UE power saving during dynamic pdcch allocations

Abstract

According to an aspect, there is provided an apparatus configured to perform the following. The apparatus communicates, via a physical downlink control channel, PDCCH, using a PDCCH time division duplex, TDD, slot pattern and using a first SSSG for monitoring a first number of PDCCH symbols in a slot. During the communicating, the apparatus receives, from an access node, PDCCH congestion information which indicates whether uplink granting, downlink assignment and special uplink-downlink slots in the cell are associated with a high PDCCH load. In response to the PDCCH congestion information indicating that the PDCCH load for at least one slot type corresponds to the high PDCCH load, the apparatus switches from using the first SSSG to using a second SSSG for monitoring a second number of PDCCH symbols for at least one slot determined based on the at least one slot type. The second number is larger than the first number.

Description

UE POWER SAVING DURING DYNAMIC PDCCH ALLOCATIONSTECHNICAL FIELD

[0001] Various example embodiments relate to wireless communicationsBACKGROUND

[0002] One of the main factors contributing to terminal device power consumption in 5GNew Radio (NR) is downlink (DL) assignment / uplink (UL) grant scheduling for terminal devices in radio resource control (RRC) connected mode. On the other hand, in the RRC connected mode, one of the main contributors to terminal device power consumption is the period and frequency of monitoring physical downlink control channel (PDCCH) for reading the scheduled grants on the uplink and downlink. Thus, by optimizing the PDCCH monitoring process, significant power savings could be achieved.SUMMARY

[0003] According to an aspect, there is provided the subject matter of the independent claims. Embodiments are defined in the dependent claims Summary to be finalized once claims are final.

[0004] One or more examples of implementations are set forth in more detail in the accompanying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims.BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Figure 1 illustrates a system to which some embodiments may be applied;

[0006] Figures 2 to 6 illustrate processes according to some embodiments;

[0007] Figure 7 illustrates signalling between an access node and one or more terminal devices according to some embodiments; and

[0008] Figure 8 illustrates an apparatus according to some embodiments.DETAILED DESCRIPTION OF SOME EMBODIMENTS

[0009] The following embodiments are only presented as examples. Although the specification may refer to “an”, “one”, or “some” embodiment(s) and / or example(s) in several locations of the text, this does not necessarily mean that each reference is made to the same embodiment s) or example(s), or that a particular feature only applies to a single embodiment and / or example. Single features of different embodiments and / or examples may also be combined to provide other embodiments and / or examples.

[0010] As used herein, “at least one of the following: ” and “at least one of ” and similar wording, where the list of two or more elements are joined by “and” or “or”, mean at least any one of the elements, or at least any two or more of the elements, or at least all the elements.

[0011] In the context of the embodiments, the term “high load” or “high PDCCH load” may correspond to a (traffic) load satisfying one or more pre-defined criteria (or one or more pre-defined conditions) for high PDCCH load (e.g., exceeding a pre-defined threshold for high PDCCH load). The term “low load” or equally “low PDCCH load” may correspond to a PDCCH load which does not correspond to “high PDCCH load”. The one or more predefined criteria (or conditions) may be defined at the access node, and they may not be necessarily known by terminal devices.

[0012] In the following, different exemplifying embodiments will be described using, as an example of an access architecture to which the embodiments may be applied, a radio access architecture based on long term evolution advanced (LTE Advanced, LTE-A) or new radio (NR, 5G), without restricting the embodiments to such an architecture, however. It is obvious for a person skilled in the art that the embodiments may also be applied to other kinds of communications networks having suitable means by adjusting parameters and procedures appropriately. Some examples of other options for suitable systems are the universal mobile telecommunications system (UMTS) radio access network (UTRAN or E- UTRAN), long term evolution (LTE, the same as E-UTRA), wireless local area network (WLAN or WiFi), worldwide interoperability for microwave access (WiMAX), Bluetooth®, personal communications services (PCS), ZigBee®, wideband code division multiple access(WCDMA), systems using ultra-wideband (UWB) technology, sensor networks, mobile ad- hoc networks (MANETs) and Internet Protocol multimedia subsystems (IMS) or any combination thereof.

[0013] Figure 1 depicts examples of simplified system architectures only showing some elements and functional entities, all being logical units, whose implementation may differ from what is shown. The connections shown in Figure 1 are logical connections; the actual physical connections may be different. It is apparent to a person skilled in the art that the system typically comprises also other functions and structures than those shown in Figure 1.

[0014] The embodiments are not, however, restricted to the system given as an example but a person skilled in the art may apply the solution to other communication systems provided with necessary properties.

[0015] The example of Figure 1 shows a part of an exemplifying radio access network.

[0016] A communications system typically comprises more than one (e / g)NodeB in which case the (e / g)NodeBs may also be configured to communicate with one another over links, wired or wireless, designed for the purpose. These links may be used for signaling purposes. The (e / g)NodeB is a computing device configured to control the radio resources of communication system it is coupled to. The NodeB may also be referred to as a base station, an access point or any other type of interfacing device including a relay station capable of operating in a wireless environment. The (e / g)NodeB includes or is coupled to transceivers. From the transceivers of the (e / g)NodeB, a connection is provided to an antenna unit that establishes bi-directional radio links to user devices. The antenna unit may comprise a plurality of antennas or antenna elements. The (e / g)NodeB is further connected to core network 110 (CN or next generation core NGC). Depending on the system, the counterpart on the CN side can be a serving gateway (S-GW, routing and forwarding user data packets), packet data network gateway (P-GW), for providing connectivity of user devices (UEs) to external packet data networks, or mobile management entity (MME), etc.

[0017] The user device (also called UE, user equipment, user terminal, terminal device, etc.) illustrates one type of an apparatus to which resources on the air interface are allocated and assigned, and thus any feature described herein with a user device may beimplemented with a corresponding apparatus, such as a relay node. An example of such a relay node is a layer 3 relay (self-backhauling relay) towards the base station.

[0018] The user device typically refers to a portable computing device that includes wireless mobile communication devices operating with or without a subscriber identification module (SIM), including, but not limited to, the following types of devices: a mobile station (mobile phone), smartphone, personal digital assistant (PDA), handset, device using a wireless modem (alarm or measurement device, etc.), laptop and / or touch screen computer, tablet, game console, notebook, and multimedia device. It should be appreciated that a user device may also be a nearly exclusive uplink only device, of which an example is a camera or video camera loading images or video clips to a network. A user device may also be a device having capability to operate in Internet of Things (loT) network which is a scenario in which objects are provided with the ability to transfer data over a network without requiring human-to-human or human-to-computer interaction. The user device (or in some embodiments a layer 3 relay node) is configured to perform one or more of user equipment functionalities. The user device may also be called a subscriber unit, mobile station, remote terminal, access terminal, user terminal or user equipment (UE) just to mention but a few names or apparatuses.

[0019] Various techniques described herein may also be applied to a cyber-physical system (CPS) (a system of collaborating computational elements con-trolling physical entities). CPS may enable the implementation and exploitation of massive amounts of interconnected ICT devices (sensors, actuators, processors microcontrollers, etc.) embedded in physical objects at different locations. Mobile cyber physical systems, in which the physical system in question has inherent mobility, are a subcategory of cyber-physical systems. Examples of mobile physical systems include mobile robotics and electronics transported by humans or animals.

[0020] It should be understood that, in Figure 1, user devices are depicted to include 2 antennas only for the sake of clarity. The number of reception and / or transmission antennas may naturally vary according to a current implementation.

[0021] Additionally, although the apparatuses have been depicted as single entities, different units, processors and / or memory units (not all shown in Figure 1) may be implemented.

[0022] 5G enables using multiple input - multiple output (MIMO) antennas, many more base stations or nodes than the LTE (a so-called small cell concept), including macro sites operating in co-operation with smaller stations and employing a variety of radio technologies depending on service needs, use cases and / or spectrum available. 5G mobile communications supports a wide range of use cases and related applications including video streaming, augmented reality, different ways of data sharing and various forms of machine type applications, including vehicular safety, different sensors and real-time control. 5G is expected to have multiple radio interfaces, namely below 6GHz, cmWave and mmWave, and also being integradable with existing legacy radio access technologies, such as the LTE. Integration with the LTE may be implemented, at least in the early phase, as a system, where macro coverage is provided by the LTE and 5G radio interface access comes from small cells by aggregation to the LTE. In other words, 5G is planned to support both inter-RAT operability (such as LTE-5G) and inter-RI operability (inter-radio interface operability, such as below 6GHz - cmWave, below 6GHz - cmWave - mmWave). One of the concepts considered to be used in 5G networks is network slicing in which multiple independent and dedicated virtual sub-networks (network instances) may be created within the same infrastructure to run services that have different requirements on latency, reliability, throughput and mobility.

[0023] The current architecture in LTE networks is fully distributed in the radio and fully centralized in the core network. The low latency applications and services in 5G require to bring the content close to the radio which leads to local break out and multi-access edge computing (MEC). 5G enables analytics and knowledge generation to occur at the source of the data. This approach requires leveraging resources that may not be continuously connected to a network such as laptops, smartphones, tablets and sensors. MEC provides a distributed computing environment for application and service hosting. It also has the ability to store and process content in close proximity to cellular subscribers for faster response time. Edge computing covers a wide range of technologies such as wireless sensor networks, mobile data acquisition, mobile signature analysis, cooperative distributed peer-to-peer ad hoc networking and processing also classifiable as local cloud / fog computing and grid / mesh computing, dew computing, mobile edge computing, cloudlet, distributed data storage and retrieval, autonomic self-healing networks, remote cloud services, augmented and virtual reality, data caching, Internet of Things (massive connectivity and / or latency critical),critical communications (autonomous vehicles, traffic safety, real-time analytics, time- critical control, healthcare applications).

