Device and method for supporting efficient pre-synchronization of UE during handover in NTN in wireless communication system

Abstract

The present disclosure relates to a wireless communication system. Specifically, the present disclosure relates to a device and method for supporting efficient pre-synchronization of a user equipment (UE) during handover in a non-terrestrial network (NTN) in a wireless communication system.

Description

Device and method for supporting efficient pre-synchronization of UE during handover in NTN in a wireless communication system

[0001] The present disclosure relates to a wireless communication system. Specifically, the present disclosure relates to an apparatus and method for supporting efficient pre-synchronization of user equipment (UE) during handover in a Non-Terrestrial Network (NTN) in a wireless communication system.

[0002]

[0003] Wireless communication systems are being widely deployed to provide various types of communication services, such as voice and data. Generally, a wireless communication system is a multiple access system capable of supporting communication with multiple users by sharing available system resources (bandwidth, transmission power, etc.). Examples of multiple access systems include CDMA (Code Division Multiple Access), FDMA (Frequency Division Multiple Access), TDMA (Time Division Multiple Access), OFDMA (Orthogonal Frequency Division Multiple Access), and SC-FDMA (Single Carrier Frequency Division Multiple Access).

[0004]

[0005] To solve the aforementioned problems, the present disclosure provides an apparatus and method for supporting efficient pre-synchronization of a terminal (user equipment, UE) during handover in a Non-Terrestrial Network (NTN) in a wireless communication system.

[0006] The technical problems to be solved in this disclosure are not limited to those mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art to which this disclosure belongs from the description below.

[0007]

[0008] According to various embodiments of the present disclosure, a method performed by a terminal (user equipment, UE) is provided, comprising: receiving time-series synchronization information from a source base station, the time-series synchronization information including three-dimensional location information of candidate target base stations for handover of the terminal and time-varying prediction information for said three-dimensional location information; determining parameters for synchronization of said candidate target base stations based on said received time-series synchronization information; and transmitting a synchronization signal to a specific target base station of one of said candidate target base stations based on said parameters.

[0009] According to various embodiments of the present disclosure, a method performed by a source base station comprises: receiving time-series synchronization information from candidate target base stations for handover of a terminal (user equipment, UE), the time-series synchronization information including three-dimensional location information of the candidate target base stations and time-varying prediction information regarding the three-dimensional location information; and transmitting the time-series synchronization information to the terminal, wherein the synchronization between the terminal and a specific target base station among the candidate target base stations is based on parameters associated with the time-series synchronization information.

[0010] According to various embodiments of the present disclosure, a terminal (user equipment, UE) is provided, comprising: a transceiver; at least one processor; and at least one memory operably connected to the at least one processor and storing instructions for performing operations when executed by the at least one processor, wherein the operations include all steps of a method performed by the terminal according to various embodiments of the present disclosure.

[0011] According to various embodiments of the present disclosure, a source base station is provided, comprising: a transceiver; at least one processor; and at least one memory operably connected to the at least one processor and storing instructions for performing operations when executed by the at least one processor, wherein the operations include all steps of a method performed by the source base station according to various embodiments of the present disclosure.

[0012] According to various embodiments of the present disclosure, a control device for controlling a terminal (user equipment, UE) in a wireless communication system comprises at least one processor and at least one memory operably connected to said at least one processor, wherein the at least one memory stores instructions for performing operations based on execution by said at least one processor, and said operations include all steps of a method performed by the terminal according to various embodiments of the present disclosure.

[0013] According to various embodiments of the present disclosure, a control device for controlling a source base station in a wireless communication system comprises at least one processor and at least one memory operably connected to said at least one processor, said at least one memory stores instructions for performing operations based on execution by said at least one processor, said operations include all steps of a method performed by a source base station according to various embodiments of the present disclosure.

[0014] According to various embodiments of the present disclosure, one or more non-transitory computer-readable media storing one or more instructions, wherein the one or more instructions perform operations based on execution by one or more processors, and said operations include all steps of a method performed by a terminal according to various embodiments of the present disclosure.

[0015] According to various embodiments of the present disclosure, one or more non-transitory computer-readable media storing one or more instructions, wherein the one or more instructions perform operations based on execution by one or more processors, and the operations include all steps of a method performed by a source base station according to various embodiments of the present disclosure.

[0016]

[0017] To solve the aforementioned problems, the present disclosure may provide an apparatus and method for supporting efficient pre-synchronization of a terminal (user equipment, UE) during handover in a Non-Terrestrial Network (NTN) in a wireless communication system.

[0018]

[0019] The drawings attached below are intended to aid in understanding the present disclosure and may provide embodiments of the present disclosure together with the detailed description. However, the technical features of the present disclosure are not limited to specific drawings, and the features disclosed in each drawing may be combined with one another to form new embodiments. Reference numerals in each drawing may denote structural elements.

[0020] FIG. 1 is a diagram illustrating an example of physical channels used in a system applicable to the present disclosure and a general signal transmission method using them.

[0021] FIG. 2 is a drawing illustrating an example of a wireless frame structure used in a system applicable to the present disclosure.

[0022] FIG. 3 is a drawing illustrating an example of a slot structure used in a system applicable to the present disclosure.

[0023] FIG. 4 is a drawing illustrating an example of a slot structure of a wireless frame used in a system applicable to the present disclosure.

[0024] FIG. 5 is a diagram illustrating an example of data flow in a system applicable to the present disclosure.

[0025] FIG. 6 is a drawing illustrating an example of the structure of an NG-RAN in a system applicable to the present disclosure.

[0026] FIG. 7 is a diagram illustrating an example of an interface protocol structure for F1-C in a system applicable to the present disclosure.

[0027] FIG. 8 is a drawing illustrating an example of an urban air mobility (UAM) aircraft in a system applicable to the present disclosure that includes an onboard system (e.g., a system capable of operating as a donor gNB or UE relay) connected to an NTN and / or ground network (TN) to provide extended backhaul connectivity for passenger terminals.

[0028] FIG. 9 is a drawing illustrating an example of a signal flow diagram according to various embodiments of the present disclosure.

[0029] FIG. 10 is a drawing illustrating an example of a signal flow diagram according to various embodiments of the present disclosure.

[0030] FIG. 11 is a drawing illustrating an example of the operation process of a terminal in a system applicable to the present disclosure.

[0031] FIG. 12 is a diagram illustrating an example of the operation process of a source base station in a system applicable to the present disclosure.

[0032] FIG. 13 is a drawing illustrating an example of the structure of a first node and a second node in a system applicable to the present disclosure.

[0033]

[0034] In various embodiments of the present disclosure, "A or B" may mean "only A," "only B," or "both A and B." Alternatively, in various embodiments of the present disclosure, "A or B" may be interpreted as "A and / or B." For example, in various embodiments of the present disclosure, "A, B or C" may mean "only A," "only B," "only C," or "any combination of A, B and C."

[0035] In various embodiments of the present disclosure, a slash ( / ) or a comma used may mean "and / or." For example, "A / B" may mean "A and / or B." Accordingly, "A / B" may mean "only A," "only B," or "both A and B." For example, "A, B, C" may mean "A, B or C."

[0036] In various embodiments of the present disclosure, "at least one of A and B" may mean "only A," "only B," or "both A and B." Additionally, in various embodiments of the present disclosure, the expressions "at least one of A or B" or "at least one of A and / or B" may be interpreted as synonymous with "at least one of A and B."

[0037] Additionally, in various embodiments of the present disclosure, “at least one of A, B and C” may mean “only A,” “only B,” “only C,” or “any combination of A, B and C.” Also, “at least one of A, B or C” or “at least one of A, B and / or C” may mean “at least one of A, B and C.”

[0038] Additionally, parentheses used in various embodiments of the present disclosure may mean "for example." Specifically, when indicated as "control information (PDCCH)," "PDCCH" may be proposed as an example of "control information." In other words, the "control information" of various embodiments of the present disclosure is not limited to "PDCCH," and "PDDCH" may be proposed as an example of "control information." Furthermore, even when indicated as "control information (i.e., PDCCH)," "PDCCH" may be proposed as an example of "control information."

[0039] Technical features described individually within one drawing in various embodiments of the present disclosure may be implemented individually or simultaneously.

[0040]

[0041] Common signal transmission methods in 3GPP

[0042] Physical channels and general signal transmission

[0043] FIG. 1 is a diagram illustrating an example of physical channels used in a system applicable to the present disclosure and a general signal transmission method using them. Specifically, FIG. 1 illustrates physical channels used in a 3GPP system and a general signal transmission.

[0044] Figure 1 illustrates physical channels used in a 3GPP system and general signal transmission. In a wireless communication system, a terminal receives information from a base station via a downlink (DL) and transmits information to the base station via an uplink (UL). The information transmitted and received by the base station and the terminal includes data and various control information, and various physical channels exist depending on the type and purpose of the information they transmit and receive.

[0045] When the power is turned on again after being off, or when a terminal newly enters a cell, it performs an initial cell search operation, such as synchronizing with the base station (S11). To do this, the terminal receives PSCH (Primary Synchronization Channel) and SSCH (Secondary Synchronization Channel) from the base station to synchronize with the base station and obtain information such as cell ID (cell identity). In addition, the terminal can obtain cell broadcast information by receiving PBCH (Physical Broadcast Channel) from the base station. Furthermore, during the initial cell search phase, the terminal can check the downlink channel status by receiving DL RS (Downlink Reference Signal).

