WO2020198978A1

WO2020198978A1 - Handover for inter-core network node

Info

Publication number: WO2020198978A1
Application number: PCT/CN2019/080531
Authority: WO
Inventors: Xiang Xu; Philippe Godin; Jeroen Wigard
Original assignee: Nokia Shanghai Bell Co., Ltd.; Nokia Solutions And Networks Oy; Nokia Technologies Oy
Priority date: 2019-03-29
Filing date: 2019-03-29
Publication date: 2020-10-08
Also published as: CN113661733B; CN113661733A; EP3949507A1; EP3949507A4

Abstract

Embodiments of the present disclosure relate to handover for inter-core network node. A network device transmits at a network device to a source core network node, a request for handover from the source core network node to a target core network node, the request for handover comprising handover assistance information provided by a source network module of the network device, the source network module obtaining the handover assistance information from a target network module; receives a response to the request for handover from the source core network node, the response comprising an updated context to be used in the target network module; and transmits based on the updated context, a radio handover command to a terminal device. In this way, the messages exchanged between the network device and the core network node are reduced.

Description

HANDOVER FOR INTER-CORE NETWORK NODE

FIELD

Example embodiments of the present disclosure generally relate to the field of communication techniques and in particular, to a method, device, apparatus and computer readable storage medium for handover for inter-core network node.

BACKGROUND

In recent years, different communication technologies have been proposed to improve communication performances, such as, the New Radio (NR) (also referred to 5 generation (5G) ) system. Some new network architecture, for example, supporting satellite access, has been proposed. Typically, in such communications system, the satellite comprises some logical module (s) performing as a network device (for example, gNB) and connecting to a core network node (for example, access and mobility management function (AMF) ) . However, when the satellite is not geo-stationary, the satellite may need to connect to various AMFs depending on the satellite’s position. Therefore, it is now desirable to provide an efficient mechanism for handover between different AMFs.

SUMMARY

In general, example embodiments of the present disclosure provide a solution for wireless positioning measurement.

In a first aspect, there is provided a method implemented at a network device. The method comprises transmitting, at a network device to a source core network node, a request for handover from the source core network node to a target core network node, the request for handover comprising handover assistance information provided by a source network module of the network device, the source network module obtaining the handover assistance information from a target network module; receiving a response for handover to the request for handover from the source core network node, the response for handover comprising an updated context to be used in the target network module; and transmitting, based on the updated context, a radio handover command to a terminal device.

In a second aspect, there is provided a method implemented at a source core network device. The method comprises receiving, at a source core network node from a network device a request for handover from the source core network node to a target core network node, the request for handover comprising handover assistance information provided by a source network module of the network device, the source network module obtaining the handover assistance information from a target network module; transmitting a context request for creating context of a terminal device to the target core network node based on the handover assistance information, the context request including the handover assistance information and a context of the terminal device; receiving a context response to the context request from the target core network node, the context response comprising an updated context of the terminal device; and transmitting to the network device a response for handover to the request for handover based on the updated context.

In a third aspect, there is provided a method implemented at a target core network device. The method comprises receiving, at a target core network node from a source core network node, a context request for creating context of a terminal device, the context request comprising handover assistance information and being generated by the source core network node based on the handover assistance information in a request for handover transmitted by a source network module of a network device, the source network module being connected to the source core network node, the network device having a target network module to be connected to the target core network node; transmitting a context response to the context request comprising an updated context of the terminal device to the source core network node.

In a fourth aspect, there is provided a device. The device comprises at least one processor; and at least one memory including computer program codes; the at least one memory and the computer program codes are configured to, with the at least one processor, cause the device to transmit, at a network device to a source core network node, a request for handover from the source core network node to a target core network node, the request for handover comprising handover assistance information provided by a source network module of the network device, the source network module obtaining the handover assistance information from a target network module. The device is also caused to receive a response to the request for handover from the source core network node, the response comprising an updated context to be used in the target network module. The device is further caused to transmit, based on the updated context, a radio handover command to a terminal device.

In a fifth aspect, there is provided a device. The device comprises at least one processor; and at least one memory including computer program codes; the at least one memory and the computer program codes are configured to, with the at least one processor, cause the device to at a source core network node from a network device a request for handover from the source core network node to a target core network node, the request for handover comprising handover assistance information provided by a source network module of the network device, the source network module obtaining the handover assistance information from a target network module. The device is also caused to transmit a context request for creating context of a terminal device to the target core network node based on the handover assistance information, the context request including the handover assistance information and a context of the terminal device. The device is further caused to receive a context response to the context request from the target core network node, the context response comprising an updated context of the terminal device. The device is also caused to transmit a response for handover to the request for handover based on the updated context to the network device.

In a sixth aspect, there is provided a device. The device comprises at least one processor; and at least one memory including computer program codes; the at least one memory and the computer program codes are configured to, with the at least one processor, cause the device to receive, at a target core network node from a source core network node, a context request for creating context of a terminal device, the context request comprising handover assistance information obtained from a request for handover transmitted by a source network module of a network device, the source network module being connected to the source core network node, the network device having a target network module to be connected to the target core network node. The device is also caused to transmit a context response to the context request comprising an updated context of the terminal device to the source core network node.

In a seventh aspect, there is provided an apparatus comprising means for transmitting, at a network device to a source core network node, a request for handover from the source core network node to a target core network node, the request for handover comprising handover assistance information provided by a source network module of the network device, the source network module obtaining the handover assistance information from a target network module; means for receiving a response for handover to the request for handover from the source core network node, the response for handover comprising an updated context to be used in the target network module; and means for transmitting a radio handover command based on the updated context to a terminal device.

In an eighth aspect, there is provided an apparatus comprising means for at a source core network node from a network device a request for handover from the source core network node to a target core network node, the request for handover comprising handover assistance information provided by a source network module of the network device, the source network module obtaining the handover assistance information from a target network module; means for transmitting a context request for creating context of a terminal device to the target core network node based on the handover assistance information, the context request including the handover assistance information and a context of the terminal device; means for receiving a context response to the context request from the target core network node, the context response comprising an updated context of the terminal device; and means for transmitting a response for handover to the request for handover based on the updated context to the network device.

In a ninth aspect, there is provided an apparatus comprising means for receiving, at a target core network node from a source core network node, a context request for creating context of a terminal device, the context request comprising handover assistance information obtained from a request for handover transmitted by a source network module of a network device, the source network module being connected to the source core network node, the network device having a target network module to be connected to the target core network nod; and means for a context response to the context request comprising an updated context of the terminal device to the source core network node.

In the tenth aspect, there is provided a non-transitory computer readable medium comprising program instructions for causing an apparatus to perform at least the method according to first aspect or the third aspect.

