Patent Description:
IAB has been introduced in Release <NUM> (Rel-<NUM>) of 3GPP specifications as a key enabler for fast and cost-efficient deployments. IAB nodes use the same or different spectrum and air interface for access and backhaul, creating a hierarchical wireless multi-hop (multiple backhaul links) network between sites. The hops eventually terminate at an IAB donor that is connected by means of a conventional fixed backhaul to the core network. An IAB node contains a mobile termination (MT) part that acts as user equipment (UE) towards its parent distributed unit (DU), and a DU part that acts as a base station towards the mobile terminal and/or the child IAB node. An IAB donor contains a central unit (CU) part and a DU part. An IAB DU can provide one or more cells to serve UEs.

Due to possible failures on the backhaul (BH) connections or changes in the IAB topology or IAB mobility, an IAB node may need to change its serving node which can be under the same or different IAB donor(s). In the latter case, a procedure of handover and connection to a new IAB donor is time consuming. This may result in an interruption of connections and services at the UEs connected to the IAB node.

<CIT> relates to a method and apparatus for lossless uplink data transmission of an IAB network in a wireless communication system.

<CIT> provides a connection establishment method and device, a set access backhaul node and a storage medium. The method comprises acquiring address information of a first centralized unit (CU) and establishing connection with the first CU according to the address information of the first CU.

In general, example embodiments of the present disclosure provide devices, methods, apparatuses and computer readable media for transferring traffic in IAB communication.

In a first aspect, there is provided a first apparatus. The first apparatus comprises means for transmitting, at a first Central Unit-Control Plane (CU-CP) of a first Integrated Access and Backhaul (IAB) donor to a second CU-CP of a second IAB donor, a request to transfer target traffic via a Distributed Unit (DU) of the second IAB donor, the request comprising first information of the target traffic, wherein the first information comprises at least one of: a traffic type indicating whether the target traffic comprises user plane traffic or control plane traffic, or a Quality of Service parameter for the target traffic; and means for receiving, from the second CU-CP, second information to be used for configuring the target traffic to be routed via the DU of the second IAB donor, wherein the second information, determined by the second CU-CP, is based on the first information.

In a second aspect, there is provided a second apparatus. The second apparatus comprises means for receiving, at a second Central Unit-Control Plane (CU-CP) of a second Integrated Access and Backhaul (IAB) donor from a first CU-CP of a first IAB donor, a request to transfer target traffic via a Distributed Unit (DU) of the second IAB donor, the request comprising first information of the target traffic, wherein the first information comprises at least one of: a traffic type indicating whether the target traffic comprises user plane traffic or control plane traffic, or a Quality of Service parameter for the target traffic; means for determining, based on the first information, second information to be used for the target traffic; and means for transmitting the second information to the first CU-CP.

Through the more detailed description of some example embodiments of the present disclosure in the accompanying drawings, the above and other objects, features and advantages of the present disclosure will become more apparent, wherein:.

Further, when a particular feature, structure, or characteristic is described in connection with an example embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

As used herein, the term "communication network" refers to a network following any suitable communication standards, such as Long Term Evolution (LTE), LTE-Advanced (LTE-A), Wideband Code Division Multiple Access (WCDMA), High-Speed Packet Access (HSPA), Narrow Band Internet of Things (NB-IoT), New Radio (NR) and so on. Furthermore, the communications between a terminal device and a network device in the communication network may be performed according to any suitable generation communication protocols, including, but not limited to, the first generation (<NUM>), the second generation (<NUM>), <NUM>, <NUM>, the third generation (<NUM>), the fourth generation (<NUM>), <NUM>, the future fifth generation (<NUM>) communication protocols, and/or any other protocols either currently known or to be developed in the future. Embodiments of the present disclosure may be applied in various communication systems. Given the rapid development in communications, there will of course also be future type communication technologies and systems with which the present disclosure may be embodied. It should not be seen as limiting the scope of the present disclosure to only the aforementioned system.

As used herein, the term "network device" refers to a node in a communication network via which a terminal device accesses the network and receives services therefrom. The network device may refer to a base station (BS) or an access point (AP), for example, a node B (NodeB or NB), an evolved NodeB (eNodeB or eNB), a NR NB (also referred to as a gNB), a Remote Radio Unit (RRU), a radio header (RH), a remote radio head (RRH), a relay, a low power node such as a femto, a pico, and so forth, depending on the applied terminology and technology. Also, an IAB-node or IAB-DU is an example of network device. In the following description, the terms "network device", "BS", and "node" may be used interchangeably.

Example embodiments of the present disclosure are directed to a radio access network with wireless backhaul of the access points. The backhaul can be multi-hop or meshed. An important application of embodiments of the present disclosure is for IAB communication in a 3GPP IAB network with terminal devices, IAB nodes and wired IAB donor nodes. In the following, embodiments of the present disclosure will be described with reference to the 3GPP IAB network. It is to be understood that embodiments of the present disclosure may also be applied to any other network with wireless backhaul.

<FIG> illustrates a block diagram of a system <NUM> for IAB communication. As shown in <FIG>, the system <NUM> comprises a core network (CN) <NUM>, an IAB donor <NUM>, IAB nodes <NUM>-<NUM> and <NUM>-<NUM> (collectively referred to as "IAB nodes <NUM>" or individually referred to as "IAB node <NUM>"), and terminal devices <NUM>-<NUM>, <NUM>-<NUM> and <NUM>-<NUM> (collectively referred to as "terminal devices <NUM>" or individually referred to as "terminal device <NUM>"). As used herein, the terms "IAB node" and "IAB device" can be used interchangeably. The terms "IAB donor node", "IAB donor" and "IAB donor device" can be used interchangeably.

In the architecture as shown in <FIG>, the CN interfaces are terminated at the IAB donor <NUM> and therefore the relaying is only radio access network (RAN) functionality. The architecture leverages a split gNB architecture for the CU and DU so that the CU functions are at the IAB donor <NUM> and the DU function is at the IAB donor DU <NUM> or at the IAB node <NUM>. For the connection setup and communication with the parent node (which can be another IAB node or the IAB donor), the IAB node <NUM> hosts the MT function corresponding to UE operation or a part of the UE operation.

The IAB donor <NUM> may comprise a CU <NUM> (also referred to as "IAB donor CU <NUM>") and a DU <NUM> (also referred to as "IAB donor DU <NUM>"). It is to be understood that the CU <NUM> and DU <NUM> may be implemented in the same device, or in different devices. The CU <NUM> may further comprise a CU-Control Plane (CU-CP) <NUM>, and one or more CU-User Plane (CU-UP) <NUM>. It is to be understood that the CU-CP <NUM> and CU-UP <NUM> may be implemented in the same device, or in different devices. The IAB node <NUM>-<NUM> may comprise a MT part <NUM>-<NUM> and a DU <NUM>-<NUM>. The IAB node <NUM>-<NUM> may comprise a MT part <NUM>-<NUM> and a DU <NUM>-<NUM>. The MT parts <NUM>-<NUM> and <NUM>-<NUM> are also collectively referred to as "IAB MTs <NUM>" or individually referred to as "IAB MT <NUM>". The DUs <NUM>-<NUM> and <NUM>-<NUM> are also collectively referred to as "IAB DUs <NUM>" or individually referred to as "IAB DU <NUM>".

The IAB donor DU <NUM> or each IAB DU <NUM> can provide one or more cells to serve terminal devices and/or one or more IAB-MTs <NUM>. For example, as shown in <FIG>, the IAB donor DU <NUM> serves the terminal device <NUM>-<NUM>, the IAB DU <NUM>-<NUM> serves the terminal device <NUM>-<NUM> and the IAB DU <NUM>-<NUM> serves the terminal device <NUM>-<NUM>.

