Patent Description:
A communication system can be seen as a facility that enables communication sessions between two or more entities such as user terminals, base stations/access points and/or other nodes by providing carriers between the various entities involved in the communications path. A communication system can be provided for example by means of a communication network and one or more compatible communication devices. The communication sessions may comprise, for example, communication of data for carrying communications such as voice, electronic mail (email), text message, multimedia and/or content data and so on. Non-limiting examples of services provided comprise two-way or multi-way calls, data communication or multimedia services and access to a data network system, such as the Internet. In a wireless communication system at least a part of a communication session between at least two stations occurs over a wireless link.

A user can access the communication system by means of an appropriate communication device or terminal. A communication device of a user is often referred to as user equipment (UE) or user device. A communication device is provided with an appropriate signal receiving and transmitting apparatus for enabling communications, for example enabling access to a communication network or communications directly with other users. The communication device may access a carrier provided by a station or access point, and transmit and/or receive communications on the carrier.

The communication system and associated devices typically operate in accordance with a given standard or specification which sets out what the various entities associated with the system are permitted to do and how that should be achieved. Communication protocols and/or parameters which shall be used for the connection are also typically defined. One example of a communications system is UTRAN (<NUM> radio). Another example of an architecture that is known as the long-term evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) radio-access technology. Another example communication system is so called <NUM> radio or new radio (NR) access technology.

<CIT> discloses a method and device for allocating an EPS bearer identifier. The method includes mapping a session/connection to an EPS bearer and requesting a UE or an AMF to allocate an EPS bearer identifier to a mapped EPS bearer.

<NPL> discloses that the AMF may assign EBIs (BPS bearer identifier) and that these may be sent to the SMF.

<NPL> discusses a 5GS handover procedure and notes that the procedure does not clearly describe how to map a PDU session to a PDN connection. It discusses which entities need to know the EPS bearer information and which entity allocates EPS bearer ID.

It discloses that EBI is allocated by the AMF and looks at how to minimise session management behaviours in the AMF and how to resolve EBI exhaustion.

According to an aspect there is provided an apparatus according to claim <NUM>.

According to an aspect there is provided a method according to claim <NUM>.

According to an aspect there is provided a computer program comprising computer executable code which when run on at least one processor is configured to perform the steps of the method of claim <NUM>.

According to an aspect there is provided a method according to claim <NUM>.

According to an aspect there is provided a computer program comprising computer executable code which when run on at least one processor is configured to perform the steps in the method of claim <NUM>.

In the above, many different aspects have been described. It should be appreciated that further aspects may be provided by the combination of any two or more of the aspects described above.

Various other aspects are also described in the following detailed description and in the attached claims.

One or more of the following aspects relate to the following technical specifications, the content of which is incorporated herein by reference.

In the following certain embodiments are explained with reference to mobile communication devices capable of communication via a wireless cellular system and mobile communication systems serving such mobile communication devices. Before explaining in detail the exemplifying embodiments, certain general principles of a wireless communication system, access systems thereof, and mobile communication devices are briefly explained with reference to <FIG> to assist in understanding the technology underlying the described examples.

<FIG> illustrates an example of a wireless communication system <NUM>. The wireless communication system <NUM> comprises wireless communication devices <NUM>, <NUM>, <NUM>. The wireless communication devices <NUM>, <NUM>, <NUM> are provided wireless access via at least one base station <NUM> and <NUM> or similar wireless transmitting and/or receiving node or point. The base stations may be evolved node Bs (eNB), next generation node Bs (gNBs) or other. Base stations <NUM> and <NUM> are typically controlled by at least one appropriate control apparatus. The controller apparatus may be part of the base stations <NUM> and <NUM>.

Base stations <NUM> and <NUM> are connected to a wider communications network <NUM> via gateway <NUM>.

Base stations <NUM>, <NUM> and <NUM> associated with smaller cells may also be connected to the network <NUM>, for example by a separate gateway function and/or via the macro level stations. The base stations <NUM>, <NUM> and <NUM> may be pico or femto level base stations or the like. In the example, base stations <NUM> and <NUM> are connected via a gateway <NUM> whilst base station <NUM> connects via the base station <NUM>. In some embodiments, the smaller base stations <NUM>, <NUM> and <NUM> may not be provided.

<FIG> illustrates an example of a control apparatus <NUM>, for example to be integrated with, coupled to and/or otherwise for controlling a base station, such as the base stations <NUM>, <NUM>, <NUM>, <NUM> or <NUM> shown on <FIG>. The control apparatus <NUM> can be arranged to allow communications between a user equipment and a core network. For this purpose the control apparatus comprises at least one random access memory (RAM) 211a and at least on read only memory (ROM) 211b, at least one processor <NUM>, <NUM> and an input/output interface <NUM>. The at least one processor <NUM>, <NUM> is coupled to the RAM 211a and the ROM 211b. Via the interface the control apparatus <NUM> can be coupled to relevant other components of the base station. The at least one processor <NUM>, <NUM> may be configured to execute an appropriate software code <NUM> to implement one or more of the following aspects. The software code <NUM> may be stored in the ROM 211b.

It shall be appreciated that similar components can be provided in a control apparatus provided elsewhere in the network system, for example in a core network (CN) entity or function.

The control apparatus <NUM> can be interconnected with other control entities. The control apparatus <NUM> and functions may be distributed between several control units. In some embodiments, each base station can comprise a control apparatus. In alternative embodiments, two or more base stations may share a control apparatus.

