IAB MT-DU Resource Misalignment Notification to Groups Background of the Invention

Abstract

A system and method for reducing signaling overhead between an integrated access and backhaul (IAB) node and its parent node when switching between multiple timing alignment cases is disclosed. According to some embodiments, the method includes transmitting one or more sets of desired guard symbol numbers for each of two or more timing switching groups. The method further includes receiving one or more sets of provided guard symbol numbers for each of the two or more timing switching groups and determining available time resources for uplink transmission and / or downlink reception in two adjacent time units based on one of the one or more sets of provided guard symbol numbers for one of the two or more timing switching groups corresponding to a timing alignment case used in two adjacent time units.

Description

[Technical field]

[0001] RELATED APPLICATIONS (CROSS REFERENCE TO RELATED APPLICATIONS) This application claims the benefit of U.S. Provisional Patent Application No. 63 / 135,235, filed January 8, 2021, the disclosure of which is incorporated herein by reference in its entirety.

[0002] The present disclosure relates to systems and methods for reducing signaling overhead between an Integrated Access and Backhaul (IAB) node and its parent node when switching between multiple timing alignment cases. [Background technology]

[0003] 5G Radio Access Network (RAN) Architecture The current fifth-generation (5G) RAN architecture is described in the 3rd Generation Partnership Project (3GPP®) Technical Specification (TS) 38.401 v16.3.0, section 6.1.1 ("Overall Architecture of NG-RAN"). 5G RAN is referred to as Next Generation RAN (NG-RAN). Figure 1 shows the overall architecture of NG-RAN contained in TS 38.401.

[0004] The NG-RAN architecture shown in FIG. 1 can be further described as follows: The NG-RAN includes a set of New Radio Base Stations (gNBs) connected to a fifth generation core (5GC) via their respective NG interfaces. The gNBs can support Frequency Division Duplex (FDD) mode, Time Division Duplex (TDD) mode, or dual mode operation. Multiple gNBs can be interconnected via an Xn interface. The gNBs may comprise a gNB Central Unit (gNB-CU) and one or more gNB Distributed Units (gNB-DUs). The gNB-CU and gNB-DUs are connected via an F1 logical interface. One gNB-DU is connected to only one gNB-CU. To ensure flexibility, a gNB-DU can be connected to multiple gNB-CUs by appropriate implementation. NG, Xn, and F1 are logical interfaces. The NG-RAN is layered into a Radio Network Layer (RNL) and a Transport Network Layer (TNL). The NG-RAN architecture, i.e. the NG-RAN logical nodes and the interfaces between them, are specified as part of the RNL. For each NG-RAN interface (NG, Xn, F1) the associated TNL protocols and functions are specified. The TNL provides services for user plane transport and signaling transport.

[0005] A gNB may also be connected to a Long Term Evolution (LTE) enhanced Node B (eNB) via an X2 interface. Another architecture option is when an LTE eNB connected to an Evolved Packet Core (EPC) network is connected via an X2 interface to a so-called nr-gNB, which is a gNB that is not directly connected to a Core Network (CN) but is connected to an eNB via X2 only to perform dual connectivity.

[0006] The architecture of Figure 1 can be extended by putting the gNB-CU into two entities: one gNB-CU user plane part (gNB-CU-UP) serves the user plane and can host the PDCP protocol, and one gNB-CU control plane part (gNB-CU-CP) serves the control plane and can host the Packet Data Convergence Protocol (PDCP) and Radio Resource Control (RRC) protocols. The gNB-DU can host the Radio Link Control (RLC), Medium Access Control (MAC), and Physical (PHY) protocols.

[0007] Overview of Integrated Access and Backhaul (IAB) Densification, achieved by deploying an increasing number of base stations (e.g., macro or micro base stations), is one of the mechanisms that can be used to meet the growing demand for more bandwidth / capacity in mobile networks. Deploying small cells operating in the millimeter wave (mmw) band is an attractive deployment option for these purposes, since more spectrum is available in this band. However, deploying optical fiber to small cells, the usual way to deploy small cells, would eventually be very expensive and impractical. Therefore, using wireless links to connect small cells to the operator's network is a more flexible, faster time to market, cheaper and more practical alternative. One such solution is the IAB network, which allows operators to utilize part of their radio resources for backhaul links.

[0008] Figure 2 shows an example of an IAB deployment supporting multiple hops. An IAB-donor node (IAB donor for short) has a wired connection to the core network, and an IAB node is connected wirelessly to an IAB donor using NR, either directly or indirectly via another IAB node. The connection between an IAB donor / node and a UE is called an access link, while the connection between two IAB nodes or between an IAB donor and an IAB node is called a backhaul link.

[0009] FIG. 3 shows an adjacent upstream node, which is located close to an IAB donor node of an IAB node, and is also called the "parent node" (or parent IAB node) of the node. As shown in FIG. 3, an adjacent downstream node is located further away from the IAB donor node of the IAB node, and is called the "child node" of the IAB node. The backhaul link between the parent node and the IAB node is called the parent (backhaul) link, and the backhaul link between the IAB node and the child node is called the child (backhaul) link.

[0010] IAB Architecture One major difference of the IAB architecture compared to the Rel-10 LTE relay (in addition to the lower layer differences) is that the IAB architecture adopts a central unit / distributed unit (CU / DU) split of the gNB, where time-critical functions are realized in the IAB-DU, which is close to the radio part, and less time-critical functions are pooled in the IAB-donor-CU, preserving the opportunity for centralization. Based on this architecture, the IAB donor includes both CU and DU functions. In particular, the IAB architecture includes all CU functions of IAB nodes under the same IAB donor. Each IAB node then hosts the DU functions of the gNB. To be able to send and receive radio signals to and from the upstream IAB nodes or IAB donors, each IAB node has a mobile termination (MT), which is a logical unit that provides the requisite set of UE-like functions. The IAB node establishes an RLC channel to the UE and / or MT of the IAB node to which it is connected via the IAB-DU. An IAB node establishes a backhaul radio interface toward a serving IAB node or an IAB donor via an IAB-MT. Figure 4 shows a reference diagram of a two-hop chain of IAB nodes located under an IAB donor. In particular, Figure 4 shows that each of the IAB nodes includes an IAB-DU and an IAB-MT.

[0011] IAB Topology Wireless backhaul links are vulnerable to occlusion, for example, by moving objects such as vehicles, by seasonal changes (leaves), by severe weather conditions (rain, snow, or hail), or by infrastructure changes (new buildings). Such vulnerabilities also apply to nodes. Traffic fluctuations can also result in uneven load distribution on wireless backhaul links, leading to local link or node congestion. Considering these concerns, the IAB topology supports redundant paths as another difference compared to Rel-10 LTE relays.

[0012] Figure 5 shows spanning tree (ST) and directed acyclic graph (DAG) as two examples of topologies considered in IAB. These two examples of topologies considered in IAB show that one IAB node can have multiple child nodes and / or multiple parent nodes. Multi-connectivity or route redundancy can be used for backup purposes. Redundant routes can also be used simultaneously, for example, to achieve load balancing, reliability, or other functions.

[0013] Resource Coordination In the case of in-band operation (meaning that the access link and backhaul link use the same frequency spectrum), the IAB node is typically subject to half-duplex constraints, i.e., the IAB node can only operate in either transmit or receive mode at a time. The Release 16 (Rel-16) IAB standard primarily considers the time division multiplexing (TDM) case, where the MT and DU resources of the same IAB node are separated in time. Based on this consideration of half-duplex in the TDM case, the following resource types are defined in the Rel-16 IAB for IAB-MT and IAB-DU, respectively:

[0014] From an IAB-MT perspective, as in the IAB standard for Release 15, the following time domain resources may be indicated for the parent link: downlink (DL) time resource, uplink (UL) time resource, and flexible (F) time resource.

[0015] From the IAB-DU perspective, the child link has the following types of time resources: DL time resource, UL time resource, F time resource, and Not Available (NA) time resource (resource not used for communication on the DU's child link).

[0016] Each of the DL time resource types, UL time resource types and F time resource types of a DU child link can belong to one of two categories: ● Hard (H): The corresponding time resource is always available for the DU child link. ● Soft (S): The availability of corresponding time resources for DU child links is explicitly and / or implicitly controlled by the parent node.

[0017] IAB-DU resources are configured per cell, and the H / S / NA attributes of the DU resource configuration are explicitly indicated for each resource type (D / U / F) of each slot. As a result, the semi-static time domain resources of the DU part can be of seven types in total: downlink hard (DL-H), downlink soft (DL-S), uplink hard (UL-H), uplink soft (UL-S), flexible hard (FH), flexible soft (FS), and not available (NA). Table 1 in Figure 5A shows the coordination relationship between MT and DU resources.

[0018] Additionally, the IAB-DU functionality may accommodate multiple cells, including cells operating on different carrier frequencies. Similarly, the IAB-MT functionality may accommodate multiple carrier frequencies. This may be implemented by one IAB-MT unit operating on multiple carrier frequencies, or by multiple IAB-MT units, each operating on a different carrier frequency. The H / S / NA attributes for the per-cell IAB-DU resource configuration should take into account the associated IAB-MT carrier frequency.

[0019] Resource misalignment between IAB-MT and IAB-DU Figure 6 shows three timing properties of an IAB node that cause timing misalignment between IAB-MT and IAB-DU resources: ● Tp: The difference between the DL transmission timing at the parent node (DU) and the DL reception timing at the IAB node (MT). Tp is equal to the propagation time between the parent node and the IAB node. ●TA: Timing advance, i.e., the difference between the uplink (UL) transmit timing and the downlink (DL) receive timing at the IAB node (MT). ●TΔ: The difference between the uplink reception timing and the downlink transmission timing at the IAB node (DU)

[0020] The timing misalignment between IAB-MT and IAB-DU resources, including but not limited to the above three parameters and their determination and estimation, makes it difficult to actually implement the desired coordination between IAB-MT and IAB-DU, as listed in Table 1 of FIG. 5A.

[0021] FIG. 7 shows an example of resource availability conflict due to propagation delay and receive timing advance. According to this embodiment, slot k of IAB-DU resources is configured for DL ​​Tx, and slot k of IAB-MT resources is configured for DL ​​Rx, which are offset depending on the propagation delay and DL Tx timing configuration of the IAB node. If slot k of IAB-DU resources is a hard resource, the parent node should not schedule a transmission in slot k to MT. Since slot k of IAB-MT resources in DL is delayed by propagation delay, slot (k-1) of IAB-MT resources is also delayed by propagation delay, which appears to the parent node as available for scheduling some transmission. If the parent node schedules DL Tx to IAB-MT in slot (k-1), the last part of the transmission may not be received by the IAB node because it overlaps with slot k of IAB-DU resources, which is a hard resource and unavailable for MT.

[0022] To avoid such resource conflicts in IAB nodes, RAN1#98bis (R1-1911723, "RAN1 Agreement for Rel-16 IAB", 3GPP TSG RAN WG1 Meeting#98bis, October 2019) agreed as follows: Excerpt from RAN1#98bis begins The parent IAB node may be aware of the number of symbols Ng that the parent IAB node wishes not to use at the edge (start or end) of a slot when the child IAB node is transitioning between a child MT and a child DU. Separately or additionally, the child IAB node may be aware of the number of guard symbols that the parent IAB node provides. Ng is provided, potentially redundantly, for each of the eight possible transitions. [This table of positions is reproduced in Figure 7A.] If Ng is not given, it is assumed to be 0. End of excerpt from RAN1#98bis

[0023] FIG. 8 shows the "8 possible transitions" (marked with dashed lines) disclosed in the table of RAN1#98bis (reproduced in FIG. 8A). For example, transition (1) in FIG. 8 shows that in slot k-1, the IAB-MT of the IAB node performs DL Rx (downlink reception) and in slot k, the IAB-DU of the IAB node performs DL Tx (downlink transmission). Transition (2) in FIG. 8 also shows the contention situation shown in FIG. 7, i.e., in slot k-1, the IAB-MT of the IAB node performs DL_RX, and in slot k, a change of operation occurs, so that the IAB-DU of the IAB node performs UL_RX. As shown in FIG. 7, some of the last symbols of the resources for DL_RX of the IAB-MT overlap with some of the first symbols of the resources for UL_RX of the IAB-DU due to propagation delay and other factors.

