CN113348698B

CN113348698B - Mobile augmentation of terminal devices

Info

Publication number: CN113348698B
Application number: CN201980090448.8A
Authority: CN
Inventors: 李海涛; S·赛瓦加纳帕西; J-P·科斯基南
Original assignee: Nokia Shanghai Bell Co Ltd; Nokia Solutions and Networks Oy
Current assignee: Nokia Shanghai Bell Co Ltd; Nokia Solutions and Networks Oy
Priority date: 2019-01-28
Filing date: 2019-01-28
Publication date: 2023-01-13
Anticipated expiration: 2039-01-28
Also published as: CN113348698A; WO2020154855A1

Abstract

Example embodiments of the present disclosure relate to methods, devices, apparatuses and computer-readable storage media for mobility augmentation of terminal devices. In an example embodiment, a terminal device is served by a source access network device connected to a source core network device and determines a cell reselection from a source cell of the source access network device to a target cell of a target access network device connected to a target core network device. If a connection indication is received from the target access network device to enable a connection recovery procedure for data forwarding over a source backhaul link between the source access network device and the source core network device, the terminal device sends a connection recovery request to the target access network device for initiating the connection recovery procedure. The terminal device receives a connection restoration response from the target access network device indicating whether a connection establishment procedure is to be initiated.

Description

Mobile augmentation of terminal devices

Technical Field

Example embodiments of the present disclosure relate generally to the field of communications, and, in particular, to methods, devices, apparatuses, and computer-readable storage media for mobility augmentation of terminal devices.

Background

Technology for Long Term Evolution (LTE) connectivity to fifth generation core networks (5G-CNs) allows Radio Access Network (RAN) level interworking and provides a migration path between LTE access networks and the 5G-CN. Machine Type Communication (MTC) and narrowband internet of things (NB-IoT) do not allow the use of this technology due to tighter scheduling and narrower frequency bands. For third generation partnership project (3 GPP) release 16 (Rel-16), to further enhance NB-IoT, inter-radio access technology (inter-RAT) mobility in "idle" mode is proposed and various inter-RAT mobility scenarios are discussed.

Conventionally, MTC or NB-IoT User Equipment (UE) served by an evolved LTE (eete) eNodeB (eNB) connected to a 5G-CN may enter an "inactive" state after data transmission. The UE may trigger a Radio Resource Control (RRC) recovery procedure if the UE wants to access an lte cell or a different lte cell. Similarly, for a UE served by an LTE eNB connected to an Evolved Packet Core (EPC), the UE may enter a suspended or "idle" state after data transmission, and an RRC recovery procedure may be triggered when the UE intends to access an LTE cell that may or may not be the same as the currently serving LTE cell. The specific procedures of the two RRC recovery procedures are different, e.g., different security related Information Elements (IEs) may be included in the RRC message.

When a UE moves from LTE coverage to LTE coverage, it is often necessary to trigger a Tracking Area Update (TAU) procedure so that a device or entity in the EPC, such as a Mobility Management Entity (MME), is aware of the UE and pages the UE when Network Attached Storage (NAS) Downlink (DL) data or signaling arrives. The TAU procedure involves both an Attached Storage (AS) message exchange and a NAS message exchange. Thus, when a UE moves between LTE coverage and LTE coverage, signaling overhead and UE power consumption can be very high.

Disclosure of Invention

In general, example embodiments of the present disclosure provide methods, devices, apparatuses, and computer-readable storage media for mobility augmentation of terminal devices.

In a first aspect, a method is provided. In the method, a terminal device is served by a source access network device connected to a source core network device and determines a cell reselection from a source cell of the source access network device to a target cell of a target access network device connected to a target core network device. If a connection indication is received from the target access network device to enable a connection recovery procedure for data forwarding over a source backhaul link between the source access network device and the source core network device, the terminal device sends a connection recovery request to the target access network device for initiating the connection recovery procedure. The terminal device receives a connection restoration response from the target access network device indicating whether a connection establishment procedure is to be initiated.

In a second aspect, a method is provided. In the method, a target access network device receives a connection recovery request for initiating a connection recovery procedure from a terminal device served by a source access network device connected to a source core network device. And the target access network equipment sends a switching request to the source access network equipment so as to acquire the context of the terminal equipment. The target access network device receives a handover response from the source access network device, the handover response indicating whether backhaul switching from a source backhaul link between the source access network device and the source core network device to a target backhaul link between the target access network device and the target core network device is required. And the target access network equipment sends a connection recovery response to the terminal equipment based on the switching response.

In a third aspect, a method is provided. In the method, a source access network device is connected to a source core network device and serves a terminal device. The source access network device receives a handover request for acquiring a context of the terminal device from a target access network device connected to the target core network device. The source access network device determines whether a backhaul exchange is required from a source backhaul link between the source access network device and the source core network device to a target backhaul link between the target access network device and the target core network device. The source access network device sends a handover response to the target access network device based on the determination.

In a fourth aspect, an apparatus is provided that includes at least one processor and at least one memory including computer program code. The at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus to perform the method according to the first, second or third aspect.

In a fifth aspect, there is provided an apparatus comprising means for performing the method according to the first, second or third aspect.

In a sixth aspect, a computer readable storage medium having a computer program stored thereon is provided. The computer program, when executed by a processor of an apparatus, causes the apparatus to perform the method according to the first, second or third aspect.

It should be understood that the summary is not intended to identify key or essential features of the example embodiments of the disclosure, nor is it intended to be used to limit the scope of the disclosure. Other features of the present disclosure will become readily apparent from the following description.

Drawings

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

FIG. 1 illustrates an example environment in which example embodiments of the present disclosure may be implemented;

fig. 2 illustrates an example signaling procedure in a movement of a terminal device from a source access network device to a target access network device, according to some example embodiments of the present disclosure.

Fig. 3 illustrates an example signaling procedure in which a connection establishment procedure is not initiated, in accordance with some example embodiments of the present disclosure;

figure 4 illustrates an example signaling procedure in which a connection establishment procedure is initiated, in accordance with some example embodiments of the present disclosure;

fig. 5 shows a flow diagram of an example method according to some example embodiments of the present disclosure;

fig. 6 shows a flowchart of an example method according to some other example embodiments of the present disclosure;

fig. 7 shows a flowchart of an example method according to yet other example embodiments of the present disclosure;

fig. 8 shows a simplified block diagram of a device suitable for implementing an example embodiment of the present disclosure.

