Integrated access backhaul configuration

Abstract

A method for operating an integrated access backhaul (IAB) node in a wireless communication network is proposed. The IAB node is arranged to wirelessly transmit backhaul traffic with a parent node and a child node. The method comprises: receiving a duplex mode configuration message from a parent node; sending a duplex mode configuration message to a child node; receiving a duplex mode configuration confirmation message from the child node; applying the duplex mode included in the duplex mode configuration message received from the parent node after receiving the duplex mode configuration confirmation message from the child node; and sending a duplex mode configuration confirmation message to the parent node.

Description

Technical Field

[0001] The present invention relates to techniques for configuring an integrated access backhaul (IAB). In particular, certain examples relate to IAB configuration for a new radio (NR) air interface of a wireless communication network, such as the IAB configuration that has been proposed for a fifth generation (5G) wireless communication network. Background Art

[0002] Wireless or mobile (cellular) communication networks, in which mobile terminals (UEs, such as mobile phones (handsets)) communicate via radio links with a network of base stations or other wireless access points or nodes, have developed rapidly over many generations. The 3rd Generation Partnership Project (3GPP) designed, specified and standardized the technology for mobile wireless communication networks. The 4th generation (4G) systems are now widely deployed.

[0003] The 3GPP standards for 4G systems include an evolved packet core (EPC) and enhanced-UTRAN (E-UTRAN: Enhanced Universal Terrestrial Radio Access Network). E-UTRAN uses Long Term Evolution (LTE) radio technology. LTE is often used to refer to the entire system including both EPC and E-UTRAN, and LTE is used in this sense in the remainder of this document. LTE should also be considered to include LTE enhancements (e.g., Advanced LTE and LTE Pro (Professional LTE)), which provide enhanced data rates over LTE.

[0004] The trend towards greater data throughput continues as 3GPP is currently working on standardizing fifth generation (5G) network technology. As part of this, a new air interface is being developed, which may be referred to as 5G New Radio (5GNR) or simply NR. Although NR is built on established LTE technology, NR is designed to support a variety of services and use case scenarios envisioned for 5G networks. One aspect of NR is the use of wireless backhaul to reduce network deployment costs and enhance network flexibility by allowing the topology of the network to be reconfigured. For conventional wireless communication networks such as LTE, base stations (referred to as enhanced Node Bs, eNBs in LTE) are connected to the core network via a wired backhaul (BH) link. The base station is responsible for wireless communication with mobile devices so that these devices can access the core network. Alternatively, the base station can be connected to the core network via a dedicated point-to-point wireless link, which is completely separate from the process of allowing devices to wirelessly access the base station. As part of NR, it is proposed that device access to the core network and wireless backhaul can be integrated, which may be referred to as integrated access backhaul (IAB). That is, within a single transmission frame for an NR base station (referred to herein as an IAB node), both backhaul communications and mobile device access communications can be incorporated. It will be appreciated that transmission timing and coordination for IAB presents challenges that have not yet been fully resolved.

[0005] IAB is a feature by which the air interface between nodes or base stations is used to provide backhaul connectivity and access to user equipment UE. Configuration of such a system involves careful selection of signaling to ensure reliable and efficient connectivity between nodes and with the UE.

[0006] Certain network features have been agreed upon at the standardization level. These features are summarized below and are used to provide background information for the present invention.

[0007] Physical layer specifications [RAN1-led, RAN2, RAN3, RAN4]:

[0008] Specification of the Synchronization Signal Block (SSB) / Remaining Minimum System Information (RMSI) period assumed by the IAB node for NR initial access.

[0009] Specifications extended to Rel. 15 to support the use of SSBs (via time division multiplexing (TDM) and / or frequency division multiplexing (FDM)) orthogonal to the SSBs used for UEs for IAB inter-node discovery and measurements, including additional SSB-based RRM Measurement Timing Configuration (SMTC) periods and time domain mapping of SSB locations (e.g., to enable muting mode to handle half-duplex constraints).

[0010] Extended specification of Random Access Channel (RACH) timing and periodicity for backhaul RACH resources (with respect to access RACH resources) and associated network coordination mechanisms for selecting such parameters such that access and backhaul (BH) are orthogonal due to half-duplex constraints (i.e., a node cannot transmit and receive simultaneously).

[0011] Specification of mechanisms for resource multiplexing between backhaul and access links. This includes:

[0012] Specification for semi-static configuration of IAB node / IAB donor distributed unit (DU) resources in case of TDM operation subject to half-duplex constraints. This should be forward compatible to allow support for half-duplex scenarios where FDM and spatial division multiplexing (SDM) resources are shared between backhaul and access links.

[0013] Specification of time resource types for sublinks of DU: DL hard, DL soft, UL hard, UL soft, flexible hard, flexible soft, unavailable

[0014] Specification for dynamic indication (L1 signaling) of the availability of soft resources for child IAB node DUs

[0015] • Specification of the required sending / receiving rules for IAB nodes and related behavior regarding time resource utilization as discussed in clause 7.3.3 of TR 38.874.

[0016] • Specification of mechanisms to support “Case-1” OTA timing alignment.

[0017] During SI, the following agreement is reached between RAN1#94 and RAN1#95 as follows.

[0018] protocol:

[0019] Solution 1-B means that for inter-IAB cell search and measurement in phase 2, the SSB that may be muted is not on the currently defined synchronization grid of the SA frequency layer, and for the non-standalone (NSA) frequency layer, the SSB is sent outside the SMTC configured for the accessing UE

[0020] Solution 1-A means that the SSB used for inter-IAB cell search in phase 2 is on the currently defined synchronization grid of the SA frequency layer, while for the NSA frequency layer, the SSB is sent inside the SMTC configured for the accessing UE

[0021] protocol:

[0022] When performing inter-IAB cell search in Phase 2, the IAB node shall not silence SSB transmissions targeting UE cell search and measurements.

[0023] For standalone (SA), it means that the SSB sent on the currently defined synchronization grid follows the currently defined period for initial access

[0024] Refers to solution 1-B implying that inter-IAB cell search for phase 2 may be TDMed by muted SSBs at least with SSBs used for UE cell search and measurements

[0025] protocol:

[0026] Supports both solution 1-A and solution 1-B

[0027] o Enhancements to off-raster SSB, e.g. new periodicity and temporal mappings can be considered

[0028] protocol:

[0029] Capture the following conclusions for IAB SI TR:

[0030] RAN1 has studied various physical layer aspects of integrated access and backhaul and has determined that support for the following features and solutions is beneficial and feasible from a RAN1 perspective:

[0031] Mechanisms for discovering IAB nodes and managing backhaul links in both SA and NSA deployments, taking into account half-duplex constraints at the IAB nodes and multi-hop topologies, including:

[0032] o Solutions that reuse the same set of SSBs used to access the UE, and solutions that use SSBs that are orthogonal (TDM and / or FDM) to the SSBs used to access the UE

[0033] One of the main goals of IAB is to provide RAN-based mechanisms to support dynamic routing to accommodate short-term blocking and transmission of delay-sensitive traffic on BH links under half-duplex constraints. There are three RA (resource allocation) modes defined, namely TDM, FDM and SDM. Regardless of which RA scheme is applied, IAB node discovery and measurement are always problematic, especially for millimeter wave (mmWave) where links may be prone to blocking. For SSB-based solutions, it has been agreed that two sub-solutions will be supported:

[0034] - Solution 1-A) Reuse the same set of SSBs used to access the UE:

[0035] - In this case, the SSB used for inter-IAB cell search in phase 2 is located on the currently defined synchronization grid of the SA frequency layer, while for the NSA frequency layer, the SSB is sent inside the SMTC configured for the accessing UE.

