Method, terminal device and network device for non-terrestrial network satellite handover

Abstract

This application provides a method, terminal device, and network device for satellite handover in non-terrestrial networks, which helps improve the access success rate of RACH-free handover in NTN cells. The method includes: receiving a first handover command, the first handover command instructing the terminal device to perform a satellite handover from a first satellite network coverage area to a second satellite network coverage area; before performing the satellite handover, performing a first synchronization with the second satellite network according to first parameters, at least a portion of the first parameters being determined based on information in the first handover command.

Description

Technical Field

[0001] This application relates to the field of communication technology, and more specifically, to a method, terminal equipment, and network equipment for satellite handover in non-terrestrial networks. Background Technology

[0002] To improve user experience and reduce the latency of terminal devices switching from the source cell to the target cell, random access channel-less (RACH-less) handover has been introduced.

[0003] However, in non-terrestrial network (NTN) systems, the propagation delay between terminal devices and network devices is significant. During RACH-less satellite handovers in NTN systems, terminal devices may be unable to utilize the uplink resources configured in the target satellite network, leading to handover access failure. Summary of the Invention

[0004] This application provides a method, terminal device, and network device for satellite handover in non-terrestrial networks. The various aspects involved in the embodiments of this application are described below.

[0005] In a first aspect, a method for satellite handover to a non-terrestrial network is provided, comprising: receiving a first handover command, the first handover command being used to instruct a terminal device to perform a satellite handover from a first satellite network coverage area to a second satellite network coverage area; prior to performing the satellite handover, performing a first synchronization with the second satellite network according to first parameters, at least a portion of the first parameters being determined based on information in the first handover command.

[0006] In a second aspect, a method for satellite handover to a non-terrestrial network is provided, comprising: sending a first handover command to a terminal device, the first handover command being used to instruct the terminal device to perform a satellite handover from a first satellite network coverage area to a second satellite network coverage area; wherein the first handover command is used to determine at least some parameters in a first parameter, the first parameter being used for the terminal device to perform a first synchronization with the second satellite network before performing the satellite handover.

[0007] Thirdly, a method for satellite handover in a non-terrestrial network is provided, comprising: receiving a handover request sent by a first satellite network; sending handover response information to the first satellite network, wherein the handover response information is used by the first satellite network to determine a first handover command, the first handover command being used to instruct a terminal device to perform a satellite handover from the coverage area of ​​the first satellite network to the coverage area of ​​a second satellite network; wherein the first handover command is used to determine at least some parameters in a first parameter, the first parameter being used by the terminal device to perform a first synchronization with the second satellite network before performing the satellite handover.

[0008] Fourthly, a terminal device is provided, the terminal device comprising: a receiving unit for receiving a first handover command, the first handover command being used to instruct the terminal device to perform a satellite handover from a first satellite network coverage area to a second satellite network coverage area; and an execution unit for performing a first synchronization with the second satellite network according to first parameters before performing the satellite handover, wherein at least some of the first parameters are determined according to information in the first handover command.

[0009] Fifthly, a network device is provided, the network device corresponding to a first satellite network, the network device comprising: a transmitting unit, configured to send a first handover command to a terminal device, the first handover command being configured to instruct the terminal device to perform a satellite handover from the coverage area of ​​the first satellite network to the coverage area of ​​a second satellite network; wherein, the first handover command is configured to determine at least some parameters in a first parameter, the first parameter being configured for the terminal device to perform a first synchronization with the second satellite network before performing the satellite handover.

[0010] In a sixth aspect, a network device is provided, the network device corresponding to a second satellite network, the network device comprising: a receiving unit for receiving a handover request sent by a first satellite network; and a sending unit for sending handover response information to the first satellite network, the handover response information being used by the first satellite network to determine a first handover command, the first handover command being used to instruct the terminal device to perform a satellite handover from the coverage area of ​​the first satellite network to the coverage area of ​​the second satellite network; wherein the first handover command is used to determine at least some parameters in a first set of parameters, the first parameters being used by the terminal device to perform a first synchronization with the second satellite network before performing the satellite handover.

[0011] A seventh aspect provides a communication device including a memory and a processor, the memory for storing a program and the processor for calling the program in the memory to perform the method as described in any one of the first to third aspects.

[0012] Eighth aspect, an apparatus is provided, including a processor for calling a program from memory to perform the method as described in any one of the first to third aspects.

[0013] A ninth aspect provides a chip including a processor for calling a program from memory, causing a device having the chip mounted to perform the method as described in any one of the first to third aspects.

[0014] A tenth aspect provides a computer-readable storage medium having a program stored thereon that causes a computer to perform the method described in any one of the first to third aspects.

[0015] Eleventh aspect: A computer program product is provided, comprising a program that causes a computer to perform the method as described in any one of the first to third aspects.

[0016] In a twelfth aspect, a computer program is provided that causes a computer to perform the method described in any one of the first to third aspects.

[0017] In this embodiment of the application, after receiving the first handover command, the terminal device can perform a first synchronization with the second satellite network before executing the satellite handover. The first synchronization can be performed based on the handover-related time information in the first handover command. By performing the first synchronization, the terminal device can achieve synchronization with the second satellite network before the satellite handover, thereby avoiding missing the uplink resources configured for the terminal device by the second satellite network, which helps to improve the access success rate of the terminal device. Attached Figure Description

[0018] Figure 1 This is the wireless communication system used in the embodiments of this application.

[0019] Figure 2 This is an NTN system used in the embodiments of this application.

[0020] Figure 3 This is another NTN system used in the embodiments of this application.

[0021] Figure 4 This is a schematic diagram of a TA configuration applicable to an embodiment of this application.

[0022] Figure 5 This is a flowchart illustrating a method for NTN satellite handover provided in an embodiment of this application.

[0023] Figure 6 This is a schematic diagram of the timing relationship for the first synchronization of terminal devices.

[0024] Figure 7 This is a flowchart illustrating another possible implementation of an embodiment of this application.

[0025] Figure 8 This is a flowchart illustrating another possible implementation of an embodiment of this application.

[0026] Figure 9 This is a schematic diagram of the structure of a terminal device provided in an embodiment of this application.

[0027] Figure 10 This is a schematic diagram of the structure of a network device provided in an embodiment of this application.

[0028] Figure 11 This is a schematic diagram of the structure of another network device provided in an embodiment of this application.

[0029] Figure 12 This is a schematic structural diagram of a communication device provided in an embodiment of this application. Detailed Implementation

[0030] The technical solutions of the embodiments of this application will now be described with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art without creative effort regarding the embodiments of this application are within the scope of protection of this application.

[0031] The embodiments of this application can be applied to various communication systems. For example, the embodiments of this application can be applied to Global System for Mobile Communication (GSM), Code Division Multiple Access (CDMA), Wideband Code Division Multiple Access (WCDMA), General Packet Radio Service (GPRS), Long Term Evolution (LTE), Advanced Long Term Evolution (LTE-A), New Radio (NR), evolution systems of NR, LTE-based access to unlicensed spectrum (LTE-U), NR-based access to unlicensed spectrum (NR-U), NTN, Universal Mobile Telecommunication System (UMTS), Wireless Local Area Networks (WLAN), Wireless Fidelity (WiFi), and 5th-generation (5G) systems. The embodiments of this application can also be applied to other communication systems, such as future communication systems. These future communication systems could be, for example, sixth-generation (6G) mobile communication systems or satellite communication systems.

[0032] Traditional communication systems support a limited number of connections and are easy to implement. However, with the development of communication technology, communication systems can support not only traditional cellular communication but also one or more other types of communication. For example, a communication system can support one or more of the following communication methods: device-to-device (D2D) communication, machine-to-machine (M2M) communication, machine-type communication (MTC), enhanced machine-type communication (eMTC), vehicle-to-vehicle (V2V) communication, and vehicle-to-everything (V2X) communication. The embodiments of this application can also be applied to communication systems that support the above-mentioned communication methods.

[0033] The communication system in this application embodiment can be applied to carrier aggregation (CA) scenarios, dual connectivity (DC) scenarios, and standalone (SA) network deployment scenarios.

[0034] The communication system in this application embodiment can be applied to unlicensed spectrum. This unlicensed spectrum can also be considered a shared spectrum. Alternatively, the communication system in this application embodiment can also be applied to licensed spectrum. This licensed spectrum can also be considered a dedicated spectrum.

[0035] The embodiments of this application can be applied to NTN systems. As an example, the NTN system may include a 4G-based NTN system, an NR-based NTN system, an Internet of Things (IoT)-based NTN system, and a narrowband Internet of Things (NB-IoT)-based NTN system.

[0036] A communication system may include one or more terminal devices. The terminal devices mentioned in the embodiments of this application may also be referred to as user equipment (UE), access terminal, user unit, user station, mobile station, mobile station (MS), mobile terminal (MT), remote station, remote terminal, mobile device, user terminal, terminal, wireless communication equipment, user agent, or user device, etc.

[0037] In some embodiments, the terminal device may be a station (ST) in a WLAN. In some embodiments, the terminal device may be a cellular phone, cordless phone, session initiation protocol (SIP) phone, wireless local loop (WLL) station, personal digital assistant (PDA) device, handheld device with wireless communication capabilities, computing device or other processing device connected to a wireless modem, in-vehicle device, wearable device, terminal device in a next-generation communication system (e.g., NR system), or terminal device in a future evolved public land mobile network (PLMN) network, etc.

[0038] In some embodiments, the terminal device may be a device that provides voice and / or data connectivity to a user. For example, the terminal device may be a handheld device, an in-vehicle device, etc., with wireless connectivity. As some specific examples, the terminal device may be a mobile phone, tablet, laptop, PDA, mobile internet device (MID), wearable device, virtual reality (VR) device, augmented reality (AR) device, wireless terminal in industrial control, wireless terminal in self-driving, wireless terminal in remote medical surgery, wireless terminal in smart grid, wireless terminal in transportation safety, wireless terminal in smart city, wireless terminal in smart home, etc.

[0039] In some embodiments, the terminal device may be deployed on land. For example, the terminal device may be deployed indoors or outdoors. In some embodiments, the terminal device may be deployed on water, such as on a ship. In some embodiments, the terminal device may be deployed in the air, such as on an airplane, balloon, or satellite.

[0040] In addition to terminal devices, the communication system may also include one or more network devices. In this embodiment, the network device can be a device for communicating with the terminal device; this network device may also be referred to as an access network device or a radio access network device. For example, the network device may be a base station. In this embodiment, the network device may refer to a radio access network (RAN) node (or device) that connects the terminal device to the wireless network. Base stations can broadly encompass various names listed below, or be replaced by names such as: NodeB, Evolved NodeB (eNB), Next Generation NodeB (gNB), Relay Station, Access Point, Transmitting and Receiving Point (TRP), Transmitting Point (TP), Master NodeB, Secondary NodeB (SeNB), Multimode Radio (MSR) Node, Home Base Station, Network Controller, Access Node, Wireless Node, Access Point (AP), Transmitting Node, Transceiver Node, Baseband Unit (BBU), Remote Radio Unit (RRU), Active Antenna Unit (AAU), Remote Radio Head (RRH), Central Unit (CU), Distributed Unit (CU) Base stations can be macro base stations, micro base stations, relay nodes, donor nodes, or similar entities, or combinations thereof. A base station can also refer to a communication module, modem, or chip installed within the aforementioned equipment or apparatus. A base station can also be a mobile switching center, equipment performing base station functions in D2D, V2X, and M2M communications, network-side equipment in 6G networks, or equipment performing base station functions in future communication systems. Base stations can support networks using the same or different access technologies. The embodiments of this application do not limit the specific technologies or equipment forms used in the network equipment.

