GB2588096A

GB2588096A - Improvements in and relating to dynamic path switching

Info

Publication number: GB2588096A
Application number: GB1914327.0A
Authority: GB
Inventors: Shariat Mehrdad; Kim Sunghoon; Lee Hoyeon
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 2019-10-04
Filing date: 2019-10-04
Publication date: 2021-04-21
Anticipated expiration: 2039-10-04
Also published as: GB2588096B8; GB2588096B; GB2588096A8; GB201914327D0

Abstract

Disclosed is a method of path switching in a system where a first User Equipment, (UE) is operable to communicate with a second UE via either a first direct path 30 or a second path 40 via a telecommunication network and wherein the active path is switched between the first and second paths, or vice-versa, in response to a trigger derived from: a) either one of the first and second UEs; b) the telecommunication network; or c) an application running on one of the UEs. The first path may be a ProSe path and the second path may be via a 5G core network. The trigger may be the result of relative proximity changes observed by one of the UEs.

Description

Improvements in and relating to Dynamic Path Switching The present invention relates to the dynamic switching of communication paths in the context of a mobile device or User Equipment (UE) operable with a telecommunication network. It relates particularly to the switching between a first and second mode of communication between two UEs where one involves direct communication between the devices and the other involves the telecommunication network relaying all messages and signals.

Proximity Services (ProSe) (specifically the direct communication) has been enhanced to support V2X services over LTE. For Fifth Generation Systems (5G5), the proximity services are expected to be an important system wide enabler to support various applications and services.

Another class of commercial services has recently emerged termed as Network-controlled Interactive services (NCIS) that share some commonality of requirements with public safety services and applications. NCIS refers to a kind of service which needs at least 2 UEs to join and share data, e.g. interactive gaming or data sharing. Those UEs in the same NCIS session are grouped together as one NCIS group, and the group is determined by application layer (i.e. NCIS application server).

Many interactive services occur in localised areas e.g. entertainment in a home party or a bar, or educational services in an office, or interactive gaming in an entertainments centre, or new generation of Augmented Reality/Virtual Reality (AR/VR) services improving the user experience at different venues like shopping malls, stadiums or other social events.

It is desirable that the 5G System be enhanced to support proximity-based services with one common architecture to take advantage of economies of scale, i.e. such architecture can be used for both public safety and commercial proximity services, where applicable.

For either form of service (Public Safety vs. commercial services), the requirements for throughput, latency, reliability and resource/power utilisation may be enhanced by employing dynamic path switching schemes where direct communication in the user plane (UP) with other users in Proximity (ProSe), termed as the ProSe Communication path, enables another degree of freedom to maintain service quality of experience, in addition to the conventional path through core network i.e. 5GC path between users.

In order to guarantee service requirements such as user data rate and latency requirements for different proximity applications, it is desirable that the 5G system is able to dynamically determine the appropriate UP path to exchange interactive service data either via the ProSe Communication path (direct) or via the 5GC path as shown in Figure 1.

Figure 1 shows a first UE 10 in communication with a second UE 20. The communication between the two UEs may be performed via a ProSe path 30 or via the 5G Core 40.

According to the present invention there is provided an apparatus and method as set forth in the appended claims. Other features of the invention will be apparent from the dependent

claims, and the description which follows.

According to an aspect of the present invention, there is provided a method of path switching in a system where a first User Equipment, UE, is operable to communicate with a second UE via either a first direct path or a second path via a telecommunication network and wherein the active path is switched between the first and second paths, or vice-versa, in response to a trigger derived from: a) either one of the first and second UEs; b) the telecommunication network; or c) an application running on one of the UEs.

In an embodiment, the first path is a ProSe path and the second path is via a 5G Core network.

In an embodiment, the active path is switched, Quality of Service, QoS, parameters are mapped between the two paths.

In embodiments, various signal flows are created as set out in the description.

Embodiments of the invention provide novel procedures, notification parameters, call flows and triggers for dynamic path switching between ProSe path and 5GC path in different scenarios either for public safety applications or for network-controlled interactive services.

