WO2020253948A1

WO2020253948A1 - Session management function selection policy with limited assistance information provided by a user equipment

Info

Publication number: WO2020253948A1
Application number: PCT/EP2019/066037
Authority: WO
Inventors: Sung Hwan Won
Original assignee: Nokia Technologies Oy
Priority date: 2019-06-18
Filing date: 2019-06-18
Publication date: 2020-12-24

Abstract

A method comprises causing an access and mobility management function to transmit a request to a policy control function related to session management function selection policy for a respective communications device. The method comprises receiving a response to the request from the policy control function, the response including one or more triggers which cause the access and mobility function to communicate with the policy control function when a protocol data unit session of the respective communication device is to be associated with one or more of a data network name and single network slice selection assistance information.

Description

SESSION MANAGEMENT FUNCTION SELECTION POLICY WITH LIMITED ASSISTANCE INFORMATION PROVIDED BY USER EQUIPMENT

The present disclosure relates to an apparatus, methods, and computer programs and in particular but not exclusively for apparatus, methods and computer programs to be used in a communications system.

Background

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 communications devices.

Access to the communication system may be by means of an appropriate communications device or terminal. A communications 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 communications device. The communications 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.

Summary

According to an aspect, there is provided a method comprising: causing an access and mobility management function to transmit a request to a policy control function related to session management function selection policy for a respective communications device; and receiving a response to the request from the policy control function, the response including one or more triggers which cause the access and mobility function to communicate with the policy control function when a protocol data unit session of the respective communication device is to be associated one or more of a data network name and single network slice selection assistance information.

The request may comprise one of a request to update the session management function selection policy and a request to update the session management function selection policy. The method may comprise causing a message to be sent by the apparatus of the access and mobility function to said policy control function when one or more conditions associated with the one or more triggers occur.

The method may comprise causing a message to be sent by the access and mobility function to said policy control function when one or more conditions associated with the one or more triggers occur during establishment of a protocol data unit session.

The method may comprise receiving from policy control function one or more of one or more of a data network name and single network slice selection assistance information in response to said message.

One or more of said triggers may have one or more conditions associated therewith, said one or more conditions comprising one or more of: the communications device providing no data network name, the communications device providing no single network slice selection assistance information and the communication providing a data network name that is to be updated.

The method may comprise causing the access and mobility function to send one or more of a data network name and single network slice selection assistance information to the policy control function when one or more of a data network name and single network slice selection assistance information is provided by the respective communications device.

The causing of the access and mobility function to send one or more of a data network name and single network slice selection assistance information to the policy control function may occur during establishment of a packet data unit session. The method may performed in an access and mobility function or by an apparatus in the access and mobility function.

According to another aspect there is provided an apparatus comprising at least one processor and at least one memory including computer code for one or more programs, the at least one memory and the computer code configured, with the at least one processor, to cause the apparatus at least to: cause a request to be transmitted a policy control function related to session management function selection policy for a respective communications device; and receive a response to the request from the policy control function, the response including one or more triggers which cause the access and mobility function to communicate with the policy control function when a protocol data unit session of the respective communication device is to be associated one or more of a data network name and single network slice selection assistance information.

The request may comprise one of a request to update the session management function selection policy and a request to update the session management function selection policy. The at least one memory and the computer code may be configured, with the at least one processor, to cause the apparatus to cause a message to be sent to said policy control function when one or more conditions associated with the one or more triggers occur.

The at least one memory and the computer code may be configured, with the at least one processor, to cause the apparatus to cause a message to be sent by the access and mobility function to said policy control function when one or more conditions associated with the one or more triggers occur during establishment of a protocol data unit session.

The at least one memory and the computer code may be configured, with the at least one processor, to cause the apparatus to receive from policy control function one or more of one or more of a data network name and single network slice selection assistance information in response to said message.

The at least one memory and the computer code may be configured, with the at least one processor, to cause the apparatus to send one or more of a data network name and single network slice selection assistance information to the policy control function when one or more of a data network name and single network slice selection assistance information is provided by the respective communications device.

The causing of the sending one or more of a data network name and single network slice selection assistance information to the policy control function may occur during establishment of a packet data unit session.

The apparatus be in or be an access and mobility function.

According to an aspect there is provided an apparatus comprising circuitry configured to: cause a request to be transmitted a policy control function related to session management function selection policy for a respective communications device; and receive a response to the request from the policy control function, the response including one or more triggers which cause the access and mobility function to communicate with the policy control function when a protocol data unit session of the respective communication device is to be associated one or more of a data network name and single network slice selection assistance information.

The request may comprise one of a request to update the session management function selection policy and a request to update the session management function selection policy. The circuitry may be configured to cause the apparatus to cause a message to be sent to said policy control function when one or more conditions associated with the one or more triggers occur.

The circuitry may be configured to cause the apparatus to cause a message to be sent by the access and mobility function to said policy control function when one or more conditions associated with the one or more triggers occur during establishment of a protocol data unit session.

The circuitry may be configured to cause the apparatus to receive from policy control function one or more of one or more of a data network name and single network slice selection assistance information in response to said message.

The circuitry may be configured to cause the apparatus to cause the sending of one or more of a data network name and single network slice selection assistance information to the policy control function when one or more of a data network name and single network slice selection assistance information is provided by the respective communications device.

