Switching to dual connectivity

Abstract

Embodiments of the present disclosure relate to methods, devices, and computer-readable storage media for switching to dual connections. According to embodiments of the present disclosure, a terminal device receives a connection reconfiguration message from a source network device, the connection reconfiguration message including configurations of a target primary network device and a target secondary network device to be connected to the terminal device. The terminal device performs parallel random access to the target primary network device and the target secondary network device. If the terminal device successfully connects to the target secondary network device but fails to connect to the target primary network device, the terminal device will reconnect to the target primary network device. In addition, the target secondary network device will indicate the result of the random access to the target primary network device. In this way, the solution can improve the success rate of switching to dual connections.

Description

Technical Field

[0001] Embodiments of the present disclosure relate generally to the field of telecommunications, and in particular to methods, apparatus, and computer-readable media for handover to dual connectivity. Background Art

[0002] In Release 15 of the 3GPP specification, inter-radio access technology (inter-RAT) handover to E-UTRA New Radio (NR) Dual Connectivity (EN-DC) is not supported. For example, a source NR network device (such as a next-generation NodeB, also referred to as a "gNB") can only first handover a terminal device (such as a user equipment) from a gNB to a target Long Term Evolution (LTE) network device (such as an evolved NodeB, also referred to as an "eNodeB" or "eNB"), and then configure EN-DC by adding a secondary network device after the handover. A direct inter-RAT handover from NR to EN-DC needs to be introduced, which can reduce signaling overhead and ensure consistent high data rates for enhanced mobile broadband (eMBB) services. Summary of the invention

[0003] In general, example embodiments of the present disclosure provide methods, apparatus, and computer-readable media for handover to dual connectivity.

[0004] In a first aspect, a method is provided. The method includes receiving, at a first device, a connection reconfiguration message from a fourth device connected to the first device, the connection reconfiguration message including a first configuration about a second device and a second configuration about a third device; performing a first random access to the second device based on the first configuration and a second random access to the third device based on the second configuration to connect to the second device and the third device; and in response to a failure of the first random access and a success of the second random access, reconnecting to the second device based on the first configuration while maintaining connection to the third device.

[0005] In a second aspect, a method is provided. The method sends a connection reconfiguration message from a second device to a fourth device connected to a first device, the connection reconfiguration message including configurations about the second device and a third device to be connected to the first device, so that the first device can perform a first random access to the second device and a second random access to the third device; determines whether the first random access and the second random access are successful; and causes the first device to reconnect to the second device based on determining that the first random access fails and the second random access is successful.

[0006] In a third aspect, a method is provided. The method includes receiving, at a third device, a request from a second device to add a third device to provide dual connectivity for a first device; sending to the second device a confirmation including a second configuration about the third device so that the first device can perform random access to the third device based on the second configuration; determining whether the random access is successful or failed; and sending a result of the determination to the second device.

[0007] In a fourth aspect, a first device is provided. The first device includes at least one processor; and at least one memory including computer program code. The at least one memory and the computer program code are configured to, together with the at least one processor, cause the first device to receive a connection reconfiguration message from a fourth device connected to the first device, the connection reconfiguration message including a first configuration about a second device and a second configuration about a third device; perform a first random access to the second device based on the first configuration and a second random access to the third device based on the second configuration to connect to the second device and the third device; and in response to a failure of the first random access and a success of the second random access, reconnect to the second device based on the first configuration while maintaining connection to the third device.

[0008] In a fifth aspect, a second device is provided. The second device includes at least one processor; and at least one memory including computer program code. The at least one memory and the computer program code are configured to, together with the at least one processor, cause the second device to send a connection reconfiguration message to a fourth device connected to the first device, the connection reconfiguration message including configurations about the second device and a third device to be connected to the first device, so that the first device can perform a first random access to the second device and a second random access to the third device; determine whether the first random access and the second random access are successful; and according to determining that the first random access fails and the second random access is successful, reconnect the first device to the second device.

[0009] In a sixth aspect, a third device is provided. The third device includes at least one processor; and at least one memory including computer program code. The at least one memory and the computer program code are configured to, together with the at least one processor, cause the third device to receive a request from a second device to add a third device to provide dual connectivity for a first device; send a confirmation including a second configuration about the third device to the second device so that the first device can perform random access to the third device based on the second configuration; determine whether the random access is successful or failed; and send the result of the determination to the second device.

[0010] In a seventh aspect, a device is provided. The device includes a component for receiving a connection reconfiguration message from a fourth device connected to the first device at a first device, the connection reconfiguration message including a first configuration about a second device and a second configuration about a third device; a component for performing a first random access to the second device based on the first configuration and a second random access to the third device based on the second configuration to connect to the second device and the third device; and a component for reconnecting to the second device based on the first configuration while maintaining connection to the third device in response to a failure of the first random access and a success of the second random access.

[0011] In an eighth aspect, an apparatus is provided. The apparatus includes a component for sending a connection reconfiguration message from a second device to a fourth device connected to a first device, the connection reconfiguration message including configurations about the second device and a third device to be connected to the first device, so that the first device can perform a first random access to the second device and a second random access to the third device; a component for determining whether the first random access and the second random access are successful; and a component for causing the first device to reconnect to the second device based on determining that the first random access fails and the second random access is successful.

[0012] In a ninth aspect, an apparatus is provided. The apparatus includes a component for receiving, at a third device, a request for adding a third device to provide dual connectivity for a first device from a second device; a component for sending to the second device a confirmation including a second configuration about the third device so that the first device can perform random access to the third device based on the second configuration; a component for determining whether the random access is successful or failed; and a component for sending a result of the determination to the second device.

[0013] In a tenth aspect, a computer program product is provided, the computer program product being stored on a computer readable medium and comprising machine executable instructions, wherein when the machine executable instructions are executed, the machine executes the method according to the first aspect, the second aspect or the third aspect.

[0014] In an eleventh aspect, there is a computer-readable storage medium including program instructions stored thereon. When the instructions are executed by a device, the device performs the method according to the first aspect, the second aspect or the third aspect.

[0015] It should be understood that the invention summary is not intended to determine the key or essential features of the embodiments of the present disclosure, nor is it intended to limit the scope of the present disclosure. Other features of the present disclosure will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above and other objects, features and advantages of the present disclosure will become more apparent through a more detailed description of some example embodiments of the present disclosure in the accompanying drawings, in which:

[0017] Figure 1 shows an example communication network in which example embodiments of the present disclosure may be implemented;

[0018] Figure 2 A schematic diagram showing interactions between devices according to some example embodiments of the present disclosure;

[0019] Figure 3 A schematic diagram showing interactions between devices according to some example embodiments of the present disclosure;

[0020] Figure 4 A schematic diagram showing interactions between devices according to some example embodiments of the present disclosure;

[0021] Figure 5 A flowchart illustrating an example method for handover to dual connectivity according to some example embodiments of the present disclosure;

[0022] Figure 6 A flowchart illustrating an example method for handover to dual connectivity according to some example embodiments of the present disclosure;

[0023] Figure 7 A flowchart illustrating an example method for handover to dual connectivity according to some example embodiments of the present disclosure;

[0024] Figure 8 shows a simplified block diagram of an apparatus suitable for implementing an embodiment of the present disclosure; and

[0025] Fig. 9 A block diagram of an example computer-readable medium is shown according to some example embodiments of the present disclosure.

[0026] Throughout the drawings, the same or similar reference numerals refer to the same or similar elements. DETAILED DESCRIPTION

[0027] The principles of the present disclosure will now be described with reference to some example embodiments. It should be understood that the description of the example embodiments is only for the purpose of illustrating and helping those skilled in the art to understand and implement the present disclosure, and does not represent any limitation on the scope of the present disclosure. The disclosure described herein can be implemented in various other ways except for the way described below.