The IAB MT <NUM> of an IAB node <NUM> may act as a UE towards its parent node. For example, the IAB MT <NUM>-<NUM> may act as a UE towards the IAB donor <NUM> (i.e., the IAB donor DU <NUM>) and the IAB MT <NUM>-<NUM> may act as a UE towards the IAB node <NUM>-<NUM> (i.e., the IAB DU <NUM>-<NUM>). On the child links, the IAB DU <NUM> of an IAB node <NUM> may act as a network device (such as, gNB) towards its next-hop IAB node. For example, the IAB donor DU <NUM> may act as a gNB towards the IAB node <NUM>-<NUM> and the IAB DU <NUM>-<NUM> may act as a gNB towards the IAB node <NUM>-<NUM>. On the access links, the IAB donor <NUM> and the IAB nodes <NUM> may act as normal network devices, providing radio interfaces for the terminal devices <NUM> in their coverage areas.

BH radio link control (RLC) channel(s) can be set up between the IAB MT <NUM> and a DU of the parent node and an adaptation layer called a Backhaul Adaptation Protocol (BAP) is agreed to be on top of a RLC layer. The IAB DU <NUM> connects to the IAB donor CU <NUM> with an F1 interface which supports IAB functions. For example, the IAB DU <NUM>-<NUM> connects to the IAB donor CU <NUM> via the F1 interface <NUM> and the IAB DU <NUM>-<NUM> connects to the IAB donor CU <NUM> via the F1 interface <NUM>. The F1 interface may comprise a F1-C interface and a F1-U interface. The IAB DU <NUM> connects to the IAB Donor CU-CP <NUM> via the F1-C interface, and the IAB DU <NUM> connects to the IAB Donor CU-UP <NUM> via the F1-U interface.

The F1 interface traffic includes the traffic of the F1-U interface (also referred to as "F1-U traffic") and the traffic of the F1-C interface (also referred to as "F1-C traffic"). The F1 interface traffic is transported on top of the adaptation layer. The IAB thus implements L2 relaying. To enable the downlink (DL) F1 traffic routed to the serving IAB donor DU <NUM> for the IAB node <NUM>, the IAB node <NUM> is assigned with an Internet Protocol (IP) address(s) (e.g., outer IP address when IPSec tunnel is enabled) that is anchored in the IAB donor DU <NUM>. When the IAB donor CU <NUM> sends the DL F1 traffic to the IAB node <NUM>, the F1 traffic is routed to the IAB donor DU <NUM> based on the IP address. The IAB donor DU <NUM> maps the DL F1 traffic to a related BH RLC channel based on a configuration that is previously configured by the IAB donor CU <NUM>. The configuration includes the differentiated services code point (DSCP) and/or Internet Protocol Version <NUM>(IPv6) Flow Label and/or IP address in order to identify the DL F1 traffic, as well as the related BH RLC channel information. This requires that the IAB donor CU <NUM> (e.g., donor CU-CP or donor CU-UP) uses specific DSCP and/or IPv6 Flow Label and/or IP address in order to support the traffic mapping in the IAB donor DU <NUM>.

Moreover, during topology adaptation, the serving IAB donor DU for an IAB node <NUM> may be changed from a source IAB donor DU to a target IAB donor DU. Accordingly, the IAB node <NUM> may get a new IP address(s) that is anchored in the target IAB donor DU.

Communications in the environment <NUM> may be implemented according to any proper communication protocol(s), comprising, but not limited to, cellular communication protocols of the first generation (<NUM>), the second generation (<NUM>), the third generation (<NUM>), the fourth generation (<NUM>) and the fifth generation (<NUM>) and on the like, wireless local network communication protocols such as Institute for Electrical and Electronics Engineers (IEEE) <NUM> and the like, and/or any other protocols currently known or to be developed in the future. Moreover, the communication may utilize any proper wireless communication technology, comprising but not limited to: Code Divided Multiple Address (CDMA), Frequency Divided Multiple Address (FDMA), Time Divided Multiple Address (TDMA), Frequency Divided Duplexer (FDD), Time Divided Duplexer (TDD), Multiple-Input Multiple-Output (MIMO), Orthogonal Frequency Divided Multiple Access (OFDMA) and/or any other technologies currently known or to be developed in the future.

In an aspect, due to possible failures on the BH connections or changes in the IAB topology or IAB mobility, an IAB node may need to change its serving node. Such change of the backhaul topology may involve the change of the parent IAB node of the IAB node or even the IAB donor. The latter case where the IAB donor is changed may be considered as Inter-Donor topology adaptation. In another aspect, topology redundancy has been proposed to enable robust operation, for example, in case of backhaul link blockage, and to balance load across backhaul links. In the scenario of Inter-Donor topology redundancy, an IAB node having a plurality of IAB DUs may have a plurality of F1 interfaces with a plurality of IAB donor CUs where an IAB DU is interfaced with a respective IAB donor CU.

<FIG> and <FIG> illustrate example IAB environments <NUM> and <NUM> in which embodiments of the present disclosure can be implemented. As shown in <FIG> and <FIG>, the environments <NUM> and <NUM> comprise an IAB donor <NUM> (also referred to as "first IAB donor" or "source donor" or "donor1" in the following), an IAB donor <NUM> (also referred to as "second IAB donor" or "target donor" or "donor2" in the following), an IAB node <NUM> (also referred as "source parent cell" or "source parent"), an IAB node <NUM> (also referred as "target parent cell" or "target parent"), an IAB node <NUM> and terminal devices <NUM>-<NUM> and <NUM>-<NUM> (collectively referred to as "terminal devices <NUM>" or individually referred to as "terminal device <NUM>").

The IAB donor <NUM> comprises a CU <NUM> (also referred to as "IAB donor CU <NUM>" or "donor1 CU <NUM>" in the following) and a DU <NUM> (also referred to as "IAB donor DU <NUM>" or "donor1 DU <NUM>" in the following). The IAB donor CU <NUM> may comprises a CU-CP <NUM> also referred to as "donor1 CU-CP <NUM>" in the following and a CU-UP <NUM> also referred to as "donor1 CU-UP <NUM>" in the following.

The IAB donor <NUM> comprises a CU <NUM> (also referred to as "IAB donor CU <NUM>" or "donor2 CU <NUM>" in the following) and a DU <NUM> (also referred to as "IAB donor DU <NUM>" or "donor2 DU <NUM>" in the following). The IAB donor CU <NUM> may comprises a CU-CP <NUM> also referred to as "donor2 CU-CP <NUM>" in the following and a CU-UP <NUM> also referred to as "donor2 CU-UP <NUM>" in the following.

The IAB node <NUM>, which acts as an intermediate node between the IAB donor <NUM> and the IAB node <NUM>, comprises a MT <NUM> and a DU <NUM>. Likewise, the IAB node <NUM>, which acts as an intermediate node between the IAB donor <NUM> and the IAB node <NUM>, comprises a MT <NUM> and a DU <NUM>.

