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1. WO2020108769 - DISPOSITIFS ET PROCÉDÉS DE CONTINUITÉ DE SERVICE DANS UN RÉSEAU DE COMMUNICATION 5G

Note: Texte fondé sur des processus automatiques de reconnaissance optique de caractères. Seule la version PDF a une valeur juridique

[ EN ]
DESCRIPTION

DEVICES AND METHODS FOR SERVICE CONTINUITY IN A 5G COMMUNICATION NETWORK

TECHNICAL FIELD

In general, the present invention relates to communication networks. More specifically, the present invention relates to devices and methods for providing service continuity for failure scenarios of network nodes, in particular base stations in a 5G communication network.

BACKGROUND

The next generation of the mobile and wireless communications, namely, the fifth generation (5G) envisions new use cases, services and applications, such as enhanced mobile broadband (eMBB), ultra-reliable low latency communications (URLLC), and massive machine-type communications (mMTC). Any combinations of these use cases can also be possible, such as ultra-reliable communications, low-latency communications, or low-latency eMBB communications. Among these enhanced Vehicular to everything (eV2X) can be seen as special 5G service type, which can include both safety and non safety services. One of the key requirements of eV2X services is the critical latency (3-10ms) and reliability (99.999% and higher), which may need to be adapted on demand, due to new application requests (e.g. Level of Automation change, dynamic group-UE formations) or network changes (network congestion to core network and/or access network entities, mode of transmission/operation change). One key challenge under these requirements is to ensure service continuity for V2X communications without any temporary loss of service or loss of data packets. Thus, the radio access network (RAN) of a 5G communication network will need to support V2X/URLLC services for user plane (UP), control plane (CP) or both to ensure meeting the reliability and coverage

requirements.

Virtualization of network functions (NFs), i.e. providing NFs as software implemented on the physical infrastructure of a network, is one of the key enablers to allow for flexibility and end-to-end (E2E) optimization in 5G communication networks. However, as more and more network functions are being virtualized, i.e. implemented in software, the risk of malfunctions of these network functions due to software failures increases as well. Thus, in addition to failures of the network hardware providing the execution environment for the virtualized network functions, failures of the software implementing the virtualized network functions must be dealt with in a 5G communication network as well.

For instance, a failure of a RAN node, in particular base station of a 5G communication network may happen in software (SW), hardware (HW) or both, and the levels of failure can vary, such as a partial failure, complete failure, control plane failure and/or user plane failure. Generally, the PHY/RF communication layers are less probable to experience a failure, because the PHY communication layer could be able to deal with such failures due to, for instance, multiple antennas being available. However, small cells

(Planned/Unplanned) as well as road-side units (RSUs), which are configured to boost performance in dense areas, if necessary, are generally low power, low cost nodes and, thus, may be more vulnerable to partial/complete SW/HW failures.

One approach to handle partial/complete SW/HW failures of a RAN node in a mobile communication network is a forced or normal handover to another RAN node even if the failure is only partial. That is, when the failure occurs, e.g., in a macro base station (BS), the user equipments (UEs) served by this BS are handed over to neighboring cells of the communication network. One drawback of this approach is the delay caused by the handover which may be not acceptable for time critical communication services. For instance, for group-V2X communications, this may have a strong impact on the other BSs (overload, congestions) and UEs using other services. Moreover, this approach only works if the network coverage is sufficient for the UEs to be handed over to a new BS.

A second approach is to equip BSs with additional/redundant SW/HW, so as to ensure availability by redundancy at the same RAN node, such as by providing

additional/redundant protocol stacks to RAN nodes. This approach has been used in cloud-RAN/centralized-RAN (C-RAN) deployments, where a baseband unit (BBU) can have a back-up deployment for ensuring availability. Although this second approach might be viable for specific nodes of a 5G communication network, especially highly

sophisticated equipment, it is less viable for the multitude of low-power/low cost nodes, i.e. base stations providing small cells in a 5G communication network, because of the increased complexity and costs due to redundant SW and/or HW.