[0028] In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0029] References in this disclosure to "one embodiment," "an embodiment," "an example embodiment," etc. indicate that the described embodiment may include a particular feature, structure, or characteristic, but not every embodiment necessarily includes the particular feature, structure, or characteristic. Furthermore, such phrases do not necessarily refer to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in conjunction with an example embodiment, it is considered to be within the knowledge of those skilled in the art to affect such feature, structure, or characteristic in conjunction with other embodiments (whether or not explicitly described).

[0030] It should be understood that although the terms "first" and "second" etc. may 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 element. For example, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element without departing from the scope of the exemplary embodiments. As used herein, the term "and / or" includes any and all combinations of one or more of the listed terms.

[0031] The terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the example embodiments. As used herein, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises", "comprising", "has", "having", "includes", and / or "including" when used herein specify the presence of the features, elements, and / or components, etc., but do not exclude the presence or addition of one or more other features, elements, components, and / or combinations thereof.

[0032] As used in this application, the term "circuitry" may refer to one, more, or all of the following:

[0033] (a) a pure hardware circuit implementation (such as an implementation using only analog and / or digital circuitry), and

[0034] (b) a combination of hardware circuitry and software such as (where applicable):

[0035] (i) a combination of analog and / or digital hardware circuits and software / firmware, and

[0036] (ii) any portion of hardware processor(s) (including digital signal processor(s)), software and memory(s) with software that work together to cause a device (such as a mobile phone or server) to perform various functions, and

[0037] (c) Hardware circuits and / or processor(s), such as microprocessor(s) or portions of microprocessor(s), that require software (e.g., firmware) to operate, but which may not be present when the software is not required for operation.

[0038] This definition of circuitry applies to all uses of the term in this application, including in any claims. As another example, as used in this application, the term circuitry also covers an implementation of only a hardware circuit or processor (or multiple processors) or a portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware. For example, if applicable to a particular claim element, the term circuitry also covers a baseband integrated circuit or processor integrated circuit for a mobile device, or a similar integrated circuit in a server, cellular network device, or other computing or network device.

[0039] As used herein, the term "communication network" refers to a network that follows any suitable communication standard, such as long term evolution (LTE), advanced LTE (LTE-A), wideband code division multiple access (WCDMA), high speed packet access (HSPA), narrowband Internet of Things (NB-IoT), new radio (NR), etc. In addition, the communication between the terminal equipment and the network equipment in the communication network can be performed according to the communication protocol of any suitable generation, including but not limited to the first generation (1G), second generation (2G), 2.5G, 2.75G, third generation (3G), fourth generation (4G), 4.5G, future fifth generation (5G) communication protocol, and / or and / or any other protocol currently known or developed in the future. The embodiments of the present disclosure can be applied to various communication systems. In view of the rapid development of communication, there will certainly be communication technologies and systems that can embody future types of the present disclosure. It should not be considered that the scope of the present disclosure is limited to the above-mentioned system.

[0040] As used herein, the term "network device" refers to a node in a communication network, via which a terminal device accesses the network and receives services from it. A network device may refer to a base station (BS) or an access point (AP), such as a NodeB (NodeB or NB), an evolved NodeB (eNodeB or eNB), a NR NB (also known as a gNB), a remote radio unit (RRU), a radio head (RH), a remote radio head (RRH), a relay, a low-power node (such as a femto, a micro), etc., depending on the terminology and technology applied. In the following description, the terms "network device", "BS" and "node" may be used interchangeably.

[0041] The term "terminal device" refers to any terminal device that can perform wireless communication. As an example and not limitation, the terminal device may also be referred to as a communication device, a user equipment (UE), a subscriber station (SS), a portable subscriber station, a mobile station (MS) or an access terminal (AT). The terminal device may include, but is not limited to, a mobile phone, a cellular phone, a smart phone, a voice over IP (VoIP) phone, a wireless local loop phone, a tablet computer, a wearable terminal device, a personal digital assistant (PDA), a portable computer, a desktop computer, an image acquisition terminal device such as a digital camera, a game terminal device, a music storage and playback device, a vehicle-mounted wireless terminal device, a wireless endpoint, a mobile station, a laptop embedded device (LEE), a laptop mounted device (LME), a USB dongle, a smart device, a wireless client device (CPE), an Internet of Things (IoT) device, a watch or other wearable device, a head mounted display (HMD), a vehicle, a drone, medical equipment and applications (e.g., remote surgery), industrial equipment and applications (e.g., robots and / or other wireless devices operating in industrial and / or automated processing chain environments), consumer electronic devices, equipment operating on commercial and / or industrial wireless networks, etc. In the following description, the terms "terminal device", "communication device", "terminal", "user equipment" and "UE" may be used interchangeably.

[0042] Although the functions described herein may be performed in fixed and / or wireless network nodes in various example embodiments, in other example embodiments, the functions may be implemented in a user equipment device (such as a cellular phone or a tablet or a laptop or a desktop computer or a mobile IoT device or a fixed IoT device). For example, the user equipment device may be appropriately equipped with corresponding capabilities as described in conjunction with (multiple) fixed and / or wireless network nodes. The user equipment device may be a user device and / or a control device (such as a chipset or a processor) configured to control the user device when installed in the user device. Examples of such functions include boot server functions and / or home subscriber servers, which may be implemented in the user equipment device by providing software to the user equipment device, the software being configured to cause the user equipment device to perform operations from the perspective of these functions / nodes.

[0043] As mentioned above, in Release 15 (Rel-15) of the 3GPP specification, inter-RAT handover (HO) to EN-DC is not supported. For example, the source gNB can only first handover the UE from the gNB to the target eNB, and then configure EN-DC by adding a secondary network device after the handover. It is necessary to introduce direct inter-RAT handover from NR to EN-DC, which can reduce the signaling overhead and ensure a consistent high data rate for eMBB services.

[0044] In the 3GPP specification TS 37.340 (10.9 eNB / gNB to Master Node Change), during the handover process from eNB to EN-DC, the current signaling requires that the UE must first complete the handover (MN) to the target master node (SN) before the access to the secondary node is completed. This is performed in two steps: the target MN first receives the RRC Connection Reconfiguration Complete message (to complete the handover), and then the target MN notifies the target SN of the handover success via an X2 message (SgNB Reconfiguration Complete message) to add the target SN. In addition, the specification does not clarify whether the UE can start access to the SN in parallel.

[0045] For one-step handover to EN-DC, the goal is to reduce the dual connectivity (DC) configuration delay and quickly restore the service data rate after the handover process. Some existing solutions propose to perform random access to both the target MN and the target SN in parallel for fast SN activation in HO to EN-DC. This solution acknowledges the need for fast / parallel access, but at the same time, in the event of a HO failure to the master cell group (MCG), it is difficult to recover the user plane (discarding delivered downlink / uplink packets) in the UE implementation, which wastes radio resources and power and should therefore be avoided. The biggest problem with this solution is that it only considers the MCG failure scenario. There is no discussion of the case where the SN can communicate with the UE via signaling radio bearer 3 (SRB3) in the absence of SRB1 and SRB2. Therefore, this solution is not a complete and feasible solution.

[0046] Furthermore, during the Rel-16 mobility enhancement work, the so-called Dual Active Protocol Stack (DAPS) handover is being specified. In this concept, the UE can communicate with both the source cell and the target cell at the same time, and if the target cell fails while the source cell communication is still ongoing, the UE can fall back to the source cell without re-establishment. However, in DAPS handover, the UE can establish a connection with a single target node at any time, but not with two target nodes at the same time.

