Patent Description:
For example, one parameter in providing good performance and capacity for a given communications protocol in a communications network is the concept of User Equipment (UE) Route Selection Policy (URSP) rules as defined in the third generation partnership project (3GPP) technical specification (TS) <NUM> entitled "Policy and charging control framework for the <NUM> System (5GS); Stage <NUM>", version <NUM>. <NUM> (and also in 3GPP TS <NUM> entitled "System architecture for the <NUM> System (5GS)", version <NUM>. <NUM>, and 3GPP TS <NUM> entitled "Procedures for the <NUM> System (5GS)", version <NUM>. URSP rules, if present, are used by the UE to determine Single Network Slice Selection Assistance Information (S-NSSAI), Data Network Name (DNN) and Session and Service Continuity (SCC) mode for Protocol data Unit (PDU) Session establishment, to establish one or multiple PDU sessions using one or more S-NSSAIs.

URSP rules can be pre-configured or provisioned to the UE. If URSP rules are not available in the UE, or there is no matching URSP rule, and there is no UE local configuration, the UE does not indicate S-NSSAI in the PDU Session Establishment procedure. Network-initiated Non-Access Stratum (NAS) transport procedure can be used by the Access Management Function (AMF), or similar, in the core network to update one or more URSP rules for the UE (and for providing the same to the UE).

The procedure used by the UE to associate applications to PDU sessions using URSP rules are described in aforementioned 3GPP TS <NUM>, clause <NUM>. <NUM>, as summarized in the following where the UE associates application traffic to PDU sessions using URSP rules in a three-step process.

First, the UE selects a URSP rule. In more detail, for a newly detected application, the UE evaluates the URSP rules in the order of rule precedence and determines if the application is matching the traffic descriptor of any URSP rule. If a URSP rule is found this URSP rule is applicable to the application.

Second, the UE selects a Route Selection Descriptor (RSD). In more detail, the UE selects an RSD within the selected URSP rule in the order of the Route Selection Descriptor Precedence. The UE selects an RSD that fulfills conditions. These conditions are checked by the UE and are not included in the URSP rule definition. If any S-NSSAI(s) is present, the S-NSSAI(s) must also be in the Allowed NSSAI. If any DNN is present and the DNN is a Local Area Data Network (LADN) DNN, the UE is in the area of availability of this LADN. If Access Type preference is present and set to Multi-Access, the UE supports Access Traffic Steering, Switching and Splitting (ATSSS).

Third, the UE selects a PDU session. In more detail, the UE determines if there is an existing PDU session that matches all components in the selected Route Selection Descriptor. When a matching PDU session exists, the UE associates the application to the existing PDU session, i.e. routes the traffic of the detected application on this PDU session. If none of the existing PDU sessions matches, the UE tries to establish a new PDU session using the values specified by the selected Route Selection Descriptor. If the PDU Session Establishment Request is accepted, the UE associates the application to this new PDU session. If the UE fails to establish a PDU session with any of the Route Selection Descriptors, the UE tries other URSP rules in the order of Rule Precedence with matching Traffic Descriptors, except the URSP rule with the "match-all" Traffic descriptor, if any.

In addition, the UE reevaluates the validity of the URSP rules when certain conditions are met. For example, one condition could be that the URSP rule is updated by the Policy and Control Function (PCF), or similar, in the core network. Another conditions could be that there is a change of Allowed NSSAI or Configured NSSAI or change of LADN DNN availability.

However, there is still a need for an improved session establishment procedure for the UE.

The <NPL>" discloses a solution for adding support for delivering background data transfer policies to the UE. The main problem addressed by this document is to complete the information included in the policy related to background data transfer. The solution comprises including the Background Data Transfer Reference ID and network area information in the policy description. It is disclosed that the Background Data Transfer Policy may be part of a URSP rule and delivered to the UE via the UE Configuration Update procedure. The policy is sent to the UE when the policy is selected, when the UE enters the location, and/or when the time window is approaching. The UE may activate the policy when the PDU Session is established.

The <NPL>" discloses a solution for adding support for unified access control in SNPNs (Stand-alone Non-Public Networks). It is disclosed including unified access control information configured per non-public network (i.e., as part of the subscription information that the UE has for a given non-public network) to prevent access to SNPNs for authorized UE(s) in case of network congestion/overload.

An object of embodiments herein is to provide efficient session establishment for a terminal device. Specific embodiments are defined by the dependent claims.

