ALIGNING DU/MT TRANSMISSION TIMING

A method, system and apparatus are disclosed for aligning Distributed Unit/Mobile Termination (DU/MT) transmission timing. In one embodiment, a method in a network node includes adjusting a first transmission timing to align with a second transmission timing, the first transmission timing comprising one of a Distributed Unit, DU, and a Mobile Terminated Unit, MT, transmission timing at the network node and the second transmission timing comprising another one of the DU and the MT transmission timing at the network node. In another embodiment, a method in a network node includes receiving an MT transmission based at least in part on an adjustment of a first transmission timing to align with a second transmission timing.

FIELD

The present disclosure relates to wireless communications, and in particular, to aligning Distributed Unit/Mobile Termination (DU/MT) transmission timing.

BACKGROUND

In the Third Generation Partnership Project (3GPP) Release 16 (Rel-16), there is an ongoing Work Item (WI) for Integrated Access Backhaul (IAB) based on an earlier study item documented in 3GPP Technical Report (TR) 38.874. One purpose of IAB is to replace existing wired backhaul or a wireless backhaul with flexible wireless backhaul using the existing 3GPP bands, providing not only backhaul but also existing cellular services in the same node.

Each IAB node holds a Distributed Unit (DU) function and a Mobile Termination (MT) function as shown in a reference architecture, an example of which is depicted inFIG.1. Via the MT, the IAB node connects to an upstream IAB node, which could also be an IAB donor node. Via the DU, the IAB node establishes radio link control (RLC) channels to MTs of downstream IAB nodes or provides access links to wireless devices (WDs).FIG.1conceptually shows an example of the possible connections for an IAB node, including access link to WDs and backhaul links to both an upstream parent and a downstream child IAB node.

An IAB node may carry out at least two types of transmissions:MT transmissions towards a parent IAN node, andDU transmissions towards devices and child IAB nodes.

The timing of MT transmissions is controlled by the parent node in the same way as the timing of WD transmissions is controlled by the serving cell:When initially accessing a parent node by a random-access procedure, the MT is provided with an initial timing-correction command as part of the random-access response.After the connection to the parent node has been established, the MT transmission timing can be further adjusted based on subsequent timing-advance (TA) commands provided by the parent node by means of medium access control (MAC) control element (CE) signalling.

The parent-node control of the MT transmission timing typically aims at aligning the parent-node reception timing of different WD and MT transmissions received by the parent node. By aligning the reception timing of different WD and MT transmissions, the receiver-side orthogonality between frequency-multiplexed transmissions, is retained. Furthermore, a single discrete Fourier transform (DFT) can be used at the parent node for the demodulation of the different transmissions. The reception timings of the different WD and MT transmissions may not be perfectly aligned but should preferably be aligned at least within the span of the cyclic prefix (CP).

Regarding the timing of DU transmissions, there is a statement in the 3GPP specifications that, for operation in unpaired spectrum, the downlink transmission timing of all cells with overlapping coverage should be mutually aligned within a window of 3 μs (see for example 3GPP Technical Specification (TS) 38.133). This also applies for cells created by an IAB node DU, at least in cases of operation in unpaired spectrum.

Such alignment of the downlink transmission timing between nodes can be achieved in several ways, including, for example, the use of global positioning system (GPS) reception at the IAB node together with an agreed absolute transmission timing. However, IAB also supports over-the-air (OTA) based transmission-timing alignment where an IAB node can derive its DU transmission timing solely from signals received from the parent node.

The basic principle of OTA-based transmission-timing alignment is that the IAB node should set its DU transmission timing an amount Tpropahead of the timing of signals received from the parent node, where Tpropis the propagation time from the parent node to the IAB node. In this way, the DU transmission timing of the IAB node is aligned with the DU transmission timing of its parent node, in line with the general requirement of aligned downlink transmission timing between cells. The task of OTA-based transmission-timing alignment may thus be equivalent to accurately estimating the propagation time between the IAB node and its parent node.

FIG.2illustrates an example of the timing relation (transmit and receive timing) between the DU and MT on each side of an IAB backhaul link (DU at the parent node and MT at the child node), according to current specifications. Given an offset TAbetween the downlink reception timing and uplink transmission timing at the MT and an offset TΔbetween the uplink reception timing and downlink transmission timing at the parent-node DU, it can be seen that the propagation time can be estimated as {circumflex over (T)}prop=(TA−TΔ)/2.

Offset TAis inherently known at the child node while offset TΔis known at the parent node. To enable the child node to estimate the parent-to-child propagation time, and thus to enable OTA-based timing alignment, the 3GPP specifications support that the parent node provides TΔto the child node by means of medium access control (MAC) control element (CE) signaling.

SUMMARY

Some embodiments advantageously provide methods, systems, and apparatuses for aligning Distributed Unit/Mobile Termination (DU/MT) transmission timing.

In one embodiment, a method implemented in a network node configured to communicate with at least one parent node over a backhaul network includes optionally, receiving a command related to timing alignment from a parent node; and adjusting a Distributed Unit (DU) transmission timing to align with at least one Mobile Terminated Unit (MT) transmission timing based at least in part on the command.

In another embodiment, a method implemented in a network node configured to communicate with at least one child node over a backhaul network includes sending a command related to timing alignment to a child node; and receiving a transmission based at least in part on a timing, the timing being adjusted to align the child node's Distributed Unit (DU) transmission timing with at least one Mobile Terminated Unit (MT) transmission timing based at least in part on the command.

According to an aspect of the present disclosure, a method implemented in a network node configured to communicate with a parent network node over a backhaul network is provided. The network node comprises a Mobile Terminated Unit, MT, and a Distributed Unit, DU, and the method comprises adjusting a first transmission timing to align with a second transmission timing, the first transmission timing comprising one of a DU and an MT transmission timing at the network node and the second transmission timing comprising another one of the DU and the MT transmission timing at the network node; and transmitting a signaling according to the adjustment of the first transmission timing.

In some embodiments of this aspect, the method further includes performing, by the MT comprised in the network node, an MT transmission to the parent network node; and transmitting the signaling comprises transmitting, by the DU comprised in the network node, a DU transmission to one of a child network node and a wireless device (WD), the MT and DU transmissions at the network node being timing aligned according to the adjustment of the first transmission timing. In some embodiments of this aspect, the first and second transmissions are one of frequency-division multiplexed and spatial-division multiplexed. In some embodiments of this aspect, the adjustment of the first transmission timing comprises an adjustment of the DU transmission timing to align with the MT transmission timing.