[0046] After completing the initial cell search, the terminal can obtain more specific system information by receiving the PDCCH (Physical Downlink Control Channel) and the corresponding PDSCH (Physical Downlink Control Channel) (S12).

[0047] Subsequently, the terminal may perform a Random Access Procedure to complete the connection to the base station (S13~S16). Specifically, the terminal transmits a preamble through a PRACH (Physical Random Access Channel) (S13) and receives a RAR (Random Access Response) for the preamble through a PDCCH and a corresponding PDSCH (S14). Subsequently, the terminal transmits a PUSCH (Physical Uplink Shared Channel) using scheduling information within the RAR (S15) and may perform a Conflict Resolution Procedure such as a PDCCH and a corresponding PDSCH (S16).

[0048] A terminal that has performed the procedure described above may subsequently perform PDCCH / PDSCH reception (S17) and PUSCH / PUCCH (Physical Uplink Control Channel) transmission (S18) as a general uplink / downlink signal transmission procedure. The control information transmitted by the terminal to the base station is referred to as UCI (Uplink Control Information). UCI includes HARQ ACK / NACK (Hybrid Automatic Repeat and reQuest Acknowledgement / Negative-ACK), SR (Scheduling Request), CSI (Channel State Information), etc. CSI includes CQI (Channel Quality Indicator), PMI (Precoding Matrix Indicator), RI (Rank Indication), etc. UCI is generally transmitted via PUCCH, but it may be transmitted via PUSCH if control information and data need to be transmitted simultaneously. Additionally, the terminal may transmit UCI non-periodically via PUSCH in response to requests / instructions from the network.

[0049]

[0050] OFDM (Orthogonal Frequency Division Multiplexing) Numerology

[0051] The new RAT system uses the OFDM transmission method or a similar transmission method. The new RAT system may follow OFDM parameters different from those of LTE. Alternatively, the new RAT system may follow the existing LTE / LTE-A numerology but have a larger system bandwidth (e.g., 100 MHz). Or, a single cell may support multiple numerologies. That is, UEs operating with different numerologies can coexist within a single cell.

[0052]

[0053] radio frame structure

[0054] FIG. 2 is a drawing illustrating an example of the structure of a wireless frame used in a system applicable to the present disclosure.

[0055] In NR, uplink and downlink transmissions consist of frames. A radio frame has a length of 10 ms and is defined as two 5 ms half-frames (HF). A half-frame is defined as five 1 ms subframes (SF). A subframe is divided into one or more slots, and the number of slots within a subframe depends on the subcarrier spacing (SCS). Each slot contains 12 or 14 OFDM(A) symbols depending on the cyclic prefix (CP). When a standard CP is used, each slot contains 14 symbols. When an extended CP is used, each slot contains 12 symbols. Here, the symbols may include OFDM symbols (or CP-OFDM symbols) or SC-FDMA symbols (or DFT-s-OFDM symbols).

[0056] Table 1 illustrates how the number of symbols per slot, the number of slots per frame, and the number of slots per subframe vary depending on the SCS when a standard CP is used.

[0057] SCS (15*2^u)N slot symb N frame,u slot N subframe,u slot 15KHz (u=0)1410130KHz (u=1)1420260KHz (u=2)14404120KHz (u=3)14808240KHz (u=4)1416016

[0058] N slot symb is the number of symbols in the slot. N frame,uslot is the number of slots within the frame. N subframe,u slot is the number of slots within the subframe.

[0059]

[0060] Table 2 illustrates how, when extended CP is used, the number of symbols per slot, the number of slots per frame, and the number of slots per subframe vary depending on the SCS.

[0061] SCS (15*2^u)N slot symb N frame,u slot N subframe,u slot 60KHz (u=2)12404

[0062] NR supports multiple numerologies (or subcarrier spacing (SCS)) to support various 5G services. For example, when the SCS is 15 kHz, it supports a wide area in traditional cellular bands; when the SCS is 30 kHz / 60 kHz, it supports dense-urban, lower latency, and wider carrier bandwidth; and when the SCS is 60 kHz or higher, it supports a bandwidth greater than 24.25 GHz to overcome phase noise.

[0063] The NR frequency band can be defined by two types of frequency ranges (FR1, FR2). The numerical values ​​of the frequency ranges may change; for example, the two types of frequency ranges (FR1, FR2) may be as shown in Table 3 below. For convenience of explanation, among the frequency ranges used in the NR system, FR1 may mean "sub 6GHz range" and FR2 may mean "above 6GHz range" and may be referred to as millimeter wave (mmW).

[0064] Frequency Range designationCorresponding frequency rangeSubcarrier SpacingFR1450MHz - 6000MHz15, 30, 60kHzFR224250MHz - 52600MHz60, 120, 240kHz

[0065] As described above, the numerical value of the frequency range of the NR system may change. For example, FR1 may include a band of 410 MHz to 7125 MHz as shown in Table 4 below. That is, FR1 may include a frequency band of 6 GHz (or 5850, 5900, 5925 MHz, etc.) or higher. For example, the frequency band of 6 GHz (or 5850, 5900, 5925 MHz, etc.) or higher included within FR1 may include an unlicensed band. The unlicensed band may be used for various purposes, for example, for communication for vehicles (e.g., autonomous driving).

[0066] Frequency Range designationCorresponding frequency rangeSubcarrier SpacingFR1410MHz - 7125MHz15, 30, 60kHzFR224250MHz - 52600MHz60, 120, 240kHz

[0067] In an NR system, the OFDM(A) numerology (e.g., SCS, CP length, etc.) can be configured differently among multiple cells that are merged into a single terminal. Accordingly, the (absolute time) interval of a time resource (e.g., SF, slot, or TTI) (collectively referred to as TU (Time Unit) for convenience) composed of the same number of symbols can be configured differently among the merged cells.

[0068]

[0069] FIG. 3 is a drawing illustrating an example of a slot structure used in a system applicable to the present disclosure.

[0070] A slot contains multiple symbols in the time domain. For example, in the case of a standard CP, one slot contains 7 symbols, whereas in the case of an extended CP, one slot contains 6 symbols. A carrier contains multiple subcarriers in the frequency domain. A Resource Block (RB) is defined as multiple (e.g., 12) consecutive subcarriers in the frequency domain. A Bandwidth Part (BWP) is defined as multiple consecutive (P)RBs in the frequency domain and can correspond to a single numerology (e.g., SCS, CP length, etc.). A carrier can contain up to N (e.g., 5) BWPs. Data communication is performed through the active BWPs, and only one BWP can be active for a single terminal. In the resource grid, each element is referred to as a Resource Element (RE) and can be mapped to a single complex symbol.

[0071]

[0072] FIG. 4 is a drawing illustrating an example of a slot structure of a wireless frame used in a system applicable to the present disclosure.

[0073] Figure 4 illustrates the slot structure of a frame of an NR system as an exemplary system.

[0074] The frame structure of NR is characterized by a self-contained structure in which a DL control channel, DL or UL data, and a UL control channel can all be included within a single slot unit, as shown in the example of FIG. 4. In this case, DL data scheduling information and UL data scheduling information can be transmitted in the DL control channel, while ACK / NACK information for DL ​​data, CSI information (modulation and coding scheme information, MIMO transmission-related information, etc.), and scheduling requests can be transmitted in the UL control channel. In FIG. 4, a time gap for DL-to-UL or UL-to-DL switching may exist between the control area and the data area. Additionally, some of the DL control, DL data, UL data, and UL control channels may not be configured within a single slot. Alternatively, the order of channels constituting a single slot may vary (for example, DL control, DL data, UL control, UL data, or UL control, UL data, DL control, DL data, etc.).

[0075]

[0076] Explanation of background technology

[0077] The 3rd Generation Partnership Project (3GPP) Long-Term Evolution (LTE) is a technology that enables high-speed packet communication. Many schemes have been proposed for the LTE objective, including those aimed at reducing user and provider costs, improving service quality, and expanding and improving coverage and system capacity. As an upper-level requirement, 3GPP LTE requires reduced cost per bit, increased service availability, flexible use of a frequency band, a simple structure, an open interface, and adequate power consumption of a terminal.

[0078] Work has begun at the International Telecommunication Union (ITU) and 3GPP to develop requirements and specifications for new radio (NR) systems. 3GPP must identify and develop the technical components necessary to successfully standardize new radio access technology (RAT) while timely satisfying both urgent market demands and the longer-term requirements set by the International Mobile Telecommunications (IMT)-2020 process of the ITU Radio Communication Sector (ITU-R). Furthermore, NR must be able to utilize all spectrum bands, at least up to 100 GHz (gigahertz), so that they can remain available for radio communication in the distant future. (Work has started in international telecommunication union (ITU) and 3GPP to develop requirements and specifications for new radio (NR) systems. 3GPP has to identify and develop the technology components needed for successfully standardizing the new RAT timely satisfying both the urgent market needs, and the more long-term requirements set forth by the ITU radio communication sector (ITU-R) international mobile telecommunications (IMT)-2020 process.Further, the NR should be able to use any spectrum band ranging at least up to 100 GHz that may be made available for wireless communications even in a more distant future.).

[0079] NR aims to be a single technical framework that addresses all usage scenarios, requirements, and deployment scenarios, including enhanced mobile broadband (eMBB), massive machine-type communications (mMTC), ultra-reliable and low-latency communications (URLLC), etc. NR must be inherently forward compatible.