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

BRIEF DESCRIPTION OF THE DRAWINGS

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

Fig. 1 illustrates an example communication network in which example embodiments of the present disclosure may be implemented;

Fig. 2 illustrates an example scenario of the communication network in which example embodiments of the present disclosure may be implemented;

Fig. 3 illustrates a schematic diagram of interactions among devices according to according to conventional technologies;

Fig. 4 illustrates a schematic diagram of simplified interactions among devices according to conventional technologies;

Fig. 5 illustrates a schematic diagram of interactions among devices according to some example embodiments of the present disclosure;

Fig. 6 illustrates a flowchart of a method implemented at a network device according to some example embodiments of the present disclosure;

Fig. 7 illustrates a flowchart of a method implemented at a source core network node according to some example embodiments of the present disclosure;

Fig. 8 illustrates a flowchart of a method implemented at a target core network node according to some example embodiments of the present disclosure;

Fig. 9 illustrates a simplified block diagram of an apparatus that is suitable for implementing example embodiments of the present disclosure; and

Fig. 10 illustrates a schematic diagram of an example computer readable medium in accordance with some example embodiments of the present disclosure.

Throughout the drawings, the same or similar reference numerals represent the same or similar element.

DETAILED DESCRIPTION

Principle of the present disclosure will now be described with reference to some example embodiments. It is to be understood that these example embodiments are described only for the purpose of illustration and help those skilled in the art to understand and implement the present disclosure, without suggesting any limitation as to the scope of the disclosure. The disclosure described herein can be implemented in various manners other than the ones 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 skills in the art to which this disclosure belongs.

References in the present disclosure to “one example embodiment, ” “an example embodiment, ” “an example embodiment, ” and the like indicate that the example embodiment described may include a particular feature, structure, or characteristic, but it is not necessary that every example embodiment includes the particular feature, structure, or characteristic. Moreover, such. phrases are not necessarily referring to the same example embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an example embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other example embodiments whether or not explicitly described.

It shall 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. For example, a first element could be termed a second element, and similarly, a second element could be termed a first element, without departing from the scope of example embodiments. As used herein, the term “and/or” includes any and all combinations of one or more of the listed terms.

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

As used in this application, the term “circuitry” may refer to one or more or all of the following:

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

(b) combinations of hardware circuits and software, such as (as applicable) :

(i) a combination of analog and/or digital hardware circuit (s) with software/firmware and

(ii) any portions of hardware processor (s) with software (including digital signal processor (s) ) , software, and memory (ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and

(c) hardware circuit (s) and or processor (s) , such as a microprocessor (s) or a portion of a microprocessor (s) , that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation.

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

As used herein, the term “communication network” refers to a network following any suitable communication standards, such as Long Term Evolution (LTE) , LTE-Advanced (LTE-A) , Wideband Code Division Multiple Access (WCDMA) , High-Speed Packet Access (HSPA) , Narrow Band Internet of Things (NB-IoT) and so on. Furthermore, the communications between a terminal device and a network device in the communication network may be performed according to any suitable generation communication protocols, including, but not limited to, the first generation (1G) , the second generation (2G) , 2.5G, 2.75G, the third generation (3G) , the fourth generation (4G) , 4.5G, the future fifth generation (5G) communication protocols, and/or any other protocols either currently known or to be developed in the future. Example embodiments of the present disclosure may be applied in various communication systems. Given the rapid development in communications, there will of course also be future type communication technologies and systems with which the present disclosure may be embodied. It should not be seen as limiting the scope of the present disclosure to only the aforementioned system.

Embodiments of the present disclosure may be applied in various communication systems. Given the rapid development in communications, there will of course also be future type communication technologies and systems with which the present disclosure may be embodied. It should not be seen as limiting the scope of the present disclosure to only the aforementioned system. For the purpose of illustrations, embodiments of the present disclosure will be described with reference to 5G communication system.

The term “core network node” refers to any application or entity that provides Access and Mobility Management function, Session Management function (SMF) , User plane function (UPF) , etc. By way of example rather than limitation, the core network node may be an AMF, a SMF, a UPF, etc. In other embodiments, the core network node may be any other suitable application or entity.

The term “terminal device” refers to any end device that may be capable of wireless communication. By way of example rather than limitation, a terminal device may also be referred to as a communication device, 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 not limited to, a mobile phone, a cellular phone, a smart phone, voice over IP (VoIP) phones, wireless local loop phones, a tablet, a wearable terminal device, a personal digital assistant (PDA) , portable computers, desktop computer, image capture terminal devices such as digital cameras, gaming terminal devices, music storage and playback appliances, vehicle-mounted wireless terminal devices, wireless endpoints, mobile stations, laptop-embedded equipment (LEE) , laptop-mounted equipment (LME) , USB dongles, smart devices, wireless customer-premises equipment (CPE) , an Intemet of Things (loT) device, a watch or other wearable, a head-mounted display (HMD) , a vehicle, a drone, a medical device and applications (e.g., remote surgery) , an industrial device and applications (e.g., a robot and/or other wireless devices operating in an industrial and/or an automated processing chain contexts) , a consumer electronics device, a device operating on commercial and/or industrial wireless networks, and the like. In the following description, the terms “terminal device” , “communication device” , “terminal” , “user equipment” and “UE” may be used interchangeably.

The term “network device” used herein refers to a physical node which can be implemented at any suitable devices and includes a subset of the network modules. The network device may be stationary, or non-stationary. By way of example rather than limitation, the network device may be a spacebome vehicles, for example, it can be a Satellite (including Low Earth Orbiting (LEO) satellite, Medium Earth Orbiting (MEO) satellite, Geostationary Earth Orbiting (GEO) satellite as well as Highly Elliptical Orbiting (HEO) satellite. The network device may also be an airborne vehicle, for example, it can be a High Altitude Platforms (HAPs) encompassing Unmanned Aircraft Systems (UAS) including Lighter than Air UAS (LTA) , Heavier than Air UAS (HTA) , all operating in altitudes typically between 8 and 50 km, quasi-stationary. The network device may also be a groundborne vehicle, or a seaborne vehicle. In other embodiments, the network device may be any suitable entity.

The term “network module” used herein refers to a logical module which can be implemented at any suitable devices and performs as an access device. Specifically, the network module is implemented on the network device. By way of example rather than limitation, network module may perform as a base station (BS) , a gateway, a registration management entity, and other suitable function in a communication system. The term “base station” or “BS” represents a node B (NodeB or NB) , an evolved NodeB (eNodeB or eNB) , a NR NB or next generation NB (also referred to as a gNB) , an Integrated Access and Backhaul node (referred to as an IAB node) , a Remote Radio Unit (RRU) , a radio header (RH) , a remote radio head (RRH) , a relay, a low power node such as a femto, a pico, and so forth.

