Interface fault recovery for n3mb with single or split access nodes

Abstract

A network access node receives an indication of an interval between expected receptions of echo requests across a tunnel that uses an interface between a network element in a core network of a cellular network to the network access node of the cellular network. The network access node determines a threshold time period based on the interval, detects the absence of an echo request for a time period greater than the threshold time period, and determines a tunnel failure using the interface. Due to the failure of the tunnel, the network access node triggers the establishment of a new tunnel using the interface. Various techniques are disclosed for determining that the failure has occurred and recovered from the failure, including establishing a new MBS session or using a new transport address for the current MBS session.

Description

Technical Field

[0001] Examples of embodiments herein relate generally to wireless networks, and more particularly to failure recovery of interfaces in MBS (Multicast and Broadcast Services). Background Art

[0002] Multicast and Broadcast Service (MBS) is a technology used in wireless systems such as cellular systems that enables broadcast or multicast services to be delivered from network elements in the core network of the cellular system to access nodes in the cellular system. The access nodes provide access to the cellular system by user equipment (UE) and will be the ultimate consumer of the service.

[0003] Various network elements are interconnected by links, and interfaces are run on these links, which have known protocols for communication between elements. These interfaces can use tunnels, which are instances of interfaces that support corresponding protocols and broadcast sessions. Tunnels have a starting point and an end point, such as a network element of the user plane, and an access node. Sometimes, the tunnel and therefore the interface used for a broadcast session may fail. Importantly, when this happens, the event can be recovered from it. Summary of the invention

[0004] This section is intended to include examples, and is not intended to be limiting of the examples.

[0005] In one exemplary embodiment, a method is disclosed, the method comprising: receiving, by a network access node in a cellular network, an indication of an interval between expected receptions of echo requests across a tunnel that uses an interface between a network element in a core network of the cellular network to a network access point of the cellular network; determining, by the network access node, a threshold time period based on the interval; detecting, by the network access node, an absence of echo requests for a time period greater than the threshold time period; determining, by the network access node based on the detection, a failure of a tunnel that uses the interface; and triggering, by the network access node, establishment of a new tunnel that uses the interface due to the failure of the tunnel.

[0006] Another exemplary embodiment includes a computer program including instructions for performing the method of the previous paragraph when the computer program is run on a device. A computer program according to this paragraph, wherein the computer program is a computer program product including a computer readable medium carrying instructions embodied therein for use with the device. Another example is a computer program according to this paragraph, wherein the program is directly loadable into an internal memory of the device.

[0007] An exemplary apparatus includes: one or more processors and one or more memories storing instructions, which instructions, when executed by the one or more processors, cause the apparatus to at least perform: receiving, by a network access node in a cellular network, an indication of an interval between expected receptions of echo requests traversing a tunnel, the tunnel using an interface between a network element in a core network of the cellular network to a network access point of the cellular network; determining, by the network access node, a threshold time period based on the interval; detecting, by the network access node, the absence of echo requests for a time period greater than the threshold time period; determining, by the network access node, a failure of a tunnel using the interface based on the detection; and triggering, by the network access node, establishment of a new tunnel using the interface due to the failure of the tunnel.

[0008] An exemplary computer program product includes a computer-readable storage medium carrying instructions that, when executed by the apparatus, cause the apparatus to at least perform: receiving, by a network access node in a cellular network, an indication of an interval between expected receptions of echo requests across a tunnel that uses an interface between a network element in a core network of the cellular network to a network access point of the cellular network; determining, by the network access node, a threshold time period based on the interval; detecting, by the network access node, an absence of echo requests for a time period greater than the threshold time period; determining, by the network access node, a failure of a tunnel that uses the interface based on the detection; and triggering, by the network access node, establishment of a new tunnel that uses the interface due to the failure of the tunnel.

[0009] In another exemplary embodiment, an apparatus includes components for performing the following: receiving, by a network access node in a cellular network, an indication of an interval between expected receptions of echo requests across a tunnel that uses an interface between a network element in a core network of the cellular network to a network access point of the cellular network; determining, by the network access node, a threshold time period based on the interval; detecting, by the network access node, an absence of echo requests for a time period greater than the threshold time period; determining, by the network access node based on the detection, a failure of a tunnel that uses the interface; and triggering, by the network access node, establishment of a new tunnel that uses the interface due to the failure of the tunnel.

[0010] In an exemplary embodiment, a method is disclosed, the method comprising: receiving, by a second network element in a core network of a cellular network from a first network element in the core network, an indication of a tunnel failure of an interface for transmitting an MBS session between a network access node and the first network element, the indication comprising: an indication of an address associated with a network access node using the tunnel; retrieving, by the second network element, an identification of the network access node based on the address; and indicating, by the second network element to a third network element in the core network, the failure of the tunnel used for forwarding to the network access node, the indication using at least the identification of the network access node, the indication also requesting release of the MBS session.

[0011] Another exemplary embodiment includes a computer program including instructions for performing the method of the previous paragraph when the computer program is run on a device. A computer program according to this paragraph, wherein the computer program is a computer program product including a computer readable medium carrying instructions embodied therein for use with the device. Another example is a computer program according to this paragraph, wherein the program is directly loadable into an internal memory of the device.

[0012] An exemplary apparatus comprises: one or more processors and one or more memories storing instructions, which instructions, when executed by the one or more processors, cause the apparatus to at least perform: receiving, by a second network element in a core network of a cellular network from a first network element in the core network, an indication of a tunnel failure of an interface for transmitting an MBS session between a network access node and the first network element, the indication comprising: an indication of an address associated with a network access node using the tunnel; retrieving, by the second network element, an identification of the network access node based on the address; and indicating, by the second network element to a third network element in the core network, the failure of the tunnel used for forwarding to the network access node, the indication using at least the identification of the network access node, the indication also requesting release of the MBS session.

[0013] An exemplary computer program product includes a computer-readable storage medium carrying instructions, which, when executed by the device, causes the device to at least perform: receiving, by a second network element in a core network of a cellular network from a first network element in the core network, an indication of a tunnel failure of an interface for transmitting an MBS session between a network access node and the first network element, the indication comprising: an indication of an address associated with a network access node using the tunnel; retrieving, by the second network element, an identification of the network access node based on the address; and indicating, by the second network element to a third network element in the core network, the failure of the tunnel used for forwarding to the network access node, the indication using at least the identification of the network access node, the indication also requesting release of the MBS session.

[0014] In another exemplary embodiment, an apparatus includes components for performing the following: receiving, by a second network element in a core network of a cellular network from a first network element in the core network, an indication of a tunnel failure of an interface for transmitting an MBS session between a network access node and the first network element, the indication comprising: an indication of an address associated with a network access node using the tunnel; retrieving, by the second network element, an identification of the network access node based on the address; and indicating, by the second network element to a third network element in the core network, the failure of the tunnel used for forwarding to the network access node, the indication using at least the identification of the network access node, the indication also requesting release of the MBS session.

[0015] In an exemplary embodiment, a method is disclosed, the method comprising: using, by a network access node, a tunnel for transmitting an interface of an MBS session between the network access node and a first network element in a core network, receiving an indication of a tunnel failure from a second network node via a third network element in the core network, the indication also indicating that the MBS session is to be released; releasing the MBS session by the network access node; and sending, by the network access node via the third network element in the core network, an indication to the second network element that the interface is no longer used for the MBS session and that the MBS session is released.

[0016] Another exemplary embodiment includes a computer program including instructions for performing the method of the previous paragraph when the computer program is run on a device. A computer program according to this paragraph, wherein the computer program is a computer program product including a computer readable medium carrying instructions embodied therein for use with the device. Another example is a computer program according to this paragraph, wherein the program is directly loadable into an internal memory of the device.

[0017] An exemplary apparatus comprises: one or more processors and one or more memories storing instructions, which instructions, when executed by the one or more processors, cause the apparatus to at least perform: receiving, by a network access node, an indication of a tunnel failure using an interface for transmitting an MBS session between the network access node and a first network element in a core network, via a third network element in the core network, from a second network node, the indication also indicating that the MBS session is to be released; releasing the MBS session by the network access node; and sending, by the network access node, via the third network element in the core network, to the second network element an indication that the interface is no longer used for the MBS session and that the MBS session is released.

[0018] An exemplary computer program product includes a computer-readable storage medium carrying instructions, which, when executed by the device, causes the device to at least perform: using a tunnel of an interface for transmitting an MBS session between the network access node and a first network element in a core network, by a network access node, receiving an indication of a tunnel failure from a second network node via a third network element in the core network, the indication also indicating that the MBS session is to be released; releasing the MBS session by the network access node; and sending an indication by the network access node to the second network element via the third network element in the core network that the interface is no longer used for the MBS session and the MBS session is released.

[0019] In another exemplary embodiment, an apparatus includes components for performing the following: using, by a network access node, a tunnel for transmitting an interface of an MBS session between the network access node and a first network element in a core network, receiving an indication of a tunnel failure from a second network node via a third network element in the core network, the indication also indicating that the MBS session is to be released; releasing the MBS session by the network access node; and sending, by the network access node via the third network element in the core network, an indication to the second network element that the interface is no longer used for the MBS session and that the MBS session is released.

[0020] In an exemplary embodiment, a method is disclosed, the method comprising: receiving, by a second network element in a core network from a first network element in the core network of a cellular network, an indication of a tunnel failure of an interface for transmitting an MBS session between a network access node and the first network element, the indication comprising: an indication of an address associated with a network access node using the tunnel; retrieving, by the second network element, an identification of the network access node based on the address; and indicating, by the second network element, to a third network element at least one of the following items for forwarding to the network access node: a failure of the tunnel in the core network, or a request for a new transport address of a network access node for use as a new tunnel endpoint for the MBS session.

[0021] Another exemplary embodiment includes a computer program including instructions for performing the method of the previous paragraph when the computer program is run on a device. A computer program according to this paragraph, wherein the computer program is a computer program product including a computer readable medium carrying instructions embodied therein for use with the device. Another example is a computer program according to this paragraph, wherein the program is directly loadable into an internal memory of the device.

[0022] An exemplary apparatus comprises: one or more processors and one or more memories storing instructions, which instructions, when executed by the one or more processors, cause the apparatus to at least perform: receiving, by a second network element in a core network from a first network element in a core network of a cellular network, an indication of a tunnel failure of an interface for transmitting an MBS session between a network access node and the first network element, the indication comprising: an indication of an address associated with a network access node using the tunnel; retrieving, by the second network element, an identification of the network access node based on the address; and indicating, by the second network element to a third network element, for forwarding to the network access node, at least one of the following items: a failure of the tunnel in the core network, or a request for a new transport address of a network access node for use as a new tunnel endpoint for the MBS session.

[0023] An exemplary computer program product includes a computer-readable storage medium carrying instructions, which, when executed by the device, causes the device to at least perform: receiving, by a second network element in a core network from a first network element in the core network of a cellular network, an indication of a tunnel failure of an interface for transmitting an MBS session between a network access node and the first network element, the indication comprising: an indication of an address associated with an access node for a network using a tunnel; retrieving, by the second network element, an identification of the network access node based on the address; and indicating, by the second network element to a third network element, for forwarding to the network access node, at least one of the following items: a failure of the tunnel in the core network, or a request for a new transport address of a network access node for use as a new tunnel endpoint for the MBS session.

[0024] In another exemplary embodiment, an apparatus includes components for performing the following: receiving, by a second network element in a core network from a first network element in the core network of a cellular network, an indication of a tunnel failure of an interface for transmitting an MBS session between a network access node and the first network element, the indication comprising: an indication of an address associated with a network access node using the tunnel; retrieving, by the second network element, an identification of the network access node based on the address; and indicating, by the second network element to a third network element, for forwarding to the network access node, at least one of: a failure of the tunnel in the core network, or a request for a new transport address of a network access node for use as a new tunnel endpoint for the MBS session.