[0047] Embodiments of the present disclosure provide a solution for switching to dual connectivity. According to embodiments of the present disclosure, a UE receives a connection reconfiguration message from a source node, and the connection reconfiguration message includes configurations about a target MN and a target SN to be connected to the UE. The UE performs random access to the target MN and the target SN in parallel. If the UE successfully connects to the target SN but fails to connect to the target MN, the UE will reconnect to the target MN. In addition, the target SN indicates the result of the random access (e.g., success or failure) to the target MN. For the target MN, different actions can be selected based on whether SRB3 exists between the target SN and the UE. In this way, embodiments of the present disclosure can reduce signaling overhead and improve the success rate of switching to dual connectivity.

[0048] Figure 1 An example communication network 100 is shown in which example embodiments of the present disclosure may be implemented. The communication network 100 includes a terminal device 110 and network devices 120, 130, and 140. Each of the network devices 120, 130, and 140 may provide one or more cells. Figure 1 As shown, for example, network device 120 may provide cell 101, network device 120 may provide cell 102, and network device 130 may provide cell 103. It should be understood that the number of networks, terminal devices, and / or cells is given for illustrative purposes and does not imply any limitation on the scope of the present disclosure. Communication network 100 may include any suitable number of network devices, terminal devices, and / or cells suitable for implementing the present disclosure.

[0049] In some example embodiments, some or all of network devices 120, 130, and 140 may use the same RAT, such as LTE, NR, etc. Alternatively, in some example embodiments, network devices 120, 130, and 140 may use different RATs. For example, network device 140 may be a gNB, while network devices 130 and 140 may both be eNBs. As another example, network devices 120, 130, and 140 may all be gNBs. For another example, network device 120 and network device 140 may be gNBs, while network device 130 may be an eNB. It should be appreciated that the scope of the present disclosure is not limited in this respect.

[0050] The communication in the communication system 100 can be implemented according to any (multiple) appropriate communication protocols, including but not limited to cellular communication protocols of the first generation (1G), second generation (2G), third generation (3G), fourth generation (4G) and fifth generation (5G), wireless local area network communication protocols such as Institute of Electrical and Electronics Engineers (IEEE) 802.11, and / or any other protocol currently known or developed in the future. In addition, the communication can utilize any appropriate 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 duplexer (FDD), time division duplexer (TDD), multiple input multiple output (MIMO), orthogonal frequency division multiple access (OFDMA), and / or any other technology currently known or developed in the future.

[0051] like Figure 1 As shown, initially, the terminal device 110 may be connected to the network device 140, which is also referred to as the "source network device" or "source node" hereinafter. The source node 140 may initiate a switch to a dual connection by sending a switching request to the network device 120 acting as the target master network device. Hereinafter, the network device 120 may also be referred to as the "target master network device" or "target master node (T-MN)". In order to provide dual connectivity for the terminal device 110, the T-MN 120 may select the network device 130 as the target secondary network device and send a request to add the network device 130 as the target secondary network device (e.g., an SgNB add request). Hereinafter, the network device 130 may also be referred to as the "target secondary network device" or "target secondary node (T-SN)". The T-SN 130 may feedback to the T-MN 120 a confirmation including the configuration of the secondary cell group (SCG) (e.g., an SgNB add request confirmation). T-MN 120 may send a handover request confirmation including configurations about both T-MN 120 and T-SN 130 to source node 140. Source node 140 may send a connection reconfiguration message (e.g., an RRC connection reconfiguration message) including configurations about both T-MN 120 and T-SN 130 to terminal device 110.

[0052] In some example embodiments, terminal device 110 may perform random access to T-MN 120 and T-SN 130 in parallel based on the configuration received from source node 140. With respect to T-SN 130, it may send a result of the random access to T-MN 120, such as via an X2 / Xn interface. For example, the result may indicate whether the random access to T-SN 130 performed by terminal device 110 is successful or failed.

[0053] With respect to T-MN 120, in some example embodiments, if terminal device 110 successfully accesses T-MN 120, T-MN 120 may perform normal actions to complete the handover process, as in conventional solutions. If T-MN 120 receives an indication from T-SN 130 that random access to T-SN 130 performed by terminal device 110 is successful, T-SN 130 may regard the handover as partially successful and the relevant UE context may be established. If T-MN 120 receives an indication from T-SN 130 that random access to T-SN 130 performed by terminal device 110 is successful but terminal device 110 fails to access T-MN 120 (e.g., T304 timer of T-MN 120 expires), different actions may be selected based on whether SRB3 exists between T-SN 130 and terminal device 110.

[0054] In some example embodiments, if SRB3 is established between T-SN 130 and terminal device 110 and if T-MN 120 receives an indication of the presence of SRB3, T-MN 120 may determine that the handover has failed and send a request to release the target slave node to T-SN 130. T-SN 130 may then send a connection release message (such as an RRC release message) to terminal device 110 via SRB3. In some example embodiments, if SRB3 does not exist between T-SN 130 and terminal device 110 or if T-MN 120 does not receive an indication of the presence of SRB3, T-SN 130 may maintain the connection with terminal device 110 and T-MN 120 may wait for a connection re-establishment message (such as an RRC re-establishment message) from terminal device 110. To facilitate this, in some example embodiments, upon receiving the SgNB-SN 130 Add Request Acknowledgement from T-MN 120, T-MN 120 may initiate a timer with a longer expiration time to monitor for a connection re-establishment message from terminal device 110.

[0055] With respect to terminal device 110, in some example embodiments, if terminal device 110 successfully accesses T-SN 130 but fails to access T-MN 120 (e.g., T304 timer of T-MN 120 expires), terminal device 110 may reconnect to T-MN 120 based on the configuration regarding T-MN 120 received via the connection reconfiguration message. Reconnection to T-MN 120 may be performed in several ways.

[0056] In some example embodiments, after the T304 timer expires, the terminal device 110 may initiate a new timer with an expiration time of N*t304, where t304 represents the original expiration time of the T304 timer and N>0. Once the new timer is initiated, the terminal device 110 may attempt to reconnect to the T-MN 120 within each time period of the new timer (e.g., one or more times of t304). If the terminal device 110 has attempted to reconnect to the T-MN 120 up to N times but failed, that is, the new timer expires, the terminal device 110 may fall back to the source node 140 configured with the configuration for performing cell selection. In some example embodiments, the expiration time of the new timer may be configured by the T-MN 120 to the terminal device 110 in a handover request confirmation including (multiple) information elements indicating the values ​​of t304 and N or indicating the value of t304 and the new expiration time of the new timer (e.g., equal to N*t304). Alternatively, in some example embodiments, the expiry time of the new timer may be configured by T-MN 120 to terminal device 110 in a reconfiguration message (e.g., an RRC reconfiguration message) sent from T-SN 130 via SRB3 (if present). For example, the reconfiguration message may include an information element indicating the value of t304 and N or indicating the value of t304 and the new expiry time of the new timer (e.g., equal to N*t304).

[0057] Alternatively, in some example embodiments, after the expiration of the T304 timer, the terminal device 110 may perform cell selection. After selecting the cell 102 provided by the T-MN 120 as a suitable cell, the terminal device 110 may send a connection re-establishment request (e.g., an RRC connection re-establishment request) to the T-MN 120 using a cell radio network temporary identifier (C-RNTI) and a physical cell identity assigned to the T-MN 120. Otherwise, the terminal device 110 may fall back to the source node 140. In some example embodiments, if the terminal device 110 receives a connection release message (such as an RRC release message) from the T-SN 130 via SRB3 (if configured) during reconnection to the T-MN 120, the terminal device 110 may fall back to the source node 140 after searching for any possible cells.