[0041] Base stations can be fixed or mobile. For example, a helicopter or drone can be configured to act as a mobile base station, and one or more cells can move depending on the location of the mobile base station. In other examples, a helicopter or drone can be configured as a device to communicate with another base station.

[0042] In some deployments, the network device in this application embodiment may refer to a CU or a DU, or the network device may include both a CU and a DU. The gNB may also include an AAU.

[0043] By way of example and not limitation, in the embodiments of this application, the network device may have mobility characteristics; for example, the network device may be a mobile device. In some embodiments of this application, the network device may be a satellite or a balloon station. In some embodiments of this application, the network device may also be a base station located on land, water, or other similar locations.

[0044] In this embodiment, the network device can provide services to a cell. The terminal device communicates with the network device through the transmission resources (e.g., frequency domain resources, or spectrum resources) used by the cell. The cell can be the cell corresponding to the network device (e.g., a base station). The cell can belong to a macro base station or to a base station corresponding to a small cell. The small cell can include: metro cell, micro cell, pico cell, femto cell, etc. These small cells have the characteristics of small coverage area and low transmission power, and are suitable for providing high-speed data transmission services.

[0045] For example, Figure 1 This is a schematic diagram of the architecture of a communication system provided in an embodiment of this application. Figure 1 As shown, the communication system 100 may include a network device 110, which may be a device that communicates with a terminal device 120 (or a communication terminal, terminal). The network device 110 can provide communication coverage for a specific geographical area and can communicate with terminal devices located within that coverage area.

[0046] Figure 1 An exemplary diagram shows a network device and two terminal devices. In some embodiments of this application, the communication system 100 may include multiple network devices and each network device may include other numbers of terminal devices within its coverage area. This application does not limit the scope of the embodiments.

[0047] For example, Figure 2 This is a schematic diagram of an architecture of the NTN system mentioned above. Figure 2 The NTN system 200 shown uses satellite 210 as its airborne platform. For example... Figure 2 As shown, the satellite radio access network includes a satellite 210, a service link 220, a feeder link 230, terminal equipment 240, a gateway (GW) 250, and a network 260 including base stations and a core network.

[0048] Satellite 210 is a spacecraft based on a space platform. Service link 220 refers to the link between satellite 210 and terminal equipment 240. Feeder link 230 refers to the link between gateway 250 and satellite 210. The Earth-based gateway 250 connects satellite 210 to a base station or core network, depending on the chosen architecture.

[0049] Figure 2 The NTN architecture shown is a bend-type transponder architecture. In this architecture, the base station is located on Earth behind gateway 250, and satellite 210 acts as a relay. Satellite 210 operates as a relay that forwards signals from feeder link 230 to serving link 220, or forwards signals from serving link 220 to feeder link 230. That is, satellite 210 does not have the function of a base station; communication between terminal device 240 and the base station in network 260 needs to be relayed through satellite 210.

[0050] For example, Figure 3 This is a schematic diagram of another architecture for the NTN system. (Example:) Figure 3 As shown, the satellite radio access network 300 includes a satellite 310, a service link 320, a feeder link 330, terminal equipment 340, a gateway 350, and a network 360. Figure 2 The difference is that satellite 310 has base station 312, while the network 360 behind gateway 350 only includes the core network.

[0051] Figure 3 The NTN architecture shown is a regenerative transponder architecture. In this architecture, satellite 310 carries base station 312, which can be directly connected to the Earth-based core network via a link. Satellite 310 functions as a base station, and terminal device 340 can communicate directly with satellite 310. Therefore, satellite 310 can be referred to as a network device.

[0052] exist Figure 2 and Figure 3 The communication system with the architecture shown may include multiple network devices, and each network device may include other terminal devices within its coverage area. This application embodiment does not limit this.

[0053] In the embodiments of this application, Figures 1 to 3 The communication system shown may also include other network entities such as a mobility management entity (MME) and an access and mobility management function (AMF), but this application does not limit this.

[0054] It should be understood that devices with communication functions in the network / system of this application embodiment can be referred to as communication devices. Figure 1Taking the communication system 100 shown as an example, the communication equipment may include a network device 110 and a terminal device 120 with communication functions. The network device 110 and the terminal device 120 may be the specific devices described above, which will not be repeated here. The communication equipment may also include other devices in the communication system 100, such as network controllers, mobility management entities and other network entities. This application embodiment does not limit this.

[0055] To facilitate understanding, some related technical knowledge involved in the embodiments of this application is first introduced. The following related technologies are optional solutions and can be arbitrarily combined with the technical solutions of the embodiments of this application, all of which fall within the protection scope of the embodiments of this application. The embodiments of this application include at least some of the following contents.

[0056] NTN system

[0057] With the development of communication technologies, communication systems (such as 5G) will integrate the market potential of satellite and terrestrial network infrastructure. For example, the 5G standard makes NTN, including satellite segments, part of the recognized 3rd Generation Partnership Project (3GPP) 5G connectivity infrastructure.

[0058] NTN refers to a network or network segment that uses radio frequency (RF) resources on satellite or unmanned aerial system (UAS) platforms. Taking satellites as an example, communication satellites are classified according to their orbital altitude into low Earth orbit (LEO) satellites, medium Earth orbit (MEO) satellites, geostationary Earth orbit (GEO) satellites, and highly elliptical orbit (HEO) satellites. LEO is a geocentric orbit with an altitude of 2000 kilometers or less, or at least 11.25 cycles per day, with an eccentricity of less than 0.25. Most man-made objects in outer space are located in LEO. LEO satellites orbit the Earth at high speeds (mobility), but in predictable or deterministic orbits.

[0059] Satellites at different orbital altitudes have different orbital periods.

[0060] LEO: Typical altitude is 250-1500 km, orbital period is 90-120 minutes.

[0061] MEO: Typical altitude is 5,000-25,000 km, and orbital period is 3-15 hours.

[0062] GEO: The altitude is approximately 35,786 kilometers, and the orbital period is 24 hours.

[0063] From the example of satellites mentioned earlier Figure 2 and Figure 3 It is known that typical scenarios for terminal devices accessing the NTN system involve NTN transparent payloads or NTN regenerated payloads. Among these, Figure 2 The bent-tube transponder architecture shown corresponds to the NTN transparent payload. Figure 3 The regenerative transponder architecture shown corresponds to the NTN regenerative payload.

[0064] In NTN systems, the propagation delay between terminal devices and network devices depends primarily on the altitude of the spaceborne or airborne platform and the type of payload within the NTN. Compared to terrestrial networks (TN), the propagation delay between terminal devices and network devices in NTN systems is significantly longer. For example, in traditional NR cellular networks, the propagation delay of terrestrial mobile systems is typically less than 1 millisecond, while the propagation delay in NTN systems ranges from several milliseconds to hundreds of milliseconds.

[0065] NTN satellite switching

[0066] In an NTN system, the terminal device performs a satellite handover from the source NTN satellite (NTN1) to the target NTN satellite (NTN2). During the handover process, the terminal device typically starts two timers to enhance the timing relationship. These two timers are timer T304 and timer T430.

[0067] When the terminal device begins satellite handover, it starts timer T304. During the handover process, once timer T304 expires, the terminal device initiates a radio resource control (RRC) connection re-establishment procedure with the target NTN cell.

[0068] To synchronize with NTN2 for downlink (DL) and uplink (UL) connections, the terminal device starts timer T430. As mentioned earlier, the source satellite NTN1 and the terminal device on Earth will move relative to each other; therefore, the availability of the source satellite NTN1's auxiliary information (NTN-config) becomes crucial. Timer T430 ensures that the terminal device continuously receives valid auxiliary information from the source satellite NTN1. For example, timer T430 can control the terminal device to obtain valid auxiliary information from the system information block (SIB) 19, ensuring that the auxiliary information from the source NTN1 obtained by the terminal device before handover is complete is still valid.

[0069] The auxiliary information for the source satellite NTN1 includes satellite ephemeris and common timing advance (TA) parameters. For NTN1, the network side can broadcast ephemeris information and common TA parameters. For example, SIB19 includes satellite auxiliary information for NTN access. Before connecting to NTN2, the terminal device has a valid Global Navigation Satellite System (GNSS) position, satellite ephemeris information, and common TA.

[0070] When a terminal device makes a random access to a target cell, it needs to determine the common transfer tone (TA) and the specific TA between the target cell and the corresponding satellite. The terminal device can establish synchronization with the target cell using the determined TA value and send uplink channels to complete the satellite handover.

[0071] Due to the high speed of the satellite, the location (TA) between the terminal device and the satellite base station changes rapidly. When the satellite is orbiting the Earth at a constant speed in a circular motion at an altitude of 1200km, the change in relative position caused by the low speed of the terminal device is negligible compared to the rapid movement of the satellite.

[0072] Since the time delay drift and Doppler frequency shift caused by satellite motion can be accurately calculated based on the satellite's position, direction of motion, and velocity, the change in TA (Transient Aspect Ratio) can be estimated. However, for Physical Uplink Shared Channel (PUSCH) transmissions supporting demodulation reference signal (DMRS) bundling events, TA can only be updated at the boundaries of the time domain window (TDW). For example, within the interval of the actual time domain window (A-TDW), the terminal device is allowed to update the common TA and the terminal device-specific TA between the A-TDWs of each DMRS bundling window. For NTN (Network Terminate), the ability to maintain phase continuity and power consistency also depends on the terminal device implementation for autonomous TA adjustment and frequency adjustment.

[0073] In connected mode, terminal devices need to continuously update TA and frequency pre-compensation. Terminal devices can be configured to report TA in connected mode; event-triggered TA reporting (TAR) is also supported in connected mode. In some embodiments, the TA reporting process can be controlled by two parameters: offsetThresholdTA and timingAdvanceSR. TAR is triggered in three scenarios: the MAC layer receives an indication from the RRC layer to perform TAR; the terminal device has not previously reported a TA value to the current serving cell when offsetThresholdTA is configured at the RRC layer; and the difference between the current TA information and the previously reported TA information is equal to or greater than offsetThresholdTA (if this parameter is configured). Therefore, during handover, the RRC layer notifies the MAC layer to perform TAR, and a MAC protocol data unit (PDU) can contain at most one MAC CE for TAR. The MAC CE for TAR should be generated based on the latest estimated TA value of the terminal device before the MAC PDU is packaged.

[0074] NTN TA synchronization mechanism

[0075] In some communication systems (e.g., NR), a key characteristic of uplink transmission is orthogonal multiple access in time and frequency for different terminal devices, meaning that uplink transmissions from different terminal devices within the same cell do not interfere with each other. To ensure the orthogonality of uplink transmission and avoid intra-cell interference, network devices require that the signals from different terminal devices with different frequency domain resources arrive at the network device at approximately the same time.