[0025] In an exemplary embodiment, a method is disclosed, the method comprising: using a tunnel of an interface for transmitting an MBS session between the network access node and a first network element in a core network, by a network access node, receiving at least one of an indication of a tunnel failure or an indication of a request for a new transport address to be used as a tunnel endpoint for the MBS session from a second network node via a third network element in the core network; determining, by the network access node, a new transport address associated with the MBS session; and sending, by the network access node to a second network element via the third network element in the core network, an indication of the new transport address associated with the MBS session to be used as a new tunnel endpoint for transmission between the first network element and the network access node.

[0026] Another exemplary embodiment includes a computer program including instructions for performing the method of the previous paragraph when the computer program is run on a device. A computer program according to this paragraph, wherein the computer program is a computer program product including a computer readable medium carrying instructions embodied therein for use with the device. Another example is a computer program according to this paragraph, wherein the program is directly loadable into an internal memory of the device.

[0027] An exemplary apparatus comprises: one or more processors and one or more memories storing instructions, which instructions, when executed by the one or more processors, cause the apparatus to at least perform: using, by a network access node, a tunnel of an interface for transmitting an MBS session between the network access node and a first network element in a core network, receiving, via a third network element in the core network, from a second network node an indication of a tunnel failure, or an indication indicating a request for a new transport address to be used as a tunnel endpoint for the MBS session; determining, by the network access node, a new transport address associated with the MBS session; and sending, by the network access node, to a second network element via the third network element in the core network, an indication of a new transport address associated with the MBS session to be used as a new tunnel endpoint for transmission between the first network element and the network access node.

[0028] An exemplary computer program product includes a computer-readable storage medium carrying instructions, which, when executed by the device, causes the device to at least perform: using, by a network access node, a tunnel of an interface for transmitting an MBS session between the network access node and a first network element in a core network, receiving, from a second network node via a third network element in the core network, at least one of an indication of a tunnel failure, or an indication of a request for a new transport address to be used as a tunnel endpoint for the MBS session; determining, by the network access node, a new transport address associated with the MBS session; and sending, by the network access node to a second network element via the third network element in the core network, an indication of a new transport address associated with the MBS session to be used as a new tunnel endpoint for transmission between the first network element and the network access node.

[0029] In another exemplary embodiment, an apparatus includes components for performing the following: using, by a network access node, a tunnel of an interface for transmitting an MBS session between the network access node and a first network element in a core network, receiving, from a second network node via a third network element in the core network, at least one of an indication of a tunnel failure or an indication of a request for a new transport address to be used as a tunnel endpoint for the MBS session; determining, by the network access node, a new transport address associated with the MBS session; and sending, by the network access node to a second network element via the third network element in the core network, an indication of a new transport address associated with the MBS session to be used as a new tunnel endpoint for transmission between the first network element and the network access node.

[0030] In an exemplary embodiment, a method is disclosed, the method comprising: receiving, by a second network element in a core network from a first network element in the core network of a cellular network, an indication of a tunnel failure of an interface for transmitting an MBS session between a network access node and the first network element, the indication comprising: an indication of an address associated with a network access node using the tunnel; retrieving, by the second network element, an identification of the network access node based on the address; and indicating, by the second network element to a third network element in the core network, the failure of the tunnel used for forwarding to the network access node, the indication using at least the identification of the network access node, the indication also having a notification of a failure of the MBS session associated with the tunnel.

[0031] Another exemplary embodiment includes a computer program including instructions for performing the method of the previous paragraph when the computer program is run on a device. A computer program according to this paragraph, wherein the computer program is a computer program product including a computer readable medium carrying instructions embodied therein for use with the device. Another example is a computer program according to this paragraph, wherein the program is directly loadable into an internal memory of the device.

[0032] An exemplary apparatus comprises: one or more processors and one or more memories storing instructions, which instructions, when executed by the one or more processors, cause the apparatus to at least perform: receiving, by a second network element in a core network from a first network element in the core network of a cellular network, an indication of a tunnel failure of an interface for transmitting an MBS session between a network access node and the first network element, the indication comprising: an indication of an address associated with a network access node using the tunnel; retrieving, by the second network element, an identification of the network access node based on the address; and indicating, by the second network element to a third network element in the core network, a failure of a tunnel for forwarding to the network access node, the indication using at least the identification of the network access node, the indication also having a notification of a failure of the MBS session associated with the tunnel.

[0033] An exemplary computer program product includes a computer-readable storage medium carrying instructions, which, when executed by the device, causes the device to at least perform: receiving, by a second network element in a core network from a first network element in the core network of a cellular network, an indication of a tunnel failure of an interface for transmitting an MBS session between a network access node and the first network element, the indication comprising: an indication of an address associated with a network access node using a tunnel; retrieving, by the second network element, an identification of the network access node based on the address; and indicating, by the second network element to a third network element in the core network, a failure of a tunnel used for forwarding to the network access node, the indication using at least the identification of the network access node, the indication also having a notification of a failure of the MBS session associated with the tunnel.

[0034] In another exemplary embodiment, an apparatus includes components for performing the following: receiving, by a second network element in a core network from a first network element in the core network of a cellular network, an indication of a tunnel failure of an interface for transmitting an MBS session between a network access node and the first network element, the indication comprising: an indication of an address associated with a network access node using the tunnel; retrieving, by the second network element, an identification of the network access node based on the address; and indicating, by the second network element to a third network element in the core network, a failure of the tunnel used for forwarding to the network access node, the indication using at least the identification of the network access node, the indication also having a notification of a failure of the MBS session associated with the tunnel.

[0035] In an exemplary embodiment, a method is disclosed, the method comprising: receiving, by a network access node, an indication of a tunnel failure from a second network element via a third network element in the core network using a tunnel of an interface for transmitting an MBS session between the network access node and a first network element in a core network; determining, by the network access node, to release a current transport address associated with the MBS session and to obtain a new transport address for the MBS session; and establishing, by the network access node, a new tunnel using an interface for transmitting the MBS session with a current PLMN of the core network or another PLMN of another core network; and sending, by the network access node, an indication of a new transport address to be used with a new tunnel for the MBS session to one of a second network element in the core network of the current PLMN or a second network element in another core network of another PLMN.

[0036] Another exemplary embodiment includes a computer program including instructions for performing the method of the previous paragraph when the computer program is run on a device. A computer program according to this paragraph, wherein the computer program is a computer program product including a computer readable medium carrying instructions embodied therein for use with the device. Another example is a computer program according to this paragraph, wherein the program is directly loadable into an internal memory of the device.

[0037] An exemplary apparatus comprises: one or more processors and one or more memories storing instructions, which instructions, when executed by the one or more processors, cause the apparatus to at least perform: using, by a network access node, a tunnel of an interface for transmitting an MBS session between the network access node and a first network element in a core network, receiving an indication of a tunnel failure from a second network element via a third network element in the core network; determining, by the network access node, to release a current transport address associated with the MBS session and to obtain a new transport address for the MBS session; establishing, by the network access node, a new tunnel using an interface for transmitting the MBS session with a current PLMN of the core network or another PLMN of another core network; and sending, by the network access node, an indication of a new transport address to be used with a new tunnel for the MBS session to one of a second network element in the core network of the current PLMN or a second network element in another core network of another PLMN.

[0038] An exemplary computer program product includes a computer-readable storage medium carrying instructions, which, when executed by the device, causes the device to at least perform: using a tunnel of an interface for transmitting an MBS session between the network access node and a first network element in a core network, by a network access node, receiving an indication of a tunnel failure from a second network element via a third network element in the core network; determining, by the network access node, to release a current transport address associated with the MBS session and obtain a new transport address for the MBS session; and establishing, by the network access node, a new tunnel, the new tunnel using an interface for transmitting the MBS session with a current PLMN of the core network or another PLMN of another core network; and sending, by the network access node, an indication of a new transport address to be used with a new tunnel for the MBS session to one of a second network element in the core network of the current PLMN or a second network element in another core network of another PLMN.

[0039] In another exemplary embodiment, an apparatus includes components for performing the following: a network access node uses a tunnel of an interface for transmitting an MBS session between the network access node and a first network element in a core network, receiving an indication of a tunnel failure from a second network element via a third network element in the core network; the network access node determines to release a current transport address associated with the MBS session and obtains a new transport address for the MBS session; and the network access node establishes a new tunnel, the new tunnel using an interface for transmitting the MBS session with a current PLMN of the core network or another PLMN of another core network; and the network access node sends an indication of a new transport address to be used with a new tunnel for the MBS session to one of a second network element in the core network of the current PLMN or a second network element in another core network of another PLMN.

[0040] In an exemplary embodiment, a method is disclosed, the method comprising: a second network element in a core network, for transmitting an indication of a tunnel failure of an interface of an MBS session between a network access node and a first network element, the indication comprising: an indication of an address associated with a network access node using the tunnel; retrieving, by the second network element, an identification of the network access node based on the address; and indicating, by the second network element to a third network element in the core network, the failure of the tunnel for forwarding to the network access node, the indication using at least the identification of the network access node, the indication also having a notification of a failure of the MBS session associated with the tunnel and requesting release of the MBS session.

[0041] Another exemplary embodiment includes a computer program including instructions for performing the method of the previous paragraph when the computer program is run on a device. A computer program according to this paragraph, wherein the computer program is a computer program product including a computer readable medium carrying instructions embodied therein for use with the device. Another example is a computer program according to this paragraph, wherein the program is directly loadable into an internal memory of the device.

[0042] An exemplary apparatus comprises: one or more processors and one or more memories storing instructions, which instructions, when executed by the one or more processors, cause the apparatus to at least perform: a second network element in a core network, for transmitting an indication of a tunnel failure of an interface for an MBS session between a network access node and a first network element, the indication comprising: an indication of an address associated with a network access node using a tunnel; retrieving, by the second network element, an identification of the network access node based on the address; and indicating, by the second network element to a third network element in the core network, a failure of a tunnel for forwarding to the network access node, the indication using at least the identification of the network access node, the indication also having a notification of a failure of the MBS session associated with the tunnel and requesting release of the MBS session.

[0043] An exemplary computer program product includes a computer-readable storage medium carrying instructions, which, when executed by the device, causes the device to at least perform: a second network element in a core network, for transmitting an indication of a tunnel failure of an interface for an MBS session between a network access node and a first network element, the indication comprising: an indication of an address associated with a network access node using a tunnel; retrieving, by the second network element, an identification of the network access node based on the address; and indicating, by the second network element to a third network element in the core network, a failure of a tunnel for forwarding to the network access node, the indication using at least the identification of the network access node, the indication also having a notification of a failure of the MBS session associated with the tunnel and requesting release of the MBS session.

[0044] In another exemplary embodiment, an apparatus includes components for performing the following: a second network element in a core network, for transmitting an indication of a tunnel failure of an interface for an MBS session between a network access node and a first network element, the indication comprising: an indication of an address associated with a network access node using the tunnel; retrieving, by the second network element, an identification of the network access node based on the address; and indicating, by the second network element to a third network element in the core network, a failure of a tunnel for forwarding to the network access node, the indication using at least the identification of the network access node, the indication also having a notification of a failure of the MBS session associated with the tunnel and requesting release of the MBS session.

[0045] In an exemplary embodiment, a method is disclosed, the method comprising: a network access node using a tunnel of an interface for transmitting an MBS session between the network access node and a first network element in a core network, receiving an indication of a tunnel failure from a second network element via a third network element in the core network, and requesting release of the MBS session; the network access node determining to release a current transport address associated with the MBS session and obtaining a new transport address for the MBS session; and the network access node establishing a new tunnel using an interface for transmitting the MBS session to one of the second network elements in the core network of a current PLMN or one of the second network elements in the core network of another PLMN; and the network access node sending an indication of a new transport address to be used with the new tunnel for the MBS session to one of the second network elements in the core network of the current PLMN or one of the second network elements in another core network of another PLMN.

[0046] Another exemplary embodiment includes a computer program including instructions for performing the method of the previous paragraph when the computer program is run on a device. A computer program according to this paragraph, wherein the computer program is a computer program product including a computer readable medium carrying instructions embodied therein for use with the device. Another example is a computer program according to this paragraph, wherein the program is directly loadable into an internal memory of the device.

