB200 (first cell).

[0071] In step S6, UE100 may perform synchronization with the LTM candidate cell (second cell) before receiving the cell switching command MAC CE from the first cell. Such synchronization may be called Early Sync. Here, UE100 may perform Downlink Synchronization (DL Synchronization) with the LTM candidate cell and then perform Early Timing Advance (TA) acquisition (i.e., UL Early Sync) with the LTM candidate cell requested by gNB200 (serving cell). This is performed by a CFRA triggered by a PDCCH order from the first cell. Note that if DCI Format 1_0 is used and all "Frequency domain resource assignment" fields in the DCI are set to "1", the DCI is treated as a PDCCH order. Furthermore, if EarlyUlSyncConfig is set on UE100, the PDCCH order may include a cell indicator that shows the corresponding RACH transmission cell, i.e., which LTM candidate cell UE100 should send a random access preamble (RA preamble) to.

[0072] UE100 transmits an RA preamble to the designated LTM candidate cell (second cell). To minimize the interruption of serving cell communication by CFRA to the LTM candidate cell, during early synchronization, UE100 does not receive a Random Access Response (RAR) from the LTM candidate cell for the purpose of obtaining the TA value. The TA value of the LTM candidate cell (target cell) is indicated by the cell switching command MAC CE in step S9. The TA value is used to adjust the uplink transmission timing of UE100.

[0073] In step S7, UE100 performs a Layer 1 (L1) measurement on the configured LTM candidate cell and transmits a measurement report (also referred to as "L1 measurement report (L1 MR)") including the L1 measurement result to gNB200 (first cell). The L1 measurement result may be, for example, L1-RSRP and / or L1-SINR.

[0074] In step S8, the gNB200 decides to switch the serving cell to the target cell (second cell).

[0075] In step S9, the gNB200 (first cell) sends a cell switching command MAC CE to the UE100, which includes the candidate setting index (setting ID) of the target cell. The cell switching command MAC CE may include the TA value obtained by UL early synchronization (i.e., the TA value derived based on the RA preamble).

[0076] In step S10, UE100 switches to the settings for the target cell (second cell). Specifically, UE100 detaches from the first cell and applies the settings for the target cell (second cell).

[0077] In step S11, if the serving cell switch requires the execution of a random access procedure (for example, if the cell switch command MAC CE does not contain a valid TA value), UE 100 executes a random access procedure on the target cell (RACH-based LTM cell switch). However, if UE 100 does not need to obtain the TA of the target cell during the serving cell switch (for example, if the cell switch command MAC CE contains a valid TA value), the random access procedure can be skipped (RACH-less LTM cell switch).

[0078] In step S12, UE100 indicates that the serving cell switch to the target cell has been successfully completed by sending, for example, an RRC Reconfiguration Complete message to the target cell (second cell). Subsequently, UE100 may perform steps S6 to S12 multiple times for subsequent LTM serving cell switches based on the settings provided in step S4.

[0079] (4) Basic Operation Example Regarding L1 Measurement Report Based on the above configuration and operation, a basic operation example regarding the L1 measurement report according to the embodiment will be described.

[0080] As described above, in LTM, the gNB200 performs LTM-related control (also referred to as "LTM control") based on the L1 measurement report from the UE100. For example, the gNB200 selects a target beam (and / or target cell) based on the L1 measurement report and triggers an LTM cell switch for the selected target. Furthermore, the gNB200 may select a candidate beam (and / or target cell) to trigger early synchronization based on the L1 measurement report.

[0081] The L1 measurement results included in the L1 measurement report include the reference signal received power (RSRP). Such an RSRP is also called L1-RSRP. There are two types of L1-RSRP: SS-RSRP, which is obtained by measuring the SSB as the reference signal, and CSI-RSRP, which is obtained by measuring the CSI-RS as the reference signal. SS-RSRP is defined as the linear average of the power levels (in [W]) of the resource elements carrying the secondary synchronization signal (SSS). The measurement time resources for SS-RSRP are limited to the SS / PBCH block measurement time setting (SMTC) window period. When SS-RSRP is used as the L1-RSRP by the reporting settings, the limitation of measurement time resources by the SMTC window period may not apply. On the other hand, CSI-RSRP is defined as the linear average of the power levels (in watts) of resource elements of the antenna port carrying the CSI reference signal set up for RSRP measurement, over set CSI-RS opportunities within the measurement frequency band under consideration.

[0082] 3GPP Release 18 envisions the use of periodic L1 measurement reports. Such periodic L1 measurement reports may require the UE100 to transmit L1 measurement reports at a high transmission frequency, potentially increasing the load on the UE100 (power consumption, etc.). On the other hand, 3GPP Release 19 is considering the introduction of event-triggered L1 measurement reports (also referred to as "event-triggered L1 measurement").

[0083] In event-triggered L1 measurements, the use of beam-level measurement results for event evaluation is fundamental. However, event-triggered L1 measurements may also be performed at the cell level. In event-triggered L1 measurement reports, UE100 transmits an L1 measurement report to gNB200 when the radio quality conditions (also referred to as "entering conditions" or "first radio quality conditions") corresponding to the L1 LTM measurement event are met. In other words, in event-triggered L1 measurement reports, UE100 does not need to transmit an L1 measurement report during periods when the set radio quality conditions are not met, thus reducing the load on UE100. UE100 also performs an LTM event evaluation at L1 or L2, which evaluates whether the L1 LTM measurement event has been met. Furthermore, UE100 transmits the L1 measurement report at L1 or L2.

[0084] L1 LTM measurement events may support beam-specific quality-based events such as: - Event LTM1: The serving cell's beam is better than the absolute threshold; - Event LTM2: The serving cell's beam is worse than the absolute threshold; - Event LTM3: The LTM candidate cell's beam is better than the serving cell's beam by a certain offset; - Event LTM4: The LTM candidate cell's beam is better than the absolute threshold; - Event LTM5: The serving cell's beam is worse than absolute threshold 1, and the LTM candidate cell's beam is better than another absolute threshold 2.

[0085] Furthermore, the UE100 uses either a beam from the serving cell or an adjacent cell for event evaluation. The L1 measurement resource settings in the LTM configuration support SSB and CSI-RS beam configurations. For event LTM3 and event LTM5, the same reference signal type is used for the serving cell and adjacent cells. Also, the L1 measurement results included in the L1 measurement report, as shown in Figure 6, are beam-specific measurement values ​​A after L1 filtering. １ That's fine.

[0086] Figure 9 shows an example of an L1 measurement report for an event trigger according to the embodiment. In the illustrated example, it is assumed that event LTM4 is set from gNB200 to UE100 as the L1 LTM measurement event.

[0087] The UE100 evaluates (determines) whether the L1 wireless quality conditions (entering conditions, leaving conditions) corresponding to the set L1 LTM measurement event have been met. Hereinafter, these L1 wireless quality conditions will also be referred to as "L1 event conditions" and "L1 events." Note that "meeting the event conditions" is synonymous with "meeting the entering conditions" or "entering into the event," and "not meeting the event conditions" is synonymous with "meeting the leaving conditions" or "leaving from the event." The state in which the event conditions are met (i.e., the state in which the entering conditions are met) will also be referred to as the "entered state," and the state in which the event conditions are not met (i.e., the state in which the leaving conditions are met) will also be referred to as the "leaved state."

[0088] When a UE100 receives an L1 LTM measurement event from gNB200, it sends an L1 measurement report to gNB200 when the entering conditions corresponding to the L1 LTM measurement event are met. The entering conditions may also be conditions in which a hysteresis value (offset value) is assigned to the reference value (threshold) in the L1 LTM measurement event.

[0089] Such L1 measurement reports may be periodic L1 measurement reports. That is, UE100 may start transmitting periodic L1 measurement reports when the entering conditions corresponding to the set L1 LTM measurement event are met.

[0090] By receiving an L1 measurement report triggered by such an event, the gNB200 can determine that the entering condition has been met in the UE100 and, for example, initiate LTM control. It is also desirable that the gNB200 be able to determine when the L1 LTM measurement event is no longer met in the UE100. If the gNB200 can determine that the L1 LTM measurement event is no longer met in the UE100, it can, for example, terminate LTM control, which could enable appropriate and efficient LTM control.

[0091] UE100 starts (triggers) the transmission of periodic L1 measurement reports when the entering condition is met. At least one of the following can be set for UE100: hysteresis value (offset value), TTT (Time To Trigger), reporting interval (reportInterval), and reporting amount (reportAmount). If TTT is set, UE100 may start (trigger) the transmission of L1 measurement reports in accordance with the duration that the first radio quality condition (entering condition) has been met for the TTT time. If reporting interval (reportInterval) is set, UE100 may transmit L1 measurement reports at a frequency corresponding to the reporting interval (reportInterval). If reporting amount (reportAmount) is set, UE100 may transmit L1 measurement reports a number of times corresponding to the reporting amount (reportAmount).

