Method and apparatus for handling radio access technology or frequency selection priority

Abstract

Embodiments of the present disclosure provide methods and apparatus for handling radio access technology or frequency selection priority (RFSP). A method performed by a policy control entity includes setting an effective time for a radio access technology or frequency selection priority (RFSP) index for a user equipment (UE) moving from a first network to a second network. The method further includes sending, to a mobility management entity in the first network, a first message including the RFSP index and a valid time for the RFSP index. The valid time of the RFSP index indicates the time at which the RFSP index will be used in the second mobility management entity when the UE is in the second network.

Description

Technical Field

[0001] Non-limiting and exemplary embodiments of the present disclosure generally relate to the field of communication technology, and more particularly to methods and apparatus for handling radio access technology or frequency selection priority (RFSP). Background Art

[0002] This section introduces aspects that may help to better understand the present disclosure. Therefore, the statements in this section should be read in this context and should not be understood as admissions about what is or is not in the prior art.

[0003] In communication networks defined by the 3rd Generation Partnership Project (3GPP), such as LTE (Long Term Evolution) and NR (New Radio), in order to support radio resource management in the RAN (Radio Access Network), a mobility management entity (such as an Access and Mobility Function (AMF) or a Mobility Management Entity (MME)) may provide the RAN (Radio Access Network) with a parameter "Index for Radio Access Technology (RAT) / Frequency Selection Priority" (RFSP Index). The RAN maps the RFSP Index to a locally defined configuration so that a specific Radio Resource Management (RRM) policy is applied taking into account any available information in the RAN. The RFSP Index is user equipment (UE) specific and applies to all radio bearers. Examples of how the RAN may use this parameter include deriving UE-specific cell reselection priorities to control idle mode residency and / or deciding to redirect an active mode UE to a different frequency layer or RAT.

[0004] The mobility management entity (e.g. AMF or MME) may receive the subscribed RFSP index from a data management node (e.g. UDM (Unified Data Management) or HSS (Home Subscriber Server)) (e.g. during the registration process). For non-roaming subscribers, depending on the operator's configuration, the mobility management entity (e.g. AMF or MME) may select the RFSP index in use according to one of the following procedures:

[0005] - the RFSP index in use is the same as the subscribed RFSP index, or

[0006] -AMF selects the RFSP index in use based on the subscribed RFSP index, locally configured operator policy, allowed NSSAI (Network Slice Selection Assistance Information) and UE related context information available at the AMF (including the UE's usage settings) if received during the registration process.

[0007] One example of how the AMF may use the “UE’s usage setting” is to select the RFSP value forcing idle mode camped on Evolved Universal Terrestrial Radio Access (E-UTRA) for UEs acting in a “voice centric” manner, in case a particular registration area does not support NR voice and contains NR cells.

[0008] The AMF may report the subscribed RFSP index received from the UDM to the PCF (Policy Control Function) for further evaluation. When receiving the authorized RFSP index from the PCF, the AMF shall replace the subscribed RFSP index with the authorized RFSP index.

[0009] The AMF stores the received subscribed RFSP index value and the RFSP index value in use. During the registration process, the AMF may update the RFSP index value in use (for example, if the UE-related context information in the AMF has changed, the AMF may need to update the RFSP index value in use). When the RFSP index value in use changes, the AMF immediately provides the updated RFSP index value in use to the NG-RAN (Next Generation Radio Access Network) node by modifying the existing UE context or by establishing a new UE context in the RAN or by being configured to include the updated RFSP index value in use in the Next Generation Application Protocol (NGAP) downlink non-access stratum (NAS) transmission message (if no user plane establishment is required). Summary of the invention

[0010] This Summary is intended to introduce some concepts in a simplified form that are further described in the Detailed Description below. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

[0011] There are several problems in existing RFSP processing solutions.

[0012] 3GPP TR 23.700-89 V0.1.0, the disclosure of which is incorporated herein by reference in its entirety, includes the following key issues.

[0013] Key Issue #1: Consistency of RFSP index when UE moves from 5GC (fifth generation core network) to EPC (evolved packet core).

[0014] Currently, most operators run 4G (fourth generation) and 5G (fifth generation) converged networks. To promote 5G services, the subscription data of the UE can be set to access 5G first, that is, the RFSP index of the subscription is a value of "5G has a higher priority than 4G". In some scenarios, the PCF can adjust the RFSP index to guide the UE from 5G to 4G according to dynamic network conditions.

[0015] For example, upon receiving a network congestion prediction from NWDAF (Network Data Analysis Function), the PCF may move some of the “5G-first” UEs consuming low-value applications to 4G access.

[0016] Based on the request from AF (Application Function), PCF can move the requested UE from 5G to 4G.

[0017] When a UE registers with the EPC, the MME selects the RFSP index in use based on the subscribed RFSP index, locally configured operator policies, and UE-related context information available at the MME. If the EPC decides that the UE needs to fall back to 5G, the MME will provide the eNB (evolved NodeB) with a "5G-first" RFSP index.

[0018] To avoid network issues such as the ping-pong problem where the 5GC keeps sending the UE to the EPC based on the authorized RFSP index from the PCF while the MME only has the subscribed RFSP index and kicks the UE back to 5G immediately in the above scenario, this key issue will study the AM (Access and Mobility) policy control on the RFSP index consistency when the UE moves from the 5GC to the EPC:

[0019] -Does the current interworking process support the MME receiving the RFSP index in use from the 5GC? If not, what enhancements are required?

[0020] - If the MME obtains an in-use RFSP index during a handover procedure or idle mode mobility procedure, how and when does it revert to the subscribed RFSP index.

[0021] -Whether and how the MME should receive any updates of the RFSP index from the 5GC when the UE is under EPC.

[0022] As described in the key issues of 3GPP TR 23.700-89 V0.1.0, there are two potential issues:

[0023] Problem 1. Ping-Pong problem, i.e., a UE in 5GS (5G system) is directed to the Evolved Packet System (EPS) due to certain conditions (e.g., network congestion, applications in use), and then immediately directed back to 5GS.

[0024] Question 2. Once the UE is steered to EPS (from 5GS), how to steer the UE back to 5GS when the conditions in 5GS in Question 1 above no longer apply.

[0025] Solution #1 in TR 23.700-89v0.1.0 implies significant changes to the 5GS to EPS mobility procedures and the intra-EPS mobility procedures.

[0026] To overcome or alleviate at least one of the above problems or other problems, embodiments of the present disclosure propose an improved solution for processing RFSP.

[0027] In a first aspect of the present disclosure, a method performed by a policy control entity is provided. The method includes: setting a valid time for a radio access technology or frequency selection priority (RFSP) index for a user equipment (UE) moving from a first network to a second network. The method further includes: sending a first message including an RFSP index and a valid time for the RFSP index to a mobility management entity in the first network. The valid time for the RFSP index indicates a time when the RFSP index will be used in a second mobility management entity when the UE is in the second network.

[0028] In an embodiment, the method further comprises: determining that a change in the value of the RFSP index indicates a change for the user equipment from prioritizing the first network access to prioritizing the second network access. In response to said determining, a validity time for the RFSP index is included in the first message.

[0029] In an embodiment, the first network comprises a 3rd Generation Partnership Project (3GPP) Fifth Generation System (5GS), and the second network comprises a 3GPP Evolved Packet System (EPS).

[0030] In an embodiment, the first message comprises at least one of an access and mobility management entity policy control create response or an access and mobility management entity policy control update notification.

[0031] In an embodiment, the policy control entity comprises a Policy Control Function (PCF).

[0032] In an embodiment, the mobility management entity comprises an Access and Mobility Function (AMF).

[0033] In an embodiment, the second mobility management entity is a Mobility Management Entity (MME).

[0034] In an embodiment, the RFSP index indicates a preferred 3GPP EPS access.

[0035] In a second aspect of the present disclosure, a method performed by a first mobility management node is provided. The method includes sending a second message to a second mobility management entity in a second network, the second message including a radio access technology or frequency selection priority (RFSP) index and a valid time for a user equipment (UE) moving from the first network to the second network for the RFSP index. The valid time for the RFSP index indicates the time when the RFSP index will be used in the second mobility management entity when the UE is in the second network.

[0036] In an embodiment, the first network comprises a 3rd Generation Partnership Project (3GPP) Fifth Generation System (5GS), and the second network comprises a 3GPP Evolved Packet System (EPS).

[0037] In an embodiment, the method further comprises receiving a first message from a policy control entity, the first message comprising the RFSP index and a validity time for the RFSP index. The method further comprises storing the validity time for the RFSP index.

[0038] In an embodiment, the first message comprises at least one of an access and mobility management entity policy control create response or an access and mobility management entity policy control update notification.

[0039] In an embodiment, the policy control entity comprises a Policy Control Function (PCF).

[0040] In an embodiment, the first mobility management entity is an Access and Mobility Function (AMF) and the second mobility management entity is a Mobility Management Entity (MME).

[0041] In an embodiment, the second message is sent to the second mobility management entity during at least one of a 5GS to EPS handover procedure using an N26 interface or a 5GS to EPS idle mode mobility procedure using an N26 interface.

[0042] In an embodiment, the second message comprises at least one of a forward redirection request or a context response.

[0043] In an embodiment, the RFSP index indicates a preferred 3GPP EPS access.

[0044] In a third aspect of the present disclosure, a method performed by a second mobility management node is provided. The method includes receiving a second message from a first mobility management entity in a first network, the second message including a radio access technology or frequency selection priority (RFSP) index and a valid time for a user equipment (UE) moving from the first network to a second network for the RFSP index. The valid time for the RFSP index indicates the time when the UE will use the RFSP index in the second mobility management entity when the UE is in the second network. The method further includes using the RFSP index within a time period indicated by the valid time until the valid time expires.

[0045] In an embodiment, the method further comprises performing a RFSP index re-evaluation when a validity time for the RFSP index expires.

[0046] In an embodiment, the method further comprises storing the RFSP index and a validity time for the RFSP index.

[0047] In an embodiment, the second message comprises at least one of a forward redirection request or a context response.

[0048] In an embodiment, the first mobility management entity is an Access and Mobility Function (AMF) and the second mobility management entity is a Mobility Management Entity (MME).

[0049] In an embodiment, the second message is received from the first mobility management entity during at least one of a 5GS to EPS handover procedure using an N26 interface or a 5GS to EPS idle mode mobility procedure using an N26 interface.

[0050] In an embodiment, the RFSP index indicates a preferred 3GPP EPS access.

[0051] In a fourth aspect of the present disclosure, a policy control node is provided. The policy control node includes a processor and a memory coupled to the processor. The memory stores instructions executable by the processor. The policy control node is operable to set a valid time for a radio access technology or frequency selection priority (RFSP) index for a user equipment (UE) moving from a first network to a second network. The policy control node is also operable to send a first message containing an RFSP index and a valid time for the RFSP index to a mobility management entity in the first network. The valid time for the RFSP index indicates the time when the RFSP index will be used in the second mobility management entity when the UE is in the second network.

[0052] In a fifth aspect of the present disclosure, a first mobility management node is provided, comprising a processor and a memory coupled to the processor. The memory stores instructions executable by the processor. The first mobility management node is operable to send a second message to a second mobility management entity in a second network, the second message comprising a radio access technology or frequency selection priority (RFSP) index and a valid time for a user equipment (UE) moving from the first network to the second network for the RFSP index. The valid time for the RFSP index indicates the time when the RFSP index will be used in the second mobility management entity when the UE is in the second network.