The causing of the sending of one or more of a data network name and single network slice selection assistance information to the policy control function may occur during establishment of a packet data unit session.

The apparatus be in or be an access and mobility function.

According to another aspect there is provided an apparatus comprising means for: causing a request to be transmitted a policy control function related to session management function selection policy for a respective communications device; and receiving a response to the request from the policy control function, the response including one or more triggers which cause the access and mobility function to communicate with the policy control function when a protocol data unit session of the respective communication device is to be associated one or more of a data network name and single network slice selection assistance information.

The request may comprise one of a request to update the session management function selection policy and a request to update the session management function selection policy.

The means may be for causing the apparatus to cause a message to be sent to said policy control function when one or more conditions associated with the one or more triggers occur. The means may be for causing the apparatus to cause a message to be sent by the access and mobility function to said policy control function when one or more conditions associated with the one or more triggers occur during establishment of a protocol data unit session.

The means may be for causing the apparatus to receive from policy control function one or more of one or more of a data network name and single network slice selection assistance information in response to said message.

The means may be for causing sending of one or more of a data network name and single network slice selection assistance information to the policy control function when one or more of a data network name and single network slice selection assistance information is provided by the respective communications device.

The causing of the access and mobility function to send one or more of a data network name and single network slice selection assistance information to the policy control function may occur during establishment of a packet data unit session.

The apparatus be in or be an access and mobility function.

According to another aps method comprising: receiving at an apparatus in policy control function from an access and mobility management function a request related to session management function selection policy for a respective communications device; and causing a response to be transmitted to the access and mobility function, the response including one or more triggers which cause the access and mobility function to communicate with the policy control function when a protocol data unit session of the respective communication device is to be associated with one or more of a data network name and single network slice selection assistance information.

The method may comprise receiving a message from the access and mobility function when one or more conditions associated with the one or more triggers occur.

The method may comprise receiving a message from the access and mobility function when one or more conditions associated with the one or more triggers occur during establishment of a protocol data unit session. The method may comprise causing the policy control function to provide one or more of one or more of a data network name and single network slice selection assistance information in response to said message.

The method may comprise receiving from the access and mobility function one or more of a data network name and single network slice selection assistance information to the policy control function when one or more of a data network name and single network slice selection assistance information is provided by the respective communications device.

The receiving of one or more of a data network name and single network slice selection assistance information may occur during establishment of a packet data unit session

The method may performed in a policy control function or by an apparatus in the policy control function.

According to another aspect there is provided an apparatus comprising at least one processor and at least one memory including computer code for one or more programs, the at least one memory and the computer code configured, with the at least one processor, to cause the apparatus at least to: receive from an access and mobility management function a request related to session management function selection policy for a respective communications device; and cause a response to be transmitted to the access and mobility function, the response including one or more triggers which cause the access and mobility function to communicate with the policy control function when a protocol data unit session of the respective communication device is to be associated with one or more of a data network name and single network slice selection assistance information.

The at least one memory and the computer code may be configured, with the at least one processor, to cause the apparatus to receive a message from the access and mobility function when one or more conditions associated with the one or more triggers occur.

The at least one memory and the computer code may be configured, with the at least one processor, to cause the apparatus to receive a message from the access and mobility function when one or more conditions associated with the one or more triggers occur during establishment of a protocol data unit session.

The at least one memory and the computer code may be configured, with the at least one processor, to cause the apparatus to cause the policy control function to provide one or more of one or more of a data network name and single network slice selection assistance information in response to said message.

The at least one memory and the computer code may be configured, with the at least one processor, to cause the apparatus to receive from the access and mobility function one or more of a data network name and single network slice selection assistance information to the policy control function when one or more of a data network name and single network slice selection assistance information is provided by the respective communications device.

The receiving of one or more of a data network name and single network slice selection assistance information may occur during establishment of a packet data unit session.

The apparatus may be or in a policy control function.

According to an aspect there is provided an apparatus comprising circuitry configured to: receive from an access and mobility management function a request related to session management function selection policy for a respective communications device; and cause a response to be transmitted to the access and mobility function, the response including one or more triggers which cause the access and mobility function to communicate with the policy control function when a protocol data unit session of the respective communication device is to be associated with one or more of a data network name and single network slice selection assistance information.

The circuitry may be configured to cause the apparatus to receive a message from the access and mobility function when one or more conditions associated with the one or more triggers occur. The circuitry may be configured to cause the apparatus to receive a message from the access and mobility function when one or more conditions associated with the one or more triggers occur during establishment of a protocol data unit session.

The circuitry may be configured to cause the apparatus to cause the policy control function to provide one or more of one or more of a data network name and single network slice selection assistance information in response to said message.

The circuitry may be configured to cause the apparatus to receive from the access and mobility function one or more of a data network name and single network slice selection assistance information to the policy control function when one or more of a data network name and single network slice selection assistance information is provided by the respective communications device.

The apparatus may be or in a policy control function.

According to an aspect there is provided an apparatus comprising means for: receiving from an access and mobility management function a request related to session management function selection policy for a respective communications device; and causing a response to be transmitted to the access and mobility function, the response including one or more triggers which cause the access and mobility function to communicate with the policy control function when a protocol data unit session of the respective communication device is to be associated with one or more of a data network name and single network slice selection assistance information.

