Communication equipment, base station, and communication method

Abstract

To enable proper cell group SSSG switching.MEANS FOR SOLVING THE PROBLEM: A communication apparatus (100) has one or a plurality of cell groups configured by a base station (200), and comprises: a receiver (110) configured to receive, from the base station (200), downlink control information (DCI) including an information field related to monitoring a physical downlink control channel (PDCCH) in a serving cell belonging to any cell group of the one or the plurality of cell groups; and a controller (120) configured to execute a procedure related to monitoring the PDCCH on the basis of 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.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present disclosure relates to a communication device, a base station, and a method used in a mobile communication system.

Background Art

[0002] In recent years, in 3GPP (3rd Generation Partnership Project), which is a standardization project for mobile communication systems, power saving technologies for reducing the power consumption of user equipment in the Radio Resource Control (RRC) connected state have been considered for introduction into the fifth generation (5G) system. For example, by increasing the period of the search space corresponding to the candidate timing where the Physical Downlink Control Channel (PDCCH) is arranged, the power consumption required for monitoring the PDCCH can be reduced.

[0003] As such a technology, a plurality of Search Space Set Groups (SSSGs) including a search space set group (SSSG) having a normal search space period and an SSSG for power saving having a longer search space period or no search space than the normal search space period are set for a user equipment, and a technology has been proposed in which a base station dynamically instructs the user equipment to switch the SSSG (see Non-Patent Documents 1 to 3). Thereby, while being able to apply an optimal SSSG according to the traffic state of the user equipment, the power consumption of the user equipment can be reduced.

[0004] <00000l5>In addition, there is also a technology of SSSG switching (hereinafter referred to as "cell group SSSG switching") in which a cell group composed of a plurality of cells capable of switching SSSGs simultaneously is set for a user equipment, and the SSSG is switched simultaneously for all serving cells in the cell group.

Prior Art Documents

Non-Patent Documents

[0005]

Non-Patent Document 1

[0006] The communication device according to the first embodiment is a communication device in which one or more cell groups are set by a base station, and comprises a receiving unit that receives downlink control information (DCI) from the base station, which includes an information field for monitoring the physical downlink control channel (PDCCH), in a serving cell belonging to any of the one or more cell groups, and a control unit that executes a procedure for monitoring the PDCCH based on a value set in the information field. The procedure for monitoring the PDCCH is applied to all serving cells in the cell group to which the serving cell that received the DCI belongs.

[0007] A base station according to the second embodiment is a base station that configures one or more cell groups for a communication device, and comprises a transmitting unit that transmits downlink control information (DCI) including an information field for monitoring a physical downlink control channel (PDCCH) to the communication device in a serving cell belonging to any of the one or more cell groups, and a control unit that controls a procedure for monitoring the PDCCH based on a value set in the information field. The procedure for monitoring the PDCCH is applied to all serving cells in the cell group to which the serving cell that received the DCI belongs.

[0008] A method relating to a third aspect is a method to be performed in a communication device in which one or more cell groups are configured by a base station, comprising the steps of: receiving downlink control information (DCI) from the base station in a serving cell belonging to one of the one or more cell groups, which includes an information field for monitoring a physical downlink control channel (PDCCH); and performing a procedure for monitoring the PDCCH based on a value set in the information field. The procedure for monitoring the PDCCH is applied to all serving cells in the cell group to which the serving cell that received the DCI belongs.

[0009] A method relating to a fourth aspect is a method performed by a base station that configures one or more cell groups for a communication device, comprising the steps of: transmitting downlink control information (DCI) including an information field for monitoring a physical downlink control channel (PDCCH) to the communication device in a serving cell belonging to any of the one or more cell groups; and controlling a procedure for monitoring the PDCCH based on a value set in the information field. The procedure for monitoring the PDCCH is applied to all serving cells in the cell group to which the serving cell that received the DCI belongs. [Brief explanation of the drawing]

[0010] The purposes and other purposes, features and benefits of this disclosure will become clearer from the detailed description below, with reference to the attached drawings. Those drawings are: [Figure 1] Figure 1 is a diagram showing the configuration of a mobile communication system according to an embodiment. [Figure 2] Figure 2 is a diagram showing an example of the protocol stack configuration according to the embodiment. [Figure 3] Figure 3 is a diagram illustrating the search space and SSSG switching according to the embodiment. [Figure 4]Figure 4 is a diagram illustrating the search space and SSSG switching according to the embodiment. [Figure 5] Figure 5 is a diagram illustrating the search space and SSSG switching according to the embodiment. [Figure 6] Figure 6 is a diagram showing the UE configuration according to the embodiment. [Figure 7] Figure 7 is a diagram showing the base station configuration according to this embodiment. [Figure 8] Figure 8 is a diagram showing a first example of cell group SSSG switching according to the first embodiment. [Figure 9] Figure 9 is a diagram showing a second example of cell group SSSG switching according to the first embodiment. [Figure 10] Figure 10 is a diagram showing an example configuration of the SSSG switching MAC CE according to the first embodiment. [Figure 11] Figure 11 is a diagram showing the operation according to the second embodiment. [Figure 12] Figure 12 is a diagram showing the operation according to the second embodiment, focusing on the downlink. [Figure 13] Figure 13 is a diagram showing the operation according to the second embodiment, focusing on the upward link. [Figure 14] Figure 14 is a diagram showing the operation according to the third embodiment. [Figure 15] Figure 15 is a diagram showing the operation according to the fourth embodiment. [Figure 16] Figure 16 is a diagram showing a first example of the configuration of information elements included in an RRC message according to the fourth embodiment. [Figure 17] Figure 17 is a diagram showing a first example of the configuration of information elements included in an RRC message according to the fourth embodiment. [Figure 18] Figure 18 is a diagram showing a second example of the configuration of information elements included in an RRC message according to the fourth embodiment. [Figure 19] Figure 19 is a diagram showing a second example of the configuration of information elements included in an RRC message according to the fourth embodiment. [Figure 20]FIG. 20 is a diagram showing the operation according to the fifth embodiment, [Figure 21] FIG. 21 is a diagram showing a specific example 1 of the operation using the 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.

Embodiments of the Invention

[0011] In the cell group SSSG switching, the cell group set in the user equipment is not limited to one, and a plurality of cell groups can be set in the user equipment. As a result of the inventors' detailed study, when a user equipment with a plurality of cell groups set therein receives an SSSG switching instruction from the base station, it is not clear which cell group's serving cell's SSSG should be switched simultaneously, and a problem has been found that the cell group SSSG switching cannot be appropriately performed.

[0012] Therefore, an object of the present disclosure is to enable appropriate cell group SSSG switching.

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

[0014] <First Embodiment>

[0015] (System Configuration) First, referring to FIG. 1, the configuration of the mobile communication system 1 according to the present embodiment will be described. The mobile communication system 1 is, for example, a system compliant with the technical specifications (Technical Specification: TS) of 3GPP. Hereinafter, as the mobile communication system 1, a fifth-generation system (5th Generation System: 5GS) of the 3GPP standard, that is, a mobile communication system based on NR (New Radio) will be described as an example.

[0016] The mobile communication system 1 includes a network 10 and user equipment (UE) 100 that communicates with the network 10. The network 10 includes a 5G radio access network, NG-RAN (Next Generation Radio Access Network) 20, and a 5G core network, 5GC (5G Core Network) 30.

[0017] UE100 is a device used by a user. UE100 is a mobile device such as a smartphone or other mobile phone terminal, tablet terminal, notebook PC, communication module, or communication card. UE100 may be a vehicle (e.g., car, train, etc.) or a device installed therein. UE100 may be a transport vehicle other than a vehicle (e.g., ship, airplane, etc.) or a device installed therein. UE100 may be a sensor or a device installed thereon. Note that UE100 may also be referred to by other names such as mobile station, mobile terminal, mobile device, mobile unit, subscriber station, subscriber terminal, subscriber device, subscriber unit, wireless station, wireless terminal, wireless device, wireless unit, remote station, remote terminal, remote device, or remote unit.

[0018] NG-RAN20 includes multiple base stations 200. Each base station 200 manages at least one cell. A cell constitutes the smallest unit of a communication area. A cell belongs to one frequency (carrier frequency) and consists of one component carrier. The term "cell" may represent a radio communication resource, or it may represent a communication target of the UE100. Each base station 200 can communicate wirelessly with UE100s located within its own cell. The base station 200 communicates with the UE100 using the RAN (Radio Access Network) protocol stack. The base station 200 provides NR user plane and control plane protocol terminations toward the UE100 and is connected to the 5GC30 via the NG interface. Such NR base stations 200 are sometimes referred to as gNodeB (gNB).

[0019] 5GC30 includes a core network device 300. The core network device 300 includes, for example, an AMF (Access and Mobility Management Function) and / or a UPF (User Plane Function). The AMF manages the mobility of the UE100. The UPF provides functions specifically for user plane processing. The AMF and UPF are connected to the base station 200 via an NG interface.

[0020] Next, with reference to Figure 2, an example of the protocol stack configuration according to this embodiment will be described.

[0021] The protocol for the radio section between UE100 and base station 200 has a physical (PHY) layer, a MAC (Medium Access Control) layer, an RLC (Radio Link Control) layer, a PDCP (Packet Data Convergence Protocol) layer, and an RRC layer.

[0022] The PHY layer performs coding and decoding, modulation and demodulation, antenna mapping and demapping, and resource mapping and demapping. Data and control information are transmitted between the PHY layer of UE100 and the PHY layer of base station 200 via a physical channel.

[0023] The MAC layer performs data priority control, retransmission processing using Hybrid ARQ (HARQ), and random access procedures. Data and control information are transmitted between the MAC layer of UE100 and the MAC layer of base station 200 via the transport channel. The MAC layer of base station 200 includes a scheduler. The scheduler determines the transport format for the uplink and downlink (transport block size, modulation and coding scheme (MCS)) and the resources to be allocated to UE100.

