How to prevent communication disruptions

Abstract

According to one embodiment, a method for preventing communication failure is described, the method comprising: receiving a first request for establishment of a first communications session from a mobile terminal, establishing the first communications session via a first radio access network, receiving a second request for a second communications session from the mobile terminal, determining whether the second communications session should be a backup communications session for the first communications session, and establishing the second communications session via the second radio access network, wherein if the second communications session should be a backup communications session for the first communications session, the second radio access network is controlled to avoid allocation of communications resources for data exchange between the mobile terminal and a server via the second communications session until notified otherwise.

Description

[Technical Field]

[0001] The present disclosure relates to a communication method that prevents communication failures. [Background technology]

[0002]

[0003] In communications, especially over mobile communications networks, reliability plays an important role. This includes the need for a communications network to be able to quickly compensate for a failed communications connection. This can be achieved by providing redundant resources, for example, by providing two parallel communications connections in parallel for communications, but this may be undesirable as it may result in a waste of communications resources if there is no failure and the communications resources for the backup paths are not used.

[0003] Therefore, a resource-efficient approach to prevent communication failures is desirable. Summary of the Invention

[0004] According to one embodiment, there is provided a method for preventing communication failure, the method comprising: receiving a first request from the mobile terminal for establishment of a first communications session between the mobile terminal and a server, the first communications session being requested to be provided via a first wireless access network; establishing a first communication session between the mobile terminal and a server over a first wireless access network; receiving a second request from the mobile terminal for a second communication session between the mobile terminal and the server, the second communication session requested to be provided over a second wireless access network; determining whether the second communication session should be a backup communication session for the first communication session; establishing a second communication session between the mobile terminal and the server via a second radio access network, wherein if the second communication session is to be a backup communication session for the first communication session, the second radio access network is controlled to avoid allocating communication resources for data exchange between the mobile terminal and the server via the second communication session until notified otherwise; Includes. [Brief explanation of the drawings]

[0005] In the drawings, like reference characters generally refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. In the following description, various aspects are described with reference to the following drawings:

[0006] [Figure 1] 1 illustrates a wireless communication system. [Figure 2] An example is shown in which a user equipment (UE) is connected to a first radio access network (RAN) and a second RAN that belong to the same public land mobile network (PLMN). [Figure 3] An example is shown in which a UE is connected to a first RAN belonging to a first PLMN and a second RAN belonging to a second PLMN. [Figure 4] 3 shows a flow diagram illustrating the registration procedure for the single SIM (Subscriber Identity Module) scenario of FIG. 2. [Figure 5] 3 shows a flow diagram illustrating PDU (Protocol Data Unit) session establishment for the single SIM scenario of FIG. 2. [Figure 6] This shows the failure handling in case of an edge server malfunction. [Figure 7] 1 illustrates failure handling in case of a radio access network failure. [Figure 8] 1 illustrates paging management according to an embodiment. [Figure 9]1 illustrates mobility management according to an embodiment. [Figure 10] 4 shows a flow diagram illustrating the registration procedure for the multi-SIM scenario of FIG. 3. [Figure 11] 4 shows a flow diagram illustrating PDU session establishment for the multi-SIM scenario of FIG. 3. [Figure 12] Describes the fault handling in case of a PLMN failure. [Figure 13] 1 shows a flow diagram illustrating a method for preventing communication failure, according to an embodiment. [Figure 14] 1 shows a flow diagram illustrating a method for performing communication with a server, according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0007] The following detailed description refers to the accompanying drawings, which show, by way of illustration, specific details and aspects of the present disclosure in which the present invention may be practiced. Other aspects may be utilized, and structural, logical, and electrical changes may be made without departing from the scope of the present disclosure. The various aspects of the present disclosure are not necessarily mutually exclusive, in that some aspects of the present disclosure may be combined with one or more other aspects of the present disclosure to form new aspects.

[0008] Various examples corresponding to aspects of the present disclosure are described below.

[0009] Example 1 is a method for preventing communication failure, shown in FIG.

[0010] Example 2 is the method of example 1, further comprising allocating communication resources for the second communication session upon failure of the first communication session.

[0011] Example 3 is the method of example 1 or 2, including detecting a failure of the first communications session and, upon detecting the failure of the first communications session, notifying the second radio access network to allocate communications resources for the second communications session.

[0012] Example 4 is the method of example 3, wherein detecting a failure of the first communication session includes detecting a failure of the first radio access network and / or one or more network functions providing the first communication session.

[0013] Example 5 is the method of any one of Examples 2 to 4, wherein notifying the second radio access network to allocate communications resources for the second communications session includes triggering paging of the mobile terminal via the second radio access network.