According to a first aspect there is presented a terminal device for establishing a communication session with a local serving network. The terminal device comprises processing circuitry. The processing circuitry is configured to cause the terminal device to obtain an indication of traffic to be communicated. The traffic is associated with a traffic descriptor. The processing circuitry is configured to cause the terminal device to select a URSP rule for the traffic to be communicated in a communication session with the local serving network. The URSP rule is selected in accordance with the traffic descriptor and in accordance with a validity condition for the communication session. The validity condition at least pertains to network support for IMS in the local serving network. The processing circuitry is configured to cause the terminal device to establish a communication session with the local serving network for communicating the traffic according to the selected URSP rule.

According to a second aspect there is presented a terminal device for establishing a communication session with a local serving network. The terminal device comprises an obtain module configured to obtain an indication of traffic to be communicated. The traffic is associated with a traffic descriptor. The terminal device comprises a select module configured to select a URSP rule for the traffic to be communicated in a communication session with the local serving network. The URSP rule is selected in accordance with the traffic descriptor and in accordance with a validity condition for the communication session. The validity condition at least pertains to network support for IMS in the local serving network. The terminal device comprises an establish module configured to establish a communication session with the local serving network for communicating the traffic according to the selected URSP rule.

According to a third aspect there is presented a method for establishing a communication session with a local serving network. The method is performed by a terminal device. The method comprises obtaining an indication of traffic to be communicated. The traffic is associated with a traffic descriptor. The method comprises selecting a URSP rule for the traffic to be communicated in a communication session with the local serving network. The URSP rule is selected in accordance with the traffic descriptor and in accordance with a validity condition for the communication session. The validity condition at least pertains to network support for IMS in the local serving network. The method comprises establishing a communication session with the local serving network for communicating the traffic according to the selected URSP rule.

According to a fourth aspect there is presented a computer program for establishing a communication session with a local serving network. The computer program comprises computer program code which, when run on processing circuitry of a terminal device, causes the terminal device to perform a method according to the third aspect.

According to a fifth aspect there is presented a policy control function, PCF, entity for enabling a terminal device to establish a communication session with a local serving network. The PCF entity comprises processing circuitry. The processing circuitry is configured to cause the PCF entity to obtain a modification to a URSP rule used by the terminal device for establishing a communication session with the local serving network for communicating traffic. The URSP rule is associated with a validity condition. The validity condition at least pertains to network support for IMS in the local serving network. The processing circuitry is configured to cause the PCF entity to provide the modification of the URSP rule towards the terminal device.

According to a sixth aspect there is presented a policy control function, PCF, entity for enabling a terminal device to establish a communication session with a local serving network. The PCF entity comprises an obtain module configured to obtain a modification to a URSP rule used by the terminal device for establishing a communication session with the local serving network for communicating traffic. The URSP rule is associated with a validity condition. The validity condition at least pertains to network support for IMS in the local serving network. The PCF entity comprises a provide module configured to provide the modification of the URSP rule towards the terminal device.

According to a seventh aspect there is presented a method for enabling a terminal device to establish a communication session with a local serving network. The method is performed by a policy control function, PCF, entity of the local serving network. The method comprises obtaining a modification to a URSP rule used by the terminal device for establishing a communication session with the local serving network for communicating traffic. The URSP rule is associated with a validity condition. The validity condition at least pertains to network support for IMS in the local serving network. The method comprises providing the modification of the URSP rule towards the terminal device.

According to an eight aspect there is presented a computer program for enabling a terminal device to establish a communication session with a local serving network, the computer program comprising computer program code which, when run on processing circuitry of a PCF entity, causes the PCF entity to perform a method according to the seventh aspect.

According to a ninth aspect there is presented a computer program product comprising a computer program according to at least one of the fourth aspect and the eight aspect and a computer readable storage medium on which the computer program is stored. The computer readable storage medium could be a non-transitory computer readable storage medium.

Advantageously these methods, these terminal devices, these PCF entities, and these computer programs provide efficient session establishment for the terminal devices.

Advantageously these methods, these terminal devices, these PCF entities, and these computer programs enable a URSP rule in the terminal device only to be triggered, or used, if the conditions e.g. for IMS Voice over PS support apply. This prevents unnecessary session establishment setup to allow the terminal device to register to the IMS, even if no IMS voice service is supported in the local serving network.

