Multi-connectivity management for service continuity during mobility of a user equipment

Abstract

This disclosure is concerned with service continuity during mobility of user equipment (UE) in a mobile network. The disclosure proposes multi-connectivity management of the UE to ensure the service continuity, instead of a handover. The disclosure provides a multi-connectivity management entity, which is configured to process a multi-connectivity data structure, which is associated with the UE, based on a notified first event or second event. The first event indicates that a connection with a second RAT node has become available for the UE. The second event indicates that an established connection of the UE with a first RAT node has to be released. The entity adds a first entry related to the second RAT node into the data structure if the first event is notified, or deletes a second entry related to the first RAT node from the data structure if the second event is notified.

Description

[0001] MULTI-CONNECTIVITY MANAGEMENT FOR SERVICE CONTINUITY DURING MOBILITY OF A USER EQUIPMENT

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to mobile networks, and is concerned with service continuity during mobility of user equipment (UE) in the mobile network. The disclosure proposes a multi-connectivity management of the UE to ensure the service continuity, instead of a handover. To this end, the disclosure provides a multi-connectivity management entity for managing connectivity of the UE, a mobility management entity for managing mobility of the UE, a multi -connectivity UE, and a session management entity for managing sessions of the UE. The disclosure also provides the corresponding methods and computer programs.

[0004] BACKGROUND

[0005] Ina 3rdGeneration Partnership Project (3GPP) mobile telecommunication system, a cellular network comprises a Radio Access Network (RAN) and a Core Network (CN). The RAN manages the radio frequency spectrum, and provides wireless connectivity to the mobile end-devices, which are commonly referred to as UE or Mobile Terminal (MT). The CN performs control and management operations, and provides the UE with connectivity to external Data Networks (DN) like the Internet.

[0006] The RAN is realized with a group of strategically located, geographically dispersed Base Stations (BS) or gNodeBs (gNBs) - which are generally referred to as Radio Access Technology (RAT) nodes in this disclosure - wherein these RAT nodes are connected to the CN via a backhaul network. For each UE, the serving RAT node creates a wireless channel to provide a bearer service (data channel) when the UE powers up, or when the UE resumes to an ACTIVE mode from an IDLE mode, or during HO when the UE enters a coverage area of the RAT node. The RAT node is also responsible for connecting the UE to the CN’s Control Plane (CP), and to forward signaling traffic between the UE and CN CP entities, so as to enable authentication, registration, Protocol Data Unit (PDU) session establishment, and mobility.

[0007] During PDU session establishment for enabling data transmission, the RAT node creates one or more tunnels for each UE between the RAT node and the CN User Plane (UP), and transmits the UE’s UP traffic on these tunnels. The bearer is essentially a data transmission channel between the UE and the RAT node in 5G (and between the UE, the RAT node and the CN UP in 4G Long-Term Evolution (LTE)), and each bearer is associated with a specific set of Quality of Service (QoS) properties. Multiple bearers can be established to provide different QoS treatments to traffic generating from the same UE. Thereby, each QoS flow of multiple QoS flows can be transported on a dedicated bearer, which corresponds to the QoS properties required by the associated traffic.

[0008] During mobility, a UE moves from one cell to another, wherein a cell represents the coverage area offered by a certain RAT node. When the UE moves from one cell to the other, or when a RAT node wants to perform load balancing, or when the signal conditions experienced by a UE drop below an expected threshold, traditionally, a HO of the UE is performed (see illustration in FIG. 1). The HO ensures session (and thus service) continuity and allows the desired QoS to be maintained for the UE.

[0009] During HO, a series of signaling messages are exchanged between the source RAT node - i.e. the RAT node the UE is currently connected to - and a target RAT node - i.e. the RAT node, to which the UE is to be handed over - and their respective CN CPs. The messages are exchanged with the goal of reassigning the UE’s resources present in the source RAT node in the target RAT node. Three different types of HO exist: (1) Intra RAT node HO, wherein the UE moves between cells, but remains connected to the same RAT node, e.g., the RAT node hands the UE over to a different signal in the spectrum offered by the same RAT node; (2) Inter RAT node HO, wherein the HO is from a source RAT node to a target RAT node; and (3) Inter-RAT HO, wherein the HO is between a source RAT node and a target RAT node of different technology (e.g., the source RAT node could be a gNB, while the target RAT node is an eNB). During Inter RAT node HO and during Inter-RAT HO, the CNs are also involved.

[0010] When a UE connects to a network, the respective RAT node, which provides radio resources of the network to the UE, instructs the UE to perform signal quality measurements, and indicates the reporting frequency for the said measurements to the UE. The 3GPP standard has proposed a set of measurements and HO event triggers and corresponding formulas, which are used to identify when a HO should be triggered. Examples of such HO events / triggers and formulas used to identify the events / triggers from the received measurement reports of the UE, as per 3 GPP TS 38.331, are shown in the two tables below (respectively taken from 3GPP TS 38.331, “5G; NR; Radio Resource Control (RRC); Protocol specification (Release 15)” and from Techplayon, “ 5G NR Measurement Events” [https: / / www.techplayon.com / 5g-m-measurement-events / ], A HO may generally be performed in the following three stages:

[0011] 1. During the HO preparation stage, the Access and Mobility Management Function (AMF) sends the UE’s context information containing roaming and access restriction information to the RAT node. The RAT node configures the measurement procedures and the UE periodically reports the measurements to the network. Upon receiving the measurements from the UE, the source RAT node makes a decision for HO, and issues a HO request message to a target RAT node with the necessary information. The target RAT node then prepares the HO, and sends a HO acknowledgement to the source RAT node.

[0012] 2. During the HO execution stage, the source RAT node sends a RRC -reconfiguration message to the UE, with the information to access the target RAT node. The UE then synchronizes to the target RAT node, and releases its resources from the source RAT node.

[0013] 3. During the HO completion stage, the target RAT node notifies the source RAT node that the HO of the UE is completed. The source RAT node then sends the buffered data for the UE to the target RAT node, which in turn sends it to the UE. The target RAT node also sends a path switch request to the AMF, to trigger the CN to send the UE’s downlink (DL) data to the target RAT node. The target RAT node sends the MT CONTEXT RELEASE signal to the source RAT node, and as a response the source RAT node releases the radio and CP resources allocated to the UE. With this the HO procedure is finished.