[0014] Example 6 is the method of any one of Examples 2 to 4, including triggering a second radio access network to allocate communications resources for the second communications session by transmitting downlink data to a user plane function providing the second communications session.

[0015] Example 7 is the method of any one of Examples 1 to 6, including receiving a failure indication from the mobile terminal indicating a failure of the first communications session, and upon receipt of the failure indication, notifying the second radio access network to allocate communications resources for the second communications session.

[0016] Example 8 is the method of any one of Examples 1-7, including switching the mobile terminal to a Radio Resource Control idle or inactive state upon establishment of the second communication session.

[0017] Example 9 is the method of any one of Examples 1 to 8, including detecting a failure of the first communication session and, upon detecting the failure of the first communication session, transitioning the mobile terminal to a Radio Resource Control connected state.

[0018] Example 10 is the method of any one of Examples 1 to 9, wherein the second request from the mobile terminal for the second communications session provided to the server by the second radio access network includes an indication that the second communications session should be a backup communications session for the first communications session, and determining whether the second communications session should be a backup communications session for the first communications session includes determining, based on the indication, that the second communications session should be a backup communications session for the first communications session.

[0019] Example 11 includes the method of any one of Examples 1-10, wherein the first communication session and the second communication session are Protocol Data Unit (PDU) sessions.

[0020] Example 12 is the method of any one of Examples 1 to 11, wherein the server implements an application function, and the first communication session and the second communication session are communication sessions with the application function.

[0021] Example 13 is the method of any one of Examples 1 to 12, wherein the mobile terminal is subscribed to a communication network that includes both the first radio access network and the second radio access network.

[0022] Example 14 is the method of example 13, wherein the first communication session and the second communication session are established by the same session management component of the communication network.

[0023] Example 15 is the method of any one of Examples 1 to 14, wherein the mobile terminal has a first subscription with a first communications network including a first radio access network and a second subscription with a second communications network including a second radio access network.

[0024] Example 16 is the method of Examples 1-15, wherein the first communication session is established by a first session management component belonging to the first communication network, and the second communication session is established by a second session management component belonging to the second communication network.

[0025] Example 17 is the method of any one of Examples 1 to 16, wherein the first communication session and the second communication session are provided over the same User Plane Function (UPF).

[0026] Example 18 is the method of any one of Examples 1 to 17, wherein the first communication session and the second communication session are provided over different user plane functions.

[0027] Example 19 is the method of any one of Examples 1 to 18, receiving a first registration request from the mobile terminal for registering the mobile terminal with the first communication network before receiving the first request, and registering the mobile terminal with the first communication network; receiving a second registration request from the mobile terminal for registering the mobile terminal in the second communication network before receiving the second request, and registering the mobile terminal in the second communication network; Including, the second registration request includes an indication that the registration with the second communications network is a backup registration; The method, wherein determining whether the second communication session should be a backup communication session for the first communication session includes determining, based on the instruction, that the second communication session should be a backup communication session for the first communication session.

[0028] Example 20 is the method of any one of Examples 1-19, wherein the communications resources include at least one of radio resources, control plane resources, and user plane resources.

[0029] Example 21 is a communications network having a first radio access network and a second radio access network and one or more control components configured to perform the method of any one of Examples 1-20.

[0030] Example 22 is the communication network of example 21, wherein the one or more control components include at least one Access and Mobility Management Function (AMF) and / or at least one Session Management Function (SMF).

[0031] Example 23 is a method for performing communication with a server, as shown in FIG.

[0032] Example 24 is a mobile terminal configured to perform the method of example 23.

[0033] It should be noted that one or more features of any of the foregoing examples may be combined with any one of the other examples. In particular, examples described in relation to devices are equally valid for methods.

[0034] According to further embodiments, there is provided a computer program and computer readable medium comprising instructions that, when executed by a computer, cause the computer to perform the method of any one of the preceding examples.

[0035] Various examples are described in more detail below.

[0036] FIG. 1 shows a wireless communication system 100, which is configured, for example, in accordance with 5G (5th-Generation), i.e., 5GS, as defined by 3GPP (registered trademark) (3rd-Generation Partnership Project).

[0037] The wireless communication system 100 includes a mobile wireless terminal device 102, such as a User Equipment (UE), Nano Equipment (NE), etc. The mobile wireless terminal device 102, also called a subscriber terminal, forms the terminal side, while the other components of the wireless communication system 100 described below are part of the mobile wireless communication network side, i.e., part of the mobile wireless communication network (e.g., Public Land Mobile Network, PLMN).

[0038] Furthermore, the wireless communication system 100 includes a radio access network 103, which may include a plurality of radio access network nodes, i.e., base stations, configured to provide wireless access in accordance with 5G radio access technology (5G New Radio). It should be noted that the wireless communication system 100 may also be configured in accordance with LTE (Long Term Evolution) or other mobile wireless communication standards, although 5G is used herein as an example. Each radio access network node 103 may provide wireless communication with mobile wireless terminal devices 102 over the air interface. It should be noted that the radio access network 103 may include any number of radio access network nodes.

