COMMUNICATION DEVICE, BASE STATION, AND COMMUNICATION METHOD

Abstract

A communication method comprising a step (S201) for, in an RRC idle state or an RRC inactive state, acquiring from a base station (200) a system information block indicating a plurality of TRS resource set configurations, and a step (S203) for receiving from the base station (200) the TRS using a TRS resource set configuration selected from the plurality of TRS resource set configurations. The system information block includes condition information designating, for each of the TRS resource set configurations, a condition for enabling the communication device (100) to select the TRS resource set configuration.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on and claims the benefit of priority to Patent Application No. 2021-125815, filed on July 30, 2021, and Patent Application No. 2021-209118, filed on December 23, 2021, the entire contents of which are incorporated herein by reference. [Technical field]

[0002] The present disclosure relates to a communication device, a base station, and a communication method used in a mobile communication system. [Background technology]

[0003] In a mobile communication system that complies with the technical specifications of 3GPP (registered trademark; the same applies below) (3rd Generation Partnership Project), a standardization project for mobile communication systems, the reference signals (RS) that are set individually for a communication device in a Radio Resource Control (RRC) connected state include a Channel State Information-RS (CSI-RS) and a Tracking Reference Signal (TRS). The CSI-RS is a reference signal for measuring the Channel Quality Indicator (CQI) and performing Layer 3 measurements. The TRS is a reference signal for time-frequency synchronization (time-frequency tracking).

[0004] In 3GPP, discussions are underway to standardize technology for reducing power consumption for communication devices in an RRC idle state or an RRC inactive state. In such technology, it is being considered to make TRS resources (also called "TRS opportunities") configured for communication devices in an RRC connected state available for communication devices in an RRC idle state or an RRC inactive state (see, for example, Non-Patent Document 1). Specifically, a base station broadcasts multiple TRS resource settings (TRS configurations) by a system information block (also called "broadcast information").

[0005] A communication device in an RRC idle state or an RRC inactive state can achieve synchronization without receiving an SSB (SS / PBCH Block) by receiving a TRS using a TRS resource setting set by a system information block, and can shorten the wake-up duration from establishing synchronization to monitoring paging. Furthermore, by not receiving an SSB, an increase in power consumption due to receiving an SSB is suppressed. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] 3GPP contribution: R1-2105435, “Discussion on TRS / CSI-RS occasion(s) for idle / inactive UEs” Summary of the Invention

[0007] When multiple TRS resource set configurations are transmitted in a system information block, the communication device selects one of the available TRS resource set configurations and receives the TRS using the selected TRS resource set configuration. However, it is not clear how the communication device selects the TRS resource set configuration, and there is a concern that the communication device may not be able to appropriately select the TRS resource set configuration.

[0008] Therefore, the present disclosure aims to provide a communication device, a base station, and a communication method that enable appropriate selection of a TRS resource set configuration even when multiple TRS resource set configurations are transmitted in a system information block.

[0009] A communication device according to a first aspect is a device that performs time-frequency synchronization in downlink using a tracking reference signal (TRS). The communication device (100) includes: a control unit (120) that acquires a system information block (400) indicating a plurality of TRS resource set configurations from a base station (200) in a radio resource control (RRC) idle state or an RRC inactive state; and a receiving unit (112) that receives the TRS from the base station (200) using a TRS resource set configuration selected from the plurality of TRS resource set configurations. The system information block (400) includes, for each of the TRS resource set configurations, condition information (410) that specifies a condition under which the communication device (100) can select the TRS resource set configuration.

[0010] A base station according to a second aspect is a device used in a mobile communication system. The base station (200) includes a transmitter (211) that transmits a tracking reference signal (TRS) used by a communication device (100) for time-frequency synchronization in downlink and a system information block (400) indicating a plurality of TRS resource set configurations. The system information block (400) includes condition information (410) that specifies a condition under which the communication device (100) can select the TRS resource set configuration for each of the TRS resource set configurations.

[0011] A communication method according to a third aspect is a method used in a communication device (100) that performs time-frequency synchronization in downlink using a tracking reference signal (TRS). The communication method includes a step (S201) of acquiring from a base station (200) a system information block (400) indicating multiple TRS resource set configurations in a radio resource control (RRC) idle state or an RRC inactive state, and a step (S203) of receiving the TRS from the base station (200) using a TRS resource set configuration selected from the multiple TRS resource set configurations. The system information block (400) includes, for each of the TRS resource set configurations, condition information (410) that specifies a condition under which the communication device (100) can select the TRS resource set configuration. [Brief description of the drawings]

[0012] [Figure 1] 1 is a diagram showing a configuration of a mobile communication system according to an embodiment. [Diagram 2] FIG. 2 is a diagram illustrating an example of the configuration of a protocol stack in the mobile communication system according to the embodiment. [Diagram 3] FIG. 1 illustrates an example of operation of a UE in an RRC connected state. [Figure 4] FIG. 1 illustrates an example of operation for a UE in an RRC idle state or an RRC inactive state. [Diagram 5] A diagram showing an example of the operation of a UE in an RRC idle state or an RRC inactive state for receiving a TRS. [Figure 6] FIG. 2 is a diagram showing the configuration of a UE according to an embodiment. [Figure 7] FIG. 2 is a diagram illustrating a configuration of a base station according to an embodiment. [Figure 8] A diagram showing an operation for reducing the amount of information in a system information block according to one embodiment. [Figure 9] FIG. 11 is a diagram illustrating an example of a configuration of a system information block according to an embodiment. [Figure 10] A diagram showing the definition of some parameters in a system information block according to one embodiment. [Figure 11] A diagram showing the definition of some parameters in a system information block according to one embodiment. [Figure 12] FIG. 13 illustrates paging subgrouping. [Figure 13] A diagram illustrating operations related to the selection of a TRS resource configuration according to one embodiment. [Figure 14] FIG. 11 is a diagram illustrating an example of a configuration of a system information block according to an embodiment. [Figure 15] FIG. 13 is a diagram showing an operation according to a modified example. [Figure 16] FIG. 11 is a diagram showing a first configuration example of a system information block according to a modified example. [Figure 17] FIG. 13 is a diagram showing a second configuration example of a system information block according to a modified example. [Figure 18] FIG. 13 is a diagram showing an operation according to a modified example. [Figure 19] FIG. 1 is a diagram for explaining an overview of eDRX. [Figure 20] FIG. 1 is a diagram for explaining problems related to eDRX. [Figure 21] FIG. 13 is a diagram showing an operation according to a modified example. [Figure 22] FIG. 13 is a diagram showing an example of the configuration of a system information block according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] A mobile communication system according to an embodiment will be described with reference to the drawings. In the description of the drawings, the same or similar parts are denoted by the same or similar reference numerals.

[0014] (Configuration of a mobile communication system) A configuration of a mobile communication system 1 according to an embodiment will be described with reference to Fig. 1. The mobile communication system 1 is, for example, a system that complies with the 3GPP Technical Specification (TS). In the following, the mobile communication system 1 will be described by taking as an example a 3GPP standard 5th Generation System (5GS), that is, a mobile communication system based on NR (New Radio).

[0015] The mobile communication system 1 includes a network 10 and a communication device (User Equipment: UE) 100 that communicates with the network 10. The network 10 includes a Next Generation Radio Access Network (NG-RAN) 20 that is a 5G radio access network, and a 5G Core Network (5GC) 30 that is a 5G core network.

[0016] The UE 100 is a device used by a user. The UE 100 is a mobile device such as a mobile phone terminal such as a smartphone, a tablet terminal, a notebook PC, a communication module, or a communication card. The UE 100 may be a vehicle (e.g., a car, a train, etc.) or a device provided therein. The UE 100 may be a transport body other than a vehicle (e.g., a ship, an airplane, etc.) or a device provided therein. The UE 100 may be a sensor or a device provided therein. The UE 100 may be called by another name such as a mobile station, a mobile terminal, a mobile device, a mobile unit, a subscriber station, a subscriber terminal, a subscriber device, a subscriber unit, a wireless station, a wireless terminal, a wireless device, a wireless unit, a remote station, a remote terminal, a remote device, or a remote unit.

[0017] The NG-RAN 20 includes a plurality of base stations 200. Each base station 200 manages at least one cell. A cell constitutes the smallest unit of a communication area. For example, one cell belongs to one frequency (carrier frequency) and is composed of one component carrier. The term "cell" may represent a wireless communication resource, and may represent a communication target of the UE 100. Each base station 200 can perform wireless communication with the UE 100 located in its own cell. The base station 200 communicates with the UE 100 using a protocol stack of the RAN. The base station 200 provides NR user plane and control plane protocol terminations toward the UE 100, and is connected to the 5GC 30 via an NG interface. Such an NR base station 200 may be referred to as a gNodeB (gNB).

[0018] The 5GC 30 includes a core network device 300. The core network device 300 includes, for example, an Access and Mobility Management Function (AMF) and / or a User Plane Function (UPF). The AMF performs mobility management of the UE 100. The UPF provides a function specialized for user plane processing. The AMF and the UPF are connected to the base station 200 via an NG interface.

[0019] An example of the configuration of a protocol stack in the mobile communication system 1 according to the embodiment will be described with reference to FIG.

[0020] The protocol for the wireless section between UE 100 and base station 200 includes a physical (PHY) layer, a medium access control (MAC) layer, a radio link control (RLC) layer, a packet data convergence protocol (PDCP) layer, and a radio resource control (RRC) layer.

[0021] The PHY layer performs encoding / decoding, modulation / demodulation, antenna mapping / demapping, and resource mapping / demapping. Data and control information are transmitted between the PHY layer of the UE 100 and the PHY layer of the base station 200 via a physical channel.

[0022] A physical channel is composed of multiple OFDM symbols in the time domain and multiple subcarriers in the frequency domain. One subframe is composed of multiple OFDM symbols in the time domain. A resource block is a resource allocation unit and is composed of multiple OFDM symbols and multiple subcarriers. A frame can be composed of 10 ms and can include 10 subframes, each composed of 1 ms. A subframe can include a number of slots according to the subcarrier interval.

[0023] Among the physical channels, the Physical Downlink Control Channel (PDCCH) plays a central role for purposes such as downlink scheduling assignments, uplink scheduling grants, and transmission power control.