[0053] In a sixth aspect of the present disclosure, a second mobility management node is provided. The second mobility management node includes a processor and a memory coupled to the processor. The memory stores instructions executable by the processor. The second mobility management node is operable to receive a second message from a first mobility management entity in a first network, the second message including a radio access technology or frequency selection priority (RFSP) index and a valid time for a user equipment (UE) moving from the first network to a second network for the RFSP index. The valid time for the RFSP index indicates the time when the RFSP index will be used in the second mobility management entity when the UE is in the second network. The second mobility management node is also operable to use the RFSP index within a time period indicated by the valid time until the valid time expires.

[0054] In a seventh aspect of the present disclosure, a policy control node is provided. The policy control node includes a setting module, the setting module being configured to set a valid time for a radio access technology or frequency selection priority (RFSP) index for a user equipment (UE) moving from a first network to a second network. The valid time for the RFSP index indicates the time when the RFSP index will be used in a second mobility management entity when the UE is in the second network. The policy control entity further includes a sending module, configured to send a first message containing the RFSP index and the valid time for the RFSP index to a mobility management entity in the first network.

[0055] In an embodiment, the policy control entity further comprises a determining module configured to determine that a change in the value of the RFSP index indicates a change for the user equipment from prioritizing the first network access to prioritizing the second network access. In response to the determining, a validity time for the RFSP index is included in the first message.

[0056] In an eighth aspect of the present disclosure, a first mobility management node is provided. The first mobility management node includes a sending module configured to send a second message to a second mobility management entity in a second network, the second message including a radio access technology or frequency selection priority (RFSP) index and a valid time for a user equipment (UE) moving from the first network to the second network for the RFSP index. The valid time for the RFSP index indicates a time when the RFSP index will be used in the second mobility management entity when the UE is in the second network.

[0057] In an embodiment, the first mobility management entity further comprises a first receiving module configured to receive the RFSP index from the policy control entity.

[0058] In an embodiment, the first mobility management entity further comprises a determining module configured to determine that a change in the value of the RFSP index indicates a change for the user equipment from prioritizing the first network access to prioritizing the second network access.

[0059] In an embodiment, the first mobility management entity further comprises a setting module configured to set a valid time for the RFSP index.

[0060] In an embodiment, the first mobility management entity further comprises a first storage module configured to store a validity time for the RFSP index.

[0061] In an embodiment, the first mobility management entity further comprises a second receiving module configured to receive a first message including the RFSP index and a valid time for the RFSP index from the policy control entity.

[0062] In an embodiment, the first mobility management entity further comprises a second storage module configured to store a validity time for the RFSP index.

[0063] In a ninth aspect of the present disclosure, a second mobility management node is provided. The second mobility management node includes a receiving module configured to receive a second message from a first mobility management entity in a first network, the second message including a radio access technology or frequency selection priority (RFSP) index and a valid time for a user equipment (UE) moving from the first network to a second network for the RFSP index. The valid time for the RFSP index indicates the time when the RFSP index will be used in the second mobility management entity when the UE is in the second network. The second mobility management entity further includes a using module configured to use the RFSP index within a time period indicated by the valid time until the valid time expires.

[0064] In an embodiment, the second mobility management entity further comprises a storage module configured to store the RFSP index and a valid time for the RFSP index.

[0065] In an embodiment, the second mobility management entity further comprises an execution module configured to perform RFSP index re-evaluation when a validity time for the RFSP index expires.

[0066] In the tenth aspect of the present disclosure, a computer-readable storage medium is provided, which stores instructions. When the instructions are executed by at least one processor, the instructions cause the at least one processor to perform any one of the methods according to the first, second and third aspects of the present disclosure.

[0067] In an eleventh aspect of the present disclosure, a computer program product is provided, comprising instructions, which, when executed on at least one processor, cause the at least one processor to perform any one of the methods according to the first, second and third aspects of the present disclosure.

[0068] By applying the solution proposed according to the embodiments of the present disclosure, many advantages can be achieved. For example, in some embodiments of the present invention, the benefit is to allow the UE to be directed back to a network such as 5GS after a configurable time / valid time expires. In some embodiments of the present invention, the ping-pong problem can be alleviated with minimal impact on the first network (e.g., 5GS) and the second network (e.g., EPS). In some embodiments of the present invention, the proposed solution can minimize the impact on the first network (e.g., 5GS) and the second network (e.g., EPS). The embodiments of the present invention are not limited to the above-mentioned features and advantages. Those skilled in the art will recognize other features and advantages after reading the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] The above and other aspects, features and advantages of various embodiments of the present disclosure will become more apparent through the following detailed description with reference to the accompanying drawings, in which the same reference numerals or letters are used to represent the same or equivalent elements. In order to facilitate a better understanding of the embodiments of the present disclosure, the accompanying drawings are shown and are not necessarily drawn to scale, in which:

[0070] Figure 1a Schematically illustrates a high-level architecture in a fifth generation network according to an embodiment of the present disclosure;

[0071] Figure 1b The architecture of the migration scenario for EPC and 5G CN according to an embodiment of the present disclosure is schematically shown;

[0072] Figure 1cThe non-roaming architecture for interworking between 5GS and EPC / E-UTRAN according to an embodiment of the present disclosure is schematically shown;

[0073] Figure 2a is a flow chart for 5GS to EPS handover using single registration mode of N26 according to an embodiment of the present disclosure;

[0074] Figure 2b is a flow chart for 5GS to EPS idle mode mobility using N26 interface according to an embodiment of the present disclosure;

[0075] Figure 2c is a flowchart of establishing an AM policy association with a newly selected PCF according to an embodiment of the present disclosure;

[0076] Figure 2d is a flow chart of AM policy association modification initiated by PCF according to an embodiment of the present disclosure;

[0077] Figure 3 is a flowchart of a method according to an embodiment of the present disclosure;

[0078] Figure 4 is a flowchart of a method according to an embodiment of the present disclosure;

[0079] Figure 5 is a flowchart of a method according to an embodiment of the present disclosure;

[0080] Figure 6 is a flowchart of a method according to an embodiment of the present disclosure;

[0081] Figure 7 is a flowchart of a method according to an embodiment of the present disclosure;

[0082] Figure 8 is a flowchart of a method according to an embodiment of the present disclosure;

[0083] Fig. 9 is a block diagram of an apparatus suitable for practicing some embodiments of the present disclosure;

[0084] Fig.10 is a block diagram illustrating a policy control entity in a first network according to an embodiment of the present disclosure;

[0085] Fig.11 is a block diagram illustrating a first mobility management entity in a first network according to an embodiment of the present disclosure; and

[0086] Fig.12 is a block diagram illustrating a second mobility management entity in a second network according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0087] Embodiments of the present disclosure are described in detail with reference to the accompanying drawings. It should be understood that these embodiments are discussed only for the purpose of enabling those skilled in the art to better understand and thus realize the present disclosure, rather than suggesting any limitation on the scope of the present disclosure. References to features, advantages or similar language throughout the specification do not mean that all features and advantages that can be implemented with the present disclosure should be in or in any single embodiment of the present disclosure. On the contrary, the language referring to features and advantages should be understood to mean that specific features, advantages or characteristics described in conjunction with the embodiments are included in at least one embodiment of the present disclosure. In addition, in one or more embodiments, the features, advantages and characteristics described in the present disclosure may be combined in any suitable manner. Those skilled in the relevant art will recognize that the present disclosure may be practiced without one or more of the specific features or advantages of a particular embodiment. In other cases, additional features and advantages may be recognized in certain embodiments, and the additional features and advantages may not exist in all embodiments of the present disclosure.

[0088] As used herein, the term "network" refers to a network that complies with any suitable communication standard, such as New Radio (NR), Long Term Evolution (LTE), Advanced LTE (LTE-A), Wideband Code Division Multiple Access (WCDMA), High Speed ​​Packet Access (HSPA), Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), Single Carrier Frequency Division Multiple Access (SC-FDMA), and other wireless networks. A CDMA network can implement radio technologies such as Universal Terrestrial Radio Access (UTRA). UTRA includes WCDMA and other variants of CDMA. A TDMA network can implement radio technologies such as Global System for Mobile Communications (GSM). An OFDMA network can implement radio technologies such as Evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDMA, Ad-hoc networks, wireless sensor networks, etc. In the following description, the terms "network" and "system" may be used interchangeably. In addition, communication between two devices in a network may be performed according to any suitable communication protocol, including but not limited to communication protocols defined by standard organizations such as 3GPP. For example, the communication protocol may include first generation (1G), 2G, 3G, 4G, 4.5G, 5G communication protocols and / or any other protocol currently known or developed in the future.

[0089] The term "network device" or "network node" refers to any suitable network function (NF) that can be implemented in a (physical or virtual) network element of a communication network. For example, a network function can be implemented as a network element on dedicated hardware, as a software instance running on dedicated hardware, or as a virtualized function instantiated on an appropriate platform (e.g., on a cloud infrastructure). For example, a 5G system (5GS) may include multiple NFs, such as AMF (Access and Mobility Function), SMF (Session Management Function), AUSF (Authentication Service Function), UDM (Unified Data Management), PCF (Policy Control Function), AF (Application Function), NEF (Network Exposure Function), UPF (User Plane Function) and NRF (Network Repository Function), RAN (Radio Access Network), SCP (Service Communication Agent), NWDAF (Network Data Analysis Function), NSSF (Network Slice Selection Function), NSSAAF (Network Slice Specific Authentication and Authorization Function), etc. For example, a 4G system (e.g., LTE) may include an MME (Mobility Management Entity), an HSS (Home Subscriber Server), a Policy and Charging Rules Function (PCRF), a Packet Data Network Gateway (PGW), a PGW Control Plane (PGW-C), a Serving Gateway (SGW), an SGW Control Plane, an E-UTRAN Node B (eNB), etc. In other embodiments, the network functions may include different types of NFs, e.g., depending on the specific network.

[0090] The network device may be an access device with access function in a communication network, through which the terminal device accesses the network and receives services from it. The access network device may include a base station (BS), an access point (AP), a multi-cell / multicast coordination entity (MCE), a controller, or any other suitable device in a wireless communication network. The BS may be, for example, a Node B (NodeB or NB), an evolved NodeB (eNodeB or eNB), a next generation NodeB (gNodeB or gNB), a remote radio unit (RRU), a radio head (RH), an integrated access and backhaul (IAB) node, a remote radio head (RRH), a repeater, a low power node (e.g., a femto, a pico), etc.

[0091] Yet another example of an access network device includes a multi-standard radio (MSR) wireless device such as an MSRBS, a network controller such as a radio network controller (RNC) or a base station controller (BSC), a base transceiver station (BTS), a transmission point, a transmission node, a positioning node, etc. However, more generally, a network node may represent any suitable device (or group of devices) that is capable of, configured, arranged and / or operable to enable a terminal device to access a wireless communication network and / or to provide certain services to a terminal device that has accessed the wireless communication network.

