Terminal device, network node for OD-SSB handling, and methods thereof

Abstract

Embodiments of the present disclosure relate to methods, apparatus for on-demand SSB transmission and handling, e.g. measurement and reporting, and specifically under the scenario of SCell activation. Configuration of on-demand SSB introduced by the disclosure is indicated to a terminal device and the on-demand SSB is triggered for transmission. The terminal device receives the on- demand SSB, measures and reports the measurement based on the indication. The network node can determine whether to activate a specific SCell depending on the quality of the Scell which is indicated by the measurement report.

Description

TERMINAL DEVICE, NETWORK NODE FOR OD-SSB HANDLING, AND METHODSTHEREOFThis application claims the benefit of provisional patent application serial number US63 / 663968, filed 6 / 25 / 2024, the disclosure of which is hereby incorporated herein by reference in its entirety.TECHNICAL FIELD

[0001] The non-limiting and exemplary embodiments of the present disclosure generally relate to the technical field of communications, and specifically to methods and apparatuses for procedures of on-demand SSB handling.BACKGROUND

[0002] In telecommunication system, Synchronization / PBCH block (SSB) carries specific signals for initial cell search or establishing Downlink Synchronization by a user equipment (UE). It can be measured by the UE to get Received Signal Received Power (RSRP) or Received Signal Received Quality (RSRQ) of a cell and to report measurement reports to a serving node of the UE. The components of an SSB includes Primary Sync Signal (PSS), Secondary Sync Signal (SSS) and (Physical Broadcast Channel) PBCH, and the PBCH carries essential system information such as Master Information Block (MIB). In LTE, not all PSS / SSS occurrence include PBCH. While in NR, all three of those components appear in every occurrence.

[0003] Periodicity and location of SSB transmissions are defined by the network. Multiple SSBs are transmitted in a localized burst set. In NR, beamforming techniques are used to improve SSB coverage and reduce interference. Within an SS burst set, multiple SSBs can be transmitted in different beams and SSB can be used for beam measurement. The transmission of SSBs within a localized burst set is confined to a 5 ms window and the SSB and SSB burst set are repeated in a periodic manner. The SSB periodicity can be configured from the value set {5, 10, 20, 40, 80, 160} ms. Figure 1 illustratively shows the relationship between an SSB burst set with 4 SSBs and an SSB periodicity.

[0004] To inform a UE with a SSB measurement periodicity, SSB measurement time configuration (SMTC) is introduced in NR. SMTC consists of SMTC periodicity and SMTC window length. In NR, since different beams can be configured to cover different spatial implementation, UE do not need to measure all the spatial directions. The beams to be measured can be controlled or configurable through SMTC window. SMTC window length indicates the location of the SSB to be measured within the SSB burst set. A signaling carrying information of a SMTC window informs the UE of the timing and periodicity of SSBs that the UE can use for measurements. The SMTC window periodicity can be configured from the value set {5, 10, 20, 40, 80, 160} ms, matching the possible SSB periodicities. As is shown in Figure 1, an SMTC periodicity may be larger than an SSB periodicity, since a UE might not need to monitor all SSB sets from a network node. The SMTC window duration can be configured from the value set {1, 2, 3, 4, 5} ms. An SMTC window duration may also be simply called as SMTC duration, SMTC length, SMTC occasion duration or SMTC occasion length etc.

[0005] Master Cell Group (MCG) and Secondary Cell Group (SCG) are concepts in dual connectivity (DC). It may be simply understood that the MCG is located in a group in which a cell in which the UE first initiates random access (RACH) is located. There may be many cells under the MCG. The one being used for initiating initial access is called Primary Cell (PCell). As the name suggests, PCell is the most important cell in the MCG. The PCell under the MCG and the Secondary Cell(s) (SCell) under the MCG are combined by using a carrier aggregation (CA, CA) technology. Similarly, there is a primary cell under the SCG, the PSCel I, which can also be simply understood as a cell for which initial access is initiated under the SCG. The PSCell and SCell(s) under the SCG are also combined through CA. Since most signaling messages are sent only on the PCell and PSCell, the 3GPP specification defines a concept SPCell including both the PCell and the PSCell.

[0006] On-demand SSB (OD SSB) is discussed in ongoing NR evolution, which may be provided "temporarily" to UEs whose functionality or performance may be improved if additional signals for e.g., loop conversion, synchronization, measurements, or other signal processing steps are available. Some scenarios where on-demand SSBs are expected to be useful include:SCell quality measurements upon SCell configuration;• Synchronization upon SCell activation;• Timing / Frequency tracking for an active serving cell;• RRM measurements on serving or neighbour cells.

[0007] In some scenarios, a cell may transmit baseline SSBs at a lower rate, e.g. 160 ms, or even without periodic SSBs being transmitted as a baseline. Network may then activate additional SSBs or SSB burst sets, e.g. with periodicity 20 ms or 5 ms, respectively, in association with certain corresponding procedures. On-demand SSBs may be one-shot transmissions or limited-duration SSB bursts, with or without a recurrent structure. The on-demand SSBs may be transmitted during a specified or configured time window. They can also be transmitted until further notice, e.g., until an explicit notification to the UE. Further, they may be transmitted at same or at a different power level to the baseline SSBs, and their spatial configuration can also differ from that of the baseline SSB.

[0008] Network energy saving as of great importance for environmental sustainability and reducing of environmental impact such as greenhouse gas emissions, has been considered by the 3GPP standard. On-demand SSB is one of the approaches for network energy saving since with dynamic SSB transmission for dynamic needs, baseline SSBs can be dramatically decreased or even cut off in some specific cells. Thus, it is also beneficial for operational cost savings for the operators.

[0009] In the current 3GPP Release 19 discussion, an aim is to study and specify on- demand SSB as well as adaptation of common signal and / or channel transmissions. Relevant objective is how on-demand SSB can be used by UE for SCell time / frequency synchronization, L1 / L3 measurements and SCell activation.SUMMARY

[0010] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

[0011] In a first aspect of the present disclosure, there is provided a method implemented at a network node. In the method, the network node sends an on-demand SSB indication to a terminal device as an on-demand SSB triggering signal, indicating on-demand SSB associated with a secondary cell for the terminal device. The network node initiates on- demand SSB transmission to be received by the terminal device. It also transmits an SCell activation signal for the associated SCell to the terminal device. Then, it might receive a failure message from the terminal device that its received OD-SSB is not enough. For example, the received OD-SSBs are less than needed for either SCell activation or OD-SSB measurement.

[0012] In an example, the network node may decide whether to activate the SCell based on a measurement report received which is associated with the on-demand SSB indication. Only when the measurement report indicates a good enough quality of the SCell, the SCell activation indication or command is decided to be sent. In another example, the network node may decide to send out more OD-SSBs so that the terminal device can fulfill the SCcell activation or OD-SSB measurement. In addition or as an alternative, it may decide to send out baseline SSBs for SCell activation.

[0013] In a second aspect of the present disclosure, there is provided a method implemented at a terminal device. In the method, the terminal device receives an on-demand SSB indication from a network node providing a serving cell for it, and then receives on-demand SSB according to the on-demand SSB indication. The terminal device then performs measurement on the received on-demand SSB.

[0014] In an example, the terminal device may send, based at least in part on at least one rule, measurement report about the received on-demand SSB. In an example, the terminal device may receive an SCell activation signal for the associated SCell. In an example, the terminal device may receive the SCell activation signal after the measurement report associated with the on- demand SSB indication is sent.

[0015] In an example, the terminal device receives insufficient number of OD-SSBs such that either the SCell activation or the measurement report can't be fulfilled. It may transmit a failure message to the network node indicating the insufficient OD-SSBs it has received according to the on-demand SSB indication..

[0016] In the third aspect of the present disclosure, a network node is provided. The network node comprises a processor and a memory coupled to the processor, the memory containing instructions executable by the processor, whereby the network node is operative to perform the method according to the first aspect.

[0017] In the fourth aspect of the present disclosure, a terminal device is provided. The terminal device comprises a processor and a memory coupled to the processor, the memory containing instructions executable by the processor, whereby the terminal device is operative to perform the method according to the second aspect.

