CN114786210A

CN114786210A - Return route optimization method in 5G IAB non-activated state

Info

Publication number: CN114786210A
Application number: CN202210424557.2A
Authority: CN
Inventors: 段红光; 罗一静; 毛翔宇; 郑建宏
Original assignee: Chongqing University of Post and Telecommunications
Current assignee: Chongqing University of Post and Telecommunications
Priority date: 2022-04-21
Filing date: 2022-04-21
Publication date: 2022-07-22

Abstract

The invention relates to a return route optimization method in a 5G IAB (inter-integrated access point) inactive state, belonging to the technical field of communication. The method comprises the following steps: s1: initiating a recovery flow by the IAB-node-MT; s2: and carrying out IAB backhaul route optimization. The invention provides an IAB-node-MT processing method in an RRC-INACTIVE state in an IAB backhaul network structure. To address the support for IAB-node mobility in 3gpp rel-18. In the IAB return network architecture, if the node IAB-node-MT is in an RRC-INACTIVE state, the IAB-node-CU starts a periodic return route optimization timer, periodically requests the IAB-node-MT to report measurement, and executes a return route optimization process.

Description

Return route optimization method under 5G IAB non-activated state

Technical Field

The invention belongs to the technical field of communication, and relates to a return route optimization method in a 5G IAB (inter-integrated access bus) inactive state.

Background

Compared with Long Term Evolution (LTE), the 5G NR supports a large-scale antenna technology and a multi-beam technology, and therefore the 5G NR can provide a higher system rate and provide conditions for 5G NR development and IAB backhaul application. An Integrated Access and Backhaul (IAB) base station is an Integrated Access link and a wireless Backhaul link Integrated with the base station, where the wireless Access link is a communication link between UE and an IAB-node, and the wireless Backhaul link is a communication link between the IAB-node, and provides a data Backhaul channel, so that the IAB-node does not need a wired transmission network for data Backhaul. Based on the method, the IAB-node is easier to deploy in a dense scene, and the burden of deploying a wired transmission network is reduced.

The IAB-node provides wireless access and service wireless backhaul for User Equipment (UE). The IAB donor base station (home IAB base station) provides a wireless return function for the IAB-node and provides an interface between the UE and the core network. As shown in fig. 1 and fig. 2, the IAB donor base station is in wired connection with the core network, the IAB-node base station is not in wired connection with the core network, and 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 perform necessary enhancements on the existing functions and interfaces of NR, so the IAB-node also supports the interfaces Uu, F1, E1, NG, X2, etc., and the IAB base station includes the functions of the gNB base station, called cell IAB-DU (IAB-node-DU) and Mobile Terminal (MT) functions, called IAB-MT. The IAB-MT (IAB-node-MT) function is defined as a part of the function of the mobile terminal, is integrated in the IAB base station, and is connected with the AB node base station or other IAB-nodes through the wireless backhaul link.

As shown in FIG. 2, an IAB-node is composed of two parts, IAB-DU and IAB-MT, namely IAB-node-DU and IAB-node-MT. The IAB-node-MT and the IAB-node-DU of the father node are communicated through a Uu interface, and the IAB-node-DU and the IAB-node-CU are communicated through an F1 interface.

In all of the above interfaces, FIG. 3 shows the protocol stack of F1-U between IAB-DU and IAB-denor-CU-UP, and FIG. 4 shows the protocol stack of F1-C between IAB-DU and IAB-denor-CU-CP. F1-U and F1-C traffic is transmitted over two backhaul hop nodes. The F1 interface requires security.

In addition, in the IAB system structure of the 5G NR, a Backhaul Adaptation Protocol (BAP) module is added, and the functions as shown in fig. 5 are mainly completed.

Firstly, the method comprises the following steps: it is determined whether the packet has reached the BAP sublayer of the destination node, i.e. the IAB-node or IAB-donor DU. This may occur if the BAP address in the packet BAP header matches a BAP address configured by RRC on IAB-node or by F1AP on IAB-node.

Secondly, the method comprises the following steps: the next hop node of a packet that has not yet reached the destination is determined. This applies to packets arriving from a previous hop on the BAP sublayer or to packets received from the IP layer.

The essence of the method is to complete the return routing function, and the mapping relation is configured and completed by the IAB-donor CU when the F1 interface is established.

Before the 3GPP Rel-17 release, the deployment of IAB-nodes is basically in a static state, i.e. the deployment location of IAB-nodes in the IAB backhaul network structure does not change frequently. Therefore, if the radio link failure occurs in the IAB-node child node, the return routing reconfiguration is re-established or initiated by the IAB-node CU. Backhaul route optimization is enhanced in 3GPP Rel-17 release. The requirement of an IAB-node mobile scene is increased in the Rel-18 version, which puts higher requirements on an IAB backhaul network architecture. The invention provides a complete solution for solving the problems existing in the 3GPP Rel-17 return route optimization and the IAB-node moving requirement provided by Rel-18.

Disclosure of Invention

In view of this, the present invention provides a backhaul route optimization method in a 5G IAB inactive state.

In order to achieve the purpose, the invention provides the following technical scheme:

a return route optimization method under a 5G IAB inactive state comprises the following steps:

s1: initiating a recovery flow by the IAB-node-MT in an RRC-INACTIVE state;

s2: the IAB-donor initiates the backhaul route optimization process.

