Handover in scenarios where both source and target distributed units are co-located

Abstract

Embodiments of the present disclosure relate to apparatus, methods, devices and computer readable storage media for handover in scenarios when source and target distributed units are co-located. The method comprises, at a first device, the first device sending an indication to a second device to use a deferred handover for a handover of a third device from the second device to a fourth device, the fourth device being co-located with the second device, wherein by using the deferred handover, at least a part of downlink data buffered at the second device is to be transmitted to the third device before performing the handover of the third device.

Description

Technical Field

[0001] Various exemplary embodiments of this disclosure generally relate to the telecommunications field, and more particularly to methods, apparatus, devices, and computer-readable storage media for switching in scenarios where both a source distributed unit (DU) and a target DU are co-located. Background Technology

[0002] The 3rd Generation Partnership Project (3GPP) has proposed a regenerative non-terrestrial network (NTN) architecture with gNB-DU on satellites. Satellites can also carry Centralized Unit-User Plane (CU-UP), User Plane Function (UPF), and other features. This architecture supports three types of service links: fixed earth links, quasi-fixed earth links, and mobile earth links. Summary of the Invention

[0003] In a first aspect of this disclosure, a first apparatus is provided. The first apparatus includes: at least one processor; and at least one memory, at least one memory storing instructions that, when executed by the at least one processor, cause the first apparatus to at least: send an instruction to a second apparatus requesting the second apparatus to use a delayed switching, the delayed switching being for a switch of a third apparatus from the second apparatus to a fourth apparatus, the fourth apparatus being co-located with the second apparatus, wherein, by using the delayed switching, at least a portion of DL data buffered at the second apparatus is to be sent to the third apparatus before the switch of the third apparatus is performed.

[0004] In a second aspect of this disclosure, a second apparatus is provided. The second apparatus includes: at least one processor; and at least one memory, the memory storing instructions that, when executed by the at least one processor, cause the first apparatus to at least: receive from the first apparatus an instruction requesting the second apparatus to use a delayed switching, the delayed switching being for a third apparatus switching from the second apparatus to a fourth apparatus; and perform the delayed switching for the third apparatus, wherein, by using the delayed switching, at least a portion of DL data buffered at the second apparatus is to be sent to the third apparatus before the switching of the third apparatus is performed.

[0005] In a third aspect of this disclosure, a third apparatus is provided. The third apparatus includes: at least one processor; and at least one memory, the memory storing instructions that, when executed by the at least one processor, cause the third apparatus to at least: receive DL data buffered at the second apparatus, the second apparatus performing a delayed switching for a switching of the third apparatus from the second apparatus to a fourth apparatus; and perform the switching based on at least one of a switching triggering condition or a buffered DL data delivery state.

[0006] In a fourth aspect of this disclosure, a method is provided. The method includes: sending an instruction from a first device to a second device requesting the second device to use a delayed switching, the delayed switching being for a switching of a third device from the second device to a fourth device, the fourth device being co-located with the second device, wherein by using the delayed switching, at least a portion of DL data buffered at the second device is to be sent to the third device before the switching of the third device is performed.

[0007] In a fifth aspect of this disclosure, a method is provided. The method includes: receiving from a first device an instruction requesting a second device to use a delayed switching, the delayed switching being for a third device switching from the second device to a fourth device; and performing a delayed switching for the third device, wherein by using the delayed switching, at least a portion of DL data buffered at the second device is to be sent to the third device before the switching of the third device is performed.

[0008] In a sixth aspect of this disclosure, a method is provided. The method includes: receiving DL data buffered at a second device from a second device, the second device performing a delayed handover, the delayed handover being a handover of a third device from the second device to a fourth device; and performing the handover based on at least one of a handover triggering condition or a buffered DL data delivery state.

[0009] In a seventh aspect of this disclosure, a first apparatus is provided. The first apparatus includes components for sending an instruction to a second apparatus requesting the second apparatus to use a delayed switching, the delayed switching being for a third apparatus to switch from the second apparatus to a fourth apparatus, the fourth apparatus being co-located with the second apparatus, wherein by using the delayed switching, at least a portion of DL data buffered at the second apparatus is to be sent to the third apparatus before the switching of the third apparatus is performed.

[0010] In an eighth aspect of this disclosure, a second apparatus is provided. The second apparatus includes: means for receiving from a first apparatus an instruction requesting the second apparatus to use a delayed switching for a third apparatus to switch from the second apparatus to a fourth apparatus; and means for performing the delayed switching for the third apparatus, wherein by using the delayed switching, at least a portion of DL data buffered at the second apparatus is to be sent to the third apparatus before the switching of the third apparatus is performed.

[0011] In a ninth aspect of this disclosure, a third apparatus is provided. The third apparatus includes: means for receiving DL data buffered at a second apparatus, the second apparatus performing a delayed handover for a handover of the third apparatus from the second apparatus to a fourth apparatus; and means for performing the handover based on at least one of a handover triggering condition or a buffered DL data delivery state.

[0012] In a tenth aspect of this disclosure, a computer-readable medium is provided. The computer-readable medium includes instructions stored thereon that cause a device to perform at least the method according to the fourth aspect.

[0013] In the eleventh aspect of this disclosure, a computer-readable medium is provided. The computer-readable medium includes instructions stored thereon that cause a device to perform at least the method according to the fifth aspect.

[0014] In a twelfth aspect of this disclosure, a computer-readable medium is provided. The computer-readable medium includes instructions stored thereon that cause a device to perform at least the method according to a sixth aspect.

[0015] It should be understood that the summary portion is not intended to identify key or essential features of the embodiments of this disclosure, nor is it intended to limit the scope of this disclosure. Other features of this disclosure will become readily apparent from the following description. Attached Figure Description

[0016] Some exemplary embodiments will now be described with reference to the accompanying drawings, in which: Figure 1 An example communication environment in which example embodiments of this disclosure may be implemented is shown; Figure 2 Signaling diagrams based on a normal handover process according to some example embodiments of the present disclosure are shown; Figure 3 Signaling diagrams of example procedures based on conditional switching according to some example embodiments of the present disclosure are shown; Figure 4 An example scenario of full migration of Mobile Integrated Access and Backhaul (IAB) according to some example embodiments of the present disclosure is shown; Figure 5 A flowchart is shown illustrating a method implemented at a first device according to some exemplary embodiments of the present disclosure; Figure 6 A flowchart is shown illustrating a method implemented at a second device according to some example embodiments of the present disclosure; Figure 7 A flowchart is shown illustrating a method implemented at a third device according to some example embodiments of the present disclosure; Figure 8 A simplified block diagram of a device suitable for implementing example embodiments of the present disclosure is shown; and Figure 9 A block diagram of an example computer-readable medium according to some example embodiments of the present disclosure is shown.

[0017] In all the accompanying drawings, the same or similar reference numerals denote the same or similar elements. Detailed Implementation

[0018] The principles of this disclosure will now be described with reference to some exemplary embodiments. It should be understood that these embodiments are described for illustrative purposes only and to help those skilled in the art to understand and implement this disclosure, without implying any limitation on the scope of this disclosure. The embodiments described herein can be implemented in various ways other than those described below.

[0019] In the following description and claims, unless otherwise defined, 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 pertains.

[0020] References to "an embodiment," "embodiment," "example embodiment," etc., in this disclosure indicate that the described embodiment may include a particular feature, structure, or characteristic, but not every embodiment includes that particular feature, structure, or characteristic. Furthermore, these phrases do not necessarily refer to the same embodiment. In addition, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is to be noted that those skilled in the art will recognize, whether explicitly described or not, that such feature, structure, or characteristic is affected by other embodiments.

