Methods, user equipment and non-terrestrial gnodeb

Abstract

The present disclosure relates to a method for a User Equipment (UE), a UE performing said method, a method for a non-terrestrial gNodeB, and to a non- terrestrial gNodeB performing said method. The method for the UE comprises initiating an MBS, Multicast and Broadcast Service, session with a target Non- Terrestrial Network, NTN, MBS cell based on one of a) a conditional MBS configuration obtained from a source NTN MBS cell, or b) upon command from the source NTN MBS cell.

Description

[0001] 202407128

[0002] 1

[0003] TITLE

[0004] Methods, User Equipment and Non-Terrestrial gNodeB

[0005] TECHNNICAL FIELD

[0006] The 3rd Generation Partnership Project (3GPP) is a standards organization which develops protocols for mobile telephony and is known for the development and maintenance of various standards, including second generation (2G), third generation (3G), fourth generation (4G), Long Term Evolution (LTE), and fifth generation (5G) standards.

[0007] The 5G network has been designed as a Service Based Architecture (SBA) or, in other words, a system architecture in which the system functionality is achieved by a set of network functions providing services to other authorized network functions, enabling them to access those services. The 5G network may comprise a plurality of base stations (e.g., Next Generation NodeB (gNB), etc.) that serve multiple cells across a particular area.

[0008] The present disclosure relates to a method for a User Equipment (UE), a UE performing said method, a method for a non-terrestrial gNodeB, and a non-terrestrial gNodeB performing said method.

[0009] BACKGROUND

[0010] The (Multimedia) Broadcast Multicast Service (MBS) feature provides significant value to NTN (Non-Terrestrial Network) systems by leveraging the inherently large coverage area of satellites compared to terrestrial networks (TNs). Although the 5G specifications make terrestrial MBS features available for NTN, enhancements may be required. This is because the intended service area for a broadcast is often smaller than the full coverage of a satellite's footprint (the Uu air interface cell). The main objective is to specify how the intended service area of a broadcast service is signaled over an NR (New Radio) NTN. For example, System Information Block (SIB) signaling may be used to indicate the intended service area. 202407128

[0011] 2

[0012] For example, the intended broadcast service area may be defined as a geographical area, which can be represented either by a reference location and a radius or by a set of one or more polygons. When a UE is not located within any intended service area for the broadcast services it is interested in, it may not need to re-acquire the up-to-date Multicast Control Channel (MCCH). When a UE is outside the intended area, it might not establish Multicast Radio Bearers (MRBs) for an MBS session. A UE may initiate the broadcast MRB establishment procedure upon entering the intended area and may initiate the release procedure upon leaving it.

[0013] For each MBS service, one or more intended service area Identifiers (IDs) may be included in the MCCH. In some examples, the complete list of intended service areas and their associated IDs may also be included in the MCCH. Alternatively, this information will be provided in a new or existing System Information Block (SIB). For example, the UE may skip re-acquiring the MCCH when it is not within the intended service area of any of its interested broadcast services. The mapping between an MBS service ID and its corresponding intended service area may be provided to the UE via System Information.

[0014] For a broadcast session that is not intended for service continuity, the service area may be restricted solely to the serving cell. Service continuity may be improved by considering the intended service area. This could be achieved in one of two ways: either by providing the intended service area within each neighbor cell in the MBSBroadcastConfiguration for every MBS broadcast session, or by providing the intended service area in SIB21 or a new SIB (to be determined in 3GPP discussions) for each MBS broadcast session, or for each Frequency Selection Area Identity (FSAI).

[0015] As specified in TS 38.331 5.9.1 .3, changes to the information carried on the MCCH occur in a synchronized manner using a modification period. This means that MCCH information can only be changed at specific, predefined radio frames. When the network needs to alter this information, it notifies the UEs about the upcoming change via the Physical Downlink Control Channel (PDCCH). This notification is sent 202407128

[0016] 3 at the start of the modification period. According to TS 38.212 clause 7.3.1.5.1 , the notification uses a 2-bit bitmap to specify the nature of the change. If the Most Significant Bit (MSB) is set to '1', it indicates the start of one or more new MBS services. If the Least Significant Bit (LSB) is set to '1', it indicates other types of modifications, such as a change in the configuration of an ongoing MBS session, the stopping of a session, or a modification of neighboring cell information. A UE will continue to use its previously acquired MCCH information until it successfully acquires the new information.

[0017] According to TS 38.331 5.9.2.2, a UE shall initiate the MCCH information acquisition procedure when it becomes interested in receiving MBS broadcast services. This procedure can be triggered by several events, such as upon powering on or moving into a cell that provides SIB20, upon receiving SIB20 for a Secondary Cell (SCell) through dedicated signaling, or upon receiving a notification that new MBS services have started. A UE that is already receiving data via a broadcast MRB will re-initiate the procedure if it receives a notification of an MCCH information modification. The specification includes two notes clarifying that it is up to the UE's implementation to handle the possibility of missing a change notification and to use the User Service Description (USD) to avoid trying to acquire the MCCH when it is outside the service area. It is also noted that this procedure overwrites any stored MCCH information, as delta configurations are not used for MCCH.

[0018] TS 38.331 5.7.19 details the procedure for a soft satellite switch with resynchronization for a UE in RRC (Radio Resource Control) CONNECTED mode. This procedure is initiated when SIB19 includes the SatSwitchWithReSync and t- Service information elements. If t-ServiceStart is also included, the UE (which supports soft satellite switch with synchronization) begins acquiring downlink synchronization with the Special Cell (SpCell) served by the new satellite at some point between the time indicated by t-ServiceStart and the time indicated by t- Service. At the time of t-Service, the UE performs a sequence of actions: it stops timer T430 if it is running, informs its lower layers that uplink synchronization is lost, synchronizes to the downlink of the new SpCell indicated by ntn-Config in SatSwitchWithReSync, if the UE has not previously synchronized to the DL of the 202407128

[0019] 4

[0020] SpCell, it starts timer T430 with the timer value set to ntn-UISyncValidityDuration from the subframe indicated by epochTime in ntn-Config in SatSwitchWithReSync, and finally, it informs its lower layers once uplink synchronization has been successfully obtained again.

[0021] Based on 3GPP discussions, the proposed flow and linkage of information required for a UE to receive MBS may be as follows. The process begins at the Non-Access Stratum (NAS) layer, which provides the User Service Description (USD). The USD contains the Temporary Mobile Group Identity (TMGI) and the Service Area details (including service area ID, FSAI). This high-level information is then propagated through various system information blocks and control channels in the Radio Access Network. SIB20 provides the UE with the necessary information to acquire the MCCH and the Multicast Traffic Channel (MTCH). SIB21 provides the MBS Frequency Selection Area Identity (FSAI) for both intra-frequency and inter-frequency cases. The MBSConfig via MCCH, whose changes are announced via Downlink Control Information (DCI), carries the detailed service list, the TMGI, MTCH scheduling information, and the service area representation, linking everything together for the UE.

[0022] In TS 38.300, the Conditional Handover (CHO) procedure is described. After the source gNB (the 5G base station) decides to use CHO, it sends CHO requests to one or more candidate cells belonging to one or more candidate gNBs. A CHO request message is sent for each candidate cell. Once the candidate gNBs respond with their configurations, the source gNB sends an RRCReconfiguration message to the UE, containing the configurations of the candidate cells and the specific conditions under which the UE should execute the handover. The UE sends an RRCReconfigurationComplete message to the source gNB. If early data forwarding is applied, the source gNB sends the EARLY STATUS TRANSFER message. The UE maintains its connection to the source gNB while it begins to evaluate these conditions for the candidate cell(s). As soon as a condition is met for one of the candidate cells, the UE detaches from the source gNB, applies the stored configuration for that selected cell, and completes the handover by sending an RRCReconfigurationComplete message to the new target gNB. The UE releases 202407128

[0023] 5 stored CHO configurations after successful completion of RRC handover procedure. The target gNB then confirms the successful handover to the source gNB, which in turn cancels the pending CHO procedure with any other candidate gNBs.

[0024] TS 38.300 16.10.6.5 defines how service continuity for MBS is maintained for UE states. The mobility principles build upon existing 5G functions. NR MBS supports frequency layer prioritization, where gNBs can be configured with the MBS FSA IDs of their cells and can exchange this information with neighboring gNBs over the Xn interface. Mobility procedures for MBS reception allow the UE to start or continue receiving MBS service(s) when changing cells. To help the UE, the gNB may indicate in the MCCH a list of neighbor cells that provide the same MBS services. This allows the UE, e.g., to request unicast reception of the service before moving to a cell not providing the MBS broadcast service(s) using PTM transmission. To avoid having to read system information or MCCH on neighbor frequencies, the UE can be made aware of which frequencies provide which MBS services through the User Service Description (USD), as defined in TS 26.517, or through a combination of the USD and SIB21 . The UE can request unicast reception of the service after moving to a cell not providing the MBS broadcast service(s) using PTM transmission. In RRCJDLE and RRCJNACTIVE, the UE applies the normal cell reselection rules with the following modifications: the UE, which is receiving or interested in receiving MBS broadcast service(s) via PTM and can only receive these MBS broadcast service(s) via PTM while camping on the frequency providing these MBS broadcast service(s), is allowed to make this frequency highest priority when the conditions described in TS 38.304

[0010] are met. When the MBS broadcast service(s) which the UE is interested in are no longer available (after the end of the session) or the UE is no longer interested in receiving the service(s), the UE no longer prioritizes the frequency providing these MBS broadcast service(s).

[0025] In the RRC_CONNECTED state (TS 38.300 16.10.6.5.2), to ensure service continuity, the UE can send an MBS Interest Indication message to the gNB. This message may comprise the following pieces of information: a list of MBS frequencies that the UE is either currently receiving or interested in receiving, the priority between receiving those MBS frequencies and any unicast or multicast bearers, and a list of 202407128

[0026] 6 specific MBS broadcast services that the UE is interested in (in case SIB20 is provided for PCell or SCell). The gNB can use this information for more efficient scheduling and resource configuration. This interest indication can also be exchanged between the source and target gNBs during a handover.

[0027] For the actual delivery of broadcast data (TS 38.300 16.10.6.5A), the gNB can use Point-to-Multipoint (PTM) transmission, which involves delivering a single copy of MBS data packets to a group of UEs using a group-common PDCCH.

[0028] In TS 38.300 16.10.6.6, the physical layer aspects for MBS are defined. A CFR configured by SIB is defined for broadcast scheduling as an 'MBS frequency region' consisting of a number of contiguous PRBs whose bandwidth is equal to or larger than CORESETO and having the same numerology as CORESETO, and broadcast scheduling may have specific characteristics (e.g., PDCCH and PDSCH configurations). The NG-RAN node may configure an additional RedCap CFR when the bandwidth of the configured default CFR exceeds the (e)RedCap UE capability. A UE only monitors one CFR at a time. An (e)RedCap UE monitors the RedCap CFR if configured, otherwise the (e)RedCap UE monitors the default CFR if the bandwidth of the default CFR is within the UE capability. The NG-RAN node ensures that a UE does not receive two DCIs simultaneously (i.e. , one associated with the RedCap CFR and another associated with the default CFR) with the same G-RNTI or the same MCCH-RNTI. The maximum number of MIMO layers is one for MBS broadcast scheduling. RB-level rate matching and RE-level rate matching around LTE-CRS configured by higher layer signalling are supported for MCCH and MTCH. Slot-level repetition is supported for MTCH. HARQ-ACK feedback is not supported for MBS broadcast. Only dynamic scheduling is supported for MBS broadcast.