[0092] On the other hand, when the radio quality conditions corresponding to the L1 LTM measurement event (also referred to as "leaving conditions" or "second radio quality conditions") are met, the transmission of periodic L1 measurement reports may be terminated. The leaving conditions may be conditions to which a hysteresis value (offset value) is assigned to the reference value (threshold, etc.) in the L1 LTM measurement event. Therefore, if gNB200 is unable to receive periodic L1 measurement reports from UE100, it can be inferred that the leaving conditions have been met at UE100.

[0093] (5) MAC CE Transmission Control In 3GPP Release 19, support for truncated MR MAC CEs, which are MAC CEs with reduced size, is being considered for event-triggered L1 measurement reports. (5.1) Truncated MR MAC CE There is a limit to the size of the MAC PDU (TBS: Transport Block Size) allocated to UE100. Therefore, if the size of the measurement report MAC CE is larger than the size of the free space in the MAC PDU, a problem occurs in which the entire measurement report MAC CE cannot be transmitted. In such cases, UE100 transmits a portion of the measurement report MAC CE using the free space in the MAC PDU described later, discarding the remaining portion of the measurement report MAC CE, or transmitting it in the next MAC PDU. In this case, since only the portion of the measurement report MAC CE that can be stored in the free area of ​​the MAC PDU is transmitted, the UE 100 can transmit some beam measurements using a truncated measurement report (MR) MAC CE corresponding to the size of the free area of ​​the MAC PDU. (5.2) MAC PDU A MAC PDU is a unit of data exchanged in the MAC layer and is a byte-aligned (e.g., aligned to octet boundaries) bit sequence. Figure 9 shows an example of an uplink (UL) MAC PDU according to the embodiment. The UL MAC PDU 500 includes one or more MAC subPDUs as shown in Figure 9. The configuration of a MAC subPDU can be one of the following patterns. MAC subPDU patterns: • A MAC subheader + a MAC SDU (Service Data Unit) • A MAC subheader + a MAC CE • A MAC subheader + padding area • A MAC subheader (including padding area) only Here, the MAC SDU (Service Data Unit) is the RLC PDU (RLC Protocol Data Unit) passed from the RLC layer. The padding area is the free space placed at the end of the MAC PDU.

[0094] The above MAC subheader format is one of the following formats: • R / F / LCID / (eLCID) / L: A general MAC subheader format. • (LX) / R / LCID / (eLCID): A format used for fixed-size MAC CEs and / or padding. • (LX) / R / LCID: A format used for MAC SDUs including UL CCCH (Uplink Common Control Channel). Here, LCID (Logical Channel ID) indicates the identification information of the logical channel. F (Format) indicates the MAC subheader format. L (Length) indicates the length of the MAC SDU or MAC CE. R / F are reserved bits or bits used for future extensions. eLCID (extended LCID) is a field for extending the LCID.

[0095] As shown in Figure 9, in the UL MAC PDU, the MAC subPDU containing the MAC CE is placed after all MAC subPDUs, including the MAC SDU, and before the MAC subPDU containing the free area 501. The measurement report MAC CE of this disclosure is stored in the free area, i.e., the padding area, contained in the MAC subPDU at the end of the MAC PDU. For this reason, the free area of ​​the MAC PDU is also referred to as the "padding area". (5.3) Padding BSR

[0096] In addition to truncated measurement reports (MAC CEs), another type of truncated MAC CE that can utilize the free space of a MAC PDU is the Padding Buffer Status Report (Padding BSR).

[0097] The buffer status report informs the gNB200 of the amount of data stored in the UE100's transmit buffer. Of the buffer status reports, the padding buffer status report is transmitted in the MAC CE format (Figure 14), which will be described later. Based on the information in the received buffer status report, the gNB200 allocates appropriate resources to the UE100.

[0098] Unlike the normal buffer status report, which the UE 100 sends when the amount of data in the buffer exceeds a certain threshold and / or when requested by the gNB 200, the padding buffer status report is placed in the free area 501 of the MAC PDU 500 as shown in Figure 9 and transmitted. The padding buffer status report is truncated by reduction or minimization so that it fits in the free area. In this way, by utilizing the free area 501 of the MAC PDU 500, the UE 100 can notify the gNB 200 of the buffer status without consuming additional radio resources. (6) Outline of the Embodiment

[0099] When both the measurement report MAC CE and the buffer status report MAC CE satisfy their respective transmission conditions, the question arises as to how to transmit them using the free area 501 of the MAC PDU 500.

[0100] Therefore, this embodiment provides a method that enables smooth transmission of MAC CEs even when the transmission of measurement report MAC CEs and the transmission of buffer status report MAC CEs conflict. In the following description, truncated measurement report MAC CEs may be simply referred to as "measurement report MAC CEs," and padding buffer status reports may be simply referred to as "buffer status reports."

[0101] The communication method according to this embodiment is a communication method executed by UE 100 in a mobile communication system that supports LTM (L1 / L2-Triggered Mobility), and comprises: determining which MAC CE to place in the free area from the measurement report MAC CE and buffer status report MAC CE according to a predetermined rule when both conditions are met: a first condition for transmitting a measurement report MAC CE (Control Element) that can be placed in the free area of ​​a MAC (Medium Access Control) PDU (Protocol Data Unit); and a second condition for transmitting a buffer status report MAC CE that can be placed in the free area. and transmitting the MAC PDU on which the determined MAC CE is placed to gNB 200.

[0102] The UE 100 according to this embodiment is a user device used in a mobile communication system that supports LTM (L1 / L2-Triggered Mobility), and comprises a control unit 130 and a transmission unit 120. The control unit 130 determines which MAC CE to place in the free area from among the measurement report MAC CE and buffer status report MAC CE according to a predetermined rule, depending on whether both conditions are met: a first condition for transmitting a measurement report MAC CE (Control Element) that can be placed in the free area of ​​the MAC (Medium Access Control) PDU (Protocol Data Unit), and a second condition for transmitting a buffer status report MAC CE that can be placed in the free area. The transmission unit 120 transmits the MAC PDU on which the determined MAC CE is placed to the gNB 200.

[0103] (6.1) First condition The first condition is an event condition for which a measurement report MAC CE is sent, and includes, for example, at least one of the following conditions among the L1 LTM measurement events described above:

[0104] - The serving cell's beam deteriorates below an absolute threshold. - The LTM candidate cell's beam improves by a certain offset compared to the serving cell's beam. - The LTM candidate cell's beam improves above an absolute threshold. - The serving cell's beam deteriorates below an absolute threshold 1, AND the LTM candidate cell's beam improves above another absolute threshold 2. Determining the first condition includes, for example, UE100 detecting a beam that has entered the event condition in event evaluation, determining for each detected beam whether the beam's entering state continued for a certain time (TTT: Time to Trigger), and if it is determined that the beam's entering state continued for a certain time (TTT), triggering the transmission of a measurement report MAC CE.

[0105] The first condition may include, for example, a transmission condition (arrival of the transmission time) when measurement reports are transmitted periodically, instead of the above event condition. Information specifying the first condition may be transmitted in advance from gNB200 to UE100 and stored in memory by UE100.

[0106] (6.2) Second condition The second condition includes, for example, at least one of the following conditions:

[0107] - The amount of the transmit buffer of UE100 exceeds a set threshold - An instruction to transmit a buffer status report (including padding BSR) is received from gNB200 - The RRC is reconfigured - New data is received - It is time to transmit according to the transmission cycle The second condition may also include, in addition to the above conditions, that padding bits are inserted into the MAC PDU and / or that the free capacity (number of padding bits) of the MAC PDU is greater than or equal to the size of the padding BSR.

[0108] The information specifying the second condition may be transmitted in advance from gNB200 to UE100 and stored in memory by UE100.

[0109] (6.3) A predetermined rule for determining which MAC CE to place in the free area among the predetermined rule measurement report MAC CE and buffer status report MAC CE will be described. The UE 100 may have previously received information specifying the predetermined rule from the gNB 200 and the predetermined rule may be set in the UE 100.

[0110] (6.3.1) Priority Condition 1 The prescribed rule may be, for example, a rule that always prioritizes the measurement report MAC CE over the buffer status report MAC CE (Priority Condition 1). By always prioritizing the transmission of the measurement report MAC CE to the gNB200, the occurrence of RLF (Radio Link Failure) is reduced due to the delay of the measurement report, which is information related to handover.

[0111] (6.3.2) Priority Condition 2 The prescribed rule may be, for example, a rule that always prioritizes the buffer status report MAC CE over the measurement report MAC CE (Priority Condition 2). Prioritizing the transmission of the buffer status report, which determines the amount of the next UL grant, can more reliably maintain the communication speed.