Throughout the drawings, the same or similar reference numbers refer to the same or similar elements.

Detailed Description

The principles of the present disclosure will now be described with reference to a few exemplary embodiments. It is understood that these example embodiments are described solely for the purpose of illustration and to assist those skilled in the art in understanding and practicing the disclosure, and are not intended to suggest any limitation as to the scope of the disclosure. The disclosure described herein may be implemented in various other ways than those described below.

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.

As used herein, the term "access network device" refers to a device via which a terminal device or UE is able to access a communication network. Examples of BSs include relays, access Points (APs), transmission points (TRPs), node BS (NodeB or NB), evolved NodeB (eNodeB or eNB), gigabit NodeB (gNB), remote radio modules (RRUs), radio Heads (RH), remote Radio Heads (RRHs), low power nodes (such as femtos, pico), and the like.

As used herein, the term "source access network device" refers to an access network device that is currently serving a terminal device when the terminal device moves to another access network device. As used herein, the term "target access network device" refers to an access network device to which the terminal device is moving towards and is therefore to be handed over.

As used herein, the term "core network device" refers to a device that is capable of communicating with an access network device in a core network and providing services to terminal devices. Examples of core network devices may include a Mobile Switching Center (MSC), an MME, an operations and management (O & M) node, an Operations Support System (OSS) node, a self-organizing network (SON) node, a location node such as an enhanced mobile services location center (E-SMLC), and/or a Mobile Data Terminal (MDT).

As used herein, the term "source core network device" refers to a core network device that is currently serving a terminal device when the terminal device moves to another core network device. As used herein, the term "target core network device" refers to a core network device to which the terminal device is moving towards and is therefore to be handed over.

As used herein, the term "terminal device" or "user equipment" (UE) refers to any terminal device capable of wireless communication with each other or a base station. Communication may involve the transmission and/or reception of wireless signals using electromagnetic signals, radio waves, infrared signals, and/or other types of signals suitable for the transmission of information over the air. In some example embodiments, the UE may be configured to transmit and/or receive information without direct human interaction. For example, the UE may transmit information to the network device on a predetermined schedule, triggered by an internal or external event, or in response to a request from the network side.

Examples of UEs include, but are not limited to, user Equipment (UE), such as a smartphone, wireless-enabled tablet, laptop Embedded Equipment (LEE), laptop installation equipment (LME), and/or wireless Customer Premises Equipment (CPE). For purposes of discussion, some example embodiments will be described with reference to a UE as an example of a terminal device, and the terms "terminal device" and "user equipment" (UE) may be used interchangeably within the context of this disclosure.

As used herein, the term "circuitry" may refer to one or more or all of the following:

(a) Hardware-only circuit implementations (such as implementations in analog and/or digital circuitry only); and

(b) A combination of hardware circuitry and software, such as (as applicable): (i) A combination of analog and/or digital hardware circuit(s) and software/firmware, and (ii) hardware processor(s) with software (including digital signal processor (s)), any portion of software and memory(s) that work in conjunction to cause a device such as a mobile telephone or server to perform various functions; and

(c) Hardware circuit(s) and/or processor(s), such as microprocessor(s) or a portion of microprocessor(s), that require software (e.g., firmware) to operate, but which may not be present when not required for operation.

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

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. The term "comprising" and its variants are to be understood as open-ended terms meaning "including but not limited to". The term "based on" should be understood as "based at least in part on". The terms "one embodiment" and "embodiment" should be understood as "at least one embodiment". The term "another embodiment" should be understood as "at least one other embodiment". Other definitions (whether explicit or implicit) may be included below.

As used herein, the terms "first," "second," and the like may be used herein to describe various elements, which should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element may be termed a second element, and, similarly, a second element may be termed a first element, without departing from the scope of example embodiments. As used herein, the term "and/or" includes any and all combinations of one or more of the listed terms.

Example embodiments of the present disclosure provide a modified signaling scheme for inter-cell and inter-core network movement of a terminal device. With this procedure, the terminal device is currently served by a source access network device connected to a source core network device, and when the terminal device moves, a cell reselection to a target cell of a target access network device connected to a target core network device is determined. The terminal equipment sends a connection recovery request to the target access network equipment to initiate a connection recovery process.

Then, the target access network device sends a handover request to the source access network device. In response to the handover request, the source access network device determines whether to switch a source backhaul link between the source access network device and the source core network device to a target backhaul link between the target access network device and the target core network device. The source access network device sends a handover response to the target access network device based on the determination of the backhaul exchange. In addition, the target access network device sends a connection recovery response based on the handover response. Accordingly, the terminal device determines whether to initiate a connection establishment procedure.

Through such a signaling procedure, when the terminal device moves from a source cell of the source access network device to a target cell of the target access network device, the terminal device may establish a connection with the target access network device in a more flexible and efficient manner. In this way, the movement of the terminal device, in particular between different core networks, may be enhanced.

FIG. 1 illustrates an example environment 100 in which example embodiments of the present disclosure may be implemented. The environment 100, which is part of a communication network, includes a terminal device 105, which is currently served by a source access network device 110, and the source access network device 110 is connected to a source core network device 115. As shown, the terminal device 105 is moving from a source cell 120 of a source access network device 110 to a target cell 125 of a target access network device 130 connected to a target core network device 135.

The access network device and the core network device may be implemented by any suitable device and may conform to any suitable communication standard or protocol. In some example embodiments, the source access network device 110 may be implemented by an lte eNB and the source core network device 130 may be implemented by a device or entity in the 5G-CN. Additionally, the target access network device 130 may be implemented by an LTE eNB and the target core network device 135 may be implemented by an MME in the EPC.

It is to be understood that in fig. 1, the number of terminal devices, access network devices, and core network devices are shown for illustrative purposes only, and do not pose any limitation on the scope of the present disclosure. Environment 100 may include any suitable number of terminal devices, access network devices, and core network devices.