[0029] In TS 38.300 16.10.6.7, shared processing is defined. If the UE in RRC_CONNECTED state is receiving or is interested in receiving an MBS broadcast service from a non-serving cell as described in TS 38.306

[0011] , the UE may use the MBS Interest Indication message to inform the serving gNB about the parameters used for the non-serving cell broadcast reception as described in TS 38.331

[0012] , The gNB may enable the sending of the MBS Interest Indication by including an indication 202407128

[0030] 7 in SIB1 . The UE may indicate to the serving cell the UE capability for receiving MBS broadcast service from a non-serving cell. It is up to the gNB implementation to consider the MBS Interest Indication and the UE capability for receiving MBS broadcast service from a non-serving cell, if indicated, when scheduling the UE. In case the UE only reports the frequency for broadcast service reception from the nonserving cell in the MBS Interest Indication because some parameters (e.g., SCS, bandwidth) are not available, the UE may transmit an updated MBS Interest Indication once the parameters are available to the UE. It is up to the network implementation to enable the UE to acquire these parameters from the non-serving cell.

[0031] The MBS Interest Indication procedure is defined in TS 38.331 5.9.4. The purpose of this procedure is to allow a UE in RRC_CONNECTED state to inform the network that it is interested in receiving MBS broadcast services and to specify the priority of this reception relative to its unicast and multicast traffic. This message can only be sent after Access Stratum (AS) security has been activated. An MBS capable UE in RRC_CONNECTED may initiate the procedure in several cases including upon successful connection establishment / resume, upon entering or leaving the broadcast service area, upon MBS broadcast session start or stop, upon change of interest, upon change of priority between MBS broadcast reception and unicast / multicast reception, upon change to a PCell providing SIB21 (i.e. , where the SIB1 scheduling information contains SIB21 ), upon receiving SIB20 of an SCell via dedicated signalling, upon handover, and upon RRC connection re-establishment, upon change to a PCell providing nonServingCellMII in SIB1 , upon starting or stopping reception of MBS broadcast service on a non-serving cell, upon change of CFR information or subcarrier spacing for MBS broadcast reception on a non-serving cell. If the UE does not have the CFR information and subcarrier spacing for MBS broadcast reception on a non-serving cell at the time it sends the MBS Interest Indication, the UE sends another MBS Interest Indication after it has acquired this information from the nonserving cell.

[0032] The MBSInterestlndication message (according to TS 38.331 ) is used to inform the network that the UE is receiving / interested to receive or no longer 202407128

[0033] 8 receiving / interested to receive MBS broadcast service(s) via a broadcast MRB. As signalling radio bearer, SRB1 is used, with RLC-SAP: AM, logical channel: DCCH and direction: UE to Network. The IE MBS-NonServinglnfoList is used to inform the network of the frequencies, CFR information, and subcarrier spacing for MBS broadcast reception on the non-serving cell. MBSInterestlndication-r17 is a sequence containing MBSInterestlndication-r17-IEs, containing an optional list of MBS frequencies (mbs-Freql_ist-r17), an optional flag to indicate high priority for MBS reception (mbs-Priority-r17), and an optional list of services (mbs-ServiceList-r17). An updated version, MBSInterestlndication-v1800, adds the mbs-NonServinglnfoList-r18 field, which is used to inform the network of the frequencies, CFR information, and subcarrier spacing for MBS broadcast reception on a non-serving cell.

[0034] There are defined standard-specific measurement / mobility and service continuity enhancements between terrestrial and non-terrestrial networks (NTN-TN and NTN- NTN). For NTN-NTN mobility, specific cell reselection enhancements for earthmoving cell, the timing-based and location-based cell reselection for quasi-earth-fixed cell in Release 17 is the starting point. Specific NTN-NTN handover enhancements for radio connected (RRC_CONNECTED) UEs in quasi-earth-fixed cell and earthmoving cell are to be defined to reduce the signaling overhead. Specific cell reselection enhancements for not connected (RRCJDLE / INACTIVE) UEs to reduce UE power consumption are about to be defined, and NTN-TN mobility is prioritized.

[0035] At least for pre-allocated grant, for the confirmation of RACH-less handover completion, a reuse of LTE approach is known, i.e. , the UE Contention Resolution Identity MAC CE is used, but the UE ignores the content of this field. Currently, RACH-less handover is limited to NTNs at the same orbit and speed. The synchronization among source and target cells is not an issue in NTN RACH-less handover. The LTE approach of confirming the handover completion is reused for both pre-allocated grant and dynamic grant.

[0036] At least the scenario of intra-satellite handover within the same gNB is possible, and the scenarios of intra-satellite HO between gNBs, inter-satellite HO within the same gNB and inter-satellite HO between gNBs may also be possible, as long as UE uplink 202407128

[0037] 9 transmission synchronization can be maintained by applying correct Timing Advance (TA) pre-com pensation in the target cell. In other words, there are some approaches in supporting RACH-less handover in NTN.

[0038] US 2020275291 A1 titled “REDUCING COVERAGE PROBLEMS VIA DYNAMIC MEASUREMENTS” provides a method in a radio communication network providing a service for a plurality of devices, the method comprising: determining a service outage probability for a device that is going to move to a sub-area of a coverage area of the network, the service outage probability associated with said sub-area; in response to determining that the service outage probability exceeds a threshold, requesting a measurement device to move to said sub-area and to perform one or more radio frequency measurements; determining whether the service outage probability exceeds another threshold based at least on the requested one or more radio frequency measurements; and triggering at least one action if the service outage probability exceeds said another threshold.

[0039] EP 4270817 A1 titled “METHOD FOR COMPUTING OR ESTIMATING A SPECIFIC SERVICE TIME INTERVAL OR A SPECIFIC SERVICE TIME INFORMATION OF OR RELATED TO A USER EQUIPMENT IN A MOBILE COMMUNICATION NETWORK BEING OR AT LEAST COMPRISING A PART CORRESPONDING TO OR BEING A NON-TERRESTRIAL NETWORK, USER EQUIPMENT, SYSTEM OR MOBILE COMMUNICATION NETWORK, PROGRAM AND COMPUTER- READABLE MEDIUM” describes that a the user equipment computes or generates an estimation of the specific service time interval or the specific service time information, the estimation being based on the location information of its own position and the reference location information.”

[0040] US 2021092781 A1 titled “Determining Coverage Availability Estimates of Mobile Non-Terrestrial Access Node” discloses the determination of an availability of a connection to a mobile non-terrestrial access node of a wireless communication system, determining, at the wireless device, coverage availability estimates of the mobile non-terrestrial access node, and determining at the wireless device, if the determined coverage availability estimates indicate a periodic coverage of the mobile 202407128

[0041] 10 non-terrestrial access node, a power save mode or one or more connection attempts to the mobile non-terrestrial access node, on the basis of a time period according to a periodicity of the determined coverage availability estimates.

[0042] EP 0995323 A2 titled “DETERMINING THE LOCATION OF A SUBSCRIBER UNIT IN A MOBILE COMMUNICATION SYSTEM” describes that a mobile telephone system employs a fleet of satellites and a set of gateway ground stations arranged around the globe for handling communications to and from mobile communication subscriber units such as mobile telephones. Signals are transmitted between a subscriber unit and the nearest gateway via one or more of the satellites. The gateway system is configured to process telephone call connection requests from a mobile subscriber unit based upon the location of the subscriber unit. The location of the subscriber unit is employed, for example, to determine how telephone numbers are to be parsed and how to properly route emergency telephone calls to the nearest appropriate emergency service centers. Multiple location mapping schemes are employed to facilitate a determination of the location of a subscriber unit and to assist in routing emergency calls. In one implementation, each location with the service area of the system is mapped into a set of uniformly sized and shaped information cells. Each information cell includes pointers to data structures defining, among other things, the service providers that are permitted to process calls to or from that location and the nearest emergency services center. Each location is also mapped into at least one virtual service provider cell which includes service provider preferences and requirements for handling a call to from that location and including a unique location identifier. A specific implementation for use with the Global System for Mobile Communication (GSM) is described.

[0043] EP 3248302 A1 titled “METHOD AND APPARATUS FOR BEAM SELECTION FOR A MULTIBEAM MULTI-SATELLITE COMMUNICATIONS SYSTEM” describes a method of designing beam patterns to increase aggregate capacity within a satellite communications system, comprising: determining a first beam pattern of a plurality of user spot beams of a first satellite serving a first geographic area; identifying a plurality of high traffic regions within the first geographic area covered by the first beam pattern; determining the user spot beams of the first beam pattern covering 202407128

[0044] 11 each of the plurality of high traffic regions; determining a normalized distance metric for each of the user spot beams of the first beam pattern covering each of the plurality of high traffic regions; and plotting a second beam pattern of a second satellite such that at least one of a plurality of user spot beams of the second beam pattern has a lower normalized distance metric for at least one of the plurality of high traffic regions relative to the normalized distance metrics of the user spot beams of the first beam pattern covering each of the plurality of high traffic region.

[0045] US 2010261476 A1 titled “Method and Equipment for Transferring Information of Neighboring Cell in Wireless Communications System” describes a method for transferring information of a neighboring cell in a wireless communications system including locating position information of user equipment (UE) when detecting that the UE is in a service connection state, and if determining that the UE is in a coverage threshold range of a micro-cell adjacent to a current macro-cell according to the position information of the UE, transferring information of the micro-cell to the UE. Corresponding network equipment is also provided.

[0046] WO 2022235321 A1 titled “SYSTEMS AND METHODS FOR SUPPORTING LOCATION BASED MOBILITY FOR 5G SATELLITE ACCESS TO A WIRELESS NETWORK” describes, that a Registration Area (RA) supporting UE satellite access to a serving PLMN may correspond to a geodetic area (e.g. a circle) and may be determined by a network node (e.g. AMF) based on a current geodetic location of the UE. The UE may access a radio cell supported by a satellite for a serving PLMN. The UE may determine whether the radio cell provides coverage for the RA, e.g., based on whether an updated geodetic location of the UE is inside the RA or based on whether a geodetic coverage area of the radio cell covers at least part of the RA. The UE may perform a Registration with the serving PLMN via the radio cell when the radio cell is determined to not provide coverage for the RA. The serving PLMN may page the UE, when idle, using radio cells whose coverage includes at least part of the RA.

[0047] US 2024023011 A1 titled “METHOD, DEVICE, AND SYSTEM FOR CELL ACCESS IN WIRELESS NETWORKS” describes cell coverage, cell search, cell access, cell 202407128

[0048] 12 selection, and cell measurement in wireless networks. Performed by a User Equipment (UE) in a wireless network, the method including determining a cell coverage information associated with a search limitation of the UE. In this disclosure, various embodiments are disclosed to facilitate the UE to: detect cell coverage condition; handle certain cell coverage condition; and stop or relax certain UE activities during certain cell coverage condition.

[0049] EP 4271038 A1 titled “CELL RESELECTION METHOD AND APPARATUS, COMMUNICATION DEVICE, AND STORAGE MEDIUM” describes a cell reselection method, applied to a terminal. The method comprises: determining, according to a serving duration determined on the basis of auxiliary information, an execution operation of executing cell reselection, wherein the serving duration is a duration during which a non-terrestrial network (NTN) serving cell is capable of providing a service to a terminal, and the auxiliary information comprises coverage information and ephemeris information of the NTN serving cell and / or reference serving duration information during which the NTN serving cell is capable of providing the service.

[0050] US 2020015237 A1 titled “METHOD AND APPARATUS FOR CONTROLLING NETWORK DEVICE, METHOD AND APPARATUS FOR SENDING CONTROL INFORMATION, AND METHOD AND APPARATUS FOR SENDING DATA” describes a method and an apparatus for controlling a network device, a method and an apparatus for sending control information, and a method and an apparatus for data. According to technical solutions provided in the present disclosure, network devices providing network services for different over-the-air areas are scheduled to different time grids, so that the terminal devices located in different over-the-air areas send data to respective corresponding network devices within different time grids, thereby avoiding signal interference and improving network quality.

