Patent Description:
With the advent of the fourth industrial revolution, the demand for the mobility by cyber-physical applications of vertical industries, such as smart industrial manufacturing, industrial robot control, smart autonomous driving control, smart energy, telemedicine, and the like, is getting more and more urgent. As a result, <NUM> communication systems need to play an irreplaceable role in the technology development of vertical industries since a <NUM> communication network can provide mobility and flexibility to applications of vertical industries. Different applications may have different requirements for <NUM> communications. Typically, ultra-reliable low latency communication (URLLC) is required for those cyber-physical applications which have periodic deterministic communications between their central servers for controlling real time machine production and controlled application clients (also referred to as APPs). The communication service availability highly depends on the latency and reliability of the logical communication link, as well as the survival time of a communication message defined by a cyber-physical application. If the latency of a message is not within the range of the survival time, the received message is considered "not available".

According to the specification 3GPP TS <NUM>, periodic deterministic communications of a cyber-physical application for a <NUM> system should meet the following requirements. Firstly, the message packets of each application must arrive at the scheduled time. The system is considered unavailable if an expected message is not received within a specified time. Secondly, ultra-availability requirements for the communication service of provided by a <NUM> system demand a service availability of at least <NUM>%. Thirdly, very strict failure recovery time from a few milliseconds to <NUM> milliseconds. However, such requirements of ultra-reliable low latency communication (URLLC) provide a great challenge for a <NUM> communication system. The patent application <CIT> shows a network in which data is sent to the UE through two different bearers and a packet duplication function is used to split the data into the two bearers.

The present disclosure provides a network entity, a communication network, a method, and a computer program product, as defined in the appended set of claims, for improved ultra-reliable low latency communication in a <NUM> communication network.

According to a first aspect a network entity for providing redundant data paths for communication of data between a user equipment, UE, and at least one user plane function, UPF, of a core network in a communication network, in particular a <NUM> communication network is provided. The network entity may be implemented in software and/or hardware in the communication network. The network entity may comprise, for instance, one or more network functions and/or one or more physical network devices.

The network entity is configured to establish a first packet data unit, PDU session for the UE using a primary next generation radio access network, NG-RAN, implementing a first protocol stack, wherein the first protocol stack of the primary NG-RAN includes at least one first GPRS tunnelling protocol user plane, GTP-U, entity and a first service data adaption protocol, SDAP, entity. The establishment of the first PDU session includes establishing at least one first GTP-U tunnel between a core network of the communication network and the primary NG-RAN. The network entity is further configured to establish a second PDU session for the UE using a secondary NG-RAN implementing a second protocol stack, wherein the second protocol stack of the secondary NG-RAN includes at least one second GTP-U entity and a second SDAP entity, wherein the establishment of the second PDU session includes establishing at least one second GTP-U tunnel between the core network (of the communication network and the secondary NG-RAN.

The network entity provides a first packet duplication and elimination, PDE, entity in the first GTP-U entity and/or the first SDAP entity of the primary NG-RAN and a second PDE entity in the second GTP-U entity and/or the second SDAP entity of the secondary NG-RAN. The first PDE entity is configured to:.

In a further possible implementation form of the first aspect, the first GTP-U entity is configured to extract the first downlink Ethernet frame or DetNet-IP packet from the payload of a first GPRS tunnelling protocol packet data unit, GTP PDU received by the primary NG-RAN through the first GTP-U tunnel for obtaining the first downlink Ethernet frame or DetNet-IP packet by the first PDE entity.

In a further possible implementation form of the first aspect, the network entity is configured to further establish at least one further GTP-U tunnel between the first GTP-U entity or the further first GTP-U entity of the primary NG-RAN and the second GTP-U entity or a further second GTP-U entity of the secondary NG-RAN for communicating user data related to the UE, wherein the first GTP-U entity or the further first GTP-U entity is configured to generate a GTP-U PDU based on the copy of the first downlink SDU for forwarding the GTP-U PDU to the second GTP-U entity or the further second GTP-U entity of the secondary NG-RAN through the at least one further GTP-U tunnel.

In a further possible implementation form of the first aspect, the first PDE entity of the primary NG-RAN is further configured to:.

In a further possible implementation form of the first aspect, the first PDE entity is further configured to provide the copy of the first downlink SDU or the copy of the first uplink SDU to the first GTP-U entity or the further first GTP-U entity together with information indicative of whether the respective Ethernet frame or DetNet-IP packet is intended for the UE or the core network of the communication network.

In a further possible implementation form of the first aspect, the second PDE entity of the secondary NG-RAN is configured to:.

In a further possible implementation form of the first aspect, the second PDE entity of the secondary NG-RAN is further configured to:.

According to a second aspect a communication network, in particular a <NUM> communication network for providing redundant data paths for communication of data between a user equipment, UE, and at least one user plane function, UPF, of a core network of the communication network is provided. The communication network comprises a primary next generation radio access network, NG-RAN, for establishing a first packet data unit, PDU session for the UE using a first protocol stack, wherein the first protocol stack includes at least one first GPRS tunnelling protocol user plane, GTP-U, entity and a first service data adaption protocol, SDAP, entity, wherein the first PDU session includes at least one first GTP-U tunnel between a core network of the communication network and the primary NG-RAN. The communication network further comprises a secondary NG-RAN for establishing a second PDU session for the UE using a second protocol stack, wherein the second protocol stack includes at least one second GTP-U entity and a second SDAP entity, wherein the second PDU session includes at least one second GTP-U tunnel between the core network of the communication network and the secondary NG-RAN.

Moreover, the communication network comprises a first packet duplication and elimination, PDE, entity in the first GTP-U entity and/or the first SDAP entity of the primary NG-RAN and a second PDE entity in the second GTP-U entity and/or the second SDAP entity (of the secondary NG-RAN. The first PDE entity is configured to:.

In a further possible implementation form of the second aspect, the first GTP-U entity is configured to extract the first downlink Ethernet frame or DetNet-IP packet from the payload of a first GPRS tunnelling protocol packet data unit, GTP PDU received by the primary NG-RAN through the first GTP-U tunnel for obtaining the first downlink Ethernet frame or DetNet-IP packet by the first PDE entity.

