Method and apparatus for acquiring multicast control channel in non-terrestrial network

Abstract

The present disclosure relates to a method and an apparatus for providing a multicast and broadcast service in a non-terrestrial network. A method of 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 preset so that a multicast-broadcast service (MBS) is provided, information regarding the coverage range of the MBS; and transmitting, to the terminal, an MBS signal for providing the MBS.

Description

Method and apparatus for acquiring a multicast control channel in a non-terrestrial network

[0001] The present disclosure relates to a multicast control channel acquisition technology in a non-terrestrial network, and more specifically, to a multicast control channel acquisition technology that acquires a multicast control channel based on the location of a terminal and intended service area information in a non-terrestrial network.

[0002] Along with the advancement of information and communication technology, various wireless communication technologies can be developed. Representative wireless communication technologies include LTE (long term evolution), NR (new radio), and 6G (6th Generation), which are defined in the 3GPP (3rd generation partnership project) standards. LTE can be one of the wireless communication technologies among 4G (4th Generation) wireless communication technologies, and NR can be one of the wireless communication technologies among 5G (5th Generation) wireless communication technologies.

[0003] To handle the surge in wireless data following the commercialization of 4G communication systems (e.g., communication systems supporting LTE), not only the frequency bands of 4G communication systems (e.g., frequency bands below 6 GHz) but also 5G communication systems (e.g., communication systems supporting NR) that use frequency bands higher than those of 4G communication systems (e.g., frequency bands above 6 GHz) may be considered. 5G communication systems can support eMBB (enhanced Mobile BroadBand), URLLC (Ultra-Reliable and Low Latency Communication), and mMTC (massive Machine Type Communication).

[0004] Meanwhile, multicast and broadcast services can serve as a method for resource-efficient transmission to multiple users requiring the reception of the same content. Multimedia broadcast and multicast service (NR MBS) technologies designed to efficiently provide such services can primarily deliver multicast and broadcast services based on terrestrial networks (TN). Unlike terrestrial networks, non-terrestrial networks (NTNs), such as low earth orbit (LEO) satellites, can possess high-speed mobility characteristics, have wide cell radii, experience relatively long propagation delays, and operate in power-constrained environments. Therefore, MBS technologies suitable for non-terrestrial network environments may be required. Furthermore, in an NTN environment, satellites can provide MBS to terminals. To utilize MBS, terminals can periodically receive and update the MBS control channel (MCCH). Terminals may be located outside the MBS service coverage area. In such cases, the terminal can reacquire the MCCH simply by receiving an MCCH change notification, which may result in unnecessary power consumption and processing burden.

[0005] The objective of the present disclosure to solve the above-mentioned problems is to provide a method and apparatus for acquiring a multicast control channel in a non-terrestrial network based on the location of a terminal and intended service area information in a non-terrestrial network.

[0006] A method for obtaining a multicast control channel in a non-terrestrial network according to a first embodiment of the present disclosure for achieving the above objective may include, as a method of a terminal, receiving information about at least one intended service area (ISA) of multicast and broadcast services (MBS) from a non-terrestrial base station; obtaining location information of the terminal; and determining whether to initiate a broadcast MRB (MBS radio bearer) setting procedure based on the location information and the information about the at least one ISA.

[0007] Here, the step of determining whether to initiate a broadcast MRB setup procedure based on the location information and information about the at least one ISA may include: a step of determining whether the terminal is located within the at least one ISA based on the location information and information about the at least one ISA; and a step of determining whether to initiate the broadcast MRB setup procedure based on the result of the determination.

[0008] Here, the step of determining whether to initiate the broadcast MRB setting procedure based on the above judgment result includes the step of deciding not to initiate the broadcast MRB setting procedure based on the fact that the terminal is not located within the at least one ISA, and the acquisition operation of the initial MCCH (MBS control channel) based on the decision not to initiate the MRB setting procedure may be omitted.

[0009] Herein, the method may further include the step of receiving the MCCH change notification from the non-ground base station by monitoring the MCCH change notification; and the step of determining whether to reacquire the MCCH based on the location information and information about the at least one ISA based on the fact that the MCCH has changed.

[0010] Here, the step of determining whether to reacquire the MCCH based on the location information and the information regarding the at least one ISA may further include: a step of determining whether the terminal is located within the at least one ISA based on the location information and the information regarding the at least one ISA; and a step of determining whether to reacquire the MCCH based on the result of the determination.

[0011] Here, the step of determining whether to reacquire the MCCH based on the above judgment result may include the step of deciding not to reacquire the MCCH based on the fact that the terminal is not located within the at least one ISA.

[0012] Here, the step of receiving warning area information associated with a warning service at the non-ground base station may be further included.

[0013] Here, the step of receiving warning area information associated with a warning service at the non-ground base station may include the step of receiving a first system information block (SIB) containing warning area coordinates, which is the warning area information, from the non-ground base station.

[0014] Here, the step of receiving warning area information associated with a warning service at the non-ground base station may include: receiving at least one second SIB including at least one warning area segment, which is the warning area information, from the non-ground base station; and determining the game area information from the at least one warning area segment.

[0015] Here, the method further includes the step of receiving an MBS broadcast setting message containing an MBS session information list through MCCH, wherein the MBS session information list may include mapping information of at least one TMGI (temporary mobile group identity) and at least one ISA ID (identifier).

[0016] Here, the mapping information may indicate that at least one TMGI is associated with different ISAs.

[0017] Here, the step of determining whether to initiate a broadcast MRB setup procedure based on the location information and information about at least one ISA may include: determining an ISA ID corresponding to the at least one ISA based on the location information; determining a TMGI associated with the ISA ID based on mapping information between at least one TMGI (temporary mobile group identity) and at least one ISA ID; and determining whether to initiate the broadcast MRB setup procedure for an MBS session corresponding to the determined TMGI.

[0018] Meanwhile, a method for acquiring a multicast control channel in a non-terrestrial network according to a second embodiment of the present disclosure for achieving the above objective may include, as a method of a non-terrestrial base station, a step of transmitting information about at least one intended service area (ISA) of multicast and broadcast services (MBS) to a terminal; and a step of transmitting an MBS broadcast setting to the terminal to determine whether to initiate a broadcast MRB (MBS radio bearer) setting procedure at the terminal based on the information about the at least one ISA and the location information of the terminal.

[0019] Here, the MBS broadcasting settings include an MBS session information list, and the MBS session information list may include mapping information of at least one TMGI (temporary mobile group identity) and at least one ISA ID (identifier).

[0020] Here, the method may further include the step of transmitting an MCCH (MBS control channel) change notification to the terminal based on the change in the MBS broadcast setting.

[0021] Herein, the method further includes the step of transmitting warning area information associated with a warning service to the terminal, wherein the warning area information may be transmitted through at least one of a first SIB containing warning area coordinates or at least one second SIB containing at least one warning area segment.

[0022] Meanwhile, a multicast control channel acquisition device in a non-terrestrial network according to a third embodiment of the present disclosure for achieving the above objective comprises, as a terminal, at least one processor, and said at least one processor may cause said terminal to receive information about at least one intended service area (ISA) of multicast and broadcast services (MBS) from a non-terrestrial base station; to acquire location information of said terminal; and to determine whether to initiate a broadcast MRB (MBS radio bearer) setup procedure based on said location information and information about said at least one ISA.

[0023] Here, in order to determine whether to initiate a broadcast MRB setup procedure based on the location information and information about the at least one ISA, the at least one processor determines whether the terminal is located within the at least one ISA based on the location information and information about the at least one ISA; and causes to decide not to initiate the broadcast MRB setup procedure based on the fact that the terminal is not located within the at least one ISA, and based on the decision not to initiate the MRB setup procedure, the acquisition operation of the initial MCCH (MBS control channel) may be omitted.

[0024] Here, the at least one processor may cause the terminal to receive an MCCH change notification from the non-ground base station by monitoring the MCCH change notification; determine whether the terminal is located within the at least one ISA based on the location information and information about the at least one ISA based on the MCCH change; and decide not to reacquire the MCCH based on the fact that the terminal is not located within the at least one ISA.

[0025] Here, the at least one processor further causes the terminal to receive warning area information associated with a warning service at the non-ground base station, and the warning area information may be received through at least one of a first SIB including warning area coordinates or at least one second SIB including at least one warning area segment.

[0026] According to the present disclosure, the terminal determines whether to initiate a broadcast MRB (MBS radio bearer) setup procedure using information regarding its location and the intended service area, thereby preventing unnecessary MRB setup outside the intended service area. Additionally, when the terminal is located outside the intended service area, it may not perform an initial MCCH (MBS control channel) acquisition procedure or an MCCH reacquisition procedure, thereby reducing unnecessary wireless resource consumption and terminal power consumption.

[0027] FIG. 1 is a conceptual diagram illustrating embodiments of a non-ground network.

[0028] FIG. 2 is a conceptual diagram illustrating embodiments of a non-ground network.

[0029] FIG. 3 is a block diagram illustrating embodiments of entities constituting a non-ground network.

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

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

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

[0033] FIG. 7 is a conceptual diagram showing 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 geographical information indicating a service area.

[0035] FIGS. 9a through 9f are conceptual diagrams illustrating embodiments of a method for providing geographical information indicating a service area, including time.

[0036] FIG. 10 is a conceptual diagram showing embodiments of service areas divided into allowed service areas and prohibited areas.

[0037] FIG. 11 is a conceptual diagram illustrating embodiments of a method for associating service area information with MBS services.

[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 showing embodiments of the range of the intended service area list transmitted as a signal in a specific cell.

[0042] The present disclosure is capable of various modifications and may have various embodiments, and specific embodiments are illustrated in the drawings and described in detail. However, this is not intended to limit the present disclosure to specific embodiments, and it should be understood that it includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the present disclosure.

[0043] Terms such as "first," "second," etc., may be used to describe various components, but said components should not be limited by said terms. Such terms are used solely for the purpose of distinguishing one component from another. For example, without departing from the scope of the present disclosure, the first component may be named the second component, and similarly, the second component may be named the first component. The term "and / or" includes a combination of a plurality of related described items or any of a plurality of related described items.

[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 one or more combinations of A and B". Additionally, 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 one or more combinations of A and B".

[0045] When it is stated that one component is "connected" or "connected" to another component, it should be understood that while it may be directly connected or connected to that other component, there may also be other components in between. On the other hand, when it is stated that one component is "directly connected" or "directly connected" to another component, it should be understood that there are no other components in between.

[0046] In the present disclosure, a phrase containing "~ case (e.g., when ~)" may be expressed as a phrase containing "~ based on (e.g., based on ~)" or a phrase containing "~ in response to (e.g., in response to ~)". In other words, a phrase containing "~ case" may be interpreted as identical or similar to a phrase containing "~ based on" or a phrase containing "~ in response to".

[0047] The terms used in this disclosure are used merely to describe specific embodiments and are not intended to limit this disclosure. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this disclosure, terms such as “comprising” or “having” are intended to specify the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0048] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which this disclosure pertains. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this disclosure.

[0049] 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 of the present disclosure, the same reference numerals are used for identical components in the drawings, and redundant descriptions of identical components are omitted.

[0050] A communication network to which embodiments according to the present disclosure are applied will be described. The communication system may be a non-terrestrial network (NTN), a 4G (4th Generation) communication network (e.g., an LTE (long-term evolution) communication network), a 5G (5th Generation) communication network (e.g., an NR (new radio) communication network), a 6G (6th Generation) communication network, etc. The 4G communication network, the 5G communication network, and the 6G communication network may be classified as terrestrial networks.

[0051] Non-terrestrial networks may operate based on LTE technology and / or NR technology. Non-terrestrial networks 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 the 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 "communication system."

[0052] FIG. 1 is a conceptual diagram illustrating embodiments of a non-ground network.

[0053] Referring to FIG. 1, the non-ground network may include a satellite (110), a communication node (120), a gateway (130), a data network (140), etc. The non-ground network illustrated in FIG. 1 may be a non-ground network based on a transparent payload. 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 about 35,786 km) satellite, a HEO (high elliptical orbit) satellite, or an UAS (unmanned aircraft system) platform. The UAS platform may include a HAPS (high altitude platform station).

[0054] The communication node (120) may include a communication node located on the ground (e.g., UE (user equipment), terminal) and a communication node located off the ground (e.g., airplane, 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 communication services to the communication node (120) using one or more beams. The shape of the receiving range (footprint) of the satellite (110) beam may be elliptical.

[0055] A communication node (120) can communicate with a satellite (110) (e.g., downlink communication, uplink communication) 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. If dual connectivity (DC) is supported, the communication node (120) can be connected to the satellite (110) as well as other base stations (e.g., base stations supporting LTE and / or NR functions), and can perform DC operations based on technology defined in LTE and / or NR specifications.

[0056] 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 an 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 can be performed based on the NG-C / U interface.

[0057] 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 an NR-Uu interface, and communication between the base station and the core network (e.g., AMF, UPF, SMF) may be performed based on an NG-C / U interface.

[0058] FIG. 2 is a conceptual diagram illustrating embodiments of a non-ground network.

