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

Abstract

Provided in the present application are a method for non-terrestrial network satellite handover, a terminal device, and a network device, which help the terminal device to determine a retransmission resource for performing a satellite handover. The method is used in a satellite handover from a first satellite network coverage area to a second satellite network coverage area, and comprises: receiving a first handover command, the first handover command comprising first information, the first information being used by a terminal device to determine a first resource for performing an uplink transmission to a second satellite network during the satellite handover process, and the satellite handover being a RACH-less handover and / or a CHO.

Description

Method, terminal equipment and network equipment for non-terrestrial network satellite switching Technical Field

[0001] The present application relates to the field of communication technology, and more specifically, to a method, terminal equipment, and network equipment for non-terrestrial network satellite switching. Background Art

[0002] In order to improve user experience and reduce the delay of terminal equipment switching from a source cell to a target cell, random access channel-less (RACH-less) handover (RACH-less handover) is introduced.

[0003] However, in some communication systems (e.g., non-terrestrial networks (NTN)), the propagation delay between terminal devices and network equipment is significant. When performing RACH-free handover in these communication systems, how the terminal device determines the resources for uplink transmission is a technical problem that needs to be solved urgently.

[0004] Summary of the Invention

[0005] The present application provides a method, terminal device, and network device for non-terrestrial network satellite handover. The following describes various aspects of the embodiments of the present application.

[0006] In a first aspect, a method for non-terrestrial network satellite handover is provided, which is applied to satellite handover from a first satellite network coverage area to a second satellite network coverage area, including: receiving a first handover command, the first handover command including first information, the first information being used by a terminal device to determine a first resource for uplink transmission to the second satellite network during the satellite handover, the satellite handover being RACH-free handover and / or CHO.

[0007] In a second aspect, a method for non-terrestrial network satellite switching is provided, which is applied to satellite switching from a first satellite network coverage area to a second satellite network coverage area, including: sending a first switching request to the second satellite network; sending a first switching command to a terminal device according to a request confirmation corresponding to the first switching request, the first switching command including first information, and the first information is used by the terminal device to determine a first resource for uplink transmission to the second satellite network during the satellite switching process, and the satellite switching is RACH-free switching and / or CHO.

[0008] In a third aspect, a method for non-terrestrial network satellite switching is provided, which is applied to satellite switching from a first satellite network coverage area to a second satellite network coverage area, including: receiving a first switching request sent by the first satellite network; sending a request confirmation corresponding to the first switching request to the first satellite network, the request confirmation being used to determine a first switching command, the first switching command including first information, the first information being used by a terminal device to determine a first resource for uplink transmission to the second satellite network during the satellite switching process, the satellite switching being RACH-free switching and / or CHO.

[0009] In a fourth aspect, a terminal device is provided, including: a receiving unit for receiving a first switching command, wherein the first switching command is used to instruct the terminal device to perform a satellite switching from a first satellite network coverage area to a second satellite network coverage area, the first switching command including first information, and the first information is used by the terminal device to determine a first resource for uplink transmission to the second satellite network during the satellite switching process, and the satellite switching is a RACH-free switching and / or CHO.

[0010] In a fifth aspect, a network device is provided, which is a network device corresponding to a first satellite network, and the network device includes: a first sending unit, used to send a first switching request to a second satellite network; a second sending unit, used to send a first switching command to a terminal device according to a request confirmation corresponding to the first switching request, the first switching command being used to instruct the terminal device to perform a satellite switching from the first satellite network coverage area to the second satellite network coverage area, the first switching command including first information, and the first information being used by the terminal device to determine a first resource for uplink transmission to the second satellite network during the satellite switching process, and the satellite switching being a RACH-free switching and / or CHO.

[0011] In a sixth aspect, a network device is provided, which is a network device corresponding to a second satellite network, and the network device includes: a receiving unit, used to receive a first switching request sent by a first satellite network; a sending unit, used to send a request confirmation corresponding to the first switching request to the first satellite network, the request confirmation is used to determine a first switching command, the first switching command is used to instruct a terminal device to perform a satellite switching from the first satellite network coverage area to the second satellite network coverage area, the first switching command includes first information, the first information is used by the terminal device to determine a first resource for uplink transmission to the second satellite network during the satellite switching process, and the satellite switching is a RACH-free switching and / or CHO.

[0012] In a seventh aspect, a communication device is provided, comprising a memory and a processor, wherein the memory is used to store a program, and the processor is used to call the program in the memory to execute the method described in any one of the first to third aspects.

[0013] In an eighth aspect, a device is provided, comprising a processor for calling a program from a memory to execute the method as described in any one of the first to third aspects.

[0014] In a ninth aspect, a chip is provided, comprising a processor for calling a program from a memory so that a device equipped with the chip executes the method described in any one of the first to third aspects.

[0015] In a tenth aspect, a computer-readable storage medium is provided, on which a program is stored, wherein the program enables a computer to execute the method as described in any one of the first to third aspects.

[0016] In an eleventh aspect, a computer program product is provided, comprising a program, wherein the program enables a computer to execute the method according to any one of the first to third aspects.

[0017] In a twelfth aspect, a computer program is provided, wherein the computer program enables a computer to execute the method as described in any one of the first to third aspects.

[0018] In this embodiment of the present application, the first handover command includes first information for a terminal device to determine an uplink transmission resource. Thus, after receiving the first information, the terminal device can determine the first resource to be used for handover when performing a satellite handover from the first satellite network coverage area to the second satellite network coverage area. Indicated by the first information, the terminal device can promptly perform uplink transmission to the second satellite network without the need for a random access channel, thereby more efficiently performing a satellite handover. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] FIG1 is a wireless communication system used in an embodiment of the present application.

[0020] FIG2 is an NTN system used in an embodiment of the present application.

[0021] FIG3 is another NTN system applied in an embodiment of the present application.

[0022] FIG4 is a schematic diagram of a RACH-free handover process applicable to an embodiment of the present application.

[0023] FIG5 is a flow chart of a method for NTN satellite switching provided in an embodiment of the present application.

[0024] FIG6 is a schematic diagram of a possible implementation manner of determining the first resource based on a timer.

[0025] FIG. 7 is a schematic diagram of another possible implementation manner of determining the first resource based on a timer.

[0026] FIG8 is a flowchart of a possible implementation of the method shown in FIG5 .

[0027] FIG9 is a flow chart of a possible implementation of a decision-making switching mode.

[0028] FIG10 is a flow chart of another possible implementation of the decision-making switching mode.

[0029] FIG11 is a flowchart illustrating another possible implementation of a decision-making switching mode.

[0030] FIG12 is a schematic structural diagram of a terminal device provided in an embodiment of the present application.

[0031] FIG13 is a schematic structural diagram of a network device provided in an embodiment of the present application.

[0032] FIG14 is a schematic structural diagram of another network device provided in an embodiment of the present application.

[0033] FIG15 is a schematic structural diagram of a communication device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0034] The following will describe the technical solutions in the embodiments of this application in conjunction with the drawings in the embodiments of this application. Obviously, the embodiments described are part of the embodiments of this application, not all of the embodiments. With respect to the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0035] The embodiments of the present application can be applied to various communication systems. For example, the embodiments of the present application can be applied to global system of mobile communication (GSM) system, code division multiple access (CDMA) system, wideband code division multiple access (WCDMA) system, general packet radio service (GPRS), long term evolution (LTE) system, advanced long term evolution (LTE-A) system, new radio (NR) system, evolution system of NR system, LTE-based access to unlicensed spectrum (LTE-U) system on unlicensed spectrum, NR-based access to unlicensed spectrum (NR-U) system on unlicensed spectrum, NTN system, universal mobile telecommunication system (UMTS), wireless local area networks (WLAN), wireless fidelity (WiFi), and fifth generation communication (5th-generation, 5G) system. The embodiments of the present application can also be applied to other communication systems, such as future communication systems. The future communication system may be, for example, a sixth-generation (6G) mobile communication system or a satellite communication system.

[0036] Traditional communication systems support a limited number of connections and are easy to implement. However, with the development of communication technology, communication systems can not only support traditional cellular communications, but also support one or more other types of communications. For example, a communication system can support one or more of the following communications: 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, etc. The embodiments of the present application can also be applied to communication systems that support the above-mentioned communication methods.

[0037] The communication system in the embodiment of the present application can be applied to a carrier aggregation (CA) scenario, a dual connectivity (DC) scenario, and a standalone (SA) networking scenario.

[0038] The communication system in the embodiments of the present application can be applied to unlicensed spectrum. The unlicensed spectrum can also be considered a shared spectrum. Alternatively, the communication system in the embodiments of the present application can also be applied to licensed spectrum. The licensed spectrum can also be considered a dedicated spectrum.

[0039] The embodiments of the present application can be applied to NTN systems. As examples, NTN systems may include NTN systems based on fourth-generation communications (4G), NTN systems based on NR, NTN systems based on the Internet of Things (IoT), and NTN systems based on narrowband Internet of Things (NB-IoT).

[0040] A communication system may include one or more terminal devices. The terminal devices mentioned in the embodiments of the present application may also be referred to as user equipment (UE), access terminal, subscriber unit, subscriber station, mobile station, mobile station (MS), mobile terminal (MT), remote station, remote terminal, mobile device, user terminal, terminal, wireless communication device, user agent or user device, etc.

[0041] 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, a cordless phone, a session initiation protocol (SIP) phone, a wireless local loop (WLL) station, a personal digital assistant (PDA) device, a handheld device with wireless communication capabilities, a computing device or other processing device connected to a wireless modem, an in-vehicle device, a wearable device, a terminal device in a next-generation communication system (e.g., a NR system), or a terminal device in a future-evolved public land mobile network (PLMN) network.

[0042] In some embodiments, a 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 connection capabilities. As some specific examples, the terminal device may be a mobile phone, a tablet computer, a laptop computer, a PDA, a mobile internet device (MID), a wearable device, a virtual reality (VR) device, an augmented reality (AR) device, a wireless terminal in industrial control, a wireless terminal in self-driving, a wireless terminal in remote medical surgery, a wireless terminal in a smart grid, a wireless terminal in transportation safety, a wireless terminal in a smart city, a wireless terminal in a smart home, etc.

[0043] In some embodiments, the terminal device can be deployed on land. For example, the terminal device can be deployed indoors or outdoors. In some embodiments, the terminal device can be deployed on the water, such as on a ship. In some embodiments, the terminal device can be deployed in the air, such as on an airplane, a balloon, or a satellite.

[0044] In addition to the terminal device, the communication system may also include one or more network devices. The network device in the embodiment of the present application may be a device for communicating with the terminal device, and the network device may also be referred to as an access network device or a radio access network device. The network device may be, for example, a base station. The network device in the embodiment of the present application may refer to a radio access network (RAN) node (or device) that connects the terminal device to a wireless network. The base station can broadly cover various names as follows, or be replaced with the following names, such as: NodeB, evolved NodeB (eNB), next generation NodeB (gNB), relay station, access point, transmission point (transmitting and receiving point, TRP], transmitting point (transmitting point, TP]), master station MeNB, secondary station SeNB, multi-standard radio (MSR) node, home base station, network controller, access node, wireless node, access point (AP), transmission node, transceiver node, baseband unit (BBU), remote radio unit (RRU), active antenna unit (AAU), remote radio head (RRH), central unit (CU), distributed unit (distributed unit, DU), positioning node, etc. The base station can be a macro base station, a micro base station, a relay node, a donor node or the like, or a combination thereof. The base station can also refer to a communication module, a modem or a chip used to be set in the aforementioned equipment or device. The base station can also be a mobile switching center and a device that performs the base station function in D2D, V2X, and M2M communications, a network side device in a 6G network, a device that performs the base station function in a future communication system, etc. The base station can support networks with the same or different access technologies. The embodiments of the present application do not limit the specific technology and specific device form adopted by the network equipment.

[0045] 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 based on the location of the mobile base station. In other examples, a helicopter or drone can be configured to act as a device that communicates with another base station.

[0046] In some deployments, the network device in the embodiments of the present application may refer to a CU or a DU, or the network device may include a CU and a DU. The gNB may also include an AAU.

[0047] By way of example and not limitation, in embodiments of the present application, a network device may be mobile, for example, a mobile device. In some embodiments of the present application, the network device may be a satellite or balloon station. In some embodiments of the present application, the network device may also be a base station located on land, water, or the like.

[0048] In an embodiment of the present application, the network device can provide services for a cell, and the terminal device communicates with the network device through the transmission resources used by the cell (for example, frequency domain resources, or spectrum resources). The cell can be a cell corresponding to the network device (for example, a base station). The cell can belong to a macro base station or a base station corresponding to a small cell. The small cells here may include: metro cells, micro cells, pico cells, femto cells, etc. These small cells have the characteristics of small coverage and low transmission power, and are suitable for providing high-speed data transmission services.

