WO2025091470A1

WO2025091470A1 - Enhancements to handover

Info

Publication number: WO2025091470A1
Application number: PCT/CN2023/129630
Authority: WO
Inventors: Basavaraj KIRAGI; Shubhranshu Singh; Yuan Sheng QIAN; Rainer Liebhart; Sean Kelley
Original assignee: Nokia Shanghai Bell Co Ltd; Nokia Solutions and Networks Oy; Nokia Technologies Oy
Current assignee: Nokia Shanghai Bell Co Ltd; Nokia Solutions and Networks Oy; Nokia Technologies Oy
Priority date: 2023-11-03
Filing date: 2023-11-03
Publication date: 2025-05-08
Anticipated expiration: 2026-05-03

Abstract

Example embodiments of the present disclosure relate to enhancements to a terminal device handover. In an aspect, during a handover from a first cell of a first access network to a second cell of a second access network, a second core network receives from a first core network, a first closed group identity (ID) of the first cell; and determines, based on the first closed group ID, a second closed group ID which is associated with the other one of the CSG ID or the CAG ID. In this way, the second closed group ID is to be used by the target cell, and the access control from the first cell to the second cell can be achieved by the second core network based on the second closed group ID and the related subscription information.

Description

ENHANCEMENTS TO HANDOVER

FIELD

Various example embodiments relate to the field of communication and in particular, to devices, methods, apparatuses and computer readable storage media for enhancements to a terminal device handover.

BACKGROUND

With the development of communication technology, in Release-19, a study item on Femto support in fifth generation (5G) communication networks was proposed. In Long Term Evolution (LTE) Femto networks, the closed subscriber group (CSG) designates a set of authorized users allowed access to specific CSG cells within a public land mobile network (PLMN) through designated CSG identities (IDs) . In 5G, the closed access group (CAG) serves a similar purpose, granting specific subscribers access to designated CAG cells associated with CAG IDs. However, there are still some issues related to cells in communication networks, especially Femto cells in 4G, 5G, or the like, which need to be further studied and addressed.

SUMMARY

In general, example embodiments of the present disclosure provide a solution for improving or enhancing handover of the terminal device between two cellular types.

In a first aspect, there is provided a second core network. The second core network may comprise: at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the second core network at least to perform: during a handover of a device from a first cell of a first access network to a second cell of a second access network, receiving, from a first core network associated with the first access network, a first closed group identity (ID) of the first cell, wherein the first cell belongs to one of a closed subscriber group (CSG) or a closed access group (CAG) , the second cell belongs to the other one of the CSG or the CAG, and the first closed group ID is associated with the one of the CSG or the CAG; and determining, based on the first closed group ID, a second closed group ID which is associated with the other one of the CSG ID or the CAG ID.

In a second aspect, there is provided a first access network. The first access network may comprise: at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the first access network at least to perform: during a handover for a device from a first cell of the first access network to a second cell of a second access network, determining a closed group identity (ID) of the second cell based on a cell ID of the second cell, wherein the first cell belongs to one of a closed subscriber group (CSG) or a closed access group (CAG) , and the second cell belongs to the other one of the CSG or the CAG; and transmitting, to a first core network, the closed group ID of the second cell.

In a third aspect, there is provide a device. The device may comprise: at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the device at least to perform: during a handover of the device from a first cell of a first access network to a second cell of a second access network, obtaining a closed group identity (ID) of the second cell, wherein the first cell belongs to one of a closed subscriber group (CSG) or a closed access group (CAG) , and the second cell belongs to the other one of the CSG or the CAG; and transmitting, to the first access network, a measurement report including the closed group ID of the second cell.

In a fourth aspect, there is provided a second core network. The second core network may comprise: at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the second core network at least to perform during a handover of a device from a first cell of a first access network to a second cell of a second access network, receiving, from a first core network associated with the first access network, a closed group identity (ID) of the first cell, wherein the first cell belongs to one of a closed subscriber group (CSG) or a closed access group (CAG) , and the second cell belongs to the other one of the CSG or the CAG; based on receiving the closed group ID of the first cell, obtaining, from a network function, a list of allowed closed group IDs of the device associated with the other one of the CSG or the CAG; and transmitting the list of allowed closed group IDs to the second access network.

In a fifth aspect, there is provided a method implemented at a second core network. The method may comprise: during a handover of a device from a first cell of a first access network to a second cell of a second access network, receiving, from a first core network associated with the first access network, a first closed group identity (ID) of the first cell, wherein the first cell belongs to one of a closed subscriber group (CSG) or a closed access group (CAG) , the second cell belongs to the other one of the CSG or the CAG, and the first closed group ID is associated with the one of the CSG or the CAG; and determining, based on the first closed group ID, a second closed group ID which is associated with the other one of the CSG ID or the CAG ID.

In a sixth aspect, there is provided a method implemented at a first access network. The method may comprise: during a handover for a device from a first cell of the first access network to a second cell of a second access network, determining a closed group identity (ID) of the second cell based on a cell ID of the second cell, wherein the first cell belongs to one of a closed subscriber group (CSG) or a closed access group (CAG) , and the second cell belongs to the other one of the CSG or the CAG; and transmitting, to a first core network, the closed group ID of the second cell.

In a seventh aspect, there is provided a method implemented at a device. The method may comprise during a handover of the device from a first cell of a first access network to a second cell of a second access network, obtaining a closed group identity (ID) of the second cell, wherein the first cell belongs to one of a closed subscriber group (CSG) or a closed access group (CAG) , and the second cell belongs to the other one of the CSG or the CAG; and transmitting, to the first access network, a measurement report including the closed group ID of the second cell.

In an eighth aspect, there is provided a method implemented at a second core network. The method may comprise during a handover of a device from a first cell of a first access network to a second cell of a second access network, receiving, from a first core network associated with the first access network, a closed group identity (ID) of the first cell, wherein the first cell belongs to one of a closed subscriber group (CSG) or a closed access group (CAG) , and the second cell belongs to the other one of the CSG or the CAG; based on receiving the closed group ID of the first cell, obtaining, from a network function, a list of allowed closed group IDs of the device associated with the other one of the CSG or the CAG; and transmitting the list of allowed closed group IDs to the second access network.

In a ninth aspect, there is provided an apparatus. The apparatus may comprises: means for during a handover of a device from a first cell of a first access network to a second cell of a second access network, receiving, from a first core network associated with the first access network, a first closed group identity (ID) of the first cell, wherein the first cell belongs to one of a closed subscriber group (CSG) or a closed access group (CAG) , the second cell belongs to the other one of the CSG or the CAG, and the first closed group ID is associated with the one of the CSG or the CAG; and means for determining, based on the first closed group ID, a second closed group ID which is associated with the other one of the CSG ID or the CAG ID.

In a tenth aspect, there is provided an apparatus. The apparatus may comprises: means for during a handover for a device from a first cell of the first access network to a second cell of a second access network, determining a closed group identity (ID) of the second cell based on a cell ID of the second cell, wherein the first cell belongs to one of a closed subscriber group (CSG) or a closed access group (CAG) , and the second cell belongs to the other one of the CSG or the CAG; and means for transmitting, to a first core network, the closed group ID of the second cell.

In an eleventh aspect, there is provided an apparatus. The apparatus may comprises: means for during a handover of the device from a first cell of a first access network to a second cell of a second access network, obtaining a closed group identity (ID) of the second cell, wherein the first cell belongs to one of a closed subscriber group (CSG) or a closed access group (CAG) , and the second cell belongs to the other one of the CSG or the CAG; and means for transmitting, to the first access network, a measurement report including the closed group ID of the second cell.

In a twelfth aspect, there is provided an apparatus. The apparatus may comprises: means for during a handover of a device from a first cell of a first access network to a second cell of a second access network, receiving, from a first core network associated with the first access network, a closed group identity (ID) of the first cell, wherein the first cell belongs to one of a closed subscriber group (CSG) or a closed access group (CAG) , and the second cell belongs to the other one of the CSG or the CAG; means for based on receiving the closed group ID of the first cell, obtaining, from a network function, a list of allowed closed group IDs of the device associated with the other one of the CSG or the CAG; and means for transmitting the list of allowed closed group IDs to the second access network.

In a thirteenth aspect, there is provided a non-transitory computer readable medium comprising program instructions that, when executed by an apparatus, cause the apparatus at least to perform at least the method according to any one of the above fifth to eighth aspects.

In a fourteenth aspect, there is provided a computer program comprising instructions, which, when executed by an apparatus, cause the apparatus at least to perform the method according to any one of the above fifth to eighth aspects.

In a fifteenth aspect, there is provided a second core network. The second core network comprises: a receiving circuitry configured to during a handover of a device from a first cell of a first access network to a second cell of a second access network, receive , from a first core network associated with the first access network, a first closed group identity (ID) of the first cell, wherein the first cell belongs to one of a closed subscriber group (CSG) or a closed access group (CAG) , the second cell belongs to the other one of the CSG or the CAG, and the first closed group ID is associated with the one of the CSG or the CAG; and a determining circuitry configured to determine, based on the first closed group ID, a second closed group ID which is associated with the other one of the CSG ID or the CAG ID.

In a sixteenth aspect, there is provided a first access network. The first access network may comprise: a determining circuitry configured to during a handover for a device from a first cell of the first access network to a second cell of a second access network, determine a closed group identity (ID) of the second cell based on a cell ID of the second cell, wherein the first cell belongs to one of a closed subscriber group (CSG) or a closed access group (CAG) , and the second cell belongs to the other one of the CSG or the CAG; and a transmitting circuitry configured to transmit, to a first core network, the closed group ID of the second cell.

In a seventeenth aspect, there is provide a device. The device may comprise: a obtaining circuitry configured to during a handover of the device from a first cell of a first access network to a second cell of a second access network, obtain a closed group identity (ID) of the second cell, wherein the first cell belongs to one of a closed subscriber group (CSG) or a closed access group (CAG) , and the second cell belongs to the other one of the CSG or the CAG; and a transmitting circuitry configured to transmit, to the first access network, a measurement report including the closed group ID of the second cell.

In an eighteenth aspect, there is provided a second core network. The second core network may comprise: a receiving circuitry configured to during a handover of a device from a first cell of a first access network to a second cell of a second access network, receive, from a first core network associated with the first access network, a closed group identity (ID) of the first cell, wherein the first cell belongs to one of a closed subscriber group (CSG) or a closed access group (CAG) , and the second cell belongs to the other one of the CSG or the CAG; a obtaining circuitry configured to obtain from a network function, based on receiving the closed group ID of the first cell, a list of allowed closed group IDs of the device associated with the other one of the CSG or the CAG; and a transmitting circuitry configured to transmit the list of allowed closed group IDs to the second access network.

