Communication control method

Abstract

Embodiments relate to a communication control method for a mobile communication system in which a first communication between a remote user equipment and a base station through a direct link and a second communication between the remote user equipment and the base station through an indirect link via a relay user equipment may be performed. The communication control method comprises the step that a base station sends association information to remote user equipment, wherein the association information associates a PDCP entity with an RLC entity of a direct link and an SRAP entity of an indirect link. Further, the communication control method includes a step in which the remote user equipment associates the PDCP entity with the RLC entity and the SRAP entity according to the association information.

Description

Technical Field

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

[0002] For a mobile communication system based on the 3rd Generation Partnership Project (3GPP) standard, a sidelink relay technology using a user equipment as a relay node is being studied (for example, see "3GPP TS 38.300 V16.8.0 (2021-12)"). Sidelink relay is a technology in which a relay node, referred to as a relay user equipment (relay UE), intervenes in the communication between a base station and a remote user equipment (remote UE) and relays the communication. Summary of the invention

[0003] In a first aspect, a communication control method is a communication control method in a mobile communication system, the mobile communication system being configured to perform a first communication on a direct link between a remote user equipment and a base station and to perform a second communication on an indirect link between the remote user equipment and the base station via a relay user equipment. The communication control method comprises: the base station sending association information to the remote user equipment, the association information associating a PDCP entity with an RLC entity of the direct link and an SRAP entity of the indirect link. The communication control method comprises: the remote user equipment associating the PDCP entity with the RLC entity and the SRAP entity according to the association information.

[0004] In a second aspect, a communication control method is a communication control method in a mobile communication system, the mobile communication system being configured to perform a first communication on a direct link between a remote user equipment and a base station and to perform a second communication on an indirect link between the remote user equipment and the base station via a relay user equipment. The communication control method comprises: the base station sending association information to the remote user equipment, the association information associating a PDCP entity with a first RLC entity of the direct link and a second RLC entity of the indirect link. The communication control method comprises: the remote user equipment configuring an SRAP entity, the SRAP entity associating the PDCP entity with the first RLC entity and the second RLC entity according to the association information.

[0005] In a third aspect, a communication control method is a communication control method in a mobile communication system, the mobile communication system being configured to perform a first communication on a direct link between a remote user equipment and a base station and to perform a second communication on an indirect link between the remote user equipment and the base station via a relay user equipment. The communication control method comprises: the base station sends activation indication information to the remote user equipment, the activation indication information indicating activation or deactivation of the direct link and indicating activation or deactivation of the indirect link. The communication control method comprises: the remote user equipment activates or deactivates the direct link and activates or deactivates the indirect link according to the activation indication information. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 is a diagram showing a configuration example of a mobile communication system according to the first embodiment.

[0007] Figure 2 is a diagram showing a configuration example of a UE according to the first embodiment.

[0008] Figure 3 is a diagram showing a configuration example of a gNB according to the first embodiment.

[0009] Figure 4 is a diagram showing a configuration example of a protocol stack of a user plane according to the first embodiment.

[0010] Figure 5 is a diagram showing a configuration example of a protocol stack of a control plane according to the first embodiment.

[0011] Figure 6 is a diagram showing a hypothetical scenario according to the first embodiment.

[0012] Figure 7 is a diagram showing a configuration example of a protocol stack of a user plane in a hypothetical scenario according to the first embodiment.

[0013] Figure 8 is a diagram showing a configuration example of a protocol stack of a control plane in a hypothetical scenario according to the first embodiment.

[0014] Fig. 9 is a diagram showing a configuration example of a mobile communication system according to the first embodiment.

[0015] Fig.10 is a diagram showing a configuration example of a protocol stack according to the first embodiment.

[0016] Fig.11 is a diagram showing an operation example according to the first embodiment.

[0017] Fig.12 is a diagram showing an operation example according to the first embodiment.

[0018] Fig.13 is a diagram showing a configuration example of a protocol stack according to a modification of the first embodiment.

[0019] Fig.14 is a diagram showing an operation example according to the second embodiment.

[0020] Fig.15 is a diagram showing a configuration example of a mobile communication system according to the third embodiment.

[0021] Fig.16 is a diagram showing a configuration example of a mobile communication system according to a fourth embodiment.

[0022] Fig.17 is a diagram showing an operation example according to the fourth embodiment.

[0023] Fig.18 is a diagram showing an operation example according to the fifth embodiment. DETAILED DESCRIPTION

[0024] The mobile communication system according to the embodiment is described with reference to the accompanying drawings. In the description of the drawings, the same or similar reference numerals represent the same or similar parts.

[0025] Configuration example of mobile communication system

[0026] In the embodiment, a configuration example of a mobile communication system is described. In the embodiment, the mobile communication system 1 is a 3GPP 5G system. Specifically, the radio access scheme in the mobile communication system 1 is a new radio (NR) as a radio access scheme of 5G. Note that Long Term Evolution (LTE) may be at least partially applied to the mobile communication system 1. Future mobile communication systems such as 6G may be applied to the mobile communication system 1.

[0027] Figure 1 is a diagram showing a configuration example of a mobile communication system 1 according to the embodiment.

[0028] like Figure 1 As shown, the mobile communication system 1 includes a user equipment (UE) 100 , a 5G radio access network (next generation radio access network (NG-RAN)) 10 , and a 5G core network (5GC) 20 .

[0029] UE 100 is a mobile wireless communication device. UE 100 may be any device as long as UE 100 is used by a user. Examples of UE 100 include a mobile phone terminal (including a smart phone) or a tablet terminal, a notebook PC, a communication module (including a communication card or a chipset), a sensor or a device provided on a sensor, a vehicle or a device provided on a vehicle (vehicle UE), and a flying object or a device provided on a flying object (air UE).

[0030] The NG-RAN 10 includes a base station (referred to as a "gNB" in the 5G system) 200. The gNB 200 is interconnected via an Xn interface which is an interface between base stations. Each gNB 200 manages one or more cells. The gNB 200 performs wireless communication with the UE 100, which has established a connection to the cell of the gNB 200. The gNB 200 has a radio resource management (RRM) function, a function of routing user data (hereinafter, referred to as "data"), a measurement control function for mobility control and scheduling, and the like. "Cell" is used as a term to represent the smallest unit of a wireless communication area. "Cell" is also used as a term to represent a function or resource used to perform wireless communication with the UE 100. One cell belongs to one carrier frequency. Note that, hereinafter, "cell" and base station may be used indiscriminately.

[0031] Note that the gNB 200 may be connected to an evolved packet core (EPC) corresponding to a core network of LTE. The LTE base station may also be connected to the 5GC 20. The LTE base station and the gNB 200 may be connected to each other via an inter-base station interface.

[0032] 5GC 20 includes an access and mobility management function (AMF) and a user plane function (UPF) 300. AMF performs various types of mobility control, etc. for UE 100. AMF manages the mobility of UE 100 by communicating with UE 100 using non-access stratum (NAS) signaling. UPF controls data transmission. AMF and UPF 300 are connected to gNB 200 via an NG interface, which is an interface between a base station and a core network.

[0033] User equipment configuration

[0034] In the embodiment, a configuration example of the UE 100 as the user equipment is described. Figure 2 is a diagram showing a configuration example of UE 100 .

[0035] like Figure 2 As shown, UE 100 includes a receiver 110 , a transmitter 120 , and a controller 130 .

[0036] The receiver 110 performs various types of reception under the control of the controller 130. The receiver 110 includes an antenna and converts (down-converts) a radio signal received by the antenna into a baseband signal (received signal) and then outputs the baseband signal to the controller 130.

[0037] The transmitter 120 performs various types of transmission 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 then transmits the radio signal from the antenna.

[0038] The controller 130 performs various types of control in the UE 100. The controller 130 includes at least one memory and at least one processor electrically connected to the memory. The memory stores programs to be executed by the processor and information to be used for processing by the processor. The processor may include a baseband processor and a CPU. The baseband processor performs modulation and demodulation, encoding and decoding of baseband signals, etc. The CPU executes the program stored in the memory, thereby performing various types of processing. Note that in each of the following embodiments, the controller 130 may perform corresponding processing operations or corresponding operations in the UE 100.

[0039] Configuration example of a base station

[0040] In the embodiment, a configuration example of gNB 200 as a base station is described. Figure 3 is a diagram showing a configuration example of gNB 200.

[0041] like Figure 3 As shown, gNB 200 includes a transmitter 210, a receiver 220, a controller 230 and a backhaul communicator 240.