The IAB node <NUM> comprises a MT <NUM> (also referred to as "IAB MT <NUM>" in the following) and at least one DU <NUM>-<NUM> (also referred to as "IAB DU <NUM>-<NUM>" in the following). For example, as shown in <FIG>, in some example embodiments, the IAB node <NUM> may further comprise a DU <NUM>-<NUM> (also referred to as "IAB DU <NUM>-<NUM>" in the following). The DUs <NUM>-<NUM> and <NUM>-<NUM> may be collectively referred to as "IAB DUs <NUM>" or individually referred to as "IAB DU <NUM>". It is to be understood that the number of DUs in the IAB node <NUM> shown in <FIG> and <FIG> is only for the purpose of illustration without suggesting any limitation to the scope of the present disclosure.

<FIG> shows a topology adaptation scenario. The IAB node <NUM> is initially connected to the IAB node <NUM> and thus the IAB donor <NUM> acts as a serving IAB donor for the IAB node <NUM>. During a topology adaptation, the IAB node <NUM> migrates from the source IAB node <NUM> to the target IAB node <NUM> of a different CU. Accordingly, as shown in <FIG>, an F1 interface <NUM> (including the F1-C interface and the F1-U interface) between the IAB DU <NUM> (for example, DU <NUM>-<NUM>) and the IAB donor CU <NUM> is established, and a BH link between the IAB MT <NUM> and the DU <NUM> is also established. After topology adaptation, an F1 interface <NUM> between the IAB DU <NUM> (for example, DU <NUM>-<NUM>) and the IAB donor CU <NUM> is established, and a BH link between the IAB MT <NUM> and the DU <NUM> is also established.

<FIG> shows a topology redundancy scenario. As shown in <FIG>, the IAB node <NUM> is connected to both the IAB nodes <NUM> and <NUM> and thus the IAB donors <NUM> and <NUM> act as serving IAB donors for the IAB node <NUM>. The F1 interface <NUM> between the IAB DU <NUM>-<NUM> and the IAB donor CU <NUM> is established. The BH link between the IAB MT <NUM> and the DU <NUM> is also established. An F1 interface <NUM> between the IAB DU <NUM>-<NUM> and the IAB donor CU <NUM> is established. The BH link between the IAB MT <NUM> and the DU <NUM> is also established. It is also possible that the IAB node <NUM> only have one DU, and the DU in the IAB node <NUM> only has the F1 interface <NUM> or the F1 interface <NUM>.

It is to be understood that the number of IAB donors, IAB nodes, and terminal devices connected to the IAB nodes is only for the purpose of illustration without suggesting any limitation to the scope of the present disclosure. It is also to be understood that the number of CUs, DUs and MTs is only for the purpose of illustration without suggesting any limitation to the scope of the present disclosure. The communication system may include any suitable number of IAB donors, IAB nodes, and terminal devices adapted for implementing example embodiments of the present disclosure. For example, in some example embodiments, the IAB node <NUM> may be directly connected to an IAB donor, e.g., the IAB donor <NUM> or <NUM>. For another example, in some example embodiments, there may be more than one intermediate IAB node between the IAB node <NUM> and an IAB donor, e.g., the IAB donor <NUM> or <NUM>. The transmission path via the DU <NUM> and one or more intermediate IAB nodes (for example, IAB node <NUM>) is referred to as a "source path". The transmission path via the DU <NUM> and one or more intermediate IAB nodes (for example, IAB node <NUM>) is referred to as a "target path".

Conventionally, traffic between the CU of an IAB donor and the IAB node cannot be transmitted and routed via a DU of another IAB donor. For example, according to conventional solutions, in <FIG> and <FIG>, the traffic of F1 interface <NUM> could only be transmitted via the source path, and the traffic of F1 interface <NUM> or F1 interface <NUM> could only be transmitted via the target path. In the topology adaptation scenario where a serving IAB donor for an IAB node is changed from a source IAB donor to a target IAB donor, a CU of the source IAB donor cannot send its DL F1 traffic to the IAB node via the target path, i.e. via a DU of the target IAB donor, and a CU of the target IAB donor cannot send its DL F1 traffic to the IAB node via the source path, i.e. via a DU of the source IAB donor. This means only that one of the F1 interface (either F1 interface <NUM>, or F1 interface <NUM>/<NUM>) could be activated at any given time. Since establishment of a secure connection between the IAB node and the target IAB donor is time consuming, an interruption of connections and services at the terminal devices connected to the IAB node may be resulted. Therefore, it is desirable in topology adaptation scenario that the F1 traffic between the CU of the source IAB donor and an IAB node can be transmitted and routed via the DU of the target IAB donor, so that the IAB node can be first handed over to the target donor, setup the BH RLC channel with target parent cell, and continue the F1 traffic between the source IAB donor and IAB node routed via the target path, before the security connection is established via the target path. For example, according to some embodiments of the present disclosure, the traffic sent from IAB donor CU <NUM> to the IAB node <NUM> is routed to DU <NUM> and is further transmitted to the IAB node <NUM>, by setting the target IP address of the IP header to the IAB node <NUM>'s IP address that is anchored in the DU <NUM>. When the IAB <NUM> node send uplink traffic to CU <NUM>, the traffic is sent via the target path, i.e. the traffic is sent to the intermediate IAB node <NUM> and is further transmitted to the DU <NUM>, and the DU <NUM> then forwards the traffic to the CU <NUM>. By using the target path for the traffic of the F1 interface <NUM>, it enables the IAB donor CU <NUM> to first handover the IAB to the target donor, while the F1 traffic for the F1 interface <NUM> can still be transmitted via the target path. This can reduce the interruption to the UE.

According to some other embodiments of the present disclosure, the interruption may be reduced by first establishing the F1 interface <NUM> over the source path. The traffic for the F1 interface between the target donor and an IAB node may be transmitted over the source path, i.e. via a DU of the source donor. For example, the traffic sent from the IAB donor CU <NUM> to the IAB node <NUM> is routed to the DU <NUM> and is further transmitted to IAB node <NUM>, by setting the target IP address of the IP header to the IAB node <NUM>'s IP address that is anchored in the DU <NUM>. When the IAB <NUM> node send uplink traffic to the CU <NUM>, the traffic is sent via the source path, i.e. the traffic is sent to the intermediate IAB node <NUM> and is further transmitted to the DU <NUM>, and the DU <NUM> then forwards the traffic to CU <NUM>. By using the source path for the F1 interface <NUM>, it enables the IAB donor CU <NUM> to initiate the handover procedure for the UEs connected to the IAB node <NUM>, while the IAB node <NUM> is still connected to the IAB donor <NUM>. This allows the source donor to first handover the UEs to the target donor then handover the IAB node to the target donor, thus reducing the interruption.

In the topology redundancy scenario where an IAB node is connected to at least two IAB donor and the BH RLC channels are established between the IAB node and a source parent cell (e.g. between the IAB node <NUM> and the IAB node <NUM>) and between the IAB node and a target parent cell (e.g. between the IAB node <NUM> and the IAB node <NUM>), according to conventional solutions, the traffic between a CU of a first IAB donor and the IAB node cannot be transmitted and routed via a DU of a second IAB donor, and the traffic between a CU of a second IAB donor and the IAB node cannot be transmitted and routed via a DU of a first IAB donor. For example, if a path from a DU of the first IAB donor to the IAB node is blocked, the DL F1 traffic of the first IAB donor cannot be routed to the IAB node. Thus, the benefit of topology redundancy is lost. Therefore, it is desirable in topology redundancy scenario that the traffic between the CU of the first IAB donor and the IAB node can be transmitted and routed via the DU of the second IAB donor, and the traffic between the CU of the second IAB donor and the IAB node can be transmitted and routed via the DU of the first IAB donor.

