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

Abstract

An embodiment of the present disclosure provides a method and apparatus for handling radio access technology or frequency selection preference (RFSP). The method performed by a policy control entity includes setting a validity time of a radio access technology or frequency selection preference (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 the RFSP index and a validity time of the RFSP index to a mobility management entity of the first network. The validity time of the RFSP index indicates a time for which the RFSP index is used by the second mobility management entity while the UE is in the second network.

Description

[Technical Field]

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

[0002] This section introduces aspects that may facilitate a better understanding of the present disclosure, and accordingly, the statements in this section are to be read in this light and not understood as admissions about what is in the prior art or what is not in the prior art.

[0003] In communication networks such as the Long Term Evolution (LTE) and New Radio (NR) defined by the 3rd Generation Partnership Project (3GPP), to support radio resource management in the radio access network (RAN), a mobility management entity, such as an access and mobility function (AMF) or a mobile management entity (MME), can provide the radio access network (RAN) with a parameter called the "Radio Access Technology (RAT) / Frequency Selection Priority Index (RFSP Index)." The RFSP Index is mapped by the RAN to a locally defined configuration to apply a specific radio resource management (RRM) strategy, taking into account all information available in the RAN. The RFSP Index is user equipment (UE) specific and applies to all radio bearers. Examples of how this parameter is used in the RAN include deriving a UE-specific cell reselection priority to control idle mode camping or to decide to redirect an active UE to a different frequency layer or RAT.

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

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

[0006] - The AMF selects the RFSP index in use based on the subscribed RFSP indexes, the locally configured operator policy, the allowed NSSAIs (Network Slice Selection Assistance Information) and the context information about the UE available to the AMF (including the UE's usage preferences if received during the registration procedure).

[0007] An example of how the AMF can use the "UE Usage Settings" is to select an RFSP value that forces idle mode camping in Evolved Universal Terrestrial Radio Access (E-UTRA) for UEs operating in a "voice-centric" manner when voice over NR is not supported in a particular Registration Area and an NR cell is included.

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

[0009] The AMF maintains the received subscribed RFSP index values ​​and the RFSP index value in use. During the registration procedure, the AMF may update the RFSP index value in use (e.g., if context information about the UE in the AMF changes, 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, if user plane establishment is not required, by being configured to include the updated RFSP index value in use in a Next Generation Application Protocol (NGAP) downlink Non-Access Stratum (NAS) transport message. Summary of the Invention

[0010] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. 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] Existing RFSP processing solutions have several problems.

[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: RFSP index consistency when UE moves from 5GC (5th Generation Core Network) to EPC (Evolved Packet Core).

[0014] Currently, most carriers operate networks that integrate 4G (fourth generation) and 5G (fifth generation). To facilitate 5G services, the UE's subscription data may be initially configured for 5G access. For example, the subscribed RFSP index may be a value indicating that 5G has a higher priority than 4G. In some scenarios, the PCF may adjust the RFSP index to direct the UE from 5G to 4G depending on dynamic network conditions.

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

[0016] In response to a request from an AF (Application Function), the PCF may 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 context information about the UE available at the MME. If the EPC determines that the UE needs to switch back to 5G, the MME provides the eNB (evolved NodeB) with a "5G preferred" RFSP index.

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

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

[0020] - When and how the MME resumes the subscription RFSP index if it obtains an RFSP index in use during a handover procedure or idle mode mobility procedure.

[0021] -If the UE is under EPC, should the MME receive any updates to the RFSP index from the 5GC and how?

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

[0023] Issue 1: Ping-pong problem. For example, a 5GS (5G system) UE is directed to an Evolved Packet System (EPS) due to certain conditions (such as network congestion or an application in use), and then immediately directed back to 5GS.

[0024] Issue 2. How to point the UE to 5GS after it has been pointed to EPS (from 5GS) if the 5GS conditions in Issue 1 above no longer apply.

[0025] Solution #1 of TR23.700-89 v0.1.0 implies significant changes to mobility procedures from 5GS to EPS and within EPS.

[0026] To overcome or mitigate at least one of the above-mentioned problems or other problems, embodiments of the present disclosure propose an improved solution for handling RFSPs.

[0027] In a first aspect of the present disclosure, a method is provided that is performed by a policy control entity. The method includes configuring a validity period of a radio access technology or frequency selection preference (RFSP) index for a user equipment (UE) moving from a first network to a second network. The method further includes transmitting a first message to a mobility management entity of the first network, the first message including the RFSP index and a validity period of the RFSP index. The validity period of the RFSP index indicates a period of time that the RFSP index will be used by the second mobility management entity while the UE is in the second network.

[0028] In one embodiment, the method further includes determining that a change in the value of the RFSP index indicates a change from a preference for first network access to a preference for second network access for the user equipment, and in response to the determination, a validity time of the RFSP index is included in the first message.

[0029] In one embodiment, 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).

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

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

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

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

[0034] In one embodiment, the RFSP index indicates a priority for 3GPP EPS access.

[0035] In a second aspect of the present disclosure, there is provided a method performed by a first mobility management node, the method including transmitting, to a second mobility management entity of a second network, a second message including a radio access technology or frequency selection preference (RFSP) index of a user equipment (UE) moving from the first network to the second network and a validity time of the RFSP index, the validity time of the RFSP index indicating a time period during which the RFSP index will be used by the second mobility management entity while the UE is in the second network.

[0036] In one embodiment, 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).

[0037] In one embodiment, the method further includes receiving a first message from the policy control entity, the first message including the RFSP index and a validity time of the RFSP index. The method further includes storing the validity time of the RFSP index.

[0038] In one embodiment, the first message includes 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 one embodiment, the policy control entity includes a Policy Control Function (PCF).

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

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

[0042] In one embodiment, the second message includes at least one of a Forward Relocation Request or a Context Response.

[0043] In one embodiment, the RFSP index indicates a priority for 3GPP EPS access.

[0044] In a third aspect of the present disclosure, a method is provided that is performed by a second mobility management node. The method includes receiving, from a first mobility management entity of a first network, a second message that includes a radio access technology or frequency selection preference (RFSP) index for a user equipment (UE) moving from the first network to a second network and a validity time of the RFSP index. The validity time of the RFSP index indicates a time period during which the RFSP index will be used at the second mobility management entity while the UE is in the second network. The method further includes using the RFSP index for a period indicated by the validity time until the validity time expires.

[0045] In one embodiment, the method further includes performing a re-evaluation of the RFSP index when the validity period of the RFSP index expires.

[0046] In one embodiment, the method further includes storing the RFSP index and a validity time of the RFSP index.

[0047] In one embodiment, the second message includes at least one of a Forward Relocation Request or a Context Response.

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

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

[0050] In one embodiment, the RFSP index indicates a priority for 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 includes instructions executable by the processor. The policy control node is operable to set a validity time of a radio access technology or frequency selection priority (RFSP) index of a user equipment (UE) moving from a first network to a second network. The policy control node is further operable to send a first message to a mobility management entity of the first network, the first message including the RFSP index and a validity time of the RFSP index. The validity time of the RFSP index indicates a time period during which the RFSP index will be used by the second mobility management entity while the UE is in the second network.

[0052] In a fifth aspect of the present disclosure, a first mobility management node is provided, including a processor and a memory coupled to the processor, the memory including instructions executable by the processor. The first mobility management node is operable to transmit, to a second mobility management entity of the second network, a second message including a radio access technology or frequency selection preference (RFSP) index of a user equipment (UE) moving from a first network to a second network and a validity time of the RFSP index. The validity time of the RFSP index indicates a time period during which the RFSP index will be used by the second mobility management entity while 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 includes instructions executable by the processor. The second mobility management node is operable to receive a second message from a first mobility management entity of the first network, the second message including a radio access technology or frequency selection preference (RFSP) index of a user equipment (UE) moving from a first network to a second network and a validity time of the RFSP index. The validity time of the RFSP index indicates a time period during which the RFSP index will be used at the second mobility management entity while the UE is in the second network. The second mobility management node is further operable to use the RFSP index for a period indicated by the validity time until the validity 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 configured to set a validity time of a radio access technology or frequency selection priority (RFSP) index of a user equipment (UE) moving from a first network to a second network. The validity time of the RFSP index may indicate a time period during which the RFSP index is used in a second mobility management entity while the UE is in the second network. The policy control entity further includes a sending module configured to send a first message to the mobility management entity of the first network, the first message including the RFSP index and the validity time of the RFSP index.

