User Equipment and Base Station Involved in Control Channel Signaling

Abstract

The present disclosure relates to a user equipment (UE) having a processor that operates a monitoring function involving monitoring a downlink control channel of an unlicensed radio cell based on one of a plurality of groups of search space sets (SSSs). The unlicensed radio cell is controlled by a base station operating in an unlicensed spectrum and communicating with the user equipment. One of the plurality of groups of SSSs is configured to be a default group of SSSs. The processor determines one of the plurality of SSSs for performing the monitoring function in response to the downlink control channel. The monitoring function is not performed during a non-monitoring period. When performing the monitoring function after the non-monitoring period, the processor determines to perform the monitoring function based on the default group of SSSs.

Description

[Technical Field]

[0001] The present disclosure is directed to methods, devices, and articles in communication systems, such as 3GPP® communication systems. [Background technology]

[0002] Currently, the 3rd Generation Partnership Project (3GPP) is working on technical specifications for the next generation of cellular technology, also known as the fifth generation (5G).

[0003] One objective is to provide a single technical framework that addresses all usage scenarios, requirements, and deployment scenarios (see, for example, Section 6 of Non-Patent Document 1), including at least enhanced mobile broadband (eMBB), ultra-reliable low-latency communications (URLLC), and massive machine-type communications (mMTC). For example, deployment scenarios for eMBB may include indoor hotspots, dense urban areas, suburban areas, wide-area urban areas, and high-speed networks. Deployment scenarios for URLLC may include industrial control systems, mobile health management (remote monitoring, remote diagnosis, and remote treatment), real-time vehicle control, and wide-area monitoring and control systems for smart grids. Deployment scenarios for mMTC may include scenarios using a large number of devices with low-latency data transmission, such as smart wearables and sensor networks. eMBB and URLLC services are similar in that they both require extremely high bandwidth, but differ in that URLLC services preferably require extremely low latency.

[0004] The second objective is to achieve forward compatibility: backward compatibility to Long Term Evolution (LTE, LTE-A) cellular systems is not required, which facilitates the design of entirely new systems and / or the introduction of new features. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] TR 38.913 version 15.0.0 [Non-patent document 2] 3GPP TS 38.300 v15.6.0 [Non-patent document 3] 3GPP TS 38.211 v15.6.0 [Non-patent document 4] ITU-R M.20183 [Non-Patent Document 5] TS 23.501 v16.1.0 [Non-patent document 6] 3GPP Technical Standard TS 36.321, 15.6.0 [Non-Patent Document 7] TS 38.321, version 15.7.0 [Non-patent document 8] 3GPP TS 38.321 v15.6.0 [Non-Patent Document 9] 3GPP TS 38.133 v16.0.0 [Non-Patent Document 10] TS 38.331 v15.6.0 [Non-Patent Document 11] 3GPP TS 38.889 v16.0.0 [Non-Patent Document 12] ETSI 301 893 [Non-Patent Document 13] TS 38.212 v15.6.0 [Non-Patent Document 14] 3GPP TS 38.213, version 15.7.0 Summary of the Invention

[0006] One non-limiting and exemplary embodiment facilitates providing a procedure that facilitates an improved switching procedure for switching between groups of search space sets used by a UE in a downlink control channel monitoring function and used by a base station in a control information transmission function.

[0007] In one embodiment, the technology disclosed herein features a user equipment (UE) having: a processor of the UE that operates a monitoring function involving monitoring a downlink control channel of an unlicensed radio cell based on one of a plurality of groups of search space sets, the unlicensed radio cell operating in an unlicensed spectrum and controlled by a base station in communication with the user equipment; and one of the plurality of groups of search space sets configured to be a default group of search space sets. The processor determines one of the plurality of search space set groups for performing the monitoring function in response to the downlink control channel. The monitoring function is not performed during a non-monitoring period. When performing the monitoring function after the non-monitoring period, the processor determines to perform the monitoring function based on the default group of search space sets.

[0008] It should be noted that the general or specific embodiments may be implemented as a system, a method, an integrated circuit, a computer program, a storage medium, or any selective combination thereof.

[0009] Further benefits and advantages of the disclosed embodiments and various implementations will become apparent from the specification and drawings. These benefits and / or advantages may be obtained individually by the various embodiments and features of the specification and drawings, although they need not all be present to obtain one or more of such benefits and / or advantages. [Brief explanation of the drawings]

[0010] Exemplary embodiments will now be described in more detail with reference to the accompanying drawings.

[0011] [Figure 1] FIG. 1 illustrates an example architecture of a 3GPP NR system. [Figure 2] 1 is a schematic diagram showing the division of functions between NG-RAN and 5GC. [Figure 3] FIG. 1 is a sequence diagram of an RRC connection setup / reconfiguration procedure. [Figure 4] A schematic diagram showing the usage scenarios of enhanced mobile broadband (eMBB), massive machine-type communications (mMTC), and ultra-reliable low-latency communications (URLLC). [Figure 5] FIG. 1 is a block diagram illustrating an example 5G system architecture for a non-roaming scenario. [Figure 6] FIG. 10 is a diagram illustrating the DRX operation of a mobile terminal according to a short DRX cycle and a long DRX cycle, in particular, the DRX opportunities and on-periods. [Figure 7] A diagram showing an example LAA scenario with several licensed and unlicensed cells. [Figure 8] A diagram illustrating channel occupation of an unlicensed channel by a gNB and the transmission of a corresponding COT indication. [Figure 9] A diagram showing the configuration of search space sets in different SSS groups. [Figure 10] A diagram illustrating switching between different SSS groups depending on the COT state of the gNB. [Figure 11] A diagram showing one exemplary implementation form of SSS group switching operation for a UE of parallel operation of DRX functionality and problems arising therefrom. [Figure 12] A diagram showing another exemplary implementation of SSS group switching operation for a UE of parallel operation of DRX functionality and problems arising therefrom. [Figure 13] FIG. 1 illustrates an exemplary simplified structure of a UE and a gNB. [Figure 14] FIG. 1 illustrates the structure of a UE according to an exemplary implementation of an improved SSS group switching procedure. [Figure 15] FIG. 10 is a flow diagram of UE operation according to an example implementation of an improved SSS group switching procedure. [Figure 16] A diagram showing the structure of a base station according to an exemplary implementation of an improved SSS group switching procedure. [Figure 17] 1 is a flow diagram of a base station operation in accordance with an exemplary implementation of an improved SSS group switching procedure. [Figure 18] FIG. 10 illustrates how the improved SSS group switching procedure is applied in parallel to the operation of the DRX function, where the switching is explicitly controlled by the gNB and the UE. [Figure 19] FIG. 10 illustrates how the improved SSS group switching procedure is applied in parallel to the operation of the DRX function, where the switching is controlled implicitly by the gNB and the UE, in particular according to the COT structure. [Figure 20] FIG. 10 is a flow diagram of UE operation according to another example implementation of the improved SSS group switching procedure. [Figure 21] FIG. 10 illustrates how the improved SSS group switching is applied in parallel to the operation of the DRX function, where the UE's knowledge of the COT structure when exiting a non-monitoring period influences which SSS group to use. [Figure 22]FIG. 10 illustrates how the improved SSS group switching is applied in parallel to the operation of the DRX function, where the UE's knowledge of the COT structure when exiting a non-monitoring period influences which SSS group to use. [Figure 23] FIG. 10 illustrates another improvement to monitoring functionality according to an exemplary implementation. DETAILED DESCRIPTION OF THE INVENTION

[0012] 5G NR System Architecture and Protocol Stack

[0013] 3GPP is working on the next release of fifth-generation cellular technology (simply known as 5G), which includes the development of a new radio access technology (NR) that will operate in frequencies up to 100 GHz. The first version of the 5G standard was completed at the end of 2017, allowing for the testing and commercial deployment of smartphones compliant with the 5G NR standard.

[0014] In particular, the overall system architecture assumes an NG-RAN (Next Generation Radio Access Network) with gNBs, which terminate NG radio access user plane (SDAP / PDCP / RLC / MAC / PHY) and control plane (RRC) protocols. The gNBs are interconnected with each other via an Xn interface. The gNBs are also connected to an NGC (Next Generation Core) via a Next Generation (NG) interface, more specifically to an AMF (Access and Mobility Management Function) (e.g., a specific core entity that runs the AMF) via an NG-C interface, and to a UPF (User Plane Function) (e.g., a specific core entity that runs the UPF) via an NG-U interface. The NG-RAN architecture is shown in Figure 1 (see, for example, Section 4 of Non-Patent Document 2).

[0015] The user plane protocol stack in NR (see, for example, Section 4.4.1 of Non-Patent Document 2) includes a PDCP (Packet Data Convergence Protocol) sublayer, an RLC (Radio Link Control) sublayer, and a MAC (Medium Access Control) sublayer, which are terminated at the gNB on the network side. In addition, a new access stratum (AS) sublayer (SDAP, Service Data Adaptation Protocol) is introduced above PDCP (see, for example, Section 6.5 of Non-Patent Document 2). NR also defines a control plane protocol stack (see, for example, Section 4.4.2 of Non-Patent Document 2). An overview of Layer 2 functions is provided in Section 6 of Non-Patent Document 2. The functions of the PDCP sublayer, RLC sublayer, and MAC sublayer are described in sections 6.4, 6.3, and 6.2, respectively, of Non-Patent Document 2. The functions of the RRC layer are described in section 7 of Non-Patent Document 2.

[0016] For example, the medium access control layer handles scheduling and scheduling-related functions, including multiplexing of logical channels and handling of various numerologies.

[0017] The physical layer (PHY) is responsible for, for example, coding, PHY HARQ processing, modulation, multi-antenna processing, and mapping of signals to appropriate physical time-frequency resources. The physical layer also handles mapping of transport channels to physical channels. The physical layer provides services to the MAC layer in the form of transport channels. A physical channel corresponds to a set of time-frequency resources used for transmitting a specific transport channel, and each transport channel is mapped to a corresponding physical channel. For example, physical channels are the PRACH (Physical Random Access Channel), PUSCH (Physical Uplink Shared Channel), and PUCCH (Physical Uplink Control Channel) for the uplink, and the PDSCH (Physical Downlink Shared Channel), PDCCH (Physical Downlink Control Channel), and PBCH (Physical Broadcast Channel) for the downlink.

[0018] NR use cases / deployment scenarios include enhanced mobile broadband (eMBB), ultra-reliable and low-latency communications (URLLC), and massive machine-type communications (mMTC), which have diverse requirements for data rates, latency, and coverage. For example, eMBB is expected to support peak data rates (20 Gbps downlink and 10 Gbps uplink) and user-perceived data rates on the order of three times those offered by IMT-Advanced. In contrast, URLLC has more stringent requirements, including extremely low latency (user plane latency of 0.5 ms for UL and DL, respectively) and high reliability (1-10 Mbps within 1 ms). -5) and mMTC requires high connection density (1 km in urban environments). 2 1,000,000 devices per second), wide coverage in harsh environments, and extremely long battery life (15 years) to lower device costs may be preferably required.

[0019] Therefore, an OFDM numerology (e.g., subcarrier spacing, OFDM symbol duration, cyclic prefix (CP) duration, number of symbols per scheduling interval) suitable for one use case may not work well for another use case. For example, low-latency services may preferably require a shorter symbol duration (and therefore a larger subcarrier spacing) and / or fewer symbols per scheduling interval (also referred to as TTI) than mMTC services. Furthermore, deployment scenarios with large channel delay spreads may preferably require a longer CP duration than scenarios with small delay spreads. To maintain comparable CP overhead, the subcarrier spacing should be optimized depending on the delay spread. In NR, more than one value of subcarrier spacing may be supported. Therefore, subcarrier spacings of 15 kHz, 30 kHz, 60 kHz, ... are currently being considered. Symbol duration T u and the subcarrier spacing Δf is given by the formula (Δf=1 / T u ) As in LTE systems, the term "resource element" can be used to denote the smallest resource unit consisting of one subcarrier for the length of one OFDM / SC-FDMA symbol.

[0020] In the new radio system 5G-NR, a resource grid of subcarriers and OFDM symbols is defined for each numerology and carrier in the uplink and downlink, respectively. Each element in the resource grid is called a resource element and is identified based on its frequency index in the frequency domain and its symbol position in the time domain (see Non-Patent Document 3). For example, downlink and uplink transmissions consist of frames with a duration of 10 ms, and each frame consists of 10 subframes, each with a duration of 1 ms. In 5G NR implementations, the number of consecutive OFDM symbols per subframe depends on the subcarrier spacing configuration. For example, with a subcarrier spacing of 15 kHz, one subframe has 14 OFDM symbols (assuming a normal cyclic prefix, similar to an LTE-compliant implementation). On the other hand, with a subcarrier spacing of 30 kHz, one subframe has two slots, each consisting of 14 OFDM symbols.

[0021] An overview is given by the following table from section 4 of [3]:

[0022] [Table 1]

[0023] [Table 2]

[0024] Split of 5G NR functions between NG-RAN and 5GC

[0025] Figure 2 shows the division of functions between NG-RAN and 5GC. The logical nodes of NG-RAN are gNB or ng-eNB. The logical nodes of 5GC are AMF, UPF, and SMF.