Embodiments of the invention provide novel (or enhanced) signalling procedures and exchange of parameters related to QoS indication, handling and mapping QoS parameters between ProSe path and 5GC path.

Embodiments of the invention provide novel triggers for path switching based on relative proximity changes observed by UE (UE-driven), QoS changes observed by Radio-Access Network (Network-driven) or Group topology changes observed by Application Function (AF-driven).

Although a few preferred embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the invention, as defined in the appended claims.

For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example only, to the accompanying diagrammatic drawings in which: Figure 1 shows an example of ProSe path vs. 5GC path between two UEs, according to an embodiment of the present invention; Figure 2 shows a representation of a call flow according to an embodiment of the present invention; Figure 3 shows more detail of a step shown in Figure 2; Figure 4 shows a representation of a call flow according to an embodiment of the present invention Figure 5 shows a representation of a call flow according to an embodiment of the present invention Figure 6 shows a representation of a call flow according to an embodiment of the present invention Figure 7 shows more detail of a step shown in Figure 6; Figure 8 shows a representation of a call flow according to an embodiment of the present invention, and Figure 9 shows a representation of a call flow according to an embodiment of the present invention, In the following embodiments of the invention, it is assumed that two example users, referred to as UE A (10) and UE FIG (20) have already established a Public Safety/NCIS session together over 5GC path (40) but due to some triggering condition to be described below, they decide to switch the path from 5GC (40) to a ProSe (30) direct communication path to continue their joint session.

Figure 2 shows a first scenario according to an embodiment of the present invention. This represents a UE-driven path switch from 5GC path to ProSe path.

Figure 2, and the following figures, show various network functions/entities, whose functions and definitions are known in the art in at least: 3GPP TS 23.501, 3GPP TS 23.502 and 3GPP TS 23.503. The various known functions of these network functions/entities is varied/enhanced as set out in the following paragraphs.

For completeness, the various functions/entities shown are: User Equipment: UE, (Radio) Access Network: (R)AN, Access and Mobility Management Function: AMF, Session Management Function: SMF, User Plane Function: UPF, Unified Data Repository: UDR, Network Exposure Function: NEF, Application Function: AF.

In this scenario, it is assumed that UE A (10) runs periodic group discovery over PC5-D in coordination with an Application Server, even though it is already in a Public Safety/NCIS session with UE F (20) over 5GC path (40). Alternatively, UE A may be triggered to run group discovery based on a proximity "notification alert" from Proximity Function (PF) in a similar manner as captured in TS 23.303 for LIE ProSe.

In 5G Core (5GC), the corresponding services for proximity "notification alert" may be deployed as an extended set of services for a current network function (NF) within 5GC (e.g. PCF) or as part of a newly added NF for this purpose within Service-Based Architectures (SBA).

The service flow steps for the first scenario shown in Figure 2 are as below. Note that Figure 3 shows a more detailed view of step S4 Details of each step are: Si. During Group discovery, as described above, UE A identifies that UE F has moved to the proximity range of UE A. 52. UE A sends direct communication request to initiate the unicast layer-2 link establishment.

This request also includes PC5 QoS flows/ parameters (for ProSe path) mapped based on former 5GC path QoS parameters to meet Public Safety/NCIS session service requirements. UE F accepts the direct communication request and confirms the support of ProSe path QoS flows / parameters received.

QoS parameters are mapped between the two paths to ensure that a suitable or required level of service is experienced by the UEs after the active path has been switched. If the new path does not satisfy QoS requirements, then path switching does not proceed.

33. Both UEs (10, 20) initiate PDU session modification request for the pair of Uu links involved (over 5GC path) also including a new parameter "PDU session to be deactivated".

They also include the negotiated ProSe path QoS parameters in the request.

54. PDU session modification/ deactivation is described in more detail in Figure 3: S4a. The AMF invokes "Nsmf_PDUSession_UpdateSMContext" including "SM Context ID" and "N2 SM information".