[0014] On a different note, the 3GPP Release 15 TR 38.811, the Release 16 TR 38.821, the Release 17 TR 23.700-28, and the Release 18 TR 23.700-27 study and propose necessary technologies to extend the coverage of a Terrestrial Network (TN) using a NonTerrestrial Network (NTN). With the increasing rate of mobility, a large number of small cell base stations in 5G, and an increased interest to improve the QoS and network resource utilization, the UEs are increasingly equipped with multiple network interfaces e.g., 4G, 5G and Wireless Fidelity (Wi-Fi), and will most-likely be extended to include 6G and NTN related interfaces.

[0015] Every network environment is dynamic in nature, and hence at any given time there are some congested links, while some links are underutilized. For this reason, multi -connectivity has gained interest in the recent years, as it has the potential to improve reliability, scalability, and throughput along with a noticeable reduction in latency experienced by current mobile end users. However, the current cellular network standards, namely 3 GPP, limit the UE to a maximum of only two simultaneous connections (4G and 5G) in Dual Connectivity (DC), Multi Radio Dual Connectivity (MR-DC) and Access Traffic Steering, Switching & Splitting (ATSSS) (5G and Wi-Fi) solutions (as per Release 18).

[0016] MR-DC was proposed in Release 15 in TS 37.340, which allowed a maximum of two different RAT nodes in the coverage area of a UE to provide wireless connectivity to the UE. MR-DC uses a Master Node (MN) and the Secondary Node (SN) relationship to handle user sessions. An interface (Xn-C for NR / X2-C for EPC) is provided between the MN and SN for CP signaling and coordination and another interface (Xn-U) is provided between MN, SN and UP (e.g., User Plane Function (UPF)) for data transmission. A CP connection also exists between the MN and the CN CP entities (e.g., the AMF in 5GC and an MME with EPC) for each MR-DC UE. The MN and SN control their own radio resources, including the allocation of the resources. In MR-DC, a UE is configured with two MAC entities, one each for Master Cell Group (MCG) and Secondary Cell Group (SCG) and up to two SD AP entities are available for each PDU session, one each for the MN and the SN. The necessary information for initial configuration of the UE is handled by the MN with dedicated RRC signaling.

[0017] ATSSS was proposed in 3GPP 5G Release 16 in TS 24.193 to incorporate a Multipath Transmission Control Protocol (MPTCP). The three S’s in ATSSS provide the following functionalities: (a) Steering, wherein the best link between 5G or WiFi is used for transporting user traffic based on QoS, (b) Switching, wherein HO is performed between the 5G and Wi-Fi links without service interruption to the other link during mobility, and (c) Splitting, wherein 5G and Wi-Fi links are used simultaneously for transporting user traffic.

[0018] SUMMARY

[0019] The present disclosure and its solutions are further based on the following considerations regarding the above background.

[0020] HO management solutions are operationally complex, very tightly integrated and time-consuming. Moreover, during HO there is a non-negligible brief period called Handover Interruption Time (HIT), during which the UE can neither transmit nor receive any data. The Session and Service Continuity Mode 1&3, which is offered by 5G to ensure seamless connectivity to UEs, is performed mainly in the CN, while in the RAN the traditional HOs are still the norm. The source RAT node performs the HO to a target RAT node with duplicate resources (DAPS) until the HO is completed to ensure session continuity. As a consequence, the resources of the network are not being utilized efficiently, since the source RAT node cannot allocate the resources to other UEs until the entire HO procedure is completed. Moreover, when a RAT node is overloaded and wants to perform a HO to a neighboring target RAT node, the target RAT node may also be at its peak capacity and refuse the HO, leading to a ping-pong effect. In addition, the Handover Failure (HoF) rate is expected to increase at high frequencies, for example, due to HO command transmission failures. In 5G networks with a large number of small cells, the user mobility will inadvertently lead to frequent HOs, and service interruptions due to increased signaling. For 6G applications, the HIT and HoF should be minimized to ensure no service interruptions. The heterogeneity in RATs (e.g., LTE, 5G New Radio (NR), 6G THz, NTN, Wi-Fi) and their communication infrastructure equipment’s like the RAT nodes, pose many challenges to enable seamless communication in mobile communication networks, especially when the user is mobile (due to the complex and latency inducing handover procedures). Hence, the current HO solutions should either be improved or better alternatives should be invented.

[0021] Multi -connectivity has the potential to ease some of the adverse effects experienced with the current HO procedures. However, when it comes to 3GPP standards, as per TS 24. 193 and TS 23.501, 3GPP defines a multi-access PDU session as a session, which can use either one 3 GPP access network or one non-3GPP access network, or simultaneously one 3 GPP access network and one non-3GPP access network. Hence, solutions like MR-DC and ATSSS face scalability issue and in fact they support only dual-connectivity and not multi -connectivity. Even though MR-DC can be expanded to more than two RAT nodes, it is not trivial due to a significant increase in complexity arising from the coordination between the multiple different RAT nodes in the MN-SN setting. Even though multiple different connections are available for a UE, 3 GPP has limited the number of simultaneous connections for a UE to a maximum of two networks. Due to the availability of NTN, and 4G, 5G, Wi-Fi and possibly 6G in the future, UE’s will be enhanced with multiple network capabilities and should be able to take advantage of multiple available connections to not only ensure service connectivity but also to maximize throughput and minimize latency which are essential requirements of future 6G applications.

[0022] Therefore, an exemplary solution to leverage multiple simultaneous connections in the network and distribute packets from a QoS flow on all available connections was provided. This improves the throughput and latency experienced by the UEs, especially, during mobility, and also improves the resource utilization in the network along with ensuring service continuity for mobile users. In particular, in this exemplary solution, in order to leverage the benefits of multiple available connections simultaneously for a UE and to support Service Data Flow (SDF) distribution (referred to as QoS flows in 5G) over multiple data channels offered by either a single RAT node or multiple RAT nodes regardless of their access technologies, a Service data flow Distribution Table (SDT) and a Service data flow Distribution Manager (SDM) were proposed to be implemented in the UE and UP (both (R)AN and Core UP). FIG. 2 illustrates this solution generally.

[0023] The SDT is provided in the UE and UP (in Layer 2 or above) of the protocol stack, in order to capture SDF or QoS or traffic profile (e.g., mmtc, uRLLC, etc.) mapping to available networks and their corresponding data channels, e.g., provided by the network operator. The SDM is provided in the UE and UP (in Layer 2 or above) to map the data packets from each SDF or QoS flow to available network(s) and their corresponding data channels by querying the SDT.

