Method and apparatus for handling satellite handover in wireless communication system

Abstract

A method and user equipment for handling satellite handover in a wireless communication system are provided, in which the method comprises: receiving a system information block 19 (SIB19) at a first timing at which the user equipment is in a radio resource control idle state (RRCIDLE) or a radio resource control inactive state (RRCINACTIVE); and on the basis that the SatSwitch WithResync and the t-Service are included in the SIB19, determining to initiate a satellite handover with resynchronization when the user equipment is in a Radio Resource Control Connected State (RRCCONNECTED) at a second timing.

Description

[0001] Cross - Reference to Related Applications

[0002] This application claims the priority and benefit of U.S. Provisional Patent Application No. 63 / 625,216, filed on January 25, 2024, and U.S. Provisional Patent Application No. 63 / 549,298, filed on 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 particularly, to methods and apparatuses for handling satellite handovers in a wireless communication system. Background Art

[0004] With the rapid growth in the demand for transferring 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 packet communication can provide IP - bearer voice, multimedia, multicast, and on - demand communication services to users of mobile communication devices.

[0005] An exemplary network structure is the Evolved Universal Terrestrial Radio Access Network (E - UTRAN). The E - UTRAN system can provide high data throughput to enable the above - mentioned IP - bearer voice and multimedia services. Currently, the 3GPP standards organization is discussing new radio technologies for the next generation (e.g., 5G). Thus, changes to the current body of the 3GPP standards are currently being submitted and considered to evolve and complete the 3GPP standards. Summary of the Invention

[0006] Methods, systems, and apparatuses for handling satellite handovers in a wireless communication system are provided. A User Equipment (UE) can correctly perform a satellite handover with resynchronization when the satellite handover occurs. In the case where the UE receives System Information Block 19 (SIB19) while in the Radio Resource Control idle state (RRC_IDLE) or the Radio Resource Control inactive state (RRC_INACTIVE) (and later enters the Radio Resource Control connected state (RRC_CONNECTED)), the 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, where the UE is in RRC_IDLE or RRC_INACTIVE at the first timing; and determining to initiate a satellite handover with resynchronization at a second timing when the UE is in RRC_CONNECTED based on SatSwitchWithResync and t-Service being included in SIB19. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0009] Figure 2 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 A functional block diagram of a communication system according to an embodiment of the present invention;

[0011] Figure 4 A functional block diagram of the program code of Figure 3 according to an embodiment of the present invention;

[0012] Figure 5 A reproduction of Figure 16 .14.1-1: General illustration of NTN in 3GPP TS 38.300 V18.0.0 draft;

[0013] Figure 6 A reproduction of Figure 16 .14.2.1-1: Illustration of timing relationship (for co-located gNB and NTN gateway) in 3GPP TS 38.300 V18.0.0 draft;

[0014] Figure 7 A reproduction of Figure 5 .3.5.1-1: RRC reconfiguration success in 3GPP TS 38.331 V18.0.0 draft;

[0015] Figure 8 A reproduction of Figure 5 .3.5.1-2: RRC reconfiguration failure in 3GPP TS 38.331 V18.0.0 draft;

[0016] Figure 9 An example diagram of seamless PCI handover according to an embodiment of the present invention;

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

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

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

[0020] Figure 13 An example diagram of problems with satellite handover according to an embodiment of the present invention;

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

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

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

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

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

[0026] Figure 19 is a literal proposal of an implementation based on [3] 3GPP TS 38.331 V18.0.0 according to an embodiment of the present invention, regardless of the RRC state when / after the UE receives SIB19, based on the time indicated by t-Service, after the time indicated by t-ServiceStart, or the time between the time indicated by t-ServiceStart and the time indicated by t-Service when the UE is in the RRC_CONNECTED state and the timer T304 is not running, the UE determines whether to perform / initiate a satellite handover with resynchronization;

[0027] Figure 20 is a literal proposal of an implementation based on [3] 3GPP TS 38.331 V18.0.0 according to an embodiment of the present invention, regardless of the RRC state when / after the UE receives SIB19, based on the time indicated by t-Service, after the time indicated by t-ServiceStart, or the time between the time indicated by t-ServiceStart and the time indicated by t-Service when the UE is in the RRC_CONNECTED state and the timer T304 is not running, the UE determines whether to perform / initiate a satellite handover with resynchronization;

[0028] Figure 21 is a literal proposal of an implementation based on [3] 3GPP TS 38.331 V18.0.0 according to an embodiment of the present invention, regardless of the RRC state when / after the UE receives SIB19, based on the time indicated by t-Service, after the time indicated by t-ServiceStart, or the time between the time indicated by t-ServiceStart and the time indicated by t-Service when the UE is in the RRC_CONNECTED state and the timer T304 is not running, the UE determines whether to perform / initiate a satellite handover with resynchronization;

[0029] Figure 22A flowchart of a method of 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 at least the UE being in an RRC connected state at a second timing and / or regardless of the RRC state of the UE at the first timing; and performing a satellite handover with resynchronization at the second timing;

[0030] Figure 23 A text proposal based on the implementation of [3] 3GPP TS 38.331 V18.0.0 according to an embodiment of the present invention, wherein regardless of the RRC state of the UE when / after receiving 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;

[0031] Figure 24 A text proposal based on the implementation of 3GPP TS 38.331 V18.0.0 [3] according to an embodiment of the present invention, wherein regardless of the RRC state of the UE when / after receiving 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;

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

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

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

[0035] The present invention described herein can be applied to or implemented in the exemplary wireless communication systems and devices described below. Additionally, the present invention is mainly described in the context of the 3GPP architecture reference model. However, it should be understood that those skilled in the art can easily adapt and implement aspects of the present invention using and in 3GPP2 network architectures as well as other network architectures with the disclosed information.

[0036] The exemplary wireless communication systems and devices described below employ a wireless communication system that supports broadcast services. Wireless communication systems are widely deployed to provide various types of communications, such as voice, data, etc. These systems can 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, 3GPP2 Ultra Mobile Broadband (UMB), 3GPP New Radio (NR), or some other modulation techniques.

[0037] Specifically, the exemplary wireless communication systems and devices described below can be designed to support one or more standards, such as those provided by the consortium named "3rd Generation Partnership Project" and referred to herein as 3GPP, including: [1] 3GPP TS 38.300 V18.0.0 Draft, "NR, Overall Description of NR and NG-RAN, 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 Unchanged PCI", Apple Inc. The standards and documents listed above are hereby expressly and fully incorporated herein by reference in their entireties.

[0038] Figure 1 A multi-access wireless communication system according to an embodiment of the present invention is shown. The access network 100 (access network, AN) includes multiple antenna groups, one including 104 and 106, another including 108 and 110, and still another including 112 and 114. In Figure 1 this, only two antennas are shown for each antenna group. However, more or fewer antennas can be utilized for each antenna group. The access terminal (AT) 116 communicates with antennas 112 and 114, where antennas 112 and 114 transmit information to the access terminal 116 via the forward link 120 and receive information from the AT 116 via the reverse link 118. The AT 122 communicates with antennas 106 and 108, where antennas 106 and 108 transmit information to the AT 122 via the forward link 126 and receive information from the AT 122 via the reverse link 124. In an FDD system, the communication links 118, 120, 124, and 126 can use different frequencies for communication. For example, the forward link 120 can use a frequency different from the frequency used by 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 access terminals in a sector of the area covered by the access network 100.

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

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

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

[0043] In one embodiment, each data stream is transmitted via a respective transmit antenna. The TX data processor 214 formats, encodes, and interleaves the traffic data of the data streams based on a particular encoding scheme selected for each data stream to provide encoded data.