It is to be understood that the summary section is not intended to identify key or essential features of 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, in which:

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

Fig. 2 illustrates a signal process for UE handover from the LTE cell to 5G cell;

Fig. 3A illustrates an example signaling process for enhancing UE handover between 5G CAG cell and LTE CSG cell in accordance with some embodiments of the present disclosure;

Fig. 3B illustrates an example signal process for enhancing UE handover between 5G CAG cell and LTE CSG cell in accordance with some embodiments of the present disclosure;

Fig. 4 illustrates an example signal process for enhancing UE handover between 5G CAG cell and LTE CSG cell in accordance with some embodiments of the present disclosure;

Fig. 5 illustrates an example signal process for enhancing UE handover between 5G CAG cell and LTE CSG cell in accordance with some embodiments of the present disclosure;

Fig. 6 illustrates an example signal process for enhancing UE handover between 5G CAG cell and LTE CSG cell in accordance with some embodiments of the present disclosure;

Fig. 7 illustrates an example signal process for enhancing UE handover between 5G CAG cell and LTE CSG cell in accordance with some embodiments of the present disclosure;

Fig. 8A illustrates an example signal process for enhancing UE handover from LTE CSG cell to 5G CAG cell in accordance with some embodiments of the present disclosure;

Fig. 8B illustrates an example signal process for enhancing UE handover from LTE CSG cell to 5G CAG cell in accordance with some embodiments of the present disclosure;

Fig. 9 illustrates an example signal process for enhancing UE handover from LTE CSG cell to 5G CAG cell in accordance with some embodiments of the present disclosure;

Fig. 10 illustrates an example signal process for enhancing UE handover from LTE CSG cell to 5G CAG cell in accordance with some embodiments of the present disclosure;

Fig. 11 illustrates an example signal process for enhancing UE handover from LTE CSG cell to 5G CAG cell in accordance with some embodiments of the present disclosure;

Fig. 12 illustrates an example signal process for enhancing UE handover from LTE CSG cell to 5G CAG cell in accordance with some embodiments of the present disclosure;

Fig. 13 illustrates a flowchart of an example method implemented at a second core network in accordance with some other embodiments of the present disclosure;

Fig. 14 illustrates a flowchart of an example method implemented at a first access network in accordance with some other embodiments of the present disclosure;

Fig. 15 illustrates a flowchart of an example method implemented at a terminal device 110 in accordance with some other embodiments of the present disclosure;

Fig. 16 illustrates a flowchart of an example method implemented at a second core network in accordance with some other embodiments of the present disclosure;

Fig. 17 illustrates a simplified block diagram of a device that is suitable for implementing some embodiments of the present disclosure; and

Fig. 18 illustrates a block diagram of an example of a computer-readable medium in accordance with some embodiments of the present disclosure.

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

DETAILED DESCRIPTION

Principles of the present disclosure will now be described with reference to some example embodiments. It is to be understood that these 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 may 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 embodiment, ” “an embodiment, ” “an example embodiment, ” and the like indicate that the embodiment described may include a particular feature, structure, or characteristic, but it is not necessary that every embodiment includes the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an 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 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 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 “includes” , “including” , “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 herein, “at least one of the following: <a list of two or more elements>” and “at least one of <a list of two or more elements>” and similar wording, where the list of two or more elements are joined by “and” or “or” , mean at least any one of the elements, or at least any two or more of the elements, or at least all the elements.

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. 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.

As used herein, the term “network device” or “network” refers to a node in a communication network via which a terminal device accesses the network and receives services therefrom. The network device may refer to a base station (BS) or an access point (AP) , for example, a node B (NodeB or NB) , an evolved NodeB (eNodeB or eNB) , a NR NB (also referred to as a gNB) , 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, depending on the applied terminology and technology.

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 Internet 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.

As mentioned above, in Release-19, a study item on Femto support in 5G was proposed. In LTE Femto networks, the CSG designates a set of authorized users allowed access to specific CSG cells within a PLMN through designated CSG IDs. A CSG cell is a cell broadcasting one or several CSG IDs. A base station hosting CSG cells is called a Home eNode B (HeNB) or 4G/LTE Femto base station. That is to say, these cells are managed by HeNBs or 4G/LTE Femto base stations. Membership in CSG is defined in user subscriptions and UE settings. When a UE attempts connection to a CSG cell, the mobility management entity of the network verifies access rights based on subscription data, that is to say, whether the UE is allowed to do so considering the subscription data.

In 5G, the CAG serves a similar purpose, granting specific subscribers access to designated CAG cells associated with CAG IDs. That is to say, a CAG identifies a group of subscribers who are permitted/allowed to access one or more CAG cells associated to the CAG ID. A CAG cell is a cell broadcasting one or several CAG IDs. A base station hosting CAG cells is called a home gNode B (HgNB) or 5G Femto base station. That is to say, these cells are managed by Home gNode B (HgNBs) or 5G Femto base stations. The CAG concept is like the CSG concept in LTE but was originally introduced in the context of PNI-NPNs to prevent UE (s) , which are not allowed to access the NPN via the associated cell (s) , from automatically selecting and accessing the associated CAG cell (s) . CAG based access control was introduced in 3GPP Release-16. That is to say, as introduced in 3GPP Release-16, the CAG concept, akin to CSG, emerged within Public Network Integrated Non-Public Network (PNI-NPN) contexts to prevent unauthorized UEs from accessing associated CAG cells, ensuring controlled network access. In the present disclosure, it is assumed that the CAG concept as defined for PNI-NPN is re-used for 5G Femto deployments enabling Femto access control in 5G. This assumption allows to minimize the effort in 3GPP and is already hinted to in the study item proposals that were submitted to SA, SA2 and RAN plenary.

The proposed study item (SWS-230037) in Release-19 addressing Femto support within the 5G framework acknowledges the necessity to accommodate subscribers accessing 5G Femto cells and the management of access control by the CAG owner or authorized administrators. The integration of 5G Femto within the existing ecosystem requires addressing access control complexities, potentially leveraging concepts like the CSG Subscriber Server (CSS) from EPS (evolved packet system) .

The introduction of 5G Femto in R19 necessitates the consideration of mobility between CSG cells of LTE and CAG cells of 5G. This is particularly crucial in scenarios where enterprises incrementally overlay 5G Femto onto LTE Femto deployments, requiring seamless handover mechanisms for UEs transitioning between the two cellular types. Therefore, the challenge of enabling seamless mobility between LTE CSG cells and 5G CAG cells also emerges. With the gradual introduction of 5G Femto over LTE Femto deployments, a solution for smooth handover between CSG and CAG cells becomes crucial.

In view of above discussions and analysis, there is provided a solution for improving or enhancing UE handover, particularly for enhancing seamless handover mechanisms for UEs transitioning between the two cellular types. In some example embodiments of the present disclosure, the second core network receives from a first core network associated with the first access network, a first closed group identity (ID) of the first cell, wherein the first cell belongs to one of a closed subscriber group (CSG) or a closed access group (CAG) , the second cell belongs to the other one of the CSG or the CAG, and the first closed group ID is associated with the one of the CSG or the CAG, and then the second core network. The second core network further determines, based on the first closed group ID, a second closed group ID which is associated with the other one of the CSG ID or the CAG ID. In this way, the determined second closed group ID is to be used by the target cell, and the access control from the first cell to the second cell can be achieved by the second core network based on the second closed group ID and the related subscription information.

For illustrative purposes, principle and example embodiments of the present disclosure for enhancing UE handover will be described below. However, it should be noted that these embodiments are given to enable the skilled in the art to understand inventive concepts of the present disclosure and implement the solution as proposed herein, and not intended to limit scope of the present disclosure in any way.

Fig. 1 illustrates an example network environment 100 in which example embodiments of the present disclosure may be implemented. The environment 100, which may be a part of a communication network, includes terminal devices and network devices. As illustrated in Fig. 1, the communication network 100 may include a terminal device 110 (hereinafter may also be referred to as a user equipment 110 or a UE 110) . The communication network 100 may further include a first access network 120, a second access network 130. The terminal device 110 may establish a radio link to the first access network 120 and the second access network 130 by using a dual connectivity (DC) technology or a multi-connectivity technology. The first access network 120 (hereinafter, also referred as to a source access network) may be, for example, a serving or source base station, and the serving cell is a cell configured by a network for the terminal device to perform uplink and downlink transmission. The second access network 130 (hereinafter, also referred as to a target access network) may be, for example, a target base station to be connected by the UE 110. The operating frequency band change or switch is realized by a handover (HO) procedure. The HO procedure will trigger the switch of both the UL and DL of a terminal device from a source access network to a target access network.

As illustrated in Fig. 1, the source access network 120 serve respective areas 120-1, 120-2 (also called as cells 120-1, 120-2, the portion of the source access network utilize to serve a respective area also referred to as a cell herein) using different frequency bands in both DL and UL. These source cells, for example, cells 120-1 and 120-2, may form one of a closed subscriber group (CSG) and a closed access group (CAG) . Similarly, the target access network 130 serve respective areas 130-1, 130-2 (also called as cells 130-1, 130-2) using different frequency bands in both DL and UL. These target cells, for example, cells 130-1 and 130-2, may form the other of the CSG and the CAG. That is to say, the source cell 120-1 or 120-2 belongs to one of the CSG and the CAG, and the target cell 130-1 or 130-2 belongs to the other of the CSG and the CAG.

As illustrated in Fig. 1, the communication network 100 may also include a first core network 140 for the source access network 120, and the first core network 140 may comprise an element 140-1 and an element 140-2. The communication network 100 may also include a second core network 150 for the target access network 130, and the second core network 150 may comprises an element 150-1 and an element 150-2. If the source access network 120 is a LTE CSG cell, the first core network 140 may include a mobility management entity (MME) as the element 140-1, and a home subscriber server (HSS) as the element 140-2, and if the target access network 130 is a 5G CAG cell, the second core network 150 may include an access and mobility management function (AMF) as the element 150-1, and a unified data management (UDM) as the element 150-2, and vice versa. N26 interface is the interface between 4G core network and 5G core network (between MME and AMF) and used for 4G and 5G interoperability.

It is to be understood that the number of network devices and terminal devices is given only for the purpose of illustration without suggesting any limitations. The system 100 may include any suitable number of network devices and/or terminal devices adapted for implementing embodiments of the present disclosure. Although not shown, it would be appreciated that one or more terminal devices may be located in the environment 100.