In a further possible implementation form of the second aspect, the network entity is configured to further establish at least one further GTP-U tunnel between the first GTP-U entity or 'the further first GTP-U entity of the primary NG-RAN and the second GTP-U entity or the further second GTP-U entity of the secondary NG-RAN for communicating user data related to the UE, wherein the first GTP-U entity or the further first GTP-U entity is configured to generate a GTP-U PDU based on the copy of the first downlink SDU for forwarding the GTP-U PDU to the second GTP-U entity or the further second GTP-U entity of the secondary NG-RAN through the at least one further GTP-U tunnel.

In a further possible implementation form of the second aspect, the first PDE entity of the primary NG-RAN is further configured to:.

In a further possible implementation form of the second aspect, the first PDE entity is further configured to provide the copy of the first downlink SDU or the copy of the first uplink SDU to the first GTP-U entity or the further first GTP-U entity together with information indicative of whether the respective Ethernet frame or DetNet-IP packet is intended for the UE or the core network of the communication network.

In a further possible implementation form of the second aspect, the second PDE entity of the secondary NG-RAN is configured to:.

According to a third aspect a method for providing redundant data paths for communication of data for a user equipment, UE, in a communication network, in particular a <NUM> communication network is provided. The method comprises the steps of:.

The method further comprises the following steps performed by the second PDE entity:.

According to a fourth aspect a computer program product is provided, comprising a non-transitory computer-readable storage medium for storing program code which causes a computer or a processor to perform the method according to the third aspect, when the program code is executed by the computer or the processor.

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

equipment, UE, and at least one user plane function, UPF, of a core network of the communication network is provided. The communication network comprises a primary next generation radio access network, NG-RAN, for establishing a first packet data unit, PDU session for the UE using a first protocol stack, wherein the first protocol stack includes at least one first GPRS tunnelling protocol user plane, GTP-U, entity and a first service data adaption protocol, SDAP, entity, wherein the first PDU session includes at least one first GTP-U tunnel between a core network of the communication network and the primary NG-RAN. The communication network further comprises a secondary NG-RAN for establishing a second PDU session for the UE using a second protocol stack, wherein the second protocol stack includes at least one second GTP-U entity and a second SDAP entity, wherein the second PDU session includes at least one second GTP-U tunnel between the core network of the communication network and the secondary NG-RAN.

In a further possible implementation form of the second aspect, the second PDE entity of the secondary NG-RAN is further configured to:.

In a further possible implementation form of the second aspect, the second PDE entity is further configured to provide the copy of the second downlink SDU or the copy of the second uplink SDU to the second GTP-U entity or the further second GTP-U entity together with information indicative of whether the respective Ethernet frame or DetNet-IP packet is intended for the UE or the core network of the communication network.

In a further possible implementation form of the second aspect, the first PDE entity of the primary NG-RAN is configured to receive the copy of the second downlink SDU and/or the copy of the second uplink SDU from the first GTP-U entity or the further first GTP-U entity of the primary NG-RAN.

In a further possible implementation form of the second aspect, the first PDE entity is further configured to extract a first set of downlink stream identifiers from the first downlink Ethernet frame or DetNet-IP packet; store the set of first downlink stream identifiers in a memory, if it cannot be found in the memory; extract the second downlink Ethernet frame or DetNet-IP packet from the copy of the second downlink SDU received from the first GTP-U entity or the further first GTP-U entity; extract a second set of downlink stream identifiers from the second downlink Ethernet frame or DetNet-IP packet and store the second set of downlink stream identifiers in the memory, if it cannot be found in the memory; associate the first set of downlink stream identifiers with the second set of downlink stream identifiers as a redundant pair of stream identifier sets.

In a further possible implementation form of the second aspect, the first PDE entity is further configured to extract a first set of uplink stream identifiers from the first uplink Ethernet frame or DetNet-IP packet and store the first set of uplink stream identifiers in a memory, if it cannot be found in the memory; extract the second uplink Ethernet frame or DetNet-IP packet from the copy of the second uplink SDU received from the first GTP-U entity or the further first GTP-U entity; extract a second set of uplink stream identifiers from the second uplink Ethernet frame or DetNet-IP packet and store the second set of uplink stream identifiers in the memory, if it cannot be found in the memory; associate the first set of uplink stream identifiers with the second set of uplink stream identifiers as a redundant pair of stream identifier sets.

In a further possible implementation form of the second aspect, the first PDE entity is further configured to replace the second set of downlink stream identifiers in the second downlink Ethernet frame or DetNet-IP packet with the first set of downlink stream identifiers to obtain the first downlink Ethernet frame or DetNet-IP packet;.

In a further possible implementation form of the second aspect, the first PDE entity is further configured replace the second set of uplink stream identifiers in the second uplink Ethernet frame or DetNet-IP packet with the first set of uplink stream identifiers to obtain the first uplink Ethernet frame or DetNet-IP packet;.

In a further possible implementation form of the second aspect, the first PDE entity is further configured to extract a sequence number from a Ethernet frame or DetNet-IP packet, wherein the Ethernet frame or DetNet-IP packet is the first downlink Ethernet frame or DetNet-IP packet from the first GTP-U entity or the first uplink Ethernet frame or DetNet-IP packet from the first PDCP entity or the second downlink Ethernet frame or DetNet-IP packet from first GTP-U entity or the further first GTP-U entity or the second uplink Ethernet frame or DetNet-IP packet from the first GTP-U entity or the further first GTP-U entity;.

In a further possible implementation form of the third aspect, the method further comprises the following steps performed by the second PDE entity:.

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

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 present disclosure or specific aspects in which embodiments of the present disclosure may be used. It is understood that embodiments of the present disclosure may be used in other aspects and comprise structural or logical changes not depicted in the figures.

For instance, it is to be 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.

Before describing different embodiments in more detail, in the following some technical background as well as terminology concerning cellular communication networks, in particular in accordance with the 3GPP <NUM> standard will be introduced making use of one or more of the following abbreviations:.

<FIG> shows a <NUM> communication system <NUM> that enables two URLLC application endpoints, namely a URLLC controlling server <NUM> and a controlled URLLC client 101a (implemented on a UE <NUM> also referred to as App 101a) to communicate with each other using Ethernet or IP traffic. As illustrated in <FIG>, the <NUM> communication system <NUM> (between the UE <NUM> and one or two UPFs <NUM>, <NUM>) as one portion of the endpoint communication link provides a <NUM> service to deliver the Ethernet or IP traffic to the endpoints. In other words, the endpoints (UE <NUM> and UPF <NUM>, <NUM>) of the <NUM> user plane receive the URLLC Endpoint User Data Traffic Streams of Ethernet frames or IP packets, in particular DetNet-IP packets, while the <NUM> system <NUM> transfers the URLLC Endpoint User Data Traffic Streams as the payload of <NUM> user-plane data packets.