[0044] The encoded data of each data stream can be multiplexed with pilot data using OFDM techniques. The pilot data is typically a known data pattern that is processed in a known manner and can be used at the receiver system to estimate the channel response. Subsequently, the multiplexed pilot and encoded data for the data stream are modulated (e.g., symbol mapped) based on a particular modulation scheme selected for each data stream (e.g., BPSK, QPSK, M-PSK, or M-QAM) to provide modulated symbols. The data rate, encoding, and modulation for each data stream can be determined by instructions executed by a processor 230. A memory 232 is coupled to the processor 230.

[0045] Then, the modulated symbols of all data streams are provided to a TX MIMO processor 220, which can further process the modulated symbols (e.g., for OFDM). The TX MIMO processor 220 then provides N T streams of modulated symbols to N TTransmitters (TMTRs) 222a through 222t. In some embodiments, the TX MIMO processor 220 applies beamforming weights to the symbols of the data stream and the antennas from which the symbols are transmitted.

[0046] Each transmitter 222 receives and processes a respective symbol stream to provide one or more analog signals, and further conditions (e.g., amplifies, filters, and upconverts) the analog signals to provide a modulated signal suitable for transmission via the MIMO channel. The N T modulated signals from transmitters 222a through 222t are then transmitted from N T antennas 224a through 224t.

[0047] At the receiver system 250, the transmitted modulated signals are received by N R antennas 252a through 252r, and the signals received from each antenna 252 are provided to respective receivers (RCVRs) 254a through 254r. Each receiver 254 conditions (e.g., filters, amplifies, and downconverts) the respective received signal, digitizes the conditioned signal to provide samples, and further processes the samples to provide a corresponding "received" symbol stream.

[0048] The RX data processor 260 then receives and processes the N R received symbol streams from the N R receivers 254 based on specific receiver processing techniques to provide N T "detected" symbol streams. The RX data processor 260 then demodulates, deinterleaves, and decodes each detected symbol stream to recover the traffic data 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 the TX data processor 214 at the transmitter system 210.

[0049] The processor 270 periodically determines which precoding matrix (discussed below) to use. The processor 270 formulates a reverse link message that includes a matrix index portion and a rank value portion.

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

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

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

[0053] Go to Figure 3 , this figure shows an alternative simplified functional block diagram of a communication device according to an embodiment of the present invention. As Figure 3 shown, the communication device 300 in a wireless communication system can be utilized to implement Figure 1 the UEs (or ATs) 116 and 122 in, and the wireless communication system is preferably an NR system. The communication device 300 can 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 the received signals to the control circuit 306, and wirelessly output the signals generated by the control circuit 306.

[0054] Figure 4 is a simplified block diagram of the program code 312 shown in Figure 3 in accordance with an embodiment of the present invention. In this embodiment, the 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. The layer 3 portion 402 generally performs radio resource control. The layer 2 portion 404 generally performs link control. The layer 1 portion 406 generally performs physical connection.

[0055] For an LTE, LTE-A, or NR system, the layer 2 portion 404 may include a Radio Link Control (RLC) layer and a Medium Access Control (MAC) layer. The layer 3 portion 402 may include a Radio Resource Control (RRC) layer.

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

[0057] Any sentence, paragraph, (sub)bullet point, key point, action, or claim described in each of the following inventive paragraphs or sections may be implemented independently and separately to form a specific method or device. Dependencies such as "based on", "more specifically", "example", etc. in the following disclosure of the present invention are only one possible embodiment that does not limit the specific method or device.

[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] *************************** Quote start [1] *****************************

[0060] 16.14 Non-terrestrial network

[0061] 16.14.1 Overview

[0062] Figure 16 .14.1-1 Examples of non-terrestrial networks (NTNs) are described below, which provide non-terrestrial NR access to UEs via NTN payloads and NTN gateways, 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 is from 3GPP TS 38.300 V18.0.0 draft Figure 16 .14.1-1: Reproduction of the overall illustration of the 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] - The NTN gateway can serve multiple NTN payloads;

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

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

[0069] …

[0070] Three types of serving links are supported:

[0071] - Earth-fixed: Provided by a beam that constantly covers the same geographical area (e.g., in the case of a GSO satellite);

[0072] - Quasi-earth-fixed: Provided by a beam that covers a geographical area for a limited period and a different geographical area during another period (e.g., in the case of an NGSO satellite that generates steerable beams);

[0073] - Earth-mobile: Provided by a beam whose coverage area slides on the earth's surface (e.g., in the case of an NGSO satellite that generates fixed or non-steerable beams).

[0074] Using an NGSO satellite, the gNB can provide a quasi-earth-fixed serving link or an earth-mobile serving link, while the gNB operating with a GSO satellite can provide an earth-fixed serving link.

[0075] In this release, the NTN-capable UE has GNSS functionality.

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

[0077] 16.14.2 Timing and Synchronization

[0078] 16.14.2.1 Scheduling and Timing

[0079] The DL and UL are aligned at the uplink time synchronization reference point (RP), with an offset given by N TA,偏移 as defined in clause 4.2 of TS38.213.

[0080] To accommodate the propagation delay in NTN, several timing relationships are enhanced by a common timing advance (common TA) and two offsets K 偏移 and k mac as follows:

[0081] - The common TA is a configured timing offset that is equal to the RTT between the RP and the NTN payload.

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

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

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

[0085] The offset k mac is used to delay the application of downlink configurations indicated by MAC CE commands on the PDSCH (see TS 38.213) and in the estimation of the UE-gNB RTT (see TS 38.321). When the downlink and uplink frame timings are not aligned at the gNB, the offset can be provided by the network. k mac is also used in the random access procedure to determine the start time of the RAR window / MsgB window after Msg1 / MsgA transmission (see TS 38.213).

[0086] The serving link RTT, the feeder link RTT, the RP, the common TA, k mac and T TA (see clause 16.14.2.2) are shown in Figure 16 .14.2.1-1.

[0087] Figure 6 is a reproduction of Figure 16 .14.2.1-1: Illustration of timing relationships (for co-located gNB and NTN gateway) in 3GPP TS 38.300 draft version V18.0.0.

[0088] …

[0089] 16.14.2.2 Timing advance and frequency pre-compensation

[0090] For the serving cell, the network broadcasts the valid ephemeris information and the common TA parameter. The UE shall have a valid GNSS position as well as the ephemeris and the common TA before connecting to the NTN cell. To achieve synchronization, before and during connecting to the NTN cell, the UE shall calculate the RTT between the UE and the RP based on the GNSS position, the ephemeris and the common TA parameter (see clause 4.2 in TS 38.213), and as Figure 16Pre - compensate the TTA autonomously for the RTT between the UE and the RP as shown in 14.2.1 - 1 (see clause 4.3 of TS38.211).

[0091] The UE shall calculate the Doppler shift of the serving link by considering the UE position and ephemeris and pre - compensate it autonomously in the uplink transmission. If the UE does not have a valid GNSS position and / or a valid ephemeris and common TA, the UE shall not transmit until these two are regained.

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

[0093] The UE may be configured to report the timing advance during the random access procedure or in the connected mode. In the connected mode, event - triggered reporting of the timing advance 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 described in 9.2.1 apply to mobility in RRC_IDLE of NTN, and the same principles described in 9.2.2 apply to mobility in RRC_INACTIVE of NTN, unless specified otherwise below.

[0098] The network may broadcast multiple tracking area codes (TAC) per PLMN in NR NTN cells. The change of TAC in the system information is under network control, i.e., it may not be precisely synchronized with the real - time illumination of the beams on the ground.

[0099] For NTN - TN mobility, the network may broadcast cell information about NR TN and EUTRA TN coverage areas in SIB25. This is supported for geostationary, quasi - geostationary, and earth - mobile cells. The coverage information includes a list of geographical TN regions and also indicates the associated frequency information. The UE may skip TN measurements based on the broadcast TN coverage information.