[0047] An exemplary apparatus comprises: one or more processors and one or more memories storing instructions, which, when executed by the one or more processors, cause the apparatus to at least perform: using, by a network access node, a tunnel of an interface for transmitting an MBS session between the network access node and a first network element in a core network, receiving an indication of a tunnel failure from a second network element via a third network element in the core network, and requesting release of the MBS session; determining, by the network access node, to release a current transport address associated with the MBS session, and obtaining a new transport address for the MBS session; and establishing, by the network access node, a new tunnel using an interface for transmitting the MBS session to one of a second network element in a core network of a current PLMN or a second network element in a core network of another PLMN; and sending, by the network access node, an indication of a new transport address to be used with a new tunnel for the MBS session to one of the second network elements in the core network of the current PLMN or one of the second network elements in another core network of another PLMN.

[0048] An exemplary computer program product includes a computer-readable storage medium carrying instructions, which, when executed by the device, causes the device to at least perform: using, by a network access node, a tunnel of an interface for transmitting an MBS session between the network access node and a first network element in a core network, receiving an indication of a tunnel failure from a second network element via a third network element in the core network, and requesting release of the MBS session; determining, by the network access node, to release a current transport address associated with the MBS session and to obtain a new transport address for the MBS session; and establishing, by the network access node, a new tunnel, the new tunnel using an interface for transmitting the MBS session to one of the second network elements in the core network of a current PLMN or one of the second network elements in the core network of another PLMN; and sending, by the network access node, an indication of a new transport address to be used with a new tunnel for the MBS session to one of the second network elements in the core network of the current PLMN or one of the second network elements in another core network of another PLMN.

[0049] In another exemplary embodiment, an apparatus includes components for performing the following: a network access node uses a tunnel of an interface for transmitting an MBS session between the network access node and a first network element in a core network, receives an indication of a tunnel failure from a second network element via a third network element in the core network, and requests release of the MBS session; the network access node determines to release a current transport address associated with the MBS session and obtains a new transport address for the MBS session; and the network access node establishes a new tunnel, the new tunnel using an interface for transmitting the MBS session to one of the second network elements in the core network of a current PLMN or one of the second network elements in the core network of another PLMN; and the network access node sends an indication of a new transport address to be used with a new tunnel for the MBS session to one of the second network elements in the core network of the current PLMN or one of the second network elements in another core network of another PLMN. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In the attached picture:

[0051] Figure 1 is a signaling diagram of an example called Embodiment 1 for N3MB failure recovery;

[0052] Figure 2A is a signaling diagram called embodiment 2A for N3MB failure recovery in a non-RAN sharing situation;

[0053] Figure 2B is a signaling diagram called embodiment 2B for N3MB failure recovery in non-RAN sharing;

[0054] Figure 2C is a signaling diagram of an example called embodiment 2C for N3MB failure recovery in RAN sharing and non-RAN sharing scenarios;

[0055] Figure 2D is a signaling diagram of an example called embodiment 2D for N3MB failure recovery in RAN sharing and non-RAN sharing scenarios; and

[0056] Figure 3 is a block diagram of one possible and non-limiting exemplary system in which exemplary embodiments may be practiced. DETAILED DESCRIPTION

[0057] Abbreviations that may appear in the specification and / or drawings are defined below at the end of the Detailed Description section.

[0058] The word "exemplary" as used herein means "serving as an example, instance, or illustration". Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred over other embodiments. All embodiments described in this detailed description are exemplary embodiments intended to enable those skilled in the art to make or use the invention, rather than to limit the scope of the invention which is defined by the claims.

[0059] When more than one reference numeral, word or abbreviation with “ / ” is used in this specification, generally in this specification, “ / ” can be interpreted as “or”, “and” or “both”. As used herein, “at least one of the following: ” and “<at least one of a list of two or more elements>” and similar expressions (wherein a list of two or more elements is connected by “and” or “or”) refer to at least any one of these elements, or at least any two or more of these elements, or at least all of these elements.

[0060] Unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" used herein also include the plural forms. It will also be understood that the terms "comprises", "comprising", "having", "having", "including" and / or "comprising" when used herein specify the presence of stated features, elements and / or components, etc., but do not preclude the presence or addition of one or more other features, elements, components and / or combinations thereof.

[0061] Any flowchart or signaling diagram in this document (see Figure 1 , Figure 2A , Figure 2B , Figure 2C and Figure 2D ) are all considered to be logical flow diagrams and illustrate the operation of exemplary methods according to exemplary embodiments, the result of execution of computer program instructions embodied on a computer readable memory, the functions performed by logic implemented in hardware, and / or the interconnected components for performing the functions. Block diagrams (such as Figure 3 ) also illustrates the operation of an exemplary method according to an exemplary embodiment, the results of execution of computer program instructions embodied on a computer readable memory, functions performed by logic implemented in hardware, and / or interconnected components for performing functions.

[0062] An overview of the technical field is now provided.

[0063] Since Release 15, it is possible to split the gNB. As we all know, a gNB is a network element that provides UEs with access to the cellular network. A gNB can also be called NG-RAN (Next Generation Radio Access Network), where the RAN provides UEs with access to the cellular network. Since Release 15, the gNB can be split between the CU (Central Unit) containing the higher layer protocols and the DU (Distributed Unit) containing the lower layer protocols. Furthermore, the CU itself can be split into a control plane part called CU-CP and a user plane part called CU-UP.

[0064] The topic of interest is Multicast and Broadcast Services (MBS) in Release 17. 3GPP finalized the work item for support of Multicast and Broadcast Systems (MBS) in New Radio (NR) Release 17 (see Huawei RP-193248, "New Work Item onNR support of Multicast and Broadcast Services" (3GPP TSG RAN Meeting #86, Sitges, Spain, December 9-12, 2019)). Here, point-to-multipoint (PTM) transmission is expected to efficiently provide MBS services to multiple users by using the same radio framework as unicast transmission. Release 17 only enables UEs in RRC_CONNECTED state to receive multicast services. In addition, Release 17 specifies broadcast reception in all RRC states.

[0065] According to 3GPP TS23.247 (for example, see 3GPP TS23.247 V18.3.0 (2023-09)), the delivery of MBS data from 5GC to NG-RAN is carried out through the N3mb interface from MB-UPF to gNB. Data can be delivered through the N3mb interface (via unicast transmission or via multicast transmission).

[0066] For broadcast sessions in Release 17, N3mb establishment is always triggered from top to bottom, i.e. the AMF sends a broadcast establishment request to the gNB to establish the broadcast session context, and the gNB sends back the transport address for the corresponding N3mb communication.

[0067] Another topic of interest is MBS in Release 18. In Release 18, 3GPP agreed to an additional work item (see RP-231829, CATT, CBN, “Revised WID: Enhancements of NR Multicast and Broadcast Services” (3GPP TSG RAN Meeting #101, Bangalore, India, September 11-15, 2023)) for supporting multicast and broadcast systems (MBS) including RAN3 work, as follows:

[0068] “Study and, if necessary, specify enhancements to improve resource efficiency of MBS broadcast reception in RAN sharing scenarios [RAN3]”.

[0069] The "Resource Efficiency in RAN Sharing" feature includes sharing the radio resources of all participants of RAN sharing. This feature is also known as "RAN Sharing Resource Utilization".

[0070] As part of this new Release 18 feature for resource efficiency of RAN sharing, RAN3 has agreed that the gNB can decide to establish one or more N3mb tunnels to the 5GCs of different PLMNs participating in RAN sharing. For example, if RAN sharing involves PLMN1, PLMN2, PLMN3, the gNB can decide to establish N3mb with only 5GC1 for PLMN1, or with both 5GC1 for PLMN1 and 5GC2 for PLMN2, or with three 5GC1, 5GC2, 5GC3 for PLMN 1, 2, 3. This is the decision of the gNB.

[0071] As part of this new Release 18 feature for resource efficiency of RAN sharing (also known as "RAN shared resource usage"), RAN3 also agreed that N3mb can also be newly setup from the bottom up, i.e. triggered by the gNB. This is due to the previous agreement that the gNB decides the number of N3mb tunnels the gNB wants, and answers the following scenario: if the gNB decides to only establish one N3mb with 5GC1 for PLMN1 (e.g. to avoid redundancy on N3mb), while the radio resources are shared between PLMN1, PLMN2, PLMN3, then 5GC1 may decide to release the broadcast session, while 5GC2, 5GC3 want to continue the broadcast session to the UE via PLMN2 and PLMN3. 5GC1 will then release the broadcast session, which will release the N3mb between the gNB and 5GC1, meaning that there will be no N3mb for the gNB to receive the data to be delivered to the UE via PLMN2 and PLMN3. In this case, the gNB can newly trigger the establishment of a new N3mb to 5GC2 of PLMN2 or 5GC3 of PLMN3 so that the gNB receives broadcast data from MB-UPF2 of PLMN2 or MB-UPF3 of PLMN3, respectively.

[0072] Now that an overview of the technical area has been provided, a description of the problems in this area is provided below. As part of the Release 18 feature for "Resource efficiency of RAN sharing" (described above), Samsung in R3-233948 (see Samsung's "(TP for BLCR TS37.483) Discussion on MBS RAN sharing" (3GPP TSG-RAN WG3#12, Toulouse, France, August 21-25, 2023)) addressed the use case where N3mb may fail in the special case where the gNB is split between the control plane gNB-CU-CP and the user plane gNB-CU-UP.

[0073] In the case where the gNB is shared among three PLMN1, PLMN2, PLMN3 and the gNB decides to establish N3mb only to 5GC1 of PLMN1 (see above), the gNB needs to trigger the establishment of N3mb to 5GC2 of PLMN2 or 5GC3 of PLMN3 as an alternative, but the establishment is triggered by the gNB-CU CP, and the gNB-CU CP is unaware of the N3mb failure of 5GC1.

[0074] Samsung proposes that the gNB-CU UP informs the gNB-CU CP of a failure in the user plane N3mb so that the gNB-CU-CP can trigger the establishment of N3mb to 5GC2 or 5GC3 for replacement. See Tdoc R3-233948:

[0075] “If NG-RAN is a split architecture, for the second trigger, only gNB-CU-UP knows whether there is DL data flow from CN. Therefore, the new message should be triggered by gNB-CU-UP initially. gNB-CU-UP notifies that there is no data transmission to gNB-CU-CP due to user plane failure. Then gNB CU-CP can issue the message to another core network.”

[0076] Note that Samsung's "second trigger" is as follows: "When the shared NG-RAN fails to receive the DL data flow from the CN (e.g., due to a failure in the user plane), the NG-RAN attempts to acquire the DL data flow via the user plane of another CN."

[0077] This still creates problems, as described below.

[0078] A major issue that needs to be addressed is how to recover from a failure of the user plane N3mb in the gNB in ​​the MBS. These two issues can be addressed for both:

[0079] 1) Single-chip gNB, and

[0080] 2) Split gNB (i.e., there is an open E1 interface between gNB-CU CP and gNB-CU UP).

[0081] This problem can also be solved in the following cases:

[0082] 1) when “RAN shared resource efficiency” (or “RAN shared resource usage”) is not applicable (prior to Release 18 features), and

[0083] 2) When “RAN shared resource efficiency” (or “RAN shared resource usage”) is applicable (using Release 18 features).

[0084] In R3-233948, Samsung relies on the gNB-CU UP to detect the absence of data transmission and inform the gNB-CU CP, and then the gNB-CU CP triggers a new establishment of N3mb to the 5GC again. Also note that Samsung R3-233948 only covers RAN sharing cases, where the gNB-CU CP triggers the establishment of N3mb to the 5GC of another PLMN participating in RAN sharing.

[0085] However, Samsung's technology may not work because the gNB-CU UP or gNB not receiving data does not necessarily mean that N3mb is faulty and should be restored. Instead, the lack of data reception may simply be due to the suspension of data delivery for the broadcast application function.