[0024] Additionally, RAN1#99 (R1-1913600, "RAN1 Agreement for Rel-16 IAB", 3GPP TSG RAN WG1 Meeting#99, November 2019) agreed to the following: Excerpt from RAN1#99 begins The desired and provided guard symbols are provided per cell, using 3 bits for each of the 8 transitions to indicate the number of guard symbols. Rel-16 supports a range of 0 to 4 symbols per transition. Additional entries are reserved for future use. ●A new parameter, GuardSymbol-SCS, is also provided that indicates the reference SCS (subcarrier spacing) used for the guard symbols (FR1: {15kHz, 30kHz, 60kHz}, FR2: {60kHz, 120kHz}). End of excerpt from RAN1#99

[0025] The guard symbols for IAB and MAC CE are specified in 3GPP TS 38.321 ("NR; Medium Access Control (MAC) Protocol Specification"): Excerpt from TS 38.321 begins 5.18.19 Guard Symbols for IAB For IAB operation, the MAC entity on the IAB-DU or IAB-donor-DU reserves a sufficient number of symbols at the beginning and / or end of the slot where a child IAB-node switches operation from its IAB-DU to its IAB-MT function and from its IAB-MT to its IAB-DU function. The MAC entity on the IAB-DU or IAB-donor-DU informs the child node of the number of guard symbols it provides via the Provided Guard Symbols MAC CE. The IAB-MT on the child node can inform the parent IAB-DU or IAB-donor-DU of the desired number of guard symbols via the Desired Guard Symbols MAC CE. Upon receiving the Provided Guard Symbols MAC CE, the MAC entity: ●Indicate to lower layers the number of guard symbols provided and the SCS configuration for the indicated serving cell. The MAC entity: 1> If the desired guard symbol query is not triggered: 2> Trigger a desired guard symbol query to this serving cell. If the MAC entity has UL resources allocated for a new transmission, it: 1> For each desired guard symbol query that has been triggered and not cancelled: 2> If the allocated UL resources can accommodate the desired guard symbol MAC CE and its subheader as a result of the LCP defined in clause 5.4.3.1: 3> Instruct the multiplex assembly procedure to generate the desired guard symbol MAC CE. 3> Cancel this desired guard symbol query. A separate value for the number of guard symbols is specified for each of the following eight switching scenarios (see Table 5.18.19-1): [Table 5.18.19-1 is reproduced in Figure 8A] 6.1.3.22 Guard Symbol MAC CE The Guard Symbols MAC CE (i.e., Provided Guard Symbols MAC CE and Desired Guard Symbols MAC CE) are identified by a MAC subheader with eLCID as specified in Table 6.2.1-1b for DL-SCH and Table 6.2.1-2b for UL-SCH. It is of fixed size and consists of four octets defined as follows (Figure 6.1.3.22-1): ●R: Reserved bit, set to 0. Serving Cell ID: This field indicates the identity of the serving cell to which the MAC CE applies. The length of the field is 5 bits. ● Subcarrier Spacing (SCS): This field indicates the subcarrier spacing used as the basis for the guard interval. The length of this field is 2 bits. The values ​​of the SCS field are shown in Table 6.1.3.22-2. ● Number of Guard Symbols (NmbGSi): This field indicates the number of guard symbols for the switching scenarios shown in Table 5.18.19-1. The number of guard symbols can take values ​​in the range from 0 to 4. The larger values ​​5 to 7 are reserved. [Figure 6.1.3.22-1 and Table 6.1.3.22-2 of 3GPP TS 38.321 are reproduced in Figure 8B.] End of excerpt from TS 38.321

[0026] Timing Alignment TR 38.874 ("3rd Generation Partnership Project, Technical Specification Group, Radio Access Networks; NR Study on Integrated Access and Backhaul, Release 16") considers various cases of transmit timing alignment across IAB nodes and IAB donors. TR 38.874 lists the following cases: Excerpt from TR38.874 begins 7.4IAB-Node Synchronization and Timing Alignment Case #1: DL transmit timing alignment across IAB-node and IAB-donor: If DL TX and UL RX are not aligned at the parent node, additional information about alignment is required for the child node to properly set the DL TX timing to synchronize with the OTA-based timing. ● Case #2: IAB - DL and UL transmit timing are aligned within the node. ● Case #3: DL and UL receive timing are aligned within the IAB-node. ●Case #6 (Case #1 DL transmission timing + Case #2 UL transmission timing): o The DL transmission timing of all IAB-nodes is aligned with the DL timing of the parent IAB-node or donor. o The uplink transmission timing of an IAB-node may be aligned to the downlink transmission timing of an IAB-node. ●Case #7 (Case #1 DL transmission timing + Case #3 UL reception timing): o The DL transmission timing of all IAB-nodes is aligned with the parent IAB-node or donor DL ​​timing. o The UL receive timing of the IAB-node may be aligned to the DL receive timing of the IAB-node. If the DL TX and UL RX are not aligned at the parent node, additional information about the alignment is required for the child node to properly set the DL TX timing to synchronize with the OTA-based timing. End of excerpt from TR38.874

[0027] That is, case #1 is a timing alignment case where DL transmit timing alignment is provided across the IAB node and the IAB donor, case #6 is a timing alignment case where DL transmit timing alignment is provided across the IAB node and the IAB donor and the DL transmit timing and the UL transmit timing are aligned within the IAB node, and case #7 is a timing alignment case where DL transmit timing alignment is provided across the IAB node and the IAB donor and the DL receive timing and the UL receive timing are aligned within the IAB node. Summary of the Invention

[0028] An embodiment for reducing signaling overhead between an integrated access and backhaul (IAB) node and its parent node when switching between multiple timing alignment cases occurs is disclosed in the present disclosure. According to one embodiment, a method performed by an IAB node includes transmitting one or more sets of desired guard symbol numbers for each of two or more timing switching groups to a parent IAB node, where each timing switching group of the two or more timing switching groups includes one or more timing alignment cases. Each set of desired guard symbol numbers includes desired guard symbol numbers for one or more timing alignment cases included in each timing switching group of the two or more timing switching groups. The method further includes receiving, from the parent IAB node, respectively, one or more sets of provided guard symbol numbers for the two or more timing switching groups, and determining available time resources for uplink transmission and / or downlink reception in two adjacent time units (e.g., slots) based on one of the one or more sets of provided guard symbol numbers for one of the two or more timing switching groups corresponding to a timing alignment case used in the two adjacent time units (e.g., slots). Thus, the systems and methods disclosed in this disclosure reduce the signaling overhead used for the number of desired and provided guard symbols when an IAB node performs switching between two or more timing alignment cases.

[0029] The IAB node includes an IAB Mobile Termination (IAB-MT) and an IAB Distribution Unit (IAB-DU), and the desired number of guard symbols is the number of symbols that the IAB-MT indicates to a parent IAB node that the IAB-MT will not use for the IAB-MT the slots in which the IAB node transitions between the IAB-MT and the IAB-DU. The provided number of guard symbols is the number of symbols not to be used for the IAB-MT in the slots in which the IAB node transitions between the IAB-MT and the IAB-DU.

[0030] According to an embodiment, the method further comprises performing uplink transmission and / or downlink reception in two adjacent time units based on the determined available time resources.

[0031] According to one embodiment, the one or more sets of desired guard symbol numbers include multiple sets of desired guard symbol numbers, the two or more timing switching groups include multiple timing switching groups, the one or more timing alignment cases include one or more timing alignment cases for each of the two or more timing switching groups, and the one or more sets of provided guard symbol numbers include multiple sets of provided guard symbol numbers.

[0032] According to one embodiment, the method further includes changing a timing alignment configuration of the IAB node to a timing alignment configuration corresponding to a particular timing alignment case among a plurality of timing alignment cases in a particular timing switching group among a plurality of timing switching groups, and sending information to the parent IAB node to notify the parent IAB node of the change in the timing alignment configuration of the IAB node.

[0033] According to one embodiment, the method further comprises determining available time resources for uplink transmission and / or downlink reception in two adjacent time units, the method comprising determining the available time resources for uplink transmission and / or downlink reception in two adjacent time units based on one of a plurality of sets of provided guard symbol numbers for a particular timing switching group corresponding to a particular timing alignment case.

[0034] According to one embodiment, the one or more sets of desired guard symbol numbers comprise a single set of desired guard symbol numbers, the two or more timing switching groups comprise timing switching groups, the one or more timing alignment cases include one or more of the timing alignment cases for the timing switching groups, and the one or more sets of provided guard symbol numbers comprise a set of provided guard symbol numbers.

[0035] According to one embodiment, respectively transmitting one or more sets of desired guard symbol numbers for two or more timing switching groups to a parent IAB node includes transmitting the set of desired guard symbol numbers for the timing switching groups to the parent IAB node in response to a first occurrence of a corresponding change in a timing alignment configuration of the IAB node, and transmitting information notifying the parent IAB node of the change in the timing alignment configuration of the IAB node.

[0036] According to one embodiment, the two or more timing switching groups in the method include one or more of the following: A first timing switching group including one or more of the following timing alignment cases: o Switching from IAB-MT reception (Rx) in timing case #1 to IAB-DU transmission (Tx) in timing case #1. o Switching from IAB-MT Rx in timing case #1 to IAB-DU Rx in timing case #1. o Switching from IAB-MT Tx in timing case #1 to IAB-DU Tx in timing case #1. o Switching from IAB-MT Tx in timing case #1 to IAB-DU Rx in timing case #1. o Switching from IAB-DU Rx in timing case #1 to IAB-MT Tx in timing case #1. o Switching from IAB-DU Rx in timing case #1 to IAB-MT Rx in timing case #1. o Switching from IAB-DU Tx in timing case #1 to IAB-MT Tx in timing case #1. o Switching from IAB-DU Tx in timing case #1 to IAB-MT Rx in timing case #1. A second timing switching group that includes one or more of the following timing alignment cases: o Switching from IAB-MT Rx in timing case #1 to IAB-DU Tx in timing case #6. o Switching from IAB-MT Rx in timing case #1 to IAB-DU Rx in timing case #7. o Switching from IAB-MT Tx in timing case #1 to IAB-DU Tx in timing case #6. o Switching from IAB-MT Tx in timing case #1 to IAB-DU Rx in timing case #7. o Switching from IAB-DU Rx in timing case #1 to IAB-MT Tx in timing case #6. o Switching from IAB-DU Rx in timing case #1 to IAB-MT Rx in timing case #7. o Switching from IAB-DU Tx in timing case #1 to IAB-MT Tx in timing case #6. o Switching from IAB-DU Tx in timing case #1 to IAB-MT Rx in timing case #7. A third timing switching group that includes one or more of the following timing alignment cases: o Switching from IAB-MT Rx in timing case #7 to IAB-DU Tx in timing case #1. o Switching from IAB-MT Rx in timing case #7 to IAB-DU Rx in timing case #1. o Switching from IAB-MT Tx in timing case #6 to IAB-DU Tx in timing case #1. o Switching from IAB-MT Tx in timing case #6 to IAB-DU Rx in timing case #1. o Switching from IAB-DU Rx in timing case #7 to IAB-MT Tx in timing case #1. o Switching from IAB-DU Rx in timing case #7 to IAB-MT Rx in timing case #1. o Switching from IAB-DU Tx in timing case #6 to IAB-MT Tx in timing case #1. o Switching from IAB-DU Tx in timing case #6 to IAB-MT Rx in timing case #1. A fourth timing switching group including one or more of the following timing alignment cases: o Switching from IAB-MT Rx in timing case #7 to IAB-DU Tx in timing case #6. o Switching from IAB-MT Rx in timing case #7 to IAB-DU Rx in timing case #7. o Switching from timing case #6 IAB-MT Tx to timing case #6 IAB-DU Tx. o Switching from IAB-MT Tx in timing case #6 to IAB-DU Rx in timing case #7. o Switching from IAB-DU Rx in timing case #7 to IAB-MT Tx in timing case #6. o Switching from IAB-DU Rx in timing case #7 to IAB-MT Rx in timing case #7. o Switching from timing case #6 IAB-DU Tx to timing case #6 IAB-MT Tx. o Switching from IAB-DU Tx in timing case #6 to IAB-MT Rx in timing case #7.

[0037] Case #1 is a timing alignment case where DL transmit timing alignment is provided across the IAB node and the IAB donor, case #6 is a timing alignment case where DL transmit timing alignment is provided across the IAB node and the IAB donor and the DL transmit timing and the UL transmit timing are aligned within the IAB node, and case #7 is a timing alignment case where DL transmit timing alignment is provided across the IAB node and the IAB donor and the DL receive timing and the UL receive timing are aligned within the IAB node.

[0038] According to one embodiment, the one or more timing alignment cases include one or more of the following: Case #1 and Case #1. Case #1 and Case #6. Case #1 and Case #7. Case #6 and Case #1. Case #7 and Case #1. Case #6 and Case #7. Case #7 and Case #6. Case #6 and Case #6. Case #7 and Case #7.

[0039] According to one embodiment, the one or more timing alignment cases correspond to one or more of the following resource misalignments: IAB-MT Rx to IAB-DU Tx. IAB-MT Rx to IAB-DU Rx. IAB-MT Tx to IAB-DU Tx. IAB-MT Tx to IAB-DU Rx. IAB-DU Rx to IAB-MT Tx. IAB-DU Rx to IAB-MT Rx. IAB-DU Tx to IAB-MT Tx. IAB-DU Tx to IAB-MT Rx.

[0040] According to one embodiment, transmitting one or more sets of desired guard symbol numbers for two or more timing switching groups, respectively, to a parent IAB node includes transmitting one or more sets of desired guard symbol numbers for two or more timing switching groups, respectively, to the parent IAB node via one or more media access control (MAC) control elements (CEs).

[0041] According to one embodiment, each MAC CE of the one or more MAC CEs includes a reserved bit to indicate that one of the two or more timing switching groups is not group 1.