[0024] The RLC layer transmits data to the receiving RLC layer by utilizing the functions of the MAC layer and PHY layer. Data and control information are transmitted between the RLC layer of UE100 and the RLC layer of base station 200 via a logical channel.

[0025] The PDCP layer performs header compression / decompression, and encryption / decryption.

[0026] An SDAP (Service Data Adaptation Protocol) layer may be provided as a layer above the PDCP layer. The SDAP layer maps IP flows, which are the units in which the core network performs QoS control, to wireless bearers, which are the units in which the AS (Access Stratum) performs QoS control.

[0027] The RRC layer controls the logical channel, transport channel, and physical channel in response to the establishment, re-establishment, and release of the radio bearer. RRC signaling for various settings is transmitted between the RRC layer of UE100 and the RRC layer of base station 200. If there is an RRC connection between the RRC of UE100 and the RRC of base station 200, UE100 is in the RRC connected state. If there is no RRC connection between the RRC of UE100 and the RRC of base station 200, UE100 is in the RRC idle state. If the RRC connection between the RRC of UE100 and the RRC of base station 200 is suspended, UE100 is in the RRC inactive state.

[0028] The NAS layer, located above the RRC layer, handles session management and mobility management for the UE100. NAS signaling is transmitted between the UE100's NAS layer and the mobility management device 221's NAS layer. In addition to the wireless interface protocol, the UE100 also has an application layer and other components.

[0029] (Search space and SSSG switching) Next, the search space and SSSG switching according to this embodiment will be described with reference to Figures 3 to 5. In this embodiment, the search space may also be referred to as a search space set.

[0030] The base station 200 sets a search space on the UE 100 that corresponds to the candidate timing for the placement of the PDCCH. 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. The UE 100 then receives a physical downlink control channel (PDSCH) and / or transmits a physical uplink control channel (PUSCH) according to the resource allocation (scheduling) indicated by the DCI. For example, the UE 100 may monitor a set of candidate PDCCHs according to the corresponding search space. That is, the UE 100 may monitor a set of candidate PDCCHs in the control resource set (CORESET) of the downlink BWP (DL BWP: BandWidth Part) in the serving cell where PDCCH monitoring is set, according to the corresponding search space. Here, monitoring may mean decoding each of the candidate PDCCHs according to the DCI format being monitored.

[0031] As shown in Figure 3, in step S1, the base station 200 sends an RRC message to the UE 100 containing configuration information regarding the PDCCH (PDCCH configuration information) and performs various settings regarding the PDCCH on the UE 100. This RRC message is a UE-specific RRC message and may be, for example, an RRC Reconfiguration message. Here, the configuration information regarding the PDCCH includes the search space period (also referred to as the PDCCH monitoring period), the search space offset (also referred to as the PDCCH monitoring offset), the search space duration (e.g., the number of consecutive slots), the symbol for PDCCH monitoring, the aggregation level, the type of search space, and the DCI format. Here, the type of search space may include a UE-specific search space (USS) and / or a common search space (CSS).

[0032] DCI formats include scheduled DCI formats used for scheduling PDSCH or PUSCH, and non-scheduled DCI formats not used for such scheduling. DCI transmitted in scheduled DCI format is called scheduled DCI, and DCI transmitted in non-scheduled DCI format is called non-scheduled DCI.

[0033] 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.

[0034] In step S2, UE100 starts monitoring PDCCH in the search space configured 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 each configured in UE100. UE100 monitors PDCCH (DCI) based on these settings. For example, base station 200 may configure UE100 to monitor DCI format 1_0 and DCI format 0_0 in a certain search space. Alternatively, base station 200 may configure UE100 to monitor DCI format 1_1 and DCI format 0_1 ​​in a certain search space. Furthermore, base station 200 may configure UE100 to monitor DCI format 1_2 and DCI format 0_2 in a certain search space. In other words, for example, when a CSS is set for a certain search space, the base station 200 may be configured to monitor candidates for PDCCH for DCI format 1_0 and DCI format 0_0. Also, when a CSS is set for a certain search space, the base station 200 may be configured to monitor candidates for PDCCH for DCI format 2_0. Also, when a USS is set for a certain search space, the base station 200 may be configured to monitor candidates for PDCCH for DCI format 1_0 and DCI format 0_0, or DCI format 1_1 and DCI format 0_1. Also, when a USS is set for a certain search space, the base station 200 may be configured to monitor candidates for PDCCH for DCI format 1_0 and DCI format 0_0, or DCI format 1_2 and DCI format 0_2.

[0035] In step S3, UE100 receives and detects the DCI addressed to its own UE from base station 200. For example, UE100 performs blind decoding of the PDCCH using the C-RNTI (Cell-Radio Network Temporary Identifier), MCS-C-RNTI (Modulation and Coding Scheme-C-RNTI), or CS-RNTI (Configured Scheduling-RNTI) assigned to UE100 by base station 200, and acquires the DCI that was successfully decoded as the DCI addressed to its own UE. Here, the DCI transmitted from base station 200 has CRC parity bits added that have been scrambled by the C-RNTI, MCS-C-RNTI, or CS-RNTI.

[0036] If DCI indicates a PDSCH scheduling, in step S4, UE100 receives downlink data from base station 200 on the scheduled PDSCH.

[0037] If DCI indicates a PUSCH scheduling, in step S5, UE100 transmits uplink data to base station 200 on the scheduled PUSCH.

[0038] Thus, UE100 monitors PDCCH in the search space configured by base station 200. In this embodiment, base station 200 switches the search space settings applied by UE100 in order to reduce the power consumption of UE100 when it is in the RRC connected state. Here, each search space (each search space setting) may be associated with one CORESET. Also, the search space settings may be set for each of one or more DL BWPs.

[0039] For example, as shown in Figure 4, the base station 200 sets SSSG#0, which has a normal search space period, and SSSG#1, which is for power saving and has a longer search space period than the normal search space period, on the UE100. Here, SSSG is a set (group) of search spaces, and may also be called a search space set (SSS) or search space group (SSG). For example, SSSG may be a set (group) of search spaces to which the same settings are applied. Note that Figure 4 shows an example in which the base station 200 sets two SSSGs, SSSG#0 and SSSG#1, on the UE100, but three or more SSSGs may be set on the UE100 for each of one or more BWPs (e.g., DL BWP). Also, although an example is shown in which an SSSG with a long search space period is set as SSSG#1 for power saving, an SSSG that does not have a search space may be set as SSSG#1 for power saving. In this case, UE100 can further reduce power consumption by omitting (skipping) PDCCH monitoring during the SSSG#1 period. Here, "#0" in SSSG#0 and "#1" in SSSG#1 represent the index (also called the 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 the index. For example, base station 200 may set a set (group) of search spaces for UE100 by setting an index associated with the one or more search space sets. Here, in this embodiment, the name SSSG is merely an example, and the name does not matter as long as it is a set (group) of search spaces to which one or more search space sets are associated. Also, a set (group) of search spaces does not have to have a search space (no search space is set). For example, if no search space exists, UE100 does not have to perform PDCCH monitoring (monitoring of PDCCH candidates).In other words, if no search space exists, UE100 may skip monitoring the PDCCH.

[0040] Base station 200 instructs UE100 to switch the SSSG. Base station 200 instructs the switch from SSSG#0 to SSSG#1 using an unscheduled DCI (e.g., DCI format 2_0). However, scheduled DCI may also be used as the SSSG switch instruction, not just unscheduled DCI. UE100 begins monitoring the PDCCH in SSSG#1 with a symbol after a switch delay from the last PDCCH symbol in SSSG#0. This switch delay is set by base station 200 to UE100 using upper-layer signaling (i.e., RRC messages).

[0041] Switching from SSSG#1 to SSSG#0 can be initiated by base station 200 via DCI, similar to switching from SSSG#0 to SSSG#1, or UE100 can switch from SSSG#1 to SSSG#0 using a timer. Such a timer (switching timer) is set from base station 200 to UE100 via upper-layer signaling (i.e., RRC message). Upon detection of the DCI instruction to switch to SSSG#1, UE100 begins monitoring the PDCCH in SSSG#1 and starts the timer by setting its value to the value set by the upper layer. UE100 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.

[0042] While this section describes SSSG switching within a single cell, as shown in Figure 5, multiple serving cells can be configured on UE100 through carrier aggregation. Figure 5 shows an example where Serving Cell #1, corresponding to Component Carrier #1, and Serving Cell #2, corresponding to Component Carrier #2, are configured on UE100. In such cases, it is more efficient to perform SSSG switching on a cell group basis, rather than individually for each cell. For example, Base Station 200 sends an SSSG switching DCI to UE100 in Serving Cell #1, and UE100 simultaneously switches the SSSGs of Serving Cells #1 and #2 from SSSG#0 to SSSG#1. Such cell groups are configured from Base Station 200 to UE100 via upper-layer signaling (i.e., RRC messages). For example, in carrier aggregation, Base Station 200 may configure one primary cell and one or more secondary cells. That is, a serving cell includes both a primary and a secondary cell. Furthermore, one or more Bandwidth Parts (BWPs) may be configured in each of the one or more serving cells configured in the UE100. For example, up to four BWPs may be configured in one serving cell. Here, a BWP 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 in one serving cell. In addition, one or more Control Resource Sets (CORESETs) may be configured in one DL BWP. Here, a CORESET may include resources in the time domain and / or frequency domain configured for monitoring the PDCCH. For example, a CORESET may consist of a predetermined number of symbols (e.g., 1 to 3 symbols) and a predetermined number of resource blocks (RBs) (e.g., 6n (n≧1)RBs).