Optionally, the S1 specifically includes:

s11: the IAB-node-MT in the RRC-INVITVE state periodically measures, decodes paging and decodes the system message content broadcasted by the service cell IAB-node-DU according to the paging indication, wherein the service cell IAB-node-DU is also called as source cell IAB-node-DU; if the IAB-node-MT is reading paging and reading system message process fails or the service cell IAB-node-DU measurement does not meet the resident condition, the IAB-node-MT immediately initiates a cell reselection process, if the cell reselection fails, the IAB-node-DU measurement initiates a cell selection process, and a new service cell IAB-node-DU node is selected, which is also called a target cell IAB-node-DU;

in the process of cell reselection and selection of the IAB-node-MT, the IAB-node-DU of the service cell only meets the residence condition, namely the cell is not forbidden, and the received signal quality meets the residence requirement, the IAB-node-MT does not automatically select other IAB-node nodes;

s12: the IAB-node-MT initiates an RRC recovery process on an IAB-node-DU of a target cell; firstly, an IAB-node-MT node initiates a random access process according to system message parameters of an IAB-node-DU received from a target cell, 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 the F1 connection does not exist between the target IAB-node-DU and the IAB-node-CU, the target cell IAB-node-DU requests the IAB-node-CU to establish the F1 connection, and the RRC recovery message is submitted to the IAB-node-CU node through an F1-C interface in the target cell IAB-node-DU;

s14: after the IAB-node-MT node sends an RRC recovery message, immediately performing measurement report, and measuring cell information and measurement strength of a cell supporting the IAB in an RRC-INACTIVE state; the target cell IAB-node-DU node forwards the message to the IAB-node-CU node;

s15: the IAB-node-CU establishes a return route for the IAB-node-MT node according to the current IAB return network architecture and the whole IAB return network load distribution condition, and the IAB-node-CU requires the IAB-node-MT to continuously reside in the target cell IAB-node-DU or switch to other cell IAB-node-DU nodes according to the reported measurement;

s16: after the IAB-node-CU node completes the return route configuration of the IAB-node-MT node, the return route channel between the source cell IAB-node-DU and the IAB-node-CU is released, and the F1 interface between the source cell IAB-node-DU and the IAB-node-CU is released.

Optionally, the S2 specifically includes:

s21: the IAB-donor-CU records whether an IAB-node-MT migrating to the RRC-ACTIVE state exists in the IAB return network, and if yes, a return Route Optimization Timer, T-Route-Optimization-Timer, is started; when the timer is overtime, starting an IAB (inter-integrated access bus) return route optimization process, and enabling the IAB-donor-CU to measure and report the IAB-node-MT which requests to be in the RRC-INACTIVE state;

s22: through an F1 interface, an IAB-node3 node receives a paging request from an IAB-node-CU, and then the IAB-node3 node initiates a paging process through an IAB-node-DU of a service cell;

s23: the IAB-node-MTs of the IAB-node2 node and the IAB-node1 node receive pages sent by the serving cell IAB-node-DU. After receiving the paging, the IAB-node-MT initiates an RRC connection establishment process;

s24: after RRC signaling connection is established between the IAB-node-MT and the service cell IAB-node-DU, the IAB-node-CU initiates a measurement process; requesting IAB-node-MTs of an IAB-node1 node and an IAB-node2 node to report measurement results;

s25: the IAB-node-CU optimizes the return routes of the IAB-node1 and the IAB-node2 according to the load condition of the current IAB return network and the measurement reports of the IAB-node1 node and the IAB-node2 node;

s26: the IAB-donor-CU finally determines the optimal return route of the IAB-node1 node and the IAB-node2 node, if the IAB-donor-CU is the IAB-node1 node and the IAB-node2 node provides a new return route, the old return route is released after the new return route is established, and the IAB-node-MT is moved to the RRC-INACTIVE state or the RRC-CONNECTED state according to the service conditions of the IAB-node1 node and the IAB-node2 node.

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

the IAB backhaul network structure comprises 2 IAB-donors and 6 IAB-node nodes; after power-on, a path (1) communication connection exists between the IAB-donor1 and the IAB-donor, namely, an Xn interface in the definition of 3 GPP; paths (2) to (7) indicate that an actual communication connection exists, and path (8) indicates that the IAB-node-MT of IAB-node5 node can receive a signal transmitted from the IAB-node-DU of IAB-node2 node; path (9) indicates that the IAB-node-MT of IAB-node6 node can receive the signal sent by the IAB-node-DU from IAB-node 2;

scene 1: the IAB-node nodes migrate in the same IAB-node, namely an RRC (radio resource control) connection recovery process of the IAB-node6 node, wherein the IAB-node3 is an IAB-node of a source service cell, and the IAB-node2 is an IAB-node of a target cell;

step 101: the IAB-node-MT of the IAB-node6 node in RRC-INACTIVE state is performing periodic paging listening and measurement procedures. If the service cell IAB-node3 node is found to be unavailable, the reason may be that the IAB-node3 node fails, and the IAB-node3 node or the IAB-node6 node moves, so that the IAB-node6 node is not in the signal coverage of the IAB-node3 node; the IAB-node-MT in the IAB-node6 immediately initiates a cell reselection process or a cell selection process until the IAB-node6 searches the IAB-node2 node, namely the IAB-node-DU sends cell information;

as long as the IAB-node2 node is not prohibited and the quality of a signal received by IAB-node2 by IAB-node6 node IAB-node-MT meets the camping requirement, specifically referring to 3GPP TS38.304, IAB-node6 does not reselect the IAB-node2 node;

