COMMUNICATION DEVICE, BASE STATION, AND COMMUNICATION METHOD

Abstract

A communication device (100) for which one or more cell groups are set by a base station (200) comprises: a reception unit (110) that receives, from the base station (200), downlink control information (DCI) which includes an information field related to monitoring of a physical downlink control channel (PDCCH), in a serving cell which belongs to any cell group of the one or more cell groups; and a control unit (120) that performs a procedure related to the monitoring of the PDCCH on the basis of the value set in the information field. The procedure related to the monitoring of the PDCCH is applied to all serving cells within the cell group to which the serving cell where the DCI has been received belongs.

Description

CROSS-REFERENCE TO RELATED ART

[0001] This application is based on and claims the benefit of priority to patent application No. 2021-079361, filed on May 7, 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 method for use in a mobile communication system. [Background technology]

[0003] In recent years, the 3rd Generation Partnership Project (3GPP), a standardization project for mobile communication systems, has been considering introducing power saving technology to the 5th generation (5G) system, which reduces the power consumption of user equipment in a radio resource control (RRC) connected state. For example, by lengthening the period of the search space corresponding to the candidate timing for allocating the physical downlink control channel (PDCCH), the power consumption required for monitoring the PDCCH can be reduced.

[0004] As such a technique, a technique has been proposed in which a user device is configured with multiple SSSGs, including a search space set group (SSSG) having a normal search space period and a power saving SSSG with a search space period longer than the normal search space period or with no search space, and the base station dynamically instructs the user device to switch the SSSG (see Non-Patent Documents 1 to 3). This makes it possible to apply an optimal SSSG according to the traffic state of the user device, while reducing the power consumption of the user device.

[0005] There is also a technology for SSSG switching (hereinafter referred to as "cell group SSSG switching") in which a cell group consisting of multiple cells whose SSSG can be switched simultaneously is configured in the user equipment, and the SSSG is switched simultaneously for all serving cells in the cell group. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] 3GPP contribution R1-2100170 “DCI-based power saving adaptation solutions” [Non-Patent Document 2] 3GPP contribution R1-2100593 “On enhancements to DCI-based UE power saving during DRX active time” [Non-Patent Document 3] 3GPP contribution R1- 2101476 “DCI-based power saving adaptation during DRX Active Time” Summary of the Invention

[0007] A communication device according to a first aspect is a communication device in which one or more cell groups are set by a base station, and includes a receiver that receives downlink control information (DCI) including an information field related to monitoring of a physical downlink control channel (PDCCH) from the base station in a serving cell belonging to any one of the one or more cell groups, and a controller that executes a procedure related to monitoring the PDCCH based on a value set in the information field. The procedure related to monitoring the PDCCH is applied to all serving cells in the cell group to which the serving cell from which the DCI is received belongs.

[0008] A base station according to a second aspect is a base station that sets one or more cell groups for a communication device, and includes a transmitter that transmits downlink control information (DCI) including an information field related to monitoring a physical downlink control channel (PDCCH) to the communication device in a serving cell that belongs to any one of the one or more cell groups, and a controller that controls a procedure related to monitoring the PDCCH based on a value set in the information field. The procedure related to monitoring the PDCCH is applied to all serving cells in the cell group to which the serving cell in which the DCI is received belongs.

[0009] A method according to a third aspect is a method executed by a communication device in which one or more cell groups are set by a base station, and includes the steps of receiving, from the base station, downlink control information (DCI) including an information field related to monitoring of a physical downlink control channel (PDCCH) in a serving cell belonging to any one of the one or more cell groups, and performing a procedure related to monitoring the PDCCH based on a value set in the information field. The procedure related to monitoring the PDCCH is applied to all serving cells in the cell group to which the serving cell from which the DCI is received belongs.

[0010] A method according to a fourth aspect is a method executed by a base station that sets one or more cell groups for a communication device, and includes the steps of: transmitting, to the communication device, downlink control information (DCI) including an information field related to monitoring of a physical downlink control channel (PDCCH) in a serving cell that belongs to any one of the one or more cell groups; and controlling a procedure related to monitoring of the PDCCH based on a value set in the information field. The procedure related to monitoring of the PDCCH is applied to all serving cells in the cell group to which the serving cell in which the DCI is received belongs. [Brief description of the drawings]

[0011] The above and other objects, features and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which: [Figure 1] FIG. 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 a protocol stack configuration according to an embodiment; [Diagram 3] FIG. 3 is a diagram for explaining search spaces and SSSG switching according to an embodiment; [Figure 4] FIG. 4 is a diagram for explaining search spaces and SSSG switching according to an embodiment; [Diagram 5] FIG. 5 is a diagram for explaining search space and SSSG switching according to the embodiment; [Figure 6] FIG. 6 is a diagram showing a configuration of a UE according to an embodiment; [Figure 7] FIG. 7 is a diagram showing a configuration of a base station according to an embodiment; [Figure 8] FIG. 8 is a diagram showing a first operation example of cell group SSSG switching according to the first embodiment; [Figure 9] FIG. 9 is a diagram showing a second operation example of cell group SSSG switching according to the first embodiment; [Figure 10] FIG. 10 is a diagram showing a configuration example of an SSSG switching MAC CE according to the first embodiment; [Figure 11] FIG. 11 is a diagram showing an operation according to the second embodiment; [Figure 12] FIG. 12 is a diagram illustrating an operation according to the second embodiment, focusing on a downlink. [Figure 13] FIG. 13 is a diagram illustrating an operation according to the second embodiment, focusing on an uplink. [Figure 14] FIG. 14 is a diagram showing an operation according to the third embodiment; [Figure 15] FIG. 15 is a diagram showing an operation according to the fourth embodiment; [Figure 16] FIG. 16 is a diagram illustrating a first configuration example of information elements included in an RRC message according to the fourth embodiment; [Figure 17] FIG. 17 is a diagram illustrating a first configuration example of information elements included in an RRC message according to the fourth embodiment; [Figure 18] FIG. 18 is a diagram showing a second configuration example of information elements included in an RRC message according to the fourth embodiment; [Figure 19] FIG. 19 is a diagram illustrating a second configuration example of information elements included in an RRC message according to the fourth embodiment; [Figure 20] FIG. 20 is a diagram showing an operation according to the fifth embodiment; [Figure 21] FIG. 21 is a diagram showing a specific example 1 of an operation using a switching timer according to the fifth embodiment; [Figure 22] FIG. 22 is a diagram showing a specific example 2 of the operation using the switching timer according to the fifth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] In the cell group SSSG switching, the cell group set in the user equipment is not limited to one, and multiple cell groups may be set in the user equipment. As a result of detailed study by the inventors, when a user equipment in which multiple cell groups are set receives an SSSG switching instruction from a base station, it is not clear which cell group the SSSGs of serving cells belonging to should be switched at the same time, and the cell group SSSG switching cannot be performed appropriately.

[0013] Therefore, an object of the present disclosure is to enable cell group SSSG switching to be performed appropriately.

[0014] 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.

[0015] First Embodiment

[0016] (System Configuration) First, the configuration of a mobile communication system 1 according to this embodiment will be described with reference to Fig. 1. The mobile communication system 1 is, for example, a system that complies with the Technical Specification (TS) of 3GPP. In the following, the mobile communication system 1 will be described by taking as an example a 5th Generation System (5GS) of the 3GPP standard, that is, a mobile communication system based on NR (New Radio).

[0017] The mobile communication system 1 includes a network 10 and a 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.

[0018] 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.

[0019] 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. 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 the cell. The base station 200 communicates with the UE 100 using a protocol stack of a Radio Access Network (RAN). The base station 200 provides an NR user plane and a control plane protocol termination for 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).

[0020] 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.

[0021] Next, an example of the configuration of a protocol stack according to this embodiment will be described with reference to FIG.

[0022] The protocol of the wireless section between the UE 100 and the 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 an RRC layer.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] The PDCP layer performs header compression / decompression and encryption / decryption.

[0027] 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).

[0028] 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.

[0029] 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 mobility management device 221. The UE 100 has an application layer and the like in addition to the protocol of the radio interface.

[0030] (Search space and SSSG switching) Next, a search space and SSSG switching according to this embodiment will be described with reference to Figures 3 to 5. In this embodiment, a search space may be referred to as a search space set.

[0031] The base station 200 sets, for the UE 100, a search space corresponding to a candidate timing at which the PDCCH is arranged. The UE 100 in the RRC connected state monitors the PDCCH in the set search space, and receives downlink control information (DCI) carried by the PDCCH. Then, the UE 100 receives a physical downlink control channel (PDSCH) and / or transmits a physical uplink control channel (PUSCH) according to resource allocation (scheduling) indicated by the DCI. For example, the UE 100 may monitor a set of PDCCH candidates according to the corresponding search space. That is, the UE 100 may monitor a set of PDCCH candidates in a control resource set (CORESET) in a downlink BWP (DL BWP: BandWidth Part) in a serving cell in which the PDCCH monitoring is set, according to the corresponding search space. Here, monitoring may indicate decoding each of the PDCCH candidates according to the monitored DCI format.

[0032] As shown in FIG. 3, in step S1, base station 200 transmits an RRC message including setting information (PDCCH setting information) related to PDCCH to UE 100, and performs various settings related to PDCCH for UE 100. This RRC message is a UE-specific RRC message, and may be, for example, an RRC Reconfiguration message. Here, the setting information related to PDCCH includes a search space period (also referred to as a PDCCH monitoring period), a search space offset (also referred to as a PDCCH monitoring offset), a search space period (for example, the number of consecutive slots), a symbol for PDCCH monitoring, an aggregation level, a search space type, a DCI format, and the like. Here, the search space type may include a UE-specific search space (USS: UE-specific Search Space) and / or a UE-common search space (CSS: Common Search Space).