[0024] In NR, the UE 100 can use a bandwidth narrower than the system bandwidth (i.e., the bandwidth of the cell). The base station 200 configures the UE 100 with a bandwidth portion (BWP) consisting of consecutive PRBs. The UE 100 transmits and receives data and control signals in the active BWP. For example, up to four BWPs can be configured for the UE 100. Each BWP may have a different subcarrier interval, and may overlap with each other in frequency. When multiple BWPs are configured for the UE 100, the base station 200 can specify which BWP to activate by control in the downlink. This allows the base station 200 to dynamically adjust the UE bandwidth according to the amount of data traffic of the UE 100, etc., and can reduce UE power consumption.

[0025] For example, the base station 200 can configure up to three control resource sets (CORESETs) for each of up to four BWPs on the serving cell. The CORESET is a radio resource for control information to be received by the UE 100. Up to 12 CORESETs can be configured for the UE 100 on the serving cell. Each CORESET has an index of 0 to 11. For example, the CORESET is composed of six resource blocks (PRBs) and one, two, or three consecutive OFDM symbols in the time domain.

[0026] The MAC layer performs data priority control, retransmission processing using hybrid ARQ (HARQ), random access procedures, etc. Data and control information are transmitted between the MAC layer of the UE 100 and the MAC layer of the base station 200 via a transport channel. The MAC layer of the base station 200 includes a scheduler. The scheduler determines the uplink and downlink transport format (transport block size, modulation and coding scheme (MCS)) and the resources to be allocated to the UE 100.

[0027] The RLC layer transmits data to the RLC layer on the receiving side by using the functions of the MAC layer and the PHY layer. Data and control information are transmitted between the RLC layer of the UE 100 and the RLC layer of the base station 200 via logical channels.

[0028] The PDCP layer performs header compression / decompression and encryption / decryption.

[0029] A Service Data Adaptation Protocol (SDAP) layer may be provided above the PDCP layer. The Service Data Adaptation Protocol (SDAP) layer maps IP flows, which are units for QoS control by the core network, to radio bearers, which are units for QoS control by the access stratum (AS).

[0030] The RRC layer controls logical channels, transport channels, and physical channels according to the establishment, re-establishment, and release of radio bearers. RRC signaling for various settings is transmitted between the RRC layer of the UE 100 and the RRC layer of the base station 200. When there is an RRC connection between the RRC of the UE 100 and the RRC of the base station 200, the UE 100 is in an RRC connected state. When there is no RRC connection between the RRC of the UE 100 and the RRC of the base station 200, the UE 100 is in an RRC idle state. When the RRC connection between the RRC of the UE 100 and the RRC of the base station 200 is suspended, the UE 100 is in an RRC inactive state.

[0031] The NAS layer located above the RRC layer performs session management and mobility management for the UE 100. NAS signaling is transmitted between the NAS layer of the UE 100 and the NAS layer of the core network device 300 (AMF). The UE 100 has an application layer and the like in addition to the protocol of the radio interface.

[0032] (Assumed scenario) With reference to FIG. 3 to FIG. 5, an assumed scenario in the mobile communication system 1 according to the embodiment will be described.

[0033] FIG. 3 shows an example of the operation of the UE 100 in the RRC connected state.

[0034] In step S11, base station 200 configures CSI-RS resources and / or TRS resources individually for UE 100. Specifically, base station 200 transmits UE-dedicated RRC signaling including a set of CSI-RS resource configuration parameters and / or a set of TRS resource configuration parameters to UE 100.

[0035] For example, a parameter set for configuring TRS / CSI-RS is CSI-ResourceConfig / NZP-CSI-RS-ResourceSet, and includes bwp-ID, resourceType, trs-Info, repetition, powerControlOffset, powerControlOffsetSS, requisiteDomainAllocation, firstOFDMSymbolInTimeDomain, Density, startingRB, nrofRBs, and subcarrierSpacing as respective parameters (see 3GPP TS38.331). Here, trs-Info is a parameter indicating whether or not the antenna ports of all NZP-CSI-RS resources in the CSI-RS resource set are the same. Here, the parameter set in this embodiment may be referred to as a parameter set.

[0036] In step S12, base station 200 transmits CSI-RS and / or TRS to UE 100 using the configured CSI-RS resource and / or TRS resource. CSI-RS and TRS are examples of downlink reference signals. UE 100 receives CSI-RS and / or TRS. UE 100 performs CQI measurement and Layer 3 measurement using CSI-RS. UE 100 performs time-frequency synchronization using TRS.

[0037] In step S13, the base station 200 and the UE 100 perform data communication.

[0038] In this manner, for UE 100 in the RRC connected state, CSI-RS resources and / or TRS resources are individually configured for UE 100.

[0039] FIG. 4 illustrates an example of operation for a UE 100 in an RRC idle state or an RRC inactive state.

[0040] The UE 100 in the RRC idle state or the RRC inactive state monitors paging from the base station 200. Specifically, the UE 100 checks whether there is paging addressed to the UE 100 by receiving a PDCCH (Physical Downlink Control Channel) from the base station 200. For example, the UE 100 may receive a paging message by receiving (decoding) downlink control information (DCI) to which a CRC (Cyclic Redundancy Check) parity bit scrambled by a P-RNTI (Paging Radio Network Temporary Identifier) ​​is added in the PDCCH. Here, the base station 200 may set the P-RNTI for the UE 100. The DCI may be a DCI format used for scheduling a PDSCH (Physical Downlink Shared Channel). That is, the paging message may be transmitted in the PDSCH. Here, the DCI to which the CRC parity bit scrambled by the P-RNTI is added is also referred to as a paging DCI. Here, in order to reduce power consumption, the UE 100 discontinuously monitors paging using discontinuous reception (DRX). Such a cycle for monitoring paging is called a DRX cycle. A frame in which the UE 100 should monitor paging is called a paging frame (PF), and a subframe in which the UE 100 should monitor paging is called a paging occasion (PO).

[0041] In step S21, the base station 200 transmits an SSB to the UE 100. The SSB is another example of a downlink reference signal. The SSB includes a primary synchronization signal (PSS), a secondary synchronization signal (SSS), a physical broadcast channel (PBCH), and a demodulation reference signal (DMRS). For example, the SSB may be composed of four consecutive OFDM symbols in the time domain. The SSB may also be composed of 240 consecutive subcarriers (i.e., 20 resource blocks) in the frequency domain. The PBCH is a physical channel that carries a master information block (MIB). The UE 100 performs time and frequency synchronization by receiving the SSB.

[0042] In step S22, UE 100 monitors and receives paging in PO. Note that UE 100 maintains a wake-up state from receiving SSB in step S21 to PO. Therefore, the longer the time from the reception timing of SSB to the timing of PO, the longer the wake-up duration becomes, and the more the power consumption of UE 100 increases.

[0043] In 3GPP, discussions are being conducted toward standardization of a technology for reducing power consumption for a UE 100 in an RRC idle state or an RRC inactive state. In such a technology, it is being considered to make a TRS resource (also referred to as a "TRS opportunity") configured for a UE 100 in an RRC connected state available for a UE 100 in an RRC idle state or an RRC inactive state. Specifically, the base station 200 broadcasts a plurality of TRS resource configurations by a system information block (also referred to as "broadcast information"). Here, in this embodiment, the TRS resource configuration may include one or more parameters used to configure a CSI-RS resource and / or a TRS resource.

[0044] 5 shows an example of an operation of the UE 100 in the RRC idle state or the RRC inactive state to receive the TRS. The TRS may be a CSI-RS used for tracking purposes. That is, in this embodiment, the TRS resource may include a CSI-RS resource.

[0045] In step S31, the base station 200 broadcasts a system information block (SIB) indicating multiple TRS resource configurations. Specifically, the base station 200 transmits a system information block including multiple TRS resource configuration parameter sets on a broadcast channel. Such a system information block may be an existing system information block other than the system information block type 1 (SIB1), or may be a newly introduced type of system information block. The UE 100 receives the system information block and acquires multiple TRS resource configuration parameter sets (i.e., multiple TRS resource set configurations).

[0046] Here, the TRS resource configuration parameter group (TRS resource set configuration) for configuring the TRS for the UE 100 in the RRC idle state or the RRC inactive state may be only a part of the parameter group configured for the UE 100 in the RRC connected state. For example, the parameters bwp-Id, resourceType, repetition, aperiodicTriggeringOffset, trs-Info, powerControlOffset, nrofPorts, firstOFDMSymbolInTimeDomain2, cdm-Type, and density may be predefined fixed values ​​without being configured by the system information block. That is, these parameters may not be included in the system information block.

[0047] The base station 200 may notify the UE 100 of a TRS resource configuration (TRS resource set configuration) to which the TRS is actually transmitted, among a plurality of TRS resource configurations (a plurality of TRS resource set configurations) configured in the system information block, as an available TRS resource configuration. Such notification may be performed by layer 1 signaling (for example, DCI) or layer 3 signaling (for example, system information block). For example, the base station 200 may transmit information indicating whether the TRS is transmitted in one or a plurality of configured TRS resources (hereinafter, also referred to as first information, Availability indication). That is, the first information may be used to indicate a TRS resource configuration (and / or a TRS resource) available for transmitting the TRS. For example, the first information may be included in a paging DCI. Also, the first information may be included in a DCI to which a CRC parity bit scrambled by an RNTI other than the P-RNTI (hereinafter, also referred to as a first RNTI) is added. For example, the base station 200 may configure the first RNTI for the UE 100. That is, the layer 1 signaling may include a paging DCI and / or a DCI to which a CRC parity bit scrambled by the first RNTI is added. Also, the first information may be included in the layer 3 signaling (e.g., a system information block).

[0048] For example, a correspondence between each bit (bit field) of the first information and one or more TRS resource configurations may be specified, and a value set to each bit of the first information may be used to indicate whether a TRS is transmitted in a TRS resource corresponding to one or more TRS resource configurations. For example, when a bit of the first information is set to "1", it may be indicated that a TRS is transmitted in a TRS resource based on the corresponding TRS resource configuration. That is, when a bit of the first information is set to "1", it may be indicated that the corresponding TRS resource configuration (and / or the TRS resource) is available for transmitting a TRS. Also, when a bit of the first information is set to "0", it may be indicated that a TRS is not transmitted in a TRS resource based on the corresponding TRS resource configuration. That is, when a bit of the first information is set to "0", it may be indicated that the corresponding TRS resource configuration (and / or the TRS resource) is unavailable for transmitting a TRS.