Advantageously these methods, these terminal devices, these PCF entities, and these computer programs allows to have multiple URSP rules also for the same DNN, and in case of the IMS DNN, there are URSP rules that could always triggered, or used, independent of IMS voice support indication, there are URSP rules that could only be triggered, or used, if IMS voice is supported, and there are URSP rules that could only be triggered, or used, if IMS voice is not supported.

Advantageously these methods, these terminal devices, these PCF entities, and these computer programs thereby allow a fine grain control of the terminal device behavior e.g. in roaming cases. If also having conditions like MNC and MCC, certain URSP rules are only triggered, or used, if the terminal device is connected to a network with this MNC and MCC, e.g. in the home network or only in particular roaming networks.

It is to be noted that any feature of the first, second, third, fourth, fifth, sixth seventh, eight, and ninth aspects may be applied to any other aspect, wherever appropriate. Likewise, any advantage of the first aspect may equally apply to the second, third, fourth, fifth, sixth, seventh, eight, and/or ninth aspect, respectively, and vice versa.

<FIG> is a schematic diagram illustrating a communication network <NUM> where embodiments presented herein can be applied. As the skilled person understands, the communication network <NUM> of <FIG> is simplified compared to a real communication network <NUM> and show parts most relevant for the present disclosure. The communication network <NUM> comprises a home network 110a and a local serving network 110b representing a roaming network. The home network 110a and the local serving network 110b each provide network access to a terminal device (TD) <NUM>. According to non-limiting examples the terminal devices <NUM> is any of a portable wireless device, mobile station, mobile phone, handset, wireless local loop phone, user equipment (UE), smartphone, laptop computer, tablet computer, wireless modem, wireless sensor device, network equipped vehicle, or Internet of Things (IoT) device.

Each of the home network 110a and the local serving network nob comprises a respective PCF entity 300a, 300b. Each of the home network 110a and the local serving network 110b is configured to, over a respective link 170a, 170b, communicate with a packet data network (PDN) <NUM>, such as the Internet.

Depending on the physical location of the terminal device <NUM>, a communication session is established either with the home network 110a over wireless radio link 160a or with the local serving network 110b over wireless radio link 160b. The terminal device <NUM> is thereby enabled to access services of, and exchanging data with, the packet data network <NUM>.

As noted above, there is a need for an improved session establishment procedure for the terminal device <NUM>.

In more detail, currently a URSP rule may match (if the Traffic Descriptor matches the application traffic sent by the terminal device <NUM>) according to 3GPP TS <NUM> and then a PDU session is established irrespective of some of the current network conditions. For example, a URSP rule containing the IMS DNN may be triggered and used even if the AMF in the local serving network 110b does not indicate IMS Voice support to the terminal device <NUM>. That is, a PDU session to the IMS DNN may be established independently of whether IMS voice is indicated as being supported in the local serving network 110b or not. However, the terminal device <NUM> may have multiple URSP rules for the same DNN, and in case of the IMS DNN, only a subset of the URSP rules should be triggered and used if IMS voice is not supported and possibly all URSP rules should be triggered and used if IMS voice is supported. There might also be a need to trigger and use a URSP rule only if IMS voice over PS is not supported, allowing thereby a fine grain control of the terminal device behavior. This could be of particular use in roaming cases (but not limited to roaming).

In particular, the list of conditions to select a valid RSD according to a URSP rule are limited and does not consider IMS Voice over PS support by the local serving network 110b. The terminal device <NUM> might therefore select a valid RSD according to any existing criteria, but the PDU session establishment will fail if the local serving network 110b does not support IMS Voice over PS. This could e.g. be the case if roaming agreements do not allow the establishment of a PDU session to this DNN. In this respect, the Session Management Function (SMF) in the HPLMN might reject it, and/or the AMF in the local serving network 110b might reject it.

The embodiments disclosed herein therefore relate to mechanisms for establishing a communication session with a local serving network 110b and enabling a terminal device <NUM> to establish a communication session with a local serving network nob. In order to obtain such mechanisms, there is provided a terminal device <NUM>, a method performed by the terminal device <NUM>, a computer program product comprising code, for example in the form of a computer program, that when run on processing circuitry of the terminal device <NUM>, causes the terminal device <NUM> to perform the method. In order to obtain such mechanisms, there is further provided a PCF entity 300b, a method performed by the PCF entity 300b, and a computer program product comprising code, for example in the form of a computer program, that when run on processing circuitry of the PCF entity 300b, causes the PCF entity 300b to perform the method.