[0092] The term "terminal device" refers to any terminal device that can access a communication network and receive services therefrom. As an example and not limitation, a terminal device refers to a mobile terminal, a user equipment (UE) or other suitable device. A UE may be, for example, a subscriber station (SS), a portable subscriber station, a mobile station (MS) or an access terminal (AT). Terminal devices may include, but are not limited to, portable computers, image capture terminal devices such as digital cameras, game terminal devices, music storage and playback devices, mobile phones, cellular phones, smart phones, voice over IP (VoIP) phones, wireless local loop phones, tablet computers, wearable devices, personal digital assistants (PDAs), portable computers, desktop computers, wearable terminal devices, vehicle-mounted wireless terminal devices, wireless endpoints, mobile stations, laptop embedded devices (LEEs), laptop mounted devices (LMEs), USB dongles, smart devices, wireless customer premises equipment (CPEs), etc. In the following description, the terms "terminal device", "terminal", "user equipment" and "UE" may be used interchangeably. As an example, a terminal device may represent a UE configured to communicate in accordance with one or more communication standards (e.g., 3GPP's LTE standard or NR standard) issued by 3GPP (3rd Generation Partnership Project). As used herein, a "user equipment" or "UE" may not necessarily have a "user" in terms of a human user who owns and / or operates the associated device. In some embodiments, a terminal device may be configured to send and / or receive information without direct human interaction. For example, when triggered by an internal or external event, or in response to a request from a communication network, a terminal device may be designed to send information to the network according to a predetermined schedule. Alternatively, a UE may represent a device that is intended to be sold to a human user or operated by a human user but may not initially be associated with a specific human user.

[0093] As another example, in an Internet of Things (IoT) scenario, a terminal device may represent a machine or other device that performs monitoring and / or measurement, and sends the results of such monitoring and / or measurement to another terminal device and / or network device. In this case, the terminal device may be a machine-to-machine (M2M) device, which may be referred to as a machine type communication (MTC) device in the 3GPP context. As a specific example, the terminal device may be a UE that implements the 3GPP Narrowband Internet of Things (NB-IoT) standard. Specific examples of such machines or devices are sensors, metering devices (e.g., electricity meters, industrial machinery) or household or personal appliances (e.g., refrigerators, televisions), personal wearable devices (e.g., watches), etc. In other scenarios, a terminal device may represent a vehicle or other device that is capable of monitoring and / or reporting its operating status or other functions related to its operation.

[0094] References in the specification to "one embodiment," "an embodiment," "an exemplary embodiment," etc. indicate that the described embodiment may include a particular feature, structure, or characteristic, but not necessarily every embodiment includes the particular feature, structure, or characteristic. Furthermore, these phrases do not necessarily refer to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in conjunction with an embodiment, whether or not explicitly described, it is considered to be within the knowledge of those skilled in the art to affect such feature, structure, or characteristic in relation to other embodiments.

[0095] It should be understood that although the terms "first" and "second" etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. For example, without departing from the scope of the exemplary embodiments, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed terms.

[0096] As used herein, the phrase "at least one of A and B" or "at least one of A or B" should be understood to mean "only A, only B, or both A and B". The phrase "A and / or B" should be understood to mean "only A, only B, or both A and B".

[0097] 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 when used herein, the terms "including," "comprising," "having," “Having”, “containing” and / or “comprising” specifies the existence of stated features, elements and / or components etc., but does not preclude the existence or addition of one or more other features, elements, components and / or combinations thereof.

[0098] Note that these terms used in this article are only used to facilitate description and to distinguish between nodes, devices or networks, etc. As technology develops, other terms with similar / same meanings may also be used.

[0099] In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0100] Although the subject matter described herein can be implemented in any suitable type of system using any suitable components, the embodiments disclosed herein are directed to systems that conform to Figure 1a-1c For simplicity, the communication system of the exemplary system architecture shown is described. Figure 1a-1cThe system architecture of FIG. 1 depicts only some exemplary elements. In practice, the communication system may also include any additional elements suitable for supporting communication between terminal devices or between a wireless device and another communication device (e.g., a landline phone, a service provider, or any other network node or terminal device). The communication system may provide communication and various types of services to one or more terminal devices to facilitate the terminal devices to access and / or use services provided by or via the communication system.

[0101] Figure 1a The high-level architecture in the fifth generation network according to an embodiment of the present disclosure is schematically shown. For example, the fifth generation network may be 5GS. Figure 1a The architecture is similar to that described in 3GPP TS23.501V17.2.0 Figure 4 .2.3-2, the disclosure of which is incorporated herein by reference in its entirety. Figure 1a The system architecture may include some exemplary elements, such as AUSF, AMF, DN (data network), NEF, NRF, NSSF, PCF, SMF, UDM, UPF, AF, UE, (R)AN, SCP (service communication agent), NSSAAF (network slice specific authentication and authorization function), NSACF (network slice admission control function), etc.

[0102] According to an exemplary embodiment, Figure 1a As shown, the UE can establish a signaling connection with the AMF through reference point N1. The signaling connection can realize the NAS (non-access layer) signaling exchange between the UE and the core network, including the signaling connection between the UE and the (R)AN and the N2 connection between the (R)AN and the AMF for the UE. The (R)AN can communicate with the UPF through reference point N3. The UE establishes a protocol data unit (PDU) session to the DN (data network, such as an operator network or the Internet) through the UPF through reference point N6.

[0103] like Figure 1a As further shown in FIG. 1 , the exemplary system architecture also includes some reference points such as N1, N2, N3, N4, N6, N9 and N15, which can support the interaction between NF services in the NF. For example, these reference points can be implemented through corresponding NF service-based interfaces and by specifying some NF service consumers and providers and their interactions to perform specific system processes. The PCF provides the AM-related policies for the registered UE to the AMF via the N15 interface. The AMF can obtain the AM policy during the AM policy association establishment / modification process.

[0104] Figure 1aThe various NFs shown in the figure may be responsible for functions such as session management, mobility management, authentication, security, etc. AUSF, AMF, DN, NEF, NRF, NSSF, PCF, SMF, UDM, UPF, AF, UE, (R)AN, SCP, NSACF may include, for example, the functions defined in clause 6.2 of 3GPP TS23.501 V17.2.0.

[0105] Figure 1b The architecture of the migration scenario for EPC and 5G CN (core network) according to an embodiment of the present disclosure is schematically shown, which is consistent with 3GPP TS23.501V17.2.0 Figure 5 .17.1.1-1 is the same.

[0106] Deployments based on different 3GPP architecture options (i.e., EPC-based or 5GC-based) and UEs with different capabilities (EPC NAS and 5GC NAS) can coexist simultaneously in one PLMN.

[0107] It is assumed that a UE capable of supporting 5GC NAS procedures is also capable of supporting EPC NAS (i.e., the NAS procedures defined in 3GPP TS 23.401 V17.3.0, the disclosure of which is incorporated herein by reference in its entirety) to operate in a legacy network, for example in roaming scenarios.

[0108] The UE shall use EPC NAS or 5GC NAS procedures depending on the core network serving the UE.

[0109] To support smooth migration, it is assumed that the EPC and 5GC have access to a common subscriber database, i.e., in the case of the EPC this is the HSS and in the case of the 5GC this is the UDM, acting as the master database for a given user, as defined in 3GPP TS 23.002 V17.0.0, the disclosure of which is incorporated herein by reference in its entirety. The PCF may use the Nudr service defined in 3GPP TS 23.502 V17.2.1 (the disclosure of which is incorporated herein by reference in its entirety) to access the UDR (Unified Data Repository), which serves as a common subscriber database for a given user identified by a SUPI.

[0110] UEs supporting EPC-based dual connectivity with secondary RAT NR only:

[0111] - Initial access is always performed over E-UTRA (LTE-Uu) but never over NR;

[0112] - Perform EPC NAS procedures (i.e., mobility management, session management, etc.) over E-UTRA as defined in 3GPP TS 24.301 V17.5.0, the disclosure of which is incorporated herein by reference in its entirety.

[0113] Support for UEs residing on 5G systems using 5GC NAS:

[0114] - Perform initial access towards 5GC through E-UTRAN or NR connected to 5GC;

[0115] - If supported and required, initial access towards EPC is performed through E-UTRAN;

[0116] -If the UE also supports EPC NAS, EPC NAS or 5GC NAS procedures (i.e., mobility management, session management, etc.) are performed through E-UTRAN or NR, depending on whether the UE requests 5GC access or EPC access, respectively.

[0117] Clause 5.17.2.2 of 3GPP TS23.501V17.2.0 describes the interworking procedure using the N26 interface. The interworking procedure using the N26 interface enables the exchange of MM and SM states between the source network and the target network. The N26 interface can be intra-PLMN (public land mobile network) or inter-PLMN (for example, used to enable inter-PLMN mobility). When the interworking procedure using N26 is used, the UE operates in single registration mode. For 3GPP access, the network retains only one valid MM (mobility management) state for the UE in the AMF or MME. For 3GPP access, the AMF or MME is registered in the HSS+UDM.

[0118] Support of the N26 interface between the AMF in 5GC and the MME in EPC is required to enable seamless session continuity for inter-system changes (e.g. for voice services).

[0119] Clause 5.17.2.3 of 3GPP TS23.501 V17.2.0 describes the interworking process without N26 interface. For interworking without N26 interface, IP address preservation is provided to UE on inter-system mobility by storing and obtaining SMF+PGW-C and corresponding APN / DNN information via HSS+UDM. In such networks, the AMF also provides an indication to the UE during the initial registration in 5GC that interworking without N26 is supported, or the MME may optionally provide an indication of interworking without N26 during the attach procedure in EPC, as defined in 3GPP TS23.502 V17.2.1 and 3GPP TS23.401 V17.3.0. During the attach procedure as described in 3GPP TS 23.401 V17.3.0 clause 5.3.2.1 and during initial registration and mobility registration update in 5GC, the UE provides an indication that it supports the request type flag "handover" for the PDN connection request.

[0120] Figure 1c The non-roaming architecture for interworking between 5GS and EPC / E-UTRAN according to an embodiment of the present disclosure is schematically shown, which is consistent with 3GPP TS23.501V17.2.0. Figure 4 .Same as 3.1-1.

[0121] The N26 interface is the inter-CN interface between the MME and the 5GS AMF to enable interworking between the EPC and the NG core. Support for the N26 interface in the network is optional for interworking. N26 supports a subset of the functionality supported by S10 (critical for interworking).

[0122] Figure 2a is a 5GS to EPS handover flow chart for single registration mode using N26 according to an embodiment of the present disclosure, which is consistent with 3GPP TS23.502V17.2.1 Figure 4 .11.1.2.1-1 is the same.

[0123] As described in clause 4.11.1.2.1 of 3GPP TS 23.502 V17.2.1, in step 3. AMF sends Forward Relocation Request as described in clause 5.5.1.2.2 (S1-based Handover, Normal) of 3GPP TS 23.401 V17.3.0, with the following modifications and clarifications:

[0124] -The parameter "Return to Preference" may be included. Return to Preference is an optional indication issued by the MME, indicating that the UE prefers to return to the 5GS PLMN when access is later changed to the 5GS shared network. The MME can use this information as specified in 3GPP TS23.501V17.2.0.

[0125] - The SGW address and TEID for both control plane or EPS bearers in this message enables the target MME to select a new SGW.

[0126] -AMF determines the direct forwarding flag based on the configuration and direct forwarding path availability to inform the target MME whether direct data forwarding is applicable.

[0127] - The AMF includes mapped SM EPS UE context for PDU sessions with and without active UP connection.

[0128] – Subject to operator policy, if the secondary RAT access restriction conditions are the same for EPS and 5GS, the AMF may set the EPS secondary RAT access restriction conditions based on the UE’s subscription data.

[0129] For description of other steps, please refer to clause 4.11.1.2.1 of 3GPP TS23.502V17.2.1.