Communications in the network environment 100 may be implemented according to any proper communication protocol (s) , comprising, but not limited to, the third generation (3G) , the fourth generation (4G) , the fifth generation (5G) or beyond, wireless local network communication protocols such as institute for electrical and electronics engineers (IEEE) 802.11 and the like, and/or any other protocols currently known or to be developed in the future. Moreover, the communication may utilize any proper wireless communication technology, comprising but not limited to: multiple-input multiple-output (MIMO) , orthogonal frequency division multiplexing (OFDM) , time division multiplexing (TDM) , frequency division multiplexing (FDM) , code division multiplexing (CDM) , Bluetooth, ZigBee, and machine type communication (MTC) , enhanced mobile broadband (eMBB) , massive machine type communication (mMTC) , ultra-reliable low latency communication (URLLC) , carrier aggregation (CA) , dual connection (DC) , and new radio unlicensed (NR-U) technologies.

Hereinafter, a signal process 200 for UE handover from the LTE cell to 5G cell will be described with reference to Fig. 2.

For the purpose of discussion, the process 200 may be described with reference to Fig. 1. Process 200 illustrates the phase of the Single Registration-based Interworking from EPS to 5GS procedure.

As shown in Fig. 2, at step 1, the evolved universal terrestrial radio access network (E-UTRAN) performs the handover initiation. At step 2, the E-UTRAN transmits a handover required message to MME. At step 3, the MME transmits a Forward Relocation request message over N26 interface to the initial AMF. At step 4, the initial AMF invokes the Nsmf_PDUSession_CreateSMContext service operation (UE Evolved Packet System (EPS) packet data network (PDN) Connection, initial AMF ID, data Forwarding information, Target ID) on the Session Management Function (SMF) and indicates HO Preparation Indication (to avoid switching the UP path) . The initial AMF ID uniquely identifies the initial AMF serving the UE.

At step 5, if dynamic PCC is deployed, the SMF+ PGW (PDN gateway) -C (default V-SMF via H-SMF for home-routed scenario) may initiate SMF initiated SM Policy Modification towards the policy control function (PCF) . At step 6, the SMF+PGW-C requests the PGW-U+UPF (user plane function) to allocate the CN Tunnel Info for PDU Session. At step 7, the SMF+PGW-C sends a Nsmf_PDUSession_CreateSMContext Response to the initial AMF. At step 8, for home-routed roaming scenario only, the default V-SMF selects a default v-UPF and initiates an N4 Session Establishment procedure with the selected default v-UPF. At step 8a, based on the received S-NSSAI from the SMF+PGW-C, the initial AMF may reselect a target AMF, and invokes Namf_Communication_CreateUEContext request to the selected target AMF.

At step 9, the target AMF sends a Handover Request message to the NG-RAN (Next Generation RAN) . At step 10, the NG-RAN sends a Handover Request Acknowledge message to the target AMF. At step 11, the target AMF sends an Nsmf_PDUSession_UpdateSMContext Request message to the SMF for updating N3 tunnel information. At step 12, the SMF+PGW-C performs preparations for N2 Handover by indicating N3 UP address and Tunnel ID of NG-RAN to the UPF if N2 Handover is accepted by NG-RAN. At step 13, the SMF+PGW-C sends Nsmf_PDUSession_UpdateSMContext Response to the target AMF. At step 13a, the target AMF invokes Namf_Communication_CreateUEContext response (Cause) to the initial AMF. At step 14, the target AMF sends the message Forward Relocation Response to the MME. At step 15, it creates indirect data Forwarding tunnel request response between the MME and the SGW (serving gateway) .

In the process 200, handover challenges between LTE and 5G networks, specifically regarding transitions between CSG and CAG cells (for example, form LTE CSG cell to 5G CAG cell and vice versa) , reveal some issues.

For the first issue, during N26-based handover, when a UE migrates from an LTE CSG cell to a 5G CAG cell, a significant problem emerges: the target AMF lacks awareness of the CAG ID for the target NR cell, along with the UE's subscribed CAG ID list. This lack of information impedes the target AMF's ability to execute effective access control measures. That is to say, in the case of N26 based handover, when UE moves from LTE CSG cell to 5G CAG cell, the target AMF will not know the CAG ID of the target NR cell and of the subscribed CAG ID list to perform access control.

For the second issue, when transitioning from a 5G CAG cell to an LTE CSG cell, a distinct challenge arises. The mechanism for deducing CSG-related information from provided CAG details within the EPS remains unclear. This gap in knowledge inhibits the EPS's capacity to extract essential CSG-specific data from the given CAG data during the handover process. That is to say, in case of handover from 5G CAG cell to LTE CSG cell, it is not known how the EPS can deduce CSG information from the provided CAG information.

Hereinafter, an example signal process 300A for enhancing UE handover between 5G CAG cell and LTE CSG cell and solving at least some of the above-mentioned issues in accordance with some embodiments of the present disclosure will be described with reference to Fig. 3A. For the purpose of discussion, the process 300A may be described with reference to Fig. 3A. The process 300A may involve the terminal device 110, the first or source access networks 12, the first core network 140 (for example, the element 140-1) , and the second core network 150 (for example, the element 150-1) as illustrated in Fig. 1. It would be appreciated that although the process 300A has been described in the communication environment 100 of Fig. 1, this process may be likewise applied to other communication scenarios with similar issues.

In the process 300A, it should be noted that if the cell of the source access network 120 belongs to one of the CSG and the CAG, the cell of the target access network 130 belongs to the other of the CSG and the CAG. If the cell of the source access network 120 belongs to the CSG, the first core network 140 for the source access network 120 may include the MME, and the second core network 150 for the target access network 130 may include the AMF. On the contrary, if the cell of the source access network 120 belongs to the CAG, the first core network 140 for the source access network 120 includes the AMF, the second core network 150 for the target access network 130 may include the MME.

It should be noted that the process 300A is performed during a phase of a handover for the terminal device 110 from a first cell (for example, cell 120-1, also referred to as a source cell) of a first access network 120 to a second cell (for example, cell 130-1, also referred to as a target cell) of a second access network 130.

As shown in Fig. 3A, in process 300A, the measurement report reported by the UE will include the closed group ID of the target cell. Specifically, the terminal device 110 obtains (305) a closed group identity (ID) of the second cell 130-1. If the second cell 130-1 is a 5G CAG cell, the closed group ID is the CAG ID, and if the second cell 130-1 is a 4G CSG cell, the closed group ID is the CSG ID. That is to say, the first cell 120-1 belongs to one of the CSG or the CAG, and the second cell 130-1 belongs to the other one of the CSG or the CAG. In some embodiments, the terminal device 110 decodes 5G SIB1 broadcast message received from the second access network 130 to read CAG-ID of the target cell 130-1, and includes the CAG ID and other related information in the measurement report.

Then, the terminal device 110 transmits (310) the measurement report including the closed group ID of the second cell 130-1 to the first access network 120. The first access network 120 receives (315) the measurement report including the closed group ID of the second cell 130-1. Then, the first access network 120 transmits (320) the measurement report including the closed group ID of the second cell 130-1 to the first core network 140 (for example, the element 140-1) for example via a handover required message. The first core network 140 (for example, the element 140-1) receives (325) the closed group ID of the second cell 130-1 for example via the handover required message. Then, the first core network 140 (for example, the element 140-1) transmits (330) the closed group ID of the second cell 130-1 to the second core network 150 (for example, the element 150-1) , for example via a forward relocation request message. That is to say, the closed group ID of the second cell 130-1 is available in the forward relocation request message.

Then, the second core network 150, for example, element 150-1, performs access control based on the closed group ID of the second cell 130-1 and subscription information 110 associated with the other one of the CSG or the CAG. For example, if the target cell 130-1 is a 5G CAG cell, the second core network 150 will include the AMF, and the AFM may perform CAG cell access control based on the CAG ID of the target cell and the CAG related subscription information 110 (for example, a list of allowed CAG IDs of the terminal device 110) . The CAG related subscription information 110 may be obtained from the element 150-2 (for example, a UDM) of the second core network 150.

By including the closed group ID (for example, CAG ID or CSG ID) of the target cell in the measurement report and reporting this ID to the core network, the respective core network for the target cell may be aware of the closed group ID of the target cell. For example, the AMF for the 5G CAG cell may be aware of the CAG ID of the target 5G CAG or NR cell and also can obtain the subscribed CAG ID list from the UDM. Alternatively, the MME for the LTE CSG cell may be aware of the CSG ID of the target LTE CSG cell and also can obtain the subscribed CSG ID list from the HSS. Based on both of CAG ID and CAG related subscription data, the AMF may perform access control for this 5G NR target cell, or based on CSG ID and CSG related subscription data, the MME may perform access control for this LTE target cell.

Hereinafter, an example signal process 300B for enhancing UE handover between 5G CAG cell and LTE CSG cell and solving at least some of the above-mentioned issues in accordance with some embodiments of the present disclosure will be described with reference to Fig. 3B. For the purpose of discussion, the process 300B may be described with reference to Fig. 3B. The process 300B may involve the terminal device 110, the first or source access networks 12, and the first core network 140 (for example, a first element 140-1) as illustrated in Fig. 1.

In the process 300B, it should be noted that if the cell of the source access network 120 belongs to one of the CSG and the CAG, the cell of the target access network 130 belongs to the other of the CSG and the CAG. It should be noted that the process 300B is performed during a phase of a handover for the terminal device 110 from a first cell (for example, cell 120-1, also referred to as a source cell) of a first access network 120 to a second cell (for example, cell 130-1, also referred to as a target cell) of a second access network 130.

The difference between the process 300A and process 300B will be described hereinafter. The access control is performed (345) by the first core network based on the closed group ID of the second cell and related subscription information, rather the second core network as described in Fig. 3A.

When receiving the closed group ID of the second cell from the first access network 120, the first core network 140 (for example, the element 140-1) may retrieve subscription information from combined user data management (UDM) and home subscriber server (HSS) . For example, if the first cell or source cell is a CSG cell, and the second cell or target cell is a CAG cell, when receiving the CAG ID (which is included in the measurement report of the UE) of the target cell from the source eNB, the MME associated with the source eNB may further retrieve a CAG related subscription information (for example, allowed list of CAG IDs, one or more CAG IDs and the like) from the combined UDM and HSS, and then perform access control based on the received CAG ID and the retrieved CAG related subscription information. Alternatively, if the first cell or source cell is a CAG cell, and the second cell or target cell is a CSG cell, when receiving the CSG ID (which is included in the measurement report of the UE) of the target cell from the source gNB, the AMF associated with the source gNB may further retrieve a CSG related subscription information (for example, allowed list of CSG IDs) from the combined UDM and HSS, and then perform access control based on the received CSG ID and the retrieved CSG related subscription information.