[0051] WO 2022208475 A1 titled “CELL RESELECTION USING EXPECTED CELL SERVING TIME” describes a method performed by a wireless device for cell selection or reselection in a non-terrestrial network (NTN) comprises determining whether to perform one or more cell selection or reselection measurements based on a cell selection or reselection criteria. The cell selection or reselection criteria is 202407128

[0052] 13 based on a signal quality of a serving cell and a relationship between the wireless device and a satellite or spot beam of the NTN. Upon determining that the cell selection or reselection criteria for performing measurements is satisfied, performing the one or more cell selection or reselection measurements.

[0053] WO 2024171147 A1 titled “ASSISTED MEASUREMENT PROCEDURE UNDER NTN DISCONTINUOUS COVERAGE” describes systems and methods for assisted operational procedures under Non-Terrestrial Network (NTN) discontinuous coverage. In some embodiments, a method performed by a User Equipment (UE) for adapting one or more operational procedures includes: determining, based on cell assistance information, whether at least two cells of a plurality of cells meet one or more measurement similarity conditions. In response to determining that the at least two cells of the plurality of cells meet the one or more measurement similarity conditions, the UE adapts one or more operational procedures. This might enable smooth transition of the ongoing communication / session across cells served or managed by satellites in discontinuous coverage scenario. This enables UE power saving as it searches only the cells which are likely available at the UE location upon resumption of the satellite coverage. This avoids or minimizes the loss of paging reception upon resumption of the satellite coverage.

[0054] WO 2024011193 A1 titled “CELL RESELECTION ENHANCEMENTS FOR NONTERRESTRIAL NETWORKS” describes systems, methods, and devices related to dynamic cell reselection management. A device may receive reference location and radius of a Non-Terrestrial Network (NTN) cell from system information. The device may predict a trajectory of an NTN cell center based on the received reference location and satellite ephemeris data from the system information. The device may determine when the device will leave a coverage of a current serving cell based on a device location and the predicted trajectory. The device may perform relaxed measurements for intra-frequency, inter-frequency, or inter radio access technology (RAT) neighbor cell measurements during a service time of the current serving cell.

[0055] EP 4268509 A1 titled “METHOD AND APPARATUS FOR CELL RESELECTION IN

[0056] WIRELESS COMMUNICATION SYSTEM” describes a cell reselection in wireless 202407128

[0057] 14 communications. According to an embodiment of the present disclosure, a method performed by a wireless device in a wireless communication system comprises: receiving information related to a service time of a neighbor cell; obtaining a cell quality of the neighbor cell based on a measurement on the neighbor cell; determining a remaining service time for the neighbor cell as a time period from a current time point to an end time point of the service time of the neighbor cell; and performing a cell reselection to the neighbor cell based on the cell quality of the neighbor cell and the remaining service time for the neighbor cell.

[0058] CN 115276756 A titled “Low earth orbit satellite constellation optimization design method for guaranteeing service quality” describes.

[0059] WO 2022206557 A1 titled “COMMUNICATION METHOD AND APPARATUS” describes a low-orbit satellite constellation optimization design method capable of guaranteeing service quality, and belongs to the technical field of wireless communication. According to the method, the reliability, the effectiveness and the completeness of the satellite constellation are comprehensively considered, and the definition of the satellite constellation service quality is given. The error rate, the signal-to-noise ratio and the survivability are introduced to represent the reliability of the satellite constellation; introducing a coverage rate to represent the effectiveness of the satellite constellation; and representing the completeness of the users in the satellite constellation through the user matching degree. On this basis, setting a service quality threshold value and calculating a service quality value, setting the ratio of the total system capacity of the target area to the constellation construction cost as a target function, and iteratively optimizing the target function value by using the global search capability of the genetic algorithm to obtain an initial constellation solution; and carrying out secondary optimization on the initial solution by using the local search capability of the tabu search algorithm to output an optimal constellation parameter. The method is oriented to regional users, and efficient and economical low-orbit satellite constellations are optimally designed according to user requirements and service quality assurance. 202407128

[0060] 15

[0061] WO 2023272715 A1 titled “COMMUNICATION SYSTEMS, METHODS, AND NON- TRANSITORY COMPUTER-READABLE STORAGE DEVICES USING JOINT INITIAL ACCESS WITH TERRESTRIAL AND NON-TERRESTRIAL COMMUNICATION NODES” describes a communication system, a method, and one or more non-transitory computer-readable storage devices allowing joint a user equipment to perform initial access with terrestrial and non-terrestrial communication nodes of a service area. The service area is partitioned into terrestrial initial-access zones and non-terrestrial initial-access zones with each terrestrial initial-access zone associated with one or more of the terrestrial communication nodes and each non- terrestrial initial-access zone associated with at least one of the non-terrestrial communication nodes. The user equipment uses positioning reference signals from positioning anchors to determine its location, determine a zone from the terrestrial and non-terrestrial initial-access zones based on the location, select one of the terrestrial and non-terrestrial communication nodes based on the determined zone, and establishing communication with the selected communication node.

[0062] WO 2024011193 A1 titled “CELL RESELECTION ENHANCEMENTS FOR NON- TERRESTRIAL NETWORKS” describes systems, methods, and devices related to dynamic cell reselection management. A device may receive reference location and radius of a Non-Terrestrial Network (NTN) cell from system information. The device may predict a trajectory of an NTN cell center based on the received reference location and satellite ephemeris data from the system information. The device may determine when the device will leave a coverage of a current serving cell based on a device location and the predicted trajectory. The device may perform relaxed measurements for intra-frequency, inter-frequency, or inter radio access technology (RAT) neighbor cell measurements during a service time of the current serving cell.

[0063] IN 201717013617 A titled “BEAM FORMING AND POINTING IN A NETWORK OF UNMANNED AERIAL VEHICLES (UAVS) FOR BROADBAND ACCESS” describes Systems and methods configured to form and point beams from one or more unmanned aerial vehicles (UAVs) toward a target coverage area on the ground. One embodiment describes dividing the target coverage area on the ground among multiple UAVs when each UAV antenna system generates static beams. Another 202407128

[0064] 16 embodiment describes dividing the target coverage area on the ground among multiple UAVs when their antenna systems are capable of dynamically steering their respective beams. Another set of embodiments describe systems and method to allow multiple UAVs to provide service in the same area on the ground using the same spectrum.

[0065] CN 116054913 A titled “Satellite communication method and device, electronic equipment and nonvolatile storage medium” describes a satellite communication method and device, electronic equipment and a nonvolatile storage medium. The method comprises the steps that an air-ground wireless coverage electronic map of a target area is determined, and the air-ground wireless coverage electronic map comprises position information of all terminal devices in the target area and signal quality of all the terminal devices; a first target communication service is determined from communication services in the target area according to the air-ground wireless coverage electronic map, the first target communication service is a communication service borne by high-frequency waves, and the signal quality of the first target communication service is lower than a preset signal quality threshold value; and bearing the first target communication service through the target satellite network. The technical problem that the high-frequency signal cannot cover the whole area due to the fact that only the ground high-frequency base station is responsible for the high-frequency signal transmission service in the prior art is solved.

[0066] US 2018367961 A1 titled “METHOD AND APPARATUS FOR OPERATING RESOURCES IN WIRELESS COMMUNICATION SYSTEM” describes a method for providing a broadcast service of an MBMS coordination entity (MCE) in a mobile communication system, and an MCE for performing the same. The method comprises the steps of: transmitting a terminal counting request message to at least one base station in a multicast-broadcast single frequency network (MBSFN) area; receiving a counting result message comprising the number of terminals receiving a multimedia broadcast multicast service (MBMS) session for each cell of the base station from the base station; and determining MBMS resource allocation for each cell in the MBSFN area on the basis of the counting result message. In addition, it is 202407128

[0067] 17 possible to provide a base station and a terminal operating together with the MCE, and a method for the operation thereof.

[0068] US 2008267109 A1 titled “METHOD AND APPARATUS OF RESOURCE MANAGEMENT FOR MULTIMEDIA BROADCAST MULTICAST SERVICES” describes a method and apparatus of resource management for multimedia broadcast multicast services (MBMS. A wireless transmit / receive unit (WTRU) sends a measurement report and an MBMS reception performance report to a network. Single frequency network (SFN) area change may be made based on cell reselection information, WTRU macro-diversity MBMS reception performance, neighbor cell signal strength reported by a WTRU, interference level measured by the WTRU, a number of WTRUs in a cell, service priority, WTRU class, WTRU mobility trend, WTRU location to a cell center, WTRU MBMS reception interference level, etc. The MBMS service on / off decision and / or point-to-point (PTP) to point-to-multipoint (PTM) switching may be made based on a channel condition of a WTRU. The channel condition may be determined based on whether the WTRU is in in-sync or out-of- sync in MBMS reception, consecutive negative acknowledgements (NAKs) within a certain time window, measured pathloss from a reference channel, etc.

[0069] US 2013223393 A1 titled “METHOD FOR COORDINATING INTER-CELL INTERFERENCE AND BASE STATION” describes method for coordinating inter-cell interference and a base station using same. A first base station receives from the second base station a configuration request message for requesting a radio resource setting to coordinate inter-cell interference. The first base station transmits to the second base station a configuration response message as a response to the configuration request message.

[0070] US 2009196174 A1 titled “VIRTUAL SCHEDULING IN HETEROGENEOUS NETWORKS” describes virtual management of wireless resources in a mobile communication environment. By way of example, access terminals in the communication environment can maintain connections with nearby network transmitters and report factors pertinent to wireless scheduling to a central entity, such as a macro base station. The macro base station can employ those factors in 202407128

[0071] 18 improving wireless communications for other serving cells within or near to a macro coverage area served by the macro base station. By maintaining information pertinent to prevailing wireless conditions, quality of service requirements, pilot signal reports, mobility management considerations, and so on, of transmissions within the cell, significant interference reduction can be implemented for the macro coverage area, or nearby coverage areas.

[0072] US 2014219115 A1 titled “SIGNALING FOR CONFIGURATION OF DOWNLINK COORDINATED MULTIPOINT COMMUNICATIONS” describes devices, methods, computer-readable media, and systems configurations for configuration of downlink coordinated multipoint (CoMP) communications in a wireless communication network. A user equipment (UE) may receive, from an evolved Node B (eNB), a radio resource control (RRC) transmission including channel state informations (CSI) reference signal (RS) parameters for a plurality of transmission points. The UE may subsequently receive a medium access control (MAC) control element (CE) including a plurality of index bits corresponding to one or more activated transmission points of the plurality of transmission points for which the feedback module is to generate CSI- RS feedback. The eNB may dynamically update the transmission points that are activated for CSI-RS feedback. The UE may receive another MAC CE from the eNB to notify the UE of the updated set of activated transmission points.

[0073] US 2018145810 A1 titled “TECHNIQUES FOR TRANSMITTING AND RECEIVING SYNCHRONIZATION SIGNALS OVER AN UNLICENSED RADIO FREQUENCY SPECTRUM BAND” describes a first method may include receiving at a user equipment (UE) over an unlicensed radio frequency spectrum band an indication of a time window associated with a transmission of a synchronization signal, and monitoring the unlicensed radio frequency spectrum band during the time window to receive a synchronization signal from a base station. A second method may include transmitting an indication of a time window associated with a transmission of a synchronization signal; performing a plurality of clear channel assessments (CCAs) on an unlicensed radio frequency spectrum band during the time window; and transmitting the synchronization signal over the unlicensed radio frequency spectrum 202407128

[0074] 19 band at a transmission time during the time window. The transmission time may be based at least in part on a result of at least one of the CCAs.

[0075] US 2004053606 A1 titled “Service priorities in multi-cell network” describes a method of determining cell allocation for a user in a wireless network, the network having a plurality of cell types and users having at least one of a plurality of service types, including defining a priority table comprising, for each service type, a priority for each cell type.

