Completing non-access stratum procedures in storage and forwarding architectures

Abstract

Embodiments of the present disclosure relate to storing amp at a non-terrestrial network (NTN); an apparatus, method, apparatus, and computer-readable storage medium for completing a non-access stratum (NAS) procedure in a forwarding (Samp; F) architecture. The method comprises: obtaining, from a first Radio Access Network (RAN) device, an indication comprising a unique identifier, the unique identifier being allocated by the first RAN device, determining that an RRC procedure or a NAS procedure cannot be completed via the first RAN device; and if it is determined that a paging message from the second RAN device indicating that the apparatus continues the uncompleted RRC procedure or the uncompleted NAS procedure is received, transmitting to the second RAN device to continue the uncompleted RRC procedure or the uncompleted NAS procedure by using the stored context of the apparatus.

Description

TECHNICAL FIELD

[0001] Embodiments of the present disclosure generally relate to the field of telecommunications, and more specifically to devices, methods, apparatuses, and computer-readable storage media for completing non-access stratum (NAS) procedures in a non-terrestrial network (NTN) store-and-forward (S&F) architecture, especially by using more than one radio access network (RAN) node. BACKGROUND

[0002] The Third Generation Partnership Project (3GPP) has initiated discussions for NTN for New Radio (NR) and Narrow Band-Internet of Things (NB-IoT). During the discussions, S&F operations have been proposed, which can allow a satellite to provide service to NTN terminal device(s) even in periods / areas where the satellite does not have simultaneous connectivity with a terminal device and a core network (CN) device. SUMMARY

[0003] Generally, example embodiments of the present disclosure provide solutions for completing NAS procedures in an NTN S&F architecture.

[0004] In a first aspect, an apparatus is provided. The apparatus comprises at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: obtain, from a first RAN device, an indication comprising a unique identifier, the unique identifier being assigned by the first RAN device; determine that a radio resource control (RRC) procedure or a non-access stratum (NAS) procedure cannot be completed via the first RAN device; and if a paging message from a second RAN device indicating that the apparatus continues the uncompleted RRC procedure or the uncompleted NAS procedure is received, send, to the second RAN device, a request for a communication between the apparatus and the second RAN device to continue the uncompleted RRC procedure or the uncompleted NAS procedure by using a stored context of the apparatus.

[0005] In a second aspect, an apparatus is provided. The apparatus comprises at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: obtain, from a CN device, a configuration of at least one unique identifier for at least one terminal device; assign, to the terminal device, a unique identifier of the terminal device from the at least one unique identifier in a case that the apparatus does not have simultaneous connectivity with a core network device; and send, to the terminal device, an indication comprising the unique identifier to be stored as a context of the terminal device.

[0006] In a third aspect, an apparatus is provided. The apparatus comprises at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to send, to a first RAN device, a configuration of at least one unique identifier for at least one terminal device before the terminal device is connected with the first RAN device.

[0007] In a fourth aspect, an apparatus is provided. The apparatus comprises at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to receive, from a core network device, a message comprising a context of a terminal device created by a first RAN device, the message being used to resume the context of the terminal device at the apparatus to continue an uncompleted RRC procedure or an uncompleted NAS procedure with the terminal device; send a paging message indicating the terminal device to continue the uncompleted RRC procedure or the uncompleted NAS procedure; and receive, from the terminal device, a request for a communication between the apparatus and the terminal device to continue the uncompleted RRC procedure or the uncompleted NAS procedure by using the context received from the core network device.

[0008] In a fifth aspect, a method is provided. The method comprises obtaining, from a first RAN device, an indication comprising a unique identifier, the unique identifier being assigned by the first RAN device; determining that an RRC procedure or a NAS procedure cannot be completed via the first RAN device; and if a paging message from a second RAN device is received indicating the apparatus to continue the uncompleted RRC procedure or the uncompleted NAS procedure, sending, to the second RAN device, to continue the uncompleted RRC procedure or the uncompleted NAS procedure by using a stored context of the apparatus.

[0009] In a sixth aspect, a method is provided. The method comprises obtaining, from a CN device, a configuration of at least one unique identifier for at least one terminal device; assigning, to a terminal device, a unique identifier of the terminal device from the at least one unique identifier in a case that the first RAN device does not have a simultaneous connection with the core network device; and sending, to the terminal device, an indication comprising the unique identifier to be stored as a context of the terminal device.

[0010] In a seventh aspect, a method is provided. The method comprises sending, to a first RAN device, a configuration of at least one unique identifier for at least one terminal device before the terminal device is connected with the first RAN device.

[0011] In an eighth aspect, a method is provided. The method includes receiving a message from a core network device, the message including a context of a terminal device created by a first RAN device, the message being for resuming the context of the terminal device at a second RAN device to continue an uncompleted RRC procedure or an uncompleted NAS procedure with the terminal device; sending a paging message indicating the terminal device to continue the uncompleted RRC procedure or the uncompleted NAS procedure; and receiving a request from the terminal device for communication between the second RAN device and the terminal device to continue the uncompleted RRC procedure or the uncompleted NAS procedure by using the context received from the core network device.

[0012] In a ninth aspect, an apparatus is provided, comprising: means for obtaining, from a first RAN device, an indication including a unique identifier, the unique identifier being assigned by the first RAN device; means for determining that an RRC procedure or a non-access stratum, NAS, procedure cannot be completed via the first RAN device; and means for sending, to a second RAN device, if a paging message from the second RAN device is received indicating the apparatus to continue the uncompleted RRC procedure or the uncompleted NAS procedure, to continue the uncompleted RRC procedure or the uncompleted NAS procedure by using a stored context of the apparatus.

[0013] In a tenth aspect, an apparatus is provided, comprising: means for obtaining, from a CN device, a configuration of a pool of unique identifiers for at least one terminal device; means for assigning, to a terminal device, a unique identifier of the terminal device from the at least one unique identifier in a case that the apparatus does not have a simultaneous connection with the core network device; and means for sending, to the terminal device, an indication including the unique identifier to be stored as a context of the terminal device.

[0014] In an eleventh aspect, an apparatus is provided, comprising: means for sending, to a first RAN device, a configuration of at least one unique identifier for at least one terminal device before the terminal device is connected with the first RAN device.

[0015] In a twelfth aspect, an apparatus is provided, comprising: means for receiving a message from a core network device, the message including a context of a terminal device created by a first RAN device, the message being for resuming the context of the terminal device at the apparatus to continue an uncompleted RRC procedure or an uncompleted NAS procedure with the terminal device; means for sending a paging message indicating the terminal device to continue the uncompleted RRC procedure or the uncompleted NAS procedure; and means for receiving a request from the terminal device for communication between the apparatus and the terminal device to continue the uncompleted RRC procedure or the uncompleted NAS procedure by using the context received from the core network device.

[0016] In a thirteenth aspect, there is provided a computer readable medium having stored thereon a computer program, which, when executed by at least one processor of an apparatus, causes the apparatus to perform the method according to the fifth aspect, the sixth aspect, the seventh aspect, or the eighth aspect.

[0017] Other features and advantages of embodiments of the present disclosure will also become apparent from the following description of the embodiments with reference to the drawings, which illustrate, by way of example, the principles of embodiments of the present disclosure. BRIEF DESCRIPTION OF DRAWINGS

[0018] Embodiments of the present disclosure are presented in the context of examples, and their advantages are explained in more detail below with reference to the drawings.

[0019] Figure 1 An example environment in which example embodiments of the present disclosure can be implemented is shown; Figure 2 Signaling diagrams showing examples of procedures according to some example embodiments of the present disclosure are shown; Figure 3 Flow diagrams showing example methods of completing NAS procedures in an NTN S&F architecture according to some example embodiments of the present disclosure are shown; Figure 4 Flow diagrams showing example methods of completing NAS procedures in an NTN S&F architecture according to some example embodiments of the present disclosure are shown; Figure 5 Flow diagrams showing example methods of completing NAS procedures in an NTN S&F architecture according to some example embodiments of the present disclosure are shown; Figure 6 Flow diagrams showing example methods of completing NAS procedures in an NTN S&F architecture according to some example embodiments of the present disclosure are shown; Figure 7 Simplified block diagrams of devices suitable for implementing example embodiments of the present disclosure are shown; and Figure 8 Block diagrams of example computer readable media according to some embodiments of the present disclosure are shown.

