Method and apparatus for hop-by-hop flow control

Abstract

The present disclosure relates to methods and apparatus. According to some embodiments according to the present disclosure, a method performed by a communication device comprises receiving, from a base station, first configuration information indicating a threshold value to configure the communication device, wherein the threshold value is associated with an amount of data; determining, based on the threshold value, whether congestion occurs at the communication device; and transmitting, to a first parent node, a congestion indication via a Backhaul Adaptation Protocol (BAP) signaling message when it is determined that the congestion occurs at the communication device.

Description

TECHNICAL FIELD

[0001] The present disclosure relates generally to wireless communication technology, and more particularly to hop-by-hop flow control in a wireless communication system. BACKGROUND

[0002] In the Third Generation Partnership Project (3GPP), the deployment of relay nodes (RNs) in wireless communication systems is promoted. One goal of deploying RNs is to improve the coverage area of a base station (BS, also referred to as a gNB in 5G networks) by improving the throughput of mobile devices (also referred to as user equipment (UE)) located in coverage holes or far away from the BS, which can result in relatively low signal quality.

[0003] In a wireless communication system employing RNs, a BS that can provide connectivity to at least one RN is referred to as a donor BS (or donor node or donor). A RN can connect to a donor BS via a backhaul link, can skip one or more RNs before reaching a donor BS, or can connect directly to a donor BS. For New Radio (NR) communication networks, 3GPP is envisioning an Integrated Access and Backhaul (IAB) architecture for supporting multi-hop relaying, where a donor node with multi-connectivity is also supported by an IAB node. That is, an IAB node can have multiple active routes to a donor BS via multiple parent IAB nodes. Multi-hop networks can provide more range expansion than single-hop networks. This is relatively more beneficial for wireless communications at frequencies higher than 6 GHz, which have limited range when using single-hop backhauling. Multi-hop backhauling further enables bypassing obstacles, such as buildings in urban environments for deployments in clusters.

[0004] In a wireless communication system, congestion or overload can occur at an intermediate IAB node, which can be accessed by child nodes (e.g., access IAB nodes or UEs). An intermediate IAB node can have more than one parent node or more than one child node. These factors can increase the difficulty of flow control. Therefore, there is a need for improved methods for flow control in a wireless communication system to support multi-hop backhauling and multi-connectivity. SUMMARY

[0005] Embodiments of the present disclosure provide a method of a communication device. The method can include receiving, from a base station, first configuration information indicating a threshold value to configure the communication device, wherein the threshold value is associated with an amount of data, determining whether congestion occurs at the communication device based on the threshold value, and transmitting, to a first parent node, a congestion indication via a backhaul adaptation protocol (BAP) signaling message when it is determined that the congestion occurs at the communication device.

[0006] In an embodiment of the present application, receiving the first configuration information can include receiving the first configuration information at a mobile termination (MT) of the communication device via a radio resource control (RRC) signaling message. In another embodiment of the present application, receiving the first configuration information can include receiving the first configuration information at a distributed unit (DU) of the communication device via an Fl signaling message.

[0007] In an embodiment of the present application, congestion can occur at a first ingress RLC channel between a first parent node and a communication device. Determining whether congestion occurs at the communication device based on a threshold can include determining, at a distributed unit (DU) of the communication device, a first amount of data of a radio link control (RLC) entity associated with the first ingress RLC channel and a second amount of data of a BAP entity associated with the first ingress RLC channel, and determining that the congestion occurs at the communication device when a sum of the first amount of data and the second amount of data is equal to or greater than the threshold. Determining the first amount of data can include determining the first amount of data based on a size of at least one of: RLC service data units (SDUs) that are not included in RLC data protocol data units (PDUs), RLC SDU segments that are not included in RLC data PDUs, RLC data PDUs waiting for initial transmission, and RLC data PDUs waiting for retransmission. Determining the second amount of data can include determining the second amount of data based on a size of at least one of: BAP service data units (SDUs) for which a BAP data protocol data unit (PDU) has not been built, BAP data PDUs that have not been submitted to a lower layer, and BAP control PDUs that have not been submitted to a lower layer.

[0008] In an embodiment of the present application, a distributed unit (DU) of the communication device can determine whether the congestion occurs. The method can further include notifying, by the DU of the communication device, a mobile termination (MT) of the communication device of the occurrence of the congestion when the DU of the communication device determines that the congestion occurs at the communication device. The method can further include generating, by the MT of the communication device, a BAP control element including the congestion indication. Transmitting the congestion indication to the first parent node can include transmitting, by the MT of the communication device, the BAP control element to the first parent node.

[0009] In an embodiment of the present application, the first parent node can be the only parent node of the communication device. In another embodiment of the present application, the communication device can have a plurality of parent nodes, and the first parent node is one of the plurality of parent nodes.

[0010] In an embodiment of the present application, the method can further include receiving, from a base station, second configuration information indicating an association of each of a plurality of ingress RLC channels between the plurality of parent nodes and the communication device with one of the plurality of parent nodes, wherein the second configuration information indicates that the first ingress RLC channel of the plurality of ingress RLC channels is associated with the first parent node.

[0011] In another embodiment of the present application, the method can further include receiving, from a base station, third configuration information indicating an association of an ingress RLC channel between the communication device and a plurality of parent nodes of the communication device with the plurality of parent nodes, wherein each ingress RLC channel is configured to be associated with two or more of the plurality of parent nodes, wherein the third configuration information indicates that the first ingress RLC channel is associated with the first parent node and at least one second parent node of the plurality of parent nodes. The method can further include transmitting, to the at least one second parent node, the congestion indication via a BAP signaling message when it is determined that the congestion occurs at the communication device.

[0012] Another embodiment of the present disclosure provides a method of a base station. The method can include transmitting, to a communication device, first configuration information indicating a threshold value to configure a congestion indication of the communication device, wherein the threshold value is associated with an amount of data.

[0013] In an embodiment of the present application, the first configuration information can be transmitted to a mobile termination (MT) of the communication device via a radio resource control (RRC) signaling message. In another embodiment of the present application, the first configuration information can be transmitted to a distributed unit (DU) of the communication device via an Fl signaling message.

[0014] In an embodiment of the present application, the method can further include transmitting, to the communication device, second configuration information indicating an association of an ingress RLC channel between the communication device and a plurality of parent nodes of the communication device with the plurality of parent nodes, wherein each ingress RLC channel is configured to be associated with two or more of the plurality of parent nodes, and transmitting, to the communication device, a duplicated downlink transmission via the two or more parent nodes. The method can further include receiving, at the base station, a congestion indication, wherein the congestion indication indicates that congestion occurs at the communication device, and taking an action to reduce the congestion at the communication device in response to the congestion indication. In an embodiment of the present application, taking the action to reduce the congestion at the communication device can include deactivating at least one of the two or more parent nodes such that a downlink transmission is not transmitted from the at least one parent node to the communication device.

[0015] In an embodiment of the present application, receiving the congestion indication at the base station can include receiving the congestion indication from an upstream node of the communication device. In another embodiment of the present application, receiving the congestion indication at the base station can include receiving the congestion indication from the communication device via a radio resource control (RRC) signaling message.

