HK40018401A - Method and device for network-initiated packet data unit (pdu) session establishment - Google Patents

Description

Method and arrangement for network initiated packet data unit, PDU, session establishment in a telecommunication network

Technical Field

The present disclosure relates generally to packet data unit, PDU, session establishment between a user equipment, UE, and a data network identified by a data network name, DNN, in a telecommunications network, and more particularly to network initiated PDU session establishment when registering a UE in a fifth generation core network 5, GC, telecommunications system.

Background

In a fourth generation 4G evolved packet core, EPC, system, a user equipment, UE, may attach to a 4G/EPC system to obtain a connection to a packet data network, PDN. A PDN connection is defined as an association between a UE (e.g. represented by an internet protocol IP address) and a packet data network PDN (represented by an access point name APN).

An APN is a label according to the domain name system DNS naming convention that describes an access point to a packet data network. A list of authorized/subscribed APNs for a given UE and characteristics of the PDN connection for each APN (e.g. IP versus non-IP type, default quality of service QoS, etc.) are stored in a home subscriber server HSS of the telecommunication system as part of the subscription information for each UE or subscriber.

The subscription profile information may contain at least a configuration of a default APN. A given UE may have at most two default APNs, e.g., one default APN for a PDN of "IP" type and another default APN that may belong to a PDN of "non-IP" type.

Prior to the third generation partnership project 3GPP release 15(3GPP Rel-15), to deliver the first set of 5G standards, in the attach procedure, the UE should include a PDN connection request procedure, and the EPC core network should establish a PDN connection for the default APN when the UE does not provide an APN. A UE connected in long term evolution LTE/EPC should have at least one active PDN connection, otherwise LTE/EPC will detach the UE from the system.

Voice over LTE (VoLTE) UEs based on ir.92 IP multimedia subsystem IMS voice and short message service SMS profiles support the use of APNs during attach procedures and also rely on a default APN for the first PDN connection that has to be established.

In 3GPP Rel-15, a feature has been introduced that allows "attach without PDN connection" where the UE can connect to the LTE/EPC system without any active PDN connection. This feature is controlled by an additional "PDN connection limited" flag. When this flag is set, and if the mobility management entity MME and the UE support attachment without PDN connectivity, the flag indicates to the MME: the MME will not establish any non-emergency PDN connections for the user.

The possibility of a UE attaching to a 5G telecommunications network without an active PDN connection has become the baseline mode of operation in 5G, in addition to the fact that the concepts of PDN connection and APN have been renamed to packet data unit PDU session and data network name DNN, respectively.

Furthermore, according to the current releases of the technical specifications 3GPP TS 23.501 and 23.502, PDU sessions can only be established upon request by the UE. At most, the 5GC can trigger a specific application in the UE according to a request from the application server AS. Upon receiving such a trigger message, the UE shall pass the message to the application identified in the UE, where the application identified in the UE may establish a PDU session with a particular DNN.

Currently, there is no mechanism defined in 3GPP for the 5GC itself to trigger the UE to establish a PDU session in the 5 GC. In other words, the current 5GC may not have the same behavior as the EPC with respect to the processing of the default APN/DNN. If the user subscription marks IMSAPN/DNN as the default APN, the 5GC will not trigger the establishment of DNN during registration of the 5 GC.

Existing mechanisms for PDU session establishment may be: the initiation by the UE after invocation by an application server outside the 5GC network can also be initiated by the network NW, even in this NW-initiated approach, the actual PDU session is established by the UE.

The network-initiated PDU session establishment procedure currently defined by 3GPP is suitable as a device triggering mechanism for internet of things IoT devices, for which the mechanism requires the UE to establish a PDU session triggered by the IoT application platform. The device trigger request is accomplished by sending an SMS to the UE, including information required for the UE (i.e., 5GC) to support SMS.

However, for certain services (such as, but not limited to, IP multimedia subsystem, IMS, voice services), the network-initiated PDU session establishment procedure currently defined in 3GPP is not appropriate. It is expected that these devices will always connect to the IMS by running a PDU session. In case that the network-initiated PDU session setup procedure is not supported in the 5GC, the PDU session setup procedure is delegated to the UE. Thus, proper UE configuration is advantageous for proper service delivery and user experience.

Disclosure of Invention

There is provided a method of establishing a packet data unit, PDU, session between a user equipment, UE, and a data network identified by a data network name, DNN, in a telecommunications network comprising an access and mobility function, AMF, and a policy control function, PCF.

In a first aspect of the disclosure, the method, when executed in an AMF of a telecommunications network, comprises the steps of: receiving, by the AMF, a registration request initiated by the UE for registering the UE in the telecommunications network; retrieving, by the AMF, PDU session establishment information from the PCF, wherein the retrieving step is triggered upon receipt of a registration request; receiving, by the AMF, PDU session establishment information from the PCF, the PDU session establishment information including one or more DNNs with which the UE is to establish a PDU session, and sending, by the AMF, instructions to the UE, the instructions including one or more DNNs for establishing at least one PDU session between the UE and at least one of the one or more DNNs upon receiving the instructions.