[0024] The communication system is also able to communicate with other networks, such as a public switched telephone network or the Internet 112, or utilize services provided by them. The communication network may also be able to support the usage of cloud services, for example at least part of core network operations may be carried out as a cloud service (this is depicted in Figure 1 by “cloud” 114). The communication system may also comprise a central control entity, or a like, providing facilities for networks of different operators to cooperate for example in spectrum sharing.

[0025] Edge cloud may be brought into the RAN by utilizing network function virtualization (NVF) and software defined networking (SDN). Using edge cloud may mean access node operations to be carried out, at least partly, in a server, host or node operationally coupled to a remote radio head or unit (RU) or base station comprising radio parts. It is also possible that node operations will be distributed among a plurality of servers, nodes or hosts. Application of cloudRAN architecture enables RAN real time functions being carried out at the RAN side (in a distributed unit, DU 104) and non-real time functions being carried out in a centralized manner (in a central or centralized unit, CU 108). Thus, in summary, the RAN may comprise at least one distributed access node comprising a central unit, one or more distributed units communicatively connected to the central unit and one or more (remote) radio heads or units, each of which is communicatively connected to at least one of the one or more distributed units.

[0026] It should also be understood that the distribution of labor between core network operations and base station operations may differ from that of the LTE or even be nonexistent. Some other technology advancements probably to be used are Big Data and all-IP, which may change the way networks are being constructed and managed. 5G (or new radio, NR) networks are being designed to support multiple hierarchies, where MEC servers can be placed between the core and the base station or nodeB (gNB). It should be appreciated that MEC can be applied in 4G networks as well.

[0027] 5G may also utilize satellite communication to enhance or comple-ment the coverage of 5G service, for example by providing backhauling. Possible use cases are providing service continuity for machine-to-machine (M2M) or Internet of Things (loT) devices or for passengers on board of vehicles, or ensuring service availability for criticalcommunications, and future rail-way / maritime / aeronautical communications. Satellite communication may utilize geostationary earth orbit (GEO) satellite systems, but also low earth orbit (LEO) satellite systems, in particular mega-constellations (systems in which hundreds of (nano)satellites are deployed). Each satellite 106 in the mega-constellation may cover several satellite-enabled network entities that create on-ground cells. The on-ground cells may be created through an on-ground relay node 104 or by a gNB located on-ground or in a satellite.

[0028] It is obvious for a person skilled in the art that the depicted system is only an example of a part of a radio access system and in practice, the system may comprise a plurality of (e / g)NodeBs, the user device may have an access to a plurality of radio cells and the system may comprise also other apparatuses, such as physical layer relay nodes or other network elements, etc. At least one of the (e / g)NodeBs or may be a Home(e / g)nodeB. Additionally, in a geographical area of a radio communication system a plurality of different kinds of radio cells as well as a plurality of radio cells may be provided. Radio cells may be macro cells (or umbrella cells) which are large cells, usually having a diameter of up to tens of kilometers, or smaller cells such as micro-, femto- or picocells. The (e / g)NodeBs of Figure 1 may provide any kind of these cells. A cellular radio system may be implemented as a multilayer network including several kinds of cells. Typically, in multilayer networks, one access node provides one kind of a cell or cells, and thus a plurality of (e / g)NodeBs are required to provide such a network structure.

[0029] For fulfilling the need for improving the deployment and performance of communication systems, the concept of “plug-and-play” (e / g)NodeBs has been introduced. Typically, a network which is able to use “plug-and-play” (e / g)Node Bs, includes, in addition to Home (e / g)NodeBs (H(e / g)nodeBs), a home node B gateway, or HNB-GW (not shown in Figure 1). A HNB Gateway (HNB-GW), which is typically installed within an operator’s network may aggregate traffic from a large number of HNBs back to a core network.

[0030] 6G architecture is targeted to enable easy integration of everything, such as a network of networks, joint communication and sensing, non-terrestrial networks and terrestrial communication. 6G systems are envisioned to encompass machine learning algorithms as well as local and distributed computing capabilities, where virtualized network functions can be distributed over core and edge computing resources. Far edge computing,where computing resources are pushed to the very edge of the network, will be part of the distributed computing environment, for example in “zero-delay” scenarios. 5G systems may also employ such capabilities. More generally, the actual (radio) communication system is envisaged to be comprised of one or more computer programs executed within a programmable infrastructure, such as general -purpose computing entities (servers, processors, and like).

[0031] As mentioned above, in the RRC connected mode, one of the main contributors to terminal device power consumption is the period and frequency of monitoring physical downlink control channel (PDCCH) for reading the scheduled grants on the uplink and downlink. In general, a given terminal device (e.g., a terminal device 100, 102 of Figure 1) may decode PDCCH (or associated downlink control information, DCI) per time slot based on control resource set (CORESET) and search space configurations. The CORESET defines where, in time-frequency domain, the terminal device should search for PDCCH candidates while the search space defines how the search for the PDCCH candidates should be performed. The search space refers to the area in the downlink resource grid where PDCCH may be carried out. The search space may be configured per bandwidth part (BWP). The search space configuration may define one or more sets of Control Channel Elements (CCE) and Aggregation for the terminal device.

[0032] At least two different types of search spaces may be defined: a Common Search Space (CSS) or UE-specific search space (USS). A UE Specific Search Space is dedicated for each specific terminal device. The UE Specific Search Space may be informed to the terminal device via an RRC signaling message. Thus, a terminal device may, first, need to complete the RRC establishment in order to acquire information about the UE-specific search space. Common Search Space is the specific search space that every terminal device typically needs to search for the signals for UE (e.g„ PDCCH for System Information Blocks, SIBs) or signaling message that is applied to every terminal device before dedicated channel is established for a specific UE (e.g., PDCCH used during random access channel, RACH, process). For example, a terminal device may need to detect PDCCH for SIB1 reception or various DCI (PDCCH) during RACH process (e.g., DCI for Msg2 / Msg4 reception

[0033] Initially, and based on the RRC state associated with the terminal device, the terminal device may know which search space to monitor among different search spacetypes. For instance, TypeO-PDCCH CSS for decoding System Information Blocks (SIBs) that are encoded with System Information Radio Network Temporary Identifier (SI-RNTI), Type2-PDCCH for paging encoded with P-RNTI, or UE-specific PDCCH used for scheduling data encoded with C-RNTI. Then with the received information from CORESET and search spaces, the terminal device may apply blind decoding hypothesis to detect the corresponding DCI among the candidates in each aggregation level. The DCI may consist of scheduling information for uplink such as formats 0 0 or 0 1, or for downlink with formats 1 0 or 1 1, among several other DCI formats used for different purposes. At this point the UE has sufficient information sent to it from the cell, and with the DCI contents it can continue to receive or transmit other channels such as Physical Downlink Shared Channel (PDSCH), or Physical Uplink Shared Channel (PUSCH).

[0034] The embodiments to be discussed below are based on use of so-called search space set group (SSSG) switching in combination with dynamic PDCCH symbol adjustment functionality. Before discussing the problems associated with this operation, the SSSG switching and dynamic PDCCH allocation are discussed in general for completeness and for facilitating the following discussion of the embodiments.

[0035] In SSSG switching, a terminal device (i.e., a UE) may be provided a group index for a respective Type3-PDCCH common search space (CSS) set or a UE-specific search space set for PDCCH monitoring on a serving cell. The group index may be provided in a dedicated field c&\\Q secirchSpace(jroiipIdI.islrl6. If the terminal device is not provided searchSpaceGroupIdList-rl6 for a search space set, the following procedures may not be applicable for PDCCH monitoring according to the search space set.

[0036] If a terminal device is provided searchSpaceSwitchingGroupList-rl6, indicating one or more groups of serving cells, the following procedures apply to all serving cells within each group; otherwise, the following procedures apply only to a serving cell for which the terminal device is provided searchSpaceGroupIdList-rl6.

[0037] When a terminal device is provided searchSpaceGroupIDList-rl6, the terminal device resets PDCCH monitoring according to search space sets with group index 0, if provided by searchSpaceGroupIdList-rl6.

[0038] A terminal device may be provided by searchSpaceSwitchingDelay-rl6 a number of symbols Pswitchwhere a minimum value of Pswitchis provided in Table 1 belowfor UE processing capability 1 and UE processing capability 2 and subcarrier spacing (SCS) configured onC. If the terminal device indicates a corresponding capability, the terminal device applies the Pswitchvalue for UE processing capability 2; otherwise, the terminal device applies the Pswitchvalue for UE processing capability 1 for SCS

[0039] Table I: Minimum value of Eswitch[symbols]

[0040] A terminal device may optionally be provided, by searchSpaceSwitchingTimer-r 16. a timer value. The terminal device decrements the timer value by one after each slot for a reference SCS configuration p.