[0049] Here, as described later, one or more TRS resource configurations corresponding to each bit of the first information may be individual TRS configuration parameter sets. That is, a correspondence between each bit of the first information and one or more individual TRS configuration parameter sets may be specified, and a value set to each bit of the first information may be used to indicate whether a TRS is transmitted in a TRS resource corresponding to one or more individual TRS configuration parameter sets.

[0050] Also, for example, the correspondence between a value set in a bit (bit field) of the first information and one or more TRS resource configurations may be set by the base station 200. For example, the base station 200 may transmit information used for setting the correspondence between a value set in a bit of the first information and one or more TRS resource configurations in a system information block. For example, the correspondence between a first value (e.g., “01”) set in a bit of the first information and one or more TRS resource configurations (e.g., the first TRS resource configuration) may be set. Also, the correspondence between a second value (e.g., “10”) set in a bit of the first information and one or more TRS resource configurations (e.g., the second TRS resource configuration) may be set. Also, the correspondence between a third value (e.g., “11”) set in a bit of the first information and one or more TRS resource configurations (e.g., the third TRS resource configuration) may be set. Here, the multiple TRS resource configurations may include all TRS resource configurations set by the base station 200. That is, when UE 100 receives first information set to a first value (e.g., "01"), it may assume that the TRS will be transmitted in a TRS resource based on the corresponding one or more TRS resource configurations (e.g., the first TRS resource configuration). Also, when UE 100 receives first information set to a second value (e.g., "10"), it may assume that the TRS will be transmitted in a TRS resource based on the corresponding one or more TRS resource configurations (e.g., the second TRS resource configuration). Also, when UE 100 receives first information set to a third value (e.g., "11"), it may assume that the TRS will be transmitted in a TRS resource based on the corresponding one or more TRS resource configurations (e.g., the third TRS resource configuration).

[0051] Here, as described later, one or more TRS resource configurations corresponding to the value set in the bit of the first information may be an individual TRS configuration parameter set. That is, the correspondence between the value set in the bit (bit field) of the first information and one or more individual TRS configuration parameter sets may be set by the base station 200.

[0052] In addition, the number of bits (bit length) of the first information may be determined based on the number of individual TRS setting parameter sets set by base station 200.

[0053] In step S32, base station 200 transmits a TRS. UE 100 selects one TRS resource configuration (available TRS resource configuration) from one or more TRS resource configurations, and receives the TRS using the selected TRS resource configuration. For example, UE 100 may select (determine) an available TRS resource configuration for transmitting the TRS based on the first information. That is, UE 100 may select (determine) whether or not the TRS is transmitted in the configured TRS resource based on the first information. UE 100 can achieve time and frequency synchronization by receiving the TRS without receiving an SSB.

[0054] In step S33, UE 100 monitors and receives paging in PO. Note that UE 100 maintains a awake state from when it receives TRS in step S31 until PO. If the time from the reception timing of TRS to the timing of PO is short, the wake-up duration is short, and the power consumption of UE 100 is reduced. Also, UE 100 can reduce the power consumption associated with the reception of SSB by not receiving SSB.

[0055] However, when multiple TRS resource configurations are transmitted in a system information block in step S31, the amount of information in the system information block may be huge, so there is a concern that overhead increases and utilization efficiency of radio resources may decrease. In particular, since the system information block is broadcast information that is periodically transmitted, utilization efficiency of radio resources may decrease significantly. In one embodiment described later, an operation for reducing the amount of information in the system information block that transmits multiple TRS resource configurations will be described.

[0056] Furthermore, the UE 100 that has received the system information block selects one TRS resource configuration (available TRS resource configuration) from one or more TRS resource configurations, and receives the TRS using the selected TRS resource configuration. However, it is not clear how the UE 100 selects the TRS resource configuration, and there is a concern that the selection of the TRS resource configuration in the UE 100 may not be performed appropriately. In one embodiment described later, an operation for appropriately selecting a TRS resource configuration will be described.

[0057] (Configuration of communication device) The configuration of the UE 100 according to the embodiment will be described with reference to Fig. 6. The UE 100 includes a communication unit 110 and a control unit 120.

[0058] The communication unit 110 performs wireless communication with the base station 200 by transmitting and receiving radio signals to and from the base station 200. The communication unit 110 has at least one transmission unit 111 and at least one reception unit 112. The transmission unit 111 and the reception unit 112 may be configured to include multiple antennas and RF circuits. The antenna converts a signal into radio waves and radiates the radio waves into space. The antenna also receives radio waves in space and converts the radio waves into a signal. The RF circuit performs analog processing of the signal transmitted and received via the antenna. The RF circuit may include a high-frequency filter, an amplifier, a modulator, a low-pass filter, and the like.

[0059] The control unit 120 performs various controls in the UE 100. The control unit 120 controls communication with the base station 200 via the communication unit 110. The above-mentioned and below-mentioned operations of the UE 100 may be operations controlled by the control unit 120. The control unit 120 may include at least one processor capable of executing a program and a memory that stores the program. The processor may execute a program to perform the operation of the control unit 120. The control unit 120 may include a digital signal processor that performs digital processing of signals transmitted and received via the antenna and the RF circuit. The digital processing includes processing of a protocol stack of the RAN. The memory stores a program executed by the processor, parameters related to the program, and data related to the program. The memory may include at least one of a ROM (Read Only Memory), an EPROM (Erasable Programmable Read Only Memory), an EEPROM (Electrically Erasable Programmable Read Only Memory), a RAM (Random Access Memory), and a flash memory. All or a part of the memory may be included in the processor.

[0060] In the UE 100 configured in this manner, the control unit 120 acquires a system information block indicating multiple TRS resource configurations from the base station 200 in an RRC idle state or an RRC inactive state. The receiving unit 112 receives a TRS from the base station 200 using a TRS resource configuration selected from the multiple TRS resource configurations. The control unit 120 performs time-frequency synchronization (time-frequency tracking) in the downlink using the TRS.

[0061] In one embodiment, the system information block includes, as separate information elements, a set of TRS configuration parameters common to two or more TRS resource configurations and a set of individual TRS configuration parameters that may have different values ​​for each TRS resource configuration. By defining such a common TRS configuration parameter set as one information element, it becomes possible to consolidate two or more parameters having the same value between two or more TRS resource configurations into one. That is, it becomes possible to reduce redundantly signaled parameters. Therefore, even when a plurality of TRS resource configurations are transmitted in a system information block, overhead is reduced and a decrease in radio resource utilization efficiency is suppressed.

[0062] In one embodiment, the system information block includes condition information for each TRS resource configuration (TRS resource set configuration) that specifies a condition under which the UE 100 can select the TRS resource configuration. This allows the UE 100 to appropriately select a TRS resource configuration to be applied to TRS reception from among multiple TRS resource configurations based on the condition information. Therefore, even when multiple TRS resource configurations are transmitted in the system information block, it is possible to appropriately select a TRS resource configuration.

[0063] (Base station configuration) The configuration of the base station 200 according to the embodiment will be described with reference to Fig. 7. The base station 200 includes a communication unit 210, a network interface 220, and a control unit 230.

[0064] The communication unit 210 receives, for example, a radio signal from the UE 100 and transmits a radio signal to the UE 100. The communication unit 210 has at least one transmission unit 211 and at least one reception unit 212. The transmission unit 211 and the reception unit 212 may be configured to include an RF circuit. The RF circuit performs analog processing of a signal transmitted and received via an antenna. The RF circuit may include a high-frequency filter, an amplifier, a modulator, a low-pass filter, and the like.

[0065] The network interface 220 transmits and receives signals to and from the network. For example, the network interface 220 receives signals from adjacent base stations connected via an Xn interface, which is an interface between base stations, and transmits signals to the adjacent base stations. The network interface 220 also receives signals from the core network device 300 connected via an NG interface, and transmits signals to the core network device 300.

[0066] The control unit 230 performs various controls in the base station 200. For example, the control unit 230 controls communication with the UE 100 via the communication unit 210. The control unit 230 also controls communication with a node (for example, an adjacent base station, the core network device 300) via the network interface 220. The operations of the base station 200 described above and below may be operations under the control of the control unit 230. The control unit 230 may include at least one processor capable of executing a program and a memory that stores the program. The processor may execute a program to perform the operation of the control unit 230. The control unit 230 may include a digital signal processor that performs digital processing of signals transmitted and received via the antenna and the RF circuit. The digital processing includes processing of a protocol stack of the RAN. The memory stores the program executed by the processor, parameters related to the program, and data related to the program. All or a part of the memory may be included in the processor.

[0067] In base station 200 configured in this manner, transmission unit 211 transmits a TRS used by UE 100 for time-frequency synchronization in downlink, and system information block 400 indicating a plurality of TRS resource configurations.

[0068] In one embodiment, the system information block includes, as separate information elements, a set of TRS configuration parameters common to two or more TRS resource configurations and a set of individual TRS configuration parameters that may have different values ​​for each TRS resource configuration. As a result, as described above, even when a plurality of TRS resource configurations are transmitted in the system information block, overhead is reduced and a decrease in radio resource utilization efficiency is suppressed.

[0069] In one embodiment, the system information block includes, for each TRS resource configuration (TRS resource set configuration), condition information that specifies a condition under which the TRS resource configuration can be selected by the UE 100. As a result, as described above, even when a plurality of TRS resource configurations are transmitted in the system information block, it is possible to appropriately select the TRS resource configuration.

[0070] (System Information Block Information Reduction Actions) An operation related to reducing the amount of information of a system information block according to an embodiment will be described with reference to Fig. 8 and Fig. 9. This operation is based on the above-described configuration and operation. Fig. 8 illustrates such an operation. The UE 100 is in an RRC idle state or an RRC inactive state.

[0071] In step S101, the base station 200 (transmitter 211) broadcasts a system information block (SIB) indicating N (N≧2) TRS resource configurations. In one embodiment, the system information block includes, as separate information elements, one common TRS configuration parameter set common to the N TRS resource configurations and N individual TRS configuration parameter sets that may have different values ​​for each TRS resource configuration. Here, the one common TRS configuration parameter set common to the N TRS resource configurations may be a parameter set including one or more parameters used in the TRS resource configuration, and may be a parameter set used in common for the N TRS resource configurations. In addition, the individual TRS configuration parameter set that may have different values ​​for each TRS resource configuration may be a parameter set including one or more parameters used in the TRS resource configuration, and may be a parameter set used individually for each of the N TRS resource configurations.