[0043] The following primarily describes the case where carrier aggregation is configured on UE100 and SSSG switching is performed on a cell group basis (cell group SSSG switching). In such cell group SSSG switching, the cell group configured on UE100 is not limited to one; multiple cell groups can be configured on UE100. 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, we assume that a serving cell can belong to only one cell group. That is, a serving cell may be configured by the base station 200 to belong to only one cell group.

[0044] When multiple cell groups are configured on the UE100, the UE100, upon receiving an SSSG switching instruction from the base station 200, does not know which cell group's serving cells should be switched simultaneously. Therefore, when multiple cell groups are configured on the UE100, there is a problem in that the UE100 cannot properly perform cell group SSSG switching. In this embodiment, the PDCCH monitoring based on the SSSG switching described above is also referred to as the PDCCH monitoring procedure.

[0045] (User device configuration) Next, the configuration of the UE100 according to this embodiment will be described with reference to Figure 6. The UE100 includes a communication unit 110 and a control unit 120.

[0046] 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 transmitter may 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 signals. The RF circuit performs analog processing of the signals transmitted and received via the antenna. The RF circuit may include a high-frequency filter, an amplifier, a modulator, and a low-pass filter, etc.

[0047] The control unit 120 performs various controls on the UE 100. The control unit 120 controls communication with the base station 200 via the communication unit 110. The operations of the UE 100 described above and below may be operations controlled by the control unit 120. The control unit 120 may include at least one program-executable processor and memory for storing the program. The processor may execute the program to perform the operations 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 RF circuit. This digital processing includes processing of the RAN protocol stack. The memory stores the program executed by the processor, parameters related to the program, and data related to the program. The memory may include at least one of ROM (Read Only Memory), EPROM (Erasable Programmable Read Only Memory), EEPROM (Electrically Erasable Programmable Read Only Memory), RAM (Random Access Memory), and flash memory. All or part of the memory may be contained within the processor.

[0048] In the UE100 configured in this way, multiple cell groups for cell group SSSG switching are set in the UE100. The communication unit 110 receives an SSSG switching instruction from the base station 200 that instructs the switching of the SSSG in a serving cell belonging to one of the multiple cell groups. For example, the SSSG switching instruction is an SSSG switching DCI that instructs the switching of the SSSG. The control unit 120 identifies the cell group to which the serving cell to which the SSSG switching instruction was detected belongs from among the multiple cell groups as the target cell group for SSSG switching. Then, in response to the receipt of 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, the control unit 120 utilizes the property that a single serving cell can belong to only one cell group to identify the cell group to which the serving cell to which the SSSG switching instruction was detected belongs as the target cell group for SSSG switching. As a result, even if multiple cell groups are set in the UE100, the UE100 can appropriately perform cell group SSSG switching.

[0049] Alternatively, the communication unit 110 may receive an SSSG switching instruction from the base station 200 that includes a cell group identifier for the cell group to be switched on the SSSG, or the cell identifiers of the cells included in the target cell group. Such an SSSG switching instruction may also be an SSSG switching medium access control (MAC) control element (CE). The control unit 120 identifies the target cell group to be switched on the SSSG from among multiple cell groups based on the cell identifier or cell group identifier included in the SSSG switching instruction. Then, in response to the receipt of 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, because the cell group identifier for the cell group to be switched on the SSSG, or the cell identifiers of the cells 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 multiple cell groups are set on the UE 100.

[0050] (Base station configuration) Next, with reference to Figure 7, the configuration of the base station 200 according to this embodiment will be described. The base station 200 includes a communication unit 210, a network interface 220, and a control unit 230.

[0051] The communication unit 210, for example, receives a radio signal from the UE 100 and transmits a radio signal to the UE 100. The communication unit 210 may include one or more receivers for receiving radio signals and one or more transmitters for transmitting radio signals.

[0052] The network interface 220 transmits and receives signals to and from the network. For example, the network interface 220 receives signals from an adjacent base station connected via the Xn interface, which is an inter-base station interface, and transmits signals to the adjacent base station. The network interface 220 also receives signals from a core network device 300 connected via the NG interface, and transmits signals to the core network device 300.

[0053] The control unit 230 performs various controls on 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 nodes (e.g., adjacent base stations, core network equipment 300) via the network interface 220. The operations of the base station 200 described above and below may be operations controlled by the control unit 230. The control unit 230 may include at least one processor capable of executing programs and a memory for storing programs. The processor may execute programs to perform the operations 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 RF circuit. This digital processing includes processing of the RAN protocol stack. The memory stores programs executed by the processor, parameters related to the programs, and data related to the programs. All or part of the memory may be contained within the processor.

[0054] In the base station 200 configured in this way, the communication unit 210 transmits an SSSG switching instruction to the UE 100 instructing the switching of the SSSG in a serving cell belonging to one of the multiple cell groups set in the UE 100. For example, the SSSG switching instruction is an SSSG switching DCI that instructs the switching of the SSSG. Specifically, the communication unit 110 transmits the SSSG switching instruction to the UE 100 in a serving cell belonging to the cell group to be switched. This makes it possible to implicitly indicate the target cell group by which the SSSG switching instruction is transmitted, without including the cell group identifier of the cell group to be switched or the cell identifier of a cell belonging to the target cell group in the SSSG switching instruction.

[0055] Alternatively, the communication unit 210 may send an SSSG switching instruction to the UE 100 that includes the cell group identifier of the SSSG switching target cell group or the cell identifier of a cell included in the target cell group. Such an SSSG switching instruction may also be an SSSG switching MAC CE. In this way, by including the cell group identifier of the SSSG switching target cell group or the cell identifier of a cell included in the target cell group in the SSSG switching instruction, the SSSG switching target cell group can be explicitly indicated. For this reason, the communication unit 210 may also send 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 sent to the UE 100 in the primary cell (PCell) among a group of serving cells.

[0056] (Example of the first operation of switching cell groups SSSG) Next, with reference to Figure 8, a first example of cell group SSSG switching according to this embodiment will be described. The first example of operation is one in which the base station 200 implicitly indicates the cell group to be switched to UE 100. It is assumed that UE 100 is in an RRC connected state.

[0057] In step S11, the base station 200 (communication unit 210) sends an RRC message to the UE 100 that includes cell group configuration information regarding the cell group configuration, along with the PDCCH configuration information described above. 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 configuration information may be configured as a cell list for each cell group. Each cell list may include the 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 configuration information (including SSSG configuration information). That is, multiple SSSGs may be individually configured for each cell group. Here, a default SSSG may be specified for each cell group. Details of the default SSSG will be described in the fifth embodiment below.

[0058] In step S12, the UE100 (control unit 120) stores and applies the configuration information contained in the RRC message received in step S11, and controls communication with the base station 200 based on this configuration information. Here, the cell group set in the UE100 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 consists of serving cells #13, #14, #15, and #16.

[0059] In step S13, the base station 200 (communication unit 210) determines the cell group to be switched to SSSG and transmits the SSSG switching DCI to the UE 100 in the serving cell belonging to that 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.

[0060] The SSSG switching DCI may be the scheduling DCI described above. This allows the UE100 to be notified of the scheduling of the PDSCH or PUSCH, and the UE100 to be instructed to switch over the SSSG, thereby enabling efficient SSSG switching.

[0061] The SSSG switching DCI may be the non-scheduled DCI described above. This allows the UE100 to be instructed to switch SSSGs even when there is no data to send or receive. The non-scheduled DCI may be a DCI that can be sent simultaneously to multiple UE100s. For example, the non-scheduled DCI may be sent by applying a common RNTI (Radio Network Temporary Identifier) ​​to multiple UE100s.

[0062] In step S14, the UE100 (control unit 120) identifies the cell group to which the serving cell for which the SSSG switching DCI was detected belongs as the SSSG switching target cell group. This allows the SSSG switching target cell group to be appropriately identified even if an identifier indicating the SSSG switching target cell group is not included in the SSSG switching DCI.

[0063] For example, if the SSSG switching DCI is received in serving cell #1, the UE100 (control unit 120) identifies cell group #1, to which serving cell #1 belongs, as the cell group subject to SSSG switching. Alternatively, if the SSSG switching DCI is received in serving cell #10, the UE100 (control unit 120) identifies cell group #3, to which serving cell #10 belongs, as the cell group subject to SSSG switching.

[0064] In step S15, the UE100 (control unit 120) simultaneously switches the SSSGs for all serving cells in the SSSG switching target cell group identified in step S14. For example, the UE100 (control unit 120) switches the SSSGs of all serving cells in the SSSG switching target cell group from the default SSSG (e.g., SSSG#0) to a power-saving SSSG (e.g., SSSG#1) all at once. In other words, the UE100 may determine the cell group to which the PDCCH monitoring procedure is applied based on the serving cell that detected the SSSG switching DCI. That is, if the UE100 detects an SSSG switching DCI in a serving cell, it may apply the PDCCH monitoring procedure to the cell group to which that serving cell belongs. In other words, UE100 may receive cell group configuration information used to configure one or more cell groups, and if it detects an SSSG switch DCI in a serving cell associated with (belonging to) a certain cell group, it may apply the PDCCH monitoring procedure to a certain cell group associated with (belonging to) the serving cell that detected the SSSG switch DCI. In other words, UE100 may receive cell group configuration information used to configure one or more cell groups, and if it detects an SSSG switch DCI in a serving cell associated with (belonging to) a certain cell group, it may apply the PDCCH monitoring procedure to the cell group that detected the SSSG switch DCI. Here, UE100 may apply the PDCCH monitoring procedure to all serving cells in that cell group.

