Method and apparatus for providing multicast and broadcast services in non-terrestrial network

Abstract

The present disclosure relates to a method and apparatus for providing multicast and broadcast services in a non-terrestrial network The method for a non-terrestrial network base station may be provided, the method comprising the steps of: transmitting, to a terminal, service area information including, for each of a plurality of service areas pre-configured so that the MBS are provided, information regarding the effective range of multicast-broadcast services (MBS); and transmitting, to the terminal, an MBS signal for providing the MBS.

Description

Method and device for providing multicast and broadcast services in a non-terrestrial network

[0001] The present disclosure relates to a technology for providing multicast and broadcast services in a non-terrestrial network, and more particularly, to a technology for providing multicast and broadcast services in a non-terrestrial network that enables providing multicast and broadcast services to a specific region in a non-terrestrial network using a satellite having a large cell radius.

[0002] Advances in information and communication technology (ICT) can lead to the development of various wireless communication technologies. Representative wireless communication technologies include LTE (long term evolution), NR (new radio), and 6G (6th Generation), all of which are defined by the 3rd Generation Partnership Project (3GPP) standards. LTE can be one of the 4th Generation (4G) wireless communication technologies, and NR can be one of the 5th Generation (5G) wireless communication technologies.

[0003] In order to process the rapidly increasing amount of wireless data following the commercialization of 4G communication systems (e.g., communication systems supporting LTE), 5G communication systems (e.g., communication systems supporting NR) that use a higher frequency band (e.g., a frequency band higher than 6 GHz) than the frequency band of the 4G communication system (e.g., a frequency band below 6 GHz) may be considered. 5G communication systems may support enhanced Mobile Broadband (eMBB), Ultra-Reliable and Low Latency Communication (URLLC), and massive Machine Type Communication (mMTC).

[0004] Meanwhile, multicast and broadcast services can be resource-efficient transmission methods for multiple users requesting the same content. NR MBS (multimedia broadcast and multicast service) technologies, which efficiently provide such multicast and broadcast services, can primarily provide multicast and broadcast services based on terrestrial networks (TNs). Unlike terrestrial networks, non-terrestrial networks (NTNs) can feature high-speed mobility, such as low Earth orbit (LEO) satellites, wide cell radius, relatively long propagation delays, and can operate in power-constrained environments. Therefore, MBS technologies suitable for non-terrestrial network environments may be required.

[0005] The purpose of the present disclosure to solve the above problems is to provide a method and device for providing multicast and broadcast services in a non-terrestrial network using a satellite having a large cell radius, which enables providing multicast and broadcast services to a specific region.

[0006] In order to achieve the above object, a method for providing multicast and broadcast services in a non-terrestrial network according to a first embodiment of the present disclosure may include, as a method of a non-terrestrial network base station, the step of transmitting service area information including information on an effective range of a multicast-broadcast services (MBS) service to a terminal for each of a plurality of service areas preset to provide the MBS service; and the step of transmitting an MBS signal for providing the MBS service to the terminal.

[0007] Here, the service area information may include geographic information indicating the shape of each of the plurality of service areas.

[0008] Here, at least one service area among the plurality of service areas has a circular shape, and the at least one piece of geographic information may include information on a reference point of the circular shape and distance information from the reference point.

[0009] Here, at least one of the plurality of service areas may have an elliptical shape or a polygonal shape.

[0010] Here, the service area information may include non-geographic information for modeling each of the plurality of service areas.

[0011] Here, the non-geographic information may include at least one of a beam index, a mapped cell identifier, a tracking area identifier (TAI), a service identifier, a temporary mobile group identity (TMGI), a session identifier, a G-RNTI, an MRB, or an SSB associated with the MBS service.

[0012] Here, the service area information may include information on an allowed service area and information on a prohibited service area for the MBS service.

[0013] Here, the step of transmitting the service area information to the terminal may include a step of generating system information including the service area information; and a step of transmitting the system information to the terminal to deliver the service area information to the terminal.

[0014] Here, the system information may be at least one of SIB (system information block) 1, SIB6, SIB7, SIB19, SIB20, or SIB25.

[0015] Here, the size of the transmission range of the MBS signal may be larger than the size of the service area corresponding to the service area information.

[0016] Here, if the non-terrestrial network base station is a global mobile cell, a step of transmitting information about a reference time for each of the plurality of service areas may be further included.

[0017] Meanwhile, a method for providing multicast and broadcast services in a non-terrestrial network according to a second embodiment of the present disclosure for achieving the above object may include, as a terminal method, the steps of: receiving service area information including information on an effective range of a multicast-broadcast services (MBS) service from a non-terrestrial network base station; acquiring a location of the terminal; identifying a service area matching the location based on the service area information; and, when the service area matching the location is identified, receiving an MBS signal associated with the identified service area to selectively receive the MBS service from the non-terrestrial network base station.

[0018] Here, a step of not receiving the MBS service may be further included if a service area matching the location is not confirmed.

[0019] Here, if a service area matching the location is not confirmed, the step of receiving the MBS service and the step of not performing decoding on the MBS signal may be further included.

[0020] Here, the method may further include a step of receiving information on a reference time for each of the plurality of service areas from the non-terrestrial network base station; and a step of calculating a service area after a specific time according to satellite movement using the ephemeris information of the non-terrestrial network base station and the information on the reference time.

[0021] Here, the step of selectively receiving the MBS service may include a step of starting a MRB (Multicast Radio Bearer) setup procedure when the location information matches the service area information; and a step of releasing the setup MRB when the location information does not match the service area information.

[0022] Meanwhile, a device for providing multicast and broadcast services in a non-terrestrial network according to a third embodiment of the present disclosure for achieving the above object includes, as a terminal, at least one processor, wherein the at least one processor causes the terminal to receive service area information including information on an effective range of a multicast-broadcast services (MBS) service from a non-terrestrial network base station; acquire a location of the terminal; identify a service area matching the location based on the service area information; and, when the service area matching the location is identified, receive an MBS signal associated with the identified service area, thereby causing the terminal to selectively receive the MBS service from the non-terrestrial network base station.

[0023] Here, the at least one processor may further cause the terminal not to receive the MBS service if a service area matching the location is not confirmed.

[0024] Here, the at least one processor may further cause the terminal to receive the MBS service if a service area matching the location is not confirmed; and not to perform decoding on the MBS signal.

[0025] Here, the at least one processor may further cause the terminal to receive information about a reference time for each of the plurality of service areas from the non-terrestrial network base station; and to calculate a service area after a specific time according to satellite movement using ephemeris information of the non-terrestrial network base station and the information about the reference time.

[0026] According to the present disclosure, satellites with large cell radiuses can efficiently provide specialized multicast and broadcast services, such as those specific to specific areas, such as by country or region, in non-terrestrial networks. Accordingly, in a non-terrestrial network based on satellites with large cell radiuses, terminals within a cell can receive multicast and broadcast services differentiated by location.

[0027] Figure 1 is a conceptual diagram illustrating a first embodiment of a non-terrestrial network.

[0028] Figure 2 is a conceptual diagram illustrating a second embodiment of a non-terrestrial network.

[0029] FIG. 3 is a block diagram illustrating a first embodiment of entities constituting a non-terrestrial network.

[0030] Figure 4 is a conceptual diagram illustrating embodiments of a system for supporting 5G MBS (5th generation multimedia broadcast and multicast service).

[0031] FIG. 5 is a conceptual diagram illustrating embodiments of a method for providing multimedia and broadcasting services within a terrestrial network cell.

[0032] FIG. 6 is a conceptual diagram illustrating embodiments of a method for providing multimedia and broadcasting services within a non-terrestrial network cell.

[0033] Figure 7 is a conceptual diagram illustrating embodiments of transmitting information about a service area from a base station to a terminal within a non-terrestrial network cell.

[0034] FIGS. 8A to 8F are conceptual diagrams illustrating embodiments of a method for providing geographic information indicating a service area.

[0035] FIGS. 9A to 9F are conceptual diagrams illustrating embodiments of a method for providing geographic information representing a service area, including time.

[0036] Figure 10 is a conceptual diagram illustrating examples of service areas divided into permitted service areas and prohibited areas.

[0037] Figure 11 is a conceptual diagram illustrating embodiments of a method for associating service area information and MBS service.

[0038] FIG. 12 is a flowchart illustrating embodiments of a method for providing multicast and broadcast services in a non-terrestrial network of a base station.

[0039] FIG. 13 is a flowchart illustrating embodiments of a method for providing multicast and broadcast services in a non-terrestrial network of a terminal.

[0040] FIG. 14 is a flowchart illustrating embodiments of a method for providing multicast and broadcast services in a non-terrestrial network of a terminal.

[0041] FIG. 15 is a conceptual diagram illustrating embodiments of the range of a list of intended service areas to be signaled in a specific cell.

[0042] This disclosure may be subject to various modifications and various embodiments. Specific embodiments are illustrated and described in detail in the drawings. However, this is not intended to limit the disclosure to specific embodiments, but rather to encompass all modifications, equivalents, and alternatives falling within the spirit and technical scope of the disclosure.

[0043] While terms such as "first" and "second" may be used to describe various components, these components should not be limited by these terms. These terms are used solely to distinguish one component from another. For example, without departing from the scope of the present disclosure, a first component could be referred to as a "second component," and similarly, a second component could also be referred to as a "first component." The term "and / or" includes a combination of multiple related items described herein or any of multiple related items described herein.

[0044] In embodiments of the present disclosure, “at least one of A and B” may mean “at least one of A or B” or “at least one of combinations of one or more of A and B.” Furthermore, in embodiments of the present disclosure, “at least one of A and B” may mean “at least one of A or B” or “at least one of combinations of one or more of A and B.”

[0045] When a component is referred to as being "connected" or "connected" to another component, it should be understood that it may be directly connected or connected to that other component, but that there may be other components intervening. Conversely, when a component is referred to as being "directly connected" or "connected" to another component, it should be understood that there are no other components intervening.

[0046] The terminology used in this disclosure is only used to describe specific embodiments and is not intended to limit the present disclosure. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this disclosure, it should be understood that the terms "comprises" or "has" indicate the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but do not preclude the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0047] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person of ordinary skill in the art to which this disclosure pertains. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and shall not be interpreted in an idealized or overly formal sense unless explicitly defined herein.

[0048] Hereinafter, preferred embodiments of the present disclosure will be described in more detail with reference to the attached drawings. In order to facilitate an overall understanding in describing the present disclosure, identical reference numerals are used for identical components in the drawings, and redundant descriptions of identical components are omitted.

[0049] A communication network to which embodiments of the present disclosure are applied will be described. The communication system may be a non-terrestrial network (NTN), a 4th Generation (4G) communication network (e.g., a long-term evolution (LTE) communication network), a 5th Generation (5G) communication network (e.g., a new radio (NR) communication network), a 6th Generation (6G) communication network, etc. The 4G communication network, the 5G communication network, and the 6G communication network can be classified as terrestrial networks.

[0050] The non-terrestrial network may operate based on LTE technology and / or NR technology. The non-terrestrial network may support communication in frequency bands above 6 GHz as well as in frequency bands below 6 GHz. 4G communication networks may support communication in frequency bands below 6 GHz. 5G communication networks may support communication in frequency bands above 6 GHz as well as in frequency bands below 6 GHz. The communication networks to which embodiments according to the present disclosure are applied are not limited to those described below, and the embodiments according to the present disclosure may be applied to various communication networks. Here, the term "communication network" may be used interchangeably with the term "communication system."

[0051] Figure 1 is a conceptual diagram illustrating a first embodiment of a non-terrestrial network.

[0052] Referring to FIG. 1, the non-terrestrial network may include a satellite (110), a communication node (120), a gateway (130), a data network (140), etc. The non-terrestrial network illustrated in FIG. 1 may be a transparent payload-based non-terrestrial network. The satellite (110) may be a LEO (low earth orbit, altitude 300 to 1,500 km) satellite, a MEO (medium earth orbit, altitude 7,000 to 25,000 km) satellite, a GEO (geostationary earth orbit, altitude approximately 35,786 km) satellite, a HEO (high elliptical orbit) satellite, or a UAS (unmanned aircraft system) platform. The UAS platform may include a HAPS (high altitude platform station).

[0053] The communication node (120) may include a communication node located on the ground (e.g., a user equipment (UE), a terminal) and a communication node located off the ground (e.g., an airplane, a drone). A service link may be established between the satellite (110) and the communication node (120), and the service link may be a radio link. The satellite (110) may provide a communication service to the communication node (120) using one or more beams. The shape of the reception range (footprint) of the beam of the satellite (110) may be elliptical.

[0054] The communication node (120) can perform communication (e.g., downlink communication, uplink communication) with the satellite (110) using LTE technology and / or NR technology. Communication between the satellite (110) and the communication node (120) can be performed using an NR-Uu interface. When DC (dual connectivity) is supported, the communication node (120) can be connected to not only the satellite (110) but also other base stations (e.g., base stations supporting LTE and / or NR functions), and can perform DC operations based on technologies defined in the LTE and / or NR standards.

[0055] The gateway (130) may be located on the ground, and a feeder link may be established between the satellite (110) and the gateway (130). The feeder link may be a wireless link. The gateway (130) may be referred to as a "non-terrestrial network (NTN) gateway." Communication between the satellite (110) and the gateway (130) may be performed based on a NR-Uu interface or a satellite radio interface (SRI). The gateway (130) may be connected to a data network (140). A "core network" may exist between the gateway (130) and the data network (140). In this case, the gateway (130) may be connected to the core network, and the core network may be connected to the data network (140). The core network may support NR technology. For example, the core network may include an access and mobility management function (AMF), a user plane function (UPF), a session management function (SMF), etc. Communication between the gateway (130) and the core network may be performed based on the NG-C / U interface.

[0056] Alternatively, a base station and a core network may exist between the gateway (130) and the data network (140). In this case, the gateway (130) may be connected to the base station, the base station may be connected to the core network, and the core network may be connected to the data network (140). The base station and the core network may support NR technology. Communication between the gateway (130) and the base station may be performed based on the NR-Uu interface, and communication between the base station and the core network (e.g., AMF, UPF, SMF) may be performed based on the NG-C / U interface.

[0057] Figure 2 is a conceptual diagram illustrating a second embodiment of a non-terrestrial network.

[0058] Referring to FIG. 2, the non-terrestrial network may include satellite #1 (211), satellite #2 (212), a communication node (220), a gateway (230), a data network (240), etc. The non-terrestrial network illustrated in FIG. 2 may be a regenerative payload-based non-terrestrial network. For example, each of satellites #1-2 (211, 212) may perform a regenerative operation (e.g., a demodulation operation, a decoding operation, a re-encoding operation, a re-modulation operation, and / or a filtering operation) on a payload received from another entity constituting the non-terrestrial network (e.g., a communication node (220), a gateway (230)) and transmit the regenerated payload.