[0042] The transmitter 210 performs various types of transmission 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 then transmits the radio signal from the antenna.

[0043] The receiver 220 performs various types of reception under the control of the controller 230. The receiver 220 includes an antenna and converts (down-converts) a radio signal received by the antenna into a baseband signal (received signal) and then outputs the baseband signal to the controller 230.

[0044] The controller 230 performs various types of control for the gNB 200. The controller 230 includes at least one processor and at least one memory. The memory stores programs to be executed by the processor and information to be used for processing by the processor. The processor may include a baseband processor and a CPU. The baseband processor performs modulation and demodulation, encoding and decoding of baseband signals, etc. The CPU executes the program stored in the memory, thereby performing various types of processing. Note that in each of the following embodiments, the controller 230 may perform a corresponding processing operation or a corresponding operation in the gNB 200.

[0045] The backhaul communicator 240 is connected to the neighboring base station via the Xn interface. The backhaul communicator 240 is connected to the AMF and UPF 300 via the NG interface. Note that the gNB 200 may include a central unit (CU) and a distributed unit (DU) (ie, the functions are divided), and the two units may be connected via the F1 interface.

[0046] Configuration example of protocol stack

[0047] Figure 4 is a diagram showing a configuration example of a protocol stack of a radio interface of a user plane that processes data.

[0048] like Figure 4 As shown, the radio interface protocol of the user plane 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 in the following, layers and entities may be used without distinction.

[0049] The PHY layer performs encoding and decoding, modulation and demodulation, antenna mapping and demapping, and resource mapping and 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.

[0050] The MAC layer performs priority control of data, retransmission processing by hybrid ARQ (HARQ: Hybrid Automatic Repeat Request), a random access procedure, 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 transport format (transport block size, modulation and coding scheme (MCS)) in uplink and downlink and the resource blocks to be allocated to UE 100.

[0051] The RLC layer transmits data to the RLC layer of the receiving side by using the functions of the MAC layer and the 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 a logical channel.

[0052] The PDCP layer performs header compression and decompression, and encryption and decryption.

[0053] The SDAP layer performs mapping between IP flows (as a unit of QoS (Quality of Service) control performed by the core network) and radio bearers (as a unit of QoS control performed by the AS (Access Stratum)). Note that when the RAN is connected to the EPC, there is no need to provide SDAP.

[0054] Figure 5 : is a diagram showing the configuration of a protocol stack of a radio interface of a control plane that processes signaling (control signals).

[0055] like Figure 5 As shown, the protocol stack of the radio interface of the control plane includes a radio resource control (RRC) layer and a non-access stratum (NAS) layer, instead of Figure 4 The SDAP layer shown in .

[0056] RRC signaling for various configurations is transmitted between the RRC layer of UE 100 and the RRC layer of gNB 200. The RRC layer controls logical channels, transport channels, and physical channels according to the establishment, reestablishment, and release of radio bearers. When there is a connection (RRC connection) between the RRC of UE 100 and the RRC of gNB 200, UE 100 is in the RRC connected state. When there is no connection (RRC connection) between the RRC of UE 100 and the RRC of gNB 200, UE 100 is in the RRC idle state. When the RRC connection is suspended, UE 100 is in the RRC inactive state.

[0057] The NAS layer located 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.

[0058] Note that the UE 100 includes an application layer in addition to the protocol of the radio interface.

[0059] First embodiment

[0060] A first embodiment is described.

[0061] Hypothetical scenario

[0062] According to the first embodiment, a hypothetical scenario of the mobile communication system 1 is described. Figure 6 is a diagram showing a hypothetical scenario.

[0063] like Figure 6As shown, a scenario using sidelink relay is assumed, in which relay UE 100-2 intervenes in the communication between gNB 200-1 and remote UE 100-1 and relays the communication. In other words, in this scenario, gNB 200-1 and remote UE 100-1 communicate via relay UE 100-2.

[0064] The remote UE 100-1 performs wireless communication (sidelink communication) with the relay UE 100-2 over the PC5 interface (sidelink) used as an inter-UE interface. The relay UE 100-2 performs wireless communication (Uu communication) with the gNB 200-1 over the NR Uu interface. Therefore, the remote UE 100-1 communicates with the gNB 200-1 indirectly via the relay UE 100-2. The Uu communication includes uplink communication and downlink communication.

[0065] Example configuration of the protocol stack in a hypothetical scenario

[0066] Describes a configuration example of a protocol stack in a hypothetical scenario.

[0067] Figure 7 is a diagram showing an example of a protocol stack of a user plane in a hypothetical scenario. Figure 7 It is also an example of a protocol stack of a user plane in a relay via the relay UE 100 - 2 , ie, a U2N (UE to Network) relay.

[0068] Figure 8 is a diagram showing an example of a protocol stack of a control plane in a hypothetical scenario. Figure 8 It is also an example of the protocol stack of the control plane in the U2N relay.

[0069] like Figure 7 As shown, gNB 200-1 includes a Uu-SRAP (Sidelink Relay Adaptation Protocol) layer, a Uu-RLC layer, a Uu-MAC layer, and a Uu-PHY layer for communication on the NR Uu interface (Uu communication).

[0070] The relay UE 100-2 includes a Uu-SRAP layer, a Uu-RLC layer, a Uu-MAC layer, and a Uu-PHY layer for communication on the NR Uu interface (Uu communication). The relay UE 100-2 includes a PC5-SRAP layer, a PC5-RLC layer, a PC5-MAC layer (PC5), and a PC5-PHY layer for communication on the PC5 interface (PC5 communication).

[0071] The remote UE 100-1 includes a Uu-SDAP layer and a Uu-PDCP layer for communication on a Uu interface (Uu). The remote UE 100-1 includes a PC5-SRAP layer, a PC5-RLC layer, a PC5-MAC layer (PC5), and a PC5-PHY layer for communication on a PC5 interface (PC5 communication).

[0072] like Figure 8 As shown, in the control plane, the Uu-RRC layer is set to replace the Uu-SDAP layer of the user plane.

[0073] like Figure 7 and Figure 8 As shown, the SRAP layer is set on the Uu interface and the PC5 interface. Each SRAP layer is an example of a so-called adaptation layer. The SRAP layer exists only in the layer 2 relay and does not exist in the layer 3 relay. The SRAP layer exists in the remote UE 100-1, the relay UE 100-2, and the gNB 200-1. In addition, the SRAP layer includes two layers of PC5-SRAP and Uu-SRAP. PC5-SRAP and Uu-SRAP each have a bearer mapping function. For example, the bearer mapping function is as follows. In other words, the Uu-SRAP of the gNB 200-1 and the remote UE 100-1 perform mapping between the bearer (Uu-PDCP) and the PC5 RLC channel (PC5-RLC). 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 an identification function of the remote UE 100 - 1 .

[0074] Note that although Figure 7 and Figure 8 Although not shown in the figure, each of the remote UE 100-1 and the relay UE 100-2 may include an RRC layer for PC5. Such an RRC layer is referred to as a "PC5-RRC layer". The PC5-RRC connection between the remote UE 100-1 and the relay UE 100-2 corresponds to the PC5 unicast link one by one, and the PC5-RRC connection is established after the PC5 unicast link is established.

[0075] although Figure 7 and Figure 8 Although not shown in the figure, each of the remote UE 100-1 and the relay UE 100-2 may include a PC5-S (signaling) protocol layer. The PC5-S protocol layer is an upper layer of the PDCP layer. Like the PC5-RRC layer, the PC5-S protocol layer is also a layer for controlling information transmission.

[0076] Communication Control Method According to the First Embodiment

[0077] In 3GPP, multipath (or multilink) UE to network (U2N) side link relay may be discussed. Multipath U2N side link relay refers to relay (communication) in which one path is a direct link (in other words, Uu) and the other path is an indirect link (in other words, U2N side link relay). A direct link is a link between a network (e.g., gNB) and a remote UE 100-1 that does not involve a relay UE 100-2. An indirect link is a link between a network and a remote UE 100-1 via a relay UE 100-2.

[0078] At the same time, 3GPP defines a split bearer. The split bearer includes a split bearer implemented by dual connectivity (DC) and a split bearer implemented by multicast and broadcast service (MBS). When a split bearer implemented by DC is configured, the PDCP entity is associated with the RLC entity of the primary cell group (MCG) and the RLC entity of the secondary cell group (SCG). When a split bearer implemented by MBS is configured, the PDCP entity is associated with the RLC entity of point-to-multipoint (PTM) and the RLC entity of PTP (point-to-point). In any split bearer, the PDCP entity is the anchor point that associates the two divided RLC entities with each other.

