A backhaul routing optimization method in a 5G IAB inactive state

Abstract

The present invention relates to a backhaul route optimization method in a 5G IAB inactive state, and belongs to the field of communication technology. The method includes: S1: IAB‑node‑MT initiates a recovery process; S2: performs IAB backhaul route optimization. The present invention proposes a method for processing IAB‑node‑MT in an RRC‑INACTIVE state in an IAB backhaul network structure. To solve the support for IAB‑node node mobility in 3GPP Rel‑18. In the IAB backhaul network architecture, if there is a node IAB‑node‑MT in an RRC‑INACTIVE state, the IAB‑donor‑CU will start a periodic backhaul route optimization timer, and the IAB‑donor‑CU periodically requests the IAB‑node‑MT to report measurements and execute the backhaul route optimization process.

Description

Technical Field

[0001] The present invention belongs to the field of communication technology and relates to a backhaul route optimization method in a 5G IAB inactive state. Background Art

[0002] Compared with Long Term Evolution (LTE), 5G NR supports massive antenna technology and multi-beam technology, so 5G NR can provide higher system rates, providing conditions for the development of 5G NR and IAB backhaul applications. The so-called Integrated Access and Backhaul (IAB) base station is a base station that integrates wireless access links and wireless backhaul links, where the wireless access link is the communication link between the UE and the IAB-node, and the wireless backhaul link is the communication link between the IAB-nodes, providing a data backhaul channel, so the IAB-node does not need a wired transmission network for data backhaul. Based on this, IAB-node is easier to deploy in dense scenarios, reducing the burden of deploying wired transmission networks.

[0003] IAB-node provides wireless access and wireless backhaul for user equipment (UE). IABdonor base station (belonging to IAB base station) provides wireless backhaul function to IAB-node and provides interface between UE and core network. Figure 1 and Figure 2 As shown in the figure, the IAB donor base station maintains a wired connection with the core network, and there is no wired connection between the IAB-node base station and the core network. The IAB-node is connected to the IAB donor base station through a wireless backhaul link, so that the UE is connected to the core network. The IAB-node will make necessary enhancements to the existing functions and interfaces of the NR, so the IAB-node also supports interfaces such as Uu, F1, E1, NG, and X2, and the IAB base station includes the functions of the gNB base station, called the cell IAB-DU (IAB-noded-DU) and the mobile terminal (Mobile-Termination, MT) function, called IAB-MT. Among them, the IAB-MT (IAB-node-MT) function is defined as a part of the mobile terminal function, integrated in the IAB base station, and connected to the AB donor base station or other IAB-nodes through a wireless backhaul link.

[0004] like Figure 2As shown, the IAB-node node consists of two parts, IAB-DU and IAB-MT, namely IAB-node-DU and IAB-node-MT. The child node IAB-node-MT communicates with the parent node IAB-node-DU through the Uu interface, and the IAB-node-DU communicates with the IAB-donor-CU through the F1 interface.

[0005] In all the above interfaces, Figure 3 The protocol stack of F1-U between IAB-DU and IAB-donor-CU-UP is shown. Figure 4 The protocol stack of F1-C between IAB-DU and IAB-donor-CU-CP is shown. F1-U and F1-C traffic is transmitted through two return hop nodes. The F1 interface needs to be protected.

[0006] In addition, a backhaul adaptation protocol (BAP) module is added to the IAB system structure of 5G NR, which mainly completes the following tasks: Figure 5 Function.

[0007] First: Determine if the packet has reached the BAP sublayer of the destination node, i.e., IAB-node or IAB-donorDU. This occurs if the BAP address in the packet's BAP header matches the BAP address configured via RRC on the IAB-node or via F1AP on the IAB-node.

[0008] Second: Determine the next hop node for packets that have not yet reached the destination. This applies to packets arriving from the previous hop on the BAP sublayer or packets received from the IP layer.

[0009] Its essence is to complete the backhaul routing function. This mapping relationship is configured by IAB-donorCU when the F1 interface is established.

[0010] Before the 3GPP Rel-17 version, the deployment of IAB-node was basically in a static state, that is, the deployment position of IAB-node in the IAB backhaul network structure would not change frequently. Therefore, if a wireless link failure occurs in the IAB-node child node, the backhaul route is rebuilt or the IAB-node CU initiates the reconfiguration of the backhaul route. In the 3GPP Rel-17 version, the backhaul route optimization is enhanced. In the Rel-18 version, the IAB-node mobile scenario requirements are also added, which puts higher requirements on the IAB backhaul network architecture. The present invention proposes a complete solution to the problems existing in the 3GPP Rel-17 backhaul route optimization and the IAB-node mobile requirements proposed in Rel-18. Summary of the invention

[0011] In view of this, an object of the present invention is to provide a backhaul route optimization method in a 5G IAB inactive state.

[0012] In order to achieve the above object, the present invention provides the following technical solutions:

[0013] A backhaul route optimization method in a 5G IAB inactive state, the method comprising the following steps:

[0014] S1: The IAB-node-MT in the RRC-INACTIVE state initiates the recovery process;

[0015] S2: IAB-donor starts the backhaul route optimization process.

[0016] Optionally, the S1 is specifically:

[0017] S11: The IAB-node-MT in the RRC-INACITVE state will periodically measure, interpret paging, and interpret the system message content broadcast by the serving cell IAB-node-DU according to the paging indication. The serving cell IAB-node-DU is also called the source cell IAB-node-DU. If the IAB-node-MT fails in interpreting the paging and system message, or the measurement of the serving cell IAB-node-DU does not meet the resident conditions, the IAB-node-MT immediately initiates a cell reselection process. If the cell reselection fails, the cell selection process is initiated to select a new serving cell IAB-node-DU node, also called the target cell IAB-node-DU.

