Method and apparatus for handling satellite handover in a wireless communication system

Abstract

A method and user equipment for handling satellite handover in a wireless communication system are provided, wherein the method includes: receiving a system information block 19 (SIB19) at a first timing, wherein the user equipment is in a Radio Resource Control Idle (RRC_IDLE) or Radio Resource Control Inactive (RRC_INACTIVE) state at the first timing; and determining, based on SatSwitchWithResync and t-Service contained in SIB19, to initiate a satellite handover with resynchronization at a second timing when the user equipment is in a Radio Resource Control Connected (RRC_CONNECTED) state.

Description

[0001] Cross-references to related applications

[0002] This application claims priority and benefit to U.S. Provisional Patent Application No. 63 / 625,216, filed January 25, 2024, and U.S. Provisional Patent Application No. 63 / 549,298, filed February 2, 2024; each of the listed and cited applications and publications is incorporated herein by reference in its entirety. Technical Field

[0003] This disclosure generally relates to wireless communication networks, and more specifically, to methods and apparatus for handling satellite handover in wireless communication systems. Background Technology

[0004] With the rapid growth in demand for transmitting large amounts of data to and from mobile communication devices, traditional mobile voice communication networks have evolved into networks that communicate using Internet Protocol (IP) data packets. This IP data packet communication can provide users of mobile communication devices with IP-bearing voice, multimedia, multicast, and video-on-demand communication services.

[0005] An exemplary network architecture is the Evolved Universal Terrestrial Radio Access Network (E-UTRAN). E-UTRAN systems can provide high data throughput to enable the aforementioned IP-based voice and multimedia services. Currently, the 3GPP standards organization is discussing new radio technologies for next-generation technologies (e.g., 5G). Therefore, changes to the current core of the 3GPP standards are currently being submitted and considered to facilitate their evolution and completion. Summary of the Invention

[0006] Methods, systems, and apparatus are provided for handling satellite handover in wireless communication systems. User equipment (UE) can correctly perform satellite handover with resynchronization when a satellite handover occurs. When a UE receives system information block 19 (SIB19) while in a Radio Resource Control (RRC) idle state (RRC_IDLE) or a Radio Resource Control (RRC) inactive state (RRC_INACTIVE) (and subsequently enters a Radio Resource Control (RRC) connected state (RRC_CONNECTED)), a UE in the RRC_CONNECTED state can initiate a satellite handover with resynchronization.

[0007] In various embodiments, a method for a UE includes: receiving SIB19 at a first timing, wherein the UE is in RRC_IDLE or RRC_INACTIVE at the first timing; and determining, based on SatSwitchWithResync and t-Service included in SIB19, to initiate a satellite handover with resynchronization at a second timing when the UE is in RRC_CONNECTED. Attached Figure Description

[0008] Figure 1 A diagram showing a wireless communication system according to an embodiment of the present invention is shown;

[0009] Figure 2 This is a block diagram of a transmitter system (also referred to as an access network) and a receiver system (also referred to as a user equipment or UE) according to an embodiment of the present invention;

[0010] Figure 3 This is a functional block diagram of a communication system according to an embodiment of the present invention;

[0011] Figure 4 This is according to an embodiment of the present invention. Figure 3 Functional block diagram of the program code;

[0012] Figure 5 It is from the 3GPP TS 38.300V18.0.0 draft. Figure 16 .14.1-1: Reproduction of the overall diagram of NTN;

[0013] Figure 6 It is from the 3GPP TS 38.300V18.0.0 draft. Figure 16 .14.2.1-1: Reproduction of the diagram of timing relationships (for co-located gNB and NTN gateways);

[0014] Figure 7 It is the 3GPP TS 38.331V18.0.0 draft. Figure 5 3.5.1-1: Reproduction of successful RRC reconfiguration;

[0015] Figure 8 It is the 3GPP TS 38.331V18.0.0 draft. Figure 5 3.5.1-2: Reproduction of RRC reconfiguration failure;

[0016] Figure 9 This is an example diagram of constant PCI switching according to an embodiment of the present invention;

[0017] Figure 10 This is an example diagram of hard satellite handover according to an embodiment of the present invention;

[0018] Figure 11 This is an example diagram of soft satellite handover according to an embodiment of the present invention;

[0019] Figure 12 This is an example diagram of satellite handover according to an embodiment of the present invention;

[0020] Figure 13 This is an example diagram illustrating a satellite handover problem according to an embodiment of the present invention;

[0021] Figure 14 This is an example diagram of satellite handover according to an embodiment of the present invention;

[0022] Figure 15 This is a textual proposal based on an embodiment of the present invention based on [3] 3GPP TS 38.331V18.0.0, wherein the UE determines whether to perform / initiate a satellite handover with resynchronization regardless of the RRC status when / after the UE receives SIB19;

[0023] Figure 16 This is a textual proposal based on an embodiment of the present invention based on [3] 3GPP TS 38.331V18.0.0, wherein regardless of the RRC state when the UE receives SIB19, the UE determines whether to perform / initiate a satellite handover with resynchronization based on whether the UE is in the RRC_CONNECTED state at the time indicated by t-Service or during the time between the time indicated by t-ServiceStart and the time indicated by t-Service;

[0024] Figure 17 This is a textual proposal based on an embodiment of the present invention based on [3] 3GPP TS 38.331V18.0.0, wherein regardless of the RRC state when the UE receives SIB19, the UE determines whether to perform / initiate a satellite handover with resynchronization based on whether the UE is in the RRC_CONNECTED state at the time indicated by t-Service or during the time between the time indicated by t-ServiceStart and the time indicated by t-Service;

[0025] Figure 18This is a textual proposal based on an embodiment of the present invention based on [3] 3GPP TS 38.331V18.0.0, wherein regardless of the RRC state when the UE receives SIB19, the UE determines whether to perform / initiate a satellite handover with resynchronization based on whether the UE is in the RRC_CONNECTED state at the time indicated by t-Service or during the time between the time indicated by t-ServiceStart and the time indicated by t-Service;

[0026] Figure 19 This is a textual proposal based on the implementation of [3] 3GPP TS 38.331V18.0.0 according to an embodiment of the present invention. Regardless of the RRC status when the UE receives SIB19, the UE determines whether to perform / initiate a satellite handover with resynchronization based on the time when the UE is in the RRC_CONNECTED state and the time is not running, based on the time indicated by t-Service, after the time indicated by t-ServiceStart, or between the time indicated by t-ServiceStart and the time indicated by t-Service.

[0027] Figure 20 This is a textual proposal based on the implementation of [3] 3GPP TS 38.331V18.0.0 according to an embodiment of the present invention. Regardless of the RRC status when the UE receives SIB19, the UE determines whether to perform / initiate a satellite handover with resynchronization based on the time when the UE is in the RRC_CONNECTED state and the time is not running, based on the time indicated by t-Service, after the time indicated by t-ServiceStart, or between the time indicated by t-ServiceStart and the time indicated by t-Service.

[0028] Figure 21 This is a textual proposal based on the implementation of [3] 3GPP TS 38.331V18.0.0 according to an embodiment of the present invention. Regardless of the RRC status when the UE receives SIB19, the UE determines whether to perform / initiate a satellite handover with resynchronization based on the time when the UE is in the RRC_CONNECTED state and the time is not running, based on the time indicated by t-Service, after the time indicated by t-ServiceStart, or between the time indicated by t-ServiceStart and the time indicated by t-Service.

[0029] Figure 22This is a flowchart of a method for a UE in a wireless communication system according to an embodiment of the present invention, the method comprising: receiving system information in an NTN cell at a first timing; determining to perform / initiate a satellite handover with resynchronization based on the UE being in an RRC connection state at least at a second timing and / or regardless of the UE's RRC state at the first timing; and performing a satellite handover with resynchronization at the second timing.

[0030] Figure 23 This is a textual proposal based on an embodiment of the present invention based on [3] 3GPP TS 38.331V18.0.0, wherein regardless of the RRC state when the UE receives SIB19, the UE determines to perform / initiate a first satellite handover with resynchronization based on the time when the UE is in the RRC_CONNECTED state at the time indicated by t-Service, after the time indicated by t-ServiceStart, or between the time indicated by t-ServiceStart and the time indicated by t-Service;

[0031] Figure 24 This is a textual proposal of an embodiment based on 3GPP TS 38.331V18.0.0[3] according to an embodiment of the present invention, wherein regardless of the RRC state when the UE receives SIB19, the UE determines to perform / initiate a first satellite handover with resynchronization based on the time when the UE is in the RRC_CONNECTED state at the time indicated by t-Service, after the time indicated by t-ServiceStart, or between the time indicated by t-ServiceStart and the time indicated by t-Service;

[0032] Figure 25 This is a textual proposal based on the implementation of [3] 3GPP TS 38.331V18.0.0 according to an embodiment of the present invention, based on the fact that the UE is not in the RRC_CONNECTED state, the UE determines not to perform / initiate a second action during satellite handover with resynchronization;

[0033] Figure 26 This is a textual proposal based on an embodiment of the present invention, according to [3] 3GPP TS 38.331V18.0.0, wherein the UE performs a second satellite handover with resynchronization;

[0034] Figure 27This is a flowchart of a method for a UE in a wireless communication system according to an embodiment of the present invention. The method includes: receiving SIB19 at a first timing, wherein the UE is in RRC_IDLE or RRC_INACTIVE at the first timing; and determining, based on SatSwitchWithResync and t-Service included in SIB19, to initiate a satellite handover with resynchronization at a second timing when the UE is in RRC_CONNECTED. Detailed Implementation

[0035] The invention described herein can be applied to or implemented in the exemplary wireless communication systems and apparatus described below. Furthermore, the invention is described primarily in the context of the 3GPP architecture reference model. However, it should be understood that, with the aid of the disclosed information, those skilled in the art can readily adapt and implement aspects of the invention in 3GPP2 network architectures and other network architectures.

[0036] The exemplary wireless communication systems and apparatus described below employ wireless communication systems that support broadcast services. Wireless communication systems are widely deployed to provide various types of communication, such as voice and data. These systems may be based on Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Orthogonal Frequency Division Multiple Access (OFDMA), 3GPP Long Term Evolution (LTE) Radio Access, 3GPP Long Term Evolution Advanced (LTE-A) Radio Access, and 3GPP2 Ultra Mobile Broadband (UMB). 3GPP New Radio (NR), or some other modulation technology.

[0037] Specifically, the exemplary wireless communication systems and apparatus described below may be designed to support one or more standards, such as those provided by the consortium referred to herein as 3GPP, which is named the “Third Generation Partnership Project”, including: [1] 3GPP TS 38.300 V18.0.0 draft, “NR, NR and NG-RAN General Description, Phase 2”; [2] 3GPP TS 38.321 V18.0.0 draft, “NR, MAC Protocol Specification”; [3] 3GPP TS 38.331 V18.0.0 draft, “NR, RRC Protocol Specification”; [4] R2-2308373, “Satellite Handover: PCI Change without L3 Handover”, NEC; and [5] R2-2310307, ​​“Satellite Handover with Invariant PCI”, Apple Inc. The standards and documents listed above are hereby expressly and entirely incorporated herein by reference in their entirety.

[0038] Figure 1 A multiple access wireless communication system according to an embodiment of the present invention is illustrated. Access network 100 (AN) includes multiple antenna groups, one containing antennas 104 and 106, another containing antennas 108 and 110, and yet another containing antennas 112 and 114. Figure 1 In the diagram, only two antennas are shown for each antenna group; however, more or fewer antennas can be used for each antenna group. Access Terminal (AT) 116 communicates with antennas 112 and 114, which transmit information to AT 116 via forward link 120 and receive information from AT 116 via reverse link 118. AT 122 communicates with antennas 106 and 108, which transmit information to AT 122 via forward link 126 and receive information from AT 122 via reverse link 124. In an FDD system, communication links 118, 120, 124, and 126 can use different frequencies for communication. For example, forward link 120 can use a different frequency than the reverse link 118.

[0039] Each group of antennas and / or the area in which they are designed to communicate is often referred to as a sector of the access network. In an embodiment, each antenna group is designed to communicate with an access terminal in a sector of the area covered by access network 100.

[0040] In communications via forward links 120 and 126, the transmit antennas of access network 100 can utilize beamforming to improve the signal-to-noise ratio of the forward links for different access terminals 116 and 122. Furthermore, compared to an access network that transmits to all its access terminals via a single antenna, an access network that uses beamforming to transmit to access terminals randomly distributed throughout its coverage area typically causes less interference to access terminals in adjacent cells.

[0041] An AN can be a fixed station or base station used for communication with a terminal, and can also be referred to as an access point, Node B, base station, enhanced base station, eNodeB, or other terminology. An AT can also be referred to as User Equipment (UE), wireless communication device, terminal, access terminal, or other terminology.