[0079] Considering multi-path U2N sidelink relay and split bearer, a “multi-link split bearer” is also conceivable. A “multi-link split bearer” is, for example, a split bearer including a direct link and an indirect link.

[0080] 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 at the same time.

[0081] However, "multi-link split bearer" allows the remote UE 100-1 to use the two links to send the same data or to use the two links to send different data. "Multi-link split bearer" also allows the remote UE 100-1 to use one link for the control plane (CP) and another link for the user plane (UP). In this way, "multi-link split bearer" can support various operations.

[0082] “Multi-link split bearer” is applicable to various forms of sidelink relay.

[0083] For example, Fig. 9 A configuration example of the mobile communication system 1 is shown when "multi-link split bearer" is applied to intra-cell link relay. Such "multi-link split bearer" is called "intra-cell U2N multi-link split bearer".

[0084] For example, Fig.15A configuration example of the mobile communication system 1 when "multi-link split bearer" is applied to inter-cell side link relay is shown. Such "multi-link split bearer" is called "inter-cell U2N multi-link split bearer".

[0085] In addition, for example, Fig.16 A configuration example of the mobile communication system 1 when "multi-link split bearer" is applied to the inter-gNB side link relay is shown. This "multi-link split bearer" is called "inter-gNB U2N multi-link split bearer".

[0086] In addition, for example, Fig.18 A configuration example of the mobile communication system 1 is shown when "multi-link split bearer" is applied to UE to UE (U2U) side link relay. Such "multi-link split bearer" is called "U2U multi-link split bearer".

[0087] The first embodiment describes "intra-cell U2N multi-link split bearer". The third embodiment describes "inter-cell U2N multi-link split bearer". In addition, the fourth embodiment describes "inter-gNB U2N multi-link split bearer". In addition, the fifth embodiment describes "U2U multi-link split bearer".

[0088] Note that in each mobile communication system 1, a first communication on a direct link between a remote user equipment (e.g., remote UE 100-1) and a base station (e.g., gNB 200-1) and a second communication on an indirect link between the remote user equipment and the base station via a relay user equipment (e.g., relay UE 100-2) are implemented.

[0089] Fig.10 is a diagram showing a configuration example of a protocol stack for multi-link split bearer. Fig.10 It is also a diagram showing a configuration example of the protocol stack of gNB200-1 and remote UE 100-1.

[0090] like Fig.10 As shown, the PDCP entity is associated with the RLC entity in the direct link (Uu RLC entity) and the SRAP entity in the indirect link. This makes it possible to configure the split bearer anchored by PDCP in the same and / or similar manner as the split bearer implemented by DC. In other words, a multi-link split bearer can be configured by associating the PDCP entity with the RLC entity in the direct link and the SRAP entity in the indirect link.

[0091] Specifically, first, the base station (e.g., gNB 200-1) sends association information to the remote user equipment (e.g., remote UE 100-1), which associates the PDCP entity with the RLC entity in the direct link and the SRAP entity in the indirect link. Secondly, the remote user equipment associates the PDCP entity with the RLC entity and the SRAP entity according to the association information.

[0092] This allows, for example, the remote UE 100-1 to associate the PDCP entity with the RLC entity and the SRAP entity, which enables configuration of "multi-link split bearer" in direct links and indirect links.

[0093] The configuration method of split bearer includes the following method: when the direct link is established before the indirect link, the indirect link is configured, and the SRAP entity in the indirect link is associated with the PDCP entity. The configuration method includes the following method: when the indirect link is established before the direct link, the direct link is configured, and the RLC entity in the direct link is associated with the PDCP entity. The former is described first, and then the latter is described.

[0094] Note that Fig.10 As shown, one MAC entity can be configured for two links. One MAC entity (Uu-MAC and PC5-MAC) can be configured for each of the two links.

[0095] Hereinafter, NR Uu (or Uu) may be used to represent a direct link, and PC5 may be used to represent an indirect link. For example, Fig.10 The Uu RLC shown indicates the RLC in the direct link, and Fig.10 The PC5 RLC shown indicates RLC in an indirect link. Hereinafter, entities and layers may be used without distinction.

[0096] Operation Example 1 According to the First Embodiment

[0097] In the first embodiment, Operation Example 1 is described.

[0098] Operation Example 1 is an operation example of a configuration example of “intra-cell U2N multi-link split bearer” when a direct link is established in advance.

[0099] Fig.11 is a diagram showing Operation Example 1 according to the first embodiment.

[0100] like Fig.11 As shown, in step S10, a direct link is established between the remote UE 100-1 and the gNB 200-1 without involving the relay UE 100-2. Note that at this time, no indirect link is established.

[0101] In step S11, the remote UE 100-1 sends a measurement report (MeasurementReport) message to the gNB 200-1 via a direct link. The measurement report message includes identification information of the relay UE 100-2 (no indirect link is established) and measurement results for the relay UE 100-2.

[0102] In step S12, in response to receiving the measurement report message, the gNB 200-1 sends an RRC reconfiguration message to the remote UE 100-1. The RRC reconfiguration message includes the following information.

[0103] First, it includes information of an RLC entity (RLC channel) in a direct link and information of an SRAP entity in an indirect link, and the RLC entity and the SRAP entity are to be associated with a PDCP entity (a data radio bearer (DRB) or a signaling radio bearer (SRB)). Specifically, the information may be an identifier of an RLC entity to be associated with a PDCP entity and an identifier of an SRAP entity to be associated with a PDCP entity. Alternatively, the information may be association information for associating these identifiers. For example, Fig.10 As shown, the association information is sufficient as long as it is information that can associate the PDCP entity with the RLC entity in the direct link and the SRAP in the indirect link.

[0104] Second, information indicating that the direct link is to be maintained even after the indirect link is established is included. The remote UE 100-1 can send a measurement report message, whose trigger condition is that the radio quality for the relay UE 100-2 is better than the radio quality for the gNB 200-1 on the direct link side (step S11). However, in order to configure the "intra-cell U2N multi-link split bearer", it is necessary to maintain the connection with the direct link instead of disconnecting the connection. Therefore, the gNB 200-1 includes information indicating that the direct link is to be maintained even when receiving the measurement report message in the RRC reconfiguration message. Hereinafter, the information indicating that the direct link is to be maintained may be referred to as "direct link maintenance indication information". Note that, instead of the direct link maintenance indication information, the above-mentioned associated information may imply an indication that the direct link is to be maintained.

[0105] Third, it includes information indicating the establishment of a PC5 (indirect link) connection with the relay UE 100-2. This information may be referred to as "indirect link establishment indication information". Similarly, instead of the indirect link establishment indication information, the above-mentioned association information may imply an indication that a PC5-RRC connection is to be established. The indirect link establishment indication information may include identification information (UEID, L2 ID or L2 destination ID) of the relay UE 100-2. In this case, the identification information may be indirect link establishment indication information, which indicates to the remote UE 100-1 that a PC5-RRC connection (indirect link) is to be established with the relay UE 100-2. In addition, the indirect link establishment indication information may include configuration information of the entities of PC5-SRAP, PC5-RLC, PC5-MAC and PC5-PHY.

[0106] Fourth, information indicating whether the remote UE 100-1 sends an RRC reconfiguration complete (RRCReconfigurationComplete) message to the relay UE 100-2 through a direct link or an indirect link is included. Such information may be referred to as "transmission indication information". When the transmission indication information indicates transmission through an indirect link, the RRC reconfiguration complete message may be the first message to the relay UE 100-2 in the RRC idle state or the RRC inactive state. The first message is a message that enables the relay UE 100-2 in the RRC idle state or the RRC inactive state to initiate an RRC connection with the gNB 200-1.

[0107] In step S14, the remote UE 100-1 establishes a PC5-RRC connection with the indicated relay UE 100-2. The remote UE 100-1 establishes the PC5-RRC connection, for example, by sending an RRCReconfigurationSidelink message to the relay UE 100-2. The remote UE 100-1 may perform relay reselection to reselect the relay UE 100-2 with the best radio quality, and establish a PC5-RRC connection with the relay UE 100-2 instead of the indicated relay UE 100-2. Relay reselection is, for example, a process in which the remote UE 100-1 reselects the relay UE 100-2 due to movement or the like. In this case, the remote UE 100-1 may send the identification information (UEID, L2 ID or L2 destination ID) of the relay UE 100-2 obtained through relay reselection to the gNB 200-1, with which the PC5-RRC connection is established. The identification information may be included in a subsequent RRC reconfiguration complete message. Note that, according to the direct link maintenance indication information, the remote UE 100-1 maintains the connection with the direct link even after the PC5-RRC connection is established with the relay UE 100-2. When the remote UE 100-1 establishes the PC5-RRC connection with the relay UE 100-2, the PDCP entity may be associated with the SRAP entity and the RLC entity (UuRLC entity) according to the association information.