According to the proposed method, the telecommunication network initiates a PDU session setup. That is, triggered by the registration procedure of the UE, the telecommunication network (i.e., AMF) provides the UE with information about the PDU session that the telecommunication network expects to establish when the registration procedure is completed. For example, the AMF may instruct the UE to establish a PDU session directly or immediately after the UE registers in the telecommunication network.

One of the advantages of this solution is that the telecommunication network does not need to rely on proper UE configuration. The telecommunications network controls which PDU sessions are to be established and which DNNs are used for PDU sessions.

This approach is advantageous for mobile network operator MNO services (e.g. IP multimedia subsystem, IMS, voice services), where the establishment of a corresponding PDU session can be indicated to the UE based on subscription information in e.g. a unified data management, UDM, function. In this case, the telecommunications network may ensure that the UE may use PDU sessions that may be required for these types of services when registered in the network or telecommunications system (e.g. a fifth generation core network 5GC telecommunications system).

According to an embodiment of the present disclosure, PDU session setup information received by the AMF from the PCF is included in the UE policy data or the UE policy. In accordance with the present disclosure, providing UE policies to the AMF through the PCF is an established procedure that may be advantageously enhanced by sending PDU session setup information to the AMF.

In another embodiment, wherein the UE policy data received by the AMF from the PDU comprises UE routing policy, URSP, data comprising one or more DNNs for establishing the PDU session by the UE.

According to the present disclosure, the UE policy data may include PDU session type information specifying a type of PDU session, e.g., an IMS voice session to be established with a corresponding DNN of the one or more DNNs.

In an embodiment of the disclosure, the instructions sent by the AMF to the UE may include UE policy data received by the AMF. Since the policy rules may be updated by the MNO, for example, when an updated set of policy rules related to the UE (including one or more DNNs for which a PDU session is to be established) is received by the AMF from the PCF, the updated set of policy rules is forwarded by the AMF to the UE in accordance with the present disclosure.

In a second aspect of the disclosure, the method, when executed in a UE of a telecommunications network, comprises the steps of: initiating, by a UE, a registration request for registering the UE in a telecommunications network; receiving, by the UE, an instruction from an AMF of the telecommunications network in response to the registration request, the instruction including one or more DNNs for establishing at least one PDU session between the UE and at least one of the one or more DNNs, and the UE establishing at least one PDU session with the at least one of the one or more DNNs upon receiving the instruction.

Since the UE receives information for establishing at least one PDU session from the AMF upon registration with the telecommunications network, additional procedures and signaling in the UE for retrieving and updating information related to DNN and PDU sessions are effectively avoided. For example, the telecommunications network need not rely on proper UE configuration, as the telecommunications network controls which PDU sessions to establish, and which DNNs to use for these PDU sessions.

For example, the DNN may be provided to the UE in a registration complete message. Such registration complete message is a known message in the registration procedure of the UE with the telecommunication network (e.g. 5GC) indicating to the UE that the UE has successfully registered in the telecommunication network. According to the present disclosure, for example, the particular message may be extended with a new information element for conveying a list of DNNs with which the UE should establish a PDU session.

In an embodiment of the second aspect of the disclosure, the instructions received by the UE from the AMF comprise UE policy data, and the UE establishes at least one PDU session according to these UE policy data. For example, upon registration in a telecommunications network (e.g., a 5GC network of a telecommunications system), an IMS voice-capable UE may be instructed to establish a PDU session related to IMS DNN.

According to another embodiment of the second aspect of the present disclosure, when establishing a plurality of sessions with different DNNs, the UE establishes different PDU sessions with different DNNs of the one or more DNNs, respectively, in a sequential manner.

Prior to the step of establishing at least one PDU session by the UE, the UE may first check whether any PDU sessions are to be established with the data network identified by the one or more received DNNs. Thus, the instructions themselves may provide information on when to establish the PDU session, or the UE determines whether to start establishing the PDU session by interpreting the received instructions. Thus, the AMF only provides the UE with the type of instructions and/or the content of the instructions, including how the instructions are processed by the UE.

In a third aspect of the disclosure, the method, when executed in a PCF of a telecommunications network, comprises the steps of: receiving, by the PCF, a request from the AMF for PDU session setup information for the UE, and sending, by the PCF to the AMF, the PDU session setup information including one or more DNNs for establishing at least one PDU session between the UE and at least one of the one or more DNNs.

In an embodiment according to the third aspect of the present disclosure, the PCF sends PDU session setup information in the UE policy data.

In another embodiment of the method according to the third aspect of the present disclosure, the PCF subscribes to events available in the network relating to UE policy data; updating the UE policy data based on the event related to the UE policy data, and transmitting PDU session establishment information in the updated UE policy data.

In this way, it is ensured that the UE receives update information for establishing at least one PDU session upon registration with the telecommunications network, without requiring additional procedures and signaling in the UE for updating information related to DNN and PDU sessions. Furthermore, the telecom operator does not need to rely on appropriate UE updates.

