Patent Description:
The Third Generation Partnership Project (3GPP) is currently developing the standards for 5GS, which refers to the new generation of radio systems and network architecture. <NUM> is expected to provide higher bitrates and coverage than the current LTE systems. Some estimate that <NUM> will provide bitrates one hundred times higher than LTE offers. <NUM> is also expected to increase network expandability up to hundreds of thousands of connections. The signal technology of <NUM> is anticipated to be improved for greater coverage as well as spectral and signaling efficiency.

In view of the co-existence of <NUM> and <NUM> communication technologies, 3GPP has defined some procedures concerning inter-system mobility. For example, 3GPP has defined, in TS <NUM>, that when a user equipment (UE) establishes a packet data network (PDN) Connection in EPS, a competent Mobility Management Entity (MME) of the UE decides whether the PDN connection supports 5GS Interworking based on information such as user equipment capability, subscription data. 3GPP TS <NUM> has also defined that MME shall delete the PDN connection which is not applicable for 5GS interworking after mobility from EPS to 5GS.

<NPL>, discloses a new indication flag, "5GS Interworking without N26," in the Indication Flags Information Element (IE) within the Create Session Request message to convey whether N26 is supported or not.

<NPL>, discloses a method for introducing a "Return Preferred" indication in the forward relocation request and context response messages.

<NPL>, discloses a method for clarifying the behavior of both mobile management entity (MME) and (access and mobility management function) AMF based on the "Return Preferred" indication over N26.

<NPL>, discloses a method for addressing the risk of the AMF required to release PDU Sessions associated with a single - network slice selection assistance information (S-NSSAls) not allowed according to the UE's subscribed S-NSSAIs during mobility from EPS to 5GS.

Furthermore, the embodiments of the invention are those defined by the claims. Moreover, examples and embodiments, which are not covered by the claims are presented not as embodiments of the invention, but as background art or examples useful for understanding the invention.

The existing protocols, however, still fail to cover certain scenarios in which the respective network node, such as an MME or a gateway node, cannot function properly due to a lack of information on the updated 5GS interworking.

Accordingly, there exists a desire for an improvement of 5GS interworking handling.

Implementations of the technique presented herein are described herein below with reference to the accompanying drawings, in which:.

<FIG> illustrates some of the functional blocks within a conventional EPS network architecture and the named interfaces between them. To be more specific, <FIG> includes a Home Subscriber Service (HSS), an MME, a Serving General Packet Radio Service Support Node (SGSN), a UE, an Evolved Universal Terrestrial Radio Access Network (E-UTRAN) node, an SGW, and a PGW. The named interfaces are logical connections between entities.

<FIG> illustrates some of the functional blocks within a <NUM> network architecture and the named interfaces between them. To be more specific, <FIG> includes an Authentication Server Function (AUSF), a Unified Data Management (UDM) block, a Core Access and Authentication Management Function (AMF), an SMF, a PCF, an Application Function (AF), a UE, a (Radio) Access Network ((R)AN), a User Plane Function (UPF), and a Data Network (DN). For simplicity, the (R)AN will be hereinafter referred to as "the RAN. " The named interfaces are logical connections between entities.

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

As described above, during inter-MME mobility, because the 5GS interworking status is not received from a source MME, a target MME does not know the 5GS interworking status of the PDN connection which makes the target MME not able to decide which PDN connection can be transferred to AMF during subsequent mobility from EPS to 5GS. This cannot fulfil the requirement as defined in TS <NUM> Version <NUM>. <NUM> (Technical Specification Group Services and System Aspects; Procedures for the <NUM> System; Stage <NUM> (Release16), hereinafter referred to as "TS <NUM>"), and results in hanging PDN connection(s) in the upstream nodes such as SGW, PGW-C, PCRF or PCF.

3GPP TS <NUM> has defined that when UE establishes a PDN Connection in EPS, the MME decides if the PDN connection supports 5GS Interworking based on information such as UE capability, subscription data. As specified in clause <NUM>. <NUM>, when the UE requests to establish a PDN connection to an Access Point Name (APN), the MME may use the UE's support for 5GC NAS indication included in the UE Network Capability and/or UE's subscription from HSS that includes UE's mobility restriction parameters related to 5GS and/or indication of support for interworking with 5GS for this APN to determine if PGW-C+SMF or a standalone PGW-C should be selected. It is noted that, if restriction for Core Network Type indicates that the UE can access to 5GC, it implies that the UE has <NUM> subscription data.