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

[0101] The NTN ephemeris is provided in SIB19. In an NTN cell, it contains the NTN payload ephemeris of the serving cell and optionally the NTN payload ephemeris of neighboring cells.

[0102] 16.14.3.2 Mobility in RRC_CONNECTED

[0103] 16.14.3.2.1 Handover

[0104] Unless specified otherwise below, the same principles described in 9.2.3.2 apply:

[0105] During mobility between NTN and the terrestrial network (TN), there is no requirement for the UE to be connected to both NTN and TN simultaneously.

[0106] Note: NTN-TN handover refers to mobility in both directions, i.e., from NTN to TN (inward) and from TN to NTN (outward).

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

[0108] The UE may 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 handover

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

[0112] NTN supports the following additional triggering conditions based on which the UE may perform CHO to a candidate cell as defined in TS38.331

[12] :

[0113] - Event A4 based on RRM measurements;

[0114] - Time-based triggering condition;

[0115] - Location-based triggering condition.

[0116] At least in the case of hard satellite handovers where the service discontinuity gap duration is assumed to be zero or negligible, the time-based or location-based triggering conditions can be configured independently of the measurement conditions for CHO in NTN. Otherwise, the 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] The 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 determines how the UE evaluates time- or location-based trigger conditions and events based on RRM measurements.

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

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

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

[0122] 16.14.3.2.3 Satellite handover with resynchronization

[0123] Satellite handover with a resynchronization procedure is supported based on hard and soft satellite handovers in a quasi-geostationary scenario with the same SSB frequency and the same gNB. By maintaining the same PCI over the geographical area covered by the quasi-geostationary beam, satellite handover with resynchronization avoids L3 mobility of UEs in the cell. CHO can be configured concurrently with satellite handover with a resynchronization procedure.

[0124] For soft satellite handover, the UE may start synchronizing with the target satellite before the source satellite ends serving the cell. It is not required for the UE to be connected to the source satellite when the UE hands over to the target satellite.

[0125] 16.14.3.3 Measurements

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

[0127] The network can be configured:

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

[0129] - Measurement gaps based on multiple SMTCs;

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

[0131] The adjustment of SMTC by NW control can be based on UE assistance information reported in RRC_CONNECTED. The UE in RRC_IDLE / RRC_INACTIVE can adjust SMTC based on its location and the assistance information in SIB19.

[0132] The UE assistance information consists of the propagation delay difference of the serving link between the serving cell and the neighboring cell.

[0133] For the UE in the idle / inactive mode, it is determined by the UE implementation whether to perform NTN neighboring cell measurements on the cells indicated in SIB3 / SIB4 rather than those included in SIB19.

[0134] For the UE in the connected mode, it is determined by the UE implementation whether to perform NTN neighboring cell measurements on the cells included in the measurement configuration rather than those included in SIB19.

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

[0136] - The timing information 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 serving the current geographical area;

[0138] - The location information refers to:

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

[0140] - In the case of a mobile earth cell scenario, it refers to the reference location of the serving cell at the epoch time and the distance threshold to the reference location.

[0141] The initiation of time-based measurements can be applicable to the serving link handover situation for cell (re)selection.

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

[0143] ************************Quotation ends********************************

[0144] The handling of the UL synchronization timer (e.g., T430) is specified as follows 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):

[0145] ***********************Quote 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 an NTN cell, the UE in RRC_CONNECTED shall:

[0150] 1> Start or restart T430 of the serving cell, where 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 SatSwitchWithReSync and t-Service are included 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 a 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 shall attempt to re-acquire SIB19 through the UE implementation before the end of the duration indicated by ntn-UlSyncValidityDuration and epochTime.

[0157] *************************Next Citation********************************

[0158] 5.2.2.6 T430 Expiry

[0159] The UE shall:

[0160] 1> If the T430 of the serving cell expires and if in RRC_CONNECTED:

[0161] 2> Notify the lower layer of UL 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 of when UL synchronization is obtained;

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

[0166] *************************Next Citation********************************

[0167] 5.3.5 RRC Reconfiguration

[0168] 5.3.5.1 Overview

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

[0170] Figure 8 is from Draft 3GPP TS 38.331 V18.0.0 Figure 5 .3.5.1-2: Reproduction of failed RRC reconfiguration.

[0171] …

[0172] 5.3.5.3 UE Receives RRCReconfiguration

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

[0174] …

[0175] 1> If the RRCReconfiguration contains a masterCellGroup:

[0176] 2> Perform cell group configuration for the received masterCellGroup according to 5.3.5.5;

[0177] …

[0178] 5.3.5.5 Cell group configuration

[0179] 5.3.5.5.1 Overview

[0180] …

[0181] The UE performs the following actions based on the received CellGroupConfig IE:

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

[0183] 2> Perform reconfiguration with synchronization according to 5.3.5.5.2;

[0184] …

[0185] 5.3.5.5.2 Reconfiguration with synchronization

[0186] The UE shall perform the following actions to perform reconfiguration with synchronization.

[0187] 1> If AS security is not activated, then perform the actions specified in 5.3.11 after transitioning to RRC_IDLE, with the release cause "other", and the procedure ends after the release cause;

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

[0189] …

[0190] 2> If this procedure is performed for the MCG, or if this procedure is performed for an SCG that is not indicated as deactivated in the E-UTRA or NR RRC message in which the RRCReconfiguration message is embedded, 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>Start 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>Start timer T430 according to the target cell NTN-config, 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>Consider the SCell of this cell group in the SCellToAddModList that is not included in the RRCReconfiguration message (if configured) as being in the deactivated state;

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

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

[0203] 3>If rach-LessHO is included:

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

[0205] 3>If any additional fields not previously covered are included in the received reconfigurationWithSync, then configure the lower layers according to the additional fields.

[0206] …

[0207] 5.3.5.13 Conditional Reconfiguration

[0208] 5.3.5.13.1 Overview

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

[0210] …

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

[0212] …

[0213] 5.3.5.13.4 Conditional Reconfiguration Evaluation

[0214] The UE shall:

[0215] 1> For each condReconfigId within VarConditionalReconfig:

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

[0217] …

[0218] 4> Consider a cell having a physical cell identity that matches the value indicated in ServingCellConfigCommon included in reconfigurationWithSync within the masterCellGroup in the received condRRCReconfig as an applicable cell;

[0219] …

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

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

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

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

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

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

[0226] 5> Consider the event associated with the measId as 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 leaving condition applicable to this event associated with condReconfigId (i.e., the event corresponding to the condEventId of the corresponding condTriggerConfig within VarConditionalReconfig) is satisfied for the applicable cell; or

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

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

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

[0232] 5> Consider the event associated with the measId as not satisfied;

[0233] 3> If the events associated with all measIds within the condTriggerConfig of the applicable cell are satisfied:

[0234] 4> Consider the applicable cells associated with the condReconfigId as the triggered cells;

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

[0236] …

[0237] 5.3.5.13.5 Conditional Reconfiguration Execution

[0238] The UE shall:

[0239] …

[0240] 2> Consider the triggered cells as the selected cells for conditional reconfiguration execution;

[0241] 1> For the selected cells of conditional reconfiguration execution:

[0242] …

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

[0244] *************************Next Citation********************************

[0245] 5.7.19 Satellite Handover with Resynchronization in RRC_CONNECTED

[0246] The UE shall:

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

[0248] 1> Notify the lower layer of the loss of UL synchronization due to the satellite handover with resynchronization;

[0249] 1> Start resynchronization with the DL of the SpCell of the satellite service indicated by ntn-Config in SatSwitchWithReSync;

[0250] 1> Start timer T430, where the timer value is set to the 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: It remains to be further studied whether the UE can obtain DL synchronization from the target satellite without losing UL synchronization with the source satellite in the soft handover scenario.

