Communication control method, cellular communication system, user device, program, and chipset

Abstract

To provide a communication control method, a cellular communication system, user equipment, a program, and a chip set for collecting information during operation in order to autonomously optimize a network or improve communication conditions.SOLUTION: In a communication control method used in a cellular communication system, a user device performs LBT (Listen Before Talk) on an unlicensed frequency, and the user device transmits, to a base station, a report including information indicating the number of LBT failures and information regarding the radio conditions between the user device and the base station.SELECTED DRAWING: None

Description

Technical Field

[0001] The present disclosure relates to a communication control method used in a cellular communication system.

Background Art

[0002] In 3GPP (Third Generation Partnership Project) (registered trademark; the same shall apply hereinafter), which is a standardization project for cellular communication systems, the introduction of a new relay node called an IAB (Integrated Access and Backhaul) node has been under consideration (see, for example, "3GPP TS 38.300 V16.5.0 (2021-03)"). One or more relay nodes are interposed in the communication between a base station and a user device and perform relaying for this communication.

Summary of the Invention

[0003] The communication control method according to the first aspect is a communication control method used in a cellular communication system. The communication control method includes a communication device executing LBT (Listen Before Talk). Further, the communication control method includes the communication device storing, as statistical information, the number of successes and the failure rate in the downlink direction of the executed LBT in a memory, and storing, as statistical information, the number of successes and the failure rate in the uplink direction of the executed LBT in the memory. Furthermore, the communication control method includes the communication device transmitting the statistical information to a higher-level node of the communication device.

[0004] The communication control method according to the second aspect is a communication control method used in a cellular communication system. The communication control method includes a communication device performing LBT and storing statistical information in a memory. Further, the communication control method includes a communication device detecting a predetermined event. Furthermore, when the predetermined event is caused by an LBT failure which is statistical information, the communication control method includes the communication device transmitting a first RLF (Radio Link Failure) report to a higher-level node of the communication device, and when the predetermined event is caused by statistical information other than the LBT failure, not transmitting the first RLF report to the higher-level node.

Brief Description of Drawings

[0005]

Figure 1

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[0006] A cellular communication system according to an embodiment will be described with reference to the drawings. In the description of the drawings, the same or similar parts are denoted by the same or similar reference numerals.

[0007] (Configuration of Cellular Communication System) First, a configuration example of a cellular communication system according to an embodiment will be described. A cellular communication system according to an embodiment is a 3GPP 5G system. Specifically, the radio access method in the cellular communication system is NR (New Radio), which is a 5G radio access method. However, LTE (Long Term Evolution) may be at least partially applied to the cellular communication system. Also, future cellular communication systems such as 6G may be applied to the cellular communication system.

[0008] FIG. 1 is a diagram showing a configuration example of a cellular communication system 1 according to an embodiment.

[0009] As shown in FIG. 1, the cellular communication system 1 includes a 5G core network (5GC) 10, user equipment (UE: User Equipment) 100, base station devices (hereinafter sometimes referred to as "base stations") 200-1, 200-2, and IAB nodes 300-1, 300-2. The base station 200 may be called a gNB (next generation Node B).

[0010] In the following, an example where the base station 200 is an NR base station will be mainly described, but the base station 200 may be an LTE base station (i.e., eNB (evolved Node B)).

[0011] Note that in the following, the base stations 200-1 and 200-2 may be referred to as gNB200 (or base station 200), and the IAB nodes 300-1 and 300-2 may be referred to as IAB node 300, respectively.

[0012] The 5GC 10 has an AMF (Access and Mobility Management Function) 11 and a UPF (User Plane Function) 12. The AMF 11 is a device that performs various mobility controls for the UE 100. The AMF 11 manages information on the area where the UE 100 is located by communicating with the UE 100 using NAS (Non-Access Stratum) signaling. The UPF 12 is a device that performs transfer control of user data, etc.

[0013] Each gNB200 is a fixed radio communication node and manages one or more cells. A cell is a term indicating the smallest unit of a radio communication area. A cell may be used as a term indicating a function or resource for performing radio communication with the UE 100. Also, a cell may be used without distinguishing it from a base station such as gNB200. One cell belongs to one carrier frequency.

[0014] Each gNB200 is interconnected with the 5GC 10 via an interface called the NG interface. In FIG. 1, two gNB200-1 and gNB200-2 connected to the 5GC 10 are illustrated.

[0015] Each gNB 200 may be divided into a Central Unit (CU) and a Distributed Unit (DU). The CU and the DU are interconnected via an interface called the F1 interface. The F1 protocol is a communication protocol between the CU and the DU, and includes an F1-C protocol which is a control plane protocol and an F1-U protocol which is a user plane protocol.