Fig. 1 shows an example communication network 100 in which example embodiments of the present disclosure can be implemented. The network 100 includes a core network node 110, a network device 120, a terminal device 130, a non-terrestrial network (NTN) gateway 140 and a data network 150. It is to be understood that the number of the core network node, the network device, the terminal device, the NTN gateway and the data network is only for the purpose of illustration without suggesting any limitations. The network 100 may include any suitable number of core network nodes, network device, terminal devices, NTN gateways and data networks adapted for implementing example embodiments of the present disclosure.

Although not shown, it would be appreciated that one or more terminal devices may be served by the network device 120. Only for the purpose of illustration without suggesting any limitations, NR-Uu radio interface may be used on the service link between the terminal device 130 and the network device 120, and satellite radio interface (SRI) may be used on the feeder link between the NTN gateway 140 and the network device 120.

Although not shown, it should be noted that the network device 120 could comprise a subset of network modules. Each network module functions as, for example, a gNB, a gNB Distributed Unit (gNB-DU) , a base station, an eNodeB, and any suitable element that could serve the terminal device 130.

However, in some cases that the network device 120, such as, satellite, is not geo-stationary, the network module performing as network device (such as, gNB) may need to connect to various core network nodes, such as, AMFs, depending on a position of the network device 120. For example, when the network device 120 leaves the coverage of current core network node, and enters the coverage of another core network node, the network module may change the next generation application protocol (NGAP) interface from one core network node to another core network node. Such scenario may be illustrated by referring Fig. 2.

Fig. 2 shows an example scenario 200 of the communication network 100 in which example embodiments of the present disclosure may be implemented. As is illustrated in Fig. 2, the example scenario 200 includes two core network nodes 110-1 and 110-2 (collectively referred to as network node (s) 110” ) , two NTN gateways 140-1 and 140-2 (collectively referred to as NTN gateway (s) 140) , and one network device 120. It is to be understood that the number of the core network node, the NTN gateway and the network device is only for the purpose of illustration without suggesting any limitations. The example scenario 200 may include any suitable number of the core network node, the NTN gateway and the network device.

As shown in Fig. 2, at T1, the network device 120 only connects to the NTN gateway 140-1/the core network node 110-1. At T2, the network device 120 connects to both the NTN gateways 140-1/the core network node 110-1 and the NTN gateway 140-2/the core network nodes 110-2 for a short period. At T3, the network device 120 only connects to the NTN gateways 140-2/the core network nodes 110-2.

Typically, one option to move the terminal devices served by the network module on the network device from source core network node to target core network node is to use a N2-based handover procedure. Fig. 3 is a schematic diagram of interactions among terminal device, source network module (such as, source gNB) , target network module (such as, target gNB) , source core network node (such as, source AMF) , target core network node (such as, target AMF) , target-user-plane function (T-UPF) , session management function entity (SMF) , source or serving user-plane function (S-UPF) and UPF according to a conventional N2-based handover procedure.

First, the source network module determines 305 to trigger a relocation via N2 interface, and then the source network module transmits 310 a Handover Required message to the source core network node. After receiving the Handover Required message, the source core network node may perform 315 a selection of the target corer network node, such as T-AFM selection. As the target core network node is determined, the source core network node transmits 320 a Namf_Communication_CreateUEContext Request message to the target core network node.

After receiving the Namf_Communication_CreateUEContext Request message, the target core network node may transmit 330 a Nsmf_PDUSession_UpdateSMContext Request message to the SMF. Then the SMF checks if N2 Handover can be accepted. If the terminal device has moved out of the service area of the UPF connecting to source network module, the SMF selects 332 a new intermediate UPF, as target UPF.

The SMF sends 334 N4 Session Modification Request message to UPF and receives 336 a Session Modification Request message from the UPF. These two operations are used for N4 session modification. Besides that, The SMF sends 338 N4 Session Establishment Request message to the T-UPF and receives 340 a N4 Session Establishment Response message from the T-UPF. These two operations are used for N4 session establishment.

After that, the SMF transmits 345 Nsmf_PDUSession_UpdateSMContext Response message to the target core network node. The AMF supervises 350 the Nsmf_PDUSession_UpdateSMContext Response messages from the involved SMFs and then sends 355 a Handover Request message to the target network module. Further, if a subscription information includes Tracing Requirements, the target core network node provides the target RAN with Tracing Requirements in the Handover Request. In response to the Handover Request message, the target network module may respond 360 a Handover Request Acknowledge.

After receiving the Handover Request Acknowledge, the target network node sends 362 Nsmf_PDUSession_UpdateSMContext Request message to SMF. The SMF sends 364 N4 Session Modification Request message to the T-UPF and receives 366 a N4 Session Modification Response message from the T-UPF. Besides that, the SMF sends 368 N4 Session Modification Request message to S-UPF and receives 370 a N4 Session Modification Response message from the S-UPF. These two operations are used for N4 session modification. After that, the SMF transmits 375 Nsmf_PDUSession_UpdateSMContext Response message to the target core network node.

The target core network node transmits 380 a Namf_Communication_CreateUEContext Response message to the source core network node. After receiving such message, the source core network node may transmit 385 Handover Command message to the source network module. Then, the source core network node forwards 390 a Handover Command message to the terminal device.

The AMF is usually considered as ground device, and the network device (such as, the gNB on a satellite) comprising the network module (s) . Dependent on the characteristics of the network device (such as geo-stationary or non-geo-stationary) , the network device (such as the gNB on a satellite) can be considered as a geo-stationary device or a non-geo-stationary device. It can be seen, during the conventional N2-based inter-core network nodes handover, at least four messages need to be exchanged between the ground device and the network device (such as the gNB on a satellite) . Specifically, two messages exchanged between the source network module and the source core network node, and two messages exchanged between the target network module and the target core network node.

As one network device may comprise more than one network modules, in some scenario, both the source network module and the target network module are collocated in the same network device. For this scenario, conventional N2-based inter-core network nodes handover may be used for inter-AMF handover.

Fig. 4 illustrates a schematic diagram of interactions among devices according to conventional N2-based handover in case that both the source network module and the target network module are collocated in the same network device. As illustrated in Fig. 4, two network modules (i.e. source network module and target network module) are implemented on the same network device. Source network module and target network module are configured with different tracking area identity (TAI) /physical cell identities (PCI) , or any other network identity.

The procedure of inter-core network handover needs four steps: First, at 410, one of the core network nodes (i.e. source core network node) is serving the terminal devices. Then, at 420, another core network node (i.e. target core network node) initiates a stream control transmission protocol (SCTP) /next generation (NG) interface setup with target core network node. The target network module uses a different TAI/PCI with the source network module for NG interface setup with target core network node. This ensures the source network module to initiate N2-based handover will be routed to target core network node.

At 430, after the SCTP/NG interface is setup between the target network module and the target core network node, when it is time for performing handover of inter-core network node, the source network module initiates enhanced N2-based handover procedure to move all connected terminal devices to the target core network node. The target network module starts operation over the air transmission. The source network module stops operation over the air transmission. Finally, after all terminal devices are move to target core network node. At 440, the source network module tears down the SCTP/NG with the source core network node.