[0130] Figure 2b is a flowchart of 5GS to EPS idle mode mobility using N26 interface according to an embodiment of the present disclosure, which is consistent with 3GPP TS23.502V17.2.1 Figure 4 .Same as 11.1.3.2-1.

[0131] As described in clause 4.11.1.3.2 of 3GPP TS23.502V17.2.1, in step 6.AMF responds to the MME with a context response message, which carries the mapped MM context (including the mapped security context), return preference and SM EPSUE context (default and dedicated GBR (guaranteed bit rate) bearers). If the verification of integrity protection fails, the AMF returns an appropriate error cause. Return preference is an optional indication of the AMF, indicating that the UE prefers to return to the 5GS PLMN when access is changed to the 5GS shared network later. The AMF can start implementation-specific (protection) timers for the UE context.

[0132] Based on the received context and the tracking area indicated by the RAN, the MME can determine whether the UE is performing inter-RAT mobility to or from NB-IoT.

[0133] For description of other steps, please refer to clause 4.11.1.3.2 of 3GPP TS23.502V17.2.1.

[0134] Figure 2c is a flowchart of establishing an AM policy association with a newly selected PCF according to an embodiment of the present disclosure, which is consistent with 3GPP TS23.502V17.2.1 Figure 4 .Same as 16.1.2-1.

[0135] As described in 3GPP TS 23.502 V17.2.1 clause 4.16.1, there are three cases considered for AM policy association establishment:

[0136] 1. Initial registration of UE with the network.

[0137] 2. AMF reallocation with PCF change during handover process and registration process.

[0138] 3. EPS to 5GS mobility when there is no existing AM policy association between the AMF and PCF for this UE.

[0139] The process involves both roaming and non-roaming scenarios.

[0140] In non-roaming situations, the role of V-PCF (visiting PCF) is performed by PCF. For roaming scenarios, V-PCF interacts with AMF.

[0141] In step 1., based on local policy, AMF decides to establish an AM policy association with the (V-)PCF, and then performs steps 2 to 3 under the following conditions.

[0142] In step 2., [Conditional] If the AMF has not obtained the access and mobility policy for the UE, or if the access and mobility policy in the AMF is no longer valid, the AMF requests the PCF to apply the operator policy for the UE from the PCF. The AMF sends Npcf_AMPolicyControl_Create to the (V-)PCF to establish an AM policy control association with the (V-)PCF. The request contains the following information: SUPI, Internal Group (see 3GPP TS 23.501 V17.2.0 clause 5.9.7), Subscription Notification Indication and (if available) Service Area Restriction, RFSP Index, Subscribed UE-AMBR, Subscribed UE-Slice-MBR List, Allowed NSSAI, Target NSSAI (see 3GPP TS 23.501 V17.2.0 clause 5.3.4.3.3), GPSI retrieved from UDM during Update Location procedure, possibly including Access Type and RAT Type, PEI, ULI, UE Time Zone and Serving Network (PLMN ID, or PLMN ID and NID, see 3GPP TS 23.501 V17.2.0 clause 5.34).

[0143] When AMF uses NWDAF, it can add the NWDAF that provides services to the UE identified by the NWDAF instance ID. According to the NWDAF service instance, an analysis ID is further included.

[0144] In step 3. (V)-PCF responds to the Npcf_AMPolicyControl_Create service operation. (V)-PCF provides access and mobility related policy information (e.g. service area restrictions) as defined in 3GPP TS23.503V17.3.0 clause 6.5. In addition, (V)-PCF may provide a policy control request trigger for AM policy association to AMF. In non-roaming cases, PCF may subscribe to analytics from NWDAF as defined in 3GPP TS23.503V17.3.0 clause 6.1.1.3.

[0145] The AMF is implicitly subscribed in the (V-)PCF to be notified of changes in policy.

[0146] The (V-)PCF may register with the BSF as the PCF that handles AM policy association for this UE. This is performed using the Nbsf_Management_Register operation, providing the UE SUPI / GPSI and PCF identity as input.

[0147] In step 4. [Conditional] AMF deploys access and mobility related policy information, which includes storing the service area restriction and policy control request trigger associated with the AM policy, providing the service area restriction to the UE, providing the RFSP index, UE-AMBR, UE-Slice-MBR list, service area restriction to the NG-RAN as defined in 3GPP TS23.501V17.2.0, and requesting notification of establishment and termination of SM policy association to the (DNN, S-NSSAI) list and UE binding to the PCF.

[0148] Figure 2d is a flowchart of AM policy association modification initiated by PCF according to an embodiment of the present disclosure, which is consistent with 3GPPTS23.502V17.2.1 Figure 4 .Same as 16.2.2-1.

[0149] As described in 3GPP TS 23.502 V17.2.1 clause 4.16.1, the AM policy association modification process may be initiated by an internal PCF event or by the PCF obtaining relevant analysis information from the NWDAF.

[0150] The following procedure applies to AM policy association modification due to situation B.

[0151] The process driven by PCF internal events is applicable to both roaming and non-roaming scenarios, while when driven by NWDAF, it is applicable only to non-roaming scenarios.

[0152] Before triggering this procedure, an AM policy association is established with the V-PCF in case of roaming and with the PCF in case of non-roaming, as described in 3GPP TS23.502V17.2.1 clause 4.16.1.2.

[0153] In non-roaming situations, the role of V-PCF is performed by PCF. For roaming scenarios, V-PCF interacts with AMF.

[0154] NOTE: V-PCF / PCF stores access and mobility control policy information provided to AMF.

[0155] In step 1. [Conditional] The PCF determines within the new state of the UE context that a new policy is required, which may be triggered by the AF as described in clause 4.15.6.9, or by a notification from the UDR. This may be triggered by obtaining relevant analysis information from the NWDAF, as described in clause 6.1.1.3 of 3GPP TS 23.503 V17.3.0.

[0156] In step 2. the (V-)PCF in the roaming case and the PCF in the non-roaming case make a policy decision. The PCF may also decide to subscribe to a new analysis ID from the NWDAF as described in 3GPP TS 23.503 V17.3.0 clause 6.1.1.3.

[0157] In step 3. the (V-)PCF in the roaming case and the PCF in the non-roaming case sends Npcf_AMPolicyControl_UpdateNotify, which includes the AM policy association ID associated with the SUPI defined in 3GPP TS29.507. The policy update may include service area restrictions, UE-AMBR, RFSP index value, access layer time distribution indication and Uu time synchronization error budget. If the AF has previously subscribed to the event request for the service area coverage allocation result in step 1, the (V-)PCF checks whether the allocated service area coverage has changed and sends the corresponding notification to the AF using Npcf_AMPolicyAuthorization_Notify defined in clause 6.3.1.18 of 3GPP TS 23.503V17.3.0.

[0158] In step 4, the AMF deploys and stores updated access and mobility related policy information, which includes storing the service area restriction and policy control request trigger associated with the AM policy, providing the service area restriction to the UE, providing the RFSP index, UE-AMBR, service area restriction to the NG-RAN, and optionally providing the access layer time distribution indication and Uu time synchronization error budget to the NG-RAN, and requesting notification of establishment and termination of SM policy association to the (DNN, S-NSSAI) list and UE binding information from the PCF.

[0159] Clause 4.3.6 of 3GPP TS 23.401 V17.3.0 describes the radio resource management function.

[0160] To support Radio Resource Management in E-UTRAN, the MME provides the parameter "Index for RAT / Frequency Selection Priority" (RFSP Index) to the eNodeB via S1. The eNodeB maps the RFSP Index to a locally defined configuration in order to apply a specific RRM policy. The RFSP Index is UE specific and applies to all radio bearers. Examples of how E-UTRAN may use this parameter:

[0161] - Derive UE specific cell reselection priorities to control idle mode residency.

[0162] - Decide to redirect an active mode UE to a different frequency layer or RAT.

[0163] The MME receives the subscribed RFSP index and subscribed ARPI from the HSS (e.g., during the attach procedure). For non-roaming users, depending on the operator's configuration, the MME selects the RFSP index and ARPI in use according to one of the following procedures:

[0164] – the RFSP index in use is the same as the subscribed RFSP index, or

[0165] - The MME selects the RFSP index in use based on the subscribed RFSP index, locally configured operator policies and UE-related context information available at the MME, including the UE's usage settings and voice domain preference for E-UTRAN if received during the attach and tracking area update procedures (see clause 4.3.5.9 of 3GPP TS 23.401 V17.3.0).

[0166] - the ARPI in use is the same as the subscribed ARPI, or

[0167] - The MME selects the ARPI in use based on the subscribed ARPI, locally configured operator policies and UE related context information available at the MME.

[0168] For roaming users, the MME may select the RFSP index and ARPI in use based on the visited network policy, but may take into account input from the HPLMN (e.g., a pre-configured RFSP index value / ARPI value for each HPLMN, or a single RFSP index value / single ARPI value to be used for all roamers regardless of the HPLMN).

[0169] The MME forwards the RFSP index and ARPI in use to the eNodeB via S1. The RFSP index and ARPI in use are also forwarded from the source eNodeB to the target eNodeB when X2 is used for intra-E-UTRAN handover, UE context retrieval, or dual connectivity using a secondary RAN node.

[0170] The MME stores the subscribed RFSP index and ARPI value and the RFSP index and ARPI value in use received from the HSS. During the tracking area update process, the MME may update the RFSP index / ARPI value in use (for example, if the UE-related context information in the MME has changed, the MME may need to update the RFSP index / ARPI value in use). When the RFSP index / ARPI value in use changes, the MME immediately provides the updated RFSP index / ARPI value in use to the eNodeB by modifying the existing UE context or by establishing a new UE context in the eNodeB or by being configured to include the updated RFSP index / ARPI value in use in the downlink NAS transmission message (if the user plane does not need to be established). During the inter-MME mobility process, the source MME forwards both the RFSP index and ARPI value to the target MME. The target MME can replace the received RFSP index and ARPI value in use with a new RFSP index value in use or a new ARPI value, which is based on the operator's policy and the UE-related context information available at the target MME.

[0171] The S1 message that transmits the RFSP index and ARPI to the eNodeB is specified in 3GPP TS 36.413. For further information on E-UTRAN, refer to 3GPP TS 36.300.

[0172] To support a mixed RAN with ARPI-capable and non-ARPI-capable RAN nodes, the MME sends the ARPI in use in the S1 interface PATCH SWITCH ACKNOWLEDGEMENT and HANDOVER REQUEST messages.

[0173] Figure 3A flow chart of a method according to an embodiment of the present disclosure is shown, and the method can be performed by a device implemented in a policy control entity, or by a device communicatively coupled to the policy control entity, or by a device implemented as a policy control entity. Therefore, the device can provide components for completing various parts of the method 300 and components for completing other processes together with other components.

[0174] At block 302, a policy control entity may set a validity time for a radio access technology or frequency selection priority (RFSP) index for a user equipment (UE) moving from a first network to a second network.

[0175] In an embodiment, the policy control entity may be in the first network.

[0176] In an embodiment, the policy control entity may set a validity time for a radio access technology or frequency selection priority (RFSP) index. The validity time for the RFSP index indicates the time when the RFSP index will take effect or be used. In an embodiment, the validity time of the RFSP index indicates the time when the RFSP index will take effect or be used when the UE is in the EPS.

[0177] In an embodiment, the validity time for the RFSP index indicates a time during which the RFSP index is to be used in a second mobility management entity when the UE is in the second network.