Base stations and associated controllers may communicate with each other via a fixed line connection and/or via a radio interface. The logical connection between the base stations can be provided for example by an X2 or the like interface. This interface can be used for example for coordination of operation of the base stations and performing reselection or handover operations.

<FIG> illustrates an example of a user equipment or wireless communication device <NUM>, such as the wireless communication device <NUM>, <NUM> or <NUM> shown on <FIG>. The wireless communication device <NUM> may be provided by any device capable of sending and receiving radio signals. Non-limiting examples comprise a mobile station (MS) or mobile device such as a mobile phone or what is known as a 'smart phone', a computer provided with a wireless interface card or other wireless interface facility (e.g., USB dongle), personal data assistant (PDA) or a tablet provided with wireless communication capabilities, machine-type communications (MTC) devices, IoT type communication devices or any combinations of these or the like. A device may provide, for example, communication of data for carrying communications. The communications may be one or more of voice, electronic mail (email), text message, multimedia, data, machine data and so on.

The device <NUM> may receive signals over an air or radio interface <NUM> via appropriate apparatus for receiving and may transmit signals via appropriate apparatus for transmitting radio signals. In <FIG> transceiver apparatus is designated schematically by block <NUM>. The transceiver apparatus <NUM> may be provided for example by means of a radio part and associated antenna arrangement. The antenna arrangement may be arranged internally or externally to the mobile device.

The wireless communication device <NUM> may be provided with at least one processor <NUM>, at least one memory ROM 302a, at least one RAM 302b and other possible components <NUM> for use in software and hardware aided execution of tasks it is designed to perform, including control of access to and communications with access systems and other communication devices. The at least one processor <NUM> is coupled to the RAM 211a and the ROM 211b. The at least one processor <NUM> may be configured to execute an appropriate software code <NUM> to implement one or more of the following aspects. The software code <NUM> may be stored in the ROM 211b.

The processor, storage and other relevant control apparatus can be provided on an appropriate circuit board and/or in chipsets. This feature is denoted by reference <NUM>. The device may optionally have a user interface such as key pad <NUM>, touch sensitive screen or pad, combinations thereof or the like. Optionally one or more of a display, a speaker and a microphone may be provided depending on the type of the device.

One or more of the following aspects more specifically relate to interworking between a <NUM> system (5GS - defined in 3GPP TS <NUM>) and evolved packet core network or system (EPS - defined in 3GPP TS <NUM>). However, it will be understood that some of these aspects may be transposed to other radio access technology systems.

This interworking between 5GS and EPS assumes the possibility (upon UE mobility between 5GS and EPS) to move data connections (called "Packet Data Unit (PDU) Sessions" in 5GS and "Packet Data Network (PDN) connections" in EPC) between 5GS and EPS. A PDU Session is a data connection between a terminal and a data network. The data network may be identified by a (DNN) Data Network Name.

EPS differentiates traffic within a PDN connection by so-called "bearers" carrying traffic that share the same quality of service (QoS) requirements over the EPS. These bearers may be identified by respective EPS Bearer Identifier (EBIs) within the EPS.

Mobility between 5GS to EPS assumes that 5GS allocates EBI(s) for traffic that may later on be moved to EPS (regardless of whether mobility to EPS would actually take place later on). For data connections that may later on be moved to EPS, EBI allocation may take place at the establishment of the data connection. Generally, only one EBI is needed at the establishment of the data connections but in some specific cases more than one EBI may be needed. Currently EBI allocation is done by an access management function (AMF) under request of a session management function (SMF). EBI allocation may not be needed for data connections not eligible for mobility between 5GS and EPS. The SMF may be the entity that determines (e.g. based on the target DNN of the data connections) whether a data connection is eligible for mobility between 5GS and EPS and how many EBI(s) are needed at data connection establishment. An allocated EBI may be associated with an allocation retention priority (ARP) of the traffic exchanged over the corresponding EPS bearer. The procedures for EBI allocation are defined in 3GPP TS <NUM> (see section <NUM>.

<FIG> and <FIG> show a schematic representation of a diagram of a data connection establishment procedure for a home routed roaming data connection according to section <NUM>. <NUM> of 3GPP TS <NUM>. The following steps are discussed in details in section <NUM>. <NUM> of 3GPP TS <NUM> and therefore are merely listed hereafter for the sake of conciseness.

In step <NUM>, a UE may send a PDU Session Establishment Request to an AMF via a radio access network (RAN).

In step <NUM>, the AMF may select an SMF. More specifically, the AMF may select a V-SMF, that is the SMF of a visited public land mobile network (PLMN).

In step 3a, the AMF may send an Nsmf_PDUSession_CreateSMContext Request to the V-SMF.

In step 3b, the V-SMF may send an Nsmf_PDUSession_CreateSMContext response to the AMF.

In step <NUM>, the V-SMF may select a user plane function (UPF). More specifically, the V-SMF may select V-UPF, the UPF of the visited PLMN.

In step 5a, the V-SMF may sends an N4 Session Establishment Request to the V-UPF.

In step 5b, the V-UPF may send an N4 Session Establishment Response to the V-SMF.

In step <NUM>, the V-SMF may send an Nsmf_PDUSession_Create Request to a H-SMF, the SMF of the home PLMN.

In step <NUM>, the H-SMF may retrieve session management (SM) subscription data from a user data management (UDM).

In step <NUM>, the H-SMF may perform PDU session authentication/authorization.

In step 9a, the H-SMF may select a policy control function (PCF). More specifically, the H-PCF may select the PCF of the home PLMN.

In step 9b, the H-SMF may perform SM association establishment or SMF initiated SM policy association modification.