[0039] The wireless communication system 100 further comprises a Core Network (CN, here 5GC) 108 comprising an Access and Mobility Management Function (AMF) 101 connected to the RAN 103 and a Unified Data Management (UDM) 104. Here, and in the following examples, the UDM may further comprise an actual UE subscription database, known for example as a Unified Data Repository (UDR). The Core Network 108 further comprises an Authentication Server Function (AUSF) 109 and one or more Policy Control Functions (PCFs), in this example a first PCF 106 and a second PCF 107.

[0040] The core network 108 further includes a plurality of Session Management Functions (SMFs), in this example a first Session Management Function (SMF) 110 and a second Session Management Function (SMF) 112, and a plurality of User Plane Functions (UPFs), in this example a first User Plane Function (UPF) 111 and a second User Plane Function (UPF) 113. The SMFs 110, 112 are for processing Protocol Data Unit (PDU) sessions, i.e., for creating, updating and deleting PDU sessions and managing session contexts with the User Plane Functions (UPFs).

[0041] The core network 108 further includes an Application Function (AF) 105. Although the AF 105 is shown as being directly connected to the SMFs 110, 112 and PCFs 106, 107, it may also be connected to them via a Network Exposure Function (NEF), particularly if the AF 105 is maintained by a third party (i.e., a party other than the operator of the mobile wireless communications system 100).

[0042] The AF 105 allows an application to request the 5G system 100 to support a specific Quality of Service (QoS) for the UE 102 that establishes a PDU to provide communication services to the application.

[0043] In the example of Figure 1, the UE 102 is connected to a single RAN 103. However, the UE 102 may be connected to multiple RANs. The RANs may belong to the same PLMN (thus allowing the UE to use a single Subscriber Identity Module (SIM)), or may belong to different PLMNs (thus allowing the UE to have multiple SIMs associated with them (e.g., a multi-USIM UE)).

[0044] FIG. 2 shows an example in which a UE 201 is connected to a first RAN 202 and a second RAN 203 that belong to the same PLMN.

[0045] The RANs 202, 203 are connected to the same AMF 204 and UPF 205. The AMF 204 and UPF 205 are connected to an SMF 206, which is connected to an application function 207 (e.g., application function 105), which is assumed here to be running on edge computing node E1.

[0046] 3 shows an example in which a UE 301 is connected to a first RAN 302 belonging to a first PLMN 304 and a second RAN 303 belonging to a second PLMN 305. Each PLMN 304, 305 has its own AMF 306, 307 connected to each RAN 302, 303, a respective UPF 308, 309 connected to each RAN 302, 303, and a respective SMF 310, 311 connected to each AMF 306, 307 and UPF 308, 309.

[0047] Each RAN 302, 302 is connected to an application function located in E1 312 via a respective UPF 308, 309.

[0048] In both Figures 1 and 2, there is thus a first path via the first RAN 202, 302 to the application function at E1 207, 312, and a second path via the second RAN 203, 303 to the application function at E1 207, 312.

[0049] The second path may be a backup path for the first path (which acts as the "main" path).

[0050] According to the 5G Ultra Reliable Low Latency Coordination (URLLC) mechanism, both paths are always on, i.e., active. Therefore, the UE replicates packets it wants to send to E1 207, 312 (e.g., according to the IEEE Frame Replication and Elimination (FRER) protocol) and forwards them to the same application server. If E1 207, 312 or the application functionality at E1 207, 312 goes down, the sessions on both paths are released.

[0051] In contrast, according to various embodiments, the second path (i.e., the backup or redundant path) and the nodes forming it (at least those involved in this path) are kept asleep (also called silent) until they are needed as a backup for the first path. In the example of Figure 3, this relates to the second PLMN 305. In particular, for example, radio resources are not allocated to the second path until the second path is needed as a backup for the first path.

[0052] It should be noted that with regard to the RAN edge connection, the RAN 203, 303 may periodically exchange health check messages with the E1 207, 312 to detect if the E1 has failed or become unreachable, and may then send traffic via both backups, possibly to a backup edge server.

[0053] In the following, firstly embodiments relating to the single SIM case of FIG. 2 are discussed, and secondly, further below, embodiments relating to the multiple SIM case of FIG.

[0054] In the scenario of Figure 2, UE 201 has N1 (Non-Access Stratum (NAS) connection) per RAN (e.g., via each base station or RAN node), i.e., UE 201 has two NAS connections.