An embodiment of the method according to the third aspect of the present disclosure, wherein the updated UE policy data comprises UE routing policy, URSP, data and DNN selection policy data, the URSP data comprising: session and service continuity SSC mode selection policy MSP data and network slice selection policy NSSP data, wherein both the sscmscp data and NSSP data determine the SSC mode and slice to be selected for a PDU session to be established by a UE. The DNN selection policy data is arranged as at least one of: determining a PDU session to be used by the UE; determining when a new PDU session should be established with a new DNN and indicating the access type of the PDU session to be requested to a certain DNN.

In a fourth aspect of the present disclosure, an access and mobility function, AMF, or AMF node, arranged for initiating a packet data unit, PDU, session between a registered user equipment, UE, and a data network identified by a data network name, DNN, in a telecommunications network is presented, the AMF comprising:

-a receiving module arranged for receiving a registration request initiated by a UE for registering the UE in a telecommunications network;

-a retrieving module arranged for retrieving PDU session setup information from a policy control function PCF in the telecommunications network, wherein the retrieving module is activated upon reception of a registration request by the receiving module, the receiving module further being arranged for receiving PDU session setup information from the PCF, the PDU session setup information comprising a list of one or more DNNs with which the UE is to establish a PDU session, and

-an instructing module arranged for instructing the UE to establish at least one PDU session between the UE and at least one DNN of the list of one or more DNNs.

In a fifth aspect of the present disclosure, a user equipment, UE, is presented, which is arranged for establishing a packet data unit, PDU, session in a telecommunication network between the UE and a data network identified by a data network name, DNN, the UE comprising:

-a registration module configured for initiating a registration request for registering the UE in the telecommunication network;

-a receiving module arranged for receiving, from an access and mobility function AMF in the telecommunications network, a list of one or more DNNs with which the UE is to establish a PDU session, and

-a PDU establishing module arranged for establishing at least one PDU session between the UE and at least one DNN of the list of one or more DNNs.

In a sixth aspect of the present disclosure a policy and control function, PCF, or PCF node, arranged for initiating a packet data unit, PDU, session between a registered user equipment, UE, and a data network identified by a data network name, DNN, the PCF comprising:

-a receiving module arranged for receiving a request for PDU session setup information for a UE from an access and mobility function, AMF, in a telecommunication network, and

-a sending module arranged for sending a list of one or more DNNs to the AMF for establishing, by the UE, at least one PDU session with at least one DNN of the list of one or more DNNs.

In a seventh aspect of the present disclosure, there is provided a computer program product comprising a computer readable storage medium, the computer program product having instructions which, when executed on at least one processor, cause the at least one processor to perform a method according to a respective one of the first, second and third aspects of the present disclosure.

It will be appreciated that separate computer program products may be provided in connection with the access and mobility functions AMF, the user equipment UE and the policy control function PCF, respectively.

The above-mentioned and other features and advantages of the present disclosure will be best understood from the following description with reference to the accompanying drawings. In the drawings, like reference numerals denote identical parts or parts performing identical or similar functions or operations.

Drawings

Fig. 1 schematically shows a part of the architecture of a fifth generation 5G telecommunications network.

Fig. 2 schematically shows the initiation of a data network name DNN session in a system according to the prior art.

Fig. 3 schematically shows the initiation of a DNN session in another system according to the prior art.

Fig. 4 schematically illustrates an embodiment of a method according to the present disclosure.

Fig. 5 schematically illustrates an embodiment of a method according to the present disclosure.

Fig. 6 schematically illustrates the basic steps involved in a method according to the present disclosure.

Fig. 7 schematically illustrates the basic steps involved in a method according to the present disclosure.

Fig. 8 schematically illustrates the basic steps involved in a method according to the present disclosure.

Fig. 9 schematically shows an example of a network element.

Fig. 10 schematically shows an example of a network element.

Fig. 11 schematically shows an example of a network element.

Detailed Description

In fig. 1, reference numeral 50 denotes a reference architecture of the 5G system. The 5G system architecture includes the following selection of network functions NF:

authentication server function AUSF 55

Access and mobility management function AMF56

A data network DN (e.g. operator service) internet access or third party service 54

Network exposure function NEF62

-NF repository function NRF 61

-network slice selection function NSSF 63

Policy control function PCF60

Session management function SMF 57

Unified data management UDM 59

User plane function UPF 53

Application function AF 58

User equipment UE51

- (radio) access network (R) AN 52.

The functional description of these network functions is specified in 3GPP standard 23.501 "system architecture for 5G systems" in clause 6, the contents of which are incorporated herein by reference. In particular, in fig. 1, reference numeral 50 indicates the system architecture of the 5G telecommunication network in the non-roaming case. I.e. the UE51 is in the telecommunications network to which it originally belongs (i.e. is registered). In other words, the UE51 is in the home telecommunication network.