However, there are some issues of using current inter-AMF handover procedure (such as, N2-based handover procedure) . One network module of the network device may support thousands or tens of thousands of connected terminal devices. Since all terminal devices served by the network module of the network device need to use N2-based handover in a very short period, it can cause sudden significant signalling load between the network module on the network device, and the core network node on the ground. Also, due to the long latency between the core network node on the ground and the network device on a satellite, handover all terminal devices may require a long period.

In order to address at least some of the above problems and other potential problems, according to example embodiments of the present disclosure, there is proposed a solution for handover for inter-core network node. As discussed above, A conventional N2-based handover needs at least four NGAP messages, i.e. HANDOVER REQUIRED, HANDOVER REQUEST, HANDOVER REQUEST ACKNOWLEDGE, and HANDOVER COMMAND exchanged during the handover procedure between the core network node on the ground and the network device on a satellite. Since both of the source network module 160-1 and the target network module 160-2 are collocated on the same network device 120, it is possible that the source network module 160-1 and the target network module 160-2 can share the context of the terminal device 130 (such as RAN UE NGAP ID, PDU session information, and so on) , or exchange the context or other configuration via internal or proprietary communication. Considering this, this present disclosure proposed solution of enhanced N2-based handover call flow.

In this solution, when the source network module 160-1 initiates a handover for inter-core network node 160 (also referred to inter-AMF handover, or N2-based handover) , the request for handover transmitted by the source network module 160-1 may comprise some addition parameters which are usually provided by the target network module 160-2 in the subsequent operations (such as handover resource allocation) according to a conventional N2-based handover procedure. In addition, an updated context of the terminal device 130 is transmitted to the target network node 1602-2 via the source network module 160-1 of the network device 120 by the target core network node 110-2 rather than transmitted to the target network module 160-2 during the handover procedure (such as handover resource allocation) .

In this way, the messages that needed to be exchanged between the target core network node 110-2 and the target network module 160-2 can be skipped. Therefore, the latency caused by the handover and the number of NGAP messages exchanged between the network device 120 and the core network node 110 are reduced.

It should be noted that, although the present disclosure is particularly advantageous for the scenario that the source network module and the target network module are collocated on the same network device, this proposed solution is also can be applied in the scenario that the source network module and the target network module are located on different network devices. In such scenario, the source network module obtains the addition parameters which usually be provided by the target network module 160-2 in the subsequent operations via some external communication from the target network module before transmitting the request for handover. In this way, the messages that needed to be exchanged between the target core network node 110-2 and the target network module 160-2 also can be skipped.

Principle and implementations of the present disclosure will be described in detail below with reference to Fig. 5, which shows a schematic diagram of interactions 500 in accordance with example embodiments of the present disclosure. The interactions 500 may be implemented at any suitable devices. Only for the purpose of illustrations, the interactions 500 are described to be implemented at the terminal device 130, the network device 120 comprising the source network module 160-1 and the target network module 160-2 (collectively referred to as “network module (s) 160) , source core network node 110-1 and target core network node 110-2 (collectively referred to as “core network node (s) 110) T-UPF 170, SMF 171, S-UPF 172 and UPF 173, as illustrated in Fig. 5, during the interactions 500.

It is to be understood that the numbers of terminal devices, core network nodes, network modules, network devices, T-UPFs, SMFs, S-UPFs, and UPFs shown in Fig. 5 are given for the purpose of illustration without suggesting any limitations. The interactions 500 may include any suitable number of terminal devices, core network nodes, network modules, network devices, T-UPFs, SMFs, S-UPFs, and UPFs.

The source network module 160-1 may determine 505 to initiate a handover from the source core network node 110-1 to the target core network node 110-1. In some example embodiment, the determination is based on the satellite’s ephemeris data.

Alternatively, or in addition, the determination is based on configuration information, for example, a scheduling configuration about some starting point for setup SCTP/NGAP with the target core network node 110-2, or a specific location/time to change the connection with the core network. Specifically, the source network module 160-1 may transmit the request for handover at the starting time point or position preconfigured for the handover from the source core network node 110-1 to the target core network node 110-2.

Alternatively, or in addition, the determination is based on whether a resource between the target network module 160-2 and the target core node 110-2 is available, such as, the NGAP interface between the network device 120 and the target core network node 110-2, has been established. Specifically, the source network module 160-1 may transmit the request for handover after the availability of a resource between the target network module and the target core network node.

In this way, the handover for inter-core network node is not based on the measurement report of the terminal device 130. Therefore, it is more flexible to trigger the handover for inter-core network node.

The source network module 160-1 and the target network module 160-2 are collocated on the same network device 120, such that the source network module 160-1 and the target network module 160-2 can share the context of the terminal device 130 (such as RAN UE NGAP ID, PDU session information, and so on) , or exchange 510 the context of the terminal device 130 or other configuration via internal or proprietary communication.

It should be appreciated that

operations

505 and 510 are optional operations. In some other embodiment, the interactions may start at operation 515.

The source network module 160-1 transmits 515 a request for handover from the source core network node 110-1 to the target core network node 110-2, such as HANDOVER REQUIRED message, to the source core network node 110-1. As discussed above, the source network module 160-1 and the target network module 160-2 can share their resource, information and configurations and so on. Therefore, the request for handover may comprise handover assistance information.

In some example, the handover assistance information comprises information about a target radio access network resource allocated by the target network module 160-2, for example, the target downlink (DL) NG-U User Plane (UP) full qualified tunnel endpoint identity (F-TEID) , the DL Forwarding UP Transport Network Layer (TNL) Information used to deliver forwarded DL Protocol Data Units (PDUs) , and other Session Management (SM) N2 information allocated by the target network module 160-2, the security parameters (such as indicates whether UP integrity protection and UP ciphering is performed or not for the concerned PDU session, security capabilities, etc. ) supported in the target network module 160-2. Alternatively, or in addition, the handover assistance information may indicate target network module 160-2 use same resource as source network module 160-1, for example, the target downlink (DL) full qualified tunnel endpoint identity (F-TEID) and other Session Management (SM) N2 information are the same for source network module 160-1 and target network module 160-2.

Alternatively, or in addition, the the handover assistance information may further comprise an indication indicating to the target core network node 110-2 to avoid transmitting a request for the handover resource allocation to target network module 160-2. For example, the handover assistance information comprises a flag “source assisted handover command” to inform the source core network node 110-1 to initiate N2-based handover, and target core network node 110-2 without contacting target network module 160-2. The flag may also indicate the context of the terminal device is shared between the source network module 160-1 and target network module 160-2, therefore no need for target core network node 110-2 contact target network module 160-2 for handover resource allocation.