[0024] In particular, the SDM in the UE (SDM-UE) can be located in a new layer-2 sublayer between the IP and above the SDAP sublayer in the 3GPP 5G (and beyond 5G) protocol stack. The SDM-UE queries the SDT with a QoS Identifier (QI), and receives a list of Access Networks (ANs) and their corresponding data channels as the response. The SDM selects an AN node (if >1) and a corresponding data channel and forwards the packet to the corresponding SDAP entity in the next sublayer. There are multiple SDAP entities in the SDAP layer, one each for every connected network (currently a 3 GPP standard for 5G). The SDAP forwards the packet to the selected AN over the selected data channel.

[0025] The SDM in the UP (SDM-UP) can be located in a new layer-2 sublayer between the IP and above the MAC / Ethemet sublayer in Core UP and above the SDAP sublayer in the 3GPP 5G (and beyond 5G) protocol stack. The UPF and RAT nodes (e.g., BSs) receive the SDT from the CN e.g., the UPF receives it from SMF via N4 signaling during PDU session establishment. The UPF maintains multiple N3 tunnels with each AN node that is available for the PDU session (informed by SMF or derived from SDT). The UPF receives Qis from a Session Management Function (SMF), and the SDM-UP uses the QI to query the SDT and selects an AN (if >1) to send the packet. The RAN receives the packet and uses the QI marking in the packet, and the SDM-UP in RAN queries the SDT and receives the data channel on which to forward the packet to UE. The RAN forwards the packet to UE over the selected data channel.

[0026] The SDT can be located along with the SDM in a new layer-2 sublayer between the IP and above the SDAP sublayer in the 3 GPP 5G (and beyond 5G) protocol stack. This sublayer may have a process to add and / or modify and / or delete the SDT table input as per MNO (e.g., Session Management Function (SMF)) or Operating System (OS) command. This sublayer may have a process to receive and respond to queries from SDM-UE / SDM-UP and Mobile Network Operator (MNO) (e.g., SMF / OS, etc.).

[0027] However, the above-described exemplary solution still needs to be enhanced with features to provide service continuity for mobile users, and minimize the adverse effects experienced with the current HO management solutions. The exemplary solution may not yet sufficiently provide a solution for mobile users.

[0028] Generally, an objective of this disclosure is to improve seamless service continuity during mobility, in order to reduce the complexity of current HO management solutions, to reduce HIT, and to reduce HoF. In particular, an objective is to provide an implementation for creating and / or updating the above-mentioned SDT during mobility of a UE. Another objective is to provide an implementation for defining the inputs used for creating and / or updating the SDT during mobility.

[0029] These and other objectives are achieved by the solutions of this disclosure as described in the independent claims. Advantageous implementations are further described in the dependent claims. A first aspect of this disclosure provides a multi -connectivity management entity for managing connectivity of a UE, wherein the multi -connectivity management entity is configured to: receive a notification of a first event or of a second event from a mobility management entity, wherein the first event indicates that a connection with a second RAT node has become available for the UE, wherein the UE has an established connection with a first RAT node, and wherein the second event indicates that the connection of the UE with the first RAT node has to be released; and process a multi -connectivity data structure, which is associated with the UE, by adding a first entry related to the second RAT node into the data structure if the first event is notified, or by deleting a second entry related to the first RAT node from the data structure if the second event is notified; wherein the first and second entry of the multi -connectivity data structure respectively indicate a respective QoS profile and / ortraffic profile for the connection of the UE with the first and second RAT node.

[0030] The multi-connectivity management entity is also referred to as Multi Access Feature (MAF) in this disclosure. The data structure may be the SDT mentioned above with respect to the exemplary solution. The MAF, i.e. the entity of the first aspect, is configured to create and / or update the data structure, e.g. SDT. The inputs for creating and / or updating the data structure, e.g. SDT, during mobility of the UE are the indications of the first or second event, e.g. indications of event triggers like Al and A2 as described above. The MAF of the first aspect enables seamless service continuity during UE mobility. Thereby, the complex HO management is avoided, and HIT and HoF are reduced.

[0031] In an implementation form of the first aspect, each entry of the multi-connectivity data structure indicates a respective QoS profile and / or traffic profile for a respective connection of the UE with a respective RAT node.

[0032] In an implementation form of the first aspect, the multi-connectivity data structure is a table, which maps the QoS profiles and / or traffic profiles to available networks and connections provided in said networks.

[0033] In particular, the table may be the SDT.

[0034] In an implementation form of the first aspect, processing the multi-connectivity data structure comprises creating the data structure and adding the first entry, or comprises updating the data structure by adding the first entry and / or deleting the second entry.

[0035] In this way, the multi-connectivity of the UE can be managed seamlessly during the UE’s mobility.

[0036] In an implementation form of the first aspect, the multi-connectivity management entity is further configured to send the processed multi-connectivity data structure to at least one of: the UE, the first RAT node, the second RAT node, and a core network user plane entity.

[0037] In an implementation form of the first aspect, the multi -connectivity management entity is an individual CN CP function.

[0038] In an implementation form of the first aspect, the multi -connectivity management entity is incorporated into a CN CP function, for instance, into an AMF.

[0039] A second aspect of this disclosure provides a mobility management entity for managing mobility of a UE, wherein the mobility management entity is configured to: receive a notification of a first event or of a second event from a first RAT node, which has an established connection with the UE, wherein the first event indicates that a connection with a second RAT node has become available for the UE, and wherein the second event indicates that the connection of the UE with the first RAT node has to be released; and request the UE to establish the connection with the second RAT node if the first event is notified, or to release the connection with the first RAT node if the second event is notified.

[0040] The mobility management entity of the second aspect supports the MAF of the first aspect, and helps to provide the above- described advantages.

[0041] In an implementation form of the second aspect, the mobility management entity is a CN CP function, for example, an AMF.

[0042] A third aspect of this disclosure provides a multi -connectivity UE, wherein the UE is configured to: perform respective signal quality measurements related to a serving cell managed by a first RAT, node, which has an established connection with the UE, and of a neighboring cell managed by a second RAT node; send a notification of the signal quality measurements to the first RAT node; receive a request from a mobility management entity to establish a connection with the second RAT node or to release the connection with the first RAT node; and establish the connection with the second RAT node or release the connection with the first RAT node according to the request; and forward the request to a session management entity to cause a session, which is associated with the connection of the UE with the first RAT node, to be also associated with the connection of the UE with the second RAT node, or to release the session associated with the connection of the UE with the first RAT node.