In this process 300B, the combined UDM and HSS is used, and the subscription information is retrieved from a combined UDM and HSS. When receiving the closed group ID of the second cell and related subscription information from the combined UDM and HSS, the access control is performed directly by the first core network without transferring the closed group ID of the second cell to the second core network.

Hereinafter, an example signal process 400 for enhancing UE handover between 5G CAG cell and LTE CSG cell and solving at least some of the above-mentioned issues in accordance with some embodiments of the present disclosure will be described with reference to Fig. 4. For the purpose of discussion, the process 400 may be described with reference to Fig. 4. The process 400 may involve the terminal device 110, the first or source access networks 12, and the first core network 140 (for example, the element 140-1) as illustrated in Fig. 1.

In the process 400, it should be noted that if the cell of the source access network 120 belongs to one of the CSG and the CAG, the cell of the target access network 130 belongs to the other of the CSG and the CAG. It should be noted that the process 400 is performed during a phase of a handover for the terminal device 110 from a first cell (for example, cell 120-1, also referred to as a source cell) of a first access network 120 to a second cell (for example, cell 130-1, also referred to as a target cell) of a second access network 130.

As shown in Fig. 4, in process 400, the terminal device 110 obtains (405) the first closed group identity (ID) of the second cell 130-1. In some embodiments in which the target cell is a 5G NR cell, the first closed group ID is the CAG ID of the second cell, and the terminal device 110 decodes 5G SIB1 broadcast message received from the second access network 130 to read CAG-ID of the target cell 130-1, and includes the CAG ID in the measurement report. In some embodiments in which the second cell or second cell is a 4G LTE cell, the first closed group ID is the CSG ID of the second cell.

Then, the terminal device 110 transmits (410) the measurement report including the first closed group ID of the second cell 130-1 to the first access network 120. The first access network 120 receives (415) the measurement report including the first closed group ID of the second cell 130-1. Then, the first access network 120 transmits (420) the first closed group ID of the second cell 130-1 to the first core network 140 (for example, the element 140-1) , for example via a handover required message. The first core network 140 (for example, the element 140-1) receives (425) the first closed group ID of the second cell 130-1 for example via the handover required message.

In this process 400, the first core network 140 (for example, the element 140-1) determines (430) based on the first closed group ID of the second cell, a second closed group ID of the second cell. Then, the first core network 140 (for example, the element 140-1) performs (435) access control based on the determined second closed group ID and subscription information.

It is assumed that the CAG IDs and CSG IDs in the UE subscription information are allocated according to the same rules, that is to say, the CAG and CSG subscription information are aligned, e.g., CAG ID and CSG ID are allocated from the same pool of values and follow the same semantics. For example, if CAG and CSG subscription information are aligned, e.g., CAG ID and CSG ID are allocated from the same pool of values and follow the same semantics, then MME (based on CSG subscription information) can perform CAG based access control for the target NR cell by identifying CSG and CAG information. For example, the target CAG ID can be assumed to be the same as the source CSG ID or the target CAG ID can be known via a configured table that maps the target NR cell ID to a CAG ID. As a result, during handover from a source CSG cell to a target CAG cell, the MME can directly use the CAG ID of the target cell reported by the UE to convert or map the CAG ID into a CSG ID according to the allocation rules, and then the MME may use subscription data for the CSG to perform target cell access control. Alternatively, during handover from a source CAG cell to a target CSG cell, the AMF can directly use the CSG ID of the target cell reported by the UE to convert or map the CSG ID into a CAG ID according to the rules, and then the AMF may use the subscription data for the CAG to perform target cell access control.

In this process, by allocating the CAG ID and the CSG ID according to the same rules, there is no need to transfer the CAG ID of the target cell reported in the measurement report from MME to AMF, or there is no need to transfer the CSG ID of the target cell reported in the measurement report from AMF to MME.

Hereinafter, an example signal process 500 for enhancing UE handover between 5G CAG cell and LTE CSG cell and solving at least some of the above-mentioned issues in accordance with some embodiments of the present disclosure will be described with reference to Fig. 5. For the purpose of discussion, the process 500 may be described with reference to Fig. 5. The process 500 may involve the first core network 140 (for example, the element 140-1) and the second core network 150 (for example, the element 150-1) as illustrated in Fig. 1.

In the process 500, it should be noted that if the cell of the source access network 120 belongs to one of the CSG and the CAG, the cell of the target access network 130 belongs to the other of the CSG and the CAG. That is to say, the element 140-1 of the first core network 140 is one of the MME and the AMF, and the element 150-1 of the second core network 150 is the other one of the MME and the AMF. It should be noted that the process 500 is performed during a phase of a handover for the terminal device 110 from a first cell (for example, cell 120-1, also referred to as a source cell) of a first access network 120 to a second cell (for example, cell 130-1, also referred to as a target cell) of a second access network 130.

In this process 500, the measurement report reported by the UE will not include the closed group ID of the target cell, but will include the closed group ID of the source cell. Currently, for example, MME sends CSG ID in the Forward Relocation Request message, but this CSG ID is ignored by AMF as this feature is not yet supported in the specification. However, in the process 500, for example, the AMF will obtain a CAG ID based on the received CSG ID. Specifically, the first core network 140 (for example, the element 140-1) transmits (505) the first closed group ID of the first cell associated with one of the CSG ID or CAG ID to the second core network by N26 interface, for example via a Forward Relocation Request message. For example, the MME may transmit the CSG ID of the source cell to the AMF via the Forward Relocation Request message, or the AMF may transmit the CAG ID of the source cell to the MME via N26 interface. The second core network 150 (for example, the element 150-1) receives (510) the first closed group ID of the first cell. Then, the second core network 150 (for example, the element 150-1) determines (515) , based on the first closed group ID, a second closed group ID which is associated with the other one of the CSG ID or the CAG ID. In this process, it is assumed that the target cell will use the determined second closed group ID. For example, the AMF may determine a CAG ID to be used by the target cell based on the received CSG ID of source cell, and alternatively, the MME may determine a CSG ID to be used by the target cell based on the received CAG ID of source cell.

In some embodiments, the second core network 150 (for example, the element 150-1) maps the first closed group ID into the second closed group ID used by the second cell based on at least one operator specific policy. In some embodiments, the second core network 150 (for example, the element 150-1) obtains, from an element or a network function 150-2, for example, a UDM or a HSS, the second closed group ID which is mapped to the first closed group ID.

Then, the second core network 150 (for example, the element 150-1) performs (520) , based on the second closed group ID and subscription information associated with the other one of the CSG or the CAG, access control of the terminal device for the second cell. The subscription information may be obtained from the element 150-2 of the second core network 150.

In this process, for example, the measurement report of the UE does not include the CAG ID of the target cell (for example, a 5G NR cell) , but includes the CSG ID of the source cell (for example, a LTE cell) . By determining the CAG ID based on the received CSG ID (for example, by mapping the CSG ID into a CAG ID according to some operator policies) and assuming that the target cell uses the mapped CAG ID, the CAG ID of the target cell can be known by the AMF by this mapping. Then the AMF can perform the access control based on the mapped CAG ID and CAG related subscription data.

Hereinafter, an example signal process 600 for enhancing UE handover between 5G CAG cell and LTE CSG cell and solving at least some of the above-mentioned issues in accordance with some embodiments of the present disclosure will be described with reference to Fig. 6. For the purpose of discussion, the process 600 may be described with reference to Fig. 6. The process 600 may involve the first access network 120, the first core network 140 (for example, the element 140-1) and the second core network 150 (for example, the element 150-1) as illustrated in Fig. 1.

In the process 600, it should be noted that if the cell of the source access network 120 belongs to one of the CSG and the CAG, the cell of the target access network 130 belongs to the other of the CSG and the CAG. That is to say, the element 140-1 of the first core network 140 is one of the MME and the AMF, and the element 150-1 of the second core network 150 is the other one of the MME and the AMF. It should be noted that the process 600 is performed during a phase of a handover for the terminal device 110 from a first cell (for example, cell 120-1, also referred to as a source cell) of a first access network 120 to a second cell (for example, cell 130-1, also referred to as a target cell) of a second access network 130.

In this process 600, the measurement report reported by the UE will not include the closed group ID of the target cell, but will include the closed group ID of the source cell. However, in this process 600, for example, the CAG ID of target 5G NR cell can be obtained at the first access network, or the CSG ID of target LTE cell can be obtained at the first access network. Specifically, the first access network 120 determines (605) a closed group identity (ID) of the second cell based on a cell ID of the second cell. For example, the first access network 120 (for example, a source eNB) may determine a CAG ID of a 5G NR target cell based on the target cell ID reported by the UE. For example, alternatively, the first access network 120 (for example, a source gNB) may determine a CSG ID of a LTE target cell based on the target cell ID reported by the UE. In some embodiments, the first access network 120 maps, based on a configured table, the cell ID of the second cell to the closed group ID of the second cell.

Then, the first access network 120 transmits (610) the closed group ID of the second cell to the first core network 140 (for example, the element 140-1) . The first core network 140 (for example, the element 140-1) receives (615) the closed group ID of the second cell, and then the first core network 140 (for example, the element 140-1) transmits (620) the closed group ID of the second cell to the second core network 150 (for example, the element 150-1) , and then the second core network 150 (for example, the element 150-1) receives (625) the closed group ID of the second cell. Then, the second core network 150 (for example, the element 150-1) performs (630) access control based on the closed group ID of the second cell and the subscription information.

In this process, for example, the CAG ID of the target 5G NR cell can be determined by the source access network by mapping the target cell ID to the CAG ID. Then the AMF will be aware of the CAG ID of the target 5G NR cell and can perform CAG access control based on the CAG ID of the target cell and the CAG related subscription data. For example, the CSG ID of the target LTE cell can be determined by the source access network by mapping the target cell ID to the CSG ID. Then the MME will be aware of the CSG ID of the target LTE cell and can perform CSG access control based on the CSG ID of the target cell and the CSG related subscription data.

