Method and device for uplink synchronization processing for satellite handover in wireless communication

Abstract

Provided are an uplink synchronization processing method and device for satellite handover in wireless communication. Accordingly, a user equipment can process the uplink synchronization of satellite handover, thereby avoiding a reduction in transmission efficiency. The user equipment can also appropriately process resources and / or configurations during satellite handover. A method for a user equipment includes: receiving an indication of uplink synchronization loss from an upper layer; and in response to receiving the indication of uplink synchronization loss: not performing an uplink transmission on a serving cell; and determining whether to clear one or more hybrid automatic repeat request buffers based on whether the uplink synchronization loss is caused by a satellite handover.

Description

[0001] Cross - Reference to Related Applications

[0002] This application claims priority and the benefit of U.S. Provisional Patent Application No. 63 / 537,728, filed on September 11, 2023, U.S. Provisional Patent Application No. 63 / 537,759, filed on September 11, 2023, and U.S. Provisional Patent Application No. 63 / 545,290, filed on October 23, 2023; each of the cited applications and publications is incorporated herein by reference in its entirety. Technical Field

[0003] The present disclosure generally relates to wireless communication networks, and more particularly, to methods and apparatuses for uplink (UL) synchronization processing for satellite handover in a wireless communication system. Background Art

[0004] With the rapid growth in the demand for transmitting large amounts of data to and from mobile communication devices, traditional mobile voice communication networks have evolved into networks that communicate using Internet Protocol (IP) packets. Such 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 architecture 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 3rd Generation Partnership Project (3GPP) standards organization is discussing new next - generation (e.g., 5G) radio technologies. Thus, changes to the current body of the 3GPP standards are currently being submitted and considered to evolve and complete the 3GPP standards. rd Generation Partnership Project, 3GPP) standard organization is discussing new next - generation (e.g., 5G) radio technologies. 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 uplink (UL) synchronization processing for satellite handover in a wireless communication system are provided. Thus, a User Equipment (UE) can handle UL synchronization for satellite handover, thereby avoiding a reduction in transmission efficiency. The UE can also appropriately handle resources and / or configurations during satellite handover.

[0007] In various embodiments, a method for a UE in a wireless communication system includes: receiving an indication of uplink synchronization loss from an upper layer; and in response to receiving the indication of uplink synchronization loss: not performing an uplink transmission on a serving cell, and determining whether to clear one or more Hybrid Automatic Repeat Request (HARQ) buffers based on whether the uplink synchronization loss is caused by a satellite handover.

[0008] In various embodiments, a method for a UE in a wireless communication system includes: receiving system information, where the system information includes at least a first Non-Terrestrial Network (NTN) configuration, time information, and an indication of a satellite handover; in response to receiving the system information, starting or restarting a timer based on the first NTN configuration; initiating a satellite handover procedure based on the indication of the satellite handover being included in the system information; stopping the timer immediately after the timing indicated by the time information; after stopping the timer, considering that uplink (UL) synchronization has been lost; determining whether to clear one or more HARQ buffers based on whether the UL synchronization is lost due to a satellite handover; performing downlink (DL) synchronization with a cell served by a satellite indicated in the indication of the satellite handover; after performing DL synchronization, starting a timer based on a second NTN configuration included in the indication of the satellite handover; and after starting the timer, considering that UL synchronization has been obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 Drawings showing a wireless communication system according to an embodiment of the present invention.

[0010] Figure 2 is a block diagram of a transmitter system (also referred to as an access network) and a receiver system (also referred to as a user equipment or UE) according to an embodiment of the present invention.

[0011] Figure 3 is a functional block diagram of a communication system according to an embodiment of the present invention.

[0012] Figure 4 is according to an embodiment of the present invention Figure 3 of the program code.

[0013] Figure 5 is in 3GPP TS 38.300 V17.5.0 Figure 16 .14.1-1: Reproduction of the overall illustration of NTN.

[0014] Figure 6 is in 3GPP TS 38.300 V17.5.0 Figure 16Reproduction of the timing relationship diagram of 0.14.2.1-1 (for co-located gNB and NTN gateway).

[0015] Figure 7 is from 3GPP TS 38.211 V17.5.0 Figure 4 .3.1-1: Reproduction of uplink-downlink timing association

[0016] Figure 8 is from 3GPP TS 38.321 V17.5.0 Figure 6 .1.3.4-1: Reproduction of the timing advance command MAC CE

[0017] Figure 9 is from 3GPP TS 38.321 V17.5.0 Figure 6 .1.3.56-1: Reproduction of the timing advance report MAC CE

[0018] Figure 10 is from 3GPP TS 38.331 V17.5.0 Figure 5 .3.3.1-1: Reproduction of RRC connection establishment (successful)

[0019] Figure 11 is from 3GPP TS 38.331 V17.5.0 Figure 5 .3.5.1-1: Reproduction of RRC reconfiguration (successful)

[0020] Figure 12 is from 3GPP TS 38.331 V17.5.0 Figure 5 .3.5.1-2: Reproduction of RRC reconfiguration (failed)

[0021] Figure 13 is from 3GPP TS 38.331 V17.5.0 Figure 5 .3.7.1-1: Reproduction of RRC connection re-establishment (successful)

[0022] Figure 14 is from 3GPP TS 38.331 V17.5.0 Figure 5 .3.7.1-2: Reproduction of RRC re-establishment fallback to RRC establishment (successful)

[0023] Figure 15 is from 3GPP TS 38.331 V17.5.0 Figure 5 .3.13.1-1: Reproduction of RRC connection resume (successful)

[0024] Figure 16It is in 3GPP TS 38.331 V17.5.0 Figure 5 .3.13.1-2: Reproduction of RRC connection resume falling back to RRC connection establishment (successful).

[0025] Figure 17 It is an example drawing of satellite handover according to an embodiment of the present invention.

[0026] Figure 18 It is a flowchart of a method of a UE according to an embodiment of the present invention, the method including: receiving a first indication of satellite handover; performing DL synchronization with a serving cell at an opportunity; receiving NTN-specific system information; after performing DL synchronization with the serving cell, determining whether to trigger a TA report based on whether it is provided by the network; and if the indication is provided by the network in the NTN-specific system information, triggering a TA report.

[0027] Figure 19 It is a flowchart of a method of a UE according to an embodiment of the present invention, the method including: receiving a configuration of satellite handover; initiating a satellite handover at an opportunity; in response to the satellite handover, performing DL and / or UL (re)synchronization with the serving cell; in response to the satellite handover, re-acquiring system information related to NTN; and in response to the satellite handover, not considering that the time alignment timer has expired.

[0028] Figure 20 It is an example drawing of hard satellite handover according to an embodiment of the present invention.

[0029] Figure 21 It is an example drawing of hard satellite handover according to an embodiment of the present invention.

[0030] Figure 22 It is an example drawing of soft satellite handover according to an embodiment of the present invention.

[0031] Figure 23 It is an example drawing of soft satellite handover according to an embodiment of the present invention.

[0032] Figure 24 It is an example drawing of UL synchronization processing for satellite handover according to an embodiment of the present invention.

[0033] Figure 25Flowchart of a method of a UE, the method comprising: receiving a first indication of a satellite handover; receiving NTN configuration of a target satellite; performing DL synchronization with the target satellite at an occasion; in response to performing DL synchronization with the target satellite, stopping a UL synchronization timer for a serving cell; after the UL synchronization timer stops, starting a UL synchronization timer for the serving cell based on the NTN configuration of the target satellite; not considering that the UL synchronization timer has expired at t-Service based on the NTN configuration of the target satellite being available; and when the UL synchronization timer is running, performing a RA procedure for the satellite handover.

[0034] Figure 26 Flowchart of a method of a UE, the method comprising: receiving an indication of uplink synchronization loss from an upper layer; and in response to receiving the indication of uplink synchronization loss: not performing an uplink transmission on a serving cell, and determining whether to clear one or more HARQ buffers based on whether the uplink synchronization loss is caused by a satellite handover.

[0035] Figure 27 Flowchart of a method of a UE, the method comprising: receiving system information, wherein the system information at least includes a first NTN configuration, time information, and an indication of a satellite handover; in response to receiving the system information, starting or restarting a timer based on the first NTN configuration; initiating a procedure for a satellite handover based on the indication of the satellite handover being included in the system information; stopping the timer immediately after the occasion indicated by the time information; after stopping the timer, considering that the UL synchronization has been lost; determining whether to clear one or more HARQ buffers based on whether the UL synchronization is lost due to a satellite handover; performing DL synchronization with a cell served by the satellite indicated in the indication of the satellite handover; after performing the DL synchronization, starting a timer based on a second NTN configuration included in the indication of the satellite handover; and after starting the timer, considering that the UL synchronization has been obtained. Detailed implementation

[0036] The present invention described herein can be applied to or implemented in the exemplary wireless communication systems and apparatuses described below. Additionally, the present invention is mainly described in the context of the 3GPP architecture reference model. However, it should be understood that with the disclosed information, those skilled in the art can easily adapt to use and implement aspects of the present invention in 3GPP2 network architectures and other network architectures.

[0037] 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, and so on. 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), 3GPP2 Ultra Mobile Broadband (UMB), WiMax, 3GPP New Radio (NR), or some other modulation techniques.

[0038] Specifically, the exemplary wireless communication systems and devices described below can be designed to support one or more standards, such as those provided by an association named "3rd Generation Partnership Project" (referred to as 3GPP in this document), including: [1] 3GPP TS 38.300 V17.5.0, "NR, Overall Description of NR and NG-RAN, Phase 2"; [2] 3GPP TS 38.211 V17.5.0, "NR, Physical Channels and Modulation"; [3] 3GPP TS 38.321 V17.5.0, "NR, MAC Protocol Specification"; [4] 3GPP TS 38.331 V17.5.0, "NR, RRC Protocol Specification"; [5] R2-2309341, "Phase 3 of RRC CR for Running NR NTN Rel-18"; [6] R2-2308373, "Satellite Handover: PCI Change without L3 Handover", NEC; [7] R2-2304273, "LS Regarding Unchanged PCI"; [8] R2-2307623, "Details of Satellite Handover with Unchanged PCI", Qualcomm; [9] 3GPP TS 38.331 V17.6.0, ", NR, RRC Protocol Specification"; and

[10] R2-2310307, "Satellite Handover with Unchanged PCI", Apple. The standards and documents listed above are hereby expressly and fully incorporated herein by reference in their entireties.

[0039] Figure 1A multi - access wireless communication system according to an embodiment of the present invention is shown. The access network 100 (AN) includes a plurality of antenna groups, where one antenna group includes 104 and 106, another antenna group includes 108 and 110, and yet another antenna group includes 112 and 114. In Figure 1 this example, only two antennas are shown for each antenna group; however, each antenna group may utilize more or fewer antennas. 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 may communicate using different frequencies. For example, the forward link 120 may use a frequency different from the frequency used by the reverse link 118.

[0040] Each antenna group and / or the area in which the antenna group is designed to communicate is often referred to as a sector of the access network. In an embodiment, the antenna groups are each designed to communicate with access terminals in a sector of the area covered by the access network 100.

[0041] In the communication via the forward links 120 and 126, the transmitting antennas of the access network 100 may utilize beamforming to improve the signal - to - noise ratio of the forward links for different access terminals 116 and 122. Additionally, compared to an access network that transmits to all its access terminals via a single antenna, an access network that uses beamforming to transmit to access terminals randomly dispersed within its coverage generally causes less interference to access terminals in adjacent cells.

[0042] The AN may be a fixed station or a base station for communicating with terminals and may also be referred to as an access point, Node B, base station, enhanced base station, eNodeB, gNB, or some other term. The AT may also be referred to as a user equipment (UE), a wireless communication device, a terminal, an access terminal, or some other term.

[0043] 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 a user equipment (UE)) in a MIMO system 200. At the transmitter system 210, traffic data for several data streams is provided from a data source 212 to a transmit (TX) data processor 214.

[0044] In one embodiment, each data stream is transmitted via a respective transmission antenna. The TX data processor 214 formats, encodes, and interleaves the traffic data for the data stream based on a particular decoding scheme selected for each data stream to provide encoded data.

[0045] The encoded data for 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. Then, the multiplexed pilot data and the encoded data for the data stream can be modulated (i.e., symbol mapped) based on a particular modulation scheme selected for each data stream (e.g., BPSK, QPSK, M-PK, or M-QAM) to provide modulated symbols. The data rate, encoding, and modulation for each data stream can be determined by instructions implemented by the processor 230. The memory 232 is coupled to the processor 230.

[0046] Next, the modulated symbols for all data streams are provided to the TX MIMO processor 220, which may further process the modulated symbols (e.g., for OFDM). Then, the TX MIMO processor 220 provides N T modulated symbol streams to N T transmitters (TMTRs) 222a through 222t. In some embodiments, the TX MIMO processor 220 applies beamforming weights to the symbols of the data streams and the antennas from which the symbols are transmitted.

[0047] Each transmitter 222 receives and processes the respective symbol stream to provide one or more analog signals and further conditions the analog signals (e.g., amplifies, filters, and upconverts) to provide a modulated signal suitable for transmission over the MIMO channel. Then, N T modulated signals from transmitters 222a through 222t are transmitted from N T antennas 224a through 224t.

[0048] 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 the respective received signal (e.g., filters, amplifies, and downconverts), digitizes the conditioned signal to provide samples, and further processes the samples to provide a corresponding "received" symbol stream.

[0049] Next, the RX data processor 260 receives N R symbol streams from N R receivers 254 and processes the N R received symbol streams based on a specific receiver processing technique to provide N T "detected" symbol streams. Next, the RX data processor 260 demodulates, deinterleaves, and decodes each detected symbol stream to recover the service 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.

[0050] 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.

[0051] The reverse link message may include various types of information regarding the communication link and / or the received data streams. Next, the reverse link message is processed by the TX data processor 238 (which also receives service data for several data streams from the data source 236), modulated by the modulator 280, conditioned by the transmitters 254a to 254r, and transmitted back to the transmitter system 210.

[0052] 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. Next, the processor 230 determines which precoding matrix to use to determine the beamforming weights and then processes the extracted message.

[0053] The memory 232 may be used to temporarily store some buffered / computed data from the 240 or 242 via the processor 230, store some buffered data from 212, or store some specific program code. In addition, the memory 272 may be used to temporarily store some buffered / computed data from the 260 via the processor 270, store some buffered data from 236, or store some specific program code.

[0054] Turning 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 therein, the communication device 300 in a wireless communication system can be utilized to implement Figure 1UEs (or ATs) 116 and 122 therein, and the wireless communication system is preferably an NR system. The communication device 300 may include an input device 302, an output device 304, a control circuit 306, a central processing unit (CPU) 308, a memory 310, program code 312, and a transceiver 314. The control circuit 306 executes the program code 312 in the memory 310 through the CPU 308, thereby controlling the operation of the communication device 300. The communication device 300 may receive signals input by a user through the input device 302 (such as a keyboard or keypad), and may output images and sounds through the output device 304 (such as 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.

[0055] Figure 4 is according to an embodiment of the present invention Figure 3 is a simplified block diagram of the program code 312 shown in. In this embodiment, the program code 312 includes an application layer 400, a layer 3 part 402, and a layer 2 part 404, and is coupled to a layer 1 part 406. The layer 3 part 402 generally implements radio resource control. The layer 2 part 404 generally implements link control. The layer 1 part 406 generally implements physical connection.

[0056] For an LTE, LTE-A, or NR system, the layer 2 part 404 may include a Radio Link Control (RLC) layer and a Medium Access Control (MAC) layer. The layer 3 part 402 may include a Radio Resource Control (RRC) layer.

[0057] 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.

[0058] Any sentence, paragraph, (sub) bullet point, key point, action, or claim described in each inventive paragraph or section below may be implemented independently and separately to form a specific method or device. The correlations 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 a specific method or device.

[0059] The general description of Rel-17 NR non-terrestrial network (NTN) is specified in TS 38.300 ([1] 3GPP TS 38.300 V17.5.0) as follows:

[0060] *************************Quote start [1]*********************

[0061] 16.14 Non-terrestrial network

[0062] 16.14.1 Overview

[0063] 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, thus depicting the service link between the NTN payload and the UE, and the feeder link between the NTN gateway and the NTN payload.

[0064] Figure 5 is in 3GPP TS 38.300 V17.5.0 Figure 16 .14.1-1: Reproduction of the overall illustration of NTN.

[0065] …

[0066] The NTN payload transparently forwards the radio protocols received from the UE (via the service link) to the NTN gateway (via the feeder link), and vice versa. The following connectivity is supported by the NTN payload:

[0067] - The NTN gateway can serve multiple NTN payloads;

[0068] - The NTN payload can be served by multiple NTN gateways.

[0069] …

[0070] Supports three types of service links:

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

[0072] - Quasi-earth-fixed: Provided by beams that cover a geographical area for a limited period and different geographical areas during another period (e.g., in the case of NGSO satellites that generate steerable beams);

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

[0074] With NGSO satellites, the gNB can provide quasi-earth-fixed service links or earth-mobile service links, while the gNB operating with GSO satellites can provide earth-fixed service links.