[0253] ***********************End of citation********************************

[0254] ***********************Start of citation [2]*****************************

[0255] 5.2a Maintenance of UL Synchronization

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

[0257] 1> If an indication of uplink synchronization 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 indication of uplink synchronization is received after an indication of uplink synchronization loss due to a satellite handover with resynchronization (see clause 5.7.19 of TS 38.331):

[0259] 3> Set the N TA value (as defined in TS 38.211) to zero for the PTAG;

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

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

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

[0263] 2> Empty all HARQ buffers;

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

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

[0266] ************************End of citation********************************

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

[0268] **********************Start of citation [3]*****************************

[0269] 6.3.1 System Information Block

[0270] -SIB19

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

[0272] SIB19 Information Elements

[0273]

[0274]

[0275]

[0276]

[0277] **************************Next citation******************************** - NTN-Config IE NTN-Config provides the parameters required for the UE to access NR via NTN access.

[0278] NTN-Config Information Elements

[0279]

[0280]

[0281]

[0282]

[0283]

[0284] ***************************End of citation********************************

[0285] The following protocol was made for satellite handover with resynchronization in the 3GPP RAN2 meeting. Throughout this disclosure, the following are interchangeable: invariant Physical Cell Identity (PCI) mechanism, invariant PCI (handover), PCI invariant (handover), satellite handover / handover (without PCI change), satellite handover / handover with invariant PCI, satellite handover with resynchronization, and / or satellite handover with resynchronization.

[0286] In the RAN2 #121bis meeting:

[0287] - In the quasi-geostationary cell case, for hard satellite handover (without key change) with 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 the main technical issues are identified by RAN1.

[0288] In the RAN2 #122 meeting:

[0289] - In the hard handover invariant PCI scenario (i.e., no handover), the UE needs to know the time when the UE attempts to resynchronize.

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

[0291] In the RAN2 #123 meeting:

[0292] - An explicit indication will be introduced to enable invariant PCI handover.

[0293] - The invariant PCI mechanism can be applied to cases where the coverage gap is zero or negligible. Whether we need to support scenarios that require the introduction of t-gap or t-start is subject to further study (For Further Study, FFS).

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

[0295] - In the invariant PCI case, the User Equipment (UE) considers the uplink (UL) synchronization timer to expire at t-Service (the current cell stop time) to stop any UL operations.

[0296] - For RACH-based solutions without changing PCI, 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 satellite handover.

[0299] - RAN2 confirmed that satellite handover with unchanged PCI is only applicable to the quasi-geostationary fixed system.

[0300] - Only one target satellite information (i.e., NTN-config) of the serving cell is provided in SIB19.

[0301] - Soft satellite handover in Rel-18 is supported.

[0302] - There will be an indication of whether to use hard handover or soft handover.

[0303] - At least in soft satellite handover, the network provides the UE with the SSB information of the target satellite.

[0304] - In soft satellite handover, the UE can start synchronizing with the target satellite before the T-service of the source satellite.

[0305] - T-start is introduced, which indicates the earliest time when the UE can start synchronizing with the target satellite (the actual signaling needs further study). In the soft handover scenario, the T-start of the target satellite is earlier than the T-service of the source satellite.

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

[0307] - When the UE switches to the target satellite, it is not required for the UE to be connected to the source satellite.

[0308] In the RAN2#124 meeting:

[0309] - A new target satellite configuration is introduced, e.g., ntn-TargetSatConfig, and the NTN-config of the target satellite is provided in it for a specific signaling format regarding the target satellite information in SIB19. The presence of this information indicates support for satellite handover without PCI change.

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

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

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

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

[0314] - For soft satellite handover, as a baseline, it is sufficient to provide the "SSB time offset" of the target satellite in SIB19.

[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 is equal to T-service, i.e., hard handover.

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

[0317] - During the satellite handover procedure, the UE shall reset the L3 filter for serving cell radio resource management (RRM) measurements and radio link monitoring (RLM), and it depends on the UE implementation (i.e., no RAN2 specification impact).

[0318] - If the UE receives a handover (HO) command before initiating the satellite handover procedure (i.e., before the time point 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 CHO (for different cells) and satellite handover procedures are configured, the UE initiates the earlier triggered procedure; whether the two procedures are triggered simultaneously depends on the UE implementation.

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

[0322] A non-terrestrial network (NTN) can be regarded as an NG-RAN consisting of next-generation Node B (gNB), where the gNB provides non-terrestrial New Radio (NR) access to user equipment (UE) by means of an NTN payload and an NTN gateway on an airborne or spaceborne NTN vehicle. The UE can link to, camp on, and / or connect to an NTN network involving air / space transmission. The NTN can include various platforms, including Low Earth Orbit (LEO) satellites, Medium Earth Orbit (MEO) satellites, High Elliptical Orbit (HEO) satellites, Geostationary Orbit (GEO) satellites, Geostationary Synchronous Orbit (GSO) satellites, Non-Geostationary Synchronous Orbit (NGSO) satellites, and / or High Altitude Platform Station (HAPS). The LEO satellite can have an earth-fixed beam (e.g., the beam is temporarily fixed at a position during a period) or an earth-moving beam (e.g., the beam moves continuously together with the satellite). The NTN can provide wide-area coverage and network (NW) access in scenarios where a terrestrial network (TN) is not feasible (such as deserts, polar regions, and / or on an airplane).

[0323] The NW can provide NTN information to the UE. The NTN information can be or can be referred to as satellite (assisted) information. The NTN information can be the parameters required for the UE to access the NW via NTN access. The NTN information can be or include 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 the NTN information to the UE, for example, via a serving cell, in NTN-specific system information (e.g., System Information Block 19 (SIB19)) or a Radio Resource Control (RRC) message (e.g., RRCReconfiguration). The NTN-specific system information can be an SIB including NTN information. Throughout this disclosure, SIB19 can be the system information for the serving cell. SIB19 can be NTN-specific system information. SIB19 can contain satellite-assisted information. SIB19 can contain the uplink (UL) synchronization information of the NTN. The system information can be referred to as the system information block.

[0324] The NTN configuration (e.g., NTN-Config) can be or include (at least) an epoch time (e.g., epochTime), a validity duration (e.g., ntn-UlSyncValidityDuration), satellite ephemeris (e.g., ephemerisInfo), and / or a common timing advance (TA) (e.g., ta-Info). The validity duration (e.g., ntn-UlSyncValidityDuration) can indicate the maximum time for which a UE can apply satellite information and / or NTN-specific system information (e.g., SIB19) without obtaining new satellite information and / or NTN-specific system information. The validity duration (e.g., ntn-UlSyncValidityDuration) and / or the epoch time (e.g., epochTime) can be associated with (or applied to) the following: 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). The time information (e.g., t-Service) can be the deactivation time of the serving cell. The time information (e.g., t-Service) can be the occasion when the UE will leave the coverage area of the serving cell. The time information (e.g., t-Service) can indicate the time information regarding when the serving cell will stop providing service to its currently covered area.

[0325] Throughout this disclosure, one, some, and / or all instances of "NTN configuration" can correspond to, can be supplemented by, and / or can be replaced by "NTN information", "satellite information", "NTN-Config", and / or "assistive information".