step 102: the IAB-node-MT of the IAB-node6 node initiates a random access process on an IAB-node2 node of a new serving cell and sends an RRC recovery message to an IAB-node2 node of the serving cell; if an F1 interface exists between the IAB-node2 node of the serving cell and IAB-node2, the IAB-node2 sends RRCResuRequest to an IAB-node-CU of an IAB-node2 node through the F1 interface;

step 103: the IAB-node2 node IAB-node CU continues to wait for the measurement information reported by the IAB-node6 node; the measurement report comprises the IAB cell identifier and the signal strength which are searched in the process of searching the cell by the IAB-node6 node;

step 104: the IAB-donor-CU of the IAB-donor2 plans the return route for the IAB-node6 node, and configures the return route for the IAB-node6 node through the RRCRECONFIGULIZATION message; in the scenario of this embodiment, the IAB-donor-CU of the IAB-donor2 configures the IAB-node2 node as the serving cell node of the IAB-node 6; and completing establishing an F1 interface between the IAB-donor2 and the IAB-node 6;

step 105: IAB-donor2 releases the F1 connection between IAB-donor2 and IAB-node6 node, namely path (4) and path (7) path; and according to the traffic volume of the IAB-node6 node, the IAB-node-MT of the IAB-node6 node is transferred to an RRC-CONNECTED or RRC-INACTIVE state;

scene 2: the IAB-node migrates in different IAB-donors, namely the RRC connection recovery process of the IAB-node5 node;

step 201: in the process of periodic paging monitoring and measurement, if the IAB-node-MT of the IAB-node5 node in the RRC-INACTIVE state is found out that the IAB-node1 node in the serving cell is unavailable, the reason may be that the IAB-node1 node fails, and the position of the IAB-node1 or the IAB-node5 node moves, so that the IAB-node5 node is not in the signal coverage area of the IAB-node1 node in the serving cell; 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 the IAB-node2 node, and the IAB-node-DU sends cell information;

step 202: the IAB-node5 node IAB-node-MT initiates a random access process on a new service cell IAB-node2 node, and sends an RRC recovery message to a service cell IAB-node2 node; if an F1 interface exists between the serving cell IAB-node2 node and IAB-donor2, the serving cell IAB-node2 sends RRCResumRequest to the IAB-donor-CU of the IAB-donor2 node through the F1 interface;

step 203: the IAB-node5 node is not an IAB-node2 subordinate branch node, the IAB-node2 node initiates a switching process to the IAB-node1 node, the parameters of the IAB-node5 node in the IAB-node1 node are transmitted to the IAB-node2 node, and the IAB-node2 node completes routing back of the IAB-node5 node;

step 204: the IAB-node2 node IAB-node-CU continues waiting for the measurement information reported by the IAB-node5 node, wherein the measurement report comprises the IAB cell identifier and the signal strength which are searched in the process of searching the cell by the IAB-node 5;

step 205: an IAB-donor-CU of the IAB-donor2 carries out return route planning for the IAB-node5 node and configures a return route of the IAB-node5 node through an RRCRECONfigure message; in the scenario of an embodiment, the IAB-donor-CU of IAB-donor2 will configure IAB-node2 node as the serving target node of IAB-node 5; completing the establishment of an F1 interface between the IAB-donor2 and the IAB-node 5;

step 206: IAB-donor1 releases the F1 connection between IAB-donor1 and IAB-node5, namely the path (2) and the path (6); and the IAB-donor2 transfers the IAB-node-MT of the IAB-node5 node to RRC-CONNECTED or RRC-INACTIVE state according to the traffic volume of the IAB-node5 node;

in addition to the above discussion, the IAB-node5 node and the IAB-node6 node reselect and select an IAB-node-DU scene of a new serving cell, and trigger the IAB-node-CU to perform return route adjustment;

the periodic return route optimization process comprises the following steps:

step 301: if the monitoring Timer T-Route-Optimization-Timer of the IAB-denor-CU of the IAB-denor node is overtime, the IAB-denor-CU starts a return Route Optimization process;

step 302: the IAB-node-CU requests the IAB-node-DU of the IAB-node3 to send a paging message through an F1 interface between the IAB-node-CU and the IAB-node 2;

step 303: the IAB-node-MT of the IAB-node6 in the RRC-INACTIVE receives the paging, then initiates an RRC recovery process, in the step, the IAB-node-MT firstly initiates a random access process, then sends an RRCResuRequest message, receives the RRCResume message, and finally recovers the RRCResuComplete; in the RRCRESume message, the IAB-donor-CU requests the IAB-node-MT to report the measurement information;

step 304: the IAB-node-MT reports a measurement result MeasurementReport message according to the requirement of the IAB-node-CU;

step 305: the IAB-node-CU node receives the measurement message reported by the IAB-node-MT, starts a return route optimization algorithm process and formulates an optimal return route for the IAB-node6 node; if a plurality of nodes with IAB-nodes in RRC-INACTIVE state exist under the IAB-donor-CU node, collecting and finishing the measurement reported by all IAB-node-MT nodes in RRC-INACTIVE state, and starting the return route optimization algorithm process;

step 306: the IAB-donor-CU nodes reconfigure the return route through RRCREConfigure messages; the reception of RRCREConfigure Compleete indicates that the reconfiguration is completed;

the message transmission between the IAB-node3 and the IAB-node is completed through an F1-C interface between the IAB-node3 and the IAB-node.