[0042] Figure 2 This is a simplified block diagram of an embodiment of the transmitter system 210 (also referred to as the access network) and receiver system 250 (also referred to as the access terminal (AT) or user equipment (UE)) in the MIMO system 200. At the transmitter system 210, service data for multiple data streams is provided from the data source 212 to the transport (TX) data processor 214.

[0043] In one embodiment, each data stream is transmitted via a corresponding transmit antenna. The TX data processor 214 formats, decodes, and interleaves the service data of the data streams based on a specific decoding scheme selected for each data stream to provide decoded data.

[0044] OFDM technology can be used to multiplex the decoded data and pilot data of each data stream. The pilot data is typically a known data pattern processed in a known manner and can be used at the receiver system to estimate the channel response. The multiplexed pilot and decoded data for said data stream are then modulated (e.g., symbol mapping) based on a specific modulation scheme (e.g., BPSK, QPSK, M-PSK, or M-QAM) selected for each data stream to provide modulated symbols. The data rate, decoding, and modulation for each data stream can be determined by instructions executed by processor 230. Memory 232 is coupled to processor 230.

[0045] The modulation symbols of all data streams are then provided to the TX MIMO processor 220, which can further process the modulation symbols (e.g., for OFDM). The TX MIMO processor 220 then... T A modulation symbol stream is provided to N TTransmitters (TMTRs) 222a to 222t. In some embodiments, the TX MIMO processor 220 applies beamforming weights to symbols of the data stream and the antennas transmitting said symbols therefrom.

[0046] Each transmitter 222 receives and processes a corresponding symbol stream to provide one or more analog signals, and further modulates (e.g., amplifies, filters, and up-converts) the analog signals to provide modulated signals suitable for transmission via a MIMO channel. Then, from N... T Antennas 224a to 224t transmit N from transmitters 222a to 222t. T A modulated signal.

[0047] At receiver system 250, by N R Each antenna 252a to 252r receives the transmitted modulated signal and provides the signal received from each antenna 252 to a corresponding receiver (RCVR) 254a to 254r. Each receiver 254 modulates (e.g., filters, amplifies, and down-converts) the corresponding received signal, digitizes the modulated signal to provide a sample, and further processes the sample to provide a corresponding "received" symbol stream.

[0048] The RX data processor 260 then uses specific receiver processing technology from N R 254 receivers receive and process N R Each received symbol stream provides N T Each detected symbol stream is then demodulated, deinterleaved, and decoded by the RX data processor 260 to recover the service data used for the data stream. The processing performed by the RX data processor 260 is complementary to the processing performed by the TX MIMO processor 220 and TX data processor 214 at the transmitter system 210.

[0049] Processor 270 periodically determines which pre-decoding matrix to use (discussed below). Processor 270 formulates a reverse link message including the matrix index part and the rank part.

[0050] The reverse link message may include various types of information about the communication link and / or the received data stream. The reverse link message is then processed by the TX data processor 238 (which also receives service data from several data streams from the data source 236), modulated by the modulator 280, regulated by the transmitters 254a to 254r, and transmitted back to the transmitter system 210.

[0051] At transmitter system 210, the modulated signal from receiver system 250 is received by antenna 224, regulated by receiver 222, demodulated by demodulator 240, and processed by RX data processor 242 to extract the reverse link message transmitted by receiver system 250. Next, processor 230 determines which pre-decoding matrix to use to determine beamforming weights and then processes the extracted message.

[0052] Memory 232 can be used to temporarily store some buffered / calculated data from 240 or 242 via processor 230, some buffered data from 212, or some specific program code. Furthermore, memory 272 can be used to temporarily store some buffered / calculated data from 260 via processor 270, some buffered data from 236, or some specific program code.

[0053] Go to Figure 3 This figure illustrates an alternative simplified functional block diagram of a communication device according to an embodiment of the present invention. Figure 3 As shown, the communication device 300 in the wireless communication system can be used to achieve... Figure 1 The UE (or AT) 116 and 122 are used, and the wireless communication system is preferably an NR system. The communication device 300 may include an input device 302, an output device 304, a control circuit 306, a central processing unit (CPU) 308, a memory 310, program code 312, and a transceiver 314. The control circuit 306 executes the program code 312 in the memory 310 via the CPU 308, thereby controlling the operation of the communication device 300. The communication device 300 can receive signals input by a user via the input device 302 (e.g., a keyboard or keypad) and can output images and sounds via the output device 304 (e.g., a monitor or speaker). The transceiver 314 is used to receive and transmit wireless signals, pass received signals to the control circuit 306, and wirelessly output signals generated by the control circuit 306.

[0054] Figure 4 According to an embodiment of the present invention Figure 3 The diagram shows a simplified block diagram of program code 312. In this embodiment, program code 312 includes an application layer 400, a layer 3 portion 402, and a layer 2 portion 404, and is coupled to a layer 1 portion 406. Layer 3 portion 402 typically performs radio resource control. Layer 2 portion 404 typically performs link control. Layer 1 portion 406 typically performs physical connections.

[0055] For LTE, LTE-A, or NR systems, layer 2, part 404, may include a Radio Link Control (RLC) layer and a Medium Access Control (MAC) layer. Layer 3, part 402, may include a Radio Resource Control (RRC) layer.

[0056] Any two or more of the following paragraphs, (sub)bullets, points, actions, or claims described in each paragraph or section of the invention may be logically, reasonably, and appropriately combined to form a particular method.

[0057] Any sentence, paragraph, (sub)bullet, point, action, or claim described in each of the following invention paragraphs or sections can be implemented independently and separately to form a particular method or apparatus. Dependencies such as "based on," "more specifically," and "example" in the following invention disclosure are merely one possible embodiment and do not limit the specific method or apparatus.

[0058] The general description of Rel-18 NR non-terrestrial network (NTN) is specified in TS 38.300 ([1] 3GPP TS 38.300 V18.0.0 draft), as follows:

[0059] **************************Citation begins[1]*****************************

[0060] 16.14 Non-terrestrial networks

[0061] 16.14.1 Overview

[0062] Figure 16 .14.1-1 The following describes an example of a non-terrestrial network (NTN) that provides non-terrestrial NR access to a UE via an NTN payload and an NTN gateway, thereby depicting the service link between the NTN payload and the UE, and the feeder link between the NTN gateway and the NTN payload.

[0063] Figure 5 It is from the 3GPP TS 38.300V18.0.0 draft. Figure 16 .14.1-1: Reproduction of the overall diagram of NTN.

[0064] …

[0065] The NTN payload transparently forwards radio protocols received from the UE (via the serving link) to the NTN gateway (via the feeder link) and vice versa. The following connectivity is supported by the NTN payload:

[0066] - An NTN gateway can serve multiple NTN payloads;

[0067] -NTN payloads can be served by multiple NTN gateways.

[0068] Note 2: In this version, the NTN payload can change the carrier frequency before retransmitting the carrier frequency to the serving link, and vice versa (on the feed link, respectively).

[0069] …

[0070] Supports three types of service links:

[0071] - Earth-fixed: Provided by beams that continuously cover the same geographical area (e.g., in the case of GSO satellites);

[0072] - Quasi-Earth fixed: Provided by a beam that covers a geographic area for a limited time period and a different geographic area for another time period (e.g., the case of an NGSO satellite that produces a steerable beam);

[0073] - Earth movement: provided by a beam that slides across the Earth's surface over a coverage area (e.g., the case of NGSO satellites that produce fixed or non-unmaneuverable beams).

[0074] Using NGSO satellites, gNBs can provide quasi-Earth fixed service links or Earth mobile service links, while gNBs operated using GSO satellites can provide Earth fixed service links.

[0075] In this version, UEs that support NTN have GNSS functionality.

[0076] In NTN, distance refers to Euclidean distance.

[0077] 16.14.2 Timing and Synchronization

[0078] 16.14.2.1 Scheduling and Timing

[0079] DL and UL are aligned at the uplink time synchronization reference point (RP), with N TA,偏移 The given offset (see Clause 4.2 of TS38.213).

[0080] To accommodate the propagation delay in NTN, common timing advance (common TA) and two offsets K are used. 偏移 and k mac To enhance several timing relationships:

[0081] - Common TA is the configured timing offset of the RTT between the RP and NTN payloads.

[0082] -K 偏移 It is the configured scheduling offset that needs to be greater than or equal to the sum of the service link RTT and the common TA.

[0083] -k mac It is the configured offset that is approximately equal to the RTT between RP and gNB.

[0084] Scheduling offset K 偏移 This is to allow the UE sufficient processing time between downlink reception and uplink transmission, see TS 38.213.

[0085] Offset k mac This offset is used to delay the application of downlink configurations indicated by the MAC CE command on the PDSCH (see TS 38.213) and in the estimation of UE-gNB RTT (see TS 38.321). When downlink and uplink frame timings are misaligned at the gNB, this offset can be provided by the network. mac It is also used in the random access procedure to determine the start time of the RAR window / MsgB window after the Msg1 / MsgA transmission (see TS 38.213).

[0086] Service Link RTT, Feed Link RTT, RP, Common TA, k mac And T TA (See Clause 16.14.2.2) in Figure 16 As shown in .14.2.1-1.

[0087] Figure 6 It is from the 3GPP TS 38.300V18.0.0 draft. Figure 16 .14.2.1-1: Reproduction of the diagram of timing relationship (for co-located gNB and NTN gateways).

[0088] …

[0089] 16.14.2.2 Timing Advancement and Frequency Precompensation

[0090] For the serving cell, the network broadcasts valid ephemeris information and common TA parameters. The UE should have a valid GNSS location, ephemeris, and common TA before connecting to the NTN cell. For synchronization, before and during connection to the NTN cell, the UE should calculate the RTT between the UE and the RP based on the GNSS location, ephemeris, and common TA parameters (see Clause 4.2 in TS 38.213), and as follows... Figure 16The autonomous pre-compensation TTA for RTT between UE and RP is shown in .14.2.1-1 (see Clause 4.3 of TS38.211).

[0091] The UE should calculate the Doppler shift of the serving link by taking into account the UE's location and ephemeris, and autonomously pre-compensate for it during uplink transmission. If the UE does not have a valid GNSS location and / or a valid ephemeris and common TA, the UE should not transmit until it regains both.

[0092] In connected mode, the UE should be able to continuously update timing advance and frequency pre-compensation.

[0093] The UE can be configured to report timing advances during random access procedures or in connected mode. In connected mode, event-triggered reporting of timing advances is supported.

[0094] …

[0095] 16.14.3 Mobility and State Transitions

[0096] 16.14.3.1 Mobility in RRC_IDLE and RRC_INACTIVE

[0097] The same principles as described in 9.2.1 apply to mobility in NTN’s RRC_IDLE, and the same principles as described in 9.2.2 apply to mobility in NTN’s RRC_INACTIVE, unless otherwise specified below.

[0098] The network can broadcast multiple Tracking Area Codes (TACs) per PLMN in an NR NTN cell. Changes to TACs in the system information are under network control, meaning they may not be precisely synchronized with the real-time illumination of the beam on the ground.

[0099] For NTN-TN mobility, the network can broadcast cell information about NR TN and EUTRA TN coverage areas in SIB25. This is supported for fixed, quasi-fixed, and mobile cells. Coverage information includes a list of geographic TN areas and also indicates associated frequency information. UEs can skip TN measurements based on broadcast TN coverage information.

[0100] The UE can implicitly determine the network type (terrestrial or non-terrestrial) by the presence of cellBarredNTN in SIB1.

[0101] NTN ephemeris tables are provided in SIB19. An NTN cell contains the NTN load ephemeris table of the serving cell and optionally includes the NTN load ephemeris tables of neighboring cells.

[0102] 16.14.3.2 Mobility in RRC_CONNECTED

[0103] 16.14.3.2.1 Handover

[0104] Unless otherwise specified below, the same principle described in 9.2.3.2 applies:

[0105] During mobility between the NTN and the terrestrial network (TN), the UE does not need to be connected to both the NTN and the TN simultaneously.

[0106] Note: NTN TN handover refers to mobility in two directions, namely from NTN to TN (moving in) and from TN to NTN (moving out).

[0107] In this version of the manual, NTN does not support DAPS handover.

[0108] The UE can support mobility between gNBs operating with NTN payloads in different orbits (e.g., GSO, NGSO at different altitudes).

[0109] NTN supports RACH-free handover as specified in TS 38.321.

[0110] 16.14.3.2.2 Conditional Transfer

[0111] Unless otherwise specified below, the same principles described in 9.2.3.4 apply to NTN.

[0112] NTN supports the following additional triggering conditions, upon which the UE can execute a CHO to a candidate cell, as defined in TS38.331

[12] :

[0113] - Event A4 based on RRM measurement;

[0114] - Time-based triggering conditions;

[0115] - Location-based triggering conditions.