[0108] In step S15, the remote UE 100-1 sends an RRC reconfiguration complete (RRCReconfigurationComplete) message to the gNB 200-1 through the direct link according to the transmission indication information. Alternatively, in step S16, the remote UE 100-1 sends an RRC reconfiguration complete message to the relay UE 100-2 through the PC5 link according to the transmission indication information. The remote UE 100-1 may send a PC5-RRC message obtained by encapsulating the RRC reconfiguration complete message to the relay UE 100-2 to send the RRC reconfiguration complete message through the PC5 link. Alternatively, the remote UE 100-1 may send an RRCReconfigurationComplete message on a designated side link bearer (SL-SRB or SL-DRB). In either case of step S15 or step S16, the RRC reconfiguration complete message (or PC5-RRC message) may include information about the cell ID of the connection destination.

[0109] As described above, "intra-cell U2N multi-link split bearer" is configured.

[0110] Operation Example 2 According to the First Embodiment

[0111] In the first embodiment, Operation Example 2 is described.

[0112] Operation Example 2 is an operation example of a configuration example of “intra-cell U2N multi-link split bearer” when a direct link is established in advance.

[0113] Fig.12 is a diagram showing Operation Example 2 according to the first embodiment.

[0114] like Fig.12 As shown, in step S20, an indirect link is established between the remote UE 100-1 and the gNB 200-1 via the relay UE 100-2. Note that at this time, no direct link is established between the remote UE 100-1 and the gNB 200-1.

[0115] In step S21, the remote UE 100-1 sends a measurement report message to the gNB 200-1 via the relay UE 100-2. The remote UE 100-1 sends the measurement report message as a PC5-RRC message (MeasurementReportSidelink message), and the relay UE 100-2 sends the measurement report message as an RRC message (MeasurementReport message) to the gNB 200-1.

[0116] In step S22, gNB 200-1 sends an RRC reconfiguration message to remote UE 100-1 via an indirect link in response to receiving the measurement report message. The RRC reconfiguration message includes the following information.

[0117] First, as in operation example 1, information of an RLC entity (RLC channel) in a direct link and an SRAP entity in an indirect link is included, and the RLC entity and the SRAP entity are to be associated with a PDCP entity (a data radio bearer (DRB) or a signaling radio bearer (SRB)). Specifically, the information may be an identifier of an RLC entity to be associated with a PDCP entity and an identifier of an SRAP entity to be associated with a PDCP entity. Alternatively, the information may be association information for associating these identifiers. For example, Fig.10 As shown, the association information is sufficient as long as it is information that can associate the PDCP entity with the RLC entity in the direct link and the SRAP in the indirect link.

[0118] Second, information indicating that the indirect link is to be maintained even after the direct link is established is included. As in operation example 1, this is to maintain the indirect link and configure "intra-cell U2N multi-link split bearer". Hereinafter, the information indicating that the indirect link is to be maintained even after the direct link is established may be referred to as "indirect link maintenance indication information". Note that, instead of the indirect link maintenance indication information, the above-mentioned associated information may imply an indication that the indirect link is to be maintained.

[0119] Third, information indicating the establishment of a direct link with gNB 200-1 is included. Such information may be referred to as "direct link establishment indication information". Instead of the direct link establishment indication information, the above-mentioned association information may imply an indication of the establishment of a direct link. The direct link establishment indication information may include configuration information of the RLC, MAC, and PHY entities in the direct link.

[0120] Fourth, information indicating whether to send the RRC reconfiguration complete (RRCReconfigurationComplete) message through a direct link or to send the PC5-RRC message through an indirect link ("transmission indication information") is included. The transmission indication information may be information indicating that transmission is always through a direct link.

[0121] In step S24, the remote UE 100-1 establishes a direct link with the gNB 200-1. The remote UE 100-1 establishes the direct link using the control information and the like included in the RRC reconfiguration message received in step S22. When establishing the direct link, the remote UE 100-1 may associate the PDCP entity with the SRAP entity and the RLC entity (Uu RLC entity) according to the association information.

[0122] In step S25, the remote UE 100-1 sends an RRC reconfiguration complete message through a direct link according to the transmission indication information. Alternatively, in step S26, the remote UE 100-1 sends a PC5-RRC message through an indirect link according to the transmission indication information.

[0123] As described above, "intra-cell U2N multi-link split bearer" is configured.

[0124] Modification of the First Embodiment

[0125] A modification of the first embodiment is described.

[0126] The first embodiment describes an example in which one PDCP (DRB or SRB) is associated with an RLC entity in a direct link and an SRAP entity in an indirect link. For example, one SRAP entity may be associated with an RLC entity in a direct link and an RLC entity in an indirect link.

[0127] Specifically, first, the base station (e.g., gNB 200-1) sends association information to the remote user equipment (e.g., remote UE 100-1), which associates the PDCP entity with the first RLC entity in the direct link (e.g., Uu RLC entity) and the second RLC entity in the indirect link (e.g., PC5 RLC entity). Secondly, the remote user equipment configures the SRAP entity according to the association information, which associates the PDCP entity with the first RLC entity and the second RLC entity.

[0128] Fig.13 is a diagram showing a configuration example of a protocol stack according to a modification of the first embodiment.

[0129] like Fig.13 As shown, SRAP is associated with an RLC entity in a direct link (Uu RLC), wherein, for SRAP, one bearer (DRB or SRB) is associated with two RLC entities.

[0130] Basically, the operation example 1 and the operation example 2 of the first embodiment can be applied to this configuration. In other words, when the direct link is previously established (operation example 1), the RRC reconfiguration message ( Fig.12 It is sufficient that step S12) in includes the following information.

[0131] First, it includes information indicating that the association between the PDCP entity (DRB or SRB) and the RLC entity in the direct link is released. For example, since the direct link is established, the PDCP entity is on the direct link side (for example, Fig.10 Before associating an SRAP entity with an RLC entity in the direct link, releasing the association between the associated PDCP entity and the RLC entity in the direct link. Including information indicating that the association is to be released. Note that the information may be implicit information.

[0132] Second, information for establishing an SRAP entity is included. Specifically, association information for associating a PDCP entity (DRB or SRB) with an RLC (Uu RLC) entity in a direct link and an RLC (PC5 RLC) entity (RLC channel) in an indirect link is included. As in operation example 1, the association information may be association information for associating an identifier of an entity.

[0133] As described above, the remote UE 100-1 may configure a SRAP entity that associates the PDCP entity with two RLC entities according to the association information.

[0134] When an indirect link is previously established (operation example 2), the RRC reconfiguration message ( Fig.12 It is sufficient that step S22) in includes the following information.

[0135] In other words, information for updating the SRAP entity is included in the RRC reconfiguration message. Specifically, association information for associating the PDCP entity (DRB or SRB) with the RLC (Uu RLC) entity (RLC channel) in the direct link is included. The association information may be information for associating an identifier of the entity. The association information may be information for associating the PDCP entity with the RLC entity in the direct link and the RLC entity in the indirect link.

[0136] As described above, the remote UE 100-1 may configure a SRAP entity that associates the PDCP entity with two RLC entities according to the association information.

[0137] The operation of the SRAP entity so configured is described.

[0138] The header (SRAP header) of the SRAP Data PDU includes identification information (UEID (temporary ID or local ID)) of the remote UE 100-1 that performs U2N relay and the bearer ID (Uu radio bearer ID) of the remote UE 100-1.

[0139] Here, the following two points can be considered.

[0140] First, as described above, the SRAP entity has a bearer mapping function and an identification function of the remote UE 100-1. Therefore, the UEID and the bearer ID included in the SRAP header are used. However, these functions are functions performed by the SRAP entity configured on the indirect link side, and are not essentially required on the direct link side. Therefore, the UEID and the bearer ID included in the SRAP header are not too necessary on the direct link side. Alternatively, the UEID included in the SRAP header is not considered to be required on the direct link side.