The means may be for receiving a message from the access and mobility function when one or more conditions associated with the one or more triggers occur.

The means may be for receiving a message from the access and mobility function when one or more conditions associated with the one or more triggers occur during establishment of a protocol data unit session. The means may be for causing the policy control function to provide one or more of one or more of a data network name and single network slice selection assistance information in response to said message.

The means may be for receiving from the access and mobility function one or more of a data network name and single network slice selection assistance information to the policy control function when one or more of a data network name and single network slice selection assistance information is provided by the respective communications device.

The apparatus may be or in a policy control function.

According to another aspect, there is a method comprising: causing a message to be sent by an access and mobility function to said policy control function when one or more conditions associated with the one or more triggers occur for example during establishment of a protocol data unit session; and receiving from policy control function one or more of one or more of a data network name and single network slice selection assistance information in response to said message.

According to another aspect, there is an apparatus comprising means for: causing a message to be sent by an access and mobility function to said policy control function when one or more conditions associated with the one or more triggers occur for example during establishment of a protocol data unit session; and receiving from policy control function one or more of one or more of a data network name and single network slice selection assistance information in response to said message.

According to another aspect, there is a method comprising: receiving a message from an access and mobility function when one or more conditions associated with the one or more triggers occur for example during establishment of a protocol data unit session; and providing to the access and mobility function one or more of one or more of a data network name and single network slice selection assistance information in response to said message.

According to another aspect, there is an apparatus comprising means for: receiving a message from an access and mobility function when one or more conditions associated with the one or more triggers occur for example during establishment of a protocol data unit session; and providing to the access and mobility function one or more of one or more of a data network name and single network slice selection assistance information in response to said message

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 cause any of the previously described methods to be performed.

According to an aspect, there is provided a computer readable medium comprising program instructions stored thereon for performing at least one of the above methods.

According to an aspect, there is provided a non-transitory computer readable medium comprising program instructions stored thereon for performing at least one of the above methods.

According to an aspect, there is provided a non-volatile tangible memory medium comprising program instructions stored thereon for performing at least one of the above methods.

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.

Brief Description of the Figures

Embodiments will now be described, by way of example only, with reference to the accompanying Figures in which:

Figure 1 shows a schematic representation of a communication system;

Figure 2 shows a schematic representation of a communications device;

Figure 3 shows a schematic representation of an apparatus;

Figure 4 shows a schematic representation of a non-volatile memory medium storing instructions which when executed by a processor allow a processor to perform one or more of the steps of the method of some embodiments;

Figure 5 shows a first signalling flow of some embodiments;

Figure 6 shows a second signalling flow of some embodiments;

Figure 7 shows a third signalling flow of some embodiments:

Figure 8 shows a method performed by an apparatus of an access and mobility function; and Figure 9 shows a method performed by an apparatus of a policy control function. Detailed Description of the Figures

In the following certain embodiments are explained with reference to communications devices capable of communication via a wireless cellular system and communication systems serving such communications devices. Before explaining in detail the exemplifying embodiments, certain general principles of a wireless communication system, access systems thereof, and communications devices are briefly explained with reference to Figures 1 to 4 to assist in understanding the technology underlying the described examples.

An example of wireless communication systems are architectures standardized by the 3rd Generation Partnership Project (3GPP). A latest 3GPP based development is often referred to as 5G. Other examples of radio access system comprise those provided by base stations of systems that are based on technologies such as wireless local area network (WLAN) and/or WiMAX (Worldwide Interoperability for Microwave Access). It should be appreciated that although some embodiments are described in the context of a 5G system, other embodiments may be provided in any other suitable system including but not limited to subsequent systems or similar protocols defined outside the 3 GPP forum.

Reference is made to Figure 1 which shows an example system in which some embodiments may be provided. The system may be a wireless communications. It should be appreciated that the system of Figure 1 is a 5G system but other embodiments may be used in association with any other suitable standard or system.

A communications device 102 is provided. This will be referred to as a UE but it should be appreciated that the device may be any suitable communications device and the term UE is intended to cover any such device. Some examples of communications devices are discussed below and as used in this document the term UE is intended to cover any one or more of those devices and/or any other suitable device.

The communications device has a wireless connection to an access node AN 104. This access node may be a gNB or a ng-eNB. It should be appreciated that the information exchange between the UE and the AMF may alternatively take place over a non 3GPP access to the 5GC (5G core network.). For example this may be over a non 3GPP interworking function for non- 3gpp access N3IWF, a trusted non 3GPP access function TNGF, an access gateway for wireline access W-AGF, or any other similar function.

The AN 104 is configured to communicate with an access and mobility management function (AMF) 110. The AMF may provide functions which relate to UE-based authentication, authorisation, registration, mobility and/or connection management. The AMF 110 is configured to communicate with a session management function (SMF) 112. The SMF may provide session management functions, such allocating Internet Protocol (IP) addresses to UEs.

The AMF 110 and the SMF 112 are configured to communicate with a policy control function (PCF) 114. The PCF may determine policies about mobility and session management for a given UE for the UE, AMF or SMF to enforce.