Due to strict availability and reliability requirements, in order to ensure the ultra-availability of periodic deterministic communications, the URLLC endpoints may duplicate each Ethernet frame or IP packet and send these to the destination via two independent paths, while the receiving endpoints eliminate the duplication of received frames/packets. With such a dual redundant transmission the URLLC Endpoint User Data Traffic Streams of Ethernet frames or IP packets are hardly impacted by abnormal events, such as a packet loss on the communication link or a communication network failure. Such kind of dual-packet redundant communications generally applies one of the so-called frame replication and elimination for reliability (FRER) protocols, e.g., IEEE <NUM>. 1CB, IEC <NUM>-<NUM>'s Parallel Redundancy Protocol (PRP), HSR (High-Availability Seamless Redundancy), or IETF RFC <NUM> Architecture of Deterministic Networking (DetNet) on the top of the Ethernet/IP protocol. Deterministic Networking (DetNet) operated at the IP/MPLS layer provides a capability for the delivery of data flows with extremely low packet loss rates and/or bounded end-to-end delivery latency. The DetNet layer can encapsulate the IP layer packet as the URLLC endpoint user data packet, called DetNet-IP packet, for sending to access points (e.g., UE or the core network) of <NUM> system. Each of the two URLLC application endpoints, namely the URLLC controlling server <NUM> and the controlled URLLC client 101a might use one or two sets of stream identifiers for sending and/or receiving the redundant Ethernet frame or DetNet-IP packet traffic via two independent paths, one set of stream identifiers using for one path and another set of stream identifiers for another path (in case one set of stream identifiers, the traffic sending both two path with the same set of stream identifiers). The sets of stream identifiers using in two independent paths for sending/or receiving traffic are called the redundant pair of stream identifier sets of an URLLC endpoint. A common feature of these FRER protocols is that an accumulating sequence number (SN) is applied into each frame/packet in the sending endpoints. At the receiving endpoint, the duplicate frames are eliminated based on parameter set of stream identifiers (for an Ethernet stream, such as the source/and destination Ethernet MAC addresses, VLAN identifier, and protocol type, etc.; for an IP based stream, such as IP source/and destination addresses, MPLS flow identifier, and protocol types, source/and destination port number, etc.) and the sequence number in the headers of those frame/packets (the sequence number in DetNet layer for DetNet-IP packet).

As shown in <FIG>, each application message of the URLLC endpoints is duplicated and encapsulated into two redundant Ethernet frames/DetNet-IP packets by using one of the corresponding FRER protocols to send to the <NUM> communications system <NUM>, for instance, via a data network (DN) <NUM>. These Ethernet frames/DetNet-IP packets are referred to as "URLLC endpoint user data frames/packets" here. The headers of periodic URLLC endpoint user data frames/packets may contain stream identifiers and a sequence number according to one of the above-mentioned FRER protocols. When periodic URLLC endpoint user data frames/packets are transferred to the user plane endpoint (UPF <NUM>, <NUM> or UE <NUM>) of the <NUM> system <NUM> over two independent paths, the <NUM> system <NUM> can reliably transfer these Ethernet frames/DetNet-IP packets into another <NUM> endpoint at a predetermined time. This challenge must be addressed by the <NUM> communication system <NUM> to be used for communications of URLLC applications of vertical industries.

To support ultra-reliable low latency communication (URLLC) for vertical industry applications, the <NUM> system <NUM> should be able to reliably transfer the URLLC endpoint user data frames/packets within a predetermined time range. An end-to-end dual connectivity solution based on two end-to-end dual redundant user plane data paths is described in 3GPP TS <NUM>. As described therein, two redundant PDU (packet data unit) sessions are used to support two mutually redundant URLLC endpoint user data streams (as shown in <FIG> and <FIG> and will be described in more detail below) between the URLLC server <NUM> and the URLLC client 101a. The PDU session spans from the UE <NUM> via the NG-RAN <NUM>, <NUM> to the UPF <NUM>, <NUM>. In the N3 interface between the NG-RAN <NUM>, <NUM> and UPF <NUM>, <NUM>, one PDU session is supported by a user-plane tunnel established between UPF1 <NUM> and the master NG-RAN <NUM>, while another PDU session is supported by another user plane tunnel established between the UPF2 <NUM> and the master NG-RAN <NUM> or established between the UPF2 <NUM> and the secondary NG-RAN <NUM>. Between the UE <NUM> and the NG-RAN <NUM>, <NUM>, the two PDU sessions are supported by the dual connectivity in low radio protocol stacks defined in 3GPP TS <NUM> (as will be described in more detail in the context of <FIG> and <FIG> further below).

According to 3GPP TS <NUM>, there are four types of dual connectivity for the NG-RAN, which will be described in the following under further reference to <FIG> and <FIG>.

<FIG> illustrates the dual connectivity (DC) of master NG-RAN terminated split radio bearers (left diagram in <FIG>) and secondary NG-RAN terminated split radio bearers (right diagram in <FIG>), respectively. The two core network (CN) user plane tunnels and two split radio bearers used for the user plane data transfer of the two redundant PDU sessions are all terminated in the same NG-RAN. The PDCP duplication is performed for the secondary radio bearer.

<FIG> illustrates the dual connectivity with the master cell group (MCG) radio bearers (left diagram in <FIG>) and with the secondary cell group (SCG) radio bearers (right diagram in <FIG>), respectively. The radio bearers in a NG-RAN <NUM>, <NUM> are used for the two redundant PDU sessions. As illustrated in <FIG> and <FIG>, each NG-RAN may comprise a GTP entity (also referred to as GTP-U entity <NUM>, <NUM>, a SDAP entity <NUM>, <NUM>, a PDCP entity <NUM>, <NUM>, a RLC entity <NUM>, <NUM>, a MAC layer entity <NUM>, <NUM> and a PHY layer entity <NUM>, <NUM> in the respective protocol stack.