[0026] In particular, the gNB and ng-eNB handle the following key functions: - Radio Resource Management functions, such as Radio Bearer Control, Radio Admission Control, Connection Mobility Control, and dynamic resource allocation (scheduling) to UEs in both uplink and downlink directions. - IP header compression, encryption, and data integrity protection - AMF selection at UE attach time when routing to an AMF cannot be determined from information provided by the UE - Routing of user plane data to the UPF - Routing control plane information to AMF - Establishing and releasing connections - Scheduling and sending paging messages - Scheduling and transmission of system broadcast information (sent from AMF or OAM) - Configuring measurements and measurement reporting for mobility and scheduling - Transport-level packet marking in the uplink - Session Management - Network slicing support - QoS flow management and mapping to data radio bearers - Support for UEs in RRC_INACTIVE state - NAS message delivery function - Wireless Access Network Sharing - Dual Connectivity - Tight interworking between NR and E-UTRA

[0027] The Access and Mobility Management Function (AMF) handles the following main functions: - Termination of Non-Access Stratum (NAS) signaling - NAS signaling security - Access Stratum (AS) security control - Core Network (CN) inter-node signaling for mobility between 3GPP access networks - Reachability for idle mode UEs (including control and execution of paging retransmissions) - Registration Area Management - Support for intra-system and inter-system mobility - Access Authentication - Access authentication, including roaming rights checks - Mobility management controls (subscriptions and policies) - Network slicing support - Selection of Session Management Function (SMF)

[0028] Furthermore, the User Plane Function (UPF) handles the following main functions: - Anchor points for intra-RAT / inter-RAT mobility (when applicable) - External PDU session points for interconnection with data networks - Packet routing and forwarding - User plane part of packet inspection and policy rule enforcement - Traffic usage reports - An uplink classifier to support routing of traffic flows to the data network - Branching points to support multi-homed PDU sessions - User plane QoS processing (e.g., packet filtering, gating, UL / DL rate enforcement) - Uplink traffic validation (SDF to QoS flow mapping) - Downlink packet buffering and downlink data notification triggering

[0029] Finally, the Session Management Function (SMF) handles the following major functions: - Session Management - UE IP address allocation and management - UP function selection and control - Configuring traffic steering in the User Plane Function (UPF) to route traffic to the correct destination - Policy enforcement and QoS control parts - Downlink data notification

[0030] RRC connection establishment and reconfiguration procedures

[0031] Figure 3 shows the interactions between the UE, gNB, and AMF (5GC entity) in the NAS part when the UE transitions from RRC_IDLE to RRC_CONNECTED (see non-patent document 2).

[0032] RRC is a higher layer signaling protocol used to configure the UE and the gNB. In particular, during this transition, the AMF prepares UE context data (e.g., including PDU session context, security keys, UE radio capabilities, and UE security capabilities) and sends it to the gNB via an INITIAL CONTEXT SETUP REQUEST. The gNB then activates AS security with the UE by sending a SecurityModeCommand message to the UE and the UE responding with a SecurityModeComplete message. The gNB then performs reconfiguration to establish signaling radio bearer 2 (SRB2) and data radio bearer (DRB). The gNB then sends an RRCReconfiguration message to the UE and receives an RRCReconfigurationComplete message from the UE in response. In the case of a signaling-only connection, these steps related to RRCReconfiguration are skipped because SRB2 and DRB are not established. Finally, the gNB notifies the AMF that the establishment procedure is complete via an INITIAL CONTEXT SETUP RESPONSE.

[0033] Thus, the present disclosure provides a fifth-generation core (5GC) entity (e.g., AMF, SMF, etc.) having, in operation, a control circuit that establishes a next-generation (NG) connection with a gNodeB so that a signaling radio bearer is established between the gNodeB and a user equipment (UE), and a transmitter that, in operation, transmits an initial context setup message to the gNodeB via the NG connection. In particular, the gNodeB transmits radio resource control (RRC) signaling including a resource allocation configuration information element to the UE via the signaling radio bearer. The UE then performs uplink transmission or downlink reception based on the resource allocation configuration.

[0034] Usage scenarios for IMT-2020 and beyond

[0035] Figure 4 shows some use cases for 5G NR. The 3GPP NR (3rd Generation Partnership Project New Radio) considers three use cases that are envisioned to support a wide variety of services and applications via IMT-2020. The enhanced mobile broadband (eMBB) phase 1 specifications have been finalized. Current and future work will include standardization for ultra-reliable and low-latency communications (URLLC) and large-scale machine-type communications, in addition to further extending eMBB support. Figure 4 shows some examples of envisioned usage scenarios for IMT beyond 2020 (see, for example, Figure 2 in Non-Patent Document 4).

[0036] URLLC use cases have stringent requirements for capabilities such as throughput, latency, and availability, and are envisioned as one of the enablers of future vertical applications, such as wireless control of industrial manufacturing or production processes, remote medical surgery, power distribution automation in smart grids, and transportation safety. URLLC's ultra-high reliability is supported by identifying technologies to meet the requirements set by [Non-Patent Document 1]. For NR URLLC in Release 15, key requirements include a user plane target latency of 0.5 ms for the uplink (UL) and 0.5 ms for the downlink (DL). A typical URLLC requirement for a single packet transmission is a block error rate (BLER) of 1E-5 for a 32-byte packet size with a user plane latency of 1 ms.

[0037] From a physical layer perspective, reliability can be improved in many possible ways. Current scope for improving reliability includes defining separate CQI tables for URLLC, more compact DCI formats, PDCCH repetition, etc. However, as NR becomes more stable and developed (a key requirement for NR URLCC), the scope for achieving ultra-high reliability may increase. Specific use cases for NR URLCC in Release 15 include augmented reality / virtual reality (AR / VR), e-health, e-safety, and mission-critical applications.

[0038] Furthermore, the technology enhancements targeted by NR URLCC aim to improve latency and reliability. Technology enhancements for improving latency include configurable numerology, non-slot-based scheduling with flexible mapping, grant-free (configured grant) uplink, slot-level repetition of data channels, and downlink preemption. Preemption means that a transmission for which resources have already been allocated is aborted and the already allocated resources are used for another transmission requested later with smaller latency / higher priority requirements. Thus, a previously granted transmission is preempted by a later transmission. Preemption applies regardless of the specific service type. For example, a transmission of service type A (URLCC) can be preempted by a transmission of service type B (e.g., eMBB). Technology enhancements for improving reliability include dedicated CQI / MCS tables for a target BLER of 1E-5.

[0039] The mMTC (Massive Machine Type Communication) use case is characterized by a very large number of connected devices transmitting relatively small amounts of data that are generally latency sensitive. The devices need to be low cost and have extremely long battery life. From an NR perspective, utilizing very narrow bandwidth portions is one possible solution to achieve power savings from the UE perspective, enabling long battery life.

[0040] As mentioned above, it is expected that the range of reliability in NR will expand. One key requirement for all cases, especially for URLLC and mMTC, is high or ultra-high reliability. Several mechanisms can be considered to improve reliability from a radio perspective and a network perspective. In general, there are several key areas that can help improve reliability. These areas include compact control channel information, data channel / control channel repetition, and diversity related to the frequency, time, and / or spatial domains. These areas are generally applicable to reliability, regardless of the specific communication scenario.

[0041] For NR URLLC, further use cases with more stringent requirements have been identified, e.g., in factory automation, the transport industry, and power supply. The more stringent requirements include higher reliability (up to 10 times faster) depending on the use case. 6 level), higher availability, packet sizes up to 256 bytes, time synchronization on the order of a few microseconds (values ​​range from 1 to a few microseconds depending on the frequency range), and low latency on the order of 0.5-1 ms (target latency for the user plane in particular is 0.5 ms).

[0042] Furthermore, for NR URLLC, several technology enhancements are recognized from the physical layer perspective. In particular, PDCCH (Physical Downlink Control Channel) enhancements related to compact DCI, PDCCH repetition, and increased PDCCH monitoring. Furthermore, UCI (Uplink Control Information) enhancements related to HARQ (Hybrid Automatic Repeat Request) enhancements and CSI feedback enhancements are recognized. PUSCH enhancements related to minislot-level hopping and retransmission / repetition are also recognized. The term "minislot" refers to a transmission time interval (TTI) containing fewer symbols than a slot (a slot containing 14 symbols).

[0043] QoS Control

[0044] The 5G Quality of Service (QoS) model is based on QoS flows and supports both QoS flows that require a guaranteed flow bit rate (GBR QoS flows) and QoS flows that do not require a guaranteed flow bit rate (non-GBR QoS flows). Therefore, at the NAS level, QoS flows are the finest granularity of QoS differentiation in a PDU session. Within a PDU session, QoS flows are identified by a QoS Flow ID (QFI) carried in the encapsulation header over the NG-U interface.

[0045] The 5GC establishes one or more PDU sessions for each UE. The NG-RAN establishes at least one Data Radio Bearer (DRB) for each UE along with the PDU session, and can then configure additional DRBs for the QoS flows of that PDU session (as determined by the NG-RAN, e.g., as described above with reference to Figure 3). The NG-RAN maps packets belonging to different PDU sessions to different DRBs. NAS-level packet filters in the UE and the 5GC associate UL and DL packets with QoS flows, and AS-level mapping rules in the UE and the NG-RAN associate UL and DL QoS flows with DRBs.

[0046] Figure 5 shows the 5G NR non-roaming reference architecture (see section 4.23 of 3GPP TS 36544-10000). Application Functions (AFs) (e.g., external application servers handling the 5G services exemplarily described in Figure 4) interact with the 3GPP Core Network to provide services. For example, they support application influence on traffic routing, access Network Exposure Functions (NEFs), or interact with a policy framework (see Policy Control Function PCF) for policy control (e.g., QoS control). Based on the operator's deployment, Application Functions (AFs) deemed trusted by the operator can be allowed to interact directly with the relevant Network Functions. Application Functions (AFs) not permitted by the operator to directly access Network Functions interact with the relevant Network Functions using an external exposure framework via the NEF.

[0047] Figure 5 shows further functional units of the 5G architecture: Network Slice Selection Function (NSSF), Network Repository Function (NRF), Unified Data Management (UDM), Authentication Server Function (AUSF), Access and Mobility Management Function (AMF), Session Management Function (SMF), and Data Network (DN) (e.g., operator services, internet access, or third-party services). All or part of the core network functions and application services may be located in and run on a cloud computing environment.

[0048] Therefore, the present disclosure provides an application server (e.g., an AF in a 5G architecture) having a transmitter that, during operation, sends a request including QoS requirements for at least one of URLLC, eMBB, and mMTC services to at least one of 5GC functions (e.g., NEF, AMF, SMF, PCF, UPF, etc.) to establish a PDU session including a radio bearer between a gNodeB and a UE in accordance with the QoS requirements, and a control circuit that, during operation, performs the service using the established PDU session.

[0049] Discontinued Reception (DRX) in LTE and 5G NR

[0050] An exemplary implementation of a discontinuous reception (DRX) function in 5G NR with PDCCH monitoring according to the currently standardized version is described below in a simplified and abbreviated form.

[0051] To reduce battery consumption in the UE, a mechanism is used to minimize the time the UE spends monitoring the PDCCH, called the Discontinued Reception (DRX) function. The DRX function can be configured for RRC_IDLE. In this case, the UE uses a specific DRX value or a default DRX value (defaultPagingCycle). The default paging cycle is broadcast in the system information and can have values ​​of 32, 64, 128, or 256 radio frames. The UE needs to wake up for one paging occasion per DRX cycle, where a paging occasion is one subframe. The DRX function can also be configured for an "RRC_CONNECTED" UE, so that it is not necessary to constantly monitor the downlink control channel for downlink control information (or, simply, the UE does not need to monitor the PDCCH) (see Chapter 5.7 of 3GPP TS 36.110).

[0052] The following parameters are available to define the DRX UE behavior: e.g., the duration of the On-Duration during which the mobile node is active (i.e., in DRX Active Time) and the duration during which the mobile node is in DRX (i.e., not in DRX Active Time).