[0049] For example, Figure 1 is a schematic diagram of the architecture of a communication system provided in an embodiment of the present application. As shown in Figure 1, the communication system 100 may include a network device 110, which may be a device that communicates with a terminal device 120 (or also referred to as a communication terminal or terminal). The network device 110 may provide communication coverage for a specific geographic area and may communicate with terminal devices located within the coverage area.

[0050] Figure 1 exemplarily shows a network device and two terminal devices. In some embodiments of the present 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, which is not limited in the embodiments of the present application.

[0051] For example, Figure 2 illustrates an architecture diagram of the aforementioned NTN system. NTN system 200 in Figure 2 utilizes satellite 210 as an aerial platform. As shown in Figure 2, the satellite radio access network includes satellite 210, service link 220, feeder link 230, terminal equipment 240, gateway (GW) 250, and network 260, including base stations and a core network.

[0052] Satellite 210 is a spacecraft based on a space platform. Service link 220 refers to the link between satellite 210 and terminal device 240. Feeder link 230 refers to the link between gateway 250 and satellite 210. Earth-based gateway 250 connects satellite 210 to a base station or core network, depending on the architecture selected.

[0053] The NTN architecture shown in Figure 2 is a bent-pipe transponder architecture. In this architecture, a base station is located on Earth behind gateway 250, with satellite 210 acting as a relay. Satellite 210 operates as a relay, forwarding signals from feeder link 230 to service link 220, or vice versa. In other words, satellite 210 does not function as a base station; communications between terminal device 240 and base stations in network 260 must be relayed through satellite 210.

[0054] Figure 3 illustrates another NTN system architecture. As shown in Figure 3, satellite radio access network 300 includes satellite 310, service link 320, feeder link 330, terminal equipment 340, gateway 350, and network 360. Unlike Figure 2, satellite 310 has a base station 312, while network 360 behind gateway 350 consists solely of a core network.

[0055] The NTN architecture shown in Figure 3 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.

[0056] The communication system of the architecture shown in Figures 2 and 3 may include multiple network devices, and each network device may include other number of terminal devices within its coverage area, which is not limited in the embodiments of the present application.

[0057] In the embodiment of the present application, the communication system shown in Figures 1 to 3 may also include other network entities such as a mobility management entity (MME) and an access and mobility management function (AMF), but the embodiment of the present application does not limit this.

[0058] It should be understood that in the embodiments of the present application, a device having a communication function in a network / system may be referred to as a communication device. Taking the communication system 100 shown in FIG1 as an example, the communication device may include a network device 110 and a terminal device 120 having a communication function. The network device 110 and the terminal device 120 may be the specific devices described above and will not be described in detail here. The communication device may also include other devices in the communication system 100, such as a network controller, a mobility management entity, and other network entities, which are not limited in the embodiments of the present application.

[0059] For ease of understanding, some relevant technical knowledge involved in the embodiments of this application is first introduced. The following related technologies can be combined with the technical solutions of the embodiments of this application as optional solutions, and they all fall within the scope of protection of the embodiments of this application. The embodiments of this application include at least part of the following contents.

[0060] NTN system

[0061] As communication technologies develop, communication systems (e.g., 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.

[0062] NTN refers to a network or network segment that utilizes radio frequency (RF) resources on satellite or unmanned aerial system (UAS) platforms. Taking satellites as an example, communications satellites are categorized by orbital altitude into low Earth orbit (LEO), medium Earth orbit (MEO), geostationary Earth orbit (GEO), and high elliptical orbit (HEO). LEO is an Earth-centered orbit with an altitude of 2,000 kilometers or less, or with at least 11.25 cycles per day and 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 speed (mobility) but in predictable or deterministic orbits.

[0063] Satellites at different orbital altitudes have different orbital periods.

[0064] LEO: Typical altitude is 250-1500 km, with an orbital period of 90-120 minutes.

[0065] MEO: Typical altitude is 5,000-25,000 km, and orbital period is 3-15 hours.

[0066] GEO: Altitude is approximately 35,786 kilometers, and the orbital period is 24 hours.

[0067] As shown in Figures 2 and 3, which used satellites as examples, typical scenarios for terminal devices accessing the NTN system involve either an NTN transparent payload or an NTN regenerative payload. The bent-pipe transponder architecture shown in Figure 2 corresponds to the NTN transparent payload, while the regenerative transponder architecture shown in Figure 3 corresponds to the NTN regenerative payload.

[0068] In an NTN system, the propagation delay between terminal devices and network equipment depends primarily on the altitude of the satellite or airborne platform and the type of payload in the NTN. Compared to terrestrial networks (TN), the propagation delay between terminal devices and network equipment in an NTN system is significantly longer. For example, in the cellular networks used in traditional NR, the propagation delay of terrestrial mobile systems is typically less than 1 millisecond, while the propagation delay of NTN systems ranges from a few milliseconds to hundreds of milliseconds.

[0069] NTN systems are highly mobile, and aerial platforms like satellites cover large areas. Therefore, terminal devices must switch cells promptly to maintain stable communications. For simplicity, the following explanation uses satellites as an example.

[0070] No RACH switching

[0071] When the source cell, target cell, and terminal device are synchronized, a RACH-free handover (HO) solution can be introduced to reduce handover latency and improve user experience. RACH-free handover is also known as RACH-less handover. In a synchronous network, the subframe boundaries between the source cell and the target cell can be considered aligned. Therefore, the terminal device can switch from the source cell to the target cell at the time agreed upon by the three parties without the need for a random access process. For example, when the source cell, target cell, and terminal device are synchronized, the terminal device can switch from the source cell to the target cell at the system frame number (SFN) agreed upon by the three parties without the need for random access.

[0072] One of the main purposes of the random access channel (RACH) procedure during a handover is to obtain the timing advance (TA) of the target cell. In the case of a RACH handover, the RACH procedure allows the terminal device to obtain the TA of the target cell. In the absence of a 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.

[0073] Another purpose of the RACH process during handover is to obtain uplink (UL) permission transmission. In the absence of a RACH process in the target cell, an uplink grant needs to be allocated in the target cell. In some embodiments, for the initial uplink transmission in a RACH-free handover, a pre-allocated grant in a RACH-free handover command is supported. That is, the target cell can be pre-allocated via an uplink grant (UL-grant) in the handover command. The pre-allocated uplink grant can remain valid for a period of time, starting from the time the terminal device achieves synchronization with the target cell. For example, when a RACH-free handover is performed in the NR terrestrial network, the propagation delay between the terminal device and the network device is low. Based on the delay information propagated between the terminal device and the network device, the target cell can appropriately configure the time domain position of the uplink resource 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.

[0074] Configured Scheduling (CS) Mechanism

[0075] In a 3GPP wireless network, the uplink grant in the downlink control information (DCI) can be used to dynamically schedule the transmission of the physical uplink shared channel (PUSCH). Exemplarily, the network can use DCI format 0_0 or DCI format 0_1 ​​for configuration. Exemplarily, in a scenario with a random access process, the network can use the UL grant response message in the random access (for example, a random access response (RAR) scenario) for configuration. Exemplarily, PUSCH transmission can be configured by a semi-statically configured UL grant configuration grant (CG).

[0076] CG refers to a semi-persistent grant of radio resources, wherein transmission during the CG period does not require dynamic scheduling of radio resources. Therefore, CG transmission can also be called unauthorized transmission or data transmission without resource request. There are two types of CG transmissions, namely type 1 (type1) transmission and type 2 (type2) transmission. Type 1 and type 2 of CG are distinguished by the field rrc-ConfiguredUplinkGrant in the message element (information element, IE) ConfiguredGrantConfig. For example, in type 1 transmission, the network side will configure the time and frequency resources (provided by rrc-ConfiguredUplinkGrant), and the terminal device does not need to wait for DCI to be activated and can directly transmit. For example, in type 2 transmission, since there are no time and frequency resources provided by rrc-ConfiguredUplinkGrant, after the terminal device receives ConfiguredGrantConfig (which does not include rrc-ConfiguredUplinkGrant), it also needs to receive limited DCI activation and determine the uplink authorization based on the DCI information before it can transmit. The DCI used for activation may be scrambled with a configuration scheduling radio network temporary identifier (CS-radio network temporary identifier, CS-RNTI).

[0077] Once the CG transmission configuration is activated, the terminal device will always perform uplink transmissions on a periodic basis (unless the terminal device is in an inactive state). Exemplarily, the minimum transmission period of the uplink configuration authorization is 2 symbols. Assuming the subcarrier spacing is 15KHz, then 1slot=14symbols. If the configuration authorization transmission period is configured as 2 symbols, the terminal device will perform 7 uplink transmissions in 1 time slot. Exemplarily, when the uplink configuration authorization period is configured as 14 symbols, the terminal device will perform uplink transmissions in each uplink time slot.

[0078] Compared with CG transmission, when dynamically allocating uplink resources, the network must schedule according to the DCI content each time. Therefore, configuring granted transmission can save the air interface transmission time of the terminal device sending scheduling request (SR), buffer status report (BSR), and the NTN network using uplink DCI to indicate resources.

[0079] Specifically, rrc-ConfiguredUplinkGrant is used to provide uplink authorization for CG type 1 transmission. If this item is default, it means it is CG type 2. ConfiguredGrantConfig is used to configure uplink transmission of type 1 and type 2. As mentioned above, uplink transmission of type 1 and type 2 does not require DCI dynamic scheduling. In other words, the uplink authorization of type 1 is configured by the radio resource control (RRC) parameter (rrc-ConfiguredUplinkGrant), while the uplink authorization of type 2 can only start transmission after being activated by receiving the CS-RNTI-scrambled DCI.

[0080] During the handover process of the terminal device, the configuration scheduling mechanism of the downlink (DL) is called semi-persistent scheduling (SPS), and the configuration scheduling mechanism of the uplink is called CG.

[0081] The downlink configuration and scheduling (CS / SPS) process involves the NTN network sending an RRC message to configure all parameters required for physical downlink shared channel (PDSCH) scheduling. Examples of RRC messages include RRC setup or RRC reconfiguration messages. The terminal device monitors the physical downlink control channel (PDCCH) to receive the DCI with the CS-RNTI sent by the target NTN. The terminal device can determine the relevant parameters for PDSCH transmission based on the DCI information.

[0082] The uplink configuration process includes type 1 process and type 2 process for CG transmission. For type 1 process: the NTN network configures all parameters required for PUSCH scheduling by sending RRC messages, and the terminal device can send PUSCH without any specific physical layer trigger (for example, DCI trigger). In this case, the terminal device will also monitor PDCCH to prevent the target NTN from sending other types of DCI. For type 2 process: the NTN network configures all parameters required for PUSCH scheduling by sending RRC messages. When NTN wants to start authorizing (scheduling) PUSCH, it will send DCI masked with CS-RNTI. Once the terminal device processes the DCI with CS-RNTI, it can send PUSCH according to the scheduling in RRC. PUSCH resources can be dynamically scheduled by DCI 0_0 / 0_1 / 0_2.

[0083] In the NTN system, as satellites move, terminal devices frequently need to perform satellite handovers from the source NTN satellite (NTN1) to the target NTN satellite (NTN2). Compared to cellular networks used in some communication systems (e.g., NR), the propagation delay between the terminal device and the satellite in the NTN is longer, and the propagation delay of the air interface required for the terminal device to correctly receive the handover command is also longer. Introducing RACH-free handover in the NTN system can effectively reduce the interaction between the terminal device and network equipment, thereby improving handover efficiency.

[0084] As mentioned above, for the initial uplink transmission in RACH-free handover, it is necessary to support the pre-allocated grant in the RACH-free handover command. In the NTN system, RACH-free handover of NTN can be supported regardless of whether the handover is performed within a satellite with the same feeder link or within a satellite with different feeder links. Satellites with the same feeder link refer to satellites with the same gateway or network equipment (for example, gNB). After the introduction of RACH-free handover in NTN, the interaction between the terminal device and the target NTN in the handover process is reduced, thereby quickly accessing the target network. For example, the terminal device does not need to perform a random access process, but directly establishes communication based on the resources pre-configured by the target NTN.

[0085] For ease of understanding, the specific process for NTN RACH-free handover is exemplarily described below in conjunction with Figure 4. Figure 4 illustrates the interaction between the terminal device, the source NTN, and the target NTN.

[0086] 4 , in step S410 , the terminal device sends a measurement control and report to the source NTN. The terminal device reports the measurement report to the cell of the source NTN.