[0016] Yet another embodiment of the disclosure provides an apparatus. In accordance with some embodiments of the disclosure, the apparatus includes at least one non-transitory computer-readable medium having computer-executable instructions stored therein, at least one receiving circuitry, at least one transmitting circuitry, and at least one processor coupled to the at least one non-transitory computer-readable medium, the at least one receiving circuitry, and the at least one transmitting circuitry, wherein the at least one non-transitory computer-readable medium and the computer-executable instructions are configured to, with the at least one processor, cause the apparatus to perform a method in accordance with some embodiments of the disclosure. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to describe the manner in which the advantages and features of the disclosure can be obtained, a description of the disclosure is presented herein in reference to particular embodiments thereof, which are illustrative in nature and do not limit the scope of the disclosure.

[0018] Figure 1A illustrative wireless communication system in accordance with some embodiments of the disclosure is described;

[0019] Figure 1A illustrative wireless communication system in accordance with some embodiments of the disclosure is described;

[0020] Figure 2A illustrative wireless communication system in accordance with some embodiments of the disclosure is described;

[0021] Figure 2A illustrative wireless communication system in accordance with some embodiments of the disclosure is described;

[0022] Figure 3 a flowchart illustrating an example procedure for handling per-hop flow control in accordance with some embodiments of the disclosure is described;

[0023] Figure 4 a flowchart illustrating an example procedure for handling per-hop flow control in accordance with some embodiments of the disclosure is described; and

[0024] Figure 5 an example block diagram of an apparatus in accordance with some embodiments of the disclosure is described. DETAILED DESCRIPTION

[0025] The detailed description of drawings is intended as an overview of preferred embodiments of the disclosure and is not intended to represent the only form in which the disclosure can be practiced. It should be understood that the same or equivalent functions can be accomplished by different embodiments that are intended to be encompassed within the spirit and scope of the disclosure.

[0026] Figure 1A A wireless communication system 100 is illustrated in accordance with some embodiments of the disclosure.

[0027] Reference Figure 1A The wireless communication system 100 can include an IAB donor node (e.g., donor node 110), some IAB nodes (e.g., IAB node 120A, IAB node 120B, IAB node 120C, and IAB node 120D), and some UEs (e.g., UE 130A and UE 130B). Although only one donor node is illustrated in Figure 1A more donor nodes. Similarly, although only four IAB nodes are illustrated in Figure 1A more or fewer IAB nodes. Although only two UEs are illustrated in Figure 1A more or fewer UEs.

[0028] IAB node 120A is directly connected to donor node 110. IAB node 120D is directly connected to donor node 110. According to some other embodiments of the disclosure, IAB node 120A can be connected to donor node(s) other than donor node 110. According to some other embodiments of the disclosure, IAB node 120D can be connected to donor node(s) other than donor node 110.

[0029] IAB node 120C can reach donor node 110 via IAB node 120D. IAB node 120D is a parent node of IAB node 120C. In other words, IAB node 120C is a child node of IAB node 120D. IAB node 120B can reach donor node 110 via IAB node 120C and IAB node 120D. IAB node 120C and IAB node 120D are upstream nodes of IAB node 120B, and IAB node 120C is a parent node of IAB node 120B. In other words, IAB node 120B is a child node of IAB node 120C. IAB node 120B and IAB node 120C are downstream nodes of IAB node 120D. UE 130A is directly connected to IAB node 120A, and UE 130B is directly connected to IAB node 120B. In other words, UE 130A and UE 130B are served by IAB node 120A and IAB node 120B, respectively. In some other embodiments of the disclosure, UE 130A and UE 130B can also be referred to as child nodes of IAB node 120A and IAB node 120B, respectively.

[0030] According to some other embodiments of the disclosure, each of IAB node 120A, IAB node 120B, IAB node 120C, and IAB node 120D can be directly connected to one or more UEs.

[0031] According to some other embodiments of the disclosure, each of IAB node 120A, IAB node 120B, IAB node 120C, and IAB node 120D can be directly connected to one or more IAB nodes.

[0032] In wireless communication system 100 that provides multi-hop relaying, a wireless backhaul link can fail due to, for example, but not limited to, blockage by mobile object(s) (e.g., vehicle(s)), foliage (caused by seasonal changes), new building(s) (e.g., infrastructure changes). This backhaul link failure can occur on a physically stationary IAB node or a mobile IAB node. Link switching techniques have been developed to address this issue.

[0033] For example, assume that a radio link failure (RLF) occurs on a backhaul link between donor node 110 and IAB node 120D, then IAB node 120D can establish a link to another donor node (not shown). In other words, IAB node 120D can switch from the link between IAB node 120D and donor node 110 to the link between IAB node 120D and another donor node (not shown).

[0034] For example, assume that an RLF occurs on a backhaul link between two IAB nodes (e.g., IAB node 120D and IAB node 120C), then IAB node 120C can establish a link to another IAB node (e.g., IAB node 120A). In other words, IAB node 120C can switch from the link between IAB node 120C and IAB node 120D to the link between IAB node 120C and candidate IAB node 120A.

[0035] Moreover, traffic variations can create uneven load distribution on the wireless backhaul links, leading to local link or node congestion.

[0036] Figure 1B An example wireless communication system 100A in accordance with some embodiments of the disclosure is illustrated.

[0037] Reference Figure 1B Wireless communication system 100A can include IAB donor 140, IAB node 150A, IAB node 150B, UE 160A, UE 160B, UE 160C, and Next Generation Core (NGC) 170.

[0038] Each of IAB node 150A and IAB node 150B can include a Distributed Unit (DU) and a Mobile Termination (MT). In the context of the present disclosure, the MT is referred to as a function residing in an IAB node that terminates the radio interface layer of the backhaul Uu interface towards an IAB donor or other IAB nodes. An IAB node can connect to an upstream IAB node or BS (e.g., IAB donor) via the MT function. An IAB node can connect to UEs and downstream IAB nodes via the DU.

[0039] IAB node 150A can connect to upstream IAB node 150B via MT 152A function. IAB node 150A can connect to UE 160A via DU 151A. IAB node 150B can connect to an upstream IAB node or IAB donor 140 via MT 152B function. IAB node 150B can connect to UE 160B via DU 151B. IAB node 150B can connect to downstream IAB node 150A via DU 151B.

[0040] In some embodiments of the present disclosure, Figure 1BThe IAB nodes 150A and 150B in FIG. 1 can be Layer 2 (L2) IAB nodes. For example, each of the IAB node 150A and the IAB node 150B can host a Backhaul Adaptation Protocol (BAP) layer, a Radio Link Control (RLC) layer, a Medium Access Control (MAC) layer, and a Physical (PHY) layer. In some embodiments of the disclosure, the BAP layer in the MT of an IAB node can support pre-processing. The BAP layer can submit BAP data Protocol Data Units (PDUs) to the RLC layer before receiving a UL grant. In other words, the BAP layer can submit packets to lower layers before the packets are requested by the lower layers. Referring back to Figure 1A , Figure 1A The IAB nodes 120A, 120B, 120C, and 120D in FIG. 1 can be Layer 2 (L2) IAB nodes.

