Core Network Node and Method for Supporting Redundant URLLC Connections

Abstract

A core network node and a method for supporting redundant URLLC connections are provided that allow a URLLC-enabled UE to determine whether it has been able to initiate a URLLC-type PDU session establishment. [Solution] A method for supporting URLLC with a network indication in a URLLC support indication exchange and registration procedure between network nodes, comprising: a URLLC-enabled UE 3 initiating a registration procedure with the network by triggering a registration request message; an NG-RAN node 5 selecting an AMF 710; if URLLC support is a subscription-based service, the AMF 710 querying a UDM / UDR 720 to verify the UE's subscription to URLLC before indicating URLLC support to the UE 3; and if the network supports URLLC, indicating URLLC support to the UE 3.

Description

Technical Field

[0001] The present disclosure relates to a communication system. The present disclosure is particularly related to, but not limited to, a wireless communication system and its devices operating according to 3rd Generation Partnership Project (3GPP) standards or their equivalents or derivatives. The present disclosure is related to, but not limited to, the provision of Ultra Reliable and Low Latency Communication (URLLC) in a so-called "5G" (or "Next Generation") system.

Background Art

[0002] The 3GPP SA2 working group is working on an Ultra Reliable Low Latency Communication (URLLC) research item. The purpose is to study and evaluate potential architecture enhancements for supporting URLLC services in a 5G system. Specifically, the following aspects are targeted. · Exploration of the main issues for meeting URLLC requirements regarding latency, jitter, and reliability in a 5G system as defined in TS22.261 · Research on ways to minimize the impact of user equipment (UE) mobility on latency and jitter between the access network (AN) and the core network (CN), and within the CN. · Research on ways to achieve transmission with higher reliability than that of a single N3 and N9 user plane tunnel and the NFs in the user plane path. · Research on ways to monitor the QoS of QoS flows with URLLC requirements. · Research on potential impacts on charging and policy control

[0003] SA2 defines a solution (TR23.725, 6.1) that enables a terminal device to set up two redundant PDU sessions through a 5G network (see Figure 1). As a result, the network always attempts to separate the paths of the two redundant PDU sessions whenever possible. The 3GPP network provides two paths from the device. The first PDU session goes from the UE through NG-RAN node 1 501 to UPF1 751 operating as a PDU session anchor, and the second PDU session goes from the UE through NG-RAN node 2 502 to UPF2 752 operating as a PDU session anchor. Based on these two independent PDU sessions, two independent paths are set up. This solution is based on the Dual Connectivity function supported by both LTE and NR. The UE sets up two PDU sessions. One PDU session reaches UPF1 751 operating as a PDU session anchor through MNG-RAN node 501, and the other PDU session reaches UPF2 752 operating as a PDU session anchor through SNG-RAN node 502. Even if the traffic through UPF1 751 and UPF2 752 can be routed through different user plane nodes within the Data Network (DN), UPF1 751 and UPF2 752 are connected to the same Data Network (DN). UPF1 751 and UPF2 752 are controlled by SMF1 731 and SMF2 732 respectively, and SMF1 731 and SMF2 732 may match depending on the operator settings for SMF selection. It depends on upper layer protocols such as IEEE TSN (Time Sensitive Networking) FRER (Frame Replication and Elimination for Reliability) to manage the replication and removal of redundant packets / frames on duplicate paths. Summary of the Invention

Problems to be Solved by the Invention

[0004] Assume that the above URLLC solutions TR23.725, 6.1, and other URLLC solutions have the following deployment compatibility between the RAN node and the Core Network Nodes: · The core network UPF deployment coordinates with the RAN deployment and supports redundant user plane paths. · The underlying transport topology collaborates with the RAN and UPF deployments and supports redundant user plane paths. · The physical network topology and geographical distribution of functions also support redundant user plane paths to the extent required by the operator.

[0005] However, it would be difficult or impossible for the operator to meet these assumptions to ensure that a UE requiring a redundant user path (i.e., a URLLC user connection) is always connected to the RAN and core network nodes that support URLLC (i.e., support user path redundancy) (see Figure 1).

[0006] The following are not guaranteed. · [Problem 1] A URLLC capable UE selects a URLLC supporting SMF - Currently, the UE does not know which SMF is the URLLC supporting SMF. · [Problem 2] A URLLC capable UE selects a URLLC supporting NG-RAN - Currently, the UE does not know which NG-RAN is the URLLC supporting NG-RAN. · [Problem 3] A URLLC supporting NG-RAN selects a URLLC supporting AMF - Currently, the NG-RAN does not have information on which AMF among the set of AMFs it is connected to is the AMF that supports URLLC. It is not practical (i.e., not cost-effective) for all connected AMFs to support URLLC. ·[Problem 4] The AMF supporting URLLC selects the SMF supporting URLLC - Currently, the AMF does not have information on which SMF is the SMF that supports URLLC. It is not practical (i.e., not cost-effective) for all SMFs that the AMF can select to be SMFs that support URLLC.

Means for Solving the Problem

[0007] According to one aspect of the present disclosure, a core network node includes means for receiving a request for establishment of a Protocol Data Unit (PDU) session for Ultra Reliable low Latency Communication (URLLC), and means for rejecting the establishment of the PDU session by the redundancy handling when it is determined that redundancy handling for the PDU session is not permitted, wherein the redundancy handling is Frame Replication and Elimination For Reliablity (FRER) of IEEE 802.1CB.