[0087] In step S420, the source NTN makes a handover decision (HO decision) to determine a target NTN.

[0088] In step S430, the source NTN sends a handover request (HO request) to the target NTN.

[0089] In step S440, the target NTN sends a handover request acknowledgement (HO request acknowledge (ACK)) to the source NTN.

[0090] In step S450, the source NTN sends a handover command to the terminal device, including a RACH-less HO configuration. The terminal device receives the RACH-less HO command from the source NTN. The command may include a pre-allocated grant, a beam index associated with a synchronization signal block (SSB) (which may also represent a synchronization signal / physical broadcast channel block (SS / PBCH block)), and resource reservation. After receiving the handover command, the terminal device starts a timer related to the handover.

[0091] The terminal device starts the timer T304 when starting the handover. During the handover process, once the timer T304 expires, the terminal device will initiate an RRC connection re-establishment process to the target NTN.

[0092] During downlink and uplink synchronization, the terminal device starts timer T430. As previously mentioned, the source NTN and the terminal device on Earth will move relative to each other, so the source NTN's auxiliary information (NTN-config) may be subject to validity issues. Timer T430 is used to ensure that the terminal device can continuously obtain valid source NTN auxiliary information. For example, timer T430 can be used to control the terminal device to obtain valid auxiliary information in the system information block (SIB) 19, ensuring that the source NTN auxiliary information obtained by the terminal device before the handover is completed is valid.

[0093] The source NTN's assistance information can include satellite ephemeris and common TA parameters. For the source NTN, the network can broadcast ephemeris information and common TA parameters. For example, SIB19 contains satellite assistance information for NTN access. Before connecting to the target NTN, the terminal device must have a valid global navigation satellite system (GNSS) position, satellite ephemeris information, and common TA parameters.

[0094] In step S460, the terminal device sends an initial uplink transmission. The initial uplink transmission is sent using an available uplink grant. The initial uplink transmission includes sending an RRCReconfigurationComplete message. The uplink grant may correspond to the RRC layer, the media access control (MAC) layer, and the physical (PHY) layer.

[0095] In step S470, the terminal device receives an acknowledgment (RACH-less HO ACK) from the target NTN, thereby completing the RACH-less handover. After receiving the handover completion information, the terminal device stops timer T304 based on RRC signaling.

[0096] The above describes the specific process of performing RACH-free handover in the NTN in conjunction with FIG. 4 . In step S450 , the handover command sent by the source NTN includes the uplink resources pre-configured by the target NTN for the terminal device.

[0097] However, due to the long propagation delay of the NTN system, the terminal device may miss the configured uplink resources during the process of accessing the target NTN, resulting in a handover access failure. For example, due to the delay of the handover command from the target NTN to the terminal device, the source NTN may also experience radio link control (RLC) layer retransmissions or hybrid automatic repeat request (HARQ) retransmissions when forwarding the handover command, which increases the propagation delay of this part of the air interface of the terminal device and makes it impossible to access successfully. Therefore, when introducing RACH-free handover in the NTN scenario, how the target NTN can reserve and pre-configure uplink resources in the RACH-free handover command to improve the success rate of terminal device handover access is a technical problem that needs to be solved.

[0098] Furthermore, due to significant propagation delays, the initial uplink transmission from a terminal device may fail, necessitating retransmission. For example, if a terminal device fails to receive feedback from the target NTN, it may need to retransmit the PUSCH. In this scenario, the terminal device must consider whether to retransmit and which resources to use. The target NTN also needs to consider whether the pre-allocated grant has been configured with uplink transmission resources for retransmission.

[0099] Therefore, in a RACH-free handover or other satellite handover without a random access channel, how the terminal device determines the uplink transmission resources is a technical problem that needs to be solved urgently.

[0100] Based on this, embodiments of the present application provide a method for NTN satellite handover. Through this method, a terminal device can determine resources for uplink transmission in the absence of a random access channel (RACH) and / or conditional handover (CHO), thereby determining the time-frequency resources for uplink transmission in the absence of a random access channel or determined resources, thereby effectively performing satellite handover.

[0101] For ease of understanding, the method proposed in an embodiment of the present application is described in detail below with reference to FIG5 . The method shown in FIG5 is performed by a terminal device. This method can also be used for interaction between the terminal device, a first satellite network, and a second satellite network. This method is applied to a satellite handover from a first satellite network coverage area to a second satellite network coverage area.

[0102] The terminal device is any of the terminal devices described above. In some embodiments, the terminal device is a communication device that provides services to satellites in an NTN system. In some embodiments, the terminal device is a communication device with a low service transmission rate.

[0103] The first and second satellite networks are NTN networks that integrate ground-based infrastructure and aerial platforms such as satellites. As previously mentioned, the satellites and other aerial platforms in the first and second satellite networks can serve as network devices, providing services, or acting as relays. Taking satellites as an example, the network devices corresponding to the first and second satellite networks can be satellites or ground-based base stations. For simplicity, the satellite corresponding to the first satellite network can be referred to as the first satellite, and the satellite corresponding to the second satellite network can be referred to as the second satellite. The network devices corresponding to the first satellite network can be referred to as the first network devices, and the network devices corresponding to the second satellite network can be referred to as the second network devices.

[0104] The first satellite network is the NTN network currently providing services to the terminal device. The first satellite network may also be referred to as the source NTN or source satellite network. In some embodiments, the first satellite network provides services to the terminal devices within the coverage area through its corresponding network devices.

[0105] The network device corresponding to the first satellite network is the communication device currently providing services to the terminal device. In some embodiments, the network device may be a device in relative motion with the terminal device. For example, the first network device may be a base station on a satellite providing services to the terminal device. In another example, the first network device may be a base station installed on a low-altitude aircraft. In some embodiments, the network device may be stationary relative to the terminal device or the Earth. For example, when a satellite in the first satellite network acts as a relay, the first network device may be a base station on the ground communicating with the satellite via a gateway.

[0106] 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 a source cell. In some embodiments, the first satellite network coverage area may include one or more terrestrial network cells.

[0107] The second satellite network is an NTN network that provides services to the terminal device after the first satellite network. The second satellite network may also be referred to as a target NTN or target satellite network. In some embodiments, the second satellite network provides services to the terminal devices within its coverage area through its corresponding network equipment. In some embodiments, the first satellite network may determine multiple satellite networks that can provide services to the terminal device based on satellite motion trajectories and / or ephemeris information, and then determine a second satellite network. In some embodiments, the terminal device may determine the second satellite network from multiple candidates through signal measurement.

[0108] The network device corresponding to the second satellite network is the next communication device to provide services to the terminal device. In some embodiments, the second network device can be a device that moves relative to the terminal device, or can be a device that is stationary relative to the terminal device or relative to the earth, which will not be described in detail here.

[0109] 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 a target cell. In some embodiments, the second satellite network coverage area may include one or more terrestrial network cells.

[0110] Satellite handover may be handover of a satellite corresponding to the area where the terminal device is located. Exemplarily, satellite handover may be cell handover. Exemplarily, the physical cell identifier of the coverage area remains unchanged during satellite handover.

[0111] 5 , in step S510 , the terminal device receives a first switching command.

[0112] The first handover command received by the terminal device comes from the first satellite network. That is, the first satellite network currently providing service to the terminal device instructs the terminal device to perform a handover. In some embodiments, a network device corresponding to the first satellite network sends the first handover command to the terminal device.

[0113] In some embodiments, before the terminal device performs satellite handover, the network device corresponding to the first satellite network may send a first handover request to the network device corresponding to the second satellite network. The second satellite network may provide a request confirmation corresponding to the first handover request based on the first handover request. The first satellite network may send the first handover command in step S510 to the terminal device based on the request confirmation.

[0114] 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. In some embodiments, due to satellite movement, the area where the terminal device is located changes from the coverage area of ​​the first satellite network to the coverage area of ​​the second satellite network, necessitating a handover. In some embodiments, due to movement of the terminal device or edge communication, the area where the terminal device is located changes from the coverage area of ​​the first satellite network to the coverage area of ​​the second satellite network, necessitating a handover.

[0115] The first handover command can be a satellite handover command in various modes. That is, satellite handover can be one of various handover modes. These various handover modes can include the RACH-free handover described above, CHO (Channel Handover) requiring certain conditions to be met, or a combination of RACH-free handover and CHO. The combination of RACH-free handover and CHO is essentially a combination of RACH-free handover and CHO.

[0116] In some embodiments, the satellite handover is a RACH-free handover. When the terminal device is handed over to the second satellite network coverage area, it does not access the network through a random access channel.

[0117] In some embodiments, the satellite handover is CHO. The terminal device may store the first handover command and perform handover from the first satellite network coverage area to the second satellite network coverage area when a condition of the first handover command is met.

[0118] In some embodiments, satellite handover combines RACH-free handover with CHO. As an example, the configuration information related to RACH-free handover can be a trigger condition for CHO. As an example, CHO can also be used to trigger RACH-free handover. This will be explained in detail later in conjunction with the decision-making method for the handover method.

[0119] In some embodiments, when there are multiple switching modes, the terminal device or the first satellite network or the second satellite network needs to determine the selected switching mode through decision-making. The decision-making method for multiple switching modes will be exemplified below with reference to Figures 9 to 11.

[0120] The first handover command includes first information. The first information is used by the terminal device to determine a first resource for uplink transmission to the second satellite network during the satellite handover process. As previously described, since the terminal device may not perform handover based on the RACH, the terminal device needs to determine a resource for initial uplink transmission. Furthermore, if the initial uplink transmission fails, the terminal device may need to perform an uplink retransmission to more efficiently execute the satellite handover.

[0121] In some embodiments, the uplink transmission during the satellite handover process may include one or more uplink transmissions performed by the terminal device to the second satellite network. For example, the uplink transmission may include an initial uplink transmission performed by the terminal device to the second satellite network. For example, the uplink transmission may include one or more uplink retransmissions performed by the terminal device.

[0122] In some embodiments, uplink retransmission is used by a terminal device to retransmit an initial uplink transmission or other uplink transmission during satellite handover in various situations. Exemplarily, an uplink retransmission may be an uplink transmission performed by a terminal device when it has not received an access confirmation. Exemplarily, an uplink retransmission may be an uplink transmission performed by a terminal device when it has not received feedback regarding the initial uplink transmission. Exemplarily, when an uplink retransmission is an autonomous retransmission, the terminal device may perform multiple retransmissions based on preconfigured parameters. Exemplarily, an uplink retransmission may be a retransmission performed when a handover fails.

[0123] Exemplarily, the uplink retransmission may be a retransmission of a shared channel or a retransmission of a control channel, which is not limited herein. For example, the uplink retransmission may be a retransmission of a PUSCH.

[0124] The uplink retransmission may be HARQ retransmission or RLC layer retransmission, which is not limited here.

[0125] In some embodiments, the uplink retransmission is an uplink HARQ retransmission, and the uplink HARQ mode (uplink HARQ-mode) can be used to set the HARQ mode of each HARQ process identity (ID). The HARQ mode may include mode A and mode B. HARQ mode A indicates a case where HARQ feedback is enabled, and HARQ mode B indicates a case where HARQ feedback is disabled.

[0126] For example, the first / leftmost bit in the uplink HARQ mode parameter corresponds to HARQ process ID 0, the next bit corresponds to HARQ process ID 1, and so on. Bits corresponding to HARQ process IDs for unconfigured modes are ignored. A bit set to 1 indicates HARQ mode A, and a bit set to 0 indicates HARQ mode B. This parameter field can be used for both signaling radio bearers (SRBs) and data radio bearers (DRBs).

[0127] The first resources may include preconfigured resources and / or dynamically scheduled resources for handover. In some embodiments, the first resources include multiple time-frequency resources configured or scheduled by the second satellite network for the satellite handover. For example, the first resources may be preconfigured resources for satellite handover. Preconfigured resources may also be referred to as reserved resources. In another example, the first resources may be dynamically scheduled resources for satellite handover. In another example, the first resources may include preconfigured resources and dynamically scheduled resources.

[0128] In some embodiments, the first resources include resources for initial uplink transmission and / or uplink transmission resources for uplink retransmission. For example, in a handover without a random access channel, the terminal device may determine the resources for initial uplink transmission based on the first information. For example, in the event of a failure in the initial uplink transmission, the terminal device may also determine whether to perform uplink retransmission and the resources to use for the uplink retransmission based on the first information.

[0129] In some embodiments, the first resources used for the initial uplink transmission may include some or all of the time-frequency resources in the preconfigured resources, or may include some or all of the dynamically scheduled resources. In other words, the resources preconfigured or dynamically scheduled by the second satellite network must meet the initial uplink transmission requirements of the terminal device.