In step <NUM>, the H-SMF may select a user plane function (UPF). More specifically, the H-UPF may select the UPF of the home PLMN.

In step <NUM>, the H-SMF may perform SMF initiated SM policy association modification.

In step 12a, the H-SMF may send an N4 Session Establishment Request to the H-UPF.

In step 12b, the H-UPF may send an N4 Session Establishment response to the H-SMF.

In step <NUM>, the H-SMF may send an Nsmf_PDUSession_Create Response to the V-SMF.

In step <NUM>, the V-SMF may send a Namf_Communication_N1N2MessageTransfer message to the AMF.

In step <NUM>, the AMF may send a N2 PDU session request to the RAN.

In step <NUM>, the UE and the RAN may perform RRC reconfiguration.

In step <NUM>, the RAN may send an N2 PDU session request acknowledgement to the AMF.

In step <NUM>, the AMF may send an Nsmf_PDUSession_UpdateSMContext Request to the V-SMF.

In step 19a, the V-SMF may send an N4 Session Modification Request to the V-UPF.

In step 19b, the V-UPF may send an N4 Session Modification Response to the V-SMF.

In step <NUM>, the V-SMF may send an Nsmf_PDUSession_UpdateSMContext Response to the AMF.

In step <NUM>, the V-SMF may send an Nsmf_PDUSession_SMContextStatusNotify message to the AMF.

In step <NUM>, the H-SMF may generate an IPv6 Router Advertisement and send it to the UE via N4 and the H-UPF and V-UPF.

In step <NUM>, the H-SMF may unsubscribe to the modifications of session management subscription data for the DNN and the S-NSSAI for the PDU session. The SMF may deregister for the PDU session.

The above procedure is a home routed roaming scenario because the SMF controlling the PDU Session and the UPF interfacing the DN are in the home PLMN. The V-SMF controls the local user plane resources.

In the above procedure, the V-SMF requests the H-SMF for the creation of the PDU Session at step <NUM> and the H-SMF answers at step <NUM>. The H-SMF would need to retrieve the allocated EBI before step <NUM> in order to transfer the allocated EBI to the UE via steps <NUM> to <NUM>. However, the EBI allocation is currently expected to be done via the V-SMF context of the PDU Session (H-SMF initiated Nsmf_ PDUSession_Update operation) using a procedure defined in 3GPP TS <NUM> V15. <NUM> Figure <NUM>. <NUM>-<NUM> which is not represented in the call flow. This H-SMF initiated Nsmf_ PDUSession_Update operation cannot actually be done before the H-SMF returns the Nsmf_PDUSession_Create response in step <NUM>. Therefore the H-SMF cannot retrieve the allocated EBI before step <NUM>. Therefore, the above procedure is incorrect and cannot work.

For information, the procedure for EBI allocation is defined in 3GPPTS <NUM> Figure <NUM>. <NUM>-<NUM> whose step <NUM> reads: "If the PGW-C+SMF (or H-SMF in case of home routed case), determines, e.g. based on operator policies, S-NSSAI, User Plane Security Enforcement information, that EPS bearer ID(s) needs to be assigned to the QoS flow(s) in the PDU Session, PGW-C+SMF invokes Namf_Communication_EBIAssignment Request (PDU Session ID, ARP list) (via V-SMF Nsmf_PDUSession_Update in case of home routed case). When V-SMF receives Nsmf_PDUSession_Update request from H-SMF for EPS bearer ID allocation request, V-SMF needs to invoke Namf_Communication_EBIAssignment Request (PDU Session ID, ARP list). If the PGW-C+SMF (or H-SMF in case of home-routed roaming) serves multiple PDU sessions for the same DNN but different S-NSSAIs for a UE then the SMF shall only request EBIs for PDU sessions served by a common UPF (PSA). In case different UPF (PSA) are serving those PDU sessions, then the SMF chooses one of the UPF (PSA) for this determination based on operator policy".

This means the current stage <NUM> call flow and specification is not consistent and cannot be implemented at stage <NUM> protocol level.

Furthermore, in many environments the vast majority of PDU Sessions are eligible for 5GS to EPS interworking. Requiring to add within a PDU Session establishment procedure step <NUM> (EBI assignment request) and step <NUM> (EBI assignment response) of section <NUM>. <NUM> of 3GPP TS <NUM> consists in an extra signalling burden. These extra signalling steps should preferably be avoided (in Home routed roaming scenarios and/or in non-roaming LBO roaming scenarios).

One or more of the following aspect propose that, for a PDU session supporting EPS interworking, the AMF may pre-assign one or more EBIs to the PDU session and/or may associate a default ARP received in subscription information during registration for the related S-NSSAI and/or DNN to these EBIs. The AMF includes EBI Information that contains the one or more EBIs and the associated default ARP in the Nsmf_PDUSession_CreateSMContext Request it sends to the SMF to establish the SM Context of the PDU session. This may be done for some or all types of PDU sessions (e.g. home routed roaming PDU sessions, non-roaming PDU sessions and/or local breakout roaming PDU sessions).

For a home route roaming PDU session, the V-SMF forwards the one or more EBIs and associated default ARP to the H-SMF in the Nsmf_PDUSession_Create Request. The H-SMF may return in the Nsmf_PDUSession_Create Response EBI information telling the V-SMF whether these EBIs have been used as allocated by the AMF, revoked and/or used with a modified ARP.

When the one or more EBIs are being revoked or used with a modified ARP, the SMF (e.g. V-SMF for a home routed roaming PDU session) may invoke the EBI Assignment service operation to update the AMF with the EBIs revoked or used with a modified ARP.