[0059] Referring to FIG. 2, the non-ground network may include satellite #1 (211), satellite #2 (212), a communication node (220), a gateway (230), a data network (240), etc. The non-ground network illustrated in FIG. 2 may be a regenerative payload-based non-ground network. For example, each of satellites #1-2 (211, 212) may perform a regenerative operation (e.g., demodulation, decoding, re-coding, re-modulation, and / or filtering) on ​​a payload received from other entities constituting the non-ground network (e.g., communication node (220), gateway (230)), and may transmit the regenerative payload.

[0060] Each of satellites #1-2 (211, 212) may be a LEO satellite, MEO satellite, GEO satellite, HEO satellite, or UAS platform. A UAS platform may include a 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) band or an optical band. The ISL may be established optionally. Communication nodes (220) may include communication nodes located on the ground (e.g., UE, terminal) and communication nodes located off the ground (e.g., airplane, drone). A service link (e.g., a wireless link) may be established between satellite #1 (211) and communication nodes (220). Satellite #1 (211) can provide communication services to a communication node (220) using one or more beams.

[0061] The communication node (220) can communicate with satellite #1 (211) (e.g., downlink communication, uplink communication) 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 satellite #1 (211) as well as other base stations (e.g., base stations supporting LTE and / or NR functions) and can perform DC operations based on technology defined in the LTE and / or NR specifications.

[0062] 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.

[0063] Communication between each of satellites #1-2 (211, 212) and the gateway (230) can be performed based on an NR-Uu interface or SRI. The gateway (230) can 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) can be connected to the core network, and the core network can 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 can be performed based on an NG-C / U interface.

[0064] 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 an NR-Uu interface, and communication between the base station and the core network (e.g., AMF, UPF, SMF) may be performed based on an NG-C / U interface.

[0065] Meanwhile, entities constituting the non-terrestrial network shown in FIGS. 1 and 2 (e.g., satellite, communication node, gateway, etc.) can be configured as follows.

[0066] FIG. 3 is a block diagram illustrating embodiments of entities constituting a non-ground network.

[0067] Referring to FIG. 3, the entity (300) may include at least one processor (310), a memory (320), and a transceiver (330) that communicates by being connected to a network. Additionally, 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 communicate with one another by being connected by a bus (370).

[0068] However, each component included in the entity (300) may be connected via individual interfaces or individual buses centered around the processor (310), rather than via a common bus (370). For example, the processor (310) may be connected via a dedicated interface 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).

[0069] The processor (310) can execute a program command stored in at least one of the memory (320) and the storage device (360). The processor (310) may mean a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor on which the methods according to embodiments of the present disclosure are performed. Each of the memory (320) and the storage device (360) may be composed of at least one of a volatile storage medium and a non-volatile storage medium. For example, the memory (320) may be composed of at least one of read-only memory (ROM) and random access memory (RAM).

[0070] Meanwhile, in non-terrestrial networks, scenarios can be defined as shown in Table 1 below.

[0071] NTN shown in Fig. 1, NTNGEO shown in Fig. 2, Scenario A, BLEO (Adjustable Beam) Scenario C1, Scenario D1, LEO (Beam Moving with Satellite) Scenario C2, Scenario D2

[0072] In the non-ground network shown in FIG. 1, if the satellite (110) is a GEO satellite (e.g., a GEO satellite that supports transparent functions), this may be referred to as “Scenario A”. In the non-ground network shown in FIG. 2, if satellite #1-2 (211, 212) is a GEO satellite (e.g., a GEO that supports regenerative functions), this may be referred to as “Scenario B”.

[0073] In the non-ground network illustrated in FIG. 1, if the satellite (110) is an LEO satellite having steerable beams, this may be referred to as "Scenario C1". In the non-ground network illustrated in FIG. 1, if the satellite (110) is an LEO satellite having beams that move with the satellite, this may be referred to as "Scenario C2". In the non-ground network illustrated in FIG. 2, if satellite #1-2 (211, 212) is an LEO satellite having steerable beams, this may be referred to as "Scenario D1". In the non-ground network illustrated in FIG. 2, if satellite #1-2 (211, 212) is an LEO satellite having beams that move with the satellite, this may be referred to as "Scenario D2". The parameters for the scenarios defined in Table 1 may be defined as shown in Table 2 below.

[0074] Scenarios A and B Scenarios C and D Elevation 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 Capacity (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 RTD (Round Trip Delay) (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) - 41.77ms (1200km altitude) Scenario D: (Regenerate Payload: Service Link Only) - 12.89ms (600km altitude) - 20.89ms (1200km altitude) Maximum differential latency within a single cell 10.3ms 3.12ms (600km altitude) 3.18ms (1200km altitude) Service Link NR or 6G Feeder Link 3GPP or non-3GPP defined radio interface

[0075] In addition, in the scenarios defined in Table 1, the delay constraint can be defined as shown in Table 3 below.

[0076] Scenario A Scenario B Scenario C1-2 Scenario D1-2 Satellite Altitude 35,786 km 600 km Maximum RTD at radio interface between base station and UE 541.75 ms (Worst case) 270.57 ms 28.41 ms 12.88 ms Minimum RTD at radio interface between base station and UE 477.14 ms 238.57 ms 8 ms 4 ms

[0077] Meanwhile, multicast and broadcast services can be a method for resource-efficient transmission to multiple users who require the reception of the same content. Due to the advantage of being able to provide a single transmission to multiple users, the 3GPP (3rd generation partnership project) introduced MBMS (multicast and broadcast multimedia service) technology, which enables multicast and broadcast services based on cellular mobile communication networks, in order to efficiently provide multimedia services starting from the WCDMA (wideband code division multiple access)-based 3G (3rd generation) standard.

[0078] This MBMS technology can support wider coverage than mobile communication technologies based on unicast transmission in a cellular environment, and it can deliver the same data to multiple users through the same physical resources, which can be a significant difference from mobile communication transmission technologies.

[0079] Meanwhile, MBMS technology was first standardized in the WCDMA-based Release 6 3G ​​specification and was introduced to efficiently provide mobile TV services over 3G mobile communication networks. However, MBMS technology may not provide satisfactory performance because it is difficult to efficiently process the increased multipath channel effects caused by the MBSFN (multicast broadcase single frequency network) through RAKE receivers. Furthermore, MBMS technology did not receive much attention at that time due to the low volume of media consumption via mobile devices.

[0080] Subsequently, starting around 2008, 3GPP began full-scale standardization of LTE (long-term evolution) based on OFDM (orthogonal frequency division multiplexing) technology. As a result, driven by LTE broadband services, the demand for media via mobile devices gradually increased. Later, in Release 9, standardization of MBMS technology based on LTE technology was carried out. Consequently, eMBMS (evolved multimedia broadcast and multicast service) technology was standardized to support high transmission rates by utilizing the wide bandwidth of LTE and to enable efficient MBSFN configuration by adjusting the cyclic prefix (CP) of OFDM.

[0081] Since the introduction of eMBMS technology, improvements to MBMS service functions have been carried out for several years, from Release 10 to Release 13. First, in Release 10, to efficiently operate MBSFN, the transmission status of MBMS was adjusted based on the distribution of terminals receiving MBMS services, and a function to dynamically adjust the MBMS service area was added. Subsequently, in Release 11, MBMS service continuity and service quality were improved in terminal inter-cell handover situations and on LTE multi-frequency networks.

[0082] Release 12 focused on improving MBMS services by utilizing terminal feedback information and added the Mood (MBMS operation on demand) function, which enables or disables MBMS based on feedback. In Release 13, separate from previous efforts to improve MBFSN operational efficiency, the efficient coexistence of MBMS transmission and unicast transmission within a single cell was sought in response to the demands of mobile operators. As a result, SC-PTM (single cell point to multipoint) technology was included as part of the MBMS technology. From this point on, MBMS transmission became capable of applying various functions used by unicast transmission technology within a single cell.

[0083] Subsequently, as 5G (5th generation) standardization progressed starting with Release 15, various requirements for 5G technology may have been defined. As part of this, requirements for 5G broadcasting were also defined. In particular, 3GPP included as 5G broadcasting requirements conditions that not only support linear broadcasting services with wide coverage similar to terrestrial broadcasting services, but also enable efficient coexistence with unicast in narrow service areas and dynamic changes. Based on this, 3GPP included 5G MBS technology in the Release 17 specification standardization.

[0084] Meanwhile, NR (new radio) MBS technologies designed to efficiently provide multicast and broadcast services can primarily provide multicast and broadcast services based on terrestrial networks (TN). Unlike terrestrial networks, non-terrestrial networks (NTN) can possess high-speed mobility characteristics, such as low earth orbit (LEO) satellites, have a wide cell radius, have relatively long propagation delay times, and operate in power-constrained environments. Therefore, it may be necessary to analyze whether the technologies applied in NR MBS are feasible in a non-terrestrial network environment.

[0085] In such an NTN environment, the satellite can provide MBS to the terminal. To use MBS, the terminal can periodically receive and update the MCCH (MBS control channel). The terminal may be located outside the MBS service coverage area. In such cases, the terminal may reacquire the MCCH simply by receiving an MCCH change notification, which may result in unnecessary power consumption and processing burden.

[0086] The present disclosure aims to solve the problems of the aforementioned prior art and to efficiently provide multicast and broadcasting services specialized for specific areas, such as by country or region, while minimizing the impact of existing TN and NTN standards and technologies in non-terrestrial networks using GEO (geostationary earth orbit) and LEO satellites having large cell radii.

[0087] The present disclosure aims to solve the problems of the aforementioned prior art and may provide an apparatus and method for providing multicast and broadcast services in a non-terrestrial network that can distinguish multicast and broadcast services that can be received according to the location of terminals within a cell in a satellite-based NTN such as GEO and LEO. However, the technical problems to be solved by the embodiments of the present disclosure are not limited to the technical problems described above, and other technical problems may exist.

[0088] Meanwhile, the present disclosure described below will explain a method for providing multicast and broadcast services in a non-terrestrial network. In particular, the present disclosure will explain a method for providing MBS services that 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, LEO satellites, etc., which have large cell radii. For MBS broadcast services, there may be no restrictions on the type of satellite orbit.

[0089] In this regard, as 5G standardization progressed at 3GPP starting with Release 15, various requirements for 5G technology may have been defined. As part of this, requirements for 5G broadcasting were also defined. In particular, 3GPP included as 5G broadcasting requirements conditions not only linear broadcasting services that support wide coverage like terrestrial broadcasting services, but also the ability to efficiently coexist with unicast in narrow service areas and enable dynamic changes. Based on this, 3GPP included 5G MBS technology in the Release 17 specification standardization.

[0090] FIG. 4 is a conceptual diagram showing embodiments of a system for supporting 5G MBS (5th generation multimedia broadcast and multicast service).

[0091] Referring to FIG. 4, the system may include user equipment (UE), new generation-radio access networks (NG-RAN) which are base stations, an access and mobility management function (AMF) device, a multicast / broadcast user plane function (MB-UPF) device, a multicast / broadcast session management function (MB-SMF) device, a session management function (SMF) device, a multicast / broadcast service function (MBSF) device, a multicast / broadcast service traffic function (MBSTF) device, an application function (AF) device / application server (AS) device, a user plane function (UPF) device, etc.

[0092] 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. 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-RANs, and UEs may be improved existing network functions.

[0093] The key features of 5G MBS technology may be as follows.

[0094] - Introduction of a group scheduling mechanism to allow simultaneous reception of MBS and unicast at the terminal

[0095] - Multicast and shared delivery in the 5G core

[0096] - 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

[0097] - Support for service continuity and lossless handover

[0098] - Receiving broadcast services regardless of the terminal's RRC (radio resource control) status

[0099] - Support for MBS services on existing network nodes

[0100] Looking at it in more detail from the perspective of network architecture, the 5G system network structure has been improved with the goal of supporting MBS services by reusing existing legacy 5G systems as much as possible, and the following new network features have been introduced to support 5G MBS.

[0101] - MB UPF: MB UPF is an entry point for the 5GS (5G system) and can function as a session anchor for the 5GS.

[0102] - MB SMF: MBS SMF can be an MBS session management and user plane function based on policy rules for multicast and broadcast services.

[0103] - MBSF: MBSF can support service level functions that interact with AF (Application Function / Application Server) and MB SMF for MBS session operations.

[0104] - MBSTF: MBSTF is a media anchor for MBS data traffic and can support common packet transmission features available in IP multicast-supported applications, such as framing, multiple flows, and packet encoding.

[0105] Based on improved existing network functions along with newly added network functions, 5GC can support two delivery methods, 5GC SD (shared MBS traffic delivery) and ID (individual MBS traffic delivery), to deliver MBS data traffic from MB-UPF to NG-RAN.

[0106] The SD forwarding method may be used to strategically 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, it can transmit a single copy of the MBS data packet to each NG-RAN node. This single copy of the 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, it can forward a single copy of the MBS data packet to the UPF. The UPF can then separate and transmit copies for each individual terminal. The ID forwarding method may not utilize resources efficiently. However, it may be an essential method to use when NR-RAN nodes do not possess MBS support capabilities but data transmission for MBS sessions is required.

[0107] Next, from a protocol perspective, 5G MBS technology improves upon existing NR protocols to support both multicast and broadcast services, which have the following different characteristics. First, target services in multicast mode may have specific quality of service (QoS) requirements that must be guaranteed by the network, similar to unicast.