[0021] It should be understood that although terms such as "first," "second," etc., preceding nouns may be used herein to describe various elements, these elements should not be limited by these terms. These terms are used only to distinguish one element from another, and they do not restrict the order of the nouns. For example, without departing from the scope of the exemplary embodiments, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element. As used herein, the term "and / or" includes any and all combinations of one or more of the listed terms.

[0022] As used herein, “at least one of the following: ” and “at least one of ” and similar expressions, where the list of two or more elements is connected by “and” or “or”, means at least one of these elements, or at least any two or more of these elements, or at least all of these elements.

[0023] As used herein, unless explicitly stated otherwise, the execution step “in response to A” does not indicate that the step is performed immediately after “A” occurs, but may include one or more intermediate steps.

[0024] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary 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 should also be understood that the terms “comprising,” “including,” “having,” “possessing,” “containing,” and / or “covering,” as used herein, specify the presence of the stated features, elements, and / or components, but do not exclude the presence or addition of one or more other features, elements, components, and / or combinations thereof.

[0025] As used in this application, the term "circuit" may refer to one or more or all of the following: (a) Hardware circuit implementation only (e.g., implemented with purely analog and / or digital circuits) and (b) A combination of hardware circuitry and software, such as (if applicable): (i) A combination of (multiple) analog and / or digital hardware circuits and software / firmware, and (ii) Any part of a hardware processor having software (including (multiple) digital signal processors, software, and (multiple) memories that work together to enable a device (such as a mobile phone or server) to perform various functions), and (c) A hardware circuit (multiple) and / or a processor (multiple) that requires software (e.g., firmware) for operation, such as a microprocessor (multiple) or part of a microprocessor, but which may be absent when the software is not required for operation.

[0026] This definition of "circuit" applies to all uses of the term in this application (including in any claim). As a further example, as used in this application, the term "circuit" also covers only hardware circuitry or processors (or processors), or portions of hardware circuitry or processors and their accompanying software and / or firmware implementations. For example, where applicable to a particular claim element, the term "circuit" also covers baseband integrated circuits or processor integrated circuits for mobile devices or similar integrated circuits in servers, cellular network devices, or other computing or network devices.

[0027] As used herein, the term "communication network" refers to any network that conforms to any suitable communication standard, such as New Radio (NR), Long Term Evolution (LTE), LTE-A Advanced (LTE-A), Wideband Code Division Multiple Access (WCDMA), High-Speed ​​Packet Access (HSPA), Narrowband Internet of Things (NB-IoT), etc. Furthermore, communication between terminal devices and network devices in a communication network can be performed according to any suitable generation of communication protocol, including but not limited to 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 protocols, and / or any other currently known or under development protocols. Embodiments of this disclosure can be applied to a variety of communication systems. Given the rapid development of communications, there will inevitably be communication technologies and systems that embody future types of this disclosure. The scope of this disclosure should not be considered limited to the aforementioned systems.

[0028] As used herein, the term "network device" refers to a node in a communications network through which terminal devices access the network and receive services. Depending on the terminology and technology applied, a network device can refer to a base station (BS) or access point, such as a Node B (NodeB or NB), an evolved Node B (eNodeB or eNB), an NR NB (also known as a gNB), a distributed unit (gNB-DU) of a gNB, or a central unit (gNB-CU) of a gNB, a remote radio unit (RRU), a radio header (RH), a remote radio header end (RRH), a relay, an integrated access and backhaul (IAB) node, a low-power node (such as a femtosecond or picosecond), a non-terrestrial network (NTN) or non-terrestrial network equipment (such as satellite network equipment, low Earth orbit (LEO) satellites, and geostationary Earth orbit (GEO) satellites), spacecraft network equipment, etc. In some example embodiments, the radio access network (RAN) may be based on a split architecture. A network device may include a central unit (CU) and one or more distributed units (DUs).

[0029] The term "terminal device" refers to any terminal device capable of wireless communication. By way of example and not limitation, terminal device may also refer to communication equipment, user equipment (UE), subscriber station (SS), portable subscriber station, mobile station (MS), or access terminal (AT). Terminal devices may include, but are not limited to, mobile phones, cellular phones, smartphones, Voice over IP (VoIP) phones, wireless local loop phones, tablets, wearable terminal devices, personal digital assistants (PDAs), portable computers, desktop computers, image acquisition terminal devices (such as digital cameras), gaming terminal devices, music storage and playback devices, in-vehicle wireless terminal devices, wireless endpoints, mobile stations, laptop embedded equipment (LEE), laptop mounted equipment (LME), USB dongles, smart devices, wireless customer premises equipment (CPE), Internet of Things (IoT) devices, watches or other wearable devices, head-mounted displays (HMDs), vehicles, drones, medical devices and applications (e.g., remote surgery), industrial devices and applications (e.g., robots and / or other wireless devices operating in the context of industrial and / or automated processing chains), consumer electronic devices, devices operating on commercial and / or industrial wireless networks, etc. The terminal equipment may also correspond to the mobile termination (MT) portion of an IAB node (e.g., a relay node). In the following description, the terms "terminal equipment," "communication equipment," "terminal," "user equipment," and "UE" are used interchangeably.

[0030] As used herein, the terms “resource,” “transmission resource,” “resource block,” “physical resource block” (PRB), “uplink resource,” or “downlink resource” can refer to any resource used to perform communication, such as communication between a terminal device and a network device, including resources in the time domain, frequency domain, spatial domain, code domain, or any other combination of time, frequency, spatial, and / or code domain resources used to enable communication. In the following, unless explicitly stated otherwise, resources in the frequency and time domains will be used as examples of transmission resources used to describe some exemplary embodiments of this disclosure. Note that the exemplary embodiments of this disclosure are equally applicable to other resources in other domains.

[0031] Figure 1 An example communication environment 100 in which exemplary embodiments of the present disclosure may be implemented is illustrated. In the communication environment 100, the communication environment 100 may include first device 110-1 and first device 110-2. Hereinafter, first device 110-1 and first device 110-2 may also be collectively referred to as first device 110. In some scenarios, first device 110-1 and first device 110-2 may communicate with each other. In some example embodiments, first device 110 may include a network device (e.g., gNB-CU).

[0032] like Figure 1 As shown, the communication environment 100 may also include a second device 120 and a fourth device 140. The second device 120 or the fourth device 140 may each include network equipment (e.g., gNB-DU). In some scenarios, the second device 120 and the fourth device 140 are co-located, for example, deployed at the same satellite, which may be referred to as a non-terrestrial network (NTN) regenerative architecture.

[0033] The second device 120 can communicate with the first device 110-1, and the fourth device 140 can communicate with the first device 110-2. For example, the second device 120 can communicate with the first device 110-1 via a transmission network node (e.g., a gateway (GW)) and / or the fourth device 140 can communicate with the first device 110-2 via a transmission network node (e.g., a gateway (GW)).

[0034] The communication environment 100 may also include a third device 130, which may include a terminal device (e.g., a UE). In some scenarios, the third device 130 may perform inter-DU handover, for example, from the second device 120 to the fourth device 140. For example, when the second device 120 may be unable to serve the third device 130.

[0035] In the following description, for illustrative purposes, some example embodiments are described, wherein a first device 110-1 operates as a source CU, a second device 120 operates as a source DU for switching a third device 130, and a first device 110-2 operates as a target CU and a fourth device 140 operates as a target DU for switching a third device 130.