S4b. SMF initiates SM policy association modification where PCF is also updated based on SM policy association modification.

54c. PCF (or any newly defined NF taking the role) authorises negotiated ProSe path QoS parameters and accordingly updates the UDR.

S4d. The SMF sends an N4 Session Modification Request (if any) message to the UPF of the PDU Session and UPF proceeds with any changes and acknowledges the modification.

S4e. SMF responds the AMF on "Nsmf PDUSession_UpdateSMContext".

55. The AMF sends N2 resource release message to the R(AN). 35 S6. The relevant resources on Access Network (AN) level are released / modified.

Following the above steps, the Public Safety/NCIS session continues over the direct link established between UE A (10) and UE F (20).

Figure 4 shows a second scenario according to an embodiment of the present invention. This scenario represents a network-driven path switch from 5GC path to Prose path.

In this scenario, it is assumed that RAN-level triggers initiate a path switch from 5GC path to ProSe path.

The service flow steps for the second scenario shown in Figure 4 are as below.

Details of each step are: S11. R(AN) decides that the Public Safety/NCIS QoS requirements cannot be met over 5GC path based on UE (L1/L2) measurement reports over Uu or some newly imposed admission control policy.

512. R(AN) sends a newly proposed QoS notification N2 message including related PDU session ID(s), N2 SM information to the AMF. Unlike AN initiated notification control as captured in 23.502, it is assumed that the newly proposed QoS notification is applicable for both GBR and non-GBR flows when a target QoS parameter cannot be met.

S13. The AMF invokes "Nsmf PDUSession_UpdateSMContext" including "SM Context ID" and "N2 SM information." S14. SMF initiates SM policy association modification to deactivate both PDU sessions over 5GC path. PCF is also updated based on SM policy association modification.

S15. SMF responds the AMF on "Nsmf PDUSession_UpdateSMContext". This includes Ni SM container that carries the "PDU Session Modification Command" that the AMF shall provide to the UE. In particular, Ni SM Container includes new ProSe path CoS rules and parameters for ProSe path communication.

516. The AMF transfers the SM container to the corresponding UEs via Ni.

S17. The AMF also sends N2 resource release message to the R(AN).

S18. At the same time, UE A sends direct communication request to initiate the unicast layer-2 link establishment incl. Prose path QoS rules and parameters provided by the network. UE F accepts the request and confirms the support of ProSe path QoS flows / parameters received.

819. Relevant resources on AN-level are released! modified.

Figure 5 shows a third scenario according to an embodiment of the present invention. This scenario represents an application-driven path switch from 5GC path to ProSe path.

In this scenario, it is assumed that the application server (at Application Function -AF level) notices a change in network topology/ proximity arrangement and decides to initiate a path switch from 5GC path to ProSe path. Furthermore, it is assumed that PCF (or any newly added NF taking its role) has already subscribed to UDR to receive notifications on any service parameter updates from application server.

The service flow steps for the third Scenario as shown in Figure 5 are as below.

Details of each step are: 521. PCF subscribes to UDR to receive notifications on any service-level parameter changes.

S22. The App. Server during a direct group discovery by UE A (over PC5-D) identifies UE F has moved to the proximity range for the current service. Similar to the first scenario, direct group discovery either runs periodically or may be triggered based on a proximity "notification alert" from PF (or any other new NF taking that role within 5GC) as already captured in TS 23.303.

823. The App. Server invokes a "ServiceParameter Update" service operation through NEF as an AF.

S24. The NEF stores the App. Server provided information within the UDR.

825. The PCF receives the notification of data change from UDR (which it has already subscribed to in step S21.).

826. NEF responds on "ServiceParameter_Update" to the AF.

827. PCF initiates PDU selection policy update via invoking "N1N2MessageTransfer" communication service provided by AMF.

528. The PDU selection policy update is conveyed to UEs (A, F) via Ni DL message.

S29. UE A sends direct communication request to initiate the unicast layer-2 link establishment incl. ProSe path QoS rules and parameters provided by the AF/ PCF. UE F accepts the request and confirms the support of ProSe path QoS flows /parameters received.