[0041] Referring back to Figure 1B A BS (e.g., the IAB donor 140) can include at least one DU to support UEs and MTs of downstream IAB nodes. One DU of a BS can support at least one cell. One cell can be supported by only one DU of a BS or one DU of an IAB node.

[0042] A central unit (CU) 141 included in the IAB donor 140 controls the DUs of all IAB nodes (e.g., the IAB node 150A and the IAB node 150B) and the DU(s) (e.g., the DU 142) residing in the donor 140. The DU(s) and the CU of the IAB donor can be co-located or can be located in different locations. The DU(s) and the CU of the IAB donor are connected via an Fl interface. In other words, the Fl interface provides a means for interconnecting the CU and the DU(s) of the IAB donor. The Fl application protocol (FlAP) supports the functions of the Fl interface through certain FlAP signaling procedures.

[0043] In some embodiments of the disclosure, the CU 141 of the IAB donor 140 can host the Radio Resource Control (RRC), the Service Data Adaptation Protocol (SDAP), and the Packet Data Convergence Protocol (PDCP) layers of the IAB donor 140. The DU 142 of the IAB donor 140 can host the Backhaul Adaptation Protocol (BAP) layer, the Radio Link Control (RLC) layer, the Medium Access Control (MAC) layer, and the Physical (PHY) layer of the IAB donor 140.

[0044] The wireless communication system 100A is in a standalone (SA) mode, where each IAB node has only one parent node. In some other embodiments of the disclosure, the wireless communication system can be in a non-standalone (NSA) mode, where one or more IAB nodes can have more than one parent node.

[0045] Figure 2AAn example wireless communication system 200A in SA mode is illustrated in accordance with some embodiments of the present disclosure.

[0046] Referring to 2A, the wireless communication system 200A can include an IAB donor 210, an IAB node 220A, an IAB node 220B, an IAB node 220C, an IAB node 220D, a UE 230A, and a UE 230B. Although for simplicity, Figure 2A Only downlink communications are illustrated from upstream nodes to downstream nodes (e.g., from the IAB donor 210 to the IAB node 220A, from the IAB node 220A to the IAB node 220B, from the IAB node 220B to the IAB node 220C, and from the IAB node 220C to the UE 230A, to the UE 230B, and to the IAB node 220D), but it should be considered that uplink communications can be present in the opposite direction.

[0047] Similar to the IAB nodes and the IAB donor in Figure 1B Figure 2A The IAB nodes (e.g., the IAB node 220A, the IAB node 220B, the IAB node 220C, the IAB node 220D) in Figure 2A (not illustrated in Figure 2A (not illustrated in

[0048] As illustrated in Figure 2A A UE (e.g., the UE 230A or the UE 230B) can access the IAB donor 210 via the IAB nodes 220C, 220B, and 220A. On the downlink, the DU of an IAB node (e.g., the IAB node 220B) can not be aware of the downlink buffer status of its child node (e.g., the IAB node 220C). Congestion can occur at any of the IAB nodes 220C, 220B, and 220A. For example, assuming that the capacity of the link from the IAB node 220C to the UE 230A can be less than the capacity of the link from the IAB node 220B to the IAB node 220C, then in this case, downlink data congestion can occur at the IAB node 220C because the ingress data rate from the IAB node 220B to the IAB node 220C (which is scheduled by the DU of the IAB node 220B) can be greater than the egress data rate from the IAB node 220C to the UE 230A (which can be scheduled by the DU of the IAB node 220C for the UE 230A). When congestion occurs at the IAB node 220C, the IAB node 220C can perform packet retransmission, or even can have to drop packet(s), which can adversely affect the quality of service or performance of the wireless communication system 200A.

[0049] ​Similarly, if the capacity of the link from IAB node 220B to IAB node 220C is relatively smaller than the capacity of the link from IAB node 220A to IAB node 220B, congestion and packet drops can occur at IAB node 220B.

[0050] Various flow control techniques have been developed to address this issue. For example, end-to-end flow control techniques can help address the issue of packet drops at the IAB node(s) due to downlink data congestion. In this solution, for example, the CU of the IAB donor 210 in Figure 2A may take corresponding action(s) (e.g., reduce the data rate on the downlink) to mitigate downlink data congestion according to the congestion reports from the IAB node(s). However, end-to-end flow control can sometimes fail to pinpoint the node(s) suffering from congestion, and the response speed can be relatively slow.

[0051] Hop-by-hop flow control techniques can be used to alleviate congestion. Hop-by-hop flow control techniques can be employed individually or in combination with end-to-end flow control techniques for handling congestion at the IAB node(s). For example, an IAB node suffering from congestion (also referred to as a “congested IAB node”) can report relevant information to its parent node(s) (e.g., a parent IAB node or a donor node), which can perform flow control and mitigate downlink data congestion. The hop-by-hop flow control procedure will be described in detail below.

[0052] Figure 2B An example wireless communication system 200B in a non-standalone (NSA) mode is illustrated in accordance with some embodiments of the present disclosure.

[0053] As Figure 2B illustrated in Figure 2B , the wireless communication system 200B can include a donor node (e.g., IAB donor 210’), some IAB nodes (e.g., IAB node 220A’, IAB node 220B’, IAB node 220C’, and IAB node 220D’), and some UEs (e.g., UE 230’). It should be understood that a wireless communication system in the NSA mode according to some other embodiments of the present disclosure can have various structures other than the example structure illustrated in

[0054] Similar to the IAB nodes and the IAB donor in Figure 1B , the IAB nodes (e.g., IAB node 220A’, IAB node 220B’, IAB node 220C’, and IAB node 220D’) in Figure 2B may include respective MTs and DUs (not illustrated in Figure 2B ), and the IAB donor 210 can include at least one DU and a CUFigure 2B (Not specified in the text).

[0055] about Figure 2A The above descriptions of IAB donor 210, IAB node 220A, IAB node 220B, IAB node 220C, IAB node 220D, and UE 230A can also be applied to Figure 2B The wireless communication system 200B differs in that, in the wireless communication system 200B, multiple connectivity is configured for one or more IAB nodes (e.g., IAB node 220C'). Dual connectivity can be considered a special case of multiple connectivity. In some instances, IAB donor 210' can be configured such that IAB node 220A' is the master node (MN) and IAB node 220B' is the auxiliary node (SN) at IAB node 220C'. For example, IAB donor 210' can configure IAB node 220A' to have a cell group (CG) ID of "0", indicating that IAB node 220A' is the MN. IAB donor 210' can configure IAB node 220B' to have a CG ID of "1", indicating that IAB node 220B' is the SN.

[0056] For example, such as Figure 2B As shown, IAB node 220C' can connect to more than one parent IAB node, including IAB node 220A' and IAB node 220B'. In other words, IAB node 220A' and IAB node 220B' both serve the same child IAB node, such as IAB node 220C'. In this case, IAB node 220C' will have multiple routes to the donor node (such as IAB donor 210') via multiple parent IAB nodes (such as IAB node 220A' and IAB node 220B'). For example, IAB node 220C' can reach IAB donor 210' via IAB node 220A' (Route A: IAB donor 210' <-> IAB node 220A' <-> IAB node 220C'). Alternatively, IAB node 220C' can reach IAB donor 210' via IAB node 220B' (Route B: IAB donor 210' <-> IAB node 220B' <-> IAB node 220C'). From the perspective of a downstream node of IAB node 220C' (e.g., IAB node 220D'), IAB node 220D' also has multiple routes to IAB donor 210' via IAB node 220C'. Note that multiple connectivity can also be configured for one or more other IAB nodes in a wireless communication system.

