Mechanism for transitioning to another cell without handover in non-terrestrial network

Abstract

The present disclosure relates to transitioning to another cell without handover in a non-terrestrial network (NTN). Specifically, an NTN device sends information related to an NTN device set to a terminal, and a first device receives auxiliary information of the NTN device from a second device. The auxiliary information at least indicates the type of cell switching. The first device skips buffer purge and security key update regardless of the type of cell handover. In this way, no-handover cell handover can be achieved.

Description

Technical Field

[0001] Various example embodiments of the present disclosure relate generally to the field of telecommunications, and more particularly to methods, devices, apparatus, and computer-readable storage media for switching to another cell without handover in a non-terrestrial network (NTN). Background Art

[0002] The Third Generation Partnership Project (3GPP) has initiated discussions on NTN. For example, the feasibility of using the fifth generation (5G) new radio (NR) standard to support non-terrestrial networks has been studied during 3GPP releases 15 and 16. In particular, it is assumed that the user equipment (UE) supporting NTN has global navigation satellite system (GNSS) capabilities. In the NTN system, 5G base stations (gNBs) or gNB functions are deployed on satellites or relayed by satellites in a transparent manner to provide communication coverage over very large areas that cellular networks may not be able to reach. Such functions can be used to globally connect Internet of Things (IoT) devices and provide personal communications in remote areas. Summary of the invention

[0003] In a first aspect of the present disclosure, a first device is provided. The first device includes: at least one processor; and at least one memory storing instructions, which, when executed by the at least one processor, cause the first device to: receive auxiliary information for switching from a source non-terrestrial device to a target non-terrestrial device from a second device, wherein the auxiliary information includes an indication of a cell identity change associated with the switching; and cause at least one of the following to be maintained as a plurality of alternatives for indication: a hybrid automatic repeat request HARQ buffer, a security key for radio communication, or a cell configuration.

[0004] In a second aspect of the present disclosure, a second device is provided. The second device includes: at least one processor; and at least one memory storing instructions, which, when executed by the at least one processor, cause the second device to: send auxiliary information for switching from a source non-terrestrial device to a target non-terrestrial device to a first device, wherein the auxiliary information includes an indication of a cell identity change associated with the switching; and cause at least one of the following to be maintained as a plurality of alternatives for indication: a hybrid automatic repeat request HARQ buffer, or a security key for radio communication, or a cell configuration.

[0005] In a third aspect of the present disclosure, a method is provided. The method includes: receiving assistance information for handover from a source non-terrestrial device to a target non-terrestrial device from a second device, wherein the assistance information includes an indication of a cell identity change associated with the handover; and causing at least one of the following to be maintained for multiple alternatives for the indication: a hybrid automatic repeat request HARQ buffer, a security key for radio communication, or a cell configuration.

[0006] In a fourth aspect of the present disclosure, a method is provided. The method includes: sending auxiliary information for handover from a source non-terrestrial device to a target non-terrestrial device to a first device, wherein the auxiliary information includes an indication of a cell identity change associated with the handover; and maintaining multiple alternatives for indicating at least one of the following: a hybrid automatic repeat request HARQ buffer, or a security key for radio communication, or a cell configuration.

[0007] In a fifth aspect of the present disclosure, a first apparatus is provided. The first apparatus comprises: a component for receiving auxiliary information for handover from a source non-terrestrial device to a target non-terrestrial device from a second device, wherein the auxiliary information comprises an indication of a cell identity change associated with the handover; and a component for maintaining multiple alternatives for indicating at least one of the following: a hybrid automatic repeat request HARQ buffer, a security key for radio communication, or a cell configuration.

[0008] In a sixth aspect of the present disclosure, a second device is provided. The second device includes: a component for sending auxiliary information for switching from a source non-terrestrial device to a target non-terrestrial device to a first device, wherein the auxiliary information includes an indication of a cell identity change associated with the switching; and a component for maintaining multiple alternatives for indicating at least one of the following: a hybrid automatic repeat request HARQ buffer, or a security key for radio communication, or a cell configuration.

[0009] In a seventh aspect of the present disclosure, a computer-readable medium is provided, wherein the computer-readable medium includes instructions stored thereon, and the instructions are used to cause a device to at least execute the method according to the third aspect.

[0010] In an eighth aspect of the present disclosure, a computer-readable medium is provided, wherein the computer-readable medium includes instructions stored thereon, and the instructions are used to cause a device to at least execute the method according to the fourth aspect.

[0011] It should be understood that the present invention summary is not intended to identify the key or essential features of the embodiments of the present disclosure, nor is it intended to be used to limit the scope of the present disclosure. Other features of the present disclosure will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Some example embodiments will now be described with reference to the accompanying drawings, in which:

[0013] Figure 1 An example communication environment is shown in which example embodiments of the present disclosure may be implemented;

[0014] Figure 2shows a signaling diagram for switching to another cell without handover in an NTN in which example embodiments of the present disclosure may be implemented;

[0015] Figure 3 A flow chart showing a method of switching to another cell without handover in an NTN according to some example embodiments of the present disclosure;

[0016] Figure 4 A flowchart showing a method implemented at a first device according to some example embodiments of the present disclosure is shown;

[0017] Figure 5 A flowchart showing a method implemented at a second device according to some example embodiments of the present disclosure is shown;

[0018] Figure 6 shows a simplified block diagram of a device suitable for implementing an example embodiment of the present disclosure; and

[0019] Figure 7 A block diagram of an example computer-readable medium is shown according to some example embodiments of the present disclosure.

[0020] Throughout the drawings, the same or similar reference numerals refer to the same or similar elements. DETAILED DESCRIPTION

[0021] The principles of the present disclosure will now be described with reference to some example embodiments. It should be understood that these embodiments are described only for the purpose of illustration and are helpful for those skilled in the art to understand and implement the present disclosure without implying any limitation on the scope of the present disclosure. In addition to the methods described below, the embodiments described herein can be implemented in various ways.

[0022] In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0023] References in this disclosure to "one embodiment," "an embodiment," "an example embodiment," etc., indicate that the described embodiment may include a particular feature, structure, or characteristic, but not every embodiment necessarily includes the particular feature, structure, or characteristic. Furthermore, such phrases do not necessarily refer to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in conjunction with an embodiment, it is considered to be within the knowledge of those skilled in the art to affect such feature, structure, or characteristic in conjunction with other embodiments (whether or not explicitly described).