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

[0076] 16.14.2 Timing and Synchronization

[0077] 16.14.2.1 Scheduling and Timing

[0078] The DL and UL are aligned at the uplink time synchronization reference point (RP) with an offset given by N TA，offset (see clause 4.2 of TS 38.213).

[0079] To accommodate the propagation delay in NTN, several timing relationships are enhanced by Common Timing Advance (Common TA) and two offsets K offset and k mac :

[0080] - The Common TA is a configured timing offset equal to the RTT between the RP and the NTN payload.

[0081] - K offset is a configured scheduling offset that needs to be greater than or equal to the sum of the service link RTT and the Common TA.

[0082] - k mac is a configured offset approximately equal to the RTT between the RP and the gNB.

[0083] The scheduling offset K offset is used to allow sufficient processing time at the UE between downlink reception and uplink transmission, see TS 38.213.

[0084] The offset k mac is used to delay the application of downlink configurations indicated by MAC CE commands on the PDSCH (see TS38.213), and for the estimation of the UE-gNB RTT (see TS 38.321[3]). 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).

[0085] At Figure 16.14.2.1-1 describes the service link RTT, feeder link RTT, RP, common TA, k mac and T TA (see Clause 16.14.2.2).

[0086] Figure 6 is the reproduction of the timing relationship of Figure 16 .14.2.1-1 (for co-located gNB and NTN gateway) in 3GPP TS 38.300 V17.5.0.

[0087] …

[0088] 16.14.2.2 Timing Advance and Frequency Pre-Compensation

[0089] For the serving cell, the network broadcasts the valid ephemeris information and the common TA parameters. The UE shall have a valid GNSS position as well as ephemeris and 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, ephemeris and common TA parameters (see Clause 4.2 in TS 38.213), and pre-compensate T autonomously for the RTT between the UE and the RP as shown in Figure 16 .14.2.1-1 (see Clause 4.3 in TS 38.211[2]). TA (see Clause 4.3 in TS 38.211[2]).

[0090] The UE shall calculate the Doppler shift of the service 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 valid ephemeris and common TA, the UE shall not transmit before regaining both of them.

[0091] In the connected mode, the UE shall be able to continuously update the timing advance and frequency pre-compensation.

[0092] 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.

[0093] ********************End of citation*************************

[0094] The general description of the timing advance (TA) is specified in TS 38.300 ((in [1] 3GPP TS 38.300 V17.5.0)) as follows:

[0095] ********************Quotation start [1]********************

[0096] 9.2.9 Timing Advance

[0097] In RRC_CONNECTED, the gNB is responsible for maintaining the timing advance to keep L1 synchronized. Serving cells with UL having the same applicable timing advance and using the same timing reference cell are grouped in a TAG. Each TAG contains at least one serving cell with a configured uplink, and the mapping of each serving cell to the TAG is configured by RRC.

[0098] For the primary TAG, the UE uses the PCell as the timing reference, only sharing the spectrum channel access, where in some cases an SCell can also be used (see clause 7.1 of TS 38.133). In the secondary TAG, the UE can use any of the activated Scells in this TAG as the timing reference cell, but should not change the timing reference cell unless necessary.

[0099] The timing advance update is sent by the gNB to the UE via a MAC CE command. Such a command restarts a TAG-specific timer that indicates whether L1 can be synchronized: when the timer is running, L1 is considered synchronized, otherwise, L1 is considered unsynchronized (in this case, uplink transmissions can only occur via MSG1 / MSGA).

[0100] *************************Quotation end********************

[0101] TA information including the definitions and formulas for calculating TA parameters is specified in TS 38.211 ([2] 3GPP TS 38.211 V17.5.0) as follows:

[0102] ********************Quotation start [2]********************

[0103] 4.3 Frame Structure

[0104] 4.3.1 Frames and Subframes

[0105] Downlink, uplink, and sidelink transmissions are organized into frames with a duration of T f =(Df max N f / 100)·T c =10 ms, and each frame consists of T sf =(Dfmax N f (N / 1000)·T c is composed of ten sub - frames with a duration of 1 ms. The number of consecutive OFDM symbols per sub - frame is Each frame is divided into two semi - frames of equal size. Each semi - frame has five sub - frames, where semi - frame 0 consists of sub - frames 0 - 4 and semi - frame 1 consists of sub - frames 5 - 9.

[0106] On a carrier, there is a set of frames in the uplink and a set of frames in the downlink.

[0107] The uplink frame number i for transmission from the UE will start before the corresponding downlink frame at the UE. where

[0108] · - N TA and N TA，offset are given by Clause 4.2 of [TS 38.213], except that for msgA transmission on PUSCH with N TA = 0;

[0109] · - given by Clause 4.2 of [TS 38.213] is derived according to the higher - layer parameters ta - Common, ta - CommonDrift, and ta - CommonDriftVariant (if configured), otherwise

[0110] · - given by Clause 4.2 of [TS 38.213] is calculated by the UE based on the UE location and higher - layer parameters related to the serving - satellite - ephemeris (if configured), otherwise

[0111] Figure 7 is in 3GPP TS 38.211 V17.5.0 Figure 4 .3.1 - 1: Uplink - downlink timing association reproduction.

[0112] *************************Quote end********************

[0113] The maintenance of UL time alignment and TA reporting in NTN is specified in TS 38.321 ([3] 3GPP TS 38.321 V17.5.0) as follows:

[0114] *************************Quote start [3]********************

[0115] 5.2 Maintenance of Uplink Time Alignment

[0116] The RRC configures the following parameters for the maintenance of UL time alignment:

[0117] - timeAlignmentTimer (per TAG), which controls the duration required for the MAC entity to perform uplink time alignment for the serving cell considered to belong to the associated TAG;

[0118] …

[0119] The MAC entity shall:

[0120] 1> When receiving a timing advance command MAC CE, and if N has been maintained using the indicated TAG TA (as defined in TS 38.211 [2]), then:

[0121] 2> Apply the timing advance command for the indicated TAG;

[0122] …

[0123] 3> Start or restart the timeAlignmentTimer associated with the indicated TAG.

[0124] 1> When receiving a timing advance command in a random access response message for the serving cell belonging to the TAG or in an MSG B for the SpCell:

[0125] 2> If the MAC entity has not selected a random access preamble among the contention-based random access preambles:

[0126] 3> Apply the timing advance command for this TAG;

[0127] 3> Start or restart the timeAlignmentTimer associated with this TAG.

[0128] 2> Otherwise, if the timeAlignmentTimer associated with this TAG is not running:

[0129] 3> Apply the timing advance command for this TAG;

[0130] 3> Start the timeAlignmentTimer associated with this TAG;

[0131] 3> When contention resolution is considered unsuccessful as described in Clause 5.1.5; or

[0132] 3> When contention resolution is considered successful for SI requests as described in clause 5.1.5 after transmitting HARQ feedback containing the UE contention resolution identity MAC CE for the MAC PDU:

[0133] 4> Stop the timeAlignmentTimer associated with this TAG.

[0134] …

[0135] 2> Otherwise:

[0136] 3> Ignore the received timing advance command.

[0137] 1> When an absolute timing advance command is received in response to the transmission of an MSGA containing a C-RNTI MAC CE as specified in clause 5.1.4a:

[0138] 2> Apply the timing advance command to the PTAG;

[0139] 2> If there is an ongoing positioning SNR transmission in RRC_INACTIVE as described in clause 5.26:

[0140] 3> Start or restart the inactivePosSRS-TimeAlignmentTimer associated with the indicated TAG.

[0141] …

[0142] 3> Start or restart the timeAlignmentTimer associated with the PTAG.

[0143] …

[0144] 1> When an instruction is received from the upper layer to start the TimeAlignmentTimer associated with the PTAG:

[0145] 2> Start the TimeAlignmentTimer associated with the PTAG.

[0146] 1> When the timeAlignmentTimer expires:

[0147] 2> If the timeAlignmentTimer is associated with the PTAG:

[0148] 3> Clear all HARQ buffers for all serving cells;

[0149] 3> Notify RRC to release the PUCCH (if configured) for all serving cells;

[0150] 3> Notify RRC to release the SRS (if configured) for all serving cells;

[0151] 3> Clear any configured downlink assignments and configured uplink grants;

[0152] 3> Clear any PUSCH resources for semi-persistent CSI reporting;

[0153] 3> Consider all running timeAlignmentTimers to have expired;

[0154] 3> Maintain the N of all TAGs TA (defined in TS 38.211 [2]).

[0155] 2> Otherwise, if the timeAlignmentTimer is associated with the STAG, then for all serving cells belonging to this TAG:

[0156] 3> Clear all HARQ buffers;

[0157] 3> Notify RRC to release the PUCCH (if configured);

[0158] 3> Notify RRC to release the SRS (if configured);

[0159] 3> Clear any configured downlink assignments and configured uplink grants;

[0160] 3> Clear any PUSCH resources for semi-persistent CSI reporting;

[0161] 3> Maintain the N of this TAG TA (defined in TS 38.211 [2]).

[0162] …

[0163] When the MAC entity stops uplink transmission due to the fact that the maximum uplink transmission timing difference between the TAGs of the MAC entity or the maximum uplink transmission timing difference between the TAGs of any MAC entity of the UE is exceeded, the MAC entity considers the timeAlignmentTimer associated with the SCell to have expired.

[0164] When the timeAlignmentTimer associated with the TAG to which the serving cell belongs is not running, the CG-SDT procedure is not in progress, and the SRS transmission in RRC_INACTIVE as in clause 5.26 is not in progress, the MAC entity shall not perform any uplink transmission on this serving cell other than random access preamble and MSGA transmission. In addition, when the timeAlignmentTimer associated with the PTAG is not running, the CG-SDT procedure is not in progress, and the SRS transmission in RRC_INACTIVE as in clause 5.26 is not in progress, the MAC entity shall not perform any uplink transmission on any serving cell other than random access preamble and MSGA transmission on the SpCell. When the cg-SDT-TimeAlignmentTimer is not running and the inactivePosSRS-TimeAlignmentTimer is not running during an ongoing CG-SDT procedure triggered as in clause 5.27, the MAC entity shall not perform any uplink transmission other than random access preamble and MSGA transmission.

[0165] ********************Next citation*************************

[0166] 5.4.8 Timing Advance Reporting

[0167] The Timing Advance Reporting procedure is used in non-terrestrial networks to provide the gNB with an estimate of the UE's Timing Advance value (i.e., T as defined in the UE's TA formula, see clause 4.3.1 of TS 38.211 [2]). TA , see clause 4.3.1 of TS 38.211 [2].

[0168] RRC controls Timing Advance Reporting by configuring the following parameters:

[0169] - offsetThresholdTA;

[0170] - timingAdvanceSR.

[0171] If any of the following events occurs, a Timing Advance report (TAR) shall be triggered:

[0172] - After an indication from the upper layer to trigger Timing Advance Reporting;

[0173] - After the upper layer configures offsetThresholdTA, if the UE has not previously reported the Timing Advance value to the current serving cell;

[0174] - If the change between the current estimate of the timing advance value and the last reported timing advance value is equal to or greater than offsetThresholdTA (if configured).

[0175] The MAC entity shall:

[0176] 1> If the timing advance reporting procedure determines that at least one TAR has been triggered and not cancelled, then:

[0177] 2> If the UL-SCH resource is available for a new transmission due to logical channel prioritization and the UL-SCH resource can accommodate the timing advance reporting MAC CE plus its sub-header, then:

[0178] 3> Indicate to the multiplexing and assembler to generate a timing advance reporting MAC CE as defined in clause 6.1.3.56.

[0179] 2> Otherwise

[0180] 3> If timingAdvanceSR is configured with the value enabled:

[0181] 4> Trigger a scheduling request.

[0182] Note: The UL-SCH resource is considered available if the MAC entity has been configured with, has received, or has determined an uplink grant. If the MAC entity has determined at a given point in time that the UL-SCH resource is available, this does not necessarily imply that the UL-SCH resource is available at that point in time.

[0183] Even when multiple events have triggered a timing advance report, the MAC PDU shall contain at most one timing advance reporting MAC CE. The timing advance reporting MAC CE shall be generated based on the latest available estimate of the UE's timing advance value prior to the assembly of the MAC PDU.

[0184] When the MAC PDU is transmitted and this PDU contains a timing advance reporting MAC CE, all triggered timing advance reports shall be cancelled.

[0185] ********************Next citation*************************

[0186] 6.1.3.4 Timing advance command MAC CE

[0187] The timing advance command MAC CE is identified by a MAC sub-header with the LCID specified in Table 6.2.1-1.

[0188] It has a fixed size and consists of a single octet defined as follows (Figure 6 .1.3.4-1):

[0189] - TAG Identity (TAG ID): This field indicates the TAG identity of the addressed TAG. A TAG containing a SpCell has a TAG identity of 0. The length of the field is 2 bits;

[0190] - Timing Advance Command: This field indicates the index value T of the amount of timing adjustment that must be applied to control the MAC entity (as specified in TS 38.213). A (0, 1, 2, …, 63). The length of the field is 6 bits.

[0191] Figure 8 is in 3GPP TS 38.321 V17.5.0 Figure 6 .1.3.4-1: Reproduction of the Timing Advance Command MAC CE.

[0192] ******************** Next citation *************************

[0193] 6.1.3.56 Timing Advance Report MAC CE

[0194] The Timing Advance Report MAC CE is identified by a MAC sub-header with the LCID specified in Table 6.2.1-2. It has a fixed size and consists of two octets defined as follows ( Figure 6 .1.3.56-1):

[0195] - R: Reserved bit, set to 0;

[0196] - Timing Advance: In FR1, the Timing Advance field indicates the smallest integer number of time slots greater than or equal to the Timing Advance value using a subcarrier spacing of 15 kHz (see clause 4.3.1 of TS 38.211 [2]). The length of the field is 14 bits.

[0197] Figure 9 is in 3GPP TS 38.321 V17.5.0 Figure 6 .1.3.56-1: Reproduction of the Timing Advance Report MAC CE.

[0198] ************************* Citation end ********************

[0199] The RRC connection / reconfiguration procedures and TA reporting procedures in the upper layer (i.e., RRC) are specified in TS 38.331 ([4] 3GPP TS 38.331 V17.5.0) as follows:

[0200] *************************Quotation start [4]********************

[0201] 5.3.3 RRC connection establishment

[0202] 5.3.3.1 Overview

[0203] Figure 10 is in 3GPP TS 38.331 V17.5.0 Figure 5 .3.3.1-1: Reproduction of RRC connection establishment (successful).

[0204] …

[0205] The purpose of this procedure is to establish an RRC connection. RRC connection establishment involves the establishment of SRB1. The procedure is also used to transfer initial NAS dedicated information / messages from the UE to the network.

[0206] The network applies the procedure as described, for example, as follows:

[0207] - When establishing an RRC connection;

[0208] - When the UE is resuming or re-establishing an RRC connection and the network is unable to retrieve or verify the UE context. In this case, the UE receives RRCSetup and responds with RRCSetupComplete.

[0209] …

[0210] 5.3.3.2 Initiation

[0211] The UE initiates the procedure when the upper layer requests the establishment of an RRC connection while the UE is in RRC_IDLE and it has obtained the basic system information, or for sidelink communication as specified in clause 5.3.3.1a.

[0212] Before initiating this procedure, the UE shall ensure that it has valid and up-to-date basic system information as specified in clause 5.2.2.2.

[0213] After initiating the procedure, the UE shall then:

[0214] …

[0215] 2> Apply the preset MAC cell group configuration as specified in 9.2.2;

[0216] 2> Apply the CCCH configuration as specified in 9.1.1.2;

[0217] 2> Apply the timeAlignmentTimerCommon included in SIB1;

[0218] 1> Start timer T300;

[0219] 1> Initiate the transmission of the RRCSetupRequest message according to 5.3.3.3;

[0220] 5.3.3.3 Actions related to the transmission of the RRCSetupRequest message

[0221] The UE shall set the content of the RRCSetupRequest message as follows:

[0222] …

[0223] 1> If the ta-Report configuration has the value enabled and the UE supports TA reporting:

[0224] 2> Indicate to the lower layer the initiation of TA reporting;

[0225] The UE shall submit the RRCSetupRequest message to the lower layer for transmission.

[0226] *************************Next citation********************

[0227] 5.3.5 RRC Reconfiguration

[0228] 5.3.5.1 Overview

[0229] Figure 11 It is in 3GPP TS 38.331 V17.5.0 Figure 5 .3.5.1-1: Reproduction of RRC Reconfiguration (successful).

[0230] Figure 12 It is in 3GPP TS 38.331 V17.5.0 Figure 5 .3.5.1-2: Reproduction of RRC Reconfiguration (failed).

[0231] The purpose of this procedure is to modify the RRC connection, such as establishing / modifying / releasing RB / BH RLC channels / Uu relay RLC channels / PC5 relay RLC channels, performing reconfiguration with synchronization, setting / modifying / releasing measurements, adding / modifying / releasing SCell and cell groups, adding / modifying / releasing conditional handover configurations, adding / modifying / releasing conditional PSCell change or conditional PSCell addition configurations. As part of the procedure, NAS dedicated information can be transferred from the network to the UE.