[0055] In one 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 from a preference for first network access to a preference for second network access for the user equipment, and in response to the determining, a validity time of 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 transmitting module configured to transmit a second message to a second mobility management entity in the second network, the second message including a radio access technology or frequency selection preference (RFSP) index of a user equipment (UE) moving from a first network to a second network and a validity time of the RFSP index. The validity time of the RFSP index may indicate a time period during which the RFSP index will be used by the second mobility management entity while the UE is in the second network.

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

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

[0059] In one embodiment, the first mobility management entity further includes a setting module configured to set a validity time of the RFSP index.

[0060] In one embodiment, the first mobility management entity further includes a first storage module configured to store the validity time of the RFSP index.

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

[0062] In one embodiment, the first mobility management entity further includes a second storage module configured to store the validity time of 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 the first network, the second message including a radio access technology or frequency selection preference (RFSP) index of a user equipment (UE) moving from a first network to a second network and a validity time of the RFSP index. The validity time of the RFSP index may indicate a time period during which the RFSP index will be used at the second mobility management entity while the UE is in the second network. The second mobility management entity further includes a using module configured to use the RFSP index for a period indicated by the validity time until the validity time expires.

[0064] In one embodiment, the second mobility management entity further includes a storage module configured to store the RFSP index and the validity time of the RFSP index.

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

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

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

[0068] By applying the proposed solution according to the embodiments of the present disclosure, many advantages may be achieved. For example, in some embodiments herein, an advantage is that a UE is permitted to return to a network, such as 5GS, after a configurable / valid time has expired. In some embodiments herein, the ping-pong problem may be mitigated while minimizing the impact on a first network, such as 5GS, and a second network, such as EPS. In some embodiments herein, the proposed solution may minimize the impact on a first network, such as 5GS, and a second network, such as EPS. The embodiments herein are not limited to the features and advantages described above. Those skilled in the art will recognize additional features and advantages upon reading the following detailed description. [Brief explanation of the drawings]

[0069] The above and other aspects, features, and advantages of various embodiments of the present disclosure will become more fully apparent from the following detailed description, taken by way of example only with reference to the accompanying drawings, in which like reference numerals and letters are used to designate like or equivalent elements, and in which: The drawings are illustrated to facilitate an understanding of embodiments of the present disclosure and are not necessarily drawn to scale:

[0070] [Figure 1A] 1 illustrates a schematic diagram of a high-level architecture in a fifth generation network according to one embodiment of the present disclosure;

[0071] [Figure 1B] 1 illustrates an architecture of an EPC and 5G CN migration scenario according to one embodiment of the present disclosure;

[0072] [Figure 1C] 1 illustrates a schematic diagram of a non-roaming architecture for interworking between 5GS and EPC / E-UTRAN according to one embodiment of the present disclosure;

[0073] [Figure 2A] 1 is a flowchart of a handover from 5GS to EPS in single registration mode by N26 according to one embodiment of the present disclosure;

[0074] [Figure 2B] 1 is a flowchart of idle mode mobility from 5GS to EPS using N26 interface according to an embodiment of the present disclosure;

[0075] [Figure 2C] 1 is a flowchart of AM Policy Association Establishment by a newly selected PCF according to an embodiment of the present disclosure;

[0076] [Figure 2D] 1 is a flowchart of an AM Policy Association Modification initiated by a PCF according to one embodiment of the present disclosure;

[0077] [Figure 3] 1 shows a flowchart of a method according to one embodiment of the present disclosure;

[0078] [Figure 4] 1 shows a flowchart of a method according to another embodiment of the present disclosure;

[0079] [Figure 5] 1 shows a flowchart of a method according to another embodiment of the present disclosure;

[0080] [Figure 6]1 shows a flowchart of a method according to another embodiment of the present disclosure;

[0081] [Figure 7] 1 shows a flowchart of a method according to another embodiment of the present disclosure;

[0082] [Figure 8] 1 shows a flowchart of a method according to another embodiment of the present disclosure;

[0083] [Figure 9] 1 is a block diagram illustrating an apparatus suitable for implementing some embodiments of the present disclosure;

[0084] [Figure 10] 1 is a block diagram illustrating a policy control entity in a first network according to one embodiment of the present disclosure;

[0085] [Figure 11] FIG. 2 is a block diagram illustrating a first mobility management entity in a first network according to an embodiment of the present disclosure.

[0086] [Figure 12] FIG. 2 is a block diagram illustrating a second mobility management entity in a second network according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0087] Embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. It should be understood that these embodiments are discussed solely for the purpose of enabling those skilled in the art to better understand and therefore practice the present disclosure, and are not intended to imply any limitations on the scope of the present disclosure. Throughout this specification, references to features, advantages, or similar language do not imply that all of the features and advantages that may be achieved by the present disclosure should or are present in any single embodiment of the present disclosure. Rather, language referring to features and advantages is understood to mean that the particular feature, advantage, or characteristic described in connection with an embodiment is included in at least one embodiment of the present disclosure. Furthermore, the described features, advantages, and characteristics of the present disclosure may be combined in any suitable manner in one or more embodiments. Those skilled in the relevant art will recognize that the present disclosure may be practiced without one or more specific features or advantages of a particular embodiment. In other examples, additional features and advantages may be recognized in certain embodiments that may not be present in all embodiments of the present disclosure.

[0088] As used herein, the term "network" refers to a network that conforms to any suitable communication standard, such as New Radio (NR), Long Term Evolution (LTE), LTE-Advanced (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 may implement a radio technology such as Universal Terrestrial Radio Access (UTRA). UTRA includes other variants of WCDMA and CDMA. A TDMA network may implement a radio technology such as Global System for Mobile Communications (GSM). An OFDMA network may implement wireless 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. Furthermore, communication between two devices in the network may be performed according to any suitable communication protocol, including, but not limited to, communication protocols defined by standardization organizations such as 3GPP. For example, the communication protocol may include first generation (1G), 2G, 3G, 4G, 4.5G, 5G communication protocols, and / or other protocols 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 network element (physical or virtual) of a communications network. For example, a network function may be implemented as a network element on dedicated hardware, as a software instance running on dedicated hardware, or as a virtualized function instantiated on a suitable platform (e.g., cloud infrastructure). For example, a 5G system (5GS) may include multiple NFs, such as an AMF (Access and Mobility Function), an SMF (Session Management Function), an AUSF (Authentication Service Function), an UDM (Unified Data Management), a PCF (Policy Control Function), an AF (Application Function), an NEF (Network Exposure Function), an UPF (User Plane Function), and an NRF (Network Repository Function), a RAN (Radio Access Network), a SCP (Service Communication Proxy), an NWDAF (Network Data Analysis Function), an NSSF (Network Slice Selection Function), and an NSSAAF (Network Slice Specific Authentication and Authorization Function). For example, a 4G system (such as LTE) may include an MME (Mobile 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 (SGW-C), an E-UTRAN Node B (eNB), etc. In other embodiments, the network functions may include different types of NFs, depending, for example, on the particular network.

[0090] The network device may be an access network device having an access function in a communication network through which a terminal device accesses the network and receives services therefrom. 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 Node B (eNodeB or eNB), a next generation Node B (gNodeB or gNB), a remote radio unit (RRU), a radio header (RH), an integrated access and backhaul (IAB) node, a remote radio head (RRH), a relay, a low-power node such as a femto, a pico, etc.

[0091] Further examples of access network devices include multi-standard radio (MSR) radio equipment such as an MSR BS, a network controller such as a radio network controller (RNC) or base station controller (BSC), a base transceiver station (BTS), a transmission point, a transmitting node, a positioning node, and / or the like. However, more generally, a network node may represent any suitable device (or group of devices) capable of, configured, arranged, and / or operable to enable and / or provide terminal devices with access to a wireless communication network or to provide some service to terminal devices that have accessed the wireless communication network.