[0080] The following technologies, devices, and systems may be applied to various wireless multiple access systems. Examples of multiple access systems include code division multiple access (CDMA) systems, frequency division multiple access (FDMA) systems, time division multiple access (TDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single carrier frequency division multiple access (SC-FDMA) systems, and multicarrier frequency division multiple access (MC-FDMA) systems. CDMA may be implemented through wireless technologies such as universal terrestrial radio access (UTRA) or CDMA2000. TDMA may be implemented through wireless technologies such as the global system for mobile communications (GSM), general packet radio service (GPRS), or enhanced data rates for GSM evolution (EDGE). OFDMA can be implemented through wireless technologies such as the Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, or evolved UTRA (E-UTRA).UTRA is part of the Universal Mobile Telecommunications System (UMTS). The 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) is part of the evolved UMTS (E-UMTS) that uses E-UTRA. 3GPP LTE adopts OFDMA in the downlink (DL) and SC-FDMA in the uplink (UL). Evolutions of 3GPP LTE include LTE-A (advanced), LTE-A Pro, and / or 5G NR (new radio). (The following techniques, apparatuses, and systems may be applied to a variety of wireless multiple access systems. Examples of the multiple access systems include a code division multiple access (CDMA) system, a frequency division multiple access (FDMA) system, a time division multiple access (TDMA) system, an orthogonal frequency division multiple access (OFDMA) system, a single carrier frequency division multiple access (SC-FDMA) system, and a multicarrier frequency division multiple access (MC-FDMA) system. CDMA may be embodied through radio technology such as universal terrestrial radio access (UTRA) or CDMA2000.TDMA may be embodied through radio technology such as global system for mobile communications (GSM), general packet radio service (GPRS), or enhanced data rates for GSM evolution (EDGE). OFDMA may be embodied through radio technology such as institute of electrical and electronics engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, or evolved UTRA (E-UTRA). UTRA is a part of a universal mobile telecommunications system (UMTS). 3rd generation partnership project (3GPP) long term evolution (LTE) is a part of evolved UMTS (E-UMTS) using E-UTRA. 3GPP LTE employs OFDMA in DL and SC-FDMA in UL. Evolution of 3GPP LTE includes LTE-A (advanced), LTE-A Pro, and / or 5G NR (new radio).).

[0081] For convenience of description, implementations of the present disclosure are mainly described with respect to a 3GPP-based wireless communication system. However, the technical features of the present disclosure are not limited thereto. For example, although the following detailed description is given based on a mobile communication system corresponding to a 3GPP-based wireless communication system, aspects of the present disclosure that are not limited to a 3GPP-based wireless communication system are applicable to other mobile communication systems.

[0082] For terms and technologies used in this disclosure that are not specifically described, wireless communication standard documents published prior to this disclosure may be referenced.

[0083] 3GPP LTE / EPS

[0084] - 3GPP TS 36.211: Physical channels and modulation

[0085] - 3GPP TS 36.212: Multiplexing and channel coding

[0086] - 3GPP TS 36.213: Physical layer procedures

[0087] - 3GPP TS 36.214: Physical layer; Measurements

[0088] - 3GPP TS 36.300: Overall description

[0089] - 3GPP TS 36.304: User Equipment (UE) procedures in idle mode

[0090] - 3GPP TS 36.306: User Equipment (UE) radio access capabilities

[0091] - 3GPP TS 36.314: Layer 2 - Measurements

[0092] - 3GPP TS 36.321: Medium Access Control (MAC) protocol

[0093] - 3GPP TS 36.322: Radio Link Control (RLC) protocol

[0094] - 3GPP TS 36.323: Packet Data Convergence Protocol (PDCP)

[0095] - 3GPP TS 36.331: Radio Resource Control (RRC) protocol

[0096] - 3GPP TS 36.413: S1 Application Protocol (S1AP)

[0097] - 3GPP TS 36.423: X2 Application Protocol (X2AP)

[0098] - 3GPPP TS 22.125: Unmanned Aerial System support in 3GPP; Stage 1

[0099] - 3GPP TS 23.303: Proximity-based services (Prose); Stage 2

[0100] - 3GPP TS 23.401: General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access

[0101] - 3GPP TS 23.402: Architecture enhancements for non-3GPP accesses

[0102] - 3GPP TS 23.286: Application layer support for V2X services; Functional architecture and information flows

[0103] - 3GPP TS 24.301: Non-Access-Stratum (NAS) protocol for Evolved Packet System (EPS); Stage 3

[0104] - 3GPP TS 24.302: Access to the 3GPP Evolved Packet Core (EPC) via non-3GPP access networks; Stage 3

[0105] - 3GPP TS 24.334: Proximity-services (ProSe) User Equipment (UE) to ProSe function protocol aspects; Stage 3

[0106] - 3GPP TS 24.386: User Equipment (UE) to V2X control function; protocol aspects; Stage 3

[0107] 3GPP NR / 5GS

[0108] - 3GPP TS 38.211: Physical channels and modulation

[0109] - 3GPP TS 38.212: Multiplexing and channel coding

[0110] - 3GPP TS 38.213: Physical layer procedures for control

[0111] - 3GPP TS 38.214: Physical layer procedures for data

[0112] - 3GPP TS 38.215: Physical layer measurements

[0113] - 3GPP TS 38.300: NR and NG-RAN Overall Description

[0114] - 3GPP TS 38.304: User Equipment (UE) procedures in idle mode and in RRC inactive state

[0115] - 3GPP TS 38.321: Medium Access Control (MAC) protocol

[0116] - 3GPP TS 38.322: Radio Link Control (RLC) protocol

[0117] - 3GPP TS 38.323: Packet Data Convergence Protocol (PDCP)

[0118] - 3GPP TS 38.331: Radio Resource Control (RRC) protocol

[0119] - 3GPP TS 37.324: Service Data Adaptation Protocol (SDAP)

[0120] - 3GPP TS 37.340: Multi-connectivity; Overall description

[0121] - 3GPP TS 23.501: System Architecture for the 5G System

[0122] - 3GPP TS 23.502: Procedures for the 5G System

[0123] - 3GPP TS 23.503: Policy and Charging Control Framework for the 5G System; Stage 2

[0124] - 3GPP TS 24.501: Non-Access-Stratum (NAS) protocol for 5G System (5GS); Stage 3

[0125] - 3GPP TS 24.502: Access to the 3GPP 5G Core Network (5GCN) via non-3GPP access networks

[0126] - 3GPP TS 24.526: User Equipment (UE) policies for 5G System (5GS); Stage 3

[0127]

[0128] 3GPP V2X

[0129] - 3GPP TS 23.285: Architecture enhancements for V2X services

[0130] - 3GPP TR 23.786: Evolved Packet System (EPS) and the 5G System (5GS) to support advanced V2X services

[0131] - 3GPP TS 23.287: Architecture enhancements for 5G System (5GS) to support Vehicle-to-Everything (V2X) services

[0132] - 3GPP TS 24.587: Vehicle-to-Everything (V2X) services in 5G System (5GS); Stage 3

[0133] - 3GPP TS 24.588: Vehicle-to-Everything (V2X) services in 5G System (5GS); User Equipment (UE) policies; Stage 3

[0134]

[0135] FIG. 5 is a diagram illustrating an example of data flow in a system applicable to the present disclosure.

[0136] Figure 5 illustrates a data flow example in the 3GPP NR (new radio) system.

[0137] In FIG. 5, "RB" represents a radio bearer, and "H" represents a header. Radio bearers are classified into two groups: data radio bearers (DRBs) for user plane data and signaling radio bearers (SRBs) for control plane data. A medium access control (MAC) protocol data unit (PDU) is transmitted to or received from an external device using radio resources through the physical (PHY) layer. The MAC PDU reaches the PHY layer in the form of a transport block. (In FIG. 5, "RB" denotes a radio bearer, and "H" denotes a header. Radio bearers are categorized into two groups: data radio bearers (DRB) for user plane data and signaling radio bearers (SRB) for control plane data. The MAC PDU is transmitted / received using radio resources through the PHY layer to / from an external device. The MAC PDU arrives to the PHY layer in the form of a transport block.)

[0138] In the PHY layer, the uplink transport channels UL-SCH (uplink shared channel) and RACH (random access channel) are mapped to the physical channels PUSCH (physical uplink shared channel) and PRACH (physical random access channel), respectively, and the downlink transport channels DL-SCH (downlink shared channel), BCH (broadcast channel), and PCH (paging channel) are mapped to PDSCH (physical downlink shared channel), PBCH (physical broadcast channel), and PDSCH, respectively. In the PHY layer, the uplink control information (UCI) is mapped to PUCCH (physical uplink control channel), and the downlink control information (DCI) is mapped to PDCCH (physical downlink control channel). MAC PDUs associated with UL-SCH are transmitted via PUSCH by the UE (user equipment) based on the UL grant, and MAC PDUs associated with DL-SCH are transmitted via PDSCH by the BS (base station) based on the DL assignment.(In the PHY layer, the uplink transport channels UL-SCH and RACH are mapped to their physical channels PUSCH and PRACH, respectively, and the downlink transport channels DL-SCH, BCH and PCH are mapped to PDSCH, PBCH and PDSCH, respectively. In the PHY layer, uplink control information (UCI) is mapped to PUCCH, and downlink control information (DCI) is mapped to PDCCH. A MAC PDU related to UL-SCH is transmitted by a UE via a PUSCH based on an UL grant, and a MAC PDU related to DL-SCH is transmitted by a BS via a PDSCH based on a DL assignment.).