The terminal device 105 may communicate with the source access network device 110 and the target access network device 130, or with another terminal device (not shown) directly or via the source access network device 110 or the target access network device 130. The communication may follow any suitable communication standard or protocol, such as Universal Mobile Telecommunications System (UMTS), long Term Evolution (LTE), LTE-advanced (LTE-a), evolved long term evolution (eete), fifth generation (5G) NR, wireless fidelity (Wi-Fi), and Worldwide Interoperability for Microwave Access (WiMAX) standards, and employ any suitable communication technology, including, for example, multiple Input Multiple Output (MIMO), orthogonal Frequency Division Multiplexing (OFDM), time Division Multiplexing (TDM), frequency Division Multiplexing (FDM), code Division Multiplexing (CDM), bluetooth (tooth), zigBee, and Machine Type Communication (MTC), enhanced mobile broadband (eMBB), large scale Machine Type Communication (MTC), narrowband internet of things (NB-IoT), and ultra-reliable low latency communication (URLLC) technologies.

The access network devices may communicate with the corresponding core network devices in a wired or wireless manner. The access network devices may communicate with each other via a communication interface, such as an X2 interface. The core network devices may communicate with each other via a dedicated interface. These communications may use any suitable communications technology that is known or will be developed in the future.

In the environment 100, when the terminal device 105 is moving into a target cell 125 of a target access network device 130, the terminal device 105 may reselect to the target access network device 130, for example, through cell reselection. In various example embodiments of the disclosure, the terminal device 105 sends a connection recovery request (e.g., an RRC connection recovery request message) to the target access network device 130 to initiate the connection recovery request. Upon receiving the connection recovery request, the target access network device 130 sends a handover request to the source access network device 110 to cause the source access network device 110 to determine whether a source backhaul link between the source access network device 110 and the source core network device 115 is to be handed over to a target backhaul link between the target access network device 130 and the target core network device 135.

The source access network device 110 may release the context of the terminal device 105 if needed or determined to perform a backhaul exchange. If no backhaul exchange is needed or determined to be not performed, the source access network device 110 may continue to communicate with the terminal device 105 using the source backhaul link through forwarding by the target access network device 130.

Fig. 2 illustrates an example signaling procedure 200 in the movement of the terminal device 105 from the source access network device 110 to the target access network device 130, according to some example embodiments of the present disclosure.

In process 200, the terminal device 105 determines (205) a cell reselection to the target cell 125 of the target access network device 130. For example, when moving from the source cell 120 to the target cell 125, the terminal device 105 may reselect to the target access network device 130 through cell reselection. In some example embodiments, cell reselection may be performed from the 5G-CN to the EPC. For example, a terminal device 105 in the "inactive" state is currently served by the 5G-CN and reselects an LTE cell in the EPC. The terminal device 105 may obtain information about the target CN connection from the system information broadcast by the target access network device 130.

The terminal device 105 receives (210) a connection indication from the target access network device to enable a connection recovery procedure for forwarding data over the source backhaul link between the source access network device 110 and the source core network device 115, i.e. without a backhaul exchange from the source backhaul link to the target backhaul link between the target access network device 130 and the target core network device 135. In this way, the terminal device 105 may determine whether data forwarding is enabled by the target access network device 130.

For example, target access network device 130 may broadcast a connection indication in a System Information Block (SIB) to indicate that the connection recovery procedure is to be enabled for data forwarding. If the target access network device 130 does not enable data forwarding using the connection recovery procedure, the terminal device 105 enters an "idle" state and triggers the connection establishment procedure. If the connection recovery procedure is allowed to be used, the terminal device 105 may send a connection recovery request to the target access network device 130.

The terminal device 105 sends (215) a connection recovery request to the target access network device 130 to initiate a connection recovery procedure. The connection restoration process may include any suitable suspension or restoration process known or to be developed in the future. For example, the connection recovery procedure may be implemented by an RRC recovery procedure. In this case, the connection resumption request may be implemented by an RRC connection resumption request message.

In some example embodiments, to save power consumption, if extended discontinuous reception (eDRX) is activated, the terminal device 105 may defer the transmission of the connection resumption request until a Paging Time Window (PTW).

To save power consumption, in other example embodiments, the connection resume request may be sent by terminal device 105 upon arrival of Uplink (UL) data to save power consumption of terminal device 105. For example, if Power Saving Mode (PSM) is activated, terminal device 105 may defer transmission of the connection resume request until UL data arrives.

In some example embodiments, the terminal device 105 may determine whether to initiate the connection recovery procedure based on the time from the arrival of UL data to the trigger opportunity of the connection establishment procedure to further reduce UL transmission delay. For example, if UL data (e.g., NAS data) arrives, the terminal device 105 may determine whether the time from arrival of the UL data to the available trigger opportunity for the connection establishment procedure (e.g., TAU procedure) is greater than a predetermined threshold. The threshold may be predefined based on actual service requirements, such as latency requirements. If the time is greater than the predetermined threshold, indicating that the trigger opportunity is relatively late, the terminal device 105 may send a connection recovery request to the target access network device 130. Otherwise, the terminal device 105 may enter an "idle" state and initiate a connection establishment procedure in a trigger opportunity.

The connection restoration request may contain information about the source access network device 110. For example, in an example embodiment where the source access network device 110 is an lte eNB, the connection resume request may include a resume Identification (ID) and a security ID based on the context of the terminal device 105 in the source lte cell. Additionally, the connection restoration request may contain an indication indicating the movement of the terminal device 105 from the source cell 120. In the case where the source access network device 110 is an lte eNB, the indication may be implemented by a flag to indicate movement from 5GC.

Upon receiving the connection restoration request, the target access network device 130 sends (220) a handover request to the source access network device 110 with a context for acquiring the terminal device 105. The handover request may be sent between the two access network devices via the X2 interface. In an example embodiment where the source access network device 110 is an eLTE eNB and the target access network device 130 is an LTE eNB, the handover request may be carried in an X2 application protocol (X2 AP) message. Using the X2AP message, the target access network device 130 may indicate to the source access network device 110 that the terminal device 105 has moved out of the EPC area.