[0043] The UE leverages multi-connectivity to ensure service continuity during mobility. HO of the UE can be avoided. The above- described advantages are achieved with help of the UE of the third aspect.

[0044] In an implementation form of the third aspect, the multi -connectivity UE is configured to periodically measure a signal strength of the serving cell and a signal strength of the neighboring cell as the respective signal quality measurements.

[0045] A fourth aspect of this disclosure provides a session management entity for managing sessions of a UE, wherein the session management entity is configured to: receive a request from the UE, which has an established connection with a first RAT, node, to establish a connection with a second RAT node; and cause a session, which is associated with the connection of the UE with the first RAT node, to be also associated with the connection of the UE with the second RAT node; and send a QoS profile of the session, which is associated with the connection of the UE with the first RAT node, to the second RAT node.

[0046] The session management entity of the second aspect supports the MAF of the first aspect, and helps to provide the above- described advantages.

[0047] In an implementation form of the fourth aspect, the session management entity is a CN CP function, for example, a SMF.

[0048] In an implementation form of the fourth aspect, the session is a PDU, session.

[0049] A fifth aspect of this disclosure provides a method for managing connectivity of a UE, wherein the method comprises: receiving a notification of a first event or of a second event from a mobility management entity, wherein the first event indicates that a connection with a second RAT node has become available for the UE, wherein the UE has an established connection with a first RAT node, and wherein the second event indicates that the connection of the UE with the first RAT node has to be released; and processing a multi -connectivity data structure, which is associated with the UE, by adding a first entry related to the second RAT node into the data structure if the first event is notified, or by deleting a second entry related to the first RAT node from the data structure if the second event is notified; wherein the first and second entry of the multi-connectivity data structure respectively indicate a respective QoS profile and / or traffic profile for the connection of the UE with the first and second RAT node.

[0050] A sixth aspect of this disclosure provides a method for managing mobility of a UE, wherein the method comprises: receiving a notification of a first event or of a second event from a first RAT node, which has an established connection with the UE, wherein the first event indicates that a connection with a second RAT node has become available for the UE, and wherein the second event indicates that the connection of the UE with the first RAT node has to be released; and requesting the UE to establish the connection with the second RAT node if the first event is notified, or to release the connection with the first RAT node if the second event is notified.

[0051] A seventh aspect of this disclosure provides a method for a multi -connectivity UE, wherein the method comprises: performing respective signal quality measurements related to a serving cell managed by a first RAT node, which has an established connection with the UE, and of a neighboring cell managed by a second RAT node; sending a notification of the signal quality measurements to the first RAT node; receiving a request from a mobility management entity to establish a connection with the second RAT node or to release the connection with the first RAT node; and establishing the connection with the second RAT node or release the connection with the first RAT node according to the request; and forwarding the request to a session management entity to cause a session, which is associated with the connection of the UE with the first RAT node, to be also associated with the connection of the UE with the second RAT node, or to release the session associated with the connection of the UE with the first RAT node.

[0052] An eighth aspect of this disclosure provides a method for managing sessions of a UE, wherein the method comprises: receiving a request from the UE, which has an established connection with a first RAT, node, to establish a connection with a second RAT node; and causing a session, which is associated with the connection of the UE with the first RAT node, to be also associated with the connection of the UE with the second RAT node; and sending a quality of service, QoS, profile of the session, which is associated with the connection of the UE with the first RAT node, to the second RAT node.

[0053] The above-described methods of the fifth to eighth aspect correspond to the entities of the first to fourth aspect. Accordingly, the methods may have implementation forms corresponding to the implementation forms of the respective entities. The methods and their respective implementation forms achieve the same advantages as described for the entities and their implementation forms.

[0054] A ninth aspect of this disclosure provides a computer program comprising instructions which, when the program is executed by a processor, cause the processor to perform the method according to one of the fifth, sixth, seventh or eighth aspect.

[0055] A tenth aspect of this disclosure provides a non-transitory storage medium storing executable program code which, when executed by a processor, causes the method according to the fifth, sixth, seventh or eighth aspect or any of its implementation forms to be performed.

[0056] According to the above aspects and implementation forms, instead of establishing a new connection with a target RAT node, and to hand over the complete context of the UE, and to release the connection with the source RAT node - which involves complex measurements, reporting, signaling and buffering between the UE, the RAT nodes and / or the CN - the solutions of this disclosure propose using multi -connectivity to ensure the service continuity during mobility. That is, multi -connectivity is used instead of conventional HO. Every time a new connection is available in the network, a UE may connect to it, and may distribute packets from a flow across all connections, and may release connections that are no longer needed or are underperforming. Thereby, the need for HO during mobility is avoided. As a result, the UE experiences uninterrupted service continuity with no HIT and HoF. In addition, the UE experiences improved throughput and reliability in the network along with uninterrupted service.

[0057] It has to be noted that all entities, elements, units and means described in the present application could be implemented by software or hardware elements or any kind of combination thereof. All steps performed by the various entities described in the present application, as well as the functionalities described to be performed by the various entities, are intended to mean that the respective entity is adapted to or configured to perform the respective steps and functionalities. Even if, in the following description of specific embodiments, a specific functionality or step to be performed by external entities is not reflected in the description of a specific detailed element of that entity, which performs that specific step or functionality, it should be clear for a skilled person that these methods and functionalities can be implemented by respective software or hardware elements, or any kind of combination thereof.

[0058] BRIEF DESCRIPTION OF DRAWINGS

[0059] The above described aspects and implementation forms are explained in the following description in relation to the enclosed drawings, in which:

[0060] FIG. 1 illustrates a conventional HO solution in 3 GPP with duplicate resources.

[0061] FIG. 2 illustrates generally an exemplary solution using multi-connectivity to reduce the adverse effects of HO during mobility of a UE.

[0062] FIG. 3 shows various entities according to this disclosure, which each contribute to the solutions provided in this disclosure.

[0063] FIG. 4 illustrates the MAF according to this disclosure.

[0064] FIG. 5 shows a flow-diagram of an operation of the MAF based on event triggers Al and A2.

[0065] FIG. 6 shows a flow-diagram illustrating the operation of the involved entities of this disclosure.

[0066] FIG. 7 shows messages exchanged between different entities in a mobile communication system with the MAF.

[0067] FIG. 8 shows a 3GPP 5G system architecture.

[0068] FIG. 9 shows an embodiment with the MAF being a standalone function in the CP of a mobile communication system like 3 GPP.