Embodiments of the present disclosure provide a solution for transferring traffic in IAB communication, so as to solve the above problem and one or more of other potential problems. In this solution, a first IAB donor (e.g., a CU-CP of the first IAB donor) transmits to a second IAB donor (e.g., a CU-CP of the second IAB donor) a request to transfer target traffic via a DU of the second IAB donor. The target traffic may comprise F1 traffic between the first IAB donor and the IAB node. In some example embodiments, the target traffic may comprise F1-C traffic between the CU-CP of the first IAB donor and the IAB node. Alternatively, or in addition, in some example embodiments, the target traffic may comprise F1-U traffic between the CU-UP of the first IAB donor and the IAB node. The request comprises characteristic information of the target traffic. The first IAB donor then receives, from the second IAB donor, traffic identification information to be used for configuring the target traffic. This solution enables an IAB donor to route traffic to an IAB node via another IAB donor, for example, via a DU of the other IAB donor. In this way, this solution can improve the reliability and robustness of the IAB communication. For example, in the topology adaptation scenario, this solution can allow the UEs continuing the transmission and reception before the F1-C interface and F1-U interface are migrated to the target Donor, thus reducing the impacts on the UEs served by the migrating IAB node during an Inter-Donor topology adaptation. For another example, in the topology redundancy scenario, this solution can increase the number of available routing paths.

Some example embodiments are now detailed below. <FIG> illustrates a flowchart illustrating an example process <NUM> for transferring traffic according to some embodiments of the present disclosure. For the purpose of discussion, the process <NUM> will be described with reference to <FIG> and <FIG>. The process <NUM> at least involves the IAB donor <NUM> and the IAB donor <NUM>. In some example embodiments, the process <NUM> may further involve the IAB node <NUM>.

As shown in block <NUM> of <FIG>, in some example embodiments, the IAB node <NUM> may be initially connected to the IAB donor <NUM>. For example, the F1 interface <NUM> is setup between the donor1 CU <NUM> and the DU <NUM>. In this situation, F1 traffic may be transmitted from the donor1 CU <NUM> to the IAB node <NUM>, e.g., the IAB DU <NUM> as shown in <FIG> and <FIG>. For example, the F1-C traffic from the CU-CP <NUM> to the IAB DU <NUM> in the IAB node <NUM> may be routed <NUM> to the donor1 DU <NUM>. The donor1 DU <NUM> may then perform the traffic mapping to a related BH RLC channel, and transmit <NUM> the F1-C traffic to the IAB DU <NUM> over wireless backhaul. Likewise, the F1-U traffic from the CU-UP <NUM> to the IAB DU <NUM> in the IAB node <NUM> may be routed <NUM> to the donor1 DU <NUM>. The donor1 DU <NUM> may perform the traffic mapping to a related BH RLC channel, and then transmit <NUM> the F1-U traffic to the IAB DU <NUM>.

In some example embodiments, for example in the topology redundancy scenario, the IAB node <NUM> may be connected to both the IAB donor <NUM> and the IAB donor <NUM>, either directly connected to the donor DUs of IAB donor <NUM> and IAB donor <NUM>, or with one or more intermediate nodes between the IAB node <NUM> and the donor DUs of IAB donor <NUM> and IAB donor <NUM>. In this situation, the F1-C/U traffic may be transmitted from the donor <NUM> CU <NUM> to the IAB node <NUM> and from the donor2 CU <NUM> to the IAB node <NUM>.

In the example process <NUM>, the IAB donor <NUM> transmits <NUM> to the IAB donor <NUM> a request to transfer target traffic of an interface between the IAB donor <NUM> and the IAB node <NUM> via the donor2 DU <NUM> of the IAB donor <NUM>. The target traffic may comprise F1 traffic between the IAB donor <NUM> and the IAB node <NUM>. In some example embodiments, the target traffic may comprise F1-C traffic between the CU-CP <NUM> of the IAB donor <NUM> and the IAB node <NUM>. Alternatively, or in addition, the target traffic may comprise F1-U traffic between the CU-UP <NUM> of the IAB donor <NUM> and the IAB node <NUM>. In the following, such a request may be referred to as a "route request" for the purpose of discussion without any limitation to the scope of the present disclosure. For example, the CU-CP <NUM> of the donor1 CU <NUM> may transmit the route request to the CU-CP <NUM> of the donor2 CU <NUM>. The route request may request the IAB donor <NUM> to enable transferring the target traffic (e.g., F1-C/U traffic from the donor1 CU <NUM>) to the IAB node <NUM> via the donor2 DU <NUM>.

A trigger for transmitting the route request may depend on specific scenarios. In the topology adaptation scenario as shown in <FIG>, the IAB node <NUM> may migrate from the IAB node <NUM> to the IAB node <NUM>. Thus, the IAB MT <NUM> may be going to connect to the DU <NUM> of the IAB node <NUM>. In this scenario, the trigger for transmitting the route request may be a handover decision made by the donor1 CU <NUM>, e.g., due to a load balance reason or any other reasons. In the topology redundancy scenario as shown in <FIG>, the IAB node <NUM> may be connected to both the IAB donor <NUM> and the IAB donor <NUM>. In this scenario, the trigger for transmitting the route request may be establishment of the connection to the IAB donor <NUM>. Alternatively, or in addition, the trigger for transmitting the route request may be backhaul link blockage in a route path from the IAB donor <NUM> to the IAB node <NUM> or load balance across backhaul links. It is to be understood that the above triggers are provided as examples and the scope of the present disclosure is not limited in this regard.

The route request may include identity information of the IAB node <NUM>. For example, the route request may include an identity of the IAB MT <NUM>.

The route request may include characteristic information (also referred to as "first information") of the target traffic to be routed. In some example embodiments, the characteristic information may include a traffic type indicating whether the target traffic comprise control plane traffic or user plane traffic. For example, the traffic type may indicate that the target traffic comprises F1-C traffic, or F1-U traffic, or traffic other than the F1-C traffic and F1-U traffic. In some other example embodiments, the traffic type may be not included or indicate that the target traffic comprises both F1-C traffic and F1-U traffic, which means that the F1-C traffic and F1-U traffic are treated in a same way. If the target traffic comprises the F1-C traffic, the traffic type may further indicate whether the F1-C traffic includes F1-C signaling associated with a UE, or F1-C signaling not associated with a UE.

Alternatively, or in addition, in some example embodiments, the characteristic information may include a Quality of Service (QoS) parameter for the target traffic. The QoS parameter may include, but not limited to, <NUM> QoS Identifier (5QI), priority level, Maximum Flow Bit Rate Downlink, Maximum Flow Bit Rate Uplink, Guaranteed Flow Bit Rate Downlink, Guaranteed Flow Bit Rate Uplink, packet delay budget, packet error rate, etc. If the target traffic comprises the F1-U traffic, the characteristic information may include at least one of the above QoS parameters for the F1-U traffic. The QoS parameter may also be needed for F1-C traffic.

In some example embodiments, the target traffic may be directed to at least one terminal devices in communication with the IAB node <NUM>, for example, UEs. Accordingly, the characteristic information may further include an identity of the at least one terminal device. For example, the traffic type and/or the QoS parameter may be provided for each of the UEs and thus the characteristic information may further an identity of each of the UEs. Alternatively, or in addition, the characteristic information may further include an identity of a data radio bearer (DRB) for the at least one terminal device. For example, the traffic type and/or the QoS parameter may be provided for each DRB of a UE and thus the characteristic information may further an identity of the DRB for the UE. Similarly, the characteristic information may include an identity of a tunnel for the at least one terminal device. For example, the traffic type and/or the QoS parameter may be provided for each F1-U tunnel of a UE and thus the characteristic information may further an identity of the F1-U tunnel for the UE.