In some embodiments of this aspect, the adjustment of the DU transmission timing to align with the MT transmission timing is based at least in part on a timing window. In some embodiments of this aspect, the method further comprises receiving a command comprising the timing window from one of the parent network node, a centralized unit, CU, and an operations, administration, and maintenance, OAM, function. In some embodiments of this aspect, the timing window indicates an amount of deviation allowed for the DU transmission timing relative to an ideal timing alignment of the DU transmission timing to the MT transmission timing. In some embodiments of this aspect, the timing window is one of symmetric and asymmetric about the ideal timing alignment. In some embodiments of this aspect, the timing window is based at least in part on an output power associated with the DU.

In some embodiments of this aspect, the method further includes transmitting an indication of the output power associated with the DU to the parent network node and receiving a command comprising the timing window based on the transmitted indication of the output power. In some embodiments of this aspect, the method further includes receiving a broadcast comprising a plurality of timing windows associated with a plurality of output power values. In some embodiments of this aspect, the method further includes receiving a command comprising a reference window for a reference output power and deriving the timing window from the reference window, the reference output power and an actual output power associated with the DU.

In some embodiments of this aspect, the adjustment of the first transmission timing comprises an adjustment of an MT transmission timing to align with a DU transmission timing is based at least in part on two different types of MT transmission timings, a first type of MT transmission timing following a timing control command from the parent network node and a second type of MT transmission timing aligning to the DU transmission timing at the network node. In some embodiments of this aspect, the first type of MT transmission timing following the timing control command is not aligned to the DU transmission timing at the network node. In some embodiments of this aspect, the first type of MT transmission timing is based at least in part on a relation between the first and second types of MT transmission timings.

In some embodiments of this aspect, the relation is one of derived by and signaled to the parent network node. In some embodiments of this aspect, the adjustment of the MT transmission timing to align with the DU transmission timing is based at least in part on a timing window. In some embodiments of this aspect, the method further includes receiving a command comprising the timing window from one of the parent network nodes, a centralized unit, CU, and an operations, administration, and maintenance, OAM, function. In some embodiments of this aspect, the timing window indicates an amount of deviation allowed for the second type of MT transmission timing relative to the first type of MT transmission timing. In some embodiments of this aspect, the timing window is one of symmetric and asymmetric about the first type of MT transmission timing.

In some embodiments of this aspect, the adjustment of the first transmission timing comprises an adjustment of an MT transmission timing to align with a DU transmission timing following a timing control command from the parent network node. In some embodiments of this aspect, the adjustment of the MT transmission timing following the timing control command is aligned to the DU transmission timing at the network node. In some embodiments of this aspect, the method further includes signaling information about one of a requested adjustment of the MT transmission timing and an estimated propagation time to the parent network node, the timing control command being based at least in part on the signaled information. In some embodiments of this aspect, the method further includes determining a timing offset between the MT and DU transmission timings based at least in part on a timing misalignment of at least one other network node.

In some embodiments of this aspect, a method implemented in a network node configured to communicate with a child network node over a backhaul network is provided. The method comprises transmitting a signaling related to a timing alignment; and receiving a Mobile Terminated Unit, MT, transmission based at least in part on an adjustment of a first transmission timing to align with a second transmission timing, the first transmission timing comprising one of a Distributed Unit, DU, and an MT transmission timing at the child network node and the second transmission timing comprising another one of the DU and the MT transmission timing at the child network node.

In some embodiments of this aspect, the MT transmission received from the child network node is one of frequency-division multiplexed and spatial-division multiplexed with a DU transmission at the child network node. In some embodiments of this aspect, the adjustment of the first transmission timing comprises an adjustment of the DU transmission timing to align with the MT transmission timing. In some embodiments of this aspect, the adjustment of the DU transmission timing to align with the MT transmission timing is based at least in part on a timing window. In some embodiments of this aspect, transmitting the signaling comprises transmitting a command comprising the timing window. In some embodiments of this aspect, the timing window indicates an amount of deviation allowed for the DU transmission timing relative to an ideal timing alignment of the DU transmission timing to the MT transmission timing.

In some embodiments of this aspect, the timing window is one of symmetric and asymmetric about the ideal timing alignment. In some embodiments of this aspect, the timing window is based at least in part on an output power associated with the DU comprised in the child network node. In some embodiments of this aspect, the method further includes receiving an indication of the output power associated with the DU comprised in the child network node; and wherein transmitting the signaling comprises transmitting a command comprising the timing window based on the received indication of the output power. In some embodiments of this aspect, transmitting the signaling comprises transmitting a broadcast comprising a plurality of timing windows associated with a plurality of output power values. In some embodiments of this aspect, transmitting the signaling comprises transmitting a command comprising a reference window for a reference output power, the timing window being derived at the child network node from the reference window, the reference output power and an actual output power associated with the DU comprised in the child network node.

In some embodiments of this aspect, the adjustment of the first transmission timing comprises an adjustment of an MT transmission timing to align with a DU transmission timing based at least in part on two different types of MT transmission timings, a first type of MT transmission timing following a timing control command from the network node and a second type of MT transmission timing aligning to the DU transmission timing at the child network node. In some embodiments of this aspect, the first type of MT transmission timing following the timing control command is not aligned to the DU transmission timing at the child network node. In some embodiments of this aspect, the first type of MT transmission timing is based at least in part on a relation between the first and second types of MT transmission timings.

In some embodiments of this aspect, the relation is one of derived by the network node and received from the child network node. In some embodiments of this aspect, the adjustment of the MT transmission timing to align with the DU transmission timing is based at least in part on a timing window. In some embodiments of this aspect, transmitting the signaling comprises transmitting a command comprising the timing window. In some embodiments of this aspect, the timing window indicates an amount of deviation allowed for the second type of MT transmission timing relative to the first type of MT transmission timing. In some embodiments of this aspect, the timing window is one of symmetric and asymmetric about the first type of MT transmission timing. In some embodiments of this aspect, transmitting the signaling comprises transmitting a timing control command to the child network node, the adjustment of the first transmission timing comprises an adjustment of an MT transmission timing to align with a DU transmission timing following the timing control command.