Hereinafter, an example signal process 700 for enhancing UE handover between 5G CAG cell and LTE CSG cell and solving at least some of the above-mentioned issues in accordance with some embodiments of the present disclosure will be described with reference to Fig. 7. For the purpose of discussion, the process 700 may be described with reference to Fig. 7. The process 700 may involve the first core network 140 (for example, the element 140-1) , the second core network 150 (for example, the element 150-1) , and the second access network 130 as illustrated in Fig. 1.

In the process 700, it should be noted that if the cell of the source access network 120 belongs to one of the CSG and the CAG, the cell of the target access network 130 belongs to the other of the CSG and the CAG. That is to say, the element 140-1 of the first core network 140 is one of the MME and the AMF, and the element 150-1 of the second core network 150 is the other one of the MME and the AMF. It should be noted that the process 700 is performed during a phase of a handover for the terminal device 110 from a first cell (for example, cell 120-1, also referred to as a source cell) of a first access network 120 to a second cell (for example, cell 130-1, also referred to as a target cell) of a second access network 130.

In this process 700, the measurement report reported by the UE will not include the closed group ID of the target cell, but will include the closed group ID of the source cell. However, the CAG ID of the target cell is known to the second or target access network. The second or target access network may perform the access control based on the CAG ID of the target cell. Specifically, the first core network 140 (for example, the element 140-1) transmits (705) the closed group ID of the first cell associated with one of the CSG ID or CAG ID to the second core network 150 (for example, the element 150-1) via N26 interface. The second core network 150 (for example, the element 150-1) receives (710) the closed group ID of the first cell.

Then, based on receiving the closed group ID of the first cell, the second core network 150 (for example, the element 150-1) obtains (715) , from an element or a network function 150-2 of the second core network 150, a list of allowed closed group IDs (e.g., one or more allowed closed group IDs) of the terminal device associated with the other one of the CSG or the CAG. AMF receives CSG ID from MME and waits to perform access control until the UE performs a mobility registration update after HO is executed. For example, the AFM obtains from a UDM the list of allowed CAG IDs (e.g., one or more CAG IDs) of the terminal device 110, and the MME obtains from a HSS the list of allowed CSG IDs (e.g., one or more CSG IDs) of the terminal device 110. Then, the second core network 150 (for example, the element 150-1) transmits (715) the list of allowed closed group IDs to the second access network 130. The second access network 130 performs (730) based on a closed group ID of the second cell and the list of allowed closed group IDs, access control of the terminal device for the second cell. For example, an eNB performs CSG cell access control based on the CSG ID of the second cell and the list of allowed CSG IDs, or a gNB performs CAG cell access control based on the CAG ID of the second cell and the list of allowed CAG IDs. It should be noted that the second core network 150 (for example, the element 150-1) can also perform (735) access control based on the closed group ID of the second cell and the obtained list of allowed closed group IDs, instead of transmitting the list of allowed closed group IDs to the second access network 130 and performing access control there.

In this process, by transmitting the list of allowed CSG IDs or CAG IDs directly to the target access network, the target access network can perform access control based on the received list of allowed CSG IDs or CAG IDs and based on its own CSG ID or CAG ID.

Hereinafter, example signal processes 800 to 1200 for enhancing UE handover from LTE CSG cell to 5G CAG cell in accordance with some embodiments of the present disclosure will be described with reference to Figs. 8 to 12. In this process, it is assumed that the terminal device or UE 110 is both 4G and 5G capable. It should be noted when applying the processes 800 to 1200, the associated steps 0 to 2 and 4 to 16 as described in Fig. 2 will not be changed. As described in Figure 4.11.1.2.2.2-1 of TS 23.502, in Step 10, NG-RAN is expected not to reject the handover with a Handover Failure for the Femto specific CAG cell at target gNB. Further, it should be noted that the processes 800 to 1200 are all applicable in case of intra-PLMN as well as for inter-PLMN roaming cases.

For step 3 as described in Fig. 2, currently, MME sends CSG ID in the Forward Relocation Request message, but this is ignored by AMF as this feature is not yet supported in the specification. Upon receiving Forward Relocation Request messing including CSG ID from MME, at least part of processes 800 to 1200 can be applied to step 3. These processes 800 to 1200 support different deployment requirements.

Hereinafter, an example signal process 800A for enhancing UE handover from LTE CSG cell to 5G CAG cell in accordance with some embodiments of the present disclosure will be described with reference to Fig. 8A.

As shown in Fig. 8A, at step 0, the UE 110 transmits UEMeasurementReport message with CSG-ID to EPS (eNB) , in which the eNB is an example of the first access network 120. As step 1, the UE 110 moves into the proximity of 5G-NR, in which the 5G-NR is an example of the second access network 130. In this step, the UE 110 decodes 5G SIB1 broadcast message received from 5G-NR to read CAG-ID of the target cell, and then the UE 110 includes CAG-ID and related information as part of UEMeasurementReport message and sends the UEMeasurementReport message to the eNB. Then, the eNB decides to trigger HO based on based on UEMeasurementReport received from UE.

At step 2, the eNB sends Handover required message to MME by including target cell CAG-ID received from the UE in UEMeasurementReport. Then, at step 3, the MME sends Forward Relocation request message over N26 by including target cell CAG-ID therein and sending the Forward Relocation request message to AMF. The MME is an example of the element 140-1 of the first core network 140, and the AMF is an example of the element 150-1 of the second core network 150. At step 4, the AMF queries the UDM for the MobilityRestrictionList, which includes a list of allowed CAG IDs e.g., one or more CAG IDs) for the UE. Then at step 5, the AMF performs CAG-based cell access control based on MobilityRestrictionList (for example, the list of allowed CAG IDs for the UE) and the received CAG ID of the target cell. For example, at step 6, if the AMF accepts the handover request from MME, then allow the handover to target cell (5G-NR) , otherwise the AMF reject the handover request with proper rejection code (e.g., access not allowed etc. ) . Then, the UE Handover is completed and served by 5G-NR and AMF (5GS) . It should be noted that the process is applicable for both inside PLMN and inter PLMN roaming case.

In this signaling process 800A, the UE reports CAG information of the target cell via UE measurement report to source eNB. This requires an update of the measurement report to include the CAG information. The eNB provides the target cell CAG information to MME which sends these data to AMF in forward relocation request. Then, AMF performs CAG-based access control based on the MobilityRestrictionList obtained from the UDM and the received CAG ID of the target cell.

Hereinafter, an example signal process 800B for enhancing UE handover from LTE CSG cell to 5G CAG cell in accordance with some embodiments of the present disclosure will be described with reference to Fig. 8B.

The difference between the process 800A and process 800B will be described hereinafter. In process 800B, the access control is performed by the MME based on the received CAG ID of the target CAG cell and CAG-related subscription information obtained from the combined UDM and HSS. For example, at step 3, the MME retrieves the subscription information from the combined UDM and HSS, and at step 4, the MME performs access control for the target cell based on the received CAG ID and the retrieved subscription information from combined UDM and HSS. Then, at step 5, the handover is accepted or rejected.

In this process 800B, the combined UDM and HSS is used, and the MME retrieves the subscription information from the combined UDM and HSS. For example, when receiving the CAG ID of the target cell (included in the measurement report) from source eNB, the MME may retrieve CAG-related subscription information (for example, allowed list of CAG IDs, which is part of the subscription information) from combined UDM and HSS directly and then perform access control based on the list of CAG IDs, instead of transferring the CAG ID of the target cell to the AMF and then performing access control at the AMF.

Hereinafter, an example signal process 900 for enhancing UE handover from LTE CSG cell to 5G CAG cell in accordance with some embodiments of the present disclosure will be described with reference to Fig. 9.

As shown in Fig. 9, at step 0, the UE 110 transmits UEMeasurementReport message with CAG-ID to EPS (eNB) , at step 0, the UE 110 transmits UEMeasurementReport message with CSG-ID to EPS (eNB) , in which the eNB is an example of the first access network 120. As step 1, the UE 110 moves into the proximity of 5G-NR, in which the 5G-NR is an example of the second access network 130. In this step, the UE 110 decodes 5G SIB1 broadcast message received from 5G-NR to read CAG-ID of the target cell, and then the UE 110 sincludes CAG-ID and related information as part of UEMeasurementReport message and sends the UEMeasurementReport message to the eNB. Then, the eNB decides to trigger HO based on based on UEMeasurementReport received from UE.

The difference between the process 800A and the process 900 will be described below. In process 900, it is assumed that the CAG ID and CSG ID in the UE subscription information are allocated according to the same rules, that is to say, the CAG and CSG subscription information are aligned, e.g., CAG ID and CSG ID are allocated from the same pool of values and follow the same semantics. As a result, the MME can directly use the CAG ID reported by the UE to convert or map the CAG ID into a CSG ID in accordwith the allocation rules. The MME may use the access control rules for the CSG to perform target cell access control. That is to say, the MME, based on CSG subscription information including list of allowed CSG IDs (e.g., one or more CSG IDs) obtained from HSS for the UE, can perform CAG based access control for the target NR cell by identifying CSG ID information and CAG ID information. The MME may decide whether to allow access, and if the CAG ID can be converted into a CSG ID, the presence or absence of the converted CSG ID in the list of allowed CSG IDs will be used by the MME as the basis for access acceptance or access rejection of access.

In some embodiments, the target CAG ID can be assumed to be the same as the source CSG ID. In some embodiments, the target CAG may be known via a configured table that maps the target NR cell ID to a CAG ID, and then the CAG ID may be converted into CSG ID according to the rules.

Hereinafter, an example signal process 1000 for enhancing UE handover from LTE CSG cell to 5G CAG cell in accordance with some embodiments of the present disclosure will be described with reference to Fig. 11. In this process, the UE will not decode 5G SIB1 broadcast message received from 5G-NR and thus not include the CAG ID of the target cell in the measurement report, and this thus an update of the measurement report typically sent by the UE is not required.

As shown in Fig. 10, at step 1, the evolved universal terrestrial radio access network (E-UTRAN) performs the handover initiation, and the E-UTRAN may be an example of the source eNB or the first access network 120. At step 2, the E-UTRAN transmits a handover required message to MME, and the MME may be an example of the element 140-1 of the first core network 140. At step 3, the MME transmits a Forward Relocation request message over N26 interface to the initial AMF, and the initial AMF may be an example of the element 150-1 of the second core network 150. The Forward Relocation request message may include the CSG related information (such as CSG ID) of the source cell, if the UE source cell is a CSG cell. That is to say, in the forward relocation request message of Step 3 from MME to AMF, the source cell CSG ID is provided to AMF, and thus CSG ID is an available information in the forward relocation request message.