Fig. 2 is a schematic diagram illustrating the initiation of a data network name DNN session in a system according to the prior art. In particular, reference numeral 100 indicates a signaling diagram highlighting the sequence of events and signaling that occur in establishing a packet data unit, PDU, session between the UE51 and the data network identified by the DNN. The application server 101 sends a device trigger request 102 to the network exposure function NEF 62. NEF62 then authenticates 103 UE51 and ensures that UE51 is authorized to receive data in the telecommunications network. Once authentication and authorization 103 is performed, NEF62 retrieves information 104 about the subscriber service NF from UDM 59. Retrieval typically includes requesting information from the UDM 59 and receiving the requested information from the UDM 59.

Upon identifying an NF, NEF62 sends a device trigger request 105 to the corresponding AMF56 of the identified NF. When the AMF56 receives the device trigger request 105, it forwards the request 106 to the corresponding UE51 and receives the device trigger response 106. The received device trigger response 106 is then forwarded to the UDM 19 and then back to the application server 101 in instances 107, 108, respectively. As is clear from the signaling diagram, the initial trigger request is generated by the application server 101, which in turn is generated by the particular application through the UE 51. Furthermore, in a system operating according to the signaling diagram 100, the network does not provide any information about which DNN or APN the UE51 should be connected to. Thus, UE51 establishes a connection with the default DNN.

Fig. 3 schematically shows the initiation of a DNN session in another system according to the prior art. According to the method 150 shown in fig. 3, the UE51 sends a registration request 1 to the (R) AN 52. Upon receipt of registration request 1, (R) AN 52 selects AMF56, as described in 3GPP TS 23.501, clause 6.3.5.

The (R) AN 52 communicates a registration request 3 to the new AMF 56. Alternatively, if the UE51 is registered in another AMF66, the new AMF56 requests 4 UE context from the old AMF 66. In response to the optional request 4, the old AMF66 responds 5 to the new AMF56 for a Namf _ Communication _ UEContextTransfer call by including the UE's subscription permanent identifier SUPI and mobility management MM context. If SUPI is neither provided by the UE51 nor retrieved from the old AMF66, the identity request procedure 6, 7 is initiated by the AMF56 to send an identity request message 6 to the UE51, which identity request message 6 is responded to by the UE51 with an identity response message 7, which identity response message 7 comprises the subscription hidden identifier SUCI. The UE generates SUCI from SUPI. To ensure confidentiality, it is proposed to transmit SUCI instead of SUPI over a radio interface as one measure in 5 GC.

In the next step, the AMF56 may decide 8 to initiate UE authentication by invoking AUSF 55. If AMF56 obtained SUCI in the previous step, AMF56 will authenticate UE51 and will obtain SUPI as a result of the authentication procedure. The AUSF 55 will perform authentication 9 of the UE and at the same time the AMF56 will initiate NAS security functions. If the AMF has changed, the new AMF56 notifies 10 the old AMF66 that registration of the UE51 in the new AMF56 is complete by calling a Namf _ Communication _ registration completion Notification service operation.

If PEI is not provided by the UE nor retrieved from the old AMF66, the identity request procedure 11 is initiated by the AMF56 to retrieve PEI by sending an identity request message to the UE. Optionally, the new AMF56 initiates the ME identity check 12 by calling the N5g-eir _ MEIdentityCheck _ Get service operation.

The PEI check is performed as described in 3GPP TS 23.501, clause 4.7.

If step 14 is to be performed, the new AMF56 selects 13 the UDM 59 based on SUPI. As described in clause 6.3.8 of 3GPP TS 23.501, the AMF56 selects UDM 59. If a change has occurred to the AMF56 since the last registration, or if the UE51 provides SUPI that does not reference a valid context in the AMF56, or if the UE51 is registered to the same AMF, it is already registered to a non-3 GPP access, i.e. the UE51 registers with the non-3 GPP access and initiates the registration procedure to add the 3GPP access, the new AMF56 registers 14a, 14b with the UDM 59 and subscribes to notifications when the UDM 59 de-registers the AMF 56. The AMF56 retrieves the subscription data and subscribes to notifications when the subscription data is modified.

When the UDM 59 stores the relevant access type with the serving AMF56 as shown in step 14a, it will cause the UDM to initiate 14c numm UEContextManagement _ DeregistrationNotification (if present) to the old AMF66 corresponding to the 3GPP access. The old AMF66 deletes the MM context of the UE 51.

The new AMF56 conditionally selects 15PCF 60 based on SUPI. AMF56 sends the 16Npcf _ ampolicocontrol _ Get service operation to PCF60 to retrieve access and mobility policies for UE51 and UE policies.

UE51 then registers 16 with PCF60, according to the prior art. PCF60 provides the necessary policy information 16a to AMF 56. Alternatively, AMF56 calls 17 Namf _ EventExposure _ Notify, if necessary. As described above, the AMF56 may decide to modify 18 the N2AP UE-TNLA binding to the N3IWF 152. This is done in case the AMF is changed and the old AMF66 has an existing N2AP UE-TNLA binding to the N3IWF for the UE. The N3IWF 152 provides a corresponding N2 response 19 to the new AMF 56.