[0055] The AMF 204 maintains two N2 interfaces (i.e., one interface with the first RAN 202 and one interface with the second RAN 203). The UE 201 and the network side (e.g., the AMF 204 and / or the RAN 203 and / or further components) cooperate to determine which path is the main path and which path is the backup path. As long as the main path works correctly, the backup (i.e., redundant) path is inactive (i.e., "silent") and user plane traffic is exchanged via the main path (active path).

[0056] FIG. 4 shows a flow diagram 400 illustrating the registration procedure for the single SIM scenario of FIG.

[0057] A UE 401 corresponding to the UE 201, a first RAN 402 corresponding to the first RAN 202, a second RAN 403 corresponding to the second RAN 203, and an AMF 404 corresponding to the AMF 204 are involved in the flow.

[0058] At 405, the UE 401 requests registration for the main path with the network (i.e., the path via the first RAN 402), which the AMF 404 accepts at 406.

[0059] At 407, the UE 401 determines that a backup path should be established.

[0060] In response, at 408, the UE 401 finds a second RAN 403 for the backup path and sends a Silent Registration Request, i.e., a registration request message including an indication that the request is for backup (or redundancy) purposes, to the network.

[0061] In the silent registration request, the UE 401 can indicate the assigned GUAMI (Global Unique AMF ID) of the AMF 404 for registration 405 and 406 via the first RAN 402, so that the second RAN 403 can select the same AMF 404 as for the main path. Alternatively, if the UE 401 does not provide a GUAMI in the silent registration request, the second RAN 403 can select a new AMF. The new AMF identifies the (old) AMF 404 from the UDM 104, so that the new AMF can extract the UE context from the (old) AMF 404.

[0062] The purpose of silent registration is that a UE context is created in the second RAN 403, the network function and the core network (so that there is no need to communicate with the CN control plane (CP) for N3 establishment) for proactive failure handling and reduced service disruption time. The network side configures the network components accordingly, and at 409, the AMF 404 sends a registration accept for the second path to the UE 401, but the second RAN 403 does not allocate any radio resources to the UE 401 (until the redundant path is active).

[0063] The AMF 404 includes the redundancy policy in the RRC Inactive Assistance Information it sends to the second RAN 403. This information specifies the RRC policy for the backup path to the RAN and instructs the RAN to use the RRC inactive mechanism, i.e., to keep the second path inactive (until it should be activated as a backup for the first path). The AMF 404 and the UE 401 maintain two sets of state information, one set for each path.

[0064] FIG. 5 shows a flow diagram 500 illustrating PDU session establishment for the single SIM scenario of FIG.

[0065] The flow involves UE 501 corresponding to UE 201, a first RAN 502 corresponding to first RAN 202, a second RAN 503 corresponding to second RAN 203, an AMF 504 corresponding to AMF 204, an SMF 505 corresponding to SMF 206, a first UPF 506, and a second UPF 507. Note that although the paths use different UPFs in this example, they may also be the same UPF, as seen in the example of Figure 2. Furthermore, note that the path may include an intermediate SMF (I-SMF) and / or an intermediate UPF (I-UPF) between the RAN and the UPF.

[0066] At 508, the UE 501 requests a PDU session establishment (Estb.) via the first RAN 502 (with which it is registered according to FIG. 4).

[0067] In response to the request, the SMF 505 establishes, at 509, an active N3 interface with the first UPF 506 and, at 510, a redundant (backup) N3 interface with the second UPF 507 based on the redundancy profile. At 511, the SMF 505 confirms the PDU session establishment.

[0068] At 512, the UE 501 then has an active user plane connection with the first UPF 506.

[0069] At 513, the UE 501 sends a silent PDU session request via the second RAN 503 (with which it has silent registration according to FIG. 4).

[0070] The silent PDU session request includes the same parameters (e.g., S-NSSAI, DNN (Data Network Name), and the same or a different PDU session ID) as the active PDU session (i.e., the session requested in 508), but it includes an indication that it is for a redundant path.

[0071] The AMF 504 selects the same SMF 505 and sends it a silent PDU session request.

[0072] The SMF 505 checks the PDU session context at 514 and sends the new flow details for the second RAN 503 to the second UPF 507 at 515 .

[0073] At 516, the SMF 505 sends a PDU Session Accept to the second RAN 503 for N3 establishment, including details of the first UPF 506 and the second UPF 507.

[0074] In the PDU session accept message, the SMF 505 designates the active node as the first UPF 506 and the redundant node as the second UPF 507.

[0075] At 517, the UE 501 then has a backup user plane connection with the second UPF 507. However, after receiving the PDU session accept message at 516, the UE 501 enters the RRC_Inactive state, i.e., the second RAN 503 does not allocate any radio resources to the UE 501.

[0076] FIG. 6 illustrates the fault handling in case of a failure of E1 604.