The access node AN 104 is configured to communicate with a user plane function (UPF) 106. The UPF 106 is configured to communicate with a data network DN 108.

Figure 2 illustrates an example of a communications device 300, such as the wireless communications device 102, 104 or 105 shown on Figure 1. The wireless communications device 300 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 communications devices or any combinations of these or the like.

The device 300 may receive signals over an air or radio interface 307 via appropriate apparatus for receiving and may transmit signals via appropriate apparatus for transmitting radio signals. In Figure 2 transceiver apparatus is designated schematically by block 306. The transceiver apparatus 306 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 communications device 300 may be provided with at least one processor 301a and at least one memory. The at least one memory may comprise at least one ROM 302a and/or at least one RAM 302b. The communications device may comprise other possible components 303 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 communications devices. The at least one processor 301 is coupled to the at least one memory. The at least one processor 301 may be configured to execute an appropriate software code 308 to implement one or more of the following aspects. The software code 308 may be stored in the at least one memory, for example in the at least one 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 304. The device may optionally have a user interface such as key pad 305, 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.

Communication protocols and/or parameters which shall be used for the connection are also typically defined. The communications devices may access the communication system based on various access techniques.

An example apparatus is shown in Figure 3. Figure 3 shows an example of an apparatus 200 for a network function such as an AMF or PCF or SMF any other suitable function. The apparatus comprises at least one memory. The at least one memory may be at least one random access memory (RAM) 211a and/or at least one read only memory (ROM) 211b, at least one processor 212, 213 and an input/output interface 214. The at least one processor 212, 213 is coupled to the RAM 211a and the ROM 211b. The at least one processor 212, 213 may be configured to execute an appropriate software code 215 to implement one or more of the following aspects. The software code 215 may be stored in the ROM 211b.

Figure 4 shows a schematic representation of non-volatile memory media 1600a (e.g. computer disc (CD) or digital versatile disc (DVD)) and 1200b (e.g. universal serial bus (USB) memory stick) storing instructions and/or parameters 1602 which when executed by a processor allow the processor to perform one or more of the steps of any of the methods of any of the embodiments.

One or more of the following aspects relate to a 5G system (5GS). (5G is sometimes referred to as new radio (NR)). However, it will be understood that some of these aspects may be transposed to other radio access technology systems such as UTRAN (3G radio), the long term evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) and/or any other suitable system.

If there is a need to establish a new PDU (protocol data unit) session, a UE generates a PDU (protocol data unit) session establishment request. This may be a session management SM message exchanged between a UE and an SMF. The SM message may be a 5G SM message. The UE may encapsulate the SM message in an UL non access stratum (NAS) transport message. This may be a mobility management message (MM) exchanged between a UE and an AMF. The MM message may be a 5G MM. In order to assist SMF selection by the AMF, the UE may include in the UL NAS Transport message, S-NSSAI (single network slice selection assistance information). If available, the UE may include a mapped S-NSSAI. If available, the UE may include a DNN (data network name) In some embodiments, S-NSSAI may provide an indication of an expected service set. A network slice is a logical end to end network. Each slice may serve a particular service type. A communications device may access a plurality of slices over the same (R)AN (or 5G AN entity connecting the UE to the 5GC), for example. The S-NSSAI is used to identify a network slice that supports a specific set of services. In some embodiments, a S-NSSAI may comprise a SST (slice/service type) and/or a SD (slice differentiator).

However, any of an S-NSSAI (and, if available, a mapped S-NSSAI) and a DNN may not be available when the UE requests PDU session establishment. For example, if the route selection descriptor associated with the traffic descriptor matching the application requesting a PDU session association does not include an S-NSSAI or a DNN, the UE may not include an S-NSSAI or a DNN in the UL NAS transport message.

The AMF may derive the S-NSSAI using one or more of the following:

If the user’s subscription context contains one default S-NSSAI, the AMF uses the default S-NSSAI as the S-NSSAI for the PDU session.

If the user’s subscription context contains two or more default S-NSSAIs, the AMF uses one of the default S-NSSAIs selected by operator policy as the S-NSSAI for the PDU session.

If the user’s subscription context contains no default S-NSSAIs, the AMF uses an S- NSSAI selected based on operator policy as the S-NSSAI for the PDU session.

If the DNN is not available, the AMF derives the DNN as follows using the S-NSSAI (either provided by the UE or selected by the AMF such as described above):

If the user’s subscription context contains the default DNN for the S-NSSAI, the AMF uses the default DNN as the DNN.

If the user’s subscription does not contain the default DNN for the S-NSSAI, the AMF uses a locally configured DNN as the DNN.

Some embodiments may address how the AMF selects a single default S-NSSAI among multiple default S-NSSAIs and a single S-NSSAI among S-NSSAIs in the allowed NSSAI (if no S-NSSAI is provided by the UE).

Some embodiments may address how a DNN is determined according to operator policy (if no DNN is provided by the UE).

