Communication control method

Abstract

To provide a mobile communication system, a communication control method used therefor, a program and a chip set for grasping the abnormality of a PC5 link, and for performing various processing such as data-transmission stop to the abnormality.SOLUTION: In a mobile communication system capable of performing a first communication on a predetermined link between a first remote user apparatus and a predetermined apparatus and a second communication on an indirect link between the first remote user apparatus and the predetermined apparatus via a second relay user apparatus, when the first remote user apparatus detects an abnormality of the indirect link, the first remote user apparatus transmits an abnormality notification message including information indicating the abnormality to the predetermined apparatus via the predetermined link. 200. When an abnormality notification message is transmitted from the first remote user device, communication to the indirect link is interrupted.SELECTED DRAWING: Figure 14

Description

[Technical Field]

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

[0002] In mobile communication systems based on the 3GPP (3rd Generation Partnership Project) (registered trademark; hereinafter the same) standard, a sidelink relay technology using a user equipment as a relay node is being studied (see, for example, "3GPP TS 38.300 V16.8.0(2021-12)"). Sidelink relay is a technology in which a relay node called a relay user equipment (Relay UE) intervenes in communication between a base station and a remote user equipment (Remote UE) and relays this communication. Summary of the Invention

[0003] A first aspect of the present invention provides a communication control method for a mobile communication system that enables a first communication over a predetermined link between a first remote user device and a predetermined device, and a second communication over an indirect link between the first remote user device and the predetermined device via a second relay user device. The communication control method includes a step in which the first remote user device detects an abnormality in the indirect link. The communication control method also includes a step in which the first remote user device transmits an abnormality notification message including information indicating the abnormality to the predetermined device via the predetermined link.

[0004] A communication control method according to a second aspect is a communication control method in a mobile communication system capable of a first communication on a predetermined link between a first remote user equipment (UE) and a base station and a second communication on an indirect link between the first remote user equipment (UE) and the base station via a second relay user equipment (UE), the communication control method comprising the steps of: when the second relay user equipment (UE) has handed over to another base station, transmitting a first handover notification message including information indicating the handover to the first remote user equipment (UE) via the indirect link; and when the first remote user equipment (UE) has handed over to another base station, transmitting a second handover notification message including information indicating the handover to the second relay user equipment (UE) via the indirect link.

[0005] A communication control method according to a third aspect is a communication control method in a mobile communication system capable of a first communication over a predetermined link between a first remote user equipment and a predetermined device and a second communication over an indirect link between the first remote user equipment and the predetermined device via a second relay user equipment, the communication control method including a step of the first remote user equipment performing a relay station reselection process, and a step of the first remote user equipment transmitting a relay station reselection notification message to the predetermined device via the predetermined link, the relay station reselection notification message including identification information of a third relay user equipment selected by the relay station reselection process.

[0006] A fourth aspect of the present invention provides a communication control method for a mobile communication system that enables a first communication over a predetermined link between a first remote user equipment and a predetermined device, and a second communication over an indirect link between the first remote user equipment and the predetermined device via a second relay user equipment. The communication control method includes a step of the first remote user equipment detecting a radio link failure in the indirect link, and a step of the first remote user equipment not performing relay reselection when a radio quality of the predetermined link is equal to or greater than a threshold. [Brief explanation of the drawings]

[0007] [Figure 1]FIG. 1 is a diagram showing an example of the configuration of a mobile communication system according to the first embodiment. [Figure 2] FIG. 2 is a diagram illustrating an example of the configuration of a UE according to the first embodiment. [Figure 3] FIG. 3 is a diagram illustrating an example of the configuration of a gNB according to the first embodiment. [Figure 4] FIG. 4 is a diagram illustrating an example of the configuration of a protocol stack of a user plane according to the first embodiment. [Figure 5] FIG. 5 is a diagram illustrating an example of the configuration of a protocol stack of a control plane according to the first embodiment. [Figure 6] FIG. 6 is a diagram illustrating an assumed scenario according to the first embodiment. [Figure 7] FIG. 7 is a diagram illustrating an example of the configuration of a protocol stack of a user plane in an assumed scenario according to the first embodiment. [Figure 8] FIG. 8 is a diagram illustrating an example of the configuration of a protocol stack of a control plane in an assumed scenario according to the first embodiment. [Figure 9] FIG. 9 is a diagram illustrating an example of the configuration of a mobile communication system according to the first embodiment. [Figure 10] FIG. 10 is a diagram illustrating an example of the configuration of a mobile communication system according to the first embodiment. [Figure 11] FIG. 11 is a diagram illustrating an example of the configuration of a mobile communication system according to the first embodiment. [Figure 12] FIG. 12 is a diagram illustrating an example of the configuration of a mobile communication system according to the first embodiment. [Figure 13] FIG. 13 is a diagram illustrating an example of the configuration of a mobile communication system according to the first embodiment. [Figure 14] FIG. 14 is a diagram illustrating an example of operation according to the first embodiment. [Figure 15] FIG. 15 is a diagram illustrating an example of operation according to the second embodiment. [Figure 16] FIG. 16 is a diagram illustrating an example of operation according to the third embodiment. [Figure 17] FIG. 17 is a diagram illustrating an example of operation according to the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] A mobile communication system according to an embodiment will be described with reference to the drawings. In the description of the drawings, the same or similar parts are denoted by the same or similar reference numerals.

[0009] (Example of a mobile communication system configuration) An example of the configuration of a mobile communication system according to one embodiment will be described. The mobile communication system 1 according to one embodiment is a 3GPP 5G system. Specifically, the radio access method in the mobile communication system 1 is NR (New Radio), which is a 5G radio access method. However, LTE (Long Term Evolution) may be applied at least partially to the mobile communication system 1. Furthermore, future mobile communication systems such as 6G may also be applied to the mobile communication system 1.

[0010] FIG. 1 is a diagram showing an example of the configuration of a mobile communication system 1 according to an embodiment.