[0130] In some embodiments, the first resource used for uplink retransmission may include at least a portion of the time-frequency resources in the preconfigured resources for handover. For example, when the satellite handover is RACH-free handover, the second satellite network needs to indicate a pre-allocated uplink grant to the terminal device. This uplink grant is used by the terminal device to send an initial uplink transmission.

[0131] Exemplarily, when preconfiguring resources, the second satellite network may configure corresponding reserved resources for uplink retransmissions. In other words, the grant pre-allocated by the second satellite network can be used by the terminal device for both initial uplink transmission and uplink retransmissions. In this scenario, the pre-allocated grant may include pre-configured resources for uplink retransmissions, allowing the terminal device to perform retransmissions without network scheduling.

[0132] Exemplarily, when pre-configured resources are used for HARQ retransmissions, the HARQ process configuration is similar to that for grant configuration. In a pre-configured grant, the HARQ process ID depends on the pre-assigned grant timing. Optionally, when the pre-assigned uplink grant is primarily used to transmit an RRC reconfiguration complete message, the second satellite network can define the HARQ process to ensure that the generated HARQ process ID belongs to the same HARQ mode as that used for subsequent transmissions. For example, if pre-assigned UL grants and uplink HARQ modes are configured during a handover, it is easy to define whether the HARQ process belongs to HARQ Mode A or Mode B. For another example, regardless of the pre-assigned grant timing, if an uplink HARQ mode is configured, the HARQ process used for the pre-assigned UL grant belongs to HARQ Mode A.

[0133] In some embodiments, the first resource used for uplink retransmission includes dynamically scheduled resources for satellite handover. Dynamically scheduled resources are time-frequency resources that are adjusted or scheduled in real time by the second satellite network based on communication conditions. For example, the dynamically scheduled resources may be indicated by a DCI indicating resource configuration. The terminal device may obtain an uplink grant by monitoring the PDCCH of the second satellite network.

[0134] Exemplarily, when the second satellite network does not receive the initial uplink transmission within the pre-allocated authorization time, it may indicate the dynamic authorization to the terminal device by sending DCI.

[0135] For example, in order to obtain an uplink grant, the terminal device may need to perform beam selection. Through beam selection, the terminal device may determine one or more beams to monitor the PDCCH.

[0136] Optionally, the terminal device and the network (NW) can select beams separately. For example, during DL synchronization between the terminal device and the second satellite network, the terminal device can determine an appropriate SSB based on signal quality and use the beam corresponding to that SSB to monitor the PDCCH of the target cell. On the network side, after receiving the measurement results of the beam forwarded by the first satellite network, the second satellite network can determine the best beam or beams for the cell to use for sending dynamic grants.

[0137] Optionally, the network selects a beam and signals the terminal device. The second satellite network determines a beam based on the beam measurement results forwarded by the first satellite network and indicates the selected beam index to the terminal device in a first handover command. If no beam indication is provided in the first handover command, the second satellite network may transmit the PDCCH on all beams, and the terminal device monitors in all beams.

[0138] Alternatively, if the second satellite network does not obtain beam measurements from the first satellite network, the second satellite network cannot determine a suitable beam. Therefore, the second satellite network can only transmit the PDCCH on all beams. The terminal device can detect the PDCCH on the appropriate beam. For example, the terminal device can perform beam selection based on reference signal received power (RSRP). As another example, the terminal device can select the beam corresponding to the best RSRP during DL synchronization.

[0139] Optionally, the SR is associated with the SSB, and the network sends a scheduling request configuration (generated by the second satellite network and included in the first handover command) to the terminal device. For example, the SR resources may correspond one-to-one to the SSB. The terminal device selects an appropriate SSB beam based on the beam quality, and then the terminal device sends a scheduling request associated with the selected SSB to the second satellite network. The second satellite network can determine the SSB selected by the terminal device through the association between the SSB and the SR, and use the corresponding beam to send a dynamic grant to the terminal device. The terminal device can release the SR configuration after the handover.

[0140] In some embodiments, the first resource may include pre-configured resources and dynamically scheduled resources. That is, the terminal device may perform uplink retransmission using both pre-configured resources and dynamically scheduled resources.

[0141] In some embodiments, the first resource may be a continuous time-frequency resource, a time-frequency resource set at a certain time interval, or a time-frequency resource with a variable interval, which is not limited here.

[0142] The first information may indicate the first resource to the terminal device through a variety of parameters, so that the terminal device can determine the time-frequency resources for the initial uplink transmission and / or uplink retransmission. In some embodiments, the first information may clearly indicate the time domain information and frequency domain information of the resource, so that the terminal device can transmit or detect. In some embodiments, the first information may be related to the resource configuration in the first handover command. For example, in a RACH-free handover, the information of the pre-allocated authorization in the first handover command may be related to the first information. For another example, in a RACH-free handover, the dynamic scheduling information in the first handover command may be related to the first information.

[0143] In some embodiments, the first information may include one or more of the following parameters: a first duration corresponding to pre-configured resources for satellite switching; a second duration for triggering uplink retransmission in satellite switching; a third duration corresponding to dynamically scheduled resources for satellite switching; and a first offset value corresponding to the second satellite network.

[0144] Optionally, the first offset value may be used to delay the uplink grant corresponding to the preconfigured resource. The first offset value may be a specific offset value for the second satellite network coverage area. For example, the first offset value may be a specific K value for the second satellite network coverage area. offset The specific K offset Can be used to delay pre-allocated uplink grants.

[0145] Optionally, the preconfigured resources for satellite handover refer to resources reserved by the second satellite network for satellite handover. In this scenario, the first duration may be a time period indicating reserved resources. For example, the end of the first duration indicates that no subsequent reserved resources are configured, and the terminal device can only perform uplink retransmissions using dynamically scheduled resources.

[0146] As an example, the first duration may be determined based on the first offset value. The first duration may include the time period corresponding to the first offset value, or may not include the time period corresponding to the first offset value. For example, the first duration may include the time period corresponding to the first offset value and the time period corresponding to the pre-configured resources. That is, the first duration takes into account the time period before the initial uplink transmission of the terminal device. The interval between the time point when the terminal device receives the first switching command and the time point when the terminal device is able to send the initial PUSCH is generally the switching interruption time plus the cell-specific K offset For another example, the first duration may not include the time period corresponding to the first offset value, but may only be used to indicate the time period for reserved resources.

[0147] Optionally, the second duration for triggering uplink retransmission refers to a time period for the terminal device to determine a retransmission opportunity. For example, at the end position of the second duration, the terminal device triggers uplink retransmission.

[0148] Optionally, the dynamic scheduling resource for satellite handover refers to a dynamic grant configured by the second satellite network for the terminal device to access. In this scenario, the third duration can be used by the terminal device to determine when it can detect the PDCCH indicating the dynamic grant.

[0149] Exemplarily, the first duration may be greater than the second duration, so that the terminal device can use the pre-configured resources for uplink retransmission. In this scenario, the terminal device can trigger uplink retransmission within the time period corresponding to the reserved resources.

[0150] As an example, the first duration may include multiple second durations. For example, the second satellite network configures multiple available uplink grants within the first duration, and the second duration may occur at each available configured grant opportunity and trigger uplink retransmission at the end.

[0151] Exemplarily, the first duration may be equal to the second duration, and the preconfigured resources are not used for uplink retransmission. However, when the uplink retransmission is a HARQ retransmission, the terminal device may autonomously perform HARQ retransmission after sending the initial uplink transmission.

[0152] Exemplarily, the third duration may be greater than the first duration, so that the terminal device can determine the timing of detecting the PDCCH. In this scenario, the terminal device can use dynamic scheduling resources for uplink retransmission.

[0153] To facilitate the terminal device's determination of the first resource configured or scheduled by the second satellite network, the terminal device may configure one or more timers based on the parameters in the first information. For example, the terminal device may determine the first resource for uplink retransmission by setting timers associated with the aforementioned multiple time parameters. For example, upon receiving a handover command, the terminal device may initiate different timers to distinguish between uplink retransmission using reserved resources or dynamically scheduled resources.

[0154] Exemplarily, the terminal device may start at least one of a plurality of timers for determining the first resource based on the first information. The plurality of timers include a first timer corresponding to the first duration, a second timer corresponding to the second duration, and a third timer corresponding to the third duration.

[0155] When the first timer and the second timer are configured, the terminal device may start the first timer and / or the second timer upon receiving the first switching command. In other words, the terminal device may start the first timer and the second timer simultaneously, or may start the first timer and the second timer sequentially at a certain time interval.

[0156] As an example, when the first duration is greater than the second duration, the terminal device starts the first timer and the second timer after receiving the first handover command. Before the second timer expires, the terminal device can perform an initial uplink transmission or other handover-related uplink transmission based on preconfigured resources. During the period when the second timer expires and the first timer has not expired, the terminal device performs an uplink retransmission based on the preconfigured resources.

[0157] When the three timers are configured, upon receiving the first switching command, the terminal device may start the three timers simultaneously or sequentially. Starting the three timers simultaneously may facilitate configuration and monitoring of all timers.

[0158] As an example, when the first duration is greater than the second duration and the third duration is greater than the first duration, after receiving the first handover command, the terminal device simultaneously starts the first, second, and third timers. Before the second timer expires, the terminal device may perform an initial uplink transmission or other handover-related uplink transmission based on preconfigured resources. During the period between the expiration of the second timer and the expiration of the first timer, the terminal device performs an uplink retransmission based on the preconfigured resources. During the period between the expiration of the first timer and the expiration of the third timer, the terminal device detects downlink control information from the second satellite network indicating dynamically scheduled resources to perform an uplink retransmission.

[0159] As an example, when the first timer and the second timer are started and the first duration is greater than the second duration, the second timer can be started multiple times to effectively utilize discontinuous reserved resources for uplink retransmission. For example, when a transmission block in the configuration grant corresponding to the first timer has multiple transmission opportunities, the second timer can be started at each transmission opportunity until the first timer expires.

[0160] When a first timer is configured, upon receiving a first handover command, the terminal device may start the first timer. After sending an initial uplink transmission, if the first timer has not expired, the terminal device may perform an autonomous retransmission based on pre-configured resources. Autonomous retransmissions before the expiration of the first timer are, for example, HARQ retransmissions.

[0161] To facilitate configuration or scheduling of the first resource by the second satellite network, the second satellite network may also start one or more timers based on the configuration parameters. For example, after sending the handover command, the second satellite network may start corresponding timers to facilitate receiving an initial uplink transmission or an uplink retransmission from the terminal device. For example, the second satellite network may determine the time period corresponding to the reserved resource based on the timer, and thereby determine the timing for receiving the initial uplink transmission. For another example, the second satellite network may determine the PDCCH transmission time based on the timer, and determine the timing for receiving an uplink retransmission based on a dynamic grant in the DCI.

[0162] For example, the second satellite network may start a fourth timer, which may be associated with at least one of the first duration, the second duration, and the third duration. The fourth timer enables the second satellite network to detect an initial uplink transmission or an uplink retransmission sent by the terminal device.

[0163] For ease of understanding, the following takes RACH-free handover as an example and describes various possible implementations of determining the first resource based on a timer in conjunction with FIG. 6 and FIG. 7 .

[0164] In some embodiments, the terminal device or the network side device can be configured to support a new grant timer without a RACH handover command, that is, the first timer described above. The first timer can be a HO-GrantTimer. The reserved resources can be applied within the time corresponding to the first timer.

[0165] In some embodiments, the terminal device or the network side device may define a retransmission timer HO-RetransmissionTimer for the pre-allocated uplink grant in the RACH-free handover, which is the second timer mentioned above. As mentioned above, the duration of the HO-GrantTimer timer may be greater than or equal to the duration of the HO-RetransmissionTimer timer.

[0166] In some embodiments, the terminal device or the network-side device may further define a handover timer, HO-Timer, for RACH-free handover, namely the third timer described above. The third timer is used to define a time period for performing satellite handover. Therefore, the duration of the third timer is generally greater than the durations of the first timer and the second timer.

[0167] As an example, when two timers are configured and the first duration is greater than the second duration, the terminal device may start the first timer and the second timer after receiving the first switching command. The first timer and the second timer may be started simultaneously or sequentially based on a certain time interval.

[0168] For ease of understanding, the following uses the example of a terminal device starting a timer, in conjunction with Figure 6, to illustrate a possible implementation method for determining the first resource based on a timer. Referring to Figure 6, at time T0, the first timer and the second timer are simultaneously started. T0 to T2 is the first duration of the first timer, and T0 to T1 is the second duration of the second timer. That is, the second timer expires at time T1, and the first timer expires at time T2.