[0178] At block 304, the policy control entity may send a first message including an RFSP index and a validity time for the RFSP index to a mobility management entity in the first network.

[0179] In an embodiment, the policy control entity comprises a Policy Control Function (PCF).In an embodiment, the mobility management entity comprises an Access and Mobility Function (AMF).In an embodiment, the second mobility management entity is a Mobility Management Entity (MME).

[0180] In an embodiment, the policy control entity may send a first message to the mobility management entity, the first message including the RFSP index and a valid time for the RFSP index.

[0181] The term "validate" may mean that the mobility management entity should use the RFSP index directly before the validity time for the RFSP index expires. For example, the mobility management entity should not re-evaluate or re-select the RFSP index.

[0182] The policy control entity may be any suitable network function that may provide a policy control function.In an embodiment, the policy control entity comprises a policy control function (PCF).

[0183] The mobility management entity may be any suitable network function that can provide mobility management functions. In an embodiment, the mobility management entity comprises an access and mobility function (AMF).

[0184] The effective time for the RFSP index can be determined or obtained in a variety of ways. For example, the effective time for the RFSP index can be provided to the policy control entity by an application node (such as an application function or an application server, etc.). The effective time for the RFSP index can be determined by the policy control entity according to certain standards. The RFSP index can be configured with a fixed effective time. Different RFSP indexes can have different effective times. The effective time for the RFSP index can be determined according to a policy or rule. The effective time for the RFSP index can be configured by the operator. The effective time for the RFSP index can be determined based on the user's subscription data. The effective time for the RFSP index can be determined based on the service type, service quality requirements or data volume of the UE. The effective time for the RFSP index can be determined based on the application in use. The effective time for the RFSP index can be determined based on the network situation.

[0185] In an embodiment, the RFSP index may have no validity time (ie, the RFSP index has no expiration time).

[0186] The validity time for the RFSP index may be in any suitable form, such as a timestamp.

[0187] The RFSP index may be set to any suitable value. There may be a mapping relationship from the RFSP index to cell selection and RAT / frequency priority. The policy control entity may store or know the mapping relationship.

[0188] In an embodiment, the RFSP index indicates a preference for 3GPP EPS access. In other embodiments, the RFSP index may indicate a preference for any other suitable network access.

[0189] In an embodiment, the validity time for the RFSP index further indicates the time when the RFSP index will take effect in a specific network. The specific network can be any suitable network, such as 3GPP 2G, 3G, 4G networks, etc. For example, when the UE is accessing a specific network, the validity time for the RFSP index will take effect in the specific network. When the UE has accessed other networks other than the specific network, the validity time for the RFSP index will not take effect in the specific network. In other words, the validity time for the RFSP index can be ignored in other networks.

[0190] In an embodiment, the specific network includes 3GPP EPS.

[0191] The first message may be any suitable message, such as an existing message or a new message.

[0192] In an embodiment, the first message comprises at least one of an access and mobility management entity policy control create response or an access and mobility management entity policy control update notification.

[0193] For example, Figure 2c As shown in , during the process of establishing the AM policy association with the newly selected PCF, the RFSP index and the validity time for the RFSP index may be included in the Npcf_AMPolicyControl_Create response. Figure 2d As shown in FIG. 4 , during the AM policy association modification procedure initiated by the PCF, the RFSP index and the validity time for the RFSP index may be included in Npcf_AMPolicyControl_UpdateNotify.

[0194] Blocks 302 and 304 may be triggered to execute due to various reasons.

[0195] As a first example, based on local policy, the mobility management entity (eg, AMF) decides to establish an AM policy association with the policy control entity, and then executes blocks 302 and 304 under the following conditions.

[0196] If the mobility management entity (e.g., AMF) has not yet obtained the access and mobility policy for the UE, or if the access and mobility policy in the mobility management entity (e.g., AMF) is no longer valid, the mobility management entity (e.g., AMF) requests the policy control entity (e.g., PCF) to apply the operator policy for the UE from the policy control entity (e.g., PCF). The mobility management entity (e.g., AMF) sends an AM policy control creation request to the policy control entity to establish an AM policy control association with the policy control entity. The policy control entity sends an AM policy control creation response to the mobility management entity, which may include an RFSP index and a valid time for the RFSP index.

[0197] As a second example, the AM policy association modification process may be initiated by an internal policy control entity event, or by the policy control entity obtaining relevant analysis information from a network data analysis function, and then blocks 302 and 304 are executed under the following conditions.

[0198] The policy control entity stores access and mobility control policy information provided to the mobility management entity. The PCF internally determines that a new state of the UE context requires a new policy, which can be triggered by the AF or by a notification from the unified data repository. This can be triggered by obtaining relevant analysis information from the network data analysis function. The policy control entity makes a policy decision. The policy control entity sends an AM policy control update notification, which may include an RFSP index and a valid time for the RFSP index.

[0199] Figure 4 A flow chart of a method according to another embodiment of the present disclosure is shown, which can be executed by a device implemented in a policy control entity, or by a device communicatively coupled to a policy control entity, or by a device implemented as a policy control entity. In this way, the device can provide components for completing various parts of the method 400 and components for completing other processes together with other components. For some parts that have been described in the above embodiments, their description is omitted here for the sake of brevity.

[0200] At block 402, the policy control entity may determine that a change in the value of the RFSP index indicates a change for the user equipment from prioritizing a first network access to prioritizing a second network access. In response to the determination, a validity time for the RFSP index is included in a first message.

[0201] The first network access may be any suitable RAT. The second network access may be any suitable RAT.

[0202] In an embodiment, the first network access comprises a 3rd Generation Partnership Project (3GPP) Fifth Generation System (5GS) access, and the second network access comprises a 3GPP Evolved Packet System (EPS) access.

[0203] In an embodiment, the first network comprises a 3rd Generation Partnership Project (3GPP) Fifth Generation System (5GS), and the second network comprises a 3GPP Evolved Packet System (EPS).

[0204] For example, there may be a mapping relationship from the RFSP index to the cell selection and RAT / frequency priority that may exist. The policy control entity may store or know the mapping relationship. During the AM policy association establishment process initiated by the mobility management entity with the policy control entity, or during the AM policy association modification process initiated by the PCF, the policy control entity may make access and mobility policies for the UE. The access and mobility policies may include an authorized RFSP index. The authorized RFSP index may be different from the RFSP index provided by the mobility management entity. For example, the RFSP index provided by the mobility management entity may indicate priority for the first network access, while the authorized RFSP index may indicate priority for the second network access. The policy control entity may then determine that the change in the value of the RFSP index indicates a change from priority for the first network access to priority for the second network access for the user equipment.

[0205] At block 404, a policy control entity may set a validity time for a radio access technology or frequency selection priority (RFSP) index for a user equipment (UE) moving from a first network to a second network. The validity time for the RFSP index indicates a time when the RFSP index will be used in a second mobility management entity when the UE is in the second network. Block 404 and Figure 3 The same as block 302 of FIG.

[0206] At block 406, the policy control entity may send a first message including the RFSP index and a validity time for the RFSP index to a mobility management entity in the first network. Figure 3 The same as block 304 of FIG.

[0207] Figure 5 A flowchart of a method according to another embodiment of the present disclosure is shown, which can be executed by a device implemented in a first mobility management entity, or by a device communicatively coupled to the first mobility management entity, or by a device implemented as a first mobility management entity. In this way, the device can provide components for completing various parts of the method 500 and components for completing other processes together with other components. For some parts that have been described in the above embodiments, their description is omitted here for the sake of brevity.

[0208] At block 502, a first mobility management entity may send a second message to a second mobility management entity in a second network, the second message including a radio access technology or frequency selection priority (RFSP) index and a validity time for the RFSP index for a user equipment (UE) moving from the first network to the second network.

[0209] In an embodiment, the first mobility management entity may be in the first network.

[0210] In an embodiment, the validity time for the RFSP index indicates a time during which the RFSP index is to be used in a second mobility management entity when the UE is in the second network.

[0211] In an embodiment, the RFSP index indicates a preferred 3GPP EPS access.

[0212] In an embodiment, the validity time for the RFSP index further indicates the time when the RFSP index will be effective in a particular network.

[0213] In an embodiment, the specific network includes 3GPP EPS.

[0214] The first mobility management entity may be any suitable network function capable of providing a mobility management function. For example, the first mobility management entity may be an AMF or an MME.

[0215] The second mobility management entity may be any suitable network function capable of providing mobility management functions. For example, the first mobility management entity may be an AMF or an MME.

[0216] In an embodiment, the first mobility management entity is an AMF and the second mobility management entity is an MME.

[0217] In an embodiment, the first mobility management entity is an AMF and the second mobility management entity is an AMF.

[0218] In an embodiment, the first mobility management entity is an MME and the second mobility management entity is an MME.

[0219] In an embodiment, the second message is sent to the second mobility management entity during at least one of the S1 based handover procedure described in clause 5.5.1.2 of 3GPP TS 23.401 V17.3.0 or the S1 based dual active protocol stack (DAPS) handover procedure described in clause 5.5.1.2.2a of 3GPP TS 23.401 V17.3.0.

[0220] In an embodiment, the second message includes at least one of a forward relocation request or a context response described in 3GPP TS 23.401 V17.3.0 and 3GPP TS 23.502 V17.2.1.

[0221] In an embodiment, the valid time for the RFSP index may be set by the first mobility management entity. For example, the RFSP index may be provided by the policy control entity, and then the first mobility management entity sets the valid time for the RFSP index. As another example, the first mobility management entity (e.g., AMF or MME) may select the RFSP index in use and then set the valid time for the RFSP index.

[0222] In another embodiment, the validity time for the RFSP index may be set by the policy control entity and sent to the first mobility management entity, as described in methods 300 and 400 .

[0223] Figure 6 A flowchart of a method according to another embodiment of the present disclosure is shown, which can be executed by a device implemented in a first mobility management entity, or by a device communicatively coupled to the first mobility management entity, or by a device implemented as a first mobility management entity. In this way, the device can provide components for completing various parts of the method 600 and components for completing other processes together with other components. For some parts that have been described in the above embodiments, their description is omitted here for the sake of brevity.

[0224] At block 602, the first mobility management entity may receive an RFSP index from a policy control entity. For example, the RFSP index may be an RFSP index authorized by the policy control entity. Figure 2c and 2d As described in, the AMF can receive the RFSP index from the PCF.

[0225] The policy control entity may be any suitable network function capable of providing a policy control function.In an embodiment, the policy control entity comprises a Policy Control Function (PCF).

[0226] At block 604, the first mobility management entity may determine that the change in the value of the RFSP index indicates a change for the user equipment from prioritizing a first network access to prioritizing a second network access.

[0227] The first network access may be any suitable RAT. The second network access may be any suitable RAT.

[0228] In an embodiment, the first network access comprises a 3rd Generation Partnership Project (3GPP) Fifth Generation System (5GS) access, and the second network access comprises a 3GPP Evolved Packet System (EPS) access.

[0229] In an embodiment, the first network comprises a 3rd Generation Partnership Project (3GPP) Fifth Generation System (5GS) and the second network comprises a 3GPP Evolved Packet System (EPS).