[0232] …

[0233] 5.3.5.2 Initiation

[0234] The network can initiate an RRC reconfiguration procedure to the UE in RRC_CONNECTED. The network applies the procedure as described below:

[0235] - Establishment of RB (not SRB1, which is established during RRC connection establishment) is performed only when AS security has been activated;

[0236] …

[0237] - reconfigurationWithSync is included in the masterCellGroup only when AS security has been activated, and SRB2 with at least one DRB or multicast MRB or SRB2 for IAB is set and not suspended;

[0238] - conditionalReconfiguration for CPC is included only when at least one RLC bearer is set in the SCG;

[0239] - conditionalReconfiguration for CHO or CPA is included only when AS security has been activated, and SRB2 with at least one DRB or multicast MRB or SRB2 for IAB is set and not suspended.

[0240] 5.3.5.3 UE's Reception of RRCReconfiguration

[0241] The UE shall perform the following actions immediately after receiving RRCReconfiguration or after performing conditional reconfiguration (CHO, CPA or CPC):

[0242] …

[0243] 1> If RRCReconfiguration contains masterCellGroup:

[0244] 2>Perform cell group configuration for the received masterCellGroup according to 5.3.5.5;

[0245] …

[0246] 1>If the RRCReconfiguration message contains conditionalReconfiguration:

[0247] 2>Perform conditional reconfiguration as specified in 5.3.5.13;

[0248] …

[0249] 1>Otherwise (RRCReconfiguration is received via SRB1):

[0250] …

[0251] 2>If reconfigurationWithSync is included in the spCellConfig of the MCG:

[0252] 3>If the ta-Report configuration has the value enabled and the UE supports TA reporting:

[0253] 4>Indicate to the lower layer the initiation of TA reporting;

[0254] 2>Submit the RRCReconfigurationComplete message to the lower layer via SRB1 for transmission using the new configuration;

[0255] ********************Next citation*************************

[0256] 5.3.7 RRC connection re-establishment

[0257] 5.3.7.1 Overview

[0258] Figure 13 is in 3GPP TS 38.331 V17.5.0 Figure 5 .3.7.1-1: Reproduction of RRC connection re-establishment (successful).

[0259] Figure 14 is in 3GPP TS 38.331 V17.5.0 Figure 5 .3.7.1-2: Reproduction of RRC re-establishment fallback to RRC establishment (successful).

[0260] The purpose of this procedure is to re - establish the RRC connection. A UE in RRC_CONNECTED that has already activated AS security for SRB2 and at least one DRB / multicast MRB setup or for SRB2 in the case of IAB can initiate this procedure to continue the RRC connection. If the network can find and verify a valid UE context, or if the UE context cannot be retrieved and the network responds with RRCSetup according to clause 5.3.3.4, the connection re - establishment is successful.

[0261] …

[0262] 5.3.7.2 Initiation

[0263] The UE initiates the procedure when one of the following conditions is met:

[0264] 1> According to 5.3.10, after detecting a radio link failure of the MCG and t316 is not configured; or

[0265] 1> According to 5.3.10, after detecting a radio link failure of the MCG when SCG transmission is paused; or

[0266] 1> According to 5.3.10, after detecting a radio link failure of the MCG when a PSCell change or PSCell addition is in progress; or

[0267] 1> According to 5.3.10, after detecting a radio link failure of the MCG when the SCG is deactivated; or

[0268] 1> According to clause 5.3.5.8.3, after a synchronous re - configuration failure of the MCG; or

[0269] 1> According to clause 5.4.3.5, after moving due to an NR failure; or

[0270] 1> After receiving an integrity check failure indication for SRB1 or SRB2 from the lower layer, unless an integrity check failure is detected on the RRCReestablishment message; or

[0271] 1> According to clause 5.3.5.8.2, after an RRC connection re - configuration failure; or

[0272] …

[0273] After initiating the procedure, the UE shall then:

[0274] …

[0275] 1> If the UE is not configured with attemptCondReconfig:

[0276] 2> Reset the MAC;

[0277] 2> Release spCellConfig (if configured);

[0278] 2> Suspend all RBs and the BH RLC channels for IAB-MT and the Uu relay RLC channels for L2 U2N relay UEs, except for SRB0 and the broadcast MRB;

[0279] 2> Release the MCG SCell (if configured);

[0280] …

[0281] 3> Perform cell selection according to the cell selection procedure as specified in TS 38.304.

[0282] …

[0283] 5.3.7.3 Actions after cell selection when T311 is in progress

[0284] After selecting a suitable NR cell, the UE shall then:

[0285] …

[0286] 2> Apply the predefined MAC cell group configuration as specified in 9.2.2;

[0287] …

[0288] 2> Apply the timeAlignmentTimerCommon included in SIB1;

[0289] 2> Initiate the transmission of the RRCReestablishmentRequest message according to 5.3.7.4;

[0290] …

[0291] 5.3.7.4 Actions related to the transmission of the RRCReestablishmentRequest message

[0292] The UE shall set the content of the RRCReestablishmentRequest message as follows:

[0293] …

[0294] 1> If the ta-Report configuration has a value of enabled and the UE supports TA reporting:

[0295] 2> Indicate to the lower layer the initiation of TA reporting;

[0296] 1> Submit the RRCReestablishmentRequest message to the lower layer for transmission.

[0297] *************************Next citation********************

[0298] 5.3.12 UE Actions Immediately after PUCCH / SRS Release Request

[0299] After receiving a PUCCH release request from the lower layer, for all bandwidth parts of the indicated serving cell, the UE shall immediately:

[0300] 1> Release the PUCCH-CSI-Resource configured in CSI-ReportConfig;

[0301] 1> Release the SchedulingRequestResourceConfig instance configured in PUCCH-Config.

[0302] After receiving an SRS release request from the lower layer, for all bandwidth parts of the indicated serving cell, the UE shall immediately:

[0303] 1> Release the SRS-Resource instance configured in SRS-Config.

[0304] After receiving the positioning CRS configuration for the RRC_INACTIVE release request from the lower layer, the UE shall immediately:

[0305] 1> Release the configured srs-PosRRC-Inactive.

[0306] *************************Next citation********************

[0307] 5.3.13 RRC Connection Reestablishment

[0308] 5.3.13.1 Overview

[0309] Figure 15 It is in 3GPP TS 38.331 V17.5.0 Figure 5 .3.13.1-1: Reproduction of RRC connection reestablishment (successful).

[0310] Figure 16 It is in 3GPP TS 38.331 V17.5.0 Figure 5 .3.13.1-2: Reproduction of RRC connection reestablishment fallback to RRC connection establishment (successful).

[0311] …

[0312] The purpose of this procedure is to resume a suspended RRC connection, including resuming SRBs, DRBs, and multicast MRBs, or to perform RNA update. This procedure is also used to initiate SDT in RRC_INACTIVE.

[0313] …

[0314] 5.3.13.2 Initiation

[0315] When the upper layer or the AS (when responding to RAN paging, after triggering RNA update when the UE is in RRC_INACTIVE, for NR sidelink communication / discovery / V2X sidelink communication as specified in Clause 5.3.13.1a) requests the resume of a suspended RRC connection or requests the initiation of the resume for SDT as specified in Clause 5.3.13.1b, the UE initiates the procedure.

[0316] Before initiating this procedure, the UE shall ensure that it has valid and up-to-date basic system information as specified in Clause 5.2.2.2.

[0317] After initiating the procedure, the UE shall then:

[0318] …

[0319] 2> Apply the preconfigured MAC cell group configuration as specified in 9.2.2;

[0320] …

[0321] 2> Apply the timeAlignmentTimerCommon included in SIB1;

[0322] …

[0323] 1> If the ta-Report configuration has a value of enabled and the UE supports TA reporting:

[0324] 2> Indicate to the lower layer the initiation of TA reporting;

[0325] …

[0326] 1> Initiate the transmission of an RRCResumeRequest message or an RRCResumeRequest1 according to 5.3.13.3.

[0327] *************************Quotation ends********************

[0328] Some configurations related to NTN and TAR can be provided by the NW as specified in TS 38.331 ([4] 3GPP TS 38.331 V17.5.0):

[0329] ******************** Citation start [4] ********************

[0330] - RRCReconfiguration

[0331] The RRCReconfiguration message is a command to modify the RRC connection. It can convey information for measurement configuration, mobility control, radio resource configuration (including RB, MAC main configuration, and physical channel configuration), and AS security configuration.

[0332]

[0333]

[0334]

[0335] ************************* Next citation ********************

[0336] - RRCResume The RRCResume message is used to resume a suspended RRC connection.

[0337]

[0338]

[0339] ************************* Next citation ************************* - RRCSetup The RRCSetup message is used to establish SRB1.

[0340]

[0341]

[0342] ******************** Next citation ************************* - SIB19

[0343] SIB19 contains satellite - assisted information for NTN access.

[0344] SIB19 information element

[0345]

[0346]

[0347]

[0348]

[0349] ********************Next citation*************************

[0350] -CellGroupConfig

[0351] The CellGroupConfig IE is used to configure a master cell group (MCG) or a secondary cell group (SCG). A cell group includes one MAC entity, a set of logical channels with associated RLC entities, and a primary cell (SpCell) and one or more secondary cells (SCells).

[0352] CellGroupConfig information element

[0353] --Configuration of a cell group:

[0354]

[0355]

[0356]

[0357]

[0358] *************************Next citation********************

[0359] -MAC-CellGroupConfigIEMAC-CellGroupConfig is used to configure the MAC parameters of a cell group, including DRX. MAC-CellGroupConfig information element

[0360]

[0361]

[0362]

[0363] ********************Next Citation************************* - NTN-Config provides the parameters required for the UE to access NR via NTN access. NTN-Config information element

[0364]

[0365]

[0366]

[0367]

[0368]

[0369]

[0370] ********************Next Citation*************************

[0371] -ServingCellConfigCommon

[0372] IE ServingCellConfigCommon is used to configure cell-specific parameters of the serving cell of the UE. The IE contains the parameters that the UE will typically obtain from the SSB, MIB, or SIB when accessing the cell from IDLE. Through this IE, when configuring an SCell or an additional cell group (SCG) for the UE, the network provides this information in dedicated signaling. The network also provides this information for the SpCell (MCG and SCG) immediately after a reconfiguration with synchronization.

[0373] ServingCellConfigCommon information element

[0374]

[0375] ********************Next Citation*************************

[0376] -TAR-Config

[0377] IE TAR-Config is used to configure timing advance reporting in a non-terrestrial network.

[0378] TAR-Config information element

[0379]

[0380]

[0381]

[0382] *************************Quotation ends********************

[0383] The handling of the validity timer (or UL synchronization timer) (e.g., T430) is specified in TS 38.331 ([4] 3GPP TS 38.331 V17.5.0 and [9] 3GPP TS 38.331 V17.6.0) and TS 38.321 ([3] 3GPP TS 38.321 V17.5.0) as follows:

[0384] *************************Quotation starts [4]*********************

[0385] 5.2.2.4.21 Actions upon receiving SIB19

[0386] Upon receiving SIB19, a UE in RRC_CONNECTED shall immediately:

[0387] 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;

[0388] Note: The UE shall attempt to re-acquire SIB19 through the UE implementation before the end of the duration indicated by the ntn-UlSyncValidityDuration and epochTime.

[0389] ********************Next quotation*************************

[0390] 5.2.2.6 Expiry of T430

[0391] The UE shall:

[0392] 1> If T430 of the serving cell expires and if in RRC_CONNECTED:

[0393] 2> Notify the lower layer that UL synchronization has been lost;

[0394] 2> Obtain SIB19 as defined in Clause 5.2.2.3.2;

[0395] 2> After successfully obtaining SIB19:

[0396] 3> Notify the lower layer of when UL synchronization is obtained;

[0397] 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.

[0398] *************************End of citation********************

[0399] *************************Start of citation [9]*********************

[0400] 5.3.5.5 Cell group configuration

[0401] 5.3.5.5.1 Overview

[0402] …

[0403] The UE performs the following actions based on the received CellGroupConfig IE:

[0404] 1> If CellGroupConfig contains spCellConfig with reconfigurationWithSync:

[0405] 2> Perform reconfiguration with synchronization according to 5.3.5.5.2;

[0406] …

[0407] 5.3.5.5.2 Reconfiguration with synchronization

[0408] The UE shall perform the following actions to perform reconfiguration with synchronization.

[0409] 1> If AS security is not activated, perform the actions immediately after going to RRC_IDLE as specified in 5.3.11, with the release cause 'other', and after the release cause, the procedure ends immediately;

[0410] 1> Stop timer T430 (if it is running);

[0411] …

[0412] 2> If this procedure is executed for the MCG, or if this procedure is executed for an SCG not indicated as deactivated in the E-UTRA or NR RRC message in which the RRCReconfiguration message is embedded, then:

[0413] 3> Start timer T304 for the corresponding SpCell, where the timer value is set to t304 as included in reconfigurationWithSync;

[0414] …

[0415] 2> Start DL synchronization with the target SpCell;

[0416] 2> Apply the specified BCCH configuration defined in 9.1.1.1 to the target SpCell;

[0417] 2> Obtain the MIB of the target SpCell, which is scheduled as specified in TS 38.213;

[0418] 2> If NTN-Config is configured for the target cell:

[0419] 3> Start timer T430 according to the target cell NTN-Config, where the timer value is set to the ntn-UlSyncValidityDuration starting from the subframe indicated by the free epochTime;

[0420] …

[0421] 3> Reset the MAC entity of this cell group;

[0422] 3> Consider the SCell(s) of this cell group in the SCellToAddModList that are not included in the RRCReconfiguration message (if configured) as being in the deactivated state;

[0423] 3> Apply the value of newUE-Identity as the C-RNTI for this cell group;

[0424] 3> Configure the lower layers according to the received spCellConfigCommon;

[0425] 3> If any additional fields not previously covered are included in the received reconfigurationWithSync, configure the lower layers according to the additional fields.

[0426] ********************Next citation*************************

[0427] 5.3.5.13 Conditional Reconfiguration

[0428] 5.3.5.13.1 General Description

[0429] The network configures one or more candidate target SpCells for the UE in 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. The network provides configuration parameters for the target SpCell in the ConditionalReconfiguration IE.

[0430] …

[0431] 5.3.5.13.4 Conditional Reconfiguration Evaluation

[0432] The UE shall:

[0433] 1> For each condReconfigId within VarConditionalReconfig:

[0434] 2> If the RRCReconfiguration within condRRCReconfig includes a masterCellGroup containing reconfigurationWithSync:

[0435] 3> Consider a cell having a physical cell identity matching the value indicated in ServingCellConfigCommon included in reconfigurationWithSync within the masterCellGroup in the received condRRCReconfig as an applicable cell;

[0436] …

[0437] 2> For each measId included in the measIdList within VarMeasConfig indicated in the condExecutionCond or condExecutionCondSCG associated with the condReconfigId:

[0438] 3> If the condEventId is associated with condEventT1, and if the entry conditions for this event applicable to the applicable cell (i.e., the event corresponding to the condEventId of the corresponding condTriggerConfig within VarConditionalReconfig) have been met; or

[0439] 3> 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) has been satisfied for the applicable cells during the corresponding timeToTrigger defined for this event within VarConditionalReconfig; or

[0440] 3> 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) has been satisfied for all applicable cells after layer 3 filtering performed during the corresponding timeToTrigger defined for this event within VarConditionalReconfig:

[0441] 4> It is considered that the event associated with the measId has been satisfied;

[0442] 3> If the measId of this event associated with condReconfigId has been modified; or

[0443] 3> If condEventId is associated with condEventT1, and if the departure condition applicable to this event associated with condReconfigId (i.e., the event corresponding to the condEventId of the corresponding condTriggerConfig within VarConditionalReconfig) has been satisfied for the applicable cells; or

[0444] 3> If condEventId is associated with condEventD1, and if the departure condition applicable to this event associated with condReconfigId (i.e., the event corresponding to the condEventId of the corresponding condTriggerConfig within VarConditionalReconfig) has been satisfied for the applicable cells during the corresponding timeToTrigger defined for this event within VarConditionalReconfig; or

[0445] 3> If condEventId is associated with condEventA3, condEventA4, or condEventA5, and if the departure condition applicable to this event (i.e., the event corresponding to the condEventId of the corresponding condTriggerConfig within VarConditionalReconfig) has been satisfied for all applicable cells after layer 3 filtering during the corresponding timeToTrigger defined for this event within VarConditionalReconfig:

[0446] 4> It is considered that the event associated with the measId is not satisfied;

[0447] 2> If the events associated with all measIds within the condTriggerConfig of the applicable cell have been satisfied:

[0448] 3> Consider the applicable cell associated with the condReconfigId as the triggered cell;

[0449] 3> Initiate conditional reconfiguration execution as specified in 5.3.5.13.5;

[0450] …

[0451] 5.3.5.13.5 Conditional Reconfiguration Execution

[0452] The UE shall:

[0453] 1> For the selected cells of the conditional reconfiguration execution:

[0454] 2> Apply the stored condRRCReconfig of the selected cells and perform the actions specified in 5.3.5.3;

[0455] *************************Quote ends********************

[0456] *************************Quote starts [3]*********************

[0457] 5.2a Maintenance of UL Synchronization

[0458] For each serving cell, the MAC entity shall:

[0459] 1> If an indication of uplink synchronization has been received from the upper layer (see clause 5.2.2.6 of TS 38.331 [4]):

[0460] 2> Allow uplink transmissions on the serving cell.