[0076] To ensure time synchronization on the network device side, different terminal devices have their own uplink timing (TA). The uplink and downlink clocks on the network device side are identical, but the uplink and downlink clocks on the terminal device side are offset. The network device can control the arrival time of uplink signals from different terminal devices by appropriately controlling the offset of each terminal device.

[0077] As mentioned earlier, DL and UL communications in NTN have a greater propagation delay than terrestrial networks. To accommodate the larger propagation delay in NTN, a common TA and two scheduling offsets (K) are used. offset and K mac This is used to enhance timing relationships during transmission.

[0078] The common TA is the offset configured in the system, corresponding to the round-trip time (RTT) between the reference point (RP) and the NTN load. K offset This is the configured scheduling offset, which is typically greater than or equal to the sum of the service link's RTT and the common TA. K mac It is the configured offset, which is usually greater than or equal to the RTT between the reference point and the network device.

[0079] To facilitate understanding, the following will be combined with... Figure 4 This paper provides a brief explanation of several parameters related to the TA mechanism and timing relationship in the NTN system. Figure 4 The communication system 400 shown includes a satellite 410, a terminal device 420, a reference point 430, and a gateway 440. Among them, the RTT 402 between the satellite 410 and the terminal device 420 is a service link; and the RTT 403 between the satellite 410 and the gateway 440 is a feeder link.

[0080] In some embodiments, reference point 430 may be an uplink time synchronization reference point. The uplink time synchronization reference point may be a point where DL and UL perform frame alignment based on offsets given by frequency bands and / or subcarrier spacing, etc.

[0081] exist Figure 4In this context, RTT404 between satellite 410 and reference point 430 corresponds to the common TA. The common TA is a network-controlled TA common to all terminal devices in an NTN cell (non-terrestrial cell). The common TA may include any timing offsets determined by the network as necessary. In some examples, the common common TA may be determined by the cell-specific network device or another network device to pre-compensate for feeder link delays between the satellite and the network device or gateway.

[0082] The value of the public TA can be determined based on the one-way propagation delay. common (t) is determined to pre-compensate for the two-way propagation delay between the uplink time synchronization reference point and the serving satellite. common The formula for determining (t) is as follows:

[0083]

[0084] Among them, TA common TA commonDrift And TA commonDriftVariation These are provided by the information elements TACommon, TACommonDrift, and TACommonDriftVariation configured in the RRC layer, respectively. epoch This refers to the epoch time corresponding to TACommon, TACommonDrift, and TACommonDriftVariation. Delay common (t) can be the distance between the serving satellite and the uplink time synchronization reference point at time t divided by the speed of light. If TACommon, TACommonDrift, and TACommonDriftVariation are not configured in the RRC layer, the value of the common TA is 0.

[0085] See also Figure 4 The RTT401 between terminal device 420 and reference point 430 corresponds to the scheduling offset K. offset As the configured scheduling offset, K offset It can be used to resolve the timing relationships between scheduling and transmission in various uplink communications. In some scenarios, K offset It can be used to compensate for propagation delay in NTN. K offset It can also be called scheduling time offset or timing offset value.

[0086] In some embodiments, K offset It can be configured by network devices (e.g., base stations).

[0087] In some embodiments, K offsetIt can be cell-specific, terminal device-specific, or beam-specific. For example, a corresponding K can be configured for each beam from the same satellite and / or the same NTN cell. offset value.

[0088] K offset The value of can be set to a beam-level or cell-level parameter. For example, for different NTNs, K offset The values ​​may differ. For example, K offset The value needs to be determined based on the actual scenario. In some scenarios, the cell-specific K of the NTN cell can be calculated at least in part based on the distance of the feeder link between the base station or gateway and the satellite, as well as the maximum possible distance to the terminal equipment. offset value.

[0089] The above combination Figure 4 This paper introduces the propagation delay and related configuration parameters in the NTN system. For terminal devices within the NTN service area, at time T1, the actual TA value T corresponding to the terminal device is... TA It can be determined according to the following formula:

[0090]

[0091] Among them, T c Indicates the set time granularity, N TA It is the TA value indicated in the TA command from the base station, N TA，offset This represents a fixed offset value associated with the frequency band and / or subcarrier spacing. Indicates public TA, This indicates a UE-specific TA.

[0092] The terminal device can estimate this latency itself to pre-compensate for the service link delay between the terminal device and the satellite. In some embodiments, A value of 0 can be supported (e.g., for non-terrestrial base stations). In some embodiments, the terminal device may use higher-level ephemeris parameters of the serving satellite (if provided) and determine its location based on the location using the serving satellite and its own location. For example, This can be determined by the location of the terminal device and the relevant parameters of the serving satellite ephemeris table configured in the RRC layer. If the RRC layer does not have ephemeris information (ephemerisInfo) configured, If the RRC layer ephemeris parameters of the configured service satellites are available, the terminal device can... Pre-compensate for bidirectional transmission delays on the service link.

[0093] NTA Commands can be set within the Media Access Control (MACCE) element. For Physical Random Access Channel (PRACH) transmissions, it is defined as 0.

[0094] In some embodiments, the base station may transmit indications of synchronization parameters (ephemeris and common TA), scheduling timing offsets (e.g., K...). offset ) and RTT between the reference point and the base station (e.g., K mac In the system information block, the base station can transmit PUSCH at a specific frequency (e.g., approximately once every few seconds).

[0095] No RACH handover (HO)

[0096] When synchronizing the source cell, target cell, and terminal device, a RACH-free handover solution can be introduced to reduce handover latency and improve user experience. In a synchronized network, the subframe boundaries between the source and target cells can be considered aligned. Therefore, the terminal device can hand over from the source cell to the target cell at a time agreed upon by all three parties, eliminating the need for a random access procedure. For example, when synchronizing the source cell, target cell, and terminal device, the terminal device can hand over from the source cell to the target cell using the agreed-upon system frame number (SFN) without requiring random access.

[0097] Because no random access procedure is performed, RACH-less handovers require ensuring complete synchronization between the source and target cells throughout the entire handover process. In NTN systems, RACH-less handovers are supported regardless of whether the handover occurs within satellites with the same feeder link or satellites with different feeder links. Satellites with the same feeder link refer to those with the same gateway or network equipment (e.g., gNB).

[0098] One of the main purposes of the RACH procedure during handover is to obtain the TA (Target Time) of the target cell. Under RACH handover conditions, the terminal device can obtain the TA of the target cell through the RACH procedure. Without the RACH procedure, when the source and target cells are time-synchronized, the terminal device can obtain the target cell TA without an explicit TA command.

[0099] Another objective of the RACH procedure during handover is to obtain uplink granted transmissions. In the absence of a RACH procedure in the target cell, uplink grants need to be allocated within the target cell. In some embodiments, for the initial UL transmission in a RACH-free handover, pre-allocation of grants in the RACH-free handover command is supported. That is, the target cell can pre-allocate uplink grants (UL-grants) through the handover command. The pre-allocated uplink grants can remain valid for a period of time, starting from the point where the terminal device achieves synchronization with the target cell. For example, during a RACH-free handover in an NR terrestrial network, the propagation delay between the terminal device and network devices is low. Based on the propagation delay information between the terminal device and network devices, the target cell can appropriately configure the temporal location of uplink resources in the handover command to facilitate the sending of an RRCReconfigurationComplete message (i.e., a handover completion message) when the terminal device accesses the target cell.

[0100] However, the propagation delay between the terminal device and the satellite in NTN is relatively large. The large propagation delay of the part of the air interface for the terminal device to correctly receive the handover command may cause the terminal device to miss the configured uplink resources during the process of accessing the target cell, resulting in handover access failure.

[0101] For example, in the PUSCH transmission supporting DMRS bonding described above, the TA can only be updated at the TDW boundary. In handover scenarios, since the terminal device has never communicated with the target cell before the handover, the target cell may not accurately know the terminal device's TA value. If the TA determined by the target cell is less than the terminal device's true TA value, the offset value indicated by the downlink control information (DCI) when the target base station schedules uplink may be less than the terminal device's true TA value. Because the target base station schedules uplink resources based on an inaccurate TA value, the terminal device may be unable to use the pre-configured uplink resources when it receives the physical downlink control channel (PDCCH). For example, the uplink resources may have already been missed by the terminal device, leading to access failure.

[0102] For example, when a terminal device performs a RACH-free handover, if the terminal device... If there is a deviation in the bidirectional transmission delay on the pre-compensated service link, it will cause uplink and downlink synchronization issues in the TA (Target Asynchronous Link). If uplink and downlink synchronization issues occur, when the terminal device switches to the target NTN2, there will be no available pre-configured or dynamically configured resources, resulting in a handover failure.

[0103] For example, during a RACH-free handover in an NTN, after receiving the terminal's measurement report, source NTN1 selects (handovers) the target cell and sends a RACH-free handover request message to target NTN2. Upon receiving this handover request message, target NTN2 pre-allocates resources, which may further include the target NTN's K... offset The time parameters of the target NTN2 include parameters such as the common TA. Since there is no RACH preamble transmission and response message during a no-RACH process, the network indicates (implicitly or explicitly) that the TA in the target cell is the same as that in the source cell. However, the TA of the terminal device in the target cell and the source cell may not be the same, so the time adjustment value of the terminal device in the target cell may be incorrect, leading to handover failure.

[0104] In summary, when introducing RACH-free handover in NTN scenarios, ensuring the success rate of terminal device handover access becomes a problem that needs to be solved.

[0105] It should be noted that the problem mentioned above, where the handover fails due to an error between the target network's TA value and the actual value when introducing RACH-free handover in the NTN system, is only an example. The embodiments of this application can be applied to any handover type scenario where the propagation delay is large and the target network cannot determine the actual TA value through random access.

[0106] Based on this, this application proposes a method for satellite handover in a non-terrestrial network (NTN). This method allows the terminal device to perform a first synchronization based on the configuration information of the second satellite network before satellite handover, enabling the terminal device to utilize the uplink resources configured in the second satellite network in a timely manner, and also facilitating synchronization between the first satellite network, the second satellite network, and the terminal device.

[0107] To facilitate understanding, the following will be combined with... Figure 5 The methods proposed in the embodiments of this application will be described in detail. It should be understood that... Figure 5 The method shown is executed by the terminal device.

[0108] The terminal device can be any of the terminal devices described above. In some embodiments, the terminal device is a communication device providing services to satellites in the NTN system. In some embodiments, the terminal device is a communication device with a low service transmission rate.

[0109] See Figure 5 In step S510, the first switching command is received.

[0110] The first handover command received by the terminal device comes from the first satellite network. That is, the network device corresponding to the first satellite network sends the first handover command to the terminal device to instruct it to switch from the coverage area of ​​the first satellite network to the coverage area of ​​the second satellite network. In an NTN system, the first satellite network can be referred to as source NTN1, and the second satellite network can be referred to as target NTN2. In some embodiments, after determining the network device corresponding to the second satellite network, the first satellite network sends a handover preparation message to the second satellite network. After receiving the handover response from the second satellite network, the first satellite network sends the first handover command to the terminal device.