[0139]

[0140] FIG. 6 is a drawing illustrating an example of the structure of an NG-RAN in a system applicable to the present disclosure.

[0141] FIG. 6 shows an example of the overall architecture of an NG-RAN to which the technical features of the present disclosure can be applied.

[0142] The term "base station" as used in this disclosure has the same meaning as gNB (gNodeB) as defined in 3GPP standards and may be used interchangeably depending on the context. For example, where the term "gNB" is used in parts of the drawings or description, it means "base station" of the same concept. However, "gNB" is a designation used in 5G systems, and a different designation may be used in future 6G or subsequent communication systems, and this disclosure may apply equally to such changes in terminology. (In the present disclosure, the term "base station" has the same meaning as "gNB (gNodeB)" defined in the 3GPP standard and may be used interchangeably depending on the context. For example, where the term "gNB" is used in this specification or drawings, it refers to the same concept as a "base station." However, "gNB" is a term used in the 5G communication system, and different terminology may be adopted in future generations such as 6G or later; the present disclosure is equally applicable regardless of such terminology changes.)

[0143] Referring to FIG. 6, a gNB (next generation node B) may include a gNB-CU (central unit) (hereinafter, gNB-CU may be simply referred to as CU) and one or more gNB-DU (distributed unit) (hereinafter, gNB-DU may be simply referred to as DU).

[0144] The gNB-CU is a logical node hosting the RRC (radio resource control), SDAP (service data adaptation protocol), and PDCP (packet data convergence protocol) protocols of the gNB or the RRC and PDCP protocols of the en-gNB (evolved node B). The gNB-CU controls the operation of at least one gNB-DU.

[0145] The gNB-DU is a logical node hosting the RLC (radio link control), MAC (medium access control), and physical layers of the gNB or the en-gNB. The operation of the gNB-DU is partly controlled by the gNB-CU. One gNB-DU supports one or multiple cells. One cell is supported by only one gNB-DU.

[0146] The gNB-CU and gNB-DU are connected via the F1 interface. The gNB-CU terminates the F1 interface connected to the gNB-DU. The gNB-DU terminates the F1 interface connected to the gNB-CU. A single gNB-DU is connected to only one gNB-CU. However, a gNB-DU can be connected to multiple gNB-CUs through appropriate implementation. The F1 interface is a logical interface. In the case of NG-RAN, the NG and Xn-C interfaces for a gNB composed of gNB-CUs and gNB-DUs are terminated at the gNB-CU. In the case of E-UTRAN-NR dual connectivity (EN-DC), the S1-U and X2-C interfaces for a gNB composed of gNB-CUs and gNB-DUs are terminated at the gNB-CU. The gNB-DUs connected to the gNB-CU appear as only a single gNB to other gNBs and the 5GC (5G core network). (The gNB-CU and gNB-DU are connected via an F1 interface. The gNB-CU terminates the F1 interface connected to the gNB-DU. The gNB-DU terminates the F1 interface connected to the gNB-CU. One gNB-DU is connected to only one gNB-CU. However, the gNB-DU may be connected to multiple gNB-CUs by appropriate implementation. The F1 interface is a logical interface. For NG-RAN, the NG and Xn-C interfaces for a gNB consisting of a gNB-CU and gNB-DUs, terminate in the gNB-CU.For E-UTRAN-NR dual connectivity (EN-DC), the S1-U and X2-C interfaces for a gNB consisting of a gNB-CU and gNB-DUs, terminate in the gNB-CU. The gNB-CU and connected gNB-DUs are only visible to other gNBs and the 5GC as a gNB.).

[0147] The functions of the F1 interface include the following F1 control (F1-C) functions.

[0148] (1) F1 interface management function. The error indication function is used to notify gNB-DU or gNB-CU that an error has occurred. The reset function is used to initialize peer entities after node setup and after a failure event. This procedure can be used by both gNB-DU and gNB-CU. The F1 setup function enables gNB-DU and gNB-CU to exchange application-level data necessary for proper interoperability over the F1 interface. F1 setup is initiated by gNB-DU. The gNB-CU configuration update and gNB-DU configuration update functions enable updating application-level configuration data necessary for proper interoperability between gNB-CU and gNB-DU via the F1 interface, and can enable or disable cells. The F1 configuration and gNB-DU configuration update functions enable the transmission of single network slice selection assistance information (S-NSSAI) supported by the gNB-DU. The F1 resource coordination function is used to transmit information regarding frequency resource sharing between the gNB-CU and the gNB-DU. ((1) F1 interface management function. The error indication function is used by the gNB-DU or gNB-CU to indicate to the gNB-CU or gNB-DU that an error has occurred.The reset function is used to initialize the peer entity after node setup and after a failure event occurred. This procedure can be used by both the gNB-DU and the gNB-CU. The F1 setup function allows to exchange application level data needed for the gNB-DU and gNB-CU to interoperate correctly on the F1 interface. The F1 setup is initiated by the gNB-DU. The gNB-CU configuration update and gNB-DU configuration update functions allow to update application level configuration data needed between gNB-CU and gNB-DU to interoperate correctly over the F1 interface, and may activate or deactivate cells. The F1 setup and gNB-DU configuration update functions allow to inform the single network slice selection assistance information (S-NSSAI) supported by the gNB-DU. The F1 resource coordination function is used to transfer information about frequency resource sharing between gNB-CU and gNB-DU.).

[0149] (2) System Information management function. Scheduling of system broadcast information is performed by the gNB-DU. The gNB-DU is responsible for transmitting system information according to available scheduling parameters. The gNB-DU is responsible for encoding the NR master information block (MIB). When broadcasting of system information block type-1 (SIB1) and other SI (system information) messages is required, the gNB-DU is responsible for encoding SIB1 and the gNB-CU is responsible for encoding other SI messages. ((2) System Information management function. Scheduling of system broadcast information is carried out in the gNB-DU. The gNB-DU is responsible for transmitting the system information according to the scheduling parameters available. The gNB-DU is responsible for the encoding of NR master information block (MIB). In case broadcast of system information block type-1 (SIB1) and other SI messages is needed, the gNB-DU is responsible for the encoding of SIB1 and the gNB-CU is responsible for the encoding of other SI messages.)

[0150] (3) F1 UE context management function. The F1 UE context management function supports the setup and modification of the entire UE context required. The setup of the F1 UE context is initiated by the gNB-CU and is accepted or rejected by the gNB-DU based on admission control criteria (e.g., resource unavailability). The modification of the F1 UE context can be initiated by either the gNB-CU or the gNB-DU. The receiving node may accept or reject the modification. The F1 UE context management function also supports the release of the context previously set by the gNB-DU. The release of the context is triggered either directly by the gNB-CU or upon a request received from the gNB-DU. The gNB-CU requests the gNB-DU to release the UE context when the UE enters the RRC_IDLE or RRC_INACTIVE state. ((3) F1 UE context management function. The F1 UE context management function supports the establishment and modification of the necessary overall UE context. The establishment of the F1 UE context is initiated by the gNB-CU and accepted or rejected by the gNB-DU based on admission control criteria (eg, resource not available). The modification of the F1 UE context can be initiated by either gNB-CU or gNB-DU. The receiving node can accept or reject the modification.The F1 UE context management function also supports the release of the context previously established in the gNB-DU. The release of the context is triggered by the gNB-CU either directly or following a request received from the gNB-DU. The gNB-CU request the gNB-DU to release the UE Context when the UE enters RRC_IDLE or RRC_INACTIVE.).

[0151] This function can also be used to manage DRBs and SRBs, that is, to set, modify, and release DRB and SRB resources. The setting and modification of DRB resources are triggered by the gNB-CU and accepted / rejected by the gNB-DU based on resource reservation information and quality of service (QoS) information to be provided to the gNB-DU. For each DRB to be set or modified, the S-NSSAI may be provided to the gNB-DU by the gNB-CU during the UE context setup procedure and the UE context modification procedure. (This function can be also used to manage DRBs and SRBs, ie, establishing, modifying and releasing DRB and SRB resources. The establishment and modification of DRB resources are triggered by the gNB-CU and accepted / rejected by the gNB-DU based on resource reservation information and QoS information to be provided to the gNB-DU. For each DRB to be setup or modified, the S-NSSAI may be provided by gNB-CU to the gNB-DU in the UE context setup procedure and the UE context modification procedure.)

[0152] Mapping between QoS flows and wireless bearers is performed by the gNB-CU, and the granularity of bearer-related management on F1 is the wireless bearer level. In the case of NG-RAN, the gNB-CU provides aggregated DRB QoS profiles and QoS flow profiles to the gNB-DU, and the gNB-DU accepts the request or rejects it with an appropriate cause value. To support packet duplication for carrier aggregation (CA) within the gNB-DU, a single data wireless bearer must be established with two GPRS (general packet radio service) tunneling protocol (GTP)-U tunnels between the gNB-CU and the gNB-DU. (The mapping between QoS flows and radio bearers is performed by gNB-CU and the granularity of bearer related management over F1 is radio bearer level. For NG-RAN, the gNB-CU provides an aggregated DRB QoS profile and QoS flow profile to the gNB-DU, and the gNB-DU either accepts the request or rejects it with appropriate cause value. To support packet duplication for intra-gNB-DU carrier aggregation (CA), one data radio bearer should be configured with two GPRS tunneling protocol (GTP)-U tunnels between gNB-CU and a gNB-DU.)