[0065] (Second example of cell group SSSG switching operation) Next, referring to Figure 9, a second example of cell group SSSG switching according to this embodiment will be explained, mainly focusing on the differences from the first example of operation described above. The second example of operation is one in which the base station 200 explicitly indicates the cell group to be switched to UE 100. It is assumed that UE 100 is in an RRC connected state.

[0066] The operations in steps S21 and S22 are the same as those in steps S11 and S12 described above.

[0067] In step S23, the base station 200 (communication unit 210) determines the cell group to be switched to by SSSG and transmits an SSSG switching MAC CE to the UE 100 that includes the cell group identifier of the cell group to be switched to by SSSG or the cell identifier of the serving cell belonging to the cell group to be switched to by SSSG. The base station 200 (communication unit 210) may also transmit an SSSG switching MAC CE to the UE 100 for a serving cell that does not belong to the cell group to be switched to by SSSG. The UE 100 (communication unit 110) receives the SSSG switching MAC CE.

[0068] In step S24, the UE100 (control unit 120) identifies the cell group to be switched for the SSSG from among multiple cell groups based on the cell identifier or cell group identifier included in the SSSG switching MAC CE. If the SSSG switching MAC CE includes a cell identifier, the UE100 (control unit 120) identifies the cell group to which the serving cell indicated by the cell identifier included in the SSSG switching MAC CE belongs as the target cell group.

[0069] For example, if the cell identifier included in the SSSG switching MAC CE indicates serving cell #1, the UE100 (control unit 120) identifies cell group #1, to which serving cell #1 belongs, as the cell group targeted for SSSG switching. Alternatively, if the cell identifier included in the SSSG switching MAC CE indicates serving cell #10, the UE100 (control unit 120) identifies cell group #3, to which serving cell #10 belongs, as the cell group targeted for SSSG switching.

[0070] In step S25, the UE100 (control unit 120) simultaneously switches the SSSGs for all serving cells in the cell group targeted for SSSG switching, as identified in step S24. For example, the UE100 (control unit 120) switches all SSSGs for all serving cells in the cell group targeted for SSSG switching from the default SSSG (e.g., SSSG#0) to a power-saving SSSG (e.g., SSSG#1) at once.

[0071] The SSSG switching MAC CE may further include an SSSG identifier indicating the SSSG to be switched to. In step S25, the UE100 (control unit 120) may simultaneously switch all serving cells in the SSSG switching target cell group identified in step S24 to the SSSG to be switched to indicated by the SSSG identifier.

[0072] The SSSG switching MAC CE may further include a BWP identifier indicating the bandwidth portion (BWP) to which the SSSG switching target cell group belongs. The UE100 (control unit 120) may identify the BWP of the SSSG switching target cell group identified in step S24 based on the BWP identifier.

[0073] Next, with reference to Figure 10, an example configuration of the SSSG switching MAC CE according to this embodiment will be described. The SSSG switching MAC CE may also be referred to as the "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 consists of the following fields and has a fixed size.

[0074] - Serving Cell ID (Cell Identifier): This field indicates the ID of the serving cell to which MAC CE applies, and the field length is, for example, 5 bits. If the serving cell indicated by the Serving Cell ID is set as part of a cell group, this MAC CE applies to all serving cells in the cell group to which that serving cell belongs.

[0075] -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.

[0076] - Search Space Set Group ID (SSSG Identifier): This field indicates the Search Space Set Group (SSSG) that the UE monitors for PDCCH, i.e., the SSSG to which it will switch. The field length is, for example, 8 bits.

[0077] -R: This is a reserved bit and is set to "0".

[0078] Furthermore, in this second operational example, at least a portion of the information contained in the SSSG switching MAC CE may be included in the SSSG switching DCI in the first operational example described above.

[0079] (Example of change) In the first example of cell group SSSG switching described above, an example was explained in which the base station 200 implicitly indicates the cell group to be switched to the UE 100 using the SSSG switching DCI. However, the base station 200 may implicitly indicate the cell group to be switched to the UE 100 using the SSSG switching MAC CE instead of the SSSG switching DCI. That is, the SSSG switching DCI in the first example of cell group SSSG switching described above may be read as the SSSG switching MAC CE. In such a modified example, the UE 100 (control unit 120) may identify the cell group to which the serving cell detected by the SSSG switching MAC CE belongs as the target cell group. In such a modified example, the SSSG switching MAC CE may also include an SSSG identifier indicating the SSSG to be switched to. The UE 100 (control unit 120) may simultaneously switch all serving cells in the cell group to the SSSG to be switched to indicated by the SSSG identifier. Furthermore, in such an example of modification, the SSSG switching MAC CE may also include a BWP identifier indicating the bandwidth portion (BWP) to which the target cell group belongs.

[0080] In the second example of cell group SSSG switching described above, an example was given in which the base station 200 explicitly indicates the cell group to be switched to UE100 using the SSSG switching MAC CE. However, the base station 200 may also explicitly indicate the cell group to be switched to UE100 using the SSSG switching DCI instead of the SSSG switching MAC CE. That is, the cell group identifier of the cell group to be switched to SSSG or the cell identifier of the serving cell belonging to the cell group to be switched to SSSG may be included in the SSSG switching DCI. In such an example of modification, the SSSG switching DCI may be a scheduling DCI. Alternatively, the SSSG switching DCI may be a non-scheduling DCI.

[0081] <Second Embodiment> Next, a second embodiment will be described with reference to Figure 11. In the second embodiment, it is assumed that the SSSG switching DCI is used as the SSSG switching instruction, and in particular, that the scheduling DCI is mainly used as the switching instruction DCI.

[0082] When using a scheduling DCI as the switching instruction DCI, HARQ processing, which is data retransmission processing by HARQ, may be required. Therefore, if the UE100 immediately starts switching to the power saving state, there is a concern that HARQ processing may not be performed properly. For this reason, the UE100 (control unit 120) suspends the start of the switching instructed by the switching instruction DCI while the retransmission-related timer associated with the HARQ processing for data scheduled by the switching instruction DCI (scheduling DCI) is operating.

[0083] As shown in Figure 11, in step S51, the UE 100 (communication unit 110) receives a scheduling DCI as a switching instruction DCI from the base station 200 on the PDCCH. Such a scheduling DCI may include an information field indicating the PDSCH resource or PUSCH resource assigned to the UE 100, as well as an information field indicating the SSSG to be switched to.

[0084] In step S52, the UE100 (communication unit 110) receives or transmits data scheduled by the scheduling DCI. For example, the UE100 (communication unit 110) receives downlink data using the allocated PDSCH resource or transmits uplink data using the allocated PUSCH resource. When the UE100 (communication unit 110) receives downlink data, the UE100 (control unit 120) attempts to decode the received downlink data and provides HARQ feedback, i.e., ACK or NACK, to the base station 200 indicating whether the data decoding was successful. When the UE100 (communication unit 110) transmits uplink data, the UE100 (control unit 120) receives HARQ feedback, i.e., ACK or NACK, from the base station 200 indicating whether the base station 200 succeeded in decoding the uplink data. The UE100 (control unit 120) manages the HARQ processing for each piece of data to be received or transmitted using a timer, and continues the HARQ processing until the data decoding of the data is completed.

[0085] In step S53, the UE100 (control unit 120) determines whether any of the following retransmission-related timers used for HARQ processing are currently operating.

[0086] • Downlink HARQ RTT timer (drx-HARQ-RTT(Round Trip Time)-TimerDL) This timer is used for HARQ processing of downlink data and defines the minimum period until downlink allocation for HARQ retransmission expected by the MAC entity of UE100. UE100 (control unit 120) activates the downlink HARQ RTT timer in response to the transmission of HARQ feedback for downlink data. UE100 (control unit 120) does not need to monitor PDCCH while the downlink HARQ RTT timer is operating.

[0087] • Downlink retransmission timer (drx-RetransmissionTimerDL) This timer is used for HARQ processing of downlink data and defines the maximum period until a downlink retransmission is received. If the downlink data has not been successfully decoded when the downlink HARQ RTT timer expires, the UE100 (control unit 120) starts the downlink retransmission timer. While the downlink retransmission timer is operating, the UE100 (control unit 120) monitors the PDCCH and waits for the retransmission data.

[0088] • Uplink HARQ RTT Timer (drx-HARQ-RTT-TimerUL) This timer is used for HARQ processing of uplink data and defines the minimum period until the MAC entity of UE100 receives a HARQ retransmission grant. UE100 (control unit 120) activates the downlink retransmission timer in response to the transmission of uplink data. UE100 (control unit 120) does not need to monitor PDCCH while the uplink HARQ RTT timer is operating.

[0089] • Uplink retransmission timer (drx-RetransmissionTimerUL) This timer is used for HARQ processing of uplink data and defines the maximum period until uplink retransmission permission is received. UE100 (control unit 120) starts the uplink retransmission timer when the uplink HARQ RTT timer expires. UE100 (control unit 120) monitors the PDCCH while the uplink retransmission timer is operating.

[0090] If any of these retransmission-related timers are operating (step S53: YES), in step S54, the UE100 (control unit 120) postpones the start of the switch instructed by the switch instruction DCI received in step S51.

[0091] In contrast, if none of the retransmission-related timers are operating (step S53: NO), in step S55, the UE100 (control unit 120) starts or executes the switching instructed by the switching instruction DCI received in step S51. For example, the UE100 (control unit 120) may execute the SSSG switching from the first slot after the retransmission-related timers have expired.

[0092] Thus, in the second embodiment, the period during which the retransmission-related timer is operating constitutes at least a portion of the switch delay time of the switch instructed by the switching instruction DCI. Furthermore, if the switch delay time is set by upper-layer signaling (RRC message), the UE100 (control unit 120) may, even after the switch delay time set by the upper-layer signaling has elapsed, postpone the start of the switch instructed by the switching instruction DCI during the period during which the retransmission-related timer is operating.