[0111] The first satellite network coverage area is the area where the first satellite network provides communication services. In some scenarios, the first satellite network coverage area may also be referred to as the source cell. In some embodiments, the first satellite network provides services to terminal devices within the coverage area through its corresponding network equipment. In some embodiments, the first satellite network coverage area may include one or more terrestrial network cells.

[0112] The second satellite network coverage area is the area where the second satellite network provides communication services. In some scenarios, the second satellite network coverage area may also be referred to as the target cell. In some embodiments, the second satellite network provides services to terminal devices within the coverage area through its corresponding network equipment. In some embodiments, the second satellite network coverage area may include one or more terrestrial network cells.

[0113] Satellite handover refers to the switching of satellites corresponding to the area where the terminal device is located. In some embodiments, satellite handover may be cell handover. In some embodiments, the physical cell identity (PCI) of the coverage area remains unchanged during satellite handover.

[0114] The network device corresponding to the first satellite network is a communication device that provides services to the terminal device at the current moment. This network device can be a network device that moves relative to the terminal device. In some embodiments, the network device corresponding to the first satellite network can be a base station that provides services to the terminal device via satellites in the NTN system. For example, the network device corresponding to the first satellite network can be a non-geostationary earth orbit (NGEO) satellite. In some embodiments, the network device corresponding to the first satellite network can be a non-satellite mobile network device. For example, the network device corresponding to the first satellite network can be a base station installed on a low-altitude aircraft. For simplicity, the "first satellite network" mentioned below may also refer to the network device corresponding to the first satellite network.

[0115] The network device corresponding to the second satellite network is the next network device to provide services to the terminal device. In some embodiments, the first satellite network can determine the network device corresponding to the second satellite network on its own. For example, since the satellite's trajectory can be determined, the first satellite network can determine the second satellite network corresponding to the terminal device without the terminal device's measurement report. Typically, the network device corresponding to the second satellite network is a network device whose trajectory can be predicted. For example, the network device corresponding to the second satellite network can be a satellite in the NTN system. The first satellite network can determine the network device that will provide services to the terminal device based on ephemeris information. Alternatively, the network device corresponding to the second satellite network can be a non-satellite mobile network device. The first satellite network can determine the network device that will provide services to the terminal device based on preset parameters. For simplicity, the second satellite network mentioned below can also refer to the network device corresponding to the second satellite network.

[0116] The first handover command can be a command indicating that the terminal device cannot perform satellite handover via RACH. For example, the first handover command is a RACH-free handover command. Alternatively, the first handover command may not provide the terminal device with resources for random access. The embodiments of this application will be specifically described below using RACH-free handover as an example.

[0117] In some embodiments, the first satellite network may determine whether to send a RACH-free handover command to the terminal device based on the actual situation. In some embodiments, when the terminal device needs to hand over to the target NTN2 in the source NTN1 due to satellite movement or other reasons, it may prefer RACH-free handover to reduce handover latency.

[0118] The information in the first handover command can be used by the terminal device to perform satellite handover. For example, the first handover command may include handover information configured by the second satellite network for the terminal device, so that the terminal device can establish communication with the second satellite network. Alternatively, before performing a RACH-free handover, the terminal device needs to receive configuration information for handover from the first satellite network, and this information can be carried in the first handover command.

[0119] In some embodiments, the first switching command may include a pre-assigned authorization.

[0120] In some embodiments, the first switching command may include time-related parameters of the second satellite network.

[0121] In step S520, before performing satellite handover, a first synchronization is performed with the second satellite network based on the first parameters.

[0122] After receiving the first handover command, the terminal device usually does not need to perform satellite handover immediately. Therefore, the terminal device can prepare for satellite handover before performing it.

[0123] In some embodiments, the terminal device may determine the timing for satellite handover after receiving a first handover command. For example, the terminal device may determine whether immediate handover is necessary based on the results of measurements performed in the first satellite network. Alternatively, the terminal device may immediately activate a timing device after receiving the first handover command and determine when to perform satellite handover based on the timing device. Or, the terminal device may comprehensively consider both the measurement results and the timing device to determine when to perform satellite handover.

[0124] As one example, the measurement performed by the terminal device in the first satellite network may be a measurement performed by the terminal device on different reference signals of the first satellite network, and is not limited thereto.

[0125] As an example, the result of the measurement performed by the terminal device in the first satellite network can be referred to as the first measurement result of performing the measurement on the first satellite network. Exemplarily, the first measurement result may be the reference signal received power (RSRP), the reference signal received quality (RSRQ), or the reference signal strength indicator (RSSI), or multiple parameters mentioned above, without limitation here.

[0126] As an example, the timing device started by the terminal device after receiving the first handover command can be called a first timer. That is, the terminal device starts the first timer after receiving the first handover command and before performing the satellite handover. The first timer can be an existing timer or a newly configured timer. For example, the first timer can be a newly configured timer T. m .

[0127] As an example, the first timer can also be set and started in the first satellite network.

[0128] As one example, the duration of the timing device can be a fixed value configured by the higher layer, or it can be determined according to the service type of the terminal device, or it can be dynamically adjusted according to the communication environment, without any limitation here.

[0129] The first synchronization between the terminal device and the second satellite network refers to the terminal device performing initial synchronization with the second satellite network based on information provided by the first satellite network. Since this initial synchronization occurs before satellite handover, meaning that the terminal device has not yet established communication with the second satellite network, the terminal device is synchronizing with a virtual network; therefore, this initial synchronization can also be called virtual synchronization.

[0130] Because the terminal device cannot establish a connection with the second satellite network via the random access channel, the second satellite network cannot determine the terminal device's true TA value. To prevent the terminal device from missing uplink resources scheduled for it by the second satellite network, it is necessary to ensure synchronization between the terminal device, the first satellite network, and the second satellite network. Specifically, the terminal device and the first satellite network are already synchronized; therefore, the terminal device needs to establish synchronization with the second satellite network.

[0131] The first synchronization is used for time alignment between the terminal device and the second satellite network, and can also be called the first alignment.

[0132] In some embodiments, the first synchronization includes uplink synchronization and / or downlink synchronization. Both uplink and downlink synchronization refer to the time synchronization of transmissions between the terminal device and the second satellite network. For example, to maintain uplink and downlink synchronization with the second satellite network, the terminal device can adjust the timing of its initial uplink transmission based on received information to synchronize with the corresponding uplink transmission timing of the second satellite network.

[0133] In some embodiments, the duration of the first synchronization can be determined based on the required satellite handover time, or it can be determined based on the first timer described above. For example, when the duration of the first timer expires, the terminal device stops performing the first synchronization.

[0134] The first parameter for the terminal device to perform initial synchronization with the second satellite network can be determined based on various parameter information used for synchronization. It should be noted that the first parameter can be used solely for initial synchronization, or it can be used by the terminal device for satellite handover. Therefore, the first parameter can be used by the terminal device for initial synchronization and / or satellite handover.

[0135] In some embodiments, the first parameter can be determined based on the location information of the terminal device and / or the configuration information of the second satellite network used for satellite handover. In NTN, the first parameter can also be determined based on the ephemeris information of the second satellite. For example, the second satellite can be a network device corresponding to the second satellite network.

[0136] As one embodiment, the configuration information for satellite handover may include timing and synchronization parameters of the second satellite network. For example, the first parameter may include information such as scheduling timing offset (e.g., scheduling offset corresponding to the second satellite network), round-trip time between the communication device and the reference point, target base station associated with the second satellite network, common TA, and the effective duration of the common TA associated with it.

[0137] As an example, in an NTN cell, the first parameter also includes satellite ephemeris information, the effective duration of the ephemeris associated with the satellite ephemeris information, and other information. The indication of the satellite ephemeris information may include trajectory data associated with the satellite, such as satellite position and velocity as a function of time.

[0138] As an example, when the first parameter includes an indication of ephemeris information and an indication of public TA, the terminal device can calculate the total TA value based on these parameters provided by the network device to perform synchronization in the first synchronization and satellite handover.

[0139] As one example, the location information of the terminal device can be determined based on GNSS. For instance, in order to achieve synchronization before and during connection to the target NTN2 cell, the terminal device calculates the service link RTT based on its GNSS location and satellite ephemeris, and autonomously pre-compensates the RTT. TA The terminal device calculates the frequency Doppler shift by considering its location and satellite ephemeris information. If the terminal device lacks both valid location and valid satellite ephemeris information, it cannot communicate with the network until both are regained.

[0140] At least some of the parameters in the first parameter are determined based on information in the first handover command. In some embodiments, some parameters in the first parameter are determined based on the first handover command, and some information is already determined by the terminal device. For example, the location parameter of the terminal device in the first parameter may be known to the terminal device, and this information is not required in the first handover command. In some embodiments, all parameters in the first parameter are determined based on the first handover command. For example, the location information, configuration information, and ephemeris information used to determine the first parameter are all carried in the information in the first handover command. In this case, the location information of the terminal device may also be determined and notified by the first satellite network.

[0141] In some embodiments, when the first parameter is only used for the first synchronization, the information in the first parameter may only include a portion of the information in the first switching command.

[0142] In some embodiments, when the first parameter is used to perform the first synchronization and satellite handover, the information in the first parameter may include all information of the first handover hit.

[0143] In some embodiments, the terminal device can also perform first synchronization based on a first scheduling offset. Since the scheduling offsets of the first and second satellite networks are different, there will be a discrepancy in the scheduling time between uplink and downlink, and the terminal device cannot use the second scheduling offset corresponding to the first satellite network as a reference for first synchronization. Since the terminal device has not yet fully switched to the second satellite network, even if the first handover command includes a third scheduling offset corresponding to the second satellite network, the third scheduling offset cannot be used as a reference for first synchronization. The first scheduling offset proposed in this application embodiment can be determined based on the time parameters of the first and second satellite networks, which can be shared by the second satellite network and the terminal device. In some scenarios, the second satellite network can perform uplink resource scheduling based on the first scheduling offset, and the terminal device can also perform uplink transmission based on the first scheduling offset, thereby helping to avoid the terminal device missing uplink resources. Furthermore, first synchronization based on the scheduling offset can enable the terminal device to synchronize with the second satellite network while maintaining synchronization with the first satellite network.

[0144] To facilitate understanding, the following example uses the NTN system, combined with... Figure 6 An illustrative explanation is provided regarding the timing relationship between the first scheduling offset and other scheduling offsets. Figure 6 This diagram illustrates the timing relationship between the terminal device and the second satellite network during the first synchronization. It should be understood that this diagram is merely an example and not a limitation. Figure 6 The relationship between the various parameters and Figure 4 Similar, for the sake of brevity, in Figure 4 Terms already explained will not be repeated.

[0145] See Figure 6 Satellite 610 is the network equipment corresponding to the first satellite network, and satellite 650 is the network equipment corresponding to the second satellite network. Figure 6 It is known that satellite 610 and satellite 650 communicate with the same gateway 640, therefore the satellite handover performed by terminal device 620 is a handover between satellites with the same feeder link.