[0036] - Solution 1-B): Use SSB that is orthogonal (TDM and / or FDM) to the SSB used to access the UE:

[0037] - In this case, the SSBs that may be muted for inter-IAB cell search and measurement in Phase 2 are not on the currently defined synchronization grid of the SA frequency layer, while for the NSA frequency layer, the SSBs are sent outside the SMTC configured for the accessing UE. Summary of the invention

[0038] Technical issues

[0039] Embodiments of the present invention are directed to solving problems identified in the prior art, whether mentioned herein or not.In particular, embodiments of the present invention are directed to providing inter-node discovery and measurement techniques for IAB nodes subject to half-duplex constraints.

[0040] Certain examples of the present invention aim to address the issue of transmission timing and coordination of IAB.

[0041] Solution to the problem

[0042] According to a first aspect of the present invention, there is provided a method for operating an integrated access backhaul IAB node in a wireless communication network, the IAB node being arranged to wirelessly transmit backhaul services with a parent node and a child node, the method comprising: receiving a duplex mode configuration message from a parent node; sending a duplex mode configuration message to a child node; receiving a duplex mode configuration confirmation message from a child node; after receiving a duplex mode configuration confirmation message from a child node, applying the duplex mode contained in the duplex mode configuration message received from the parent node; and sending a duplex mode configuration confirmation message to the parent node. The configuration of different duplex modes provides enhanced flexibility and is important in many scenarios. When the load in the uplink and downlink changes, configuring a new duplex mode can meet the changed load in the uplink and downlink to provide a better quality of service (QoS) level. When two IAB nodes have severe cross-link interference with each other, reconfiguring the duplex mode can reduce the interference.

[0043] According to a second aspect of the present invention, there is provided an integrated access backhaul IAB node in a wireless communication network, the IAB node being arranged to wirelessly communicate backhaul traffic with a parent node and a child node and further arranged to perform the above method.

[0044] According to a third aspect of the present invention, there is provided a computer-readable storage medium having computer-executable instructions stored thereon, which cause the computer to execute the above method when the computer executes the computer-executable instructions.

[0045] According to a fourth aspect of the present invention, there is provided a method for configuring a node in a telecommunications network, wherein the node is operable to perform integrated access backhaul (IAB), the method comprising the steps of selectively silencing one or more SSB transmissions such that during the silencing period, the node is able to monitor SSB transmissions from another node.

[0046] In an embodiment, one or more SSB transmissions are selectively muted on an individual SSB basis or on a burst set basis.

[0047] In an embodiment, the one or more SSB transmissions are muted in a complementary manner between any two given nodes.

[0048] In an embodiment, one or more neighboring nodes exchange SSB configuration information and adjust their SSB configurations accordingly.

[0049] In an embodiment, a host node or a parent node provides SSB configuration for all child nodes or their next-level child nodes.

[0050] In an embodiment, selective quiescing is performed such that the node and any connected nodes are cooperatively quiesced.

[0051] In an embodiment, selective quiescing is performed such that only nodes in the same hop are cooperatively quiesced.

[0052] In an embodiment, the muting and SSB configurations depend on the topology and can be configured / reconfigured in a semi-permanent manner or in a dynamic manner through upper layer signaling.

[0053] In an embodiment, an SMTC orthogonal to the access UE SMTC is provided to allow a node to measure the SSB of a neighboring node, so that an additional SMTC is configured in both the RRC connected state and the RRC idle state.

[0054] In an embodiment, some or all of the information included in the PBCH is removed from the SSB or muted.

[0055] In an embodiment, the node mobile terminal MT assumes an SSB configuration and an SSB measurement period different from those assumed when first accessing the network.

[0056] In an embodiment, the node is operable to perform integrated access backhaul IAB with a status indicator to distinguish IAB MTs from access UEs.

[0057] Another aspect of the invention provides a computer program comprising instructions arranged to, when executed, implement a method and / or apparatus according to any one of the above aspects. Another aspect provides a machine readable storage storing such a program.

[0058] Advantageous Effects of the Invention

[0059] The present disclosure provides inter-node discovery and measurement techniques for IAB nodes subject to half-duplex constraints.Certain examples of the present disclosure address the issue of transmission timing and coordination for IAB. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Hereinafter, embodiments of the present invention will be further described with reference to the accompanying drawings, in which:

[0061] Figure 1 An arrangement of three IAB nodes is shown;

[0062] Figure 2a -d shows a general process for transmitting configuration messages within an IAB network including a host node and N IAB nodes;

[0063] Figure 3 An example of duplex mode configuration messaging according to a centralized approach is shown;

[0064] Figure 4 An example of duplex mode configuration messaging according to a distributed approach is shown;

[0065] Figure 5 An example of processing duplex mode configuration according to a distributed approach is shown;

[0066] Figure 6 An example of a signaling procedure for duplex mode configuration messaging is shown;

[0067] Figure 7 An example of message transmission between IAB nodes is shown;

[0068] Figure 8 An example of the structure of an IAB node is shown;

[0069] Fig. 9 An SSB coordinated within an SSB burst set for inter-node discovery according to an embodiment of the present invention is presented;

[0070] Fig.10 A silent solution (on all IAB nodes) according to an embodiment of the present invention is shown;

[0071] Fig.11 A hop order based muting scheme according to an embodiment of the present invention is presented; and

[0072] Fig.12 Another muting scheme based on hopping sequence according to an embodiment of the present invention is presented. DETAILED DESCRIPTION

[0073] Embodiments of the present invention will now be described in the context of a 5G wireless communication network, and in particular in the context of an NR radio access network that forms part of the 5G wireless communication network. It will be appreciated that the present invention is not limited to any particular radio access technology. That is, the concept of the IAB in which backhaul traffic and network access traffic share transmission frames is equally applicable to other wireless communication systems in which it is desired to deploy base stations with wireless backhaul. References to specific 3GPP constructs in certain examples should not be construed as limiting the ability of the present invention to be applied to other wireless communication networks.