[0086] It should also be appreciated that the solution for the gNB-CU UP or gNB to detect N3mb failure in the case of broadcast session delivery is not trivial. This is because 3GPP has decided that for broadcast, due to the fact that MBS data delivery is downlink only, the gNB will not be provided with the uplink transport address of the N3mb tunnel. However, this 3GPP decision also indirectly means that the gNB-CU UP or gNB cannot issue the GTP echo request message that 3GPP nodes typically use to detect user plane failures (see 3GPP TS29.281, e.g., Section 7.2.1 of 3GPP TS29.281 V18.0.0 (2023-06)).

[0087] With respect to the terminology used herein, the term "N3mb" is used to refer to a path or GTP tunnel on the N3mb interface used by a particular broadcast session for data stream delivery. The term "N3mb failure" is used to refer to a failure of a path or GTP tunnel on the N3mb interface used by a particular broadcast session for data stream delivery.

[0088] The examples in this document propose to solve at least the above mentioned problems in multiple possible ways, which are described in two main embodiments and their corresponding sub-embodiments. Note that all the following descriptions are for the general case of a split gNB (i.e., with gNB-CU CP and gNB-CU UP), however, these examples are also fully applicable to the case of a monolithic (non-split) gNB by considering all the interactions reported below between the gNB-CU CP and the gNB-CU UP as gNB internal (i.e., not through the open E1 interface).

[0089] First, the first example embodiment (hereinafter referred to as embodiment 1) is described. This example introduces a method for helping gNB-CU UP or gNB detect N3mb failure. This example uses Figure 1 , Figure 1 is a signaling diagram of an example called Embodiment 1 for N3MB failure recovery. Figure 1 CU UP 110, CU CP 115, MB-SMF 99-1 and MB-UPF 99-2 are illustrated. As previously described, the access node of the gNB 70 can be monolithic, or can be divided into a split gNB 70 as shown, with CU UP 110 and CU CP 115. MB-SMF 99-1 and MB-UPF 99-2 are examples of elements 99 of the core network 90, which can also be referred to as network functions.

[0090] As described above, the gNB-CU UP 110 cannot issue a GTP echo request to detect an N3mb failure (hereinafter, "N3mb failure" will refer to a failure of a path or a GTP tunnel on the N3mb interface used by a broadcast session for data stream delivery), but the gNB-CU UP 110 can receive an echo request generated by the MB-UPF 99-2, which monitors N3mb (hereinafter, "N3mb" will refer to a path or a GTP tunnel on N3mb used by a broadcast session for data stream delivery). If the MB-UPF 99-2 monitors N3mb, the MB-UPF 99-2 will issue an echo request message to the gNB 70 at regular intervals (for example, every three minutes). If the gNB-CU UP 110 is able to know the interval, the gNB-CU UP 110 will be able to notice that no echo request has been received from the MB-UPF 99-2 for more than three minutes, and thus infer an N3mb failure. To cope with the possible loss of one echo request, the gNB may also infer an N3mb failure after not receiving more than one (i.e., multiple) consecutive echo request messages.

[0091] Therefore, embodiment 1 includes the gNB-CU UP 110 learning the repetition timer of the echo request issued by the MB-UPF, and detecting the N3mb failure based on this. There are three examples for this aspect.

[0092] In option 1a 120-1a, the gNB-CU UP is configured with an MB-UPF repetition timer value for echo request and uses the value to detect N3mb failure. In box 125, the gNB-CU UP is configured with an MB-UPF repetition timer value for echo request, which can be for TMGI (i.e., each broadcast session). The MB-UPF repetition timer value used in this article is considered to be an indication of the interval between the expected reception of echo requests across the tunnel formed using N3mb. See box 185. This also applies to options 1b and 1c. As indicated in box 126, where the configuration may result in an interval, the interval includes a configuration interval used as an O&M (operation and maintenance) system. Although broadcast sessions are used in the examples herein, more generally, MBS sessions may be used. For example, the configuration may be for an MBS session rather than a broadcast session. In addition, the interval may be received from an SMF, a multicast-broadcast SMF, a UPF, or a multicast-broadcast UPF. See box 190.

[0093] In response to detecting that the duration since it received the last echo request from the MB-UPF is greater than (>) a timer value or greater than (>) a configurable multiple of the timer value, at step 4, in box 150, the gNB-CU UP 110 detects an N3mb failure using the timer value, see box 151. In box 151, this is considered as the CU UP 110 notifying the gNB-CU CP 115 in signaling 155 at step 5 using an indication of the N3mb failure and an indication of the MBS session involved identified by its temporary mobile group identity (e.g., "TMGI 1"). At step 6, in box 160, the gNB-CU CP 115 triggers a new N3mb establishment. Triggering N3mb establishment in all the following descriptions refers to triggering the establishment of a GTP tunnel on the N3mb interface for broadcast session data flow delivery.

[0094] In option 1b, at step 2, the gNB-CU CP receives the MB-UPF repetition timer value for the echo request from the MB-SMF 99-1. Earlier at step 1, the MB-SMF 99-1 has been configured with this timer value or has received an indication of the value to be used for the timer from the MB-UPF 99-1. Then, at step 3, the gNB-CU CP sends the MB-UPF repetition timer value to the gNB-CU UP.

[0095] More specifically, at step 2, in signaling 135, the gNB-CU CP receives from the MB-SMF the MB-UPF repetition timer value of the echo request, which may be for TMGI, i.e., for the broadcast session, or not. At step 1, in signaling 130, the MB-SMF 99-1 has been configured with the timer value or has received the timer value from the MB-UPF. At step 3, in signaling 140, the gNB-CU CP also sends the MB-UPF repetition timer value of the echo request to the gNB-CU UP.

[0096] At step 4 and blocks 150 and 151, the gNB-CU UP 110 uses the timer value to detect N3mb failure. At step 5, in signaling 155, the CU UP 110 notifies the gNB-CU CP 115. At step 6 and block 160, the gNB-CU CP triggers a new N3mb establishment.

[0097] In option 1c, the MB-UPF 99-2 issues a downlink packet over N3mb or sends an echo request message over N3mb, including an indication of the value of the MB-UPF repetition timer, see signaling 145. If the repetition timer value is for an MBS session (TMGI), an indication of "TMGI 1" may also be included. The downlink packet may be the first downlink packet of a broadcast session (respectively, echo request message), but not necessarily. At step 4 and boxes 150 and 151, the gNB-CU UP 110 uses the timer value to detect an N3mb failure. At step 5, in signaling 155, the CU UP 110 notifies the gNB-CU CP 115. At step 6 and in box 160, the gNB-CU CP triggers a new N3mb establishment.

[0098] Embodiment 2 is now described. One idea of ​​embodiment 2 is to rely on (multiple) elements in the core network (e.g., 5GC) to resolve the N3mb failure. The starting point in the example is that the MB-UPF detects the N3mb failure.

[0099] Reference now Figure 2A Describing embodiment 2a for non-RAN sharing case, Figure 2A is a signaling diagram for N3MB failure recovery in non-RAN sharing scenarios.

[0100] As an overview, upon receiving the MB-UPF notification of N3mb failure (including the gNB IP address towards which the N3mb path failure was detected), the MB-SMF instructs the AMF to issue a broadcast session release request to the corresponding gNB, including an indication of the cause of the user plane N3mb failure. The gNB-CU CP releases the broadcast session and notifies the 5GC (e.g., core network 90) back that the CUCP cannot establish any other N3mb (e.g., due to the absence of RAN sharing). Therefore, the MB-SMF triggers another broadcast session establishment towards the gNB.

[0101] Further details of signaling are as follows.

[0102] Step 1: In signaling 202, the MB-UPF 99-2 notifies the MB-SMF 99-1 of the N3mb failure, including the relevant IP address (associated with the gNB 70). When the MB-UPF 99-2 indicates the N3mb failure to the MB-SMF 99-1, this is performed using the IP address (the address associated with the gNB). When other addresses are mentioned in this document, these addresses refer to transport addresses.

[0103] Step 2: Upon receiving the MB-UPF notification of the N3mb failure (including the IP address of the gNB 70), the MB-SMF 99-1 instructs the AMF 99-3 to issue a broadcast session release request to the corresponding gNB, including an indication of the cause of the user plane N3mb failure. This occurs in part in box 204, where the MB-SMF retrieves the corresponding gNB ID and instructs the AMF to release the current broadcast session. In more detail, the MB-SMF 99-1 knows the mapping between the IP address used in the MB UPF and the corresponding gNB ID. The MB-SMF 99-1 generates a broadcast release request, but needs to tell the AMF to which gNB to issue the broadcast release request.

[0104] Steps 3, 4, 5: In signaling 206 of step 3, MB-SMF 99-1 issues an update message to AMF 99-3 including TMGI, gNB ID and an indication of N3mb failure. The gNB-CU CP 115 receives (signaling 208) the NGAP broadcast (bcast) session release message including the TMGI and the indication of N3mb failure, and releases (box 209) the broadcast session and indicates back to the 5GC (signaling 210) that it cannot establish any other N3mb (reason: there is no N3mb in this example, although RAN sharing cannot be used either). Signaling 210 is from CU CP 115 to AMF 99-3 and via AMF to MB-SMF 99-1. CU CP 115 also signals an E1AP broadcast release request with an indication of TMGI to CU UP 110, see signaling 212.

[0105] Regarding the update message in signaling 206, MB-SMF 99-1 constructs a broadcast release request (or Figure 2B The AMF 99-3 receives a modification request as shown in the figure below) and encapsulates it in a generic "Update" message that the MB-SMF sends to the AMF. The AMF then relays the message. Thus, for example, the AMF 99-3 does not need to be aware of the request for a new transport address (such as Figure 2B As shown), because the AMF can relay the broadcast release request from the MB-SMF, which is configured to request a new transport address, i.e., the transport address.

[0106] Step 6: As a result of the previous signaling, MB-SMF 99-1 instructs AMF 99-3 via box 214 to trigger another broadcast session establishment request to the gNB, and instructs AMF to establish another broadcast session, as shown in signaling 216.

[0107] Steps 7, 8: The gNB receives the signaling 216 and, in response, establishes (block 217) a new broadcast session. In signaling 216, the MB-SMF 99-1 signals an NGAP Broadcast Setup Request to the CU CP 115 via the AMF 99-3. In signaling 218, the CU CP 115 responds to the MB-SMF 99-1 via the AMF 99-3 with an NGAP Broadcast Setup Response message, which includes an indication of the MBS session information, including, for example, the (new) transport address. In signaling 220 of step 8, the CU CP 115 also issues an E1AP Broadcast Setup Request message indicating the (new) TMGI.

[0108] Embodiment 2b in the case of non-RAN sharing is now described. Figure 2B , Figure 2B It is a signaling diagram of embodiment 2B for N3MB failure recovery in non-RAN sharing situation.

[0109] As an overview, upon receiving the MB-UPF notification of N3mb failure (including the gNB IP address towards which the N3mb path failure was detected), the MB-SMF instructs the AMF to send a Broadcast Session Modification Request to the corresponding gNB, including a request for a new N3mb transport address, optionally with an indication of the cause of the N3mb failure. The cause may also be an implicit indication (rather than an explicit indication) of the request for a new N3mb transport address.

[0110] The gNB-CU CP retrieves the new transport address for the broadcast session from the gNB-CU UP and requests the gNB-CU UP to switch. The gNB-CU CP sends the new transport address back to the 5GC in the NGAP Broadcast Modification Response message. The MB-SMF instructs the MB-UPF to start delivering MBS data to the new gNB transport address (and stop delivering MBS data to the old gNB transport address). Part of the technology in this article involves the transport address, that is, how to get the new transport address for the broadcast session from the gNB over N3mb. The transport address is typically an IP address (associated with the gNB) and a GTP tunnel endpoint (of the gNB) which is used by the broadcast session to deliver data over N3mb (data is downlink only).

[0111] An example of description of each step is as follows.

[0112] Step 1: MB-UPF notifies MB-SMF of the N3mb failure, including the relevant IP address of the gNB. This is described as signaling 202 above.