In some embodiments, during the registration procedure, using a SMF selection policy association establishment or modification procedure, the AMF may receive, from the PCF, information for S-NSSAI acquisition and/or DNN acquisition. The information may be a trigger. If the trigger is set in the AMF, the AMF contacts a PCF if the conditions such as set out below are met. The information may be used by the AMF to decide whether to contact a PCF during the PDU session establishment if:

the UE does not indicate the S-NSSAI and/or DNN, and S-NSSAI and/or DNN cannot be determined; and/or

the DNN provided by the UE needs to be replaced

Using the SMF selection policy association establishment or modification procedure, the AMF may contact the PCF to acquire an S-NSSAI and/or a DNN.

A registration procedure of some embodiments will now be described.

In the following the PCF may be a visiting PCF (V-)PCF. References to a PCF may be to a home PCF or a (V-)PCF.

If the new AMF selects a new PCF, the new AMF may performs SMF selection policy association establishment with the selected PCF. This will be described in more detail with reference to Figure 5.

If the PCF identified by the PCF ID included in UE context from the old AMF is used, the new AMF may perform SMF selection policy association modification with the PCF. This will be discussed in more detail with reference to Figure 6

If supported, the PCF may provide the AMF with a trigger for S-NSSAI acquisition and/or a trigger for DNN acquisition.

Instead of providing the trigger for DNN acquisition, the PCF may provide one or more S-NSSAIs each of which is associated with a DNN. The S-NSSAI may be an S-NSSAI included in the allowed NSSAI and it may not be associated with a default DNN and the associated DNN may be a subscribed one. Thus the AMF may send a set of S-NSSAIs each of which is included in the allowed NSSAI, is not associated with a default DNN and a list of subscribed DNNs to the PCF.

In some embodiments, the PCF can send a unified trigger which can be used for all cases where DNN and/or S-NSSAI should be replaced or determined. The unified trigger may be a single trigger which makes an AMF contact a PCF when one or more of the following conditions occur:

a DNN provided by the UE needs to be replaced,

an S-NSSAI is not provided by the UE and either there is no default S-NSSAI or there are more than one default S-NSSAI, and

a DNN is not provided by the UE and the default DNN for the S-NSSAI (if available) is not available. In other embodiments there may be a for example one or more of the following triggers: a trigger for DNN replacement, a trigger for S-NSSAI selection, and a trigger for DNN selection.

By way of example, one or more of the following cases may be supported:

A. DNN provided by the UE needs to be replaced;

B. S-NSSAI is not provided by the UE and either there is no default S-NSSAI or there are more than one default S-NSSAI; and

C. DNN is not provided by the UE and the default DNN for the S-NSSAI (if available) is not available,

The trigger may include DNN for replacement.

Reference is made to Figure 5 which shows a SMF selection policy association establishment with a new selected PCF of some embodiments.

This procedure may be used for example in LBO (local break out) and/or non-roaming scenarios. In case of LBO roaming, all SMFs and UPFs may be located in the visited PLMN. In a home-routed roaming scenario, an anchor UPF and corresponding SMF are located in the home PLMN and other UPF/SMF are located in the visited PLMN.

In step 1, the AMF may, based on local policies, decide to establish a SMF selection policy association with the PCF.

In step 2, the AMF requests the PCF to apply SMF selection policies for the UE from the PCF. This may be requested if, for example, the AMF has not yet obtained a SMF selection policy for the UE or if the SMF selection policy in the AMF is no longer valid.

The AMF may send a request to the PCF to establish an SMF selection policy control association with the PCF. The request may be a Npcf SMFSelectionPolicyControl Create message.

The request may include one or more of the following information: a user identifier, for example SUPI (subscriber permanent identifier), internal group information, and one or more UE capabilities.

In some embodiments, alternatively or additionally, the request may include, if available, a GPSI (generic public subscription identifier). This may be retrieved from the UDM (user data management) during for example an update location procedure.

In some embodiments, alternatively or additionally, the request may include one or more of access type and RAT (radio access technology), PEI (permanent equipment identifier), ULI (user location information), UE time zone, and serving network. The subscription data for an UE in a UDR (unified data repository) or other data store may associate the subscriber with one or more groups. A group is identified by an internal group identifier. A UE can belong to one or more groups.

The internal-group identifier(s) corresponding to an UE may be used to apply local policies and to store this information in the UDR.

In some embodiments, the request may include one or more S-NSSAIs in the allowed NSSAI. For example, the request may include a set of S-NSSAIs each of which is included in the allowed NSSAI. One or more or all of the S-NSSAIs may not be associated with a default DNN. Alternatively or additionally, the request may comprise one or more subscribed DNN(s). This is provided for the respective user equipment. This information may be determined in the AMF.

In some embodiments, alternatively or additionally, the request may include an allowed NSSAI (if the allowed NSSAI does not contain any S-NSSAI which is one of the UE’s subscribed S-NSSAI(s) and is marked as default or the allowed NSSAI contains more than one S-NSSAI which is one of the UE’s subscribed S-NSSAI(s) and is marked as default).

In step 3, the PCF responds to the request received in step 2. The PCF may provide in the response a SMF selection related policy control request trigger. This may comprise for example one or more of a list of DNNs subject for replacement, S-NSSAI acquisition information, and DNN acquisition information. The -NSSAI acquisition information, and DNN acquisition information may comprise one or more triggers.

Alternatively or additionally, the PCF can send a set of S-NSSAIs each of which is included in the allowed NSSAI and is not associated with a default DNN. Each of the S- NSSAIs of the set may be associated with a subscribed DNN.