In some embodiments of this aspect, the adjustment of the MT transmission timing following the timing control command is aligned to the DU transmission timing at the child network node. In some embodiments of this aspect, the method further comprises receiving information about one of a requested adjustment of the MT transmission timing and an estimated propagation time from the child network node, the transmitted timing control command being based at least in part on the received information. In some embodiments of this aspect, the method further includes determining a timing offset between the MT and DU transmission timings based at least in part on a timing misalignment of at least one other network node.

According to yet another aspect, a network node comprising a memory and a processor, the memory comprising instructions and the processor configured to execute the instructions to perform any one or more of the methods above.

DETAILED DESCRIPTION

With the timing assumptions, an example of which is shown inFIG.2, the transmit timing of the MT and DU of an IAB node are not mutually aligned. For the first release of 3GPP New Radio (NR) (also called 5thGeneration or 5G), the assumption has been that, at least in the typical case, the DU and MT transmissions of an IAB node are time multiplexed, which may make it less important for full alignment of the DU and MT transmissions (e.g., the mis-alignment between the DU and MT transmissions may be handle by guard symbols that are anyway used to provide time for switching between the DU and MT).

However, scenarios with simultaneous MT and DU transmission within a carrier are also contemplated. There are, in that case, two alternatives for the DU/MT multiplexing:Frequency-division multiplexing (FDM), that is, simultaneous DU and MT transmissions that are separated in the frequency domain, for example, by transmission within different resources blocks within a carrier; andSpatial-division multiplexing, (SDM), that is, simultaneous DU and MT transmissions that are separated in the spatial domain, for example, by transmitting within different beams or from different antenna panels pointing in different directions, within the same IAB node.

Both these arrangements of multiplexing DU and MT transmissions may be considered by a 3GPP Release-17 (Rel-17) work item on enhanced IAB.

Simultaneous DU and MT transmission is, implementation-wise, simplified if the DU and MT transmission timings are mutually aligned as illustrated inFIG.3, for example. However, as outlined above, this is typically not the case for IAB node DU and MT transmissions based on the Release 16 timing specifications.

Thus, there is a desire for new solutions that enable an IAB node to align the timing of its DU and MT transmissions. Such solutions may, at the same time, take into account, for example, the possible desire to:Align, at least to some extent, DU transmissions between cells within a certain window; and/orAlign the reception, at a parent node, of different MT and WD transmissions within a certain window.

Some embodiments of the present disclosure may provide for one or more of the following three approaches for aligning the DU and MT transmission timings:

Approach 1: The MT transmission timing of the IAB node is controlled by the parent node as for current 3GPP Release 16, including not taking into account any specific desire to align the MT and DU transmission timings. The IAB node may then autonomously align the DU transmission timing to the MT transmission timing, seeFIG.4, for example. Arrangements may be taken so that the DU transmission timing does not deviate too much from, for example, the downlink transmission timing of other cells (including the DU transmission timing of its own parent). This may be addressed by embodiment 1, described in more detail below.

Approach 2: The DU transmission timing of the IAB node is, in one way or another, kept aligned with the parent DU TX timing, as for current (3GPP Release 16) OTA DU timing assumptions. The IAB node may then align the MT transmission timing to the DU transmission timing, an example of which is shown inFIG.5. This implies that the parent IAB node does no longer have control of the MT transmission timing with possible mis-alignment in the parent-node reception timing of different MT and WD transmissions. This may be addressed by embodiment 2, described in more detail below.

Approach 3: The MT transmission timing is controlled by the parent IAB node as for current 3GPP Release 16, but taking into account, directly or indirectly, any desire to align the IAB node MT and DU transmission timing. This may be addressed by embodiment 3, described in more detail below.

Some embodiments of the present disclosure may advantageously provide tools for aligning the DU and MT transmission timings of an IAB node, thereby enabling more efficient FDM and/or SDM between the DU and MT transmissions. The transmission alignment is such that the impact on network operation, as well as, reception at parent nodes may be within acceptable limits.

The term “signaling” used herein may comprise any of: high-layer signaling (e.g., via Radio Resource Control (RRC) or a like), lower-layer signaling (e.g., via a physical control channel or a broadcast channel), or a combination thereof. The signaling may be implicit or explicit. The signaling may further be unicast, multicast or broadcast. The signaling may also be directly to another node or via a third node.

Signaling may generally comprise one or more symbols and/or signals and/or messages. A signal may comprise or represent one or more bits. An indication may represent signaling, and/or be implemented as a signal, or as a plurality of signals. One or more signals may be included in and/or represented by a message. Signaling, in particular control signaling, may comprise a plurality of signals and/or messages, which may be transmitted on different carriers and/or be associated to different signaling processes, e.g. representing and/or pertaining to one or more such processes and/or corresponding information. An indication may comprise signaling, and/or a plurality of signals and/or messages and/or may be comprised therein, which may be transmitted on different carriers and/or be associated to different acknowledgement signaling processes, e.g. representing and/or pertaining to one or more such processes. Signaling associated to a channel may be transmitted such that represents signaling and/or information for that channel, and/or that the signaling is interpreted by the transmitter and/or receiver to belong to that channel. Such signaling may generally comply with transmission parameters and/or format/s for the channel.

An indication (e.g., an indication of a timing window, etc.) generally may explicitly and/or implicitly indicate the information it represents and/or indicates. Implicit indication may for example be based on position and/or resource used for transmission. Explicit indication may for example be based on a parametrization with one or more parameters, and/or one or more index or indices corresponding to a table, and/or one or more bit patterns representing the information.

The term “radio measurement” used herein may refer to any measurement performed on radio signals. Radio measurements can be absolute or relative. Radio measurement may be called as signal level which may be signal quality and/or signal strength. Radio measurements can be e.g. intra-frequency, inter-frequency, inter-RAT measurements, CA measurements, etc. Radio measurements can be unidirectional (e.g., DL or UL) or bidirectional (e.g., Round Trip Time (RTT), Receive-Transmit (Rx-Tx), etc.). Some examples of radio measurements: timing measurements (e.g., Time of Arrival (TOA), timing advance, RTT, Reference Signal Time Difference (RSTD), Rx-Tx, propagation delay, etc.), angle measurements (e.g., angle of arrival), power-based measurements (e.g., received signal power, Reference Signals Received Power (RSRP), received signal quality, Reference Signals Received Quality (RSRQ), Signal-to-interference-plus-noise Ratio (SINR), Signal Noise Ratio (SNR), interference power, total interference plus noise, Received Signal Strength Indicator (RSSI), noise power, etc.), cell detection or cell identification, radio link monitoring (RLM), system information (SI) reading, etc. The inter-frequency and inter-RAT measurements are carried out by the WD in measurement gaps unless the WD is capable of doing such measurement without gaps. Examples of measurement gaps are measurement gap id #0(each gap of 6 ms occurring every 40 ms), measurement gap id #1(each gap of 6 ms occurring every 80 ms), etc. The measurement gaps are configured at the WD by the network node.