[0069] FIG. 10 shows an embodiment with the MAF being a feature inside a CP function of a mobile communication system, like the AMF in 3 GPP.

[0070] FIG. 11 shows a method according to this disclosure.

[0071] FIG. 12 shows a method according to this disclosure. FIG. 13 shows a method according to this disclosure.

[0072] FIG. 14 shows a method according to this disclosure.

[0073] DETAILED DESCRIPTION OF EMBODIMENTS

[0074] As mentioned above, the solution of this disclosure bases on the multi-connectivity scenario and leveraging the exemplary solution described above and shown in FIG. 2. Every time a new connection is available, a UE connects to it, thereby eliminating the need for a HO during mobility of the UE. The SDT may be used to support the multi -connectivity as described above. However, the exemplary solution is enhanced as described in the following.

[0075] FIG. 3 shows various entities according to this disclosure, which each contribute to the enhancement of the exemplary solution. In particular, FIG. 3 shows a multi-connectivity management entity 300 (referred to as MAF 300 in the following), a mobility management entity 303 (short MME 303 in the following), a multi-connectivity UE 301, and a session management entity 310 (short SME 301 in the following), wherein each entity is proposed in this disclosure. FIG. 3 also shows a first RAT node 305 and a second RAT node 304. These RAT nodes 304, 305 may respectively be a BS, such as a gNB, or eNB, or other access node, and combinations of different RATs are possible.

[0076] The UE 301 has an established connection to the first RAT node 305. The UE 301 is configured to perform various signal quality measurements, for instance, as instructed by the first RAT node 305. These include signal quality measurements related to the serving cell managed by the first RAT node 305, and signal quality measurements of at least one neighboring cell managed by the second RAT node 304. The UE 301 is further configured to send a notification 309 indicating or including these signal quality measurements to the first RAT node 305.

[0077] The first RAT node 305 is configured to, based on the signal quality measurements received from the UE 301, send a notification 307 of a first event or of a second event to the MME 303. The first event indicates that a connection with the second RAT node 304 has become available for the UE 301 - e.g. if the signal quality measurement of the UE 301 is above a first threshold (which correlates to event trigger Al). The second event indicates that the connection of the UE 301 with the first RAT node 305 has to be released - e.g. if the signal quality measurement of the UE 301 is below a second threshold (which correlates to event trigger A2).

[0078] The MME 303, which is for managing mobility of the UE 301, is configured to receive the notification 307. Based thereon, the MME 303 can provide a notification 302 of the first event or the second event to the MAF 300. For instance, the MME 303 can forward the notification 307 as the notification 302, or can extract the information regarding the first and second event from the notification 307, and add it to the notification 302.

[0079] The MAF 300 is for managing the connectivity of the UE 310, and is configured to receive the notification 302 of the first event or second event from the MME 303. The MAF 300 is further configured to process a multi -connectivity data structure 306, which is associated with the UE 301. The data structure 306 may be a table, for instance, the SDT. The MAF 300 is configured to add a first entry related to the second RAT node 304 into the data structure 306, if the first event is notified, or to delete a second entry related to the first RAT node 305 from the data structure 306, if the second event is notified. The first and second entry respectively indicate a respective QoS profile and / or traffic profile for the connection of the UE 301 with the first and second RAT node 304, 305. The data structure 306 may map different QoS profiles and / or traffic profiles to available networks and connections provided in said networks. Accordingly, each entry of the data structure 306 may indicate a respective QoS profile and / or traffic profile for a respective connection of the UE 301 with a respective RAT node, e.g. the first or second RAT node 304, 305.

[0080] The MME 303 is further configured to send a request 308 to the UE 301 to establish the connection with the second RAT node 304 if the first event is notified, or to release the connection with the first RAT node 305 if the second event is notified.

[0081] The UE 301 is configured to receive this request 308, and to establish the connection with the second RAT node 304 or release the connection with the first RAT node 305 according to the request 308. In addition, the UE 301 is configured to forward the request 308 to the SME 310 (or to send a message including or at least correlating to this request 308), in order to cause a session, which is associated with the connection of the UE 301 with the first RAT node 305, to be also associated with the connection of the UE 301 with the second RAT node 304, or to cause a release of the session associated with the connection of the UE 301 with the first RAT node 305.

[0082] Accordingly, the SME 310, which is for managing sessions of the UE 301, is configured to receive the request 308 from the UE 301. According to the request 308, the SME 310 is configured to cause the session, which is associated with the connection of the UE 301 with the first RAT node 305, to be also associated with the connection of the UE 301 with the second RAT node 304. Further, the SME 310 is configured to send an indication 311 of the QoS profile of the session to the second RAT node 304.

[0083] The entities 300, 301, 303 and 310 of FIG. 3 may respectively comprise a processor (not shown) or processing circuitry configured to perform, conduct or initiate various operations of the respective entity 300, 301, 303 and 310 described herein. The processing circuitry may comprise hardware and / or the processing circuitry may be controlled by software. The hardware may comprise analog circuitry or digital circuitry, or both analog and digital circuitry. The digital circuitry may comprise components such as application-specific integrated circuits (ASICs), field-programmable arrays (FPGAs), digital signal processors (DSPs), or multi-purpose processors. The entities 300, 301, 303 and 310 may respectively further comprise memory circuitry, which stores one or more instruction(s) that can be executed by the processor or by the processing circuitry, in particular under control of the software. For instance, the memory circuitry may comprise a non-transitory storage medium storing executable software code which, when executed by the processor or the processing circuitry, causes the various operations of the respective entity 300, 301, 303 and 310 to be performed. In one embodiment, the processing circuitry comprises one or more processors and a non-transitory memory connected to the one or more processors. The non-transitory memory may carry executable program code which, when executed by the one or more processors, causes the respective entity 300, 301, 303 and 310 to perform, conduct or initiate the operations or methods described herein.

[0084] The solutions of this disclosure, which are described in FIG. 3, are achieved based on the new entity referred to as MAF 300. FIG. 4 illustrates an example of the MAF 300 according to this disclosure and its maintained data structure 306 (the SDT in this case). FIG. 5 shows a flow-diagram of an operation of the MAF 300 based on the event triggers Al and A2.