The source access network device 110 determines (225) whether to perform a backhaul exchange from a source backhaul link between the source access network device 110 and the source core network device 115 to a target backhaul link between the target access network device 130 and the target core network device 135. For example, source access network device 110 may verify the security of the handover request and make a decision whether to enable backhaul switching based on the verification. If the backhaul exchange is determined, the source access network device 110 may move the session of the terminal device 105 out.

In some example embodiments, the source access network device 110 may notify the source core network device 115 of the movement of the terminal device 105. For example, the source access network device 110 may send an indication to the source core network device 115 to indicate that the terminal device 105 has moved out of the source cell 120. The source core network device 115 may also send an indication to the target core network device 135 to inform the terminal device 105 that it is moving into the target cell 125.

Based on the determination (225), the source access network device 110 sends (230) a handover response to the target access network device 130 to indicate whether a backhaul exchange is required. Similar to the handover request, a handover response may be sent between the two access network devices via the X2 interface. In the case where the source access network device 110 is an LTE eNB and the target access network device 130 is an LTE eNB, the handover response may be carried in an X2AP message.

In some example embodiments, the source access network device 110 may release the context of the terminal device 105 if a backhaul exchange is required. Further, the source access network device 110 may notify the source core network device 115 that the terminal device 105 has moved out of the source coverage area 115 and cannot page. If no backhaul exchange is required, the source access network device 110 will continue to communicate with the terminal device 105 through forwarding by the target access network device 130.

As shown in fig. 2, based on the handover response, the target access network device 130 sends (235) a connection recovery response to the terminal device 110 so that the terminal device 105 can determine whether to initiate a connection establishment procedure. The connection establishment procedure may be any suitable establishment procedure known or to be developed in the future. For example, the connection establishment procedure may be implemented by a TAU procedure.

For example, if the handover response indicates that a backhaul exchange is required, the connection restoration response may indicate that the connection restoration request is denied. Thus, the terminal device 105 may determine to initiate the connection establishment procedure. In this case, the terminal device 105 may first enter an "idle" state and then initiate a connection establishment procedure for establishing a new context in the target cell 125. In some example embodiments, the target access network device 130 may notify the target core network device 135 of the CN change.

If the handover response indicates that no switching from the source backhaul link to the target backhaul link is to occur, the target access network device 130 may send a connection recovery response indicating that the connection recovery request is allowed. In this case, the target access network device 130 may determine to forward the communication between the terminal device 105 and the source access network device 110.

The higher layer functionality in the source cell 120 may still be used by the terminal device 105 through forwarding by the target access network device 130. Accordingly, target access network device 130 may configure terminal device 110 to switch only the functionality of the lower layers, such as the Radio Link Control (RLC), medium Access Control (MAC), and Physical (PHY) layers, to target cell 125.

In example embodiments where the source access network device 110 is an LTE eNB and the target access network device 130 is an LTE eNB, 5G security and Packet Data Convergence Protocol (PDCP) functionality may still be used by the terminal device 105 and the relevant context of 5G is maintained. After the connection recovery procedure is completed, user Plane (UP) data transmission continues through forwarding by the target eNB via the 5G User Plane Gateway (UPGW) of the source lte eNB.

If the terminal device 105 has UL data to transmit, the terminal device 105 may send the UL data to the target access network device 130. The target access network device 130 then forwards the UL data to the source access network device 110. After the UL data transmission is completed, the UE enters an "idle" state and will trigger further connection recovery procedures or connection establishment procedures (e.g., TAU procedures or service request procedures) for future service requests.

Using the signaling scheme provided herein, in the case where the source access network device 110 is an LTE eNB and the target access network device 130 is an LTE eNB, the terminal device 105 may trigger an RRC connection recovery procedure upon reselecting an LTE cell connected to the EPC to enable the source LTE eNB to decide whether to release the context of the terminal device 105 or enable data forwarding via the target cell while maintaining a 5GC connection. The terminal device 105 may have a new configuration of RLC, MAC and PHY layers for the target LTE cell, and an old configuration of security for the PDCP and source LTE cells.

Thus, data of the 5GC cell can be forwarded via the EPC cell, and the 5GPDCP and security can still be used for data transmission. Further, when the source lte eNB decides to release the context and the UE enters an "idle" state in a new cell, the 5GC may be informed of the UE's movement to the EPC.

As an alternative example, in an example embodiment where the source access network device 110 is an LTE eNB and the target access network device 130 is an LTE eNB, the terminal device 105 may initiate a connection establishment procedure after UL data is available for transmission. Two example signaling procedures in the movement of the terminal device 105 will be discussed with reference to fig. 3 and 4. In these examples, source access network device 110 and source core network device 115 are 5G (or LTE) devices, and target access network device 130 and target core network device 135 are LTE devices.

Fig. 3 illustrates an example signaling procedure 300 in which a connection establishment procedure is not initiated, according to some example embodiments of the present disclosure.

In process 300, the target access network device 130 (e.g., LTE eNB) broadcasts 305 support for a connection recovery procedure (i.e., no backhaul exchange) for data forwarding over a source backhaul link between the source access network device 110 and the source core network device 115. A terminal device 105 (e.g., UE) served by a source access network device 110 (e.g., an lte eNB) reselects (310) a target cell 125 (e.g., target cell) after UL NAS data arrives. For example, the terminal device 105 sends (315) a connection recovery request (e.g., RRC connection recovery request message) to the target access network device 130 to indicate movement from the 5GC. The target access network device 130 sends (320) a handover request to the source access network device 110 to indicate the movement from the 5GC.

In this example, the source access network device 110 decides (325) not to perform the backhaul exchange. For example, the source access network device 110 indicates (330) to the source core network device 115 (e.g., in a 5 GC) that the end device 105 is moving out of the 5GC. For example, the source core network device 115 indicates (335) to the target core network device 135 (e.g., in the EPC) that the terminal device 105 is moving into the EPC. The source access network device 110 sends (340) a handover response to the target access network device 130 to require forwarding of the 5G-PDCP packet via the LTE RLC/MAC/PHY layer. The target access network device 120 sends 345 a connection recovery response (e.g., an RRC connection recovery message) to the terminal device 105 to exchange only the functions at the RLC/MAC/PHY layer while maintaining the PDCP and 5G security contexts.