[0116] At least in the case of hard satellite handover where the service discontinuity gap duration is assumed to be zero or negligible, time-based or location-based triggering conditions can be configured independently of the measurement conditions used for CHO in NTN. Otherwise, time-based or location-based triggering conditions are always configured together with one of the measurement-based triggering conditions (CHO events A3 / A4 / A5), as defined in TS 38.331.

[0117] Time-based or location-based triggering conditions are always configured together with one of the measurement-based triggering conditions (CHO events A3 / A4 / A5), as defined in TS 38.331.

[0118] The UE implementation scheme determines how the UE evaluates time- or location-based triggering conditions and events based on RRM measurements.

[0119] When using time-based triggering conditions, the source gNB can send the corresponding parameters to a single target gNB via the source NG-RAN node to the target NG-RAN node transparent container during NG-C-based handover, see TS23.502. The source gNB sends the corresponding CHO configuration to the UE in an RRC reconfiguration message during handover execution.

[0120] When using time-based triggering conditions, the source NG-RAN node should consider the time indicated to the UE to determine when to begin early data forwarding to the target NG-RAN node.

[0121] Time-based CHOs can be performed without RACH.

[0122] 16.14.3.2.3 Satellite handover with resynchronization

[0123] Based on hard and soft satellite handover in quasi-earth fixed scenarios with the same SSB frequency and gNB, satellite handover with resynchronization procedures is supported. By maintaining the same PCI over the geographic area covered by the quasi-earth fixed beam, satellite handover with resynchronization avoids L3 mobility of UEs in the cell. CHO can be configured simultaneously with satellite handover with resynchronization procedures.

[0124] For soft satellite handover, the UE can begin synchronizing with the target satellite before the source satellite ceases service to the cell. The UE does not need to connect to the source satellite when handing over to the target satellite.

[0125] 16.14.3.3 Measurement

[0126] Unless otherwise specified below, the same principles as described in 9.2.4 apply to measurements in NTN.

[0127] Network configurable:

[0128] -Depending on UE capabilities, multiple SMTCs are performed in parallel per carrier for a given set of cells;

[0129] - Measurement gap based on multiple SMTCs;

[0130] - Auxiliary information provided in SIB19 (e.g., ephemeris, common TA parameters, k) mac This is used by the UE to perform measurements on neighboring cells in RRC_IDLE / RRC_INACTIVE / RRC_CONNECTED.

[0131] SMTC NW control adjustments can be based on UE auxiliary information reported in RRC_CONNECTED. UEs in RRC_IDLE / RRC_INACTIVE can adjust SMTC based on their location and auxiliary information in SIB19.

[0132] UE auxiliary information consists of the difference in service link propagation delay between the serving cell and neighboring cells.

[0133] For UEs in idle / inactive mode, the UE implementation scheme determines whether to perform NTN neighbor cell measurements for cells indicated in SIB3 / SIB4 but not included in SIB19.

[0134] For UEs in connected mode, the UE implementation scheme determines whether to perform NTN neighbor cell measurements for cells included in the measurement configuration but not in SIB19.

[0135] IUE can perform time-based and location-based measurements on neighboring cells in RRC_IDLE / RRC_INACTIVE:

[0136] - Timing and location information associated with the serving cell are provided in SIB19;

[0137] - The timing information refers to the UTC time when the serving cell stops providing service to the current geographic area;

[0138] -Location information refers to:

[0139] - In the quasi-Earth fixed cell scenario, it refers to the reference location of the serving cell and the distance threshold to the reference location.

[0140] - In the context of Earth moving cells, this refers to the reference location of the serving cell and the distance threshold to the reference location at the new epoch time.

[0141] Time-based measurement initiation can be applied to feed link handover scenarios during cell (re)selection.

[0142] The measurement rules for cell reselection based on timing and location information are specified in Clause 5.2.4.2 of TS 38.304.

[0143] *****************************End of quotation********************************

[0144] The handling of UL synchronization timers (e.g., T430) is specified in TS 38.331 ([3] 3GPP TS 38.331 V18.0.0 draft) and TS 38.321 ([2] 3GPP TS 38.321 V18.0.0 draft) as follows:

[0145] *****************************Citation start[3]*****************************

[0146] 5.2.2 System Information Acquisition

[0147] 5.2.2.4 Actions after receiving system information

[0148] 5.2.2.4.21 Actions after receiving SIB19

[0149] After receiving SIB19 in the NTN cell, the UE should in RRC_CONNECTED:

[0150] 1> Start or restart the T430 of the serving cell, wherein the timer value is set to the ntn-UlSyncValidityDuration of the serving cell starting from the subframe indicated by the epochTime of the free serving cell;

[0151] 1> If it includes SatSwitchWithReSync and t-Service, and the UE supports hard satellite handover with resynchronization:

[0152] 2> If t-ServiceStart is included, and the UE supports soft satellite handover with resynchronization:

[0153] 3> Perform a satellite handover with resynchronization between the time indicated by t-ServiceStart and the time indicated by t-Service for the serving cell, as specified in 5.7.19.

[0154] 2> Otherwise:

[0155] 3> Perform satellite handover with resynchronization at the time indicated by t-Service for the serving cell, as specified in 5.7.19.

[0156] Note: The UE should attempt to reacquire SIB19 via the UE implementation scheme before the duration indicated by ntn-UlSyncValidityDuration and epochTime expires.

[0157] *******************************Next quote******************************

[0158] 5.2.2.6T430 expires

[0159] UE should:

[0160] 1> If the serving cell's T430 expires and it is in RRC_CONNECTED:

[0161] 2> Notify the lower-level UL of synchronization loss;

[0162] 2> Obtain SIB19 as defined in Clause 5.2.2.3.2;

[0163] 2> After successfully obtaining SIB19:

[0164] 3> Notify the lower layer when UL synchronization is obtained;

[0165] Note: The exact time of obtaining UL synchronization (after acquiring SIB19) depends on the UE implementation scheme, and the exact time can be from the subframe indicated by epochTime, and optionally before the subframe indicated by epochTime.

[0166] *******************************Next quote******************************

[0167] 5.3.5 RRC Reconfiguration

[0168] 5.3.5.1 Overview

[0169] Figure 7 It is the 3GPP TS 38.331V18.0.0 draft. Figure 5 3.5.1-1: Reproduction of successful RRC reconfiguration.

[0170] Figure 8 It is the 3GPP TS 38.331V18.0.0 draft. Figure 5 3.5.1-2: Reproduction of RRC reconfiguration failure.

[0171] …

[0172] 5.3.5.3 UE receives RRC Reconfiguration

[0173] The UE shall perform the following actions upon receiving an RRCReconfiguration, during a conditional reconfiguration (CHO, CPA, or CPC), or during an LTM cell handover:

[0174] …

[0175] 1> If RRCReconfiguration contains masterCellGroup:

[0176] 2> According to 5.3.5.5, perform cell group configuration for the received masterCellGroup;

[0177] …

[0178] 5.3.5.5 Cell Group Configuration

[0179] 5.3.5.5.1 Overview

[0180] …

[0181] Based on the received CellGroupConfig IE, the UE performs the following actions:

[0182] 1> If CellGroupConfig contains spCellConfig with reconfigurationWithSync:

[0183] 2> Perform a synchronized reconfiguration according to 5.3.5.5.2;

[0184] …

[0185] 5.3.5.5.2 Features synchronized reconfiguration

[0186] The UE will perform the following actions to perform a synchronous reconfiguration.

[0187] 1> If AS security is not activated, then the action is performed as specified in 5.3.11 after going to RRC_IDLE, with the release reason being "other", and the program ends after the release reason;

[0188] 1> Stop timer T430 (if it is running);

[0189] …

[0190] 2> If this procedure is executed against an MCG, or if this procedure is executed against an SCG in which an E-UTRA or NR RRC message containing an embedded RRCReconfiguration message is not indicated as deactivated, then:

[0191] 3> Start timer T304 for the corresponding SpCell, where the timer value is set to t304, as included in reconfigurationWithSync;

[0192] …

[0193] 2> Begin DL synchronization with the target SpCell;

[0194] 2> Apply the specified BCCH configuration defined in 9.1.1.1 to the target SpCell;

[0195] 2> Obtain the MIB of the target SpCell, which is scheduled as specified in TS 38.213

[13] ;

[0196] 2> If NTN-Config is configured for the target cell:

[0197] 3> Based on the target cell NTN-config, start timer T430, where the timer value is set to ntn-UlSyncValidityDuration starting from the subframe indicated by epochTime;

[0198] …

[0199] 3> Reset the MAC entity of this cell group;

[0200] 3> Treat SCells of this cell group (if configured) that are not included in the SCellToAddModList in the RRCReconfiguration message as being in a deactivated state;

[0201] 3> Apply the value of newUE-Identity as the C-RNTI for this cell group;

[0202] 3> Configure the lower layer according to the received spCellConfigCommon;

[0203] 3> If it contains rach-LessHO:

[0204] 4> Configure the lower layer according to the rach-LessHO configuration for the target SpCell;

[0205] 3> If the received reconfigurationWithSync contains any additional fields not previously covered, then configure the lower layer based on those additional fields.

[0206] …

[0207] 5.3.5.13 Conditional Reconfiguration

[0208] 5.3.5.13.1 Overview

[0209] In a conditional reconfiguration, the network configures one or more candidate target SpCells for the UE. The UE evaluates the conditions of each configured candidate target SpCell. The UE applies a conditional reconfiguration associated with one of the target SpCells that meets the associated execution conditions.

[0210] …

[0211] The network provides configuration parameters for the target SpCell in ConditionalReconfiguration IE.

[0212] …

[0213] 5.3.5.13.4 Conditional Reconfiguration Assessment

[0214] UE should:

[0215] 1> For each condReconfigId within VarConditionalReconfig:

[0216] 2> If the RRCReconfiguration within condRRCReconfig includes a masterCellGroup containing reconfigurationWith Sync:

[0217] …

[0218] 4> Cells with physical cell identities that match the values ​​indicated in ServingCellConfigCommon contained in reconfigurationWithSync within the masterCellGroup in the received condRRCReconfig are considered applicable cells;

[0219] …

[0220] 2> For each measId contained in the measIdList within the VarMeasConfig indicated in the condExecutionCond, condExecutionCondSCG, or condExecutionCondPSCell associated with condReconfigId:

[0221] 3> If condTriggerConfig is not configured with nesEvent:

[0222] 4> If condEventId is associated with condEventT1, and if the entry conditions for this event associated with condReconfigId (i.e., the event corresponding to condEventId in the corresponding condTriggerConfig within VarConditionalReconfig) have been met for the applicable cell; or

[0223] 4> If condEventId is associated with condEventD1, and if the applicable cell for the corresponding timeToTrigger period defined for this event in VarConditionalReconfig has met the entry conditions applicable to this event associated with condReconfigId (i.e., the event corresponding to condEventId of the corresponding condTriggerConfig in VarConditionalReconfig); or

[0224] 4> If condEventId is associated with condEventD2, and if the applicable cell for the corresponding timeToTrigger period defined for this event in VarConditionalReconfig has met the entry conditions for this event associated with condReconfigId (i.e., the event corresponding to condEventId of the corresponding condTriggerConfig in VarConditionalReconfig); or

[0225] 4> If condEventId is associated with condEventA3, condEventA4, or condEventA5, and if the entry conditions for this event associated with condReconfigId (i.e., the event corresponding to condEventId of the corresponding condTriggerConfig within VarConditionalReconfig) are met for all measurements after Layer 3 filtering performed during the corresponding timeToTrigger period defined for this event in VarConditionalReconfig) in the applicable cell:

[0226] 5> The event associated with the measId is considered to have been satisfied;

[0227] 4> If the measId of this event associated with condReconfigId has been modified; or

[0228] 4> If condEventId is associated with condEventT1, and if the leave condition applicable to this event associated with condReconfigId (i.e., the event corresponding to condEventId of the corresponding condTriggerConfig within VarConditionalReconfig) has been met for the applicable cell; or

[0229] 4> If condEventId is associated with condEventD1, and if the leave condition applicable to this event associated with condReconfigId (i.e., the event corresponding to condEventId of the corresponding condTriggerConfig within VarConditionalReconfig) is met for the applicable cell during the corresponding timeToTrigger period defined for this event in VarConditionalReconfig; or

[0230] 4> If condEventId is associated with condEventD2, and if the leave condition applicable to this event (i.e., the event corresponding to condEventId of the corresponding condTriggerConfig within VarConditionalReconfig) is met for the applicable cell during the corresponding timeToTrigger period defined for this event in VarConditionalReconfig; or

[0231] 4> If condEventId is associated with condEventA3, condEventA4, or condEventA5, and if the leave condition applicable to this event associated with condReconfigId (i.e., the event corresponding to condEventId of the corresponding condTriggerConfig within VarConditionalReconfig) is satisfied for all measurements after Layer 3 filtering performed during the corresponding timeToTrigger period defined for this event in VarConditionalReconfig) for the applicable cells:

[0232] 5> Events associated with the measId are considered unsatisfied;

[0233] 3> If the events associated with all measIds in the applicable cell's condTriggerConfig have been satisfied:

[0234] 4> The applicable cell associated with the condReconfigId is considered the triggered cell;

[0235] 4> Initiate a conditional reconfiguration execution as specified in 5.3.5.13.5;

[0236] …

[0237] 5.3.5.13.5 Conditional Reconfiguration Execution

[0238] UE should:

[0239] …

[0240] 2> The cell to be triggered is considered as the selected cell for conditional reconfiguration execution;

[0241] 1> For selected cells where conditional reconfiguration is performed:

[0242] …

[0243] 3> Apply the stored condRRCReconfig of the selected cell and perform the actions specified in 5.3.5.3;

[0244] *******************************Next quote******************************

[0245] 5.7.19 Satellite handover with resynchronization in RRC_CONNECTED

[0246] UE should:

[0247] 1> Stop timer T430 (if it is running);

[0248] 1> Notify the lower layer that UL synchronization has been lost due to satellite handover with resynchronization;

[0249] 1> Begin resynchronizing the DL of the SpCell of the satellite service as indicated by ntn-Config in SatSwitchWithReSync;

[0250] 1> Start timer T430, where the timer value is set to ntn-UlSyncValidityDuration starting from the subframe indicated by epochTime in ntn-Config in SatSwitchWithReSync;

[0251] 1> Notify the lower layer when UL synchronization is obtained.