[0146] Figure 6 Reference point 630 and Figure 4 The reference point 430 is the same, and 601-604 are the same. Figure 4 401 to 404 are the same. 601 corresponds to the scheduling offset of satellite 610, i.e., the second scheduling offset. 605 corresponds to the scheduling offset between satellite 650 and terminal device 620, i.e., the first scheduling offset. 606 represents the common TA between satellite 650 and gateway 640, i.e., the common TA of the second satellite network. 607 corresponds to the scheduling offset of satellite 650, i.e., the third scheduling offset.

[0147] In some embodiments, after receiving a first handover command, the terminal device can determine the first scheduling offset based on a first parameter. For example, the time parameters of the first satellite network and the second satellite network in the first parameter can be used to determine the first scheduling offset. The time parameter may include a second parameter. The second parameter represents the time difference caused by the distance between the first satellite network and the second satellite network.

[0148] For example, the first scheduling offset can be determined based on the second scheduling offset and the second parameter. The scheduling offset is K as described above. offset The second scheduling offset corresponding to the first satellite network can be represented by K. offset1 This indicates that the third scheduling offset corresponding to the second satellite network can be represented by K. offset2 Indicated. Since the first scheduling offset is a parameter introduced for the first synchronization between the terminal equipment and the second satellite network, the first scheduling offset can be represented by K. offset2-temp express.

[0149] In some scenarios, the first scheduling offset K offset2-temp Determined according to the following formula:

[0150] K offset2-temp =K offset1 +(T2-T1);

[0151] Where T2 represents the reference time when the first satellite network switches to the second satellite network, and T1 represents the current reference time of the first satellite network.

[0152] Combination Figure 6 The transmission time for the first satellite network corresponding to satellite 610 is T1, and the transmission time for the second satellite network corresponding to satellite 620 is T2. First scheduling offset K offset2-temp The calculation based on the above formula takes into account the first scheduling offset and the transmission time difference between the two satellites.

[0153] The first synchronization can be used to determine a third parameter for the terminal device to perform satellite handover. In some embodiments, the third parameter may include one or more of the following parameters: the TA (Transmission Time) for the terminal device to perform satellite handover; the first time point at which the terminal device performs satellite handover; and the first time-domain location of the terminal device when performing uplink transmission to the second satellite network during satellite handover.

[0154] In some embodiments, the third parameter may also be determined based on one or more of the following information: a first scheduling offset; a third scheduling offset corresponding to the first satellite network; first timer parameters; and a first measurement result of the terminal device performing measurements on the first satellite network. The parameters of the first timer may include, for example, the start time point and duration range of the first timer.

[0155] In some embodiments, the TA (Transmission Timing) for satellite handover performed by the terminal device can be determined in multiple ways. During satellite handover, after receiving the TA command in slot n, the terminal device should adjust the uplink transmission timing (UL) according to the TA command in slot n+k+1. That is, the scheduling offset can be used to determine which uplink slot is used for its uplink transmission, while the TA is used to determine when to send uplink frames / slots. Therefore, it is necessary to determine the TA of the target satellite and the scheduling offsets for uplink and downlink scheduling separately.

[0156] As one embodiment, the first synchronization can determine the TA (Tracking Time) for the terminal device to perform satellite handover. Exemplarily, the terminal device can use a first scheduling offset as a reference for adjusting the TA to prepare for synchronization with the second satellite network. For example, after receiving a first handover command, the terminal device starts the first timer described above, and when the first timer starts counting, adjusts the TA according to the first scheduling offset for satellite handover. The TA determined based on the first scheduling offset can be the TA for the first synchronization or the TA for determining satellite handover.

[0157] As one embodiment, the TA (Tracking Time) for satellite handover performed by the terminal device can also be determined based on information in the first handover command. For example, the terminal device can calculate the total TA for satellite handover based on synchronization parameters received from the network device.

[0158] As an example, the time difference (TA) of the terminal device in the second satellite network can also be estimated based on the TA in the first satellite network. For example, the terminal device can obtain the transmission time difference (i.e., T1-T2) between the first and second satellite networks based on the first handover command. Assuming that the uplink propagation delay is the same as the downlink propagation delay, the terminal device can derive the virtual second satellite network or the TA2 of the second satellite network from the TA1 of the first satellite network using the following formula:

[0159] TA2 = TA1 – 2(T1 – T2).

[0160] Optionally, if no explicit command is displayed indicating the time of the network device corresponding to the second satellite network, the first satellite network to which the terminal device belongs can send a request message requesting the time from the second satellite network. The second satellite network can then send its own time in response. The second satellite network can also send other satellite parameters so that the first satellite network can identify the time of the second satellite network.

[0161] In some embodiments, the first time point at which the terminal device performs satellite handover can be determined in various ways. The first time point is the timing of the satellite handover as described above. As mentioned earlier, the first time point can be determined based on a first measurement result and a first timer. The start time of the first timer can be used to determine the time of receiving the first handover command. The duration range of the first timer can be used to limit the duration of handover preparation and / or first synchronization by the terminal device for satellite handover.

[0162] As an example, the first time point can also be determined based on the first synchronization. For instance, since the first timer is associated with the first synchronization, determining the first time point based on the first synchronization can be replaced by determining it based on the first timer. Furthermore, the relationship between the first scheduling offset and the third scheduling offset in the first synchronization can be used to determine the first time point.

[0163] As an example, if the first measurement result indicates that satellite handover should not be performed at the current time, the first time point can be determined automatically by the first timer and / or the terminal device. The terminal device determining the time point automatically means that it can determine the timing for satellite handover based on information such as the service type.

[0164] In some embodiments, the third parameter further includes a first time-domain location of the terminal device when performing an uplink transmission to the second satellite network during satellite handover. This uplink transmission may be the initial uplink transmission for the terminal device during satellite handover. By determining the first time-domain location, complete synchronization can be achieved before and during the terminal device's connection to the second satellite network. With the first satellite network, the second satellite network, and the terminal device synchronized, the initial uplink transmission can match the uplink grant scheduled by the second satellite network.

[0165] As an example, if the first measurement result indicates that a satellite handover should be performed at the current time, that is, if the first measurement result shows that a handover needs to be performed immediately, the terminal device needs to perform a satellite handover according to the first handover command. If the first measurement result indicates that a satellite handover should not be performed at the current time, that is, if the terminal device does not need to perform a handover immediately, the first time threshold can be determined according to the first timer, or determined by the terminal device itself.

[0166] As an example, the first measurement result indicates that when a satellite handover is performed at the current time, if the first scheduling offset is equal to the third scheduling offset, the second time domain position is determined based on the third scheduling offset; if the first scheduling offset is less than the third scheduling offset, the second time domain position is determined based on the first scheduling offset and the difference between the first scheduling offset and the third scheduling offset; if the first scheduling offset is greater than the third scheduling offset, the second time domain position is determined based on the first scheduling offset.

[0167] For ease of understanding, the following is based on the first scheduling offset K. offset2-temp Offset K from the third scheduling offset2 The three size relationships are explained in detail in the embodiments for determining the first time threshold or the first time point.

[0168] Example 1: K offset2-temp =K offset2 .

[0169] Regardless of whether the first timer expires, if the first measurement result measured by the terminal device in the first satellite network needs to be switched immediately, the terminal device will start a RACH-free handover and simultaneously start data transmission in the second satellite network.

[0170] If the first measurement result does not require immediate switching, the terminal device will initiate a RACH-free handover when the first timer duration expires, simultaneously commencing data transmission to the second satellite network. If the first timer duration has not expired, the terminal device can continue using the first satellite network until the timer duration expires.

[0171] Example 2: K offset2-temp <K offset2 .

[0172] If the terminal device needs to immediately switch over the first measurement result measured in the first satellite network, regardless of whether the first timer duration has been reached, the terminal device begins a RACH-free handover. If the terminal device receives a TA command in time slot n of the first satellite network, in order to maintain uplink and downlink synchronization with the second satellite network, the corresponding uplink transmission timing in the second satellite network is adjusted to start from uplink time slot n+k+1+2. μ ·(K offset2-temp )+2 μ ·(K offset2 -K offset2-temp Transmission begins. Here, μ is determined based on the subcarrier spacing, and k is determined based on the transmission response duration and the number of time slots. It should be understood that the value of k can be determined with reference to the relevant 3GPP specifications. In some scenarios, k can also be determined based on the PUSCH transmission timing, i.e., the timing related to k2. The PUSCH transmission timing may include the timing of the PUSCH transmission channel state information (CSI) report.

[0173] If the first measurement result does not require immediate switching, the terminal device will initiate a RACH-free handover when the first timer duration expires, simultaneously commencing data transmission to the second satellite network. If the first timer duration has not expired, the terminal device can continue using the first satellite network until the timer duration expires.

[0174] Example 3: K offset2-temp >K offset2 .

[0175] If the terminal device needs to immediately switch over the first measurement result measured in the first satellite network, after the network device issues the first handover command, the terminal device begins a RACH-free handover regardless of whether the first timer duration has been reached. If the terminal device receives a TA command in time slot n of the first satellite network, in order to maintain uplink and downlink synchronization with the second satellite network, the corresponding uplink transmission timing in the second satellite network is adjusted to start from uplink time slot n+k+1+2. μ ·(K offset2-temp Transmission begins.

[0176] If the initial measurement result does not require immediate handover, even if the network side issues the first handover command, the terminal device can decide whether to handover immediately or wait. Alternatively, the terminal device can initiate a RACH-free handover when the first timer duration expires, simultaneously starting data transmission to the second satellite network. If the first timer duration has not expired, the terminal device can continue communicating with the first satellite network, temporarily suspending the handover. The terminal device will only initiate the handover when the first timer duration expires.

[0177] Optionally, the terminal device can also decide to switch if the first timer duration has not been reached. The terminal device can wait for K... offset2-temp -K offset2 During the time slot, it continuously sends reference signals to the second satellite network or repeats the previous data packet to wait for uplink and downlink synchronization to be completed.

[0178] Depend on Figure 5 It is understood that through the first synchronization performed before satellite handover, the terminal device can synchronize with the virtual second satellite network based on the first scheduling offset. The second satellite network can also determine the first scheduling offset. When the second satellite network schedules uplink resources based on the first scheduling offset, the terminal device that synchronizes based on the first scheduling offset can avoid missing the uplink scheduling resources configured for the terminal device by the second satellite network. Through the first synchronization, synchronization between the first satellite network, the second satellite network, and the terminal device can also be achieved, thereby realizing RACH-free satellite handover.

[0179] Following the initial synchronization, the first satellite network, the second satellite network, and the terminal device achieve synchronization, allowing the terminal device to perform satellite handover. For example, when the satellite handover is a non-RACH handover, the terminal device can send an initial uplink transmission to the second satellite network using available uplink grants (RRC, MAC PHY) and receive acknowledgment information from the second satellite network.

[0180] In some embodiments, when the first satellite network, the second satellite network, and the terminal device are synchronized, the subframe boundaries between the first satellite network and the second satellite network are aligned. At a time agreed upon by both parties (e.g., SFN), the terminal device switches from the first satellite network to the second satellite network.