Thus, there is a need for improved devices and methods for providing service continuity for failure scenarios of network nodes, in particular base stations in a communication network, in particular a 5G communication network.

SUMMARY

It is an object of the invention to provide improved devices and methods for providing service continuity for failure scenarios of network nodes, in particular base stations in a communication network, in particular a 5G communication network.

The foregoing and other objects are achieved by the subject matter of the independent claims. Further implementation forms are apparent from the dependent claims, the description and the figures.

According to a first aspect, the invention relates to a network control entity for a wireless, in particular 5G communication network. The wireless communication network comprises a plurality of network nodes, in particular base stations, wherein each network node defines a set of functions, in particular protocol functions, to communicate with a user equipment, UE, of the wireless communication network. The network control entity is adapted to: select for a first network node (herein also referred to as "serving node"), that communicates with the UE, a second network node (herein also referred to as "donor node"); configure the second network node to concurrently process at least a subset of functions of the first network node to communicate with the UE; and trigger the second network node to provide the subset of functions to the UE. The network control entity can be adapted to trigger the second network node to provide the subset of functions to the UE, in case of a failure of the subset of functions of the first network node, i.e. a partial network node failure so that the other, i.e. remaining functions of the first network node and the subset of functions provided by the second network node together provide the set of functions of the first network node for communicating with the user equipment. A function of the first network node and the second network node can be a function for exchanging critical V2X information with the user equipment of the wireless

communication network. The network control entity can be a single or distributed physical entity, such as a server, and/or can comprise one or more network functions implemented on one or more physical devices of the communication network.

In a further possible implementation form of the first aspect, the network control entity is further adapted to configure the second network node to provide the subset of functions of the first network node for a defined time duration only.

In a further possible implementation form of the first aspect, the network control entity is further adapted to define the subset of functions of the first network node for concurrently processing by the second network node.

In a further possible implementation form of the first aspect, the network control entity is further adapted to provide configuration information to the first network node and/or the second network node, wherein the configuration information comprises one or more of:

- an identifier of the first network node,

- an identifier of the second network node,

- network parameters

- protocol function parameters (L1 , L2, L3 protocols),

- resource configuration parameters,

- RRM policies,

- service type,

- slice information.

In a further possible implementation form of the first aspect, the network control entity is further adapted

- to obtain network-related information, in particular from a fault management entity and/or a management monitoring and/or data analytics entity, such as a MDAF, located in a management plane of the wireless communication network and/or from a network monitoring and/or data analytics entity, such as a NWDAF, located in a core network of the wireless communication network; and

- to select the first network node and/or the second network node on the basis of the network-related information.

In a further possible implementation form of the first aspect, the first network node and/or the second network node is one of:

a base station, in particular a central unit or a distributed unit;

a road side unit, in particular user equipment;

a cloud-processing unit, in particular an operator-independent cloud processing unit.

In a further possible implementation form of the first aspect, the functions of the first network node and the second network node comprise a plurality of access network (AN) communication layers of a AN communication protocol stack for exchanging information with the user equipment. Thus, in an embodiment, the second network node is configured to provide, in case of a failure of one or more of the plurality of AN communication layers of the protocol stack of the first network node, the respective one or more of the plurality of communication layers of the first network node for communicating with the user equipment.

In a further possible implementation form of the first aspect, the functions of the first network node and the second network node comprise a respective communication interface with a core network of the wireless communication network, wherein the second network node is configured to provide, in case of a failure of the communication interface of the first network node with the core network, the communication interface of the first network node with the core network by acting as a relay using the communication interface of the second network node with the core network for exchanging data with the user equipment.

According to a second aspect the invention relates to a first network node (i.e. a serving node), in particular base station of a wireless, in particular 5G communication network, wherein the first network node defines a set of functions, in particular protocol functions, to communicate with a user equipment, UE, of the wireless communication network. The first network node is adapted, in response to a failure of a subset of functions of the first network node, i.e. a partial network node failure, to provide the set of functions of the first network node on the basis of the other functions of the first network node and a subset of functions corresponding to the subset of functions of the first network node provided by a second network node (i.e. the donor node) of the wireless communication network.