[0011] As shown in FIG. 1, the mobile communication system 1 includes a user equipment (UE) 100, a 5G radio access network (NG-RAN) 10, and a 5G core network (5GC) 20.

[0012] The UE 100 is a mobile wireless communication device. The UE 100 may be any device that is used by a user. For example, the UE 100 may be a mobile phone terminal (including a smartphone), a tablet terminal, a laptop PC, a communication module (including a communication card or a chipset), a sensor or a device provided in a sensor, a vehicle or a device provided in a vehicle (Vehicle UE), or an aircraft or a device provided in an aircraft (Aerial UE).

[0013] The NG-RAN 10 includes a base station (called a "gNB" in a 5G system) 200. The gNBs 200 are connected to each other via an Xn interface, which is an interface between base stations. The gNB 200 manages one or more cells. The gNB 200 performs wireless communication with a UE 100 that has established a connection with its own cell. The gNB 200 has a radio resource management (RRM) function, a routing function for user data (hereinafter simply referred to as "data"), and a measurement control function for mobility control and scheduling. The term "cell" is used to indicate the smallest unit of a wireless communication area. The term "cell" is also used to indicate a function or resource that performs wireless communication with a UE 100. One cell belongs to one carrier frequency. In the following, the term "cell" and a base station may be used interchangeably.

[0014] In addition, the gNB200 can also be connected to the EPC (Evolved Packet Core), which is the LTE core network. The LTE base station can also be connected to the 5GC20. The LTE base station and the gNB200 can also be connected via an inter-base station interface.

[0015] The 5GC20 includes an Access and Mobility Management Function (AMF) and a User Plane Function (UPF) 300. The AMF performs various mobility controls for the UE 100. The AMF manages the mobility of the UE 100 by communicating with the UE 100 using Non-Access Stratum (NAS) signaling. The UPF controls data forwarding. The AMF and UPF 300 are connected to the gNB 200 via an NG interface, which is an interface between a base station and a core network.

[0016] (Configuration of user device) Next, a configuration example of the UE 100, which is a user equipment according to an embodiment, will be described. FIG.

[0017] As shown in FIG. 2, the UE 100 includes a receiving unit 110, a transmitting unit 120, and a control unit .

[0018] The receiving unit 110 performs various types of reception under the control of the control unit 130. The receiving unit 110 includes an antenna, and converts (down-converts) a radio signal received by the antenna into a baseband signal (received signal) and outputs the baseband signal to the control unit 130.

[0019] The transmitter 120 performs various transmissions under the control of the controller 130. The transmitter 120 includes an antenna, and converts (up-converts) a baseband signal (transmission signal) output by the controller 130 into a radio signal and transmits it from the antenna.

[0020] The control unit 130 performs various controls in the UE 100. The control unit 130 includes at least one memory and at least one processor electrically connected to the memory. The memory stores programs executed by the processor and information used in processing by the processor. The processor may include a baseband processor and a CPU. The baseband processor performs modulation / demodulation and encoding / decoding of baseband signals. The CPU executes programs stored in the memory to perform various processes. Note that the control unit 130 may perform each process and / or each operation in the UE 100 in each of the embodiments described below.

[0021] (Base station configuration example) Next, a configuration example of the gNB 200, which is a base station according to an embodiment, will be described. Fig. 3 is a diagram illustrating a configuration example of the gNB 200.

[0022] As shown in FIG. 3, the gNB 200 has a transmitter 210, a receiver 220, a controller 230, and a backhaul communication unit 240.

[0023] The transmitter 210 performs various transmissions under the control of the controller 230. The transmitter 210 includes an antenna, and converts (up-converts) a baseband signal (transmission signal) output by the controller 230 into a radio signal and transmits it from the antenna.

[0024] The receiving unit 220 performs various types of reception under the control of the control unit 230. The receiving unit 220 includes an antenna, and converts (down-converts) a radio signal received by the antenna into a baseband signal (received signal) and outputs the baseband signal to the control unit 230.

[0025] The control unit 230 performs various controls in the gNB 200. The control unit 230 includes at least one processor and at least one memory. The memory stores programs executed by the processor and information used in processing by the processor. The processor may include a baseband processor and a CPU. The baseband processor performs modulation / demodulation and encoding / decoding of baseband signals. The CPU executes programs stored in the memory to perform various processes. Note that the control unit 230 may perform each process and / or each operation in the gNB 200 in each of the embodiments described below.

[0026] The backhaul communication unit 240 is connected to neighboring base stations via an Xn interface. The backhaul communication unit 240 is connected to the AMF and UPF 300 via an NG interface. Note that the gNB 200 is configured (i.e., functionally divided) with a CU (Central Unit) and a DU (Distributed Unit), and both units may be connected via an F1 interface.

[0027] (Example of protocol stack configuration) FIG. 4 is a diagram showing an example of the configuration of a protocol stack of a radio interface of a user plane that handles data.

[0028] As shown in Fig. 4, the user plane radio interface protocol includes a physical (PHY) layer, a medium access control (MAC) layer, a radio link control (RLC) layer, a packet data convergence protocol (PDCP) layer, and a service data adaptation protocol (SDAP) layer. Note that hereinafter, the terms "layer" and "entity" may be used interchangeably.

[0029] The PHY layer performs encoding / decoding, modulation / demodulation, antenna mapping / demapping, and resource mapping / demapping. Data and control information are transmitted between the PHY layer of the UE 100 and the PHY layer of the gNB 200 via a physical channel.

[0030] The MAC layer performs data priority control, retransmission processing using Hybrid ARQ (HARQ), random access procedures, etc. Data and control information are transmitted between the MAC layer of UE 100 and the MAC layer of gNB 200 via a transport channel. The MAC layer of gNB 200 includes a scheduler. The scheduler determines the uplink and downlink transport format (transport block size, modulation and coding scheme (MCS)) and the resource blocks to be allocated to UE 100.