[0153] Through this function, gNB-CU requests gNB-DU to set up or change the special cell (SpCell) for the UE, and gNB-DU either accepts the request or rejects it with an appropriate cause value.

[0154] Through this function, the gNB-CU requests the setup of the secondary cell(s, SCell(s)) from the gNB-DU, and the gNB-DU responds to the gNB-CU by accepting all, some, or none of the SCell(s). The gNB-CU requests the removal of the SCell(s) for the UE.

[0155] (4) RRC message transfer function. This function allows to transfer RRC messages between gNB-CU and gNB-DU. RRC messages are transferred over F1-C. The gNB-CU is responsible for the encoding of the dedicated RRC message using assistance information provided by gNB-DU.

[0156] (5) Paging function. The gNB-DU is responsible for transmitting paging information according to the provided scheduling parameters. The gNB-CU provides paging information so that the gNB-DU can calculate the correct paging occasion (PO) and paging frame (PF). The gNB-CU determines the paging assignment (PA). The gNB-DU consolidates all paging records for a specific PO, PF, and PA, encodes the final RRC message, and broadcasts the paging message to each PO and PF within the PA. ((5) Paging function. The gNB-DU is responsible for transmitting the paging information according to the scheduling parameters provided. The gNB-CU provides paging information to enable the gNB-DU to calculate the exact paging occasion (PO) and paging frame (PF). The gNB-CU determines the paging assignment (PA). The gNB-DU consolidates all the paging records for a particular PO, PF and PA, and encodes the final RRC message and broadcasts the paging message on the (respective PO, PF in the PA.)

[0157] (6) Warning message information transfer function. This function enables cooperation with the warning message transmission procedures over the NG interface. The gNB-CU is responsible for encoding the warning-related SI message and transmitting it along with other warning-related information so that the gNB-DU can broadcast it over the radio interface.

[0158]

[0159] FIG. 7 is a diagram illustrating an example of an interface protocol structure for F1-C in a system applicable to the present disclosure.

[0160] FIG. 7 shows an interface protocol structure for F1-C to which technical features of the present disclosure can be applied.

[0161] The transport network layer (TNL) is based on Internet protocol (IP) transport and includes a stream control transmission protocol (SCTP) layer above the IP layer. The application layer signaling protocol is called the F1 application protocol (E1AP).

[0162]

[0163] Part II: Background Information, and the Problem Identified and Solution Proposed

[0164] Problem Definition - Some Important Topics for Design Consideration:

[0165] Abstract: (Abstract:)

[0166] We propose reviewing and integrating a new use case titled "Immersive Media Services for Urban Air Mobility (UAM)" enabled by 6G Terrestrial Networks (TN) and Non-Terrestrial Networks (NTN). By leveraging both 6G TN and NTN, this use case demonstrates the potential for continuous, high-quality media services within UAM vehicles and ensures coverage even in challenging or remote areas where terrestrial networks alone may be insufficient. This hybrid approach provides a comprehensive connectivity solution that addresses the high mobility and dynamic network requirements of UAM operations. (It is proposed to review and incorporate a new use case titled Immersive Media Services for Urban Air Mobility (UAM) Enabled by 6G Terrestrial Network (TN) and Non-Terrestrial Network (NTN). By leveraging both 6G TN and NTN, this use case demonstrates the potential for continuous high-quality media service in UAM vehicles, ensuring coverage even in challenging or remote areas where terrestrial networks alone may be insufficient. This hybrid approach provides a comprehensive connectivity solution, addressing the high mobility and dynamic network requirements of UAM operations.)

[0167] References

[0168]

[0169] [x1] Urban Air Mobility, https: / www.airbus.com / en / innovation / low-carbon-aviation / urban-air-mobility, AIRBUS, accessed in May 2024.

[0170] [x2] Urban Air Mobility (UAM) Concept of Operations, https: / www.faa.gov / air-taxis / uam_blueprint, Federal Aviation Administration of US Department of Transportation, Aug. 2023.

[0171] [x3] Urban Air Mobility, https: / rotorcraft.arc.nasa.gov / Research / Programs / UrbanAirMobility.html, US NASA, 2024.

[0172] [x4] NASA Urban Air Mobility (UAM) Reference Vehicles, https: / sacd.larc.nasa.gov / uam-refs / , US NASA, Jan. 2024.

[0173] [x5] Future Mobility, https: / www.hyundai.com / worldwide / en / newsroom / future-mobility, HYUNDAI ([x5] Future Mobility, https: / www.hyundai.com / worldwide / en / newsroom / future-mobility, HYUNDAI)

[0174] [x6] LG Uplus, Near-Future Vertical Applications in Korea: K-UAM, https: / / nextgalliance.org / wp-content / uploads / 2024 / 05 / Near-future-Vertical-Applications-in-Korea-K-UAM_6GF_NGA_Joint_Workshop_JKim_final.pdf, Next G Alliance / Korea 6G Forum Joint Workshop

[0175] x.1 Use case on Immersive Media Services for Urban Air Mobility (UAM) Enabled by 6G TN and NTN

[0176] x.1.1 Description

[0177] In an Urban Air Mobility (UAM) environment, passengers on UAM vehicles (e.g., air taxis, drones) can access immersive media services such as (ultra)high-definition live streaming, real-time news, and interactive 3D content. By utilizing hybrid network solutions that combine 6G cellular (i.e., ground networks or TN) and non-ground network (NTN) connectivity (e.g., satellite), passengers experience uninterrupted, high-quality media services with immersive content tailored to their preferences, regardless of altitude or coverage gaps. This hybrid connectivity ensures consistent quality even when UAM vehicles pass through urban corridors or low-coverage areas. (In an urban air mobility (UAM) setting, passengers on UAM vehicles (eg, air taxis, drones) can access immersive media services such as (ultra-) high-definition live-streaming, real-time news, and interactive 3D content. Leveraging a hybrid network solution that combines 6G cellular (ie, terrestrial network or TN) and non-terrestrial network (NTN) connectivity (eg, satellite), passengers experience uninterrupted This hybrid connectivity ensures consistent quality even when UAM vehicles transition through urban corridors or low-coverage areas.)

[0178] To ensure uninterrupted immersive media services during UAM flights, a hybrid network infrastructure equipped with 6G TN and NTN provides overlapping coverage with seamless handovers. UAM vehicles are equipped with devices compatible with both 6G and satellite signals, enabling "non-conventional" continuous connectivity (i.e., seamless and ultra-reliable against potential interruptions during mobility). Immersive media content is delivered efficiently through edge computing, while passengers authenticate and receive personalized content recommendations based on connectivity and their preferences.

[0179] x.1.2 Pre-conditions

[0180] The following conditions are considered necessary to support the aforementioned immersive media service with respect to network infrastructure, UE (or UAM as a communication entity), data availability / sharing for edge computing, and security (such as authorized use of data and / or information).

[0181] 1. UE Compatibility (of UAM vehicle): UAM vehicles are equipped with hybrid 6G-NTN compatible onboard devices (in the form of UE or gNB (or base station)) and relevant transmit / receive capabilities optimized to transmit / receive both terrestrial and satellite signals.

[0182] 2. Typical Cruise Speeds of UAM Vehicles: Most UAM vehicles (including eVTOL (electric Vertical Take-Off and Landing) aircraft) are designed to operate within the cruise speed ranges between 100–200 mph (or 160–320 km / h). Specific examples include:

[0183] a. Joby Aviation's eVTOL: Up to 200 mph (320 km / h)

[0184] b. Lilium Jet: 154 mph (248 km / h) during cruising

[0185] c. Vertical Aerospace VX4: 150 mph (241 km / h) (c. Vertical Aerospace VX4: 150 mph (241 km / h))

[0186] d. Airbus CityAirbus NextGen: 120 km / h (75 mph) for urban deployments

[0187] 3. Network Infrastructure: 6G terrestrial base stations (or gNBs) and NTN satellites provide overlapping coverage and possess dynamic handover capabilities that support seamless switching between 6G and NTN, ensuring continuous HD (high-definition) media service during flight.

[0188] Note: A low Earth orbit (LEO) environment is assumed, but other constellations such as geostationary orbit (GEO) are also applicable.

[0189] 4. Data Availability and Edge Computing: Immersive media content providers are connected to both terrestrial and satellite edge computing infrastructure, enabling efficient, latency-sensitive access to media content.

[0190] 5. Security / Authentication: Passengers share their profiles or preferences with the immersive media service provider, allowing the system to adjust and optimize media recommendations based on connectivity availability and passenger preferences.

[0191] Note: Passengers can be authenticated for media services during pre-flight check-in or during flights. The immersive media service provider may be the airline or an authorized third party related to the UAM service. However, detailed subscription models are not the primary focus.

[0192] x.1.3 Service Flows

[0193] To clarify the intended time window for providing immersive media services to passengers during UAM services, two steps (i.e., a preparation step and a completion step for UAM operation) are included in the service flow.