[0033] There are two types of DCI formats: a scheduling DCI format used for scheduling a PDSCH or a PUSCH, and a non-scheduling DCI format not used for such scheduling. DCI transmitted in a scheduling DCI format is called a scheduling DCI, and DCI transmitted in a non-scheduling DCI format is called a non-scheduling DCI.

[0034] Scheduling DCI formats include downlink DCI formats used for PDSCH scheduling (e.g., DCI format 1_0, DCI format 1_1, DCI format 1_2) and uplink DCI formats used for PUSCH scheduling (e.g., DCI format 0_0, DCI format 0_1, DCI format 0_2). On the other hand, non-scheduling DCI formats include, for example, DCI format 2_0 and DCI format 2_6.

[0035] In step S2, UE 100 starts monitoring the PDCCH in a search space set by base station 200. For example, DCI format 1_0, DCI format 0_0, DCI format 1_1, DCI format 0_1, DCI format 1_2, and DCI format 0_2 are set in UE 100. UE 100 monitors the PDCCH (DCI) based on the setting. For example, base station 200 may set UE 100 to monitor DCI format 1_0 and DCI format 0_0 in a certain search space. Also, base station 200 may set UE 100 to monitor DCI format 1_1 and DCI format 0_1 ​​in a certain search space. Also, base station 200 may set UE 100 to monitor DCI format 1_2 and DCI format 0_2 in a certain search space. That is, for example, when a CSS is configured for a certain search space, the base station 200 may configure the UE 100 to monitor PDCCH candidates for DCI format 1_0 and DCI format 0_0. When a CSS is configured for a certain search space, the base station 200 may configure the UE 100 to monitor PDCCH candidates for DCI format 2_0. When a USS is configured for a certain search space, the base station 200 may configure the UE 100 to monitor PDCCH candidates for DCI format 1_0 and DCI format 0_0, or DCI format 1_1 and DCI format 0_1. When a USS is configured for a certain search space, the base station 200 may configure the UE 100 to monitor PDCCH candidates for DCI format 1_0 and DCI format 0_0, or DCI format 1_2 and DCI format 0_2.

[0036] In step S3, UE 100 receives and detects DCI addressed to itself from base station 200. For example, UE 100 performs blind decoding of PDCCH using C-RNTI (Cell-Radio Network Temporary Identifier) ​​and MCS-C-RNTI (Modulation and Coding Scheme-C-RNTI) or CS-RNTI (Configured Scheduling-RNTI) assigned to UE 100 by base station 200, and acquires successfully decoded DCI as DCI addressed to itself. Here, CRC parity bits scrambled by C-RNTI and MCS-C-RNTI or CS-RNTI are added to DCI transmitted from base station 200.

[0037] If the DCI indicates scheduling of the PDSCH, in step S4, the UE 100 receives downlink data from the base station 200 on the scheduled PDSCH.

[0038] If the DCI indicates scheduling of the PUSCH, in step S5, the UE 100 transmits uplink data to the base station 200 on the scheduled PUSCH.

[0039] In this manner, the UE 100 monitors the PDCCH in the search space set by the base station 200. In this embodiment, the base station 200 switches the search space setting applied by the UE 100 in order to reduce the power consumption of the UE 100 in the RRC connected state. Here, each of the search spaces (each of the search space settings) may be related to one CORESET. Also, the search space setting may be set for each of one or more DL BWPs.

[0040] For example, as shown in FIG. 4, the base station 200 configures the UE 100 with an SSSG#0 having a normal search space period and an SSSG#1 for power saving, which has a search space period longer than the normal search space period. Here, the SSSG is a set (group) of search spaces, and may be referred to as a search space set (SSS) or a search space group (SSG). For example, the SSSG may be a set (group) of search spaces to which the same configuration is applied. Note that, in FIG. 4, an example is shown in which the base station 200 configures two SSSGs, SSSG#0 and SSSG#1, for the UE 100, but three or more SSSGs may be configured for each of one or more BWPs (e.g., DL BWPs) for the UE 100. Also, an example is shown in which an SSSG with a long search space period is configured as the SSSG#1 for power saving, but an SSSG without a search space may be configured as the SSSG#1 for power saving. In this case, since UE100 omits (skips) monitoring of the PDCCH during the period of SSSG#1, further power consumption reduction is possible. Here, "#0" in SSSG#0 and "#1" in SSSG#1 indicate an index (also referred to as a search space group ID) for a set (group) of search spaces. That is, one or more search space sets may be associated with a set (group) of search spaces identified by an index. For example, base station 200 may set a set (group) of search spaces for UE100 by setting an index related to the one or more search space sets. Here, in this embodiment, the name SSSG is merely an example, and any name is acceptable as long as it is a set (group) of search spaces to which one or more search space sets are associated. In addition, the set (group) of search spaces may not have a search space (a search space may not be set). For example, when there is no search space, UE100 may not perform monitoring of the PDCCH (monitoring of candidates for the PDCCH).That is, when the search space does not exist, the UE 100 may skip monitoring the PDCCH.

[0041] The base station 200 instructs the UE 100 to switch the SSSG. The base station 200 instructs the UE 100 to switch from SSSG#0 to SSSG#1 using a non-scheduling DCI (for example, DCI format 2_0). However, the non-scheduling DCI is not the only option, and a scheduling DCI may be used as the SSSG switching instruction. The UE 100 starts monitoring the PDCCH in the SSSG#1 at the symbol after the switch delay time (Switch delay) from the last symbol of the PDCCH in the SSSG#0. Such a switch delay time is set by the base station 200 to the UE 100 by higher layer signaling (i.e., an RRC message).

[0042] Switching from SSSG#1 to SSSG#0 may be instructed by base station 200 using DCI, as in the case of switching from SSSG#0 to SSSG#1, or UE 100 may switch from SSSG#1 to SSSG#0 using a timer. Such a timer (switching timer) is set in UE 100 by base station 200 using higher layer signaling (i.e., an RRC message). UE 100 starts monitoring the PDCCH in SSSG#1 in response to detection of a switching instruction DCI to SSSG#1, and starts the timer by setting the timer value to a value set by the higher layer. UE 100 decrements the timer value, and when the timer expires, stops monitoring the PDCCH in SSSG#1, and starts monitoring the PDCCH in SSSG#0 after a switch delay time (Switch delay).

[0043] Here, SSSG switching within one cell has been described, but as shown in FIG. 5, multiple serving cells may be configured in the UE 100 by carrier aggregation. FIG. 5 shows an example in which a serving cell #1 corresponding to a component carrier #1 and a serving cell #2 corresponding to a component carrier #2 are configured in the UE 100. In such a case, it is more efficient to perform SSSG switching in units of a cell group consisting of multiple cells, rather than performing SSSG switching for each cell individually. For example, the base station 200 transmits SSSG switching DCI in the serving cell #1 to the UE 100, and the UE 100 simultaneously switches the SSSGs of the serving cells #1 and #2 from SSSG #0 to SSSG #1. Such a cell group is configured in the UE 100 by the base station 200 through higher layer signaling (i.e., an RRC message). For example, in carrier aggregation, the base station 200 may configure one primary cell and one or more secondary cells. That is, the serving cells include the primary cell and the secondary cell. Also, one or more Band Width Parts (BWPs) may be configured in each of one or more serving cells configured in the UE 100. For example, up to four BWPs may be configured for one serving cell. Here, the BWPs may include a downlink BWP (DL BWP) and / or an uplink BWP (UL BWP). That is, up to four DL BWPs and / or up to four UL BWPs may be configured for one serving cell. Also, one or more Control Resource Sets (CORESETs) may be configured for one DL BWP. Here, the CORESET may include resources in the time domain and / or frequency domain configured for monitoring the PDCCH. For example, the CORESET may be configured with a predetermined number of symbols (for example, 1 to 3 symbols) and a predetermined number of Resource Blocks (RBs) (for example, 6n (n≧1) RBs).

[0044] In the following, a case will be mainly described where carrier aggregation is configured in the UE 100 and SSSG switching is performed on a cell group basis (cell group SSSG switching). In such cell group SSSG switching, the cell group configured in the UE 100 is not limited to one, and multiple cell groups may be configured in the UE 100. An example of such cell grouping is shown below: Cell group #1: Serving cells #1, #2, #3, #4 Cell group #2: Serving cells #5, #6, #7, #8 Cell group #3: Serving cells #9, #10, #11, #12 Cell group #4: Serving cells #13, #14, #15, #16 Here, it is assumed that one serving cell can belong to only one cell group, that is, one serving cell may be configured by base station 200 to belong to only one cell group.

[0045] When such a plurality of cell groups are set in the UE 100, the UE 100 that receives the SSSG switching instruction from the base station 200 does not know which cell group the SSSGs of the serving cells belonging to should be switched at the same time. Therefore, when a plurality of cell groups are set in the UE 100, there is a problem that the UE 100 cannot appropriately perform the cell group SSSG switching. In this embodiment, the PDCCH monitoring based on the above-mentioned SSSG switching is also referred to as a PDCCH monitoring procedure.

[0046] (User device configuration) Next, a configuration of the UE 100 according to this embodiment will be described with reference to Fig. 6. The UE 100 includes a communication unit 110 and a control unit 120.

[0047] 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 receiver and at least one transmitter. The receiver and the transmitter may be configured to include an antenna and an RF circuit. 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.

[0048] 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.