[0074] Now refer to Figure 1 The principle of integrated access backhaul is described in more detail. In an integrated access backhaul (IAB) within a wireless communication network, an IAB node will be connected to a parent node and one or more child nodes. That is, each IAB node is allowed to have multiple child nodes. Each IAB node includes a base station that allows a device to have radio access to the network and performs backhaul communication to transmit access data with the core network.

[0075] Figure 1 Three nodes are shown: parent node 1, IAB node 2, and child node 3. It will be understood that each of nodes 1 to 3 may be the same IAB node, and Figure 1 The notations "parent" and "child" in relate only to a particular IAB node (in this case, node 2). That is, for child node 3, its parent node is node 2, and its child nodes are not shown, but would logically appear in Figure 1 As an exception to this, for each IAB chain of nodes, there will be a first node that has a wired or dedicated wireless connection to the core network, and this node may be referred to as a host node. A host node has no parent node, but acts as a parent node with respect to its child nodes (or, if it has multiple child nodes, each of its child nodes). As another exception, there will be an IAB node that has no backhaul connection to any subsequent child nodes. Figure 1 The host node is not shown, but logically it will appear as indicated by arrow 4. Figure 1 As mentioned above, another exception is that an IAB node may have more than one child node. The IAB configuration technology disclosed herein is also applicable to an IAB node having more than one child node.

[0076] Figure 1 Further shown is an access device in wireless communication with IAB node 2. Likewise, other access devices may also be in wireless communication with node 1 and node 3. For the specific example of IAB node 2, this topology results in backhaul (BH) downlink (DL) and uplink (UL) communications with parent node 1 and child node 3, and access DL and UL communications with mobile device 5.

[0077] The 3GPP RAN1 working group agreed on time division multiplexing (TDM) of BH links and access links for IAB nodes at the #94 meeting held in Gothenburg, Sweden on August 20, 2018. In particular, for IAB node TDM, the agreement supports at least the following cases, as shown in Table 1:

[0078]

[0079] Table 1: Situation agreed upon in RAN1#94.

[0080] In Table 1, the requirements for TDM between two links are given for 16 different cases. For each link, a notation Lx,y is given, where x represents the party with which the IAB node is communicating (P-parent node; C-child node; A-access, i.e., equipment of the wireless access network), and y represents whether the service is uplink (UL) or downlink (DL). For example, L P,DL represents the downlink BH communication from the parent node, while L C,UL Represents uplink BH communication from a child node. It will be noted that situations 9 to 12 indicate that in some cases, uplink or downlink communication can be shared between an access device and a child node for link 2. Table 1 represents possible scenarios in which a node can transmit and receive simultaneously - i.e., in which link 1 and link 2 can be used simultaneously. For current IAB technology, it is still challenging for a node to transmit and receive simultaneously. A more practical arrangement provided by Table 1 is that a node either transmits or receives at any instant. That is, the links specified for each situation indicate that two different uplink or downlink links can be applied simultaneously. Time sharing can be provided at the symbol level.

[0081] Column 4 indicates whether a mode of TDM needs to be defined for links 1 and 2 for each case. It will be noted that for cases 13 to 16, both links are connected to a child node and an access device: there is no link to the parent node. The 3GPP Release 15 standard mechanism can be applied to determine the TDM between two links. However, it will be noted that for cases 1 to 12, only one mode is agreed for TDM between links 1 and 2, but a method for determining the appropriate mode has not yet been agreed. Mechanisms need to be designed for implementing TDM between links 1 and 2, and in particular a way of designing a mode for integrating BH and access data at the IAB node needs to be identified.

[0082] The 3GPP RAN1 working group has agreed that a given mode may include simultaneous support for multiple cases, but not how this may be achieved. Table 1 identifies two types of links that may be supported simultaneously, but there may be multiple instances of each type of link at any given time: for example, communicating with multiple sub-nodes and / or access devices. Similarly, there is agreement that each IAB node may be configured with IAB node-specific resources available for link time, but there is no agreement on the details of the adaptation period and granularity (e.g., slot / symbol / subframe level) of the mode provided to the IAB node, nor how to explicitly or implicitly indicate the resources or provide a suitable signaling mechanism for the necessary TDM mode at each IAB node.

[0083] Different duplex modes are supported in NR (as shown in Table 2, below and derived from 3GPP TS 38.211; “NR; Physical channels and modulation”, Version 15.3.0, dated September 27, 2018, available from https: / / portal.3gpp.org / desktopmodules / Specifications / SpecificationDetails.aspx? specificationId=3213 obtained). However, duplex modes for TDM of BH links and access links are not currently supported. As can be seen in Table 2, 61 different duplex modes are defined for downlink (D) and uplink (U) data with different symbols within a time frame slot, where X indicates that the symbol is not used (i.e., the symbol is empty). The formats represented in row 0 or row 61 of Table 2 are only used by nodes for access services: that is, they do not contain wireless BH and therefore cannot support IAB nodes. Formats 62 to 255 are reserved for future use. There is a clear need to define how TDM of BH links and access links can be implemented without causing conflicts between the BH link to the parent node and the BH link to the child node.

[0084]

[0085] Table 2: Format defined by 3GPP TS 38.211.

[0086] It is an object of some embodiments of the present invention to propose a process for implementing duplex mode configuration and necessary signaling. Another object of some embodiments of the present invention is to propose design principles for duplex mode design of TDM for BH links and access links. Some embodiments of the present invention provide enhanced flexibility with dynamic duplex mode configuration.

[0087] Reference now Figure 2a , which shows an example of a general IAB configuration message transmission process. Figure 2a A host node 0 (a node directly coupled to the core network as described above) and N IAB nodes are shown, where N is a real number. IAB nodes NThere are no child nodes. In particular, the host node can be a macro / micro node connected to a wired backhaul. For each IAB node, the backhaul is done wirelessly. Each node sends a duplex mode configuration message to its child nodes. For example, node 0 sends a message to node 1 01 Each node returns a duplex mode configuration confirmation message to its parent node. For example, node N sends a confirmation message to node N-1. N,N-1 Upon receiving the confirmation message from its child node, the IAB node applies the new duplex mode it previously received from its parent node before sending the confirmation message to its parent node. It will be appreciated that by waiting until its child node has confirmed the configuration message (and therefore until after the child node has applied the new duplex mode), it is ensured that the IAB node does not begin using the new duplex configuration included for communicating with its child node before the child node is ready to properly receive communications from the IAB node. This prevents attempts from being made to transmit data to the child node until it is ready to receive it.

[0088] It will be appreciated that where an IAB node has multiple child nodes, it will then wait until a confirmation message has been received from each child node before it applies the new duplex mode itself. There is no limit to the length of the IAB node chain. However, it will be appreciated that the greater the number of IAB nodes, the greater the time delay between the host node 0 sending the configuration message and receiving the confirmation message.