[0024] It should be understood that, although the terms "first", "second", etc. in front of nouns etc. may be used in this article to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element, and they do not limit the order of the nouns. For example, without departing from the scope of the example embodiments, the first element may be referred to as the second element, and similarly, the second element may be referred to as the first element. As used herein, the term "and / or" includes any and all combinations of one or more of the listed terms.

[0025] As used herein, “at least one of: ” and “at least one of ” and similar expressions (wherein a list of two or more elements is connected by “and” or “or”) refer to at least any one of the elements, or at least any two or more of the elements, or at least all of the elements.

[0026] As used herein, unless explicitly stated, performing a step “in response to A” does not mean performing the step immediately after “A” occurs, but may include one or more intermediate steps.

[0027] The terms used herein are used only for the purpose of describing specific embodiments and are not intended to limit the example embodiments. As used herein, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that when used herein, the terms "comprises", "comprising", "has", "having", "includes", and / or "including" specify the presence of features, elements, and / or parts, etc., but do not exclude the presence or addition of one or more other features, elements, parts, and / or combinations thereof.

[0028] As used in this application, the term "circuitry" may refer to one or more or all of the following: 1. Hardware circuit implementation only (e.g., implementation only in analog and / or digital circuits), and 2. A combination of hardware circuitry and software such as (if applicable): (i) a combination of analog and / or digital hardware circuitry and software / firmware, and (ii) hardware processors (including digital signal processors), software and Any parts of memory that work together to enable a device such as a mobile phone or server to perform various functions; and (c) A hardware circuit and / or processor that requires software (eg, firmware) for operation, such as a microprocessor or portion of a microprocessor, but the software may not be present when not required for operation.

[0029] This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of only a hardware circuit or processor (or multiple processors) or a portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware. The term circuitry also covers, for example and if applicable to a particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in a server, cellular network device, or other computing or network device.

[0030] As used herein, the term "communication network" refers to a network that complies with any suitable communication standard, for example, New Radio (NR), Long Term Evolution (LTE), Advanced LTE (LTE-A), Wideband Code Division Multiple Access (WCDMA), High Speed ​​Packet Access (HSPA), Narrowband Internet of Things (NB-IoT), etc. In addition, the communication between the terminal device and the network device in the communication network can be performed according to any suitable generation communication protocol, including but not limited to the first generation (1G), second generation (2G), 2.5G, 2.75G, third generation (3G), fourth generation (4G), 4.5G, fifth generation (5G), sixth generation (6G) communication protocol and / or any other protocol currently known or developed in the future. The embodiments of the present disclosure can be applied to various communication systems. In view of the rapid development of communication, there are of course future types of communication technologies and systems that can implement the present disclosure. It should not be considered that the scope of the present disclosure is limited to the above-mentioned system.

[0031] As used herein, the term "network device" refers to a node in a communication network via which a terminal device accesses the network and receives services from it. A network device may refer to a base station (BS) or an access point (AP), such as a Node B (NodeB or NB), an evolved Node B (eNodeB or eNB), a NR NB (also known as a gNB), a remote radio unit (RRU), a radio head (RH), a remote radio head (RRH), a repeater, an integrated access and backhaul (IAB) node, a low-power node such as a femto, a micro), a non-terrestrial network (NTN) or a non-terrestrial network device (such as a satellite network device, a low earth orbit (LEO) satellite and a geosynchronous orbit (GEO) satellite, an aircraft network device, etc.), depending on the terminology and technology applied. In some example embodiments, a radio access network (RAN) split architecture includes a centralized unit (CU) and one or more distributed units (DU).

[0032] As used herein, the term "non-terrestrial network (NTN)" may refer to a network involving non-terrestrial flying objects. For example, an NTN network may include a satellite communication network, a high altitude platform system (HAPS), and / or an air-to-ground network. The term "NTN equipment" may refer to network equipment involved in an NTN. For example, an NTN equipment may be a satellite that may host a radio access network (RAN) node.

[0033] The term "terminal device" refers to any terminal device capable of wireless communication. As an example and not limitation, the terminal device may also be referred to as a communication device, a user equipment (UE), a subscriber station (SS), a portable subscriber station, a mobile station (MS) or an access terminal (AT). The terminal device may include, but is not limited to, a mobile phone, a cellular phone, a smart phone, a voice over IP (VoIP) phone, a wireless local loop phone, a tablet computer, a wearable terminal device, a personal digital assistant (PDA), a portable computer, a desktop computer, an image capture terminal device such as a digital camera, a game terminal device, a music storage and playback facility, a vehicle-mounted wireless terminal device, a wireless endpoint, a mobile station, a laptop embedded device (LEE), a laptop mounted device (LME), a USB dongle, a smart device, a wireless customer premises equipment (CPE), an Internet of Things (IoT) device, a watch or other wearable device, a head mounted display (HMD), a vehicle, a drone, medical equipment and applications (e.g., remote surgery), industrial equipment and applications (e.g., robots and / or other wireless devices operating in industrial and / or automatic processing chain environments), consumer electronic devices, equipment operating on commercial and / or industrial wireless networks, etc. The terminal device may also correspond to the mobile terminal (MT) part of an IAB node (eg, a relay node).In the following description, the terms "terminal device", "communication device", "terminal", "user equipment" and "UE" may be used interchangeably.

[0034] As used herein, the terms "resource", "transmission resource", "resource block", "physical resource block" (PRB), "uplink resource" or "downlink resource" may refer to any resource used to perform communication (e.g., communication between a terminal device and a network device), such as a resource in the time domain, a resource in the frequency domain, a resource in the spatial domain, a resource in the code domain, or any other combination of time domain, frequency domain, spatial domain and / or code domain resources to achieve communication. In the following, unless explicitly stated, resources in the frequency domain and the time domain will be used as examples of transmission resources for describing some example embodiments of the present disclosure. It should be noted that the example embodiments of the present disclosure are also applicable to other resources in other domains.

[0035] As used herein, the term "hybrid automatic repeat request (HARQ)" may refer to a combination of high-rate forward error correction (FEC) and automatic repeat request (ARQ) error control, which is implemented to correct erroneous packets from the physical layer. The term "HARQ process" may refer to a stop and wait process for sending data. Each HARQ process has an independent HARQ buffer. The term "buffer clear" used herein may refer to a mechanism for deleting data stored in a buffer. The term "security key change" used herein may refer to a mechanism for updating security information for a communication.