530. Both UEs initiate PDU session modification request for the pair of Uu links (over 5GC path) including the newly proposed parameter "PDU session to be deactivated".

531. PDU session modification is followed in similar steps as shown in Figure 3, except step S4c. (relating PCF authorisation) is omitted.

532. The AMF also sends N2 resource release message to the R(AN).

533. Relevant resources on AN-level are released! modified.

In the following embodiments it is assumed that two example users termed as UE A (10) and UE G (20) have already established a Public Safety/NCIS session together over a ProSe path but due to some triggering condition, as described below, they decide to switch from ProSe direct communication path to 5GC path to continue their joint session.

Figure 6 shows a fourth scenario according to an embodiment of the present invention. This represents a UE-driven path switch from ProSe path to 5GC path UE A (10) and UE G (20) have already established a Public Safety/NCIS session over ProSe path when they were in proximity. The service flow steps for this fourth Scenario as shown in Figure 6 and 7 and as set out below.

Details of each step are: S41. [Trigger a] UE A during direct group discovery identifies UE G is moving out of the proximity range for the current service. Similar to the first and third scenarios (shown in Figures 2 and 5), direct group discovery either runs periodically or may be triggered based on a proximity "notification alert" from PF (or any other new NF taking that role within 5GC) as already captured in TS 23.303.

S42. [Trigger b] Due to degradation in channel state based on L1/L2 measurements and indications on PC5-U, either UE A or G identifies that the ProSe path QoS requirements can not be supported anymore.

S43. [Based on Trigger b, conditional to PC5-S availability] UE A notifies UE G for path switch to 5GC path via PC5-S. This request also includes Suggested 5GC path QoS flows / parameters mapped based on former ProSe path QoS parameters to meet Public Safety/NCIS session service requirements. UE G accepts the path switch request and confirms support of 5GC path QoS flows / parameters received.

S44. Both UEs initiate PDU session modification request to (re)activate 5GC path via Uu links. They also specify packet filters based on either Suggested 5GC path QoS parameters over PC5-S [conditional to PC5-S availability] or Expected 5GC path QoS parameters given the former ProSe path QoS parameters and pre-configured rules within UEs.

S45. Each UE (re)activates corresponding PDU session over 5GC path following procedure illustrated in Figure 7 (similar to the situation illustrated in Figure 3), in particular PCF authorises the suggested/expected 5GC path QoS parameters for UE A and UE G and updates UDR accordingly.

S46. The AMF sends N2 PDU session (re-activation) request message to the R(AN).

547. (R)AN sets up the related AN-level resources.

Following the above steps, the Public Safety/NCIS service continues over the 5GC path established between UE A, UE G. Figure 8 shows a fifth scenario according to an embodiment of the present invention. This scenario represents a Network-driven path switch from ProSe path to 5GC path.

In this scenario, it is assumed that RAN-level triggers initiate a path switch from ProSe path to 5GC path.

The service flow steps for the fifth scenario shown in Figure 8 are as below.

Details of each step are: S51. (R)AN decides that the Public Safety/NCIS QoS requirements can not be met over PC5 based on UE measurements (over PC5-U) and a corresponding notification.

552. (R)AN sends an N2 message including "PDU Session ID(s)"and "N2 SM information" to the AMF.

553. The AMF invokes "Nsmf PDUSession_UpdateSMContext" including "SM Context ID" and "N2 SM information".

554. SMF initiates SM policy association modification to (re)activate (or establish) PDU sessions over 5GC path. PCF is also updated based on SM policy association modification.

S55. SMF responds the AMF on "Nsmf PDUSession_UpdateSMContext". This includes Ni SM container that carries the "PDU Session Modification Command".

356. The AMF transfers the SM container to the corresponding UEs via N1. N1 SM Container includes new 5GC QoS rules and parameters.