[0049] In the UE 100 configured in this way, a plurality of cell groups for cell group SSSG switching are set in the UE 100. The communication unit 110 receives an SSSG switching instruction from the base station 200 instructing switching of the SSSG in a serving cell belonging to any one of the plurality of cell groups. For example, the SSSG switching instruction is an SSSG switching DCI instructing switching of the SSSG. The control unit 120 specifies, from among the plurality of cell groups, a cell group to which a serving cell in which the SSSG switching instruction is detected belongs as a target cell group to which the SSSG switching instruction is to be switched. Then, in response to receiving the SSSG switching instruction, the control unit 120 simultaneously switches the SSSG for all serving cells in the specified target cell group. In this way, the control unit 120 utilizes the property that one serving cell can belong to only one cell group, and specifies the cell group to which the serving cell in which the SSSG switching instruction is detected belongs as a target cell group for SSSG switching. This allows the UE 100 to appropriately perform cell group SSSG switching even when a plurality of cell groups are set in the UE 100.

[0050] Alternatively, the communication unit 110 may receive an SSSG switching instruction including a cell group identifier of a cell group to be switched to the SSSG or a cell identifier of a cell included in the cell group from the base station 200. Such an SSSG switching instruction may be an SSSG switching medium access control (MAC) control element (CE). The control unit 120 identifies a target cell group to be switched to the SSSG from among a plurality of cell groups based on the cell identifier or cell group identifier included in the SSSG switching instruction. Then, in response to receiving the SSSG switching instruction, the control unit 120 simultaneously switches the SSSG for all serving cells in the identified target cell group. In this way, since the cell group identifier of the cell group to be switched to the SSSG or the cell identifier of a cell included in the target cell group is included in the SSSG switching instruction, the UE 100 can appropriately perform cell group SSSG switching even when a plurality of cell groups are set in the UE 100.

[0051] (Base station configuration) Next, the configuration of the base station 200 according to this embodiment will be described with reference to Fig. 7. The base station 200 has a communication unit 210, a network interface 220, and a control unit 230.

[0052] The communication unit 210, for example, receives a wireless signal from the UE 100 and transmits a wireless signal to the UE 100. The communication unit 210 may include one or more receivers that receive the wireless signal and one or more transmitters that transmit the wireless signal.

[0053] 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.

[0054] 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.

[0055] In the base station 200 configured in this manner, the communication unit 210 transmits to the UE 100 an SSSG switching instruction instructing SSSG switching in a serving cell belonging to any one of a plurality of cell groups set in the UE 100. For example, the SSSG switching instruction is an SSSG switching DCI instructing SSSG switching. Specifically, the communication unit 110 transmits the SSSG switching instruction to the UE 100 in a serving cell belonging to a SSSG switching target cell group. This makes it possible to implicitly indicate the target cell group by the serving cell from which the SSSG switching instruction is transmitted, even if the cell group identifier of the SSSG switching target cell group or the cell identifier of a cell belonging to the target cell group is not included in the SSSG switching instruction.

[0056] Alternatively, the communication unit 210 may transmit an SSSG switching instruction to the UE 100, the SSSG switching instruction including a cell group identifier of the SSSG switching target cell group or a cell identifier of a cell included in the target cell group. Such an SSSG switching instruction may be an SSSG switching MAC CE. In this way, the SSSG switching target cell group can be explicitly indicated by including a cell group identifier of the SSSG switching target cell group or a cell identifier of a cell included in the target cell group in the SSSG switching instruction. Therefore, the communication unit 210 may transmit an SSSG switching instruction to the UE 100 in a serving cell that does not belong to the SSSG switching target cell group. For example, the SSSG switching instruction may always be transmitted to the UE 100 in a primary cell (PCell) among a plurality of serving cells.

[0057] (First operation example of cell group SSSG switching) Next, a first operation example of cell group SSSG switching according to this embodiment will be described with reference to Fig. 8. The first operation example is an operation example in which the base station 200 implicitly indicates the SSSG switching target cell group to the UE 100. Note that the UE 100 is assumed to be in an RRC connected state.

[0058] In step S11, the base station 200 (communication unit 210) transmits an RRC message including cell group setting information related to the setting of a cell group together with the above-mentioned PDCCH setting information to the UE 100. The UE 100 (communication unit 110) receives the RRC message. This RRC message is a UE-specific RRC message, and may be, for example, an RRC Reconfiguration message. The cell group setting information may be configured as a cell list for each cell group. Each cell list may include a cell identifier of each serving cell belonging to the corresponding cell group. In the RRC message, each cell group may be individually associated with PDCCH setting information (including SSSG setting information). That is, multiple SSSGs may be individually set for each cell group. Here, a default SSSG may be specified for each cell group. Details of the default SSSG will be described in a fifth embodiment described later.

[0059] In step S12, the UE 100 (control unit 120) stores and applies the setting information included in the RRC message received in step S11, and controls communication with the base station 200 based on the setting information. Here, the cell group set in the UE 100 is, for example, Cell group #1: Serving cells #1, #2, #3, #4 Cell group #2: Serving cells #5, #6, #7, #8 Cell group #3: Serving cells #9, #10, #11, #12 Cell group #4: Serving cells #13, #14, #15, #16.

[0060] In step S13, the base station 200 (communication unit 210) determines an SSSG switching target cell group, and transmits an SSSG switching DCI to the UE 100 in a serving cell belonging to the target cell group. The UE 100 (communication unit 110) receives the SSSG switching DCI. Specifically, the UE 100 (communication unit 110) detects the SSSG switching DCI by blind decoding of the PDCCH.

[0061] The SSSG switching DCI may be the above-mentioned scheduling DCI. This allows the scheduling of the PDSCH or PUSCH to be notified to the UE 100 and the SSSG switching to be instructed to the UE 100, thereby realizing efficient SSSG switching.

[0062] The SSSG switching DCI may be the above-mentioned non-scheduling DCI. This allows the UE 100 to instruct SSSG switching even when there is no data to be transmitted or received by the UE 100. The non-scheduling DCI may be a DCI that can be simultaneously transmitted to a plurality of UEs 100. For example, the non-scheduling DCI may be transmitted by applying a common RNTI (Radio Network Temporary Identifier) ​​to a plurality of UEs 100.

[0063] In step S14, the UE 100 (control unit 120) identifies a cell group to which a serving cell in which the SSSG switching DCI is detected belongs as an SSSG switching target cell group. This makes it possible to appropriately identify the SSSG switching target cell group even if an identifier indicating the SSSG switching target cell group is not included in the SSSG switching DCI.

[0064] For example, when the SSSG switching DCI is received by the serving cell #1, the UE 100 (control unit 120) specifies the cell group #1 to which the serving cell #1 belongs as the cell group to be subjected to SSSG switching. Alternatively, when the SSSG switching DCI is received by the serving cell #10, the UE 100 (control unit 120) specifies the cell group #3 to which the serving cell #10 belongs as the cell group to be subjected to SSSG switching.

[0065] In step S15, UE 100 (control unit 120) simultaneously switches the SSSG for all serving cells in the SSSG switching target cell group identified in step S14. For example, UE 100 (control unit 120) collectively switches the SSSG of all serving cells in the SSSG switching target cell group from a default SSSG (e.g., SSSG #0) to a power saving SSSG (e.g., SSSG #1). That is, UE 100 may determine a cell group to which the PDCCH monitoring procedure is applied based on a serving cell in which the SSSG switching DCI is detected. That is, when UE 100 detects the SSSG switching DCI in a serving cell, it may apply the PDCCH monitoring procedure to a cell group to which the serving cell belongs. That is, UE100 may receive cell group setting information used to set one or more cell groups, and when SSSG switch DCI is detected in a serving cell related to (belonging to) a certain cell group, apply the PDCCH monitoring procedure to a certain cell group to which a serving cell that detected the SSSG switch DCI is related (belongs to). That is, UE100 may receive cell group setting information used to set one or more cell groups, and when SSSG switch DCI is detected in a serving cell related to (belonging to) a certain cell group, apply the PDCCH monitoring procedure to a certain cell group that detected the SSSG switch DCI. Here, UE100 may apply the PDCCH monitoring procedure to all serving cells in the cell group.

[0066] (Second operation example of cell group SSSG switching) Next, a second operation example of cell group SSSG switching according to the present embodiment will be described with reference to Fig. 9, focusing mainly on differences from the above-mentioned first operation example. The second operation example is an operation example in which the base station 200 explicitly indicates the SSSG switching target cell group to the UE 100. It is assumed that the UE 100 is in an RRC connected state.

[0067] The operations in steps S21 and S22 are similar to those in steps S11 and S12 described above.

[0068] In step S23, the base station 200 (communication unit 210) determines an SSSG switching target cell group, and transmits an SSSG switching MAC CE including a cell group identifier of the SSSG switching target cell group or a cell identifier of a serving cell belonging to the SSSG switching target cell group to the UE 100. The base station 200 (communication unit 210) 、S A serving cell that does not belong to the SSG switching target cell group may transmit the SSSG switch MAC CE to the UE 100. The UE 100 (communication unit 110) receives the SSSG switch MAC CE.

[0069] In step S24, UE 100 (control unit 120) identifies a target cell group for SSSG switching from among a plurality of cell groups based on a cell identifier or a cell group identifier included in the SSSG switching MAC CE. When the SSSG switching MAC CE includes a cell identifier, UE 100 (control unit 120) identifies a cell group to which a serving cell indicated by a cell identifier included in the SSSG switching MAC CE belongs as a target cell group.

[0070] For example, when a cell identifier included in the SSSG switching MAC CE indicates serving cell #1, the UE 100 (control unit 120) specifies cell group #1 to which the serving cell #1 belongs as a cell group to be subjected to SSSG switching. Alternatively, when a cell identifier included in the SSSG switching MAC CE indicates serving cell #10, the UE 100 (control unit 120) specifies cell group #3 to which the serving cell #10 belongs as a cell group to be subjected to SSSG switching.

