WO2023173290A1

WO2023173290A1 - Paging enhancement for radio resource control (rrc) inactive

Info

Publication number: WO2023173290A1
Application number: PCT/CN2022/080951
Authority: WO
Inventors: Tianyi Li; Chao Xu; Jixing TANG
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2022-03-15
Filing date: 2022-03-15
Publication date: 2023-09-21

Abstract

The present disclosure is related to paging enhancement for RRC Inactive. A method at a first network node for paging a UE that is in an RRC_INACTIVE state with a first RAN node and in a CM-CONNECETED state with the first network node comprises: receiving, from the first RAN node, a first message indicating a paging failure for the UE; and triggering one or more paging procedures for the UE to be performed at one or more second RAN nodes.

Description

PAGING ENHANCEMENT FOR RADIO RESOURCE CONTROL (RRC) INACTIVE

Technical Field

The present disclosure is related to the field of telecommunications, and in particular, to methods, network nodes, and RAN nodes for paging enhancement for Radio Resource Control (RRC) Inactive.

Background

Nowadays, people will use their mobile devices (e.g., a mobile phone, a tablet, etc. ) for their study, work, and/or entertainment every day. The most popular radio access technologies (RATs) used by the mobile devices comprise: 4G Long Term Evolution (LTE) , 5G New Radio (NR) , or the like. Among numerous technologies employed by 4G or 5G, paging is obviously one of the most important technologies.

Paging is the mechanism in which a network notifies its user equipment (UE) of downlink data arrival or any other event related to the UE. Then, the UE may decode the content (e.g. Paging Cause) of the paging message and the UE has to initiate an appropriate procedure, for example, a random access procedure. Paging, also referred to as the Network-Initiated Service Request, is used for signaling between a UE and the network when the UE is in the RRC_IDLE/CM_IDLE state. The operator can configure the Paging procedure to reduce the number of paging messages, which in turn can contribute to reduction in the network load. By reducing the number of paging messages, fewer resources are allocated to the network. The available resources can be used for handling more users. Less paging also reduces the signaling in the radio access network.

In 5G NR, a new RRC state is introduced to complement the existing states, RRC_IDLE and RRC_CONNECTED. The new state is referred to as RRC_INACTIVE and allows a UE to benefit from several aspects of the two original states. The RRC_INACTIVE state enables an efficient UE sleeping, a fast and lightweight transition from sleeping to active states and joint access optimizations. Due to different characteristics between the RRC_IDLE and RRC_INACTIVE states, a different paging mechanism is needed for UEs in RRC_INACTIVE state. For example, a UE in RRC_INACTIVE state may be also in CM_CONNECTED state, and therefore its serving Access &Mobility Management Function (AMF) may not be aware of that the UE is sleeping and it will not initiate a paging procedure for the UE as it will do for a UE in the RRC_IDLE state.

Summary

According to a first aspect of the present disclosure, a method at a first network node for paging a UE that is in an RRC_INACTIVE state with a first RAN node and in a CM-CONNECETED state with the first network node is provided. The method comprises: receiving, from the first RAN node, a first message indicating a paging failure for the UE; and triggering one or more paging procedures for the UE to be performed at one or more second RAN nodes.

In some embodiments, the step of triggering the one or more paging procedures for the UE comprises: transmitting, to at least one of the second RAN nodes, at least one second message for triggering the one or more paging procedures to be performed at the one or more second RAN nodes to page the UE. In some embodiments, the step of triggering the one or more paging procedures for the UE comprises: transmitting, to one of the one or more second RAN nodes, a second message for triggering the one or more paging procedures to be performed at the one or more second RAN nodes to page the UE, wherein the second message comprises information from which the one or more second RAN nodes can be determined. In some embodiments, the step of triggering the one or more paging procedures for the UE comprises: transmitting, to each of the one or more second RAN nodes, a second message for triggering a paging procedure to be performed at the corresponding second RAN node to page the UE. In some embodiments, the step of triggering the one or more paging procedures for the UE comprises: transmitting, to at least two of the one or more second RAN nodes, second messages, respectively, each of the second messages triggering paging procedures to be performed at a part of the one or more second RAN nodes to page the UE, wherein each of the second messages comprises information from which a part of the one or more second RAN nodes can be determined, and each of the one or more second RAN nodes can be determined by the information comprised in at least one of the one or more second messages.

In some embodiments, at least one of the second messages is an NG Application Protocol (NGAP) paging message for paging the UE. In some embodiments, the NGAP paging message comprises an information element (IE) indicating at least one of: identifiers of one or more of the second RAN nodes; identifiers of one or more cells associated with one or more of the second RAN nodes; identifiers of one or more tracking areas (TA) associated with one or more of the second RAN nodes; and an identifier of a UE context for the UE within the first RAN node; and the UE context for the UE. In some embodiments, when the IE indicates multiple second RAN nodes and/or multiple cells, the order of the multiple second RAN nodes and/or the multiple cells in the IE is determined by the first network node.

In some embodiments, the method further comprises: receiving, from one of the one or more second RAN nodes, a third message indicating that the UE establishes a new RRC connection or resumes a released RRC connection that was established between the UE and the first RAN node; and performing a UE context setup procedure for the UE with the second RAN node, from which the third message is received, in response to the third message indicating that the UE establishes a new RRC connection. In some embodiments, the method further comprises: instructing the first RAN node to release UE context for the UE in response to the third message indicating that the UE establishes a new RRC connection. In some embodiments, the method further comprises: triggering the one or more second RAN nodes and/or the first RAN node to stop the paging procedures for the UE in response to receiving the third message.

In some embodiments, the one or more second RAN nodes are not RAN nodes associated with any cell or area indicated by a RAN-based Notification Area (RNA) configured at the first RAN node for the UE. In some embodiments, the paging failure indicated by the first message is the earliest paging failure that is resulted from a RAN paging procedure initiated by the first RAN node for the UE. In some embodiments, the one or more paging procedures initiated at the one or more second RAN nodes are performed concurrently with a RAN paging procedure initiated by the first RAN node for the UE. In some embodiments, before the step of triggering the one or more paging procedures for the UE, the method further comprises: determining the one or more second RAN nodes, at which the one or more paging procedures for the UE are to be performed, at least based on historical mobility data for the UE. In some embodiments, the step of determining the one or more second RAN nodes comprises: for each of other RAN nodes than the first RAN node, counting a number of handovers or/and mobility registration updates of the UE from the first RAN node to the corresponding one of the other RAN nodes; and determining one or more of the other RAN nodes that have the top numbers of handovers or/and mobility registration updates as the one or more second RAN nodes.

In some embodiments, the step of determining the one or more second RAN nodes comprises: for each of cells associated with the first RAN node and for each of other cells than the cells associated with the first RAN node, counting a number of handovers or/and mobility registration updates of the UE from the corresponding cell associated with the first RAN node to the corresponding one of the other cells; and determining one or more RAN nodes that are associated with one or more of the other cells having the top numbers of handovers or/and mobility registration updates as the one or more second RAN nodes. In some embodiments, the step of determining the one or more second RAN nodes comprises: determining the one or more second RAN nodes by an Artificial Intelligence (AI) model that is trained at least based on the historical mobility data for the UE. In some embodiments, the AI model is trained with a cost function as follows:

TotalCost = Signal ^(1-λ)*Latency ^λ

wherein the ″TotalCost″ is the cost to be calculated, ″Signal″ indicates a signaling amount required for paging the UF, ″Latency″ indicates a paging latency, and ″λ″ indicates a regularization factor for balancing the paging latency and the signaling amount.

In some embodiments, the ″Signal″ and the ″Latency″ are normalized as follows:

wherein ″Number of RAN nodes″ indicates a number of RAN nodes involved in the paging procedure, ″Number of RAN nodes in TA list″ indicates a number of RAN nodes comprised in the TA list involved in the paging procedure, ″Paging Timeout″ indicates a paging timeout value for the paging procedure, and ″Maximum allowed paging wait time″ indicates the maximum allowed paging wait time configured at the RAN node.

In some embodiments, the AI model is trained with a cost function as follows:

wherein the ″TotalCost″ is the cost to be calculated, ″SuccRate (i -1, t, conf) ″ indicates the paging success rate for the i -1 ^th paging at a given time t and a given confidence level of conf, ″NumOfEnb (i, t, conf) ″ indicates a number of RAN nodes involved in the paging procedure for the i ^th paging at a given time t and a given confidence level of conf, ″Timeout (i -1) ″ indicates a timeout value for the i -1 ^th paging, and ″λ″ indicates a regularization factor for balancing the number of RAN nodes involved in the paging procedure and the timeout value.

In some embodiments, before the step of receiving the first message, the method further comprises: transmitting, to the first RAN node, a fourth message for triggering a RAN paging procedure for the UE. In some embodiments, the first message is at least one of: an ″RRC INACTIVE TRANSITION REPORT″ message or an uplink (UL) N2 message comprising an RRC state IE of ″Inactive″ ; a ″Location Report″ message comprising an ″Age of Location″ IE, the ″Age of Location″ IE indicating that an RNA-based RAN paging fails at the first network node; In some embodiments, a ″Location Reporting Failure Indication″ message comprising a cause of ″UE in RRC_INACTIVE state not reachable″ ; and a message comprising a ″User Location Information (ULI) ″ IE comprising an ″Age of Location″ IE, the ″Age of Location″ IE indicating that an RNA-based RAN paging fails at the first network node.

In some embodiments, the first RAN node is the last RAN node that serves the UE before the UE transitions to the RRC_INACTIVE state. In some embodiments, the first network node is an AMF.

According to a second aspect of the present disclosure, a first network node is provided. The first network node comprises a processor and a memory storing instructions which, when executed by the processor, cause the processor to perform the method of any of the first aspect.

According to a third aspect of the present disclosure, a first network node for paging a UE that is in an RRC_INACTIVE state with a first RAN node and in a CM-CONNECETED state with the first network node is provided. The first network node comprises: a receiving module configured to receive, from the first RAN node, a first message indicating a paging failure for the UE; and a triggering module configured to trigger one or more paging procedures for the UE to be performed at one or more second RAN nodes. In some embodiments, the first network node comprises one or more further modules configured to perform the method of any of the first aspect.

According to a fourth aspect of the present disclosure, a method at a first network node for paging a UE that is in an RRC_INACTIVE state with a first RAN node and in a CM-CONNECETED state with the first network node is provided. The method comprises: determining one or more third RAN nodes and/or one or more cells associated with the one or more third RAN nodes at least based on historical mobility data for the UE; and transmitting, to the first RAN node, a fifth message for indicating at least one of the one or more third RAN nodes and/or at least one of the one or more cells that can be used for paging the UE.

In some embodiments, the fifth message is a message comprising a ″Core Network Assistance Information for RRC INACTIVE″ IE. In some embodiments, the ″Core Network Assistance Information for RRC INACTIVE″ IE comprises an IE indicating at least one of: identifiers of one or more of the third RAN nodes; identifiers of one or more cells associated with one or more of the third RAN nodes; and identifiers of one or more TAs associated with one or more of the third RAN nodes. In some embodiments, when the IE indicates multiple third RAN nodes and/or multiple cells, the order of the multiple third RAN nodes and/or the multiple cells in the IE is determined by the first network node. In some embodiments, the step of determining the one or more third RAN nodes comprises: for each of other RAN nodes than the first RAN node, counting a number of handovers and/or mobility registration updates of the UE from the first RAN node to the corresponding one of the other RAN nodes; and determining one or more of the other RAN nodes that have the top numbers of handovers and/or mobility registration updates as the one or more third RAN nodes. In some embodiments, the step of determining the one or more third RAN nodes comprises: for each of cells associated with the first RAN node and for each of other cells than the cells associated with the first RAN node, counting a number of handovers or/and mobility registration updates of the UE from the corresponding cell associated with the first RAN node to the corresponding one of the other cells; and determining one or more RAN nodes that are associated with one or more of the other cells having the top numbers of handovers or/and mobility registration updates as the one or more third RAN nodes. In some embodiments, the step of determining the one or more third RAN nodes comprises: determining the one or more third RAN nodes by an AI model that is trained at least based on the historical mobility data for the UE.

In some embodiments, the AI model is trained with a cost function as follows:

TotalCost = Signal ^(1-λ)*Latency ^λ

wherein the ″TotalCost″ is the cost to be calculated, ″Signal″ indicates a signaling amount required for paging the UE, ″Latency″ indicates a paging latency, and ″λ″ indicates a regularization factor for balancing the paging latency and the signaling amount.

In some embodiments, the AI model is trained with a cost function as follows:

In some embodiments, the method further comprises: transmitting, to the first RAN node, a fourth message for triggering a RAN paging procedure for the UE. In some embodiments, the first RAN node is the last RAN node that serves the UE before the UE transitions to the RRC_INACTIVE state. In some embodiments, the first network node is an AMF.

According to a fifth aspect of the present disclosure, a first network node is provided. The first network node comprises a processor and a memory storing instructions which, when executed by the processor, cause the processor to perform the method of any of the fourth aspect.

According to a sixth aspect of the present disclosure, a first network node for paging a UE that is in an RRC_INACTIVE state with a first RAN node and in a CM-CONNECETED state with the first network node is provided. The first network node comprises: a determining module configured to determine one or more third RAN nodes and/or one or more cells associated with the one or more third RAN nodes at least based on historical mobility data for the UE; and a transmitting module configured to transmit, to the first RAN node, a fifth message for indicating at least one of the one or more third RAN nodes and/or at least one of the one or more cells that can be used for paging the UE. In some embodiments, the first network node comprises one or more further modules configured to perform the method of any of the fourth aspect.

According to a seventh aspect of the present disclosure, a method at a second RAN node for paging a UE that is in an RRC_INACTIVE state with a first RAN node and in a CM-CONNECETED state with a first network node is provided. The method comprises: receiving, from the first network node, a second message for triggering a paging procedure for the UE while the first RAN node is performing a RAN paging procedure for the UE; and performing a paging procedure for the UE in response to the received second message.

In some embodiments, when the second message indicates one or more other second RAN nodes that can be used for paging the UE, the method further comprises: updating an RNA configured for the UE with the indicated one or more other second RAN nodes. In some embodiments, the RNA is updated in an order as follows: the last visited RAN node; the indicated one or more other second RAN nodes; RAN nodes in a TA list for a specific Public Land Mobile Network (PLMN) ; and RAN nodes in all TA lists. In some embodiments, the second message is an NGAP paging message for paging the UE. In some embodiments, the NGAP paging message comprises an IE indicating at least one of: identifiers of one or more second RAN nodes; identifiers of one or more cells associated with one or more second RAN nodes; identifiers of one or more TA associated with one or more second RAN nodes; and an identifier of a UE context for the UE within the first RAN node; and the UE context for the UE. In some embodiments, when the IE indicates multiple second RAN nodes and/or multiple cells, the order of the multiple second RAN nodes and/or the multiple cells in the IE is determined by the first network node.