[0108] Therefore, a terminal receiving multicast data may be in an RRC connected state. Through dedicated RRC signaling, radio resource configurations, such as MBS radio bearer (MRB) configuration and physical layer configuration, can be provided as the basis for interaction between the terminal and the base station. Additionally, if reliable transmission is required for cell boundary users, the transmission may switch from PTM to PTP.

[0109] If multicast data does not arrive, the multicast session may be deactive, and terminals belonging to 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.

[0110] Conversely, broadcast mode can be provided to all users within coverage regardless of the RRC status. Broadcast mode may have a mechanism similar to LTE's SC-PTM. To deliver broadcast data to terminals out of connection, radio resource settings for broadcast mode can be periodically transmitted via the MBS control channel (MCCH). From this, terminals can apply settings for the MBS traffic channel. Broadcast mode may not require interaction between the terminal and the base station. Therefore, the network does not receive feedback on the transmission status from the terminal and can transmit data in a best-effort manner.

[0111] The existing NR protocol can be improved as follows to support both multicast and broadcast modes having the characteristics described above.

[0112] - SDAP (Service Data Adaptation Protocol) Layer: To support MBS, the RAN can define new MBS radio bearers (MRBs). The SDAP layer can provide a one-to-one mapping between MBS sessions and MRBs that serves multiple MBS QoS flows (QFs) based on demand QoS and network policies. Since MBS exists only for downlink transport, it may not support uplink SDAP features such as reflective QoS and network-initiated QF remapping.

[0113] - PDCP (Packet Data Convergence Protocol): PDCP for MBS may differ from PDCP for unicast services. In PDCP for MBS, the PDCP entity may support a split MRB connected to one PTM RLC and one PTP RLC (radio link control). Through this, the base station can transmit MBS packets via PTP RLC, PTM RLC, or both RLCs depending on reliability requirements. If the base station sends PDCP packets of the same sequence via both RLCs, the terminal can discard the later-arriving packet through the PDCP duplicate detection function.

[0114] - RLC: RLC can support PTP RLC and PTM RLC. PTM RLC can be a group-common RLC. All terminals configured to have 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) mode. In contrast, PTP RLC can be a terminal-dedicated RLC. 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 via ARQ. The base station can select the appropriate RLC for transmitting packets by considering factors such as the required reliability, the terminal's link quality, and cell congestion status.

[0115] - MAC (medium access control): To reduce terminal power consumption, MBS session-specific DRX (discontinuous reception) can be configured on terminals receiving MBS data. Additionally, MAC can manage physical layer parameters related to MBS, such as MBS SPS (semi-persistent scheduling) or HARQ. Unlike unicast SPS, which uses CS-RNTI for SPS activation, deactivation, and retransmission, MBS SPS can be controlled by both unicast signaling via CS-RNTI and multicast signaling via G-CS-RNTI.

[0116] Finally, improvements in terms of the physical layer were largely made in terms of BWP (bandwidth part) operation and HARQ operation. First, in terms of BWP, the Release 17 specification introduced the concept of MBS common frequency resources (CFR), which allows multiple terminals to receive MBS receptions including group common PDSCH (physical downlink shared channel) or PDSCH in common.

[0117] 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 terminal to support simultaneous reception of unicast and multicast within the same time slot. Sub-carrier 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 the perspective of HARQ operation, unlike LTE eMBMS or SC-PTM, HARQ-ARQ feedback and HARQ retransmission can flexibly support the following three options for high-reliability transmission in multicast mode.

[0118] - ACK (positive acknowledgment) / NACK (negative acknowledgment) based HARQ-ACK feedback: A terminal can provide feedback on an ACK or NACK over the terminal's dedicated PUCCH (physical uplink control channel) resources. This method can be effective for a small number of terminals receiving multicast data.

[0119] - NACK-based HARQ-ACK feedback: A terminal can only provide NACK feedback on a common PUCCH resource shared with other terminals in the same group. This method can be resource-efficient. However, the base station cannot detect cases where terminals fail to decode PDCCH information.

[0120] - HARQ-ARQ feedback not applied: The terminal may not send any feedback regarding received data. When the terminal's QoS requirements for multicast data are low, the base station may use this method to reduce resource consumption.

[0121] The base station can dynamically switch between ACK / HARQ-based HARQ-ACK feedback and non-feedback modes via RRC signaling or DCI (downlink control information). Finally, NR MBS improves upon existing NR technology to support mobility and service continuity. While previous generations supported mobility and service continuity at the RAN level, NR MBS supports lossless mobility and service continuity at the packet level, thereby minimizing the impact on existing RAN protocols. The implemented packet-level service continuity can be based on packet-level sequence number synchronization, which ensures that identical packets have the same PDCP sequence number within the service continuity support area. This packet number synchronization enables the maintenance of a naturally configured MRB at the terminal during handover.

[0122] NR MBS technologies designed to efficiently provide multicast and broadcast services having the characteristics described above can primarily provide multicast and broadcast services based on terrestrial mobile communication networks. Unlike terrestrial networks, non-terrestrial networks can possess high-speed mobility characteristics, such as LEO satellites, have a wide cell radius, have relatively long propagation delay times, and operate in power-constrained environments. Therefore, it may be necessary to analyze whether the technologies applied in NR MBS are feasible in a non-terrestrial network environment.

[0123] 5G NTN standardization can aim to standardize minimum specifications for operation in the NTN environment while minimizing impact on existing TN specifications. Considering this, it can be predicted that technologies for providing efficient multimedia and broadcasting services in 5G NTN will utilize existing TN technologies as much as possible rather than introducing technologies optimized for the NTN environment, and will be achieved through improvements in areas requiring modification or addition due to the NTN-specific environment.

[0124] First, we can examine aspects related to parts that require modification or deletion to apply basic NR MBS technology to NTN. It is predicted that most of the aforementioned technologies considered for the existing TN's 5G NR MBS can be applied as is to 5G NTN MBS technology. Meanwhile, regarding areas requiring additional improvement, changes to timer parameter values ​​at the protocol layer due to long propagation latency may be considered. However, for this part, the method used in the previous Releases 17 and 18 to modify parameter values ​​of the existing NR protocol due to long propagation latency can be applied as is.

[0125] Next, we can examine aspects that require new additions for NTN MBS in addition to existing NR MBS technology. In 5G NR MBS, the multicast or broadcast service area can be considered as the entire coverage area of ​​a single RAN node. This is because the coverage of a single RAN node is relatively smaller compared to NTN, allowing multicast and broadcast service areas to be distinguished at the RAN node coverage 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 can have cell coverage ranging from over 100 km to over 1,000 km. Therefore, a specific NTN cell may include multiple regions or national areas. Given the characteristics of broadcast or multicast services, there may be a need to provide services separated by country or region. Considering regulatory aspects or the provision of emergency services, a new method can be added to NTN to distinguish multicast and broadcast service areas within a single RAN node coverage area, unlike the existing TN.

[0126] To solve these problems, the present disclosure may propose a method for efficiently providing multicast and broadcasting services specialized for specific regions, such as by country and region, in non-terrestrial networks using GEO, LEO satellites, etc., which have large cell radii, while minimizing the impact of existing TN technical standards.

[0127] Specifically, the present disclosure may propose a method to distinguish whether a multicast and broadcast service can be received based on the location of terminals as well as the group ID, in order to efficiently provide multicast and broadcast services specialized for specific regions, such as by country and region, while minimizing the impact of existing TN and NTN standards and technologies in non-terrestrial networks using GEO, LEO satellites, etc., which have a large cell radius.

[0128] Preferred embodiments according to the present disclosure may be described in detail below. The embodiments described in detail below may explain the present disclosure by assuming an NR-based satellite mobile communication system. However, the method disclosed in the present disclosure may be broadly applicable to any other mobile communication system having a wide cell area.

[0129] In this regard, according to an embodiment of the present disclosure, a terminal may receive MBS communication within a service area. For example, the terminal may receive MBS communication from an NTN cell. For example, the terminal may receive MBS communication from a TN cell. For example, the terminal may receive MBS communication from both a TN cell and an NTN cell. For example, a network entity forming a TN cell or an NTN cell may apply a delay offset to the MBS communication. Accordingly, the UE may receive MBS communication from each network entity (TN / NTN) simultaneously. Additionally, the MBS communication may include multicast control channel (MCCH) data, multicast traffic channel (MTCH) data, or both. For example, MTCH data may be encrypted. On the other hand, MCCH data may not be encrypted. The terminal may use a decryption key to decrypt the MTCH data.

[0130] For example, a network entity (satellite) can encrypt MBS communication and transmit the encrypted MBS communication through an NTN cell. For example, a terminal may be located within a service area. In such a case, the network entity (satellite) can provide the terminal with a decryption key related to the encrypted MBS communication. The terminal within the service area can decode the encrypted MBS communication using the received decryption key. A UE outside the service area cannot decode the encrypted MBS communication.

[0131] More specifically, broadcast communication services may be delivered to terminals through broadcast sessions. Terminals may receive broadcast communication services in the RRC_IDLE, RRC_INACTIVE, and RRC_CONNECTED states. In the case of broadcast communication services, the same service and the same specific content data may be provided simultaneously to all terminals within a designated geographic area. All terminals within the broadcast service area defined in TS 23.247 or all terminals within the intended service area connected to an NTN that supports MBS broadcast may have the right to receive the data.

[0132] FIG. 5 is a conceptual diagram showing embodiments of a method for providing multimedia and broadcasting services within a terrestrial network cell.

[0133] Referring to Fig. 5, in the case of TN, the coverage of base stations may be relatively small compared to the area of ​​each region or country. Therefore, multiple base stations may provide multicast and broadcasting services within a single region or country. In this TN scenario, multiple base stations built in the country or region may differentiate the broadcasting and multicast services provided by each base station built in the country or region in order to provide broadcasting and multicast services by country or region.

[0134] For example, multiple base stations can provide broadcast service 1 in a first country. Multiple base stations can provide broadcast service 2 in a second country. In this case, multiple base stations established in the first country can provide broadcast service 1, and multiple base stations established in the second country can provide broadcast service 2. In this way, multiple base stations can provide broadcast services separately by country. If a specific terminal (UE #1, UE #2) is located in the first country, the terminal is connected to a base station established in the first country, so naturally, it cannot receive broadcast service 2 provided outside the coverage area. If a specific terminal (UE #3) is located in the second country, the terminal is connected to a base station established in the second country, so naturally, it cannot receive broadcast service 1 provided outside the coverage area.

[0135] In addition, multiple base stations can provide multicast 1 service (broadcast) in the first region of the first country. Multiple base stations can provide multicast 2 service (broadcast) in the second region of the first country. Multiple base stations can provide multicast 3 service (broadcast) in the third region of the first country. Multiple base stations can provide multicast 4 service (broadcast) in the first region of the second country. Multiple base stations can provide multicast 5 service (broadcast) in the second region of the second country. Multiple base stations can provide multicast 6 service (broadcast) in the third region of the second country.

[0136] In this way, multiple base stations can provide multicast services separately by country and region. 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 established in the second region of the first country, it naturally cannot receive multicast 1 and multicasts 3 through 6 that are provided outside 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 established in the third region of the first country, it naturally cannot receive multicast 1, multicast 2, and multicasts 4 through 6 that are provided outside 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 established in the second region of the second country, it naturally cannot receive multicasts 1 through 4 and multicast 6 that are provided outside the coverage area. That is, in a TN environment, a base station established in the corresponding region can provide services to terminals located in a specific country or a specific region. Therefore, the services that terminals located in specific countries and regions can receive can be easily limited.

[0137] FIG. 6 is a conceptual diagram showing embodiments of a method for providing multimedia and broadcasting services within a non-terrestrial network cell.

[0138] Referring to Fig. 6, in the case of the NTN scenario, the existing TN's LTE MBMS or NR MBS can be transmitted so that all services provided by a single RAN node can be received by all terminals within the service area. Therefore, coverage can be established in the NTN cell across multiple countries or multiple regions. Consequently, the broadcast and multimedia services that a terminal in a specific region can receive cannot be limited.

[0139] For example, in the aforementioned FIG. 5, TN terminal 1 (UE #1) cannot receive other services other than the broadcasting and multicast services of the first country and the broadcasting and multicast services of the second region. However, as shown 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.) capable of receiving the multicast and broadcasting services is configured, it can receive the broadcasting and multicast services of the first country; and even if it is located in the second region, it can also receive the broadcasting and multicast services of the first and third regions, which are different regions. This may imply that a problem may arise where services cannot be restricted by country or region. Therefore, an additional solution may be required to resolve this problem in an NTN environment, unlike in a TN environment.

[0140] FIG. 7 is a conceptual diagram showing embodiments of transmitting information about a service area from a base station to a terminal within a non-terrestrial network cell.

[0141] Referring to FIG. 7, in a method for providing multicast and broadcast services in a non-terrestrial network, a base station may provide information to a terminal regarding the area in which the corresponding service can be received for each multicast and broadcast service in order to solve the aforementioned problem. Accordingly, the base station may restrict the terminal from receiving the corresponding multicast and broadcast service even if the terminal is equipped with a factor (e.g., G-RNTI, etc.) that can receive the corresponding service, if the terminal is not located in the corresponding area (service area).

[0142] This method of providing optional MBS services based on terminal location is equipped with a function that allows NTN terminals to mandatorily estimate their own location, so it is expected that it can be applied without significantly affecting NTN standards.