In a further possible implementation form of the second aspect, the first network node is adapted to provide session information about a session for exchanging information with the user equipment, i.e. session-related protocol info to the second network node. The session information can include: RRM/RLM measurements; DRB/SRB configurations; protocol configurations (e.g. HARQ timings); slice-support information (e.g., slice ID, S-NSSAI, UE); and/or UE context information. More specifically, for the PHY communication layer (Baseband) the session information can include: specific RNTIs used per UE and session; specific RNTIs used per Group/session; and/or channel coding/modulation

related configuration information. For the MAC communication layer the session information can include: adaptive and non-adaptive HARQ configuration information; HARQ process ID; and/or dynamic or grant-free (typel , type 2) scheduling configuration information. For the RLC communication layer, the session information can include configuration information such as sequence numbering. For the PDCP communication layer, the session information can include configuration information such as PDCP layer duplication or ciphering related encryption/decryption key information or sequence numbering. For the SDAP communication layer, the session information can include configuration information such as QoS flow to radio bearer mapping.

In a further possible implementation form of the second aspect, the first network node is adapted to provide context information about the user equipment, in particular an UE identifier, to the second network node.

In a further possible implementation form of the second aspect, the first network node and/or the second network node is one of:

a base station, in particular a central unit or a distributed unit;

a road side unit, in particular user equipment;

a cloud-processing unit, in particular an operator-independent cloud processing unit.

In a further possible implementation form of the second aspect, the functions of the first network node and the second network node comprise a plurality of AN communication layers of a AN communication protocol stack for communicating with the user equipment.

In a further possible implementation form of the second aspect, the functions of the first network node and the second network node comprise a respective communication interface with a core network of the wireless communication network and wherein the second network node is configured to provide, in case of a failure of the communication interface of the first network node with the core network, the communication interface of the first network node with the core network by acting as a relay using the communication interface of the second network node with the core network for exchanging data with the user equipment.

According to a third aspect the invention relates to a second network node (i.e. a donor node), in particular base station, of a wireless, in particular 5G communication network. The second network node defines a set of functions, in particular protocol functions to communicate with a user equipment, UE, of the wireless communication network. The second network node is configured to concurrently process at least a subset of functions of a first network node of the wireless communication network for communicating with the UE and to provide the subset of functions to the UE.

In a further possible implementation form of the second aspect, the second network node is adapted to receive configuration information from a network control entity of the wireless communication network having selected/configured the second network node, wherein the configuration information configures the second network node to provide, in response to a failure of the subset of functions of the first network node, the subset of functions.

In a further possible implementation form of the second aspect, the second network node is adapted to notify the first network node and/or a network control entity of the wireless communication network having selected/configured the second network node that the second network node is configured, in response to a failure of the subset of functions of the first network node, i.e. a partial network node failure, to provide the subset of functions.

In a further possible implementation form of the second aspect, the first network node and/or the second network node is one of:

a base station, in particular a central unit or a distributed unit;

a road side unit, in particular user equipment;

a cloud-processing unit, in particular an operator-independent cloud processing unit.

In a further possible implementation form of the second aspect, the functions of the first network node and the second network node comprise a plurality of AN communication layers of a AN communication protocol stack for communicating, i.e. exchanging information with the user equipment.

In a further possible implementation form of the second aspect, the plurality of functions of the first network node and the second network node comprise a respective

communication interface with a core network of the wireless communication network and wherein the second network node is configured to provide, in case of a failure of the communication interface of the first network node with the core network, the

communication interface of the first network node with the core network by acting as a

relay using the communication interface of the second network node with the core network for exchanging data with the user equipment.

According to a fourth aspect the invention relates to a wireless communication network comprising a network control entity according to the first aspect of the invention, a first, i.e. serving network node according to the second aspect of the invention and a second, i.e. donor network node according to the third aspect of the invention.