[0072] For example, the common TRS configuration parameter group includes at least one of a parameter indicating the frequency range of the TRS, a parameter indicating the power offset of the TRS relative to the synchronization signal, a parameter indicating the periodicity and time offset of the TRS, and a parameter related to the Quasi Co-Location (QCL) of the TRS. Since these parameters have the same value among N TRS resource configurations, the parameters are defined as one for the N TRS resource configurations, thereby reducing the number of parameters to be signaled redundantly.

[0073] The individual TRS configuration parameter group includes at least one of a parameter indicating a frequency direction allocation of the TRS, a parameter indicating a time direction allocation of the TRS, and a parameter indicating a scrambling identifier of the TRS. These parameters may have different values ​​among the N TRS resource configurations, and therefore are defined individually for each of the N TRS resource configurations.

[0074] The UE 100 (receiving unit 112) receives a system information block from the base station 200. Then, the UE 100 (control unit 120) acquires one common TRS setting parameter set and N individual TRS setting parameter sets from the received system information block.

[0075] In step S102, the UE 100 (control unit 120) selects one of the TRS resource configurations (available TRS resource configurations) from among the N TRS resource configurations. The UE 100 (control unit 120) acquires an overall TRS configuration parameter set corresponding to the selected TRS resource configuration by combining an individual TRS configuration parameter set and a common TRS configuration parameter set corresponding to the selected TRS resource configuration. For example, the UE 100 (control unit 120) may select (determine) one of the individual TRS configuration parameter sets from among the N individual TRS configuration parameter sets based on the first information (values ​​set in bits of the first information). That is, the UE 100 (control unit 120) may select an individual TRS configuration parameter set based on the first information, and identify a TRS resource configuration available for transmitting a TRS from the selected individual TRS configuration parameter set and the common TRS configuration parameter set.

[0076] That is, the first information may be applied to the individual TRS setting parameter set. Also, the first information may not be applied to the common TRS setting parameter set. For example, the first information may be used to indicate an individual TRS setting parameter set for identifying a TRS resource to which a TRS is transmitted (i.e., a TRS resource setting available for transmitting a TRS). For example, as described above, a correspondence between each of the bits (bit field) of the first information and one or more individual TRS setting parameter sets may be specified, and one or more individual TRS setting parameter sets may be indicated using a value set to each of the bits of the first information. Also, a correspondence between a value set to each of the bits (bit field) of the first information and one or more individual TRS setting parameter sets may be set by base station 200, and one or more individual TRS setting parameter sets may be indicated using a value set to each of the bits of the first information. Here, each of the one or more individual TRS setting parameter sets may be identified by an identifier (for example, NZP-CSI-RS-ResourceId described later).

[0077] Also, the number of bits of the first information may be determined based on the number of individual TRS setting parameter groups set by the base station 200. For example, when two individual TRS setting parameter groups are set by the base station 200, the number of bits of the first information may be two bits. Also, when four individual TRS setting parameter groups are set by the base station 200, the number of bits of the first information may be four bits. In this way, by determining the number of bits of the first information based on the number of individual TRS setting parameter groups set by the base station 200, it is possible to reduce the amount of information exchanged between the base station 200 and the UE 100.

[0078] In step S103, the UE 100 (receiving unit 112) receives a TRS from the base station 200 by using a combination of an individual TRS setting parameter group and a common TRS setting parameter group corresponding to the TRS resource setting selected in step S102. The UE 100 (control unit 120) performs time-frequency synchronization (time-frequency tracking) in the downlink based on the received TRS. Note that the TRS may be transmitted from the base station 200 to another UE 100 in the RRC connected state.

[0079] Here, when the first information is used to instruct an available TRS resource configuration for the transmission of TRS, a validity period for the instruction may be set. That is, when the first information is used to instruct the transmission of TRS in the TRS resource, a period during which the transmission of TRS in the TRS resource is valid may be set. For example, the base station 200 may transmit information for setting (and / or instructing) the validity period by including it in the layer 3 signaling (for example, a system information block) and / or the layer 1 signaling (for example, DCI). In addition, the validity period may be set as a valid time (for example, a timer value) or may be set as the number of paging cycles. For example, when the validity period is set and the UE 100 receives the first information indicating the transmission of TRS in the TRS resource, the UE 100 may consider that the TRS is transmitted in the TRS resource during the validity period. That is, when the validity period is set and the UE 100 receives the first information indicating the available TRS resource configuration, the UE 100 may consider that the available TRS resource configuration is valid during the validity period.

[0080] Here, UE 100 may start (or re-start) the validity period based on reception of first information indicating transmission of TRS in the TRS resource (i.e., first information indicating an available TRS resource configuration). For example, UE 100 may start (or re-start) the validity period when the value of the received first information is different from the value of the previously received first information. Also, UE 100 may continue the validity period when the value of the received first information is the same as the value of the previously received first information.

[0081] Here, as described above, the TRS resource configuration indicated by the first information may be an individual TRS configuration parameter set. That is, the validity period may be applied to the individual TRS configuration parameter set. Also, the validity period may not be applied to the common TRS configuration parameter set. For example, the validity period may be used to indicate a period during which an individual TRS configuration parameter set for identifying a TRS resource in which a TRS is transmitted (that is, a TRS resource configuration available for transmitting a TRS) is valid. For example, when the validity period is set and the UE 100 receives the first information indicating the individual TRS configuration parameter set, the UE 100 may consider that the TRS is transmitted in a TRS resource identified using the individual TRS configuration parameter set (and the common TRS configuration parameter set) during the validity period. That is, when the validity period is set and the UE 100 receives the first information indicating an available individual TRS configuration parameter set, the UE 100 may consider that the individual TRS configuration parameter set is valid during the validity period. That is, the UE 100 may identify a TRS resource configuration available for transmitting a TRS from a valid dedicated TRS configuration parameter set and a common TRS configuration parameter set.

[0082] In step S104, UE 100 monitors and receives paging in the PO. Note that UE 100 may maintain a awake state from when it receives the TRS in step S103 until the PO. If the time from the reception timing of the TRS to the timing of the PO is short, the wake-up duration is short, and the power consumption of UE 100 is reduced. In addition, UE 100 can reduce the power consumption associated with the reception of SSB by not receiving SSB.

[0083] As described above, the communication method used by the UE 100 performing time-frequency synchronization in downlink using a TRS includes step S101 of acquiring, in a radio resource control (RRC) idle state or an RRC inactive state, a system information block 400 indicating N TRS resource configurations from the base station 200, and step S103 of receiving a TRS from the base station 200 using a TRS resource configuration selected from the N TRS resource configurations. The system information block includes, as separate information elements, one common TRS configuration parameter set common to the N TRS resource configurations, and N individual TRS configuration parameter sets that can have different values ​​for each TRS resource configuration.

[0084] 9 shows a configuration example of a system information block 400 according to an embodiment. Here, a configuration example in the case described in the RRC technical specification (TS38.331) is shown. Note that the system information block 400 that transmits the TRS resource configuration is assumed to be a newly introduced type of system information block (SIBXX), but may be a configuration example in which a new information element is added to an existing type of system information block.

[0085] The system information block (SIBXX) 400 includes the configuration of the CSI-RS for tracking for use by the UE 100 in RRC idle or RRC inactive state.

[0086] Specifically, the system information block (SIBXX) 400 includes either a first dedicated TRS setting list (nzp-CSI-RS-ResourceSetListForTracking-r17) 401A or a second dedicated TRS setting list (nzp-CSI-RS-ResourceListForTracking-r17) 401B. Note that "-r17" means that the information elements are introduced in Release 17 of the 3GPP technical specifications, but these information elements may be introduced in Release 18 or later.

[0087] The first individual TRS configuration list (nzp-CSI-RS-ResourceSetListForTracking-r17) 401A is an example of a group of N individual TRS configuration parameters. The first individual TRS configuration list (nzp-CSI-RS-ResourceSetListForTracking-r17) 401A is a list of N (1..maxNrofNZP-CSI-RS-ResourceSets) TRS resource set configurations (NZP-CSI-RS-ResourceSetSIB-r17) 403A. The TRS resource set configuration (NZP-CSI-RS-ResourceSetSIB-r17) 403A is a collection of multiple TRS resource configurations.

[0088] The second individual TRS configuration list (nzp-CSI-RS-ResourceListForTracking-r17) 401B is another example of a group of N individual TRS configuration parameters. The second individual TRS configuration list (nzp-CSI-RS-ResourceListForTracking-r17) 401B is a list of N (1 .. maxNrofNZP-CSI-RS-Resources) TRS resource configurations (NZP-CSI-RS-ResourceSIB-r17) 403B.

[0089] In addition, the system information block (SIBXX) 400 includes one common TRS setting parameter set (nzp-CSI-RS-ResourceCommon-r17 / NZP-CSI-RS-ResourceCommon-r17) 402.

[0090] Each TRS resource set configuration (NZP-CSI-RS-ResourceSetSIB-r17) 403A included in the first individual TRS configuration list (nzp-CSI-RS-ResourceSetListForTracking-r17) 401A includes a TRS resource set identifier (nzp-CSI-ResourceSetId-r17 / NZP-CSI-RS-ResourceSetId) and an identifier (NZP-CSI-RS-ResourceId) of each TRS resource configuration (NZP-CSI-RS-ResourceSIB-r17) included in the set. In other words, one TRS resource set configuration is configured by the TRS resource configuration (NZP-CSI-RS-ResourceSIB-r17) indicated by each identifier (NZP-CSI-RS-ResourceId).