[0020] In all of the drawings, like or similar reference numerals can refer to like or similar elements throughout the drawings. 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 for illustrative purposes only and help the skilled person to understand and implement the present disclosure without suggesting any limitation on the scope of the present disclosure. The embodiments described herein can be implemented in various ways other than those described below.

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

[0023] References in the disclosure to “one embodiment”, “an embodiment”, “example embodiments”, etc., indicate that the embodiment described can include a particular feature, structure, or characteristic, but every embodiment can not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of those skilled in the art to effect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

[0024] It should be understood that although the terms “first”, “second”, etc. can be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element without departing from the scope of the example embodiments. As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed terms.

[0025] As used herein, “at least one of ” and “one or more of ” and similar phrases, where the list of two or more elements is preceded by “at least one of” or “one or more of”, means at least one of any one of the elements, or at least any two or more of the elements.

[0026] As used herein, unless expressly stated otherwise, performing a step “in response to” A does not indicate that the step is performed immediately following the occurrence of “A” and can include one or more intervening steps.

[0027] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of 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 the terms “comprises”, “comprising”, “includes” and / or “including” when used herein, specify the presence of stated features, elements and / or components etc. but do not preclude the presence or addition of one or more other features, elements, components and / or combinations thereof.

[0028] As used in this application, the term “circuitry” can refer to one or more or all of the following: (a) hardware-only circuitry implementations (such as implementations in only analog and / or digital circuitry) and (b) combinations of hardware circuits and software, such as (as applicable): (i) combinations of analog and / or digital hardware circuits with software / firmware and (ii) any portions of hardware processor(s) with software (including digital signal processors), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions and (c) hardware circuit(s) and / or processor(s), such as a microprocessor(s) or a portion of a microprocessor(s), that requires software (e.g., firmware) for operation, but has no software present.

[0029] This definition of circuit 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 circuit encompasses a hardware-only implementation or a processor(s) or a portion thereof and / or a hardware-only implementation of a hardware circuit or processor(s) and its (or their) accompanying software and / or firmware that work together to cause an apparatus, such as a mobile phone or a server, to perform various functions described herein. And, as applied to a particular claim element, the term circuit encompasses a baseband integrated circuit or processor integrated circuit such as found in a mobile device or server, cellular network device, or other computing or network device, if applicable to the particular claim element.

[0030] As used herein, the term “communication network” refers to a network that follows any suitable communication standard, such as New Radio (NR), Long Term Evolution (LTE), LTE-Advanced (LTE-A), Wideband Code Division Multiple Access (WCDMA), High-Speed Packet Access (HSPA), Narrow Band Internet of Things (NB-IoT), Enhanced Machine Type Communications (eMTC), etc. Further, communication between terminal devices and network devices in a communication network can be performed in accordance with 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 protocols that are currently known or developed in the future. Embodiments of the present disclosure can be applied in various communication systems. In view of the rapid development in communications, it is clear that there will also be future communication technologies and systems that can implement the present disclosure. The scope of the present disclosure should not be limited to the aforementioned systems only.

[0031] As used herein, the terms “network device,” “radio network device,” and / or “radio access network device” refer to a node in a communication network via which terminal devices access the network and receive services therefrom. The network device can refer to a base station (BS) or an access point (AP), e.g., a NodeB (NodeB or NB), an Evolved NodeB (eNodeB or eNB), an NR NB (also referred to as gNB), a remote radio unit (RRU), a remote radio head (RRH), a relay, an integrated access and backhaul (IAB) node, a low power node (such as a femto, pico), a non-terrestrial network (NTN) or non-terrestrial network device (such as a satellite network device, non-geostationary orbit (NGSO) satellite, and geostationary orbit (GSO) satellite), aircraft network device, etc., depending on the terminology used and the technology applied. In some example embodiments, a gNB comprises a central unit (CU) and a distributed unit (DU). In some other example embodiments, part of a radio access network device or all of a radio access network device can be embedded on an NTN vehicle in the air or space.

[0032] The term “terminal device” refers to any terminal device capable of wireless communication. By way of example, and without limitation, a terminal device can also be referred to as a communication device, user equipment (UE), subscriber station (SS), portable subscriber station, mobile station (MS), or access terminal (AT). A terminal device can include, but is not limited to, a mobile telephone, a cellular telephone, a smart phone, a voice over Internet Protocol (VoIP) phone, a wireless local loop phone, a tablet, 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 appliance, a vehicle-mounted wireless terminal device, a wireless endpoint, a mobile station, a laptop-embedded equipment (LEE), a laptop-mounted equipment (LME), a USB dongle, a smart device, a wireless customer-premise equipment (CPE), an Internet of Things (loT) device, a watch or other wearable, a head-mounted display (HMD), a vehicle, a drone, a medical appliance or application, such as a remote surgery appliance or application, an industrial appliance or application, such as an industrial robot or other wireless devices operating in an industrial and / or an automated processing chain context, a consumer electronics, a device operating on a business and / or a

[0033] As used herein, the term “resource”, “transmission resource”, “resource block”, “physical resource block” (PRB), “uplink resource” or “downlink resource” can refer to any resource used for performing communication, e.g., a communication between a terminal device and a network device, such as a resource in time domain, a resource in frequency domain, a resource in spatial domain, a resource in code domain, or any other resource enabling communication, etc. In the following, unless explicitly stated, a resource in both frequency and time domain will be used as an example of a transmission resource for describing some example embodiments of the present disclosure. It is noted that example embodiments of the present disclosure equally apply to other resources in other domains.

[0034] Figure 1 An example communication network 100 in which embodiments of the present disclosure can be implemented is shown. As shown, the communication network 100 can comprise a terminal device 110. In the following, the terminal device 110 can also be referred to as a UE. Figure 1

[0035] The communication network 100 can further comprise a first RAN device 120-1 and a second RAN device 120-2. In the following, the first RAN device 120-1 or the second RAN device 120-2 can also be referred to as a network device in a RAN, which can also be referred to as a BS, gNB or eNB. In some scenarios, the first RAN device 120-1 or the second RAN device 120-2 can be hosted in a satellite. The terminal device 110 can communicate with the first RAN device 120-1 in a coverage of the first RAN device 120-1, e.g., a geographical area of the terminal device 110 is served by a satellite beam or cell from the first RAN device 120-1. Thereafter, at a different time, the terminal device 110 can communicate with the second RAN device 120-2 in a coverage of the second RAN device 120-2, e.g., a geographical area of the terminal device 110 is served by a satellite beam or cell from the second RAN device 120-2.

[0036] ​Further, the communication network 100 can also include a core network (CN) device 130. In the following, the CN device 130 can also be referred to as a network function in the CN, such as an access and mobility management function (AMF), or a mobility management entity (MME), a home subscriber server (HSS), etc. The terminal device 110 can communicate with the CN device 130, e.g., for performing a NAS procedure between the terminal device 110 and the CN device 130 via the RAN device 120-1 and / or 120-2. The NAS procedure can be a registration procedure in a 5G system, or an attach procedure in an LTE system, or a service request procedure, etc. The connection or communication between the RAN device 120-1 (or 120-2) and the CN device 130 can be based on an S1 application protocol (S1AP) in an LTE system, or a next generation application protocol (NGAP) in a 5G system, or any other application protocol.

[0037] In some scenarios, the communication network 100 can refer to an NTN network, and the RAN devices 120-1 and 120-2 can be implemented in and move with satellites. More specifically, the satellites are NGSO satellites. In some other scenarios, the communication network 100 can also refer to any other suitable network.

[0038] It should be appreciated that Figure 1 The number of network devices and terminal devices shown is given for purposes of illustration only and is not intended to be limiting. The communication network 100 can include any suitable number of network devices and terminal devices.