If only one EBI is included in the Nsmf_PDUSession_CreateSMContext or Nsmf_PDUSession_Create Request, but the SMF (H-SMF for a home routed roaming PDU session) needs to assign more than one EBI, the SMF may complete first the establishment of the PDU session with one EBI, and then may invoke the AMF EBI Assignment service operation (and Nsmf_PDUSession_Update service operation for a home routed roaming PDU session) to request the allocation of additional EBIs to the PDU session, using existing procedures.

<FIG> and <FIG> show a schematic representation of a diagram of a registration procedure according to section <NUM>. <NUM> of 3GPP TS <NUM>. The following steps are discussed in details in section <NUM>. <NUM> of 3GPP TS <NUM> and therefore are merely listed for the sake of conciseness.

In step <NUM>, a UE may send a registration request to the RAN.

In step <NUM>, the RAN may perform AMF selection. More specifically, the RAN may select a new AMF.

In step <NUM>, the RAN may send a registration request to the new AMF.

In step <NUM>, the new AMF may send an Namf_Communication_UEContextTransfer message to an old AMF.

In step <NUM>, the old AMF may send an Namf_Communication_UEContextTransfer message to the new AMF.

In step <NUM>, the new AMF may send an identity request to the UE.

In step <NUM>, the UE may send an identity response to the new AMF.

In step <NUM>, the new AMF may select an authentication server function AUSF.

In step <NUM>, the new AMF may initiate UE authentication by invoking the selected AUSF.

In step <NUM>, the new AMF may send an Namf_Communication_RegistrationCompleteNotify message to the old AMF.

In step <NUM>, if a permanent equipment identifier has not been already provided by the UE nor retrieved from the old AMF, the new AMF may send an identity request to the UE. The UE may send an identity response to the new AMF.

In step <NUM>, the new AMF may send an N5g-eir_EquipmentldentityCheck_Get message and may perform a permanent equipment identifier check with an equipment identity register (EIR).

In step <NUM>, the new AMF may perform UDM selection.

In step 14a, the new AMF may send a Nudm_UECM_Registration message to the UDM to register with the UDM.

In step 14b, the new AMF may send a Nudm_SDM_Get message to the UDM to retrieve subscription data for the UE.

In step 14c, the new AMF may send a Nudm_SDM_Suscribe message to the UDM to be notified when the subscription data for the UE is modified.

In step 14d, the UDM may send a Nudm_UECM_DeregistrationNotify message to the old AMF to remove the subscription data for the UE.

In step 14e, the old AMF may send Nudm_SDM_Unsubscribe to no longer be notified when the subscription data for the UE is modified.

In step <NUM>, the new AMF may perform PCF selection.

In step <NUM>, the new AMF may perform an access management Policy Association Modification.

In step <NUM>, the new AMF may send an Nsmf_PDUSession_UpdateSMContext message to the SMF to activate one or more user plane connections of one or more PDU Sessions. The new AMF may send an Nsmf_PDUSession_ReleaseSMContext message to the SMF to release any network resources related to the PDU Session.

In step <NUM>, the new AMF may send an AMF Mobility Request to a N3 interworking function (N3IWF).

In step <NUM>, the N3IWF may send an AMF Mobility Response to the new AMF.

In step 20a, the old AMF may perform an AMF-initiated UE Policy Association Termination with the PCF.

In step <NUM>, the new AMF may send a registration accept message to the UE.

In step 21b, the new AMF may perform a UE Policy Association Establishment with the PCF.

In step <NUM>, the UE may send a registration complete message to the new AMF.

In step <NUM>, the new AMF may send an Nudm_SDM_Info to the UDM.

In the above procedure, the AMF may receive the subscription data for the UE in step 14b. This may include the SMF selection subscription data (see section <NUM>. <NUM> and section <NUM>. <NUM> of 3GPP TS <NUM> or Table <NUM>. <NUM>-<NUM> of 3GPP TS <NUM>).

One or more aspects supplement this data with a default ARP to use for the PDU session for an S-NSSAI and/or DNN. That is, in step 14b the new AMF may receive the default ARP to use for the PDU session for an S-NSSAI and/or DNN from the UDM. This is in contrast with existing solutions where only the SMF receives the default ARP from the UDM in session management subscription data within the 5gQoSProfile (see sections <NUM>. <NUM> of 3GPP TS <NUM>).

<FIG> and <FIG> show a schematic representation of a diagram of data connection establishment procedure for a home routed roaming data connection.

The procedure differs from the procedure of <FIG> and <FIG> in that in step 3a for PDU sessions supporting 5GS to EPS interworking (as determined e.g. from the iwkEpsInd subscription information, see section <NUM>. <NUM> of 3GPP TS <NUM> and/or from the UE NAS capabilities), the AMF may pre-assign one or more EBI to the PDU session and/or associate the default ARP received in the subscription information during registration. The AMF includes the one or more EBIs and the default ARP in the Nsmf_PDUSession_CreateSMContext Request.

The procedure differs from the procedure of <FIG> and <FIG> also in that in step <NUM> the V-SMF forwards EBI Information that contains the one or more EBIs and/or default ARP to the H-SMF in the Nsmf_PDUSession_Create Request.

The procedure differs from the procedure of <FIG> and <FIG> in that in step <NUM> the H-SMF may indicate in the Nsmf_PDUSession_Create Response EBI Information indicating whether the one or more EBIs have been used with the default ARP, have been revoked or used with a modified ARP.