In these example embodiments, which identity(ies) of the terminal device, the DRB and the tunnel is included in the characteristic information may depend on mapping of UE-bearers to BH RLC channels. As an example, in the case of <NUM>:<NUM> mapping of UE-bearers to BH RLC channels, the traffic type and/or the QoS parameter may be provided for each DRB of a UE. Accordingly, the characteristic information may comprise an identity of the UE as well as an identity of each DRB or F1-U tunnel of the UE. In the following, the identity of the DRB is also referred to as a "DRB identity" and the identity of the F1-U tunnel is also referred to as a "F1-U tunnel identity".

In some example embodiments, the route request may further comprise a suggestion on transferring the target traffic. As an example, the route request may comprise a suggested value for a DSCP of the target traffic or an Internet Protocol Version <NUM> (IPv6) Flow Label for the target traffic, which may be provide by the donor1 CU <NUM>. The suggested value may be a value used by the donor1 CU <NUM> for transmitting the same or similar type of target traffic. For example, the DSCP and/or IPv6 Flow Label are used for the F1-C traffic or F1-U traffic sent from donor1 CU <NUM> to the IAB node <NUM>, that are routed via the donor1 DU <NUM>. As another example, the route request may include other information or preference related to the QoS of the target traffic.

The route request may be implemented in any suitable manner. The route request may reuse another request. For example, the route request may be an Xn HANDOVER REQUEST message for the IAB MT <NUM> or an Xn S-NODE ADDITION REQUEST message. Alternatively, the route request may be a request dedicated for transferring traffic via a DU of a different IAB donor.

As shown in <FIG>, after receiving the route request from the IAB donor <NUM>, the IAB donor <NUM> (e.g., the donor2 CU <NUM>) determines <NUM> traffic identification information or traffic mapping information (also referred to as "second information") based on the characteristic information of the target traffic. The traffic identification information is to be used for configuring and transferring the target traffic. For example, at least part of the traffic identification information may be incorporated by the donor1 CU <NUM> into an IP packet header of a F1 packet, such that the IAB donor <NUM> (e.g., the DU <NUM>) can identify the F1 packet and maps the F1 packet to an appropriate BH RLC channel. After receiving the route request from the IAB donor <NUM>, the IAB donor <NUM> (e.g., the donor2 CU <NUM>) may establish the BH RLC channel(s) between the IAB node and the target parent node, for example, between IAB node <NUM> and IAB node <NUM> as shown in <FIG> and <FIG>. The establishment of the BH RLC channel(s) may consider the characteristic information of the target traffic. The establishment of the BH RLC channel(s) may also be performed early, for example, when the parent cell is added as a secondary node for the IAB node in topology redundancy scenario. The IAB node <NUM> is configured with the uplink traffic mapping and routing information, which is to be used to transmit the target traffic. The intermediate IAB node(s) are also configured with the traffic mapping and routing information, which is to be used to transmit/route the target traffic.

The IAB donor <NUM> may allocate a transport layer address for the IAB node <NUM>. For example, the CU-CP <NUM> of the donor2 CU <NUM> may allocate an IP address to the IAB node <NUM>. In some example embodiments, the CU-CP <NUM> may allocate a Backhaul Adaptation Protocol (BAP) address to be used by the IAB node <NUM>. For example, the IAB node <NUM> can identify a BAP packet that needs to be terminated at the IAB node <NUM> by checking the BAP address of the Routing Identity part against a previously allocated BAP address. The CU-CP <NUM> may also allocate a routing identity to be used by traffic of a terminal device. The CU-CP <NUM> may also allocate a BAP path identity.

The IAB donor <NUM> may further allocate a DSCP for the target traffic. The DSCP for the target traffic may be allocated by the donor2 CU <NUM> based on the characteristic information, e.g., the QoS parameter. As an example, traffic with a QoS of #A may be allocated with a DSCP of #C and traffic with a QoS of #B may be allocated with a DSCP of #D.

Alternatively, or in addition, the IAB donor <NUM> may allocate a Flow Label for the target traffic, e.g., an IPv6 Flow Label for the target traffic. The Flow Label for the target traffic may be allocated by the donor2 CU <NUM> based on the characteristic information, e.g., the QoS parameter.

In the case of <NUM>:<NUM> mapping of UE-bearers to BH RLC channels, the traffic identification information may be determined for each DRB or F1-U tunnel of the terminal device. For example, the donor2 CU <NUM> may allocate the DSCP or the Flow Label for traffic of each DRB of a UE.

In the example embodiments where the route request comprises the suggestion on transferring the target traffic, the donor2 CU <NUM> may determine the traffic identification information by taking into account for the suggestion. For example, if the route request comprises a suggested DSCP for the target traffic, the donor2 CU <NUM> may allocate the suggested DSCP to the target traffic. Alternatively, the donor2 CU <NUM> may not take into account for the suggestion and determine the traffic identification information based on its own configuration. For example, the donor2 CU <NUM> may allocate a DSCP different from the suggested DSCP for the target traffic.

In some example embodiments, as shown in <FIG>, upon determining the traffic identification information, the donor2 CU <NUM> may configure <NUM> the donor2 DU <NUM> to be prepared to route the target traffic. The donor2 CU <NUM> may further configure BAP routing tables for all the IAB nodes along a path from the DU <NUM> to the IAB node <NUM>, for example, for the IAB nodes <NUM> and <NUM> shown in <FIG> and <FIG>. For example, the donor2 CU <NUM> may transmit configuration information (also referred to as "third information") to the donor2 DU <NUM> for configuring the donor2 DU <NUM> to route the target traffic. The configuration information may at least indicate a rule of mapping the target traffic to the BH RLC channels based on the traffic identification information. As an example, the configuration information may indicate that F1 traffic with a DSCP of #E shall be mapped to the BH RLC channel #<NUM>. The configuration information may further indicate the BAP routing tables.

Continuing with the example process <NUM>, the IAB donor <NUM> transmits <NUM> the traffic identification information to the IAB donor <NUM>. For example, the CU-CP <NUM> of the donor2 CU <NUM> may transmit the traffic identification information to the CU-CP <NUM>. The traffic identification information may be transmitted in a response to the route request.

The traffic identification information may include the transport layer address of the IAB node <NUM>. For example, the traffic identification information may include an IP address of the IAB node <NUM> allocated by the donor2 CU <NUM>. Alternatively, or in addition, the traffic identification information may include the BAP address of the IAB node <NUM> and/or a BAP path identity.

The traffic identification information may further include the DSCP for the target traffic allocated by the donor2 CU <NUM>. Alternatively, or in addition, the traffic identification information may include the Flow Label for the target traffic, e.g., the IPv6 Flow Label for the target traffic.

In the case of <NUM>:<NUM> mapping of UE-bearers to BH RLC channels, the traffic identification information may be provided for each DRB or F1-U tunnel of the terminal device. For example, the DSCP or the Flow Label may be provided for traffic of each DRB of a UE. The traffic identification information may also include the identity of the terminal device, the DRB identity or the F1-U tunnel identity related to the terminal device. The traffic identification information may also include a routing identity for the terminal device.