The target access network device 130 forwards the data transmission between the terminal device 105 and the source access network device 110 (350). After the data transfer is complete, the target access network device 130 sends 355 a connection release message (e.g., an RRC connection release message) to the terminal device 105.

Fig. 4 illustrates an example signaling procedure 400 in which a connection establishment procedure is initiated, according to some example embodiments of the present disclosure.

In the process 400, the actions (or operations) 405 to 420 in the process 400 are the same as the actions (or operations) 305 to 320, and are not described herein again. In this example, upon receiving the handover request from the target access network device 130, the source access network device 110 decides (425) to perform the backhaul exchange. Then, the same actions 430 and 435 as actions 330 and 335 are performed so that the source core network device and the target core network device can be aware of the movement of the terminal device 105. The source access network device 110 sends (440) a handover response to the target access network device 130 indicating the release of the UE context. The terminal device 105 sends 450 a connection establishment request (e.g., RRC connection request) to the target access network device 130 to initiate a connection establishment procedure (e.g., TAU procedure).

Fig. 5 illustrates a flow diagram of an example method 500, according to some example embodiments of the present disclosure. The method 500 may be implemented at a terminal device 105 as shown in fig. 1. For discussion purposes, the method 500 will be described with reference to fig. 1.

At block 505, the terminal device 105 determines a cell reselection from the source cell 120 of the source access network device 110 to the target cell 125 of the target access network device 130. At block 510, the terminal device 105 receives a connection indication from the target access network device 130 to enable a connection recovery procedure for data forwarding over a source backhaul link between a source access network device and a source core network device. At block 515, the terminal device 105 sends a connection recovery request to the target access network device 130 for initiating a connection recovery procedure. At block 520, the terminal device 105 receives a connection recovery response from the target access network device 130 indicating whether a connection establishment procedure is to be initiated.

In some example embodiments, the connection indication may be broadcast from the target access network device 130.

In some example embodiments, the terminal device 105 may send a connection recovery request in response to the arrival of uplink data. In some example embodiments, if the power saving mode is activated, the terminal device 105 may defer the transmission of the connection resume request until the arrival of uplink data.

In some example embodiments, the terminal device 105 may determine whether the time from the arrival of uplink data to the available trigger opportunity for the connection establishment procedure is greater than a predetermined threshold. If it is determined that the time is greater than the predetermined threshold, the terminal device 105 may send a connection recovery request to the target access network device 130.

In some example embodiments, if extended discontinuous reception is activated, terminal device 105 may defer transmission of the connection resumption request until the paging time window.

In some example embodiments, terminal device 105 may determine that a connection establishment procedure is not required if the connection restoration response indicates that the connection restoration request is allowed. The terminal device 105 may further transmit uplink data to the target access network device.

In some example embodiments, terminal device 105 may determine to initiate the connection establishment procedure if the connection recovery response indicates that the connection recovery request is denied. The terminal device 105 may send a connection establishment request to the target access network device 130 to initiate the connection establishment procedure.

In some example embodiments, the terminal device 105 may enter an idle state. The terminal device 105 may send a connection establishment request in an idle state. In some example embodiments, the terminal device 105 may send a connection establishment request to initiate a connection establishment procedure in response to uplink data being transmitted.

In some example embodiments, the connection restoration request includes an indication of movement of the terminal device from the source cell 120 of the source access network device 110. In some example embodiments, the connection recovery procedure may include a radio resource control connection recovery procedure. In some example embodiments, the connection establishment procedure may include a tracking area update procedure. In some example embodiments, the source core network device may comprise a fifth generation core network device and the target core network device may comprise an evolved packet core network device.

Fig. 6 shows a flowchart of an example method 600 according to some other example embodiments of the present disclosure. The method 600 may be implemented at the target access network device 130 as shown in fig. 1. For discussion purposes, the method 600 will be described with reference to fig. 1.

At block 605, the target access network device 130 receives a connection recovery request from the terminal device 105 to initiate a connection recovery procedure. At block 610, the target access network device 130 sends a handover request to the source access network device 110 for obtaining the context of the terminal device 105. At block 615, the target access network device 130 receives 110 a handover response from the source access network device indicating whether a backhaul exchange from a source backhaul link between the source access network device 110 and the source core network device 115 to a target backhaul link between the target access network device 130 and the target core network device 135 is required. At block 620, the target access network device 130 sends a connection recovery response to the terminal device 105 based on the handover response.

In some example embodiments, the target access network device 130 may broadcast the connection indication to enable a connection recovery procedure for data forwarding over the source backhaul link (i.e., no backhaul exchange).

In some example embodiments, if the handover response indicates that backhaul switching is not required, the target access network device 130 may send a connection restoration response to indicate that the connection restoration request is allowed.

In some example embodiments, the target access network device 130 may receive uplink data from the terminal device 105.

In some example embodiments, if extended discontinuous reception is activated, the target access network device 130 may defer the transmission of the connection resumption request until the paging time window. Target access network device 130 may also forward uplink data to source access network device 110.

In some example embodiments, the handover response indicates that a backhaul exchange is required, and the target access network device 130 may send a connection restoration response to indicate that the connection restoration request is denied.

In some example embodiments, the target access network device 130 may receive a connection establishment request from the terminal device 105 to initiate a connection establishment procedure. In some example embodiments, the connection establishment procedure may include a tracking area update procedure.

In some example embodiments, at least one of the connection restoration request and the handover request may contain an indication of movement of the terminal device 105 from the source cell of the source access network device 110.

In some example embodiments, the connection recovery procedure may include a radio resource control connection recovery procedure. In some example embodiments, the source core network device may comprise a fifth generation core network device and the target core network device comprises an evolved packet core network device.

Fig. 7 shows a flowchart of an example method 700 according to still other example embodiments of the present disclosure. Method 700 may be implemented at a source access network device 110 as shown in fig. 1. For discussion purposes, the method 700 will be described with reference to fig. 1.