[0057] In some embodiments of the disclosure, only one of the multiple routes from an IAB node to an IAB donor can be active, while the remaining routes of the multiple routes can be in a standby state. No data transmission and reception can be allowed on the routes in the standby state. For example, referring to Figure 2B At IAB node 220C', route A (IAB donor 210' <-> IAB node 220A' <-> IAB node 220C') can be active, but route B (IAB donor 210' <-> IAB node 220B' <-> IAB node 220C') can be in a standby state. In other words, IAB node 220C' can be connected to IAB node 220B', but there can be no data communication (e.g., data transmission or reception) on route B at that time.

[0058] In some embodiments of the disclosure, two or more of the multiple routes from an IAB node to an IAB donor can be active. For example, referring to Figure 2B At IAB node 220C', both route A and route B can be active. In other words, IAB node 220C' can transmit or receive data on both route A and route B at the same or different times.

[0059] On the downlink, from the perspective of an IAB node, a radio link control (RLC) channel between the IAB node and a parent node of the IAB node is referred to as an ingress RLC channel, and a RLC channel between the IAB node and a child node of a given IAB node is referred to as an egress RLC channel. Each RLC channel can correspond to a logical channel.

[0060] In some embodiments of the disclosure, an IAB donor can configure an association of ingress RLC channels with one or more parent nodes of an IAB node. In other words, a downlink transmission from the IAB donor can be transmitted to the IAB node through the one or more parent nodes of the IAB node as configured by the IAB donor.

[0061] For example, in some embodiments of the disclosure, an IAB donor can configure an IAB node in a manner that each of the ingress RLC channels of the IAB node is associated with one parent node (hereinafter, “associated parent node”) of the IAB node. This configuration is hereinafter referred to as multi-connectivity scheme I. Under this scheme, no local link selection is supported at the IAB node. One RLC entity and one backhaul adaptation protocol (BAP) entity can be configured for each RLC channel at the IAB node. Under this scheme, each RLC entity at the IAB node is configured to be associated with one peer RLC entity at the associated parent node; and each BAP entity at the IAB node is configured to be associated with one peer BAP entity at the associated parent node.

[0062] For example, referring to Figure 2B , the IAB donor 210' can configure an ingress RLC channel A of the IAB node 220C' (which can carry downlink transmissions for voice communications) to be associated with one parent node of the IAB node 220C' (e.g., the IAB node 220B'). The IAB donor 210' can configure an ingress RLC channel B of the IAB node 220C' (which can carry downlink transmissions for streaming communications) to be associated with a different parent node (e.g., the IAB node 220A') or the same parent node (e.g., the IAB node 220B'). In this way, the IAB node 220C' can receive data for the ingress RLC channel A via the IAB node 220B', and can receive data for the ingress RLC channel B via the IAB node 220A' or the IAB node 220B', as configured by the IAB donor 210'.

[0063] In some other embodiments of the disclosure, the IAB donor can configure an IAB node in a manner that each of the ingress RLC channels of the IAB node is associated with two or more parent nodes (hereinafter, "associated parent nodes") of the IAB node, and the IAB donor can autonomously select one of the associated parent nodes for downlink transmissions of the ingress RLC channels based on certain criteria including, for example, channel quality or load of the associated parent nodes. The channel quality can be determined based on at least one or more of: reference signal received power (RSRP), reference signal strength indicator (RSSI), or reference signal received quality (RSRQ). Other channel quality metrics can also be employed. This configuration is hereinafter referred to as the multi-connectivity scheme II.

[0064] Under this scheme, local link selection is supported at the IAB node. As mentioned above, at the IAB node, one RLC entity and one backhaul adaptation protocol (BAP) entity can be configured for each RLC channel. Under this scheme, each RLC entity (or BAP entity) at the IAB node can be configured to be associated with two or more peer RLC entities (or BAP entities) at two or more associated parent nodes.

[0065] For example, referring to Figure 2B , the IAB donor 210' can configure ingress RLC channels (e.g., RLC channel A and RLC channel B) of the IAB node 220C' to be associated with both the IAB node 220A' and the IAB node 220B'. The IAB donor 210' can autonomously select the IAB node 220A' or the IAB node 220B' for transmitting downlink transmissions carried by the ingress RLC channels of the IAB node 220C'.

[0066] In yet other embodiments of the disclosure, an IAB donor can configure an IAB node in a manner that each of the ingress RLC channels of the IAB node is associated with two or more parent nodes (hereinafter, “associated parent nodes”) of the IAB node, and the IAB donor can transmit downlink transmissions to each of the associated parent nodes. This configuration is hereinafter referred to as the multi-connectivity scheme III.

[0067] Under this scheme, duplicated links are supported at the IAB node. That is, the IAB donor can transmit duplicated downlink data to two or more associated parent nodes of the IAB node. The IAB node can receive the same data from the two or more associated parent nodes. The IAB node can keep only one copy (e.g., the earliest received copy) of the downlink data, and can discard other copies of the downlink data.

[0068] As mentioned above, at the IAB node, one RLC entity and one backhaul adaptation protocol (BAP) entity can be configured for each RLC channel. Under this scheme, each RLC entity (or BAP entity) at the IAB node can be configured to be associated with two or more peer RLC entities (or BAP entities) at two or more associated parent nodes. The IAB donor can transmit duplicated data to the IAB node via the two or more associated parent nodes.

[0069] For example, referring to Figure 2B , the IAB donor 210’ can configure the ingress RLC channels (e.g., RLC channel A and RLC channel B) of the IAB node 220C’ to be associated with both the IAB node 220A’ and the IAB node 220B’. The IAB donor 210’ can transmit downlink transmissions carried by the RLC channels of the IAB node 220C’ to both the IAB node 220A’ and the IAB node 220B’. In this way, the reliability of the downlink transmissions can be improved.

[0070] The RLC channels between an IAB node and its parent IAB nodes can include at least one backhaul (BH) ingress RLC channel.

[0071] As mentioned above with respect to the wireless communication system 200A in the SA mode Figure 2A , downlink data congestion can occur at the IAB node. In a wireless communication system in the NSA mode, downlink data congestion can similarly occur at the IAB node.

[0072] For example, referring to Figure 2B, assuming that the IAB donor 210' can transmit a streaming communication to the UE 230' via the IAB node 220B' and the IAB node 220C', then the capacity of the link from the IAB node 220C' to the UE 230' can be less than the capacity of the link from the IAB node 220B' to the IAB node 220C', in which case downlink data congestion can occur at the IAB node 220C' because the ingress data rate from the IAB node 220B' to the IAB node 220C' (which is scheduled by the DU of the IAB node 220B') can be greater than the egress data rate from the IAB node 220C' to the UE 230' (which can be scheduled by the DU of the IAB node 220C' for the UE 230'). Similarly, congestion can occur at any of the IAB nodes 220A', 220B', and 220D'. As mentioned above, a hop-by-hop flow control procedure can be employed to mitigate this congestion, and will be described below with respect to Figure 3 A detailed description of a hop-by-hop flow control procedure is provided.