[0018] During the cell reselection and selection process of IAB-node-MT, if the serving cell IAB-node-DU only meets the residency condition, that is, the cell is not prohibited and the received signal quality meets the residency requirement, then IAB-node-MT will not automatically select other IAB-node nodes;

[0019] S12: IAB-node-MT initiates an RRC recovery process on the target cell IAB-node-DU; first, the IAB-node-MT node initiates a random access process according to the system message parameters received from the target cell IAB-node-DU, and then reports an RRC recovery message;

[0020] S13: The target cell IAB-node-DU receives the RRC recovery message from the IAB-node-MT. If there is no F1 connection between the target IAB-node-DU and the IAB-donor-CU, the target cell IAB-node-DU requests the IAB-donor-CU to establish an F1 connection, and the target cell IAB-node-DU submits the RRC recovery message to the IAB-donor-CU node through the F1-C interface;

[0021] S14: After sending the RRC recovery message, the IAB-node-MT node immediately performs measurement reporting, reporting the cell information and measurement strength of the IAB-supporting cell measured in the RRC-INACTIVE state; the target cell IAB-node-DU node forwards the message to the IAB-donor-CU node;

[0022] S15: The IAB-donor-CU establishes a backhaul route for the IAB-node-MT node according to the current IAB backhaul network architecture and the load distribution of the entire IAB backhaul network. The IAB-donor-CU requires the IAB-node-MT to continue to reside in the target cell IAB-node-DU, or switch to other cell IAB-node-DU nodes according to the reported measurements;

[0023] S16: After the IAB-node-CU node completes the backhaul routing configuration for the IAB-node-MT node, it releases the backhaul routing path between the source cell IAB-node-DU and IAB-donor-CU, and releases the F1 interface between the source cell IAB-node-DU and IAB-donor-CU.

[0024] Optionally, S2 is specifically:

[0025] S21: IAB-donor-CU records whether there is an IAB-node-MT that has migrated to the RRC-INACTIVE state in the IAB backhaul network. If so, the backhaul route optimization timer, T-Route-Optimization-Timer, is started. When the timer times out, an IAB backhaul route optimization process is started, and the IAB-donor-CU requests the IAB-node-MT in the RRC-INACTIVE state to perform measurement reporting.

[0026] S22: IAB-node3 receives a paging request from IAB-donor-CU via the F1 interface, and IAB-node3 initiates a paging process via the serving cell IAB-node-DU;

[0027] S23: The IAB-node-MT of the IAB-node2 node and the IAB-node1 node receives the paging sent by the serving cell IAB-node-DU. After receiving the paging, the IAB-node-MT initiates the RRC connection establishment process;

[0028] S24: After the RRC signaling connection is established between the IAB-node-MT and the serving cell IAB-node-DU, the IAB-donor-CU initiates a measurement process; requests the IAB-node-MTs of the IAB-node1 and IAB-node2 nodes to report the measurement results;

[0029] S25: IAB-donor-CU optimizes the backhaul routes of IAB-node1 and IAB-node2 according to the current load of the IAB backhaul network and the measurement reports received from IAB-node1 and IAB-node2.

[0030] S26: IAB-donor-CU will eventually determine the best backhaul route for IAB-node1 and IAB-node2. If IAB-donor-CU provides a new backhaul route for IAB-node1 and IAB-node2, the old backhaul route will be released after the new backhaul route is established, and IAB-node-MT will be migrated to RRC-INACTIVE or RRC-CONNECTED state according to the service conditions of IAB-node1 and IAB-node2.

[0031] Optionally, S2 specifically includes: in the IAB backhaul network structure, the backhaul route optimization method application specifically includes scenario 1 and scenario 2;

[0032] Among them, the IAB backhaul network structure has 2 IAB-donors and 6 IAB-nodes; after power-on, there is a communication connection between IAB-donor1 and IAB-donor via path (1), which is the Xn interface defined in 3GPP; in addition, paths (2) to (7) indicate that there is an actual communication connection, and path (8) indicates that the IAB-node-MT of IAB-node5 can receive the signal sent by the IAB-node-DU of IAB-node2; path (9) indicates that the IAB-node-MT of IAB-node6 can receive the signal sent by the IAB-node-DU of IAB-node2;

[0033] Scenario 1: The IAB-node migrates within the same IAB-donor, i.e., the IAB-node6 RRC recovery connection process, IAB-node3 is the source serving cell IAB-node, and IAB-node2 is the target cell IAB-node;

[0034] Step 101: The IAB-node-MT of the IAB-node6 node in the RRC-INACTIVE state is performing periodic paging monitoring and measurement. If it is found that the serving cell IAB-node3 node is unavailable, the reason may be that the IAB-node3 node fails, the IAB-node3 node or the IAB-node6 node moves, resulting in the IAB-node6 node being out of the signal coverage of the IAB-node3 node; then the IAB-node-MT in the IAB-node6 node immediately initiates a cell reselection process or a cell selection process until the IAB-node6 node searches for the IAB-node2 node IAB-node-DU to send cell information;

[0035] As long as IAB-node2 is not prohibited and the quality of the signal received by IAB-node-MT from IAB-node2 meets the residency requirement, refer to 3GPP TS38.304 for details, IAB-node6 will not reselect to IAB-node2;

[0036] Step 102: the IAB-node-MT of the IAB-node6 node initiates a random access process on the new serving cell IAB-node2 node, and sends an RRC recovery message to the serving cell IAB-node2 node; if there is an F1 interface between the serving cell IAB-node2 node and IAB-donor2, the serving cell IAB-node2 sends RRCResumeRequest to the IAB-donor-CU of the IAB-donor2 node through the F1 interface;