[0008] According to another aspect of the present disclosure, a method executed by a core network node includes receiving a request for establishment of a Protocol Data Unit (PDU) session for Ultra Reliable low Latency Communication (URLLC), and rejecting the establishment of the PDU session by the redundancy handling when it is determined that redundancy handling for the PDU session is not permitted, wherein the redundancy handling is Frame Replication and Elimination For Reliablity (FRER) of IEEE 802.1CB.

Advantages of the Invention

[0009] In one aspect, a core network node, a method in a core network node, can provide a technique for managing redundancy for PDU session(s).

Brief Description of the Drawings

[0010]

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[0011] To avoid URLLC connection establishment (e.g., user redundant path establishment) failures, the following aspects are provided. 1) The network indicates URLLC support during UE registration such that UE 3 requests user path redundancy only when the network supports URLLC. This aspect solves issues 1, 2, and 3. 2) URLLC support negotiation between the AMF 710 and the NG-RAN node 5. This aspect solves issue 2. 3) The NG-RAN node 5 broadcasts the URLLC support indication. This aspect addresses issue 1. 4) URLLC support SMF selection. This aspect solves issue 3. 5) URLLC support via a specified network slice. When the network uniformly supports URLLC throughout the registration area, this aspect solves issues 1, 2, and 3.

[0012] The First Aspect - Network indication of URLLC support during UE registration

[0013] The first aspect provides a network indication of URLLC support during the UE registration procedure. This enables UE 3 to request URLLC (e.g., PDU session establishment with user path redundancy) only when the network supports URLLC. An exemplary procedure for the network indication of URLLC support is schematically shown in FIG. 2.

[0014] 1) The URLLC-capable UE3 starts the registration procedure with the network by triggering a Registration Request message. If the UE3 supports URLLC (e.g., user plane redundancy), the UE3 indicates its own capabilities / support for URLLC by adding a URLLC capability indication parameter (or other indication to indicate the UE3's capability to support PDU session establishment with user plane redundancy required for short URLLC) to the registration request message. The URLLC capability / support parameter can be a specified parameter within the registration request message or part of the UE network capability information element (see Figure 3). The registration request message is included in an RRC message (e.g., an RRC Connection Request message, an RRC Connection Complete message, or other AS message) (e.g., in the form of an NAS PDU, container, or message). The UE3 can also include its own capability / support indication for URLLC support in the RRC message itself, either as a specified parameter or as part of the UE capability information element. The URLLC capability / support indication within the RRC message will assist the NG-RAN node 5 in selecting an AMF that supports URLLC in cases where not all connected AMFs support URLLC.

[0015] 2) The NG-RAN node 5 selects the AMF710. If the RRC message from the UE3 includes an indication of URLLC support / capability, the NG-RAN node 5 selects an AMF710 that supports URLLC. The NG-RAN node 5 may select the AMF710 based on the combination of the URLLC support / capability indication within the RRC message and the NSSAI (list of S-NSSAIs). The NG-RAN node 5 transfers the registration request message from the UE3 to the selected AMF710 within an N2 Setup Request message.

[0016] 3) If the URLLC support is a subscription-based service, the AMF 710 may query the UDM / UDR 720 via the Nudm_SDM_Get procedure or other procedures for retrieving UE subscriber information from the UDM / UDR 720. The URLLC UE subscription is the subscriber data information stored in the UDM / UDR 720. This information indicates whether the UE 3 is permitted for the establishment of URLLC including redundant user plane path establishment. This indication may be made for each UE, for each PDU session, or for each subscribed S-NSSAI (Subscribed S-NSSAI). The AMF 710 may obtain the URLLC capability / support indication from the PCF.

[0017] 4) When the network supports URLLC, the AMF 710 indicates the URLLC support to the UE 3. If the URLLC support is a subscription-based service, the AMF 710 verifies the subscription of the UE for URLLC before the indication of the URLLC support to the UE 3. The AMF 710 may also consider the operator policy or configuration before indicating the URLLC support. For example, if none of the SMFs connected to the AMF 710 support the URLLC function, the AMF 710 shall indicate to the UE 3 that the URLLC is not supported. Unless all conditions are satisfied, the AMF 710 indicates that the URLLC is not supported.

[0018] 5) The AMF 710 indicates URLLC support to the UE 3 within a Registration Accept message. The AMF 710 can include URLLC support parameters in the registration accept message. The AMF 710 can include URLLC support parameters for each allowed S-NSSAI. The AMF 710 can include a URLLC cause parameter associated with the URLLC support parameter. The URLLC support parameter may indicate the following. URLLC support = URLLC is supported, or URLLC is rejected, or URLLC is not supported, or not subscribed to URLLC, or URLLC is not supported at this location, and / or URLLC is not supported by the vPLMN. The AMF 710 may also indicate URLLC support within a UE Configuration Update message, especially if the support for URLLC has changed while the UE 3 is still in the same registration area. The AMF 710 can include URLLC support parameters for each allowed S-NSSAI. The AMF 710 sends the registration accept message to the UE 3 via the NG-RAN node 5 within an N2 Setup Response message. The AMF 710 can also include a URLLC support indication in the N2 Setup Response message itself. In this way, the AMF 710 configures or updates the NG-RAN node 5 with the AMF capabilities for URLLC support. The NG-RAN node 5 uses the AMF capabilities for URLLC support when selecting an AMF for the new registration of a UE having capabilities for URLLC, for example, when selecting a URLLC-capable AMF for a URLLC-capable UE.