[0041] A terminal device may be provided, via SearchSpaceSwitchTrigger-rl6, a location of a search space set group switching flag field for a serving cell in a DCI format 2 0. In such a case, at least some of the following features may apply.If the terminal device detects a DCI format 2 0 and a value of the search space set group switching flag field in the DCI format 2 0 is 0, the terminal device starts monitoring PDCCH according to search space sets with group index 0, and stops monitoring PDCCH according to search space sets with group index 1, on the serving cell at a first slot that is at least Pswitchsymbols after the last symbol of the PDCCH with the DCI format 2 0.If the terminal device detects a DCI format 2 0 and a value of the search space set group switching flag field in the DCI format 2 0 is 1, the terminal device starts monitoring PDCCH according to search space sets with group index 1, and stops monitoring PDCCH according to search space sets with group index 0, on the serving cell at a first slot that is at least Pswitchsymbols after the last symbol of the PDCCH with the DCI format 2 0, and the terminal device sets the timer value to the value provided by searchSpaceSw itchingTimer-r 16.If the terminal device monitors PDCCH on a serving cell according to search space sets with group index 1, the terminal device starts monitoring PDCCH on the serving cell according to search space sets with group index 0, and stops monitoring PDCCH according to search space sets with group index 1, on the serving cell at the beginning of the first slot that is at least Pswitchsymbols after a slot where the timer expires or after a last symbol of a remaining channel occupancy duration for the serving cell that is indicated by DCI format 2 0.

[0042] If a terminal device is provided SearchSpaceSwitchTrigger-r 16 for a serving cell, the at least some of the following features may apply.If the terminal device detects a DCI format by monitoring PDCCH according to a search space set with group index 0, the terminal device starts monitoring PDCCH according to search space sets with group index 1, and stops monitoring PDCCH according to search space sets with group index 0, on the serving cell at a first slot that is at least Pswitchsymbols after the last symbol of the PDCCH with the DCI format, the terminal device sets the timer value to the value provided by searchSpaceSwitchingTimer-r!6 if the terminal device detects a DCI format by monitoring PDCCH in any search space set.If the terminal device monitors PDCCH on a serving cell according to search space sets with group index 1, the terminal device starts monitoring PDCCH on the serving cell according to search space sets with group index 0, and stops monitoring PDCCH according to search space sets with group index 1, on the serving cell at the beginning of the first slot that is at least Pswitchsymbols after a slot where the timer expires or, if the terminal device is provided a search space set to monitor PDCCH for detecting a DCI format 2 0, after a last symbol of a remaining channel occupancy duration for the serving cell that is indicated by DCI format 2 0.

[0043] A terminal device may determine a slot and a symbol in the slot to start or stop PDCCH monitoring according to search space sets for a set of serving cells, provided by searchSpaceSwitchingGroupList-r!6, based on the smallest SCS configuration . of the active BWPs in the set of serving cells and, if any, in the serving cell where the terminal device receives a PDCCH and detects a corresponding DCI format 2 0 triggering the start or stop of PDCCH monitoring according to search space sets.

[0044] As mentioned above, the embodiments may be based on use of the SSSG switching functionality discussed above in combination with the following dynamic PDCCHsymbol adjustment functionality. In an exemplary scenario, an access node may configure a terminal device specific search space for uplink and downlink data transfer so that monitoringSymbolsWithinSlot = 11000000000000 for time division duplex (TDD) and monitoringSymbolsWithinSlot = 11100000000000 for frequency division duplex (FDD) and monitoringSlotPeriodicityAndOffset = 1 slot. Here, the monitoringSlotPeriodicityAndOffset field defines slots for PDCCH monitoring configured as periodicity and offset while the monitoringSymbolsWithinSlot field defines symbols for PDCCH monitoring in said slots configured for PDCCH monitoring. The most significant (left) bit of monitoringSymbolsWithinSlot represents the first orthogonal frequency division multiplexing (OFDM) symbol in a slot. The least significant (right) bit of monitoringSymbolsWithinSlot represents the last symbol. The monitoringSymbolsWithinSlot field indicates the starting OFDM symbols that the terminal device should search within for a search space. Thus, the value of '11000000000000' indicates that the terminal device should start searching from the first and second OFDM symbols for TDD while the value of '11100000000000' indicates that the terminal device should start searching from the first, second and third OFDM symbols for FDD. This search space configuration may be accompanied with a 1 symbol CORESET.

[0045] According to the dynamic PDCCH functionality, the access node may activate, e.g., in the aforementioned exemplary scenario, an internal feature to dynamically determine how many PDCCH symbols are needed in every slot for uplink and downlink data. The number of PDCCH symbols in a slot is dynamically adjusted by the access node so that, in high PDCCH load conditions, a larger number of PDCCH symbols is provided compared to the number defined in the search space configuration so that a larger number of terminal devices can be scheduled leading to fewer PDCCH starved terminal devices. Alternatively, the number of PDCCH symbols in a slot may be dynamically adjusted by the access node so that, in low PDCCH load conditions, a smaller number of PDCCH symbols is provided compared to the number given in the search space configuration so that cell throughput can be increased by using the unused PDCCH symbols for physical downlink shared channel (PDSCH) when the number of terminal devices presents in the cell is sufficiently small. For example, even if monitoringSymbolsWithinSlot = 11100000000000 is configured to a terminal device in a particular slot, the access node may choose to send PDCCH traffic in only the first symbol. Note that only the terminal devices that receive a DCI scheduling a PDSCH in the same slot will know the PDSCH starting symbol (e.g., start symbol = 1) inthe corresponding start and length indicator (SLIV) thereby the terminal device is able to deduce that PDCCH monitoring is not needed from symbol 1 in that slot. In this situation, all other terminal devices will still be monitoring the PDCCH in symbol 1 and 2 and performing blind decodes.

[0046] The problem described here is related to the interworking of SSSG switching functionality and the dynamic PDCCH symbol adjustment functionality. SSSG may be used to save terminal device power when the dynamic PDCCH symbol adjustment functionality is enabled in the cell. For example, when the dynamic PDCCH functionality is enabled, a cell may have one of two states for the number of PDCCH symbols in a slot as shown in Table II. In Table II (and in the following description of the embodiments), “DL assignment slot” is a downlink slot having a valid KI (but an invalid K2), “UL granting slot” is a downlink slot having a valid K2 (but an invalid KI) and ’’special DL+UL slot” is a slot with a valid KI and K2, e.g., a special slot in DDDSU (downlink-downlink-downlink-special- uplink) slot structure, so both UL and DL directions are required for PDCCH in such a slot. KI is a slot offset between the scheduled PDSCH and the uplink slot (or a special uplinkdownlink slot also known as a mixed slot) where the acknowledgment / negative acknowledgement (ACK / NACK) feedback is meant to be sent. K2 is a slot offset between DCI (an uplink grant) and its scheduled physical uplink shared channel (PUSCH). A valid KI or K2 means KI or K2 having a value supported by the access node (i.e., a value enabling PDSCH transmissions or uplink grant transmission, respectively). Whether the PDCCH load in a cell corresponds to a low PDCCH load or to a high PDCCH load may be determined, by the access node, for a certain duration, for example, using an analytical method or an artificial intelligence / machine-learning solution by analyzing the current state of the cell.

[0047] Table II: SSSG functionality for terminal device power saving

[0048] A terminal device may be configured with up to a maximum of 3 SSSGs (called typically GroupO, Group 1 & Group2) in a serving cell based on the PDCCH load of the cell. For example, it may be defined that in GroupO monitoringSymbolsWithinSlot = 10000000000000 and in Group 1 monitoringSymbolsWithinSlot = 11000000000000. In such a case, when there is a high PDCCH load in the cell, the terminal device may be indicated to switch to Group 1 and stop PDCCH monitoring in the GroupO, e.g., by sending downlink control information format 2 0 (DCI 2 0) to perform increased PDCCH monitoring. At this state, however, further terminal device power saving cannot be achieved as the terminal devices will already be monitoring the maximum number of PDCCH symbols. At a low PDCCH load in the cell, the terminal device needs to be switched to GroupO because a DL+UL slot can have 1 or 2 PDCCH symbols according to Table II.

[0049] The access node may measure the PDCCH load separately in the UL and DL directions. Consequently, for example, DL slots may have a high PDCCH load while UL slots or DL+UL slots may have a low PDCCH load. The terminal device power saving may be operating at a low efficiency in such a case because whenever an access node allocates 2 symbols for any 1 slot type among DL assignment slot, UL granting slot or special DL+UL slot, all terminal devices must be switched to Groupl (i.e., they must monitor both first and second PDCCH symbols). Table III explains the inefficiency which may occur in detail.

[0050] Table III: When SSSG is configured with Groupl, terminal device monitors PDCCH symbols 0 and 1 even when only the special slot (slots 3 and 8) is having a high PDCCH load in the DDDSU slot format in TDD.

[0051] The embodiments overcome or at least alleviate the aforementioned problems. Namely, the embodiments enable terminal device power savings when dynamic PDCCH functionality is enabled in the cell and the terminal device is also configured with SSSG. This terminal device power saving is based on interworking between dynamic PDCCH symbol adjustment functionality in the access node and SSSG so that the access nodes signals all the RRC connected and active terminal devices who support the proposed PDCCH monitoring capability whether the UL granting, DL assignment or special UL+DL slots have high PDCCH load. Consequently, the access node is able to configure the SSSGs to save terminal device power efficiently while the dynamic PDCCH symbol adjustment functionality is able to improve terminal device and cell throughput. Based on the configuration information provided by the access node, the terminal device may start monitoring the PDCCH slot pattern according to the assigned search space set group and the congested slot type.