Thus, embodiments of the invention provide a pro-active and/or dynamic RAN node failure healing solution to avoid service discontinuity, by configuring a failsafe protocol stack to a target RAN node for the case that failure happens at the source RAN node. As described above, the network control entity provided by embodiments of the invention may be configured/parameterized by management functions (e.g. Fault Management) of the communication network. Embodiments of the invention enable a very fast and reliable failure recovery, for instance, for URLLC/V2X services with minimum service disruption in case of a UP/CP protocol failure, which avoids having to perform a handover to neighboring network nodes (which use back-up access connectivity). Thus, embodiments of the invention can ensure service continuity for ongoing traffic with minimal CP latency and high availability.

Details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description, drawings, and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following embodiments of the invention are described in more detail with reference to the attached figures and drawings, in which:

Fig. 1 is a diagram illustrating a configuration message flow in a 5G communication network comprising a network control entity, a first network node and a second network according to an embodiment of the invention;

Fig. 2 is a diagram illustrating a configuration message flow in a 5G communication network for configuring a network control entity according to an embodiment of the invention;

Fig. 3 is a diagram illustrating an operation message flow in a 5G communication network comprising a network control entity, a first network node and a second network according to an embodiment of the invention;

Fig. 4 is a diagram illustrating a configuration and operation message flow in a 5G communication network comprising a network control entity, a first network node and a second network according to a further embodiment of the invention;

Fig. 5 is a diagram illustrating a configuration and operation message flow in a 5G communication network comprising a network control entity, a first network node and a second network according to a further embodiment of the invention; and

Fig. 6 is a diagram illustrating a configuration message flow in a 5G communication network comprising a network control entity, a first network node and a second network according to a further embodiment of the invention.

In the following identical reference signs refer to identical or at least functionally equivalent features.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In the following description, reference is made to the accompanying figures, which form part of the disclosure, and which show, by way of illustration, specific aspects of embodiments of the invention or specific aspects in which embodiments of the present invention may be used. It is understood that embodiments of the invention may be used in other aspects and comprise structural or logical changes not depicted in the figures. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims.

For instance, it is understood that a disclosure in connection with a described method may also hold true for a corresponding device or system configured to perform the method and vice versa. For example, if one or a plurality of specific method steps are described, a corresponding device may include one or a plurality of units, e.g. functional units, to perform the described one or plurality of method steps (e.g. one unit performing the one or plurality of steps, or a plurality of units each performing one or more of the plurality of steps), even if such one or more units are not explicitly described or illustrated in the figures. On the other hand, for example, if a specific apparatus is described based on one or a plurality of units, e.g. functional units, a corresponding method may include one step to perform the functionality of the one or plurality of units (e.g. one step performing the functionality of the one or plurality of units, or a plurality of steps each performing the functionality of one or more of the plurality of units), even if such one or plurality of steps are not explicitly described or illustrated in the figures. Further, it is understood that the features of the various exemplary embodiments and/or aspects described herein may be combined with each other, unless specifically noted otherwise.

Figure 1 is a diagram illustrating a configuration message flow in a 5G communication network 100 according to an embodiment of the invention. The 5G communication network 100 comprises a core network and a radio access network (RAN) or short access network (AN) including a first RAN node, in particular base station 103 (referred to as serving node in figure 1 ) and a second RAN node, in particular base station 105 (referred to as donor node in figure 1 ). Both the serving node 103 as well as the donor node 105 are configured to provide an user equipment (UE) 101 access to the communication network 100. To this end, a respective set of software functions, in particular protocol software functions is implemented on the serving node 103 and the donor node 105 for communicating with the UE 101 .

The 5G communication network 100 further comprises a network control entity 1 10, which in figure 1 is referred to as“Failsafe Node Configurator (FNC)”. As will be described in more detail below, the FNC 1 10 is adapted to: select for the serving node 103, that communicates with the UE 101 , a second network node, namely the donor node 105; configure the donor node 105 to concurrently process at least a subset of the software functions of the serving node 103 for communicating with the UE 101 ; and trigger, for instance, in response to a failure of a subset of the software functions of the serving node 103, the donor node 105 to provide the subset of software functions to the UE 101 . In this way, the UE 101 will be provided with a continuous communications service despite, for instance, a partial failure of a subset of the software functions of the serving node 103. Although some of the software functions for communicating with the UE 101 are now provided by the donor node 105, this change is transparent for the UE 101 .