[0037] Step 103: IAB-donor2 node IAB-donor-CU continues to wait for measurement information reported by IAB-node6 node; the measurement report includes the IAB cell identifier and signal strength that have been searched by IAB-node6 node during the cell search process;

[0038] Step 104: the IAB-donor-CU of IAB-donor2 will plan the backhaul route for the IAB-node6 node, and configure the IAB-node6 node backhaul route through the RRCReconfiguration message; in the scenario of this embodiment, the IAB-donor-CU of IAB-donor2 will configure the IAB-node2 node as the serving cell node of IAB-node6; and complete the establishment of the F1 interface between IAB-donor2 and IAB-node6;

[0039] Step 105: IAB-donor2 releases the original F1 connection between IAB-donor2 and IAB-node6, namely, path (4) and path (7); and according to the traffic situation of IAB-node6, migrates IAB-node-MT of IAB-node6 to RRC-CONNECTED or RRC-INACTIVE state;

[0040] Scenario 2: IAB-node migration within different IAB-donors, i.e., IAB-node5 RRC recovery connection process;

[0041] Step 201: During the periodic paging monitoring and measurement process, if the IAB-node-MT of the IAB-node5 node in the RRC-INACTIVE state finds that the serving cell IAB-node1 node is unavailable, the reason may be that the IAB-node1 node fails, the IAB-node1 or IAB-node5 node moves, resulting in the IAB-node5 node not being in the signal coverage of the serving cell IAB-node1 node; then the IAB-node-MT of the IAB-node6 node immediately initiates a cell reselection process or a cell selection process until the IAB-node5 node searches for the IAB-node2 node IAB-node-DU to send cell information;

[0042] Step 202: the IAB-node5 node IAB-node-MT initiates a random access process on the new serving cell IAB-node2 node, and sends an RRC recovery message to the serving cell IAB-node2 node; if there is an F1 interface between the serving cell IAB-node2 node and IAB-donor2, the serving cell IAB-node2 sends RRCResumeRequest to the IAB-donor-CU of the IAB-donor2 node through the F1 interface;

[0043] Step 203: IAB-node5 is not a lower-level branch node of IAB-donor2, so IAB-donor2 initiates a handover process to IAB-donor1, passes the parameters of IAB-node5 in IAB-donor1 to IAB-donor2, and IAB-donor2 completes the backhaul route planning of IAB-node5;

[0044] Step 204: the IAB-donor2 node IAB-donor-CU continues to wait for the measurement information reported by the IAB-node5 node. The measurement report includes the IAB cell identifier and signal strength that have been searched by the IAB-node5 during the cell search process.

[0045] Step 205: the IAB-donor-CU of IAB-donor2 will plan the backhaul route for the IAB-node5 node, and configure the IAB-node5 node backhaul route through the RRCReconfiguration message; in the scenario of the embodiment, the IAB-donor-CU of IAB-donor2 will configure the IAB-node2 node as the service target node of IAB-node5; and complete the establishment of the F1 interface between IAB-donor2 and IAB-node5;

[0046] Step 206: IAB-donor1 releases the original F1 connection between IAB-donor1 and IAB-node5, namely, the path (2) and the path (6); and IAB-donor2 migrates the IAB-node-MT of IAB-node5 to the RRC-CONNECTED or RRC-INACTIVE state according to the traffic of IAB-node5;

[0047] In addition to the above-discussed scenario where IAB-node5 and IAB-node6 reselect the new serving cell IAB-node-DU, IAB-donor-CU is triggered to adjust the backhaul route;

[0048] The periodic backhaul route optimization process is as follows:

[0049] Step 301: When the monitoring timer T-Route-Optimization-Timer of the IAB-donor-CU of the IAB-donor node times out, the IAB-donor-CU starts the backhaul route optimization process;

[0050] Step 302: The IAB-donor-CU requests the IAB-node-DU of the IAB-node3 to send a paging message through the F1 interface between the IAB-donor-CU and the IAB-node2;

[0051] Step 303: When the IAB-node-MT of IAB-node6 in RRC-INACTIVE receives paging, the RRC recovery process is initiated. In this step, the IAB-node-MT first initiates a random access process, then sends a RRCResumeRequest message, receives a RRCResume message, and finally recovers RRCResumeComplete; in the RRCResume message, the IAB-donor-CU requests the IAB-node-MT to report measurement information;

[0052] Step 304: IAB-node-MT reports the measurement result MeasurementReport message according to the request of IAB-donor-CU;

[0053] Step 305: The IAB-donor-CU node receives the measurement message reported by the IAB-node-MT, starts the backhaul route optimization algorithm process, and formulates the best backhaul route for the IAB-node6 node; if there are multiple IAB-nodes in RRC-INACTIVE state under the IAB-donor-CU node, the backhaul route optimization algorithm process is started only after the measurement reported by all IAB-node-MT nodes in RRC-INACTIVE state is collected;

[0054] Step 306: The IAB-donor-CU node reconfigures the backhaul route through the RRCReconfigure message; receiving the RRCReconfigureComplete message indicates that the reconfiguration is complete;

[0055] The message transmission between IAB-node3 and IAB-donor is completed through the F1-C interface between them.

[0056] The beneficial effects of the present invention are:

[0057] First: the present invention proposes a method for processing the IAB-node-MT in the RRC-INACTIVE state in the IAB backhaul network structure, so as to solve the problem of removing the support for IAB-node mobility in 3GPP Rel-18.

[0058] Second: In the prior art, for a terminal in the RRC-INACTIVE state, if the terminal or the network moves and the terminal resides in a new cell, and if the RNA (RAN-Based Notification Area) does not change, the terminal does not perform any processing and does not need to inform the network. According to the characteristics of IAB, the present invention proposes that as long as the IAB-node-MT reselects any new IAB-node-DU node, the RRC recovery establishment process is immediately started.