[0076] US 2009264142 A1 titled “INTERCELL INTERFERENCE MITIGATION” describes methods and apparatus for mitigating intercell interference in wireless communication systems utilizing substantially the same operating frequency band across multiple neighboring coverage areas. The operating frequency band may be shared across multiple neighboring or otherwise adjacent cells, such as in a frequency reuse one configuration. The wireless communication system can synchronize one or more resource allocation regions or zones across the multiple base stations, and can coordinate a permutation type within each resource allocation zone. The base stations can coordinate a pilot configuration in each of a plurality of coordinated resource allocation regions. Subscriber stations can be assigned resources in a coordinated resource allocation region based on interference levels. A subscriber station can determine a channel estimate for each of multiple base stations in the coordinated resource allocation region to mitigate interference.

[0077] US 2013155936 A1 titled “METHOD, APPARATUS AND SYSTEM FOR CONFIGURING ENERGY-SAVING CELL” describes a network node obtains information for configuring serviceless Multicast Broadcast Single Frequency Network (MBSFN) sub-frames of a first cell; and the network node configures serviceless MBSFN sub-frames of a neighboring cell of the first cell by alternating the serviceless MBSFN sub-frames of the neighboring cell with the serviceless MBSFN sub-frames of the first cell according to the information for configuring the serviceless MB SFN sub-frames of the first cell. In the method for configuring the first cell, the serviceless MBSFN sub-frames of the neighboring cell alternate with the serviceless 202407128

[0078] 20

[0079] MBSFN sub-frames of the first cell, thereby reducing interference between cells and improving stability of the system.

[0080] US 2017026946 A1 titled “METHOD FOR TRANSMITTING AND RECEIVING CONTROL INFORMATION OF A MOBILE COMMUNICATION SYSTEM” describes method for transmitting control information in a mobile communication system that includes: determining a control channel resource for transmitting control information by means of the data channel region; and transmitting the control information using the determined control channel resource. A capacity for control information, which increases for multiple user multiple-input multiple-out (MIMOs) in a heterogeneous network environment, for heterogeneous network interference control using carrier aggregation, for frequent use of a multicast-broadcast single frequency network (MBSFN) subframe, and for a CoMP transmission control, may be satisfied. Further, an adaptive resource allocation based on a requested capacity for control information may be enabled, and the efficient utilization of resources may also be enabled.

[0081] US 2016345338 A1 titled “METHOD AND APPARATUS FOR APPLYING RESOURCES IN HETEROGENEOUS NETWORK SYSTEM” describes a method and an apparatus for applying wireless resources in order to control inter-cell interference in a heterogeneous network system. The method for applying wireless resources provided by the present invention generates an almost blank subframe (ABS) pattern on the basis of the type of data transmitted from at least one of a first base station and a second base station, applies a non-ABS or an ABS to wireless resources of the first base station according to the generated ABS pattern, and performs data communication by using the wireless resources to which the ABS has been applied.

[0082] US 2013250885 A1 titled “COORDINATED MULTIPOINT COMMUNICATION NETWORK WITH MULTIPLE COOPERATING eNBs AND METHOD FOR BEAMFORMING COORDINATION WITH INTERFERENCE SUPPRESSION” describes embodiments of an enhanced Node-B (eNB) configured to operate as a serving eNB in a coordinated multi-point (CoMP) communication network and method herein. The serving eNB precodes signals for transmission to user 202407128

[0083] 21 equipment (UE) using a precoding matrix that is selected based on a reference PMI for a beamformed transmission in accordance with a modulation and coding scheme (MCS) that is selected from a modified CQI. When operating in coordination mode, on more cooperating eNBs are configured to suppress interference to the UE using coordination PM Is during the resource block allocated for the beamformed transmission.

[0084] According to TS 38.300, the source gNB dispatches a HANDOVER CANCEL message to any other signaling connections or candidate target gNBs in order to cancel the CHO for the UE. Consequently, all resource reservations are canceled, even though UEs may arrive after the first CHO at other configured target cells.

[0085] In the following, a solution is proposed: because satellite movements are deterministic and recurring, it is advisable to predict UE mobility and cluster UEs accordingly. By determining several suitable CHO configurations — i.e. , a sequence of multiple CHO candidates — and pre-allocating UL grants in a recurring or semi- persistent fashion, the system can take into account each UE’s QoS requirements and mobility characteristics.

[0086] The benefits of this approach include enhanced CHO configurations and improved service continuity, owing to accurate UE mobility prediction. Moreover, the network signaling becomes more efficient, resulting in a reduction of handover messages overall.

[0087] In scenarios where earth-moving cells are employed, such as those served by LEO satellites, a user equipment (UE) that is interested in a particular MBS service or that has already established an MBS session may encounter service degradation. This degradation leads to a poor user experience. For instance, media access and provisioning for passengers in vehicles can be interrupted or noticeably affected when the UE transitions from one MBS service area to another.

[0088] When a UE receives MBS service information, it also obtains a service-specific estimated service time from the gNB. This information can be delivered either 202407128

[0089] 22 through a System Information Message (SIB) or a UE-specific message, such as an RRC reconfiguration message. Using the estimated service time, the UE determines whether to initiate the MBS service. The benefit of this approach is that the UE becomes aware of MBS service availability, which improves service continuity and minimizes MBS service interruptions.

[0090] Earth-moving cells cover intended MBS service areas for a limited time. When UE leaves an intended MBS service area, while receiving a service of interest that is covered by one satellite’s cells, and enters another intended MBS service area where the service of interest is also available but provided through another (neighboring) satellite’s cell, the service may not be continued seamlessly, which results in poor user experience. UE may face interference and thus degraded user experience when neighboring satellites are providing MBS at the same radio resources.

[0091] SUMMARY

[0092] Various examples of the proposed concept are based on the finding that service continuity can be improved if the source MBS cell (i.e., the gNodeB providing the source MBS cell) coordinates the handover of a UE using (or being interested in) an MBS cell, by providing the UE either with a conditional MBS configuration (so the UE can make the handover to the target cell’s MBS service when the conditions are met) or with a command to perform the handover to the target MBS cell. For example, the UE may receive intended MBS service area information of neighboring satellite cells that provide a service of interest. This may include a time indication when a next / neighboring satellite cell starts / stops serving an intended MBS service area where the service of interest is provided. MBS source and target cells may coordinate allocation of MBS resources (e.g., time / frequency / space). As a result, the UE is aware of when MBS service of interest is available in the “intended MBS service area” of neighboring satellite cells and will tune to the corresponding MBS frequency in a timely manner. This way, a user’s MBS experience can be improved through coordinated MBS resource management among neighboring cells. 202407128

[0093] 23

[0094] Various examples of the present disclosure are based on the finding that enabling seamless and efficient transition of multicast and broadcast service sessions (MBS) between terrestrial and non-terrestrial networks (NTN) is beneficial for future communication systems. The proposed concept addresses the technical problem of initiating, coordinating, and switching MBS sessions with target NTN MBS cells while minimizing handover latency, avoiding resource conflicts, and ensuring reliable service continuity for user equipment (UE). This improves overall network performance by allowing UEs to remain subscribed to multicast content across multiple NTN cells with minimal disruption. The present disclosure also provides device embodiments that can execute the methods described herein.

[0095] Various examples of the present disclosure relate to a method for a UE. The method comprises initiating an MBS (Multicast and Broadcast Service) session with a target Non-Terrestrial Network (NTN) MBS cell based on one of: (a) a conditional MBS configuration obtained from a source NTN MBS cell, or (b) upon command from the source NTN MBS cell. This way, the NTN MBS source cell can coordinate service continuity, leading to an improved experience at the UE.

[0096] For example, the conditional MBS configuration may comprise a criterion for switching from an MBS session with the source NTN MBS cell to an MBS session with the target NTN MBS cell. This way, the UE can make the transfer according to objective criteria and without having to wait for a command by the gNodeB of the source NTN MBS cell.

[0097] The goal of suitably timing the switch to a target NTN MBS cell is to ensure that the UE can suitably receive the MBS service. Therefore, the signal level of the respective signals associated with the MBS service may be used to trigger the initiation of the MBS session with the target NTN MBS cell. In other words, the criterion may be based on a signal level threshold with respect to a signal level of the target NTN MBS cell and / or the source NTN MBS cell. This includes both the actual signal level as well as the difference of signal levels / received signal strengths between source and target cell. For example, the criterion may include that the signal level of the target 202407128

[0098] 24

[0099] NTN MBS cell is greater than a minimum and the signal level different (target-source) is greater than X.

[0100] In many cases, the coverage area of NTN MBS cells is known. Therefore, to allow for an improved transition without having to rely on periodically measuring the signal levels of the source and target NTN MBS cells, the condition may be based on the spatial relationship between the source NTN MBS cell, the target NTN MBS cell, and the UE. In other words, the criterion may be based on at least one of a location of the UE, a location of an intended MBS service area of the source NTN MBS cell, a location of an intended MBS service area of the target NTN MBS cell, or a distance between locations (e.g., based on a location / distance of the UE to a reference location of the NTN MBS target cell or time to enter coverage area / cross distance threshold of target cell).

[0101] To deliver the conditional configuration to the UE, the system may employ the UE to receive the conditional MBS configuration from the source NTN MBS cell, for example via a Radio Resource Control, RRC, reconfiguration message.

[0102] In many cases, MBS services may have a fixed start and stop time. To anticipate availability of neighboring MBS services, the method may comprise receiving information on one or more service start and stop times of one or more neighboring NTN MBS cells from the NTN MBS source cell, and initiating the MBS session based on the information on the service start and stop time. This way, the start and stop times may be taken into account, to avoid an initiation of an MBS session that does not exist yet or anymore.

[0103] To allow the UE to more quickly tune into the MBS service (or allow for measurements that can be used for the conditional initiation), the method may comprise receiving information on an MBS resource allocation of the target NTN MBS cell from the source NTN MBS cell. The act of initiating the MBS session may be based on the information on the MBS resource allocation. 202407128

[0104] 25

[0105] In some examples, the method may comprise determining availability of an MBS service of interest in neighboring NTN MBS cells based on the intended MBS service area information received from the source NTN MBS cell, and initiating the MBS session based on the intended MBS service area information. This way, the UE can be informed about the MBS services available in neighboring cells.

[0106] The goal of providing the intended MBS service area information to the UE is to enable the UE to initiate the MBS session as it approaches (or crosses over into) the intended MBS service area. Therefore, the intended MBS service area information may include the location of the intended MBS service area. In other words, the intended MBS service area information may comprise information on a reference location within the intended MBS service area.

[0107] To enable timely handover, the method may comprise determining the distance to the intended MBS service area of one or more neighboring NTN MBS cells, and initiating the MBS session when approaching the intended MBS service area. This way, service continuity may be provided when approaching another intended MBS service area.

[0108] To further improve the transition, the method may comprise predicting (e.g., using Artificial Intelligence) the time of entering the intended MBS service area of a neighboring NTN MBS cell, and initiating the MBS session based on the predicted time of entering the intended MBS service area. Similarly, the time of leaving an intended MBS service area may be predicted. In other words, the method may comprise predicting a time of leaving the intended MBS service area of an NTN MBS cell. For example, the method may comprise initiating reception of an MBS service of interest via unicast transmission if no intended MBS service area is available.

[0109] For example, initiating the MBS session may comprise detaching from the cell served by a serving gNB, the serving gNB providing the source NTN MBS cell, initiating resynchronization, and initiating the MBS session with a target gNB that provides the target NTN MBS cell. 202407128

[0110] 26

[0111] Another aspect of the present disclosure relates to a method for a Non-Terrestrial gNB providing a source NTN MBS cell. The method comprises providing, to a user equipment, UE, one of a conditional MBS configuration with respect to one or more target NTN MBS cells, or a command to initiate an MBS service session with the target NTN MBS cell. This way, the gNodeB can coordinate service continuity, leading to an improved experience at the UE.