[0018] In a fifth aspect of the present disclosure, a UE is provided. It comprises an antenna configured to send and receive wireless signals, radio front-end circuitry connected to the antenna and to processing circuitry, and configured to condition signals communicated between the antenna and the processing circuitry, the processing circuitry being configured to perform any of the steps of any of the second aspect. The UE also comprises an input interface connected to the processing circuitry and configured to allow input of information into the UE to be processed by the processing circuitry, an output interface connected to the processing circuitry and configured to output information from the UE that has been processed by the processing circuitry; and a battery connected to the processing circuitry and configured to supply power to the UE.

[0019] Embodiments herein may provide many advantages, of which a non-exhaustive list of examples follows. In some embodiments herein, since SSB transmission can be triggered when they are needed (i.e. on-demand), the default periodic SSB transmissions of a secondary cell of a UE can be more sparse, or entirely removed, which enables longer sleep periods and energy savings in a network node. In some embodiments herein, since the network node (e.g. PCell) can avoid activating an unknown SCell even when that cell does not transmit static SSB. At the same time, UE can also achieve the power saving based on on-demand SSB.

[0020] In some embodiments herein, Scell activation delay is kept low for SSB-less Scells, including when the SCell does not co-locate with PCell or other Scells may be assumed. In some embodiments herein, transmission of separate indications for on-demand SSB activation and / or deactivation are not required, as it can be contained / implied in measurement reportingconfiguration and / or Scell activation / deactivation signaling. The embodiments herein are not limited to the features and advantages mentioned above. A person skilled in the art will recognize additional features and advantages upon reading the following detailed description.BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The above and other aspects, features, and benefits of various embodiments of the present disclosure will become more fully apparent, by way of example, from the following detailed description with reference to the accompanying drawings, in which like reference numerals or letters are used to designate like or equivalent elements. The drawings are illustrated for facilitating better understanding of the embodiments of the disclosure and not necessarily drawn to scale, in which:Figure 1 illustrates relationship between SSB and SMTC;Figure 2 shows a method implemented by a network node according to an embodiment of the present disclosure;Figure 3 shows an octet of SCell Activation / Deactivation MAC CE as defined by the current standard;Figure 4a and 4b illustrate different scenarios for on-demand SSB triggering, in which the SCell activation signaling could be in different relative positions to the on-demand SSB indication (i.e., on-demand SSB triggering) in time domain;Figure 5 shows a method implemented by a terminal device according to an embodiment of the present disclosure;Figure 6 depicts a structure of a network node to perform the methods according to the embodiments of the present disclosure;Figure 7 depicts a structure of a terminal device to perform the methods according to the embodiments of the present disclosure;Figure 8 depicts a structure of a user equipment as an example to perform the methods according to the embodiments of the present disclosure;Figure 9 shows a method implemented by a terminal device according to some embodiments of the present disclosure;Figure 10 shows a method implemented by a network node according to some embodiments of the present disclosure.DETAILED DESCRIPTION

[0022] The embodiments of the present disclosure are described in detail with reference to the accompanying drawings. It should be understood that these embodiments are discussed only for the purpose of enabling those skilled persons in the art to better understand and thus implement the present disclosure, rather than suggesting any limitations on the scope of the present disclosure. Reference throughout this specification to features, advantages, or similar language does not imply that all of the features and advantages that may be realized with the present disclosure should be or are in any single embodiment of the disclosure. Rather, language referring to the features and advantages is understood to mean that a specific feature, advantage, or characteristic described in connection with an embodiment is included in at least one embodiment of the present disclosure. Furthermore, the described features, advantages, and characteristics of the disclosure may be combined in any suitable manner in one or more embodiments. One skilled in the relevant art will recognize that the disclosure may be practiced without one or more of the specific features or advantages of a particular embodiment. In other instances, additional features and advantages may be recognized in certain embodiments that may not be present in all embodiments of the disclosure.

[0023] As used herein, the term "network" refers to a network following any suitable communication standards such as new radio (NR), long term evolution (LTE), LTE-Advanced, wideband code division multiple access (WCDMA), high-speed packet access (HSPA), Code Division Multiple Access (CDMA), Time Division Multiple Address (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency-Division Multiple Access (OFDMA), Single carrier frequency division multiple access (SC-FDMA) and other wireless networks. A CDMA network may implement a radio technology such as Universal Terrestrial Radio Access (UTRA), etc. UTRA includes WCDMA and other variants of CDMA. A TDMA network may implement a radio technology such as Global System for Mobile Communications (GSM). An OFDMA network may implement a radio technology such as Evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB),IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDMA, Ad-hoc network, wireless sensor network, etc. In the following description, the terms "network" and "system" can be used interchangeably. Furthermore, the communications between two devices in the network may be performed according to any suitable communication protocols, including, but not limited to, the communication protocols as defined by a standard organization such as 3GPP. For example, the communication protocols may comprise the first generation (1G), 2G, 3G, 4G, 4.5G, 5G, 6G communication protocols, and / or any other protocols either currently known or to be developed in the future.

[0024] The term "network device" or "network node" or "network function" refers to any suitable function which can be implemented in a network entity (physical or virtual) of a communication network. For example, the network function can be implemented either as a network element on a dedicated hardware, as a software instance running on a dedicated hardware, or as a virtualized function instantiated on an appropriate platform, e.g. on a cloud infrastructure.

[0025] The network device may be an access network device with accessing function in a communication network via which a terminal device accesses to the network and receives services therefrom. The access network device may include a base station (BS), an access point (AP), a multi-cell / multicast coordination entity (MCE), a controller or any other suitable device in a wireless communication network. The BS may be, for example, a node B (NodeB or NB), an evolved NodeB (eNodeB or eNB), a next generation NodeB (gNodeB or gNB), a remote radio unit (RRU), a radio header (RH), an Integrated Access and Backhaul (IAB) node, a remote radio head (RRH), a relay, a low power node such as a femto, a pico, and so forth.

[0026] Yet further examples of the access network device comprise multi-standard radio (MSR) radio equipment such as MSR BSs, network controllers such as radio network controllers (RNCs) or base station controllers (BSCs), base transceiver stations (BTSs), transmission points, transmission nodes, positioning nodes and / or the like. More generally, however, the network node may represent any suitable device (or group of devices) capable, configured, arranged, and / or operable to enable and / or provide a terminal device access to a wireless communicationnetwork or to provide some service to a terminal device that has accessed to the wireless communication network.

[0027] Virtualizing means creating virtual versions of apparatuses or devices which may include virtualizing hardware platforms, storage devices and networking resources. As used herein, virtualization can be applied to a provider edge node and relates to an implementation in which at least a portion of the functionality is implemented as one or more virtual components (e.g., via one or more applications, components, functions, virtual machines or containers executing on one or more physical processing nodes in one or more networks).

[0028] In some embodiments, some or all of the functions described herein may be implemented as virtual components executed by one or more virtual machines implemented in one or more virtual environments hosted by one or more of hardware nodes.

[0029] The functions may be implemented by one or more applications (which may alternatively be called software instances, virtual appliances, network functions, virtual nodes, virtual network functions, etc.) operative to implement some of the features, functions, and / or benefits of some of the embodiments disclosed herein. Applications are run in virtualization environment which provides hardware comprising processing circuitry and memory. Memory contains instructions executable by processing circuitry whereby application is operative to provide one or more of the features, benefits, and / or functions disclosed herein.

[0030] During operation, processing circuitry executes software to instantiate the hypervisor or virtualization layer, which may sometimes be referred to as a virtual machine monitor (VMM). Virtualization layer may present a virtual operating platform that appears like networking hardware to virtual machine.

[0031] The term "terminal device" refers to any end device that can access a communication network and receive services therefrom. By way of example and not limitation, the terminal device refers to a mobile terminal, user equipment (UE), or other suitable devices. The UE may be, for example, a Subscriber Station (SS), a Portable Subscriber Station, a Mobile Station (MS), or an Access Terminal (AT). The terminal device may include, but not limited to, a portable computer, an image capture terminal device such as a digital camera, a gaming terminal device, a music storage and a playback appliance, a mobile phone, a cellular phone, a smartphone, a voice over IP (VoIP) phone, a wireless local loop phone, a tablet, a wearable device, a personal digital assistant (PDA), a portable computer, a desktop computer, a wearable terminal device, a vehicle-mounted wireless terminal device, a wireless endpoint, a mobile station, a laptop-embedded equipment (LEE), a laptop-mounted equipment (LME), a USB dongle, a smart device, a wireless customer-premises equipment (CPE) and the like. In the following description, the terms "terminal device", "terminal", "user equipment" and "UE" may be used interchangeably. As one example, a terminal device may represent a UE configured for communication in accordance with one or more communication standards promulgated by the 3GPP (3rd Generation Partnership Project), such as 3GPP LTE standard or NR standard. As used herein, a "user equipment" or "UE" may not necessarily have a "user" in the sense of a human user who owns and / or operates the relevant device. In some embodiments, a terminal device may be configured to transmit and / or receive information without direct human interaction. For instance, a terminal device may be designed to transmit information to a network on a predetermined schedule, when triggered by an internal or external event, or in response to requests from the communication network. Instead, a UE may represent a device that is intended for sale to, or operation by, a human user but that may not initially be associated with a specific human user.