At step 3a, upon receiving the CSG related information (such as CSG ID) of the source cell, the AMF may determine a CAG related information (such as a CAG ID) based on the CSG related information of the source cell. In some embodiments, the AMF maps received CSG ID into corresponding CAG ID based on operator specific policies. These policies can be configured by the operator via network management in the AMF. In some embodiments, the AMF may fetch mapped CAG ID associated with the received CSG ID from another network function, such as UDM. The AMF may be configured with information concerning when or how to fetch data from UDM, e.g., based on target cell or target gNB.

In this process 1000, it is assumed that the target NR cell uses the mapped CAG ID. If the CSG ID is not allowed to be mapped into a CAG ID according to the policies, the handover will be rejected, or if the CSD ID cannot be mapped to the CAG ID due to the mapping algorithm, the handover will be rejected.

Then, at step 3b, upon receiving the CSG related information (such as CSG ID) of the source cell, the AMF may be triggered to obtain the CAG subscription data (for example, a list of allowed CAG IDs for the UE) from the UDM. If the mapped CAG ID is included in the list of allowed CAG IDs, the AMF will allow the handover to the target cell which uses the mapped CAG ID. Otherwise, if the mapped CAG ID is not included in the list of allowed CAG IDs, the AMF will reject the handover request to the target cell with an appropriate (e.g., proper) rejection code. That is to say, the AMF performs access control based on mapped CAG ID and CAG related subscription data (for example, a list of allowed CAG IDs for the UE, which is part of mobility restriction list) as retrieved in step 3b. If the UE is a member of target cell CAG, that is to say, the UE is allowed to access this target cell as specified in subscription data (for example, the mobility restriction list) or the mapped CAG ID is in the list of allowed CAG IDs for the UE, HO should be allowed to process, otherwise HO is rejected.

Hereinafter, an example signal process 1100 for enhancing UE handover from LTE CSG cell to 5G CAG cell in accordance with some embodiments of the present disclosure will be described with reference to Fig. 11. In this process, the UE will not decode the 5G SIB1 broadcast message received from 5G-NR and thus not include the CAG ID of the target cell in the measurement report, and this thus an update of the measurement report typically sent the UE is not required.

As shown in Fig. 11, at step 1, the evolved universal terrestrial radio access network (E-UTRAN) performs the handover initiation, and the E-UTRAN may be an example of the source eNB or the first access network 120. The Source eNB may have a table configured allowing the Source eNB to map the target NR cell ID as reported by the UE to CAG ID.

At step 2, the E-UTRAN transmits a handover required message including the mapped CAG ID to the MME, which may be an example of the element 140-1 of the first core network 140. At step 3, the MME transmits a Forward Relocation request message including the mapped CAG ID over N26 interface to the initial AMF, which may be an example of the element 150-1 of the second core network 150. Therefore, the Forward Relocation request message as transmitted in step 3 may include the CAG related information (such as CAG ID) of the target cell.

Then, at step 3a, the AMF obtains the CAG subscription data (for example, a list of allowed CAG IDs for the UE) from the UDM. If the mapped CAG ID obtained from the source eNB is included in the list of allowed CAG IDs, the AMF will allow the handover to the target cell which uses the mapped CAG ID. Otherwise, if the mapped CAG ID is not included in the list of allowed CAG IDs, the AMF will reject the handover request to the target cell with proper rejection code. That is to say, the AMF performs access control based on mapped CAG ID determined by the source eNB and CAG related subscription data (for example, a list of allowed CAG IDs for the UE, which is part of mobility restriction list) as retrieved in step 3a. As used herein, a list of items (e.g., CAG IDs) refers to one or more of the items.

Hereinafter, an example signal process 1200 for enhancing UE handover from LTE CSG cell to 5G CAG cell in accordance with some embodiments of the present disclosure will be described with reference to Fig. 12. In this process, the UE will not decode 5G SIB1 broadcast message received from 5G-NR and thus not include the CAG ID of the target cell in the measurement report, and thus an update of the measurement report typically sent by a UE is not required.

As shown in Fig. 12, at step 1, the evolved universal terrestrial radio access network (E-UTRAN) performs the handover initiation, and the E-UTRAN may be an example of the source eNB or the first access network 120. At step 2, the E-UTRAN transmits a handover required message to MME, which may be an example of the element 140-1 of the first core network 140. At step 3, the MME transmits a Forward Relocation request message over N26 interface to the initial AMF, which may be an example of the element 150-1 of the second core network 150. The Forward Relocation request message may include the CSG related information (such as CSG ID) of the source cell, if the UE source cell is a CSG cell. That is to say, in forward relocation request message of Step 3 from MME to AMF, the source cell CSG ID is provided to AMF, and thus CSG ID is an available information in the forward relocation request message.

At step 3a, upon receiving the CSG related information (such as CSG ID) of the source cell, the AMF may be triggered to obtain the CAG related subscription data, which is part of mobility restriction list, from the UDM, and then the AMF can fetch the list of allowed CAG IDs for the UE from the CAG related subscription data. That is to say, the list of allowed CAG IDs for the UE may be part of mobility restriction list as retried in step 3a. Then, at step 3b, the AMF provides the list of allowed CAG IDs to the target gNB. Based on the received list of allowed CAG IDs and the CAG IDs of this target gNB, the target gNB will perform the CAG-cell access control.

It should be noted that the processes 800, 1000 to 1200 may also be applicable for the handover from the 5G NR cell to the 4G LTE cell. In the handover from the 5G NR cell to the 4G LTE cell, the source cell is a 5G NR cell, and the target cell is a 4G LTE cell, and the MMF and the AMF are interchanged, and the UDM and HSS are interchanged, and in the processes 800, the UE reports the CSG ID of the target cell via the measurement report to the source gNB. In processes 1000 to 1200, the UE reports the CAG ID of the source cell via the measurement report to the source gNB.

Constraints within current 4G specifications may include that UEs served by an eNB do not including CAG information in measurement reports for NR cells, and the 4G system lacks knowledge of the 5G Mobility and Access Restrictions List (MRL) , impacting the 4G system’s ability to determine compatibility between CAG cells and UE mobility restrictions.

Considering above constraints, the processes 800 to 1200 as described above aim to enable seamless mobility for UE between LTE CSG cells and 5G CAG cells. For the MME behavior: the MME communicates source CSG cell information to 5G system during N26-based handovers as described in processes 800 to 1200. For the AMF behavior, upon receiving a handover request from the MME containing CSG information as part of a forward relocation request, the AMF processes the request accordingly as described in processes 800 to 1200. For the UE behavior, UEs provide CAG and CSG information of the source cell and the target cell within measurement reports to the source Radio Access Network (RAN) as described in processes 800 and 900, and UEs provide CAG or CSG information of the source cell within measurement reports to the source Radio Access Network (RAN) as described in processes 1000 to 1200. For the source RAN logic, the source RAN (for example, a source eNB or a source gNB) employs logic to map cell IDs to corresponding CAG/CSG information as described in process 1100. Furthermore, the processes 800 to 1200 as described above do not require many changes to the call flow for Handover from 4G EPS to 5G-NR or vice-versa.

Fig. 13 illustrates a flowchart of an example method 1300 implemented at a second core network in accordance with some other embodiments of the present disclosure. For the purpose of discussion, the method 1300 will be described from the perspective of the second core network 150 with reference to Fig. 1. The method 1300 may correspond to the operations performed by the second core network 150, for example, the element 150-1, at process 500 in Fig. 5.

As shown in Fig. 13, at block 1310, during a phase of a handover for the terminal device from a first cell of a first access network to a second cell of a second access network, the second core network 150 receives from a first core network associated with the first access network, a first closed group identity (ID) of the first cell, wherein the first cell belongs to one of a closed subscriber group (CSG) or a closed access group (CAG) , the second cell belongs to the other one of the CSG or the CAG, and the first closed group ID is associated with the one of the CSG or the CAG. At block 1320, the second core network 150 determines based on the first closed group ID, a second closed group ID which is associated with the other one of the CSG ID or the CAG ID.

In some embodiments, the second core network performs access control of the device for the second cell, based on the determined second closed group ID and subscription information. In some embodiments, the first closed group ID of the first cell is transmitted and received via a forward relocation request message from the first core network to the second core network by a N26 interface. In some embodiments, the second closed group ID is to be used by the second cell, and is obtained by mapping the first closed group ID into the second closed group ID. In other words, determining the second closed group ID based on the first closed group ID comprises mapping the first closed group ID into the second closed group ID. In some embodiments, the first closed group ID is mapped into the second closed group ID by the second core network, based on at least one operator policy. In some embodiments, the second closed group ID is mapped to the first closed group ID by a network function. In other words, the mapping is performed by a network function.

In some embodiments, the first cell belongs to the CSG, the second cell belongs to the CAG, the first closed group ID of the first cell is a CSG ID of the first cell, and the second closed group ID is a CAG ID to be used by the second cell, and the subscription information is obtained from a user data management (UDM) ; or the first cell belongs to the CAG, the second cell belongs to the CSG, the first closed group ID of the first cell is a CAG ID of the first cell, and the second closed group ID is a CSG ID to be used by the second cell, and the subscription information is obtained from a home subscriber server (HSS) .

Fig. 14 illustrates a flowchart of an example method 1400 implemented at a first access network in accordance with some other embodiments of the present disclosure. For the purpose of discussion, the method 1400 will be described from the perspective of the first access network 120 with reference to Fig. 1. The method 1400 may correspond to the operations performed by the first access network at process 600 in Fig. 6.

At block 1410, during a handover for a device from a first cell of the first access network to a second cell of a second access network, the first access network 120 determines a closed group identity (ID) of the second cell based on a cell ID of the second cell, wherein the first cell belongs to one of a closed subscriber group (CSG) or a closed access group (CAG) , and the second cell belongs to the other one of the CSG or the CAG. At block 1420, the first access network 120 transmits to a first core network, the closed group ID of the second cell.

In some embodiments, the closed group ID of the second cell is further transmitted via a forward relocation request message to a second core network. In some embodiments, the transmitting the closed group ID of the second cell is via a transmission configure to cause the closed group ID of the second cell to be further transmitted via a forward relocation request message to a second core network. In some embodiments, the closed group ID of the second cell is determined by mapping, based on a configured table, the cell ID of the second cell to the closed group ID of the second cell. In some embodiments, the determining the closed group ID of the second cell comprises mapping, based on a configured table, the cell ID of the second cell to the closed group ID of the second cell. In some embodiments, access control is performed by the second core network based on the closed group ID of the second cell and subscription information. In some embodiments, the transmitting the closed group ID of the second cell is via a transmission configured to cause access control to be is performed by the second core network based on the closed group ID of the second cell and subscription information.