The PCF can send the set of S-NSSAIs instead of the trigger for DNN acquisition,

In some embodiments, the trigger may be a unified trigger which may be used wherever the DNN and/or S-NSSAI needs to be replaced or needs to be determined.

In some embodiments, the trigger may include an S-NSSAI that the AMF should use in case the UE does not provide any S-NSSAI during establishment of a PDU session.

In some embodiments, the trigger may include a list of S-NSSAIs each of which is associated with a DNN. The AMF can use the list if the UE does not provide any DNN during establishment of a PDU session.

The AMF may implicitly subscribed in the PCF to be notified of changes in policies associated with the UE. In step 4, the AMF may deploys the SMF Selection related policy information. This may comprise storing the policy control request trigger of the SMF selection policy association and/or a set of S-NSSAIs each of which is included in the allowed NSSAI and is not associated with a default DNN and each of which NSSAIs is associated with a subscribed DNN.

Reference is made to Figure 6 which shows a SMF selection modification procedure with a PCF during an AMF relocation.

This procedure may apply in LBO and non-roaming scenarios.

In step 1 , when the old AMF and the new AMF belong to the same PLMN (public land mobile network), the old AMF may transfers to the new AMF the SMF selection policy association information. This may include one or more of the policy control request trigger(s) and the PCF ID (identity). The new AMF may retrieve a UE context from the old AMF.

For the LBO case, the new AMF may alternatively or additionally receive the V-PCF ID.

In step 2, the new AMF decides to establish a UE context with the PCF and contacts the PCF identified by the PCF ID received in step 1. The new AMF may decide to establish a UE context based on local policies. The AMF may make a decision to establish a policy association.

In step 3, the new AMF sends an update message to the PCF to update the SMF selection policy association with the (V-)PCF. The message may be a Npcf SMFSelectionPolicyControl Update message.

The message may include one or more of the following information: access type and RAT, PEI, ULI, UE time zone, service network.

In some embodiments, the request may include one or more allowed NSSAIs and/or a subset of allowed NSSAIs. For example, the request may include a set of S-NSSAIs each of which is included in the allowed NSSAIs. One or more or all of the set of S-NSSAIs may not be associated with a default DNN. Alternatively or additionally, the request may comprise one or more subscribed DNN(s).

The PCF may update the stored information provided by the old AMF with the information provided by the new AMF.

In step 4, the PCF may update the policy decision based on the information provided by the new AMF. The PCF may provide a response to the new AMF. The response may be as described in relation to step 4 of Figure 5. In step 5, the new AMF may deploys the SMF selection control policy. This may comprise storing the policy control request trigger of the SMF selection policy association and/or a set of S-NSSAIs each of which is included in the allowed NSSAI and is not associated with a default DNN and each of which NSSAIs is associated with a subscribed DNN.

Some embodiments may be used during PDU session establishment. Reference is made to Figure 7 which shows a signalling flow during a SMF selection policy association modification initiated by an AMF.

This procedure may apply in LBO and/or non-roaming scenarios.

If the UE does not provide an S-NSSAI or does not provide a DNN, the AMF may send a request for a selection policy control update to the PCF. This request may be a Npcf SMFSelectionPolicyControl Update request message.

Alternatively or additionally, if the UE does not provide a DNN and the S-NSSAI is available, the AMF can use a set of S-NSSAIs each of which is included in the allowed NSSAI and is not associated with a default DNN. Each of the S-NSSAIs may be associated with a subscribed DNN. This may be used to decide the DNN associated with the available S-NSSAI. The S-NSSAI may be available because the UE provided the S-NSSAI, the AMF acquired the S-NSSAI from PCF, or the AMF made a selection of the S-NSSAI.

In the case of the unified trigger which addresses all cases where the DNN and/or S- NSSAI should be replaced or determined, the conditions for the AMF to contact the PCF can be as follows: the AMF contacts the PCF if the DNN and/or the S-NSSAI needs to be replaced or determined.

Referring now to step 1 of Figure 7, when a policy control request trigger condition is met, the AMF updates SMF selection policy association and provides information on the conditions that have changed to the PCF by invoking an update to the SMF selection policy. This may be done by causing the AMF to send a request or message to the PCF. The message may be a Npcf SMFSelectionPolicyControl Update.

The AMF may first check if the DNN is requested by the UE.

A) If the U E included a D N N, the AM F checks if the D N N can be used for SM F selection.

1) If the AMF cannot select an SMF with the DNN, the AMF may requests the PCF to perform a DNN replacement or send back a DF NAS transport message indicating that the SM message is not sent to the SMF. In case of DNN replacement, the AMF may replace the S-NSSAI as well, if received from the PCF. When the AMF requests from the PCF, the DNN replacement including the DNN requested by the UE, the AMF may indicate the S-NSSAI requested by the UE, if available. The PCF may send an S-NSSAI if the AMF does not send an S-NSSAI.

2) If the AMF can select an SMF with the DNN, the AMF may request the PCF to provide S-NSSAI for the DNN in case the UE did not provide an S-NSSAI. To be distinguished from DNN replacement, the AMF may indicate, in addition to the DNN received from the UE, that the request is for S-NSSAI acquisition.