However, the end-to-end dual redundant user plane paths shown in <FIG> and <FIG> based on the dual-connectivity between the NG-RANs <NUM>, <NUM> and the UE <NUM> have at least the following reliability defects. Preventing single point of failure is a basic principle of the reliability design. However, the two redundant end-to-end user-plane transmission paths have the following single point of failure in the dual-connectivity provided by the NG-RANs <NUM>, <NUM>. For the dual connectivity with split radio bearers (<FIG>), the first single point of failure is that both user-plane transmission tunnels connected with the core network <NUM> are terminated in the same NG-RAN (master or secondary NG-RAN <NUM>, <NUM>). The processing of transport layer protocols (IP and GTP-U) of the two user plane tunnels may be another first single point of failure. The PDCP layer may also be a single point of failure because RLC frames of one NG-RAN (e.g., the secondary NG-RAN <NUM>) are duplicated by the PDCP layer of the counterpart NG-RAN (e.g., the master NG-RAN <NUM>) and transmitted over the Xn interface.

Regardless of the dual connectivity of the master cell group (MCG) radio bearers or of the secondary cell group (SCG) radio bearers, since the RLC frames of the two redundant paths are processed at the same MAC layer <NUM>, <NUM>, the MAC layer <NUM>, <NUM> is the single point of failure of the two redundant paths. In addition, data packets of the two redundant paths use the same NG-RAN radio bearers to transmit data to the air interface. This might be also another single point of failure of the two redundant paths.

Due to constraints of limited radio resources and mutual radio interference between narrowly separated frequency bands, practically it is difficult to arrange the radio network coverage to each service area with more than two cells simultaneously. This is the main reason why the URLLC solution is based on the dual connectivity of not more than two radio bearers. However, once one of the two cells experiences a hardware failure, normally it takes a long time, e.g., hours, to recover the cell experiencing the failure and the availability of service in this area covered by the cell experiencing the failure may be impacted for a long time. The failure of one radio cell in the dual connectivity in the solution described above will cause that one user plane path is not available for a long time. Obviously, the availability of the remaining user plane path is unlikely to be able to support the URLLC applications.

The <NUM> communication system or network <NUM> usually consists of multiple disjoint subnets, such as the core network <NUM>, backbone network <NUM>, and the radio access network(s) <NUM>, <NUM>. Each subnet usually consists of one or more network functions (such as the AMF <NUM> and the SMFs <NUM> shown in <FIG>), and a network function usually consists of multiple hardware and software modules. From the perspective of software and hardware, the communication path of URLLC endpoint user data streams in the <NUM> system <NUM> consists of multiple complex communication chains. If a hardware or software module in one of the communication chains is in failure or operating abnormally, it may cause the endpoint user data frames/packets transferred by the <NUM> system <NUM> to experience an error, or packet loss, or the increase of transmission latency which impacts the availability of the related communication path. In addition, due to environmental factors, the transmission latency and packet loss rate over the air interface may be unstable. Assuming one of the dual redundant user plane paths is unavailable due to a hardware or software module in failure or operating abnormally in this path of the core network <NUM>, backbone network <NUM>, or NG-RAN <NUM>, <NUM> (as illustrated in <FIG>), while the communication over the air interface is unstable to cause a packet loss or longer transmission delay in another path, the two events will cause the two redundant user plane data communication paths to become unavailable simultaneously.

The goal for <NUM> to support ultra-reliable low latency communication (URLLC) for vertical industry applications is to transfer the URLLC endpoint user data frames/packets to interface connection points of the vertical industry applications without any error and within a predetermined time range. Since the availability and reliability requirements of vertical industry applications are much higher than those of traditional telecommunication applications, a dual redundant paths' solution to be used for transferring the dual redundant URLLC endpoint user data frames/packets has been proposed in 3GPP TS <NUM>; System architecture for the <NUM> System (5GS); Stage <NUM>, Release <NUM>. However, as already mentioned above, there may arise availability and reliability defects in the solution disclosed therein.

Thus, there is a need to enhance the availability and reliability to support applications of ultra-reliable low latency communication (URLLC) by eliminating or mitigating those defects in the proposed 3GPP solution mentioned above. As will be described in more detail in the following, this need is addressed by one or more of the embodiments disclosed herein.

More specifically, to support URLLC for vertical industry applications, the <NUM> system <NUM> is facing a challenge of providing communications with ultra-high availability and reliability. There are two factors to be considered here. The first factor is that any momentary error or disturbance in a software or hardware module of the communication path which is used for transferring the URLLC endpoint user data streams could impact the availability of this communication. The second factor is that the availability of the radio link may be affected by environmental factors. For strict requirements of availability and reliability given to a <NUM> communication path with multiple communication chains, even though two redundant user plane data paths are applied into the transportation of the same URLLC endpoint user data streams, the unavailability of both two redundant user data communication paths could happen. Thus, embodiments disclosed herein allow improving the availability and reliability in case multiple abnormal events happened in the two redundant paths simultaneously.

As already described above, there may be availability and reliability defects of single point of failure in the dual-connectivity solution of NG-RAN radio protocol stacks in the solution disclosed in 3GPP TS <NUM>; System architecture for the <NUM> System (5GS); Stage <NUM>, Release <NUM>. Embodiments disclosed herein allow preventing such a single point of failure in two redundant <NUM> end-to-end user-plane transmission paths.

Two main embodiments of the invention will be described in the following under reference to <FIG> and <FIG>. Similar to the solutions described above, two redundant PDU sessions are used to support the two mutually redundant URLLC endpoint user data streams communicating between the application server <NUM> and the client 101a. One PDU session spans from the UE <NUM> via the Master NG-RAN <NUM> to the UPF1 <NUM> (in the core network <NUM>), while the other PDU Session spans from the UE <NUM> via the Secondary NG-RAN <NUM> to the UPF2 <NUM> (in the core network <NUM>). One main difference between the embodiments disclosed herein and the conventional solution(s) described above is that the radio interface dual connectivity through the PDCP layer <NUM>, <NUM> of one of the NG-RANs <NUM>, <NUM> communicating with the RLC layer <NUM>, <NUM> of the other one of the NG-RANs <NUM>, <NUM> (as illustrated in <FIG> and <FIG> and disclosed in 3GPP TS <NUM>, NR; Multi-connectivity; Overall description; Stage-<NUM>, release <NUM>) is not employed by embodiments of the invention because of the defect of the single point of failure of the conventional solution.

More specifically, according to a first main embodiment a network entity for providing redundant data paths for communication of data for the UE <NUM> in the <NUM> communication network <NUM> is provided. The network entity is configured to establish a PDU session for the UE <NUM> using the primary or Master NG-RAN <NUM> implementing a first protocol stack, wherein the first protocol stack includes at least one first GTP-U entity <NUM> and a first SDAP entity <NUM>, wherein the establishment of the first PDU session includes establishing at least one first GTP-U tunnel between the core network <NUM> of the <NUM> communication network <NUM> and the primary NG-RAN <NUM>.