[0085] The MAF 300 is configured to create and / or update the SDT 306 based on the available connections of the UE 301, including during mobility of the UE. The MAF 300 thus helps enabling uninterrupted UE sessions during mobility of the UE, and leveraging multi-connectivity to reduce the HIT and HoF rate to zero. Further, the MAF 300 may provide dynamic SDTs to the UE 301, RAN nodes 304, 305, and UPF, in order to leverage multi-connectivity during mobility, and to reduce the complexity of conventional HO mechanisms. The MAF 300 thus helps extending and simplifying session and service continuity mode to the RAN during UE mobility. The event triggers Al, A2 shown in FIG. 5 relate to the first event and the second event, respectively. Al indicates that a new connection to the second RAT node 304 has become available for the UE 301. A2 indicates that the serving / connection of the first RAT node 305 to the UE 301 has become worse (e.g., lower than a threshold). In case of the event trigger Al, the first event is notified, and the UE 301 shall connect to the newly available second RAT node 304. In case of the event trigger A2, the second event is notified, and the UE 301 shall disconnect from the underperforming connection with the first RAT node 305. The flow of notifications / messages 309, 307, 302, 308 and 311 is as in FIG. 3.

[0086] The formulas to validate the event triggers Al and A2 may be as follows. Al = Msl - Hysl > Threshl (trigger event); A2 = Ms2 + Hys2 < Thresh2 (trigger event). Threshl and Thresh2 may be network specific thresholds, and could be identical, i.e. Threshl = Thresh2. Msl indicates the measurement results of the serving cell of the first RAT node 305 obtained by the UE 301. Ms2 indicates the measurement results of the neighboring cell of the second RAT node 305 obtained by the UE 301. Both may be included in a general measurement result Ms. Hysl and Hys2 denote hysteresis parameters for the events, and could be identical, i.e. Hysl = Hys2.

[0087] FIG. 6 shows a flow-diagram illustrating the operation of the involved entities of this disclosure. In particular, FIG. 6 shows in detail the operation of the MAF 300, which is implemented in a mobile CN CP. Once a UE 301 is connected to the network and starts moving, it periodically measures the signal quality of the serving cell managed by the first (source) RAT node 305, and any new neighboring cell, for instance, of the second (target) RAT node 304. The UE 301 reports the measurements to the first RAT node 305.

[0088] Upon receiving the signal quality measurements from the UE 301, the first RAT node 304 checks, if the trigger conditions for the events Al and A2 are met. If any one of the events is identified, then the first RAT node 305 reports the event to the MME 303 (e.g., a MM function like AMF) in the CN CP. The MME 303 forwards the event to the MAF 300, and checks which event was triggered. If the triggered event is A2, then it requests 308 the UE 301 to release its connection to the first RAT node 305, whereas if the event is Al then it instructs the UE 301 to establish a multi-access PDU session with the new RAT node 304. Based on the instruction 308 received from the MME 303, the UE 301 performs the necessary actions. That is, in case of Al it establishes a new PDU session over the second RAT node 304, and in the case of A2 it releases the connection with the first RAT node 305. It also forwards the request to establish a PDU session on the second RAT node 304 TRAT in case of event A2 to the SME 310, e.g. the SMF.

[0089] Upon receiving the requests from the UE 301, the SME 310 accordingly updates the mobile CN UP entity such as UPF, in order to continue the session of the UE 301 also on the second RAT node 305. Further, it forwards the QoS profile 311 of the PDU session to the target RAT node 304. Based on the received QoS profile 311, the second RAT node 304 generates the traffic profile and forwards it to the UE 301 and the MME 303.

[0090] Meanwhile, after receiving the event trigger Al or A2, the MAF 300 checks if an SDT 306 already exists for the UE 301. If an SDT 306 is not found, the MAF 300 creates a default SDT 306 for the UE 301, and checks if the triggered event is Al, and retrieves the traffic profile of the second RAT node 304, and adds a new entry for the second RAT node 304 in the SDT 306. If an SDT 306 is found for the UE 301, the MAF 300 checks if the triggered event is A2, and removes the entry or entries for the first RAT node 304 from the SDT 306. The MAF 300 sends the updated or new SDT 306 to the UE 301, the RAT nodes 304, 305, and the core UP nodes.

[0091] FIG. 7 shows messages exchanged between the various entities 301, 305, 304, 303, 310, and 300 in a mobile communication system including the MAF 300. In particular, the sequence of messages exchanged between the participating entities is shown for an embodiment when the MAF 300 is a CN CP network function. In this exemplary sequence diagram, the UE 301 (here labelled as MT) is assumed to be already connected to the first RAT node 304 (source RAT (SRAT) node) and is located in a mobile environment where both the UE 301 and the first RAT node 305 BSs can be mobile (which is an expected case once NTN and TN integration is completed in 3 GPP).

[0092] Additionally, the MAF 300 may be able to send and receive messages directly to / from the UE 301 (via the RAT nodes), or the messages can be relayed through an access and / or mobility management function (the MME 303) for security related concerns. Initially, the UE 301 measures the signal strength of all the cells in its vicinity, and reports 309 the measurement to the first RAT node 305 periodically. The first RAT node 304 checks for event trigger conditions to identify if the event A1 / A2 should be triggered. If an event is identified, the first RAT node 305 reports 307 the event to the MME 303. The MME 303 forwards the event trigger to the MAF 300. The MAF 300 checks which event has been triggered and accordingly sends the outcome of the triggered event to the UE 301. After receiving the outcome from the MAF 300, assuming event A2 has occurred, the UE 301 sends a multi-access PDU session establishment request 308 to the SME 301, which in turn updates the UP in the CN to continue the UE’s session on the new second RAT node 304. The SME 310 also generates the QoS rules for the PDU session and forwards them to the second RAT node 304 to generate the traffic profile. The second RAT node 304 generates the traffic profile and sends it to the UE 301 and MAF 300. Based on the received event the MAF 300 updates / creates the SDT 306, and adds or removes the entries of the first and / or second RAT nodes 305 / 304 from the SDT 306, and forwards the updated SDT 306 to the UE 301, the RAT nodes 304, 305, and the core UP node 401.

[0093] FIG. 8 shows a 3GPP 5G system architecture. The solutions of this disclosure are applicable to methods, devices and mechanisms in communication systems like 3GPP communication systems (as shown). The solutions mainly apply to the UE 301 and the CN of the 3GPP mobile communication systems. The solutions may involve the 3GPP UE, may involve CP entities in the CN - such as AMF and SMF - and may involve the UP entity in the CN - like the UPF - and may involve the UP entity in the RAN - like eNB, gNB, etc. The solutions involve the newly proposed MAF inside the CP core and the SDT and SDM from the exemplary solution mentioned above.