In this way, since the source network module 160-1 and target network module 160-2 are collocated in the same network device 120, the source network module 160-1 can provide the information about a target radio access network resource on behalf of the target network module 160-2. Such information is usually provided by target network module 160-2 in the handover resource allocation procedure. Therefore, the target network module 160-2 may not transmit the information about a target radio access network resource, such as the target RAN N2 SM information in the subsequent handover resource allocation procedure. This is different to conventional N2-based handover that the handover assistance information is provided to the target core network node 110-2 during the handover procedure, as illustrated in Fig. 3. More Specifically, in the conventional N2-based handover, the target network module 160-2 transmits 360 a message, such as, Handover Request Acknowledge to provide the handover assistance information to the target core network node 110-2 as illustrated in Fig. 3. As discussed above, by this present disclosure, such message has been skipped as illustrated in Fig. 5.

Upon receipt of the request for handover, the source core network node 110-1 selects 520 the target core network node 110-2. Then, the source core network node 110-1 transmits 525 a context request for creating context of the terminal device 130 to the target core network node 110-2 based on the handover assistance information. Specifically, the source core network node 110-1 may transmit a message comprising the handover assistance information, such as, Namf_Communication_CreateUEContext Request, to the target core network node 110-2. Further, the context request may comprise the NGAP UE context information used between the source core network node 110-1 and source network module 160-1, such as, RAN UE NGAP ID (or any other identity to identify the UE in the source network module 160-1) , and so on. Since the context of the terminal device is shared between the source network module 160-1 and target network module 162-0, the RAN UE NGAP ID or any identity to identify the terminal device in the source network module 160-1 can also be reused to identify the terminal device in the target network module 160-2. In case the target network module 160-2 wants to allocate a different identify for the terminal device, this identify is provided to source network module 160-1, which is further provided to the source core network node 110-1 as part of the handover assistance information.

In this way, the handover assistance information which usually be provided by the target network module 160-2 is provided to the target core network node 110-2 by the source network module 160-1, such that the target core network node 110-2 does not need to contact with the target network module 160-2 during the handover procedure.

The target core network node may transmit 530 a Nsmf_PDUSession_UpdateSMContext Request message to the SMF 171. The SMF 171 checks if N2 Handover can be accepted. If the terminal device has moved out of the service area of the UPF 173 connecting to source network module, the SMF 171 selects 532 a new intermediate UPF 173.

The SMF 171 sends 534 N4 Session Modification Request message to UPF 173 and receives 536 a Session Modification Response message from the UPF 173. These two operations are used for N4 session modification. Besides that, The SMF 171 sends 538 N4 Session Establishment Request message to the T-UPF 170 and receives 540 a N4 Session Establishment Response message from the T-UPF 170. These two operations are used for N4 session establishment. The SMF 171 transmits 545 Nsmf_PDUSession_UpdateSMContext Response message to the target core network node. The AMF supervises 550 the Nsmf_PDUSession_UpdateSMContext Response messages from the involved SMFs.

As discussed above, the target core network node 110-2 has obtained the handover assistance information. Based on the handover assistance information, such as, the indication indicating to the target core network node to avoid transmitting a request for the handover resource allocation, the target core network node 110-2 can assume that the same resource is allocated in the target network module 160-2, thus the target core network node 110-2 can simply consider the handover resource allocation is performed, without the interaction with target network module 160-2. As illustrated in Fig. 5, messages exchanges between the target core network node 110-2 and target network module 160-2 (i.e. Handover Request, Handover Request Acknowledge) are skipped. Specifically, the operation of transmitting 555 a Handover Request message from target core network node 110-2 to the target network module 160-2, and the operation of transmitting 560 a Handover Response message from the target network module 160-2 to target core network node 110-2 are skipped.

Further, the target network node 110-2 sends 562 Nsmf_PDUSession_UpdateSMContext Request message to SMF 171. The SMF 171 sends 564 N4 Session Modification Request message to the T-UPF 170 and receives 566 a N4 Session Modification Response message from the T-UPF 170. These two operations are used for N4 session modification. Besides that, the SMF 171 sends 568 N4 Session Modification Request message to S-UPF 172 and receives 570 a N4 Session Modification Response message from the S-UPF 172. These two operations are used for N4 session modification.

It should be noted that the operations 562 to 575 may be optimized by combining the operations the operation 562 to 575 with the operations 530 to 545. For example, the target core network node 110-2 already know the resource allocated in the target network module 160-2 after 525, the core network node 110-2 can use 530 Nsmf_PDUSession_UpdateSMContext Request message to update SM context including the N2 SM information received from the source core network node 110-1, therefore 562 can be skipped and expediate the handover procedure.

Then, the target core network node 110-2 transmits 580 a context response to the source core network node 110-1. The context response comprises an updated context of the terminal device 130.

Specifically, the target core network node 110-2 may transmit a message comprising the updated context, such as, Namf_Communication_CreateUEContext Response, to the source core network node 110-1.

In some example embodiments, the updated context comprises the context of the terminal device 130 updated by the target core network node 110-2, which may include an identity of the terminal device 130, such as, the AMF UE NGAP ID, allocated by the target core network node 110-2. Alternatively, or in addition, the updated context further comprises the UpLink (UL) NG-U User Plane Transport Network Layer (UP TNL) Information which is the UPF endpoint of the NG-U transport bearer for delivery of UL PDUs, the Additional UL NG-U UP which is the UPF endpoint of the additional NG-U transport bearer for delivery of UL PDUs, the new security context (such as security algorithms, keys, etc) , UE Aggregate Maximum Bit Rate, Core Network Assistance Information, New Security Context Indicator, Allowed NSSAI, Mobility Restriction List, etc, to be used in target network module 160-2. Alternatively, the updated context may include an indication indicating no update to the UE context, for example, same context as used in the source network module 160-1.

The source network module 160-1 generates a response for handover including the updated UE context received in the context response, and then transmits 585 the response for handover to the source network module 160-1. Since the source network module 160-1 and the target network module 160-2 are collocated on the same network device 120, the target network module 160-2 can receive the updated context of the terminal device 130 by information obtained from the source network module 160-1 or other mechanism via internal or proprietary communication. This is different to conventional N2-based handover that the updated context is provided to the target network module 160-2 during the handover resource allocation procedure, as illustrated in Fig. 3. More Specifically, in the conventional N2-based handover, the target core network node 110-2 transmits 355 a message, such as, Handover Request to provide the updated context to the target network module 160-2 as illustrated in Fig. 3. As discussed above, by this present disclosure, such message has been skipped.

The source network module 160-1 may transmit 590 a radio handover command based on the updated context to the terminal device 130 to trigger to terminal device 130 to switch from the network module 160-1 to the target network module 160-2.

In some example embodiments, the source network module 160-1 generates the radio handover command comprising a radio resource control (RRC) container based on the updated context. Alternatively, the target network module 160-2 generates the radio handover command and share it with the source network module 160-1.