[0230] For example, there may be a mapping relationship from an RFSP index to cell selection and RAT / frequency priority. The first mobility management entity may store or know the mapping relationship. During the establishment of an AM policy association with a policy control entity initiated by the mobility management entity or during the modification of an AM policy association initiated by the PCF, the policy control entity may formulate access and mobility policies for the UE. The access and mobility policies may include an authorized RFSP index. The authorized RFSP index may be different from the RFSP index provided by the mobility management entity. For example, the RFSP index provided by the mobility management entity may indicate priority for the first network access, while the authorized RFSP index may indicate priority for the second network access. The first mobility management entity may then determine that a change in the value of the RFSP index indicates a change from priority for the first network access to priority for the second network access for the user equipment.

[0231] At block 606, the first mobility management entity may set a validity time for the RFSP index.

[0232] The validity period for the RFSP index can be determined or obtained in various ways. For example, the validity period for the RFSP index can be determined by the first mobility management entity according to certain standards. The RFSP index can be configured with a fixed validity period. Different RFSP indexes can have different validity periods. The validity period for the RFSP index can be determined according to a policy or rule. The validity period for the RFSP index can be configured by the operator. The validity period for the RFSP index can be determined based on the subscription data of the subscriber. The validity period for the RFSP index can be determined according to the service or data volume of the UE. The validity period for the RFSP index can be determined according to the network situation.

[0233] In an embodiment, the RFSP index may have no validity time (ie, the RFSP index has no expiration time).

[0234] The validity time for the RFSP index may be in any suitable form, such as a timestamp.

[0235] The RFSP index may be set to any suitable value. There may be a mapping relationship from the RFSP index to cell selection and RAT / frequency priority. The first mobility management entity may store or know the mapping relationship.

[0236] In an embodiment, the RFSP index indicates a preference for 3GPP EPS access. In other embodiments, the RFSP index may indicate a preference for any other suitable network access.

[0237] In an embodiment, the validity time for the RFSP index further indicates the time when the RFSP index will take effect in a specific network. The specific network can be any suitable network, such as 3GPP 2G, 3G, 4G networks, etc. For example, when the UE is accessing a specific network, the validity time for the RFSP index will take effect in the specific network. When the UE has accessed other networks other than the specific network, the validity time for the RFSP index will not take effect in the specific network. In other words, the validity time for the RFSP index can be ignored in other networks.

[0238] At block 608, the first mobility management entity may store a validity time for the RFSP index.

[0239] At block 610, the first mobility management entity may send a second message to a second mobility management entity in a second network, the second message including a radio access technology or frequency selection priority (RFSP) index and a validity time for the RFSP index for a user equipment (UE) moving from the first network to the second network. The validity time for the RFSP index indicates a time when the RFSP index will be used in the second mobility management entity when the UE is in the second network.

[0240] In an embodiment, the first mobility management entity is an Access and Mobility Function (AMF) and the second mobility management entity is a Mobility Management Entity (MME).

[0241] In an embodiment, the second message is sent to the second mobility management entity during at least one of the 5GS to EPS handover procedure using the N26 interface described in Section 4.11.1.2.1 of 3GPP TS23.502 V17.2.1 or the 5GS to EPS idle mode mobility procedure using the N26 interface described in Section 4.11.1.3.2 of 3GPP TS23.502 V17.2.1.

[0242] Figure 7 A flowchart of a method according to another embodiment of the present disclosure is shown, which can be executed by a device implemented in a first mobility management entity, or by a device communicatively coupled to the first mobility management entity, or by a device implemented as a first mobility management entity. In this way, the device can provide components for completing various parts of the method 700 and components for completing other processes together with other components. For some parts that have been described in the above embodiments, their description is omitted here for the sake of brevity.

[0243] At block 702, a first mobility management entity may receive a first message including an RFSP index and a validity period for the RFSP index from a policy control entity. Figure 3 Box 304 and Figure 4 As described in block 406 of , the policy control entity may send the first message to the first mobility management entity, and the first mobility management entity may then receive the first message.

[0244] In an embodiment, the first message comprises at least one of an access and mobility management entity policy control create response or an access and mobility management entity policy control update notification.

[0245] At block 704, the first mobility management entity may store a validity time for the RFSP index.

[0246] At block 706, the first mobility management entity may send a second message to a second mobility management entity in the second network, the second message including a radio access technology or frequency selection priority (RFSP) index and a validity time for the RFSP index for a user equipment (UE) moving from the first network to the second network. In an embodiment, the validity time for the RFSP index indicates a time when the RFSP index will be used in the second mobility management entity when the UE is in the second network.

[0247] In an embodiment, the first mobility management entity is an Access and Mobility Function (AMF) and the second mobility management entity is a Mobility Management Entity (MME).

[0248] In an embodiment, the second message is sent to the second mobility management entity during at least one of the 5GS to EPS handover procedure using the N26 interface described in Section 4.11.1.2.1 of 3GPP TS23.502 V17.2.1 or the 5GS to EPS idle mode mobility procedure using the N26 interface described in Section 4.11.1.3.2 of 3GPP TS23.502 V17.2.1.

[0249] Figure 8 A flowchart of a method according to another embodiment of the present disclosure is shown, which can be executed by a device implemented in a second mobility management entity, or by a device communicatively coupled to the second mobility management entity, or by a device implemented as a second mobility management entity. In this way, the device can provide components for completing various parts of method 800 and components for completing other processes together with other components. For some parts that have been described in the above embodiments, their description is omitted here for the sake of brevity.

[0250] At block 802, a second mobility management entity may receive a second message from a first mobility management entity in a first network, the second message including a radio access technology or frequency selection priority (RFSP) index and a validity time for the RFSP index for a user equipment (UE) moving from the first network to a second network. The validity time for the RFSP index indicates a time when the RFSP index will be used in the second mobility management entity when the UE is in the second network.

[0251] In an embodiment, the second mobility management entity may be in the second network.

[0252] For example, the first mobility management entity may be Figure 5 At block 502 of the first mobility management entity, the second message is sent to the second mobility management entity, and then the second mobility management entity may receive the second message from the first mobility management entity.

[0253] At block 804, the second mobility management entity may optionally store the RFSP index and a validity time for the RFSP index.

[0254] At block 806, the second mobility management entity may use the RFSP index for a time period indicated by the validity time until the validity time expires.

[0255] In an embodiment, the second mobility management entity may ensure that the RFSP index is valid before the validity time for the RFSP index expires.

[0256] At block 808, optionally, when the validity time for the RFSP index expires, the second mobility management entity may perform RFSP index re-evaluation. For example, the second mobility management entity may perform RFSP index re-evaluation as described in clause 4.3.6 of 3GPP TS 23.401 V17.3.0.

[0257] In an embodiment, the second message comprises at least one of a forward redirection request or a context response.

[0258] In an embodiment, the first mobility management entity is an Access and Mobility Function (AMF) and the second mobility management entity is a Mobility Management Entity (MME).

[0259] In an embodiment, a second message is received from the first mobility management entity during at least one of a 5GS to EPS handover procedure using an N26 interface or a 5GS to EPS idle mode mobility procedure using an N26 interface.

[0260] In an embodiment, the first mobility management entity is an MME and the second mobility management entity is an MME.

[0261] In an embodiment, the second message is received from the first mobility management entity during at least one of an S1 based handover procedure or an S1 based dual active protocol stack (DAPS) handover procedure.

[0262] In an embodiment, the RFSP index indicates a preferred 3GPP EPS access.

[0263] In an embodiment, the validity time for the RFSP index further indicates the time when the RFSP index will be valid or used in a specific network.

[0264] In an embodiment, the specific network includes 3GPP EPS.

[0265] In an embodiment, when the PCF provides the authorized RFSP index to the AMF,

[0266] -If the PCF knows the mapping from RFSP index to cell selection and RAT / frequency priority, and the PCF determines that the change in the authorized RFSP index value indicates a change from prioritized 5G access to prioritized 4G access for the UE, the PCF includes a validity time (e.g., a new information element (IE) "RFSPinUseExpiryTime") that indicates the time when this RFSP index will take effect or be used if the UE moves to the EPS.

[0267] - If the PCF is not aware of the mapping from RFSP index to cell selection and RAT / frequency priority, the PCF does not include a validity time.

[0268] In an embodiment, when the AMF receives the authorized RFSP index from the PCF,

[0269] - If the PCF provides a validity time, the AMF stores the validity time.

[0270] - Otherwise, if the PCF does not provide a validity time, and if the AMF knows the mapping from RFSP index to cell selection and RAT / frequency priority, and determines that the change in the authorized RFSP index value indicates a change of the UE from priority 5G access to priority 4G access, the AMF sets and stores a validity time (e.g., "RFSPinUseExpiryTime") indicating the time when the RFSP index will take effect or be used if the UE moves to EPS.

[0271] In an embodiment, if NG-RAN triggers a handover before "RFSPinUseExpiryTime" expires, the AMF shall include a new IE "RFSPinUseExpiryTime" in the Forward Relocation Request to the MME. If NG-RAN triggers a release with redirection, the UE shall perform a Tracking Area Request procedure and the AMF shall include a new IE "RFSPinUseExpiryTime" in the Context Response before "RFSPinUseExpiryTime" expires.

[0272] In an embodiment, when the MME receives RFSPinUseExpiryTime, the MME will ensure that the "RFSP index in use" is valid. When the validity time indicated in RFSPinUseExpiryTime expires, the MME will perform a RFSP index re-evaluation.

[0273] In an embodiment, the PCF sets the validity time when authorizing the RFSP index.

[0274] In an embodiment, the AMF sets the validity time and provides it to the MME.

[0275] In an embodiment, the MME selects the RFSP index according to whether the validity time of the RFSP index has expired.

[0276] In an embodiment, the proposed solution contains 3 parts: PCF to AMF, AMF to MME and MME to MME.

[0277] PCF to AMF

[0278] If the PCF knows the mapping from RFSP index to cell selection and RAT / frequency priority, and if the PCF determines that the change in the authorized RFSP index value indicates a change of the UE from prioritized 5G access to prioritized 4G access, the PCF includes a validity time (working name "RFSPinUseExpiryTime") that indicates the time when this RFSP index will take effect or be used if the UE moves to the EPS.

[0279] AMF to MME

[0280] In AMF:

[0281] If the PCF provides a validity time, the AMF stores the validity time.

[0282] Otherwise, if the PCF does not provide a validity time, if the AMF knows the mapping from RFSP index to cell selection and RAT / frequency priority, and determines that the change in the authorized RFSP index value indicates a change in the UE from priority 5G access to priority 4G access, the AMF sets and stores a validity time (working name "RFSPinUseExpiryTime") indicating the time when this RFSP index will take effect or be used if the UE moves to EPS.

[0283] If the NG-RAN triggers the handover before the "RFSPinUseExpiryTime" expires. Clause 4.11.1.2.1 of 3GPP TS 23.502 V17.2.1 (5GS to EPS handover using N26 interface) is reused with the following additions:

[0284] - In step 3, when the AMF sends the Forward Relocation Request to the MME, the AMF further includes a timestamp indicating to the MME that the "RFSP Index in Use" should be used before the indicated time expires.

[0285] If the NG-RAN triggers a release with redirection, the UE shall perform the Tracking Area Request procedure. Clause 4.11.1.3.2 of 3GPP TS 23.502 V17.2.1 (5GS to EPS Idle Mode Mobility using N26 interface) is reused and the following is added:

[0286] - In step 6, when the AMF sends the Context Response to the MME, the AMF will also include a timestamp indicating to the MME that the "RFSP Index in Use" should be used before the indicated time expires.