[0059] Third: During the RRC recovery and establishment process, the present invention requires the IAB-node-MT node to immediately perform measurement reporting to inform the IAB-donor-CU node of the wireless coverage around the IAB-node-MT, so that the IAB-donor-CU can configure the best backhaul route for the IAB-node-MT.

[0060] Fourth: In the IAB backhaul network architecture, there is an IAB-node node under the IAB-donor node. As long as there is a node IAB-node-MT in the RRC-INACTIVE state, the IAB-donor-CU will start a periodic backhaul route optimization timer. The IAB-donor-CU periodically requests the IAB-node-MT to report measurements and execute the backhaul route optimization process.

[0061] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0063] Figure 1 5G NR IAB system architecture;

[0064] Figure 2 The IAB backhaul network topology in 5G NR;

[0065] Figure 3 F1-U interface for 5G NR IAB;

[0066] Figure 4 F1-C interface for 5G NR IAB;

[0067] Figure 5 Backhaul routing and BH RLC channel selection on the BAP sublayer;

[0068] Figure 6 Initiate recovery process for IAB-node-MT;

[0069] Figure 7 Optimize the process of IAB-donor return routing;

[0070] Figure 8 Optimize the architecture of IAB backhaul network;

[0071] Fig. 9 Migrate IAB-node within the same IAB-donor;

[0072] Fig.10 Migrate IAB-node to different IAB-donors;

[0073] Fig.11 Periodic backhaul routing optimization process for IAB-donor. DETAILED DESCRIPTION

[0074] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and the features in the embodiments can be combined with each other without conflict.

[0075] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0076] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "rear", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances. Specific embodiments

[0078] In the IAB backhaul network, in order to save air wireless resources, when there is no data transmission between the IAB-node-MT and the serving cell IAB-node-DU for a long time, the IAB-node-MT can be migrated to the RRC-INACTIVE state. In this state, due to the movement of the IAB-node-MT node, the interpretation of the serving cell IAB-node-DU paging or system message fails, the serving cell IAB-node-DU measurement does not meet the residency requirement, or the IAB-node-MT is no longer in the serving cell IAB-node-DU coverage area. Then the IAB-node-MT immediately initiates the IAB-node-DU cell search process and initiates the recovery process on the IAB-node-DU cell that has been searched. Re-establish the F1 connection between its IAB-node-MT and IAB-donor-CU.

[0079] Among the IAB-node child nodes controlled by the IAB-donor-CU, if there is a node IAB-node-MT that migrates to the RRC-INACTIVE state, the IAB-donor-CU periodically requires all IAB-nodes that enter the RRC-INACTIVE state to perform measurement reporting, and the IAB-donor-CU performs backhaul route optimization operations based on the measurement reporting results.

[0080] In the present invention, the IAB-node in the RRC-INACTIVE state no longer supports the RNA (RAN-based Notification Area) update process, nor does it support the periodic RNA update process.

[0081] The recovery process initiated by IAB-node-MT in the present invention is as follows: Figure 6 As shown:

[0082] If there is no service transmission between IAB-node-MT and the serving cell IAB-node-DU (Source IAB-node-DU) for a long time, the IAB-donor-CU releases the RRC connection of IAB-node-MT through the serving cell IAB-node-DU and requires IAB-node-MT to enter the RRC-INACTIVE state. In this state, IAB-node-MT will periodically interpret paging, system messages and measurements.

[0083] Step 1: In the RRC-INACITVE state, the IAB-node-MT periodically performs measurements, interprets paging, and interprets the system message content broadcast by the serving cell IAB-node-DU according to the paging indication. In this state, if the IAB-node-MT interprets the paging, fails to interpret the system message, or the measurement of the serving cell IAB-node-DU does not meet the resident conditions, the IAB-node-MT immediately initiates the cell reselection process. If the cell reselection fails, the cell selection process is initiated to select a new IAB-node-DU cell, which is called the target cell IAB-node-DU (Target IAB-node-DU). Figure 6 Middle 1 step.

[0084] Further description, during the cell reselection and selection process performed by IAB-node-MT, as long as the serving cell IAB-node-DU meets the residence condition, that is, the cell is not prohibited and the received signal quality meets the residence requirement, the IAB-node-MT will not automatically select other IAB-node nodes.

[0085] Step 2: IAB-node-MT initiates the RRC recovery process on the target cell IAB-node-DU. First, IAB-node-MT initiates a random access process based on the received IAB-node-DU cell system message parameters, and then reports the RRC recovery message. Figure 6 Step 2 or 3.

[0086] Step 3: The target cell IAB-node-DU receives the RRC recovery message from the IAB-node-MT. If there is no F1 connection between the target cell IAB-node-DU and the IAB-donor-CU, the target cell IAB-node-DU requests the IAB-donor-CU to establish an F1 connection, and the target cell IAB-node-DU submits the RRC recovery message to the IAB-donor-CU node through the F1-C interface. Figure 6 Middle 4, 6 steps.

[0087] Step 4: After sending the RRC recovery message, IAB-node-MT immediately reports the measurement information and measurement strength of the IAB-supporting cell measured in the RRC-INACTIVE state. The target cell IAB-node-DU will forward the message to the IAB-donor-CU node. Figure 6 Steps 5 and 6.

[0088] Step 5: IAB-donor-CU establishes a backhaul route for IAB-node-MT based on the current IAB backhaul network architecture and the load distribution of the entire IAB backhaul network. IAB-donor-CU can request IAB-node-MT to continue to reside in the target cell IAB-node-DU, or switch to another cell IAB-node-DU based on the reported measurement. Figure 6 Steps 8, 9, 10, and 11.