A cell may be generally a communication cell, e.g., of a cellular or mobile communication network, provided by a node. A serving cell may be a cell on or via which a network node (the node providing or associated to the cell, e.g., base station or gNodeB) transmits and/or may transmit data (which may be data other than broadcast data) to a user equipment, in particular control and/or user or payload data, and/or via or on which a user equipment transmits and/or may transmit data to the node; a serving cell may be a cell for or on which the user equipment is configured and/or to which it is synchronized and/or has performed an access procedure, e.g., a random access procedure, and/or in relation to which it is in a RRC_connected or RRC_idle state. e.g., in case the node and/or user equipment and/or network follow the NR-standard. One or more carriers (e.g., uplink and/or downlink carrier/s and/or a carrier for both uplink and downlink) may be associated to a cell.

The term “node” is used herein and may indicate an IAB node. In some embodiments, the terms “child” and “descendent” are used interchangeably. The shortened terms “parent”, “child” and “donor” may be used to indicate a parent IAB node, a child IAB node and an IAB donor node, respectively.

Some embodiments provide for arrangements for aligning Distributed Unit/Mobile Termination (DU/MT) transmission timing.

In some embodiments, a network node16is configured to include an adjustment unit32which is configured to optionally, receive a command related to timing alignment from a parent node; and adjust a Distributed Unit (DU) transmission timing to align with at least one Mobile Terminated Unit (MT) transmission timing based at least in part on the command.

In some embodiments, a network node16is configured to include an alignment unit34which is configured to send a command related to timing alignment to a child node; and receive a transmission based at least in part on a timing, the timing being adjusted to align the child node's Distributed Unit (DU) transmission timing with at least one Mobile Terminated Unit (MT) transmission timing based at least in part on the command.

Thus, the network node16further has software74stored internally in, for example, memory72, or stored in external memory (e.g., database, storage array, network storage device, etc.) accessible by the network node16via an external connection. The software74may be executable by the processing circuitry68. The processing circuitry68may be configured to control any of the methods and/or processes described herein and/or to cause such methods, and/or processes to be performed, e.g., by network node16. Processor70corresponds to one or more processors70for performing network node16functions described herein. The memory72is configured to store data, programmatic software code and/or other information described herein. In some embodiments, the software74may include instructions that, when executed by the processor70and/or processing circuitry68, causes the processor70and/or processing circuitry68to perform the processes described herein with respect to network node16. For example, processing circuitry68of the network node16may include adjustment unit32and/or alignment unit34configured to perform network node methods discussed herein, such as the methods discussed with reference toFIGS.12,13,14,15as well as, other figures.

The communication system10further includes the WD22already referred to. The WD22may have hardware80that may include a radio interface82configured to set up and maintain a wireless connection64with a network node16serving a coverage area18in which the WD22is currently located. The radio interface82may be formed as or may include, for example, one or more RF transmitters, one or more RF receivers, and/or one or more RF transceivers.

The processing circuitry84may be configured to control any of the methods and/or processes described herein and/or to cause such methods, and/or processes to be performed, e.g., by WD22. The processor86corresponds to one or more processors86for performing WD22functions described herein. The WD22includes memory88that is configured to store data, programmatic software code and/or other information described herein. In some embodiments, the software90and/or the client application92may include instructions that, when executed by the processor86and/or processing circuitry84, causes the processor86and/or processing circuitry84to perform the processes described herein with respect to WD22.

In some embodiments, the inner workings of the network node16, WD22, and host computer24may be as shown inFIG.7and independently, the surrounding network topology may be that ofFIG.6.

In some embodiments, the host computer24includes processing circuitry42and a communication interface40that is configured to a communication interface40configured to receive user data originating from a transmission from a WD22to a network node16. In some embodiments, the WD22is configured to, and/or comprises a radio interface82and/or processing circuitry84configured to perform the functions and/or methods described herein for preparing/initiating/maintaining/supporting/ending a transmission to the network node16, and/or preparing/terminating/maintaining/supporting/ending in receipt of a transmission from the network node16.

AlthoughFIGS.6and7show various “units” such as adjustment unit32, and alignment unit34as being within a respective processor, it is contemplated that these units may be implemented such that a portion of the unit is stored in a corresponding memory within the processing circuitry. In other words, the units may be implemented in hardware or in a combination of hardware and software within the processing circuitry. In addition, such units, e.g., mobile terminated unit and distributed unit in a respective IAB network node may be associated with one or more corresponding radio interfaces for the transmission and reception described herein.

FIG.12is a flowchart of an exemplary process in a network node16(e.g., network node16a, child IAB node) according to some embodiments of the present disclosure. One or more Blocks and/or functions and/or methods performed by the network node16may be performed by one or more elements of network node16such as by adjustment unit32in processing circuitry68, processor70, radio interface62, etc. according to the example method. The example method includes optionally, receiving (Block S134), such as via adjustment unit32, processing circuitry68, processor70, communication interface60and/or radio interface62, a command related to timing alignment from a parent node. The method includes adjusting (Block S136), such as via adjustment unit32, processing circuitry68, processor70, communication interface60and/or radio interface62, a Distributed Unit (DU) transmission timing to align with at least one Mobile Terminated Unit (MT) transmission timing based at least in part on the received command.

In some embodiments, the command indicates a timing window. In some embodiments, the timing window is based at least in part on an output power associated with the DU. In some embodiments, the adjusting the DU transmission timing to align with the at least one MT transmission timing further includes adjusting, such as via adjustment unit32, processing circuitry68, processor70, communication interface60and/or radio interface62, the DU transmission timing based on two different types of MT transmissions, a first type following a timing control command from the parent node and a second type being aligned with the DU transmission timing. In some embodiments, the method further includes signaling, such as via adjustment unit32, processing circuitry68, processor70, communication interface60and/or radio interface62, a requested adjustment of the MT transmission timing to the parent node; and/or determining, such as via adjustment unit32, processing circuitry68, processor70, communication interface60and/or radio interface62, a timing offset based at least in part on a timing misalignment of at least one other node.