[0287] In MME:

[0288] When the MME receives RFSPinUseExpiryTime, the MME shall store it and ensure that the "RFSP Index in Use" is valid. When the validity time indicated in RFSPinUseExpiryTime expires, the MME shall perform RFSP Index re-evaluation as specified in clause 4.3.6 of 3GPP TS23.401V17.3.0.

[0289] (Old / Source) MME to (New / Target) MME

[0290] If the UE further moves to another MME before the validity time (RFSPinUseExpiryTime) expires, the old MME includes the RFSPinUseExpiryTime in the Forward Relocation Request or Context Response from the old MME to the new MME.

[0291] When the new / target MME receives the validity time (RFSPinUseExpiryTime), the MME shall store it and ensure that the "RFSP Index in use" is valid. When the validity time indicated in RFSPinUseExpiryTime expires, the MME shall perform RFSP Index re-evaluation as specified in 3GPP TS23.401V17.3.0 clause 4.3.6.

[0292] In an embodiment, a solution to key issue #1 in 3GPP TR 23.700-89 V0.1.0 is proposed, as follows:

[0293] It is assumed that the AMF knows the mapping from RFSP index to cell selection and RAT / frequency priority that the RAN usually knows (see Annex I of 3GPP TS 36.300 V16.7.0 and Annex D of 3GPP TS 38.300 V16.8.0). Note that the RFSP index is also called "SPID" (Subscriber Profile ID) for RAT / frequency priority.

[0294] When the AMF receives the authorized RFSP index from the PCF, if the AMF knows that the authorized RFSP index corresponds to a value for which 4G should have priority, the AMF may store the time when this RFSP index should apply in the UE context (working name "RFSPinUseExpiryTime").

[0295] If the NG-RAN triggers the handover before "RFSPinUseExpiryTime", the AMF shall include such new parameter "RFSPinUseExpiryTime" in the Forward Relocation Request to the MME.

[0296] If the NG-RAN triggers a release with redirection, the UE shall perform the Tracking Area Request procedure and if the time is before "RFSPinUseExpiryTime", the AMF shall include a new parameter "RFSPinUseExpiryTime" in the Context Response.

[0297] When the MME receives RFSPinUseExpiryTime, the MME shall use the "RFSP Index in Use". When RFSPinUseExpiryTime expires, the MME shall perform RFSP Index re-evaluation as specified in 3GPP TS23.401V17.3.0 Section 4.3.6 and send the updated RFSP Index to the eNB, which may steer the UE to 5GS.

[0298] By the above operation, the UE is allowed to be directed back to 5GS after a configurable time, and the ping-pong problem can be alleviated even if the UE moves to EPS, without requiring the AMF-PCF association to be maintained.

[0299] This proposal is only for scenarios with N26 deployment.

[0300] In an embodiment, it is proposed to include the following changes in 3GPP TR 23.700-89 V0.1.0.

[0301] 6.X Solution #X: AMF notifies MME to use “RFSP in use” for a period of time

[0302] 6.X.1 Description

[0303] This solution addresses KI#1 for deployment scenarios with N26. In this solution,

[0304] - It is assumed that the AMF knows the mapping from RFSP index to cell selection and RAT / frequency priority which is generally known to the RAN (see Annex I of 3GPP TS 36.300 V16.7.0 and Annex D of 3GPP TS 38.300 V16.8.0). Note that the RFSP index is also called "SPID" (Subscriber Profile ID) for RAT / frequency priority.

[0305] - When the AMF receives the authorized RFSP index from the PCF, if the AMF knows that the authorized RFSP index corresponds to a value for which 4G should have priority, the AMF may store the time when this RFSP index should apply in the UE context (working name "RFSPinUseExpiryTime").

[0306] - If the NG-RAN triggers a handover before "RFSPinUseExpiryTime", the AMF shall include a new parameter "RFSPinUseExpiryTime" in the Forward Relocation Request to the MME. If the NG-RAN triggers a Release with Redirection, the UE shall perform a Tracking Area Request procedure and if the time is before "RFSPinUseExpiryTime", the AMF shall include a new parameter "RFSPinUseExpiryTime" in the Context Response.

[0307] - When the MME receives RFSPinUseExpiryTime, the MME shall use the "RFSP Index in use". When the time indicated in RFSPinUseExpiryTime expires, the MME shall perform RFSP Index re-evaluation as specified in 3GPP TS23.401V17.3.0 section 4.3.6.

[0308] NOTE: If the UE is not directed to EPS by NG-RAN before the time indicated in RFSPinUseExpiryTime expires, no action needs to be taken in the AMF.

[0309] 6.X.2 Procedure

[0310] 3GPP TS23.502 V17.2.1, clause 4.11.1.2.1 (5GS to EPS handover using N26 interface) is reused and the following is added:

[0311] - In step 3, when the AMF sends the Forward Relocation Request to the MME, the AMF further includes a timestamp indicating to the MME that the "RFSP Index in Use" should be used before the indicated time expires. When the indicated time expires, the MME re-evaluates the RFSP index as specified in 3GPP TS 23.401 V17.3.0 clause 4.3.6.

[0312] 3GPP TS23.502 V17.2.1, clause 4.11.1.3.2 (5GS to EPS idle mode mobility using N26 interface) is reused and the following is added:

[0313] - In step 6, when the AMF sends the Context Response to the MME, the AMF also includes a timestamp indicating to the MME that the "RFSP Index in use" should be used before the indicated time expires. When the indicated time expires, the MME re-evaluates the RFSP index as specified in 3GPP TS 23.401 V17.3.0 clause 4.3.6.

[0314] If the UE moves further from one MME to another MME before the time indicated in RFSPinUseExpiryTime expires, the old MME includes RFSPinUseExpiryTime in the Forward Relocation Request or Context Response from the old MME to the new MME.

[0315] 6.X.3 Impact

[0316] Impact on interfaces:

[0317] N26 and S10: Introduce an additional IE (working name “RFSPinUseExpiryTime”) to indicate the expiration time of the “RFSP index in use”.

[0318] Impact on AMF:

[0319] - When the PCF provides the authorized RFSP index, the AMF needs to know that the new value indicates that 4G has priority and then decide to store a timer (in the form of an expiration time) in the UE context and send it in the following GTP-C v2 message to inform the MME that the "RFSP index in use" should be used before the indicated time expires:

[0320] -Forward Relocation Request

[0321] -Contextual Response

[0322] Impact on MME:

[0323] - When a new timer is received in a Forward Relocation Request or Context Response, the MME shall store it in the UE context and use the "RFSP Index in Use" received from the AMF or old MME. When the indicated time expires, the MME re-evaluates the RFSP Index as specified in 3GPP TS 23.401 V17.3.0 clause 4.3.6.

[0324] By applying the solution proposed according to the embodiments of the present disclosure, many advantages can be achieved. For example, in some embodiments of the present invention, the benefit is to allow the UE to be directed back to a network such as 5GS after a configurable time / valid time expires. In some embodiments of the present invention, the ping-pong problem can be alleviated with minimal impact on the first network (e.g., 5GS) and the second network (e.g., EPS). In some embodiments of the present invention, the proposed solution can minimize the impact on the first network (e.g., 5GS) and the second network (e.g., EPS). The embodiments of the present invention are not limited to the above-mentioned features and advantages. Those skilled in the art will recognize other features and advantages after reading the following detailed description.

[0325] Fig. 9 900 is a block diagram showing an apparatus suitable for practicing some embodiments of the present disclosure. For example, the above-mentioned policy control entity, the first mobility management entity or the second mobility management entity may be implemented as the apparatus 900 or implemented by the apparatus 900.

[0326] The device 900 includes at least one processor 921, such as a digital processor (DP), and at least one memory (MEM) 922 coupled to the processor 921. The device 900 may also include a transmitter TX and a receiver RX923 coupled to the processor 921. The MEM 922 stores a program (PROG) 924. The PROG 924 may include instructions that, when executed on the associated processor 921, enable the device 900 to operate according to embodiments of the present disclosure. The combination of at least one processor 921 and at least one MEM 922 may form a processing device 925 suitable for implementing various embodiments of the present disclosure.

[0327] Various embodiments of the present disclosure may be implemented by a computer program executable by one or more of the processor 921 , software, firmware, hardware, or a combination thereof.

[0328] The MEM 922 may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology such as, by way of non-limiting example, semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory.

[0329] Processor 921 may be of any type suitable to the local technical environment, and may include, by way of non-limiting example, one or more of a general purpose computer, a special purpose computer, a microprocessor, a digital signal processor (DSP), and a processor based on a multi-core processor architecture.

[0330] In embodiments where the apparatus is implemented as or at a policy control entity, the memory 922 stores instructions executable by the processor 921 whereby the policy control entity operates according to any of the methods described above in relation to policy control entities.

[0331] In embodiments where the apparatus is implemented as or at a first mobility management entity, the memory 922 stores instructions executable by the processor 921 whereby the first mobility management entity operates according to any method as described above in relation to the first mobility management entity.

[0332] In embodiments where the apparatus is implemented as or at a second mobility management entity, the memory 922 stores instructions executable by the processor 921 whereby the second mobility management entity operates according to any method related to a second mobility management entity as described above.

[0333] Fig.10 1 is a block diagram showing a policy control entity in a first network according to an embodiment of the present disclosure. As shown in the figure, the policy control entity 1000 includes a setting module 1001, which is configured to set a valid time for a radio access technology or frequency selection priority (RFSP) index for a user equipment (UE) moving from a first network to a second network. The valid time for the RFSP index indicates the time when the RFSP index will be used in a second mobility management entity when the UE is in the second network. The policy control entity 1000 further includes a sending module 1002, which is configured to send a first message including an RFSP index and a valid time for the RFSP index to a mobility management entity in the first network.

[0334] In an embodiment, the policy control entity 1000 further comprises a determining module 1003 configured to determine that a change in the value of the RFSP index indicates a change for the user equipment from prioritizing the first network access to prioritizing the second network access. In response to the determination, a validity time for the RFSP index is included in the first message.

[0335] Fig.11 1 is a block diagram showing a first mobility management entity in a first network according to an embodiment of the present disclosure. As shown in the figure, the first mobility management entity 1100 includes a sending module 1101, which is configured to send a second message to a second mobility management entity in a second network, the second message including a radio access technology or frequency selection priority (RFSP) index and a valid time for the RFSP index for a user equipment (UE) moving from the first network to the second network. The valid time for the RFSP index indicates the time when the RFSP index will be used in the second mobility management entity when the UE is in the second network.

[0336] In an embodiment, the first mobility management entity 1100 further includes a first receiving module 1102 configured to receive an RFSP index from a policy control entity.

[0337] In an embodiment, the first mobility management entity 1100 further comprises a determining module 1103 configured to determine that a change in the value of the RFSP index indicates a change for the user equipment from prioritizing the first network access to prioritizing the second network access.

[0338] In an embodiment, the first mobility management entity 1100 further includes a setting module 1104 configured to set a valid time for the RFSP index.

[0339] In an embodiment, the first mobility management entity 1100 further includes a first storage module 1105 configured to store a valid time for the RFSP index.

[0340] In an embodiment, the first mobility management entity 1100 further includes a second receiving module 1106 configured to receive a first message including an RFSP index and a valid time for the RFSP index from the policy control entity.

[0341] In an embodiment, the first mobility management entity 1100 further includes a second storage module 1107 configured to store a valid time for the RFSP index.