[0252] Editor's Note: Whether the UE can obtain DL synchronization from the target satellite without losing UL synchronization with the source satellite in a soft handover scenario requires further research.

[0253] *******************************End of quotation******************************

[0254] *******************************Quotation start[2]***************************

[0255] 5.2a Maintenance of UL Synchronization

[0256] For each serving cell, the MAC entity should:

[0257] 1> If an uplink synchronization indication has been received from the upper layer (see Clauses 5.2.2.6 and 5.7.19 of TS 38.331):

[0258] 2> If an uplink synchronization indication is received after an indication of uplink synchronization loss due to satellite handover with resynchronization (see Clause 5.7.19 of TS 38.331):

[0259] 3> For PTAG, N TA The value (as defined in TS 38.211) is set to zero;

[0260] 3> Indicate the difference Koffset with a value of zero to the lower level.

[0261] 2> Allow uplink transmission on the serving cell.

[0262] 1> If an indication of uplink synchronization loss is received from the upper layer, or due to uplink synchronization loss caused by a satellite handover with resynchronization (see Clauses 5.2.2.6 and 5.7.19 of TS 38.331):

[0263] 2> Clear all HARQ buffers;

[0264] 2> Do not perform any uplink transmissions on the serving cell.

[0265] Note: The MAC entity suspends all UL operations (e.g., stops RACH, SR, and UL HARQ operations) after receiving an indication of uplink synchronization loss, and resumes operations upon receiving an indication of uplink synchronization.

[0266] *******************************End of quotation******************************

[0267] Some configuration (information) related to NTN and / or satellites may be provided by NW, as specified in TS 38.331 ([3] 3GPP TS38.331 V18.0.0 draft):

[0268] *******************************Quotation start[3]***************************

[0269] 6.3.1 System Information Block

[0270] -SIB19

[0271] SIB19 contains satellite auxiliary information for NTN access.

[0272] SIB19 Information Elements

[0273]

[0274]

[0275]

[0276]

[0277] *****************************Next Citation******************************* -NTN-ConfigIE NTN-Config provides the parameters required for a UE to access NR via NTN.

[0278] NTN-Config Information Elements

[0279]

[0280]

[0281]

[0282]

[0283]

[0284] *******************************End of quotation******************************

[0285] The following protocols were adopted at the 3GPP RAN2 meeting for satellite handover with resynchronization. Throughout this disclosure, the following are interchangeable: unchanged Physical Cell Identity (PCI) mechanism, unchanged PCI (handover), PCI unchanged (handover), satellite handover / handover (without PCI change), satellite handover / handover with unchanged PCI, satellite handover with resynchronization, and / or satellite handover with resynchronization.

[0286] At the RAN2#121bis meeting:

[0287] - In quasi-Earth fixed cell scenarios, for hard satellite handover (without key change) in the same synchronization signal block (SSB) frequency and the same next-generation node B (gNB), satellite handover without PCI change (no L3 mobility required) is supported, unless a major technical problem is identified via RAN1.

[0288] During the RAN2#122 meeting:

[0289] - In a hard handover with invariant PCI scenario (i.e., no handover), the UE needs to know the time it will attempt to resynchronize.

[0290] The t-Service in SIB19 can also be interpreted by a Rel-18 UE in connected mode to know that a satellite change or feed link change has occurred.

[0291] During the RAN2#123 meeting:

[0292] - An explicit instruction will be introduced to enable invariant PCI switching.

[0293] The invariant PCI mechanism can be applied to situations where the coverage gap is zero or negligible. Whether we need to support scenarios requiring the introduction of t-gap or t-start requires further investigation (FFS).

[0294] - The PCI invariant procedure can be executed without performing the Random Access Channel (RACH).

[0295] - In the case of constant PCI, the User Equipment (UE) considers that the uplink (UL) synchronization timer expires at t-Service (current cell stop time) to stop any UL operation.

[0296] - Under the condition of unchanged PCI, for RACH-based solutions, the UE can trigger RACH immediately after synchronizing with the downlink (DL) of the new satellite.

[0297] In the RAN2#123bis meeting:

[0298] - The network provides the UE with the synchronization information of the target satellite in advance via broadcast signaling before the satellite handover.

[0299] -RAN2 confirms that satellite handover with unchanged PCI is only applicable to quasi-geostationary systems.

[0300] - SIB19 provides information on only one target satellite for the serving cell (i.e., NTN-config).

[0301] -Supports soft satellite switching in Rel-18.

[0302] - An indication will be provided as to whether to use a hard switch or a soft switch.

[0303] - At least during soft satellite handover, the network provides the UE with the target satellite's SSB information.

[0304] - In soft satellite handover, the UE can begin synchronization with the target satellite before the source satellite's T-service.

[0305] - A T-start is introduced, which indicates the earliest time when the UE can begin synchronization with the target satellite (the actual signaling needs further investigation). In a soft handover scenario, the target satellite's T-start is earlier than the source satellite's T-service.

[0306] - For soft satellite handover, the exact time when the UE begins synchronization with the target satellite (between T-start and T-service) depends on the UE implementation scheme.

[0307] - When the UE switches to the target satellite, the UE does not need to connect to the source satellite.

[0308] During the RAN2#124 meeting:

[0309] - Introduce a new target satellite configuration, such as ntn-TargetSatConfig, which provides the NTN-config of the target satellite for a specific signaling format regarding target satellite information in SIB19. The presence of this information indicates support for satellite handover without PCI changes.

[0310] - At least for soft handover, a "SSB time offset" is required between the source satellite and the target satellite. The "SSB time offset" is specified as a new IE and has the same format as the "offset" in SSB-MTC4.

[0311] -Target satellite SSB tracking is handled autonomously by the UE based on the provided SSB time offset.

[0312] - The "SSB time offset" between the source satellite and the target satellite should be provided in SIB19.

[0313] - Supports implicit indication to notify the UE whether it is a hard handover or a soft handover.

[0314] - For soft satellite handover, providing the target satellite's "SSB time offset" in SIB19 as a baseline is sufficient.

[0315] -T-start is sent explicitly (in the same format as T-service). If T-start is not sent, it is assumed that T-start equals T-service, i.e., a hard handover.

[0316] - For R18, we clarify that sending a T-start higher than T-service is an unforeseen situation, and the UE will assume that T-start = T-service.

[0317] - During satellite handover procedures, the UE should reset the L3 filter for serving cell radio resource management (RRM) measurements and radio link monitoring (RLM), depending on the UE implementation (i.e., without RAN2 specification impact).

[0318] - If the UE receives a handover (HO) command before the UE initiates the satellite handover procedure (i.e., before the time of satellite handover), the UE will immediately initiate the HO procedure.

[0319] - Conditional handover (CHO) and satellite handover procedures can be configured simultaneously.

[0320] - When configuring CHO (for different cells) and satellite handover procedures, the UE initiates the earlier triggered procedure; whether both procedures are triggered simultaneously depends on the UE implementation plan.

[0321] This feature will be referred to as "satellite handover with resynchronization".

[0322] A non-terrestrial network (NTN) can be viewed as an NG-RAN composed of next-generation node Bs (gNBs) that provide non-terrestrial New Radio (NR) access to user equipment (UEs) via NTN payloads and NTN gateways on airborne or spaceborne NTN vehicles. UEs can link to, pre-occupy, and / or connect to NTN networks involving airborne / spaceborne transmission. NTNs can include various platforms, including low Earth orbit (LEO) satellites, medium Earth orbit (MEO) satellites, highly elliptical orbit (HEO) satellites, geostationary orbit (GEO) satellites, geostationary geosynchronous orbit (GSO) satellites, non-geostationary geosynchronous orbit (NGSO) satellites, and / or high-altitude communication platforms (HAPS). LEO satellites may have earth-fixed beams (e.g., beams temporarily fixed at one location for a period of time) or earth-moving beams (e.g., beams continuously moving along with the satellite). NTN can provide extensive area coverage in situations where terrestrial networks (TN) are not feasible (e.g., deserts, polar regions, and / or on airplanes) and provide network (NW) access.

[0323] The NW can provide NTN information to the UE. NTN information can be, or may be referred to as, satellite (auxiliary) information. NTN information can be parameters required for the UE to access the NW via NTN access. NTN information can be, or includes at least NTN configuration (e.g., NTN-Config), time information (e.g., t-Service), reference location (e.g., referenceLocation), and distance threshold (e.g., distanceThresh). The NW can provide NTN information to the UE, for example, via the serving cell, in NTN-specific system information (e.g., System Information Block 19 (SIB19)) or Radio Resource Control (RRC) messages (e.g., RRCReconfiguration). NTN-specific system information can be an SIB that includes NTN information. Throughout this disclosure, SIB19 can be system information for the serving cell. SIB19 can be NTN-specific system information. SIB19 can contain satellite auxiliary information. SIB19 can contain NTN uplink (UL) synchronization information. System information can be referred to as a system information block.

[0324] NTN configuration (e.g., NTN-Config) may be or include (at least) the epoch time (e.g., epochTime), validity duration (e.g., ntn-UlSyncValidityDuration), satellite ephemeris (e.g., ephemerisInfo), and / or common timing advance (TA) (e.g., ta-Info). The validity duration (e.g., ntn-UlSyncValidityDuration) may indicate the maximum time a UE can apply satellite information and / or NTN-specific system information (e.g., SIB19) without acquiring new satellite information and / or NTN-specific system information (e.g., SIB19). The validity duration (e.g., ntn-UlSyncValidityDuration) and / or epoch time (e.g., epochTime) may be associated with (or applied to) NTN-specific system information (e.g., SIB19), NTN configuration (e.g., NTN-Config), satellite information, satellite ephemeris (e.g., ephemerisInfo), and / or common TA (e.g., ta-Info). Time information (e.g., t-Service) may be the service termination time of the serving cell. Timing information (e.g., t-Service) can be the time when a UE will leave the coverage area of ​​the serving cell. Timing information (e.g., t-Service) can indicate when the serving cell will cease providing service to the area it currently covers.

[0325] Throughout this disclosure, one, some, and / or all instances of “NTN Configuration” may correspond to “NTN Information,” “Satellite Information,” “NTN-Config,” and / or “Auxiliary Information,” and may be supplemented by and / or replaced by them.

[0326] The UE will use a timer (e.g., an uplink (UL) synchronization timer) to maintain UL synchronization (e.g., for the serving cell) and / or the validity of the NTN information based on NTN information. The UE will start or restart a UL synchronization timer (e.g., T430) with a validity duration (e.g., ntn-UlSyncValidityDuration) indicated by a free corresponding epoch time (e.g., epochTime), where the validity duration (e.g., ntn-UlSyncValidityDuration) and epoch time (e.g., epochTime) are provided for the serving cell. The UE will apply the epoch time (e.g., epochTime) as the start time of the UL synchronization timer (e.g., T430). The UE will apply the validity duration (e.g., ntn-UlSyncValidityDuration) as the length of the UL synchronization timer (e.g., T430). The UL synchronization timer (e.g., T430) can be started and / or run based on, for example, NTN information of the serving cell. A validity duration (e.g., ntn-UlSyncValidityDuration) and / or a UL synchronization timer (e.g., T430) can indicate the duration for which satellite information or a portion of satellite information (e.g., ephemerisInfo, ta-Info) is valid. For example, when the UL synchronization timer (e.g., T430) is running, satellite information (a portion) can be considered valid. When the UL synchronization timer (e.g., T430) is not running, satellite information (a portion) can be considered invalid. A UL synchronization timer (e.g., T430) can indicate the duration for which UL synchronization is acquired or maintained based on satellite information or a portion of satellite information (e.g., ephemerisInfo, ta-Info). For example, when the UL synchronization timer (e.g., T430) is running, UL can be considered synchronized, or UL synchronization can be considered acquired. When the UL synchronization timer (e.g., T430) is not running, UL can be considered desynchronized, or UL synchronization can be considered lost.