In some embodiments, the first cell belongs to the CSG, the second cell belongs to the CAG, the closed group ID of the second cell is a CAG ID of the second cell, and the subscription information is to be obtained from a user data management (UDM) ; or the first cell belongs to the CAG, the second cell belongs to the CSG, the closed group ID of the second cell is a CSG ID of the second cell, and the subscription information is to be obtained from a home subscriber server (HSS) .

Fig. 15 illustrates a flowchart of an example method 1500 implemented at a terminal device 110 in accordance with some other embodiments of the present disclosure. For the purpose of discussion, the method 1500 will be described from the perspective of the terminal device 110 with reference to Fig. 1. The method 1500 may correspond to the operations performed by the terminal device at processes 300A, process 300B and 400 in Figs. 3A, 3B and 4.

As shown in Fig. 15, during a handover of the device from a first cell of a first access network to a second cell of a second access network, at block 1510, the terminal device obtains a closed a closed group identity (ID) of the second cell, wherein the first cell belongs to one of a closed subscriber group (CSG) or a closed access group (CAG) , and the second cell belongs to the other one of the CSG or the CAG. At block 1520 the terminal device transmits to the first access network, a measurement report including the closed group ID of the second cell.

In some embodiments, the closed group ID of the second cell is further transmitted from the first access network to a first core network via a handover required message. In some embodiments, the closed group ID of the second cell is further transmitted from the first core network to a second core network via a forward relocation request message. In some embodiments, the second core network performs access control for the second cell, based on the closed group ID of the second cell and subscription information.

In some embodiments, the first cell belongs to the CSG, the second cell belongs to the CAG, the closed group ID of the second cell is a CAG ID of the second cell, and the subscription information is obtained from a user data management (UDM) ; or the first cell belongs to the CAG, the second cell belongs to the CSG, the closed group ID of the second cell is a CSG ID of the second cell, and the subscription information is obtained from a home subscriber server (HSS) .

In some embodiments, the closed group ID of the second cell is a first closed group ID of the second cell, wherein the first closed group ID of the second cell is associated with one of the CSG or the CAG, and the first core network determines, based on the first closed group ID of the second cell, a second closed group ID of the second cell, wherein the second closed group ID of the second cell is associated with the other one of the CSG or the CAG; and the first core network further performs access control based on the second closed group ID of the second cell and subscription information.

In some embodiments, the first closed group ID of the second cell is associated with the CAG, and the second closed group ID of the second cell is associated with the CSG, and the subscription information is CSG related subscription information and obtained from a home subscriber server (HSS) , or the first closed group ID of the second cell is associated with the CSG, and the second closed group ID of the second cell is associated with the CAG, and the subscription information is CAG related subscription information and obtained from a user data management (UDM) .

In some embodiments, the first closed group ID of the second cell is the same as the second closed group ID of the first cell. In some embodiments, the first closed group ID of the second cell and the second closed group ID of the second cell are allocated from a same pool and follow the same semantics.

In some embodiments, the first core network performs access control for the second cell, based on the closed group ID of the second cell and subscription information. In some embodiments, the first cell belongs to the CSG, the second cell belongs to the CAG, the closed group ID of the second cell is a CAG ID of the second cell, and the subscription information is CAG related subscription information obtained from combined user data management (UDM) and home subscriber server (HSS) ; or the first cell belongs to the CAG, the second cell belongs to the CSG, the closed group ID of the second cell is a CSG ID of the second cell, and the subscription information is CSG related subscription information obtained from the combined UDM and HSS.

Fig. 16 illustrates a flowchart of an example method 1600 implemented at a second core network in accordance with some other embodiments of the present disclosure. For the purpose of discussion, the method 1600 will be described from the perspective of the second core network 150 with reference to Fig. 1. The method 1600 may correspond to the operations performed by the second core network 150, for example, the element 150-1 in process 700 of Fig. 7.

As shown in Fig. 16, during a handover of a device from a first cell of a first access network to a second cell of a second access network, at block 1610, the second core network receives from a first core network associated with the first access network, a closed group identity (ID) of the first cell, wherein the first cell belongs to one of a closed subscriber group (CSG) or a closed access group (CAG) , and the second cell belongs to the other one of the CSG or the CAG. At block 1620, the second core network, based on receiving the closed group ID of the first cell, obtains, from a network function, a list of allowed closed group IDs of the device associated with the other one of the CSG or the CAG. At block 1630, the second core network transmits the list of allowed closed group IDs to the second access network.

In some embodiments, the closed group ID of the first cell is transmitted from the first core network to the second core network and received by the second core network from the first core network via a forward relocation request message. In some embodiments, the closed group ID of the first cell is a CSG ID, and the list of allowed closed group ID of the device is a list of allowed CAG IDs, and the second access network performs access control based on the list of allowed CAG IDs and a CAG ID of the second cell; or the closed group ID of the first cell is a CAG ID, and the list of allowed closed group ID of the device is a list of allowed CSG IDs, and the second access network performs access control based on the list of allowed CSG IDs and a CSG ID of the second cell.

In some embodiments, an apparatus (for example, the second core network 150, for example, element 150-1) capable of performing the method 1300 may comprise means for performing the respective steps of the method 1300. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

In some embodiments, the apparatus comprises: means for during a handover of a device from a first cell of a first access network to a second cell of a second access network, receiving, from a first core network associated with the first access network, a first closed group identity (ID) of the first cell, wherein the first cell belongs to one of a closed subscriber group (CSG) or a closed access group (CAG) , the second cell belongs to the other one of the CSG or the CAG, and the first closed group ID is associated with the one of the CSG or the CAG; and means for determining, based on the first closed group ID, a second closed group ID which is associated with the other one of the CSG ID or the CAG ID.

In some embodiments, the second core network performs access control of the device for the second cell, based on the determined second closed group ID and subscription information. In some embodiments, the first closed group ID of the first cell is transmitted via a forward relocation request message from the first core network to the second core network. In some embodiments, the second closed group ID is to be used by the second cell, and is obtained by mapping the first closed group ID into the second closed group ID.

In some embodiments, the first closed group ID is mapped into the second closed group ID by the second core network, based on at least one operator policy. In some embodiments, the second closed group ID is mapped to the first closed group ID by a network function.

In some embodiments, the apparatus further comprises means for performing other steps in some embodiments of the method 1300. In some 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 embodiments, an apparatus (for example, a first access network 120) capable of performing the method 1400 may comprise means for performing the respective steps of the method 1400. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

In some embodiments, the apparatus comprises means for during a handover for a device from a first cell of the first access network to a second cell of a second access network, determining a closed group identity (ID) of the second cell based on a cell ID of the second cell, wherein the first cell belongs to one of a closed subscriber group (CSG) or a closed access group (CAG) , and the second cell belongs to the other one of the CSG or the CAG; and means for transmitting, to a first core network, the closed group ID of the second cell.

In some embodiments, the closed group ID of the second cell is further transmitted via a forward relocation request message to a second core network. In some embodiments, the closed group ID of the second cell is determined by mapping, based on a configured table, the cell ID of the second cell to the closed group ID of the second cell.

In some embodiments, access control is performed by the second core network based on the closed group ID of the second cell and subscription information. In some embodiments, the first cell belongs to the CSG, the second cell belongs to the CAG, the closed group ID of the second cell is a CAG ID of the second cell, and the subscription information is obtained from a user data management (UDM) ; or the first cell belongs to the CAG, the second cell belongs to the CSG, the closed group ID of the second cell is a CSG ID of the second cell, and the subscription information is obtained from a home subscriber server (HSS) .

In some embodiments, the apparatus further comprises means for performing other steps in some embodiments of the method 1400. In some 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 embodiments, an apparatus (for example, a terminal device of Fig. 1) capable of performing the method 1500 may comprise means for performing the respective steps of the method 1500. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

In some embodiments, the apparatus comprises: means for during a handover of the device from a first cell of a first access network to a second cell of a second access network, obtaining a closed group identity (ID) of the second cell, wherein the first cell belongs to one of a closed subscriber group (CSG) or a closed access group (CAG) , and the second cell belongs to the other one of the CSG or the CAG; and means for transmitting, to the first access network, a measurement report including the closed group ID of the second cell.

In some embodiments, the closed group ID of the second cell is further transmitted from the first access network to a first core network via a handover required message. In some embodiments, the closed group ID of the second cell is further transmitted from the first core network to a second core network via a forward relocation request message.

In some embodiments, the second core network performs access control for the second cell, based on the closed group ID of the second cell and subscription information. In some embodiments, the first cell belongs to the CSG, the second cell belongs to the CAG, the closed group ID of the second cell is a CAG ID of the second cell, and the subscription information is obtained from a user data management (UDM) ; or the first cell belongs to the CAG, the second cell belongs to the CSG, the closed group ID of the second cell is a CSG ID of the second cell, and the subscription information is obtained from a home subscriber server (HSS) .

In some embodiments, the first closed group ID of the second cell is associated with the CAG, and the second closed group ID of the second cell is associated with the CSG, and the subscription information is CSG related subscription information and obtained from a home subscriber server (HSS) , or the first closed group ID of the second cell is associated with the CSG, and the second closed group ID of the second cell is associated with the CAG, and the subscription information is CAG related subscription information and obtained from a user data management (UDM) . In some embodiments, the first closed group ID of the second cell is the same as the second closed group ID of the first cell. In some embodiments, the first closed group ID of the second cell and the second closed group ID of the second cell are allocated from a same pool and follow the same semantics.

In some embodiments, the apparatus further comprises means for performing other steps in some embodiments of the method 1500. In some 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 embodiments, an apparatus (for example, the second core network 150, especially, the element 150-1) capable of performing the method 1600 may comprise means for performing the respective steps of the method 1600. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

In some embodiments, the apparatus comprises: means for during a handover of a device from a first cell of a first access network to a second cell of a second access network, receiving, from a first core network associated with the first access network, a closed group identity (ID) of the first cell, wherein the first cell belongs to one of a closed subscriber group (CSG) or a closed access group (CAG) , and the second cell belongs to the other one of the CSG or the CAG; means for based on receiving the closed group ID of the first cell, obtaining, from a network function, a list of allowed closed group IDs of the device associated with the other one of the CSG or the CAG; and means for transmitting the list of allowed closed group IDs to the second access network.