[0092] The term "terminal device" refers to any end device capable of accessing and receiving services from a communications network. By way of example and not limitation, a terminal device may refer to a mobile terminal, 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 terminals such as digital cameras, gaming terminal devices, music storage and playback appliances, mobile phones, cellular phones, smartphones, Voice over IP (VoIP) phones, wireless local loop phones, tablets, wearable devices, personal digital assistants (PDAs), portable computers, desktop computers, wearable terminal devices, in-vehicle wireless terminal devices, wireless endpoints, mobile stations, laptop embedded devices (LEEs), laptop mounted devices (LMEs), USB dongles, smart devices, wireless customer premises equipment (CPEs), and the like. 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 according to one or more communications standards promulgated by 3GPP (Third Generation Partnership Project) (such as the 3GPP LTE or NR standards). As used herein, "user equipment" or "UE" may not necessarily have a "user" in the sense of a human user who owns and / or operates the associated device. In some embodiments, a terminal device may be configured to transmit and / or receive information without direct human intervention. For example, a terminal device may be designed to transmit information to a network on a predetermined schedule, when triggered by an internal or external event, or in response to a request from the communications network. Instead, a UE may represent a device intended for sale to or operation by a human user, but which may not initially be associated with a particular human user.

[0093] As yet another example, in an Internet of Things (IoT) scenario, a terminal device may represent a machine or other device that performs monitoring and / or measurements and transmits results of such monitoring and / or measurements to another terminal device and / or network equipment. In this case, the terminal device may be a Machine-to-Machine (M2M) device, which may be referred to in the 3GPP context as a Machine-Type Communication (MTC) device. As a particular 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 include sensors, metering devices such as power meters, industrial machinery, or home or personal appliances (e.g., refrigerators, televisions, watches, and other personal wearable devices). In other scenarios, the terminal device may represent a vehicle or other equipment that can monitor and / or report its operating state or other functions related to its operation.

[0094] References herein to "one embodiment," "one embodiment," "exemplary embodiment," etc. indicate that the described embodiment may include a particular feature, structure, or characteristic, but not all embodiments need include the particular feature, structure, or characteristic. Moreover, such phrases do not necessarily refer to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in connection with one embodiment, it is such that it is within the knowledge of one of ordinary skill in the art to affect such feature, structure, or characteristic in connection with other embodiments, whether or not explicitly stated.

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

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

[0097] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit 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 is further understood that as used herein, the terms "comprises," "comprising," "has," "having," "includes," and / or "including" specify the presence of stated features, elements, and / or components, etc., but do not exclude the presence or addition of one or more other features, elements, components, and / or combinations thereof.

[0098] Please note that these terms used in this document are only used to briefly describe and distinguish between nodes, devices, networks, etc. As technology evolves, other terms with similar / identical meanings may also be used.

[0099] In the following description and claims, unless otherwise defined, 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 may be implemented in any suitable type of system using any suitable components, the embodiments disclosed herein will be described in connection with a communications system conforming to the exemplary system architecture illustrated in FIGS. 1A-1C. For simplicity, the system architectures of FIGS. 1A-1C show only a few example elements. In practice, a communications system may further include any additional elements suitable for supporting communications between terminal devices or between a wireless device and another communications device (such as a landline telephone, a service provider, or any other network node or terminal device). A communications system may provide communications and various types of services to one or more terminal devices and facilitate terminal devices' access to and / or use of services provided by or via the communications system.

[0101] FIG. 1A schematically illustrates a high-level architecture of a fifth-generation network according to an embodiment of the present disclosure. For example, the fifth-generation network may be a 5GS network. The architecture of FIG. 1A is the same as FIG. 4.2.3-2 described in 3GPP TS 23.501 V17.2.0, the entire disclosure of which is incorporated herein by reference. The system architecture of FIG. 1A may include several exemplary elements, such as an AUSF, an AMF, a DN (Data Network), an NEF, an NRF, an NSSF, a PCF, an SMF, a UDM, a UPF, an AF, a UE, an (R)AN, an SCP (Service Communication Proxy), an NSSAAF (Network Slice-Specific Authentication and Authorization Function), and an NSACF (Network Slice Admission Control Function).

[0102] According to an example embodiment, a UE may establish a signaling connection with the AMF via reference point N1, as shown in FIG. 1A. This signaling connection may enable NAS (non-access stratum) signaling exchange between the UE and the core network, including a signaling connection between the UE and the (R)AN and an N2 connection for this UE between the (R)AN and the AMF. The (R)AN may communicate with the UPF via reference point N3. The UE may establish a protocol data unit (PDU) session to a DN (a data network, e.g., an operator network or the Internet) via the UPF via reference point N6.

[0103] As further shown in FIG. 1A, the exemplary system architecture also includes several reference points, such as N1, N2, N3, N4, N6, N9, and N15, which may support interactions between NF services within the NF. For example, these reference points may be realized through corresponding NF service-based interfaces, by identifying consumers and providers of several NF services and their interactions to perform specific system procedures. Policies regarding AM are provided from the PCF to the AMF for registered UEs via the N15 interface. The AMF may obtain the AM policy during an AM Policy Association Establishment / Modification procedure.

[0104] The various NFs shown in Figure 1A may be responsible for functions such as session management, mobility management, authentication, security, etc. The AUSF, AMF, DN, NEF, NRF, NSSF, PCF, SMF, UDM, UPF, AF, UE, (R)AN, SCP, and NSACF may include functions defined, for example, in section 6.2 of 3GPP TS 23.501 V17.2.0.

[0105] FIG. 1B schematically illustrates the architecture of an EPC and a 5G CN (Core Network) migration scenario according to one embodiment of the present disclosure, and is the same as FIG. 5.17.1.1-1 of 3GPP TS 23.501 V17.2.0.

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

[0107] It is expected that a UE capable of supporting 5GC NAS procedures may also be capable of supporting EPC NAS (i.e., NAS procedures defined in 3GPP TS 23.401 V17.3.0, the disclosure of which is incorporated herein by reference in its entirety) operating in legacy networks (e.g., in the case of roaming).

[0108] The UE uses EPC NAS or 5GC NAS procedures depending on the core network providing the service.

[0109] To support a smooth transition, the EPC and 5GC shall have access to a common subscriber database (HSS for the EPC and UDM for the 5GC) that serves 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 uses 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 a Unified Data Repository (UDR) that serves as the common subscriber database for a given user identified by a SUPI.

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

[0111] - Always perform initial access via E-UTRA (LTE-Uu), but never via NR;

[0112] - Perform EPC NAS procedures (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] UEs that support camping in a 5G system with a 5GC NAS:

[0114] - Initial access is performed either via E-UTRAN connecting to 5GC or via NR towards 5GC;

[0115] If supported and necessary, perform initial access via E-UTRAN towards the EPC;

[0116] If the UE also supports EPC NAS, it will perform EPC or 5GC NAS procedures (e.g., mobility management, session management) over E-UTRAN or NR, respectively, depending on whether the UE requests 5GC or EPC access.

[0117] Section 5.17.2.2 of 3GPP TS 23.501 V17.2.0 describes the interworking procedure over the N26 interface. The interworking procedure using the N26 interface enables the exchange of MM and SM states between source and target networks. The N26 interface can be either intra-PLMN (Public Land Mobile Network) or inter-PLMN (e.g., to enable inter-PLMN mobility). When the interworking procedure with N26 is used, the UE operates in single registration mode. In 3GPP access, the network keeps only one valid MM (Mobility Management) state for the UE, either in the AMF or the MME. In 3GPP access, either the AMF or the MME is registered to the HSS+UDM.

[0118] Support for the N26 interface between the 5GC AMF and the EPC MME is necessary to enable seamless session continuity (such as voice services) during system changes.

[0119] Section 5.17.2.3 of 3GPP TS 23.501 V17.2.0 describes an interworking procedure without using the N26 interface. In interworking without using the N26 interface, IP address retention is provided to the UE during intersystem mobility by storing and retrieving SMF+PGW-C and corresponding APN / DNN information via HSS+UDM. In such a network, the AMF may also notify the UE that interworking without N26 is supported during initial registration in 5GC, or the MME may optionally notify the UE that interworking without N26 is supported during the EPC attach procedure as defined in 3GPP TS 23.502 V17.2.1 and 3GPP TS 23.401 V17.3.0. The UE provides indication of support for the Request Type flag "handover" in the PDN connection request during the attach procedure described in section 5.3.2.1 of 3GPP TS 23.401 V17.3.0 and during initial registration and mobility registration update in 5GC.

[0120] FIG. 1C schematically illustrates a non-roaming architecture for interworking between 5GS and EPC / E-UTRAN according to one embodiment of the present disclosure, which is the same as FIG. 4.3.1-1 of 3GPP TS 23.501 V17.2.0.