[0093] Furthermore, the switching delay time may include the period during which the following retransmission-related timers are operating.

[0094] • The duration during which drx-HARQ-RTT-TimerDL, which was launched for the corresponding HARQ process with the first symbol after DL HARQ feedback transmission has finished, is running: • The duration during which drx-RetransmissionTimerDL is running if the corresponding HARQ process for the first symbol after drx-HARQ-RTT-TimerDL has expired fails to decrypt successfully: • The duration during which drx-HARQ-RTT-TimerUL, which was started for the corresponding HARQ process at the first symbol after the completion of the first transmission (within the bundle) of the corresponding PUSCH transmission, is running: The period during which drx-RetransmissionTimerUL, initiated for the corresponding HARQ process with the first symbol after the expiration of drx-HARQ-RTT-TimerUL, is running.

[0095] Furthermore, if UE100 (control unit 120) is executing multiple HARQ processes, the start of the switchover instructed by the switchover instruction DCI may be postponed if at least one of the retransmission-related timers for those multiple HARQ processes is operating. For example, UE100 may perform an SSSG switchover based on the expiration of drx-RetransmissionTimerDL corresponding to all HARQ processes and / or the expiration of drx-RetransmissionTimerUL corresponding to all HARQ processes (for example, from the first slot after expiration).

[0096] Furthermore, UE100 (control unit 120) may perform the above operations when it receives a configured DL assignment (i.e., a downlink DCI format with a CRC scrambled by CS-RNTI) and / or a configured UL grant (i.e., an uplink DCI format with a CRC scrambled by CS-RNTI).

[0097] Furthermore, while this embodiment utilizes various existing timers for DRX, it is not limited to these, and timers used for HARQ processing and retransmission processing of PDCCH skipping and / or SSSG switching set in the upper layer may also be used. Examples of such timers include DCIbasedPowerSaving-HARQ-RTT-TimerDL, DCIbasedPowerSaving-HARQ-RTT-TimerUL, DCIbasedPowerSaving-RetransmissionTimerDL, and DCIbasedPowerSaving-RetransmissionTimerUL. 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.

[0098] Next, referring to Figure 12, the operation according to the second embodiment will be explained, focusing on the downlink.

[0099] In step S101, the UE100 (communication unit 110) receives the downlink scheduling DCI as a switching instruction DCI on the PDCCH. The downlink scheduling DCI is a DCI that allocates radio resources (i.e., PDSCH resources) for downlink data. The UE100 (communication unit 110) receives downlink data from the base station 200 using the PDSCH resources allocated by the downlink scheduling DCI. The UE100 (control unit 120) attempts to decode the received downlink data.

[0100] In step S102, the UE100 (communication unit 110) sends HARQ feedback to the base station 200 indicating whether or not it succeeded in decoding the downlink data received in step S102.

[0101] In step S103, the UE100 (control unit 120) starts the downlink HARQ RTT timer in response to the transmission of HARQ feedback corresponding to the downlink data. While the downlink HARQ RTT timer is operating, the UE100 (control unit 120) suspends the start of the switchover instructed by the switchover instruction DCI.

[0102] If the downlink HARQ RTT timer expires (step S104: YES), in step S105, the UE100 (control unit 120) determines whether or not the downlink data has been successfully decoded. If the downlink data has been successfully decoded (step S105: YES), in step S106, the UE100 (control unit 120) starts the switching instructed by the switching instruction DCI.

[0103] On the other hand, if the decoding of the downlink data is unsuccessful (step S105: NO), in step S107, the UE100 (control unit 120) starts the downlink retransmission timer in response to the expiration of the downlink HARQ RTT timer. While the downlink retransmission timer is operating, the UE100 (control unit 120) monitors PDCCH and suspends the start of the switchover indicated by the switchover instruction DCI.

[0104] If the downlink retransmission timer expires (step S108: YES), in step S106, the UE100 (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 UE100 (control unit 120) may stop the downlink retransmission timer and return to step S102.

[0105] Next, referring to Figure 13, the operation according to the second embodiment will be explained, focusing on the uplink.

[0106] In step S201, UE100 (communication unit 110) receives the uplink scheduling DCI as a switching instruction DCI on the PDCCH. The uplink scheduling DCI is a DCI that allocates radio resources (i.e., PUSCH resources) for uplink data.

[0107] In step S202, UE100 (communication unit 110) transmits uplink data to base station 200 using the PUSCH resources allocated by the uplink scheduling DCI.

[0108] In step S203, the UE100 (control unit 120) starts the uplink HARQ RTT timer in response to the transmission of uplink data. While the uplink HARQ RTT timer is operating, the UE100 (control unit 120) suspends the start of the switchover instructed by the switchover instruction DCI.

[0109] If the uplink HARQ RTT timer expires (step S204: YES), in step S205, the UE100 (control unit 120) starts the uplink retransmission timer. While the uplink retransmission timer is operating, the UE100 (control unit 120) monitors PDCCH and suspends the start of the switchover indicated by the switchover instruction DCI.

[0110] If the uplink retransmission timer expires (step S206: YES), in step S207, the UE100 (control unit 120) starts the switching instructed by the switching instruction DCI.

[0111] Thus, according to the second embodiment, when UE100 receives a scheduling DCI as a switching instruction, it suspends the start of the switching while the retransmission-related timer associated with the HARQ processing for the data scheduled by the scheduling DCI is operating. This makes it possible to perform HARQ processing appropriately even when a scheduling DCI is used as a switching instruction.

[0112] In the second embodiment, CSI reporting to the base station 200 may be considered. For example, if UE100, which has received a switching instruction DCI, is instructed by the scheduling DCI to make an aperiodic CSI report to the base station 200, UE100 (control unit 120) may transmit the CSI report to the base station 200 in the scheduled PUSCH and may postpone the start of the switching instructed by the switching instruction DCI until this CSI report is made. Then, in response to transmitting the CSI report in the scheduled PUSCH, UE100 (control unit 120) may start the switching instructed by the switching instruction DCI. Details of the CSI report will be explained in the third embodiment described later.

[0113] <Third Embodiment> Next, a third embodiment will be described with reference to Figure 14.

[0114] Since the period when the UE100 is in power-saving mode is considered to be a period during which data transmission and reception are temporarily suspended, it is desirable to reduce the power consumption required for SRS transmission, CSI measurement, and CSI reporting.

[0115] Here, SRS transmission refers to the operation in which the base station 200 transmits an SRS, which is an uplink physical signal used for channel estimation to estimate the channel state of the uplink, to the base station 200. The UE100 performs SRS transmission according to the settings from the base station 200. SRS reporting is an operation for uplink link adaptation. Link adaptation is the process of adapting the modulation and coding scheme (MCS) applied to data transmission to the channel state. During periods when the UE100 is in power-saving mode, the need for uplink link adaptation is low, so SRS transmission is suppressed.

[0116] CSI measurement refers to the operation of measuring a reference signal used to estimate the channel state of the downlink, and UE100 performs CSI measurement according to the settings from base station 200. For example, UE100 performs CSI measurement based on at least one of the channel state information reference signal (CSI-RS) and the synchronization signal / physical broadcast channel (SS / PBCH) block transmitted by base station 200. CSI reporting refers to the operation of transmitting a CSI report to base station 200 that shows the channel state estimated according to the results of the CSI measurement, and UE100 performs CSI reporting according to the settings from base station 200. For example, the channel status includes one or more of the following: channel quality indicator (CQI), rank indicator (RI), precoding matrix indicator (PMI), SS / PBCH block resource indicator (SSBRI), CSI-RS resource indicator (CRI), layer indicator (LI), and Layer 1 reference signal received power (L1-RSRP). CSI reporting may be performed on PUCCH or PUSCH. CSI measurement and CSI reporting are operations for downlink link adaptation. During periods when UE100 is in power-saving mode, the need for downlink link adaptation is low, so CSI measurement and CSI reporting are suppressed.

[0117] As shown in Figure 14, in step S301, the UE 100 (control unit 120) performs predetermined control to control at least one of the following operations: SRS transmission to base station 200, CSI measurement, and CSI reporting to base station 200, in a first state where PDCCH is monitored in the search space. The UE 100 (control unit 120) may periodically perform at least one of the following operations: SRS transmission, CSI measurement, and CSI reporting, in the first state. For example, the UE 100 (control unit 120) may perform at least one of the following operations in the first state: periodic SRS transmission and periodic CSI reporting. Periodic SRS transmission may include semi-persistent SRS transmission. Periodic CSI reporting may include semi-persistent CSI reporting performed on PUCCH or PUSCH.

[0118] In step S302, the UE100 (communication unit 110) receives a switching instruction DCI on the PDCCH that instructs switching to a second state (e.g., a power-saving state) in which the search space settings are different from the first state. In the third embodiment, the switching instruction DCI is not limited to the scheduling DCI described above, but may also be a non-scheduling DCI. The switching instruction DCI may include an information field indicating the SSSG to be switched to.

[0119] In step S303, the UE100 (control unit 120) performs a control different from the predetermined control for at least one of the operations among SRS transmission, CSI measurement, and CSI reporting, in response to receiving the switching instruction DCI.

[0120] For example, UE100 (control unit 120) stops at least one of the following operations: SRS transmission, CSI measurement, and CSI reporting, during the switch delay from the first state to the second state. UE100 (control unit 120) may also stop periodic SRS transmission and periodic CSI reporting during the switch delay. Such control is defined as: "During the switch delay, which is represented by the Pswitch symbol, the UE..." • Periodic SRS transmission and semi-persistent SRS transmission • Semi-persistent CSI configured for PUSCH • Periodic CSI reporting, which is L1-RSRP performed on PUCCH, when ps-TransmitPeriodicL1-RSRP is not configured with the value true. This can also be expressed as: "If ps-TransmitOtherPeriodicCSI is not configured with the value true, it is not expected that periodic CSI reporting other than L1-RSRP will be performed on PUCCH."