[0036] However, in some example embodiments, the operations described in connection with the first device 110-1 can be implemented at the first device 110-2, and the operations described in connection with the second device 120 can be implemented at the fourth device 140.

[0037] It should be understood that Figure 1 The number of terminal devices and network devices shown is given for illustrative purposes and does not imply any limitation. The communication environment 100 may include any suitable number of terminal devices and network devices.

[0038] In some example embodiments, the link from the network device to the end device is referred to as a downlink (DL), and the link from the end device to the network device is referred to as an uplink (UL). In the DL, the network device is a transmitting (TX) device (or transmitter), and the end device is a receiving (RX) device (or receiver). In the UL, the end device is a TX device (or transmitter), and the network device is an RX device (or receiver).

[0039] Communication in communication environment 100 can be implemented according to any suitable communication protocol, including but not limited to cellular communication protocols such as first-generation (1G), second-generation (2G), third-generation (3G), fourth-generation (4G), fifth-generation (5G), and sixth-generation (6G), wireless local network communication protocols such as IEEE 802.11, and / or any other currently known or future-developed protocols. Furthermore, communication can 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 Extended OFDM (DFT-s-OFDM), and / or any other currently known or future-developed technologies.

[0040] As described above, the handover can occur in scenarios where the second device 120 and the fourth device 140 are co-located. An example scenario is an NTN regenerative architecture with a DU on a satellite.

[0041] NTN regenerative architecture can support several types of service links. For example, NTN regenerative architecture can support geostationary networks, which can always be provided by multiple beams continuously covering the same geographic area (e.g., in the case of geostationary orbit (GSO) satellites). As another example, NTN regenerative architecture can support quasi-geostationary networks, which can be provided by multiple beams covering one geographic area for a limited time period and a different geographic area for another time period (e.g., in the case of non-geostationary orbit (NGSO) satellites generating steerable beams). As yet another example, NTN regenerative architecture can support geomobile networks, which can be provided by multiple beams whose coverage area slides across the Earth's surface (e.g., in the case of NGSO satellites generating fixed or non-steerable beams).

[0042] NTN regenerative architectures can support Feeder Link Switchover (FLSO). During NTN operation, it may be necessary to switch the satellite's feeder link from one NTN GW to another. This could be due to, for example, maintenance, traffic offloading, or (for NGSO) because the NGSO satellite moves out of the visible range relative to the current NTN GW.

[0043] FLSO can include soft FLSO and hard FLSO. With soft FLSO, the NTN payload can connect to more than one NTN gateway during a given time period; that is, temporary overlap can be ensured during transitions between feeder links. For NTN regenerative architectures with DUs on satellites, FLSO can change the CU. In this case, when the CU changes, all connected UEs in the cell need to switch from CU1 (e.g., the source CU) to CU2 (e.g., the target CU).

[0044] For hard FLSO, the NTN payload can be connected to only one NTN gateway at any given time; that is, radio link interruption may occur during the transition between feeder links.

[0045] refer to Figure 1 For NTN regeneration with gNB-DU on a satellite, when soft FLSO is performed and the CU is changed (e.g., from the first device 110-1 to the first device 110-2), the satellite needs to host at least two gNB-DUs (e.g., the second device 120 and the fourth device 140). The second device 120 (considered the source DU) can be connected to the first device 110-1 (considered the source CU), and the F1 transport network connection between the second device 120 and the first device 110-1 can use a GW or an NTN GW. The first device 110-2 (considered the target CU) can be connected to the fourth device 140 (considered the target DU), and the F1 transport network connection between the fourth device 140 and the first device 110-2 can use another GW or an NTN GW.

[0046] During soft FLSO, a third device 130 (e.g., a UE) can switch from a second device 120 connected to the first device 110-1 to a fourth device 140 connected to the first device 110-2. In this case, the second device 120 (e.g., the source cell) and the fourth device 140 (e.g., the target cell) may have similar coverage areas.

[0047] In this NTN regenerative architecture, there is a problem in the following scenario: when a third device 130 connected to a physical node needs to switch from a second device 120 to a co-located fourth device 140, the physical node co-located with the second device 120 which acts as a source service device for the third device 130, and the fourth device 140 which will act as a target service device for connecting the third device 130 to different first devices.

[0048] For example, during a handover (HO) / conditional handover (CHO) between gNB-DUs, untransmitted DL data buffered in the source DU (i.e., the second device 120) will be discarded, and the first device 110 must re-forward the DL data (which has already been buffered in the second device 120) to the fourth device 140 (which is co-located with the source second device 120) based on the downlink data delivery status (DDDS) received from the second device 120. This is inefficient.

[0049] In Radio Link Control Unacknowledged Mode (RLC UM), the third device 130 will not receive DL data that has been sent to the second device 120 but not to the third device 130, because the first device 110 does not retain them. This results in DL data loss.

[0050] During FLSO involving CU changes, even if the second device 120 can forward unsent DL data (received from the first device 110-1) to the fourth device 140, the fourth device 140 will subsequently send it to the third device 130. The fourth device 140 can also send DL data received from the first device 110-2. The third device 130 will receive both DL data originating from (and encrypted by) the first device 110-1 and DL data originating from (and encrypted by) the first device 110-2. However, the third device 130 cannot distinguish between them. The third device 130 will be unable to decrypt the received DL data until its application layer is able to remove duplicate data.

[0051] In view of the above problems, the exemplary embodiments of this disclosure propose a new solution for handover scenarios when both the source DU and the target DU are co-located. In this solution, the first device 110 sends an instruction to the second device 120 requesting the second device 120 to use delayed handover for a handover of the third device 130 from the second device 120 to the fourth device 140, which is co-located with the second device 120. By using delayed handover, at least a portion of the DL data buffered at the second device 120 is sent to the third device 130 before the handover is performed. In other words, delayed handover means that after the first device 110 makes a decision to handover to the third device 130, the third device 130 does not immediately perform or initiate the handover. Depending on whether the third device 130 supports conditional handover, delayed handover can be implemented by enhancing normal handover, in which the data to the third device 130 is... RRCReconfigurationThe (RRC reconfiguration) message is first buffered in the second device 120, and then delivered to the third device 130 when at least a portion of the DL data buffered at the second device 120 has been sent to the third device 130. Alternatively, the delayed handover can be achieved by enhancing the conditional handover, wherein the third device 130 performs or executes the conditional handover when at least a portion of the DL data buffered at the second device 120 has been sent to the third device 130.

[0052] In this way, unsent DL data buffered in the source DU can be sent to the UE instead of being discarded, whether during normal or conditional handover. Furthermore, when the UE needs to hand over from the source DU to a co-located target DU, duplicate data is avoided from being sent from the CU to the target DU, even though the source and target DUs can be connected to different CUs.

[0053] The exemplary embodiments of this disclosure will now be described in detail with reference to the accompanying drawings.

[0054] Now for reference Figure 2 This illustrates signaling diagram 200 of an example procedure based on normal handover according to some example embodiments of the present disclosure. For example... Figure 2 As shown, signaling diagram 200 relates to a first device 110, a second device 120, a third device 130, and a fourth device 140. For discussion purposes, reference will be made to... Figure 1 Discuss signaling diagram 200.

[0055] exist Figure 1 In some scenarios, the second device 120 and the fourth device 140 are co-located. The second device 120 can be connected to the first device 110-1. The fourth device 140 can be connected to the first device 110-2. For clarity, the XnAP signaling between the first device 110-1 and the first device 110-2 can be omitted. Figure 2 In the image, only a single first device 110 is shown.