[0077] Before the failure (see FIG. 1 610 ), the UE 601 has a connection to E1 604 via the first RAN 602 and the first UPF 603 .

[0078] After a failure (i.e., failure of E1 604) (see FIG. 2 611), the UE 601 has a connection to the backup E1 607 via the first RAN 602 and the second UPF 606.

[0079] FIG. 7 illustrates the failure handling in case of a failure of the first RAN 702.

[0080] Before the failure (see FIG. 1 710 ), the UE 701 has a connection to E1 704 via the first RAN 702 and the first UPF 703 .

[0081] After a failure (i.e., failure of RAN 702) (see FIG. 2 711), the UE 701 has a connection to E1 704 via the second RAN 705 and the first UPF 703.

[0082] The UE 701 may detect a failure of the first RAN 702 at the RRC layer and send an RRC connection message to the second RAN 705 upon the failure of the first RAN 702.

[0083] The second RAN 705 may detect a failure of the first RAN 702, for example, by exchanging periodic ECHO messages over the X2 interface, and may notify the UE 701 to activate a redundant path, for example, by paging the UE 701 when the UE 701 is in RRC IDLE.

[0084] The AMF 504 may also notify the second RAN 705 of the failure of the first RAN 702 via the N2 interface, so that the second RAN 705 notifies the UE 701 to activate a redundant path, for example, by paging the UE 701 when the UE 701 is in RRC IDLE.

[0085] It should be noted that when the UE 701 or the second RAN 705 detects a failure of the first RAN 702, the second RAN 705 may notify the AMF of the path change so that the AMF updates the UE context.

[0086] FIG. 8 illustrates paging management according to an embodiment.

[0087] The AMF 803 makes paging decisions based on context, including redundancy, i.e., the AMF 803 considers that there are active and redundant nodes.

[0088] Therefore, when the active path and backup path are established according to FIG. 5 and the first UPF 805 receives downlink data from the UE 801 and notifies the SMF 804 (which then notifies the AMF 803 of the downlink notification), the AMF 803 initiates paging via the first RAN 802.

[0089] The AMF 803 may need to page all RAN nodes within a registration area (assuming the first RAN 802 and the second RAN 806 are part of a tracking area). In this case, both the first RAN 802 and the second RAN 806 send a page (i.e., one or more paging messages) to the UE 801. When the UE 801 changes from idle to connected, the UE 801 sends a service request via the first RAN 802 but not the second RAN 806.

[0090] FIG. 9 illustrates mobility management according to an embodiment.

[0091] It is assumed that the second RAN 903 covers the coverage areas of both the first RAN 902 and the third RAN 903, and the UE 901 moves from the coverage area of the first RAN 902 to the coverage area of the third RAN 904. In this case, according to one embodiment, an Xn handover occurs, and the UE context is updated with the third RAN 903 as the active RAN (e.g., the corresponding RAN node is set as the active node). A similar mechanism can also be applied to a redundant node handover (i.e., a handover from the second RAN 903 to the fourth RAN).

[0092] Now, in the following, embodiments relevant to the multiple SIM case of FIG. 3 will be discussed.

[0093] These embodiments relate to the use of a multi-USIM UE 301 for redundancy mechanisms. To this end, the UE 301 and PLMNs 304, 305 exchange redundancy support capabilities; for example, the UE transmits redundancy support capabilities (e.g., support for silent or redundancy registration) to the PLMN's network, which in turn shares its redundancy support capabilities with the UE. Based on the capability support, the UE 301 can determine an active PLMN 304 and a redundant PLMN 305. The UE 301 then registers with both PLMNs but keeps one of the PLMNs in redundant and / or silent mode.

[0094] The UE 301 provides details about the backup PLMN 305 to the E1 312 (typically an Application Server (AS) or Application Function (AF)) so that the E1 312 does not send (eg, forward) data packets over the backup path.

[0095] Upon detection of a failure, UE 301 (or E1 312) activates a redundant (i.e., backup) path, and data is exchanged between UE 301 and E1 312 via the backup path, i.e., via the second PLMN 305. For example, for activation, UE 301 triggers a service request to establish a user plane via the second PLMN 305. In the case of activation by E1 312, E1 sends downlink packets via the redundant path, which causes the backup PLMN 305 to page UE 301 to activate the user plane connection via the backup PLMN 305.

[0096] FIG. 10 shows a flow diagram 1000 illustrating the registration procedure for the multi-SIM scenario of FIG.

[0097] The UE 1001 corresponding to the UE 301, the first RAN 1002 corresponding to the first RAN 301, the second RAN 1003 corresponding to the second RAN 303, the first AMF 1004 corresponding to the first AMF 306, and the second AMF 1005 corresponding to the second AMF 307 are involved in this flow.