[0042] According to one embodiment, each MAC CE of the one or more MAC CEs includes one or more of subcarrier spacing (SCS) bits to indicate that one or more sets of desired guard symbol numbers correspond to one or more of Group 2, Group 3, or Group 4, respectively.

[0043] According to one embodiment, receiving one or more sets of numbers of guard symbols provided for two or more timing switching groups, respectively, includes receiving one or more sets of numbers of guard symbols provided for two or more timing switching groups, respectively, from a parent IAB node via one or more MAC CEs.

[0044] According to one embodiment, each MAC CE of one or more MAC CEs includes one or more bits indicating one of two or more timing switching groups for which the MAC CE includes a respective set of the number of guard symbols provided.

[0045] According to one embodiment, transmitting one or more sets of desired guard symbol numbers for two or more timing switching groups to a parent IAB node, respectively, includes transmitting at least one of the one or more sets of desired guard symbol numbers as a difference relative to a reference set of desired guard symbol numbers.

[0046] According to one embodiment, receiving one or more sets of numbers of provided guard symbols for two or more timing switching groups, respectively, includes receiving at least one of the one or more sets of numbers of provided guard symbols as a difference relative to a reference set of numbers of provided guard symbols.

[0047] According to one embodiment, each of the guard symbol timing switching groups additionally comprises: • Switching from IAB-MT(DL)Rx in timing case A to IAB-DU flexible (i.e., either Tx or Rx) in timing case B. • Switching from IAB-MT(UL)Tx in timing case A to IAB-DU flexible (i.e., either Tx or Rx) in timing case B. • Switching from IAB-DU flexible (i.e., either Tx or Rx) in timing case A to IAB-MT(DL)Rx in timing case B. ● Switching from IAB-DU flexible (i.e., either Tx or Rx) in timing case A to IAB-MT(UL)Tx in timing case B, where timing case A and timing case B can be any of timing case #1, timing case #6, and timing case #7.

[0048] According to one embodiment, the IAB node is adapted to transmit to a parent IAB node one or more sets of desired guard symbol numbers for each of two or more timing switching groups, each timing switching group of the two or more timing switching groups including one or more timing alignment cases, each set of desired guard symbol numbers including desired guard symbol numbers for one or more timing alignment cases included in the respective timing switching group of the two or more timing switching groups. The IAB node is further adapted to receive from the parent IAB node, respectively, the one or more sets of provided guard symbol numbers for the two or more timing switching groups, and determine available time resources for uplink transmission and / or downlink reception in two adjacent time units (e.g., slots) based on one of the one or more sets of provided guard symbol numbers for one of the two or more timing switching groups corresponding to a timing alignment case used in the two adjacent time units (e.g., slots).

[0049] According to one embodiment, the IAB node includes a processing circuit configured to cause the IAB node to transmit to a parent IAB node one or more sets of desired guard symbol numbers for each of two or more timing switching groups, each timing switching group including one or more timing alignment cases, each set of desired guard symbol numbers including desired guard symbol numbers for one or more timing alignment cases included in the respective timing switching group of the two or more timing switching groups. The processing circuit is further configured to cause the IAB node to receive from the parent IAB node, respectively, the one or more sets of provided guard symbol numbers for the two or more timing switching groups, and to determine available time resources for uplink transmission and / or downlink reception in two adjacent time units (e.g., slots) based on one of the one or more sets of provided guard symbol numbers for one of the two or more timing switching groups corresponding to a timing alignment case used in the two adjacent time units (e.g., slots).

[0050] According to one embodiment, a method performed by a parent IAB node includes receiving from the IAB node one or more sets of desired guard symbol numbers for each of two or more timing switching groups, each timing switching group of the two or more timing switching groups including one or more timing alignment cases, each set of desired guard symbol numbers including desired guard symbol numbers for one or more timing alignment cases included in a respective timing switching group of the two or more timing switching groups. The method further includes transmitting to the IAB node, respectively, one or more sets of provided guard symbol numbers for the two or more timing switching groups, and determining available time resources for uplink transmission and / or downlink reception in two adjacent time units (e.g., slots) based on one of the one or more sets of provided guard symbol numbers for one of the two or more timing switching groups corresponding to a timing alignment case used in the two adjacent time units (e.g., slots).

[0051] According to one embodiment, the method further includes receiving information from the IAB node notifying a parent IAB node of a change in the timing alignment configuration of the IAB node to a timing alignment configuration corresponding to a particular timing alignment case among a plurality of timing alignment cases in a particular timing switching group among the plurality of timing switching groups.

[0052] According to one embodiment, receiving one or more sets of desired guard symbol numbers for two or more timing switching groups, respectively, includes receiving the set of desired guard symbol numbers for the timing switching groups from the IAB node in response to a first occurrence of a corresponding change in a timing alignment configuration of the IAB node.

[0053] According to one embodiment, receiving one or more sets of desired guard symbol numbers for two or more timing switching groups, respectively, from the IAB node includes receiving one or more sets of desired guard symbol numbers for two or more timing switching groups, respectively, from the IAB node via one or more MAC CEs.

[0054] According to one embodiment, transmitting one or more sets of the number of provided guard symbols for two or more timing switching groups, respectively, includes transmitting one or more sets of the number of provided guard symbols for two or more timing switching groups, respectively, to an IAB node via one or more MAC CEs.

[0055] According to one embodiment, receiving one or more sets of desired guard symbol numbers for two or more timing switching groups, respectively, from the IAB node includes receiving at least one of the one or more sets of desired guard symbol numbers as a difference relative to a reference set of desired guard symbol numbers.

[0056] According to one embodiment, transmitting one or more sets of numbers of provided guard symbols for two or more timing switching groups, respectively, includes transmitting at least one of the one or more sets of numbers of provided guard symbols as a difference relative to a reference set of numbers of provided guard symbols.

[0057] According to one embodiment, the parent IAB node is adapted to receive from the IAB node one or more sets of desired guard symbol numbers for each of two or more timing switching groups, each timing switching group of the two or more timing switching groups including one or more timing alignment cases, each set of desired guard symbol numbers including desired guard symbol numbers for one or more timing alignment cases included in each timing switching group of the two or more timing switching groups. The parent IAB node is further adapted to transmit to the IAB node, respectively, the one or more sets of provided guard symbol numbers for the two or more timing switching groups, and determine available time resources for uplink transmission and / or downlink reception in two adjacent time units (e.g., slots) based on one of the one or more sets of provided guard symbol numbers for one of the two or more timing switching groups corresponding to a timing alignment case used in the two adjacent time units (e.g., slots).

[0058] According to one embodiment, the parent IAB node includes a processing circuit configured to cause the parent IAB node to receive from the IAB node one or more sets of desired guard symbol numbers for each of two or more timing switching groups, each timing switching group including one or more timing alignment cases, each set of desired guard symbol numbers including desired guard symbol numbers for one or more timing alignment cases included in the respective timing switching group of the two or more timing switching groups. The processing circuit is further configured to cause the parent IAB node to transmit to the IAB node, respectively, the one or more sets of provided guard symbol numbers for the two or more timing switching groups, and to determine available time resources for uplink transmission and / or downlink reception in two adjacent time units (e.g., slots) based on one of the one or more sets of provided guard symbol numbers for one of the two or more timing switching groups corresponding to a timing alignment case used in the two adjacent time units (e.g., slots). [Brief description of the drawings]

[0059] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate several aspects of the present disclosure and, together with the description, serve to explain the principles of the disclosure.

[0060] [Figure 1] shows the overall architecture of the New Generation Radio Access Network (NG-RAN) contained in TS 38.401.

[0061] [Diagram 2] shows an example of an Integrated Access Backhaul (IAB) deployment supporting multiple hops.

[0062] [Diagram 3]shows the parent node, IAB node, and child node in NG-RAN.

[0063] [Figure 4] denotes the two-hop chain of IAB nodes under an IAB donor.

[0064] [Diagram 5] shows two examples of topologies considered by the IAB.

[0065] [Figure 5A] 1 illustrates the coordination relationship between IAB Mobile Termination (IAB-MT) resources and IAB Distributed Unit (IAB-DU) resources.

[0066] [Figure 6] shows three timing characteristics at an IAB node that cause timing misalignment between IAB-MT and IAB-DU resources.

[0067] [Figure 7] Illustrates an example of contention for resource availability due to propagation delay and receive timing advance.

[0068] [Figure 7A] shows the eight possible transitions with potential overlaps in RAN1#98bis.

[0069] [Figure 8] shows the eight possible transitions disclosed in the table of RAN1#98bis (reproduced in FIG. 8A).

[0070] [Figure 8A] is reproduced from Table 5.18.19-1 of 3rd Generation Partnership Project (3GPP) Technical Specification (TS) 38.321.

[0071] [Figure 8B] reproduces Figure 6.1.3.22-1 and Table 6.1.3.22-2 of 3GPP TS 38.321.

[0072] [Figure 9] 1 illustrates an example of a Radio Access Network (RAN) having an IAB architecture in which embodiments of the present disclosure may be implemented.

[0073] [Figure 10] 1 illustrates multiple timing switching groups (Group-1, Group-2, Group-3, and Group-4) according to some embodiments of the present disclosure.

[0074] [Figure 11] 1 is a flow chart illustrating one embodiment of a method of operation of an IAB node and a parent IAB node.

[0075] [Figure 12] 4 is a flow chart illustrating another embodiment of a method of operation of an IAB node and a parent IAB node.

[0076] [Figure 13] 1 is a schematic diagram of a wireless access node according to some embodiments of the present disclosure.

[0077] [Figure 14] 2 is a schematic block diagram of a wireless access node according to some other embodiments of the present disclosure.

[0078] [Figure 15] 1 is a schematic diagram illustrating a virtualized embodiment of a radio access node according to some embodiments of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0079] The embodiments described below represent information that enables those skilled in the art to implement the embodiments and show the best mode of implementing the embodiments. Upon reading the following description in light of the accompanying drawings, those skilled in the art will understand the concepts of the present disclosure and recognize applications of these concepts not specifically addressed herein. It is to be understood that these concepts and applications are within the scope of the present disclosure.

[0080] Wireless Node: As used herein, a "wireless node" is either a wireless access node or a wireless communication device.

[0081] Radio Access Node: As used herein, a "radio access node" or "radio network node" or "radio access network node" is any node in a radio access network (RAN) of a cellular communications network that operates to transmit and / or receive signals wirelessly. Some examples of radio access nodes include, but are not limited to, a base station (e.g., a New Radio (NR) base station (gNB) in a Third Generation Partnership Project (3GPP) Fifth Generation (5G) NR network, or an enhanced or evolved Node B (eNB) in a 3GPP Long Term Evolution (LTE) network), a high-power or macro base station, a low-power base station (e.g., a micro base station, a pico base station, a Home eNB, etc.), a relay node, a network node implementing some of the functionality of a base station (e.g., a network node implementing a gNB Central Unit (gNB-CU) or a network node implementing a gNB Distributed Unit (gNB-DU)), or a network node implementing some of the functionality of some other type of radio access node.

[0082] Core Network Node: As used herein, a "core network node" is a node that implements a core network function or any kind of node in any core network. Examples of core network nodes include a mobility management entity (MME), a packet data network gateway (P-GW), a service capability publishing function (SCEF), a home subscriber server (HSS), etc. Some other examples of core network nodes include nodes that implement an access and mobility management function (AMF), a user plane function (UPF), a session management function (SMF), an authentication server function (AUSF), a network slice selection function (NSSF), a network publishing function (NEF), a network function (NF) repository function (NRF), a policy control function (PCF), a unified data management (UDM), etc.

[0083] Communication Device: As used herein, a "communication device" is any type of device that has access to an access network. Some examples of communication devices include, but are not limited to, a mobile phone, a smartphone, a sensor device, a meter, a vehicle, a home appliance, a medical device, a media player, a camera, or any type of consumer electronics, such as, but not limited to, a television, a radio, a light, a tablet computer, a laptop, or a personal computer (PC). A communication device can be a portable, handheld, computer-embedded, or vehicle-mounted mobile device that allows for communication of voice and / or data over wireless or wired connections.

[0084] Wireless Communication Device: One type of communication device is a wireless communication device, which may be any type of wireless device that accesses (i.e., is served by and provided with wireless services by) a wireless network (e.g., a cellular network). Some examples of wireless communication devices include, but are not limited to, user equipment devices (UEs) in 3GPP networks, machine type communication (MTC) devices, and Internet of Things (IoT) devices. Such wireless communication devices may be or may be integrated into mobile phones, smartphones, sensor devices, meters, vehicles, home appliances, medical devices, media players, cameras, or any type of consumer electronics, such as, but not limited to, televisions, radios, lighting fixtures, tablet computers, laptops, or PCs. Wireless communication devices may be portable, handheld, computer-embedded, or vehicle-mounted mobile devices that allow for communication of voice and / or data over a wireless connection.

[0085] Network Node: As used herein, a "network node" is any node that is part of the RAN or in the core network of a cellular communications network / system.

[0086] Transmit / Receive Point (TRP): According to some embodiments, a TRP can be either a network node, a radio head, a spatial relationship, or a transmission configuration indicator (TCI) state. According to some embodiments, a TRP can be represented by a spatial relationship or a TCI state. According to some embodiments, a TRP can use multiple TCI states.