3GPP TS <NUM> has also defined that an MME shall delete a PDN connection which is not applicable for 5GS interworking after mobility from EPS to 5GS. Without knowing the 5GS interworking status, however, the MME may have difficulty in deciding which PDN connection(s) should be deleted.

<FIG> illustrates an example of 5GS interworking handling in EPS during inter-MME mobility according to the present disclosure. The steps of <FIG> are described as below.

Step <NUM>, 5GS interworking status may be stored in an MME for each active PDN connection. The 5GS interworking status indicates whether the PDN connection supports interworking between an EPS and a 5GS.

The 5GS interworking status may be stored in an MME in the UE context (as specified in 3GPP TS <NUM>, Version <NUM>. <NUM>, Technical Specification Group Services and System Aspects; General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access; Stage <NUM> (Release <NUM>), hereinafter referred to as "TS <NUM>", clause <NUM>. In particular, the 5GS interworking status may be determined based on UE network capability and/or UE subscription data.

Step <NUM>, an inter-MME mobility procedure is initiated from a source MME to a target MME. In the present example, the inter-MME mobility procedure is an idle mobility.

Step <NUM>, the target MME sends a context request to the source MME.

Step <NUM>, in response to the context request, the source MME may send a context response back to the target MME which includes the 5GS interworking status. As an example, the 5GS interworking status may be included in the context response in the form of a 5GS Interworking Indication, "5GSIWKI" (as specified in 3GPP TS <NUM>, Version <NUM>. <NUM>, Technical Specification Group Services and System Aspects; Policy and Charging Control Framework for the <NUM> System; Stage <NUM> (Release <NUM>), hereinafter referred to as "TS <NUM>," clause <NUM>). The 5GS interworking indication may further be included in an Indication Flags IE for each PDN connection, e.g., in MME/SGSN/AMF UE EPS PDN Connections IE. It can be understood that an alternative new indication may also be considered.

Step <NUM>, the idle mobility continues.

<FIG> illustrates another example of 5GS interworking handling in EPS during inter-MME mobility according to the present disclosure. The steps of <FIG> are described as below.

Step <NUM>, similar to step <NUM> described with reference to <FIG>, 5GS interworking status may be stored in an MME for each active PDN connection. The 5GS interworking status may indicate whether the PDN connection supports interworking between an EPS and a 5GS. The 5GS interworking status may further be stored in an MME in the UE context, as specified in 3GPP TS <NUM>. In particular, the 5GS interworking status may be determined based on UE network capability and/or UE subscription data.

Step <NUM>, an inter-MME mobility procedure is initiated from a source MME to a target MME. In the present example, the inter-MME mobility procedure is an S1 based handover procedure.

Step <NUM>, the source MME sends a Forward Relocation Request to a target MME which includes the 5GS interworking status. As an example, the 5GS interworking status may be included, in the form of a 5GS Interworking Indication, "5GSIWKI", as specified in 3GPP TS <NUM>, in an Indication Flags IE for each PDN connection, e.g., in MME/SGSN/AMF UE EPS PDN Connections IE. It can be understood that an alternative new indication may also be considered.

Step <NUM>, the target MME sends a Forward Relocation Response back to the source MME in response to the Forward Relocation Request.

Step <NUM>, the S1 based handover procedure continues.

The 5GS interworking indication sent from the source MME to the target MME enables the target MME to correctly determine, for a given PDN connection, whether it is allowed to be moved to 5GS during inter-MME mobility procedure. This can avoid the hanging PDN connections in upstream nodes, e.g., SGW, PGW, PCRF or PCF, when mobility from EPS to 5GS happens.

Further, during inter-MME handover, because the "NR Restriction in 5GS" and/or "Core Network Type Restrictions" are not received from the source MME, the target MME cannot set "NR Restriction in 5GS" and "Core Network Type Restrictions" in the Handover Restriction List IE in Handover Request message correctly which is not aligned with what is defined in 3GPP TS <NUM> Version <NUM>. <NUM>, Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access Network (E-UTRAN); S1 Application Protocol (S1AP); (Release <NUM>), hereinafter referred to as "TS <NUM>". The absence of "NR Restriction in 5GS" and "Core Network Type Restrictions" may thus result in misbehavior in a target eNB which should inform a UE which target cell(s) can be accessed.