[0089] The process of waiting for a confirmation message from a child node before applying the duplex mode received from the parent node can be referred to as configure-and-wait. In particular, the host node will send a duplex mode configuration message to its child nodes. The host node will not reconfigure or apply a new configuration until it has received feedback from its child nodes.

[0090] There may be cases where the duplex configuration is unsuccessful. An example is when a child node responds to its parent node with a negative acknowledgement (NACK) / unavailable on the duplex mode configuration due to a message packet being lost or the configuration being unavailable. In this case, the parent node may send another configuration message with the same duplex mode, or with a different duplex mode but the same duplex granularity (time slot / subframe / symbol level). This is Figure 2b This is illustrated in FIG. 1 , which shows an additional message NACK and reconfiguration message _01-1, which follows message _01 and is Figure 2a As shown in FIG. 1 , the IAB node 1 sends a duplex mode configuration message before.

[0091] Alternatively, different duplex modes with different duplex granularity (time slot / subframe / symbol level) may be needed. Figure 2c As shown in the figure, the message _01 is followed by Figure 2bAdditional messages are sent in a similar manner as shown in .

[0092] If all these attempts still fail to configure the child node, the parent node needs to retain its current duplex mode configuration and wait for the next configuration opportunity. Figure 2b and 2c The same method as shown includes Figure 2d Each IAB node will receive a message indicating the duplex mode configuration from its parent node and send a duplex mode configuration message to its child nodes.

[0093] Host node 0 can send a new duplex configuration message later 01 ,like Figure 2a This may occur when a change in the amount of backhaul data received from the child IAB node is detected. Alternatively, the new duplex configuration message may be caused by a detected change in the IAB network topology, or may be performed periodically. The skilled person will appreciate that other factors may trigger the sending of a new duplex mode configuration message. For a distributed method of duplex mode configuration, as described below in conjunction with Figure 4 As described, it is possible that a specific IAB node other than the host node may send a new duplex mode configuration message to its child nodes to provide a new duplex mode configuration. This may cause the child node to similarly send a new duplex mode configuration to its child nodes, etc. In other words, it is possible that the duplex mode configuration message may only require reconfiguration of a portion of the IAB chain.

[0094] Two methods for generating a duplex mode configuration message will now be described, which are referred to herein as a centralized method and a distributed method.

[0095] In the centralized approach, each duplex mode configuration message contains the duplex mode and identification for the recipient child node, grandchild node and forwarded through all subsequent IAB nodes. That is, the duplex mode is transmitted from the host node to each child node in a centralized manner. The host node is responsible for determining the duplex mode of all nodes. Figure 3 FIG. 4 depicts a duplex mode configuration message according to a centralized method. It can be seen that the first duplex mode configuration message 01 (From the host node 0 Send to IAB node 1 ) includes the duplex mode configuration message within itself 12 (From IAB node 1 Send to IAB node 2 ), together with the IAB node 1 duplex mode. Upon receiving the duplex mode configuration message 01When the IAB node 1 removes the duplex mode intended to be applied at the IAB node 1, and sends the duplex mode configuration message 12 Forwarded to IAB node 2 A similar process is repeated on each IAB node until the final child node is reached. Each step along the chain removes its own duplex mode. It should be noted that the granularity of the duplex mode can be different for different child nodes. For example, in the message 01 In the example, the duplex mode configuration for IAB node 1 may be a symbol-level configuration, while the duplex mode configuration for IAB node 2 may be a slot-level configuration. In addition, the duplex modes for different nodes are not necessarily the same, which provides greater flexibility to minimize cross-link interference.

[0096] A centralized approach may be advantageous in cases where the host node has significantly greater processing power than the IAB node. In this case, the host node can perform all calculations required to determine the appropriate duplex mode for each node, allowing a simpler implementation of the IAB node. It may also be that the host node has access to a greater amount of information about the performance of the network, allowing it to more appropriately determine the duplex mode, and thus determine the air interface resource allocation at each node. It may also be the case that the child nodes form a tree structure, so the host node can determine the duplex mode for all child nodes to minimize cross-link interference.

[0097] In a distributed approach, the duplex mode configuration message contains only the duplex mode of the intended child node recipient. The duplex mode can be transmitted from the IAB node to the child nodes in a distributed manner. Each IAB node and the host node only determines the duplex mode for its child nodes. Figure 4 The distributed approach is illustrated in FIG, where the host nodes are shown completely independently of each other. 0 To IAB node N A series of duplex mode configuration messages for each node of the IAB. It should be noted that the granularity of the duplex mode can be different for different child nodes. For example, the duplex mode configuration for IAB node 1 can be a symbol-level configuration, while the duplex mode configuration for IAB node 2 can be a slot-level configuration. In addition, the duplex modes for different nodes are not necessarily the same, which provides greater flexibility to minimize cross-link interference.

[0098] A distributed approach may be advantageous in situations where the host node does not have sufficient processing power to calculate the entire setting of duplex modes for each node (e.g., in situations where there are a large number of nodes). Furthermore, it will be appreciated that for a centralized approach, the host node must have full knowledge of the topology of the entire IAB chain; in contrast, for a distributed approach, each node is only required to receive its own duplex mode from its parent node and to be aware of its one or more child nodes.

[0099] According to the distributed approach, the duplex mode for a child node generated by the IAB node depends on the duplex mode received from its parent node. In particular, this is necessary to ensure that the child node is configured to communicate with the IAB node during a period when the IAB node itself does not have to communicate with its parent node. In order to enable the distributed approach, a duplex mode processor is provided at each IAB node. It will be understood that the duplex mode processor can be a dedicated task processor, or can be a general-purpose processor in the IAB node, or a processor shared with another task performed by the IAB node.

[0100] Figure 5 An example of processing a duplex mode configuration at an IAB node according to a distributed approach is shown. A duplex mode processor receives the duplex mode configuration of the IAB node from a parent node. The processor generates a suitable duplex mode configuration for its child node that does not conflict with its own duplex mode configuration. Avoiding conflicts may include avoiding the need for the IAB node to send and receive data in the same time slot / subframe / symbol.

[0101] The design of the message indicating the duplex mode configuration will now be described. In each duplex mode, the parent node needs to explicitly inform its child nodes about the backhaul uplink (BHU) and backhaul downlink (BHD) transmission slots / symbols / subframes: respectively, the transmission slots / symbols / subframes used for communication from the child node to the parent node, and vice versa. The duplex mode configuration message must include enough information to allow the child node to reserve these transmission slots / symbols / subframes only for backhaul transmissions (BHU or BHD). The granularity of the duplex mode configuration can be at the slot / symbol / subframe level.