[0112] To control when the UE should initiate a target MBS session, the conditional MBS configuration may specify the condition for initiating an MBS service with a target NTN MBS cell.

[0113] In many cases, MBS services may have a fixed start and stop times. To anticipate MBS service availability, the method may comprise providing, to the UE, information on one or more service start and stop times of one or more MBS services in one or more neighboring NTN MBS cells. This way, the UE can tune into the MBS service at the time it is available.

[0114] To allow the UE to more quickly tune into the MBS service (or allow for measurements that can be used for the conditional initiation), the method may comprise providing to the UE information on an MBS resource allocation of the target NTN MBS cell.

[0115] To avoid resource conflicts, the gNodeB may coordinate allocation of MBS resources with one or more neighboring MBS cells. Accordingly, the method may comprise coordinating allocation of MBS resources with one or more neighboring MBS cells. Moreover, the method may comprise , providing, to the UE, information on an MBS resource allocation of the one or more neighboring (NTN) MBS cells. In particular, coordinating allocation of MBS resources may comprise providing information on an MBS resource allocation to the target NTN MBS cell, and receiving a confirmation regarding the MBS resource allocation from the target NTN MBS cell. This way, the source and target NTN MBS cells may avoid usage of the same frequencies in regions where the coverage of two NTN MBS cells may overlap. 202407128

[0116] 27

[0117] Once the use of MBS resources is coordinated, the results may be communicated to the core network. In other words, the method may comprise providing an MBS resource allocation notification to a core network entity of the Non-Terrestrial gNB after coordinating the allocation of MBS resources.

[0118] If serving and target gNB cannot agree on resource allocation, the target gNB may reject the MBS RA indication / coordination request (e.g., due to load, or resource constraints) and sends a NACK (negative acknowledgment) to the serving gNB. Then, both serving and target gNB may send an MBS resource allocation coordination request to the core network entity (AMF) for conflict resolution and determination of MBS resource allocations. The core network entity (e.g., AMF) may reply to serving and target gNB and provide respective MBS resource allocations.

[0119] An aspect of the present disclosure relates to a UE comprising a wireless transceiver, a processor coupled with a memory in which computer program instructions are stored, said instructions being configured to implement the abovedescribed method for the UE.

[0120] An aspect of the present disclosure relates to a Non-Terrestrial gNB comprising a wireless transceiver, a processor coupled with a memory in which computer program instructions are stored, said instructions being configured to implement the abovedescribed method for the gNodeB.

[0121] This objective discussed above is achieved according to the invention by means of the technical characteristics mentioned in the independent claims. Main benefit(s) of the invention are fewer handover messages, efficient network signalling, and overall an improved service continuity.

[0122] BRIEF DESCRIPTION OF THE DRAWINGS

[0123] Fig. 1 a shows a block diagram of a UE, a NTN serving gNodeB providing a source NTN MBS cell, and of a cellular mobile communication system comprising the UE and the NTN serving gNodeB; 202407128

[0124] 28

[0125] Fig. 1 b shows a flowchart of a method for a UE;

[0126] Fig. 2 shows a flowchart of a method for a Non-Terrestrial gNB providing a source NTN MBS cell;

[0127] Fig. 3 shows a scenario where each of the two Low Earth Orbit (LEO) satellites provides wireless access in three different radio cells covering various intended MBS service areas;

[0128] Fig. 4 shows a scenario where neighboring radio cells provide time indications;

[0129] Fig. 5 shows a scenario where satellites or gNBs operating neighboring and potentially overlapping radio cells coordinate the allocation of MBS radio resources;

[0130] Fig. 6 shows the interaction between Serving gNB, Target gNB and CN (AMF);

[0131] Fig. 7 shows the interaction between UE, Serving gNB, Target gNB, and CN (AMF);

[0132] Fig. 8 shows the flowchart for the UEside; and

[0133] Fig. 9 shows the flowchart for the Serving gNB.

[0134] DETAILED DESCRIPTION

[0135] The detailed description set forth below, with reference to annexed drawings, is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing a thorough 202407128

[0136] 29 understanding of the various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. In particular, although terminology from 3GPP 5G NR may be used in this disclosure to exemplify embodiments herein, this should not be seen as limiting the scope of the invention.

[0137] Some of the embodiments contemplated herein will now be described more fully with reference to the accompanying drawings. Other embodiments, however, are contained within the scope of the subject matter disclosed herein; the disclosed subject matter should not be construed as limited to only the embodiments set forth herein; rather, these embodiments are provided by way of example to convey the scope of the subject matter to those skilled in the art.

[0138] Generally, all terms used herein are to be interpreted according to their ordinary meaning in the relevant technical field, unless a different meaning is clearly given and / or is implied from the context in which it is used. All references to a / an / the element, apparatus, component, means, step, etc. are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any methods disclosed herein do not have to be performed in the exact order disclosed, unless a step is explicitly described as following or preceding another step and / or where it is implicit that a step must follow or precede another step. Any feature of any of the embodiments disclosed herein may be applied to any other embodiment, wherever appropriate. Likewise, any advantage of any of the embodiments may apply to any other embodiment, and vice versa. Other objectives, features and advantages of the enclosed embodiments will be apparent from the following description.

[0139] In some embodiments, a more general term “network node” or “network entity” may be used and may correspond to any type of radio network node or any network node which communicates with a UE (directly or via another node) and / or with another network node. Examples of network nodes are NodeB, MeNB, ENB, a network node belonging to MCG or SCG, base station (BS), multi-standard radio (MSR) radio node such as MSR BS, eNodeB, gNodeB, network controller, radio network controller 202407128

[0140] 30

[0141] (RNC), base station controller (BSC), relay, donor node controlling relay, base transceiver station (BTS), access point (AP), transmission points, transmission nodes, RRU, RRH, nodes in distributed antenna system (DAS), core network node (e.g. Mobile Switching Center (MSC), Mobility Management Entity (MME), etc.), Operations & Maintenance (O&M), Operations Support System (OSS), Self Optimized Network (SON), positioning node (e.g. Evolved-Serving Mobile Location Centre (E-SMLC)), Minimization of Drive Tests (MDT), test equipment (physical node or software), etc.

[0142] In some embodiments, the non-limiting term user equipment (UE) or wireless device may be used and may refer to any type of wireless device communicating with a network node and / or with another UE in a cellular or mobile communication system. Examples of UE are target device, device to device (D2D) UE, machine type UE or UE capable of machine to machine (M2M) communication, PDA, PAD, Tablet, mobile terminals, smartphone, laptop embedded equipped (LEE), laptop mounted equipment (LME), USB dongles, UE category Ml, UE category M2, ProSe UE, V2V UE, V2X UE, etc.

[0143] Additionally, terminologies such as base station / gNodeB and UE should be considered non-limiting and do, in particular, not imply a certain hierarchical relation between the two; in general, “gNodeB” could be considered as device 1 and “UE” could be considered as device 2, and these two devices communicate with each other over some radio channel. In the following, the transmitter or receiver could be either gNodeB (gNB), or UE.

[0144] As will be appreciated by one skilled in the art, aspects of the embodiments may be embodied as a system, apparatus, method, or program product. Accordingly, embodiments may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.), or an embodiment combining software and hardware aspects.

[0145] For example, the disclosed embodiments may be implemented as a hardware circuit comprising custom very-large-scale integration (“VLSI”) circuits or gate arrays, off- 202407128

[0146] 31 the-shelf semiconductors such as logic chips, transistors, or other discrete components. The disclosed embodiments may also be implemented in programmable hardware devices such as field programmable gate arrays, programmable array logic, programmable logic devices, or the like. As another example, the disclosed embodiments may include one or more physical or logical blocks of executable code which may, for instance, be organized as an object, procedure, or function.

[0147] Furthermore, embodiments may take the form of a program product embodied in one or more computer readable storage devices storing machine readable code, computer readable code, and / or program code, referred hereafter as code. The storage devices may be tangible, non-transitory, and / or non-transmission. The storage devices may not embody signals. In a certain embodiment, the storage devices only employ signals for accessing code.

[0148] Any combination of one or more computer readable media may be utilized. The computer readable medium may be a computer readable storage medium. The computer readable storage medium may be a storage device storing the code. The storage device may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, holographic, micromechanical, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing.

[0149] More specific examples (a non-exhaustive list) of the storage devices would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random-access memory (“RAM”), a read-only memory (“ROM”), an erasable programmable read-only memory (“EPROM” or Flash memory), a portable compact disc read-only memory (“CD-ROM”), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer-readable storage medium may be any tangible medium that can contain or store a program for use by or in connection with an instruction execution system, apparatus, or device. 202407128

[0150] 32

[0151] Code for carrying out operations for embodiments may be any number of lines and may be written in any combination of one or more programming languages including an object-oriented programming language such as Python, Ruby, Java, Smalltalk, C++, or the like, and conventional procedural programming languages, such as the “C” programming language, or the like, and / or machine languages such as assembly languages. The code may execute entirely on the user’s computer, partly on the user’s computer, as a stand-alone software package, partly on the user’s computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user’s computer through any type of network, including a local area network (“LAN”), wireless LAN (“WLAN”), or a wide area network (“WAN”), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider (“ISP”)))

[0152] Furthermore, the described features, structures, or characteristics of the embodiments may be combined in any suitable manner. In the following description, numerous specific details are provided, such as examples of programming, software modules, user selections, network transactions, database queries, database structures, hardware modules, hardware circuits, hardware chips, etc., to provide a thorough understanding of embodiments. One skilled in the relevant art will recognize, however, that embodiments may be practiced without one or more of the specific details, or with other methods, components, materials, and so forth. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of an embodiment. Reference throughout this specification to “one embodiment,” “an embodiment,” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, appearances of the phrases “in one embodiment,” “in an embodiment,” and similar language throughout this specification may, but do not necessarily all refer to the same embodiment; they mean “one or more but not all embodiments”, unless expressly specified otherwise. The terms “including,” “comprising,” “having,” and variations thereof mean “including but not limited to,” unless expressly specified otherwise. An enumerated listing of items does not imply that any or all of the items are mutually exclusive, unless 202407128

[0153] 33 expressly specified otherwise. The terms “a,” “an,” and “the” also refer to “one or more” unless expressly specified otherwise.

[0154] Aspects of the embodiments are described below with reference to schematic flowchart diagrams and / or schematic block diagrams of methods, apparatuses, systems, and program products according to embodiments. It will be understood that each block of the schematic flowchart diagrams and / or schematic block diagrams, and combinations of blocks in the schematic flowchart diagrams and / or schematic block diagrams, can be implemented by code. This code may be provided to a processor of a general-purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine such that the instructions which execute via the processor of the computer or other programmable data processing apparatus create means for implementing the functions / acts specified in the flowchart diagrams and / or block diagrams.

[0155] The code may also be stored in a storage device that can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the storage device produce an article of manufacture including instructions which implement the function or act specified in the flowchart diagrams and / or block diagrams.

[0156] The code may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus, or other devices to produce a computer implemented process such that the code which executes on the computer or other programmable apparatus provides processes for implementing the functions / acts specified in the flowchart diagrams and / or block diagrams.

[0157] The flowchart diagrams and / or block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of apparatuses, systems, methods, and program products according to various embodiments. In this regard, each block in the flowchart diagrams and / or block diagrams may represent a 202407128

[0158] 34 module, segment, or portion of code, which includes one or more executable instructions of the code for implementing the specified logical function(s).