<FIG> shows another example of 5GS interworking handling in EPS during inter-MME handover according to the present disclosure. The steps of <FIG> are described as below.

Step <NUM>, "NR in 5GS Not Allowed" and/or "Core-Network-Restrictions" may be received from HSS and stored in a source MME. "NR in 5GS Not Allowed" may be obtained from Access-Restriction-Data in subscription data. It is noted that this step is optional in case "NR in 5GS Not Allowed" and "Core-Network-Restrictions" are already stored in the source MME.

"Access-Restriction-Data" and "Core-Network-Restrictions" are specified in 3GPP TS <NUM> Version <NUM>. <NUM> (Technical Specification Group Core Network and Terminals; Evolved Packet System (EPS); Mobility Management Entity (MME) and Serving GPRS Support Node (SGSN) related interfaces based on Diameter protocol (Release <NUM>), hereinafter referred to as "TS <NUM>"), clause <NUM>. <NUM> and <NUM>. <NUM>, respectively.

Step <NUM>, an inter-MME handover procedure from the source MME to a target MME is initiated.

Step <NUM>, the source MME sends a "Forward Relocation Request" message to the target MME, in which "NR Restriction in 5GS" and/or "Core Network Type Restrictions" are included. Such information may be included in the Mobility Management (MM) Context, or as a separate information element included in the message level.

Step <NUM>, the target MME sends to the source MME a "Forward Relocation Response" message.

Step <NUM>, the inter-MME handover procedure continues and the target MME may include the "NR Restriction in 5GS" and/or "Core Network Type Restrictions" in Handover Restriction List IE in Handover Request message to be sent to a target eNB.

TS <NUM> has defined the Handover Restriction List IE in Handover Request message and that the Handover Restriction List IE includes "NR Restriction in 5GS" and "Core Network Type Restrictions" (clause <NUM>.

As specified in clause <NUM>. <NUM> of TS <NUM>, Handover Request message is sent by an MME to a target eNB to request the preparation of resources. In particular, TS <NUM> specifies in clause <NUM>. <NUM> that If the Handover Restriction List IE is contained in the Handover Request message, the target eNB shall store this information in the UE context. On the other hand, If the Handover Restriction List IE is not contained in the Handover Request message, the target eNB shall consider that no roaming and no access restriction apply to the UE.

In view of the foregoing, since the target eNB can obtain a complete Handover Restriction List IE which includes "NR Restriction in 5GS" and "Core Network Type Restrictions" during inter-MME handover procedure, the misbehavior in eNB can be avoided.

Still further, in a network where N26 is deployed (i.e. 5GSNN26 is not set to "<NUM>"), when 5GS interworking status is changed, e.g., due to UE network capability change (i.e., N1 mode is disabled or enabled) or subscription data change (i.e., Core-Network-Restrictions change, or APN level Interworking-5GS-Indicator change), PGW-C+SMF cannot get the updated information. This may result in some misbehavior and waste of resource in the network or result in that the PDN connection cannot be enabled for 5GS interworking in time.

As an example, when UE Network capability is changed from Enabled N1 to disable N1, PGW-C+SMF may still send <NUM> related QoS parameter via the (e)PCO IE, which may lead to unpredictable error in UE, and extra/useless signaling towards UE over air and the network even if UE ignores the content of (e)PCO for 5GS parameters.

As another example: when UE supports N1 mode and the restriction of 5GS interworking by subscription data is removed e.g., Core-Network-Restrictions does not restrict 5GC anymore or Interworking-5GS-Indicator is set, PGW-C+SMF shall be notified to be able to send 5GS parameters via the (e)PCO IE, to facilitate the mobility towards 5GS.

<FIG> shows another example of 5GS interworking handling in EPS according to the present disclosure. The steps of <FIG> are described as below.

Step <NUM>, a PDN connection is established between a UE and a gateway node, which may be a PGW-C combined with an SMF, hereinafter PGW-C+SMF. 5GS interworking indication and 5GS interworking without N26 indication are set accordingly. During the PDN connection establishment procedure, UE may indicate whether it supports 5GS parameters removal in (e)PCO in PDN connectivity request message.