[0031] The RLC layer transmits data to the RLC layer on the receiving side using the functions of the MAC layer and PHY layer. Data and control information are transmitted between the RLC layer of the UE 100 and the RLC layer of the gNB 200 via logical channels.

[0032] The PDCP layer performs header compression / decompression and encryption / decryption.

[0033] The SDAP layer maps IP flows, which are the units for Quality of Service (QoS) control by the core network, to radio bearers, which are the units for QoS control by the Access Stratum (AS). Note that if the RAN is connected to the EPC, SDAP is not necessary.

[0034] FIG. 5 is a diagram showing the configuration of a protocol stack of a radio interface of a control plane that handles signaling (control signals).

[0035] As shown in FIG. 5, the protocol stack of the radio interface of the control plane has a Radio Resource Control (RRC) layer and a Non-Access Stratum (NAS) layer instead of the SDAP layer shown in FIG.

[0036] RRC signaling for various settings is transmitted between the RRC layer of UE100 and the RRC layer of gNB200. The RRC layer controls logical channels, transport channels, and physical channels according to the establishment, re-establishment, and release of radio bearers. When there is a connection (RRC connection) between the RRC of UE100 and the RRC of gNB200, UE100 is in an RRC connected state. When there is no connection (RRC connection) between the RRC of UE100 and the RRC of gNB200, UE100 is in an RRC idle state. When the RRC connection is interrupted (suspended), UE100 is in an RRC inactive state.

[0037] The NAS layer, which is positioned above the RRC layer, performs session management, mobility management, etc. NAS signaling is transmitted between the NAS layer of the UE 100 and the NAS layer of the AMF 300.

[0038] The UE 100 has an application layer and the like in addition to the radio interface protocol. [First embodiment] Next, a first embodiment will be described.

[0039] (Assumed scenario) Here, an assumed scenario in the mobile communication system 1 according to the first embodiment will be described. Fig. 6 is a diagram showing an assumed scenario.

[0040] As shown in Fig. 6, a scenario is assumed in which a relay UE 100-2 is interposed in communication between a gNB 200-1 and a remote UE 100-1, and sidelink relay is used to relay this communication. In other words, this is a scenario in which the gNB 200-1 and the remote UE 100-1 communicate via the relay UE 100-2.

[0041] The remote UE 100-1 performs wireless communication (sidelink communication) with the relay UE 100-2 over a PC5 interface (sidelink), which is an interface between UEs. The relay UE 100-2 performs wireless communication (Uu communication) with the gNB 200-1 over an NR Uu interface. As a result, the remote UE 100-1 indirectly communicates with the gNB 200-1 via the relay UE 100-2. The Uu communication includes uplink communication and downlink communication.

[0042] (Example of protocol stack configuration in assumed scenario) Next, an example of the configuration of a protocol stack in a hypothetical scenario will be described.

[0043] Fig. 7 is a diagram illustrating an example of a user plane protocol stack in an assumed scenario. Fig. 7 is also an example of a user plane protocol stack in relaying via a relay UE 100-2 (i.e., U2N (UE to Network) relaying).

[0044] Fig. 8 shows an example of a protocol stack of the control plane in the assumed scenario. Fig. 8 is also an example of a protocol stack of the control plane in U2N relay.

[0045] As shown in Figure 7, gNB200-1 has a Uu-SRAP (Sidelink Relay Adaptation Protocol) layer, a Uu-RLC layer, a Uu-MAC layer, and a Uu-PHY layer used for communication (Uu communication) on the NR Uu interface.

[0046] The relay UE 100-2 has a Uu-SRAP layer, a Uu-RLC layer, a Uu-MAC layer, and a Uu-PHY layer used for communication on the NR Uu interface (Uu communication). Also, the relay UE 100-2 has a PC5-SRAP layer, a PC5-RLC layer, a PC5-MAC layer, and a PC5-PHY layer used for communication on the PC5 interface (PC5 communication).

[0047] The remote UE 100-1 has a Uu-SDAP layer and a Uu-PDCP layer used for communication (Uu) on the Uu interface, and also has a PC5-SRAP layer, a PC5-RLC layer, a PC5-MAC layer, and a PC5-PHY layer used for communication (PC5 communication) on the PC5 interface.

[0048] As shown in FIG. 8, in the control plane, a Uu-RRC layer is arranged in place of the Uu-SDAP layer of the user plane.

[0049] As shown in Figures 7 and 8, an SRAP layer is arranged on the Uu interface and the PC5 interface. The SRAP layer is an example of a so-called adaptation layer. The SRAP layer exists only in Layer 2 relay and does not exist in Layer 3 relay. The SRAP layer also exists in all of the remote UE 100-1, relay UE 100-2, and gNB 200-1. Furthermore, there are two SRAP layers: PC5-SRAP and Uu-SRAP. The PC5-SRAP and Uu-SRAP have a bearer mapping function. For example, they have the following bearer mapping function. That is, the Uu-SRAP of the remote UE 100-1 and the gNB 200-1 maps the bearer (Uu-PDCP) to the PC5 RLC channel (PC5-RLC). Furthermore, the PC5-SRAP and Uu-SRAP of the relay UE 100-2 perform mapping between the PC5 RLC channel (PC5-RLC) and the Uu RLC channel (Uu-RLC). Furthermore, the Uu-SRAP has a function of identifying the remote UE 100-1.

[0050] 7 and 8, each of the remote UE 100-1 and the relay UE 100-2 may have an RRC layer for PC5. Such an RRC layer is called a "PC5-RRC layer." There is a one-to-one correspondence between the PC5-RRC connection and the PC5 unicast link between the remote UE 100-1 and the relay UE 100-2, and the PC5-RRC connection is established after the PC5 unicast link is established.

[0051] 7 and 8, each of the remote UE 100-1 and the relay UE 100-2 may have a PC5-S (Signaling) protocol layer. The PC5-S protocol layer is a layer above the PDCP layer. Like the PC5-RRC layer, the PC5-S protocol layer is also a layer for transmitting control information.