[0039] The communication in the communication environment 100 can be implemented according to any suitable communication protocol(s), including but not limited to cellular communication protocols of first generation (1G), second generation (2G), third generation (3G), fourth generation (4G), fifth generation (5G), sixth generation (6G), etc., wireless local area network communication protocols such as Institute of Electrical and Electronics Engineers (IEEE) 802.11, and / or any other protocol that is currently known or developed in the future. Further, the communication can utilize any suitable wireless communication techniques, including but not limited to code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), frequency division duplexing (FDD), time division duplexing (TDD), multiple-input multiple-output (MIMO), orthogonal frequency division multiple access (OFDMA), discrete Fourier transform spread OFDM (DFT-s-OFDM), and / or any other techniques that are currently known or developed in the future.

[0040] As mentioned above, S&F operations have been proposed which can refer to a discontinuous coverage scenario where a UE can only have coverage from a satellite occasionally and temporarily. It is also possible that the discontinuous coverage scenario can be extended by defining that a satellite is not always connected with a CN device. In the following, a RAN device can be referred to as eNB, gNB or any other suitable RAN device.

[0041] For example, in an example communication network 100 as Figure 1 illustrated, a first RAN device 120-1 can not always or simultaneously be connected with a terminal device 110 and a CN device 130. When a satellite moves to a geographical area of the terminal device 110, the first RAN device 120-1 can provide a cell coverage covering a geographical area 102, the terminal device 110 can be connected with the first RAN device 120-1. However, at the same time, the first RAN device 120-1 can not have a connection with the CN 130. At a later (or earlier) time, the first RAN device 120-1 can be connected to the CN 130, but the first RAN device 120-1 can move out of the geographical area of the terminal device 110 and can not be able to connect with the terminal device 110. That is, the possibility of UE connectivity and CN connectivity can be at different time instances.

[0042] That is, in the S&F mode, a RAN device / satellite can only have a connection with a CN device for a certain time. Similarly, the RAN device / satellite has a connection with a UE for a certain time. The RAN device / satellite can not have both connections, i.e. a connection with a UE and a connection with a CN device, at the same time.

[0043] The S&F architecture enables a low-cost deployment consisting of only a few satellites and a few ground stations. This means that the connection cost per device can be further reduced at the cost of only being able to support delay-tolerant data.

[0044] Furthermore, the LTE NAS attach procedure (or NR NAS registration procedure) can require multiple interactions between a terminal device and a RAN device (hosted in a satellite) and between the RAN device and a CN device (e.g. a network node on the ground). By assuming that a RAN device has a simultaneous connection with a terminal device and a CN device, the NAS procedure can thus be completed by using only one RAN device.

[0045] However, in the S&F scenario, a RAN device can only be able to connect with a terminal device or with a CN device for a certain time, but not have a simultaneous connection with both a terminal device and a CN device. This leads to a problem of completion of the NAS procedure, as it is not possible to complete the NAS procedure by using only one RAN device.

[0046] For example, by using a NAS procedure asFigure 1 In the illustrated example, first, the first RAN device 120-1 moves in the geographic area of the terminal device 110, and the terminal device 110 can initiate an RRC setup procedure. Then, the first RAN device 120-1 can move out of the geographic area of the terminal device 110, and can connect with the CN device 130 (e.g., AMF or MME), and the first RAN device 120-1 can send INITIAL UE MESSAGE to the CN device 130. The message can include the RAN UE NGAP ID (or simply AP ID) allocated by the first RAN device 120-1. Then, the CN device 130 can determine, for example, that the second RAN device 120-2 can serve the terminal device 110, and then send DL NAS TRANSPORT to the second RAN device 120-2.

[0047] In this case, the second RAN device 120-2 can reject DL NAS TRANSPORT message because the message includes the mandatory RAN UE NGAP ID allocated by the first RAN device 120-1, which is unknown to the second RAN device 120-2.

[0048] Even if the second RAN device 120-2 does not reject DL NAS TRANSPORT message and continues the following procedure, when the second RAN device 120-2 moves in the geographic area of the terminal device 110, the second RAN device 120-2 cannot continue the RRC procedure because the second RAN device 120-2 does not have any context for the terminal device, e.g., timing advance, current RRC state, RRC messages exchanged between the terminal device 110 and the first RAN device 120-1, etc.

[0049] Therefore, the terminal device 110 can only restart the RRC setup procedure. Then, when the second RAN device 120-2 has a connection with the CN device 130, the second RAN device 120-2 sends INITIAL UE MESSAGE to the CN device 130. However, the additional procedure will fail again, e.g., the CN device 130 can send DL NAS TRANSPORT to the new RAN device, and the new RAN device can repeat the above procedure. As a result, the terminal device 110 cannot complete the NAS registration procedure. This problem also occurs when the satellite hosts the RAN device and some CN devices (e.g., MME or AMF), and other CN devices (e.g., home subscriber server (HSS)) are on the ground.

[0050] In this case, a mechanism to support the terminal device to complete the NAS procedure in the S&F scenario is desired. The present disclosure proposes a solution for completing the NAS procedure in the S&F by using more than one RAN device.

[0051] In this solution, the CN device 130 can configure a pool of identifiers (or a list of identifiers) for the terminal device and send the configuration of the pool (or the list of identifiers) to the RAN device. During an RRC procedure or a NAS procedure, the first RAN device can assign a unique identifier selected from the pool to the terminal device. The first RAN device can indicate the unique identifier to the CN device, and the CN device can also indicate the unique identifier of the terminal device in a procedure for resuming the UE context at the second RAN device to be connected with the terminal device. If the terminal device receives a paging message including the unique identifier from the second RAN device, the terminal device 110 can continue or complete the RRC procedure or the NAS procedure with the second RAN device.

[0052] Example embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings.

[0053] Reference will now be made to Figure 2 which shows a signaling diagram 200 for communication according to some example embodiments of the present disclosure. As Figure 2 shown, the signaling diagram 200 involves a terminal device 110, a first RAN device 120-1, a second RAN device 120-2, and a CN device 130. For discussion purposes, the signaling diagram 200 is described with reference to Figure 1 .

[0054] In some scenarios, the first RAN device 120-1 and the RAN device 120-2 can be hosted in satellites, respectively.

[0055] As Figure 2 shown, the CN device 130 can configure a pool of identifiers (IDs) or a list of identifiers. For example, the pool of identifiers can include a set of terminal device IDs. When the first RAN device 120-1 has a connection with the CN device 130, the CN device 130 can send (202) the configuration of the pool of IDs to the first RAN device 120-1. The IDs can be used later when the terminal device connects with the first RAN device 120-1. This step can be performed before the terminal device connects with the first RAN device 120-1.

[0056] The IDs as described above can be unique for each CN device 130, e.g., the IDs are unique for each Access and Mobility Management Function (AMF) in a 5G system. For example, the IDs can be 5G-S Temporary Mobile Subscriber Identity (5G S-TMSI).

[0057] Then, the first RAN device 120-1 can lose the connection with the CN device 130 and move in a geographical area of the terminal device 110.

[0058] When the first RAN device 120-1 has a connection with the terminal device 110, the terminal device 110 can initiate a NAS registration procedure. For example, the terminal device 110 first sends (204) RRCSetupRequest to the first RAN device 120-1. The first RAN device 120-1 can allocate a unique identifier for the terminal device 110 from a pool of IDs configured by the CN device 130 and send (206) an indication of the allocated unique identifier for the terminal device 110 to the terminal device 110 in response to the RRC setup request.

[0059] It should be appreciated that the RRCSetupRequest message received by the first RAN device 120-1 does not include a 5G-S-TMSI, the first RAN device 120-1 can know, for example, that this is the first time the terminal device 110 is started or that the geographical area of the terminal device 110 is outside the previous registration area. The first RAN device 120-1 can then allocate a unique identifier to the terminal device 110.

[0060] If the terminal device 110 determines that the response to RRCSetupReques t includes the allocated unique identifier for the terminal device 110, the terminal device 110 can know that the NAS procedure cannot be completed with the first RAN device 120-1 and the first RAN device 120-1 will not provide any NAS response but can be obtained from another RAN device.

[0061] After receiving the response to the RRC setup request from the first RAN device 120-1, the terminal device 110 can send (208) NAS REGISTRATION REQUEST to the first RAN device 120-1 during RRC connection setup. However, the first RAN device 120-1 can then move out of the geographical area of the terminal device 110 and stop serving the terminal device 110.