[0071] In step S25, UE 100 (control unit 120) simultaneously switches the SSSGs of all serving cells in the SSSG switching target cell group identified in step S24. For example, UE 100 (control unit 120) simultaneously switches the SSSGs of all serving cells in the SSSG switching target cell group from a default SSSG (e.g., SSSG #0) to a power saving SSSG (e.g., SSSG #1).

[0072] The SSSG switching MAC CE may further include an SSSG identifier indicating a switching destination SSSG. In step S25, the UE 100 (control unit 120) may simultaneously switch all serving cells in the SSSG switching target cell group identified in step S24 to the switching destination SSSG indicated by the SSSG identifier.

[0073] The SSSG switching MAC CE may further include a BWP identifier indicating a bandwidth portion (BWP) to which the SSSG switching target cell group belongs. The UE 100 (control unit 120) may identify the BWP of the SSSG switching target cell group identified in step S24 based on the BWP identifier.

[0074] Next, a configuration example of the SSSG switching MAC CE according to this embodiment will be described with reference to Fig. 10. The SSSG switching MAC CE may be referred to as a "Serving Cell Set based Search Space Set Group Indication MAC CE". The SSSG switching MAC CE may be configured to be identifiable by a MAC PDU subheader having an eLCID defined for the SSSG switching MAC CE. The SSSG switching MAC CE is configured with the following fields and has a fixed size.

[0075] Serving Cell ID (Cell Identifier): This field indicates the ID of the serving cell to which the MAC CE applies, and the length of the field is, for example, 5 bits. If the serving cell indicated by the serving cell ID is configured as part of a cell group, this MAC CE applies to all serving cells in the cell group to which the serving cell belongs.

[0076] -BWP ID (BWP Identifier): This field indicates the downlink BWP to which this MAC CE applies. The length of the BWP ID field is, for example, 2 bits.

[0077] -Search Space Set Group ID (SSSG Identifier): This field indicates the Search Space Set Group (SSSG) for which the UE monitors the PDCCH, i.e., the SSSG to which the UE is to switch. The length of the field is, for example, 8 bits.

[0078] -R: Reserved bit, set to "0".

[0079] At least a part of the information included in the SSSG switching MAC CE in this second operation example may be included in the SSSG switching DCI in the above-mentioned first operation example.

[0080] (Example of change) In the above-mentioned first operation example of cell group SSSG switching, an example has been described in which the base station 200 implicitly indicates the SSSG switching target cell group to the UE 100 by the SSSG switching DCI. However, the base station 200 may implicitly indicate the SSSG switching target cell group to the UE 100 by the SSSG switching MAC CE instead of the SSSG switching DCI. That is, the SSSG switching DCI in the above-mentioned first operation example of cell group SSSG switching may be read as the SSSG switching MAC CE. In such a modified example, the UE 100 (control unit 120) may specify, as the target cell group, a cell group to which a serving cell in which the SSSG switching MAC CE is detected belongs. Also, in such a modified example, the SSSG switching MAC CE may include an SSSG identifier indicating a switching destination SSSG. The UE 100 (control unit 120) may simultaneously switch all serving cells in the SSSG switching target cell group to the switching destination SSSG indicated by the SSSG identifier. Furthermore, in such a modified example, the SSSG switching MAC CE may further include a bandwidth portion (BWP) identifier indicating the BWP to which the target cell group belongs.

[0081] In the above-mentioned second operation example of cell group SSSG switching, an example has been described in which the base station 200 explicitly indicates the SSSG switching target cell group to the UE 100 by the SSSG switching MAC CE. However, the base station 200 may explicitly indicate the SSSG switching target cell group to the UE 100 by the SSSG switching DCI instead of the SSSG switching MAC CE. That is, the cell group identifier of the SSSG switching target cell group or the cell identifier of the serving cell belonging to the SSSG switching target cell group may be included in the SSSG switching DCI. In such a modified example, the SSSG switching DCI may be a scheduling DCI. Alternatively, the SSSG switching DCI may be a non-scheduling DCI.

[0082] <Second embodiment> Next, a second embodiment will be described with reference to Fig. 11. In the second embodiment, it is assumed that an SSSG switching DCI is used as an SSSG switching instruction, and in particular, it is mainly assumed that a scheduling DCI is used as a switching instruction DCI.

[0083] When a scheduling DCI is used as a switching instruction DCI, since a HARQ process, which is a data retransmission process by HARQ, may be necessary, there is a concern that the HARQ process may not be performed appropriately if the UE 100 immediately starts switching to the power saving state. Therefore, the UE 100 (control unit 120) suspends the start of switching instructed by the switching instruction DCI while a retransmission-related timer associated with the HARQ process for data scheduled by the switching instruction DCI (scheduling DCI) is operating.

[0084] 11, in step S51, UE 100 (communication unit 110) receives a scheduling DCI as a switching instruction DCI on a PDCCH from base station 200. Such a scheduling DCI may include an information field indicating a switching destination SSSG in addition to an information field indicating a PDSCH resource or a PUSCH resource allocated to UE 100.

[0085] In step S52, the UE 100 (communication unit 110) receives or transmits data scheduled by the scheduling DCI. For example, the UE 100 (communication unit 110) receives downlink data using the assigned PDSCH resource, or transmits uplink data using the assigned PUSCH resource. When the UE 100 (communication unit 110) receives downlink data, the UE 100 (control unit 120) attempts data decoding of the received downlink data, and feeds back HARQ feedback indicating whether or not the data decoding has been successful, i.e., ACK or NACK, to the base station 200. When the UE 100 (communication unit 110) transmits uplink data, the UE 100 (control unit 120) receives HARQ feedback indicating whether or not the base station 200 has successfully decoded the uplink data, i.e., ACK or NACK, from the base station 200. The UE 100 (control unit 120) manages the HARQ process for each piece of data to be received or transmitted using a timer, and continues the HARQ process until data decoding of the data is completed.

[0086] In step S53, the UE 100 (control unit 120) determines whether or not any of the following retransmission related timers used in the HARQ process is in operation.

[0087] Downlink HARQ RTT timer (drx-HARQ-RTT(Round Trip Time)-TimerDL) This timer is used for HARQ processing of downlink data and specifies the minimum period until downlink allocation for HARQ retransmission expected by the MAC entity of UE 100. UE 100 (control unit 120) starts the downlink HARQ RTT timer in response to transmission of HARQ feedback for downlink data. UE 100 (control unit 120) does not need to monitor the PDCCH while the downlink HARQ RTT timer is operating.

[0088] Downlink retransmission timer (drx-RetransmissionTimerDL) This timer is used for HARQ processing of downlink data and specifies the maximum period until receiving downlink retransmission. When the downlink HARQ RTT timer expires, the UE 100 (control unit 120) starts the downlink retransmission timer if the downlink data decoding is not successful. During the operation of the downlink retransmission timer, the UE 100 (control unit 120) monitors the PDCCH and waits for retransmission data.

[0089] Uplink HARQ RTT timer (drx-HARQ-RTT-TimerUL) This timer is used for HARQ processing of uplink data and specifies the minimum period until the MAC entity of the UE 100 receives a HARQ retransmission grant. The UE 100 (control unit 120) starts the downlink retransmission timer in response to transmission of uplink data. The UE 100 (control unit 120) does not need to monitor the PDCCH while the uplink HARQ RTT timer is operating.

[0090] Uplink retransmission timer (drx-RetransmissionTimerUL) This timer is used for the HARQ process of uplink data and specifies the maximum period until an uplink retransmission permission is received. The UE 100 (control unit 120) starts the uplink retransmission timer when the uplink HARQ RTT timer expires. The UE 100 (control unit 120) monitors the PDCCH while the uplink retransmission timer is operating.

[0091] If any of these retransmission-related timers is operating (step S53: YES), in step S54, the UE 100 (control unit 120) suspends the start of switching instructed by the switching instruction DCI received in step S51.

[0092] On the other hand, if none of the retransmission related timers are operating (step S53: NO), in step S55, the UE 100 (control unit 120) starts or executes the switching instructed by the switching instruction DCI received in step S51. For example, the UE 100 (control unit 120) may execute the SSSG switching from the first slot after the retransmission related timers expire.

[0093] In this way, in the second embodiment, the period during which the retransmission-related timer is operating constitutes at least a part of the switch delay of the switch instructed by the switch instruction DCI. Note that, when the switch delay is set by higher layer signaling (RRC message), the UE 100 (control unit 120) may suspend the start of the switch instructed by the switch instruction DCI during the period during which the retransmission-related timer is operating, even if the switch delay set by the higher layer signaling has elapsed.

[0094] The switching delay time may also include a period during which a retransmission-related timer is running, such as:

[0095] The duration of the drx-HARQ-RTT-TimerDL started for the corresponding HARQ process at the first symbol after the end of DL HARQ feedback transmission: The duration of the drx-RetransmissionTimerDL, which is started if the corresponding HARQ process of the first symbol after the drx-HARQ-RTT-TimerDL expires is not successfully decoded: The duration of the running drx-HARQ-RTT-TimerUL started for the corresponding HARQ process at the first symbol after the end of the first transmission (in a bundle) of the corresponding PUSCH transmission: ·The duration of the running drx-RetransmissionTimerUL, started for the corresponding HARQ process at the first symbol after the expiration of the drx-HARQ-RTT-TimerUL.

[0096] Furthermore, when UE 100 (control unit 120) is executing a plurality of HARQ processes, if at least one retransmission-related timer of the plurality of HARQ processes is operating, the initiation of switching instructed by the switching instruction DCI may be suspended. For example, UE 100 may execute SSSG switching based on expiration of drx-RetransmissionTimerDL corresponding to all HARQ processes and / or expiration of drx-RetransmissionTimerUL corresponding to all HARQ processes (for example, from the first slot after expiration).