In some embodiments, the closed group ID of the first cell is transmitted from the first core network to the second core network via a forward relocation request message. In some embodiments, the closed group ID of the first cell is a CSG ID, and the list of allowed closed group ID of the device is a list of allowed CAG IDs obtained from a user data management (UDM) , and the second core network or the second access network performs access control based on the list of allowed CAG IDs and a CAG ID of the second cell; or the closed group ID of the first cell is a CAG ID, and the list of allowed closed group ID of the device is a list of allowed CSG IDs obtained from a home subscriber server (HSS) , and the second core network or the second access network performs access control based on the list of allowed CSG IDs and a CSG ID of the second cell.

In some embodiments, the apparatus further comprises means for performing other steps in some embodiments of the method 1600. In some 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.

Fig. 17 is a simplified block diagram of a device 1700 that is suitable for implementing embodiments of the present disclosure. The device 1700 may be provided to implement the communication device, for example the terminal device 110, the access networks 120, 130, the elements 140-1, 140-2, 150-1 and 150-2 of the core network as shown in Fig. 1. As shown, the device 1700 includes one or more processors 1710, one or more memories 1720 coupled to the processor 1710, and one or more communication modules 1740 coupled to the processor 1710.

The communication module 1740 is for bidirectional communications. The communication module 1740 has at least one antenna to facilitate communication. The communication interface may represent any interface that is necessary for communication with other network devices.

The processor 1710 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 1700 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 1720 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) 1724, 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) 1722 and other volatile memories that may not last in the power-down duration.

A computer program 1730 includes computer executable instructions that are executed by the associated processor 1710. The program 1730 may be stored in the ROM 1724. The processor 1710 may perform any suitable actions and processing by loading the program 1730 into the RAM 1722.

The embodiments of the present disclosure may be implemented by means of the program so that the device 1700 may perform any process of the disclosure as discussed with reference to Figs. 3 to 16. The embodiments of the present disclosure may also be implemented by hardware or by a combination of software and hardware.

In some embodiments, the program 1730 may be tangibly contained in a computer readable medium which may be included in the device 1700 (such as in the memory 1720) or other storage devices that are accessible by the device 1700. The device 1700 may load the program 1730 from the computer readable medium to the RAM 1722 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. 18 illustrates an example of the computer readable medium 1800 in form of CD or DVD in accordance with some embodiments of the present disclosure. The computer readable medium has the program 1730 stored thereon. It is noted that although the computer-readable medium 1800 is depicted in form of CD or DVD, the computer-readable medium 1800 may be in any other form suitable for carry or hold the program 1730.

Generally, various 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 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 or 700 as described above with reference to Fig. 6 to Fig. 7. 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 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. The term “non-transitory, ” as used herein, is a limitation of the medium itself (i.e., tangible, not a signal) as opposed to a limitation on data storage persistency (e.g., RAM vs. ROM) .

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 embodiments. Certain features that are described in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features that may be described in the context of a single embodiment may also be implemented in multiple 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 may be disclosed as example forms of implementing the claims.

Claims

A second core network comprising:

at least one processor; and

at least one memory storing instructions that, when executed by the at least one processor, cause the second core network at least to perform:

during a handover of a device from a first cell of a first access network to a second cell of a second access network, receiving, from a first core network associated with the first access network, a first closed group identity (ID) of the first cell, wherein the first cell belongs to one of a closed subscriber group (CSG) or a closed access group (CAG) , the second cell belongs to the other one of the CSG or the CAG, and the first closed group ID is associated with the one of the CSG or the CAG; and

determining, based on the first closed group ID, a second closed group ID which is associated with the other one of the CSG ID or the CAG ID.
The second core network of claim 1, wherein the instructions, when executed by the at least one processor, further cause the second core network at least to perform:

performing access control of the device for the second cell, based on the determined second closed group ID and subscription information.
The second core network of claim 1, wherein the first closed group ID of the first cell is received via a forward relocation request message from the first core network to the second core network.
The second core network of claim 1, wherein the second closed group ID is to be used by the second cell, and the determining comprises mapping the first closed group ID into the second closed group ID.
The second core network of claim 4, wherein the mapping is based on at least one operator policy.
The second core network of claim 4, wherein the mapping is performed by a network function.
The second core network of claim 2, wherein:

the first cell belongs to the CSG, the second cell belongs to the CAG, the first closed group ID of the first cell is a CSG ID of the first cell, and the second closed group ID is a CAG ID to be used by the second cell, and the subscription information is obtained from a user data management (UDM) ; or

the first cell belongs to the CAG, the second cell belongs to the CSG, the first closed group ID of the first cell is a CAG ID of the first cell, and the second closed group ID is a CSG ID to be used by the second cell, and the subscription information is obtained from a home subscriber server (HSS) .
A first access network comprising:

at least one processor; and

at least one memory storing instructions that, when executed by the at least one processor, cause the first access network at least to perform:

during a handover for a device from a first cell of the first access network to a second cell of a second access network, determining a closed group identity (ID) of the second cell based on a cell ID of the second cell, wherein the first cell belongs to one of a closed subscriber group (CSG) or a closed access group (CAG) , and the second cell belongs to the other one of the CSG or the CAG; and

transmitting, to a first core network, the closed group ID of the second cell.
The first access network of claim 8, wherein the transmitting the closed group ID of the second cell is via a transmission configure to cause the closed group ID of the second cell to be further transmitted via a forward relocation request message to a second core network.
The first access network of claim 7, wherein the determining the closed group ID of the second cell comprises mapping, based on a configured table, the cell ID of the second cell to the closed group ID of the second cell.
The first access network of claim 8, wherein the transmitting the closed group ID of the second cell is via a transmission configured to cause access control to be is performed by the second core network based on the closed group ID of the second cell and subscription information.
The first access network of claim 11, wherein the first cell belongs to the CSG, the second cell belongs to the CAG, the closed group ID of the second cell is a CAG ID of the second cell, and the subscription information is to be obtained from a user data management (UDM) ; or

the first cell belongs to the CAG, the second cell belongs to the CSG, the closed group ID of the second cell is a CSG ID of the second cell, and the subscription information is to be obtained from a home subscriber server (HSS) .
A method comprising:

during a handover of a device from a first cell of a first access network to a second cell of a second access network, obtaining, by the device, a closed group identity (ID) of the second cell, wherein the first cell belongs to one of a closed subscriber group (CSG) or a closed access group (CAG) , and the second cell belongs to the other one of the CSG or the CAG; and

transmitting, by the device, to the first access network, a measurement report including the closed group ID of the second cell.
The method of claim 13 further comprising:

transmitting the closed group ID of the second cell from the first access network to a first core network via a handover required message.
The method of claim 14 further comprising:

transmitting the closed group ID of the second cell from the first core network to a second core network via a forward relocation request message.
The method of claim 15further comprising:

performing, by the second core network, access control for the second cell based on the closed group ID of the second cell and subscription information.
The method of claim 16, wherein

the first cell belongs to the CSG, the second cell belongs to the CAG, the closed group ID of the second cell is a CAG ID of the second cell, and the subscription information is obtained from a user data management (UDM) ; or

the first cell belongs to the CAG, the second cell belongs to the CSG, the closed group ID of the second cell is a CSG ID of the second cell, and the subscription information is obtained from a home subscriber server (HSS) .
The method of claim 14, wherein the closed group ID of the second cell is a first closed group ID of the second cell, wherein the first closed group ID of the second cell is associated with one of the CSG or the CAG, and wherein the method further comprises:

determining, by the first core network, based on the first closed group ID of the second cell, a second closed group ID of the second cell, wherein the second closed group ID of the second cell is associated with the other one of the CSG or the CAG; and

performing, by the first core network, access control based on the second closed group ID of the second cell and subscription information.
The method of claim 18, wherein:

the first closed group ID of the second cell is associated with the CAG, and the second closed group ID of the second cell is associated with the CSG, and the subscription information is CSG related subscription information and obtained from a home subscriber server (HSS) , or

the first closed group ID of the second cell is associated with the CSG, and the second closed group ID of the second cell is associated with the CAG, and the subscription information is CAG related subscription information and obtained from a user data management (UDM) .
The method of claim 19, wherein the first closed group ID of the second cell is the same as the second closed group ID of the first cell.
The method of claim 19, wherein the first closed group ID of the second cell and the second closed group ID of the second cell are allocated from a same pool and follow the same semantics.
The method of claim 13 further comprising:

performing, by the first core network, access control for the second cell, based on the closed group ID of the second cell and subscription information.
The method of claim 22, wherein the first cell belongs to the CSG, the second cell belongs to the CAG, the closed group ID of the second cell is a CAG ID of the second cell, and the subscription information is CAG related subscription information obtained from combined user data management (UDM) and home subscriber server (HSS) ; or

the first cell belongs to the CAG, the second cell belongs to the CSG, the closed group ID of the second cell is a CSG ID of the second cell, and the subscription information is CSG related subscription information obtained from the combined UDM and HSS.
A second core network comprising:

at least one processor; and

at least one memory storing instructions that, when executed by the at least one processor, cause the second core network at least to perform:

during a handover of a device from a first cell of a first access network to a second cell of a second access network, receiving, from a first core network associated with the first access network, a closed group identity (ID) of the first cell, wherein the first cell belongs to one of a closed subscriber group (CSG) or a closed access group (CAG) , and the second cell belongs to the other one of the CSG or the CAG;

based on the receiving the closed group ID of the first cell, obtaining, from a network function, one or more allowed closed group IDs of the device associated with the other one of the CSG or the CAG; and

transmitting the one or more allowed closed group IDs to the second access network.
The second core network of claim 24, wherein the closed group ID of the first cell is received via a forward relocation request message from the first core network to the second core network.
The second core network of claim 24, wherein the instructions, when executed by the at least one processor, cause the second core network at least to perform:

performing access control based on the one or more allowed closed group IDs and the closed group ID of the first cell; and wherein:

the closed group ID of the first cell is a CSG ID, and the one or more allowed closed group IDs of the device is one or more allowed CAG IDs obtained from a user data management (UDM) , and

the second core network or the second access network performs access control based on the one or more allowed CAG IDs and a CAG ID of the second cell; or

the closed group ID of the first cell is a CAG ID, and the one or more allowed closed group ID of the device is one or more allowed CSG IDs obtained from a home subscriber server (HSS) , and

the second core network or the second access network performs access control based on the list of allowed CSG IDs and a CSG ID of the second cell.