[0058] With respect to the source node 140, in some example embodiments, all resources allocated to the terminal device 110 may be retained until a UE context release message is received from the T-MN 120 or the terminal device 110 successfully reconnects to the source node 140. After the terminal device 110 successfully reconnects to the source node 140, the source node 140 may notify the T-MN 120 of the handover failure. With respect to the source node 140 and the two target nodes 120 and 130, early data forwarding in the handover process and forwarding of data retrieved from the target node to the source node 140 in the event of a handover failure may be performed in a manner similar to conventional solutions.

[0059] Figure 2 A schematic diagram of an interaction 200 between devices according to some example embodiments of the present disclosure is shown. The interaction 200 may be implemented at any suitable device. For illustrative purposes only, the interaction 200 will be described below with reference to UE 110, T-MN 120, T-SN 130 and source node 140.

[0060] like Figure 2 As shown, source node 140 may send 201 a handover request to T-MN 120 to initiate a handover. In some example embodiments, the handover may be an inter-RAT handover or an intra-RAT handover depending on the respective RATs used by source node 140, T-MN 120 and T-SN 130.

[0061] In response to the handover request from the source node 140, the T-MN 120 may select the node 130 as the T-SN and send 202 a request to add the node 130 as the T-SN (e.g., an SgNB add request). The T-SN 130 may feedback 203 a confirmation (e.g., an SgNB add request confirmation) including the configuration of the SCG to the T-MN 120. For illustration purposes only, it is assumed that the confirmation does not include the SRB3 configuration.

[0062] Upon receiving the confirmation, the T-MN 120 may initiate 220 a timer to monitor for random access from the terminal device 110. The T-MN 120 may send 204 a handover request confirmation including configurations regarding both the T-MN 120 and the T-SN 130 to the source node 140. Since the T-MN 120 did not receive the SRB3 configuration from the T-SN 130, the handover request confirmation may not include the SRB3 configuration here. The source node 140 may send 205 a connection reconfiguration message (e.g., an RRC connection reconfiguration message) to the terminal device 110 including configurations regarding both the T-MN 120 and the T-SN 130. The connection reconfiguration message may not include the SRB3 configuration.

[0063] Upon receiving configurations for both T-MN 120 and T-SN 130 via a connection reconfiguration message that does not include SRB3 configuration, UE 110 may perform a first random access 206A to T-MN 120 and a second random access 206B to T-SN 130 in parallel. Assume that the second random access to T-SN 130 is successful 230 without establishing SRB3. T-SN 130 may send 207 a result indicating success of the second random access to T-MN 120. In this case, since SRB3 is not established, the result may also include an indication that SRB3 is not established.

[0064] It is also assumed that the first random access to the T-MN 120 fails, and therefore the UE 110 may reconnect 208 to the T-MN 120 based on the configuration indicated in the connection reconfiguration message. For example, the UE 110 may send a connection reestablishment message (e.g., an RRC connection reestablishment message) to the T-MN 120. In response to the connection reestablishment message being sent, the terminal device 110 may initiate 240 a timer to monitor the result of the reconnection. The T-MN 120 may wait for a connection reestablishment message from the UE 110 until its timer initiated at 220 expires. In response to the success of the reconnection to the T-MN 120, the T-MN 120 may send 209 a reconfiguration complete message (e.g., an SgNB reconfiguration complete message) to the T-SN 130. In response to the success of the reconnection to T-MN 120 , UE 110 may send 210 a connection reconfiguration complete message to T-MN 120 , and T-MN 120 may send 211 a UE context release message to source node 140 .

[0065] Figure 3 A schematic diagram of an interaction 300 between devices according to some example embodiments of the present disclosure is shown. The interaction 300 may be implemented at any suitable device. For illustrative purposes only, the interaction 300 will be described below with reference to UE 110, T-MN 120, T-SN 130 and source node 140.

[0066] like Figure 3 As shown, source node 140 may send 301 a handover request to T-MN 120 to initiate a handover. In some example embodiments, depending on the respective RATs used by source node 140, T-MN 120 and T-SN 130, the handover may be an inter-RAT handover or an intra-RAT handover.

[0067] In response to the handover request from the source node 140, the T-MN 120 may select the node 130 as the T-SN and send 302 a request (e.g., SgNB add request) for adding the node 130 as the T-SN. The T-SN 130 may feedback 303 a confirmation (e.g., SgNB add request confirmation) including the configuration of the SCG to the T-MN 120. For illustration purposes only, it is assumed that the confirmation includes the SRB3 configuration.

[0068] Upon receiving the confirmation, the T-MN 120 may initiate 320 a timer to monitor for random access from the terminal device 110. The T-MN 120 may send 304 a handover request confirmation including configurations regarding both the T-MN 120 and the T-SN 130 to the source node 140. Since the T-MN 120 receives the SRB3 configuration from the T-SN 130, the T-MN 120 may forward the SRB3 configuration to the source node 140 via the handover request confirmation. The source node 140 may send 305 a connection reconfiguration message (e.g., an RRC connection reconfiguration message) including configurations regarding both the T-MN 120 and the T-SN 130 to the terminal device 110. The connection reconfiguration message may also include the SRB3 configuration.

[0069] Upon receiving configurations for both T-MN 120 and T-SN 130 via a connection reconfiguration message that does not include SRB3 configuration, UE 110 may perform a first random access 306A to T-MN 120 and a second random access 306B to T-SN 130 in parallel. Assuming that SRB3 is established between T-SN 130 and UE 110 based on the SRB3 configuration, the second random access to T-SN 130 succeeds 330. T-SN 130 may send 307 a result indicating the success of the second random access to T-MN 120. In this case, since SRB3 has been established, the result may also include an indication that SRB3 has been established.

[0070] It is also assumed that the first random access to the T-MN 120 fails, and therefore the UE 110 may reconnect 308 to the T-MN 120 based on the configuration indicated in the connection reconfiguration message. For example, the UE 110 may send a connection reestablishment message (e.g., an RRC connection reestablishment message) to the T-MN 120. In response to the connection reestablishment message being sent, the terminal device 110 may initiate 340 a timer to monitor the result of the reconnection. Due to the existence of SRB3, the T-MN 120 may instruct 309 the T-SN 130 to release the UE 110. For example, the T-MN 120 may send a release request (e.g., an SgNB release request) to the T-SN 130. The T-SN 130 may then send a connection release message (e.g., an RRC connection release message) to the UE 110 via SRB3. In response to the connection release message from the T-SN 130, the UE 110 reconnects 311 to the source node 140.

[0071] Figure 4 A schematic diagram of an interaction 400 between devices according to some example embodiments of the present disclosure is shown. The interaction 400 may be implemented at any suitable device. For illustrative purposes only, the interaction 400 will be described below with reference to UE 110, T-MN 120, T-SN 130 and source node 140.

[0072] like Figure 4 As shown, source node 140 may send 401 a handover request to T-MN 120 to initiate a handover. In some example embodiments, the handover may be an inter-RAT handover or an intra-RAT handover depending on the respective RATs used by source node 140, T-MN 120, and T-SN 130.

[0073] In response to the handover request from the source node 140, the T-MN 120 may select the node 130 as the T-SN and send 402 a request (e.g., SgNB add request) to add the node 130 as the T-SN. The T-SN 130 may feedback 403 a confirmation (e.g., SgNB add request confirmation) including the configuration of the SCG to the T-MN 120. For illustration purposes only, it is assumed that the confirmation does not include the SRB3 configuration.

