WO2021214378A1

WO2021214378A1 - Secondary f1-c interface for integrated access and backhaul (iab) node

Info

Publication number: WO2021214378A1
Application number: PCT/FI2021/050188
Authority: WO
Inventors: Henri Markus Koskinen
Original assignee: Nokia Solutions and Networks Oy
Current assignee: Nokia Solutions and Networks Oy
Priority date: 2020-04-24
Filing date: 2021-03-17
Publication date: 2021-10-28
Anticipated expiration: 2022-10-24
Also published as: EP4140191A4; EP4140191A1

Abstract

According to at least some example embodiments, a method of operating a master donor next generation Node B (gNB) of a communications network, the communications network further including a secondary donor gNB and an integrated access and backhaul (IAB) node, includes generating, by the master donor gNB, a request to set up a secondary control interface between the secondary donor gNB and the IAB node; and sending the request.

Description

SECONDARY Fl-C INTERFACE FOR INTEGRATED ACCESS AND BACKHAUL

(IAB) NODE

TECHNICAL FIELD

[OOOl] One or more example embodiments relate to secondary Fl-C interface for an integrated access and backhaul (IAB) node.

BACKGROUND

[0002] Fifth generation (5G) wireless communications networks are the next generation of mobile communications networks. Standards for 5G communications networks are currently being developed by the Third Generation Partnership Project (3GPP). These standards are known as 3GPP New Radio (NR) or 5G NR standards. Next generation radio access network (NG-RAN) is a radio access technology (RAT) for 5G NR and long-term evolution (LTE) communications networks. Integrated access and backhaul (IAB) technology supports wireless relaying in NG-RAN.

SUMMARY

[0003] The scope of protection sought for various example embodiments of the invention is set out by the independent claims. The example embodiments and features, if any, described in this specification that do not fall under the scope of the independent claims are to be interpreted as examples useful for understanding various example embodiments.

[0004] According to at least some example embodiments, a method of operating a master donor next generation Node B (gNB) of a communications network, the communications network further including a secondary donor gNB and an integrated access and backhaul (IAB) node, includes generating, by the master donor gNB, a request to set up a secondary control interface between the secondary donor gNB and the IAB node. [0005] The request to set up a secondary control interface between the secondary donor gNB and the IAB node may be generated such that the request includes identities of user equipment (UEs) for which contexts exist at the IAB node.

[0006] The request may be a Secondary-Node Addition Request.

[0007] The request generated by the master donor gNB may further identify data radio bearers of the UEs.

[0008] The request generated by the master donor gNB may further include an indication of identities of UEs that the secondary donor gNB is to use in signaling to the IAB node.

[0009] The method may further include receiving, at the master donor gNB from the secondary donor gNB, a request acknowledgement, the request acknowledgement including a gNB-DU ID that has been allocated to the IAB node by the secondary donor gNB.

[0010] The request acknowledgement may be a Secondary-Node Addition Request Acknowledge.

[0011] The method may further include generating, by the master donor gNB, a message such that the message includes the gNB-DU ID; and sending the message to the IAB node.

[0012] The message may be a radio resource control (RRC) reconfiguration message.

[0013] According to at least some example embodiments, a method of operating a secondary donor next generation Node B (gNB) of a communications network, the communications network further including a master donor gNB and an integrated access and backhaul (IAB) node, includes receiving, at the secondary donor gNB, a first message including identities of user equipment (UEs) for which contexts exist on a primary control interface at the IAB node; and sending, by the secondary donor gNB on a secondary control interface between the secondary donor gNB and the IAB node, a configuration message that identifies at least one of the UEs using at least one of the identities included in the first message.

[0014] The method may further include receiving, at the secondary donor gNB, an indication that causes the secondary donor gNB to set up the secondary control interface between the secondary donor gNB and the IAB node.

[0015] The indication may further include a backhaul adaption protocol (BAP) routing ID.

[0016] The method may further include generating, by the secondary donor gNB, a backhaul (BH) routing configuration message that includes the BAP routing ID; and sending the backhaul (BH) routing configuration message to the IAB node. [0017] The received first message may further include identities of data radio bearers of the UEs.

[0018] The first message may further include an indication of identities the secondary donor gNB is to use in signaling to the IAB node.

[0019] The method may further include sending a UE context modification request to the IAB node based on the indication of identities the secondary donor gNB is to use in signaling to the IAB node.

[0020] The method may further include allocating a gNB DU ID to the IAB node; generating a second message that includes the gNB DU ID; and sending the second message to the master donor gNB.

[0021] The method may further include receiving, at the secondary donor gNB from the IAB node, an FI setup request; determining whether the FI setup request includes the gNB DU ID; and determining that the FI setup request is a request to setup a secondary Fl-C interface, in response to determining that the FI setup request included the gNB DU ID.

[0022] According to at least some example embodiments, a method of operating an integrated access and backhaul (IAB) node of a communications network, the communications network further including a master donor next generation Node B (gNB) and a secondary donor gNB, includes receiving, at the IAB node on a secondary control interface between the IAB node and the secondary donor gNB, a configuration message including an identity of a user equipment (UE) to which the configuration message pertains; identifying a UE to which the configuration message pertains as a UE associated, on a primary control interface of the IAB node, with the identity in the configuration message; and performing the configuration on the UE identified. [0023] The method may further include receiving, at the IAB node, an indication that causes the IAB node to set up the secondary control interface between the IAB node and the secondary donor gNB.

[0024] The method may further include generating a request to setup a secondary Fl-C interface with the secondary donor gNB, and sending the request to the secondary donor gNB.

[0025] The method may further include receiving, at the IAB node, a UE context modification request and a mapping of data radio bearers (DRBs) to at least one secondary cell group (SCG) backhaul (BH) radio link control (RLC) channel.

[0026] The method may further include generating an F 1 UE context modification response that includes an indication of downlink transport network layer (TNL) information that is specific to use of SCG BH RLC channels of the IAB node.