[0121] The N26 interface is an 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 functions supported on S10 (functions essential for interworking).

[0122] FIG. 2A is a flowchart of a handover from 5GS to EPS in single registration mode via N26 according to one embodiment of the present disclosure, and is the same as FIG. 4.11.1.2.1-1 of 3GPP TS 23.502 V17.2.1.

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

[0124] - The parameter "Return preferred" may be included. Return preferred is an optional indication by the MME that the UE preferentially returns to a 5GS PLMN upon a subsequent access change to a 5GS shared network. The MME may use this information as specified in 3GPP TS 23.501 V17.2.0.

[0125] - The SGW address and TEID of both the control plane or EPS bearer in the message causes the target MME to select a new SGW.

[0126] - The AMF determines the Direct Forwarding Flag based on the configuration and direct forwarding path availability and notifies the target MME whether direct data forwarding is applicable.

[0127] - The AMF includes SM EPS UE contexts associated with PDU sessions with and without active UP connections.

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

[0129] For other steps, refer to Section 4.11.1.2.1 of 3GPP TS 23.502 V17.2.1.

[0130] FIG. 2B is a flowchart of idle mode mobility from 5GS to EPS using the N26 interface according to one embodiment of the present disclosure, and is the same as FIG. 4.11.1.3.2-1 of 3GPP TS 23.502 V17.2.1.

[0131] As described in section 4.11.1.3.2 of 3GPP TS 23.502 V17.2.1, in step 6, the AMF responds to the MME with a Context Response message containing the associated MM context (including the associated security context), Return preferred, and SM EPS UE context (default and dedicated GBR (Guaranteed Bit Rate) bearers). If the integrity protection verification fails, the AMF returns an appropriate error cause. Return preferred is an optional indication by the AMF to preferentially return the UE to a 5GS PLMN in a subsequent access change to a 5GS shared network. The AMF may start an implementation-specific (guard) timer for the UE context.

[0132] The MME determines from the received context and the tracking area indicated by the RAN whether the UE is performing inter-RAT mobility to or from NB-IoT.

[0133] For other procedures, refer to Section 4.11.1.3.2 of 3GPP TS 23.502 V17.2.1.

[0134] FIG. 2C is a flowchart of AM Policy Association Establishment with a newly selected PCF according to an embodiment of the present disclosure, which is the same as FIG. 4.16.1.2-1 of 3GPP TS 23.502 V17.2.1.

[0135] As described in 3GPP TS 23.502 V17.2.1, section 4.16.1, there are three possible cases for establishing an AM policy association:

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

[0137] 2. AMF reallocation due to PCF change during handover and registration procedures

[0138] 3. Move from EPS to 5GS if there is no existing AM policy association between AMF and PCF for this UE

[0139] This procedure is relevant for both roaming and non-roaming scenarios.

[0140] In the non-roaming case, the role of V-PCF (VISITED PCF) is performed by the PCF. In the roaming scenario, the V-PCF interacts with the AMF.

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

[0142] In step 2, [conditional] if the AMF has not yet obtained the UE's Access and Mobility Policy or if the AMF's Access and Mobility Policy is no longer valid, the AMF requests the PCF to apply the UE's Operator Policy 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 Indicator, and, if available, Service Area Restrictions, RFSP Index, subscribed UE-AMBR, list of subscribed UE-Slice-MBR, Allowed NSSAI, Target NSSAI (see 3GPP TS 23.501 V17.2.0, clause 5.3.4.3.3), GPSI obtained from UDM during location update procedure, and may include 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] If the AMF uses an NWDAF, it may add an NWDAF that provides a service to the UE identified by the NWDAF instance ID. For each NWDAF service instance, an Analytics ID is also included.

[0144] In step 3, the (V)-PCF responds to the Npcf_AMPolicyControl_Create service operation. The (V)-PCF provides access and mobility-related policy information (such as service area restrictions) as defined in section 6.5 of 3GPP TS 23.503 V17.3.0. Additionally, the (V)-PCF may provide a Policy Control Request Trigger for AM Policy Association to the AMF. In the non-roaming case, the PCF may subscribe to analytics from the NWDAF as defined in section 6.1.1.3 of 3GPP TS 23.503 V17.3.0.

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

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

[0147] In step 4, [conditional] the AMF stores the service area restriction and policy control request trigger for the AM policy association as specified in 3GPP TS 23.501 V17.2.0, provides the service area restriction to the UE, and configures the access and mobility policies including the RFSP index, the list of UE-AMBR, UE-Slice-MBR, the service area restriction to the NG-RAN, and the request for notification of the establishment of the SM policy association and the termination of the list of (DNN, S-NSSAI) with the PCF for the UE binding.

[0148] FIG. 2D is a flowchart of an AM Policy Association Modification initiated by a PCF according to one embodiment of the present disclosure, and is the same as FIG. 4.16.2.2-1 of 3GPP TS 23.502 V17.2.1.

[0149] As described in section 4.16.1 of 3GPP TS 23.502 V17.2.1, the AM policy association change procedure can be initiated by an event within the PCF or by the PCF obtaining appropriate analysis information from the NWDAF.

[0150] The following procedures are applicable to the change of AM policy association according to Case B:

[0151] Procedures driven by events internal to the PCF apply to both roaming and non-roaming scenarios, while those driven by the NWDAF apply only to non-roaming scenarios.

[0152] Before this procedure is triggered, an AM policy association is established with the V-PCF in the roaming case, or with the PCF in the non-roaming case, as described in section 4.16.1.2 of 3GPP TS 23.502 V17.2.1.

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

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

[0155] In step 1. [Conditional] The PCF internally determines that the new status of the UE context requires a new policy which may be triggered by the AF as described in clause 4.15.6.9 or by notification from the UDR. This may be triggered by obtaining appropriate 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 policy decision is made by the (V-)PCF in the roaming case and by the PCF in the non-roaming case. The PCF may also decide to subscribe to a new analytics ID from the NWDAF as described in section 6.1.1.3 of 3GPP TS 23.503 V17.3.0.

[0157] In step 3, the (V-)PCF in the roaming case or the PCF in the non-roaming case sends an Npcf_AMPolicyControl_UpdateNotify containing the AM Policy Association ID associated with the SUPI defined in 3GPP TS 29.507. The policy update may include service area restrictions, UE-AMBR, RFSP index value, access stratum time distribution notification, and Uu time synchronization error budget. If the AF previously subscribed to event requests resulting from the service area coverage allocation in step 1, the (V-)PCF checks whether the assigned service area coverage has changed and sends the respective notification to the AF using an Npcf_AMPolicyAuthorization_Notify as defined in clause 6.3.1.18 of 3GPP TS 23.503 V17.3.0.

[0158] In step 4, the AMF configures and stores the updated access and mobility policy information, including storing the Service Area Restrictions and Policy Control Request Trigger of AM Policy Association, providing the service area restrictions to the UE, providing the RFSP index, UE-AMBR, service area restrictions to the NG-RAN, and optionally providing the access stratum time distribution notification and Uu time synchronization error budget to the NG-RAN, and requesting notification of the establishment of SM policy association and the termination of the list (DNN, S-NSSAI) with the PCF for UE binding information.

[0159] Section 4.3.6 of 3GPP TS 23.401 V17.3.0 describes radio resource management functions.

[0160] To support E-UTRAN radio resource management, the MME provides the parameter "RAT / Frequency Selection Priority Index" (RFSP index) to the eNodeB via S1. The RFSP index maps to a configuration defined locally by the eNodeB to apply a specific RRM strategy. The RFSP index is UE specific and applies to all radio bearers. Examples of how this parameter is used by E-UTRAN:

[0161] - Deriving UE-specific cell reselection priorities to control idle mode camping

[0162] - Deciding to redirect a UE in active mode 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 subscribers, the MME selects the RFSP index and ARPI in use according to one of the following procedures, depending on the operator's configuration:

[0164] - The RFSP index in use is the same as the subscribed RFSP index

[0165] - The MME selects the RFSP index in use based on the subscribed RFSP index, the locally configured operator policy and, if received during the Attach and Tracking Area Update procedure, the UE related context information available at the MME, including the UE usage preferences and voice domain preference for E-UTRAN (see clause 4.3.5.9 of 3GPP TS 23.401 V17.3.0).

[0166] - The ARPI in use is identical to the subscribed ARPI.