The invention has the beneficial effects that:

firstly, the method comprises the following steps: the invention provides a processing method for an IAB-node-MT to be in an RRC-INACTIVE state in an IAB backhaul network structure. To address the removal of support for IAB-node mobility at 3GPP Rel-18.

Secondly, the method comprises the following steps: in the prior art, since the terminal or the network moves, the terminal in the RRC-INACTIVE state 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 notify the network. The invention provides that the IAB-node-MT immediately starts the RRC recovery establishment process as long as any new IAB-node-DU node is reselected according to the characteristics of the IAB.

Thirdly, the method comprises the following steps: in the RRC recovery establishing process, the invention requires the IAB-node-MT node to immediately carry out measurement report and informs the IAB-node-CU node of the wireless coverage condition around the IAB-node-MT. And the IAB-donor-CU configures the optimal return route for the IAB-node-MT conveniently.

Fourthly: in the IAB return network architecture, an IAB-node exists below the IAB-node, as long as the node IAB-node-MT is in an RRC-INACTIVE state, the IAB-node-CU starts a periodic return route optimization timer, periodically requests the IAB-node-MT to report and measure, and executes a return route optimization process.

Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims thereof.

Drawings

For a better understanding of the objects, aspects and advantages of the present invention, reference will now be made to the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a 5G NR IAB system architecture;

fig. 2 is an IAB backhaul network topology in 5G NR;

FIG. 3 is the F1-U interface of the 5G NR IAB;

FIG. 4 is the F1-C interface of the 5G NR IAB;

FIG. 5 shows backhaul routing and BH RLC channel selection on the BAP sublayer;

FIG. 6 is an IAB-node-MT initiated recovery procedure;

FIG. 7 is an IAB-donor backhaul route optimization flow;

fig. 8 is an IAB backhaul network optimization architecture;

FIG. 9 shows the migration of IAB-node nodes within the same IAB-node;

FIG. 10 illustrates the migration of an IAB-node within a different IAB-node;

fig. 11 is a process of IAB-donor periodic backhaul route optimization.

Detailed Description

The following embodiments of the present invention are provided by way of specific examples, and other advantages and effects of the present invention will be readily apparent to those skilled in the art from the disclosure herein. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention. It should be noted that the drawings provided in the following embodiments are only for illustrating the basic idea of the present invention in a schematic way, and the features in the following embodiments and examples may be combined with each other without conflict.

Wherein the showings are for the purpose of illustrating the invention only and not for the purpose of limiting the same, and in which there is shown by way of illustration only and not in the drawings in which there is no intention to limit the invention thereto; 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 an actual product; it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.

The same or similar reference numerals in the drawings of the embodiments of the present invention correspond to the same or similar components; in the description of the present invention, it should be understood that if there is an orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "front", "rear", etc., based on the orientation or positional relationship shown in the drawings, it is only for convenience of description and simplification of description, but it is not intended to indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore the terms describing the positional relationship in the drawings are only used for illustrative purposes and are not to be construed as limiting the present invention, and the specific meaning of the terms described above will be understood by those skilled in the art according to the specific circumstances.

DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION

In the IAB backhaul network, in order to save air radio 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 may be moved to the RRC-INACTIVE state. In this state, the interpretation of the paging or system message of the serving cell IAB-node-DU fails due to the movement of the IAB-node-MT node, and the measurement of the serving cell IAB-node-DU does not satisfy the camping or the IAB-node-MT is not in the coverage area of the serving cell IAB-node-DU. The IAB-node-MT immediately initiates an IAB-node-DU cell search procedure and initiates a recovery procedure on the IAB-node-DU cell that has been searched. And F1 connection between the IAB-node-MT and the IAB-node-CU is reestablished.

In an IAB-node sub-node controlled by the IAB-donor-CU, if the node IAB-node-MT is transferred to the RRC-INACTIVE state, the IAB-donor-CU periodically requires all IAB-nodes entering the RRC-INACTIVE state to carry out measurement report, and carries out return route optimization operation according to the measurement report result.

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

The recovery flow initiated by the IAB-node-MT in the present invention is shown in fig. 6:

and the IAB-node-MT and the serving cell IAB-node-DU (Source IAB-node-DU) node have no service transmission for a long time, the IAB-node-CU releases the RRC connection of the IAB-node-MT through the serving cell IAB-node-DU, and the IAB-node-MT is required to enter an RRC-INACTIVE state. In this state, the IAB-node-MT will periodically interpret pages, system messages and measurements.

Step 1: in the RRC-INDITVE state, the IAB-node-MT periodically measures, interprets paging and interprets system message content broadcasted by the serving cell IAB-node-DU according to paging indication. In this state, if the IAB-node-MT interprets the paging and interprets the system message unsuccessfully, or the measurement on the serving cell IAB-node-DU does not satisfy the resident condition, the IAB-node-MT immediately initiates a cell reselection process, and if the cell reselection fails, initiates a cell selection process to select a new IAB-node-DU cell, which is called a Target cell IAB-node-DU (Target IAB-node-DU). As in step 1 of fig. 6.

Further, in the process of performing cell reselection and selection by the IAB-node-MT, as long as the serving cell IAB-node-DU satisfies the camping condition, that is, the cell is not barred, and the received signal quality satisfies the camping requirement, the IAB-node-MT does not automatically select to another IAB-node.