[0089] Step 6: After the IAB-node-CU node completes the backhaul routing configuration for the IAB-node-MT node, it releases the backhaul routing path between the source service cell IAB-node-DU and IAB-donor-CU, and releases the F1 interface between the source service cell IAB-node-DU (Source IAB-node-DU) and IAB-donor-CU. Figure 6 12 steps in.

[0090] The above process completes the migration process of IAB-node-MT from the source service cell IAB-node-DU node to the target service cell IAB-node-DU node. IAB-donor-CU migrates IAB-node-MT to RRC-INACTIVE or RRC-CONNECTED state according to the service situation of IAB-node-MT.

[0091] The backhaul routing optimization process in the present invention is as follows: Figure 7 shown.

[0092] In the IAB backhaul network, the IAB-donor-CU controls multiple IAB-nodes, among which the IAB-node-MT of the IAB-node migrates to the RRC-INACTIVE state. Assume that there are three IAB-nodes under the IAB-donor, namely IAB-node1, IAB-node2 and IAB-node3. IAB-node1 and IAB-node2 migrate to the RRC-INACTIVE state.

[0093] Step 1: IAB-donor-CU records whether the subordinate node IAB-node-MT has migrated to the RRC-INACTIVE state. If so, it starts the backhaul route optimization timer, T-Route-Optimization-Timer. When the timer times out, a backhaul route optimization process is started. IAB-donor-CU requests the node that has entered the RRC-INACTIVE state to perform measurement reporting. Figure 7 Middle 1 step.

[0094] Step 2: IAB-node3 receives a request from IAB-donor-CU via the F1 interface, and IAB-node3 initiates a paging process via the serving cell IAB-node-DU. Figure 7 Steps 1 and 4.

[0095] Step 3: The IAB-node-MTs of IAB-node2 and IAB-node1 receive the paging sent by the serving cell IAB-node-DU and initiate the RRC connection establishment process. Figure 7 Medium 2,5 steps.

[0096] Step 4: After the RRC signaling connection between IAB-node-MT and serving cell IAB-node-DU is established, IAB-donor-CU initiates the measurement process. It requests IAB-node-MT of IAB-node1 and IAB-node2 to report the measurement results. Figure 7 Steps 3 and 6.

[0097] Step 5: IAB-donor-CU optimizes the backhaul routes of IAB-node1 and IAB-node2 according to the current load of the IAB backhaul network and the measurement reports received from IAB-node1 and IAB-node2. Figure 7 7 steps in.

[0098] Step 6: AB-donor-CU will calculate the final backhaul route and configure it to IAB-node1 and IAB-node2. If a new backhaul route is provided for IAB-node1 and IAB-node2, the old backhaul route will be released after the new backhaul route is established, and their IAB-node-MT will be migrated to RRC-INACTIVE or RRC-CONNECTED state according to the business conditions of IAB-node1 and IAB-node2. Figure 7 Middle 8 steps.

[0099] In order to more clearly illustrate the application of the present invention in a specific IAB backhaul network structure, as shown in FIG. Figure 8The following is an IAB application system architecture. In this system, there are 2 IAB-donors and 6 IAB-node devices. After the entire system is powered on, there is a path (1) connection between IAB-donor1 and IAB-donor, which is the Xn interface defined by 3GPP. In addition, paths (2) to (7) indicate that there is an actual connection. Path (8) indicates that the IAB-node-MT of IAB-node5 can receive the signal sent by the IAB-node-DU of IAB-node2. Path (9) indicates that the IAB-node-MT of IAB-node6 can receive the signal sent by the IAB-node-DU of IAB-node2.

[0100] exist Figure 8 In the IAB backhaul network architecture, since the IAB-node-DU of IAB-node5 and IAB-node6 has no data transmission for a long time, the IAB-node-DU of IAB-node1, the parent node of IAB-node5, requires the IAB-node-MT of IAB-node5 to enter the RRC-INACTIVE state; the IAB-node-DU of IAB-node3, the parent node of IAB-node6, requires the IAB-node-MT of IAB-node6 to enter the RRC-INACTIVE state.

[0101] According to 3GPP's requirements for IAB-node equipment, the IAB-node-MT in RRC-INACTIVE needs to perform paging monitoring and measurement, and interpret system messages as needed.

[0102] In this embodiment, there are two scene processings, and the following description uses scene 1 and scene 2 respectively.

[0103] Scenario 1: The IAB-node migrates within the same IAB-donor, i.e., the RRC recovery connection process of IAB-node6. In this scenario, IAB-node3 is the source IAB-node and also the serving IAB-node, and IAB-node2 is the target IAB-node.

[0104] Step 1: The IAB-node-MT of IAB-node6 in RRC-INACTIVE state finds that the service node IAB-node3 is unavailable during periodic paging monitoring and measurement. The reason may be that IAB-node3 fails, IAB-node3 or IAB-node6 moves, resulting in IAB-node6 not being in the signal coverage of IAB-node3. Then the IAB-node-MT of IAB-node6 immediately initiates a cell reselection process or a cell selection process until IAB-node6 searches for IAB-node2 and IAB-node-DU sends cell information. Fig. 9 Middle 1 step.

[0105] In this embodiment, as long as IAB-node2 is not prohibited and the quality of the signal received by IAB-node6 IAB-node-MT from IAB-node2 meets the residency requirement, refer to 3GPP TS38.304 for details, IAB-node6 will not reselect to IAB-node2.

[0106] Step 2: IAB-node6 IAB-node-MT initiates a random access process on IAB-node2 and sends an RRC recovery message (RRCResumeRequest) to IAB-node2. If there is an F1 interface between IAB-node2 and IAB-donor2, IAB-node2 sends RRCResumeRequest to IAB-donor-CU of IAB-donor2 through the F1 interface. Fig. 9 Steps 2, 3, 4.