[0327] Based on current specifications (e.g., [2] 3GPP TS 38.321V18.0.0 draft and [3] 3GPP TS38.331V18.0.0 draft), upon receiving SIB19, the UE immediately starts a UL synchronization timer (e.g., T430) based on the serving cell's NTN configuration. In response to receiving a handover command (e.g., RRCReconfiguration and ReconfigurationWithSync), the UE stops the UL synchronization timer (e.g., T430) and then starts a new UL synchronization timer (e.g., T430). When the UE performs and / or implements a handover (or reconfigures using synchronization), the UE stops the UL synchronization timer (e.g., T430). Then, the UE starts a new UL synchronization timer (e.g., T430) based on the target cell's NTN configuration.

[0328] The UE will reacquire SIB19 before the UL synchronization timer expires. In RRC connected mode, after the UL synchronization timer expires, the UE can assume uplink synchronization is lost and acquire SIB19. In response to acquiring SIB19, the UE can assume uplink synchronization is achieved. If uplink synchronization is considered lost, the UE can clear the Hybrid Automatic Repeat Request (HARQ) buffer and may not perform UL transmission on the serving cell. If uplink synchronization is considered (achieved), the UE can perform UL transmission on the serving cell. When the UL synchronization timer is running, the serving cell can be considered to have achieved uplink synchronization in RRC connected mode (e.g., uplink synchronization achieved). When the UL synchronization timer is not running and / or expires, the serving cell can be considered to have not achieved uplink synchronization in RRC connected mode (e.g., uplink synchronization lost).

[0329] Throughout this disclosure, the UL synchronization timer can be a timer for the serving cell (or source cell). The UL synchronization timer can be a UL synchronization timer for the target cell (or neighboring cells). The UL synchronization timer can be a validity timer. The UL synchronization timer can be timer T430. The UL synchronization timer can be used to maintain / evaluate UL synchronization, such as when the UE is in an NTN or when the UE is connected to a satellite. The UL synchronization timer can indicate / process the duration for which (associated) auxiliary information is valid. The UL synchronization timer can indicate / dispose of the duration for which the UE can apply (associated) satellite information, for example, without acquiring new satellite information. The UL synchronization timer can be used in an NTN. The UL synchronization timer (e.g., T430) may not be used in a TN. The UL synchronization timer (e.g., T430) can be an NTN-specific timer. The UL synchronization timer can be different from a TA timer (e.g., TimeAlignmentTimer). The UL synchronization timer may not be used to maintain UL TA. The UL synchronization timer can be associated with a cell. The UL synchronization timer may not be associated with a TA group. When (associated) satellite information is valid, the UE can consider the UL to be synchronized.

[0330] In an NTN, the NW (Network Controller) providing service to the UE on the ground may remain unchanged, but the satellite between the UE and the NW may change due to satellite handover or satellite movement. To prevent L3 mobility issues such as handover caused by satellite handover, and to reduce signaling overhead and / or downtime, a satellite handover mechanism with resynchronization will be supported in the NTN. The satellite handover mechanism avoids UE mobility within the cell by maintaining the same Physical Cell Identity (PCI) across geographical areas. A satellite handover with resynchronization can be, or may be referred to as a satellite handover without PCI change and / or a handover with unchanged PCI. A satellite handover with resynchronization can be, or may be referred to as a mechanism without L3 mobility (e.g., handover). When a satellite handover occurs, the UE can maintain its cell configuration without changing the gNB. Signaling such as handover (HO) commands can be reduced. The UE should not trigger an RRC reconfiguration procedure. Because satellite ephemeris tables (e.g., ephemerisInfo) and / or common TAs (e.g., ta-Info) may differ, the UE can perform resynchronization with the serving cell. The UE can perform downlink (DL) and / or UL synchronization with the serving cell. The UE can (re)acquire SIB19. In satellite handover with resynchronization, the UE can switch / change the serving satellite without performing handover, receiving RRC (re)configuration, changing the serving cell's PCI, and / or changing the serving gNB.

[0331] Throughout this disclosure, satellite handover with resynchronization can be (replaced by / equivalent to) a procedure with constant PCI handover, cell handover with resynchronization, `satSwitchWithResync`, cell handover with constant PCI, hard / soft satellite handover, satellite handover without PCI change, resynchronization or the like, and / or any combination of the foregoing. Examples of constant PCI handover are... Figure 9 As shown in (quoted from [4]R2-2308373).

[0332] The UE can be instructed (by a network node) to perform (or initiate) a satellite handover with resynchronization, for example, via system information (e.g., SIB19). The UE can receive a configuration (or indication) for the satellite handover with resynchronization. This configuration (or indication) can instruct the UE to perform (or initiate) a satellite handover with resynchronization (e.g., at a specific timing such as t-Service). The configuration can be included in the system information (e.g., SIB19). The configuration (or indication) can be `satSwitchWithResync`. Throughout this disclosure, `satSwitchWithResync` can be an indication that enables / triggers a satellite handover with resynchronization.

[0333] The UE can perform (or initiate) a satellite handover with resynchronization, for example, in response to (receiving) an indication (or configuration) of a satellite handover with resynchronization. The UE can perform (or initiate) a satellite handover with resynchronization, for example, at a specific time, at t-Service, before t-Service, after t-Service, or at t-Start. The specific time can be indicated by the network node. The specific time can be indicated in system information (e.g., SIB19). The specific time can be a second timing. The specific time can be (or indicate) the cell stop time (e.g., t-Service). The specific time can be (or indicate) the handover start time (e.g., t-Start). The cell stop time (e.g., t-Service) can be (or indicate) when a cell provided via the NTN will cease providing service to its currently covered area. The handover start time (e.g., t-Start) can be (or indicate) when a second satellite will provide service to the area (or cell) currently covered or served by the first satellite. The handover start time (e.g., t-ServiceStart) can be (or indicate) when a satellite handover with resynchronization can begin or be performed. Throughout this disclosure, t-ServiceStart can be the satellite handover start time, and t-Service can be the (serving) cell (service) stop time. Throughout this disclosure, t-ServiceStart can be represented by subtracting t-Gap from t-Service.

[0334] In response to a satellite handover with resynchronization (e.g., if an indication of a satellite handover with resynchronization is received, during a satellite handover with resynchronization, after the initiation of a satellite handover with resynchronization, when a satellite handover with resynchronization is initiated, and / or if a satellite handover with resynchronization is initiated, at a cell stop time such as t-Service), the UE may or may not:

[0335] - Treat the UL synchronization timer (e.g., T430) as expired;

[0336] - Stop the UL synchronization timer (e.g., T430);

[0337] - Start timer T430, where the timer value is set to ntn-UlSyncValidityDuration from the subframe indicated by epochTime in (ntn-Config) in SatSwitchWithReSync;

[0338] - For example, after the cell stop time (e.g., t-Service), and / or until a new differential Koffset (e.g., Media Access Control (MAC) control element (CE)) is received, the use of the UE-specific Koffset (if configured) is stopped;

[0339] - For example, use a cell-specific Koffset after the cell stop time (e.g., t-Service), and / or use a cell-specific Koffset until a new differential Koffset (e.g., MAC CE) is received;

[0340] - Perform DL (re)synchronization with the serving cell (or NW);

[0341] -Initiate resynchronization of the DL with the special cell (SpCell) of the satellite service indicated in SatSwitchWithReSync (ntn-Config);

[0342] - (Re)acquire SIB19 (and / or SIB1, SIB2);

[0343] - (Re)acquire (e.g., the serving cell's NTN-related configuration, such as the ephemeris, contained in SIB19);

[0344] - Trigger the random access (RA) procedure;

[0345] - Perform UL synchronization with the serving cell (or NW);

[0346] - Notify the lower layer that UL synchronization has been lost due to satellite handover with resynchronization; and / or

[0347] - Notify the lower level when UL synchronization is obtained.

[0348] Satellite handover with resynchronization can be or may include soft satellite handover and / or hard satellite handover. Throughout this disclosure, "soft satellite handover" can mean "soft satellite handover with resynchronization." Throughout this disclosure, "hard satellite handover" can mean "hard satellite handover with resynchronization." Soft satellite handover or hard satellite handover can be indicated by the NW. The NW can provide an indication of the satellite handover type (e.g., soft satellite handover or hard satellite handover). The NW can provide t-ServiceStart and / or Synchronization Signal Block (SSB) information for soft satellite handover. The indication can be parameters, t-ServiceStart, and / or SSB information.

[0349] For hard satellite handover, after disconnecting from the old satellite (e.g., the source satellite, the first satellite), the UE can connect to a new satellite (e.g., the target satellite, the second satellite) (or synchronize with it). An example of hard satellite handover is... Figure 10 As shown in [5]R2-2310307. Serving satellites can be at a point in time (e.g., Figure 10 The handover time (t-Service) is used for handover. The first satellite (e.g., Figure 10 STA1 in the context can be a serving satellite prior to the satellite handover and / or the time point. The second satellite (e.g., Figure 10 STA2 in the context can be a serving satellite after a satellite handover and / or a specific time point. The first and second satellites can provide service to the same cell (e.g., using the same PCI). The first satellite can be the source satellite. The second satellite can be the target satellite.

[0350] For soft satellite handover, the UE can connect to (or synchronize with) a new satellite (e.g., a target satellite, a second satellite) before disconnecting from the old satellite (e.g., the source satellite, the first satellite). An example of soft satellite handover is... Figure 11 As shown in [5]R2-2310307. Serving satellites can be used for a duration (e.g., Figure 11 The handover occurs during the T-duration (between t-ServiceStart and t-Service). The first satellite (e.g., Figure 11 STA1) and the second satellite (e.g., Figure 11 STA2 in the context of the service provides service / coverage for the same area during the duration stated. The duration can begin with t-ServiceStart and end with t-Service. The first satellite can be the service satellite that served before satellite handover and / or t-ServiceStart. The second satellite (e.g., Figure 11 STA2 in the context can be the serving satellite after satellite handover and / or t-Service. The first and second satellites can provide service to the same cell (e.g., using the same PCI). The first satellite can be the source satellite. The second satellite can be the target satellite.

[0351] Throughout this disclosure, satellite handover with resynchronization can be, can be referred to as, can be replaced by and / or can include hard satellite handover with resynchronization and / or soft satellite handover with resynchronization.

[0352] Based on the current NR RRC specification ([3]TS 38.331v18.0.0), when the UE is in RRC_CONNECTED, the UE performs an action upon receiving SIB19 (as specified in section 5.2.2.4.21 of TS 38.331 ([3]3GPP TS 38.331V18.0.0 draft)), including checking SatSwitchWithReSync in SIB19 to determine whether to perform a satellite handover with resynchronization. In other words, based on the current NR RRC specification, the UE determines whether to perform a satellite handover with resynchronization at a timing when the UE receives SIB19 (e.g., at the first timing). If SIB19 contains SatSwitchWithResync and t-Service and the UE supports satellite handover with resynchronization, the UE determines whether to perform a satellite handover with resynchronization based on the UE's RRC state at the timing of receiving SIB19 (e.g., at the first timing). In other words, satellite handover with resynchronization is only performed when the UE is in RRC_CONNECTED at the timing of receiving SIB19 (e.g., the first timing). Figure 12 An example is shown where the UE receives SIB19 at a first timing in RRC_CONNECTED and initiates a satellite handover at a second timing in RRC_CONNECTED. However, for example, at the first timing, the UE may be in the RRC_IDLE (or RRC_INACTIVE) state when it receives SIB19. If the UE is in the RRC_IDLE or RRC_INACTIVE state at the timing of receiving SIB19 (e.g., the first timing), the UE will not perform a satellite handover with resynchronization, even if SIB19 contains SatSwitchWithReSync and t-Service and the UE is in RRC_CONNECTED at t-Service (e.g., the second timing). The UE may enter RRC_CONNECTED after receiving SIB19, and the UE may be in RRC_CONNECTED at the time indicated by t-Service (or between the time indicated by t-ServiceStart and the time indicated by t-Service). In this situation, based on current specifications, the UE does not perform the action (to perform a satellite handover with resynchronization) because it is not in the RRC_CONNECTED state when it receives SIB19. The UE can determine not to initiate a satellite handover with resynchronization after receiving SIB19 in the RRC_IDLE or RRC_INACTIVE state (e.g., at the first timing). An example of this problem is... Figure 13 As shown in the image.