[0053] - On-duration: The duration in a downlink subframe, i.e., more specifically, in a subframe with a PDCCH (also referred to as a PDCCH subframe), that the user equipment receives and monitors the PDCCH after waking up from DRX. Note that the term "PDCCH" here refers to the PDCCH, the EPDCCH (in the subframe if configured), or the R-PDCCH in case of a relay node where the R-PDCCH is configured and not suspended. If the user equipment successfully decodes the PDCCH, it stays awake / active and starts the inactivity timer [1 to 200 subframes; 16 steps: 1 to 6, 10 to 60, 80, 100, 200]. - DRX inactivity timer : The period in downlink subframes that the UE waits to successfully decode the PDCCH since the last successful decoding of the PDCCH. If the UE fails to decode the PDCCH during this period, it re-enters DRX. The UE shall restart the inactivity timer after one successful decoding of the PDCCH for the first transmission only (i.e., not for a retransmission) [1 to 2560 subframes; 22 steps, 10 spare: 1 to 6, 8, 10 to 60, 80, 100 to 300, 500, 750, 1280, 1920, 2560] - DRX Retransmission Timer : Specifies the number of consecutive PDCCH subframes in which downlink retransmissions are expected by the UE after the first available retransmission time [1 to 33 subframes, 8 steps: 1, 2, 4, 6, 8, 16, 24, 33]. - DRX Short Cycle : Specifies the periodic repetition of the on duration followed by a possible inactive period for short DRX cycles. This parameter is optional. [2 to 640 subframes; 16 steps: 2, 5, 8, 10, 16, 20, 32, 40, 64, 80, 128, 160, 256, 320, 512, 640] - DRX short cycle timerSpecifies the number of consecutive subframes for which the UE follows a short DRX cycle after the DRX Inactivity Timer expires. This parameter is optional. [1 to 16 subframes] - Long DRX Cycle Start offset Specifies the periodic repetition of an On Duration followed by a possible inactive period for the DRX long cycle, and the subframe offset at the start of the On Duration (determined by the formula defined in Section 5.7 of Non-Patent Document 6). [Cycle length 10 to 2560 subframes; 16 steps: 10, 20, 30, 32, 40, 64, 80, 128, 160, 256, 320, 512, 640, 1024, 1280, 2048, 2560; offset is an integer between [0 and the subframe length of the selected cycle]].

[0054] The total duration that a UE is in an awake state is called the "active time" or DRX active time. The active time includes, for example, the on duration of a DRX period, the time during which the UE performs continuous reception while the inactivity timer has not expired, and the time during which the UE performs continuous reception while waiting for a downlink retransmission after one HARQ RTT. Similarly, for the uplink, the UE is in the awake state (i.e., DRX active time) in subframes in which it can receive an uplink retransmission grant on the PDCCH, i.e., every 8 ms after the first uplink transmission, until the maximum number of retransmissions is reached. Based on the above, the minimum active time is a fixed length equal to the on duration, and the maximum active time is variable, for example, depending on the activity of the PDCCH.

[0055] The definition of Active Time in the 5G NR standard is given in section 5.7 of Non-Patent Document 7 as follows:

[0056] [Table 3]

[0057] A "DRX period" or "DRX off period" is a period of a downlink subframe during which the UE can skip receiving the downlink channel for battery saving purposes, i.e., there is no need to monitor the downlink channel. The DRX operation provides the mobile terminal with the opportunity to repeatedly deactivate the radio circuitry (according to the currently active DRX period) to save power. Whether the UE actually stays in DRX (i.e., is inactive) during the DRX period can be determined by the UE. For example, the UE may perform inter-frequency measurements that cannot normally be performed during an On-Duration and therefore need to be performed at another time, e.g., during the DRX off time.

[0058] To satisfy the conflicting requirements, two DRX cycles (short and long) can be configured for each UE. The short DRX cycle is optional; that is, only the long DRX cycle can be used. The transition between the short DRX cycle, the long DRX cycle, and continuous reception is controlled either by a timer or an explicit command from the eNodeB. In a sense, the short DRX cycle can be considered as a confirmation period in case a late packet arrives before the UE enters the long DRX cycle. If data arrives at the eNodeB while the UE is in the short DRX cycle, the data is scheduled for transmission in the next on duration, after which the UE resumes continuous reception. On the other hand, if no data arrives at the eNodeB during the short DRX cycle, the UE assumes that packet activity has ended for the time being and enters the long DRX cycle.

[0059] During Active Time, the UE monitors the PDCCH, reports the configured Sounding Reference Signal (SRS), and reports Channel Quality Information (CQI), Precoding Matrix Indicator (PMI), Rank Indicator (RI), and Precoder Type Indication (PTI) on the PUCCH. If the UE is not in Active Time, Type 0 Trigger SRS and CQI, PMI, RI, and PTI on the PUCCH may not be reported. If CQI masking is configured for the UE, reporting of CQI, PMI, RI, and PTI on the PUCCH is limited to On-Duration subframes.

[0060] FIG. 6 discloses an example of DRX operation. The UE checks for scheduling messages (which can also be called downlink / uplink assignments and are indicated, for example, by the C-RNTI (Cell Radio Network Temporary Identifier) ​​on the PDCCH) during the "on duration," which is the same for both the long and short DRX cycles. If a scheduling message is received during the "on duration," the UE starts an "inactivity timer" and continues to monitor the PDCCH every subframe while the inactivity timer is running. During this period, the UE can be considered to be in "continuous reception mode." Each time a scheduling message is received while the inactivity timer is running, the UE restarts the inactivity timer. When the inactivity timer expires, the UE transitions to the short DRX cycle and starts the "short DRX cycle timer" (assuming a short DRX cycle is configured). When the short DRX cycle timer expires, the UE transitions to the long DRX cycle. The short DRX cycle can also be initiated by the DRX MAC control element. The eNB may send a DRX MAC control element at any time to immediately place the UE into a DRX cycle, i.e., a short DRX cycle (if configured as such) or a long DRX cycle (if a short DRX cycle is not configured).

[0061] The basic concept of DRX as described above for LTE also applies to the new 5G NR, with some differences: standardization is underway to define DRX (see section 5.7 of Non-Patent Document 8 entitled "Discontinuous Reception (DRX)").

[0062] It should be noted that the term PDCCH can refer, for example, to a PDCCH with a common search space, or a PDCCH with a UE-specific search space, or even to a Group Common PDCCH (GC-PDCCH) in 5G NR. Thus, conceptually, the 5G-NR DRX mechanism works as shown in Figure 6.

[0063] To summarize the above within the context of improved concepts and aspects for PDCCH monitoring as described below, a UE monitors the PDCCH using timers to control the On-Duration time and the DRX inactive time, respectively, and the UE needs to continue monitoring the PDCCH for DRX operation while the corresponding timer is running.

[0064] RRM (Radio Resource Management) measurements

[0065] Radio Resource Measurement (RRM) encompasses a wide range of techniques and procedures, including power control, scheduling, cell search, cell reselection, and radio link or connection monitoring / measurement (see "Requirements for support for radio resource management" in Non-Patent Document 9). NR 5G RRC supports three states: RRC Idle, RRC Inactive, and RRC Connected (see Section 4.2.1 in Non-Patent Document 10). RRM techniques and reporting mechanisms support UE mobility. RRM-related operations performed by a UE can be broadly divided based on the UE's RRC state, for example, whether the UE is in RRC_IDLE, RRC_INACTIVE, or RRC_CONNECTED.

[0066] For example, for a UE in IDLE state, RRM is involved in cell selection and cell reselection, while for a UE in INACTIVE state, RRM is involved in cell reselection. Cell selection allows the UE to select a suitable cell to camp on to access available services. Cell reselection allows the UE to select a more suitable cell to camp on.

[0067] One important aspect of cell selection and cell reselection is the radio measurements that the UE needs to perform for the serving cell and neighboring cells. Once the UE is camped on a cell, it must periodically search for a better cell according to cell reselection criteria.

[0068] To briefly outline the basics of measurements, a UE (NR device) can perform measurements based on reference signals (e.g., CSI-RS, SS blocks, etc.) and derive measurement results from them, which can be used internally by the UE (e.g., for cell (re)selection in IDLE or INACTIVE) or by other entities, such as a base station for mobility control (e.g., handover in CONNECTED), after receiving some or all of the measurement results in a corresponding measurement report.

[0069] Measurements can be categorized into at least three measurement types. Intra-frequency NR measurement Inter-frequency NR measurement Inter-RAT measurements

[0070] Access to unlicensed spectrum

[0071] To meet the ever-increasing demand for wireless broadband communications, a "Study on NR-based Access to Unlicensed Spectrum" has been conducted (see, for example, Non-Patent Document 11). This study details various regulatory requirements for unlicensed operation in bands below 7 GHz, e.g., the 5 GHz and 6 GHz bands, and discusses different deployment scenarios. Furthermore, it discusses design goals, features, and solutions, and provides performance evaluations.

[0072] This study identifies five possible deployment scenarios (see, for example, Section 6 of Non-Patent Document 11): Scenario A: Carrier aggregation between licensed band NR (PCell) and NR-U (SCell) and / or NR-U SCell, which may have both DL and UL, or DL ​​only; Scenario B: Dual connectivity between licensed band LTE (PCell) and NR-U (PSCell); Scenario C: Standalone NR-U; Scenario D: NR cell where DL is an unlicensed band and UL is a licensed band; and Scenario E: Dual connectivity between licensed band NR (PCell) and NR-U (PSCell).

[0073] Additionally, depending on the region and band, regulatory requirements must be taken into account. Such requirements may include dynamic frequency selection (DFS), transmit power control (TPC), listen-before-talk (LBT), and discontinuous transmission with a limited maximum transmission duration (also known as channel occupancy period (COT)). All of these requirements for different regions and bands in 5 GHz must be addressed at the system design level, recognizing that their scope is to create a single global solution framework for NR-based access to unlicensed spectrum.

[0074] Listen-Before-Talk (LBT) for Unlicensed Spectrum

[0075] The Listen-Before-Talk (LBT) procedure is defined as a mechanism by which a device performs a clear channel assessment (CCA) check before using a channel. According to one exemplary implementation, CCA utilizes at least energy detection to determine the presence or absence of other signals on unlicensed channels to determine whether the channel is occupied or vacant, respectively. For example, European and Japanese regulations mandate the use of LBT in unlicensed bands. Apart from regulatory requirements, such carrier sensing via LBT is considered one method for fair sharing of unlicensed spectrum and, therefore, a key feature for fair and friendly operation in unlicensed spectrum in a single global solution framework.

[0076] In unlicensed spectrum, channel availability is not necessarily guaranteed. Furthermore, some regions, such as Europe and Japan, prohibit continuous transmission and impose restrictions on the maximum duration of a transmission burst (maximum channel occupancy) in unlicensed spectrum. Therefore, discontinuous transmission with a limited maximum transmission duration is a feature for 5G NR.

[0077] According to this European regulation on LBT, devices must observe the channel for a certain minimum time during CCA (e.g., 20 μs for Europe, see Section 4.8.3 of 3GPP TS 12). A channel is considered occupied if the detected energy level exceeds a set CCA threshold (e.g., −73 dBm / MHz for Europe, see Section 4.8.3 of 3GPP TS 12). Conversely, a channel is considered free (unoccupied) if the detected power level is below the set CCA threshold. If a channel is determined to be occupied, the device does not transmit on that channel at this time. Depending on the LBT category (e.g., Category 4 LBT, described below), the transmitter may repeatedly perform CCA, optionally with a backoff period in between, until the channel is confirmed to be free. If the channel is classified as free, the device is allowed to transmit immediately. The maximum transmission duration is limited to facilitate fair resource sharing with other devices operating on the same band.

[0078] Furthermore, the total time that a device transmits on a given carrier without re-evaluating the carrier's availability (i.e., LBT / CCA) is defined as the channel occupation period (COT) (see, for example, section 4.8.3.1 of 3GPP TS 26.1106, 2011). The channel occupation period must be in the range of 1 ms to 10 ms, and the maximum channel occupation period may be, for example, 4 ms as currently defined in Europe.

[0079] Additionally, there is a minimum idle time during which the UE is not allowed to transmit after transmitting on an unlicensed cell, and this minimum idle time is at least 5% of the channel occupancy period. Towards the end of the idle period, the UE may perform a new CCA, etc. Furthermore, CCA may not be required within a certain period after receiving a signal by another entity, e.g., within 16 μs as part of a shared COT. For example, DL-to-UL and UL-to-DL switching within a shared gNB COT does not require LBT.

[0080] To comply with this European Regulation on LBT, 3GPP studies (see section 8.2 of 3GPP Non-Patent Document 11) classify NR-based access to unlicensed spectrum into four different categories:

[0081] Category 1: Immediate transmission after a short switching gap. This is used for the transmitter to transmit immediately after a switching gap inside the COT. The switching gap from receive to transmit is to accommodate the transceiver turnaround time and is no more than 16 μs.

[0082] Category 2: LBT without random backoff. The duration for which the channel is sensed idle before the transmitting entity transmits is deterministic.

[0083] Category 3: LBT with random backoff with a fixed-size contention window. The LBT procedure has the following steps as one of its components: The transmitting entity sets a random number N within the contention window. The size of the contention window is specified by the minimum and maximum values ​​of N. The size of the contention window is fixed. The random number N is used in the LBT procedure to determine the duration for which the channel is sensed as idle before the transmitting entity transmits on the channel.

[0084] Category 4: LBT with random backoff with a variable-sized contention window. The LBT procedure has the following as one of its components: The transmitting entity sets a random number N within the contention window. The size of the contention window is specified by the minimum and maximum values ​​of N. The transmitting entity can change the size of the contention window when setting the random number N. The random number N is used in the LBT procedure to determine the duration for which the channel is sensed as idle before the transmitting entity transmits on the channel.

[0085] Different categories of channel access schemes can be used for transmission in COT and depending on the channel / signal being transmitted.

[0086] As a result, operation for unlicensed radio cells requires that any transmitter performs Listen-Before-Talk as described above, which also applies to the transmission of PDCCH by the base station and may consequently affect PDCCH monitoring by the UE.

[0087] Many different functions operated by the UE (see examples above) involve monitoring the PDCCH and therefore may be affected by an LBT failure of a gNB acquiring an unlicensed cell (which can also be expressed as acquiring unlicensed spectrum of an unlicensed radio cell).