[0027] The indication of downlink TNL information may include per-data radio bearer (DRB) general packet radio service (GPRS) tunneling protocol (GTP)-U tunnel endpoint identifiers that are specific to use of SCG BH RLC channels of the IAB-node. [0028] According to at least some example embodiments, a master donor next generation Node B (gNB) of a communications network incudes a processor; and memory storing computer-executable instructions that, when executed by the processor, causes the processor to perform operations including generating a request to set up a secondary control interface between a secondary donor gNB of the communications network and an integrated access and backhaul (IAB) node of the communications network.

[0029] According to at least some example embodiments, secondary donor next generation Node B (gNB) of a communications network includes a processor; and memory storing computer-executable instructions that, when executed by the processor, causes the processor to perform operations including receiving a first message including identities of user equipment (UEs) for which contexts exist on a primary control interface at an integrated access and backhaul (IAB) node of the communications network, the primary control interface being between the IAB node and a master donor gNB; and sending, by the secondary donor gNB on a secondary control interface between the secondary donor gNB and the IAB node, a configuration message that identifies at least one of the UEs using at least one of the identities included in the first message.

[0030] According to at least some example embodiments, an integrated access and backhaul (IAB) node of a communications network includes a processor; and memory storing computer-executable instructions that, when executed by the processor, causes the processor to perform operations including receiving, on a secondary control interface between the IAB node and a secondary donor next generation Node B (gNB) of the communications network, a configuration message including an identity of a user equipment (UE) to which the configuration message pertains; identifying a UE to which the configuration message pertains as a UE associated, on a primary control interface between the IAB node and a master donor gNB of the communications network, with the identity in the configuration message; and performing the configuration on the identified UE.

[0031] According to at least some example embodiments, a radio network element of a communications network includes means for generating a request to set up a secondary control interface between a secondary donor next generation Node B (gNB) of the communications network and an integrated access and backhaul (IAB) node of the communications network.

[0032] According to at least some example embodiments, a radio network element of a communications network includes means for receiving a first message including identities of user equipment (UEs) for which contexts exist on a primary control interface at an integrated access and backhaul (IAB) node of the communications network, the primary control interface being between the IAB node and a master donor next generation Node B (gNB); and means for sending, by the secondary donor gNB on a secondary control interface between the secondary donor gNB and the IAB node, a configuration message that identifies at least one of the UEs using at least one of the identities included in the first message.

[0033] According to at least some example embodiments, a radio network element of a communications network includes means for receiving, on a secondary control interface between the radio network element and a secondary donor next generation Node B (gNB) of the communications network, a configuration message including an identity of a user equipment (UE) to which the configuration message pertains; means for identifying a UE to which the configuration message pertains as a UE associated, on a primary control interface between the radio network element and a master donor gNB of the communications network, with the identity in the configuration message; and means for performing the configuration on the identified UE.

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Example embodiments will become more fully understood from the detailed description given herein below and the accompanying drawings, wherein like elements are represented by like reference numerals, which are given by way of illustration only and thus are not limiting of this disclosure.

[0035] FIG. 1 is a diagram illustrating a portion of a communications network according to at least some example embodiments.

[0036] FIG. 2 illustrates an example embodiment of a radio network element. [0037] FIGS. 3 A and 3B are communication timing diagrams illustrating a process of establishing a secondary Fl-C interface according to at least some example embodiments.

[0038] It should be noted that these figures are intended to illustrate the general characteristics of methods, structure and/or materials utilized in certain example embodiments and to supplement the written description provided below. These drawings are not, however, to scale and may not precisely reflect the precise structural or performance characteristics of any given embodiment, and should not be interpreted as defining or limiting the range of values or properties encompassed by example embodiments. The use of similar or identical reference numbers in the various drawings is intended to indicate the presence of a similar or identical element or feature.

DETAILED DESCRIPTION

[0039] Various example embodiments will now be described more fully with reference to the accompanying drawings in which some example embodiments are shown.

[0040] Detailed illustrative embodiments are disclosed herein. However, specific structural and functional details disclosed herein are merely representative for purposes of describing example embodiments. The example embodiments may, however, be embodied in many alternate forms and should not be construed as limited to only the embodiments set forth herein.

[0041] It should be understood that there is no intent to limit example embodiments to the particular forms disclosed. On the contrary, example embodiments are to cover all modifications, equivalents, and alternatives falling within the scope of this disclosure. Like numbers refer to like elements throughout the description of the figures.