[0087] It should be noted that the present specification focuses on 3GPP cellular communication systems and therefore 3GPP terminology or terminology similar to 3GPP terminology is often used, however, the concepts disclosed herein are not limited to 3GPP systems.

[0088] It should be noted that in the description herein, reference may be made to the term "cell", however, particularly with regard to 5G NR concepts, a beam may be used instead of a cell, and thus it is important to note that the concepts described herein are equally applicable to both cells and beams.

[0089] 9 illustrates an example of a Radio Access Network (RAN) 900 with an Integrated Access and Backhaul (IAB) architecture in which embodiments of the present disclosure may be implemented. Note that optional features are represented by dashed lines / boxes. According to embodiments described herein, the RAN 900 is a Next Generation RAN (NG-RAN) (part of a 5G System (5GS) including NG-RAN and a 5th Generation Core (5GC)) or an Evolved Universal Terrestrial Radio Access Network (E-UTRAN) (part of an Evolved Packet System (EPS) including an Evolved Packet Core (EPC)).

[0090] As will be appreciated by those skilled in the art, the RAN 900 includes several IAB nodes 902. Specifically, according to this embodiment, the IAB nodes 902 include an IAB donor node 902-0 and one or more additional IAB nodes referred to as IAB nodes 902-1 through 902-N. The IAB nodes 902-0 through 902-N are base stations (e.g., gNBs, ng-eNBs, or eNBs), according to some embodiments. The IAB donor node 902-0 preferably has a wired backhaul connection to a core network (not shown) and includes a CU 903, sometimes referred to herein as an "IAB-donor CU."

[0091] The IAB nodes 902-0 to 902-N include respective MTs 904-0 to 904-N and respective DUs 906-0 to 906-N. The MTs 904-1 to 904-N may be referred to herein as IAB-MTs 904-1 to 904-N. Similarly, the DUs 906-0 to 906-N may be referred to herein as IAB-DUs 906-0 to 906-N. The IAB nodes 902-0 to 902-N provide wireless access to respective UEs 908-0 to 908-N. Note that for clarity, only one UE 908 is shown for each of the IAB nodes 902-0 to 902-N, although it should be appreciated that each of the IAB nodes 902-0 to 902-N may provide wireless access to many UEs 908. Additionally, a single IAB node 902 may provide backhaul to multiple child IAB nodes. Also, note that the topology of the IAB architecture shown in Figure 9 is only one example: other topologies may be used (see, for example, the spanning tree (ST) topology and the directed acyclic graph (DAG) topology shown in Figure 5).

[0092] In this specification, IAB node 902-i (also referred to as "network IAB node" in this specification) refers to the i-th IAB node, where "i" is any value in the range of 1 to N. IAB node 902-p (e.g., p=i-1 in the example of FIG. 9) is called the "parent IAB node" of IAB node 902-i, and IAB node 902-c (e.g., c=i+1 in the example of FIG. 9) is called the "child IAB node" of IAB node 902-i. Here, 902-2 is used as an example of the reference number of an IAB node, and 902-1 is used as an example of the reference number of a parent node of IAB node 902-2.

[0093] Currently, some kind of challenge or challenges exist. The IAB in Rel-16 focuses on timing case #1, where the IAB-MT904 and IAB-DU906 operate in a time division multiplexed (TDM) manner. This is a basic explanation of the already specified guard symbol signaling for misalignment of IAB-MT904 and IAB-DU906 resources. One of the main objectives for the next release of the IAB (IAB in Rel-17) is to specify extensions for simultaneous transmission and / or reception at an IAB node. When transmitting simultaneously, the IAB node 902-2 operates with timing case #6. When receiving simultaneously, the IAB node 902-2 operates with timing case #7. Therefore, an IAB node 902 supporting Rel-17's IAB needs to frequently switch between three timing cases, namely, case #1, case #6, and case #7, each of which leads to different guard symbols between the IAB-MT 904 and IAB-DU 906 resources.

[0094] Each time the timing alignment case is changed, the IAB node 902-2 may send a new set of desired guard symbol numbers to the parent node 902, which may then respond with a new set of provided guard symbol numbers. However, sending and receiving (exchanging) sets of desired and provided guard symbol numbers each time there is a change between these timing alignment cases may cause unnecessary signaling overhead and may cause unnecessary delays for the parent node's scheduling decisions for the affected resources in the IAB-MT 904.

[0095] Certain aspects of the present disclosure and their embodiments may provide solutions to the above or other problems. An embodiment of the proposed solution extends the IAB network with the potential to reduce unnecessary delays and overheads associated with frequent switching of timing alignment cases. Disclosed herein is a system and method for reducing signaling overhead between an IAB node 902-2 and its parent node 902-1 when switching between multiple timing alignment cases is performed. According to an embodiment, an IAB node 902-2 may transmit to a parent IAB node 902-1 one or more sets of desired guard symbol numbers for each of two or more timing switching groups, each timing switching group of the two or more timing switching groups including one or more timing alignment cases, each set of desired guard symbol numbers including the desired guard symbol numbers for one or more timing alignment cases included in the respective timing switching group of the two or more timing switching groups.

[0096] The IAB node 902-2 may receive from the parent IAB node 902-1 one or more sets of provided guard symbol numbers for two or more timing switching groups, respectively. The IAB node 902-2 may determine available time resources for uplink transmission and / or downlink reception in two adjacent time units (e.g., slots) based on one of the one or more sets of provided guard symbol numbers for one of the two or more timing switching groups corresponding to a timing alignment case used in the two adjacent time units (e.g., slots).

[0097] When IAB node 902-2 changes its operating mode, and thereby uses a different timing alignment case, it can implicitly or explicitly notify parent IAB node 902-1 of the change, and both IAB node 902-2 and parent IAB node 902-1 change to using the corresponding set of guard symbols.

[0098] Certain embodiments may provide one or more of the following technical advantages: The systems and methods disclosed herein reduce the signaling overhead used for the desired and provided guard symbol numbers when the IAB node 902-2 switches between two or more timing alignment cases. The decision delay caused by guard symbol updates is also reduced because both the parent IAB node 902-1 and the IAB node 902-2 can perform fast switching to use corresponding sets of guard symbols according to the timing alignment case performed at the IAB node.

[0099] The systems and methods disclosed herein enable switching between various timing alignment cases with minimal overhead. According to one embodiment, an IAB node 902-2 transmits multiple sets of desired guard symbol numbers to its parent IAB node 902-1. Each set of desired guard symbol numbers corresponds to one of multiple timing switching groups, such as Group-1, Group-2, Group-3, and Group-4 shown in FIG. 10, and each set of multiple timing switching groups corresponds to one of a wide variety of combinations of timing alignment cases in two consecutive time units (e.g., slots) used for transmission and reception between the parent IAB node 902-1 and the IAB node 902-2 (i.e., between the IAB-MT 904-2 of the IAB node 902-2 and the IAB-DU 906-1 of the parent IAB node 902-1). For example, Group-2 (shown in FIG. 10) includes a set of at least eight desired numbers of guard symbols corresponding to eight different timing alignment cases between the IAB-MT 904-2 of IAB node 902-2 and the IAB-DU 906-2 of IAB node 902-2, respectively. For example, each set of desired guard symbol numbers may be provided in a desired guard symbol medium access control (MAC) control element (CE) such as or similar to that shown in Table 5.18.19-1 or Figure 6.1.3.22-1 of TS 38.321 ("NR; Medium Access Control (MAC) Protocol Specification"): NmbGS1, NmbGS2, ..., and NmbGS8 (reproduced in FIGS. 8A and 8B).

[0100] According to one embodiment, after the parent IAB node 902-1 receives the sets of desired guard symbol numbers from the IAB node 902-2, the parent IAB node 902-1 stores the received sets of desired guard symbol numbers (e.g., in the memory of the parent IAB node 902-1). In response, the parent IAB node 902-1 transmits the sets of provided guard symbol numbers to the IAB node 902-2. Similar to the desired guard symbol numbers, each set of provided guard symbol numbers corresponds to one of the timing switching groups, such as group-1, group-2, group-3, and group-4 shown in FIG. 10.

[0101] Each of the multiple timing switching groups includes a set of provided symbols of guard symbols corresponding to multiple different combinations of IAB-MT and IAB-DU resources. For example, each set of provided guard symbols may be included in a Provided Guard Symbols MAC CE such as NmbGS1, NmbGS2, ..., NmbGS8, etc., or similar, as shown in Table 5.18.19-1 or Figure 6.1.3.22-1 of TS 38.321 ("NR; Medium Access Control (MAC) Protocol Specification"). The IAB node 902-2 then stores (e.g., in a memory of the IAB node 902-2) the received multiple sets of provided symbols of guard symbols.

[0102] The guard symbols between IAB-MT and IAB-DU resources in Rel-16 are for the case where both slot (k-1) and slot k are operational in case #1 timing alignment where IAB-MT and IAB-DU are in TDM mode, as shown in “Group-1” in FIG. 10, and this set of eight guard symbols is hereinafter referred to as Group-1 guard symbols.

[0103] The Rel-17 IAB allows for concurrent transmission and reception. This allows the IAB node 902-2 to operate with case #1, case #6 or case #7 timing. When case #6 timing alignment is used or implemented by the IAB node 902-2 or parent IAB node 902-1, the IAB-MT UL Tx timing is changed to be aligned with the IAB-DU DL Tx timing. When case #7 timing alignment is used, the IAB-DU UL Rx timing is changed to be aligned with the IAB-MT DL Rx timing. Thus, some of the desired guard symbol counts will be changed compared to the guard symbols of group 1 when the combination of timing alignment cases in slot(k-1) and slot k is as follows: ●Case #1 and Case #6. ●Case #1 and Case #7. ●Case #6 and Case #1. ●Case #7 and Case #1. ●Case #6 and Case #7. ●Case #7 and Case #6. ●Case #6 and Case #6. ●Case #7 and Case #7.

[0104] FIG. 10 summarizes the changes for “Group 2,” “Group 3,” and “Group 4,” and the shaded cells in the table shown indicate table cells in which the number of guard symbols is a different value from that of Group 1.

[0105] Note that in FIG. 10, the values ​​of the non-shaded cells are not changed from the perspective of resource misalignment, but the internal processing time of IAB node 902-2 may be changed to include a change in the transmission and reception mode: • From Tx / Rx of either IAB-MT or IAB-DU to Tx / Rx of both IAB-MT and IAB-DU as in group 2. • From Tx / Rx of both IAB-MT and IAB-DU to Tx / Rx of either IAB-MT or IAB-DU as in group 3. • Concurrent transmit to concurrent receive, or vice versa as in group 4. Therefore, the desired number of guard symbols for these cells may also vary compared to the values ​​for Group 1.

[0106] According to the present disclosure, there may be at least two exemplary embodiments for IAB node 902-2 and parent IAB node 902-1 to communicate the desired number of guard symbols and the number provided corresponding to various combinations of timing alignment cases in two consecutive time units (e.g., slots):

[0107] First embodiment 11 is a flow chart illustrating one embodiment of the operation of the IAB node 902-2 and the parent IAB node 902-1 (which may be the donor node 902-0). Optional steps are represented by boxes.

[0108] Optionally, the IAB node 902-2 may generate one or more sets of desired guard symbol numbers for each of two or more timing switching groups, each timing switching group of the two or more timing switching groups including one or more timing alignment cases, each set of desired guard symbol numbers including desired guard symbol numbers for one or more timing alignment cases included in the respective timing switching group of the two or more timing switching groups (step 1100). Alternatively, the IAB node 902-2 may receive one or more sets of desired guard symbol numbers from an external device or operator (e.g., a user) of the IAB node 902-2 (step 1100).

[0109] An example of a "set of desired guard symbol numbers" is the number of guard symbols included in the desired guard symbol MAC CE disclosed in Technical Specification (TS) 38.321 ("NR; Medium Access Control (MAC) Protocol Specification"). The desired guard symbol MAC CE includes a set of guard symbol numbers that the IAB-MT 904-2 of the IAB node 902-2 indicates to the parent IAB node 902-1 not to use for the IAB-MT 904-2 of the IAB node 902-2 in slots where the IAB node 902-2 transitions between downlink reception / uplink transmission via the IAB-MT 904-2 and downlink transmission / uplink reception via the IAB-DU 906-2.

[0110] IAB node 902-2 may transmit to parent IAB node 902-1 one or more sets of desired guard symbol numbers for two or more timing switching groups, respectively (step 1102), each timing switching group of the two or more timing switching groups including one or more timing alignment cases, each set of desired guard symbol numbers including desired guard symbol numbers for one or more timing alignment cases included in each timing switching group of the two or more timing switching groups.

[0111] Optionally, transmitting to the parent IAB node 902-1 one or more sets of desired guard symbol numbers for two or more timing switching groups, respectively, includes transmitting to the parent IAB node 902-1 one or more sets of desired guard symbol numbers for two or more timing switching groups, respectively, via one or more MAC CEs.