In some embodiments, the paging procedure is performed with a P-Radio Network Temporary Identifier (P-RNTI) and/or I-RNTI assigned for the UE. In some embodiments, when the paging procedure is performed with a P-RNTI assigned for the UE, the method further comprises: receiving, from the UE, a message for establishing a new RRC connection; and performing a UE context setup procedure for the UE with the first network node. In some embodiments, when the paging procedure is performed with an I-RNTI assigned for the UE, the method further comprises: receiving, from the UE, a message for resuming a released RRC connection that was established between the UE and the first RAN node; and retrieving a UE context for the UE from the first RAN node with the I-RNTI. In some embodiments, the method further comprises: stopping the paging procedure for the UE in response to the message received from the UE.In some embodiments, the second RAN node is not a RAN node associated with any cell or area indicated by an RNA configured at the first RAN node for the UE. In some embodiments, the first RAN node is the last RAN node that serves the UE before the UE transitions to the RRC_INACTIVE state. In some embodiments, the first network node is an AMF.

According to an eighth aspect of the present disclosure, a second RAN node is provided. The second RAN node comprises a processor and a memory storing instructions which, when executed by the processor, cause the processor to perform the method of any of the seventh aspect.

According to a ninth aspect of the present disclosure, a second RAN node for paging a UE that is in an RRC_INACTIVE state with a first RAN node and in a CM-CONNECETED state with a first network node is provided. The second RAN node comprises: a receiving module configured to receive, from the first network node, a second message for triggering a paging procedure for the UE while the first RAN node is performing a RAN paging procedure for the UE; and a performing module configured to perform a paging procedure for the UE in response to the received second message. In some embodiments, the second RAN node comprises one or more further modules configured to perform the method of any of the seventh aspect.

According to a tenth aspect of the present disclosure, a method at a first RAN node for paging a UE that is in an RRC_INACTIVE state with the first RAN node and in a CM-CONNECETED state with a first network node is provided. The method comprises: receiving, from the first network node, a fifth message for indicating one or more third RAN nodes and/or one or more cells associated with the one or more third RAN nodes that can be used for paging the UE, the one or more third RAN nodes and/or the one or more cells being determined at least based on historical mobility data for the UE.

In some embodiments, the fifth message is a message comprising a ″Core Network Assistance Information for RRC INACTIVE″ IE. In some embodiments, the ″Core Network Assistance Information for RRC INACTIVE″ IE comprises an IE indicating at least one of: identifiers of one or more of the third RAN nodes; identifiers of one or more cells associated with one or more of the third RAN nodes; and identifiers of one or more TA associated with one or more of the third RAN nodes. In some embodiments, when the IE indicates multiple third RAN nodes and/or multiple cells, the order of the multiple third RAN nodes and/or the multiple cells in the IE is determined by the first network node. In some embodiments, the method further comprises: receiving, from the first network node, a fourth message for triggering a RAN paging procedure for the UE. In some embodiments, the first RAN node is the last RAN node that serves the UE before the UE transitions to the RRC_INACTIVE state. In some embodiments, the first network node is an AMF.

According to an eleventh aspect of the present disclosure, a first RAN node is provided. The first RAN node comprises a processor and a memory storing instructions which, when executed by the processor, cause the processor to perform the method of any of the tenth aspect.

According to a twelfth aspect of the present disclosure, a first RAN node for paging a UE that is in an RRC_INACTIVE state with a first RAN node and in a CM-CONNECETED state with a first network node is provided. The first RAN node comprises: a receiving module configured to receive, from the first network node, a fifth message for indicating one or more third RAN nodes and/or one or more cells associated with the one or more third RAN nodes that can be used for paging the UE, the one or more third RAN nodes and/or the one or more cells being determined at least based on historical mobility data for the UE. In some embodiments, the first RAN node comprises one or more further modules configured to perform the method of any of the tenth aspect.

According to a thirteenth aspect of the present disclosure, a computer program comprising instructions is provided. The instructions, when executed by at least one processor, cause the at least one processor to carry out the method of any of the first aspect, the fourth aspect, the seventh aspect, and/or the tenth aspect.

According to a fourteenth aspect of the present disclosure, a carrier containing the computer program of the thirteenth aspect is provided. In some embodiments, the carrier is one of an electronic signal, optical signal, radio signal, or computer readable storage medium.

According to a fifteenth aspect of the present disclosure, a telecommunications system is provided. The telecommunications system comprises one or more UEs, a first network node of the second, third, fifth, and/or sixth aspects, and one or more second RAN nodes of the eighth and/or ninth aspects and/or one or more first RAN nodes of the eleventh and/or twelfth aspects.

Brief Description of the Drawings

The foregoing and other features of the present disclosure will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. Understanding that these drawings depict only several embodiments in accordance with the disclosure and therefore are not to be considered limiting of its scope, the disclosure will be described with additional specificity and detail through use of the accompanying drawings.

Fig. 1 is a block diagram illustrating an exemplary telecommunications network in which paging enhancement for RRC INACTIVE may be applicable according to an embodiment of the present disclosure.

Fig. 2 is an overview diagram illustrating an exemplary RRC state machine and state transitions with which a UE according to an embodiment of the present disclosure is operable.

Fig. 3 is an overview diagram illustrating an exemplary Connection Management (CM) state machine and state transitions with which a UE according to an embodiment of the present disclosure is operable.

Fig. 4 is a diagram illustrating an exemplary RAN paging procedure that is applicable in paging enhancement for RRC INACTIVE according to an embodiment of the present disclosure.

Fig. 5 is a diagram illustrating an exemplary Core Network (CN) paging procedure that is applicable in paging enhancement for RRC INACTIVE according to an embodiment of the present disclosure.

Fig. 6A through Fig. 6C are block diagrams illustrating an exemplary telecommunications network in which RAN paging and CN paging may be applicable according to some embodiments of the present disclosure.

Fig. 7 is a diagram illustrating an exemplary overall procedure for paging enhancement for RRC INACTIVE according to an embodiment of the present disclosure.

Fig. 8 is a diagram illustrating an exemplary procedure for paging enhancement for RRC INACTIVE according to an embodiment of the present disclosure.

Fig. 9 is a diagram illustrating another exemplary procedure for paging enhancement for RRC INACTIVE according to another embodiment of the present disclosure.

Fig. 10 is a diagram illustrating yet another exemplary procedure for paging enhancement for RRC INACTIVE according to yet another embodiment of the present disclosure.

Fig. 11 is a flow chart of an exemplary method at a first network node for paging a UE that is in an RRC_INACTIVE state with a first RAN node and in a CM-CONNECETED state with the first network node according to an embodiment of the present disclosure.

Fig. 12 is a flow chart of another exemplary method at a first network node for paging a UE that is in an RRC_INACTIVE state with a first RAN node and in a CM-CONNECETED state with the first network node according to another embodiment of the present disclosure.

Fig. 13 is a flow chart of an exemplary method at a second RAN node for paging a UE that is in an RRC_INACTIVE state with a first RAN node and in a CM-CONNECETED state with a first network node according to an embodiment of the present disclosure.

Fig. 14 is a flow chart of an exemplary method at a first RAN node for paging a UE that is in an RRC_INACTIVE state with a first RAN node and in a CM-CONNECETED state with a first network node according to an embodiment of the present disclosure.

Fig. 15 schematically shows an embodiment of an arrangement which may be used in a network node and/or a RAN node according to an embodiment of the present disclosure.

Fig. 16 is a block diagram of an exemplary first network node according to an embodiment of the present disclosure.

Fig. 17 is a block diagram of an exemplary first network node according to an embodiment of the present disclosure.

Fig. 18 is a block diagram of an exemplary second RAN node according to an embodiment of the present disclosure.

Fig. 19 is a block diagram of an exemplary first RAN node according to an embodiment of the present disclosure.

Detailed Description

Hereinafter, the present disclosure is described with reference to embodiments shown in the attached drawings. However, it is to be understood that those descriptions are just provided for illustrative purpose, rather than limiting the present disclosure. Further, in the following, descriptions of known structures and techniques are omitted so as not to unnecessarily obscure the concept of the present disclosure.

Those skilled in the art will appreciate that the term ″exemplary″ is used herein to mean ″illustrative, ″ or ″serving as an example, ″ and is not intended to imply that a particular embodiment is preferred over another or that a particular feature is essential. Likewise, the terms ″first″ and ″second, ″ and similar terms, are used simply to distinguish one particular instance of an item or feature from another, and do not indicate a particular order or arrangement, unless the context clearly indicates otherwise. Further, the term ″step, ″ as used herein, is meant to be synonymous with ″operation″ or ″action. ″ Any description herein of a sequence of steps does not imply that these operations must be carried out in a particular order, or even that these operations are carried out in any order at all, unless the context or the details of the described operation clearly indicates otherwise.

Conditional language used herein, such as ″can, ″ ″might, ″ ″may, ″ ″e.g., ″ and the like, unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements and/or states. Thus, such conditional language is not generally intended to imply that features, elements and/or states are in any way required for one or more embodiments or that one or more embodiments necessarily include logic for deciding, with or without author input or prompting, whether these features, elements and/or states are included or are to be performed in any particular embodiment. Also, the term ″or″ is used in its inclusive sense (and not in its exclusive sense) so that when used, for example, to connect a list of elements, the term ″or″ means one, some, or all of the elements in the list. Further, the term ″each, ″ as used herein, in addition to having its ordinary meaning, can mean any subset of a set of elements to which the term ″each″ is applied.

The term ″based on″ is to be read as ″based at least in part on. ″ The term ″one embodiment″ and ″an embodiment″ are to be read as ″at least one embodiment. ″ The term ″another embodiment″ is to be read as ″at least one other embodiment. ″ Other definitions, explicit and implicit, may be included below. In addition, language such as the phrase ″at least one of X, Y and Z, ″ unless specifically stated otherwise, is to be understood with the context as used in general to convey that an item, term, etc. may be either X, Y, or Z, or a combination thereof.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limitation of example embodiments. As used herein, the singular forms ″a″ ; ″an″ ; and ″the″ are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms ″comprises″ ; ″comprising″ ; ″has″ ; ″having″ ; ″includes″ and/or ″including″ ; when used herein, specify the presence of stated features, elements, and/or components etc., but do not preclude the presence or addition of one or more other features, elements, components and/or combinations thereof. It will be also understood that the terms ″connect (s) , ″ ″connecting″ ; ″connected″ ; etc. when used herein, just mean that there is an electrical or communicative connection between two elements and they can be connected either directly or indirectly, unless explicitly stated to the contrary.

Of course, the present disclosure may be carried out in other specific ways than those set forth herein without departing from the scope and essential characteristics of the disclosure. One or more of the specific processes discussed below may be carried out in any electronic device comprising one or more appropriately configured processing circuits, which may in some embodiments be embodied in one or more application-specific integrated circuits (ASICs) . In some embodiments, these processing circuits may comprise one or more microprocessors, microcontrollers, and/or digital signal processors programmed with appropriate software and/or firmware to carry out one or more of the operations described above, or variants thereof. In some embodiments, these processing circuits may comprise customized hardware to carry out one or more of the functions described above. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Although multiple embodiments of the present disclosure will be illustrated in the accompanying Drawings and described in the following Detailed Description, it should be understood that the disclosure is not limited to the disclosed embodiments, but instead is also capable of numerous rearrangements, modifications, and substitutions without departing from the present disclosure that as will be set forth and defined within the claims.

Further, please note that although the following description of some embodiments of the present disclosure is given in the context of 5G New Radio (NR) , the present disclosure is not limited thereto. In fact, as long as paging for UE in the RRC_INACTIVE state is involved, the inventive concept of the present disclosure may be applicable to any appropriate communication architecture, for example, to Global System for Mobile Communications (GSM) /General Packet Radio Service (GPRS) , Enhanced Data Rates for GSM Evolution (EDGE) , Code Division Multiple Access (CDMA) , Wideband CDMA (WCDMA) , Time Division -Synchronous CDMA (TD-SCDMA) , CDMA2000, Worldwide Interoperability for Microwave Access (WiMAX) , Wireless Fidelity (Wi-Fi) , Long Term Evolution (LTE) , 5G NR, etc. Therefore, one skilled in the arts could readily understand that the terms used herein may also refer to their equivalents in any other infrastructure. For example, the term ″User Equipment″ or ″UE″ used herein may refer to a mobile device, a mobile terminal, a mobile station, a user device, a user terminal, a wireless device, a wireless terminal, an IoT device, a vehicle, or any other equivalents. For another example, the term ″gNB″ used herein may refer to a base station, a base transceiver station, an access point, a hot spot, a NodeB (NB) , an evolved NodeB (eNB) , a network element, a network node, or any other equivalents. Further, the term ″node″ used herein may refer to a UE, a functional entity, a network entity, a network element, a network equipment, or any other equivalents.

Further, following 3GPP documents are incorporated herein by reference in their entireties:

- 3GPP TS 23.501 V16.8.0 (2021-03) , Technical Specification, 3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; System architecture for the 5G System (5GS) ; Stage 2 (Release 16) ;

- 3GPP TS 23.502 V16.8.0 (2021-03) , Technical Specification, 3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; Procedures for the 5G System (5GS) ; Stage 2 (Release 16) ;

- 3GPP TS 38.413 V16.5.0 (2021-04) , Technical Specification, 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; NG-RAN; NG Application Protocol (NGAP) (Release 16) ;

- 3GPP TS 38.423 V16.5.0 (2021-04) , Technical Specification, 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; NG-RAN; Xn application protocol (XnAP) (Release 16) ; and

- 3GPP TS 38.300 V16.5.0 (2021-03) , Technical Specification, 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; NR; NR and NG-RAN Overall Description; Stage 2 (Release 16) .

Fig. 1 is a block diagram illustrating an exemplary telecommunications network 10 in which paging enhancement for RRC Inactive may be applicable according to an embodiment of the present disclosure. Although the telecommunications network 10 is a network defined in the context of 5G NR, the present disclosure is not limited thereto.

As shown in Fig. 1, the network 10 may comprise one or more UEs 100 and a (radio) access network ( (R) AN) 105, which could be a base station, a Node B, an evolved NodeB (eNB) , a gNB, or an AN node which provides the UEs 100 with access to other parts of the network 10. Further, the network 10 may comprise its core network portion comprising (but not limited to) an AMF 110, a Session Management Function (SMF) 115, a Policy Control Function (PCF) 120, an Application Function (AF) 125, a Network Slice Selection Function (NSSF) 130, an AUthentication Server Function (AUSF) 135, a Unified Data Management (UDM) 140, a Network Exposure Function (NEF) 145, a Network Repository Function (NRF) 150, one or more User Plane Functions (UPFs) 155, and a Network Data Analytics Function (NWDAF) 165. As shown in Fig. 1, these entities may communicate with each other via the service-based interfaces, such as, Namf, Nsmf, Npcf, etc. and/or the reference points, such as, N1, N2, N3, N4, N6, N9, etc.

However, the present disclosure is not limited thereto. In some other embodiments, the network 10 may comprise additional network functions, less network functions, or some variants of the existing network functions shown in Fig. 1. For example, in a network with the 4G architecture, the entities which perform these functions (e.g., mobility management entity (MME) ) may be different from those shown in Fig. 1 (e.g., the AMF 110) . For another example, in a network with a mixed 4G/5G architecture, some of the entities may be same as those shown in Fig. 1, and others may be different. Further, the functions shown in Fig. 1 are not essential to the embodiments of the present disclosure. In other words, some of them may be missing from some embodiments of the present disclosure.