[0036] The term "Radio Link Control (RLC)" as used herein may refer to a layer 2 protocol used on the air interface. The RLC layer may provide fully reliable transport services for the selected transmission. The term "Packet Data Convergence Protocol (PDCP)" as used herein may refer to a layer between the Radio Resource Control (RRC) on the upper side of the control protocol stack and the Radio Link Control (RLC) on the lower side. The PDCP layer provides services to the upper layer, which is the RRC or Service Data Adaptation Protocol (SDAP), and obtains services and inputs from the RLC layer, the Medium Access Control (MAC) layer, and the Physical (PHY) layer. The term "handover" or "satellite handover" as used herein may refer to a mechanism by which the UE will not be disconnected but the NTN equipment through which the data is sent is switched and the UE is resynchronized with the NTN equipment.

[0037] The term "physical cell identity (PCI)" used herein may refer to an identifier included in a system information block (SIB) and may be derived after decoding a primary synchronization signal / secondary synchronization signal (PSS / SSS) signal, and which helps a UE identify and distinguish neighboring cells at the physical layer.

[0038] As mentioned above, the feasibility of using the 5G NR standard to support non-terrestrial networks has been studied. There are different types of satellite orbits that have been studied for NR access, including low earth orbit (LEO) satellites between 500-1500km altitude. LEO is assumed to be the most relevant case. During the study project, it was assumed that the typical beam footprint size for LEO satellites was between 100-1000km radius.

[0039] In some solutions, an unchanged physical cell identity (ID) (PCI) mobility mechanism has been implemented in line with the goal of reducing signaling overhead and simplifying the radio resource control (RRC) procedures for the UE. In particular, after a satellite handover, the serving gNB (on the ground) does not change, so the cell configuration can be maintained without changing the PCI, frequency and other cell configuration parameters (e.g., servingCellconfigCommon). The satellite handover is then almost transparent to the UE, which does not require the performance of L3 mobility (i.e., handover procedures). The conditions for the working mechanism may be that the network (NW) should instruct the UE how / when to perform DL and UL synchronization after a satellite handover, or that the network will accept an interruption gap for the UE to detect the new timing and adapt. For example, the mechanism can be applied to scenarios where NTN cells can be deployed as quasi-Earth Fixed Cells (EFC). The mechanism can also be applied to Earth Mobile Cells. The network needs to have components for avoiding Radio Link Failure (RLF) during this interruption gap (i.e., after the "old" cell disappears and before the "new" cell takes over). Furthermore, in Release 18, the focus is on a transparent architecture, and the simplest case is when the cell is provided by the same gNB, i.e., a cell with a fixed PCI is provided by the same gNB, so only the satellite node changes. However, some terminal devices (e.g., Release 17 devices) do not support the unchanged PCI mobility mechanism. Therefore, a solution is needed to switch to another cell without handover in the non-terrestrial network NTN.

[0040] According to an example embodiment, a first device receives auxiliary information of an NTN device from a second device. The auxiliary information at least indicates a cell identity change associated with a handover. The first device skips buffer clearing, security key refreshing, and cell configuration updating for multiple indicated alternatives. This enables cell handover without handover.

[0041] Figure 1 1 shows an example communication network 100 in which embodiments of the present disclosure may be implemented. Figure 1 As shown, the communication network 100 may include a first device 110. The communication network 100 may also include a second device 120. In addition, the communication network 100 may also include a first NTN device 130-1 and a second NTN device 130-2. For illustration purposes only, the first NTN device 130-1 may be described as a source NTN device, and the second NTN device 130-2 may be described as a target NTN device. In some scenarios, the first NTN device 130-1 or the second NTN device 130-2 may be hosted in a satellite.

[0042] In some example embodiments, if the first device 110 is a terminal device and the second device 120 is a network device, the link from the second device 120 to the first device 110 is referred to as a downlink (DL), and the link from the first device 110 to the second device 120 is referred to as an uplink (UL). In the DL, the second device 120 is a transmitting (TX) device (or transmitter), and the first device 110 is a receiving (RX) device (or receiver). In the UL, the first device 110 is a TX device (or transmitter), and the second device 120 is an RX device (or receiver).

[0043] It should be understood that Figure 1 The number of network devices and terminal devices shown is given for illustrative purposes and does not imply any limitation. Communication network 100 may include any suitable number of network devices and terminal devices.

[0044] The communication in the communication environment 100 may be implemented according to any suitable communication protocol, including but not limited to cellular communication protocols of the first generation (1G), the second generation (2G), the third generation (3G), the fourth generation (4G), the fifth generation (5G), the sixth generation (6G), etc. indicating narrowband Internet of Things (NB-IoT) and enhanced machine type communication (eMTC), wireless local area network communication protocols such as Institute of Electrical and Electronics Engineers (IEEE) 802.11, etc., and / or any other protocol currently known or developed in the future. In addition, the communication may utilize any suitable wireless communication technology, including but not limited to: code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), frequency division duplex (FDD), time division duplex (TDD), multiple input multiple output (MIMO), orthogonal frequency division multiple access (OFDM), discrete Fourier transform spread OFDM (DFT-s-OFDM) and / or any other technology currently known or developed in the future.

[0045] In some example solutions, satellite handover with PCI unchanged in transparent EFC-based deployment can be applied to the communication network 100. For example, a stationary first device 110 is being served by a first NTN device 130-1 (i.e., cell 101). When the first NTN device 130-1 moves away from the first device 110 and a second NTN device 130-2 becomes closer, the second device 120, which is routed through the first NTN device 130-1 serving the cell, can indicate when the first NTN device 130-1 will be turned off, when the second NTN device 130-2 will become available, and how to perform resynchronization to the new cell.

[0046] After the second NTN device 130-2 takes over (i.e., provides the cell 102), the first device 110 may perform DL / UL synchronization operations to resume TX / RX. In this case, even if the first device 110 is being served by the new NTN device (i.e., the second NTN device 130-2), it does not change the serving gNB, so it can maintain the cell configuration. In some example embodiments, the first NTN device 130-1 and the second NTN device 130-2 may be configured with the same PCI, the same UE context, and the same protocol stack (including synchronization signal block (SSB) generation, encoding / decoding, modulation / demodulation, the same control resource set (CORESET) configuration, and handover routing). In addition, according to the reference of the UE, the first NTN device 130-1 and the second NTN device 130-2 may introduce different frequency (i.e., Doppler) and timing drifts.

[0047] Satellite handover can be decomposed in two additional scenarios: i) hard satellite handover and ii) soft satellite handover. The latter considers specific cells that overlap between NTN cells radiated by the first NTN device 130-1 and the second NTN device 130-2, while the former considers coverage that does not overlap in time between the old cell (i.e., cell 101) and the new cell (i.e., 102). For soft satellite handover, it can be assumed that the first NTN device 130-1 and the second NTN device 130-2 send SSBs simultaneously (possibly with the same PCI, but different time / frequency offsets), thereby allowing the first device 110 to gracefully switch to the new (incoming) satellite.

