WO2022145309A1 - 通信制御方法 - Google Patents

通信制御方法 Download PDF

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Publication number
WO2022145309A1
WO2022145309A1 PCT/JP2021/047564 JP2021047564W WO2022145309A1 WO 2022145309 A1 WO2022145309 A1 WO 2022145309A1 JP 2021047564 W JP2021047564 W JP 2021047564W WO 2022145309 A1 WO2022145309 A1 WO 2022145309A1
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WIPO (PCT)
Prior art keywords
node
iab
relay node
local rerouting
message
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PCT/JP2021/047564
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English (en)
French (fr)
Japanese (ja)
Inventor
真人 藤代
ヘンリー チャン
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Kyocera Corp
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Kyocera Corp
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Application filed by Kyocera Corp filed Critical Kyocera Corp
Priority to CN202180095175.3A priority Critical patent/CN116897556A/zh
Priority to JP2022573022A priority patent/JP7397221B2/ja
Priority to EP21915169.3A priority patent/EP4258732A4/en
Publication of WO2022145309A1 publication Critical patent/WO2022145309A1/ja
Priority to US18/346,409 priority patent/US20230345346A1/en
Anticipated expiration legal-status Critical
Priority to JP2023202792A priority patent/JP7592143B2/ja
Ceased legal-status Critical Current

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W40/00—Communication routing or communication path finding
    • H04W40/02—Communication route or path selection, e.g. power-based or shortest path routing
    • H04W40/22—Communication route or path selection, e.g. power-based or shortest path routing using selective relaying for reaching a BTS [Base Transceiver Station] or an access point
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/0005—Control or signalling for completing the hand-off
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L45/00—Routing or path finding of packets in data switching networks
    • H04L45/22—Alternate routing
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L45/00—Routing or path finding of packets in data switching networks
    • H04L45/28—Routing or path finding of packets in data switching networks using route fault recovery
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L47/00—Traffic control in data switching networks
    • H04L47/10—Flow control; Congestion control
    • H04L47/12—Avoiding congestion; Recovering from congestion
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W40/00—Communication routing or communication path finding
    • H04W40/24—Connectivity information management, e.g. connectivity discovery or connectivity update
    • H04W40/248—Connectivity information update
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W40/00—Communication routing or communication path finding
    • H04W40/24—Connectivity information management, e.g. connectivity discovery or connectivity update
    • H04W40/28—Connectivity information management, e.g. connectivity discovery or connectivity update for reactive routing
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/20—Control channels or signalling for resource management
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W28/00—Network traffic management; Network resource management
    • H04W28/02—Traffic management, e.g. flow control or congestion control
    • H04W28/08—Load balancing or load distribution

Definitions

  • the present disclosure relates to a communication control method used in a cellular communication system.
  • 3GPP Third Generation Partnership Project
  • IAB Integrated Access and Backhaul
  • One or more relay nodes intervene in the communication between the base station and the user device, and relay the communication.
  • the communication control method is the communication control method used in the cellular communication system.
  • the communication control method includes that a relay node intervening between a parent node and a child node receives a flow control feedback message from the parent node or the child node. Further, the communication control method is a path to the parent node or the child node to which the flow control feedback message is transmitted according to the elapse of a certain period after the relay node receives the flow control feedback message. It has to perform local rerouting to forward data packets to different alternate paths.
  • the communication control method is the communication control method used in the cellular communication system.
  • the communication control method includes a relay node intervening between a parent node and a child node attempting to transfer a data packet to the parent node or the child node. Further, the communication control method performs local rerouting in which, when the relay node cannot transfer the data packet for a certain period of time, the data packet is transferred to an alternative path different from the path to the parent node or the child node. Have to do.
  • the communication control method is the communication control method used in the cellular communication system.
  • the communication control method is that the relay node receives a flow control feedback control message, receives a failure notification between the backhaul links between the relay node and another relay node, and data for a certain period of time. It has the ability to perform local rerouting to forward a data packet to an alternative path different from the path to the other relay node, depending on the fact that the packet could not be forwarded and at least one execution condition is met. .. Further, the communication control method includes that the relay node executes the local rerouting and then stops the local rerouting when the stop condition is satisfied.
  • the communication control method is the communication control method used in the cellular communication system.
  • a donor base station having a first relay node under its control transmits a first message regarding local rerouting to the first relay node, and the first relay node is described by the first relay node. It has an operation related to local rerouting in response to the reception of the first message.
  • FIG. 1 is a diagram showing a configuration example of a cellular communication system according to an embodiment.
  • FIG. 2 is a diagram showing the relationship between the IAB node, the parent node (Parent nodes), and the child node (Child nodes).
  • FIG. 3 is a diagram showing a configuration example of a gNB (base station) according to an embodiment.
  • FIG. 4 is a diagram showing a configuration example of an IAB node (relay node) according to an embodiment.
  • FIG. 5 is a diagram showing a configuration example of a UE (user device) according to an embodiment.
  • FIG. 6 is a diagram showing an example of a protocol stack for RRC connection and NAS connection of IAB-MT.
  • FIG. 7 is a diagram showing an example of a protocol stack for the F1-U protocol.
  • FIG. 8 is a diagram showing an example of a protocol stack for the F1-C protocol.
  • FIG. 9 is a diagram showing an example of local rerouting in the first embodiment.
  • FIG. 10 is a diagram showing an example of local rerouting in the first embodiment.
  • FIG. 11 is a diagram showing an operation example of the first embodiment.
  • FIG. 12 is a diagram showing an example of local rerouting in the second embodiment.
  • FIG. 13 is a diagram showing an example of local rerouting in the second embodiment.
  • FIG. 14 is a diagram showing an operation example in the second embodiment.
  • FIG. 15 is a diagram showing an example of local rerouting in the third embodiment.
  • FIG. 16 is a diagram showing an example of local rerouting in the third embodiment.
  • FIG. 17 is a diagram showing an operation example in the third embodiment.
  • FIG. 18 is a diagram showing an example of a stop instruction in the fourth embodiment.
  • FIG. 19 is a diagram showing an example of a stop instruction in the fourth embodiment.
  • FIG. 20 is a diagram showing an operation example in the fourth embodiment.
  • FIG. 21 is a diagram showing an example of local rerouting in the fifth embodiment.
  • FIG. 22 is a diagram showing an operation example of the fifth embodiment.
  • FIG. 23 is a diagram showing an example of notification by the IAB node of the sixth embodiment.
  • FIG. 24 is a diagram showing an operation example of the sixth embodiment.
  • FIG. 25 is a diagram showing an operation example of the seventh embodiment.
  • FIG. 25 is a diagram showing an operation example of the seventh embodiment.
  • FIG. 26 is a diagram showing another operation example of the seventh embodiment.
  • FIG. 27 is a diagram showing an operation example of the eighth embodiment.
  • FIG. 28 is a diagram showing an operation example of the ninth embodiment.
  • FIG. 29 is a diagram showing an operation example in the tenth embodiment.
  • FIG. 30 is a diagram showing an operation example in the eleventh embodiment.
  • FIG. 31 is a diagram showing an operation example of the twelfth embodiment.
  • FIG. 32 is a diagram showing the type of BH RLF notification.
  • FIG. 33 is a diagram showing the transmission option of the extended BH RLF indication.
  • FIG. 34 is a diagram relating to the execution of CHO.
  • FIG. 35 is a diagram showing a specific solution for avoiding re-establishment to descendant nodes.
  • FIG. 35 is a diagram showing a specific solution for avoiding re-establishment to descendant nodes.
  • FIG. 35 is a diagram showing a specific solution for avoiding re-establ
  • FIG. 36 is a diagram showing a comparison of the mechanism of lossless distribution of UL data in the case of hop-by-hop RLCARQ.
  • FIG. 37 is a diagram showing options of “C) Introducing UL status distribution”.
  • FIG. 38 is a diagram showing RAN2 signaling problems that can occur with IAB node movement between donors.
  • the cellular communication system 1 is a 5G system of 3GPP.
  • the wireless access system in the cellular communication system 1 is NR (New Radio), which is a 5G wireless access system.
  • NR New Radio
  • LTE Long Term Evolution
  • the cellular communication system 1 may be applied to a future cellular communication system such as 6G.
  • FIG. 1 is a diagram showing a configuration example of the cellular communication system 1 according to the embodiment.
  • the cellular communication system 1 includes a 5G core network (5GC) 10, a user device (UE: User Equipment) 100, and a base station device (hereinafter, may be referred to as a “base station”) 200. It has -1,200-2, and IAB nodes 300-1,300-2.
  • the base station 200 may be referred to as a gNB.
  • the base station 200 may be an LTE base station (that is, an eNB).
  • base stations 200-1 and 200-2 may be referred to as gNB200 (or base station 200), and IAB nodes 300-1 and 300-2 may be referred to as IAB node 300, respectively.
  • the 5GC10 has an AMF (Access and Mobility Management Function) 11 and an UPF (User Plane Function) 12.
  • the AMF 11 is a device that performs various mobility controls and the like for the UE 100.
  • the AMF 11 manages information on the area in which the UE 100 is located by communicating with the UE 100 using NAS (Non-Access Stratum) signaling.
  • the UPF 12 is a device that controls transfer of user data and the like.
  • Each gNB 200 is a fixed wireless communication node and manages one or a plurality of cells.
  • Cell is used as a term to indicate the smallest unit of wireless communication area.
  • Cell may be used as a term to indicate a function or resource for wireless communication with the UE 100.
  • One cell belongs to one carrier frequency.
  • Each gNB200 is interconnected with the 5GC10 via an interface called an NG interface.
  • FIG. 1 illustrates two gNB200-1 and gNB200-2 connected to 5GC10.