[0059] Each of satellites #1-2 (211, 212) may be a LEO satellite, MEO satellite, GEO satellite, HEO satellite, or UAS platform. The UAS platform may include HAPS. Satellite #1 (211) may be connected to satellite #2 (212), and an inter-satellite link (ISL) may be established between satellite #1 (211) and satellite #2 (212). The ISL may operate in a radio frequency (RF) frequency or an optical band. The ISL may be configured optionally. The communication node (220) may include a communication node located on the ground (e.g., a UE, terminal) and a communication node located off the ground (e.g., an airplane, a drone). A service link (e.g., a wireless link) may be established between satellite #1 (211) and the communication node (220). Satellite #1 (211) can provide communication services to a communication node (220) using one or more beams.

[0060] The communication node (220) can perform communication (e.g., downlink communication, uplink communication) with satellite #1 (211) using LTE technology and / or NR technology. Communication between satellite #1 (211) and the communication node (220) can be performed using an NR-Uu interface. If DC is supported, the communication node (220) can be connected to not only satellite #1 (211) but also other base stations (e.g., base stations supporting LTE and / or NR functions), and can perform DC operations based on technologies defined in the LTE and / or NR standards.

[0061] The gateway (230) may be located on the ground, and a feeder link may be established between satellite #1 (211) and the gateway (230), and a feeder link may be established between satellite #2 (212) and the gateway (230). The feeder link may be a wireless link. If an ISL is not established between satellite #1 (211) and satellite #2 (212), a feeder link between satellite #1 (211) and the gateway (230) may be established mandatorily.

[0062] Communication between each of satellites #1-2 (211, 2122) and the gateway (230) may be performed based on the NR-Uu interface or SRI. The gateway (230) may be connected to a data network (240). A "core network" may exist between the gateway (230) and the data network (240). In this case, the gateway (230) may be connected to the core network, and the core network may be connected to the data network (240). The core network may support NR technology. For example, the core network may include AMF, UPF, SMF, etc. Communication between the gateway (230) and the core network may be performed based on the NG-C / U interface.

[0063] Alternatively, a base station and a core network may exist between the gateway (230) and the data network (240). In this case, the gateway (230) may be connected to the base station, the base station may be connected to the core network, and the core network may be connected to the data network (240). The base station and the core network may support NR technology. Communication between the gateway (230) and the base station may be performed based on the NR-Uu interface, and communication between the base station and the core network (e.g., AMF, UPF, SMF) may be performed based on the NG-C / U interface.

[0064] Meanwhile, entities (e.g., satellites, communication nodes, gateways, etc.) constituting the non-terrestrial network illustrated in FIGS. 1 and 2 can be configured as follows.

[0065] FIG. 3 is a block diagram illustrating a first embodiment of entities constituting a non-terrestrial network.

[0066] Referring to FIG. 3, an entity (300) may include at least one processor (310), a memory (320), and a transmission / reception device (330) that is connected to a network and performs communication. In addition, the entity (300) may further include an input interface device (340), an output interface device (350), a storage device (360), etc. Each component included in the entity (300) may be connected by a bus (370) and communicate with each other.

[0067] However, each component included in the entity (300) may be connected through an individual interface or individual bus centered around the processor (310), rather than a common bus (370). For example, the processor (310) may be connected to at least one of a memory (320), a transmission / reception device (330), an input interface device (340), an output interface device (350), and a storage device (360) through a dedicated interface.

[0068] The processor (310) can execute program commands stored in at least one of the memory (320) and the storage device (360). The processor (310) may refer to a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor in which methods according to embodiments of the present disclosure are performed. Each of the memory (320) and the storage device (360) may be configured with at least one of a volatile storage medium and a non-volatile storage medium. For example, the memory (320) may be configured with at least one of a read-only memory (ROM) and a random access memory (RAM).

[0069] Meanwhile, in non-terrestrial networks, scenarios can be defined as shown in Table 1 below.

[0070] NTN shown in Fig. 1 NTNGEO shown in Fig. 2 Scenario A Scenario BLEO (steerable beam) Scenario C1 Scenario D1 LEO (beam moving with satellite) Scenario C2 Scenario D2

[0071] In the non-terrestrial network illustrated in FIG. 1, if the satellite (110) is a GEO satellite (e.g., a GEO satellite supporting a transparent function), this may be referred to as “Scenario A.” In the non-terrestrial network illustrated in FIG. 2, if the satellites #1-2 (211, 212) are GEO satellites (e.g., a GEO supporting a regenerative function), this may be referred to as “Scenario B.”

[0072] In the non-terrestrial network illustrated in FIG. 1, if the satellite (110) is a LEO satellite having steerable beams, this may be referred to as "Scenario C1." In the non-terrestrial network illustrated in FIG. 1, if the satellite (110) is a LEO satellite having beams move with the satellite, this may be referred to as "Scenario C2." In the non-terrestrial network illustrated in FIG. 2, if satellites #1-2 (211, 212) are LEO satellites having steerable beams, this may be referred to as "Scenario D1." In the non-terrestrial network illustrated in FIG. 2, if satellites #1-2 (211, 212) are LEO satellites having beams move with the satellite, this may be referred to as "Scenario D2." Parameters for the scenarios defined in Table 1 may be defined as shown in Table 2 below.

[0073] Scenario A and B Scenario C and D Altitude 35,786 km 600 km 1,200 km Spectrum (service link) < 6 GHz (e.g., 2 GHz) > 6 GHz (e.g., DL 20 GHz, UL 30 GHz) Maximum channel bandwidth capability (service link) 30 MHz for band < 6 GHz 1 GHz for band > 6 GHz Maximum distance between satellite and communication node (e.g., UE) at minimum elevation angle 40,581 km 1,932 km (600 km altitude) 3,131 km (1,200 km altitude) Maximum round trip delay (RTD) (propagation delay only) Scenario A: 541.46 ms (service and feeder links) Scenario B: 270.73 ms (service link only) Scenario C: (Transparent payload: service and feeder links) - 25.77 ms (600 km altitude) - 41.77 ms (1200 km altitude) Scenario D: (Regeneration payload: only service link) - 12.89 ms (600 km altitude) - 20.89 ms (1200 km altitude) Maximum differential delay within a cell 10.3 ms 3.12 ms (600 km altitude) 3.18 ms (1200 km altitude) Service link NR or 6G Feeder link 3GPP or non-3GPP defined radio interface

[0074] Additionally, in the scenarios defined in Table 1, the delay constraint can be defined as shown in Table 3 below.

[0075] Scenario A Scenario B Scenario C1-2 Scenario D1-2 Satellite altitude 35,786 km 600 km Maximum RTD on the air interface between the base station and the UE 541.75 ms (worst case) 270.57 ms 28.41 ms 12.88 ms Minimum RTD on the air interface between the base station and the UE 477.14 ms 238.57 ms 8 ms 4 ms

[0076] Meanwhile, multicast and broadcast services can be resource-efficient transmission methods for multiple users requesting the same content. Due to this advantage of enabling single transmission to multiple users, the 3rd generation partnership project (3GPP) introduced MBMS (multicast and broadcast multimedia service) technology, which enables multicast and broadcast services based on cellular mobile communication networks, starting with the 3rd generation (3G) standard based on wideband code division multiple access (WCDMA).

[0077] This MBMS technology can support wider coverage than mobile communication technologies based on unicast transmission in a cellular environment, and can be significantly different from mobile communication transmission technologies in that it can deliver the same data to multiple users through the same physical resources.

[0078] Meanwhile, MBMS technology was first standardized in the WCDMA-based Release 6 3G ​​standard and was introduced to efficiently deliver mobile television services over 3G mobile networks. However, MBMS technology may not provide satisfactory performance due to the difficulty in efficiently handling the increased multipath channel effects caused by the multicast broadcase single frequency network (MBSFN) through RAKE receivers. Furthermore, due to the limited media consumption on mobile devices at the time, MBMS technology did not receive significant attention.

[0079] Since then, 3GPP has been actively standardizing LTE (long-term evolution) based on OFDM (orthogonal frequency division multiplexing) technology since around 2008. As a result, demand for media through mobile devices has gradually increased, thanks to LTE broadband services. Later, standardization of MBMS technology based on LTE technology was carried out in Release 9. As a result, eMBMS (evolved multimedia broadcast and multicast service) technology was standardized to support high transmission rates by utilizing the wide bandwidth of LTE and to efficiently configure MBSFN by controlling the CP (cyclic prefix) of OFDM.

[0080] Since the introduction of eMBMS technology, improvements to MBMS service functionality have been ongoing for several years, from Release 10 to Release 13. First, Release 10 adjusted MBMS transmission based on the distribution of MBMS-enabled UEs to efficiently operate the MBSFN, and added functionality to dynamically adjust MBMS service areas. Release 11 then improved MBMS service continuity and quality during inter-cell handovers and on LTE multi-frequency networks.

[0081] Release 12 focused on improving MBMS services by leveraging terminal feedback information, and added the Mood (MBMS operation on demand) feature, which activates or deactivates MBMS based on feedback. Release 13, separate from previous efforts to improve MBFSN operational efficiency, sought to address the needs of mobile operators by enabling efficient coexistence of MBMS and unicast transmission within a single cell. As a result, single cell point-to-multipoint (SC-PTM) technology was incorporated as part of MBMS technology. From this point on, MBMS transmission could now apply various functions used by unicast transmission technology within a single cell.

[0082] Since then, with the standardization of 5G (5th generation) progressing, starting with Release 15, various requirements for 5G technology have been defined. As part of this, requirements for 5G broadcasting have also been defined. Specifically, 3GPP included requirements for 5G broadcasting, including linear broadcasting services that support wide coverage, similar to terrestrial broadcasting services, as well as conditions for efficient coexistence with unicast services in narrow service areas and dynamic changes. Based on this, 3GPP included 5G MBS technology in its Release 17 standardization.

[0083] Meanwhile, new radio (NR) MBS technologies, designed to efficiently provide multicast and broadcast services, primarily rely on terrestrial networks (TNs). Unlike terrestrial networks, non-terrestrial networks (NTNs) can feature high-speed mobility, such as low Earth orbit (LEO) satellites. They can also have wide cell radiuses, relatively long propagation delays, and operate in power-constrained environments. Therefore, it may be necessary to analyze the feasibility of technologies applied in NR MBS in non-terrestrial network environments.

[0084] The present disclosure is intended to solve the problems of the prior art described above, and may be used to efficiently provide specialized multicast and broadcasting services for specific areas such as by country / region while minimizing the influence of existing TN and NTN standards and technologies in non-terrestrial networks using geostationary earth orbit (GEO) and LEO satellites having a large cell radius.

[0085] The present disclosure is intended to solve the problems of the above-mentioned prior art, and may aim to provide a device and method for providing multicast and broadcast services in a non-terrestrial network, which can distinguish multicast and broadcast services that can be received according to the locations of terminals within a cell in a satellite-based NTN such as GEO and LEO.

[0086] Meanwhile, the present disclosure described below will describe a method for providing multicast and broadcast services in a non-terrestrial network. In particular, the present disclosure will describe a method for providing MBS services, which efficiently provides specialized multicast and broadcast services for specific areas, such as by country or region, while minimizing the impact of existing TN and NTN standards and technologies in a non-terrestrial network using GEO and LEO satellites with large cell radii. MBS broadcast services may not be restricted by satellite orbit type.

[0087] In this regard, as 3GPP standardized 5G, starting with Release 15, various requirements for 5G technology may have been defined. As part of this, requirements for 5G broadcasting were also defined. Specifically, 3GPP included conditions for 5G broadcasting, including linear broadcasting services that support wide coverage, such as terrestrial broadcasting services, as well as conditions for efficient coexistence with unicast services in narrow service areas and dynamic changes. Based on this, 3GPP included 5G MBS technology in its Release 17 standardization.

[0088] Figure 4 is a conceptual diagram illustrating embodiments of a system for supporting 5G MBS (5th generation multimedia broadcast and multicast service).

[0089] Referring to FIG. 4, the system may include user equipment (UE), new generation-radio access networks (NG-RANs) as base stations, access and mobility management function (AMF) devices, multicast / broadcast user plane function (MB-UPF) devices, multicast / broadcast-session management function (MB-SMF) devices, session management function (SMF) devices, multicast / broadcast service function (MBSF) devices, multicast / broadcast service traffic function (MBSTF) devices, application function (AF) devices / application server (AS) devices, user plane function (UPF) devices, etc.

[0090] Here, 5GC (5G core network) may include AMF, SMF, UPF, MB-UPF, MB-SMF, MBSF, MBSTF, AF / AS, etc. And, 5G RAN may include NG-RANs. It may include AMF, SMF, UPF, MB-UPF, MB-SMF, MBSF, MBSTF, AF / AS, etc. MB-UPF, MB-SMF, MBSF, MBSTF may be newly added network functions. AMF, SMF, UPF, AF / AS, some NG-RAN, UE may be improved existing network functions.

[0091] Key features of 5G MBS technology may include:

[0092] - Introduction of a group scheduling mechanism to allow simultaneous reception of MBS and unicast at the terminal.

[0093] - Multicast and broadcast delivery (shared delivery) on the 5G core

[0094] - Enhanced reliability through support for ARQ (automatic repeat request) and HARQ (hybrid automatic repeat and request) for dynamic service conversion between PTM (point-to-multipoint) and PTP (point-to-point) transmissions.

[0095] - Support for service continuity and lossless handover

[0096] - Receive broadcast services regardless of the RRC (radio resource control) status of the terminal.

[0097] - Support for MBS services on existing network nodes

[0098] Looking at it in more detail from a network architecture perspective, the 5G system network structure has been improved with the goal of supporting MBS services by reusing the existing legacy 5G system as much as possible, and the following new network functions have been introduced to support 5G MBS.

[0099] - MB UPF: MB UPF is an entry point to 5GS ((5G system)) and can act as a session anchor for 5GS.

[0100] - MB SMF: MBS SMF may be an MBS session management and user plane function based on policy rules for multicast and broadcast services.

[0101] - MBSF: MBSF can support service level functions that interact with AF (Application Function / Application Server) and MB SMF for MBS session operations.

[0102] - MBSTF: MBSTF is a media anchor for MBS data traffic and can support common packet transport functions available in IP multicast-enabled applications, such as framing, multi-flow, and packet encoding.

[0103] Building on the improved existing network capabilities along with newly added network capabilities, 5GC can support two delivery methods to deliver MBS data traffic from MB-UPF to NG-RAN: 5GC SD (shared MBS traffic delivery) and ID (individual MBS traffic delivery).

[0104] The SD forwarding method may be used to allocate 5GC resources for MBS data transmission. In the SD forwarding method, when the MB-UPF has packets to transmit to multiple terminals receiving MBS session data, a single copy of the MBS data packet can be transmitted to each NG-RAN node. This single-copy packet may not be dedicated to a single terminal and may be shared by multiple terminals. In contrast, in the ID forwarding method, when the MB-UPF has packets to transmit to multiple terminals receiving MBS session data, a single copy of the MBS data packet can be forwarded to the UPF. The UPF can then transmit separate copies to each individual terminal. The ID forwarding method may not utilize resources efficiently. However, it may be a necessary method when an NR-RAN node does not have MBS support capabilities but data transmission for an MBS session is required.