According to this proposed solution, the number of NGAP messages exchanged between the network device 120 and the core network node 110 are reduced from four messages to two messages. This enables an efficient and fast handover for inter core network node, without causing sudden significant signalling load between the network module 160 on the network device 120, such as satellite, and the core network node 110 on the ground.

Fig. 6 illustrates a flow chart of a method 600 in accordance with example embodiments of the present disclosure. The method 600 may be implemented at any suitable devices, for example. Only for the purpose of illustrations, the method 600 is described to be implemented at the network device 120.

At block 610, the network device 120 may transmit a request for handover from the source core network node 110-1 to a target core network node 110-2. Further, the request comprises handover assistance information which provided by a target network module 160-2 of the network device 120. The source network module 160-1 is connected to the source core network node 110-1, and the network device 120 have a target network module 160-2 to be connected to the target core network node 110-2. The source network module 160-1 and target network module 160-2 are collocated, or can share UE context via internal or proprietary communication.

In some example embodiments, the network device 120 transmits the request at a starting time point or position preconfigured for the handover from the source core network node 110-1 to the target core network node 110-2.

Alternatively, or in addition, the network device 120 transmits the request after the interface between the target network module 160-2 and the target core node 110-2 has been allocated.

In some example embodiments, the handover assistance information comprises at least one of: information about a target radio access network resource such as the N2 SM information allocated by the target network module 160-2, and an indication indicating to the target core network node to avoid transmitting a request for a handover resource allocation.

In some example embodiments, the information about the target radio access network resource allocated by the target network module comprises at least one of: a downlink user plane full qualified tunnel endpoint identity, a downlink forwarding transport network layer information, a security parameter and an indication indicating the target network module to use a same resource as the source network module.

At block 620, the network device 120 receives a response to the request for handover from the source core network node 110-1. The response comprises an updated context to be used in the target network module 160-2 and is generated by the source core network node 110-1 based on the updated context comprised in a context response. The context response is transmitted from the target core network node 110-2 in response to receiving from the source core network node 110-1 a context request generated based on the handover assistance information in the request for handover.

In some example embodiments, the updated context comprises an identity of the terminal device 130 allocated by the target core network node. Alternatively, or in addition, the updated context further comprises a security context to be used by the target network module 160-2 when terminal device 130 connects to target network module 160-2 and the target core network node 110-1.

At block 630, the network device 120 transmits to a terminal device 130 a handover command based on the updated context.

In some example embodiments, the network device 120 generating the handover command comprising a radio resource control container based on the updated context comprised in the response for handover.

Fig. 7 illustrates a flow chart of a method 700 in accordance with example embodiments of the present disclosure. The method 700 may be implemented at any suitable devices. Only for the purpose of illustrations, the method 700 is described to be implemented at the source core network node 110-1.

At block 710, the source core network node 110-1 receives a request for handover from the source core network node 110-1 to a target core network node 110-2 from a network device 120. The request comprises handover assistance information provided by a target network module 160-2 of the network device 120. The source network module 160-1 is connected to the source core network node 110-1, and the network device 120 has a target network module 160-2 to be connected to the target core network node 110-2. The source network module 160-1 and target network module 160-2 are collocated, or can share UE context via internal or proprietary communication.

In some example embodiments, the handover assistance information comprises at least: information about a target radio access network resource such as the N2 SM information allocated by the target network module 160-2, and an indication indicating to the target core network node to avoid transmitting a request for the handover resource allocation.

In some example embodiments, the context of the terminal device in the context request comprises at least one of: a radio access network user equipment next generation application protocol identity, and an identity to identify the terminal device in the target network module.

At block 720, the source core network node 110-1 transmits a context request for creating context of a terminal device 130 to the target core network node 110-2 based on the handover assistance information.

In some example embodiments, the context request comprises the handover assistance information. Alternatively, or in addition, the context request includes the UE context used between the source network module 160-1 and source core network node 110-1, such as, RAN UE NGAP ID, and so on.

At block 730, the source core network node 110-1 receive a context response to the context request, the context response comprising an updated context generated by the target core network node 110-2. The updated context comprises the context of the terminal device 130 updated by the target core network node 110-2, which may include an identity of the terminal device 130, such as, the AMF UE NGAP ID, allocated by the target core network node 110-2. Alternatively, or in addition, the updated context further comprises the new security context, UE Aggregate Maximum Bit Rate, Core Network Assistance Information, New Security Context Indicator, Allowed NSSAI, Mobility Restriction List, etc, to be used in target network module 160-2. At block 740, the source core network node 110-1 transmits to the network device 120 a response to the request for handover based on the updated context.

In some example embodiments, the response to the request for handover comprises at least one of: an identity of the terminal device allocated by the target core network node, an uplink user plane transport network layer information, an additional uplink user plane transport network layer information, a security context for communication between the terminal device and the target network module, and an indication indicating no change to the context of the terminal device.

Fig. 8 illustrates a flow chart of a method 800 in accordance with example embodiments of the present disclosure. The method 800 may be implemented at any suitable devices. Only for the purpose of illustrations, the method 800 is described to be implemented at the target core network node 110-2.

At block 810, the target core network node 110-2 receives from a source core network node 110-1, a context request for creating context of a terminal device 120. The context request comprised handover assistance information and is generated by the source core network node 110-1 based on the handover assistance information in a request transmitted by a source network module 160-1 of a network device 120. The source network module 160-1 is connected to the source core network node 110-1. The network device 120 has a target network module 160-2 to be connected to the target core network node 110-2.

In some example embodiments, the handover assistance information comprises at least one of: information about a target radio access network resource such as the N2 SM information allocated by the target network module 160-2 and an indication indicating to the target core network node to avoid transmitting a request for a handover resource allocation. Alternatively, or in addition, the context request includes the UE context used between the source network module 160-1 and source core network node 110-1.

At block 820, the source core network node 110-2 transmits to the source core network node 110-1 a context response to the context request comprising an updated context of the terminal device 120, such that the the source core network node 110-1 transmits a response for handover based on the updated context to the network device 120.

In some example embodiments, the updated context comprises an identity of the terminal device allocated by the target core network node. Alternatively, or in addition, the updated context further comprises a security context to be used by the target network module when the terminal device connects to the target network module and the target core network node.

In some example embodiments, the apparatus further comprises means for performing other steps in some example embodiments of the method 600. In some example embodiments, the means comprises at least one processor; and at least one memory including computer program code, the at least one memory and computer program code configured to, with the at least one processor, cause the performance of the apparatus.

In some example embodiments, an apparatus capable of performing any of the method 600 (for example, the network device 120) may comprise means for performing the respective steps of the method 600. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

In some example embodiments, the apparatus comprises means for at a network device to a source core network node, a request for handover from the source core network node to a target core network node, the request comprising handover assistance information provided by a source network module of the network device, the source network module obtaining the handover assistance information from a target network module; means for receiving a response to the request for handover from the source core network node, the response for handover comprising an updated context to be used in the target network module; and means for transmitting a handover command based on the updated context to a terminal device.