[0019] 6) The NG-RAN node 5 sends a UE registration acceptance message to the UE3 by means of an RRC message.

[0020] 7) Based on the URLLC support indication, the UE3 executes an appropriate PDU session establishment procedure. If the URLLC support indication is included in the registration acceptance message and: a) The URLLC support indication = URLLC is supported. - URLLC is supported by the network, and the UE3 can initiate a URLLC connection (e.g., establish a PDU session with user plane redundancy) as required. b) The URLLC support indication = URLLC is rejected. - In this case, it means that although the network usually supports URLLC, its use has been rejected for some reason. In this case, the AMF710 can also include a URLLC cause parameter in the registration acceptance message to indicate the cause of the URLLC rejection. Examples of the cause of rejection can be the following use cases. + Temporarily not supported; + The network is overloaded. c) The URLLC support indication = URLLC is not supported. - URLLC is not usually supported by the network. The UE3 shall not trigger URLLC requests while in this PLMN. d) The URLLC support indication = URLLC is not subscribed. - UE3 does not have a subscription for URLLC. AMF 710 may also include URLLC cause parameters to indicate whether the subscription limit is usually per UE, or per PDU session, or per S-NSSAI. UE3 shall not trigger URLLC requests while in this PLMN. If there is a reason to clarify the subscription limit, UE3 shall follow the subscription limit, for example, not initiate URLLC for a specific PDU session or S-NSSAI. e) URLLC support indication = URLLC is not supported at this location - The network does not support URLLC at this location, for example, in this cell or TA or Registration Area. UE3 shall not initiate URLLC support requests while UE3 is in its location area, for example, cell, TA or registration area. f) URLLC support indication = URLLC is not supported by the vPLMN - URLLC is not supported by the visited PLMN. UE3 shall not trigger URLLC requests while in that vPLMN.

[0021] The lack of URLLC support indication may be interpreted by UE3 as if URLLC is not supported.

[0022] The URLLC support indication shown by the network may be a support indication that combines one or more of the following. - IEEE 802.1CB (FRER) [8] - IEEE 802.1Q [9] - Dual connectivity

[0023] The URLLC capability indication parameter shown by UE3 may be a support indication that combines one or more of the following. - IEEE 802.1CB (FRER) [8] - IEEE 802.1Q [9] - Dual connectivity

[0024] Second aspect URLLC support negotiation between AMF 710 and NG-RAN node 5

[0025] The second aspect relates to URLLC capability exchange between AMF 710 and NG-RAN node 5. The NG-RAN node 5 needs to know which of the connected AMFs is URLLC-capable so that the NG-RAN node 5 can select an AMF that supports URLLC for a UE that is URLLC-capable. First example Figure 4 schematically shows a first example of URLLC support indication exchange (i.e., URLLC capability exchange) between AMF 710 and NG-RAN node 5 during the NG connection setup procedure.

[0026] 1) When the NG-RAN node 5 starts the connection setup with one of the connected AMFs, the NG-RAN node 5 indicates its capabilities for URLLC support within the NG setup request message.

[0027] 2) The AMF 710 indicates its capabilities for URLLC support within the NG Setup Response message by including URLLC support indication parameters. Thereby, the AMF 710 configures or updates the NG-RAN node 5 with information regarding its capabilities for URLLC support. The NG-RAN node 5 stores this information (i.e., the URLLC support indication parameters of the AMF 710) and the NG-RAN node 5 uses this information for AMF selection for newly attached UEs. That is, when a URLLC-capable UE registers or re-registers with the network, the NG-RAN node 5 will select the AMF 710 that supports URLLC. The absence of URLLC support indication parameters may be interpreted by the NG-RAN node 5 as if the AMF 710 does not support URLLC. The AMF 710 may set the URLLC support indication parameters taking into account operator policies or configurations. For example, if none of the SMFs connected to the AMF 710 support the URLLC function, the AMF 710 indicates to the NG-RAN node 5 that URLLC is not supported. The AMF 710 may set the URLLC support indication parameters for each S-NSSAI.

[0028] Second Example FIG. 5 schematically shows a second example of URLLC support indication exchange (i.e., URLLC capability exchange) between the AMF 710 and the NG-RAN node 5 during the RAN Configuration Update procedure.

[0029] 1) When the NG-RAN node 5 initiates a RAN configuration update procedure for the AMF 710, the NG-RAN node 5 indicates its capabilities for URLLC support in the RAN configuration update message.