[0105] Next, from a protocol perspective, 5G MBS technology improves upon existing NR protocols to support both multicast and broadcast services, each with the following distinct characteristics. First, target services in multicast mode may have specific quality of service (QoS) requirements that must be guaranteed on the network, similar to unicast.

[0106] Therefore, a terminal receiving multicast data can be in an RRC connected state. Radio resource configurations, such as MBS radio bearer (MRB) configuration and physical layer configuration, can be provided based on interaction between the terminal and the base station via dedicated RRC signaling. Furthermore, if reliable transmission is required for cell edge users, PTM transmission can be switched to PTP transmission.

[0107] If multicast data does not arrive, the multicast session may become deactivated, and the terminals in the multicast group may transition to an inactive or idle state. These terminals may transition back to a connected state when the multicast session becomes reactive.

[0108] Conversely, broadcast mode can be provided to all users within coverage regardless of the RRC state. Broadcast mode may have a mechanism similar to LTE's SC-PTM. To deliver broadcast data to UEs outside the connected state, radio resource configuration for broadcast mode can be periodically transmitted via the MBS control channel (MCCH). UEs can then apply the configuration to the MBS traffic channel. Broadcast mode may not require interaction between UEs and the base station. Therefore, the network does not receive any transmission status feedback from UEs and can transmit data on a best-effort basis.

[0109] The existing NR protocol can be improved as follows to support both multicast and broadcast modes with the above characteristics.

[0110] - SDAP (service data adaptation protocol) layer: To support MBS, RAN can redefine MBS radio bearer (MRB). The SDAP layer can provide one-to-one mapping between MBS sessions and MRBs serving multiple MBS QoS flows (QFs) based on required QoS and network policies. Since MBS exists only for downlink transmission, it may not support uplink SDAP features such as reflective QoS and network-initiated QF remapping.

[0111] - PDCP (packet data convergence protocol): PDCP for MBS may differ from PDCP for unicast services. In PDCP for MBS, a PDCP entity can support a split MRB (multi-radio link control) that is connected to one PTM RLC and one PTP RLC (radio link control). This allows the base station to transmit MBS packets through the PTP RLC, PTM RLC, or both RLCs, depending on reliability requirements. If the base station sends PDCP packets with the same sequence through both RLCs, the terminal can discard the later-arriving packet through the PDCP duplicate detection function.

[0112] - RLC: RLC can support PTP RLC and PTM RLC. PTM RLC can be a group common RLC. All terminals configured with PTM RLC can receive the same packet using G-RNT (group radio network temporary identifier) ​​or G-CS-RNTI (group configured scheduling RNTI). Due to the synchronization complexity between PTM RLC entities between multiple terminals and the base station, PTM RLC may not support AM (acknowledged mode) mode and may operate in UM (unacknowledged mode). In contrast, PTP RLC can be a dedicated RLC for each terminal. In PTP RLC, packets can be transmitted only to specific terminals using C-RNTI (cell RNTI) or CS-RNTI (configured scheduling RNTI). PTP RLC can be transmitted reliably through ARQ. The base station can select an appropriate RLC to transmit a packet considering the required reliability, link quality of the terminal, and cell congestion status.

[0113] - MAC ((medium access control): To reduce terminal power consumption, MBS session-specific DRX (discontinuous reception) can be configured for terminals receiving MBS data. In addition, MAC can manage physical layer parameters related to MBS, such as MBS SPS (semi-persistent scheduling) or HARQ. Unlike unicast SPS that uses CS-RNTI for SPS activation, deactivation, and retransmission, MBS SPS can be controlled by both unicast signaling by CS-RNTI and multicast signaling by G-CS-RNTI.

[0114] Finally, improvements at the physical layer level have primarily been made in terms of bandwidth part (BWP) operation and HARQ operation. First, from the BWP perspective, Release 17 introduced the concept of MBS common frequency resources (CFR), which allows multiple terminals to receive MBS reception, including group common physical downlink shared channel (PDSCH) or PDSCH.

[0115] MBS CFRs can be divided into multicast CFRs and broadcast CFRs. Multicast CFRs can be defined within the dedicated active unicast BWP interval of the corresponding terminal to support simultaneous reception of unicast and multicast in the same time slot. The subcarrier spacing (SCS) and CP in the CFR can have the same values ​​as the active unicast BWP to avoid BWP switching. In contrast, broadcast CFRs can be defined within the initial BWP interval. Next, from a HARQ operation perspective, unlike LTE eMBMS or SC-PTM, HARQ-ARQ feedback and HARQ retransmission can flexibly support the following three options for highly reliable transmission in multicast mode.

[0116] - ACK (positive acknowledgment) / NACK (negative acknowledgment)-based HARQ-ACK feedback: A terminal can feedback an ACK or NACK on its dedicated PUCCH (physical uplink control channel) resources. This method can be effective for a small number of terminals receiving multicast data.

[0117] - NACK-based HARQ-ACK feedback: A terminal can only feedback NACKs on the common PUCCH resource shared with other terminals in the same group. This approach can be resource-efficient. However, the base station cannot detect cases where terminals fail to decode PDCCH information.

[0118] - HARQ-ARQ Feedback Not Applied: The terminal may not send any feedback on received data. When the terminal's QoS requirements for multicast data are low, the base station may use this method to reduce resource consumption.

[0119] The base station can dynamically switch between ACK / HARQ-based HARQ-ACK feedback and non-feedback modes through RRC signaling or downlink control information (DCI). Finally, NR MBS improves upon existing NR technologies to support mobility and service continuity. While previous generations supported mobility and service continuity at the RAN level, NR MBS supports service continuity with lossless mobility at the packet level, thereby minimizing the impact of existing RAN protocols. The applied packet-level service continuity can be based on packet-level sequence number synchronization, which ensures that identical packets have the same PDCP sequence number in areas that support service continuity. This packet number synchronization can enable the UE to maintain the MRB naturally configured during handover.

[0120] NR MBS technologies, which efficiently provide multicast and broadcast services with the aforementioned characteristics, primarily rely on terrestrial mobile communication networks to provide these services. Unlike terrestrial networks, non-terrestrial networks can feature high-speed mobility, such as LEO satellites, and can have wide cell radiuses, relatively long propagation delays, and operate in power-constrained environments. Therefore, it may be necessary to analyze the feasibility of technologies applied in NR MBS in non-terrestrial network environments.

[0121] 5G NTN standardization can aim to standardize the minimum specifications required for NTN environments while minimizing impact on existing TN specifications. Considering this, it's expected that technologies for efficient multimedia and broadcasting services in 5G NTN will reuse existing TN technologies as much as possible, rather than introducing technologies optimized for NTN environments. Furthermore, improvements will primarily focus on areas requiring modification or addition due to the NTN-specific environment.

[0122] First, we can examine aspects related to the need for modification or deletion in applying the basic NR MBS technology to NTN. Most of the technologies considered in the existing TN 5G NR MBS can be applied as is to 5G NTN MBS technology. Meanwhile, areas requiring additional improvement include changes to protocol layer timer parameter values ​​due to long propagation delays. However, these aspects can be applied as is, as was done in Release 17 and Release 18, where the parameter values ​​of the existing NR protocol were changed due to long propagation delays.

[0123] Next, we can examine the aspects that need to be newly added for NTN MBS beyond the existing NR MBS technology. In 5G NR MBS, the multicast or broadcast service area can be considered the entire area covered by a single RAN node. This is because the coverage of a single RAN node is relatively small compared to NTN, so multicast and broadcast service areas can be distinguished at the RAN node coverage area level. Based on this assumption, there may be no need to distinguish multicast and broadcast service areas within a RAN node. However, unlike TN, NTN cell coverage can range from 100 km to over 1,000 km. Therefore, multiple regions or countries may be included within a specific NTN cell. Due to the nature of broadcast or multicast services, there may be a need to provide separate services by country or region. Considering regulatory aspects and emergency service provision, a new method for distinguishing multicast and broadcast service areas within the coverage area of ​​a single RAN node can be added in NTN, unlike the existing TN.

[0124] In order to solve these problems, the present disclosure proposes a technique for efficiently providing multicast and broadcast services specialized for specific regions, such as countries and regions, while minimizing the influence of existing TN technology standards in non-terrestrial networks using GEO, LEO satellites, etc., which have large cell radii.

[0125] Specifically, the present disclosure proposes a method for efficiently providing multicast and broadcast services specialized for specific regions, such as countries and regions, while minimizing the impact of existing TN and NTN standards and technologies in non-terrestrial networks using GEO, LEO satellites, etc., which have large cell radii, by distinguishing whether the multicast and broadcast services can be received based on the location of terminals as well as the group ID.

[0126] Preferred embodiments of the present disclosure will be described in detail below. The embodiments described below may be described based on an NR-based satellite mobile communication system. However, the methods disclosed in the present disclosure can be broadly applied to any other mobile communication system with a wide cell coverage area.

[0127] In this regard, according to an embodiment of the present disclosure, a terminal can receive MBS communication within a service area. For example, the terminal can receive MBS communication from an NTN cell. For example, the terminal can receive MBS communication from a TN cell. For example, the terminal can receive MBS communication from a TN cell and an NTN cell. For example, a network entity forming a TN cell or an NTN cell can apply a delay offset to the MBS communication. Accordingly, the UE can receive MBS communication from each network entity (TN / NTN) simultaneously. In addition, the MBS communication can include multicast control channel (MCCH) data, multicast traffic channel (MTCH) data, or both. For example, the MTCH data can be encrypted. On the other hand, the MCCH data can be unencrypted. The terminal can use a decryption key to decrypt the MTCH data.

[0128] For example, a network entity (satellite) can encrypt MBS communications and transmit the encrypted MBS communications through an NTN cell. For example, a terminal may be located within the service area. In such a case, the network entity (satellite) can provide the terminal with a decryption key associated with the encrypted MBS communications. The terminal within the service area can decode the encrypted MBS communications using the received decryption key. UEs outside the service area cannot decode the encrypted MBS communications.

[0129] More specifically, broadcast communication services can be delivered to terminals via broadcast sessions. Terminals can receive broadcast communication services in the RRC_IDLE, RRC_INACTIVE, and RRC_CONNECTED states. For broadcast communication services, the same service and the same specific content data can be provided simultaneously to all terminals within a specified geographical area. All terminals within the broadcast service area defined in TS 23.247 or within the intended service area connected to an NTN supporting MBS broadcast can be authorized to receive the data.

[0130] FIG. 5 is a conceptual diagram illustrating embodiments of a method for providing multimedia and broadcasting services within a terrestrial network cell.

[0131] Referring to Figure 5, in the TN scenario, the coverage area of ​​each base station may be relatively small compared to the area of ​​each region or country. Therefore, multiple base stations can provide multicast and broadcast services within a single region or country. In this TN scenario, multiple base stations deployed in a given country or region can differentiate the broadcast and multicast services provided by each base station deployed in that country or region to provide national or regional broadcast and multicast services.

[0132] For example, multiple base stations can service (broadcast) broadcast service 1 in a first country. Multiple base stations can service (broadcast) broadcast service 2 in a second country. In this case, multiple base stations built in the first country can service broadcast service 1, and multiple base stations built in the second country can service broadcast service 2. In this way, multiple base stations can provide broadcast services by differentiating them by country. When a specific terminal (UE #1, UE #2) exists in the first country, the terminal is connected to the base station built in the first country, and therefore cannot naturally receive broadcast service 2, which is serviced outside of the coverage area. When a specific terminal (UE #3) exists in the second country, the terminal is connected to the base station built in the second country, and therefore cannot naturally receive broadcast service 1, which is serviced outside of the coverage area.

[0133] Additionally, multiple base stations can serve (broadcast) multicast 1 in a first region of a first country. Multiple base stations can serve (broadcast) multicast 2 in a second region of the first country. Multiple base stations can serve (broadcast) multicast 3 in a third region of the first country. Multiple base stations can serve (broadcast) multicast 4 in a first region of a second country. Multiple base stations can serve (broadcast) multicast 5 in a second region of the second country. Multiple base stations can serve (broadcast) multicast 6 in a third region of the second country.

[0134] In this way, multiple base stations can provide multicast services by different countries and regions. A specific terminal 1 may be located in a second region of a first country. In this case, since terminal 1 is connected to a base station built in the second region of the first country, it cannot receive multicast 1, multicast 3 to 6, which are served outside of the coverage area. A specific terminal 2 may be located in a third region of the first country. In this case, since terminal 2 is connected to a base station built in the third region of the first country, it cannot receive multicast 1, multicast 2, 4 to 6, which are served outside of the coverage area. A specific terminal 3 may be located in a second region of a second country. In this case, since terminal 2 is connected to a base station built in the second region of the second country, it cannot receive multicast 1 to 4, multicast 6, which are served outside of the coverage area. In other words, in a TN environment, a base station built in a specific region can provide services to terminals in a specific country or region. Therefore, it is easy to limit the services that can be provided to terminals located in specific countries and regions.

[0135] FIG. 6 is a conceptual diagram illustrating embodiments of a method for providing multimedia and broadcasting services within a non-terrestrial network cell.

[0136] Referring to Figure 6, in the NTN scenario, all services provided by a single RAN node, such as LTE MBMS or NR MBS, in existing TNs can be transmitted so that all terminals within the service area can receive them. Therefore, coverage can be established within an NTN cell across multiple countries or regions. Therefore, the broadcasting and multimedia services that can be received by terminals in a specific region cannot be restricted.

[0137] For example, in the aforementioned FIG. 5, TN terminal 1 (UE #1) cannot receive any services other than the broadcast and multicast services of the first country and the broadcast and multicast services of the second region. However, as illustrated in FIG. 6, in the case of NTN terminal 1 (UE #1), even if it is located in the first country, if a factor (e.g., G-RNTI, etc.) that can receive the multicast and broadcast services is configured, it can receive the broadcast and multicast services of the first country, and even if it is located in the second region, it can also receive the broadcast and multicast services of other regions, that is, the first region and the third region. This may mean that a problem may arise in which services cannot be restricted by country or region. Therefore, in an NTN environment, a solution that can solve this problem differently from a TN environment may be additionally required.

[0138] System information (e.g., SIB) can be used to ensure service continuity of MBS sessions when a UE initiates a cell reselection procedure. When performing cell reselection, the UE can preferentially select an MBS frequency that provides the MBS session of interest. By providing the intended service area for each MBS frequency in the system information, the UE can know the exact intended service area for a specific frequency to provide the desired MBS session. Therefore, it may be beneficial to prioritize an MBS frequency based on the UE's location and the intended area for each MBS frequency during cell reselection. The UE can select an MBS frequency with the highest priority based on the UE's location and the intended area information for each MBS frequency provided through system information (e.g., SIB2) during cell reselection.

[0139] A service area may encompass a portion of an NTN cell. Alternatively, a service area may encompass one or more NTN cells (or portions thereof). To model a service area, the following additional geographic area types may be considered:

[0140] -Circular (e.g. similar to TN coverage)

[0141] - More accurately approximates the shape of the intended service area with information through geographic areas (e.g. polygons).