[0097] In addition, UE 100 (control unit 120) may perform the above operation when receiving a configured DL assignment (i.e., a downlink DCI format having a CRC scrambled with the CS-RNTI) and / or a configured UL grant (i.e., an uplink DCI format having a CRC scrambled with the CS-RNTI).

[0098] In addition, in this embodiment, various existing timers for DRX are used, but the present invention is not limited to this, and timers used for HARQ processing and retransmission processing of PDCCH skipping and / or SSSG switching set in a higher layer may be used. Such timers are, for example, DCIbasedPowerSaving-HARQ-RTT-TimerDL, DCIbasedPowerSaving-HARQ-RTT-TimerUL, DCIbasedPowerSaving-RetransmissionTimerDL, DCIbasedPowerSaving-RetransmissionTimerUL, etc. Here, DCIbasedPowerSaving-HARQ-RTT-TimerDL is an example of a downlink HARQ RTT timer. DCIbasedPowerSaving-HARQ-RTT-TimerUL is an example of an uplink HARQ RTT timer. DCIbasedPowerSaving-RetransmissionTimerDL is an example of a downlink retransmission timer. DCIbasedPowerSaving-RetransmissionTimerUL is an example of an uplink retransmission timer.

[0099] Next, with reference to FIG. 12, the operation according to the second embodiment will be described with focus on the downlink.

[0100] In step S101, the UE 100 (communication unit 110) receives downlink scheduling DCI as a switching instruction DCI on the PDCCH. The downlink scheduling DCI is DCI that allocates radio resources (i.e., PDSCH resources) for downlink data. The UE 100 (communication unit 110) receives downlink data from the base station 200 using the PDSCH resources allocated by the downlink scheduling DCI. The UE 100 (control unit 120) attempts to decode the received downlink data.

[0101] In step S102, the UE 100 (communication unit 110) transmits, to the base station 200, HARQ feedback indicating whether or not the downlink data received in step S102 has been successfully decoded.

[0102] In step S103, the UE 100 (control unit 120) starts a downlink HARQ RTT timer in response to transmission of HARQ feedback corresponding to the downlink data. The UE 100 (control unit 120) suspends the start of switching instructed by the switching instruction DCI during the operation of the downlink HARQ RTT timer.

[0103] If the downlink HARQ RTT timer has expired (step S104: YES), in step S105, the UE 100 (control unit 120) determines whether the decoding of the downlink data has been successful. If the decoding of the downlink data has been successful (step S105: YES), in step S106, the UE 100 (control unit 120) starts the switching instructed by the switching instruction DCI.

[0104] On the other hand, if the downlink data has not been successfully decoded (step S105: NO), in step S107, the UE 100 (control unit 120) starts a downlink retransmission timer in response to expiration of the downlink HARQ RTT timer. During the operation of the downlink retransmission timer, the UE 100 (control unit 120) monitors the PDCCH and suspends the start of switching instructed by the switching instruction DCI.

[0105] If the downlink retransmission timer has expired (step S108: YES), in step S106, the UE 100 (control unit 120) starts the switching instructed by the switching instruction DCI. If retransmission data is received from the base station 200 while the downlink retransmission timer is operating, the UE 100 (control unit 120) may stop the downlink retransmission timer and return the process to step S102.

[0106] Next, with reference to FIG. 13, the operation according to the second embodiment will be described with a focus on the uplink.

[0107] In step S201, the UE 100 (the communication unit 110) receives an uplink scheduling DCI as a switching instruction DCI on a PDCCH. The uplink scheduling DCI is DCI that allocates radio resources (i.e., PUSCH resources) for uplink data.

[0108] In step S202, the UE 100 (communication unit 110) transmits uplink data to the base station 200 by using the PUSCH resource allocated by the uplink scheduling DCI.

[0109] In step S203, the UE 100 (control unit 120) starts an uplink HARQ RTT timer in response to the transmission of uplink data. The UE 100 (control unit 120) suspends the start of switching instructed by the switching instruction DCI while the uplink HARQ RTT timer is operating.

[0110] If the uplink HARQ RTT timer has expired (step S204: YES), in step S205, the UE 100 (control unit 120) starts an uplink retransmission timer. During the operation of the uplink retransmission timer, the UE 100 (control unit 120) monitors the PDCCH and suspends the start of switching instructed by the switching instruction DCI.

[0111] If the uplink retransmission timer has expired (step S206: YES), in step S207, the UE 100 (control unit 120) starts the switching instructed by the switching instruction DCI.

[0112] In this way, according to the second embodiment, the UE 100 that has received the scheduling DCI as a switching instruction suspends the start of switching while a retransmission-related timer associated with the HARQ process for data scheduled by the scheduling DCI is in operation. This makes it possible to appropriately perform the HARQ process even when the scheduling DCI is used as a switching instruction.

[0113] In the second embodiment, CSI reporting to base station 200 may be taken into consideration. For example, when UE 100 that has received a switching instruction DCI is instructed by a scheduling DCI to non-periodically report CSI to base station 200, UE 100 (control unit 120) may transmit a CSI report to base station 200 in a scheduled PUSCH, and may suspend initiation of switching instructed by the switching instruction DCI until this CSI report is performed. Then, UE 100 (control unit 120) may start switching instructed by the switching instruction DCI in response to transmitting the CSI report in the scheduled PUSCH. Details of CSI reporting will be described in a third embodiment described later.

[0114] <Third embodiment> Next, a third embodiment will be described with reference to FIG.

[0115] Since the period during which the UE 100 is in the power saving state is considered to be a period during which data transmission and reception is temporarily not performed, it is desirable to reduce the power consumption required for SRS transmission, CSI measurement, and CSI reporting.

[0116] Here, SRS transmission refers to an operation of transmitting an SRS, which is an uplink physical signal for channel estimation used by the base station 200 to estimate the uplink channel state, to the base station 200, and the UE 100 transmits the SRS according to the setting from the base station 200. The SRS report is an operation for uplink link adaptation. The link adaptation is to adapt the modulation and coding scheme (MCS) applied to data transmission to the channel state. During the period when the UE 100 is in the power saving state, there is little need to perform uplink link adaptation, so the SRS transmission is suppressed.

[0117] CSI measurement refers to an operation of measuring a reference signal used for estimating a downlink channel state, and UE 100 performs CSI measurement according to a setting from base station 200. For example, UE 100 performs CSI measurement based on at least one of a channel state information reference signal (CSI-RS) and a synchronization signal / physical broadcast channel (SS / PBCH) block transmitted by base station 200. CSI reporting refers to an operation of transmitting a CSI report indicating a channel state estimated according to a result of CSI measurement to base station 200, and UE 100 performs CSI reporting according to a setting from base station 200. For example, the channel state includes one or more of a channel quality indicator (CQI), a rank indicator (RI), a precoding matrix indicator (PMI), a SS / PBCH block resource indicator (SSBRI), a CSI-RS resource indicator (CRI), a layer indicator (LI), and a layer 1 reference signal received power (L1-RSRP). The CSI reporting may be performed on a PUCCH or a PUSCH. The CSI measurement and the CSI reporting are operations for downlink link adaptation. During a period in which the UE 100 is in a power saving state, the need to perform downlink link adaptation is low, and therefore, the CSI measurement and the CSI reporting are suppressed.

[0118] As shown in FIG. 14, in step S301, in a first state in which the UE 100 (control unit 120) monitors the PDCCH in a search space, the UE 100 (control unit 120) performs predetermined control to control at least one operation among SRS transmission to the base station 200, CSI measurement, and CSI reporting to the base station 200. In the first state, the UE 100 (control unit 120) 、S At least one of the operations of RS transmission, CSI measurement, and CSI reporting may be performed periodically. For example, in the first state, the UE 100 (controller 120) performs at least one of periodic SRS transmission and periodic CSI reporting. The periodic SRS transmission may include semi-persistent SRS transmission. The periodic CSI reporting may include semi-persistent CSI reporting on the PUCCH or PUSCH.

[0119] In step S302, the UE 100 (communication unit 110) receives a switching instruction DCI on the PDCCH, which instructs switching to a second state (for example, a power saving state) in which a setting related to a search space is different from the first state. In the third embodiment, the switching instruction DCI is not limited to the above-mentioned scheduling DCI, and may be a non-scheduling DCI. The switching instruction DCI may include an information field indicating a switching destination SSSG.

[0120] In step S303, in response to receiving the switching command DCI, the UE 100 (control unit 120) performs control different from the predetermined control for at least one operation among the SRS transmission, the CSI measurement, and the CSI report.

[0121] For example, the UE 100 (control unit 120) stops at least one of the operations of SRS transmission, CSI measurement, and CSI reporting within a switch delay from the first state to the second state. The UE 100 (control unit 120) may stop periodic SRS transmission and periodic CSI reporting within the switch delay time. Such control is referred to as "P switch During the switching delay time consisting of symbols, the UE Periodic SRS transmission and semi-persistent SRS transmission Semi-persistent CSI configured for PUSCH Periodic CSI reporting, which is L1-RSRP, on PUCCH when ps-TransmitPeriodicL1-RSRP is not configured with the value true. · If ps-TransmitOtherPeriodicCSI is not configured with the value true, it may be expressed as "It is not expected to perform periodic CSI reporting other than L1-RSRP on PUCCH."

[0122] The first state may be a state in which a PDCCH provided at a predetermined period is monitored in a search space, and the second state may be a state in which monitoring of the PDCCH is skipped (PDCCH skipping state). In the second state, the UE 100 (control unit 120) may not perform at least one of the operations of SRS transmission, CSI measurement, and CSI reporting.

[0123] The first state may be a state in which a PDCCH provided at a predetermined period is monitored in a search space, and the second state may be a state in which a PDCCH is monitored in a search space provided at a period longer than the predetermined period. Switching from the first state to the second state may be realized by SSSG switching. In the second state, the UE 100 (control unit 120) may perform at least one operation of SRS transmission, CSI measurement, and CSI reporting only in the time interval of the search space.