[0048] In some solutions, in the quasi-geo-fixed cell case, for hard satellite handover (no key change) in the same SSB frequency and the same gNB, satellite handover without PCI change (no L3 mobility required) can be supported. In addition, in the hard handover without changing PCI scenario (i.e., no handover), the first device 110 may need to know the time when the first device bb110 attempts to resynchronize with the second NTN device 130-2.

[0049] Exemplary embodiments of the present disclosure are described in detail below with reference to the accompanying drawings.

[0050] Reference now Figure 2 , which shows a signaling diagram 200 for communication according to some example embodiments of the present disclosure. Figure 2 As shown, the signaling diagram 200 involves the first device 110, the second device 120, the first NTN device 130-1 and the second NTN device 130-2. For the purpose of discussion, reference is made to Figure 1 2 to describe the signaling diagram 200. As an example, the first NTN device 120-1 may be a source NTN device, and the second NTN device 120-2 may be a target NTN device.

[0051] The second device 120 sends (2010) to the first device 110 assistance information for switching from the source NTN device (i.e., the first NTN device 130-1) to the target NTN device (i.e., the second NTN device 130-2). In other words, the first device 110 receives the assistance information from the second device 120. The assistance information may be sent via RRC signaling. Note that the assistance information may be sent via any suitable signaling. As an example, the first device 110 is currently connected to the first NTN device 130-1 and is to be switched from the first NTN device 130-1 to the second NTN device 130-2. In some example embodiments, the assistance information may be sent before the service provided by the first NTN device 130-1 expires. In some other example embodiments, the second device 120 may also provide a gap duration for switching. Alternatively, the second device 120 may provide the start of a cell (i.e., cell 102) provided by the second NTN device 130-2.

[0052] The assistance information includes an indication of a cell identity change associated with the handover. In some example embodiments, a Release 17 UE may ignore the indication. In some embodiments, the identity of the cell may refer to a physical cell identity. Alternatively, the identity of the cell may refer to cell-specific information in SIB1 and is used to uniquely identify a cell within the network.

[0053] In some example embodiments, the indication may include a handover with a change in cell identity. For example, the assistance information may indicate a satellite with a PCI change, where the cell provided after the satellite handover has a different PCI and the PCI is provided. For example, the cell 102 provided by the second NTN device 130-2 after the handover may have a different PCI than the cell 101 provided by the first NTN device 130-1 before the handover.

[0054] Alternatively, the indication may include a handover without a cell identity change. For example, the assistance information may indicate a satellite without a PCI change, wherein the cells provided after the satellite handover have the same PCI. The PCI may be provided with or without the assistance information.

[0055] In some other embodiments, the indication may include a switch with a virtual cell identity change. For example, the assistance information may indicate a satellite with a virtual PCI change. In this case, the PCI of cell 102 may be broadcast by the new cell change. In addition, an offset for changing the PCI calculation or indication may be provided to the first device 110 (which is a version 18 UE). Therefore, the first device can keep using the same PCI. Table 1 below shows an example of an information element (IE) indicated. Note that Table 1 is only an example and not a limitation. In some example embodiments, the first device 110 may be configured with one of the IEs, and each IE may provide a list of configuration actions described later. Table 1

[0056] The first device 110 maintains at least one of the following for multiple alternatives for indication: a HARQ buffer, a security key for radio communication, or a cell configuration. For example, the first device 110 may skip one or more of the following: HARQ buffer clearing, security key refresh, and cell configuration update. In some example embodiments, the first device 110 may maintain (2020) one or more buffers. As an example, the first device 110 may maintain one or more of the following: a HARQ buffer, an RLC buffer, a PDCP buffer, or an SDAP buffer. The first device 110 may maintain at least one of the following: a control plane configuration and a user plane configuration. In some example embodiments, the first device 110 may also maintain (2030) one or more security keys for radio communication. The first device 110 may also maintain (2031) a cell configuration. For example, the cell configuration may include one or more of the following: measurement configuration, cell information (such as frequency band, frequency, SSB position, random access channel (RACH) configuration, split bearer configuration, etc.), carrier aggregation configuration. Advantageously, even if the PCI may change, the buffer is not cleared, thereby avoiding resource waste.

[0057] The first device 110 may set (2040) the PCI of the cell 102. In some example embodiments, if the first device 110 determines that the indication indicates a handover with a cell identity change, the first device 110 may obtain a target physical cell identity associated with the second NTN device 130-2 from the auxiliary information. In this case, the first device 110 may set the physical cell identity of the serving cell to the target physical cell identity. That is, the cell 102 may have a different PCI than the cell 101. The first device 110 may maintain at least one of a HARQ buffer, a security key, or a cell configuration. In an embodiment, both the HARQ buffer and the security key are maintained. The maintained security key may include at least one of the following security keys: K gNB KRRCint , K RRCenc , K UPint , K Upenc . In general, any keys specific to PCI may be maintained.

[0058] Alternatively, if the first device 110 determines that the indication indicates a handover without a physical cell identity change, the first device 110 may maintain the physical cell identity of the serving cell unchanged. For example, cell 102 may have the same PCI as cell 101. The first device 110 may maintain at least one of the following: a HARQ buffer, a security key, or a cell configuration.

[0059] In some other embodiments, if the first device 110 determines that the indication indicates a handover with a virtually changed cell identity, the first device 110 may maintain a source cell identity associated with the first NTN device 130-1 and a target cell identity associated with the second NTN device 130-2. For example, the target cell identity may be broadcast. The first device 110 may maintain use of the source cell identity based on changing the offset of the PCI calculation or identity. The first device 110 may maintain at least one of: a HARQ buffer, a security key, or a cell configuration.

[0060] In some example embodiments, the first device 110 may perform (2050) resynchronization with the second NTN device 130-2. For example, the first device 110 may resynchronize at the beginning of the cell 102 as a new cell. Alternatively or additionally, the first device 110 may modify (2060) at least one measurement filter at the handover. For example, the first device 110 may reset the at least one measurement filter.

[0061] In some example embodiments, the assistance information may include a reference time when the assistance information is valid. For example, the assistance information may include an epoch time that occurs before the end of the gap duration of the handover. In this way, the first device 110 may have the ephemeris information of the cell 102 prepared before the handover. Alternatively or additionally, the assistance information may include the ephemeris information of the second NTN device 130-2. In some other embodiments, the assistance information may include a common delay associated with the second NTN device 130-2.