As shown in Fig. 1, the UPFs 155 are communicatively connected to the Data Network (DN) 160 which may be, or in turn communicatively connected to, the Internet, such that the UEs 100 may finally communicate its user plane data with other devices outside the network 10, for example, via the RAN 105 and the UPFs 155.

Here, some of the functions shown in Fig. 1, such as AMF 110, NWDAF 165, which may be involved in the embodiments of the present disclosure will be described in detail below.

Referring to Fig. 1, the AMF 110 may provide most of the functions that the MME provides in a 4G network as mentioned above. Below please find a brief list of some of its functions:

- Terminates the RAN Control Plane (CP) interface (N2) ;

- Non-access stratum (NAS) signaling;

- NAS ciphering and integrity protection;

- Mobility Management (MM) layer NAS termination;

- Session Management (SM) layer NAS forwarding;

- Authenticates UE;

- Manages the security context;

- Registration management;

- Connection management;

- Reachability management;

- Mobility Management; and

- Apply mobility related policies from PCF (e.g. mobility restrictions) .

Further, the NWDAF 165 may represent operator managed network analytics logical function. The NWDAF 165 may include the following functionality:

- Support data collection from Network Functions (NFs) and Application Functions (AFs) (e.g., the AMF 110, the AF 125) ;

- Support data collection from Operation, Administration, and Maintenance (OAM) ;

- NWDAF service registration and metadata exposure to NFs/AFs;

- Support analytics information provisioning to NFs, AF.

The details of the NWDAF functionality are defined in 3GPP TS 23.288.

Fig. 2 is an overview diagram illustrating an exemplary RRC state machine and state transitions with which a UE according to an embodiment of the present disclosure is operable. As shown in Fig. 2, a UE is either in the RRC_CONNECTED state or in the RRC_INACTIVE state when an RRC connection has been established. If this is not the case, i.e., no RRC connection is established, the UE is in the RRC_TDLE state. The RRC states can further be characterized as follows:

RRC IDLE:

- A UE specific discontinuous reception (DRX) may be configured by upper layers;

- UE controlled mobility based on network configuration;

- The UE may:

- monitor Short Messages transmitted with Paging-Radio Network Temporary Identifier (P-RNTI) over DCI;

- monitor a Paging channel for Core Network (CN) paging using 5G-Serving-Temporary Mobile Subscriber Identity (5G-S-TMSI) ;

- perform neighboring cell measurements and cell (re-) selection;

- acquire system information and can send system information (SI) request (if configured) .

- perform logging of available measurements together with location and time for logged measurement configured UEs.

RRC INACTIVE:

- A UE specific DRX may be configured by upper layers or by RRC layer;

- UE controlled mobility based on network configuration;

- The UE stores the UE Inactive Access Stratum (AS) context;

- A RAN-based notification area is configured by RRC layer;

The UE may:

- monitor Short Messages transmitted with P-RNTI over DCI;

- monitor a Paging channel for CN paging using 5G-S-TMSI and RAN paging using fullI-RNTI;

- perform neighboring cell measurements and cell (re-) selection;

- perform RAN-based notification area updates periodically and when moving outside the configured RAN-based notification area;

- acquire system information and can send SI request (if configured) .

RRC CONNECTED:

- The UE stores the AS context;

- Transfer of unicast data to/from UE;

- At lower layers, the UE may be configured with a UE specific DRX;

- For UEs supporting carrier aggregation (CA) , use of one or more secondary cells (SCells) , aggregated with the special cell (SpCell) , for increased bandwidth;

- For UEs supporting dual connectivity (DC) , use of one secondary cell group (SCG) , aggregated with the master cell group (MCG) , for increased bandwidth;

- Network controlled mobility within NR and to/from Evolved Universal Terrestrial Radio Access (E-UTRA) ;

- The UE may:

- monitor Short Messages transmitted with P-RNTI over DCI, if configured;

- monitor control channels associated with the shared data channel to determine if data is scheduled for it;

- provide channel quality and feedback information;

- perform neighboring cell measurements and measurement reporting;

- acquire system information;

- perform immediate minimization of drive tests (MDT) measurement together with available location reporting.

As mentioned above, in NR there is an additional RRC state ″RRC_INACTIVE″ between the RRC_CONNECTED and RRC_IDLE and a UE can optionally stay in this RRC_INACTIVE state without completely releasing the RRC connection when there is no traffic and quickly switch back to the RRC_CONNECTED state when necessary.

As shown in Fig. 2, an RRC release message with a suspendConfig IE will move the UE from the RRC_CONNECTED state to the RRC_INACTIVE state, and an RRC resume message will take it back to the RRC_CONNECTED state. Similarly, an RRC release message without a suspendConfig IE or an abnormal failure will put the UE in the RRC_IDLE state. However, the present disclosure is not limited thereto. In some other embodiments, different conditions for the state transitions may be applicable.

Fig. 3 is an overview diagram illustrating an exemplary CM state machine and state transitions with which a UE according to an embodiment of the present disclosure is operable.

Connection management comprises the functions of establishing and releasing a NAS signaling connection between a UE (e.g., the UE 100 shown in Fig. 1) and its serving AMF (e.g., the AMF 110 shown in Fig. 1) over N1. This NAS signaling connection may be used to enable NAS signaling exchange between the UE and the core network. It may comprise both the AN signaling connection between the UE and the AN (e.g., the RAN node 105 shown in Fig. 1) and the N2 connection for this UE between the AN and the AMF.

Two CM states are used to reflect the NAS signaling Connection of the UE with the AMF as shown in Fig. 3:

- CM-IDLE; and

- CM-CONNECTED.

The CM state for 3GPP access and Non-3GPP access are independent of each other, i.e. one can be in CM-IDLE state at the same time when the other is in CM-CONNECTED state.

A UE in CM-IDLE state has no NAS signaling connection established with the AMF over N1. The UE may perform cell selection/cell reselection according to TS 38.304 and PLMN selection according to TS 23.122.

There are no AN signaling connection, N2 connection and N3 connections for the UE in the CM-IDLE state.

If the UE is both in CM-IDLE state and in RM-REGISTERED state, the UE may, unless otherwise specified in TS 23.501 clause 5.3.4.1:

- Respond to paging by performing a Service Request procedure (see TS 23.502 clause 4.2.3.2) , unless the UE is in Mobile Initiated Connection Only (MICO) mode (see TS 23.501 clause 5.4.1.3) ;

- perform a Service Request procedure when the UE has uplink signaling or user data to be sent (see TS 23.502 clause 4.2.3.2) . Specific conditions apply for Local Area Data Network (LADN) , see TS 23.501 clause 5.6.5.

When the UE state in the AMF is RM-REGISTERED, UE information required for initiating communication with the UE may be stored. The AMF may be able to retrieve stored information required for initiating communication with the UE using the 5G-GUTI.

NOTE: In 5GS there is no need for paging using the SUPI/SUCI of the UE.

The UE provides 5G-S-TMSI as part of AN parameters during AN signaling connection establishment as specified in TS 38.331 and TS 36.331. The UE may enter CM-CONNECTED state whenever an AN signaling connection is established between the UE and the AN (entering RRC Connected state over 3GPP access, or at the establishment of the UE-N3IWF connectivity over untrusted non-3GPP access or the UE-TNGF connectivity over trusted non-3GPP access) , as shown in (a) of Fig. 3. The transmission of an Initial NAS message (Registration Request, Service Request or Deregistration Request) initiates the transition from CM-IDLE to CM-CONNECTED state.

When the UE states in the AMF are CM-IDLE and RM-REGISTERED, the AMF may:

- perform a network triggered Service Request procedure when it has signaling or mobile-terminated data to be sent to this UE, by sending a Paging Request to this UE (see TS 23.502 clause 4.2.3.3) , if a UE is not prevented from responding e.g. due to MICO mode or Mobility Restrictions.

The AMF may enter CM-CONNECTED state for the UE whenever an N2 connection is established for this UE between the AN and the AMF, as shown in (b) of Fig. 3. The reception of initial N2 message (e.g. N2 INITIAL UE MESSAGE) initiates the transition of AMF from CM-IDLE to CM-CONNECTED state.

The UE and the AMF may optimize the power efficiency and signaling efficiency of the UE when in CM-IDLE state e.g. by activating MICO mode (see TS 23.501 clause 5.4.1.3) .

A UE in CM-CONNECTED state has a NAS signaling connection with the AMF over N1. A NAS signaling connection uses an RRC Connection between the UE and the NG-RAN and an NGAP UE association between the AN and the AMF for 3GPP access. A UE can be in CM-CONNECTED state with an NGAP UE association that is not bound to any Transport Network Layer Association (TNLA) between the AN and the AMF. See TS 23.501 clause 5.21.1.2 for details on the state of NGAP UE association for a UE in CM-CONNECTED state. Upon completion of a NAS signaling procedure, the AMF may decide to release the NAS signaling connection with the UE.

In the CM-CONNECTED state, the UE may:

- enter CM-IDLE state whenever the AN signaling connection is released, as shown in (a) of Fig. 3, (entering RRC Idle state over 3GPP access or when the release of the UE-N3IWF connectivity over untrusted non-3GPP access or the UE-TNGF connectivity over trusted non-3GPP access is detected by the UE) , see TS 38.331 for 3GPP access.

When the UE CM state in the AMF is CM-CONNECTED, the AMF may:

- enter CM-IDLE state for the UE whenever the logical NGAP signaling connection and the N3 user plane connection for this UE are released upon completion of the AN Release procedure as specified in TS 23.502, as shown in (b) of Fig. 3.

The AMF may keep a UE CM state in the AMF in CM-CONNECTED state until the UE de-registers from the core network.

A UE in CM-CONNECTED state can be in RRC Inactive state, see TS 38.300. When the UE is in RRC Inactive state the following applies:

- UE reachability is managed by the RAN, with assistance information from core network;

- UE paging is managed by the RAN.

- UE monitors for paging with UE′s CN (5G S-TMSI) and RAN identifier.

RRC Inactive state applies to NG-RAN. UE support for RRC Inactive state is defined in TS 38.306 for NR and TS 36.306 for E-UTRA connected to 5GC. RRC Inactive is not supported by NB-IoT connected to 5GC.

The AMF may provide assistance information to the NG-RAN, to assist the NG-RAN′s decision whether the UE can be sent to RRC Inactive state except due to some exceptional cases such as:

- PLMN (or AMF set) does not support RRC Inactive;

- The UE needs to be kept in CM-CONNECTED State (e.g. for tracking) .

The ″RRC Inactive Assistance Information″ may include:

- UE specific DRX values;

- UE specific extended idle mode DRX values (cycle length and Paging Time Window length) ;

- The Registration Area provided to the UE;

- Periodic Registration Update timer;

- If the AMF has enabled MICO mode for the UE, an indication that the UE is in MICO mode;

- Information from the UE identifier, as defined in TS 38.304 for NR and TS 36.304 for E-UTRA connected to 5GC, that allows the RAN to calculate the UE′s RAN paging occasions.

The RRC Inactive Assistance Information mentioned above is provided by the AMF during N2 activation with the (new) serving NG-RAN node (i.e. during Registration, Service Request, Handover) to assist the NG RAN′s decision whether the UE can be sent to RRC Inactive state. If the AMF allocates a new Registration Area to the UE, the AMF should update the NG-RAN with the new Registration Area by sending the RRC Inactive Assistance Information accordingly.

As described with reference to Fig. 2, RRC Inactive state is part of RRC state machine, and it is up to the RAN to determine the conditions to enter RRC Inactive state. If any of the parameters included in the RRC Inactive Assistance Information changes as the result of NAS procedure, the AMF may update the RRC Inactive Assistance Information to the NG-RAN node.

When the UE is in CM-CONNECTED state, if the AMF has provided RRC Inactive assistance information, the RAN node may decide to move a UE to CM-CONNECTED with RRC Inactive state.

The state and ″endpoints″ (in the case of Dual Connectivity configuration) of the N2 and N3 reference points are not changed by the UE entering CM-CONNECTED with RRC Inactive state. A UE in RRC inactive state is aware of the RAN Notification area (RNA) and periodic RAN Notification Area Update timer.

The 5GC network is not aware of the UE transitions between CM-CONNECTED with RRC Connected and CM-CONNECTED with RRC Inactive state, unless the 5GC network is notified via N2 notification procedure in TS 23.502 clause 4.8.3.

At transition into CM-CONNECTED with RRC Inactive state, the NG-RAN configures the UE with a periodic RAN Notification Area Update timer taking into account the value of the Periodic Registration Update timer value indicated in the RRC Inactive Assistance Information, and uses a guard timer with a value longer than the RAN Notification Area Update timer value provided to the UE.

If the periodic RAN Notification Area Update guard timer expires in NG-RAN, the NG-RAN may initiate AN Release procedure as specified in TS 23.502, clause 4.2.6.

When the UE is in CM-CONNECTED with RRC Inactive state, the UE may perform PLMN selection procedures as defined in TS 23.122 and TS 24.501.

When the UE is CM-CONNECTED with RRC Inactive state, the UE may resume the RRC Connection due to:

- Uplink data pending;

- Mobile initiated NAS signaling procedure;

- As a response to RAN paging;

- Notifying the network that it has left the RAN Notification Area;

- Upon periodic RAN Notification Area Update timer expiration.

If the UE resumes the connection in a different NG-RAN node within the same PLMN or equivalent PLMN, the UE AS context is retrieved from the old NG-RAN node and a procedure is triggered towards the CN (see TS 23.502, clause 4.8.2) .

When UE is in CM-CONNECTED with RRC Inactive state, if RAN has received Location Reporting Control message from AMF with the Reporting Type indicating single stand-alone report, the RAN may perform RAN paging before reporting the location to AMF.

When UE is in CM-CONNECTED with RRC Inactive state, if RAN has received Location Reporting Control message from AMF with the Reporting Type indicating continuously reporting whenever the UE changes cell, the RAN may send a Location Report message to AMF including UE′s last known location with time stamp.

When UE is in CM-CONNECTED with RRC Inactive state, if RAN has received Location Reporting Control message from AMF with the Reporting Type of the Area Of Interest based reporting, the RAN may send a Location Report message to AMF including UE presence in the Area Of Interest (i.e. IN, OUT, or UNKNOWN) and the UE′s last known location with time stamp.

When the UE is in CM-CONNECTED with RRC Inactive state, if the old NG-RAN node that sends the UE into RRC Inactive state receives the downlink N2 signaling, it initiates the RAN paging as defined in TS 38.300. If the UE resumes the RRC Connection towards a different NG-RAN node, the old NG-RAN node includes the ″UE Context Transfer″ indication into a response container to the NF (e.g. AMF or SMF) that generates such N2 downlink signaling. Then the NF may reattempt the same procedure when the path switch from the old NG-RAN node to the new NG-RAN node is complete.