[0052] The embodiments may be employed for 5G NR and / or 6G for enabling terminal device power savings. For example, this type of dynamic PDCCH symbol adjustment functionality may be employed in future gNB deployments with the emergenceof artificial intelligence / machine learning where the gNB can predict the PDCCH load in different slot types based on historical measurements of PDCCH usage. For example, said historical measurements of PDCCH usage may relate at or correspond to least one of the following parameters or properties:• The number of free channel control elements (being indicative amount of free capacity),• the number of available channel control elements (CCEs) (being indicative of the PDCCH capacity),• number of slots with PDCCH starvation (amount of congested PDCCH slots where PDSCH is free),• the number of slots capable of allocating PDCCH grants,• the number of RRC connected terminal devices in the cell (indicates general load of the cell),• average traffic amount per terminal device in the cell (indicates average traffic level in the cell - smaller number requires more PDCCH capacity),• the number of small data packets in the cell - (high number requires more PDCCH capacity),• the number of Voice over New Radio (VoNR) connections in the cell - large number of VoNR calls means high amount of small data packets and thus requires more PDCCH capacity,• configured radio network planning parameterization - depending on the active feature / functionality different amount of PDCCH capacity is needed• closed loop power control (CLPC),• BWP switch,• proactive scheduling,• latency targets in the cell (low latency targets allows lower amount of the RRC connections and thus less PDCCH capacity) or• radio frequency (RF) conditions in the cell (terminal devices in poor RF conditions require higher AL, and thus more PDCCH capacity.

[0053] Figure 2 illustrates a process according to embodiments for dynamic PDCCH allocation according to embodiments. The illustrated process of Figure 2 may be performed by an apparatus which may be a terminal device or a part thereof. The terminal device maybe one of the terminal device 100, 102 of Figure 1. In the following, the entity performing the process is called simply an apparatus without loss of generality

[0054] The apparatus is initially communicating, in block 201, via a PDCCH, using a PDCCH TDD slot pattern and using a first SSSG for monitoring a first number of PDCCH symbols in a slot for one or more slots defined in the PDCCH TDD slot pattern. Said first number of PDCCH symbols may be, for example, a single PDCCH symbol (e.g., the first or initial PDCCH symbol). For example, if the first PDCCH symbol is used for PDCCH, the other 13 PDCCH symbols may be used for PDSCH which enables increasing of the cell throughput. The PDCCH TDD slot pattern may have been configured previously to the apparatus by an access node, as will be described in connection with later embodiments.

[0055] In the following, it is assumed that the apparatus is currently using only the first SSSG for monitoring (i.e., no other SSSGs are currently being used). However, in some other embodiments, the apparatus may also be initially using a second SSSG for monitoring a second number of PDCCH symbols in a slot for one or more other slots defined in the PDCCH TDD slot pattern. In either case, the apparatus may have been configured earlier to support both first and second SSSGs. Here, the second number is larger than the first number The second number of PDCCH symbols may be, e.g., two PDCCH symbols (e.g., the first two PDCCH symbols). If the first two PDCCH symbols are used for PDCCH, then the other 12 PDCCH symbols may be used for PDSCH. . For example, the first and second SSSGs (equally called GroupO and Groupl) may be defined as follows: GroupO: monitoringSymbolsWithinSlot = 10000000000000 and Groupl : monitoringSymbolsWithinSlot = 11000000000000.

[0056] The PDCCH TDD slot pattern employed by the apparatus may comprise one or more uplink slots, one or more downlink slots and / or one or more special uplink-downlink slots. The one or more downlink slots may comprise one or more uplink granting slots (i.e., being downlink slots for transmitting uplink grants) and one or more downlink assignment slots (i.e., being downlink slots for transmitting downlink assignments). In some embodiments, the PDCCH TDD slot pattern may be, for example, a DDDSU slot pattern (i.e., a downlink-downlink-downlink-special-uplink slot pattern).

[0057] During the communicating, the apparatus receives, in block 202, from an access node, PDCCH congestion information (equally called PDCCH load information). The PDCCH congestion information indicates at least whether or not one or more uplink grantingslots, one or more downlink assignment slots and one or more special uplink-downlink slots in the cell are associated with a high PDCCH load. In other words, the PDCCH congestion information indicates which of the aforementioned three slot types in the cell are associated with a high PDCCH load and which with a low PDCCH load (i.e., a load which is not considered a high PDCCH load). What is considered a high PDCCH load may be defined by the access node. A high PDCCH load may be, for example, a PDCCH load satisfying one or more pre-defined criteria for a high PDCCH load (e.g., a PDCCH load exceeding a predefined threshold). One or more separate pre-defined criteria (e.g., a separate pre-defined threshold) may be defined (at the access node) for each slot type or the same one or more pre-defined criteria (e.g., the same pre-defined threshold) may be used for each slot type. The one or more pre-defined criteria may not be defined in the PDCCH congestion information itself, that is, the one or more pre-defined criteria employed by the access node may not be visible to the apparatus (i.e., to the terminal device). The PDCCH congestion information may been seen as implicit SSSG switching information as, to alleviate the PDCCH load of any slot types suffering from high PDCCH load, at least one slot associated with the high PDCCH load slot type(s) should be switched to use the aforementioned second SSSG for monitoring a larger number of PDCCH symbols.

[0058] It should be emphasized that the PDCCH load in the case of the uplink granting slot (and partially also in the case of the special uplink-downlink slot) corresponds to the PDCCH load associated with uplink slot related signalling over the PDCCH. Such uplink slot related PDCCH signalling may relate, e.g., to allocations and / or scheduling for uplink communication (at one or more uplink slots).

[0059] In some embodiments, the PDCCH congestion information may be or comprise a three-bit data field for indicating zero or more slot types which are associated with high PDCCH load. For example, the PDCCH congestion information may be defined as shown in Table IV below. In Table IV, “DL+UL” indicates the special uplink-downlink slot. Also, “KI” and “K2” in Table IV indicate that switching concerns downlink time slots with valid KI and K2 supported by the access node, respectively.

[0060] Table IV: The PDCCH congestion information for indicating which slot type(s) that have a high PDCCH load.

[0061] The PDCCH congestion information may be communicated by the access node as a (new) dedicated field of DCI 2 0. Thus, the receiving in block 202 may comprise receiving, from the access node, DCI 2 0 comprising the PDCCH congestion information as a dedicated field of the DCI 2 0.

[0062] In response to the PDCCH congestion information indicating that the PDCCH load for at least one slot type of uplink granting slot, downlink assignment slot or special uplink-downlink slot of the PDCCH TDD slot pattern is high in block 203, the apparatus switches, in block 204, from using the first SSSG to using the second SSSG for monitoring the second number of PDCCH symbols for at least one slot determined based on the at least one slot type. The second number of PDCCH symbols is assumed to be larger than the first number of PDCCH symbols. The second number of PDCCH symbols may be, for example, 2.

[0063] The determining of the at least one slot to be switched in block 204 may carried out as described in the following.

[0064] If said at least one slot type (associated with high PDCCH load) comprises the uplink granting slot, said at least one slot switched in block 204 comprises one or more downlink slots having a valid K2 supported by the access node for enabling uplink grant transmissions (but no valid KI). It should be noted that while 3GPP supports K2 values between 0 and 32, the access node (e.g., a gNB) may support only a subset of those values. Thus, only a few slots may be usable in practice for sending an uplink grant. For example, if the access node supports K2 = 2, then the slot index 2 is a slot with valid K2. Thus, if the first and second SSSGs correspond to monitoring of one and two PDCCH symbols, respectively, the apparatus may be switched to monitor the two PDCCH symbols (PDCCH SymbolO & PDCCH Symbol 1) in slots with a valid K2 = 2 while still monitoring only 1 PDCCH symbol (PDCCH SymbolO) in the slots with a valid KI.

[0065] Table V shows an exemplary DDDSU slot structure for the case where only uplink granting slots (i.e., downlink slots with valid K2 but invalid KI) are encountering high PDCCH load following the appropriate switching in block 204. In this example, power saving of 37.5% is achievable by switching only the downlink slots with valid K2 (here K2 = 2) to use the second SSSG (i.e., to monitor both PDCCH SymbolO & PDCCH Symbol 1). The power saving is calculated here and in the following examples relative to the case where the second SSSG is used in all slots.Table VSlot index 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9Slot type D D D S U D D D S U D D D S _U D D D S U PDCCH ”i F T i o T’ i ”1 i o T’ i T’ T o T i T oSymbol 0

[0066] If said at least one slot type associated with high PDCCH load comprises the downlink slot, said at least one slot switched in block 204 comprises one or more downlink slots having a valid KI supported by the access node for enabling PDSCH transmissions, i.e., for enabling PDCCH downlink assignment transmission, (but an invalid K2). Similar to as described for the high PDCCH load in uplink, the access node (e.g., a gNB) may support only a subset of the values defined by 3GPP for K2. Thus, only a few slots may be usable in practice for sending an uplink grant. For example, if the access node supports KI = 2, then the slot index 2 is a slot with valid KI. Thus, if the first and second SSSGs correspond tomonitoring of one and two PDCCH symbols, respectively, the apparatus may be switched to monitor the two PDCCH symbols (PDCCH SymbolO & PDCCH Symbol 1) in slots with a valid K2 = 2 while still monitoring only 1 PDCCH symbol (PDCCH SymbolO) in the slots with a valid KI.