  • Each gNB 200 may be divided into an aggregate unit (CU: Central Unit) and a distributed unit (DU: Distributed Unit).
  • the CU and DU are connected to each other via an interface called an F1 interface.
  • the F1 protocol is a communication protocol between the CU and the DU, and includes the F1-C protocol, which is a control plane protocol, and the F1-U protocol, which is a user plane protocol.
  • the cellular communication system 1 supports IAB that enables wireless relay of NR access by using NR in the backhaul.
  • the donor gNB200-1 is a terminal node of the NR backhaul on the network side and is a donor base station having an additional function to support IAB.
  • the backhaul can be multi-hop through multiple hops (ie, multiple IAB nodes 300).
  • FIG. 1 an example in which the IAB node 300-1 wirelessly connects to the donor gNB200-1, the IAB node 300-2 wirelessly connects to the IAB node 300-1, and the F1 protocol is transmitted in two backhaul hops. Is shown.
  • the UE 100 is a mobile wireless communication device that performs wireless communication with a cell.
  • the UE 100 may be any device as long as it is a device that performs wireless communication with the gNB 200 or the IAB node 300.
  • the UE 100 is a mobile phone terminal, a tablet terminal, a notebook PC, a sensor or a device provided in the sensor, and / or a vehicle or a device provided in the vehicle.
  • the UE 100 wirelessly connects to the IAB node 300 or gNB 200 via an access link.
  • FIG. 1 shows an example in which the UE 100 is wirelessly connected to the IAB node 300-2.
  • the UE 100 indirectly communicates with the donor gNB200-1 via the IAB node 300-2 and the IAB node 300-1.
  • FIG. 2 is a diagram showing the relationship between the IAB node 300, the parent node (Parent nodes), and the child node (Child nodes).
  • each IAB node 300 has an IAB-DU corresponding to a base station functional unit and an IAB-MT (Mobile Termination) corresponding to a user equipment functional unit.
  • IAB-DU corresponding to a base station functional unit
  • IAB-MT Mobile Termination
  • the adjacent node (that is, the upper node) on the NR Uu radio interface of the IAB-MT is called the parent node.
  • the parent node is the parent IAB node or the DU of the donor gNB200.
  • the radio link between the IAB-MT and the parent node is called a backhaul link (BH link).
  • FIG. 2 shows an example in which the parent nodes of the IAB node 300 are the IAB nodes 300-P1 and 300-P2. The direction toward the parent node is called upstream. Seen from the UE 100, the upper node of the UE 100 may correspond to the parent node.
  • the adjacent node (that is, the lower node) on the NR access interface of the IAB-DU is called a child node.
  • the IAB-DU manages the cell in the same manner as the gNB200.
  • the IAB-DU terminates the NR Uu radio interface to the UE 100 and lower IAB nodes.
  • the IAB-DU supports the F1 protocol to the CU of donor gNB200-1.
  • FIG. 2 shows an example in which the child nodes of the IAB node 300 are the IAB nodes 300-C1 to 300-C3, the UE 100 may be included in the child nodes of the IAB node 300.
  • the direction toward the child node is called downstream.
  • FIG. 3 is a diagram showing a configuration example of gNB 200.
  • the gNB 200 has a wireless communication unit 210, a network communication unit 220, and a control unit 230.
  • 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 has a reception unit 211 and a transmission 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) a radio signal received by the antenna into a baseband signal (received signal), and outputs the radio signal to the control unit 230.
  • the transmission unit 212 performs various transmissions under the control of the control unit 230.
  • the transmission unit 212 includes an antenna, converts (up-converts) a baseband signal (transmission signal) output by the control unit 230 into a radio signal, and transmits the baseband signal (transmission signal) from the antenna.
  • the network communication unit 220 performs wired communication (or wireless communication) with 5GC10 and wired communication (or wireless communication) with other adjacent gNB200.
  • the network communication unit 220 has a reception unit 221 and a transmission unit 222.
  • the receiving unit 221 performs various types of reception 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 transmission unit 222 performs various transmissions under the control of the control unit 230.
  • the transmission unit 222 transmits the transmission signal output by the control unit 230 to the outside.
  • the control unit 230 performs various controls on 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 a program executed by the processor and information used for processing by the processor.
  • the processor may include a baseband processor and a CPU (Central Processing Unit).
  • the baseband processor modulates / demodulates and encodes / decodes the baseband signal.
  • the CPU executes a program stored in the memory to perform various processes.
  • the processor performs processing of each layer described later. Further, the control unit 230 may perform each process in the gNB 200 in each of the following embodiments.
  • FIG. 4 is a diagram showing a configuration example of the IAB node 300.
  • the IAB node 300 has a wireless communication unit 310 and a control unit 320.
  • the IAB node 300 may have a plurality of wireless communication units 310.
  • 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.
  • the wireless communication unit 310 has 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) a radio signal received by the antenna into a baseband signal (received signal), and outputs the radio signal to the control unit 320.
  • the transmission unit 312 performs various transmissions under the control of the control unit 320.
  • the transmission unit 312 includes an antenna, converts (up-converts) a baseband signal (transmission signal) output by the control unit 320 into a radio signal, and transmits the baseband signal (transmission signal) from the antenna.
  • the control unit 320 performs various controls on 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 a program executed by the processor and information used for processing by the processor.
  • the processor may include a baseband processor and a CPU.
  • the baseband processor modulates / demodulates and encodes / decodes the baseband signal.
  • the CPU executes a program stored in the memory to perform various processes.
  • the processor performs processing of each layer described later. Further, the control unit 320 may perform each process in the IAB node 300 in each of the following embodiments.
  • FIG. 5 is a diagram showing a configuration example of the UE 100. As shown in FIG. 5, the UE 100 has a wireless communication unit 110 and a control unit 120.
  • the wireless communication unit 110 performs wireless communication on the access link, that is, wireless communication with the gNB 200 and wireless communication with the IAB node 300. Further, the wireless communication unit 110 may perform wireless communication on the side link, that is, wireless communication with another UE 100.
  • the wireless communication unit 110 has a reception unit 111 and a transmission 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) a radio signal received by the antenna into a baseband signal (received signal), and outputs the radio signal to the control unit 120.
  • the transmission unit 112 performs various transmissions under the control of the control unit 120.
  • the transmission unit 112 includes an antenna, converts (up-converts) a baseband signal (transmission signal) output by the control unit 120 into a radio signal, and transmits the baseband signal (transmission signal) from the antenna.
  • the control unit 120 performs various controls on the UE 100.
  • the control unit 120 includes at least one memory and at least one processor electrically connected to the memory.
  • the memory stores a program executed by the processor and information used for processing by the processor.
  • the processor may include a baseband processor and a CPU.
  • the baseband processor modulates / demodulates and encodes / decodes the baseband signal.
  • the CPU executes a program stored in the memory to perform various processes.
  • the processor performs processing of each layer described later.
  • the control unit 130 may perform each process in the UE 100 in each of the following embodiments.
  • FIG. 6 is a diagram showing an example of a protocol stack for RRC connection and NAS connection of IAB-MT.
  • the IAB-MT of the IAB node 300-2 includes a physical (PHY) layer, a MAC (Medium Access Control) layer, an RLC (Radio Link Control) layer, and a PDCP (Packet Data Control Protocol). It has a layer, an RRC (Radio PHY Control) layer, and a NAS (Non-Access Stratum) layer.
  • PHY physical
  • MAC Medium Access Control
  • RLC Radio Link Control
  • PDCP Packet Data Control Protocol
  • It has a layer, an RRC (Radio PHY Control) layer, and a NAS (Non-Access Stratum) layer.
  • the PHY layer performs coding / decoding, modulation / demodulation, antenna mapping / demapping, and resource mapping / demapping.
  • Data and control information are transmitted 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 via a physical channel.
  • the MAC layer performs data priority control, retransmission processing by hybrid ARP (Hybrid Automatic Repeat request), random access procedure, and the like. Data and control information are transmitted 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 via the transport channel.
  • the MAC layer of the IAB-DU includes a scheduler. The scheduler determines the transport format (transport block size, modulation / coding method (MCS)) of the upper and lower links and the allocated resource block.
  • the RLC layer transmits data to the receiving RLC layer by using the functions of the MAC layer and the PHY layer. Data and control information are transmitted 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 via a logical channel.
  • the PDCP layer performs header compression / decompression and encryption / decryption. Data and control information are transmitted via the radio bearer between the PDCP layer of the IAB-MT of the IAB node 300-2 and the PDCP layer of the donor gNB200.
  • the RRC layer controls logical channels, transport channels, and physical channels according to the establishment, re-establishment, and release of radio bearers.
  • RRC signaling for various settings is transmitted between the RRC layer of the IAB-MT of the IAB node 300-2 and the RRC layer of the donor gNB200. If there is an RRC connection with the donor gNB200, the IAB-MT is in the RRC connected state. If there is no RRC connection with the donor gNB200, the IAB-MT is in the RRC idle state.
  • the NAS layer located above the RRC layer performs session management, mobility management, etc.
  • NAS signaling is transmitted between the NAS layer of the IAB-MT of the IAB node 300-2 and the AMF11.
  • FIG. 7 is a diagram showing a protocol stack related to the F1-U protocol.
  • FIG. 8 is a diagram showing a protocol stack for the F1-C protocol.
  • the donor gNB200 is divided into CU and DU.
  • each of the IAB-MT of the IAB node 300-2, the IAB-DU of the IAB node 300-1 and the IAB-MT of the IAB node 300-1 and the DU of the donor gNB200 are above the RLC layer. It has a BAP (Backhaul Adjustment Protocol) layer as a layer.
  • the BAP layer is a layer that performs routing processing and bearer mapping / demapping processing. In the backhaul, the IP layer is transmitted via the BAP layer, which enables routing in multiple hops.