The network entity is further configured to establish a second redundant PDU session for the UE <NUM> using the secondary NG-RAN <NUM> implementing a second protocol stack, wherein the second protocol stack includes at least one second GTP-U entity <NUM> and a second SDAP entity <NUM>, wherein the establishment of the second PDU session includes establishing at least one second GTP-U tunnel between the core network <NUM> of the <NUM> communication network <NUM> and the secondary NG-RAN <NUM>.

As illustrated in <FIG> and <FIG>, the network entity is further configured to provide a first packet duplication and elimination, PDE, entity <NUM> in the first GTP-U entity <NUM> and/or the first SDAP entity <NUM> of the primary NG-RAN <NUM> and a second PDE entity <NUM> in the second GTP-U entity <NUM> and/or the second SDAP entity <NUM> of the secondary NG-RAN <NUM>.

The first PDE entity <NUM> is configured to: (a) obtain a first downlink Ethernet frame or DetNet-IP packet <NUM> (illustrated in <FIG>) from the first GTP-U entity <NUM>; (b) generate a first downlink service data unit, SDU, wherein the first downlink SDU comprises the first downlink Ethernet frame or DetNet-IP packet <NUM>; (c) generate a first downlink packet data unit, PDU, based on the first downlink SDU, wherein the first downlink PDU comprises the first downlink Ethernet frame or DetNet-IP packet <NUM> for providing the first downlink PDU to the first SDAP entity <NUM> or a first PDCP entity <NUM> of the primary NG-RAN <NUM>; and (d) provide a copy of the first downlink SDU to the first GTP-U entity <NUM> for forwarding the copy of the first downlink SDU to the secondary NG-RAN <NUM>.

In an embodiment, the second PDE entity <NUM> is configured to: (a) obtain a second downlink Ethernet frame or DetNet-IP packet <NUM> from the second GTP-U entity <NUM>; (b) generate a second downlink service data unit, SDU, wherein the first downlink SDU comprises the second downlink Ethernet frame or DetNet-IP packet <NUM>; (c) generate a second downlink packet data unit, PDU, based on the second downlink SDU, wherein the second downlink PDU comprises the second downlink Ethernet frame or DetNet-IP packet <NUM> for providing the second downlink PDU to the second SDAP entity <NUM> or a second packet data convergence protocol, PDCP, entity <NUM> of the secondary NG-RAN <NUM>; and (d) provide a copy of the second downlink SDU to the second GTP-U entity <NUM> for forwarding the copy of the second downlink SDU to the primary NG-RAN <NUM>.

According to embodiments disclosed herein, in the Xn interface between the master NG-RAN <NUM> and the secondary NG-RAN <NUM>, the master NG-RAN <NUM> may trigger the establishment of at least one user plane data tunnel <NUM> (referred to as GTP-U tunnel <NUM>) for transferring data streams supported by the own default PDU session for the UE <NUM> to the secondary NG-RAN <NUM>, while the secondary NG-RAN <NUM> acknowledges the request of the master, i.e. the primary NG-RAN <NUM> for using the at least one user plane data tunnel <NUM> (referred to as GTP-U tunnel <NUM>) by providing the user plane tunnel endpoint information for transferring the data streams supported by the secondary NG-RAN's own default PDU session for the UE <NUM>. After the establishment, the at least one user plane data tunnel <NUM> is used for mutually transferring the downlink (sent from the URLLC server <NUM>) and uplink (sent from the URLLC client 101a) URLLC endpoint user data streams, i.e. Ethernet frames or DetNet-IP packets. Since each NG-RAN <NUM>, <NUM> is established on each own default PDU session to support transferring one of the two redundant URLLC user data (downlink and uplink) streams, establishing the at least one user plane data tunnel <NUM> in the Xn interface enables each NG-RAN <NUM>, <NUM> to receive both downlink and uplink URLLC endpoint user data streams supported by the counterpart NG-RAN's default PDU session for the UE <NUM>. Thus, each NG-RAN <NUM>, <NUM> may receive both the two redundant URLLC endpoint user data streams in both downlink and uplink.

Each NG-RAN <NUM>, <NUM> may use one or two user plane data tunnels, i.e., GTP-U tunnels <NUM> to transfer URLLC endpoint user streams, i.e. Ethernet frames or DetNet-IP packets supported by its own default PDU session for the UE <NUM> to the other NG-RAN <NUM>, <NUM>. In case of two user plane data tunnels, i.e., GTP-U tunnels <NUM> to transfer URLLC endpoint user streams, i.e. Ethernet frames or DetNet-IP packets, the two NG-RANs <NUM>, <NUM> may agree on one user plane data tunnel used for the downlink flow direction data streams and another user plane data tunnel used for the uplink flow direction data streams. In an embodiment, in case of establishing only one user plane data tunnel, such as the user plane data tunnel <NUM>, the header of this user plane data (i.e., GTP-U) tunnel packet (including the Ethernet frame or DetNet-IP packet as payload) may include the information for identifying the flow direction of data streams, i.e., downlink or uplink.

Since each NG-RAN <NUM>, <NUM> may receive both the two redundant URLLC endpoint user data streams in both downlink and uplink, in an embodiment, each NG-RAN <NUM>, <NUM> may extract the "endpoint user data stream identifiers" (including, for instance, source and destination Ethernet MAC addresses, VLAN tag identifiers or source and destination IP addresses, MPLS tag identifiers, next level protocol type, (e.g. TCP or UDP), source and destination ports) and the sequence number from a received Ethernet frame or a received DetNet-IP packet. The data packets transferred with the default PDU sessions for the UE <NUM> of the two NG-RANs <NUM>, <NUM> received by each NG-RAN may encapsulate the Ethernet frames or DetNet-IP packets of the two redundant URLLC endpoint user data streams. The data packets may be the downlink (from the core network <NUM>) or uplink (from the UE <NUM>) PDU data packets supported by the own NG-RAN's default PDU session, or the user plane data (i.e., GTP-U) packets from the Xn interface encapsulating the Ethernet frames or DetNet-IP packets supported by the counterpart NG-RAN's default PDU session for the UE <NUM>. Normally (without data loss in a communication), for a given data flow direction, i.e., downlink or uplink, each NG-RAN <NUM>, <NUM> may be able to deliver two Ethernet frames or DetNet-IP packets (each in one of the two redundant endpoint user data streams related to the same UE <NUM>) with properties of the same stream endpoint identifier mapping logic, same sequence number, and probably with the same sending time stamp, from two received data packets.