[0042] FIG. 1 is a diagram illustrating a portion of a communications network 100 according to at least some example embodiments. As is illustrated in FIG. 1, the communications network 100 includes next generation radio access network (NG- RAN) and Third Generation Partnership Project (3GPP) 5G New Radio (NR) radio access technology. For example, referring to FIG. 1, communications network 100 includes an integrated access and backhaul (IAB) node 110, a master donor next generation Node B (gNB) 120A, and a secondary donor gNB 120B. According to at least some example embodiments, a primary Fl-C interface 130A and a first NR Uu interface 140A exist between the IAB node 110 and the master donor gNB 120A, a secondary Fl-C interface 130B and a second NR Uu interface 140B exist between the IAB node 110 and the secondary donor gNB 120B, and an Xn interface 150 exists between the master donor gNB 120A and the secondary donor gNB 120B. According to at least some example embodiments, a primary Fl-C interface (e.g., the primary Fl-C interface 130A) is an Fl-C interface between an IAB node and a master donor gNB. According to at least some example embodiments, a secondary Fl-C interface (e.g., the secondary Fl-C interface 130B) is an Fl-C interface between an IAB node, which is associated with a master donor gNB, and a donor gNB (e.g., a secondary donor gNB) other that the master donor gNB. Further, though not illustrated, the IAB node 110 may provide an NR Uu interface to UEs in the communications network 100. Further, though not illustrated, communications network 100 may further include 5G core (5GC) network elements and may be a part of a 5G system (5GS). For example, the master and secondary donor gNBs 120A and 120B may each be connected to an access and mobility management function (AMF) element. Additionally, though not illustrated, the communications network 100 may further include long-term evolution (LTE) network elements that are connected to one or more of the IAB node 110, master donor next generation Node B (gNB) 120A, and secondary donor gNB 120B. Examples of such LTE elements include, but are not limited to, LTE radio access technology (RAT) network elements (e.g., evolved universal mobile telecommunications system (UMTS) terrestrial radio access network (E-UTRAN) network elements) such as evolved node Bs (eNBs), and LTE core network elements (e.g., evolved packet core (EPC) network elements) such as mobility management entities (MMEs). An example structure which may be used to embody one or more radio network elements (e.g., donor gNBs, IAB nodes, UEs, etc.) of the communications network 100 will now be discussed below with respect to FIG. 2 [0043] FIG. 2 illustrates an example embodiment of a radio network element. In the example illustrated in FIG. 2, the radio network element is a gNB (i.e., gNB 102). [0044] As shown, the gNB 102 includes: a memory 740; a processor 720 connected to the memory 740; various interfaces 760 connected to the processor 720; and one or more antennas or antenna panels 765 connected to the various interfaces 760. The various interfaces 760 and the antenna 765 may constitute a transceiver for transmitting/receiving data to/from a UE, a gNB, and/or other radio network element via a plurality of wireless beams. According to example embodiments, the memory 740, processor 720, and interfaces 760, collectively, are an example of a CU of the gNB 102, and the one or more antennas or antenna panels 765 are an example of a DU or DUs of the gNB 102. The master and secondary donor gNBs 120A and 120B may each have the same structure and function as that described with respect to the gNB 102.

[0045] As will be appreciated, depending on the implementation of the gNB 102, the gNB 102 may include many more components than those shown in FIG. 2. However, it is not necessary that all of these generally conventional components be shown in order to disclose the illustrative example embodiment.

[0046] The memory 740 may be a computer readable storage medium that generally includes a random access memory (RAM), read only memory (ROM), and/or a permanent mass storage device, such as a disk drive. The memory 740 also stores an operating system and any other routines/ modules/ applications for providing the functionalities of the gNB (e.g., functionalities of a gNB, methods according to example embodiments, etc.) to be executed by the processor 720. These software components may also be loaded from a separate computer readable storage medium into the memory 740 using a drive mechanism (not shown). Such separate computer readable storage medium may include a disc, tape, DVD/CD-ROM drive, memory card, or other like computer readable storage medium (not shown). In some example embodiments, software components may be loaded into the memory 740 via one of the various interfaces 760, rather than via a computer readable storage medium. [0047] The processor 720 may be configured to carry out instructions of a computer program by performing the arithmetical, logical, and input/ output operations of the system. Instructions may be provided to the processor 720 by the memory 740.

[0048] The various interfaces 760 may include components that interface the processor 720 with the one or more antennas 765, or other input/output components. As will be understood, the various interfaces 760 and programs stored in the memory 740 to set forth the special purpose functionalities of the gNB 102 will vary depending on the implementation of the gNB 102.

[0049] The interfaces 760 may also include one or more user input devices (e.g., a keyboard, a keypad, a mouse, or the like) and user output devices (e.g., a display, a speaker, or the like).

[0050] Further, though the radio network element of FIG. 2 is illustrated as a gNB, other network elements (e.g., other radio access and backhaul network elements, central units (CUs), IAB nodes, eNBs, ng-eNBs, UEs, or the like) may also have the structure of the network element illustrated in FIG. 2. In this regard, for example, the memory 740 may store an operating system and any other routines/ modules/ applications for providing the functionalities of the IAB nodes, donor gNBs, UEs, etc. (e.g., functionalities of these elements, methods according to the example embodiments, etc.) to be executed by the processor 720. For example, the IAB node 110, master donor gNB 120A and/or secondary donor gNB 120B may be embodied by the network element illustrated in FIG. 2, in which case the memory 740 stores computer-executable instructions that, when executed by the processor 720, cause the processor to perform the operations described in the present disclosure as being performed by the IAB node 110, master donor gNB 120A and/or secondary donor gNB 120B.

[0051] Table 1, below, provides a list of a number of abbreviations used in the present specification:

[0052] Returning to FIG. 1, the communications network 100 implements IAB technology. For example, the master donor gNB 120A and the secondary donor gNB 120B are examples of IAB donors. An IAB donor is a gNB part of the fixed network, which serves as a point of attachment to that fixed network for IAB nodes. In the present specification, the terms “donor gNB” and “IAB donor” may be considered synonymous. According to IAB-related work associated with 3GPP Release 16 (Rel- 16), the donor gNB has been defined as being responsible for: configuration of BAP addresses and routing for all IAB nodes attached via that donor gNB; and configuration of bearer mapping in all IAB nodes attached via that donor gNB.

[0053] Bearer mapping refers to a selection of a backhaul RLC channel for transmission of packets received over other backhaul RLC channels, or over radio bearers of UEs served by an IAB node. A child-parent relationship among IAB nodes is defined, such that a parent node provides radio cells over which a child node connects to the fixed network.

[0054] According to IAB-related work associated with 3GPP Release 17 (Rel-17), new radio dual connectivity (NR-DC) may be used to facilitate switching between use of IAB backhaul links configured by different donor gNBs. [0055] Dual connectivity (DC) is defined on a high level in 3 GPP technical specification (TS) 37.340 V16.0.0 (2019-12). Inter-donor DC of IAB nodes refers to a configuration where the master cell group (MCG) and secondary cell group (SCG) of (the MT part of) an IAB node are provided by two other, different, nodes that have different donor gNBs (or are part of the donor gNB, in the case that the cell group is provided by a donor-gNB-DU directly).