  • the PDU (Protocol Data Unit) of the BAP layer is transmitted by the backhaul RLC channel (BH NR RLC channel).
  • BH NR RLC channel backhaul RLC channel
  • Each BH link constitutes a plurality of backhaul RLC channels. This makes it possible to prioritize traffic and control QoS (Quality of Service).
  • QoS Quality of Service
  • 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 gNB 200.
  • the protocol stack of the F1-C protocol has an F1AP layer and an SCTP (Stream Control Transmission Protocol) layer instead of the GTP-U layer and the UDP layer shown in FIG. 7.
  • SCTP Stream Control Transmission Protocol
  • IAB-DU and IAB-MT of IAB may be simply described as the processing or operation of "IAB".
  • IAB-DU of the IAB node 300-1 sends a BAP layer message to the IAB-MT of the IAB node 300-2, and the IAB node 300-1 sends the message to the IAB node 300-2.
  • the processing or operation of the DU or CU of the IAB donor 200 may also be described simply as the processing or operation of the "IAB donor".
  • the upstream direction and the uplink (UL) direction may be used without distinguishing between the upstream direction and the uplink (UL) direction.
  • the downstream direction and the downlink (DL) direction may be used without distinction.
  • the donor gNB 200 may be referred to as an IAB donor 200.
  • flow control In the cellular communication system 1, flow control may be performed. Flow control can avoid packet drop-related congestion (or congestion, hereinafter sometimes referred to as “congestion”) at the IAB node 300 and the IAB donor 200.
  • congestion packet drop-related congestion
  • Downstream flow control in 3GPP is supported by the BAP sublayer.
  • the IAB node 300 transmits feedback information regarding the buffer size available in each ingress (inflow) BH RLC channel to the parent node.
  • the feedback information is transmitted using the BAP Control PDU.
  • Flow control in the upstream direction is not specified in 3GPP, and it is said that it is performed by UL scheduling on the MAC layer (or by UL grant) due to implementation dependence.
  • local rerouting may be performed.
  • 3GPP in local rerouting, when a line failure (BH RLF (Backhaul Radio Link Faille)) occurs on the backhaul link, data packets are transferred via an alternative path.
  • BH RLF Backhaul Radio Link Faille
  • the IAB donor 200 sets the routing for each IAB node 300. Then, each IAB node 300 selects a relay node that transfers data packets from a plurality of relay nodes according to the routing setting. Local rerouting may be done by ignoring such routing settings and choosing an alternative path as described above.
  • the following control may be performed by combining the flow control and local rerouting explained above. That is, when the IAB node 300 receives the uplink flow control feedback (UL Flow control feedback) message from the parent node, it performs local rerouting (local rerouting). In other words, when the IAB node 300 receives the message from the parent node, it selects an alternative path and forwards the data packet to another parent node on the alternative path.
  • UL Flow control feedback uplink flow control feedback
  • local rerouting local rerouting
  • the IAB node 300 receives the uplink flow control feedback message and immediately performs local rerouting, the data to the alternative path is improved even though the congestion status of the parent node that sent the message is improved. Packets may be forwarded.
  • the relay node intervening between the parent node and the child node receives the flow control feedback message from the parent node or the child node.
  • the relay node forwards the data packet to an alternative path different from the path to the parent node or child node that sent the flow control feedback message, depending on the elapse of a certain period of time after receiving the flow control feedback message. Perform local rerouting.
  • the IAB node 300 can see the congestion status of the parent node or the child node for a certain period of time even if the IAB node 300 receives the flow control feedback message. Therefore, the IAB node 300 can maintain the path to the parent node before a certain period of time elapses if the congestion situation is improved.
  • FIG. 9 is a diagram showing an example of local rerouting when the IAB node 300-T receives a flow control feedback message from the parent node IAB node 300-P1.
  • the IAB node 300-T receives the message from the IAB node 300-P1, and after a certain period of time, a data packet is sent to the other parent node IAB node 300-P2 on the alternative path.
  • the flow control feedback message in this case is an uplink flow control feedback message.
  • FIG. 10 is a diagram showing an example of local rerouting when the IAB node 300-T receives a flow control feedback message from the child node IAB node 300-C1.
  • the IAB node 300-T receives the message from the IAB node 300-C1, and after a certain period of time, a data packet is sent to the other child node IAB node 300-C2 on the alternative path.
  • the flow control feedback message in this case is a downlink flow control feedback (DL Flow control fedback) message.
  • DL Flow control fedback downlink flow control feedback
  • the flow control feedback message may be transmitted as a BAP layer message such as BAP Control PDU.
  • BAP Control PDU a BAP layer message
  • MAC CE and / or RRC messages may be used as the flow control feedback message.
  • FIG. 11 is a diagram showing an operation example in the first embodiment.
  • the IAB node 300-T When the IAB node 300-T starts processing in step S10, it receives a flow control feedback message from the parent node 300-P1 or the child node 300-C1 in step S11.
  • the IAB node 300-T measures a certain period of time.
  • the fixed period is the period after the IAB node 300-T receives the flow control feedback message.
  • the IAB node 300-T Upon receiving the message, for example, the IAB node 300-T activates a timer to measure a certain period of time. Further, the fixed period may be preset by the IAB donor 200 or the parent node 300-P1 or may be included in the flow control feedback message.
  • the IAB node 300-T for example, causes a timer to count, and when the count value reaches a certain period, it determines that the certain period has expired and the certain period has elapsed.
  • the IAB node 300-T may use the number of times the flow control feedback message is received for the measurement in a certain period. That is, when the IAB node 300-T receives the flow control feedback message from the parent node 300-P1 or the child node 300-C1, the counter is incremented. The IAB node 300-T determines that a certain period of time has elapsed when the counter value reaches the threshold value.
  • the threshold may be preset by the IAB donor 200 or the parent node 300-P1 or may be included in the flow control feedback message.
  • the IAB node 300-T may combine the determination by the timer and the determination by the counter for the measurement in a certain period.
  • the IAB node 300-T activates the timer and increments the counter when the flow control feedback message is first received. If the counter value reaches the threshold value before the timer expires, the IAB node 300-T determines that a certain period of time has elapsed. When the timer expires, the IAB node 300-T resets (ie, sets to zero) the counter value.
  • step S13 the IAB node 300-T executes local rerouting according to the elapse of a certain period of time.
  • the IAB node 300-T receives the flow control feedback message from the parent node 300-P1, and after a certain period of time, transfers the data packet to an alternative path different from the path for the parent node 300-P1.
  • the alternative path is the same as the alternative path when the destination of the data packet is the path to the parent node 300-P1.
  • the IAB node 300-T receives the flow control feedback message from the child node 300-C1, and after a certain period of time, transfers the data packet to an alternative path different from the path for the child node 300-C1.
  • the alternative path is the same as the alternative path when the destination of the data packet is the path to the child node 300-C1.
  • the local rerouting may include the process of selecting an alternative path and / or sending a packet to the alternative path.
  • step S14 the IAB node 300-T ends a series of processes.
  • the local rerouting may be executed without elapse of a certain period of time.
  • BH RLF Type 1 Indication, Type 2 Indication, or Type 1/2 Indication may be used instead of the flow control feedback message.
  • Type1 Indication is an example of a failure occurrence notification indicating that BH RLF has been detected (RLF detected).
  • Type 2 Indication is an example of a failure occurrence notification indicating that recovery from BH RLF is being attempted (Trying to recover).
  • Type1 / 2 Indication is also an example of failure occurrence notification, and is a notification used when Type1 Indication and Type2 Indication are not distinguished.
  • Type3 Indication is a recovery notification indicating that the IAB node 300-T has recovered from the BH RLF.
  • Type4 Indication is an example of a recovery failure notification indicating that the IAB node 300-T has failed to recover from the BH RLF.
  • the execution determination of local rerouting may be made according to the request from the parent node 300-P1 or the child node 300-C1.
  • the parent node 300-P1 or the child node 300-C1 includes an identifier indicating whether or not local rerouting should be performed in the flow control giveback message.
  • the IAB node 300-T determines whether or not to perform local rerouting based on the identifier.
  • the parent node 300-P1 or the child node 300-C1 can control the local rerouting of the IAB node 300-T according to the congestion situation.
  • the IAB node 300 executes local rerouting when the data packet cannot be transferred to the parent node or the child node, for example, for a certain period of time.
  • the relay node for example, IAB node 300
  • the relay node intervening between the parent node and the child node attempts to transfer the data packet to the parent node or the child node.
  • the relay node executes local rerouting to transfer the data packet to an alternative path different from the path to the parent node or the child node.
  • the IAB node 300 can give up on the current parent node or child node and send a data packet to an alternative path, so that the latency due to data packet transfer can be reduced. Become.
  • FIG. 12 is a diagram showing an example of local rerouting in the upstream direction with respect to the IAB node 300-T.
  • the IAB node 300-T executes local rerouting when the data packet cannot be transferred to the parent node IAB node 300-P1 for a certain period of time. That is, the IAB node 300-T transfers the data packet to the IAB node 300-P2 on an alternative path different from the path for the IAB node 300-P1.
  • FIG. 13 is a diagram showing an example of local rerouting in the downstream direction with respect to the IAB node 300-T.
  • the IAB node 300-T executes local rerouting when the data packet cannot be transferred to the child node IAB node 300-C1 for a certain period of time. That is, the IAB node 300-T transfers the data packet to the IAB node 300-C2 on an alternative path different from the path for the IAB node 300-C1.
  • FIG. 14 is a diagram showing an operation example in the second embodiment.
  • the data packet is transferred to the parent node 300-P1 or the child node 300-C1 in step S21.