[0159] It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of order as noted in the Figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in reverse order, depending upon the functionality involved. Other steps and methods may be conceived that are equivalent in function, logic, or effect to one or more blocks, or portions thereof, of the illustrated Figures.

[0160] Although various arrow types and line types may be employed in the flowchart and / or block diagrams, they are understood not to limit the scope of the corresponding embodiments. Indeed, some arrows or other connectors may be used to indicate only the logical flow of the depicted embodiment. For instance, an arrow may indicate a waiting or monitoring period of unspecified duration between enumerated steps of the depicted embodiment. It will also be noted that each block of the block diagrams and / or flowchart diagrams, and combinations of blocks in the block diagrams and / or flowchart diagrams, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and code.

[0161] The description of elements in each figure may refer to elements of preceding figures. Like numbers refer to like elements in all figures, including alternate embodiments of like elements.

[0162] The detailed description set forth below, with reference to annexed drawings, is intended to describe various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of the various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. Although 202407128

[0163] 35 terminology from 3GPP 5G NR may be used in this disclosure to exemplify embodiments herein, this should not be seen as limiting the scope of the invention.

[0164] Fig. 1a shows a block diagram of a UE 10, a non-terrestrial serving gNodeB 20 providing a source NTN MBS cell, and of a cellular mobile communication system comprising the UE 10 and the NTN serving gNodeB 20. The UE 10 comprises a wireless transceiver 12, a processor 14, and a memory 16. The processor 14 is coupled with the wireless transceiver 12 and with the memory 16. For example, the UE 10 may use the wireless transceiver to communicate with terrestrial and nonterrestrial radio access network components, such as the non-terrestrial gNodeB 20 of the cellular mobile communication system. The functionality of the UE 10 may be provided by the processor 14, which may be configured to execute computer program instructions stored in the memory 16 to provide its functionality. For example, the processor 14 may use the wireless transceiver 12 to communicate in the cellular mobile communication system. The UE, e.g., the processor 14, is configured to perform the method of Fig. 1b.

[0165] Similarly, the non-terrestrial serving gNodeB 20 comprises a wireless transceiver 22, a processor 24, and a memory 26. The processor 24 is coupled with the wireless transceiver 22 and with the memory 26. For example, the non-terrestrial gNodeB 20 may use the wireless transceiver to communicate with UEs and other entities of the cellular mobile communication system, such as a feeder station. The functionality of the non-terrestrial gNodeB may be provided by the processor 24, which may be configured to execute computer program instructions stored in the memory 26 to provide its functionality. For example, the processor 24 may use the wireless transceiver 22 to communicate in the cellular mobile communication system. The non-terrestrial gNodeB, e.g. the processor 24, is configured to perform the method of Fig. 2.

[0166] Fig. 1 b shows a flowchart of a method for the UE. The method comprises obtaining 120 information (such as a conditional MBS configuration) or a command from a source NTN MBS cell, and ultimately from the non-terrestrial gNodeB 20 that provides the source NTN MBS cell. The method comprises initiating 150 an MBS 202407128

[0167] 36 session with a target NTN MBS cell based on one of a) a conditional MBS configuration obtained from the source NTN MBS cell, or b) upon command from the source NTN MBS cell.

[0168] Fig. 2 shows a flowchart of a method for the non-terrestrial gNB 20 that provides the source NTN MBS cell. The method comprises providing 230 to the UE 10, one of a) the conditional MBS configuration with respect to one or more target NTN MBS cells, or b) the command to initiate an MBS service session with the target NTN MBS cell.

[0169] The present disclosure relates to a concept for providing service continuity for MBS services. In the proposed scenario, the UE 10 uses an MBS service (e.g., a video broadcast) provided by the non-terrestrial gNodeB 20 in an NTN MBS cell provided by the non-terrestrial gNodeB 20. As the UE 10 is moving relative to the coverage area (or intended MBS service area) of the MBS cell provided by the non-terrestrial gNodeB, it may, at some point, lose the ability to consume the MBS service provided in the NTN MBS cell (in this context, an NTN MBS cell is a cell provided by a non- terrestrial gNodeB, such as a satellite-based gNodeB, in which at least one MBS service is provided). Therefore, the UE 10 may switch to receiving the MBS service from another NTN MBS cell (i.e. , the target NTN MBS cell), which may be provided by another non-terrestrial gNodeB.

[0170] To inform this switch to a different NTN MBS cell, the serving non-terrestrial gNodeB may help the UE 10. In some examples, this can be done by providing the conditional MBS configuration with respect to one or more target NTN MBS cells. This conditional MBS configuration may comprise a criterion for switching from an MBS session with the source NTN MBS cell to an MBS session with the target NTN MBS cell. It may work similarly to the conditional handover (CHO), in that the UE receives the criterion (or criteria) that triggers the switch to another NTN MBS cell. For example, the criterion may be based on a signal level threshold with respect to a signal level of the target NTN MBS cell and / or the source NTN MBS cell. In other words, when the signal level of the target NTN MBS cell is high enough (e.g., above a threshold, above the signal level of the source NTN MBS cell, or by an offset greater than the signal level of the source NTN MBS cell) and / or if the signal level of 202407128

[0171] 37 the source NTN MBS cell is too low (e.g., below a threshold, below the signal level of the target NTN MBS cell, or by an offset lower than the signal level of the target NTN MBS cell), the MBS session with the target NTN MBS cell may be initiated. This includes both the actual signal level as well as the difference of signal levels / received signal strengths between source and target cell. For example, the criterion may include that the signal level of the target NTN MBS cell is greater than a minimum and the signal level different (target-source) is greater than X.

[0172] Another factor (that is closely correlated with the respective signal levels) is the location of the UE 10 in relation to the source NTN MBS cell (i.e., the intended service area of the source NTN MBS cell) and target NTN MBS cell (i.e., the intended service area of the target NTN MBS cell). In other words, the criterion may be based on at least one of a location of the UE, a location of an intended MBS service area of the source NTN MBS cell, a location of an intended MBS service area (e.g., a reference location of the intended MBS service area) of the target NTN MBS cell, or a distance between any of these locations. For example, the non-terrestrial gNodeB may provide intended MBS service area information of one or more potential target NTN MBS cells to the UE (e.g., as part of the conditional MBS configuration or separately thereof). The UE may use this information, in combination with the criterion, which may be based on at least one of a location of the UE, a location of an intended MBS service area of the source NTN MBS cell, or a location of an intended MBS service area of the target NTN MBS cell, to decide whether and when to initiate the MBS session with the target gNodeB.

[0173] To enable this, the intended MBS service area information may comprise information about a reference location within the intended MBS service area. For example, the reference location may specify a midpoint as well as a radius of the intended MBS service area. Alternatively, or additionally, the reference location may specify a polygon defining the intended MBS service area. The UE may use this information to determine whether it is approaching or within the intended MBS service area. In other words, the method for the UE may comprise determining 140 a distance to the intended MBS service area of one or more neighboring NTN MBS cells, and initiating the MBS session when approaching the intended MBS service area. In some 202407128

[0174] 38 examples, machine learning / artificial intelligence may be used to predict a time when the UE enters the intended MBS service area (e.g., a time-series prediction that may or may not be informed by the road the UE is travelling on). In other words, the method for the UE may comprise predicting 145 a time of entering the intended MBS service area of a neighboring NTN MBS cell, and initiating the MBS session based on the predicted time of entering the intended MBS service area. Similarly, the time of leaving an intended MBS service area may be predicted. In other words, the method may comprise predicting 145 a time of leaving the intended MBS service area of an NTN MBS cell. For example, the method may comprise initiating reception of an MBS service of interest via unicast transmission if no intended MBS service area is available.

[0175] In some cases, the serving gNodeB may “know” which MBS service is consumed or desired by the UE. For example, the method for the UE may comprise establishing 110 a MBS session with the source NTN MBS cell (i.e., with the non-terrestrial serving gNodeB 20). Alternatively, the method for the UE may comprise providing 110 information on MBS session(s) of interest to the non-terrestrial serving gNodeB 20, so the serving gNodeB 20 can provide useful information to the UE 10. In this case, the information / command provided to the UE may be based on the MBS session that the UE 10 actually consumes or desires to consume.

[0176] In some cases, no such information is exchanged. In this case, it may be up to the UE 10 to check which potential target NTN MBS cells provide the MBS service that the UE wants to consume. In other words, the method for the UE 10 may comprise determining 130 availability of an MBS service of interest in neighboring NTN MBS cells based on the intended MBS service area information received from the source NTN MBS cell, and initiating the MBS session based on the intended MBS service area information.

[0177] Similarly, in some cases, NTN MBS cells might provide an MBS service for a limited time (e.g., a television stream between 6 am and midnight), or a specific program, such as a live concert, during a time slot that coincides with the live concert. The source NTN MBS cell may provide the UE with information on when an MBS service 202407128

[0178] 39 is provided by the potential target MBS cells. In other words, the method for the nonterrestrial gNodeB may comprise providing 230, to the UE, information on one or more service start and stop times of one or more MBS services in one or more neighboring NTN MBS cells. Accordingly, the method for the UE may comprise receiving 120 information on one or more service start and stop times of one or more neighboring NTN MBS cells from the NTN MBS source cell, and initiating the MBS session based on the information on the service start and stop times.

[0179] As can be seen in Figs. 3 to 5, intended MBS service areas may overlap (Areas 1 , 2.1 , 2.2, 3 in Fig. 3). Moreover, even if the intended MBS service areas do not overlap, the cells may overlap (see PCI #0 to #5 in Fig. 3, with PCI being the Physical Cell Identity). Therefore, there may be contention regarding the use of MBS resources. As a result, the non-terrestrial gNodeBs may coordinate among each other which MBS resources (time, frequency, space) are used in which intended MBS service area. For example, the method for the non-terrestrial gNodeB 20 may comprise coordinating 220 allocation of MBS resources with one or more neighboring MBS cells. This may include providing information on an MBS resource allocation to the target NTN MBS cell, and receiving a confirmation regarding the MBS resource allocation from the target NTN MBS cell. Moreover, this may include providing 225 an MBS resource allocation notification to a core network entity (such as AMF, Access and Mobility Management Function) of the Non-Terrestrial gNB after coordinating allocation of MBS resources. The process of coordinating the resources is shown in more detail in connection with Figs. 5 and 6.

[0180] Once the MBS resource allocation is coordinated among the non-terrestrial gNodeBs (if necessary), the UE may be provided with information on the MBS resources, so it can “tune in” to the MBS service. Accordingly, the method for the non-terrestrial gNodeB 20 may comprise providing 230 to the UE 10 information on an MBS resource allocation of the target NTN MBS cell (e.g., of the one or more neighboring NTN MBS cells). Accordingly, the method for the UE 10 may comprise receiving 120 information on an MBS resource allocation of the target NTN MBS cell (e.g., the one or more neighboring NTN MBS cells) from the source NTN MBS cell and initiating the MBS session based on the information on the MBS resource allocation. 202407128

[0181] 40

[0182] In general, the process of initiating 150 the MBS session may comprise detaching from the cell served by a serving gNB, the serving gNB providing the source NTN MBS cell, initiating re-synchronization, and initiating the MBS session with a target gNB that provides the target NTN MBS cell.

[0183] For example, the UE may receive the information, such as the conditional MBS configuration, the intended MBS service information, the information on the MBS resource allocation, the information on the start and stop times, etc., from the source NTN MBS cell, for example via a Radio Resource Control, RRC, reconfiguration message.