[0112] (6.3.3) Priority Condition 3 The prescribed rule may be a rule that follows a priority condition (priority condition 3) which alternately prioritizes measurement report MAC CEs and buffer status report MAC CEs. This allows both measurement report and buffer status report information to be transmitted to the gNB200 in a balanced manner. In the case of priority condition 3, the UE100 may keep in memory information indicating whether the MAC CE placed in the free area of ​​the previously transmitted MAC PDU is a measurement report or a buffer status report. For example, the UE100 may keep in memory toggle information indicating whether the MAC CE placed in the free area of ​​the previously transmitted MAC PDU is a measurement report or a buffer status report, and switch the toggle information each time a MAC PDU is transmitted to alternately transmit measurement report MAC CEs and buffer status report MAC CEs.

[0113] (6.3.4) Priority Condition 4 The prescribed rule may be a rule that follows a priority condition (priority condition 4) that, if a full (i.e., untruncated) buffer status report MAC CE or a full (i.e., untruncated) measurement report MAC CE has been sent most recently, the report that was not full will be given priority. In this case, the UE 100 keeps in memory, for example, toggle information indicating whether or not a full measurement report MAC CE was sent last time, and / or toggle information indicating whether or not a full buffer status report MAC CE was sent last time. Based on the toggle information, if the UE 100 sent a full measurement report MAC CE last time, it sends a buffer status report MAC CE, and if it sent a full buffer status report MAC CE last time, it sends a measurement report MAC CE.

[0114] (6.3.5) Priority Condition 5 The prescribed rule may be a rule that follows a priority condition (priority condition 5) that prioritizes the measurement report MAC CE if a full (i.e., untruncated) measurement report MAC CE has not yet been sent. In this case, the UE 100 keeps toggle information in memory indicating whether or not a full measurement report MAC CE has been sent, and based on the toggle information, sends a measurement report MAC CE if a full measurement report MAC CE has not yet been sent.

[0115] (6.3.6) Priority Condition 6 The prescribed rule may be a rule that follows a priority condition (priority condition 6) that prioritizes a buffer status report MAC CE if a full (i.e., untruncated) buffer status report MAC CE has not yet been sent. In this case, UE100 keeps toggle information in memory indicating whether or not a full buffer status report MAC CE has been sent, and based on the toggle information, sends a buffer status report MAC CE if a full buffer status report MAC CE has not yet been sent.

[0116] (6.3.7) Priority Condition 7 A measurement report MAC CE includes a first measurement report MAC CE with higher priority and a second measurement report MAC CE with lower priority than the first measurement report MAC CE, and when the first measurement report MAC CE and the second MAC CE are transmitted in the free space of different MAC PDUs, the prescribed rule may be a rule that follows a priority condition (priority condition 7) that prioritizes the first measurement report MAC CE over the buffer status report MAC CE and prioritizes the buffer status report MAC CE over the second measurement report MAC CE.

[0117] If the UE100 cannot store all beam measurements in the measurement report MAC CE, it can store the remaining unreported beam measurements in a separate MAC CE and transmit them. The measurement report MAC CE containing the higher-priority beam measurements is the first measurement report MAC CE transmitted (first measurement report MAC CE) and takes precedence over subsequent measurement report MAC CEs (second measurement report MAC CEs). The second measurement report MAC CE is also called a Subsequent MR MAC CE and is not limited to being transmitted all at once, but also includes cases where it is transmitted in multiple parts.

[0118] The second measurement report MAC CE is transmitted according to at least one of the following transmission conditions, for example.

[0119] Conditions for sending the second measurement report MAC CE: - There are unreported beam measurement values ​​(there are beam measurement values ​​being held) - The maximum number of reportable beams (N) has not been reached - A certain period of time has not elapsed since the transmission of the first measurement report MAC CE or the previous measurement report MAC CE - No new beam measurement values ​​have been acquired (the next measurement has not been performed) - If it is determined that at least one of the above conditions for setting the transmission of Subsequent MR MAC CE is met, that is, if there is a second measurement report MAC CE following the first measurement report MAC CE, UE100 will prioritize the first measurement report MAC CE over the buffer status report MAC CE, and prioritize the buffer status report MAC CE over the second MAC CE, and place them in the available area of ​​the MAC PDU.

[0120] (6.3.8) Other prescribed rules Determining which MAC CEs to place in the free area from among the measurement report MAC CEs and buffer status report MAC CEs according to prescribed rules includes placing both the measurement report MAC CE and the buffer status report MAC CE in the free area. For example, the size of each MAC CE may be reduced so that the total size of the measurement report MAC CE and the buffer status report MAC CE is less than or equal to the size of the free area, and both the measurement report MAC CE and the buffer status report MAC CE may be placed in multiple locations in the free area. For example, the size of the measurement report MAC CE and the buffer status report MAC CE may be minimized and placed in multiple locations in the free area of ​​the MAC PDU.

[0121] If reducing or minimizing the size of the measurement report MAC CE and the buffer status report MAC CE still results in a size larger than the available space in the MAC PDU, then either the reduced or minimized measurement report MAC CE or the reduced or minimized buffer status report MAC CE may be determined according to the above priority conditions and placed in the available space in the MAC PDU.

[0122] Furthermore, if the size of the free space in the MAC PDU is larger than the minimum size of the measurement report MAC CE, and the minimum size of the buffer status report MAC CE is less than or equal to the size of the free space, the minimum size buffer status report MAC CE may be placed in the free space.

[0123] (7) Figures 10 to 13 of the operation diagrams of the UE100 according to the embodiment show examples of the operation of the UE100 according to the embodiment. In each example of operation, when the first and second conditions described above are met, that is, when the transmission of the measurement report MAC CE and the transmission of the buffer status report MAC CE are triggered, the UE100 uses the free area of ​​the MAC PDU to send the MAC CE to the gNB200. The following describes each example of operation of the UE100.

[0124] (7.1) Example of operation of UE100 Figure 10 shows an example of operation of UE100 according to the embodiment.

[0125] The receiving unit 110 of UE100, which is in an RRC connected state with the cell of gNB200, receives UL Grant from gNB200 (step S31).

[0126] The control unit 130 of the UE100 to which UL Grant has been assigned determines whether the first and second conditions described above have been met (step S32), and if both conditions are met, proceeds to step S33. In this embodiment, an example of the operation of the UE100 when the first and second conditions are met is described, but if only the first condition is met, the measurement report MAC CE transmission procedure is executed, and if only the second condition is met, the buffer status report MAC CE transmission procedure is executed.

[0127] The control unit 130 of UE100 determines whether the measurement report MAC CE and buffer status report MAC CE that have triggered transmission meet any of the priority conditions of the predetermined rules described above (step S33).

[0128] The control unit 130 of the UE 100 determines which MAC CEs to place in the MAC PDU free area based on the determination of the priority conditions in step S33 (step S34). For example, if the predetermined rule is priority condition 1, the control unit 130 of the UE 100 decides to place the measurement report MAC CE in the MAC PDU free area. For example, if the predetermined rule is priority condition 2, the control unit 130 of the UE 100 decides to place the buffer status report MAC CE in the MAC PDU free area. For example, if the predetermined rule is priority conditions 3 to 6, the control unit 130 of the UE 100 refers to the toggle information described above and decides to place the MAC CEs that it has decided to transmit based on the toggle information in the MAC PDU free area.

[0129] The control unit 130 of UE100 generates a MAC PDU with the MAC CE determined in step S34 and transmits it to gNB200 via the transmission unit 120 (step S35).

[0130] Of the measurement report MAC CE and buffer status report MAC CE, any reports that were not transmitted in steps S34 to S35 may be discarded. Such untransmitted reports may be pending for a predetermined time and then transmitted through the processing in steps S34 to S35.

[0131] As described above, by determining which MAC CEs to place in the free area of ​​the MAC PDU according to predetermined priority conditions, the transmission procedure can be executed smoothly even if there is a conflict between the transmission of measurement report MAC CEs and buffer status report MAC CEs that utilize the free area of ​​the MAC PDU.

[0132] (7.2) Example 2 of operation of UE100 Figure 11 shows Example 2 of operation of UE100 according to the embodiment. In Example 2 of operation of UE100, steps S51 and S52 are the same as steps S31 and S32 in Example 1 of operation in Figure 11, so their explanation is omitted.

[0133] The control unit 130 of the UE100 to which UL Grant has been assigned reduces the size of the measurement report MAC CE and the buffer status report MAC CE, respectively (step S53). In this case, each size may be set to its minimum size. The minimum size of the measurement report MAC CE is, for example, a MAC CE that includes one beam measurement value and its subheader. The minimum size of the buffer status report MAC CE is, for example, a Short BSR MAC CE (Figure 14A), which will be described later.

[0134] The control unit 130 of UE100 determines whether the free space of the MAC PDU of the MAC CE is less than or equal to the total size of the reduced-size measurement report MAC CE and buffer status report MAC CE (i.e., the size of the multiplexed MAC CE) (step S54). If the size of the free space is less than or equal to the size of the multiplexed MAC CE, the process proceeds to step S55. If the size of the multiplexed MAC CE exceeds the size of the free space, either the measurement report MAC CE or the buffer status report MAC CE may be determined and placed in the free space according to the same priority condition determination as in operation example 1 of Figure 11 (S33 in Figure 10).