  • step S22 the IAB node 300-T executes local rerouting when the data packet cannot be transferred for a certain period of time.
  • A1 "When the data packet cannot be transferred for a certain period of time" means that even if the IAB node 300-T transmits a scheduling request (SR (Scheduling Request)) to the parent node 300-P1 a certain number of times. , This is the case where UL grant is not received from the parent node 300-P1.
  • SR Service Request
  • A2 or "when the data packet cannot be transferred for a certain period of time" means that the IAB node 300-T sends the SR or the buffer status report (BSR) to the parent node 300-P1 for a certain period of time. , UL grant is not received.
  • (A3) or "when the data packet cannot be transferred for a certain period of time" is a case where the number of retransmissions of HARQ / RLC to the parent node 300-P1 of the IAB node 300-T reaches a certain number of times. However, in this case, even when the number of retransmissions of HARQ / RLC reaches a certain number of times, it is desirable before the number of retransmissions becomes RLF.
  • (B2) or "when the data packet cannot be transferred for a certain period of time" is a case where the radio state between the IAB node 300-T and the child node 300-C1 falls below a certain value.
  • the radio state in this case is notified to the IAB node 300-T by the measurement report from the child node 300-C1.
  • the "fixed number of times”, “fixed time”, and “fixed value” in the above (A1) to (B3) may be set by the parent node 300-P1 or the IAB donor 200. Further, the IAB node 300-T may measure the "constant time” by using an internal timer. Further, the "fixed number of times”, “fixed time”, “fixed value”, and timer are set for each BH RLC channel, each LCG (Logical Channel Group), each source and / or destination, and the routing ID. Each may be present or measured separately. The timer value and the BH RLC channel or the like may be associated with each other.
  • the flow control withdrawal feedback message is a message for notifying that the IAB node 300 that has transmitted the message has returned from the congested state to the normal non-congested state.
  • the IAB node makes a judgment by itself and executes local rerouting.
  • the third embodiment is an embodiment of the second embodiment regarding how to stop the local rerouting when the local rerouting is executed on the IAB node 300.
  • the relay node stops the local rerouting when a certain period of time has elapsed after executing the local rerouting. This makes it possible, for example, to stop the local rerouting that the IAB node 300 has started executing at its own discretion.
  • FIG. 15 is a diagram showing an example when local rerouting is executed in the upstream direction.
  • the IAB node 300-T transfers a data packet to the IAB node 300-P2 on the alternative path to perform local rerouting.
  • the IAB node 300-T stops the local rerouting after executing the local rerouting for a certain period of time.
  • FIG. 16 is a diagram showing an example when local rerouting is executed in the downstream direction.
  • the IAB node 300-T stops the local rerouting when the local rerouting is executed for the IAB node 300-C2 for a certain period of time.
  • FIG. 17 is a diagram showing an operation example in the third embodiment.
  • the timer starts counting from the time when the execution of local rerouting is determined in step S31. In other words, local rerouting is in progress while the timer is running. Then, the timer of the IAB node 300-T counts the count value until the count value reaches a predetermined timer value.
  • the predetermined timer value may be set for the IAB node 300-T by, for example, the parent node 300-P1 (or the parent node 300-P2) or the IAB donor 200. Further, a predetermined timer value may be set for each alternative path.
  • step S32 the IAB node 300-T stops local rerouting when the count value reaches a predetermined timer value, that is, when the timer expires. Specifically, the IAB node 300-T transfers the data packet to the path according to the routing setting, and in the example of FIGS. 15 and 16, to the path to the parent node 300-P1 or the child node 300-C1. Try to do that.
  • the IAB donor 200 manages the IAB topology constructed by the subordinate IAB node 300. Further, the IAB donor 200 can grasp the congestion state and the like at each IAB node 300.
  • the IAB-CU of the IAB donor 200 provides the routing setting for the IAB-DU of each IAB node 300.
  • the routing settings provided include the routing ID and the BAP address of the next hop.
  • Each IAB node 300 performs routing based on the routing ID stored in the BAP header of the data packet.
  • the routing ID is composed of a (destination) BAP address and a BAP path ID.
  • each IAB node 300 determines that the data packet has reached the destination.
  • the (destination) BAP address does not match the own BAP address
  • each IAB node 300 transfers the received data packet to the IAB node 300 of the BAP address of the next hop according to the routing setting.
  • the routing setting by the IAB donor 200 is performed by, for example, the BAP MAPPING CONFIGURATION message of F1-AP.
  • the routing settings are centrally managed by the IAB donor 200. Then, when the data packet can be transferred at the IAB node 300 according to such a routing setting, the IAB donor 200 takes the initiative to stop the local rerouting. This makes it possible to support centralized management by the IAB donor 200.
  • a fourth embodiment is an example in which the IAB donor 200 thus stops the local rerouting running at the IAB node 300.
  • the donor base station for example, IAB donor 200
  • the first relay node stops local rerouting in response to receiving the first message.
  • FIG. 18 shows an example in which the IAB node 300-T is executing local rerouting to the IAB node 300-P2 in the upstream direction.
  • the IAB-CU of the IAB donor 200 sends a message indicating a stop instruction to the IAB-DU of the IAB node 300-T.
  • the IAB node 300-T stops local rerouting to the IAB node 300-P2.
  • FIG. 19 shows an example in which the IAB node 300-T is performing local rerouting to the IAB node 300-C2 in the downstream direction.
  • the IAB node 300-T receives the message indicating the stop instruction from the IAB donor 200, the IAB node 300-T stops the local rerouting to the IAB node 300-C2.
  • FIG. 20 is a diagram showing an operation example in the fourth embodiment.
  • step S40 When the IAB node 300 starts processing in step S40, it executes local rerouting in step S41.
  • step S42 when the IAB donor 200 is in a predetermined state, a message indicating a stop instruction for local rerouting is transmitted to the IAB node 300-T.
  • the "predetermined state" is a case where the IAB donor 200 monitors the load (or congestion) status for each route and detects a path in which the load is lower than a certain value.
  • each IAB node 300 transmits the load status to the IAB donor 200 using an F1-AP message or an RRC message.
  • the IAB donor 200 can monitor the load status for each route.
  • the IAB donor 200 sends a message indicating a stop instruction based on this load condition.
  • the message indicating the stop instruction is transmitted by the F1-AP message or the RRC message.
  • the message indicating the stop instruction may include, for example, the following information. That is, the BH RLC Channel ID may be included in the message. In this case, the BH RLC Channel having the ID is the target of the stop instruction. Alternatively, the BH LCG ID may be included in the message. In this case as well, the BH LCG having the ID is the target of the stop instruction. Alternatively, the message may include a routing ID composed of a destination ID and a path ID. In this case, the route of the routing ID is the target of the stop instruction. Alternatively, the alternative path ID may be included in the message. In this case, the alternative path of the alternative path ID is the target of the stop instruction.
  • the message indicating the stop instruction may include a valid period of the stop instruction in addition to the above-mentioned ID. In this case, the validity period may be represented by a timer value or the like.
  • step S43 the IAB node 300 stops the local rerouting in response to receiving the message indicating the stop instruction of the local rerouting. Stopping local rerouting means stopping data transmission to the alternate path, (re) selecting the path based on the routing settings (that is, the main path used before local rerouting), and to the (re) selected path. Data transmission of, may be included.
  • step S44 the IAB node 300 ends a series of processes.
  • the IAB donor 200 may send a message indicating a stop local rerouting start instruction to the IAB node 300.
  • the message may include a routing ID that is the target of the start instruction and an ID of the alternative path.
  • the IAB node 300 can grasp which alternative path of which routing ID starts local rerouting based on the information.
  • the IAB donor 200 may send a message indicating a change (or update) instruction of the local rerouting to the IAB node 300.
  • the message may include a routing ID to be changed and an ID of an alternative path.
  • the message may include information indicating local rerouting to a path indicating the next priority (eg, if the first priority path is currently selected, the second priority, etc.), or the IAB. It may contain information indicating local rerouting to a path different from the path currently selected on the node 300.
  • the IAB donor 200 may send a message indicating an instruction to maintain or cancel the maintenance or cancellation of the local rerouting that is being executed or stopped to the IAB node 300.
  • the IAB node 300 receives a message indicating the maintenance of the local rerouting being executed or stopped, the IAB node 300 maintains the decision to execute or stop the local rerouting as it is.
  • the IAB node 300 receives a message indicating the release of the maintenance of the local rerouting that is being executed or stopped, the IAB node 300 cancels the decision to execute the local rerouting or the decision to stop the local rerouting.
  • the validity period of the maintenance may be set.
  • the IAB node 300 starts the timer when it receives the message indicating the maintenance. While the timer is running, the IAB node 300 maintains a decision (state) to execute or stop local rerouting. The IAB node 300 does not have to maintain the decision (state) of executing or stopping local rerouting when the timer expires. In other words, the IAB node 300 can make a decision to perform or stop local rerouting.
  • the timer value may be preset by the IAB donor 200 or the parent node, or may be set by a message indicating the maintenance.
  • the message described above as another example is transmitted as, for example, an F1-AP message or an RRC message.
  • the IAB donor 200 In the fourth embodiment, an example in which the IAB donor 200 explicitly instructs the IAB node 300 to start local rerouting has been described. In the fifth embodiment, the IAB donor 200 notifies each IAB node 300 of the BHR RLF in the downstream direction of each IAB node 300 as assist information when deciding to perform local rerouting on each IAB node 300. It is an example to do.
  • the IAB-MT of the IAB node 300 detects the BH radio link failure (BH RLF) in the upstream direction of the IAB node. Therefore, in the IAB node 300, there is basically no means for detecting the BH RLF in the downstream direction.