[0181] In some embodiments, the first satellite network, the second satellite network, and the terminal device can synchronize via RRC signaling. Once synchronization is complete, the first satellite network stops downlink transmission to the terminal device, the second satellite network provides uplink authorization to the terminal device, and the terminal device establishes communication with the second satellite network.

[0182] In some embodiments, when the terminal device switches to a second satellite network scenario, the T430 starts timing. The T430 can be used to control uplink synchronization (UL synchronization) and uplink synchronization loss (UL synchronization lost). This is also specifically reflected at the MAC layer.

[0183] For example, when the terminal device is in uplink synchronization, normal uplink transmission can be performed. If the RRC layer notifies the MAC layer that the terminal device is currently out of uplink synchronization due to a T430 timeout, the MAC layer must stop all hybrid automatic repeat reQuest (HARQ) buffers and cannot perform any uplink transmission.

[0184] In some embodiments, satellite handover by the terminal device may fail. For example, if the first handover command is a RACH-free handover, the handover will fail if the conditions for a RACH-free handover cannot be met. A RACH-free handover failure means that the terminal device cannot successfully access the second satellite network using the RACH-free procedure; for example, the second satellite network cannot successfully decode the initial uplink transmission from the terminal device, or the terminal device does not receive confirmation of handover completion from the network before T304 expires. After T304 expires, the terminal device will perform a reconstruction procedure.

[0185] If the terminal device continuously performs a RACH-less handover, it may never succeed. To address this issue, the terminal device can support a rollback function. This rollback function allows the terminal device to roll back from a RACH-less handover to a RACH-based handover. For example, if a RACH-less handover is the first handover and a RACH-based handover is the second handover, the terminal device can support rolling back from the first handover to the second handover. Alternatively, the terminal device can also perform a rollback from the first handover to the second handover based on instructions from the network device.

[0186] In some scenarios, a RACH-less handover failure at the terminal device may only result in a data transmission failure. If a fallback to RACH-based handover is implemented immediately upon failure, it could still lead to significant handover latency. To address this issue, the terminal device can only fall back to RACH-based handover after multiple RACH-less handover failures.

[0187] In some embodiments, the terminal device can determine the number of first handover failures by setting a first threshold. For example, the number of times a first handover needs to be performed can be set as the first threshold. If the number of first handover failures performed by the terminal device exceeds the first threshold, it falls back to a second handover.

[0188] As one embodiment, the terminal device can determine the number of RACH-less handover failures by setting a first threshold. Exemplarily, the number of RACH-less handover failures can be set as a threshold (i.e., the first threshold). If the number of RACH-less handover failures by the terminal device exceeds the first threshold, it falls back to RACH-based handover.

[0189] In some scenarios, no-RACH handover can be combined with a constant PCI. When the PCI remains constant, network devices can implicitly or explicitly indicate the N of the second satellite network to the terminal devices. TA If a RACH-free handover is combined with a PCI-unchanged scenario, the terminal device only needs to perform a downlink synchronization process. This simplifies the entire RACH-free handover process between satellites with the same gateway / base station, and helps reduce latency in PCI-unchanged scenarios.

[0190] In some scenarios, the first satellite network may also use other signaling methods instead of handover commands to indicate a RACH-free handover.

[0191] The preceding text introduced the problems and solutions related to RACH-less handover in the NTN system based on embodiments of this application. For ease of understanding, the following section will combine... Figure 7 and Figure 8 Examples of embodiments of this application are provided for illustration.

[0192] Figure 7 Taking NTN as an example, the entire synchronization process of the terminal device in synchronizing with the first satellite network (source NTN1) and the second satellite network (target NTN2) is introduced.

[0193] See Figure 7 In step S701, the terminal device synchronizes with NTN1 in the source NTN1. For example... Figure 7 As shown, the terminal device and the source NTN1 achieve synchronization at synchronization point 1.

[0194] In steps S702 and S703, as the satellite moves or the location of the terminal device changes, the TA1 of the terminal device in the source NTN1 changes. Regardless of whether it's a quasi-fixed or quasi-mobile cell, the first satellite network continuously notifies the terminal device to adjust TA1 by sending TA commands. When the terminal device receives a TA command... p1 When there is a deviation, the terminal device will adjust the timing in the next time slot or several time slots with TA1 = 2T. P1 send.

[0195] In source NTN1, the TA command for adjusting the TA after the terminal device enters the connected state is issued to the terminal device by the network side via TimingAdvance Command MAC CE. The TA index corresponding to the TA command represents the current NTN1. TA The adjustments to be made. In other words, the network will send MAC CE-related TA commands to the terminal devices to adjust the transmission TA.

[0196] In step S704, the terminal device synchronizes with the source NTN1 again.

[0197] In step S705, the terminal device receives a no-RACH handover command. When the timer of the source NTN1 or the timer T of the terminal device... m When the first timer starts, the terminal device prepares for switching. During timer T... m Within this timeframe, initial uplink and downlink alignment with target NTN2 begins, i.e., the first synchronization. The terminal device performs initial alignment based on its own location and the satellite parameters of target NTN2 received from source NTN1. At this point, the terminal device has not yet switched to target NTN2; relative to the terminal device, the virtual reference time point (synchronization point 2) of target NTN2 is... Figure 7 The dashed line in the middle.

[0198] In step S706, the terminal device has not yet received information from NTN2. Based on the time difference between the source NTN1 and the target NTN2, a temporary K can be obtained. offset2-temp The terminal devices are in the same location, according to T p1 The time difference between the source NTN1 and the target NTN2 can be used to estimate T. p1,2 The value of TA. 1,2 =2T p1,2 The terminal device will be in T m Adjust your TA within the timer. For example, TA 1,2 =TA1–2(T1–T2).

[0199] In step S707, the terminal device in timer T m It is synchronized with the virtual NTN2.

[0200] In step S708, the terminal device starts timer T304 and sends an initial uplink transmission including an RRCReconfigurationComplete message using available uplink grants (RRC, MAC, PHY). The terminal device performs uplink and downlink synchronization with the actual target NTN2.

[0201] In step S709, the target NTN2 confirms that the RACH-free handover has been completed. Timer T304 is stopped.

[0202] Steps S710 and S711 are the same as steps S701 and S702, and the terminal device successfully communicates with NTN2.

[0203] like Figure 7 As shown, the terminal equipment ensures uplink and downlink time synchronization before, during, and after the handover process.

[0204] Figure 8 This introduction is based on the perspective of the interaction between terminal devices and the first and second satellite networks.

[0205] See Figure 8 In step S810, the terminal device receives a RACH-free handover command sent by the first satellite network, i.e., the first handover command.

[0206] In step S820, the terminal device or the first satellite network starts the first timer.

[0207] In step S830, within the first timer, the terminal device initially aligns with the uplink and downlink of the second satellite network (first synchronization).

[0208] In step S840, the terminal device starts timer T304.

[0209] In step S850, the terminal device performs uplink and downlink synchronization and starts timer T430.

[0210] In step S860, the terminal device sends an initial uplink transmission. This initial uplink transmission is sent using available uplink grants (RRC, MAC, PHY). The initial uplink transmission includes the transmission of an RRCReconfigurationComplete message.

[0211] In step S870, the terminal device receives confirmation from the network (NW) that the handover without RACH has been completed.

[0212] In step S880, the terminal device stops timer T304.

[0213] The above text combined Figures 1 to 8The method embodiments of this application are described in detail below. Figures 9 to 12 The present application provides a detailed description of the apparatus embodiments. It should be understood that the descriptions of the apparatus embodiments correspond to the descriptions of the method embodiments; therefore, any parts not described in detail can be found in the foregoing method embodiments.

[0214] Figure 9 This is a schematic block diagram of a terminal device according to an embodiment of this application. The terminal device 900 can be any of the terminal devices described above. Figure 9 The terminal device 900 shown includes a receiving unit 910 and an execution unit 920.

[0215] The receiving unit 910 can be used to receive a first handover command, which instructs the terminal device to perform a satellite handover from the first satellite network coverage area to the second satellite network coverage area.

[0216] The execution unit 920 can be used to perform a first synchronization with the second satellite network according to a first parameter before performing a satellite handover, wherein at least some of the first parameters are determined according to information in the first handover command.

[0217] Optionally, the terminal device 900 further includes a first determining unit, which can be used to determine a first scheduling offset based on a first parameter after receiving the first handover command and before performing satellite handover, the first scheduling offset being used for first synchronization.

[0218] Optionally, the first scheduling offset is determined based on the second scheduling offset and the second parameter, wherein the second scheduling offset corresponds to the first satellite network, and the second parameter is the time difference caused by the distance between the first satellite network and the second satellite network.

[0219] Optionally, the first scheduling offset is determined according to the following formula:

[0220] K offset2-temp =K offset1 +(T2-T1);

[0221] Among them, K offset2-temp K represents the first scheduling frequency shift. offset1 T1 represents the second scheduling offset, T2 represents the reference time when the first satellite network switches to the second satellite network, and T1 represents the current reference time of the first satellite network.

[0222] Optionally, the execution unit 920 is further configured to start a first timer after receiving the first handover command and before performing satellite handover, the first timer being used to determine the execution duration of the first synchronization.

[0223] Optionally, the third parameter includes one or more of the following parameters: the TA at which the terminal device performs satellite handover; the first time point at which the terminal device performs satellite handover; and the first time domain position at which the terminal device transmits uplink data to the second satellite network during satellite handover.

[0224] Optionally, the first synchronization is used to determine the third parameter for the terminal device to perform satellite handover. The third parameter is determined based on one or more of the following information: a first scheduling offset; a third scheduling offset corresponding to the second satellite network; a first timer parameter; and a first measurement result of the terminal device performing a measurement on the first satellite network.

[0225] Optionally, the first measurement result indicates that satellite switching should be performed at the current time. The terminal device 900 also includes a second determining unit, which can be used to determine the first time domain position based on the third scheduling offset if the first scheduling offset is equal to the third scheduling offset; determine the first time domain position based on the first scheduling offset and the difference between the first scheduling offset and the third scheduling offset if the first scheduling offset is less than the third scheduling offset; and determine the first time domain position based on the first scheduling offset if the first scheduling offset is greater than the third scheduling offset.

[0226] Optionally, the first time-domain position is determined based on the second time-domain position of the terminal device receiving the TA command. When the second time-domain position is time slot n, if the first scheduling offset K offset2-temp Less than the third scheduling offset value K offset2 The first time domain position is time slot n+k+1+2 μ ·(K offset2-temp )+2 μ ·(K offset2 -K offset2-temp If the first scheduling offset K offset2-temp Greater than the third scheduling offset value K offset2 The first time domain position is time slot n+k+1+2 μ ·(K offset2-temp ); where μ is determined based on the subcarrier spacing, and k is determined based on the transmission response duration and the number of time slots.

[0227] Optionally, the first measurement result indicates that satellite switching will not be performed at the current time, and the first time point is determined automatically based on the first timer and / or the terminal equipment.

[0228] Optionally, the first parameter is determined based on at least one of the following: the location information of the terminal device, the configuration information of the second satellite network for satellite handover, and the ephemeris information of the second satellite.

[0229] Optionally, the first switching command is a no-RACH switching command.