[0016] The cellular communication system 1 supports an IAB that enables wireless relay of NR access using NR in the backhaul. The donor gNB (or donor node. Hereinafter, it may be referred to as the "donor node") 200-1 is a terminal node of the NR backhaul on the network side and is a donor base station equipped with additional functions to support the IAB. The backhaul enables multi-hop via a plurality of hops (i.e., a plurality of IAB nodes 300).

[0017] In FIG. 1, an example is shown in which the IAB node 300-1 is wirelessly connected to the donor node 200-1, the IAB node 300-2 is wirelessly connected to the IAB node 300-1, and the F1 protocol is transmitted over two backhaul links.

[0018] UE100 is a mobile wireless communication device that performs wireless communication with a cell. UE100 can be any device as long as it can perform wireless communication with gNB200 or IAB node 300. For example, UE100 can be a mobile phone terminal, a tablet terminal, a notebook PC, a sensor or a device provided in a sensor, a vehicle or a device provided in a vehicle, a drone or a device provided in a drone. UE100 wirelessly connects to IAB node 300 or gNB200 via an access link. FIG. 1 shows an example where UE100 is wirelessly connected to IAB node 300-2. UE100 communicates indirectly with donor node 200-1 via IAB node 300-2 and IAB node 300-1. In FIG. 1, an example is shown where IAB node 300-2 and IAB node 300-1 play the role of relay nodes.

[0019] FIG. 2 is a diagram showing the relationship between IAB node 300 and parent nodes and child nodes.

[0020] As shown in FIG. 2, each IAB node 300 has an IAB-DU corresponding to a base station function unit and an IAB-MT (Mobile Termination) corresponding to a user equipment function unit.

[0021] An adjacent node (i.e., a higher-level node) on the NR Uu radio interface of IAB-MT is called a parent node. The parent node is the DU of the parent IAB node or donor node 200. The radio link between IAB-MT and the parent node is called a backhaul link (BH link). In FIG. 2, an example is shown where the parent nodes of IAB node 300 are IAB nodes 300-P1 and 300-P2. Note that the direction towards the parent node is called upstream. From the perspective of UE100, the higher-level node of UE100 can correspond to the parent node.

[0022] An adjacent node (i.e., a lower node) on the NR access interface of the IAB-DU is called a child node. Similar to the gNB200, the IAB-DU manages cells. The IAB-DU terminates the NR Uu radio interface to the UE100 and the lower IAB nodes. The IAB-DU supports the F1 protocol to the CU of the donor node 200-1. In Fig. 2, an example is shown where the child nodes of the IAB node 300 are IAB nodes 300-C1 to 300-C3, but the UE100 may be included in the child nodes of the IAB node 300. Note that the direction towards the child node is called downstream.

[0023] Also, all IAB nodes 300 connected to the donor node 200 via one or more hops form a directed acyclic graph (DAG) topology rooted at the donor node 200 (hereinafter sometimes referred to as the "topology"). In this topology, as shown in Fig. 2, adjacent nodes on the interface of the IAB-DU are child nodes, and adjacent nodes on the interface of the IAB-MT are parent nodes. The donor node 200 centrally performs, for example, resource, topology, and route management of the IAB topology. The donor node 200 is a gNB that provides network access to the UE100 via a network of backhaul links and access links.

[0024] (Configuration of Base Station) Next, the configuration of the gNB200, which is a base station according to the embodiment, will be described. Fig. 3 is a diagram showing a configuration example of the gNB200. As shown in Fig. 3, the gNB200 includes a radio communication unit 210, a network communication unit 220, and a control unit 230.

[0025] The wireless communication unit 210 performs wireless communication with the UE 100 and wireless communication with the IAB node 300. The wireless communication unit 210 includes a receiving unit 211 and a transmitting unit 212. The receiving unit 211 performs various receptions under the control of the control unit 230. The receiving unit 211 includes an antenna, converts (down-converts) the wireless signal received by the antenna into a baseband signal (received signal), and outputs it to the control unit 230. The transmitting unit 212 performs various transmissions under the control of the control unit 230. The transmitting unit 212 includes an antenna, converts (up-converts) the baseband signal (transmitted signal) output by the control unit 230 into a wireless signal, and transmits it from the antenna.

[0026] The network communication unit 220 performs wired communication (or wireless communication) with the 5GC 10 and wired communication (or wireless communication) with other adjacent gNBs 200. The network communication unit 220 includes a receiving unit 221 and a transmitting unit 222. The receiving unit 221 performs various receptions under the control of the control unit 230. The receiving unit 221 receives a signal from the outside and outputs the received signal to the control unit 230. The transmitting unit 222 performs various transmissions under the control of the control unit 230. The transmitting unit 222 transmits the transmitted signal output by the control unit 230 to the outside.