  • BH RLF BH radio link failure
  • the IAB node 300 can execute local rerouting by receiving a notification from the IAB donor 200 that BH RLF has occurred in the downstream direction of the own node 300. Such a notification can assist the decision of local rerouting in the downstream direction at the IAB node 300.
  • the donor base station (for example, IAB donor 200) transmits the first message to the first relay node.
  • the first message indicates that a radio link failure has occurred in the backhaul link in the downstream direction from the first relay node to the second relay node under the first relay node.
  • the first relay node performs local rerouting in response to receiving the first message.
  • FIG. 21 is a diagram showing an example of local rerouting in the fifth embodiment.
  • the IAB donor 200 detects the BH RLF in the downstream direction of the IAB node 300-T
  • the IAB donor 200 notifies the IAB node 300-T of the occurrence of the DL BH RLF. It may be determined that the IAB donor 200 has detected the DL BH RLF in the IAB node 300-T, for example, when the measurement report is received from the IAB node 300-C which is a child node of the IAB node 300-T. ..
  • the IAB donor 200 notifies the IAB node 300-T of the occurrence of DL BH RLF at the IAB node 300-T.
  • the IAB node 300-T Upon receiving the notification of the occurrence of DL BH RLF, the IAB node 300-T performs local rerouting and transfers the data packet to another child node on the alternative path.
  • FIG. 22 is a diagram showing an operation example of the fifth embodiment.
  • the IAB donor 200 detects the RLF in the DL direction at the IAB node 300-T in step S51.
  • the IAB-CU of the IAB donor 200 receives the measurement report from the IAB-MT of the child node 300-C of the IAB node 300-T, so that the IAB donor 200 receives the measurement report, and the IAB donor 200 receives the DL BH RLF at the IAB node 300-T. May be detected.
  • the IAB donor 200 receives the MCG (Master) from the child node 300-C. Receives Cell Group) Failure Information and / or SCG (Secondary Cell Group) Failure Information.
  • the IAB donor 200 may detect the DL BH RLF at the IAB node 300-T.
  • the IAB donor 200 notifies the IAB node 300-T that DL BH RLC has occurred.
  • the IAB-CU of the IAB donor 200 may send the notification to the IAB-DU of the IAB node 300 using an RRC message or an F1-AP message.
  • step S53 the IAB node 300-T performs a predetermined operation in response to receiving the notification.
  • a predetermined operation there is local rerouting. That is, the IAB node 300-T transfers a data packet to another child node on the alternative path by local rerouting to the link (or child node 300-C) where the DL BH RLF is generated. ..
  • a predetermined operation there is a stop of DL transmission. That is, the IAB node 300-T stops the transmission of the data packet to the child node 300-C.
  • step S54 the IAB node 300 (and the IAB donor 200) ends a series of operations.
  • the IAB donor 200 when the IAB donor 200 detects that the DL BH RLF in the IAB node 300-T has recovered, the DL BH RLF has recovered to the IAB node 300-T. May be notified.
  • the IAB-CU of the IAB donor 200 may notify the IAB-DU of the IAB node 300-T by using an RRC message or an F1-AP message to notify that the DL BH RLF has recovered.
  • the sixth embodiment is an example of notifying the IAB donor 200 when the IAB node 300 determines to start or stop the execution of the local rerouting. That is, first, a second message indicating that the first relay node (for example, IAB node 300) has determined to start or stop the execution of local rerouting is sent to the donor base station (for example, IAB donor 200). Send.
  • the IAB donor 200 can grasp whether or not the local rerouting is performed at the IAB node 300. Then, the IAB donor 200 can instruct the IAB node 300 to stop or start the running local rerouting described in the fourth embodiment.
  • FIG. 23 is a diagram showing an example of notification by the IAB node 300-T.
  • FIG. 23 is an example in which it is determined to execute local rerouting in the downstream direction of the IAB node 300-T.
  • the IAB node 300-T determines whether to start or stop the execution of the local rerouting from the child node 300-C1 to the child node 300-C2, the IAB node 300-T sends a message to that effect to the IAB donor 200. Send.
  • the IAB donor 200 sends a message instructing the permission or prohibition of the execution start or execution stop of the local rerouting in the IAB node 300-T, as necessary, in response to the reception of the message. It may be transmitted to T.
  • the IAB node 300-T starts or stops execution of local rerouting in response to receiving a message instructing permission or prohibition. Specifically, for example, it is as follows.
  • the IAB node 300-T when the IAB node 300-T receives a message indicating permission to start execution from the IAB donor 200 in response to the determination to start execution, the IAB node 300-T starts executing local rerouting in response to receiving the message. .. Further, when the IAB node 300-T receives a message indicating prohibition of execution start from the IAB donor 200 in response to the determination of execution start, the IAB node 300-T does not execute local rerouting in response to the reception of the message. Further, when the IAB node 300-T receives a message indicating permission to stop execution from the IAB donor 200 in response to the determination to stop execution, the local rerouting during execution is stopped in response to the reception of the message. do. Further, when the IAB node 300-T receives a message indicating prohibition of execution stop from the IAB donor 200 in response to the determination of execution stop, the local rerouting during execution is stopped in response to the reception of the message. Continue running without doing anything.
  • FIG. 23 shows an example of starting execution of local rerouting in the downstream direction at the IAB node 300-T, but it is a case of starting execution of local rerouting in the upstream direction at the IAB node 300-T. You may.
  • FIG. 24 is a diagram showing an operation example of the sixth embodiment.
  • the IAB node 300-T When the IAB node 300-T starts the process in step S60 and determines in step S61 to start or stop the execution of local rerouting, the IAB node 300-T sends a message to the IAB donor 200.
  • the message may include information indicating which route was the target of local rerouting.
  • the information may be a BH RLC Channel ID.
  • the information may be a BH LCG ID.
  • the information may be a routing ID consisting of a destination ID and a path ID.
  • the message may include information indicating to which route the local rerouting was performed.
  • the information may be an alternative path ID.
  • the alternative path ID may be represented by a routing ID or a path ID.
  • the message may include information (reason information) indicating why the execution of local rerouting is started or stopped.
  • the information may be received from BH RLF's Type 1 Indication, Type 2 Indication, Type 1/2 Indication, Type 3 Indication, or Type 4 Indication.
  • the information may be from the reception of a flow control feedback message or a flow control withdrawal feedback message.
  • the information may be that a certain period of time has passed after receiving the flow control feedback message or the flow control withdrawal feedback message.
  • the information may be due to the inability to transfer the data packet (or the case where the data packet cannot be transferred for a certain period of time in the second embodiment).
  • the information may be instructed by the parent node.
  • the message may be transmitted as an RRC message or an F1-AP message.
  • the IAB donor 200 may send a message indicating permission or prohibition to the IAB node 300-T.
  • the IAB donor 200 may indicate the routing ID or path ID of the local rerouting destination to the message.
  • the message may also be transmitted as an RRC message or an F1-AP message.
  • the IAB node 300-T can start or not execute local rerouting in response to receiving a message indicating permission or prohibition.
  • step S61 when the IAB node 300 determines to execute the local rerouting, the IAB node 300 may ask the IAB donor 200 to execute the local rerouting by transmitting a message to the IAB donor 200.
  • step S62 the IAB donor 200 will instruct the IAB node 300 to permit or prohibit the inquiry.
  • the seventh embodiment is an example in which the IAB node 300 is determined to execute or stop the local rerouting by combining a plurality of execution conditions.
  • the relay node receives the flow control feedback control message, and the failure occurrence notification between the backhaul links between the relay node and the other relay node is notified. Transfer the data packet to an alternative path that is different from the path to the other relay node, depending on whether at least one execution condition is met: that the data packet was received and that the data packet could not be transferred for a certain period of time. Perform local rerouting. Second, after the relay node executes the local rerouting, the local rerouting is stopped when the stop condition is satisfied.
  • FIG. 25 is a diagram showing an operation example of the seventh embodiment.
  • the IAB node 300 executes local rerouting when one or more execution conditions are met in step S71.
  • the IAB node 300 executes local rerouting when at least one of the three execution conditions is met.
  • step S72 the IAB node 300 stops the local rerouting when the stop condition is met.
  • the stop condition is, for example, reception of Type 3 Indication of BH RLF. Even if the IAB node 300 starts the local rerouting in step S71, the IAB node 300 stops the local rerouting in response to receiving the Type 3 Indication.
  • step S73 the IAB node 300 ends a series of processes.
  • FIG. 26 is a diagram showing another operation example of the seventh embodiment.
  • the IAB node 300 executes local rerouting when a certain execution condition is met in step S81.
  • the execution condition is at least one of the above three execution conditions (C1) to (C3).
  • step S82 the IAB node 300 stops local rerouting when the stop condition corresponding to the execution condition is met.
  • the stop condition corresponding to the execution condition is, for example, "a flow control withdrawal feedback message has been received" in contrast to an execution condition of "a flow control feedback message has been received".
  • the IAB node 300 starts local rerouting in step S81 under the execution condition that "the flow control feedback message has been received”.
  • the IAB node 300 stops the local rerouting if the stop condition of "received the flow control withdrawal feedback message" is satisfied.
  • the stop condition corresponding to the execution condition is a condition having the opposite content to the execution condition.
  • step S83 the IAB node 300 ends a series of processes.
  • the eighth embodiment is an example in which the IAB donor 200 sets the execution condition used by the IAB node 300 from a plurality of execution conditions for the IAB node 300.
  • a donor base station for example, IAB donor 200
  • a relay node for example, IAB node 300
  • FIG. 27 is a diagram showing an operation example of the eighth embodiment.
  • the IAB donor 200 sets the execution condition used by the IAB node 300 from the plurality of execution conditions of the local rerouting for the IAB node 300 in the step S91.