Step <NUM>, due to UE network capability change or subscription data change, the 5GS interworking status or MME's capability of N26 interworking may be changed.

The 5GS interworking status may be changed from supported (i.e., the respective PDN connection supports 5GS interworking) to not supported (i.e., the respective PDN connection does not support 5GS interworking), or from not supported to supported. The MME's capability of N26 interworking may be changed during inter-MME inter-PLMN without SGW change mobility procedure.

3GPP TS <NUM> Version <NUM>. <NUM> has defined that UE can disable N1 mode and 3GPP TS <NUM> Version <NUM>. <NUM> has defined the N1 mode in UE network capability IE and that UE shall initiate TAU procedure to notify the MME the changed UE network capability, e.g., when N1 mode is disabled or enabled.

Step <NUM>, the MME sends a Modify Bearer Request via an SGW to the PGW-C+SMF.

The MME may use another message, e.g., Change Notification Request instead of the Modify Bearer Request.

The Modify Bearer Request may include one or more of 5GS Interworking Indication, 5GS Interworking Change Indication, 5GS Interworking without N26 Indication, 5GS Interworking N26 Change Indication and UE capability change indication. The 5GS Interworking Indication indicates whether 5GS interworking is supported; 5GS Interworking Change Indication indicates whether 5GS Interworking status is changed; 5GS Interworking without N26 Indication indicates whether 5GS Interworking without N26 is supported; 5GS Interworking N26 Change Indication indicates whether MME supporting of 5GS interworking with N26 is changed; UE capability change indication indicates whether the 5GS interworking status change is due to UE network capability change.

The above-mentioned indications may be included reusing existing Indication Flags IE or included in another new IE, e.g., PGW Indication Flags.

In the present example, the Modify Bearer Request comprises updated information indicating that the 5GS interworking status with respect to the PDN connection is changed from not supported to supported.

Step <NUM>, the PGW-C+SMF sends a Modify Bearer Response via the SGW to the MME.

Step <NUM>, based on the received Modify Bearer Request, the PGW-C generates the 5GS parameters associated with the PDN connection and each bearer of the PDN connection.

The 5GS parameters associated with the PDN connection comprise S-NSSAI, QoS rules, Session-AMBR and QoS flow description. Among the 5GS parameters, QoS rules, Session-AMBR and QoS flow description are 5GS QoS parameters.

Step <NUM>, the PGW-C+SMF sends an Update Bearer Request to the MME via the SGW for each bearer of the PDN. The Update Bearer Request comprises the 5GS parameters generated by the PGW-C+SMF.

The Update Bearer Request may include an (e)PCO IE which may further include parameters such as the "S-NSSAI", "QoS rules", "Session-AMBR", and "QoS flow descriptions". 3GPP TS <NUM> Version <NUM>. <NUM> has defined the 5GS related parameters in (e)PCO, such as S-NSSAI, Session-AMBR, QoS rules, QoS flow descriptions. The (e)PCO definition is referred to by 3GPP TS <NUM>. Furthermore, if a PDU Session ID is originally generated by the PGW-C+SMF for the PDN connection, PGW-C+SMF may also include the PDC session ID in the (e)PCO IE.

Step <NUM>, the MME may send Modify EPS Bearer Context Request to a UE. In the message, the (e)PCO received from PGW-C+SMF is transparently forwarded to UE.

Step <NUM>, upon receiving the new 5GS parameters, i.e., "S-NSSAI", "QoS rules", "Session-AMBR", and "QoS flow descriptions", the UE associates them with the PDN connection or each bearer of the PDN connection. Such PDN connection is considered as eligible for 5GS interworking or eligible for 5GS interworking with or without N26 from now.

Step <NUM>, the UE responds to the MME with Modify EPS Bearer Context Response.

Step <NUM>, the MME sends Update Bearer Response to the PGW-C+SMF via the SGW.

Steps <NUM>, <NUM>, <NUM> are similar to steps <NUM>, <NUM> and <NUM>, respectively, the description of which thus will not be repeated for the sake of conciseness. It is noted, however, that in the present example referring to <FIG>, the Modify Bearer Request comprises updated information indicating that the 5GS interworking status with respect to the PDN connection is changed from without N26 to with N26 while the 5GS interworking is kept supported.