[0135] The control unit 130 of UE100 places the multiplexed MAC CE in the available area of ​​the MAC PDU (step S55).

[0136] The control unit 130 of UE100 transmits the MAC PDU containing the multiplexed MAC CE to gNB200 (step S56).

[0137] As described above, by reducing the total size of the measurement report MAC CE and buffer status report MAC CE to a size that fits within the free space of the MAC PDU, even if there is a conflict between sending the measurement report MAC CE and sending the buffer status report MAC CE, both of which utilize the free space of the MAC PDU, both can be sent simultaneously, thus enabling smooth execution of the transmission procedure.

[0138] In the above operation example 2, the control unit 130 of UE 100 follows the priority condition determination in operation example 1 ("No" in step S54) if the size of the multiplexed MAC CEs exceeds the free area of ​​the MAC PDU, but is not limited to this. The control unit 130 of UE 100 may, if the free area size is larger than the minimum size of the measurement report MAC CE and the minimum size of the buffer status report MAC CE is less than or equal to the size of the free area, prioritize placing the buffer status report MAC CE with the smallest size in the free area of ​​the MAC PDU and transmitting it. Measurement report MAC CEs that are not transmitted may be discarded. Such untransmitted measurement report MAC CEs may be pending for a predetermined time and then placed in the free area of ​​the next MAC PDU and transmitted.

[0139] (7.3) Operation Example 3 of UE100 Figures 12 and 13 show Operation Example 3 of UE100 according to the embodiment. In Operation Example 3 of UE100, steps S71 and S72 are the same as steps S31 and S32 in Operation Example 1 of Figure 10, so their explanation is omitted.

[0140] The control unit 130 of the UE100 to which UL Grant has been assigned determines whether the measurement report MAC CE is the first measurement report MAC CE (step S73). If the measurement report MAC CE is the first measurement report MAC CE, the process proceeds to step S74; otherwise, the process proceeds to step S76.

[0141] As mentioned above, the first measurement report MAC CE is the first measurement report MAC CE transmitted, containing high-priority beam measurement values, and is transmitted before the second measurement report MAC CE, which contains relatively lower-priority beam measurement values. The second measurement report MAC CE is also called a Subsequent MR MAC CE, and is not limited to being transmitted all at once, but also includes cases where it is transmitted in multiple parts.

[0142] The control unit 130 of UE100 places the first measurement report MAC CE in an empty area of ​​the MAC PDU of MAC CE (step S74), and transmits the MAC PDU to gNB200 via the transmission unit 120 (step S75).

[0143] The control unit 130 of UE100 determines whether or not there are any unsent buffer status reports MAC CEs (step S76). If there are any unsent buffer status reports MAC CEs, the process proceeds to step S77; if there are no unsent buffer status reports MAC CEs, the process proceeds to step S79.

[0144] The control unit 130 of UE100 places the buffer status report MAC CE in the available area of ​​the MAC PDU of MAC CE (step S77), and transmits the MAC PDU to gNB200 via the transmission unit 120 (step S78).

[0145] The control unit 130 of UE100 places the second measurement buffer status report MAC CE in an empty area of ​​MAC PDU (step S79), and transmits the MAC PDU to gNB200 via the transmission unit 120 (step S80).

[0146] If there are any unsent second measurement report MAC CEs after step S80, the processes in steps S76 to S80 may be repeated. Furthermore, the processes in steps S76 to S80 may be terminated when the transmission conditions for the second measurement report MAC CE described above are no longer met.

[0147] As described above, even when measurement report MAC CEs are sent in multiple parts, a smooth transmission procedure that takes priority into account can be executed by prioritizing the first measurement report MAC CE, which has a higher priority, over the buffer status report MAC CE, and prioritizing the second measurement report MAC CE, which has a lower priority.

[0148] (8) Example of BSR MAC CE Configuration Figure 14 shows an example of the configuration of a buffer status report (hereinafter also referred to as BSR). There are two types of BSR configurations: Short BSR as shown in Figure 14A and Long BSR as shown in Figure 14B. Note that these MAC CE configuration examples may also be MAC CE configuration examples for Short Truncated BSR and Long Truncated BSR, respectively.

[0149] As shown in Figure 14A, the Short BSR MAC CE has a fixed size of one octet and includes a field that stores the LCG (Logical Channel Group) ID, which is the identification information of the logical channel group, and a Buffer Size, which indicates the amount of data in the buffer for each LCG.

[0150] As shown in Figure 14B, the Long BSR MAC CE has flag information indicating whether or not each LCG has a Buffer Size, and a field for storing the Buffer Size of LCGs that have a Buffer Size. The size of the Long BSR MAC CE is variable depending on the Buffer Size of the LCGs it stores.

[0151] In padded BSRs, if a BSR MAC CE has data that can be transmitted by multiple LCGs (Logical Channel Groups), a Short BSR MAC CE is generated if the free space (number of padding bits) of the MAC PDU is less than or equal to the size of the Short BSR and its subheader, and a Long BSR MAC CE is generated if the free space is greater than the size of the Short BSR and its subheader.

[0152] Furthermore, in Short BSRs, the BSR of the LCG including the highest-priority LCH (Logical Channel) may be reported, while in Long BSRs, the LCG(s) including the LCH(s) in order of priority may be reported. Also, if the LCHs have the same priority, they may be reported in order of LCG ID.

[0153] UE100 may send a regular (non-padding BSR) Short BSR MAC CE if only a single LCG (i.e., not multiple LCGs) has data that can be transmitted, and send a Short BSR MAC CE or a Long BSR MAC CE with padding BSR if there is data that can be transmitted to LCGs other than the reported LCG.

[0154] (9) Example of the structure of the measurement report MAC CE In 3GPP Release 19, it is being considered that the measurement report MAC CE should include the following various types of information as basic information.

[0155] - Beam information: SSBRI / CRI, or LTM setting identification information + SSBRI / CRI - Beam radio quality information: L1-RSRP, or SINR - L1 LTM measurement event information: Measurement event identification information, or measurement report setting identification information (ReportConfigID) - Measurement report MAC CE maximum number of reported beams (N): The maximum number of reported beams (N) is set by gNB200.

[0156] Additionally, as optional information, the measurement report MAC CE may include information about the beam currently in use by UE100 and information about the radio quality of said beam. The presence or absence of this optional information may be set by gNB200.

[0157] Furthermore, 3GPP Release 19 is considering using SSBRI and CRI as beam identification information in LTM MR MAC CE, and setting the maximum number of reported beams (N) in event-triggered L1 LTM measurement reports to be the number of beams that can be stored in the measurement report MAC CE. In addition, 3GPP Release 19 is considering allowing the network to control (set) whether or not to report beam measurement values ​​that do not meet the event conditions, including two types of beam measurement values, SSB and CSI-RS, in a single measurement report MAC CE, and supporting Truncated measurement report MAC CEs.

[0158] Furthermore, since the maximum number of beams (N) reported for beam measurement values ​​in the MAC CE measurement report can be set via the network, it can be assumed that the MAC CE measurement report format is of variable length. Therefore, if the number of beam measurement values ​​is smaller than the set maximum number of beams (N), the efficiency of wireless resource utilization can be improved by reducing the size of the MAC CE measurement report. Consequently, how to reduce the size of the MAC CE measurement report becomes a challenge.

[0159] To reduce the size of the measurement report MAC CE by controlling the amount of information stored in the measurement report MAC CE, the following processes can be considered, for example: UE100 may store identification information in the measurement report MAC CE indicating whether the beam measurement is an SSB (Synchronization Signal Block) measurement or a CSI-RS (Channel State Information - Reference Signal) measurement. Alternatively, UE100 may store beam measurement values ​​of the same type (e.g., SSB and / or CSI-RS) in the measurement report MAC CE, and not store beam measurement values ​​of different types in the measurement report MAC CE. This eliminates the need for identification information indicating the type of beam measurement. UE100 may also store identification information in the measurement report MAC CE indicating whether the L1 measurement result of the beam measurement stored in the measurement report MAC CE is L1-RSRP (Reference Signal Received Power) or L1-SINR (Signal to Interference plus Noise Ratio). Alternatively, UE100 may store beam measurement values ​​of the same L1 measurement result type in the measurement report MAC CE, but may not store beam measurement values ​​of different L1 measurement result types in the measurement report MAC CE. This eliminates the need for identification information indicating the type of beam measurement result. UE100 may also store flag information in the measurement report MAC CE to determine whether two or more beam measurement values ​​are beam measurement values ​​for the same cell. When including multiple consecutive beam measurement values ​​from the same candidate cell, by providing flag information indicating whether or not it is the same candidate cell as the previous beam measurement value, the storage of the candidate cell identifier (e.g., LTM candidate ID or MeasID) for beam measurement values ​​from the same cell as the previous beam measurement value can be omitted. This reduces the overhead of MAC CE because it eliminates the need to repeatedly assign the same candidate cell identifier.When UE100 stores the beam measurement values ​​of multiple cells in the measurement report MAC CE, it may store the highest beam measurement value for each of the multiple cells in the measurement report MAC CE. Even if gNB200 is configured to store the beam measurement information of the current serving beam in the measurement report MAC CE, UE100 may be controlled not to store the beam measurement information of the current serving beam in the measurement report MAC CE.