Reference is now made to <FIG> illustrating a method for establishing a communication session with a local serving network 110b as performed by the terminal device <NUM> according to an embodiment.

S102: The terminal device <NUM> obtains an indication of traffic to be communicated. The traffic is associated with a traffic descriptor.

S104: The terminal device <NUM> selects a URSP rule for the traffic to be communicated in a communication session with the local serving network 110b. The URSP rule is selected in accordance with the traffic descriptor and in accordance with a validity condition for the communication session. The validity condition at least pertains to network support for IMS in the local serving network 110b.

S106: The terminal device <NUM> establishes a communication session with the local serving network 110b for communicating the traffic according to the selected URSP rule.

The terminal device <NUM> thus has at least one URSP rule, each having at least on validity condition related to support for IMS in the local serving network 110b. The terminal device <NUM> checks whether the condition apply when determining which URSP rule to trigger, or use, and then establishes a communication session accordingly.

Embodiments relating to further details of establishing a communication session with a local serving network 110b as performed by the terminal device <NUM> will now be disclosed.

Each URSP rule might be associated with validity conditions (one or multiple) that the URSP rule should only be triggered, or used, if the associated validity conditions are matched.

One of those validity conditions could be whether the local serving network 110b indicates IMS Voice over PS Support. That is, according to the invention the validity condition pertaining to network support for IMS requires that IMS voice over PS is supported in the local serving network 110b.

Thereby, if the AMF (or MME) provides an IMS Voice over PS support indication to the terminal device <NUM>, and IMS Voice over PS is supported, then the terminal device <NUM> can trigger, or use, any of the URSP rules that fulfil that condition.

However, not all URSP rules for IMS services must have such a condition, e.g. there can be one rule with such a condition for a first S-NSSAI (denoted S-NSSAI_x) and a second rule without such a condition for a second S-NSSAI (denoted S-NSSAI_y), and then the condition is an optional element in the URSP rule, but the terminal device <NUM> should support it.

In some aspects the validity condition further pertains to at least one of: emergency support in the local serving network 110b, the local serving network 110b supporting interworking over network interface N26, the local serving network 110b supporting interworking without network interface N26, which mobile country code (MCC) the local serving network 110b has, and which mobile network code (MNC) the local serving network 110b has.

In some aspects the URSP rule is selected from a set of URSP rules. Further, the terminal device <NUM> might be configured to select an RSD within the selected URSP rule. In further aspects, the URSP rule is selected only among those URSP rules in the set of URSP rules for which the validity condition for the communication session is fulfilled. The RSD might then be selected within the URSP rule with matching validity conditions.

There may be different ways for the terminal device <NUM> to have access to URSP rules.

According to a first example, the terminal device 200a is pre-configured with URSP rules. In particular, according to an embodiment, the URSP rule and/or the validity condition (and thus RSDs) is configured in the terminal device (<NUM>).

According to a second example, URSP rules may be provisioned to the terminal device <NUM> using a network-initiated NAS transport procedure. In particular, according to an embodiment, the URSP rule and/or the validity condition (and thus RSDs) is provided to the terminal device <NUM> from a PCF entity 300a of the home network 110a of the terminal device <NUM>.

Further, the PCF entity 300b in the local serving network 110b might provide URSP rules that comprise additional RSD components supported in the local serving network 110b, such as IMS Voice over PS support, to the terminal device <NUM>.

Further, the PCF entity 300b in the local serving network 110b might modify existing URSP rules to address requirements in the local serving network 110b and provide these modified URSP rules to the terminal device <NUM>. Hence, according to an embodiment, the terminal device <NUM> is configured to perform (optional) steps S108 and S110:.

As indicated by S112 in <FIG>, upon having updated the URSP rule, step S102 might be entered again (but with the thus modified URSP rule).

There could be different ways in which URSP rules could be modified.

In some aspects the modification defines one or more new URSP rules, possible with one or more new validity conditions for each new URSP rule. That is, according to an embodiment, the modification defines a new URSP rule with associated validity condition. The validity condition might be associated with the RSD within the URSP rule.

In some aspects the modification defines one or more new conditions to one or more existing URSP rules (thus without changing the URSP rule(s) as such). That is, according to an embodiment, the modification defines a new validity condition for the URSP rule.