[0067] Table VI shows an exemplary DDDSU slot structure for the case where only downlink slots with valid KI are encountering high PDCCH load following the appropriate switching in block 204. In this example, power saving of 25% is achievable by switching only the downlink slots with valid KI (here KI = {3, 4}) to use the second SSSG (i.e., to monitor both PDCCH SymbolO & PDCCH Symbol 1).Table VI

[0068] If said at least one slot type (associated with high PDCCH load) comprises the special uplink-downlink slot, said at least one slot switched in block 204 comprises one or more one or more special uplink-downlink slots having valid KI and K2 supported by the access node.

[0069] Table VII shows an exemplary DDDSU slot structure for the case where the special uplink-downlink slots with valid KI & K2 are encountering high PDCCH load following the appropriate switching in block 204. In this example, power saving of 37.5% is achievable by switching only the special uplink-downlink slots with valid KI & K2 (as defined in connection with Tables V & VI) to use the second SSSG (i.e., to monitor both PDCCH SymbolO & PDCCH Symbol 1).Table VII

[0070] Table VIII shows in which slots a terminal device can expect to receive two PDCCH symbols based on the valid KI & K2 values that the access node supports and the switching field (yyy) indicated by the DCI. In Table IX, the valid KO, KI and K2 values are assumed to be KO = 0, KI = {1, 2, 3, 4} and K2 = { 1, 2}. Here, KO is an offset between the downlink slot where the PDCCH (DCI) for downlink scheduling is received and the downlink slot where PDSCH data is scheduled. Two search space set groups are configured here for GroupO to monitor only the first PDCCH symbol and for Group 1 to monitor both first and second PDCCH symbols in a slot, i.e., GroupO: monitoringSymbolsWithinSlot = 10000000000000 and Group 1: monitoringSymbolsWithinSlot = 11000000000000. Switching field (yyy) is altered to indicate which slots are in high load according to embodiments (particularly the ones described in connection with Figures 2 to 4).Table VIII

[0071] In some embodiments, the valid (i.e., supported) values of KI and K2 (and K0) may be indicated to the terminal device as a part of the RRC configuration. Subsequently, at uplink grant (K2) or downlink DCI (KI, K0) the value for individual transmission is indicated through DCI.

[0072] Figure 3 shows a terminal device state machine for the slot type based search space switching mechanism discussed in connection with Figure 2. Figure 3 correspond to the embodiments where the PDCCH congestion information is provided in the form given in Table IV as a part of DCI 2 0. Figure 3 corresponds to a single slot type (called “slot type x” in Figure 3) which may be any of the uplink granting slot, the downlink assignment slotor the special uplink-downlink slot. Similar mechanism may be implemented for all of said slot types.

[0073] Referring to Figure 3, the terminal device state machine comprises two states 301, 302. In the first state 301, the terminal device monitors GroupO (i.e., the first SSSG) in a particular slot type (“slot type x”) and stops monitoring (i.e., does not monitor) Group 1 (i.e., the second SSSG) in said slot type. In the second state 302, the terminal device monitors Groupl (i.e., the second SSSG) in the slot type and stops monitoring (i.e., does not monitor) GroupO (i.e., the first SSSG) in the slot type.

[0074] The terminal device is able to move from the first state 301 to the second state 302 by receiving (or detecting), in element 303, DCI 2_0 comprising any switching field corresponding to said slot type (e.g., 000, 010, 100 or 110 for the downlink slot). When in the second state 302, the terminal device may remain in the second state 302 when detecting, in element 304, DCI 2 0 comprising any switching field corresponding to said slot type. For example, if the slot type x correspond to a downlink assignment slot, detecting DCI 2 0 comprising any switching field indicating high load only for the downlink assignment slot or for the downlink assignment slot and for uplink granting slot and / or special uplinkdownlink slot.

[0075] The terminal device is able to move from the second state back to the first state via two different mechanisms in element 305. The terminal device moves from the second state to the first state in response to detecting DCI 2 0 comprising a switching field which does not correspond to said slot type (e.g., 001, Oi l, 101 and 111 for the downlink assignment slot). The terminal device moves from the second state to the first state also in response to a timer for monitoring Groupl expiring. The timer may have been started when the second state 302 was entered. A timer may be defined separately for the different slot types.

[0076] While the functionalities Figure 3 were discussed in connection with a specific example where DCI 2 0 is used for communication the switching field having a particular form and the first and second SSSGs correspond to GroupO and Groupl, the features introduced in connection with Figure 3 (e.g., moving from the second SSSG to the first SSSG when there is no longer high PDCCH to free up PDCCH symbol resources and / or when a timer expires) may be applied, mutatis mutandis, also in connection with the more general embodiment of Figure 2.

[0077] Thus, referring to Figure 2, the apparatus may, following the switching in block204, receive, from the access node, further PDCCH congestion information. In response to the further PDCCH congestion information indicating that the PDCCH load for at least one of said at least one slot type of uplink granting slot, downlink assignment slot or special uplink-downlink slot of the PDCCH TDD slot pattern fails to correspond to the high PDCCH load (as defined by the access node), the apparatus may switch back to using the first SSSG for said at least one of said at least one slot type. Alternatively or additionally, in response to the further PDCCH congestion information indicating that the PDCCH load for at least one further slot type of uplink granting slot, downlink assignment slot or special uplink-downlink slot of the PDCCH TDD slot pattern corresponds to the high PDCCH load, the apparatus may switch from using the first SSSG to using the second SSSG for said at least one further slot type, where said at least one further slot type is different from the at least one slot type (mentioned previously in connection with blocks 203, 204). The further PDCCH congestion information may, in general, be defined in a similar manner as described above for the PDCCH congestion information received in block 202 (though obviously the exact per-slot-type congestion status may be different).

[0078] Figure 4 illustrates a process according to embodiments for dynamic PDCCH allocation according to embodiments. The illustrated process of Figure 4 may be performed by an apparatus which may be an access node (e.g., a distributed or a non-distributed access node) or a part thereof. The access node may be the access node 104 of Figure 1. The process of Figure 4 corresponds to a process carried out at the access node side in parallel with the process of Figure 2 being carried out at the terminal device side. In the following, the entity performing the process is called simply an apparatus without loss of generality.

[0079] Referring to Figure 4, the apparatus monitors, in block 401, uplink and downlink related PDCCH loads in a cell. The apparatus may monitor in block 401 at least PDCCH load associated with the different slot types (i.e. downlink assignment slot, uplink granting slot and the special uplink-downlink slot). For example, the apparatus may measure the uplink and downlink related PDCCH loads periodically with a pre-defined period (e.g., 20 ms). As mentioned above, the uplink related PDCCH load (equally called uplink PDCCH load) should be understood as the PDCCH load associated with uplink related signalling over the PDCCH (e.g., signalling relating to allocations and / or scheduling for uplink communication). The monitoring may be performed per slot type.

[0080] The apparatus transmits, in block 402, to one or more terminal devices in the cell, PDCCH congestion information defined based on the monitored uplink and downlink related PDCCH loads. The PDCCH congestion information indicates whether or not one or more uplink granting slots, one or more downlink assignment slots and one or more special uplink-downlink slots in the cell are associated with a high PDCCH load. As described above, the high PDCCH load may be defined (by the apparatus) as a PDCCH load satisfying one or more pre-defined criteria for the high PDCCH load (e.g., a PDCCH load exceeding a pre-defined threshold). Thus, the apparatus may compare the monitored uplink and downlink related PDCCH loads per slot type against one or more pre-defined criteria to derive the PDCCH congestion information. Only the (binary) indication regarding whether or not the aforementioned slot types correspond to a high PDCCH load may be communicated to the one or more terminal devices, that is, the one or more pre-defined criteria for evaluating whether a PDCCH load is high or the exact PDCCH load values may not be communicated (at least not in most embodiments). Here, the one or more terminal devices may be RRC connected and active terminal devices. The one or more pre-defined criteria (e.g., a predefined threshold) may be defined (by the apparatus) to be the same or different for different slot types and / or for different terminal devices. The PDCCH congestion information may be defined as described in connection with Figure 2 and / or 3.

[0081] Figure 5 illustrates an alternative process according to embodiments for dynamic PDCCH allocation according to embodiments. The illustrated process of Figure 5 may be performed by an apparatus which may be a terminal device or a part thereof. The terminal device may be one of the terminal device 100, 102 of Figure 1. In the following, the entity performing the process is called simply an apparatus without loss of generality

[0082] Similar to Figure 2, the apparatus is initially communicating, in block 501, via PDCCH, using a PDCCH TDD slot pattern and using a first SSSG for monitoring a first number of PDCCH symbols in a slot for one or more slots defined in the PDCCH TDD slot pattern. Said first number of PDCCH symbols may be, for example, a single PDCCH symbol (e.g., the first or initial PDCCH symbol). The PDCCH TDD slot pattern may have been configured previously to the apparatus by an access node, as will be described in connection with later embodiments.

[0083] During the communicating, the apparatus receives, in block 502, from an access node, SSSG switching information. Here, it is assumed that the SSSG switchinginformation indicates at least one slot of the PDCCH TDD slot pattern to be switched from the first SSSG to a second SSSG for monitoring a second number of PDCCH symbols. The second number of PDCCH symbols is larger than the first number of PDCCH symbols. In general, the first and second SSSGs may be defined as described above.

[0084] In some embodiments, the SSSG switching information may be comprised in a dedicated field of the DCI 2 0. Thus, the receiving in block 502 may comprise receiving from the access node, DCI 2 0 comprising the SSSG switching information as a dedicated field of the DCI 2 0.