[0194]

[0195] FIG. 8 is a drawing illustrating an example of an urban air mobility (UAM) aircraft in a system applicable to the present disclosure that includes an onboard system (e.g., a system capable of operating as a donor gNB or UE relay) connected to an NTN and / or ground network (TN) to provide extended backhaul connectivity for passenger terminals.

[0196] 1. Pre-flight setup: During flight check-in, passengers connect their devices to the UAM's "onboard system" to access media services and select from various content options. This service can customize media options for each passenger based on their preferences and dynamically adjusts recommendations based on expected network coverage along the flight path. Note: The term "onboard system" on the UAM airframe refers to a 3GPP entity capable of providing connectivity to one or more user equipment (UEs), acting, for example, as a donor gNB or UE relay. (1. Pre-Flight Setup: During flight check-in, passengers connect their devices to the UAM's "onboard system" for media service access and select from various content options. The service is enabled to tailor media options for each passenger based on preferences, dynamically adjusting recommendations based on anticipated network coverage along the flight path. Note: The term "onboard system" mounted on a UAM vehicle is a 3GPP entity that can provide connectivity to one or more UEs, eg, acting as a donor gNB or UE Relay.)

[0197] 2. Initiation of Immersive Media Services: Upon (vertical) takeoff, the "onboard system" installed on the UAM (e.g., a donor gNB or UE relay customized for the UAM) initiates high-definition (HD) streaming to the passenger device (i.e., UE) via a 6G cellular network if ground coverage is available to the onboard system. The onboard system continuously checks for the availability of a non-terrestrial network (NTN) connection and compares the suitability of the choice between the terrestrial network (TN) and NTN connections, and prepares for a seamless handover (HO) if cellular coverage is limited and / or if other applicable criteria defined by the mobile (satellite) network operator or service contract are met. Note: The U.S. Federal Aviation Administration (FAA) and other aviation authorities mandate so-called "airplane mode" regulations for safety reasons. However, details on how these regulations affect service scenarios are for further study and are not the primary focus of this use case. (2. Initiation of Immersive Media Service: Upon (vertical) takeoff, the "onboard system" mounted on UAM (eg, donor gNB or UE Relay customized to UAM) initiates HD streaming for its passenger devices (ie, UEs) via the 6G cellular network if terrestrial coverage is available for that onboard system.The onboard system keeps checking the availability of NTN connectivity and compare the relevance of choice between TN and NTN connectivity, getting ready for a seamless HO if cellular coverage becomes limited and / or if other applicable criteria, defined by the mobile (satellite) network operator or by a service agreement, are satisfied. Note: The US Federal Aviation Administration (FAA) and other aviation authorities mandate so-called "airplane mode" rules for safety reasons. However, details on how such rules affect the service scenario is FFS and is not the primary focus in this use case.).

[0198] 3. Media Streaming via Hybrid Connectivity: As the UAM aircraft moves, the "onboard system" maintains seamless connectivity to meet traffic demands generated by passenger devices. When approaching low-coverage areas or higher altitudes, the system switches to NTN to maintain continuity. The network dynamically adjusts data flow between 6G and NTN networks as needed to optimize bandwidth and minimize interruptions. For interactive content (e.g., VR (virtual reality)), low-latency satellite links help maintain responsiveness, supporting an immersive passenger experience. (3. Media Streaming with Hybrid Connectivity: As the UAM vehicle travels, the "onboard system" seamlessly maintain the connectivity to meet the traffic demand incurred by the passengers' devices. When approaching low-coverage areas or higher altitudes, the system shifts to NTN to maintain continuity. The network dynamically adjusts data flow between 6G and NTN networks as needed to optimize bandwidth and minimize interruptions. For interactive content (eg, VR), low-latency satellite links help maintain responsiveness, supporting immersive passenger experiences.)

[0199]

[0200] 4. Ultra-fine Handover in Flight: The "Onboard System" synchronizes data between edge servers and satellite networks to reduce latency during network switching, ensure uninterrupted streaming, and minimize buffering during handover. Even when using low earth orbit (LEO) satellites, the "Onboard System" can maintain ultra-fine synchronization with both the so-called source gNB and target gNB using various new methods when switching from one LEO to another, from LEO to TN, or from TN to LEO. (4. Ultra-fine Handover during Flight: The "onboard system" synchronizes data between edge servers and satellite networks, reducing latency when switching networks, ensuring uninterrupted streaming, and minimizing buffering during handovers. The "onboard system" is able to maintain ultra-fine synchronization using a variety of novel methods with both so-called the source gNB and the target gNB even when using LEO satellite(s): when switching from an LEO to another, from an LEO to TN, or from TN to an LEO.)

[0201] 5. End of Service Inherently Determined by the UAM Transportation Service Completion: As the UAM vehicle approaches its destination, the hybrid system transitions back to a 6G terrestrial connection, preparing passengers for network continuity after disembarkation. Passengers receive prompts to save content or queue downloads before arrival. Note: Details about the service or business model for ending the immersive media service upon completion of the UAM transportation service are not the primary focus of this use case.

[0202] x.1.4 Post-conditions The "onboard system" maintained ultra-fine synchronization with the source gNB and target gNB, which enabled ultra-fine HO. Passengers enjoyed immersive media service from the "onboard system" connectivity to personal network connections upon disembarkation, allowing content access continuity if desired. NOTE: See NOTE 1 of clause x.1.6 for the term "ultra-fine HO".

[0203] x.1.5 Existing features partly or fully covering the use case functionality Some normative requirements related to support NTN connectivity in TS 22.261 Some normative requirements related to support media service in TS 22.263

[0204] Potential new requirements needed to support x.1.6 use cases [PR.x.1.6-001] The 6GS (6G System) must provide means to support micro-synchronization with a 6G network (e.g., source gNB in ​​an NTN environment) to perform micro-HO when requested by an application. Note 1: The term "micro-HO" is intended to describe non-conventional micro-level interrupt quantities, for example, for immersive media communications, in contrast to the traditional term "service continuity," which is broadly interpreted to support traditional media types on cellular communication networks. [PR.x.1.6-002] The 6GS must provide means to enable and disable support for micro-synchronization with a 6G network (e.g., source gNB in ​​an NTN environment) to perform micro-HO when requested by an application. [PR.x.1.6-003] 6GS shall provide a means to acquire and provide predictive information (e.g., Doppler predictive information of the "onboard system" relative to the target satellite gNB) so that the 6G network can maintain ultra-fine synchronization (e.g., with the source gNB in ​​NTN environments). Note 2: Details of "predictive information" are beyond the scope of stage-1 research. (x.1.6 Potential New Requirements needed to support the use case [PR.x.1.6-001] 6GS shall provide a means to support ultra-fine synchronization with 6G network (e.g., with the source gNB in ​​NTN settings) in order to perform ultra-fine HO, if requested by an application.NOTE 1: The term "ultra-fine HO" is intended to describe a non-conventional micro-level interruption quantity, e.g., for immersive media communication, as opposed to convention term "service continuity" that is generously interpreted to support conventional media types over the cellular communication network. [PR.x.1.6-002] 6GS shall provide a means to activate and deactivate the support of ultra-fine synchronization with 6G network (e.g., with the source gNB in NTN settings) in order to perform ultra-fine HO, if requested by an application. [PR.x.1.6-003] 6GS shall provide a means to obtain and provide prediction information (e.g., predictive information on Doppler for an "onboard system" relative to the target satellite gNB) for 6G network to be able to maintain ultra-fine synchronization (e.g., with the source gNB in NTN settings). NOTE 2: The details of "predictive information" is out of the scope of stage-1 study.).

[0205]

[0206] Composition and Method of the Invention

[0207] In the present disclosure, '()' can be interpreted as both excluding the contents inside () and including the contents inside the parentheses.

[0208] In the present disclosure, ' / ' may mean including (and) all of the contents separated by / or including (or) only some of the separated contents.

[0209] The term "base station" as used in this disclosure has the same meaning as gNB (gNodeB) as defined in 3GPP standards and may be used interchangeably depending on the context. For example, where the term "gNB" is used in parts of the drawings or description, it means "base station" of the same concept. However, "gNB" is a designation used in 5G systems, and a different designation may be used in future 6G or subsequent communication systems, and this disclosure may apply equally to such changes in terminology. (In the present disclosure, the term "base station" has the same meaning as "gNB (gNodeB)" defined in the 3GPP standard and may be used interchangeably depending on the context. For example, where the term "gNB" is used in this specification or drawings, it refers to the same concept as a "base station." However, "gNB" is a term used in the 5G communication system, and different terminology may be adopted in future generations such as 6G or later; the present disclosure is equally applicable regardless of such terminology changes. Proposed Method

[0210] Scope: (1) when a UE (user equipment) needs to perform a handover from an LEO (low earth orbit) satellite to another LEO satellite;

[0211] When the source gNB (next generation node B) (e.g., LEO1) initiates the HO, it can include a "Request time-series information on sync" to the (candidate) target gNB, as shown in the figure.

[0212] "Request time-series information on sync" may include time and 3D (3-dimensional) location information over a specific period and its estimated functions or values ​​over time.

[0213] If the target gNB(s) receive this request from the source gNB, the (candidate) target gNB(s) should generate those information (time, 3D location information of the satellite gNB) and their time-varying values ​​or functions.

[0214] After that, these will be provided to the source gNB.

[0215] The source gNB will send this information to the UE (user equipment).