[0112] Optionally, transmitting to the parent IAB node 902-1 one or more sets of desired guard symbol numbers for two or more timing switching groups, respectively, includes transmitting at least one of the one or more sets of desired guard symbol numbers as a difference relative to a reference set of desired guard symbol numbers.

[0113] Optionally, the parent IAB node 902-1 may generate multiple sets of the number of guard symbols provided for two or more timing switching groups, respectively (step 1104). Alternatively, the parent IAB node 902-1 may receive multiple sets of the number of guard symbols provided from an external device or operator (e.g., a user) of the parent IAB node 902-1 (step 1104).

[0114] An example of a "set of numbers of provided guard symbols" is the number of guard symbols included in the Provided Guard Symbol MAC CE disclosed in TS 38.321 ("NR; Medium Access Control (MAC) Protocol Specification"). The Provided Guard Symbol MAC CE includes a set of numbers of symbols not used for the IAB-MT 904-2 of the IAB node 902-2 in a slot in which the IAB node 902-2 transitions between downlink reception / uplink transmission via the IAB-MT 904-2 and downlink transmission / uplink reception via the IAB-DU 906-2, as described in 3GPP TS 38.213, V16.3.0, Physical Layer Procedures for Control ("For the serving cell of the IAB-MT, the IAB-MT may be provided with the number of symbols not used for the IAB-MT in a slot in which the IAB node transitions between the IAB-MT and IAB node DU by guard-SymbolsProvided").

[0115] IAB node 902-2 may receive one or more sets of provided guard symbol numbers for two or more timing switching groups, respectively, from parent IAB node 902-1 (step 1106).

[0116] Optionally, the IAB node 902-2 may receive one or more sets of provided guard symbol numbers for two or more timing switching groups from the parent IAB node 902-1 via one or more MAC CEs, respectively, where each MAC CE of the one or more MAC CEs includes one or more bits indicating one of the two or more timing switching groups for which the MAC CE includes a respective set of provided guard symbol numbers (step 1106).

[0117] Optionally, the IAB node 902-2 may receive at least one of the one or more sets of numbers of provided guard symbols as a difference relative to a reference set of numbers of provided guard symbols (step 1106).

[0118] Optionally, the IAB node 902-2 may change its timing alignment configuration to a timing alignment configuration corresponding to a particular one of a plurality of timing alignment cases in a particular one of a plurality of timing switching groups (step 1108) and explicitly or implicitly indicate the change in the timing alignment configuration of the IAB node 902-2 to its parent IAB node 902-1 (step 1110).

[0119] The IAB node 902-2 may determine the downlink reception or uplink transmission of the IAB-MT 904-2 in two adjacent time units (e.g., slots) based on the available time resources for the downlink transmission or uplink reception of the IAB-DU 906-2 and / or one of one or more sets of provided guard symbol numbers for one of two or more timing switching groups corresponding to the timing alignment case used in the two adjacent time units (e.g., slots) (step 1112).

[0120] Optionally, the IAB node 902-2 may perform uplink transmission and / or downlink reception in two adjacent time units based on the determined available time resources. For example, the IAB node 902-2 may not use a time slot at the (start or end) edge corresponding to the number of provided guard symbols when the IAB node 902-2 transitions between the IAB-MT 904-2 and the IAB-DU 906-2 (step 1114).

[0121] The parent IAB node 902-2 may determine available time resources for uplink transmission and / or downlink reception in two adjacent time units (e.g., slots) based on one of one or more sets of desired guard symbol numbers for one of two or more timing switching groups corresponding to the timing alignment case used in the two adjacent time units (e.g., slots) (step 1116).

[0122] Optionally, the parent IAB node 902-1 may perform uplink transmission and / or downlink reception in two adjacent time units based on the determined available time resources. For example, the parent IAB node 902-1 may not use the time slot of the (start or end) edge corresponding to the desired number of guard symbols when the IAB node 902-2 performs a transition between the IAB-MT 904-2 and the IAB-DU 906-2 (1118).

[0123] Optionally, IAB node 902-2 may send a signal to parent IAB node 902-1 updating the set of desired number of guard symbols (step 1120). Optionally, parent IAB node 902-1 can send a signal to IAB node 902-2 updating the set of provided number of guard symbols (step 1122).

[0124] The switching or transition may occur from one slot (e.g., slot (k-1)) to the next slot (e.g., slot k). According to one embodiment, each set of desired guard symbol numbers for each timing switching group (Group-1 through Group-4) includes at least eight non-negative values ​​representing the number of guard symbols corresponding to multiple timing alignment cases, as shown in FIG. 10: ●Group-1: o Switching from IAB-MT Rx in timing case #1 to IAB-DU Tx in timing case #1. o Switching from IAB-MT Rx in timing case #1 to IAB-DU Rx in timing case #1. o Switching from IAB-MT Tx in timing case #1 to IAB-DU Tx in timing case #1. o Switching from IAB-MT Tx in timing case #1 to IAB-DU Rx in timing case #1. o Switching from IAB-DU Rx in timing case #1 to IAB-MT Tx in timing case #1. o Switching from IAB-DU Rx in timing case #1 to IAB-MT Rx in timing case #1. o Switching from IAB-DU Tx in timing case #1 to IAB-MT Tx in timing case #1. o Switching from IAB-DU Tx in timing case #1 to IAB-MT Rx in timing case #1.

[0125] ●Group-2: o Switching from IAB-MT Rx in timing case #1 to IAB-DU Tx in timing case #6. o Switching from IAB-MT Rx in timing case #1 to IAB-DU Rx in timing case #7. o Switching from IAB-MT Tx in timing case #1 to IAB-DU Tx in timing case #6. o Switching from IAB-MT Tx in timing case #1 to IAB-DU Rx in timing case #7. o Switching from IAB-DU Rx in timing case #1 to IAB-MT Tx in timing case #6. o Switching from IAB-DU Rx in timing case #1 to IAB-MT Rx in timing case #7. o Switching from IAB-DU Tx in timing case #1 to IAB-MT Tx in timing case #6. o Switching from IAB-DU Tx in timing case #1 to IAB-MT Rx in timing case #7.

[0126] ●Group-3: o Switching from IAB-MT Rx in timing case #7 to IAB-DU Tx in timing case #1. o Switching from IAB-MT Rx in timing case #7 to IAB-DU Rx in timing case #1. o Switching from IAB-MT Tx in timing case #6 to IAB-DU Tx in timing case #1. o Switching from IAB-MT Tx in timing case #6 to IAB-DU Rx in timing case #1. o Switching from IAB-DU Rx in timing case #7 to IAB-MT Tx in timing case #1. o Switching from IAB-DU Rx in timing case #7 to IAB-MT Rx in timing case #1. o Switching from IAB-DU Tx in timing case #6 to IAB-MT Tx in timing case #1. o Switching from IAB-DU Tx in timing case #6 to IAB-MT Rx in timing case #1.

[0127] ●Group-4: o Switching from IAB-MT Rx in timing case #7 to IAB-DU Tx in timing case #6. o Switching from IAB-MT Rx in timing case #7 to IAB-DU Rx in timing case #7. o Switching from timing case #6 IAB-MT Tx to timing case #6 IAB-DU Tx. o Switching from IAB-MT Tx in timing case #6 to IAB-DU Rx in timing case #7. o Switching from IAB-DU Rx in timing case #7 to IAB-MT Tx in timing case #6. o Switching from IAB-DU Rx in timing case #7 to IAB-MT Rx in timing case #7. o Switching from timing case #6 IAB-DU Tx to timing case #6 IAB-MT Tx. o Switching from IAB-DU Tx in timing case #6 to IAB-MT Rx in timing case #7.

[0128] Optionally, parent IAB node 902-1 may control a change in time mode operation in IAB node 902-2, for example, by sending a control signal to IAB node 902-2. IAB node 902-2 may change the time mode operation corresponding to one of the time alignment cases, for example, from case #1 at slot (k-1) to case #6 at slot k, based on the control signal sent from parent IAB node 902-1.

[0129] When IAB node 902-2 changes the timing mode operation in which it operates, IAB node 902-2 may implicitly or explicitly notify parent IAB node 902-1 about the change in timing mode operation. According to the RAN1 Chairman's Note ("RAN1 Chairman's Note", 3GPP TSG RAN WG1 Meeting #103e, November 2020), it is agreed that the control of case #6 timing mode operation in IAB node 902-2 is by the parent IAB node 902-1, which is intended for uplink transmission.

[0130] * * * * * Beginning of excerpt from RAN1 Chairman's Note * * * * * Agreement Case 6 timing mode operation at an IAB-node is controlled by the parent IAB node that is intended for UL transmission. * * * * * END EXCERPT FROM RAN1 CHAIRMAN'S NOTES * * * * *

[0131] Thus, the parent IAB node 902-1 will implicitly know when the IAB node 902-2 starts or stops operating during case #6 timing mode operation. That is, the IAB node 902-2 does not need to notify the parent IAB node 902-1 of the timing mode operation change from case #6 to case #1 or case #7. In other cases, the IAB node 902-2 may explicitly notify the parent IAB node 902-1 by sending a signal to the parent IAB node 902-1 when (i) changing from case #1 or case #6 timing to case #7 timing, or (ii) changing from case #7 timing to case #1 timing.

[0132] For example, if IAB node 902-2 changes its timing mode operation from case #6 in slot (k-1) to case #1 or case #7 in slot k, IAB node 902-2 may not need to inform parent IAB node 902-1 of the change in timing mode operation because the change from case #6 to other cases (case #1, case #7) may be initiated or controlled by parent IAB node 902-1. Thus, parent IAB node 902-1 already knows about the change in timing mode operation in IAB node 902-2.

[0133] Second embodiment 12 is a flow chart illustrating another embodiment of a method of operation of the IAB node 902-2 and parent IAB node 902-1. Optional steps are represented by boxes.

[0134] Optionally, the IAB node 902-2 may generate one or more sets of desired guard symbol numbers (step 1200), or may receive one or more sets of desired guard symbol numbers from an external device or operator (e.g., a user) of the IAB node 902-2 (step 1200).

[0135] Optionally, the IAB node 902-2 may determine that a timing configuration has occurred that corresponds to a first occurrence of one of the timing alignment cases for a particular timing switching group (step 1202). The first occurrence is one of the following time alignment cases: ●Case #1 and Case #1. ●Case #1 and Case #6. ●Case #1 and Case #7. ●Case #6 and Case #1. ●Case #7 and Case #1. ●Case #6 and Case #7. ●Case #7 and Case #6. ●Case #6 and Case #6. ●Case #7 and Case #7.

[0136] The Timing Switching group includes resource misalignments that occur in the timing alignment cases: ●From IAB-MT Rx to IAB-DU Tx. ●From IAB-MT Rx to IAB-DU Rx. ●From IAB-MT Tx to IAB-DU Tx. ●From IAB-MT Tx to IAB-DU Rx. ●From IAB-DU Rx to IAB-MT Tx. ●From IAB-DU Rx to IAB-MT Rx. ●IAB-DU Tx to IAB-MT Tx; and, ●From IAB-DU Tx to IAB-MT Rx.

[0137] The IAB node 902-2 may send to the parent IAB node 902-1 a single set of desired guard symbol numbers for two or more timing switching groups for the first occurrence, where each timing switching group of the two or more timing switching groups includes one or more timing alignment cases, and the single set of desired guard symbol numbers includes the desired guard symbol numbers for the one or more timing alignment cases included in each timing switching group of the two or more timing switching groups (step 1204).

[0138] Optionally, the IAB node 902-2 may transmit a single set of desired guard symbol numbers for two or more timing switching groups, respectively, to the parent IAB node 902-1 via one or more MAC CEs.

[0139] Optionally, IAB node 902-2 may transmit a single set of desired numbers of guard symbols as deltas relative to a reference set of desired numbers of guard symbols.

[0140] Optionally, the parent IAB node 902-1 may generate one or more sets of provided guard symbol numbers, e.g., Provided Guard Symbols disclosed in relevant standards such as Technical Specification (TS) 38.321, NR; Medium Access Control (MAC) Protocol Specification (e.g., 5.18.19 Guard Symbols for IAB) (step 1206). Alternatively, the parent IAB node 902-1 may receive one or more sets of provided guard symbol numbers from an external device or operator (e.g., a user) of the parent IAB node 902-1 (step 1206).

[0141] IAB node 902-2 may receive a single set of provided guard symbol numbers for each of two or more timing switching groups from parent IAB node 902-1 (step 1208).

[0142] Optionally, the IAB node 902-2 may receive a single set of provisioned guard symbol numbers for two or more timing switching groups from the parent IAB node 902-1 via one or more MAC CEs, respectively.

[0143] Optionally, each MAC CE of the one or more MAC CEs may comprise one or more bits indicating one of two or more timing switching groups that the MAC CE includes a respective set of the number of guard symbols provided.

[0144] Optionally, IAB node 902-2 may receive a single set of numbers of provided guard symbols as deltas relative to a reference set of numbers of provided guard symbols.

[0145] The IAB node 902-2 may determine available time resources for uplink transmission and / or downlink reception in two adjacent time units (e.g., slots) based on a single set of provided guard symbol numbers for one of two or more timing switching groups corresponding to the timing alignment case used in the two adjacent time units (e.g., slots) (step 1210).