[0184] The wireless transceiver(s) 12, 22 may serve as an interface for communicating in the cellular mobile communication system. The wireless transceiver(s) 12, 22 may correspond to one or more inputs and / or outputs for receiving and / or transmitting information, which may be in digital (bit) values or analog, according to a specified code or protocol, within a module, between modules, or between modules of different entities. For example, a wireless transceiver may comprise interface circuitry configured to receive and / or transmit information. In examples, a wireless transceiver may comprise any means for obtaining, receiving, transmitting, or providing analog or digital signals or information, e.g., any connector, contact, pin, register, input port, output port, conductor, lane, etc., which allows providing or obtaining a signal or information. The wireless transceiver(s) 12, 22 may be configured to communicate (transmit, receive, or both) in a wireless manner. The wireless transceiver(s) 12, 22 may comprise further components to enable communication in a (mobile) communication system or network; such components may include transceiver (transmitter and / or receiver) components, such as one or more Low-Noise Amplifiers (LNAs), one or more Power-Amplifiers (PAs), one or more duplexers, one or more diplexers, one or more filters or filter circuitry, one or more converters, one or more mixers, accordingly adapted radio frequency components, one or more antennas, etc. For example, the respective wireless transceiver(s) 12, 22 may enable radio communication with UEs and communication between base stations, which can be directly and / or indirectly wired and / or wireless, respectively. 202407128

[0185] 41

[0186] For example, the processor(s) 14, 24 can be implemented using one or more processing units, processing devices, or any means for processing, such as a processor, a computer, or a programmable hardware component equipped with appropriately adapted software. Thus, the described function of the processor(s) 14, 24 can be executed in software, running on one or more programmable hardware components. Such components may include a general-purpose processor, a Digital Signal Processor (DSP), a microcontroller, and more.

[0187] In at least some embodiments, the memory / memories 16, 26 may comprise at least one element of the group of a computer-readable storage medium, such as an magnetic or optical storage medium, e.g. a hard disk drive, a flash memory, Floppy- Disk, Random Access Memory (RAM), Programmable Read Only Memory (PROM), Erasable Programmable Read Only Memory (EPROM), an Electronically Erasable Programmable Read Only Memory (EEPROM), or a network storage.

[0188] More details and aspects of the UE 10 and non-terrestrial gNodeB 20 are mentioned in connection with the proposed concept or one or more examples described above or below (e.g. Fig. 3 to 9). The UE 10 and non-terrestrial gNodeB 20 may comprise one or more additional optional features corresponding to one or more aspects of the proposed concept or one or more examples described above or below.

[0189] Fig. 3 illustrates a scenario where each of the two Low Earth Orbit (LEO) satellites provides wireless access in three different radio cells, which are labeled with a corresponding Physical Cell Identifier (PCI). Further, both satellites provide wireless access to Multicast and Broadcast Services (MBS) in different geographically confined “intended (MBS) service areas”. For example, the intended MBS service area #1 is partly covered by radio cell #0, which is operated by LEO satellite #1 and provides MBS on frequency set f_0, as well as radio cell #1 , which is operated by LEO satellite #2 and provides MBS on frequency set f_1 . Furthermore, within intended MBS service area #1 , areas exist where coverage of radio cell #1 and radio cell #2 overlap. 202407128

[0190] 42

[0191] Fig. 4 depicts a scenario where neighboring radio cells provide time indications (t- ServiceStart, t-ServiceStop, referred to as “t-SeSt”) for indicating when MBS service will start or stop in the respective intended MBS service area. These time indications can be received by a UE when it is still under the coverage of serving radio cell #0. For example, the UE may receive respective time indications (t-SeSt) as well as MBS frequency set indications from further neighboring cells (e.g., radio cells #1 , #2, #3) covering various intended MBS service areas, e.g., areas #1 , #2.1 , #2.2, #3. Depending on the UE’s further movements and MBS service interests, these indications will enable the UE to ensure service continuity when entering a neighboring cell that provides the same service of interest.

[0192] Fig. 5 illustrates a scenario where satellites or gNBs operating neighboring and potentially overlapping radio cells coordinate the allocation of MBS radio resources. For example, the intended MBS service area #1 is partly covered by radio cell #0, which is operated by LEO satellite #1 providing MBS on frequency set f_0, as well as radio cell #1 , which is operated by LEO satellite #2 providing MBS on frequency set f_1. A first radio cell initiates MBS resource coordination with its neighboring radio cells to avoid interfering MBS transmissions, particularly in overlap areas.

[0193] The UE initiates a MBS session with a target MBS cell that serves an intended MBS service area.

[0194] > 1 ) based on conditional MBS configuration, including criteria, such as signal level thresholds of serving or target cells.

[0195] > 2) or upon command from the source MBS cell.

[0196] The MBS source cell (e.g., the non-terrestrial serving gNodeB) determines and provides the configuration for conditional MBS initiation to the UE (e.g., via a RRC reconfiguration message). The MBS source cell may indicate service start and stop times of neighboring MBS cells to the UE (e.g., as a system information message or dedicated signaling). The MBS source and target cells may coordinate allocation of MBS resources (e.g., time / frequency / space). The MBS source cell may indicate MBS resource allocation to the MBS target cell. The MBS target cell may change / update the MBS allocation accordingly and confirm to the source MBS cell. The MBS source 202407128

[0197] 43 cell may indicate MBS resource allocation of the target MBS cell to the UE (e.g., via RRC reconfiguration message).

[0198] The UE may receive intended MBS service area information for a next or one or more neighboring satellite cells that provide a service of interest. This may include a time indication of when a next or neighboring satellite cell starts or stops serving an intended MBS service area, where the service of interest is provided. The UE may receive the above data via NAS signaling (e.g., as part of User Service Description (USD), system information message (e.g., MBS configuration message, SIB20, SIB21 ) or via dedicated signaling).

[0199] The UE may determine availability of an MBS service of interest in next or neighboring satellite cells based on the “intended MBS service area” information, which may include a reference (center) location and distance threshold or radius or another geographical representation (e.g., set of polygons).

[0200] When the UE receives the “intended MBS service area information of next / neighboring satellite cells that provide a service of interest (which may include the time indication when a neighboring satellite cell starts / stops serving an intended MBS service area, where the service of interest is provided), the UE may determine a distance to the received “intended MBS service area” of next / neighboring satellite cells. If the UE is approaching or close to the border of the intended service area of the serving cell (i.e., the source MBS cell) and neighbor cell (i.e. , the target MBS cell), the UE may use the provided time indication to check whether, when, and for how long the service of interest is available in the neighboring intended MBS service area, which is or will be served by another satellite. Using Al (Artificial Intelligence) and ML (Machine Learning)-based techniques, the UE may predict its time of entering neighboring intended MBS service area as well as estimates MBS service times (e.g., using own location / movement data, neighbor cell measurements). The UE may initiate tuning to the MBS frequency (e.g., provided via SIB21 ) of the neighboring satellite’s cell for enabling smooth MBS service continuity. 202407128

[0201] 44

[0202] Beneficially, the UE is aware of when MBS service of interest is available in an “intended MBS service area” of neighboring satellite cells and will tune to the corresponding MBS frequency in a timely manner to enable smooth service continuity. User's MBS experience can be improved through coordinated MBS resource management among neighboring cells.

[0203] Fig. 6 shows the interaction between Serving gNB, Target gNB and CN (AMF). The CN (AMF) sends the MBS config, incl. USD and service area information to the Serving gNB. The Serving gNB determines the MBS resource allocation and sends an MBS resource allocation (RA) indication / coordination request to the target gNB. The target gNB checks the MBS RA indication / coordination request and updates its MBS resource allocation. The target gNB sends an ACK (acknowledgment) of the MBS RA indication / coordination request to the Serving gNB. The Serving gNB sends an MBS resource allocation notification to the CN (AMF) and after that, the target gNB sends the MBS resource allocation notification to the CN (AMF). If serving and target gNB cannot agree on resource allocation, the target gNB rejects the MBS RA indication / coordination request (e.g., due to load, or resource constraints) and sends a NACK (negative acknowledgment) to the serving gNB. Then, both serving and target gNB send an MBS resource allocation coordination request to the CN (AMF) for conflict resolution and determination of MBS resource allocations. The CN entity (e.g., AMF) replies to serving and target gNB and provides respective MBS resource allocations.

[0204] Fig. 7 shows the interaction between UE, Serving gNB, Target gNB and CN (AMF). UE and the Serving gNB initiate the MBS session. The Serving gNB determines a conditional MBS configuration and sends a RRC re-configuration including the conditional MBS configuration to UE. The UE checks the conditions for MBS session initiation. UE and Target gNB then detach from the Serving gNB and initiate resynchronization. UE and Target gNB then initiate the MBS session.

[0205] Fig. 8 shows the flowchart for the UE-side. The UE receives conditional MBS configuration from the serving gNB. Then, the UE evaluates the MBS conditions and checks if MBS initiation conditions are met. If this is the case, the UE establishes an 202407128

[0206] 45

[0207] MBS session with the target NB. If this is not the case, the UE returns to evaluating the MBS conditions.

[0208] Fig. 9 shows the flowchart for the Serving gNB. The Serving gNB receives MBS configuration data incl. USD and service area information. The Serving gNB determines an MBS resource allocation and sends an updated MBS resource allocation (RA) indication / request to neighboring (non-terrestrial) gNB(s). If the ACK is received, the Serving gNB sends an MBS resource allocation notification to CN (AMF); if not, it returns to sending an updated MBS resource allocation (RA) indication / request to neighboring (non-terrestrial) gNB(s). This updated RA may be the result of the coordination by the CN / AMF. Then the Serving gNB checks if an MBS session is initiated with the UE. If this is the case, the Serving gNB determines a conditional MBS configuration and sends the conditional MBS configuration to the UE.

[0209] UE is aware of when MBS service of interest is available in the “intended MBS service area” of neighboring satellite cells and will tune to the corresponding MBS frequency in a timely manner. User’s MBS experience is improved through coordinated MBS resource management among neighboring cells.

[0210] More details and aspects of the method for enhanced MBS service continuity are mentioned in connection with the proposed concept or one or more examples described above or below (e.g. Fig. 1a to 2). The method for enhanced MBS service continuity may comprise one or more additional optional features corresponding to one or more aspects of the proposed concept or one or more examples described above or below.

[0211] An example (e.g., Example 1 ) relates to a method for Enhanced MBS Service Continuity for an Non Terresterial Network (NTN), characterized by, UE initiates MBS session with target MBS cell that serves intended MBS service area based on conditional MBS configuration, including criteria, such as signal level thresholds of serving or target cells or upon command from the source MBS cell. 202407128

[0212] 46

[0213] Another example (e.g., Example 2) relates to a previous example (e.g., Example 1 ) or to any other example, further comprising that MBS source cell determines and provides configuration for conditional MBS initiation to UE (e.g., via RRC reconfiguration message).

[0214] Another example (e.g., Example 3) relates to a previous example (e.g., Example 1 or 2) or any other example, further comprising that the MBS source cell indicates service start and stop times of neighbor MBS cells to UE (e.g., system information message, dedicated signaling).

[0215] Another example (e.g., Example 4) relates to a previous example (e.g., one of Examples 1 to 3) or to any other example, further comprising that the MBS source and target cells coordinate allocation of MBS resources (e.g., time / frequency / space).

[0216] Another example (e.g., Example 5) relates to a previous example (e.g., one of Examples 1 to 4) or to any other example, further comprising that the MBS source cell indicates MBS resource allocation to MBS target cell.

[0217] Another example (e.g., Example 6) relates to a previous example (e.g., one of Examples 1 to 5) or to any other example, further comprising that the MBS target cell will change / update MBS allocation accordingly and confirm to source MBS cell.

[0218] Another example (e.g., Example 7) relates to a previous example (e.g., one of Examples 1 to 6) or to any other example, further comprising that the MBS source cell indicates MBS resource allocation of target MBS cell to UE (e.g., via RRC reconfiguration message).