[0098] It is assumed that the UE 1001 determines which PLMN should be the active PLMN 304 and which PLMN should be the redundant (backup) PLMN 305, for example, based on signaling strength and / or UE subscription, and / or taking into account operator policy and / or UE implementation logic.

[0099] At 1006, the UE 1001 requests registration for the main path with the network (i.e., via the first PLMN 304, i.e., via the first RAN 1002). The first AMF 1004 accepts the registration at 1007.

[0100] At 1008, the UE 1001 determines that a backup path should be established.

[0101] In response, at 1009, the UE 1001 sends a silent registration request, i.e., a registration request message including an indication that the request is for backup (or redundancy) purposes (i.e., a Redundant Registration Indication included in the request), to the second PLMN 305.

[0102] Based on this indication, the second PLMN 305 (specifically, the second AMF 1005) determines that the registration is for redundancy purposes and registers the UE 1001 with the second PLMN 305.

[0103] The purpose of silent registration is that a context for the UE 1001 is created in the second PLMN 305 (including network functions, especially of the core network) in preparation for failures and to reduce service interruption time.

[0104] The second AMF 1005 confirms the registration at 1010. The UE 1001 enters either RRC_inactive mode or RRC_IDLE mode.

[0105] FIG. 11 shows a flow diagram 1100 illustrating PDU session establishment for the multi-SIM scenario of FIG.

[0106] The flow involves a UE 1101 corresponding to UE 301, a first RAN 1102 corresponding to first RAN 302, a second RAN 1103 corresponding to second RAN 303, a first SMF 1104 corresponding to first SMF 310, a second SMF 1105 corresponding to second SMF 311, a first UPF 1106 corresponding to first UPF 308, a second UPF 1107 corresponding to second UPF 309, and an edge node 1108 (i.e., an application function running there) corresponding to E1 312.

[0107] It is assumed that both PLMNs 304, 305 are connectable to the same edge node 1108. For the UE 1101, the URSP (UE Route Selection Policy) rule parameters (e.g., S-NSSAI, DNN) may differ between the PLMNs 304, 305 for the same application, but the UE 1101 can reach the same application server via different PLMNs 304, 304.

[0108] At 1109, the UE 1101 requests a PDU session establishment (Estb.) via the first RAN 1102 (with which it registered according to FIG. 10). .

[0109] In response to the request, the first SMF 1104 establishes an active N3 interface with the first UPF 1106, at 1110. At 1111, the first SMF 1104 confirms the PDU session establishment.

[0110] The UE 1101 then has an (active) user plane connection to the first UPF 1106 at 1112.

[0111] At 1113, the UE 1101 sends a silent PDU session request via the second RAN 1103 (with which it has silent registration according to FIG. 10) for a session to the same E1 1108.

[0112] The second SMF 1105 creates a corresponding PDU session context at 1114 and acknowledges the PDU session request at 1115. Since it is a PDU session, no resources are allocated to the second UPF 1107 and the second RAN 1103, and only the context is stored.

[0113] The UE 1101 then has a (silent) user plane connection to the second UPF 1107 at 1116.

[0114] At 1117, the UE 1101 and E1 1108 synchronize the redundant PLMN 305. Because the UE 1101 has two different PDU sessions (and therefore two different IP addresses) through different PLMNs 304, 305, the UE 1101 informs E1 1108 which PLMN (IP address) is to be used as the active session and which PLMN (IP address) is to be used as the backup session. Unless the first session fails, the UE 1101 and E1 1108 communicate only through the active path, not through the redundant path.

[0115] FIG. 12 illustrates the failure handling in the case of a failure of the first PLMN 1204.

[0116] Before the failure (FIG. 1210), the UE 1201 has a connection to E1 1212 via the first RAN 1201 and the first UPF 1208.

[0117] After the failure (FIG. 2 1211), the UE 1201 has a connection to E1 1204 via the second RAN 1203 and the second UPF 1209.

[0118] A failure of the first PLMN 1204 (e.g., failure of the RAN 1202 or a core network function such as the UPF 1208) may be detected by the UE and / or E1 1212. Upon detection by the UE 1201, the UE 1201 changes to the active RRC in the redundant PLMN 1205 and activates the redundant path. It then updates the AF E1 1212 regarding the activation of the redundant path.

[0119] In case of detection by E1 1212 (i.e., AF performed by E1), E1 1212 transmits downlink packets via the redundant path (i.e., via the second PLMN 1205), in which case the second PLMN 1205 performs paging to the UE 1201 to activate the redundant path.

[0120] In the single SIM case of Figure 2, UE 201 appears to have a single point of attachment, whereas in the multi-SIM case of Figure 3, UE 301 appears to have two points of attachment (to two different PLMNs).