  • the execution conditions that are set are
  • (D5) One or more of the threshold value, timer value, and number of times upper limit value related to the above (D1) to (D4). Further, the IAB donor 200 may set the stop condition described in the seventh embodiment to the IAB node 300.
  • the setting is performed, for example, by the IAB donor 200 transmitting an RRC message or an F1-AP message including one or more execution conditions (and a stop condition) to the IAB node 300.
  • step S92 the IAB node 300 starts (or stops) local rerouting when the situation meets the set execution condition (or stop condition).
  • the IAB node 300 starts (or stops) local rerouting when one or more of the execution conditions are met.
  • step S93 the IAB node 300 ends a series of processes.
  • a ninth embodiment is an example in which an alternative path for local rerouting is set in the IAB donor 200.
  • the ninth embodiment is an example in which the alternative path is set by the IAB donor 200, specifically, the routing ID set by the IAB donor 200 by the routing setting and the routing ID of the alternative path are linked and set.
  • the donor base station (eg, IAB donor 200) for the first relay node (eg, IAB node 300) contains information about the alternative path associated with information about the main path. Set the path. Second, the first relay node selects an alternative path based on the alternative path setting.
  • FIG. 28 is a diagram showing an operation example of the ninth embodiment.
  • an alternative path (alternative path (s)) is set for the IAB node 300 in step S101 in addition to the main path.
  • the main path is, for example, the path set in the IAB node 300 by the routing setting by the IAB donor 200 described in the fourth embodiment.
  • the main path for each IAB node 300 is set in advance by the routing setting.
  • the alternative path is, for example, a path selected when local rerouting is performed at the IAB node 300.
  • the main path is the path from IAB node 300-T to IAB node 300-P1 or 300-C1
  • the alternative path is from IAB node 300-T to IAB node 300-P2 or 300.
  • -It is a path to C2.
  • the IAB donor 200 includes the information about the alternative path in the BAP MAPPING CONFIGURATION (BAP mapping setting) message or the RRC Reconnection (RRC setting) message of the F1-AP, and the IAB node 300. Send to. As a result, the IAB donor 200 sets an alternative path for the IAB node 300.
  • BAP MAPPING CONFIGURATION BAP mapping setting
  • RRC Reconnection RRC setting
  • the information about the alternative path may include a plurality of information corresponding to a plurality of alternative paths.
  • the information regarding the alternative path includes the linking information between the routing ID of the main path and the routing ID of the alternative path.
  • the information regarding the alternative path may include the routing ID of the alternative path, and the routing ID of the main path may be specified corresponding to the routing ID to perform the association (or association).
  • a grouping ID may be used as the association information.
  • the grouping ID is an ID defined for grouping the path ID of the main path and the path ID of the alternative path. The grouping ID associates the routing ID of the main path with the routing ID of the alternative path.
  • the information about the alternative path includes the destination ID of the alternative path.
  • the destination ID of the alternative path is the same as the destination ID of the main path.
  • the two destination IDs may be different.
  • the information about the alternative path includes the path ID of the alternative path.
  • the path ID of the alternative path may be different from or the same as the path ID of the main path.
  • a list of next hop BAP addresses (Next Hop BAP Address) may be set for each routing ID.
  • the first entry in the list may be identified as the next hop BAP address of the main path, and the second and subsequent entries may be identified as the next hop BAP address of the alternative path.
  • the order of the entries in the list may represent the priority of the next hop BAP address.
  • the information about the alternative path includes the routing ID of the alternative path.
  • the information about the alternative path may further include the following information. That is, corresponding to (or tied to) an alternative path,
  • Ingress BH RLC CH ID (Ingress BH RLC CH ID) May be included in whole or in part.
  • the information regarding the alternative path may further include the following information. That is, corresponding to (or tied to) an alternative path,
  • the priority setting of the above (F1) is setting information so that alternative paths are selected in descending order of priority. For example, when the priority "1", "2", ... Of a plurality of alternative paths are included in the setting information, the IAB node 300 selects the alternative path having the priority "1" when performing local rerouting. Attempt packet transfer. As a result, if the packet cannot be forwarded, the IAB node 300 selects an alternative path of priority "2". Alternatively, if the setting information includes the following information, there is no need to set the priority.
  • the IAB node 300 may select an alternative path in the order of the alternative path in the donor DU, the alternative path in the donor, and the alternative path between the donors.
  • the selection probability setting in (F2) above is the selection probability displayed as a percentage or an antilogarithm (0 to 1) for each alternative path.
  • the IAB node 300 uses a random number to select an alternative path based on the random number value and the selection probability. For example, suppose there are three alternative paths and each selection probability is ⁇ 0.5, 0.3, 0.2 ⁇ . In this case, the IAB node 300 selects the alternative path having the first selection probability when the random number value is 0.4, and the alternative path having the second selection probability when the random number value is 0.7. If the random number value is 0.9, the alternative path having the third selection probability is selected.
  • the total value of the selection probabilities is preferably 100% (or 1).
  • the above (F3) is a timer value indicating a valid period set for each alternative path and a timer value indicating a prohibited period.
  • the timer value is used as follows.
  • the IAB node 300 starts counting by the timer when an alternative path is selected by local rerouting or when packet transfer is started to the alternative path. Then, the IAB node 300 can use the selected alternative path when the count value by the timer does not reach the timer value indicating the valid period (during running). On the other hand, the IAB node 300 stops (or prohibits) the use of the alternative path when the count value by the timer reaches the timer value indicating the valid period (when the timer expires). Then, the IAB node 300 starts counting by the timer after the end (or stop or prohibition) of the executed local rerouting.
  • the IAB node 300 prohibits the use of the terminated alternative path.
  • the alternative path is excluded from the selection candidates and another alternative path is selected while local rerouting continues.
  • the IAB node 300 can use the terminated alternative path.
  • the alternative path may be a candidate for alternative path selection.
  • step S102 when performing local rerouting, the IAB node 300 selects an alternative path based on the alternative path setting set by the IAB donor 200, and attempts packet transfer.
  • step S103 the IAB node 300 ends a series of processes.
  • the IAB donor 200 may change the routing setting because the performance of the entire topology is deteriorated.
  • the tenth embodiment is an example of stopping (or canceling) the operation of local rerouting when the routing setting is changed.
  • the first relay node (for example, IAB node 300) starts local rerouting.
  • the donor base station eg, IAB donor 200
  • the first relay node stops local rerouting in response to receiving the first message.
  • FIG. 29 is a diagram showing an operation example in the tenth embodiment.
  • step S110 When the IAB node 300 starts processing in step S110, it starts local rerouting in step S111.
  • the IAB donor 200 updates the routing setting of the IAB node because it has detected a performance degradation of the entire topology.
  • the IAB donor 200 may detect a performance deterioration of the entire topology by receiving a message from the IAB node 300 indicating a load status such as an increase in the load at the IAB node 300. Then, the IAB donor 200 sends a message indicating the setting update to all the IAB nodes 300 under the control.
  • the message may be an F1-AP message or an RRC message.
  • step S113 the IAB node 300 stops local rerouting in response to receiving a message indicating a setting update. For example, it is assumed that local rerouting is started by receiving Type 2 Indication of BF RLF. In such a case, "stop” means that the "stop” does not have to wait for the Type 3 Indication, and the reception of the Type 3 Indication at the IAB node 300 does not have to be expected.
  • step S114 the IAB node 300 ends a series of processes.
  • the eleventh embodiment is an example in which the IAB donor 200 transmits the load information of each path to the IAB node 300.
  • a donor base station for example, IAB donor 200
  • a first relay node for example, IAB node 300
  • the first relay node executes or stops local rerouting based on the load information.
  • the IAB donor 200 transmits the load information of each path to the IAB node 300, so that the IAB node 300 can select an alternative path with a good load condition when local rerouting is performed. This makes it possible to prevent data packet transfer delays and prevent performance degradation of the entire topology.
  • FIG. 30 is a diagram showing an operation example in the eleventh embodiment.
  • the IAB donor 200 When the IAB donor 200 starts the process in step S120, the IAB donor 200 transmits a message including the load information of each path to the IAB node 300 in step S121.
  • the opportunity for the IAB donor 200 to send the message is, for example, as follows. That is, the IAB donor 200 may send the message periodically. Alternatively, the IAB donor 200 may send the message when requested by the IAB node 300.
  • the "request" in this case is, for example, a request transmitted from the IAB node 300 in response to the determination regarding local rerouting when the IAB node 300 makes a determination regarding local rerouting.
  • the IAB donor 200 sends the message when it deems it necessary. "When it is determined to be necessary" is, for example, when the load on a certain path is significantly increased. Since the IAB donor 200 can acquire load information from the IAB node 300 on the path, based on this load information, it is determined that the load has increased remarkably when the load of a certain path rises above the threshold value in a short time. You may.
  • the "load information of each path" included in the message including "load information of each path" transmitted by the IAB donor 200 is, for example, at the load level for each routing ID or the load level for each path ID. be.
  • the load level is displayed, for example, as a percentage of 0 to 100%.
  • the IAB donor 200 can increase the priority of low-load paths. This makes it possible for the IAB node 300 to increase the possibility of selecting a path having a low load as an alternative path.
  • the priority information set in the IAB node 300 can be updated. Therefore, for example, when the IAB donor 200 detects that the load of a certain path has become high, it is possible to set the priority of the path set in the IAB node 300 to be low by updating the priority information. Become. This makes it possible to update the priority information of each path set by the routing setting by the IAB donor 200 by transmitting a message in step S121.
  • the priority information using the message in step S121 can be updated more frequently than the setting by the routing setting.
  • step S122 the IAB node 300 performs a predetermined operation using the load information.