B) If the UE did not include a DNN, the AMF checks if the S-NSSAI is provided by the UE.

1) If the UE provided an S-NSSAI and the DNN needs to be decided based on operator policy, one of the following options may be provide. The AMF may request the PCF to provide a DNN indicating the S-NSSAI. Alternatively, the AMF may select the DNN based on the set of S-NSSAIs each of which is included in the allowed NSSAI and is not associated with a default DNN and each of which is associated with a subscribed DNN, if received from the PCF.

2) If the UE did not provide an S-NSSAI, the AMF may request the PCF to provide the DNN and S-NSSAI. The request may indicate that neither S-NSSAI nor DNN is indicated by the UE. This may be done explicit or implicitly (e.g. by providing neither S-NSSAI nor DNN).

In case of a unified trigger, if the AMF is provisioned with the trigger and the S-NSSAI and/or DNN should be determined based on operator policy and/or should be replaced, the AMF may request the PCF to provide the DNN and/or S-NSSAI provided DNN and/or S- NSSAI received from the UE, if available.

The PCF may provide the requested information (DNN and/or S-NSSAI) to the AMF.

In step 2 the PCF stores the information received in step 1 and makes the policy decision.

In step 3, the PCF responds to the AMF of the updated SMF selection related policy control information and the updated policy control request trigger parameters.

In step 4, the AMF may deploy the SMF selection control policy. This may include storing the policy control request trigger of the SMF selection policy association. This may comprising using the selected DNN for SMF selection and provisioning the selected DNN to the SMF. Thus in some embodiments, during the registration procedure, the AMF may send allowed NSSAI (a set of one or more S-NSSAIs) to the PCF when it requests to create/update the SMF selection policy association.

During the PDU session establishment procedure:

When the UE does not provide any S-NSSAI and:

if there is no subscribed S-NSSAI marked as default, then one of the subscribed S-NSSAI may be selected according to operator policy.

When the UE does not provide any DNN and there is no default DNN associated with the selected S-NSSAI, a subscribed DNN may be selected according to operator policy.

if there is only one subscribed S-NSSAI marked as default, then the S-NSSAI may be selected.

if there is more than one subscribed S-NSSAI marked as default, then one of the subscribed S-NSSAI may be selected according to operator policy.

When the UE provides an S-NSSAI, the UE does not provide any DNN, and there is no default DNN associated with the S-NSSAI provided by the UE, a subscribed DNN may be selected according to operator policy.

In case S-NSSAI/DNN selection according to operator policy is required, the AMF contacts the PCF. The AMF provides the S-NSSAI or DNN (if any is provided by the UE) to the PCF and the PCF provides the AMF with the parameter (S-NSSAI or DNN) not provided by the AMF.

It should be appreciated that any of the steps described previously may be performed by a respective apparatus in the entity or the entity itself. The apparatus may be provided by any suitable hardware such as circuitry. In other embodiments, the apparatus may be provided by at least one processor and at least one memory. In some embodiments, the apparatus may be as described in relation to Figure 3. In other embodiments, the apparatus may be implemented in any other suitable manner.

Reference is made to Figure 8. Figure 8 shows a method which may be performed by an access and mobility management function. The method may be performed by an apparatus in the access and mobility management function. The apparatus may be provided by any suitable hardware such as circuitry. In other embodiments, the apparatus may be provided by at least one processor and at least one memory. In some embodiments, the apparatus may be as described in relation to Figure 3. In other embodiments, the apparatus may be implemented in any other suitable manner. The apparatus may be the access and mobility management function.

The method may comprise in step SI causing an access and mobility management function to transmit a request to a policy control function related to session management function selection policy for a respective communications device.

The method may comprise in step S2, receiving a response to the request from the policy control function, the response including one or more triggers which cause the access and mobility function to communicate with the policy control function when a protocol data unit session of the respective communication device is to be associated with one or more of a data network name and single network slice selection assistance information.

Reference is made to Figure 9. Figure 9 shows a method which may be performed by a policy control function. The method may be performed by an apparatus in the policy control function. The apparatus may be provided by any suitable hardware such as circuitry. In other embodiments, the apparatus may be provided by at least one processor and at least one memory. In some embodiments, the apparatus may be as described in relation to Figure 3. In other embodiments, the apparatus may be implemented in any other suitable manner. The apparatus may the policy function.

The method comprises in step Tl, receiving at an apparatus in policy control function from an access and mobility management function a request related to session management function selection policy for a respective communications device.

The method comprises in step T2, causing a response to be transmitted to the access and mobility function, the response including one or more triggers which cause the access and mobility function to communicate with the policy control function when a protocol data unit session of the respective communication device is to be associated with one or more of a data network name and single network slice selection assistance information.

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. For example, the above aspects are not limited to 5GS. These aspects may be transposed to other radio access technology systems.

The embodiments may thus vary within the scope of the attached claims. In general, some embodiments may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. For example, some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device, although embodiments are not limited thereto. While various embodiments may be illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof

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., in Figures 5 to 9 may represent program steps, or interconnected logic circuits, blocks and functions, or a combination of program steps and logic circuits, blocks and functions. The software may be stored on such physical media as memory chips, or memory blocks implemented within the processor, magnetic media such as hard disk or floppy disks, and optical media such as for example DVD and the data variants thereof, CD.