[0141] Second, whether the SRAP header is required depends on whether the SRAP entity is associated with an RLC (Uu RLC) entity in a direct link on the other side (receiving side).

[0142] Therefore, the SRAP entity of the remote UE 100-1 performs any one of the following operations: outputs the SRAP SDU to the first RLC entity (e.g., the RLC entity in the direct link) without applying the SRAP header to the SRAP SDU; or outputs the SRAP PDU to the first RLC entity, wherein the SRAP header including the bearer ID but not the UEID is applied to the SRAP SDU.

[0143] Specifically, the operation of the SRAP entity of the remote UE 100-1 is as follows (step S30).

[0144] Specifically, the SRAP entity processes the SRAP data SDU in a transparent mode (TM). In other words, the SRAP entity outputs the SRAP data SDU to the RLC entity in the direct link without applying the SRAP header to the SRAP data SDU. Note that in this case, the SRAP entity performs selection (or mapping) of the RLC entity (or RCL channel) in the direct link. Alternatively, the SRAP entity may output the SRAP data SDU to the RLC entity in the direct link after removing the SRAP header from the SRAP data PDU once created. Alternatively, the SRAP entity may output the SRAP data SDU to the RLC entity in the direct link, wherein a SRAP header including a bearer ID but not including the UEID of the remote UE 100-1 is applied to the SRAP data SDU. In this case, the SRAP entity may select and output a data PDU format different from the data PDU format of the PC5-RRC message.

[0145] gNB 200-1 may perform the following configuration on remote UE 100-1 so that the SRAP entity of remote UE 100-1 performs the above operations.

[0146] First, gNB 200-1 can configure whether to apply the SRAP header for the remote UE 100-1. Specifically, it can be configured whether to remove the SRAP header. Alternatively, the designation of the TM can be configured. The designation of the TM can be a designation of the processing mode. Alternatively, the configuration can be configured for each mapped RLC entity. In this case, the configuration can be configured for each LCID or each RLC channel ID. For example, logical channel ID (LCID) #3 can be configured to be in TM, and LCID #4 can be configured to be in normal mode (SRAP header applied). Alternatively, the processing mode can be configured to be specified for each entry in the mapping table.

[0147] Second, when the SRAP header is applied, it is possible to configure whether the SRAP header includes the bearer ID of the remote UE 100-1 without including the identification information (UEID) of the remote UE 100-1. In this case, it is possible to configure whether to use another data PDU format. Alternatively, it is possible to configure whether to apply a complete SRAP header including the bearer ID and identification information of the remote UE 100-1.

[0148] The gNB 200-1 may perform the above configuration by sending an RRC message (e.g., an RRC reconfiguration message) including such configuration information to the remote UE 100-1. The remote UE 100-1 performs the above processing according to the above configuration (step S30).

[0149] Second embodiment

[0150] The second embodiment is described below. The second embodiment is an embodiment of the operation method in "intra-cell U2N multi-link split bearer".

[0151] Specifically, first, the base station (e.g., gNB 200-1) sends activation indication information to the remote user equipment (e.g., remote UE 100-1), and the activation indication information indicates activation or deactivation of the direct link and indicates activation or deactivation of the indirect link. Secondly, the remote user equipment activates or deactivates the direct link and activates or deactivates the indirect link according to the activation indication information.

[0152] For example, this makes it possible to support various operations in the mobile communication system 1, such as using two links to transmit different data or to transmit the same data.

[0153] Specifically, the following operations are assumed.

[0154] (1) Whether to use only one branch or two branches.

[0155] (2) Whether the two branches are used to send and receive different data (such as in carrier aggregation) or to send and receive the same data (such as in PDCP duplication).

[0156] (3) Whether both branches are used to send data for both the control plane (CP) and the user plane (UP), or one branch is used for the CP and the other branch is used for the UP (CP / UP separation), respectively.

[0157] (4) Whether both branches are used for transmission and reception (two-way relay), or whether one branch is used as a transmission branch and the other branch is used as a reception branch (one-way relay), respectively.

[0158] Note that a branch refers to either a direct link or an indirect link.

[0159] The above situation (1) can be implemented by activating one branch and deactivating the other branch. The remote UE 100-1 can use the activated branch to send and receive data.

[0160] In the case of (1) above, when use of one of the branches is allowed, the remote UE 100-1 can send and receive data on the primary link, and when the amount of data buffered for transmission is greater than a threshold, the remote UE 100-1 can send and receive data on both the secondary link and the primary link. Here, the primary link is a link that can always send and receive data, and the secondary link is a link that can send and receive data when a certain condition is met.

[0161] In the above case (2), whether the remote UE 100-1 sends the same data or different data can be configured through RRC messages, PDCP control PDU, etc. sent from gNB 200-1.

[0162] In the case of (3) above, data of the UP may be transmitted in one branch or two branches, and control signals of the CP may also be transmitted in one branch or two branches.

[0163] In the case of (4) above, UL data and DL data may be sent on the same link. UL data may be sent on an indirect link, and DL data may be sent on a direct link. In addition, UL data may be sent on a direct link, and DL data may be sent on an indirect link.

[0164] The following describes the configuration method to achieve this operation.

[0165] Operation Example According to the Second Embodiment

[0166] Fig.14 is a diagram showing an operation example according to the second embodiment.

[0167] like Fig.14 As shown, gNB 200-1 sends an RRC reconfiguration message to remote UE 100-1 (step S12 or step S20). The transmission timing of the RRC reconfiguration message is the same and / or similar to the transmission timing of the RRC reconfiguration message in the first embodiment. Therefore, gNB 200-1 can send the RRC reconfiguration message via a direct link (step S12) or via an indirect link (step S20). The RRC reconfiguration message includes each of the information described in the first embodiment.

[0168] In the second embodiment, the RRC reconfiguration message further includes usage restriction information of the direct link and the indirect link.

[0169] First, the use restriction information may be information indicating that the two branches are allowed to be used (the case of (1) above). In this case, the use restriction information may include information indicating that the two branches are used to send and receive different data (sending and receiving first data in one branch, and sending and receiving second data in the other branch), or may include information indicating that the two branches are used to send and receive the same data (the case of (2) above). In this case, the use restriction information may include information indicating the initial activation or deactivation state of each branch.

[0170] Secondly, the usage restriction information may be information indicating that one branch is allowed to be used (the case of (1) above). In this case, the usage restriction information may include link indication information indicating a continuously available main link and an auxiliary link that is available when a condition is met (the case of (1) above). In addition, the link indication information may include a threshold for allowing the use of the auxiliary link (i.e., to use two branches). The threshold may be a threshold for the amount of transmission data buffer. In this case, the condition for using the auxiliary link is that the transmission data amount buffer exceeds the threshold. The threshold may be a threshold for radio quality. In this case, the condition for using the auxiliary link is that the radio quality is better than the threshold or the radio quality is worse than the threshold. In addition, the usage restriction information may include information indicating a link for CP and a link for UP (the case of (3) above). In addition, the usage restriction information may include information indicating a UL transmission link and a DL reception link (the case of (4) above).

[0171] The gNB 200-1 may send information indicating activation or deactivation of a direct link and indicating activation or deactivation of an indirect link to the remote UE 100-1 (step S40 or step S41). Such information may be referred to as "activation indication information". The gNB 200-1 may send any one of a MAC CE, a PDCP control PDU, or an RRC message including activation indication information to the remote UE 100-1. The RRC message may be an RRC reconfiguration message. In this case, the RRC reconfiguration message may include usage restriction information and activation indication information.

[0172] gNB 200-1 may send activation indication information through a direct link when a direct link is established (step S40), or may send activation indication information through an indirect link when an indirect link is established (step S41).

[0173] In step S42, the remote UE 100-1 performs the following predetermined operation according to the usage restriction information (and the activation indication information).

[0174] First, when receiving the activation indication information, the remote UE 100-1 activates or deactivates the direct link and activates or deactivates the indirect link according to the activation indication information.

[0175] Second, upon receiving usage restriction information indicating that the use of two branches is allowed, the remote UE 100-1 monitors a physical downlink control channel (PDCCH) (in a direct link) and / or a physical sidelink control channel (PSCCH) (in an indirect link) for the activated branch. When the remote UE 100-1 can use two branches but one branch is deactivated, the remote UE 100-1 can perform the above monitoring on the activated branch. The remote UE 100-1 can also use the activated branch to send the same data or different data. In other words, according to the usage restriction information indicating that the direct link and the indirect link are to be used to send and receive the same data, the remote UE 100-1 sends the same data to the direct link and the indirect link. According to the usage restriction information indicating that the direct link and the indirect link are to be used to send and receive different data, the remote UE 100-1 sends first data to the direct link and sends second data different from the first data to the indirect link.