[0326] The UE will use a timer (e.g., uplink (UL) synchronization timer) to maintain UL synchronization (e.g., for the serving cell) and / or the validity of NTN information based on the NTN information. The UE will start or restart the UL synchronization timer (e.g., T430) with a validity duration (e.g., ntn-UlSyncValidityDuration) starting from a subframe with a free corresponding epoch time (e.g., epochTime) indication, where the validity duration (e.g., ntn-UlSyncValidityDuration) and the epoch time (e.g., epochTime) are provided for the serving cell. The UE will apply the epoch time (e.g., epochTime) as the start timing 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, the NTN information of the serving cell. The validity duration (e.g., ntn-UlSyncValidityDuration) and / or the UL synchronization timer (e.g., T430) can indicate the duration when satellite information or a part of the satellite information (e.g., ephemerisInfo, ta-Info) is valid. For example, when the UL synchronization timer (e.g., T430) is running, the satellite information (a part of it) can be considered valid. When the UL synchronization timer (e.g., T430) is not running, the satellite information (a part of it) can be considered invalid. The UL synchronization timer (e.g., T430) can indicate the duration when UL synchronization is obtained or maintained based on satellite information or a part of the 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 obtained. When the UL synchronization timer (e.g., T430) is not running, UL can be considered out of sync, or UL synchronization can be considered lost.

[0327] Based on the current specifications (e.g., [2] 3GPP TS 38.321 V18.0.0 Draft and [3] 3GPP TS 38.331 V18.0.0 Draft), upon receiving SIB19, the UE immediately starts the UL synchronization timer (e.g., T430) based on the NTN configuration of the serving cell. 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 the UL synchronization timer (e.g., T430). When the UE performs and / or executes a handover (or a reconfiguration with synchronization), the UE stops the UL synchronization timer (e.g., T430). Then, the UE starts the UL synchronization timer (e.g., T430) based on the NTN configuration of the target cell.

[0328] The UE will re-acquire SIB19 before the UL synchronization timer expires. After the UL synchronization timer expires in the RRC connected mode, the UE may consider that the uplink synchronization is lost and acquire SIB19. In response to acquiring SIB19, the UE may consider that it has obtained uplink synchronization. If it is considered that the uplink synchronization is lost, the UE may clear the hybrid automatic repeat request (HARQ) buffer and may not perform UL transmission on the serving cell. If uplink synchronization is considered (obtained), the UE may perform UL transmission on the serving cell. When the UL synchronization timer is running, the serving cell may be considered to achieve uplink synchronization (e.g., obtain uplink synchronization) in the RRC connected mode. When the UL synchronization timer is not running and / or has expired, the serving cell may be considered not to achieve uplink synchronization (e.g., uplink synchronization is lost) in the RRC connected mode.

[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 the UL synchronization timer for the target cell (or neighboring cell). 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 NTN, when the UE is connected to a satellite. The UL synchronization timer can indicate / handle the duration when the (associated) auxiliary information is valid. The UL synchronization timer can indicate / dispose of the duration when the UE can apply the (associated) satellite information, for example, without obtaining new satellite information. The UL synchronization timer can be used in NTN. The UL synchronization timer (e.g., T430) may not be used in TN. The UL synchronization timer (e.g., T430) can be an NTN-specific timer. The UL synchronization timer can be different from the TA timer (e.g., TimeAlignmentTimer). The UL synchronization timer can not be used to maintain UL TA. The UL synchronization timer can be associated with a cell. The UL synchronization timer can not be associated with a TA group. When the (associated) satellite information is valid, the UE can consider UL to be synchronized.

[0330] In NTN, the NW serving the UE on the ground can remain unchanged, while the satellite between the UE and the NW on the ground may change due to satellite handover or satellite movement. To prevent L3 mobility such as handover caused by satellite handover, etc., and to reduce signaling overhead and / or interruption time, a mechanism for satellite handover with resynchronization will be supported in NTN. The satellite handover mechanism avoids the mobility of the UE in the cell by maintaining the same physical cell identity (PCI) over a geographical area. The satellite handover with resynchronization can be or can be called a satellite handover without PCI change and / or an invariant PCI handover. The satellite handover with resynchronization can be or can be called a mechanism without L3 mobility (e.g., handover). When the satellite handover occurs, the UE can maintain the cell configuration without changing the gNB. Signaling such as handover (HO) commands can be reduced. The UE should not trigger the RRC reconfiguration procedure. Since the satellite ephemeris (e.g., ephemerisInfo) and / or the common TA (e.g., ta-Info) may be different, 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)obtain SIB19. In the satellite handover with resynchronization, the UE can switch / change the serving satellite without performing a handover, without receiving RRC (re)configuration, without changing the PCI of the serving cell, and / or without changing the serving gNB.

[0331] Throughout this disclosure, satellite handover with resynchronization can be (substituted for / equivalent to) a procedure of invariant PCI handover, cell handover with resynchronization, satSwitchWithResync, cell handover with invariant PCI, hard / soft satellite handover, satellite handover without PCI change, resynchronization or the like, and / or any combination of the above. Examples of invariant PCI handover are shown in Figure 9 (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) of a satellite handover with resynchronization. The configuration (or indication) of a satellite handover with resynchronization can instruct the UE to perform (or initiate) a satellite handover with resynchronization (e.g., at a specific timing such as t-Service, etc.). The configuration can be included in the system information (e.g., SIB19). The configuration (or indication) can be satSwitchWithResync. The configuration (or indication) can be included in satSwitchWithResync. Throughout this disclosure, satSwitchWithResync can be an indication to (enable / trigger) a satellite handover with resynchronization.

[0333] The UE may 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 may 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 may be indicated by a network node. The specific time may be indicated in system information (e.g., SIB19). The specific time may be a second timing. The specific time may be (or indicate) the cell stop time (e.g., t-Service). The specific time may be (or indicate) the handover start time (e.g., t-Start). The cell stop time (e.g., t-Service) may be (or indicate) the time when the cell provided via NTN will stop serving its currently covered area. The handover start time (e.g., t-Start) may be (or indicate) the time when the second satellite will start serving the area (or cell) currently covered or served by the first satellite. The handover start time (e.g., t-ServiceStart) may be (or indicate) when a satellite handover with resynchronization can start or be performed. Throughout this disclosure, t-ServiceStart may be the satellite handover start time, and t-Service may be the (service) cell (service) stop time. Throughout this disclosure, t-ServiceStart may be represented as t-Service minus t-Gap.

[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 initiating a satellite handover with resynchronization, and / or if a satellite handover with resynchronization is initiated, at a cell stop time such as t-Service, etc.), the UE may or may not:

[0335] - Consider 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 starting from the subframe indicated by epochTime in SatSwitchWithReSync(ntn-Config);

[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, stop using the UE-specific Koffset (if configured);

[0339] - For example, use the cell-specific Koffset after the cell stop time (e.g., t-Service), and / or use the 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] - Start re-synchronization of the DL with the special cell (SpCell) of the satellite service indicated in SatSwitchWithReSync (in ntn-Config);

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

[0343] - (Re-)acquire the NTN-related configuration (e.g., ephemeris) of the serving cell (e.g., included in SIB19);

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

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

[0346] - Notify the lower layer of the loss of UL synchronization due to a satellite handover with re-synchronization; and / or

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

[0348] A satellite handover with re-synchronization can be or can include a soft satellite handover and / or a hard satellite handover. Throughout this disclosure, a "soft satellite handover" can be a "soft satellite handover with re-synchronization". Throughout this disclosure, a "hard satellite handover" can be a "hard satellite handover with re-synchronization". A soft satellite handover or a 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 the t-ServiceStart and / or Synchronization Signal Block (SSB) information for a soft satellite handover. The indication can be a parameter, t-ServiceStart, and / or SSB information.