S57. The AMF sends N2 PDU session (re-activation) request message to the R(AN).

558. (R)AN sets up related AN-level resources.

Following the above steps, the Public Safety/NCIS service continues over 5GC path established between UE A and UE G. Figure 9 shows a six scenario according to an embodiment of the present invention. This scenario represents an application-driven path switch from ProSe path to 5GC path.

In this scenario, it is assumed that Application server (at Application Function level) notices a change in network topology/ proximity arrangement and decides to initiate a path switch from ProSe path to 5GC path. Furthermore, it is assumed that PCF (or any newly added NF taking its role) has already subscribed to UDR to receive notifications on any service parameters update from application server.

The service flow steps for the sixth scenario shown in Figure 9 are as below.

Details of each step are: 561. PCF subscribes to UDR to receive notifications on any service-level parameter changes.

862. The App. Server during a direct group discovery by UE A (over PC5-D) identifies UE G is moving out of the proximity range for the current service. This is similar to the first, their and fourth scenario set out above, where direct group discovery either runs periodically or may be triggered based on a proximity "notification alert' from PF (or any other new NF taking that role within 5GC) as already captured in TS 23.303.

863. The App. Server invokes a "ServiceParameter Update" service operation through NEF as an AF.

S64. The NEF stores the App. Server provided information within the UDR.

S65. The PCF receives the notification of data change from UDR (which it has already subscribed to in step S61.

566. NEF responds on "ServiceParameter_Update" to the AF.

567. PCF initiates PDU selection policy update via invoking "N1N2MessageTransfer" communication service provided by AMF.

568. The PDU selection policy update is conveyed to UEs (A, G) via Ni DL message.

569. Both UEs initiate PDU session modification request to reactivate 5GC path via Uu links. They also specify packet filters based on 5GC QoS parameters provided by AF/PCF in the request.

S70. PDU session reactivation is followed as captured in Figure 7 (fourth scenario), except step 845cc (on PCF authorisation) is omitted.

S71. The AMF sends N2 PDU session (re-activation) request message to the R(AN). 572. (R)AN sets up related AN-level resources.

Following the above steps, the Safety/NCIS service continues over 5GC path established between UE A (10) and UE G (20).

By means of one of the aforementioned embodiments, it is possible to switch On either direction) path between Prose and 5GC. The embodiments set out the possible triggers for such a switch and the steps which are required in order to activate the switch.

Although presented in terms of ProSe and 5GC, the skilled person will readily appreciate that other network topologies and/or protocols which rely on direct communication between UEs and also network-driven communication between the same devices will benefit from embodiments of the invention.

At least some of the example embodiments described herein may be constructed, partially or wholly, using dedicated special-purpose hardware. Terms such as 'component', 'module or 'unit' used herein may include, but are not limited to, a hardware device, such as circuitry in the form of discrete or integrated components, a Field Programmable Gate Array (FPGA) or Application Specific Integrated Circuit (ASIC), which performs certain tasks or provides the associated functionality. In some embodiments, the described elements may be configured to reside on a tangible, persistent, addressable storage medium and may be configured to execute on one or more processors. These functional elements may in some embodiments include, by way of example, components, such as software components, object-oriented software components, class components and task components, processes, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuitry, data, databases, data structures, tables, arrays, and variables. Although the example embodiments have been described with reference to the components, modules and units discussed herein, such functional elements may be combined into fewer elements or separated into additional elements. Various combinations of optional features have been described herein, and it will be appreciated that described features may be combined in any suitable combination. In particular, the features of any one example embodiment may be combined with features of any other embodiment, as appropriate, except where such combinations are mutually exclusive. Throughout this specification, the term "comprising" or "comprises" means including the component(s) specified but not to the exclusion of the presence of others.

Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

CLAIMS1. A method of path switching in a system where a first User Equipment, UE, is operable to communicate with a second UE via either a first direct path or a second path via a telecommunication network and wherein the active path is switched between the first and second paths, or vice-versa, in response to a trigger derived from: a) either one of the first and second UEs; b) the telecommunication network; or c) an application running on one of the UEs.
2. The method of claim 1 wherein the first path is a ProSe path and the second path is via a 5G Core network.
3. The method of claim 1 wherein when the active path is switched, Quality of Service, QoS, parameters are mapped between the two paths.
4. The method of any preceding claim wherein if the trigger is derived from a), this is as a result of relative proximity changes observed by one of the first and second UEs.
5. The method of any preceding claim wherein if the trigger is derived from a), the following steps are performed: Si. During Group discovery, a first UE identifies that a second UE has moved to the proximity range of the first UE; S2. The first UE sends a direct communication request to initiate a unicast layer-2 link establishment, the request including QoS flows/ parameters mapped based on former 5GC path QoS parameters to meet Public Safety/NCIS session service requirements, and the second UE accepts the direct communication request and confirms the support of path QoS flows! parameters received; S3. Both first and second UEs initiate PDU session modification request for the pair of Uu links involved, also including a parameter "PDU session to be deactivated" and including negotiated ProSe path QoS parameters in the request; 54a. AMF invokes "Nsmf PDUSession_UpdateSMContext" including "SM Context ID" and "N2 SM information"; S4b. SMF initiates SM policy association modification wherein PCF is also updated based on SM policy association modification; S4c. PCF authorises negotiated ProSe path QoS parameters and accordingly updates UDR; S4d. The SMF sends an N4 Session Modification Request Of any) message to a UPF of the PDU Session and UPF proceeds with any changes and acknowledges the modification; S4e. The SMF responds to the AMF on "Nsmf PDUSession_UpdateSMContext"; 55. The AMF sends N2 resource release message to R(AN); and 56. The relevant resources on Access Network (AN) level are released / modified.
6. The method on any of claims 1 to 4 wherein if the trigger is derived from a), the following steps are performed: 541 the first UE, during direct group discovery, identifies that the second UE is moving out of proximity range for the current service, or S42. due to degradation in channel state based on L1/L2 measurements and indications on PC5-U, either the first or second UE identifies that ProSe path QoS requirements mau not be supported anymore; S43. If 542 applies, the first UE notifies the second UE of a path switch to 5GC path via PC5-S, the request including suggested 5GC path QoS flows / parameters mapped based on former ProSe path QoS parameters to meet Public Safety/NCIS session service requirements, and the second UE accepts the path switch request and confirms support of 5GC path QoS flows! parameters received; S44. Both first and second UEs initiate PDU session modification request to activate 5GC path via Uu links, and both UEs also specify packet filters based on either suggested 5GC path QoS parameters over PC5-5 or Expected 5GC path QoS parameters given former ProSe path QoS parameters and pre-configured rules within UEs; S45. Each of the first and second UE activates corresponding PDU session over 5GC path; 546. AMF sends N2 PDU session (re-activation) request message to the R(AN); and S47. (R)AN sets up related AN-level resources.
7. The method of any of claims 1 to 3 wherein if the trigger is derived from b), this is as a result of QoS changes observed by Radio-Access Network.
8. The method of any of claims 1 to 3, if the trigger is derived from b), or claim 7, wherein the following steps are performed: S11. R(AN) decides that Public Safety/NC IS QoS requirements cannot be met over 5GC path based on UE (L1/L2) measurement reports over Uu; S12. R(AN) sends a QoS notification message including related PDU session ID(s), N2 SM information to AMF; 513. The AMF invokes "Nsmf_PDUSession_UpdateSMContext" including "SM Context ID" and "N2 SM information"; S14. SMF initiates SM policy association modification to deactivate PDU sessions and PCF is also updated based on SM policy association modification; S15. The SMF responds to the AMF on "Nsmf PDUSession_UpdateSMContext", including Ni SM container that carries the "PDU Session Modification Command" that the AMF provides to the UEs; S16. The AMF transfers the SM container to the corresponding UEs via Ni; S17. The AMF sends N2 resource release message to the R(AN); S18. A first UE sends direct communication request to initiate the unicast layer-2 link establishment including QoS rules and parameters provided by the network and the second UE accepts the request and confirms the support of QoS rules and parameters received; and S19. Relevant resources on AN-level are released / modified.