[0113] Step 2: Upon receiving the MB-UPF notification of N3mb failure (e.g., IP address of gNB), MB-SMF 99-1 instructs AMF 99-3 to issue a Broadcast Session Modification Request to the corresponding gNB, including a request for a new transport address (ask), optionally with a cause indicating N3mb failure. See box 221.

[0114] Steps 3, 4: Upon receiving the broadcast session modification request message from AMF 99-3, the gNB-CU CP 115 retrieves the new transport address of the broadcast session from the gNB-CU UP and requests the gNB-CU UP to switch to the new transport address to receive the data of the broadcast session. As previously described, the signaling 223 of the update message can be configured with a modification request, which in this example at least requests the new transport address as the transport address. The modification request is encapsulated in the update message in signaling 223, and this is relayed by AMF 99-3 in signaling 222. That is, in signaling 222, AMF 99-3 sends an NGAP broadcast session modification request message to CU CP 115, which indicates the TMGI of the broadcast session, a request for a new transport address, and at least one of an N3mb failure indication. CU CP 115 also sends an E1AP broadcast modification request in signaling 224, which has an indication of the TMGI and a switch to the new transport address. CU UP 110 also sends an E1AP Broadcast Modify Response message to CU CP 115 in signaling 226 indicating the new transport address.

[0115] Step 5: The gNB-CU CP 115 sends the new transport address back to the 5GC in the NGAP Broadcast Modification Response message. This signaling 228 passes through the AMF 99-3 and ends at the MB-SMF 99-1.

[0116] Step 6: MB-SMF 99-1 forwards the new transport address received from the gNB-CU CP to MB-UPF 99-2 in signaling 230.

[0117] Note that this set of steps results in the use of the same broadcast session, but with a new transport address (which provides the IP address associated with gNB 70 and the GTP tunnel endpoint associated with gNB 7).

[0118] Now, in Figure 2C Another embodiment involving RAN sharing and non-RAN sharing scenarios, namely embodiment 2C, is described in . As an overview, upon receiving the MB-UPF notification of N3mb failure (including the gNB IP address towards which the N3mb path failure was detected), the MB-SMF instructs the AMF to notify the corresponding gNB of the N3mb failure. Upon receiving the MB-SMF notification, the gNB-CU CP can take action, namely triggering a new N3mb establishment to the 5GC (MB-SMF) of the same or another PLMN. Figure 2C In the present invention, AMF 99-31, MB-SMF 1 99-11 and MB-UPF 99-21 are located in PLMN 1 290-1, while AMF 2 99-32, MB-SMF 2 99-12 and MB-UPF 2 99-22 are located in PLMN 290-2.

[0119] An example of the steps involved follows.

[0120] Step 1: MB-UPF 1 notifies MB-SMF 1 of the N3mb failure, including the relevant IP address (corresponding to the gNB). This is signaling 202.

[0121] Step 2: Upon receiving the MB-UPF notification of the N3mb failure (e.g., with an indication of the IP address), the MB-SMF 199-11 instructs the AMF to notify the corresponding gNB of the N3mb failure. See box 232. Again, this can be performed by the MB-SMF 1 99-11 configuring an update message in signaling 233 to encapsulate a broadcast (bcast) session notification (or notification) failure, which is then passed by the AMF 99-3 to the CU CP 115.

[0122] Steps 3, 4: Upon receiving the N3mb failure notification from the MB-SMF / AMF, the gNB-CU CP releases the previous downlink transport address to the gNB-CU UP. This involves the AMF 99-3 receiving an update message with an indication of at least one of the TMGI, gNB ID and N3mb failure in signaling 233, and then forwarding an NGAP broadcast session notification (or notification) message with an indication of the TMGI and N3mb failure to the CU CP 115 in signaling 235. In box 234, the CU CP 115 decides to release the relevant current transport address associated with the broadcast session and then obtains a new transport address. This involves sending an E1AP broadcast release request with a TMGI indication to the CU UP 110 using signaling 236.

[0123] Steps 5, 6: In response to receiving the N3mb failure notification from the MB-SMF / AMF, the gNB-CU CP 115 retrieves the new transport address (via signaling 240) (note that signaling 236 and 240 can be combined) and triggers a new N3mb establishment to the MB-SMF 299-12 of another PLMN (or can be again to the MB-SPF 1 99-11 of the same PLMN, as shown in block 239), including the new transport address. See block 238, where IP address more generally means "transport address" = IP address + tunnel endpoint. The trigger uses signaling 242, which involves an NGAP broadcast session transport request with an indication of the new transport address from the CU CP 115 to the AMF 2 99-32 and through the AMF 99-32 to the MB-SMF 99-12. Step 6 sends the new transport address from the MB-SMF 2 99-12 to the MB-UPF 99-22.

[0124] Now, in Figure 2D Embodiment 2d involving RAN sharing and non-RAN sharing cases is described in . As an overview, upon receiving the MB-UPF notification of N3mb failure (including the gNB IP address towards which the N3mb path failure was detected), the MB-SMF instructs the AMF to issue a broadcast session release request to the corresponding gNB, including an indication of the cause of the user plane N3mb failure. The gNB-CU CP releases the broadcast session and triggers N3mb establishment with the 5GC of the same or another PLMN.

[0125] These steps can be found in Figure 2D is described below. Figure 2DIn the present invention, AMF 99-31, MB-SMF 1 99-11 and MB-UPF 99-21 are located in PLMN 1 290-1, while AMF 299-32, MB-SMF 2 99-12 and MB-UPF 2 99-22 are located in PLMN 290-2.

[0126] Step 1: MB-UPF notifies MB-SMF of the N3mb failure, including the relevant IP address. This is signaling 202.

[0127] Step 2: Upon receiving the MB-UPF notification (IP address of gNB) of N3mb failure, MB-SMF 1 99-11 instructs the AMF to send a broadcast session release request including the new cause of the user plane N3mb failure. See box 250. The signaling 244 of the update message may be configured with a session release request, which is then passed by the AMF in signaling 246.

[0128] Steps 3, 4: Upon receiving a broadcast session release request with a cause of N3mb failure from MB-SMF / AMF, the gNB-CU CP 115 releases the previous downlink transport address to the gNB-CU UP. See box 234. This also involves an update message in signaling 244 with an indication of at least one of TMGI, gNB ID, and N3mb failure; and AMF 99-3 sends an NGAP broadcast session release in signaling 246 with an indication of TMGI and N3mb failure. CU CP 115 sends an NGAP broadcast release response with a TMGI indication to MB-SMF1 99-11 in signaling 244. CU CP 115 also sends an E1AP broadcast release message request with a TMGI indication to CU UP 110 in signaling 236.

[0129] Steps 5, 6: Upon receiving a broadcast session release request with N3mb failure cause from MB-SMF / AMF, the gNB-CU CP 110 retrieves the new transport address and triggers (block 238) a new N3mb establishment to the MB-SMF 2 99-12 of another PLMN (or may be again to the MB-SPF 1 99-11 of the same PLMN, see block 239), including the new transport address. This occurs in signaling 240 between CU UP 110 and CU CP 115, and in signaling 242 of the NGAP broadcast session transfer request with an indication of the new transport address. That is, the trigger uses signaling 242 involving an NGAP broadcast session transfer request with an indication of the new transport address from CU CP 115 to AMF 2 99-32 and through AMF 99-32 to MB-SMF 99-12. Step 6 sends the new transport address from MB-SMF 2 99-12 to MB-UPF 99-22.

[0130] Go to Figure 3 , which shows a block diagram of one possible and non-limiting example of a cellular network 1 connected to a user equipment (UE) 10. Figure 3 A number of network elements are shown in the cellular network of FIG: gNB 70; and core network 90. Figure 3 In the example, a user equipment (UE) 10 wirelessly communicates with a gNB 70 of a cellular network 1 via a radio link 11. The gNB 70 is a network access node of the cellular network 1, as the gNB provides the UE or UE 10 with access to the cellular network 1.

[0131] This example illustrates a "monolithic" gNB 70, as one "block" of circuitry and corresponding program information. However, as described above, the gNB 70 can be a split gNB, where the upper layers are split into CU UP 110 and CU CP 115, and the lower layers are split into (multiple) DUs (possibly with (multiple) RUs) 71. Programs 72, (multiple) processors 73, memory 75 and other circuitry 76 are located in each of the elements 71, 110, 115. The RF portion (77 and 78) of the gNB 70 is implemented in the DU / RU, which communicates over the radio link 11. The elements 71, 110 and 115 communicate using (multiple) links 74. An example is the E1AP mentioned above.

[0132] UE 10 is a wireless communication device, such as a mobile device, configured to access a cellular network. UE 10 is shown as having one or more antennas 28. Ellipse 2 indicates that there may be multiple UEs 108 communicating wirelessly with gNB 70 via a radio link. UE 10 includes one or more processors 13, one or more memories 15, and another circuit system 16. Another circuit system 16 includes one or more receivers (Rx) 17 and one or more transmitters (Tx) 18. Program 12 is used to cause UE 10 to perform the operations described herein. For UE 10, another circuit system 16 may include a circuit system such as a user interface element (not shown) for a display.

[0133] As a network element of the cellular network 1, the gNB 70 provides the UE 10 with access to the cellular network 1 and access to the data network 91 via the core network 90 (e.g., via the user plane function (UPF) of the core network 90). Therefore, the gNB 70 can be regarded as a network access node (as described above) and as a base station. The gNB 70 is shown as having one or more antennas 58. Generally, the gNB 70 can be referred to as a RAN node 70, although many people will refer to it as a gNB (gNode B, i.e., a base station for the new radio NR). However, there are many other examples of RAN nodes, including eNB (evolved Node B) or TRP (transmission reception point). The gNB 70 includes one or more processors 73, one or more memories 75, and another circuit system 76. The other circuit system 76 includes one or more receivers (Rx) 77 and one or more transmitters (Tx) 78. The program 72 is used to enable the gNB 70 to perform the operations described herein.

[0134] Note that gNB 70 may also be implemented via other wireless technologies, such as Wi-Fi (a wireless network protocol used by devices to communicate without a direct cable connection). In the case of Wi-Fi, link 11 may be characterized as a wireless link.

[0135] Two or more gNBs 70 communicate using, for example, link(s) 79. Link(s) 79 may be wired or wireless or both, and may implement, for example, an Xn interface for 5G (fifth generation), an X2 interface for LTE (long term evolution), or other suitable interfaces for other standards.

[0136] The cellular network 1 may include a core network 90 as a second element or set of elements, which may include core network functions and provide a connection to a data network 91 (such as a telephone network and / or a data communication network (e.g., the Internet)) via one or more links 81. The core network 90 includes one or more processors 93, one or more memories 95, and another circuit system 96. The other circuit system 96 includes one or more receivers (Rx) 97 and one or more transmitters (Tx) 98. The program 92 is used to enable the core network 90 to perform the operations described herein.

[0137] The core network 90 may be a 5GC (5G core network). The core network 90 may implement or include a plurality of elements 99, also referred to as elements, also referred to as network functions (NFs) 99, and the program 92 may include one or more NFs in the NF 99. The element 99 may be an individual computing system or a network function, which itself is implemented by a computing system. In more detail, the 5G core network may use hardware such as a memory, a processor, and a virtualization layer. It may be a single independent computing system, a distributed computing system, or a cloud computing system. The NF 99 of the core network 90 may be a container or a virtual machine running on the hardware of the (multiple) computing systems constituting the core network 90.