[0032] As yet another example, in an Internet of Things (loT) scenario, a terminal device may represent a machine or other device that performs monitoring and / or measurements, and transmits the results of such monitoring and / or measurements to another terminal device and / or network equipment. The terminal device may in this case be a machine-to-machine (M2M) device, which may in a 3GPP context be referred to as a machine-type communication (MTC) device. As one particular example, the terminal device may be a UE implementing the 3GPP narrow band internet of things (NB-loT) standard. Particular examples of such machines or devices are sensors, metering devices such as power meters, industrial machinery, or home or personal appliances, for example refrigerators, televisions, personal wearables such as watches etc. In other scenarios, a terminal device may represent a vehicle or other equipment that is capable of monitoring and / or reporting on its operational status or other functions associated with its operation.

[0033] The term signal or radio signal used herein can be any physical signal or physical channel. Examples of DL physical signals are reference signal (RS) such as PSS, SSS, CSI-RS, DMRS signals in SS / PBCH block (SSB), discovery reference signal (DRS), Cell RS (CRS), positioning RS (PRS) etc. RS may be periodic e.g. RS occasion carrying one or more RSs may occur with certain periodicity e.g. 20 ms, 40 ms etc. The RS may also be aperiodic.

[0034] Each SSB carries NR-PSS, NR-SSS and NR-PBCH in a plurality of successive symbols, 4 as the number of an example. One or multiple SSBs are transmit in one SSB burst which is repeated with certain periodicity e.g. 5 ms, 10 ms, 20 ms, 40 ms, 80 ms or 160 ms. A UE is configured with information about SSB on cells of certain carrier frequency by one or more SS / PBCH block measurement timing configuration (SMTC) configurations. The SMTC configuration comprising parameters such as SMTC periodicity, SMTC occasion length in time or duration, SMTC time offset w.r.t reference time (e.g. serving cell's SFN) etc. Therefore, SMTC occasion may also occur with certain periodicity e.g. 5 ms, 10 ms, 20 ms, 40 ms, 80 ms and 160 ms. Examples of uplink (UL) physical signals are reference signal such as sounding RS (SRS), Demodulation RS (DMRS), etc. The term physical channel refers to any channel carrying higher layer information e.g. data, control etc. Examples of physical channels are PBCH, NPBCH, PDCCH, PDSCH, sPUCCH, sPDSCH, sPUCCH, sPUSCH, MPDCCH, NPDCCH, NPDSCH, E-PDCCH, PUSCH, PUCCH, NPUSCH etc.

[0035] Aperiodic-temporary reference symbol (A-TRS) used herein is a Rel-17 application of the CSI-RS for UE measurement to settle the AGC during the secondary cell activation timeline. A-TRS can be typical NZP CSI-RS which follow the configuration from higher layer.

[0036] The term time resource used herein may correspond to any type of physical resource or radio resource expressed in terms of length of time. Examples of time resources are: symbol, time slot, subframe, radio frame, TTI, interleaving time, slot, sub-slot, mini-slot, system frame number (SFN) cycle, hyper-SFN (H-SFN) cycle etc.

[0037] References in the specification to "one embodiment," "an embodiment," "an example embodiment," and the like indicate that the embodiment described may include a particular feature, structure, or characteristic, but it is not necessary that every embodiment includes the particular feature, structure, or characteristic. Moreover, such phrases are notnecessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

[0038] It is noted that these terms as used in this document are used only for ease of description and differentiation among nodes, devices or networks etc. With the development of the technology, other terms with the similar / same meanings may also be used.

[0039] In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skills in the art to which this disclosure belongs.

[0040] Current 3GPP standard is discussing about procedures and signaling methods to support on-demand SSB SCell operation for UEs in connected mode configured with CA, for both intra- / inter-band CA. and on-demand SSB transmission can be used by UE for at least SCell time / frequency synchronization, L1 / L3 measurements and SCell activation, and is supported for FR1 and FR2 in non-shared spectrum. This disclosure will provide specific methods and procedures for on-demand SSB SCell operation for the UEs.

[0041] From energy consumption's perspective, transmission of periodic reference signals like SSBs is one of the major energy consumption sources in network operation. For a PCell, SSBs have to be always on in order to help a UE acquire time / frequency synchronization, downlink automatic gain control (AGC) and L1 / L3 measurements. For CA SCells, SSB is mainly needed for SCell activation and SCell operation. For SCell activation, a UE needs to acquire time / frequency sync information and AGC to complete the SCell activation. For energy saving purpose, SSBs of an SCell can be transmitted very sparsely, or even no regular SSB transmission for the SCell, configured by an SCell configuration. And when an SCell is to be activated, SSBs with high rate can enable fast activation of the SCell, and later in a SCell operation process, SSBs can be 'switched' to a sparse transmission. Therefore, the baseline 'always-on' periodic SSB transmission on SCells can be minimized.

[0042] Since on-demand SSB transmission has different periodicity, e.g., more intense periodicity, compared with baseline SSB transmission. In some places, baseline SSB transmissionis called as legacy or static SSB transmission or relaxed SSB transmission or default SSB transmission. In an example, baseline SSB transmission may be with 160ms periodicity and on- demand SSB transmission is 20ms in periodicity. In another example, baseline SSB transmission may be off and on-demand SSB transmission is 20ms in periodicity.

[0043] In yet another example, enabling or applying on-demand SSB transmission reflects SSB transmission from sparser periodicity in baseline SSB to more intense periodicity in on- demand SSB, e.g., from off to 20ms, or from 20ms to 160ms. After that, disabling or not applying on-demand SSB transmission reflects SSB transmission from more intense periodicity in on- demand SSB to sparser periodicity in baseline SSB, e.g., from 20ms to off or from 160ms to 20ms. Those SSB transmissions can be controlled by the network and indicated to a UE for which it is serving.

[0044] The disclosure provides a mechanism about on-demand SSB transmission as well as measurement and report of the on-demand SSB, especially related to SCell activation. Baseline SSBs of the SCell could exist with sparse periodicity or even be disabled, which can be combined with on-demand SSBs and enables longer sleep periods and energy savings in the NW. Baseline SSBs of the SCell can follow legacy configuration and therefore will not be expanded for description hereinafter.

[0045] According to the disclosure, a method embodiment performed by a network node for on-demand SSB transmission includes the following steps: transmitting (201) an on-demand SSB indication to a terminal device for which the network node is serving, wherein on-demand SSBs indicated by the indication are associated with a secondary cell (SCell) having been configured for the terminal device; initiating (202) on- demand SSB transmission to be received by the terminal device; and transmitting (203) an SCell activation signal for the associated SCell to the terminal device. Figure 2 depicts those main steps where between the initiating step and the SCell activation command step (203) there is an arrow with dotted line, not only showing the possibility that the initiating step could be later or at the same time, but indicating there could be other steps happened in-between. We will explain in further details later.

[0046] Scenario applied for the embodiment comprises a first serving cell (cel 11) and a first network node (NN1) managing or serving cell 1 being comprised in a first network (NW1), and at least a second serving cell (cel 12) and a second network node (NN2) managing or serving cel 12 being comprised in a second network (NW2). A terminal device, e.g., a UE, is configured to operate in cel 11 and cell2, and in a particular example, cel 11 is SpCell or PCell, cel 12 is SCell.

[0047] In an embodiment, the on-demand SSB indication of the associated SCell (cell2) should carry or carry or indicate necessary information for measurement and reporting. For instance, the on-demand SSB indication carries a configuration of on-demand SSB, or it directs the configuration of on-demand SSB is configured to the UE by another signaling, e.g., RRC signaling or L1 / L2 signaling, and in meanwhile it indicates to enable measuring and / or reporting on-demand SSB. Configuration of on-demand SSB should include identity of the SCell (e.g., cell2), such as cell index / ID on which on-demand SSB is transmitted. Note that there may be more than one cell to be measured with one on-demand SSB on each cell or one on-demand SSB covering more than one cell.