[0052] (Communication control method according to the first embodiment) In 3GPP, multipath (or multilink) U2N (UE to Network) sidelink relay may be discussed. Multipath U2N sidelink relay refers to relaying (communication) in which one path is a direct link (i.e., Uu) and the other path is an indirect link (i.e., U2N sidelink relay). The direct link refers to a link between a network (e.g., gNB) and a remote UE 100-1 that does not go through a relay UE 100-2. The indirect link refers to a link between a network and a remote UE 100-1 that goes through a relay UE 100-2.

[0053] On the other hand, 3GPP specifies split bearers. Split bearers include those based on DC (Dual Connectivity) and those based on MBS (Multicast and Broadcast Service). When a split bearer based on DC is established, the PDCP entity is linked to the RLC entity of the MCG (Master Cell Group) and the RLC entity of the SCG (Secondary Cell Group). When a split bearer based on MBS is established, the PDCP entity is linked to the RLC entity for PTM (Point-to-Multipoint) and the RLC entity for PTP (Point-to-Point). In either split bearer, the PDCP entity serves as the anchor point linking the two split RLC entities.

[0054] Considering multipath U2N sidelink relay and split bearer, a "multi-link split bearer" can also be considered. The "multi-link split bearer" is, for example, a split bearer consisting of a direct link and an indirect link.

[0055] In 3GPP, a priority is defined between UL transmission (direct link) and sidelink relay (indirect link). Therefore, for example, it is not assumed that the remote UE 100-1 performs UL transmission and sidelink relay simultaneously.

[0056] However, the "multilink split bearer" allows the remote UE 100-1 to transmit the same data using two links or to transmit different data using two links. Also, the "multilink split bearer" allows the remote UE 100-1 to use one link for a control plane (CP) and the other link for a user plane (UP). In this way, the "multilink split bearer" makes it possible to support various operations.

[0057] "Multi-link split bearer" is applicable to various forms of sidelink relay.

[0058] For example, Fig. 9 shows a configuration example of the mobile communication system 1 when a "multi-link split bearer" is applied to intra-cell sidelink relay. Such a "multi-link split bearer" is called an "intra-cell U2N multi-link split bearer."

[0059] 10 shows an example of the configuration of the mobile communication system 1 when a "multi-link split bearer" is applied to sidelink relay between cells (Inter-cell). Such a "multi-link split bearer" is called an "Inter-cell U2N multi-link split bearer."

[0060] Furthermore, for example, Figure 11 shows a configuration example of the mobile communication system 1 when a "multi-link split bearer" is applied to sidelink relay between gNBs (Inter-gNB). Such a "multi-link split bearer" is called an "Inter-gNB U2N multi-link split bearer."

[0061] 12 shows an example of the configuration of the mobile communication system 1 when a "multi-link split bearer" is applied to two indirect links established between the network and the remote UE 100-1. Such a "multi-link split bearer" is called a "multi-relays U2N multi-link split bearer."

[0062] 13 shows an example of the configuration of the mobile communication system 1 when a "multi-link split bearer" is applied to U2U (UE to UE) sidelink relay. Such a "multi-link split bearer" is called a "U2U multi-link split bearer."

[0063] The first embodiment is an embodiment that can be applied to each form of the multi-link split bearer set up in this way.

[0064] For example, in the "intra-cell U2N multi-link split bearer" shown in Fig. 9, there is a problem in that the gNB 200-1 cannot determine whether the PC5 link between the remote UE 100-1 and the relay UE 100-2 is normal or abnormal. This point is similar to the configurations of Fig. 10 to 12. In the case of the "U2U multi-link split bearer" shown in Fig. 13, there is a problem in that the second remote UE 100-12 on the other hand cannot determine the state of the PC5 link between the first remote UE 100-11 and the relay UE 100-2.

[0065] On the other hand, the other link (the direct link in FIGS. 9 to 11 and FIG. 13, and one of the indirect links in FIG. 12) may be usable.

[0066] Therefore, in the first embodiment, an example will be described in which, when a remote UE 100-1 (or a second remote UE 100-12) detects an abnormality in the PC5 link, it transmits an abnormality notification message to the gNB 200-1 (or a first remote UE 100-11) via the other link.

[0067] Specifically, first, a first remote user equipment (e.g., the remote UE 100-1 or the first remote UE 100-11) detects an abnormality in the indirect link. Second, the first remote user equipment transmits an abnormality notification message including information indicating the abnormality to a predetermined device (e.g., the gNB 200-1 or the second remote UE 100-12) via a predetermined link (e.g., another link different from the indirect link).

[0068] This allows the gNB 200-1 (or the second remote UE 100-12) to recognize the abnormality in the PC5 link. Then, the gNB 200-1 can perform various processes in response to the abnormality, such as stopping data transmission.

[0069] The first embodiment is applicable to a mobile communication system (e.g., mobile communication system 1) that enables a first communication on a predetermined link between a first remote user device and a predetermined device, and a second communication on an indirect link between the first remote user device and the predetermined device via a second relay user device.

[0070] Here, the first remote user equipment is, for example, the remote UE 100-1 or the first remote UE 100-11. The predetermined device is, for example, the gNB 200-1 or the second remote UE 100-12. The predetermined link is, for example, an indirect link or a direct link. The second relay user equipment is, for example, the relay UE 100-2 or the second relay UE 100-22.

[0071] The other embodiments are also basically applicable to such a mobile communication system 1.

[0072] (Operation example according to the first embodiment) Fig. 14 is a diagram illustrating an example of operation according to the first embodiment. Fig. 14 illustrates an example of operation when an "intra-cell U2N multi-link split bearer" (Fig. 9) is set as the split bearer.

[0073] 14, a direct link (Uu) is established between the remote UE 100-1 and the gNB 200-1 (step S10). Also, an indirect link (PC5, Uu) is established between the remote UE 100-1 and the gNB 200-1 via the relay UE 100-2 (step S11). A multilink split bearer (i.e., an "intra-cell U2N multilink split bearer") is set up by the direct link and the indirect link.