[0121] In the single SIM case, there may be a single control component that establishes a first communication session via the first RAN 202 and the first UPF 205, and a second communication session via the second RAN 203 and the first UPF 205. In this case, the second communication session should be silent (i.e., not used for transmitting useful data, for example).

[0122] The fault detection component (which may be the UE 201 or the control component) is configured to detect a fault in the first RAN 202. Upon detecting the fault in the first RAN 202, the fault detection component is configured to configure the UE 201, the second RAN 203, and the first UPF 205 to switch the second communication session from silent to active.

[0123] In the multi-SIM case, there may be two control components, where a first control component establishes a first communication session via a first RAN 302 and a first UPF 308, and a second control component establishes a second communication session via a second RAN 303 and a second UPF 309, where the second communication session should be silent (i.e., not used for transmitting useful data, for example).

[0124] The fault detection component (which may be the UE 301, the first control component, or the second RAN 303) is configured to detect a fault in the first RAN 302. Upon detecting the fault in the first RAN 302, the fault detection component is configured to configure the UE 301, the second RAN 303, and the second UPF 309 to switch the second communication session from silent to active.

[0125] In summary, according to various embodiments, a method is provided as depicted in FIGS.

[0126] FIG. 13 shows a flow diagram 1300 illustrating a method for preventing communication failures.

[0127] At 1301, a first request is received from a mobile terminal for establishment of a first communication session between the mobile terminal and a server, where the first communication session is requested to be provided over a first wireless access network.

[0128] At 1302, a first communication session is established between a mobile terminal and a server over a first wireless access network.

[0129] At 1303, a second request is received from the mobile terminal for a second communication session between the mobile terminal and the server, where the second communication session is requested to be provided over a second wireless access network.

[0130] At 1304, it is determined whether the second communication session is to be a backup communication session for the first communication session.

[0131] At 1305, a second communications session is established between the mobile terminal and the server via a second wireless access network, where the second wireless access network is controlled to avoid allocating communications resources for data exchange between the mobile terminal and the server via the second communications session if the second communications session is to be a backup communications session for the first communications session, until notified otherwise.

[0132] FIG. 14 shows a flow diagram 1400 illustrating a method for performing communication with a server.

[0133] At 1401, a first request for establishment of a first communication session between the mobile terminal and a server is sent from the mobile terminal, where the first communication session is requested to be provided via a first wireless access network.

[0134] At 1402, a second request is transmitted from the mobile terminal for a second communications session between the mobile terminal and a server, where the second communications session is requested to be provided over a second radio access network and the second request includes an indication that the second communications session is to be a backup communications session for the first communications session, and where allocation of communications resources for the backup communications session may be avoided (e.g., delayed) until notified otherwise.

[0135] At 1403, a failure in the first communication session is detected by the mobile terminal.

[0136] At 1404, upon detection of a failure of the first communication session, a second radio access network is notified by the mobile terminal to allocate communication resources for the second communication session.

[0137] In other words, according to various embodiments, a backup (communication) path for an active (communication) path is established but is silent (or inactive), i.e., radio resources are not allocated to the backup path until a backup for the active path is required due to the active path failing.

[0138] This means, for example, that the allocation of frequency channels, time slots, radio resource elements, etc. for the backup path (i.e., for the second communication session) is delayed (at least for the transmission of useful data) until the backup path is activated (i.e., activated to replace the (failed) active path).

[0139] The approach of Figures 13 and / or 14 thus enables fast recovery of (user plane) communication sessions to handle RAN failure scenarios by establishing silent (redundant) paths via a backup RAN (e.g., one or more backup RAN nodes) without wasting radio resources.

[0140] The methods of Figures 13 and 14 may be performed by components of a mobile terminal and / or a communication network implemented by one or more circuits. A "circuit" may be understood as any kind of logic implementing entity, which may be a special-purpose circuit or a processor executing software stored in memory, firmware, or a combination thereof. Thus, a "circuit" may be a hardwired logic circuit or a programmable logic circuit, such as a programmable processor, e.g., a microprocessor. A "circuit" may also be a processor executing software, e.g., any kind of computer program. Any other kind of implementation of each of the aforementioned functions may also be understood as a "circuit."

[0141] According to various embodiments, a communication network includes at least one component configured to provide a communication service to access an (application) server, a detection component configured to detect a failure of one or more components, and an access component configured to use a redundant path through a redundant network component (to provide a second communication session).