[0094] FIG. 9 shows an embodiment of this disclosure, wherein the MAF 300 is a standalone function in the CP of a mobile communication system, like 3 GPP. In the 3 GPP system shown in FIG. 9, the proposed changes of the solution are as follows. The MAF 300 is added in the CN CP as a network function, namely the MAF network function. The MAF 300 receives the event triggers Al and A2 and traffic profile of the RAT nodes 304, 305 to which the UE 301 is connected to and wants to connect to. Based on the event triggers, and measurement reports of the available RAT nodes 304, 305, the network policy, the UE’s radio capabilities, and its current SDT 306, the MAF 300 generates the updated SDTs 306 and forwards them to the UE 301. RAT nodes 304, 305, and UP nodes.

[0095] FIG. 10 shows an embodiment of this disclosure, wherein the MAF 300 is a feature inside a CP function of a mobile communication system, like the AMF in 3GPP. In the 3GPP system shown in FIG. 10, the proposed changes of the solution are as follows. The MAF 300 is added in the CN CP as a feature inside the MME 303, namely the AMF network function in this case. The MAF 300 receives the event triggers Al and A2 and traffic profile of the RAT nodes 304, 305, to which the UE 301 is connected to and wants to connect to. Based on the event triggers, measurement reports of the available RAT nodes 304, 305, the network policy, the UE’s radio capabilities, and its current SDT 301, the MAF 300 generates the updated SDTs 306 and forwards them to the UE 301, the RAT nodes 304, 305, and the UP nodes.

[0096] The MAF 300 thereby helps to ensure session continuity for mobile users (UEs 301), to increase throughput, and to reduce latency for UEs 301, and to improve resource efficiency of the network. FIG. 11 shows a method 1100 for managing connectivity of a UE 301. The method 1100 may be performed by the MAF 300 described above. The method 300 comprises a step 301 of receiving 1101 the notification 302 of the first event or of the second event from a MME 303. The method 1100 then comprises a step 1102 of processing the multi -connectivity data structure 306 by adding the first entry related to the second RAT node 304 into the data structure 306 if the first event is notified, or by deleting the second entry related to the first RAT node 305 from the data structure 306 if the second event is notified.

[0097] FIG. 12 shows a method 1200 for managing mobility of a 301. The method 1200 may be performed by the MME 303 described above. The method 1200 comprises a step 1201 of receiving the notification 307 of the first event or of the second event from the first RAT node 305. Further, the method 100 comprises a step 1202 of requesting the UE 301 to establish the connection with the second RAT node 304 if the first event is notified, or to release the connection with the first RAT node 305 if the second event is notified.

[0098] FIG. 13 shows a method 1300 for a multi-connectivity user equipment UE 301. The method 1300 comprises a step 1301 of performing respective signal quality measurements related to a serving cell managed by the first RAT node 305 and of a neighboring cell managed by the second RAT node 304. Further, the method 1300 comprises a step 1302 of sending the notification 309 of the signal quality measurements to the first RAT node 305. The method 1300 also comprises a step 1303 of receiving the request 308 from the MME 303 to establish the connection with the second RAT node 304 or to release the connection with the first RAT node 305. Further, the method 1300 comprises a step 1304 of establishing the connection with the second RAT node 304 or releasing the connection with the first RAT node 305 according to the request 308. The method 1300 then comprises a step 1305 of forwarding the request 308 to the SME 310, to cause a session, which is associated with the connection of the UE 301 with the first RAT node 305, to be also associated with the connection of the UE 301 with the second RAT node 304, or to release the session associated with the connection of the UE 301 with the first RAT node 305.

[0099] FIG. 14 shows a method 1400 for managing sessions of a UE 301. The method 1400 may be performed by the SME 310. The method 1400 comprises a step 1401 of receiving the request 308 from the UE 301 to establish a connection with a second RAT node 304. Further, the method 1400 comprises a step 1402 of causing a session, which is associated with the connection of the UE 301 with the first RAT node 305, to be also associated with the connection of the UE 301 with the second RAT node 304. Then, the method 1400 comprises a step of sending 403 the QoS, profile of the session, which is associated with the connection of the UE 301 with the first RAT node 305, to the second RAT node 304.

[0100] In summary, the solutions of this disclosure provide several advantages. The MAF 300 enables a new and efficient way of achieving service continuity during mobility of a UE 301, namely via leveraging multi -connectivity of the UE 301. HIT and HoF can be avoided entirely in this way, as no conventional HO is performed. Further, the throughput may be increased and the latency reduced for the UEs. Additionally, resource efficiency of the network may be improved.

[0101] The event triggers Al and A2 for generating or updating the SDT 306 may result in simplified measurements to identify when a UE 301 should connect or disconnect to or from a RAT node 304 or 305.

[0102] The present disclosure has been described in conjunction with various embodiments as examples as well as implementations. However, other variations can be understood and effected by those persons skilled in the art and practicing the claimed matter, from the studies of the drawings, this disclosure and the independent claims. In the claims as well as in the description the word “comprising” does not exclude other elements or steps and the indefinite article “a” or “an” does not exclude a plurality. A single element or other unit may fulfill the functions of several entities or items recited in the claims. The mere fact that certain measures are recited in the mutual different dependent claims does not indicate that a combination of these measures cannot be used in an advantageous implementation.

Claims

CLAIMS1. A multi -connectivity management entity (300) for managing connectivity of a user equipment, UE, (301) wherein the multi -connectivity management entity (300) is configured to: receive a notification (302) of a first event or of a second event from a mobility management entity (303), wherein the first event indicates that a connection with a second radio access technology, RAT node (304) has become available for the UE (301), wherein the UE (301) has an established connection with a first RAT node (305), and wherein the second event indicates that the connection of the UE (301) with the first RAT node (305) has to be released; and process a multi -connectivity data structure (306), which is associated with the UE (301), by adding a first entry related to the second RAT node (304) into the data structure (306) if the first event is notified, or by deleting a second entry related to the first RAT node (305) from the data structure (306) if the second event is notified; wherein the first and second entry of the multi-connectivity data structure (306) respectively indicate a respective quality of service, QoS, profile and / or traffic profile for the connection of the UE (301) with the first and second RAT node (304, 305).

2. The multi -connectivity management entity (300) according to claim 1, wherein each entry of the multi -connectivity data structure (306) indicates a respective QoS profile and / or traffic profile for a respective connection of the UE (301) with a respective RAT node (305, 304).