[0142] For MBS broadcast services, both Earth Fixed Cell (EFC) and Earth Moving Cell (EMC) can be supported. The intended service area for MBS broadcasts can be provided through system information. For MBS broadcasts, methods for including service area information can consider SIB20 / SIB21 / MBSBroadcastConfiguration. If an intended service area (e.g., geographical area / TN coverage) is provided for MBS broadcast services, the area can be associated with the MBS session.

[0143] An intended broadcast service area may be defined as a geographic area expressed by (one or more) reference locations and a radius or (one or more) polygons. If a terminal does not belong to any intended service area of ​​the broadcast service of interest, it may not need to (re)acquire the latest MCCH. If a terminal does not belong to any intended service area of ​​the broadcast service of interest, it may not need to (re)acquire the latest MCCH.

[0144] For MBS broadcast services targeting a specific area, terminals supporting the feature cannot establish an MRB (MBS Radio Bearer) for an MBS session associated with that area when outside the service area. For MBS broadcast services targeting a specific area, terminals supporting the feature can initiate the broadcast MRB establishment procedure when within the service area, and initiate the broadcast MRB release procedure when leaving the service area.

[0145] Each MBS service may include one or more intended service area IDs on the MCCH. A list of intended service areas (and their associated IDs) may be included on the MCCH. Alternatively, the list of intended service areas may be provided through a new SIB or an existing SIB. Furthermore, if a UE is not within the intended service area of ​​a broadcast service of interest, MCCH re-reception may be omitted.

[0146] Encoding of TN coverage can be reused for defining circular geographic areas using the tn-ReferenceLocation-r18 and tn-DistanceRadius-r18 encoding schemes. Polygon encoding can be reused for defining polygonal geographic areas. The name of the intended service area can be considered the name of the information element (IE) representing the geographic area.

[0147] The intended service area signaled by the MBS BC service may include not only the current serving cell but also overlapping neighboring cells. The geographic information of the intended service area may be semi-static and may not be updated frequently. A new System Information Block (SIB) may be defined to include a list of intended service areas and associated pointers. The pointers may point to the intended service areas by index, ID, or other means within the list. Updating the intended service area information in the new SIB may follow the existing SIB modification procedure.

[0148] Area information can be represented as a reference location and a set of radii or polygons. This can result in significant signaling overhead and be inefficient if used repeatedly across multiple locations. From this perspective, area information can be defined in a new or existing SIB, with an area ID assigned to each area. This approach allows locations requiring area information to reference only the area ID, resulting in significantly less signaling overhead than signaling the entire area definition.

[0149] The intended service area (consisting of one or more circles or polygons) is defined in a new or existing SIB, and each area can be associated with an area ID. This allows locations requiring service area information to include only the corresponding area ID. Alternatively, each area can use an area index. This approach can be efficient due to its small data size. Furthermore, the lookup mechanism can be simple, resulting in faster processing. However, because it relies on the list order, it can be problematic when changed. Furthermore, global uniqueness may not be guaranteed.

[0150] In this regard, if not all intended service areas are provided through a new SIB in a given cell, the list is likely to be updated frequently. This frequency of updates to intended service area information may increase, particularly if the cell is an Emergency Communication (EMC) cell. Intended service area information can be provided not only through Access Stratum (AS) signaling but also through Non-Access Stratum (NAS) signaling. Using a Unique Identifier (ID) allows for more flexible reference handling across multiple cells and networks. Considering this, an ID-based approach may be a more appropriate way to indicate intended service areas in a new SIB. It is expected that an ID-based reference approach will contribute to increased efficiency in managing and updating intended service areas.

[0151] System information can remain the same even when broadcast services are added or released. RAN nodes can update system information when a new broadcast service is initiated (where the MSB of the MCCH change notification in the MBS DCI indicates a session addition). In this case, the intended service area of ​​the newly added broadcast service session can be added to the list.

[0152] Another solution is to include relevant information in the MCCH. This approach offers simpler signaling than using system information, and may loosen the coupling between the MCCH and the SIB. This means that MCCH updates may not result in system information updates. However, since changes in the intended service area can trigger MCCH modifications, the UE can always perform MCCH acquisition and re-acquisition when there is a broadcast session of interest. Until the MCCH is updated, the UE cannot determine whether it is within the intended service area of ​​the broadcast service session of interest.

[0153] Enhancements to omit MCCH monitoring when the terminal is not within the intended service area of ​​the broadcast service of interest may include:

[0154] Alternative 1: Use MCCH Modification Informa- tion (DCI) to indicate intended service area updates.

[0155] The terminal may be configured to re-acquire the MCCH only if the MCCH Modification Notification DCI indicates an intended service area update.

[0156] Alternative 2: Establish a larger revision cycle for updates to the intended service area of ​​the broadcast service.

[0157] A service area modification cycle can consist of multiple MCCH modification cycles. Therefore, if a terminal is not within the intended service area, it may not need to re-acquire MCCH within the service area modification cycle.

[0158] In both alternatives, when a new broadcast session is added, the terminal can always re-acquire the MCCH. MBS service continuity can be improved in two ways.

[0159] -Provide neighboring cell information:

[0160] A serving base station can provide a list of neighboring cells that provide the same MBS broadcast service as the current cell on the MCCH. This allows the terminal to request the service unicast before moving to a cell that does not provide the MBS broadcast service via PTM (Public Simultaneous Multiple Transmission) transmission.

[0161] -MBS frequency layer priority support:

[0162] NR MBS can provide an MBS Frequency Selection Assistance ID (FSAI) for MBS broadcast sessions on each frequency (including both same and different frequencies). By adding the concept of intended service area, base stations can further enhance service continuity.

[0163] As a specific improvement measure, the intended service area within the adjacent cell can be provided for each broadcast service session in the adjacent cell configuration. When reselecting a cell, the terminal may need to determine frequency priority based on whether the MBS broadcast service of interest is available on the corresponding frequency at the current location. To this end, the intended service area for each frequency can be provided in system information (e.g., SIB) for each MBS broadcast service.

[0164] System information can provide a list of FSAIs for each frequency (including identical and different frequencies). The terminal can derive a mapping between TMGI and frequency using the mapping between temporary mobile group identity (TMGI) and FSAI in the User Service Description (USD) and the mapping between frequency and FSAI in SIB21.

[0165] The connection between FSA and MBS broadcasting services

[0166] Understanding 1: FSAI #x -> Single MBS Broadcast Session

[0167] In such cases, since an FSA ID is clearly associated with a single MBS broadcast session, the intended service area can simply be provided to each FSA ID.

[0168] Understanding 2: FSAI #x -> Multiple MBS Broadcast Sessions

[0169] In such cases, each FSA may need to explicitly indicate the MBS broadcast service session and its intended service area.

[0170] Figure 7 is a conceptual diagram illustrating embodiments of transmitting information about a service area from a base station to a terminal within a non-terrestrial network cell.

[0171] Referring to Figure 7, in a method for providing multicast and broadcast services in a non-terrestrial network, the base station can, to address the aforementioned issues, provide terminals with information regarding the areas in which each multicast and broadcast service can be received. Accordingly, the base station can restrict terminals from receiving the multicast and broadcast service if they are not located within the relevant area (service area), even if the terminals have a factor (e.g., G-RNTI) that enables them to receive the service.

[0172] This method of providing optional MBS services based on terminal location is expected to be applicable without significantly affecting the NTN standard, as it includes a function that allows NTN terminals to mandatorily estimate their own locations.

[0173] In other words, when a satellite RAN node provides information about the broadcast and multicast services it provides, it can additionally inform the terminal of the valid range of each broadcast and multicast service. The terminal can then determine whether it is within the valid range of the service based on its location. If the terminal is within the valid range, it can then take action to receive the service.

[0174] For example, terminal 1 (UE #1) illustrated in FIG. 7 can receive a parameter (e.g., G-RNTI, etc.) for using two broadcast services and six multicast services from a satellite RAN node. In this case, according to the existing TN standard, all two broadcast services and six multicast services provided by the satellite RAN node can be received. However, according to the selective MBS service provision method considering the terminal location of the present disclosure, terminal 1 can obtain (estimate) its own location through a GNSS (global navigation satellite system), etc. Terminal 1 can check the service area matching its location (in other words, the valid area of ​​each service provided by the satellite RAN node). Based on this, terminal 1 can selectively receive only broadcast service 1 of a first country and multicast service 2 of a second region.

[0175] In summary, the base station of the non-terrestrial network of the present disclosure can transmit MBS transmission signals to terminals for providing MBS services. Additionally, the base station can transmit service area information, including information about the effective range of the MBS service, to the terminals for each of a plurality of service areas preset to provide MBS services.

[0176] Meanwhile, the present disclosure may consider the following three scenarios in relation to the service area meaning the effective range of the MBS service and the transmission range of the MBS transmission signal for providing the MBS service.

[0177] First, in the first scenario (S1), the intended service area may be part of an NTN cell or a multi-cell. In this first scenario, the base station can transmit MBS transmission signals (MBS service content) to terminals only within the intended service area. In the second scenario (S2), the intended service area may be part of an NTN cell or a multi-cell. However, in the second scenario, the base station can transmit MBS transmission signals (MBS service content) to terminals even outside the intended service area. In the third scenario (S3), the intended service area may consist of a list of NTN cells or tracking areas.

[0178] In this regard, in the first scenario (S1), the service area may coincide with the satellite's beam footprint. This situation can be exemplified when the beam coverage of the service area is relatively large. Considering this first scenario (S1), different MBS sessions may be associated with different geographic areas. Information for such association may be transmitted to the terminal via a system information block (SIB), etc. Furthermore, the third scenario (S3) is expected to be supported via existing NR specifications for supporting TN broadcast services. The multicast and broadcast service provisioning techniques in non-terrestrial networks of the present disclosure may preferably be implemented targeting S1 and S2.

[0179] Meanwhile, for the first scenario (S1), multiple physical beams dedicated to each service area within a single cell may be required. These beams may have flexible patterns capable of accommodating various types of service areas. However, this may be difficult to implement in actual satellite systems, particularly those with Earth-mobile cells. However, the multicast and broadcast service provisioning techniques of the present disclosure in non-terrestrial networks may be more preferably applied to, but are not limited to, the second scenario (S2).

[0180] According to the second scenario (S2), the transmission range of the MBS transmission signal can be set to be larger than the service area corresponding to the service area information. Specifically, a base station of a non-terrestrial network can transmit service area information, including information about the effective range of the MBS service, to the terminal for each of the multiple service areas preset to provide the MBS service.

[0181] Additionally, a base station of a non-terrestrial network can transmit an MBS transmission signal to provide MBS services to a terminal. Furthermore, a terminal that receives such service area information can receive the MBS service using an MBS transmission signal associated with service area information that matches the terminal's location information. Meanwhile, according to one embodiment of the present disclosure, the service area information may include geographical area information indicating the shape of each of a plurality of service areas.

[0182] FIGS. 8A to 8F are conceptual diagrams illustrating embodiments of a method for providing geographic information indicating a service area.

[0183] Referring to Fig. 8a, the service area can be represented as a single circle based on a reference point and distance. Referring to Fig. 8b, the service area can be represented as a shape using a reference point and two distances (distance 1, distance 2). Referring to Fig. 8c, the service area can be represented as a polynomial shape using points 1 to N, where N can be a positive integer. Referring to Figs. 8d to 8f, each service area can be represented in a composite manner using different display methods.

[0184] Referring back to FIG. 8A, at least some of the plurality of service areas may have a circular shape. Accordingly, geographic information indicating the shape of the corresponding service area may include information on a reference point of the circular shape and distance information from the reference point (e.g., radius information, diameter information, etc.). Meanwhile, with respect to the format of geographic information for defining the shape of the service area, the TN coverage encoding method of SIB25 defined in TS 38.331 may be reused to define a circular service area. Specifically, the center point and radius of the circular service area may be defined, respectively, through the tn-ReferenceLocation-r18 and tn-DistanceRadius-r18 elements, but is not limited thereto.

[0185] This method (circular display method) can only provide two types of information to indicate a service area: reference point information (e.g., coordinate information) and distance information, such as the radius or diameter of the circle. This can offer the advantage of relatively low signaling overhead. However, it can be difficult to express the shape of the service area in detail. Therefore, if the service area is not circular, it can be difficult to clearly represent it.

[0186] In contrast, the oval-based service area display method illustrated in FIG. 8b can provide additional distance information compared to the circular-based display method. Therefore, signaling overhead may be high. However, the oval-based service area display method may have the advantage of being able to display the service area relatively clearly. Specifically, when applying the oval-based service area display method, the geographic information for the service area may include information about the reference point, as well as the first distance (distance 1) and the second distance (distance 2) from the reference point.

[0187] In addition, the polygon-based service area display method illustrated in FIG. 8c can relatively clearly express the service area by displaying the service area in the shape of a polygon composed of multiple vertices. However, the signaling overhead may be very high. Specifically, when the polygon-based service area display method is applied, the geographic information for the service area may include information of a plurality of vertices (e.g., coordinate information; vertex 1 (point 1), vertex 2 (point 2), 쪋, vertex N (point N)). The service area can be specified by connecting each vertex. Here, N can be a positive integer. In other words, according to one embodiment of the present disclosure, at least some of the plurality of service areas may have an elliptical shape or a polygonal shape.

[0188] Meanwhile, according to one embodiment of the present invention, the polygon encoding method defined in TS 37.355 can be reused to define a polygon-shaped service area. For example, the coordinate information of the vertices constituting the polygon can be defined using the encoding method. By reusing these encoding methods, service areas of various shapes can be efficiently defined while maintaining compatibility with existing standards.

[0189] In this regard, RAN2 may have had a similar discussion when introducing a new System Information Block (SIB25) for TN coverage signaling in Release 18 NTN. However, defining a service area as a circular shape can reduce signaling overhead. However, defining a service area as a circular shape may have the disadvantage that it is difficult to express the service area more accurately than a geographic information-based method that defines the shape of the service area in more detail. Based on the respective pros and cons in terms of accuracy and signaling overhead, it was concluded that in Release 18 NTN, SIB25 can be defined by the coordinates of a reference point (center location) and a radius, and the corresponding geographic area information is provided through a list of overlapping individual areas.

[0190] Considering this, a similar approach that defines the shape of a service area as a circular shape (circle-based format) can be similarly applied to the detailed format of service area information for the scope of MBS services. Furthermore, a similar approach that defines the shape of a service area as a circular shape (circle-based format) can provide an efficient and flexible means of expressing various types of service areas through NW implementations by using a list of nestable circles as the geographic area format of the service area information for MBS services.

[0191] In this regard, a similar approach that defines the shape of the service area as a circular shape (circle-based format) to more precisely represent the service area can designate individual circles included in the list of service area information for the effective range of MBS services as allowed or prohibited areas.