And 2, step: the IAB-node-MT initiates an RRC recovery process on the target cell IAB-node-DU. Firstly, the IAB-node-MT initiates a random access process according to the received parameters of the IAB-node-DU cell system message, and then reports an RRC recovery message. As shown in

steps

2 and 3 in fig. 6.

And step 3: the target cell IAB-node-DU receives the RRC recovery message from the IAB-node-MT, and if there is no F1 connection between the target cell IAB-node-DU and the IAB-node-CU, the target cell IAB-node-DU requests the IAB-node-CU to establish an F1 connection, and the RRC recovery message is submitted to the IAB-node-CU node through the F1-C interface in the target cell IAB-node-DU. As shown in

steps

4 and 6 in fig. 6.

And 4, step 4: and immediately carrying out measurement report after the IAB-node-MT sends the RRC recovery message, and measuring the cell information and the measurement strength of the cell supporting the IAB in the RRC-INACTIVE state. The target cell IAB-node-DU will forward the message to the IAB-node-CU node. As shown in

steps

5 and 6 in fig. 6.

And 5: and the IAB-node-CU establishes a return route for the IAB-node-MT according to the current IAB return network architecture and the load distribution condition of the whole IAB return network, and can request the IAB-node-MT to continuously reside in the target cell IAB-node-DU and can also switch to other cell IAB-node-DUs according to reported measurement. As shown in

steps

8, 9, 10 and 11 of fig. 6.

Step 6: after the IAB-node-CU node completes the return route configuration for the IAB-node-MT node, the return route path between the Source serving cell IAB-node-DU and the IAB-node-CU is released, and the F1 interface between the Source serving cell IAB-node-DU and the IAB-node-CU is released. As shown at step 12 in fig. 6.

The process completes the process of migrating the IAB-node-MT from the IAB-node-DU node of the source service cell to the IAB-node-DU node of the target service cell, and the IAB-node-CU migrates the IAB-node-MT to the RRC-ACTIVE or RRC-CONNECTED state according to the service condition of the IAB-node-MT.

The backhaul route optimization process of the present invention is shown in fig. 7.

In the IAB backhaul network, the IAB-node-CU will control a plurality of IAB-node nodes below, wherein an IAB-node-MT in which an IAB-node exists migrates to the RRC-INACTIVE state, assuming that three IAB-node nodes exist under the IAB-node, i.e., IAB-node1, IAB-node2, and IAB-node 3. IAB-node1 and IAB-node2 have migrated to RRC-INACTIVE state.

Step 1: the IAB-donor-CU records whether the IAB-node-MT of the subordinate node is transferred to an RRC-INACTIVE state or not, and if yes, a return Route Optimization Timer, T-Route-Optimization-Timer, is started. If the timer times out, a backhaul route optimization procedure is started. And the IAB-donor-CU requests the node entering the RRC-INACTIVE state to carry out measurement report. As in step 1 of fig. 7.

Step 2: IAB-node3 receives a request from an IAB-node-CU over the F1 interface, then IAB-node3 initiates the paging procedure over the serving cell IAB-node-DU. As shown in

steps

1 and 4 in fig. 7.

And 3, step 3: and the IAB-node-MTs of the IAB-node2 and the IAB-node1 receive the paging sent by the IAB-node-DU of the serving cell and initiate an RRC connection establishment process. As shown in

steps

2 and 5 of fig. 7.

And 4, step 4: and after the RRC signaling connection between the IAB-node-MT and the service cell IAB-node-DU is established, the IAB-node-CU initiates a measurement process. Requesting IAB-node-MTs of IAB-node1 and IAB-node2 to report the measurement result. As shown in

steps

3 and 6 in fig. 7.

And 5: and the IAB-node-CU optimizes the return routes of the IAB-node1 and the IAB-node2 according to the load condition of the current IAB return network and the received measurement reports of the IAB-node1 and the IAB-node 2. As shown in step 7 of fig. 7.

Step 6: and the AB-donor-CU configures the calculated final return route to the IAB-node1 and IAB-node2 nodes, if a new return route is provided for IAB-node1 and IAB-node2, the old return route is released after the new return route is established, and the IAB-node-MT of the AB-node is transferred to an RRC-INACTIVE state or an RRC-CONNECTED state according to the service conditions of IAB-node1 and IAB-node 2. As shown in step 8 of fig. 7.

To illustrate the application of the present invention in a specific IAB backhaul network structure, fig. 8 is an architecture of an IAB application system, in which there are 2 IAB-donors and 6 IAB-node devices. After the whole system is powered on, a path (1) connection exists between the IAB-donor1 and the IAB-donor, namely, an Xn interface in the 3GPP definition. Further, paths (2) to (7) indicate that an actual connection exists, and path (8) indicates that the IAB-node-MT of IAB-node5 can receive a signal transmitted from the IAB-node-DU of IAB-node 2. Path (9) indicates that IAB-node-MT of IAB-node6 can receive the signal sent from IAB-node-DU of IAB-node 2.

In the IAB backhaul network architecture of fig. 8, since no data transmission is performed for a long time between IAB-node5 and IAB-node-DU of IAB-node6, the IAB-node-DU of parent node IAB-node1 of IAB-node5 requests IAB-node-MT of IAB-node5 to enter RRC-INACTIVE state; the IAB-node-DU of parent node IAB-node3 of IAB-node6 requests the IAB-node-MT of IAB-node6 to enter the RRC-INACTIVE state.