[0138] The core network functions of 5G may include access and mobility management functions (such as access and mobility management function (AMF)) provided by network function 99, session management functions (such as session management function (SMF)) provided by network functions. The core network functions for access and mobility management in LTE (Long Term Evolution) networks may be provided by MME (Mobility Management Entity) and / or SGW (Serving Gateway) functions, which route data to the data network. Many other functions are also possible, such as Figure 3As shown in the example: AMF; SMF; MME; SGW; GMLC (Gateway Mobile Location Center); LMF (Location Management Function); UDM (Unified Data Management) / UDR (Unified Data Repository); NRF (Network Repository Function); and / or E-SMLC (Evolved Serving Mobile Location Center). MB-SMF (1, 2) and MB-UPF (1) are also included. Note that for one core network 90 and its corresponding PLMN 290, these will be constructed as MB-SMF (1) and MB-UPF (1), while for different core networks 90 and their corresponding PLMN 290, these will be constructed as MB-SMF (2). These are merely exemplary core network functions that can be provided by the core network 90, and note that both 5G and LTE core network functions can be provided by the core network 90. ​​The gNB 70 is coupled to the core network 90 via a backhaul link 31. The gNB 70 and the core network 90 may include an NG (Next Generation) interface for 5G, or an S1 interface for LTE, or other suitable interfaces for other radio access technologies, for communicating via the backhaul link 31.

[0139] In the data network 91, there is a computer-readable medium 94. The computer-readable medium 94 contains instructions that, when downloaded and installed into the memory 15, 75 or 95 of the corresponding UE 10, gNB 70 and / or (multiple) core network element 90 and executed by (multiple) processors 13, 73 or 93, cause the corresponding device to perform the corresponding actions described herein. The computer-readable medium 94 may be implemented in other forms, such as via an optical disk or a memory stick.

[0140] Programs 12, 72 and 92 include instructions stored by corresponding one or more memories 15, 75 or 95. When the instructions are executed by corresponding one or more processors 13, 73 or 93, the corresponding device 10, 70 or 90 performs the operations described herein. Computer-readable memory 15, 75 or 95 can be any type suitable for the local technical environment, and can be implemented using any suitable data storage technology, such as semiconductor-based memory devices, flash memory, firmware, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. Computer-readable memory 15, 75 and 95 can be a component for performing storage functions. Processors 13, 73 and 93 can be any type suitable for the local technical environment, and as non-limiting examples, can include one or more of a general-purpose computer, a special-purpose computer, a microprocessor, a digital signal processor (DSP) and a processor based on a multi-core processor architecture. Processors 13, 73 and 93 can be components for causing their corresponding devices to perform functions such as those described herein.

[0141] The receivers 17, 77 and 97 and the transmitters 18, 78 and 98 may implement a wired or wireless interface. The receiver and transmitter may be combined together as a transceiver.

[0142] The cellular network 1 can implement network virtualization, which is a process of combining hardware and software network resources and network functions into a single software-based management entity (virtual network). Network virtualization involves platform virtualization, which is usually combined with resource virtualization. Network virtualization is divided into two categories: one is external, which combines many networks or network parts into a virtual unit; the other is internal, which provides network-like functions for software containers on a single system. Note that the virtualized entities (such as network function 99) generated by network virtualization are still implemented using hardware such as processor 73 and / or 93 and memory 75 and / or 95 to some extent, and such virtualized entities will also produce technical effects.

[0143] Without limiting the scope, interpretation, or application of the following claims in any way, the technical effects and / or advantages of one or more example embodiments disclosed herein relate to the following. If the NG-RAN is a split architecture, and for the above-mentioned second trigger, only the gNB-CU-UP knows whether there is DL data flow from the CN. Therefore, the new message should initially be triggered by the gNB-CU-UP. The gNB-CU-UP notifies that there is no data transmission to the gNB-CU-CP due to a failure in the user plane. The gNB-CU-CP can then send the message to another core network.

[0144] The following are additional examples.

[0145] Example 1. A method includes: receiving, by a network access node in a cellular network, an indication of an interval between expected receipt of echo requests across a tunnel that uses an interface between a network element in a core network of the cellular network to a network access point of the cellular network; determining, by the network access node, a threshold time period based on the interval; detecting, by the network access node, an absence of echo requests for a time period greater than the threshold time period; determining, by the network access node based on the detection, a failure of the tunnel that uses the interface; and triggering, by the network access node, establishment of a new tunnel that uses the interface due to the failure of the tunnel.

[0146] Example 2. The method of example 1, wherein receiving the indication of the interval comprises receiving a configured interval to be used as the indicated interval from an O&M (operation and maintenance) system.

[0147] Example 3. The method of example 1, wherein receiving the indication of the interval comprises: receiving the indication of the interval from a session management function or a multicast broadcast session management function.

[0148] Example 4. The method of Example 1, wherein receiving the indication of the interval comprises: receiving the indication of the interval from a user plane function or a multicast broadcast user plane function.

[0149] Example 5. The method according to Example 4, wherein the indication of the interval is received from a user plane function or a multicast broadcast user plane function via a session management function or a multicast broadcast session management function.

[0150] Example 6. The method of Example 4, wherein the indication of the interval is received from the user plane function or the multicast broadcast user plane function in a data packet or an echo request message sent by the user plane function or the multicast broadcast user plane function.

[0151] Example 7. The method of any one of Examples 1 to 6, wherein the indication of the interval is for a multicast broadcast service (MBS) session.

[0152] Example 8. The method according to any one of Examples 1 to 6, wherein the network access node comprises: a first unit for a user plane and a second unit for a control plane, and wherein: the method further comprises: indicating a failure of the tunnel by the first unit to the second unit; and triggering establishment of a new tunnel is performed by the second unit.

[0153] Example 9. A method, comprising: receiving, by a second network element in a core network of a cellular network, from a first network element in the core network, an indication of a failure of a tunnel of an interface for transmitting an MBS session between a network access node and the first network element, the indication comprising: an indication of an address associated with a network access node using the tunnel; retrieving, by the second network element, an identification of the network access node based on the address; and indicating, by the second network element to a third network element in the core network, the failure of the tunnel for forwarding to the network access node, indicating at least using the identification of the network access node, indicating also requesting release of the MBS session.

[0154] Example 10. The method of Example 9, wherein the indication further indicates a cause value indicating a failure of an interface through which the MBS session is transmitted.

[0155] Example 11. The method of example 9 or 10, further comprising: receiving, by the second network element, an indication from the network access node that the MBS session has been released; and requesting, by the second network element, from the network access node via the third network element, another establishment of the MBS session.

[0156] Example 12. A method, comprising: using, by a network access node, a tunnel for transmitting an interface for an MBS session between the network access node and a first network element in a core network, receiving, from a second network node via a third network element in the core network, an indication of a tunnel failure, the indication also indicating that the MBS session is to be released; releasing, by the network access node, the MBS session; and sending, by the network access node via the third network element in the core network, to the second network element an indication that the interface is no longer used for the MBS session and that the MBS session is released.

[0157] Example 13. A method, comprising: receiving, by a second network element in a core network from a first network element in the core network of a cellular network, an indication of a tunnel failure of an interface for transmitting an MBS session between a network access node and the first network element, the indication comprising: an indication of an address associated with a network access node using the tunnel; retrieving, by the second network element, an identification of the network access node based on the address; and indicating, by the second network element to a third network element for forwarding to the network access node, at least one of: a failure of the tunnel in the core network, or a request for a new transport address of a network access node for use as a new tunnel endpoint for the MBS session.

[0158] Example 14. The method of Example 13, wherein the indication further indicates at least one of a tunnel failure of an interface through which the MBS session is transmitted or an identification of the MBS session.

[0159] Example 15. The method of any of Examples 13 or 14, further comprising receiving, by the second network element, an indication of a new transport address to be used as a tunnel endpoint associated with the MBS session.

[0160] Example 16. A method, comprising: using a tunnel of an interface for transporting an MBS session between the network access node and a first network element in a core network, receiving, by a network access node, at least one of an indication of a tunnel failure or an indication of a request for a new transport address to be used as a tunnel endpoint for the MBS session from a second network node via a third network element in the core network; determining, by the network access node, a new transport address associated with the MBS session; and sending, by the network access node, to a second network element via the third network element in the core network, an indication of the new transport address associated with the MBS session to be used as a new tunnel endpoint for transports between the first network element and the network access node.

[0161] Example 17. A method, comprising: receiving, by a second network element in a core network from a first network element in the core network of a cellular network, an indication of a failure of a tunnel of an interface for transmitting an MBS session between a network access node and the first network element, the indication comprising: an indication of an address associated with a network access node using the tunnel; retrieving, by the second network element, an identification of the network access node based on the address; and indicating, by the second network element to a third network element in the core network, a failure of the tunnel for forwarding to the network access node, the indication using at least the identification of the network access node, the indication also having a notification of a failure of the MBS session associated with the tunnel.

[0162] Example 18. A method, comprising: receiving, by a network access node, an indication of a tunnel failure from a second network element via a third network element in the core network using a tunnel of an interface for transmitting an MBS session between the network access node and a first network element in a core network; determining, by the network access node, to release a current transport address associated with the MBS session and to obtain a new transport address for the MBS session; and establishing, by the network access node, a new tunnel using an interface for transmitting the MBS session with a current PLMN of the core network or another PLMN of another core network; and sending, by the network access node, an indication of a new transport address to be used with the new tunnel for the MBS session to one of a second network element in the core network of the current PLMN or a second network element in another core network of the other PLMN.

[0163] Example 19. A method, comprising: receiving, by a second network element in a core network from a first network element in the core network of a cellular network, an indication of a failure of a tunnel of an interface for transmitting an MBS session between a network access node and the first network element, the indication comprising: an indication of an address associated with a network access node using the tunnel; retrieving, by the second network element, an identification of the network access node based on the address; and indicating, by the second network element to a third network element in the core network, a failure of the tunnel for forwarding to the network access node, the indication using at least the identification of the network access node, the indication also having a notification of a failure of the MBS session associated with the tunnel and requesting release of the MBS session.

[0164] Example 20. A method, comprising: using, by a network access node, a tunnel of an interface for transmitting an MBS session between the network access node and a first network element in a core network, receiving an indication of a tunnel failure from a second network element via a third network element in the core network, and requesting release of the MBS session; determining, by the network access node, to release a current transport address associated with the MBS session and to obtain a new transport address for the MBS session; and establishing, by the network access node, a new tunnel using an interface for transmitting the MBS session to one of a second network element in a core network of a current PLMN or a second network element in a core network of another PLMN; and sending, by the network access node, to one of the second network elements in the core network of the current PLMN or one of the second network elements in another core network of another PLMN, an indication of a new transport address to be used with the new tunnel for the MBS session.

[0165] Example 21. The method according to any of the preceding method examples, wherein the network element is a network function in a core network.

[0166] Example 22. A computer program comprising instructions for performing a method according to any one of Examples 1 to 21 when the computer program is run on a device.

[0167] Example 23. The computer program according to example 22, wherein the computer program is a computer program product comprising a computer readable medium carrying instructions embodied therein for use with an apparatus.

[0168] Example 24. The computer program according to example 22, wherein the computer program is directly loadable into an internal memory of the device.

[0169] Example 25. An apparatus comprising means for performing the following: receiving, by a network access node in a cellular network, an indication of an interval between expected receipt of echo requests through a tunnel that uses an interface between a network element in a core network of the cellular network to a network access point of the cellular network; determining, by the network access node, a threshold time period based on the interval; detecting, by the network access node, an absence of echo requests for a time period greater than the threshold time period; determining, by the network access node based on the detection, a failure of the tunnel that uses the interface; and triggering, by the network access node, establishment of a new tunnel that uses the interface due to the failure of the tunnel.

[0170] Example 26. The apparatus of Example 25, wherein receiving the indication of the interval comprises receiving a configured interval to be used as the indicated interval from an O&M (operation and maintenance) system.

[0171] Example 27. The apparatus according to Example 25, wherein receiving the indication of the interval comprises receiving the indication of the interval from a session management function or a multicast broadcast session management function.

[0172] Example 28. The apparatus according to Example 25, wherein receiving the indication of the interval comprises: receiving the indication of the interval from a user plane function or a multicast broadcast user plane function.

[0173] Example 29. The apparatus according to Example 28, wherein the indication of the interval is received from a user plane function or a multicast broadcast user plane function via a session management function or a multicast broadcast session management function.