[0230] Optionally, the handover command indicates a first handover, and the terminal device supports rolling back from the first handover to a second handover, which is based on RACH.

[0231] Optionally, the execution unit 920 is further configured to perform a second switch if the number of failures of the first switch is greater than a first threshold.

[0232] Optionally, the first synchronization includes uplink synchronization and / or downlink synchronization.

[0233] Figure 10 This is a schematic block diagram of a network device according to an embodiment of this application. The network device 1000 can be any of the network devices corresponding to the first satellite network described above. Figure 10 The network device 1000 shown includes a transmitting unit 1010.

[0234] The sending unit 1010 can be used to send a first handover command to a terminal device. The first handover command is used to instruct the terminal device to perform a satellite handover from the coverage area of ​​the first satellite network to the coverage area of ​​the second satellite network. The first handover command is used to determine at least some of the parameters in the first parameters. The first parameters are used for the terminal device to perform a first synchronization with the second satellite network before performing the satellite handover.

[0235] Optionally, after sending the first handover command and before the terminal device performs satellite handover, the network device 1000 further includes an execution unit that can be used to start a first timer, which is used to determine the execution duration of the first synchronization.

[0236] Optionally, the first parameter is determined based on at least one of the following: the location information of the terminal device, the configuration information of the second satellite network for satellite handover, and the ephemeris information of the second satellite.

[0237] Optionally, the first switching command is a no-RACH switching command.

[0238] Optionally, the handover command indicates a first handover, and network device 1000 supports rolling back from the first handover to a second handover, which is based on RACH.

[0239] Optionally, if the number of failures of the first handover exceeds the first threshold, a second handover is performed.

[0240] Optionally, the first synchronization includes uplink synchronization and / or downlink synchronization.

[0241] Figure 11 This is a schematic block diagram of another network device according to an embodiment of this application. The network device 1100 can be any of the network devices corresponding to the second satellite network described above. Figure 11The network device 1100 shown includes a receiving unit 1110 and a transmitting unit 1120.

[0242] The receiving unit 1110 can be used to receive a handover request sent by the first satellite network;

[0243] The transmitting unit 1120 can be used to send handover response information to the first satellite network. The handover response information is used by the first satellite network to determine a first handover command. The first handover command is used to instruct the terminal device to perform a satellite handover from the coverage area of ​​the first satellite network to the coverage area of ​​the second satellite network. The first handover command is used to determine at least some of the parameters in the first parameters. The first parameters are used by the terminal device to perform a first synchronization with the second satellite network before performing the satellite handover.

[0244] Optionally, the first parameter is determined based on at least one of the following: the location information of the terminal device, the configuration information of the second satellite network for satellite handover, and the ephemeris information of the second satellite.

[0245] Optionally, the first switching command is a no-RACH switching command.

[0246] Optionally, the handover command indicates a first handover, and network device 1100 supports a fallback from the first handover to a second handover, which is based on RACH.

[0247] Optionally, if the number of failures of the first handover exceeds the first threshold, a second handover is performed.

[0248] Optionally, the first synchronization includes uplink synchronization and / or downlink synchronization.

[0249] Figure 12 The diagram shown is a schematic structural diagram of a communication device according to an embodiment of this application. Figure 12 The dashed lines indicate that the unit or module is optional. The device 1200 can be used to implement the methods described in the above method embodiments. The device 1200 can be a chip, a terminal device, or a network device.

[0250] Apparatus 1200 may include one or more processors 1210. The processor 1210 may support apparatus 1200 in implementing the methods described in the preceding method embodiments. The processor 1210 may be a general-purpose processor or a special-purpose processor. For example, the processor may be a central processing unit (CPU). Alternatively, the processor may be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or any conventional processor.

[0251] The apparatus 1200 may further include one or more memories 1220. The memories 1220 store a program that can be executed by the processor 1210, causing the processor 1210 to perform the methods described in the preceding method embodiments. The memories 1220 may be independent of the processor 1210 or integrated within the processor 1210.

[0252] The device 1200 may also include a transceiver 1230. The processor 1210 can communicate with other devices or chips via the transceiver 1230. For example, the processor 1210 can send and receive data with other devices or chips via the transceiver 1230.

[0253] This application also provides a computer-readable storage medium for storing a program. This computer-readable storage medium can be applied to a terminal device or network device provided in this application embodiment, and the program causes a computer to execute the methods performed by the terminal device or network device in the various embodiments of this application.

[0254] The computer-readable storage medium can be any available medium that a computer can read, or a data storage device such as a server or data center that integrates one or more available media. The available medium can be magnetic media (e.g., floppy disks, hard disks, magnetic tapes), optical media (e.g., digital video discs, DVDs), or semiconductor media (e.g., solid-state disks, SSDs), etc.

[0255] This application also provides a computer program product. The computer program product includes a program. This computer program product can be applied to a terminal device or network device provided in this application embodiment, and the program causes a computer to execute the methods performed by the terminal or network device in various embodiments of this application.

[0256] In the above embodiments, implementation can be achieved, in whole or in part, through software, hardware, firmware, or any combination thereof. When implemented using software, it can be implemented, in whole or in part, as a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of this application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another via wired (e.g., coaxial cable, fiber optic, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means.

[0257] This application also provides a computer program. This computer program can be applied to a terminal device or network device provided in this application, and the computer program causes the computer to execute the methods performed by the terminal or network device in various embodiments of this application.

[0258] In this application, the terms "system" and "network" are used interchangeably. Furthermore, the terminology used in this application is only for explaining specific embodiments of the application and is not intended to limit the application. The terms "first," "second," "third," and "fourth," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish different objects, not to describe a specific order. In addition, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion.

[0259] In the embodiments of this application, the term "instruction" can be a direct instruction, an indirect instruction, or an indication of a relationship. For example, A instructing B can mean that A directly instructs B, such as B being able to obtain information through A; it can also mean that A indirectly instructs B, such as A instructing C, so B can obtain information through C; or it can mean that there is a relationship between A and B.

[0260] In the embodiments of this application, the term "correspondence" may indicate a direct or indirect correspondence between two things, or an association between two things, or a relationship such as instruction and being instructed, configuration and being configured.

[0261] In the embodiments of this application, "predefined" or "preconfigured" can be implemented by pre-storing corresponding codes, tables, or other means that can be used to indicate relevant information in the device (e.g., including terminal devices and network devices). This application does not limit the specific implementation method. For example, predefined can refer to what is defined in the protocol.

[0262] In the embodiments of this application, the term "protocol" may refer to standard protocols in the field of communications, such as LTE protocols, NR protocols, and related protocols applied in future communication systems. This application does not limit the scope of these protocols.

[0263] In the embodiments of this application, determining B based on A does not mean determining B solely based on A; B can also be determined based on A and / or other information.

[0264] In the embodiments of this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0265] In the various embodiments of this application, the order of the above-mentioned processes does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0266] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0267] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0268] In addition, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0269] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for satellite handover in non-terrestrial networks, characterized in that, include: Receive a first handover command, the first handover command being used to instruct the terminal device to perform a satellite handover from a first satellite network coverage area to a second satellite network coverage area; Before performing the satellite handover, a first synchronization is performed with the second satellite network according to a first parameter, wherein at least some of the first parameters are determined based on information in the first handover command; Wherein, the first synchronization is used to determine the third parameter for the terminal device to perform the satellite handover, the third parameter including: the first time domain position of the terminal device when performing the satellite handover and transmitting uplink to the second satellite network; The third parameter is determined based on the following information: a first scheduling offset used for the first synchronization; a third scheduling offset corresponding to the second satellite network; and a first measurement result of the terminal device performing a measurement on the first satellite network. The first measurement result indicates that the satellite switch should be performed at the current time. The method further includes: if the first scheduling offset is equal to the third scheduling offset, determining the first time domain position based on the third scheduling offset; if the first scheduling offset is less than the third scheduling offset, determining the first time domain position based on the first scheduling offset and the difference between the first scheduling offset and the third scheduling offset; if the first scheduling offset is greater than the third scheduling offset, determining the first time domain position based on the first scheduling offset.

2. The method according to claim 1, characterized in that, After receiving the first handover command but before performing the satellite handover, the method further includes: The first scheduling offset is determined based on the first parameter.

3. The method according to claim 2, characterized in that, The first scheduling offset is determined based on the second scheduling offset and the second parameter. The second scheduling offset corresponds to the first satellite network, and the second parameter is the time difference caused by the distance between the first satellite network and the second satellite network.

4. The method according to claim 3, characterized in that, The first scheduling offset is determined according to the following formula: K offset2-temp =K offset1 +(T2-T1); Among them, K offset2-temp K represents the first scheduling offset. offset1 T1 represents the second scheduling offset, T2 represents the reference time when the first satellite network is operating to the second satellite network, and T1 represents the current reference time of the first satellite network.

5. The method according to any one of claims 1-4, characterized in that, After receiving the first handover command but before performing the satellite handover, the method further includes: Start the first timer, which is used to determine the execution duration of the first synchronization.

6. The method according to any one of claims 1-4, characterized in that, The third parameter also includes one or more of the following parameters: The terminal device performs the TA for the satellite handover; The terminal device executes the first time point of the satellite handover.

7. The method according to claim 6, characterized in that, The third parameter is also determined based on the first timer parameter.

8. The method according to claim 1, characterized in that, The first time-domain position is determined based on the second time-domain position of the terminal device receiving the TA command, where the second time-domain position is time slot n. If the first scheduling offset K offset2-temp Less than the third scheduling offset value K offset2 The first time domain position is time slot n+k+1+2 μ ∙(K offset2-temp )+2 μ ∙(K offset2 -K offset2-temp ); If the first scheduling offset K offset2-temp Greater than the third scheduling offset value K offset2 The first time domain position is time slot n+k+1+2 μ ∙(K offset2-temp ); Where μ is determined by the subcarrier spacing, and k is determined by the transmission response duration and the number of time slots.

9. The method according to claim 7, characterized in that, The first measurement result indicates that the satellite switch will not be performed at the current time, and the first time point is determined automatically based on the first timer and / or the terminal device.

10. The method according to any one of claims 1-4, characterized in that, The first parameter is determined based on at least one of the following: the location information of the terminal device, the configuration information of the second satellite network for satellite switching, and the ephemeris information of the second satellite.

11. The method according to any one of claims 1-4, characterized in that, The first handover command is a RACH handover command without a random access channel.

12. The method according to claim 11, characterized in that, The first handover command indicates a first handover, and the terminal device supports rolling back from the first handover to a second handover, which is based on RACH.

13. The method according to claim 12, characterized in that, The method further includes: If the number of failures of the first switching exceeds the first threshold, the second switching is performed.

14. The method according to any one of claims 1-4, characterized in that, The first synchronization includes uplink synchronization and / or downlink synchronization.