[0349] For a hard satellite handover, after disconnecting from the old satellite (e.g., the source satellite, the first satellite), the UE can connect to the new satellite (e.g., the target satellite, the second satellite) (or synchronize with it). An example of a hard satellite handover is shown in Figure 10 (quoted from [5]R2-2310307). The serving satellite can perform a handover at a time point (e.g., Figure 10 the handover time in, t-Service). The first satellite (e.g., Figure 10 STA1 in) can be the serving satellite before the satellite handover and / or the time point. The second satellite (e.g., Figure 10 STA2 in) can be the serving satellite after the satellite handover and / or the time point. The first satellite and the second satellite can serve 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 a soft satellite handover, before disconnecting from the old satellite (e.g., the source satellite, the first satellite), the UE can connect to the new satellite (e.g., the target satellite, the second satellite) (or synchronize with it). An example of a soft satellite handover is shown in Figure 11 (quoted from [5]R2-2310307). The serving satellite can perform a handover during a duration (e.g., Figure 11 T-duration in, between t-ServiceStart and t-Service). The first satellite (e.g., Figure 11 STA1 in) and the second satellite (e.g., Figure 11 STA2 in) provide service / coverage for the same area during the duration. The duration can start from t-ServiceStart and end at t-Service. The first satellite can be the serving satellite before the satellite handover and / or t-ServiceStart. The second satellite (e.g., Figure 11 STA2 in) can be the serving satellite after the satellite handover and / or t-Service. The first satellite and the second satellite can serve 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, a satellite handover with resynchronization can be, can be referred to as, can be substituted for, and / or can include a hard satellite handover with resynchronization and / or a soft satellite handover with resynchronization.

[0352] Based on the current NR RRC specification ([3]TS 38.331 v18.0.0), when the UE is in RRC_CONNECTED, the UE performs actions after receiving SIB19 (as specified in Section 5.2.2.4.21 of TS 38.331 ([3]3GPP TS 38.331 V18.0.0 draft)), including checking SatSwitchWithReSync in SIB19 to determine whether to perform satellite handover with resynchronization. In other words, based on the current NR RRC specification, the UE determines whether to perform satellite handover with resynchronization at the timing when the UE receives SIB19 (e.g., at the first timing). If SatSwitchWithResync and t-Service are included in SIB19 and the UE supports satellite handover with resynchronization, the UE determines whether to perform satellite handover with resynchronization based on the RRC state of the UE at the timing of SIB19 reception (e.g., the first timing). That is, satellite handover with resynchronization is performed only 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 the first timing in RRC_CONNECTED and initiates a satellite handover at the 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 receiving SIB19. If the UE is in the RRC_IDLE or RRC_INACTIVE state at the timing of receiving SIB19 (e.g., the first timing), then even if SatSwitchWithReSync and t-Service are included in SIB19 and the UE is in RRC_CONNECTED at t-Service (e.g., the second timing), the UE will not perform satellite handover with resynchronization. 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 case, based on the current specification, the UE does not perform an action (to perform satellite handover with resynchronization) because it is not in the RRC_CONNECTED state when receiving SIB19. The UE may determine not to initiate satellite handover with resynchronization after receiving SIB19 in the RRC_IDLE or RRC_INACTIVE state (e.g., at the first timing). An example of the problem is shown in Figure 13 is shown.

[0353] For example, according to the current specification, the UE may 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 include 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 stop serving its currently covered area). After receiving SIB19, the UE may perform an initial access to the serving cell (e.g., an RRC connection establishment procedure) at a second timing. The UE may enter the RRC_CONNECTED state at or after the second timing. After the UE enters the RRC_CONNECTED state, the serving satellite may 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 the coverage of the serving satellite at or after the third timing.

[0354] On the other hand, the UE may be in the RRC_CONNECTED when receiving SIB19. Based on the current NR RRC specification, when the UE is in the RRC_CONNECTED state, the UE performs actions after receiving SIB19 (as specified in section 5.2.2.4.21 of [3] 3GPP TS 38.331 V18.0.0 draft), and the UE may 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 may leave the RRC_CONNECTED (and / or enter the RRC_IDLE or RRC_INACTIVE). In this case, based on the current specification, when the UE is in the RRC_IDLE (or RRC_INACTIVE) state, the UE still performs a satellite handover with resynchronization.

[0355] In addition, based on the protocol in the RAN2 meeting, the UE shall perform a conditional handover (CHO) / handover or an earlier triggered satellite handover with resynchronization. According to the current specification, regardless of whether there is a triggered / initiated / ongoing CHO / handover procedure, the UE may perform a satellite handover with resynchronization. The UE may trigger a CHO / handover procedure and then still perform a satellite handover with resynchronization.

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

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

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

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

[0360] The first timing can be the time when / after the UE receives system information. The system information can be NTN-specific system information. The system information can be SIB19. The system information can include one or more NTN configurations (e.g., NTN-Config). The system information can include the NTN configuration (e.g., NTN-Config) for the serving cell of the serving satellite. The system information can include the NTN configuration (e.g., NTN-Config) for the serving cell or neighboring cell of the target satellite. The system information can include the NTN configuration (e.g., NTN-Config) for the target cell of the serving satellite or target satellite. The system information can include the service stop time of the serving cell (e.g., t-Service). The system information can include an indication / configuration of 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) can be before the stop time of the serving cell (e.g., t-Service).

[0361] The second timing can be the time indicated by the network. The second timing can be the time indicated by the service stop time of the serving cell (e.g., t-Service). The second timing can be the 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 the RRC_CONNECTED state. The second timing can be the time when / after the UE enters the RRC_CONNECTED state.

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

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

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

[0367] - The system information contains the service stop time 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, a timer (e.g., T304) is not running.

[0370] The UE may determine to perform / initiate a satellite handover with resynchronization regardless of whether the UE is in the RRC connected state at the first timing (e.g., after receiving SIB19). The UE may determine to perform a satellite handover with resynchronization based on (or if) the UE is in any of the RRC idle state, RRC inactive state, and RRC connected state at the first timing (e.g., after receiving SIB19). Regardless of whether the UE is in the RRC idle state, RRC inactive state, or RRC connected state at the first timing (e.g., after receiving SIB19), the UE may determine to perform / initiate a satellite handover with resynchronization. Regardless of the RRC state of the UE at the first timing (e.g., after receiving SIB19), the UE may determine to perform a satellite handover with resynchronization.

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

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

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

[0374] The UE can determine to perform / initiate a satellite handover with resynchronization based on whether (or if) T304 is not in operation at a second timing (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) T304 is in operation at a second timing (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 a first timing and a second timing. The UE may not acquire (or receive) SIB19 between the time when the UE enters RRC_CONNECTED and the second timing.

[0376] When the UE is in RRC_CONNECTED, the timer T430 of the UE can be running (or the expiration of T430 may not occur). After the UE enters RRC_CONNECTED, the T430 of the UE can be running (or the expiration of T430 may not occur). The T430 of the UE can run between a first timing and a second timing (or the expiration of T430 may not occur). The T430 of the UE can run between the time when the UE enters RRC_CONNECTED and the second timing (or the expiration of T430 may not occur).

[0377] One or more of the above-described embodiments, concepts, methods, examples, actions, events, and / or conditions for determination can be combined.

[0378] To solve the problem, when receiving SIB19, not only in the case where the UE is in RRC_CONNECTED (as Figure 12 shown) but also in the case where the UE is in RRC_IDLE (or RRC_INACTIVE) (as Figure 14 shown), based on (at least) SatSwitchWithReSync and t-Service being included in SIB19, the UE can (at the timing when the UE is in RRC_CONNECTED) determine to perform / initiate a satellite handover with resynchronization.

[0379] Figure 14 Examples of the present invention are shown in. 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 resume (procedure). In response to initiating an initial access (procedure), an RRC connection establishment (procedure), and / or an RRC connection resume (procedure), the UE can enter RRC_CONNECTED. Based on (at least) SatSwitchWithResync and t-Service being included in SIB19, the UE can determine to initiate a satellite handover with resynchronization at a second timing 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 the UE receives SIB19, it can be in any one of RRC_CONNECTED, RRC_IDLE, or RRC_INACTIVE at the first timing. 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 RRC state of the UE 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 the RRC state of the UE at the second timing. The UE can determine to initiate a satellite handover with resynchronization without basing on the RRC state of the UE 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 can perform one or more of the following actions (in order):

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

[0383] - Notify the lower layer of the loss of UL synchronization due to the satellite handover with resynchronization;

[0384] - Synchronize to 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 starting from the subframe indicated by epochTime in SatSwitchWithReSync; and / or

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

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

[0388] In one or more instances, the UE is in the RRC idle (and / or RRC inactive) state at the first timing and 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 can perform / initiate initial access or RRC resume after the second timing.