[0146] Optionally, the IAB node 902-2 may perform uplink transmission and / or downlink reception in two adjacent time units based on the determined available time resources. For example, the IAB node 902-2 may not use a time slot at an edge (start or end) corresponding to the number of provided guard symbols when the IAB node 902-2 transitions between the IAB-MT 904-2 and the IAB-DU 906-2 (step 1212).

[0147] The parent IAB node 902-1 may determine available time resources for uplink transmission and / or downlink reception in two adjacent time units (e.g., slots) based on a single set of desired guard symbol numbers for one of two or more timing switching groups corresponding to the timing alignment case used in the two adjacent time units (e.g., slots) (step 1214).

[0148] Optionally, the parent IAB node 902-1 may perform uplink transmission and / or downlink reception in two adjacent time units based on the determined available time resources. For example, the parent IAB node 902-1 may not use a time slot at the (start or end) edge corresponding to the desired number of guard symbols when the IAB node 902-2 performs a transition between the IAB-MT 904-2 and the IAB-DU 906-2 (step 1216).

[0149] Other embodiments As disclosed in TS 38.321 ("NR; Medium Access Control (MAC) Protocol Specification"), the guard symbol MAC CE includes a reserved field and a field to indicate the reference subcarrier spacing (SCS) for guard spacing. Instead of specifying additional signaling to inform the parent IAB node 902-1 or IAB node 902-2 about the number of guard symbols in different groups 2, 3, and 4, the reserved bit can be used to indicate that the signaling of the guard symbol combination is for one of group 2, group 3, or group 4, but not for group 1. In this case, the SCS field is the same SCS as in the guard symbol configuration of case #1 (group-1), and instead, two bits in the SCS field can be used to flag the guard symbol combination of group-2, group-3, or group-4.

[0150] According to another embodiment, the guard symbol combination may refer to the guard symbol combination of case #1 (i.e., group 1). For example, for the guard symbol combinations of group 2, group 3, and group 4, only the differences from the guard symbol of case #1 in group 1 may be signaled.

[0151] According to another embodiment, the parent IAB node 902-1 and the IAB node 902-2 may use a predefined or higher layer (e.g., F1-AP or radio resource control (RRC)) configured approach to determine a valid number of multiple guard symbol numbers if the problematic IAB-DU resource is configured as flexible (i.e., the IAB-DU is either transmit or receive) based on received guard symbols associated with the IAB-DU Tx and / or IAB-DU Rx.

[0152] According to another embodiment, each group of guard symbols (e.g., when the number of guard symbols exceeds 8 values) is additionally considered: • Switching from IAB-MT(DL) Rx in timing case A to IAB-DU flexible (i.e., either Tx or Rx) in timing case B. • Switching from IAB-MT(UL) Tx in timing case A to IAB-DU flexible (i.e., either Tx or Rx) in timing case B. • Switching from IAB-DU flexible (i.e., either Tx or Rx) in timing case A to IAB-MT(DL) Rx in timing case B. Switching from IAB-DU flexible (i.e., either Tx or Rx) in timing case A to IAB-MT(UL) Tx in timing case B, where timing case A and timing case B can be any of timing case #1, timing case #6, and timing case #7.

[0153] Further explanation FIG. 13 is a schematic block diagram of a radio access node 1300 according to some embodiments of the present disclosure. Optional functionality is represented by dashed boxes. The radio access node 1300 may be, for example, a base station 902 or 906 or a network node implementing all or part of the functionality of a base station 902 or gNB described herein. As shown, the radio access node 1300 has a control system 1302, which has one or more processors 1304 (e.g., a central processing unit (CPU), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), etc.), a memory 1306, and a network interface 1308. The one or more processors 1304 are also referred to herein as processing circuits. Additionally, the radio access node 1300 may include one or more radio units 1310, each including one or more transmitters 1312 and one or more receivers 1314 coupled to one or more antennas 1316. The radio unit 1310 may be referred to or may be part of a radio interface circuit. According to some embodiments, the radio unit 1310 is external to the control system 1302 and is connected to the control system 1302, for example, via a wired connection (e.g., optical cable). However, according to some other embodiments, the radio unit(s) 1310 and potentially the antenna(s) 1316 are integrated with the control system 1302. The one or more processors 1304 operate to provide one or more functions of the wireless access node 1300, as described herein. According to an embodiment, the functions are implemented in software that is stored, for example, in the memory 1306 and executed by the one or more processors 1304.

[0154] For the proposed solution, an embodiment of a method of operation of the IAB node 902-2 and the parent IAB node 902-1 is disclosed. The IAB node 902-2 and the parent IAB node 902-1 are examples of the wireless access node 1320. Thus, the IAB node 902-2 and the parent IAB node 902-1 include all the components shown in the wireless access node 1320 of FIG.

[0155] FIG. 15 is a schematic block diagram illustrating a virtualized embodiment of a radio access node 1300 according to some embodiments of the present disclosure. This description is equally applicable to other types of network nodes. Additionally, other types of network nodes may have similar virtualization architectures. Again, optional functionality is represented by dashed boxes. IAB node 902-2 and parent IAB node 902-1 are illustrative of the radio access node 1320 shown in FIG. 15.

[0156] As used herein, a "virtualized" radio access node is an implementation of the radio access node 1300 in which at least a portion of the functionality of the radio access node 1300 is implemented as virtual component(s) (e.g., via virtual machine(s) running on physical processing node(s) in network(s)). As shown, in this illustration, the radio access node 1300 may include a control system 1302 and / or one or more radio units 1310, as described above. The control system 1302 may be connected to the radio unit 1310, for example, via an optical cable or the like. The radio access node 1300 includes one or more processing nodes 1500 coupled to or included as part of a network(s) 1502. If present, the control system 1302 or radio units are connected to the processing node 1500 via the network 1502. Each processing node 1500 has one or more processors 1504 (eg, a CPU, ASIC, FPGA, and / or the like), memory 1506, and a network interface 1508.

[0157] In this example, the functions 1510 of the radio access node 1300 described herein are implemented in one or more processing nodes 1500 or distributed across one or more processing nodes 1500 and the control system 1302 and / or radio unit 1310 in any desired manner. According to some particular embodiments, some or all of the functions 1510 of the radio access node 1300 described herein are implemented as virtual components executed by one or more virtual machines implemented in a virtual environment hosted by the processing node 1500. As will be appreciated by those skilled in the art, additional signaling transfer or communication between the processing node 1500 and the control system 1302 is used to perform at least some of the desired functions 1510. Notably, according to some embodiments, the control system 1302 may not be included, in which case the radio unit 1310 communicates directly with the processing node 1500 via an appropriate network interface.

[0158] According to some embodiments, a computer program is provided that includes instructions that, when executed by at least one processor, cause the at least one processor to perform functions of the radio access node 1300 or a node (e.g., processing node 1500) implementing one or more of the functions 1510 of the radio access node 1300 in a virtual environment according to any of the embodiments described herein. According to some embodiments, a carrier is provided that carries the aforementioned computer program product. The carrier is one of an electrical signal, an optical signal, a radio signal, or a computer readable storage medium (e.g., a non-transitory computer readable medium such as a memory).

[0159] FIG. 14 is a schematic block diagram of a radio access node 1300 according to some other embodiments of the present disclosure. The radio access node 1300 has one or more modules 1400, each of which is implemented in software. The modules 1400 provide the functionality of the radio access node 1300 described herein. This description is equally applicable to the processing node 1500 of FIG. 15, where the modules 1400 may be implemented in one of the processing nodes 1500 or distributed across multiple processing nodes 1500 and / or across the processing nodes 1500 and the control system 1302. The IAB node 902-2 and the parent IAB node 902-1 are examples of the radio access node 1320 shown in FIG. 15. Thus, the IAB node 902-2 and the parent IAB node 902-1 include one or more modules 1400, e.g., a medium access control (MAC) module. Any suitable step, method, feature, function, or benefit disclosed herein may be performed via one or more functional units or modules of one or more virtual devices. Each virtual device may comprise several of these functional units. These functional units may be implemented via processing circuitry, which may include one or more microprocessors or microcontrollers, as well as other digital hardware, which may include digital signal processors (DSPs), dedicated digital logic, and the like. The processing circuitry may be configured to execute program code stored in memory, which may have one or more types of memory, such as read-only memory (ROM), random access memory (RAM), cache memory, flash memory devices, optical storage devices, and the like. The program code stored in memory has program instructions for executing one or more communication and / or data communication protocols, as well as instructions for executing one or more of the techniques described herein.In some implementations, processing circuitry may be used to cause each functional unit to perform a function corresponding to the respective functional unit in accordance with one or more embodiments of the present disclosure.

[0160] Although the processes in the figures may indicate a particular order of operations performed by certain embodiments of the present disclosure, it is to be understood that such orders are exemplary (e.g., alternative embodiments may perform operations in different orders, combine certain operations, overlap certain operations, etc.).

[0161] In this disclosure, at least some of the following abbreviations may be used. In case of discrepancies between the abbreviations, how it is used above shall prevail. If listed multiple times below, the first listing shall prevail over any subsequent listings.

[0162] ●3GPP: Third Generation Partnership Project ●5G: Fifth generation ●5GC: Fifth generation core ●5GS: Fifth Generation System ●AF: Application Function AMF: Access and Mobility Function ●AN: Access Network ●AP: Access Point ●ASIC: Application Specific Integrated Circuit ●AUSF: Authentication Server Function ●CE: Control element ●CPU: Central Processing Unit ●DN: Data Network ●DSP: Digital Signal Processor eNB: Enhanced or evolved Node B ●EPS: Evolved Packet System E-UTRA: Evolved Universal Terrestrial Radio Access ●FDD: Frequency division duplex ●FPGA: Field Programmable Gate Array ●gNB: New Radio Base Station ●gNB-CU: New Radio Base Station Central Unit ●gNB-CU-CP: New Radio Base Station Central Unit Control Plane ●gNB-CU-UP: New Radio Base Station Central Unit User Plane ●gNB-DU: New Radio Base Station Distributed Unit ●HSS: Home Subscriber Server ●IAB: Integrated Access and Backhaul ●IAB-DU: Integrated Access and Backhaul Distribution Unit ●IAB-MT: Integrated Access and Backhaul Mobile Termination (Terminal) ●IoT: Internet of Things IP: Internet Protocol ●LTE: Long Term Evolution ●MAC: Medium Access Control ●MME: Mobility Management Entity ●MTC: Machine Type Communication ●NEF: Network Publishing Function ●NF: Network function ●NR: New Radio ●NRF: Network Function Repository Function ●NSSF: Network Slice Selection Function ●PC: Personal computer ●PCF: Policy Control Function ●PDCP: Packet Data Convergence Protocol ●P-GW: Packet Data Network Gateway QoS: Quality of Service ●RAM: Random Access Memory ●RAN: Radio Access Network ●RLC: Radio Link Control RNL: Radio Network Layer ROM: Read-only memory ●RRC: Radio Resource Control RRH: Remote Radio Head RTT: Round Trip Time ●SCEF: Service Capability Exposure Function ●SCS: Subcarrier spacing ●SMF: Session Management Facility ●TDD: Time Division Duplex ●TDM: Time division multiplexing ●TNL: Transport Network Layer ●UDM: Unified Data Management ●UE: User Equipment UPF: User Plane Function

[0163] Those skilled in the art will recognize improvements and modifications to the embodiments of the present disclosure, and all such improvements and modifications are deemed to be within the scope of the concepts disclosed herein.

Claims

1. A method performed by an Integrated Access and Backhaul (IAB) node (902-2), comprising: Transmitting (1102; 1204) to a parent IAB node (902-1) one or more sets of desired guard symbol numbers for each of two or more timing switching groups; each of the two or more timing switching groups includes one or more timing alignment cases; each set of desired guard symbol numbers includes a desired guard symbol number for the one or more timing alignment cases included in each timing switching group of the two or more timing switching groups; and receiving from said parent IAB node (902-1) one or more sets of provisioned guard symbol numbers for each of said two or more timing switching groups (1106; 1208); - determining available time resources for uplink transmission and / or downlink reception in two adjacent time units, based on one of one or more sets of the number of provided guard symbols for one of the two or more timing switching groups corresponding to a timing alignment case used in the two adjacent time units (1112; 1210).

2. 2. The method of claim 1 , The IAB node (902-2) includes an IAB mobility termination (IAB-MT) (904-2) and an IAB distribution unit (IAB-DU) (906-2); The method of claim 1, wherein the desired number of guard symbols is a number of symbols that the IAB-MT (904-2) indicates to the parent IAB node (902-1) not to use for the IAB-MT (904-2) in slots in which the IAB node (902-2) transitions between the IAB-MT (904-2) and the IAB-DU (906-2).

3. 3. The method according to claim 1 or 2, The IAB node (902-2) includes an IAB mobility termination (IAB-MT) (904-2) and an IAB distribution unit (IAB-DU) (906-2); The method, wherein the number of guard symbols provided is the number of symbols that should not be used for the IAB-MT (904-2) in a slot in which the IAB node (902-2) transitions between the IAB-MT (904-2) and the IAB-DU (906-2).