Further embodiments of the invention will be described in the following in two different main phases, namely (i) a configuration or pre-operation phase and (ii) an operation phase.

In the pre-operation phase, the network control entity 1 10 can be configured by the communication network 100. As illustrated in figure 2, an upper layer network entity or function, such as a fault management (FM) network entity or function 203 implemented in a management plane of the communication network 100 can activate, i.e. configure the network control entity 1 10. This activation can be triggered, for instance, on the basis of network analytics information collected about the performance of the communication network 100 or in response to a different event, such as the instantiation of a new network slice in the communication network 100. According to embodiments of the invention, the activation of the network control entity 1 10 can comprise an activation request and a corresponding response or subscribe/publish handshake, as illustrated in figure 2. The fault management entity 203 may be configured to determine the status of any available network nodes and interfaces, such as load status, availability status, or the like, on the basis of network analytics information, which can be provided by a network data analytics function (NWDAF) 201 located in the control plane of the communication network 100 and/or a management data analytics functions (MDAF) 205 located in the management plane of the communication network 100. Subsequently, the fault management entity 203 may configure the network control entity 1 10 using at least one of the following

parameters: placement of functionality; network segments to be notified; granularity of notifications; geographical area; time validity of the configuration of the network control entity 1 10; the exposure of the network control entity to one or more third parties; reserved resources.

According to further embodiments of the invention a failsafe protocol stack (FPS) can be configured on the network control entity 1 10 as part of the pre-operation phase. To this end, network analytics information about, for instance, the RAN, CN, and/or inter-BS interfaces), BS capabilities (e.g. BS type, macro, small cell, relay and radio/spectrum capabilities) and/or session information can be provided to the network control entity 1 10. According to embodiments of the invention, the network control entity 1 10 can statically or periodically or triggered by an event (e.g. the event that the number of URLLC-V2X active sessions exceed a threshold, the event that the network data analytics function (NWDAF) monitoring showed unstable performance of the communication network 100) configure (i) which further network node, in particular BS or RSU will act as the donor node 105 for the serving node 103, (ii) which software functions of the serving node 103 (e.g. which parts of the access network (AN) protocols of the serving node 103) should be implemented in a failsafe manner, i.e. should in case of a partial failure be provided by the donor node 105,

(iii) parameterization of additional and common protocols (e.g. the RRC protocol) to support the failsafe operation of the serving node 103 and/or the donor node 105 and/or

(iv) the time validity for the configuration of the serving node 103 and/or the donor node 105, e.g. how long the donor node 105 will act as the donor node for the serving node 103.

The operation phase, which will be described in more detail below, includes the partial protocol/functional processing migration/move from the serving node 103 to the donor node 105 and the operation of the serving node 103 as a kind of relay.

As already described above, the network control entity or FNC 1 10, which may be managed and parameterized by upper layer functions, such as the FM entity 203, allows to duplicate/migrate/virtualize the CP/UP software functions/protocols of the serving node 103 to other network nodes, namely the donor node 105, which are necessary to ensure service continuity in case of partial node failure.

According to embodiments of the invention the network control entity or FNC 1 10 may be configured to perform the following steps.

In a first step the network control entity or FNC 1 10 is configured to obtain as input information, comprising, the number of critical services in a cell area, the UE density, network analytics and monitoring, availability/load of neighboring network nodes, availability/conditions (capacity/delay) of back-haul/front-haul and/or user context information. This information may also be obtained in terms of data analytics, e.g., from the NWDAF 201 and/or the management data analytics function (MDAF) 205.

In a second step the network control entity or FNC 1 10 is configured to select the donor node 105 to undertake the processing in case of failure and determining the mirroring of protocols/functions to the donor node 105, capturing different levels of RAN failure.