[0088] COT indication

[0089] To improve the coordination between the UE and the gNB in ​​unlicensed operation, the gNB may transmit information about the channel occupancy state in its radio cell, for example, when the gNB acquires an unlicensed channel and / or when the gNB stops occupying an unlicensed channel.

[0090] An example is shown in Figure 8. Here, the gNB performs CCA before symbol #10 in slot n to confirm that the channel is free. Therefore, if there is a UE configured to monitor the PDCCH at symbol #10, the gNB can immediately acquire the channel and transmit a PDCCH message at symbol #10 to schedule UE data. Meanwhile, to ensure that other unscheduled UEs are aware that the gNB has acquired the channel, the gNB can transmit a COT indication, e.g., repeated every slot starting from the next slot boundary. Such repetition of the COT indication is advantageous for two reasons. First, it can improve reliability. If a UE misses one COT indication, the UE can still have another opportunity to receive such an indication. Second, such repetition is also useful when the UE wakes up in the middle of a COT for DRX operation. Different UEs may have different DRX cycles, so the UEs may wake up at different times.

[0091] Although the complete set of information to be carried in the COT indication has not yet been concluded by 3GPP, two agreed-to-be-included pieces of information are relevant to the present invention and are discussed herein: the COT duration bit field and the slot format indication (SFI) bit field. Note that it is not necessary that both fields must be in the COT indication; either one is sufficient. Illustratively, the presence of the fields is configurable by RRC signaling, as agreed upon by 3GPP.

[0092] The COT duration bit field defines where the COT ends in the time domain, and the SFI bit field defines which symbols are downlink, uplink, and flexible, respectively. The SFI bit field can also be used to indicate whether a slot is an "end-of-COT" slot or an "out-of-COT" slot.

[0093] 3GPP has not yet resolved how the COT duration and SFI indications within the COT indication can be updated. One option is that once the gNB acquires the channel, it must determine the COT duration and the SFI for the entire duration of the COT, and updates or changes are not allowed. In this sense, multiple transmissions of the COT indication within the COT, as shown in Figure 8, will carry the same information of the COT duration and SFI.

[0094] Another option, which provides more flexibility in terms of resource utilization, is to allow the COT duration and SFI to be dynamically updated within the same COT. In this way, the gNB does not need to plan the maximum COT duration and corresponding SFI at the start of channel acquisition. The gNB can plan one or several slots ahead and later decide when to extend the COT to better adapt to traffic fluctuations. For example, in FIG. 8, in slot n+1, the gNB sends a COT indication that indicates only the SFI for three slots starting from the current slot, but not the COT duration, as follows: DDDDDDDDDDDDDD;DDDDDDDDDDDDDD;DDDDDDDDDDDDDD; In slot n+2, the COT indication again indicates three slots starting from the current slot n+2 as follows: DDDDDDDDDDDDDD;DDDDDDDDDDDDDD;FUUUUUUUUUUUUU; Note that the SFI for slot n+2 and slot n+3 remains the same as indicated previously, only the SFI for slot n+4 (the new slot) is updated.

[0095] The gNB can maintain such overlapping indications to extend the COT as needed, as long as it meets the maximum allowed COT duration. Once the gNB determines, for example, at slot n+3, that slot n+5 is the last slot of the current COT, the gNB can indicate that the third slot from the current slot is the end of the COT.

[0096] Control Information - Search Space Set

[0097] PDCCH monitoring is performed by the UE to identify and receive information directed to the UE, such as control information and user traffic (e.g., DCI on the PDCCH and user data on the PDSCH indicated by the PDCCH).

[0098] Control information in the downlink, which can be called Downlink Control Information (DCI), has essentially the same purpose in 5G NR as DCI in LTE. That is, it is a special set of control information that, for example, schedules a downlink data channel (e.g., PDSCH) or an uplink data channel (e.g., PUSCH). There are several different DCI formats already defined in 5G NR (see 3GPP TS 2.0, 2013, section 7.3.1). An overview is given in the following table:

[0099] [Table 4]

[0100] In 5G NR, the PDCCH is transmitted in a radio resource region called the control resource set (CORESET). In LTE, the concept of a CORESET does not explicitly exist. Instead, the PDCCH in LTE uses the entire carrier bandwidth in the first one to three OFDM symbols (four in the narrowest case). In contrast, the CORESET in NR can occur anywhere within a slot and within the frequency range of the carrier, except that a UE is not expected to process a CORESET outside its active bandwidth part (BWP).

[0101] Thus, the UE monitors a set of PDCCH candidates in one or more CORESETs on the active DL BWP on each activated serving cell configured for PDCCH monitoring using the corresponding search space set, where monitoring means decoding each PDCCH candidate according to the monitored DCI format, e.g., as defined in clauses 10 and 11 of 3GPP TS 23.210.

[0102] In short, a search space may have multiple PDCCH candidates associated with the same aggregation level (e.g., the PDCCH candidates differ in terms of the DCI format they monitor). A search space set, in turn, may have multiple search spaces with different aggregation levels but associated with the same CORESET. Unlike LTE, as described above, when the control channel spans the entire carrier bandwidth, the bandwidth of the CORESET can be configured, for example, within the active DL frequency bandwidth portion (BWP). In other words, the CORESET configuration defines the frequency resources for the search space set and, therefore, for the configured PDCCH candidates of the search spaces within the set. The CORESET configuration also defines the duration of the search space set, which may have a length of one to three OFDM symbols. Meanwhile, the start time is configured by the search space set configuration itself, e.g., at which OFDM symbol of this search space set configuration the UE starts monitoring the PDCCHs of the search spaces of that set. In combination, the search space set configuration and the CORESET configuration provide a clear definition in frequency and time domain for the UE's PDCCH monitoring requirements. Both the CORESET configuration and the search space set configuration can be done semi-statically by RRC signaling.

[0103] The first CORESET (CORESET 0) is provided by a master information block (MIB) as part of the initial bandwidth portion configuration so that the UE can receive the remaining system information and additional configuration information from the network. After connection setup, the UE can be configured with multiple CORESETs using RRC signaling.

[0104] In NR, flexible slot formats can be configured for a UE by cell-specific and / or UE-specific higher layer signaling in a semi-static downlink / uplink allocation scheme, or by dynamic signaling by DCI format 2_0 in the group-common PDCCH (GC-PDCCH). When dynamic signaling is configured, the UE monitors the GC-PDCCH (DCI format 2_0) which carries a dynamic slot format indication (SFI).

[0105] For unlicensed operation, as already concluded in the completion of a study item (see Non-Patent Document 11), in addition to the functionality provided by DCI format 2_0 in Rel-15 NR, indication of the COT structure in the time domain has been confirmed to be beneficial. Thus, NR-U UEs can obtain the COT structure by decoding DCI format 2_0.

[0106] Switching Search Space Set Groups

[0107] 3GPP is discussing the concept of configuring at least two groups of search space sets (abbreviated as SSS or SS set) for monitoring the PDCCH. This new concept may be particularly useful for operation in unlicensed radio spectrum, where a gNB must first acquire a channel before it can subsequently be allowed to transmit the PDCCH.

[0108] For example, different SSS groups may require a UE to monitor the PDCCH until and / or for how long during one slot. This is exemplarily shown in FIG. 9. As can be seen from the figure, two different groups of search space sets are configured, where the SS set configuration for group 1 requires PDCCH monitoring at a granularity of, for example, every seventh OFDM symbol (see also the minislot granularity of every second OFDM symbol in slot n in FIG. 10), and the SS set configuration for group 2 requires PDCCH monitoring at a slot granularity (here, for example, the first two OFDM symbols of each slot). The UE is required to monitor at least the search space of the currently active SSS group. Furthermore, there may be a search space set (e.g., a common search space set) that is not part of a configured group and will always be monitored by the UE regardless of the SSS indication.

[0109] Each group may have different search space sets, and one search space set may be part of more than one SSS group.

[0110] According to one aspect of the present concepts, the UE may be configured to switch groups based on at least the following alternatives:

[0111] A first alternative includes implicit configuration by the UE detecting, for example, a DL burst, a DM-RS (Demodulation Reference Signal), or a wideband DM-RS (WB-DM-RS), or a GC-PDCCH and / or a PDCCH, and / or implicit configuration based on information about the COT structure. Here, exemplarily, it is assumed that the UE derives the corresponding SSS group from the COT status of the gNB, e.g., if the UE is within the COT of the gNB, the UE uses one specific SSS group, and if outside, the UE uses another specific SSS group. The start of the COT can be derived by the UE, for example, from explicit information (e.g., see the COT indication above) or implicitly from detection of a downlink transmission, such as one or more of the above enumeration (DL burst, DM-RS, GC-PDCCH, PDCCH). Alternatively, the end of the COT can be derived by the UE, for example, from the COT duration indication bit field in the GC-PDCCH (using DCI format 2_0) or from the SFI bit field in the GC-PDCCH (using DCI format 2_0).

[0112] A second alternative for instructing the UE to switch to a specific SSS group includes an explicit instruction, such as a bit field in the GC-PDCCH and / or PDCCH, that indicates the SSS group index the UE should monitor. If the SSS group index differs from the one currently in use, the UE knows that it needs to switch SSS groups, for example, starting at the next slot boundary. This allows the gNB to have full control over the SSS group used by the UE. For example, the gNB may decide to switch SSS groups without having to cross a COT boundary (e.g., inside or outside the COT).

[0113] FIG. 10 illustrates an exemplary implementation of SSS group switching when using implicit indication based on COT status. As can be seen from FIG. 10, it is assumed that SSS group 1 (notably, group 1 is monitored every two symbols, which differs from the example shown in FIG. 9) is used when outside the COT, and SSS group 2 is used when inside the COT. It is assumed, for example, that the UE knows the COT status at the gNB, for example, based on the COT status indication received in slot n. Optionally, the COT status indication may also indicate the COT duration, such that the UE already knows that the gNB's channel occupation ends at the 9th OFDM symbol of slot n+5.

[0114] In the above example, before the COT, the UE monitors the PDCCH according to the SSS group 1 configuration (here, for example, with minislot granularity), which can increase channel accessibility.

[0115] After the COT is confirmed, starting from the next slot boundary, PDCCH monitoring is switched to Group 2 (i.e., to slot granularity monitoring), which can reduce the control overhead during channel occupancy periods.

[0116] After the COT ends, PDCCH monitoring returns to SSS Group 1 at the next slot boundary.

[0117] Although only two different SSS groups are mentioned above, a UE may be configured with more than two SSS groups. For example, it may be advantageous to provide more than two SSS groups for wideband operation of the UE, such that different SSS groups correspond to different combinations of LBT-passed LBT bandwidths. Another scenario in which more than two SSS groups may be useful assumes that SSS group switching occurs pursuant to explicit instructions from the gNB, so that the gNB has more flexibility to apply the most appropriate group of search space sets to the UE.

[0118] 3GPP has not yet reached a final agreement on a standardized way of instructing a UE to switch SSS groups, so the above alternatives are merely examples, and other ways of configuring a UE to switch SSS groups may be possible as well.

[0119] Furthermore, many details of how to implement such switching between different groups of search space sets have yet to be worked out.

[0120] Therefore, the inventors have identified the possibility of completing and / or improving the mechanism for switching between different groups of search space sets for use in monitoring the PDCCH.

[0121] The UE performs the PDCCH monitoring function as described above, which involves switching between different SSS groups.

[0122] In addition, however, the UE performs a DRX function that alternates between monitoring periods during which the UE monitors the PDCCH and non-monitoring periods during which the UE is allowed to sleep and does not monitor the PDCCH. Other functions may also be performed by the UE that generate such non-monitoring periods during which the UE does not monitor the PDCCH. For example, the UE may be configured to perform radio measurements, but while performing the radio measurements, the UE may not be able to monitor the PDCCH (e.g., when the reference signal for the radio measurements is outside the UE's active BWP, in which case a measurement gap during which the UE does not monitor the PDCCH is required). As another example, the UE may perform uplink transmissions, and during this period, the UE may not be able to monitor the PDCCH.

[0123] However, SSS group switching relies on the UE monitoring the PDCCH, either because an explicit indication is received via the (GC-)PDCCH, or implicitly because the UE derives the gNB's COT state from downlink transmissions via the (GC)-PDCCH (see the discussion above and current understanding in 3GPP). Therefore, during and immediately after such non-monitoring periods, the UE does not know which SSS group it is supposed to use. Such undefined UE behavior should be avoided.

[0124] Such undefined UE behavior is illustrated in Figure 11. As exemplarily assumed in Figure 11, the UE is performing a PDCCH or GC-PDCCH monitoring function based on SSS group 2 and changes to SSS group 1 in slot n+1. To this end, the gNB may send an explicit instruction for the UE to switch to SSS group 1 using the PDCCH or GC-PDCCH in slot n (see the "Switch to Group 1" arrow). The UE is in DRX active time and therefore can monitor the PDCCH or GC-PDCCH and receive the instruction.