[0062] In some other example embodiments, the first RAN device 120-1 can send the unique identifier to the terminal device 110 in other RRC procedures, for example, during an RRC resume procedure or an RRC reestablishment procedure or an RRC release procedure.

[0063] Upon receiving the unique identity, the terminal device 110 knows that the NAS procedure cannot be completed with the first RAN device 120-1. In other words, part of the NAS procedure is performed via the first RAN device 120-1 and the uncompleted part of the NAS procedure is to be performed via another RAN device. In one example embodiment, the NAS procedure can be initiated by the terminal device 110, e.g., the terminal device 110 sends a NAS message to the CN device 130 via the first RAN device 120-1, however the terminal device 110 then receives a NAS response message from the CN device 130 via another RAN device. In another example embodiment, the NAS procedure can be initiated by the CN device 130, e.g., the terminal device 110 receives a NAS message from the CN device 130 via the first RAN device 120-1, however the terminal device 110 then sends a NAS response message to the CN device 130 via another RAN device.

[0064] In some example embodiments, it can be an RRC procedure performed via different RAN devices. In other words, part of the RRC procedure is performed via the first RAN device 120-1 and the uncompleted part of the RRC procedure is to be performed via another RAN device. For example, the terminal device 110 sends an RRC message to the first RAN device 120-1, however the terminal device 110 then receives an RRC response message from another RAN device. In another example, the terminal device 110 receives an RRC message from the first RAN device 120-1, however the terminal device 110 then sends an RRC response message to another RAN device.

[0065] Before the first RAN device 120-1 moves out of the geographic area of the terminal device 110, the first RAN device 120-1 can initiate an RRC release procedure to release the RRC connection between the terminal device 110 and the first RAN device 120-1. The RRC release or other RRC procedure can include information for the next RAN device to continue the NAS registration procedure. The RRC connection between the terminal device 110 and the first RAN device 120-1 can also be released implicitly because the terminal device 110 knows that the next step in the registration procedure requires feedback / information from the CN device with which the RAN device is not currently connected. If the RRC connection between the terminal device 110 and the first RAN device 120-1 is released (e.g., via an RRC release procedure) or lost, the terminal device 110 stores a context. The context can include at least one of: a unique identity assigned to the terminal device 110 by the first RAN device 120-1, an RRC state, a last RRC message sent from the terminal device 110 to the first RAN device 120-1, a last RRC message received in the terminal device 110 from the first RAN device 120-1, an indication of an incomplete RRC procedure, a NAS state, a last NAS message sent from the terminal device 110 via the first RAN device 120-1, a last NAS message received in the terminal device 110 via the first RAN device 120-1, an indication of an incomplete NAS procedure, etc.

[0066] In this case, the information for the next RAN device to continue the registration procedure can be included in any DL RRC message (e.g., RRC setup). Since there is a lack of access stratum (AS) security, RRC INACTIVE it cannot be used.

[0067] While the first RAN device 120-1 has a connection with the CN device 130, the first RAN device 120-1 can send (210) INITIAL UE MESSAGE to the CN device 130 INITIAL UE MESSAGE including the unique identifier assigned to the terminal device 110 by the first RAN device 120-1.

[0068] As another option, the unique identifier assigned to the terminal device 110 by the first RAN device 120-1 can also be included in STORE UE CONTEXTThe message is sent (212) from the first RAN device 120-1 to the CN device 130. In the message, the first RAN device 120-1 can send the context of the terminal device 110 to the CN device 130. The context of the terminal device 110 can include a unique identifier allocated by the first RAN device 120-1 for the terminal device 110, an RRC state, a last RRC message received from the terminal device 110, a last RRC message sent to the terminal device 110, an indication of an unfinished RRC procedure, a RAN application protocol (AP) context created at the first RAN device 120-1 including a RAN AP UE ID, e.g., a RAN UE NGAP ID in a 5G system, or a location of the terminal device 110, e.g., a mapping cell ID, or a tracking area code, an actual location of the terminal device, etc. Thus, the CN device 130 stores the context received from the first RAN device 120-1. The CN device 130 can also determine that a NAS procedure with the terminal device 110 is not completed via the first RAN device 120-1, e.g., the CN device can receive a NAS message from the terminal device 110 via the first RAN device 120-1, but the CN device cannot send a NAS response message to the terminal device 110 via the first RAN device 120-1 because the first RAN device 120-1 does not have a connection with the terminal device 110 when the first RAN device 120-1 has a connection with the CN device 130. The CN device 130 can store a NAS context for the terminal device 110. The NAS context includes a non-access stratum NAS state, a last NAS message sent from the CN device 130 to the terminal device 110 via the first RAN device 120-1, a last NAS message received in the CN device 130 from the terminal device 110 via the first RAN device 120-1, an indication of an unfinished NAS procedure, etc.

[0069] When the second RAN device 120-2 has a connection with the CN device 130, the CN device 130 can determine, for example, that the second RAN device 120-2 will serve the geographic area of the terminal device 110. The CN device 130 can select the second RAN device 120-2 to complete the outstanding RRC procedure or the outstanding NAS procedure for the terminal device 110. In this case, i.e., the second RAN device 120-2 will provide coverage to the terminal device 110, and the connection between the CN device 130 and the second RAN device 120-2 is available to transfer information from the CN device 130 to the second RAN device 120-2, the CN device 130 can resume (214) the context for the terminal device 110 received from the first RAN device 120-1 at the second RAN device 120-2. The CN device 130 can send (214) a message (e.g., a RESUME UE CONTEXT message) to the second RAN device 120-2 to resume the context for the terminal device at the second RAN device 120-2 to continue the outstanding RRC procedure or the outstanding NAS procedure with the terminal device 110.

[0070] In some example embodiments, the context can include a unique identifier allocated by the first RAN device 120-1 for the terminal device 110, an RRC state, a last RRC message sent from the terminal device, a last RRC message received in the terminal device, an indication of an outstanding RRC procedure, a RAN AP context including an AP ID created at the first RAN device, a location of the terminal device 110 (e.g., a mapping cell ID or tracking area code, an actual location of the terminal device, etc.), and the like.

[0071] It should be appreciated that the CN device 130 can resume the context for multiple terminal devices. That is, the RESUME UE CONTEXT message sent from the CN device 130 to the second RAN device 120-2 can include the context for more than one terminal device. Thus, it can be a non-UE associated procedure.

[0072] The second RAN device 120-2 can then reply (216) RESUME UE CONTEXT ACKNOWLEDGE to the CN device 130 with a

[0073] In some example embodiments, the message can include a mapping of the old RAN UE AP ID assigned by the first RAN device 120-1 and the new RAN UE AP ID (e.g., RAN UE NGAP ID in 5G system) assigned by the second RAN device 120-2. This mapping is used when the RAN UE AP ID assigned by the first RAN device 120-1 has been assigned by the second RAN device 120-2 to a different UE, so the second RAN device 120-2 assignment will be used by the CN device 130 to send DL NAS TRANSPORT the new RAN UE AP ID for the message.

[0074] By establishing the context of the terminal device 110 in the second RAN device 120-2, the second RAN device 120-2 will not reject the other NGAP message (e.g., the DL NAS TRANSPORT message sent). Then, the CN device 130 can send DL NAS TRANSPORT the message to the second RAN device 120-2.

[0075] Then, when the second RAN device 120-2 moves in the geographical area of the terminal device 110, the second RAN device 120-2 can initiate (218) a paging procedure for the terminal device 110. The paging message can include the unique identifier assigned by the first RAN device 120-1 for the terminal device 110 and / or a paging cause indicating that the terminal device 110 continues the uncompleted RRC procedure or the uncompleted NAS procedure by using the stored context in the terminal device 110 via communication with the second RAN device 120-2.

[0076] The terminal device 110 can monitor the S&F paging in the paging channel using the unique identifier assigned for the terminal device 110. When the terminal device 110 receives the paging message from the second RAN device 120-2 including the unique identifier of the terminal device 110 and / or a new paging cause indicating that the terminal device 110 continues the uncompleted RRC procedure or the uncompleted NAS procedure, the terminal device 110 can send (220) to the second RAN device 120-2 via the second RAN device 120-2 using the stored context the RRCContinueRequest message including the unique identifier of the terminal device 110 and / or the cause indicating that the communication is requested to continue the uncompleted RRC procedure or the uncompleted NAS procedure.