This may be done for example by extending the Nsmf_PDUSession_Create Response with one or more of the following information elements (IEs) that are currently defined and used in a H-SMF initiated Update towards the V-SMF:.

The procedure differs from the procedure of <FIG> and <FIG> in that in step <NUM>' the V-SMF updates the AMF using the Namf_EBIAssignment service operation (see section <NUM>. <NUM> of 3GPP TS <NUM>), if the H-SMF revoked some EBI(s) or modified the ARP of some EBI(s). This may require this AMF service operation to be extended to support the possibility to signal a modification of the ARP associated to an EBI.

After the PDU session is established, the H-SMF may invoke the Nsmf_PDUSession Update service operation if it needs to request the allocation of additional EBIs to the AMF, using existing procedures (see section <NUM>. <NUM> of 3GPP TS <NUM>).

<FIG> and <FIG> show a schematic representation of a diagram of data connection establishment procedure for a non-roaming data connection or a roaming local breakout data connection. The following steps are discussed in details in section <NUM>. <NUM> of 3GPP TS <NUM> and therefore are merely listed for the sake of conciseness.

In step <NUM>, a UE may send a PDU Session Establishment Request to an AMF via a RAN.

In step <NUM>, the AMF may select an SMF.

In step <NUM>, the AMF may send an Nsmf_PDUSession_CreateSMContext Request to the SMF.

In step <NUM>, the SMF may retrieve SM subscription data from a DM.

In step <NUM>, the SMF may send an Nsmf_PDUSession_CreateSMContext response to the AMF.

In step <NUM>, the SMF may perform PDU session authentication/authorization.

In step <NUM>, the SMF may select a PCF.

In step 7b, the SMF may perform SM association establishment or SMF initiated SM policy association modification.

In step <NUM>, the SMF may select a UPF.

In step <NUM>, the SMF may perform SMF initiated SM policy association modification.

In step 10a, the SMF may send an N4 Session Establishment Request to the UPF.

In step 10b, the UPF may send an N4 Session Establishment response to the SMF.

In step <NUM>, the SMF may send a Namf_Communication_N1N2MessageTransfer message to the AMF.

In step <NUM>, the UE and the RAN may perform AN-specific resource setup (PDU Session Establishment Accept).

In step <NUM>, the AMF may send an Nsmf_PDUSession_UpdatesSMContext Request to the SMF.

In step 16a, the SMF may send an N4 Session Modification Request to the UPF.

In step 16b, the UPF may send an N4 Session Modification Response to the SMF.

In step <NUM>, the SMF may send an Nsmf_PDUSession_UpdateSMContext Response to the AMF.

In step <NUM>, the SMF may send an Nsmf_PDUSession_SMContextStatusNotify message to the AMF.

In step <NUM>, the SMF may generates an IPv6 Router Advertisement and sends it to the UE via N4 and the UPF.

In step <NUM>, the SMF may unsubscribe to the modifications of session management subscription data for the DNN and the S-NSSAI for the PDU session. The SMF may deregister for the PDU session.

The procedure differs from the procedure of section <NUM>. <NUM> of 3GPP TS <NUM> in that in step <NUM> for PDU sessions supporting 5GS to EPS interworking (as determined e.g. from the iwkEpsind subscription information, see subclause <NUM>. <NUM> of TS <NUM> and/or from the UE NAS capabilities), the AMF may pre-assign one or more EBI to the PDU session and associate them with the default ARP received in the subscription information during registration. The AMF includes EBI Information that contains the one or more EBIs and the default ARP in the Nsmf_PDUSession_CreateSMContext Request.

The procedure differs from the procedure of Figures <NUM>. <NUM>-<NUM> of 3GPP TS <NUM> v5. <NUM> in that in step <NUM>' the SMF updates the AMF using the Namf_EBIAssignment service operation (see section <NUM>. <NUM> of 3GPP TS <NUM>), if it needs to revoke some EBI(s) or modify the ARP of some EBI(s). This may require this AMF service operation to be extended to support the possibility to signal a modification of the ARP associated to the one or more EBIs.

After the PDU session is established, the SMF may invoke the Namf_EBIAssignment service operation if it needs to request the allocation of additional EBIs to the AMF, using existing procedures (see section <NUM>. <NUM> of 3GPP TS <NUM>).

<FIG> show a schematic representation of a diagram of a method performed between a first function (an AMF) and a second function (an SMF) according to an aspect. The first function (the AMF) is a core network function of a first radio access technology system (5GS). The second function (the SMF) is a core network function of the first radio access technology system (5GS).

In step <NUM>, the first function (e.g. AMF) may register and receive a default ARP (e.g. see step <NUM> of <FIG> and <FIG>).

In step <NUM>, the first function (the AMF) receives a request for establishing a data connection interworking between the first radio access technology system (5GS) and a second radio access technology system (EPS) (e.g. see step <NUM> of <FIG> and <FIG> or see step <NUM> of <FIG> and <FIG>). The request may be received from a UE. The data connection may be a roaming data session, such as a home routed roaming data session or a local breakout roaming data session or a non-roaming data session.

In step <NUM>, the first function (the AMF) allocates at least one identifier (e.g. EBI) identifying traffic within the data connection in the second radio access technology system (EPS).

In step <NUM>, the first function (the AMF) generates a request for creating context for the data connection (this is, an Nsmf_PDUSession_CreateSMContext Request) comprising the at least one identifier (e.g. EBI) and/or the default ARP (e.g. see step 3a of <FIG> and <FIG> or step <NUM> of <FIG> and <FIG>).