[0160] If the event condition is such that the serving cell beam deteriorates below an absolute threshold, UE100 may store beam measurements of the same type of beam as the currently serving beam in the measurement report MAC CE.

[0161] The above processing makes it possible to reduce the size of the measurement report MAC CE. The above processing is not limited to applying to measurement report MAC CEs (including Truncated MAC CEs) that are placed in the free area of ​​the MAC PDU in the MAC CE transmission control described above. The above processing may be applied to the transmission of all measurement report MAC CEs.

[0162] The following describes an example configuration for achieving the above measurement report MAC CE size reduction.

[0163] (9.1) Example of Measurement Report MAC CE Configuration 1 The format of the measurement report MAC CE according to the embodiment is configured as shown in Figure 15. Figure 15 is Example 1 of the configuration of the measurement report MAC CE format according to the embodiment. Here, it is assumed that the LTM setting information transmitted from gNB200 to UE100 includes Beam ID (beam identification information: 4 bits), Triggered event info. (identification information of measurement report settings such as ReportConfigID: 6 bits), N (maximum number of reported beams: 4 bits), and Current beam report (current beam report: True).

[0164] As shown in Figure 15, MR MAC CE includes Common field, Variable field, and Optional field.

[0165] The Common field includes a 2-bit Reserve (R) area and a 6-bit Triggered event info. area. The Triggered event info. area stores identification information for the triggered L1 LTM measurement event, such as the ReportConfigID.

[0166] The Variable field includes a 1-bit SSBRI / CRI area, a 4-bit Beam ID area, and a 7-bit L1-RSRP / L1-SINR area for each beam. Figure 15 shows an example where four beams are stored in the Variable field. The SSBRI / CRI area stores identification information indicating whether the stored beam measurement value is an SSB measurement value or a CSI-RS measurement value. The Beam ID area stores identification information of the stored beam measurement value, such as SSBRI, CRI, etc. The L1-RSRP / L1-SINR area stores the beam measurement value corresponding to the Beam ID, i.e., the L1 measurement result (either L1-RSRP or L1-SINR).

[0167] The Optional field has the same region as the Variable field. The SSBRI / CRI region of the Optional field stores identification information indicating whether the beam measurement value of the UE's current serving beam is an SSB measurement value or a CSI-RS measurement value. The Beam ID region of the Optional field stores identification information of the beam measurement value of the UE100's current serving beam, such as SSBRI, CRI, etc. The L1-RSRP / L1-SINR region stores the beam measurement value of the UE100's current serving beam (either L1-RSRP or L1-SINR). Furthermore, if the Current beam report in the LTM configuration information transmitted from gNB200 to UE100 is "False", the measurement report MAC CE will not include the Optional field.

[0168] Here, the SSBRI / CRI region in the Variable field and Optional field is newly established, and UE100 stores identification information in this region indicating whether the type of beam measurement value stored in the measurement report MAC CE is an SSB measurement value or a CSI-RS measurement value. The information stored in the SSBRI / CRI region is, for example, flag information; if "1" is stored, it indicates that the type of beam measurement value is SSB, and if "0" is stored, it indicates that the type of beam measurement value is CSI-RS. The information stored in the SSBRI / CRI region may also be an ID, index, etc. that can identify SSBRI or CRI.

[0169] Furthermore, the SSBRI / CRI information in the above-mentioned MAC CE format is not always necessary, and in some cases, information about the type of beam measurement value may not be required. For example, when UE100 stores beam measurement values ​​of the same type in the MAC CE, identification information for the type of beam measurement value is not necessary. Specifically, for example, UE100 stores only beam measurement values ​​of the same type as the beam measurement value that triggered the generation of the MAC CE in the MAC CE, according to the LTM setting from gNB200, and does not store beam measurement values ​​of a different type.

[0170] (9.2) Measurement Report MAC CE Configuration Example 2 When UE100 reports beam measurement values ​​from multiple candidate cells together, it assigns candidate cell identification information (LTM candidate ID or MeasID) to each beam measurement value. Therefore, when multiple beam measurement values ​​exist from the same candidate cell, there is a problem in that the size of the measurement report MAC CE increases due to the repeated assignment of the same candidate cell identification information.

[0171] Therefore, in the configuration example 2 of the measurement report MAC CE according to the embodiment, each beam measurement value is given flag information indicating whether or not it is the same candidate cell as the previous beam measurement value. When UE 100 stores multiple beam measurement values ​​in the measurement report MAC CE, it stores in the measurement report MAC CE information indicating whether or not each beam measurement value stored in the measurement report MAC CE is a beam measurement value for the same cell as the previous beam measurement value.

[0172] Figure 16 shows an example configuration 2 of the measurement report MAC CE according to the embodiment. As shown in Figure 16, the measurement report MAC CE includes a Common field, a Variable field, and an Optional field. The Common field is the same as the Common field in the measurement report MAC CE configuration example 1 described in Figure 15, so its explanation is omitted.

[0173] The Variable field includes, for each beam, a 3-bit LTM candidate ID area, a 1-bit SSBRI / CRI area, a 4-bit Beam ID area, a 7-bit L1-RSRP / L1-SINR area, and a 1-bit Cont area. Figure 16 shows an example where five beams from four candidate cells are stored. The SSBRI / CRI area, Beam ID area, and L1-RSRP / L1-SINR area are the same as those described in Figure 15, so their explanation is omitted.

[0174] The LTM candidate ID area stores identification information for the cell to which the stored beam measurement value belongs. The Cont area stores information, such as flag information, indicating whether the stored beam measurement value is for the same cell as the previous beam measurement value. For example, if the flag information is "1", it indicates that the beam measurement value is for the same cell as the previous beam measurement value, and if it is "0", it indicates that the beam measurement value is not for a different cell than the previous beam measurement value. The UE100 does not assign an LTM candidate ID area to each beam measurement value depending on whether it is for the same cell as the previous beam measurement value (the value in the Cont area is "1"). For example, the second and fifth beam measurement values ​​shown in Figure 15 do not have an LTM candidate ID area because the corresponding Cont area values ​​are "1". This operation reduces the size of the measurement report MAC CE without duplicating the identification information of the same candidate cell, thereby improving the efficiency of wireless resource utilization.

[0175] (9.3) Measurement Report MAC CE Configuration Example 3 When UE100 reports beam measurement values ​​from multiple candidate cells together, a Ci field as shown in Figure 17 may be provided as a method for compressing the identifier information of the multiple candidate cells. Figure 17 is a diagram showing a measurement report MAC CE configuration example 3 according to the embodiment.

[0176] Measurement Report MAC CE Configuration Example 3 is similar to Measurement Report MAC CE Configuration Example 1 shown in Figure 15, but with eight 1-bit Ci fields added at the beginning of the Variable field. The "i" in the Ci field corresponds to "0" to "7", which are identification information for LTM candidate cells. The Ci field stores information indicating whether or not beam measurement values ​​for the candidate cell are present, such as flag information. For example, if the flag information is "1", it indicates that beam measurement values ​​for the candidate cell are present, and if it is "0", it indicates that beam measurement values ​​for the candidate cell are not present. Furthermore, if information indicating that beam measurement values ​​for a candidate cell are present is stored in the Ci field, the Variable field stores the beam measurement values ​​for the candidate cell corresponding to Ci.

[0177] By using the configuration of the measurement report MAC CE shown in Figure 17, only one beam measurement value can be reported for each candidate cell. Therefore, when UE100 stores the beam measurement values ​​of multiple cells in the measurement report MAC CE, it stores the highest beam measurement value for each of the multiple cells in the measurement report MAC CE. This operation reduces the size of the measurement report MAC CE by compressing the identifier information of multiple candidate cells, thereby improving the efficiency of wireless resource utilization.

[0178] (9.4) Measurement Report MAC CE Configuration Example 4 Measurement Report MAC CE Configuration Example 4 is a minimum bit count (minimum) configuration example of a Measurement Report MAC CE to further reduce the size of the Measurement Report MAC CE. Figure 18 is a diagram showing Measurement Report MAC CE Configuration Example 4 according to the embodiment.