[0102] According to some examples, the design of the duplex mode configuration is based on three principles. The first principle is that when switching from a downlink slot / symbol / subframe to an uplink slot / symbol / subframe, an X slot / symbol / subframe should be inserted in the middle. The X slot / symbol / subframe is an unknown subframe, symbol or slot, or is empty or blank, or can be simply ignored. The X slot / symbol / subframe can be used for UL and DL, and in some examples can contain signals for measuring channels. This is necessary to protect the switch from the downlink to the uplink, thus preventing unstable behavior. Tables 3 and 4 below provide examples of symbol-level and slot-level duplex mode configurations, respectively. Each slot can include 14 symbol periods, so that it can be seen that the symbol-level duplex mode provides a greater level of granularity. It can be seen that for each corresponding format, one or more X symbols or slots can be provided whenever switching is performed from the downlink to the uplink. In Tables 3 and 4, there are six exemplary formats presented for the duplex mode. Each table is open ended, and other formats can be defined according to the principles now described. BHU indicates the BH uplink from the IAB node to its parent node for that time slot / symbol / subframe. BHD indicates the BH downlink to the IAB from the parent node to the IAB node. U indicates the uplink from the access device or child node (according to the duplex mode defined for the child node). D indicates the downlink to the access device or child node. Therefore, upon receiving the duplex mode from its parent node, the IAB node is able to determine the duplex mode for its child node in a distributed approach, in which the BHD and BHU time slots / symbols / subframes are allocated in the D and U time slots / symbols / subframes for their own duplex modes, respectively. It will be understood that each duplex mode configuration message includes a duplex mode for a recipient child node generated according to one of the example formats shown in Tables 3 and 4 or according to the same principle.

[0103] The second principle is that there is a format whose BHU and BHD are in the subframe / symbol / timeslot of the BHD and BHU of another format. For example, format 0 in Table 3 below has BHU in time slot 3 and BHD in time slot 5, while format 2 in Table 3 has BHD in time slot 3 and BHU in time slot 5. For example, for the case of a specific IAB node, the duplex mode provided by the parent node can be format 0 of Table 3. This means that the only symbol that can be used to send BH data in the uplink is symbol 3, and the only symbol that can be used to receive downlink BH data is 5. When configuring the duplex mode for the child node, symbol 3 cannot be uplink BH (because the IAB node will be occupied to send data instead of receiving data), and symbol 5 cannot be downlink (because the IAB node is occupied to receive data instead of sending data). Therefore, the duplex mode configured for the child node must have the opposite arrangement so that symbol 3 is BHD and symbol 5 is BHU: exactly the opposite of format 0 with symbol 3 and symbol 5. As a result, for each specified format, at least one "dual" must be specified (at least for BHD and BHU).

[0104] The third principle is that BHD and BHU subframes / symbols / time slots can be converted to normal access downlink and uplink (D and U) subframes / symbols / time slots. However, normal access downlink and uplink subframes / symbols / time slots cannot be converted to BHD and BHU subframes / symbols / time slots. BHD and BHU subframes / symbols / time slots can be converted to normal access downlink and uplink subframes / symbols / time slots to make more efficient use of resources. As an example, if the IAB node configures a BHU symbol for its child node at symbol 3, the child node will only send its BH data to the IAB node at symbol 3 (if it has any BH data). However, sometimes the child node may not have BH data to send. In this case, the IAB node can use the BHU symbol for normal access uplink transmission, that is, by scheduling the mobile device (such as user equipment UE) to perform an uplink to the IAB in symbol 3. This has no effect on the child node because the child node does not have anything to send. Whenever a child node has uplink data to send, it needs to send a scheduling request in the previous BHU to let the parent node know that it has uplink data. The parent node will then use the BHD to tell the child node when the next BHU is available for uplink data transmission. In contrast, each child node will always monitor certain areas in the BHD. If there is downlink data for the child node, the child node will download data in other areas in the BHD. This does not cause problems for the UE either, because the IAB node is able to control when the UE sends uplink data: that is, whether a subframe, symbol or time slot is marked as a BHU or U has nothing to do with the UE.

[0105] Tables 3 and 4 show examples of symbol-level and slot-level duplex mode configurations. As described above, BHU indicates an IAB node transmitting to its parent IAB node, and BHD indicates an IAB node receiving from the parent IAB node. For D, it may include a DL access link and / or a DL BH link to a child IAB node. For U, it may include a UL access link and / or a UL BH link from a child IAB node. X is an unknown subframe / slot / symbol that provides a gap between DL and UL.

[0106]

[0107] Table 3: Example of symbol-level duplex mode configuration.

[0108]

[0109] Table 4: Example of slot-level duplex mode configuration.

[0110] The design of the signaling process for duplex mode configuration message transmission is now described. It will be understood that the business at the IAB node depends not only on its associated UE, but also on its parent IAB node and child IAB node, so it is expected to be highly dynamic. The duration and granularity of the adaptation period depend on this dynamic behavior. The adaptation period refers to the time frame in which the duplex mode is defined and remains unchanged. The granularity is defined according to the scale at which one link type can be switched to another link type (e.g., from BH UL to BH DL). For example, the granularity can be at the level of a subframe, symbol, or time slot as described above. For dynamic time division duplex (TDD), symbol-level granularity is already supported in NR. The IAB TDM multiplexing mode can adopt the same granularity. For the duration of the adaptation period, two alternatives can be considered: for the first alternative, a fixed adaptation period, such as 1 time slot; and for the second alternative, a configurable adaptation period.

[0111] The second alternative - a configurable adaptation period - can be configured according to several different options: first, the period can be semi-permanently configured through upper layer signaling (e.g., RRC, Media Access Control (MAC) layer control entity (CE) (MAC CE)); second, the period can be dynamically configured through Layer 1 signaling such as PDCCH / DCI, and can provide the highest flexibility; third, a combination of the first and second options can be applied, with a semi-permanent configuration as the initial configuration, but it can be overridden by dynamic configuration.

[0112] Allowing for more complex multiplexing patterns, slot-level granularity can also be supported to reduce complexity and signaling overhead. In addition to dynamic configuration, the same alternatives listed above for symbol-level granularity can also be applied here: once configured, the configuration will last at least for the duration of the adaptation period. Table 5 shown below gives an example of the duration of the defined adaptation period.

[0113] index Adaptation period (time slot) 0 1 1 2 2 4 3 8 4 16 5 32 6 64

[0114] Table 5: Duration of defined adaptation periods.

[0115] Table 5 shows how long the defined adaptation period is. For example, if 4 is configured for the adaptation period, it means that the duration of one adaptation period is 16 time slots.

[0116] For granularity, two other alternatives can be considered to indicate the multiplexing mode (symbol level or time slot level) within the adaptation period. A bitmap can be used to indicate the active link type, or a predefined table can be used. For the bitmap option, we can define a one-to-one mapping between the two indication bits and a certain link type, as shown in Table 6 below.