[0176] Third, when the remote UE 100-1 receives usage restriction information indicating that the use of one branch is allowed (the usage restriction information includes link indication information), the following operations are performed, for example. In other words, the remote UE 100-1 configures the main link and the auxiliary link according to the link indication information. The remote UE 100-1 can monitor PDCCH (direct link) and / or PSCCH (indirect link) for the activated branch in the DL direction, regardless of the main link and the auxiliary link. The remote UE 100-1 can use the main link in the UL direction to perform transmission and reception. Then, the remote UE 100-1 determines the condition for using the auxiliary link by using the threshold value included in the link indication information, and when the condition is met, uses both the main link and the auxiliary link to perform transmission.

[0177] Fourth, when the remote UE 100-1 receives the usage restriction information indicating that the use of one branch is allowed (the usage restriction information includes information indicating the link for CP and the link for UP), for example, the following operations are performed. In other words, the remote UE 100-1 sends and receives control signals by using the link specified for CP. The remote UE 100-1 sends and receives data by using the link specified for UP. Both branches can be used in the DL direction.

[0178] Fifth, when the remote UE 100-1 receives the usage restriction information indicating that the use of one branch is allowed (the usage restriction information includes information indicating the UL transmission link and the DL reception link), for example, the following operations are performed. In other words, the remote UE 100-1 performs UL transmission by using the link specified for UL. The remote UE 100-1 performs DL reception by using the link specified for DL.

[0179] Note that the above predetermined operations are only examples, and these operations may be combined appropriately. For example, the remote UE 100-1 may use two branches to transmit the same data (PDCP duplication) and use an indirect link for control signals according to the usage restriction information.

[0180] Third embodiment

[0181] A third embodiment is described.

[0182] In the third embodiment, “inter-cell U2N multi-link split bearer” is described.

[0183] Fig.15 is a diagram showing a configuration example of a mobile communication system 1 configured with “inter-cell U2N multi-link split bearer”.

[0184] like Fig.15 As shown, multiple cells are managed in one gNB 200-1. A direct link is configured between one cell (first cell) of gNB 200-1 and remote UE 100-1, and an indirect link is configured between another cell (second cell) of gNB 200-1 and remote UE 100-1. Split bearers are configured by direct links and indirect links.

[0185] From the perspective of the remote UE 100-1, although the cells are different from each other, the split bearer is configured for the same gNB 200-1. Therefore, the "inter-cell U2N multi-link split bearer" can be configured by the same and / or similar operations as those in the first embodiment. For the operation method in the "inter-cell U2N multi-link split bearer", it can be operated by the same and / or similar configuration as that in the second embodiment.

[0186] Fourth embodiment

[0187] A fourth embodiment is described.

[0188] In the fourth embodiment, “Inter-gNB U2N multi-link split bearer” is described.

[0189] Fig.16 It is a diagram showing a configuration example of a mobile communication system 1 configured with "U2N multi-link split bearer between gNBs".

[0190] like Fig.16 As shown, a direct link is configured between gNB 200-1 (hereinafter, which may be referred to as "first gNB 200-1") and remote UE 100-1. An indirect link is configured between gNB 200-2 (hereinafter, which may be referred to as "second gNB 200-2") and remote UE 100-1. Split bearers are configured by direct links and indirect links. In this way, the two different gNBs 200-1 and gNB 200-2 configure split bearers for remote UE 100-1 through direct links and indirect links.

[0191] The operation example described in the first embodiment is basically applicable to the configuration of "inter-gNB U2N multi-link split bearer". Note that, unlike the first embodiment, it is necessary to extend the Xn interface in order to achieve coordinated control between gNBs 200. The first gNB 200-1 and the second gNB 200-2 need to share the information of the relay UE 100-2 with each other. Thereafter, as in the first embodiment, the first gNB 200-1 sends an RRC reconfiguration message including the identification information of the relay UE 100-2, etc. to the remote UE 100-1, thereby achieving the configuration of "inter-gNB U2N multi-link split bearer".

[0192] Specifically, first, in response to receiving a measurement report from a remote user equipment (e.g., remote UE 100-1) through a direct link, the first base station (e.g., first gNB 200-1) sends a secondary node addition request message including the measurement report to the second base station (e.g., second gNB 200-2). Secondly, in response to receiving the secondary node addition request message, the second base station (e.g., second gNB 200-2) sends a secondary node addition request response message including identification information of the subordinate relay user equipment to the first base station. Thirdly, in response to receiving the secondary node addition request response message, the first base station sends the identification information to the remote user equipment.

[0193] This allows, for example, a remote UE 100-1 that has established a direct link with the first gNB 200-1 to establish an indirect link via a relay UE 100-2 belonging to the second gNB 200-2 based on the identification information. Therefore, an "inter-gNB U2N multi-link split bearer" can be configured.

[0194] Note that in the following description, it is assumed that the master node (MN) uses a direct link (Uu) and the SN (secondary node) uses an indirect link (PC5). Therefore, the first gNB 200-1 can be referred to as MN 200-1, and the second gNB 200-2 can be referred to as SN 200-2. The description is given under the assumption that there is also a relay UE belonging to SN 200-2.

[0195] In the following, a configuration method of “U2N multi-link split bearer between gNBs” is described.

[0196] Operation Example According to the Fourth Embodiment

[0197] Fig.17 is a diagram showing an operation example according to the fourth embodiment.

[0198] like Fig.17 As shown, in step S50, MN 200-1 and remote UE 100-1 establish a direct link. At this time, remote UE 100-1 does not establish an indirect link.

[0199] In step S51, SN 200-2 may send identification information (UEID) of relay UE 100-2 belonging to SN 200-2 itself to the neighboring gNB (here, gNB 200-1). When the identification information of relay UE 100-2 is included in the measurement report of the later stage, it is not necessary to send the identification information.

[0200] In step S52, the remote UE 100-1 sends a measurement report (MeasurementReport) message. The measurement report message includes a measurement result for the relay UE 100-2. The measurement result may include cell information (cell ID) of the serving cell of the relay UE 100-2.

[0201] In step S53, MN 200-1 determines to configure "inter-gNB U2N multi-link split bearer" for remote UE 100-1 based on the measurement result, and specifies an appropriate SN. For example, when the measurement result for a certain relay UE is equal to or greater than a predetermined value (or less than a predetermined value), MN 200-1 determines to perform the configuration and specifies the second gNB 200-2 as the appropriate SN, wherein the second gNB 200-2 has a relay UE subordinate to the second gNB 200-2. The SN (second gNB 200-2) can be specified using the cell ID included in the measurement result.

[0202] In step S54, the MN 200-1 sends an SN add request message to the second gNB 200-2 designated as the appropriate SN. The SN add request message may be, for example, a message in which the MN 200-1 requests the second gNB 200-2 to select an appropriate relay UE. The SN add request message is sent using the Xn interface. An SN modification request message may be used instead of the SN add request message. The SN add request includes a measurement result (measurement report) reported from the remote UE 100-1. The measurement result may include identification information (UEID) of the relay UE 100-2 and a measurement result for the relay UE 100-2.

[0203] In step S55, the second gNB 200-2 determines to accept the SN add request based on the measurement result, and designates an appropriate relay UE. For example, since the measurement result for the relay UE 100-2 is equal to or greater than a predetermined value (or less than a predetermined value), the second gNB 200-2 determines to accept the SN add request and designates the relay UE 100-2 as an appropriate relay UE. By accepting the SN add request, the second gNB 200-2 can, for example, become SN 200-2.

[0204] In step S56, SN 200-2 sends an SN add request reply message to MN 200-1. The SN add request reply message includes identification information (UEID, L2 ID or L2 destination ID) of the specified relay UE 100-2. Relay UE 100-2 may be a relay UE with which remote UE 100-1 is to establish a PC5-RRC connection. The SN add request reply message is also sent using the Xn interface. An SN modification request reply message may be used instead of the SN add request reply message.

[0205] In step S57, MN 200-1 sends an RRC reconfiguration message to remote UE 100-1 through a direct link. The RRC reconfiguration message includes identification information (UEID, L2 ID or L2 destination ID) of relay UE 100-2. The identification information indicates to remote UE 100-1 the relay UE with which MN 200-1 is to establish a PC5-RRC connection. Note that the RRC reconfiguration message includes the association information described in the first embodiment for associating the PDCP entity with the SRAP entity and the RLC (UuRLC) entity. The RRC reconfiguration message may include other information described in the first embodiment. The RRC reconfiguration message may include the usage restriction information described in the second embodiment.