FIG.13is a flowchart of an exemplary process in a network node16(e.g., network node16b, parent IAB node) according to some embodiments of the present disclosure. One or more Blocks and/or functions and/or methods performed by the network node16may be performed by one or more elements of network node16such as by alignment unit34in processing circuitry68, processor70, communication interface60, radio interface62, etc. according to the example method. The example method includes sending (Block S138), such as via alignment unit34, processing circuitry68, processor70, communication interface60and/or radio interface62, a command related to timing alignment to a child node. The method includes receiving (Block S140), such as via alignment unit34, processing circuitry68, processor70, communication interface60and/or radio interface62, a transmission based at least in part on a timing, the timing being adjusted to align the child node's Distributed Unit (DU) transmission timing with at least one Mobile Terminated Unit (MT) transmission timing based at least in part on the command.

In some embodiments, the command indicates a timing window. In some embodiments, the timing window is based at least in part on an output power associated with the DU. In some embodiments, the timing is adjusted to align the child node's DU transmission timing based on two different types of MT transmissions, a first type following a timing control command from the network node and a second type being aligned with the DU transmission timing. In some embodiments, the method further includes receiving, such as via alignment unit34, processing circuitry68, processor70, communication interface60and/or radio interface62, a requested adjustment of the MT transmission timing from the child node. In some embodiments, the method includes determining, such as via alignment unit34, processing circuitry68, processor70, communication interface60and/or radio interface62, a timing offset based at least in part on a timing misalignment of at least one other node.

FIG.14is a flowchart of an exemplary process in a network node16(e.g., network node16a, child IAB node) according to some embodiments of the present disclosure. One or more Blocks and/or functions and/or methods performed by the network node16may be performed by one or more elements of network node16such as by adjustment unit32in processing circuitry68, processor70, communication interface60, radio interface62, etc. according to the example method. The example method is implemented in a network node16configured to communicate with a parent network node16over a backhaul network. The network node16comprises a Mobile Terminated Unit, MT, and a Distributed Unit, DU. The method comprises adjusting (Block S142), such as by adjustment unit32in processing circuitry68, processor70, communication interface60and/or radio interface62, a first transmission timing to align with a second transmission timing, the first transmission timing comprising one of a DU and an MT transmission timing at the network node and the second transmission timing comprising another one of the DU and the MT transmission timing at the network node. The method includes transmitting (Block S144), such as by adjustment unit32in processing circuitry68, processor70, communication interface60and/or radio interface62, a signaling according to the adjustment of the first transmission timing.

In some embodiments, the method further includes performing, such as by adjustment unit32in processing circuitry68, processor70, communication interface60and/or radio interface62, by the MT comprised in the network node16, an MT transmission to the parent network node. In some embodiments, transmitting the signaling comprises transmitting, by the DU comprised in the network node, such as by adjustment unit32in processing circuitry68, processor70, communication interface60and/or radio interface62, a DU transmission to one of a child network node and a user equipment, UE, the MT and DU transmissions at the network node being timing aligned according to the adjustment of the first transmission timing.

In some embodiments, the first and second transmissions are one of frequency-division multiplexed and spatial-division multiplexed. In some embodiments, the adjustment of the first transmission timing comprises an adjustment of the DU transmission timing to align with the MT transmission timing. In some embodiments, the adjustment of the DU transmission timing to align with the MT transmission timing is based at least in part on a timing window. In some embodiments, the method further includes receiving, such as by adjustment unit32in processing circuitry68, processor70, communication interface60and/or radio interface62, a command comprising the timing window from one of the parent network node, a centralized unit, CU, and an operations, administration, and maintenance, OAM, function.

In some embodiments, the timing window indicates an amount of deviation allowed for the DU transmission timing relative to an ideal timing alignment of the DU transmission timing to the MT transmission timing. In some embodiments, the timing window is one of symmetric and asymmetric about the ideal timing alignment. In some embodiments, the timing window is based at least in part on an output power associated with the DU. In some embodiments, the method further includes transmitting, such as by adjustment unit32in processing circuitry68, processor70, communication interface60and/or radio interface62, an indication of the output power associated with the DU to the parent network node and receiving a command comprising the timing window based on the transmitted indication of the output power.

In some embodiments, the method further includes receiving, such as by adjustment unit32in processing circuitry68, processor70, communication interface60and/or radio interface62, a broadcast comprising a plurality of timing windows associated with a plurality of output power values. In some embodiments, the method further includes receiving, such as by adjustment unit32in processing circuitry68, processor70, communication interface60and/or radio interface62, a command comprising a reference window for a reference output power and deriving the timing window from the reference window, the reference output power and an actual output power associated with the DU. In some embodiments, the adjustment of the first transmission timing comprises an adjustment of an MT transmission timing to align with a DU transmission timing is based at least in part on two different types of MT transmission timings, a first type of MT transmission timing following a timing control command from the parent network node and a second type of MT transmission timing aligning to the DU transmission timing at the network node.

In some embodiments, the first type of MT transmission timing following the timing control command is not aligned to the DU transmission timing at the network node. In some embodiments, the first type of MT transmission timing is based at least in part on a relation between the first and second types of MT transmission timings. In some embodiments, the relation is one of derived by and signaled to the parent network node. In some embodiments, the adjustment of the MT transmission timing to align with the DU transmission timing is based at least in part on a timing window. In some embodiments, the method further includes receiving, such as by adjustment unit32in processing circuitry68, processor70, communication interface60and/or radio interface62, a command comprising the timing window from one of the parent network node, a centralized unit, CU, and an operations, administration, and maintenance, OAM, function.

In some embodiments, the timing window indicates an amount of deviation allowed for the second type of MT transmission timing relative to the first type of MT transmission timing. In some embodiments, the timing window is one of symmetric and asymmetric about the first type of MT transmission timing. In some embodiments, the adjustment of the first transmission timing comprises an adjustment of an MT transmission timing to align with a DU transmission timing following a timing control command from the parent network node. In some embodiments, the adjustment of the MT transmission timing following the timing control command is aligned to the DU transmission timing at the network node. In some embodiments, the method further includes signaling information about one of a requested adjustment of the MT transmission timing and an estimated propagation time to the parent network node, the timing control command being based at least in part on the signaled information. In some embodiments, the method further includes determining, such as by adjustment unit32in processing circuitry68, processor70, communication interface60and/or radio interface62, a timing offset between the MT and DU transmission timings based at least in part on a timing misalignment of at least one other network node.