[0174] Example 30. The apparatus according to Example 28, wherein the indication of the interval is received from the user plane function or the multicast broadcast user plane function in a data packet or an echo request message sent by the user plane function or the multicast broadcast user plane function.

[0175] Example 31. The apparatus of any one of Examples 25 to 30, wherein the indication of the interval is for a multicast broadcast service (MBS) session.

[0176] Example 32. The apparatus according to any one of Examples 25 to 30, wherein the network access node comprises: a first unit for a user plane and a second unit for a control plane, and wherein: the component is further configured to perform: indicating a failure of the tunnel to the second unit by the first unit; and triggering establishment of a new tunnel is performed by the second unit.

[0177] Example 33. An apparatus comprising means for performing the following: receiving, by a second network element in a core network of a cellular network, from a first network element in the core network, an indication of a failure of a tunnel of an interface used to transmit an MBS session between a network access node and the first network element, the indication comprising: an indication of an address associated with a network access node using the tunnel; retrieving, by the second network element, an identification of the network access node based on the address; and indicating, by the second network element to a third network element in the core network, the failure of the tunnel used to forward to the network access node, indicating at least using the identification of the network access node, indicating also requesting release of the MBS session.

[0178] Example 34. The apparatus according to Example 33, wherein the indication further indicates a cause value indicating a failure of an interface through which the MBS session is transmitted.

[0179] Example 35. The apparatus of any of Examples 33 or 34, wherein the component is further configured to perform: receiving, by the second network element, an indication from the network access node that the MBS session has been released; and requesting, by the second network element, from the network access node via the third network element, another establishment of the MBS session.

[0180] Example 36. An apparatus comprising means for performing each of the following: using, by a network access node, a tunnel for transmitting an interface for an MBS session between the network access node and a first network element in a core network, receiving an indication of a tunnel failure from a second network node via a third network element in the core network, the indication also indicating that the MBS session is to be released; releasing, by the network access node, the MBS session; and sending, by the network access node, via the third network element in the core network, to the second network element an indication that the interface is no longer used for the MBS session and that the MBS session is released.

[0181] Example 37. An apparatus comprising means for performing each of the following: receiving, by a second network element in a core network from a first network element in a core network of a cellular network, an indication of a tunnel failure of an interface for transmitting an MBS session between a network access node and the first network element, the indication comprising: an indication of an address associated with a network access node using the tunnel; retrieving, by the second network element, an identification of the network access node based on the address; and indicating, by the second network element to a third network element for forwarding to the network access node, at least one of: a failure of the tunnel in the core network, or a request for a new transport address of a network access node for use as a new tunnel endpoint for the MBS session.

[0182] Example 38. The apparatus according to Example 37, wherein the indication further indicates at least one of a tunnel failure of an interface through which the MBS session is transmitted or an identification of the MBS session.

[0183] Example 39. The apparatus of any of Examples 37 or 38, wherein the component is further configured to perform: receiving, by the second network element, an indication of a new transport address to be used as a tunnel endpoint associated with the MBS session.

[0184] Example 40. An apparatus comprising means for performing the following: using, by a network access node, a tunnel of an interface for transporting an MBS session between the network access node and a first network element in a core network, receiving, from a second network node via a third network element in the core network, at least one of an indication of a tunnel failure, or an indication indicating a request for a new transport address to be used as a tunnel endpoint for the MBS session; determining, by the network access node, a new transport address associated with the MBS session; and issuing, by the network access node, via the third network element in the core network, to a second network element an indication of a new transport address associated with the MBS session to be used as a new tunnel endpoint for transports between the first network element and the network access node.

[0185] Example 41. An apparatus comprising means for performing the following: receiving, by a second network element in a core network from a first network element in the core network of a cellular network, an indication of a failure of a tunnel for an interface for transmitting an MBS session between a network access node and the first network element, the indication comprising: an indication of an address associated with a network access node using the tunnel; retrieving, by the second network element, an identification of the network access node based on the address; and indicating, by the second network element to a third network element in the core network, a failure of the tunnel for forwarding to the network access node, the indication using at least the identification of the network access node, the indication also having a notification of a failure of the MBS session associated with the tunnel.

[0186] Example 42. An apparatus comprising components for performing the following: receiving, by a network access node, an indication of a tunnel failure from a second network element via a third network element in the core network using a tunnel of an interface for transmitting an MBS session between the network access node and a first network element in a core network; determining, by the network access node, to release a current transport address associated with the MBS session and to obtain a new transport address for the MBS session; and establishing, by the network access node, a new tunnel using an interface for transmitting the MBS session with a current PLMN of the core network or another PLMN of another core network; and sending, by the network access node, an indication of a new transport address to be used with the new tunnel for the MBS session to one of a second network element in the core network of the current PLMN or a second network element in another core network of the other PLMN.

[0187] Example 43. An apparatus comprising means for performing the following: receiving, by a second network element in a core network from a first network element in the core network of a cellular network, an indication of a tunnel failure of an interface for transmitting an MBS session between a network access node and the first network element, the indication comprising: an indication of an address associated with a network access node using the tunnel; retrieving, by the second network element, an identification of the network access node based on the address; and indicating, by the second network element to a third network element in the core network, a failure of the tunnel for forwarding to the network access node, the indication using at least the identification of the network access node, the indication also having a notification of a failure of the MBS session associated with the tunnel and requesting release of the MBS session.

[0188] Example 44. An apparatus comprising components for performing the following: using, by a network access node, a tunnel of an interface for transmitting an MBS session between the network access node and a first network element in a core network, receiving an indication of a tunnel failure from a second network element via a third network element in the core network, and requesting release of the MBS session; determining, by the network access node, to release a current transport address associated with the MBS session and obtain a new transport address for the MBS session; and establishing, by the network access node, a new tunnel using an interface for transmitting the MBS session to one of a second network element in a core network of a current PLMN or a second network element in a core network of another PLMN; and sending, by the network access node, to one of the second network elements in the core network of the current PLMN or one of the second network elements in another core network of another PLMN, an indication of a new transport address to be used with a new tunnel for the MBS session.

[0189] Example 45. The apparatus according to any of the preceding apparatus examples, wherein the network element is a network function in a core network.

[0190] Example 46. The apparatus according to any of the preceding apparatus examples, wherein the component comprises: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause execution of the apparatus.

[0191] Example 47. An apparatus comprising: one or more processors; and one or more memories storing instructions that, when executed by the one or more processors, cause the apparatus to perform at least: receiving, by a network access node in a cellular network, an indication of an interval between expected receipts of echo requests across a tunnel that uses an interface between a network element in a core network of the cellular network to a network access point of the cellular network; determining, by the network access node, a threshold time period based on the interval; detecting, by the network access node, an absence of echo requests for a time period greater than the threshold time period; determining, by the network access node, a failure of the tunnel that uses the interface based on the detection; and triggering, by the network access node, establishment of a new tunnel that uses the interface due to the failure of the tunnel.

[0192] Example 48. An apparatus, comprising: one or more processors; and one or more memories storing instructions, which, when executed by the one or more processors, cause the apparatus to at least perform: receiving, by a second network element in a core network of a cellular network from a first network element in the core network, an indication of a tunnel failure of an interface for transmitting an MBS session between a network access node and the first network element, the indication comprising: an indication of an address associated with a network access node using the tunnel; retrieving, by the second network element, an identification of the network access node based on the address; and indicating, by the second network element to a third network element in the core network, a failure of the tunnel used for forwarding to the network access node, the indication using at least the identification of the network access node, and the indication also requesting release of the MBS session.

[0193] Example 49. An apparatus comprising: one or more processors; and one or more memories storing instructions, which, when executed by the one or more processors, cause the apparatus to at least perform: receiving, by a network access node, an indication of a tunnel failure using an interface for transmitting an MBS session between the network access node and a first network element in a core network, from a second network node via a third network element in the core network, the indication also indicating that the MBS session is to be released; releasing, by the network access node, the MBS session; and sending, by the network access node, to the second network element via the third network element in the core network, an indication that the interface is no longer used for the MBS session and that the MBS session is released.

[0194] Example 50. An apparatus comprising: one or more processors; and one or more memories storing instructions, which, when executed by the one or more processors, cause the apparatus to at least perform: receiving, by a second network element in a core network from a first network element in a core network of a cellular network, an indication of a tunnel failure of an interface for transmitting an MBS session between a network access node and the first network element, the indication comprising: an indication of an address associated with a network access node using the tunnel; retrieving, by the second network element, an identification of the network access node based on the address; and indicating, by the second network element to a third network element, for forwarding to the network access node, at least one of the following items: a failure of the tunnel in the core network, or a request for a new transport address of a network access node for use as a new tunnel endpoint for the MBS session.

[0195] Example 51. An apparatus comprising: one or more processors; and one or more memories storing instructions, which, when executed by the one or more processors, cause the apparatus to at least perform: using, by a network access node, a tunnel for an interface for transmitting an MBS session between the network access node and a first network element in a core network, receiving, via a third network element in the core network, from a second network node an indication of a tunnel failure, or an indication indicating a request for a new transport address to be used as a tunnel endpoint for the MBS session; determining, by the network access node, a new transport address associated with the MBS session; and issuing, by the network access node, via the third network element in the core network, to a second network element an indication of a new transport address associated with the MBS session to be used as a new tunnel endpoint for transmission between the first network element and the network access node.

[0196] Example 52. An apparatus comprising: one or more processors; and one or more memories storing instructions, which, when executed by the one or more processors, cause the apparatus to at least perform: receiving, by a second network element in a core network from a first network element in the core network of a cellular network, an indication of a tunnel failure of an interface for transmitting an MBS session between a network access node and the first network element, the indication comprising: an indication of an address associated with a network access node using the tunnel; retrieving, by the second network element, an identification of the network access node based on the address; and indicating, by the second network element to a third network element in the core network, a failure of the tunnel for forwarding to the network access node, the indication using at least the identification of the network access node, the indication also having a notification of a failure of the MBS session associated with the tunnel.

[0197] Example 53. An apparatus comprising: one or more processors; and one or more memories storing instructions, which, when executed by the one or more processors, cause the apparatus to at least perform: using, by a network access node, a tunnel of an interface for transmitting an MBS session between the network access node and a first network element in a core network, receiving an indication of a tunnel failure from a second network element via a third network element in the core network; determining, by the network access node, to release a current transport address associated with the MBS session and to obtain a new transport address for the MBS session; and establishing, by the network access node, a new tunnel using an interface for transmitting the MBS session with a current PLMN of the core network or another PLMN of another core network; and sending, by the network access node, to one of a second network element in the core network of the current PLMN or a second network element in another core network of another PLMN, an indication of a new transport address to be used with a new tunnel for the MBS session.

[0198] Example 54. An apparatus comprising: one or more processors; and one or more memories storing instructions, which, when executed by the one or more processors, cause the apparatus to at least perform: receiving, by a second network element in a core network from a first network element in a core network of a cellular network, an indication of a tunnel failure of an interface for transmitting an MBS session between a network access node and the first network element, the indication comprising: an indication of an address associated with a network access node using the tunnel; retrieving, by the second network element, an identification of the network access node based on the address; and indicating, by the second network element to a third network element in the core network, a failure of the tunnel for forwarding to the network access node, the indication using at least the identification of the network access node, the indication also having a notification of a failure of the MBS session associated with the tunnel and requesting release of the MBS session.

[0199] Example 55. A device, comprising: one or more processors; and one or more memories storing instructions, which, when executed by the one or more processors, cause the device to at least perform: using, by a network access node, a tunnel of an interface for transmitting an MBS session between the network access node and a first network element in a core network, receiving an indication of a tunnel failure from a second network element via a third network element in the core network, and requesting release of the MBS session; determining, by the network access node, to release a current transport address associated with the MBS session, and obtaining a new transport address for the MBS session; and establishing, by the network access node, a new tunnel, the new tunnel using an interface for transmitting the MBS session to one of a second network element in a core network of a current PLMN or a second network element in a core network of another PLMN; and sending, by the network access node, to one of the second network elements in the core network of the current PLMN or one of the second network elements in another core network of another PLMN, an indication of a new transport address to be used with the new tunnel for the MBS session.