9. The method of any of claims 1 to 3, if the trigger is derived from b), or claim 7, wherein the following steps are performed: S51. (R)AN decides that Public Safety/NCIS QoS requirements may not be met over PC5 based on UE measurements and a corresponding notification; 852. (R)AN sends an N2 message including "PDU Session ID(s)"and "N2 SM information" to AMF; 553. The AMF invokes "Nsmf PDUSession_UpdateSMContext" including "SM Context ID" and "N2 SM information"; 554. SMF initiates SM policy association modification to (re)activate (or establish) PDU sessions over 5GC path, and PCF is updated based on SM policy association modification; 555. SMF responds to AMF on "Nsmf PDUSession_UpdateSMContext", including Ni SM container that carries the "PDU Session Modification Command"; S56. The AMF transfers the SM container to the corresponding UE via Ni, and Ni SM Container includes new 5GC QoS rules and parameters; S57. The AMF sends N2 PDU session (re-activation) request message to the R(AN); and 858. (R)AN sets up related AN-level resources.
10. The method of any of claims 1 to 3 wherein if the trigger is derived from c), this is as a result of group topology changes observed by Application Function.
11. The method of any of claims 1 to 3, if the trigger is derived from c), or claim 10, wherein the following steps are performed.521. PCF subscribes to UDR to receive notifications on any service-level parameter changes; S22. An Application Server, during a direct group discovery by the first UE identifies the second UE has moved to the proximity range for the current service; 523. The Application. Server invokes a "ServiceParameter_Update" service operation through NEF as an AF; 524. The NEF stores the Application. Server provided information within UDR; 525. PCF receives notification of data change from UDR; 526. NEF responds on "ServiceParameter_Update" to the AF; 10 527. PCF initiates PDU selection policy update via invoking "N1N2MessageTransfer" communication service provided by AMF; 528. The PDU selection policy update is conveyed to the first and second UEs via N1 DL message; 529. The first UE sends direct communication request to initiate unicast layer-2 link establishment including ProSe path QoS rules and parameters provided by the AF/ PCF, and the second UE accepts the request and confirms the support of ProSe path QoS flows /parameters received; S30. Both first and second UEs initiate PDU session modification request for the pair of Uu links including the parameter "PDU session to be deactivated"; 531. PDU session modification occurs; S32. The AMF sends N2 resource release message to the R(AN); and 833. Relevant resources on AN-level are released / modified.
12. The method of any of claims 1 to 3, if the trigger is derived from c), or claim 10, wherein the following steps are performed: S61. PCF subscribes to UDR to receive notifications on any service-level parameter changes; 862. An Application Server, during a direct group discovery by the first UE, identifies that the second UE, is moving out of proximity range for a current service; 563. The Application Server invokes a "ServiceParameter Update" service operation through NEF as an AF; S64. The NEF stores the Application Server provided information within UDR; 565. PCF receives notification of data change from the UDR; 566. The NEF responds on "ServiceParameter Update" to the AF; 10 367. PCF initiates PDU selection policy update via invoking "N1N2MessageTransfer" communication service provided by AMF; 368. The PDU selection policy update is conveyed to the first and second UEs via N1 DL message; 369. Both the first and second UEs initiate PDU session modification request to reactivate 5GC path via Uu links and also specify packet filters based on 5GC QoS parameters provided by AF/PCF in the request; 370. The PDU session is reactivated; 571. The AMF sends N2 PDU session (re-activation) request message to the R(AN); and S72. (R)AN sets up related AN-level resources.
13. A telecommunication system comprising a network and at least two UEs operable to perform the method of any preceding step.