[0062] The second device 120 may skip buffer clearing and / or security key refreshing and / or cell configuration updating for multiple alternatives indicated. In some example embodiments, the second device 120 maintains (2025) one or more buffers. As an example, the second device 120 may maintain one or more of the following: a HARQ buffer, an RLC buffer, a PDCP buffer, or an SDAP buffer. The second device 120 may maintain at least one of the following: a control plane configuration and a user plane configuration. In some example embodiments, the second device 120 may also maintain (2035) one or more security keys. In an example embodiment, the first device 110 may maintain information that may vary for handover. Advantageously, the buffer is not cleared even if the PCI changes, thereby avoiding waste of resources.

[0063] The second device 120 may set 2040 the PCI of the cell 102. For example, the second device 120 may change the PCI of the cell 101 to the PCI of the cell 102 during the gap duration for the handover.

[0064] In some example embodiments, if the indication indicates a handover with a cell identity change, the second device 120 may obtain a target cell identity associated with the second NTN device 130-2 based on the auxiliary information. In this case, the second device 120 may set the physical cell identity of the serving cell to the target physical cell identity. That is, the cell 102 may have a different identity than the cell 101. The second device 120 may maintain at least one of the following: a HARQ buffer, a security key, or a cell configuration.

[0065] Alternatively, if the indication indicates a handover without a cell identity change, the second device 120 may maintain the physical cell identity of the serving cell unchanged. For example, cell 102 may have the same PCI as cell 101. The second device 120 may maintain at least one of the following: a HARQ buffer, a security key, or a cell configuration.

[0066] In some other embodiments, if the indication indicates a handover with a virtually changed physical cell identity, the second device 120 may maintain a source cell identity associated with the first NTN device 130-1 and a target cell identity associated with the second NTN device 130-2. For example, the target cell identity may be broadcast. The second device 120 may maintain use of the source cell identity based on changing the offset of the PCI calculation or identity. The second device 120 may maintain at least one of: a HARQ buffer, a security key, or a cell configuration.

[0067] In some example embodiments, second device 120 may maintain (2045) at least one of the following states: a physical (PHY) entity state, a MAC entity state, an RLC entity state, a PDCP entity state, or an RRC entity state. For example, the states of the PHY, MAC, RLC, PDCDP, and RRC entities may be maintained as much as possible.

[0068] The second device 120 may send (2070) cell information of the cell 102 on the second NTN device 130-2. For example, the cell information may be different from or the same as the cell information of the cell 101. As an example, the second device 120 may send the SSB on the second NTN device 130-2. In some example embodiments, the second device 120 may send a demodulation reference signal on the second NTN device 130-2. Alternatively or additionally, the second device 120 may send a channel state information reference signal on the second NTN device 130-2. Note that Figure 2 The order of step 2020, step 2025, step 2030, step 2035, step 2040, step 2045, step 2050, step 2069, and step 2070 shown in FIG. 2 is only an example and not a limitation. These steps may be performed in any suitable order.

[0069] Figure 3 1 shows a flow chart of a method 300 according to an example embodiment of the present disclosure. Figure 3 As shown, the first device 110 may determine the type of handover based on the auxiliary information.

[0070] In some example embodiments, if the assistance information indicates a satellite with a PCI change, the first device 110 may set the PCI to a new PCI (i.e., a changed PCI). The first device 110 may resynchronize with the satellite information of the second NTN device 130-2 at the epoch time. The first device 110 may maintain buffers such as HARQ, RLC, and PDCP. The first device 110 may maintain security keys for communication with the second device 120. The first device 110 may reset or modify a measurement filter.

[0071] In some other example embodiments, if the assistance information indicates a satellite with no PCI changes, the first device 110 may maintain the PCI (i.e., unchanged PCI). The first device 110 may resynchronize with the satellite information of the second NTN device 130-2 at the epoch time. The first device 110 may maintain buffers such as HARQ, RLC, and PDCP. The first device 110 may maintain security keys for communication with the second device 120. The first device 110 may reset or modify the measurement filter.

[0072] Alternatively, if the assistance information indicates a satellite with a virtual PCI change, the first device 110 may maintain two PCIs. For example, one PCI may match one of the new cells (i.e., cell 102), and the virtual PCI may be the same as cell 101. The first device 110 may resynchronize with the satellite information of the second NTN device 130-2 at the epoch time. The first device 110 may maintain buffers such as HARQ, RLC, and PDCP. The first device 110 may maintain security keys for communication with the second device 120. The first device 110 may reset or modify the measurement filter.

[0073] According to the above embodiments, UE behavior is undefined regarding HARQ buffer, measurement filter, scheduling information, processing serving cell information after t-service, etc. In addition, Release 17 UEs can also stay in cells that are handed over without PCI changes because they can distinguish cells.

[0074] Figure 4 A flowchart of an example method 400 implemented at a device according to some example embodiments of the present disclosure is shown. For the purpose of discussion, Figure 1 The method 400 is described from the perspective of the first device 110.

[0075] At block 410, the first device 110 receives assistance information for handover from a source non-terrestrial device to a target non-terrestrial device from the second device 120. The assistance information indicates an indication regarding a cell identity change associated with the handover.

[0076] At block 420 , the first device 110 causes at least one of the following to be maintained for a plurality of candidates for indication: a hybrid automatic repeat request (HARQ) buffer, a security key for radio communication, or a cell configuration.

[0077] In some example embodiments, the indication of the cell identity change comprises one of: a handover with a physical cell identity change, a handover without a physical cell identity change, or a handover with a virtual physical cell identity change.

[0078] In some example embodiments, method 400 further includes: determining that the indication indicates a handover with a physical cell identity change; obtaining a target physical cell identity associated with the target non-terrestrial device from the auxiliary information; changing the physical cell identity of the serving cell to the target physical cell identity; and maintaining at least one of: a HARQ buffer, a security key, or a cell configuration.

[0079] In some example embodiments, method 400 further includes: determining that the indication indicates that the handover has no physical cell identity change; maintaining the physical cell identity of the serving cell unchanged; and maintaining at least one of: a HARQ buffer, a security key, or a cell configuration.

[0080] In some example embodiments, method 400 further includes: determining that the indication indicates that the handover has a virtual physical cell identity change; maintaining a source physical cell identity associated with the source non-terrestrial device and a target physical cell identity associated with the target non-terrestrial device; and maintaining at least one of: a HARQ buffer, a security key, or a cell configuration.