[0074] In step S12, the remote UE 100-1 detects a radio link failure (RLF) (PC5 RLF) in the PC5 link with the relay UE 100-2. For example, the remote UE 100-1 may start a timer after detecting an out-of-sync state with the relay UE 100-2 a first predetermined number of times in succession, and detect the radio link failure when the timer expires without detecting an in-sync state a second predetermined number of times in succession. Alternatively, the remote UE 100-1 may detect the radio link failure when the number of retransmissions of a packet from the remote UE 100-1 to the relay UE 100-2 reaches a maximum value. Alternatively, the remote UE 100-1 may detect an abnormality on the Uu link side (Uu RLF). When the remote UE 100-1 detects the abnormality in the Uu link, it transmits an abnormality notification message to the gNB 200-1 via the relay UE 100-2. The abnormality notification message may include information indicating that the abnormality occurred in Uu.

[0075] In step S13, the remote UE 100-1 transmits an abnormality notification message to the gNB 200-1 via the direct link. The abnormality notification message may include information indicating an abnormality in the PC5 link. The abnormality notification message may include information indicating that a PC5 RLF has occurred. The abnormality notification message may include identification information (UE ID, L2 ID, or L2 Destination ID) of the relay UE 100-2, which is the other party of the abnormality. The abnormality notification message may be transmitted as an RRC message.

[0076] 14 is a "U2U multilink split bearer" (FIG. 13), the first remote UE 100-11 transmits an abnormality notification message to the second remote UE 100-12 using the direct link (PC5). In this case, the abnormality notification message may be transmitted as a PC5-RRC message.

[0077] 14 is a "multi-relay U2N multi-link split bearer" (FIG. 12), the remote UE 100-1 transmits an abnormality notification message via the first relay UE 100-21 (e.g., first relay user equipment) in response to an abnormality in the PC5 link with the second relay UE 100-22 (e.g., second relay user equipment). The abnormality notification message may be transmitted as a PC5-RRC message in the PC5 link and as an RRC message in the Uu link.

[0078] In step S14, in response to receiving the abnormality notification message, the gNB200-1 performs processing such as stopping communication to the indirect link.

[0079] When the split bearer shown in FIG. 14 is a "U2U multi-link split bearer" (FIG. 13), the second remote UE 100-12 performs processing such as stopping communication for the indirect link in response to receiving the abnormality notification message.

[0080] 14 is an "inter-gNB U2N multi-link split bearer" (FIG. 11), the first gNB 200-1 (MN) transmits a message including information indicating the suspension of communication for the indirect link to the second gNB 200-2 (SN) using the Xn interface in response to receiving the abnormality notification message. The second gNB 200-2 performs processing such as suspension of communication for the indirect link in accordance with the message.

[0081] The first embodiment is applicable to all the above-mentioned forms of multi-split bearer (FIGS. 9 to 13). In these forms, there are cases where the remote UE 100-1 sends an abnormality notification message to the other party of the gNB 200-1 (FIGS. 9 to 12), and cases where the first remote UE 100-11 sends an abnormality notification message to the other party of the second remote UE 100-12 (or second remote user equipment) (FIG. 13). In the former case, in the "multi-relay U2N multi-link split bearer", the abnormality notification message is sent via an indirect link (an indirect link via the first relay UE 100-21). In the other cases, including the latter case, the abnormality notification message is sent via a direct link. [Second embodiment] Next, a second embodiment will be described.

[0082] The second embodiment is an example in which, when the relay UE 100-2 (or the remote UE 100-1) performs handover, a notification is sent to the remote UE 100-1 (or the relay UE 100-2).

[0083] Specifically, when a second relay user equipment (e.g., relay UE 100-2 or second relay UE 100-22) performs a handover to another base station, the first handover notification message including information indicating the handover is transmitted to a first remote user equipment (e.g., remote UE 100-1) via an indirect link; and when the first remote user equipment performs a handover to another base station, the second handover notification message including information indicating the handover is transmitted to the second relay user equipment via an indirect link.

[0084] As a result, for example, even if the relay UE 100-2 performs a handover to another base station that does not support a split bearer, the remote UE 100-1 receives the handover notification message and is therefore able to perform processing such as canceling the setup of the split bearer for the relay UE 100-2. Therefore, the remote UE 100-1 can appropriately communicate with the gNB 200-1. Similarly, even if the remote UE 100-1 performs a handover, the relay UE 100-2 receives the handover notification message and is therefore able to perform processing such as canceling the setup of the split bearer for the remote UE 100-1, and is able to appropriately communicate with the gNB 200-1.

[0085] (Example of operation according to the second embodiment) Next, an example of operation according to the second embodiment will be described.

[0086] Fig. 15 is a diagram illustrating an example of operation according to the second embodiment. Fig. 15 illustrates an example of operation when an "intra-cell U2N multi-link split bearer" (Fig. 9) is set as the split bearer.

[0087] 15, a direct link is established between the remote UE 100-1 and the gNB 200-1 (step S20), and an indirect link is established between the remote UE 100-1 and the gNB 200-1 via the relay UE 100-2 (step S21). A multilink split bearer (i.e., an "intra-cell U2N multilink split bearer") is set up between the direct link and the indirect link.

[0088] In step S22, the relay UE 100-2 performs handover to another gNB different from the gNB 200-1. The other gNB may not support split bearers.

[0089] In step S23, the relay UE 100-2 transmits a handover notification message (or a first handover message) including information indicating the handover to the remote UE 100-1 via the indirect link. The handover notification message may be transmitted as a PC5-RRC message. The handover notification message allows the remote UE 100-1 to recognize that the handover has been performed in the relay UE 100-2.

[0090] In step S24, in response to receiving the handover notification message, the remote UE 100-1 cancels the setup of the split bearer for the relay UE 100-2 and stops data transmission to the relay UE 100-2.

[0091] If the remote UE 100-1 performs handover instead of the relay UE 100-2, the following occurs.