[0179] As shown in Figure 18, Configuration Example 4 of the Measurement Report MAC CE includes only one beam measurement value and does not include an Optional field. The Optional field stores beam measurement information of the current serving (including the type of beam measurement value, beam identification information, beam measurement value, etc.) that is not necessary for selecting a target cell (beam), and therefore it is an area that can be saved. For this reason, when the UE 100 transmits a Measurement Report MAC CE with the minimum number of bits, even if the gNB 200 is set to store the beam measurement information of the current serving beam in the Measurement Report MAC CE, the UE 100 controls the system so that the beam measurement information of the current serving beam is not stored in the Measurement Report MAC CE. Furthermore, even when the UE100 transmits a normal Truncated Measurement Report MAC CE, it may be controlled not to store the beam measurement information of the current serving beam in the Measurement Report MAC CE, even if the gNB200 has configured it to do so. This operation reduces the size of the Measurement Report MAC CE to the minimum number of bits, further improving the efficiency of wireless resource utilization.

[0180] (9.5) Measurement Report MAC CE Configuration Example 5 Measurement Report MAC CE Configuration Example 5 is a configuration in which a Length region is further provided on top of Measurement Report MAC CE Configuration Example 2 shown in Figure 19, and does not include an Optional field. Figure 19 is a diagram showing Measurement Report MAC CE Configuration Example 5 according to the embodiment.

[0181] As shown in Figure 19, Configuration Example 5 of the Measurement Report MAC CE has the same regions as Configuration Example 2 of the Measurement Report MAC CE shown in Figure 16, and a 4-bit Length region is provided at the beginning of the Variable field. The Length region stores information indicating the number of beam measurement values ​​stored in the Measurement Report MAC CE. By providing this region in the Measurement Report MAC CE, the gNB200 can grasp the number of beam measurement values ​​to be reported. In particular, when a Subsequent Measurement Report MAC CE is transmitted, the gNB200 can calculate the number of unreported beam measurement values ​​by knowing the number of beam measurement values ​​to be reported from the beginning, and can receive measurement reports without omission.

[0182] Furthermore, the above-mentioned MAC CE measurement report configuration examples can be implemented not only individually but also in combination of two or more. Additionally, when combining the above-mentioned MAC CE measurement report configuration examples, some of the configurations may be modified.

[0183] Furthermore, although the above embodiments were described using only the measurement report MAC CE, this disclosure is not limited to the measurement report MAC CE and is also applicable to the Truncated measurement report MAC CE.

[0184] (10) Other Embodiments The LTM in the above embodiments may be read as conditional LTM. For example, the MCG LTM of the interCU or intraCU may be a conditional LTM of the MCG of the interCU or intraCU. Also, the SCG LTM of the intraCU described above may be a conditional LTM of the SCG of the intraCU. In a conditional LTM, for example, the RRC Reconfiguration message in step S4 of Figure 7 includes information indicating the execution conditions for LTM cell switching (e.g., wireless quality conditions) for each LTM candidate cell. Instead of the cell switching command MAC transmitted from the gNB200, the UE100 performs LTM cell switching for LTM candidate cells that meet the set execution conditions (wireless quality conditions). This eliminates the need to send and receive L1 measurement reports and cell switching command MACs, enabling faster LTM cell switching.

[0185] The above-described operation flows can be performed not only independently, but also in combination of two or more operation flows. For example, some steps of one operation flow may be added to another operation flow, or some steps of one operation flow may be replaced with some steps of another operation flow. It is not necessary to execute all steps in each flow; only some steps may be executed. Furthermore, the order of steps in each flow may be changed as appropriate.

[0186] In the embodiments and examples described above, an example was given in which the base station is an NR base station (gNB), but the base station may also be an LTE base station (eNB) or a 6G base station. Furthermore, the base station may also be a relay node such as an IAB (Integrated Access and Backhaul) node. The base station may also be a DU of an IAB node. Additionally, UE100 may be an MT (Mobile Termination) of an IAB node. That is, UE100 may be a terminal function unit (a type of communication module) for the base station to control a repeater that performs signal relay. Such a terminal function unit is referred to as an MT. Examples of MTs other than IAB-MT include, for example, NCR (Network Controlled Repeater)-MT and RIS (Reconfigurable Intelligent Surface)-MT.

[0187] Furthermore, the term "network node" primarily refers to a base station, but may also refer to a core network device or a part of a base station (CU, DU, or RU). Additionally, a network node may consist of a combination of at least a part of the core network device and at least a part of a base station.

[0188] A program may be provided that causes a computer to execute each process performed by the UE100 or gNB200. The program may be recorded on a computer-readable medium. Using a computer-readable medium, it is possible to install the program on a computer. Here, the computer-readable medium on which the program is recorded may be a non-transient recording medium. The non-transient recording medium is not particularly limited, but may be a recording medium such as a CD-ROM and / or DVD-ROM. Alternatively, the circuits that execute each process performed by the UE100 or gNB200 may be integrated, and at least a part of the UE100 or gNB200 may be configured as a semiconductor integrated circuit (chipset, SoC: System on a chip).

[0189] The functions realized by UE100 or gNB200 may be implemented in a circuit or processing circuit, including general-purpose processors, application-specific processors, integrated circuits, ASICs (Application Specific Integrated Circuits), CPUs (Central Processing Units), conventional circuits, and / or combinations thereof, programmed to realize the described functions. A processor, including transistors and / or other circuits, is considered a circuit or processing circuit. A processor may be a programmed processor that executes a program stored in memory. In this specification, circuit, unit, and means are hardware programmed to realize or perform the described functions. Such hardware may be any hardware disclosed herein, or any hardware known to be programmed to realize or perform the described functions. If the hardware is a processor that is considered to be of the type of circuit, then the circuit, means, or unit is a combination of hardware and software used to constitute the hardware and / or processor.

[0190] The phrases “based on” and “depending on / in response to” as used in this disclosure do not mean “based solely on” or “depending solely on” unless otherwise specified. The phrase “based on” means both “based solely on” and “at least partially on.” Similarly, the phrase “depending on” means both “at least partially on” and “at least partially on.” The terms “include,” “comprise,” and variations thereof do not mean that only the listed items are included, but that they may include only the listed items or that they may include additional items in addition to the listed items. Furthermore, the term “or” as used in this disclosure is not intended to mean exclusive OR. In addition, any reference to elements using designations such as “first,” “second,” etc., as used in this disclosure does not generally limit the quantity or order of those elements. These designations may be used herein as a convenient way to distinguish between two or more elements. Thus, references to first and second elements do not mean that only two elements may be employed therein, or that the first element must precede the second element in any way. In this disclosure, if articles are added by translation, such as a, an, and the in English, these articles shall be considered plural unless it is clearly indicated otherwise by the context.

[0191] Although the embodiments have been described in detail above with reference to the drawings, the specific configuration is not limited to those described above, and various design changes can be made without departing from the gist of the invention.

[0192] This application claims priority to U.S. Provisional Application No. 63 / 754129 (filed February 5, 2025), the entirety of which is incorporated into the specification of this application.

[0193] (11) First Addendum The features of the above-described embodiment are described below.

[0194] - Appendix 1 A communication method performed by a user device in a mobile communication system that supports LTM (L1 / L2-Triggered Mobility), comprising: determining which MAC CE to place in the free area from the measurement report MAC CE and the buffer status report MAC CE according to a predetermined rule, in response to both conditions being met: a first condition for transmitting a measurement report MAC CE (Control Element) that can be placed in the free area of ​​a MAC (Medium Access Control) PDU (Protocol Data Unit); and a second condition for transmitting a buffer status report MAC CE that can be placed in the free area; and transmitting the MAC PDU on which the determined MAC CE is placed to a network node.

[0195] - Appendix 2 The communication method described in Appendix 1, wherein the predetermined rule is that the measurement report MAC CE always takes precedence over the buffer status report MAC CE.

[0196] - Appendix 3 The communication method described in Appendix 1, wherein the predetermined rule is that the buffer status report MAC CE always takes precedence over the measurement report MAC CE.

[0197] - Appendix 4 The communication method described in Appendix 1, wherein the predetermined rule is to alternately prioritize the measurement report MAC CE and the buffer status report MAC CE.

[0198] - Appendix 5 The communication method described in Appendix 1, wherein the predetermined rule is to reduce the size of each MAC CE so that the total size of the measurement report MAC CE and the buffer status report MAC CE is less than or equal to the size of the free area, and to place both the measurement report MAC CE and the buffer status report MAC CE in the free area.

[0199] - Appendix 6 The communication method described in Appendix 1, wherein the predetermined rule is that if the size of the free area is greater than the minimum size of the measurement report MAC CE, and the minimum size of the buffer status report MAC CE is less than or equal to the size of the free area, the buffer status report MAC CE of the minimum size is placed in the free area.

[0200] - Appendix 7 The communication method as described in Appendix 1, wherein the measurement report MAC CE includes a first measurement report MAC CE with higher priority and a second measurement report MAC CE other than the first measurement report MAC CE with higher priority, and when the first measurement report MAC CE and the second MAC CE are transmitted in the free area of ​​different MAC PDUs, the predetermined rule is that the first MAC CE takes precedence over the buffer status report MAC CE, and the buffer status report MAC CE takes precedence over the second MAC CE.