[0192] According to an embodiment of the present disclosure, a terminal may store information about a reference point indicating a geographic location or coordinates for entering an international area from a neighboring area. Upon passing the reference point, the terminal may initiate a distance tracking process from the reference point. In other words, service area information, which includes information about the effective range of the MBS service of the present disclosure, may be defined to include information about at least one reference point indicating the boundary of each service area and distance information from the boundary reflecting the size of the service area.

[0193] In this regard, the terminal can retrieve information indicating a preset distance from the border (boundary) of a first country (e.g., "Country 1" in FIG. 11, described below). The terminal can receive MBS services of the first country while in the country (international area). In this regard, the information indicating the preset distance can be received by the terminal from, for example, the home public land mobile network (PLMN) or broadcast from an NTN serving the international area. Alternatively, the information indicating the preset distance can be retrieved from, for example, a local database of the terminal (e.g., a universal subscriber identity module (USIM) external memory, etc.).

[0194] In this regard, a terminal can receive MBS services from the first country while within a preset distance from the reference point. The terminal may move beyond the preset distance from the reference point. In such cases, the terminal may be deemed to have left the first country. Accordingly, the terminal may re-search MBS service area information to receive other MBS services with higher priority in international areas.

[0195] Meanwhile, FIGS. 8d to 8f may be a compromised display method. FIG. 8d may illustrate a method of indicating a service area using multiple circles of different sizes. FIG. 8e may illustrate a method of indicating a service area using multiple ovals of different sizes. FIG. 8f may also indicate a service area using multiple circles of different sizes, as in FIG. 8d. However, FIG. 8f may illustrate a method of distinguishing and indicating an allowed area and a prohibited area (slashed circle) for an MBS service. In other words, according to an embodiment of the present disclosure, service area information may include information on an allowed area and information on a prohibited area for an MBS service.

[0196] In terms of signaling overhead, representing geographic information about service areas in a circular format may be the simplest approach. Furthermore, this method can leverage some of the NTN configuration (e.g., NTN_config) information formats available in the existing NTN SIB19.

[0197] Meanwhile, considering signaling overhead, the methods according to FIGS. 8d and 8f can be easily applied similarly by utilizing existing SIBs. In FIG. 8f, the permitted and prohibited areas can be distinguished by adding data (e.g., 1 bit of additional data) to the service area information to indicate the type of the area, but this may not be limited thereto.

[0198] The method for displaying service areas based on geographic information, as described above with reference to FIGS. 8A to 8F, may be applicable to earth-fixed satellites with an unchanged service area reference point. In an earth-moving cell, the satellite cell may be in a continuously moving state. In such a case, in addition to the service area information provided by the existing earth-moving cell, time information regarding the relevant service area may be additionally included.

[0199] FIGS. 9A to 9F are conceptual diagrams illustrating embodiments of a method for providing geographic information representing a service area, including time.

[0200] Referring to Figures 9a to 9f, a base station of a non-terrestrial network can form a global mobile cell. Then, the base station can transmit referenceable time information for the service area to the terminal along with service area information. For example, referring to Figures 9a to 9f, the referenceable time information for the service area may refer to epoch time, but is not limited thereto.

[0201] In this regard, a terminal that receives service area information including reference time information from a base station forming an Earth-Moving Cell can use the reference time information to determine the movement of the service area according to actual satellite movement. More specifically, according to one embodiment, the terminal can calculate (calculate) information on the service area after a predetermined period of time has elapsed according to the movement of the satellite corresponding to the base station based on ephemeris information obtained from SIB 19.

[0202] In other words, according to one embodiment of the present invention, MBS broadcast services can be supported for both Earth Fixed Cells (EFCs) and Earth Moving Cells (EMCs) in an NTN. An intended service area for location-dependent services can be broadcast. This intended service area can cover one or more NTN cells (i.e., a serving cell and neighboring cells) or a portion thereof. The geographical intended service area ID can indicate the MBS broadcast session broadcast on the MCCH.

[0203] Additionally, according to one embodiment, a base station of a non-terrestrial network may utilize RRC signaling or DCI as a method of transmitting service area information to a terminal. It may be appropriate for a base station of a non-terrestrial network to transmit service area information to a terminal by allowing the terminal to receive information about MBS services, including broadcast services, in idle mode.

[0204] Meanwhile, according to one embodiment of the present disclosure, as a method for transmitting service area information to a terminal, a method of providing through a multicast control channel (MCCH), a method of providing through a new / existing system information block (SIB), etc. may be considered.

[0205] Specifically, regarding the level of detail in service area information, full details, including service area identifiers and detailed information for each area, can be provided. Alternatively, depending on the implementation of the present disclosure, only the service area identifiers may be included, with detailed information provided in a User Service Description (USD) or a new SIB.

[0206] In this regard, considering the limited payload size of the existing SIB20 (e.g., 2976 bits), providing comprehensive detailed information through MCCH may be more appropriate. In particular, since SIB20 does not currently include a multicast broadcast service (MBS) session identifier, whereas MCCH does, considering that the service area identifier must be associated with the MBS session identifier, MCCH may be more suitable, but is not limited to this.

[0207] In addition, according to one embodiment of the present disclosure, in order to optimize MCCH monitoring when a terminal is not located within any service area, the following methods may be applied. Specifically, as a first method, a method of indicating a service area update through MCCH modification notification downlink control information (DCI) may be applied. In this case, when the terminal is not located within any service area of ​​broadcast services configured to be received, the MCCH can be reacquired only when the MCCH modification notification DCI indicates an update of the service area.

[0208] Alternatively, a second method may consider applying a longer modification period for changing the service area of ​​a broadcast service. For example, a method may be applied in which the service area change cycle is set to a multiple of the MCCH change cycle. In this case, if the terminal is not located within any service area, there may be no need to reacquire the MCCH within the service area change cycle.

[0209] According to one embodiment of the present invention, the MCCH can provide a list of all broadcast services with ongoing sessions transmitted on the MTCH. Relevant information about the broadcast session can include an MBS session ID, associated G-RNTI scheduling information, one or more intended service area IDs for NTN broadcasts, and information about neighboring cells providing specific services on the MTCH. MCCH content is transmitted within a periodically occurring time-domain window, which can be referred to as an MCCH transmission window. The MCCH transmission window can be defined by an MCCH repetition period, an MCCH window duration, and a radio frame / slot offset.

[0210] Therefore, it may be preferable for a base station in a non-terrestrial network to broadcast service area information to a terminal via RRC signaling. For example, a base station in a non-terrestrial network can transmit service area information to a terminal using system information containing the service area information.

[0211] For example, a base station can include service area information in an existing SIB (system information block) by reflecting the service area information in the SIB that has already been created. In addition, according to one embodiment of the present disclosure, the service area information may be information required in various aspects, such as SIB20 (for determining whether to acquire MCCH), MBS broadcast configuration information (for determining whether to monitor MBS traffic channel (MTCH), SIB21 (for service continuity), etc.

[0212] According to one embodiment of the present invention, the SIB may include a list of intended service areas for MBS broadcast reception and associated pointers. Specifically, the SIB includes a description of the intended service areas for the broadcast service of the NTN cell. Once the intended service areas for MBS broadcast are defined, they are broadcast as a list in the SIB. Meanwhile, no requirements for the terminal related to the contents of the SIB exist separately, except for those specified in the procedures for using the corresponding system information and / or those specified in the corresponding field descriptions.

[0213] In this regard, a service area can be represented as a set of reference locations and radii or a set of polygons, which can incur significant signaling overhead and need not be repeated in multiple locations. Accordingly, according to one embodiment of the present disclosure, a method of defining service area information in a new SIB or existing SIB20 and assigning an area identifier to each area can be applied, thereby allowing locations requiring service area information to simply reference the corresponding area identifier, significantly reducing signaling overhead.

[0214] Specifically, according to one embodiment, the existing SIB utilized to convey service area information may include, but is not limited to, at least one of SIB 1, SIB 6, SIB 7, SIB 19, SIB 20, and SIB 25.

[0215] For example, SIB20 can provide a database of service areas for all broadcast service sessions. For example, if SIB20 always provides service areas for broadcast service sessions 1, 2, and 3, the MCCH can operate such that at time T0, it includes broadcast service sessions 1 and 2, at time T1, it includes session 1, and at time T2, it includes sessions 2 and 3.

[0216] According to this design, SIB20 can remain the same regardless of whether a broadcast service is added or released. However, since it may be burdensome for a radio access network (RAN) node to maintain the service area of ​​all broadcast service sessions that are not active in the cell, a scheme could be considered in which SIB20 is updated only when a new broadcast service is initiated (e.g., when the most significant bit (MSB) in the MCCH change notification of the MBS DCI indicates the addition of a session) to add the service area of ​​the newly added broadcast service session to the list.

[0217] In this regard, according to one embodiment of the present invention, in order to optimize MCCH monitoring when a terminal is not located within any service area, a first method of indicating a service area update through an MCCH modification notification DCI and a second method of applying a longer modification period for changing the service area of ​​a broadcast service may be considered.

[0218] Specifically, in the first method, when the terminal is not located within any service area of ​​the broadcast services configured to be received, the MCCH can be reacquired only when the MCCH change notification DCI indicates an update of the service area. Meanwhile, in the second method, the service area change cycle can be set to a multiple of the MCCH change cycle. In this case, when the terminal is not located within any service area, there may be no need to reacquire the MCCH within the service area change cycle.

[0219] According to one embodiment of the present disclosure, service area information may be understood to have a relatively static characteristic, and considering this characteristic, SIB20 may function as a database for the service areas of all broadcast service sessions supported by the wireless access network node.

[0220] This design has the advantage that SIB20 can remain unchanged even if the MCCH contains different broadcast service sessions at different times. However, as a compromise, one could consider updating SIB20 only when a new broadcast service is initiated, such as when the most significant bit in the MCCH change notification indicates the addition of a session.

[0221] According to this method, a terminal can operate as follows depending on its own situation. First, a terminal configured to receive a temporary mobile group identifier without a service area follows the existing MCCH acquisition procedure, a terminal configured to receive only a temporary mobile group identifier #1 but not within the corresponding service area does not perform MCCH acquisition, and a terminal configured to receive a temporary mobile group identifier #3 and within the corresponding service area can selectively perform MCCH acquisition and re-acquisition.

[0222] As another example, the base station can use the SIB to transmit service area information to the terminal by defining a new SIB that includes service area information. In other words, the service area information can be included in the SIB. The SIB can be included in an existing SIB or defined as a new SIB. In summary, the base station can use options 1 to 3 to transmit service area information to the terminal. Option 1 may be a method of extending an existing SIB or an existing MCCH. Option 2 may be a method of defining a new SIB. Option 3 may be a method of applying options 1 and 2 in combination. In this case, the base station may be relatively more preferable to apply option 2 or option 3 than option 1 when considering the insufficient number of available bits of the existing SIB or the existing MCCH, but may not be limited thereto.

[0223] In this regard, according to one embodiment of the present invention, considering the predictability and update cycle of service area information in relation to MBS broadcasting services, service area information can be provided through a new SIB. Specifically, this has the advantage of minimizing the impact of Intended Service Area (ISA) information on existing UEs and alleviating MCCH acquisition when the UE is not located in any of the defined ISAs.

[0224] Additionally, according to one embodiment of the present invention, the ISA identifier of an MBS service can be optionally included in a service announcement. This allows a terminal to recognize the ISA identifier of a specific MBS broadcast service of interest and, by combining information from a new SIB with the service announcement, mitigate MCCH acquisition. Specifically, by including the ISA identifier in the service announcement, a terminal can determine whether it is within the ISA of the MBS service of interest and only consider that area during MCCH mitigation.

[0225] Meanwhile, a terminal interested in MBS services can skip MCCH acquisition when located outside the intended service area of ​​the service. Specifically, depending on the implementation, the terminal can use its location, the ISA definition in the SIB / USD, and the mapping information between the ISA ID in the USD / Service Announcement and the MBS Service ID (TMGI) to determine whether to skip MCCH acquisition.

[0226] Furthermore, according to one embodiment of the present invention, a quasi-Earth fixed cell may be provided with information regarding the MBS broadcast configuration and services of the next satellite scheduled to service the corresponding area. This allows the terminal to avoid service interruption due to satellite changes and reduce signaling overhead. Specifically, the serving cell may signal a list of the next satellites / cells scheduled to provide the same MBS service, and this information may be provided together with satellite support information provided in other system information blocks (e.g., SIB19). This signaling may include information regarding the time, frequency, or PCI at which the next satellite begins servicing the intended service area associated with the current cell or MBS service.

[0227] For reference, according to one embodiment of the present invention, a service area identifier (ISA ID) can be expressed using an index in a service area list. Specifically, an ISA can be indicated using the index value that the service area has within the service area list, without separately assigning an ISA ID. This method has the advantage of efficiently indicating a service area without assigning an additional identifier.

[0228] Meanwhile, according to one embodiment of the present invention, service area information has a relatively semi-static nature, so frequent updates may not occur. Considering this characteristic, service area information updates in new SIBs can be implemented using existing SIB modification procedures. By reusing existing SIB modification procedures, service area information can be efficiently updated without the need to define a new update mechanism. Furthermore, because service area information is semi-static, issues related to MCCH update cycles can be minimized.

[0229] According to one embodiment of the present invention, methods for indicating service area information can be considered, such as using an index within a list or using a unique identifier (ID). The index-based method offers the advantages of small data size and a simple search mechanism, but may have the disadvantage of being dependent on list order and not guaranteeing global uniqueness.

[0230] In contrast, ID-based methods offer stable references and improved global uniqueness and readability, but can incur relatively large data sizes and additional management overhead. In particular, in EMC environments, where service area information lists can be frequently updated and service area information can be provided via both AS and NAS signaling, ID-based methods may be more effective.

[0231] For example, geographic information for a service area included in a SIB may include information about a reference location at a reference time according to an epoch time in non-terrestrial network configuration information (e.g., NTN-config), information about the distance from the reference point, etc.

[0232] Meanwhile, when a service area including multiple areas is provided, the SIB may additionally include the following information:

[0233] - MBS area identifier list (e.g. MBS-AreaIDlist)

[0234] - MBS area identifier (e.g. MBS-AreaID)

[0235] At this time, the information may be specifically included in the following SIB in relation to the existing MBS.

[0236] - Added MCCH MessageType to spare1 section in r17

[0237] - Add a new mbsBroadcastConfiguraiton configuration (e.g. mbsBrodcastConfiguraiton-r19) to the existing mbsBroadcastCofiguration

[0238] - Added MulticastMCCH MessageType r18 to s pare1 section

[0239] - Add a new mbsMulticastConfiguraiton configuration to the existing mbsMulticastCofiguration (e.g., mbsBrodcastConfiguraiton-r19)

[0240] For this purpose, the following service area information can be added to each mbs sessionInfoList in MBSBroadcastConfiguration and MBSMulticastConfiguration.

[0241] - Information about the reference location from the reference time according to the epoch time in the non-terrestrial network configuration information (e.g. NTN-config).