[0074] Upon receiving the confirmation, the T-MN 120 may initiate 420 a timer to monitor for random access from the terminal device 110. The T-MN 120 may send 404 a handover request confirmation including configurations regarding both the T-MN 120 and the T-SN 130 to the source node 140. Since the T-MN 120 did not receive the SRB3 configuration from the T-SN 130, the handover request confirmation may not include the SRB3 configuration here. The source node 140 may send 405 a connection reconfiguration message (e.g., an RRC connection reconfiguration message) including configurations regarding both the T-MN 120 and the T-SN 130 to the terminal device 110. The connection reconfiguration message may not include the SRB3 configuration.

[0075] Upon receiving configurations for both T-MN 120 and T-SN 130 via a connection reconfiguration message that does not include SRB3 configuration, UE 110 may perform a first random access 406A to T-MN 120 and a second random access 406B to T-SN 130 in parallel. Assume that the second random access to T-SN 130 succeeds 430 without establishing SRB3. T-SN 130 may send 407 a result indicating success of the second random access to T-MN 120. In this case, since SRB3 is not established, the result may also include an indication that SRB3 is not established.

[0076] It is also assumed that the first random access to the T-MN 120 fails, and therefore the UE 110 may reconnect 408 to the T-MN 120 based on the configuration indicated in the connection reconfiguration message. For example, the UE 110 may send a connection reestablishment message (e.g., an RRC connection reestablishment message) to the T-MN 120. The T-MN 120 may wait 440 for a connection reestablishment message from the UE 110 until its timer initiated at 220 expires. It is assumed here that the timer of the T-MN 120 expires and therefore the reconnection to the T-MN 120 fails. In response to the failure of the reconnection to the T-MN 120, the UE 110 may reconnect 409 to the source node 140. The source node 140 may send 410 an indication of a handover failure to the T-MN 120.

[0077] In summary, it can be seen that the embodiments of the present disclosure support random access to T-MN and T-SN in parallel in direct inter-RAT or intra-RAT handover to dual connectivity. The embodiments of the present disclosure can reduce signaling overhead and improve the success rate of handover to dual connectivity by enabling the UE to reconnect to the T-MN while maintaining a connection with the T-SN.

[0078] Figure 5FIG. 5 is a flow chart showing an example method 500 for switching to dual connectivity according to some example embodiments of the present disclosure. The method 500 may be performed in a manner such as Figure 1 For the purpose of discussion, reference will be made to the terminal device 110. Figure 1 The method 500 is described from the perspective of the terminal device 110. Hereinafter, the terminal device 110 is also referred to as the "first device 110", the target primary network device 120 is also referred to as the "second device 120", the target secondary network device 130 is also referred to as the "third device 130", and the source network device 140 is also referred to as the "fourth device 140". It should be understood that the method 500 may include additional blocks not shown and / or some of the shown blocks may be omitted, and the scope of the present disclosure is not limited in this regard.

[0079] In block 510, the first device 110 receives a connection reconfiguration message from the fourth device 140. The connection reconfiguration message may include a first configuration regarding the second device 120 and a second configuration regarding the third device 130.

[0080] In block 520 , the first device 110 performs a first random access to the second device 120 based on the first configuration and a second random access to the third device 130 based on the second configuration to connect to the second device 120 and the third device 130 .

[0081] In block 530 , in response to the failure of the first random access and the success of the second random access, the first device 110 reconnects to the second device 120 based on the first configuration while maintaining connection to the third device 130 .

[0082] In some example embodiments, the connection reconfiguration message includes configuration regarding a signaling radio bearer between third device 130 and first device 110. In some example embodiments, in response to receiving a connection release message from third device 130 via the signaling radio bearer, first device 110 disconnects from third device 130 and reconnects to fourth device 140 or to a fifth device found in a cell selection initiated by first device 110.

[0083] In some example embodiments, the first device 110 may reconnect to the second device 120 by: sending a connection re-establishment message to the second device 120; or performing a third random access to the second device 120 based on the first configuration.

[0084] In some example embodiments, first device 110 determines whether reconnection to second device 120 fails. Based on determining that reconnection to second device 120 fails, first device 110 reconnects to fourth device 140 or to a fifth device found in cell selection initiated by first device 110.

[0085] In some example embodiments, first device 110 determines whether reconnection to second device 120 has failed by initiating a timer to monitor success of reconnection to second device 120; and in response to expiration of the timer, determining that reconnection to second device 120 has failed.

[0086] In some example embodiments, the first device 110 receives the configuration regarding the timer via one of: a connection reconfiguration message; or a reconfiguration message sent from the third device via a signaling radio bearer.

[0087] In some example embodiments, the first device 110 includes a terminal device, the second device 120 includes a target primary network device, the third device 130 includes a target secondary network device, and the fourth device 140 includes a source network device that initiates switching of the terminal device to the target primary network device and the target secondary network device.

[0088] Figure 6 FIG. 6 is a flow chart showing an example method 600 for switching to dual connectivity according to some example embodiments of the present disclosure. The method 600 may be performed in a manner such as Figure 1 The target host network device 120 is shown as being implemented. For the purpose of discussion, reference will be made to Figure 1 The method 600 is described from the perspective of the target primary network device 120. Hereinafter, the terminal device 110 is also referred to as the "first device 110", the target primary network device 120 is also referred to as the "second device 120", the target secondary network device 130 is also referred to as the "third device 130", and the source network device 140 is also referred to as the "fourth device 140". It should be understood that the method 600 may include additional blocks not shown and / or some of the shown blocks may be omitted, and the scope of the present disclosure is not limited in this regard.

[0089] In box 610, the second device 120 sends a connection reconfiguration message to the fourth device 140 connected to the first device 110, and the connection reconfiguration message includes configurations about the second device 120 and the third device 130 to be connected to the first device 110, so that the first device 110 can perform a first random access to the second device 120 and a second random access to the third device 130.

[0090] In some example embodiments, before sending the connection reconfiguration message to the fourth device 140, the second device 120 sends a request to the third device 130 to add the third device 130 to provide dual connectivity for the first device 110. The second device 120 receives an acknowledgement from the third device 130 including the second configuration.

[0091] In some example embodiments, the connection reconfiguration message includes configuration regarding a first timer to be used by the first device 110 to monitor reconnection to the second device 120 .

[0092] In block 620, the second device 120 determines whether the first random access and the second random access are successful.

[0093] In some example embodiments, the second device 120 determines whether the first random access is successful by: in response to receiving an acknowledgement from the third device 130, initiating a second timer to monitor the success of the first random access; and in response to expiration of the timer, determining that the first random access has failed.

[0094] In some example embodiments, the first expiration time of the first timer is the same as the second expiration time of the second timer. Alternatively, in some example embodiments, the first expiration time is different from the second expiration time. For example, the first expiration time may be shorter or longer than the second expiration time.

[0095] In some example embodiments, the second device 120 determines whether the second random access is successful by acquiring a result of the second random access from the third device 130 , the result indicating whether the second random access is successful or failed.

[0096] In some example embodiments, the confirmation does not include configuration regarding a signaling radio bearer between the third device 130 and the first device 110, and the result includes an indication that no signaling radio bearer is established.

[0097] In some example embodiments, the confirmation comprises a configuration regarding a signaling radio bearer to be established between the third device 130 and the first device 110, and the result comprises an indication that the signaling radio bearer has been established based on the configuration.

[0098] At block 630 , the second device 120 causes the first device 110 to reconnect to the second device 120 based on determining that the first random access failed and the second random access succeeded.

[0099] In some example embodiments, second device 120 further sends a request to third device 130 to release the connection between third device 130 and first device 110 , so that third device 130 sends a connection release message to first device 110 via the signaling radio bearer.