[0092] That is, when the remote UE 100-1 performs a handover to another gNB, it transmits a handover notification message (or a second handover message) including information indicating the handover to the relay UE 100-2 via an indirect link. Then, in response to receiving the handover notification message, the relay UE 100-2 cancels the setting of the split bearer or stops data transmission to the remote UE 100-1.

[0093] The second embodiment is applicable to split bearer configurations (FIGS. 9 to 12) other than the "U2U multi-link split bearer" (FIG. 13).

[0094] Among these, in the case of the "multi-relay U2N multi-link split bearer" (FIG. 12), for example, when the second relay UE 100-22 performs a handover, the second relay UE 100-22 transmits a handover notification message to the remote UE 100-1. The remote UE 100-1 performs processing such as canceling the split bearer setting. Also, when the remote UE 100-1 performs a handover, the remote UE 100-1 transmits a handover notification message to the second relay UE 100-22 (or the first relay UE 100-21). The second relay UE 100-22 (or the first relay UE 100-21) performs processing such as canceling the split bearer setting. [Third embodiment] Next, a third embodiment will be described.

[0095] The third embodiment is an example in which, when the remote UE 100-1 (or the first remote UE 100-11) performs relay reselection, it notifies the gNB 200-1 (or the second remote UE 100-12).

[0096] Specifically, first, the first remote user equipment (e.g., the remote UE 100-1 or the first remote UE 100-11) executes a relay station reselection process. Second, the first remote user equipment transmits a relay station reselection notification message including identification information of the third relay user equipment selected by the relay station reselection process to a predetermined device (e.g., the gNB 200-1 or the second remote UE 100-12) via a predetermined link (e.g., a direct link or an indirect link).

[0097] As a result, for example, the gNB 200-1 (or the second remote UE 100-12) can recognize that relay node reselection has been performed by the remote UE 100-1 (or the first remote UE 100-11), and can therefore set up a split bearer for the new relay UE reselected by the relay node reselection. This enables appropriate communication in the mobile communication system 1.

[0098] (Operation example according to the third embodiment) Fig. 16 is a diagram illustrating an example of operation according to the third embodiment. Fig. 16 illustrates an example of operation when an "intra-cell U2N multi-link split bearer" (Fig. 9) is set as the split bearer.

[0099] 16, a direct link is established between the remote UE 100-1 and the gNB 200-1 (step S30), and an indirect link is established between the remote UE 100-1 and the gNB 200-1 via the relay UE 100-2 (step S31). A multilink split bearer (i.e., an "intra-cell U2N multilink split bearer") is set up between the direct link and the indirect link.

[0100] In step S32, the remote UE 100-1 executes relay reselection. Relay reselection is performed, for example, when the UE 100 in the RRC idle state or the RRC inactive state moves, and transitions from a current relay UE (for example, relay UE #1) to another relay UE (for example, relay UE #2). In the relay reselection, for example, the following process is performed.

[0101] That is, the remote UE 100-1 may reselect a relay station when the frequency used for sidelink communication goes out of coverage. The remote UE 100-1 may also reselect a relay station when the RSRP measurement value of the cell on which the remote UE 100-1 is camped falls below a predetermined threshold. The remote UE 100-1 selects a relay UE whose SD-RSRP (Sidelink Discovery Reference Signal Received Power) exceeds a minimum received RSRP level (minimum reception quality level) as a candidate relay UE. The remote UE 100-1 may select, from all candidate relay UEs that satisfy a predetermined criterion, a candidate relay UE with the highest quality of the radio link (i.e., PC5 unicast link) as a relay UE for reselection (e.g., third relay user equipment). The remote UE 100-1 then reselects the relay UE and camps on it.

[0102] In step S33, the remote UE 100-1 transmits a relay station reselection notification message to the gNB 200-1 via the direct link. The message includes identification information (UE ID, L2 ID, or L2 Destination ID) of the relay UE reselected by the remote UE 100-1 through relay station reselection. The message may include information indicating that the relay station reselection has been successful. The message may be transmitted as an RRC message.

[0103] In the case of the "U2U multilink split bearer" (FIG. 13), the first remote UE 100-11 performs relay station reselection (step S32) and transmits a relay station reselection notification message to the second remote UE 100-12 via the direct link (step S33).

[0104] Upon receiving the message, gNB200-1 may, if necessary, update (or change) the split bearer settings to a split bearer via the reselected relay UE (e.g., an "intra-cell U2N multi-link split bearer").

[0105] Note that the remote UE 100-1 also transmits a relay station reselection notification message if the relay station reselection fails to reselect any relay UE (step S33). The message may include information indicating that the relay station reselection fails to reselect any relay UE. Since the message does not include identification information of the reselected relay UE, the gNB 200-1 that receives the message may understand that the remote UE 100-1 was unable to reselect any relay UE by the absence of the identification information. The gNB 200-1 that receives the message deletes (de-configures) the split bearer configuration as necessary.

[0106] Like the first embodiment, the third embodiment can also be applied to all of the above-mentioned multi-split bearer forms (FIGS. 9 to 13). Among these forms, there are a case where the remote UE 100-1 transmits a relay station reselection notification message to the other party of the gNB 200-1 (FIGS. 9 to 12), and a case where the first remote UE 100-11 transmits a relay station reselection notification message to the other party of the second remote UE 100-12 (FIG. 13). In the former case, in the "multi-relay U2N multi-link split bearer" (FIG. 12), the relay station reselection notification message is transmitted via an indirect link. In the other cases, including the latter case, the relay station reselection notification message is transmitted via a direct link. [Fourth embodiment] Next, a fourth embodiment will be described.

[0107] The fourth embodiment is an embodiment regarding what processing is performed under what conditions when one link of a split bearer experiences a radio link failure (RLF).

[0108] Specifically, a first remote user equipment (e.g., a remote UE 100-1 or a first remote UE 100-11) detects a radio link failure in an indirect link. Second, the first remote user equipment does not perform relay reselection if the radio quality of a predetermined link (e.g., a direct link or an indirect link) is equal to or greater than a threshold.