In some example embodiments, the means for transmitting the request for handover comprises: means for transmitting the request for handover at a starting time point or a position preconfigured for the handover from the source core network node to the target core network node; or means for transmitting the request for handover after the availability of a resource between the target network module and the target core network node.

In some example embodiments, the handover assistance information comprises at least: information about a target radio access network resource allocated by the target network module and indicating to the target core network node to avoid transmitting a request for the handover resource allocation.

In some example embodiments, the updated context comprises at least one of: an identity of the terminal device allocated by the target core network node, an uplink user plane transport network layer information, an additional uplink user plane transport network layer information, a security context for communication between the terminal device and the target network module, and an indication indicating no change to the context of the terminal device.

In some example embodiments, the means for transmitting the handover command comprises means for generating the handover command comprising a radio resource control container based on the updated context comprised in the response for handover.

In some example embodiments, the apparatus further comprises means for performing other steps in some example embodiments of the method 700. In some example embodiments, the means comprises at least one processor; and at least one memory including computer program code, the at least one memory and computer program code configured to, with the at least one processor, cause the performance of the apparatus.

In some example embodiments, an apparatus capable of performing any of the method 700 (for example, the core network node 110-1) may comprise means for performing the respective steps of the method 700. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

In some example embodiments, the apparatus comprises means for receiving, at a source core network node from a network device a request for handover from the source core network node to a target core network node, the request for handover comprising handover assistance information provided by a source network module of the network device, the source network module being connected to the source core network node, the network device having a target network module to be connected to the target core network node; means for transmitting a context request for creating context of a terminal device to the target core network node based on the handover assistance information; means for receiving a context response to the context request from the target core network node, the context response comprising an updated context; and means for transmitting to a response for handover to the request for handover based on the updated context to the network device.

In some example embodiments, the handover assistance information comprises at least: information about a target radio access network resource allocated by the target network module and an indication indicating to the target core network node to avoid transmitting a request for a handover resource allocation.

In some example embodiments, the updated context comprises at least one of: an identity of the terminal device allocated by the target core network node, and a security context to be used by the target network module when the terminal device connects to the target network module and the target core network node.

In some example embodiments, the apparatus further comprises means for performing other steps in some example embodiments of the method 800. In some example embodiments, the means comprises at least one processor; and at least one memory including computer program code, the at least one memory and computer program code configured to, with the at least one processor, cause the performance of the apparatus.

In some example embodiments, an apparatus capable of performing any of the method 800 (for example, the core network node 110-2) may comprise means for performing the respective steps of the method 800. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

In some example embodiments, the apparatus comprises means for receiving, at a target core network node from a source core network node, a context request for creating context of a terminal device, the context request comprising handover assistance information obtained from a request for handover transmitted by a source network module of a network device, the source network module being connected to the source core network node, the network device having a target network module to be connected to the target core network node; and means for transmitting to a context response to the context request comprising an updated context of the terminal device to the source core network node.

In some example embodiments, the handover assistance information at least comprises at least one of: information about a target radio access network resource allocated by the target network module, and an indication indicating to the target core network node to avoid transmitting a request for a handover resource allocation.

Fig. 9 is a simplified block diagram of a device 900 that is suitable for implementing example embodiments of the present disclosure. The device 900 may be provided to implement the communication device, for example the core network node 110 or the network device 120 as shown in Fig. 1. As shown, the device 900 includes one or more processors 910, one or more memories 940 coupled to the processor 910, and one or more transmitters and/or receivers (TX/RX) 940 coupled to the processor 910.

The TX/RX 940 is for bidirectional communications. The TX/RX 940 has at least one antenna to facilitate communication. The communication interface may represent any interface that is necessary for communication with other network elements.

The processor 910 may be of any type suitable to the local technical network and may include one or more of the following: general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multicore processor architecture, as non-limiting examples. The device 900 may have multiple processors, such as an application specific integrated circuit chip that is slaved in time to a clock which synchronizes the main processor.

The memory 920 may include one or more non-volatile memories and one or more volatile memories. Examples of the non-volatile memories include, but are not limited to, a Read Only Memory (ROM) 924, an electrically programmable read only memory (EPROM) , a flash memory, a hard disk, a compact disc (CD) , a digital video disk (DVD) , and other magnetic storage and/or optical storage. Examples of the volatile memories include, but are not limited to, a random access memory (RAM) 922 and other volatile memories that will not last in the power-down duration.

A computer program 930 includes computer executable instructions that are executed by the associated processor 910. The program 930 may be stored in the ROM 1020. The processor 910 may perform any suitable actions and processing by loading the program 930 into the RAM 920.

The example embodiments of the present disclosure may be implemented by means of the program 930 so that the device 900 may perform any process of the disclosure as discussed with reference to Figs. 4 to 8. The example embodiments of the present disclosure may also be implemented by hardware or by a combination of software and hardware.

In some example embodiments, the program 930 may be tangibly contained in a computer readable medium which may be included in the device 900 (such as in the memory 920) or other storage devices that are accessible by the device 900. The device 900 may load the program 930 from the computer readable medium to the RAM 922 for execution. The computer readable medium may include any types of tangible non-volatile storage, such as ROM, EPROM, a flash memory, a hard disk, CD, DVD, and the like. Fig. 10 shows an example of the computer readable medium 1000 in form of CD or DVD. The computer readable medium has the program 930 stored thereon.

Generally, various example embodiments of the present 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 example embodiments of the present disclosure are illustrated and described as block diagrams, flowcharts, or using some other pictorial representations, it is to be understood that the block, apparatus, system, technique or method 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 includes computer-executable instructions, such as those included in program modules, being executed in a device on a target real or virtual processor, to carry out the method 600 to method 800 as described above with reference to Figs. 6-8. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, or the like 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 example embodiments. Machine-executable instructions for program modules may be executed within a local or distributed device. In a distributed device, program modules may be located in both local and remote storage media.

Program code for carrying out 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/operations specified in the flowcharts and/or block diagrams to be implemented. The program code may execute entirely on a 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, the computer program codes or related data may be carried by any suitable carrier to enable the device, apparatus or processor to perform various processes and operations as described above. Examples of the carrier include a signal, computer readable medium, and the like.

The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable medium may include but not limited to an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of the computer readable storage medium would 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) , an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

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 certain circumstances, multitasking and parallel processing may be advantageous. Likewise, while several specific implementation details are contained in the above discussions, these should not be construed as limitations on the scope of the present 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 may also be implemented in combination in a single example embodiment. Conversely, various features that are described in the context of a single example embodiment may also be implemented in multiple example embodiments separately or in any suitable sub-combination.