[0206] In step S58, the remote UE 100-1 establishes a PC5-RRC connection with the relay UE 100-2 according to the identification information (UEID, L2ID or L2 destination ID) included in the RRC reconfiguration message. The remote UE 100-1 establishes a PC5-RRC connection by sending an RRC reconfiguration sidelink (RRCReconfigurationSidelink) message to the relay UE 100-2. The remote UE 100-1 may send an RRC reconfiguration sidelink message to the relay UE 100-2, the RRC reconfiguration sidelink message including information indicating a connection establishment request with a network indication as a cause ("NW indicated connection request").

[0207] In step S59, the remote UE 100-1 sends an RRC reconfiguration complete (RRCReconfigurationComplete) message to the MN 200-1. The MN 200-1 sends the received RRC reconfiguration complete message to the SN 200-2 using the Xn interface.

[0208] Alternatively, in step S60, the remote UE 100-1 may send an RRC reconfiguration complete message to the SN 200-2 via the relay UE 100-2 (or through an indirect link). In response to receiving the RRC reconfiguration complete message via the relay UE 100-2, the SN 200-2 sends the RRC reconfiguration complete message to the MN 200-1. Alternatively, the SN 200-2 may send a message including information indicating that the RRC reconfiguration complete message has been received to the MN 200-1. In the PC5 link, the PC5-RRC message obtained by encapsulating the RRC reconfiguration complete message may be used for transmission. Note that when the relay UE 100-2 is in the RRC idle state or the RRC inactive state, the RRC reconfiguration complete message may be the first message described in the first embodiment. The relay UE 100-2 establishes an RRC connection with the SN 200-2 to be in the RRC connected state, thereby enabling the relay UE 100-2 to perform side link relay in the indirect link.

[0209] Alternatively, the remote UE 100-1 may send an RRC reconfiguration complete message to the MN 200-1 before establishing the PC5-RRC connection (in step S58). In this case, after establishing the PC5-RRC connection with the relay UE 100-2, the remote UE 100-1 may send a message (e.g., an RRC reconfiguration complete message) including information indicating that the PC5-RRC connection has been established to the MN 200-1.

[0210] In step S61, the relay UE 100-2 may send a message including access information to the SN 200-2, the access information indicating that the remote UE 100-1 has accessed the relay UE 100-2. The message may include identification information (UEID, L2 ID or L2 destination ID) of the remote UE 100-1. The access information may be information indicating that a PC5-RRC connection has been established.

[0211] In step S62, the SN 200-2 may update the radio configuration of the relay UE 100-2. For example, the SN 200-2 may update the configuration of the SRAP.

[0212] As described above, "intra-gNB U2N multi-link split bearer" is configured. In the mobile communication system 1 configured with "inter-gNB U2N multi-link split bearer" according to the usage restriction information included in the RRC reconfiguration message (step S57), various operations can be supported as in the second embodiment.

[0213] Fifth embodiment

[0214] A fifth embodiment is described. In the fifth embodiment, a configuration example of "U2U multi-link split bearer" is described.

[0215] Fig.18 1 is a diagram showing a configuration example of a mobile communication system 1 according to a fifth embodiment. Fig.18 As shown, a direct link (PC5) is configured between the first remote UE 100-11 and the second remote UE 100-12. An indirect link (PC5) via the relay UE 100-2 is configured between the first remote UE 100-11 and the second remote UE 100-12. The "U2U multi-link split bearer" is configured by a direct link and an indirect link.

[0216] The above embodiment may be applied when gNB 200-1 configures "U2U multi-link split bearer" for the first remote UE 100-11 and the second remote UE 100-12 and the relay UE 100-2.

[0217] For example, “U2U multi-link split bearer” may be configured by gNB 200-1 sending configuration information (such as the association information described in the first embodiment) to at least any one UE selected from the group consisting of a first remote UE 100-11, a second remote UE 100-12, and a relay UE 100-2.

[0218] For example, various operations described in the second embodiment can be supported by sending usage restriction information by gNB 200-1 to at least any one UE selected from the group consisting of a first remote UE 100-11, a second remote UE 100-12, and a relay UE 100-2.

[0219] Other embodiments

[0220] A program that causes a computer to execute each process performed by UE 100 (including relay UE 100-2, remote UE 100-1, first remote UE 100-11, and second remote UE 100-12) or gNB 200 may be provided. The program may be recorded in a computer-readable medium. Using a computer-readable medium enables the program to be installed 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.

[0221] Circuits for performing processing to be performed by UE 100 or gNB 200 may be integrated, and at least a portion of UE 100 or gNB 200 may be implemented as a semiconductor integrated circuit (chip set, system on chip (SoC)).

[0222] Unless otherwise expressly stated, the phrases "based on" and "depending on" used in this disclosure do not mean "based only on" and "depending only on". The phrase "based on" means both "based only on" and "based at least in part on". Similarly, the phrase "depending on" means both "depending only on" and "depending at least in part on". The terms "include", "comprising" and their variants do not mean "only including the items", but mean "may only include the items" or "may include not only the items but also other items". The term "or" used in this disclosure is not intended to be "exclusive or". In addition, any reference to elements using names such as "first" and "second" in this disclosure does not generally limit the number or order of these elements. These names can be used as a convenient method to distinguish two or more elements in this article. Therefore, the reference to the first element and the second element does not mean that only two elements can be adopted there or that the first element needs to be in some way before the second element. For example, when English articles such as "one", "an" and "the" are added in this disclosure by translation, these articles include plural unless otherwise clearly indicated in the context.

[0223] The embodiments have been described in detail above with reference to the drawings, but the specific configuration is not limited to the above configuration, and various design changes can be made without departing from the gist of the present disclosure. The embodiments, operation examples, and processing operations can be fully combined without contradiction.

[0224] This application claims priority to U.S. Provisional Patent Application No. 63 / 301,773 (filed on January 21, 2022), the entire contents of which are incorporated herein by reference.

[0225] Additional Notes

[0226] Features related to the above-described embodiment are described below as supplements.

[0227] (1) A communication control method in a mobile communication system, the mobile communication system being configured to perform a first communication on a direct link between a remote user equipment and a base station and to perform a second communication on an indirect link between the remote user equipment and the base station via a relay user equipment, the communication control method comprising:

[0228] sending, by the base station, to the remote user equipment, association information that associates a PDCP entity with an RLC entity of the direct link and an SRAP entity of the indirect link; and

[0229] The remote user equipment associates the PDCP entity with the RLC entity and the SRAP entity according to the association information.

[0230] (2) The communication control method according to (1) above, wherein

[0231] The sending includes any one of the following operations:

[0232] The base station sends indirect link establishment indication information to the remote user equipment, where the indirect link establishment indication information indicates that an indirect link with the relay user equipment is to be established, or

[0233] The base station sends direct link establishment indication information to the remote user equipment, where the direct link establishment indication information indicates that a direct link with the base station is to be established.

[0234] (3) The communication control method according to (1) or (2) above, further comprising:

[0235] The remote user device performs any one of the following operations:

[0236] sending direct link maintaining indication information, wherein the direct link maintaining indication information indicates that the direct link is to be maintained even after the indirect link is established; or

[0237] Indirect link maintenance indication information is transmitted, the indirect link maintenance indication information indicating that the indirect link is to be maintained even after the direct link is established.

[0238] (4) The communication control method according to any one of (1) to (3) above, further comprising:

[0239] The remote user equipment establishes an indirect link with the relay user equipment reselected through relay reselection, and

[0240] The remote user equipment sends identification information of the reselected relay user equipment to the base station.

[0241] (5) The communication control method according to any one of (1) to (4) above, wherein:

[0242] The sending includes sending, by the base station, transmission indication information to the remote user equipment, wherein the transmission indication information instructs the remote user equipment to send an RRC reconfiguration complete message to the relay user equipment. (6)

[0244] A communication control method in a mobile communication system, the mobile communication system being configured to perform a first communication on a direct link between a remote user equipment and a base station and to perform a second communication on an indirect link between the remote user equipment and the base station via a relay user equipment, the communication control method comprising:

[0245] sending, by the base station, to the remote user equipment, association information associating a PDCP entity with a first RLC entity of the direct link and a second RLC entity of the indirect link; and

[0246] The remote user equipment configures an SRAP entity, and the SRAP entity associates the PDCP entity with the first RLC entity and the second RLC entity according to the association information.