[0353] For example, according to the current specification, a UE can receive SIB19 from the serving cell at a first timing, where the UE is in the RRC_IDLE state at the first timing. SIB19 may contain at least ntn-Config (providing NTN configuration for the serving cell and / or neighboring cells), satSwitcgWithResync (indicating support for satellite handover in the serving cell), and t-Service (indicating when the serving cell will cease service to its currently covered area). After receiving SIB19, the UE can perform initial access to the serving cell (e.g., RRC connection establishment procedure) at a second timing. The UE can enter the RRC_CONNECTED state at / after the second timing. After entering the RRC_CONNECTED state, the serving satellite can be switched at a third timing indicated by t-Service. The UE may not perform a satellite handover with resynchronization at or before the third timing because the UE is not in the RRC_CONNECTED state when receiving SIB19. The serving satellite will be changed, but the UE will not perform resynchronization. The UE may lose coverage of the serving satellite at / after the third timing.

[0354] On the other hand, when the UE receives SIB19, the UE can be in RRC_CONNECTED. Based on the current NR RRC specification, when the UE is in RRC_CONNECTED, the UE performs an action after receiving SIB19 (as specified in section 5.2.2.4.21 of the draft 3GPP TS 38.331 V18.0.0 [3]), and the UE can determine to perform a satellite handover with resynchronization at the time indicated by t-Service (or between the time indicated by t-ServiceStart and the time indicated by t-Service). However, before the time indicated by t-Service (or between the time indicated by t-ServiceStart and the time indicated by t-Service), the UE can leave RRC_CONNECTED (and / or enter RRC_IDLE or RRC_INACTIVE). In this case, based on the current specification, the UE still performs a satellite handover with resynchronization when it is in RRC_IDLE (or RRC_INACTIVE).

[0355] Furthermore, based on the protocols in the RAN2 meeting, the UE should perform a conditional handover (CHO) / handover or an earlier triggered satellite handover with resynchronization. According to the current specification, the UE can perform a satellite handover with resynchronization regardless of whether a CHO / handover procedure has been triggered / initiated / is in progress. The UE can trigger a CHO / handover procedure and then still perform a satellite handover with resynchronization.

[0356] To address this issue, the UE can determine whether to perform / initiate a satellite handover with resynchronization based on one or more conditions at one or more specific timings. The specific timings may include a first timing and / or a second timing. The one or more conditions may be associated with either the first or the second timing.

[0357] The UE may determine to perform / initiate a satellite handover with resynchronization at a second timing point based on one or more of the conditions stated above. The UE may perform a satellite handover with resynchronization at a second timing point based on (or if) the one or more conditions stated above are met. The UE may not perform / initiate a satellite handover with resynchronization at a second timing point based on (or if) the one or more conditions stated above are not met.

[0358] The UE can determine whether to perform / initiate a satellite handover with resynchronization based on the UE's RRC state at one or more specific time points. The UE's RRC state can be or includes RRC idle state (RRC_IDLE), RRC inactive state (RRC_INACTIVE), and / or RRC connected state (RRC_CONNECTED). Throughout this disclosure, the following are interchangeable: RRC idle state, RRC idle mode, and RRC_IDLE (state / mode). Throughout this disclosure, the following are interchangeable: RRC inactive state, RRC inactive mode, and RRC_INACTIVE (state / mode). Throughout this disclosure, the following are interchangeable: RRC connected state, RRC connected mode, and RRC_CONNECTED (state / mode).

[0359] The UE can determine whether to perform / initiate a satellite handover with resynchronization based on whether a timer is running at a second timing point. The timer can be a related handover, CHO, and / or reconfiguration with synchronization. The timer can be a failure timer for handover, CHO, and / or reconfiguration with synchronization. The timer can be started in response to triggering / initiating / performing a procedure for handover, CHO, and / or reconfiguration with synchronization. The timer can be stopped in response to the completion of the handover, CHO, and / or reconfiguration with synchronization procedure. When the timer is running, the UE can consider the handover, CHO, and / or reconfiguration with synchronization procedure to be running. The timer can be T304.

[0360] The first timing may be the time when / after the UE receives the system information. The system information may be NTN-specific system information. The system information may be SIB19. The system information may include one or more NTN configurations (e.g., NTN-Config). The system information may include the NTN configuration for the serving cell of the serving satellite (e.g., NTN-Config). The system information may include the NTN configuration for the serving cell or neighboring cell of the target satellite (e.g., NTN-Config). The system information may include the NTN configuration for the target cell of the serving satellite or target satellite (e.g., NTN-Config). The system information may include the service stop time of the serving cell (e.g., t-Service). The system information may include an indication / configuration for satellite handover with resynchronization (e.g., SatSwitchWithReSync). The system information may or may not include the service start time of the target satellite (e.g., t-ServiceStart). The service start time of the target satellite (e.g., t-ServiceStart) may be before the service stop time (e.g., t-Service) of the serving cell.

[0361] The second timing can be a time indicated by the network. The second timing can be a time indicated by the service stop time of the serving cell (e.g., t-Service). The second timing can be a time indicated by the service stop time of the serving cell (e.g., t-Service) and the service start time of the target satellite (e.g., t-ServiceStart). The second timing can be the service stop time of the serving cell (e.g., t-Service). The second timing can be the time between the time indicated by the service start time of the target satellite (e.g., t-ServiceStart) and the time indicated by the service stop time of the serving cell (e.g., t-Service). The second timing can be the time when the UE determines to perform a satellite handover with resynchronization. The second timing can be the time when the UE is in RRC_CONNECTED. The second timing can be the time when the UE enters RRC_CONNECTED or later.

[0362] The UE can receive system information (e.g., SIB19) at a first timing and determine at a second timing whether to perform / initiate a satellite handover with resynchronization based on one or more of the conditions.

[0363] The one or more conditions can be one or more (or a combination of) the following:

[0364] - For example, regardless of which RRC state the UE is in at the first timing, the UE is in the RRC connection state at the second timing;

[0365] -The UE is in any of the RRC states at the first timing point;

[0366] - The system information includes an indication of satellite switching with resynchronization (e.g., satSwitchWithReSync);

[0367] - The system information includes the service downtime of the serving cell (e.g., t-Service);

[0368] - The UE supports satellite handover with resynchronization; and / or

[0369] - For example, at the second timing point, the timer (e.g., T304) is not running.

[0370] The UE may determine to perform / initiate a satellite handover with resynchronization without basing it on whether the UE is in an RRC connected state at the first timing point (e.g., after receiving SIB19). The UE may determine to perform a satellite handover with resynchronization based on (or if) the UE is in an RRC idle state, an RRC inactive state, or an RRC connected state at the first timing point (e.g., after receiving SIB19). The UE may determine to perform / initiate a satellite handover with resynchronization regardless of whether the UE is in an RRC idle state, an RRC inactive state, or an RRC connected state at the first timing point (e.g., after receiving SIB19). The UE may determine to perform a satellite handover with resynchronization regardless of its RRC state at the first timing point (e.g., after receiving SIB19).

[0371] The UE can determine whether to perform / initiate a satellite handover with resynchronization based on whether (or if) it is in an RRC connected state at a second timing point (e.g., indicated by t-Service and / or t-ServiceStart). Regardless of the UE's RRC state at the first timing point (e.g., after receiving SIB19), the UE can determine whether to perform / initiate a satellite handover with resynchronization based on whether (or if) it is in an RRC connected state at the second timing point (e.g., indicated by t-Service and / or t-ServiceStart). The UE can determine not to perform / initiate a satellite handover with resynchronization based on whether (or if) it is not in an RRC connected state at the second timing point (e.g., indicated by t-Service and / or t-ServiceStart). The UE can determine not to perform / initiate a satellite handover with resynchronization based on whether (or if) it is in an RRC idle / inactive state at the second timing point (e.g., indicated by t-Service and / or t-ServiceStart).

[0372] The UE can determine whether to perform / initiate a satellite handover with resynchronization based on whether (or if) it receives an SIB19 containing `satSwitchWithReSync`. The UE can determine whether to perform / initiate a satellite handover with resynchronization based on whether (or if) it receives an SIB19 containing `t-Service`. The UE can determine whether to perform / initiate a satellite handover with resynchronization based on whether (or if) it receives an SIB19 that does not contain `satSwitchWithReSync`. The UE can determine whether to perform / initiate a satellite handover with resynchronization based on whether (or if) it receives an SIB19 that does not contain `t-Service`.

[0373] The UE may determine whether to perform / initiate a satellite handover with resynchronization based on whether (or if) the UE supports satellite handover with resynchronization. The UE may determine whether to perform / initiate a satellite handover with resynchronization based on whether (or if) the UE supports hard satellite handover with resynchronization and whether `satSwitchWithReSync` and `t-Service` are included in the received SIB19. The UE may determine whether to perform / initiate a satellite handover with resynchronization based on whether (or if) the UE supports soft satellite handover with resynchronization and whether `satSwitchWithReSync`, `t-Service`, and `t-ServiceStart` are included in the received SIB19. The UE may determine not to perform / initiate a satellite handover with resynchronization based on whether (or if) the UE does not support satellite handover with resynchronization.

[0374] The UE may determine whether to perform / initiate a satellite handover with resynchronization based on whether (or if) T304 is not in operation at a second timing point (e.g., indicated by t-Service and / or t-ServiceStart). The UE may also determine not to perform / initiate a satellite handover with resynchronization based on whether (or if) T304 is in operation at a second timing point (e.g., indicated by t-Service and / or t-ServiceStart).

[0375] When the UE is in RRC_CONNECTED, the UE may not acquire (or receive) SIB19. After the UE enters RRC_CONNECTED, the UE may not acquire (or receive) SIB19. The UE may not acquire (or receive) SIB19 between the first and second timing intervals. The UE may not acquire (or receive) SIB19 between the time the UE enters RRC_CONNECTED and the second timing interval.

[0376] When the UE is in RRC_CONNECTED state, the UE's timer T430 can run (or T430 may expire and not occur). After the UE enters RRC_CONNECTED state, the UE's T430 can run (or T430 may expire and not occur). The UE's T430 can run between the first and second time intervals (or T430 may expire and not occur). The UE's T430 can run between the time the UE enters RRC_CONNECTED state and the second time interval (or T430 may expire and not occur).

[0377] One or more of the embodiments, concepts, methods, instances, behaviors, events and / or conditions described above can be combined.

[0378] To address this issue, when SIB19 is received, not only in the case where the UE is in RRC_CONNECTED (e.g.) Figure 12 (As shown) and in the case where the UE is in RRC_IDLE (or RRC_INACTIVE) (e.g.) Figure 14 As shown), based on (at least) SatSwitchWithReSync and t-Service included in SIB19, the UE can (at a time when the UE is in RRC_CONNECTED) determine to perform / initiate a satellite handover with resynchronization.

[0379] Figure 14 An example of the invention is illustrated below. The UE can receive SIB19 at a first timing, where the UE is in RRC_IDLE or RRC_INACTIVE at the first timing. The first timing can be the timing when the UE receives SIB19. For example, after receiving SIB19, the UE can enter (or transition to) RRC_CONNECTED from RRC_IDLE or RRC_INACTIVE. For example, after receiving SIB19, the UE can initiate an initial access procedure, an RRC connection establishment procedure, and / or an RRC connection recovery procedure. In response to initiating the initial access procedure, the RRC connection establishment procedure, and / or the RRC connection recovery procedure, the UE can enter RRC_CONNECTED. Based on (at least) SatSwitchWithResync and t-Service included in SIB19, the UE can determine at a second timing to initiate a satellite handover with resynchronization when the UE is in RRC_CONNECTED. The second timing can be the timing when the UE is in RRC_CONNECTED and / or the timing indicated by t-Service. The second timing can be the timing when the UE determines to initiate a satellite handover with resynchronization.

[0380] When SIB19 is received, the UE can be in any of the following states at the first timing: RRC_CONNECTED, RRC_IDLE, or RRC_INACTIVE. When the UE is in any RRC state at the first timing, the UE can determine to initiate a satellite handover with resynchronization at the second timing. Regardless of the UE's RRC state at the first timing, the UE can determine to initiate a satellite handover with resynchronization at the second timing. The UE can determine to initiate a satellite handover with resynchronization based on its RRC state at the second timing. The UE can also determine to initiate a satellite handover with resynchronization without basing it on its RRC state at the first timing. The second timing can be different from the first timing. The second timing can be later than the first timing.