[0461] 1> If an indication of uplink synchronization loss is received from the upper layer (see clause 5.2.2.6 of TS 38.331 [4]):

[0462] 2> Clear all HARQ buffers;

[0463] 2> Do not perform any uplink transmissions on the serving cell.

[0464] 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.

[0465] *************************End of citation********************

[0466] In addition, at the RAN2 meeting, the following agreements were reached for the invariant PCI mechanism (and / or satellite handover (with resynchronization)).

[0467] At the RAN2#121bis meeting:

[0468] - In the case of a quasi-geostationary cell, for hard satellite handovers with the same SSB frequency and the same gNB (without key change), satellite handovers that do not change the PCI (no L3 mobility required) are supported, unless RAN1 identifies major technical issues (as usual, RAN2 will work to minimize the specification impact to make it suitable for Rel-18).

[0469] At the RAN2#122 meeting:

[0470] - In the invariant PCI scenario for hard handovers (i.e., no handover), the UE needs to know the time when the UE attempts to resynchronize. (If the gap is very short / zero, FFS on whether a new "t-Start" / t-gap is required, or whether t-Service can be reused (i.e., no other IEs)).

[0471] At the RAN2#123 meeting:

[0472] - An explicit indication will be introduced to enable invariant PCI handovers;

[0473] - The invariant PCI mechanism can be applied to cases where the coverage gap is zero or negligible (where there is no need to introduce t-gap or t-start). FFS on whether to support scenarios that require the introduction of t-gap or t-start;

[0474] - The PCI invariant procedure can be implemented without performing RACH;

[0475] - In the case of invariant PCI, the UE considers the UL synchronization timer to expire at t-Service (the current cell stop time) to stop any UL operations. FFS on the timeAlignmentTimer handling;

[0476] - In the case of invariant PCI, for RACH-based solutions, the UE can trigger RACH immediately after DL synchronization with the new satellite.

[0477] At the RAN2#123bis meeting:

[0478] - When defining the Rel-18 invariant PCI solution, we do not consider the impact on Rel-17 UE behavior (or Rel-18 UEs that do not support invariant PCI).

[0479] - The network provides the UE with the synchronization information of the target satellite in advance via broadcast before satellite handover.

[0480] - RAN2 confirmed that satellite handovers with unchanged PCI are only applicable to quasi-geostationary systems.

[0481] - Only 1 piece of target satellite information (i.e., NTN-config) of the serving cell is provided in SIB19. FFS on accurate transmission.

[0482] - The SMTC configuration of the target satellite requires further discussion:

[0483] ■ FFS on whether and how to provide the SMTC configuration of the target satellite.

[0484] ■ FFS on how to handle SMTC adjustment.

[0485] - Support soft satellite handover in Rel-18.

[0486] - There will be an indication of whether to use hard handover or soft handover (FFS on whether it is explicit or implicit).

[0487] - At least soft satellite handover, the network provides the UE with the SSB information of the target satellite. FFS for details: The option includes, for example, indicating time offset / information or indicating different SSB indexes of the target satellite (FFS for hard satellite handover).

[0488] - In soft satellite handover, the UE can initiate synchronization with the target satellite before the T-service of the source satellite.

[0489] - T-start is introduced, which indicates the earliest time when the UE can initiate synchronization with the target satellite (FFS for actual transmission). In the soft handover scenario, the T-start of the target satellite is earlier than the T-service of the source satellite (FFS for whether T-start is also used for hard satellite handover).

[0490] - For soft satellite handover, the exact time when the UE starts synchronization with the target satellite (between T-start and T-service) depends on the UE implementation.

[0491] - When the UE hands over to the target satellite, it is not required for the UE to be connected to the source satellite.

[0492] The relevant text of satellite handover in the CR of NTN Rel-18 ([5] R2-230934) running immediately following the NR RRC specification TS 38.331 ([4] 3GPP TS 38.331 V17.5.0) is quoted as follows:

[0493] ********************* Quote start [5] ************************

[0494] SIB19 information element

[0495]

[0496]

[0497]

[0498] ************************* Quote end ********************

[0499] A non-terrestrial network (NTN) can be considered as a next-generation radio access network (NG-RAN) consisting of next-generation Node Bs (gNBs), where the NG-RAN provides non-terrestrial new radio (NR) access to user equipment (UE) by means of an NTN payload and an NTN gateway mounted on an airborne or space NTN vehicle. The UE can link to, reside on, and / or connect to the NTN network involved in air / space transmission. The NTN can include various platforms, including low Earth orbit (LEO) satellites, medium Earth orbit (MEO) satellites, highly elliptical orbit (HEO) satellites, geostationary Earth orbit (GEO) satellites, geostationary synchronous orbit (GSO) satellites, non-geostationary synchronous orbit (NGSO) satellites, and / or high altitude platform stations (HAPS). LEO satellites can have Earth-fixed beams (e.g., the beam is temporarily fixed at a position during a period of time) or Earth-moving beams (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 aircraft).

[0500] The NW can provide NTN information to the UE. 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 one or more NTN configurations (e.g., NTN-Config), time information (e.g., t-Service), reference location (e.g., referenceLocation), and distance threshold (e.g., distanceThresh). The NTN information and / or NTN configuration (e.g., NTN-Config) can be or include satellite assistance information. The NW can provide the NTN information to the UE, for example, via the serving cell, in NTN-specific system information (e.g., SIB19) or radio resource control (RRC) messages (e.g., RRCReconfiguration). The NTN-specific system information can be a system information block (SIB) that includes the NTN information. The NTN configuration (e.g., NTN-Config) can be or (at least) include epoch time (e.g., epochTime), validity duration (e.g., ntn-UlSyncValidityDuration), satellite ephemeris (e.g., ephemerisInfo), and / or common timing advance (TA) (e.g., ta-Info). The validity duration (e.g., ntn-UlSyncValidityDuration) can indicate the maximum time for which the UE can apply the satellite information and / or NTN-specific system information without obtaining new satellite information and / or NTN-specific system information (e.g., SIB19). The validity duration (e.g., ntn-UlSyncValidityDuration) and / or epoch time (e.g., epochTime) 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 stop service time of the serving cell. The time information (e.g., t-Service) can be the timing when the UE will leave the coverage area of the serving cell. The time information (e.g., t-Service) can indicate the time information about when the serving cell will stop providing service to its currently covered area.

[0501] Throughout this disclosure, SIB19 may be system information for a serving cell. SIB19 may be NTN-specific system information. SIB19 may contain satellite assistance information. SIB19 may contain uplink (UL) synchronization information for NTN. The system information may be referred to as a system information block. Throughout this disclosure, one, some, and / or all instances of "NTN configuration" may correspond to, may be supplemented by, and / or may be replaced by "NTN information", "satellite information", "NTN-Config", and / or "assistance information".

[0502] The UE shall maintain UL time alignment for the serving cell. The UE will maintain the TA value for UL / downlink (DL) transmission. The (complete) TA value is T as specified in TS 38.211 ([2] 3GPP TS 38.211 V17.5.0). TA T TA configured based on NW and / or constitutes. N TA，offset configured by the NW, for example, via n-TimingAdvanceOffset or a preset value. N TA is indicated or adjusted by a TA command. In TN, the UE uses N TA and N TA，offset to calculate T TA and may not use and The UE will receive N during the RA procedure via a random access (RA) response (e.g., random access response (RAR), MSGB). TA The UE will receive N from a timing advance command media access control (MAC) control element (CE) in RRC connected mode. TA For a random access channel (RACH) handover, N may be indicated to the UE via an RRC reconfiguration message (e.g., RRCConnectionReconfiguration). TAIs zero or the same as the Primary Timing Advance Group (PTAG). The set of serving cells with the same TA will be grouped in a Timing Advance Group (TAG). The TAG including the special cell (SpCell) is the PTAG. The TAG not including the SpCell is the secondary TAG (STAG). The UE can have one PTAG and at most three STAGs in each cell group. The SpCell is used as the timing reference for the PTAG. The activated secondary cell (SCell) of the STAG is used as the timing reference for the STAG. Also, the UE maintains a TA timer (e.g., timeAlignmentTimer) for each TAG.

[0503] In NTN, the UE will pre-compensate the TA value based on satellite assistance information (e.g., parameters in NTN-Config) and / or the UE's location. Except for N TA and N TA，offset Outside, the UE calculates / deduces for T TA also calculates / deduces and is deduced based on the common TA information of the satellite. And, is pre-compensated by the UE based on the ephemeris information using the UE location and the satellite location. is the common TA value and / or the satellite-specific TA value. is the UE-specific TA value. The UE will receive the NTN configuration and the pre-compensated TA value (e.g., T TA ) in NTN. The UE can calculate the UE-gNB round trip time (Round TripTime, RTT) as the sum of the TA value (e.g., T TA ) and kmac (scheduling offset). The UE will delay the start of the RA timer and / or the discontinuous reception (DRX) timer by the UE-gNB RTT.

[0504] In addition, the UE will report the complete TA value (e.g., T TA) and / or UE location. Since the UE pre-compensates the TA value, the NW may need to know the UE's TA value. The UE will trigger a TA report (TA Report, TAR) based on the configuration of ta-Report and / or offsetThresholdTA. If enabled by an indication (e.g., ta-Report), the UE will trigger a TAR in response to connecting to the serving cell. The UE will trigger a TAR in response to receiving and / or being configured with a TA threshold (e.g., offsetThresholdTA). The UE will trigger a TAR in response to a condition related to the TA threshold (e.g., offsetThresholdTA) being met. The TAR will be transmitted via the timing advance reporting MAC CE. More details of the TAR can be found in TS 38.321 ([3] 3GPP TS38.321V17.5.0) and TS 38.331 ([4] 3GPP TS 38.331V17.5.0).

[0505] In NTN, the NW that serves 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 avoid L3 mobility, such as handover caused by satellite handover, and to reduce transmission overhead and / or interruption time, an invariant Physical Cell Identity (PCI) mechanism will be supported in NTN. The invariant PCI mechanism can be or be referred to as satellite handover, satellite handover without changing the PCI, satellite handover with resynchronization, and / or invariant PCI handover. The invariant PCI mechanism can be or be referred to as a mechanism without L3 mobility (e.g., handover). The satellite handover mechanism avoids L3 mobility of the UE in the cell by maintaining the same PCI over a geographical area. When the satellite handovers, the UE can maintain the cell configuration without changing the gNB. Signaling such as handover 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 DL and / or UL synchronization. The UE can (re)obtain NTN-specific system information. In the invariant PCI mechanism, the UE can switch / change the serving satellite without performing handover, without receiving RRC (re)configuration, without changing the PCI of the serving cell, and / or without changing the serving gNB.

[0506] Throughout this disclosure, an invariant PCI handover can be the following (substituted by / followed by the following): procedures for invariant PCI handover, cell handover with resynchronization, satSwitchWithResync, cell handover with invariant PCI, satellite handover, hard satellite handover, satellite handover without changing the PCI, PCI invariant procedures, procedures for cell handover, procedures for resynchronization, etc., and / or combinations of the above. Throughout this disclosure, a "satellite handover" can be a "satellite handover with resynchronization". Throughout this disclosure, a "satellite handover" can be, be referred to as, substituted by, and / or equivalent to a "satellite handover with resynchronization". Figure 17 Examples of invariant PCI and / or satellite handover are shown in ([6] cited in R2-2308373). Figure 17 PCI A and PCI B in are the same PCI.

[0507] The UE can be instructed (by the network) to perform (or initiate) an invariant PCI handover and / or a satellite handover. The UE can receive a configuration (or indication) of an invariant PCI handover and / or a satellite handover. The configuration (or indication) of an invariant PCI handover and / or a satellite handover can instruct the UE to perform (or initiate) an invariant PCI handover and / or a satellite handover (e.g., at a specific timing, e.g., t-Service). 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. The UE can receive at least the timing information (e.g., t-service) of an invariant PCI handover and / or a satellite handover and / or the satellite information (e.g., NTN-Config) of the target satellite in the system information (e.g., SIB19). Throughout this disclosure, satSwitchWithResync can be an indication to (enable / trigger) an invariant PCI handover and / or a satellite handover. The UE can receive an indication to (enable / trigger) an invariant PCI handover and / or a satellite handover.

[0508] For example, in response to receiving an indication (or configuration), the UE can perform (or initiate) an invariant PCI handover and / or a satellite handover. For example, at a specific time, at t-Service, the UE can perform (or initiate) an invariant PCI handover and / or a satellite handover. The specific time (or t-Service) can be indicated by the network. The specific time (or t-Service) can be indicated in the system information (e.g., SIB19). The specific time (or t-Service) can be (or indicate) the cell stop time. The specific time (or t-Service) can be (or indicate) the time when the cell provided by the NTN stops serving its currently covered area.

[0509] In response to an invariant PCI handover and / or a satellite handover (e.g., if an indication of a satellite handover is received, during a satellite handover (procedure), after initiating a satellite handover (procedure), when initiating a satellite handover (procedure), and / or at a cell stop time such as t-Service), the UE may:

[0510] - Consider that the UL synchronization timer (e.g., for NTN, T430) has expired;

[0511] (Note: The UL synchronization timer may be different from the timeAlignmentTimer.)

[0512] - Do not use, for example, after a cell stop time (e.g., t-Service), and / or do not use the UE-specific Koffset (if configured) until a new differential Koffset (e.g., MAC CE) is received;

[0513] - Use the cell-specific Koffset, for example, after a 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;

[0514] - Perform DL (re)synchronization with the serving cell (or NW);

[0515] -(Re)acquire SIB19 (and / or SIB1, SIB2);

[0516] -(Re)acquire the NTN-related configuration (e.g., ephemeris) of the serving cell (e.g., included in SIB19);

[0517] - May or may not trigger an RA procedure; and / or

[0518] - May or may not perform UL synchronization with the serving cell (or NW).

[0519] (Note: The RA procedure may be a two-step RA or a four-step RA.)

[0520] The satellite handover may be RACH-based. The UE may trigger an RA procedure for the satellite handover. The UE may receive a configuration (or indication) indicating that the satellite handover is RACH-based. The UE may receive a configuration (or indication) indicating that the UE performs (or initiates) a RACH-based satellite handover. If the configuration (or indication) indicates that the UE performs (or initiates) a RACH-based satellite handover, the UE triggers an RA procedure for the satellite handover.

[0521] Satellite handover can be RACH-free. The UE may not trigger the RA procedure for satellite handover. The UE may receive a configuration (or indication) indicating that the satellite handover is RACH-free. The UE may receive a configuration (or indication) indicating that the UE performs (or initiates) a RACH-free satellite handover. If the configuration (or indication) indicates that the UE performs (or initiates) a RACH-free satellite handover, the UE does not trigger the RA procedure for satellite handover.

[0522] For example, the UE may receive (enable) the first indication (e.g., satSwitchWithReSync) of the invariant PCI mechanism and / or satellite handover, e.g., via the first SIB19. At, before, or after the time information (e.g., t-service), the UE may (start) performing DL synchronization (e.g., with a new satellite, with the serving cell). Before or after the timing indicated by the time information (e.g., t-service), the UE may (start) performing DL synchronization. The UE may consider the UL synchronization timer (e.g., T430) to expire at the time information (e.g., t-service). After DL synchronization, the UE may receive the second SIB19. The second SIB19 includes satellite information after switching the serving satellite. In response to receiving the second SIB19, the UE may start the UL synchronization timer (e.g., T430). In the invariant PCI mechanism or procedure (or satellite handover procedure), the UE may or may not perform RACH. After DL synchronization, the UE may or may not perform RACH. The invariant PCI mechanism and / or satellite handover may be RACH-based or RACH-free. The SIB19 may be NTN-specific system information.

[0523] The UE will pre-compensate the TA value based on the satellite assistance information in the second SIB19 (e.g., the parameters in NTN-Config). However, based on the current mechanism, the UE cannot report the complete TA value to the network after performing the invariant PCI handover. The network does not know the UE's TA and / or cannot provide the UE-specific Koffset for the UE. In the case of invariant PCI handover, it should be defined how the UE triggers or reports its TA value.

[0524] To solve the above problems, the UE may trigger TA reporting (e.g., for satellite handover) based on the NW configuration. In response to (at least) receiving the NW configuration, the UE may trigger TA reporting. Triggering TA reporting may include triggering TA reporting, indicating the lower layer / upper layer that triggers (triggers) TA reporting, calculating the (complete) TA value, generating the TAR MAC CE for TA reporting, triggering a scheduling request (SR) for TA reporting, and / or transmitting the TA report.