[0169] When the terminal device receives the first switching command at time T0, the first timer and the second timer are started. The terminal device begins to prepare for the initial uplink transmission. As mentioned above, the specific K offset Used to delay the pre-allocation of uplink grants. Therefore, the interval between the time when the terminal device receives the handover command and the time when it can send PUSCH should be the handover interruption time plus the cell-specific K offset .

[0170] Because the first duration is greater than the second duration, the first timer has not yet expired when the second timer expires. During the time period from T1 to T2, if the second satellite network does not receive the initial transmission and does not send feedback to the terminal device, the terminal device may perform an uplink retransmission. In other words, if the grant timer configured for the initial transmission of data in a RACH-free handover has not expired, the terminal device will perform an autonomous retransmission of the uplink initial transmission. Even if there is no network-scheduled retransmission, the terminal device may perform a retransmission based on the grant timer.

[0171] As an example, when three timers are configured and the third duration is greater than the first duration and the first duration is greater than the second duration, the terminal device can simultaneously start the first timer, the second timer and the third timer after receiving the first switching command.

[0172] For ease of understanding, the following uses the example of starting a timer on a terminal device, and in conjunction with Figure 7, provides an illustrative description of another possible implementation method for determining the first resource based on a timer. Referring to Figure 7, the first timer, the second timer, and the third timer are simultaneously started at time T0. T0 to T2 is the first duration of the first timer, T0 to T1 is the second duration of the second timer, and T0 to T3 is the third duration of the third timer. That is, the second timer expires at time T1, the first timer expires at time T2, and the third timer expires at time T3.

[0173] When the terminal device receives the first switching command at time T0, the three timers are started simultaneously. The terminal device begins to prepare for the initial uplink transmission. As mentioned above, the specific K offset It should be used to delay the pre-allocation of uplink grants. Therefore, the interval between the time when the terminal device receives the handover command and the time when it can send PUSCH should be the handover interruption time plus the cell-specific K offset .

[0174] Because the first duration is greater than the second duration, the first timer has not yet expired when the second timer expires. Within the second timer, autonomous retransmissions are triggered using the configured grant. After the second timer expires (between T1 and T2), if the second satellite network does not receive the initial transmission and does not send feedback to the terminal device, the terminal device performs an autonomous retransmission or initiates a retransmission at the next available configured grant opportunity. The second timer can be started at each transmission opportunity of a transmission block in the configured grant until the first timer expires. At this point, the resources for autonomous retransmissions are all pre-authorized.

[0175] When the first timer expires (between T2 and T3), dynamic resources are required for PUSCH transmission. The terminal device detects the PDCCH sent by the second satellite network. Dynamic resources are determined by detecting the DCI. Based on the DCI's schedule, the terminal device sends a PUSCH retransmission. Therefore, the terminal device needs to detect the DCI (PDCCH) and perform retransmissions between T2 and T3.

[0176] The above description, in conjunction with Figures 5 to 7 , describes a method for a terminal device to determine uplink retransmission resources based on the first information in the first handover command, and various possible implementations thereof. For ease of understanding, the following description uses RACH-free handover as an example, and in conjunction with Figure 8 , illustrates the interaction flow between communication devices in this method. The method illustrated in Figure 8 is described from the perspective of the interaction between the terminal device, the first satellite network, and the second satellite network.

[0177] 8 , in step S810, the terminal device sends a measurement report to the network device corresponding to the first satellite network. The first satellite network can determine a second satellite network that meets the requirement of RACH-free handover based on the measurement report.

[0178] In step S820, the first satellite network sends a first handover request to the second satellite network. The first handover request is used by the second satellite network to determine information about the terminal device and configure uplink resources for the terminal device for RACH-free handover. The uplink resources may include reserved resources for initial uplink transmission, as well as reserved resources for uplink retransmission or information related to dynamically scheduled resources.

[0179] In step S830, the second satellite network sends a request confirmation to the first satellite network. This request confirmation (handover response) is confirmation information corresponding to the first handover request. Typically, this request confirmation includes uplink authorization information based on RACH-free handover and the multiple durations described above, so that the first satellite network can determine the first handover command.

[0180] In step S840, the first satellite network sends a first handover command including first information to the terminal device. The first handover command is a RACH-free handover command.

[0181] In some embodiments, the terminal device's receipt of the first information indicates that the satellite switch supports retransmission. However, in scenarios with significant NTN latency, enabling uplink retransmission may result in the inability to maintain quality of service (QoS). For example, if HARQ is enabled, the terminal device must monitor the channel and wait for retransmission completion. Furthermore, in scenarios with HARQ feedback, the transmission of HARQ feedback may affect latency, potentially preventing the maintenance of QoS and high throughput.

[0182] To solve this problem, uplink retransmission can be enabled or disabled according to the communication situation during the satellite switching process, so that the second satellite network can determine whether to enable retransmission according to resource conditions or actual communication conditions.

[0183] In some embodiments, the terminal device can determine whether to enable retransmission based on the first information. Specifically, the first information is used to indicate whether to enable or disable uplink retransmission during a satellite handover. Alternatively, HARQ retransmission can be enabled or disabled during a RACH-free handover. Alternatively, enabling or disabling uplink HARQ retransmission during a satellite handover can reduce transmission delay and improve transmission efficiency based on the transmission environment.

[0184] The above describes how, after receiving a first handover command, a terminal device establishes a connection with a second satellite network using reserved resources and / or first resources. Taking RACH-free handover as an example, when the network confirms that the RACH-free handover is complete, the network may not send a media access control element (MAC CE) containing a contention resolution identifier for the terminal device, but instead may send a PDCCH / PDSCH addressed to the cell-radio network temporary identifier (C-RNTI).

[0185] In some embodiments, when the RACH-free handover is completed, the pre-allocated uplink grant may be released. That is, the pre-allocated uplink grant will be released regardless of whether the handover is successful or not.

[0186] In some embodiments, when the RACH-free handover is completed, whether the pre-allocated uplink resources are released depends on the network implementation. Exemplarily, the uplink resources can be retained by the terminal device until the handover is successful or the network side explicitly releases the resources. For example, in various scenarios such as variable radio propagation conditions, congestion in the second satellite network, synchronization failure, or expiration of the validity timer, the terminal device may not be able to access the target cell using the RACH-free handover. In this case, the terminal device may need a fallback solution. For another example, regardless of the NTN deployment, after the RACH-free handover fails, the second satellite network is likely to still be available, that is, the cell coverage has not moved away and has a valid terminal device context. Therefore, the terminal device can continue to initiate access requests.

[0187] As mentioned earlier, there are multiple handover methods for satellite handover. CHO is a handover process introduced by 3GPP for 5G in Release 16 (R16). CHO allows the terminal device to decide whether to handover after certain conditions are met. Unlike handover methods, where the network (e.g., the gNB) makes the final decision on handover, CHO is determined autonomously by the terminal device. CHO configuration is also called conditional reconfiguration.

[0188] For example, in CHO, a conditional process can be introduced to eliminate the connection between handover preparation and execution. For example, handover preparation is completed before disconnection from the first satellite network, while access to the second satellite network is completed later.

[0189] For example, in CHO, a terminal device can pre-configure a set of potential candidate satellite networks. This can be achieved by receiving appropriate handover commands from each candidate satellite network. Unlike traditional handovers, a handover command is not executed upon receipt. Instead, the handover command can be stored in the terminal device and executed only when specific conditions are met. For example, a handover command may not be executed if the link quality with a candidate satellite network falls below a specified threshold. This prevents the possibility of handover failure due to deteriorating channel conditions and helps reduce the likelihood of wireless link failure.

[0190] In summary, compared to conventional handover methods, CHO can store handover commands in the device and execute them when specific conditions are met, thereby improving access success rates. To further reduce handover delays and improve access success rates, how to integrate RACH-free handover with CHO is a technical issue that needs to be addressed.

[0191] To more efficiently perform satellite handover, whether to perform RACH-free handover or CHO can be determined based on multiple situations before handover. That is, when there is configuration information for multiple handover modes, the communication device in satellite handover can decide whether to perform RACH-free handover or CHO.

[0192] In some embodiments, the first handover command may include configuration information and trigger conditions for multiple handover modes to facilitate decision-making by different communication devices. For example, CHO-related configuration information may be provided by the first satellite network to the terminal device. In another example, CHO-related trigger conditions may be provided by one or more candidate satellite networks.

[0193] In some embodiments, the configuration information of multiple switching modes can also serve as trigger conditions for each other. In other words, multiple switching modes can be combined with each other to improve switching efficiency while meeting actual usage conditions.

[0194] For example, RACH-free handover and CHO can be combined into a single handover method to complete satellite handover. For example, CHO-related triggering conditions may include configuration information related to RACH-free handover. Among the triggering conditions for CHO handover, RACH-free configuration can be a condition. Therefore, the handover command corresponding to CHO can include uplink authorization information based on RACH-free handover and / or the duration of at least one of the three timers mentioned above. For another example, CHO can be used to trigger RACH-free handover. That is, when CHO conditions are met, RACH-free handover can be triggered.

[0195] Exemplarily, the triggering condition of CHO may also be a time-based condition.

[0196] For example, if the terminal device supports multiple switching modes, the satellite switching mode can be determined based on the actual transmission situation. As described above, the switching mode decision process can be performed by the terminal device, the first satellite network, or the second satellite network.

[0197] For ease of understanding, the method of deciding a switching mode through multiple communication devices is exemplarily described below with reference to FIG. 9 to FIG. 11 .

[0198] In some embodiments, the first satellite network may decide whether the satellite handover is a RACH-free handover or a CHO handover or a handover combining a RACH-free handover and a CHO handover. Exemplarily, the first satellite network may make the decision based on a measurement report of the terminal device.

[0199] For example, the first satellite network may determine the handover mode when making a handover decision, or may determine the handover mode before sending the first handover command to the terminal device. The decision result of the first satellite network may be sent to the terminal device via third information. The third information may indicate the decision result or directly indicate handover configuration information.

[0200] For example, if the terminal device's capabilities support both handover modes, the first satellite network may send a handover request message to one or more candidate satellite networks to determine the second information used for decision-making. The handover request confirmation message sent by the candidate satellite network to the first satellite network may include candidate configuration information for multiple handover modes, such as RACH-free handover and CHO handover. In other words, the second information may include configuration information related to RACH-free handover for one or more candidate satellite networks, as well as configuration information and triggering conditions related to CHO for one or more candidate satellite networks.

[0201] For example, the second information may also include priorities of multiple handover modes set by one or more candidate satellite networks. Upon receiving these priorities, the first satellite network may decide whether to perform RACH-free handover, CHO, or a combination of RACH-free handover and CHO. The handover mode priorities can be set or dynamically adjusted.

[0202] For example, when the first satellite network determines to perform a RACH-free handover to the second satellite network, it may send an RRCReconfiguration message or a dedicated RACH-free handover request to the terminal device. After receiving the information from the first satellite network, the terminal device initiates a RACH-free handover to the second satellite network.

[0203] Illustratively, the first satellite network can make a decision based on the terminal device's measurement report. For example, the first satellite network can set RSRP measurement thresholds for RACH-free handover and CHO, respectively, and determine the handover mode based on the RSRP measurement result of the target base station by the terminal device. For example, the first satellite network requests a specific handover mode from the target base station based on the measurement threshold reached by the target base station's measurement result. The first satellite network can also notify the terminal device of the handover mode based on the terminal device's measurement result.

[0204] For ease of understanding, the following uses the example of a first satellite network determining a handover mode during a handover decision, as illustrated in Figure 9. Figure 9 also illustrates the interaction between a terminal device, the first satellite network, and the second satellite network. As shown in Figure 9, the first satellite network determines that the satellite handover is RACH-free.

[0205] Referring to Figure 9, in step S910, a terminal device sends a measurement control and report message to a first satellite network. The measurement report message may include measurement results of one or more adjacent second satellite networks detected by the terminal device around the terminal device. The terminal device may generate a measurement report based on the measurement configuration and / or measurement control information in the received measurement control message and send it to the first satellite network.

[0206] In step S920, the first satellite network makes a handover decision based on the measurement report. In this process, the first satellite network determines the second satellite network and determines whether to perform RACH-free handover, CHO, or a combination of RACH-free handover and CHO.

[0207] In step S930, the first satellite network sends a handover request to the second satellite network. The first satellite network may send a handover request message to the second satellite network based on the measurement result.