[0242] - Distance information from the reference location

[0243] Additionally, if you provide service areas through multiple domains, the following information may be included:

[0244] - MBS area identifier list (e.g. MBS-AreaIDlist)

[0245] - MBS area identifier (e.g. MBS-AreaID)

[0246] The information may be added to the MBS service list (e.g. mbsServiceList) within an MBS interest indication message (e.g. MBSInterestIndication message) or may be added in the same manner.

[0247] Additionally, the MBS service area information proposed above can be defined for each MBS service list (e.g., mbsServiceList). Alternatively, the MBS service area information proposed above can be defined for each MBS session information list (e.g., mbs-sessionInfoList). MBS service area information can be displayed by defining a new SIB through the list indicator of the above messages.

[0248] Meanwhile, according to one embodiment of the present invention, the transmission unit of an MBS service may be determined based on the coverage of a satellite beam. For example, if the service area is smaller than the satellite footprint, it may be difficult to provide broadcast services only within the intended service area, especially in the case of a single or multiple satellite beams. Accordingly, the minimum unit of broadcast transmission may be set to the coverage of the satellite beam.

[0249] Meanwhile, in order to provide service area information, according to one embodiment of the present invention, a new information element (IntendedServiceAreaInfo-r19) may be defined as follows:

[0250] IntendedServiceAreaInfo-r19 ::= SEQUENCE {

[0251] intendedServiceAreaId-r19 IntendedServiceAreaId-r19,

[0252] intendedServiceArea-ReferenceLocation-r19 ReferenceLocation-r17,

[0253] intendedServiceArea-DistanceRadius-r19 INTEGER(0..65536)

[0254] }

[0255] Meanwhile, MBSBroadcastConfiguration-r19-IEs can be configured as shown in Table 4 below.

[0256] MBSBroadcastConfiguration-r17 ::= SEQUENCE {criticalExtensions CHOICE {mbsBroadcastConfiguration-r17 MBSBroadcastConfiguration-r17-IEs,criticalExtensionsFuture SEQUENCE {}}}MBSBroadcastConfiguration-r17-IEs ::= SEQUENCE {mbs-SessionInfoList-r17 MBS-SessionInfoList-r17 OPTIONAL, -- Need Rmbs-NeighbourCellList-r17 MBS-NeighbourCellList-r17 OPTIONAL, -- Need Sdrx-ConfigPTM-List-r17 SEQUENCE (SIZE (1..maxNrofDRX-ConfigPTM-r17)) OF DRX-ConfigPTM-r17 OPTIONAL, -- Need Rpdsch-ConfigMTCH-r17 PDSCH-ConfigBroadcast-r17 OPTIONAL, -- Need Smtch-SSB-MappingWindowList-r17 MTCH-SSB-MappingWindowList-r17 OPTIONAL, -- Need RlateNonCriticalExtension OCTET STRING OPTIONAL,nonCriticalExtension MBSBroadcastConfiguration-r19-IEsSEQUENCE {} OPTIONAL}MBSBroadcastConfiguration-r19-IEs ::= SEQUENCE {mbs-SessionAreaMapping-r19 MBS-SessionAreaMapping-r19 OPTIONAL, -- Need RnonCriticalExtension SEQUENCE {} OPTIONAL}MBS-SessionAreaMapping-r19 ::= SEQUENCE {mbs-SessionId-r19 TMGI-r17,mbs-AreaInfoList-r19 SEQUENCE (SIZE (1..maxNrofMBS-SessionPerArea-r19)) OF MBS-IntendedAreaID-r19}MBS-IntendedAreaID-r19 ::= INTEGER (0.. maxNrofMBS-Area-r19)-- TAG-MBSBROADCASTCONFIGURATION-STOP-- ASN1STOP.

[0257] Additionally, according to one embodiment of the present invention, a newly introduced SIB-related message may be configured as shown in Table 5 below.

[0258] -- ASN1START-- TAG-SIBXX-STARTSIBXX-r19 ::= SEQUENCE {intendedServiceAreaList-r19 IntendedServiceAreaList-r19 OPTIONAL, -- Need RlateNonCriticalExtension OCTET STRING OPTIONAL,...}IntendedServiceAreaList-r19 ::= SEQUENCE (SIZE (1.. maxNrofMBS-Area-r19)) OF IntendedServiceAreaInfo-r19IntendedServiceAreaInfo-r19 ::= SEQUENCE {intendedServiceAreaId-r18 MBS-IntendedAreaID-r19,areaCoordinates-r19 CHOICE {polygonArea OCTET STRING,circleArea SEQUENCE {referenceLocation-r19 ReferenceLocation-r17,distanceRadius-r19 INTEGER(0..65535)}}}-- TAG-SIBXX-STOP-- ASN1STOP

[0259] However, the specific details of the message structure, field configuration, parameters and sequence defined above are according to one embodiment of the present invention, and a person having ordinary knowledge in the technical field to which the present invention pertains will understand that the present invention can be implemented in other specific forms without changing the technical idea or essential features of the present invention.

[0260] Next, the fields of each message defined above will be described in more detail as follows.

[0261] The polygonArea within IntendedServiceAreaInfo-r19 can be defined using the polygon parameter type defined in TS 37.355, where the first / left bit contains the most significant bit.

[0262] The intendedServiceAreaList-r19 within SIBXX-r19 represents a list of intended service areas, including detailed information about each intended service area.

[0263] mbs-SessionAreaMapping-r19 within MBSBroadcastConfiguration-r19-IEs provides a mapping between MBS sessions and the geographic areas in which they are served. Each MBS session can be associated with one or more intended service areas.

[0264] pdsch-ConfigMTCH provides parameters for acquiring PDSCH for MTCH. If this field is absent, the UE uses the parameters of pdsch-ConfigMCCH to acquire PDSCH for MTCH.

[0265] mbs-SessionInfoList provides the configuration of each MBS session served via MBS broadcast in the current cell.

[0266] The mbs-NeighbourCellList field provides a list of neighboring cells that provide one or more MBS broadcast services through the current cell via broadcast MRBs. This field is used by the terminal in conjunction with the mtch-NeighbourCell field, which is signaled in the corresponding MBS-SessionInfo for each MBS session.

[0267] If an empty list is signaled, the UE assumes that the MBS broadcast service signaled in the mbs-SessionInfoList of the MBSBroadcastConfiguration message is not provided by any neighboring cell. If a non-empty list is signaled, the current serving cell does not provide information about MBS broadcast services of neighboring cells not included in the mbs-NeighbourCellList. In other words, the UE cannot determine the presence or absence of MBS services of the absent neighboring cells.

[0268] If the mbs-NeighbourCellList field is absent, the current serving cell does not provide information about MBS broadcast services of neighboring cells, which means that the terminal cannot determine the presence or absence of MBS services of neighboring cells based on the absence of this field.

[0269] Additionally, according to another embodiment of the present invention, a method for providing service area information utilizing the mapped cell ID introduced in NTN R17 may be applied. Specifically, the network can broadcast the mapped cell ID and the corresponding area information, and provide the association between the mapped cell ID and the service area. This method can also be useful for terminals to report MBS Interest Indications on a per-mapped cell basis.

[0270] Furthermore, according to one embodiment of the present invention, service area information may be provided via a System Information Block (SIB). Specifically, service area information may be provided via SIB1, which includes scheduling of all system information, or via SIB20 or SIB21, which includes MBS broadcast-related information. Furthermore, service area information may be provided via SIB6 or SIB7, which includes Earthquake and Tsunami Warning System (ETWS) notifications, or via SIB19, which includes satellite support information for NTN access. Meanwhile, considering the size and usability of service area information, it may also be considered to define a new SIB to provide the corresponding information.

[0271] Meanwhile, since the Temporary Mobile Group Identity (TMGI) and Service Area Identifier (SAI) already contain the MCC or PLMN ID, no additional improvements may be needed to handle different country information.

[0272] As another example, considering that MBS service area information is NTN-specific information, the service area information may be additionally included in SIB 19. According to one embodiment, the service area information may be reflected in SIB20, SIB21, or MBS broadcast configuration (e.g., MBSBroadcastConfiguration), and may include the following details:

[0273] -SIB20: Information required to obtain MCCH (multicast control channel) / MTCH (multicast traffic channel) configuration for MBS broadcast

[0274] -SIB21: Mapping relationship between current and / or adjacent carrier frequencies and MBS frequency selection area identities (FSAIs).

[0275] - MBS Broadcast Configuration (e.g. MBSBroadcastConfiguration): Control information applicable to MBS broadcast services transmitted via broadcast MRB.

[0276] Meanwhile, when the aforementioned detailed information is provided via SIB20 or SIB21, the terminal's operation can be optimized to avoid unnecessary tasks. For example, the aforementioned detailed information can be provided via SIB20. In this case, the terminal may be located outside the MBS service's effective range (service area) and may not receive unnecessary MBS broadcast configuration messages.

[0277] Conversely, when service area details are provided via an MBS broadcast configuration message, the MBS session ID information in the existing MBS broadcast configuration message can be reused to indicate service area information regarding the MBS service's effective range. Therefore, the base station can reduce signaling overhead for service area information.

[0278] In this regard, MBS session ID information may not be included in existing SIBs 20 and 21. Considering the existing purpose of each SIB, it may be more desirable for the base station to provide service area information via the MBS broadcast configuration message. This may be because the service area can be considered part of the control information for providing area-specific MBS broadcast services for each MBS session.

[0279] That is, according to one embodiment of the present invention, MBS-related information (e.g., MBS session list, intended broadcast service area, etc.) may be provided by being included in MBSBroadcastConfiguration within the MCCH. Specifically, the MCCH already includes MBS broadcast sessions, scheduling information, and a list of neighboring cells providing the same MBS service, and the intended service area information may be provided by being included in this existing MCCH structure.

[0280] Furthermore, according to one embodiment of the present invention, terminals outside the intended service area may not reacquire the MCCH. In the MCCH-based approach, notifications can be transmitted via the PDCCH addressed to the MCCH RNTI, ensuring that only terminals interested in the MBS receive the notification. Furthermore, a single bit can be used to indicate whether a new service will be provided.

[0281] Meanwhile, according to one embodiment of the present invention, even if an NTN terminal can receive MBS services, it may be restricted from establishing an MRB if it is located outside the MBS service area. Furthermore, the terminal may release the MRB when it leaves the intended area, but the decision to release the MRB may be based on additional conditions, such as the elapsed time or distance since leaving the MBS area. This is because the terminal cannot maintain the MRB permanently.

[0282] In this regard, according to one embodiment of the present disclosure, an NTN terminal supporting MBS broadcast can initiate a broadcast MRB setup procedure when within the intended service area. Furthermore, the terminal can initiate a broadcast MRB release procedure when leaving the intended area. However, depending on the implementation example of the present disclosure, the network may not be able to prevent the terminal from decoding service content outside the intended service area.

[0283] Additionally, according to one embodiment of the present invention, an NTN terminal can determine whether it is inside or outside the MBS service area based on the GNSS location used for other NTN purposes. Accordingly, there is no need to separately update the terminal's GNSS location for this purpose.

[0284] Additionally, according to one embodiment of the present invention, a list of ReferenceLocation-r17 and corresponding radii may be introduced to indicate a service area. When indicating a service area in the form of a polygon, the number of vertices to be signaled for a single polygon and whether each vertex should be expressed as a ReferenceLocation IE may be determined.

[0285] Meanwhile, due to the size limitations of the MBS broadcast configuration message, it may be difficult for the base station to include all information indicating service area information in the MBS broadcast configuration message. In such cases, the base station can define a new SIB as described below. Alternatively, the base station can consider an alternative approach, such as modifying the existing USD (user service description). For example, the base station can define a new SIB that includes a list of service area IDs and service area details (reference point and radius) for each MBS service area ID. Alternatively, the base station can modify the USD to include the corresponding information.

[0286] Additionally, according to an implementation example of the present disclosure, the base station may include only information related to the mapping between the MBS session ID and the corresponding intended service area ID in the MBS broadcast configuration message. The base station may then define a new SIB to include service area details (reference point and radius) for each MBS intended service area ID. Alternatively, the base station may apply a method of modifying the USD.

[0287] Meanwhile, according to one embodiment of the present disclosure, the service area information may include non-geographic information for modeling each of a plurality of service areas. Specifically, according to one embodiment of the present disclosure, the non-geographic information included in the service area information may be defined using at least one of a beam index associated with an MBS service, a mapped cell ID, a tracking area identifier (TAI), a service ID, a temporary mobile group identity (TMGI), a session ID, a G-RNTI, an MRB, and an SSB.

[0288] Figure 10 is a conceptual diagram illustrating examples of service areas divided into permitted service areas and prohibited areas.

[0289] Referring to Fig. 10, the geographical information for setting the allowed service area and the prohibited area can be defined through the coordinates of the reference point for the center position of each service area (SA) and the distance (radius, diameter) information of each circular service area, utilizing the format of SIB25 for signaling TN coverage in the NTN. This approach can be useful for representing various shapes of the intended service area through the NW implementation, and by individually defining the circular service areas corresponding to each allowed area and prohibited area, the shape of the intended service area can be more accurately approximated. For this purpose, the service area information can include a list of MBS area IDs and MBS area information (reference point and distance from the reference point) corresponding to each MBS area ID. In Fig. 10, the service areas can be distinguished by service area identifiers 1 to 7 and can be distributed in countries 1 and 2. Here, service area 1 (SA ID1) to service area 6 (SA ID 6) may be permitted service areas, and service area 7 (SA ID 7) may be prohibited service areas.

[0290] Figure 11 is a conceptual diagram illustrating embodiments of a method for associating service area information and MBS service.

[0291] Referring to Figure 11, service area information can be provided via a new SIB. The service area information can be associated with session information associated with the corresponding broadcast service (MBS service). For this purpose, various types of identification information (e.g., session ID, TGMI, G-RNTI, etc.) for broadcast service sessions can be considered. Service area information regarding the service area to be provided by each MBS service must, at a minimum, include MBS service identification information, an MBS area ID corresponding to the MBS service identification information, and detailed area information (geographic information) corresponding to each MBS area ID.

[0292] According to one embodiment of the present disclosure, for associating service area information with MBS sessions, a first method in which one service area identifier is mapped to multiple MBS session identifiers and a second method in which multiple service area identifiers are mapped to one MBS session identifier may be considered.

[0293] At this time, the second method may be preferred in terms of providing flexibility to configure an independent service area for each MBS session, and such many-to-one (N-to-1) mapping may be utilized to uniquely identify each service area portion of an MBS service within a 5G core network, but is not limited thereto.

[0294] Meanwhile, depending on the implementation example of the present invention, a terminal can receive MBS services even if it is located outside the service area. Specifically, the MBS broadcast service transmitted by the base station may be available throughout the entire cell area, and there may be no need to restrict MBS broadcast access outside the intended service area.

[0295] In this regard, according to one embodiment of the present disclosure, a terminal may operate as follows regarding frequency selection for an MBS service. During the cell reselection evaluation process, the terminal may prioritize a frequency if it is located within a geographic area associated with the MBS service it is interested in or currently receiving. For example, if the USD provides multiple frequencies for a service the terminal is interested in, the terminal can more easily determine which frequency to select based on its correlation with the service's geographic area information.