In a third step the network control entity or FNC 1 10 is configured to provide the relevant network entities and UEs for the fail-safe protocol configuration and/or adaptation.

According to embodiments of the invention, the configuration can be done statically (for a fixed node), periodically (based on monitoring) and/or event-based (based on monitoring events, URLLC/V2X sessions in an area, and the like).

As already described above in the context of figure 2, the network control entity or FNC 1 10 may be managed/controlled by an upper layer function, implemented, for instance, by the fault management (FM) function 203. The FM function 203 is configured to collect and utilize analytics data and alert the network 100 about possible network failures. According to embodiment of the invention, the FM function 203 can activate the FNC 1 10 based on the analytics or other trigger events (e.g. new slice instantiation), using a FNC activation request/response, as illustrated in figure 2, or a subscribe/publish handshake. As further illustrated in figure 2, the FM function 203 may then request network analytics to help identify the status of the available network nodes and interfaces (load, availability, etc.).

In an embodiment, the NWDAF 201 , the MDAF 205 and/or the FM function 203 can be provided to tailor the management of the FNC 1 10 based on the predicted network conditions. In an embodiment, the following messages/information elements can be exchanged: FNC activation request and response messages including information for the activation of the functionality (e.g. transaction ID, PLMN ID, segment ID, time duration, geographical area, and the like). The PLMN ID can be advantageous for the case when the Management and Control Plane may belong to a different stakeholder (e.g. operator, OEM, vertical customer). The segment ID refers to the network segments (e.g. RAN, TN, CN) or network slices, which can be regarded as different segments of the network 100 for which the FNC 1 10 can be activated.

According to embodiments of the invention, the FNC parametrization message, as illustrated in figure 2, may include information about:

Placement of functionality (in which entity to be placed)

Segments to be notified, (e.g. RAN, CN)

Granularity of notifications (real time, non-real time)

Geographical area (cell-level, TA level)

- Time validity (for which time FNC 1 10 will operate)

FNC Exposure to 3rd party (this parameter shows if the FNC 1 10 needs to be exposed as a service)

Reserved resources (if resources are needed to be reserved)

Although in figure 2 the FNC 1 10 is illustrated as a CP function, according to

embodiments of the invention the FNC can be implemented as a management plane (MP) function as well. The interactions between the NFs illustrated in figure 2 can be based on service-based architecture (SBA) principles as well as direct reference-point type interface communications. For the sake of clarity figure 2 illustrates message exchanges. As will be appreciated, however, these messages could also be or comprise information

elements/information element fields that can be encapsulated in other messages.

According to embodiment, the data analytics provided by the NWDAF 201 and/or the MDAF 205 may also be directly shared with the FNC 1 10, e.g., considering SBA principles.

As already described above in the context of figure 1 , initially network analytics (RAN,

CN), BS capabilities and/or session information can be provided to the FNC 1 10.

According to embodiments of the invention, the FNC 1 10 statically, periodically or event-triggered (e.g. number of URLLC-V2X active sessions exceeding a threshold, NWDAF monitoring showed unstable performance) configures: (i) which BS/RSU to act as the donor node 105 for the serving node 103, (ii) which part of AN protocols/functions should be made failsafe, i.e. processed by the donor node 105, in case of a failure of these AN protocols/functions at the serving node 103, (iii) parameterization of additional and common protocols to support the failsafe AN protocols/functions (e.g. RRC), and (iv) the time validity for the donor node 105.

To this end, the FNC 1 10 may be adapted to provide a corresponding configuration message to the selected donor node 105 and/or the serving node 103. As illustrated in figure 1 , this configuration message can be provided to the selected donor node 105 via the control plane 107 of the core network of the communication network 100. In an embodiment, the configuration message may include information on at least one of the following: serving node ID, donor node ID, network parameters <protocols, functions, resources, coverages timer, UE density, interfaces, and the like.