[0077] The RRCContinetRequest message sent from the terminal device 110 to the second RAN device 120-2 can also be referred to as a new RRC message, as the RRCContinetRequestThe message is not based on an AS security context previously established between the terminal device 110 and the first RAN device 120-1 or the second RAN device 120-2. The AS security context has not been established.

[0078] Based on the received unique identifier of the terminal device 110, the second RAN device 120-2 can identify the relevant UE context. The second RAN device 120-2 can continue the unfinished NAS procedure by using the recovered UE context, e.g., sending DLInformationTransport the message to the terminal device 110. The terminal device 110 continues the unfinished NAS procedure by using the stored context, e.g., sending ULInformationTransport the message to the second RAN device 120-2.

[0079] When the second RAN device 120-2 has the connection to the CN device 130 again, the second RAN device 120-2 can send UL NAS TRANSPORT the message to the CN device 130.

[0080] Similarly, the second RAN device 120-2 can send the context of the terminal device 110 to the CN device 130. The context can include the Uu context, the unique identifier of the terminal device 110, the RRC context (e.g., RRC state, last sent / received RRC message, indication of unfinished RRC procedure, etc.), the NGAP context created at the second RAN device 120-2 (e.g., RAN UE NGAP ID allocated by the second RAN device 120-2), etc. Thus, the CN device 130 can store the received context and the NAS context for the terminal device 110 and continue the RRC procedure or the NAS procedure with the terminal device 110 via another RAN device.

[0081] The above procedure can be repeated when a new RAN device arrives or leaves. By using the above procedure, the terminal device 110 can complete the NAS procedure (e.g., attach / registration procedure) by using multiple S&F RAN devices.

[0082] In the subsequent communication phase (i.e., after the attach procedure is completed), the terminal device and the RAN device can utilize the RRC inactivity / suspend / resume procedure to quickly enable connection setup.

[0083] The solution of the present disclosure enables the completion of NAS procedures using multiple RAN devices, including multiple interactions between the UE and RAN nodes and between RAN nodes and CN nodes in the S&F system. Similarly, the solution of the present disclosure enables the completion of RRC procedures using multiple RAN devices in the S&F system. The allocation of the unique UE ID enables multiple RAN nodes to handle the UE context and continue the divided NAS procedures. Further, the transmission of the new RRC connection continue request by the UE indicates to the RAN nodes that the ongoing NAS procedure is being continued.

[0084] Figure 3 A flowchart illustrating an example method 300 of completing a NAS procedure (or RRC procedure) in an NTN S&F architecture, in accordance with some example embodiments of the present disclosure, is shown. The method 300 can be implemented at a terminal device 110 as shown. For purposes of discussion, reference will be made to the example system 100 as shown in FIG. 1. Figure 1 The method 300 will be described. Figure 1

[0085] At 310, the terminal device 110 obtains an indication from a first RAN device that includes a unique identifier. In one example, the indication instructs the terminal device 110 to store a context of the terminal device including the unique identifier assigned by the first RAN device. In another example, the indication instructs the terminal device 110 to first store the unique identifier as a context of the terminal device 110 and later, for example, when an RRC connection between the terminal device 110 and the first RAN device is released or lost, other contexts of the terminal device 110 (e.g., RRC state, last transmitted RRC message, etc.) are stored.

[0086] At 320, the terminal device 110 determines that the RRC procedure or the NAS procedure cannot be completed via the first RAN device due to the RRC connection between the terminal device 110 and the first RAN device being released or lost. The terminal device 110 stores the context.

[0087] At 330, if the terminal device 110 determines that a paging message is received from a second RAN device that instructs the apparatus to continue the uncompleted RRC procedure or the uncompleted NAS procedure, at 340, the terminal device 110 sends a request to the second RAN device for communication between the terminal device and the second RAN device to continue the uncompleted RRC procedure or the uncompleted NAS procedure by using the stored context of the terminal device.

[0088] ​In some example embodiments, the terminal device may obtain from the first RAN device an indication including a unique identifier during the Radio Resource Control (RRC) establishment process, or during the RRC recovery process, or during the RRC reconstruction process, or during the RRC release process; and if the terminal device's RRC connection is released or lost, the terminal device's context may be stored.

[0089] In some example embodiments, the context of the terminal device includes at least one of the following: a unique identifier assigned to the terminal device; or an RRC status; or the last RRC message sent from the terminal device; or the last RRC message received in the terminal device; or an indication of an incomplete RRC process or NAS status; or the last NAS message sent from the terminal device; or the last NAS message received in the terminal device; or an indication of an incomplete NAS process.

[0090] In some example embodiments, the request for communication between the terminal device and the second RAN device is an RRC continue request message.

[0091] In some example embodiments, if it is determined that a unique identifier has been obtained, the terminal device may determine that the RRC process or NAS process will continue using another RAN device besides the first RAN device.

[0092] In some example embodiments, the instruction also indicates that communication with the second RAN device should continue.

[0093] In some example embodiments, the paging message received from the second RAN device includes a unique identifier of the device and / or a paging reason, which instructs the terminal device to continue an incomplete RRC process or an incomplete NAS process via communication with the second RAN device using the terminal device's stored context.

[0094] In some example embodiments, the terminal device may send a unique identifier and / or indicate the reason why communication is requested to continue an incomplete RRC process or an incomplete NAS process via the second RAN device using the stored context.

[0095] In some example embodiments, the terminal device may send an RRC message or a NAS message to a first RAN device and receive an RRC response message or a NAS response message from a second RAN device; or it may receive an RRC message or a NAS message from a first RAN device and send an RRC response message or a NAS response message to a second RAN device.

[0096] Figure 4 A flowchart illustrating an example method 400 for performing a NAS procedure in an NTN S&F architecture according to some example embodiments of the present disclosure is shown. Method 400 can be implemented as follows:Figure 1 is implemented at the first RAN device 120-1. For purposes of discussion, reference will be made to Figure 1 Method 400 is described.

[0097] At 410, the first RAN device 120-1 obtains, from the CN device, a configuration of at least one unique identifier for at least one terminal device. This can be performed prior to the terminal device connecting with the first RAN device 120-1.

[0098] At 420, the first RAN device 120-1 allocates, to the terminal device, a unique identifier of the terminal device from the at least one unique identifier when the first RAN device 120-1 does not have a simultaneous connection with the core network device.

[0099] At 430, the first RAN device 120-1 sends, to the terminal device, an indication including the unique identifier to be stored as a context of the terminal device.

[0100] In some example embodiments, the first RAN device 120-1 can send the indication to the terminal device during a radio resource control, RRC, setup procedure, or an RRC resume procedure, or an RRC reestablishment procedure, or an RRC release procedure.

[0101] In some example embodiments, the first RAN device 120-1 can determine that an RRC procedure or a NAS procedure with the terminal device cannot be completed when the apparatus does not have a simultaneous connection with the core network device.

[0102] In some example embodiments, the first RAN device 120-1 can send the indication to the terminal device during a radio resource control, RRC, setup procedure, or an RRC resume procedure, or an RRC reestablishment procedure, or an RRC release procedure.

[0103] In some example embodiments, the first RAN device 120-1 can send, to the core network device, the unique identifier allocated to the terminal device.

[0104] In some example embodiments, the unique identifier of the terminal device is sent to the core network device via at least one of: an initial UE message or a UE context store message.

[0105] In some example embodiments, the initial UE message or the UE context store message further includes a context of the terminal device.

[0106] In some example embodiments, the context of the terminal device comprises at least one of: a unique identifier assigned by the apparatus; or an RRC state; or a last RRC message sent from the terminal device; or a last RRC message received in the terminal device; or an indication for an unfinished RRC procedure or NAS state; or a last NAS message sent from the terminal device; or a last NAS message received in the terminal device; or an indication for an unfinished NAS procedure; or a RAN AP context comprising an AP ID created at the apparatus; or a location of the terminal device.