[0091] The TRS resource configuration (NZP-CSI-RS-ResourceSIB-r17) 403B includes an identifier of the TRS resource configuration (nzp-CSI-RS-ResourceId / NZP-CSI-RS-ResourceId), a parameter (frequencyDomainAllocation) indicating the allocation of the TRS in the frequency direction, a parameter (firstOFDMSymbolInTimeDomain) indicating the allocation of the TRS in the time direction, and a parameter (scramblingID / ScramblingId) indicating the scrambling identifier of the TRS. The definitions of these parameters are shown in Figure 10. The parameter (frequencyDomainAllocation) indicates the frequency domain allocation in the physical resource block according to "7.4.1.5.3" of TS38.211, and for example, only "row 1" (4 bits) is used. The parameter (firstOFDMSymbolInTimeDomain) indicates the time domain allocation in the physical resource block, specifically the first OFDM symbol of the physical resource block used for CSI-RS, and may be a value between "0" and "9", for example. Note that firstOFDMSymbolInTimeDomain indicates the first symbol in a slot, but the second symbol in the same slot can be implicitly derived using the symbol index as firstOFDMSymbolInTimeDomain+4. The parameter (scramblingID / ScramblingId) indicates the scrambling identifier according to "5.2.2.3.1" of TS 38.214. These parameters are necessary to separate each TRS (CSI-RS) from other TRS (CSI-RS), and therefore are included in the individual TRS configuration parameter group.

[0092] On the other hand, the common TRS setting parameter group (NZP-CSI-RS-ResourceCommon-r17) 402 includes a parameter (csi-FrequencyOccupation-r17 / CSI-FrequencyOccupation) indicating the frequency direction occupation range of the TRS, a parameter (powerControlOffsetSS-r17) indicating the power offset of the TRS with respect to the synchronization signal, a parameter (periodicityAndOffset-r17 / CSI-ResourcePeriodicityAndOffsetSIB-r17) indicating the periodicity and time offset of the TRS, and a parameter (qcl-InfoForTracking-r17) related to the QCL of the TRS. FIG. 11 shows the definitions of these parameters. The parameter (csi-FrequencyOccupation-r17 / CSI-FrequencyOccupation) indicates the frequency direction occupation range of the TRS by the starting resource block number (startingRB) and the number of resource blocks (nrofRBs). The parameter (powerControlOffsetSS-r17) indicates the power offset of the TRS (NZP CSI-RS) with respect to the resource element (RE) of the secondary synchronization signal (SSS). The parameter (periodicityAndOffset-r17 / CSI-ResourcePeriodicityAndOffsetSIB-r17) indicating the periodicity and time offset of the TRS indicates the periodicity and time offset of the TRS in the number of slots. The parameter (qcl-InfoForTracking-r17) related to the QCL of the TRS includes a parameter (referenceSignal-r17) indicating a downlink reference signal having a QCL relationship with the TRS, and a parameter (qcl-Type-r17) indicating the QCL relationship. These parameters are common to each TRS resource configuration with the same value.

[0093] (TRS resource setting selection behavior) Before describing the operation related to the selection of a TRS resource configuration, a paging subgrouping will be described with reference to Fig. 12. Here, in this embodiment, a resource configuration may be replaced with a resource set configuration.

[0094] Regarding paging reception, there is a mechanism called paging subgrouping to minimize the number of UEs 100 that wake up and reduce power consumption. A paging message transmitted by the base station 200 includes an identifier of each UE 100 that the network calls. A UE 100 in an RRC idle state or an RRC inactive state wakes up in a PO to monitor and receive a paging message, and when its own identifier is included in the paging message received from the base station 200, it assumes that a call has been made and performs an operation of transitioning to an RRC connected state, for example.

[0095] In this way, in the paging reception operation, all UEs 100 to which the same PO is assigned wake up in the PO to perform paging monitoring. A group of UEs to which the same PO is assigned is called a paging group. Here, UEs 100 that are not actually called by the network also wake up, resulting in extra power consumption.

[0096] Therefore, each UE 100 assigned to the same PO is classified into a paging subgroup of a small unit, and a paging subgroup ID is assigned from the network to each UE 100. FIG. 12 shows an example in which a paging group is divided into three paging subgroups with paging subgroup IDs "#1" to "#3". Although an example in which the number of UEs 100 belonging to each paging subgroup is three is shown, the number of UEs 100 belonging to each paging subgroup may be one or two, or may be four or more. The assignment of a paging subgroup ID to each UE 100 may be performed, for example, when the UE 100 is registered in the network. The network assigns a paging subgroup ID according to an identifier, a paging probability, and / or a power consumption profile of each UE 100.

[0097] For example, prior to a PO, the network (base station 200) notifies each UE 100 of the paging subgroup ID to which the UE 100 belongs that is to be called by the paging message transmitted in the PO. Each UE 100 wakes up in the PO and performs paging monitoring only when it is notified of the paging subgroup ID to which it belongs. This allows UEs 100 that belong to some paging subgroups to not wake up in the PO, thereby suppressing unnecessary power consumption.

[0098] In one embodiment, the paging subgroup ID thus assigned to the UE 100 is used as a selection condition for selecting a TRS resource configuration (TRS resource set configuration).

[0099] An operation related to the selection of a TRS resource configuration according to an embodiment will be described with reference to Fig. 13 and Fig. 14. This operation is based on the above-mentioned configuration and operation. Fig. 13 illustrates such an operation. The UE 100 is in an RRC idle state or an RRC inactive state.

[0100] In step S201, the base station 200 (transmitter 211) broadcasts a system information block (SIB) indicating N (N≧2) TRS resource configurations. In one embodiment, the system information block includes, for each TRS resource configuration, condition information specifying a condition under which the UE 100 can select the TRS resource configuration.

[0101] For example, the condition information includes an identifier that can be assigned to the UE 100. The identifier may be a paging subgroup ID that identifies a UE group (paging subgroup) to be paged. That is, the system information block includes a paging subgroup ID for each TRS resource configuration. However, the identifier is not limited to a paging subgroup ID, and may be an identifier that is assigned in advance according to the characteristics and / or state of the UE 100.

[0102] The UE 100 (receiving unit 112) receives a system information block from the base station 200. Then, the UE 100 (control unit 120) acquires each TRS resource configuration and a paging subgroup ID (condition information) from the received system information block.

[0103] In step S202, UE 100 (control unit 120) selects a TRS resource configuration that satisfies the condition indicated by the condition information from among the multiple TRS resource configurations transmitted in the system information block. Specifically, UE 100 (control unit 120) selects a TRS resource configuration (available TRS resource configuration) associated with a paging subgroup ID that matches an allocation identifier (allocated paging subgroup ID) assigned to UE 100 from among the N TRS resource configurations.

[0104] For example, the system information block includes a TRS resource setting #1 associated with a paging subgroup ID "#1", a TRS resource setting #2 associated with a paging subgroup ID "#2", and a TRS resource setting #3 associated with a paging subgroup ID "#3". If the paging subgroup ID to which the UE 100 belongs is "#1", the TRS resource setting #1 associated with the paging subgroup ID "#1" is selected.

[0105] In this way, UE 100 (control unit 120) selects a TRS resource configuration associated with the paging subgroup ID assigned to itself when the paging subgroup ID matches the paging subgroup ID in the system information block.

[0106] In step S203, the UE 100 (receiving unit 112) receives a TRS from the base station 200 using the TRS resource configuration selected in step S202. The UE 100 (control unit 120) performs time-frequency synchronization (time-frequency tracking) in the downlink based on the received TRS. Note that the TRS may be transmitted from the base station 200 to another UE 100 in the RRC connected state.

[0107] In step S204, UE 100 monitors and receives paging in the PO. Note that UE 100 may maintain a wake-up state from when it receives the TRS in step S203 until the PO. If the time from the reception timing of the TRS to the timing of the PO is short, the wake-up duration is short, and the power consumption of UE 100 is reduced. In addition, UE 100 can reduce the power consumption associated with the reception of SSB by not receiving SSB.

[0108] As described above, the communication method used by the UE 100 performing time-frequency synchronization in downlink using a TRS includes step S201 of acquiring a system information block indicating N TRS resource configurations from the base station 200 in a radio resource control (RRC) idle state or an RRC inactive state, and step S203 of receiving a TRS from the base station 200 using a TRS resource configuration selected from the N TRS resource configurations. The system information block includes, for each TRS resource configuration, condition information specifying a condition under which the UE 100 can select the TRS resource configuration.

[0109] In the above-mentioned TRS resource configuration selection operation, the UE 100 may not have its own allocation identifier. For example, the UE 100 may not support paging subgrouping, or may support paging subgrouping but may not be assigned a paging subgroup ID. In such a case, the UE 100 (control unit 120) may select a TRS resource configuration from among multiple TRS resource configurations transmitted in the system information block based on its own unique identifier.

[0110] For example, the UE 100 (control unit 120) selects a TRS resource configuration (here, a TRS resource set identifier) ​​using the following formula.

[0111] UE_ID mod (number of NZP-CSI-RS resource sets) = NZP-CSI-RS resource set ID UE_ID = 5G-S-TMSI mod 1024 (as defined in TS 38.304)

[0112] Here, the "number of NZP-CSI-RS resource sets" is the number of TRS resource configurations transmitted in the system information block (i.e., "N"). The 5G-S-TMSI is a unique identifier of the UE 100. This allows one TRS resource configuration to be smoothly selected from multiple TRS resource configurations.

[0113] Fig. 14 shows a configuration example of a system information block 400 according to an embodiment. Here, the difference between the configuration example described in the RRC technical specification (TS38.331) and the configuration example in Fig. 9 will be described.

[0114] The system information block (SIBXX) 400 includes a configuration of a CSI-RS for tracking to be used for the UE 100 in an RRC idle state or an RRC inactive state. Specifically, the system information block (SIBXX) 400 includes either a first dedicated TRS configuration list (nzp-CSI-RS-ResourceSetListForTracking-r17) 401A or a second dedicated TRS configuration list (nzp-CSI-RS-ResourceListForTracking-r17) 401B.

[0115] The first individual TRS configuration list (nzp-CSI-RS-ResourceSetListForTracking-r17) 401A is an example of a group of N individual TRS configuration parameters. The first individual TRS configuration list (nzp-CSI-RS-ResourceSetListForTracking-r17) 401A is a list of N (1..maxNrofNZP-CSI-RS-ResourceSets) TRS resource set configurations (NZP-CSI-RS-ResourceSetSIB-r17) 403A'. The TRS resource set configuration (NZP-CSI-RS-ResourceSetSIB-r17) 403A' is a collection of multiple TRS resource configurations.