[0525] The NW configuration can be an indication of TA reporting (e.g., ta-Report). The NW configuration can indicate whether TA reporting is triggered (e.g., for satellite handover). The NW configuration can be an indication of satellite handover (e.g., the first indication) (e.g., satSwitchWithReSync). The NW configuration can indicate whether the UE should initiate a satellite handover, for example, at a specific time (e.g., t-Service). The NW configuration can be an indication of the RACH type (e.g., RACH-based, RACH-less) for satellite handover, for example. The NW configuration can indicate whether the RA procedure is triggered (or initiated) for satellite handover. The NW configuration can be a new indication related to satellite handover. The NW configuration can be a new indication included / configured in the indication of satellite handover (e.g., the first indication) (e.g., satSwitchWithReSync).

[0526] Before performing a satellite handover, the UE can receive the NW configuration in NTN-specific system information (e.g., SIB19). After or following the performance of a satellite handover, the UE can receive the NW configuration in NTN-specific system information (e.g., SIB19).

[0527] Based on one or more of the following, the UE can determine whether to trigger TA reporting (e.g., for satellite handover):

[0528] -(Received) NW configuration;

[0529] -(Received) the first indication (e.g., satSwitchWithReSync);

[0530] -(Received) indication of the RACH type (e.g., RACH-based, RACH-less);

[0531] -Time information of satellite handover (e.g., t-service);

[0532] -Performing / triggering a satellite handover;

[0533] -Performing DL synchronization;

[0534] -Obtaining System Frame Number (SFN) information;

[0535] -(Received / obtained) system information (e.g., Master Information Block (MIB), SIB1, SIB19); and / or

[0536] -Performing / triggering RACH (procedure).

[0537] When receiving the first indication of satellite handover (e.g., satSwitchWithReSync), after receiving the first indication of satellite handover, in the case of receiving the first indication of satellite handover, or in response to receiving the first indication of satellite handover, the UE may trigger a TA report (e.g., for satellite handover). When the time information of satellite handover (e.g., t-service), after the time information of satellite handover, in the case of the time information of satellite handover, or in response to the time information of satellite handover, the UE may trigger a TA report (e.g., for satellite handover). When performing satellite handover, after performing satellite handover, in the case of performing satellite handover, or in response to performing satellite handover, the UE may trigger a TA report (e.g., for satellite handover). When performing DL synchronization with the serving cell, for example, after performing DL synchronization, in the case of performing DL synchronization, or in response to performing DL synchronization, the UE may trigger a TA report (e.g., for satellite handover). When triggering the RACH procedure for satellite handover, after triggering the RACH procedure for satellite handover, in the case of triggering the RACH procedure for satellite handover, or in response to triggering the RACH procedure for satellite handover, the UE may trigger a TA report (e.g., for satellite handover).

[0538] If the UE does not receive the NW configuration, the UE may not trigger a TA report for satellite handover. If the UE receives the NW configuration, the UE may trigger a TA report for satellite handover, for example, at one of the above-mentioned times.

[0539] If the UE performs a RACH-based satellite handover, the UE may trigger a TA report, for example, at one of the above-mentioned times. If the UE performs a RACH-less satellite handover, the UE may not trigger a TA report. If the UE performs a RACH-less satellite handover, the UE may trigger a TA report, for example, at one of the above-mentioned times.

[0540] In one example, the UE may receive (enable) a first indication of the invariant PCI mechanism and / or satellite handover (e.g., satSwitchWithReSync), for example, via the first SIB19. At, before, or after the time information (e.g., t-service), the UE may (start) performing DL synchronization (e.g., with a new satellite, with the serving cell). The UE may consider the UL synchronization timer (e.g., T430) to expire at the time information (e.g., t-service). After DL synchronization, the UE may receive the second SIB19. In response to receiving the second SIB19, the UE may start the UL synchronization timer (e.g., T430). The second SIB19 may include the NW configuration for TA reporting (e.g., ta-Report). After DL synchronization, the UE may not perform RACH. Based on or if the UE receives an indication of no RACH procedure, for example, together with the first indication (e.g., satSwitchWithReSync), the UE may not perform RACH. After DL synchronization, the UE may trigger TA reporting. Based on or if the UE receives the NW configuration for TA reporting (e.g., ta-Report), the UE may trigger TA reporting.

[0541] In one example, the UE may receive (enable) a first indication of the invariant PCI mechanism and / or satellite handover (e.g., satSwitchWithReSync), for example, via the first SIB19. At, before, or after the time information (e.g., t-service), the UE may (start) performing DL synchronization (e.g., with a new satellite, with the serving cell). The UE may consider the UL synchronization timer (e.g., T430) expired at the time information (e.g., t-service). After DL synchronization, the UE may receive the second SIB19. In response to receiving the second SIB19, the UE may start the UL synchronization timer (e.g., T430). The second SIB19 may not include the NW configuration of TA reporting (e.g., ta-Report). After DL synchronization, the UE may perform RACH. Based on or if the UE receives an indication of a RACH-based procedure, for example, together with the first indication (e.g., satSwitchWithReSync), the UE may perform RACH. Based on or if the UE does not receive an indication of a no-RACH procedure, for example, together with the first indication (e.g., satSwitchWithReSync), the UE may perform RACH. The UE may trigger a RACH procedure. After DL synchronization, the UE may not trigger a TA report. In response to triggering the RACH procedure, in case of triggering the RACH procedure, after triggering the RACH procedure, or after triggering the RACH procedure, the UE may not trigger a TA report. Based on or if the UE does not receive the NW configuration of TA reporting (e.g., ta-Report), the UE may not trigger a TA report.

[0542] If a TA report is triggered, the UE may generate a TAR MAC CE, for example, if UL Shared Channel (SCH) resources are available for a new transmission and the UL-SCH resources can accommodate the TAR MAC CE plus its sub-header due to logical channel prioritization.

[0543] If a TA report is triggered, the UE may trigger a scheduling request, for example, if the UE receives a configuration (e.g., timingAdvanceSR, with a value of enabled).

[0544] After receiving NTN-specific system information (e.g., SIB19), the UE will immediately start or restart a validity timer (e.g., T430) with a validity duration (e.g., ntn-UlSyncValidityDuration) starting from a subframe indicated by a free epoch time (e.g., epochTime). Before the validity timer expires, the UE can obtain NTN-specific system information (e.g., SIB19). The UE will apply the epoch time (e.g., epochTime) as the start timing of the validity timer after receiving NTN-specific system information (e.g., SIB19). The UE will apply the validity duration (e.g., ntn-UlSyncValidityDuration) as the length of the validity timer. The validity duration (e.g., ntn-UlSyncValidityDuration) and / or the validity timer (e.g., T430) can indicate the duration when satellite information or a part of satellite information (e.g., ephemerisInfo, ta-Info) is valid. After the validity timer expires in the RRC connected mode, the UE can immediately consider that uplink synchronization has been lost and / or obtain NTN-specific system information (e.g., SIB19). In response to obtaining NTN-specific system information (e.g., SIB19), the UE can consider that uplink synchronization has been obtained. If uplink synchronization is considered lost, the UE can clear the hybrid automatic repeat request (HARQ) buffer and can refrain from performing UL transmissions on the serving cell. If uplink synchronization is considered obtained, the UE can perform UL transmissions on the serving cell. When the validity timer is running, the serving cell can be considered to have achieved uplink synchronization in the RRC connected mode (e.g., uplink synchronization has been obtained). When the validity timer is not running and / or has expired, the serving cell can be considered to have not achieved uplink synchronization in the RRC connected mode (e.g., uplink synchronization has been lost). The validity timer (e.g., T430) can be a UL synchronization timer.

[0545] For invariant PCI handover and / or satellite handover (with resynchronization), the UE will perform DL synchronization and UL synchronization with the target satellite. The network may resume transmission after the satellite handover. The UE may receive an indication of the satellite handover (e.g., satSwitchWithReSync) and time information (e.g., t-service). When the UE performs UL synchronization, the UE will consider that the UL synchronization with the current satellite has been lost (e.g., by considering that T430 has expired), and then consider that it has obtained UL synchronization with the target satellite. The UE may consider that the validity timer (e.g., T430) expires at the time information (e.g., t-service). According to the current specifications (e.g., [3] 3GPP TS 38.321 V17.5.0 and [4] 3GPP TS 38.331 V17.5.0), the UE will clear all HARQ buffers immediately after the UL synchronization is lost. However, for the case of satellite handover, due to the fact that HARQ retransmission cannot be performed after the satellite handover, clearing the HARQ buffers may cause a delay in transmission.

[0546] In the present invention, in response to an invariant PCI handover (or satellite handover), the UE may not clear one or more HARQ buffers. The indication of UL synchronization loss may be differentiated based on the reason (e.g., satellite handover, T430 expiration). When the UL synchronization is lost, the UE determines whether to clear one or more HARQ buffers based on whether the UL synchronization loss is caused by a satellite handover. If the UL synchronization loss is caused by a satellite handover, the UE stops UL transmission and / or does not clear one or more HARQ buffers. If the UL synchronization loss is not caused by a satellite handover (e.g., caused by T430 expiration), the UE stops UL transmission and clears one or more HARQ buffers.

[0547] During the procedure of invariant PCI handover (or satellite handover), the UE may not clear the HARQ buffers. Based on (at least) a first condition, the UE may not clear the HARQ buffers. Based on (at least) a first condition, the UE may not perform any uplink transmission on the serving cell. The first condition may be one or more of the following:

[0548] - If an indication of uplink synchronization loss is received from the upper layer due to T430 expiring at the time information (e.g., t-service);

[0549] - If an indication of uplink synchronization loss is received from the upper layer for a satellite handover;

[0550] - If an indication of uplink synchronization loss caused by a satellite handover is received from the upper layer;

[0551] - If an indication of uplink synchronization loss is received from the upper layer during a satellite handover (procedure);

[0552] -(If an indication of uplink synchronization loss is received from the upper layer, and) if the satellite handover procedure is in progress;

[0553] -(If an indication of uplink synchronization loss is received from the upper layer, and) if a first indication (e.g., satSwitchWithReSync) of enabling the satellite mechanism has been received / configured; and / or

[0554] -(If an indication of uplink synchronization loss is received from the upper layer, and) if a first indication (e.g., satSwitchWithReSync) of enabling the satellite mechanism exists in SIB19.

[0555] (At least) based on a second condition, the UE may clear (all) HARQ buffers. (At least) based on a second condition, the UE may not perform any uplink transmission on the serving cell. The second condition may be one or more of the following:

[0556] - If an indication of uplink synchronization loss is received from the upper layer not due to the expiration of T430 at a time information (e.g., t-service);

[0557] - If an indication of uplink synchronization loss is received from the upper layer not for a satellite handover;

[0558] - If an indication of uplink synchronization loss (not caused by a satellite handover) is received from the upper layer;

[0559] - If an indication of uplink synchronization loss is not received from the upper layer during a satellite handover (procedure);

[0560] -(If an indication of uplink synchronization loss is received from the upper layer, and) if the satellite handover procedure is not in progress;

[0561] -(If an indication of uplink synchronization loss is received from the upper layer, and) if a first indication (e.g., satSwitchWithReSync) of enabling the satellite mechanism has not been received / configured; and / or

[0562] -(If an indication of uplink synchronization loss is received from the upper layer, and) if a first indication (e.g., satSwitchWithReSync) of enabling the satellite mechanism does not exist in SIB19.

[0563] In response to a satellite handover (e.g., if an indication of a satellite handover is received, during a satellite handover, after initiating a satellite handover, when initiating a satellite handover, if a satellite handover is initiated, and / or at a cell stop time such as t-Service), the UE may:

[0564] - Not clear the (UL) HARQ buffer (or all HARQ buffers) (e.g., for one serving cell, for all serving cells).

[0565] The HARQ buffer may be associated with an HARQ process. The UE may perform an initial transmission associated with the HARQ process (e.g., before the satellite handover). The UE may perform a retransmission associated with the HARQ process (e.g., HARQ retransmission) (e.g., after the satellite handover).

[0566] The UE (e.g., the MAC entity of the UE) may receive an indication of uplink synchronization loss from the upper layer (e.g., the RRC layer). In response to receiving the indication of uplink synchronization loss, the UE may not perform an uplink transmission on the serving cell and / or may determine whether to clear the HARQ buffer based on whether the uplink synchronization loss is caused by a satellite handover. Regardless of whether the uplink synchronization loss is caused by a satellite handover, the UE may not perform an uplink transmission on the serving cell. Regardless of the cause of the UL synchronization loss, the UE may not perform an uplink transmission on the serving cell. When the UE does not perform an uplink transmission on the serving cell, the UE may stop and / or suspend the UL transmission on the serving cell. Based on the cause of the UL synchronization loss, the UE may determine whether to clear the HARQ buffer. The cause of the UL synchronization loss may include a satellite handover. The cause of the UL synchronization loss may include the expiration of T430. In response to receiving the indication of uplink synchronization loss, the UE may perform a determination (e.g., regarding whether to clear the HARQ buffer and / or whether the uplink synchronization loss is caused by a satellite handover). If (at least) the uplink synchronization loss is caused by a satellite handover, the UE may not clear the HARQ buffer. If (at least) the uplink synchronization loss is not caused by a satellite handover, the UE may clear the HARQ buffer. If (at least) the uplink synchronization loss is caused by the expiration of T430, the UE may clear the HARQ buffer.

[0567] For example, a UE may receive system information (from a serving cell), where the system information includes at least an indication of satellite handover. The system information may be SIB19. The indication of satellite handover may be satSwitchWithResync. Based on the indication of satellite handover being included in the system information, the UE may initiate a procedure for satellite handover (with resynchronization). In response to initiating the procedure for satellite handover, the UE may indicate a loss of uplink synchronization. For example, in response to the loss of uplink synchronization, the UE may not perform uplink transmission on the serving cell. The UE may stop or suspend uplink transmission on the serving cell. For example, in response to the loss of uplink synchronization, based on the loss of uplink synchronization being caused by satellite handover, the UE may not clear the HARQ buffer.

[0568] For example, after receiving the system information (from the serving cell), the UE may immediately start or restart a timer. The timer may be T430. The system information may be SIB19. In response to the expiration of the timer, the UE may indicate a loss of uplink synchronization. For example, in response to the loss of uplink synchronization, the UE may not perform uplink transmission on the serving cell. The UE may stop or suspend uplink transmission on the serving cell. For example, in response to the loss of uplink synchronization, based on the loss of uplink synchronization not being caused by satellite handover, the UE may clear the HARQ buffer.

[0569] The UE may perform different actions (such as at least one or more of the actions mentioned above) for RACH-based satellite handover and RACH-less satellite handover.

[0570] Based on whether the satellite handover is RACH-based or RACH-less, the UE may determine whether to perform at least one or more of the above actions.

[0571] For example, the UE may: if the satellite handover is RACH-based, perform at least one or more of the above actions in response to the satellite handover; and / or if the satellite handover is RACH-less, not perform at least one or more of the above actions in response to the satellite handover.

[0572] For example, the UE may: if the satellite handover is RACH-less, perform at least one or more of the above actions in response to the satellite handover; and / or if the satellite handover is RACH-based, not perform at least one or more of the above actions in response to the satellite handover.

[0573] The different actions may be determined separately.

[0574] For example, the UE may: if the satellite handover is RACH-based, perform a first action but not perform a second action in response to the satellite handover; and / or if the satellite handover is RACH-free, not perform the first action but perform the second action in response to the satellite handover.

[0575] For example, the UE may: if the satellite handover is RACH-free, perform a first action but not perform a second action in response to the satellite handover; and / or if the satellite handover is RACH-based, not perform the first action but perform the second action in response to the satellite handover.

[0576] Any of the embodiments, concepts, methods, examples, actions, and / or events described above and herein may be combined fully or partially, or applied simultaneously or individually.

[0577] The UE may receive NTN-related configurations (e.g., SIB19, NTN-Config). The UE may be configured with multi-connectivity, Carrier Aggregation (CA), Dual Connectivity (DC), SCell, and / or Secondary Cell Group (SCG).

[0578] The UE may be in a cell of the NTN and / or a cell of the TN. The UE may be connected to a cell of the NTN and / or a cell of the TN. The UE may camp on a cell of the NTN and / or a cell of the TN. The UE may be connected to LEO, GEO, MEO, HEO, ATG, and / or HAPS. The UE may be connected to one or two networks (nodes). Throughout this disclosure, a cell may be, may refer to, an NTN cell or a TN cell.

[0579] 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.

[0580] 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 an (unmanned) aerial vehicle.

[0581] The network may be a base station. The network may be an access point. The network may be an eNB. The network may be a gNB. The network may be a gateway.

[0582] For the methods, alternatives, concepts, examples, and embodiments detailed above and herein, the following aspects and embodiments are possible.

[0583] Reference Figure 18 , using this and other concepts, systems, and methods of the present invention, a method 1000 for a UE in a wireless communication system includes: receiving a first indication of a satellite handover (step 1002); performing DL synchronization with a serving cell at an occasion (step 1004); receiving NTN-specific system information (step 1006); after performing DL synchronization with the serving cell, determining whether to trigger a TA report based on whether the indication is provided by the network (step 1008); and triggering a TA report if the indication is provided by the network in the NTN-specific system information (step 1010).