Fig. 4 is a diagram illustrating an exemplary RAN paging procedure that is applicable in paging enhancement for RRC INACTIVE according to an embodiment of the present disclosure. The purpose of the RAN Paging procedure is to enable an NG-RAN node to request paging of a UE in another NG-RAN node. The procedure may use non UE-associated signaling.

As shown in Fig. 4, the RAN Paging procedure may be triggered by an NG-RAN node ₁ 105-1 by sending a RAN PAGING message to an NG-RAN node ₂ 105-2 at step S410, in which necessary information e.g. UE RAN Paging Identity may be provided.

For example, the NG-RAN node ₁ 105-1 may receive downlink user data or signaling for the UE 100 which is in RRC_INACTIVE state. The NG-RAN node ₁ 105-1 may then send the paging messages to every cell or NG-RAN nodes in the RNA for the UE 100. The Inactive Radio Network Temporary Identifier (I-RNTI) may be indicated in the paging messages. If the UE 100 does not respond to the paging messages, the NG-NG-RAN nodes may repeat the paging. When the UE 100 receives the paging message in one of the RNA cells, it may send the RRCResumeRequest message to the corresponding NG-RAN node, and the corresponding NG-RAN node may proceed with the RRC Resume procedure.

If the Paging Priority IE is included in the RAN PAGING message, the NG-RAN node ₂ 105-2 may use it to prioritize paging. If the Assistance Data for RAN Paging IE is included in the RAN PAGING message, the NG-RAN node ₂ 105-2 may use it according to TS 38.300. If the UE Radio Capability for Paging IE is included in the RAN PAGING message, the NG-RAN node ₂ 105-2 may use it to apply specific paging schemes. If the Extended UE Identity Index Value IE is included in the RAN PAGING message, the NG-RAN node ₂ 105-2 may use it according to TS 36.304. When available, NG-RAN node ₁ 105-1 may include the Extended UE Identity Index Value IE in the RAN PAGING message towards an ng-eNB (e.g. NG-RAN node ₂ 105-2) .

Fig. 5 is a diagram illustrating an exemplary CN paging procedure that is applicable in paging enhancement for RRC INACTIVE according to an embodiment of the present disclosure.

The purpose of the Paging procedure is to enable an AMF (e.g., the AMF 110 shown in Fig. 1) to page a UE (e.g., the UE 100 shown in Fig. 1) in a specific NG-RAN node (e.g., the RAN node 105 shown in Fig. 1) .

As shown in Fig. 5, an AMF 110 may initiate a Paging procedure by sending a PAGING message to an NG-RAN node 105 at step S510.

At the reception of the PAGING message, the NG-RAN node 105 may perform paging of the UE 100 in cells which belong to tracking areas as indicated in the TAI List for Paging IE.

In some embodiments, the paging procedure triggered by CN may be performed with one or more widths. For example, at least one of the following widths may be adopted in a paging procedure triggered by CN:

Narrowest: This is the narrowest paging width. With this paging width, the AMF may page the NG-RAN node that was last visited by the UE. This can reduce the number of paging messages sent to the NG-RAN node.

Narrow: This is the second narrowest paging width. With this paging width, the AMF may page the list of NG-RAN nodes that were most recently visited by the UE. This can reduce the number of sent paging messages, as messages are sent to a small number of NG-RAN nodes. The number of NG-RAN nodes that are added into the latest visited NG-RAN node list is configurable.

Medium: With the medium paging width, the AMF may page the NG-RAN nodes in the tracking area last visited by the UE.

Wide: This is the largest, or widest paging width. With this paging width, the AMF may page all NG-RAN nodes in all tracking areas in the TAI list.

Typically, a wide paging profile may be used if it is necessary to find the UE quickly. However, it should be noted that in this case, paging messages are sent to all NG-RAN nodes in the TAI list, resulting a significant amount of signaling overhead. Further, the present disclosure is not limited to the widths listed above, and in some other embodiments, a different number of different widths may be used.

If the Paging DRX IE is included in the PAGING message, the NG-RAN node 105 may use it according to TS 38.304 and TS 36.304. For each cell that belongs to any of the tracking areas indicated in the TAI List for Paging IE, the NG-RAN node 105 may generate one page on the radio interface. If the Paging Priority IE is included in the PAGING message, the NG-RAN node 105 may use it according to TS 23.501. If the UE Radio Capability for Paging IE is included in the PAGING message, the NG-RAN node 105 may use it to apply specific paging schemes. If the Assistance Data for Recommended Cells IE is included in the Assistance Data for Paging IE, it may be used, together with the Paging Attempt Information IE if also present, according to TS 38.300. If the Next Paging Area Scope IE is included in the Paging Attempt Information IE, it may be used for paging the UE according to TS 38.300. If the Paging Origin IE is included in the PAGING message, the NG-RAN node 105 may transfer it to the UE 100 according to TS 38.331 and TS 36.331.

If the NB-IoT Paging eDRX Information IE is included in the PAGING message, the NG-RAN node 105 may, if supported, use it according to TS 36.304. If the NB-IoT Paging Time Window IE is included in the NB-IoT Paging eDRX Information IE, the NG-RAN node 105 may take this information into account to determine the UE′s paging occasion according to TS 36.304. The NG-RAN node 105 may take into account the reception time of the PAGING message on the NG interface to determine when to page the UE.

If the NB-IoT Paging DRX IE is included in the PAGING message, the NG-RAN node 105 may use it according to TS 36.304. If the Enhanced Coverage Restriction IE is included in the PAGING message, the NG-RAN node 105 may, if supported, use it as defined in TS 23.501. If the Paging Assistance Data for CE Capable UE IE is included in the Assistance Data for Paging IE in the PAGING message, it may be used for paging the indicated CE capable UE, according to TS 23.502. If the WUS Assistance Information IE is included in the PAGING message, the NG-RAN node 105 may, if supported, use it to determine the WUS group for the UE, as specified in TS 36.304.

If the Paging eDRX Information IE is included in the PAGING message, the NG-RAN node 105 may, if supported, use it according to TS 36.304. If the Paging Time Window IE is included in the Paging eDRX Information IE, the NG-RAN node 105 may take this information into account to determine the UE′s paging occasion according to TS 36.304. The NG-RAN node 105 may take into account the reception time of the PAGING message on the NGAP interface to determine when to page the UE.

If the CE-mode-B Restricted IE is included in the PAGING message and the Enhanced Coverage Restriction IE is not set to ″restricted″ , the NG-RAN node 105 may, if supported, use it as defined in TS 23.501. If the NPN Paging Assistance Information IE is included in the Assistance Data for Paging IE, the NG-RAN node 105 may take it into account when determining the cells where paging will be performed.

As mentioned above, 3GPP Rel. 16 introduces the RRC Inactive state, and some impacts of the RRC Inactive state on packet core and RAN comprise but not limited to:

- PLMN selection;

- Broadcast of system information;

- Cell re-selection mobility;

- Paging is initiated by NG-RAN (RAN paging) ;

- RAN-based notification area (RNA) is managed by NG-RAN;

- 5GC -NG-RAN connection (both C/U-planes) is established for UE;

- The UE Inactive AS context is stored in NG-RAN and the UE;

- NG-RAN knows the RNA which the UE belongs to.

For NR connected to 5GC, following UE identities may be used at NG-RAN level:

- I-RNTI: used to identify the UE context in RRC_INACTIVE; and

- P-RNTI: identification of Paging and System Information change notification in the downlink.

As also mentioned above, RRC_INACTIVE is a state where a UE may remain in CM-CONNECTED and can move within an area configured by NG-RAN (or the RNA) without notifying NG-RAN. In RRC_INACTIVE, the last serving gNB may keep the UE context and the UE-associated NG connection with the serving AMF and UPF.

If the last serving gNB receives DL data from the UPF or DL UE-associated signaling from the AMF (except the UE Context Release Command message) while the UE is in RRC_INACTIVE, it may page in the cells corresponding to the RNA and may send XnAP RAN Paging to neighbor gNB (s) if the RNA includes cells of the neighbor gNB(s) .

Upon RAN paging failure, the gNB may behave according to TS 23.501.

Further, as also mentioned above, the AMF may provide to the NG-RAN node the Core Network Assistance Information (CNAI) to assist the NG-RAN node′s decision whether the UE can be transitioned to RRC_INACTIVE, and to assist UE configuration and paging in RRC_INACTIVE. The CNAI may include the registration area configured for the UE, the Periodic Registration Update timer, and the UE Identity Index value. Further, it may also include the UE specific DRX, an indication if the UE is configured with Mobile Initiated Connection Only (MICO) mode by the AMF, the Expected UE Behaviour, and the UE Radio Capability for Paging. The UE registration area may be taken into account by the NG-RAN node when configuring the RNA. The UE specific DRX and UE Identity Index value may be used by the NG-RAN node for RAN paging. The Periodic Registration Update timer is taken into account by the NG-RAN node to configure Periodic RNA Update timer. The NG-RAN node may take into account the Expected UE Behaviour to assist the UE RRC state transition decision. The NG-RAN node may use the UE Radio Capability for Paging during RAN Paging.

In case the UE is not reachable at the last serving gNB, the gNB may fail any AMF initiated UE-associated class 1 procedure which allows the signaling of unsuccessful operation in the respective response message. It may trigger the NAS Non Delivery Indication procedure to report the non-delivery of any non PDU Session related NAS PDU received from the AMF as specified in TS 38.413.

If the UE accesses a gNB other than the last serving gNB and the receiving gNB does not find a valid UE Context, the receiving gNB can perform establishment of a new RRC connection instead of resumption of the previous RRC connection. UE context retrieval will also fail and hence a new RRC connection needs to be established if the serving AMF changes.

A UE in the RRC_INACTIVE state is required to initiate RNA update procedure when it moves out of the configured RNA. When receiving RNA update request from the UE, the receiving gNB may trigger the XnAP Retrieve UE Context procedure to get the UE context from the last serving gNB and may decide to move the UE back into RRC_INACTIVE state, move the UE into RRC_CONNECTED state, or move the UE into RRC_IDLE.

During the configuration of the RNA, the following information from the CNAI and Mobility Restriction List (MRL) may be considered:

- The serving cell where the UE is connected.

- The neighbor cells that have cell relation with the serving cell, e.g., cells and gNBs from local XnAP relationship.

- Cells with TAC and active PLMNs that match TAI list field advertised in CNAI.

- Cells with TACs and active PLMNs that are allowed by the MRL.

However, there are several issues with the existing paging procedures for UEs in the RRC Inactive state.

Issue 1: Paging Area problem for UE in RRC inactive

As mentioned earlier, a gNB may page UEs in RRC inactive, and both of the gNB and the UE may be configured with a corresponding RNA based on CNAI from AMF, which is used for assisting UE configuration and paging in RRC_INACTIVE. As mentioned earlier, the CNAI may include the registration area of the UE which is comprised of one or more TAs. As shown in Fig. 6A, a UE #1 100-1 and a UE #2 100-2 (both in RRC Inactive) may move out of their serving cell 105-1 and RNA cells 105-2 and no RNA update is triggered due to some uplink issues or other issues. If MT traffic is triggered, for example, when DL data destined to the UE #1 100-1 arrives at the gNB 105-1, the gNB 105-1 has to page the UE #1 100-1 in the RNA cells. In such a case, the RAN paging procedure will fail and the gNB 105-1 may trigger the serving AMF to transition from CM_CONNECTED to CM_IDLE for the UE while the UE stays in CM_CONNECTED, which may result in further problems.

Issue 2: Inappropriate RNA configuration

A legacy RNA cell configuration only includes a serving cell, MRL cells, and TAs. According to TS 38.413 Clause 9.3.1.8, Mobility Restriction List (MRL) does not provide gNB and Cell information from AMF to NG-RAN. The gNB has to configure the RNA according to local mobility relationships. Therefore, it is highly possible that gNBs in RNA are no longer good candidates for paging the UE. Let alone UE has additional RRC connection issues (e.g., unstable uplink coverage) to its serving gNB in RNA. For example, as shown in Fig. 6B, the UE 100 may not communicate with the gNB #2 105-2 due to uplink issues (e.g., poor UL link quality) , and therefore even if the UE 100 receives a paging message from the gNB#2 105-2, it cannot transmit a response to the gNB #2 105-2 with a transmission power that is strong enough to be detected by the gNB #2 105-2.

Issue 3: Deployment limitation, e.g., No available XnAP between S-gNB and T-gNB

If multiple cells belong to different areas (e.g., TAs) or there are small cells (e.g., femto-cells) , and therefore there is no XnAP signaling between S-gNB and T-gNB, or if the S-gNB and T-gNB do not have unified software release for RAN Paging Message transfers, then RAN paging is not possible. For example, as also shown in Fig. 6B, the gNB #3 105-3 cannot communicate with the gNB #2 105-2 and the gNB #1 105-1, and therefore no RAN paging can be performed in the cells served by the gNB #3 105-3 even if the UE 100 is camping in the gNB #3 105-3.

In such a scenario, RAN paging cannot be performed for UEs in RRC_INACTIVE states. Furthermore, these issues may impact RRC Resume KPI and UE mobility KPI.

Issue 4: Paging signaling and latency problem for UE in RRC Inactive

A gNB may send the paging message to all the cells indicated in the RNA. The gNB may attempt the paging for maximum times. If the paging procedure fails, the gNB may initiate UE CONTEXT RELEASE with 5GC. As shown in Fig. 6C, during the RAN paging procedure for the UE #2 100-2 that is in the RRC Inactive state, the waste of radio paging signals may be:

N _{number of cells in RNA} × M _{repeat times in RNA} + K _{number of cells in TA}× L _{number of TAs in RA} -1

As also shown in Fig. 6C, during the RAN paging procedure for the UE #1 100-1 that is in the RRC Inactive state, the waste of radio paging signals may be:

N _{number of cells in RNA} × M _{repeat times in RNA} -1

Neither I-RNTI allocation nor paging opportunities will be wasted in RNA cells, while Packet Core has nothing to handle this since DL data (e.g., NAS or DL UP traffic are buffered in gNB) . The Packet Core could not improve the situation since the Packet Core is only aware of that the UE (e.g., the UE #1 100-1 and the UE #2 100-2) is in the CM_CONNECTED state (with the RRC Inactive) , and therefore no additional AMF paging will be triggered.

Therefore, some embodiments of the present disclosure may introduce an intelligent paging method for RRC inactive UE when the RAN RNA paging area is inappropriate or not feasible.

In some embodiments, via AMF AI based adaptive paging feature, an AMF may provide the Paging List of RRC Inactive (or PLRI for short) including latest visited gNB (cell) list and/or fitting probabilistic gNB (cell) list.

In some embodiments, RAN nodes could page UEs in RNA that is determined based on PLRI that is provided by AMF, instead of Local Mobility Relationship Table. In some embodiments, the PLRI may be combined with the local mobility relationship table.

In some embodiments, considering that PLRI is an additional IE on NGAP, a RAN node may not be fully compliant or understand the IE. In such a case, AMF can also initiate paging UE with PLRI locally without notify gNB. In addition, an AMF may page a UE in the RRC Inactive state immediately when RAN Paging failure in RNA is detected by the AMF. In such a case, gNB′s RAN paging could work simultaneously with AMF paging for RRC Inactive UE.