[0216] In the above procedure, the gNB (next generation node B) can be mapped to a LEO (low Earth orbit) satellite and the UE (user equipment) can be mapped to a UAM (Urban Air Mobility); the UAM acting as a UE relay will provide connectivity to its passenger UEs.

[0217]

[0218] FIG. 9 is a drawing illustrating an example of a signal flow diagram according to various embodiments of the present disclosure.

[0219] The term "base station" as used in this disclosure has the same meaning as gNB (gNodeB) as defined in 3GPP standards and may be used interchangeably depending on the context. For example, where the term "gNB" is used in parts of the drawings or description, it means "base station" of the same concept. However, "gNB" is a designation used in 5G systems, and a different designation may be used in future 6G or subsequent communication systems, and this disclosure may apply equally to such changes in terminology. (In the present disclosure, the term "base station" has the same meaning as "gNB (gNodeB)" defined in the 3GPP standard and may be used interchangeably depending on the context. For example, where the term "gNB" is used in this specification or drawings, it refers to the same concept as a "base station." However, "gNB" is a term used in the 5G communication system, and different terminology may be adopted in future generations such as 6G or later; the present disclosure is equally applicable regardless of such terminology changes.)

[0220] Specifically, FIG. 9 illustrates an example of a handover preparation procedure between LEO (low orbit) satellites.

[0221] Referring to FIG. 9, the procedure includes a user terminal (UE), a source gNB (e.g., LEO1), a target gNB (e.g., LEO2), other potential target gNB(s), e.g., LEOx), and an Access and Mobility Management Function (AMF). The overall flow corresponds to the Handover Preparation phase.

[0222] In step 0, the AMF can provide mobility control information (Mobility control information provided by AMF) to the source gNB.

[0223] In Step 1, the UE receives Measurement Control settings from the source gNB, performs measurements based on them, and then sends measurement reports to the source gNB.

[0224] In step 2, the source gNB determines a handover (HO Decision) based on the measurement report received from the UE and mobility control information received from the AMF, etc.

[0225] In step 3, the source gNB sends a Handover Request message to the (candidate) target gNB (LEO2) and other potential target gNBs (LEOx). According to one embodiment of the present invention, the Handover Request message may include a '(add) Request time-series info on sync' for the UE to quickly acquire synchronization.

[0226] In step 4, each (candidate) target gNB that receives a handover request performs Admission Control to determine the resource allocation availability of the corresponding UE, etc.

[0227] In step 5, the (candidate) target gNB that has passed acceptance control sends a Handover Request Acknowledge message to the source gNB. The acknowledgment message may include '(add) time-series info on sync' containing the information requested in step 3. As illustrated in the left annotation of FIG. 9, this information can be 'Use "time-series info on sync" for fast sync-up with each candidate gNB'.

[0228] In step 6, the source gNB receives a handover request acknowledgment message and 'synchronization acquisition time series information' from one or more (candidate) target gNBs, and then sends an RRC Reconfiguration message containing the information to the UE.

[0229] In Step 7, the UE performs connection and synchronization with the target gNB (LEO2) based on the received RRC reconfiguration message (and 'synchronization acquisition time series information'). The UE can quickly synchronize with the target gNB by using the 'synchronization acquisition time series information'. When synchronization and connection are successfully completed, the UE completes the handover procedure by sending an RRC Reconfiguration Complete message to the target gNB.

[0230]

[0231] FIG. 10 is a drawing illustrating an example of a signal flow diagram according to various embodiments of the present disclosure.

[0232] The term "base station" as used in this disclosure has the same meaning as gNB (gNodeB) as defined in 3GPP standards and may be used interchangeably depending on the context. For example, where the term "gNB" is used in parts of the drawings or description, it means "base station" of the same concept. However, "gNB" is a designation used in 5G systems, and a different designation may be used in future 6G or subsequent communication systems, and this disclosure may apply equally to such changes in terminology. (In the present disclosure, the term "base station" has the same meaning as "gNB (gNodeB)" defined in the 3GPP standard and may be used interchangeably depending on the context. For example, where the term "gNB" is used in this specification or drawings, it refers to the same concept as a "base station." However, "gNB" is a term used in the 5G communication system, and different terminology may be adopted in future generations such as 6G or later; the present disclosure is equally applicable regardless of such terminology changes.)

[0233] Specifically, FIG. 10 illustrates the Handover Execution and Handover Completion procedures following the Handover Preparation step of FIG. 9. These procedures are based on a Conditional Handover (CHO) scenario.

[0234] In the handover execution phase, the user terminal (UE) evaluates the 'CHO conditions' pre-configured from the source gNB (LEO1). At a similar time, the source gNB performs an 'Early Status Transfer' (7a) to the target gNB (LEO2) to pre-transmit the UE's status information (e.g., PDCP SN status). Additionally, user data is forwarded from the User Plane Function (UPF) to the target gNB.

[0235] If the UE determines that the CHO conditions are satisfied, the UE detaches from the existing cell (source gNB) and attempts to synchronize with the new cell (target gNB). When synchronization is successfully completed, the UE sends a 'CHO Handover completion' message (8) (e.g., RRC reconfiguration completion message) to the target gNB (LEO2).

[0236] In the handover completion phase, the target gNB (LEO2), having received the 'CHO Handover Complete' message from the UE, transmits a 'Handover Success' message (8a) to the Access and Mobility Management Function (AMF). This message serves to inform the Core Network that the UE's serving cell has changed and to request a Path Switch. (Subsequently, the data path is updated to the target gNB through signal exchange between the AMF and the UPF.)

[0237] At the same time, the source gNB (LEO1) performs an 'SN Status Transfer' (8b) to the target gNB (LEO2) to transmit the final SN (Sequence Number) status information for sequential data transmission and prevention of loss.

[0238] Additionally, the source gNB (LEO1) sends a ‘Handover Cancel’ message (8c) to the ‘other potential target gNB(s)’ (LEOx) that were handover candidates in the preparation phase of FIG. 9 but were not ultimately selected. This is to instruct the gNBs to release the resources that were previously allocated for the UE. Subsequently, user data is transmitted through a new path between the UE, the target gNB (LEO2), and the UPF.

[0239]

[0240] [Explanation regarding the 1st Node (Terminal (user equipment, UE)) claim]

[0241] The embodiments described above will be explained in detail below with reference to FIG. 11 in terms of the operation of the terminal. The methods described below are distinguished only for the convenience of explanation, and it is obvious that as long as they are not mutually excluded, a part of one method may be substituted with a part of another method or combined with one another and applied.

[0242] FIG. 11 is a drawing illustrating an example of the operation process of a terminal in a system applicable to the present disclosure.

[0243] In step S1110, the terminal receives time-series synchronization information from a source base station, which includes three-dimensional location information of candidate target base stations for the handover of the terminal and time-varying prediction information regarding the three-dimensional location information.

[0244] In step S1120, the terminal determines parameters for synchronization for the candidate target base stations based on the received time-series synchronization information.

[0245] In step S1130, the terminal transmits a synchronization signal to a specific target base station among the candidate target base stations based on the above parameters.

[0246]

[0247] According to various embodiments of the present disclosure, the time series synchronization information may further include time information of the candidate target base stations.

[0248] According to various embodiments of the present disclosure, the prediction information may be based on a function that changes over time.

[0249] According to various embodiments of the present disclosure, the terminal may be associated with urban air mobility (UAM).

[0250] According to various embodiments of the present disclosure, the source base station and the target base station may be associated with a low earth orbit (LEO) satellite.

[0251] According to various embodiments of the present disclosure, the prediction information may include prediction information regarding the Doppler shift between the terminal and the candidate target base stations.

[0252] According to various embodiments of the present disclosure, the terminal may operate as a relay providing connectivity to a plurality of passenger terminals (passenger UEs).

[0253]

[0254] According to various embodiments of the present disclosure, a terminal is provided in a wireless communication system. The terminal includes a transceiver and at least one processor, and the at least one processor may be configured to perform a method of operation of the terminal according to FIG. 11.

[0255] According to various embodiments of the present disclosure, a device for controlling a terminal in a wireless communication system is provided. The device comprises at least one processor and at least one memory operably connected to the at least one processor. The at least one memory may be configured to store instructions for performing a method of operation of the terminal according to FIG. 11 based on execution by the at least one processor.

[0256] According to various embodiments of the present disclosure, one or more non-transitory computer-readable media (CRMs) storing one or more instructions are provided. The one or more instructions perform operations based on execution by one or more processors, and the operations may include a method of operation of a terminal according to FIG. 11.

[0257]

[0258] [Explanation regarding the 2nd node (source base station) claim]

[0259] The embodiments described above will be explained in detail below with reference to FIG. 12 regarding the operation of a source base station. The methods described below are distinguished only for the convenience of explanation, and it is understood that, as long as they are not mutually exclusive, a part of one method may be substituted with a part of another method or combined with one another and applied.

[0260] FIG. 12 is a diagram illustrating an example of the operation process of a source base station in a system applicable to the present disclosure. In the present disclosure, the base station has the same meaning as gNB and is interchangeable.

[0261] In step S1210, the source base station receives time-series synchronization information from candidate target base stations for handover of a terminal (user equipment, UE), the time-series synchronization information including three-dimensional location information of the candidate target base stations and time-varying prediction information regarding the three-dimensional location information.