4. 2. The method of claim 1, further comprising: performing uplink transmission and / or downlink reception in the two adjacent time units based on the determined available time resources (1114; 1212).

5. 5. The method according to any one of claims 1 to 4, the one or more sets of desired numbers of guard symbols include a plurality of sets of desired numbers of guard symbols; the one or more timing alignment cases include one or more timing alignment cases for each of the two or more timing switching groups; The one or more sets of numbers of provided guard symbols include a plurality of sets of numbers of provided guard symbols.

6. 6. The method of claim 1, further comprising: changing (1108) a timing alignment configuration of the IAB node (902-2) to a timing alignment configuration corresponding to a particular timing alignment case of the one or more timing alignment cases in a particular timing switching group of the two or more timing switching groups; indicating (1110) to the parent IAB node (902-1) the change in the timing alignment configuration of the IAB node (902-2); The method according to claim 1,

7. 7. The method of claim 6, wherein determining (1112; 1210) the available time resources for uplink transmission and / or downlink reception in the two adjacent time units comprises determining (1112; 1210) the available time resources for uplink transmission and / or downlink reception in the two adjacent time units based on one of a plurality of sets of the number of provided guard symbols for the particular timing switching group corresponding to the particular timing alignment case.

8. 8. The method according to claim 1, wherein the two or more timing switching groups include one or more of a first timing switching group, a second timing switching group, a third timing switching group, and a fourth timing switching group; The first timing switching group is Switching from IAB-MT Rx in Timing Case #1 to IAB-DU Tx in Timing Case #1; and Switching from Timing Case #1 IAB-MT Rx to Timing Case #1 IAB-DU Rx; and Switching from Timing Case #1 IAB-MT Tx to Timing Case #1 IAB-DU Tx; and Switching from IAB-MT Tx in Timing Case #1 to IAB-DU Rx in Timing Case #1; and Switching from IAB-DU Rx in timing case #1 to IAB-MT Tx in timing case #1; and Switching from Timing Case #1 IAB-DU Rx to Timing Case #1 IAB-MT Rx; and Switching from IAB-DU Tx in timing case #1 to IAB-MT Tx in timing case #1; and o switching from IAB-DU Tx in timing case #1 to IAB-MT Rx in timing case #1; The second timing switching group is Switching from IAB-MT Rx in timing case #1 to IAB-DU Tx in timing case #6; and Switching from IAB-MT Rx in timing case #1 to IAB-DU Rx in timing case #7; and Switching from IAB-MT Tx in timing case #1 to IAB-DU Tx in timing case #6; and Switching from IAB-MT Tx in timing case #1 to IAB-DU Rx in timing case #7; and Switching from IAB-DU Rx in timing case #1 to IAB-MT Tx in timing case #6; and Switching from IAB-DU Rx in timing case #1 to IAB-MT Rx in timing case #7; and Switching from IAB-DU Tx in timing case #1 to IAB-MT Tx in timing case #6; and o Switching from IAB-DU Tx in timing case #1 to IAB-MT Rx in timing case #7; and The third timing switching group is Switching from IAB-MT Rx in timing case #7 to IAB-DU Tx in timing case #1; and Switching from IAB-MT Rx in timing case #7 to IAB-DU Rx in timing case #1; and Switching from IAB-MT Tx in timing case #6 to IAB-DU Tx in timing case #1; and Switching from IAB-MT Tx in timing case #6 to IAB-DU Rx in timing case #1; and Switching from IAB-DU Rx in timing case #7 to IAB-MT Tx in timing case #1; and Switching from IAB-DU Rx in timing case #7 to IAB-MT Rx in timing case #1; and Switching from IAB-DU Tx in timing case #6 to IAB-MT Tx in timing case #1; and o switching from IAB-DU Tx in timing case #6 to IAB-MT Rx in timing case #1; The fourth timing switching group is Switching from IAB-MT Rx in timing case #7 to IAB-DU Tx in timing case #6; and Switching from timing case #7 IAB-MT Rx to timing case #7 IAB-DU Rx; and Switching from timing case #6 IAB-MT Tx to timing case #6 IAB-DU Tx; and Switching from IAB-MT Tx in timing case #6 to IAB-DU Rx in timing case #7; and Switching from IAB-DU Rx in timing case #7 to IAB-MT Tx in timing case #6; and Switching from timing case #7 IAB-DU Rx to timing case #7 IAB-MT Rx; and Switching from timing case #6 IAB-DU Tx to timing case #6 IAB-MT Tx; and o switching from IAB-DU Tx in timing case #6 to IAB-MT Rx in timing case #7.

9. 9. The method of claim 8, Case #1 is a timing alignment case where DL transmit timing alignment across the IAB node and the IAB donor is provided; Case #6 is a timing alignment case where DL transmit timing alignment across the IAB node and the IAB donor is provided and the DL transmit timing and UL transmit timing are aligned within the IAB node; ●Case #7 is a timing alignment case in which DL transmit timing alignment is provided across the IAB node and the IAB donor, and DL receive timing and UL receive timing are aligned within the IAB node.

10. 5. The method according to any one of claims 1 to 4, the one or more sets of desired numbers of guard symbols include a single set of desired numbers of guard symbols; The two or more timing switching groups include one timing switching group, the one or more timing alignment cases include one or more timing alignment cases for the one timing switching group; The one or more sets of numbers of provided guard symbols include one set of numbers of provided guard symbols.

11. 11. The method of claim 10, Transmitting (1102; 1204) a single set of the desired number of guard symbols for each of two or more timing switching groups includes transmitting (1102; 1204) the set of the desired number of guard symbols for the one timing switching group to the parent IAB node (902-1) in response to a first occurrence of a corresponding change in a timing alignment configuration of the IAB node (902-2); The method further comprises indicating (1110) the change in the timing alignment configuration of the IAB node (902-2) explicitly or implicitly to the parent IAB node (902-1).

12. 12. The method of claim 10 or 11, wherein the one or more timing alignment cases include: ●Case #1 and Case #1 and Case #1 and Case #6, Case #1 and Case #7, Case #6 and Case #1, ● Case #7 and Case #1, Case #6 and Case #7, Case #7 and Case #6, Case #6 and Case #6 and ● Case #7 and Case #7 and The method includes one or more of:

13. 13. The method of claim 10, wherein the one or more timing alignment cases include: ● From IAB-MT Rx to IAB-DU Tx, ● From IAB-MT Rx to IAB-DU Rx, ● From IAB-MT Tx to IAB-DU Tx, ● From IAB-MT Tx to IAB-DU Rx, ● From IAB-DU Rx to IAB-MT Tx, ● From IAB-DU Rx to IAB-MT Rx, ● From IAB-DU Tx to IAB-MT Tx, ● From IAB-DU Tx to IAB-MT Rx, A method for addressing resource misalignment of one or more of:

14. 14. The method according to claim 12 or 13, Case #1 is a timing alignment case where DL transmit timing alignment across the IAB node and the IAB donor is provided; Case #6 is a timing alignment case where DL transmit timing alignment across the IAB node and the IAB donor is provided and the DL transmit timing and UL transmit timing are aligned within the IAB node; ●Case #7 is a timing alignment case in which DL transmit timing alignment is provided across the IAB node and the IAB donor, and DL receive timing and UL receive timing are aligned within the IAB node.

15. 15. The method of claim 1, wherein transmitting (1102; 1204) to the parent IAB node (902-1) the one or more sets of desired numbers of guard symbols for each of two or more timing switching groups comprises transmitting (1102; 1204) the one or more sets of desired numbers of guard symbols for each of two or more timing switching groups to the parent IAB node (902-1) via one or more MAC CEs.

16. 16. The method of claim 15, wherein each MAC CE of the one or more MAC CEs includes a reserved bit to indicate that one of the two or more timing switching groups is not group 1.

17. 16. The method of claim 15, wherein each MAC CE of the one or more MAC CEs includes one or more subcarrier spacing (SCS) bits indicating that the one or more sets of desired numbers of guard symbols correspond to one or more of Group 2, Group 3, or Group 4, respectively.

18. 18. The method of claim 1, wherein receiving (1106; 1208) the one or more sets of numbers of guard symbols provided for each of the two or more timing switching groups comprises receiving (1106; 1208) the one or more sets of numbers of guard symbols provided for each of the two or more timing switching groups from the parent IAB node (902-1) via one or more MAC CEs.

19. 20. The method of claim 18, wherein each MAC CE of the one or more MAC CEs includes one or more bits indicating one of the two or more timing switching groups, the MAC CE including a corresponding set of numbers of provided guard symbols.

20. 20. The method of claim 1, wherein transmitting (1102; 1204) to the parent IAB node (902-1) one or more sets of desired guard symbol numbers for each of two or more timing switching groups includes transmitting (1102; 1204) at least one of the one or more sets of desired guard symbol numbers as a difference relative to a reference set of desired guard symbol numbers.

21. 20. The method of claim 1, wherein receiving one or more sets of numbers of provided guard symbols for each of the two or more timing switching groups (1106; 1208) comprises receiving at least one of the one or more sets of numbers of provided guard symbols as a difference relative to a reference set of numbers of provided guard symbols (1106; 1208).

22. 15. The method according to claim 1, wherein each of the two or more timing switching groups further comprises: Switching from IAB-MT DL Rx in timing case A to IAB-DU Flexible in timing case B; Switching from IAB-MT UL Tx in timing case A to IAB-DU Flexible in timing case B; Switching from IAB-DU Flexible in Timing Case A to IAB-MT DL Rx in Timing Case B; Switching from IAB-DU Flexible in timing case A to IAB-MT UL Tx in timing case B; wherein timing case A and timing case B are any of timing case #1, timing case #6, and timing case #7.

23. 23. The method of claim 22, wherein the parent IAB node (902-1) uses a predefined or higher layer configured technique to determine a valid number of desired guard symbols received from the IAB node (902-2) when a particular IAB-DU (906-2) resource is configured as flexible based on the received desired guard symbol number associated with an IAB-DU Tx and / or an IAB-DU Rx.

24. 23. The method of claim 22, wherein the IAB node (902-2) uses a predefined or higher layer configured technique to determine a valid number of provided guard symbols received from the parent IAB node (902-1) when a particular IAB-DU (906-2) resource is configured as flexible based on the received number of provided guard symbols associated with an IAB-DU Tx and / or an IAB-DU Rx.

25. The method according to claim 23 or 24, wherein the predefined or higher layer configured approach comprises F1-Application Protocol (F1-AP) or Radio Resource Control (RRC).

26. An integrated access and backhaul (IAB) node (902-2), Sending (1102; 1204) to a parent IAB node (902-1) one or more sets of desired guard symbol numbers for each of two or more timing switching groups, where: each timing switching group of the two or more timing switching groups includes one or more timing alignment cases; each set of desired guard symbol numbers includes a desired guard symbol number for the one or more timing alignment cases included in each timing switching group of the two or more timing switching groups; receiving from said parent IAB node (902-1) one or more sets of provisioned guard symbol numbers for each of said two or more timing switching groups (1106; 1208); An IAB node adapted to perform the following: determining (1112; 1210) available time resources for uplink transmission and / or downlink reception in the two adjacent time units based on one of one or more sets of the provided guard symbol numbers for one of the two or more timing switching groups corresponding to a timing alignment case used in the two adjacent time units.

27. 27. The IAB node (902-2) of claim 26, wherein said IAB node (902-2) is further adapted to perform the method according to any one of claims 2 to 25.

28. An integrated access and backhaul (IAB) node (902-2) having a processing circuit, the processing circuit comprising: Sending (1102; 1204) to a parent IAB node (902-1) one or more sets of desired guard symbol numbers for each of two or more timing switching groups, where: each timing switching group of the two or more timing switching groups includes one or more timing alignment cases; each set of desired guard symbol numbers includes a desired guard symbol number for the one or more timing alignment cases included in each timing switching group of the two or more timing switching groups; receiving from said parent IAB node (902-1) one or more sets of provisioned guard symbol numbers for each of said two or more timing switching groups (1106; 1208); An IAB node adapted to perform the following: determining (1112; 1210) available time resources for uplink transmission and / or downlink reception in two adjacent time units based on one of one or more sets of the provided guard symbol numbers for one of two or more timing switching groups corresponding to a timing alignment case used in the two adjacent time units.

29. A method performed by a parent Integrated Access and Backhaul (IAB) node (902-1), comprising: Receiving one or more sets of desired guard symbol numbers for each of two or more timing switching groups from an IAB node (902-2) (1102; 1204), where: each timing switching group of the two or more timing switching groups includes one or more timing alignment cases; each set of desired guard symbol numbers includes a desired guard symbol number for the one or more timing alignment cases included in each timing switching group of the two or more timing switching groups; Sending (1106; 1208) to the IAB node (902-2) one or more sets of the number of guard symbols provided for each of the two or more timing switching groups; - determining (1116; 1214) available time resources for uplink transmission and / or downlink reception in the two adjacent time units based on one of one or more sets of the number of provided guard symbols for one of the two or more timing switching groups corresponding to a timing alignment case used in the two adjacent time units.