[0208] In step S940, the second satellite network sends a handover request confirmation to the first satellite network. The second satellite network may configure and reserve the required resources (e.g., C-RNTI and / or authorization for resource configuration) and send a handover request confirmation message to the first satellite network. The handover request confirmation is, for example, an ACK message. The handover request ACK message may include information about the resources reserved and prepared for the handover. For example, the handover request ACK message may include bearer signaling to be sent as an RRC message to the terminal device to perform the handover. The signaling may include a new C-RNTI, a second satellite network security algorithm identifier for the selected security algorithm, and may also include some other parameters, such as access parameters and SIBs. If RACH-less handover is configured, the signaling may include a timing adjustment indication and an optional pre-allocated uplink grant. If necessary, the handover request ACK message may also include information for forwarding the radio network layer (RNL) or the transport network layer (TNL).

[0209] In step S950, the first satellite network sends a handover configuration without RACH to the terminal device.

[0210] In step S960, the terminal device sends an initial uplink transmission to the second satellite network.

[0211] In step S970, the second satellite network sends a RACH-free handover confirmation to the terminal device.

[0212] In some embodiments, the terminal device may decide whether the satellite handover is a RACH-free handover or a CHO handover or a handover combining a RACH-free handover and a CHO handover.

[0213] For example, the terminal device may determine, based on the second information in the first handover command, whether the satellite handover is RACH-free handover, CHO, or a combination of RACH-free handover and CHO, among multiple handover modes. The second information may, as described above, include one or more of the following information: priorities of different handover modes in one or more candidate satellite networks; configuration information related to RACH-free handover for one or more candidate satellite networks; and configuration information and triggering conditions related to CHO for one or more candidate satellite networks.

[0214] As an example, the terminal device may also determine the handover mode based on the current service level. For example, if the current service level of the terminal device is above a first threshold, satellite handover is preferentially selected as non-RACH handover. Alternatively, if the current service level of the terminal device is equal to or below the first threshold, satellite handover is selected as CHO.

[0215] For example, the terminal device may determine whether the satellite handover is RACH-free handover, CHO handover, or a combination of RACH-free handover and CHO handover based on the third information in the first handover command. The third information indicates the result of a decision made by the first satellite network or the second satellite network among multiple handover modes. In other words, after the first satellite network or the second satellite network makes a handover mode decision, it directly notifies the terminal device of the decision result.

[0216] As an embodiment, if the capabilities of the terminal device support multiple switching modes, the first satellite network can send a switching request message to one or more candidate satellite networks to determine the second information, which will not be repeated here. After receiving the configuration information, the first satellite network can send a first switching command to the terminal device. The first switching command can be carried in the RRCReconfiguration message of the RRC layer. The first switching command can include uplink authorization information based on RACH-free switching, the duration of at least one of the three timers mentioned above, and the CHO configuration and triggering conditions of the second satellite network. After receiving the information from the first satellite network, the terminal device can make a switching mode decision. For example, the terminal device can determine the switching mode based on the second information. For another example, the terminal device can flexibly select the switching mode based on the second information and the current service situation.

[0217] Alternatively, if the current service level of the terminal device is relatively high, the terminal device may prioritize RACH-free handover to facilitate seamless access to the second satellite network and ensure service continuity. Alternatively, the CHO selected by the terminal device may be triggered by RACH-free handover.

[0218] Optionally, if the current service level of the terminal device is relatively high, the terminal device may select CHO (such as time-based switching), wait for the service to end and when the switching condition is met, the terminal device initiates CHO.

[0219] Optionally, if the current service level of the terminal device is relatively low, the terminal device can only perform CHO, or CHO based on a time condition.

[0220] For ease of understanding, the following uses the terminal device's decision-making handover method as an example, with reference to Figure 10 for exemplary explanation. As shown in Figure 10, the terminal device determines that satellite handover is RACH-free handover. For the sake of brevity, steps identical to those in Figure 9 will not be repeated.

[0221] Compared with step S920 in FIG. 9 , step S1020 in FIG. 10 is only used to make a handover decision, but does not determine the handover mode.

[0222] Referring to FIG. 10 , at step S1050, the first satellite network sends a handover command to the terminal device. The handover command may include multiple handover configurations (step S950 is a RACH-free handover configuration). For example, the first satellite network may send a CHO configuration to the terminal device. The CHO configuration may include CHO configurations for multiple candidate satellite networks, specifically including handover conditions for the candidate satellite networks, handover commands for the candidate satellite networks, RRC reconfiguration parameters for handover to the candidate satellite networks, and resource information reserved for handover to the candidate satellite networks.

[0223] In step S1060, after receiving a handover command containing multiple handover configuration information, the terminal device determines that the handover mode is RACH-free handover. For example, the terminal device may evaluate the handover conditions of multiple candidate satellite networks and select a second satellite network and a handover mode from among the multiple candidate satellite networks. For example, the terminal device may measure the multiple candidate satellite networks and, based on the measurement results, determine whether any of the multiple candidate satellite networks meets the handover conditions of the target satellite network. If the terminal device determines that the second satellite network meets the handover conditions, the terminal device may select the second satellite network as the handover target.

[0224] At step S1070, the terminal device sends an initial uplink transmission. If RACH-less handover is configured, the terminal device may send a handover complete message to the second satellite network. The terminal device may successfully access the second satellite network after receiving the uplink grant. The terminal device may send a handover complete message including the C-RNTI to the second satellite network to confirm the handover, along with an uplink buffer status report, indicating that the handover process is complete for the terminal device.

[0225] In some embodiments, the second satellite network may decide whether the satellite handover is a RACH-free handover or a CHO handover or a handover combining a RACH-free handover and a CHO handover.

[0226] For example, the second satellite network may make a decision based on resource usage, which may be the resource usage of the communication services currently provided by the second satellite network, or the resource remaining for the second satellite network to maintain all current communication services, which is not limited here.

[0227] As an embodiment, if the terminal device's capabilities support multiple handover modes, the first satellite network may send a handover request message to one or more candidate satellite networks. The handover request message may include a RACH-free handover request and a CHO handover request. The second satellite network may be any one of the one or more candidate satellite networks. The second satellite network may determine the handover mode based on current resource usage. As an example, the second satellite network may make the decision based on whether it has available resources to reserve. If no resources are available to reserve, the second satellite network may only send the CHO configuration and trigger conditions. If available resources are available, the handover response message sent by the second satellite network to the first satellite network may include uplink authorization information for RACH-free handover and / or the duration of at least one of the three timers described above.

[0228] For ease of understanding, the following uses the handover decision-making method of the second satellite network as an example, with reference to Figure 11. Referring to Figure 11, the second satellite network determines that the satellite handover is RACH-free handover. For the sake of brevity, steps in Figure 11 that are identical to those in Figure 9 will not be repeated.

[0229] Compared with step S920 in FIG. 9 , step S1120 in FIG. 11 is only used to make a handover decision, but does not determine the handover mode.

[0230] Referring to FIG. 11 , at step S1130, the first satellite network sends a handover request message to the second satellite network. The second satellite network may select a handover method based on information included in the handover request message. The handover request message may include both RACH-free handover and CHO handover. However, the handover request of step S930 may only include the RACH-free handover request determined by the first satellite network.

[0231] In step S1140, after receiving the handover request, the second satellite network decides to use RACH-free handover. The first satellite network confirms receipt of the decision result through a handover request in step S1150, and sends a RACH-free handover configuration to the terminal device in step S1160.

[0232] The method embodiment of the present application is described in detail above in conjunction with Figures 1 to 11. The device embodiment of the present application is described in detail below in conjunction with Figures 12 to 15. It should be understood that the description of the device embodiment corresponds to the description of the method embodiment. Therefore, for portions not described in detail, reference can be made to the above method embodiment.

[0233] FIG12 is a schematic block diagram of a terminal device according to an embodiment of the present application. The terminal device 1200 may be any of the terminal devices described above. The terminal device 1200 shown in FIG12 includes a receiving unit 1210.

[0234] Receiving unit 1210 may be configured to receive a first handover command, where the first handover command is 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. The first handover command includes first information, where the first information is used by the terminal device to determine a first resource for uplink transmission to the second satellite network during the satellite handover process. The satellite handover is RACH-free handover and / or CHO.

[0235] Optionally, the first resource includes a switched pre-configured resource and / or a dynamically scheduled resource.

[0236] Optionally, the first information includes one or more of the following parameters: a first duration corresponding to pre-configured resources for satellite switching; a second duration for triggering uplink retransmission in satellite switching; a third duration corresponding to dynamically scheduled resources for satellite switching; and a first offset value corresponding to the second satellite network.

[0237] Optionally, the terminal device 1200 also includes a timing unit, which can be used to start at least one timer among multiple timers for determining the first resource based on the first information, the multiple timers including a first timer corresponding to the first duration, a second timer corresponding to the second duration, and a third timer corresponding to the third duration.

[0238] Optionally, the first duration is greater than the second duration, and the timing unit is used to start the first timer and the second timer after receiving the first switching command; the terminal device 1200 also includes a first processing unit, which can be used to perform uplink retransmission based on pre-configured resources within a time period when the second timer expires and the first timer has not expired.

[0239] Optionally, the first duration is greater than the second duration, and the third duration is greater than the first duration. The timing unit is used to simultaneously start the first timer, the second timer and the third timer after receiving the first switching command; the terminal device 1200 also includes a second processing unit, which can be used to perform uplink retransmission based on pre-configured resources within a time period when the second timer expires and the first timer has not expired; the detection unit can be used to detect the downlink control information of the second satellite network for indicating dynamic scheduling resources within a time period when the first timer expires and the third timer has not expired, so as to perform uplink retransmission.

[0240] Optionally, the timing unit is used to start a first timer; the terminal device 1200 also includes a third processing unit, which can be used to perform HARQ retransmission based on pre-configured resources within a time period after sending an initial uplink transmission to the second satellite network and before the first timer expires.

[0241] Optionally, the first duration is determined according to a first offset value, and the first offset value is used to delay an uplink authorization corresponding to the pre-configured resources.

[0242] Optionally, the first information is further used to indicate whether to enable or disable uplink HARQ retransmission during the satellite switching process.

[0243] Optionally, the terminal device further includes a determination unit, which is configured to decide, in multiple switching modes, whether the satellite switching is RACH-free switching or CHO, or a switching in which the RACH-free switching is combined with the CHO, based on the second information in the first switching command; or, to determine, in accordance with third information in the first switching command, whether the satellite switching is RACH-free switching or CHO, or a switching in which the RACH-free switching is combined with the CHO, where the third information is used to indicate a result of a decision made by the first satellite network or the second satellite network in multiple switching modes.

[0244] Optionally, the second satellite network is one of one or more candidate satellite networks, and the second information includes one or more of the following information: priorities of different switching modes in one or more candidate satellite networks; configuration information related to RACH-free switching of one or more candidate satellite networks; configuration information and triggering conditions related to CHO of one or more candidate satellite networks.

[0245] Optionally, the RACH-free handover combined with the CHO includes: a CHO-related triggering condition includes configuration information related to the RACH-free handover, or CHO is used to trigger the RACH-free handover.

[0246] Optionally, satellite switching is related to the current service level of the terminal device, and the determination unit is further used to prioritize satellite switching as non-RACH switching if the current service level of the terminal device is higher than a first threshold; or, if the current service level of the terminal device is equal to or lower than the first threshold, satellite switching is CHO.

[0247] FIG13 is a schematic block diagram of a network device according to an embodiment of the present application. The network device 1300 may be any network device corresponding to the first satellite network described above. The network device 1300 shown in FIG13 includes a first sending unit 1310 and a second sending unit 1320.

[0248] The first sending unit 1310 may be configured to send a first handover request to the second satellite network.

[0249] The second sending unit 1320 may be configured to send a first handover command to the terminal device according to a request confirmation corresponding to the first handover request, where the first handover command is 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. The first handover command includes first information, and the first information is used by the terminal device to determine a first resource for uplink transmission to the second satellite network during the satellite handover process. The satellite handover is a RACH-free handover and / or CHO.

[0250] Optionally, the first resource includes a switched pre-configured resource and / or a dynamically scheduled resource.

[0251] Optionally, the first information includes one or more of the following parameters: a first duration corresponding to pre-configured resources for satellite switching; a second duration for triggering uplink retransmission in satellite switching; a third duration corresponding to dynamically scheduled resources for satellite switching; and a first offset value corresponding to the second satellite network.

[0252] Optionally, the first duration is determined according to a first offset value, and the first offset value is used to delay an uplink authorization corresponding to the pre-configured resources.

[0253] Optionally, the first information is further used to indicate whether to enable or disable uplink HARQ retransmission during the satellite switching process.

[0254] Optionally, before sending the switching request to the second satellite network, the network device 1300 further includes a determining unit, which is configured to decide, based on the measurement report of the terminal device, whether the satellite switching is RACH-free switching or CHO, or a switching combining the RACH-free switching and the CHO in a plurality of switching modes.