[0296] Additionally, according to one embodiment of the present invention, the MBS broadcast service area may be provided similarly to the TN coverage area list. Specifically, it may be provided in the form of a list of reference locations and corresponding cell radii.

[0297] Furthermore, with regard to the terminal recognizing the frequency of the service of interest, the terminal can perform a mapping between the frequency and the MBS broadcast service through existing procedures (e.g., SIB21 or USD). Before receiving the MBS broadcast service, the terminal must know the frequency of the service of interest, and this frequency information can be obtained from SIB21 or USD. Therefore, simply mapping the provided geographic area to one or more MBS broadcast service frequencies may be sufficient.

[0298] Meanwhile, the service area information regarding the effective range of the MBS service disclosed in the present disclosure may be used for the following purposes. First, the service area information may be used to support location-dependent broadcast services within a portion of an NTN cell or multiple NTN cells. Second, the service area information may be used to prevent unnecessary terminal operations, including operations that receive MBS-related SI and / or MBS sessions outside the effective range (service area) of the MBS service.

[0299] With respect to the first objective, location-dependent broadcast services may be intended to distribute different content data across different MBS service areas. To support such location-based broadcast services, similar to existing MBS mechanisms, a specific portion of an MBS service area may be uniquely identified within a 5GC using an identifier (ID) for service area information, which comprises a reference point (base location, reference location) and a radius within an NTN cell or a portion of multiple NTN cells, together with an MBS session identifier (ID).

[0300] In this regard, for association with MBS sessions, service area information can be associated with MBS session IDs according to the method of Option 1 or Option 2 as follows. First, the method of Option 1 may be a method of mapping one service area ID to multiple corresponding MBS session IDs. The method of Option 2 may be a method of mapping multiple service area IDs to one MBS session ID. In this case, Option 2 may be preferred in terms of providing flexibility to configure an independent service area for each MBS session, but may not be limited thereto.

[0301] In summary, a specific portion of a service area of ​​an MBS service can be uniquely identified within a 5GC by using a service area ID together with an MBS session ID, similar to existing MBS mechanisms, to support location-dependent broadcast services. Multiple service area IDs can be mapped to a single MBS session ID to associate service areas with MBS sessions. In this regard, the base station can provide the following information to the terminal via one or more SIBs to indicate details of the service area information regarding the effective range of the MBS service associated with the MBS session ID.

[0302] -MBS Session ID List

[0303] - A list of service area IDs for the valid scope of the MBS service corresponding to each MBS session ID.

[0304] -Details of the service area for each MBS intended service area ID (reference point and radius information included in the service area information)

[0305] Below, we will describe a technique for achieving service continuity related to MBS services.

[0306] According to one embodiment of the present invention, the following methods may be applied to ensure MBS service continuity. As a first method, intended service area information (e.g., intended service area ID) associated with the current and / or neighboring carrier frequencies may be introduced into SIB21. As a second method, intended service area information associated with neighboring cells may be utilized as indicated on the MCCH.

[0307] In this regard, according to one embodiment of the present invention, an MBS broadcasting capable terminal can receive an MBS broadcasting service only at a specific frequency, and for this purpose, the terminal can operate to consider a specific frequency as a priority by considering the following conditions. As a first condition, a condition may be considered that SIB20 is included in the SIB1 scheduling information of a cell reselected by the terminal due to frequency prioritization due to MBS. As a second condition, a condition may be considered that one or more MBS FSAIs for the corresponding frequency are indicated in SIB21 of the serving cell, and the same MBS FSAI is also indicated in the MBS User Service Description (USD) of the MBS broadcasting service as specified in TS 26.517, or SIB21 is not provided in the serving cell and the corresponding frequency is included in the USD of the service, or SIB21 is provided in the serving cell but does not provide frequency mapping for the corresponding service and the corresponding frequency must be included in the USD of the service.

[0308] In addition, according to one embodiment of the present invention, when an MBS broadcast capable terminal is receiving an MBS broadcast service or is configured for reception, and SIB20 is included in cell SIB1 scheduling information of an MBS frequency monitored by the terminal, and the second condition described above is satisfied for a serving cell, the terminal may consider a cell reselection candidate frequency that cannot receive an MBS broadcast service during an MBS broadcast session as having the lowest priority.

[0309] Meanwhile, given that SIB21 includes a mapping relationship between current and / or adjacent carrier frequencies and the MBS FSAI, this existing mechanism for MBS service continuity can assume that an MBS service area maps to more than one cell. However, in an NTN system, even if the two conditions described above are met, this may not work effectively because a UE may not consider a frequency as the highest priority if the MBS intended service area for that frequency does not include the intended service area of ​​the MBS session the UE is receiving or is interested in.

[0310] To address these issues, according to one embodiment of the present invention, a new mapping relationship between current and / or adjacent carrier frequencies and MBS intended service area IDs may be defined, and a list of carrier frequencies and a list of MBS intended service area IDs for each carrier frequency may be included in SIB21.

[0311] As another example, the existing conditions for a terminal to perform MBS broadcast service cell reselection can be updated based on service area information regarding the MBS service's effective range. Specifically, in addition to the two existing conditions, a third condition can be added: the service area ID for the effective range of at least one MBS service on the corresponding frequency must be indicated in the serving cell's SIB21, and the service area ID for the effective range of the same MBS service must also be indicated for the MBS broadcast service session.

[0312] According to one embodiment of the present disclosure, MBS service continuity can be considered in two aspects. First, a serving base station can indicate a list of neighboring cells providing the same MBS broadcast service on the MCCH, thereby allowing a terminal to request unicast reception of the service before moving to a cell that does not provide the MBS broadcast service via point-to-multipoint (PTM) transmission.

[0313] Secondly, NR MBS can support MBS frequency layer priority setting for MBS broadcast sessions, where base stations provide an MBS frequency service area (MBS FSA) identifier supported on each frequency, which can include both same and different frequencies.

[0314] During an MBS broadcast session, the following two conditions can be met: an MBS broadcast-capable terminal can receive the MBS broadcast service. Alternatively, an MBS broadcast-capable terminal may be interested in receiving the MBS broadcast service. An MBS broadcast-capable terminal can only receive the MBS broadcast service by camping on the frequency that provides the MBS broadcast service. In such cases, the terminal may consider the frequency as the highest priority.

[0315] The first condition may be that the SIB1 scheduling information of the cell reselected by the terminal due to frequency prioritization by MBS includes SIB20. The second condition is satisfied if either of the following applies:

[0316] - One or more MBS FSAIs for the given frequency may be indicated in the SIB21 of the serving cell, and the same MBS FSAIs may also be indicated in the MBS User Service Description (USD) of the MBS Broadcast Service.

[0317] - SIB21 may not be available on the serving cell, and the frequency is included in the USD of this service.

[0318] - SIB21 may be provided in the serving cell, but may not provide frequency mapping for that service, and that frequency is included in the USD of that service.

[0319] Additionally, an MBS broadcast capable terminal may receive an MBS broadcast service. Alternatively, an MBS broadcast capable terminal may be interested in receiving an MBS broadcast service. In such a case, the cell SIB1 scheduling information of the MBS frequency monitored by the terminal may include SIB20, and the second condition described above may be satisfied for the serving cell. The terminal may consider a cell reselection candidate frequency that cannot receive an MBS broadcast service during an MBS broadcast session as having the lowest priority.

[0320] Meanwhile, SIB21 may include a mapping relationship between the current and / or adjacent carrier frequencies and the MBS FSAI. Considering this, it can be assumed that the MBS service area is mapped to one or more cells in the existing MBS service continuity mechanism. Conditions 1 and 2 described above may be satisfied in the NTN system. In such a situation, the MBS intended service area of ​​the corresponding frequency may not include the intended service area of ​​the MBS session that the UE can receive. Alternatively, the MBS intended service area of ​​the corresponding frequency may not include the intended service area of ​​the MBS session that the UE is interested in. In such cases, the UE may not consider the corresponding frequency as the highest priority, which may result in ineffective operation.

[0321] Therefore, improvements to existing mechanisms for MBS service continuity may be necessary. For example, the present disclosure may define a new mapping relationship between current and / or adjacent carrier frequencies and MBS intended service area IDs, and include the following information in SIB21:

[0322] -Carrier frequency list (already in SIB21)

[0323] - List of MBS intended service area IDs for each carrier frequency

[0324] As another example, the existing conditions for a terminal to perform MBS broadcast service cell reselection based on service area information about the effective range of the MBS service can be updated as follows.

[0325] An MBS broadcast-capable terminal can receive MBS broadcast services. Alternatively, an MBS broadcast-capable terminal may be interested in receiving MBS broadcast services. An MBS broadcast-capable terminal can receive MBS broadcast services by camping on a frequency that provides MBS broadcast services. In this case, the terminal may consider the frequency as the highest priority during an MBS broadcast session when the following three conditions (Conditions 1 through 3) are met.

[0326] (Condition 1) SIB20 is included in the SIB1 scheduling information of the cell reselected by the UE due to frequency priority assignment by MBS.

[0327] (Condition 2) One of the following is met:

[0328] ● One or more MBS FSAIs for the corresponding frequency are indicated in SIB21 of the serving cell. The same MBS FSAIs are also indicated in the MBS User Service Description (USD) of the MBS Broadcast Service.

[0329] ● SIB21 may not be available in the serving cell. The frequency is included in the USD for these services.

[0330] ● The serving cell may provide SIB21 but may not provide frequency mapping for the service. The frequency is included in the USD for this service.

[0331] (Condition 3) The service area ID for the effective range of one or more MBS services on the corresponding frequency may be indicated in SIB21 of the serving cell. The service area ID for the effective range of the same MBS service may also be indicated for this MBS broadcast service session.

[0332] In other words, two conditions of the existing mechanism may be met in the NTN system. In such cases, the MBS intended service area of ​​the corresponding frequency may not include the intended service area of ​​the MBS session that the terminal can receive. Alternatively, the MBS intended service area of ​​the corresponding frequency may not include the intended service area of ​​the MBS session that the terminal is interested in. In such cases, the terminal may not prioritize the corresponding frequency. Therefore, the existing mechanism for MBS service continuity may not function effectively.

[0333] The present disclosure may define a new mapping relationship between current and / or adjacent carrier frequencies and MBS intended service area IDs for existing mechanisms for MBS service continuity. Furthermore, the present disclosure may include related information in SIB21. Alternatively, the present disclosure may apply an improvement that updates the existing MBS service continuity mechanism for performing MBS broadcast service cell reselection at a terminal based on service area information regarding the effective range of the MBS service.

[0334] According to one embodiment of the present disclosure, SIB21 can be utilized during a cell reselection procedure of a terminal to ensure service continuity of an MBS session, thereby allowing the terminal to prioritize the MBS frequency on which the MBS session configured to receive is provided. In this regard, since a service area is provided for each MBS frequency through SIB21, the terminal can identify the exact service area providing the MBS session configured to receive a specific frequency.

[0335] Accordingly, the terminal can operate to process the MBS frequency with the highest priority based on its location and service area information for each MBS frequency during cell reselection. In addition, with regard to the association between the service area and the MBS session, the first method, in which a frequency service area identifier (FSAI) is associated with one MBS broadcast session, and the second method, in which one frequency service area identifier (FSAI #x) is associated with multiple MBS broadcast sessions, can be applied.

[0336] In this case, in the case of the first method, since one frequency service area identifier is clearly associated with one MBS broadcast session, there is an advantage in that the service area can be simply provided through each FSAI, whereas in contrast, in the case of the second method, the explicit MBS broadcast session of each FSA and its service area need to be clearly indicated.

[0337] According to one embodiment of the present disclosure, with respect to the association between MBS sessions and service areas, a serving base station can provide an associated service area within each neighboring cell for each broadcast service session in a neighboring cell configuration. This allows a terminal to obtain service area information in the neighboring cell in advance and request unicast reception before moving to a cell that does not provide MBS broadcast services via multipoint-to-multipoint (PTM) transmission.

[0338] Additionally, in the case of cell reselection, the terminal must determine frequency priority based on whether the MBS broadcast service it is configured to receive is available on the corresponding frequency at its current location. Specifically, the service area of ​​the MBS broadcast service provided for each frequency can be provided via SIB21, and the terminal can dynamically determine frequency priority based on this information.

[0339] FIG. 12 is a flowchart illustrating embodiments of a method for providing multicast and broadcast services in a non-terrestrial network of a base station.

[0340] Referring to FIG. 12, in step S121, the base station may transmit service area information, including information about the effective range of the MBS service, to the terminal for each of a plurality of preset service areas in which the MBS service is provided. Next, in step S122, the base station may transmit an MBS transmission signal to the terminal for providing the MBS service.

[0341] In the above description, steps S121 to S122 may be further divided into additional steps or combined into fewer steps, depending on the implementation of the present disclosure. Furthermore, some steps may be omitted as needed, and the order of steps may be changed. The method of the non-terrestrial network base station illustrated in FIG. 12 can be performed by the base station described above. Therefore, even if omitted, the description of the base station can be equally applied to the description of FIG. 12.

[0342] FIG. 13 is a flowchart illustrating embodiments of a method for providing multicast and broadcast services in a non-terrestrial network of a terminal.

[0343] Referring to FIG. 13, in step S131, the terminal may receive service area information, including information about the effective range of the MBS service, from a base station of a non-terrestrial network. Next, in step S132, the terminal may obtain location information of the terminal and match the obtained location information with the received service area information.

[0344] Meanwhile, according to one embodiment of the present disclosure, in step S132, the base station or the terminal can check (verify) the location of the terminal to confirm the accuracy of the location information of the terminal (e.g., national area ID or RA-RNTI (random access RNTI), etc.). Through this, the base station can detect cases where the location reported by the terminal is not reliable (e.g., when the terminal has provided false information in the past or the terminal is highly mobile, etc.). In this case, the base station can trigger network-based location and location information.

[0345] In this regard, when a terminal accesses the network, the NTN base station can verify the terminal's national area ID and / or RA-RNTI. If the network or base station trusts the terminal's national area ID and / or RA-RNTI, the network or base station can grant the terminal's access. Alternatively, if the network or base station does not trust the terminal's national area ID and / or RA-RNTI, the network or base station can estimate the terminal's actual location. Based on the estimate, if the terminal's national area ID and / or RA-RNTI is accurate, the network or base station can allow the terminal's access. Otherwise, the network or base station can block the terminal's access.

[0346] Meanwhile, a timer may be used, for example, to perform a trust check. For example, a terminal may use a valid country area ID or RA-RNTI. In such a case, the network or base station may establish a trust period within which it can trust the country area ID or RA-RNTI reported by the terminal as valid based on past information (e.g., the terminal's location, speed, class, etc.). The network or base station may treat the terminal's location information reported by the terminal as valid before the timer expires. For example, a terminal at a border may have a lower timer value than a terminal in a large country.