Step <NUM>, based on the received Modify Bearer Request, the PGW-C generates the 5GS QoS parameters associated with the PDN connection and each bearer of the PDN connection.

Step <NUM>, the PGW-C+SMF sends an Update Bearer Request to the MME via the SGW for each bearer of the PDN. The Update Bearer Request comprises the 5GS QoS parameters generated by the PGW-C+SMF.

The Update Bearer Request may include an (e)PCO IE which may further include parameters such as the "QoS rules", "Session-AMBR", and "QoS flow descriptions". Furthermore, if a PDU Session ID is originally generated by the PGW-C+SMF for the PDN connection, PGW-C+SMF may also include the PDC session ID in the (e)PCO IE.

Step <NUM>, upon receiving new 5GS QoS parameters, i.e., "QoS rules", "Session-AMBR", and "QoS flow descriptions", the UE associates them with the PDN connection or each bearer of the PDN connection. Such PDN connection is considered as eligible for 5GS interworking with N26 from now.

Steps <NUM>, <NUM>, <NUM> are similar to steps <NUM>, <NUM> and <NUM>, respectively, the description of which thus will not be repeated for the sake of conciseness. It is noted, however, that in the present example referring to <FIG>, the Modify Bearer Request comprises updated information indicating that the 5GS interworking status with respect to the PDN connection is changed from supported to not supported.

Step <NUM>, based on the received Modify Bearer Request, the PGW-C+SMF removes the 5GS parameters, and generates an instruction on removing the 5GS parameters associated with the PDN connection and each bearer of the PDN connection. However, PGW-C+SMF may keep the PDU session ID as being used.

Step <NUM>, the PGW-C+SMF sends an Update Bearer Request to the MME via the SGW for each bearer of the PDN. The Update Bearer Request comprises the instruction in the form of a "5GS parameters removal" parameter, which in turn is included in the (e)PCO IE. Furthermore, if a PDU Session ID is originally generated by the PGW-C+SMF for the PDN connection, PGW-C+SMF may also include the PDC session ID in the (e)PCO IE.

Step <NUM>, upon receiving the 5GS parameters removal in (e)PCO, UE removes all 5GS parameters, i.e., "S-NSSAI", "QoS rules", "Session-AMBR", and "QoS flow descriptions", associated with the PDN connection. However, the UE may keep the PDU session ID as being used.

Steps <NUM>, <NUM>, <NUM> are similar to steps <NUM>, <NUM> and <NUM>, respectively, the description of which thus will not be repeated for the sake of conciseness. It is noted, however, that in the present example referring to <FIG>, the Modify Bearer Request comprises updated information indicating that the 5GS interworking status with respect to the PDN connection is changed from with N26 to without N26 while the 5GS interworking is kept supported.

Step <NUM>, based on the received Modify Bearer Request, the PGW-C+SMF removes the 5GS QoS parameters, and generates an instruction on removing the 5GS QoS parameters associated with the PDN connection and each bearer of the PDN connection. However, PGW-C+SMF may keep the PDU session ID as being used.

Step <NUM>, the PGW-C+SMF sends an Update Bearer Request to the MME via the SGW for each bearer of the PDN. The Update Bearer Request comprises the instruction in the form of a "5GS QoS parameters removal" parameter, which in turn is included in the (e)PCO IE.

Step <NUM>, upon receiving the 5GS QoS parameters removal in (e)PCO, UE removes all 5GS QoS parameters, i.e., "QoS rules", "Session-AMBR", and "QoS flow descriptions", associated with the PDN connection. However, the UE may keep the PDU session ID as being used.

It is noted that, if 5GS Interworking status is changed from supported to not supported and UE capability change indication is set which means N1 mode is disabled, the steps performed by PGW-C+SMF for informing the UE may be skipped.

In view of the above, PGW-C+SMF can be updated with the change of 5GS interworking status. This can for example avoid the extra signaling and other resource cost used for providing 5GS parameters to UE if the 5GS interworking is changed from supported to not supported; this can automatically enable the PDN connection to be eligible for 5GS interworking if the 5GS interworking is changed from not supported to supported.