[0056] The kind of switched operation described above could be useful in a setting where a stationary IAB node is deployed within reach from parent nodes configured by different donor gNBs. Backhaul radio links from the IAB node to both the parent nodes could be configured into place (as MCG and SCG of the IAB node), and in response to a failure or blockage of a link toward one parent, the backhaul toward the other parent could be taken into use.

[0057] However, at least some conventional implementations of IAB have the attribute of a distributed unit (DU) of an IAB node being limited to only one connection to a centralized unit control plane (CU-CP) (e.g., a CU-CP of a donor gNB). For example, 3GPP TS 38.401 specifies that one gNB-DU is connected to only one gNB-CU-CP, and that the gNB-CU-CP is connected to the gNB-DU through the Fl-C interface. Thus, currently, the CU end of the Fl-C interface assumes that it has full control of, for example, the following aspects assigned by 3 GPP as to be configured by the FI application protocol (F1AP): radio cells to be activated by the DU end; what UE contexts to have; backhaul adaption protocol (BAP) routing at an IAB node; and bearer mapping at an IAB node.

[0058] Consequently, if an IAB node establishes a second Fl-C interface with a second donor gNB (i.e., while having established a first Fl-C interface with a first donor gNB), clashes between conflicting configurations of the IAB node attempted by the different CU endpoints of the different donor gNBs may occur.

[0059] Moreover in inter-donor DC of an IAB node, a secondary donor gNB would most likely be in charge of SCG BH RLC-channel configuration and mapping between those and the radio bearers of UEs served by the IAB node. Thus on a second Fl-C connection toward the secondary donor gNB, UE contexts would need to exist. However in the current F1AP signaling protocol of Fl-C, it may be difficult or, alternatively, impossible to create a UE context at the DU-endpoint without: a radio cell being activated by the DU-endpoint (e.g., because Special Cell is a mandatory part of a UE Context Setup Request); and an RRC (Re)configuration toward the UE (e.g., because the DU shall include the RRC element CellGroupConfig in UE Context Setup Response, which the CU shall send to the UE).

[0060] Accordingly, it would be advantageous to provide a method of achieving Fl-C interfaces between an IAB node and multiple donor gNBs that reduces or, alternatively, eliminates at least the following issues: (i) causing conflicts between dueling attempts of two different donor gNBs, to which an IAB-node is connected via two Fl-C interfaces, to control the configuration of the IAB-node, or (ii) requiring a UE (e.g., a UE that is attached to a DU of the IAB node) to experience RRC reconfiguration.

[0061] According to at least some example embodiments, an IAB-node that has established a first Fl-C interface with a first donor gNB may mitigate the above- referenced issues (i) and (ii) by establishing a new secondary Fl-C interface with a secondary donor gNB.

[0062] According to at least some example embodiments, the secondary Fl-C interface has at least the following properties: the new secondary Fl-C interface can have active UE contexts despite absence, on the secondary Fl-C, of active radio cells; a UE Context Setup procedure; or signaling indicating RLC/ MAC/physical (PHY) configuration of UEs (relying on another co-existing Fl-C on these aspects); signaling regarding UE contexts refers to pre-existing UE contexts created on another co-existing Fl-C and builds on top of them; the new secondary Fl-C interface may be used to configure BAP routing via nodes reachable via SCG of the IAB node; and the new secondary Fl-C interface may be used to configure mapping between radio bearers of UEs served by the IAB node and SCG BH RLC channels of the IAB node.

[0063] According to at least some example embodiments, a procedure for setting up the secondary Fl-C interface may include any or all of items A-H:

A. An indication in an FI Setup Request by which the recipient knows that the FI Setup Request is a Setup request for a secondary Fl-C interface;

B. Identities, received by a secondary donor gNB, of UEs and their DRBs for which contexts pre-exist at a DU end of the secondary Fl-C interface (e.g., a DU of an IAB node) and for which the secondary donor gNB needs to set up new contexts, and which identities the secondary donor gNB should use, in signaling toward the DU end, when referring to those UEs and DRBs;

C. Indications, received by the secondary donor gNB, of i. a BAP routing ID allocated by a master donor, and ii. quality of service (QoS) parameters and, possibly and preferably, RLC mode of DRBs of UEs for which contexts pre-exist at the DU end of the secondary Fl-C;

D. Using, by the secondary donor gNB, indication C(i) discussed above in a BAP-routing configuration of the IAB node;

E. Using, by the secondary donor gNB, the above-referenced indications B and C(ii) in a bearer-mapping configuration of the IAB node; F. An indication, sent by the secondary donor gNB, of a gNB-DU ID to be used by the IAB node to identify itself at a setup of the secondary Fl-C (which, according to at least some example embodiments, may be the same as the indication of item A) ;

G. An indication, sent by the IAB node, of downlink Transport Network Layer (TNL) information specific to use of SCG BH RLC channels; and

H. Receiving, by the master donor gNB from the secondary donor gNB, an indication that traffic can now be routed to the IAB node via its SCG. (which, according to at least some example embodiments, may be the same as the indication of item G).

[0064] At least one example of a manner in which items A-H may be used to implement a process of establishing (e.g., setting up) a secondary Fl-C interface will now be discussed below with reference to FIGS. 3A-3B. However, it will be understood that the process illustrated in FIGS. 3A-3B is an example, and that a process of establishing a secondary Fl-C interface may exclude one or more of items A-H and / or may include any or all of items A-H in a different order than that shown in FIGS. 3A-3B.

[0065] FIGS. 3 A and 3B are communication timing diagrams illustrating a process of establishing a secondary Fl-C interface according to at least some example embodiments. FIGS. 3A and 3B will be explained with reference to the IAB node 110, master donor node 120A, and secondary donor node 120B discussed above with reference to FIG. 1.