In step <NUM>, the first function (the AMF) sends the request for creating the context for the data connection (the Nsmf_PDUSession_CreateSMContext Request) comprising the at least one identifier and the default ARP to a second function (e.g. SMF) (e.g. see step 3a of <FIG> and <FIG> or step <NUM> of <FIG> and <FIG>).

In step <NUM>, the first function (e.g. AMF) may receive an update (e.g. Namf_Communication_EBIAssignment Request) comprising an indication of usage of the at least one identifier (e.g. see step <NUM>' of <FIG> and <FIG> or step <NUM>' of <FIG> and <FIG>). The indication of usage may indicate that the at least one identifier has been used with the associated allocation retention priority, that the at least one identifier has been revoked, that the at least one identifier has been used with an allocation retention priority different from the associated allocation retention priority or other.

<FIG> show a schematic representation of a diagram of a method performed between a first function (an AMF) and a second function (an SMF) according to an aspect. The first function (the AMF) may be a core network function of a first radio access technology system (5GS). The second function (the SMF) may be a core network function of the first radio access technology system (5GS).

In step <NUM>, the second function (the SMF) receives a request for creating context for a data connection (this is, an Nsmf_PDUSession_CreateSMContext Request) interworking between a first radio access technology system (5GS) and a second radio access technology system (EPS), wherein the request for creating the data connection comprises at least one identifier (e.g. EBI) identifying traffic within the data connection in the second radio access technology (EPS) (e.g. see step 3a of <FIG> and <FIG> or step <NUM> of <FIG> and <FIG>). The data connection may be a roaming data session, such as a home routed roaming data session or a local breakout roaming data session or a non-roaming data session.

In step <NUM>, the second function (e.g. SMF) may send an update (e.g. Namf_Communication_EBIAssignment Request) comprising an indication of usage of the at least one identifier (e.g. see step <NUM>' of <FIG> and <FIG> or step <NUM>' of <FIG> and <FIG>). The indication of usage may indicate that the at least one identifier has been used with the associated allocation retention priority, that the at least one identifier has been revoked, that the at least one identifier has been used with an allocation retention priority different from the associated allocation retention priority or other.

<FIG> shows a schematic representation of non-volatile memory media 1400a (e.g. computer disc (CD) or digital versatile disc (DVD)) and 1400b (e.g. universal serial bus (USB) memory stick) storing instructions and/or parameters <NUM> which when executed by a processor allow the processor to perform one or more of the steps of the methods of <FIG>.

One or more of the above aspects may present the following advantages.

The stage <NUM> specification may be corrected and made consistent, also allowing stage <NUM> protocol implementation, for the allocation of EBIs during a home route roaming PDU session establishment.

Signaling to establish any type of PDU session (home routed roaming PDU session, non-roaming PDU session and local breakout roaming PDU session) may also be reduced by avoiding the need for an extra step for the SMF to request the allocation of EBIs during the PDU session establishment (considering that the most frequent case is that of PDU Sessions eligible to mobility between 5GS and EPS and that thus require allocation of an EBI corresponding to the default Bearer).

Signalling gains may be obtained when the SMF does not need to revoke the pre-assigned EBIs nor to change the ARP associated to the pre-assigned EBIs (which will be the vast majority of cases).

It will be understood that one or more of the above aspects may be incorporated in a modified version of 3GPP TS <NUM>, for example by incorporating one or more of the following changes.

Following procedures are updated to allocate EPS bearer ID(s) towards EPS bearer(s) mapped from QoS flow(s) and provide the EPS bearer ID(s) to the NG-RAN:.

The UE requested PDU Session Establishment (Non-roaming and Roaming with Local Breakout (clause <NUM>. <NUM>) is modified as follows.

3a: For PDU sessions supporting EPS interworking (as determined e.g. from the subscription information, see Interworking with EPS indication received from UDM, see Table <NUM>. <NUM>-<NUM> and from the UE NAS capabilities), the AMF pre-assigns one EBI to the PDU session for the Default ARP received in the subscription information (see Table <NUM>. <NUM>-<NUM>), and includes in the Nsmf_PDUSession_Create SM Context Request EBI information that contains the allocated EBI together with the Default ARP.

<NUM>': The SMF updates the AMF using the Namf_EBIAssignment service operation, if the SMF needs to revoke the EBI allocated in step 3a or to modify its associated ARP.

After the PDU session is established, the SMF invokes the Namf_EBIAssignment service operation if it needs to request the AMF for allocation of additional EBIs (see Figure <NUM>. <NUM>-<NUM> below).

The UE requested PDU Session Establishment (Home-routed Roaming (clause <NUM>. <NUM>) is modified as follows.

After the PDU session is established, the H-SMF invokes the Nsmf_PDUSession Update service operation if it needs to request the AMF for allocation of additional EBIs (see Figure <NUM>. <NUM>-<NUM> below).

The UE or network requested PDU Session Modification procedure (clause <NUM>. <NUM> and <NUM>. <NUM>) is modified as follows.

NOTE <NUM>: The SMF can also decide to remove the QoS flow if it is not acceptable to continue the service when no corresponding EPS QoS parameters can be assigned.

For home routed roaming scenario, the "SMF serving the released resources" sends an N4 Session Modification Request to request the PGW-U+UPF to release N4 Session corresponding to the revoked EBI(s).

In home routed roaming case, the V-SMF starts a VPLMN initiated QoS modification for the PDU Session and the Namf_Communication_N1N2Message Transfer is invoked by the V-SMF based on the corresponding QoS modification message received from H-SMF.