[0107] Step 3: IAB-donor2 node IAB-donor-CU continues to wait for the measurement information (measurementReport) reported by IAB-node6. The measurement report contains the IAB node identifier and signal strength that IAB-node6 has searched for during the cell search process. Fig. 9 Steps 5 and 6.

[0108] Step 4: The IAB-donor-CU of IAB-donor2 plans the backhaul route of IAB-node6 and configures the backhaul route of IAB-node6 through the RRCReconfiguration message. In the scenario of the embodiment, the IAB-donor-CU of IAB-donor2 configures IAB-node2 as the target node of IAB-node6. The F1 interface is established between IAB-donor2 and IAB-node6. Fig. 9 Steps 8, 9, 10, and 11.

[0109] Step 5: IAB-donor2 releases the original F1 connection between IAB-donor2 and IAB-node6, namely, the path (4) and path (7). And according to the traffic of IAB-node6, IAB-node-MT of IAB-node6 is put into RRC-CONNECTED or RRC-INACTIVE state. Fig. 9 12 steps in.

[0110] Scenario 2: IAB-node migration within different IAB-donors, that is, the RRC recovery connection process of IAB-node5.

[0111] Step 1: The IAB-node-MT of IAB-node5 in RRC-INACTIVE state performs periodic paging monitoring and measurement and finds that the service node IAB-node1 is unavailable. The reason may be that IAB-node1 fails, IAB-node1 or IAB-node5 moves, resulting in IAB-node5 not being in the signal coverage of IAB-node1. Then the IAB-node-MT of IAB-node6 immediately initiates a cell reselection process or a cell selection process until IAB-node5 searches for IAB-node2 and IAB-node-DU sends cell information. Fig.10 Middle 1 step.

[0112] In this embodiment, as long as IAB-node1 is not prohibited and the quality of the signal received by IAB-node5 and IAB-node-MT from IAB-node1 meets the residency requirement, refer to 3GPP TS38.304 for details, IAB-node6 will not reselect to IAB-node2.

[0113] Step 2: IAB-node5 IAB-node-MT initiates a random access process on IAB-node2 and sends an RRC recovery message (RRCResumeRequest) to IAB-node2. If there is an F1 interface between IAB-node2 and IAB-donor2, IAB-node2 sends RRCResumeRequest to IAB-donor-CU of IAB-donor2 through the F1 interface. Fig.10 Steps 2, 3, 4.

[0114] Step 3: If IAB-node5 is not the IAB-donor2 control node, IAB-donor2 initiates a handover process to IAB-donor1, passes the parameters of IAB-node5 in IAB-donor1 to IAB-donor2, and IAB-donor2 completes the backhaul route planning of IAB-node5. Fig.10 Middle 4 steps.

[0115] Step 4: IAB-donor2 node IAB-donor-CU continues to wait for the measurement information (measurementReport) reported by IAB-node5. The measurement report contains the IAB node identifier and signal strength that IAB-node5 has searched for during the cell search process. Fig.10 Steps 5 and 6.

[0116] Step 5: The IAB-donor-CU of IAB-donor2 plans the backhaul route of IAB-node5 and configures the backhaul route of IAB-node5 through the RRCReconfiguration message. In the scenario of the embodiment, the IAB-donor-CU of IAB-donor2 configures IAB-node2 as the target node of IAB-node5. The F1 interface is established between IAB-donor2 and IAB-node5. Fig.10 Steps 8, 9, 10, and 11.

[0117] Step 6: IAB-donor1 releases the original F1 connection between IAB-donor1 and IAB-node5, that is, the path (2) and path (6). IAB-donor2 also sets the IAB-node-MT of IAB-node5 to RRC-CONNECTED or RRC-INACTIVE state according to the traffic of IAB-node5. Fig.10 12 steps in.

[0118] In this embodiment, in addition to the above-discussed scenario where IAB-node5 and IAB-node6 reselect a new IAB-node-DU, the IAB-donor-CU is triggered to adjust the backhaul route. The following describes the periodic backhaul route optimization process in this embodiment. In this embodiment, the processing methods of IAB-node5 and IAB-node6 are the same, and IAB-node6 will be used as an example for description.

[0119] Step 1: When the monitoring timer T-Route-Optimization-Timer of the IAB-donor-CU of the IAB-donor node times out, the IAB-donor-CU starts the backhaul route optimization process. Fig.11 Middle 1 step.

[0120] Step 2: IAB-donor-CU requests IAB-node-DU of IAB-node3 to send a paging message through the F1 interface between IAB-node2 and IAB-node3. Fig.11 Step 2 or 3.

[0121] Step 3: When the IAB-node-MT of the IAB-node6 node in RRC-INACTIVE receives the paging, it initiates the RRC recovery process. In this step, the IAB-node-MT first initiates the random access process, then sends the RRCResumeRequest message, receives the RRCResume message, and finally recovers the RRCResumeComplete. In the RRCResume message, the IAB-donor-CU requests the IAB-node-MT to report the measurement information. Fig.11 Steps 4, 5, 6, 7, 8, 9.

[0122] Step 4: IAB-node-MT reports the measurement result MeasurementReport message according to the request of IAB-donor-CU. Fig.11 Steps 10 and 11.

[0123] Step 5: The IAB-donor-CU node receives the measurement message reported by the IAB-node-MT, starts the backhaul route optimization algorithm process, and formulates the best backhaul route for the IAB-node6 node. If there are multiple IAB-nodes in RRC-INACTIVE state under the IAB-donor-CU node, the backhaul route optimization algorithm process is started only after the measurement reported by all IAB-node-MT nodes in RRC-INACTIVE state are collected. Fig.11 12 steps in.