[0056] like Figure 2 As shown, in a DU-HO (Duration-Oriented Flow) process, if the first device 100 determines, for example, that a switch from the second device 120 to the fourth device 140 is to be initiated for the third device 130, the first device 110 may send (210) an instruction to the second device 120 requesting the second device 120 to use a delayed switch for the switch to the third device 130. The delayed switch may instruct the second device 120 to continue sending buffered DL data to the third device 130 before the third device 130 performs or initiates a switch.

[0057] For example, the first device 110 can send the instruction to the second device via a message, such as an F1 Application Protocol (F1AP) message, etc. UE CONTEXT MODIFICATION REQUEST(User Equipment Context Modification Request) message, or Downlink Radio Resource Control Message Transmission (DL RRC MASSAGE TRANSFER) message, or other FIAP messages. The first device 110 can send FIAP messages, for example, UE CONTEXT MODIFICATION REQUEST The messages include the generated Radio Resource Control (RRC) reconfiguration messages.

[0058] For example, new information elements (IEs) can be introduced into F1AP messages, such as UE CONTEXT MODIFICATION REQUEST The message indicates a delay switch to be used by the second device 120. The delay switch instruction can instruct the second device 120 to... RRCReconfiguration The message is buffered until all or a certain amount of the DL data buffered at the second device 120 has been sent to the third device 130.

[0059] In cases where the first device 110 intends to use delayed switching, in addition to the IE used for "delayed switching" indication, in some embodiments, the F1AP message, for example... UE CONTEXT MODIFICATION REQUEST The message may also include other transition information, such as timing information for switching, for example, indicating that the switching of the third device 130 must be performed before a certain point in time. That is, buffered at the second device 120. RRCReconfiguration The message must be sent to the third device 130 before this timing.

[0060] In some other embodiments, UE CONTEXT MODIFICATION REQUEST The message may also include an IE for switching location information, for example, indicating that the switching of the third device 130 should be performed before the second device moves to a location. That is, a buffer is established at the second device 120 before the second device 120 (e.g., the satellite hosting the second device 120) reaches the location where the second device 120 can no longer serve the third device 130. RRCReconfiguration The message is to be sent to the third device 130.

[0061] After receiving a delay switching instruction from the first device 110, the second device 120 buffers (220). RRCReconfiguration The message is sent to the third device 130 (230) the DL data buffered at the second device 120.

[0062] Based on the delay switching instruction, in some embodiments, when the last buffered DL data or all buffered DL data or specific buffered DL data has been sent to the third device 130, the second device 120 may send (240) to the third device 130. RRCReconfigurationMessage. In some other embodiments, when a certain amount of buffered DL data has been sent to the third device 130, the second device 120 may send (240) the message to the third device 130. RRCReconfiguration Message. It should be understood that, in RRCReconfiguration Before the message is transmitted, a minimum amount of buffered DL data can be sent to the third device 130. This minimum amount of buffered DL data and / or the minimum amount of buffered DL data can also be configured by the first device 110 and used as part of a delay switching indication.

[0063] Furthermore, a wireless link connection can be guaranteed for the third device 130. That is, the second device 120 can determine whether it should send data to the third device 130 based on (a number of) other conditions indicated by the delay handover indication. RRCReconfiguration information.

[0064] In some example embodiments, the second device 120 may send a buffer to the third device 130 before the point at which the second device 120 becomes unable to serve the third device 130. RRCReconfiguration For example, even if a portion of the DL data still buffered at the second device 120 is not sent to the third device 130.

[0065] In other example embodiments, the second device 120 may send a buffer to the third device 130 before the second device 120 moves to a position where the second device 120 can no longer serve the third device 130. RRCReconfiguration For example, even if a portion of the DL data still buffered at the second device 120 is not sent to the third device 130.

[0066] The second device 120 may send a (250) DDDS message to the first device 110 to indicate the status of DL data that is currently still buffered at the second device 120 but will be sent to the third device 130 before the third device 130 performs a handover. For example, the second device 120 may indicate the highest sequence number of a Packet Data Convergence Protocol (PDCP) data unit via a DDDS message, which will be successfully delivered to the third device 130 before the third device 130 performs a handover.

[0067] For example, if the second device 120 has successfully sent DL up to PDCP SN#10, and the second device 120 still has unsent DL packets from PDCP SN#11 to #20, then the second device 120 may indicate the highest sequence number of the PDCP protocol data unit to be successfully delivered before the third device 130 performs the handover, namely sequence number #20.

[0068] In addition, the first device 110 can continue downlink transmission after receiving the DDDS message, and the second device 120 can notify the first device 110 of those DL data that have not yet been successfully sent to the third device 130 but will be sent to the third device 130 before the third device 130 performs a handover.

[0069] Then, the second device 120 can send a (260) message to the first device 110, for example, an F1AP message, for example, UE CONTEXT MODIFICATION RESPONSE information.

[0070] Now for reference Figure 3 The diagram 300 illustrates a signaling diagram of an example process based on conditional switching according to some example embodiments of the present disclosure. Figure 3 As shown, signaling diagram 300 relates to a first device 110, a second device 120, a third device 130, and a fourth device 140. For discussion purposes, reference will be made to... Figure 1 Discuss signaling diagram 300.

[0071] Figure 2 Examples and Figure 3 The difference between the examples is that the third device 110 can support condition switching. For example... Figure 3 As shown, the first device 110 can send (310) to the second device 120 via a message. RRCReconfiguration The message, such as an F1AP message, etc. DL RRC MESSAGE TRANSFER In cases where the first device 110 may expect to use delayed switching, the F1AP message may include an indication to request the second device 120 to use delayed switching.

[0072] RRCReconfiguration The message may also include new triggering conditions for conditional handover of the third device 130. For example, the third device 130 may perform handover when the last DL data or a certain amount of DL data has been received from the second device 120 or the source cell. RRCReconfiguration That is, the third device 130 can determine whether to perform a conditional switch by taking into account the buffered DL data delivery status of the second device 120.

[0073] Furthermore, this trigger condition can be used in conjunction with other trigger conditions (e.g., timing-based trigger conditions or location-based trigger conditions) to ensure that handover is triggered before the source cell disappears.

[0074] Continue to refer to Figure 3The second device 120 can forward (320) the RRC reconfiguration message including the aforementioned triggering conditions to the third device 130. The third device 130 can respond to the second device 120 with an RRC reconfiguration completion message (330). Then, the second device 120 can continue (350) DL transmission until all buffered DL data or a certain amount of buffered DL data has been sent.

[0075] Optionally or additionally, the second device 120 may send (360) buffered DL data to the third device 130 and indicate (370) the last buffered DL data to the third device 130.

[0076] In some example embodiments, when the second device 120 sends the last buffered DL data, the second device 120 may indicate that the DL data is the last buffered DL data, for example via a new flag in the header of the PDCP protocol data.

[0077] In some other embodiments, the second device 120 may pre-indicate the group number or sequence number of the last buffered DL data packet to the third device 130. Therefore, when the third device 130 receives the last buffered DL data, for example, when it receives DL data with a specific group number or sequence number, the third device 130 can know that the data is the last buffered DL data.