[0125] The UE enters a sleep period (which may also be referred to as a non-monitoring period or monitoring gap, for example) having slots n+3 to n+6 according to the DRX cycle. During this period, the PDCCH or GC-PDCCH does not need to be monitored by the UE for power saving purposes. During the monitoring gap, the UE does not know whether it has missed a further SSS group switch indication, especially if the GC-PDCCH indicates a switch to a group of UEs configured with different DRX cycles (or if an explicit switch indication is sent by the gNB during some other non-monitoring period of the UE that is not known to the gNB). Thus, the UE does not know which SSS group it is supposed to use when it exits the non-monitoring period. For example, as shown in Figure 11, the gNB transmits a further indication (e.g., using the GC-PDCCH to the UE's group) to switch back to SSS group 2 in one OFDM symbol in slot n+4. The UE shown in Figure 11 would miss such an indication in DRX OFF. Therefore, the UE's behavior regarding which SSS group to use for PDCCH monitoring is undefined. If the indication is transmitted via a UE-specific PDCCH, there is still a chance that the PDCCH will not be detected by the UE, depending on the channel conditions. Therefore, misalignment of SSS groups between the gNB and the UE may occur. In FIG. 11, for example, it is assumed that the UE continues to use the last SSS group used before the monitoring gap (i.e., SSS group 1). However, the gNB may assume that the UE is using SSS group 2, which it indicated during the monitoring gap, and therefore transmit a further SSS group switching indication in the OFDM symbol of slot n+9, which is not actually monitored by the UE. It would be beneficial to be able to limit potential misalignment to within one DRX period. For example, there is a mechanism to periodically reset the SSS group usage.

[0126] Another problematic scenario is described below with reference to FIG. 12. Similar to the scenario exemplarily assumed for FIG. 11, a monitoring gap occurs due to a DRX function operated by the UE. Instead of sending an explicit instruction "switch to group 1" (see FIG. 11), the gNB may implicitly cause the UE to switch to group 1 because SSS group switching by the UE follows the gNB's COT state (see also the discussion of FIG. 10). In the particular exemplary scenario of FIG. 12, assume that the gNB acquires an unlicensed channel at the very beginning of slot n. The UE may learn of the channel occupancy, for example, via the corresponding COT state instruction received via the PDCCH in the first or second OFDM symbol of slot n+1 (or by other means, e.g., via DL burst detection, DM-RS detection, or WB-DM-RS detection). Therefore, the UE switches to SSS group 1 at the next slot boundary (i.e., here, at slot n+1).

[0127] During monitoring gaps (here due to the DRX function), the UE cannot stay updated about the gNB's channel occupancy status. Therefore, the UE cannot distinguish between the two gNB COT state cases shown at the bottom of Figure 12. In Case 1, the gNB continues to occupy the unlicensed channel during the monitoring gap, and in Case 2, the gNB stops occupying the unlicensed channel during the monitoring gap. Therefore, when the UE becomes active again after the monitoring gap, it does not know which SSS group to use because it does not know whether it is inside or outside the channel occupancy by the gNB. Such undefined UE behavior is disadvantageous.

[0128] As a possible solution, the implementation of Figure 12 simply assumes that the UE continues to use the SSS group that was in use by the UE immediately before entering the non-monitoring time gap. However, this may not be ideal because the previous SSS group may not have been intended by the gNB to be used by the UE. For example, if the gNB no longer occupies the unlicensed channel when the UE exits the non-monitoring period, the UE should use SSS group 2.

[0129] In response to this, the inventors have identified the possibility of improving the search space set group switching performed by the UE, specifically the possibility of avoiding undefined and adverse UE behavior. Improving the SSS group switching procedure may facilitate overcoming one or more of the problems mentioned above.

[0130] UEs, base stations, and procedures that meet these needs are described below for new radio access technologies envisioned for 5G mobile communication systems, but may also be used in LTE mobile communication systems. Various implementations and modifications are also described. The following disclosure has been facilitated by, and may be based, for example, at least in part on, the above discussion and discoveries.

[0131] In general, it should be noted that many assumptions have been made herein to allow for a clear and understandable explanation of the principles underlying the present disclosure. However, these assumptions should be understood as merely examples made herein for illustrative purposes, without limiting the scope of the present disclosure. Those skilled in the art will recognize that the principles of the following disclosure and claims can be applied to a variety of scenarios and in ways not explicitly described herein.

[0132] Furthermore, some of the terms used below, such as procedures, entities, and layers, are closely related to those used in the LTE / LTE-A system or in the current 3GPP 5G standardization, even though the specific terms used in the context of new radio access technologies for upcoming 3GPP 5G communication systems have not yet been fully determined or may eventually change. Therefore, the terms may change in the future without affecting the functionality of the embodiments. Therefore, those skilled in the art will recognize that the embodiments and their scope of protection should not be limited to the specific terms illustratively used in this specification due to the lack of other more recent or finally agreed-upon terms, but should be more broadly understood in terms of the functions and concepts underlying the functions and principles of the present disclosure.

[0133] For example, a mobile station or mobile node or user terminal or user equipment (UE) is a physical entity in a communication network. A node may have several functional entities. A functional entity refers to a software or hardware module that implements and / or provides a given set of functions to other functional entities of the same or other nodes or networks. A node may have one or more interfaces that connect the node to communication facilities or media that enable the node's communications. Similarly, a network entity may have logical interfaces that connect functional entities to communication facilities or media that enable communication with other functional entities or corresponding nodes.

[0134] As used herein, the term "base station" or "radio base station" refers to a physical entity in a communication network. Similar to a mobile station, a base station may have several functional entities. A functional entity refers to a software or hardware module that implements and / or provides a set of functions to other functional entities of the same or other nodes or networks. The physical entity performs several control tasks for communication devices, including one or more scheduling and configuration tasks. It should also be noted that base station functions and communication device functions may be integrated within a single device. For example, a mobile terminal may also implement the functions of a base station for other terminals. The term used in LTE is eNB (or eNodeB), while the term currently used in 5G NR is gNB.

[0135] 13 shows a general and simplified exemplary block diagram of a user equipment (also called a communication device) and a scheduling device (here illustratively assumed to be located in a base station, e.g., an eLTE eNB (alternatively called an ng-eNB) or a 5G NR gNB). The UE and eNB / gNB communicate with each other over a (radio) physical channel using their respective transceivers.

[0136] A communication device may have a transceiver and a processing circuit. The transceiver, in turn, may have a receiver and a transmitter and / or function as both a receiver and a transmitter. The processing circuit may be one or more pieces of hardware, such as one or more processors or any LSI. Between the transceiver and the processing circuit, there is an input / output point (or node) through which the processing circuit controls the transceiver during operation, i.e., controls the receiver and / or transmitter, and exchanges receive / transmit data. The transceiver may include an RF (radio frequency) front, including one or more antennas, amplifiers, RF modulators / demodulators, etc., as a transmitter and receiver. The processing circuit may implement control tasks, such as controlling the transceiver to transmit user data and control data provided by the processing circuit and / or to receive user data and control data that are further processed by the processing circuit. The processing circuit may also be responsible for performing other processes, such as judgment, decision, calculation, measurement, etc. The transmitter may be responsible for performing the transmitting process and other processes related thereto. The receiver may be responsible for performing the receiving process and other processes related thereto (eg, monitoring the channel, etc.).

[0137] In the following, an improved SSS group switching procedure for monitoring the PDCCH is described.

[0138] Figure 14 shows a simplified exemplary UE structure according to one solution for improved SSS group switching, which may be implemented based on the general UE structure described in connection with Figure 13. The various structural elements of the UE shown in this figure may be interconnected with each other, e.g., using corresponding input / output nodes (not shown), e.g., to exchange control and user data and other signals. The UE may include additional structural elements, which are not shown for purposes of illustration.

[0139] As can be seen from FIG. 14, the UE may include a downlink control channel monitoring function circuit and a search space set group determination circuit.

[0140] Thus, in this case, as will become apparent from the disclosure below, the processing circuitry may be illustratively configured to at least partially perform one or more of: operating a monitoring function involving monitoring a downlink control channel; determining one of a plurality of search space set groups; performing a DRX function; etc.

[0141] Thus, the receiver may be exemplarily configured to at least partially perform one or more of receiving an indication of said one group of search space sets, detecting signals in the downlink, receiving information from a base station regarding channel occupancy status of the unlicensed spectrum of the radio cell, etc.

[0142] Thus, the transmitter may illustratively be configured to at least partially perform one or more of: performing uplink transmissions, etc.

[0143] One solution, which will be disclosed in more detail below, is implemented by a UE including: a processor of the UE that operates a monitoring function involving monitoring a downlink control channel of an unlicensed radio cell based on one of a plurality of groups of search space sets, the unlicensed radio cell being controlled by a base station operating in an unlicensed spectrum and communicating with the user equipment, and one of the plurality of groups of search space sets being configured to be a default group of search space sets; the processor determines one of the plurality of search space set groups for performing the monitoring function in response to the downlink control channel; the monitoring function is not performed during a non-monitoring period; and the processor determines to perform the monitoring function based on the default group of search space sets when performing the monitoring function after the non-monitoring period.

[0144] A corresponding sequence diagram for an exemplary UE behavior along the above lines is shown in FIG. 15. As can be seen from the diagram, to operate the monitoring function, the UE must first determine the corresponding group of SSSs according to the downlink control channel (e.g., explicit information obtainable from the downlink control channel or information that can be implicitly derived from the downlink control channel). Then, the UE operates the monitoring function based on the determined SSS group. The last step of the sequence diagram reflects a special case of the present solution in which the UE determines to use the default SSS group to perform the monitoring function, i.e., the case in which the monitoring function is performed after a non-monitoring period in which the monitoring function was not performed.

[0145] Correspondingly, a UE is provided that performs an exemplary improved switching procedure for switching between groups of search space sets available for use when monitoring a downlink control channel.

[0146] The drawbacks identified with prior art solutions are overcome because the UE behavior is defined when the UE does not know which SSS group to use for non-monitoring periods. This advantage can be obtained independently of how SSS group switching is controlled in the UE: by explicit instruction from the gNB or by implicit instruction (e.g., according to the gNB's COT state).

[0147] For example, first, assuming that switching SSS groups depends on an explicit instruction from the gNB, the UE cannot determine whether an explicit instruction to switch to an SSS group has been sent by the gNB during a non-monitoring period that is not expected by the NB (e.g., an explicit instruction is carried by a GC-PDCCH targeting a group of UEs, but a UE is in a non-monitoring period for radio measurements, or for uplink transmissions by the UE, or for sidelink transmissions by the UE).

[0148] Furthermore, assuming that the SSS group switching is subject to the COT state of the gNB for the unlicensed radio cell, the UE may not be able to derive the COT state at the end of the non-monitoring period during the non-monitoring period. Therefore, if the UE determines that the COT state at the time when the non-monitoring period should be exited and the execution of the monitoring function should be resumed is unknown, the UE may resort to a default SSS group. On the other hand, if the UE determines that the COT state at the time when the non-monitoring period should be exited and the execution of the monitoring function should be resumed is known, the UE may determine the corresponding SSS group in the usual way (here, for example, based on the COT state).

[0149] In either case, during the non-monitoring period, the UE was unable to obtain information regarding which SSS group to use when exiting the non-monitoring period and entering the subsequent monitoring period. By using the default SSS group when returning to the monitoring period after the non-monitoring period, the UE can determine the default SSS group with which to perform the monitoring function. Thus, the default SSS group is used regardless of the last SSS group used by the UE and regardless of the SSS group the UE would use in the hypothetical case where the non-monitoring period had not occurred.

[0150] The above solution may provide, for example, the following exception to the above: Even if the UE determines that the COT state is known at the time it needs to exit the non-monitoring period and resume performing the monitoring function, the UE may still fall back on the default SSS group, i.e., if the subsequent monitoring period is caused by an uplink transmission performed by the UE.

[0151] Thus, according to the above solution, the UE resumes performing the monitoring function based on the default SSS group when it ends the non-monitoring period, and the UE may then eventually switch from the default SSS group for the monitoring function, for example, when it receives a new switching instruction from the base station, or when the UE can again implicitly determine the correct SSS group (e.g., depending on whether the UE is in a channel occupation period of the gNB).

[0152] The non-monitoring periods mentioned in the above solutions may arise due to various parallel operations of the UE, such as DRX function, or radio measurement function, or transmission function, which alternate sleep periods (non-monitoring times) with active periods.

[0153] If the UE is operating with DRX functionality and the SSS group switch indication is transmitted via a UE-specific PDCCH, the gNB may avoid transmitting such a switch indication during non-active time because it is aware of the UE's DRX cycle. Therefore, it should be clear to the UE which group should be used in most cases. Nevertheless, there is still a possibility that the UE-specific PDCCH carrying the switch indication may not be correctly decoded by the UE. If this occurs, there will be a different understanding between the UE and the gNB regarding the SSS group in use. To recover from such an error case, a default SSS group can be used by both the UE and the gNB at the start of each DRX cycle. With such a mechanism, potential misalignment is limited to one DRX cycle in the worst case.

[0154] The default SSS group introduced by the above solution can be configured by the base station or can be hard-coded in the UE (e.g., in the chip). The default SSS group can have a different search space set. In one example implementation, the default SSS group has fine monitoring granularity, which provides distributed monitoring opportunities for the UE as slots are reached early (e.g., see the SSS group in slot n in FIG. 10 or SSS group 1 in FIG. 11).