[0109] As a result, for example, when the remote UE 100-1 detects a PC5 RLF, it will no longer unconditionally reselect a relay station, and if the wireless quality of one link is equal to or higher than a threshold, the remote UE 100-1 will be able to perform communication using that link. Therefore, appropriate communication will be possible in the mobile communication system 1.

[0110] Specifically, the first remote user device starts a timer when it detects a radio link failure, and if the timer expires without recovery from the radio link failure in the indirect link, it deletes the split bearer setting established between the direct link and the indirect link.

[0111] As a result, for example, in the remote UE 100-1, even if a PC5 RLF occurs, the remote UE 100-1 waits for recovery from the PC5 RLF until a predetermined time has elapsed, and if recovery is still not achieved, deletes the setting of the split bearer. Therefore, the split bearer can be set appropriately.

[0112] (Operation example of the fourth embodiment) Next, an example of operation according to the fourth embodiment will be described.

[0113] Fig. 17 is a diagram illustrating an example of operation according to the fourth embodiment. Fig. 17 also illustrates an example of operation when an "intra-cell U2N multi-link split bearer" (Fig. 9) is set as the split bearer.

[0114] 17, a direct link is established between the remote UE 100-1 and the gNB 200-1 (step S40), and an indirect link is established between the remote UE 100-1 and the gNB 200-1 via the relay UE 100-2 (step S41). A multilink split bearer (i.e., an "intra-cell U2N multilink split bearer") is set up between the direct link and the indirect link.

[0115] In step S42, the remote UE 100-1 detects a radio link failure (PC5 RLF) on the indirect link.

[0116] In step S43, the remote UE 100-1 starts counting a timer in response to the detection of the PC5 RLF.

[0117] In step S44, the remote UE 100-1 checks the radio quality of the direct link. Specifically, the radio quality may be Sidelink Reference Signal Received Power (SL-RSRP), Sidelink Discovery Reference Signal Received Power (SD-RSRP), or Uu RSRP. If the direct link radio quality is equal to or greater than a threshold, the remote UE 100-1 does not perform relay reselection. For example, this is because the remote UE 100-1 is capable of communication via the direct link. On the other hand, if the radio quality of the direct link is less than the threshold, the remote UE 100-1 performs relay reselection. For example, this is because the remote UE 100-1 ensures communication with the gNB 200-1 via the relay UE reselected by relay reselection. Note that this threshold may be set by the gNB 200-1.

[0118] In addition, when the split bearer is a "multi-relay U2N multi-link split bearer" (FIG. 12), if the remote UE 100-1 detects a PC5 RLF in the indirect link to the second relay UE 100-22, it checks the wireless quality of the indirect link to the first relay UE 100-21. In this case, the remote UE 100-1 may not reselect a relay station if the wireless quality is equal to or greater than a threshold, and may reselect a relay station if the wireless quality is less than the threshold. Alternatively, the remote UE 100-1 may reselect a relay station if it detects a PC5 RLF for all indirect links. In this case, the remote UE 100-1 may not reselect a relay station if it does not detect a PC5 RLF for all indirect links (for example, if it detects a PC5 RLF for one indirect link).

[0119] In step S45, when the remote UE 100-1 has recovered (returned to normal) from the PC5 RLF, the remote UE 100-1 stops counting the timer.

[0120] In step S46, if the timer expires without recovering from the PC5 RLF, the remote UE 100-1 discards the configuration of the split bearer. Alternatively, if the timer expires without recovering from the PC5 RLF, the remote UE 100-1 may delete the configuration of the link in which the radio link failure has occurred from the configuration of the split bearer.

[0121] Like the first embodiment, the fourth embodiment can be applied to all of the above-mentioned multi-split bearer configurations (FIGS. 9 to 13). Among these configurations, there are a case where the remote UE 100-1 is connected to a gNB 200-1 (FIGS. 9 to 12) and a case where the first remote UE 100-11 is connected to a second remote UE 100-12 (FIG. 13). In the former case, there are a case where a split bearer is established between a direct link and an indirect link (FIGS. 9 to 11) and a case where a split bearer is established between two indirect links (FIG. 12). In the latter case, a split bearer is established between a direct link and an indirect link.

[0122] [Other embodiments] A program may be provided that causes a computer to execute each process performed by the UE 100 (including the relay UE 100-2 and the remote UE 100-1) or the gNB 200. The program may be recorded on a computer-readable medium. Using the computer-readable medium, it is possible to install the program on a computer. Here, the computer-readable medium on which the program is recorded may be a non-transitory recording medium. The non-transitory recording medium is not particularly limited, and may be, for example, a recording medium such as a CD-ROM or a DVD-ROM.

[0123] In addition, circuits that execute each process performed by UE100 or gNB200 may be integrated, and at least a part of UE100 or gNB200 may be configured as a semiconductor integrated circuit (chip set, SoC: System on a chip).

[0124] As used in this disclosure, the terms "based on" and "depending on" do not mean "based only on" or "depending only on," unless expressly stated otherwise. The term "based on" means both "based only on" and "based at least in part on." Similarly, the term "depending on" means both "depending only on" and "depending at least in part on." The terms "include," "comprise," and variations thereof do not mean including only the listed items, but may mean including only the listed items or may include additional items in addition to the listed items. Additionally, the term "or," as used in this disclosure, is not intended to mean an exclusive or. Furthermore, any reference to elements using designations such as "first," "second," etc., as used in this disclosure does not generally limit the quantity or order of those elements. These designations may be used herein as a convenient method of distinguishing between two or more elements. Thus, a reference to a first and a second element does not imply that only two elements may be employed therein or that the first element must precede the second element in some way. In this disclosure, where articles are added by translation, such as a, an, and the in English, these articles shall include the plural unless the context clearly indicates otherwise.