[0078] The third device 130 does not execute the received command. RRCReconfiguration The message continues until the triggering condition for conditional handover is met. The third device 130 can determine (380) whether the triggering condition for conditional handover has been met. In some example embodiments, the third device 130 can determine that the triggering condition for conditional handover has been met, for example, when the last buffered DL data from the source cell has been received. That is, the triggering condition for conditional handover may include whether the last buffered DL data in the second device 120 has been received, or whether a certain amount of buffered DL data has been received from the second device 120, whether buffered DL data with a specific sequence number has been received from the second device 120, whether a time point has passed in which the second device 120 can no longer serve the third device 130, or whether the second device 120 is moving to a location. If so, the third device 130 can perform conditional handover.

[0079] In some other example embodiments, the third device 130 may determine whether to initiate a condition switch based on other triggering conditions(s), such as whether the time point when the second device 120 is unable to serve the third device has passed and / or whether the second device 120 is moving to a location where it is unable to serve the third device 130.

[0080] After determining that the triggering condition for condition switching has been met, the third device 130 can perform buffering. RRCReconfiguration The message is separated from the second device 120 and connected to the fourth device 140.

[0081] In this way, whether in a normal handover or a conditional handover, unsent DL data buffered in the second device 120 can be sent to the third device 130 instead of being discarded.

[0082] Furthermore, embodiments of this disclosure can be used in scenarios such as when the UE is in Figure 4 The handover is performed in the case of Mobile Integrated Access and Backhaul (IAB) migration (i.e., IAB DU migration) as described in the document.

[0083] Now for reference Figure 4 This illustrates an example scenario of a complete mobile IAB migration according to some example embodiments of this disclosure. For example... Figure 4 As shown, scenario 400 involves IAB donor CU 410-1 (referred to as the source CU), IAB donor CU 410-2 (referred to as the target CU), and IAB 450. A mobile IAB or mobile base station relay (MBSR) 440 has two co-located IAB DUs, namely DU 420 (referred to as the source DU) and DU 440 (referred to as the target DU). A source F1 is established between IAB donor CU 410-1 (source CU) and DU 420. A target F1 is established between IAB donor CU 410-2 (source CU) and DU 440.

[0084] During IAB-DU migration, a UE handover 430 can be performed from the source CU / DU pair to the target CU / DU pair. The serving UE's F1 is handed over from the source F1 to the target F1. Combined with... Figures 2 to 3 The described operation also applies to the switch that occurs at scene 400. Details will be omitted here.

[0085] Figure 5 A flowchart of an example method 500 implemented at a first device according to some example embodiments of the present disclosure is shown. For the purposes of discussion, [the following will be discussed]. Figure 1 Method 500 is described by the angle of the first device 110 in the middle.

[0086] In block 510, the first device 110 sends an instruction to the second device requesting the second device to use a delayed switching for a third device to switch from the second device to a fourth device, which is co-located with the second device, wherein by using the delayed switching, at least a portion of the DL data buffered at the second device is to be sent to the third device before the switching of the third device is performed.

[0087] In some example embodiments, method 500 further includes: the first device 110 sending an instruction to the second device via information elements of a message, such as an IFAP message, a UE context modification request message, or a downlink radio resource control message.

[0088] In some example embodiments, the indication includes at least one additional information element indicating at least one of the following: the switching of the third device will be performed before a certain point in time; the switching of the third device will be performed before the second device moves to a certain position; all downlink data buffered in the second device has been sent to the third device; a certain amount of downlink data buffered in the second device has been sent to the third device; or downlink data buffered in the second device with a specific sequence number has been sent to the third device.

[0089] In some example embodiments, method 500 further includes: a first device 110 receiving an indication from a second device that the highest sequence number of a Packet Data Convergence Protocol (PDCP) data unit will be successfully delivered to the third device before a switchover of the third device is performed.

[0090] In some example embodiments, method 500 further includes: the first device 110 sending a radio resource control reconfiguration message to the third device via the second device, wherein the radio resource control reconfiguration message indicates a triggering condition for a conditional switch of the third device, the triggering condition including at least one of the following: whether the last buffered DL data has been received from the second device, whether a certain amount of buffered DL data has been received from the second device, whether buffered DL data with a specific sequence number has been received from the second device, whether a time point in time when the second device is unable to serve the third device has passed, or whether the second device is moving to a location.

[0091] In some example embodiments, the first device includes a centralized unit, the second device includes a source distributed unit undergoing handover, the third device includes a terminal device, and the fourth device includes a target distributed unit undergoing handover.

[0092] Figure 6 A flowchart of an example method 600 implemented at a second device according to some example embodiments of the present disclosure is shown. For the purposes of discussion, [the following will be discussed]. Figure 1 Method 600 is described by the angle of the second device 120 in the middle.

[0093] In box 610, the second device 120 receives a request from the first device to use a delayed handover, the delayed handover being for a third device to switch from the second device to the fourth device; and In block 620, the second device 120 performs a delayed switching for the third device, wherein by using the delayed switching, at least a portion of the DL data buffered at the second device is sent to the third device before the switching of the third device is performed.

[0094] In some example embodiments, method 600 further includes: the second device 120 receiving an indication from the first device via an information element of a message (e.g., an F1AP UE context modification request message or an F1AP downlink radio resource control message).

[0095] In some example embodiments, the indication includes at least one additional information element indicating at least one of the following: the handover of the third device will be performed before a certain point in time; the handover of the third device will be performed before the second device moves to a certain position; all downlink data buffered in the second device has been sent to the third device; a certain amount of downlink data buffered in the second device has been sent to the third device; or downlink data buffered in the second device with a specific sequence number has been sent to the third device.

[0096] In some example embodiments, method 600 further includes: a second device 120 buffering radio resource control reconfiguration messages until all or a certain amount of DL data or downlink data with a specific sequence number buffered at the second device has been sent to a third device, and / or buffering radio resource control reconfiguration messages based on at least one additional information element.

[0097] In some example embodiments, method 600 further includes: the second device 120 sending a radio resource control reconfiguration message to the third device before the time point and / or before the second device moves to the location.

[0098] In some example embodiments, method 600 further includes: a second device 120 sending an instruction to a first device indicating that the highest sequence number of a Packet Data Convergence Protocol (PDCP) data unit will be successfully delivered to the third device before a switchover of the third device is performed.

[0099] In some example embodiments, method 600 further includes: after the transmission of a radio resource control reconfiguration message, the second device 120 transmits the DL data buffered at the second device to the third device.

[0100] In some example embodiments, the radio resource control reconfiguration message is sent from the first device to the third device via the second device, and wherein the radio resource control reconfiguration message indicates the triggering conditions for the condition switching of the third device, the triggering conditions including at least one of the following: whether the last buffered DL data has been received from the second device, whether a certain amount of buffered DL data has been received from the second device, whether buffered DL data with a specific sequence number has been received from the second device, or whether a time point in time when the second device is unable to serve the third device has passed, or whether the second device is moving to a location.

[0101] In some example embodiments, method 600 further includes: before the third device performs a switch, the second device 120 instructs the third device that the data packet to be sent to the third device is either the last data packet buffered at the second device or the sequence number of the last data packet to be sent from the second device.

[0102] In some example embodiments, the first device includes a centralized unit, the second device includes a source distributed unit undergoing handover, the third device includes a terminal device, and the fourth device includes a target distributed unit undergoing handover.

[0103] Figure 7 A flowchart of an example method 700 implemented at a third device according to some example embodiments of the present disclosure is shown. For the purposes of discussion, [the following will be discussed]. Figure 1 Method 700 is described by the angle of the third device 130 in the middle.

[0104] In block 710, the third device 130 receives DL data buffered at the second device from the second device, and the second device performs a delayed handover for the third device to switch from the second device to the fourth device.