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

Claims

A method, comprising:

transmitting, at a network device to a source core network node, a request for handover from the source core network node to a target core network node, the request for handover comprising handover assistance information provided by a source network module of the network device, the source network module obtaining the handover assistance information from a target network module;

receiving a response to the request for handover from the source core network node, the response comprising an updated context to be used in the target network module; and

transmitting, based on the updated context, a radio handover command to a terminal device.
The method of claim 1, wherein transmitting the request for handover comprises:

transmitting the request for handover at a starting time point or a position preconfigured for the handover from the source core network node to the target core network node, or

transmitting the request for handover after availability of a resource between the target network module and the target core network node.
The method of claim 1, wherein the handover assistance information comprises at least one of:

information about a target radio access network resource allocated by the target network module, and

an indication indicating to the target core network node to avoid transmitting a request for a handover resource allocation.
The method of claim 3, wherein the information about the target radio access network resource allocated by the target network module comprises at least one of:

a downlink user plane full qualified tunnel endpoint identity,

a downlink forwarding transport network layer information,

a security parameter, and

an indication that indicating the target network module to use a same resource as the source network module.
The method of claim 1, wherein the updated context comprises at least one of:

an identity of the terminal device allocated by the target core network node,

an uplink user plane transport network layer information,

an additional uplink user plane transport network layer information,

a security context for communication between the terminal device and the target network module, and

an indication indicating no change to the context of the terminal device.
The method of claim 1, further comprising:

generating the radio handover command comprising a radio resource control container based on the updated context comprised in the response for handover.
A method, comprising:

receiving, at a source core network node from a network device a request for handover from the source core network node to a target core network node, the request for handover comprising handover assistance information provided by a source network module of the network device, the source network module obtaining the handover assistance information from a target network module;

transmitting a context request for creating context of a terminal device to the target core network node based on the handover assistance information, the context request including the handover assistance information and a context of the terminal device;

receiving a context response to the context request from the target core network node, the context response comprising an updated context of the terminal device; and

transmitting a response to the request for handover based on the updated context to the network device.
The method of claim 7, wherein the handover assistance information comprises at least one of:

information about a target radio access network resource allocated by the target network module, and

an indication indicating to the target core network node to avoid transmitting a request for a handover resource allocation.
The method of claim 8, wherein the information about the target radio access network resource allocated by the target network module comprises at least one of:

a downlink user plane full qualified tunnel endpoint identity,

a downlink forwarding transport network layer information,

a security parameter, and

an indication indicating the target network module to use a same resource as the source network module.
The method of claim 7, wherein the context of the terminal device in the context request comprises at least one of: a radio access network user equipment next generation application protocol identity, and an identity to identify the terminal device in the target network module.
The method of claim 7, wherein the updated context comprises at least one of:

an identity of the terminal device allocated by the target core network node, and

an uplink user plane transport network layer information,

an additional uplink user plane transport network layer information,

a security context for communication between the terminal device and the target network module, and

an indication indicating no change to the context of the terminal device.
The method of claim 7, wherein the response to the request for handover comprises at least one of:

an identity of the terminal device allocated by the target core network node, and

an uplink user plane transport network layer information,

an additional uplink user plane transport network layer information,

a security context for communication between the terminal device and the target network module, and

an indication indicating no change to the context of the terminal device.
A method, comprising:

receiving, at a target core network node from a source core network node, a context request for creating context of a terminal device, the context request comprising handover assistance information obtained from a request for handover transmitted by a source network module of a network device, the source network module obtaining the handover assistance information from a target network module; and

transmitting a context response to the context request comprising an updated context of the terminal device to the source core network node.
The method of claim 13, wherein the handover assistance information comprises at least one of:

information about a target radio access network resource allocated by the target network module, and

an indication indicating to the target core network node to avoid transmitting a request for the handover resource allocation.
The method of claim 14, wherein the information about the target radio access network resource allocated by the target network module comprises at least one of:

a downlink user plane full qualified tunnel endpoint identity,

a downlink forwarding transport network layer information,

a security parameter, and

an indication indicating the target network module to use a same resource as the source network module.
The method of claim 13, wherein the context request comprises at least one of: a radio access network user equipment next generation application protocol identity, and an identity to identify the terminal device in the target network module.
The method of claim 13, wherein the updated context comprises at least one of:

an identity of the terminal device allocated by the target core network node,

an uplink NG-U user plane transport network layer information,

an additional uplink NG-U user plane transport network layer information,

a security context to be used by the target network module when the terminal device connects to the target network module and the target core network node, and

an indication indicating no change to the context of the terminal device.
A device, comprising:

at least one processor; and

at least one memory including computer program codes;

the at least one memory and the computer program codes are configured to, with the at least one processor, cause the device to perform the method of any of claims 1-6.
A device, comprising:

at least one processor; and

at least one memory including computer program codes;

the at least one memory and the computer program codes are configured to, with the at least one processor, cause the device to perform the method of any of claims 7-12.
A device, comprising:

at least one processor; and

at least one memory including computer program codes;

the at least one memory and the computer program codes are configured to, with the at least one processor, cause the device to perform the method of any of claims 13-17.
A computer readable storage medium comprising program instructions stored thereon, the instructions, when executed by a processor of a device, causing the device to perform the method of any of claims 1-6.
A computer readable storage medium comprising program instructions stored thereon, the instructions, when executed by a processor of a device, causing the device to perform the method of any of claims 7-12.
A computer readable storage medium comprising program instructions stored thereon, the instructions, when executed by a processor of a device, causing the device to perform the method of any of claims 13-17.
An apparatus, comprising:

means for transmitting, at a network device to a source core network node, a request for handover from the source core network node to a target core network node, the request for handover comprising handover assistance information provided by a source network module of the network device, the source network module obtaining the handover assistance information from a target network module;

means for receiving a response to the request for handover from the source core network node, the response comprising an updated context to be used in the target network module; and

means for transmitting, based on the updated context, a radio handover command to a terminal device.
An apparatus, comprising:

means for receiving, at a source core network node from a network device a request for handover from the source core network node to a target core network node, the request for handover comprising handover assistance information provided by a source network module of the network device, the source network module obtaining the handover assistance information from a target network module;

means for transmitting a context request for creating context of a terminal device to the target core network node based on the handover assistance information, the context request including the handover assistance information and a context of the terminal device;

means for receiving a context response to the context request from the target core network node, the context response comprising an updated context; and

means for transmitting a response to the request for handover based on the updated context to the network device.
An apparatus, comprising:

means for receiving, at a target core network node from a source core network node, a context request for creating context of a terminal device, the context request comprising handover assistance information obtained from a request for handover transmitted by a source network module of a network device, the source network module obtaining the handover assistance information from a target network module; and

means for transmitting a context response to the context request comprising an updated context of the terminal device to the source core network node.