[0116] The TRS resource set configuration (NZP-CSI-RS-ResourceSetSIB-r17) 403A' includes a paging subgroup ID (pagingSubGroupId-r17) as condition information 410 that specifies a condition under which the UE 100 can select the TRS resource set configuration. For example, the paging subgroup ID (pagingSubGroupId-r17) is a value between "0" and "7". When the UE 100 (control unit 120)'s assigned paging subgroup ID matches the paging subgroup ID (pagingSubGroupId-r17) in the TRS resource set configuration (NZP-CSI-RS-ResourceSetSIB-r17) 403A', the UE 100 (control unit 120) selects the TRS resource set configuration (NZP-CSI-RS-ResourceSetSIB-r17) 403A'.

[0117] The second individual TRS configuration list (nzp-CSI-RS-ResourceListForTracking-r17) 401B is another example of a group of N individual TRS configuration parameters. The second individual TRS configuration list (nzp-CSI-RS-ResourceListForTracking-r17) 401B is a list consisting of N (1 ..maxNrofNZP-CSI-RS-Resources) TRS resource configurations (NZP-CSI-RS-ResourceSIB-r17) 403B. Instead of including condition information 410 (pagingSubGroupId-r17) in the TRS resource set configuration (NZP-CSI-RS-ResourceSetSIB-r17) 403A', the condition information 410 (pagingSubGroupId-r17) may be included in the TRS resource configuration (NZP-CSI-RS-ResourceSIB-r17) 403B. In such a modified example, when the UE 100 (control unit 120) has its assigned paging subgroup ID matched with the paging subgroup ID (pagingSubGroupId-r17) in the TRS resource configuration (NZP-CSI-RS-ResourceSIB-r17) 403B, the UE 100 selects the TRS resource configuration (NZP-CSI-RS-ResourceSIB-r17) 403B.

[0118] In this way, the system information block 400 includes the condition information 410 for each of the N individual TRS setting parameter groups 403. That is, the system information block 400 includes, for each individual TRS setting parameter group 403, the condition information 410 that specifies a condition under which the UE 100 can select the individual TRS setting parameter group 403. This makes it possible to appropriately select one individual TRS setting parameter group 403 from the N individual TRS setting parameter groups 403. In particular, when the paging subgroup is subgrouped according to the characteristics of a certain service or traffic, it becomes possible to optimize the TRS setting parameters according to the characteristics.

[0119] (Example of changing the system information block configuration) In the above embodiment, an example has been described in which the system information block includes one common TRS configuration parameter set common to N TRS resource configurations. However, the system information block may include multiple sets of common TRS configuration parameter sets.

[0120] For example, if there is only one parameter (powerControlOffsetSS-r17) indicating the power offset of the TRS relative to the synchronization signal or one parameter (periodicityAndOffset-r17 / CSI-ResourcePeriodicityAndOffsetSIB-r17) indicating the periodicity and time offset of the TRS, it may be difficult to optimize the TRS setting parameters according to the service used by the UE 100 and the characteristics and state of the UE 100. Therefore, a plurality of sets of common TRS setting parameters are transmitted in a system information block, and each individual TRS setting parameter set is associated with one set of common TRS setting parameters. That is, in the system information block, each of the individual TRS setting parameter sets 403 is associated with one set of common TRS setting parameters among the plurality of sets.

[0121] FIG. 15 shows the operation according to this modification example. UE 100 is in the RRC idle state or the RRC inactive state.

[0122] In step S101’, the base station 200 (transmission unit 211) broadcasts a system information block (SIB) indicating N (N≥2) TRS resource settings. In this modification example, the system information block includes, as separate information elements, M (M<N) common TRS setting parameter groups and N individual TRS setting parameter groups. Each of the M (M<N) common TRS setting parameter groups is associated with two or more individual TRS setting parameter groups. The system information block may include the above-described condition information 410.

[0123] For example, a case where N = 6 and M = 3 will be described as an example. That is, the system information block includes six individual TRS setting parameter groups (individual TRS setting parameter groups #1 to #6). Here, individual TRS setting parameter groups #1 and #2 are associated with common TRS setting parameter group #1, individual TRS setting parameter groups #3 and #4 are associated with common TRS setting parameter group #2, and individual TRS setting parameter groups #5 and #6 are associated with common TRS setting parameter group #3. The common TRS setting parameter groups #1 to #3 may be different from each other in, for example, a parameter (powerControlOffsetSS-r17) indicating the power offset of the TRS with respect to the synchronization signal and a parameter (periodicityAndOffset-r17 / CSI-ResourcePeriodicityAndOffsetSIB-r17) indicating the periodicity and time offset of the TRS.

[0124] UE 100 (reception unit 112) receives the system information block from the base station 200. Then, UE 100 (control unit 120) acquires the M common TRS setting parameter groups and the N individual TRS setting parameter groups from the received system information block.

[0125] In step S102', the UE 100 (control unit 120) selects one of the TRS resource configurations (available TRS resource configurations) from among the N TRS resource configurations. The UE 100 (control unit 120) may select the TRS resource configuration based on the above-mentioned condition information 410. The UE 100 (control unit 120) combines an individual TRS configuration parameter set corresponding to the selected TRS resource configuration with a common TRS configuration parameter set corresponding to the selected TRS resource configuration to obtain an overall TRS configuration parameter set corresponding to the selected TRS resource configuration.

[0126] The operations in steps S103 and S104 are similar to those in the above-described embodiment.

[0127] Fig. 16 shows a first configuration example of the system information block 400 according to this modification. Here, the configuration example when described in the RRC technical specification (TS38.331) will be described with respect to differences from the configuration example in Fig. 9.

[0128] In this modified example, the system information block (SIBXX) 400 includes a common TRS configuration list (nzp-CSI-RS-ResourceCommonList-r17) 402 A. The common TRS configuration list (nzp-CSI-RS-ResourceCommonList-r17) 402A is a list of M (1 .. maxNrofNZP-CSI-RS-ResourceCommons) common TRS configuration parameter groups (NZP-CSI-RS-ResourceCommon-r17) 402B.

[0129] Each common TRS setting parameter group (NZP-CSI-RS-ResourceCommon-r17) 402B includes an identifier (nzp-CSI-RS-ResourceCommonId-r17 / NZP-CSI-RS-ResourceCommonId-r17) of the common TRS setting parameter group.

[0130] In addition, each TRS resource configuration (NZP-CSI-RS-ResourceSIB-r17) 403B' includes an identifier (nzp-CSI-RS-ResourceCommonId-r17 / NZP-CSI-RS-ResourceCommonId-r17) of a common TRS configuration parameter group (NZP-CSI-RS-ResourceCommon-r17) 402B associated with the TRS resource configuration.

[0131] When UE 100 (control unit 120) selects one TRS resource configuration (NZP-CSI-RS-Resource SIB-r17) 403B', it identifies a common TRS configuration parameter set (NZP-CSI-RS-ResourceCommon-r17) 402B having an identifier that matches the identifier (nzp-CSI-RS-ResourceCommonId-r17 / NZP-CSI-RS-ResourceCommonId-r17) included in the TRS resource configuration (NZP-CSI-RS-Resource SIB-r17) 403B', and combines the TRS resource configuration (NZP-CSI-RS-Resource SIB-r17) 403B' with the identified common TRS configuration parameter set (NZP-CSI-RS-ResourceCommon-r17) 402B to obtain an overall TRS configuration parameter set.

[0132] 17 shows a second configuration example of the system information block 400 according to this modification. In the second configuration example, the TRS resource set configuration (NZP-CSI-RS-ResourceSetSIB-r17) 403A' includes an identifier (nzp-CSI-RS-ResourceCommonId-r17 / NZP-CSI-RS-ResourceCommonId-r17) of the common TRS configuration parameter set (NZP-CSI-RS-ResourceCommon-r17) 402B associated with the TRS resource set configuration. That is, the common TRS configuration parameter set (NZP-CSI-RS-ResourceCommon-r17) 402B to be applied to all TRS resource configurations (NZP-CSI-RS-ResourceSIB-r17) 403B set in this TRS resource set configuration (NZP-CSI-RS-ResourceSetSIB-r17) 403A' is specified by its ID.

[0133] When the UE 100 (control unit 120) selects one TRS resource set configuration (NZP-CSI-RS-ResourceSetSIB-r17) 403A′, the UE 100 (control unit 120) selects the TRS resource set configuration (NZP-CSI-RS-ResourceSetSIB-r17) based on the identifier (nzp-CSI-RS-ResourceCommonId-r17 / NZP-CSI-RS-ResourceCommonId-r17) included in the TRS resource set configuration (NZP-CSI-RS-ResourceSetSIB-r17) 403A′. 17) Identify a common TRS setting parameter set (NZP-CSI-RS-ResourceCommon-r17) 402B to be combined with all TRS resource settings (NZP-CSI-RS-ResourceSIB-r17) 403B included in 403A', and combine the TRS resource setting (NZP-CSI-RS-ResourceSIB-r17) 403B with the identified common TRS setting parameter set (NZP-CSI-RS-ResourceCommon-r17) 402B to obtain an overall TRS setting parameter set.

[0134] (First example of change in selection behavior of TRS resource settings) In the above embodiment, an example has been described in which the paging subgroup ID assigned to the UE 100 is used as a selection condition (condition information) for selecting a TRS resource configuration (TRS resource set configuration). However, in addition to the paging subgroup ID or instead of the paging subgroup ID, a moving state and / or a receiving state may be used as a selection condition (condition information).

[0135] An operation according to this modification is shown in Fig. 18. The UE 100 is in an RRC idle state or an RRC inactive state.

[0136] The system information block (SIB) transmitted in step S201' may include moving state information indicating a moving state as condition information associated with each TRS resource configuration. The moving state information is information indicating UE mobility, and may be, for example, binary information such as moving / stationary, or multi-value information such as stationary / low speed / medium speed / high speed. In step S202', when the UE 100 (control unit 120) is in agreement with the moving state indicated by the moving state information in the system information block, the UE 100 selects a TRS resource configuration associated with the condition information 410 including the moving state information. Note that the UE 100 (control unit 120) may specify its own moving state using a GNSS or an acceleration sensor, or may specify (estimate) its own moving state based on the number of cell reselections per unit time.

[0137] For example, in the system information block, when TRS resource setting #1: "stationary", TRS resource setting #2: "slow", TRS resource setting #3: "medium", and TRS resource setting #4: "fast", UE 100 (controller 120) selects TRS resource setting #2 when the UE 100 is moving at a slow speed, and selects TRS resource setting #4 when the UE 100 is moving at a fast speed. Note that TRS resource setting #4 associated with "fast" may have a shorter TRS transmission periodicity than TRS resource setting #1 or #2 associated with "stationary" or "slow".