[0117] Link Type Indicator Parent BH DL 00 Parent BH UL 01 Access DL / Sub BH DL 10 Access UL / Sub-BH UL 11

[0118] Table 6: Mapping between two indicator bits and link type .

[0119] exist Figure 6 The option of a bitmap is also illustrated in , which provides the most flexibility, albeit with a higher signaling overhead. For example, bit 00 represents L{P, DL} - i.e., BH downlink from the parent node.

[0120] Now, how the duplex mode configuration message may be sent is described. The transmission of the duplex mode configuration message may be accomplished through semi-permanent configuration (through radio resource control (RRC) signaling) or dynamic configuration (through downlink control information (DCI)). The transmission of the duplex mode configuration confirmation message may be sent through uplink control information (UCI). This is Figure 7 Shown in.

[0121] The transmission of the duplex mode configuration message uses a table shared by all IAB nodes. The table may be a newly created table specifically for the IAB node, or may be an enhanced common duplex mode table, for example, a subframe format indicator (SFI) table, which corresponds to Table 2 given above and is derived from 3GPP TS 38.211. By using a table (whether a custom table or an extension of Table 2), as long as each IAB node has or can access a copy of the table, only a reference to the table needs to be provided in the duplex mode configuration message.

[0122] For the newly created tables specifically for IAB nodes, Tables 3 and 4 given above can be used. For the enhanced normal duplex mode table, the reserved entries can be used. An example can be found in Table 7, which extends Table 2 and is all new starting from row 62.

[0123]

[0124] Table 7: Example of enhanced symbol level duplex mode configuration.

[0125] Figure 8 A schematic diagram of the structure of an IAB node 800 is provided, which is arranged to operate according to the above example. The IAB node 800 includes: a transmitter 802, arranged to send a signal to a parent node, a child node or an access device; a receiver 604, arranged to receive a signal from a parent node, a child node or an access device; and a controller 806, arranged to control the transmitter and the receiver and perform processing such as according to the above method.

[0126] Despite Figure 8 The transmitter, receiver and controller are shown as separate elements in the drawings, but any single element or multiple elements providing equivalent functionality may be used to implement the examples of the present invention described above.

[0127] Embodiments of the present invention provide several means by which the problems identified in the prior art can be solved. These details are as follows. In the following, reference is made to solutions 1-A and 1-B to conform to the terminology used in the standardization process.

[0128] Solution 1-A

[0129] For solution 1-A, the same SSB set will be used for both the access UE and the IAB node discovery. In this case, a mechanism is needed to ensure that one IAB node can listen from another IAB node subject to half-duplex constraints. In this case, a silent mode or scheme is required, and the following two alternatives can be used.

[0130] Alternative 1: SSB burst-level silent mode

[0131] Alternative 2: SSB-level silent mode within one SSB burst set.

[0132] Alternative 1

[0133] For SSB burst set level silencing, the entire SSB burst set needs to be silenced to listen to SSBs from other IAB nodes, resulting in significant impact on accessing UEs. However, it has been agreed that the impact on Release 15 UEs should be minimized, so that such silencing may not be optimal for accessing UEs. Instead, within one SSB burst set, the location of SSBs from multiple IAB nodes can be coordinated to enable inter-node discovery subject to half-duplex constraints.

[0134] Alternative 2

[0135] Within each SSB burst set, there are multiple locations to send the SSB. However, the SSB locations are only possible locations. In other words, it is not mandatory that the SSB should be sent at all possible locations. Depending on the beam scanning requirements, anything from a single SSB to the maximum number of SSBs within one SSB burst set is possible.

[0136] In this case, one IAB node A may transmit on a subset of all possible locations, while another IAB node B may transmit on another subset that does not overlap with the subset of IAB node A, such as Fig. 9 As shown. The dotted boxes represent silent SSB transmission positions without actual SSB transmission. Both IAB Node A and IAB Node B can use these silent SSBs to listen to each other. This can be done through ssb-PositionsInBurst (SSB-Position in Burst) in SIB1. For different SSB burst sets, different SSB subsets may need to be selected to measure all possible beam directions. In other words, Fig. 9 The scheme shown, in which Node A transmits at odd positions and Node B transmits at even positions, is merely exemplary, and other muting schemes may be used as desired.

[0137] In this regard, each IAB node needs to select a subset of the SSB burst set, and this can be done semi-permanently (via RRC) or dynamically (via DCI). There are two other alternatives:

[0138] Alternative 2.1: Centralized configuration, where the host IAB node or parent IAB node configures different subsets for all child IAB nodes or only its next-level child IAB nodes;

[0139] • Alternative 2.2: Distributed configuration, where each IAB node exchanges its own SSB configuration with its surrounding IAB nodes, and the surrounding IAB nodes adjust their SSB configurations to select different SSB subsets.

[0140] Solution 1-B

[0141] For solution 1-B, SSBs that are orthogonal (TDM and / or FDM) to the SSBs used to access the UE are used for IAB inter-node discovery so that there is no impact on the access UE. Subject to half-duplex constraints, each IAB node may need to silence some of its own SSBs to listen to SSBs from other IAB nodes. Orthogonal resources for backhaul and access link detection and measurement can be achieved by silencing SSBs on IAB nodes. During these silent SSBs, the IAB node can listen to SSBs from other IAB nodes to detect possible candidate backhaul links. However, it should be noted that this silence is only required when aligning SSB transmissions for those IAB nodes that need to measure SSBs to monitor the quality of the backup backhaul links between each other. In particular, IAB nodes within the same hop can align their SSB transmissions to optimize signaling overhead. However, between different hops, other reference signals and more flexible measurements can be considered.

[0142] To introduce silent mode, two alternatives are presented:

[0143] Alternative 1: Quiesce on all IAB nodes;

[0144] • Alternative 2: Silencing based on hop order, ie, a silencing pattern within each hop.

[0145] Alternative 1

[0146] The first solution is Fig.10 (tree and silence). Silence will be performed on all IAB nodes (regardless of which hop they belong to). The benefit of this configuration is that one IAB node can always measure all possible backhaul links (both primary and backup links) and it is independent of topology changes. However, the scalability of this configuration may be limited as it requires higher signaling overhead to scale with the total number of IAB nodes involved in the inter-IAB node SSB measurement.

[0147] Alternative 2

[0148] The second solution is Fig.11 , where silence is constrained between IAB nodes belonging to the same hop (i.e., the same number of node connections from the host node). In this case, two alternatives can be considered:

[0149] Alternative 2.1: Align SSB transmissions on all IAB nodes; and

[0150] Alternative 2.2: Align SSB transmissions only on IAB nodes belonging to the same hop.

[0151] Alternative 2.1

[0152] One IAB node can measure all backup backhaul links via SSB regardless of the hop order. Such a configuration can reduce signaling overhead because the number of SSBs required is equal to the total number of IAB nodes involved in the inter-IAB node SSB measurement in each hop. Therefore, the scalability of this method is improved compared to the first solution.