[0121] The first state is a state in which a PDCCH provided at a predetermined period is monitored in the 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 UE100 (control unit 120) does not have to perform at least one of the operations of SRS transmission, CSI measurement, and CSI reporting.

[0122] The first state is a state in which a PDCCH provided at a predetermined period is monitored in the 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 achieved by SSSG switching. In the second state, the UE100 (control unit 120) may perform at least one of the following operations only within the time interval of the search space: SRS transmission, CSI measurement, and CSI reporting.

[0123] For example, in the second state, the UE 100 (control unit 120) may perform aperiodic SRS transmission only in the monitoring slot, which is a time interval of the search space. Such control may also be expressed as: "If the UE, which has been set to switch SSSG via upper-layer signaling, does not expect SRS resources to be available outside the corresponding monitoring slot to trigger aperiodic SRS transmission when the period of the search space is longer than a predetermined value (e.g., 80 milliseconds)."

[0124] Furthermore, in the second state, the UE100 (control unit 120) may perform CSI measurements only in monitoring slots that correspond to the time interval of the search space. Such control may also be expressed as, "A UE with SSSG switching set by upper-layer signaling will exclude slots other than the monitoring slot corresponding to the search space for the most recent CSI measurement opportunity for CSI reporting." Alternatively, such control may be expressed as, "A UE with SSSG switching set by upper-layer signaling will not expect CSI-RS resources to be available in slots other than the corresponding monitoring slot if the period of the search space is longer than a predetermined value (e.g., 80 milliseconds)."

[0125] Thus, according to the third embodiment, upon receiving the switching instruction DCI, the UE100 performs a different control for at least one of the operations among SRS transmission, CSI measurement, and CSI reporting than the control performed before receiving the switching instruction DCI. This makes it possible to apply control optimized for power saving conditions, such as control optimized for an extended search space period, to SRS transmission, CSI measurement, and CSI reporting, thereby reducing the power consumption required for monitoring the PDCCH and achieving further power reduction.

[0126] <Fourth Embodiment> Next, a fourth embodiment will be described with reference to Figure 15.

[0127] In the fourth embodiment, we assume an operation in which power saving is performed by switching SSSGs. Specifically, one or more SSSGs can be set in the UE100 from a variety of SSSGs, including multiple SSSGs with different search space periods and SSSGs without a search space, and flexible power saving is achieved by instructing the switching of SSSGs via DCI.

[0128] As shown in Figure 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 dedicated RRC messages transmitted individually to each UE (for example, RRCReconfiguration messages). The UE 100 (communication unit 110) receives the RRC messages.

[0129] The RRC message includes correspondence information showing the correspondence between the index of one or more SSSGs to be set on UE100 and the value set in the information field in the switching instruction DCI that instructs UE100 to switch the SSSG to be applied (hereinafter referred to as the "SSSG information field"). The one or more SSSGs include at least one of an SSSG that periodically monitors the PDCCH and an SSSG that skips monitoring of the PDCCH.

[0130] For example, when setting four SSSGs to UE100, 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 setting all four SSSGs to UE100 at once; for example, it may set the four SSSGs to UE100 in two separate steps, two SSSGs at a time. The values ​​set in the SSSG information field may be configured in 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"".

[0131] The RRC message further includes search space configuration information associated with each SSSG index. The search space configuration information includes one or more search space settings. Each search space setting includes the search space period, search space offset, search space duration (e.g., number of consecutive slots), symbol for PDCCH monitoring, aggregation level, search space type, and DCI format, etc.

[0132] For example, the search space setting information associated with SSSG index #0 is information that sets the first search space period as the search space period. The search space setting information associated with SSSG index #1 is information that sets the second search space period as the search space period. The search space setting information associated with SSSG index #2 is information that sets the third search space period as the search space period. The search space setting information associated with SSSG index #4 is information that indicates that no search space is set. In other words, SSSG index #4 is associated with search space setting information that indicates PDCCH skipping.

[0133] The RRC message may include field setting information indicating the presence or absence of the SSSG information field for each of the one or more DCI formats. A switching instruction DCI is a DCI having a DCI format that is indicated by the field setting information to have the SSSG information field. The presence or absence of the SSSG information field may be set commonly or independently for non-scheduled DCIs and / or scheduled DCIs. The presence or 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.

[0134] The RRC message may include bit setting information indicating the number of bits in the SSSG information field for each of the one or more DCI formats. The number of bits in the SSSG information field may be set directly, either commonly or independently, for non-scheduled DCIs and / or scheduled DCIs. The number of bits in the SSSG information field may be set commonly for DCI format 1_1 and DCI format 0_1, and / or commonly for DCI format 1_2 and DCI format 0_2. For example, the SSSG information field may be set to up to 2 bits for DCI format 1_1 and / or DCI format 0_1, and / or to 1 bit for DCI format 1_2 and DCI format 0_2.

[0135] The RRC message may include the timer setting value of the switching timer for one or more SSSGs. Details of such switching timers will be described in the fifth embodiment below.

[0136] In step S402, the UE100 (control unit 120) stores the information set by the base station 200.

[0137] In step S403, the base station 200 (communication unit 210) may transmit a MAC CE (hereinafter referred to as "SSSG state selection MAC CE") to the UE 100 specifying whether to activate or deactivate the 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. An activated SSSG becomes valid as the target SSSG, and a deactivated SSSG becomes invalid as the target SSSG. However, deactivation may be prohibited for the default SSSG. The default SSSG will be described in the fifth embodiment below.

[0138] For example, an SSSG state selection MAC CE is identified by a MAC subheader having an LCID defined for the SSSG state selection MAC CE. The SSSG state selection MAC CE may include a "cell ID field" indicating the serving cell to which the SSSG state selection MAC CE applies. The SSSG state selection MAC CE may also include a "Ti field" indicating activation / deactivation for each entry "i" in the SSSG index list consisting of SSSG indices. The "Ti field" includes a "T0 field" to a "T(n-1) field," and the value "1" is set for the SSSG to be activated. Here, "n" indicates the maximum number of SSSGs that can be activated, for example, "4." Assuming the case of activating SSSG index #0, deactivating SSSG index #1, activating SSSG index #2, and deactivating SSSG index #3, the "T0 field" is set to "1," the "T1 field" to "0," the "T2 field" to "1," and the "T3 field" to "1."

[0139] The SSSG information field may be configured in a bitmap format that targets 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", where "10" represents SSSG index #0 and "01" represents SSSG index #2.

[0140] In step S404, the base station 200 (communication unit 210) transmits a switching instruction DCI having an SSSG information field to the UE 100 on the PDCCH. The UE 100 (communication unit 110) receives the switching instruction DCI on the PDCCH. The UE 100 (control unit 120) may determine, based on the field setting information set by the base station 200, whether the DCI format of the detected DCI corresponds to a switching instruction DCI.

[0141] In step S405, the UE100 (control unit 120) obtains the value set in the SSSG information field of the switching instruction DCI received in step S404. The UE100 (control unit 120) may determine the number of bits in the SSSG information field based on the bit number setting information set by the base station 200, and then obtain the value set in the SSSG information field. Alternatively, the UE100 (control unit 120) may determine the number of bits in the SSSG information field based on the number of SSSG indices set in the UE100 (i.e., the number of entries in the set SSSG index list), and then obtain the value set in the SSSG information field. For example, if the number of SSSG indices set in the UE100 is "I", the UE100 (control unit 120) may calculate and determine the number of bits in the SSSG information field using an integer value obtained by rounding up the decimal part of log2(I).

[0142] In step S406, the UE100 (control unit 120) switches to the SSSG having the SSSG index corresponding to the value set in the SSSG information field in the received switching instruction DCI, based on the correspondence information set from the base station 200, and monitors the PDCCH according to the SSSG to which it is switched. For example, in the example in Figure 13, if the value set in the SSSG information field is "11", the UE100 (control unit 120) determines that it has been instructed to switch to the SSSG with SSSG index #3, and switches to the SSSG with SSSG index #3.

[0143] Next, with reference to Figures 16 and 17, a first example of the configuration of information elements included in the RRC message in the fourth embodiment will be described.

[0144] As shown in Figure 16, the RRC message includes a PDCCH configuration (PDCCH-Config) information element. This information element is used to configure UE-specific PDCCH parameters, such as the control resource set (CORESET), search space, and additional parameters for obtaining the PDCCH.

[0145] The PDCCH configuration (PDCCH-Config) information element can 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 set in UE100 (SEQUENCE (SIZE (1..maxNrofSearchSpaceSets-r17)) OF SearchSpaceSet-r17). The SSSG release list is a list of SSSGs to be unset in UE100 (SEQUENCE (SIZE (1..maxNrofSearchSpaceSets-r17)) OF SearchSpaceSet-r17). Here, "maxNrofSearchSpaceSets-r17" indicates the maximum number of configurable SSSGs.

[0146] As shown in Figure 17, each entry in the SSSG Add / Modify List and the SSSG Release List, "SearchSpaceSet-r17", consists of the SSSG index "SearchSpaceSetId-r17" and each search space setting included in this SSSG, "searcSpaces-r17". "searcSpaces-r17" is composed of a list of search space IDs (SEQUENCE (SIZE (0..maxNrofSearchSpaces-r17)) OF SearchSpaceId) of each search space setting included in this SSSG. The SSSG index "SearchSpaceSetId-r17" has the number of bits "0..maxNrofSearchSpaceSets-1-r17".

[0147] Next, with reference to Figures 18 and 19, a second example of the configuration of information elements included in the RRC message in the fourth embodiment will be described. The second example of the configuration indicates the SSSG to which each search space setting belongs in each search space setting.