[0105] In box 720, the third device 130 performs the switching based on at least one of the switching trigger condition or the buffered DL data delivery state.

[0106] In some example embodiments, method 700 further includes: a third device 130 receiving a radio resource control reconfiguration message from a first device via a second device, wherein the radio resource control reconfiguration message indicates a triggering condition for a conditional switch of the third device, the triggering condition including at least one of the following: whether the last buffered DL data has been received from the second device, whether a certain amount of buffered DL data has been received from the second device, whether buffered DL data with a specific sequence number has been received from the second device, whether a time point in time when the second device is unable to serve the third device has passed, or whether the second device is moving to a location.

[0107] In some example embodiments, method 700 further includes: after receiving a radio resource control reconfiguration message, the third device 130 receives DL data buffered at the second device from the second device.

[0108] In some example embodiments, method 700 further includes: the third device 130 instructing the second device that the data packet sent to the third device is the last data packet before the third device performs a handover, or instructing the sequence number of the last data packet to be sent from the second device before the third device performs the handover.

[0109] In some example embodiments, method 700 further includes: the third device 130 performing condition switching based on at least one of the following: when the last downlink data has been received from the second device, when a certain amount of downlink data has been received from the second device, when downlink data with a specific sequence number has been received from the second device, when the time point when the second device is unable to serve the third device has passed, or when the second device has reached that location.

[0110] In some example embodiments, the first device includes a centralized unit, the second device includes a source distributed unit undergoing handover, the third device includes a terminal device, and the fourth device includes a target distributed unit undergoing handover.

[0111] In some example embodiments, a first device capable of performing any of the methods 500 (e.g., Figure 1 The first device 110 may include a component for performing the corresponding operation of method 500. This component may be implemented in any suitable form. For example, the component may be implemented in a circuit or software module. The first device may be implemented as or included in... Figure 1 In the first device 110.

[0112] In some example embodiments, the first device includes components for sending an instruction to the second device requesting the second device to use a delayed switching, the delayed switching being for a third device switching from the second device to a fourth device, the fourth device being co-located with the second device, wherein by using the delayed switching, at least a portion of the DL data buffered at the second device is to be sent to the third device before the switching of the third device is performed.

[0113] In some example embodiments, the first device also includes a component for sending an instruction to the second device via an information element of a message (e.g., an F1AP UE Context Modification Request message or an F1AP Downlink Radio Resource Control message).

[0114] In some example embodiments, the indication includes at least one additional information element indicating at least one of the following: the switching of the third device will be performed before a certain point in time; the switching of the third device will be performed before the second device moves to a certain position; all downlink data buffered in the second device has been sent to the third device; a certain amount of downlink data buffered in the second device has been sent to the third device; or downlink data buffered in the second device with a specific sequence number has been sent to the third device.

[0115] In some example embodiments, the first device further includes a component for receiving an indication from the second device that the highest sequence number of a Packet Data Convergence Protocol (PDCP) data unit will be successfully delivered to the third device before a switchover of the third device is performed.

[0116] In some example embodiments, the first device further includes a component for sending a radio resource control reconfiguration message to the third device via the second device, wherein the radio resource control reconfiguration message indicates a triggering condition for a conditional switch of the third device, the triggering condition including at least one of the following: whether the last buffered DL data has been received from the second device, whether a certain amount of buffered DL data has been received from the second device, or whether buffered DL data with a specific sequence number has been received from the second device, whether a time point in time when the second device is unable to serve the third device has passed, or whether the second device is moving to a location.

[0117] In some example embodiments, the first device includes a centralized unit, the second device includes a source distributed unit undergoing handover, the third device includes a terminal device, and the fourth device includes a target distributed unit undergoing handover.

[0118] In some example embodiments, the first device further includes components for performing other operations in some example embodiments of method 500 or the first device 110. In some example embodiments, the components include: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause execution of the first device.

[0119] In some example embodiments, a second device capable of performing any of method 600 (e.g., Figure 1 The second device 120 may include a component for performing the corresponding operation of method 600. This component may be implemented in any suitable form. For example, the component may be implemented in a circuit or software module. The second device may be implemented as or included in... Figure 1 The second device 120 in the middle.

[0120] In some example embodiments, the second device includes: a component for receiving from the first device an instruction requesting the second device to use a delayed switching, the delayed switching being for a third device switching from the second device to the fourth device; and a component for performing the delayed switching for the third device, wherein by using the delayed switching, at least a portion of the DL data buffered at the second device is sent to the third device before the switching of the third device is performed.

[0121] In some example embodiments, the second device also includes a component for receiving an indication from the first device via an information element of a message (e.g., an F1AP UE Context Modification Request message or an F1AP Downlink Radio Resource Control message).

[0122] In some example embodiments, the indication includes at least one additional information element indicating at least one of the following: the switching of the third device will be performed before a certain point in time; the switching of the third device will be performed before the second device moves to a certain position; all downlink data buffered in the second device has been sent to the third device; a certain amount of downlink data buffered in the second device has been sent to the third device; or downlink data buffered in the second device with a specific sequence number has been sent to the third device.

[0123] In some example embodiments, the second device further includes components for buffering radio resource control reconfiguration messages until all or a certain amount of DL data or downlink data with a specific sequence number buffered at the second device has been sent to the third device, and / or buffering radio resource control reconfiguration messages based on at least one additional information element.

[0124] In some example embodiments, the second device further includes components for sending a radio resource control reconfiguration message to the third device before that time point and / or before the second device moves to that location.

[0125] In some example embodiments, the second device further includes a component for sending an instruction to the first device indicating that the highest sequence number of the Packet Data Convergence Protocol (PDCP) data unit will be successfully delivered to the third device before a switchover of the third device is performed.

[0126] In some example embodiments, the second device further includes a component for transmitting DL data buffered at the second device to the third device after the transmission of a radio resource control reconfiguration message.

[0127] In some example embodiments, the radio resource control reconfiguration message is sent from the first device to the third device via the second device, and wherein the radio resource control reconfiguration message indicates the triggering conditions for the condition switching of the third device, the triggering conditions including at least one of the following: whether the last buffered DL data has been received from the second device, whether a certain amount of buffered DL data has been received from the second device, or whether buffered DL data with a specific sequence number has been received from the second device, whether the time point at which the second device is unable to serve the third device has passed, or whether the second device is moving to a location.

[0128] In some example embodiments, the second device further includes a component for instructing the third device that the data packet to be sent to the third device is the last data packet buffered at the second device before the third device performs a handover, or for instructing the sequence number of the last data packet to be sent from the second device before the third device performs a handover.

[0129] In some example embodiments, the first device includes a centralized unit, the second device includes a source distributed unit undergoing handover, the third device includes a terminal device, and the fourth device includes a target distributed unit undergoing handover.

[0130] In some example embodiments, a third device capable of performing any method 700 (e.g., Figure 1 The third device 130 may include components for performing the corresponding operation of method 700. This device may be implemented in any suitable form. For example, it may be implemented in a circuit or software module. The second device may be implemented as or included in... Figure 1 The third device 130 in the middle.

[0131] In some example embodiments, the third device includes: a component for receiving DL data buffered at the second device from the second device, the second device performing a delayed handover for the third device from the second device to the fourth device; and a component for performing the handover based on at least one of a handover triggering condition or a buffered DL data delivery state.