According to the requirements of 3GPP for IAB-node devices, the IAB-node-MT in RRC-INACTIVE needs to perform paging listening and measurement, and perform system message interpretation as needed.

In this embodiment, there are two scene processes. The following description will be made using scene 1 and scene 2, respectively.

Scene 1: in the scenario, the IAB-node3 is a source IAB-node and is also a serving IAB-node, and the IAB-node2 is a target IAB-node.

Step 1, in the process of periodic paging monitoring and measurement, an IAB-node-MT of IAB-node6 in an RRC-INACTIVE state finds that a service node IAB-node3 is unavailable, because the IAB-node3 fails, and an IAB-node3 or an IAB-node6 node moves, the IAB-node6 is not in the signal coverage of the IAB-node3 node. The IAB-node-MT of the IAB-node6 node immediately initiates a cell reselection procedure or a cell selection procedure until the IAB-node6 searches the IAB-node2 node IAB-node-DU to send cell information. As in step 1 of fig. 9.

In this embodiment, as long as the IAB-node2 node is not barred and the quality of the signal received by IAB-node2 from IAB-node6 node IAB-node-MT meets the camping requirement, specifically referring to 3GPP TS38.304, IAB-node6 does not reselect to IAB-node2 node.

Step 2: IAB-node6 node IAB-node-MT initiates a random access procedure on IAB-node2 node and sends an RRC recovery message (RRCResumeRequest) to IAB-node2 node. If an F1 interface exists between the IAB-node2 node and the IAB-node2, the IAB-node2 sends RRCRESUMREQUEST to the IAB-node-CU of the IAB-node2 node through the F1 interface. As shown in

steps

2, 3 and 4 of fig. 9.

And step 3: the IAB-node2 node IAB-node-CU continues to wait for measurement information (measurementReport) reported by the IAB-node6, and the measurement report includes the identifier of the IAB node and the signal strength which have been searched in the process of cell search by the IAB-node 6. As shown in

steps

5 and 6 of fig. 9.

And 4, step 4: the IAB-donor-CU of the IAB-donor2 plans the return route of the IAB-node6 and configures the return route of the IAB-node6 through the RRCRECONfigure message. In the scenario of an embodiment, the IAB-donor-CU of IAB-donor2 will configure IAB-node2 node as the target node of IAB-node 6. The establishment of the F1 interface between the IAB-donor2 and the IAB-node6 is completed. As shown in

steps

8, 9, 10 and 11 of fig. 9.

And 5: IAB-donor2 released the F1 connection between IAB-donor2 and IAB-node6, namely path (4) and path (7). And according to the traffic situation of the IAB-node6, the IAB-node-MT of the IAB-node6 is in an RRC-CONNECTED or RRC-INACTIVE state. As shown at step 12 in fig. 9.

Scene 2: the IAB-node is migrated in different IAB-nodes, namely the IAB-node5 node RRC restores the connection process.

Step 1, an IAB-node-MT of IAB-node5 in RRC-INACTIVE state carries out periodic paging monitoring and measurement process, finds that a service node IAB-node1 is unavailable due to the fact that an IAB-node1 fails, and an IAB-node1 or an IAB-node5 node moves, so that an IAB-node5 is not in the signal coverage of the IAB-node 1. The IAB-node-MT of the IAB-node6 node immediately initiates a cell reselection process or a cell selection process until the IAB-node5 searches the IAB-node2 node, and the IAB-node-DU sends cell information. As in step 1 of fig. 10.

In this embodiment, as long as the IAB-node1 node is not barred and the quality of the signal received by IAB-node1 from IAB-node5 node IAB-node-MT meets the camping requirement, specifically referring to 3GPP TS38.304, IAB-node6 does not reselect to IAB-node2 node.

And 2, step: IAB-node5 node IAB-node-MT initiates a random access procedure on IAB-node2 node and sends an RRC recovery message (RRCResumeRequest) to IAB-node2 node. If an F1 interface exists between the IAB-node2 node and the IAB-donor2, the IAB-node2 sends RRCResuRequest to the IAB-donor-CU of the IAB-donor2 node through the F1 interface. As shown in

steps

2, 3 and 4 in fig. 10.

And step 3: if the IAB-node5 node is not the IAB-node2 control node, the IAB-node2 node initiates a handover process to the IAB-node1 node, transmits the parameters of the IAB-node5 node in the IAB-node1 node to the IAB-node2 node, and completes the routing planning of the IAB-node5 node return route by the IAB-node2 node, as shown in 4 steps in fig. 10.

And 4, step 4: the IAB-donor2 node IAB-donor-CU continues to wait for the measurement information (measurementReport) reported by the IAB-node5, and the measurement report includes the IAB node id and the signal strength which have been searched in the cell search process of the IAB-node 5. As shown in

steps

5 and 6 of fig. 10.

And 5: the IAB-donor-CU of the IAB-donor2 plans the return route of the IAB-node5 and configures the return route of the IAB-node5 through the RRCRECONfigure message. In the context of an embodiment, the IAB-donor-CU of IAB-donor2 will configure IAB-node2 node as the target node of IAB-node 5. The establishment of the F1 interface between the IAB-donor2 and the IAB-node5 is completed. As shown in

steps

8, 9, 10 and 11 of fig. 10.