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

[0168] For roaming subscribers, the MME may alternatively select the RFSP index and ARPI in use based on visited network policy, but taking into account input from the HPLMN (e.g., pre-configured RFSP index / ARPI values ​​per HPLMN, or a single RFSP index / ARPI value used for all roamers independent 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 if X2 is used for intra-EUTRAN handover, UE context search, or dual connectivity with a secondary RAN node.

[0170] The MME stores the subscribed RFSP index and ARPI values ​​received from the HSS and the RFSP index and ARPI values ​​in use. During a tracking area update procedure, the MME may update the RFSP index / ARPI values ​​in use (e.g., if context information for the UE in the MME changes, the MME may need to update the RFSP index / ARPI values ​​in use). If the RFSP index / ARPI values ​​in use change, the MME immediately provides the updated RFSP index / ARPI values ​​in use to the eNodeB by modifying the existing UE context, or by establishing a new UE context in the eNodeB, or by configuring the DOWNLINK NAS TRANSPORT message to include the updated RFSP index / ARPI values ​​in use if user plane establishment is not required. During an inter-MME mobility procedure, the source MME forwards both the RFSP index and ARPI values ​​to the target MME. The target MME may replace the received RFSP index value and ARPI in use value with a new RFSP index value in use or a new ARPI in use value based on the operator's policy and context information about the UE available at the target MME.

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

[0172] To support a mixed RAN with RAN nodes that support ARPI and those that do not, the MME sends ARPI In Use in the PATCH SWITCH ACKNOWLEDGEMENT and HANDOVER REQUEST messages on the S1 interface.

[0173] 3 illustrates a flowchart of a method according to one embodiment of the present disclosure, which may be performed by an apparatus implemented within / as a policy control entity or communicatively coupled to a policy control entity. In this manner, the apparatus may provide means for accomplishing various portions of method 300 and means for accomplishing other processes in conjunction with other components.

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

[0175] In one embodiment, the policy control entity may reside in the first network.

[0176] In one embodiment, the policy control entity may configure a validity time of a radio access technology or frequency selection priority (RFSP) index. The validity time of the RFSP index indicates a time when the RFSP index is valid or used. In one embodiment, the validity time of the RFSP index indicates a time when the RFSP index is valid or used when the UE is in the EPS.

[0177] In one embodiment, the validity time of the RFSP index indicates the time that the RFSP index is used by the second mobility management entity while the UE is in the second network.

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

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

[0180] In one embodiment, the policy control entity may send a first message to the mobility management entity that includes the RFSP index and a validity time of the RFSP index.

[0181] The term "take effect" may mean that the mobility management entity directly uses the RFSP index before the RFSP index expires. For example, the mobility management entity should not reevaluate or reselect the RFSP index.

[0182] The policy control entity may be any suitable network function capable of providing policy control functionality. In one embodiment, the policy control entity comprises a policy control function (PCF).

[0183] The mobility management entity may be any suitable network function capable of providing mobility management functionality. In one embodiment, the mobility management entity includes an Access and Mobility Function (AMF).

[0184] The validity time of the RFSP index may be determined or obtained in various ways. For example, the validity time of the RFSP index may be provided to a policy control entity by an application node, such as an application function or an application server. The validity time of the RFSP index may be determined by the policy control entity according to some criteria. The RFSP index may be configured with a fixed validity time. Different RFSP indexes may have different validity times. The validity time of the RFSP index may be determined according to a policy or rule. The validity time of the RFSP index may be set by an operator. The validity time of the RFSP index may be determined based on a subscriber's subscription data. The validity time of the RFSP index may be determined according to a service type, quality of service requirements, or UE data volume. The validity time of the RFSP index may be determined based on the application in use. The validity time of the RFSP index may be determined according to network conditions.

[0185] In one embodiment, the RFSP index may not have a validity time (eg, the RFSP index does not have an expiration date).

[0186] The validity time of the RFSP index may take 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. A policy control entity may maintain or know the mapping relationship.

[0188] In one 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 one embodiment, the validity time of the RFSP index further indicates the time when the RFSP index is valid in a specific network. The specific network may be any suitable network, such as a 3GPP 2G, 3G, or 4G network. For example, when the UE is accessing the specific network, the validity time of the RFSP index is valid in the specific network. When the UE is accessing another network other than the specific network, the validity time of the RFSP index is not valid in the specific network. In other words, the validity time of the RFSP index may be ignored in other networks.

[0190] In one embodiment, the particular network includes 3GPP EPS.

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

[0192] In one embodiment, the first message includes 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, during an AM policy association establishment procedure with a newly selected PCF, the RFSP index and the RFSP index validity time may be included in the Npcf_AMPolicyControl_Create Response as shown in Figure 2C. During an AM policy association modification procedure initiated by a PCF, the RFSP index and the RFSP index validity time may be included in the Npcf_AMPolicyControl_UpdateNotify as shown in Figure 2D.

[0194] Blocks 302 and 304 may be triggered to execute for a variety of reasons.

[0195] As a first example, based on a local policy, a mobility management entity such as an AMF decides to establish an AM policy association with a policy control entity, and then blocks 302 and 304 are executed under the conditions described below.

[0196] If a mobility management entity such as an AMF has not yet obtained an access and mobility policy for the UE, or if the access and mobility policy in the mobility management entity such as an AMF is no longer valid, the mobility management entity such as an AMF requests a policy control entity such as a PCF to apply an operator policy for the UE from the policy control entity such as a PCF. The mobility management entity such as an AMF sends an AM Policy Control Create 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 Create response to the mobility management entity, including an RFSP index and the validity time of the RFSP index.

[0197] As a second example, the AM policy association modification procedure may be initiated by an internal policy control entity event or by the policy control entity obtaining appropriate analysis information from a network data analysis function, after which blocks 302 and 304 are executed under the conditions described below.

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

[0199] 4 shows a flowchart of a method according to another embodiment of the present disclosure, which may be implemented in, implemented as, or performed by an apparatus communicatively coupled to a policy control entity. In this manner, the apparatus may provide means for accomplishing various portions of method 400 and means for accomplishing other processes in cooperation with other components. Some portions described in the above embodiments are omitted here for brevity.

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

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

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

[0203] In one embodiment, 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).

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

[0205] In block 404, the policy control entity may configure a validity period of 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 period of the RFSP index indicates the time period for which the RFSP index is used in the second mobility management entity while the UE is in the second network. Block 404 is the same as block 302 of FIG. 3.

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

[0207] 5 shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed by an apparatus implemented in, implemented as, or communicatively coupled to a first mobility management entity. In this manner, the apparatus may provide means for accomplishing various portions of method 500 and means for accomplishing other processes in cooperation with other components. Some portions described in the above embodiments are omitted here for brevity.

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

[0209] In one embodiment, the first mobility management entity may reside in the first network.

[0210] In one embodiment, the validity time of the RFSP index indicates the time that the RFSP index is used by the second mobility management entity while the UE is in the second network.

[0211] In one embodiment, the RFSP index indicates that 3GPP EPS access is preferred.

[0212] In one embodiment, the validity time of the RFSP index further indicates the time when the RFSP index becomes valid for a particular network.

[0213] In one embodiment, the particular network includes 3GPP EPS.

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

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

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

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

[0219] In one embodiment, the second message is sent to the second mobility management entity during at least one of an S1-based handover procedure as described in section 5.5.1.2 of 3GPP TS 23.401 V17.3.0 or an S1-based Dual Active Protocol Stack (DAPS) handover procedure as described in section 5.5.1.2.2a of 3GPP TS 23.401 V17.3.0.

[0220] In one embodiment, the second message includes at least one of a Forward Relocation Request or a Context Response, as described in 3GPP TS 23.401 V17.3.0 and 3GPP TS 23.502 V17.2.1.

[0221] In one embodiment, the validity time of the RFSP index may be set by a first mobility management entity. For example, the RFSP index may be provided by a policy control entity, and the first mobility management entity may then set the validity time of the RFSP index. As another example, the first mobility management entity, such as an AMF or an MME, may select an RFSP index in use and then set the validity time of the RFSP index.

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

[0223] 6 shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed by an apparatus implemented in, implemented as, or communicatively coupled to a first mobility management entity. In this manner, the apparatus may provide means for accomplishing various portions of method 600 and means for accomplishing other processes in cooperation with other components. Some portions described in the above embodiments are omitted here for brevity.