[0073] Figure 3 A flowchart illustrating an example procedure 300 for handling hop-by-hop flow control in accordance with some embodiments of the disclosure is described.

[0074] In Figure 3 , multi-connectivity can be configured for a communication device (e.g., the communication device 320C). For example, the communication device 320C can reach the BS 310 via the communication device 320A (Route E: BS 310 <—> communication device 320A <—> communication device 320C). The communication device 320C can also reach the BS 310 via the communication device 320B (Route F: BS 310 <—> communication device 320B <—> communication device 320C). In other words, both the communication device 320A and the communication device 320B serve the same child node, e.g., the communication device 320C. The access communication device 320D is a child node of the communication device 320C.

[0075] Although, for simplicity, the communication device 320C is configured with dual connectivity in Figure 3 , according to some embodiments of the disclosure, the communication device 320C can be connected to more than two parent nodes. Note that multi-connectivity can also be configured for one or more other communication devices in Figure 3 .

[0076] In some examples, the communication device 320A can function as the IAB node 220A' shown in Figure 2B , the communication device 320B can function as the IAB node 220B' shown in Figure 2B , the communication device 320C can function as the IAB node 220C' shown in Figure 2B , and the access communication device 320D can function as the IAB node 220D' shown inFigure 2B The IAB node 220D' or the UE 230' shown in FIG. 13, and the BS 310 can function as Figure 2B the IAB donor 210' shown in FIG. 13.

[0077] Figure 3 The communication devices (e.g., the communication device 320A, the communication device 320B, and the communication device 320C) in FIG. 13 can include respective MTs and DUs Figure 3 not illustrated in FIG. 13), and the BS 310 can include at least one DU and a CU Figure 3 not illustrated in FIG. 13).

[0078] Although the communication device 320A and the communication device 320B are connected to the same BS, e.g., the BS 310 in FIG. 13, according to some embodiments of the disclosure, the communication device 320A and the communication device 320B can be connected to different BSs. Figure 3

[0079] Referring to Figure 3 , in some embodiments of the disclosure, the procedure 300 can include operation 311 (indicated as an option by the dashed arrow). In operation 311, the BS 310 can transmit configuration information indicating a threshold value to configure the communication device 320C. The threshold value can be for congestion indication and can be associated with a data amount. For example, the threshold value can be a data size (e.g., 800 bytes) or a percentage of a data amount (e.g., 80%).

[0080] In some embodiments of the disclosure, the BS 310 can transmit the configuration information to the MT of the communication device 320C via a radio resource control (RRC) signaling message. In some other embodiments of the disclosure, the BS 310 can transmit the configuration information to the distributed unit (DU) of the communication device 320C via an Fl signaling message.

[0081] In some embodiments of the disclosure, the configuration information can indicate a cell group (CG) ID of a parent node of the communication device 320C. For example, the BS 310 can configure the communication device 320C that the CG ID of the communication device 320A is "0" and the CG ID of the communication device 320B is "1".

[0082] In some other embodiments of the disclosure, the configuration information can be pre-configured or predetermined. The configuration information can include a threshold value associated with a data amount, as described above. For example, the communication device 320C can determine the threshold value described above by itself. In these embodiments, operation 311 can be eliminated.

[0083] ​In operations 313', 313, and 315, the BS 310 can transmit downlink transmissions to the access communication device 320D via the communication devices 320A and 320C. In some embodiments of the disclosure, the BS 310 can transmit downlink transmissions to the access communication device 320D via the communication devices 320B and 320C (not shown). Figure 3

[0084] In operation 317, the communication device 320C can determine whether congestion occurs at the communication device 320C based on a threshold. In operation 319, when it is determined that congestion occurs at the communication device 320C, the communication device 320C can transmit a congestion indication to its parent node(s) (e.g., the communication device 320A) via a backhaul adaptation protocol (BAP) signaling message.

[0085] For example, in some embodiments of the disclosure, the communication device 320C can receive, from the BS 310, downlink transmissions carried by an ingress RLC channel (e.g., ingress RLC channel A) between the communication device 320C and its parent node (e.g., the communication device 320A). The communication device 320C can determine buffer size information associated with the ingress RLC channel. For example, the communication device 320C can determine, at a DU of the communication device 320C, a data amount of a radio link control (RLC) entity associated with the ingress RLC channel (e.g., data amount DV1) and a data amount of a BAP entity associated with the ingress RLC channel (e.g., data amount DV2).

[0086] In some embodiments of the disclosure, the communication device 320C can determine the data amount of the RLC entity based on a size of at least one of:

[0087] • RLC service data units (SDUs) not contained in RLC data protocol data units (PDUs);

[0088] • RLC SDU segments not contained in RLC data PDUs;

[0089] • RLC data PDUs waiting for initial transmission; and

[0090] • RLC data PDUs waiting for retransmission (RLC acknowledgement mode).

[0091] In some embodiments of the disclosure, the communication device 320C can determine the data amount of the BAP entity based on a size of at least one of:

[0092] • BAP service data units (SDUs) for which a BAP data protocol data unit (PDU) has not yet been built;

[0093] • BAP data PDUs that have not yet been submitted to a lower layer; and​

[0094] • has not been submitted to lower layer BAP control PDU.

[0095] The communication device 320C can determine the sum of the data volume DV1 and the data volume DV2. When the sum of the data volumes is determined to be equal to or greater than the threshold value described above, the communication device 320C can determine that congestion occurs at the communication device 320C. When congestion occurs at the communication device 320C, the communication device 320C can generate a BAP control element containing a congestion indication for transmission to the parent node(s) of the communication device 320C for traffic control.

[0096] In some embodiments of the disclosure, the DU of the communication device 320C can determine whether congestion occurs. In some embodiments of the disclosure, when the DU of the communication device 320C determines that congestion occurs at the communication device 320C, the DU of the communication device 320C can notify the MT of the communication device 320C of the occurrence of congestion. In some embodiments of the disclosure, the MT of the communication device 320C can generate a BAP control element containing a congestion indication. The MT of the communication device 320C can transmit the BAP control element to the parent node(s) of the communication device 320C (e.g., the communication device 320A).

[0097] In some embodiments of the disclosure, the BAP control element can contain at least one of the following:

[0098] • a desired buffer size;

[0099] • a desired bit rate;

[0100] • an actual buffer size associated with the related ingress RLC channel;

[0101] • a channel ID of the related ingress RLC channel;

[0102] • a logical channel ID of a logical channel corresponding to the related ingress RLC channel; and

[0103] • a flag indicating that the BAP control element contains BAP control information rather than service data.

[0104] The actual buffer size can refer to the data volume of an RLC entity associated with the related RLC channel, the data volume of a BAP entity associated with the related RLC channel, or a combination thereof.