At block 705, the source access network device 110 receives a handover request from the target access network device 130 to obtain a context for the terminal device 105. At block 710, the source access network device 110 determines whether a backhaul exchange is required from a source backhaul link between the source access network device 110 and the source core network device 115 to a target backhaul link between the target access network device 130 and the target core network device 135. At block 715, the source access network device 110 sends a handover response to the target access network device 130 based on the determination.

In some example embodiments, the source access network device 110 may receive uplink data from the terminal device 105 via the target access network device 130 in response to the backhaul exchange being disabled.

In some example embodiments, if the handover response indicates that backhaul switching is disabled, the source access network device 110 may send a connection restoration response to indicate that the connection restoration request is allowed.

In some example embodiments, if a backhaul exchange is required, the source access network device 110 may send an exchange indication to the source core network device 130 to indicate that the source backhaul link is to be exchanged to the target backhaul link.

In some example embodiments, the source access network device 110 may release the context of the terminal device.

In some example embodiments, the source access network device 110 may send an indication of the movement of the terminal device 105 from the source cell 120 of the source access network device 115 to the source core network device 115.

In some example embodiments, the handover request includes an indication of movement of the terminal device 105 from the source cell 120 of the source access network device 115.

In some example embodiments, the source core network device may comprise a fifth generation core network device and the target core network device comprises an evolved packet core network device.

All of the operations and features described above with reference to fig. 1 through 4 are equally applicable to methods 500 through 700 and have similar effects. Details will be omitted for simplicity.

In some example embodiments, an apparatus capable of performing the

method

500, 600 or 700 may include means for performing the respective steps of the

method

500, 600 or 700. The component may be implemented in any suitable form. For example, the components may be implemented in circuitry or software modules.

In some example embodiments, an apparatus capable of performing method 500 includes: means for determining, at a terminal device served by a source access network device connected to a source core network device, a cell reselection from a source cell of the source access network device to a target cell of a target access network device connected to a target core network device; means for receiving a connection indication from a target access network device, the connection indication to enable a connection recovery procedure for data forwarding over a source backhaul link between a source access network device and a source core network device; means for sending a connection recovery request to a target access network device for initiating a connection recovery procedure; and means for receiving a connection restoration response from the target access network device, the connection restoration response indicating whether a connection establishment procedure is to be initiated.

In some example embodiments, the connection indication may be broadcast by the target access network device.

In some example embodiments, the means for sending a connection recovery request may comprise: means for sending a connection recovery request in response to arrival of uplink data.

In some example embodiments, the means for sending a connection recovery request in response to arrival of uplink data may comprise: means for delaying transmission of a connection resume request until arrival of uplink data if the power saving mode is activated.

In some example embodiments, the means for sending the connection recovery request in response to the arrival of uplink data may include: means for determining whether a time from arrival of uplink data to an available trigger opportunity for a connection establishment procedure is greater than a predetermined threshold; and means for sending a connection recovery request to the target access network device in response to determining that the time is greater than the predetermined threshold.

In some example embodiments, the means for sending the connection recovery request may comprise: means for delaying transmission of a connection resumption request until a paging time window if extended discontinuous reception is activated.

In some example embodiments, the apparatus may further include: means for determining that a connection establishment procedure is not required in response to the connection restoration response indicating that the connection restoration request is allowed; and means for transmitting the uplink data to the target access network device.

In some example embodiments, the apparatus may further include: means for determining to initiate a connection establishment procedure in response to the connection recovery response indicating that the connection recovery request is denied; and means for sending a connection establishment request to the target access network device to initiate a connection establishment procedure.

In some example embodiments, the means for sending a connection establishment request may comprise: means for entering an idle state; and means for sending a connection establishment request in an idle state.

In some example embodiments, the means for sending a connection establishment request may comprise: means for sending a connection establishment request to initiate a connection establishment procedure in response to uplink data being transmitted.

In some example embodiments, the connection restoration request may contain an indication of movement of the terminal device from a source cell of the source access network device.

In some example embodiments, the connection recovery procedure may include a radio resource control connection recovery procedure.

In some example embodiments, the connection establishment procedure may include a tracking area update procedure.

In some example embodiments, the source core network device may comprise a fifth generation core network device and the target core network device may comprise an evolved packet core network device.

In some example embodiments, an apparatus capable of performing method 600 comprises: means for receiving, at a target access network device connected to a target core network device, a connection restoration request for initiating a connection restoration procedure from a terminal device served by a source access network device connected to a source core network device; means for sending a handover request to a source access network device for obtaining a context of a terminal device; means for receiving a handover response from a source access network device, the handover response indicating whether a backhaul exchange from a source backhaul link between the source access network device and a source core network device to a target backhaul link between a target access network device and a target core network device is required; and means for sending a connection recovery response to the terminal device based on the handover response.

In some example embodiments, the apparatus may further include: means for broadcasting a connection indication to enable a connection recovery procedure for data forwarding over the source backhaul link.

In some example embodiments, the means for sending the connection recovery response may comprise: means for sending a connection restoration response to indicate that the connection restoration request is allowed in response to the handover response indicating that backhaul switching is not required.

In some example embodiments, the apparatus may further include: means for receiving uplink data from a terminal device; and means for forwarding the uplink data to the source access network device.

In some example embodiments, the means for sending the connection recovery response may comprise: means for sending a connection restoration response to indicate that the connection restoration request is denied in response to the handover response indicating that a backhaul exchange is required.

In some example embodiments, the apparatus may further include: means for receiving a connection establishment request from a terminal device to initiate a connection establishment procedure.

In some example embodiments, the at least one of the connection resumption request and the handover request may contain an indication for movement of the terminal device from a source cell of the source access network device.

In some example embodiments, an apparatus capable of performing method 700 comprises: means for receiving, at a source access network device connected to a source core network device, a handover request from a target access network device connected to a target core network device to obtain a context of a terminal device served by the source access network device; means for determining whether a backhaul exchange is required from a source backhaul link between a source access network device and a source core network device to a target backhaul link between a target access network device and a target core network device; and means for sending a handover response to the target access network device based on the determination.

In some example embodiments, the apparatus may further include: means for receiving uplink data from the terminal device via the target access network device in response to not requiring the backhaul exchange.