[0201] - Appendix 8 The user device receives information specifying the predetermined rule from the network node using the communication method described in any of Appendix 1 to 7.

[0202] - Appendix 9 The communication method described in any of Appendix 1 to 8, wherein the user device stores identification information indicating whether the beam measurement value is an SSB (Synchronization Signal Block) measurement value or a CSI-RS (Channel State Information - Reference Signal) measurement value in the measurement report MAC CE.

[0203] - Appendix 10 The communication method according to any one of the appendices 1 to 9, wherein the user device stores flag information in the measurement report MAC CE to identify whether two or more beam measurements are beam measurements for the same cell.

[0204] - Appendix 11 When the user device stores the beam measurement values ​​of each of the multiple cells in the measurement report MAC CE, the communication method according to any one of the appendices 1 to 10 stores the highest beam measurement value for each of the multiple cells in the measurement report MAC CE.

[0205] - Appendix 12 A communication method according to any one of Appendix 1 to 11, which controls the user device so that it does not store the beam measurement information of the current serving beam in the measurement report MAC CE, even if the network node has configured the user device to store the beam measurement information of the current serving beam in the measurement report MAC CE.

[0206] - Appendix 13 The communication method according to any one of Appendix 1 to 12, wherein the user device stores the beam measurement values ​​of the same type of beam as the currently serving beam in the measurement report MAC CE when the event condition is a condition in which the serving cell beam deteriorates below an absolute threshold.

[0207] - Appendix 14 A user device used in a mobile communication system that supports LTM (L1 / L2-Triggered Mobility), comprising: a control unit that determines which MAC CE to place in the free area from the measurement report MAC CE and the buffer status report MAC CE according to a predetermined rule when both conditions are met: a first condition for transmitting a measurement report MAC CE (Control Element) that can be placed in the free area of ​​a MAC (Medium Access Control) PDU (Protocol Data Unit); and a second condition for transmitting a buffer status report MAC CE that can be placed in the free area; and a transmission unit that transmits the MAC PDU on which the determined MAC CE is placed to a network node.

[0208] (12) Second Addendum 1. Introduction In RAN#102, a work item relating to NR Mobility Expansion Phase 4 was approved. This included the objective of defining event-triggered L1 measurement reporting. In RAN2#128, the details of this topic were discussed and the following agreements were reached.

[0209] Agreements regarding L1 Event-Driven Measurement Reporting (MR): "1. The Time To Trigger (TTT) is evaluated per beam, and the measurement report is triggered only by beams that meet the conditions (entry / exit) for the entire duration of the TTT." "2. If the current beam is changed and the entry conditions are still met with the new current beam, the TTT timer is not restarted." "3. The TTT applies to the exit conditions." "4. The network can configure which RS type (SSB or CSI-RS) to use for LTM event evaluation." "5. Either CSI-RS or SSB can be configured as a candidate beam, and the measurement RS of the serving cell beam is determined based on the candidate beam to ensure the same RS type. That is, in accordance with the agreement in RAN1, the RS for the current beam of the serving cell is the QCL of the indicated TCI state. "It is either identical to RS or QCL (Quasi-Collocation)." "6. SSBRI and CRI are used to represent candidate beam IDs in LTM MR MAC CE." "7. In event-triggered L1 LTM measurement reports, Max N is the total number of beams included in MR MAC CE." "8. In event-triggered L1 LTM measurement reports, NW controls whether beams that do not satisfy the event can be reported according to N beams in MR MAC CE." "9. A single MAC CE format for event-triggered L1 measurement reports is used for both SSB and CSI-RS reference signals." "10. Supports truncated measurement report MAC CE."

[0210] This addendum discusses the details of event-triggered L1 measurement reporting.

[0211] 2. Discussion 2.1. Cell RAN2 reported in MR MAC CE agreed to support events LTM2, 3, 4, and 5 as follows: During event evaluation, event LTM2 involves only the serving cell, event LTM4 involves only the candidate cell, and events LTM3 and 5 involve both the serving cell and the candidate cell.

[0212] "3. As L1 LTM measurement events, the following LTM events are supported based on the beam-specific quality of the serving cell and candidate cell: • Event LTM2: The serving cell beam falls below the absolute threshold. • Event LTM3: The candidate cell beam is better than the serving cell beam by an offset amount. • Event LTM4: The candidate cell beam is better than the absolute threshold. • Event LTM5: The serving cell beam falls below absolute threshold 1, and the candidate cell beam is better than another absolute threshold 2."

[0213] Regarding the serving beam's measurement RS (i.e., CSI-RS or SSB), RAN2 agreed that it would be implicitly indicated by the candidate beam's measurement RS.

[0214] "5. Either CSI-RS or SSB can be configured as the candidate beam, and the measured RS of the serving cell beam is determined based on the candidate beam to ensure the same RS type. That is, in accordance with the agreement in RAN1, the RS of the serving cell for the current beam is either identical to the QCL RS of the indicated TCI state, or QCL."

[0215] Regarding Event LTM2, it is natural to assume that the current beam (either CSI-RS or SSB) is the measurement target, since the current beam is the most important beam for Event LTM2 (e.g., to constitute the subsequent Event LTM3 / 5), and the candidate cell beam is not involved in the evaluation of Event LTM2.

[0216] Proposal 1: RAN2 should clearly indicate in the configuration of Event LTM2 that the measured RS of the serving cell beam is the current beam corresponding to the object being measured (i.e., it should not have a configuration to indicate whether to use CSI-RS or SSB).

[0217] Regarding the current beam from the serving cell, RAN2 agreed that it is configurable whether the current beam information and quantity are included in MR MAC CE as follows:

[0218] "14. Additional information included in MR MAC CE: • Current beam information and quantity based on the NW configuration."

[0219] Even if the network configured the measurement report triggered by event LTM2 in that way, it is somewhat unusual that the MR MAC CE does not include "current beam information and quantity."

[0220] Proposal 2: RAN2 should clarify that the MR MAC CE triggered by event LTM2 always includes the L1 measurement result of the current beam (i.e., it is not configurable).

[0221] For events LTM3 and LTM5, since both the serving cell beam and the candidate cell beam are involved in the evaluation, it is assumed that the beam quantities from both the serving cell and the candidate cell will be included in the MR MAC CE. On the other hand, it remains unclear whether the MR MAC CE should further include the quantities of other beams from other cells (i.e., adjacent cells that are not candidate cells). Technically, it is possible to report the quantities from adjacent cells if there is sufficient space in the MR MAC CE, but this would incur additional signaling overhead. Therefore, it is somewhat preferable to include only the beam quantities from the serving cell and candidate cell in the MR MAC CE rather than leaving the inclusion of adjacent cell quantities to the network configuration.

[0222] Proposal 3: RAN2 should discuss whether the MR MAC CE triggered by either event LTM3 or event LTM5 includes only the L1 measurement results of beams from the serving cell and candidate cells (i.e., does not include beams from other cells / adjacent cells).

[0223] 2.2. It was agreed that the beam RAN2 reported at MR MAC CE would consist of the total number of beams included in MR MAC CE (i.e., "N"), and whether or not beams that do not meet the event criteria would be reported, as determined by gNB.

[0224] "7. In the event-triggered L1 LTM measurement report, the maximum N is the total number of beams included in the MR MAC CE." "8. In the event-triggered L1 LTM measurement report, NW controls whether or not to report beams that do not satisfy the event, according to the N beams in the MR MAC CE."

[0225] These agreements suggest that even if a UE has L1 measurement results for M beams and M > N, the MR MAC CE will only report with L1 measurement results for N beams. In this case, the UE needs to choose which beams to report and which not to report. The following three options are considered for the UE to determine which beams to report.

[0226] Option 1: The beam that triggered the event has the highest priority in MR MAC CE, beams that satisfy the event have the second highest priority, and the other beams (those that do not satisfy the event) have the lowest priority.

[0227] Option 2: The beams are sorted by L1-RSRP (or L1-SINR) and included in MR MAC CE in this order.

[0228] Option 3: The beams are sorted from the first (and still fulfilling) event to the last, and are included in MR MAC CE in this order.

[0229] Since it is clear that the beams that trigger / satisfy the event are the most useful information for network decisions, option 1 is considered direct.

[0230] Options 2 and 3 may, in some cases, be considered similar to option 1. Generally, option 2 would be beneficial because good beam measurement results are considered in the network. Option 3 may indicate how long each beam has satisfied the event, i.e., how stable each beam is.

[0231] The beam measurement results reported by MR MAC CE are directly related to appropriate decisions made on the network. Therefore, which beams should be included in MR MAC CE should be specified, rather than left to the UE implementation. RAN2 should discuss how the UE should select the beams to be reported.

[0232] Proposal 4: RAN2 should agree to always include the beam that triggered the event in MR MAC CE.