After receiving the traffic identification information from the IAB donor <NUM>, the IAB donor <NUM> may transmit the target traffic by using the traffic identification information to the IAB node <NUM>, which is routed to the donor2 DU <NUM>. Specifically, the donor1 CU <NUM> may incorporate at least part of the traffic identification information into the target traffic and transmit the target traffic to the IAB node <NUM>, which is routed to the donor2 DU <NUM>. The target traffic is routed to the donor2 DU <NUM>, and is further transmitted to the IAB node <NUM>. For example, the donor1 CU <NUM> may insert the DSCP and/or IPv6 Flow Label and the IP address of the IAB node <NUM> allocated by the donor2 CU <NUM> into an IP header of an IP packet including the F1 packet. The donor1 CU <NUM> may then transmit the IP packet including the F1 packet, which is routed to the donor2 DU <NUM>. The donor2 DU <NUM> performs the traffic mapping, and transmit the IP packet including the F1 packet to the IAB node <NUM>, for example, the IAB DU <NUM>. In this way, F1 traffic is routed from the IAB donor <NUM> to the IAB node <NUM> via the DU <NUM> of the IAB donor <NUM>.

In some example embodiments, the target traffic may comprise user plane traffic. The CU-CP <NUM> of the IAB donor <NUM> may transmit <NUM>, to the CU-UP <NUM>, at least part of the traffic identification information concerning the user plane traffic. The at least part of the traffic identification information concerning the user plane traffic may be referred to as "fourth information". For example, the IP address of the IAB node <NUM>, the DSCP and/or Flow Label, the identity of the terminal device, the DRB identity or the F1-U tunnel identity for F1-U traffic may be transmitted from the CU-CP <NUM> to the CU-UP <NUM>. In some other example embodiments, the CU-CP <NUM> of the IAB donor <NUM> may transmit <NUM>, to the CU-UP <NUM>, an update request including at least part of the traffic identification information (also referred to as "quality of service mapping information") concerning the user plane traffic to be updated. The update request indicates the old traffic identification information (or quality of service mapping information) to be updated by the new traffic identification information (or quality of service mapping information), for example, an old DSCP value to be updated by a new DSCP value, or an old IPv6 flow Label value to be updated by a new IPv6 Flow Label value. This update procedure may be initiated by the CU-CP <NUM>, for example, when the same type of traffic is already transmitted from the CU-UP <NUM> to the IAB node <NUM> via a donor1 DU (e.g., the DU <NUM>), and CU-CP <NUM> now decides to route the same type of traffic via a donor2 DU (e.g., the DU <NUM>). Upon the reception of the update request including the traffic identification information (or quality of service mapping information), the CU-UP <NUM> shall replace the old traffic identification information (or quality of service mapping information) by the new traffic identification information (or quality of service mapping information) for all related user plane traffic. The CU-UP <NUM> then use the new traffic identification information (or quality of service mapping information) for further user plane traffic to the IAB node <NUM>.

In these example embodiments, the CU-UP <NUM> of the IAB donor <NUM> may transmit <NUM> the user plane traffic by using at least part of the traffic identification information to the IAB node <NUM>, which is routed to donor2 DU <NUM>. The donor2 DU <NUM> performs the traffic mapping, and then transmit <NUM> the user plane traffic to the IAB node <NUM>. The user plane traffic may comprise part of the traffic identification information. For example, the IP address of the IAB node <NUM> as well as the DSCP and/or Flow Label may be inserted into the IP packet header of an IP packet including the F1-U packet at the CU-UP <NUM>. Then, the IP packet including the F1-U packet may be transmitted from the CU-UP <NUM> to the donor2 DU <NUM>. The donor2 DU <NUM> may perform the traffic mapping, and then transmit the IP packet including the F1-U packet to the IAB node <NUM>.

In some example embodiments, the target traffic may comprise control plane traffic. The CU-CP <NUM> of the IAB donor <NUM> may transmit <NUM> the control plane traffic by using at least part of the traffic identification information to the IAB node <NUM>, which is routed to the IAB donor DU <NUM>. The donor2 DU <NUM> may perform the traffic mapping, and then transmit <NUM> the control plane traffic to the IAB node <NUM>. For example, the IP address of the IAB node <NUM> as well as the DSCP and/or Flow Label for F1-C traffic may be inserted into the IP packet header of an IP packet including the F1-C packet at the CU-CP <NUM>. Then, the IP packet including the F1-C packet may be transmitted from the CU-CP <NUM> to the donor2 DU <NUM>. The donor2 DU <NUM> may map the F1-C packet to a BH RLC channel, and then transmit the IP packet including the F1-C packet to the IAB node <NUM>.

Although not shown in <FIG>, it is to be understood that the donor2 DU <NUM> may transmit <NUM> the control plane traffic and transmit <NUM> the user plane traffic to the IAB node <NUM> via the intermediate IAB node <NUM> as shown in <FIG> and <FIG>.

As can be seen from the above, in the proposed solution, both the user plane traffic and the control plane traffic from an IAB donor can be routed to an IAB node via a DU of another IAB donor. It is to be understood that the proposed solution is applicable whether the IAB node is directly or indirectly connected to the IAB donors.

In the example process <NUM>, the donor2 CU <NUM> may configure <NUM> the donor2 DU <NUM> to route the target traffic upon determining the traffic identification information. In some example embodiments, the donor2 CU <NUM> may first transmit the traffic identification information to the donor1 CU <NUM>, for example, to complete a handshake between the donor2 CU <NUM> and the donor1 CU <NUM>. If a confirmation message is received from the donor1 CU <NUM>, the donor2 CU <NUM> may configure the donor2 DU <NUM> to route the target traffic. If a rejection message is received from the donor1 CU <NUM>, the donor2 CU <NUM> may not configure the donor2 DU <NUM> to route the target traffic.

In these example embodiments, the donor1 CU <NUM> is enabled to reject to route the target traffic via the DU <NUM>. For example, in the topology adaptation scenario, if the reason of topology adaptation is other than mobility e.g., load balancing, the source Donor CU is enabled to reject the topology adaptation. A reason for rejecting may be that the traffic identification information received from the CU <NUM> supports a DSCP or QoS level lower than an acceptable DSCP or QoS level for CU <NUM>. After the CU <NUM> rejects to route the target traffic via the DU <NUM>, a new request to the CU <NUM> or a different node is sent. Alternatively, the IAB operation continues with the original topology e.g., if there is no radio link problem or a new trigger for the topology adaptation.

Although <FIG> shows acts as being performed by specific elements of the IAB donors <NUM> and <NUM>, it is only for the purpose of discussion. The acts may be performed by any suitable elements of the IAB donors <NUM> and <NUM>. The elements of the IAB donors <NUM> and <NUM> are shown separately in <FIG>, <FIG> and <FIG> for the purpose of illustration without any limitation to the scope of the present disclosure. In some example embodiments, two or more of these elements may be implemented by a same device or apparatus. For example, the DU <NUM> and the CU <NUM> of the IAB donor <NUM> may be implemented by a same device or apparatus. For another example, the CU-CP <NUM> and the CU-UP <NUM> of the IAB donor <NUM> may be implemented by a same device or apparatus.

<FIG> shows a flowchart of an example method <NUM> for IAB communication in accordance with some example embodiments of the present disclosure. The method <NUM> can be implemented at any suitable device. For example, the method <NUM> can be implemented at the CU-CP <NUM> of the IAB donor <NUM> shown in <FIG> and/or <FIG>. For the purpose of discussion, the method <NUM> will be described with reference to <FIG> and/or <FIG>. In the following, the CU-CP <NUM> of the IAB donor <NUM> is also referred to as a "first CU-CP <NUM>", and the CU-CP <NUM> of the IAB donor <NUM> is also referred to as a "second CU-CP <NUM>". It is to be understood that the method <NUM> may include additional blocks not shown and/or may omit some shown blocks, and the scope of the present disclosure is not limited in this regard.