[0132] In some example embodiments, the third device further includes a component for receiving a radio resource control reconfiguration message from the first device via the second device, wherein the radio resource control reconfiguration message indicates a triggering condition for a conditional switch of the third device, the triggering condition including at least one of the following: whether the last buffered DL data has been received from the second device, whether a certain amount of buffered DL data has been received from the second device, whether buffered DL data with a specific sequence number has been received from the second device, whether a time point in time when the second device is unable to serve the third device has passed, or whether the second device is moving to a location.

[0133] In some example embodiments, the third device also includes a component for receiving DL data buffered at the second device after receiving a radio resource control reconfiguration message.

[0134] In some example embodiments, the third device further includes a component for indicating, via the second device, that a data packet to be sent to the third device is the last data packet before the third device performs a handover, or indicating the sequence number of the last data packet to be sent from the second device before the third device performs a handover.

[0135] In some example embodiments, the third device further includes a component for initiating a conditional switch based on at least one of the following: when the last downlink data has been received from the second device, when a certain amount of downlink data has been received from the second device, when downlink data with a specific sequence number has been received from the second device, when the time point at which the second device can no longer serve the third device has passed, or when the second device has reached that location.

[0136] In some example embodiments, the first device includes a centralized unit, the second device includes a source distributed unit undergoing handover, the third device includes a terminal device, and the fourth device includes a target distributed unit undergoing handover.

[0137] Figure 8 This is a simplified block diagram of a device 800 suitable for implementing exemplary embodiments of the present disclosure. The device 800 can be provided to implement a communication device, such as... Figure 1 The first device 110, the second device 120, or the third device 130 are shown. As shown, the device 800 includes one or more processors 810, one or more memories 820 coupled to the processors 810, and one or more communication modules 840 coupled to the processors 810.

[0138] Communication module 840 is used for bidirectional communication. Communication module 840 has one or more communication interfaces to facilitate communication with one or more other modules or devices. The communication interface can represent any interface required for communication with other network elements. In some example embodiments, communication module 840 may include at least one antenna.

[0139] As a non-limiting example, processor 810 can be any type suitable for a local technology network and can include one or more of the following: general-purpose computer, special-purpose computer, microprocessor, digital signal processor (DSP), and processor based on a multi-core processor architecture. Device 800 can have multiple processors, such as application-specific integrated circuit chips that are time-dependent on a clock of a synchronous main processor.

[0140] Memory 820 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) 824, electrically programmable read-only memory (EPROM), flash memory, hard disk, optical disc (CD), digital video disc (DVD), optical disc, laser disc, and other magnetic and / or optical storage. Examples of volatile memories include, but are not limited to, random access memory (RAM) 822 and other volatile memories that will not be maintained during power outages.

[0141] Computer program 830 includes computer-executable instructions that are executed by an associated processor 810. The instructions of program 830 may include instructions for performing operations / actions of some example embodiments of this disclosure. Program 830 may be stored in memory (e.g., ROM 824). Processor 810 can perform any suitable actions and processes by loading program 830 into RAM 822.

[0142] Example embodiments of this disclosure can be implemented by means of program 830, so that device 800 can perform as described in the reference. Figures 2 to 7 Any process discussed in this disclosure. Exemplary embodiments of this disclosure may also be implemented by hardware or by a combination of software and hardware.

[0143] In some example embodiments, program 830 may be tangibly contained in a computer-readable medium, which may be included in device 800 (such as memory 820) or other storage devices accessible to device 800. Device 800 may load program 830 from the computer-readable medium into RAM 822 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 on the medium itself (i.e., tangible, not tactile) rather than on the persistence of data storage (e.g., RAM and ROM).

[0144] Figure 9 An example of a computer-readable medium 900 is shown, which may be in the form of a CD, DVD, or other optical storage disc. The computer-readable medium 900 stores a program 830 thereon.

[0145] Generally, the various embodiments of this disclosure can be implemented in hardware or dedicated circuitry, software, logic, or any combination thereof. Some aspects can be implemented in hardware, while others can be implemented in firmware or software that can be executed by a controller, microprocessor, or other computing device. Although various aspects of the embodiments of this disclosure are illustrated and described as block diagrams, flowcharts, or using some other graphical representation, it should be understood that, as non-limiting examples, the blocks, apparatuses, systems, techniques, or methods described herein can be implemented in hardware, software, firmware, dedicated circuitry or logic, general-purpose hardware or controllers or other computing devices, or some combination thereof.

[0146] Some exemplary embodiments of this disclosure also provide at least one computer program product tangibly stored on a computer-readable medium, such as a non-transitory computer-readable medium. The computer program product includes computer-executable instructions, such as those included in a program module, which are executed in a device on a target physical or virtual processor to perform any of the methods described above. Typically, a program module includes routines, programs, libraries, objects, classes, components, data structures, etc., that perform a particular task or implement a particular abstract data type. In various embodiments, the functionality of a program module can be combined or split among program modules as needed. The machine-executable instructions for a program module can execute within a local or distributed device. In a distributed device, the program module can reside in both local and remote storage media.

[0147] Program code used to perform the methods of this disclosure may be written in any combination of one or more programming languages. The program code may be provided to a processor or controller of a general-purpose computer, special-purpose computer, or other programmable data processing apparatus, such that when executed by the processor or controller, the program code causes the functions / operations specified in the flowcharts and / or block diagrams to be implemented. The program code may be executed entirely on the machine, partially on the machine, as a stand-alone software package, partially on the machine and partially on a remote machine, or entirely on a remote machine or server.

[0148] In the context of this disclosure, computer program code or related data may be carried by any suitable carrier to enable a device, apparatus, or processor to perform the various processes and operations described above. Examples of carriers include signals, computer-readable media, etc.

[0149] Computer-readable media can be computer-readable signal media or computer-readable storage media. Computer-readable media can include, but is not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatuses, or devices, or any suitable combination thereof. More specific examples of computer-readable storage media include electrical connections having one or more wires, portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fibers, portable optical disc read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination thereof.

[0150] Furthermore, although operations are described in a specific order, this should not be construed as requiring such operations to be performed in the specific order shown or sequentially, or to perform all shown operations 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 foregoing discussion, they should not be construed as limiting the scope of this disclosure, but rather as descriptions of features that may be specific to particular embodiments. Unless explicitly stated otherwise, certain features described in the context of a single embodiment may also be implemented in combination in a single embodiment. Conversely, unless explicitly stated otherwise, various features described in the context of a single embodiment may also be implemented individually or in any suitable sub-combination in multiple embodiments.

[0151] Although this disclosure has been described in language specific to structural features and / or methodological actions, it should be understood that the disclosure as defined in the appended claims is not necessarily limited to the specific features or actions described above. Rather, the specific features and actions described above are disclosed as exemplary forms for implementing the claims.

Claims

1. A first device, comprising: At least one processor; as well as At least one memory, the at least one memory storing instructions, the instructions causing the first device to at least: Send an instruction to the second device requesting the second device to use a delayed handover for a third device to switch from the second device to a fourth device, the fourth device being co-located with the second device, wherein by using the delayed handover, at least a portion of the downlink data buffered at the second device is to be sent to the third device before the handover is performed on the third device.

2. The first device according to claim 1, wherein the first device causes: The instruction is sent to the second device via the information element of the message transmitted through the UE context modification request message or downlink radio resource control message.

3. The first device according to claim 1 or 2, wherein the indication includes at least one additional information element, the at least one additional information element indicating at least one of the following: The switching of the third device will be performed before a certain point in time. The switching of the third device will be performed before the second device moves to a position. All downlink data buffered in the second device has been sent to the third device. A certain amount of downlink data buffered in the second device has been sent to the third device, or Downlink data with a specific sequence number buffered in the second device has been sent to the third device.