[0224] In 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. As described in Figures 2C and 2D, the AMF may receive the RFSP index from the PCF.

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

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

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

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

[0229] In one embodiment, 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).

[0230] For example, there may be a mapping relationship from RFSP index to cell selection and RAT / frequency priority. The first mobility management entity may maintain or know the mapping relationship. During establishment of an AM policy association with the policy control entity initiated by the mobility management entity or during a change of the AM policy association initiated by the PCF, the policy control entity may create an access and mobility policy for the UE. The access and mobility policy may include an authorized RFSP index. The authorized RFSP index may differ from the RFSP index provided by the mobility management entity. For example, the RFSP index provided by the mobility management entity may indicate a preference for first network access, and the authorized RFSP index may indicate a preference for 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 a preference for first network access to a preference for 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 time of the RFSP index may be determined or obtained in various ways. For example, the validity time of the RFSP index may be determined by the first mobility management entity according to some criteria. The RFSP index may include a fixed validity time. Different RFSP indexes may have different validity times. The validity time of the RFSP index may be determined according to a policy or rule. The validity time of the RFSP index may be set by an operator. The validity time of the RFSP index may be determined based on subscription data of a subscriber. The validity time of the RFSP index may be determined according to the service or data volume of the UE. The validity time of the RFSP index may be determined according to network conditions.

[0233] In one embodiment, the RFSP index may not have a validity time (ie, the RFSP index does not have an expiration date).

[0234] The validity time of the RFSP index may take any suitable form, such as a timestamp.

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

[0236] In one 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 one embodiment, the validity time of the RFSP index further indicates a time when the RFSP index is valid in a specific network. The specific network may be any appropriate network, such as a 3GPP 2G, 3G, or 4G network. For example, when the UE is accessing the specific network, the validity time of the RFSP index is valid in the specific network. When the UE is accessing another network other than the specific network, the validity time of the RFSP index is not valid in the specific network. In other words, the validity time of the RFSP index may be ignored in other networks.

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

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

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

[0241] In one embodiment, the second message is sent to the second mobility management entity during at least one of a 5GS to EPS handover procedure using the N26 interface as described in section 4.11.1.2.1 of 3GPP TS 23.502 V17.2.1, or a 5GS to EPS idle mode mobility procedure using the N26 interface as described in section 4.11.1.3.2 of 3GPP TS 23.502 V17.2.1.

[0242] 7 shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed by an apparatus implemented in, implemented as, or communicatively coupled to a first mobility management entity. In this manner, the apparatus may provide means for accomplishing various portions of method 700 and means for accomplishing other processes in cooperation with other components. Some portions described in the above embodiments are omitted here for brevity.

[0243] In block 702, the first mobility management entity may receive a first message from the policy control entity, the first message including an RFSP index and a validity time of the RFSP index. For example, as described in block 304 of FIG. 3 and block 406 of FIG. 4, 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 one embodiment, the first message includes 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 maintain a validity time of the RFSP index.

[0246] In 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 of the RFSP index for the user equipment (UE) moving from the first network to the second network. In one embodiment, the validity time of the RFSP index indicates the time the RFSP index will be used by the second mobility management entity while the UE is in the second network.

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

[0248] In one embodiment, the second message is sent to the second mobility management entity during at least one of a 5GS to EPS handover procedure using the N26 interface as described in section 4.11.1.2.1 of 3GPP TS 23.502 V17.2.1 or a 5GS to EPS idle mode mobility procedure using the N26 interface as described in section 4.11.1.3.2 of 3GPP TS 23.502 V17.2.1.

[0249] 8 shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed by an apparatus implemented in, implemented as, or communicatively coupled to a second mobility management entity. In this manner, the apparatus may provide means for accomplishing various portions of method 800 and means for accomplishing other processes in cooperation with other components. Some portions described in the above embodiments are omitted here for brevity.

[0250] In block 802, the second mobility management entity may receive a second message from the first mobility management entity in the first network, the second message including a radio access technology or frequency selection preference (RFSP) index for a user equipment (UE) moving from the first network to the second network and a validity time of the RFSP index. The validity time of the RFSP index may indicate a time period during which the RFSP index is used by the second mobility management entity while the UE is in the second network.

[0251] In one embodiment, the second mobility management entity may reside in a second network.

[0252] For example, the first mobility management entity may send a second message to the second mobility management entity in block 502 of FIG. 5, and the second mobility management entity may then receive the second message from the first mobility management entity.

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

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

[0255] In one embodiment, the second mobility management entity may cause the RFSP index to become valid before the expiration of the validity time of the RFSP index.

[0256] In block 808, optionally, the second mobility management entity may perform reevaluation of the RFSP index when the validity time of the RFSP index expires. For example, the second mobility management entity may perform reevaluation of the RFSP index as described in section 4.3.6 of 3GPP TS 23.401 V17.3.

[0257] In one embodiment, the second message includes at least one of a Forward Relocation Request or a Context Response.

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

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

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

[0261] In one 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 one embodiment, the RFSP index indicates that 3GPP EPS access is preferred.

[0263] In one embodiment, the validity time of the RFSP index further indicates the time the RFSP index becomes valid or can be used in a particular network.

[0264] In one embodiment, the particular network includes 3GPP EPS.

[0265] In one embodiment, the PCF provides the authorized RFSP index to the AMF.

[0266] - If the PCF is aware of the mapping from RFSP index to cell selection and RAT / frequency priority, and the PCF determines that a change in the authorized RFSP index value indicates a change from preferring 5G access to preferring 4G access for the UE, the PCF shall include a validity time (e.g., a new information element (IE) "RFSPinUseExpiryTime") indicating the time when the RFSP index will be valid or used if the UE moves to EPS.

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

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

[0269] - If the validity time is provided by the PCF, the AMF retains the validity time.

[0270] - Otherwise, if no validity time is provided by the PCF and the AMF is aware of the mapping from RFSP index to cell selection and RAT / frequency priority and determines that a change in the allowed RFSP index value indicates a change from prioritizing 5G access to prioritizing 4G access for the UE, the AMF shall set and maintain a validity time (e.g., "RFSPinUseExpiryTime") indicating the time when the RFSP index becomes valid or will be used if the UE moves to EPS.

[0271] In one embodiment, if the NG-RAN triggers a handover before the expiration of "RFSPinUseExpiryTime", the AMF includes a new IE "RFSPinUseExpiryTime" in a Forward Relocation Request to the MME. If the NG-RAN triggers a release by redirection, the UE performs a Tracking Area Request procedure and the AMF includes a new IE "RFSPinUseExpiryTime" in a context response before the expiration of "RFSPinUseExpiryTime".

[0272] In one embodiment, when the MME receives RFSPinUseExpiryTime, the MME causes the "RFSP index in use" to become valid. When the validity time indicated in RFSPinUseExpiryTime expires, the MME re-evaluates the RFSP index.

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

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

[0275] In one embodiment, the MME selects an RFSP index based on whether the validity time of the RFSP index has expired.

[0276] In one embodiment, the proposed solution includes three parts: PCF to AMF, AMF to MME, and MME to MME.

[0277] (PCF to AMF)

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

[0279] (AMF to MME)

[0280] At AMF:

[0281] If the validity time is provided by the PCF, the AMF retains the validity time.

[0282] Otherwise, if a validity time is not provided by the PCF, if the AMF is aware of the mapping from RFSP index to cell selection and RAT / frequency priority and determines that a change in the authorized RFSP index value indicates a change from prioritizing 5G access to prioritizing 4G access for the UE, the AMF shall set and maintain a validity time (working name "RFSPinUseExpiryTime") indicating the time when this RFSP index becomes valid or will be used if the UE moves to EPS.

[0283] If the NG-RAN triggers a handover before the expiration of "RFSPinUseExpiryTime", clause 4.11.1.2.1 of 3GPP TS 23.502 V17.2.1 (t5GS to EPS handover using N26 interface) is reused with the following addition:

[0284] - When the AMF sends a forwarding relocation request to the MME in step 3, the AMF further includes a timestamp indicating to the MME that the "RFSP index in use" should be used before the expiration of the notified time.