15. A method for satellite handover in non-terrestrial networks, characterized in that, include: Send a first handover command to the terminal device, the first handover command being used to instruct the terminal device to perform a satellite handover from the first satellite network coverage area to the second satellite network coverage area; Wherein, the first handover command is used to determine at least some of the parameters in the first parameters, and the first parameters are used for the terminal device to perform a first synchronization with the second satellite network before performing the satellite handover; The first synchronization is used to determine a third parameter for the terminal device to perform the satellite handover, the third parameter including: the first time domain position of the terminal device when performing the satellite handover and transmitting uplink to the second satellite network; The third parameter is determined based on the following information: a first scheduling offset used for the first synchronization; a third scheduling offset corresponding to the second satellite network; and a first measurement result of the terminal device performing a measurement on the first satellite network. The first measurement result indicates that the satellite switch should be performed at the current time. If the first scheduling offset is equal to the third scheduling offset, the first time domain position is determined according to the third scheduling offset. If the first scheduling offset is less than the third scheduling offset, the first time domain position is determined according to the first scheduling offset and the difference between the first scheduling offset and the third scheduling offset. If the first scheduling offset is greater than the third scheduling offset, the first time domain position is determined according to the first scheduling offset.

16. The method according to claim 15, characterized in that, After sending the first handover command and before the terminal device performs the satellite handover, the method further includes: Start the first timer, which is used to determine the execution duration of the first synchronization.

17. The method according to claim 15 or 16, characterized in that, The first parameter is determined based on at least one of the following: the location information of the terminal device, the configuration information of the second satellite network for satellite switching, and the ephemeris information of the second satellite.

18. The method according to claim 15 or 16, characterized in that, The first handover command is a RACH handover command without a random access channel.

19. A method for satellite handover in non-terrestrial networks, characterized in that, include: Receive a handover request sent by the first satellite network; Send handover response information to the first satellite network. The handover response information is used by the first satellite network to determine a first handover command. The first handover command is used to instruct the terminal device to perform a satellite handover from the coverage area of ​​the first satellite network to the coverage area of ​​the second satellite network. Wherein, the first handover command is used to determine at least some of the parameters in the first parameters, and the first parameters are used for the terminal device to perform a first synchronization with the second satellite network before performing the satellite handover; The first synchronization is used to determine a third parameter for the terminal device to perform the satellite handover, the third parameter including: the first time domain position of the terminal device when performing the satellite handover and transmitting uplink to the second satellite network; The third parameter is determined based on the following information: a first scheduling offset used for the first synchronization; a third scheduling offset corresponding to the second satellite network; and a first measurement result of the terminal device performing a measurement on the first satellite network. The first measurement result indicates that the satellite switch should be performed at the current time. If the first scheduling offset is equal to the third scheduling offset, the first time domain position is determined according to the third scheduling offset. If the first scheduling offset is less than the third scheduling offset, the first time domain position is determined according to the first scheduling offset and the difference between the first scheduling offset and the third scheduling offset. If the first scheduling offset is greater than the third scheduling offset, the first time domain position is determined according to the first scheduling offset.

20. The method according to claim 19, characterized in that, The first parameter is determined based on at least one of the following: the location information of the terminal device, the configuration information of the second satellite network for satellite switching, and the ephemeris information of the second satellite.

21. The method according to claim 19 or 20, characterized in that, The first handover command is a RACH handover command without a random access channel.

22. A terminal device, characterized in that, include: A receiving unit is configured to receive a first handover command, wherein the first handover command is configured to instruct the terminal device to perform a satellite handover from a first satellite network coverage area to a second satellite network coverage area. An execution unit is configured to perform a first synchronization with the second satellite network according to a first parameter before performing the satellite handover, wherein at least some of the first parameters are determined based on information in the first handover command; Wherein, the first synchronization is used to determine the third parameter for the terminal device to perform the satellite handover, the third parameter including: the first time domain position of the terminal device when performing the satellite handover and transmitting uplink to the second satellite network; The third parameter is determined based on the following information: a first scheduling offset used for the first synchronization; a third scheduling offset corresponding to the second satellite network; and a first measurement result of the terminal device performing a measurement on the first satellite network. The first measurement result indicates that the satellite handover should be performed at the current time, and the terminal device further includes: The second determining unit is configured to: determine the first time-domain position based on the third scheduling offset if the first scheduling offset is equal to the third scheduling offset; determine the first time-domain position based on the first scheduling offset and the difference between the first scheduling offset and the third scheduling offset if the first scheduling offset is less than the third scheduling offset; and determine the first time-domain position based on the first scheduling offset if the first scheduling offset is greater than the third scheduling offset.

23. The terminal device according to claim 22, characterized in that, The terminal device also includes: The first determining unit is configured to determine the first scheduling offset based on the first parameter after receiving the first switching command and before executing the satellite switching.

24. The terminal device according to claim 23, characterized in that, The first scheduling offset is determined based on the second scheduling offset and the second parameter. The second scheduling offset corresponds to the first satellite network, and the second parameter is the time difference caused by the distance between the first satellite network and the second satellite network.

25. The terminal device according to claim 24, characterized in that, The first scheduling offset is determined according to the following formula: K offset2-temp =K offset1 +(T2-T1); Among them, K offset2-temp K represents the first scheduling offset. offset1 T1 represents the second scheduling offset, T2 represents the reference time when the first satellite network is operating to the second satellite network, and T1 represents the current reference time of the first satellite network.

26. The terminal device according to any one of claims 22-25, characterized in that, The execution unit is further configured to start a first timer after receiving the first switching command and before executing the satellite switching, the first timer being configured to determine the execution duration of the first synchronization.

27. The terminal device according to any one of claims 22-25, characterized in that, The third parameter also includes one or more of the following parameters: The terminal device performs the TA for the satellite handover; The terminal device executes the first time point of the satellite handover.

28. The terminal device according to claim 27, characterized in that, The third parameter is also determined based on the first timer parameter.

29. The terminal device according to claim 22, characterized in that, The first time-domain position is determined based on the second time-domain position of the terminal device receiving the TA command, where the second time-domain position is time slot n. If the first scheduling offset K offset2-temp Less than the third scheduling offset value K offset2 The first time domain position is time slot n+k+1+2 μ ∙(K offset2-temp )+2 μ ∙(K offset2 -K offset2-temp ); If the first scheduling offset K offset2-temp Greater than the third scheduling offset value K offset2 The first time domain position is time slot n+k+1+2 μ ∙(K offset2-temp ); Where μ is determined by the subcarrier spacing, and k is determined by the transmission response duration and the number of time slots.

30. The terminal device according to claim 28, characterized in that, The first measurement result indicates that the satellite switch will not be performed at the current time, and the first time point is determined automatically based on the first timer and / or the terminal device.

31. The terminal device according to any one of claims 22-25, characterized in that, The first parameter is determined based on at least one of the following: the location information of the terminal device, the configuration information of the second satellite network for satellite switching, and the ephemeris information of the second satellite.

32. The terminal device according to any one of claims 22-25, characterized in that, The first handover command is a RACH handover command without a random access channel.

33. The terminal device according to claim 32, characterized in that, The first handover command indicates a first handover, and the terminal device supports rolling back from the first handover to a second handover, which is based on RACH.

34. The terminal device according to claim 33, characterized in that, The execution unit is further configured to perform the second switch if the number of failures of the first switch is greater than a first threshold.

35. The terminal device according to any one of claims 22-25, characterized in that, The first synchronization includes uplink synchronization and / or downlink synchronization.

36. A network device, characterized in that, The network device corresponds to the first satellite network, and the network device includes: The sending unit is configured to send a first handover command to the terminal device, the first handover command being configured to instruct the terminal device to perform a satellite handover from the first satellite network coverage area to the second satellite network coverage area; Wherein, the first handover command is used to determine at least some of the parameters in the first parameters, and the first parameters are used for the terminal device to perform a first synchronization with the second satellite network before performing the satellite handover; The first synchronization is used to determine a third parameter for the terminal device to perform the satellite handover, the third parameter including: the first time domain position of the terminal device when performing the satellite handover and transmitting uplink to the second satellite network; The third parameter is determined based on the following information: a first scheduling offset used for the first synchronization; a third scheduling offset corresponding to the second satellite network; and a first measurement result of the terminal device performing a measurement on the first satellite network. The first measurement result indicates that the satellite switch should be performed at the current time. If the first scheduling offset is equal to the third scheduling offset, the first time domain position is determined according to the third scheduling offset. If the first scheduling offset is less than the third scheduling offset, the first time domain position is determined according to the first scheduling offset and the difference between the first scheduling offset and the third scheduling offset. If the first scheduling offset is greater than the third scheduling offset, the first time domain position is determined according to the first scheduling offset.

37. The network device according to claim 36, characterized in that, After sending the first handover command and before the terminal device performs the satellite handover, the network device further includes: An execution unit is used to start a first timer, which is used to determine the execution duration of the first synchronization.

38. The network device according to claim 36 or 37, characterized in that, The first parameter is determined based on at least one of the following: the location information of the terminal device, the configuration information of the second satellite network for satellite switching, and the ephemeris information of the second satellite.

39. The network device according to claim 36 or 37, characterized in that, The first handover command is a RACH handover command without a random access channel.

40. A network device, characterized in that, The network device corresponds to the second satellite network, and the network device includes: The receiving unit is used to receive the handover request sent by the first satellite network; A sending unit is configured to send handover response information to the first satellite network. The handover response information is used by the first satellite network to determine a first handover command. The first handover command is used to instruct the terminal device to perform a satellite handover from the coverage area of ​​the first satellite network to the coverage area of ​​the second satellite network. Wherein, the first handover command is used to determine at least some of the parameters in the first parameters, and the first parameters are used for the terminal device to perform a first synchronization with the second satellite network before performing the satellite handover; The first synchronization is used to determine a third parameter for the terminal device to perform the satellite handover, the third parameter including: the first time domain position of the terminal device when performing the satellite handover and transmitting uplink to the second satellite network; The third parameter is determined based on the following information: a first scheduling offset used for the first synchronization; a third scheduling offset corresponding to the second satellite network; and a first measurement result of the terminal device performing a measurement on the first satellite network. The first measurement result indicates that the satellite switch should be performed at the current time. If the first scheduling offset is equal to the third scheduling offset, the first time domain position is determined according to the third scheduling offset. If the first scheduling offset is less than the third scheduling offset, the first time domain position is determined according to the first scheduling offset and the difference between the first scheduling offset and the third scheduling offset. If the first scheduling offset is greater than the third scheduling offset, the first time domain position is determined according to the first scheduling offset.

41. The network device according to claim 40, characterized in that, The first parameter is determined based on at least one of the following: the location information of the terminal device, the configuration information of the second satellite network for satellite switching, and the ephemeris information of the second satellite.

42. The network device according to claim 40 or 41, characterized in that, The first handover command is a RACH handover command without a random access channel.

43. A communication device, characterized in that, It includes a memory and a processor, the memory being used to store a program, and the processor being used to invoke the program in the memory to perform the method as described in any one of claims 1-21.

44. A communication device, characterized in that, Includes a processor for calling a program from memory to perform the method as described in any one of claims 1-21.

45. A chip, characterized in that, Includes a processor for calling a program from memory, causing a device on which the chip is mounted to perform the method as described in any one of claims 1-21.

46. ​​A computer-readable storage medium, characterized in that, It contains a program that causes a computer to perform the method as described in any one of claims 1-21.

47. A computer program product, characterized in that, Includes a program that causes a computer to perform the method as described in any one of claims 1-21.

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