[0381] In response to initiating a satellite handover with resynchronization, the UE may perform at least one or more of the following actions (in sequence):

[0382] - Stop timer T430 (if it is running);

[0383] - Notify the lower layer that UL synchronization has been lost due to satellite switching with resynchronization;

[0384] - Synchronize with the DL of the SpCell served by the satellite indicated by SatSwitchWithReSync;

[0385] - Start timer T430, where the timer value is set to ntn-UlSyncValidityDuration from the subframe indicated by epochTime in SatSwitchWithReSync; and / or

[0386] - Notify the lower layer when UL synchronization is achieved.

[0387] In one or more instances, the UE receives SIB19 at a first timing and the SIB19 contains a t-Service indicating a second timing.

[0388] In one or more instances, the UE is in an RRC idle (and / or RRC inactive) state at both the first and second timing points. For example, based on the fact that the UE is not in an RRC connected state at the second timing point, the UE does not perform / initiate a satellite handover with resynchronization at the second timing point. The UE may perform / initiate initial access or RRC recovery after the second timing point.

[0389] In one or more instances, the UE is in an RRC idle (and / or RRC inactive) state at a first timing and in an RRC connected state at a second timing. The UE performs initial access or RRC recovery after the first timing and before the second timing. For example, based on the UE being in an RRC connected state at the second timing, the UE performs a satellite handover with resynchronization at the second timing.

[0390] In one or more instances, the UE is in an RRC connected state at both the first and second timing points. The UE can perform / initiate initial access or RRC recovery before the first timing point. For example, based on the UE being in an RRC connected state at the second timing point, the UE performs a satellite handover with resynchronization at the second timing point.

[0391] In one or more instances, the UE is in an RRC connected state at a first timing and in an RRC idle (and / or RRC inactive) state at a second timing. The UE performs an RRC release after the first timing and before the second timing. For example, based on the fact that the UE is not in an RRC connected state at the second timing, the UE does not perform / initiate a satellite handover with resynchronization at the second timing.

[0392] Figures 15 to 21 It provides examples of textual proposals based on the current specification.

[0393] exist Figure 15 In this process, the UE determines whether to perform / initiate a satellite handover with resynchronization regardless of the RRC status when it receives SIB19 / afterwards.

[0394] exist Figures 16 to 18 In the process, regardless of the RRC status when the UE receives SIB19, the UE determines whether to perform / initiate a satellite handover with resynchronization based on whether the UE is in the RRC_CONNECTED state at the time indicated by t-Service, after the time indicated by t-ServiceStart, or between the time indicated by t-ServiceStart and the time indicated by t-Service.

[0395] exist Figures 19 to 21 In the process, regardless of the RRC status when the UE receives SIB19, the UE determines whether to perform / initiate a satellite handover with resynchronization based on whether the UE is in the RRC_CONNECTED state and timer T304 is not running at the time indicated by t-Service, after the time indicated by t-ServiceStart, or between the time indicated by t-ServiceStart and the time indicated by t-Service.

[0396] The UE can receive NTN-related configurations (e.g., SIB19, NTN-Config).

[0397] The UE can reside in an NTN cell. The UE can connect to an NTN cell. The UE can reserve an NTN cell. The UE can connect to LEO, GEO, MEO, HEO, and / or HAPS. The UE can connect to one or two networks (nodes).

[0398] The UE can be referred to as the UE, the UE's RRC layer, the UE's MAC entity, or the UE's physical layer.

[0399] The UE can be an NR device. The UE can be a Long Term Evolution (LTE) device. The UE can be a Narrowband Internet of Things (NB-IoT) device. The UE can be an Enhanced Machine-Type Communication (eMTC) device. The UE can be a device with insufficient capabilities. The UE can be a mobile phone. The UE can be a wearable device. The UE can be a sensor. The UE can be a fixed device. The UE can be an (unmanned) aerial vehicle.

[0400] A network can be a network node. A network can be a base station. A network can be an access point. A network can be an evolved Node B (eNB). A network node can be a gNB. A network can be a gateway.

[0401] Various examples and embodiments of the invention are described below. The following aspects and embodiments are possible in relation to the methods, alternatives, concepts, examples, and embodiments detailed above and herein.

[0402] See Figure 22 Regarding such and other concepts, systems and methods of the present invention, method 1000 for a first UE in a wireless communication system includes receiving system information in an NTN cell at a first timing (step 1002), determining to perform / initiate a satellite handover with resynchronization based on at least the UE being in an RRC connection state at a second timing and / or regardless of the UE's RRC state at the first timing (step 1004), and performing a satellite handover with resynchronization at the second timing (step 1006).

[0403] In various embodiments, the system information is SIB19.

[0404] In various embodiments, the first timing is the time when the UE receives system information.

[0405] In various embodiments, the second timing is the time indicated by t-Service, or the time between the time indicated by t-ServiceStart and the time indicated by t-Serving. In various embodiments, t-Service is the time information for cell service termination, or the (serving) cell (service) termination time. In various embodiments, t-ServiceStart is the time information for satellite service commencement, or the satellite handover commencement time.

[0406] In various embodiments, t-Service and / or t-ServiceStart are included in the system information.

[0407] In various embodiments, the method further includes determining to perform / initiate a satellite handover with resynchronization based on: satSwitchWithReSync being included in system information, t-Service being included in system information, the UE supporting satellite handover with resynchronization, and / or the timer not being running.

[0408] In various embodiments, the timer is T304.

[0409] In various embodiments, satellite handover with resynchronization is either hard satellite handover with resynchronization or soft satellite handover with resynchronization.

[0410] In various embodiments, the UE is in an RRC idle state or an RRC inactive state at the first timing.

[0411] In various embodiments, the method further includes performing initial access or RRC recovery after a first timing period and before a second timing period.

[0412] Now for reference Figure 3 and Figure 4 In one or more embodiments from the perspective of a UE in a wireless communication system, apparatus 300 includes program code 312 stored in memory 310 of the transmitter. CPU 308 can execute program code 312 to: (i) receive system information in an NTN cell at a first timing; (ii) determine to perform / initiate a satellite handover with resynchronization based on the UE being in an RRC connected state at least at a second timing and / or regardless of the UE's RRC state at the first timing; and (iii) perform a satellite handover with resynchronization at the second timing. Furthermore, CPU 308 can execute program code 312 to perform all the actions, steps, and methods described above, below, or otherwise herein.

[0413] Now for reference Figure 3 and Figure 4In one or more embodiments, from the perspective of NW in a wireless communication system, device 300 includes program code 312 stored in memory 310 of the transmitter. CPU 308 can execute program code 312 to: (i) transmit system information in an NTN cell at a first timing; and (ii) perform a satellite handover with resynchronization at the UE at a second timing, wherein the UE is in an RRC connected state at the second timing and / or regardless of the UE's RRC state at the first timing. Furthermore, CPU 308 can execute program code 312 to perform all the actions, steps, and methods described above, below, or otherwise herein.

[0414] The one or more conditions can be one or more (or a combination of) the following:

[0415] - For example, regardless of which RRC state the UE is in at the first timing, the UE is in the RRC connection state at the second timing;

[0416] - For example, regardless of which RRC state the UE is in at the first timing, the UE is in the RRC idle / inactive state at the second timing;

[0417] -The UE is in any of the RRC states at the first timing point;

[0418] - The system information includes an indication of satellite switching with resynchronization (e.g., satSwitchWithReSync);

[0419] - The system information includes the service downtime of the serving cell (e.g., t-Service);

[0420] - The UE supports satellite handover with resynchronization; and / or

[0421] - For example, at the second timing point, the timer (e.g., T304) is not running.

[0422] Alternatively and / or additionally, based on one or more conditions at one or more specific timings, the UE may determine whether to perform / initiate (at least) a first action and / or not to perform / initiate (at least) a second action. The UE may make this determination at a second timing based on (at least) the one or more conditions. Based on (or if) (at least) satisfying the one or more conditions, the UE may perform / initiate (at least) a first action at the second timing. Based on (or if) (at least) not satisfying the one or more conditions, the UE may not perform / initiate (at least) a first action at the second timing. Based on (or if) (at least) satisfying the one or more conditions, the UE may not perform / initiate (at least) a second action at the second timing. Based on (or if) (at least) not satisfying the one or more conditions, the UE may not perform / initiate (at least) a second action at the second timing. Based on the UE's RRC state at one or more specific timings, the UE may determine whether to perform / initiate (at least) a first action and / or a second action. Based on whether the timer is running at least at the second timing point, the UE can determine whether to perform / initiate at least the first action and / or the second action.

[0423] Throughout this disclosure, performing a satellite handover with resynchronization may include a first action and a second action. Performing a satellite handover with resynchronization may include a first action but not a second action. The UE may perform / initiate the first action during the satellite handover procedure with resynchronization. The UE may perform / initiate the second action during the satellite handover procedure with resynchronization. The UE may choose not to perform / initiate the second action during the satellite handover procedure with resynchronization. The first action and the second action may be different.

[0424] The first action and / or the second action can be one or a combination of the following:

[0425] - Dispose of or maintain the UL synchronization timer (e.g., T430):

[0426] --Stop the UL synchronization timer (e.g., T430) (e.g., if it is running); and / or

[0427] --Start the UL synchronization timer (e.g., T430), where the timer value is set to ntn-UlSyncValidityDuration from the subframe indicated by epochTime.

[0428] - Perform UL synchronization:

[0429] --Consider loss and / or acquisition of UL synchronization;

[0430] --Notify the lower layers, for example, that UL synchronization has been lost due to satellite switching with resynchronization;

[0431] --Notify the lower layer when UL synchronization is obtained;

[0432] --Clear (all) HARQ buffers;

[0433] --Pause / resume, for example, uplink transmission on the serving cell;

[0434] --For example, for the Primary Timing Advance Group (PTAG), set the Network Use Timing Advance (NTA) value to zero; and / or

[0435] --Indicate the difference Koffset with a value of zero to the lower layer.

[0436] - Perform DL (re)synchronization:

[0437] --Initiate (re)synchronization with the DL of SpCell (e.g., the target satellite service indicated by SatSwitchWithReSync);

[0438] -- Configure the Broadcast Control Channel (BCCH) to apply to SpCell (e.g., the target satellite service indicated by SatSwitchWithReSync); and / or

[0439] --Retrieve the main information block (MIB) of the target SpCell (e.g., the target satellite service indicated by SatSwitchWithReSync).

[0440] - Obtain NTN-specific system information (e.g., SIB19).

[0441] In one or more instances, the UE receives SIB19 at a first timing and the SIB19 contains a t-Service indicating a second timing.

[0442] In one or more instances, the UE is in an RRC idle (and / or RRC inactive) state at both the first and second timings. For example, based on the fact that the UE is not in an RRC connected state at the second timing, the UE does not perform / initiate a satellite handover with resynchronization at the second timing. The UE does not perform / initiate a satellite handover with resynchronization including DL (re)synchronization (e.g., DL (re)synchronization with SpCell) and / or UL synchronization (e.g., maintaining T430, notifying the lower layer of lost / acquired UL synchronization). The UE may perform / initiate initial access or RRC recovery after the second timing.

[0443] In one or more instances, the UE is in an RRC idle (and / or RRC inactive) state at both the first and second timings. The UE performs a satellite handover with resynchronization at the second timing. For example, based on the UE not being in an RRC connected state at the second timing, or based on the UE being in an RRC idle (and / or RRC inactive) state at the second timing, the UE performs DL (re)synchronization but not UL synchronization. The UE performs a satellite handover with resynchronization including DL (re)synchronization (e.g., DL (re)synchronization with SpCell) and / or excluding UL synchronization (e.g., maintaining T430, notifying the lower layer of lost / acquired UL synchronization). The UE may perform / initiate initial access or RRC recovery after the second timing.

[0444] In one or more instances, the UE is in RRC idle (and / or RRC inactive) at a first timing and in RRC connected state at a second timing. The UE performs initial access or RRC recovery after the first timing and before the second timing. For example, based on the UE being in RRC connected state at the second timing, the UE performs a satellite handover with resynchronization at the second timing. The UE performs a satellite handover with resynchronization including DL (re)synchronization (e.g., DL (re)synchronization with SpCell) and / or UL synchronization (e.g., maintaining T430, notifying the lower layer of lost / acquired UL synchronization).

[0445] In one or more instances, the UE is in an RRC connected state at a first timing and a second timing. The UE may perform / initiate initial access (e.g., RRC establishment) or RRC recovery before the first timing. For example, based on the UE being in an RRC connected state at the second timing, the UE performs a satellite handover with resynchronization at the second timing. The UE performs a satellite handover with resynchronization including DL (re)synchronization (e.g., DL (re)synchronization with SpCell) and / or UL synchronization (e.g., maintaining T430, notifying the lower layer of lost / acquired UL synchronization).