[0143] In other words, when a satellite RAN node provides information about broadcast and multicast services offered by that node, it can additionally inform the terminal of the valid range of each broadcast and multicast service. The terminal can additionally check whether it is within the valid range of the service based on its location. Subsequently, if the terminal is within the valid range, it can operate to receive the service.

[0144] For example, Terminal 1 (UE #1) illustrated in FIG. 7 may receive a parameter (e.g., G-RNTI, etc.) that enables the use of the services from a satellite RAN node that provides two broadcast services and six multicast services. In this case, according to existing TN standards, 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 acquire (estimate) its location through GNSS (global navigation satellite system), etc. Terminal 1 can identify the service area matching its location (in other words, the effective area of ​​each service provided by the satellite RAN node). Based on this, Terminal 1 can selectively receive only the broadcast service 1 of the first country and the multicast service 2 of the second region.

[0145] In summary, a base station of the non-terrestrial network of the present disclosure can transmit an MBS transmission signal to a terminal to provide an MBS service. In addition, the base station can transmit service area information to the terminal, including information on the effective range of the MBS service for each of a plurality of service areas pre-configured to provide an MBS service.

[0146] Meanwhile, regarding the service area signifying the effective range of the MBS service and the transmission range of the MBS transmission signal for providing the MBS service, the present disclosure may consider the following three scenarios.

[0147] First, in the first scenario (S1), the intended service area may be part of an NTN cell or a multicell. In this first scenario, the base station can transmit MBS transmission signals (MBS service content) to the terminal only within the service area. In the second scenario (S2), the service area may be part of an NTN cell or a multicell. However, in the second scenario, the base station can transmit MBS transmission signals (MBS service content) to the terminal even outside the service area. In the third scenario (S3), the service area may consist of a list of NTN cells or tracking areas.

[0148] In this regard, in the first scenario (S1), the service area may coincide with the satellite's beam footprint. This situation may occur, for example, when the beam coverage of the service area is relatively large. When considering this first scenario (S1), other MBS sessions may be associated with different geographical areas. Information for such association may be transmitted to the terminal via a system information block (SIB), etc. Additionally, the third scenario (S3) may be expected to be supported through existing NR specifications for supporting broadcast services of the TN. The multicast and broadcast service provision technique in a non-terrestrial network of the present disclosure may preferably be performed for S1 and S2.

[0149] Meanwhile, in the case of the first scenario (S1), multiple physical beams dedicated to each service area within a single cell may be required. These beams may have a flexible pattern capable of accommodating various types of service areas. However, this may be difficult to implement in actual satellite systems, particularly in systems where a moving earth cell exists. However, the multicast and broadcast service provision technique in a non-terrestrial network of the present disclosure may more preferably be applied to target the second scenario (S2), but is not limited thereto.

[0150] According to the second scenario (S2), the transmission range of the MBS transmission signal may be set to be larger than the service area corresponding to the service area information. Specifically, for each of the plurality of service areas pre-configured to provide MBS services, a base station of a non-terrestrial network may transmit service area information including information on the effective range of the MBS service to a terminal.

[0151] Additionally, a base station of a non-terrestrial network may transmit an MBS transmission signal to provide MBS services to a terminal. Furthermore, a terminal that receives such service area information may receive MBS services by 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 representing information regarding the shape of each of a plurality of service areas.

[0152] FIGS. 8a to 8f are conceptual diagrams illustrating embodiments of a method for providing geographical information indicating a service area.

[0153] Referring to FIG. 8a, the service area can be represented as a single circle based on a reference point and a distance. Referring to FIG. 8b, the service area can be represented as a polygon 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 through N. Here, N can be a positive integer. Referring to FIG. 8d through 8f, each service area can be represented in combination through different display methods.

[0154] Referring again to FIG. 8a, at least some of the multiple service areas may have a circular shape. Accordingly, geographic information representing the shape of the service area may include information about a reference point of the circular shape and distance information from the reference point (e.g., radius information, diameter information, etc.). Meanwhile, regarding 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 can be defined, respectively, through the tn-ReferenceLocation-r18 and tn-DistanceRadius-r18 elements, but are not limited thereto.

[0155] This method (circular display method) can provide only two types of information to represent a service area: reference point information (e.g., coordinate information) and distance information, such as the radius or diameter of the circle. For this reason, it offers the advantage of relatively low signaling overhead. However, it may be difficult to represent the shape of the service area in detail. Consequently, if the service area does not have a circular shape, it may be difficult to clearly represent it.

[0156] In contrast, the elliptical-based service area display method illustrated in FIG. 8b can provide additional distance information compared to the circular-based display method. Therefore, the signaling overhead may be large. However, the elliptical-based service area display method can have the advantage of being able to display the service area relatively clearly. Specifically, when applying the elliptical-based service area display method, the geographical information regarding the service area may include information about a reference point and a first distance (distance 1) and a second distance (distance 2) from the reference point.

[0157] In addition, the polynomial-based service area display method illustrated in FIG. 8c can represent the service area relatively clearly by displaying a service area in the form of a polygon composed of multiple vertices. However, the signaling overhead may be very high. Specifically, when applying the polynomial-based service area display method, geographical information regarding the service area may include information on multiple vertices (e.g., coordinate information; vertex 1 (point 1), vertex 2 (point 2), vertex N (point N)). The service area can be specified by connecting each vertex. Here, N may be a positive integer. In other words, according to one embodiment of the present disclosure, at least some of the multiple service areas may have an elliptical shape or a polygonal shape.

[0158] Meanwhile, according to one embodiment of the present invention, to define a service area of ​​a polygon shape, a polygon encoding method defined in TS 37.355 can be reused. For example, coordinate information of the vertices constituting the polygon can be defined through the corresponding encoding method. By reusing these encoding methods, various types of service areas can be efficiently defined while maintaining compatibility with existing standards.

[0159] In this regard, RAN2 may have engaged in similar discussions when introducing the new System Information Block (SIB25) for TN coverage signals in Release 18 NTN. However, defining the service area using a circular shape can reduce signal overhead. On the other hand, defining the service area using a circular shape has the disadvantage that it is difficult to represent the service area more accurately in the case of geographic information-based methods that define the shape of the service area in more detail. Based on the respective advantages and disadvantages in terms of accuracy and signal overhead, it was concluded in Release 18 NTN that SIB25 can be defined by reference point (center location) coordinates and a radius, and provides the corresponding geographic area information through a list of overlapping individual areas.

[0160] Considering this, a similar approach applying a method of defining 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 regarding the valid range of MBS services. Furthermore, a similar approach applying a method of defining the shape of a service area as a circular shape (circle-based format) can provide an efficient and flexible means of representing various forms of service areas resulting from NW implementation by using a list of overlapping circles as the geographical area format for the service area information of MBS services.

[0161] In this regard, to represent the service area more accurately, a similar approach that applies a method of defining the shape of the service area as a circular shape (circle-based format) can designate individual circles included in the service area information list for the valid range of the MBS service as allowed or prohibited areas.

[0162] According to an embodiment of the present disclosure, a terminal may store information regarding a reference point representing a geographical location or coordinates for entering an international area from an adjacent area. When the terminal passes the reference point, it may initiate a distance tracking process from the reference point. In other words, service area information including information regarding the effective range of the MBS service of the present disclosure may be defined to include information regarding at least one reference point representing the boundary of each service area and distance information from the boundary reflecting the size of the service area.

[0163] In this regard, the terminal can retrieve information indicating a preset distance from the border (boundary) of a first country (e.g., 'Country 1' of FIG. 11 described below). The terminal can receive MBS services of the first country while in the said country (international region). In this regard, information indicating a preset distance can be received by the terminal, for example, from a home PLMN (public land mobile network) or received via broadcast from an NTN that services the international region. Alternatively, information indicating a preset distance can be retrieved from the terminal's local database (e.g., external memory of a USIM (universal subscriber identity module), etc.).

[0164] In this regard, the terminal may receive MBS services of the first country while within a preset distance from the reference point. The terminal may move out of the preset distance from the reference point. In such a case, the terminal may determine that it has moved out of the first country. Accordingly, the terminal may re-search MBS service area information to receive other MBS services with higher priority in the international region.

[0165] Meanwhile, FIGS. 8d to 8f may represent a compromise display method. FIG. 8d may represent a method of displaying a service area using multiple circles of different sizes. FIG. 8e may represent a method of displaying a service area using multiple ellipses of different sizes. FIG. 8f may represent a service area using multiple circles of different sizes as in FIG. 8d. However, FIG. 8f may represent a method of distinguishing and displaying an allowed area and a prohibited area (slashed circle) for the MBS service. In other words, according to an embodiment of the present disclosure, the service area information may include information on the allowed area and the prohibited area for the MBS service.

[0166] In terms of signaling overhead, displaying geographical information about service areas in a circular format may be the simplest method. Furthermore, this method can utilize parts of the NTN configuration information format (e.g., NTN_config) available in the existing NTN SIB19.

[0167] Meanwhile, considering signaling overhead, the method according to FIGS. 8d and FIGS. 8f can be easily applied by similarly utilizing existing SIBs. In FIGS. 8f, the allowed area and the prohibited area can be distinguished by additionally including data (e.g., 1 bit of additional data) to indicate the type of the area in the service area information, but is not limited thereto.

[0168] With reference to FIGS. 8a through 8f, the above-described method for displaying a service area based on geographical information may be applicable to an earth-fixed satellite having a reference point of an unchanged service area. In an earth-moving cell, the satellite cell may be in a form that moves continuously. In such a case, in addition to the service area information provided by the existing earth-moving cell, time information regarding the service area may be additionally included.

[0169] FIGS. 9a through 9f are conceptual diagrams illustrating embodiments of a method for providing geographical information indicating a service area, including time.

[0170] Referring to FIGS. 9a through 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 a terminal along with service area information. For example, referring to FIGS. 9a through 9f, the referenceable time information for the service area may refer to an epoch time, but is not limited thereto.

[0171] In this regard, a terminal that receives service area information including reference time information from a base station forming an Earth moving cell can verify the movement of the service area according to the actual satellite movement using the reference time information. More specifically, according to one embodiment, the terminal can calculate information regarding the service area after a predetermined time elapsed according to the movement of the satellite corresponding to the base station based on ephemeris information obtained from SIB 19.

[0172] In other words, according to one embodiment of the present invention, MBS broadcast services may be supported for both Earth Fixed Cells (EFCs) and Earth Moving Cells (EMCs) in an NTN. A service area intended for location-dependent services may be broadcast. Such intended service area may cover one or more NTN cells (i.e., a serving cell and neighboring cells) or parts thereof. A geographic intended service area ID may indicate an MBS broadcast session broadcast in an MCCH.

[0173] In addition, 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. As a method of transmitting service area information to a terminal, it may be appropriate for the base station of a non-terrestrial network to allow the terminal in idle mode to receive information regarding MBS services, including broadcast services.

[0174] 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.

[0175] Specifically, regarding the level of detail of service area information, all detailed information, including service area identifiers and detailed information for each area, may be provided. As another example, according to an embodiment of the present invention, a method may be applied in which only the service area identifier is included and detailed information is provided by the User Service Description (USD) or a new SIB.

[0176] In this regard, considering the limited payload size of the existing SIB20 (e.g., 2976 bits), the method of providing all detailed information in an integrated manner through MCCH may be more appropriate. In particular, since SIB20 currently does not include multicast broadcast service (MBS) session identifiers, whereas MCCH includes such information, MCCH may be more suitable considering that service area identifiers must be associated with MBS session identifiers, but is not limited to this.

[0177] In addition, according to one embodiment of the present disclosure, the following method may be applied to optimize MCCH monitoring when the terminal is not located within any service area. 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 may be reacquired only when the MCCH modification notification DCI indicates a service area update.

[0178] Alternatively, as a second method, a method of applying a longer modification period for changing the service area of ​​a broadcast service may be considered. For example, a method of setting the service area change cycle as a multiple of the MCCH change cycle may be applied, in which 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.

[0179] According to one embodiment of the present invention, the MCCH may provide a list of all broadcast services having ongoing sessions transmitted over the MTCH. Relevant information for a broadcast session may include an MBS session ID, relevant G-RNTI scheduling information, one or more intended service area IDs in the case of an NTN broadcast, and information about neighboring cells providing a specific service on the MTCH. MCCH content is transmitted within a time domain window that occurs periodically, which may be referred to as the MCCH transmission window. The MCCH transmission window may be defined by an MCCH repetition period, an MCCH window duration, and a radio frame / slot offset.

[0180] Therefore, it may be preferable for a base station of a non-terrestrial network to broadcast service area information to a terminal via RRC signaling. For example, a base station of a non-terrestrial network may transmit service area information to a terminal using system information containing service area information.

[0181] For example, a base station may include service area information in a SIB by reflecting service area information in an existing system information block (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 the MBS traffic channel (MTCH)), and SIB21 (for service continuity).

[0182] According to one embodiment of the present invention, a SIB may include a list of service areas intended for receiving MBS broadcasts and associated pointers. Specifically, the SIB includes a description of the service areas intended for the broadcast service of an NTN cell, and when service areas intended for MBS broadcasts are defined, they are broadcast as a list in the SIB. Meanwhile, terminal requirements related to the contents of the SIB do not exist separately, except for requirements specified within the procedure using the relevant system information and / or requirements specified within the corresponding field description.