For each data flow direction, i.e. downlink or uplink, each NG-RAN <NUM>, <NUM> may extract the endpoint user data stream identifiers, the sequence number from the received Ethernet frames or DetNet-IP packets (of redundant URLLC endpoint user data streams). Based on extracted endpoint user data stream identifiers, the sequence number and the recorded previously received sequence numbers of the two redundant endpoint user data streams, each NG-RAN <NUM>, <NUM> identifies whether a data packet encapsulating the extracted Ethernet frame or DetNet-IP packet has been received previously.

In case the data packet encapsulating the extracted Ethernet frame or DetNet-IP packet has already been received before, the respective NG-RAN <NUM>, <NUM> may discard the respective data packet. Otherwise, the data packet is further processed by the by other data processing modules of the NG-RAN <NUM>, <NUM> in order to send the related data packets to the UE <NUM> via the radio interface (downlink) or to the core network <NUM> via the N3 interface (uplink). In addition to sending out the processed data packet from the respective NG-RAN <NUM>, <NUM> via the radio interface or the N3 interface, some further operations may be performed, i. e, if the data packet is not received from the Xn interface, the NG-RAN <NUM>, <NUM> may copy the extracted Ethernet frame or DetNet-IP packet and use it to generate a data packet, in particular a GTP-U data packet for sending the data packet to the other NG-RAN <NUM>, <NUM> via the user plane data tunnel, i.e. the GTP-U tunnel <NUM> provided by the Xn interface.

As will be appreciated, by each NG-RAN's function of duplicating the URLLC endpoint user data packet, i.e. Ethernet frame or DetNet-IP packet encapsulated in the user plane data packet of its own NG-RAN's supported PDU session to the other NG-RAN and selecting to process the first arrived data packet in the two data packets which encapsulates the two redundant endpoint user data packets, i.e. Ethernet frames or DetNet-IP packets respectively, embodiments disclosed herein provide in particular the following advantages: (i) enhancement of the availability and reliability of <NUM> communications, e.g., if one of two endpoint user data packets, i.e. Ethernet frames or DetNet-IP packets is lost in the radio communication while another endpoint user data packet is lost in the core network <NUM>, and vice versa; (ii) potential decreasing of end to end communication latency; and (iii) avoiding the single point of failure for conventional dual connectivity approaches in NG-RANs described above.

In the embodiments shown in <FIG> and <FIG>, two redundant PDU sessions are provided for supporting two mutually redundant URLLC endpoint user data streams communicating between the server <NUM> and the client 101a operating on the UE <NUM>. One PDU session spans from the UE <NUM> via the Master NG-RAN <NUM> to UPF1 <NUM> of the core network <NUM>, while the other PDU Session spans from the UE <NUM> via the Secondary NG-RAN <NUM> to the UPF2 <NUM> of the core network <NUM>.

The master NG-RAN <NUM> and the secondary NG-RAN <NUM> use their own radio resources, such as base stations or access points, to support the communication with the UE <NUM>. Embodiments disclosed herein may make use of the lower radio protocol layers' communication between the two NG-RAN functions which has been defined in 3GPP TS <NUM>, NR; Multi-connectivity; Overall description; Stage-<NUM>, release <NUM> for the dual connectivity through the PDCP layer of one NG-RAN communicating with the RLC layer of another NG-RAN (as described above in the context of <FIG> and <FIG>).

Embodiments of the invention may involve one or more of the following procedures. In a first stage, the <NUM> system <NUM> and/or an entity thereof establishes two PDU sessions with the UE <NUM> for two redundant user plane data paths with the UE <NUM> for supporting the communication of two redundant URLLC endpoint user data streams, wherein one PDU session spans from the UE <NUM> via the Master NG-RAN <NUM> to the UPF1 <NUM> of the core network <NUM>, while the other PDU session spans from the UE <NUM> via the Secondary NG-RAN <NUM> to the UPF2 <NUM> of the core network <NUM>. In an embodiment, the master NG-RAN <NUM> may request from the secondary NG-RAN <NUM> to establish the at least one user plane data tunnel, i.e. the GTP-U tunnel <NUM> via the Xn interface for communicating URLLC endpoint user data packets, i.e. Ethernet frames or DetNet-IP packets, while requesting the secondary NG-RAN <NUM> for radio resources for the UE communications. After the secondary NG-RAN <NUM> has acknowledged the establishment, by using the at least one user plane data tunnel, i.e., the GTP-U tunnel <NUM>, each NG-RAN110, <NUM> transfers URLLC endpoint user data packets, i.e. Ethernet frames or DetNet-IP packets, encapsulated in user plane data packets communicating in its own default PDU session for the UE <NUM>, to the counterpart NG-RAN <NUM>, <NUM>. In an embodiment, the corresponding request message used by the Master NG-RAN <NUM> for establishing the at least one user plane data tunnel, i.e. the GTP-U tunnel <NUM> may include one or parameters, such as information about the tunnel <NUM> for receiving URLLC endpoint user data packets, i.e. Ethernet frames or DetNet-IP packets, encapsulated in the user plane data packets communicating in the secondary NG-RAN's default PDU session for the UE <NUM>, and preference information of data flow direction (e.g., uplink or downlink).

If the secondary RAN <NUM> is able to support the functionality requested by the master NG-RAN <NUM>, e.g., processing the received downlink and uplink URLLC endpoint user data streams communicating in the master NG-RAN's default PDU session for the UE <NUM>, sending the corresponding downlink and uplink URLLC endpoint user data streams communicating in the secondary NG-RAN's PDU session for the UE <NUM>, as well as having radio resources to support the communicate with the UE <NUM>, the secondary NG-RAN <NUM> acknowledges the establishment of the user plane data tunnel in the Xn interface including to provide the tunnel information for receiving the downlink and uplink URLLC endpoint user data packets.

When each NG-RAN <NUM>, <NUM> uses this user plane data tunnel, i.e., GTP-U tunnel <NUM> established via the Xn interface to transfer URLLC endpoint user frames, i.e. Ethernet frames or DetNet-IP packets to the other NG-RAN <NUM>, <NUM>, the corresponding functionality of the respective NG-RAN <NUM>, <NUM> may include the capability as well as the necessary information for identifying the flowing direction of data streams, i.e., downlink or uplink. In an embodiment, this information may be provided in a header of the user plane tunnel data packet, i.e., GTP-U data packet, for instance, in the extension header of the user plane tunnel data packet, i.e. GTP-U packet.