[0262] In step S1220, the source base station transmits the time-series synchronization information to the terminal. Synchronization between the terminal and a specific target base station among the candidate target base stations is based on parameters associated with the time-series synchronization information.

[0263]

[0264] According to various embodiments of the present disclosure, the time series synchronization information may further include time information of the candidate target base stations.

[0265] According to various embodiments of the present disclosure, the prediction information may be based on a function that changes over time.

[0266] According to various embodiments of the present disclosure, the terminal may be associated with urban air mobility (UAM).

[0267] According to various embodiments of the present disclosure, the source base station and the target base station may be associated with a low earth orbit (LEO) satellite.

[0268] According to various embodiments of the present disclosure, the prediction information may include prediction information regarding the Doppler shift between the terminal and the candidate target base stations.

[0269] According to various embodiments of the present disclosure, the terminal may operate as a relay providing connectivity to a plurality of passenger terminals (passenger UEs).

[0270]

[0271] According to various embodiments of the present disclosure, a source base station is provided in a wireless communication system. The source base station includes a transceiver and at least one processor, and the at least one processor may be configured to perform a method of operation of the source base station according to FIG. 12.

[0272] According to various embodiments of the present disclosure, an apparatus for controlling a source base station in a wireless communication system is provided. The apparatus comprises at least one processor and at least one memory operably connected to the at least one processor. The at least one memory may be configured to store instructions for performing a method of operating a source base station according to FIG. 12 based on execution by the at least one processor.

[0273] According to various embodiments of the present disclosure, one or more non-transitory computer-readable media (CRMs) storing one or more instructions are provided. The one or more instructions perform operations based on execution by one or more processors, and the operations may include a method of operation of a source base station according to FIG. 12.

[0274]

[0275] Wireless devices applicable to the present disclosure

[0276] Hereinafter, examples of wireless devices to which various embodiments of the present disclosure are applied will be described.

[0277] FIG. 17 is a drawing illustrating an example of the structure of a first node and a second node in a system applicable to the present disclosure.

[0278] The first node (1600) may include a processor (1610), an antenna unit (1620), a transceiver (1630), and a memory (1640).

[0279] The processor (1610) performs baseband-related signal processing and may include an upper layer processing unit (1611) and a physical layer processing unit (1615). The upper layer processing unit (1611) may process operations of the MAC layer, RRC layer, or higher upper layers. The physical layer processing unit (1615) may process operations of the PHY layer. For example, if the first node (1600) is a base station device in base station-terminal communication, the physical layer processing unit (1615) may perform uplink reception signal processing, downlink transmission signal processing, etc. For example, if the first node (1600) is a first terminal device in terminal-terminal communication, the physical layer processing unit (1615) may perform downlink reception signal processing, uplink transmission signal processing, sidelink transmission signal processing, etc. In addition to performing baseband-related signal processing, the processor (1610) may also control the overall operation of the first node (1600).

[0280] The antenna section (1620) may include one or more physical antennas, and if it includes multiple antennas, it may support MIMO transmission and reception. The transceiver (1630) may include an RF (Radio Frequency) transmitter and an RF receiver. The memory (1640) may store information processed by the processor (1610) and software, operating systems, applications, etc. related to the operation of the first node (1600), and may include components such as a buffer.

[0281] The processor (1610) of the first node (1600) may be configured to implement the operation of the base station in base station-terminal communication (or the operation of the first terminal device in terminal-terminal communication) in the embodiments described in this disclosure.

[0282]

[0283] The second node (1650) may include a processor (1660), an antenna unit (1670), a transceiver (1680), and a memory (1690).

[0284] The processor (1660) performs baseband-related signal processing and may include an upper layer processing unit (1661) and a physical layer processing unit (1665). The upper layer processing unit (1661) may process operations of the MAC layer, RRC layer, or higher upper layers. The physical layer processing unit (1665) may process operations of the PHY layer. For example, if the second node (1650) is a terminal device in base station-terminal communication, the physical layer processing unit (1665) may perform downlink reception signal processing, uplink transmission signal processing, etc. For example, if the second node (1650) is a second terminal device in terminal-terminal communication, the physical layer processing unit (1665) may perform downlink reception signal processing, uplink transmission signal processing, sidelink reception signal processing, etc. In addition to performing baseband-related signal processing, the processor (1660) may also control the overall operation of the second node (1660).

[0285] The antenna section (1670) may include one or more physical antennas, and if it includes multiple antennas, it may support MIMO transmission and reception. The transceiver (1680) may include an RF transmitter and an RF receiver. The memory (1690) may store information processed by the processor (1660) and software, operating systems, applications, etc. related to the operation of the second node (1650), and may include components such as a buffer.

[0286] The processor (1660) of the second node (1650) may be configured to implement the operation of the terminal in base station-terminal communication (or the operation of the second terminal device in terminal-terminal communication) in the embodiments described in this disclosure.

[0287] In the operation of the first node (1600) and the second node (1650), the details described in the examples of the present disclosure regarding the base station and the terminal (or the first terminal and the second terminal in terminal-to-terminal communication) in base station-to-terminal communication may be applied in the same way, and redundant descriptions are omitted.

[0288]

[0289] Here, the wireless communication technology implemented in the device (1600, 1650) of the present disclosure may include LTE, NR and 6G as well as various other wireless communication technologies.

[0290]

[0291] According to various embodiments of the present disclosure, the first node (1600) corresponds to a terminal (user equipment, UE), and the second node (1650) corresponds to a source base station.

[0292]

[0293] The claims described in various embodiments of the present disclosure may be combined in various ways. For example, the technical features of the method claims of various embodiments of the present disclosure may be combined to be implemented as a device, and the technical features of the device claims of various embodiments of the present disclosure may be combined to be implemented as a method. Furthermore, the technical features of the method claims and the technical features of the device claims of various embodiments of the present disclosure may be combined to be implemented as a device, and the technical features of the method claims and the technical features of the device claims of various embodiments of the present disclosure may be combined to be implemented as a method.

Claims

In a method performed by a terminal (user equipment, UE), A step of receiving time-series synchronization information from a source base station, the time-series synchronization information including three-dimensional location information of candidate target base stations for handover of the terminal and time-varying prediction information regarding the three-dimensional location information; A step of determining parameters for synchronization of the candidate target base stations based on the received time-series synchronization information; and Based on the above parameters, the step of transmitting a synchronization signal to a specific target base station among the candidate target base stations, method. In Article 1, The above time series synchronization information further includes time information of the above candidate target base stations, method. In Article 1, The above prediction information is based on a function that changes over time, method. In Article 1, The above terminal is related to urban air mobility (UAM), method. In Article 1, The source base station and the target base station are associated with a low earth orbit (LEO) satellite. method. In Article 1, The above prediction information includes prediction information regarding the Doppler shift between the terminal and the candidate target base stations. method. In Article 1, The above terminal operates as a relay providing connectivity to multiple passenger terminals (passenger UEs). method. In a method performed by a source base station, A step of receiving time-series synchronization information from candidate target base stations for handover of a terminal (user equipment, UE), the time-series synchronization information including three-dimensional location information of said candidate target base stations and time-varying prediction information regarding said three-dimensional location information; The method includes the step of transmitting the above time series synchronization information to the terminal, Synchronization between the above terminal and a specific target base station among the above candidate target base stations is based on parameters related to the time series synchronization information, method. In Article 8, The above time series synchronization information further includes time information of the above candidate target base stations, method. In Article 8, The above prediction information is based on a function that changes over time, method. In Article 8, The above terminal is related to urban air mobility (UAM), method. In Article 8, The source base station and the target base station are associated with a low earth orbit (LEO) satellite. method. In Article 8, The above prediction information includes prediction information regarding the Doppler shift between the terminal and the candidate target base stations. method. In Article 8, The above terminal operates as a relay providing connectivity to multiple passenger terminals (passenger UEs). method. In a terminal (user equipment, UE), Transmitter / Receiver; At least one processor; and It includes at least one memory that is operablely connectable to the at least one processor and stores instructions for performing operations when executed by the at least one processor. The above operations are, Comprising all steps of the method according to any one of claims 1 to 7, Terminal. In a source base station, Transmitter / Receiver; At least one processor; and It includes at least one memory that is operablely connectable to the at least one processor and stores instructions for performing operations when executed by the at least one processor. The above operations are, Comprising all steps of the method according to any one of claims 8 through 14, Source base station. In a control device for controlling a terminal (user equipment, UE), At least one processor; and It includes at least one memory operably connected to the above at least one processor, and The above at least one memory stores instructions for performing operations based on execution by the above at least one processor, and The above operations are, Comprising all steps of the method according to any one of claims 1 to 7, controller. In a control device for controlling a source base station, At least one processor; and It includes at least one memory operably connected to the above at least one processor, and The above at least one memory stores instructions for performing operations based on execution by the above at least one processor, and The above operations are, Comprising all steps of the method according to any one of claims 8 through 14, controller. In a non-transitory computer-readable medium storing one or more instructions, The above one or more instructions perform operations based on being executed by one or more processors, and The above operations are, Comprising all steps of the method according to any one of claims 1 to 7, Computer-readable media. In a non-transitory computer-readable medium storing one or more instructions, The above one or more instructions perform operations based on being executed by one or more processors, and The above operations are, Comprising all steps of the method according to any one of claims 8 through 14, Computer-readable media.

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