There could be different types of traffics to be communicated in the communication session established in S106. In some aspects, the traffic is downlink traffic. That is, according to an embodiment, the traffic to be communicated is to be received by the terminal device <NUM>. In some aspects, the traffic is uplink traffic. That is, according to an embodiment, the traffic to be communicated is to be transmitted by the terminal device <NUM>.

There could be different types of communication sessions that are established in S106. In some embodiments, the communication session is a PDU session.

Reference is now made to <FIG> illustrating a method for enabling a terminal device <NUM> to establish a communication session with a local serving network 110b as performed by a PCF entity 300b of the local serving network 110b according to an embodiment.

S202: The PCF entity 300b obtains a modification to a URSP rule used by the terminal device <NUM> for establishing a communication session with the local serving network 110b for communicating traffic. As disclosed above, the URSP rule is associated with a validity condition. As disclosed above, the validity condition at least pertains to network support for IMS in the local serving network 110b.

S204: The PCF entity 300b provides the modification of the URSP rule towards the terminal device <NUM>.

Embodiments relating to further details of enabling a terminal device <NUM> to establish a communication session with a local serving network 110b as performed by the PCF entity 300b will now be disclosed.

In general terms, the embodiments, aspects and examples as described above with reference to the terminal device <NUM> apply also to the PCF entity <NUM>.

As disclosed above, according to the invention, the validity condition pertaining to network support for IMS requires that IMS voice over PS is supported in the local serving network 110b.

Examples of further validity conditions have been disclosed above.

As disclosed above, there could be different ways in which URSP rules could be modified.

In some aspects, the modification defines one or more new URSP rules, possible with one or more new validity conditions for each new URSP rule. That is, according to an embodiment, the modification defines a new URSP rule with associated validity condition. The validity condition might be associated with the RSD within the URSP rule.

In some aspects, the modification defines one or more new conditions to one or more existing URSP rules (thus without changing the URSP rule(s) as such). That is, according to an embodiment, the modification defines a new validity condition for the URSP rule.

There could be different ways for the PCF entity 300b to obtain the modification to the URSP rule.

In some aspects the modification to the URSP rule is made at the PCF entity 300a of the home network 110a and the PCF entity 300b obtains the modification to the URSP rule from PCF entity 300a when the terminal device <NUM> is served by the local serving network 110b. That is, according to an embodiment, the modification is obtained from a PCF entity 300a of the home network 110a of the terminal device <NUM>. In other aspects the modification to the URSP rule originates from conditions in the local serving network 110b having been changed, where the conditions cause a network policy (or just policy for short) to be modified. That is, according to an embodiment, the modification is obtained by means of a policy of the PCF entity 300b being modified.

One particular embodiment for provision of a modification of a URSP rule to the terminal device <NUM> based on at least some of the above disclosed embodiments will now be disclosed in detail with reference to the signalling diagram of <FIG>. With reference to <FIG>, the PCF entity 300a of the home network 110a will be denoted (H-)PCF 300a and the PCF entity 300b of the local serving network 110a will be denoted (V-)PCF 300b.

S301: The (H-)PCF entity 300a has access to mobile network operator policies that indicate whether an IMS application requires support of e.g. IMS voice over PS to be established. This is provided as a validity condition for a URSP rule.

S302: The (H-)PCF entity 300a sends to (V-)PCF entity 300b a URSP rule that includes a traffic descriptor to identify IMS DNN, and an RSD that includes two S-NSSAI components, denoted S-NSSAI_1 and S-NSSAI_2. The RSD component for S-NSSAI_1 requires support for IMS voice over PS and the RSD component for S-NSSAI_2 does not require support for IMS voice over PS. The (H-)PCF entity 300a sends to (V-)PCF entity 300b a URSP rule for the terminal device <NUM> that includes the support for IMS voice over PS as a validity condition to the RSD component for S-NSSAI <NUM>.

S303: The (V-)PCF entity 300b sends a response to (H-)PCF entity 300a. In a non-roaming case, this step does not apply, but the (H-)PCF entity 300a sends the URSP rule to the AMF <NUM> of the home network 110a. Further, (V-)PCF entity 300b might check the URSP rules as received from (H-)PCF entity 300a. (V-)PCF entity 300b might have different conditions per roaming partner, and (V-)PCF entity 300b might update the conditions in the RSD. The (V-)PCF entity 300b then reports to (H-)PCF entity 300a that the URSP rules have been updated.