[0107] Figure 5 A flowchart illustrating an example method 500 of completing a NAS procedure in an NTN S&F architecture, according to some example embodiments of the present disclosure, is shown. The method 500 can be implemented at a CN device 130 as shown. Figure 1 For purposes of discussion, the method 500 will be described with reference to the CN device 130 as shown. Figure 1 The method 500 will be described with reference to the CN device 130 as shown.

[0108] At 510, the CN device 130 sends, to a first RAN device, a configuration for at least one unique identifier of at least one terminal device. This can be performed before the terminal device connects with the first RAN device.

[0109] In some example embodiments, the CN device 130 can receive, from the first RAN device, a context of the terminal device created at the first RAN device; and store the context received from the first RAN device and a NAS context established with the terminal device via the first RAN device.

[0110] In some example embodiments, the context of the terminal device is sent to the core network device via at least one of: an initial UE message or a UE context storage message.

[0111] In some example embodiments, the context of the terminal device comprises at least one of: a unique identifier assigned by the first RAN device; or an RRC state; or a last RRC message sent from the terminal device; a last received RRC message received in the terminal device; an indication for an unfinished RRC procedure; a RAN AP context comprising an AP ID created at the first RAN device; or a location of the terminal device.

[0112] In some example embodiments, the NAS context comprises at least one of: a NAS state; or a NAS message sent from the terminal device; a last NAS message received in the terminal device; or an indication for an unfinished NAS procedure.

[0113] In some example embodiments, the CN device 130 can determine, via the first RAN device, that a NAS procedure with the terminal device is unfinished.

[0114] In some example embodiments, if it is determined that the uncompleted RRC procedure or the uncompleted NAS procedure with the terminal device is to be continued via the second RAN device, the CN device 130 can send a message to the second RAN device for resuming the context of the terminal device at the second RAN device to continue the uncompleted RRC procedure or the uncompleted NAS procedure with the terminal device.

[0115] In some example embodiments, the CN device 130 can receive an acknowledgement from the second RAN device to the message for resuming the context of the terminal device.

[0116] In some example embodiments, the context of the terminal device further includes a RAN UE AP ID allocated by the first RAN device, and wherein the acknowledgement includes a mapping of the RAN UE AP identifier allocated by the first RAN device and another RAN UE AP identifier allocated by the second RAN device.

[0117] In some example embodiments, the CN device 130 can send the message to the second RAN device by using the other RAN UE AP ID allocated by the second RAN device.

[0118] In some example embodiments, the CN device 130 can send a NAS message to the terminal device via the first RAN device and receive a NAS response message from the terminal device via the second RAN device; or receive a NAS message from the terminal device via the first RAN device and send a NAS response message to the terminal device via the second RAN device.

[0119] Figure 6 A flowchart of an example method 600 of completing a NAS procedure in an NTN S&F architecture is shown in accordance with some example embodiments of the present disclosure. The method 600 can be implemented at a second RAN device 120-2 as shown in Figure 1 For purposes of discussion, the method 600 will be described with reference to the example NTNS&F architecture shown in FIG. 6. Figure 1 The method 600 will be described with reference to the example NTNS&F architecture shown in FIG. 6.

[0120] At 610, the second RAN device 120-2 receives a message from a core network device, the message including a context of a terminal device created by a first RAN device for resuming the context of the terminal device at the second RAN device to continue an uncompleted RRC procedure or an uncompleted NAS procedure with the terminal device.

[0121] At 620, the second RAN device 120-2 sends a paging message indicating the terminal device to continue the uncompleted RRC procedure or the uncompleted NAS procedure.

[0122] At 630, the second RAN device 120-2 receives, from the terminal device, a request for communication between the second RAN device 120-2 and the terminal device to continue the uncompleted RRC procedure or the uncompleted NAS procedure by using the context received from the core network device.

[0123] In some example embodiments, the context received from the core network device further comprises at least one of: a unique identifier assigned to the terminal device; or an RRC state; a last RRC message transmitted from the terminal device; a last received RRC message received in the terminal device; an indication of an uncompleted RRC procedure; a RAN AP context comprising a RAN UE AP ID created at the first RAN device; or a location of the terminal device.

[0124] In some example embodiments, the second RAN device 120-2 can send, to the core network device, an acknowledgement for the message for resuming the context of the terminal device comprising at least one of another RAN UE AP identifier assigned by the apparatus and a mapping of the RAN UE AP identifier assigned by the first RAN device and the another RAN UE AP identifier assigned by the second RAN device 120-2.

[0125] In some example embodiments, the second RAN device 120-2 can send, to the core network device, an acknowledgement for the message for resuming the context of the terminal device comprising at least one of another RAN UE AP identifier assigned by the second RAN device and a mapping of the RAN UE AP identifier assigned by the first RAN device and the another RAN UE AP identifier assigned by the second RAN device.

[0126] In some example embodiments, the second RAN device 120-2 can receive, from the core network device, another message comprising another RAN UE AP ID assigned by the second RAN device 120-2.

[0127] In some example embodiments, the request for RRC continuation is for communication between the second RAN device 120-2 and the terminal device.

[0128] In some example embodiments, an apparatus capable of performing the method 300 (e.g., implemented at the terminal device 110) can comprise means for performing the respective steps of the method 300. The means can be implemented in any suitable form. For example, the means can be implemented in circuitry or software modules.

[0129] In some example embodiments, the apparatus comprises: means for obtaining, from the first RAN device, an indication comprising a unique identifier, the unique identifier being assigned by the first RAN device; means for determining that an RRC procedure or a NAS procedure cannot be completed via the first RAN device; and means for sending, to the second RAN device, a request for communication between the apparatus and the second RAN device to continue the uncompleted RRC procedure or the uncompleted NAS procedure by using the stored context of the apparatus, if it is determined that a paging message from the second RAN device indicating the apparatus to continue the uncompleted RRC procedure or the uncompleted NAS procedure is received.

[0130] In some example embodiments, the apparatus can further comprise: means for obtaining, from the first RAN device, an indication comprising the unique identifier in a RRC setup procedure, or in a RRC resume procedure, or in a RRC reestablishment procedure, or in a RRC release procedure; and means for storing a context of the apparatus if the RRC connection of the apparatus is released or lost.

[0131] In some example embodiments, the context of the apparatus comprises at least one of: a unique identifier assigned to the apparatus; or an RRC state; or a last RRC message sent from the apparatus; or a last RRC message received in the apparatus; an indication for an uncompleted RRC procedure or a NAS state; or a last NAS message sent from the apparatus; or a last NAS message received in the apparatus; or an indication for an uncompleted NAS procedure.

[0132] In some example embodiments, the request for communication between the apparatus and the second RAN device is a RRC continue request message.

[0133] In some example embodiments, if it is determined that the unique identifier is obtained, the apparatus can further comprise means for determining that the RRC procedure or the non-access stratum, NAS, procedure is to be continued with another RAN device other than the first RAN device.

[0134] In some example embodiments, the indication further indicates that the communication is to be continued with the second RAN device.

[0135] In some example embodiments, the paging message received from the second RAN device comprises the unique identifier of the apparatus and / or a paging cause, the paging message indicating the apparatus to continue the uncompleted RRC procedure or the uncompleted NAS procedure via the communication with the second RAN device by using the stored context of the apparatus.

[0136] In some example embodiments, the apparatus can further comprise means for sending, to the second RAN device, the unique identifier and / or a cause indicating that the communication is requested to continue the uncompleted RRC procedure or the uncompleted NAS procedure via the second RAN device, by using the stored context.

[0137] In some example embodiments, the apparatus can further comprise sending the RRC message or the NAS message to the first RAN device and receiving the RRC response message or the NAS response message from the second RAN device; or receiving the RRC message or the NAS message from the first RAN device and sending the RRC response message or the NAS response message to the second RAN device.

[0138] In some example embodiments, an apparatus capable of performing the method 400 (e.g., implemented at the first RAN device 120-1) can comprise means for performing the respective steps of the method 400. The means can be implemented in any suitable form. For example, the means can be implemented in circuitry or a software module.

[0139] In some example embodiments, the apparatus comprises means for obtaining, from the CN device, a configuration of at least one unique identifier for at least one terminal device; means for assigning, to the terminal device, a unique identifier of the terminal device from the at least one unique identifier in case the apparatus does not have a simultaneous connection with the core network device; and means for sending, to the terminal device, an indication to store the unique identifier as a context of the terminal device.