[0285] If the NG-RAN triggers a release by redirection, the UE performs a tracking area request procedure. Clause 4.11.1.3.2 of 3GPP TS 23.502 V17.2.1 (Idle mode mobility from 5GS to EPS using the N26 interface) is reused with the following additions:

[0286] - In step 6, when the AMF sends a context response to the MME, the AMF further includes a timestamp indicating to the MME that the "RFSP index in use" should be used before the expiration of the notified time.

[0287] At the MME:

[0288] When the MME receives RFSPinUseExpiryTime, it retains it and ensures that the "RFSP index in use" is valid. When the validity time indicated in RFSPinUseExpiryTime expires, the MME reevaluates the RFSP index as specified in 3GPP TS 23.401 V17.3.0, clause 4.3.6.

[0289] (From (old / source) MME to (new / target) MME)

[0290] If the UE moves to another MME before the expiration of the validity time (RFSPinUseExpiryTime), the old MME includes 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 retains it to ensure that the "RFSP index in use" is valid. When the validity time indicated in RFSPinUseExpiryTime expires, the MME reevaluates the RFSP index as specified in 3GPP TS 23.401 V17.3.0, clause 4.3.6.

[0292] In one 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 is aware of the mapping from RFSP index to cell selection and RAT / frequency priority, which is typically known by 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 known as the "SPID" (Subscriber Profile ID) of the RAT / frequency priority.

[0294] When the AMF receives an authorized RFSP index from the PCF, if the AMF knows that the authorized RFSP index corresponds to a value that prioritizes 4G, the AMF may retain the time until this RFSP index is applied (working name "RFSPinUseExpiryTime") in the UE context.

[0295] If the NG-RAN triggers a handover before 'RFSPinUseExpiryTime', the AMF includes a new parameter 'RFSPinUseExpiryTime' in the forwarding relocation request to the MME.

[0296] If NG-RAN triggers a release by redirection, the UE performs a tracking area request procedure, and the AMF includes a new parameter "RFSPinUseExpiryTime" in the context response if the time is before "RFSPinUseExpiryTime".

[0297] When the MME receives RFSPinUseExpiryTime, it uses the "RFSP index in use". When RFSPinUseExpiryTime expires, the MME re-evaluates the RFSP index as specified in 3GPP TS 23.401 V17.3.0 clause 4.3.6 and sends the updated RFSP index to the eNB which may direct the UE to 5GS.

[0298] As a result, the UE can return to 5GS after a configurable time, so there is no need to maintain the AMF-PCF association even when the UE moves to EPS, which can mitigate the ping-pong problem.

[0299] This proposal only addresses the N26 deployment scenario.

[0300] In one 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 certain period of time.

[0302] 6.X.1 Description

[0303] This solution addresses the deployment scenario KI#1 in N26.

[0304] - The AMF is aware of the mapping from RFSP index to cell selection and RAT / frequency priority, and it is assumed that this is generally known by 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 known as the "SPID" (Subscriber Profile ID) for the RAT / frequency priority.

[0305] When the AMF receives an authorized RFSP index from the PCF, if the AMF knows that the authorized RFSP index corresponds to a value that prioritizes 4G, the AMF may store in the UE context the time until which this RFSP index is applied (working name "RFSPinUseExpiryTime").

[0306] - If the NG-RAN triggers a handover before "RFSPinUseExpiryTime", the AMF includes the new parameter "RFSPinUseExpiryTime" in the Forward Relocation Request to the MME. If the NG-RAN triggers a release with redirection, the UE performs a Tracking Area Request procedure and the AMF includes the new parameter "RFSPinUseExpiryTime" in the context response if the time is earlier than "RFSPinUseExpiryTime".

[0307] - When the MME receives RFSPinUseExpiryTime, the MME uses the "RFSP index in use". When the time indicated in RFSPinUseExpiryTime expires, the MME reevaluates the RFSP index as specified in clause 4.3.6 of 3GPP TS 23.401 V17.3.0.

[0308] NOTE: If the UE is not directed to EPS from NG-RAN before the expiration of the time indicated by RFSPinUseExpiryTime, no action is required in the AMF.

[0309] 6.X.2 Procedures

[0310] 3GPP TS 23.502 V17.2.1, clause 4.11.1.2.1 (Handover from 5GS to EPS using N26 interface) is reused with the following additions:

[0311] In step 3, when the AMF sends the forwarding 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 expiration of the notified time. When the notified time expires, the MME reevaluates the RFSP index as specified in section 4.3.6 of 3GPP TS 23.401 V17.3.0.

[0312] 3GPP TS 23.502 V17.2.1, section 4.11.1.3.2 (Idle mode mobility from 5GS to EPS using the N26 interface) is reused with the following additions:

[0313] In step 6, when the AMF sends a context response to the MME, the AMF further includes a timestamp indicating to the MME that it should use the "RFSP index in use" before the expiration of the notified time. When the notified time expires, the MME reevaluates the RFSP index as specified in clause 4.3.6 of 3GPP TS 23.401 V17.3.0.

[0314] If the UE further moves from one MME to another MME before the expiration of the time indicated by RFSPinUseExpiryTime, 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] Interface impact:

[0317] N26 and S10: Introduction of an additional IE (working name "RFSPinUseExpiryTime") indicating the expiration time of the "RFSP index in use".

[0318] Impact on AMF:

[0319] - If the PCF provides an authorized RFSP index, the AMF must recognize that the new value prioritizes 4G and decides to keep 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 by the expiration time indicated:

[0320] - Transfer relocation request

[0321] - Context Response

[0322] Impact on MME:

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

[0324] By applying the proposed solution according to the embodiments of the present disclosure, many advantages may be achieved. For example, in some embodiments herein, an advantage is that the UE can return to a network, such as 5GS, after a configurable / valid time expires. In some embodiments herein, the ping-pong problem may be mitigated with minimal impact on a first network, such as 5GS, and a second network, such as EPS. In some embodiments herein, the proposed solution may minimize impact on a first network, such as 5GS, and a second network, such as EPS. The embodiments herein are not limited to the features and advantages described above. Those skilled in the art will recognize additional features and advantages upon reading the following detailed description.

[0325] 9 is a block diagram illustrating an apparatus suitable for implementing some embodiments of the present disclosure. For example, the policy control entity, the first mobility management entity, or the second mobility management entity described above may be implemented as or via the apparatus 900.

[0326] The apparatus 900 has at least one processor 921, such as a digital processor (DP), and at least one memory (MEM) 922 coupled to the processor 921. The apparatus 900 may further have a transmitter TX and a receiver RX 923 coupled to the processor 921. The memory 922 holds a program (PROG) 924. The PROG 924 may include instructions that, when executed on an associated processor 921, enable the apparatus 900 to operate according to embodiments of the present disclosure. The combination of the at least one processor 921 and the at least one memory 922 may form a processing means 925 adapted to perform various embodiments of the present disclosure.

[0327] Various embodiments of the present disclosure may be implemented by computer programs executable by one or more of the processor(s) 921, software, firmware, hardware, or combinations thereof.

[0328] The memory 922 may be of any type suitable for the local technology 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 and removable memory.

[0329] The processor 921 may be of any type suitable for the local technology 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 in which the device is implemented as or in a policy control entity, memory 922 includes instructions executable by processor 921 to cause the policy control entity to operate according to any of the methods associated with the policy control entities described above.

[0331] In embodiments in which the device is implemented as or in a first mobility management entity, memory 922 includes instructions executable by processor 921 to cause the first mobility management entity to operate according to any method associated with the first mobility management entity described above.

[0332] In embodiments in which the device is implemented as or in a second mobility management entity, memory 922 includes instructions executable by processor 921 to cause the second mobility management entity to operate according to any method associated with the second mobility management entity described above.

[0333] 10 is a block diagram illustrating a policy control entity in a first network according to an embodiment of the present disclosure. As illustrated, the policy control entity 1000 includes a setting module 1001 configured to set a validity time of a radio access technology or frequency selection preference (RFSP) index of a user equipment (UE) moving from a first network to a second network. The validity time of the RFSP index may indicate a time period during which the RFSP index will be used in a second mobility management entity while the UE is in the second network. The policy control entity 1000 further includes a sending module 1002 configured to send a first message to the mobility management entity of the first network, the first message including the RFSP index and the validity time of the RFSP index.

[0334] In one 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 from a preference for first network access to a preference for second network access for the user equipment, and in response to the determination, a validity time of the RFSP index is included in the first message.