[0125] Although one embodiment has been described in detail above with reference to the drawings, the specific configuration is not limited to the above, and various design changes can be made without departing from the spirit of the invention. Furthermore, the embodiments, operation examples, and processes can be appropriately combined within the scope of the present invention.

[0126] This application claims priority to U.S. Provisional Application No. 63 / 301,786 (filed January 21, 2022), the entire contents of which are incorporated herein by reference.

[0127] (Addendum) The following additional notes are about the features of the above-described embodiment.

[0128] (1) 1. A communication control method in a mobile communication system capable of a first communication on a predetermined link between a first remote user device and a predetermined device, and a second communication on an indirect link between the first remote user device and the predetermined device via a second relay user device, comprising: the first remote user device detecting an anomaly in the indirect link; and transmitting, via the first remote user device, an anomaly notification message including information representative of the anomaly to the predetermined device via the predetermined link. Communication control method.

[0129] (2) 1. A communication control method in a mobile communication system capable of a first communication on a predetermined link between a first remote user equipment (UE) and a base station, and a second communication on an indirect link between the first remote user equipment (UE) and the base station via a second relay user equipment (UE), comprising: When the second relay user equipment performs a handover to another base station, sending a first handover notification message to the first remote user equipment via the indirect link, the first handover notification message including information indicating the handover; and and when the first remote user equipment has handed over to the other base station, transmitting a second handover notification message including information indicating the handover to the second relay user equipment via the indirect link. Communication control method.

[0130] (3) 1. A communication control method in a mobile communication system capable of a first communication on a predetermined link between a first remote user device and a predetermined device, and a second communication on an indirect link between the first remote user device and the predetermined device via a second relay user device, comprising: the first remote user device performing a relay station reselection process; and transmitting, via the predetermined link, a relay station reselection notification message from the first remote user equipment to the predetermined device, the message including identification information of a third relay user equipment selected by the relay station reselection process. Communication control method.

[0131] (4) 1. A communication control method in a mobile communication system capable of a first communication on a predetermined link between a first remote user device and a predetermined device, and a second communication on an indirect link between the first remote user device and the predetermined device via a second relay user device, comprising: the first remote user device detecting a radio link failure on the indirect link; and the first remote user device not performing relay reselection if the radio quality of the predetermined link is equal to or greater than a threshold. Communication control method.

[0132] (5) the step of not performing relay station reselection includes the step of the first remote user device performing relay station reselection when the wireless quality of the predetermined link is less than the threshold. The communication control method according to (4) above.

[0133] (6) The method further includes a step of starting a timer when the first remote user device detects the radio link failure, and deleting a setup of a split bearer established between the predetermined link and the indirect link when the timer expires without recovery from the radio link failure in the indirect link. The communication control method according to (4) or (5) above.

[0134] (7) The predetermined device is a base station, the predetermined link is either a direct link between the first remote user device and the predetermined device, or an indirect link between the first remote user device and the predetermined device via a first relay user device; A communication control method according to any one of (1) to (4) above.

[0135] (8) the predetermined device is a second remote user device; the predetermined link is a direct link between the first remote user device and the predetermined device; A communication control method according to any one of (1) to (4) above.

[0136] (9) the predetermined link is either a direct link between the first remote user equipment and the base station, or an indirect link between the first remote user equipment and the base station via a first relay user equipment; The communication control method according to (2) above. [Explanation of symbols]

[0137] 10:NG-RAN (5G RAN) 20:5GC(5G CN) 100:UE 110: Receiving unit 120: Transmitter 130: Control unit 200 :gNB 210: Transmission unit 220: Receiving unit 230: Control unit 240: Backhaul communication unit

Claims

1. 1. A communication control method in a mobile communication system capable of a first communication on a direct link between a remote user equipment (UE) and a base station, and a second communication on an indirect link between the remote user equipment (UE) and the base station via a relay user equipment (REE), comprising: transmitting, by the remote user equipment, an abnormality notification message via the direct link in response to detecting a radio link failure in a PC5 link between the remote user equipment and the relay user equipment and thereby detecting an abnormality in the indirect link; When the abnormality notification message is sent, communication over the indirect link is interrupted. Communication control method.

2. 1. A remote user equipment (UE) in a mobile communication system capable of a first communication over a direct link between the remote user equipment (UE) and a base station, and a second communication over an indirect link between the remote user equipment (UE) and the base station via a relay user equipment (REE), comprising: a transmitter configured to transmit an abnormality notification message via the direct link in response to detecting an abnormality in the indirect link by detecting a radio link failure in a PC5 link between the remote user equipment and the relay user equipment; When the abnormality notification message is sent, communication over the indirect link is interrupted. Remote user device.

3. 1. A mobile communication system capable of first communication over a direct link between a remote user equipment and a base station, and second communication over an indirect link between said remote user equipment and said base station via a relay user equipment, comprising: the remote user equipment, in response to detecting a radio link failure in a PC5 link between the remote user equipment and the relay user equipment, detecting an abnormality of the indirect link, transmitting an abnormality notification message via the direct link; When the abnormality notification message is sent, communication over the indirect link is interrupted. Mobile communication system.

4. A computer of a remote user device in a mobile communication system capable of first communication on a direct link between a remote user device and a base station and second communication on an indirect link between the remote user device and the base station via a relay user device, comprising: transmitting an abnormality notification message via the direct link in response to detecting an abnormality in the indirect link by detecting a radio link failure in the PC5 link between the remote user equipment and the relay user equipment; When the abnormality notification message is sent, communication over the indirect link is interrupted. program.

5. 1. A chipset for a remote user equipment in a mobile communication system capable of a first communication on a direct link between the remote user equipment and a base station, and a second communication on an indirect link between the remote user equipment and the base station via a relay user equipment, comprising: transmitting an anomaly notification message via the direct link in response to detecting a radio link failure in a PC5 link between the remote user equipment and the relay user equipment and thereby detecting an anomaly in the indirect link; When the abnormality notification message is sent, communication over the indirect link is interrupted. Chipset.

Images