4. The first device according to any one of claims 1 to 3, wherein the first device causes: An instruction is received from the second device indicating that the highest sequence number of the Packet Data Convergence Protocol (PDCP) data unit will be successfully delivered to the third device before the handover is performed on the third device.

5. The first device according to any one of claims 1 or 2, wherein the first device causes: The radio resource control reconfiguration message is sent from the second device to the third device, wherein the radio resource control reconfiguration message indicates a triggering condition for a conditional switch of the third device, the triggering condition including at least one of the following: Has the last buffered downlink data been received from the second device? Has a certain amount of buffered downlink data been received from the second device? Has buffered downlink data with a specific sequence number been received from the second device? Has the point in time when the second device could no longer serve the third device passed, or Is the second device moving to a position? 6. The first apparatus according to any one of claims 1 to 5, wherein the first apparatus comprises a centralized unit, the second apparatus comprises a source distributed unit in the handover, the third apparatus comprises a terminal device, and the fourth apparatus comprises a target distributed unit in the handover.

7. A second device, comprising: At least one processor; as well as At least one memory, the at least one memory storing instructions, the instructions causing the first device to at least: The first device receives an instruction requesting the second device to use a delayed switching, the delayed switching being for a third device to switch from the second device to the fourth device; as well as The delayed handover is performed for the handover to the third device, wherein, by using the delayed handover, at least a portion of the downlink data buffered at the second device is sent to the third device before the handover to the third device is performed.

8. The second device according to claim 7, wherein the second device causes: The instruction is received from the first device by an information element that sends a message via a UE context modification request message or a downlink radio resource control message.

9. The second device according to claim 7 or 8, wherein the indication includes at least one additional information element, the at least one additional information element indicating at least one of the following: The switching of the third device will be performed before a certain point in time. The switching of the third device will be performed before the second device moves to a position. All downlink data buffered in the second device has been sent to the third device. A certain amount of downlink data buffered in the second device has been sent to the third device, or Downlink data with a specific sequence number buffered in the second device has been sent to the third device.

10. The second device according to claim 9, wherein the second device causes: Buffer radio resource control reconfiguration messages until all or a certain amount of downlink data buffered at the second device, or downlink data with a specific sequence number, has been sent to the third device; and / or Buffer radio resource control reconfiguration messages based on at least one additional information element.

11. The second device according to claim 10, wherein the second device causes: The radio resource control reconfiguration message is sent to the third device before the stated time point and / or before the second device moves to the stated location.

12. The second device according to any one of claims 7 to 11, wherein the second device causes: An instruction is sent to the first device indicating that the highest sequence number of the Packet Data Convergence Protocol (PDCP) data unit will be successfully delivered to the third device before the handover is performed on the third device.

13. The second device according to claim 7 or 8, wherein the second device causes: After the radio resource control reconfiguration message is sent, the downlink data buffered at the second device is sent to the third device.

14. The second apparatus of claim 13, wherein the radio resource control reconfiguration message is transmitted from the first apparatus to the third apparatus via the second apparatus, and wherein the radio resource control reconfiguration message indicates a triggering condition for a conditional switching of the third apparatus, the triggering condition including at least one of the following: Has the last buffered downlink data been received from the second device? Has a certain amount of buffered downlink data been received from the second device? Has buffered downlink data with a specific sequence number been received from the second device? Has the point in time when the second device could no longer serve the third device passed, or Is the second device moving to a position? 15. The second device according to claim 14, wherein the second device causes: The third device is instructed that the data packet to be sent to the third device is the last data packet buffered at the second device before the third device performs the handover, or the sequence number of the last data packet to be sent from the second device before the third device performs the handover is indicated.

16. The second apparatus according to any one of claims 7 to 15, wherein the first apparatus includes a centralized unit, the second apparatus includes a source distributed unit in the handover, the third apparatus includes a terminal device, and the fourth apparatus includes a target distributed unit in the handover.

17. A third device, comprising: At least one processor; as well as At least one memory, the at least one memory storing instructions, the instructions causing the third device to at least: The third device receives downlink data buffered at the second device, and the second device performs a delayed handover for the handover from the second device to the fourth device. as well as The handover is performed based on at least one of the handover triggering conditions or the buffered downlink data delivery status.

18. The third device according to claim 17, wherein the third device causes: The radio resource control reconfiguration message is received from the first device via the second device, wherein the radio resource control reconfiguration message indicates a triggering condition for a conditional switch of the third device, the triggering condition including at least one of the following: Has the last downlink data been received from the second device? Has a certain amount of downlink data been received from the second device? Has downlink data with a specific sequence number been received from the second device? Has the point in time when the second device could no longer serve the third device passed, or Is the second device moving to a position? 19. The third device according to claim 18, wherein the third device causes: After receiving the radio resource control reconfiguration message, the downlink data is received from the second device.

20. The third device according to claim 18 or 19, wherein the third device causes: The second device indicates that the data packet sent to the third device is the last data packet before the third device performs the handover, or indicates the sequence number of the last data packet to be sent from the second device before the third device performs the handover.

21. The third device according to claim 18, wherein the third device causes: The condition switching shall be performed based on at least one of the following: When the last downlink data has been received from the second device When a certain amount of downlink data has been received from the second device When downlink data with a specific sequence number has been received from the second device, or When the time point at which the second device can no longer serve the third device has passed, or When the second device has reached the said position.

22. The third apparatus according to any one of claims 17 to 21, wherein the first apparatus includes a centralized unit, the second apparatus includes the source distributed unit in the handover, the third apparatus includes a terminal device, and the fourth apparatus includes the target distributed unit in the handover.

23. A method comprising: Send an instruction to the second device requesting the second device to use a delayed handover for a third device to switch from the second device to a fourth device, the fourth device being co-located with the second device, wherein by using the delayed handover, at least a portion of the downlink data buffered at the second device is to be sent to the third device before the handover is performed on the third device.

24. A method comprising: The first device receives an instruction requesting the second device to use a delayed switching, the delayed switching being for a third device to switch from the second device to the fourth device; as well as The delayed handover is performed for the handover to the third device, wherein, by using the delayed handover, at least a portion of the downlink data buffered at the second device is sent to the third device before the handover to the third device is performed.

25. A method comprising: The third device receives downlink data buffered at the second device, and the second device performs a delayed handover for the handover of the third device from the second device to the fourth device; as well as The handover is performed based on at least one of the handover triggering conditions or the buffered downlink data delivery status.

26. A first device, comprising: A component for sending an instruction to a second device requesting the second device to use a delayed handover, the delayed handover being for a third device to switch from the second device to a fourth device, the fourth device being co-located with the second device, wherein by using the delayed handover, at least a portion of the downlink data buffered at the second device is to be sent to the third device before the handover is performed on the third device.

27. A second device, comprising: A component for receiving from a first device an instruction requesting the second device to use a delayed switching, the delayed switching being for a third device to switch from the second device to the fourth device; as well as The component for performing the delayed handover for the third device, wherein by using the delayed handover, at least a portion of the downlink data buffered at the second device is to be sent to the third device before the handover is performed on the third device.

28. A third device, comprising: Components for receiving downlink data buffered at the second device from the second device, the second device performing a delayed handover for the third device from the second device to the fourth device; as well as A component for performing the handover based on at least one of the handover triggering conditions or the buffered downlink data delivery status.

29. A computer-readable medium comprising instructions stored thereon, the instructions causing a device to perform at least the method of claim 23, the method of claim 24, or the method of claim 25.

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