As already described above, the Packet Duplication and Elimination (PDE) entities <NUM>, <NUM> may be provided in the GTP-U <NUM>, <NUM> and/or SDAP <NUM>, <NUM> software module layer of the respective NG-RAN <NUM>, <NUM> for identifying the duplication of downlink or uplink URLLC endpoint user data packets, i.e. Ethernet frames or DetNet-IP packets, which are transferred in user plane data flows of the PDU session established in each NG-RAN <NUM>, <NUM> for the UE <NUM>, and eliminating a duplicate copy, if necessary. An exemplary embodiment of the operation of the first and second PDE entity <NUM>, <NUM> is illustrated in <FIG>, which will be described in more detail further below.

The URLLC endpoint user data packet, i.e. Ethernet frame or DetNet-IP packet encapsulated <NUM> in the service data unit (SDU) of a data packet for each layer in the respective NG-RAN <NUM>, <NUM> is shown in <FIG>. In an embodiment, the header information of an URLLC endpoint user data packet, i.e. Ethernet frame or DetNet-IP packet may include a sequence number and endpoint user data stream identifiers. For instance, in case of an Ethernet frame as payload, a set of Ethernet parameters of endpoint user data stream identifiers may be included, such as source and destination Ethernet MAC addresses, VLAN tag identifiers, Ethernet type and the like. In case of an DetNet-IP packet as payload, a set of IP flow parameters of the endpoint user data stream identifiers may be included, such as source and destination IP addresses, MPLS tag identifiers, next level protocol type, source and destination ports and the like.

As already described above, the first and second PDE entity <NUM>, <NUM> of each NG-RAN <NUM>, <NUM> obtains the URLLC endpoint user data packets, i.e. Ethernet frame or DetNet-IP packets and may extract the endpoint user data stream identifiers and the sequence number from the downlink data packet received from both the N3 interface (from the core network <NUM>) and the Xn interface, as well as the uplink data packets received from both the radio interface (from the UE <NUM>) and the Xn interface. In the normal case of no packet loss in the communication process, for a given data flow direction, i.e., downlink or uplink, the first and second PDE entity <NUM>, <NUM> of each NG-RAN <NUM>, <NUM> may be able to generate two Ethernet frames or DetNet-IP packets (each in one of the two redundant endpoint user data streams related to the same UE <NUM>) with properties of the two sets of stream identifiers within a redundant pair of stream identifiers, same sequence number, and probably with the same sending time stamp, from two received data packets. As will be appreciated, this is because one of the two URLLC endpoint user data packets, i.e. Ethernet frames and/or DetNet-IP packets is provided by the other NG-RAN <NUM>, <NUM> through the user plane data tunnel, i.e., GTP-U tunnel <NUM> via the Xn interface.

For each data flow direction, i.e. downlink or uplink, the respective first and second PDE entity <NUM>, <NUM> of each NG-RAN <NUM>, <NUM> extracts endpoint user data stream identifiers, the sequence number and the recorded previously received sequence numbers of the two redundant URLLC endpoint user data packets, i.e. Ethernet frames or DetNet-IP packets, and identifies whether the URLLC endpoint user data packet, i.e. Ethernet frame or DetNet-IP packet, has already been received (as can be taken from its sequence number and endpoint user data stream identifiers, which are encapsulated in the received data packet). If this is the case, i.e. the URLLC endpoint user data packet, i.e. Ethernet frame or DetNet-IP packet has already been received, the respective PDE entity <NUM>, <NUM> may discard the duplicate data packet.

As already mentioned above, an exemplary more detailed embodiment of the operation of the first and second PDE entity <NUM>, <NUM> is illustrated in <FIG>, which comprises the following steps.

In step <NUM>, the first or second PDE entity <NUM>, <NUM> is configured to obtain the Ethernet frame or DetNet-IP packet.

In step <NUM>, the first or second PDE entity <NUM>, <NUM> is configured to extract the endpoint user data stream identifier set and the sequence number from the header of the Ethernet frame or DetNet-IP packet (the sequence number in DetNet layer for DetNet-IP packet).

In step <NUM>, the first or second PDE entity <NUM>, <NUM> is configured to verify whether the downlink or uplink endpoint user data stream identifier set (extracted in step <NUM>) related with the two redundant PDU sessions of the UE <NUM> are already stored in a memory of the respective PDE entity <NUM>, <NUM>. If this is not the case, the first or second PDE entity <NUM>, <NUM> is configured to store the downlink or uplink endpoint user data stream identifier set related with the two redundant PDU sessions of the UE <NUM> in its memory and to associate the sets of stream identifiers exacted from the downlink or uplink Ethernet frame or DetNet-IP packet streams which are encapsulated in data packet of the two redundant PDU sessions (i.e., the first PDU session and the second PDU session) respectively as a redundant pair of stream identifier sets (step <NUM> of <FIG>).

In step <NUM>, the first or second PDE entity <NUM>, <NUM> is configured to verify whether the sequence number (extracted in step <NUM>) of the endpoint user data stream related with the PDU session of the UE <NUM> is already stored in the memory of the respective PDE entity <NUM>, <NUM>, i.e., store the extracted sequence number into memory including associating the extracted sequence number with the redundant pair of stream identifier sets of the extracted set of stream identifiers if the extracted sequence number is not equal to any sequence number in memory associated with the redundant pair of stream identifier sets, wherein the extracted set of stream identifiers is one of the set of the redundant pair of stream identifier sets. If this is the case, i. e, if the extracted sequence number is equal to one of sequence numbers in memory associated with the redundant pair of stream identifier sets, wherein the extracted set of stream identifiers is one of the set of the redundant pair of stream identifier sets, the first or second PDE entity <NUM>, <NUM> is configured to discard the Ethernet frame or DetNet-IP packet and abort the operations of generating a data packet encapsulating the Ethernet frame or DetNet-IP packet to provide for the other protocol layers of the protocol stack of the respective NG-RAN <NUM>, <NUM> (step <NUM> of <FIG>).