[0155] The base station is also involved in the improved SSS group switching procedure described above. Correspondingly, the present solution also provides the following improved base station. Figure 16 shows a simplified exemplary base station structure according to one solution of the improved SSS group switching procedure, which can be implemented based on the general base station structure described in connection with Figure 13. Figure 17 shows a corresponding sequence diagram for the exemplary base station behavior along the above lines.

[0156] Such a base station includes: a processor of the base station performs a control information transmission function involving transmitting control information to a user equipment (UE) on a downlink control channel of an unlicensed radio cell based on one of a plurality of groups of search space sets; the base station controls an unlicensed radio cell operating in an unlicensed spectrum; one of the plurality of groups of search space sets is configured to be a default group of search space sets; the processor determines one of the plurality of search space set groups for performing the control information transmission function; the control information transmission function is not performed during a non-monitoring period of the UE; the UE does not perform a monitoring function involving monitoring the downlink control channel during the non-monitoring period; and the processor determines to perform the control information transmission function based on the default group of search space sets when performing the control information transmission function after the non-monitoring period.

[0157] Such a base station therefore operates in synchronization with the improved UE with regard to transmitting control information over the downlink control channel when the UE actually performs the monitoring function. To this end, the base station may determine which SSS group to use in a corresponding manner with the UE. For example, both the UE and the base station may implicitly derive the SSS group to use from the COT state of the gNB. This may include the same evaluation based on the UE's possible knowledge of the COT state of the gNB when ending the non-monitoring period, as described in detail above and below with respect to the UE.

[0158] In another example, the base station may autonomously determine which SSS group to use (e.g., among the SSS groups for which the UE is configured) and then provide an explicit indication of this determined SSS group to the UE via a downlink control channel using a control information transmission function.

[0159] Furthermore, to enable synchronization, the base station determines the non-monitoring periods of the UE, e.g., periods during which the UE does not perform the corresponding monitoring function of the downlink control channel. In one exemplary implementation, the base station is aware of the DRX function operated by the UE and, therefore, the alternating sleep and active periods defined by the DRX function. Furthermore, the base station is typically also aware of the periods during which the UE performs uplink or sidelink transmissions, and therefore, the non-monitoring periods resulting from these UE transmissions. Finally, some or all of the radio measurement gaps used by the UE to perform radio measurements are also known to the gNB, since the gNB configures the same.

[0160] In one exemplary implementation of the base station, a default SSS group can be determined by the base station, and the base station can then inform the UE about the default SSS group so that the UE has the necessary configuration to perform monitoring functions based on various SSS groups.

[0161] Figure 18 shows one example implementation of SSS group switching according to the above solutions of Figures 14 to 17. The assumptions made for Figure 18 are exactly the same as those made in relation to Figure 11. In addition, SSS group 1 is defined as the default SSS group. As is clear from Figure 18, when the UE ends the non-monitoring period and resumes the downlink control channel monitoring function in slot n+7, it determines to use the default SSS group (here, SSS group 1) for the monitoring function, regardless of whether it missed a switching instruction from the base station and regardless of the SSS group it previously used (however, in this particular example of Figure 18, the default SSS group and the SSS group previously used are the same).

[0162] The default SSS group is used to perform monitoring functions at least until the UE is instructed to switch to another specific SSS group. Here, assuming by way of example that the UE can receive a switching instruction in slot n+8, it continues to use the default SSS group in slots n+7 and n+8. Thus, at the next slot n+9, the UE may perform a determination of the corresponding SSS group 1 to use in the subsequent slot n+9, and so on. In the exemplary scenario of FIG. 18, it is assumed that the UE continues to use SSS group 1 for monitoring functions because the UE is following an explicit switching instruction from the gNB, not because it is the default SSS group.

[0163] Figure 19 shows another exemplary implementation of SSS group switching according to the above solutions of Figures 14 to 17. The assumptions made for Figure 19 are exactly the same as those made in relation to Figure 12. In addition, SSS group 1 is defined as the default SSS group. As is clear from Figure 19, when the UE ends the non-monitoring period and resumes the downlink control channel monitoring function in slot n+7, it determines to use default SSS group 1 for the monitoring function, regardless of the base station's COT status and regardless of the SSS group previously used (however, in this particular example of Figure 19, the default SSS group and the SSS group previously used are the same).

[0164] This applies to both cases of the COT state shown: when the COT state spans a monitoring gap (case 1), and when the COT ends during the monitoring gap.

[0165] The default SSS group is used to perform monitoring functions at least in slot n+7. Thus, if it is illustratively assumed that the UE is able to derive the actual COT state of the gNB during the active time of slot n+7, the UE may perform a determination of the corresponding SSS group to use in subsequent slots n+8, n+9, etc. In the exemplary scenario of FIG. 19, it is illustratively assumed that the UE continues to use SSS group 1 for monitoring functions because the UE can determine that the gNB has acquired unlicensed channels for slots n+8 and n+9, not because it is the default SSS group.

[0166] The above solution, as well as variations and further improvements thereof, are described in more detail below. For the following description of the improved SSS group switching procedure and downlink control channel monitoring procedure solution, some basic assumptions are made for illustrative purposes. Some of these assumptions are based on an exemplary 3GPP 5G NR standard-compliant implementation. While some descriptions below are primarily given with respect to a 5G NR communication system, the solution is also applicable to an LTE or LTE-A communication system.

[0167] For example, it is exemplarily assumed that the UE has already been configured with all necessary information to be able to perform the downlink control channel (PDCCH) monitoring function, which may include configuration for different search space sets and different groups of search space sets. In the following, for ease of explanation, it is exemplarily assumed that only two different groups of search space sets are configured on the UE.

[0168] In one exemplary implementation, the configuration of the search space sets can be based on mechanisms already defined in the 5G NR standard (see the discussion above), such as using RRC configuration / reconfiguration messages. Furthermore, the configuration of different groups of SSSs can illustratively rely on existing mechanisms in the 5G NR standard, such as RRC configuration / reconfiguration messages. One example of such a configuration is that each search space set is associated with a group ID. Consequently, search space sets with the same group ID belong to the same group. In such an exemplary implementation, the gNB has full control over which search space sets are included in which of the two groups, including, for example, how many PDCCH monitoring occasions a UE has per slot, and at which OFDM symbols per slot the PDCCH monitoring occasions occur. For example, the two groups can be defined to have the search space sets shown in FIG. 10 or FIG. 11.

[0169] In wideband operation where one carrier includes multiple LBT bandwidths, it may be necessary to configure three or more groups. For example, considering the inside of the COT, multiple search space set groups are configured to cover different combinations of LBT bandwidths that have passed the LBT. Then, depending on the actual LBT results, one of the groups can be activated for PDCCH monitoring within the COT.

[0170] According to one example implementation, the gNB may also determine a default SSS group. This may be, for example, one of two SSS groups. For example, SSS group 1 (see FIG. 10 or FIG. 11) may be defined as the default SSS group. SSS group 1 provides distributed monitoring opportunities within each slot, rather than providing a centralized monitoring opportunity at the beginning of each slot (e.g., as in SSS group 2 in FIGS. 10 and 11). Defining SSS group 1 as the default SSS group facilitates reducing the delay in reaching the UE immediately following a non-monitoring period.

[0171] On the other hand, SSS group 2 can also be defined by the gNB as the default SSS group when, for example, the gNB operates as a fixed frame based equipment (FBE) and attempts to acquire the channel only at the beginning of a slot. In such a case, the UE does not need to monitor the PDCCH elsewhere in the slot before checking the COT. Another scenario in which configuring SSS group 2 as the default is useful for some UEs is when these UEs are sensitive to power consumption. In such cases, using a coarser granularity for PDCCH monitoring before checking the COT can save UE power.

[0172] While the above assumes that there is only one default SSS group, certain exemplary implementations of the above improved SSS group switching procedure provide for multiple default SSS groups. For example, in a dual connectivity scenario where a UE is simultaneously connected to different base stations, a different default SSS group can be defined for each base station.

[0173] In one example of configuring a default group, RRC signaling can indicate a specific group ID as the default group. On the other hand, the default SSS group ID can also be fixed by the 3GPP 5G NR specifications so that RRC signaling for the default group ID is not required; for example, the default SSS group is hard-coded in the UE's chip or memory. Nevertheless, the gNB may still have full control over which search space sets are included in which groups. For example, the 3GPP specifications may define the SSS group with ID #0 as the default group (assuming SSS groups are numbered sequentially starting from 0), but which search space sets are included in group #0 is still up to the gNB to configure. In one exemplary 5G NR implementation, dual connectivity is implemented as follows: The UE is connected using two cell groups by a master base station and a secondary base station. The master cell group (MCG) is a group of serving cells associated with the master base station and has a primary cell (PCell) and, optionally, one or more secondary cells (SCells). Furthermore, a secondary cell group (SCG) is a group of serving cells associated with a secondary base station, and has a PCell and optionally one or more SCells. According to current 5G NR implementations, the DRX function is configured and performed per cell group (e.g., per MAC entity). In such a scenario, different default SSS groups can be defined for each cell group. For example, one default SSS group can be defined for the master cell group and other SSS groups can be defined for the secondary cell groups.

[0174] Further, by way of example, it is assumed that the UE is capable of performing the PDCCH monitoring function based on the configured search space sets, and in particular, based on all configured search space sets associated with the SSS group that is currently active.

[0175] It is further assumed that the UE performs other functions in parallel with the PDCCH monitoring function, such as one or more of a DRX function, a radio measurement function, and an uplink transmission function. Each of these functions may cause non-monitoring periods during which the UE does not perform the PDCCH monitoring function. It is also assumed that the UE is configured by the gNB to perform each of these functions, for example, based on mechanisms already defined in the 5G NR standard (see the discussion above).

[0176] Specifically, the DRX function defines different DRX cycles (short and long) using a sleep period and an active period. As described in detail above, the active time is specifically defined in the 3GPP 5G NR standard (see above), and the sleep period is a period during which the UE is not in the active time. The sleep period can be considered as a non-monitoring period during which the PDCCH monitoring function is not performed by the UE.

[0177] For example, a non-monitoring period (also called a monitoring gap) may occur due to two different DRX cycles, e.g., when the UE goes to sleep after the end of the active time in one DRX cycle and then wakes up at the start of the next DRX cycle (see, e.g., Figure 11) (see also the definition of the active time and, e.g., the timers drx-onDurationTimer, drx-InactivityTimer).

[0178] On the other hand, monitoring gaps may also occur between non-consecutive active periods within one DRX cycle. For example, the UE goes to sleep after one active time but then wakes up again to monitor the PDCCH in another active time. This other active time may be related to other reasons, such as the UE waiting for an UL or DL ​​retransmission (see also the definition of the active time and, e.g., the timers drx-RetransmissionTimerDL and drx-RetransmissionTimerUL), or the UE waiting for contention resolution for a random access procedure (see also the definition of the active time and, e.g., the timer ra-contention), or the UE waiting for a scheduling message after sending a scheduling request, or the UE waiting for a scheduling message indicating a new transmission after receiving a random access response message for a contention-free random access procedure, etc.

[0179] Assume that the UE is located in an unlicensed radio cell, for example, as in the scenario discussed in relation to Figure 7. The UE performs PDCCH monitoring functions according to the currently active SSS group.

[0180] For the following explanation of the principles underlying the present invention, it is exemplarily assumed that SSS group switching relies on an implicit instruction, according to which the UE derives the SSS group to use depending on the current channel occupancy state of the unlicensed radio cell by the gNB. Thus, for example, one of the two SSS groups (here, for example, SSS group 1) is associated with a negative gNB COT state (the unlicensed channel is not occupied by the gNB), and the other of the two SSS groups (here, for example, SSS group 2) is associated with a positive gNB COT state (the unlicensed channel is occupied by the gNB).

[0181] Figure 20 illustrates UE behavior with such an exemplary solution. As can be seen, the UE determines whether it knows the gNB COT state at the time it exits the non-monitoring period and enters the monitoring period. If the UE does not know, it may decide to use a default SSS group for the monitoring function. On the other hand, if the UE knows the COT state, it may proceed to determine an SSS group corresponding to this known COT state and operate the PDCCH monitoring function based on the determined SSS group when it exits the non-monitoring period.

[0182] This sequence of events is shown in Figure 21, which shows at the bottom two different case scenarios of gNB channel occupancy and how the corresponding improved SSS group switching works for each case.

[0183] In Case 1, we assume that the information provided by the gNB about the COT allows the UE to determine the COT state at the beginning of slot n+7, i.e., at the end of the non-monitoring period. For example, the gNB would have already provided the UE with the COT duration in slot n+1. Thus, upon knowing the COT state, the UE determines the SSS group associated with the known COT state and then uses the search space set of that SSS group to perform the monitoring function during the Active Time of slots n+7, n+8, ...