Optionally, the old AMF66 sends 20 Npcf _ amplilicocontrol _ Delete to the PCF 60. If the old AMF66 previously requested to establish a UE51 context in PCF60, the old AMF66 terminates the UE51 context in PCF60 by invoking the 20 Npcf _ ampolicocontrol _ Delete service operation. The AMF56 completes the registration process 21, 22 with the UE 51.

Fig. 4 schematically illustrates an embodiment of a method according to the present disclosure. In fig. 4, method 200 illustrates an embodiment of a method according to the present disclosure, wherein steps 1-16 are the same as steps 1-16 disclosed with respect to fig. 3 and method 150.

In accordance with the present disclosure, it is proposed that PCF60 responds 16b to the Npcf _ ampolicocontrol _ Get service operation and provides access and mobility policy data for UE51 and UE routing policy URSP to AMF 56. In the URSP, the PCF60 provides DNN selection policies. The policy contains the DNNs that the UE51 will use for the service and each DNN will contain a new indication whether a PDU session to the DNN is to be initiated immediately, i.e. as a first step immediately after the registration of the UE 51. PCF60 then requests that UE51 initiate (i.e., after and in response to the registration acknowledgement) a PDU session to the DNN immediately. The DNN selection policy may contain additional information needed for the UE to complete the PDU session setup, e.g., the PDU session type to be used.

The AMF56 provides 21a new DNN selection policy to the UE51 via NAS signaling with an indication that the 5GC expects a PDU session to be established by the UE. The UE51 checks 23 whether the DNN selection policy includes a request for establishing any PDU session. If so, the UE51 initiates 24 the establishment of the requested PDU session using existing procedures including interactions between the AMC 56, SMF 57, UDM 59, PCF60 and UPF 53 in 5 GC.

If more than one PDU session is requested to be established, e.g., if the DNN selection policy includes an indication for more than one DNN (e.g., DNN1 and DNN2), then UE51 should first establish a PDU session with DNN1 and then with DNN 2.

Fig. 5 schematically illustrates an embodiment of a method 250 according to the present disclosure. As described above, PCF60 may update the indication (policy or rule) sent to UE51 at any time. One way to achieve this is for the PCF60 to subscribe to certain events (e.g., AMF56 service Namf _ EventExposure available) or to subscribe to updates at the UDR (e.g., using the nurr _ User _ Data _ Management service). Upon the occurrence of a certain event, PCF60 may update Npcf _ amplilicocontrol _ UpdateNotify operation policy/rule to UE51 via AMF 56. As shown in fig. 5, the AMF56 may extend the UE51 configuration update procedure. A separate step may also be used, for example, where PCF60 operates a Namf _ Communication _ N1N2MessageTransfer using the AMF56 service.

According to the method 250, the AMF56 determines 251 the necessity to change the UE51 configuration for various reasons (e.g., UE mobility change, NW policy, UE subscription change, or the UE51 needs to perform a registration procedure). If the UE51 is in the CM-IDLE, the AMF56 triggers a network triggered service request.

If the service area restrictions for the UE51 are updated, the AMF56 may include a list of handover restrictions in an N2message, which N2message conveys a UE configuration update command to the UE 51. Thus, the AMF56 sends 252 a UE configuration update command to the UE51, which UE configuration update command contains UE parameters (e.g. 5G-GUTI, TAI list, allowed NSSAI, NITZ, mobility restrictions, LADN information, allowed NSSAI, NITZ, UE configuration update cause, UE policy/rules).

If the AMF56 wants to update these NAS parameters without triggering UE re-registration, the AMF56 includes only one or more of the following: 5G-GUTI, TAI list, allowed NSSAI, NITZ network identification and time zone, mobility restriction parameter, or LADN information. The AMF56 also includes in the UE configuration update command 252 a UE configuration update reason indicating whether the UE51 should acknowledge the command or, in case the command is sent to trigger a re-registration, a registration update request parameter indicating the reason for the re-registration and related information about the UE behaviour, e.g. waiting for a CM-IDLE to perform the re-registration. The AMF56 includes updated UE policies/rules, e.g., a new DNN selection policy in the case where the PCF60 has provided updated UE policies/rules.

If the UE configuration update 252 cause requires confirmation of the UE configuration update command, the UE51 will send 253 a UE configuration update complete message to the AMF 56. The AMF56 should request acknowledgement of all UE configuration updates except NITZ. If the acknowledgement is received, the UE51 executes the new/updated UE policy/rule.