FIG.15is a flowchart of an exemplary process in a network node16(e.g., network node16b, parent IAB node) according to some embodiments of the present disclosure. One or more Blocks and/or functions and/or methods performed by the network node16may be performed by one or more elements of network node16such as by alignment unit34in processing circuitry68, processor70, communication interface60, radio interface62, etc. according to the example method. The example method is implemented in a network node configured to communicate with a child network node over a backhaul network. The method comprises transmitting (Block S146), such as by alignment unit34in processing circuitry68, processor70, communication interface60and/or radio interface62, a signaling related to a timing alignment. The method includes receiving (Block S148), such as by alignment unit34in processing circuitry68, processor70, communication interface60, radio interface62, a Mobile Terminated Unit, MT, transmission based at least in part on an adjustment of a first transmission timing to align with a second transmission timing, the first transmission timing comprising one of a Distributed Unit, DU, and an MT transmission timing at the child network node and the second transmission timing comprising another one of the DU and the MT transmission timing at the child network node.

In some embodiments, the MT transmission received from the child network node is one of frequency-division multiplexed and spatial-division multiplexed with a DU transmission at the child network node. In some embodiments, the adjustment of the first transmission timing comprises an adjustment of the DU transmission timing to align with the MT transmission timing. In some embodiments, the adjustment of the DU transmission timing to align with the MT transmission timing is based at least in part on a timing window. In some embodiments, transmitting the signaling comprises transmitting such as by alignment unit34in processing circuitry68, processor70, communication interface60, radio interface62, a command comprising the timing window. In some embodiments, the timing window indicates an amount of deviation allowed for the DU transmission timing relative to an ideal timing alignment of the DU transmission timing to the MT transmission timing.

In some embodiments, the timing window is one of symmetric and asymmetric about the ideal timing alignment. In some embodiments, the timing window is based at least in part on an output power associated with the DU comprised in the child network node. In some embodiments, the method further includes receiving such as by alignment unit34in processing circuitry68, processor70, communication interface60, radio interface62, an indication of the output power associated with the DU comprised in the child network node; and wherein transmitting the signaling comprises transmitting a command comprising the timing window based on the received indication of the output power. In some embodiments, transmitting the signaling comprises transmitting such as by alignment unit34in processing circuitry68, processor70, communication interface60, radio interface62, a broadcast comprising a plurality of timing windows associated with a plurality of output power values.

In some embodiments, transmitting the signaling comprises transmitting such as by alignment unit34in processing circuitry68, processor70, communication interface60, radio interface62, a command comprising a reference window for a reference output power, the timing window being derived at the child network node from the reference window, the reference output power and an actual output power associated with the DU comprised in the child network node. In some embodiments, the adjustment of the first transmission timing comprises an adjustment of an MT transmission timing to align with a DU transmission timing based at least in part on two different types of MT transmission timings, a first type of MT transmission timing following a timing control command from the network node and a second type of MT transmission timing aligning to the DU transmission timing at the child network node. In some embodiments, the first type of MT transmission timing following the timing control command is not aligned to the DU transmission timing at the child network node.

In some embodiments, the first type of MT transmission timing is based at least in part on a relation between the first and second types of MT transmission timings. In some embodiments, the relation is one of derived by the network node and received from the child network node. In some embodiments, the adjustment of the MT transmission timing to align with the DU transmission timing is based at least in part on a timing window. In some embodiments, transmitting the signaling comprises transmitting such as by alignment unit34in processing circuitry68, processor70, communication interface60, radio interface62, a command comprising the timing window. In some embodiments, the timing window indicates an amount of deviation allowed for the second type of MT transmission timing relative to the first type of MT transmission timing.

In some embodiments, the timing window is one of symmetric and asymmetric about the first type of MT transmission timing. In some embodiments, transmitting the signaling comprises transmitting such as by alignment unit34in processing circuitry68, processor70, communication interface60, radio interface62, a timing control command to the child network node, the adjustment of the first transmission timing comprises an adjustment of an MT transmission timing to align with a DU transmission timing following the timing control command. In some embodiments, the adjustment of the MT transmission timing following the timing control command is aligned to the DU transmission timing at the child network node. In some embodiments, the method further includes receiving, such as by alignment unit34in processing circuitry68, processor70, communication interface60, radio interface62, information about one of a requested adjustment of the MT transmission timing and an estimated propagation time from the child network node, the transmitted timing control command being based at least in part on the received information. In some embodiments, the method further includes determining, such as by alignment unit34in processing circuitry68, processor70, communication interface60, radio interface62, a timing offset between the MT and DU transmission timings based at least in part on a timing misalignment of at least one other network node.

Having described the general process flow of arrangements of the disclosure and having provided examples of hardware and software arrangements for implementing the processes and functions of the disclosure, the sections below provide details and examples of arrangements for aligning Distributed Unit/Mobile Termination (DU/MT) transmission timing, which may be implemented by the network node16, wireless device22and/or host computer24.

In some aspects, embodiment 1 may be related to approach 1 discussed above. That is, the IAB node (e.g., network node16a) may adjust the DU timing to align the DU timing with the MT transmission timing, where the MT transmission timing may be controlled by timing alignment commands from the parent IAB node (e.g., network node16b). For the network to still be able to have a certain control of the DU transmission timing, for example, to ensure that the DU transmission timing does not deviate too much from the parent IAB node DU transmission timing, some embodiments provide that the IAB node (e.g., network node16a) is provided with a timing window (e.g., by parent IAB node, pre-configured/predetermined by a standard). The timing window may indicate how much the IAB node can deviate from a predetermined timing, such as an “ideal timing.” Reference is made toFIG.16which illustrates an example of embodiment 1 with a timing window indicating how much the DU transmitter (TX) timing can deviate from a predetermining timing e.g., an ideal DU TX timing. The ideal and/or predetermined timing could, for example, be the DU transmission timing according to current 3GPP Release 16.

In some embodiments, the timing window may be asymmetric, which may imply that the DU transmission timing can deviate from e.g., −Δ1to Δ2from the ideal and/or predetermined timing, seeFIG.16for example. In this case, the window is thus given by two parameters Δ1and Δ2.