[0347] Next, in step S133, the terminal can determine whether it is located within the corresponding service area. In other words, in step S133, the terminal can determine whether it is located within the corresponding service area based on its location information. If, as determined in step S133, the terminal is located within the service area, the terminal can receive MBS service from the base station using the MBS transmission signal associated with the corresponding service area information in step S134.

[0348] In contrast, if the terminal is determined to be located outside the service area as determined in step S133 (i.e., if the location information does not match the service area information), the terminal may block the MBS service associated with the corresponding service area information in step S135. In this regard, according to one embodiment of the present disclosure, in step S135, the terminal may receive an MBS transmission signal associated with the corresponding service area information from the base station. The terminal may block the MBS service by not performing decoding on the MBS transmission signal.

[0349] According to another embodiment of the present disclosure, in step S135, the terminal may block the MBS service by not receiving an MBS transmission signal associated with the corresponding service area information from the base station. In this regard, some location-dependent broadcast services may require access only within permitted areas in different cities and / or countries due to various MBS service frameworks (e.g., regulations, charges, etc.). In a TN system, the network or base station may not impose any restrictions on the terminal's actions for service reception. Furthermore, the network or base station may control MBS service accessibility by identifying a list of accessible cells or a list of tracking areas.

[0350] In NTN, location-dependent MBS service areas may exist within a portion of an NTN cell. Therefore, existing mechanisms may not function effectively in NTN networks unless improvements are introduced, such as assigning terminal location-specific service area-specific group IDs for network verification. Accordingly, to effectively manage service accessibility based on the terminal's geographic location, the following terminal behaviors related to MBS service reception can be defined.

[0351] Specifically, a terminal can receive service area information for an MBS broadcast service. Furthermore, the terminal may possess a valid identifier for receiving the service. In such cases, if the terminal is outside the service area, access to the service can be restricted.

[0352] Meanwhile, according to one embodiment of the present disclosure, the terminal may perform different operations depending on the following cases. For example, if the terminal is configured to receive a Temporary Mobile Group Identity (TMGI) without a service area, the terminal may follow the existing MCCH acquisition procedure.

[0353] For another example, if a terminal is configured to receive only TMGI #1 but is not located within the service area of ​​that TMGI, the terminal may not need to perform MCCH acquisition. For another example, if a terminal is configured to receive TMGI #3 and is located within that service area, the terminal may perform MCCH acquisition and reacquisition at times T0 and T2, but not at time T1.

[0354] In the above description, steps S131 to S135 may be further divided into additional steps or combined into fewer steps, depending on the implementation of the present disclosure. Furthermore, some steps may be omitted as needed, or the order of steps may be changed. The method of a terminal for providing multicast and broadcast services in a non-terrestrial network, as illustrated in FIG. 13, can be performed by the terminal described above. Therefore, even if omitted, the description of the terminal can be equally applied to the description of FIG. 13.

[0355] FIG. 14 is a flowchart illustrating embodiments of a method for providing multicast and broadcast services in a non-terrestrial network of a terminal.

[0356] Referring to Figure 14, when a base station forms a global mobile cell, it can transmit reference time information for the corresponding service area to the terminal along with service area information. When the base station forms a global mobile cell, the terminal can receive reference time information for the corresponding service area along with service area information in step S141.

[0357] Next, in step S142, the terminal can calculate (calculate) information on the service area after a predetermined period of time has elapsed based on the movement of the satellite corresponding to the base station, based on the astronomical information obtained from SIB19, etc.

[0358] In the above description, steps S141 to S142 may be further divided into additional steps or combined into fewer steps, depending on the implementation example of the present invention. Furthermore, some steps may be omitted as needed, and the order of the steps may be changed.

[0359] The method of receiving MBS services using service area information for the mobile cell illustrated in Figure 14 can be performed by the terminal described above. Therefore, even if omitted, the description of the terminal can be applied equally to the description of Figure 14.

[0360] FIG. 15 is a conceptual diagram illustrating embodiments of the range of a list of intended service areas to be signaled in a specific cell.

[0361] Referring to Figure 15, the following three options (three cases) can be considered to determine the scope of the list of intended service areas that should be signaled via a new SIB in a particular cell.

[0362] Option 1 (Case 1): Include the entire geographic area set by the network.

[0363] Option 1 allows the list of intended service areas to include the entire geographic area established by the network.

[0364] Option 2 (Case 2): Include the serving cell and all neighboring cells.

[0365] Option 2 allows the intended service area list to include the geographic area within the serving cell and all neighboring cells.

[0366] Option 3 (Case 3): Includes only the serving cell and its overlapping neighbor cells.

[0367] Option 3 allows the intended service area list to include only the geographic areas of the serving cell and its overlapping neighboring cells.

[0368] If option 1 is selected:

[0369] The list of intended service areas may not need to be updated frequently, even in an Earth Moving Cell (EMC) scenario. Indexes within the list can be used for easy reference. However, this may require higher signaling overhead than other options.

[0370] If option 2 or option 3 is selected:

[0371] In an EMC scenario, the list of intended service areas may require frequent updates. As the list is updated frequently, using the index as a pointer may become difficult. Option 3 can reduce signaling overhead, but it cannot fully support the intended service area information of adjacent cells, potentially impacting service continuity.

[0372] Meanwhile, if a terminal capable of receiving MBS broadcasting is receiving or wishes to receive a specific MBS broadcasting service and the MBS broadcasting service can only be received on that frequency, the frequency may be considered as the highest priority during an MBS broadcasting session if the following two conditions are met.

[0373] Condition 1:

[0374] The SIB1 scheduling information of the cell reselected by the terminal according to the MBS frequency priority will include SIB20.

[0375] Condition 2: One of the following three cases must be met:

[0376] - At least one MBS Free Service Area Identifier (FSAI) for the corresponding frequency is included in the SIB21 of the serving cell, and the same MBS FSAI is associated with the corresponding MBS broadcast service in the MBS User Service Description (USD).

[0377] - Although SIB21 is not provided in the serving cell, the frequency will be included in the USD for this service.

[0378] - SIB21 is provided in the serving cell, but frequency mapping for the service is not included, and the frequency will be included in the USD for this service.

[0379] When a UE capable of receiving MBS broadcasts is receiving or wants to receive a particular MBS broadcast service, frequencies on which it cannot receive that MBS broadcast service may be considered with the lowest priority during the MBS broadcast session.

[0380] condition:

[0381] - SIB20 will be included in the SIB1 scheduling information of the cell including the MBS frequency monitored by the terminal.

[0382] - The conditions presented in the previous condition 2) will be met in the serving cell (e.g., the MBS FSAI for the frequency is indicated in SIB21, or the frequency is included in USD, etc.)

[0383] A terminal supporting MBS broadcasting service in an NTN (Non-Terrestrial Network) environment can operate as follows.

[0384] For MBS broadcasting services targeting a specific area, terminals supporting the function must not set up MRB (MBS Radio Bearer) of MBS sessions associated with the area when they are outside the intended service area.

[0385] For MBS broadcast services targeting a specific region, a terminal supporting the feature can initiate the broadcast MRB setup procedure when within the intended service area. When the terminal leaves the intended service area, it can initiate the broadcast MRB release procedure.

[0386] Specifically, a terminal may prioritize a frequency providing the MBS of interest in a neighboring cell only if it remains within the intended service area after cell reselection. Conversely, if it finds itself outside the intended service area after cell reselection, it may not prioritize that frequency.

[0387] Option 1: Define a new mapping relationship between the current and adjacent carrier frequencies and the MBS intended service area ID.

[0388] This approach modifies SIB21 to include the following information:

[0389] - List of current and adjacent carrier frequencies

[0390] -MBS intended service area ID for each frequency

[0391] Option 2: Leverage the intended service area information of neighboring cells in new SIBs and MCCHs.

[0392] A method of providing information about the intended service area of ​​neighboring cells in new SIBs and MCCHs.

[0393] Specific application method:

[0394] Provide a list of intended service areas for each neighboring cell in the new SIB.

[0395] Providing the intended service area ID of the neighboring cell on the MCCH

[0396] How this method works:

[0397] If the terminal is receiving or wants to receive MBS broadcasts,

[0398] A frequency is considered as a top priority only if it is included in at least one of the intended service area IDs of the neighboring cell provided by MCCH.

[0399] A UE receiving or wishing to receive an MBS broadcast may consider that frequency as the highest priority if the broadcast can only be received on that frequency (but only if the UE remains within the intended service area after cell reselection).

[0400] If a terminal receiving or attempting to receive an MBS broadcast can only receive that broadcast on a specific frequency, and is outside the intended service area after cell reselection, that frequency may not be designated as the highest priority.

[0401] For service continuity, you must choose one of the following:

[0402] Introducing intended service area information (e.g. intended service area ID) associated with current and neighboring frequencies in SIB21.

[0403] Utilize the intended service area information of neighboring cells provided by MCCH

[0404] The methods according to the present invention may be implemented in the form of program instructions that can be executed by various computer means and recorded on a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, etc., either singly or in combination. The program instructions recorded on the computer-readable medium may be those specifically designed and constructed for the present invention, or may be known and available to those skilled in the computer software art.

[0405] Examples of computer-readable media include hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, and flash memory. Examples of program instructions include not only machine language codes generated by a compiler, but also high-level language codes that can be executed by a computer using an interpreter, etc. The hardware devices described above may be configured to operate with at least one software module to perform the operations of the present invention, and vice versa.

[0406] The operations of the method according to the embodiments of the present disclosure can be implemented as a computer-readable program or code on a computer-readable recording medium. A computer-readable recording medium includes any type of recording device that stores information readable by a computer system. Furthermore, a computer-readable recording medium can be distributed across network-connected computer systems, allowing the computer-readable program or code to be stored and executed in a distributed manner.

[0407] Additionally, the computer-readable recording medium may include hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, flash memory, etc. The program instructions may include not only machine language codes produced by a compiler, but also high-level language codes that can be executed by a computer using an interpreter, etc.

[0408] While some aspects of the present disclosure have been described in the context of a device, they may also represent a description of a corresponding method, wherein a block or device corresponds to a method step or a feature of a method step. Similarly, aspects described in the context of a method may also be described as a corresponding block or item or a feature of a corresponding device. Some or all of the method steps may be performed by (or using) a hardware device, such as, for example, a microprocessor, a programmable computer, or an electronic circuit. In some embodiments, at least one or more of the most important method steps may be performed by such a device.

[0409] In embodiments, a programmable logic device (e.g., a field-programmable gate array) may be used to perform some or all of the functions of the methods described herein. In embodiments, the field-programmable gate array may operate in conjunction with a microprocessor to perform one of the methods described herein. In general, the methods are preferably performed by some hardware device.

[0410] Although the present disclosure has been described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various modifications and changes may be made to the present disclosure without departing from the spirit and scope of the present disclosure as set forth in the claims below.

Claims

1. As a method of a non-terrestrial network base station, A step of transmitting service area information including information on the effective range of the MBS service to a terminal for each of a plurality of service areas preset to provide the MBS (multicast-broadcast services) service; and Comprising a step of transmitting an MBS signal for providing the MBS service to the terminal, Method of non-terrestrial network base station.

2. In claim 1, The above service area information is: Contains geographic information indicating the shape of each of the above multiple service areas, Method of non-terrestrial network base station.

3. In claim 2, At least one of the above multiple service areas has a circular shape, At least one of the above geographic information, Including information about the reference point of the above circular shape and distance information from the reference point, Method of non-terrestrial network base station.

4. In claim 2, At least one of the plurality of service areas has an elliptical shape or a polygonal shape. Method of non-terrestrial network base station.

5. In claim 1, The above service area information is: Containing non-geographic information for modeling each of the above multiple service areas, Method of non-terrestrial network base station.

6. In claim 5, The above non-geographic information is, At least one of a beam index, a mapped cell identifier, a tracking area identifier (TAI), a service identifier, a temporary mobile group identity (TMGI), a session identifier, a G-RNTI, an MRB, or an SSB associated with the MBS service, Method of non-terrestrial network base station.

7. In claim 1, The above service area information is: Contains information on permitted service areas and prohibited service areas for the above MBS service. Method of non-terrestrial network base station.

8. In claim 1, The step of transmitting the above service area information to the terminal is: A step of generating system information including the above service area information; and Including a step of transmitting the above system information to the terminal and delivering the service area information to the terminal. Method of non-terrestrial network base station.

9. In claim 8, The above system information is at least one of SIB (system information block) 1, SIB6, SIB7, SIB19, SIB20 or SIB25. Method of non-terrestrial network base station.

10. In claim 1, The size of the transmission range of the above MBS signal is larger than the size of the service area corresponding to the service area information. Method of non-terrestrial network base station.

11. In claim 1, If the above non-terrestrial network base station is a global mobile cell Further comprising a step of transmitting information about a reference time for each of the plurality of service areas. Method of non-terrestrial network base station.

12. As a terminal method, A step of receiving service area information including information on the effective range of a multicast-broadcast service (MBS) service from a non-terrestrial network base station; A step of acquiring the location of the terminal; A step of confirming a service area matching the location based on the above service area information; and When a service area matching the above location is confirmed, a step of receiving an MBS signal associated with the confirmed service area and selectively receiving the MBS service from the non-terrestrial network base station is included. Terminal method.

13. In claim 12, Further comprising a step of not receiving the MBS service if a service area matching the above location is not confirmed. Terminal method.

14. In claim 12, A step of receiving the MBS service if a service area matching the above location is not confirmed; and Further comprising a step of not performing decoding on the MBS signal, Terminal method.

15. In claim 12, A step of receiving information about a reference time for each of the plurality of service areas from the non-terrestrial network base station; and Further comprising a step of calculating a service area after a specific time according to satellite movement using ephemeris information of the non-terrestrial network base station and information about the reference time. Terminal method.

16. In claim 15, The step of selectively receiving the above MBS service is: A step of starting a MRB (Multicast Radio Bearer) setup procedure when the above location information matches the above service area information; and A method of a terminal, comprising the step of releasing a set MRB when the location information does not match the service area information.

17. As a terminal, Contains at least one processor, At least one processor of the terminal, Receive service area information including information on the effective range of a multicast-broadcast service (MBS) from a non-terrestrial network base station; Obtain the location of the above terminal; Check the service area matching the location based on the above service area information; and When a service area matching the above location is confirmed, an MBS signal associated with the confirmed service area is received, thereby causing selective reception of the MBS service from the non-terrestrial network base station. Terminal.

18. In claim 17, At least one processor of the terminal, If the service area matching the above location is not confirmed, it further causes the MBS service not to be received. Terminal.

19. In claim 17, At least one processor of the terminal, If the service area matching the above location is not confirmed, the MBS service is received; and Further causing decoding of the above MBS signal not to be performed, Terminal.

20. In claim 17, At least one processor of the terminal, Receive information about the reference time for each of the plurality of service areas from the non-terrestrial network base station; and Further causing the service area to be calculated after a specific time according to the satellite movement by using the ephemeris information of the above non-terrestrial network base station and the information about the above reference time. Terminal.

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