[0048] An on-demand SSB configuration comprises on-demand SSB transmission, on- demand SSB measurement and on-demand SSB report configuration. Note that more than one SSB configuration may for different phase / time period in the overall Scell activation procedure.

[0049] The configuration of on-demand SSB transmission may comprises SSB burst location, SSB periodicity and / or SSB starting / duration / ending time with respect to a reference point, e.g., SFN w.r.t a serving cell, e.g., cel 11. In one example, the starting / ending time may be an absolute time instant, e.g., a UTC timestamp, or any suitable combination of one or more of H-SFN, SFN, subframe number, slot number and symbol number of the serving cell. Optionally, all of those is combined with a time reference, e.g., H-SFN + SFN, H-SFN + SFN + subframe number, H-SFN + SFN + slot number, SFN + subframe number, SFN + slot number. Accordingly, the UE should initiate SSB measurement prior to or from the time instant.

[0050] In another example, the starting / ending time may be a relative time delay from receiving a predefined specific signaling from the network node, e.g., the on-demand SSB indication or an SCell activation MAC-CE command. The UE should accordingly initiate SSB measurement prior to or from the time instant.

[0051] The duration may be either expressed as a number of occasions, a time period or a start- and stop-time. Alternatively, the duration / ending time is represented by a counter or timer.

[0052] An example of the configuration of on-demand SSB transmission can be carried byServingCellConfigCommon as ssbOnDemandSSB-PositionsInBurst and ssbOnDemandSSB- periodicityServingCell as shown below.

[0053] Another example of the configuration of on-demand SSB transmission can be carried in ServingCellConfigCommonSIB as ssbOnDemandSSB-PositionsInBurst and ssbOnDemandSSB-periodicityServingCell as shown below.

[0054] It's worth noting that the on-demand SSB may keep the legacy SSB format for the UE to receive it without any implementation change. However, since the on-demand SSB is mainly for a procedure which shall be completed in a short / limited period, e.g., SCell activation, shorter measurement time is one of important metrics, so on-demand SSB doesn't need to be same as the legacy SSB configuration, e.g., in RRC meassage via ServingCellConfigCommon or ServingCellConfigCommonSIBl, for the SCell provided the legacy SSB is configured for the SCell.One typical difference or enhancement is that on-demand SSB may be defined with shorter periodicity than the legacy SSB, e.g., 5ms.

[0055] In a case that baseline SSB transmission is 'turned off', the legacy SSB configuration may be used as on-demand SSB by the UE after receiving the indication enablingon-demand SSB, which means the on-demand SSB configuration reuses (partial) format of legacy SSB configuration.

[0056] The configuration of on-demand SSB measurement may comprises measurement location, measurement periodicity and / or measurement starting / duration / ending time with respect to a reference point, e.g., SFN w.r.t a serving cell, e.g., cel 11. In an example, the starting / ending time may be an absolute time instant, e.g., a UTC timestamp, or any suitable combination of one or more of H-SFN, SFN, subframe number, slot number and symbol number of the serving cell. Optionally, any of these options is combined with a time reference, e.g.,H- SFN + SFN, H-SFN + SFN + subframe number, H-SFN + SFN + slot number, SFN + subframe number, SFN + slot number. The UE shall accordingly initiate SSB measurement prior to or from the time instant.

[0057] Alternatively, the starting / ending time may be a relative time delay from receiving a predefined specific signaling from the NW, e.g., the on-demand SSB indication or SCell activation MAC-CE command. The UE shall accordingly initiate SSB measurement prior to or from the time instant.

[0058] The duration may be either expressed as a number of occasions, a time period or a start- and stop-time. When the duration has passed, the UE falls back to baseline SSB measurement. Alternatively, the duration / ending time is represented by a counter or timer.

[0059] An example of the configuration of on-demand SSB measurement can be carried by MeasObjectNR as shown below.

[0060] In above information elements for MeasObjectNR, smtcOnDemandSSBIist is introduced as a new parameter / field to indicate SSB measurement timing configuration for the UE to measure on-demand SSB with respect to on-demand SSB configuration.

[0061] The configuration of on-demand SSB report may indicate one of reporting types, e.g., periodical report, semi-persistent report, event trigger report, aperiodic or one-shot, and parameters and / or trigger conditions of the reporting type. An example of the configuration of on-demand SSB can be carried by ReportConfigNR as shown below.

[0062] In above information elements for ReportConfigNR, reportOnDemandSSB in some embodiments is a new parameter / field to configure properties of the on-demand SSB report. reportOnDemandSSB, for example, may be periodical report, semi-persistent report, event trigger report, aperiodic or one-shot report.

[0063] In another embodiment, instead of via RRC signaling, the on demand SSB indication may be carried in a new downlink control information, DCI, in a PDCCH scrambled with a new on-demand SSB-related group RNTI, or with the C-RNTI of a specific targeted UE. In another option, the on-demand SSB indication is a media access control, MAC, control element, CE, command or carried / embedded in another MAC CE command, e.g., SCell activation MAC CE command.

[0064] In the current 3GPP technical specification 38.321, Release 18, the SCell Activation / Deactivation MAC CE of one octet is identified by a MAC subheader with LCID as specified in Table 6.2.1-1. It has a fixed size and consists of a single octet containing seven C-fields and one R-field (Reserve field). The SCell Activation / Deactivation MAC CE with one octet is defined as follows and shown in Figure 3:Ci: If there is an SCell configured for the MAC entity with SCelllndex i as specified in TS 38.331, this field indicates the activation / deactivation status of the SCell with SCelllndex i, else the MAC entity shall ignore the Ci field. The Ci field is set to 1 to indicate that the SCell with SCelllndex i shall be activated. The Ci field is set to 0 to indicate that the SCell with SCelllndex i shall be deactivated;R: Reserved bit, set to 0.

[0065] There is another MAC CE of four octets that can support up-to 31 SCell. In this MAC CE signalling, a network node has to indicate clearly the wanted activation status for each configured SCell.

[0066] Regarding the above configuration, furthermore, the indication may be received in a first slot (slot n) of a serving cell , the UE may expect SSB transmission from n+kl and start measurement on the SSB corresponding to reception of the indication command in a second slot on the serving cell, which may be in a reference slot n+kl+k2. The UE The UE may report the measurement result is no earlier than a third slot (n + kl + k3), wherein kl, k2, k3 are offset value greater than 0, or in some examples, some of Kl, k2, K3 equals to 0. For example, kl=0, if the NW starts on-demand SSB transmission when sending on-demand SSB indication at same time. Yet for example, k2=0, if the UE may be aware of SSB transmission and be able to start measurement after receiving the indication. K number represent a slot offset. The UE is aware of the real SSB transmission from receiving the indication. In one example, if the UE doesn't capture the first SSB occasion transmitted by NW, k2 also contain the SSB periodicity.

[0067] In one example, in configuration, the time for on-demand SSB transmission and the time on-demand SSB measurement are same. In another example, e.g., there are more than one UE in the coverage of on-demand SSB in a cell, the time period for on-demand SSB transmission may differ (typically longer than) from the time period for on-demand SSB measurement, since on-demand SSB measurement maybe dedicatedly for an individual UE but the time period for on-demand SSB transmission may be determined by the NW for more than one UE, and those UEs may have different conditions to be able to receive and measure on- demand SSB.

[0068] In one additional embodiment, the NW may not provide explicit starting / duration / ending time of on-demand SSB in the aforementioned indication, instead, the UE is expected to measure and report on-demand SSB until the UE could not detect the on- demand SSB. In this case, the NW may determine the length or number of on-demand SSB occasions shall be transmitted to avoid the UE missing one or more than one complete measurement on on-demand SSB.

[0069] In one additional embodiment, the NW may not provide explicit starting / duration / ending time of on-demand SSB in the aforementioned indication, instead, the UE is expected to measure and report on-demand SSB until receiving further signaling by the NW to stop or disable SSB measurement. The signalling may be a specific signalling or command especially for stopping or disabling SSB measurement or another procedure or command the UE shall execute which implicitly stops or disables SSB measurement based on the pre-defined rule.

[0070] In an embodiment, the measurement on on-demand SSB and reporting of the measurement are configured with different types. Measurement on on-demand SSB could be one-shot measurement, periodic measurement provided that on-demand SSB is transmitted periodically, contiguous measurement provided that on-demand SSB is contiguous with an ending time. Reporting could be one-shot, periodic or contiguous. Further detailed would be discussed below.