[0030] 2) The AMF710 indicates its capabilities for URLLC support in the RAN Configuration Update Acknowledge message by including URLLC support indication parameters. Thereby, the AMF710 configures or updates the NG-RAN node 5 with information regarding its capabilities for URLLC support. The NG-RAN node 5 stores this information (i.e., the URLLC support indication parameters of the AMF710) and the NG-RAN node 5 uses this information for AMF selection for newly attached UEs. That is, when a URLLC-capable UE registers or re-registers to the network, the NG-RAN node 5 will select the AMF710 that supports URLLC. The absence of URLLC support indication parameters may be interpreted by the NG-RAN node 5 as the AMF710 not supporting URLLC. The AMF710 may set the URLLC support indication parameters considering operator policies or configurations. For example, if none of the SMFs connected to the AMF710 support the URLLC function, the AMF710 indicates to the NG-RAN node 5 that URLLC is not supported. The AMF710 may set the URLLC support indication parameters for each S-NSSAI.

[0031] The third example Figure 6 schematically shows a third example of the URLLC support indication exchange (i.e., URLLC capability exchange) between the AMF710 and the NG-RAN node 5 during the AMF configuration update procedure.

[0032] 1) When AMF710 starts the AMF configuration update procedure to NG-RAN node 5, AMF710 indicates its capabilities for URLLC support in the AMF configuration update message. Thereby, AMF710 configures or updates NG-RAN node 5 with information regarding the URLLC support capabilities. NG-RAN node 5 stores this information (i.e., the URLLC support indication parameters of AMF710) and NG-RAN node 5 uses this information for AMF selection for newly attached UEs. That is, when a URLLC-capable UE registers or re-registers to the network, NG-RAN node 5 will select AMF710 that supports URLLC. The lack of URLLC support indication can be interpreted by NG-RAN node 5 as AMF710 not supporting URLLC. AMF710 may set the URLLC support indication parameters considering the operator policy or configuration. For example, if none of the SMFs connected to AMF710 support the URLLC function, AMF710 indicates to NG-RAN node 5 the unsupported URLLC. AMF710 may set the URLLC support indication parameters for each S-NSSAI.

[0033] 2) NG-RAN node 5 indicates its capabilities for URLLC support in the AMF configuration update confirmation message by including the URLLC support indication parameters.

[0034] The third aspect NG-RAN node 5 broadcasts the URLLC support indication

[0035] The third aspect proposes the URLLC support / capability broadcast by the NG-RAN node 5, that is, the URLLC support indication parameter in one of the System Information messages broadcast by the NG-RAN node 5. This indicates to the UE that URLLC is supported by the network within its cell. The main steps of the third aspect are schematically shown in FIG. 7.

[0036] 1) Preamble - The AMF 710 has already configured or updated the NG-RAN node 5 based on the information regarding whether the core network supports URLLC. The support for URLLC by the core network can be changed according to location, time, or based on the overload situation. Any change in the URLLC support by the core network is updated at the NG-RAN node 5 during the NG setup procedure, the RAN configuration update procedure, or the AMF configuration update procedure. The AMF 710 may indicate URLLC support for each S-NSSAI.

[0037] 2) When the AMF 710 indicates the core network's support for URLLC and the NG-RAN node 5 itself also supports URLLC, the NG-RAN node 5 may broadcast the URLLC support indication parameter in one of the system information to indicate to the UE that URLLC is supported in its cell. The NG-RAN node 5 may broadcast the URLLC support indication parameter for each slice or for each DNN.

[0038] 3) When the URLLC support indication parameter exists in the system information broadcast, the UE 3 recognizes that it can register for URLLC and can also trigger the establishment of a URLLC PDU session if necessary.

[0039] The fourth aspect URLLC support SMF selection

[0040] The fourth aspect proposes a method for AMF 710 to select an SMF for URLLC support. When a PDU session establishment request is initiated from a URLLC-capable UE, or when the PDU session request includes a redundancy sequence number (RSN), AMF 710 needs to select an SMF 730 that supports URLLC. AMF 710 performs NRF discovery by including URLLC parameters in an Nnrf_Discovery request (Nnrf_Discovery Request). In this way, AMF 710 selects an SMF 730 that supports URLLC (see Figure 8).

[0041] 1) The URLLC-capable UE is already registered with an AMF 710 that supports URLLC.

[0042] 2) UE3 initiates a PDU session establishment for URLLC (e.g., for a redundant user path with a redundancy sequence number).

[0043] 3) AMF 710 queries an appropriate NRF 740 within the serving PLMN by issuing an Nnrf_NFDiscovery_Request that includes a URLLC indication along with other necessary parameters for SMF selection.

[0044] 4) NRF 740 uses the URLLC indication by AMF 710 as a service parameter to discover an SMF 730 that supports URLLC. If an SMF 730 that supports URLLC is available, the procedure continues from step 5 to step 8. If an SMF 730 that supports URLLC is not available, the procedure continues from step 9.

[0045] 5) In the serving PLMN, NRF740 provides AMF710 with, in the Nnrf_NFDiscovery_Request response message, a set of, for example, FQDN(s) or IP address(es) of the discovered SMF instance(s) (e.g., SMF1 731) corresponding to URLLC or the endpoint address(es) of the SMF service instance(s) (if any). If NRF740 cannot discover an SMF corresponding to the URLLC function, NRF740 responds to AMF710 with null or an error indication. In this case, AMF710 may restart from step 3 without the URLLC indication included in the Nnrf_NFDiscovery_Request message to discover an SMF730 that does not support URLLC, i.e., a normal SMF730.