[0027] The control unit 230 performs various controls in the gNB 200. The control unit 230 includes at least one memory and at least one processor electrically connected to the memory. The memory stores programs executed by the processor and information used for the processing by the processor. The processor may include a baseband processor and a CPU (Central Processing Unit). The baseband processor performs modulation / demodulation and encoding / decoding of baseband signals, etc. The CPU executes the programs stored in the memory to perform various processes. The processor performs the processing of each layer described later. Also, the control unit 230 may perform various processes in the gNB 200 (or donor node 200) in each of the embodiments shown below.

[0028] (Configuration of Relay Node) Next, the configuration of the IAB node 300, which is a relay node (or relay node device; hereinafter, may be referred to as a "relay node") according to the embodiment, will be described. FIG. 4 is a diagram showing a configuration example of the IAB node 300. As shown in FIG. 4, the IAB node 300 includes a wireless communication unit 310 and a control unit 320. The IAB node 300 may have a plurality of wireless communication units 310.

[0029] The wireless communication unit 310 performs wireless communication (BH link) with the gNB 200 and wireless communication (access link) with the UE 100. The wireless communication unit 310 for BH link communication and the wireless communication unit 310 for access link communication may be provided separately.

[0030] The wireless communication unit 310 includes a receiving unit 311 and a transmitting unit 312. The receiving unit 311 performs various receptions under the control of the control unit 320. The receiving unit 311 includes an antenna, converts (down-converts) the radio signal received by the antenna into a baseband signal (received signal), and outputs it to the control unit 320. The transmitting unit 312 performs various transmissions under the control of the control unit 320. The transmitting unit 312 includes an antenna, converts (up-converts) the baseband signal (transmitted signal) output by the control unit 320 into a radio signal, and transmits it from the antenna.

[0031] The control unit 320 performs various controls in the IAB node 300. The control unit 320 includes at least one memory and at least one processor electrically connected to the memory. The memory stores programs executed by the processor and information used for the processing by the processor. The processor may include a baseband processor and a CPU. The baseband processor performs modulation / demodulation and encoding / decoding of baseband signals, etc. The CPU executes programs stored in the memory to perform various processes. The processor performs the processing of each layer described later. Also, the control unit 320 may perform various processes in the IAB node 300 in each of the following embodiments.

[0032] (Configuration of User Equipment) Next, the configuration of the UE100, which is a user device according to the embodiment, will be described. FIG. 5 is a diagram showing a configuration example of the UE100. As shown in FIG. 5, the UE100 includes a wireless communication unit 110 and a control unit 120.

[0033] The wireless communication unit 110 performs wireless communication on the access link, that is, wireless communication with the gNB200 and wireless communication with the IAB node 300. Also, the wireless communication unit 110 may perform wireless communication on the sidelink, that is, wireless communication with other UEs 100. The wireless communication unit 110 includes a receiving unit 111 and a transmitting unit 112. The receiving unit 111 performs various receptions under the control of the control unit 120. The receiving unit 111 includes an antenna, converts (down-converts) the wireless signal received by the antenna into a baseband signal (received signal), and outputs it to the control unit 120. The transmitting unit 112 performs various transmissions under the control of the control unit 120. The transmitting unit 112 includes an antenna, converts (up-converts) the baseband signal (transmitted signal) output by the control unit 120 into a wireless signal, and transmits it from the antenna.

[0034] The control unit 120 performs various controls in the UE100. The control unit 120 includes at least one memory and at least one processor electrically connected to the memory. The memory stores programs executed by the processor and information used for the processing by the processor. The processor may include a baseband processor and a CPU. The baseband processor performs modulation / demodulation and encoding / decoding of baseband signals, etc. The CPU executes programs stored in the memory to perform various processes. The processor performs the processing of each layer described later. Also, the control unit 120 may perform each process in the UE100 in each of the following embodiments.

[0035] (Configuration of the protocol stack) Next, the configuration of the protocol stack according to the embodiment will be described. FIG. 6 is a diagram showing an example of the protocol stack related to the RRC connection and NAS connection of the IAB-MT.

[0036] As shown in FIG. 6, the IAB-MT of the IAB node 300-2 has a physical (PHY) layer, a MAC (Medium Access Control) layer, an RLC (Radio Link Control) layer, a PDCP (Packet Data Convergence Protocol) layer, an RRC (Radio Resource Control) layer, and a NAS (Non-Access Stratum) layer.

[0037] The PHY layer performs encoding / decoding, modulation / demodulation, antenna mapping / demapping, and resource mapping / demapping. Between the PHY layer of the IAB-MT of the IAB node 300-2 and the PHY layer of the IAB-DU of the IAB node 300-1, data and control information are transmitted via a physical channel.