[0219] Another example (e.g., Example 8) relates to a previous example (e.g., one of Examples 1 to 7) or to any other example, further comprising that UE receives above data via NAS signaling (e.g., as part of User Service Description (USD), system information message (e.g., MBS configuration message, SIB20, SIB21 ) or via dedicated signaling. 202407128

[0220] 47

[0221] Another example (e.g., Example 9) relates to a previous example (e.g., one of Examples 1 to 8) or to any other example, further comprising that the UE determines availability of MBS service of interest in next / neighboring satellite cells based on “intended MBS service area” information, which includes reference (center) location and distance threshold / radius or another geographical representation (e.g., set of polygons).

[0222] Another example (e.g., Example 10) relates to a previous example (e.g., one of Examples 1 to 9) or to any other example, further comprising that when UE receives “intended MBS service area information of next / neighboring satellite cells that provide a service of interest, including a time indication when a neighboring satellite cell starts / stops serving an intended MBS service area, where the service of interest is provided”, UE determines distance to received “intended MBS service area” of next / neighboring satellite cells.

[0223] Another example (e.g., Example 11 ) relates to a previous example (e.g., one of Examples 1 to 10) or to any other example, further comprising that if UE is approaching or close to the border of intended service area of serving cell and neighbor cell, the UE uses the provided time indication to check whether, when, and for how long, the service of interest is available in the neighboring intended MBS service area, which is or will be served by another satellite.

[0224] Another example (e.g., Example 12) relates to a previous example (e.g., one of Examples 1 to 11 ) or to any other example, further comprising that by using Al and ML-based techniques the UE predicts its time of entering neighboring intended MBS service area as well as estimates MBS service times (e.g., using own location / movement data, neighbor cell measurements).

[0225] Another example (e.g., Example 13) relates to a previous example (e.g., one of Examples 1 to 12) or to any other example, further comprising that the UE initiates tuning to the MBS frequency (e.g., provided via SIB21 ) of the neighboring satellite’s cell for enabling smooth MBS service continuity. 202407128

[0226] 48

[0227] Another example (e.g., Example 14) relates to a previous example (e.g., one of Examples 1 to 13) or to any other example, further comprising that CN (AMF) sends the MBS config, incl. USD and service area information to the Serving gNB, the Serving gNB determine MBS resource allocation and sends MBS resource allocation (RA) indication / coord to the target gNB, the target gNB checks MBS RA indication / coord. request and update MBS resource allocation and the target gNB sends ACK of MBS RA indication / coord. request to the Serving gNB, the Serving gNB sends MBS resource allocation notification to CN (AMF) and after that, the target gNB sends MBS resource allocation notification to CN (AMF).

[0228] Another example (e.g., Example 15) relates to a previous example (e.g., one of Examples 1 to 14) or to any other example, further comprising that UE and the Serving gNB initiating the MBS session, the Serving gNB determines conditional MBS configuration and send the RRC re-configuration incl. conditional MBS configuration to UE, UE checks conditions for MBS session initiation, UE and target gNB then detach from serving gNB and initiate re-synchronization and then UE and target gNB initiating MBS session.

[0229] Another example (e.g., Example 16) relates to a previous example (e.g., one of Examples 1 to 15) or to any other example, further comprising that UE receives conditional MBS configuration from serving gNB, then UE evaluates MBS conditions and checks if MBS initiation conditions are met, If this is the case UE establishes MBS session with target NB, if this is not the case UE evaluates MBS conditions.

[0230] Another example (e.g., Example 17) relates to a previous example (e.g., one of Examples 1 to 16) or to any other example, further comprising that the Serving gNB receive MBS configuration data incl. USD and service area information, the Serving gNB determines MBS resource allocation and sends updated MBS resource allocation (RA) indication / request to neighbor gNB(s), if the ACK is received, the Serving gNB sends MBS resource allocation notification to CN (AMF). And then the Serving gNB checks if MBS session initiated, if this is the case the Serving gNB determines conditional MBS configuration and sends conditional MBS configuration to UE. 202407128

[0231] 49

[0232] Another example (e.g., Example 18) relates to a previous example (e.g., one of Examples 1 to 17) or to any other example, further comprising that performing UE mobility prediction and grouping UEs, whereby a determination of different suitable conditional handover configurations and / or of a sequence of multiple conditional handover candidates is done, pre-allocating uplink grants.

[0233] Another example (e.g., Example 19) relates to a previous example (e.g., one of Examples 1 to 18) or to any other example, further comprising that uplink grants is configured, a timer is allocated by a target cell.

[0234] Another example (e.g., Example 20) relates to a previous example (e.g., one of Examples 1 to 19) or to any other example, further comprising that the timer starts it receives handover configuration.

[0235] An example (e.g., Example 21 ) relates to an apparatus for Enhanced MBS Service Continuity for an Non Terresterial Network (NTN), comprising a wireless transceiver, a processor coupled with a memory in which computer program instructions are stored, said instructions being configured to implement steps of the Examples 1 to 20 or according to any other example.

[0236] An example (e.g., Example 22) relates to a User Equipment (UE) comprising an apparatus according to Example 21 (or according to any other example), whereby the UE receives SIB from serving cell, determines and reports UE mobility information by means of measurement report, receives conditional handover updated configuration, evaluates conditional handover conditions, and if they are met, performs conditional handover and reports used conditional handover configuration identifier and terminate the flow, or if they are met, UE evaluates conditional handover condition.

[0237] An example (e.g., Example 23) relates to a terrestrial network gNB (base station gNB, first target gNB, other target gNBs) comprising an apparatus according to Example 21 (or according to any other example), whereby the gNB configures 202407128

[0238] 50 measurement reporting, receives UE measurement report, uses UE QoS requirements and / or UE mobility information for grouping UEs, uses NTN ephemeris data of neighbor NTN cells or nodes, as well as beam characteristics to determine a set or a sequence of conditional handover candidate cells or beams, request handover and allocation of uplink grants from identified neighbor NTN cells or nodes, receives handover acknowledge message, including uplink grants and validity times, NTA + validity times, and load status from neighbor NTN cells or nodes, creates and sends updated conditional handover including conditional handover candidates, NTAS and validity times, uplink grantsand validity times, and additional back-off timers determined based on neighbor cell load, receives conditional handover complete message including conditional handover configuration identifier, and determines which handover or resource reservations to cancel.

[0239] An example (e.g., Example 24) relates to a Non Terrestrial Wireless communication system, wherein the terrestrial network gNB according to Example 23 (or according to any other example) comprises a processor coupled with a memory in which computer program instructions are stored, said instructions being configured to implement steps of at least one of Examples 1 to 20 (or any other example), wherein the user equipment (UE) according to Example 22 (or any other example) comprises a processor coupled with a memory in which computer program instructions are stored, said instructions being configured to implement steps of the claims at least one of Examples 1 to 20 (or any other example).

[0240] The application is relevant to wireless communications of mobile or loT devices communicating via NTN. The applications PCT / EP2024 / 071565 are DE 102024 204 345.1 are incorporated by reference. 202407128

[0241] 51

[0242] Abbreviations:

[0243] AMF: Access and Mobility Management Function

[0244] AS: Access Stratum

[0245] CE: Control Element

[0246] CFR: Common Frequency Resource

[0247] CHO: Conditional Handover

[0248] DCI: Downlink Control Information

[0249] DCCH: Dedicated Control Channel

[0250] FSAI: Frequency Selection Area Identity gNB: Next Generation Node B (5G base station)

[0251] HO: Handover

[0252] ID: Identifier

[0253] IE: Information Element

[0254] LSB: Least Significant Bit

[0255] MAC: Medium Access Control

[0256] MBS: (Multimedia) Multicast Broadcast Service

[0257] MCCH: Multicast Control Channel

[0258] MRB: Multicast Radio Bearer \

[0259] MSB: Most Significant Bit

[0260] MTCH: Multicast Traffic Channel

[0261] NAS: Non-Access Stratum

[0262] NR: New Radio

[0263] NTN: Non-Terrestrial Network

[0264] PCI: Physical Cell Identity

[0265] PDCCH: Physical Downlink Control Channel

[0266] PTM: Point-to-Multipoint RACH: Random Access Channel

[0267] RLC: Radio Link Control

[0268] RRC: Radio Resource Control

[0269] SAP: Service Access Point

[0270] SCell: Secondary Cell

[0271] SIB: System Information Block

[0272] SpCell: Special Cell 202407128

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[0274] SRB: Signalling Radio Bearer

[0275] TA: Timing Advance

[0276] TMGI: Temporary Mobile Group Identity

[0277] TN: Terrestrial Network USD: User Service Description

Claims

20240712853CLAIMS1. A method for a User Equipment, UE, comprising: initiating (150) an MBS, Multicast and Broadcast Service, session with a target Non-Terrestrial Network, NTN, MBS cell based on one of: a) a conditional MBS configuration obtained from a source NTN MBS cell, or b) upon command from the source NTN MBS cell.

2. The method according to claim 1 , wherein the conditional MBS configuration comprises a criterion for switching from an MBS session with the source NTN MBS cell to an MBS session with the target NTN MBS cell.

3. The method according to claim 2, wherein the criterion is based on a signal level threshold with respect to a signal level of the target NTN MBS cell and / or the source NTN MBS cell.

4. The method according to claim 2, wherein the criterion is based on at least one of a location of the UE, a location of an intended MBS service area of the source NTN MBS cell, a location of an intended MBS service area of the target NTN MBS cell, or a distance between locations.

5. The method according to one of the claims 1 to 4, wherein the UE receives the conditional MBS configuration from the source NTN MBS cell, for example via a Radio Resource Control, RRC, reconfiguration message.

6. The method according to one of the claims 1 to 5, wherein the method comprises receiving (120) information on one or more service start and stop times of one or more neighboring NTN MBS cells from the NTN MBS source cell, and initiating the MBS session based on the information on the service start and stop time indications.

7. The method according to one of the claims 1 to 6, wherein the method comprises receiving (120) information on an MBS resource allocation of the20240712854 target NTN MBS cell from the source NTN MBS cell, and initiating the MBS session based on the information on the MBS resource allocation.

8. The method according to one of the claims 1 to 7, wherein the method comprises determining (130) availability of an MBS service of interest in neighboring NTN MBS cells based on intended MBS service area information received from the source NTN MBS cell, and initiating the MBS session based on the intended MBS service area information.

9. The method according to claim 8, wherein the intended MBS service area information comprises information on a reference location within the intended MBS service area.

10. The method according to one of the claims 8 or 9, wherein the method comprises determining (140) a distance to the intended MBS service area of one or more neighboring NTN MBS cells, and initiating the MBS session when approaching the intended MBS service area.

11. The method according to claim 10, wherein the method comprises predicting (145) a time of entering into the intended MBS service area of a neighboring NTN MBS cell, and initiating the MBS session based on the predicted time of entering the intended MBS service area; and / or predicting (145) a time of leaving the intended MBS service area of an NTN MBS cell, and initiating reception of an MBS service of interest via unicast transmission if no intended MBS service area is available.

12. A method for a Non-Terrestrial gNB providing a source NTN, Non-Terrestrial Network, MBS, Multicast and Broadcast Services, cell, comprising: providing (230), to a user equipment, UE, one of: a) a conditional MBS configuration with respect to one or more target NTN MBS cells, or b) a command to initiate an MBS service session with the target NTN MBS cell.2024071285513. The method according to claim 12, wherein the method comprises coordinating (220) allocation of MBS resources with one or more neighboring MBS cells, and providing (230), to the UE, information on an MBS resource allocation of the one or more neighboring MBS cells.14.A UE (10) comprising a wireless transceiver (12), a processor (14) coupled with a memory (16) in which computer program instructions are stored, said instructions being configured to implement the method of one of the claims 1 to 11.

15. A Non-Terrestrial gNB (20) comprising a wireless transceiver (22), a processor (24) coupled with a memory (26) in which computer program instructions are stored, said instructions being configured to implement the method of one of the claims 12 or 13.

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