The memory may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The data processors may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASIC), gate level circuits and processors based on multi-core processor architecture, as non-limiting examples.

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.

As used in this application, the term“circuitry” may refer to one or more or all of the following:

(a) hardware-only circuit implementations (such as implementations in only analogue and/or digital circuitry);

(b) combinations of hardware circuits and software, such as: (i) a combination of analogue and/or digital hardware circuit(s) with software/firmware and

(ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as the communications device or base station to perform the various functions previously described; and

(c) hardware circuit(s) and or processor(s), such as a microprocessor(s) or a portion of a microprocessor(s), that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation.

This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and/or firmware. The term circuitry also covers, for example integrated device.

The foregoing description has provided by way of exemplary and non-limiting examples a full and informative description of some embodiments However, various modifications and adaptations may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings and the appended claims. However, all such and similar modifications of the teachings will still fall within the scope as defined in the appended claims.

Claims

1. A method comprising:

causing an access and mobility management function to transmit a request to a policy control function related to session management function selection policy for a respective communications device; and

receiving a response to the request from the policy control function, the response including one or more triggers which cause the access and mobility function to communicate with the policy control function when a protocol data unit session of the respective communication device is to be associated with one or more of a data network name and single network slice selection assistance information.

2. The method as claimed in claim 1, wherein said request comprises one of a request to update the session management function selection policy and a request to update the session management function selection policy.

3. The method as claimed in claim 1 or 2, comprising causing a message to be sent by the apparatus of the access and mobility function to said policy control function when one or more conditions associated with the one or more triggers occur.

4. The method as claimed in any preceding claim, comprising causing a message to be sent by the access and mobility function to said policy control function when one or more conditions associated with the one or more triggers occur during establishment of a protocol data unit session.

5. The method as claimed in claim 3 or 4, comprising receiving from policy control function one or more of one or more of a data network name and single network slice selection assistance information in response to said message.

6. The method as claimed in any preceding claim, wherein said one or more of said triggers have one or more conditions associated therewith, said one or more conditions comprising one or more of: the communications device providing no data network name, the communications device providing no single network slice selection assistance information and the communication providing a data network name that is to be updated.

7. The method as claimed in any preceding claim, comprising, causing the access and mobility function to send one or more of a data network name and single network slice selection assistance information to the policy control function when one or more of a data network name and single network slice selection assistance information is provided by the respective communications device.

8. The method of claim 7, wherein the causing of the access and mobility function to send one or more of a data network name and single network slice selection assistance information to the policy control function occurs during establishment of a packet data unit session.

9. A method comprising:

receiving at an apparatus in policy control function from an access and mobility management function a request related to session management function selection policy for a respective communications device; and

causing a response to be transmitted to the access and mobility function, the response including one or more triggers which cause the access and mobility function to communicate with the policy control function when a protocol data unit session of the respective communication device is to be associated with one or more of a data network name and single network slice selection assistance information.

10. The method as claimed in claim 9, wherein said request comprises one of a request to update the session management function selection policy and a request to update the session management function selection policy.

11. The method as claimed in claim 9 or 10, comprising receiving a message from the access and mobility function when one or more conditions associated with the one or more triggers occur.

12. The method as claimed in claim 9, 10 or 11, comprising receiving a message from the access and mobility function when one or more conditions associated with the one or more triggers occur during establishment of a protocol data unit session.

13. The method as claimed in claim 11 or 12, comprising causing the policy control function to provide one or more of one or more of a data network name and single network slice selection assistance information in response to said message.

14. The method as claimed in any of claims 9 to 13, wherein said one or more of said triggers have one or more conditions associated therewith, said one or more conditions comprising one or more of: the communications device providing no data network name, the communications device providing no single network slice selection assistance information and the communication providing a data network name that is to be updated.

15. The method as claimed in any of claims 9 to 14, comprising receiving from the access and mobility function one or more of a data network name and single network slice selection assistance information to the policy control function when one or more of a data network name and single network slice selection assistance information is provided by the respective communications device.

16. The method of claim 15, wherein the receiving of one or more of a data network name and single network slice selection assistance information occurs during establishment of a packet data unit session.

17. A computer program comprising computer executable code which when run on at least one processor causes the method of any one of the preceding claims to be performed.

18. An apparatus comprising at least one processor and at least one memory including computer code for one or more programs, the at least one memory and the computer code configured, with the at least one processor, to cause the apparatus at least to: cause a request to be transmitted a policy control function related to session management function selection policy for a respective communications device; and receive a response to the request from the policy control function, the response including one or more triggers which cause the access and mobility function to communicate with the policy control function when a protocol data unit session of the respective communication device is to be associated one or more of a data network name and single network slice selection assistance information.

19. An apparatus comprising at least one processor and at least one memory including computer code for one or more programs, the at least one memory and the computer code configured, with the at least one processor, to cause the apparatus at least to: receive from an access and mobility management function a request related to session management function selection policy for a respective communications device; and cause a response to be transmitted to the access and mobility function, the response including one or more triggers which cause the access and mobility function to communicate with the policy control function when a protocol data unit session of the respective communication device is to be associated with one or more of a data network name and single network slice selection assistance information.