Alternatively, in some embodiments, the timing window may be symmetric, which may imply that the DU transmission timing can deviate a time ±Δ from the ideal and/or predetermined timing. In this case, the timing window is thus given by a single parameter Δ. This case may correspond toFIG.16where Δ1=Δ2=Δ.

Thus, the IAB node (e.g., network node16a) can fully align DU transmitter (TX) timing to the MT TX timing only if the DU TX timing would still fall within the provided timing window. Also, in some embodiments, if the parent IAB node (e.g., network node16b) decides, it can set the window to a very small size around the ideal DU transmission timing, thereby restricting the DU transmission timing to the current 3GPP Release 16 DU transmission timing.

In some embodiments, the timing window may be provided to the IAB node (e.g., network node16a) by dedicated signaling provided by/via the parent IAB node (e.g., network node16b) when the IAB node MT has connected to the network. Alternatively, in some embodiments, the timing window may be provided by broadcasting IAB-related system information provided by the parent IAB node (e.g., network node16b). Information about the timing window may also be provided by the IAB node's (e.g., network node16a) CU and/or other centralized or distributed functions, such as Operations and Maintenance (OAM).

In some embodiments, the timing window may depend on a maximum output power of the IAB node DU, where the output power could be the specified maximum output power of the IAB node (e.g., network node16a). Alternatively, in some embodiments, the output power used to determine the timing window may be lower than the specified maximum output power of the IAB node (e.g., network node16a). In some embodiments, the lower output power may be determined on by the IAB node (e.g., network node16a) itself. Alternatively, the lower output power may be signaled to the IAB node (e.g., network node16a).

In some embodiments, a size of the timing window may, for example, be larger in case of lower output power of the IAB node DU (e.g., network node16a). In case of broadcast of the timing window, this may imply the broadcast of multiple timing windows, where each timing window may be associated with a certain IAB node DU transmit power or a range of IAB-node DU transmit powers. The same could be used in case of dedicated signaling. Alternatively, in the case of dedicated signaling, the IAB node (e.g., network node16a) may provide its DU output power to the network and the network then provides a single timing window, where the timing window that is provided may depend on the DU transmit power provided by the IAB node (e.g., network node16a).

In some embodiments, an IAB node (e.g., network node16a) may also be provided information of a reference window for a reference output power. In this case, the effective window may be derived, e.g., by network node16a, from the reference window and output power by a node-internal function applying a mathematical operation on these parameters, such as linear interpolation to the actual output power.

In some aspects, embodiment 2 is related to approach 2 described above. That is, the MT timing is adjusted, e.g., by network node16ato align with the DU transmission timing.

In some aspects of embodiment 2, the IAB node (e.g., network node16a) carries out two different types of MT transmissions, herein referred to as MT transmission type-1 and MT transmission type-2, respectively, an example of which is shown inFIG.17.

In some embodiments, MT transmissions of type-1 follow timing control commands by the parent IAB node (e.g., network node16b) as for current NR specifications. MT transmissions of type-1 may thus typically not be aligned with the IAB node DU transmissions. The MT transmissions of type-1 may occur with a low duty cycle and may, as one example, include transmission for measurement purposes, such as SRS (Sounding Reference Signals) as defined for current NR.

In some embodiments, MT transmissions of type-2 are not aligned with MT transmissions of type-1. Instead, the IAB node (e.g., network node16a) may, for example, align the timing of MT transmissions of type-2, with the timing of its DU transmissions as illustrated inFIG.17for example. The MT transmissions of type-2 may constitute a main part of the MT transmissions.

In some embodiments, in order for the parent IAB node (e.g., network node16b) to be able to provide the IAB node (e.g., network node16a) with time-alignment commands for type-1 transmission, measurements of the reception timing at the parent IAB node (e.g., network node16b) may preferably be carried out on MT transmissions of type-1. If the parent IAB node (e.g., network node16b) has information about the intended relation, e.g. difference, of type-1 and type-2 transmission timing of the IAB node, the parent IAB node's (e.g., network node16b) determination of time-alignment commands for type-1 transmission can be assisted by measurements of the reception timing of type-2 transmissions, if adjusted by the assumed type-1 and type-2 transmission timing relation. This information about the relation of type-1 and type-2 transmission can be derived by the parent IAB node (e.g., network node16b) (e.g. by knowing that MT transmissions of type-2 are time aligned with the IAB node DU transmissions, which may be time aligned with parent DU transmission), or by the IAB node (e.g., network node16a) signaling this information to the parent IAB node (e.g., network node16b).

In order to ensure that MT transmissions of type-2 are not received with too much timing mis-alignment at the parent IAB node (e.g., network node16b), relative to other signals received by the parent IAB node (e.g., network node16b), the IAB node (e.g., network node16a) can be provided with a timing window that indicates how much the transmission timing of MT transmissions of type-2 is allowed to deviate from the parent-controlled transmission timing of MT transmissions of type-1, an example of which can be seen inFIG.18.The timing window can be asymmetric, implying that timing of MT transmission type-2 can deviate from −Δ1to Δ2relative to MT transmissions type-1, seeFIG.18. In this case, the timing window is thus given by two, different parameters Δ1and Δ2.Alternatively, the timing window can be a symmetric, implying that the timing of MT transmission type-2 can deviate a time ±Δ from the timing of MT transmissions type-1. In this case, the timing window is thus given by a single parameter Δ. This case corresponds toFIG.18, where Δ1=Δ2=A.

In some embodiments, the timing window may either be provided to the IAB node (e.g., network node16a) by dedicated signaling provided by/via the parent IAB node (e.g., network node16b) when the IAB node MT has connected to the network. Alternatively, the timing window could be provided by broadcast IAB-related system information. Information about the timing window can also be provided by the parent IAB node's CU and/or other centralized or distributed functions, such as OAM.

In some embodiments, MT transmissions type-2 can for example be limited to a subset of the slots available for MT transmission.

In order for the parent IAB node (e.g., network node16b) to receive transmissions based on either type-1 or type-2 transmissions, the IAB node (e.g., network node16a) may further signal its determined actual difference between type-1 and type-2 transmission timings, Δactual, to the parent IAB node (e.g., network node16b).