[0584] In various embodiments, the UE does not perform a RACH procedure.

[0585] In various embodiments, the UE receives a second indication of no RACH.

[0586] In various embodiments, the NTN-specific system information is SIB19.

[0587] In various embodiments, the first indication is satSwitchWithReSync.

[0588] In various embodiments, the indication is ta-Report.

[0589] In various embodiments, the occasion is indicated by the time information of the satellite handover.

[0590] Return reference Figure 3 and 4 , in one or more embodiments from the perspective of a UE in a wireless communication system, a device 300 includes program code 312 stored in a memory 310 of a transmitter. A CPU 308 may execute the program code 312 to: (i) receive a first indication of a satellite handover; (ii) perform DL synchronization with a serving cell at an occasion; (iii) receive NTN-specific system information; (iv) after performing DL synchronization with the serving cell, determine whether to trigger a TA report based on whether the indication is provided by the network; and (v) trigger a TA report if the indication is provided by the network in the NTN-specific system information. In addition, the CPU 308 may execute the program code 312 to perform all the described actions, steps, and methods described above, below, or herein.

[0591] Return reference Figure 3 and 4, in one or more embodiments, from the perspective of the NW in a wireless communication system, the 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 a first indication of satellite handover to the UE; (ii) transmit NTN-specific system information to the UE; (iii) transmit an indication to trigger TA reporting to the UE; and (iv) receive a TA report from the UE if the indication is transmitted to the UE. In addition, the CPU 308 may execute the program code 312 to perform all the described actions, steps, and methods described above, below, or elsewhere herein.

[0592] In [8] R2-2307623, it is proposed to discuss whether it is considered that the timeAlignmentTimer expires at t-Service:

[0593]

[0594] For invariant PCI handover (or satellite handover), if the timeAlignmentTimer is considered to expire (e.g., at t-Service), the following UE actions (e.g., at t-Service) will be performed immediately after the timeAlignmentTimer expires, as specified in the current NR MAC specification (e.g., [3] 3GPP TS 38.321 V17.5.0):

[0595] - Clear (all) HARQ buffers (for all serving cells);

[0596] - (Notify RRC) Release the Physical Uplink Control Channel (PUCCH) (for all serving cells, if configured);

[0597] - (Notify RRC) Release the Sounding Reference Signal (SRS) (for all serving cells, if configured);

[0598] - Clear (any) configured downlink assignments;

[0599] - Clear (any) configured uplink grants; and

[0600] - Clear (any) Physical Uplink Shared Channel (PUSCH) resources for semi-persistent CSI reporting.

[0601] And when the timeAlignmentTimer expires, after the MAC notifies the RRC, the following UE actions shall be immediately performed, as specified in the current NR RRC specification (e.g., [4] 3GPP TS 38.331 V17.5.0):

[0602] - After receiving a PUCCH release request from the lower layer, the UE shall then (for all bandwidth parts of the indicated serving cell):

[0603] Release the PUCCH-CSI-Resource configured in the Channel State Information (CSI)-ReportConfig; and

[0604] Release the SchedulingRequestResourceConfig instance configured in the PUCCH-Config.

[0605] - After receiving an SRS release request from the lower layer, the UE shall then (for all bandwidth parts of the indicated serving cell):

[0606] Release the SRS-Resource instance configured in the SRS-Config.

[0607] However, satellite handover is mainly used in scenarios where the gNB is not changed during satellite handover, and the benefit of satellite handover (compared to handover) is to save transmission overhead by not having to send an RRC reconfiguration message to the UE. It is considered that the result of the timeAlignmentTimer expiring in satellite handover (e.g., at t-Service) is that the NW needs to transmit an RRC reconfiguration message (and / or) other signaling (e.g., MAC CE / Physical Downlink Control Channel (PDCCH) for activation, etc.) to reconfigure (and / or activate) PUCCH, SRS, the configured downlink assignment, the configured uplink grant, and / or the PUSCH resource for semi-persistent CSI reporting later (e.g., after satellite handover). In this case, the benefit of reduced transmission overhead caused by satellite handover is minimized.

[0608] To address the above problem, in response to an invariant PCI handover or satellite handover (e.g., if an indication of satellite handover is received, during the satellite handover (procedure), after initiating the satellite handover (procedure), when initiating the satellite handover (procedure), and / or if the satellite handover (procedure) is initiated), the UE may maintain: the timeAlignmentTimer (from expiring), PUCCH resources and / or configurations, SRS resources and / or configurations, configured downlink assignments, configured uplink grants, and / or PUSCH resources for semi-persistent CSI reporting. In response to a satellite handover (e.g., if an indication of satellite handover is received, during the satellite handover (procedure) and / or if the satellite handover (procedure) is initiated), the UE may maintain and / or may not release the following configurations and / or resources: PUCCH resource / configurations, SRS resource / configurations, configured downlink assignments, configured uplink grants, and / or PUSCH resources for semi-persistent CSI reporting.

[0609] In response to a satellite handover (e.g., if an indication of satellite handover is received, during the satellite handover (procedure), after initiating the satellite handover (procedure), when initiating the satellite handover (procedure), and / or if the satellite handover (procedure) is initiated, at cell stop times such as t-Service), the UE may:

[0610] - Not consider the time alignment timer to have expired;

[0611] - Not perform at least one or more actions that are performed when the time alignment timer expires;

[0612] - Continue the time alignment timer (or keep the time alignment timer running);

[0613] - Consider the time alignment timer to be running;

[0614] - Stop (or pause) the time alignment timer (e.g., if it is running); and / or

[0615] - Start (or restart) the time alignment timer.

[0616] The time alignment timer may be associated with the PTAG of the UE. The time alignment timer may be the timeAlignmentTimer.

[0617] When at least one or more of the following occur / if at least one or more of the following occur / after at least one or more of the following occur / in response to at least one or more of the following occurring, the UE may start (or resume) the time alignment timer:

[0618] - (Successfully) complete a satellite handover;

[0619] -(Successfully) complete the RA procedure;

[0620] -Receive an RAR (Random Access Response);

[0621] -Receive a timing advance command included in, for example, the RAR;

[0622] -Apply the (updated) TA value;

[0623] -Obtain the (updated) SIB19 of the serving cell;

[0624] -Obtain the (updated) ephemeris of the serving cell; and / or

[0625] -Perform UL and / or DL synchronization with the serving cell.

[0626] When the time alignment timer expires, the UE performs at least one or more actions. The at least one or more actions may include:

[0627] -Clear a HARQ buffer (or all HARQ buffers) (e.g., for all serving cells);

[0628] -(Notify RRC) to release the PUCCH (e.g., PUCCH resources and / or configurations, for all serving cells, if configured);

[0629] -(Notify RRC) to release the SRS (e.g., SRS resources and / or configurations, for all serving cells, if configured);

[0630] -Clear the configured downlink assignment (or any configured downlink assignment);

[0631] -Clear the configured uplink grant (or any configured uplink grant);

[0632] -Clear any PUSCH resources used for semi-persistent CSI reporting;

[0633] -Release the PUCCH-CSI-Resource configured in the CSI-ReportConfig (e.g., for all bandwidth parts of the indicated serving cell);

[0634] -Release the SchedulingRequestResourceConfig instances configured in the PUCCH-Config (e.g., for all bandwidth parts of the indicated serving cell); and / or

[0635] - Release the SRS-Resource instances configured in the SRS-Config (e.g., for all the bandwidth parts of the indicated serving cell).

[0636] In response to a satellite handover (e.g., if an indication of a satellite handover is received, during the satellite handover (procedure), after initiating the satellite handover (procedure), when initiating the satellite handover (procedure), and / or if the satellite handover (procedure) is initiated, at the cell stop time such as t-Service), the UE may:

[0637] - Do not release the PUCCH (e.g., PUCCH resources and / or configurations);

[0638] - Maintain (or continue) (applying or using) the current (configured) PUCCH resources and / or configurations; and / or

[0639] - Suspend the PUCCH resources and / or configurations.

[0640] When at least one or more of the following occur / if at least one or more of the following occur / after at least one or more of the following occur / in response to at least one or more of the following occurring, the UE may resume the PUCCH resources and / or configurations:

[0641] - (Successfully) complete the satellite handover;

[0642] - (Successfully) complete the RA procedure;

[0643] - Receive an RAR (Random Access Response);

[0644] - Receive a timing advance command included in, for example, the RAR;

[0645] - Apply the (updated) TA value;

[0646] - Obtain the (updated) SIB19 of the (serving cell);

[0647] - Obtain the (updated) ephemeris of the (serving cell); and / or

[0648] - Perform UL and / or DL synchronization with the serving cell.

[0649] The PUCCH resources and / or configurations may be (or include):

[0650] - PUCCH-Config (and / or the configurations in the PUCCH-Config);

[0651] - PUCCH resources (and / or resource sets);

[0652] - PUCCH resources for scheduling requests

[0653] - PUCCH resources for CSI reporting;

[0654] - PUCCH-CSI-Resource configured in CSI-ReportConfig (e.g., for all bandwidth parts of the indicated serving cell); and / or

[0655] - SchedulingRequestResourceConfig instances configured in PUCCH-Config (e.g., for all bandwidth parts of the indicated serving cell).

[0656] In response to a satellite handover (e.g., if an indication of a satellite handover is received, during the satellite handover (procedure), after initiating the satellite handover (procedure), when initiating the satellite handover (procedure), and / or if the satellite handover (procedure) is initiated, at the cell stop time such as t-Service), the UE may:

[0657] - Not release the SRS (e.g., SRS resources and / or configuration);

[0658] - Maintain (or continue) (applying or using) the current (configured) SRS resources and / or configuration; and / or

[0659] - Pause the SRS resources and / or configuration.

[0660] When at least one or more of the following occur / if at least one or more of the following occur / after at least one or more of the following occur / in response to at least one or more of the following occurring, the UE may resume the SRS resources and / or configuration:

[0661] - (Successfully) complete the satellite handover;

[0662] - (Successfully) complete the RA procedure;

[0663] - Receive an RAR (Random Access Response);

[0664] - Receive a timing advance command included in, for example, the RAR;

[0665] - Apply the (updated) TA value;

[0666] - Obtain the (updated) SIB19 of the serving cell;

[0667] - Obtain the (updated) ephemeris of the serving cell; and / or

[0668] - Perform UL and / or DL synchronization with the serving cell.

[0669] The SRS resource and / or configuration may be (or include):

[0670] - SRS-config (and / or the configuration in PUCCH-Config);

[0671] - PUCCH resources (and / or resource sets); and / or

[0672] - SRS-Resource instances configured in SRS-Config.

[0673] In response to a satellite handover (e.g., if an indication of a satellite handover is received, during the satellite handover (procedure), after initiating the satellite handover (procedure), when initiating the satellite handover (procedure), and / or if the satellite handover (procedure) is initiated, at the cell stop time such as t-Service), the UE may:

[0674] - Not clear the configured downlink assignment (or any configured downlink assignment);

[0675] - Maintain (or continue) (applying or using) the current (configured) resources and / or configuration of the configured downlink assignment;

[0676] - Pause the resources and / or configuration of the configured downlink assignment;

[0677] - Not clear the configured uplink grant (or any configured uplink grant);

[0678] - Maintain (or continue) (applying or using) the current (configured) resources and / or configuration of the configured uplink grant;

[0679] - Pause the resources and / or configuration of the configured uplink grant; and / or

[0680] - Consider the configured uplink grant and / or the configured downlink assignment to be deactivated.

[0681] When at least one or more of the following occur(s) / if at least one or more of the following occur(s) / after at least one or more of the following occur(s) / in response to at least one or more of the following occurring, the UE may resume (or activate) the resources and / or configuration of the configured downlink assignment and / or the configured uplink grant:

[0682] - (Successfully) complete the satellite handover;

[0683] - (Successfully) complete the RA procedure;

[0684] - Receive an RAR (Random Access Response);

[0685] - Receive a timing advance command included in, for example, an RAR;

[0686] - Apply the (updated) TA value;

[0687] - Obtain the (updated) SIB19 of the serving cell;

[0688] - Obtain the (updated) ephemeris of the serving cell; and / or

[0689] - Perform UL and / or DL synchronization with the serving cell.

[0690] The configured uplink grant may be of the configured grant type 1. The configured uplink grant may be of the configured grant type 2. The configured downlink assignment may be DL semi-persistent scheduling (SPS).

[0691] The configured grant types 1 and 2 may be handled differently in satellite handover.

[0692] In response to a satellite handover (e.g., if an indication of a satellite handover is received, during the satellite handover (procedure), after initiating the satellite handover (procedure), when initiating the satellite handover (procedure), and / or if the satellite handover (procedure) is initiated, at the cell stop time such as t-Service), the UE may:

[0693] - Do not clear one (or any) PUSCH resource for semi-persistent CSI reporting;

[0694] - Maintain (or continue) to apply or use the current (configured) PUSCH resource for semi-persistent CSI reporting; and / or

[0695] - Pause the PUSCH resource for semi-persistent CSI reporting.

[0696] When at least one or more of the following occur / if at least one or more of the following occur / after at least one or more of the following occur / in response to at least one or more of the following occurring, the UE may resume the PUSCH resource for semi-persistent CSI reporting:

[0697] - (Successfully) complete the satellite handover;

[0698] - (Successfully) complete the RA procedure;

[0699] - Receive an RAR (random access response);

[0700] - Receive a timing advance command included in, for example, an RAR;

[0701] - Apply the (updated) TA value;

[0702] - Obtain the (updated) SIB19 of the serving cell;

[0703] - Obtain the (updated) ephemeris of the serving cell; and / or

[0704] - Perform UL and / or DL synchronization with the serving cell.

[0705] Pausing a resource and / or configuration can be (or include) ceasing to use (or apply) the resource and / or configuration (temporarily, e.g., for a certain period until it is resumed). When a resource and / or configuration is paused, the resource and / or configuration is held (or not released).

[0706] Resuming a resource and / or configuration can be (or include) commencing to use (or apply) the (paused) resource and / or configuration.

[0707] For the methods, alternatives, concepts, examples, and embodiments detailed above and herein, the following aspects and embodiments are possible.

[0708] Reference Figure 19 , using this and other concepts, systems, and methods of the present invention, a method 1020 for a UE in a wireless communication system includes: receiving a configuration for satellite handover (step 1022); initiating a satellite handover at an opportunity (step 1024); performing DL and / or UL (re)synchronization with the serving cell in response to the satellite handover (step 1026); (re)obtaining NTN-related system information in response to the satellite handover (step 1028); and not considering that a time alignment timer has expired in response to the satellite handover (step 1030).

[0709] In various embodiments, in response to a satellite handover, the UE stops or pauses a time alignment timer.

[0710] In various embodiments, in response to a satellite handover, the UE does not clear one or more HARQ buffers associated with HARQ processes.

[0711] In various embodiments, in response to a satellite handover, the UE holds (or pauses) PUCCH resources and / or configurations.

[0712] In various embodiments, PUCCH resources and / or configurations are used for scheduling requests.

[0713] In various embodiments, PUCCH resources and / or configurations are used for CSI reporting.

[0714] In various embodiments, in response to a satellite handover, the UE holds (or pauses) SRS resources and / or configurations.

[0715] In various embodiments, in response to a satellite handover, the UE maintains (or pauses) a configured uplink grant and / or a configured downlink assignment.

[0716] In various embodiments, in response to a satellite handover, the UE maintains (or pauses) CSI reporting.

[0717] In various embodiments, the configuration of a satellite handover is an indication of an enabled satellite change.

[0718] In various embodiments, the timing is indicated by a cell out-of-service time.

[0719] In various embodiments, the timing is indicated by the configuration of a satellite handover.

[0720] Return reference Figure 3 and 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 a memory 310 of a transmitter. The CPU 308 may execute the program code 312 to: (i) receive a configuration of a satellite handover; (ii) initiate a satellite handover at a timing; (iii) perform DL and / or UL (re)synchronization with a serving cell in response to the satellite handover; (iv) (re)acquire system information related to NTN in response to the satellite handover; and (v) not consider that a time alignment timer has expired in response to the satellite handover. Additionally, the CPU 308 may execute the program code 312 to perform all of the described actions, steps, and methods described above, below, or herein.

[0721] The UE will use timers (e.g., UL synchronization timer, validity timer) to maintain UL synchronization (e.g., for the serving cell) and / or the validity of NTN information based on 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 satellite information (e.g., ephemerisInfo, ta-Info) is valid.

[0722] For example, when the UL synchronization timer (e.g., T430) is running, the (part of) satellite information can be considered valid. When the UL synchronization timer (e.g., T430) is not running, the (part of) satellite information can be considered invalid. The UL synchronization timer (e.g., T430) can indicate the duration when obtaining or maintaining UL synchronization based on satellite information or a part of satellite information (e.g., ephemerisInfo, ta-Info).