[0081] In some example embodiments, the method 400 further comprises: maintaining at least one of: a control plane configuration and a user plane configuration.

[0082] In some example embodiments, the method 400 further includes performing a resynchronization with the target non-terrestrial device.

[0083] In some example embodiments, the assistance information further includes at least one of: a reference time when the assistance information is valid, ephemeris information of the target non-terrestrial device, or a common delay associated with the target non-terrestrial device.

[0084] Figure 5 A flowchart of an example method 500 implemented at a second device according to some example embodiments of the present disclosure is shown. For the purpose of discussion, Figure 1 The method 500 is described from the perspective of the second device 120.

[0085] At block 510, the second device 120 sends assistance information for handover from a source non-terrestrial device to a target non-terrestrial device to the first device 110. The assistance information includes an indication of a cell identity change associated with the handover.

[0086] At block 520 , the second device 120 causes at least one of the following to be maintained for a plurality of candidates for indication: a hybrid automatic repeat request (HARQ) buffer, a security key for radio communication, or a cell configuration.

[0087] In some example embodiments, the indication of the cell identity change comprises one of: a handover with a physical cell identity change, a handover without a physical cell identity change, or a handover with a virtual physical cell identity change.

[0088] In some example embodiments, switching the virtual physical cell identity change indication maintains the physical cell identity and the unchanged physical cell identity.

[0089] In some example embodiments, method 500 further includes: determining that the indication indicates a handover with a physical cell identity change; changing the physical cell identity of the serving cell to a target physical cell identity associated with the target non-terrestrial device; and maintaining at least one of: a HARQ buffer, a security key, or a cell configuration.

[0090] In some example embodiments, the method 500 further includes: determining that the indication indicates that the handover has no physical cell identity change; maintaining the physical cell identity of the serving cell unchanged; and maintaining at least one of: a HARQ buffer, a security key, or a cell configuration.

[0091] In some example embodiments, method 500 further includes: determining that the indication indicates that the handover has a virtual physical cell identity change; maintaining a source physical cell identity associated with the source non-terrestrial device and a target physical cell identity associated with the target non-terrestrial device; and maintaining at least one of: a HARQ buffer, a security key, or a cell configuration.

[0092] In some example embodiments, the method 500 further comprises maintaining at least one of: a control plane configuration and a user plane configuration.

[0093] In some example embodiments, the method 500 further comprises maintaining at least one of the following states: a physical entity state, a medium access control entity state, a radio link control entity state, a packet data convergence protocol entity state, or a radio resource control entity state.

[0094] In some example embodiments, the assistance information further includes at least one of: a reference time when the assistance information is valid, ephemeris information of the target non-terrestrial device, or a common delay associated with the target non-terrestrial device.

[0095] In some example embodiments, a first device (eg, Figure 1 The first device 110 in the method 400 may include components for performing the corresponding operations of the method 400. The components may be implemented in any suitable form. For example, the components may be implemented in a circuit or a software module. The first device may be implemented as or included in Figure 1 In the first device 110.

[0096] In some example embodiments, the first device includes: a component for receiving auxiliary information for switching from a source non-terrestrial device to a target non-terrestrial device from a second device, wherein the auxiliary information includes an indication of a cell identity change associated with the switching; and a component for causing at least one of the following to be maintained for multiple alternatives for the indication: a hybrid automatic repeat request HARQ buffer, a security key for radio communication, or a cell configuration.

[0097] In some example embodiments, the indication of the cell identity change comprises one of: a handover with a physical cell identity change, a handover without a physical cell identity change, or a handover with a virtual physical cell identity change.

[0098] In some example embodiments, the first apparatus further comprises: means for determining that the indication indicates a handover with a physical cell identity change; means for obtaining a target physical cell identity associated with the target non-terrestrial device from the auxiliary information; means for changing the physical cell identity of the serving cell to the target physical cell identity; and means for maintaining at least one of: a HARQ buffer, a security key, or a cell configuration.

[0099] In some example embodiments, the first device further comprises: means for determining that the indication indicates a handover without a physical cell identity change; means for maintaining the physical cell identity of the serving cell unchanged; and means for maintaining at least one of: a HARQ buffer, a security key, or a cell configuration.

[0100] In some example embodiments, the first apparatus further comprises: means for determining that the indication indicates a handover with a virtual physical cell identity change; means for maintaining a source physical cell identity associated with a source non-terrestrial device and a target physical cell identity associated with a target non-terrestrial device; and means for maintaining at least one of: a HARQ buffer, a security key, or a cell configuration.

[0101] In some example embodiments, the first apparatus further comprises means for maintaining at least one of: a control plane configuration and a user plane configuration.

[0102] In some example embodiments, the first apparatus further comprises means for performing a resynchronization with the target non-terrestrial device.

[0103] In some example embodiments, the assistance information further includes at least one of: a reference time when the assistance information is valid, ephemeris information of the target non-terrestrial device, or a common delay associated with the target non-terrestrial device.

[0104] In some example embodiments, the first apparatus comprises a terminal device and the second apparatus comprises a network device.

[0105] In some example embodiments, the first apparatus further comprises means for performing other operations in some example embodiments of the method 400 or the first device 110. In some example embodiments, the means comprises at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the execution of the first apparatus.

[0106] In some example embodiments, a second device (eg, Figure 1 The second device 120 in the method 500 may include components for performing the corresponding operations of the method 500. The components may be implemented in any suitable form. For example, the components may be implemented in a circuit or a software module. The second device may be implemented as or included in Figure 1 In the second device 120.

[0107] In some example embodiments, the second device includes: a component for sending auxiliary information for switching from a source non-terrestrial device to a target non-terrestrial device to the first device, wherein the auxiliary information includes an indication of a cell identity change associated with the switching; and a component for causing at least one of the following to be maintained for multiple alternatives for the indication: a hybrid automatic repeat request HARQ buffer, a security key for radio communication, or a cell configuration.

[0108] In some example embodiments, the indication of the cell identity change comprises one of: a handover with a physical cell identity change, a handover without a physical cell identity change, or a handover with a virtual physical cell identity change.

[0109] In some example embodiments, switching the virtual physical cell identity change indication maintains the physical cell identity and the unchanged physical cell identity.

[0110] In some example embodiments, the second apparatus further comprises: means for determining that the indication indicates a handover with a physical cell identity change; means for changing the physical cell identity of the serving cell to a target physical cell identity associated with the target non-terrestrial device; and means for maintaining at least one of: a HARQ buffer, a security key, or a cell configuration.