At block <NUM>, the first CU-CP <NUM> transmits, to a second CU-CP <NUM>, a request to transfer target traffic of an interface between a first IAB donor <NUM> and an IAB node <NUM> via a DU <NUM> of the second IAB donor <NUM>. The request comprises first information of the target traffic.

In some example embodiments, the first information comprises at least one of: a traffic type indicating whether the target traffic comprises user plane traffic or control plane traffic, or a Quality of Service parameter for the target traffic.

In some example embodiments, the target traffic is directed to at least one device (for example, at least one UE) in communication with the IAB node <NUM>, and the first information further comprises at least one of: an identity of the at least one device, an identity of a data radio bearer for the at least one device, or an identity of a user plane tunnel for the at least one device.

At block <NUM>, the first CU-CP <NUM> receives, from the second CU-CP <NUM>, second information to be used for configuring the target traffic, in order to be routed via the DU <NUM>.

In some example embodiments, the second information comprises at least one of: a differentiated services code point for the target traffic, a IPv6 Flow Label for the target traffic, a transport layer address of the IAB node <NUM>, a Backhaul Adaptation Protocol (BAP) address of the IAB node <NUM>, a BAP path identity, an identity of at least one device (for example, at least one UE) in communication with the IAB node <NUM>, an identity of a data radio bearer for the at least one device, an identity of a user plane tunnel for the at least one device, or a routing identity for the at least one terminal device.

In some example embodiments, the target traffic comprises user plane traffic of an interface between a CU-UP <NUM> of the first IAB donor <NUM> and the IAB node <NUM>. The first CU-CP <NUM> transmits, to the CU-UP <NUM>, at least part of the second information concerning the user plane traffic.

In some example embodiments, the target traffic comprises control plane traffic of an interface between the first CU-CP <NUM> and the IAB node <NUM>. The first CU-CP <NUM> transmits to the IAB node <NUM> via the DU <NUM> of the second IAB donor <NUM>, the control plane traffic comprising at least part of the second information. In some example embodiments, prior to transmitting the control plane traffic, the first CU-CP <NUM> uses the at least part of the second information to configure a packet header of the control plane traffic.

<FIG> shows a flowchart of an example method <NUM> for IAB communication in accordance with some example embodiments of the present disclosure. The method <NUM> can be implemented at any suitable device. For example, the method <NUM> can be implemented at the CU-CP <NUM> of the IAB donor <NUM> as shown in <FIG> and/or <FIG>. For the purpose of discussion, the method <NUM> will be described with reference to <FIG> and/or <FIG>. In the following, the CU-CP <NUM> of the IAB donor <NUM> is also referred to as a "first CU-CP <NUM>", and the CU-CP <NUM> of the IAB donor <NUM> is also referred to as a "second CU-CP <NUM>". It is to be understood that the method <NUM> may include additional blocks not shown and/or may omit some shown blocks, and the scope of the present disclosure is not limited in this regard.

At block <NUM>, the second CU-CP <NUM> receives, from a first CU-CP <NUM>, a request to transfer target traffic of an interface between a first IAB donor <NUM> and an IAB node <NUM> via a DU <NUM> of the second IAB donor <NUM>. The request comprises first information of the target traffic.

At block <NUM>, the second CU-CP <NUM> determines, based on the first information, second information to be used for the target traffic.

In some example embodiments, the second information comprises at least one of: a differentiated services code point for the target traffic, an IPv6 Flow Label for the target traffic, a transport layer address of the IAB node <NUM>, a BAP address of the IAB node <NUM>, a BAP path identity, an identity of at least one device (for example, at least one UE) in communication with the IAB node <NUM>, an identity of a data radio bearer for the at least one device, an identity of a user plane tunnel for the at least one device, or a routing identity for the at least one device.

At block <NUM>, the second CU-CP <NUM> transmits the second information to the first CU-CP <NUM>.

In some example embodiments, the second CU-CP <NUM> transmits, to the DU <NUM> of the second IAB donor <NUM>, third information for configuring the DU <NUM> of the second IAB donor <NUM> to perform traffic mapping and route the target traffic to the IAB node <NUM>.

<FIG> shows a flowchart of an example method <NUM> for IAB communication in accordance with some example embodiments of the present disclosure. The method <NUM> can be implemented at any suitable device. For example, the method <NUM> can be implemented at the CU-UP <NUM> of the IAB donor <NUM> as shown in <FIG> and/or <FIG>. For the purpose of discussion, the method <NUM> will be described with reference to <FIG> and/or <FIG>. In the following, the CU-CP <NUM> of the IAB donor <NUM> is also referred to as a "first CU-CP <NUM>", and the CU-CP <NUM> of the IAB donor <NUM> is also referred to as a "second CU-CP <NUM>". It is to be understood that the method <NUM> may include additional blocks not shown and/or may omit some shown blocks, and the scope of the present disclosure is not limited in this regard.

At block <NUM>, the CU-UP <NUM> receives from a CU-CP <NUM>, fourth information for updating quality of service mapping information for user plane traffic of an interface between the CU-UP <NUM> and an IAB node <NUM>. The user plane traffic is to be transferred to the IAB node <NUM>.

In some example embodiments, the fourth information comprises at least one of: a first differentiated services code point used by the CU-UP <NUM> for the user plane traffic, a first IPv6 Flow Label used by the CU-UP <NUM> for the user plane traffic, a second differentiated services code point to be used by the CU-UP <NUM> for the user plane traffic, a second IPv6 Flow Label to be used by the CU-UP <NUM> for the user plane traffic, a transport layer address of the IAB node <NUM>, a BAP address of the IAB node, a BAP path identity, an identity of at least one device (for example, at least one UE) in communication with the IAB node <NUM>, an identity of a data radio bearer for the at least one device, an identity of a user plane tunnel for the at least one device, or a routing identity for the at least one device.

At block <NUM>, the CU-UP <NUM> transmits, to the IAB node <NUM> for example via a distributed Unit (DU) of the first IAB donor or a second IAB donor, the user plane traffic comprising at least part of the fourth information.

In some example embodiments, prior to transmitting the user plane traffic, the CU-UP <NUM> updates the quality of service mapping information using the at least part of the fourth information. The CU-UP <NUM> configures a packet header of the user plane traffic with the updated quality of service mapping information.

In some example embodiments, a first apparatus capable of performing the method <NUM> (for example, the CU-CP <NUM>) may comprise means for performing the respective operations of the method <NUM>. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module. The first apparatus may be implemented as or included in the CU-CP <NUM>.

In some example embodiments, the first apparatus comprises: means for transmitting, at a first CU-CP of a first IAB donor to a second CU-CP of a second IAB donor, a request to transfer target traffic via a DU of the second IAB donor, the request comprising first information of the target traffic; means for receiving, from the second CU-CP, second information to be used for configuring the target traffic.

In some example embodiments, the target traffic comprises user plane traffic of an interface between a CU-UP of the first IAB donor and an IAB node and the first apparatus further comprises: means for transmitting, to the CU-UP, at least part of the second information concerning the user plane traffic.

In some example embodiments, the target traffic comprises control plane traffic of an interface between the first CU-CP and an IAB node and the first apparatus further comprises: means for transmitting, to the IAB node via the DU of the second IAB donor, the control plane traffic comprising at least part of the second information. In some example embodiments, the first apparatus further comprises: means for prior to transmitting the control plane traffic, using the at least part of the second information to configure a packet header of the control plane traffic.