[0446] In one or more instances, the UE is in an RRC connected state at a first timing and in an RRC idle (and / or RRC inactive) state at a second timing. The UE performs an RRC release after the first timing and before the second timing. For example, based on the fact that the UE is not in the RRC connected state at the second timing, the UE does not perform / initiate a satellite handover with resynchronization at the second timing. The UE does not perform / initiate a satellite handover with resynchronization including DL (re)synchronization (e.g., DL (re)synchronization with SpCell) and / or UL synchronization (e.g., maintaining T430, notifying the lower layer of lost / acquired UL synchronization).

[0447] In one or more instances, the UE is in an RRC connected state at a first timing and in an RRC idle (and / or RRC inactive) state at a second timing. The UE performs a satellite handover with resynchronization at the second timing. For example, based on the UE not being in the RRC connected state at the second timing, or based on the UE being in an RRC idle (and / or RRC inactive) state at the second timing, the UE performs DL (re)synchronization but not UL synchronization. The UE performs a satellite handover with resynchronization including DL (re)synchronization (e.g., DL (re)synchronization with SpCell) and / or excluding UL synchronization (e.g., maintaining T430, notifying the lower layer of lost / acquired UL synchronization).

[0448] Figures 23 to 26 It provides examples of textual proposals based on the current specification.

[0449] exist Figures 23 to 24 Regardless of the RRC status when the UE receives SIB19, based on the UE being in the RRC_CONNECTED state at the time indicated by t-Service, after the time indicated by t-ServiceStart, or between the time indicated by t-ServiceStart and the time indicated by t-Service, the UE determines to perform / initiate a first satellite handover with resynchronization. Regardless of the RRC status when the UE receives SIB19, based on the UE being in the RRC_CONNECTED state at the time indicated by t-Service, after the time indicated by t-ServiceStart, or between the time indicated by t-ServiceStart and the time indicated by t-Service, the UE determines to perform / initiate a second satellite handover with resynchronization. The UE performs the first satellite handover with resynchronization based on section 5.7.19 of the current specification (e.g., [3] 3GPP TS 38.331 V18.0.0 draft). The UE performs the first satellite handover with resynchronization based on section 5.7.19 of the current specification (e.g., [3] 3GPP TS 38.331 V18.0.0 draft). Figure 26 A second satellite handover with resynchronization is then performed.

[0450] exist Figure 25 In this case, based on the fact that the UE is not in the RRC_CONNECTED state, the UE determines not to perform / initiate a second action during satellite handover with resynchronization.

[0451] See Figure 27Regarding such and other concepts, systems and methods of the present invention, method 1010 for a UE in a wireless communication system includes receiving SIB 19 at a first timing, wherein the UE is in RRC_IDLE or RRC_INACTIVE at the first timing (step 1012), and determining, based on SatSwitchWithResync and t-Service included in SIB 19, to initiate a satellite handover with resynchronization at a second timing when the UE is in RRC_CONNECTED (step 1014).

[0452] In various embodiments, not only when the UE is in RRC_CONNECTED when SIB19 is received at the first timing, but also when the UE is in RRC_IDLE or RRC_INACTIVE when SIB19 is received at the first timing, the UE determines to initiate a satellite handover with resynchronization at the second timing.

[0453] In various embodiments, when SIB19 is received at the first timing, the UE is in any of RRC_CONNECTED, RRC_IDLE, and / or RRC_INACTIVE.

[0454] In various embodiments, the first timing is the timing when the UE receives SIB19.

[0455] In various embodiments, the second timing is the timing when the UE is in RRC_CONNECTED and / or the timing indicated by t-Service.

[0456] In various embodiments, when the UE is in any RRC state at a first timing, the UE determines to initiate a satellite handover with resynchronization at a second timing.

[0457] In various embodiments, regardless of the UE's RRC state at the first timing, the UE determines to initiate a satellite handover with resynchronization at the second timing.

[0458] In various embodiments, the UE determines to initiate a satellite handover with resynchronization based on the UE's RRC state at a second timing and / or not based on the UE's RRC state at a first timing.

[0459] In various embodiments, the second timing is different from the first timing.

[0460] In various embodiments, the second timing is later than the first timing.

[0461] In various embodiments, the method further includes, in response to initiating a satellite handover with resynchronization: stopping timer T430 (if running), notifying the lower layer of the loss of UL synchronization due to the satellite handover with resynchronization, synchronizing with the DL of the SpCell of the satellite service indicated by SatSwitchWithReSync, starting timer T430, wherein the timer value is set to ntn-UlSyncValidityDuration from the subframe indicated by epochTime in SatSwitchWithReSync, and / or notifying the lower layer when UL synchronization is obtained.

[0462] In various embodiments, after receiving SIB19 and / or the first timing, the UE transitions from RRC_IDLE or RRC_INACTIVE to RRC_CONNECTED.

[0463] Now for reference Figure 3 and Figure 4 In one or more embodiments from the perspective of a UE in a wireless communication system, apparatus 300 includes program code 312 stored in memory 310 of the transmitter. CPU 308 can execute program code 312 to: (i) receive SIB 19 at a first timing, wherein the UE is in RRC_IDLE or RRC_INACTIVE at the first timing; and (ii) determine, at a second timing, when the UE is in RRC_CONNECTED, to initiate a satellite handover with resynchronization based on SatSwitchWithResync and t-Service included in SIB 19. Furthermore, CPU 308 can execute program code 312 to perform all the actions, steps, and methods described above, below, or otherwise herein.

[0464] Any combination of the concepts or teachings above or herein may be combined, either wholly or in part, together or to form new embodiments. The disclosed details and embodiments may be used to solve at least (but not limited to) the problems mentioned above and herein.

[0465] It should be noted that any of the methods, alternatives, steps, examples, and embodiments presented herein may be used independently, individually, and / or in combination with multiple methods, alternatives, steps, examples, and embodiments.

[0466] Various aspects of this disclosure have been described above. It should be understood that the teachings herein can be implemented in a wide variety of forms, and any particular structure, function, or both disclosed herein are merely representative. Based on the teachings herein, those skilled in the art will understand that the aspects disclosed herein can be implemented independently of any other aspects, and two or more of these aspects can be combined in different ways. For example, any number of aspects set forth herein can be used to implement an apparatus or practice. Furthermore, this apparatus or practice can be implemented or practiced by using other structures, functions, or structures and functions other than or different from one or more aspects set forth herein. As examples of some of the foregoing concepts, in some aspects, a parallel channel can be established based on a pulse repetition frequency. In some aspects, a parallel channel can be established based on a pulse position or offset. In some aspects, a parallel channel can be established based on a time-hopping sequence. In some aspects, a parallel channel can be established based on a pulse repetition frequency, a pulse position or offset, and a time-hopping sequence.

[0467] Those skilled in the art will understand that information and signals can be represented using any of a variety of different techniques and skills. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description can be represented by voltage, current, electromagnetic waves, magnetic fields or magnetic particles, light fields or light particles, or any combination thereof.

[0468] Those skilled in the art will further appreciate that the various illustrative logic blocks, modules, processors, components, circuits, and algorithm steps described in conjunction with the aspects disclosed herein can be implemented as electronic hardware (e.g., digital implementations, analog implementations, or a combination of both, designed using source decoding or some other technique) and have instructions in various forms of program or design code (which, for convenience, may be referred to herein as "software" or "software module"), or a combination of both. To clearly illustrate the interchangeability of hardware and software, the various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether this functionality is implemented as hardware or software depends on the specific application and the design constraints imposed on the system as a whole. Those skilled in the art can implement the described functionality in different ways for each specific application, but such implementation decisions should not be construed as a departure from the scope of this disclosure.

[0469] Furthermore, the various illustrative logic blocks, modules, and circuits described in connection with the aspects disclosed herein may be implemented within or executed by an integrated circuit (“IC”), access terminal, or access point. An IC may include a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, electrical components, optical components, mechanical components, or any combination thereof designed to perform the functions described herein, and may execute code or instructions residing within the IC, outside the IC, or both. A general-purpose processor may be a microprocessor, but alternatively, the processor may be any conventional processor, controller, microcontroller, or state machine. The processor may also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors combined with a DSP core, or any other such configuration.

[0470] It should be understood that any particular order or hierarchy of steps in any disclosed process is an instance of an example method. It should be understood that the specific order or hierarchy of steps in the process may be rearranged based on design preferences, while remaining within the scope of this disclosure. The appended method claims present the elements of the various steps in a sample order and are not intended to be limited to any particular order or hierarchy presented.

[0471] The steps of the methods or algorithms described in conjunction with the aspects disclosed herein can be implemented directly in hardware, with software modules executed by a processor, or a combination of both. Software modules (e.g., containing executable instructions and associated data) and other data can reside in data memory, such as RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, removable disk, CD-ROM, or any other form of computer-readable storage medium known in the art. The sample storage medium can be coupled to a machine such as a computer / processor (for convenience, this machine may be referred to herein as a "processor"), such that the processor can read information (e.g., code) from the storage medium and write information to the storage medium. The sample storage medium can be integrated with the processor. The processor and storage medium can reside in an ASIC. The ASIC can reside in a user equipment. Alternatively, the processor and storage medium can reside as discrete components in a user equipment. Furthermore, in some aspects, any suitable computer program product may include a computer-readable medium comprising code associated with one or more aspects of this disclosure. In some aspects, the computer program product may include packaging material.

[0472] While the invention has been described in conjunction with various aspects and examples, it should be understood that further modifications can be made to the invention. This application is intended to cover any changes, uses, or adaptations to the invention that generally follow the principles of the invention and include such deviations from this disclosure that fall within the scope of known and customary practice in the art to which this invention pertains.

Claims

1. A method of a user equipment (UE) comprising: include: System information block 19 (SIB19) is received at a first timing point, wherein the UE is in Radio Resource Control (RRC)_IDLE or RRC_INACTIVE at the first timing point; as well as Based on SatSwitchWithResync and t-Service included in SIB19, regardless of the UE's RRC state at the first timing, a satellite handover with resynchronization is initiated at the second timing when the UE is in RRC_CONNECTED.

2. The method according to claim 1, characterized in that, The first timing is the timing when the UE receives the SIB19.

3. The method according to claim 1, characterized in that, The second timing is the timing when the UE is in RRC_CONNECTED state or the timing indicated by t-Service.

4. The method according to claim 1, characterized in that, Based on the RRC state of the UE at the second timing, the UE determines to initiate the satellite handover with resynchronization.

5. The method according to claim 1, characterized in that, The second timing is later than the first timing.

6. The method according to claim 1, characterized in that, This further includes responding to initiating the satellite handover with resynchronization: Stop timer T430 if it is running; The lower layer is notified that uplink (UL) synchronization has been lost due to the satellite handover with resynchronization. Synchronize with the downlink (DL) of the special cell (SpCell) of the satellite service indicated by SatSwitchWithReSync; Start the timer T430, wherein the timer value is set to ntn-UlSyncValidityDuration from the subframe indicated by epochTime in SatSwitchWithReSync; and The lower layer is notified when UL synchronization is achieved.

7. The method according to claim 1, characterized in that, After receiving the SIB19, the UE enters RRC_CONNECTED from RRC_IDLE or RRC_INACTIVE.

8. A user equipment (UE), characterized in that, include: Memory; as well as A processor, operably coupled to the memory, wherein the processor is configured to execute program code to: System information block 19 (SIB19) is received at a first timing point, wherein the UE is in Radio Resource Control (RRC)_IDLE or RRC_INACTIVE at the first timing point; as well as Based on SatSwitchWithResync and t-Service included in SIB19, regardless of the UE's RRC state at the first timing, a satellite handover with resynchronization is initiated at the second timing when the UE is in RRC_CONNECTED.

9. The UE according to claim 8, characterized in that, The first timing is the timing when the UE receives the SIB19.

10. The UE according to claim 8, characterized in that, The second timing is the timing when the UE is in RRC_CONNECTED state or the timing indicated by t-Service.

11. The UE according to claim 8, characterized in that, Based on the RRC state of the UE at the second timing, the UE determines to initiate the satellite handover with resynchronization.

12. The UE according to claim 8, characterized in that, The second timing is later than the first timing.

13. The UE according to claim 8, characterized in that, The processor further executes the program code in response to initiating the satellite handover with resynchronization: Stop timer T430 if it is running; The lower layer is notified that uplink (UL) synchronization has been lost due to the satellite handover with resynchronization. Synchronize with the downlink (DL) of the special cell (SpCell) of the satellite service indicated by SatSwitchWithReSync; Start the timer T430, wherein the timer value is set to ntn-UlSyncValidityDuration from the subframe indicated by epochTime in SatSwitchWithReSync; and The lower layer is notified when UL synchronization is achieved.

14. The UE according to claim 8, characterized in that, After receiving the SIB19, the UE enters RRC_CONNECTED from RRC_IDLE or RRC_INACTIVE.

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