[0124] For example, in the second state, the UE 100 (control unit 120) may perform aperiodic SRS transmission only in monitoring slots that are time periods of the search space. Such control may be expressed as "a UE for which SSSG switching is configured by higher layer signaling does not expect SRS resources to be available in slots other than the corresponding monitoring slots to trigger aperiodic SRS transmission when the period of the search space is longer than a predetermined value (e.g., 80 milliseconds)."

[0125] Furthermore, in the second state, UE 100 (control unit 120) may perform CSI measurement only in monitoring slots, which are time intervals of the search space. Such control may be expressed as "a UE configured with SSSG switching by higher layer signaling excludes slots other than the monitoring slot corresponding to the search space from the most recent CSI measurement opportunity for CSI reporting." Also, such control may be expressed as "a UE configured with SSSG switching by higher layer signaling does not expect CSI-RS resources to be available in slots other than the corresponding monitoring slot when the period of the search space is longer than a predetermined value (e.g., 80 milliseconds)."

[0126] In this way, according to the third embodiment, the UE 100 that has received the switching command DCI performs control for at least one of the operations of SRS transmission, CSI measurement, and CSI reporting, in response to reception of the switching command DCI, that is different from the control performed before receiving the switching command DCI. This makes it possible to apply control optimized for a power saving state, for example, control optimized for an extended search space period, to SRS transmission, CSI measurement, and CSI reporting, thereby making it possible to reduce power consumption required for monitoring the PDCCH and to achieve further power saving.

[0127] <Fourth embodiment> Next, a fourth embodiment will be described with reference to FIG.

[0128] In the fourth embodiment, an operation of performing power saving by SSSG switching is assumed. Specifically, one or more SSSGs can be set in the UE 100 from various SSSGs including a plurality of SSSGs having different search space periods and an SSSG having no search space, and flexible power saving is realized by instructing the switching of the SSSG by DCI.

[0129] As shown in Fig. 15, in step S401, the base station 200 (communication unit 210) transmits one or more RRC messages to the UE 100. The one or more RRC messages may include a dedicated RRC message (e.g., an RRC Reconfiguration message) transmitted individually to the UE. The UE 100 (communication unit 110) receives the RRC message.

[0130] The RRC message includes correspondence relationship information indicating a correspondence relationship between each index of one or more SSSGs set in the UE 100 and a value set in an information field (hereinafter referred to as an "SSSG information field") in a switching instruction DCI that instructs switching of the SSSG applied by the UE 100. The one or more SSSGs include at least one of an SSSG for periodically monitoring the PDCCH and an SSSG for skipping monitoring the PDCCH.

[0131] For example, when four SSSGs are configured in the UE 100, the correspondence information includes information such as "SSSG index #0: value "00", "SSSG index #1: value "01", "SSSG index #2: value "10", and "SSSG index #3: value "11". The base station 200 is not limited to configuring these four SSSGs in the UE 100 all at once, and may configure the four SSSGs in the UE 100 in two separate sessions, for example, two SSSGs each. The value set in the SSSG information field may be configured in a bitmap format. For example, the position of the bit that is "1" (code point) may be associated with the SSSG index, such as "SSSG index #0: value "1000", "SSSG index #1: value "0100", "SSSG index #2: value "0010", and "SSSG index #3: value "0001".

[0132] The RRC message further includes search space configuration information associated with each of the SSSG indices. The search space configuration information includes one or more search space configurations. Each search space configuration includes a search space period, a search space offset, a search space duration (e.g., a number of consecutive slots), a symbol for PDCCH monitoring, an aggregation level, a type of search space, and a DCI format, etc.

[0133] For example, the search space configuration information associated with SSSG index #0 is information for setting a first search space period as the search space period. The search space configuration information associated with SSSG index #1 is information for setting a second search space period as the search space period. The search space configuration information associated with SSSG index #2 is information for setting a third search space period as the search space period. The search space configuration information associated with SSSG index #4 is information indicating that no search space is set. In other words, SSSG index #4 is associated with search space configuration information indicating PDCCH skipping.

[0134] The RRC message may include field setting information indicating the presence or absence of an SSSG information field for each of one or more DCI formats. The switching instruction DCI is a DCI having a DCI format indicated by the field setting information that the SSSG information field is present. The presence or absence (presence / absence) of the SSSG information field may be set commonly or independently for the non-scheduling DCI and / or the scheduling DCI. The presence or absence (presence / absence) of the SSSG information field may be set commonly for DCI format 1_1 and DCI format 0_1, and commonly for DCI format 1_2 and DCI format 0_2.

[0135] The RRC message may include bit number setting information indicating the number of bits of the SSSG information field for one or more DCI formats. The number of bits of the SSSG information field may be directly set for the non-scheduling DCI and / or the scheduling DCI, either in common or independently. The number of bits of the SSSG information field may be set in common for DCI format 1_1 and DCI format 0_1, and / or in common for DCI format 1_2 and DCI format 0_2. For example, an SSSG information field of up to 2 bits may be set for DCI format 1_1 and / or DCI format 0_1, and / or an SSSG information field of 1 bit may be set for DCI format 1_2 and DCI format 0_2.

[0136] The RRC message may include a timer setting value of a switching timer for each of one or more SSSGs. Details of such a switching timer will be described in a fifth embodiment described later.

[0137] In step S402, the UE 100 (control unit 120) stores the information set by the base station 200.

[0138] In step S403, the base station 200 (communication unit 210) may transmit to the UE 100 a MAC CE (hereinafter referred to as an "SSSG state selection MAC CE") that specifies activation or deactivation of an SSSG for each SSSG index. The UE 100 (communication unit 110) receives the SSSG state selection MAC CE. The SSSG state selection MAC CE instructs activation / deactivation for each SSSG index. The activated SSSG becomes valid as a switching destination SSSG, and the deactivated SSSG becomes invalid as a switching destination SSSG. However, deactivation may be prohibited for the default SSSG. The default SSSG will be described in a fifth embodiment below.

[0139] For example, the SSSG state selection MAC CE is identified by a MAC subheader having a LCID defined for the SSSG state selection MAC CE. The SSSG state selection MAC CE may include a "cell ID field" indicating a serving cell to which the SSSG state selection MAC CE applies. The SSSG state selection MAC CE may include a "Ti field" indicating activation / deactivation for each entry "i" of the SSSG index list consisting of SSSG indices. The "Ti field" includes "T0 field" to "T(n-1) field", and is set to a value of "1" for the SSSG to be activated. Here, "n" indicates the maximum number of SSSGs that can be activated, for example, "4". Assuming that SSSG index #0 is activated, SSSG index #1 is deactivated, SSSG index #2 is activated, and SSSG index #3 is deactivated, the "T0 field" is set to "1", the "T1 field" is set to "0", the "T2 field" is set to "1", and the "T3 field" is set to "1", respectively.

[0140] The SSSG information field may be configured in a bitmap format for only the activated SSSGs. For example, the first activated SSSG is mapped to code point 1 in the SSSG information field, and the second activated SSSG is mapped to code point 2 in the SSSG information field. Assuming that SSSG index #0 is activated, SSSG index #1 is deactivated, SSSG index #2 is activated, and SSSG index #3 is deactivated, the number of bits in the SSSG information field is "2", with "10" indicating SSSG index #0 and "01" indicating SSSG index #2.

[0141] In step S404, base station 200 (communication unit 210) transmits a switching instruction DCI having an SSSG information field to UE 100 on a PDCCH. UE 100 (communication unit 110) receives the switching instruction DCI on a PDCCH. UE 100 (control unit 120) may determine whether or not the DCI format of the detected DCI corresponds to the switching instruction DCI, based on field setting information set by base station 200.

[0142] In step S405, UE 100 (control unit 120) acquires the value set in the SSSG information field of the switching instruction DCI received in step S404. UE 100 (control unit 120) may acquire the value set in the SSSG information field after specifying the number of bits of the SSSG information field based on the bit number setting information set from base station 200. Alternatively, UE 100 (control unit 120) may acquire the value set in the SSSG information field after specifying the number of bits of the SSSG information field based on the number of SSSG indexes set in UE 100 (i.e., the number of entries in the set SSSG index list). For example, when the number of SSSG indexes set in UE 100 is "I", UE 100 (control unit 120) may calculate and specify the number of bits of the SSSG information field by an integer value obtained by rounding up the decimal point of log2(I).

[0143] In step S406, UE 100 (control unit 120) switches to an SSSG having an SSSG index corresponding to the value set in the SSSG information field in the received switching instruction DCI based on the correspondence relationship information set from base station 200, and monitors the PDCCH according to the switching destination SSSG. For example, in the example of Fig. 13, when the value set in the SSSG information field is "11", UE 100 (control unit 120) determines that an instruction to switch to the SSSG with SSSG index #3 has been issued, and switches to the SSSG with SSSG index #3.

[0144] Next, a first configuration example of information elements included in an RRC message in the fourth embodiment will be described with reference to Figs.

[0145] As shown in Figure 16, the RRC message includes a PDCCH configuration (PDCCH-Config) information element, which is used to configure UE-specific PDCCH parameters, such as a control resource set (CORESET), a search space, and additional parameters for acquiring the PDCCH.

[0146] The PDCCH configuration (PDCCH-Config) information element may include an SSSG addition / modification list (searchSpaceSetToAddModList) and / or an SSSG release list (searchSpaceSetToReleaseList). The SSSG addition / modification list is a list of SSSGs to be configured in UE 100 (SEQUENCE (SIZE (1..maxNrofSearchSpaceSets-r17)) OF SearchSpaceSet-r17). The SSSG release list is a list of SSSGs to be released in UE 100 (SEQUENCE (SIZE (1..maxNrofSearchSpaceSets-r17)) OF SearchSpaceSet-r17). Here, "maxNrofSearchSpaceSets-r17" indicates the maximum number of configurable SSSGs.