[0085] In some embodiments, the SSSG switching information may comprise a first SSSG switching flag for one or more slots of the PDCCH TDD slot pattern having a valid KI supported by the access node and a second SSSG switching flag for one or more slots of the PDCCH TDD slot pattern having a valid K2 supported by the access node. Thus, the SSSG switching information may comprise or consist of a two-bit data field for indicating that one, both or none of KI and K2 slots is associated with a high PDCCH load. For example, the SSSG switching information may be defined as shown in Table IX below.Table IX

[0086] In some embodiments, only one of the first and second SSSG switching flags may be comprised in the SSSG switching information.

[0087] In some embodiments, the SSSG switching information may comprise SSSG switching information defined separately for all slots of the PDCCH TDD slot pattern. In other words, one (one-bit) flag may be provided for each slot of the PDCCH TDD slot pattern. In other embodiments, the SSSG switching information may comprise SSSGswitching information defined separately for a subset of all slots of the PDCCH TDD slot pattern.

[0088] The apparatus switches, in block 503, the at least one slot to use the second SSSG based on (or directly following) the SSSG switching information.

[0089] The timer functionality discussed in connection with Figure 3 may be equally applied in the case of the process of Figure 5.

[0090] Figure 6 illustrates an alternative process according to embodiments for dynamic PDCCH allocation according to embodiments. The illustrated process of Figure 6 may be performed by an apparatus which may be an access node (e.g., a distributed or a nondistributed access node) or a part thereof. The access node may be the access node 104 of Figure 1. In the following, the entity performing the process is called simply an apparatus without loss of generality. The process of Figure 6 corresponds to a process carried out at the access node side in parallel with the process of Figure 5 being carried out at the terminal device side.

[0091] Referring to Figure 6, the apparatus monitors, in block 601, uplink and downlink related PDCCH loads in a cell, similar to block 401 of Figure 4.

[0092] The apparatus determines, in block 602, based on the uplink and downlink related PDCCH loads, SSSG switching information. The SSSG switching information is assumed to here to indicate at least one slot of a PDCCH TDD slot pattern to be switched from a first SSSG for monitoring a first number of PDCCH symbols to a second SSSG for monitoring a second number of PDCCH symbols (the second number being larger than the first number). The SSSG switching information may be defined as described in connection with Figure 5.

[0093] The apparatus transmits, in block 603, to one or more terminal devices in the cell, the SSSG switching information. The one or more terminal devices may be RRC connected and active terminal devices. As described in connection with Figure 5, the SSSG switching information may be transmitted in a dedicated field of DCI 2 0.

[0094] Figure 7 illustrates signalling according to embodiments for configuring terminal device(s) for dynamic PDCCH allocation and performing dynamic PDCCH allocation according to embodiments. The illustrated processes of Figure 7 may beperformed by an apparatus which may be an access node (e.g., a distributed or a nondistributed access node) or a part thereof and one or more apparatuses which may be one or more terminal devices (i.e., one or more UEs) or parts thereof. The access node may be the access node 104 of Figure 1, and the one or more terminal devices may be terminal devices 100, 102 of Figure 1. In the following, the entity performing the processes are called an access node and a terminal device for clarity.

[0095] Referring to Figure 7, the one or more terminal devices transmit, in message 701, terminal device capability information to the access node. It is assumed here that the terminal device capability information comprises at least PDCCH monitoring capability information indicating that the one or more terminal devices support the dynamic PDCCH symbol scheduling in TDD (e.g., according to Table IV or Table IX). While not shown in Figure 7, one or more further terminal devices may also transmit terminal device capability information to the access node. The terminal device capability information of these one or more further terminal device may not contain the PDCCH monitoring capability information. The terminal device capability information is received in block 702 by the access node.

[0096] The access node causes, in message(s) 703, configuring said one or more terminal devices based on the terminal device capability information. The terminal device may be configured to enable operation according to any of Figures 2, 3 and / or 5. The causing configuring may comprise configuring the one or more terminal devices to expect at which slot type(s) there can be high / low PDCCH load by RRC configuring (or defining) an information element (IE), e.g., a ‘ slotBased earchSpaceSwitchTrigger ’ IE. Additionally, the causing configuring may comprise subsequently indicating, to the one or more terminal devices, at which slot type(s) to expect high PDCCH load by extending the field ‘search space set group switching flag’ in DCI 2 0 (being conventionally a one-bit field) to 3 bits as defined in Table IV or to 2 bits as defined in Table IX. In other words, RRC signalling may be employed for defining a base configuration for enabling SSSG switching per slot type for the one or more terminal devices while the DCI signalling may be used for specifying the exact configuration to use (out of the ones specified by the RRC configuration). Thus, both RRC and DCI signalling may be employed for the configuration of the one or more terminal devices. The causing configuring of the one or more terminal devices in block 703 may comprise transmitting at least one configuration signal from the access node to the one ormore terminal devices and optionally transmitting at least one acknowledgment signal from the one or more terminal devices to the access node.

[0097] The access node selects, in block 704, the one or more terminal devices based on the received terminal device capability information. In other words, the access node selects, in block 704, any terminal device whose terminal device capability information comprises the PDCCH monitoring capability information.

[0098] The access node determines, in block 705, (during runtime) uplink and downlink related PDCCH loads in the cell. For example, the access node may measure the uplink and downlink related PDCCH loads. This step may correspond substantially to block 401 of Figure 4.

[0099] The access node determines, in block 706, a PDCCH TDD slot pattern for the cell based on the determined uplink and download related PDCCH loads. The access node may determine the PDCCH TDD slot pattern so that a first number (e.g., 1) or a second number (e.g., 2) of PDCCH symbols are assigned per slot based on the uplink and downlink related PDCCH loads. In some embodiments, the PDCCH slot pattern may define the first number of PDCCH symbols for at least one first slot and the second number of PDCCH symbols for at least one second slot. Here, the PDCCH TDD slot pattern comprises at least one of at least one downlink slot, at least one uplink slot or at least one special uplinkdownlink slot. In some embodiments, the PDCCH TDD slot pattern may comprise at least two or all of at least one downlink slot, at least one uplink slot or at least one special uplinkdownlink slot. The at least one downlink slot may comprise one or more uplink granting slots and / or one or more downlink assignment slots.

[0100] The access node transmits, in message(s) 707, the PDCCH TDD slot pattern to the one or more terminal devices. The transmission of block 707 may be carried out, for example, two slots before the new PDCCH TDD slot pattern is enabled at the one or more terminal devices.

[0101] The one or more terminal devices receive, in block 708, the (same) PDCCH TDD slot pattern. The one or more terminal devices may store the PDCCH TDD slot pattern to at least one memory.

[0102] The process of blocks 705 to 708 for allocating and configuring the PDCCH TDD slot pattern may be repeated with a pre-defined period. The pre-defined period may be, for example, 20 ms.

[0103] It should be noted that while the PDCCH TDD slot pattern may be used, in blocks 705 to 708, for indicating which of the first and second SSSGs to use in which slot, the payload size of the PDCCH TDD slot pattern is typically much larger compared to the PDCCH congestion information or the SSSG switching information discussed, e.g., in connection with Figures 2 and 5. For example, while the PDCCH congestion information and the SSSG switching information may be communicated as a 2 or 3 bit field, the PDCCH TDD slot pattern may take approximately 80 bits (assuming 20 ms duration). Thus, transmitting the (3 -bit) PDCCH congestion information or the (2 -bit) SSSG switching information may be considered a more efficient solution for switching certain slot(s) to use a different number of PDCCH symbols.

[0104] Following the configuration of the one or more terminal devices in elements 701 to 708, each of the one or more terminal device may carry out, in block 709, the process of any of Figures 2, 3 or 5, and the access node may carry out, in block 710, the process of Figure 4 and / or Figure 6.

[0105] In some embodiments, only one or two or three of the functionalities discussed in connection with blocks 701 to 702, block 703, block 704 and blocks 705 to 708 may be implemented.

[0106] The blocks, related functions, and information exchanges described above by means of Figures 2 to 7 are in no absolute chronological order, and some of them may be performed simultaneously or in an order differing from the given one. Other functions can also be executed between them or within them, and other information may be sent, and / or other rules applied. Some of the blocks or part of the blocks or one or more pieces of information can also be left out or replaced by a corresponding block or part of the block or one or more pieces of information.

[0107] Figure 8 provides an apparatus 801 according to some embodiments. Specifically, the apparatus 801 may be a terminal device or a part thereof or an access node or a part thereof.

[0108] The apparatus 801 may comprise one or more communication control circuitry 820, such as at least one processor, and at least one memory 840, including one or more algorithms 831 (instructions), such as a computer program code (software) wherein the at least one memory and the computer program code (software) are configured, with the at least one processor, to cause the apparatus to carry out any one of the exemplified functionalities of the terminal device or the access node described above. Said at least one memory 840 may also comprise at least one database 832.

[0109] When the one or more control circuitry 820 comprises more than one processor, the apparatus 801 may be a distributed device wherein processing of tasks takes place in more than one physical unit. Each of the at least one processor may comprise one or more processor cores. A processing core may comprise, for example, a Cortex-A8 processing core manufactured by ARM Holdings or a Zen processing core designed by Advanced Micro Devices Corporation. The one or more control circuitry 820 may comprise at least one Qualcomm Snapdragon and / or Intel Atom processor. The one or more control circuitry 820 may comprise at least one application-specific integrated circuit (ASIC). The one or more control circuitry 820 may comprise at least one field-programmable gate array (FPGA).