Therefore, some embodiments may introduce an intelligent and flexible paging method for RRC inactive UE, which may comprise at least one of (but not limited to) :

- gNB RNA paging for RRC inactive UE;

- gNB RNA paging failure indication to AMF;

- AI based paging list training and PLRI list generation on AMF (or collocated NWDAF) ;

- AMF immediately paging in PLRI for RRC inactive UE; and

- AMF N2 message including PLRI to gNB, for gNB RNA paging list update.

With the components and steps above, AMF could improve the RAN/CN paging for RRC inactive, for example, to handle paging failures due to mobility and inappropriate configuration or other issues mentioned above.

With some embodiments of the present disclosure, RAN paging coverage may be extended. AMF could page the UE which are out of RNA area or mobility area without available XnAP signaling (e.g., indoor femto-cell or small cell) for RNA paging. These scenarios may be covered by some embodiments of the present disclosure.

Further, with some embodiments of the present disclosure, KPIs can be improved. For example, via AMF and NWDAF AI capability of paging, AMF could provide a more accurate paging area than the RNA based on legacy MRL or TA. RRC resumption success ratio can be improved, while RRC radio link failure ratio, UE mobility failure ratio can be reduced. Especially, in an area where RNA paging is unavailable, the MT call drop ratio can be reduced.

Further, MT service latency can be reduced. After AMF successfully pages a UE in the RRC Inactive state with PLRI, latency of MT DL NAS and DL UP-PDU buffered can be reduced.

Fig. 7 is a diagram illustrating an exemplary overall procedure for paging enhancement for RRC INACTIVE according to an embodiment of the present disclosure. In the embodiment shown in Fig. 7, some prerequisites are needed:

- As shown at step S705, the AMF 100 and/or (collocated) NWDAF 165 may apply the AI based Paging modeling and training from mobility event and generates gNB list and TA list to balance the signaling and latency based on paging success ratio and/or confidence selection.

- As also shown at step S705, AMF 110 may generate PLRI locally.

- As shown at step S710 and S715, AMF 110 may negotiate RRC Inactive configuration with gNB #1 105-1 in CNAI:

- RRC Inactive Transition Report Request may be set to ″Subsequent state transition report″ , and PLRI may be described later.

In some embodiments, the step S715 may be a part of the step S710, and in some other embodiments, the step S715 may be separately performed from the step S710 as shown in Fig. 7.

- As shown at steps S720 and S725, UE 100 may enter RRC Inactive between gNB 105-1 and UE 100, and gNB 105-1 may notify AMF 110 that: RRC State = Inactive, for example, in legacy N2 messages.

The procedure may begin at step S730 or S735 depending on whether a paging procedure is triggered by gNB 105-1 or AMF 110.

At step S730, UE 100 is in RRC Inactive and MT traffic initiated or Location Report may be triggered:

- Location Report: Location Reporting may be initiated by at least one of:

- PRA (Presence Reporting Area) ;

- NPLI (Network Provide Location Information) ;

- MT-LR (Mobile Terminated Location Request) ; and

- AMF Event Exposure;

- or DL NAS Messages (e.g., from AMF and/or SMF) or DL UP PDU (e.g., from UPF) .

At step S735, the gNB#1 may try to page the UE 100 in its serving cell. In some embodiments, this paging is the initial paging of the UE, and therefore a very narrow paging area (e.g., the last visited/serving gNB #1 105-1) may be used.

At step S740, if the paging procedure at step S735 fails, the AMF 110 may receive a message indicating the UE RNA paging failure on the gNB 105-1, for example, via Location Report. Further, rest of the paging procedures, for example, one or more RAN paging procedures with wider areas may continue as indicated by the step S745.

Meanwhile, at step S745, the AMF 110 may initiate an adaptive paging procedure towards cells or gNBs in the Paging List for RRC Inactive, for example, that generated at step S705 or a part thereof.

At step 750a, which is a part of the step S750, the AMF 110 may initiate the adaptive paging procedure for RRC Inactive (e.g., towards the gNB #3 105-3 that has no XnAP signaling available with other gNBs) , while the gNB #1 105-1 and the gNB 105-2 may continue their RNA paging procedure. In such a case, the two procedures may be performed independently and simultaneously.

In some embodiments, the AMF Adaptive Paging Area may be different from RNA area. For example, when the AMF 110 initiates its adaptive paging procedure with the cells in PLRI, the paging procedure may not be initiated towards the cells in the PLRI that are also cells in the RNA determined by the gNB #105-1. In such a case, repeated paging procedures in a same cell may be omitted.

In some embodiments, the AMF 110 may use P_RNTI for RRC Inactive UE while RAN may use legacy I_RNTI in RNA paging for specific RRC Inactive UE. In some embodiments, T-gNB (e.g., the gNB #3 105-3) for AMF Paging shall have no available specific UE RRC Context, and therefore T-gNB may consider this specific paging as a paging for UE in CM_IDLE, and perform a paging procedure for new RRC connection purpose. In some embodiments, if T-gNB has available specific UE RRC Context (XnAP and RRC inactive RNA Paging effective) on this gNB, T-gNB may follow a legacy RNA paging procedure.

There are some key points to be noted:

- AMF may get the RRC inactive states and UE RNA paging failure as follows but not limited to:

- RRC Inactive from RRC INACTIVE TRANSITION REPORT (or UL N2 messages) ;

- RNA Paging Failure from Location Report including Age of Location (UE last known time stamps gNB) ;

- RNA Paging Failure from Location Report Failure Indication (Cause = UE in RRC_INACTIVE state not reachable) ;

- From RAN information: Any ULI IE (in Table1) including Age of Location when implicit indicates to AMF that UE is last known on RAN, which means RAN RNA Paging failure at serving cell;

- T-gNB processing in step S750.

Without the embodiments of the present disclosure, AMF shall not page any UE (in RRC inactive) for new RRC connection request purpose during this procedure. With some embodiments of the present disclosure, T-gNBs may receive new PAGING Messages from AMF for specific RRC Inactive UE. The T-gNBs which receive Paging may be determined by AMF.

- I-RNTI reallocation.

Fig. 8 is a diagram illustrating an exemplary procedure for paging enhancement for RRC INACTIVE according to an embodiment of the present disclosure. Similar to Fig. 7, before the method begins, the AMF 110 may obtain, generate, or otherwise determine a gNB List, for example, from AI-based local training. Further, the AMF 110 may match the serving cell and (optionally) PScell for RRC Inactive UE with the gNB list. The AMF 110 may then rank the matched node pair level {GNBID, NCGI} , for example, according to UE 100 and/or other UE′s mobility probability. The AMF 110 may then select one or more gNBs with the highest probability: {AMFID, NCGI/NGAP ID} pair for the specific RRC Inactive UE (UE NGAP ID) . In some embodiments, a short list of PLRI may be available with the format, for example, { {AMF1, GNBID1, NCGI2} ; {AMF1, GNBID2, NCGI3} } .

Further, the steps S805 through S825 may be similar to steps S710, S720, S730 through S740, respectively, and therefore a detailed description thereof is omitted for simplicity.

At step S830, the AMF 110 may initiate an adaptive paging procedure for an RRC Inactive UE, while RAN (e.g., the gNB #1 105-1 and gNB #2 105-2) may continue RAN paging at steps S835 and S840. The two procedures may be performed independently and simultaneously. At step S830a, the AMF may trigger a paging procedure towards the gNB #3 105-3.

As shown in Fig. 8, T-gNB (e.g., the gNB #3 105-3) for AMF paging shall have no available specific UE RRC Context for the UE 100, and T-gNB may consider this specific paging as UE 100 in CM_IDLE, and perform a new paging procedure for new RRC connection purpose, at step S845.

As shown in Fig. 8, the results of the adaptive paging procedure may comprise at least one of:

- UE Paging successful in gNB #3 105-3;

- a new RRC connection and new UE context may be set up at gNB #3 105-3 at step S850;

- the AMF 110 may initiate UE Context Release procedure in old cell served by gNB #1 105-1 at step S855; and

- the gNB #1 105-1 and gNB #2 105-2 may stop the rest part of the RAN paging opportunities.

Please note that, optionally, if AMF and T-gNB has additional specific N2 messages, PLRI may be transferred therebetween with the additional N2 messages. However, the present disclosure is not limited thereto. In some other embodiments, PLRI may be transferred with some existing N2 messages. Further, in some embodiments, RAN may update local RNA area in the below order:

- Last visit gNB;

- RNA-level gNB lists from PLRI;

- TA-level gNB lists for specific PLMN; and

- gNB lists/TA lists.

With the procedure shown in Fig. 8, the RAN paging signaling may be reduced. If gNB #3 105-3 triggers UE CONTEXT RELEASE after S845, the XnAP-based RAN Paging messages may be saved. Further, KPIs, such as RRC resumption ratio, RNA Paging Failure Ratio, may be improved. Furthermore, coverage for gNB #1 105-1′s RAN paging may be extended without TA/RA level RAN Paging and gNB #1 could add the further RNA gNBs via local configuration.

Further, the reduced paging signals over gNB may be:

N _{number of cells in RNA} × M _{repeat times in RNA} -J _{number of cells in PLRI} × L _{repeat times in AMF}

Further, RAN paging an mobility UE1 (In RRC inactive) , the reduced of XnAP shall be:

N _{number of cells with XnAP in RNA}

× (M _{max repeat times in RNA}

-K _{RNA repeats before AMF Adaptive Paging for RRC Inactive})

Fig. 9 is a diagram illustrating another exemplary procedure for paging enhancement for RRC INACTIVE according to another embodiment of the present disclosure. In the embodiment shown in Fig. 9, the AMF 110 may transmit PLRI to RAN for enhancing RAN paging. Compared with the embodiment shown in Fig. 8, the differences may comprise at least one of (but not limited to) :

- Selection for additional RNA Paging Cells are determined by AMF.

- Selected gNB #3 105-3 should have RRC Inactive enabled.

- If without XnAP, gNB #3 105-3 may page the UE 100 with I_RNTI (for example, with new N2 messages for the AMF 110 to fetch RNA paging profile/UE context from gNB #1 105-1 and/or to transfer the same to gNB #3 105-3) . If XnAP signaling is available between gNB #3 105-3 and gNB #1 105-1, then the UE context for the UE 100 may be retrieved by the gNB #3 105-3 directly.

- gNB #3 105-3 could page UE 100 with I_RNTI that is allocated by gNB #1 105-1.

Further, the steps S905 through S925 may be similar to steps S805 through S825, respectively, and therefore a detailed description thereof is omitted for simplicity.

At step S930 and S930a, the AMF 110 may initiate an adaptive paging procedure towards the gNB #3 105-3, in a similar manner to S830 and S830a, with the difference that a part or whole of the PLRI may be provided to the gNB #3 105-3. Further, the I-RNTI and/or UE context assigned/created by the gNB #1 105-1 for the UE 100 may be provided by the AMF 110 to the gNB #3 105-3 as mentioned above.

At step S933, the gNB #3 105-3 may update its RNA paging cells with the received PLRI, and determine the paging width for the UE 100. For example, the gNB #3 105-3 may determine that for the initial paging procedure for the UE, it may transmit a paging message within its own cells, and for the subsequent paging procedures, a wider paging area may be involved.

At step S945, the gNB #3 105-3 may page the UE 100 with its received I-RNTI, and at step S950 the UE 100 may respond with a request for resuming its RRC connection with the gNB #3 105-3. In such a case, the gNB #3 105-3 may retrieve the UE context for the UE 100 from the gNB #1 105-1 at step S955 if no UE context for the UE 100 is received previously, for example, at step S930a.

Fig. 10 is a diagram illustrating yet another exemplary procedure for paging enhancement for RRC INACTIVE according to yet another embodiment of the present disclosure. Compared with the embodiment shown in Fig. 9, the gNB #3 105-3 may page the UE 100 with its P_RNTI (regardless of XnAP) , and the gNB #3 105-3 may page the UE 100 with P_RNTI allocated by gNB #3 105-3.

Since the steps S1005 through S1050 are similar to the steps S905 through S950 except that the P_RNTI is used instead of I-RNTI for AMF 110′s adaptive paging, a detailed description thereof is omitted for simplicity.

Once the gNB #3 105-3 and the UE 100 resume the RRC connection therebetween with P-RNTI at step S1050, a new UE context may be set up at the gNB #3 105-3 for the UE 100 at step S1055, and the old UE context at the gNB #1 105-1 may be released at step S1060.

Further, with some embodiments of the present disclosure, KPIs can be improved. For example, via AMF and NWDAF AI capability of paging, AMF could provide a more accurate paging area (PLRI) than the RNA based on legacy MRL or TA. RRC resumption success ratio can be improved, while RRC radio link failure ratio, UE mobility failure ratio can be reduced. Especially, in an area where RNA paging is unavailable, the MT call drop ratio can be reduced.

When RRC_INACTIVE is enabled, it is expected that existing methods might no longer be suitable for constructing PLRI list. Previously, the ML paging constructs the gNB list according to probability of UE movements. However, because only current location (GnodeB ID, CellID and etc. ) and last location information are considered regardless of whether UE is in CM-IDLE or CM-CONNECTED, the area covered by the gNB list is normally too big for PLRI paging. From the perspective of AMF, when UE is in RRC_INACTIVE state, the possible area to which the UE could move is actually restricted to RNA or gNodeB geographically close to serving gNodeB. Then, the suitable PLRI list of one gNB could be learned on AMF/NWDAF as follows:

- For one gNB/Cell, if involved in Xn/N2 Handover procedure, the target gNB/Cell may be added to PLRI candidate list of this gNB/Cell.

- After some measure interval, for each gNB/Cell, a table may be obtained, for example:

SrcGnb	TargetGnb	Type	Count
gnb1	gnb2	Xn	60
gnb1	gnb3	Xn	20
gnb1	gnb4	Xn	20
gnb1	gnb5	Xn	1 0
gnb1	gnb6	N2	80
gnb1	gnb7	N2		1 0
gnb1	gnb8	N2		1 0

It means how many handover procedures happened. For example, the first row of the table means there are 60 Xn handover happens from gnb1 to gnb2.

When UE establish its new N2 connection on gnb1, in InitialContextSetup response, the AMF may include [gnb6, gnb2, gnb4, gnb3] in PLRI list. Gnb1 could utilize the PLRI list to do RAN paging. As the list contains historical information of UE movement originating from gnb1, it could improve RAN paging success rate.

If 1 ^st RAN paging for gnb1 fails for RRC_INACTIVE UE, then AMF may use [gnb5, gnb7, gnb8] to page UE. AMF may intentionally skipped gnbs in PLRI list since this list will be paged by RAN. In this way, AMF and RAN may simultaneously page UE, which could increase paging success rate.