[0066] According to at least some example embodiments, setting up the secondary Fl-C interface 13 OB includes the introduction of new procedures, such as one or more of:

-An Xn application protocol (XnAP) “S-Fl-C Addition” (request + response) for establishing the role of the secondary donor gNB 12 OB and providing confirmation to the master donor gNB 120A once complete;

-An XnAP “S-Fl-C Modification” (request + response) for providing the secondary donor gNB 120B with required information for configuration of the secondary Fl-C interface 13 OB, and providing confirmation to the master donor gNB 120A once complete; and

-An RRC or F1AP “S-Fl-C Addition” (request + response) for commanding the IAB node 110 to setup the secondary Fl-C interface 130B and provide confirmation to the master donor gNB 120A once complete.

[0067] Examples of XnAP signaling on an Xn interface are described, for example, by 3GPP TS 38.423 V16.0.0 (2019-12). Examples of F1AP signaling on an Fl-C interface are described by, for example, 3GPP TS 38.473 V16.0.0 (2019-12).

[0068] However, FIGS. 3A-3B show an example signaling flow of a process for setting up the secondary Fl-C interface 130B (after DC) between the DU part of the IAB node 110 and the secondary donor gNB 120B, where the above new XnAP procedures have been implemented as part of existing XnAP S-Node procedures instead; the request part of the above new RRC procedure has been implemented as part of the RRC reconfiguration that configures the IAB MT (i.e., a mobile termination (MT) portion of the IAB node 110) with the inter-donor DC; and the confirmation part of the above new RRC procedure has been implemented in operation 16.

[0069] Referring to FIG. 3A, in operation 1, a CU of the master donor gNB 120A sends an S-Node Addition Request to the secondary donor gNB 120B. The S-Node Addition Request may be a modified S-Node Addition Request that includes identities of UEs and their DRBs for which contexts pre-exist at the DU end of the secondary Fl-C and for which the secondary donor gNB 120B needs to set up new contexts, and an indication of which identities the secondary donor gNB 120B should use, in signaling toward the DU end (i.e., the DU of the IAB-node 110), when referring to those UEs and DRBs. The S-Node Addition Request may further include: a. a BAP routing ID allocated by the master donor gNB 120A; and b. quality of service (QoS) parameters and, optionally, an RLC mode of DRBs of UEs for which contexts pre-exist at the DU end of the secondary Fl-C interface.

[0070] In operation 2, the CU of the secondary donor gNB 12 OB may perform admission control with DU(s) interfacing this CU, and perform configuration of the BH RLC channels towards the IAB-node 110.

[0071] In operation 3, the secondary donor gNB 120B may send an S-Node Addition Request Acknowledge (ACK) to the CU of the master donor gNB 120A. According to at least some example embodiments, the S-Node Addition Request ACK may be a modified S-Node Addition Request Acknowledge (ACK) that includes an indication, from the secondary donor gNB 120B, of a gNB-DU ID to be used by the DU of the IAB-node 110 to identify itself during the setup of the secondary Fl-C interface. According to at least some example embodiments, the secondary donor gNB 120B may assign and send the gNB-DU ID to be used by the DU of the IAB-node 110 at FI Setup, so that the secondary donor gNB 120B is able to associate the IAB- node 110 with the information that the secondary donor gNB 120B received in operation 1.

[0072] In operation 4, the master donor gNB 120A may send an RRC Reconfiguration message to the IAB-node 110. According to at least some example embodiments, the master donor gNB 120A generates at least part of the RRC Reconfiguration message such that the RRC Reconfiguration message is a modified RRC Reconfiguration message that includes the gNB-DU ID received at the master donor gNB 120A from the secondary donor gNB 12 OB in operation 3, and an IP address of the CU of the secondary donor gNB 120B for setting up the secondary Fl- C interface. For example, according to at least some example embodiments, a portion of the RRC Reconfiguration message is generated by the secondary donor gNB 12 OB and sent by the secondary donor gNB 12 OB to the master donor gNB 120A in operation 3 (e.g., in or alternatively, along with, the S-Node Addition Request ACK). Further, according to at least some example embodiments, in operation 4, the master donor gNB 120A completes the RRC Reconfiguration message received in operation 3 and sends the completed RRC Reconfiguration message to the IAB node 110. Alternatively, according to at least some example embodiments, in operation 4, the master donor gNB 120A generates the entire RRC Reconfiguration message, for example, based on information received from the secondary donor gNB 120B in operation 3, and the master donor gNB 120A sends the RRC Reconfiguration message to the IAB node 110.

[0073] In operation 5, the IAB node 110 sends the master donor gNB 120A an RRC Reconfiguration Complete message.

[0074] In operation 6, the master donor gNB 120A sends the secondary donor gNB 120B a S-Node Reconfiguration Complete message.

[0075] In operation 7, at the IAB node 110, information received from the RRC Reconfiguration message sent from the master donor gNB 120A in operation 4 is passed from a mobile termination (MT) of the IAB node 110 to the DU of the IAB node 110. In operation 8, the DU of the IAB node 110 obtains in IP address for downlink (DL) traffic via the secondary donor gNB 12 OB.

[0076] Referring to FIG. 3B, in operation 9, the IAB-node 110 sends an FI Setup Request to the secondary donor gNB 120B which is routed via a DU of the master donor gNB 120A. The FI Setup Request may be generated by the IAB node 110 so as to include the gNB DU ID that was assigned to the IAB node 110 by the secondary donor gNB 12 OB in operation 3 and received at the IAB node 110 from the master donor gNB 120A in operation 4. According to at least some example embodiments, FI Request including the aforementioned gNB DU ID is an indication to the secondary donor gNB 120B that the IAB node 110 is requesting to setup the secondary Fl-C interface according to example embodiments.

[0077] In operation 10, the secondary donor gNB 120B associates the gNB-DU ID received in operation 9 with the UE contexts previously received in the S-Node Addition Request that was sent to the secondary gNB 12 OB from the master donor gNB 120A in operation 1.

[0078] In operation 11, the secondary donor gNB 120B sends an FI Setup Response to the IAB-node 110 which is routed via the DU of the master donor gNB 120A.