[0140] In some example embodiments, the apparatus comprises means for determining, in case the apparatus does not have a simultaneous connection with the core network device, that an RRC procedure or a NAS procedure with the terminal device cannot be completed.

[0141] In some example embodiments, the apparatus comprises means for sending, to the terminal device, the indication during a radio resource control, RRC, setup procedure, or a RRC resume procedure, or a RRC reestablishment procedure, or a RRC release procedure.

[0142] In some example embodiments, the apparatus comprises means for sending, to the CN device, the unique identifier assigned to the terminal device.

[0143] In some example embodiments, the unique identifier of the terminal device is sent to the core network device via at least one of: an initial UE message or a UE context store message.

[0144] In some example embodiments, the initial UE message or the UE context store message further comprises a context of the terminal device.

[0145] In some example embodiments, the context of the terminal device comprises at least one of: a unique identifier assigned by the apparatus; or an RRC state; or a last RRC message sent from the terminal device; or a last RRC message received in the terminal device; an indication of an unfinished RRC procedure; or a non-access stratum, NAS, state; or a NAS message sent from the terminal device; or a last NAS message received in the terminal device; or an indication of an unfinished NAS procedure; or a RAN AP context comprising an AP ID created at the apparatus; or a location of the terminal device.

[0146] In some example embodiments, an apparatus capable of performing the method 500 (e.g., implemented at the CN device 130) can comprise means for performing the respective steps of the method 500. The means can be implemented in any suitable form. For example, the means can be implemented in circuitry or software modules.

[0147] In some example embodiments, the apparatus comprises means for sending, to the first RAN device, a configuration of at least one unique identifier for at least one terminal device before the terminal device is connected with the first RAN device.

[0148] In some example embodiments, the apparatus comprises means for receiving, from the first RAN device, a context of the terminal device created at the first RAN device; and storing the context received from the first RAN device and a NAS context established with the terminal device via the first RAN device.

[0149] In some example embodiments, the context of the terminal device is sent to the core network device via at least one of: an initial UE message or a UE context store message.

[0150] In some example embodiments, the context of the terminal device comprises a unique identifier assigned by the first RAN device; an RRC state; a last RRC message sent from the terminal device; a last received RRC message received in the terminal device; an indication of an unfinished RRC procedure; a RAN AP context comprising an AP ID created at the first RAN device; or a location of the terminal device.

[0151] In some example embodiments, the NAS context comprises at least one of: a non-access stratum, NAS, state; or a NAS message sent from the terminal device; a last NAS message received in the terminal device; or an indication of an unfinished NAS procedure.

[0152] In some example embodiments, the apparatus comprises means for determining, via the first RAN device, that a NAS procedure with the terminal device is unfinished.

[0153] In some example embodiments, if it is determined that the uncompleted RRC procedure or the uncompleted NAS procedure with the terminal device is to be continued via the second RAN device, the apparatus comprises means for sending, to the second RAN device, a message for resuming, at the second RAN device, a context of the terminal device to continue the uncompleted RRC procedure or the uncompleted NAS procedure with the terminal device.

[0154] In some example embodiments, the apparatus comprises means for receiving, from the second RAN device, an acknowledgement to the message for resuming the context of the terminal device.

[0155] In some example embodiments, the context of the terminal device further comprises a RAN UE AP ID allocated by the first RAN device, and wherein the acknowledgement comprises a mapping of the RAN UE AP identifier allocated by the first RAN device and another RAN UE AP identifier allocated by the second RAN device.

[0156] In some example embodiments, the apparatus comprises means for sending a message to the second RAN device by using the other RAN UE AP ID allocated by the second RAN device.

[0157] In some example embodiments, the apparatus comprises means for sending a NAS message to the terminal device via the first RAN device and receiving a NAS response message from the terminal device via the second RAN device; or receiving a NAS message from the terminal device via the first RAN device and sending a NAS response message to the terminal device via the second RAN device.

[0158] In some example embodiments, an apparatus capable of performing the method 600 (e.g., implemented at the second device 120-2) can comprise means for performing the respective steps of the method 600. The means can be implemented in any suitable form. For example, the means can be implemented in circuitry or software modules.

[0159] In some example embodiments, the apparatus comprises means for receiving, from a core network device, a message comprising a context of a terminal device created by a first RAN device, means for resuming, at the apparatus, the context of the terminal device to continue an uncompleted RRC procedure or an uncompleted NAS procedure with the terminal device, means for sending a paging message indicating that the terminal device continues the uncompleted RRC procedure or the uncompleted NAS procedure, and means for receiving, from the terminal device, a request for communication between the apparatus and the terminal device to continue the uncompleted RRC procedure or the uncompleted NAS procedure by using the context received from the core network device.

[0160] In some example embodiments, the context received from the core network device further comprises at least one of: a unique identifier assigned to the terminal device; or an RRC state; a last RRC message transmitted from the terminal device; a last received RRC message received in the terminal device; an indication of an unfinished RRC procedure; a RAN AP context comprising a RAN UE AP ID created at the first RAN device; or a location of the terminal device.

[0161] In some example embodiments, the apparatus comprises means for sending, to the core network device, an acknowledgement of the message for resuming the context of the terminal device, the acknowledgement comprising at least one of: another RAN UE AP identifier assigned by the apparatus, and a mapping of the RAN UE AP identifier assigned by the first RAN device to another RAN UE AP identifier assigned by the second RAN device.

[0162] In some example embodiments, the apparatus comprises means for receiving, from the core network device, another message comprising another RAN UE AP ID assigned by the apparatus.

[0163] In some example embodiments, the request for continuing the communication between the apparatus and the terminal device is via an RRC continue request.

[0164] Figure 7 is a simplified block diagram of a device 700 suitable for implementing example embodiments of the present disclosure. The device 700 can be provided to implement a communication device, such as Figure 1 The terminal device 110, the first RAN device 120-1, the CN device 130, and the second RAN device 120-2 are shown. As shown, the device 700 includes one or more processors 710, one or more memories 720 coupled to the processors 710, and one or more communication modules 740 coupled to the processors 710.

[0165] The communication module 740 is for bidirectional communication. The communication module 740 has one or more communication interfaces to facilitate communication with one or more other modules or devices. The communication interface can represent any interface necessary to communicate with other network elements. In some example embodiments, the communication module 740 can include at least one antenna.

[0166] The processor 710 can be of any type suitable to the local technical network, and can include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multi-core processor architectures, as non-limiting examples. The device 700 can have multiple processors such as a dedicated integrated circuit chip that is time-synchronous to a clock that synchronizes the main processor.

[0167] The memory 720 can include one or more non-transitory memories and one or more transitory memories. Examples of non-transitory memories include, but are not limited to, read-only memory (ROM) 724, electrically programmable read-only memory (EPROM), flash memory, a hard disk, a compact disc (CD), a digital video disc (DVD), an optical disc, laser disc, and other magnetic storage and / or optical storage. Examples of transitory memories include, but are not limited to, random access memory (RAM) 722 and other volatile memory that does not survive duration of power loss.

[0168] The computer program 730 includes computer-executable instructions executed by the associated processor 710. The instructions of the program 730 can include instructions for performing the operations / acts of some example embodiments of the present disclosure. The program 730 can be stored in the memory (e.g., ROM 724). The processor 710 can perform any suitable action and processing by loading the program 730 into the RAM 722.

[0169] Example embodiments of the present disclosure can be implemented by the program 730 so that the device 700 can perform any process of the present disclosure as discussed with reference to Figure 2 to Figure 6 Example embodiments of the present disclosure can also be implemented by hardware or by a combination of software and hardware.

[0170] In some example embodiments, the program 730 can be tangibly embodied in a computer-readable medium, which can include other storage devices in the device 700 (such as in the memory 720) or accessible by the device 700. The device 700 can load the program 730 from the computer-readable medium into the RAM 722 for execution. In some example embodiments, the computer-readable medium can include any type of non-transitory storage medium, such as ROM, EPROM, flash memory, a hard disk, a CD, a DVD, and the like. The term “non-transitory,” as used herein with respect to a medium, is a limitation of the medium itself (i.e., tangible, as opposed to a signal), and not a limitation on the persistence of data stored thereon (e.g., RAM vs. ROM).