[0071] After receiving the on-demand SSB indication, a UE should at least initiate the on- demand SSB measurement on one cell (e.g. cell 2) and reporting (on same or different cell, e.g., cel 11) starting from receiving the on-demand SSB configuration or from the starting time indicated by the on-demand SSB configuration. After starting measurement and reporting, the UE is allowed to continue or stop the on-demand SSB measurement and reporting, with respect to different combination of the on-demand SSB transmission, measurement and reporting configuration, which are described in following examples.

[0072] In one example, the UE shall one-shot, i.e., one complete measurement based on a number of on-demand SSB occasions with respect to the measurement requirements e.g., in3GPP TS38.133, measure the on-demand SSB measurement and one-shot report themeasurement result provided the network node (NW) indicates to transmit one-shot on- demand SSB measurement and report.

[0073] In a further option, the NW requests one report without any restriction. After the UE initiate the on-demand SSB measurement, the UE shall report the one-shot measurement result after one complete measurement delay.

[0074] In another further option, the NW requests one report provided that the measurement result fulfills one or more than one condition / criterion or combination of more than one condition / criterion as below, and the UE shall report the one-shot measurement result only after at the least one measurement result fulfills the criteria. Otherwise, the UE may not send measurement report.

[0075] The condition / criterion may comprise: i) measurement power level is above than certain threshold, e.g., RSRP >H1_1, and / or RSRQ > Hl_2; ii) an offset between RSRP and a reference (e.g., a previous / last RSRP result on same cell or a RSRP result on another cell, e.g., cel 11) >H2_1, and / or the offset between RSRQ and a reference (e.g., a previous / last RSRQ result on same cell or a RSRP result on another cell, e.g., celll) >H2_1 iii) The cell for on-demand SSB is known for more than T1 ms / s, iv) The cell for on-demand SSB is unknown, and v) The cell for on-demand SSB has been not measured for more than T2 ms / s.

[0076] As specified in Clause 8.3 of TS 38.133, an SCell is known provided the following conditions are met for the SCell: during the last 5 seconds before the reception of the direct SCell configuration command, the UE has sent a valid measurement report for the SCell being directly activated, and the SSB measured remains detectable according to the cell identification conditions specified in sections 9.2 and 9.3. Otherwise, the SCell is unknown.

[0077] In another example, provided that on-demand SSB is transmitted periodically, the UE shall periodically measure the on-demand SSB measurement and periodically report the measurement result provided the NW indicates periodic on-demand SSB transmission (or measurement) and periodic on-demand SSB report, before further indication to stop on- demand SSB transmission and / or measurement.

[0078] In a further option, the NW request report without any restriction. After the UE initiate the on-demand SSB measurement, the UE shall report each measurement result after one complete measurement delay.

[0079] In another further option, the NW request one report provided that the measurement result fulfills one or more than one criterion or combination of more than one condition / criterion as below, and the UE shall report the one-shot measurement result only after at the least one measurement result fulfills the criteria. Otherwise, the UE may not send measurement report.

[0080] The condition / criterion may comprise: i) measurement power level is above than certain threshold, e.g., RSRP >H1_1, and / or RSRQ > >H1_2 ii) The offset between RSRP and a reference (e.g., a previous / last RSRP result on same cell or a RSRP result on another cell, e.g., cel 11) >H2_1, and / or the offset between RSRQ and a reference (e.g., a previous / last RSRQ result on same cell or a RSRP result on another cell, e.g., celll) >H2_2 iii) The cell for on-demand SSB is known for more than T1 ms / s, iv) The cell for on-demand SSB is unknown, and v) The cell for on-demand SSB has been not measured for more than T2 ms / s.

[0081] In yet another example, the UE shall measure the on-demand SSB measurement periodically, expecting that the SSB is periodically transmitted, and report the one-shot measurement result provided that the NW indicates periodic on-demand SSB transmission or measurement but only request one report. In one further option, the NW request one report without any restriction. In another further option, the NW request one report provided that the measurement result fulfills one or more than one condition / criterion or combination of more than one condition / criterion, which has been described in the above examples. The UE shall report the one-shot measurement result only after at the least one measurement result fulfills a criteria. Otherwise, the UE may continue measurement but not send report.

[0082] In yet another example, the UE shall measure the on-demand SSB measurement contiguously, expecting that the on-demand SSB has multiple occasions, and report the measurement result contiguously provided that the NW indicates transmission of contiguous SSB, including the ending time or duration (e.g., the time length or number of SSB occasions) ofon-demand SSB transmission. And the NW indicates contiguous SSB transmission or measurement and contiguous reports for those on-demand SSBs.

[0083] In one option, the NW requests measurement reporting without any restriction. After the UE initiates the on-demand SSB measurement, it should report each measurement result after one complete measurement delay. In a further option, the UE may stop SSB measurement or report after the time instant no SSB is transmitted or no SSB to be measured indicated by the gNB. The last measurement report shall not be sent not later than a delay threshold k3 after the time instant. In another further option, the NW requests one measurement report provided that the measurement result fulfills one or more than one condition / criterion or combination of more than one condition / criterion, which has been described in the above examples.

[0084] In yet another example, the UE should measure the on-demand SSB measurement contiguously, expecting that the on-demand SSB has multiple occasions, and report the one-shot measurement result provided that the NW indicates contiguous SSB transmission or measurement, with ending time or duration (e.g., the time length or number of SSB occasions) of on-demand SSB transmission, and the NW indicates one-shot reports for those on-demand SSBs.

[0085] In a further option, the NW request one report without any restriction. After the UE initiate the on-demand SSB measurement, the UE shall report one-short measurement result after one complete measurement delay. In another further option, the NW request one report provided that the measurement result fulfills one or more than one condition / criterion or combination of more than one condition / criterion, as described in the above examples.

[0086] In yet another example, the UE should measure the on-demand SSB measurement contiguous and report the contiguous measurement result provided the NW indicates the contiguous SSB transmission, including ending time or duration (e.g., the time length or number of SSB occasions) of on-demand SSB transmission or measurement and the NW indicates periodically reports for those SSBs.

[0087] In a further option, the NW request one report without any restriction. After the UE initiate the on-demand SSB measurement, the UE shall report the one-shot measurementresult after one complete measurement delay. In another further option, the UE may stop SSB measurement or report after the time instant no SSB is transmitted indicated by the gNB. The last measurement report shall not be sent not later than a delay threshold k3 after the time instant. In yet another further option, the NW request one report provided that the measurement result fulfills one or more than one condition / criterion or combination of more than one condition / criterion, as described in the above examples. In all these examples, Hl_l, Hl_2, H2_l, H2_2, Tl, T2 may be a predefined number or configurable by the network side.

[0088] In an embodiment, the UE transmits a signaling / message / report to inform the network node, reflecting status / condition of the cell or another cell, e.g., SpCell once certain criteria are fulfilled. Thus, the network side may decide to enable / start or update or disable / stop on-demand SSB transmission. Those could be steps executed between the initiating step 202 and SCell activation command step 203 in Figure 2. The criteria may comprise at the least one of the below:• the measurement result RSRP, and / or RSRQ on the cell or on another cell, e.g., cel 11.• the measurement result RSRP > or < H3_l, and / or RSRQ > or < H3_2 on the cell or on another cell, e.g., celll.• the offset between RSRP and a reference (a previous / last RSRP result on same cell or a RSRP result on another cell, e.g., celll), and / or the offset between RSRQ and a reference (a previous / last RSRQ result on same cell or a RSRP result on another cell, e.g., celll).• the offset between RSRP and a reference (a previous / last RSRP result on same cell or a RSRP result on another cell, e.g., celll) > or < H4_l, and / or the offset between RSRQ and a reference (a previous / last RSRQ result on same cell or a RSRP result on another cell, e.g., celll) > or < H4_2.• the cell for on-demand SSB is known.• the cell for on-demand SSB is known for more than T3 ms / s.• the cell for on-demand SSB has been measured.• the cell for on-demand SSB has been measured for more than T4 ms / s.

[0089] In the above options, H3_l, H3_2, H4_l, H4_2, T3, T4 may be a predefined fixed number or configurable by the network. The signaling / message / report may be standalone or carried / embedded as an element / parameter in other signaling, e.g., measurement report.