[0079] In operation 12, the secondary donor gNB 12 OB sends a BH Routing Configuration message to the IAB-node 110 which is routed via the DU of the master donor gNB 120A. According to at least some example embodiments, the secondary donor gNB 120B generates the BH Routing Configuration message such that the BH Routing Configuration message includes the BAP routing ID allocated by the master donor gNB 120A and sent to the secondary donor gNB 120B in operation 1.

[0080] In operation 13, the IAB-node 110 sends an FI BH Routing Configuration ACK to the secondary donor gNB 12 OB which is routed via the master donor gNB 120A.

[0081] In operation 14, the secondary donor gNB 120B sends, to the IAB-node 110 via the master donor gNB 120A, per-UE Context Modification requests and a mapping of DRBs to the SCG BH RLC channels based on the UE identities and DRBs, and the indications of which identities the secondary donor gNB 120B should use, received at the secondary gNB 120B in operation 1.

[0082] In operation 15, the IAB node 110 sends, per-UE, an FI UE Context Modification Response. The IAB node 110 may generate the per-UE FI UE Context Modification Responses as FI UE Context Modification Responses that include an indication of downlink transport network layer (TNL) information that is specific to use of the IAB node 110’s SCG BH RLC channels. For example, the indication of downlink TNL information included in the modified per-UE FI UE Context Modification Responses may be or include, for example, per-DRB general packet radio service (GPRS) tunneling protocol (GTP)-U tunnel endpoint identifiers that have been allocated by the IAB-node 110 and are specific to use of the IAB-node 110’s SCG BH RLC channels.

[0083] Point PI indicates the point where the IAB node 110 has information sufficient for sending traffic over the SCG BH RLC channels.

[0084] In operation 16, the secondary donor gNB 120B sends an S-Node Modification Required message to the CU of the master donor gNB 120A. According to at least some example embodiments, the secondary donor gNB 120B generates the S-Node Modification Required message as a modified S-Node Modification Required message that includes an indication that traffic can now be routed to the IAB-node 110 via the IAB node 110’s SCG. For example, the aforementioned indication may be the per-DRB GTP-U tunnel endpoint identifiers that were received, at the secondary donor gNB 120B from the IAB node 110, in operation 15.

[0085] Point P2 indicates the point where the master donor gNb 120A has information sufficient for sending traffic over the SCG BH RLC channels.

[0086] In operation 17, the CU of the master donor gNB 120A sends an S-Node Modification Confirmation to the secondary donor gNB 12 OB.

[0087] According to at least some example embodiments, operation 1 implements items B-C discussed above; operations 3-4 and 7 implement item F, i.e. the secondary donor gNB 120B assigns and sends a gNB-DU ID to be used by the IAB node at FI Setup, so that the secondary donor gNB 120B is able to associate the IAB node with the information that the secondary donor received in step 1; operations 9- 10 implement item A as well as the association enabled by operations 3-4 and 7; and operation 12 implements item D, where the secondary donor gNB 12 OB utilizes the routing ID received in operation 1 from the master donor. [0088] According to at least some example embodiments, operation 14 implements item E, (e.g., based on the information it received in operation 1, the secondary donor gNB 120B is able to modify pre-existing UE contexts using identifiers understood by the IAB node 110); operation 15 implements item G (e.g., the IAB node 110 allocates and sends, for example, per-DRB GTP-U tunnel endpoint identifiers specific to use of the IAB node 110’s SCG BH RLC channels); and operation 16 implements item H, (e.g., once the master donor gNB 120A receives the TNL information of operation 15, the master donor gNB 120A knows that the SCG BH RLC channels are ready for use).

[0089] According to at least some example embodiments, in the example process illustrated in FIGS. 3A-3B, the message exchange activities of operations 14-15 are done per UE served by the IAB node 110 because the FI protocol currently does not support a procedure for joint modification of multiple UE contexts.

[0090] Thus, a process of establishing a secondary Fl-C interface according to at least some example embodiments may provide an advantage of allowing an IAB node to be configured by two donor gNBs with a well-defined work split, in comparison with conventional methods of facilitating inter-donor migration of IAB nodes.

[0091] Further, the process of establishing a secondary Fl-C interface according to at least some example embodiments allows the full-fledged inter-donor handover, which is performed in accordance with some conventional methods, to be avoided. For example, when an IAB node’s radio link configured by a donor gNB deteriorates, according to some conventional methods, a full-fledged inter-donor handover of the IAB node is performed. The full-fledged inter-donor handover may include configuring, by the handover target donor gNB, backhaul radio links and routing of the IAB node (as well as the IAB node’s parent and ancestor nodes). Thus, by allowing the aforementioned full-fledged inter-donor handover of the IAB node to be avoided, the process of establishing a secondary Fl-C interface according to at least some example embodiments may result in a reduction in an amount of computational resources expended, a reduction in power consumption, and/or an increase in processing speed with respect to processors of radio network elements (e.g., processors of IAB nodes, and/or donor gNBs) involved in an inter-donor migration of an IAB node, in comparison with conventional methods of performing inter-donor migration of IAB nodes. Further, by allowing the aforementioned full-fledged inter donor handover of the IAB node to be avoided, the process of establishing a secondary Fl-C interface according to at least some example embodiments may result in a reduction in a total amount of signaling occurring on a communications network within which inter-donor migration of an IAB node is to take place, thus reducing network latency and / or network congestion of the communications network.

[0092] Although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and similarly, a second element could be termed a first element, without departing from the scope of this disclosure. As used herein, the term "and/or," includes any and all combinations of one or more of the associated listed items.

[0093] When an element is referred to as being "connected," or "coupled," to another element, it can be directly connected or coupled to the other element or intervening elements may be present. By contrast, when an element is referred to as being "directly connected," or "directly coupled," to another element, there are no intervening elements present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., "between," versus "directly between," "adjacent," versus "directly adjacent," etc.).