In some example embodiments, the apparatus may further include: means for sending a switch indication to the source core network device to indicate that the source backhaul link is to be switched to the target backhaul link in response to the backhaul switch being required.

In some example embodiments, the apparatus may further include: means for releasing context of the terminal device.

In some example embodiments, the apparatus may further include: means for sending, to a source core network device, an indication of movement of a terminal device from a source cell of the source access network device.

In some example embodiments, the handover request may contain an indication of movement of the terminal device from a source cell of the source access network device.

Fig. 8 is a simplified block diagram of a device 800 suitable for implementing an example embodiment of the present disclosure. The device 800 may be implemented at or as part of the terminal device 105, the target access network device 130, or the source access network device as shown in fig. 1.

As shown, the device 800 includes a processor 810, a memory 820 coupled to the processor 810, a communication module 830 coupled to the processor 810, and a communication interface (not shown) coupled to the communication module 830. The memory 820 stores at least a program 840. The communication module 830 is used for bi-directional communication, e.g., via multiple antennas. The communication interface may represent any interface necessary for communication.

The program 840 is assumed to include program instructions that, when executed by the associated processor 810, enable the device 800 to operate in accordance with example embodiments of the disclosure, as discussed herein with reference to fig. 1-7. The example embodiments herein may be implemented by computer software executable by the processor 810 of the device 800, or by hardware, or by a combination of software and hardware. The processor 810 may be configured to implement various example embodiments of the present disclosure.

The memory 820 may be of any type suitable to the local technology network and may be implemented using any suitable data storage technology, such as non-transitory computer readable storage media, semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory, as non-limiting examples. Although only one memory 820 is shown in device 800, there may be several physically distinct memory modules in device 800. The processor 810 may be of any type suitable for a local technology network, and may include, by way of non-limiting example, one or more of the following: general purpose computers, special purpose computers, microprocessors, digital Signal Processors (DSPs) and processors based on a multi-core processor architecture. Device 800 may have multiple processors, such as application specific integrated circuit chips that are time-dependent from a clock synchronized to the main processor.

When the device 800 is acting as a terminal device 105 or part of a terminal device 105, the processor 810 and the communication module 830 may cooperate to implement the method 500 as described above with reference to fig. 5. When the device 800 is acting as the target access network device 130 or part of the target access network device 130, the processor 810 and the communication module 830 may cooperate to implement the method 600 described above with reference to fig. 6. When device 800 is acting as a source access network device 110 or part of a source access network device 110, processor 810 and communication module 830 may cooperate to implement method 700 described above with reference to fig. 7.

All of the operations and features described above with reference to fig. 1-7 are equally applicable to the device 800 and have similar effects. Details will be omitted for the sake of simplicity.

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

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 comprises computer-executable instructions, such as those included in program modules, that are executed in a device on a target real or virtual processor to perform the

method

500, 600 or 700 as described above with reference to figures 1 to 7. Generally, program modules include routines, programs, libraries, objects, classes, components, data types, etc. that perform particular tasks or implement particular abstract data types. The functionality of the program modules may be combined or split between program modules as desired in various exemplary embodiments. Machine-executable instructions for program modules may be executed within a local or distributed device. In a distributed facility, program modules may be located in both local and remote memory storage media.

Program code for performing the methods of the present disclosure may be written in any combination of one or more programming languages. These program codes may be provided to a processor or controller of a general purpose computer, special purpose computer, or other programmable data processing apparatus, such that the program codes, when executed by the processor or controller, cause the functions/acts specified in the flowchart and/or block diagram to be performed. The program code may execute entirely on the machine, partly on the machine, as a stand-alone software package, partly on the machine and partly on a remote machine or entirely on the remote machine or server.

In the context of the present disclosure, computer program code 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 the carrier include a signal, a computer readable medium.

The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable medium may include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination thereof. More specific examples of a computer-readable storage medium include an electrical connection having one or more wires, a portable computer diskette, 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 disc read-only memory (CD-ROM), a Digital Versatile Disc (DVD), an optical storage device, a magnetic storage device, or any suitable combination thereof.

Further, while operations are depicted in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In some cases, multitasking and parallel processing may be advantageous. Also, while several specific implementation details are included in the above discussion, these should not be construed as limitations on the scope of the disclosure, but rather as descriptions of features that may be specific to particular example embodiments. Certain features that are described in the context of separate example embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple example embodiments separately or in any suitable subcombination.

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

Various example embodiments of the technology have been described. In addition to or in place of the foregoing, the following examples are described. Features described in any of the examples below may be used with any of the other examples described herein.

Claims

1. A method for communication, comprising:

determining, at a terminal device served by a source access network device connected to a source core network device, a cell reselection from a source cell of the source access network device to a target cell of a target access network device connected to a target core network device;

receiving a connection indication from the target access network device, the connection indication to enable a connection recovery procedure for data forwarding over a source backhaul link between the source access network device and the source core network device;

sending a connection recovery request to the target access network device for initiating a connection recovery process; and

receiving a connection restoration response from the target access network device, the connection restoration response indicating whether a connection establishment procedure is to be initiated.

2. The method of claim 1, wherein the connection indication is broadcast by the target access network device.

3. The method of claim 1, wherein sending the connection recovery request comprises:

sending the connection recovery request in response to arrival of uplink data.

4. The method of claim 3, wherein sending the connection recovery request in response to the arrival of the uplink data comprises:

deferring the sending of the connection resume request until the arrival of the uplink data if a power save mode is activated.

5. The method of claim 3, wherein sending the connection recovery request in response to the arrival of the uplink data comprises:

determining whether a time from the uplink data to an available trigger opportunity for a connection establishment procedure is greater than a predetermined threshold; and

in response to determining that the time is greater than the predetermined threshold, sending the connection restoration request to the target access network device.

6. The method of claim 1, wherein sending the connection restoration request comprises:

deferring the transmission of the connection resumption request until a paging time window if extended discontinuous reception is activated.

7. The method of claim 1, further comprising:

determining that the connection establishment procedure is not required in response to the connection restoration response indicating that the connection restoration request is allowed; and

and transmitting uplink data to the target access network equipment.