S304: The (V-PCF) entity 300b delivers the URSP rules to the terminal device <NUM> via the AMF <NUM> by following steps <NUM> to <NUM> in Figure <NUM>. <NUM>-<NUM> of aforementioned 3GPP TS <NUM>.

S305: The terminal device <NUM> checks the received URSP rules and upon obtaining an indication of traffic to be communicated, where the traffic is associated with a traffic descriptor, the terminal device <NUM> selects a URSP rule for the traffic to be communicated in a communication session with the local serving network 110b, where the URSP rule is selected in accordance with the traffic descriptor and in accordance with a validity condition for the communication session.

Table <NUM> shows examples of URSP rules in accordance with embodiments disclosed herein. Table <NUM> is based on an extension of Table A-<NUM> in Annex A of aforementioned 3GPP TS <NUM>.

Table <NUM> shows examples of the structure of URSP rules in accordance with embodiments disclosed herein. Table <NUM> is based on an extension of Table <NUM>. <NUM>-<NUM> in clause <NUM>. <NUM> of aforementioned 3GPP TS <NUM>.

<FIG> schematically illustrates, in terms of a number of functional units, the components of a terminal device <NUM> according to an embodiment. Processing circuitry <NUM> is provided using any combination of one or more of a suitable central processing unit (CPU), multiprocessor, microcontroller, digital signal processor (DSP), etc., capable of executing software instructions stored in a computer program product 910a (as in <FIG>), e.g. in the form of a storage medium <NUM>. The processing circuitry <NUM> may further be provided as at least one application specific integrated circuit (ASIC), or field programmable gate array (FPGA).

Particularly, the processing circuitry <NUM> is configured to cause the terminal device <NUM> to perform a set of operations, or steps, as disclosed above. For example, the storage medium <NUM> may store the set of operations, and the processing circuitry <NUM> may be configured to retrieve the set of operations from the storage medium <NUM> to cause the terminal device <NUM> to perform the set of operations. Thus the processing circuitry <NUM> is thereby arranged to execute methods as herein disclosed.

The terminal device <NUM> may further comprise a communications interface <NUM> for communications with other entities, nodes, functions, and devices of the communication network <NUM>. As such the communications interface <NUM> may comprise one or more transmitters and receivers, comprising analogue and digital components.

The processing circuitry <NUM> controls the general operation of the terminal device <NUM> e.g. by sending data and control signals to the communications interface <NUM> and the storage medium <NUM>, by receiving data and reports from the communications interface <NUM>, and by retrieving data and instructions from the storage medium <NUM>. Other components, as well as the related functionality, of the terminal device <NUM> are omitted in order not to obscure the concepts presented herein.

<FIG> schematically illustrates, in terms of a number of functional modules, the components of a terminal device <NUM> according to an embodiment. The terminal device <NUM> of <FIG> comprises a number of functional modules; an obtain module 210a configured to perform step S102, a select module 210b configured to perform step S104, and an establish module 210c configured to perform step S106. The terminal device <NUM> of <FIG> may further comprise a number of optional functional modules, such as any of an obtain module 210d configured to perform step S108, and an update module 210e configured to perform step S110. In general terms, each functional module 210a-210e may be implemented in hardware or in software. Preferably, one or more or all functional modules 210a-210e may be implemented by the processing circuitry <NUM>, possibly in cooperation with the communications interface <NUM> and/or the storage medium <NUM>. The processing circuitry <NUM> may thus be arranged to from the storage medium <NUM> fetch instructions as provided by a functional module 210a-210e and to execute these instructions, thereby performing any steps of the terminal device <NUM> as disclosed herein.

<FIG> schematically illustrates, in terms of a number of functional units, the components of a PCF entity 300b according to an embodiment. Processing circuitry <NUM> is provided using any combination of one or more of a suitable central processing unit (CPU), multiprocessor, microcontroller, digital signal processor (DSP), etc., capable of executing software instructions stored in a computer program product 910b (as in <FIG>), e.g. in the form of a storage medium <NUM>. The processing circuitry <NUM> may further be provided as at least one application specific integrated circuit (ASIC), or field programmable gate array (FPGA).

Particularly, the processing circuitry <NUM> is configured to cause the PCF entity 300b to perform a set of operations, or steps, as disclosed above. For example, the storage medium <NUM> may store the set of operations, and the processing circuitry <NUM> may be configured to retrieve the set of operations from the storage medium <NUM> to cause the PCF entity 300b to perform the set of operations. Thus the processing circuitry <NUM> is thereby arranged to execute methods as herein disclosed.