[0105] As mentioned above, multi-connectivity can be configured for the communication device 320C. In some embodiments of the disclosure, the BS 310 can configure the communication device 320C with the multi-connectivity scheme I. In other words, as explained above, the BS 310 can configure each ingress RLC channel of the communication device 320C to be associated with one parent node (hereinafter, “associated parent node”) of the communication device 320C. The communication device 320C can receive this configuration information in, for example, operation 311.

[0106] With this configuration, when the communication device 320C determines that congestion occurs at an ingress RLC channel of the communication device 320C (i.e., the buffer size associated with the ingress RLC channel is equal to or greater than the threshold value described above), the communication device 320C can transmit a congestion indication to the parent node associated with the ingress RLC channel, as configured by the BS 310.

[0107] For example, the BS 310 can configure ingress RLC channel A of the communication device 320C to be associated with the communication device 320A, and RLC channel B of the communication device 320C to be associated with the communication device 320B. According to this configuration, data of RLC channel A can be transmitted to the communication device 320C via route E (i.e., through the communication device 320A) as mentioned above, and data of RLC channel B can be transmitted to the communication device 320C via route F (i.e., through the communication device 320B) as mentioned above.

[0108] With this configuration, when the communication device 320C determines that congestion occurs at ingress RLC channel A in operation 317, the communication device 320C can transmit a congestion indication to the communication device 320A in operation 319. When the communication device 320C determines that congestion occurs at ingress RLC channel B in operation 317, the communication device 320C can transmit a congestion indication to the communication device 320B in operation 319’ (represented as an option by the dashed arrow). As mentioned above, the congestion indication can be transmitted via a corresponding Backhaul Adaptation Protocol (BAP) signaling message.

[0109] In some embodiments of the disclosure, the BS 310 can configure the communication device 320C with the multi-connectivity scheme II. In other words, as explained above, the BS 310 can configure each ingress RLC channel of the communication device 320C to be associated with two or more parent nodes (hereinafter, “associated parent nodes”) of the communication device 320C. The BS can autonomously select one of the associated parent nodes for downlink transmission of data of the ingress RLC channel of the communication device 320C. The communication device 320C can receive this configuration information in, for example, operation 311. In some embodiments of the disclosure, the multi-connectivity scheme II can be applied to a communication device by default. In these embodiments, the configuration operation (e.g., operation 311) can be eliminated.

[0110] In some embodiments of the disclosure, BS 310 can configure communication device 320C with multi-connectivity scheme III. In other words, as explained above, BS 310 can configure each ingress RLC channel of communication device 320C to be associated with two or more parent nodes (hereinafter, “associated parent nodes”) of communication device 320C. BS can transmit downlink transmissions to each associated parent node. Communication device 320C can receive this configuration information in, for example, operation 311. In some embodiments of the disclosure, multi-connectivity scheme III can be applied to a communication device by default. In these embodiments, the configuration operation (e.g., operation 311) can be eliminated.

[0111] In case communication device 320C is configured with multi-connectivity scheme II or multi-connectivity scheme III, when communication device 320C determines that congestion occurs at an ingress RLC channel of communication device 320C (i.e., the buffer size associated with the ingress RLC channel is equal to or greater than the threshold value described above), communication device 320C can transmit the congestion indication(s) to the two or more parent nodes associated with the ingress RLC channel, as configured by BS 310.

[0112] For example, BS 310 can configure ingress RLC channel A of communication device 320C to be associated with both communication device 320A and communication device 320B. With this configuration, when communication device 320C determines that congestion occurs at ingress RLC channel A in operation 317, communication device 320C can transmit a congestion indication to communication device 320A in operation 319, and can transmit a congestion indication to communication device 320B in operation 319’. The congestion indication to communication device 320A can be the same or different from the congestion indication to communication device 320B. As mentioned above, the congestion indication can be transmitted via a respective backhaul adaptation protocol (BAP) signaling message.

[0113] In operation 321, after receiving the congestion indication from communication device 320C, communication device 320A can attempt to resolve the congestion by, for example, transmitting data to communication device 320C at a relatively lower data rate. For example, communication device 320A can reduce the bit rate of the ingress RLC channel that is experiencing congestion as indicated in the congestion indication.

[0114] In some embodiments of the disclosure, the procedure 300 can include operation 323 (indicated as an option by the dashed arrow). In operation 323, the communication device 320A can transmit the received congestion indication to the BS 310. For example, when the communication device 320A is unable to resolve the congestion at the communication device 320C, the communication device 320A can transmit the received congestion indication to the BS 310. The BS 310 can take action in response to the congestion indication to reduce the congestion at the communication device 320C. Actions that can be taken by the BS 310 to reduce the congestion will be described below.

[0115] In some embodiments of the disclosure, as an alternative or in addition to transmitting a congestion indication to a parent node, the communication device 320C can transmit a congestion indication to the BS 310 via a RRC signaling message (not shown in Figure 3 In response to the congestion indication, the BS 310 can take action to reduce the congestion at the communication device 320C. For example, when the parent node(s) of the communication device 320C are unable to resolve the congestion at the communication device 320C, the communication device 320C can transmit a congestion indication to the BS 310 via a RRC signaling message (not shown in Figure 3

[0116] In some embodiments of the disclosure, the action that can be taken by the BS 310 to reduce the congestion at the communication device 320C can include the BS 310 transmitting data to the communication device 320C at a relatively lower data rate. In some embodiments of the disclosure, the communication device 320C can be configured with the multi-connectivity scheme III. That is, each ingress RLC channel of the communication device 320C is associated with two or more parent nodes of the communication device 320C. When the congestion indication indicates that congestion is occurring on an ingress RLC channel of the communication device 320C (i.e., the ingress RLC channel is experiencing congestion), the BS 310 can de-activate at least one of the two or more parent nodes associated with the ingress RLC channel such that downlink transmissions are not transmitted to the communication device 320C from the at least one deactivated parent node.

[0117] Similarly, when the communication device 320B receives a congestion indication from the communication device 320C, the communication device 320B can perform operations similar to those described above with respect to the communication device 320A. For example, the communication device 320B can attempt to resolve the congestion by, for example, transmitting data to the communication device 320C (which is experiencing congestion) at a relatively lower data rate in operation 321' (indicated as an option by the dashed arrow). In some instances, when the communication device 320B is unable to resolve the congestion at the communication device 320C, the communication device 320B can transmit the received congestion indication to the BS 310 in operation 323' (indicated as an option by the dashed arrow). ​

[0118] Although example procedure 300 shows operations 311-323', one of skill in the art will appreciate that some of operations 311-323' can be eliminated without departing from the spirit and scope of the disclosure.

[0119] Figure 4 A flowchart of an example procedure 400 for handling per-hop flow control is described in accordance with some embodiments of the present disclosure. In Figure 4 In some embodiments, communication device 420A can function as IAB node 220A shown in FIG. 2, communication device 420B can function as IAB node 220B shown in FIG. 2, communication device 420C can function as IAB node 220C shown in FIG. 2, access communication device 420D can function as IAB node 220D, UE 230A, or UE 230B shown in FIG. 2, and BS 410 can function as IAB donor 210 shown in FIG. 2.