[0723] 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) has been started, UL can be considered synchronized, or UL synchronization can be considered obtained. In response to starting the UL synchronization timer (e.g., T430), the UE can consider the UL synchronization (as obtained / as having been 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. When the UL synchronization timer (e.g., T430) stops and / or (is considered) expires, UL can be considered out of sync, or UL synchronization can be considered lost. In response to stopping the UL synchronization timer (e.g., T430), the UE can consider the UL synchronization as lost / as having been lost, and / or consider that UL synchronization loss has occurred.

[0724] Based on the current specifications (e.g., [3] 3GPP TS 38.321 V17.5.0 and [9] 3GPP TS 38.331 V17.6.0), 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.

[0725] 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 can immediately consider that the uplink synchronization has been lost and acquire SIB19. In response to acquiring SIB19, the UE can consider that the uplink synchronization has been obtained. If the uplink synchronization is considered lost, the UE can clear the HARQ buffer and can refrain from performing UL transmissions on the serving cell. If the uplink synchronization is considered obtained, the UE can perform UL transmissions on the serving cell. When the UL synchronization timer is running, the serving cell can be considered to have achieved uplink synchronization (e.g., the uplink synchronization has been obtained) in the RRC connected mode. When the UL synchronization timer is not running and / or has expired, the serving cell can be considered not to have achieved uplink synchronization (e.g., the uplink synchronization has been lost) in the RRC connected mode.

[0726] Throughout this disclosure, the UL synchronization timer may be a timer for the serving cell (or source cell). The UL synchronization timer may be a UL synchronization timer for the target cell (or neighboring cell). The UL synchronization timer may be a validity timer. The UL synchronization timer may be timer T430. The UL synchronization timer may be used to maintain / evaluate UL synchronization, e.g., when the UE is in NTN, when the UE is connected to a satellite. The UL synchronization timer may indicate / handle the duration when the (associated) auxiliary information is valid. The UL synchronization timer may indicate / handle the duration when the UE can apply the (associated) satellite information, e.g., without obtaining new satellite information. The UL synchronization timer may be used in NTN. The UL synchronization timer (e.g., T430) may not be used in TN. The UL synchronization timer (e.g., T430) may be an NTN-specific timer. The UL synchronization timer may be different from the TA timer (e.g., TimeAlignmentTimer). The UL synchronization timer may not be used to maintain UL TA. The UL synchronization timer may be associated with a cell. The UL synchronization timer may not be associated with a TA group. When the (associated) satellite information is valid, the UE may consider UL to be synchronized.

[0727] For example, in response to (receiving) an indication (e.g., satSwitchWithReSync), in response to receiving system information containing an indication (e.g., satSwitchWithReSync), the UE may perform (or initiate) a PCI-preserving handover or a satellite handover. For example, at a specific time, at t-Service, before t-Service, after t-Service, after t-Start, after receiving system information, the UE may perform (or initiate) a PCI-preserving handover or a satellite handover. The specific time may be indicated by the network. The specific time may be indicated in the system information (e.g., SIB19). 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 serve the area (or cell) currently covered or served by the first satellite. The handover start time (e.g., t-Start) may be (or indicate) the time when a PCI-preserving handover or a satellite handover can be started or performed. Throughout this disclosure, t-Start may be the handover start time, and t-Service may be the cell stop time. Throughout this disclosure, t-Start may be represented as t-Service minus t-Gap.

[0728] An invariant PCI handover or satellite handover may be or include a soft satellite handover and / or a hard satellite handover. The soft satellite handover or the hard satellite handover may be explicitly or implicitly indicated by the NW. The NW may provide an indication of the satellite handover type (e.g., soft satellite handover or hard satellite handover). The NW may provide the t-Start and / or SSB information of the soft satellite handover. The indication may be a parameter, t-Start, and / or SSB information.

[0729] For a hard satellite handover, after disconnecting from the old satellite (e.g., the source satellite, the first satellite), the UE may 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 20 (cited from

[10] R2-2310307) and Figure 21 . The serving satellite may perform a handover at a time point (e.g., Figure 20 the handover time in, t-Service). The time point may be t-Service. The first satellite (e.g., Figure 20 SAT1 in) may be the serving satellite before the satellite handover and / or the time point. The second satellite (e.g., Figure 20 SAT2 in) may be the serving satellite after the satellite handover and / or the time point. The first satellite and the second satellite may serve the same cell (e.g., having the same PCI). The first satellite may be the source satellite. The second satellite may be the target satellite. The UE may receive (enable) a first indication (e.g., satSwitchWithReSync) of the invariant PCI mechanism or satellite handover via the first SIB19. In response to receiving the first SIB19, the UE may start or restart the UL synchronization timer (e.g., T430). The UE may stop transmitting to the first satellite at t-Service and start acquiring / implementing DL synchronization with the second satellite after t-Service. The UE may consider the UL synchronization timer (e.g., T430) to expire at t-Service. After DL synchronization, e.g., in response to the expiration of the UL synchronization timer (e.g., T430), the UE may acquire the second SIB19. The second SIB19 includes satellite information after switching the serving satellite. In response to receiving the second SIB19, e.g., based on the satellite information, the UE may start the UL synchronization timer (e.g., T430). After DL synchronization and when the UL synchronization timer (e.g., T430) is running, e.g., based on the NW indication, the UE may perform the RA procedure or not perform the RA procedure. When the UL synchronization timer (e.g., T430) is running and / or when performing the RA procedure, after DL synchronization, the UE may acquire UL synchronization with the second satellite.

[0730] For soft satellite handover, the UE may connect to (or synchronize with) a new satellite (e.g., the target satellite, the second satellite) before disconnecting from the old satellite (e.g., the source satellite, the first satellite). Examples of soft satellite handover are in Figure 22 (cited in

[10] R2-2310307) and Figure 23 are shown. The serving satellite may perform the handover during a duration (e.g., Figure 22 the T-duration in, between t-Start and t-Service). The first satellite (e.g., Figure 22 SAT1 in) and the second satellite (e.g., Figure 22 SAT2 in) both provide service / coverage for the same area during the said duration. The duration may start at t-Start and end at t-Service. The first satellite may be the serving satellite before the satellite handover and / or t-Start. The second satellite (e.g., Figure 20 SAT2 in) may be the serving satellite after the satellite handover and / or t-Service. The first satellite and the second satellite may serve the same cell (e.g., having the same PCI). The first satellite may be the source satellite. The second satellite may be the target satellite. The UE may receive (enable) the first indication of the invariant PCI mechanism or satellite handover (e.g., satSwitchWithReSync) via the first SIB19. In response to receiving the first SIB19, the UE may start or restart the UL synchronization timer (e.g., T430). After t-Start (and before t-Service), the UE may start acquiring DL synchronization with the second satellite. At t-Service and / or after DL synchronization, the UE may stop transmitting to the first satellite. The UE may consider the UL synchronization timer (e.g., T430) to expire at t-Service. After DL synchronization, e.g., in response to the expiration of the UL synchronization timer (e.g., T430), the UE may acquire the second SIB19. The second SIB19 includes satellite information after switching the serving satellite. In response to receiving the second SIB19, e.g., based on the satellite information, the UE may start the UL synchronization timer (e.g., T430). After DL synchronization and when the UL synchronization timer (e.g., T430) is running, e.g., based on the NW indication, the UE may perform the RA procedure or not perform the RA procedure. When the UL synchronization timer (e.g., T430) is running and / or when performing the RA procedure, after DL synchronization, the UE may acquire UL synchronization with the second satellite.

[0731] For RACH-based satellite handover, after DL synchronization with the new satellite, the UE can immediately trigger the RA procedure. For RACH-less satellite handover, after DL synchronization with the new satellite, the UE can immediately perform UL synchronization. However, for hard satellite handover as shown in Figure 21 , the UE considers that the UL synchronization timer (e.g., T430) expires at t-Service, and starts the UL synchronization timer (e.g., T430) immediately after obtaining the new SIB19 after DL synchronization. When the UL synchronization timer (e.g., T430) is not running, the UE cannot perform UL transmission. Before starting the UL synchronization timer (e.g., T430), the UE cannot perform the triggered RA procedure or UL synchronization. There may be a time gap between DL synchronization and performing UL synchronization. For soft satellite handover as shown in Figure 23 , the time gap between DL synchronization and UL synchronization may be longer because the UE can perform DL synchronization before t-Service.

[0732] In the latest RAN2 meeting (RAN2#123bis meeting), it has been agreed that the network broadcasts the target satellite information (e.g., NTN-Config) to the UE in advance in SIB19 before satellite handover. The UE can receive the target satellite information before satellite handover instead of after performing DL synchronization with the target satellite. However, based on the current mechanism according to the RAN2 protocol, the UE still needs to wait to obtain the new SIB19 to start the UL synchronization timer (e.g., T430). Based on the expiration of the UL synchronization timer (e.g., T430), even if the UE has valid target satellite information, the UE cannot perform UL synchronization. The UE can consider that the UL synchronization timer (e.g., T430) expires immediately after t-Service. In response to the expiration of the UL synchronization timer (e.g., T430), the UE considers that UL synchronization is lost (and obtains SIB19). In response to the loss of UL synchronization, the UE clears all HARQ buffers. After DL synchronization, the UE starts T430 and considers that UL synchronization has been obtained.

[0733] Throughout this disclosure, the target NTN information may be or be referred to as the NTN information of the target satellite. The source NTN information may be or be referred to as the NTN information of the source satellite. The target NTN information may be explicitly provided in SIB19. The target NTN information may be implicitly provided in SIB19, with a parameter for indicating one of the NTN information in SIB19. The target NTN information may be provided in a list of neighboring cells. SIB19 may (at least) include first NTN information, second NTN information, and / or third NTN information. The first NTN information may be for the source satellite. The second NTN information may be for the target satellite. The third NTN information may be for the source satellite. The first NTN information may be for the serving cell. The second NTN information may be for the serving cell, the target cell, or a neighboring cell. The third NTN information may be for a neighboring cell. The first NTN information, the second NTN information, and / or the third NTN information may be different or the same NTN information.

[0734] To solve the above problem, the UE may determine whether to consider that the UL synchronization timer (e.g., T430) expires at a specific timing based on conditions. The specific timing may be the timing when the source satellite stops providing services to the current cell. The specific timing may be t-Service. The specific timing may be the timing when the UE starts to perform DL synchronization, perform satellite handover, and / or handover to the target satellite. The specific timing may be the timing when the UE performs DL synchronization, performs a PCI-invariant handover, satellite handover, and / or handover to the target satellite.

[0735] For example, based on the above conditions, the UE may not consider that the UL synchronization timer (e.g., T430) expires during the procedure of PCI-invariant handover and / or satellite handover. For example, based on the above conditions, the UE may keep the UL synchronization timer (e.g., T430) running during the procedure of PCI-invariant handover and / or satellite handover. The UE may not consider that the UL synchronization timer expires during the procedure of PCI-invariant handover and / or satellite handover. In response to the expiration of the UL synchronization timer, if the procedure of PCI-invariant handover and / or satellite handover is in progress, the UE may (re)start the UL synchronization timer.

[0736] Throughout this disclosure, when a UE determines to perform DL synchronization (e.g., with a target satellite), it may initiate procedures for PCI-constant handover and / or satellite handover. When the UE receives an indication of PCI-constant handover and / or satellite handover, it may initiate procedures for PCI-constant handover and / or satellite handover. When the UE receives system information containing an indication of PCI-constant handover and / or satellite handover, it may initiate procedures for PCI-constant handover and / or satellite handover. When the UE acquires UL synchronization, it may complete procedures for PCI-constant handover and / or satellite handover. When the UE believes it has acquired UL synchronization, the UE may acquire UL synchronization. When the UE completes the RA procedure, it may complete procedures for PCI-constant handover and / or satellite handover. When the UE believes the RA procedure has been successfully completed, it may complete procedures for PCI-constant handover and / or satellite handover. When the UE completes the non-RACH procedure, it may complete procedures for PCI-constant handover and / or satellite handover. When the UE successfully receives a PDCCH transmission addressed to a Cell Radio Network Temporary Identifier (C-RNTI) and / or a Random Access Radio Network Temporary Identifier (RA-RNTI), it may complete procedures for PCI-constant handover and / or satellite handover.

[0737] The condition(s) may be one or a combination of the following:

[0738] - Whether the NTN information of the target satellite has been received (or is received) before the PCI-constant handover and / or satellite handover;

[0739] - Whether the NTN information of the target satellite has been received (or is received) in SIB19;

[0740] - Whether the NTN information of the target satellite has been received (or is received) together with the indication of PCI-constant handover and / or satellite handover;

[0741] - Whether the NTN information of the target satellite has been received (or is received) from the source satellite;

[0742] - Whether the NTN information of the target satellite is valid or available at a specific timing;

[0743] - Whether two NTN information of the serving cell (e.g., one for the source satellite and one for the target satellite) have been provided (or are provided) in SIB19;

[0744] - Whether the NTN information or an indication of UL synchronization is provided in SIB19; and / or

[0745] - Whether the UL synchronization timer is operating based on the NTN information of the target satellite.

[0746] The UE can check the conditions at a specific timing. The UE can make a determination at a specific timing. The UE can consider that the UL synchronization timer (e.g., T430) expires at a specific timing. Based on (at least) the condition being satisfied, in response to (at least) the condition being satisfied, or if (at least) the condition is satisfied, the UE can not consider that the UL synchronization timer (e.g., T430) expires at a specific timing. Based on (at least) the condition not being satisfied, in response to (at least) the condition not being satisfied, or if (at least) the condition is not satisfied, the UE can consider that the UL synchronization timer (e.g., T430) expires at a specific timing. For example, the UE can receive SIB19 including an indication of satellite handover and (at least) the NTN information of the target satellite. The UE can initiate a PCI-invariant handover and / or a satellite handover procedure. In response to the NTN information of the target satellite being available, the UE can not consider that the UL synchronization timer (e.g., T430) expires.

[0747] To solve the above problem, during the PCI-invariant handover and / or satellite handover procedure, the UE can stop the UL synchronization timer (e.g., T430) and / or (re)start the UL synchronization timer (based on the target satellite information). The UE can stop and / or (re)start the UL synchronization timer based on (at least) one or more of the following:

[0748] - After receiving system information with satSwitchWithResync (e.g., SIB19), when receiving system information with satSwitchWithResync, or in response to receiving system information with satSwitchWithResync;

[0749] - After triggering / initiating the PCI-invariant handover and / or satellite handover procedure, when triggering / initiating the PCI-invariant handover and / or satellite handover procedure, or in response to triggering / initiating the PCI-invariant handover and / or satellite handover procedure;

[0750] - After t-Service, at t-Service, before t-Service, after t-Service, or in response to t-Service;

[0751] - After performing DL synchronization, when performing DL synchronization, before performing DL synchronization, after performing DL synchronization, or in response to performing DL synchronization;

[0752] -After stopping, at the time of stopping, after stopping the UL synchronization timer, or in response to stopping the UL synchronization timer;

[0753] -If (at least) or in response to target satellite information being available or having been received / obtained; and / or

[0754] -If (at least) or in response to the UL synchronization timer not being considered expired.

[0755] When the UL synchronization timer is running (e.g., based on source satellite information), the UE may stop the UL synchronization timer. When the UL synchronization timer is not running, the UE may start the UL synchronization timer. When the UL synchronization timer is running, the UE may restart the UL synchronization timer.

[0756] Based on (at least) the condition being satisfied, in response to (at least) the condition being satisfied, or if (at least) the condition is satisfied, the UE may stop the UL synchronization timer (e.g., T430) at, before, or after a specific timing. Based on (at least) the condition not being satisfied, in response to (at least) the condition not being satisfied, or if (at least) the condition is not satisfied, the UE may not stop the UL synchronization timer (e.g., T430) at, before, or after a specific timing. After stopping the UL synchronization timer (e.g., T430) or in response to stopping the UL synchronization timer, the UE may (re)start the UL synchronization timer (e.g., T430). For example, the UE may receive SIB19 including an indication of satellite handover and (at least) NTN information of the target satellite. The UE may initiate a PCI-invariant handover and / or a satellite handover procedure. The UE may perform DL synchronization with the target satellite. Before or after performing DL synchronization with the target satellite, the UE may stop the UL synchronization timer (e.g., T430). After stopping the UL synchronization timer (e.g., T430), the UE may (re)start the UL synchronization timer (e.g., T430) based on the NTN information of the target satellite.

[0757] The UE may stop the UL synchronization timer (e.g., T430) at the indicated timing. The indicated timing may be included in the system information (e.g., SIB19). The UE may stop the UL synchronization timer (e.g., T430) immediately after t-service. After stopping the UL synchronization timer (e.g., T430), the UE may consider UL synchronization lost. In response to UL synchronization loss caused by satellite handover, the UE determines not to clear one or more HARQ buffers. After satellite handover, the UE may continue the transmission before the satellite handover. The transmission efficiency can be improved.