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

[0391] In one or more instances, the UE is in the RRC connected state at a first timing and in the 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 UE not being in the 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 Instances based on literal proposals of the current specification are provided.

[0393] In Figure 15 the UE determines whether to perform / initiate a satellite handover with resynchronization regardless of the RRC state when / after receiving SIB19.

[0394] In Figures 16 to 18 the UE determines whether to perform / initiate a satellite handover with resynchronization regardless of the RRC state when / after receiving 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.

[0395] In Figures 19 to 21 the UE determines whether to perform / initiate a satellite handover with resynchronization regardless of the RRC state when / after receiving 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 and the timer T304 not being in operation.

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

[0397] The UE may be in a cell of the NTN. The UE may be connected to a cell of the NTN. The UE may camp on a cell of the NTN. The UE may be connected to LEO, GEO, MEO, HEO, and / or HAPS. The UE may be connected to one or two networks (nodes).

[0398] The UE may be referred to as the UE, the RRC layer of the UE, the MAC entity of the UE, or the physical layer of the UE.

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

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

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

[0402] See Figure 22 , for such and other concepts, systems, and methods of the present invention, a 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 that the UE is in an RRC connected state at a second timing and / or regardless of the RRC state of the UE 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 the 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 when the cell stops service, or the (service) cell (service) stop time. In various embodiments, t-ServiceStart is the time information when the satellite starts service, or the satellite handover start time.

[0406] In various embodiments, t-Service and / or t-ServiceStart is 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 is included in the system information, t-Service is included in the system information, the UE supports a satellite handover with resynchronization, and / or the timer is not running.

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

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

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

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

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

[0413] Now refer to Figure 3 and Figure 4, in one or more embodiments, from the perspective of the NW in a wireless communication system, apparatus 300 includes program code 312 stored in the memory 310 of the transmitter. The CPU 308 may execute the program code 312 to: (i) transmit system information in the NTN cell at a first timing; and (ii) perform a satellite handover with resynchronization at the UE at a second timing, where the UE is in the RRC connected state at the second timing and / or regardless of the RRC state of the UE at the first timing. Additionally, the CPU 308 may execute the program code 312 to perform all the described actions, steps, and methods described above, below, or elsewhere herein.

[0414] The one or more conditions may 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 connected 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;

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

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

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

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

[0422] Alternatively and / or additionally, based on one or more conditions at the one or more specific timings, the UE may determine (whether to) perform / initiate (at least) a first action and / or not perform / initiate (at least) a second action. The UE may make a determination to perform / initiate (at least) the first action and / or not perform / initiate (at least) the second action at a second timing based on (at least) the one or more conditions. Based on (or if) (at least) the one or more conditions are satisfied, the UE may perform / initiate (at least) the first action at the second timing. Based on (or if) (at least) the one or more conditions are not satisfied, the UE may not perform / initiate (at least) the first action at the second timing. Based on (or if) (at least) the one or more conditions are satisfied, the UE may not perform / initiate (at least) the second action at the second timing. Based on (or if) (at least) the one or more conditions are not satisfied, the UE may not perform / initiate (at least) the second action at the second timing. Based on (at least) the RRC state of the UE at the one or more specific timings, the UE may determine (whether to) perform / initiate (at least) the first action and / or the second action. Based on (at least) whether a timer is running at the second timing, the UE may 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 the first action and not include the second action. The UE may perform / initiate the first action during a procedure of a satellite handover with resynchronization. The UE may perform / initiate the second action during a procedure of a satellite handover with resynchronization. The UE may not perform / initiate the second action during a procedure of a satellite handover with resynchronization. The first action and the second action may be different.

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

[0425] - Dispose of or maintain a 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), e.g., where the timer value is set to the ntn-UlSyncValidityDuration starting from the subframe indicated by epochTime.

[0428] - Perform UL synchronization:

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

[0430] -- Notify the lower layer of the loss of UL synchronization due to, for example, a satellite handover with resynchronization;

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

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

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

[0434] -- For example, for the primary timing advance group (PTAG), set the network timing advance (NTA) value to zero; and / or

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

[0436] - Perform DL (re)synchronization:

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

[0438] -- Apply the broadcast control channel (BCCH) configuration to the SpCell (e.g., the target satellite service indicated by SatSwitchWithReSync); and / or

[0439] -- Obtain the master 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 SIB19 contains t-Service indicating a second timing.

[0442] In one or more instances, the UE is in the RRC idle (and / or RRC inactive) state at the first timing and the second timing. For example, based on the UE not being 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 the SpCell) and / or UL synchronization (e.g., maintaining T430, notifying the lower layer of the loss / gain of UL synchronization) at the second timing. The UE may perform / initiate initial access or RRC resume after the second timing.

[0443] In one or more instances, the UE is in the RRC idle (and / or RRC inactive) state at a first timing and 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 and based on the UE being in the RRC idle (and / or RRC inactive) state at the second timing, the UE performs DL (re) synchronization and does not perform UL synchronization. The UE performs a satellite handover with resynchronization that includes DL (re) synchronization (e.g., DL (re) synchronization with the SpCell) and / or does not include UL synchronization (e.g., maintaining T430, notifying the lower layer of loss / gain of UL synchronization). The UE may perform / initiate initial access or RRC resume after the second timing.

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

[0445] In one or more instances, the UE is in the RRC connected state at a first timing and a second timing. The UE may perform / initiate initial access (e.g., RRC establishment) or RRC resume before the first timing. For example, based on the UE being in the 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 that includes DL (re) synchronization (e.g., DL (re) synchronization with the SpCell) and / or UL synchronization (e.g., maintaining T430, notifying the lower layer of loss / gain of UL synchronization).

[0446] In one or more instances, the UE is in the RRC connected state at a first timing and in the 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 UE not being 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 that includes DL (re) synchronization (e.g., DL (re) synchronization with the SpCell) and / or UL synchronization (e.g., maintaining T430, notifying the lower layer of loss / gain of UL synchronization).

[0447] In one or more instances, the UE is in the RRC connected state at a first timing and in the 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 and based on the UE being in the RRC idle (and / or RRC inactive) state at the second timing, the UE performs DL (re)synchronization and does not perform UL synchronization. The UE performs a satellite handover with resynchronization that includes DL (re)synchronization (e.g., DL (re)synchronization with the SpCell) and / or does not include UL synchronization (e.g., maintains T430, notifies the lower layer of loss / gain of UL synchronization).

[0448] Figures 23 to 26 Instances based on literal proposals of the current specification are provided.

[0449] In Figures 23 to 24 , regardless of the RRC state when / after 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 state when / after 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 second satellite handover with resynchronization based on Figure 26 .

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

[0451] See Figure 27, For such and other concepts, systems, and methods of the present invention, method 1010 for a UE in a wireless communication system includes receiving SIB19 at a first timing, where the UE is in RRC_IDLE or RRC_INACTIVE at the first timing (step 1012), and determining to initiate a satellite handover with resynchronization at a second timing when the UE is in RRC_CONNECTED based on SatSwitchWithResync and t-Service being included in SIB19 (step 1014).

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

[0453] In various embodiments, when receiving SIB19 at the first timing, the UE is in any one 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 the first timing, the UE determines to initiate a satellite handover with resynchronization at the second timing.