[0046] 6) AMF710 invokes the Nsmf_PDUSession_CreateSMContext service operation.

[0047] 7) If SMF1 731 accepts the PDU session request, SMF1 731 responds with an Nsmf_PDUSession_CreateSMContext response message.

[0048] 8) AMF710 responds with a PDU Session Establishment Accept message. AMF710 may include a URLLC SM cause parameter (or any other notation for a parameter having the purpose of indicating the URLLC support status) in the PDU session establishment accept message. The URLLC SM cause parameter may indicate the following values (i.e., be possible). - URLLC is configured / supported - That is, the setting of the URLLC PDU session is successful. - URLLC is not configured / supported - That is, the establishment of a URLLC PDU session is not possible (for example, among the set of SMFs that can be selected by the AMF 710, there is no SMF 730 that supports available URLLC). In this case, it is assumed that the UE 3 does not initiate another PDU session request for URLLC in the current registration area. This URLLC SM cause indication may be interpreted by the UE 3 as if the PDU session was established without URLLC settings. Or, - URLLC is not configured / supported at this location - URLLC is not supported at the current location, for example, in a cell, TA, or registration area. In this case, it is assumed that the UE 3 does not initiate another PDU session request for URLLC establishment in this location area, such as a cell, TA, or registration area. This URLLC SM cause indication may be interpreted by the UE 3 as if the PDU session was established without URLLC settings. And / or, - URLLC is not configured / supported by the vPLMN - URLLC is not supported by the visited PLMN. In this case, it is assumed that the UE 3 does not initiate another PDU session request for URLLC in this vPLMN. This URLLC SM cause indication may be interpreted by the UE 3 as if the PDU session was established without URLLC settings. And / or, - URLLC is overloaded - That is, the core network is overloaded (for example, among the set of SMFs that can be selected by the AMF 710, there is an SMF 730 that supports URLLC, but the URLLC SMF is not available due to overload reasons). In this case, the AMF 710 can also return a URLLC backoff timer. If the URLLC backoff timer is included, it is assumed that the UE 3 does not initiate another URLLC PDU session establishment until the expiration of the URLLC backoff timer. This URLLC SM cause indication may be interpreted by the UE 3 as if the PDU session was established without URLLC settings. And / or, - URLLC is temporarily unavailable - Some technical obstacle or other reason that makes URLLC unavailable. In this case, the AMF 710 may also return a URLLC backoff timer. If a URLLC backoff timer is included, the UE 3 shall not initiate another URLLC PDU session establishment until the expiration of the URLLC backoff timer. This URLLC SM cause indication may be interpreted by the UE 3 as if the PDU session was established without URLLC configuration.

[0049] The absence of the URLLC SM cause parameter may be interpreted by the UE 3 as if the PDU session was established with URLLC configuration.

[0050] The absence of the URLLC SM cause parameter may be interpreted by the UE 3 as if the PDU session was established without URLLC configuration.

[0051] 9) If the NRF 740 cannot discover an SMF 730 that supports URLLC, the NRF 740 shall respond to the AMF 710 with the SMF_cause parameter in the Nnrf_NFDiscovery_Response(SMF_cause) message. The SMF cause may indicate, for example, the cause of SMF rejection as follows. - The URLLC SMF is not available / supported - That is, there is no SMF 730 that supports URLLC in the set of SMFs that the AMF 710 can select. - The URLLC support SMF is overloaded - That is, there is an SMF 730 that supports URLLC in the set of SMFs that the AMF 710 can select, but the URLLC SMF is not available due to overload. - The URLLC support SMF is temporarily unavailable - Technical or other reasons that make the URLLC SMF unavailable.

[0052] 10) AMF710 rejects the PDU session establishment by sending a PDU Session Establishment Reject message. AMF710 can include the URLLC SM cause in the PDU Session Establishment Reject message and, in some cases, can include, for example, a URLLC backoff timer indicating the following. - URLLC is not configured / supported - That is, the URLLC PDU session establishment is not possible (for example, there is no SMF730 that supports URLLC available in the set of SMFs selectable by AMF710). In this case, UE3 shall not initiate another PDU session request for URLLC in the current registration area. - URLLC is not configured / supported at this location - URLLC is not supported in the current location, for example, in a cell, TA, or registration area. In this case, UE3 shall not initiate another PDU session request for URLLC PDU session establishment in this location area, for example, in a cell, TA, or registration area. - URLLC is not configured / supported by the vPLMN - URLLC is not supported by the visited PLMN. In this case, UE3 shall not initiate another PDU session request for URLLC in this vPLMN. - URLLC is overloaded - That is, the core network is overloaded (for example, there is an SMF730 that supports URLLC in the set of SMFs selectable by AMF710, but the URLLC SMF is not available due to overload reasons). In this case, AMF710 may also return a URLLC backoff timer. If the URLLC backoff timer is included, UE3 shall not initiate another URLLC PDU session establishment until the expiration of the URLLC backoff timer. - URLLC is temporarily unavailable - Some technical obstacle or other reason that makes URLLC unavailable. In this case, the AMF 710 may also return a URLLC backoff timer. If a URLLC backoff timer is included, the UE 3 shall not initiate another URLLC PDU session establishment until the expiration of the URLLC backoff timer.