[0038] The MAC layer performs priority control of data, retransmission processing by hybrid ARQ (Hybrid Automatic Repeat reQuest), and a random access procedure, etc. Between the MAC layer of the IAB-MT of the IAB node 300-2 and the MAC layer of the IAB-DU of the IAB node 300-1, data and control information are transmitted via a transport channel. The MAC layer of the IAB-DU includes a scheduler. The scheduler determines the uplink and downlink transport formats (transport block size, modulation and coding scheme (MCS: Modulation and Coding Scheme)) and the allocated resource blocks.

[0039] The RLC layer uses the functions of the MAC layer and the PHY layer to transmit data to the RLC layer on the receiving side. Between the RLC layer of the IAB-MT of the IAB node 300-2 and the RLC layer of the IAB-DU of the IAB node 300-1, data and control information are transmitted via a logical channel.

[0040] The PDCP layer performs header compression / expansion and encryption / decryption. Between the PDCP layer of the IAB-MT of the IAB node 300-2 and the PDCP layer of the CU of the donor node 200, data and control information are transmitted via radio bearers.

[0041] The RRC layer controls logical channels, transport channels, and physical channels in response to the establishment, re-establishment, and release of radio bearers. Between the RRC layer of the IAB-MT of the IAB node 300-2 and the RRC layer of the CU of the donor node 200, RRC signaling for various settings is transmitted. When there is an RRC connection with the donor node 200, the IAB-MT is in the RRC connected state. When there is no RRC connection with the donor node 200, the IAB-MT is in the RRC idle state.

[0042] The NAS layer located above the RRC layer performs session management, mobility management, etc. Between the NAS layer of the IAB-MT of the IAB node 300-2 and the NAS layer of the AMF11, NAS signaling is transmitted.

[0043] Figure 7 is a diagram showing a protocol stack related to the F1-U protocol. Figure 8 is a diagram showing a protocol stack related to the F1-C protocol. Here, an example is shown where the donor node 200 is divided into a CU and a DU.

[0044] As shown in Figure 7, each of the IAB-MT of the IAB node 300-2, the IAB-DU of the IAB node 300-1, the IAB-MT of the IAB node 300-1, and the DU of the donor node 200 has a BAP (Backhaul Adaptation Protocol) layer as the upper layer of the RLC layer. The BAP layer is a layer that performs routing processing and bearer mapping / demapping processing. In the backhaul, by transmitting the IP layer via the BAP layer, routing over multiple hops becomes possible.

[0045] In each backhaul link, the PDU (Protocol Data Unit) of the BAP layer is transmitted by the backhaul RLC channel (BH NR RLC channel). By configuring multiple backhaul RLC channels in each BH link, traffic prioritization and QoS (Quality of Service) control are possible. The association between the BAP PDU and the backhaul RLC channel is performed by the BAP layer of each IAB node 300 and the BAP layer of the donor node 200.

[0046] Note that the CU of the donor node 200 is the gNB-CU function of the donor node 200 that terminates the F1 interface to the DU of the IAB node 300 and the donor node 200. Also, the DU of the donor node 200 is the gNB-DU function of the donor node 200 that hosts the IAB BAP sublayer and provides a wireless backhaul to the IAB node 300.

[0047] As shown in FIG. 8, the protocol stack of the F1-C protocol has an F1AP layer and an SCTP layer instead of the GTP-U layer and the UDP layer shown in FIG. 7.

[0048] Note that in the following, the processing or operations performed between the IAB-DU and the IAB-MT of the IAB may sometimes be simply described as the processing or operations of "IAB". For example, the case where the IAB-DU of the IAB node 300-1 transmits a message of the BAP layer to the IAB-MT of the IAB node 300-2 is described as the IAB node 300-1 transmitting the message to the IAB node 300-2. Also, the processing or operations of the DU or CU of the donor node 200 may sometimes be simply described as the processing or operations of the "donor node".

[0049] Also, there may be cases where the upstream direction and the uplink (UL) direction are used without distinction. Furthermore, there may be cases where the downstream direction and the downlink (DL) direction are used without distinction.

[0050] [First Embodiment] Next, the first embodiment will be described.

[0051] In 3GPP, NR-U (New Radio - Unlicensed) is defined. NR-U is a technology for performing wireless communication using the 5G wireless communication standard NR in unlicensed frequency bands (e.g., 5 GHz band) and / or licensed shared frequency bands (or shared frequency bands). In NR-U, it is also possible to combine and use unlicensed frequency bands and licensed shared frequency bands. In this way, in NR-U, by performing wireless communication using unlicensed and / or licensed shared frequency bands, it becomes possible to increase network capacity.

[0052] On the other hand, in 3GPP, SON (Self-Organizing Network) / MDT (Minimization of Drive Tests) is being studied. SON is a technology that collects information from UE100 or base station 200 and autonomously optimizes the network. Also, MDT is a technology that collects information such as wireless communication interruption from UE100 to improve the communication situation. Both are common in collecting information during operation.

[0053] In 3GPP, specifically, it has been discussed to report the number of LBT (Listen Before Talk) failures or report LBT statistical information.