[0138] The system information block (SIB) transmitted in step S201' may include reception state information indicating a reception state as condition information associated with each TRS resource configuration. The reception state information is information indicating the reception power or reception quality of a downlink reference signal, and may be, for example, binary information such as poor / good, or information such as poor / normal / good. In step S202', when the UE 100 (control unit 120)'s own reception state matches the reception state indicated by the reception state information in the system information block, the UE 100 selects a TRS resource configuration associated with the condition information 410 including the reception state information. Note that the UE 100 (control unit 120) may store the reception state when camping on the current cell, or may periodically measure the latest reception state.

[0139] For example, in the system information block, when TRS resource setting #1: "poor", TRS resource setting #2: "normal", and TRS resource setting #3: "good", UE 100 (control unit 120) selects TRS resource setting #1 when its own reception state is poor, and selects TRS resource setting #3 when its own reception state is good. Note that the TRS resource setting #1 associated with "poor" may have a larger TRS power offset (powerControlOffsetSS) set compared to the TRS resource setting #3 associated with "good".

[0140] (Second example of change in selection behavior of TRS resource settings) In the above embodiment, an example has been described in which a paging subgroup ID assigned to the UE 100 is used as a selection condition (condition information) for selecting a TRS resource configuration (TRS resource set configuration). Also, in the above first modified example, an example has been described in which a moving state and / or a receiving state is used as a selection condition (condition information).

[0141] In this modification, extended discontinuous reception (eDRX) DiscontinuousWhether the UE 100 is an eDRX UE (eDRX communication device) that performs eDRX Reception is used as a selection condition (condition information). eDRX is a technology that uses a longer DRX cycle than normal DRX in order to achieve further power saving of the UE 100. The UE 100 configured for DRX wakes up every DRX cycle to monitor the PDCCH, and when this monitoring ends, goes into a sleep state until the next DRX cycle. Therefore, by using a longer DRX cycle than normal DRX (hereinafter referred to as the "DRX cycle"), the period during which the receiver of the UE 100 can be turned off becomes longer, thereby achieving further power saving.

[0142] An overview of eDRX will be described with reference to Fig. 19. In normal DRX, the DRX cycle is set to a time length of, for example, 32 radio frames, 64 radio frames, 128 radio frames, or 256 radio frames. In contrast, the eDRX cycle used in eDRX is set to a time length that is an integer multiple of a hyperframe consisting of 1024 radio frames.

[0143] A UE 100 configured with eDRX (i.e., an eDRX UE) attempts to receive paging in a specific hyperframe (PH: Paging Hyperframe) for each eDRX cycle. At this time, the time width for monitoring paging is called a PTW (Paging Timing Window), and during the PTW period, a PO (Paging Occasion) is monitored according to normal DRX.

[0144] The TRS resource configured for the UE 100 in the RRC idle state or the RRC inactive state can obtain the above-mentioned power saving effect, so it is desirable that it can be used in the eDRX UE as well. Here, the TRS resource is configured by the system information block (SIBXX), but there is a problem that the eDRX UE may not be able to receive the TRS when the TRS resource configuration is updated.

[0145] With reference to FIG. 20, such a problem will be described. A UE configured with normal DRX (hereinafter, referred to as "DRX UE") monitors PDCCH in a PO for each DRX cycle. A DRX UE performs time-frequency tracking by receiving a TRS immediately before each PO. A configuration of TRS resources is notified to a UE 100 by a system information block (SIBXX) from a base station 200. A period during which system information such as a system information block (SIBXX) can be updated is called a modification period. That is, within one modification period, system information is maintained without being updated. When updating a configuration of TRS resources (i.e., SIBXX), a base station 200 notifies a UE 100 of a change in system information in the next modification period (so-called a short message), and changes the system information (SIBXX) at the boundary timing between a current modification period (modification period #n) and a next modification period (modification period #n+1).

[0146] On the other hand, eDRX UE monitors PDCCH at PO within PTW for each DRX cycle. eDRX UE performs time-frequency tracking by receiving TRS just before each PTW or just before each PO. A modification period for eDRX UE that is longer than a normal modification period is set for eDRX UE. Such a modification period for eDRX UE is sometimes called eDRX acquisition period.

[0147] If the boundary of a modification period is included in one eDRX acquisition period and the base station 200 updates the SIBXX at the boundary of the modification period, the eDRX UE cannot correctly receive the TRS with the changed resource configuration after the boundary timing of the modification period, and the reception of the TRS may fail. As a result, the eDRX UE cannot perform time-frequency tracking using the TRS, and cannot perform efficient PO monitoring.

[0148] An overview of the operation according to this modification will be described with reference to Fig. 21. In this modification, in order to solve the above-mentioned problem, base station 200 broadcasts an SIB (SIBXX) including TRS resource set configuration #1 for DRX UE 100A and TRS resource set configuration #2 for eDRX UE 100B as separate information elements. Here, parameters common to TRS resource set configuration #1 and TRS resource set configuration #2 may be included in SIB (SIBXX) as a common TRS configuration parameter group, as in the above-mentioned embodiment.

[0149] Base station 200 may update TRS resource set configuration #1 for DRX UE 100A at a boundary timing of a modification period (i.e., at each modification period). On the other hand, base station 200 may update TRS resource set configuration #2 for eDRX UE 100B at a boundary timing of an eDRX acquisition period (i.e., at each eDRX acquisition period).

[0150] Then, the DRX UE 100A that has received the SIB (SIBXX) selects TRS resource set configuration #1 for the DRX UE 100A, and receives TRS from the base station 200 using the selected configuration. On the other hand, the eDRX UE 100B that has received the SIB (SIBXX) selects TRS resource set configuration #2 for the eDRX UE 100B, and receives TRS from the base station 200 using the selected configuration. This makes it possible to solve the above-mentioned problem.

[0151] 22 shows a configuration example of a system information block 400 according to this modification. Here, the configuration example as described in the RRC technical specification (TS38.331) will be described, focusing on differences from the above-described embodiment.

[0152] The system information block (SIBXX) 400 includes a configuration of a CSI-RS for tracking to be used for the UE 100 in an RRC idle state or an RRC inactive state. Specifically, the system information block (SIBXX) 400 includes either a first dedicated TRS configuration list (nzp-CSI-RS-ResourceSetListForTracking-r17) 401A or a second dedicated TRS configuration list (nzp-CSI-RS-ResourceListForTracking-r17) 401B.

[0153] The first individual TRS configuration list (nzp-CSI-RS-ResourceSetListForTracking-r17) 401A is an example of a group of N individual TRS configuration parameters. The first individual TRS configuration list (nzp-CSI-RS-ResourceSetListForTracking-r17) 401A is a list of N (1..maxNrofNZP-CSI-RS-ResourceSets) TRS resource set configurations (NZP-CSI-RS-ResourceSetSIB-r17) 403A'. The TRS resource set configuration (NZP-CSI-RS-ResourceSetSIB-r17) 403A' is a collection of multiple TRS resource configurations.

[0154] The TRS resource set configuration (NZP-CSI-RS-ResourceSetSIB-r17) 403A' includes DRX information 410a indicating whether the corresponding TRS resource set configuration is for eDRX UE as condition information 410 specifying a condition under which the UE 100 can select the TRS resource set configuration. For example, the DRX information 410a may be DRX type information in which "eDRX" is set when the corresponding TRS resource set configuration is for eDRX UE, and "DRX" is set when the corresponding TRS resource set configuration is for DRX UE. Alternatively, the DRX information 410a may be an eDRX flag in which "true" is set when the corresponding TRS resource set configuration is for eDRX UE, and "false" is set when the corresponding TRS resource set configuration is for DRX UE. Alternatively, the DRX information 410a may be information that implicitly indicates whether the UE is an eDRX UE. For example, the DRX information 410a may be information indicating whether the corresponding TRS resource set configuration is for RedCap UE. RedCap UE refers to a UE having lower capabilities than a normal UE, and is a UE for which eDRX is expected to be configured.

[0155] The UE 100 (control unit 120), in response to the fact that the UE 100 itself is an eDRX UE, selects the TRS resource set configuration (NZP-CSI-RS-ResourceSetSIB-r17) 403A' associated with the DRX information 410a indicating that it is for an eDRX UE.

[0156] On the other hand, the UE 100 (control unit 120) selects the TRS resource set configuration (NZP-CSI-RS-ResourceSetSIB-r17) 403A' that is not associated with the DRX information 410a indicating that it is for eDRX UE, in response to the fact that the UE 100 (control unit 120) is not an eDRX UE (i.e., a DRX UE). In other words, the UE 100 (control unit 120) selects the TRS resource set configuration (NZP-CSI-RS-ResourceSetSIB-r17) 403A' that is associated with the DRX information 410a indicating that it is for DRX UE, in response to the fact that the UE 100 (control unit 120) is not an eDRX UE (i.e., a DRX UE).

[0157] The second individual TRS configuration list (nzp-CSI-RS-ResourceListForTracking-r17) 401B is another example of a group of N individual TRS configuration parameters. The second individual TRS configuration list (nzp-CSI-RS-ResourceListForTracking-r17) 401B is a list consisting of N (1 ..maxNrofNZP-CSI-RS-Resources) TRS resource configurations (NZP-CSI-RS-ResourceSIB-r17) 403B. Instead of including the condition information 410a (DRX information) in the TRS resource set configuration (NZP-CSI-RS-ResourceSetSIB-r17) 403A', the condition information 410a (DRX information) may be included in the TRS resource configuration (NZP-CSI-RS-ResourceSIB-r17) 403B.

[0158] In this way, the system information block 400 includes, for each dedicated TRS setting parameter group 403, DRX information as condition information 410 that specifies a condition under which the UE 100 can select the dedicated TRS setting parameter group 403. This allows the UE 100 to appropriately select one dedicated TRS setting parameter group 403 from among the N dedicated TRS setting parameter groups 403 depending on whether the UE 100 is an eDRX UE or not.

[0159] (Other embodiments) In the above-mentioned operation regarding the selection of a TRS resource configuration, an example in which a common TRS configuration parameter set is defined as one information element has been described, but in terms of appropriately selecting a TRS resource configuration, a common TRS configuration parameter set does not necessarily have to be defined. That is, the system information block may include an individual information element for each TRS resource configuration, and may not include an information element common to two or more TRS resource configurations.