[0148] As shown in Figure 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 1 to 10 "SearchSpaceExt2-r17" entries.

[0149] As shown in Figure 19, the SearchSpace information element includes "searchSpaceSetIdList-r17", which is a list of SSSG indexes to which this searchspace setting is associated. A single searchspace setting can be associated with multiple SSSGs. For SSSGs to which none of the searchspace settings configured in UE100 are associated, UE100 does not monitor PDCCH while using that SSSG.

[0150] Thus, according to the fourth embodiment, the UE100 receives correspondence information from the base station 200 that shows the correspondence between the SSSG index of one or more SSSGs set in the UE100 and the value set in the SSSG information field in the switching instruction DCI that instructs the UE100 to switch the SSSG to apply. The one or more SSSGs include at least one of an SSSG that periodically monitors the PDCCH and an SSSG that skips monitoring the PDCCH. This makes it possible to achieve flexible power saving using various SSSGs. In addition, since one SSSG information field provided in the switching instruction DCI allows specifying one of several SSSGs with different search space periods, or specifying an SSSG that does not monitor the PDCCH, the increase in the size of the DCI can be suppressed even when various SSSGs are used.

[0151] <Fifth Embodiment> Next, a fifth embodiment will be described with reference to Figure 20. In the fifth embodiment, we assume that UE100 switches SSSGs on a timer basis and that UE100 may have three or more SSSGs configured.

[0152] In the fifth embodiment, the base station 200 (control unit 230) may set one of the SSSGs set for the UE100 as the default SSSG for the UE100. For example, the base station 200 (control unit 230) may specify one of the SSSG indices set for the UE100 as "defaultSSSG-Id". The default SSSG may be one of the SSSGs set for the UE100 that is determined by a predetermined rule shared in advance by the base station 200 and the UE100. The default SSSG may be one of the SSSGs set for the UE100 by the base station 200 as the default SSSG.

[0153] As shown in Figure 20, in step S501, the UE100 (control unit 120), which has been configured with multiple SSSGs by the base station 200, monitors the PDCCH using one of the multiple SSSGs.

[0154] In step S502, UE100 (communication unit 110) receives a switching instruction DCI on the PDCCH from base station 200 instructing it to switch to another SSSG.

[0155] In step S503, the UE100 (control unit 120) switches to the SSSG specified by the switching instruction DCI and starts the timer (switching timer) associated with the SSSG.

[0156] In step S504, the UE100 (control unit 120) determines whether the switching timer has expired.

[0157] If the switching timer expires (step S504: YES), in step S505, the UE100 (control unit 120) switches to the default SSSG from among the configured SSSGs. By switching to the SSSG specified as "defaultSSSG-Id" by the base station 200, the base station 200 can determine which SSSG the UE100 has switched to. Since the switching timer is a value set by the base station 200, the base station 200 manages the switching timer in the same way as the UE100 and can determine that the switching timer has expired in the UE100.

[0158] The UE100 (control unit 120) determines the default SSSG according to a predetermined rule if the default SSSG has not been set by the base station 200, specifically, if the default SSSG has not been explicitly specified by the base station 200 as "defaultSSSG-Id". The predetermined rule is, for example, a rule specified in the 3GPP technical specifications, and is a rule that the base station 200 and the UE100 have shared in advance.

[0159] Here, the prescribed rule may be a rule that determines the default SSSG to be the SSSG corresponding to the SSSG index with the smallest value among the SSSG indices set in UE100, or the SSSG corresponding to the SSSG index with the largest value. For example, in the example in Figure 13, if the rule is to set the default SSSG to be the SSSG corresponding to the SSSG index with the smallest value, UE100 (control unit 120) will determine the SSSG with SSSG index #0 to be the default SSSG. If the rule is to set the default SSSG to be the SSSG corresponding to the SSSG index with the largest value, UE100 (control unit 120) will determine the SSSG with SSSG index #4 to be the default SSSG.

[0160] As described above, the UE100 (communication unit 110) may receive correspondence information from the base station 200 that shows the correspondence between the SSSG index set in the UE100 and the value set in the SSSG information field in the switching instruction DCI. The predetermined rule may be a rule that determines the SSSG corresponding to the SSSG index indicated by a specific value (for example, "0") as the value set in the SSSG information field in the switching instruction DCI as the default SSSG. For example, the UE100 (control unit 120) determines the SSSG having the SSSG index indicated by the value set in the SSSG information field in the switching instruction DCI as the default SSSG.

[0161] The prescribed rule may be a rule that determines the default SSSG among the SSSG indices set in UE100 that have a predetermined value (for example, index #0) corresponding to the SSSG indices.

[0162] The prescribed rule may be a rule that determines the default SSSG among the SSSGs set in UE100, excluding the SSSG that skips PDCCH monitoring. In other words, UE100 (control unit 120) may assume that no SSSG index corresponding to PDCCH skipping is set as the default SSSG.

[0163] If DRX is configured on UE100, UE100 (control unit 120) may apply a specific SSSG when switching from the DRX receive-off period to the receive-on period (active time). The prescribed rule may be a rule that determines the specific SSSG as the default SSSG. That is, UE100 (control unit 120) may determine the first SSSG that monitors PDCCH after the DRX receive-off period has elapsed as the default SSSG.

[0164] In the fifth embodiment, the UE100 (communication unit 110) may receive a scheduling DCI indicating the radio resources allocated to the UE100 as a switching instruction DCI. After receiving the scheduling DCI as a switching instruction DCI, the UE100 (control unit 120) may start the switching timer at the timing to switch to one SSSG (specifically, the slot in which the SSSG switching is performed). As described in the second embodiment, the UE100 (control unit 120) may postpone SSSG switching while the retransmission-related timer for HARQ processing is operating. For this reason, when a scheduling DCI is received as a switching instruction DCI, the switching timer is started at the timing to perform the SSSG switching, rather than at the timing of receiving the switching instruction DCI.

[0165] The UE100 (control unit 120) may use a common value as the value of the switching timer applied to two or more of the three or more SSSGs configured in the UE100. The base station 200 (control unit 230) may set a common value as the value of the switching timer applied to two or more of the three or more SSSGs configured in the UE100.

[0166] The UE100 (control unit 120) may use individual values ​​for each SSSG as the switching timer values ​​applied to each SSSG set in the UE100. The base station 200 (control unit 230) may set individual switching timer settings for each SSSG in the UE100.

[0167] The UE100 (control unit 120) may activate the switching timer associated with the SSSG at the timing (slot) when switching to the SSSG to be switched to is an SSSG that supports PDCCH skipping. When 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 time. By taking advantage of this, it is possible to minimize the impact of the switching delay time without hindering the operation of PDCCH monitoring. The UE100 (control unit 120) may also monitor the PDCCH assuming the default SSSG after the expiration of the switching timer.

[0168] Next, with reference to Figure 21, a specific example 1 of operation using the switching timer according to the fifth embodiment will be described.

[0169] As shown in Figure 21, UE100 is configured with a total of three SSSGs: Default SSSG, SSSG#x, and SSSG#y. Here, it is assumed that base station 200 (control unit 230) sets a single common switching timer value to UE100 for SSSG#x and SSSG#y, which are not the default SSSG.

[0170] During period T11, UE100 (control unit 120) monitors PDCCH using the default SSSG. UE100 (communication unit 110) receives a non-scheduling DCI instructing a switch to SSSG#x in the last search space of period T11. Since HARQ processing does not occur in the case of a non-scheduling DCI, UE100 (control unit 120) activates the switching timer upon receiving the non-scheduling DCI.

[0171] During period T12, UE100 (control unit 120) monitors PDCCH using SSSG#x while the switching timer is operating. SSSG#x is an SSSG with a longer search space period than the default SSSG. When the switching timer expires, UE100 (control unit 120) switches to the default SSSG after the switch delay has elapsed.

[0172] During period T13, UE100 (control unit 120) monitors PDCCH using the default SSSG. UE100 (communication unit 110) receives a Scheduling DCI instructing a switch to SSSG#y in the last search space of period T13. Since a HARQ process occurs in the case of a Scheduling DCI, UE100 (control unit 120) does not start the switching timer upon receiving the Scheduling DCI, but instead starts the switching timer at the timing (slot) when the switch to SSSG#y is executed.

[0173] During period T14, UE100 (control unit 120) monitors PDCCH using SSSG#y while the switching timer is operating. SSSG#y is an SSSG with a shorter search space period compared to the default SSSG. When the switching timer expires, UE100 (control unit 120) switches to the default SSSG after the switch delay has elapsed. Then, during period T15, UE100 (control unit 120) monitors PDCCH using the default SSSG.

[0174] Next, with reference to Figure 22, a specific example 2 of operation using the switching timer according to the fifth embodiment will be described.

[0175] As shown in Figure 22, UE100 is configured with a total of three SSSGs: the default SSSG, SSSG#x for PDCCH skipping, and SSSG#y for PDCCH skipping. Here, it is assumed that the base station 200 (control unit 230) sets individual switching timer values ​​for SSSG#x and SSSG#y, which are not the default SSSG, in UE100.

[0176] During period T21, UE100 (control unit 120) monitors the PDCCH using the default SSSG. UE100 (communication unit 110) receives a non-scheduling DCI instructing a switch to SSSG#x during the last search space of period T11. Since the target SSSG#x is an SSSG that supports PDCCH skipping, UE100 (control unit 120) activates a switching timer (Switching timer-1) independently configured for SSSG#x at the timing (slot) in which the switch to SSSG#x is performed.

[0177] During period T22, UE100 (control unit 120) skips monitoring of PDCCH while Switching timer-1 is operating. When Switching timer-1 expires, UE100 (control unit 120) switches to the default SSSG after the switching delay time has elapsed.