3. The multi -connectivity management entity (300) according to claim 1 or 2, wherein the multi -connectivity data structure (306) is a table, which maps the QoS profiles and / or traffic profiles to available networks and connections provided in said networks.

4. The multi-connectivity management entity (300) according to one of the claims 1 to 3, wherein processing the multiconnectivity data structure (306) comprises creating the data structure (306) and adding the first entry, or comprises updating the data structure (306) by adding the first entry and / or deleting the second entry.

5. The multi -connectivity management entity (300) according to one of the claims 1 to 4, further configured to send the processed multi-connectivity data structure (306) to at least one of: the UE (301), the first RAT node (305), the second RAT node (304), and a core network user plane entity.

6. The multi -connectivity management entity (300) according to one of the claims 1 to 5, wherein the multi -connectivity management entity (300) is an individual core network control plane function.

7. The multi -connectivity management entity (300) according to one of the claims 1 to 5, wherein the multi -connectivity management entity (300) is incorporated into a core network control plane function, for instance, into an access and mobility management function, AMF.

8. A mobility management entity (303) for managing mobility of a user equipment, UE, (301) wherein the mobility management entity (303) is configured to: receive a notification (307) of a first event or of a second event from a first radio access technology, RAT, node (305), which has an established connection with the UE (301), wherein the first event indicates that a connection with a second RAT node (304) has become available for the UE (301), and wherein the second event indicates that the connection of the UE (301) with the first RAT node (305) has to be released; andrequest (308) the UE (301) to establish the connection with the second RAT node (304) if the first event is notified, or to release the connection with the first RAT node (305) if the second event is notified.

9. The mobility management entity (303) according to claim 8, wherein the mobility management entity (303) is a core network control plane function, for example, an AMF.

10. A multi -connectivity user equipment, UE, (301) wherein the UE (301 ) is configured to : perform respective signal quality measurements related to a serving cell managed by a first radio access technology, RAT, node (305), which has an established connection with the UE (301), and of a neighboring cell managed by a second RAT node (304); send a notification (309) of the signal quality measurements to the first RAT node (305); receive a request (308) from a mobility management entity (303) to establish a connection with the second RAT node (304) or to release the connection with the first RAT node (305); and establish the connection with the second RAT node (304) or release the connection with the first RAT node (305) according to the request (308); and forward the request (308) to a session management entity (310) to cause a session, which is associated with the connection of the UE (301) with the first RAT node (305), to be also associated with the connection of the UE (301) with the second RAT node (304), orto release the session associated with the connection of the UE (301) with the first RAT node (305).

11. The multi -connectivity UE (301) according to claim 10, configured to periodically measure a signal strength of the serving cell and a signal strength of the neighboring cell as the respective signal quality measurements.

12. A session management entity (310) for managing sessions of a user equipment, UE, (301) wherein the session management entity (310) is configured to: receive a request (308) from the UE (301), which has an established connection with a first radio access technology, RAT, node (305), to establish a connection with a second RAT node (304); and cause a session, which is associated with the connection of the UE (301) with the first RAT node (305), to be also associated with the connection of the UE (301) with the second RAT node (304); and send a quality of service, QoS, profile (311) of the session, which is associated with the connection of the UE (301) with the first RAT node (305), to the second RAT node (304).

13. The session management entity (310) according to claim 12, wherein the session management entity (310) is a core network control plane function, for example, a session management function, SMF.

14. The session management entity (310) according to claim 12 or 13, wherein the session is a protocol data unit, PDU, session.

15. A method ( 1100) for managing connectivity of a user equipment, UE, (301) wherein the method (1100) comprises : receiving (1101) a notification (302) of a first event or of a second event from a mobility management entity (303), wherein the first event indicates that a connection with a second radio access technology, RAT node (304) has become available for the UE (301), wherein the UE (301) has an established connection with a first RAT node (305), and wherein the second event indicates that the connection of the UE (301) with the first RAT node (305) has to be released; andprocessing (1102) a multi-connectivity data structure (306), which is associated with the UE (301), by adding a first entry related to the second RAT node (304) into the data structure (306) if the first event is notified, or by deleting a second entry related to the first RAT node (305) from the data structure (306) if the second event is notified; wherein the first and second entry of the multi-connectivity data structure (306) respectively indicate a respective quality of service, QoS, profile and / or traffic profile for the connection of the UE (301) with the first and second RAT node (304).

16. A method (1200) for managing mobility of a user equipment, UE, (301) wherein the method (1200) comprises: receiving (1201) a notification (307) of a first event or of a second event from a first radio access technology, RAT, node, (305) which has an established connection with the UE (301), wherein the first event indicates that a connection with a second RAT node (304) has become available for the UE (301), and wherein the second event indicates that the connection of the UE (301) with the first RAT node (305) has to be released; and requesting (1202) the UE (301) to establish the connection with the second RAT node (304) if the first event is notified, or to release the connection with the first RAT node (305) if the second event is notified.

17. A method ( 1300) for a multi -connectivity user equipment, UE, (301) wherein the method (1300) comprises : performing (1301) respective signal quality measurements related to a serving cell managed by a first radio access technology, RAT, node (305), which has an established connection with the UE (301), and of a neighboring cell managed by a second RAT node (304); sending (1302) a notification (309) of the signal quality measurements to the first RAT node (305); receiving (1303) a request (308) from a mobility management entity (303) to establish a connection with the second RAT node (304) or to release the connection with the first RAT node (305); and establishing (1304) the connection with the second RAT node (304) or releasing the connection with the first RAT node (305) according to the request (308); and forwarding (1305) the request (308) to a session management entity (310) to cause a session, which is associated with the connection of the UE (301) with the first RAT node (305), to be also associated with the connection of the UE (301) with the second RAT node (304), or to release the session associated with the connection of the UE (301) with the first RAT node (305).

18. A method (1400) for managing sessions of a user equipment, UE, (301) wherein the method (1400) comprises : receiving (1401) a request (308) from the UE (301), which has an established connection with a first radio access technology, RAT, node (305), to establish a connection with a second RAT node (304); and causing (1402) a session, which is associated with the connection of the UE (301) with the first RAT node (305), to be also associated with the connection of the UE (301) with the second RAT node (304); and sending (1403) a quality of service, QoS, profile of the session, which is associated with the connection of the UE (301) with the first RAT node (305), to the second RAT node (304).1 . A computer program comprising instructions which, when the program is executed by a processor, cause the processoro perform the method (1100, 1200, 1300, 1400) according to one of the claims 15 to 18.

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