[0120] In some examples, communication device 420A can function as Figure 2A In some embodiments, communication device 420A can function as IAB node 220A shown in FIG. 2, communication device 420B can function as IAB node 220B shown in FIG. 2, communication device 420C can function as IAB node 220C shown in FIG. 2, access communication device 420D can function as IAB node 220D, UE 230A, or UE 230B shown in FIG. 2, and BS 410 can function as IAB donor 210 shown in FIG. 2. Figure 2A In some embodiments, communication device 420A can function as IAB node 220A shown in FIG. 2, communication device 420B can function as IAB node 220B shown in FIG. 2, communication device 420C can function as IAB node 220C shown in FIG. 2, access communication device 420D can function as IAB node 220D, UE 230A, or UE 230B shown in FIG. 2, and BS 410 can function as IAB donor 210 shown in FIG. 2. Figure 2A In some embodiments, communication device 420A can function as IAB node 220A shown in FIG. 2, communication device 420B can function as IAB node 220B shown in FIG. 2, communication device 420C can function as IAB node 220C shown in FIG. 2, access communication device 420D can function as IAB node 220D, UE 230A, or UE 230B shown in FIG. 2, and BS 410 can function as IAB donor 210 shown in FIG. 2. Figure 2A In some embodiments, communication device 420A can function as IAB node 220A shown in FIG. 2, communication device 420B can function as IAB node 220B shown in FIG. 2, communication device 420C can function as IAB node 220C shown in FIG. 2, access communication device 420D can function as IAB node 220D, UE 230A, or UE 230B shown in FIG. 2, and BS 410 can function as IAB donor 210 shown in FIG. 2. Figure 2A In some embodiments, communication device 420A can function as IAB node 220A shown in FIG. 2, communication device 420B can function as IAB node 220B shown in FIG. 2, communication device 420C can function as IAB node 220C shown in FIG. 2, access communication device 420D can function as IAB node 220D, UE 230A, or UE 230B shown in FIG. 2, and BS 410 can function as IAB donor 210 shown in FIG. 2.

[0121] In some embodiments, communication device 420A, 420B, and 420C, access communication device 420D, and BS 410 can perform similar operations as described above with respect to Figure 4 In some embodiments, communication device 420A, 420B, and 420C, access communication device 420D, and BS 410 can perform similar operations as described above with respect to Figure 3 In some embodiments, communication device 420A, 420B, and 420C, access communication device 420D, and BS 410 can perform similar operations as described above with respect to Figure 4 In some embodiments, communication device 420A, 420B, and 420C, access communication device 420D, and BS 410 can perform similar operations as described above with respect to

[0122] With reference to Figure 4 In some embodiments of the present disclosure, procedure 400 can include operation 411 (indicated as an option by the dashed arrow). In operation 411, BS 410 can transmit configuration information to communication device 420C as described above with respect to operation 311 in FIG. 3. In operations 413', 413, 415', and 415, BS 410 can transmit downlink transmissions to access communication device 420D via communication devices 420A, 420B, and 420C. Figure 3 In operation 417, communication device 420C can perform similar operations as described above with respect to operation 317 in FIG. 3.

[0123] In operation 417, communication device 420C can perform similar operations as described above with respect to operation 317 in FIG. 3. Figure 3communication device 420C occurs in a similar manner as described above with respect to operation 317 in FIG. 3. In operation 419, when it is determined that congestion occurs at the communication device 420C, the communication device 420C can transmit a congestion indication to its parent node (e.g., communication device 420B) via a BAP signaling message. The process of generating this BAP signaling message is similar to the process described above with respect to Figure 3 operation 319 in FIG. 3. For example, the MT of the communication device 420C can generate and transmit a BAP control element to the communication device 420B. In operation 421, the communication device 420B can attempt to resolve the congestion at the communication device 420C in a similar manner as described above with respect to Figure 3 operation 321 in FIG. 3.

[0124] In some embodiments of the disclosure, the program 400 can include operations 423 and 425 (indicated as options by dashed arrows) that similarly serve as Figure 3 operation 323 in FIG. 3. For example, in operations 423 and 425, the communication device 420B can transmit the received congestion indication to its parent node (e.g., communication device 420A), which can transmit the received congestion indication to the BS 410. The BS 410 can take actions in response to the congestion indication to reduce the congestion at the communication device 420C. The actions that can be taken by the BS 410 to reduce the congestion are similar to those described above with respect to Figure 3 operation 323 in FIG. 3.

[0125] In some embodiments of the disclosure, in addition or instead of transmitting the congestion indication to the parent node, the communication device 420C can transmit the congestion indication to the BS 410 via an RRC signaling message (not shown in FIG. 4). Figure 4

[0126] Although the example program 400 shows operations 411-425, one of skill in the art will appreciate that some of the operations 411-425 can be eliminated without departing from the spirit and scope of the disclosure.

[0127] Figure 5 An example block diagram of a device 500 according to some embodiments of the disclosure is illustrated.

[0128] As shown in FIG. 5, the device 500 can include at least one non-transitory computer- readable medium (not illustrated in FIG. 5), receiving circuitry 502, transmitting circuitry 504, and a processor 506 coupled to the non-transitory computer-readable medium (not illustrated in FIG. 5), receiving circuitry 502, and transmitting circuitry 504. The device 500 can be a BS or a communication device (e.g., an IAB node or a UE). Figure 5 Figure 5 Figure 5 As shown in FIG. 5, the device 500 can include at least one non-transitory computer- readable medium (not illustrated in FIG. 5), receiving circuitry 502, transmitting circuitry 504, and a processor 506 coupled to the non-transitory computer-readable medium (not illustrated in FIG. 5), receiving circuitry 502, and transmitting circuitry 504. The device 500 can be a BS or a communication device (e.g., an IAB node or a UE).​​​

[0129] Although elements such as processor 506, transmission circuitry 504, and receiver circuitry 502 are described in the singular in this figure, the plural form is considered unless explicitly stated otherwise. In some embodiments of this disclosure, receiver circuitry 502 and transmission circuitry 504 are combined into a single device, such as a transceiver. In some embodiments of this disclosure, device 500 may further include input devices, memory, and / or other components.

[0130] In some embodiments of this disclosure, a non-transitory computer-readable medium may store computer-executable instructions thereon to cause a processor to perform the methods relating to a communication apparatus as described above. For example, when executed, the computer-executable instructions cause processor 506 to interact with receiving circuitry system 502 and transmitting circuitry system 504 to perform actions relating to... Figure 1A , 1B The IAB node and UE described in 2A and 2B Figure 3 and 4 The steps for accessing the communication device and the communication device are described in the document.

[0131] In some embodiments of this disclosure, a non-transitory computer-readable medium may store computer-executable instructions thereon to cause a processor to perform the methods regarding the BS as described above. For example, when executed, the computer-executable instructions cause processor 506 to interact with receiver circuitry 502 and transmitter circuitry 504 to perform the methods regarding the BS. Figure 1A , 1B The IAB donors described in 2A and 2B and Figure 3 and 4 The steps of BS described in the document.