[0111] In some example embodiments, the second device further comprises: means for determining that the indication indicates a handover without a physical cell identity change; means for maintaining the physical cell identity of the serving cell unchanged; and means for maintaining at least one of: a HARQ buffer, a security key, or a cell configuration.

[0112] In some example embodiments, the second apparatus further comprises: means for determining that the indication indicates a handover with a virtual physical cell identity change; means for maintaining a source physical cell identity associated with a source non-terrestrial device and a target physical cell identity associated with a target non-terrestrial device; and means for maintaining at least one of: a HARQ buffer, a security key, or a cell configuration.

[0113] In some example embodiments, the second apparatus further comprises means for maintaining at least one of: a control plane configuration and a user plane configuration.

[0114] In some example embodiments, the second apparatus further comprises means for maintaining at least one of a physical entity state, a medium access control entity state, a radio link control entity state, a packet data convergence protocol entity state, or a radio resource control entity state.

[0115] In some example embodiments, the assistance information further includes at least one of: a reference time when the assistance information is valid, ephemeris information of the target non-terrestrial device, or a common delay associated with the target non-terrestrial device.

[0116] In some example embodiments, the first apparatus comprises a terminal device and the second apparatus comprises a network device.

[0117] In some example embodiments, the second apparatus further comprises means for performing other operations in some example embodiments of the method 500 or the second device 120. In some example embodiments, the means comprises at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause execution of the second apparatus.

[0118] Figure 6 600 is a simplified block diagram of a device 600 suitable for implementing an example embodiment of the present disclosure. The device 600 may be provided to implement a communication device, such as Figure 1 The first device 110 or the second device 120 is shown. As shown in the figure, the device 600 includes one or more processors 610, one or more memories 620 coupled to the processor 610, and one or more communication modules 640 coupled to the processor 610.

[0119] The communication module 640 is used for two-way communication. The communication module 640 has one or more communication interfaces to facilitate communication with one or more other modules or devices. The communication interface may represent any interface necessary for communicating with other network elements. In some example embodiments, the communication module 640 may include at least one antenna.

[0120] As non-limiting examples, processor 610 may be of any type suitable for a local technology network and may include one or more of the following: a general purpose computer, a special purpose computer, a microprocessor, a digital signal processor (DSP), and a processor based on a multi-core processor architecture. Device 600 may have multiple processors, such as application specific integrated circuit chips that are time slaved to a clock synchronized with a main processor.

[0121] The memory 620 may include one or more non-volatile memories and one or more volatile memories. Examples of non-volatile memories include, but are not limited to, read-only memory (ROM) 624, electrically programmable read-only memory (EPROM), flash memory, hard disk, compact disk (CD), digital video disk (DVD), optical disk, laser disk, and other magnetic storage and / or optical storage. Examples of volatile memories include, but are not limited to, random access memory (RAM) 622 and other volatile memories that do not persist during a power outage.

[0122] The computer program 630 includes computer executable instructions executed by the associated processor 610. The instructions of the program 630 may include instructions for performing the operations / actions of some example embodiments of the present disclosure. The program 630 may be stored in a memory, such as ROM 624. The processor 610 may perform any suitable actions and processes by loading the program 630 into the RAM 622.

[0123] The exemplary embodiments of the present disclosure may be implemented by a program 630 so that the device 600 may execute the Figures 2 to 5 Any process of the present disclosure discussed. The exemplary embodiments of the present disclosure may also be implemented by hardware or a combination of software and hardware.

[0124] In some example embodiments, the program 630 may be tangibly embodied in a computer-readable medium that may be included in the device 600 (such as in the memory 620) or in other storage devices accessible by the device 600. The device 600 may load the program 630 from the computer-readable medium to the RAM 622 for execution. In some example embodiments, the computer-readable medium may include any type of non-transitory storage medium, such as ROM, EPROM, flash memory, hard disk, CD, DVD, etc. As used herein, the term "non-transitory" is a limitation of the medium itself (i.e., tangible, not a signal), not a limitation on data storage persistence (e.g., RAM versus ROM).

[0125] Figure 7 An example of a computer readable medium 700 is shown, which may be in the form of a CD, DVD or other optical storage disc. The computer readable medium 700 has a program 630 stored thereon.

[0126] Generally, various embodiments of the present disclosure may be implemented in hardware or dedicated circuits, software, logic, or any combination thereof. Some aspects may be implemented in hardware, and other aspects may be implemented in firmware or software that may be executed by a controller, microprocessor, or other computing device. Although various aspects of the embodiments of the present disclosure are shown and described as block diagrams, flow charts, or using some other graphical representations, it should be understood that, as non-limiting examples, the blocks, devices, systems, techniques, or methods described herein may be implemented in hardware, software, firmware, dedicated circuits or logic, general hardware or controllers or other computing devices, or some combination thereof.

[0127] Some example embodiments of the present disclosure also provide at least one computer program product tangibly stored on a computer-readable medium (e.g., a non-transient computer-readable medium). The computer program product includes computer executable instructions, such as those instructions included in a program module that are executed in a device on a target physical or virtual processor to perform any method as described above. Typically, a program module includes routines, programs, libraries, objects, classes, components, data structures, etc. that perform specific tasks or implement specific abstract data types. The functions of the program modules can be combined or split between program modules as needed in various embodiments. Machine executable instructions for program modules can be executed in local or distributed devices. In distributed devices, program modules can be located in local and remote storage media.

[0128] The program code for executing the method of the present disclosure can be written in any combination of one or more programming languages. The program code can be provided to a processor or controller of a general-purpose computer, a special-purpose computer or other programmable data processing device so that the program code, when executed by the processor or controller, causes the realization of the function / operation specified in the flow chart and / or block diagram. The program code can be executed completely on the machine, partially on the machine, as an independent software package, partially on the machine and partially on a remote machine, or completely on a remote machine or server.

[0129] In the context of the present disclosure, computer program codes or related data may be carried by any suitable carrier to enable a device, apparatus or processor to perform various processes and operations as described above. Examples of carriers include signals, computer readable media, etc.

[0130] The computer readable medium may be a computer readable signal medium or a computer readable storage medium. The computer readable medium may include, but is not limited to, electronic, magnetic, optical, electromagnetic, infrared or semiconductor systems, devices or apparatuses, or any suitable combination of the foregoing. More specific examples of computer readable storage media would include an electrical connection with one or more wires, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage component, a magnetic storage component, or any suitable combination of the foregoing.