[0054] Here, LBT will be described.

[0055] (Regarding LBT) LBT is a technology in UE100 or base station 200 that senses (or listens) whether the channel to be used before starting transmission is free or busy, and executes transmission when it is sensed to be free.

[0056] LBT is executed in an entity lower than the MAC entity and is managed by the MAC entity. Before transmission is performed, the lower entity executes the LBT procedure. If the lower entity fails to transmit even after executing the LBT procedure, it outputs a LBT Failure Indication to the MAC entity.

[0057] When the MAC entity receives a LBT failure indication from the lower layer, it increments a counter (LBT_COUNTER) by "1". When the count value reaches or exceeds the maximum value, the MAC entity triggers a consistent LBT failure in the active BWP (BandWidth Part). Then, when the MAC entity triggers a consistent LBT failure for all BWPs, it indicates the consistent LBT failure to the upper layer. In this case, UE100 declares an RLF.

[0058] (Configuration example of the first embodiment) In the first embodiment, it is described that the IAB node 300 takes logs for the uplink and downlink respectively regarding the number of LBT successes and failure rates, and transmits this logged information as statistical information to the donor node 200.

[0059] Specifically, first, a relay node (for example, an IAB node) executes LBT. Next, the relay node stores in memory, as statistical information, the number of successes and failure rates in the downlink direction of the executed LBT, and also stores in memory, as statistical information, the number of successes and failure rates in the uplink direction of the executed LBT. Then, the relay node transmits the statistical information to the upper node of the relay node (for example, the donor node 200).

[0060] At the upper node, since the number of successful LBTs and the failure rate can be obtained separately for the uplink direction and the downlink direction, it is possible to perform predetermined processing for each of the uplink direction and the downlink direction. As a result, it becomes possible to appropriately operate the entire network formed by the IAB node 300.

[0061] FIG. 9 is a diagram showing a configuration example of the cellular communication system 1 according to the first embodiment. FIG. 9 shows a configuration example among the IAB nodes 300.

[0062] As shown in FIG. 9, the IAB node 300 has the UE 100 and the IAB node 300-C under it. The IAB node 300 forms an access link with the UE 100. The IAB node 300 and the UE 100 exchange messages and the like via the access link.

[0063] Also, the IAB node 300 forms a backhaul link with the IAB node 300-C. In the relationship between the IAB node 300 and the IAB node 300-C, the IAB node 300 is the parent node and the IAB node 300-C is the child node. The IAB node 300 and the IAB node 300-C exchange messages and the like via the backhaul link.

[0064] Furthermore, a node 500 is arranged above the IAB node 300. The node 500 may be a donor node 200 that manages the IAB nodes 300, 300-C and the UE 100. Also, the node 500 may be a parent node (IAB node) of the IAB node 300. A backhaul link is also formed between the IAB node 300 and the node 500, and messages are exchanged via the backhaul link.

[0065] (Operation example of the first embodiment) FIG. 10 is a diagram showing an operation example according to the first embodiment.

[0066] However, FIG. 10 shows an example where the IAB node 300 transmits statistical information to the donor node 200. For example, it may be an example where the UE 100 transmits statistical information to the IAB node 300 (or the donor node 200). Also, for example, it may be an example where the IAB node 300 transmits statistical information to the parent node of the IAB node 300. It may also be an example where the IAB node 300 transmits statistical information to a higher-level node of the IAB node. Further, it may be an example where the UE 100 transmits statistical information to the gNB 200.

[0067] As shown in FIG. 10, in step S10, the IAB node 300 starts processing.

[0068] In step S11, the IAB node 300 performs LBT and stores (or logs) the statistical information in the memory. The IAB node 300 may perform LBT for NR-U.

[0069] The statistical information at least includes the number of LBT failures. The count value obtained by the MAC entity of the IAB node 300 counting the LBT failure indications received from the lower-level entities may be used as the number of LBT failures.

[0070] Also, the statistical information may include the number of LBT successes or the number of consistent LBT failures. The count value obtained by the MAC entity of the IAB node 300 counting the LBT success indications received from the lower-level entities may be used as the number of LBT successes. Also, the value incremented and counted when the MAC entity of the IAB node 300 detects LBT failures for all BWPs may be used as the number of consistent LBT failures.

[0071] Furthermore, the statistical information at least includes the LBT failure rate. The IAB node 300 may calculate the LBT failure rate using the following formula.

[0072] LBT failure rate = number of LBT failures / (number of LBT failures + number of LBT successes), or LBT failure rate = Number of LBT failures / Number of LBT attempts The IAB node 300 stores the calculated LBT failure rate in the memory as statistical information.

[0073] Here, the IAB node 300 stores the statistical information in the uplink direction and the statistical information in the downlink direction in the memory. Note that the memory may be within the control unit 320 of the IAB node 300. The memory may also be within the IAB node 300 but outside the control unit 320.