[0255] Optionally, the second satellite network is one of one or more candidate satellite networks, and the network device 1300 also includes a third sending unit, which can be used to send a switching request to one or more candidate satellite networks respectively to determine the second information; wherein the second information includes one or more of the following information: the priority of different switching modes in one or more candidate satellite networks; configuration information related to RACH-free switching of one or more candidate satellite networks; configuration information and trigger conditions related to CHO of one or more candidate satellite networks.

[0256] Optionally, or the RACH-free handover combined with the CHO includes: a CHO-related triggering condition includes configuration information related to the RACH-free handover, or CHO is used to trigger the RACH-free handover.

[0257] FIG14 is a schematic block diagram of another network device according to an embodiment of the present application. The network device 1400 may be any of the network devices corresponding to the second satellite network described above. The network device 1400 shown in FIG14 includes a receiving unit 1410 and a sending unit 1420.

[0258] The receiving unit 1410 may be configured to receive a first handover request sent by a first satellite network.

[0259] A sending unit 1420 may be configured to send a request confirmation corresponding to a first handover request to the first satellite network, where the request confirmation is used to determine a first handover command, where the first handover command is used to instruct the terminal device to perform a satellite handover from an area covered by the first satellite network to an area covered by the second satellite network. The first handover command includes first information, where the first information is used by the terminal device to determine a first resource for uplink transmission to the second satellite network during the satellite handover process, where the satellite handover is RACH-free handover and / or CHO.

[0260] Optionally, the first resource includes a switched pre-configured resource and / or a dynamically scheduled resource.

[0261] Optionally, the first information includes one or more of the following parameters: a first duration corresponding to pre-configured resources for satellite switching; a second duration for triggering uplink retransmission in satellite switching; a third duration corresponding to dynamically scheduled resources for satellite switching; and a first offset value corresponding to the second satellite network.

[0262] Optionally, the network device 1400 also includes a timing unit, which can be used to start a fourth timer, and the fourth timer is related to at least one of the first duration, the second duration and the third duration; a detection unit, which can be used to detect the initial uplink transmission or uplink retransmission sent by the terminal device according to the fourth timer.

[0263] Optionally, the first duration is determined according to a first offset value, and the first offset value is used to delay an uplink authorization corresponding to the pre-configured resources.

[0264] Optionally, the first information is further used to indicate whether to enable or disable uplink HARQ retransmission during the satellite switching process.

[0265] Optionally, after receiving the first switching request sent by the first satellite network, the network device 1400 further includes a determination unit, which can be used to decide whether the satellite switching is RACH-free switching or CHO or a combination of the RACH-free switching and the CHO in multiple switching modes based on resource usage.

[0266] Optionally, the sending unit 1420 is further configured to send one or more of the following information to the first satellite network: priorities of different switching modes; configuration information related to RACH-free switching; and configuration information and triggering conditions related to CHO.

[0267] Optionally, or the RACH-free handover combined with the CHO includes: a CHO-related triggering condition includes configuration information related to the RACH-free handover, or CHO is used to trigger the RACH-free handover.

[0268] Figure 15 is a schematic block diagram of a communication device according to an embodiment of the present application. The dashed lines in Figure 15 indicate that the unit or module is optional. Apparatus 1500 may be used to implement the method described in the above method embodiment. Apparatus 1500 may be a chip, a terminal device, or a network device.

[0269] The device 1500 may include one or more processors 1510. The processor 1510 may support the device 1500 to implement the method described in the method embodiment above. The processor 1510 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 another general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic device, discrete hardware component, etc. The general-purpose processor may be a microprocessor or the processor may be any conventional processor, etc.

[0270] The apparatus 1500 may further include one or more memories 1520. The memories 1520 store programs that can be executed by the processor 1510, causing the processor 1510 to perform the methods described in the above method embodiments. The memories 1520 may be independent of the processor 1510 or integrated into the processor 1510.

[0271] The apparatus 1500 may further include a transceiver 1530. The processor 1510 may communicate with other devices or chips via the transceiver 1530. For example, the processor 1510 may transmit and receive data with other devices or chips via the transceiver 1530.

[0272] The present application also provides a computer-readable storage medium for storing a program. The computer-readable storage medium can be applied to a terminal device or network device provided in the present application, and the program enables a computer to execute the method performed by the terminal device or network device in each embodiment of the present application.

[0273] The computer-readable storage medium may be any available medium that can be read by a computer or a data storage device such as a server or data center that includes one or more available media. The available medium may be a magnetic medium (e.g., a floppy disk, a hard disk, or a magnetic tape), an optical medium (e.g., a digital versatile disc (DVD)), or a semiconductor medium (e.g., a solid state drive (SSD)).

[0274] The present application also provides a computer program product. The computer program product includes a program. The computer program product can be applied to a terminal device or network device provided in the present application, and the program causes a computer to execute the method performed by the terminal or network device in each embodiment of the present application.

[0275] In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware or any combination thereof. When implemented using software, it can be implemented in whole or in part in the form of 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, the process or function described in the embodiment of the present application is generated in whole or in part. 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 computer-readable storage medium. For example, the computer instructions can be transmitted from one website, computer, server or data center to another website, computer, server or data center via wired (e.g., coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means.

[0276] The present application also provides a computer program that can be applied to a terminal device or network device provided in the present application, and enables a computer to execute the method performed by the terminal or network device in each embodiment of the present application.

[0277] The terms "system" and "network" in this application may be used interchangeably. In addition, the terms used in this application are only used to explain the specific embodiments of this application and are not intended to limit this application. The terms "first," "second," "third," and "fourth" in the specification and claims of this application and the accompanying drawings are used to distinguish different objects rather than to describe a specific order. In addition, the terms "including" and "having," as well as any variations thereof, are intended to cover non-exclusive inclusions.

[0278] In the embodiments of this application, the term "indication" may refer to a direct indication, an indirect indication, or an indication of an association. For example, "A indicates B" may refer to a direct indication of B, e.g., B can obtain information through A; it may refer to an indirect indication of B, e.g., A indicates C, e.g., B can obtain information through C; or it may refer to an association between A and B.

[0279] In the embodiments of the present application, the term "corresponding" may indicate a direct or indirect correspondence between the two, or an association relationship between the two, or a relationship between indication and indication, configuration and configuration, etc.

[0280] In the embodiments of the present application, "pre-definition" or "pre-configuration" may be implemented by pre-storing corresponding codes, tables, or other methods that can be used to indicate relevant information in a device (e.g., including a terminal device and a network device). The present application does not limit the specific implementation method. For example, pre-definition may refer to a definition in a protocol.

[0281] In the embodiments of the present application, the "protocol" may refer to a standard protocol in the communication field, for example, it may include an LTE protocol, a NR protocol, and related protocols used in future communication systems, and this application does not limit this.

[0282] In the embodiments of the present application, determining B based on A does not mean determining B only based on A. B can also be determined based on A and / or other information.

[0283] In the embodiments of this application, the term "and / or" is simply a description of the association relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this document generally indicates that the related objects are in an "or" relationship.

[0284] In the embodiments of the present application, the size of the serial numbers of the above-mentioned processes does not mean 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 the present application.

[0285] In the several embodiments provided in this application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are merely schematic. For example, the division of the units is merely a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0286] The units described as separate components may or may not be physically separate, and 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 these units may be selected to achieve the purpose of this embodiment according to actual needs.

[0287] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit.

[0288] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A method for non-terrestrial network satellite switching, characterized in that: Applicable to satellite handover from a first satellite network coverage area to a second satellite network coverage area, the method comprising: A first switching command is received, where the first switching command includes first information, where the first information is used by the terminal device to determine a first resource for uplink transmission to the second satellite network during the satellite switching process, where the satellite switching is a random access channel (RACH)-free switching and / or a conditional switching (CHO).

2. The method according to claim 1, characterized in that The first resources include switched pre-configured resources and / or dynamically scheduled resources.

3. The method according to claim 1 or 2, characterized in that: The first information includes one or more of the following parameters: A first duration corresponding to the preconfigured resources for the satellite switching; A second duration for triggering uplink retransmission in the satellite switching; A third duration corresponding to the dynamic scheduling resources for the satellite switching; A first offset value corresponding to the second satellite network.

4. The method according to claim 3, characterized in that The method further comprises: At least one of multiple timers for determining the first resource is started according to the first information, the multiple timers including a first timer corresponding to the first duration, a second timer corresponding to the second duration, and a third timer corresponding to the third duration.

5. The method according to claim 4, characterized in that The first duration is greater than the second duration, and after receiving the first switching command, the method further includes: Starting the first timer and the second timer; During a time period when the second timer expires and the first timer has not expired, uplink retransmission is performed based on the preconfigured resources.

6. The method according to claim 4, characterized in that The first duration is greater than the second duration, the third duration is greater than the first duration, and after receiving the first switching command, the method further includes: Simultaneously start the first timer, the second timer and the third timer; Performing uplink retransmission based on the preconfigured resources within a time period when the second timer expires and the first timer has not expired; In a time period when the first timer expires and the third timer has not expired, downlink control information used by the second satellite network to indicate the dynamic scheduling resources is detected to perform uplink retransmission.

7. The method according to claim 4, characterized in that The method further comprises: Starting a first timer; Performing hybrid automatic repeat request (HARQ) retransmission based on the preconfigured resources within a period of time after sending an initial uplink transmission to the second satellite network and before the first timer expires.

8. The method according to any one of claims 3 to 7, characterized in that: The first duration is determined according to the first offset value, and the first offset value is used to delay the uplink grant corresponding to the pre-configured resource.

9. The method according to any one of claims 1 to 8, characterized in that The first information is also used to indicate whether to enable or disable uplink HARQ retransmission during the satellite switching process.

10. The method according to any one of claims 1 to 9, characterized in that The method further comprises: determining, according to the second information in the first handover command, in a plurality of handover modes whether the satellite handover is the RACH-free handover or the CHO or a handover combining the RACH-free handover and the CHO; or, It is determined according to third information in the first switching command whether the satellite switching is the RACH-free switching or the CHO or the switching of the RACH-free switching and the CHO in combination, wherein the third information is used to indicate a result of a decision made by the first satellite network or the second satellite network among the multiple switching modes.

11. The method according to claim 10, characterized in that The second satellite network is one of one or more candidate satellite networks, and the second information includes one or more of the following information: priorities of different switching modes in the one or more candidate satellite networks; Configuration information of the one or more candidate satellite networks related to the RACH-free handover; Configuration information and triggering conditions of the one or more candidate satellite networks and the CHO.

12. The method according to claim 11, characterized in that The switching of the RACH-free switching combined with the CHO includes: the triggering condition related to the CHO includes configuration information related to the RACH-free switching, or the CHO is used to trigger the RACH-free switching.

13. The method according to any one of claims 10 to 12, characterized in that: The satellite switching is related to the current service level of the terminal device, and the method further includes: If the current service level of the terminal device is higher than the first threshold, the satellite switching is preferentially selected as the RACH-free switching; or, If the current service level of the terminal device is equal to or lower than the first threshold, the satellite switches to CHO.

14. A method for non-terrestrial network satellite switching, characterized in that: Applicable to satellite handover from a first satellite network coverage area to a second satellite network coverage area, the method comprising: Sending a first switching request to the second satellite network; A first switching command is sent to the terminal device according to a request confirmation corresponding to the first switching request, the first switching command including first information, the first information being used by the terminal device to determine a first resource for uplink transmission to the second satellite network during the satellite switching process, the satellite switching being a random access channel (RACH)-free switching and / or a conditional switching (CHO).

15. The method according to claim 14, characterized in that The first resources include switched pre-configured resources and / or dynamically scheduled resources.

16. The method according to claim 14 or 15, characterized in that The first information includes one or more of the following parameters: A first duration corresponding to the preconfigured resources for the satellite switching; A second duration for triggering uplink retransmission in the satellite switching; A third duration corresponding to the dynamic scheduling resources for the satellite switching; A first offset value corresponding to the second satellite network.

17. The method according to claim 16, characterized in that The first duration is determined according to the first offset value, and the first offset value is used to delay the uplink grant corresponding to the pre-configured resource.

18. The method according to any one of claims 14 to 17, characterized in that: The first information is further used to indicate whether to enable or disable uplink hybrid automatic repeat request HARQ retransmission during the satellite switching process.

19. The method according to any one of claims 14 to 18, characterized in that Before sending the switching request to the second satellite network, the method further includes: According to the measurement report of the terminal device, it is decided in multiple switching modes whether the satellite switching is the RACH-free switching or the CHO or the switching combining the RACH-free switching and the CHO.