[0131] In addition, although the operations are depicted in a particular order, this should not be understood as requiring the operations to be performed in the particular order shown or in a sequential order, or to perform all the operations shown, to achieve the desired result. In some cases, multitasking and parallel processing may be advantageous. Similarly, although several specific implementation details are included in the above discussion, these details should not be interpreted as limitations on the scope of the present disclosure, but should be interpreted as descriptions of features specific to a particular embodiment. Unless explicitly stated, certain features described in the context of a separate embodiment may also be implemented in combination in a single embodiment. On the contrary, unless explicitly stated, the various features described in the context of a single embodiment may also be implemented in multiple embodiments individually or in any suitable sub-combination.

[0132] Although the disclosure has been described in language specific to structural features and / or methodological acts, it should be understood that the disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

1. A first device for communication, comprising: at least one processor; as well as at least one memory storing instructions, which when executed by the at least one processor cause the first device to: receiving, from a second apparatus, assistance information for handover from a source non-terrestrial device to a target non-terrestrial device, wherein the assistance information comprises an indication that there is no physical cell identity change in the handover; and At least a hybrid automatic repeat request (HARQ) buffer is caused to be maintained for the handover without the physical cell identity change.

2. The first apparatus according to claim 1, wherein the first apparatus is further caused to maintain at least one of the following for the handover without the physical cell identity change: Security keys for radio communications, Cell configuration.

3. The first device according to claim 1, wherein the first device is further configured to: determining that the indication indicates that the handover does not have a change in the physical cell identifier; Maintaining the physical cell identity of the serving cell unchanged; and Maintain at least one of the following: the security key, the cell configuration.

4. The first device according to any one of claims 1 to 3, wherein the first device is further configured to: Maintain at least one of the following: control plane configuration, user plane configuration.

5. The first device according to any one of claims 1 to 3, wherein the first device is configured to: Resynchronization with the target non-terrestrial device is performed.

6. The first device according to any one of claims 1 to 3, wherein the auxiliary information further includes at least one of the following: The reference time when the auxiliary information is valid, ephemeris information of the target non-ground device, A common delay associated with the target non-terrestrial device.

7. The first apparatus according to any one of claims 1 to 3, wherein the first apparatus comprises a terminal device, and the second apparatus comprises a network device.

8. A second device for communication, comprising: at least one processor; as well as at least one memory storing instructions, which when executed by the at least one processor cause the second device to: sending assistance information for handover from a source non-terrestrial device to a target non-terrestrial device to the first apparatus, wherein the assistance information includes an indication that there is no physical cell identity change in the handover; and At least a hybrid automatic repeat request (HARQ) buffer is caused to be maintained for the handover without the physical cell identity change.

9. The second apparatus according to claim 8, wherein the second apparatus is further caused to maintain at least one of the following for the handover without the physical cell identity change: Security keys for radio communications, Cell configuration.

10. The second device according to claim 8, wherein the second device is further configured to: determining that the indication indicates that the handover does not have a change in the physical cell identifier; Maintaining the physical cell identity of the serving cell unchanged; and Maintain at least one of the following: the security key, the cell configuration.

11. The second device according to any one of claims 8 to 10, wherein the second device is further configured to: Maintain at least one of the following: control plane configuration, user plane configuration.

12. The second device according to any one of claims 8 to 10, wherein the second device is configured to: Maintain at least one of the following states: Physical entity state, Media access control entity status, Radio link control entity status, Packet Data Convergence Protocol entity status, Radio resource control entity status.

13. The second device according to any one of claims 8 to 10, wherein the auxiliary information further includes at least one of the following: The reference time when the auxiliary information is valid, ephemeris information of the target non-ground device, A common delay associated with the target non-terrestrial device.

14. The second apparatus according to any one of claims 8 to 10, wherein the first apparatus comprises a terminal device, and the second apparatus comprises a network device.

15. A communication method, comprising: receiving, at the first apparatus, assistance information for handover from a source non-terrestrial device to a target non-terrestrial device from a second apparatus, wherein the assistance information includes an indication that the handover has no physical cell identity change; and At least a hybrid automatic repeat request (HARQ) buffer is caused to be maintained for the handover without the physical cell identity change.

16. The method according to claim 15, wherein the first device further maintains at least one of the following for the handover without the physical cell identity change: Security keys for radio communications, Cell configuration.

17. The method according to claim 15, wherein the first device further performs the following operations: determining that the indication indicates that the handover does not have a change in the physical cell identifier; Maintaining the physical cell identity of the serving cell unchanged; and Maintain at least one of the following: the security key, the cell configuration.

18. The method according to any one of claims 15 to 17, wherein the first device further performs the following operations: Maintain at least one of the following: control plane configuration, user plane configuration.

19. The method according to any one of claims 15 to 17, wherein the first apparatus performs a resynchronization with the target non-terrestrial device.

20. The method according to any one of claims 15 to 17, wherein the auxiliary information further comprises at least one of the following: The reference time when the auxiliary information is valid, ephemeris information of the target non-ground device, A common delay associated with the target non-terrestrial device.

21. The method according to any one of claims 15 to 17, wherein the first device comprises a terminal device, and the second device comprises a network device.

22. A method for communication, comprising: At the second device, sending to the first device assistance information for handover from the source non-terrestrial device to the target non-terrestrial device, wherein the assistance information includes an indication that there is no physical cell identity change in the handover; and At least a hybrid automatic repeat request (HARQ) buffer is caused to be maintained for the handover without the physical cell identity change.

23. The method of claim 22, wherein the second device is further caused to maintain at least one of the following for the handover without the physical cell identity change: Security keys for radio communications, Cell configuration.

24. The method according to claim 22, wherein the second device further performs the following operations: determining that the indication indicates that the handover has no physical cell identity change; Maintaining the physical cell identity of the serving cell unchanged; and Maintain at least one of the following: the security key, the cell configuration.

25. The method according to any one of claims 22 to 24, wherein the second device maintains at least one of the following: a control plane configuration, a user plane configuration.

26. The method according to any one of claims 22 to 24, wherein the second device maintains at least one of the following states: Physical entity state, Media access control entity status, Radio link control entity status, Packet Data Convergence Protocol entity status, Radio resource control entity status.

27. The method according to any one of claims 22 to 24, wherein the auxiliary information further comprises at least one of the following: The reference time when the auxiliary information is valid, ephemeris information of the target non-ground device, A common delay associated with the target non-terrestrial device.

28. The method according to any one of claims 22 to 24, wherein the first device comprises a terminal device, and the second device comprises a network device.

29. A computer-readable medium comprising instructions stored thereon, the instructions being configured to cause an apparatus to at least perform the method of any one of claims 15 to 28.

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