[0074] In step S12, the IAB node 300 transmits the stored statistical information to the donor node 200. The IAB node 300 may transmit the statistical information to the donor node 200 in response to an inquiry from the donor node 200.

[0075] In step S13, the donor node 200 may perform a predetermined process on the IAB node 300 based on the received statistical information. The predetermined process may be a change in the LBT-related settings. The change in the LBT-related settings may be, for example, a change in the maximum value when triggering consistent LBT failures. Also, the predetermined process may be a change in the downlink direction scheduling. Such a change may include, for example, a change in at least one of the time, frequency, and resource blocks used in the downlink direction scheduling. Further, the predetermined process may be a change in the uplink direction scheduling. Such a change may include, for example, a change in at least one of the time, frequency, and resource blocks used in the uplink direction scheduling. Further, the predetermined process may be a handover. Further, the predetermined process may be a change in the handover parameters. Further, the predetermined process may be a change in the routing table. Such a change may include, for example, the identification of congested routes, a change in traffic volume or balance, etc.

[0076] Then, the donor node 200 ends a series of processes.

[0077] [Second Embodiment] Next, the second embodiment will be described.

[0078] (Regarding RLF-Report) In 3GPP, RLF-Report is defined. That is, when a predetermined statistical information (or cause) regarding RLF (Radio Link Failure) occurs in UE100, the RLF is stored in varRLF-Report. Such causes include random access problems, the number of retransmissions in the RLC layer reaching the maximum number, LBT failures, or backhaul RLF recovery failures. UE100 also stores such causes in varRLF-Report.

[0079] Also, when a predetermined cause regarding HOF (Handover Failure) occurs in UE100, the HOF is stored in varRLF-Report. Such causes include Reconfiguration with sync Failure. UE100 also stores such causes in varRLF-Report.

[0080] Then, UE100 sets the information stored in varRLF-Report in RLF-Report and transmits a UE Information Response message including RLF-Report to the network. After RLF or HOF, UE100 transmits a UE Information Response message including RLF-Report to the reestablished cell.

[0081] However, consider the case where RLF due to LBT failure and RLF or HOF due to other causes are included in varRLF-Report, and UE100 transmits an RLF-Report after RLF or HOF. In such a case, for the RLF-Report transmitted by UE100 after RLF or HOF, the base station 200 that receives the RLF-Report does not know whether the RLF or HOF is RLF or HOF due to LBT failure or RLF or HOF due to other causes.

[0082] Therefore, in the second embodiment, when a predetermined event occurs due to LBT failure, the IAB node 300 transmits an RLF-Report to the donor node 200. On the other hand, the IAB node 300 does not transmit an RLF-Report to the donor node 200 when a predetermined event occurs due to reasons other than LBT failure.

[0083] Specifically, the relay node (for example, the IAB node 300) executes LBT and stores statistical information in the memory. Next, the relay node detects a predetermined event. Next, when the predetermined event is caused by LBT failure which is statistical information, the relay node transmits a first RLF report to the upper node of the relay node. On the other hand, when the predetermined event is caused by statistical information other than LBT failure, the relay node does not transmit a first RLF report to the upper node.

[0084] Thereby, the upper node can grasp that a predetermined event has occurred due to LBT failure.

[0085] (Operation example of the second embodiment) FIG. 11 is a diagram showing an operation example according to the second embodiment. The operation example shown in FIG. 11 also describes an operation example between the IAB node 300 and the donor node 200. Regarding the operation example shown in FIG. 11, for example, it may be an operation example between the UE 100 and the IAB node 300 (or the donor node 200), between the IAB node 300 and its parent node, and / or between the IAB node 300 and its upper node. Also, the operation example shown in FIG. 11 may be an operation example between the UE 100 and the gNB 200.

[0086] As shown in FIG. 11, in step S20, the IAB node 300 starts processing.

[0087] In step S21, the IAB node 300 performs LBT and stores statistical information in the memory. The IAB node 300 may perform LBT on a license-free frequency band and / or a license-shared frequency band (or shared frequency band). Also, the content of the statistical information and its acquisition method may be the same as those in the first embodiment. Further, the statistical information may include a random access problem, the number of retransmissions in the RLC layer reaching the maximum number, LBT failure, backhaul RLF recovery failure, synchronization Reconfiguration failure, etc. Also, the statistical information may include radio state (RSRP (Reference Signal Received Power), RSRQ (Reference Signal Received Quality), SINR (Signal to Interference and Noise Ratio), etc.), location information (latitude, longitude, altitude, etc.), information of the connected cell (cell ID, etc.). These statistical information may be detected by the IAB-MT of the IAB node 300 and stored in the memory.