In some aspects, embodiment 3 may be considered to be related to approach 3 above. In some embodiments, the parent IAB node (e.g., network node16b) adjusts its control of the IAB node MT transmission timing to assist the IAB node (e.g., network node16a) in aligning the timing of the DU transmission and MT transmission. This can be done by, for example, the IAB node (e.g., network node16a) signaling to the parent IAB node (e.g., network node16b) a requested adjustment of the MT transmission timing. Based on this, the parent IAB node (e.g., network node16b) adjusts its target received timing for the IAB node MT transmission, an example of which is shown inFIG.19. In some embodiments, the adjustment of the target received timing may be the same as the requested timing adjustment. Alternatively, the adjustment of the target received timing may be less than the requested timing adjustment.

Alternatively, or additionally, instead of signaling a requested timing adjustment, the IAB node (e.g., network node16a) may signal its estimated propagation time, based on which, the parent IAB node (e.g., network node16b) may conclude on an adjustment of the target received timing.

In some embodiments, if the MT transmission timing based on the parent IAB node (e.g., network node16b) adjusted timing control is not aligned, e.g., fully aligned with the DU transmission timing, the IAB node (e.g., network node16a) can adjust/finetune the DU transmission timing to align it with the adjusted MT transmission timing, in the same way as for embodiment 1 above. The benefit, compared to embodiment 1, may be that the adjustment of the DU transmission timing may be kept smaller.

Selection of DU/MT Time Alignment Among Multiple Nodes

In all or some of the embodiments described above, the IAB node DU/MT timing misalignment may be restricted. However, a preferred timing may be set to match the parent IAB node (e.g., network node16b). Alternatively, or additionally, the preferred timing, within the configured restrictions, may in some cases, e.g. embodiment 1, be determined based on multiple surrounding nodes. An argument for that is to make the IAB functionality transparent from the WD22perspective. Hence, to keep for example a DU TX timing within 3 μs also in relation to other network nodes or cells, the chosen timing misalignment may be chosen also taking into account other nodes. One alternative of this may be to use a weighted average of the timing misalignments among multiple surrounding cells to determine a preferred timing offset. In some embodiments, the weighting may in turn depend on received power from said cells, or an inter-site distance (ISD), if known. Another alternative may be to select the timing change such that as many as possible of the closest nodes to fall within the determined timing misalignment. In this sense, “closest” may be determined directly by knowledge of network node, e.g., gNB, locations, or indirectly from, e.g., reference signal received power (RSRP) measurements.

Some embodiments may include one or more of the following:

It is noted that the “nodes” referred to below may be IAB nodes.

Embodiment A1. A network node configured to communicate with at least one parent node over a backhaul network, the network node configured to, and/or comprising a radio interface and/or comprising processing circuitry configured to:optionally, receive a command related to timing alignment from a parent node; andadjust a Distributed Unit (DU) transmission timing to align with at least one Mobile Terminated Unit (MT) transmission timing based at least in part on the command.

Embodiment A2. The network node of Embodiment A1, wherein:the command indicates a timing window; and/orthe timing window is based at least in part on an output power associated with the DU.

Embodiment A3. The network node of any one of Embodiments A1 and A2, wherein the network node and/or the radio interface and/or the processing circuitry is configured to adjust the DU transmission timing to align with the at least one MT transmission timing by being further configured to:adjust the DU transmission timing based on two different types of MT transmissions, a first type following a timing control command from the parent node and a second type being aligned with the DU transmission timing.

Embodiment A4. The network node of any one of Embodiments A1-A3, wherein the network node and/or the radio interface and/or the processing circuitry is further configured to one or more ofsignal a requested adjustment of the MT transmission timing to the parent node; and/ordetermine a timing offset based at least in part on a timing misalignment of at least one other node.

Embodiment B1. A method implemented in a network node configured to communicate with at least one parent node over a backhaul network, the method comprising:optionally, receiving a command related to timing alignment from a parent node; andadjusting a Distributed Unit (DU) transmission timing to align with at least one Mobile Terminated Unit (MT) transmission timing based at least in part on the command.

Embodiment B2. The method of Embodiment B1, wherein:the command indicates a timing window; and/orthe timing window is based at least in part on an output power associated with the DU.

Embodiment B3. The method of any one of Embodiments B1 and B2, wherein the adjusting the DU transmission timing to align with the at least one MT transmission timing further comprises:adjusting the DU transmission timing based on two different types of MT transmissions, a first type following a timing control command from the parent node and a second type being aligned with the DU transmission timing.

Embodiment B4. The method of any one of Embodiments B1-B3, further comprising one or more of:signaling a requested adjustment of the MT transmission timing to the parent node; and/ordetermining a timing offset based at least in part on a timing misalignment of at least one other node.

Embodiment C1. A network node configured to communicate with at least one child node over a backhaul network, the network node configured to, and/or comprising a radio interface and/or comprising processing circuitry configured to:send a command related to timing alignment to a child node; andreceive a transmission based at least in part on a timing, the timing being adjusted to align the child node's Distributed Unit (DU) transmission timing with at least one Mobile Terminated Unit (MT) transmission timing based at least in part on the command.

Embodiment C2. The network node of Embodiment C1, wherein:the command indicates a timing window; and/orthe timing window is based at least in part on an output power associated with the DU.

Embodiment C3. The network node of any one of Embodiments C1 and C2, wherein the timing is adjusted to align the child node's DU transmission timing based on two different types of MT transmissions, a first type following a timing control command from the network node and a second type being aligned with the DU transmission timing.

Embodiment C4. The network node of any one of Embodiments C1-C3, wherein the network node and/or the radio interface and/or the processing circuitry is further configured to one or more ofreceive a requested adjustment of the MT transmission timing from the child node; and/ordetermine a timing offset based at least in part on a timing misalignment of at least one other node.

Embodiment D1. A method implemented in a network node configured to communicate with at least one child node over a backhaul network, the method comprising:sending a command related to timing alignment to a child node; andreceiving a transmission based at least in part on a timing, the timing being adjusted to align the child node's Distributed Unit (DU) transmission timing with at least one Mobile Terminated Unit (MT) transmission timing based at least in part on the command.

Embodiment D2. The method of Embodiment D1, wherein:the command indicates a timing window; and/orthe timing window is based at least in part on an output power associated with the DU.

Embodiment D3. The method of any one of Embodiments D1 and D2, wherein the timing is adjusted to align the child node's DU transmission timing based on two different types of MT transmissions, a first type following a timing control command from the network node and a second type being aligned with the DU transmission timing.

Embodiment D4. The method of any one of Embodiments D1-D3, further comprising one or more of:receiving a requested adjustment of the MT transmission timing from the child node; and/ordetermining a timing offset based at least in part on a timing misalignment of at least one other node.