[0147] As shown in Figure 17, "SearchSpaceSet-r17", which constitutes each entry of the SSSG addition / modification list and the SSSG release list, includes "SearchSpaceSetId-r17", which is an index of the SSSG, and "searcSpaces-r17", which are each search space setting included in this SSSG. "searcSpaces-r17" is composed of a list of search space IDs of each search space setting included in this SSSG (SEQUENCE (SIZE (0..maxNrofSearchSpaces-r17)) OF SearchSpaceId). "SearchSpaceSetId-r17", which is an index of the SSSG, has the number of bits "0..maxNrofSearchSpaceSets-1-r17".

[0148] Next, a second configuration example of the information element included in the RRC message in the fourth embodiment will be described with reference to Fig. 18 and Fig. 19. The second configuration example indicates, for each search space setting, the SSSG to which the search space setting belongs.

[0149] As shown in Fig. 18, the PDCCH configuration (PDCCH-Config) information element can include a search space addition / modification list (searchSpacesToAddModListExt2-r17). The search space addition / modification list is a list consisting of "SearchSpaceExt2-r17" from 1 to 10.

[0150] As shown in FIG. 19, the search space setting (SearchSpace) information element includes "searchSpaceSetIdList-r17" which is a list of indices of SSSGs to which this search space setting is associated. One search space setting can be associated with multiple SSSGs. For an SSSG to which none of the search space settings configured in the UE 100 is associated, the UE 100 does not monitor the PDCCH while using the SSSG.

[0151] In this way, according to the fourth embodiment, correspondence information indicating a correspondence between each SSSG index of one or more SSSGs set in the UE 100 and a value set in an SSSG information field in a switching instruction DCI instructing switching of an SSSG applied by the UE 100 is received from the base station 200. The one or more SSSGs include at least one of an SSSG that periodically monitors a PDCCH and an SSSG that skips monitoring of a PDCCH. This makes it possible to realize flexible power saving using various SSSGs. In addition, since one SSSG information field provided in the switching instruction DCI can specify one of multiple SSSGs with different search space periods or specify an SSSG that does not monitor a PDCCH, an increase in the size of the DCI can be suppressed even when various SSSGs are used.

[0152] <Fifth embodiment> Next, a fifth embodiment will be described with reference to Fig. 20. In the fifth embodiment, it is assumed that the UE 100 switches the SSSG on a timer basis, and three or more SSSGs may be set in the UE 100.

[0153] In the fifth embodiment, the base station 200 (control unit 230) may set one of the SSSGs set in the UE 100 as a default SSSG in the UE 100. For example, the base station 200 (control unit 230) may designate one of the SSSG indexes set in the UE 100 as "defaultSSSG-Id". The default SSSG may be an SSSG determined by a predetermined rule shared in advance between the base station 200 and the UE 100, among the SSSGs set in the UE 100. The default SSSG may be an SSSG set in the UE 100 by the base station 200 as the default SSSG.

[0154] As shown in FIG. 20, in step S501, the UE 100 (control unit 120), in which multiple SSSGs have been set by the base station 200, monitors the PDCCH using one of the multiple SSSGs.

[0155] In step S502, the UE 100 (communication unit 110) receives a switch instruction DCI from the base station 200 on the PDCCH, the switch instruction DCI instructing a switch to another SSSG.

[0156] In step S503, the UE 100 (control unit 120) switches to the SSSG specified in the switching instruction DCI, and starts a timer (switching timer) associated with the SSSG.

[0157] In step S504, the UE 100 (control unit 120) determines whether the switching timer has expired.

[0158] If the switching timer has expired (step S504: YES), in step S505, UE 100 (control unit 120) switches to a default SSSG from among the multiple SSSGs that have been set. Here, by switching to the SSSG specified by base station 200 as "defaultSSSG-Id", base station 200 can know the SSSG to which UE 100 has switched. Note that since the switching timer is a value set by base station 200, base station 200 manages the switching timer in the same way as UE 100, and can know that the switching timer has expired in UE 100.

[0159] When a default SSSG has not been set by the base station 200, specifically, when a default SSSG has not been explicitly specified as "defaultSSSG-Id" by the base station 200, the UE 100 (control unit 120) determines a default SSSG according to a predetermined rule. The predetermined rule is, for example, a rule defined in the technical specifications of 3GPP, and is a rule shared in advance between the base station 200 and the UE 100.

[0160] Here, the predetermined rule may be a rule that determines, as the default SSSG, the SSSG corresponding to the smallest SSSG index or the SSSG corresponding to the largest SSSG index among the SSSG indices set in the UE 100. For example, in the example of FIG. 13, if the rule is that the SSSG corresponding to the smallest SSSG index is the default SSSG, the UE 100 (control unit 120) determines the SSSG of SSSG index #0 as the default SSSG. If the rule is that the SSSG corresponding to the largest SSSG index is the default SSSG, the UE 100 (control unit 120) determines the SSSG of SSSG index #4 as the default SSSG.

[0161] As described above, UE 100 (communication unit 110) may receive correspondence information indicating the correspondence between the SSSG index set in UE 100 and the value set in the SSSG information field in the switching instruction DCI from base station 200. The predetermined rule may be a rule for determining, as the default SSSG, an SSSG corresponding to an SSSG index indicated by a specific value (e.g., "0") as the value set in the SSSG information field in the switching instruction DCI. For example, UE 100 (control unit 120) determines, as the default SSSG, an SSSG having an SSSG index indicated by a value set in the SSSG information field in the switching instruction DCI as "0".

[0162] The predetermined rule may be a rule that determines, as the default SSSG, an SSSG corresponding to an SSSG index (eg, index #0) having a predetermined value among the SSSG indices configured in the UE 100.

[0163] The predetermined rule may be a rule that determines, as a default SSSG, an SSSG other than an SSSG for skipping PDCCH monitoring, among the SSSGs set in the UE 100. That is, the UE 100 (control unit 120) may assume that an SSSG index corresponding to PDCCH skipping is not set as the default SSSG.

[0164] When DRX is configured in the UE 100, the UE 100 (control unit 120) may apply a specific SSSG when switching from a DRX reception-off period to a DRX reception-on period (active time). The predetermined rule may be a rule that determines the specific SSSG as a default SSSG. That is, the UE 100 (control unit 120) may determine the first SSSG that monitors the PDCCH after the DRX reception-off period has elapsed as the default SSSG.

[0165] In the fifth embodiment, the UE 100 (the communication unit 110) may receive, as the switching instruction DCI, a scheduling DCI indicating radio resources allocated to the UE 100. After receiving the scheduling DCI as the switching instruction DCI, the UE 100 (the control unit 120) may start a switching timer at the timing of switching to one SSSG (specifically, the slot at which the SSSG switching is executed). As described in the second embodiment, the UE 100 (the control unit 120) may suspend the SSSG switching while a retransmission-related timer related to the HARQ process is operating. For this reason, when the scheduling DCI is received as the switching instruction DCI, the switching timer is started at the timing of executing the SSSG switching, not at the timing of receiving the switching instruction DCI.

[0166] The UE 100 (control unit 120) may use a common value as a switching timer value to be applied to two or more SSSGs among the three or more SSSGs set in the UE 100. The base station 200 (control unit 230) may set a common value as a switching timer value to be applied to two or more SSSGs among the three or more SSSGs set in the UE 100.

[0167] The UE 100 (control unit 120) may use an individual value for each SSSG as the value of the switching timer to be applied to each SSSG set in the UE 100. The base station 200 (control unit 230) may set in the UE 100 an individual switching timer setting value for each SSSG.

[0168] When the SSSG to be switched to is an SSSG corresponding to PDCCH skipping, the UE 100 (control unit 120) may start a switching timer associated with the SSSG at the timing (slot) at which switching to the SSSG is started. In the PDCCH skipping state, that is, during a predetermined period in which PDCCH monitoring is skipped, the resources used for PDCCH monitoring are not occupied, and switching to the SSSG can be started at any timing. By utilizing this advantage, it is possible to minimize the effect of switching delay time without impeding the operation of PDCCH monitoring. Note that the UE 100 (control unit 120) may monitor the PDDCH assuming a default SSSG after the switching timer expires.

[0169] Next, a specific example 1 of an operation using the switching timer according to the fifth embodiment will be described with reference to FIG.

[0170] 21, a total of three SSSGs, namely, a default SSSG, SSSG#x, and SSSG#y, are set in the UE 100. Here, it is assumed that the base station 200 (control unit 230) sets in the UE 100 one common switching timer value for the SSSG#x and SSSG#y that are not the default SSSG.

[0171] In period T11, UE 100 (control unit 120) monitors the PDCCH using the default SSSG. UE 100 (communication unit 110) receives a non-scheduling DCI instructing switching to SSSG#x in the last search space of period T11. UE 100 (control unit 120) starts a switching timer when receiving the non-scheduling DCI, since HARQ processing does not occur in the case of the non-scheduling DCI.

[0172] In a period T12, the UE 100 (control unit 120) monitors the PDCCH using SSSG#x while the switching timer is operating. The SSSG#x is an SSSG with a longer search space period than the default SSSG. When the switching timer expires, the UE 100 (control unit 120) switches to the default SSSG after a switching delay time has elapsed.

[0173] In period T13, UE 100 (control unit 120) monitors the PDCCH using the default SSSG. UE 100 (communication unit 110) receives a scheduling DCI (Scheduling DCI) instructing switching to SSSG#y in the last search space of period T13. Since HARQ processing occurs in the case of a scheduling DCI, UE 100 (control unit 120) does not start a switching timer when receiving the scheduling DCI, but starts a switching timer at the timing (slot) when switching to SSSG#y is executed.