[0088] In step S22, the IAB node 300 detects a predetermined event. The predetermined event is RLF or HOF. For example, the IAB-MT of the IAB node 300 may detect RLF by detecting a random access problem, the number of retransmissions in the RLC layer reaching the maximum number, LBT failure, or backhaul RLF recovery failure. Also, for example, the IAB-MT of the IAB node 300 may detect HOF by detecting a synchronization reconfiguration failure. The IAB node 300 may detect RLF or HOF by a known method. Note that the IAB node 300 may clear the statistical information stored in step S21.

[0089] In step S23, the IAB node 300 identifies whether the predetermined event is caused by the statistical information of LBT failure. For example, when the IAB node 300 detects RLF or HOF immediately after LBT failure, it may determine that RLF or HOF is caused by the statistical information of LBT failure, and in other cases, it may determine that it is not caused by LBT failure.

[0090] In step S23, when the IAB node 300 determines that the predetermined event is caused by LBT failure (YES in step S23), it proceeds to step S24. On the other hand, in step S23, when the IAB node 300 determines that the predetermined event is not caused by LBT failure (NO in step S23), it proceeds to step S25.

[0091] In step S24, the IAB node 300 includes statistical information in the RLF-Report. That is, the IAB node 300 includes statistical information such as LBT failure in the RLF-Report. In this case, the IAB node 300 does not include other statistical information not related to the RLF and HOF in the RLF-Report. Specifically, the IAB node 300 may first clear the (past) statistical information stored in varRLF-Report, store the statistical information related to the RLF or HOF (here, LBT failure) in varRLF-Report, and include the varRLF-Report in the RLF-Report and transmit it at a predetermined timing.

[0092] On the other hand, in step S25, the IAB node 300 does not include statistical information in the RLF-Report. That is, the IAB node 300 does not include statistical information in the RLF-Report except for events due to LBT failure, so as not to transmit the RLF-Report to the donor node 200. In this case, the IAB node 300 may include and transmit other statistical information related to the RLF or HOF in the RLF-Report as before.

[0093] In step S26, the IAB node 300 transmits the RLF-Report to the donor node 200. That is, the IAB node 300 transmits an RLF-Report including an event due to LBT failure and statistical information such as LBT failure which is the cause of the event to the donor node 200.

[0094] In step S27, the donor node 200 may perform predetermined processing in response to the reception of the RLF-Report. The predetermined processing may be the same as that in the first embodiment.

[0095] Then, in step S28, the donor node 200 ends a series of processing.

[0096] (Modification of the second embodiment) Next, a modification of the second embodiment will be described. In the second embodiment, an example was described in which the IAB node 300 includes statistical information related to RLF or HOF (LBT failure) in the RLF-Report and does not transmit statistical information not related to RLF and HOF when RLF or HOF occurs. In the modification, an example in which the IAB node 300 also transmits statistical information not related to RLF and HOF will be described.

[0097] Specifically, when a predetermined event is caused by statistical information other than LBT failure, the relay node (for example, the IAB node 300) includes association information associating the statistical information with the predetermined event, together with the statistical information and the predetermined event, in the second RLF report and transmits it to the upper node (for example, the donor node 200).

[0098] Thereby, the upper node can grasp the statistical information stored in the relay node.

[0099] (Operation example of the modification) Next, an operation example of the modification will be described.

[0100] FIG. 12 is a diagram showing an operation example according to the modification. Also for the modification, an operation example between the IAB node 300 and the donor node 200 will be described, but an operation example between the UE 100 and the IAB node 300 (or the donor node 200) may also be used. Further, an operation example between the IAB node 300 and its parent node and / or between the IAB node 300 and its upper node may also be used. Also, an operation example between the UE 100 and the gNB 200 may be used.

[0101] As shown in FIG. 12, steps S30 to S32 are the same as steps S20 to S22 (FIG. 11) of the second embodiment, respectively.

[0102] In step S33, the IAB node 300 associates a predetermined event with statistical information. For example, when the IAB node 300 detects RLF or HOF immediately after the stored statistical information, the IAB node 300 associates the statistical information with RLF or HOF.

[0103] Here, the IAB node 300 generates association information indicating the association. The association information may be identification information. In this case, the first identification information corresponds to RLF, and the second identification information corresponds to HOF. Then, when the IAB node 300 associates the first statistical information with RLF, the IAB node 300 assigns the first identification information to the first statistical information. Also, when the IAB node 300 associates the second statistical information with HOF, the IAB node 300 assigns the second identification information to the second statistical information. The association method may be either one of RLF or HOF, or both. Statistical information not related to RLF and HOF may not have the association information.

[0104] In step S34, the IAB node 300 transmits the statistical information and the predetermined event to the donor node 200 together with the association information. The IAB node 300 may transmit an RLF-Report including the statistical information, the predetermined event, and the association information.