[0160] The operation sequences (and operation flows) in the above-mentioned embodiments do not necessarily have to be executed in chronological order according to the order described in the flow diagram or sequence diagram. For example, the steps in the operations may be executed in an order different from that described in the flow diagram or sequence diagram, or may be executed in parallel. Some of the steps in the operations may be deleted, and additional steps may be added to the process. The operation sequences (and operation flows) in the above-mentioned embodiments may be executed separately and independently, or two or more operation sequences (and operation flows) may be executed in combination. 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.

[0161] In the above-described embodiment, a mobile communication system based on NR has been described as an example of the mobile communication system 1. However, the mobile communication system 1 is not limited to this example. The mobile communication system 1 may be a system conforming to a TS of any of LTE or other generation systems (e.g., 6th generation) of the 3GPP standard. The base station 200 may be an eNB that provides E-UTRA user plane and control plane protocol termination toward the UE 100 in LTE. The mobile communication system 1 may be a system conforming to a TS of a standard other than the 3GPP standard. The base station 200 may be an IAB (Integrated Access and Backhaul) donor or an IAB node.

[0162] A program may be provided that causes a computer to execute each process performed by the UE 100 or the base station 200. The program may be recorded in a computer-readable medium. Using the computer-readable medium, it is possible to install the program in the 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, and may be, for example, a recording medium such as a CD-ROM or a DVD-ROM. In addition, a circuit that executes each process performed by the UE 100 or the base station 200 may be integrated, and at least a part of the UE 100 or the base station 200 may be configured as a semiconductor integrated circuit (chip set, SoC).

[0163] In the above-mentioned embodiment, "transmit" may mean performing processing of at least one layer in a protocol stack used for transmission, or may mean physically transmitting a signal wirelessly or wired. Alternatively, "transmit" may mean a combination of performing processing of at least one layer and physically transmitting a signal wirelessly or wired. Similarly, "receive" may mean performing processing of at least one layer in a protocol stack used for reception, or may mean physically receiving a signal wirelessly or wired. Alternatively, "receive" may mean a combination of performing processing of at least one layer and physically receiving a signal wirelessly or wired. Similarly, "obtain / acquire" may mean obtaining information from stored information, obtaining information from information received from another node, or obtaining the information by generating the information. Similarly, "include" and "comprise" do not mean including only the items listed, but may mean including only the items listed, or may include additional items in addition to the items listed. Similarly, in this disclosure, "or" does not mean an exclusive or, but rather a logical or.

[0164] Although the present disclosure has been described based on the embodiment, it is understood that the present disclosure is not limited to the embodiment or structure. The present disclosure also includes various modifications and modifications within the equivalent range. In addition, various combinations and forms, and other combinations and forms including only one element, more than one element, or less than one element, are also within the scope and concept of the present disclosure.

[0165] (Additional Note) The following additional notes will be given regarding features of the above-described embodiment.

[0166] (Appendix 1) A communication device (100) that performs time-frequency synchronization in a downlink using a tracking reference signal (TRS), A control unit (120) that acquires a system information block (400) indicating a plurality of TRS resource configurations from a base station (200) in a radio resource control (RRC) idle state or an RRC inactive state; A receiving unit (112) that receives the TRS from the base station (200) using a TRS resource set configuration selected from the plurality of TRS resource configurations, The system information block (400) includes, for each of the TRS resource set configurations, condition information (410) that specifies a condition under which the TRS resource set configuration is selectable by the communication device (100). A communication device (100).

[0167] (Appendix 2) The control unit (120) selects the TRS resource set configuration for which the condition indicated by the condition information (410) is satisfied from among the plurality of TRS resource set configurations. 2. The communication device (100) of claim 1.

[0168] (Appendix 3) The condition information (410) includes an identifier that can be assigned to the communication device (100); The control unit (120) selects the TRS resource set configuration associated with the condition information (410) including the identifier when an allocation identifier assigned to the communication device (100) matches the identifier. 3. The communication device (100) according to claim 1 or 2.

[0169] (Appendix 4) The identifier is a paging subgroup identifier that identifies a group of communication devices to be paged. 4. The communication device (100) according to claim 3.

[0170] (Appendix 5) When the control unit (120) does not have the allocation identifier, the control unit (120) selects a TRS resource set configuration from the plurality of TRS resource set configurations based on a unique identifier of the communication device (100). 5. The communication device (100) according to claim 3 or 4.

[0171] (Appendix 6) The condition information (410) includes movement state information indicating a movement state, The control unit (120) selects the TRS resource set configuration associated with the condition information (410) including the moving state information in response to the moving state of the communication device (100) matching the moving state indicated by the moving state information. A communication device (100) according to any one of appendix 1 to 5.

[0172] (Appendix 7) The condition information (410) includes reception status information indicating a reception status, The control unit (120) selects the TRS resource set configuration associated with the condition information (410) including the reception state information in response to a match between the reception state of the communication device (100) and the reception state indicated by the reception state information. A communication device (100) according to any one of appendix 1 to 6.

[0173] (Appendix 8) The condition information (410) includes DRX information (410a) indicating whether the corresponding TRS resource set configuration is for an eDRX communication device performing extended discontinuous reception (eDRX), The control unit (120) selects the TRS resource set configuration associated with the condition information (410) including the DRX information (410a) indicating the eDRX communication device when the communication device (100) is the eDRX communication device. A communication device (100) according to any one of claims 1 to 7.

[0174] (Appendix 9) When the communication device (100) is not the eDRX communication device, the control unit (120) selects the TRS resource set configuration associated with the condition information (410) that does not include the DRX information (410a) indicating the eDRX communication device. 9. The communication device (100) according to claim 8.

[0175] (Appendix 10) The system information block (400) includes, as separate information elements, a TRS setting parameter set (402) common to two or more TRS resource settings, and an individual TRS setting parameter set (403) that may have different values ​​for each TRS resource setting. A communication device (100) according to any one of appendix 1 to 9.

[0176] (Appendix 11) The system information block (400) includes the condition information (410) for each of the individual TRS setting parameter groups (403). 11. The communication device (100) according to claim 10.

[0177] (Appendix 12) A base station (200) for use in a mobile communication system, The communication device (100) includes a transmitter (211) for transmitting a tracking reference signal (TRS) used for time-frequency synchronization in a downlink and a system information block (400) indicating a plurality of TRS resource set configurations; The system information block (400) includes, for each of the TRS resource set configurations, condition information (410) that specifies a condition under which the TRS resource set configuration is selectable by the communication device (100). Base station (200).

[0178] (Appendix 13) A communication method for use in a communication device (100) that performs time-frequency synchronization in a downlink using a tracking reference signal (TRS), comprising: A step (S201) of acquiring a system information block (400) indicating a plurality of TRS resource set configurations from a base station (200) in a radio resource control (RRC) idle state or an RRC inactive state; and receiving the TRS from the base station (200) using a TRS resource set configuration selected from the plurality of TRS resource set configurations (S203). The system information block (400) includes, for each of the TRS resource set configurations, condition information (410) that specifies a condition under which the TRS resource set configuration is selectable by the communication device (100). Communication methods.

Claims

1. A communication device, comprising: A receiver that receives from a base station system information including a parameter indicating one value of a power offset set to two or more Tracking Reference Signal (TRS) resources, the power offset being a power offset of the TRS with respect to a synchronization signal, and a parameter list indicating values ​​of scrambling identifiers set to each of the two or more TRS resources; a control unit that controls, when the communication device is in an RRC idle state or an RRC inactive state, a validity period is set in TRS availability information for the two or more TRS resources, and downlink control information including the TRS availability information is received, to receive the TRS based on the parameter and the parameter list. Communications equipment.

2. The system information includes a parameter indicating one value of a TRS period and an offset set to the two or more TRS resources, and a parameter indicating one value of a TRS QCL (Quasi Co-Location) set to the two or more TRS resources, The control unit controls to receive the TRS based on a parameter indicating one value of the power offset, a parameter indicating one value of the TRS period and offset, a parameter indicating one value of the QCL of the TRS, and the parameter list. The communication device according to claim 1 .

3. The system information includes information for setting the validity period. The communication device according to claim 1 or 2.

4. A base station, a transmission unit that transmits to a communication device system information including a parameter indicating one value of a power offset set to two or more Tracking Reference Signal (TRS) resources, the power offset being a power offset of the TRS with respect to a synchronization signal, and a parameter list indicating values ​​of scrambling identifiers set to each of the two or more TRS resources; a control unit that controls, when the communication device is in an RRC idle state or an RRC inactive state, a validity period is set in TRS availability information for the two or more TRS resources, and downlink control information including the TRS availability information is transmitted, to transmit the TRS based on the parameter and the parameter list. Base station.

5. The system information includes a parameter indicating one value of a TRS period and an offset set to the two or more TRS resources, and a parameter indicating one value of a TRS QCL (Quasi Co-Location) set to the two or more TRS resources, The control unit controls to transmit the TRS based on a parameter indicating one value of the power offset, a parameter indicating one value of the TRS period and offset, a parameter indicating one value of the QCL of the TRS, and the parameter list. The base station according to claim 4.

6. The system information includes information for setting the validity period. The base station according to claim 4 or claim 5.

7. A communication method for a communication device, comprising: receiving, from a base station, system information including a parameter indicating one value of a power offset set to two or more Tracking Reference Signal (TRS) resources, the power offset being a power offset of the TRS with respect to a synchronization signal, and a parameter list indicating values ​​of scrambling identifiers set to each of the two or more TRS resources; When the communication device is in an RRC idle state or an RRC inactive state, a validity period is set in TRS availability information for the two or more TRS resources, and downlink control information including the TRS availability information is received, control is performed to receive the TRS based on the parameter and the parameter list. Communication methods.

8. The system information includes a parameter indicating one value of a TRS period and an offset set to the two or more TRS resources, and a parameter indicating one value of a TRS QCL (Quasi Co-Location) set to the two or more TRS resources, The controlling includes controlling to receive the TRS based on a parameter indicating one value of the power offset, a parameter indicating one value of the TRS period and offset, a parameter indicating one value of QCL (Quasi Co-Location) of the TRS, and the parameter list. The communication method according to claim 7.

9. The system information includes information for setting the validity period. The communication method according to claim 7 or 8.

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