Fig. 6 schematically illustrates the basic steps involved in a method 300 according to the present disclosure. Figure 6 shows a user equipment UE51 being registered in a telecommunications network; 600 and a data network identified by a data network name DNN, 300. The telecommunications network comprises an access and mobility function AMF 56; 66; 500 and a policy control function PCF 60; 700, and the method 300 comprises the steps of: by the AMF 56; 66; 500 receive 3; 310 is performed by the UE 51; 600 for registering the UE51 in the telecommunications network; 600.

the method 300 further comprises the steps of: by the AMF 56; 66; 500 from PCF 60; 700, retrieving 16; 320 PDU session setup information, wherein, upon receipt of 3; 310 the retrieval 16 upon registration request; step 320 is triggered. In the next step, AMF 56; 66; 500 from PCF 60; 700 receives 16 b; 330 PDU session setup information, including the UE 51; 600 one or more DNNs with which to establish a PDU session. In a further step, the AMF 56; 66; 500 to the UE 51; 600 sending 21 a; 340 instructions, the instructions comprising one or more DNNs, for causing, at the UE51, the reception of the instructions; 600 and at least one of the one or more DNNs.

The UE routing policies URSP and DNN selection policies are defined in 3GPP TS 23.503 v0.3.0 as follows:

UE routing policy URSP: the UE51 uses this policy to determine how to route outgoing traffic. Traffic may be routed to an established PDU session, may be offloaded to non-3 GPP access outside of the PDU session, or may trigger establishment of a new PDU session. The URSP policy group contains one or more of the following policies:

a) SSC pattern selection strategy sscmrsp: the UE51 uses the policy to associate UE51 applications with the SSC pattern and determine the PDU session to which the traffic should be routed. The policy is also used to determine when a new PDU session should be requested using a new SSC pattern.

b) Network slice selection policy NSSP: the UE51 uses this policy to associate the UE51 application with the SM-NSSAI and determines the PDU session to which the traffic should be routed. The policy is also used to determine when a new PDU session should be requested using a new SM-NSSAI.

c) DNN selection strategy: UE51 uses the policy to associate UE51 traffic with one or more DNNs and determines the PDU sessions to which the traffic should be routed. The policy is also used to determine when a PDU session should be requested from a new DNN. The policy may also indicate the type of access (3GPP or non-3 GPP) that a PDU session should be requested to a certain DNN.

Examples of URSP rules are as follows:

the present disclosure proposes to enhance the respective rules with a new indication for the UE to establish a PDU session as follows:

fig. 7 schematically illustrates the basic steps involved in a method 350 according to the present disclosure. Figure 7 shows a user equipment UE51 being registered in a telecommunications network; 600 and a method 350 of establishing a packet data unit, PDU, session between a data network identified by a data network name, DNN. The telecommunications network comprises an access and mobility function AMF 56; 66; 500 and a policy control function PCF 60; 700. the method 350 includes the steps of: by the UE 51; 600 initiating 1; 360 a registration request for registering the UE51 in the telecommunications network; 600. the method 350 further comprises the steps of: in response to the registration request, by the UE 51; 600 from the AMF56 of the telecommunications network; 66; 500 receiving 21 a; instructions 370, including one or more DNNs, for use at UE 51; 600 and at least one of the one or more DNNs, and a further step of: the UE 51; 600, upon receiving the instruction, establishing 24 with at least one of the one or more DNNs; 380 at least one PDU session.

Fig. 8 schematically illustrates the basic steps involved in a method 400 according to the present disclosure. Figure 8 shows a user equipment UE51 being registered in a telecommunications network; 600 and a data network identified by a data network name DNN, 400. The telecommunications network comprises an access and mobility function AMF 56; 66; 500 and a policy control function PCF 60; 700. the method 400 includes the steps of: by the PCF 60; 700 receiving 16; 410 is from AMF 56; 66; 500 for UE 51; 600 and by PCF 60; 700 to AMF 56; 66; 500 send 16 b; 420 PDU session setup information, including one or more DNNs, for use at UE 51; 600 and at least one of the one or more DNNs.

Fig. 9 schematically shows an example of a network element. More specifically, fig. 9 schematically illustrates an AMF 500 according to the present disclosure. The AMF 500 comprises a receiving module 505 arranged for receiving the data received by the UE 51; 600 for registering the UE51 in the telecommunications network; 600. the AMF 500 further comprises a retrieving module 506 arranged for retrieving information from a policy control function PCF60 in the telecommunications network; 700 retrieves PDU session establishment information, wherein the receiving module 505 activates the retrieving module 506 upon receiving a registration request. The receiving module 505 is further arranged to receive from the PCF 60; the method 700 receives PDU session setup information including a list of one or more DNNs with which the UE is to establish a PDU session. The AMF 500 further comprises an indication module 507 arranged for indicating the UE 51; 600 at the UE 51; 600 and at least one DNN in the one or more DNN lists.

In accordance with the present disclosure, the AMF 500 may provide the following services: termination of the radio access network RAN control plane CP interface, termination of the non-access stratum NAS, NAS ciphering and integrity protection, registration management, connection management, reachability management, mobility management, lawful interception, UE 51; 600 message transfer between session management function SMF, transparent proxy for routing SM messages, access authentication and authorization, transfer of short message service SMs messages with UE, security anchor function SEA, security context management SCM, etc.