[0184] In Case 2, it is assumed that the gNB dynamically determines the COT duration and thereby repeatedly extends the required channel occupancy. Therefore, the gNB repeatedly notifies the UE about the COT status in only the current slot and the next slot. For example, the GC-PDCCH indicates the COT structure for only the current slot and the next slot. In such a scenario, if the gNB determines to end the COT in the next slot, the gNB may provide a corresponding "end of COT" indication via the GC-PDCCH for the current slot. Therefore, when the UE enters the non-monitoring period at slot n+3, the UE cannot know whether the COT has been further extended by the gNB. Therefore, the gNB COT status at the start of slot n+7 is unknown to the UE. As a result, the UE returns to the default SSS group and performs the monitoring function during the active time of slot n+7 based on the search space set for the default SSS group. It is exemplarily assumed that the UE can then determine the SSS group based on the COT state in the normal manner and use this SSS group to determine the COT state during slot n+7 (here, for example, SSS group 1) so as to operate the monitoring function in slot n+8 and slot n+9.

[0185] According to an optional implementation, Figure 20 shows, with dashed lines, an alternative sequence. According to this alternative sequence, even if the gNB COT state at the time of exiting the non-monitoring period is known ("yes" in Figure 20), the UE may still decide to reset to the default SSS group, i.e., if the subsequent monitoring period (when exiting the non-monitoring period) is due to an uplink transmission performed by the UE. For example, this uplink transmission can be scheduled by the gNB after the UE sends a scheduling request to the gNB (see, e.g., Active Time Definition: "a Scheduling Request is sent on PUCCH and is pending ..."), or can be scheduled by the gNB as part of a random access procedure (see, e.g., Active Time Definition: "a PDCCH indicating a new transmission ... is not received after successful reception of a Random Access Response ...").

[0186] Such a case is illustrated in Figure 22. Here, a monitoring gap occurs between two active periods within one DRX cycle, and the additional active period is due to the uplink transmissions that the UE must perform, as described above. As is clear from Figure 22, when ending the non-monitoring period in slot n+4 and slot n+7, the UE knows the COT status in both cases (here, it is assumed, for illustrative purposes, that the gNB notified the UE of the COT duration in slot n). However, in slots n+4 and n+5 of the active period arising in connection with the uplink transmissions performed by the UE, the UE decides to use the default SSS group to perform the PDCCH monitoring function, in line with an optional implementation of the solution according to Figure 20. Meanwhile, in slots n+7, n+8, ..., the UE decides the SSS group according to the known COT status (here, SSS group 1 is used).

[0187] The reason for switching to the default SSS group in active time slots related to uplink transmissions is that the default SSS group provides finer monitoring granularity and can therefore reach the UE earlier for scheduling uplink transmissions.

[0188] Another example improvement related to the new SSS group switching concept being discussed in 3GPP is presented below: This second solution also revolves around the idea of ​​improving the monitoring of the downlink control channel in relation to SSS group switching.

[0189] This second solution is independent of the improved SSS group switching procedure described above, which introduces a default SSS group, and therefore the second solution can operate standalone or in combination with any of the improved SSS group switching procedures and variants described above.

[0190] More specifically, a UE is configured with different search space sets that the UE must monitor to obtain downlink control information from the base station. The search space sets can be UE-specific (e.g., specific to only one UE in a radio cell) or common (e.g., common to all or a group of UEs in a radio cell).

[0191] A search space set is configured to be used to convey particularly important system information, such as system information that facilitates access to a radio cell or system information that provides further scheduling information on how to acquire other system information. For example, a common search space set may be configured for this purpose. According to a second solution, such search space sets conveying particularly important system information should not be affected by SSS group switching, in that the UE monitors these SSSs regardless of the currently active SSS group. This can be achieved by including such important SSSs in all SSS groups. Alternatively, these SSSs can be configured in the UE outside of all SSS groups (i.e., not part of any configured SSS group), but they are monitored by the UE regardless of the currently active / indicated SSS group. In either case, however, the particularly important system information is acquired by the UE regardless of the SSS group currently used for the downlink control channel monitoring function.

[0192] This solution can also be used in the following exemplary 5G NR-compliant communication system: In current 5G NR-compliant communication systems, the above-mentioned particularly important information is conveyed in System Information Block 1 (SIB1) (see also Section 6.2.2 of 3GPP TS 36.2.10: "SIB1 contains information relevant when evaluating if a UE is allowed to access a cell and defines the scheduling of other system information. It also contains radio resource configuration information that is common for all UEs and barring information applied to the unified access control."). SIB1 is transmitted by the gNB in ​​a common search space set according to the parameters set by the Master Information Block (MIB) (see also TS 38.213

[13] , clause 6.2.2): the MIB contains the field pdcch-ConfigSIB1, which "Determines a common Control Resource Set (CORESET), a common search space and necessary PDCCH parameters. If the field ssb-SubcarrierOffset indicates that SIB1 is absent, the field pdcch-ConfigSIB1 indicates the frequency positions where the UE may find SS / PBCH block with SIB1 or the frequency range where the network does not provide SS / PBCH block with SIB1 (see TS 38.213

[13] , clause 13)."The common search space of SIB1 is denoted as Type-0 PDCCH Common Search Space (CSS) (see also clauses 10 and 13 of Non-Patent Document 14).

[0193] Correspondingly, the Type 0 PDCCH common search space is monitored by the UE regardless of the currently active SSS group, e.g., the Type 0 PDCCH common search space is not part of any SSS group and is therefore monitored independently by the UE.

[0194] Another improvement of this solution is presented below. A search space set monitored by a UE is associated with frequency radio resources by a corresponding control resource set (CORESET). A particularly important frequency resource set is CORESET with index 0 because it is associated with important system information (e.g., the particularly important system information described above, e.g., SIB1), but also with other important UE-specific information and parameters possibly carried in the UE-specific search space. According to this improved solution, this important frequency resource set is made mandatory in that it will also be monitored by the UE during sleep periods (e.g., sleep periods provided by a DRX function operated in the UE). For example, the search space set associated with this mandatory frequency resource set (e.g., CORESET#0) is also monitored during DRX-off periods.

[0195] In unlicensed operation, monitoring of COREST#0 and the signal synchronization block is performed within the NR-U DRS (Discovery Reference Signal) window (this window is longer in unlicensed operation than in licensed operation).

[0196] Figure 23 shows one possible exemplary implementation of the above solution. As can be seen from the figure, monitoring of SSBs (e.g., including Primary Synchronization Signals, Secondary Synchronization Signals, and PBCHs (Physical Broadcast Channels)) as well as CORESET#0 is performed by the UE during both DRX active and DRX off times. Therefore, reception of important system information and downlink synchronization are not affected by the DRX sleep function.

[0197] Further Aspects

[0198] According to a first aspect, there is provided a user equipment (UE) having a processor configured to operate a monitoring function involving monitoring a downlink control channel of an unlicensed radio cell based on one of a plurality of groups of search space sets. The unlicensed radio cell is controlled by a base station operating in an unlicensed spectrum and communicating with the user equipment. One of the plurality of groups of search space sets is configured to be a default group of search space sets. The processor determines one of the plurality of search space set groups for performing the monitoring function in response to the downlink control channel. The monitoring function is not performed during a non-monitoring period. When performing the monitoring function after the non-monitoring period, the processor determines to perform the monitoring function based on the default group of search space sets.

[0199] According to a second aspect provided in addition to the first aspect, the non-monitoring period is The sleep period determined by the DRX cycle of the discontinuous reception (DRX) function, the period during which the UE performs radio measurements, and a period during which the UE performs transmission; At least one of the following is true.

[0200] According to a third aspect provided in addition to the first or second aspect, determining the one group of the plurality of search space set groups for the monitoring function in response to the downlink control channel includes, by the processor: an indication of the one group of search space sets obtainable from the downlink control channel; detection of a signal on the downlink control channel, optionally the signal being one or more of a downlink control information message, a downlink data transmission, a downlink reference signal; channel occupancy of the unlicensed spectrum of the unlicensed radio cell by the base station, obtainable from the downlink control channel; The method is based on one or more of the following:

[0201] According to a fourth aspect provided in addition to one of the first to third aspects, a sleep period of a DRX function is defined when the UE is not in an active time. - a monitoring period defined by the DRX cycle, - the period of inactivity before the inactivity timer expires - a period during which the UE is waiting to receive a retransmission of a data packet; - a period of time during which the UE is waiting to retransmit a data packet; - a period during which the UE is waiting for resolution of a random access procedure conflict; - a period during which the UE is waiting to receive a response to a scheduling request sent by the UE; - a period during which the UE waits for a downlink control channel transmission indicating a new transmission after receiving a random access response message of a contention-free random access procedure; is in the active time for at least one of the following periods:

[0202] According to a fifth aspect provided in addition to one of the first to fourth aspects, the default group of search space sets comprises: a configuration message received from the base station controlling the unlicensed radio cell, optionally the configuration message being a Radio Resource Control (RRC) message, or predetermined information of the UE; It is constructed based on one or more of the following: In an optional implementation, the UE is connected to multiple base stations, and one default group of search space sets is configured for each base station.

[0203] According to a sixth aspect provided in addition to one of the first to fifth aspects, the processor determines, in response to the downlink control channel, to perform the monitoring function based on the default group of the search space set until determining another group of the plurality of groups of the search space set.

[0204] According to a seventh aspect provided in addition to one of the first to sixth aspects, when the processor determines to perform the monitoring function based on the default group of search space sets, the processor further considers a channel occupancy state of the unlicensed spectrum of the unlicensed radio cell by the base station, if the channel occupancy state after the non-monitoring period is known to the UE, the processor determines to perform the monitoring function based on a group of search space sets corresponding to the channel occupancy state after the non-monitoring period; if the channel occupancy state after the non-monitoring period is unknown to the UE, the processor determines to perform the monitoring function based on the default group of search space sets; and If the channel occupancy state after the non-monitoring period is known to the UE but a subsequent monitoring period is due to an uplink transmission intended by the UE, the processor determines to perform the monitoring function based on the default group of search space sets.

[0205] According to an eighth aspect provided in addition to one of the first to seventh aspects, the default group of search space sets is a group of search space sets that provide distributed monitoring occasions in a slot. In an optional implementation, the search space set is a set of search spaces, each search space including one or more candidate radio resources of the downlink control channel to monitor.

[0206] According to a ninth aspect provided in addition to any one of the first to eighth aspects, a search space set used to transmit important system information to the UE is compulsorily monitored regardless of which group of search space sets is determined by the processor. In an optional implementation, a search space set associated with a mandatory frequency resource bandwidth is compulsorily monitored by the monitoring function even during the non-monitoring period due to a discontinuous reception (DRX) function. In a further optional implementation, the important system information is system information block 1 of a 5G NR standard communication system, and optionally, the mandatory frequency resource bandwidth is defined as control resource set #0 of the 5G NR standard communication system.

[0207] According to a tenth aspect, there is provided a base station, comprising: a processor of the base station performing a control information transmission function involving transmitting control information to a user equipment (UE) on a downlink control channel of an unlicensed radio cell based on one of a plurality of groups of search space sets; the base station controls an unlicensed radio cell operating in an unlicensed spectrum; one of the plurality of groups of search space sets is configured to be a default group of search space sets; the processor determines one of the plurality of search space set groups for performing the control information transmission function; the control information transmission function is not performed during a non-monitoring period of the UE; the UE does not perform a monitoring function involving monitoring the downlink control channel during the non-monitoring period; and the processor determines to perform the control information transmission function based on the default group of search space sets when performing the control information transmission function after the non-monitoring period.

[0208] According to an eleventh aspect provided in addition to the tenth aspect, the non-monitoring period is The sleep period determined by the DRX cycle of the discontinuous reception (DRX) function, the period during which the UE performs radio measurements, and a period during which the UE performs transmission; At least one of the following is true.

[0209] According to a twelfth aspect provided in addition to the tenth or eleventh aspects, determining the one of the plurality of search space set groups for the control information transmission function is performed by the processor based on a channel occupancy state of the unlicensed spectrum of the unlicensed radio cell by the base station. In an optional implementation, during operation, a transmitter transmits an indication of the determined one of the search space set groups to a UE on a downlink control channel.

[0210] According to a thirteenth aspect provided in addition to one of the tenth to twelfth aspects, the processor determines the default group of search space sets, and a transmitter sends a configuration message to the UE to configure the UE using the determined default group of search space sets.

[0211] According to a fourteenth aspect provided in addition to one of the tenth to thirteenth aspects, when the processor determines to perform the control information transmission function based on the default group of search space sets, the processor further considers a channel occupancy state of the unlicensed spectrum of the unlicensed radio cell by the base station, if the channel occupancy state after the non-monitoring period is known to the UE, the processor determines to perform the control information transmission function based on a group of search space sets corresponding to the channel occupancy state after the non-monitoring period; if the channel occupancy state after the non-monitoring period is unknown to the UE, the processor determines to perform the control information transmission function based on the default group of search space sets; and If the channel occupancy state after the non-monitoring period is known to the UE but the subsequent monitoring period is due to an uplink transmission intended by the UE, the processor determines to perform the control information transmission function based on the default group of search space sets.