[0053] The lack of URLLC SM cause parameters may be interpreted by the UE 3 as if the PDU session was established without URLLC configuration.

[0054] Fifth aspect URLLC support via a specified network slice

[0055] The fifth aspect proposes that the URLLC support attribute is a built-in network slice attribute.

[0056] The S-NSSAI is composed of the following. - A slice / service type (SST) that indicates the expected network slice behaviour with respect to functions and services. - A slice differentiator (SD), which is optional information to complement the slice / service type(s) to distinguish between multiple network slices of the same slice / service type.

[0057] First example Propose a new slice service type (SST) value for URLLC support with redundant user plane paths - A URLLC redundant path or any other notation for SST for the purpose of establishing a PDU session with user plane redundancy (see Table 1).

[0058] Table 1 shows that the value "4" is used for URLLC support with a redundant user plane path, but the SST value may be any other value for the same purpose of URLLC support in the redundant user plane path indication. When the AMF 710 provides the Allowed NSSAI (list of allowed S-NSSAIs) to the UE 3, the URLLC function cannot be supported by the NG-RAN node 5 or the 5GC, but the AMF 710 may include the S-NSSAI designated for the URLLC redundant path. In this case, the AMF 710 may indicate to the UE 3 that the redundant user path cannot be set. When the AMF 710 provides the Allowed NSSAI (list of allowed S-NSSAIs) to the UE 3, the AMF 710 may not include the S-NSSAI designated for the URLLC redundant user path if the URLLC function cannot be supported by the NG-RAN node 5 or the 5GC. In this case, the AMF 710 may indicate to the UE 3 that a non-redundant path may still be set for that S-NSSAI.

Table 1

[0059] Second example A new slice differentiator (SD) for URLLC is proposed. The new SD includes information on whether the network slice supports redundant user path establishment.

[0060] When the AMF 710 provides the Allowed NSSAI (list of allowed S-NSSAIs) to the UE 3, the URLLC function cannot be supported by the NG-RAN node 5 or the 5GC, but the AMF 710 may include the S-NSSAI designated for the URLLC redundant path. In this case, the AMF 710 may indicate to the UE 3 that the redundant user path cannot be set. When the AMF 710 provides the UE 3 with the Allowed NSSAI (list of allowed S-NSSAIs), the AMF 710 may not include the S-NSSAI designated for the URLLC redundant user path if the URLLC functionality cannot be supported by the NG-RAN node 5 or the 5GC. In this case, the AMF 710 may indicate to the UE 3 that a non-redundant path may still be configurable for that S-NSSAI.

[0061] Advantageously, the above aspects include, but are not limited to, one or more of the following functions. 1. Negotiation of URLLC support and indication of URLLC support between network nodes by the network during the registration procedure or via system information broadcast. The URLLC-capable UE recognizes whether it can trigger the establishment of a URLLC-type PDU session and avoids establishing a PDU session due to URLLC failure if URLLC is not supported by the network. 2. Selection of a URLLC support SMF by the AMF 710 by adding new URLLC parameters in the NRF query procedure and returning the URLLC SM cause and URLLC backoff timer to the UE 3 in case of a URLLC PDU session establishment failure.

[0062] The above functions may be implemented using one or more of the following exemplary functions. 1) UE capabilities for URLLC indication in RRC messages 2) UE capabilities for URLLC indication in registration request messages 3) Network support for URLLC indication in registration acceptance and UE configuration update messages. 4) Network support for URLLC indication in system information broadcast. 5) AMF 710 support for URLLC indication in N2 setup response messages, AMF 710 configuration update messages, and RAN configuration update confirmation messages. 6) URLLC SM Cause and URLLC Backoff Timer from NRF740 and AMF710 to the UE 7) URLLC Support as UE Subscriber Information 8) URLLC Support SST and SD Values for Network Slicing

[0063] The above aspects describe an exemplary method comprising (at least some of) the following steps.

[0064] Aspect 1: 1) UE Capability for URLLC Indication in RRC Messages 2) UE Capability for URLLC Indication in Registration Request Messages 3) URLLC Support as UE Subscriber Information 4) AMF710 Support for URLLC Indication in N2 Setup Response Messages 5) Network Support for URLLC Indication in Registration Acceptance and UE Configuration Update Messages

[0065] Aspect 2: URLLC Support Information Exchange between AMF710 and NG-RAN Node 5

[0066] Aspect 3: URLLC Support by Network Broadcast in System Information

[0067] Aspect 4: Selection of SMF Supporting URLLC by AMF710 via NRF Query

[0068] Aspect 5: URLLC Support SST and SD Values for Network Slicing

[0069] Advantages

[0070] The present disclosure proposes a URLLC support indication by a network during a registration procedure so that a URLLC-capable UE can avoid a URLLC PDU session establishment failure when the network does not support URLLC.

[0071] System Overview

[0072] FIG. 9 schematically shows a mobile (cellular or wireless) communication system 1 to which the above aspects and examples are applicable.

[0073] In this network, users of mobile devices 3 (UEs) can communicate with each other and with other users via each base station 5 and the core network 7 using an appropriate 3GPP radio access technology (RAT), e.g., E-UTRA, and / or 5G RAT. It is understood that a plurality of base stations 5 form a (radio) access network, or (R)AN. Although one mobile device 3 and one base station 5 are shown in FIG. 9 for illustrative purposes, as will be understood by those skilled in the art, the system will typically include other base stations and mobile devices (UEs) when implemented.