[0110] Referring to Figure 8, the one or more control circuitry 820 of the apparatus 801 is configured to carry out functionalities described above by means of any of Figures 2 to 7 using one or more individual circuitries. It is also feasible to use specific integrated circuits, such as ASIC (Application Specific Integrated Circuit) or other components and devices for implementing the functionalities in accordance with different embodiments.

[0111] Referring to Figure 8, the apparatus 801 may further comprise different interfaces 810 such as one or more communication interfaces comprising hardware and / or software for realizing communication connectivity according to one or more communication protocols. Specifically when the apparatus 801 is a terminal device, the one or more communication interfaces 810 may comprise, for example, communication interfaces providing a connection to one or more access nodes. Specifically when the apparatus 801 is an access node, the one or more communication interfaces 810 may comprise, for example, communication interfaces providing a connection to one or more terminal device and / or to one or more core network nodes. The one or more communication interfaces 810 may comprise standard well-known components such as an amplifier, filter, frequency-converter,(de)modulator, and encoder / decoder circuitries, controlled by the corresponding controlling units, and one or more antennas. The apparatus 801 may also comprise one or more user interfaces.

[0112] Referring to Figure 8, the memory 840 may be implemented using any suitable data storage technology, such as semiconductor based memory devices, flash memory, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory.

[0113] As used in this application, the term ‘circuitry’ may refer to one or more or all of the following: (a) hardware-only circuit implementations, such as implementations in only analog and / or digital circuitry, and (b) combinations of hardware circuits and software (and / or firmware), such as (as applicable): (i) a combination of analog and / or digital hardware circuit(s) with soft- war e / firm ware and (ii) any portions of hardware processor(s) with software, including digital signal processor(s), software, and memory(ies) that work together to cause an apparatus, such as a terminal device or an access node, to perform various functions, and (c) hardware circuit(s) and processor(s), such as a microprocessor(s) or a portion of a microprocessor(s), that requires software (e.g. firmware) for operation, but the software may not be present when it is not needed for operation. This definition of ‘circuitry’ applies to all uses of this term in this application, including any claims. As a further example, as used in this application, the term ‘circuitry’ also covers an implementation of merely a hard-ware circuit or processor (or multiple processors) or a portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware.

[0114] In an embodiment, at least some of the processes described in connection with Figures 2 to 7 may be carried out by an apparatus comprising corresponding means for carrying out at least some of the described processes. Some example means for carrying out the processes may include at least one of the following: detector, processor (including dualcore and multiple-core processors), digital signal processor, controller, receiver, transmitter, encoder, decoder, memory, RAM, ROM, software, firmware, display, user interface, display circuitry, user interface circuitry, user interface software, display software, circuit, filter (low-pass, high-pass, bandpass and / or bandstop), sensor, circuitry, inverter, capacitor, inductor, resistor, operational amplifier, diode and transistor. In an embodiment, the at least one processor, the memory, and the computer program code form processing means or comprises one or more computer program code portions for carrying out one or moreoperations according to any one of the embodiments of Figures 3 to 7 or operations thereof. In some embodiments, at least some of the processes may be implemented using discrete components.

[0115] According to an embodiment, there is provided an apparatus (being, e.g., a terminal device or a part thereof) comprising means for performing: communicating, via a PDCCH, using a PDCCH TD, slot pattern and using a first SSSG for monitoring a first number of PDCCH symbols in a slot; during the communicating, receiving, from an access node, PDCCH congestion information, wherein the PDCCH congestion information indicates whether or not one or more uplink granting slots, one or more downlink assignment slots and one or more special uplink-downlink slots in the cell are associated with a high PDCCH load as defined by the access node; and in response to the PDCCH congestion information indicating that the PDCCH load for at least one slot type of uplink granting slot, downlink assignment slot or special uplink-downlink slot of the PDCCH TDD slot pattern corresponds to the high PDCCH load, switching from using the first SSSG to using a second SSSG for monitoring a second number of PDCCH symbols for at least one slot determined based on the at least one slot type, wherein the second number of PDCCH symbols is larger than the first number of PDCCH symbols.

[0116] According to an embodiment, there is provided an apparatus (being, e.g., a terminal device or a part thereof) comprising means for performing: communicating, via a PDCCH, using a PDCCH TDD slot pattern and using a first SSSG for monitoring a first number of PDCCH symbols in one or more slots defined in the PDCCH TDD slot pattern; during the communicating, receiving, from an access node, SSSG switching information indicating at least one slot of the PDCCH TDD slot pattern to be switched from the first SSSG to a second SSSG for monitoring a second number of PDCCH symbols, wherein the second number of PDCCH symbols is larger than the first number of PDCCH symbols; and switching the at least one slot to use the second SSSG based on the SSSG switching information.

[0117] According to an embodiment, there is provided an apparatus (being, e.g., an access node or a part thereof) comprising means for performing:monitoring uplink and downlink related PDCCH loads in a cell; and transmitting, to one or more terminal devices in the cell, PDCCH congestion information defined based on the uplink and downlink related PDCCH loads, wherein the PDCCH congestion information indicates whether or not one or more uplink granting slots, one or more downlink assignment slots and one or more special uplink-downlink slots in the cell are associated with respective PDCCH loads satisfying one or more pre-defined criteria for a high PDCCH load; or determining, based on the uplink and downlink related PDCCH loads, SSSG switching information and transmitting, to one or more terminal devices in the cell, the SSSG switching information, wherein the SSSG switching information indicates at least one slot of a PDCCH TDD slot pattern to be switched from a first SSSG for monitoring a first number of PDCCH symbols to a second SSSG for monitoring a second number of PDCCH symbols, the second number of PDCCH symbols being larger than the first number of PDCCH symbols.

[0118] Embodiments as described may also be carried out, fully or at least in part, in the form of a computer process defined by a computer program or portions thereof. Embodiments of the methods described in connection with Figures 2 to 7 may be carried out by executing at least one portion of a computer program comprising corresponding instructions. The computer program may be provided as a computer readable medium comprising program instructions stored thereon or as a non-transitory computer readable medium comprising program instructions stored thereon. The computer program may be in source code form, object code form, or in some intermediate form, and it may be stored in some sort of carrier, which may be any entity or device capable of carrying the program. For example, the computer program may be stored on a computer program distribution medium readable by a computer or a processor. The computer program medium may be, for example but not limited to, a record medium, computer memory, read-only memory, electrical carrier signal, tele-communications signal, and software distribution package, for example. The computer program medium may be a non-transitory medium. Coding of software for carrying out the embodiments as shown and described is well within the scope of a person of ordinary skill in the art.

[0119] According to an embodiment, there is provided a non-transitory computer readable medium having stored thereon instructions that, when executed by a computing device (for a terminal device), cause the computing device to perform:communicating, via a PDCCH, using a PDCCH TDD, slot pattern and using a first SSSG for monitoring a first number of PDCCH symbols in a slot; during the communicating, receiving, from an access node, PDCCH congestion information, wherein the PDCCH congestion information indicates whether or not one or more uplink granting slots, one or more downlink assignment slots and one or more special uplink-downlink slots in the cell are associated with a high PDCCH load as defined by the access node; and in response to the PDCCH congestion information indicating that the PDCCH load for at least one slot type of uplink granting slot, downlink assignment slot or special uplink-downlink slot of the PDCCH TDD slot pattern corresponds to the high PDCCH load, switching from using the first SSSG to using a second SSSG for monitoring a second number of PDCCH symbols for at least one slot determined based on the at least one slot type, wherein the second number of PDCCH symbols is larger than the first number of PDCCH symbols.

[0120] According to an embodiment, there is provided a non-transitory computer readable medium having stored thereon instructions that, when executed by a computing device (for a terminal device), cause the computing device to perform: communicating, via a PDCCH, using a PDCCH TDD slot pattern and using a first SSSG for monitoring a first number of PDCCH symbols in one or more slots defined in the PDCCH TDD slot pattern; during the communicating, receiving, from an access node, SSSG switching information indicating at least one slot of the PDCCH TDD slot pattern to be switched from the first SSSG to a second SSSG for monitoring a second number of PDCCH symbols, wherein the second number of PDCCH symbols is larger than the first number of PDCCH symbols; and switching the at least one slot to use the second SSSG based on the SSSG switching information.

[0121] According to an embodiment, there is provided a non-transitory computer readable medium having stored thereon instructions that, when executed by a computing device (for an access node), cause the computing device to perform: monitoring uplink and downlink related PDCCH loads in a cell; and transmitting, to one or more terminal devices in the cell, PDCCH congestion information defined based on the uplink and downlink related PDCCH loads, wherein the PDCCH congestion information indicates whether or not one or more uplink granting slots,one or more downlink assignment slots and one or more special uplink-downlink slots in the cell are associated with respective PDCCH loads satisfying one or more pre-defined criteria for a high PDCCH load; or determining, based on the uplink and downlink related PDCCH loads, SSSG switching information and transmitting, to one or more terminal devices in the cell, the SSSG switching information, wherein the SSSG switching information indicates at least one slot of a PDCCH TDD slot pattern to be switched from a first SSSG for monitoring a first number of PDCCH symbols to a second SSSG for monitoring a second number of PDCCH symbols, the second number of PDCCH symbols being larger than the first number of PDCCH symbols.