[0153] Alternative 2.2

[0154] One IAB node may not be able to measure SSB from other IAB nodes belonging to different hops. However, as mentioned above, since the half-duplex constraint does not restrict IAB nodes with hop order N and N+1, such measurement is not necessarily based on SSB only, but other reference signals such as CSI-RS / ZP CSI-RS can be used. Fig.12 As shown, allowing non-overlapping SSBs between different hops can improve resource allocation flexibility, thereby achieving higher resource usage efficiency. It should be noted that the configuration of SSBs depends on the topology, and any topology change may result in the reconfiguration of SSBs, as described below.

[0155] As described above, for alternative 1, the configuration of SSBs (eg, the number of SSBs in a measurement period) depends on the total number of IAB nodes involved in IAB inter-node discovery and measurement. Any topology changes will not affect this number.

[0156] However, for alternative solution 2, the total number of SSBs in a measurement cycle is equal to the maximum number of IAB nodes involved in the IAB inter-node discovery and measurement belonging to the same hop, so any topology change here will affect the configuration of SSBs. In order to support more dynamic topology changes, at least semi-permanent configuration / reconfiguration of SSBs for IAB inter-node discovery and measurement (e.g., through RRC) is supported, and dynamic configuration can also be considered as needed.

[0157] For solution 1-B, orthogonality can be achieved as follows:

[0158] TDM only: In this case, the accessing UE may detect an inter-node discovery SSB, which may not include SIB1 information since only signal strength measurement is required.

[0159] oAlternative 1: Same SSB transmission timing on all IAB nodes, which results in the same SSB configuration for all IAB nodes without flexibility

[0160] oAlternative 2: Different SSB transmission timing on different IAB nodes, so that different configurations can be applied to different IAB nodes, but a common SMTC can be configured. For example, the SSB offset can be defined based on the hopping sequence, which can be implicitly derived by the IAB node.

[0161] TDM+FDM: In this case, the access UE does not detect inter-node discovery.

[0162] In some cases, embodiments of the present invention provide different SMTC configurations. A different SMTC orthogonal to the access UE SMTC can be configured for the IAB node to measure the SSB. For the connected state, two SMTCs can be configured, and the second SMTC only has a different period. In order to configure this additional SMTC for IAB inter-node discovery, the following alternatives can be considered based on the current protocol:

[0163] oAlternative 1: Additional offset value required for SMTC2

[0164] oAlternative 2: SMTC3 can be configured.

[0165] For the idle state, only one SMTC should be configured. However, for inter-node discovery, at least two SMTCs should be configured for the connected state and the idle state. In this regard, it is necessary to allow two SMTCs to be configured in the idle state.

[0166] The SMTC configuration should take into account the aforementioned SSB configuration so that semi-permanent and dynamic measurements supporting dynamic topology changes are achieved. In this regard, the SMTC configuration needs to support both semi-permanent and dynamic configurations.

[0167] For measurement metrics, RSRP / RSSI / SINR / RSRQ can be used and reported. Two alternatives can be considered to report the measurement results:

[0168] Alternative 1: Report back to the parent IAB node, which then reports to the host IAB node, so that once the primary backhaul link fails, the host IAB node can collect all the information and select an appropriate backup backhaul link;

[0169] • Alternative 2: Report back to the IAB node that is sending the SSB so that each IAB node knows which backup backhaul link to use once the primary backhaul link fails.

[0170] The composition of the IAB Inter-Node Discovery SSB may need to be modified. In the Physical Broadcast Channel (PBCH) of the SSB, the Master Information Block (MIB) is carried to the UE in order to obtain the remaining system information broadcast by the network. Some of this information may not be needed, because the Discovery SSB is mainly used to measure the backup link quality, which can be based on signal strength measurements for RSRP, and does not require actual knowledge of any further details. Therefore, the size of the PBCH within the IAB Inter-Node Discovery SSB can be made smaller to reduce signaling overhead. The following alternatives can be considered:

[0171] Alternative 1: Remove PBCH from SSB so that SSB consists of only the Primary Synchronization Signal (PSS) and the Secondary Synchronization Signal (SSS);

[0172] Alternative solution 2: Reduce the size of PBCH so that it only includes some necessary information, such as CellBarredFlag.

[0173] • Alternative 3: Only the DMRS of the PBCH used for measurement is retained, and the rest of the REs of the MIB can be removed or muted to save energy.

[0174] For both alternatives, the length of the PSS and SSS may be increased so that a lower SINR for initial access may be achieved, which is desirable because the distance between IAB nodes is typically greater than the distance between an IAB node and a UE.

[0175] Once the backhaul link of the IAB node is blocked and a backup backhaul link is needed, an Out-of-Sync (OOS) event occurs and the IAB node needs to perform synchronization again. There are two possible alternatives:

[0176] Alternative 1: The IAB node may use the inter-node discovery SSB, which is orthogonal to the initial access SSB, for initial access and synchronization of the backup backhaul link;

[0177] • Alternative 2: The IAB node may use the initial access SSB directly for the backup backhaul link initial access and synchronization.

[0178] For the second alternative, the IAB node needs to synchronize again as if it is accessing the network for the first time, ie it follows the Phase 1 procedure.

[0179] The SSB discussed above is used for inter-node discovery and measurement. In the following, the SSB configuration for initial access of an IAB node MT is described.

[0180] Consider the two cases of NSA and SA. For NSA deployment, the following two cases can be considered:

[0181] Case 1: The IAB node MT can perform initial access on the LTE carrier, so that NSA is deployed from both the access UE and the IAB node MT (mobile terminal) perspectives;

[0182] Case 2: The IAB node MT can only perform initial access on the NR carrier, so that NSA is deployed only from the perspective of accessing UEs.

[0183] For case 1, since the IAB node MT has been synchronized with the host gNB on the LTE carrier through the LTE PCell, and the NR frequency carrier can be further added through the EN-DC process, it can be assumed that the period of initial access of the IAB node MT is longer to reduce power consumption and signaling overhead, and such period can be signaled using, for example, RRC through a link established on the LTE carrier.

[0184] For case 2, the IAB node MT needs to perform initial access on the NR carrier without any previously established LTE link, so that there is no periodic signaling as in case 1, i.e., no assumptions are made on the network side. The IAB node MT needs to assume an SSB periodicity for the initial access. Three alternatives can be considered as follows:

[0185] • Alternative 1: The IAB node MT assumes the same SSB period as the access UE, ie, 20 ms.

[0186] • Alternative 2: The IAB node MT assumes a longer SSB period than the access UE, ie a value from 40ms, 80ms and 160ms.

[0187] • Alternative 3: The IAB node MT may assume the same SSB period as the accessing UE when first accessing the network, and then assume a longer period that may be configured by the host or parent IAB node when accessing the network a second time and thereafter (eg when OOS occurs).