20. The method according to claim 19, characterized in that The second satellite network is one of one or more candidate satellite networks, and the method further includes: Sending a handover request to the one or more candidate satellite networks respectively to determine the second information; The second information includes one or more of the following information: priorities of different switching modes in the one or more candidate satellite networks; Configuration information of the one or more candidate satellite networks related to the RACH-free handover; Configuration information and triggering conditions of the one or more candidate satellite networks and the CHO.

21. The method according to claim 20, characterized in that The switching of the RACH-free switching combined with the CHO includes: the triggering condition related to the CHO includes configuration information related to the RACH-free switching, or the CHO is used to trigger the RACH-free switching.

22. A method for non-terrestrial network satellite switching, characterized in that: Applicable to satellite handover from a first satellite network coverage area to a second satellite network coverage area, the method comprising: receiving a first switching request sent by the first satellite network; A request confirmation corresponding to the first switching request is sent to the first satellite network, where the request confirmation is used to determine a first switching command, where the first switching command includes first information, where the first information is used by the terminal device to determine a first resource for uplink transmission to the second satellite network during the satellite switching process, and where the satellite switching is a random access channel (RACH)-free switching and / or a conditional switching (CHO).

23. The method according to claim 22, characterized in that The first resources include switched pre-configured resources and / or dynamically scheduled resources.

24. The method according to claim 22 or 23, characterized in that The first information includes one or more of the following parameters: A first duration corresponding to the preconfigured resources for the satellite switching; A second duration for triggering uplink retransmission in the satellite switching; A third duration corresponding to the dynamic scheduling resources for the satellite switching; A first offset value corresponding to the second satellite network.

25. The method according to claim 24, characterized in that The method further comprises: Starting a fourth timer, wherein the fourth timer is related to at least one of the first duration, the second duration, and the third duration; The initial uplink transmission or uplink retransmission sent by the terminal device is detected according to the fourth timer.

26. The method according to claim 24 or 25, characterized in that The first duration is determined according to the first offset value, and the first offset value is used to delay the uplink grant corresponding to the pre-configured resource.

27. The method according to any one of claims 22 to 26, characterized in that The first information is further used to indicate whether to enable or disable uplink hybrid automatic repeat request HARQ retransmission during the satellite switching process.

28. The method according to any one of claims 22 to 27, characterized in that After receiving the first switching request sent by the first satellite network, the method further includes: According to resource usage, it is decided in multiple switching modes whether the satellite switching is the RACH-free switching or the CHO or the switching combining the RACH-free switching and the CHO.

29. The method according to claim 28, characterized in that The method further comprises: Sending one or more of the following information to the first satellite network: Priorities of different switching modes; Configuration information related to the RACH-free handover; Configuration information and triggering conditions related to the CHO.

30. The method according to claim 29, characterized in that The switching of the RACH-free switching combined with the CHO includes: the triggering condition related to the CHO includes configuration information related to the RACH-free switching, or the CHO is used to trigger the RACH-free switching.

31. A terminal device, characterized in that: include: A receiving unit is used to receive a first switching command, where the first switching command is used to instruct the terminal device to perform a satellite switching from a first satellite network coverage area to a second satellite network coverage area, where the first switching command includes first information, where the first information is used by the terminal device to determine a first resource for uplink transmission to the second satellite network during the satellite switching process, and the satellite switching is a random access channel (RACH)-free switching and / or a conditional switching (CHO).

32. The terminal device according to claim 31, characterized in that: The first resources include switched pre-configured resources and / or dynamically scheduled resources.

33. The terminal device according to claim 31 or 32, characterized in that: The first information includes one or more of the following parameters: A first duration corresponding to the preconfigured resources for the satellite switching; A second duration for triggering uplink retransmission in the satellite switching; A third duration corresponding to the dynamic scheduling resources for the satellite switching; A first offset value corresponding to the second satellite network.

34. The terminal device according to claim 33, characterized in that: The terminal device further includes: A timing unit, used to start at least one timer of multiple timers used to determine the first resource according to the first information, the multiple timers including a first timer corresponding to the first duration, a second timer corresponding to the second duration, and a third timer corresponding to the third duration.

35. The terminal device according to claim 34, characterized in that: The first duration is greater than the second duration, and the timing unit is used to start the first timer and the second timer after receiving the first switching command; The terminal device further includes: The first processing unit is configured to perform uplink retransmission based on the pre-configured resources within a time period when the second timer expires and the first timer has not expired.

36. The terminal device according to claim 34, characterized in that: The first duration is greater than the second duration, the third duration is greater than the first duration, and the timing unit is used to start the first timer, the second timer and the third timer simultaneously after receiving the first switching command; The terminal device further includes: A second processing unit, configured to perform uplink retransmission based on the pre-configured resources within a time period when the second timer expires and the first timer does not expire; The detection unit is used to detect the downlink control information used by the second satellite network to indicate the dynamic scheduling resources within a time period when the first timer expires and the third timer has not expired, so as to perform uplink retransmission.

37. The terminal device according to claim 34, characterized in that: The timing unit is used to start the first timer, and the terminal device further includes: The third processing unit is configured to perform hybrid automatic repeat request HARQ retransmission based on the preconfigured resources within a time period after sending an initial uplink transmission to the second satellite network and before the first timer expires.

38. The terminal device according to any one of claims 33 to 37, characterized in that: The first duration is determined according to the first offset value, and the first offset value is used to delay the uplink grant corresponding to the pre-configured resource.

39. The terminal device according to any one of claims 31 to 38, characterized in that: The first information is also used to indicate whether to enable or disable uplink HARQ retransmission during the satellite switching process.

40. The terminal device according to any one of claims 31 to 39, characterized in that: The terminal device further includes: a determining unit, configured to decide whether the satellite handover is the RACH-free handover or the CHO or a handover combining the RACH-free handover and the CHO in a plurality of handover modes according to the second information in the first handover command; or, It is determined according to third information in the first switching command whether the satellite switching is the RACH-free switching or the CHO or the switching of the RACH-free switching and the CHO in combination, wherein the third information is used to indicate a result of a decision made by the first satellite network or the second satellite network among the multiple switching modes.

41. The terminal device according to claim 40, characterized in that: The second satellite network is one of one or more candidate satellite networks, and the second information includes one or more of the following information: priorities of different switching modes in the one or more candidate satellite networks; Configuration information of the one or more candidate satellite networks related to the RACH-free handover; Configuration information and triggering conditions of the one or more candidate satellite networks and the CHO.

42. The terminal device according to claim 41, characterized in that: The switching of the RACH-free switching combined with the CHO includes: the triggering condition related to the CHO includes configuration information related to the RACH-free switching, or the CHO is used to trigger the RACH-free switching.

43. The terminal device according to any one of claims 40 to 42, characterized in that: The satellite switching is related to the current service level of the terminal device, and the determining unit is further used for: If the current service level of the terminal device is higher than the first threshold, the satellite switching is preferentially selected as the RACH-free switching; or, If the current service level of the terminal device is equal to or lower than the first threshold, the satellite switches to CHO.

44. A network device, characterized in that: The network device is a network device corresponding to the first satellite network, and the network device includes: A first sending unit, configured to send a first switching request to the second satellite network; A second sending unit is used to send a first switching command to the terminal device according to the request confirmation corresponding to the first switching request, the first switching command is used to instruct the terminal device to perform a satellite switching from the first satellite network coverage area to the second satellite network coverage area, the first switching command includes first information, and the first information is used by the terminal device to determine a first resource for uplink transmission to the second satellite network during the satellite switching process, and the satellite switching is a random access channel RACH switching and / or a conditional switching CHO.

45. The network device according to claim 44, characterized in that The first resources include switched pre-configured resources and / or dynamically scheduled resources.

46. ​​The network device according to claim 44 or 45, characterized in that: The first information includes one or more of the following parameters: A first duration corresponding to the preconfigured resources for the satellite switching; A second duration for triggering uplink retransmission in the satellite switching; A third duration corresponding to the dynamic scheduling resources for the satellite switching; A first offset value corresponding to the second satellite network.

47. The network device according to claim 46, characterized in that The first duration is determined according to the first offset value, and the first offset value is used to delay the uplink grant corresponding to the pre-configured resource.

48. The network device according to any one of claims 44 to 47, characterized in that: The first information is further used to indicate whether to enable or disable uplink hybrid automatic repeat request HARQ retransmission during the satellite switching process.

49. The network device according to any one of claims 44 to 48, characterized in that: Before sending the switching request to the second satellite network, the network device further includes: A determination unit is used to decide whether the satellite switching is the RACH-free switching or the CHO or the switching of the RACH-free switching and the CHO in combination in a plurality of switching modes according to the measurement report of the terminal equipment.

50. The network device according to claim 49, characterized in that The second satellite network is one of one or more candidate satellite networks, and the network device further includes: A third sending unit is used to send a switching request to the one or more candidate satellite networks respectively to determine the second information; The second information includes one or more of the following information: priorities of different switching modes in the one or more candidate satellite networks; Configuration information of the one or more candidate satellite networks related to the RACH-free handover; Configuration information and triggering conditions of the one or more candidate satellite networks and the CHO.

51. The network device according to claim 50, characterized in that The switching of the RACH-free switching combined with the CHO includes: the triggering condition related to the CHO includes configuration information related to the RACH-free switching, or the CHO is used to trigger the RACH-free switching.

52. A network device, characterized in that: The network device is a network device corresponding to the second satellite network, and the network device includes: A receiving unit, configured to receive a first switching request sent by a first satellite network; A sending unit is used to send a request confirmation corresponding to the first switching request to the first satellite network, the request confirmation is used to determine a first switching command, the first switching command is used to instruct a terminal device to perform a satellite switching from the first satellite network coverage area to the second satellite network coverage area, the first switching command includes first information, the first information is used by the terminal device to determine a first resource for uplink transmission to the second satellite network during the satellite switching process, and the satellite switching is a random access channel RACH-free switching and / or a conditional switching CHO.

53. The network device according to claim 52, characterized in that: The first resources include switched pre-configured resources and / or dynamically scheduled resources.

54. The network device according to claim 52 or 53, characterized in that: The first information includes one or more of the following parameters: A first duration corresponding to the preconfigured resources for the satellite switching; A second duration for triggering uplink retransmission in the satellite switching; A third duration corresponding to the dynamic scheduling resources for the satellite switching; A first offset value corresponding to the second satellite network.

55. The network device according to claim 54, characterized in that The network device also includes: a timing unit, configured to start a fourth timer, wherein the fourth timer is related to at least one of the first duration, the second duration, and the third duration; A detection unit is used to detect the initial uplink transmission or uplink retransmission sent by the terminal device according to the fourth timer.

56. The network device according to claim 54 or 55, characterized in that: The first duration is determined according to the first offset value, and the first offset value is used to delay the uplink grant corresponding to the pre-configured resource.

57. The network device according to any one of claims 52 to 56, characterized in that: The first information is further used to indicate whether to enable or disable uplink hybrid automatic repeat request HARQ retransmission during the satellite switching process.

58. The network device according to any one of claims 52 to 57, characterized in that: After receiving the first switching request sent by the first satellite network, the network device further includes: The determination unit is used to decide whether the satellite switching is the RACH-free switching or the CHO or the switching combining the RACH-free switching and the CHO in a plurality of switching modes according to resource usage.

59. The network device according to claim 58, characterized in that The sending unit is further configured to send one or more of the following information to the first satellite network: Priorities of different switching modes; Configuration information related to the RACH-free handover; Configuration information and triggering conditions related to the CHO.

60. The network device according to claim 59, characterized in that The switching of the RACH-free switching combined with the CHO includes: the triggering condition related to the CHO includes configuration information related to the RACH-free switching, or the CHO is used to trigger the RACH-free switching.

61. A communication device, characterized in that: The invention comprises a memory and a processor, wherein the memory is used to store a program, and the processor is used to call the program in the memory to execute the method according to any one of claims 1 to 30.

62. A device, characterized in that The invention comprises a processor, which is used to call a program from a memory to execute the method according to any one of claims 1 to 30.

63. A chip, characterized in that: The device comprises a processor, which is used to call a program from a memory so that a device equipped with the chip executes a method as claimed in any one of claims 1 to 30.

64. A computer-readable storage medium, characterized in that A program is stored thereon, and the program enables a computer to execute the method according to any one of claims 1 to 30.

65. A computer program product, characterized in that The method comprises a program which causes a computer to execute the method according to any one of claims 1 to 30.

66. A computer program, characterized in that The computer program enables a computer to execute the method according to any one of claims 1 to 30.

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