And 6: IAB-donor1 releases the F1 connection, i.e., path (2) and path (6) paths, between IAB-donor1 and IAB-node 5. IAB-donor2 and according to IAB-node5 traffic status, the IAB-node-MT of IAB-node5 is in RRC-CONNECTED or RRC-INACTIVE state. As shown in step 12 of fig. 10.

In this embodiment, in addition to the above discussion, the IAB-node5 and the IAB-node6 reselect and select a new IAB-node-DU scenario, and trigger the IAB-node-CU to perform return route adjustment. The following describes the periodic backhaul route optimization procedure with respect to this embodiment. In this example, IAB-node5 was treated in the same manner as IAB-node6, and will be exemplified by IAB-node 6.

Step 1: and if the monitoring Timer T-Route-Optimization-Timer of the IAB-denor-CU of the IAB-denor node is overtime, the IAB-denor-CU starts a return Route Optimization process. As in step 1 of fig. 11.

Step 2: the IAB-node-CU requests the IAB-node-DU of IAB-node3 to send a paging message over the F1 interface with IAB-node 2. As shown in

steps

2 and 3 in fig. 11.

And step 3: and the IAB-node-MT of the IAB-node6 node in the RRC-INACTIVE receives the paging, and then initiates an RRC recovery process, wherein in the step, the IAB-node-MT firstly initiates a random access process, then sends an RRCResuRequest message, receives the RRCResume message, and finally recovers the RRCResuComplete. In the RRCRESume message, the IAB-donor-CU requests the IAB-node-MT to report the measurement information. As shown in

steps

4, 5, 6, 7, 8 and 9 of fig. 11.

And 4, step 4: and the IAB-node-MT reports a measurement result Measurementreport message according to the requirement of the IAB-donor-CU. As shown in

steps

10 and 11 of fig. 11.

And 5: and the IAB-node-CU node receives the measurement message reported by the IAB-node-MT, starts a return route optimization algorithm process and formulates an optimal return route for the IAB-node6 node. If a plurality of nodes with IAB-nodes in RRC-INACTIVE state exist under the IAB-donor-CU node, the return route optimization algorithm process is started only after the measurement reported by all IAB-node-MT nodes in the RRC-INACTIVE state is collected and completed. As shown at step 12 in fig. 11.

And 6: the IAB-donor-CU node reconfigures the return route via RRCReconfigure message. Receipt of rrcreconfigurecomplete indicates that the reconfiguration is complete.

In this scheme, message passing between the IAB-node3 and the IAB-node is completed through the F1-C interface between them.

Finally, the above embodiments are only intended to illustrate the technical solutions of the present invention and not to limit the present invention, and although the present invention has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that modifications or equivalent substitutions may be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions, and all of them should be covered by the claims of the present invention.

Claims

1. A return route optimization method under a 5G IAB inactive state is characterized in that: the method comprises the following steps:

s1: initiating a recovery flow by the IAB-node-MT in an RRC-INACTIVE state;

s2: the IAB-donor initiates the backhaul route optimization process.

2. The method of claim 1, wherein the backhaul route optimization method in 5G IAB inactive state comprises: the S1 specifically includes:

s11: the IAB-node-MT in the RRC-INDITVE state periodically measures, decodes paging and decodes the system message content broadcasted by the serving cell IAB-node-DU (also called source cell IAB-node-DU) according to the paging indication; if the IAB-node-MT is reading paging and reading system message process fails or the service cell IAB-node-DU measurement does not meet the resident condition, the IAB-node-MT immediately initiates a cell reselection process, if the cell reselection fails, the IAB-node-DU measurement initiates a cell selection process, and a new service cell IAB-node-DU node is selected, which is also called a target cell IAB-node-DU;

s12: the IAB-node-MT initiates an RRC recovery process on an IAB-node-DU of a target cell; firstly, an IAB-node-MT node initiates a random access process according to system message parameters of an IAB-node-DU of a received target cell, and then reports an RRC recovery message;

s14: after sending an RRC recovery message, an IAB-node-MT node immediately performs measurement reporting, and reports cell information and measurement strength of a cell supporting the IAB in an RRC-INACTIVE state; the target cell IAB-node-DU node forwards the message to the IAB-node-CU node;

3. The method of claim 2, wherein the backhaul route optimization method in 5G IAB inactive state comprises: the S2 specifically includes:

s21: an IAB-donor-CU records whether an IAB-node-MT migrating to an RRC-INACTIVE state exists in an IAB return network or not, and if so, a return Route Optimization Timer, T-Route-Optimization-Timer, is started; when the timer is overtime, starting an IAB (inter-integrated access bus) return route optimization process, and enabling the IAB-donor-CU to measure and report the IAB-node-MT which requests to be in the RRC-INACTIVE state;

s23: the IAB-node-MTs of the IAB-node2 node and the IAB-node1 node receive paging sent by an IAB-node-DU of a serving cell; after receiving the paging, the IAB-node-MT initiates an RRC connection establishment process;

s25: the IAB-node-CU optimizes return routes of the IAB-node1 and the IAB-node2 according to the load condition of the current IAB return network and the measurement reports of the IAB-node1 node and the IAB-node2 node;