[0183] In this regard, a service area can be represented as a set of reference locations and radii or a set of polygons, which can cause significant signaling overhead and does not need to be repeated in multiple places. Accordingly, according to one embodiment of the present disclosure, a method can be applied in which service area information is defined in a new SIB or an existing SIB20 and an area identifier is assigned to each area, thereby allowing the area identifier to be referenced where service area information is required, which can significantly reduce signaling overhead.

[0184] However, this is not limited to this; for example, the service area may be identical to the entire cell coverage. In such cases, the service area can be represented in an efficient manner that indicates it without complex geographic information. In this case, the representation of the service area may not include geographic information in the form of a polygon or circle representing the service area. Instead, the representation of the service area may use a single-bit flag to implicitly indicate that the service area corresponds to the entire cell area. For example, a specific information element (IE) may not exist in the new SIB. The absence of such a specific information element may implicitly indicate that the service area is identical to the entire serving cell.

[0185] This approach can significantly reduce signal overhead. It can be particularly efficient in scenarios where multiple services cover the entire cell area. The terminal can also determine that the service area covers the entire cell area with just a simple bit check. The terminal can omit complex geographic calculations required to determine whether it is located within the service area.

[0186] Specifically, according to one embodiment, the existing SIB used to transmit service area information may include at least one of SIB 1, SIB 6, SIB 7, SIB 19, SIB 20, and SIB 25, but may not be limited thereto.

[0187] For example, SIB20 can provide a database of service areas for all broadcast service sessions. For example, considering the case where SIB20 always provides service areas for broadcast service sessions 1, 2, and 3, MCCH can operate in such a way 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.

[0188] According to this design, SIB20 can remain the same regardless of whether broadcast services are added or deactivated. 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 method may also be considered to update SIB20 only when a new broadcast service starts (for example, 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.

[0189] In this regard, according to one embodiment of the present invention, in order to optimize MCCH monitoring when the terminal is not located within any service area, a first method of displaying 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.

[0190] Specifically, in the first method, when the terminal is not located within any service area of ​​the broadcast services configured to be received, it may reacquire the MCCH only when the MCCH change notification DCI indicates an update of the service area. Meanwhile, in the second method, the service area change cycle may be set as a multiple of the MCCH change cycle, and 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.

[0191] According to one embodiment of the present disclosure, service area information can be understood to have a relatively static characteristic, and considering this characteristic, SIB20 can function as a database for the service areas of all broadcast service sessions supported by a wireless access network node.

[0192] This design has the advantage that SIB20 can be maintained without change even if MCCH can contain different broadcast service sessions at various points in time. However, as a compromise, one could consider updating SIB20 only when a new broadcast service starts, such as when the most significant bit in the MCCH change notification indicates the addition of a session.

[0193] According to this method, the terminal may operate as follows depending on its 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 temporary mobile group identifier #1 but not within the corresponding service area does not perform MCCH acquisition; and a terminal configured to receive temporary mobile group identifier #3 and within the corresponding service area may selectively perform MCCH acquisition and reacquisition.

[0194] As another example, a base station can utilize a SIB to transmit service area information to a 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 methods Option 1 to 3 to transmit service area information to the terminal. Method Option 1 may be a method of extending an existing SIB or an existing MCCH. Method Option 2 may be a method of defining a new SIB. Method Option 3 may be a method of applying a combination of Option 1 and Option 2. In this case, considering the shortage of available bits in the existing SIB or existing MCCH, it may be relatively preferable for the base station to apply Option 2 or Option 3 compared to Option 1, but it may not be limited thereto.

[0195] 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, there is an advantage in that the impact of Intended Service Area (ISA) information on existing UEs can be minimized and MCCH acquisition can be mitigated when the terminal is not located in any of the defined ISAs.

[0196] In addition, according to one embodiment of the present invention, the ISA identifier of an MBS service may be optionally included in a Service Announcement. Through this, the terminal can recognize the ISA identifier of a specific MBS broadcasting service of interest and can mitigate MCCH acquisition by combining the information of a new SIB and a Service Announcement. Specifically, by including the ISA identifier in the Service Announcement, the terminal can determine whether it is within the ISA of the MBS service of interest and can consider only that area when mitigating MCCH.

[0197] Meanwhile, a terminal interested in the MBS service may skip MCCH acquisition when located outside the intended service area of ​​the service. Specifically, depending on the implementation, the terminal may determine whether to skip MCCH acquisition by utilizing its location, the ISA definition of SIB / USD, and mapping information between the ISA ID of USD / Service Notice and the MBS Service ID (TMGI).

[0198] In addition, according to one embodiment of the present invention, information regarding the MBS broadcast configuration and service of the next satellite scheduled to service the area may be provided in a quasi-Earth fixed cell. This allows the terminal to prevent service interruption due to satellite change and reduce signaling overhead. Specifically, the serving cell may signal a list of next satellites / cells scheduled to provide the same MBS service, and such information may be provided together with satellite support information provided in another system information block (e.g., SIB19). This signaling may include information regarding the time, frequency, or PCI when the next satellite begins service of the intended service area associated with the current cell or MBS service.

[0199] In this regard, quasi-earth fixed cells or earth-moving cells may provide in advance the intended service area (ISA) and scheduled service time for services to be provided in the future. Due to the rapid movement of satellites, the ISA may be valid for only a short period of time and may change frequently. In such situations, frequent updates to the System Information Block (SIB) / Multicast Control Channel (MCCH) may occur. To address this issue, the network may provide in advance the MBS broadcast settings and service information of satellites scheduled to service the area in the future.

[0200] Through this advance information, the terminal can prepare for satellite changes in advance and increase efficiency and battery life by reducing the frequency of acquiring unnecessary system information and MCCH. In addition, to mitigate the problem of frequent SIB updates in Earth-mobile cells, the new SIB can pre-include the ISA that is scheduled to be covered by the cell in the future. To mitigate the problem of frequent SIB updates in Earth-mobile cells, the new SIB can be configured so that the SIB's ValueTag value does not change even if the Earth-mobile cell's ISA list changes.

[0201] For reference, according to one embodiment of the present invention, a service area identifier (ISA ID) can be represented by utilizing an index of a service area list. Specifically, the ISA can be indicated using the index value that the corresponding 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 the need for additional identifier assignment.

[0202] Meanwhile, according to one embodiment of the present invention, service area information has a relatively semi-static characteristic, so frequent updates may not occur. Considering this characteristic, the update of service area information in a new SIB may follow the existing SIB modification procedure. By reusing the existing SIB modification procedure, service area information can be efficiently updated without the need to define a new update mechanism. In addition, since the service area information has a semi-static characteristic, issues related to the MCCH update cycle can also be minimized.

[0203] According to one embodiment of the present invention, as a method for indicating service area information, a method using an index within a list and a method using a unique identifier (ID) may be considered. The index-based method has the advantage of small data size and a simple search mechanism, but it may have the disadvantage of being dependent on the order of the list and unable to guarantee global uniqueness.

[0204] In contrast, while the ID-based approach enables stable referencing and can improve global uniqueness and readability, it may result in relatively large data sizes and additional management overhead. Particularly in EMC environments, considering that the list of service area information may be frequently updated and that this information can be provided through both AS signaling and NAS signaling, the ID-based approach may be more effective.

[0205] For example, geographical information regarding the service area included in the SIB may include information about the reference location at the reference time according to the epoch time in non-terrestrial network configuration information (e.g., NTN-config), distance information from the reference point, etc.

[0206] Meanwhile, if a service area including multiple areas is provided, the SIB may additionally include the following information.

[0207] - MBS area identifier list (e.g., MBS-AreaIDlist)

[0208] - MBS area identifier (e.g., MBS-AreaID)

[0209] In this case, the relevant information may be specifically included in the following SIBs in relation to existing MBS.

[0210] - Add to spare1 in MCCH MessageType r17

[0211] - Add a new mbsBroadcastConfiguration configuration to the existing mbsBroadcastConfiguration (e.g., mbsBroadcastConfiguration-r19)

[0212] - Add to the s pare1 part within MulticastMCCH MessageType r18

[0213] - Add a new m bsMulticastConfiguraiton configuration to the existing mbsMulticastConfiguraiton (e.g., mbsBrodcastConfiguraiton-r19)

[0214] To this end, the following corresponding service area information may be added for each mbs sessionInfoList within MBSBroadcastConfiguration and MBSMulticastConfiguration.

[0215] - Information regarding the reference location at the reference time based on the epoch time within non-terrestrial network configuration information (e.g., NTN-config)

[0216] - Distance information from the reference location

[0217] In addition, if service areas are provided through multiple areas, the following information may be additionally included.

[0218] - MBS area identifier list (e.g., MBS-AreaIDlist)

[0219] - MBS area identifier (e.g., MBS-AreaID)

[0220] This information may be added for each MBS service list (e.g., mbsServiceList) within an MBS Interest Indication message (e.g., MBSInterestIndication message), and may also be added in the same manner.

[0221] In addition, the MBS service area information proposed above may be defined for each MBS service list (e.g., mbsServiceList). Alternatively, the MBS service area information proposed above may be defined for each MBS session information list (e.g., mbs-sessionInfoList). The MBS service area information may be displayed by defining a new SIB through a list indicator of the messages.

[0222] 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 implement providing the service in a broadcast manner only within the actual intended service area, particularly in the case of a single satellite beam or multiple satellite beams. Accordingly, the minimum unit of broadcast transmission may be set to the coverage of the satellite beam.

[0223] Meanwhile, in order to provide service area information, according to one embodiment of the present invention, a new information element (IntendedServiceAreaInfo-r19) as follows may be defined:

[0224] IntendedServiceAreaInfo-r19 ::= SEQUENCE {

[0225] intendedServiceAreaId-r19 IntendedServiceAreaId-r19,

[0226] intendedServiceArea-ReferenceLocation-r19 ReferenceLocation-r17,

[0227] intendedServiceArea-DistanceRadius-r19 INTEGER(0..65536)

[0228] }

[0229] Meanwhile, MBSBroadcastConfiguration-r19-IEs can be configured as shown in Table 4 below.

[0230] 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.

[0231] In addition, according to one embodiment of the present invention, the newly introduced SIB-related message can be configured as shown in Table 5 below.

[0232] -- 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

[0233] However, the specific details of the message structure, field configuration, parameters, and sequence defined above are in accordance with one embodiment of the present invention, and a person skilled in the art to which the present invention belongs will understand that they may be implemented in other specific forms without changing the technical concept or essential features of the present invention.

[0234] Next, the fields of each message defined above are described in more detail as follows.

[0235] The polygonArea within IntendedServiceAreaInfo-r19 can be defined using the polygon parameter type defined in TS 37.355, wherein the first / left bit contains the most significant bit.

[0236] The intendedServiceAreaList-r19 within SIBXX-r19 represents a list of intended service areas and includes detailed information for each intended service area.

[0237] mbs-SessionAreaMapping-r19 within MBSBroadcastConfiguration-r19-IEs provides a mapping relationship between an MBS session and the geographic area where that session is served. Each MBS session can be associated with one or more intended service areas.

[0238] pdsch-ConfigMTCH provides parameters for obtaining the PDSCH for the MTCH. If this field is absent, the terminal uses the parameters of pdsch-ConfigMCCH to obtain the PDSCH for the MTCH.

[0239] mbs-SessionInfoList provides the configuration of each MBS session provided via MBS broadcast in the current cell.

[0240] mbs-NeighbourCellList provides a list of neighboring cells that provide one or more MBS broadcast services through the current cell via the broadcast MRB. This is used by the terminal in conjunction with the mtch-NeighbourCell field, which is signaled in the corresponding MBS-SessionInfo for each MBS session.

[0241] If an empty list is signaled, the terminal assumes that the MBS broadcast service signaled in the mbs-SessionInfoList of the MBSBroadcastConfiguration message is not provided by any neighbor cell. If a non-empty list is signaled, the current serving cell does not provide information about the MBS broadcast service of neighbor cells not included in the mbs-NeighbourCellList. That is, the terminal cannot determine the existence or absence of the MBS service of a missing neighbor cell.

[0242] Meanwhile, according to one embodiment of the present disclosure, the MBS-SessionInfoList may be extended to efficiently provide a mapping relationship between the session identifier (temporary mobile group identity, TMGI) of an MBS service and the intended service area identifier (intended service area ID, ISA ID). This extended MBS-SessionInfoList may explicitly indicate the intended service area associated with each MBS session for each MBS session. This allows for flexible relationships where a single MBS session can be associated with multiple intended service areas (one-to-many mapping), and multiple MBS sessions can be associated with a single intended service area (many-to-one mapping).

[0243] These extended information elements (IEs) can prevent TMGI duplication and enable clear identification of MBS sessions by intended service area. Terminals can efficiently determine available services based on their location. In particular, a single MBS session identifier can be reused across multiple intended service areas. Therefore, network operators can perform consistent session management when providing the same content to different regions.

[0244] If the mbs-NeighbourCellList field is missing, the current serving cell does not provide information about the MBS broadcast services of neighboring cells, which means that the terminal cannot determine the existence or absence of the neighboring cells' MBS services based on the absence of this field.

[0245] Additionally, according to another embodiment of the present invention, a method of providing service area information utilizing a mapped cell ID introduced in NTN R17 may be applied. Specifically, the network may broadcast the mapped cell ID and the corresponding area information, and provide an association between the mapped cell ID and the service area. This method may also be useful for terminals to report MBS Interest Indications on a mapped cell basis.