If the UE is in CM-CONNECTED state, the AMF sends N2 PDU Session Request (N2 SM information received from SMF, NAS message (PDU Session ID, N1 SM container (PDU Session Modification Command))) Message to the (R)AN.

If the UE is in CM-IDLE state and an ATC is activated, the AMF updates and stores the UE context based on the Namf_Communication_N1N2MessageTransfer and step <NUM>-<NUM> are skipped. When the UE is reachable, e.g. when the UE enters CM-CONNECTED state, the AMF forwards the N1 message to synchronize the UE context with the UE.

If a PDU Session from another SMF already exists towards the same DNN, the AMF either rejects the EBI assignment request, or revokes the EBI(s) from the existing PDU Session(s) to the same DNN but different SMF. The AMF makes the decision based on the operator policy.

The AMF stores the DNN and PGW-C+SMF in which the PDU sesson(s) support EPS interworking to UDM in clause <NUM>.

NOTE <NUM>: The above applies only when the S-NSSAI(s) for the PDU Sessions are different, otherwise the same SMF is selected for PDU Sessions to the same DNN.

The PGW-C+SMF sends an N4 Session Establishment/Modification Request to the PGW-U+UPF.

For home routed roaming scenario, if the EBI is assigned successfully, the PGW-C+SMF prepares the CN Tunnel Info for each EPS bearer. If the CN Tunnel info is allocated by the PGW-C+SMF, the PGW-U tunnel info for the EPS bearer may be provided to PGW-U+UPF. If the CN Tunnel info is allocated by PGW-U+UPF, the PGW-U+UPF sends the PGW-U tunnel info for the EPS bearer to the PGW-C+SMF. The PGW-U+UPF is ready to receive uplink packets from E-UTRAN.

NOTE <NUM>: In the home routed roaming scenario the PGW-C+SMF prepares the CN Tunnel Info for each EPS bearer and provide it to V-SMF. Thus when the UE move to EPC network, the V-SMF does not need interact with the PGW-C+SMF to get the EPS bearer context(s).

NOTE <NUM>: If the CN Tunnel info is allocated by the PGW-C+SMF and not provided to PGW-U+UPF at PDU Session establishment, when the UE moves to the target RAT the PGW-U+UPF cannot receive UL data until the PGW-C+SMF has provided the Tunnel Info to the PGW-U+UPF in N4 Session Modification. This causes a short interruption to the UL data during the intersystem handover execution.

If the PGW-C+SMF receives any EBI(s) from the AMF, it adds the received EBI(s) into the mapped EPS bearer context(s).

In home routed roaming scenario, the PGW-C+SMF generates EPS bearer context which includes per EPS bearer PGW-U tunnel information. In addition, if the default EPS bearer is generated for the corresponding PDN Connection of PDU Session (i.e. during the PDU Session establishment procedure), the PGW-C+SMF generates the PGW-C tunnel information of the PDN connection and include it in UE EPS PDN connection.

[Conditional] In non-roaming or LBO scenario, the PGW-C+SMF includes the mapped EPS bearer context(s) and the corresponding QoS Flow(s) to be sent to the UE in the N1 SM container. PGW-C+SMF also indicates the mapping between the QoS Flow(s) and mapped EPS bearer context(s) in the N1 SM container. PGW-C+SMF also includes the mapping between the received EBI(s) and QFI(s) into the N2 SM information to be sent to the NG-RAN. The PGW-C+SMF sends the N1 SM container and N2 SM information to AMF via Namf_Communication_N1N2MessageTransfer. 9b [Conditional] In home routed roaming scenario, the PGW-C+SMF sends mapped EPS bearer context(s), the mapping between the received EBI(s) and QFI(s), and EPS bearer context to V-SMF via Nsmf_PDUSession_Create Response in case of PDU Session Establishment, or via Nsmf_PDUSession_Update Request in case of PDU Session Modification. The V-SMF stores the EPS bearer context, and generates N1 SM container and N2 SM information, and forwards them to AMF via Namf_Communication_N1N2MessageTransfer.

The N1 SM container and N2 SM information are sent to the UE and NG-RAN respectively. The relevant steps of the procedure as specified in the figure above are executed.

Subscription data types used in the Nudm_SubscriberDataManagement Service are defined in Table <NUM>. <NUM>-<NUM> below.

At least a mandatory key is required for each Subscription Data Type to identify the corresponding data. Depending on the use case, for some Subscription Data Types it is possible to use one or multiple sub keys to further identify the corresponding data, as defined in Tables <NUM>. <NUM>-<NUM> and <NUM>. <NUM>-<NUM> below.

The UDM may also determine the Default Configured NSSAI for a UE, based on the PEI. The UDM generates the Routing Indicator Data for the UEs when new Routing ID Data needs to be delivered to a UE.

Service operation name: Nsmf_PDUSession_CreateSMContext.

Description: It creates an AMF-SMF association to support a PDU Session.

Input, Required: SUPI or PEI, DNN, AMF ID (AMF Instance ID).

Input, Optional: PEI, S-NSSAI(s), PDU Session Id, N1 SM container, UE location information, UE Time Zone, AN type, H-SMF identifier/address, list of alternative H-SMF(s) if available, old PDU Session ID (if the AMF also received an old PDU Session ID from the UE as specified in clause <NUM>. <NUM>), Subscription For PDU Session Status Notification, indication that the SUPI has not been authenticated, PCF ID, DNN Selection Mode, UE PDN Connection Context, GPSI, UE presence in LADN service area, GUAMI, backup AMF(s) (if NF Type is AMF), Trace Requirements. Backup AMF(s) sent only once by the AMF to the SMF in its first interaction with the SMF, UE's Routing Indicator or UDM Group ID for the UE, EBI information (that contains the allocated EBI together with the Default ARP).