[0132] Those skilled in the art will understand that the steps of the methods described in conjunction with the aspects disclosed herein can be directly embodied in hardware, a software module executed by a processor, or a combination of both. The software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art. Additionally, in some aspects, the steps of the method may reside as one or more combinations or sets of code and / or instructions on a non-transitory computer-readable medium that may be incorporated into a computer program product.

[0133] While the present disclosure has been described with reference to specific embodiments thereof, it is evident that many alternatives, modifications and variations can be apparent to those skilled in the art. For instance, various components of the described embodiments can be interchanged, added or removed in other embodiments. Also, not all of the elements of each figure are essential for the operation of the disclosed embodiments. For example, one of ordinary skill in the art of the disclosed embodiments will be able to construct and use the teachings of this disclosure without undue experimentation with the elements of the independent claims. Accordingly, the embodiments of the present disclosure as set forth herein are intended to be illustrative and not limiting. Various changes can be made without departing from the spirit and scope of the disclosure.

[0134] In this document, the terms“includes / including” or any other variation thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements does not include only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element preceded by“a” or“an” does not, without further constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus including the recited element. Also, the term“another” is defined as at least a second or more. The terms“has” and“having” are defined as“including.”

Claims

1. A method of using a communication device, comprising: Receive configuration information from the base station that indicates a threshold associated with the amount of data at the communication device; Determine whether the sum of the first data volume of the RLC entity associated with the ingress radio link control (RLC) channel between the parent node of the communication device and the communication device and the second data volume of the backhaul adaptation protocol (BAP) entity associated with the ingress RLC channel at the distributed unit (DU) of the communication device satisfies the threshold. and Based at least in part on the sum satisfying the threshold, a congestion indication is transmitted to the parent node via a BAP signaling message.

2. The method of claim 1, wherein the configuration information is received at the mobile terminal MT of the communication device via a Radio Resource Control (RRC) signaling message.

3. The method of claim 1, wherein the configuration information is received at the DU via an F1 signaling message.

4. The method of claim 1, wherein the congestion indication indicates congestion at the ingress RLC channel between the parent node and the communication device.

5. The method of claim 1, wherein, in order to satisfy the threshold, the sum of the first data quantity and the second data quantity is equal to or greater than the threshold.

6. The method of claim 1, wherein the first data volume is based on the size of at least one of the following: RLC Service Data Unit (SDU) is not included in the RLC Data Protocol Data Unit (PDU); RLC SDU segments not included in RLC data PDUs; RLC data PDU awaiting initial transmission; or RLC data PDUs awaiting retransmission.

7. The method of claim 1, wherein the second data volume is based on the size of at least one of the following: BAP Service Data Unit (SDU) has not yet been constructed for BAP Data Protocol Data Unit (PDU); BAP data PDUs that have not yet been submitted to the lower levels; or The BAP control PDU has not yet been submitted to the lower level.

8. The method of claim 1, wherein the DU determines whether the sum of the first data amount and the second data amount satisfies the threshold.

9. The method of claim 8, further comprising: When the DU of the communication device determines that the sum meets the threshold, the DU of the communication device notifies the mobile terminal MT of the communication device of the occurrence of congestion.

10. The method of claim 9, further comprising: The MT of the communication device generates a BAP control element containing the congestion indication.

11. The method of claim 10, wherein transmitting the congestion indication to the parent node comprises: The BAP control element is transmitted to the parent node by the MT of the communication device.

12. The method of claim 4, wherein the parent node is the unique parent node of the communication device.

13. The method of claim 4, wherein the communication device has a plurality of parent nodes, and the parent node is one of the plurality of parent nodes.

14. The method of claim 13, further comprising: Receive additional configuration information from the base station indicating the association between each of the plurality of ingress RLC channels between the plurality of parent nodes and the communication device and one of the plurality of parent nodes. The additional configuration information indicates that the ingress RLC channel among the plurality of ingress RLC channels is associated with one of the plurality of parent nodes.

15. The method of claim 13, further comprising: Additional configuration information is received from the base station indicating the association of an ingress RLC channel between the communication device and a plurality of its parent nodes, wherein each ingress RLC channel is configured to be associated with two or more of the parent nodes. The additional configuration information indicates that the ingress RLC channel is associated with the parent node among the plurality of parent nodes and at least one additional parent node.

16. The method of claim 15, further comprising: When it is determined that the sum meets the threshold, the congestion indication is transmitted to the at least one additional parent node via a BAP signaling message.

17. A method for establishing a base station, comprising: Configuration information indicating a threshold associated with the data volume is transmitted to the communication device, wherein the congestion indication associated with the communication device is based on the sum of the first data volume of the RLC entity associated with the ingress radio link control (RLC) channel between the parent node of the communication device and the communication device, and the second data volume of the Backhaul Adaptation Protocol (BAP) entity associated with the ingress RLC channel, at the distributed unit (DU) of the communication device, satisfying the threshold.

18. The method of claim 17, wherein the configuration information is transmitted to the mobile terminal MT of the communication device via a Radio Resource Control (RRC) signaling message.

19. The method of claim 17, wherein the configuration information is transmitted to the DU via an F1 signaling message.

20. The method of claim 17, further comprising: Additional configuration information indicating the association between the ingress RLC channel and the multiple parent nodes of the communication device is transmitted to the communication device, wherein each ingress RLC channel is configured to be associated with two or more of the multiple parent nodes; and The transmission is transmitted to the communication device via the replicated downlink through the two or more parent nodes.

21. The method of claim 17, further comprising: Receive the congestion indication, wherein the congestion indication indicates that congestion has occurred at the communication device; and Actions are taken in response to the congestion indication to reduce the congestion at the communication device.

22. The method of claim 20, further comprising: Receive the congestion indication, wherein the congestion indication indicates that congestion has occurred at the communication device; and In response to the congestion indication, deactivating at least one of the two or more parent nodes causes downlink transmissions to stop from the at least one parent node to the communication device.

23. The method of claim 21, wherein receiving the congestion indication comprises: The congestion indication is received from the upstream node of the communication device.

24. The method of claim 21, wherein receiving the congestion indication comprises: The congestion indication is received from the communication device via Radio Resource Control (RRC) signaling messages.

25. A communication device comprising: At least one memory; and At least one processor, coupled to the at least one memory and configured such that the communication device: Receive configuration information from the base station that indicates a threshold associated with the amount of data at the communication device; Determine whether the sum of the first data volume of the RLC entity associated with the ingress radio link control (RLC) channel between the parent node of the communication device and the communication device and the second data volume of the backhaul adaptation protocol (BAP) entity associated with the ingress RLC channel at the distributed unit (DU) of the communication device satisfies the threshold. and Based at least in part on the sum satisfying the threshold, a congestion indication is transmitted to the parent node via a BAP signaling message.

26. A base station, comprising: At least one memory; and At least one processor, coupled to the at least one memory and configured such that the base station: Configuration information indicating a threshold associated with the data volume is transmitted to the communication device, wherein the congestion indication associated with the communication device is based on the sum of the first data volume of the RLC entity associated with the ingress radio link control (RLC) channel between the parent node of the communication device and the communication device, and the second data volume of the Backhaul Adaptation Protocol (BAP) entity associated with the ingress RLC channel, at the distributed unit (DU) of the communication device, satisfying the threshold.

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