  • the IAB node 300 determines that the path currently used is the main path and the local rerouting is executed when the load of the main path indicated by the load information exceeds a certain value. Further, for example, the IAB node 300 determines that the path currently used is an alternative path and the local rerouting is stopped when the load of the alternative path indicated by the load information exceeds a certain value. When the priority information is used instead of the load information, the IAB node 300 determines that the local rerouting is executed when the priority information of the main path currently used is lower than the priority threshold value. On the other hand, the IAB node 300 stops the local rerouting when the priority information of the alternative path currently used is lower than the priority threshold value.
  • the constant value or priority threshold may be set by the IAB donor 200.
  • the IAB node 300 uses the load information to select an alternative path based on the following criteria when executing local rerouting. That is, the IAB node 300 selects the path having the lowest load among the loads shown in the load information as the alternative path. Alternatively, the IAB node 300 may arbitrarily select from paths whose load is below a certain level. When the priority information is used instead of the load information, the IAB node 300 selects the path having the highest priority among the priorities shown in the priority information as the alternative path. Alternatively, the IAB node 300 may select any path as an alternative path from the paths having a certain priority or higher.
  • the twelfth embodiment is an example in which the IAB-donor-DU BAP address (IAB-donor-DU BAP Address) is set in the IAB node 300 by the IAB donor 200.
  • the IAB node 300 can select the IAB-donor-DU BAP address in another IAB donor different from the IAB donor 200 as an alternative path. This enables inter-donor-DU rerouting.
  • the donor base station (for example, IAB donor 200) sets the BAP address of the donor base station to the first relay node (for example, IAB node 300).
  • the donor base station sets the BAP address of another donor base station different from the donor base station to the first relay node.
  • the first relay node decides to perform local rerouting.
  • the first relay node selects the path to the BAP address of either the BAP address of the donor base station or the BAP address of another donor base station as an alternative path.
  • the IAB-donor-DU BAP address is, for example, the BAP address of the IAB-DU in the IAB donor.
  • FIG. 31 is a diagram showing an operation example of the twelfth embodiment.
  • the IAB donor 200 sets the IAB-donor-DU BAP address of another IAB donor that can be selected as an alternative path for the IAB node 300 in step S131.
  • Another IAB donor is an IAB donor different from the IAB donor 200.
  • the BAP address of the IAB-DU belonging to another donor different from the IAB donor 200 is set.
  • the IAB donor 200 uses, for example, an F1-AP message to set the BAP address of the IAB-DU of another IAB donor.
  • the BAP address of the IAB-DU of the IAB donor 200 itself is set by the IAB donor 200 by the routing setting as described in the fourth embodiment before the present processing is performed.
  • the IAB donor 200 may have a forwarding path established in advance with the other IAB donor.
  • the IAB node 300 determines the execution of local rerouting. For example, the IAB node 300 may decide to execute local rerouting when it detects BH RLF. Alternatively, the execution of local rerouting may be performed by the opportunity described in (1st embodiment), (2nd embodiment), (4th embodiment), (7th embodiment), or (8th embodiment) described above. It may be decided.
  • the IAB node 300 selects an alternative path.
  • step S134 the IAB node 300 forwards the packet to the selected alternative path.
  • step S135 the IAB node 300 ends a series of processes.
  • 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.
  • Computer-readable media can be used to install programs on a computer.
  • the computer-readable medium on which the program is recorded may be a non-transient recording medium.
  • the non-transient recording medium is not particularly limited, but may be, for example, a recording medium such as a CD-ROM or a DVD-ROM.
  • a circuit that executes 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). ..
  • Topology Adaptation Enhancements-Procedure specifications for interdonor IAB node movement to enhance robustness and load balancing, including enhancements to reduce signaling load. -Specifications of extended functions for reducing service interruptions due to IAB node movement and BH RLF recovery. -Extended specifications for topology redundancy, including support for CP / UP isolation. Topology, Routing, and Transport Enhancements-Extension specifications to improve overall topology fairness, multi-hop delay, and congestion mitigation.
  • RAN2 discusses enhancements to RLF indications / handling with a focus on reducing service interruptions after BH RLF. CHO and potential IAB-specific extensions of CHO are under consideration. • DAPS and potential IAB-specific extensions to DAPS have not been ruled out at this time (although the lack of PDCP makes it unclear how to support DAPS). -For message bundling, RAN2 waits for further progress in RAN3, at least for topology adaptation procedures. RAN2 discusses local rerouting, including benefits for central routing decisions, and how to address overall topology goals.
  • RAN2 has agreed to "consider expanding topology adaptation to improve robustness (eg for rapid shadowing)". This means that BH RLF occurs more frequently in Rel-17 than in the case of Rel-16, as the radio state is expected to change more dynamically.
  • the problem with Rel-16 is that the child IAB node cannot transfer upstream data during parental RLF recovery, or even if data is transferred, the parent cannot transfer data due to BH RLF. Therefore, in any case, the data cannot reach the IAB donor and the service is interrupted.
  • Finding 3 Using Rel-16's BH RLF indication (type 4), data transfer is interrupted at the IAB node while the parent's RLF recovery is in progress.
  • the parent BH RLF should be notified to the child IAB node as soon as possible in order to take appropriate action to reduce the delay. This is in line with RAN2's agreement that "RAN2 will discuss the expansion of RLF indication / handling with a focus on reducing service interruptions after BH RLF.” Therefore, RAN2 should introduce a type 2 "attempting recovery" BH RLF indication. In addition, type 1 and type 2 have the same meaning.
  • Proposal 1 RAN2 should agree that the BH RLF indication type 2 "attempting recovery" has been introduced. Further consideration is needed as to whether it is transmitted via BAP Control PDU, SIB1, or both.
  • the BH link is not under the RLF (ie, "recovered"), as shown in option 2 of FIG. 33.
  • the option will no longer be broadcast. Therefore, the downstream IAB node and UE recognize whether the BH link has been restored based on the absence of type 2 indications in SIB1.
  • the downstream IAB node can quickly know the BH link recovery.
  • the disadvantage is that its recovery is unknown. Therefore, RAN2 should consider whether Type 3 indications are really needed.
  • Proposal 2 If Proposal 1 can be agreed, RAN2 should consider whether explicit BH RLF indications, ie, type 3 "BH link recovery", should be introduced when BH RLF is gone. ..
  • Proposal 1 and / or Proposal 2 can be agreed, the operation of the IAB-MT that received the indication should be considered while the BH link is recovering. It has been proposed that IAB-MT reduce / stop SR when it receives a Type 2 indication and resume operation when it receives a Type 3 indication (ie, the parent IAB node loses BH RLF). .. This is one of the desirable IAB-MT behaviors when the parent node attempts to restore the BH link. It is assumed that other IAB-MT operations such as interrupting all RBs are also possible.
  • Proposal 3 RAN2 should agree to reduce / stop scheduling requests after IAB-MT receives a Type 2 indication and resume scheduling requests when the parent node runs out of BH RLF. be.
  • RAN2 will discuss the expansion of RLF indication / handling with a focus on reducing service interruptions after BH RLF", rather, which IAB-MT should do to reduce service interruptions.
  • CHO conditional handover
  • a common aspect of local rerouting and CHO is the need for certain trigger conditions. Therefore, Type 2 indications may function for such purposes. Therefore, in addition to Proposal 3, RAN2 should discuss the behavior of other IAB-MTs when the parent is trying to recover from BH RLF.
  • Proposal 4 RAN2 should discuss the behavior of other IAB-MTs when receiving Type 2 BH RLF indications. Further consideration is needed, such as triggering local rerouting and / conditional handover.
  • Conditional Handover (Extended conditional handover) Conditional Handover (CHO) is introduced in Rel-16 to improve mobility robustness.
  • CHO can be used for the specified Rel-16 IAB.
  • RAN2 agreed that "CHO and potential IAB-specific extensions of CHO are under consideration.” Therefore, in addition to the Rel-16 CHO baseline, it is worth considering the CHO extension of eIAB.
  • the Rel-16 CHO as shown in FIG. 34, when the corresponding CHO event (A3 / A5) is satisfied, or when the selected cell is a CHO candidate as a result of cell selection for RRC reestablishment. Is executed.
  • the CHO event A3 / A5 can be met when the IAB node experiences BH RLF on the BH link.
  • these trigger conditions cannot be satisfied in the RLF peculiar to IAB, that is, the RLF by receiving the BH RLF indication (type 4) because the radio state of the BH link of the IAB node itself is good.
  • one of the desirable actions is to execute CHO when the IAB node receives the BH RLF indication.
  • Findings 4 Rel-16 CHO has a CHO event A3 at IAB-MT because the parent's BH RLF recovery is in progress and even if it fails, the BH link between IAB-MT and the parent is still good. Not automatically triggered / executed by / A5.
  • Proposal 5 RAN2 should discuss whether additional trigger conditions for CHO are specified, at least when the IAB node receives the BH RLF indication (type 4). If additional trigger conditions are introduced, further consideration is needed to determine whether they are applicable to Type 2.
  • the current specification states, "If performing a conditional reconfiguration triggers multiple NR cells, the choice depends on the UE implementation. For example, the UE considers the beam and beam quality. Select one of the cells triggered for execution. " This is primarily intended for UEs.
  • Finding 5 In Rel-16 CHO, when multiple candidate cells trigger CHO execution, which cell is selected depends on the implementation of the UE.
  • IAB-MT For IAB-MT, it is always best if IAB-MT chooses one of the implementation-triggered cells, depending on local radio quality etc., because the purpose of the entire topology is properly handled by the IAB donor. Not exclusively. Therefore, RAN2 should discuss how to confirm the execution of CHO for IAB donor control for additional trigger conditions such as Proposal 5.