[0171] Figure 8 An example of a computer-readable medium 800 is shown, which can be in the form of a CD, DVD, or other optical storage disk. The computer-readable medium 800 has the program 730 stored thereon.

[0172] In general, the various embodiments of the present disclosure can be implemented in hardware or special-purpose circuits, software, logic or any combination thereof. Some aspects can be implemented in hardware, while other aspects can be implemented in firmware or software which can be executed by a controller, microprocessor or other computing device. While various aspects of embodiments of the present disclosure are illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein can be implemented in, as non-limiting examples, hardware, software, firmware, special-purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

[0173] Some example embodiments of the present 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 executed by a device, such as those included in program modules, to perform any of the methods as described above on a target physical or virtual processor. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, etc. that perform particular tasks or implement particular abstract data types. The functionality of the program modules can be combined or split between program modules as desired in various embodiments. Machine executable instructions for program modules can be executed within a local or distributed device. In a distributed device, program modules can be located in both local and remote storage media.

[0174] Program code for carrying out methods 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, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the program code, when executed by the processor or controller, causes the machine to perform the functions / acts specified in the flowcharts and / or block diagrams. The program code can be executed entirely on a machine, partially on a machine, as a stand-alone software package, partially on a machine and partially on a remote machine or entirely on a remote machine or server.

[0175] In the context of the present disclosure, computer program code or related data can be carried by any suitable carrier to enable a device, apparatus or processor to perform the various processes and operations as described above. Examples of carriers include signals, computer readable media, etc.

[0176] 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 will 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.

[0177] Furthermore, although operations are described in a specific order, this should not be construed as requiring that such operations be performed in the specific order shown or sequentially, or requiring that all shown operations be performed to achieve the desired result. In some cases, multitasking and parallel processing may be advantageous. Similarly, while several specific implementation details are included in the above discussion, these should not be construed as limiting the scope of this disclosure, but rather as a description 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.

[0178] 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. An apparatus comprising: At least one processor; as well as At least one memory, the at least one memory storing instructions, the instructions causing the device to at least: Obtain an indication including a unique identifier from a first radio access network (RAN) device, the unique identifier being assigned by the first RAN device. It is determined that the Radio Resource Control (RRC) procedure or the Non-Access Stratum (NAS) procedure cannot be completed via the first RAN device; as well as If a paging message from the second RAN device instructing the device to continue an incomplete RRC process or an incomplete NAS process is received, a request for communication between the device and the second RAN device is sent to the second RAN device to continue the incomplete RRC process or the incomplete NAS process by using the stored context of the device.

2. The apparatus of claim 1, wherein the apparatus further causes: Obtain from the first RAN device the indication including the unique identifier during the RRC establishment process, or during the RRC recovery process, or during the RRC reconstruction process, or during the RRC release process; and If the RRC connection of the device is released or lost, the context of the device is stored.

3. The apparatus of claim 1 or 2, wherein the context of the apparatus includes at least one of the following: The unique identifier assigned to the device; or RRC status; or The last RRC message sent from the device; or The last RRC message received in the device; or Instructions for incomplete RRC procedures, or Non-access tier NAS status; or The last NAS message sent from the device; or The last NAS message received in the device; or Instructions for incomplete NAS processes.

4. The apparatus of claim 1, wherein the apparatus further causes: If it is determined that the unique identifier has been acquired, it is determined that the RRC process or the non-access stratum NAS process will continue using another RAN device other than the first RAN device.

5. The apparatus of claim 1, wherein the paging message received from the second RAN device includes the unique identifier of the apparatus and / or a paging reason, the paging message instructing the apparatus to continue the unfinished RRC process or the unfinished NAS process via communication with the second RAN device by using the stored context of the apparatus.

6. The apparatus of claim 1, wherein the apparatus further causes: By using the stored context, the unique identifier is sent to the second RAN device and / or the reason why the communication is requested to continue the incomplete RRC process or the incomplete NAS process via the second RAN device.

7. The apparatus of claim 1, wherein the apparatus further causes: Send an RRC message or a NAS message to the first RAN device, and receive an RRC response message or a NAS response message from the second RAN device; or Receive RRC messages or NAS messages from the first RAN device; and Send an RRC response message or a NAS response message to the second RAN device.

8. An apparatus comprising: At least one processor; as well as At least one memory, the at least one memory storing instructions, the instructions causing the device to at least: Obtain the configuration of at least one unique identifier for at least one terminal device from the core network device; In the absence of simultaneous connection with the core network device, a unique identifier of the terminal device is assigned to the terminal device from the at least one unique identifier. as well as Send an instruction to the terminal device including the unique identifier to be stored as the context of the terminal device.

9. The apparatus of claim 8, wherein the apparatus further causes: If the device does not have a simultaneous connection with the core network device, it is determined that the RRC process or NAS process with the terminal device cannot be completed.

10. The apparatus of claim 8, wherein the apparatus further causes: The instruction is sent to the terminal device during the Radio Resource Control (RRC) establishment process, or RRC recovery process, or RRC reconstruction process, or RRC release process.

11. The apparatus of claim 8, wherein the apparatus is further caused to: Send the unique identifier assigned to the terminal device to the core network device.

12. An apparatus comprising: At least one processor; as well as At least one memory, the at least one memory storing instructions, the instructions causing the device to at least: Before the terminal device connects to the first radio access network (RAN) device, a configuration for at least one unique identifier for at least one terminal device is sent to the first RAN device.

13. The apparatus of claim 12, wherein the apparatus is further caused to: Receive the context of the terminal device created at the first RAN device from the first RAN device; and The context received from the first RAN device and the NAS context established between the first RAN device and the terminal device are stored.

14. The apparatus of claim 13, wherein the NAS context includes at least one of the following: Non-access tier NAS status; or NAS messages sent from the terminal device; The last NAS message received in the terminal device; or Instructions for incomplete NAS processes.

15. The apparatus according to claims 12 to 14, wherein the apparatus is further caused to: If it is determined that an incomplete RRC procedure or an incomplete NAS procedure with the terminal device needs to be continued via a second RAN device, a message is sent to the second RAN device to restore the context of the terminal device at the second RAN device to continue the incomplete RRC procedure or the incomplete NAS procedure with the terminal device.

16. The apparatus of claim 15, further causing: The acknowledgment received from the second RAN device for the message used to restore the context of the terminal device, wherein the context of the terminal device further includes a RAN UE AP identifier assigned by the first RAN device, and wherein the acknowledgment includes a mapping between the RAN UE AP identifier assigned by the first RAN device and another RAN UE AP identifier assigned by the second RAN device.

17. The apparatus according to claim 15 or 16, wherein the apparatus is further caused to: A message is sent to the second RAN device using the other RAN UE AP identifier assigned by the second RAN device.

18. The apparatus according to claims 12 to 17, wherein the apparatus further causes: Sending a NAS message to the terminal device via the first RAN device, and receiving a NAS response message from the terminal device via the second RAN device; or Receive NAS messages from the terminal device via the first RAN device; as well as The NAS response message is sent to the terminal device via the second RAN device.

19. An apparatus comprising: At least one processor; as well as At least one memory, the at least one memory storing instructions, the instructions causing the device to at least: Receive a message from the core network device, the message including the context of the terminal device created by the first RAN device, the message being used to restore the context of the terminal device at the device to continue with any incomplete Radio Resource Control (RRC) or Incomplete Non-Access Stratum (NAS) procedures of the terminal device; Send a paging message instructing the terminal device to continue the incomplete RRC process or the incomplete NAS process; as well as Receive a request from the terminal device for communication between the device and the terminal device to continue an unfinished RRC process or an unfinished NAS process by using the context received from the core network device.

20. The apparatus of claim 19, further causing: Sending an acknowledgment to the core network device for the message used to restore the context of the terminal device, the acknowledgment including at least one of the following: another RAN UE AP identifier assigned by the device and a mapping between the RAN UE AP identifier assigned by the first RAN device and the other RAN UE AP identifier assigned by the device.

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