[0122] The term “non-transitory”, as used herein, is a limitation of the medium itself (that is, tangible, not a signal) as opposed to a limitation on data storage persistency (for example, RAM vs. ROM).

[0123] Reference throughout this specification to one embodiment or an embodiment means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present solution. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment.

[0124] As used herein, a plurality of items, structural elements, compositional elements, and / or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. In addition, various embodiments and example of the present solution may be referred to herein along with alternatives for the various components thereof. It is understood that such embodiments, examples, and alternatives are not to be construed as de facto equivalents of one another, but are to be considered as separate and autonomous representations of the present solution.

[0125] Even though embodiments have been described above with reference to examples according to the accompanying drawings, it is clear that the embodiments are not restricted thereto but can be modified in several ways within the scope of the appended claims. Therefore, all words and expressions should be interpreted broadly and they are intended to illustrate, not to restrict, the embodiment. It will be obvious to a person skilledin the art that, as technology advances, the inventive concept can be implemented in various ways. Further, it is clear to a person skilled in the art that the described embodiments may, but are not required to, be combined with other embodiments in various ways.INDUSTRIAL APPLICABILITY

[0126] At least some embodiments find industrial application in wireless communications.

Claims

CLAIMS1. An apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to perform: communicating, via a physical downlink control channel, PDCCH, using a PDCCH time division duplex, TDD, slot pattern and using a first search space set group, SSSG, for monitoring a first number of PDCCH symbols in a slot; during the communicating, receiving, from an access node, PDCCH congestion information, wherein the PDCCH congestion information indicates whether or not one or more uplink granting slots, one or more downlink assignment slots and one or more special uplink-downlink slots in the cell are associated with a high PDCCH load as defined by the access node; and in response to the PDCCH congestion information indicating that the PDCCH load for at least one slot type of uplink granting slot, downlink assignment slot or special uplinkdownlink slot of the PDCCH TDD slot pattern corresponds to the high PDCCH load, switching from using the first SSSG to using a second SSSG for monitoring a second number of PDCCH symbols for at least one slot determined based on the at least one slot type, wherein the second number of PDCCH symbols is larger than the first number of PDCCH symbols.

2. The apparatus of claim 1, wherein the downlink assignment slot is a downlink slot having a valid KI supported by the access node for enabling physical downlink shared channel, PDSCH, transmissions; and / or the uplink granting slot is a downlink slot having a valid K2 supported by the access node for enabling uplink grant transmissions; and / or the special uplink-downlink slot is a slot having valid KI and K2 supported by the access node.

3. The apparatus according to any preceding claim, wherein the at least one memory and the instructions are configured, with the at least one processor, to cause the apparatus to perform:following the switching, receiving, from the access node, further PDCCH congestion information; and in response to the further PDCCH congestion information indicating that PDCCH load for at least one of said at least one slot type of uplink granting slot, downlink assignment slot or special uplink-downlink slot of the PDCCH TDD slot pattern fails to correspond to the high PDCCH load, switching back to using the first SSSG for said at least one of said at least one slot type; and / or in response to the further PDCCH congestion information indicating that PDCCH load for at least one further slot type of uplink granting slot, downlink assignment slot or special uplink-downlink slot of the PDCCH TDD slot pattern corresponds to the high PDCCH load, switching from using the first SSSG to using the second SSSG for said at least one further slot type, wherein said at least one further slot type is different from the at least one slot type.

4. The apparatus according to any preceding claim, wherein the receiving of the PDCCH congestion information comprises: receiving, from the access node, downlink control information format 2 0, DCI 2 0, wherein the DCI 2 0 comprises the PDCCH congestion information as a dedicated field of the DCI 2 0.

5. An apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to perform: communicating, via a PDCCH, using a PDCCH TDD slot pattern and using a first SSSG for monitoring a first number of PDCCH symbols in one or more slots defined in the PDCCH TDD slot pattern; during the communicating, receiving, from an access node, SSSG switching information indicating at least one slot of the PDCCH TDD slot pattern to be switched from the first SSSG to a second SSSG for monitoring a second number of PDCCH symbols, wherein the second number of PDCCH symbols is larger than the first number of PDCCH symbols; and switching the at least one slot to use the second SSSG based on the SSSG switching information.

6. The apparatus of claim 5, wherein the SSSG switching information comprises: a first SSSG switching flag for one or more slots of the PDCCH TDD slot pattern having a valid KI supported by the access node; and / or a second SSSG switching flag for one or more slots of the PDCCH TDD slot pattern having a valid K2 supported by the access node.

7. The apparatus according to any of claims 5 to 6, wherein the receiving of the SSSG switching information comprises: receiving, from the access node, DCI 2 0, wherein the DCI 2 0 comprises the SSSG switching information as a dedicated field of the DCI 2 0.

8. The apparatus according to any preceding claim, wherein the at least one memory and the instructions are configured, with the at least one processor, to cause the apparatus to perform: starting a timer for monitoring the second SSSG in response to the switching to using the second SSSG; and in response to the timer expiring, switching from using the second SSSG back to using the first SSSG for said at least one slot.

9. An apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to perform: monitoring uplink and downlink related PDCCH loads in a cell; and transmitting, to one or more terminal devices in the cell, PDCCH congestion information defined based on the uplink and downlink related PDCCH loads, wherein the PDCCH congestion information indicates whether or not one or more uplink granting slots, one or more downlink assignment slots and one or more special uplink-downlink slots in the cell are associated with respective PDCCH loads satisfying one or more pre-defined criteria for a high PDCCH load; or determining, based on the uplink and downlink related PDCCH loads, SSSG switching information and transmitting, to one or more terminal devices in the cell, the SSSG switching information, wherein the SSSG switching information indicates at least one slotof a PDCCH TDD slot pattern to be switched from a first SSSG for monitoring a first number of PDCCH symbols to a second SSSG for monitoring a second number of PDCCH symbols, the second number of PDCCH symbols being larger than the first number of PDCCH symbols.

10. The apparatus of claim 9, wherein the at least one memory and the instructions are configured, with the at least one processor, to cause the apparatus to perform, before the monitoring: determining uplink and downlink related PDCCH loads in the cell; determining a PDCCH TDD slot pattern for the cell so that one or two PDCCH symbols are assigned per slot based on the uplink and downlink related PDCCH loads, wherein the PDCCH TDD slot pattern comprises at least one downlink slot, at least one uplink slot and at least one special uplink-downlink slot; and transmitting the PDCCH TDD slot pattern to the one or more terminal devices.

11. The apparatus of claim 9 or 10, wherein the at least one memory and the instructions are configured, with the at least one processor, to cause the apparatus to perform, before the monitoring: causing configuring one or more terminal devices for dynamic PDCCH symbol scheduling in TDD in the cell, wherein the dynamic PDCCH symbol scheduling enables dynamic slot-specific scheduling of the first number or the second number of PDCCH symbols depending on a PDCCH load in the cell; and / or causing configuring the one or more terminal devices in the cell with the first SSSG and the second SSSG.

12. The apparatus of claim 11, wherein the causing of the configuring of the one or more terminal devices in the cell with the first and second SSSGs comprises: causing configuring the one or more terminal devices with a radio resource control, RRC, parameter for adding a location for a SSSG switching field in DCI 2 0, wherein the transmitting of the PDCCH congestion information or the SSSG switching information comprises: transmitting the PDCCH congestion information or the SSSG switching information in the SSSG switching field of the DCI 2 0.

13. The apparatus according to any of claims 9 to 12, wherein the at least one memory and the instructions are configured, with the at least one processor, to cause the apparatus to perform: receiving terminal device capability information from a plurality of terminal devices, wherein the terminal device capability information received from at least one terminal device comprises PDCCH monitoring capability information indicating support for dynamic PDCCH symbol scheduling in TDD; and selecting the one or more terminal devices based on the terminal device capability information.

14. The apparatus according to any of claims 9 to 13, wherein the one or more terminal devices are RRC connected and active terminal devices.

15. The apparatus according to any preceding claim, wherein the first number is one and the second number is two.

16. A method comprising: communicating, via a physical downlink control channel, PDCCH, using a PDCCH time division duplex, TDD, slot pattern and using a first SSSG for monitoring a first number of PDCCH symbols in a slot; during the communicating, receiving, from an access node, PDCCH congestion information, wherein the PDCCH congestion information indicates whether or not one or more uplink granting slots, one or more downlink assignment slots and one or more special uplink-downlink slots in the cell are associated with a high PDCCH load as defined by the access node; and in response to the PDCCH congestion information indicating that the PDCCH load for at least one slot type of uplink granting slot, downlink assignment slot or special uplinkdownlink slot of the PDCCH TDD slot pattern corresponds to the high PDCCH load, switching from using the first SSSG to using a second SSSG for monitoring a second number of PDCCH symbols for at least one slot determined based on the at least one slot type, wherein the second number of PDCCH symbols is larger than the first number of PDCCH symbols.

17. A method comprising:communicating, via a PDCCH, using a PDCCH TDD slot pattern and using a first SSSG for monitoring a first number of PDCCH symbols in one or more slots defined in the PDCCH TDD slot pattern; during the communicating, receiving, from an access node, SSSG switching information indicating at least one slot of the PDCCH TDD slot pattern to be switched from the first SSSG to a second SSSG for monitoring a second number of PDCCH symbols, wherein the second number of PDCCH symbols is larger than the first number of PDCCH symbols; and switching the at least one slot to use the second SSSG based on the SSSG switching information.

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