[0335] 11 is a block diagram illustrating a first mobility management entity in a first network according to one embodiment of the present disclosure. As shown, the first mobility management entity 1100 has a transmitting module 1101 configured to transmit a second message to a second mobility management entity in a second network, the second message including a radio access technology or frequency selection preference (RFSP) index and a validity time of the RFSP index for a user equipment (UE) moving from the first network to the second network. The validity time of the RFSP index may indicate a time period during which the RFSP index will be used by the second mobility management entity while the UE is in the second network.

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

[0337] In one 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 from preferring the first network access to preferring the second network access for the user equipment.

[0338] In one embodiment, the first mobility management entity 1100 further comprises a setting module 1104 configured to set a validity time of the RFSP index.

[0339] In one embodiment, the first mobility management entity 1100 further comprises a first storage module 1105 configured to hold a validity time of the RFSP index.

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

[0341] In one embodiment, the first mobility management entity 1100 further includes a second storage module 1107 configured to hold the validity time of the RFSP index.

[0342] 12 is a block diagram illustrating a second mobility management entity in a second network according to one embodiment of the present disclosure. As shown, the second mobility management entity 1200 includes a receiving module 1201 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 preference (RFSP) index and a validity time of the RFSP index for a user equipment (UE) moving from the first network to the second network. The validity time of the RFSP index may indicate a time period during which the RFSP index will be used at the second mobility management entity while the UE is in the second network. The second mobility management entity 1200 further includes a using module 1202 configured to use the RFSP index for a period indicated by the validity time until the validity time expires.

[0343] In one embodiment, the second mobility management entity 1200 further comprises a storage module 1203 configured to retain the RFSP index and the validity time of the RFSP index.

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

[0345] The term unit or module, as used herein, may have its 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 respective tasks, procedures, calculations, output, and / or display functions, etc.

[0346] The functional unit enables the policy control entity, the first mobility management entity, or the second mobility management entity to have no fixed processor or memory, and any computing resource and recording resource can be allocated 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 utilization efficiency of network resources and the flexibility of the network.

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

[0348] According to one aspect of the present disclosure, there is provided a computer-readable storage medium bearing instructions that, when executed by at least one processor, cause the at least one processor to perform any of the methods described above.

[0349] Furthermore, the present disclosure may provide a carrier containing such a computer program, the carrier being one of an electronic signal, an optical signal, a radio signal, or a computer-readable storage medium, which may be, for example, an optical compact 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 may be implemented by various means, such that an apparatus implementing one or more functions of a corresponding apparatus described in the embodiments may be composed of not only prior art means but also means for implementing one or more functions of the corresponding apparatus described in the embodiments, and may include separate means for each separate function, or means that can be configured to perform two or more functions. For example, these techniques may be implemented in hardware (one or more devices), firmware (one or more devices), software (one or more modules), or a combination thereof. In the case of firmware or software, implementation may be through modules (e.g., procedures, functions, etc.) that perform the functions described herein.

[0351] The exemplary embodiments herein have been described above with reference to block diagrams and flowchart illustrations of methods and apparatuses. 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 means, including computer program instructions. These computer program instructions can be loaded into a general-purpose computer, special-purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, when executed on the computer or other programmable data processing apparatus, create means for performing the functions identified in the flowchart block or blocks.

[0352] Furthermore, while operations are shown in a particular order, this should not be understood as requiring such operations to be performed in the particular order or sequence shown, or that all of the operations shown be performed, to achieve desirable results. In certain situations, multitasking and parallel processing may be advantageous. Similarly, while some specific implementation details are included in the above discussion, these should not be construed as limitations on the scope of the subject matter described herein, but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable subcombination.

[0353] While the specification contains many specific implementation details, these should not be construed as limiting the scope of any implementation or what may be claimed, but rather as descriptions of features that may be specific to particular embodiments of a particular implementation. Certain features that are described in this specification in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable subcombination. Furthermore, while features may be described above as working in a particular combination, and even initially claimed as such, one or more features from a claimed combination may, in some cases, be separated from the combination, and the claimed combination may be directed to subcombinations or variations of the subcombination.

[0354] It will be obvious to those skilled in the art that with the advancement of technology, the concept of the present invention can be implemented in various ways. The above-described embodiments are given to illustrate, not to limit, the present disclosure, and it should be understood that modifications and variations are required without departing from the spirit and scope of the present disclosure, as can be easily understood by those skilled in the art. Such modifications and variations are considered to be within the scope of the present disclosure and the appended claims. The protective scope 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 a validity time of a radio access technology or frequency selection priority (RFSP) index of a user equipment (UE) moving from the first network to a second network (302); sending (304) a first message including the RFSP index and the validity time of the RFSP index to a first mobility management entity of the first network; The validity time of the RFSP index indicates the time during which the RFSP index is used in a second mobility management entity while the UE is in the second network. method.

2. determining (402) that a change in the value of the RFSP index indicates a change from a preference for first network access to a preference for second network access for the user equipment; In response to the determination, the validity period of the RFSP index is included in the first message. The method of claim 1.

3. The first message includes 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. The method of claim 1.

4. The RFSP index indicates that 3GPP EPS access is preferred. The method of claim 1.

5. A method (500) performed by an Access and Mobility Function (AMF) in a first network conforming to a Third Generation Partnership Project (3GPP) Fifth Generation System (5GS) standard, comprising: sending (502) a second message to a mobility management entity (MME) of a second network that conforms to the 3GPP Evolved Packet System (EPS) standard, the second message including a radio access technology or frequency selection preference (RFSP) index of a user equipment (UE) moving from the first network to the second network and a validity time of the RFSP index; the validity time of the RFSP index indicates a time during which the RFSP index is used in the MME while the UE is in the second network; The validity period of the RFSP index is provided by a policy control entity in the first network. method.

6. receiving (702) a first message from the policy control entity, the first message including the RFSP index and the validity time of the RFSP index; and maintaining the validity time of the RFSP index (704). The method of claim 5.

7. The first message includes 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. The method of claim 6.

8. The second message is sent to the MME 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. The method of claim 5.

9. The second message includes at least one of a Forward Relocation Request or a Context Response. The method of claim 5.

10. The RFSP index indicates that 3GPP EPS access is preferred. The method of claim 5.

11. A method (800) performed by a mobility management entity (MME) in a second network that conforms to the Third Generation Partnership Project (3GPP) Evolved Packet System (EPS) standard, comprising: receiving a second message from an Access and Mobility Function (AMF) of a first network conforming to a 3GPP 5th Generation System (5GS) standard, the second message including a Radio Access Technology or Frequency Selection Preference (RFSP) index and a validity time of the RFSP index for a user equipment (UE) moving from the first network to the second network (802), the validity time of the RFSP index indicating a time during which the RFSP index will be used in the MME while the UE is in the second network (803); using the RFSP index for a period indicated by the validity time until the validity time expires (806); The validity period of the RFSP index is provided by a policy control entity in the first network. method.

12. and performing a re-evaluation of the RFSP index when the validity period of the RFSP index expires (808). The method of claim 11.

13. and maintaining (804) the RFSP index and the validity time of the RFSP index. The method of claim 11.

14. The second message includes at least one of a Forward Relocation Request or a Context Response. The method of claim 11.

15. The second message is received from the AMF 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. The method of claim 11.

16. The RFSP index indicates that 3GPP EPS access is preferred. The method of claim 11.

17. A policy control entity (900), A processor (921); a memory (922) coupled to the processor (921), the memory (922) containing instructions executable by the processor (921); The policy control entity (900) executes the method according to any one of claims 1 to 4 according to the instructions. Policy Control Entity.

18. An Access and Mobility Function (AMF) (900) conforming to the 3rd Generation Partnership Project (3GPP) 5th Generation System (5GS) standard, comprising: A processor (921); a memory (922) coupled to the processor (921), the memory (922) including instructions executable by the processor (921); The AMF (900) executes the method according to any one of claims 5 to 10 according to the instructions. A.M.F.

19. A mobility management entity (MME) (900) conforming to the Third Generation Partnership Project (3GPP) Evolved Packet System (EPS) standard, comprising: A processor (921); a memory (922) coupled to the processor (921), the memory (922) including instructions executable by the processor (921); The MME (900) executes the method according to any one of claims 11 to 16 according to the instructions. MME.

20. comprising instructions which, when executed by at least one processor, cause said at least one processor to perform the method of any one of claims 1 to 16. Computer program.

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