[0247] (7) The communication control method according to (6) above, further comprising:

[0248] The SRAP entity of the remote user equipment performs any one of the following operations:

[0249] outputting the SRAP SDU to the first RLC entity without adding a SRAP header to the SRAP SDU, or

[0250] Outputting a SRAP PDU to the first RLC entity, the SRAP PDU being obtained by adding a SRAP header including a bearer ID but not including a UEID to the SRAP SDU.

[0251] (8) A communication control method in a mobile communication system, the mobile communication system being configured to perform a first communication on a direct link between a remote user equipment and a base station and to perform a second communication on an indirect link between the remote user equipment and the base station via a relay user equipment, the communication control method comprising:

[0252] Sending, by the base station, activation indication information to the remote user equipment, the activation indication information indicating activation or deactivation of the direct link and indicating activation or deactivation of the indirect link; and

[0253] The remote user equipment activates or deactivates the direct link and activates or deactivates the indirect link according to the activation indication information.

[0254] (9) The communication control method according to (8) above, wherein

[0255] The sending includes sending link indication information by the base station to the remote user equipment, wherein the link indication information indicates a continuously available primary link and an auxiliary link that is available when a condition is met, and

[0256] The link indication information includes a threshold for allowing use of the auxiliary link.

[0257] (10) The communication control method according to (8) or (9) above, wherein:

[0258] The sending includes sending, by the base station, usage restriction information, the usage restriction information indicating that the direct link and the indirect link are to be used to send and receive the same data, and

[0259] The remote user equipment also sends the same data on the direct link and the indirect link according to the usage restriction information.

[0260] (11) A communication control method in a mobile communication system, the mobile communication system being configured to perform a first communication on a direct link between a remote user equipment and a first base station and to perform a second communication on an indirect link between the remote user equipment and a second base station via a relay user equipment, the communication control method comprising:

[0261] In response to receiving a measurement report from a remote user equipment through the direct link, the first base station sends a secondary node addition request message including the measurement report to the second base station;

[0262] In response to receiving the secondary node adding request message, the second base station sends a secondary node adding request reply message to the first base station, wherein the secondary node adding request reply message includes identification information of a relay user equipment belonging to the second base station; and

[0263] In response to receiving the secondary node addition request response message, the first base station sends the identification information to the remote user equipment.

[0264] (12) The communication control method according to (11) above, further comprising:

[0265] The second base station sends identification information of the relay user equipment to the first base station.

[0266] (13) The communication control method according to (11) or (12), further comprising:

[0267] An RRC reconfiguration side link message is sent by the remote user equipment to the relay user equipment, wherein the RRC reconfiguration side link message includes information indicating a connection establishment request indicated by the network.

[0268] (14) The communication control method according to any one of (11) to (13) above, further comprising:

[0269] In response to receiving an RRC reconfiguration complete message from the remote user equipment via the relay user equipment, the second base station sends the RRC reconfiguration complete message to the first base station.

[0270] (15) The communication control method according to any one of (11) to (14) above, further comprising:

[0271] The relay user equipment sends access information to the second base station, where the access information indicates access performed by the remote user equipment.

[0272] (16) The communication control method according to any one of (11) to (15) above, further comprising:

[0273] After establishing a PC5-RRC connection with the relay user equipment, the remote user equipment sends an RRC reconfiguration completion message to the first base station.

Claims

1. A communication control method in a mobile communication system, the mobile communication system being configured to perform a first communication on a direct link between a remote user equipment and a base station and to perform a second communication on an indirect link between the remote user equipment and the base station via a relay user equipment, the communication control method comprising: The base station sends association information to the remote user equipment, wherein the association information associates the PDCP entity with the RLC entity of the direct link and the SRAP entity of the indirect link; as well as The remote user equipment associates the PDCP entity with the RLC entity and the SRAP entity according to the association information.

2. The communication control method according to claim 1, wherein: The sending includes any one of the following operations: The base station sends indirect link establishment indication information to the remote user equipment, where the indirect link establishment indication information indicates that an indirect link with the relay user equipment is to be established, or The base station sends direct link establishment indication information to the remote user equipment, where the direct link establishment indication information indicates that a direct link with the base station is to be established.

3. The communication control method according to claim 2, further comprising: The remote user device performs any one of the following operations: sending direct link maintaining indication information, wherein the direct link maintaining indication information indicates that the direct link is to be maintained even after the indirect link is established; or Those Indirect link maintenance indication information is transmitted, the indirect link maintenance indication information indicating that the indirect link is to be maintained even after the direct link is established.

4. The communication control method according to claim 1, further comprising: The remote user equipment establishes an indirect link with the relay user equipment reselected through relay reselection, and The remote user equipment sends identification information of the reselected relay user equipment to the base station.

5. The communication control method according to claim 1, wherein: The sending includes sending, by the base station, transmission indication information to the remote user equipment, wherein the transmission indication information instructs the remote user equipment to send an RRC reconfiguration complete message to the relay user equipment.

6. A communication control method in a mobile communication system, the mobile communication system being configured to perform a first communication on a direct link between a remote user equipment and a base station and to perform a second communication on an indirect link between the remote user equipment and the base station via a relay user equipment, the communication control method comprising: Sending association information, by the base station, to the remote user equipment, the association information associating a PDCP entity with a first RLC entity of the direct link and a second RLC entity of the indirect link; as well as The remote user equipment configures an SRAP entity, and the SRAP entity associates the PDCP entity with the first RLC entity and the second RLC entity according to the association information.

7. The communication control method according to claim 6, further comprising: The SRAP entity of the remote user equipment performs any one of the following operations: outputting the SRAP SDU to the first RLC entity without adding a SRAP header to the SRAP SDU, or Outputting a SRAP PDU to the first RLC entity, the SRAP PDU being obtained by adding a SRAP header including a bearer ID but not including a UEID to the SRAP SDU.

8. A communication control method in a mobile communication system, the mobile communication system being configured to perform a first communication on a direct link between a remote user equipment and a base station and to perform a second communication on an indirect link between the remote user equipment and the base station via a relay user equipment, the communication control method comprising: Sending, by the base station, activation indication information to the remote user equipment, the activation indication information indicating activation or deactivation of the direct link and indicating activation or deactivation of the indirect link; as well as The remote user equipment activates or deactivates the direct link and activates or deactivates the indirect link according to the activation indication information.

9. The communication control method according to claim 8, wherein: The sending includes sending link indication information by the base station to the remote user equipment, wherein the link indication information indicates a continuously available primary link and an auxiliary link that is available when a condition is met, and The link indication information includes a threshold for allowing use of the auxiliary link.

10. The communication control method according to claim 8, wherein: The sending includes sending, by the base station, usage restriction information, the usage restriction information indicating that the direct link and the indirect link are to be used to send and receive the same data, and The remote user equipment also sends the same data on the direct link and the indirect link according to the usage restriction information.

11. A communication control method in a mobile communication system, the mobile communication system being configured to perform a first communication on a direct link between a remote user equipment and a first base station and to perform a second communication on an indirect link between the remote user equipment and a second base station via a relay user equipment, the communication control method comprising: In response to receiving a measurement report from a remote user equipment through the direct link, the first base station sends a secondary node addition request message including the measurement report to the second base station; In response to receiving the secondary node adding request message, the second base station sends a secondary node adding request reply message to the first base station, where the secondary node adding request reply message includes identification information of a relay user equipment belonging to the second base station; as well as In response to receiving the secondary node addition request response message, the first base station sends the identification information to the remote user equipment.

12. The communication control method according to claim 11, further comprising: The second base station sends identification information of the relay user equipment to the first base station.

13. The communication control method according to claim 11, further comprising: The remote user equipment sends an RRC reconfiguration side link message to the relay user equipment, wherein the RRC reconfiguration side link message includes information indicating a connection establishment request indicated by the network.

14. The communication control method according to claim 11, further comprising: In response to receiving an RRC reconfiguration complete message from the remote user equipment via the relay user equipment, the second base station sends the RRC reconfiguration complete message to the first base station.

15. The communication control method according to claim 11, further comprising: The relay user equipment sends access information to the second base station, where the access information indicates access performed by the remote user equipment.

16. The communication control method according to claim 11, further comprising: After establishing a PC5-RRC connection with the relay user equipment, the remote user equipment sends an RRC reconfiguration completion message to the first base station.

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