[0074] Each base station 5 controls one or more associated cells (either directly or via other nodes such as home base stations, relays, remote radio heads, and / or distributed units). A base station 5 that supports the E-UTRA / 4G protocol may be referred to as an "eNB", and a base station 5 that supports the NextGeneration / 5G protocol may be referred to as a "gNB". In this example, the base station 5 forms part of a "Next Generation" RAN (NG-RAN) that supports 5G communication. It is understood that some base stations 5 may be configured to support both 4G and 5G, and / or any other 3GPP or non-3GPP communication protocol.

[0075] The mobile device 3 and its serving base station 5 are connected via an appropriate air interface (e.g., the so-called "Uu" interface, etc.). Adjacent base stations 5 are connected to each other via an appropriate base station interface for the base station interface (such as the so-called "X2" interface and / or "Xn" interface, etc.). The base station 5 is also connected to the core network node via an appropriate interface (such as the so-called "S1", "N1", "N2", and / or "N3" interfaces, etc.).

[0076] To support communication in the communication system 1, the core network 7 typically includes logical nodes (or "functions"). Typically, for example, the core network 7 of a "Next Generation" / 5G system will include a control plane function (CPF) 10 and a user plane function (UPF) 11 in addition to other functions. Such control plane functions (and user plane functions) may provide the functions of AMF 710, UDM / UDR 720, SMF 730, and / or NRF 740 as discussed in the above manner.

[0077] A connection from the core network 7 to an external IP network 20 (such as the Internet) is also provided.

[0078] The components of this system 1 are configured to perform the above-described manner.

[0079] User Equipment (UE)

[0080] FIG. 10 is a block diagram showing more details of the main components of the UE (mobile device 3) shown in FIG. 9. As shown, the UE 3 includes a transceiver circuit 31 operable to transmit signals to and receive signals from connected nodes via one or more antennas 33. Although not necessarily shown, the UE will of course have all the normal functions of a conventional mobile device (such as user interface 35), which may be provided by any one or any combination of hardware, software, and firmware as required. The controller 37 controls the operation of the UE according to the software stored in the memory 39. The software may be pre-installed in the memory 39, for example, and / or downloaded via the telecommunications network 1 or from a removable data storage device (RMD). The software includes, among other things, an operating system 41 and a communication control module 43. The communication control module 43 is responsible for corresponding to (generating / sending / receiving) signaling messages including uplink / downlink data packets between the UE 3 and other nodes (such as (R)AN nodes 5 and core network nodes) according to any one of the above-described manners.

[0081] (R)AN node

[0082] FIG. 11 is a block diagram showing in more detail the main components of the exemplary (R) AN node 5 (base station) shown in FIG. 9. As shown, the (R) AN node 5 receives signals from connected UE3 (s) via one or more antennas 53, transmits signals to the UE3, and transmits signals to other network nodes (directly or indirectly) via the network interface 55 and receives signals from the node, and includes a transceiver circuit 51 operable to do so. The network interface 55 typically includes a suitable base station, e.g., a base station interface such as (X2 / Xn), and a suitable base station, e.g., a core network interface such as (S1 / N1 / N2 / N3, etc.). The controller 57 controls the operation of the (R) AN node 5 according to software stored in the memory 59. The software may be pre-installed in the memory 59, for example, and / or downloaded via the telecommunications network 1 or from a removable data storage device (RMD). The software includes, among other things, an operating system 61 and a communication control module 63. The communication control module 63 is responsible for handling (generating / sending / receiving) signaling between the (R) AN node 5 and other nodes such as UE3 and core network nodes / network elements. Such signaling includes messages (and their information elements) properly formatted according to any one of the above-described manners.

[0083] Core network node

[0084] FIG. 12 is a more detailed block diagram showing the main components (network elements or functions) of the general core network node shown in FIG. 9. As shown, the core network node includes a transceiver circuit 71 operable to transmit signals to and receive signals from other nodes (including UE3 and (R) AN node 5) via a network interface 75. A controller 77 controls the operation of the core network node according to software stored in a memory 79. The software may be pre-installed in the memory 79, for example, and / or downloaded via a telecommunications network 1 or from a removable data storage device (RMD). The software includes, among other things, an operating system 81 and at least a communication control module 83. The communication control module 83 is responsible for handling (generating / sending / receiving) signaling between the core network node and other nodes such as UE3, (R) AN node 5, and other core network nodes. Such signaling includes messages (and their information elements) properly formatted according to any one of the above-described manners.

[0085] Variations and Alternatives

[0086] The detailed aspects have been described above. As will be understood by those skilled in the art, numerous variations and alternatives can be made to the above aspects and the advantages of the present disclosure implemented therein can be obtained. Only some of these alternatives and variations are described herein by way of example.

[0087] In the above description, the UE, (R)AN node, and core network node have been described as having several individual modules (such as communication control modules) for ease of understanding. These modules may be provided in this way, for example, for a specific application in which an existing system is modified to implement the present disclosure, or for other applications in a system designed from the beginning with the features of the present invention in mind. On the other hand, these modules may be incorporated into the operating system or the entire code, and thus, these modules may not be distinguishable as separate entities. These modules may be implemented in software, hardware, firmware, or a combination thereof.