[0174] In period T14, while the switching timer is operating, UE 100 (control unit 120) monitors the PDCCH using SSSG#y. SSSG#y is an SSSG with a shorter search space period than the default SSSG. When the switching timer expires, UE 100 (control unit 120) switches to the default SSSG after a switching delay time (Switch delay) has elapsed. Then, in period T15, UE 100 (control unit 120) monitors the PDCCH using the default SSSG.

[0175] Next, a second specific example of an operation using the switching timer according to the fifth embodiment will be described with reference to FIG.

[0176] 22, a total of three SSSGs, a default SSSG, an SSSG#x for PDCCH skipping, and an SSSG#y for PDCCH skipping, are set in the UE 100. Here, it is assumed that the base station 200 (control unit 230) sets individual switching timer values ​​in the UE 100 for the SSSG#x and SSSG#y that are not the default SSSG.

[0177] In period T21, UE 100 (control unit 120) monitors the PDCCH using a default SSSG. UE 100 (communication unit 110) receives a non-scheduling DCI instructing switching to SSSG#x in the last search space of period T11. Since the switching destination SSSG#x is an SSSG corresponding to PDCCH skipping, UE 100 (control unit 120) starts a switching timer (Switching timer-1) set independently for SSSG#x at the timing (slot) when switching to SSSG#x is executed.

[0178] In a period T22, the UE 100 (control unit 120) skips monitoring the PDCCH while the switching timer-1 is operating. When the switching timer-1 expires, the UE 100 (control unit 120) switches to the default SSSG after a switch delay has elapsed.

[0179] In period T23, UE 100 (control unit 120) monitors the PDCCH using the default SSSG. UE 100 (communication unit 110) receives a scheduling DCI (Scheduling DCI) instructing switching to SSSG#y in the last search space of period T23. Since the switching destination SSSG#x is an SSSG corresponding to PDCCH skipping, UE 100 (control unit 120) starts a switching timer (Switching timer-2) set independently for SSSG#y at the timing (slot) when switching to SSSG#y is executed. The timer value of Switching timer-2 is greater than the timer value of Switching timer-1.

[0180] In period T24, UE 100 (control unit 120) skips monitoring the PDCCH while switching timer-2 is operating. When switching timer-2 expires, UE 100 (control unit 120) switches to the default SSSG after a switch delay has elapsed. Then, in period T25, UE 100 (control unit 120) monitors the PDCCH using the default SSSG.

[0181] In this way, according to the fifth embodiment, even if the UE 100 switches the SSSG on a timer basis and three or more SSSGs can be set in the UE 100, the base station 200 can grasp the SSSG to which the SSSG is to be switched by defining a default SSSG. Therefore, it becomes possible to switch to various SSSGs on a timer basis.

[0182] <Other embodiments> In the above embodiment, the base station 200 may include a plurality of units. The plurality of units may include a first unit hosting a higher layer included in a protocol stack and a second unit hosting a lower layer included in the protocol stack. The higher layer may include an RRC layer, an SDAP layer, and a PDCP layer, and the lower layer may include an RLC layer, a MAC layer, and a PHY layer. The first unit may be a Central Unit (CU), and the second unit may be a Distributed Unit (DU). The plurality of units may include a third unit performing processing below the PHY layer. The second unit may perform processing above the PHY layer. The third unit may be a Radio Unit (RU). The base station 200 may be one of the plurality of units, and may be connected to other units of the plurality of units. The base station 200 may also be an Integrated Access and Backhaul (IAB) donor or an IAB node.

[0183] In the above embodiment, the mobile communication system 1 has been described by taking an example of a mobile communication system based on NR. 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 one of LTE and other generation systems (e.g., 6th generation) of the 3GPP standard. The base station 200 may be an eNB that provides an E-UTRA user plane and control plane protocol termination for 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. Similarly, the mobile communication system to which carrier aggregation is applied has been described by way of example, but is not limited thereto, and may be a mobile communication system to which dual connectivity is applied, and the operation example using a primary cell (PCell) may be an operation using a special cell (SpCell).

[0184] The steps in the operations of the above-described 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. Furthermore, each of the above-described operation flows is not limited to being executed separately and independently, but may be executed by combining two or more operation flows. For example, some steps of one operation flow may be added to another operation flow, or some steps of one operation flow may be replaced with some steps of another operation flow.

[0185] 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 (System-on-a-Chip)).

[0186] 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. Also, "obtain / acquire" may mean obtaining information from information received from another node. Alternatively, "obtain / acquire" may mean obtaining information by generating information. Similarly, "include" and "comprise" do not mean including only the listed items, but may include only the listed items. Also, "include" and "comprise" mean including additional items in addition to the listed items. Similarly, in this disclosure, "or" does not mean an exclusive or, but does mean a logical or.

[0187] 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.

Claims

1. A receiving unit (110) that receives an RRC message from a base station (200) including information for determining whether or not an information field related to monitoring of a physical downlink control channel (PDCCH) is present in a downlink control information (DCI) format used for scheduling a physical downlink shared channel (PDSCH); A control unit (120) for controlling monitoring of the PDCCH in a downlink BWP of a serving cell, The control unit (120) When it is determined based on the information that an information field regarding monitoring of the PDCCH exists in the DCI format, switching of a group of a search space set for monitoring of the PDCCH is performed based on a first value set in the information field regarding monitoring of the PDCCH, and skipping of monitoring of the PDCCH is performed based on a second value set in the information field regarding monitoring of the PDCCH. A communication device (100).

2. The control unit is Based on the information, it is determined whether a DCI format used for scheduling a physical uplink shared channel (PUSCH) has an information field related to monitoring the PDCCH; Switching a group of search space sets for monitoring the PDCCH based on the first value set in an information field regarding monitoring of the PDCCH included in a DCI format used for scheduling the PUSCH; skipping the monitoring of the PDCCH based on the second value set in an information field regarding the monitoring of the PDCCH included in a DCI format used for scheduling the PUSCH. The communication device according to claim 1 .

3. The DCI format used for scheduling the PDSCH is a C-RNTI (Cell-Radio Network Temporary Identifier), MCS-C-RNTI (Modulation and Coding Scheme-C-RNTI), or CS-RNTI (Configured Scheduling-RNTI) to which a CRC parity bit scrambled is added. The communication device (100) of claim 1.

4. The RRC message includes information for configuring one or more cell groups. A communication device (100) according to any one of claims 1 to 3.

5. A transmission unit (210) that transmits an RRC message including information for determining whether or not an information field related to monitoring of a physical downlink control channel (PDCCH) is present in a downlink control information (DCI) format used for scheduling a physical downlink shared channel (PDSCH), to a communication device (100); A control unit (230) for controlling monitoring of the PDCCH in a downlink BWP of a serving cell, The control unit (230) When the DCI format indicates based on the information that an information field regarding monitoring of the PDCCH exists, the DCI format indicates switching of a group of a search space set for monitoring of the PDCCH based on a first value set in the information field regarding monitoring of the PDCCH, and indicates skipping of monitoring of the PDCCH based on a second value set in the information field regarding monitoring of the PDCCH. Base station (200).

6. The information is used to determine whether an information field regarding monitoring of the PDCCH is present in a DCI format used for scheduling a physical uplink shared channel (PUSCH); The control unit is Instructing switching of a group of a search space set for monitoring the PDCCH based on the first value set in an information field regarding monitoring of the PDCCH included in a DCI format used for scheduling the PUSCH; Instruct skipping of monitoring of the PDCCH based on the second value set in an information field regarding monitoring of the PDCCH included in a DCI format used for scheduling the PUSCH. The base station (200) of claim 5.

7. The DCI format used for scheduling the PDSCH is a C-RNTI (Cell-Radio Network Temporary Identifier), MCS-C-RNTI (Modulation and Coding Scheme-C-RNTI), or CS-RNTI (Configured Scheduling-RNTI) to which a CRC parity bit scrambled is added. The base station (200) according to claim 5.

8. The RRC message includes information for configuring one or more cell groups. A base station (200) according to any of claims 5 to 7.

9. A communication method for use in a communication device (100), comprising: Receiving an RRC message from a base station (200), the RRC message including information for determining whether or not an information field related to monitoring of a physical downlink control channel (PDCCH) is present in a downlink control information (DCI) format used for scheduling a physical downlink shared channel (PDSCH); and controlling monitoring of the PDCCH in a downlink BWP of a serving cell; In the step of controlling monitoring of the PDCCH, when it is determined that an information field regarding monitoring of the PDCCH exists in the DCI format based on the information, Switching a group of search space sets for monitoring the PDCCH based on a first value set in an information field regarding monitoring the PDCCH, and skipping monitoring of the PDCCH based on a second value set in an information field regarding monitoring the PDCCH. Communication methods.

10. determining whether a DCI format used for scheduling a physical uplink shared channel (PUSCH) includes an information field related to monitoring the PDCCH based on the information; A step of switching a group of search space sets for monitoring the PDCCH based on the first value set in an information field regarding monitoring of the PDCCH included in a DCI format used for scheduling the PUSCH. and, and skipping monitoring of the PDCCH based on the second value set in an information field regarding monitoring of the PDCCH included in a DCI format used for scheduling the PUSCH. The communication method according to claim 9.

11. The DCI format used for scheduling the PDSCH is a C-RNTI (Cell-Radio Network Temporary Identifier), MCS-C-RNTI (Modulation and Coding Scheme-C-RNTI), or CS-RNTI (Configured Scheduling-RNTI) to which a scrambled CRC parity bit is added. The communication method according to claim 9.

12. The RRC message includes information for configuring one or more cell groups. A communication method according to any one of claims 9 to 11.

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