Further, when compared with previous AI-based training method, the following tuning methods are proposed:

ML paging model may be trained with a cost function as follows:

TotalCost = Signal ^(1-λ) *Latency ^λ

In some embodiments, the AI model may be trained with a cost function as follows:

Intuitively understanding of auto tuning of ML paging model with both Signal and Latency. An log algorithm may be applied to the cost function. As clearly shown in the equations, two features, signal and latency (both are discrete value) are considered. The cost of each profile and confidence could be present as one point in 2D space. For the parameter λ, [0, 1] , assuming the min cost point is at (opt_sig, opt_lat) , this parameter may control the slope of the boundary line across the min cost point. Then larger value of λ means more prioritization in latency. Then, the auto tuning is to find the min distance to the boundary.

In some embodiments, normalization of signaling and latency in cost function may be performed. Scaling can be done to make range of signaling and latency to [0, 1] , for example, min-max normalization.

wherein ″Number of RAN nodes″ indicates a number of RAN nodes involved in the paging procedure, ″Number of RAN nodes in TA list″ indicates a number of RAN nodes comprised in the TA list involved in the paging procedure, ″Paging Timeout″ indicates a paging timeout value for the paging procedure, and ″Maximum allowed paging wait time″ indicates the maximum allowed paging wait time configured at the RAN node. In some embodiments, ″Maximum allowed paging wait time″ may be 15 seconds.

Further, in some embodiments, the parameter λ is CLI configurable. In some embodiments, it is not directly configured by a customer, but the present disclosure is not limited thereto. Further, some pre-defined values of λ may be provided for ML paging profile, for example:

- 0 for least signaling

- 0.75 for less signaling;

- 1 for balanced;

- 1.25 for less latency;

- 2 for least latency.

Some N2 messages comprising ULI IE that include UE′s last known location information are listed below:

Further, an example of improved CNAI for RRC INACTIVE may be provided as follows:

Further, an example of IEs in a paging message may be provided as follows:

This paging message is sent by the AMF and is used to page a UE in one or several tracking areas. Direction: AMF → NG-RAN node

An example of PLRI IE may be provided as follows:

Further, an example of IEs in UE context information within the RETRIEVE UE CONTEXT RESPONSE message may be provided as follows:

Fig. 11 is a flow chart of an exemplary method 1100 at a first network node for paging a UE that is in an RRC_INACTIVE state with a first RAN node and in a CM- CONNECETED state with the first network node according to an embodiment of the present disclosure. The method 1100 may be performed at an AMF (e.g., the AMF 110 shown in Fig. 1) . The method 1100 may comprise step S1110 and S1120. However, the present disclosure is not limited thereto. In some other embodiments, the method 1100 may comprise more steps, less steps, different steps, or any combination thereof. Further the steps of the method 1100 may be performed in a different order than that described herein. Further, in some embodiments, a step in the method 1100 may be split into multiple sub-steps and performed by different entities, and/or multiple steps in the method 1100 may be combined into a single step.

The method 1100 may begin at step S1110 where a first message indicating a paging failure for the UE may be received from the first RAN node.

At Step S1120, one or more paging procedures for the UE may be triggered to be performed at one or more second RAN nodes.

In some embodiments, the step of triggering the one or more paging procedures for the UE may comprise: transmitting, to at least one of the second RAN nodes, at least one second message for triggering the one or more paging procedures to be performed at the one or more second RAN nodes to page the UE. In some embodiments, the step of triggering the one or more paging procedures for the UE may comprise: transmitting, to one of the one or more second RAN nodes, a second message for triggering the one or more paging procedures to be performed at the one or more second RAN nodes to page the UE, wherein the second message may comprise information from which the one or more second RAN nodes can be determined. In some embodiments, the step of triggering the one or more paging procedures for the UE may comprise: transmitting, to each of the one or more second RAN nodes, a second message for triggering a paging procedure to be performed at the corresponding second RAN node to page the UE. In some embodiments, the step of triggering the one or more paging procedures for the UE may comprise: transmitting, to at least two of the one or more second RAN nodes, second messages, respectively, each of the second messages triggering paging procedures to be performed at a part of the one or more second RAN nodes to page the UE, wherein each of the second messages may comprise information from which a part of the one or more second RAN nodes can be determined, and each of the one or more second RAN nodes can be determined by the information comprised in at least one of the one or more second messages.

In some embodiments, at least one of the second messages may be an NGAP paging message for paging the UE. In some embodiments, the NGAP paging message may comprise an IE indicating at least one of: identifiers of one or more of the second RAN nodes; identifiers of one or more cells associated with one or more of the second RAN nodes; identifiers of one or more TA associated with one or more of the second RAN nodes; and an identifier of a UE context for the UE within the first RAN node; and the UE context for the UE. In some embodiments, when the IE indicates multiple second RAN nodes and/or multiple cells, the order of the multiple second RAN nodes and/or the multiple cells in the IE may be determined by the first network node.

In some embodiments, the method 1100 may further comprise: receiving, from one of the one or more second RAN nodes, a third message indicating that the UE establishes a new RRC connection or resumes a released RRC connection that was established between the UE and the first RAN node; and performing a UE context setup procedure for the UE with the second RAN node, from which the third message is received, in response to the third message indicating that the UE establishes a new RRC connection. In some embodiments, the method 1100 may further comprise: instructing the first RAN node to release UE context for the UE in response to the third message indicating that the UE establishes a new RRC connection. In some embodiments, the method 1100 may further comprise: triggering the one or more second RAN nodes and/or the first RAN node to stop the paging procedures for the UE in response to receiving the third message.

In some embodiments, the one or more second RAN nodes may be not RAN nodes associated with any cell or area indicated by an RNA configured at the first RAN node for the UE. In some embodiments, the paging failure indicated by the first message may be the earliest paging failure that is resulted from a RAN paging procedure initiated by the first RAN node for the UE. In some embodiments, the one or more paging procedures initiated at the one or more second RAN nodes may be performed concurrently with a RAN paging procedure initiated by the first RAN node for the UE. In some embodiments, before the step of triggering the one or more paging procedures for the UE, the method 1100 may further comprise: determining the one or more second RAN nodes, at which the one or more paging procedures for the UE are to be performed, at least based on historical mobility data for the UE. In some embodiments, the step of determining the one or more second RAN nodes may comprise: for each of other RAN nodes than the first RAN node, counting a number of handovers and/or mobility registration updates of the UE from the first RAN node to the corresponding one of the other RAN nodes; and determining one or more of the other RAN nodes that have the top numbers of handovers and/or mobility registration updates as the one or more second RAN nodes.

In some embodiments, the step of determining the one or more second RAN nodes may comprise: for each of cells associated with the first RAN node and for each of other cells than the cells associated with the first RAN node, counting a number of handovers and/or mobility registration updates of the UE from the corresponding cell associated with the first RAN node to the corresponding one of the other cells; and determining one or more RAN nodes that are associated with one or more of the other cells having the top numbers of handovers and/or mobility registration updates as the one or more second RAN nodes. In some embodiments, the step of determining the one or more second RAN nodes may comprise: determining the one or more second RAN nodes by an Artificial Intelligence (AI) model that is trained at least based on the historical mobility data for the UE. In some embodiments, the AI model may be trained with a cost function as follows:

TotalCost = Signal ^(1-λ)*Latency ^λ

wherein the ″TotalCost″ may be the cost to be calculated, ″Signal″ may indicate a signaling amount required for paging the UE, ″Latency″ indicates a paging latency, and ″λ″ may indicate a regularization factor for balancing the paging latency and the signaling amount.

In some embodiments, the ″Signal″ and the ″Latency″ may be normalized as follows:

wherein ″Number of RAN nodes″ may indicate a number of RAN nodes involved in the paging procedure, ″Number of RAN nodes in TA list″ may indicate a number of RAN nodes comprised in the TA list involved in the paging procedure, ″Paging Timeout″ may indicate a paging timeout value for the paging procedure, and ″Maximum allowed paging wait time″ may indicate the maximum allowed paging wait time configured at the RAN node.

wherein the ″TotalCost″ may be the cost to be calculated, ″SuccRate (i -1, t, conf) ″ may indicate the paging success rate for the i -1 ^th paging at a given time t and a given confidence level of conf, ″NumOfEnb (i, t, conf) ″ may indicate a number of RAN nodes involved in the paging procedure for the i ^th paging at a given time t and a given confidence level of conf, ″Timeout (i -1) ″ may indicate a timeout value for the i -1 ^th paging, and ″λ″ may indicate a regularization factor for balancing the number of RAN nodes involved in the paging procedure and the timeout value.

In some embodiments, before the step of receiving the first message, the method 1100 may further comprise: transmitting, to the first RAN node, a fourth message for triggering a RAN paging procedure for the UE. In some embodiments, the first message may be at least one of: an ″RRC INACTIVE TRANSITION REPORT″ message or an UL N2 message comprising an RRC state IE of ″Inactive″ ; a ″Location Report″ message comprising an ″Age of Location″ IE, the ″Age of Location″ IE indicating that an RNA-based RAN paging fails at the first network node; In some embodiments, a ″Location Reporting Failure Indication″ message comprising a cause of ″UE in RRC_INACTIVE state not reachable″ ; and a message comprising a ″User Location Information (ULI) ″ IE comprising an ″Age of Location″ IE, the ″Age of Location″ IE indicating that an RNA-based RAN paging fails at the first network node.

In some embodiments, the first RAN node may be the last RAN node that serves the UE before the UE transitions to the RRC_INACTIVE state. In some embodiments, the first network node may be an AMF.

Fig. 12 is a flow chart of an exemplary method 1200 at a first network node for paging a UE that is in an RRC_INACTIVE state with a first RAN node and in a CM-CONNECETED state with the first network node according to an embodiment of the present disclosure. The method 1200 may be performed at an AMF (e.g., the AMF 110 shown in Fig. 1) . The method 1200 may comprise step S1210 and S1220. However, the present disclosure is not limited thereto. In some other embodiments, the method 1200 may comprise more steps, less steps, different steps, or any combination thereof. Further the steps of the method 1200 may be performed in a different order than that described herein. Further, in some embodiments, a step in the method 1200 may be split into multiple sub-steps and performed by different entities, and/or multiple steps in the method 1200 may be combined into a single step.

The method 1200 may begin at step S1210 where one or more third RAN nodes and/or one or more cells associated with the one or more third RAN nodes may be determined at least based on historical mobility data for the UE.

At step S1220, a fifth message for indicating at least one of the one or more third RAN nodes and/or at least one of the one or more cells that can be used for paging the UE may be transmitted to the first RAN node.

In some embodiments, the fifth message may be a message comprising a ″Core Network Assistance Information for RRC INACTIVE″ IE. In some embodiments, the ″Core Network Assistance Information for RRC INACTIVE″ IE may comprise an IE indicating at least one of: identifiers of one or more of the third RAN nodes; identifiers of one or more cells associated with one or more of the third RAN nodes; and identifiers of one or more TAs associated with one or more of the third RAN nodes. In some embodiments, when the IE indicates multiple third RAN nodes and/or multiple cells, the order of the multiple third RAN nodes and/or the multiple cells in the IE may be determined by the first network node. In some embodiments, the step of determining the one or more third RAN nodes may comprise: for each of other RAN nodes than the first RAN node, counting a number of handovers and/or mobility registration updates of the UE from the first RAN node to the corresponding one of the other RAN nodes; and determining one or more of the other RAN nodes that have the top numbers of handovers and/or mobility registration updates as the one or more third RAN nodes. In some embodiments, the step of determining the one or more third RAN nodes may comprise: for each of cells associated with the first RAN node and for each of other cells than the cells associated with the first RAN node, counting a number of handovers and/or mobility registration updates of the UE from the corresponding cell associated with the first RAN node to the corresponding one of the other cells; and determining one or more RAN nodes that are associated with one or more of the other cells having the top numbers of handovers and/or mobility registration updates as the one or more third RAN nodes. In some embodiments, the step of determining the one or more third RAN nodes may comprise: determining the one or more third RAN nodes by an AI model that is trained at least based on the historical mobility data for the UE.

TotalCost = Signal ^(1-λ)*Latency ^λ

wherein the ″TotalCost″ may be the cost to be calculated, ″Signal″ may indicate a signaling amount required for paging the UE, ″Latency″ may indicate a paging latency, and ″λ″ may indicate a regularization factor for balancing the paging latency and the signaling amount.

In some embodiments, the method 1200 may further comprise: transmitting, to the first RAN node, a fourth message for triggering a RAN paging procedure for the UE. In some embodiments, the first RAN node may be the last RAN node that serves the UE before the UE transitions to the RRC_INACTIVE state. In some embodiments, the first network node may be an AMF.

Fig. 13 is a flow chart of an exemplary method 1300 at a second RAN node for paging a UE that is in an RRC_INACTIVE state with a first RAN node and in a CM-CONNECETED state with a first network node according to an embodiment of the present disclosure. The method 1300 may be performed at a RAN node (e.g., the gNB 105-3) . The method 1300 may comprise step S1310 and S1320. However, the present disclosure is not limited thereto. In some other embodiments, the method 1300 may comprise more steps, less steps, different steps, or any combination thereof. Further the steps of the method 1300 may be performed in a different order than that described herein. Further, in some embodiments, a step in the method 1300 may be split into multiple sub-steps and performed by different entities, and/or multiple steps in the method 1300 may be combined into a single step.

The method 1300 may begin at step S1310 where a second message for triggering a paging procedure for the UE may be received from the first network node while the first RAN node is performing a RAN paging procedure for the UE.

At step S1320, a paging procedure for the UE may be performed in response to the received second message.

In some embodiments, when the second message may indicate one or more other second RAN nodes that can be used for paging the UE, the method 1300 may further comprise: updating an RNA configured for the UE with the indicated one or more other second RAN nodes. In some embodiments, the RNA may be updated in an order as follows: the last visited RAN node; the indicated one or more other second RAN nodes; RAN nodes in a TA list for a specific PLMN; and RAN nodes in all TA lists. In some embodiments, the second message may be an NGAP paging message for paging the UE. In some embodiments, the NGAP paging message may comprise an IE indicating at least one of: identifiers of one or more second RAN nodes; identifiers of one or more cells associated with one or more second RAN nodes; identifiers of one or more TA associated with one or more second RAN nodes; and an identifier of a UE context for the UE within the first RAN node; and the UE context for the UE. In some embodiments, when the IE indicates multiple second RAN nodes and/or multiple cells, the order of the multiple second RAN nodes and/or the multiple cells in the IE may be determined by the first network node.

In some embodiments, the paging procedure may be performed with a P-Radio Network Temporary Identifier (P-RNTI) and/or I-RNTI assigned for the UE. In some embodiments, when the paging procedure is performed with a P-RNTI assigned for the UE, the method 1300 may further comprise: receiving, from the UE, a message for establishing a new RRC connection; and performing a UE context setup procedure for the UE with the first network node. In some embodiments, when the paging procedure is performed with an I-RNTI assigned for the UE, the method 1300 may further comprise: receiving, from the UE, a message for resuming a released RRC connection that was established between the UE and the first RAN node; and retrieving a UE context for the UE from the first RAN node with the I-RNTI. In some embodiments, the method 1300 may further comprise: stopping the paging procedure for the UE in response to the message received from the UE. In some embodiments, the second RAN node may be not a RAN node associated with any cell or area indicated by an RNA configured at the first RAN node for the UE. In some embodiments, the first RAN node may be the last RAN node that serves the UE before the UE transitions to the RRC_INACTIVE state. In some embodiments, the first network node may be an AMF.