30. 30. The method of claim 29, The IAB node (902-2) includes an IAB-mobility termination (IAB-MT) (904-2) and an IAB distribution unit (IAB-DU) (906-2); The method of claim 1, wherein the desired number of guard symbols is the number of symbols that the IAB-MT indicates to the parent IAB node (902-1) not to be used for the IAB-MT in a slot in which the IAB node (902-2) transitions between the IAB-MT (904-2) and the IAB-DU (906-2).

31. 31. The method of claim 29 or 30, The IAB node (902-2) includes an IAB mobility termination unit (IAB-MT) (904-2) and an IAB distribution unit (IAB-DU) (906-2); A method in which the number of guard symbols provided is the number of symbols that should not be used for the IAB-MT in a slot in which the IAB node (902-2) transitions between the IAB-MT (904-2) and the IAB-DU (906-2).

32. 30. The method of claim 29, further comprising: performing uplink transmission and / or downlink reception in the two adjacent time units based on the determined available time resources (1118; 1216).

33. 33. The method of any one of claims 29 to 32, comprising: the one or more sets of desired numbers of guard symbols include a plurality of sets of desired numbers of guard symbols; The two or more timing switching groups include a plurality of timing switching groups, the one or more timing alignment cases include one or more timing alignment cases for each of the two or more timing switching groups; The one or more sets of numbers of provided guard symbols include a plurality of sets of numbers of provided guard symbols.

34. 34. The method of claim 33 further comprising: receiving (1110) information from the IAB node (902-2) informing the parent IAB node (902-1) to change a timing alignment configuration of the IAB node (902-2) to a timing alignment configuration corresponding to a particular timing alignment case of the one or more timing alignment cases in a particular timing switching group of the plurality of timing switching groups.

35. 35. The method of claim 34, wherein determining the available time resources for uplink transmission and / or downlink reception in the two adjacent time units (1116; 1214) comprises determining the available time resources for uplink transmission and / or downlink reception in the two adjacent time units based on one of a plurality of sets of the number of provided guard symbols for the particular timing switching group corresponding to the particular timing alignment case (1116; 1214).

36. 36. The method of any one of claims 29 to 35, wherein the two or more timing switching groups include one or more of a first timing switching group, a second timing switching group, a third timing switching group, and a fourth timing switching group; The first timing switching group is Switching from IAB-MT Rx in Timing Case #1 to IAB-DU Tx in Timing Case #1; and Switching from Timing Case #1 IAB-MT Rx to Timing Case #1 IAB-DU Rx; and Switching from Timing Case #1 IAB-MT Tx to Timing Case #1 IAB-DU Tx; and Switching from IAB-MT Tx in Timing Case #1 to IAB-DU Rx in Timing Case #1; and Switching from IAB-DU Rx in timing case #1 to IAB-MT Tx in timing case #1; and Switching from Timing Case #1 IAB-DU Rx to Timing Case #1 IAB-MT Rx; and Switching from IAB-DU Tx in timing case #1 to IAB-MT Tx in timing case #1; and o switching from IAB-DU Tx in timing case #1 to IAB-MT Rx in timing case #1; The second timing switching group is Switching from IAB-MT Rx in timing case #1 to IAB-DU Tx in timing case #6; and Switching from IAB-MT Rx in timing case #1 to IAB-DU Rx in timing case #7; and Switching from IAB-MT Tx in timing case #1 to IAB-DU Tx in timing case #6; and Switching from IAB-MT Tx in timing case #1 to IAB-DU Rx in timing case #7; and Switching from IAB-DU Rx in timing case #1 to IAB-MT Tx in timing case #6; and Switching from IAB-DU Rx in timing case #1 to IAB-MT Rx in timing case #7; and Switching from IAB-DU Tx in timing case #1 to IAB-MT Tx in timing case #6; and o Switching from IAB-DU Tx in timing case #1 to IAB-MT Rx in timing case #7; and The third timing switching group is Switching from IAB-MT Rx in timing case #7 to IAB-DU Tx in timing case #1; and Switching from IAB-MT Rx in timing case #7 to IAB-DU Rx in timing case #1; and Switching from IAB-MT Tx in timing case #6 to IAB-DU Tx in timing case #1; and Switching from IAB-MT Tx in timing case #6 to IAB-DU Rx in timing case #1; and Switching from IAB-DU Rx in timing case #7 to IAB-MT Tx in timing case #1; and Switching from IAB-DU Rx in timing case #7 to IAB-MT Rx in timing case #1; and Switching from IAB-DU Tx in timing case #6 to IAB-MT Tx in timing case #1; and o switching from IAB-DU Tx in timing case #6 to IAB-MT Rx in timing case #1; The fourth timing switching group is Switching from IAB-MT Rx in timing case #7 to IAB-DU Tx in timing case #6; and Switching from timing case #7 IAB-MT Rx to timing case #7 IAB-DU Rx; and Switching from timing case #6 IAB-MT Tx to timing case #6 IAB-DU Tx; and Switching from IAB-MT Tx in timing case #6 to IAB-DU Rx in timing case #7; and Switching from IAB-DU Rx in timing case #7 to IAB-MT Tx in timing case #6; and Switching from timing case #7 IAB-DU Rx to timing case #7 IAB-MT Rx; and Switching from timing case #6 IAB-DU Tx to timing case #6 IAB-MT Tx; and o switching from IAB-DU Tx in timing case #6 to IAB-MT Rx in timing case #7.

37. 37. The method of claim 36, Case #1 is a timing alignment case where DL transmit timing alignment across the IAB node and the IAB donor is provided; Case #6 is a timing alignment case where DL transmit timing alignment across the IAB node and the IAB donor is provided and the DL transmit timing and UL transmit timing are aligned within the IAB node; ●Case #7 is a timing alignment case in which DL transmit timing alignment is provided across the IAB node and the IAB donor, and DL receive timing and UL receive timing are aligned within the IAB node. Do.

38. 33. The method of any one of claims 29 to 32, comprising: the one or more sets of desired numbers of guard symbols include a single set of desired numbers of guard symbols; The two or more timing switching groups include one timing switching group, the one or more timing alignment cases include one or more timing alignment cases for the one timing switching group; The one or more sets of numbers of provided guard symbols include one set of numbers of provided guard symbols.

39. 39. The method of claim 38, wherein receiving (1102; 1204) a single set of desired numbers of guard symbols for each of two or more timing switching groups comprises receiving (1102; 1204) a set of desired numbers of guard symbols for the one timing switching group from the IAB node (902-2) in response to a first occurrence of a corresponding change in a timing alignment configuration of the IAB node (902-2), the method comprising indicating (1110), either explicitly or implicitly, the change in the timing alignment configuration of the IAB node (902-2) to the parent IAB node (902-1).

40. 40. The method of claim 38 or 39, wherein the one or more timing alignment cases include: ●Case #1 and Case #1 and Case #1 and Case #6, Case #1 and Case #7, Case #6 and Case #1, ● Case #7 and Case #1, Case #6 and Case #7, Case #7 and Case #6, Case #6 and Case #6 and ● Case #7 and Case #7 and The method includes one or more of:

41. 41. The method of claim 40, Case #1 is a timing alignment case where DL transmit timing alignment across the IAB node and the IAB donor is provided; Case #6 is a timing alignment case where DL transmit timing alignment across the IAB node and the IAB donor is provided and the DL transmit timing and UL transmit timing are aligned within the IAB node; ●Case #7 is a timing alignment case in which DL transmit timing alignment is provided across the IAB node and the IAB donor, and DL receive timing and UL receive timing are aligned within the IAB node.

42. 42. The method of any one of claims 29 to 41, wherein the one or more timing alignment cases include: ● From IAB-MT Rx to IAB-DU Tx, ● From IAB-MT Rx to IAB-DU Rx, ● From IAB-MT Tx to IAB-DU Tx, ● From IAB-MT Tx to IAB-DU Rx, ● From IAB-DU Rx to IAB-MT Tx, ● From IAB-DU Rx to IAB-MT Rx, ● From IAB-DU Tx to IAB-MT Tx, ● From IAB-DU Tx to IAB-MT Rx, A method for addressing resource misalignment of one or more of:

43. 43. The method of any one of claims 29 to 42, wherein receiving (1102; 1204) from the IAB node (902-2) one or more sets of the desired number of guard symbols for each of two or more timing switching groups comprises receiving (1102; 1204) from the IAB node (902-2) one or more sets of the desired number of guard symbols for each of two or more timing switching groups via one or more MAC CEs.

44. 44. The method of claim 43, wherein each MAC CE of the one or more MAC CEs includes a reserved bit to indicate that one of the two or more timing switching groups is not group 1.

45. 44. The method of claim 43, wherein each MAC CE of the one or more MAC CEs includes one or more subcarrier spacing (SCS) bits to indicate that the one or more sets of desired numbers of guard symbols correspond to one or more of Group 2, Group 3, or Group 4, respectively.

46. 46. ​​The method of claim 29, wherein transmitting (1106; 1208) the one or more sets of numbers of guard symbols provided for the two or more timing switching groups respectively comprises transmitting (1106; 1208) the one or more sets of numbers of guard symbols provided for each of the two or more timing switching groups to the IAB node (902-2) via one or more MAC CEs.

47. 47. The method of claim 46, wherein each MAC CE of the one or more MAC CEs includes one or more bits indicating one of the two or more timing switching groups, the MAC CE including a corresponding set of numbers of provided guard symbols.

48. 48. The method of claim 29, wherein receiving (1102; 1204) from the IAB node (902-2) one or more sets of desired guard symbol numbers for each of two or more timing switching groups includes receiving (1102; 1204) at least one of the one or more sets of desired guard symbol numbers as a difference relative to a reference set of desired guard symbol numbers.

49. 49. The method of claim 29, wherein transmitting (1106; 1208) the one or more sets of numbers of provided guard symbols for each of the two or more timing switching groups comprises transmitting (1106; 1208) at least one of the one or more sets of numbers of provided guard symbols as a difference with respect to a reference set of numbers of provided guard symbols.

50. 49. The method of any one of claims 29 to 48, wherein each of the two or more timing switching groups further comprises: Switching from IAB-MT DL Rx in timing case A to IAB-DU Flexible in timing case B; Switching from IAB-MT UL Tx in timing case A to IAB-DU Flexible in timing case B; Switching from IAB-DU Flexible in Timing Case A to IAB-MT DL Rx in Timing Case B; switching from IAB-DU flexible in timing case A to IAB-MT UL Tx in timing case B, where timing case A and timing case B are any of timing case #1, timing case #6, and timing case #7.

51. 51. The method of claim 50, wherein the parent IAB node (902-1) uses a predefined or higher layer configured technique to determine a valid number of the desired number of guard symbols received from the IAB node (902-2) when a particular IAB-DU (906-2) resource is configured as flexible based on the received desired number of guard symbols associated with an IAB-DU Tx and / or an IAB-DU Rx.

52. 51. The method of claim 50, wherein the IAB node (902-2) uses a predefined or higher layer configured technique to determine a valid number of the provided guard symbol numbers received from the parent IAB node (902-1) when a particular IAB-DU (906-2) resource is configured as flexible based on the received provided guard symbol numbers associated with an IAB-DU Tx and / or an IAB-DU Rx.

53. 53. The method of claim 51 or 52, wherein the predefined or higher layer configured approach comprises F1-Application Protocol (F1-AP) or Radio Resource Control (RRC).

54. A parent integrated access and backhaul (IAB) node (902-1), Receiving (1102; 1204) one or more sets of desired guard symbol numbers for each of two or more timing switching groups from an IAB node (902-2), where: each timing switching group of the two or more timing switching groups includes one or more timing alignment cases; each set of desired guard symbol numbers includes a desired guard symbol number for the one or more timing alignment cases included in each timing switching group of the two or more timing switching groups; Sending to the IAB node (902-2) one or more sets of the number of guard symbols provided for each of the two or more timing switching groups (1106; 1208); A parent IAB node adapted to perform the following: determining (1116; 1214) available time resources for uplink transmission and / or downlink reception in the two adjacent time units based on one of one or more sets of the provided guard symbol numbers for one of the two or more timing switching groups corresponding to a timing alignment case used in the two adjacent time units.

55. A parent IAB node (902-1) according to claim 54, wherein said parent IAB node (902-1) is further adapted to perform the method according to any one of claims 29 to 53.

56. a parent integrated access and backhaul (IAB) node (902-1), the parent IAB node having processing circuitry, the processing circuitry providing to the parent IAB node (902-1): Receiving one or more sets of desired guard symbol numbers for each of two or more timing switching groups from an IAB node (902-2) (1102; 1204), where: each timing switching group of the two or more timing switching groups includes one or more timing alignment cases; each set of desired guard symbol numbers includes a desired guard symbol number for the one or more timing alignment cases included in each timing switching group of the two or more timing switching groups; Sending to the IAB node (902-2) one or more sets of the number of guard symbols provided for each of the two or more timing switching groups (1106; 1208); A parent IAB node configured to: determine (1116; 1214) available time resources for uplink transmission and / or downlink reception in the two adjacent time units based on one of one or more sets of the provided guard symbol numbers for one of the two or more timing switching groups corresponding to a timing alignment case used in the two adjacent time units.

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