In some example embodiments, the first information comprises at least one of: a traffic type indicating whether the target traffic comprises user plane traffic or control plane traffic, or a Quality of Service parameter for the target traffic. In some example embodiments, the target traffic is directed to at least one device in communication with an IAB node, and the first information further comprises at least one of: an identity of the at least one device, an identity of a data radio bearer for the at least one device, or an identity of a user plane tunnel for the at least one device.

In some example embodiments, the second information comprises at least one of: a differentiated services code point for the target traffic, an IPv6 Flow Label for the target traffic, a transport layer address of an IAB node, a BAP address of the IAB node, a BAP path identity, an identity of at least one device in communication with the IAB node, an identity of a data radio bearer for the at least one device, an identity of a user plane tunnel for the at least one device, or a routing identity for the at least one device.

In some example embodiments, a second apparatus capable of performing the method <NUM> (for example, the CU-CP <NUM>) may comprise means for performing the respective operations of the method <NUM>. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module. The first apparatus may be implemented as or included in the CU-CP <NUM>.

In some example embodiments, the second apparatus comprises: means for receiving, at a second CU-CP of a second IAB from a first CU-CP of a first IAB donor, a request to transfer target traffic via a DU of the second IAB donor, the request comprising first information of the target traffic; means for determining, based on the first information, second information to be used for the target traffic; and means for transmitting the second information to the first CU-CP.

In some example embodiments, the second apparatus further comprises means for transmitting, to the DU of the second IAB donor, third information for configuring the DU of the second IAB donor to perform traffic mapping and route the target traffic to the IAB node.

In some example embodiments, a third apparatus capable of performing the method <NUM> (for example, the CU-UP <NUM>) may comprise means for performing the respective operations of the method <NUM>. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module. The first apparatus may be implemented as or included in the CU-UP <NUM>.

In some example embodiments, the third apparatus comprises: means for receiving, at a CU-UP of a first IAB donor from a first CU-CP of the first IAB donor, fourth information for updating quality of service mapping information for user plane traffic of an interface between the CU-UP and an IAB node, the user plane traffic to be transferred to the IAB node; and means for transmitting, to the IAB node, the user plane traffic comprising at least part of the fourth information.

In some example embodiments, the third apparatus further comprises: means for prior to transmitting the user plane traffic, updating the quality of service mapping information using the at least part of the fourth information; and means for configuring a packet header of the user plane traffic with the updated quality of service mapping information.

In some example embodiments, the fourth information comprises at least one of: a first differentiated services code point used by the CU-UP for the user plane traffic, a first Internet Protocol Version <NUM>(IPv6) Flow Label used by the CU-UP for the user plane traffic, a second differentiated services code point to be used by the CU-UP for the user plane traffic, a second Internet Protocol Version <NUM>(IPv6) Flow Label to be used by the CU-UP for the user plane traffic, a transport layer address of the IAB node, a Backhaul Adaptation Protocol (BAP) address of the IAB node, a Backhaul Adaptation Protocol (BAP) path identity, an identity of at least one device in communication with the IAB node, an identity of a data radio bearer for the at least one device, an identity of a user plane tunnel for the at least one device, or a routing identity for the at least one device.

<FIG> is a simplified block diagram of a device <NUM> that is suitable for implementing embodiments of the present disclosure. For example, the IAB node <NUM>, the IAB donor <NUM>, the IAB donor <NUM>, CU-CP <NUM>, CU-UP <NUM>, CU <NUM>, CU-CP <NUM>, CU <NUM>, DU <NUM> shown in <FIG> and/or <FIG> can be implemented by the device <NUM>. As shown, the device <NUM> includes one or more processors <NUM>, one or more memories <NUM> coupled to the processor <NUM>, and one or more communication modules <NUM> coupled to the processor <NUM>.

It should be appreciated that future networks may utilize network functions virtualization (NFV) which is a network architecture concept that proposes virtualizing network node functions into "building blocks" or entities that may be operationally connected or linked together to provide services. A virtualized network function (VNF) may comprise one or more virtual machines running computer program codes using standard or general type servers instead of customized hardware. Cloud computing or data storage may also be utilized. In radio communications, this may mean node operations to be carried out, at least partly, in a central/centralized unit, CU, (e.g. server, host or node) operationally coupled to distributed unit, DU, (e.g. a radio head/node). It should also be understood that the distribution of labour between core network operations and base station operations may vary depending on implementation.

In an embodiment, the server may generate a virtual network through which the server communicates with the distributed unit. In general, virtual networking may involve a process of combining hardware and software network resources and network functionality into a single, software-based administrative entity, a virtual network. Such virtual network may provide flexible distribution of operations between the server and the radio head/node. In practice, any digital signal processing task may be performed in either the CU or the DU and the boundary where the responsibility is shifted between the CU and the DU may be selected according to implementation.

Therefore, in an embodiment, a CU-DU architecture is implemented. In such case the device <NUM> may be comprised in a central unit (e.g. a control unit, an edge cloud server, a server) operatively coupled (e.g. via a wireless or wired network) to a distributed unit (e.g. a remote radio head/node). That is, the central unit (e.g. an edge cloud server) and the distributed unit may be stand-alone apparatuses communicating with each other via a radio path or via a wired connection. Alternatively, they may be in a same entity communicating via a wired connection, etc. The edge cloud or edge cloud server may serve a plurality of distributed units or a radio access networks. In an embodiment, at least some of the described processes may be performed by the central unit. In another embodiment, the device <NUM> may be instead comprised in the distributed unit, and at least some of the described processes may be performed by the distributed unit.

In an embodiment, the execution of at least some of the functionalities of the device <NUM> may be shared between two physically separate devices (DU and CU) forming one operational entity. Therefore, the apparatus may be seen to depict the operational entity comprising one or more physically separate devices for executing at least some of the described processes. In an embodiment, such CU-DU architecture may provide flexible distribution of operations between the CU and the DU. In practice, any digital signal processing task may be performed in either the CU or the DU and the boundary where the responsibility is shifted between the CU and the DU may be selected according to implementation. In an embodiment, the device <NUM> controls the execution of the processes, regardless of the location of the apparatus and regardless of where the processes/functions are carried out.

The present disclosure also provides at least one computer program product tangibly stored on a non-transitory computer readable storage medium. The computer program product includes computer-executable instructions, such as those included in program modules, being executed in a device on a target real or virtual processor, to carry out the method <NUM> as described above with reference to <FIG>, the method <NUM> as described above with reference to <FIG>, and the method <NUM> as described above with reference to <FIG>. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, or the like that perform particular tasks or implement particular abstract data types. The functionality of the program modules may be combined or split between program modules as desired in various embodiments. Machine-executable instructions for program modules may be executed within a local or distributed device. In a distributed device, program modules may be located in both local and remote storage media.

Claim 1:
An apparatus comprising:
means for transmitting, at a first Central Unit-Control Plane, CU-CP (<NUM>), of a first Integrated Access and Backhaul, IAB, donor (<NUM>) to a second CU-CP (<NUM>) of a second IAB donor (<NUM>), a request to transfer target traffic via a Distributed Unit, DU (<NUM>), of the second IAB donor (<NUM>), the request comprising first information of the target traffic, wherein the first information comprises at least one of: a traffic type indicating whether the target traffic comprises user plane traffic or control plane traffic, or a Quality of Service parameter for the target traffic; and
means for receiving, from the second CU-CP (<NUM>), second information to be used for configuring the target traffic to be routed via the DU (<NUM>) of the second IAB donor, wherein the second information, determined by the second CU-CP (<NUM>), is based on the first information