[0100] In some example embodiments, second device 120 further sends a request to reconfigure the first timer to third device 130, so that third device 130 sends a reconfiguration message for reconfiguring the first timer to first device 110 via a signaling radio bearer.

[0101] In some example embodiments, the first device 110 includes a terminal device, the second device 120 includes a target primary network device, the third device 130 includes a target secondary network device, and the fourth device 140 includes a source network device that initiates switching of the terminal device to the target primary network device and the target secondary network device.

[0102] Figure 7 FIG. 7 is a flow chart showing an example method 700 for switching to dual connectivity according to some example embodiments of the present disclosure. The method 700 may be performed in a manner such as Figure 1 The target auxiliary network device 130 is implemented as shown. For the purpose of discussion, reference will be made to Figure 1 The method 700 is described from the perspective of the target secondary network device 130. Hereinafter, the terminal device 110 is also referred to as the "first device 110", the target primary network device 120 is also referred to as the "second device 120", the target secondary network device 130 is also referred to as the "third device 130", and the source network device 140 is also referred to as the "fourth device 140". It should be understood that the method 700 may include additional blocks not shown and / or some of the shown blocks may be omitted, and the scope of the present disclosure is not limited thereto.

[0103] At block 710 , the third device 130 receives a request from the second device 120 to add the third device 130 to provide dual connectivity for the first device 110 .

[0104] In block 720 , the third device 130 sends an acknowledgement including the second configuration regarding the third device 130 to the second device 120 to enable the first device 110 to perform random access to the third device 130 based on the second configuration.

[0105] In block 730 , the third device 130 determines whether the random access is successful or failed.

[0106] In block 740 , the third device 130 transmits the result of the determination to the second device 120 .

[0107] In some example embodiments, the confirmation does not include configuration regarding a signaling radio bearer between the third device 130 and the first device 110, and the result includes an indication that no signaling radio bearer is established.

[0108] In some example embodiments, the confirmation includes configuration regarding a signaling radio bearer to be established between the third device 130 and the first device 110. In response to the success of the random access, the third device 130 establishes a signaling radio bearer between the third device 130 and the first device 110 based on the configuration.

[0109] In some example embodiments, third device 130 sends the result to second device 120 by, in response to a signaling radio bearer being established between third device 130 and first device 110 , sending to second device 120 a result including an indication that the signaling radio bearer has been established.

[0110] In some example embodiments, in response to receiving a request from second device 120 to release the connection between third device 130 and first device 110 , third device 130 sends a connection release message to first device 110 via a signaling radio bearer.

[0111] In some example embodiments, first device 110 is configured with a timer. In response to receiving a request to reconfigure the timer of first device 110 from second device 120, third device 130 sends a reconfiguration message for reconfiguring the timer of first device 110 to first device 110 via a signaling radio bearer.

[0112] In some example embodiments, the first device 110 includes a terminal device, the second device 120 includes a target primary network device, the third device 130 includes a target secondary network device, and the fourth device 140 includes a source network device that initiates switching of the terminal device to the target primary network device and the target secondary network device.

[0113] In some example embodiments, an apparatus capable of executing method 500 may include a component for executing the corresponding steps of method 500. The component may be implemented in any suitable form. For example, the component may be implemented in a circuit system or a software module.

[0114] In some example embodiments, an apparatus (e.g., terminal device 110) capable of executing method 500 includes: a component for receiving, at a first device, a connection reconfiguration message from a fourth device connected to the first device, the connection reconfiguration message including a first configuration regarding a second device and a second configuration regarding a third device; a component for performing a first random access to the second device based on the first configuration and a second random access to the third device based on the second configuration to connect the second device and the third device; and a component for reconnecting to the second device based on the first configuration while maintaining connection to the third device in response to a failure of the first random access and a success of the second random access.

[0115] In some example embodiments, the connection reconfiguration message includes a configuration regarding a signaling radio bearer between the third device and the first device, and the apparatus capable of performing method 500 further includes: a component for disconnecting from the third device in response to receiving a connection release message from the third device via the signaling radio bearer; and a component for reconnecting to a fourth device or to a fifth device found in a cell selection initiated by the first device.

[0116] In some example embodiments, the means for reconnecting to the second device comprises: means for sending a connection re-establishment message to the second device; or means for performing a third random access to the second device based on the first configuration.

[0117] In some example embodiments, the apparatus capable of performing method 500 further includes: a component for determining whether reconnection to the second device has failed; and a component for reconnecting to a fourth device or to a fifth device found in the cell selection initiated by the first device based on determining that reconnection to the second device has failed.

[0118] In some example embodiments, means for determining whether reconnection to the second device has failed includes means for initiating a timer to monitor success of reconnection to the second device; and means for determining that reconnection to the second device has failed in response to expiration of the timer.

[0119] In some example embodiments, the apparatus capable of performing method 500 further includes: means for receiving configuration regarding the timer via one of: a connection reconfiguration message; or a reconfiguration message sent from a third device via a signaling radio bearer.

[0120] In some example embodiments, the first device comprises a terminal device, the second device comprises a target primary network device, the third device comprises a target secondary network device, and the fourth device comprises a source network device that initiates a handover of the terminal device to the target primary network device and the target secondary network device.

[0121] In some example embodiments, an apparatus capable of executing method 600 may include a component for executing the corresponding steps of method 600. The component may be implemented in any suitable form. For example, the component may be implemented in a circuit system or a software module.

[0122] In some example embodiments, an apparatus capable of executing method 600 (e.g., target master network device 120) includes: a component for sending a connection reconfiguration message from a second device to a fourth device connected to a first device, the connection reconfiguration message including configurations regarding the second device and a third device to be connected to the first device, so that the first device can perform a first random access to the second device and a second random access to the third device; a component for determining whether the first random access and the second random access are successful; and a component for causing the first device to reconnect to the second device based on determining that the first random access has failed and the second random access has succeeded.

[0123] In some example embodiments, the connection reconfiguration message includes configuration regarding a first timer to be used by the first device to monitor reconnection to the second device.

[0124] In some example embodiments, the apparatus capable of performing method 600 further includes: a component for sending a request to a third device to add a third device to provide dual connectivity for the first device before sending a connection reconfiguration message to a fourth device; and a component for receiving a confirmation including the second configuration from the third device.

[0125] In some example embodiments, the means for determining whether the first random access is successful includes: means for initiating a second timer to monitor the success of the first random access in response to receiving an acknowledgement from the third device; and means for determining that the first random access has failed in response to expiration of the timer.

[0126] In some example embodiments, the means for determining whether the second random access is successful includes means for obtaining a result of the second random access from a third device, the result indicating whether the second random access is successful or failed.

[0127] In some example embodiments, the confirmation does not include configuration regarding a signaling radio bearer between the third device and the first device, and the result includes an indication that no signaling radio bearer is established.

[0128] In some example embodiments, the confirmation comprises a configuration regarding a signalling radio bearer to be established between the third device and the first device, and the result comprises an indication that the signalling radio bearer has been established based on the configuration.

[0129] In some example embodiments, the apparatus capable of performing method 600 further includes means for sending a request to release a connection between the third device and the first device to the third device, so that the third device sends a connection release message to the first device via a signaling radio bearer.

[0130] In some example embodiments, the connection reconfiguration message includes configuration of a first timer to be used by the first device to monitor reconnection to the second device, and the apparatus capable of executing method 600 further includes: a component for sending a request to reconfigure the first timer to a third device, such that the third device sends a reconfiguration message for reconfiguring the first timer to the first device via a signaling radio bearer.