[0105] In step S35, the donor node 200 may perform a predetermined process on the IAB node 300 in response to the reception of the association information, the statistical information, and the predetermined event. The predetermined process may be the same as that in the first embodiment.

[0106] [Other Embodiments] A program may be provided that causes a computer to execute each process performed by the UE 100, gNB 200, or IAB node 300. The program may be recorded on a computer-readable medium. By using the computer-readable medium, it is possible to install the program on the computer. Here, the computer-readable medium on which the program is recorded may be a non-transitory recording medium. The non-transitory recording medium is not particularly limited, and may be, for example, a recording medium such as a CD-ROM or a DVD-ROM.

[0107] Alternatively, circuits that execute each process performed by the UE 100, gNB 200, or IAB node 300 may be integrated, and at least a part of the UE 100, gNB 200, or IAB node 300 may be configured as a semiconductor integrated circuit (chipset, SoC: System on a chip).

[0108] As used in this disclosure, the terms "based on" and "depending on" do not mean "only based on" or "only depending on" unless otherwise specified. The term "based on" means both "only based on" and "at least partially based on". Similarly, the term "depending on" means both "only depending on" and "at least partially depending on". Also, "obtain / acquire" may mean obtaining information from stored information, obtaining information from information received from other nodes, or obtaining the information by generating the information. The terms "include", "comprise", and their variants do not mean including only the listed items, but may include only the listed items or may further include additional items in addition to the listed items. Also, the term "or" used in this disclosure is not intended to be an exclusive disjunction. Furthermore, any reference to elements using designations such as "first", "second", etc. used in this disclosure does not generally limit the quantity or order of those elements. These designations may be used in this specification as a convenient way to distinguish between two or more elements. Therefore, a reference to a first and a second element does not mean that only two elements can be employed there or that the first element must precede the second element in some form. In this disclosure, for example, when articles are added by translation, such as a, an, and the in English, these articles shall be construed to include pluralities unless the context clearly indicates otherwise.

[0109] As described above in detail with reference to the drawings for one embodiment, the specific configuration is not limited to the above, and various design changes and the like can be made without departing from the gist. Also, it is possible to combine all or part of each embodiment within a non - conflicting range.

[0110] This application claims the priority of Japanese Patent Application No. 2021-115338 (filed on July 12, 2021), and all of its contents are incorporated into the specification of this application.

Description of Reference Numerals

[0111] 1: Mobile communication system 10: 5GC 11: AMF 100: UE 110: Radio communication unit 120: Control unit 200(200-1, 200-2): gNB (donor node) 210: Radio communication unit 220: Network communication unit 230: Control unit 300: IAB node 310: Radio communication unit 320: Control unit

Claims

1. A communication control method for use in a cellular communication system, comprising: A user equipment performs a listen before talk (LBT) on an unlicensed frequency; The user equipment transmits a report to a network, the report including information indicating the number of LBT failures and information regarding a radio condition between the user equipment and a base station; The LBT is performed by a lower entity in the user equipment, The information indicating the number of LBT failures is based on the number of LBT failure indications received by an entity higher than the lower entity from the lower entity. Communications control method.

2. A cellular communication system having a user equipment and a base station, The user equipment performs LBT (Listen Before Talk) on an unlicensed frequency, The user equipment transmits a report to a network, the report including information indicating the number of failures of the LBT and information regarding a radio condition between the user equipment and the base station; The LBT is performed by a lower entity in the user equipment, The information indicating the number of LBT failures is based on the number of LBT failure indications received by an entity higher than the lower entity from the lower entity. Cellular communication systems.

3. A user equipment in a cellular communication system, comprising: A control unit that executes LBT (Listen Before Talk) for an unlicensed frequency; A transmitter configured to transmit a report to a network, the report including information indicating the number of LBT failures and information regarding a radio condition between the user equipment and a base station, The LBT is performed by a lower entity in the user equipment, The information indicating the number of LBT failures is based on the number of LBT failure indications received by an entity higher than the lower entity from the lower entity. User equipment.

4. A user equipment in a cellular communication system, A process of performing LBT (Listen Before Talk) on an unlicensed frequency; and transmitting a report to a network, the report including information indicating the number of LBT failures and information regarding a radio condition between the user equipment and a base station; The LBT is performed by a lower entity in the user equipment, The information indicating the number of LBT failures is based on the number of LBT failure indications received by an entity higher than the lower entity from the lower entity. program.

5. A chipset for a user equipment in a cellular communication system, comprising: Executing Listen Before Talk (LBT) on unlicensed frequencies; and transmitting a report to a network, the report including information indicating the number of LBT failures and information regarding a radio condition between the user equipment and a base station; The LBT is performed by a lower entity in the user equipment, The information indicating the number of LBT failures is based on the number of LBT failure indications received by an entity higher than the lower entity from the lower entity. Chipset.

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