[0178] During period T23, UE100 (control unit 120) monitors the PDCCH using the default SSSG. UE100 (communication unit 110) receives a scheduling DCI instructing a switch to SSSG#y in the last search space of period T23. Since the target SSSG#x is the SSSG that supports PDCCH skipping, UE100 (control unit 120) activates a switching timer (Switching timer-2) independently set for SSSG#y at the timing (slot) when the switch to SSSG#y is executed. The timer value of Switching timer-2 is greater than the timer value of Switching timer-1.

[0179] During period T24, UE100 (control unit 120) skips monitoring of PDCCH while Switching timer-2 is operating. When Switching timer-2 expires, UE100 (control unit 120) switches to the default SSSG after the switch delay has elapsed. Then, during period T25, UE100 (control unit 120) monitors PDCCH using the default SSSG.

[0180] Thus, according to the fifth embodiment, even when the UE100 performs SSSG switching on a timer basis and three or more SSSGs may be configured on the UE100, the base station 200 can determine the target SSSG by defining a default SSSG. Therefore, it becomes possible to perform timer-based switching for various SSSGs.

[0181] <Other Embodiments> In the embodiments described above, the base station 200 may include a plurality of units. The plurality of units may include a first unit that hosts the higher layer included in the protocol stack, and a second unit that hosts the lower layer included in the protocol stack. The higher layer may include the RRC layer, SDAP layer, and PDCP layer, and the lower layer may include the RLC layer, MAC layer, and PHY layer. The first unit may be a CU (Central Unit), and the second unit may be a DU (Distributed Unit). The plurality of units may include a third unit that performs processing below the PHY layer. The second unit may perform processing above the PHY layer. The third unit may be a RU (Radio Unit). 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 IAB (Integrated Access and Backhaul) donor or IAB node.

[0182] In the embodiments described above, a mobile communication system based on NR was used as an example for the mobile communication system 1. However, the mobile communication system 1 is not limited to this example. The mobile communication system 1 may be a system compliant with a TS of either LTE or another generation system of the 3GPP standard (e.g., 6th generation). The base station 200 may be an eNB that provides E-UTRA user plane and control plane protocol termination directed to UE100 in LTE. The mobile communication system 1 may be a system compliant with a TS of a standard other than the 3GPP standard. Similarly, although a mobile communication system applying carrier aggregation was used as an example, it is not limited to this, and may be a mobile communication system applying dual connectivity, and the example of operation using a primary cell (PCell) may be an example of operation using a special cell (SpCell).

[0183] The steps in the operation of the above-described embodiment do not necessarily have to be executed chronologically in the order shown in the flowchart or sequence diagram. For example, the steps in the operation may be executed in a different order than that shown in the flowchart or sequence diagram, or they may be executed in parallel. Also, some steps in the operation may be deleted, or further steps may be added to the process. Furthermore, each of the above-described operation flows can be implemented not only separately and independently, but also 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.

[0184] A program may be provided that causes a computer to execute each process performed by the UE100 or base station 200. The program may be recorded on a computer-readable medium. Using a computer-readable medium, it is possible to install the program on a computer. Here, the computer-readable medium on which the program is recorded may be a non-transient recording medium. The non-transient recording medium is not particularly limited, but may be a recording medium such as a CD-ROM or DVD-ROM. Alternatively, the circuits that execute each process performed by the UE100 or base station 200 may be integrated, and at least a part of the UE100 or base station 200 may be configured as a semiconductor integrated circuit (chipset, SoC (System-on-a-Chip)).

[0185] In the embodiments described above, "transmit" may mean processing at least one layer in the protocol stack used for transmission, or it may mean physically transmitting a signal wirelessly or via a wire. Alternatively, "transmit" may mean a combination of processing at least one layer and physically transmitting a signal wirelessly or via a wire. Similarly, "receive" may mean processing at least one layer in the protocol stack used for reception, or it may mean physically receiving a signal wirelessly or via a wire. Alternatively, "receive" may mean a combination of processing at least one layer and physically receiving a signal wirelessly or via a wire. Similarly, "obtain / acquire" may mean obtaining information from stored information. Also, "obtain / acquire" may mean obtaining information from information received from other nodes. Alternatively, "obtain / acquire" may mean obtaining information by generating the information. Similarly, “include” and “comprise” do not mean that only the listed items are included, but rather that they may include only the listed items. Also, “include” and “comprise” may include additional items in addition to the listed items. Similarly, in this disclosure, “or” does not mean exclusive OR, but rather logical OR.

[0186] This disclosure is described in accordance with the embodiments, but it is understood that this disclosure is not limited to such embodiments or structures. This disclosure also includes various modifications and variations within the equivalence. In addition, various combinations and forms, as well as other combinations and forms that include only one, more, or fewer of those elements, fall within the scope and concept of this disclosure.

Claims

1. A receiving unit that receives a radio resource control (RRC) message from a base station, which includes information determining whether an information field related to monitoring the physical downlink control channel (PDCCH) exists in a first downlink control information (DCI) format used for scheduling the physical downlink shared channel (PDSCH) and a second DCI format used for scheduling the physical uplink shared channel (PUSCH), The system includes a control unit that controls the monitoring of the PDCCH on the downlink BWP of the serving cell, The control unit, If it is determined that the first DCI format contains an information field related to monitoring the PDCCH, then a group of search space sets for monitoring the PDCCH is switched based on the value set in the information field related to monitoring the PDCCH included in the first DCI format. If, based on the aforementioned information, it is determined that the second DCI format contains an information field related to monitoring the PDCCH, then the group of search space sets for monitoring the PDCCH is switched based on the value set in the information field related to monitoring the PDCCH included in the second DCI format. Communication device.

2. The second DCI format is further comprising a CRC parity bit that has been scrambled by any of the following: C-RNTI (Cell-Radio Network Temporary Identifier), MCS-C-RNTI (Modulation and Coding Scheme-C-RNTI), and CS-RNTI (Configured Scheduling-RNTI). The communication device according to claim 1.

3. The first DCI format is further modified by adding a CRC parity bit that has been scrambled using one of the following methods: C-RNTI (Cell-Radio Network Temporary Identifier), MCS-C-RNTI (Modulation and Coding Scheme-C-RNTI), or CS-RNTI (Configured Scheduling-RNTI). The communication device according to claim 1.

4. The information field for monitoring the PDCCH is an information field in which a value indicating the switching of the group of the search space set is set. A communication device according to any one of claims 1 to 3.

5. A transmitting unit transmits a radio resource control (RRC) message to a communication device, which includes information determining whether an information field for monitoring the physical downlink control channel (PDCCH) exists in a first downlink control information (DCI) format used for scheduling the physical downlink shared channel (PDSCH) and a second DCI format used for scheduling the physical uplink shared channel (PUSCH). The system includes a control unit that controls the monitoring of the PDCCH on the downlink BWP of the serving cell, The control unit, If, based on the information described above, it is indicated that the first DCI format contains an information field for monitoring the PDCCH, then a switch in the group of search space sets for monitoring the PDCCH is instructed based on the value set in the information field for monitoring the PDCCH included in the first DCI format. If, based on the information described above, it is indicated that the second DCI format contains an information field for monitoring the PDCCH, then it is indicated to switch the group of search space sets for monitoring the PDCCH based on the value set in the information field for monitoring the PDCCH included in the second DCI format. Base station.

6. The second DCI format is further comprising a CRC parity bit that has been scrambled by any of the following: C-RNTI (Cell-Radio Network Temporary Identifier), MCS-C-RNTI (Modulation and Coding Scheme-C-RNTI), and CS-RNTI (Configured Scheduling-RNTI). The base station according to claim 5.

7. The first DCI format is further modified by adding a CRC parity bit that has been scrambled using one of the following methods: C-RNTI (Cell-Radio Network Temporary Identifier), MCS-C-RNTI (Modulation and Coding Scheme-C-RNTI), or CS-RNTI (Configured Scheduling-RNTI). The base station according to claim 5.

8. The information field for monitoring the PDCCH is an information field in which a value indicating the switching of the search space set group is set. A base station according to any one of claims 5 to 7.

9. A communication method used in communication devices, The steps include receiving a Radio Resource Control (RRC) message from a base station that includes information determining whether an information field for monitoring the physical downlink control channel (PDCCH) exists in a first downlink control information (DCI) format used for scheduling the physical downlink shared channel (PDSCH) and a second DCI format used for scheduling the physical uplink shared channel (PUSCH), The system includes the step of controlling the monitoring of the PDCCH in the downlink BWP of the serving cell, In the aforementioned control step, If it is determined that the first DCI format contains an information field related to monitoring the PDCCH, then a group of search space sets for monitoring the PDCCH is switched based on the value set in the information field related to monitoring the PDCCH included in the first DCI format. If, based on the aforementioned information, it is determined that the second DCI format contains an information field related to monitoring the PDCCH, then the group of search space sets for monitoring the PDCCH is switched based on the value set in the information field related to monitoring the PDCCH included in the second DCI format. Communication method.

10. The second DCI format is further comprising a CRC parity bit that has been scrambled by any of the following: C-RNTI (Cell-Radio Network Temporary Identifier), MCS-C-RNTI (Modulation and Coding Scheme-C-RNTI), and CS-RNTI (Configured Scheduling-RNTI). The communication method described in claim 9.

11. The first DCI format is further modified by adding a CRC parity bit that has been scrambled using one of the following methods: C-RNTI (Cell-Radio Network Temporary Identifier), MCS-C-RNTI (Modulation and Coding Scheme-C-RNTI), or CS-RNTI (Configured Scheduling-RNTI). The communication method described in claim 9.

12. The information field for monitoring the PDCCH is an information field in which a value indicating the switching of the group of the search space set is set. A communication method according to any one of claims 9 to 11.

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