<FIG> is a flowchart illustrating a method <NUM> according to an embodiment of the present disclosure. The method <NUM> is performed at a network device, e.g. a first MME.

In step S1001, the first MME sends an indicator for a PDN connection to a second MME. In an embodiment, the indicator may indicate whether the PDN connection supports interworking between an EPS and a 5GS. In an embodiment, the indicator may be determined by the first MME based on UE network capability and/or UE subscription data. In an embodiment, the indicator indicates whether the PDN connection is allowed to be moved from an evolved packet system (EPS) to a fifth generation system (5GS). In an embodiment, the indicator indicates whether the PDN connection is allowed to be moved from the EPS to the 5GS via N26.

In an embodiment, prior to sending the indicator to the second MME, the first MME may first receive a context request from the second MME, step S1003. The step S1001 of sending may then further comprise sending a context response message to the second MME. The indicator may be included in the context response message for the PDN connection. In an example of the embodiment, the indicator may be included in an indication flags IE of the context response message for the PDN connection.

In an embodiment, the step S1001 of sending may comprise sending a forward relocation request to the second MME. The indicator may be included in the forward relocation request for the PDN connection. In an example of the embodiment, the indicator may be included in an indication flags IE of the forward relocation request for the PDN connection.

<FIG> is a flowchart illustrating a method <NUM> according to an embodiment of the present disclosure. The method <NUM> is performed at a network device, e.g. a second MME.

In step S1101, the second MME receives an indicator for a PDN connection from a first MME. In an embodiment, the indicator may indicate whether the PDN connection supports interworking between an EPS and a 5GS. In an embodiment, the indicator may be determined based on UE network capability and/or UE subscription data. In an embodiment, the indicator indicates whether the PDN connection is allowed to be moved from an evolved packet system (EPS) to a fifth generation system (5GS). In an embodiment, the indicator indicates whether the PDN connection is allowed to be moved from the EPS to the 5GS via N26.

In an embodiment, prior to receiving the indicator from the first MME, the second MME may first send a context request to the first MME, step S1103. The step S1101 of receiving may then further comprise receiving a context response message from the first MME. The indicator may be included in the context response message for the PDN connection. In an example of the embodiment, the indicator may be included in an indication flags IE of the context response message for the PDN connection.

In an embodiment, the step S1101 of receiving may comprise receiving a forward relocation request from the first MME. The indicator may be included in the forward relocation request for the PDN connection. In an example of the embodiment, the indicator may be included in an indication flags IE of the forward relocation request for the PDN connection.

In step <NUM>, the first MME sends a message to a second MME. The message may comprise 5GS related restriction data which is applicable to a UE. In an embodiment, the 5GS related restriction data may comprise at least one of NR restriction in 5GS and Core Network Type Restrictions.

In an embodiment, the message may be a forward relocation request. In an example of this embodiment, the method <NUM> may further comprise a step S1203 of receiving a forward relocation response from the second MME.

In step <NUM>, the second MME receives a message from a first MME. The message may comprise 5GS related restriction data which is applicable to a UE. In an embodiment, the 5GS related restriction data may comprise at least one of NR restriction in 5GS and Core Network Type Restrictions.

In an embodiment, the message may be a forward relocation request. In an example of this embodiment, the method <NUM> may further comprise a step S1303 of sending a forward relocation response to the first MME.

In an embodiment, the method <NUM> may further comprise a step <NUM> of including the at least one of NR Restriction in 5GS and Core Network Type Restrictions in a Hanover Restriction List IE in a handover request message to be sent to a target eNB.

<FIG> is a flowchart illustrating a method <NUM> according to an embodiment of the present disclosure. The method <NUM> is performed at a network device, e.g. an MME.

In step <NUM>, the MME sends a first message to a gateway node. The first message may comprise updated information, the updated information indicating a change of interworking status with a fifth generation system for a PDN connection.

In an embodiment, the gateway node may be a PGW-C combined with an SMF.

In an embodiment, the method <NUM> may further comprise the step <NUM> of receiving a second message from the gateway node in response to the first message. In an example of this embodiment, the second message may comprise 5GS parameters associated with the PDN connection, the 5GS parameters being generated by the gateway node. In another example of this embodiment, the second message may comprise 5GS QoS parameters associated with the PDN connection. In yet another example of this embodiment, the second message may comprise a first instruction on removing 5GS parameters associated with the PDN connection. In yet another example of this embodiment, the second message may comprise a second instruction on removing 5GS QoS parameters associated with the PDN connection.