[0131] In some example embodiments, the first device comprises a terminal device, the second device comprises a target primary network device, the third device comprises a target secondary network device, and the fourth device comprises a source network device that initiates a handover of the terminal device to the target primary network device and the target secondary network device.

[0132] In some example embodiments, an apparatus capable of executing method 700 may include a component for executing the corresponding steps of method 700. The component may be implemented in any suitable form. For example, the component may be implemented in a circuit system or a software module.

[0133] In some example embodiments, an apparatus capable of performing method 700 (e.g., target secondary network device 130) includes: a component for receiving, at a third device, from a second device, a request to add a third device to provide dual connectivity for a first device; a component for sending to the second device a confirmation including a second configuration regarding the third device so that the first device can perform random access to the third device based on the second configuration; a component for determining whether the random access is successful or failed; and a component for sending a result of the determination to the second device.

[0134] In some example embodiments, the confirmation does not include configuration regarding a signaling radio bearer between the third device and the first device, and the result includes an indication that no signaling radio bearer is established.

[0135] In some example embodiments, the confirmation includes configuration regarding a signaling radio bearer to be established between the third device and the first device.An apparatus capable of performing method 700 further includes means for establishing a signaling radio bearer between the third device and the first device based on the configuration in response to success of the random access.

[0136] In some example embodiments, the means for sending the result to the second device comprises means for sending the result to the second device including an indication that the signaling radio bearer has been established, in response to the signaling radio bearer being established between the third device and the first device.

[0137] In some example embodiments, the apparatus capable of performing method 700 further includes means for sending a connection release message to the first device via a signaling radio bearer in response to receiving a request from the second device to release the connection between the third device and the first device.

[0138] In some example embodiments, the first device is configured with a timer, and the apparatus capable of performing method 700 further includes a component for sending a reconfiguration message for reconfiguring the timer of the first device to the first device via a signaling radio bearer in response to receiving a request to reconfigure the timer of the first device from the second device.

[0139] In some example embodiments, the first device comprises a terminal device, the second device comprises a target primary network device, the third device comprises a target secondary network device, and the fourth device comprises a source network device that initiates a handover of the terminal device to the target primary network device and the target secondary network device.

[0140] Figure 8 is a simplified block diagram of a device 800 suitable for implementing an embodiment of the present disclosure. Figure 1 The terminal device 110, the target primary network device 120, the target secondary network device 130 and / or the source network device 140 shown can be implemented by the device 800. As shown in the figure, the device 800 includes one or more processors 810, one or more memories 820 coupled to the processor 810, and one or more communication modules 840 coupled to the processor 810.

[0141] The communication module 840 is used for two-way communication. The communication module 840 has at least one antenna to facilitate communication. The communication interface may represent any interface necessary to communicate with other network elements.

[0142] Processor 810 may be of any type suitable for the local technology network, and may include, as non-limiting examples, one or more of a general purpose computer, a special purpose computer, a microprocessor, a digital signal processor (DSP), and a processor based on a multi-core processor architecture. Device 800 may have multiple processors, such as application specific integrated circuit chips that are time slaved to a clock synchronized with a main processor.

[0143] The 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, compact disk (CD), digital video disk (DVD), and other magnetic storage and / or optical storage. Examples of volatile memories include, but are not limited to, random access memory (RAM) 822 and other volatile memories that do not persist during power outages.

[0144] The computer program 830 includes computer executable instructions that are executed by the associated processor 810. The program 830 may be stored in the ROM 824. The processor 810 may perform any suitable actions and processes by loading the program 830 into the RAM 822.

[0145] The embodiments of the present disclosure may be implemented by a program 830, so that the device 800 may execute the Figure 2-Figure 7 Any process of the present disclosure discussed. The embodiments of the present disclosure may also be implemented by hardware or a combination of software and hardware.

[0146] In some example embodiments, the program 830 may be tangibly embodied in a computer-readable medium, which may be included in the device 800 (such as the memory 820) or other storage device accessible to the device 800. The device 800 may load the program 830 from the computer-readable medium to the RAM 822 for execution. The computer-readable medium may include any type of tangible non-volatile memory, such as ROM, EPROM, flash memory, hard disk, CD, DVD, etc. Fig. 9 An example of a computer readable medium 900 in the form of a CD or DVD is shown. The computer readable medium has a program 830 stored thereon.

[0147] It should be understood that future networks may utilize network function virtualization (NFV), which is a network architecture concept that proposes virtualizing network node functions into "building blocks" or entities that can be operationally connected or linked together to provide services. A virtualized network function (VNF) may include one or more virtual machines that use standard or general-purpose servers rather than customized hardware to run computer program code. Cloud computing or data storage may also be used. In radio communications, this may mean that node operations are at least partially performed in a central / centralized unit CU (e.g., a server, host, or node) that is operationally coupled to a distributed unit DU (e.g., a radio head / node). Node operations may also be distributed among multiple servers, nodes, or hosts. It should also be understood that the distribution of work between core network operations and base station operations may vary depending on the implementation.

[0148] In one embodiment, the server can generate a virtual network through which the server communicates with the distributed unit. In general, a virtual network can involve the process of combining hardware and software network resources and network functions into a single software-based management entity (virtual network). Such a virtual network can provide a flexible distribution of operations between the server and the radio head / node. In practice, any digital signal processing task can be performed in the CU or DU, and the boundary of the transfer of responsibilities between the CU and the DU can be selected according to the implementation.

[0149] Thus, in one embodiment, a CU-DU architecture is implemented. In this case, the device 800 may be included in a central unit (e.g., a control unit, an edge cloud server, a server) that is operably coupled (e.g., via a wireless or wired network) to a distributed unit (e.g., a remote radio head / node). That is, the central unit (e.g., an edge cloud server) and the distributed units may be independent devices that communicate with each other via a radio path or via a wired connection. Alternatively, they may be in the same entity that communicates via a wired connection, etc. The edge cloud or edge cloud server may serve multiple distributed units or radio access networks. In one embodiment, at least some of the described processes may be performed by the central unit. In another embodiment, the device 800 may instead be included in a distributed unit, and at least some of the described processes may be performed by the distributed unit.

[0150] In one embodiment, the execution of at least some functions of the device 800 can be shared between two physically separate devices (DU and CU) that form an operational entity. Therefore, the device can be regarded as depicting an operational entity including one or more physically separate devices for performing at least some of the described processes. In one embodiment, such a CU-DU architecture can provide a flexible distribution of operations between the CU and the DU. In practice, any digital signal processing task can be performed in the CU or the DU, and the boundary of the transfer of responsibilities between the CU and the DU can be selected according to the implementation. In one embodiment, the device 800 controls the execution of the process regardless of the location of the device and where the process / function is executed.

[0151] Generally, various embodiments of the present disclosure may be implemented using hardware or dedicated circuits, software, logic, or any combination thereof. Some aspects may be implemented using hardware, while other aspects may be implemented using firmware or software that may be executed by a controller, microprocessor, or other computing device. Although various aspects of the embodiments of the present disclosure are illustrated and described as block diagrams, flow charts, or using some other graphical representations, it should be understood that, as non-limiting examples, the blocks, devices, systems, techniques, or methods described herein may be implemented using hardware, software, firmware, dedicated circuits or logic, general-purpose hardware or controllers or other computing devices, or some combination thereof.

[0152] The present disclosure also provides at least one computer program product tangibly stored on a non-transitory computer-readable storage medium. The computer program product includes computer executable instructions, such as instructions included in a program module, which are executed in a device on a target real or virtual processor to perform the above referenced Figure 5 The method 500 described above is as referenced Figure 6Method 600 described above, and / or as referenced above Figure 7 Method 700 described. Typically, program modules include routines, programs, libraries, objects, classes, components, data structures, etc. that perform specific tasks or implement specific abstract data types. In various embodiments, the functions of program modules can be combined or split between program modules as needed. The machine executable instructions of program modules can be executed in local or distributed devices. In distributed devices, program modules can be located in both local and remote storage media.