[0246] In addition, according to one embodiment of the present invention, service area information may be provided through a System Information Block (SIB). Specifically, service area information may be provided through SIB1, which includes the scheduling of all system information, or through SIB20 or SIB21, which includes information related to MBS broadcasting. Additionally, it may be provided through SIB6 or SIB7, which includes tsunami warning system (ETWS) notifications, or through SIB19, which includes satellite support information for NTN access. Meanwhile, considering the size or utility of the service area information, defining a new SIB to provide the information may also be considered.

[0247] In this regard, according to one embodiment of the present disclosure, SIB6 can provide warning area coordinates relatively coarsely compared to SIB7 for geo-fencing of an earthquake and tsunami warning system (ETWS). SIB7 can provide warning area coordinates relatively finely compared to SIB6. SIB6 does not support segmentation and cannot contain detailed area information due to message size limitations (maximum 2976 bits). Therefore, SIB6 can realistically provide approximate area information. On the other hand, SIB7 can accommodate more detailed area information because it supports segmentation.

[0248] In this design, SIB6 can provide warning area coordinate information elements through the warning area coordinates (e.g., warningAreaCoordinates) field. SIB7 can provide warning area coordinate information elements in the form of segments through the warning area coordinate segment (e.g., warningAreaCoordinatesSegment) field. When warning area coordinates are provided, the warning area message segment number (e.g., warningMessageSegmentNumber) field can be applied to both the warning message and the warning area coordinate segment. Through this, the satellite can provide information efficiently by consistently managing segment information.

[0249] The terminal can receive warning area information associated with a warning service from a non-terrestrial network base station. For example, the terminal can receive SIB6 containing warning area coordinates, which are warning area information, from a non-terrestrial network base station. The terminal can transmit the warning area coordinates to an upper layer.

[0250] The terminal can receive at least one SIB7 containing at least one warning area segment, which is warning area information, from a non-terrestrial network base station. The terminal can assemble game area information from at least one warning area segment. The terminal can transmit the assembled warning area coordinates to an upper layer.

[0251] Meanwhile, regarding SIBs for defining new ISAs, new System Information Blocks (SIBs) defining the intended Service Area (ISA) can be designed to be cell-specific. This may mean that each cell can independently broadcast its own ISA configuration. This cell-specific approach can allow for the provision of different ISAs for each cell and each frequency layer. As a result, system flexibility can be significantly improved. The network can apply granular control over service areas and MBS session mappings and may include frequency-specific configurations.

[0252] As an alternative to the cell-specific SIB approach, there may be a region-specific SIB approach. The region-specific SIB approach assumes that the serving cell and adjacent cells can share the same ISA set. The region-specific SIB approach can make it difficult to distinguish cell-specific or frequency-specific ISA configurations. The cell-specific SIB approach may increase signal overhead. However, the benefits of increased system flexibility and accurate service area mapping can offset the increase in signal overhead.

[0253] Additionally, according to an embodiment of the present disclosure, a serving cell may provide a list of intended service areas for adjacent cells through a new system information block. This information can play an important role in maintaining service continuity when moving between cells at a terminal. In particular, the terminal can utilize the list of intended service areas to determine in advance whether the adjacent cell supports the currently received MBS service. Through the list of intended service areas, the terminal can determine in advance whether the area to which it may move is included in the intended service area of ​​the corresponding service.

[0254] The ISA information of adjacent cells may include a service area identifier and geographical information for each area. The terminal can utilize the service area identifier and geographical information for each area to optimize cell reselection decisions. For example, the terminal can identify an adjacent cell containing the intended service area of ​​the currently received MBS service and establish a strategy to minimize service interruption when moving to that cell.

[0255] Meanwhile, since TMGI (Temporary Mobile Group Identity) and SAI (Service Area Identifier) ​​already include MCC or PLMN ID, additional improvements may not be necessary for processing different country information.

[0256] As another example, considering that MBS service area information is information specialized for NTN, the service area information may additionally be 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.

[0257] -SIB20: Information required to obtain the MCCH (multicast control channel) / MTCH (multicast traffic channel) configuration for MBS broadcast

[0258] -SIB21: Mapping relationship between current and / or adjacent carrier frequencies and MBS FSAI (frequency selection area identities)

[0259] - MBS Broadcast Configuration (e.g., MBSBroadcastConfiguration): Control information applicable to MBS broadcast services transmitted via the Broadcast MRB.

[0260] Meanwhile, when the aforementioned detailed information is provided via SIB20 or SIB21, the operation of the terminal can be optimized to avoid unnecessary operations on the terminal. For example, the above detailed information may be provided via SIB20. In this case, the terminal may be located outside the valid range (service area) of the MBS service and may not receive unnecessary MBS broadcast setting messages.

[0261] Conversely, when details regarding the service area are provided through an MBS broadcast setup message, the MBS session ID information from an existing MBS broadcast setup message can be reused to indicate service area information regarding the valid range of the MBS service. Therefore, the base station can reduce signal overhead for service area information.

[0262] In this regard, MBS session ID information may not be included in the existing SIB 20 and SIB 21. Considering the original purpose of each SIB, it may be more desirable for the base station to provide service area information through MBS broadcast setup messages. This may be because the service area can be considered as part of the control information for providing area-specific MBS broadcast services for each MBS session.

[0263] 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 the 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.

[0264] Additionally, according to one embodiment of the present invention, terminals outside the intended service area may not reacquire the MCCH. In the case of an MCCH-based method, a notification may be transmitted via a PDCCH addressed to an MCCH RNTI, thereby allowing only terminals interested in the MBS to receive the notification. Additionally, a single bit may indicate whether a new service will be provided.

[0265] Meanwhile, according to one embodiment of the present invention, even if an NTN terminal can receive MBS services, it may be restricted from setting an MRB if it is located outside the MBS service area. Additionally, the terminal may release the MRB when it leaves the intended area, but the release of the MRB may be determined based on additional conditions, such as the time elapsed or distance after leaving the MBS area. This is because the terminal cannot maintain the MRB permanently.

[0266] In this regard, according to one embodiment of the present invention, an NTN terminal supporting MBS broadcast may initiate a broadcast MRB setup procedure when it is within an intended service area. Additionally, the terminal may initiate a broadcast MRB release procedure when it leaves the intended area. However, according to an embodiment of the present invention, the network may not be able to prevent the terminal from decoding service content outside the intended service area.

[0267] In addition, 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 a GNSS location used for other NTN purposes. Accordingly, there is no need to separately update the terminal's GNSS location for this purpose.

[0268] Additionally, according to one embodiment of the present invention, a ReferenceLocation-r17 and a list of 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 represented as ReferenceLocation IE may be determined.

[0269] Meanwhile, due to size limitations of the MBS broadcast setup message, it may be difficult for the base station to include all information representing service area details in the MBS broadcast setup message. In such cases, the base station may define a new SIB in the manner described below. Alternatively, the base station may consider alternative approaches, such as modifying the existing USD (user service description): for example, the base station may define a new SIB that includes a list of service area IDs and service area details (base points and radii) for each MBS service area ID. Alternatively, the base station may modify the USD to include such information.

[0270] Additionally, according to an embodiment of the present disclosure, a base station may include only information regarding the mapping between an MBS session ID and a corresponding intended service area ID in an MBS broadcast setup message. Subsequently, the base station may define a new SIB to include service area details (base point and radius) for each MBS intended service area ID. Alternatively, the base station may apply a method of modifying the USD.

[0271] Meanwhile, according to one embodiment of the present disclosure, 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.

[0272] FIG. 10 is a conceptual diagram showing embodiments of service areas divided into allowed service areas and prohibited areas.

[0273] Referring to FIG. 10, geographical information for distinguishing and setting allowed service areas and prohibited areas can be defined by utilizing the SIB25 format for signaling TN coverage in NTN, through the coordinates of a reference point for the center location of each service area (SA) and distance (radius, diameter) information for each service area in a circular shape. This approach can be useful for representing various forms of intended service areas through NW implementation, and the shape of the intended service area can be more accurately approximated by individually defining circular service areas corresponding to each of the allowed and prohibited areas. To this end, the service area information may 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, service areas can be distinguished by service area identifiers 1 through 7 and may be distributed across Country 1 and Country 2. Here, service areas 1 (SA ID1) to 6 (SA ID 6) may be allowed service areas, and service area 7 (SA ID 7) may be prohibited service areas.

[0274] FIG. 11 is a conceptual diagram illustrating embodiments of a method for associating service area information with MBS services.

[0275] Referring to Fig. 11, service area information can be provided through a new SIB. The service area information may be associated with session information linked to the corresponding broadcast service (MBS service). To this end, various types of identification information for the broadcast service session (e.g., session ID, TGMI, G-RNTI, etc.) may be considered. Accordingly, the service area information regarding the service area that each MBS service intends to provide must include at least 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.

[0276] According to one embodiment of the present disclosure, for the association of service area information and MBS sessions, a first method in which one service area identifier is mapped to a plurality of MBS session identifiers and a second method in which a plurality of service area identifiers are mapped to one MBS session identifier may be considered.

[0277] In this case, the second method may be preferred in terms of providing flexibility to configure independent service areas for each MBS session, and such many-to-one (N-to-1) mapping can be used to uniquely identify service area portions of MBS services within a 5G core network, but is not limited to this.

[0278] Meanwhile, according to an embodiment 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 in the entire cell area, and there may be no need to restrict access to MBS broadcasts outside the intended service area.

[0279] In this regard, according to one embodiment of the present invention, a terminal may operate as follows regarding frequency selection for an MBS service. During the cell reselection evaluation process, the terminal may give priority to a corresponding frequency if the terminal is located within a geographical area associated with the MBS service of interest or currently being received. For example, if the USD provides multiple frequencies for a service of interest to the terminal, it may be easier to determine which frequency to select based on the association with the geographical area information of the service.

[0280] In addition, according to one embodiment of the present invention, the MBS broadcast service area may be provided in a manner similar to a TN coverage area list. Specifically, it may be provided in the form of a list of reference locations and corresponding cell radii.

[0281] In addition, regarding the terminal's recognition of the frequency of a service of interest, the terminal may perform mapping between the frequency and the MBS broadcast service through existing procedures (e.g., SIB21 or USD). The terminal must know the frequency of the service of interest before receiving the MBS broadcast service, and this frequency information can be obtained from SIB21 or USD. Therefore, it may be sufficient to map a provided geographic area to one or more MBS broadcast service frequencies.

[0282] Meanwhile, service area information regarding the effective range of the MBS service disclosed in this disclosure may be used for the following purposes. First, the service area information may be used to support location-dependent broadcast services within an NTN cell or a portion of a plurality of NTN cells. Next, the service area information may be used for the purpose of preventing unnecessary terminal operations, including the operation of receiving MBS-related SI and / or MBS sessions outside the effective range (service area) of the MBS service.

[0283] Regarding the first purpose, location-dependent broadcast services may be intended to distribute different content data to different MBS service areas. To support these location-dependent broadcast services, similar to existing MBS mechanisms, a specific part of the service area of ​​an MBS service may be uniquely identified within 5GC by using an identifier (ID) for service area information consisting of a reference point (reference location, reference location) and a radius within an NTN cell or a part of a plurality of NTN cells, together with an MBS session identifier (ID).

[0284] In this regard, for association with MBS sessions, service area information may 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 independent service areas for each MBS session, but is not limited thereto.

[0285] In summary, to support location-dependent broadcast services, specific parts of the service area of ​​an MBS service can be uniquely identified within the 5GC by using a service area ID together with an MBS session ID, similar to existing MBS mechanisms. In this case, multiple service area IDs can be mapped to a single MBS session ID to establish an association between the service area and the MBS session. In this regard, the base station may provide the following information to the terminal through one or more SIBs to display details of service area information regarding the valid range of the MBS service associated with the MBS session ID to the terminal.

[0286] -MBS Session ID List

[0287] - List of service zone IDs for the valid scope of the MBS service corresponding to each MBS session ID

[0288] - Details of the service area by each MBS Intended Service Area ID (base point and radius information included in the service area information)

[0289] Below, we will explain the techniques for achieving Service Continuity related to MBS services.

[0290] 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 neighbor carrier frequency may be introduced into SIB21. As a second method, intended service area information associated with neighbor cells as indicated in MCCH may be utilized.

[0291] In this regard, according to one embodiment of the present invention, an MBS broadcasting-enabled terminal may receive MBS broadcasting services only at a specific frequency, and to this end, the terminal may operate to prioritize the specific frequency by considering the following conditions. As a first condition, a condition may be considered in which SIB20 is included in the SIB1 scheduling information of the cell re-selected by the terminal due to frequency priority assignment caused by MBS. As a second condition, a condition may be considered in which one or more MBS FSAIs of the corresponding frequency are indicated in the SIB21 of the serving cell, and the same MBS FSAI is also indicated in the MBS User Service Description (USD) of this MBS broadcasting service as specified in TS 26.517, or in which SIB21 is not provided in the serving cell and the corresponding frequency is included in the USD of this service, or in which SIB21 is provided in the serving cell but no frequency mapping for the corresponding service is provided and the corresponding frequency must be included in the USD of this service.