[0188] To support alternatives 2 and 3, the IAB node MT needs to know that it is an IAB node, not an ordinary access UE. Such information needs to be configured to the IAB node even before it is activated, and made available once the IAB node is activated. It can be a Boolean indicator with two initial configuration states, for example: "0" indicates that the current device is an access UE device, and "1" indicates that the current device is an IAB node. With this information, the IAB node MT knows that it should assume a different SSB period.

[0189] It should be noted that when a longer period is assumed by the IAB node MT on the NR carrier, the access UE assumes the original period, e.g. 20ms.

[0190] Throughout the specification and claims of this specification, the words "comprise" and "include" and their variations mean "including but not limited to", and they are not intended to (and do not) exclude other components, integers or steps. Throughout the specification and claims of this specification, unless the context requires otherwise, the singular includes the plural. In particular, where an indefinite article is used, this specification should be understood to contemplate the plural as well as the singular, unless the context requires otherwise.

[0191] Features, integers or characteristics described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All features disclosed in this specification (including any accompanying claims, abstract and drawings) and / or all steps of any method or process disclosed may be combined in any combination, except combinations in which at least some of such features and / or steps are mutually exclusive. The invention is not limited to the details of any foregoing embodiments. The invention extends to any one novel feature or any novel combination of features of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any one novel step or any novel combination of steps of any method or process disclosed.

[0192] The reader's attention is directed to all papers and documents filed concurrently with or previous to the present specification, which are related to the present application and which are open to public inspection, and the contents of all such papers and documents are incorporated herein by reference.

[0193] The various embodiments of the present invention may also be implemented by computer executable instructions stored on a computer readable storage medium, such that when the instructions are executed, causes a computer to operate in accordance with any other aforementioned embodiments.

[0194] The above embodiments should be understood as illustrative examples of the present invention. Other embodiments of the present invention are contemplated. It should be understood that any feature described with respect to any one embodiment may be used alone or in combination with other features described, and may also be used in combination with one or more features of any other embodiment, or in combination with any combination of any other embodiment. In addition, equivalents and modifications not described above may also be used without departing from the scope of the present invention as defined by the appended claims.

Claims

1. A method of operating an integrated access backhaul (IAB) node (800) in a wireless communication network, the IAB node being arranged to wirelessly communicate backhaul traffic with a host IAB node, the method comprising: receiving a first duplex mode configuration message from a host IAB node, the first duplex mode configuration message including a first duplex mode indicating a first configuration of a time slot within a transmission frame and an identifier of a child node of the IAB node; sending a negative acknowledgement message to the host IAB node as a response to the first duplex mode configuration message; receiving, from the donor IAB node, a second duplex mode configuration message including a second duplex mode indicating a second configuration of symbols in the time slot; Sending a confirmation message to the host IAB node as a response to the second duplex mode configuration message; as well as A second duplex mode indicating a second configuration of symbols in the time slots included in the second duplex mode configuration message received from the donor IAB node is applied.

2. The method according to claim 1, wherein: The confirmation message is sent via uplink control information UCI.

3. The method according to claim 1, wherein: The second duplex mode includes an X symbol between a downlink transmission symbol and a subsequent uplink transmission symbol.

4. The method according to claim 1, wherein: The second duplex mode indicates that the IAB node performs the following: Backhaul uplink BHU; Backhaul downlink BHD; Uplink U from a subnode or access device; or Downlink D to a subnode or access device.

5. The method according to claim 4, further comprising: The BHD or BHU symbols in the second duplex mode received from the donor IAB node are converted into D or U symbols.

6. The method according to claim 1, wherein: The first duplex mode corresponds to a format among a format defined for an access node and a format defined for an IAB node.

7. The method according to claim 1, further comprising: Sending a third duplex mode configuration message to a subnode corresponding to the identifier, the third duplex mode configuration message including a third duplex mode indicating a third configuration of symbols in a time slot; receiving a negative acknowledgement message from the child node as a response to the third duplex mode configuration message; as well as A fourth duplex mode configuration message is sent to the child node, the fourth duplex mode configuration message including a fourth duplex mode indicating a fourth configuration of time slots within a transmission frame.

8. An integrated access backhaul IAB node (800) in a wireless communication network, the IAB node being arranged to wirelessly communicate backhaul traffic with a host IAB node, the IAB node comprising: A transmitter (802) and a receiver (804); as well as A controller (806), coupled to the transmitter and the receiver and configured to: controlling the receiver to receive a first duplex mode configuration message from the host IAB node, the first duplex mode configuration message including a first duplex mode indicating a first configuration of time slots within a transmission frame and an identifier of a child node of the IAB node, controlling the transmitter to send a negative acknowledgement message to the donor IAB node as a response to the first duplex mode configuration message, controlling the transmitter to receive, from the donor IAB node, a second duplex mode configuration message including a second duplex mode indicating a second configuration of symbols in the time slot; controlling the transmitter to send a confirmation message to the host IAB node as a response to the second duplex mode configuration message; as well as A second duplex mode indicating a second configuration of symbols in the time slots included in the second duplex mode configuration message received from the donor IAB node is applied.

9. A method of operating a host integrated access backhaul IAB node in a wireless communication network, the host IAB node being arranged to wirelessly communicate backhaul traffic with an IAB node, the method comprising: Sending a first duplex mode configuration message to the IAB node, the first duplex mode configuration message including a first duplex mode indicating a first configuration of a time slot in a transmission frame and an identifier of a child node of the IAB node; receiving, from the IAB node, a negative acknowledgement message in response to the first duplex mode configuration message; sending a second duplex mode configuration message including a second duplex mode indicating a second configuration of symbols in a time slot to the IAB node; receiving, from the IAB node, an acknowledgement message as a response to the second duplex mode configuration message; as well as In response to receiving the acknowledgement message, a second duplex mode is applied indicating a second configuration of symbols in the time slots.

10. A host integrated access backhaul IAB node in a wireless communication network, the host IAB node being arranged to wirelessly communicate backhaul traffic with an IAB node, the host IAB node comprising: Transmitters and receivers; as well as A controller is coupled to the transmitter and the receiver and is configured to: Controlling the transmitter to send a first duplex mode configuration message to the IAB node, the first duplex mode configuration message including a first duplex mode indicating a first configuration of a time slot within a transmission frame and an identifier of a child node of the IAB node; controlling the receiver to receive a negative acknowledgement message from the IAB node as a response to the first duplex mode configuration message; controlling the receiver to send a second duplex mode configuration message including a second duplex mode indicating a second configuration of symbols in the time slot to the IAB node; controlling the receiver to receive, from the IAB node, an acknowledgement message as a response to the second duplex mode configuration message; as well as In response to receiving the acknowledgement message, a second duplex mode is applied indicating a second configuration of symbols in the time slots.

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