In an embodiment, the MME communicates with the gateway node via an SGW.

In an embodiment, the 5GS parameters associated with the PDN connection comprise S-NSSAI, QoS rules, Session-AMBR and QoS flow description, and the 5GS QoS parameters associated with the PDN connection comprise QoS rules, Session-AMBR and QoS flow description.

In an embodiment, the first message may be a modify bearer request or a change notification request.

In an embodiment, the second message may be an update bearer request. In an example of the embodiment, the update bearer request comprises an (e)PCO IE for carrying the 5GS parameters or 5GS QoS parameters. As an example, the (e)PCO IE may further comprise a PDU session ID, when the PDU session ID is originally generated by the gateway node for the PDN connection. The (e)PCO IE may be transparently forwarded by the MME to a UE associated with the PDN connection.

<FIG> is a flowchart illustrating a method <NUM> according to an embodiment of the present disclosure. The method <NUM> is performed at a network device, e.g. a gateway node.

In step <NUM>, the MME receives a first message from an MME. The first message may comprise updated information, the updated information indicating a change of interworking status with a fifth generation system for a PDN connection.

In an embodiment, the method <NUM> may further comprise the step <NUM> of sending a second message to the MME in response to the first message. In an example of this embodiment, the second message may comprise 5GS parameters associated with the PDN connection, the 5GS parameters being generated by the gateway node. In another example of this embodiment, the second message may comprise 5GS QoS parameters associated with the PDN connection. In yet another example of this embodiment, the second message may comprise a first instruction on removing 5GS parameters associated with the PDN connection. In yet another example of this embodiment, the second message may comprise a second instruction on removing 5GS QoS parameters associated with the PDN connection.

In an embodiment, the gateway node communicates with the MME via an SGW.

In an embodiment, the second message may be an update bearer request. In an example of the embodiment, the update bearer request may comprise an (e)PCO IE for carrying the 5GS parameters or 5GS QoS parameters. As an example, the (e)PCO IE may further comprise a PDU session ID, when the PDU session ID is originally generated by the gateway node for the PDN connection. The (e)PCO IE may be transparently forwarded by the MME to a UE associated with the PDN connection.

<FIG> is a block diagram of a network device <NUM> according to embodiments of the present disclosure, which can be, e.g., the network device as described in connection with <FIG>.

The network device <NUM> includes a processor <NUM> and a memory <NUM>. Optionally, the network device <NUM> may further include a transceiver <NUM> coupled to the processor <NUM>. The memory <NUM> contains instructions <NUM> executable by the processor <NUM> to cause the network device <NUM> to perform the actions of one of the methods <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM>, respectively. Take method <NUM> for example, the memory <NUM> may contain instructions that, when executed by the processor <NUM>, cause the network device <NUM> to send an indicator for a PDN connection to a second MME. In an embodiment, the indicator indicates whether the PDN connection supports interworking between an EPS and a 5GS. In an embodiment, the indicator indicates whether the PDN connection is allowed to be moved from an evolved packet system (EPS) to a fifth generation system (5GS). In an embodiment, the indicator indicates whether the PDN connection is allowed to be moved from the EPS to the 5GS via N26.

It should be noted that, more details described with reference to <FIG> also apply here and may be omitted.

The memory <NUM> may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor based memory terminal devices, magnetic memory terminal devices and systems, optical memory terminal devices and systems, fixed memory and removable memory, as non-limiting examples.

The processor <NUM> may be of any type suitable to the local technical environment, and may include one or more of general purpose processors, special purpose processors (e.g., Application Specific Integrated Circuit (ASICs)), microprocessors, digital signal processors (DSPs) and processors based on multicore processor architecture, as non-limiting examples.

Claim 1:
A method (<NUM>) performed by a first mobility management entity, MME, the method comprising:
sending (S1001) an indicator for a packet data network, PDN, connection to a second MME,
wherein the indicator indicates whether the PDN connection is allowed to be moved from an evolved packet system, EPS, to a fifth generation system, 5GS, and
wherein the indicator is included in an indication flags information element, IE, of context response message or forward relocation request for the PDN connection .