[0292] In addition, according to one embodiment of the present invention, when an MBS broadcasting-enabled terminal is receiving an MBS broadcasting service or a configuration for reception is prepared, SIB20 is included in the cell SIB1 scheduling information of the MBS frequency monitored by the terminal, and as long as the second condition described above is satisfied for the serving cell, the terminal may consider a cell reselection candidate frequency that cannot receive the MBS broadcasting service during the MBS broadcasting session as having the lowest priority.

[0293] Meanwhile, considering that SIB21 includes a mapping relationship between the current and / or adjacent carrier frequency and the MBS FSAI, this existing mechanism for MBS service continuity can assume that the MBS service area is mapped to one or more cells. However, in NTN systems, even if the two aforementioned conditions are satisfied, it may not function effectively because the terminal may not consider the frequency as the highest priority if the MBS intended service area of ​​the corresponding frequency does not include the intended service area of ​​the MBS session that the terminal is receiving or interested in.

[0294] To solve these problems, according to one embodiment of the present invention, a new mapping relationship between current and / or adjacent carrier frequencies and MBS intent service area IDs can be defined, and a list of carrier frequencies and a list of MBS intent service area IDs for each carrier frequency can be included in SIB21.

[0295] As another example, the terminal can update existing conditions for performing MBS broadcast service cell reselection based on service area information regarding the valid range of the MBS service. Specifically, in addition to the two existing conditions, a third condition may be added such that a service area ID for the valid range of one or more MBS services of the corresponding frequency is displayed on the SIB21 of the serving cell, and that the same service area ID for the valid range of the MBS service must also be displayed for this MBS broadcast service session.

[0296] According to one embodiment of the present disclosure, MBS service continuity can be considered in the following two aspects. In the first aspect, a serving base station may indicate a list of neighboring cells that provide the same MBS broadcast service in 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.

[0297] In a second aspect, NR MBS can support MBS frequency layer priority settings for MBS broadcast sessions, wherein base stations provide MBS frequency service area (MBS FSA) identifiers supported at each frequency, which may include both the same frequency and different frequencies.

[0298] During an MBS broadcast session, the following two conditions may be met: An MBS broadcast-enabled terminal may receive the MBS broadcast service; or, an MBS broadcast-enabled terminal may be interested in receiving the MBS broadcast service. An MBS broadcast-enabled terminal may receive the MBS broadcast service only by camping on the frequency providing the MBS broadcast service. In such a case, the terminal may regard that frequency as having the highest priority.

[0299] The first condition may be that SIB20 is included in the SIB1 scheduling information of the cell re-selected by the terminal due to frequency priority assignment caused by MBS. The second condition is satisfied if any one of the following applies.

[0300] - One or more MBS FSAIs of the corresponding frequency may be listed in the serving cell's SIB21, and the same MBS FSAI is also listed in the MBS User Service Description (USD) of the MBS broadcast service.

[0301] - SIB21 may not be provided in the serving cell, and the corresponding frequency is included in this service's USD.

[0302] - SIB21 is provided in the serving cell but may not provide frequency mapping for the corresponding service, and the corresponding frequency is included in the USD of these services.

[0303] Additionally, an MBS broadcast-enabled terminal may receive the MBS broadcast service. Alternatively, an MBS broadcast-enabled terminal may be interested in receiving the MBS broadcast service. In such cases, SIB20 may be included in the cell SIB1 scheduling information of the MBS frequency monitored by the terminal, and the aforementioned second condition may be satisfied for the serving cell. The terminal may consider cell reselection candidate frequencies that cannot receive the MBS broadcast service during the MBS broadcast session as having the lowest priority.

[0304] Meanwhile, SIB21 may include a mapping relationship between the current and / or adjacent carrier frequency and the MBS FSAI. Considering this, it can be assumed that in existing mechanisms for MBS service continuity, the MBS service area is mapped to one or more cells. Conditions 1 and 2 described above may be satisfied in an 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 can be received by the terminal. Alternatively, the MBS intended service area of ​​the corresponding frequency may not include the intended service area of ​​the MBS session of interest to the terminal. In such a case, it may not operate effectively because the terminal may not regard the corresponding frequency as the highest priority.

[0305] 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 may include the following information in SIB21.

[0306] - List of carrier frequencies (already present in SIB21)

[0307] - List of MBS Intended Service Area IDs by Carrier Frequency

[0308] As another example, based on service area information regarding the valid range of the MBS service, the existing conditions for the terminal to perform MBS broadcast service cell reselection can be updated as follows.

[0309] - An MBS broadcast-enabled terminal may receive an MBS broadcast service. Or, an MBS broadcast-enabled terminal may be interested in receiving an MBS broadcast service. An MBS broadcast-enabled terminal may receive an MBS broadcast service by camping on a frequency that provides an MBS broadcast service. In such a case, the terminal may consider the frequency to have the highest priority during an MBS broadcast session when the following three conditions (conditions 1 through 3) are met.

[0310] (Condition 1) SIB20 is included in the SIB1 scheduling information of the cell re-selected by the UE due to frequency priority assignment by MBS.

[0311] (Condition 2) Satisfies one of the following

[0312] ● One or more MBS FSAIs of the corresponding frequency are displayed in the serving cell's SIB21. The same MBS FSAIs are also displayed in the MBS User Service Description (USD) of the MBS broadcast service.

[0313] ● SIB21 may not be provided in the serving cell. The corresponding frequency is included in the USD of these services.

[0314] ● SIB21 is provided in the serving cell, but it may not provide frequency mapping for the corresponding service. The corresponding frequency is included in this service's USD.

[0315] (Condition 3) Service area IDs for the effective range of one or more MBS services of the corresponding frequency may be displayed on the SIB21 of the serving cell. Service area IDs for the effective range of the same MBS service may also be displayed for this MBS broadcast service session.

[0316] In other words, two conditions of the existing mechanism may be satisfied in an 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 of interest to the terminal. In such cases, the terminal may not prioritize that frequency. For this reason, the existing mechanism for MBS service continuity may not function effectively.

[0317] 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. Additionally, the present disclosure may include relevant information in SIB21. Alternatively, the present disclosure may apply improvements to update existing MBS service continuity mechanisms for performing MBS broadcast service cell reselection at a terminal based on service area information regarding the effective range of the MBS service.

[0318] According to an embodiment of the present disclosure, a single MBS service may be broadcast over different frequency carriers in an NTN. This may mean that in a large-scale or regionally partitioned MBS deployment, the MBS session ID may be separated from the physical layer carrier. Through this structure, the same MBS session may be broadcast over different frequency carriers in neighboring cells. As a result, optimization of frequency reuse, compliance with regional spectrum allocation, and assurance of service continuity for UEs moving through different regions may be possible.

[0319] To support efficient service continuity, the intended service area identifier may be associated with a frequency carrier. This association may be included in SIB21. SIB21 may include intended service area information associated with the current and / or neighboring frequency carriers. This allows the terminal to select an appropriate frequency carrier based on its location and the MBS service of interest, and to maintain service continuity during cell reselection.

[0320] The terminal can select a frequency with priority when it is located within the intended service area of ​​the MBS service of interest. The terminal can lower the priority of the corresponding frequency when it is not located within the intended service area of ​​the MBS service of interest. This mechanism can prevent the unnecessary prioritization of frequencies for which the terminal cannot actually receive the service, reduce power consumption, and enable the efficient utilization of network resources.

[0321] 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 enabling the terminal to set priority on the MBS frequency provided by the MBS session configured to receive. In this regard, as 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.

[0322] Accordingly, the terminal can operate to process the corresponding MBS frequency with the highest priority based on its location and service area information for each MBS frequency during cell reselection. In addition, regarding the relationship between the service area and the MBS session, a first method in which a Frequency Service Area Identifier (FSAI) is associated with a single MBS broadcast session, a second method in which a single Frequency Service Area Identifier (FSAI #x) is associated with multiple MBS broadcast sessions, etc., may be applied.

[0323] At this time, 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 that the service area can be simply provided through each FSAI, whereas in the case of the second method, the explicit MBS broadcast session of each FSA and the service area for it need to be clearly indicated.

[0324] According to one embodiment of the present disclosure, regarding the association between an MBS session and a service area, a serving base station may provide an associated service area within a neighbor cell for each broadcast service session in a neighbor cell configuration. Through this, a terminal may identify the service area information in the neighbor 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.

[0325] In addition, in the case of cell reselection, the terminal must determine frequency priority based on whether the MBS broadcast service configured to be received is provided by the corresponding frequency at the current location. Specifically, the service area of ​​the MBS broadcast service provided for each frequency may be provided via SIB21, and the terminal can dynamically determine frequency priority based on this.

[0326] According to one embodiment of the present disclosure, a non-terrestrial network may utilize mapped cell IDs from the non-terrestrial network for MBS broadcast services. An access and mobility management function (AMF) may provide a base station with service area information for MBS broadcast services. The service area information for MBS broadcast services may include a list of cell IDs, a list of tracking area identifiers, and / or a list of MBS intended service areas.

[0327] The mapping between mapped cell IDs and geographic areas can be configured in a radio access network (RAN) and a core network. A specific geographic location can be mapped to multiple mapped cell IDs. These mapped cell IDs can be configured to represent different geographic areas (e.g., overlapping and / or different sizes).

[0328] The base station may be responsible for configuring a mapped cell ID based on location information received from the terminal. This mapping may be pre-configured. This mapping may be left to implementation according to operator policy, for example. This mapped cell ID can be used to efficiently transmit the terminal's location information to the core network and can support the regional provision of MBS broadcast services.

[0329] 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.

[0330] Referring to FIG. 12, in step S121, the base station may transmit service area information to the terminal, which includes information on the effective range of the MBS service for each of the plurality of service areas pre-configured to provide the MBS service. Next, in step S122, the base station may transmit an MBS transmission signal to provide the MBS service to the terminal.

[0331] In the foregoing description, steps S121 to S122 may be further subdivided into additional steps or combined into fewer steps, depending on an embodiment of the present disclosure. Additionally, some steps may be omitted as necessary, and the order between steps may be changed. The method of the non-terrestrial network base station illustrated in FIG. 12 may be performed by the base station described above. Therefore, even if omitted, the description of the base station may be equally applicable to the description of FIG. 12.

[0332] FIG. 13 is a flowchart illustrating embodiments of a method for providing multicast and broadcast services in a non-terrestrial network of a terminal.

[0333] Referring to FIG. 13, in step S131, the terminal can 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 can obtain location information of the terminal and match the obtained location information with the received service area information.

[0334] Meanwhile, according to one embodiment of the present disclosure, in step S132, the base station or the terminal may verify the location of the terminal to confirm the accuracy of the terminal's location information (e.g., country area ID or RA-RNTI (random access RNTI), etc.). Through this, the base station may know if the location reported by the terminal is unreliable (e.g., if the terminal has provided false information in the past or if the terminal is in a state of high mobility). At this time, the base station may trigger network-based location and location information.

[0335] In this regard, when a terminal accesses the network, the NTN base station may verify the terminal's country area ID and / or RA-RNTI. If the network or base station trusts the country area ID and / or RA-RNTI, the network or base station may authorize the terminal's access. Alternatively, if the network or base station does not trust the terminal's country area ID and / or RA-RNTI, the network or base station may estimate the terminal's actual location. Based on the estimate, if the terminal's country area ID and / or RA-RNTI are accurate, the network or base station may allow access to the terminal. Otherwise, the network or base station may block the terminal's access.

[0336] 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 set a trust period during which the country area ID or RA-RNTI reported by the terminal is trusted as valid based on historical 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 located at a border may have a smaller timer value set compared to a terminal located in a wide country.

[0337] Next, in step S133, the terminal can determine whether the terminal is located within the corresponding service area. In other words, in step S133, the terminal can verify whether the terminal is located within the corresponding service area based on its location information. If, as a result of the determination in step S133, the terminal is located within the service area, in step S134, the terminal can receive MBS services from the base station using an MBS transmission signal associated with the corresponding service area information.

[0338] In contrast, if, as a result of the determination in step S133, it is determined that the terminal is located outside the service area (in other words, if the location information does not match the service area information), the terminal may block the MBS service associated with the 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 service area information from a base station. The terminal may block the MBS service by not performing decoding for the MBS transmission signal.

[0339] According to another embodiment of the present disclosure, at step S135, the terminal may block the MBS service in a manner such that it does not receive an MBS transmission signal associated with the corresponding service area information from the base station. In this regard, some location-dependent broadcast services may need to be accessed only within areas permitted in different cities and / or countries due to various MBS service frameworks (e.g., regulations, billing, etc.). In a TN system, the network or base station may not impose restrictions on the terminal's operation regarding service reception. Furthermore, the network or base station may control MBS service accessibility by identifying an accessible cell list or a tracking area list.

[0340] In the case of NTN, location-dependent MBS service areas may exist within a portion of an NTN cell. Therefore, unless improvements such as the assignment of location- and service area-specific group IDs for network verification are introduced, existing mechanisms may not function effectively in NTN networks. Accordingly, to effectively manage service accessibility based on the geographical location of the terminal, the following terminal behaviors related to MBS service reception can be defined.

[0341] Specifically, the terminal may receive service area information regarding the MBS broadcast service. Additionally, 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 may be restricted.

[0342] 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) that has no service area, the terminal may follow the existing MCCH acquisition procedure.