Output, Optional: Cause, PDU Session ID, N2 SM information, N1 SM container, S-NSSAI(s), EBI information (that contains the revoked EBI or the updated ARP).

When the PDU Session is for Emergency services for a UE without USIM, the AMF provides the PEI and not the SUPI as identifier of the UE. When the PDU Session is for Emergency services of an unauthenticated UE with an USIM, the AMF shall provide both the SUPI and the PEI and shall provide an indication that the SUPI has not been authenticated.

See clause <NUM>. <NUM>, clause <NUM>. <NUM>, clause <NUM>. <NUM> and clause <NUM>. <NUM> for details on the usage of this service operation.

Service operation name: Nsmf_PDUSession_Create.

Description: Create a new PDU Session in the H-SMF or create an association with an existing PDN connection in the home PGW-C+SMF.

Input, Required: SUPI, V-SMF ID, DNN, V-CN Tunnel Info, addressing information allowing the H-SMF to request the V-SMF to issue further operations about the PDU Session.

Input, Optional: S-NSSAI, PCO, Requested PDU Session Type, 5GSM Core Network Capability, Requested SSC mode, PDU Session ID, Number Of Packet Filters, UE location information, subscription get notified of PDU Session status change, PEI, GPSI, AN type, PCF ID, DNN Selection Mode, UE's Routing Indicator or UDM Group ID for the UE, Always-on PDU Session Requested, information provided by V-SMF related to charging in home routed scenario (see TS <NUM> [<NUM>]), EBI information (that contains the allocated EBI together with the Default ARP).

Output, Required: Result Indication, and if success in addition: QFI(s), QoS Profile(s), Session-AMBR, QoS Rule(s), QoS Flow level QoS parameters if any for the QoS Flow(s) associated with the QoS rule(s), H-CN Tunnel Info, Enable pause of charging indication, Selected PDU Session Type and SSC mode.

Output, Optional: PDU Session ID, S-NSSAI, Cause, PCO, UE IP address, IPv6 Prefix allocated to the PDU Session, information needed by V-SMF in case of EPS interworking such as the PDN Connection Type, Reflective QoS Timer, Always-on PDU Session Granted, information provided by H-SMF related to charging in home routed scenario (see TS <NUM> [<NUM>]), EBI information (that contains the revoked EBI or the updated ARP).

See clause <NUM>. <NUM>, clause <NUM>. <NUM> and clause <NUM>. <NUM> for details on the usage of this service operation.

Service operation name: Namf_Communication_EBIAssignment.

Description: The consumer NF uses this service operation to request a bunch of EPS Bearer IDs for a PDU Session, optionally to indicate to the AMF the list of EBI(s) to be released or to indicate ARP relationship with an EBI to be changed.

Inputs, Required: SUPI, PDU Session ID,.

Input, Optional: ARP list, Released EBI list, new (EBI, ARP) relationship.

Outputs, Optional: a list of <ARP, EBI> pair.

The consumer NF invokes the Namf_Communication_EBIAssignment service operation when it determines that one or more EPS Bearer IDs are required for EPS QoS mapping for a PDU Session. The ARP list indicates the number of the requested EBIs, and the corresponding ARP. The AMF uses the ARP list (including ARP priority level, the pre-emption capability and the pre-emption vulnerability) and the S-NSSAI to prioritize the EBI request, AMF can revoke the EBI from an ongoing lower priority PDU Session, if the maximum number of EBIs have been reached and a session with a higher priority requests an EBI. The AMF responds the consumer NF with a cause which indicates whether the assignment is successful or not. If the assignment is successful, the AMF provides a list of <ARP, EBI> pair to the consumer NF.

If the consumer NF determines that some EBIs are not needed, the consumer NF indicates the EBI(s) that can be released in the Released EBI list.

It is noted that while the above describes example embodiments, there are several variations and modifications which may be made to the disclosed solution without departing from the scope of the present invention.

The embodiments may be implemented by computer software stored in a memory and executable by at least one data processor of the involved entities or by hardware, or by a combination of software and hardware. Further in this regard it should be noted that any procedures, e.g., as in <FIG>, may represent program steps, or interconnected logic circuits, blocks and functions, or a combination of program steps and logic circuits, blocks and functions.

Alternatively or additionally some embodiments may be implemented using circuitry. The circuitry may be configured to perform one or more of the functions and/or method steps previously described. That circuitry may be provided in the base station and/or in the communications device.

The term circuitry also covers, for example integrated device.

Claim 1:
An apparatus comprising:
at least one processor; and
at least one memory including computer program code;
the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to:
receive, by a first function, a request for establishing a data connection supporting interworking between a first radio access technology system and a second radio access technology system;
allocate, by a first function, at least one identifier identifying traffic within the data connection in the second radio access technology system; and
cause, by the first function, the at least one identifier to be sent to a second function; wherein the first radio access technology system is a <NUM> system;
the second radio access technology is an Evolved packet system;
the at least one identifier is an Evolved packet system bearer identifier;
the first function is an access management function;
the second function is a session management function;
characterized in that
the at least one identifier is sent to the second function in a Nsmf_PDUSession_CreateSMContext Request; and/or
the at least one identifier is sent to the second function in a Nsmf_PDUSession_Create Request.