[0090] In an example, the UE requests the NW to enable on-demand SSB transmission however, configuration of on-demand SSB transmission is determined by the NW. In another option, the UE requests the NW to enable on-demand SSB transmission with recommended or suggested configuration of on-demand SSB transmission. Still, it is the network side to decide.

[0091] According to the above embodiments, there may be more than one on-demand SSB indication indicating transmitting / not transmitting on-demand SSB with different on- demand SSB configurations on one cell for the UE. Note that the on-demand SSB indication may enable SSB transmission or disable it. Here, the indication not transmitting is to disable SSB when on-demand SSB is on. More than one SSB configuration may for different phase / time period in the overall Scell activation procedure.

[0092] In an additional embodiment, the UE on-demand SSB report / indication includes one or more than one of the below: a. In one option, the measurement result RSRP, and / or RSRQ on the cell providing on-demand SSB transmission. b. In one option, the offset between RSRP and a reference (a previous / last RSRP result on same cell or a RSRP result on another cell, e.g., cel 11), and / or the offset between RSRQ and a reference (a previous / last RSRQ result on same cell or a RSRP result on another cell, e.g., cell 1), on the cell providing on-demand SSB transmission. c. In one option, an indication indicating that the cell for on-demand SSB is known. d. In one option, an indication indicating that the cell for on-demand SSB has been measured. e. In one option, the number of occasions that on-demand SSBs from a cell has been received or measured. f. In one option, the number of occasions that on-demand SSBs from a cell has been received or measured during the time period defined by the start time / duration / end time of on-demand SSB transmission or on-demand SSB measurement.

[0093] In one embodiment, the on-demand SSB measurement is defined as L3 measurement. The UE shall report L3-RSRP with SSB indexes. The NW then in turn send TCI indication command to the UE, the TCI state herein is selected based on one of the latest reported SSB indexes. Alternatively, the UE may only report L3-RSRP with one SSB index which has the highest RSRP, the UE may wait for the TCI indication command to indicate the SSB index or the UE may autonomously indicate the SSB index. Yet alternatively again, the UE may only determine and report L3-RSRP with one SSB index whose RSRP is higher than a threshold, the UE may wait for the TCI indication command to indicate the SSB index or the UE may autonomously indicate the SSB index.

[0094] In one embodiment, the on-demand SSB measurement is defined as LI measurement. The UE shall report Ll-RSRP with SSB indexes. The NW then in turn send TCIindication command to the UE, the TCI state herein is selected based on one of the latest reported SSB indexes. Alternatively, the UE may only report Ll-RSRP with one SSB index which has the highest RSRP, the UE may wait for the TCI indication command to indicate the SSB index or the UE may autonomously indicate the SSB index. Yet alternatively again, the UE may only determine and report Ll-RSRP with one SSB index whose RSRP is higher than a threshold, the UE may wait for the TCI indication command to indicate the SSB index or the UE may autonomously indicate the SSB index.

[0095] From a UE's perspective, in one embodiment, measurement reporting will be suspended, skipped or stopped after receiving a signaling for disable on-demand SSB transmission, and will be started / resumed when on-demand SSB is deactivated, after receiving a signaling for enable on-demand SSB. For example, the UE is expected to stop the periodic measurement reporting from time instance Til when receiving on-demand SSB deactivation indication / command by the NW. Or, the UE is expected to activate the periodic measurement reporting from time instance T12 when receiving on-demand SSB activation indication or command by the NW.

[0096] In another embodiment, measurement reporting will be suspended, skipped or stopped, or started / resumed based on NW indication. The NW can configure N times periodic reporting for corresponding on-demand SSB measurement. After N times reporting, the UE will stop the measurement reporting. If the number is absent, the UE shall continue measurement reporting until receiving on-demand SSB deactivation. In another example, the NW can configure a timer, and the UE shall perform periodic reporting till the timer expires. If the timer is absent, the UE shall continue the measurement reporting until receiving on-demand SSB deactivation.

[0097] In yet another embodiment, the disclosure is to discuss specifically how on- demand indication is used for SCell activation. A deactivated SCell to a user equipment can be a cell having been configured for the UE while is not activated yet. The NW can configure the RRC configuration about measurement objects (MOs) MeasObjectNR to the UE for monitoring the deactivated SCell's quality by measuring baseline SSBs with respect to a measurement cycle measCycleSCell. The measCycleSCell defines the measurement density from at least 160 subframes to 1280 sub-frames per SSB measurement. To achieve better NW's power saving, the NW can further mute SSBs for during the deactivated SCell. Either the SSB configured in measCycleSCell or no SSB is represented by baseline SSB here. Under this situation, the on- demand SSB based procedure is described as follow.

[0098] When a network node plans to activate a deactivated SCell for a UE, it will firstly initiates on-demand SSB transmission on the deactivated SCell and triggers the UE, on the PCell serving the UE, to perform deactivated SCell measurement (i.e., SSB measurement on SCell). By an on-demand SSB indication associated with the deactivated SCell and correspondingly received measurement report, it can check cell quality of the SCell prior to activating it. The NW may further decide to activate the Scell with respect to the on-demand SSB report, otherwise When the NW plans to activate the deactivated SCell for the UE, it appears that the NW firstly initiates on-demand SSB transmission on the deactivated SCell and triggers the UE, on the PCell serving the UE, to perform deactivated SCell measurement (i.e., SSB measurement on SCell), by on-demand SSB indication, to check the cell quality prior to activating SCell. After that, the NW may further decide to activate the Scell with respect to the on-demand SSB report, as shown by the latest arrow in Figure 4a, otherwise to keep the candidate Scell deactivated.

[0099] A method embodiment for activation of a deactivated SCell is herein described from a system's view. When an SCell is deactivated, the NW configures the deactivated SCell with baseline SSB transmission, e.g. SSB off or sparse SSB periodicity. At the same time, NW may indicate the UE to suspend the measurement. NW indicates the UE to start the measurement on-demand SSBs for the deactivated Scell to evaluate if the target SCell should be activated. The NW in meanwhile transmits on-demand SSB, e.g., with an intense SSB periodicity.

[0100] The UE then performs on-demand SSB measurement for the deactivated Scell and report the measurement results, as instructed by the indication, which is an on-demand SSB indication. If a poor radio condition, e.g., signal strength or signal quality is lower than a predefined or configurable threshold, is received, the NW may decide not to activate the Scell and switch the SSB transmission back to baseline SSB transmission. Once the deactivated Scell is reported with good-enough radio conditions, the NW determines and further indicates the Scell activation to the UE, e.g. via Scell activation MAC-CE command.

[0101] If the UE measures and reports the on-demand SSB successfully before receiving SCell activation MAC-CE command, or not later than X5 ms / s after receiving SCell activation MAC-CE command, the SCell (deactivated) is treated as known to the UE. X5 is the maximum delay for known condition after SCell activation MAC-CE command. Alternatively, If the UE measures and reports the on-demand SSB successfully earlier than X6 ms / s before receiving SCell activation MAC-CE command, the deactivated SCell is treated as known to the UE. X6 is the maximum delay for known condition before SCell activation MAC-CE command. Otherwise,the SCell is treated as unknown to the UE. When the SCell is treated as known to the UE, it performs Scell activation and reports the valid CSI reporting.

[0102] Time sequence could be different, and the UE couldn't know in advance. The on- demand SSB indication sent to the UE is prior to SCell activation MAC CE command, as shown by the latest arrow in Figure 4a, however, the UE may have completed measurement after the time instant when receiving SCell activation MAC CE command.

[0103] The on-demand SSB indication could also be sent to the UE along with SCell activation MAC CE command, shown in Figure 4b. When the on-demand SSB indication sent to the UE is later than SCell activation MAC CE command, it shouldn't be XI ms / s later than SCell activation MAC CE command.

[0104] According to the disclosure, a method embodiment performed by a terminal device, exchangeable as mentioned as a UE, for on-demand SSB handling includes the following steps: receiving (501) an on-demand SSB indication from a network node providing a serving cell for the terminal device, the on-demand SSBs indicated by the indication are associated with an SCell having been configured for the terminal device; receiving (502) on-demand SSB according to the on-demand SSB indication; and performing measurement on the received on- demand SSB. It could be seen that the terminal device / UE has previously received configuration of that associated SCell.