If the sequence number (extracted in step <NUM>) is not stored in its memory, the first or second PDE entity <NUM>, <NUM> is further configured to verify whether the corresponding received data packet has been received as part of the PDU session of the NG-RAN <NUM>, <NUM> which the respective PDE entity <NUM>, <NUM> is part of (step <NUM> of <FIG>).

If it is determined in step <NUM> of <FIG> that the corresponding received data packet has not been received as part of the PDU session of the NG-RAN <NUM>, <NUM> which the respective PDE entity <NUM>, <NUM> belongs to (i.e., the corresponding received data packet is received from Xn interface), the first or second PDE entity <NUM>, <NUM> is further configured in step <NUM> of <FIG> to replace the stream identifier set of the endpoint user data stream inside the data packet with the stream identifier set of its corresponding counterpart redundant endpoint user data stream (if existing). The first or second PDE entity <NUM>, <NUM> is configured to continue processing by recording the sequence number in its memory associated with the endpoint user data stream and by providing the data packets to other protocol layers of the protocol stack of the respective NG-RAN <NUM>, <NUM> (step <NUM> of <FIG>).

If it is determined in step <NUM> of <FIG> that the corresponding data packet has been received as part of the PDU session of the NG-RAN <NUM>, <NUM> the respective PDE entity <NUM>, <NUM> belongs to, the first or second PDE entity <NUM>, <NUM> is further configured in step <NUM> of <FIG> to use the obtained Ethernet frame or DetNet-IP packet as payload and the corresponding tunnel information for assembling a corresponding GTP-U packet <NUM> (as illustrated in <FIG>) and to send the assembled GTP-U packet <NUM> via the Xn interface to the other NG-RAN. The first or second PDE entity <NUM>, <NUM> is configured to continue processing by storing the sequence number in its memory including associating with the endpoint user data stream identifier set (see previous description of step <NUM>) and by providing the data packets to other protocol layers of the protocol stack of the respective NG-RAN <NUM>, <NUM> (step <NUM> of <FIG>).

By establishing the at least one user plane data tunnel, i.e. GTP-U tunnel <NUM> via the Xn interface for mutually communicating URLLC endpoint user data stream encapsulated in the user plane data flow of the PDU session established in each NG-RAN <NUM>, <NUM> for the UE <NUM>, each NG-RAN <NUM>, <NUM> receives two URLLC endpoint user data streams transferred by the user plane data flows of the two redundant PDU sessions. This allows preventing the single point of failure of the conventional solution described above.

Due to the functionality of the first and second PDE entity <NUM>, <NUM> to identify duplication of downlink or uplink URLLC endpoint user data packets, i.e. Ethernet frames or IP DetNet-packets, and to eliminate duplicate packets, the availability and reliability of <NUM> communications can be improved. For instance, if one of two data packets of the two redundant PDU sessions is lost in radio communication, the respective first or second PDE entity <NUM>, <NUM> can recover the lost packet smoothly by regenerating the lost data packet to communicate with the core network <NUM> and vice versa. Moreover, the end-to-end communication latency may be decreased. Furthermore, by including the information for identifying the data flow direction of the user data streams in the extended header of a PDU data packet transmitted via the Xn interface, the respective PDE entity <NUM>, <NUM> advantageously can identify whether the data flow is a downlink data flow or an uplink data flow.

<FIG> is a flow diagram illustrating a method <NUM> for providing redundant data paths for communication of data for the UE <NUM> in the <NUM> communication network <NUM>.

The method <NUM> further comprises the following steps performed by the first PDE entity <NUM>:.

The method <NUM> may be performed by the network entity and/or the <NUM> communication network <NUM> described above. Thus, further features of the method <NUM> result directly from the functionality of the network entity and the <NUM> communication network as well as their different embodiments described above and below.

The person skilled in the art will understand that the "blocks" ("units") of the various figures (method and apparatus) represent or describe functionalities of embodiments of the present disclosure (rather than necessarily individual "units" in hardware or software) and thus describe equally functions or features of apparatus embodiments as well as method embodiments (unit = step).

In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus, and method may be implemented in other manners. For example, the described embodiment of an apparatus is merely exemplary. For example, the unit division is merely logical function division and may be another division in an actual implementation.

Claim 1:
A network entity for providing redundant data paths for communication of data for a user equipment, UE, (<NUM>) in a communication network (<NUM>), wherein the network entity is configured to:
establish a first packet data unit, PDU session for the UE (<NUM>) using a primary next generation radio access network, NG-RAN, (<NUM>) implementing a first protocol stack, wherein the first protocol stack includes at least one first GPRS tunnelling protocol user plane, GTP-U, entity (<NUM>) and a first service data adaption protocol, SDAP, entity (<NUM>), wherein the establishment of the first PDU session includes establishing at least one first GTP-U tunnel between a core network (<NUM>) of the communication network (<NUM>) and the primary NG-RAN (<NUM>);
establish a second PDU session for the UE (<NUM>) using a secondary NG-RAN (<NUM>) implementing a second protocol stack, wherein the second protocol stack includes at least one second GTP-U entity (<NUM>) and a second SDAP entity (<NUM>), wherein the establishment of the second PDU session includes establishing at least one second GTP-U tunnel between the core network (<NUM>) of the communication network (<NUM>) and the secondary NG-RAN (<NUM>); and
provide a first packet duplication and elimination, PDE, entity (<NUM>) in the first GTP-U entity (<NUM>) and/or the first SDAP entity (<NUM>) of the primary NG-RAN (<NUM>) and a second PDE entity (<NUM>) in the second GTP-U entity (<NUM>) and/or the second SDAP entity (<NUM>) of the secondary NG-RAN (<NUM>), wherein the first PDE entity (<NUM>) is configured to:
(a) obtain a first downlink Ethernet frame or DetNet-IP packet (<NUM>) from the first GTP-U entity (<NUM>);
(b) generate a first downlink service data unit, SDU, wherein the first downlink SDU comprises the first downlink Ethernet frame or DetNet-IP packet (<NUM>);
(c) generate a first downlink packet data unit, PDU, based on the first downlink SDU, wherein the first downlink PDU comprises the first downlink Ethernet frame or DetNet-IP packet (<NUM>) for providing the first downlink PDU to the first SDAP entity (<NUM>) or a first packet data convergence protocol, PDCP, entity (<NUM>) of the primary NG-RAN (<NUM>); and
(d) provide a copy of the first downlink SDU to the first GTP-U entity (<NUM>) or a further first GTP-U entity for forwarding the copy of the first downlink SDU to the secondary NG-RAN (<NUM>).