[0142] The at least one component configured to provide a communication service may be, for example, a component of a first radio access network and / or a core network function. The component may be in a first public land mobile network, and the redundant network component may be in a second public land mobile network, or vice versa. The detection component may be a mobile terminal and / or a radio access network and / or a core network function and / or an application server. The core network function may be an Access and Mobility Management Function (AMF) and / or a Session Management Function (SMF) and / or a User Plane Function (UPF) and / or a Policy Change Function (PCF) and / or a Unified Data Management (UDM). The redundant component enables registration of the mobile terminal and / or establishment of communication without allocating communication resources. The communication resources may be, for example, radio resources allocated by the second radio access network and resources allocated by the core network component. The access component may be a mobile terminal and / or an application server.

[0143] While specific embodiments have been described, it should be understood by those skilled in the art that various changes in form and details may be made in those specific embodiments without departing from the spirit and scope of the disclosed embodiments as defined by the appended claims. The scope is therefore indicated by the appended claims, and all changes that come within the meaning and range of equivalency of the claims are therefore intended to be embraced.

Claims

1. A method for preventing communication failure, comprising: receiving a first request from a mobile terminal for establishment of a first communications session between the mobile terminal and a server, the first communications session being requested to be provided via a first radio access network; establishing the first communication session between the mobile terminal and the server via the first radio access network; receiving a second request from the mobile terminal for a second communications session between the mobile terminal and the server, the second communications session requested to be provided via a second radio access network; determining whether the second communication session should be a backup communication session for the first communication session; establishing the second communication session between the mobile terminal and the server via the second radio access network, wherein if the second communication session is to be a backup communication session for the first communication session, the second radio access network is controlled to avoid allocating communication resources for data exchange between the mobile terminal and the server via the second communication session until notified to allocate communication resources for the second communication session, wherein avoiding allocation of communication resources for data exchange comprises not allocating radio resources to the second radio access network; detecting a failure of the first communications session and, upon detecting the failure of the first communications session, notifying the second radio access network to allocate communications resources for the second communications session, wherein detecting the failure of the first communications session includes detecting a failure of the first radio access network and / or one or more core network functions providing the first communications session; A method having the following.

2. and allocating communication resources for the second communication session upon failure of the first communication session. The method of claim 1.

3. Informing the second radio access network to allocate communication resources for the second communication session includes triggering paging of the mobile terminal via the second radio access network. The method of claim 2.

4. triggering the second radio access network to allocate communications resources for the second communications session by sending downlink data to a user plane function providing the second communications session. The method of claim 2.

5. receiving a failure indication from the mobile terminal indicating a failure of the first communications session, and upon receipt of the failure indication, notifying the second radio access network to allocate communications resources for the second communications session.

5. The method according to any one of claims 1 to 4.

6. switching the mobile terminal to a Radio Resource Control idle or inactive state upon establishment of the second communication session. The method of claim 1.

7. detecting a failure of the first communication session and, upon detecting the failure of the first communication session, switching the mobile terminal to a Radio Resource Control connected state. The method of claim 1.

8. the second request from the mobile terminal for the second communications session, which is provided to the server by the second radio access network, includes an indication that the second communications session should be a backup communications session for the first communications session; determining whether the second communications session should be a backup communications session for the first communications session includes determining, based on the instruction, that the second communications session should be a backup communications session for the first communications session. The method of claim 1.

9. The server implements application functionality; the first communication session and the second communication session are communication sessions with the application function; The method of claim 1.

10. receiving a first registration request from the mobile terminal for registering the mobile terminal with a first communication network before receiving the first request, and registering the mobile terminal with the first communication network; receiving a second registration request from the mobile terminal for registering the mobile terminal in a second communication network before receiving the second request, and registering the mobile terminal in the second communication network; and the second registration request includes an indication that the registration with the second communications network is a backup registration; determining whether the second communications session should be a backup communications session for the first communications session includes determining, based on the instruction, that the second communications session should be a backup communications session for the first communications session. The method of claim 1.

11. A communications network comprising the first radio access network and the second radio access network and one or more control components configured to perform the method of any one of claims 1 to 4.

12. 1. A method for performing communication with a server, comprising: sending, by the mobile terminal, a first request for establishment of a first communications session between the mobile terminal and a server, the first communications session being requested to be provided via a first radio access network; sending, by the mobile terminal, a second request for a second communications session between the mobile terminal and the server, the second communications session being requested to be provided via a second radio access network, the second request including an indication that the second communications session is a backup communications session for the first communications session, and wherein allocation of communications resources may be avoided for the backup communications session until notified to allocate communications resources for the second communications session, and avoiding allocation of communications resources for data exchange includes not allocating radio resources to the second radio access network; detecting, by the mobile terminal, a failure of the first communications session, wherein detecting the failure of the first communications session comprises detecting a failure of the first radio access network and / or one or more core network functions providing the first communications session; notifying, by the mobile terminal, the second radio access network upon detection of a failure of the first communications session, to allocate communications resources for the second communications session; A method having the following.

13. A mobile terminal configured to perform the method of claim 12.

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