[0094] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the singular forms "a," "an," and "the," are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises," "comprising," "includes," and/or "including," when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. [0095] It should also be noted that in some alternative implementations, the functions/ acts noted may occur out of the order noted in the figures. For example, two figures shown in succession may in fact be executed substantially concurrently or may sometimes be executed in the reverse order, depending upon the functionality/ acts involved.

[0096] Specific details are provided above to provide a thorough understanding of example embodiments. However, it will be understood by one of ordinary skill in the art that example embodiments may be practiced without these specific details. For example, systems may be shown in block diagrams so as not to obscure the example embodiments in unnecessary detail. In other instances, well-known processes, structures and techniques may be shown without unnecessary detail in order to avoid obscuring example embodiments.

[0097] As discussed herein, illustrative embodiments will be described with reference to acts and symbolic representations of operations (e.g., in the form of flow charts, flow diagrams, data flow diagrams, structure diagrams, block diagrams, etc.) that may be implemented as program modules or functional processes include routines, programs, objects, components, data structures, etc., that perform particular tasks or implement particular abstract data types and may be implemented using existing hardware at, for example, existing UE, base stations, eNBs, RRHs, gNBs, femto base stations, network controllers, computers, Central Units (CUs), ng-eNBs, other radio access or backhaul network elements, or the like. Such existing hardware may be processing or control circuitry such as, but not limited to, one or more processors, one or more Central Processing Units (CPUs), one or more controllers, one or more arithmetic logic units (ALUs), one or more digital signal processors (DSPs), one or more microcomputers, one or more field programmable gate arrays (FPGAs), one or more System-on-Chips (SoCs), one or more programmable logic units (PLUs), one or more microprocessors, one or more Application Specific Integrated Circuits (ASICs), or any other device or devices capable of responding to and executing instructions in a defined manner.

[0098] Although a flow chart may describe the operations as a sequential process, many of the operations may be performed in parallel, concurrently or simultaneously. In addition, the order of the operations may be re-arranged. A process may be terminated when its operations are completed, but may also have additional steps not included in the figure. A process may correspond to a method, function, procedure, subroutine, subprogram, etc. When a process corresponds to a function, its termination may correspond to a return of the function to the calling function or the main function.

[0099] As disclosed herein, the term "storage medium," "computer readable storage medium" or "non-transitory computer readable storage medium” may represent one or more devices for storing data, including read only memory (ROM), random access memory (RAM), magnetic RAM, core memory, magnetic disk storage mediums, optical storage mediums, flash memory devices and/or other tangible machine-readable mediums for storing information. The term "computer readable medium" may include, but is not limited to, portable or fixed storage devices, optical storage devices, and various other mediums capable of storing, containing or carrying instruction (s) and/or data.

[0100] Furthermore, example embodiments may be implemented by hardware, software, firmware, middleware, microcode, hardware description languages, or any combination thereof. When implemented in software, firmware, middleware or microcode, the program code or code segments to perform the necessary tasks may be stored in a machine or computer readable medium such as a computer readable storage medium. When implemented in software, a processor or processors will perform the necessary tasks. For example, as mentioned above, according to one or more example embodiments, at least one memory may include or store computer program code, and the at least one memory and the computer program code may be configured to, with at least one processor, cause a network element or network device to perform the necessary tasks. Additionally, the processor, memory and example algorithms, encoded as computer program code, serve as means for providing or causing performance of operations discussed herein.

[0101] A code segment of computer program code may represent a procedure, function, subprogram, program, routine, subroutine, module, software package, class, or any combination of instructions, data structures or program statements. A code segment may be coupled to another code segment or a hardware circuit by passing and/or receiving information, data, arguments, parameters or memory contents. Information, arguments, parameters, data, etc. may be passed, forwarded, or transmitted via any suitable technique including memory sharing, message passing, token passing, network transmission, etc.

[0102] The terms “including” and/or “having,” as used herein, are defined as comprising (i.e., open language). The term “coupled,” as used herein, is defined as connected, although not necessarily directly, and not necessarily mechanically. Terminology derived from the word “indicating” (e.g., “indicates” and “indication”) is intended to encompass all the various techniques available for communicating or referencing the object/ information being indicated. Some, but not all, examples of techniques available for communicating or referencing the object /information being indicated include the conveyance of the object /information being indicated, the conveyance of an identifier of the object /information being indicated, the conveyance of information used to generate the object /information being indicated, the conveyance of some part or portion of the object /information being indicated, the conveyance of some derivation of the object /information being indicated, and the conveyance of some symbol representing the object /information being indicated.

[0103] According to example embodiments, UE, base stations, eNBs, RRHs, gNBs, femto base stations, network controllers, computers, Central Units (CUs), ng-eNBs, other radio access or backhaul network elements, or the like, may be (or include) hardware, firmware, hardware executing software or any combination thereof. Such hardware may include processing or control circuitry such as, but not limited to, one or more processors, one or more CPUs, one or more controllers, one or more ALUs, one or more DSPs, one or more microcomputers, one or more FPGAs, one or more SoCs, one or more PLUs, one or more microprocessors, one or more ASICs, or any other device or devices capable of responding to and executing instructions in a defined manner.

[0104] Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments of the invention. However, the benefits, advantages, solutions to problems, and any element(s) that may cause or result in such benefits, advantages, or solutions, or cause such benefits, advantages, or solutions to become more pronounced are not to be construed as a critical, required, or essential feature or element of any or all the claims.

Claims

What is claimed is:

1. A method of operating a master donor next generation Node B (gNB) of a communications network, the communications network further including a secondary donor gNB and an integrated access and backhaul (IAB) node, the method comprising: generating, by the master donor gNB, a request to set up a secondary control interface between the secondary donor gNB and the IAB node; and sending the request.

2. The method of claim 1, wherein the request generated by the master donor gNB further includes an indication of identities of UEs that the secondary donor gNB is to use in signaling to the IAB node.