[0212] According to a fifteenth aspect, there is provided a method, performed by a user equipment (UE), comprising the steps of: operating a monitoring function involving monitoring a downlink control channel of an unlicensed radio cell based on one of a plurality of groups of a search space set, the unlicensed radio cell being controlled by a base station operating in an unlicensed spectrum and communicating with the user equipment, wherein one of the plurality of groups of search space sets is configured to be a default group of search space sets; determining, in response to the downlink control channel, one of the plurality of search space set groups for performing the monitoring function; The monitoring function is not performed during non-monitoring periods, determining, when to perform the monitoring function after the non-monitoring period, to perform the monitoring function based on the default group of search space sets; A method is provided, comprising:

[0213] Hardware and Software Implementations of the Disclosure

[0214] The present disclosure can be realized by software, hardware, or software in conjunction with hardware. Each functional block described in the above embodiments can be realized, in whole or in part, by an LSI such as an integrated circuit. Furthermore, each process described in each embodiment can be controlled, in whole or in part, by the same LSI or a combination of LSIs. The LSI may be formed as an individual chip, or a single chip may be formed to include some or all of the functional blocks. The LSI may include a data input and a data output connected thereto. Here, LSIs are sometimes referred to as ICs, system LSIs, super LSIs, or ultra LSIs depending on their level of integration. However, technologies for realizing integrated circuits are not limited to LSIs and may be realized using dedicated circuits, general-purpose processors, or dedicated processors. Furthermore, FPGAs (Field Programmable Gate Arrays), which can be programmed after LSI fabrication, or reconfigurable processors, which allow the connections and settings of circuit cells arranged within LSIs to be reconfigured, may also be used. The present disclosure can be realized as digital or analog processing. If future integrated circuit technology replaces LSI as a result of advances in semiconductor technology or other derivative technologies, the functional blocks can be integrated using that future integrated circuit technology. Biotechnology is also applicable.

[0215] The present disclosure may be implemented by any type of apparatus, device, or system having communication capabilities, referred to as a communications apparatus.

[0216] The communication device may have a transceiver and processing / control circuitry. The transceiver may have a receiver and a transmitter and / or function as both a receiver and a transmitter. The transceiver may include an RF (radio frequency) module including an amplifier, an RF modulator / demodulator, etc., and one or more antennas as a transmitter and a receiver.

[0217] Some non-limiting examples of such communication devices include telephones (e.g., mobile phones, smartphones), tablets, personal computers (PCs) (e.g., laptops, desktops, notebooks), cameras (e.g., digital still / video cameras), digital players (digital audio / video players), wearable devices (e.g., wearable cameras, smart watches, tracking devices), game consoles, digital book readers, telehealth / telemedicine devices, vehicles (e.g., automobiles, airplanes, ships) that provide communication capabilities, and various combinations thereof.

[0218] Communications devices are not limited to portable or mobile devices, but may include any type of non-portable or fixed equipment, device, or system, such as, for example, smart home devices (e.g., appliances, lighting, smart meters, control panels), vending machines, or any other "things" in an "Internet of Things" network.

[0219] Communications may include, for example, the exchange of data via cellular systems, wireless LAN systems, satellite systems, and the like, as well as various combinations thereof.

[0220] A communications device may have devices such as controllers or sensors connected to the communications device to perform the communications functions described in this disclosure. For example, a communications device may have a controller or sensor that generates control or data signals used by the communications device to perform the communications functions of the communications device.

[0221] Communications equipment may also include infrastructure facilities, such as base stations, access points, or any other equipment, device, or system that communicates with or controls the equipment in the above non-limiting examples.

[0222] Furthermore, the various embodiments may be implemented by means of software modules, which are executed by a processor or directly in hardware. A combination of software modules and hardware implementations is also possible. The software modules can be stored on any kind of computer-readable storage medium, for example RAM, EPROM, EEPROM, flash memory, registers, hard disks, CD-ROM, DVD, etc. Furthermore, it should be noted that individual features of the different embodiments may also be the subject of other embodiments, individually or in any combination.

[0223] Those skilled in the art will recognize that various changes and / or modifications may be made to the present disclosure as set forth in the specific embodiments, and the present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims

1. A communication device, a processor configured to, during operation, operate a monitoring function that involves monitoring a downlink control channel of an unlicensed radio cell based on one of a plurality of groups of search space sets, the unlicensed radio cell being controlled by a base station operating in an unlicensed spectrum and in communication with the communication device, the plurality of groups of search space sets being configured to include a first default group of search space sets and a second default group of search space sets; During operation, the processor determines, in response to the downlink control channel, one group of the plurality of groups of search space sets for performing the monitoring function; the first default group includes distributed monitoring occasions, and the second default group includes centralized monitoring occasions at the beginning of each slot; The monitoring function is not performed during non-monitoring periods; the processor determines, when executing the monitoring function after the non-monitoring period, to execute the monitoring function based on a default group to which the base station is associated, out of the first default group and the second default group; Communication equipment.

2. The non-monitoring period is A sleep period defined by the DRX cycle of a discontinuous reception (DRX) function; - the time period during which the communication device performs radio measurements; and the duration during which the communication device performs a transmission; At least one of the following is true: The communication device according to claim 1 .

3. Determining the one group of the plurality of groups of search space sets for the monitoring function in response to the downlink control channel includes, by the processor: an indication of the one group of search space sets, obtainable from the downlink control channel; detection of a signal on the downlink control channel, the signal being one or more of a downlink control information message, a downlink data transmission, and a downlink reference signal; channel occupancy of the unlicensed spectrum of the unlicensed radio cell by the base station, obtainable from the downlink control channel; based on one or more of 3. The communication device according to claim 1 or 2.

4. A sleep period of the DRX function is defined when the communication device is not in an active time; The communication device a monitoring period defined by a DRX cycle, - the period of inactivity before the inactivity timer expires, - a period during which the communication device is waiting to receive a retransmission of the data packet; the period during which the communication device waits to retransmit the data packet; a period during which the communication device is waiting for resolution of a random access procedure conflict; a period of time during which the communication device is waiting to receive a response to a scheduling request sent by the communication device; a period during which the communication device waits for a downlink control channel transmission indicating a new transmission after receiving a random access response message of a contention-free random access procedure; during at least one or more of the active time periods, The communication device according to claim 1 .

5. The default group of search space sets is a configuration message received from the base station controlling the unlicensed radio cell, the configuration message being a Radio Resource Control (RRC) message, or - predetermined information of the communication device; and The communication device is connected to a plurality of base stations, and one default group of search space sets is configured for each base station. The communication device according to claim 1 .

6. the processor determines, in response to the downlink control channel, to perform the monitoring function based on the default group of search space sets until determining another group of the plurality of groups of search space sets. The communication device according to claim 1 .

7. When the processor determines to perform the monitoring function based on the default group of search space sets, the processor further considers a channel occupancy state of the unlicensed spectrum of the unlicensed radio cell by the base station, if the channel occupancy state after the non-monitoring period is known to the communications device, the processor determines to perform the monitoring function based on a group of search space sets that corresponds to the channel occupancy state after the non-monitoring period; if the channel occupancy status after the non-monitoring period is unknown to the communication device, the processor determines to perform the monitoring function based on the default group of search space sets; and if the channel occupancy state after the non-monitoring period is known to the communications device, but a subsequent monitoring period is due to an uplink transmission intended by the communications device, the processor determines to perform the monitoring function based on the default group of search space sets. The communication device according to claim 1 .

8. a search space set is a set of search spaces, each search space including one or more candidate radio resources of the downlink control channel to monitor; The communication device according to claim 1 .

9. a search space set used to transmit critical system information to the communication device is compulsorily monitored regardless of which group of search space sets is determined by the processor; The search space set associated with the required frequency resource bandwidth is forcibly monitored by the monitoring function even during the non-monitoring period due to a discontinuous reception (DRX) function; The important system information is system information block 1 of a 5G NR standard communication system, and the required frequency resource bandwidth is defined as control resource set #0 of the 5G NR standard communication system. The communication device according to claim 1 .

10. A base station, a processor configured to perform a control information transmission function that, in operation, involves transmitting control information to a communication device on a downlink control channel of an unlicensed radio cell based on one of a plurality of groups of search space sets, the base station controlling the unlicensed radio cell operating in an unlicensed spectrum, the plurality of groups of search space sets including a first default group and a second default group of search space sets; the first default group includes distributed monitoring occasions, and the second default group includes centralized monitoring occasions at the beginning of each slot; The processor, during operation, determines one group of the plurality of groups of search space sets for performing the control information transmission function; the control information transmission function is not performed during a non-monitoring period of the communication device, and the communication device does not perform a monitoring function involving monitoring the downlink control channel during the non-monitoring period; When the processor executes the control information transmission function after the non-monitoring period, the processor determines to execute the control information transmission function based on a default group to which the base station is associated, out of the first default group and the second default group. Base station.

11. The non-monitoring period is A sleep period defined by the DRX cycle of a discontinuous reception (DRX) function; - the time period during which the communication device performs radio measurements; and the duration during which the communication device performs a transmission; At least one of the following is true: The base station of claim 10.

12. Determining the one group of the plurality of groups of search space sets for the control information transmission function includes, by the processor: channel occupancy of the unlicensed spectrum of the unlicensed radio cell by the base station; is carried out based on a transmitter, during operation, transmitting an indication of the determined one group of search space sets to a communication device on a downlink control channel; The base station according to claim 10 or 11.

13. the processor, during operation, determines the default group of search space sets; and the transmitter, during operation, transmits a configuration message to the communication device to configure the communication device with the determined default group of search space sets. The base station of claim 10.

14. When the processor determines to perform the control information transmission function based on the default group of search space sets, the processor further considers a channel occupancy state of the unlicensed spectrum of the unlicensed radio cell by the base station, if the channel occupancy state after the non-monitoring period is known to the communications device, the processor determines to perform the control information transmission function based on a group of search space sets corresponding to the channel occupancy state after the non-monitoring period; if the channel occupancy status after the non-monitoring period is unknown to the communication device, the processor determines to perform the control information transmission function based on the default group of search space sets; and if the channel occupancy state after the non-monitoring period is known to the communications device, but the subsequent monitoring period is due to an uplink transmission intended by the communications device, the processor determines to perform the control information transmission function based on the default group of search space sets. The base station of claim 10.

15. 1. A method comprising the steps of: activating a monitoring function involving monitoring a downlink control channel of an unlicensed radio cell based on one of a plurality of groups of search space sets, the unlicensed radio cell being controlled by a base station operating in an unlicensed spectrum and in communication with the communication device, the plurality of groups of search space sets being configured to include a first default group and a second default group of search space sets, the first default group including distributed monitoring occasions and the second default group including centralized monitoring occasions at the beginning of each slot; determining, in response to the downlink control channel, one group of the plurality of groups of search space sets for performing the monitoring function; The monitoring function is not performed during non-monitoring periods; determining whether to perform the monitoring function after the non-monitoring period based on a default group to which the base station is associated, out of the first default group and the second default group; A method comprising:

16. A method comprising the steps of: performing a control information transmission function involving transmitting control information to a communication device on a downlink control channel of an unlicensed radio cell based on one of a plurality of groups of a search space set, the base station controlling the unlicensed radio cell operating in an unlicensed spectrum, the plurality of groups of search space sets configured to include a first default group and a second default group of search space sets, the first default group including distributed monitoring occasions and the second default group including centralized monitoring occasions at the beginning of each slot; determining one group of the plurality of groups of search space sets for performing the control information transmission function; the control information transmission function is not performed during a non-monitoring period of the communication device, and the communication device does not perform a monitoring function involving monitoring the downlink control channel during the non-monitoring period; determining, when the control information transmission function is to be executed after the non-monitoring period, to execute the control information transmission function based on a default group to which the base station is associated, of the first default group and the second default group; A method comprising:

17. An integrated circuit for controlling processing of a communication device, the processing comprising: a process for operating a monitoring function involving monitoring a downlink control channel of an unlicensed radio cell based on one of a plurality of groups of search space sets, the unlicensed radio cell operating in an unlicensed spectrum and controlled by a base station in communication with the communication device, the plurality of groups of search space sets being configured to include a first default group and a second default group of search space sets, the first default group including distributed monitoring occasions and the second default group including centralized monitoring occasions at the beginning of each slot; determining, in response to the downlink control channel, one group of the plurality of groups of search space sets for performing the monitoring function; The monitoring function is not performed during non-monitoring periods; a process of determining whether to execute the monitoring function after the non-monitoring period based on a default group to which the base station is associated, out of the first default group and the second default group; , an integrated circuit.

18. An integrated circuit for controlling processing of a base station, the processing comprising: a process for performing a control information transmission function involving transmitting control information to a communication device on a downlink control channel of an unlicensed radio cell based on one of a plurality of groups of a search space set, the base station controlling the unlicensed radio cell operating in an unlicensed spectrum, the plurality of groups of search space sets being configured to include a first default group and a second default group of search space sets, the first default group including distributed monitoring occasions and the second default group including centralized monitoring occasions at the beginning of each slot; determining one of the plurality of groups of search space sets for performing the control information transmission function; the control information transmission function is not performed during a non-monitoring period of the communication device, and the communication device does not perform a monitoring function involving monitoring the downlink control channel during the non-monitoring period; a process of determining to execute the control information transmission function based on a default group to which the base station is associated, out of the first default group and the second default group, when the control information transmission function is to be executed after the non-monitoring period; , an integrated circuit.

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