[0233] Proposal 5: RAN2 should discuss how the UE determines which other beams to report (i.e., beams other than the one that triggered the event) (e.g., based on whether they satisfy the event criteria, the order of beam quality, and / or the order of beam stability).

[0234] 2.3. The truncated MR MAC CE RAN2 agreed to the introduction of the truncated MR MAC CE. "10. Support the truncated measurement reporting MAC CE."

[0235] However, the reasons and methods for using the shortened MR MAC CE have not been sufficiently discussed. According to the paper proposing the above agreement, the shortened MR MAC CE is intended for use when the uplink (UL) grant is limited, i.e., when the transport block size (TBS) is not sufficient to carry a "normal" MR MAC CE.

[0236] Proposal 6: RAN2 should ensure that a shortened MR MAC CE is triggered if the "normal" MR MAC CE is not delivered in this UL grant.

[0237] The paper further suggests that "subsequent" shortened MR MAC CEs could report the remaining beam measurement results, making it possible for multiple MR MAC CEs to report all beams. This would be useful, for example, when the network needs more beam measurements for better decisions, but delays in reporting (i.e., waiting for the next UL grant) could cause the measurements to become outdated. RAN2 should discuss whether it is beneficial for multiple MR MAC CEs across different UL grants to report all beam measurement results that a UE has at a given time.

[0238] Proposal 7: RAN2 should discuss whether the “subsequent” shortened MR MAC CE reports the remaining beam that was not reported by the “initial” shortened MR MAC CE.

[0239] According to the current specifications, two types of shortened MAC CEs are defined: shortened BSR and shortened BFR. A shortened BSR is used as a padding BSR when multiple LCGs (Logical Channel Groups) have transmittable data, while a shortened BFR is used when there are no candidate beams in that MAC CE. Considering measurement reports, it may be useful if an MR MAC CE is transmittable within the padding bits (like a padding BSR), but it does not make sense if there are no candidate beams in an MR MAC CE triggered by a particular event (like a shortened BFR). Therefore, RAN2 should discuss whether shortened MR MAC CEs can be transmitted within the padding bits of a MAC PDU.

[0240] Proposal 8: RAN2 should discuss whether a shortened MR MAC CE can be transmitted within the padding bits (like the padding BSR).

[0241] 2.4. MR MAC CE Format RAN2 agreed that beam information and beam quantities for up to N beams could be included in the measurement report MAC CE. It is clear that triggered event information is not related to N beams (i.e., only one piece of information is needed per MAC CE).

[0242] "14. Basic information included in MR MAC CE: • Beam information: Further consideration is needed regarding whether to use SSBRI / CRI or (LTM configuration ID + SSB / CSI-RS ID) for N beams. • Beam quantity: L1-RSRP or SINR (according to RAN1) for N beams. • Triggered event information (e.g., ReportConfigID). MR MAC CE can contain up to N beams (further consideration is needed regarding whether beams should satisfy the event). N can be configured by NW."

[0243] "15. Additional information included in MR MAC CE: • Current beam information and quantity based on the NW configuration."

[0244] RAN2 further agreed that SSBRI and CRI would be used as beam IDs for MR MAC CE, and that a single MAC CE format would be defined for both SSB and CSI-RS.

[0245] "6. In the LTM MR MAC CE, SSBRI and CRI are used to represent candidate beam IDs." "7. In the event-triggered L1 LTM measurement report, Maximum N is the total number of beams included in the MR MAC CE." "8. In the event-triggered L1 LTM measurement report, NW controls whether beams that do not satisfy the event can be reported, according to the N beams in the MR MAC CE." "9. A single MAC CE format for event-triggered L1 measurement reports is used for both the SSB and CSI-RS reference signals."

[0246] Regarding the reporting of "N beams," it is quite natural to assume that the MAC CE should be variable length, since "N" is configurable (and therefore variable), and it is efficient to reduce the MAC CE size when the number of beam measurement results is less than the configured "N". To begin examining the details of the MR MAC CE format, RAN2 should first agree that the MR MAC CE should be variable length.

[0247] Proposal 9: RAN2 should agree that MR MAC CE should be of variable length.

[0248] Regarding the current beam included as additional information, it is unclear whether it should be counted as one of the "N beams." Furthermore, since the current beam is evident from the perspective of the serving cell, it should also be clarified whether information about the current beam (i.e., SSBRI or CRI) is truly necessary.

[0249] Proposal 10: RAN2 should clarify whether the current beam counts as "N beams" and whether beam information (i.e., SSBRI / CRI) is truly necessary.

[0250] For the beam information field and beam quantity field, it should be assumed that the definition / specification of the CSI feedback should be reused. For the current bit widths, SSBRI and CRI depend on the configuration (i.e., the number of SSB / CSI-RS resources in the corresponding resource set), while RSRP and SINR are 7 bits each for absolute values ​​and 4 bits each for differential values.

[0251] RAN2 agreed that "a single MAC CE format for event-triggered L1 measurement reporting will be used for both SSB and CSI-RS reference signals." This is certainly possible because the bit widths of SSBRI and CRI are the same (when the same number of SSB and CSI-RS resources are configured). In this case, it will be discussed how the network knows whether the beam ID reported in MR MAC CE refers to SSBRI or CRI. If "triggered event information" is associated with a beam ID type (SSB or CSI-RS), the beam ID type reported in MR MAC CE can be implicitly known. However, this is only applicable to beams involved in event evaluation. Since RAN2 agreed that "the network controls whether beams that do not satisfy an event can report," "beams that do not satisfy an event" may not be involved in event evaluation (e.g., beams from serving cells / LTM candidate cells for different event evaluations, or beams from other neighboring cells). Therefore, depending on the type of beam the MR MAC CE can report, an explicit one-bit designation will be required for each beam ID within the MR MAC CE to distinguish whether the beam ID refers to SSBRI or CRI.

[0252] Furthermore, since the bit widths of L1-RSRP and L1-SINR are similarly the same, it is also possible to consider using the same format for both. In that case, a similar argument would be applicable, namely, a separate explicit one-bit designation would be needed for each beam quantity in MR MAC CE to distinguish whether the quantity refers to L1-RSRP or L1-SINR.

[0253] Proposal 11: RAN2 should agree that the same MR MAC CE format should be used for both measurements (i.e., L1-RSRP and L1-SINR).

[0254] Proposal 12: RAN2 should discuss whether an explicit one-bit indication is required in MR MAC CE to distinguish between SSB and CSI-RS (and, if agreed, to distinguish between L1-RSRP and L1-SINR).

[0255] Currently, the L1 filter is left to the implementation of the UE, and for Rel-19, "RAN2 assumes that filtering of the L1 measurement results is necessary. Whether a defined L1 filtering is required or whether it can be left to the implementation of the UE is up to RAN1." Regardless of whether the L1 filter is standardized or not, the filter coefficients change dynamically, for example, due to the movement speed of the UE. Therefore, reporting "L1 filter information," such as the number of L1-RSRP samples, may be useful because the gNB may optimize its own L1 filter when making cell switch decisions.

[0256] Proposal 13: RAN2 should discuss whether or not to report L1 filter information in MR MAC CE.

[0257] 1: Mobile communication system 5: Network 10: RAN 11: L1 filter 12: Beam integration / selection unit 13: L3 filter 14: Evaluation unit 15: L3 beam filter 16: Beam selection unit 20: CN 100: UE 110: Receiving unit 120: Transmitting unit 130: Control unit 140: Wireless communication unit 200: gNB 210: Transmitting unit 220: Receiving unit 230: Control unit 240: Network communication unit 241: Transmitting unit 242: Receiving unit 250: Wireless communication unit 300: AMF / UPF

Claims

A communication method performed by a user device in a mobile communication system that supports LTM (L1 / L2-Triggered Mobility), To generate an event-triggered L1 measurement report MAC (Medium Access Control) CE (Control Element), To generate a buffer status report MAC CE, This includes transmitting the L1 measurement report MAC CE to the network node with priority over the buffer status report MAC CE, according to predetermined rules. Communication method. 　 At least one of the L1 measurement report MAC CE and the buffer status report MAC CE can be placed in the available space of the MAC PDU (Protocol Data Unit). The communication method according to claim 1. 　 The user device receives information specifying the predetermined rule from the network node. The communication method according to claim 1. 　 The user device is configured to set the maximum number of report beams that can be stored in the L1 measurement report MAC CE. The communication method according to claim 1. 　 The user device determines whether to generate a reduced-size L1 measurement report MAC CE depending on the uplink wireless resources. The communication method according to claim 1. A user device used in a mobile communication system that supports LTM (L1 / L2-Triggered Mobility), A control unit that generates an event-triggered L1 measurement report MAC (Medium Access Control) CE (Control Element) and a buffer status report MAC CE, The system includes a transmission unit that transmits the L1 measurement report MAC CE to the network node with priority over the buffer status report MAC CE, according to predetermined rules. User device.

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