3. A method of operating a secondary donor next generation Node B (gNB) of a communications network, the communications network further including a master donor gNB and an integrated access and backhaul (IAB) node, the method comprising: receiving, at the secondary donor gNB, a first message including identities of user equipment (UEs) for which contexts exist on a primary control interface at the IAB node; and sending, by the secondary donor gNB on a secondary control interface between the secondary donor gNB and the IAB node, a configuration message that identifies at least one of the UEs using at least one of the identities included in the first message.

4. The method of claim 3, further comprising: receiving, at the secondary donor gNB, an indication that causes the secondary donor gNB to set up the secondary control interface between the secondary donor gNB and the IAB node.

5. The method of claim 3, further comprising: receiving a backhaul adaption protocol (BAP) routing ID; generating, by the secondary donor gNB, a backhaul (BH) routing configuration message that includes the BAP routing ID; and sending the backhaul (BH) routing configuration message to the IAB node.

6. The method of claim 3, wherein the identities of the UEs included in the first message are identities the secondary donor gNB is to use in signaling to the IAB node, wherein the method comprises: sending a UE context modification request to the IAB node based on the indication of identities the secondary donor gNB is to use in signaling to the IAB node, and wherein the UE context modification request is the configuration message.

7. The method of claim 3, further comprising: allocating a gNB DU ID to the IAB node; generating a second message that includes the gNB DU ID; and sending the second message to the master donor gNB.

8. The method of claim 7, further comprising: receiving, at the secondary donor gNB from the IAB node, an FI setup request; determining whether the FI setup request includes the gNB DU ID; and determining that the F 1 setup request is a request to setup a secondary Fl-C interface, in response to determining that the FI setup request included the gNB DU ID.

9. A method of operating an integrated access and backhaul (IAB) node of a communications network, the communications network further including a master donor next generation Node B (gNB) and a secondary donor gNB, the method comprising: receiving, at the IAB node on a secondary control interface between the IAB node and the secondary donor gNB, a configuration message including an identity of a user equipment (UE) to which the configuration message pertains; identifying a UE to which the configuration message pertains as a UE associated, on a primary control interface of the IAB node, with the identity in the configuration message; and performing the configuration on the UE identified.

10. The method of claim 9, further comprising: receiving, at the IAB node, an indication that causes the IAB node to set up the secondary control interface between the IAB node and the secondary donor gNB.

11. The method of claim 9, further comprising: generating a request to setup a secondary Fl-C interface with the secondary donor gNB, and sending the request to the secondary donor gNB.

12. The method of claim 9, further comprising: receiving a gNB-DU ID that has been allocated to the IAB node; and generating a request to setup a secondary Fl-C interface with the secondary donor gNB by generating an FI request that includes the gNB-DU ID, and sending the FI request to the secondary donor gNB.

13. The method of claim 9, wherein receiving the configuration message comprises: receiving, at the IAB node, a UE context modification request and a mapping of data radio bearers (DRBs) to at least one secondary cell group (SCG) backhaul (BH) radio link control (RLC) channel.

14. The method of claim 13, further comprising: generating an FI UE context modification response that includes an indication of downlink transport network layer (TNL) information that is specific to use of SCG BH RLC channels of the IAB node, wherein the indication of downlink TNL information includes per-data radio bearer (DRB) general packet radio service (GPRS) tunneling protocol (GTP)-U tunnel endpoint identifiers that are specific to use of SCG BH RLC channels of the IAB-node.

15. A master donor next generation Node B (gNB) of a communications network, the master donor gNB comprising: a processor; and memory storing computer-executable instructions that, when executed by the processor, causes the master donor gNB, generating a request to set up a secondary control interface between a secondary donor gNB of the communications network and an integrated access and backhaul (IAB) node of the communications network; and sending the request.

16. A secondary donor next generation Node B (gNB) of a communications network, the secondary gNB comprising: a processor; and memory storing computer-executable instructions that, when executed by the processor, causes the the secondary gNB to perform operations including, receiving a first message including identities of user equipment (UEs) for which contexts exist on a primary control interface at an integrated access and backhaul (IAB) node of the communications network, the primary control interface being between the IAB node and a master donor gNB; and sending, by the secondary donor gNB on a secondary control interface between the secondary donor gNB and the IAB node, a configuration message that identifies at least one of the UEs using at least one of the identities included in the first message.

17. An integrated access and backhaul (IAB) node of a communications network, the IAB node comprising: a processor; and memory storing computer-executable instructions that, when executed by the processor, causes the the IAB node to perform operations including, receiving, on a secondary control interface between the IAB node and a secondary donor next generation Node B (gNB) of the communications network, a configuration message including an identity of a user equipment (UE) to which the configuration message pertains; identifying a UE to which the configuration message pertains as a UE associated, on a primary control interface between the IAB node and a master donor gNB of the communications network, with the identity in the configuration message; and performing the configuration on the identified UE.

18. A radio network element of a communications network, the radio network element comprising: means for generating a request to set up a secondary control interface between a secondary donor next generation Node B (gNB) of the communications network and an integrated access and backhaul (IAB) node of the communications network; and means for sending the request.

19. A radio network element of a communications network, the radio network element comprising: means for receiving a first message including identities of user equipment (UEs) for which contexts exist on a primary control interface at an integrated access and backhaul (IAB) node of the communications network, the primary control interface being between the IAB node and a master donor next generation Node B (gNB); and means for sending, by the secondary donor gNB on a secondary control interface between the secondary donor gNB and the IAB node, a configuration message that identifies at least one of the UEs using at least one of the identities included in the first message.

20. A radio network element of a communications network, the radio network element comprising: means for receiving, on a secondary control interface between the radio network element and a secondary donor next generation Node B (gNB) of the communications network, a configuration message including an identity of a user equipment (UE) to which the configuration message pertains; means for identifying a UE to which the configuration message pertains as a UE associated, on a primary control interface between the radio network element and a master donor gNB of the communications network, with the identity in the configuration message; and means for performing the configuration on the identified UE.