[0088] Each controller may include, for example, a computer processor implemented by one or more hardware, a microprocessor, a central processing unit (CPU), an arithmetic logic unit (ALU), an input / output (IO) circuit, an internal memory / cache (program and / or data), a processing register, a communication bus (e.g., control, data, and / or address bus), a direct memory access (DMA) function, and any suitable form of processing circuit including, but not limited to, a counter, pointer, and / or timer implemented in hardware or software.

[0089] In the above aspect, many software modules have been described. As would be understood by those skilled in the art, the software modules may be provided in a compiled form or an uncompiled form, and may be supplied to the UE, (R)AN node, and core network node as signals on a computer network or on a recording medium. Further, the functions executed by some or all of this software may be executed using one or more dedicated hardware circuits. However, the use of software modules is preferred because it facilitates the updates of the UE, (R)AN node, and core network node in order to update their functions.

[0090] The above embodiments can also be applied to "non-mobile" or generally fixed user equipment.

[0091] Various other variations will be apparent to those skilled in the art and will not be described in further detail herein.

Prior Art Documents

Non-Patent Documents

[0092]

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

Non-Patent Document 4

Non-Patent Document 5

[0093] Abbreviations

[0094] 5GC 5G Core Network 5GS 5G System 5G-AN 5G Access-Network AMF Access and Mobility Management Function AN Access-Network AS Access Stratum DC Dual Connectivity DN Data Network DNN Data Network Name FQDN Fully Qualified Domain Name FRER Frame Replication and Elimination for Reliability GCF Global Certification Forum MNG-RAN Master Next Generation Radio Access-Network NAS Non-Access Stratum NEF Network Exposure Function NF Network Function NG-RAN Next Generation Radio Access-Network NR New Radio NRF Network Repository Function PDU Protocol Data Unit PLMN Public land mobile network QoS Quality of Service (R)AN (Radio) Access‐Network RRC Radio Resource Control SD Slice Differentiator SNG‐RAN Slave Next Generation Radio Access‐Network SMF Session Management Function S‐NSSAI Single Network Slice Selection Assistance Information SST Slice / Service Type TSN Time Sensitive Networking UDR Unified Data Repository UPF User Plane Function URLLC Ultra Reliable Low Latency Communication VPLMN Visited Public land mobile network

[0095] Definition

[0096] For the purposes of this specification, 3GPP TR 21.905 [1], and the terms and definitions given below apply. Terms defined in this specification, if they are also in 3GPP TR 21.905 [1], take precedence over the definitions of the same terms.

[0097] The present disclosure has been described above with reference to several aspects, but the present disclosure is not limited to each aspect. The configuration and details of the present disclosure can be changed in various ways that can be understood by those skilled in the art within the scope of the present disclosure.

[0098] This application is based on European Patent Application No. 19150842.3 filed on January 8, 2019, claims the benefit of its priority, and the disclosure thereof is incorporated herein by reference in its entirety.

Description of Reference Numerals

[0099] 1 Communication system 3 UE 31 Transceiver circuit 33 Antenna 35 User interface 37 Controller 39 Memory 41 Operating system 43 Communication control module 5 NG-RAN node 51 Transceiver circuit 53 Antenna 55 Network interface 57 Controller 59 Memory 61 Operating system 63 Communication control module 501 NG-RAN node 1 502 NG-RAN node 2 7 Core network 71 Transceiver circuit 75 Network interface 77 Controller 79 Memory 81 Operating System 83 Communication Control Module 710 AMF 720 UDM / UDR 730 SMF 731 SMF1 732 SMF2 740 NRF 750 UPF 751 UPF1 752 UPF2 10 CPF 11 UPF 20 External IP Network

Claims

1. A first core network node, comprising: means for receiving, from a user equipment (UE), a first request for establishing a Protocol Data Unit (PDU) session for Ultra Reliable Low Latency Communication (URLLC); means for transmitting, to a Network Repository Function (NRF), a second request for selecting a second core network node; means for receiving, from the NRF, a first response to the second request; means for selecting the second core network node when the first response indicates that the NRF has discovered the second core network node, wherein the second core network node supports redundancy; means for transmitting, to the UE, a second response indicating rejection of the establishment of the PDU session when the first response indicates that the NRF has been unable to discover the second core network node; wherein the redundancy is Frame Replication and Elimination For Reliability (FRER) of IEEE 802.1CB; A first core network node.

2. A method of a first core network node, comprising: receiving, from a user equipment (UE), a first request for establishing a Protocol Data Unit (PDU) session for Ultra Reliable Low Latency Communication (URLLC); transmitting, to a Network Repository Function (NRF), a second request for selecting a second core network node; receiving, from the NRF, a first response to the second request; selecting the second core network node when the first response indicates that the NRF has discovered the second core network node, wherein the second core network node supports redundancy; transmitting, to the UE, a second response indicating rejection of the establishment of the PDU session when the first response indicates that the NRF has been unable to discover the second core network node. The redundancy handling is Frame Replication and Elimination For Reliability (FRER) of IEEE 802.1CB, A method in a first core network node.

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