  • the IAB donor may set priority information associated with CHO candidates in the CHO setting. The IAB-MT should select the highest priority cell from all triggered CHO candidates that meet a particular radio quality (such as S-criterion).
  • Proposal 6 RAN2 should consider whether IAB donor-controlled CHO execution is required as an additional extension if all candidate cells trigger CHO upon receipt of BH RLF indication.
  • Rel-17 should aim to apply local rerouting to other cases agreed by RAN2 to improve load balancing, signaling reduction, robustness and / or service interruption.
  • BH RLF indications as in Proposal 4 (to improve robustness / service interruption) and / or by receiving flow control feedback (for load balancing / congestion mitigation), etc.
  • BH It is worth considering additional conditions for starting / stopping local rerouting other than RLF. That is, in general, parents and / or children should be able to conditionally trigger local rerouting of IAB nodes.
  • Finding 6 In Rel-16, local rerouting is allowed only in the case of BH RLF. This improves robustness and service interruptions.
  • Proposal 7 RAN2 should discuss whether additional conditions will be introduced to start / stop local rerouting. This allows other IAB nodes to be triggered, such as by receiving a BH RLF indication and / or receiving flow control feedback as in Proposal 4.
  • Finding 7 In the local rerouting of Rel-16, which path is selected as an alternative path depends on the implementation of IAB-MT.
  • IAB donors should become more important if local rerouting is extended beyond the case of BH RLF. It is clear that the IAB donor can set an alternative path, as the IAB node must select an alternative path when performing local rerouting. Modeling of alternative paths requires further consideration, such as whether the alternative paths have the same routing ID.
  • Proposal 8 RAN2 should consider whether the IAB donor can set an alternative path to the IAB node in addition to the routing settings of Rel-16.
  • IAB donors should be aware of local rerouting, even if they start / stop local rerouting on the IAB node for the coexistence of local rerouting and the purpose of the entire topology. Good things should be considered. For example, the IAB donor may consider whether the overall topology objective is still achieved, based on the awareness of which IAB node is currently performing local rerouting. If the IAB donor finds that the overall topology goal cannot be achieved, the IAB donor may instruct the IAB node to start / stop local rerouting, or the IAB donor may change the routing settings for the entire IAB topology. ..
  • Proposal 9 RAN2 should discuss whether the IAB node needs to notify the IAB donor when local rerouting starts / stops.
  • Proposal 10 RAN2 should discuss whether the IAB donor can instruct the IAB node to start / stop local rerouting.
  • Finding 8 In Rel-16, when the IAB node attempts an RRC re-establishment request to a descendant node, the IAB node must wait for the failure and finally move to idle.
  • Proposal 11 RAN2 should agree that optimization of cell (re) selection is considered to avoid re-establishment to inappropriate nodes (eg, descendant nodes).
  • the common concept is considered to be that the IAB-MT is provided in either the allow list or the block list for the purpose of cell selection. obtain.
  • allow and block lists have advantages depending on the topology and the location of the IAB nodes. And there are disadvantages.
  • the block list may be more appropriate to reduce overhead, for example because it contains only the downstream IAB nodes of the IAB node of concern and, in some cases, only a small number of child IAB nodes.
  • Findings 9 The allow list and block list have advantages and disadvantages depending on the topology and location of the IAB node.
  • the IAB donor or parent IAB node
  • Proposal 12 RAN2 should agree that the IAB-MT will be provided with an allow list or block list (ie, a selection structure) for the purpose of cell selection to avoid re-establishment to descendant nodes. Further consideration is needed as to whether these lists can also be used for cell reselection procedures.
  • an allow list or block list ie, a selection structure
  • Proposal 12 can be agreed, further consideration should be given to how the information (ie, permit list or block list) is provided.
  • Option 1 assumes a CHO setting and may require some extensions.
  • Option 2 envisions additional indications, such as type 2 BH RLF indications.
  • Option 3 is intended to provide information about the entire topology that is not in the existing configuration.
  • Option 5 is supposed to be set by OAM, but as the reporter pointed out, this is suspicious.
  • Proposal 13 RAN2 should agree that the allow list / block list is dynamically provided by the parent IAB node or IAB donor each time the topology changes. Further studies are needed for details.
  • the second solution "Reroute buffered PDCP PDUs at intermediate IAB nodes," was supported as an implementation choice at the BAP layer. Further, the BAP layer may be executed "for example, data buffering in the transmission part of the BAP entity is implementation-dependent until the RLC-AM entity receives the acknowledgment". These BAP implementations were considered to avoid packet loss in the "most" cases of the Rel-16 deployment scenario, i.e. when using fixed IAB nodes, but are not perfect, for example, as in Figure 36. rice field.
  • the third solution “Introduction of UL status distribution,” was a promising solution for guaranteeing lossless distribution of UL data in consideration of the evaluation results cited in FIG. 36.
  • the idea was to delay the RLC ARQ to the UE so that it would start when PDCP data recovery in the UE was needed.
  • a fixed IAB node was assumed, it was considered rare that UL packets were dropped due to a topology change, so it was not specified in Rel-16.
  • RAN2 should discuss, in addition to the results captured by TR, an extended mechanism to ensure lossless delivery within the L2 multihop network.
  • Proposal 14 is a solution identified in TR38.874, a mechanism that guarantees lossless delivery under conditions where topology changes may occur frequently based on some form of "UL status delivery". Should be agreed to be introduced.
  • C-2 should be an extended baseline for Rel-17 for lossless delivery of UL packets.
  • Finding 10 C-2, which is the solution to "introduction of UL status distribution", may be an extended baseline for Rel-17, which can also be implemented for Rel-16.
  • Rel-17 should assume a dynamic topology change that causes UL packet loss
  • the extension of Rel-17 will support C-2 as a standard support function.
  • At least the stage 2 specification should explain the overall mechanism based on C-2. Otherwise, the 3GPP standard does not guarantee lossless delivery during the handover of the IAB node.
  • small changes such as RLC and / or BAP are expected in stage 3, but details may not be specified as they are considered internal behavior of the IAB node.
  • Proposal 15 RAN2 should agree to specify an RLC ARQ mechanism for lossless delivery of UL packets in stage 2. This delays the transmission of the ACK to the child node / UE before receiving the ACK from the parent IAB node (ie, C-2). Whether or not to specify in stage 3 / how to specify it needs further consideration.
  • Rel-17 aims to specify the movement of the Interdonor IAB node, which will provide robust operation and will be applied to mobile IAB nodes.
  • the movement of the Interdonor IAB node of Rel-17 is performed during the active phase, so the movement of the Interdonor IAB node of one IAB node affects the entire topology. causes a service interruption.
  • moving an interdonor IAB node in Rel-17 is a method of moving all IAB nodes in the IAB topology to another IAB donor, specifically an RRC reconfiguration with synchronization (ie, a handover command). Need to be considered how is provided to these affected IAB nodes.
  • -Case 1 When the parent is moved first, the RRC signaling path between the child and the source donor is released. Therefore, it is unclear how the child node can be moved.
  • -Case 2 When the child is first moved, the RRC signaling path to the target donor via the parent node has not yet been established. Therefore, it is unclear how the child node will access the target donor (ie, how to complete the RRC reconfiguration and send it to the target donor).
  • the CHO may be reused using some extensions of the child node. That is, when the parent node is moved, the CHO is executed on the child node.
  • the transmission of the child node's RRC reconfiguration to the target donor may be delayed, for example, by its parent node.
  • the overall procedure for moving interdonor IAB nodes is being considered in RAN3, but RAN2 needs to consider the impact of RAN2 on how to reconfigure multiple IAB nodes in a multi-hop network.
  • Proposal 16 RAN2 needs to consider how to reconfigure the multi-hop IAB node for interdonor IAB node movement.

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3GPP TS 38.300, September 2020 (2020-09-01)
CATT: "On Remaining Open Issues of IAB Routing", 3GPP DRAFT; R2-1914385, 3RD GENERATION PARTNERSHIP PROJECT (3GPP), MOBILE COMPETENCE CENTRE ; 650, ROUTE DES LUCIOLES ; F-06921 SOPHIA-ANTIPOLIS CEDEX ; FRANCE, vol. RAN WG2, no. Reno, USA; 20191118 - 20191122, 8 November 2019 (2019-11-08), Mobile Competence Centre ; 650, route des Lucioles ; F-06921 Sophia-Antipolis Cedex ; France , XP051816469 *
INTEL CORPORATION: "Discussion on Topology-wide fairness and flow control enhancement", 3GPP DRAFT; R2-2009200, 3RD GENERATION PARTNERSHIP PROJECT (3GPP), MOBILE COMPETENCE CENTRE ; 650, ROUTE DES LUCIOLES ; F-06921 SOPHIA-ANTIPOLIS CEDEX ; FRANCE, vol. RAN WG2, no. Electronic meeting; 20201102 - 20201113, 23 October 2020 (2020-10-23), Mobile Competence Centre ; 650, route des Lucioles ; F-06921 Sophia-Antipolis Cedex ; France , XP051942207 *
LG ELECTRONICS INC.: "Consideration on routing enhancement", 3GPP DRAFT; R2-2007295, 3RD GENERATION PARTNERSHIP PROJECT (3GPP), MOBILE COMPETENCE CENTRE ; 650, ROUTE DES LUCIOLES ; F-06921 SOPHIA-ANTIPOLIS CEDEX ; FRANCE, vol. RAN WG2, no. electronic; 20200817 - 20200828, 7 August 2020 (2020-08-07), Mobile Competence Centre ; 650, route des Lucioles ; F-06921 Sophia-Antipolis Cedex ; France , XP051912063 *
See also references of EP4258732A4

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JP2024023471A (ja) 2024-02-21
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JP7397221B2 (ja) 2023-12-12
US20230345346A1 (en) 2023-10-26

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