[0124] Step 6: The IAB-donor-CU node reconfigures the backhaul route through the RRCReconfigure message. Receiving the RRCReconfigureComplete message indicates that the reconfiguration is complete.

[0125] In this solution, the message transmission between IAB-node3 and IAB-donor is completed through the F1-C interface between them.

[0126] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A backhaul route optimization method in a 5G IAB inactive state, characterized in that: The method comprises the following steps: S1: The IAB-node-MT in the RRC-INACTIVE state initiates the recovery process; S2: IAB-donor starts the backhaul route optimization process; The S1 is specifically: S11: The IAB-node-MT in the RRC-INACITVE state will periodically measure, interpret paging, and interpret the system message content broadcast by the serving cell IAB-node-DU according to the paging indication. The serving cell IAB-node-DU is also called the source cell IAB-node-DU. If the IAB-node-MT fails in interpreting the paging and system message, or the measurement of the serving cell IAB-node-DU does not meet the resident conditions, the IAB-node-MT immediately initiates a cell reselection process. If the cell reselection fails, the cell selection process is initiated to select a new serving cell IAB-node-DU node, also called the target cell IAB-node-DU. During the cell reselection and selection process of IAB-node-MT, if the serving cell IAB-node-DU only meets the residency condition, that is, the cell is not prohibited and the received signal quality meets the residency requirement, then IAB-node-MT will not automatically select other IAB-node nodes; S12: IAB-node-MT initiates an RRC recovery process on the target cell IAB-node-DU; first, the IAB-node-MT node initiates a random access process according to the system message parameters received from the target cell IAB-node-DU, and then reports an RRC recovery message; S13: The target cell IAB-node-DU receives the RRC recovery message from the IAB-node-MT. If there is no F1 connection between the target IAB-node-DU and the IAB-donor-CU, the target cell IAB-node-DU requests the IAB-donor-CU to establish an F1 connection, and the target cell IAB-node-DU submits the RRC recovery message to the IAB-donor-CU node through the F1-C interface; S14: After sending the RRC recovery message, the IAB-node-MT node immediately performs measurement reporting, reporting the cell information and measurement strength of the IAB-supporting cell measured in the RRC-INACTIVE state; the target cell IAB-node-DU node forwards the message to the IAB-donor-CU node; S15: The IAB-donor-CU establishes a backhaul route for the IAB-node-MT node according to the current IAB backhaul network architecture and the load distribution of the entire IAB backhaul network. The IAB-donor-CU requires the IAB-node-MT to continue to reside in the target cell IAB-node-DU, or switch to other cell IAB-node-DU nodes according to the reported measurements; S16: After the IAB-node-CU node completes the backhaul routing configuration for the IAB-node-MT node, it releases the backhaul routing path between the source cell IAB-node-DU and the IAB-donor-CU, and releases the F1 interface between the source cell IAB-node-DU and the IAB-donor-CU; The S2 is specifically: S21: IAB-donor-CU records whether there is an IAB-node-MT that has migrated to the RRC-INACTIVE state in the IAB backhaul network. If so, the backhaul route optimization timer, T-Route-Optimization-Timer, is started. When the timer times out, an IAB backhaul route optimization process is started, and the IAB-donor-CU requests the IAB-node-MT in the RRC-INACTIVE state to perform measurement reporting. S22: IAB-node3 receives a paging request from IAB-donor-CU via the F1 interface, and IAB-node3 initiates a paging process via the serving cell IAB-node-DU; S23: The IAB-node-MTs of the IAB-node2 and IAB-node1 nodes receive paging sent by the serving cell IAB-node-DU; after receiving the paging, the IAB-node-MT initiates an RRC connection establishment process; S24: After the RRC signaling connection is established between the IAB-node-MT and the serving cell IAB-node-DU, the IAB-donor-CU initiates a measurement process; requests the IAB-node-MTs of the IAB-node1 and IAB-node2 nodes to report the measurement results; S25: IAB-donor-CU optimizes the backhaul routes of IAB-node1 and IAB-node2 according to the current load of the IAB backhaul network and the measurement reports received from IAB-node1 and IAB-node2. S26: IAB-donor-CU will eventually determine the best backhaul route for IAB-node1 and IAB-node2. If IAB-donor-CU provides a new backhaul route for IAB-node1 and IAB-node2, the old backhaul route will be released after the new backhaul route is established, and IAB-node-MT will be migrated to RRC-INACTIVE or RRC-CONNECTED state according to the service conditions of IAB-node1 and IAB-node2.