Fig. 14 is a flow chart of an exemplary method 1400 at a first RAN node for paging a UE that is in an RRC_INACTIVE state with the first RAN node and in a CM-CONNECETED state with a first network node according to an embodiment of the present disclosure. The method 1400 may be performed at a RAN node (e.g., the gNB 105-1) . The method 1400 may comprise a step S1410. However, the present disclosure is not limited thereto. In some other embodiments, the method 1400 may comprise more steps, different steps, or any combination thereof. Further the steps of the method 1400 may be performed in a different order than that described herein. Further, in some embodiments, a step in the method 1400 may be split into multiple sub-steps and performed by different entities, and/or multiple steps in the method 1400 may be combined into a single step.

The method 1400 may begin at step S1410 where a fifth message for indicating one or more third RAN nodes and/or one or more cells associated with the one or more third RAN nodes that can be used for paging the UE may be received from the first network node, and the one or more third RAN nodes and/or the one or more cells may be determined at least based on historical mobility data for the UE.

In some embodiments, the fifth message may be a message comprising a ″Core Network Assistance Information for RRC INACTIVE″ IE. In some embodiments, the ″Core Network Assistance Information for RRC INACTIVE″ IE comprises an IE indicating at least one of: identifiers of one or more of the third RAN nodes; identifiers of one or more cells associated with one or more of the third RAN nodes; and identifiers of one or more TA associated with one or more of the third RAN nodes. In some embodiments, when the IE indicates multiple third RAN nodes and/or multiple cells, the order of the multiple third RAN nodes and/or the multiple cells in the IE may be determined by the first network node. In some embodiments, the method 1400 may further comprise: receiving, from the first network node, a fourth message for triggering a RAN paging procedure for the UE. In some embodiments, the first RAN node may be the last RAN node that serves the UE before the UE transitions to the RRC_INACTIVE state. In some embodiments, the first network node may be an AMF.

Fig. 15 schematically shows an embodiment of an arrangement which may be used in a first network node (e.g., AMF) and/or a RAN node according to an embodiment of the present disclosure. Comprised in the arrangement 1500 are a processing unit 1506, e.g., with a Digital Signal Processor (DSP) or a Central Processing Unit (CPU) . The processing unit 1506 may be a single unit or a plurality of units to perform different actions of procedures described herein. The arrangement 1500 may also comprise an input unit 1502 for receiving signals from other entities, and an output unit 1504 for providing signal (s) to other entities. The input unit 1502 and the output unit 1504 may be arranged as an integrated entity or as separate entities.

Furthermore, the arrangement 1500 may comprise at least one computer program product 1508 in the form of a non-volatile or volatile memory, e.g., an Electrically Erasable Programmable Read-Only Memory (EEPROM) , a flash memory and/or a hard drive. The computer program product 1508 comprises a computer program 1510, which comprises code/computer readable instructions, which when executed by the processing unit 1506 in the arrangement 1500 causes the arrangement 1500 and/or the first network node and/or the network node in which it is comprised to perform the actions, e.g., of the procedure described earlier in conjunction with Fig. 7 through Fig. 14 or any other variant.

The computer program 1510 may be configured as a computer program code structured in computer program modules 1510A -1510B. Hence, in an exemplifying embodiment when the arrangement 1500 is used in a first network node, the code in the computer program of the arrangement 1500 includes: a module 1510A configured to receive, from the first RAN node, a first message indicating a paging failure for the UE;and a module 1510B configured to trigger one or more paging procedures for the UE to be performed at one or more second RAN nodes.

The computer program 1510 may be further configured as a computer program code structured in computer program modules 1510C -1510D. Hence, in an exemplifying embodiment when the arrangement 1500 is used in a first network node, the code in the computer program of the arrangement 1500 includes: a module 1510C configured to determine one or more third RAN nodes and/or one or more cells associated with the one or more third RAN nodes at least based on historical mobility data for the UE; and a module 1510D configured to transmit, to the first RAN node, a fifth message for indicating at least one of the one or more third RAN nodes and/or at least one of the one or more cells that can be used for paging the UE.

The computer program 1510 may be further configured as a computer program code structured in computer program modules 1510E -1510F. Hence, in an exemplifying embodiment when the arrangement 1500 is used in a second RAN node, the code in the computer program of the arrangement 1500 includes: a module 1510E configured to receive, from the first network node, a second message for triggering a paging procedure for the UE while the first RAN node is performing a RAN paging procedure for the UE; and a module 1510F configured to perform a paging procedure for the UE in response to the received second message.

The computer program 1510 may be further configured as a computer program code structured in computer program modules 1510G. Hence, in an exemplifying embodiment when the arrangement 1500 is used in a first RAN node, the code in the computer program of the arrangement 1500 includes: a module 1510G configured to receive, from the first network node, a fifth message for indicating one or more third RAN nodes and/or one or more cells associated with the one or more third RAN nodes that can be used for paging the UE, the one or more third RAN nodes and/or the one or more cells being determined at least based on historical mobility data for the UE.

The computer program modules could essentially perform the actions of the flow illustrated in Fig. 7 through Fig. 14, to emulate the first network node and/or the RAN node. In other words, when the different computer program modules are executed in the processing unit 1506, they may correspond to different modules in the first network node and/or the RAN node.

Although the code means in the embodiments disclosed above in conjunction with Fig. 15 are implemented as computer program modules which when executed in the processing unit causes the arrangement to perform the actions described above in conjunction with the figures mentioned above, at least one of the code means may in alternative embodiments be implemented at least partly as hardware circuits.

The processor may be a single CPU (Central processing unit) , but could also comprise two or more processing units. For example, the processor may include general purpose microprocessors; instruction set processors and/or related chips sets and/or special purpose microprocessors such as Application Specific Integrated Circuit (ASICs) . The processor may also comprise board memory for caching purposes. The computer program may be carried by a computer program product connected to the processor. The computer program product may comprise a computer readable medium on which the computer program is stored. For example, the computer program product may be a flash memory, a Random-access memory (RAM) , a Read-Only Memory (ROM) , or an EEPROM, and the computer program modules described above could in alternative embodiments be distributed on different computer program products in the form of memories within the first network node and/or the RAN nodes.

Correspondingly to the method 1100 as described above, an exemplary first network node is provided. Fig. 16 is a block diagram of a first network node 1600 according to an embodiment of the present disclosure. The first network node 1600 may be, e.g., the AMF 110 in some embodiments.

The first network node 1600 may be configured to perform the method 1100 as described above in connection with Fig. 11. As shown in Fig. 16, the first network node 1600 may comprise a receiving module 1610 configured to receive, from the first RAN node, a first message indicating a paging failure for the UE; and a triggering module 1620 configured to trigger one or more paging procedures for the UE to be performed at one or more second RAN nodes.

The above modules 1610 and/or 1620 may be implemented as a pure hardware solution or as a combination of software and hardware, e.g., by one or more of: a processor or a micro-processor and adequate software and memory for storing of the software, a Programmable Logic Device (PLD) or other electronic component (s) or processing circuitry configured to perform the actions described above, and illustrated, e.g., in Fig. 11. Further, the first network node 1600 may comprise one or more further modules, each of which may perform any of the steps of the method 1100 described with reference to Fig. 11.

Correspondingly to the method 1200 as described above, an exemplary first network node is provided. Fig. 17 is a block diagram of a first network node 1700 according to an embodiment of the present disclosure. The second network node 1700 may be, e.g., the AMF 110 in some embodiments.

The first network node 1700 may be configured to perform the method 1200 as described above in connection with Fig. 12. As shown in Fig. 17, the first network node 1700 may comprise a determining module 1710 configured to determine one or more third RAN nodes and/or one or more cells associated with the one or more third RAN nodes at least based on historical mobility data for the UE; and a transmitting module 1720 configured to transmit, to the first RAN node, a fifth message for indicating at least one of the one or more third RAN nodes and/or at least one of the one or more cells that can be used for paging the UE.

The above modules 1710 and/or 1720 may be implemented as a pure hardware solution or as a combination of software and hardware, e.g., by one or more of: a processor or a micro-processor and adequate software and memory for storing of the software, a PLD or other electronic component (s) or processing circuitry configured to perform the actions described above, and illustrated, e.g., in Fig. 12. Further, the first network node 1700 may comprise one or more further modules, each of which may perform any of the steps of the method 1200 described with reference to Fig. 12.

Correspondingly to the method 1300 as described above, an exemplary second RAN node is provided. Fig. 18 is a block diagram of a second RAN node 1800 according to an embodiment of the present disclosure. The second RAN node 1800 may be, e.g., the gNB 105-3 in some embodiments.

The second RAN node 1800 may be configured to perform the method 1300 as described above in connection with Fig. 13. As shown in Fig. 18, the second RAN node 1800 may comprise a receiving module 1810 configured to receive, from the first network node, a second message for triggering a paging procedure for the UE while the first RAN node is performing a RAN paging procedure for the UE; and a performing module 1820 configured to perform a paging procedure for the UE in response to the received second message.

The above modules 1810 and/or 1820 may be implemented as a pure hardware solution or as a combination of software and hardware, e.g., by one or more of: a processor or a micro-processor and adequate software and memory for storing of the software, a PLD or other electronic component (s) or processing circuitry configured to perform the actions described above, and illustrated, e.g., in Fig. 13. Further, the second RAN node 1800 may comprise one or more further modules, each of which may perform any of the steps of the method 1300 described with reference to Fig. 13.

Correspondingly to the method 1400 as described above, an exemplary first RAN node is provided. Fig. 19 is a block diagram of a first RAN node 1900 according to an embodiment of the present disclosure. The first RAN node 1900 may be, e.g., the gNB 105-1 in some embodiments.

The first RAN node 1900 may be configured to perform the method 1400 as described above in connection with Fig. 14. As shown in Fig. 19, the first RAN node 1900 may comprise a receiving module 1910 configured to receive, from the first network node, a fifth message for indicating one or more third RAN nodes and/or one or more cells associated with the one or more third RAN nodes that can be used for paging the UE, the one or more third RAN nodes and/or the one or more cells being determined at least based on historical mobility data for the UE.

The above module 1910 may be implemented as a pure hardware solution or as a combination of software and hardware, e.g., by one or more of: a processor or a micro-processor and adequate software and memory for storing of the software, a PLD or other electronic component (s) or processing circuitry configured to perform the actions described above, and illustrated, e.g., in Fig. 14. Further, the first RAN node 1900 may comprise one or more further modules, each of which may perform any of the steps of the method 1400 described with reference to Fig. 14.

The present disclosure is described above with reference to the embodiments thereof. However, those embodiments are provided just for illustrative purpose, rather than limiting the present disclosure. The scope of the disclosure is defined by the attached claims as well as equivalents thereof. Those skilled in the art can make various alternations and modifications without departing from the scope of the disclosure, which all fall into the scope of the disclosure.

Claims

A method (1100) at a first network node (110) for paging a user equipment (UE) (100) that is in an RRC_INACTIVE state with a first Radio Access Network (RAN) node (105-1) and in a CM-CONNECETED state with the first network node (110) , the method (1100) comprising:

receiving (S740, S825, S925, S1025, S1110) , from the first RAN node (105-1) , a first message indicating a paging failure for the UE (100) ; and

triggering (S750a, S830a, S930a, S1030a, S1120) one or more paging procedures for the UE (100) to be performed at one or more second RAN nodes (105-3) .
The method (1100) of claim 1, wherein the step of triggering the one or more paging procedures for the UE (100) comprises:

transmitting (S750a, S830a, S930a, S1030a) , to at least one of the second RAN nodes (105-3) , at least one second message for triggering the one or more paging procedures to be performed at the one or more second RAN nodes (105-3) to page the UE (100) .
The method (1100) of claim 2, wherein the step of triggering the one or more paging procedures for the UE (100) comprises:

transmitting (S750a, S830a, S930a, S1030a) , to one of the one or more second RAN nodes (105-3) , a second message for triggering the one or more paging procedures to be performed at the one or more second RAN nodes (105-3) to page the UE (100) ,

wherein the second message comprises information from which the one or more second RAN nodes (105-3) can be determined.
The method (1100) of claim 2, wherein the step of triggering the one or more paging procedures for the UE (100) comprises:

transmitting (S750a, S830a, S930a, S1030a) , to each of the one or more second RAN nodes (105-3) , a second message for triggering a paging procedure to be performed at the corresponding second RAN nodes (105-3) to page the UE (100) .
The method (1100) of claim 2, wherein the step of triggering the one or more paging procedures for the UE (100) comprises:

transmitting (S750a, S830a, S930a, S1030a) , to at least two of the one or more second RAN nodes (105-3) , second messages, respectively, each of the second messages triggering paging procedures to be performed at a part of the one or more second RAN nodes (105-3) to page the UE (100) ,

wherein each of the second messages comprises information from which a part of the one or more second RAN nodes (105-3) can be determined, and each of the one or more second RAN nodes (105-3) can be determined by the information comprised in at least one of the one or more second messages.
The method (1100) of any of claims 2 to 5, wherein at least one of the second messages is an NG Application Protocol (NGAP) paging message for paging the UE (100) .
The method (1100) of claim 6, wherein the NGAP paging message comprises an information element (IE) indicating at least one of:

- identifiers of one or more of the second RAN nodes (105-3) ;

- identifiers of one or more cells associated with one or more of the second RAN nodes (105-3) ;

- identifiers of one or more tracking areas (TAs) associated with one or more of the second RAN nodes (105-3) ; and

- an identifier of a UE context for the UE (100) within the first RAN node (105-1) ; and