4. The method according to claim 2, wherein the backhaul route optimization method in the 5G IAB inactive state is: the S2 specifically includes: the return route optimization method is applied to an IAB return network structure and specifically comprises a scene 1 and a scene 2;

the IAB backhaul network structure comprises 2 IAB-donors and 6 IAB-node nodes; after power-on, a path (1) communication connection exists between the IAB-donor1 and the IAB-donor, namely, an Xn interface in the definition of 3 GPP; paths (2) to (7) indicate that an actual communication connection exists, and path (8) indicates that the IAB-node-MT of IAB-node5 node can receive a signal transmitted from the IAB-node-DU of IAB-node2 node; path (9) indicates that the IAB-node-MT of IAB-node6 node can receive the signal sent by IAB-node-DU from IAB-node 2;

scene 1: the IAB-node migrates in the same IAB-node, namely the RRC connection recovery process of the IAB-node6 node, wherein the IAB-node3 is an IAB-node of a source service cell, and the IAB-node2 is an IAB-node of a target cell;

step 101: the IAB-node-MT of the IAB-node6 node in the RRC-INACTIVE state carries out periodic paging monitoring and measurement processes; if the service cell IAB-node3 node is unavailable, because the IAB-node3 node fails, the IAB-node3 node or the IAB-node6 node moves, so that the IAB-node6 node is not in the signal coverage range of the IAB-node3 node; the IAB-node-MT in the IAB-node6 immediately initiates a cell reselection process or a cell selection process until the IAB-node6 searches the IAB-node2 node, namely the IAB-node-DU sends cell information;

as long as the IAB-node2 node is not prohibited and the quality of the signal received by IAB-node2 by IAB-node6 node IAB-node-MT meets the residence requirement, specifically referring to 3GPP TS38.304, IAB-node6 does not reselect to the IAB-node2 node;

step 102: the IAB-node-MT of the IAB-node6 node initiates a random access process on a new serving cell IAB-node2 node and sends an RRC recovery message to a serving cell IAB-node2 node; if an F1 interface exists between the IAB-node2 node of the serving cell and IAB-node2, the IAB-node2 sends RRCResuRequest to an IAB-node-CU of an IAB-node2 node through the F1 interface;

step 103: the IAB-node2 node IAB-node CU continues to wait for the measurement information reported by the IAB-node6 node; the measurement report contains IAB-node6 node which has searched IAB cell identification and signal strength in the process of cell search;

step 104: an IAB-donor-CU of the IAB-donor2 carries out return route planning for the IAB-node6 node and configures a return route of the IAB-node6 node through an RRCRECONfigure message; in the scenario of this embodiment, an IAB-donor-CU of the IAB-donor2 configures an IAB-node2 node as a serving cell node of the IAB-node 6; and completing establishing an F1 interface between the IAB-donor2 and the IAB-node 6;

step 105: IAB-donor2 releases F1 connection between the IAB-donor2 and the IAB-node6 node, namely a path (4) and a path (7); and according to the traffic volume of the IAB-node6 node, the IAB-node-MT of the IAB-node6 node is transferred to an RRC-CONNECTED or RRC-INACTIVE state;

step 201: in the process of periodic paging monitoring and measurement, if the IAB-node-MT of the IAB-node5 node in the RRC-INACTIVE state is found to be unavailable in the IAB-node1 node in the serving cell, the reason may be that the IAB-node1 node fails, and the position of the IAB-node1 or the IAB-node5 node moves, so that the IAB-node5 node is not in the signal coverage range of the IAB-node1 node in the serving cell; 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 the IAB-node2 node, and the IAB-node-DU sends cell information;

step 202: the IAB-node5 node IAB-node-MT initiates a random access process on a new service cell IAB-node2 node, and sends an RRC recovery message to a service cell IAB-node2 node; if an F1 interface exists between the IAB-node2 node of the serving cell and IAB-node2, the IAB-node2 sends RRCResuRequest to an IAB-node-CU of an IAB-node2 node through the F1 interface;

step 203: the IAB-node5 node is not an IAB-node2 subordinate branch node, the IAB-node2 node initiates a switching process to the IAB-node1 node, the parameters of the IAB-node5 node in the IAB-node1 node are transmitted to the IAB-node2 node, and the IAB-node2 node completes the routing back of the IAB-node5 node;

step 204: an IAB-node2 node IAB-node CU continues to wait for measurement information reported by an IAB-node5 node, wherein the measurement report comprises an IAB cell identifier and signal strength which are searched in the process of searching the cell by the IAB-node 5;

step 206: IAB-donor1 releases F1 connection between IAB-donor1 and IAB-node5, namely a path (2) and a path (6); the IAB-donor2 transfers the IAB-node-MT of the IAB-node5 node to RRC-CONNECTED or RRC-INACTIVE state according to the traffic volume of the IAB-node5 node;

except for the above discussion, the IAB-node5 node and the IAB-node6 node reselect and select the new service cell IAB-node-DU scene, and trigger the IAB-node-CU to perform return route adjustment;

the periodic return route optimization process comprises the following steps:

step 303: when the IAB-node-MT of the IAB-node6 in the RRC-INACTIVE receives the paging, the IAB-node-MT initiates an RRC recovery process, in the step, the IAB-node-MT initiates a random access process firstly, then sends an RRCResemeRequest message, receives the RRCReseme message and finally recovers the RRCResemeComplete; in the RRCRESume message, the IAB-donor-CU requests the IAB-node-MT to report the measurement information;

step 304: the IAB-node-MT reports a measurement result Measurementreport message according to the requirements of the IAB-node-CU;

step 306: the IAB-donor-CU nodes reconfigure the return route through RRCREConfigure messages; receiving RRCRECONfigure Compleete to indicate that the reconfiguration is completed;