[0105] The UE would further receive an SCell activation signal, probably the SCell activation MAC CE as shown by Figure 3 or another four actets MAC CE as aforementioned for the associated SCell. The receiving of the SCell activation signal could be later, at the same time or earlier than receiving (502) step or measuring (503) step, as fully discussed in this disclosure in different embodiments. For simplicity, it is not shown in Figure 5 but can be seen in Figure 4a or 4b.

[0106] Figure 5 doesn't include a reporting of measurement report on the on-demand SSB while the UE would probably send out the measurement report, given that it is configured with an unrestricted measurement report style, or the criteria / condition for reporting is met. While when the criteria / condition for reporting isn't met, no measurement report would be sent to the network node.

[0107] From the UE's perspective, it expects to receive on-demand SSB indication along with SCell activation MAC CE command, or not later than X1+X1_1 ms / s after the SCell activation MAC CE command, where Xl_l is the margin for UE receiving and processing. Considering an allowed delay from the NW transmitting on-demand SSB to the UE being able measure the SSB denoted as X2, the UE expects to receive on-demand SSB indication not laterthan X1+X1_1 +X2 ms / s after the SCell activation MAC CE command. Considering a measurement delay denoted as X3, the UE expects to receive on-demand SSB indication not later than X1+X1_1+X2+X3 ms / s after the SCell activation MAC CE command. Otherwise, the UE may determine SCell activation procedure as failed.

[0108] The network node may sends two (groups of) on-demand SSB, one being for the deactivated Scell before receiving SCell activation command, the other being applied after SCell activation command, i.e., during Scell activation. And the UE shall update measurement regarding to the updated on-demand SSB during SCell activation procedure.

[0109] In a further embodiment after the SCell is activated, the NW further indicates the UE of baseline SSB transmission after receiving the CSI reporting. Alternatively, the UE shall skip measurement on on-demand SSB after completing SCell activation operation even no explicit indication from the NW. Despite of that, the UE may alternatively determine and trigger measurement on baseline SSB after completing SCell activation operation provided the baseline SSB is configured for the SCell.

[0110] In a scenario, if the UE cannot complete on-demand SSB measurement, the UE may send a failure message to the NW indicating that the SCell activation cannot completed due to lacking SSBs / undetectable SSBs for measurement. As a response of the failure message, in one option, the NW may suspend / stop on-demand SSB operation / scheme and transmit baseline SSB from now on. In another option, the NW may transmit another on-demand SSB for the UE to receive. The NW may further restart SCell activation by sending Scell activation command with the baseline SSB transmission or updated on-demand SSB.

[0111] At the moment, since the SCell activation isn't ready, the UE may send the failure message on PUCCH / PUSCH in SCell provided there is any known / assumed TCI state / UL spatial relation for the PUCCH / PUSCH in SCell. Or the UE may send the failure message on PUCCH / PUSCH in PCell. Or the UE may contain the failure message in a RACH or RACH-like procedure to the network node.

[0112] An embodiment of a network node is provided by the disclosure. The network node (600), as illustrated by Figure 6, includes a processor and a memory coupled to the processor, the memory containing instructions executable by the processor, whereby the network node is operative to perform methods of a network node described in the disclosure.

[0113] An embodiment of a terminal device is provided by the disclosure. The terminal device (700), as illustrated by Figure 7, includes a processor and a memory coupled to the processor, the memory containing instructions executable by the processor, whereby theterminal device is operative to perform the method of a terminal device described in the disclosure.

[0114] An embodiment of a UE is provided by the disclosure. As illustrated by Figure 8, it comprises an antenna configured to send and receive wireless signals, radio front-end circuitry connected to the antenna and to processing circuitry, and configured to condition signals communicated between the antenna and the processing circuitry, the processing circuitry being configured to perform any of the steps of any of the second aspect. The UE also comprises an input interface connected to the processing circuitry and configured to allow input of information into the UE to be processed by the processing circuitry, an output interface connected to the processing circuitry and configured to output information from the UE that has been processed by the processing circuitry; and a battery connected to the processing circuitry and configured to supply power to the UE. A similar embodiment of a network node is also provided, with similar structure as illustrated by Figure 8, too.

[0115] Although the computing devices described herein (e.g., UEs, network nodes, hosts) may include the illustrated combination of hardware components, other embodiments may comprise computing devices with different combinations of components. It is to be understood that these computing devices may comprise any suitable combination of hardware and / or software needed to perform the tasks, features, functions and methods disclosed herein. Determining, calculating, obtaining or similar operations described herein may be performed by processing circuitry, which may process information by, for example, converting the obtained information into other information, comparing the obtained information or converted information to information stored in the network node, and / or performing one or more operations based on the obtained information or converted information, and as a result of said processing making a determination. Moreover, while components are depicted as single boxes located within a larger box, or nested within multiple boxes, in practice, computing devices may comprise multiple different physical components that make up a single illustrated component, and functionality may be partitioned between separate components. For example, a communication interface may be configured to include any of the components described herein, and / or the functionality of the components may be partitioned between the processing circuitry and the communication interface. In another example, non-computationally intensive functions of any of such components may be implemented in software or firmware and computationally intensive functions may be implemented in hardware.