[0343] As 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. As yet another example, if a terminal is configured to receive TMGI #3 and is located within the service area of ​​that TMGI, the terminal may perform MCCH acquisition and reacquisition at times T0 and T2, but may not perform them at time T1.

[0344] In the foregoing description, steps S131 through S135 may be further divided into additional steps or combined into fewer steps, depending on an embodiment of the present disclosure. Additionally, some steps may be omitted as necessary, and the order between steps may be changed. The method of a terminal for providing multicast and broadcast services in a non-terrestrial network illustrated in FIG. 13 may be performed by the terminal described above. Therefore, even if omitted, the description of the terminal may be equally applicable to the description of FIG. 13.

[0345] FIG. 14 is a flowchart illustrating embodiments of a method for providing multicast and broadcast services in a non-terrestrial network of a terminal.

[0346] Referring to FIG. 14, when a base station forms a global mobile cell, it can transmit reference time information for the corresponding service area along with service area information to a terminal. In this way, when the base station forms a global mobile cell, at step S141, the terminal can receive reference time information for the corresponding service area along with service area information.

[0347] Next, in step S142, the terminal can calculate information regarding the service area after a predetermined time elapsed according to the movement of the satellite corresponding to the base station, based on the astronomical ephemeral information obtained from SIB19, etc.

[0348] In the description above, steps S141 to S142 may be further divided into additional steps or combined into fewer steps, depending on the embodiment of the present invention. Additionally, some steps may be omitted as necessary, and the order between steps may be changed.

[0349] A method for a terminal to receive MBS services using service area information for a mobile earth cell illustrated in FIG. 14 can be performed by the terminal described above. Therefore, even if the content described for the terminal is omitted, it can be applied equally to the description of FIG. 14.

[0350] FIG. 15 is a conceptual diagram showing embodiments of the range of the intended service area list transmitted as a signal in a specific cell.

[0351] Referring to Fig. 15, the following three options (three cases) can be considered to determine the range of the intended service area list that must be transmitted as a signal through a new SIB in a specific cell.

[0352] Option 1 (Case 1): Include the entire geographic area set in the network

[0353] Option 1 may include the entire geographic area set by the network in the list of intended service areas.

[0354] Option 2 (Case 2): Include serving cell and all adjacent cells

[0355] Option 2 allows the intended service area list to include geographic areas within the serving cell and all adjacent cells.

[0356] Option 3 (Case 3): Include only serving cells and nested adjacent cells

[0357] Option 3 allows the intended service area list to include only the geographic areas of the serving cell and adjacent cells that overlap with that cell.

[0358] If Option 1 is selected:

[0359] The intended service area list may not need to be updated frequently, even in Earth Moving Cell (EMC) scenarios. It can be easily referenced using an index within the list. However, this may require higher signaling overhead compared to other options.

[0360] If Option 2 or Option 3 is selected:

[0361] In EMC scenarios, frequent updates to the list of intended service areas may be required. As the list is modified frequently, it may be difficult to use an index as a pointer. Option 3 can reduce signal overhead, but it may affect service continuity because it does not fully support the intended service area information of adjacent cells.

[0362] As a technical means for achieving the above-mentioned technical problem, a method of a terminal operating in a non-terrestrial network according to one embodiment of the present disclosure may include receiving information on an intended service area (ISA), acquiring location information of the terminal, and determining whether to acquire a multicast control channel (MCCH) based on the location information of the terminal and the information on the intended service area. If the terminal is located outside all intended service areas, the initial acquisition of the MCCH may be skipped.

[0363] A method of a terminal operating in a non-terrestrial network according to one embodiment of the present disclosure may include receiving an MCCH change notification and determining whether to reacquire the MCCH based on the location information of the terminal and the intended service area information. The step of determining whether to reacquire the MCCH may skip MCCH reacquisition if the terminal is not located in any of the intended service areas. The MCCH change notification may include information regarding a dedicated field indicating a change in mapping between the MBS service and the intended service area.

[0364] The step of determining whether to reacquire the MCCH allows the MCCH to be reacquired regardless of the terminal's location if the dedicated field indicates a mapping change. The intended service area information may be received through a System Information Block (SIB). The step of determining whether to acquire the MCCH allows the MCCH to be acquired if the terminal is located within an intended service area associated with the MBS service configured for the terminal to receive. The intended service area information may include a plurality of intended service area identifiers (ISA IDs) and geographical information for each intended service area. To reduce the frequency of MCCH reacquisition performed in response to the MCCH change notification, a service area change cycle that is relatively longer than the MCCH change cycle may be applied.

[0365] A method of a terminal operating in a non-terrestrial network according to one embodiment of the present disclosure may include the step of calculating a change in a service area according to satellite movement using reference time information received together with the intended service area information and satellite ephemeris information when the terminal belongs to a Earth moving cell. A method of a base station operating in a non-terrestrial network according to one embodiment of the present disclosure may include the step of transmitting intended service area (ISA) information to the terminal, the information including information that enables the terminal to determine whether to acquire an MCCH based on the location of the terminal.

[0366] A base station operating in a non-terrestrial network according to one embodiment of the present disclosure may include a processor and a memory that stores one or more instructions executed by said processor. The one or more instructions may be executed to transmit to said terminal information intended for service area (ISA) including information that enables said terminal to determine whether to acquire an MCCH based on the location of said terminal. The above-described means for solving the problem are merely exemplary and should not be interpreted as intended to limit the present disclosure. In addition to the above-described exemplary embodiments, additional embodiments may exist in the drawings and the detailed description of the invention.

[0367] According to the means for solving the problem of the present disclosure described above, in a non-terrestrial network using GEO, LEO satellites, etc., having a large cell radius, it is possible to efficiently provide multicast and broadcast services specialized for specific areas, such as by country or region, while minimizing the impact of existing TN and NTN standards and technologies. According to the means for solving the problem of the present disclosure described above, in a satellite-based NTN such as GEO and LEO, it is possible to provide an apparatus and method for providing multicast and broadcast services in a non-terrestrial network that can distinguish receivable multicast and broadcast services according to the location of terminals within the cell. However, the effects obtainable from the present disclosure are not limited to those described above, and other effects may exist.

[0368] The methods according to the present invention may be implemented in the form of program instructions that can be executed through various computer means and recorded on a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, etc., either alone or in combination. The program instructions recorded on the computer-readable medium may be those specifically designed and configured for the present invention, or they may be those known and available to those skilled in the art of computer software.

[0369] 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 machine code, such as that produced by a compiler, as well as high-level language code that can be executed by a computer using an interpreter, etc. The aforementioned hardware devices may be configured to operate as at least one software module to perform the operation of the present invention, and vice versa.

[0370] The operation of the method according to an embodiment 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 all types of recording devices in which information that can be read by a computer system is stored. Additionally, the computer-readable recording medium may be distributed across networked computer systems, allowing the computer-readable program or code to be stored and executed in a distributed manner.

[0371] In addition, computer-readable recording media may include hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, and flash memory. Program instructions may include machine code, such as that generated by a compiler, as well as high-level language code that can be executed by a computer using an interpreter, etc.

[0372] Some aspects of the present disclosure have been described in the context of a device, but may also be described according to 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 according to 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 of the most important method steps may be performed by such a device.

[0373] In the 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 the embodiments, the field-programmable gate array may operate with a microprocessor to perform one of the methods described herein. Generally, it is preferable that the methods be performed by some hardware device.

[0374] Although the present disclosure has been described with reference to preferred embodiments, those skilled in the art will understand that various modifications and changes can be made to the present disclosure without departing from the spirit and scope of the present disclosure as set forth in the following claims.

Claims

1. As a method of a terminal, A step of receiving information about at least one intended service area (ISA) of multicast and broadcast services (MBS) from a non-terrestrial base station; A step of obtaining location information of the above terminal; and A step including determining whether to initiate a broadcast MRB (MBS radio bearer) setup procedure based on the above location information and information regarding at least one ISA. Method of the terminal.

2. In Claim 1, The step of determining whether to initiate a broadcast MRB setup procedure based on the above location information and information regarding the at least one ISA is: A step of determining whether the terminal is located within the at least one ISA based on the above location information and information regarding the at least one ISA; and A step including determining whether to initiate the broadcast MRB setting procedure based on the above judgment result, Method of the terminal.

3. In Claim 2, The step of determining whether to initiate the broadcast MRB setting procedure based on the above judgment result is: The method includes the step of deciding not to initiate the broadcast MRB setup procedure based on the fact that the terminal is not located within at least one ISA, and Based on the decision not to initiate the above MRB setup procedure, the acquisition operation of the initial MCCH (MBS control channel) is omitted, Method of the terminal.

4. In Claim 1, A step of receiving the MCCH change notification from the non-terrestrial network base station by monitoring the MCCH change notification; and Based on the change in MCCH, the method further includes the step of determining whether to reacquire MCCH based on the location information and information regarding at least one ISA. Method of the terminal.

5. In Claim 4, The step of determining whether to reacquire the MCCH based on the above location information and information regarding the at least one ISA is: A step of determining whether the terminal is located within the at least one ISA based on the above location information and information regarding the at least one ISA; and A method further comprising the step of determining whether to reacquire the MCCH based on the above judgment result. Method of the terminal.

6. In Claim 5, The step of determining whether to reacquire the MCCH based on the above judgment result is: A step comprising deciding not to reacquire the MCCH based on the fact that the terminal is not located within at least one ISA. Method of the terminal.

7. In Claim 1, A method further comprising the step of receiving warning area information associated with a warning service at the above-mentioned non-ground base station. Method of the terminal.

8. In Claim 7, The step of receiving warning area information associated with a warning service at the above-mentioned non-ground base station is, A method comprising the step of receiving a first system information block (SIB) containing warning area coordinates, which is warning area information, from the above-mentioned non-ground base station. Method of the terminal.

9. In Claim 7, The step of receiving warning area information associated with a warning service at the above-mentioned non-ground base station is, A step of receiving at least one second SIB including at least one warning area segment, which is the warning area information, from the above-mentioned non-ground base station; and A step comprising determining the game area information from at least one warning area segment, Method of the terminal.

10. In Claim 1, The method further includes the step of receiving an MBS broadcast setting message containing a list of MBS session information via MCCH, and The above MBS session information list includes mapping information between at least one TMGI (temporary mobile group identity) and at least one ISA ID (identifier), Method of the terminal.

11. In Claim 10, The above mapping information indicates that the at least one TMGI is associated with different ISAs, Method of the terminal.

12. In Claim 1, The step of determining whether to initiate a broadcast MRB setup procedure based on the above location information and information regarding the at least one ISA is: A step of determining an ISA ID corresponding to at least one ISA based on the above location information; A step of determining a TMGI associated with an ISA ID based on mapping information between at least one TMGI (temporary mobile group identity) and at least one ISA ID; and A step including determining whether to initiate the broadcast MRB setup procedure for the MBS session corresponding to the determined TMGI, Method of the terminal.

13. As a method of a non-terrestrial base station, A step of transmitting information about at least one intended service area (ISA) of multicast and broadcast services (MBS) to a terminal; and A step comprising transmitting an MBS broadcast setting to the terminal to determine whether to initiate a broadcast MRB (MBS radio bearer) setting procedure at the terminal based on information regarding at least one ISA and location information of the terminal. Non-ground base station method.

14. In Claim 13, The above MBS broadcasting setting includes an MBS session information list, and the MBS session information list includes mapping information of at least one TMGI (temporary mobile group identity) and at least one ISA ID (identifier). Non-ground base station method.

15. In Claim 13, The method further includes the step of transmitting an MCCH (MBS control channel) change notification to the terminal based on the change in the above MBS broadcast settings. Non-ground base station method.

16. In Claim 13, The method further includes the step of transmitting warning area information associated with the warning service to the terminal, The above warning area information is transmitted through at least one of a first SIB including warning area coordinates or at least one second SIB including at least one warning area segment, Non-ground base station method.

17. As a terminal, It includes at least one processor, The above at least one processor is the terminal, Receiving information about at least one intended service area (ISA) of multicast and broadcast services (MBS) from a non-terrestrial base station; Obtain location information of the above terminal; and Causing to determine whether to initiate a broadcast MRB (MBS radio bearer) setup procedure based on the above location information and information regarding the above at least one ISA, Terminal.

18. In Claim 17, In order to determine whether to initiate a broadcast MRB setup procedure based on the above location information and information regarding the above at least one ISA, the above at least one processor, the terminal, Determining whether the terminal is located within the at least one ISA based on the above location information and information regarding the at least one ISA; and Causing a decision not to initiate the broadcast MRB setup procedure based on the fact that the terminal is not located within at least one ISA, and Based on the decision not to initiate the above MRB setup procedure, the acquisition operation of the initial MCCH (MBS control channel) is omitted, Terminal.

19. In Claim 17, The above at least one processor is the terminal, By monitoring MCCH change notifications, the MCCH change notifications are received from the non-ground base station; Based on the change in MCCH, determining whether the terminal is located within the at least one ISA based on the location information and information regarding the at least one ISA; and Causing a decision not to reacquire the MCCH based on the fact that the terminal is not located within at least one ISA, Terminal.

20. In Claim 17, The above at least one processor is the terminal, Further causing the above-mentioned non-ground base station to receive warning area information associated with the warning service, and The above warning area information is received through at least one of a first SIB containing warning area coordinates or at least one second SIB containing at least one warning area segment, Terminal.

Images