The AMF 500 further includes: receivers 501, 502 arranged to receive signals from other network elements in a telecommunications network; and transmitters 503, 504 arranged to transmit signals to other network elements in the telecommunications network. Those skilled in the art understand that the receivers 501, 502 and transmitters 503, 504 may be implemented as a single entity in the network, e.g., a transceiver. The AMF 500 further comprises a memory 509 arranged to store any intermediate values and/or a computer program product which, when executed by the processor 510, causes the AMF 500 to perform a method according to an aspect of the present disclosure. All internal components of the AMF 500 communicate with each other using an internal bus 508.

Fig. 10 schematically shows an example of a network element. More specifically, fig. 10 schematically illustrates a user equipment 600 according to the present disclosure. The UE 600 comprises a registration module 605 arranged for initiating a registration request for registering the UE 600 in a telecommunications network. The UE 600 further comprises a receiving module 606 arranged for receiving from an access and mobility function AMF56 in the telecommunications network; 66; 500 receives a list of one or more DNNs with which UE 600 is to establish a PDU session. UE 600 also includes a PDU establishing module 607 arranged for establishing at least one PDU session between UE 600 and at least one DNN of the list of one or more DNNs.

The UE 600 further includes: a receiver 601, 602 arranged to receive signals from other network elements in a telecommunications network; and transmitters 603, 604 arranged to transmit signals to other network elements in the telecommunications network. Those skilled in the art understand that the receivers 601, 602 and transmitters 603, 604 may be implemented as a single entity in the network, e.g., a transceiver. The UE 600 further comprises a memory 609 arranged to store any intermediate values and/or a computer program product which, when executed by the processor 610, causes the UE 600 to perform a method according to an aspect of the present disclosure. All internal components of the UE 600 communicate with each other using an internal bus 608.

Fig. 11 schematically shows an example of a network element. More specifically, fig. 11 illustrates a PCF node 700 according to the present disclosure. PCF 700 comprises a receiving module 705 arranged for receiving from an access and mobility function AMF56 in a telecommunications network; 66; 500 receive for UE 51; 600 of PDU session setup information. PCF 700 also includes a sending module 706 arranged to send to AMF 56; 66; 500 sends a list of one or more DNNs for use by UE 51; 600 establish at least one PDU session with at least one DNN from the one or more DNN lists.

PCF 700 further comprises: a receiver 701, 702 arranged to receive signals from other network elements in a telecommunications network; and transmitters 703, 704 arranged to transmit signals to other network elements in the telecommunications network. Those skilled in the art understand that the receivers 701, 702 and transmitters 703, 704 may be implemented as a single entity in the network, e.g., a transceiver. PCF 700 further comprises a memory 709 arranged to store any intermediate values and/or computer program products which, when executed by processor 710, cause PCF 700 to perform a method according to an aspect of the present disclosure. All internal components of PCF 700 communicate with each other using internal bus 708.

Other variations to the disclosed examples can be understood and effected by those skilled in the art in practicing the claimed disclosure, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. A computer program may be stored/distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the internet or other wired or wireless telecommunication systems. Any reference signs in the claims shall not be construed as limiting the scope.

The present disclosure is not limited to the examples disclosed above, and those skilled in the art may make modifications and enhancements without necessarily applying the inventive techniques, without departing from the scope of the present disclosure as disclosed in the appended claims.

Claims (16)

1. A method of establishing a packet data Unit, PDU, session between a registered user Equipment, UE, (51; 600) and a data network identified by a data network name, DNN, in a telecommunication network comprising an Access and mobility function, AMF, (56; 66; 500) and a policy control function, PCF, (60; 700), the method comprising the steps of:

-the AMF (56; 66; 500) receiving (3; 310) a registration request initiated by a UE (51; 600) for registering the UE (51; 600) in the telecommunication network;

-said AMF (56; 66; 500) retrieving (16; 320) PDU session establishment information from said PCF (60; 700), wherein said retrieving (16; 320) step is triggered upon receipt (3; 310) of said registration request;

-said AMF (56; 66; 500) receiving (16 b; 330) PDU session setup information from said PCF (60; 700), said PDU session setup information comprising one or more DNNs with which said UE (51; 600) is to establish a PDU session, and

-the AMF (56; 66; 500) sending (21 a; 340) an instruction to the UE (51; 600) comprising one or more DNNs for establishing at least one PDU session between the UE (51; 600) and at least one of the one or more DNNs upon reception of the instruction.

2. The method of claim 1, wherein the PDU session setup information received by the AMF from the PCF is included in UE policy data.

3. The method of claim 2, wherein the UE policy data comprises UE routing policy, URSP, data, and the URSP data comprises the one or more DNNs used to establish PDU sessions by the UE.

4. The method of claim 2 or 3, wherein the UE policy data includes PDU session type information specifying a type of PDU session to be established with a respective DNN of the one or more DNNs.