According to embodiments of the invention, the selected donor node 105 can also be provided with information about a current or future communication session between the serving node 103 and the UE 101. As illustrated in figure 1 , this information can be provided by means of a session related protocol information message from the serving node 103 to the donor node 105. The session related protocol information message may include session information (such as, RRM/RLM measurements, DRB/SRB

configurations, protocol configurations, e.g. HARQ timings), slice-support information (e.g., slice ID, S-NSSAI, UE), and/or UE context information.

More specifically, for the PHY layer (Baseband), the session related protocol information message may include specific RNTIs used per UE and session, specific RNTIs used per group/session, and/or channel coding/modulation related configuration information.

For the MAC layer the session related protocol information message may include adaptive and non-adaptive HARQ configuration information, HARQ process ID, and/or dynamic or grant-free (typel , type 2) scheduling configuration information.

For the RLC layer, the session related protocol information message may include RLC layer configuration such as sequence numbering.

For the PDCP layer, the session related protocol information message may include PDCP layer configuration information, such as PDCP layer duplication or ciphering related encryption/decryption key information or sequence numbering.

For the SDAP layer, the session related protocol information message may include SDAP layer configuration information, such as a QoS flow to radio bearer mapping.

As already described above, according to embodiments of the invention, the serving node 103 and the donor node 105 can be any type of RAN access node, for instance, a 5G base station (BS), a gNB, a ng-eNB, and/or CU-DUs of a disaggregated gNB. The interface between the serving node 103 and the donor node 105 can depend on the type of the nodes, and thus can be e.g. the Xn or the X2 interface.

Under further reference to figure 3, in the following embodiments of the invention will be described in more detail in the operational phase, i.e. when a failure event is detected and the failed software functions of the serving node 103 are provided by the donor node 105. In the example illustrated in figure 3, the serving node 104 experiences a failure for the AN communication protocols/functions above the PHY layer. In this case, the donor node 105 is configured to add (using RRC-to-PHY signaling) the serving node 103 as L1 Access Point (AP), with the identification of Failsafe L1 AP (meaning that this is not a normal L1 relay and the UE 101 keeps using the old PCI so that no handover is required). The network 100, in particular its RAN and CN engages then the UE 101 to failsafe mode and tags the ongoing session as using a failsafe-AP Service. As will be appreciated, the split between the donor node 105 and the serving node 103 in this example is at the MAC level. So, in this exemplary embodiment, the L2 processing happens at the donor node 103, while the L1/RF processing happens at the serving node 104, i.e. the AP (normal L1 AP as relay operation).

According to embodiments of the invention, one or more of the following messages can be exchanged, as illustrated in the example of figure 3.

According to an embodiment, as illustrated in figure 3, a failsafe protocol stack (FPS) addition and configuration message can be transmitted from the donor node 105 to the serving node 103, which in the example of figure 3 experiences a L2 Failure. This message can be an RRC message and can add the serving node 103 as L1 Relay/AP. Moreover, this message can notify the serving node 103 on how to configure its L1 AP functionality for certain bearers when the failsafe mode becomes active. To this end, the message can include, e.g., information on bearer configurations and L1 parameterizations for the newly added L1 AP.

According to an embodiment, as illustrated in figure 3, a failsafe (FS) mode activation message can be transmitted from the donor node 105 to the core network - CP (CN-C)

107 to activate the serving node 103 as L1 AP. This message can include information, such as session ID, configuration, UP/CP Functions, timer, new transport point termination (S1 or NG), SRB/DRB parameters and/or bearer configuration.

As will be appreciated, with the mechanism described above the connection between the serving node 103 and the UE 101 can be maintained, e.g., for both data and control as well as for both uplink (UL) and downlink (DL). In other words, for the UE 101 this mechanism is transparent for the UE 101 in that the UE 101 still considers to be communicating with the serving node 103 only.