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

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

[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, where the timer value is set to ntn-UlSyncValidityDuration starting 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 enters RRC_CONNECTED from RRC_IDLE or RRC_INACTIVE.

[0463] Now refer to 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 may execute program code 312 to: (i) receive SIB19 at a first timing, where the UE is in RRC_IDLE or RRC_INACTIVE at the first timing; and (ii) determine to initiate a satellite handover with resynchronization at a second timing when the UE is in RRC_CONNECTED based on SatSwitchWithResync and t-Service being included in SIB19. Additionally, CPU 308 may execute program code 312 to perform all of the described actions, steps, and methods described above, below, or herein.

[0464] Any combination of the concepts or teachings above or herein may be fully or partially combined together or formed into new embodiments. The disclosed details and embodiments can be used to at least (but not limited to) solve the problems mentioned above and herein.

[0465] It should be noted that any one of the methods, alternatives, steps, examples, and embodiments presented herein can be applied independently, individually, and / or together with multiple methods, alternatives, steps, examples, and embodiments combined together.

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

[0467] Those skilled in the art will appreciate that any of a variety of different technologies and techniques can be used to represent information and signals. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description can be represented by voltages, currents, electromagnetic waves, magnetic fields or magnetic particles, optical fields or optical particles, or any combination thereof.

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

[0469] In addition, the various illustrative logical blocks, modules, and circuits described in connection with the aspects disclosed herein may be implemented within or performed by an integrated circuit (“IC”), an access terminal, or an access point. The 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 in both cases. The general-purpose processor may be a microprocessor, but in the alternative, 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 in conjunction with a DSP core, or any other such configuration.

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

[0471] The steps of a method or algorithm described in connection with the aspects disclosed herein may be implemented directly in hardware, in a software module executed by a processor, or in a combination of the two. Software modules (e.g., including executable instructions and associated data) and other data may reside in a data memory, such as RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, a hard disk, a removable disk, a CD-ROM, or any other form of computer-readable storage medium known in the art. A sample storage medium may be coupled to a machine, such as a computer / processor (for convenience, the 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 may be integral with the processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user equipment. In the alternative, the processor and the storage medium may reside as discrete components in the user equipment. Additionally, in some aspects, any suitable computer program product may include a computer-readable medium that includes code associated with one or more of the aspects of the present disclosure. In some aspects, the computer program product may include packaging material.

[0472] Although the present invention has been described in connection with various aspects and examples, it is to be understood that the invention is capable of further modifications. This application is intended to cover any variations, uses, or adaptations of the invention, which generally follow the principles of the invention and include such departures from the present disclosure as come within the known and customary practice within the art to which the invention pertains.

Claims

1. A method for a user equipment, characterized in that, Comprising: Receiving System Information Block 19 (SIB19) at a first timing, wherein at the first timing the user equipment is in Radio Resource Control idle or Radio Resource Control inactive; And Based on SatSwitchWithResync and t-Service being included in the SIB19, determining to initiate a satellite handover with resynchronization at a second timing when the user equipment is in Radio Resource Control connected.

2. The method according to claim 1, characterized in that, Not only when the user equipment is in Radio Resource Control connected at the first timing when receiving the SIB19, but also when the user equipment is in Radio Resource Control idle or Radio Resource Control inactive at the first timing when receiving the SIB19, the user equipment determines to initiate the satellite handover with resynchronization at the second timing.

3. The method according to claim 1, characterized in that, At the first timing, the user equipment is in any one of Radio Resource Control connected, Radio Resource Control idle or Radio Resource Control inactive.

4. The method according to claim 1, characterized in that The first timing is the timing when the user equipment receives the SIB19.

5. The method according to claim 1, wherein The second timing is the timing when the user equipment is in Radio Resource Control connected or the timing indicated by the t-Service.

6. The method according to claim 1, characterized in that, When the user equipment is in any Radio Resource Control state at the first timing or regardless of the Radio Resource Control state of the user equipment at the first timing, the user equipment determines to initiate the satellite handover with resynchronization at the second timing.

7. The method according to claim 1, characterized in that, Based on the Radio Resource Control state of the user equipment at the second timing or not based on the Radio Resource Control state of the user equipment at the first timing, the user equipment determines to initiate the satellite handover with resynchronization.

8. The method according to claim 1, characterized in that, The second timing is different from or later than the first timing.

9. The method according to claim 1, characterized in that, Further comprising in response to initiating the satellite handover with resynchronization: Stopping timer T430 if the timer T430 is running; Notifying the lower layer of the loss of uplink synchronization due to the satellite handover with resynchronization; Synchronizing with the downlink of the special cell of the satellite service indicated by the SatSwitchWithReSync; Starting the timer T430, wherein the timer value is set to ntn-UlSyncValidityDuration starting from the subframe indicated by the epochTime in the SatSwitchWithReSync; and Notifying the lower layer when uplink synchronization is obtained.

10. The method according to claim 1, characterized in that, The user equipment enters Radio Resource Control connected from Radio Resource Control idle or Radio Resource Control inactive after receiving the SIB19.

11. A user equipment, characterized in that, Comprising: A memory; And A processor operatively coupled to the memory, wherein the processor is configured to execute program code to: Receive System Information Block 19 (SIB19) at a first timing, wherein the user equipment is in Radio Resource Control (RRC) idle or Radio Resource Control (RRC) inactive at the first timing; And Based on SatSwitchWithResync and t-Service being included in the SIB19, determine to initiate a satellite handover with resynchronization at a second timing when the user equipment is in Radio Resource Control (RRC) connected.

12. The user equipment according to claim 11, characterized in that, The user equipment determines to initiate the satellite handover with resynchronization at the second timing not only when the user equipment is in Radio Resource Control (RRC) connected at the first timing when receiving the SIB19, but also when the user equipment is in Radio Resource Control (RRC) idle or Radio Resource Control (RRC) inactive at the first timing when receiving the SIB19.

13. The user equipment according to claim 11, characterized in that At the first timing, the user equipment is in any one of Radio Resource Control (RRC) connected, Radio Resource Control (RRC) idle, or Radio Resource Control (RRC) inactive.

14. The user equipment according to claim 11, characterized in that, The first timing is the timing when the user equipment receives the SIB19.

15. The user equipment according to claim 11, wherein The second timing is the timing when the user equipment is in Radio Resource Control (RRC) connected or the timing indicated by the t-Service.

16. The user equipment according to claim 11, characterized in that, When the user equipment is in any Radio Resource Control (RRC) state at the first timing or regardless of the Radio Resource Control (RRC) state of the user equipment at the first timing, the user equipment determines to initiate the satellite handover with resynchronization at the second timing.

17. The user equipment according to claim 11, characterized in that, Based on the Radio Resource Control (RRC) state of the user equipment at the second timing or not based on the Radio Resource Control (RRC) state of the user equipment at the first timing, the user equipment determines to initiate the satellite handover with resynchronization.

18. The user equipment according to claim 11, characterized in that, The second timing is different from or later than the first timing.

19. The user equipment according to claim 11, characterized in that, The processor further executes the program code in response to initiating the satellite handover with resynchronization to: Stop timer T430 if the timer T430 is running; Notify the lower layer of the loss of uplink synchronization due to the satellite handover with resynchronization; Synchronize with the downlink of the special cell of the satellite service indicated by the SatSwitchWithReSync; Start the timer T430, where the timer value is set to ntn-UlSyncValidityDuration starting from the subframe indicated by the epochTime in the SatSwitchWithReSync; and Notify the lower layer when uplink synchronization is obtained.

20. The user equipment according to claim 11, characterized in that, The user equipment enters Radio Resource Control (RRC) connected from Radio Resource Control (RRC) idle or Radio Resource Control (RRC) inactive after receiving the SIB19.

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