8. The method of claim 1, further comprising:

determining that the connection establishment procedure is to be initiated in response to the connection restoration response indicating that the connection restoration request is denied; and

and sending a connection establishment request to the target access network equipment to initiate the connection establishment process.

9. The method of claim 8, wherein sending the connection establishment request comprises:

entering an idle state; and

and sending the connection establishment request in the idle state.

10. The method of claim 8, wherein sending the connection establishment request comprises:

sending the connection establishment request to initiate the connection establishment procedure in response to uplink data being transmitted.

11. The method of claim 1, wherein the connection restoration request includes an indication of movement of the terminal device from the source cell of the source access network device.

12. The method of claim 1, wherein the connection recovery procedure comprises a radio resource control connection recovery procedure.

13. The method of claim 1, wherein the connection establishment procedure comprises a tracking area update procedure.

14. The method of claim 1, wherein the source core network device comprises a fifth generation core network device and the target core network device comprises an evolved packet core network device.

15. A method for communication, comprising:

receiving, at a target access network device connected to a target core network device, a connection recovery request to initiate a connection recovery procedure from a terminal device served by a source access network device connected to a source core network device;

sending a switching request for acquiring the context of the terminal equipment to the source access network equipment;

receiving a handover response from the source access network device, the handover response indicating whether a backhaul exchange from a source backhaul link between the source access network device and the source core network device to a target backhaul link between the target access network device and the target core network device is required; and

and sending a connection recovery response to the terminal equipment based on the switching response.

16. The method of claim 15, further comprising:

a connection indication is broadcast to enable a connection recovery procedure for data forwarding over the source backhaul link.

17. The method of claim 15, wherein sending the connection recovery response comprises:

sending the connection restoration response to indicate that the connection restoration request is allowed in response to the handover response indicating that the backhaul exchange is not required.

18. The method of claim 17, further comprising:

receiving uplink data from the terminal device; and

forwarding the uplink data to the source access network device.

19. The method of claim 15, wherein sending the connection recovery response comprises:

in response to the handover response indicating that the backhaul exchange is required, sending the connection restoration response to indicate that the connection restoration request is denied.

20. The method of claim 19, further comprising:

a connection establishment request to initiate a connection establishment procedure is received from the terminal device.

21. The method of claim 20, wherein the connection establishment procedure comprises a tracking area update procedure.

22. The method of claim 15, wherein at least one of the connection recovery request and the handover request includes an indication of movement of the terminal device from a source cell of the source access network device.

23. The method of claim 15, wherein the connection recovery procedure comprises a radio resource control connection recovery procedure.

24. The method of claim 15, wherein the source core network device comprises a fifth generation core network device and the target core network device comprises an evolved packet core network device.

25. A method for communication, comprising:

receiving, at a source access network device connected to a source core network device, a handover request for acquiring a context of a terminal device served by the source access network device from a target access network device connected to a target core network device;

determining whether a backhaul exchange is required from a source backhaul link between the source access network device and the source core network device to a target backhaul link between the target access network device and the target core network device; and

sending a handover response to the target access network device based on the determination.

26. The method of claim 25, further comprising:

receiving uplink data from the terminal device via the target access network device in response to not requiring the backhaul exchange.

27. The method of claim 25, further comprising:

in response to the backhaul exchange being required, sending a switch indication to the source core network device to indicate that the source backhaul link is to be switched to the target backhaul link.

28. The method of claim 27, further comprising:

and releasing the context of the terminal equipment.

29. The method of claim 25, further comprising:

sending, to the source core network device, an indication of movement of the terminal device from a source cell of the source access network device.

30. The method of claim 25, wherein the handover request includes an indication for movement of the terminal device from a source cell of the source access network device.

31. The method of claim 25, wherein the source core network device comprises a fifth generation core network device and the target core network device comprises an evolved packet core network device.

32. An apparatus for communication, comprising:

at least one processor; and

at least one memory including computer program code;

the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus to perform the method of any of claims 1-14.

33. An apparatus for communication, comprising:

at least one processor; and

at least one memory including computer program code;

the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus to perform the method of any of claims 15-24.

34. An apparatus for communication, comprising:

at least one processor; and

at least one memory including computer program code;

the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus to perform the method of any of claims 25-31.

35. A network for communication comprising the apparatus of claim 32, the apparatus of claim 33 and the apparatus of claim 34.

36. An apparatus for communication, comprising:

means for determining, at a terminal device served by a source access network device connected to a source core network device, a cell reselection from a source cell of the source access network device to a target cell of a target access network device connected to a target core network device;

means for receiving a connection indication from the target access network device, the connection indication to enable a connection recovery procedure for data forwarding over a source backhaul link between the source access network device and the source core network device;

means for sending a connection recovery request to the target access network device for initiating a connection recovery procedure; and

means for receiving a connection recovery response from the target access network device, the connection recovery response indicating whether a connection establishment procedure is to be initiated.

37. An apparatus for communication, comprising:

means for receiving, at a target access network device connected to a target core network device, a connection recovery request for initiating a connection recovery procedure from a terminal device served by a source access network device connected to a source core network device;

means for sending a handover request to the source access network device for obtaining a context of the terminal device;

means for receiving a handover response from the source access network device indicating whether a backhaul exchange is required from a source backhaul link between the source access network device and the source core network device to a target backhaul link between the target access network device and the target core network device; and

means for sending a connection recovery response to the terminal device based on the handover response.

38. An apparatus for communication, comprising:

means for receiving, at a source access network device connected to a source core network device, a handover request from a target access network device connected to a target core network device to obtain a context for a terminal device served by the source access network device;

means for determining whether a backhaul exchange is required from a source backhaul link between the source access network device and the source core network device to a target backhaul link between the target access network device and the target core network device; and

means for sending a handover response to the target access network device based on the determination.

39. A computer readable storage medium comprising program instructions stored thereon which, when executed by a processor of a device, cause the device to perform the method of any of claims 1 to 14.

40. A computer readable storage medium comprising program instructions stored thereon that, when executed by a processor of an apparatus, cause the apparatus to perform the method of any of claims 15 to 24.

41. A computer readable storage medium comprising program instructions stored thereon which, when executed by a processor of an apparatus, cause the apparatus to perform the method of any of claims 25 to 31.