Under further reference to figure 4, in the following embodiments of the invention will be described in the context of a central unit (CU)/distributed unit (DU) base station architecture envisaged by 5G new radio (NR), which splits the gNB into two parts, namely the CU which includes RRC/SDAP/PDCP and the DU which includes lower protocols (RLC, MAC, PHY). A new interface is specified between CU-DU, namely F1 (F1 -U and F1 -C) which allows for the lower layer split. In the exemplary embodiment shown in figure 4 the serving node 103 is a serving DU 103 and the donor node 105 is a donor DU 105 both connected to a common CU 106. The exemplary embodiment shown in figure 4 illustrates the case, where the serving DU 103 has a failure and the CU 106 or the donor DU 105 requires a failsafe protocol configuration to ensure undisrupted V2X services. In this case, the FNC 1 10 (if not co-located with the CU 106, which is a variant covered by further embodiments of the invention) provides the configuration to the CU 106 via N2 signaling, as illustrated in figure 4. This message or any abstracted version thereof is provided in F1 to the DUs. More specifically, a configuration message can be provided, which comprises information about: DU ID, Donor CU ID, Network Parameters <protocols, functions, resources, coverages timer, UE density, and the like.

As can be taken from figure 4, in a further stage session related protocol information, which can contain UE context info, can then be sent from the serving DU 103 to the CU 106, for instance, periodically. When a failure happens and is discovered, a failsafe mode activation message from the CU 106 to the donor DU 105 can be used for activating the serving DU 103 (experiencing the partial failure) as L1 AP. Similar to the embodiments described above, the failsafe mode activation message may include the following information: session ID, configuration, UP/CP functions, timer, SRB/DRB parameters and/or bearer configuration, and/or new transport point termination (S1 or NG).

Figure 5 illustrates a further exemplary embodiment of the invention in the context of an interface failure, in particular a failure of the RAN-CN interface and/or a service-based interface (SBI) of the communication network 100. In that case the serving node 103 still operates, but the interface to the CN has failed. According to embodiments of the invention, the donor node 105 can be pre-configured to support also this type of failure. Similar to embodiments described above traffic can be relayed from the CN of the communication network to the serving node 103 via the donor node 105.

Figure 6 illustrates a further exemplary embodiment of the invention in the context of a V2X Road Side Unit (RSU) deployment. In this case, the serving node 103 and the donor node are implemented as RSUs. As illustrated in figure 6, the configuration of the donor node 105 can be part of a V2X-Control Function and/or proximity service (ProSE)

Function and/or part of the CN of the communication network 100. The configuration is sent by the FNC 1 10 to the donor node (D-RSU2) 105 which can be a BS or a V2X-UE. If the failsafe serving node (RSU1 ) 103 is a gNB, the interface for the configuration message is a N2 message and for notification is a Un/Uu message. If the failsafe serving node (RSU1 ) 103 is a V2X-UE, the interface for the configuration message is V2 or PC3 and for notification PC5-C.

While a particular feature or aspect of the disclosure may have been disclosed with respect to only one of several implementations, such feature or aspect may be combined with one or more other features or aspects of the other implementations as may be desired and advantageous for any given or particular application. Furthermore, to the extent that the terms "include", "have", "with", or other variants thereof are used in either the detailed description or the claims, such terms are intended to be inclusive in a manner similar to the term "comprise". Also, the terms "exemplary", "for example" and "e.g." are merely meant as an example, rather than the best or optimal. The terms“coupled” and “connected”, along with derivatives may have been used. It should be understood that these terms may have been used to indicate that two elements cooperate or interact with each other regardless whether they are in direct physical or electrical contact, or they are not in direct contact with each other.

Although specific aspects have been illustrated and described herein, it will be

appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations may be substituted for the specific aspects shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations or variations of the specific aspects discussed herein.

Although the elements in the following claims are recited in a particular sequence with corresponding labeling, unless the claim recitations otherwise imply a particular sequence for implementing some or all of those elements, those elements are not necessarily intended to be limited to being implemented in that particular sequence.

Many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the above teachings. Of course, those skilled in the art readily recognize that there are numerous applications of the invention beyond those described herein. While the present invention has been described with reference to one or more particular embodiments, those skilled in the art recognize that many changes may be made thereto without departing from the scope of the present invention. It is therefore to be understood that within the scope of the appended claims and their equivalents, the invention may be practiced otherwise than as specifically described herein.