2. According to claim 1, a backhaul route optimization method in a 5G IAB inactive state is characterized in that: The S2 specifically includes: the backhaul route optimization method is applied in the IAB backhaul network structure, specifically including scenario 1 and scenario 2; Among them, the IAB backhaul network structure has 2 IAB-donors and 6 IAB-nodes. After power-on, there is a path (1) between IAB-donor1 and IAB-donor for communication connection, that is, the Xn interface defined in 3GPP is used for communication connection. In addition, paths (2) to (7) indicate that there is an actual communication connection. Path (8) indicates that the IAB-node-MT of IAB-node5 can receive the signal sent by the IAB-node-DU of IAB-node2. Path (9) indicates that the IAB-node-MT of IAB-node6 can receive the signal sent by the IAB-node-DU of IAB-node2. Scenario 1: The IAB-node migrates within the same IAB-donor, i.e., the IAB-node6 RRC recovery connection process, IAB-node3 is the source serving cell IAB-node, and IAB-node2 is the target cell IAB-node; Step 101: The IAB-node-MT of the IAB-node6 node in the RRC-INACTIVE state is performing periodic paging monitoring and measurement processes; if it is found that the serving cell IAB-node3 node is unavailable, the reason is that the IAB-node3 node fails, the IAB-node3 node or the IAB-node6 node moves, resulting in the IAB-node6 node being out of the signal coverage of the IAB-node3 node; then the IAB-node-MT in the IAB-node6 node immediately initiates a cell reselection process or a cell selection process until the IAB-node6 node searches for the IAB-node2 node IAB-node-DU to send cell information; As long as IAB-node2 is not prohibited and the quality of the signal from IAB-node2 received by IAB-node-MT of IAB-node6 meets the residency requirement, IAB-node6 will not reselect to IAB-node2. Step 102: the IAB-node-MT of the IAB-node6 node initiates a random access process on the new serving cell IAB-node2 node, and sends an RRC recovery message to the serving cell IAB-node2 node; if there is an F1 interface between the serving cell IAB-node2 node and IAB-donor2, the serving cell IAB-node2 sends RRCResumeRequest to the IAB-donor-CU of the IAB-donor2 node through the F1 interface; Step 103: IAB-donor2 node IAB-donor-CU continues to wait for measurement information reported by IAB-node6 node; the measurement report includes the IAB cell identifier and signal strength that have been searched by IAB-node6 node during the cell search process; Step 104: the IAB-donor-CU of IAB-donor2 will plan the backhaul route for the IAB-node6 node, and configure the IAB-node6 node backhaul route through the RRCReconfiguration message; the IAB-donor-CU of IAB-donor2 will configure the IAB-node2 node as the serving cell node of IAB-node6; and complete the establishment of the F1 interface between IAB-donor2 and IAB-node6; Step 105: IAB-donor2 releases the original F1 connection between IAB-donor2 and IAB-node6, namely, path (4) and path (7); and according to the traffic situation of IAB-node6, migrates IAB-node-MT of IAB-node6 to RRC-CONNECTED or RRC-INACTIVE state; Scenario 2: IAB-node migration within different IAB-donors, i.e., IAB-node5 RRC recovery connection process; Step 201: During the periodic paging monitoring and measurement process, if the IAB-node-MT of the IAB-node5 node in the RRC-INACTIVE state finds that the serving cell IAB-node1 node is unavailable, the reason may be that the IAB-node1 node fails, the IAB-node1 or IAB-node5 node moves, resulting in the IAB-node5 node not being in the signal coverage of the serving cell IAB-node1 node; then the IAB-node-MT of the IAB-node6 node immediately initiates a cell reselection process or a cell selection process until the IAB-node5 node searches for the IAB-node2 node IAB-node-DU to send cell information; Step 202: the IAB-node5 node IAB-node-MT initiates a random access process on the new serving cell IAB-node2 node, and sends an RRC recovery message to the serving cell IAB-node2 node; if there is an F1 interface between the serving cell IAB-node2 node and IAB-donor2, the serving cell IAB-node2 sends RRCResumeRequest to the IAB-donor-CU of the IAB-donor2 node through the F1 interface; Step 203: IAB-node5 is not a lower-level branch node of IAB-donor2, so IAB-donor2 initiates a handover process to IAB-donor1, passes the parameters of IAB-node5 in IAB-donor1 to IAB-donor2, and IAB-donor2 completes the backhaul route planning of IAB-node5; Step 204: the IAB-donor2 node IAB-donor-CU continues to wait for the measurement information reported by the IAB-node5 node. The measurement report includes the IAB cell identifier and signal strength that have been searched by the IAB-node5 during the cell search process. Step 205: the IAB-donor-CU of IAB-donor2 will plan the backhaul route for the IAB-node5 node, and configure the IAB-node5 node backhaul route through the RRCReconfiguration message; the IAB-donor-CU of IAB-donor2 will configure the IAB-node2 node as the service target node of IAB-node5; and the F1 interface is established between IAB-donor2 and IAB-node5; Step 206: IAB-donor1 releases the original F1 connection between IAB-donor1 and IAB-node5, namely, the path (2) and the path (6); and IAB-donor2 migrates the IAB-node-MT of IAB-node5 to the RRC-CONNECTED or RRC-INACTIVE state according to the traffic of IAB-node5. In addition to the scenarios mentioned in scenarios 1 and 2 where IAB-node5 and IAB-node6 reselect the new serving cell IAB-node-DU, triggering IAB-donor-CU will adjust the backhaul route; The periodic backhaul route optimization process is as follows: Step 301: When the monitoring timer T-Route-Optimization-Timer of the IAB-donor-CU of the IAB-donor node times out, the IAB-donor-CU starts the backhaul route optimization process; Step 302: The IAB-donor-CU requests the IAB-node-DU of the IAB-node3 to send a paging message through the F1 interface between the IAB-donor-CU and the IAB-node2; Step 303: When the IAB-node-MT of IAB-node6 in RRC-INACTIVE receives paging, the RRC recovery process is initiated. In this step, the IAB-node-MT first initiates a random access process, then sends a RRCResumeRequest message, receives a RRCResume message, and finally recovers RRCResumeComplete; in the RRCResume message, the IAB-donor-CU requests the IAB-node-MT to report measurement information; Step 304: IAB-node-MT reports the measurement result MeasurementReport message according to the request of IAB-donor-CU; Step 305: The IAB-donor-CU node receives the measurement message reported by the IAB-node-MT, starts the backhaul route optimization algorithm process, and formulates the best backhaul route for the IAB-node6 node; if there are multiple IAB-nodes in RRC-INACTIVE state under the IAB-donor-CU node, the backhaul route optimization algorithm process is started only after the measurement reported by all IAB-node-MT nodes in RRC-INACTIVE state is collected; Step 306: The IAB-donor-CU node reconfigures the backhaul route through the RRCReconfigure message; receiving the RRCReconfigureComplete message indicates that the reconfiguration is complete; The message transmission between IAB-node3 and IAB-donor is completed through the F1-C interface between them.

Images