[0200] As used in this application, the term "circuitry" may refer to one, more, or all of the following:

[0201] (a) pure hardware circuit implementation (such as implementation in analog and / or digital circuitry only), and

[0202] (b) a combination of hardware circuitry and software, such as (as applicable): (i) a combination of analog and / or digital hardware circuitry and software / firmware, and (ii) any portion of hardware processor(s) (including digital signal processor(s)), software and memory(s) with software, which work together to enable a device (such as a mobile phone or server) to perform various functions, and

[0203] (c) Hardware circuits and / or processor(s), such as microprocessor(s) or portions of microprocessor(s), that require software (e.g., firmware) to operate, but where the software may not be present, for operation.

[0204] This definition of circuitry applies to all uses of the term in this application, including in any claims. As another example, as used in this application, the term circuitry also covers an implementation of only a hardware circuit or processor (or multiple processors) or a portion of a hardware circuit or processor and its accompanying software and / or firmware. For example, if applicable to a particular claim element, the term circuitry also covers a baseband integrated circuit or processor integrated circuit for a mobile device, or a similar integrated circuit in a server, cellular network device, or other computing or network device.

[0205] The embodiments herein may be implemented in software (executed by one or more processors), hardware (e.g., application specific integrated circuits), or a combination of software and hardware. In example embodiments, the software (e.g., application logic, instruction sets) is maintained on any of a variety of conventional computer-readable media. In the context of this document, a "computer-readable medium" may be any one or more media that can contain, store, communicate, propagate, or transport instructions for use by or in connection with an instruction execution system, apparatus, or device (such as a computer), where an example of a computer is, for example, a computer program product. Figure 3 . Computer-readable media may include computer-readable storage media (e.g., memories 15, 75, and 95 or other devices), which may be any one or more media that can contain, store, and / or transmit instructions for use by or in conjunction with an instruction execution system, apparatus, or device (such as a computer). Computer-readable storage media do not include propagating signals and therefore may be considered non-transient. The term "non-transient" as used herein is a limitation on the medium itself (i.e., tangible, not a signal), not on the persistence of data storage (e.g., RAM, random access memory vs. ROM, read-only memory).

[0206] If desired, the different functions discussed herein may be performed in different orders and / or concurrently with each other. In addition, if desired, one or more of the above functions may be optional or may be combined.

[0207] Although various aspects of the invention are set out in the independent claim, further aspects of the invention include other combinations of features of the described embodiments and / or dependent claims with features of the independent claim, not just the combinations explicitly set out in the claim.

[0208] It should also be noted herein that although the above describes example embodiments of the invention, these descriptions should not be viewed in a limiting sense. On the contrary, several variations and modifications may be made without departing from the scope of the invention as defined in the appended claims.

[0209] The following abbreviations that may appear in the specification and / or drawings are defined as follows:

[0210] 3GPP Third Generation Partnership Project

[0211] 5G Fifth Generation

[0212] 5GC Fifth Generation Core

[0213] AMF Access and Mobility Management Function

[0214] bcast Broadcast

[0215] CU CP Central Unit Control Plane

[0216] CU UP Central Unit User Plane

[0217] DU Distributed Unit

[0218] E-SMLC Evolved Serving Mobile Location Center

[0219] GMLC Gateway Mobile Location Center

[0220] E1AP E1 Application Protocol

[0221] eNB (or eNodeB) Evolved Node B (e.g., LTE base station)

[0222] gNB (or gNodeB) 5G / NR base station

[0223] GPRS General Packet Radio Service

[0224] GTP GPRS Tunneling Protocol

[0225] I / F Interface

[0226] IP Internet Protocol

[0227] LMF Location Management Function

[0228] LTE Long Term Evolution

[0229] MBS Multicast and Broadcast Service

[0230] MB-SMF Multicast Broadcast Session Management Function

[0231] MB-UPF Multicast Broadcast User Plane Function

[0232] MME Mobility Management Entity

[0233] NF Network Function

[0234] ng or NG Next Generation

[0235] NGAP NG Application Protocol

[0236] NG-RAN Next Generation Radio Access Node

[0237] NR New Radio

[0238] NRF Network Repository Features

[0239] N / W or NW network

[0240] PLMN Public Land Mobile Network

[0241] PTM Point to Multipoint

[0242] RAN Radio Access Network

[0243] Rel version

[0244] RF

[0245] RRC Radio Resource Control

[0246] RU Radio Unit

[0247] Rx Receiver

[0248] SGW Service Gateway

[0249] SMF session management functions

[0250] SN Serial Number

[0251] TMGI or TMGI Temporary Mobility Group Identifier

[0252] TRP Transmission Reception Point

[0253] Tx Transmitter

[0254] UDM Unified Data Management

[0255] UDR Unified Data Repository

[0256] UE User Equipment (e.g. wireless device, usually a mobile device)

[0257] UPF User Plane Function

Claims

1. A method for a multicast broadcast session management function (MB-SMF) of a core network of a cellular network, the method comprising: receiving, from a multicast broadcast user plane function (MB-UPF), an indication of a failure of a tunnel of an interface for conveying a multicast broadcast service (MBS) session between a network access node and the MB-UPF, the indication comprising: an address associated with the network access node using the tunnel; retrieving an identification of the network access node based on the address; and A failure of the tunnel for forwarding to the network access node is indicated to an access and mobility management function (AMF).

2. The method according to claim 1, wherein the indication further comprises: Indicates the identifier of the MBS session.

3. The method according to claim 1, further comprising: An indication of a new transport address to be used as a tunnel endpoint associated with the MBS session is received.

4. The method of claim 1, wherein the indication comprises: Using the identification of the network access node, indicating to the AMF a failure of the tunnel for forwarding to the network access node.

5. The method of claim 4, wherein the indication comprises: Indicating an identifier of the MBS session associated with the failed tunnel.

6. A device for a core network of a cellular network, the device comprising: Multicast Broadcast Session Management Function (MB-SMF), configured to perform: receiving, from a multicast broadcast user plane function (MB-UPF), an indication of a failure of a tunnel of an interface for conveying a multicast broadcast service (MBS) session between a network access node and the MB-UPF, the indication comprising: an address associated with the network access node using the tunnel; retrieving an identification of the network access node based on the address; and A failure of the tunnel for forwarding to the network access node is indicated to an access and mobility management function (AMF).

7. The apparatus according to claim 6, wherein the indication further comprises: Indicates the identifier of the MBS session.

8. The apparatus of claim 6, wherein the MB-SMF is further configured to perform: An indication of a new transport address to be used as a tunnel endpoint associated with the MBS session is received.

9. The apparatus of claim 6, wherein the indication comprises: Using the identification of the network access node, indicating to the AMF a failure of the tunnel for forwarding to the network access node.

10. The apparatus of claim 9, wherein the indication comprises: Indicating an identifier of the MBS session associated with the failed tunnel.

11. A computer-readable medium comprising instructions, which, when executed by at least one processor of a device of a core network of a cellular network, cause the device to perform the method according to any one of claims 1 to 5.

12. A computer program comprising instructions, wherein when the computer program is executed by at least one processor of a device of a core network of a cellular network, the device is caused to perform the method according to any one of claims 1 to 5.

13. A method for a network access node of a cellular network, the method comprising: receiving at least one of the indications of a tunnel failure using a tunnel for transporting an interface for a multicast broadcast service (MBS) session from a multicast broadcast session management function (MB-SMF) via an access and mobility management function (AMF) between the network access node and a multicast broadcast user plane function (MB-UPF); determining a new transport address associated with the MBS session; as well as An indication of the new transport address associated with the MBS session is issued to the MB-SMF via the AMF to be used as a new tunnel endpoint for the transmission between the MB-UPF and the network access node.

14. A network access node for a cellular network, the network access node comprising: means for receiving at least one of the indications of a tunnel failure using a tunnel of an interface for conveying a multicast broadcast service (MBS) session from a multicast broadcast session management function (MB-SMF) via an access and mobility management function (AMF) between the network access node and a multicast broadcast user plane function (MB-UPF); means for determining a new transport address associated with the MBS session; as well as Means for issuing an indication of the new transport address associated with the MBS session to the MB-SMF via the AMF to be used as a new tunnel endpoint for the transmission between the MB-UPF and the network access node.

15. A computer-readable medium comprising instructions which, when executed by at least one processor of a device of a core network of a cellular network, cause the network access node to execute: receiving at least one of the indications of a tunnel failure using a tunnel for transporting an interface for a multicast broadcast service (MBS) session from a multicast broadcast session management function (MB-SMF) via an access and mobility management function (AMF) between the network access node and a multicast broadcast user plane function (MB-UPF); determining a new transport address associated with the MBS session; and An indication of the new transport address associated with the MBS session is issued to the MB-SMF via the AMF to be used as a new tunnel endpoint for the transmission between the MB-UPF and the network access node.

16. A computer program comprising instructions, wherein when the computer program is executed by at least one processor of a network access node of a cellular network, the network access node is caused to perform: receiving at least one of the indications of a tunnel failure using a tunnel for transporting an interface for a multicast broadcast service (MBS) session from a multicast broadcast session management function (MB-SMF) via an access and mobility management function (AMF) between the network access node and a multicast broadcast user plane function (MB-UPF); determining a new transport address associated with the MBS session; and An indication of the new transport address associated with the MBS session is issued to the MB-SMF via the AMF to be used as a new tunnel endpoint for the transmission between the MB-UPF and the network access node.

17. A method for a network access node of a cellular network, the method comprising: receiving an indication of a failure of the tunnel using a tunnel of an interface for transmitting a multicast broadcast service (MBS) session from a second network node via a third network element of the core network between the network access node and a first network element of a core network; Determining to release a current transport address associated with the MBS session and obtaining a new transport address for the MBS session; establishing a new tunnel using the interface used to transmit the MBS session with another cellular network; as well as An indication of the new transport address to be used with the new tunnel for the MBS session is sent to a multicast broadcast session management function (MB-SMF) of a core network of the other cellular network.

18. A network access node for a cellular network, the network access node comprising: means for receiving an indication of a tunnel failure using a tunnel for conveying an interface for a Multicast Broadcast Service (MBS) session of the core network from a Multicast Broadcast Session Management Function (MB-SMF) via an Access and Mobility Management Function (AMF) of the core network between the network access node and a Multicast Broadcast User Plane Function (MB-UPF) of the core network of the cellular network; means for determining to release a current transport address associated with the MBS session and to obtain a new transport address for the MBS session; means for establishing a new tunnel using said interface used to communicate said MBS session with another cellular network; as well as Means for sending an indication of the new transport address to be used with the new tunnel for the MBS session to a Multicast Broadcast Session Management Function (MB-SMF) of a core network of the other cellular network.

19. A computer-readable medium comprising instructions which, when executed by at least one processor of a device of a core network of a cellular network, cause the network access node to execute: receiving an indication of a failure of the tunnel using a tunnel of an interface for transmitting a multicast broadcast service (MBS) session from a second network node via a third network element of the core network between the network access node and a first network element of a core network; Determining to release a current transport address associated with the MBS session and obtaining a new transport address for the MBS session; establishing a new tunnel using the interface used to transmit the MBS session with another cellular network; as well as An indication of the new transport address to be used with the new tunnel for the MBS session is sent to a multicast broadcast session management function (MB-SMF) of a core network of the other cellular network.

20. A computer program comprising instructions, wherein when the computer program is executed by at least one processor of a network access node for a cellular network, the network access node is caused to perform: receiving an indication of a failure of the tunnel using a tunnel of an interface for transmitting a multicast broadcast service (MBS) session from a second network node via a third network element of the core network between the network access node and a first network element of a core network; Determining to release a current transport address associated with the MBS session and obtaining a new transport address for the MBS session; establishing a new tunnel using the interface used to transmit the MBS session with another cellular network; as well as An indication of the new transport address to be used with the new tunnel for the MBS session is sent to a multicast broadcast session management function (MB-SMF) of a core network of the other cellular network.

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