[0342] Fig.121 is a block diagram illustrating a second mobility management entity in a second network according to an embodiment of the present disclosure. As shown in the figure, the second mobility management entity 1200 includes a receiving module 1201, which is configured to receive a second message from a first mobility management entity in a first network, the second message including a radio access technology or frequency selection priority (RFSP) index and a valid time for the RFSP index for a user equipment (UE) moving from the first network to the second network. The valid time for the RFSP index indicates the time when the RFSP index will be used in the second mobility management entity when the UE is in the second network. The second mobility management entity 1200 further includes a using module 1202, which is configured to use the RFSP index within a time period indicated by the valid time until the valid time expires.

[0343] In an embodiment, the second mobility management entity 1200 further includes a storage module 1203 configured to store the RFSP index and a valid time for the RFSP index.

[0344] In an embodiment, the second mobility management entity 1200 further includes an execution module 1204 configured to perform RFSP index re-evaluation when the validity time of the RFSP index expires.

[0345] The term unit or module may have the conventional meaning in the field of electronics, electrical devices and / or electronic devices, and may include, for example, electrical and / or electronic circuits, devices, modules, processors, memories, logical solid-state and / or discrete devices, computer programs or instructions for performing corresponding tasks, processes, calculations, output and / or display functions, etc., such as those described herein.

[0346] By using the functional unit, the policy control entity, the first mobility management entity or the second mobility management entity may not need a fixed processor or memory, and any computing resources and storage resources may be arranged from the policy control entity, the first mobility management entity or the second mobility management entity in the communication system. The introduction of virtualization technology and network computing technology can improve the efficiency of network resource utilization and network flexibility.

[0347] According to one aspect of the present disclosure, a computer program product is provided, which is tangibly stored on a computer-readable storage medium and includes instructions. When the instructions are executed on at least one processor, the instructions cause the at least one processor to perform any of the methods described above.

[0348] According to one aspect of the present disclosure, a computer-readable storage medium is provided, which stores instructions. When the instructions are executed on at least one processor, the instructions cause the at least one processor to perform any of the methods described above.

[0349] In addition, the present disclosure may also provide a carrier containing the above-mentioned computer program, wherein the carrier is one of an electronic signal, an optical signal, a radio signal or a computer-readable storage medium. The computer-readable storage medium may be, for example, an optical disc or an electronic storage device, such as a RAM (random access memory), a ROM (read-only memory), a flash memory, a magnetic tape, a CD-ROM, a DVD, a Blu-ray disc, etc.

[0350] The techniques described herein can be implemented in various ways so that the device that implements one or more functions of the corresponding device described with the embodiments includes not only prior art components, but also components for implementing one or more functions of the corresponding device described with the embodiments, and it can include separate components for each separate function or components that can be configured to perform two or more functions. For example, these techniques can be implemented in hardware (one or more devices), firmware (one or more devices), software (one or more modules), or a combination thereof. For firmware or software, the implementation can be accomplished by modules (e.g., processes, functions, etc.) that perform the functions described herein.

[0351] Exemplary embodiments of the present invention have been described above with reference to the block diagrams and flowchart illustrations of the methods and apparatus. It will be understood that each block of the block diagrams and flowchart illustrations and combinations of blocks in the block diagrams and flowchart illustrations, respectively, can be implemented by various components including computer program instructions. These computer program instructions can be loaded onto a general-purpose computer, a special-purpose computer, or other programmable data processing device to produce a machine, whereby the instructions executed on the computer or other programmable data processing device create components for implementing the functions specified in the flowchart block or blocks.

[0352] In addition, although the operations are depicted in a particular order, this should not be understood as requiring that the operations be performed in the particular order shown or in sequence, or that all illustrated operations be performed to achieve the desired results. In some cases, multitasking and parallel processing may be advantageous. Similarly, although the above discussion contains several specific implementation details, these should not be interpreted as limitations on the scope of the subject matter described herein, but should be interpreted as descriptions of features that may be specific to a particular embodiment. Certain features described in the context of a separate embodiment may also be implemented in combination in a single embodiment. On the contrary, the various features described in the context of a single embodiment may also be implemented in multiple embodiments individually or in any suitable sub-combination.

[0353] Although this specification contains many specific implementation details, these should not be interpreted as limitations on the scope of any implementation or the scope of what may be claimed, but rather should be interpreted as descriptions of features that may be specific to a particular embodiment of a particular implementation. Certain features described in this specification in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, the various features described in the context of a single embodiment may also be implemented in multiple embodiments individually or in any suitable sub-combination. In addition, although the above-mentioned features may be described as working in certain combinations, or even initially claimed to be so protected, in some cases one or more features from the claimed combination may be deleted from the combination, and the claimed combination may be directed to a sub-combination or a variation of the sub-combination.

[0354] It is obvious to those skilled in the art that, as technology advances, the inventive concept can be implemented in various ways. The above embodiments are given for the purpose of describing rather than limiting the present disclosure, and it should be understood that, as those skilled in the art will readily appreciate, modifications and variations can be made without departing from the spirit and scope of the present disclosure. Such modifications and variations are considered to be within the scope of the present disclosure and the appended claims. The scope of protection of the present disclosure is defined by the appended claims.

Claims

1. A method (300) performed by a policy control entity in a first network, comprising: Setting (302) a validity time for a radio access technology or frequency selection priority RFSP index for a user equipment UE moving from the first network to a second network; and sending (304) a first message including the RFSP index and the validity time for the RFSP index to a mobility management entity in the first network, The validity time for the RFSP index indicates a time during which the RFSP index will be used in a second mobility management entity when the UE is in the second network.

2. The method according to claim 1, further comprising: determining (402) that a change in the value of the RFSP index indicates a change for the user equipment from a preferred first network access to a preferred second network access, Wherein, in response to the determination, the validity time for the RFSP index is included in the first message.

3. The method according to claim 2, wherein: The first network includes a 3rd Generation Partnership Project 3GPP fifth generation system 5GS, and the second network includes a 3GPP Evolved Packet System EPS.

4. The method according to any one of claims 1 to 3, wherein: The first message includes at least one of the following: Access and mobility management entity policy control create response, or Access and mobility management entity policy control update notification.

5. The method according to any one of claims 1 to 4, wherein: The policy control entity includes a policy control function PCF; wherein the mobility management entity includes an access and mobility function AMF; wherein the second mobility management entity is a mobility management entity MME.

6. The method according to any one of claims 1 to 5, wherein: The RFSP index indicates a priority 3GPP EPS access.

7. A method (500) performed by a first mobility management entity in a first network, comprising: sending (502) a second message to a second mobility management entity in a second network, the second message comprising a radio access technology or frequency selection priority RFSP index and a validity time for the RFSP index for a user equipment UE moving from the first network to the second network, The validity time for the RFSP index indicates a time during which the RFSP index will be used in the second mobility management entity when the UE is in the second network.

8. The method according to claim 7, wherein: The first network includes a 3rd Generation Partnership Project 3GPP fifth generation system 5GS, and the second network includes a 3GPP Evolved Packet System EPS.

9. The method according to claim 7 or 8, further comprising: receiving (702) a first message including the RFSP index and the validity time for the RFSP index from a policy control entity; as well as The validity time for the RFSP index is stored (704).

10. The method according to claim 9, wherein: The first message includes at least one of the following: Access and mobility management entity policy control create response, or Access and mobility management entity policy control update notification.

11. The method according to any one of claims 9 to 10, wherein: The policy control entity includes a policy control function PCF.

12. The method according to any one of claims 7 to 11, wherein: The first mobility management entity is an access and mobility function, AMF, and the second mobility management entity is a mobility management entity, MME.

13. The method according to any one of claims 7 to 12, wherein: The second message is sent to the second mobility management entity during at least one of the following procedures: 5GS to EPS handover process using N26 interface, or 5GS to EPS idle mode mobility procedures using the N26 interface.

14. The method according to any one of claims 7 to 13, wherein: The second message includes at least one of the following: A forward relocation request, or Contextual response.

15. The method according to any one of claims 7 to 14, wherein: The RFSP index indicates a priority 3GPP EPS access.

16. A method (800) performed by a second mobility management entity in a second network, comprising: receiving (802) a second message from a first mobility management entity in a first network, the second message comprising a radio access technology or frequency selection priority RFSP index and a validity time for the RFSP index for a user equipment UE moving from the first network to the second network, wherein the validity time for the RFSP index indicates a time when the RFSP index is to be used in the second mobility management entity when the UE is in the second network; and The RFSP index is used (806) for a time period indicated by the validity time until the validity time expires.

17. The method according to claim 16, further comprising: When the validity time for the RFSP index expires, RFSP index re-evaluation is performed (808).

18. The method according to claim 16, further comprising: The RFSP index and the validity time for the RFSP index are stored (804).

19. The method according to any one of claims 16-17, wherein: The second message includes at least one of the following: A forward relocation request, or Contextual response.

20. The method according to any one of claims 16 to 18, wherein: The first mobility management entity is an access and mobility function, AMF, and the second mobility management entity is a mobility management entity, MME.

21. The method according to any one of claims 16 to 20, wherein: The second message is received from the first mobility management entity during at least one of the following processes: 5GS to EPS handover process using N26 interface, or 5GS to EPS idle mode mobility procedures using the N26 interface.

22. The method according to any one of claims 16 to 21, wherein: The RFSP index indicates a priority 3GPP EPS access.

23. A policy control entity (900), comprising: Processor(921); as well as A memory (922) coupled to the processor (921), the memory (922) storing instructions executable by the processor (921), whereby the policy control entity (900) is operable to: Setting a validity time for a radio access technology or frequency selection priority RFSP index for a user equipment UE moving from a first network to a second network; and sending a first message including the RFSP index and the validity time for the RFSP index to a mobility management entity in the first network, The validity time for the RFSP index indicates a time during which the RFSP index will be used in the second mobility management entity when the UE is in the second network.

24. The policy control entity according to claim 23, wherein: The policy control entity is further operable to perform the method of any one of claims 2 to 6.

25. A first mobility management entity (900), comprising: Processor(921); as well as a memory (922) coupled to the processor (921), the memory (922) storing instructions executable by the processor (921), whereby the first mobility management entity (900) is operable to: sending a second message to a second mobility management entity in the second network, the second message comprising a radio access technology or frequency selection priority RFSP index and a validity time for the RFSP index for a user equipment UE moving from the first network to the second network, The validity time for the RFSP index indicates a time during which the RFSP index will be used in the second mobility management entity when the UE is in the second network.

26. The first mobility management entity according to claim 25, wherein: The first mobility management entity is further operable to perform the method of any one of claims 8 to 15.

27. A second mobility management entity (900), comprising: Processor(921); as well as a memory (922) coupled to the processor (921), the memory (922) storing instructions executable by the processor (921), whereby the second mobility management entity (900) is operable to: receiving a second message from a first mobility management entity in a first network, the second message comprising a radio access technology or frequency selection priority RFSP index and a validity time for the RFSP index for a user equipment UE moving from the first network to a second network, wherein the validity time for the RFSP index indicates a time when the RFSP index is to be used in the second mobility management entity when the UE is in the second network; as well as The RFSP index is used within a time period indicated by the validity time until the validity time expires.

28. The second mobility management entity according to claim 27, wherein: The second mobility management entity is further operable to perform the method of any one of claims 17 to 22.

29. A computer-readable storage medium storing instructions which, when executed by at least one processor, cause the at least one processor to perform the method according to any one of claims 1 to 22.

30. A computer program product comprising instructions which, when executed by at least one processor, cause the at least one processor to perform the method according to any one of claims 1 to 22.

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