- the UE context for the UE (100) .
The method (1100) of claim 7, wherein when the IE indicates multiple second RAN nodes (105-3) and/or multiple cells, the order of the multiple second RAN nodes (105-3) and/or the multiple cells in the IE is determined by the first network node (110) .
The method (1100) of any of claims 1 to 8, further comprising:

receiving (S850, S1055) , from one of the one or more second RAN nodes (105-3) , a third message indicating that the UE (100) establishes a new Radio Resource Control (RRC) connection or resumes a released RRC connection that was established between the UE (100) and the first RAN node (105-1) ; and

performing (S850, S1055) a UE context setup procedure for the UE (100) with the second RAN node (105-3) , from which the third message is received, in response to the third message indicating that the UE (100) establishes a new RRC connection.
The method (1100) of claim 9, further comprising:

instructing (S855, S1060) the first RAN node (105-1) to release UE context for the UE (100) in response to the third message indicating that the UE (100) establishes a new RRC connection.
The method (1100) of claim 9 or 10, further comprising:

triggering the one or more second RAN nodes (105-3) and/or the first RAN node (105-1) to stop the paging procedures for the UE (100) in response to receiving the third message.
The method (1100) of any of claims 1 to 11, wherein the one or more second RAN nodes (105-3) are not RAN nodes associated with any cell or area indicated by a RAN-based Notification Area (RNA) configured at the first RAN node (105-1) for the UE (100) .
The method (1100) of any of claims 1 to 12, wherein the paging failure indicated by the first message is the earliest paging failure that is resulted from a RAN paging procedure initiated by the first RAN node (105-1) for the UE (100) .
The method (1100) of any of claims 1 to 13, wherein the one or more paging procedures initiated at the one or more second RAN nodes (105-3) are performed concurrently with a RAN paging procedure initiated by the first RAN node (105-1) for the UE (100) .
The method (1100) of any of claims 1 to 14, wherein before the step of triggering the one or more paging procedures for the UE (100) , the method (1100) further comprises:

determining (S705, S750, S830, S930, S1030) the one or more second RAN nodes (105-3) , at which the one or more paging procedures for the UE (100) are to be performed, at least based on historical mobility data for the UE (100) .
The method (1100) of claim 15, wherein the step of determining the one or more second RAN nodes (105-3) comprises:

for each of other RAN nodes than the first RAN node (105-1) , counting a number of handovers and/or mobility registration updates of the UE (100) from the first RAN node (105-1) to the corresponding one of the other RAN nodes; and

determining one or more of the other RAN nodes that have the top numbers of handovers and/or mobility registration updates as the one or more second RAN nodes (105-3) .
The method (1100) of claim 15, wherein the step of determining the one or more second RAN nodes (105-3) comprises:

for each of cells associated with the first RAN node (105-1) and for each of other cells than the cells associated with the first RAN node (105-1) , counting a number of handovers and/or mobility registration updates of the UE (100) from the corresponding cell associated with the first RAN node (105-1) to the corresponding one of the other cells; and

determining one or more RAN nodes that are associated with one or more of the other cells having the top numbers of handovers and/or mobility registration updates as the one or more second RAN nodes (105-3) .
The method (1100) of claim 15, wherein the step of determining the one or more second RAN nodes (105-3) comprises:

determining the one or more second RAN nodes (105-3) by an Artificial Intelligence (AI) model that is trained at least based on the historical mobility data for the UE (100) .
The method (1100) of claim 18, wherein the AI model is trained with a cost function as follows:

TotalCost = Signal ^(1-λ) *Latency ^λ

wherein the ″TotalCost″ is the cost to be calculated, ″Signal″ indicates a signaling amount required for paging the UE (100) , ″Latency″ indicates a paging latency, and ″λ″ indicates a regularization factor for balancing the paging latency and the signaling amount.
The method (1100) of claim 19, wherein the ″Signal″ and the ″Latency″ are normalized as follows:

wherein ″Number of RAN nodes″ indicates a number of RAN nodes involved in the paging procedure, ″Number of RAN nodes in TA list″ indicates a number of RAN nodes comprised in the TA list involved in the paging procedure, ″Paging Timeout″ indicates a paging timeout value for the paging procedure, and ″Maximum allowed paging wait time″ indicates the maximum allowed paging wait time configured at the RAN node.
The method (1100) of claim 18, wherein the AI model is trained with a cost function as follows:

wherein the ″TotalCost″ is the cost to be calculated, ″SuccRate (i-1, t, conf) ″ indicates the paging success rate for the i-1 ^th paging at a given time t and a given confidence level of conf, ″NumOfEnb (i, t, conf) ″ indicates a number of RAN nodes involved in the paging procedure for the i ^th paging at a given time t and a given confidence level of conf, ″Timeout (i-1) ″ indicates a timeout value for the i-1 ^th paging, and ″λ″ indicates a regularization factor for balancing the number of RAN nodes involved in the paging procedure and the timeout value.
The method (1100) of any of claims 1 to 21, wherein before the step of receiving the first message, the method (1100) further comprises:

transmitting, to the first RAN node (105-1) , a fourth message for triggering a RAN paging procedure for the UE (100) .
The method (1100) of any of claims 1 to 22, wherein the first message is at least one of:

- an ″RRC INACTIVE TRANSITION REPORT″ message or an uplink (UL) N2 message comprising an RRC state IE of ″Inactive″ ;

- a ″Location Report″ message comprising an ″Age of Location″ IE, the ″Age of Location″ IE indicating that an RNA-based RAN paging fails at the first network node (110) ;

- a ″Location Reporting Failure Indication″ message comprising a cause of ″UE (100) in RRC_INACTIVE state not reachable″ ; and

- a message comprising a ″User Location Information (ULI) ″ IE comprising an ″Age of Location″ IE, the ″Age of Location″ IE indicating that an RNA-based RAN paging fails at the first network node (110) .
The method (1100) of any of claims 1 to 23, wherein the first RAN node (105-1) is the last RAN node that serves the UE (100) before the UE (100) transitions to the RRC_INACTIVE state.
The method (1100) of any of claims 1 to 24, wherein the first network node (110) is an Access &Mobility Management Function (AMF) .
A method (1200) at a first network node (110) for paging a UE (100) that is in an RRC_INACTIVE state with a first RAN node (105-1) and in a CM-CONNECETED state with the first network node (110) , the method (1200) comprising:

determining (S705, S930, S1030, S1210) one or more third RAN nodes and/or one or more cells associated with the one or more third RAN nodes at least based on historical mobility data for the UE (100) ; and

transmitting (S750a, S930a, S1030a, S1220) , to the first RAN node (105-1) , a fifth message for indicating at least one of the one or more third RAN nodes and/or at least one of the one or more cells that can be used for paging the UE (100) .
The method (1200) of claim 26, wherein the fifth message is a message comprising a ″Core Network Assistance Information for RRC INACTIVE″ IE.
The method (1200) of claim 27, wherein the ″Core Network Assistance Information for RRC INACTIVE″ IE comprises an IE indicating at least one of:

- identifiers of one or more of the third RAN nodes;

- identifiers of one or more cells associated with one or more of the third RAN nodes; and

- identifiers of one or more TAs associated with one or more of the third RAN nodes.
The method (1200) of claim 28, wherein when the IE indicates multiple third RAN nodes and/or multiple cells, the order of the multiple third RAN nodes and/or the multiple cells in the IE is determined by the first network node (110) .
The method (1200) of any of claims 26 to 29, wherein the step of determining the one or more third RAN nodes comprises:

for each of other RAN nodes than the first RAN node (105-1) , counting a number of handovers and/or mobility registration updates of the UE (100) from the first RAN node (105-1) to the corresponding one of the other RAN nodes; and

determining one or more of the other RAN nodes that have the top numbers of handovers and/or mobility registration updates as the one or more third RAN nodes.
The method (1200) of any of claims 26 to 29, wherein the step of determining the one or more third RAN nodes comprises:

for each of cells associated with the first RAN node (105-1) and for each of other cells than the cells associated with the first RAN node (105-1) , counting a number of handovers and/or mobility registration updates of the UE (100) from the corresponding cell associated with the first RAN node (105-1) to the corresponding one of the other cells; and

determining one or more RAN nodes that are associated with one or more of the other cells having the top numbers of handovers and/or mobility registration updates as the one or more third RAN nodes.
The method (1200) of any of claims 26 to 29, wherein the step of determining the one or more third RAN nodes comprises:

determining the one or more third RAN nodes by an AI model that is trained at least based on the historical mobility data for the UE (100) .
The method (1200) of claim 32, wherein the AI model is trained with a cost function as follows:

TotalCost = Signal ^(1-λ) *Latency ^λ

wherein the ″TotalCost″ is the cost to be calculated, ″Signal″ indicates a signaling amount required for paging the UE (100) , ″Latency″ indicates a paging latency, and ″λ″ indicates a regularization factor for balancing the paging latency and the signaling amount.
The method (1200) of claim 33, wherein the ″Signal″ and the ″Latency″ are normalized as follows:

wherein ″Number of RAN nodes″ indicates a number of RAN nodes involved in the paging procedure, ″Number of RAN nodes in TA list″ indicates a number of RAN nodes comprised in the TA list involved in the paging procedure, ″Paging Timeout″ indicates a paging timeout value for the paging procedure, and ″Maximum allowed paging wait time″ indicates the maximum allowed paging wait time configured at the RAN node.
The method (1200) of claim 32, wherein the AI model is trained with a cost function as follows:

wherein the ″TotalCost″ is the cost to be calculated, ″SuccRate (i-1, t, conf) ″ indicates the paging success rate for the i-1 ^th paging at a given time t and a given confidence level of conf, ″NumOfEnb (i, t, conf) ″ indicates a number of RAN nodes involved in the paging procedure for the i ^th paging at a given time t and a given confidence level of conf, ″Timeout (i-1) ″ indicates a timeout value for the i-1 ^th paging, and ″λ″ indicates a regularization factor for balancing the number of RAN nodes involved in the paging procedure and the timeout value.
The method (1200) of any of claims 26 to 35, further comprising:

transmitting, to the first RAN node (105-1) , a fourth message for triggering a RAN paging procedure for the UE (100) .
The method (1200) of any of claims 26 to 36, wherein the first RAN node (105-1) is the last RAN node that serves the UE (100) before the UE (100) transitions to the RRC_INACTIVE state.
The method (1200) of any of claims 26 to 37, wherein the first network node (110) is an AMF.
A first network node (110, 1500, 1600, 1700) , comprising:

a processor (1506) ;

a memory (1508) storing instructions which, when executed by the processor (1506) , cause the processor (1506) to perform the method (1100, 1200) of any of claims 1 to 38.
A method (1300) at a second RAN node (105-3) for paging a UE (100) that is in an RRC_INACTIVE state with a first RAN node (105-1) and in a CM-CONNECETED state with a first network node (110) , the method (1300) comprising:

receiving (S750a, S830a, S930a, S1030a, S1310) , from the first network node (110) , a second message for triggering a paging procedure for the UE (100) while the first RAN node (105-1) is performing a RAN paging procedure for the UE (100) ; and

performing (S750a, S845, S945, S950, S1045, S1050, S1320) a paging procedure for the UE (100) in response to the received second message.
The method (1300) of claim 40, wherein when the second message indicates one or more other second RAN nodes (105-3) that can be used for paging the UE (100) , the method (1300) further comprises:

updating (S933, S1033) an RNA configured for the UE (100) with the indicated one or more other second RAN nodes (105-3) .
The method (1300) of claim 41, wherein the RNA is updated in an order as follows:

- the last visited RAN node;

- the indicated one or more other second RAN nodes (105-3) ;

- RAN nodes in a TA list for a specific Public Land Mobile Network (PLMN) ; and

- RAN nodes in all TA lists.
The method (1300) of any of claims 40 to 42, wherein the second message is an NGAP paging message for paging the UE (100) .
The method (1300) of claim 43, wherein the NGAP paging message comprises an IE indicating at least one of:

- identifiers of one or more second RAN nodes (105-3) ;

- identifiers of one or more cells associated with one or more second RAN nodes (105-3) ;

- identifiers of one or more TA associated with one or more second RAN nodes (105-3) ; and

- an identifier of a UE context for the UE (100) within the first RAN node (105-1) ; and

- the UE context for the UE (100) .
The method (1300) of claim 44, wherein when the IE indicates multiple second RAN nodes (105-3) and/or multiple cells, the order of the multiple second RAN nodes (105-3) and/or the multiple cells in the IE is determined by the first network node (110) .
The method (1300) of any of claims 40 to 45, wherein the paging procedure is performed with a P-Radio Network Temporary Identifier (P-RNTI) and/or I-RNTI assigned for the UE (100) .
The method (1300) of any of claims 40 to 46, wherein when the paging procedure is performed with a P-RNTI assigned for the UE (100) , the method (1300) further comprises:

receiving (S845, S1050) , from the UE (100) , a message for establishing a new RRC connection; and

performing (S850, S1055) a UE context setup procedure for the UE (100) with the first network node (110) .
The method (1300) of any of claims 40 to 46, wherein when the paging procedure is performed with an I-RNTI assigned for the UE (100) , the method (1300) further comprises:

receiving (S950) , from the UE (100) , a message for resuming a released RRC connection that was established between the UE (100) and the first RAN node (105-1) ; and

retrieving (S955) a UE context for the UE (100) from the first RAN node (105-1) with the I-RNTI.
The method (1300) of claim 47 or 48, further comprising:

stopping the paging procedure for the UE (100) in response to the message received from the UE (100) .
The method (1300) of any of claims 40 to 49, wherein the second RAN node (105-3) is not a RAN node associated with any cell or area indicated by an RNA configured at the first RAN node (105-1) for the UE (100) .
The method (1300) of any of claims 40 to 50, wherein the first RAN node (105-1) is the last RAN node that serves the UE (100) before the UE (100) transitions to the RRC_INACTIVE state.
The method (1300) of any of claims 40 to 51, wherein the first network node (110) is an AMF.
A second RAN node (105-3, 1500, 1800) , comprising:

a processor (1506) ;

a memory (1508) storing instructions which, when executed by the processor (1506) , cause the processor (1506) to perform the method (1300) of any of claims 40 to 52.
A method (1400) at a first RAN node (105-1) for paging a UE (100) that is in an RRC_INACTIVE state with the first RAN node (105-1) and in a CM-CONNECETED state with a first network node (110) , the method (1400) comprising:

receiving (S710, S1410) , from the first network node (110) , a fifth message for indicating one or more third RAN nodes and/or one or more cells associated with the one or more third RAN nodes that can be used for paging the UE (100) , the one or more third RAN nodes and/or the one or more cells being determined at least based on historical mobility data for the UE (100) .
The method (1400) of claim 54, wherein the fifth message is a message comprising a ″Core Network Assistance Information for RRC INACTIVE″ IE.
The method (1400) of claim 55, wherein the ″Core Network Assistance Information for RRC INACTIVE″ IE comprises an IE indicating at least one of:

- identifiers of one or more of the third RAN nodes;

- identifiers of one or more cells associated with one or more of the third RAN nodes; and

- identifiers of one or more TA associated with one or more of the third RAN nodes.
The method (1400) of claim 56, wherein when the IE indicates multiple third RAN nodes and/or multiple cells, the order of the multiple third RAN nodes and/or the multiple cells in the IE is determined by the first network node (110) .
The method (1400) of any of claims 54 to 57, further comprising:

receiving (S730) , from the first network node (110) , a fourth message for triggering a RAN paging procedure for the UE (100) .
The method (1400) of any of claims 54 to 58, wherein the first RAN node (105-1) is the last RAN node that serves the UE (100) before the UE (100) transitions to the RRC_INACTIVE state.
The method (1400) of any of claims 54 to 59, wherein the first network node (110) is an AMF.
A first RAN node (105-1, 1500, 1900) , comprising:

a processor (1506) ;

a memory (1508) storing instructions which, when executed by the processor (1506) , cause the processor (1506) to perform the method (1400) of any of claims 54 to 60.
A computer program (1510) comprising instructions which, when executed by at least one processor (1506) , cause the at least one processor (1506) to carry out the method (1100, 1200, 1300, 1400) of any of claims 1 to 38, 40 to 52, and 54 to 60.
A carrier (1508) containing the computer program (1510) of claim 62, wherein the carrier (1508) is one of an electronic signal, optical signal, radio signal, or computer readable storage medium.
A telecommunications system (10, 60, 60′, 60″) comprising:

one or more UEs (100) ;

a first network node (110) of claim 39; and

one or more second RAN nodes (105-3) of claim 53 and/or one or more first RAN nodes (105-1) of claim 61.