[0153] The program code for executing the method of the present disclosure can be written in any combination of one or more programming languages. These program codes can be provided to a processor or controller of a general-purpose computer, a special-purpose computer or other programmable data processing device so that the program code causes the function / operation specified in the flow chart and / or block diagram to be realized when executed by the processor or controller. The program code can be executed completely on the machine, partially on the machine, as an independent software package, partially on the machine and partially on a remote machine, or completely on a remote machine or server.

[0154] In the context of the present disclosure, computer program codes or related data may be carried by any suitable carrier to enable a device, apparatus or processor to perform various processes and operations as described above. Examples of carriers include signals, computer readable media, etc.

[0155] The computer readable medium can be a computer readable signal medium or a computer readable storage medium. The computer readable medium can include, but is not limited to, electronic, magnetic, optical, electromagnetic, infrared or semiconductor systems, devices or equipment, or any suitable combination of the foregoing. A more specific example of a computer readable storage medium will include an electrical connection with one or more wires, a portable computer floppy disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0156] In addition, although the operations are described in a particular order, this should not be understood as requiring such operations to be performed in the particular order shown or in order or performing all the operations shown to obtain the desired result. In some cases, multitasking and parallel processing may be advantageous. Similarly, although several specific implementation details are included in the above discussion, these should not be interpreted as limitations on the scope of the present disclosure, but rather descriptions of features that may be specific to a particular embodiment. Certain features described in the context of a separate embodiment may also be implemented in combination in a single embodiment. On the contrary, the various features described in the context of a single embodiment may also be implemented in multiple embodiments individually or in any suitable sub-combination.

[0157] Although the present disclosure has been described in language specific to structural features and / or methodological acts, it should be understood that the present disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Instead, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

1. A communication method, comprising: At a first device, receiving a connection reconfiguration message from a fourth device connected to the first device, the connection reconfiguration message including a first configuration about a second device and a second configuration about a third device; performing a first random access to the second device based on the first configuration and a second random access to the third device based on the second configuration to connect to the second device and the third device; In response to a failure of the first random access and a success of the second random access, performing the following: If there is no signaling radio bearer 3 SRB3 between the third device and the first device or the second device does not receive an indication of the existence of the SRB3, reconnect to the second device based on the first configuration while maintaining connection to the third device; or If the SRB3 is established between the third device and the first device and the second device receives an indication that the SRB3 exists, a connection release message is received from the third device via the SRB3.

2. The method according to claim 1, wherein the connection reconfiguration message includes configuration regarding a signaling radio bearer between the third device and the first device, and the method further comprises: disconnecting the connection with the third device in response to receiving a connection release message from the third device via the signaling radio bearer; as well as Reconnect to the fourth device, or connect to a fifth device found in the cell selection initiated by the first device.

3. The method of claim 1 , wherein reconnecting to the second device comprises: Sending a connection re-establishment message to the second device; or Perform a third random access to the second device based on the first configuration.

4. The method according to claim 1, further comprising: determining whether the reconnection to the second device fails; as well as According to determining that the reconnection to the second device fails, reconnect to the fourth device, or connect to a fifth device found in the cell selection initiated by the first device.

5. The method according to any one of claims 1 to 4, wherein determining whether the reconnection to the second device fails comprises: initiating a timer to monitor success of the reconnection to the second device; as well as In response to expiration of the timer, it is determined that the reconnection to the second device has failed.

6. A first device, comprising: at least one processor; as well as at least one memory including computer program code; The at least one memory and the computer program code are configured to, together with the at least one processor, cause the first device to execute: receiving a connection reconfiguration message from a fourth device connected to the first device, the connection reconfiguration message including a first configuration about the second device and a second configuration about the third device; performing a first random access to the second device based on the first configuration and a second random access to the third device based on the second configuration to connect to the second device and the third device; In response to a failure of the first random access and a success of the second random access, performing the following: If there is no signaling radio bearer 3 SRB3 between the third device and the first device or the second device does not receive an indication of the existence of the SRB3, reconnect to the second device based on the first configuration while maintaining connection to the third device; or If the SRB3 is established between the third device and the first device and the second device receives an indication that the SRB3 exists, a connection release message is received from the third device via the SRB3.

7. The first device of claim 6, wherein the connection reconfiguration message comprises configuration regarding a signaling radio bearer between the third device and the first device, and wherein the at least one memory and the computer program code are configured to, together with the at least one processor, cause the first device to execute: in response to receiving a connection release message from the third device via the signaling radio bearer, disconnecting the connection with the third device; and Reconnect to the fourth device, or connect to a fifth device found in the cell selection initiated by the first device.

8. The first device of claim 6, wherein the at least one memory and the computer program code are configured to, together with the at least one processor, cause the first device to perform: Sending a connection re-establishment message to the second device; or Perform a third random access to the second device based on the first configuration.

9. The first device of claim 6, wherein the at least one memory and the computer program code are configured to, together with the at least one processor, cause the first device to perform: determining whether the reconnection to the second device fails; and According to determining that the reconnection to the second device fails, reconnect to the fourth device, or connect to a fifth device found in the cell selection initiated by the first device.

10. The first device according to any one of claims 6 to 9, wherein the at least one memory and the computer program code are configured to, together with the at least one processor, cause the first device to execute: initiating a timer to monitor success of the reconnection to the second device; and In response to expiration of the timer, it is determined that the reconnection to the second device has failed.

11. A computer-readable storage medium comprising program instructions stored thereon, which instructions, when executed by an apparatus, cause the apparatus to perform: receiving a connection reconfiguration message from a fourth device connected to the first device, the connection reconfiguration message including a first configuration about the second device and a second configuration about the third device; performing a first random access to the second device based on the first configuration and a second random access to the third device based on the second configuration to connect to the second device and the third device; In response to a failure of the first random access and a success of the second random access, performing the following: If there is no signaling radio bearer 3 SRB3 between the third device and the first device or the second device does not receive an indication of the existence of the SRB3, reconnect to the second device based on the first configuration while maintaining connection to the third device; or If the SRB3 is established between the third device and the first device and the second device receives an indication that the SRB3 exists, a connection release message is received from the third device via the SRB3.

12. The computer-readable storage medium of claim 11, wherein the connection reconfiguration message comprises configuration regarding a signaling radio bearer between the third device and the first device, and wherein the computer-readable medium further comprises instructions that cause the first device to execute: in response to receiving a connection release message from the third device via the signaling radio bearer, disconnecting the connection with the third device; and Reconnect to the fourth device, or connect to a fifth device found in the cell selection initiated by the first device.

13. The computer-readable storage medium of claim 11, wherein the computer-readable medium further comprises instructions that cause the first device to execute: Sending a connection re-establishment message to the second device; or Perform a third random access to the second device based on the first configuration.

14. The computer-readable storage medium of claim 11, wherein the computer-readable medium further comprises instructions that cause the first device to execute: determining whether the reconnection to the second device fails; and According to determining that the reconnection to the second device fails, reconnect to the fourth device, or connect to a fifth device found in the cell selection initiated by the first device.

15. The computer-readable storage medium according to any one of claims 11 to 14, wherein the computer-readable storage medium further comprises the following instructions, the instructions causing the first device to execute: initiating a timer to monitor success of the reconnection to the second device; and In response to expiration of the timer, it is determined that the reconnection to the second device has failed.

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