[0116] In certain embodiments, some or all of the functionality described herein may be provided by processing circuitry executing instructions stored on in memory, which in certainembodiments may be a computer program product in the form of a non-transitory computer- readable storage medium. In alternative embodiments, some or all of the functionality may be provided by the processing circuitry without executing instructions stored on a separate or discrete device-readable storage medium, such as in a hard-wired manner. In any of those particular embodiments, whether executing instructions stored on a non-transitory computer- readable storage medium or not, the processing circuitry can be configured to perform the described functionality. The benefits provided by such functionality are not limited to the processing circuitry alone or to other components of the computing device, but are enjoyed by the computing device as a whole, and / or by end users and a wireless network generally.EMBODIMENT EXAMPLESGroup A EmbodimentsAl. A method performed by a network node for on-demand SSB transmission, comprising: transmitting an on-demand SSB indication to a terminal device for which the network node is serving, wherein on-demand SSBs indicated by the indication are associated with a secondary cell (SCell) having been configured for the terminal device; initiating on-demand SSB transmission to be received by the terminal device; and transmitting an SCell activation signal for the associated SCell to the terminal device.A2. The method of embodiment Al, wherein the on-demand SSB indication comprises at least one on-demand SSB configuration of the associated SCell, or an indication directing to an on-demand SSB configuration by another signaling, and an indication to enable measuring and reporting of the on-demand SSB.A3. The method of embodiment A2, wherein the on-demand SSB configuration comprises configuration for on-demand SSB transmission, measurement on the transmitted on-demand SSBs and reporting of the measurement.A4. The method of embodiment A3, wherein the configuration for on-demand SSB transmission comprises at least one of on-demand SSB transmission periodicity, and starting / duration / ending time with respect to a reference point; wherein the configuration for on-demand SSB measurement comprises at least one of measurement periodicity, and starting / duration / ending time for measurement with respect to a reference point; and / or wherein the configuration for reporting of the measurement indicates one of: a periodic report, a semi-persistent report, an event trigger report, or a one-shot report.A5. The method of any of the embodiments Al to A4, wherein the configuration for on-demand SSB transmission is carried in ServingCellConfigCommonSIB or ServingCellConfigCommon, and MeasObjectNR and ReportObjectNR.A6. The method of any of the embodiment Al to A4, wherein the on-demand SSB indication is carried in a Downlink Control Information, DCI, signaling, or a media access control, MAC, control element, CE, command.A7. The method of any of embodiments A3 to A6, wherein the measurement on on-demand SSBs and reporting of the measurement are configured as one of the following: one-shot measurement and one-shot / conditional measurement report;periodic measurement and periodic measurement report when corresponding on- demand SSB transmission is periodic; periodic measurement and one-shot / conditional measurement report, when corresponding on-demand SSB transmission is periodic; contiguous measurement and contiguous measurement report, when corresponding on-demand SSB transmission is contiguous with an ending time; contiguous measurement and one-shot / conditional measurement report when corresponding on-demand SSB transmission is contiguous with an ending time; and contiguous measurement and periodic report when corresponding on-demand SSB transmission is contiguous with an ending time.A8. The method of any of the previous embodiments, further comprising: receiving measurement report of the transmitted on-demand SSB, and determining to activate the associated SCell based on the received measurement report.A9. The method of any of the previous embodiments, further comprising: receiving an indication from the terminal device to enable, update or disable on-demand SSB transmission.A10. The method of any of the previous embodiments, prior to transmitting the on-demand SSB indication, further comprising, configuring the terminal device with a SCell configuration of the SCell.Group B EmbodimentsBl. A method performed by a terminal device for on-demand SSB handling, comprising: receiving an on-demand SSB indication from a network node providing a serving cell for the terminal device, wherein on-demand SSBs indicated by the indication are associated with a secondary cell (SCell) having been configured for the terminal device; receiving on-demand SSB according to the on-demand SSB indication; performing measurement on the received on-demand SSB.B2. The method of embodiment Bl, further comprising: receiving an SCell activation signal for the associated SCell.B3. The method of embodiment Bl or B2, wherein the on-demand SSB indication comprises at least one on-demand SSB configuration of the associated SCell, oran indication directing to an on-demand SSB configuration by another signaling, and an indication to enable measuring and reporting of the on-demand SSB.B4. The method of embodiment B3, wherein the on-demand SSB configuration comprises configuration for on-demand SSB transmission, measurement on the transmitted on-demand SSBs and reporting of the measurement.B5. The method of embodiment B4, wherein the configuration for on-demand SSB transmission comprises at least one of on-demand SSB transmission periodicity, and starting / duration / ending time with respect to a reference point; wherein the configuration for on-demand SSB measurement comprises at least one of measurement periodicity, and starting / duration / ending time for measurement with respect to a reference point; and / or wherein the configuration for reporting of the measurement indicates one of: a periodic report, a semi-persistent report, an event trigger report, or a one-shot report.B6. The method of any of the embodiment Bl to B5, wherein the configuration for on-demand SSB transmission is received in ServingCellConfigCommonSIB or ServingCellConfigCommon, and MeasObjectNR and ReportObjectNR.B7. The method of any of the embodiments Bl to B5, wherein the on-demand SSB indication is received in a Downlink Control Information, DCI, signaling, or a media access control, MAC, control element, CE, command.B8. The method of any of the embodiments B4 to B7, wherein the on-demand SSB configuration indicates one of the following: one-shot measurement and one-shot / conditional measurement report; periodic measurement and periodic measurement report when corresponding on- demand SSB transmission is periodic; periodic measurement and one-shot / conditional measurement report, when corresponding on-demand SSB transmission is periodic; contiguous measurement and contiguous measurement report, when corresponding on-demand SSB transmission is contiguous with an ending time; contiguous measurement and one-shot / conditional measurement report when corresponding on-demand SSB transmission is contiguous with an ending time; and contiguous measurement and periodic report when corresponding on-demand SSB transmission is contiguous with an ending time.B9. The method of any of the previous embodiments in Group B, further comprising: transmitting a measurement report based on measurement on the received on-demand SSB.BIO. The method of any of the previous embodiments in Group B, comprising: transmitting an indication to the network node to enable, update or disable on-demand SSB transmission, where the indication is carried in a measurement report.Bll. The method of any of the previous embodiments in Group B, further comprising: performing SCell activation for the associated SCell.Group C EmbodimentsCl. A network node for on-demand SSB transmission, comprising: a processor and a memory coupled to the processor, wherein the memory containing instructions executable by the processor, whereby the network node is operative to perform any of the steps of any of the Group A embodiments.C2. A terminal device for on-demand SSB handling, comprising: a processor and a memory coupled to the processor, wherein the memory containing instructions executable by the processor, whereby the terminal device is operative to perform any of the steps of any of the Group B embodiments.C3. A user equipment (UE) for on-demand SSB handling, comprising: an antenna configured to send and receive wireless signals; radio front-end circuitry connected to the antenna and to processing circuitry, and configured to condition signals communicated between the antenna and the processing circuitry; the processing circuitry being configured to perform any of the steps of any of the Group B embodiments; an input interface connected to the processing circuitry and configured to allow input of information into the UE to be processed by the processing circuitry; an output interface connected to the processing circuitry and configured to output information from the UE that has been processed by the processing circuitry; and a battery connected to the processing circuitry and configured to supply power to the UE.C4. A network node for on-demand SSB transmission, comprising: an antenna configured to send and receive wireless signals;radio front-end circuitry connected to the antenna and to processing circuitry, and configured to condition signals communicated between the antenna and the processing circuitry; the processing circuitry being configured to perform any of the steps of any of the Group A embodiments; an input interface connected to the processing circuitry and configured to allow input of information into the network node to be processed by the processing circuitry; an output interface connected to the processing circuitry and configured to output information from the network node that has been processed by the processing circuitry.

Claims

CLAIMS1. A method implemented in a terminal device for on-demand SS / PBCH block, OD-SSB, handling, comprising: receiving, from a network node, a configuration of a secondary cell, SCell, for the terminal device; receiving an OD-SSB indication from the network node, indicating transmission of on-demand SSBs associated with the SCell; receiving an SCell activation message of the SCell; receiving and measuring OD-SSBs according to the OD-SSB indication; and transmitting a failure indication to the network node when the received OD-SSBs are insufficient.

2. The method of Claim 1, after transmitting the failure indication, further comprising: receiving, from the network node, a configuration for baseline SSBs and / or another OD-SSB indication with different transmission parameters from the OD-SSB indication previously received.

3. The method of Claims 1 or 2, wherein the failure indication indicates: the SCell activation failure or the measurement failure due to insufficient OD-SSBs associated with the SCell being received.

4. The method of any of Claims 1 to 3, wherein the OD-SSB indication indicates OD-SSB transmission parameters and configuration for measurement on the transmitted OD-SSBs and / or reporting of the measurement.

5. The method of any of the preceding claims, wherein the receiving OD-SSBs comprising: starting to receive the OD-SSBs at Slot n+kl when the OS-SSB indication is received at Slot n.

6. The method of any of Claim 5, wherein the starting to receive the OD-SSBs comprising: starting to receive the OD-SSBs after an additional processing duration from Slot n+kl.

7. The method of any of the preceding claims, further comprising: receiving an indication from the network node that the measurement on the indicated OD-SSB associated with the SCell is disabled.

8. The method of any of the Claims 1 to 6, wherein the OS-SSB indication comprises: a starting time with respect to a reference point of the OD-SSB transmission, and a duration or ending time of the OD-SSB transmission; or a number of OD-SSB occasions to be transmitted.

9. A terminal device configured for OD-SSB handling, comprising: an antenna configured to send and receive wireless signals; radio front-end circuitry connected to the antenna and to processing circuitry, and configured to condition signals communicated between the antenna and the processing circuitry; the processing circuitry being configured to perform any of the steps of any of Claims 1 to 8;an input interface connected to the processing circuitry and configured to allow input of information into the terminal device to be processed by the processing circuitry; an output interface connected to the processing circuitry and configured to output information from the terminal device that has been processed by the processing circuitry.

10. A method implemented in a network node for OD-SSB handling, comprising: transmitting, to a terminal device, a configuration of a secondary cell, SCell, for the terminal device; transmitting, to the terminal device, an SCell activation message of the configured SCell; transmitting an OD-SSB indication to the terminal device, indicating transmission of OD-SSBs associated with the SCell; receiving a failure indication from the terminal device indicating that the OD-SSBs received from the network node are insufficient.

11. The method of Claim 10, wherein the failure indication indicates: the SCell activation failure or a measurement failure due to insufficient OD-SSBs associated with the SCell being received.

12. The method of Claim 10, after receiving the failure indication, further comprising: transmitting, to the terminal device, configuration for baseline SSBs and / or another OD-SSB indication with different transmission parameters from the OD-SSB indication previously transmitted.

13. The method of any of Claims 10 to 12, wherein the OD-SSB indication indicates an OD-SSB transmission scheme and configuration for measurement on the transmitted OD-SSBs and / or reporting of the measurement.

14. The method of any of Claims 10 to 13, wherein the receiving the failure indication comprising: receiving the failure indication on PUCCH / PUSCH in a primary cell of the terminal device served by the network node; or receiving the failure indication on PUCCH in the SCell.

15. A network node configured for OD-SSB handling, comprising: an antenna configured to send and receive wireless signals; radio front-end circuitry connected to the antenna and to processing circuitry, and configured to condition signals communicated between the antenna and the processing circuitry; the processing circuitry being configured to perform any of the steps of any of Claims 10 to 14; an input interface connected to the processing circuitry and configured to allow input of information into the network node to be processed by the processing circuitry; an output interface connected to the processing circuitry and configured to output information from the network node that has been processed by the processing circuitry.

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