5. A method according to claim 2, 3 or 4, wherein the instruction comprises the UE policy data.

6. A method of establishing a packet data Unit, PDU, session between a registered user Equipment, UE, (51; 600) and a data network identified by a data network name, DNN, in a telecommunication network comprising an Access and mobility function, AMF, (56; 66; 500) and a policy control function, PCF, (60; 700), the method comprising the steps of:

-the UE (51; 600) initiating (1; 360) a registration request for registering the UE (51; 600) in the telecommunication network;

-in response to the registration request, the UE (51; 600) receiving (21 a; 370) an instruction from an AMF (56; 66; 500) of the telecommunications network, the instruction comprising one or more DNNs for establishing at least one PDU session between the UE (51; 600) and at least one of the one or more DNNs, and

-the UE (51; 600), upon receiving the instruction, establishing (24; 380) at least one PDU session with at least one of the one or more DNNs.

7. The method according to claim 6, wherein the instruction comprises UE policy data and the UE (51; 600) establishes the at least one PDU session in accordance with the UE policy data.

8. The method of claim 6 or 7, wherein the UE (51; 600) establishes different PDU sessions with different ones of the one or more DNNs, respectively, in a sequential manner.

9. A method of establishing a packet data Unit, PDU, session between a registered user Equipment, UE, (51, 600) and a data network identified by a data network name, DNN, in a telecommunication network comprising an Access and mobility function, AMF, (56; 66; 500) and a policy control function, PCF, (60; 700), the method comprising the steps of:

-the PCF (60; 700) receiving (16; 410) a request for PDU session setup information for the UE (51; 600) from an AMF (56; 66; 500), and

-the PCF (60; 700) sending (16 b; 420) PDU session setup information to the AMF (56; 66; 500), the PDU session setup information comprising one or more DNNs for establishing at least one PDU session between the UE (51; 600) and at least one of the one or more DNNs.

10. The method of claim 9, wherein the PCF transmits the PDU session setup information in UE policy data.

11. The method of claim 10, further comprising the step of:

-said PCF (60; 700) subscribing to events relating to UE policy data available in said network;

-said PCF (60; 700) updating UE policy data based on said event (51; 600) related to UE policy data, and

-said PCF (60; 700) sending said PDU session establishment information in updated UE policy data.

12. The method of claim 11, wherein the updated UE policy data comprises UE routing policy, URSP, data and DNN selection policy data, wherein the URSP data comprises:

-session and service continuity SSC pattern selection policy MSP data, and

-network slice selection policy, NSSP, data, wherein both sscmscp data and NSSP data determine the SSC pattern and slice selected for a PDU session to be established by the UE (51; 600), the DNN selection policy data being arranged for at least one of:

-determining a PDU session to be used by the UE (51; 600);

-determining when a new PDU session should be established with a new DNN, and

-indicating the access type of the PDU session to be requested to a certain DNN.

13. An access and mobility function, AMF, (56; 66; 500) arranged for initiating a packet data unit, PDU, session between a registered user equipment, UE, (51; 600) and a data network identified by a data network name, DNN, in a telecommunications network, the AMF (56; 66; 500) comprising:

-a receiving module (505) arranged for receiving a registration request initiated by the UE (51; 600) for registering the UE (51; 600) in the telecommunication network;

-a retrieving module (506) arranged for retrieving PDU session establishment information from a policy control function, PCF, (60; 700) in the telecommunication network, wherein the retrieving module (506) is activated upon reception of the registration request by the receiving module (505), the receiving module (505) further being arranged for receiving PDU session establishment information from the PCF (60; 700), the PDU session establishment information comprising a list of one or more DNNs with which the UE (51; 600) is to establish a PDU session, and

-an instructing module (507) arranged for instructing the UE (51; 600) to establish at least one PDU session between the UE (51; 600) and at least one DNN of the list of one or more DNNs.

14. A user Equipment, UE, (51; 600) arranged for establishing a packet data Unit, PDU, session between the UE (51; 600) and a data network identified by a data network name, DNN, in a telecommunication network, the UE (51; 600) comprising:

-a registration module (605) arranged for initiating a registration request in the telecommunication network for registering the UE (51; 600);

-a receiving module (606) arranged for receiving a list of one or more DNNs with which the UE (51; 600) is to establish a PDU session from an Access and mobility function, AMF, (56; 66; 500) in the telecommunications network, and

-a PDU establishment module (607) arranged for establishing at least one PDU session between the UE (51; 600) and at least one DNN of the list of one or more DNNs.

15. A policy and control function, PCF, (60; 700) arranged for initiating a packet data Unit, PDU, session between a registered user Equipment, UE, (51; 600) and a data network identified by a data network name, DNN, the PCF (60; 700) comprising:

-a receiving module (705) arranged for receiving a request for PDU session establishment information for the UE (51; 600) from an Access and mobility function, AMF, (56; 66; 500) in a telecommunication network, and

-a sending module (706) arranged for sending a list of one or more DNNs to the AMF (56; 66; 500) for the UE (51; 600) to establish at least one PDU session with at least one DNN of the list of one or more DNNs.

16. A computer program product comprising a computer-readable storage medium comprising instructions that, when executed on at least one processor, cause the at least one processor to perform the method according to any one of claims 1-12.