[0758] For example, a UE may receive system information (e.g., via a serving cell), where the system information includes at least a first NTN configuration, time information, and an indication of satellite handover. The system information may be SIB19. The indication of satellite handover may be satSwitchWithResync. The time information may be t-Service. The time information may indicate when an NTN cell (e.g., the serving cell) will stop serving its currently covered area. The first NTN configuration may be NTN-Config (for the serving cell, for the cell receiving the system information). The first NTN configuration may include at least a first validity duration and a first epoch time. In response to receiving the system information, the UE may start or restart a timer based on the first NTN configuration. The timer may be a UL synchronization timer and / or a validity timer. The timer may be T430. The UE may start or restart the timer, where the timer value is set to the first validity duration starting from the subframe indicated by the free first epoch time. Based on the indication of satellite handover being included in the system information, the UE may initiate a satellite handover procedure. The UE may stop the timer immediately after the timing indicated by the time information. After stopping the timer, the UE may consider that UL synchronization has been lost. The UE may determine whether to clear the HARQ buffer based on whether UL synchronization has been lost due to satellite handover. If and / or based on (at least) UL synchronization being lost due to satellite handover, the UE may not clear the HARQ buffer. The UE may perform DL synchronization with the cell served by the (target) satellite indicated, for example, in the indication of satellite handover. After performing DL synchronization, the UE may start a timer based on a second NTN configuration included in the indication of satellite handover. The second NTN configuration may be NTN-Config (for the target satellite, for the cell served by the target satellite). The second NTN configuration may include at least a second validity duration and a second epoch time. The UE may start the timer, where the timer value is set to the second validity duration starting from the subframe indicated by the free second epoch time. After starting the timer, the UE may consider that UL synchronization has been obtained.

[0759] For example, as Figure 24As shown, an indication for satellite handover (e.g., satSwitchWithResync) is received in system information (e.g., SIB19), and the UE can initiate a satellite handover procedure. After the timing indicated by the time information (e.g., t-Service) in the system information (e.g., SIB19), the UE can immediately stop a timer (e.g., T430). In response to stopping the timer (e.g., T430), the UL can consider that UL synchronization has been lost and / or stop UL transmission on the serving cell. For example, in response to stopping the timer (e.g., T430), considering that UL synchronization is lost due to satellite handover, UL synchronization loss is caused by satellite handover, and UL transmission is stopped, the UE may not clear the HARQ buffer. The UE can perform DL synchronization (e.g., read the SSB of the target satellite and / or the cell served by the target satellite). For example, after DL synchronization, the UL can start a timer (e.g., T430). In response to starting the timer (e.g., T430), the UE can consider that UL synchronization has been obtained and / or perform UL transmission on the serving cell.

[0760] In addition, when receiving the NTN information of the target satellite, after receiving the NTN information of the target satellite, or in response to receiving the NTN information of the target satellite, the UE may not start or restart the UL synchronization timer (e.g., T430). After receiving SIB19, based on the NTN information of the source satellite, the UE can immediately start or restart the UL synchronization timer (e.g., T430). After receiving SIB19, based on the NTN information of the target satellite, the UE may not start or restart the UL synchronization timer (e.g., T430). The UE can receive the first NTN information and the second NTN information via SIB19. (In response to receiving SIB19) Based on the first NTN information rather than the second NTN information, the UE can start or restart the UL synchronization timer (e.g., T430). (In response to receiving SIB19) The UE may not start or restart the UL synchronization timer (e.g., T430). The first NTN information is for the source satellite and / or the serving cell. The second NTN information is for the target satellite. The second NTN information is for the serving cell, the target cell, or an adjacent cell.

[0761] For the methods, alternatives, concepts, examples, and embodiments detailed above and herein, the following aspects and embodiments are possible.

[0762] Reference Figure 25, using this and other concepts, systems, and methods of the present invention, a method 1040 for a UE in a wireless communication system includes: receiving a first indication of a satellite handover (step 1042); receiving the NTN configuration of the target satellite (step 1044); performing DL synchronization with the target satellite at an opportunity (step 1046); in response to performing DL synchronization with the target satellite, stopping the UL synchronization timer for the serving cell (step 1048); after the UL synchronization timer stops, starting the UL synchronization timer for the serving cell based on the NTN configuration of the target satellite (step 1050); based on the NTN configuration of the target satellite being available, not considering the UL synchronization timer to have expired at t-Service (step 1052); and when the UL synchronization timer is running, performing a RA procedure for the satellite handover (step 1054).

[0763] In various embodiments, the opportunity is indicated by t-Service or an opportunity between t-Start and t-Service.

[0764] In various embodiments, the first indication is satSwitchWithReSync.

[0765] In various embodiments, the first indication and the NTN configuration of the target satellite are received in SIB19.

[0766] Return reference Figure 3 and 4 , in one or more embodiments from the perspective of a UE in a wireless communication system, an apparatus 300 includes program code 312 stored in a memory 310 of a transmitter. A CPU 308 may execute the program code 312 to: (i) receive a first indication of a satellite handover; (ii) receive the NTN configuration of the target satellite; (iii) perform DL synchronization with the target satellite at an opportunity; (iv) in response to performing DL synchronization with the target satellite, stop the UL synchronization timer for the serving cell; (v) after the UL synchronization timer stops, start the UL synchronization timer for the serving cell based on the NTN configuration of the target satellite; (vi) based on the NTN configuration of the target satellite being available, not consider the UL synchronization timer to have expired at t-Service; and (vii) when the UL synchronization timer is running, perform a RA procedure for the satellite handover. Additionally, the CPU 308 may execute the program code 312 to perform all the described actions, steps, and methods described above, below, or herein.

[0767] Reference Figure 26, using this and other concepts, systems, and methods of the present invention, a method 1060 for a UE in a wireless communication system includes: receiving an indication of uplink synchronization loss from an upper layer (step 1062); and in response to receiving the indication of uplink synchronization loss: not performing an uplink transmission on the serving cell, and determining whether to clear one or more HARQ buffers based on whether the uplink synchronization loss is caused by a satellite handover (step 1064).

[0768] In various embodiments, the method further includes: if the uplink synchronization loss is caused by a satellite handover, not clearing one or more HARQ buffers; and if the uplink synchronization loss is not caused by a satellite handover, clearing one or more HARQ buffers.

[0769] In various embodiments, the method further includes: receiving system information, where the system information at least includes an indication of a satellite handover; based on the indication of the satellite handover being included in the system information, initiating a procedure for a satellite handover; and in response to initiating the procedure for a satellite handover, indicating uplink synchronization loss.

[0770] In various embodiments, the indication of the satellite handover is satSwitchWithResync.

[0771] In various embodiments, the system information is SIB19.

[0772] In various embodiments, the method further includes: immediately starting or restarting a timer after receiving the system information; and in response to the expiration of the timer, indicating uplink synchronization loss.

[0773] In various embodiments, the timer is T430.

[0774] In various embodiments, the upper layer is the RRC layer.

[0775] Return reference Figure 3 and 4 , in one or more embodiments from the perspective of a UE in a wireless communication system, an apparatus 300 includes program code 312 stored in a memory 310 of a transmitter. A CPU 308 may execute the program code 312 to: (i) receive an indication of uplink synchronization loss from an upper layer; and (ii) in response to receiving the indication of uplink synchronization loss: not perform an uplink transmission on the serving cell, and determine whether to clear one or more HARQ buffers based on whether the uplink synchronization loss is caused by a satellite handover. Additionally, the CPU 308 may execute the program code 312 to perform all the described actions, steps, and methods described above, below, or herein.

[0776] Reference Figure 27, using this and other concepts, systems, and methods of the present invention, a method 1070 for a UE in a wireless communication system includes: receiving system information, where the system information at least includes a first NTN configuration, time information, and an indication of satellite handover (step 1072); in response to receiving the system information, starting or restarting a timer based on the first NTN configuration (step 1074); based on the indication of satellite handover being included in the system information, initiating a satellite handover procedure (step 1076); stopping the timer immediately after the timing indicated by the time information (step 1078); after stopping the timer, considering that UL synchronization has been lost (step 1080); determining whether to clear one or more HARQ buffers based on whether UL synchronization has been lost due to satellite handover (step 1082); performing DL synchronization with the cell served by the satellite indicated in the indication of satellite handover (step 1084); after performing DL synchronization, starting a timer based on a second NTN configuration included in the indication of satellite handover (step 1086); and after starting the timer, considering that UL synchronization has been obtained (step 1088).

[0777] In various embodiments, the time information indicates when the NTN cell will stop serving the area currently covered by the NTN cell.

[0778] In various embodiments, the system information is SIB19.

[0779] In various embodiments, the time information is t-Service.

[0780] In various embodiments, the indication of satellite handover is satSwitchWithResync.

[0781] In various embodiments, the first NTN configuration and / or the second NTN configuration is NTN-Config.

[0782] In various embodiments, the first NTN configuration at least includes a first validity duration and a first epoch time, and / or the second NTN configuration at least includes a second validity duration and a second epoch time.

[0783] In various embodiments, the timer is T430.

[0784] In various embodiments, the UE starts or restarts the timer from the subframe indicated by the first epoch time, where the timer value is set to the first validity duration, and / or the UE starts the timer from the subframe indicated by the second epoch time, where the timer value is set to the second validity duration.

[0785] In various embodiments, the second NTN configuration is associated with the cell served by the satellite indicated in the indication of satellite handover.

[0786] In various embodiments, the method further comprises: if the uplink synchronization loss is caused by a satellite handover, not clearing one or more HARQ buffers; and if the uplink synchronization loss is not caused by a satellite handover, clearing one or more HARQ buffers.

[0787] Return reference Figure 3 and 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 a transmitter. CPU 308 may execute program code 312 to: (i) receive system information, where the system information at least includes a first NTN configuration, time information, and an indication of a satellite handover; (ii) in response to receiving the system information, start or restart a timer based on the first NTN configuration; (iii) initiate a satellite handover procedure based on the indication of a satellite handover being included in the system information; (iv) stop the timer immediately after the timing indicated by the time information; (v) after stopping the timer, consider UL synchronization to be lost; (vi) determine whether to clear one or more HARQ buffers based on whether UL synchronization is lost due to a satellite handover; (vii) perform DL synchronization with the cell served by the satellite indicated in the indication of the satellite handover; (viii) after performing DL synchronization, start a timer based on a second NTN configuration included in the indication of the satellite handover; and (ix) after starting the timer, consider UL synchronization to have been obtained. Additionally, CPU 308 may execute program code 312 to perform all of the described actions, steps, and methods described above, below, or elsewhere herein.

[0788] Any combination of the concepts or teachings above or herein may be fully or partially combined or formed into a new embodiment together. The disclosed details and embodiments can be used to at least (but not limited to) solve the problems mentioned above and herein.

[0789] It should be noted that any one of the methods, alternatives, steps, examples, and embodiments presented herein may be applied independently, individually, and / or together with multiple methods, alternatives, steps, examples, and embodiments combined together.

[0790] The various aspects of the present disclosure have been described above. It should be understood that the teachings herein can be embodied 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 will appreciate that the aspects disclosed herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, an apparatus can be implemented or a method can be practiced using any number of the aspects set forth herein. Additionally, this apparatus can be implemented or this method can be practiced using other structures, functions, or a combination of structures and functions in addition to or different from one or more of the aspects set forth herein. As an example 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.

[0791] Those skilled in the art will understand that any of a variety of different techniques and technologies can be used to represent information and signals. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referred to throughout the above description can be represented by voltage, current, electromagnetic waves, magnetic fields or magnetic particles, optical fields or optical particles, or any combination thereof.

[0792] 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., a digital implementation, an analog implementation, or a combination of both, 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 this interchangeability of hardware and software, the various illustrative components, blocks, modules, circuits, and steps have been generally 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.

[0793] In addition, various illustrative logical blocks, modules, and circuits described in connection with the aspects disclosed herein can be implemented within or performed by an integrated circuit ("IC"), an access terminal, or an access point. The IC can 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 can execute code or instructions residing within the IC, outside the IC, or in both cases. The general-purpose processor can be a microprocessor, but in the alternative, the processor can be any conventional processor, controller, microcontroller, or state machine. The processor can 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.

[0794] It should be understood that any specific order or hierarchy of steps in any disclosed process is an example of a sample method. It should be understood that, based on design preferences, the specific order or hierarchy of steps in a process can 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.

[0795] The steps of a method or algorithm described in connection with the various aspects disclosed herein can 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 can 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. The exemplary storage medium can be coupled to a machine such as, for example, a computer / processor (for convenience, the machine can 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 exemplary storage medium can be integral with the processor. The processor and the storage medium can reside in an ASIC. The ASIC can reside in a user device. In an alternative, the processor and the storage medium can reside as discrete components in a user device. Additionally, in some aspects, any suitable computer program product can include a computer-readable medium that includes code associated with one or more aspects of the present disclosure. In some aspects, the computer program product can include packaging material.

[0796] Although the invention has been described in connection with various aspects and examples, it is to be understood that the invention is capable of further modification. This application is intended to cover any variations, uses, or adaptations of the invention that generally follow the principles of the invention and include such departures from the present disclosure as come within the known and customary practice in the art to which the invention pertains.

Claims

1. A method for a user equipment, characterized in that, Comprising: Receiving an indication of uplink synchronization loss from an upper layer; And In response to receiving the indication of uplink synchronization loss: Not performing uplink transmission on the serving cell; And Determining whether to clear one or more hybrid automatic repeat request buffers based on whether the uplink synchronization loss is caused by a satellite handover.

2. The method according to claim 1, wherein Further comprising: If at least the uplink synchronization loss is caused by the satellite handover, not clearing the one or more hybrid automatic repeat request buffers; And If at least the uplink synchronization loss is not caused by the satellite handover, clearing the one or more hybrid automatic repeat request buffers.

3. The method according to claim 1, wherein Further comprising: Receiving system information, where the system information at least contains an indication of satellite handover; Initiating a satellite handover procedure based on the indication of satellite handover being included in the system information; And In response to initiating the satellite handover procedure, indicating the uplink synchronization loss.

4. The method according to claim 3, characterized in that, The indication of satellite handover is satSwitchWithResync, and / or the system information is SIB19.

5. The method according to claim 1, characterized in that, Further comprising: Starting or restarting a timer immediately after receiving the system information; and In response to the expiration of the timer, indicating the uplink synchronization loss.

6. The method according to claim 5, characterized in that The timer is T430, and / or the system information is SIB19.

7. A method for a user equipment, characterized in that, Comprising: Receiving system information, where the system information at least contains a first non-terrestrial network configuration, time information, and an indication of satellite handover; In response to receiving the system information, starting or restarting a timer based on the first non-terrestrial network configuration; Initiating a satellite handover procedure based on the indication of satellite handover being included in the system information; Stopping the timer immediately after the timing indicated by the time information; After stopping the timer, considering the uplink synchronization to be lost; Determining whether to clear one or more hybrid automatic repeat request buffers based on whether the uplink synchronization is lost due to satellite handover; Performing downlink synchronization with the cell served by the satellite indicated in the indication of satellite handover; After performing the downlink synchronization, starting the timer based on a second non-terrestrial network configuration included in the indication of satellite handover; and After starting the timer, considering the uplink synchronization to have been obtained.

8. The method according to claim 7, wherein The time information indicates when the non-terrestrial network cell will stop serving the area currently covered by the non-terrestrial network cell, and / or the time information is t-Service.

9. The method according to claim 7, wherein The first non-terrestrial network configuration at least contains a first validity duration and a first epoch time, and / or the second non-terrestrial network configuration at least contains a second validity duration and a second epoch time.

10. The method according to claim 9, wherein The user equipment starts or restarts the timer from the subframe indicated by the first epoch time, where the timer value is set to the first validity duration, and / or the user equipment starts the timer from the subframe indicated by the second epoch time, where the timer value is set to the second validity duration.

11. A user equipment, characterized in that, Comprising: Memory; and a processor operatively coupled to the memory, wherein the processor is configured to execute program code to: receive an indication of uplink synchronization loss from an upper layer; in response to receiving the indication of uplink synchronization loss: not perform uplink transmission on a serving cell; and determine whether to clear one or more hybrid automatic repeat request buffers based on whether the uplink synchronization loss is caused by a satellite handover.

12. The user equipment according to claim 11, characterized in that, The processor is further configured to execute the program code to: not clear the one or more hybrid automatic repeat request buffers if at least the uplink synchronization loss is caused by the satellite handover; and clear the one or more hybrid automatic repeat request buffers if at least the uplink synchronization loss is not caused by the satellite handover.

13. The user equipment according to claim 11, characterized in that The processor is further configured to execute the program code to: receive system information, wherein the system information at least includes an indication of a satellite handover; initiate a satellite handover procedure based on the indication of the satellite handover being included in the system information; and indicate the uplink synchronization loss in response to initiating the satellite handover procedure.

14. The user equipment according to claim 13, characterized in that, The indication of the satellite handover is satSwitchWithResync, and / or the system information is SIB19.

15. The user equipment according to claim 11, characterized in that The processor is further configured to execute the program code to: start or restart a timer immediately after receiving the system information; and indicate the uplink synchronization loss in response to the timer expiring.

16. The user equipment according to claim 15, wherein The timer is T430, and / or the system information is SIB19.

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