The PCF entity 300b may further comprise a communications interface <NUM> for communications with other entities, nodes, functions, and devices of the communication network <NUM>. As such the communications interface <NUM> may comprise one or more transmitters and receivers, comprising analogue and digital components.

The processing circuitry <NUM> controls the general operation of the PCF entity 300b e.g. by sending data and control signals to the communications interface <NUM> and the storage medium <NUM>, by receiving data and reports from the communications interface <NUM>, and by retrieving data and instructions from the storage medium <NUM>. Other components, as well as the related functionality, of the PCF entity 300b are omitted in order not to obscure the concepts presented herein.

<FIG> schematically illustrates, in terms of a number of functional modules, the components of a PCF entity 300b according to an embodiment. The PCF entity 300b of <FIG> comprises a number of functional modules; an obtain module 310a configured to perform step S302, and a provide module 310b configured to perform step S304. The PCF entity 300b of <FIG> may further comprise a number of optional functional modules, as illustrated by functional module 310c. In general terms, each functional module 310a-310c may be implemented in hardware or in software. Preferably, one or more or all functional modules 310a-310c may be implemented by the processing circuitry <NUM>, possibly in cooperation with the communications interface <NUM> and/or the storage medium <NUM>. The processing circuitry <NUM> may thus be arranged to from the storage medium <NUM> fetch instructions as provided by a functional module 310a-310c and to execute these instructions, thereby performing any steps of the PCF entity 300b as disclosed herein.

The PCF entity 300b may be provided as a standalone device or as a part of at least one further device. For example, the PCF entity 300b may be provided in a core network node. Further, functionality of the PCF entity 300b may be distributed between at least two devices, or nodes. These at least two nodes, or devices, may either be part of the same network part (such as the radio access network or the core network) or may be spread between at least two such network parts. In general terms, instructions that are required to be performed in real time may be performed in a device, or node, operatively closer to the cell than instructions that are not required to be performed in real time.

Thus, a first portion of the instructions performed by the PCF entity 300b may be executed in a first device, and a second portion of the instructions performed by the PCF entity 300b may be executed in a second device; the herein disclosed embodiments are not limited to any particular number of devices on which the instructions performed by the PCF entity 300b may be executed. Hence, the methods according to the herein disclosed embodiments are suitable to be performed by a PCF entity 300b residing in a cloud computational environment. Therefore, although a single processing circuitry <NUM> is illustrated in <FIG> the processing circuitry <NUM> may be distributed among a plurality of devices, or nodes. The same applies to the functional modules 310a-310c of <FIG> and the computer program 920b of <FIG>.

<FIG> shows one example of a computer program product 910a, 910b comprising computer readable means <NUM>. On this computer readable means <NUM>, a computer program 920a can be stored, which computer program 920a can cause the processing circuitry <NUM> and thereto operatively coupled entities and devices, such as the communications interface <NUM> and the storage medium <NUM>, to execute methods according to embodiments described herein. The computer program 920a and/or computer program product 910a may thus provide means for performing any steps of the terminal device <NUM> as herein disclosed. On this computer readable means <NUM>, a computer program 920b can be stored, which computer program 920b can cause the processing circuitry <NUM> and thereto operatively coupled entities and devices, such as the communications interface <NUM> and the storage medium <NUM>, to execute methods according to embodiments described herein. The computer program 920b and/or computer program product 910b may thus provide means for performing any steps of the PCF entity 300b as herein disclosed.

Claim 1:
A terminal device (<NUM>) for establishing a communication session with a local serving network (110b), the terminal device (<NUM>) comprising processing circuitry (<NUM>), the processing circuitry being configured to cause the terminal device (<NUM>) to:
obtain a modification of a User Equipment Route Selection Policy, URSP, rule and a validity condition;
obtain an indication of traffic to be communicated, the traffic being associated with a traffic descriptor;
select the User Equipment Route Selection Policy, URSP, rule for the traffic to be communicated in a communication session with the local serving network (110b), the URSP rule being selected in accordance with the traffic descriptor and in accordance with the validity condition, the validity condition at least pertaining to network support for IMS in the local serving network (110b); and
establish a communication session with the local serving network (nob) for communicating the traffic according to the selected URSP rule;
wherein the communication session is a protocol data unit, PDU, session;
wherein the validity condition pertaining to network support for IMS requires that IMS voice over PS is supported in the local serving network (nob).